Whole document restricted, see Access Instructions file below for details of how to access the print copy. / A dramatic increase in referrals of infants with non-synostotic positional plagiocephaly and brachycephaly has occurred since the adoption of supine sleep position recommendations to prevent sudden infant death syndrome (SIDS). Repeated positioning of the soft infant skull on firm surfaces is postulated to cause flattening of infant heads. There are concerns that parents who are worried about their infants' head shapes may reject SIDS prevention guidelines. This thesis was undertaken to provide greater understanding of the determinants, prevalence and natural history of non-synostotic aberrant head shapes. It includes a literature review that summarises the historical background, anatomy and skull growth of the infant cranium, clinical characteristics of non-synostotic plagiocephaly and brachycephaly, cephalometry methods, prevalence, risk factors, prevention, treatment and outcomes. Three studies were conducted. Firstly, a case control study was undertaken to investigate a range of possible risk factors. One hundred cases from plagiocephaly clinics and 94 community controls were administered a questionnaire covering obstetric, sociodemographic, infant, and infant care factors. Infants with plagiocephaly were significantly more likely to be male, firstborn, premature, supine sleeping, less active, to have a preferential head orientation at 6 weeks, to have a developmental delay, and to have a less educated mother. They were likely not to have had the head position varied when being put down to sleep in the first 6 weeks, and to have had less than 5 minutes a day of prone play time in the first 6 weeks. Next, a study of a new digital photographic technique that was developed to measure infant head shape used 31 plagiocephaly cases and 29 controls. The method, named HeadsUpTM, used an elastic band to define the head shape in the fronto-occipital plane. A digital camera recorded the head shape, and custom-written software quantified measurements from the photos. Compared with the conventional flexicurve measuring method, the HeadsUpTM method was more acceptable to both mothers and infants and less variable on measures of plagiocephaly and brachycephaly. Although it is recognised that head shape is a continuum from perfectly symmetrical to severely asymmetrical, thresholds were calculated to allow dichotomisation between "normal" and abnormal. The cut-off for cephalic index [(head width/head length) * l00] was identified as 93%, while the cut-off for the oblique cranial length ratio (the ratio of the longer cross-diagonal length to the shorter cross-diagonal length) was identified to be 106%. Beyond these points, brachycephaly and plagiocephaly, respectively, are deemed to exist. Finally, a prospective cohort study of 200 newborn infants combined the methods from both previous studies to further enlarge on determinants, prevalence and natural history of the condition. Ninety-one percent of the children were followed to two years of age. Using the cut-off points determined in the photo study, it was seen that 29.5% of the cohort developed plagiocephaly or brachycephaly at some time during the first 8 months, after which there were no new cases. Prevalence of plagiocephaly at 6 weeks was 16.0%, increasing to 19.7% at 4 months, then reducing to 9.2%, 6.8% and 3.3% at 8, 12, and 24 months respectively. Risk factor analysis was conducted on the 6-week and 4-month cases and controls. Significant determinants identified were: male gender, a limitation of head rotation, supine sleep position, more than 21 hours of supine-lying time a day at 6 weeks, head position when put down to sleep not varied in first 6 weeks, maternal reporting of low activity level at 4 months, and average-to-difficult temperament at 4 months. Although the cohort study showed that nearly all infants improved over time, there were a few persistent cases. Heads in the cohort were wider and shorter than those measured in infants during earlier decades when prone and side sleeping positions were the norm, highlighting a need for further research to provide age-specific norms for cephalic index in supine-sleeping infants. The photo study cases, recruited from plagiocephaly clinics, were in general of greater severity than the cohort cases. Further research is needed to allow early identification of infants who do not improve over time. Although supine sleeping is a risk factor for the development of plagiocephaly, this position is highly protective against SIDS and should be maintained. However, varying the head position at sleep, providing tummy time, limiting supine-lying time when awake, and awareness and treatment of head rotation problems may help to prevent the condition. These practices need to be confirmed in future studies of primary prevention.

Hypnosis has been used as a treatment modality to change physiological functioning almost since it was discovered. Particularly, it has been used in the treatment of psychosomatic illnesses. A series of studies was planned to explore the use of hypnosis within the context of recent advances in the field of psychoneuroimmunology. Type I hypersensitivity reactions were chosen as indicators of immunological functioning in allergy. Study One: This study using modern methodology and statistical analyses set out to test the hypothesis that it was possible to decrease reactions to histamine by hypnotic suggestion. Five subjects, all asthmatic and untrained in hypnosis, were given three hypnotic sessions where they were asked to control their reactions to histamine. These sessions were to be compared to three baseline sessions. A decrease in reactions was noted on the second administration of histamine calling into question studies that relied on a two session comparison. On subsequent sessions much unexplained variance was encountered, with the day upon which the sessions took place contributing significant amounts of the variance, giving rise to questions about what could cause these day to day changes. Study Two: Given the results of Study One, a method was subsequently devised in which serial, five-fold dilutions of allergen or histamine were administered to the subject's forearm with a standard Osterballe-type prick lancetter and reactions were recorded photographically on slide film. Areas were determined by computer-assisted image analysis. Seven healthy volunteers were tested for 8 sessions (testing included Profile of Moods Scale and Brief Mood Rating questionnaires, blood pressure, pulse and skin temperature). Mean wheal size and titration gradient data from allergen reactions correlated strongly with the psychological factor of liveliness but not irritability, although no manipulation of mood was involved. A stepwise regression analysis accounted for 61% of the variance of the allergen data, and 31% was from the liveliness factor alone. Thus, the more lively the subject felt, the smaller was the allergic response. The third study looked at a sample of 117 adult New Zealand subjects who volunteered to be tested with the Harvard Group Scale of Hypnotic Susceptibility (Form A). 38 of these people also were tested on a second test used to assess hypnotisability, the Creative Imagination Scale. Results indicated that the CIS can be administered with a minimum of preamble negating the value of special "think-with" instructions. It appears from the evidence in this study that both the CIS and the HGSHS:A measure characteristics that are stable over the years since the tests were first published. Reassuringly, they both can be used throughout the adult age group, with neither age nor sex testing differentially. The means and standard deviations were found to be similar to those of university aged students from various countries and cultures around the world over the years. The two hypnotisability tests were found to be correlated with each other but on a factor analysis each loaded separately giving evidence that the two tests are assessing different but related abilities. Study Four was an intervention study using 38 subjects who participated in a control session and cognitive-hypnotic intervention session that used the skin test methodology developed in Study Two. When the results of the two sessions were compared, significant decreases were found in the size of the wheals after skin testing with allergen or histamine. The hypnotic method employed in this study used three specific procedures that appear to have contributed to the high success rate: challenge to the assumption that the subject has 'no imagination', self-generated scenes and the entire process had the seriousness removed so there was little or no fear of failure. Again, the significance of mood variables was considerable in ameliorating the skin test responses, and hypnotisability was a significant factor in predicting success at being able to use the intervention. Overall, these four studies have revealed that hypnosis can be used to change at least one aspect of physiological functioning, reactivity to skin tests. Mood variables have emerged as important mediators, with implications that mood should be assessed whenever physiological variables are being measured.

Literature review Pertussis mortality and morbidity Mass immunisation was associated with a decrease in pertussis mortality and a profound reduction in pertussis incidence. Despite this pertussis remains prevalent. Infants account for the majority of pertussis deaths and hospitalisations. Immunisation Pertussis vaccines protect against disease rather than infection. Despite immunisation pertussis remains endemic. The efficacy of different whole cell and acellular pertussis vaccines varies considerably. There has only been a small increase in immunisation coverage in New Zealand over the past 25 years. Currently between 80% and 90% of New Zealand children receive the primary immunisation series. Other epidemiological features Bordetella pertussis is a highly infectious organism. Neither infection nor immunisation results in lifelong immunity. Pertussis affects all age groups. It is more severe in females than in males. The incidence has always been highest in infants and children but the reported incidence in adults is increasing. Pertussis epidemics occur at four yearly intervals. The epidemic periodicity has not been changed by immunisation. Risk factors for pertussis Contemporary case control studies from the United States have shown that exposure to someone outside of the home with pertussis increases the risk of introduction of pertussis into the home and that infants of adolescent mothers and of mothers with a preceding coughing illness are at increased risk of pertussis. Small sample size and imprecise measurement of immunisation status have compromised these studies. Other factors associated with an increased risk of pertussis in infants include younger age, low birth weight, the infant's immunisation status and household crowding. Prior to this current case control study there was no knowledge on the effect of infant characteristics, infant immunisation status, parental and household characteristics, or socioeconomic factors on the risk of pertussis in infants. Methods The pertussis mortality and hospital discharge statistics and notification data from 1872 to 2000 were reviewed. The characteristics of children hospitalised with pertussis during the 1995 to 1997 epidemic were described. Risk factors for pertussis in infants were determined using a case control study with two different control groups. A matched case-control design was used to compare infants with pertussis with well control infants from the community. An unmatched design was used to compare infants hospitalised with pertussis to infants hospitalised with other acute respiratory illnesses. Results Historical review of pertussis epidemiology Immunisation was associated with a significant decline in pertussis mortality rates in New Zealand. Pertussis incidence rates in New Zealand are five and 10 times higher than in the United Kingdom or the United States. New Zealand pertussis hospital discharge rates increased from 1920 to 1950, decreased from 1950 to 1970 and have been increasing since then. The severity of disease among those hospitalised in New Zealand is comparable to other developed countries. Case control study of risk factors for pertussis in infants In the community control sample factors associated with incomplete immunisation included poverty and household crowding, advice from a doctor that immunisations be delayed and the caregiver not having a record of the infant's immunisations. Primary and secondary pertussis in case households occurred in all age groups. Over half of the primary cases were infants. Factors associated with an increased risk of pertussis included incomplete immunisation of the infant, children five to nine years of age living in the household, household members with pertussis during the preceding two months and the family doctor advising that an immunisation be delayed. Preschool attendance by a household member was associated with a decreased risk of pertussis. Infants of low birth weight and infants with younger mothers were not at increased risk of pertussis. In a multivariate analysis, non-immunisation of other children in the household and the presence of someone in the household with clinical pertussis were associated with an increased risk of pertussis in infants. The associations between household members with cough and the risk of pertussis varied with the age of the household members and imply an age dependent disease modifying effect of immunisation. For many of the children in the study households it seems unlikely that any health professional knew whether or not they were fully immunised. Conclusions Immunisation reduced pertussis mortality in New Zealand. Pertussis hospitalisation rates are increasing despite improvements in the immunisation schedule. Sustained sub-optimal immunisation coverage appears to be the dominant reason for New Zealand’s excessive pertussis disease burden. Primary school aged children are important in household pertussis transmission.

This thesis sets out to explore some psychosomatic dimensions of chronic musculoskeletal pain. Pain is a phenomenon which is universally recognised and experienced but nevertheless presents a very real epistemological problem. For convenience, the philosophical approach chosen here is that of linguistic parallelism which views pain as a range of abstract concepts defined in a variety of ‘languages’ or disciplines in a complementary and interactive way. Psychiatric formulations of pain include the concepts of conversion, object relations and the associations of pain with a developmental history of suffering and defeat and a diagnosis of depression. These ideas have been to some extent confirmed by nomothetic studies of pain patients. Chronic, as opposed to acute, pain is associated with a broad range of physical, emotional and social changes and is a problem of such clinical magnitude that special multidisciplinary clinics have now become a feature of clinical services in most large centres. My own experience as a psychiatrist working in the Auckland Pain Clinic is described in this thesis. Over a four year period, 172 patients were assessed, comprising 15-20% of the total referrals to the clinic. The modal age was 45-54 years, with a male/female ratio of 7:10. The duration of pain was 5-10 years, the back being the most common site and musculoskeletal pain was by far the most frequent presentation. Most of the patients presented with psychiatric disorders in the neurotic-personality disorder spectrum; depression, anxiety and hysteria being frequent diagnoses. These findings are similar to other studies reviewed. Treatment was instituted in half of the patients seen and half of the treated patients improved or recovered. One third of the original sample returned a completed follow-up questionnaire 18 months to 5 years after presentation. Just under a half remained improved or recovered, the treated patients faring no better or wrose than those who refused or were not offered treatment, or who were referred elsewhere. There was a high rate of further consultation amongst all groups, but especially so for those who declined treatment. The treated patients and those referred elsewhere were significantly more likely to have found the psychiatric consultation helpful. EMG feedback, drug withdrawal and psychotherapy were more frequently associated with improvement than pharmacotherapy on short-term evaluation. On follow-up only EMG feedback maintained an advantage, Issues which emerged were the relationships between chronic pain, depression and antidepressant medication response; the role of anxiety and tension in chronic pain and the strong tendency towards continued help seeking amongst the majority of patients. Muscle tension has been invoked in the aetiology and maintenance of a variety of pain syndromes. The most intensively researched areas have been tension headache and temporomandibular joint pain where EMG feedback has become an established treatment technique, although there is still some controversy as to whether EMG feedback has any advantage over relaxation training as such. The use of EMG feedback training in other musculoskeletal conditions has been less well researched and doubt remains as to the role of generalised muscle tension in the causation of these conditions. An EMG feedback study was undertaken at the Auckland Pain Clinic using a within-subjects control- design. Eighteen subjects (12 females and 6 males) with neck and back pain were studied in terms of subjective reports of pain and EMG activity measurements under standardised conditions. Three conditions were compared, viz EMG feedback training, a control condition and a waiting list condition. The sequences of presentation of these conditions was counterbalanced in a design using two sets of latin squares to pick up any order effects. EMG feedback was the only treatment which significantly reduced EMG activity across sessions. An order effect was evident in that biofeedback was most effective when presented first but less so when presented after the control condition. Although estimates of present pain correlated with EMG activity, there was no statistical difference between pain score reductions when EMG feedback and control conditions were compared. Pain scores tended to decline during both conditions but the scores for “worst pain over one week” tended to rise. During the waiting list condition, present pain tended to increase while “worst pain over one week” tended to decline. Eleven subjects experienced an overall decrease in pain scores at the end of the study, while seven had increased pain. Declines in pain scores tended to be associated with a biofeedback training effect but this was not statistically significant. Improvement in pain was associated with high Present pain/EMG correlations when a rank order correlation was computed. This study provides some support for the use of relaxation methods in the management of musculoskeletal pain. It suggests that muscle tension may well play a role in the production and/or maintenance of musculoskeletal pain, although it does not account for all of the variance. The more interpersonal factor of illness behavior may well explain some aspects of pain not accounted for by pathophysiological factors such as muscle tension. Parson’s notions of the sick role and Mechanic’s concept of illness behavior have stimulated the by Pilowsky and Spence. We have made use of this questionnaire development of an “illness behavior questionnaire”/in a study involving 200 pain patients. A cluster analysis of these results produced profiles very similar to those found in Adelaide and adds validity to the groupings described by pilowsky and spence. Characteristically, patients with chronic pain tend to view their problems in somatic terms and to deny other problems in their lives, or if problems are admitted, to ascribe these problems to their pain. Illness behaviour profiles were found to cut across diagnostic categories when results from patients overlapping between the clinical diagnostic study and the illness behavior study were analysed. These illness attitudes therefore seemed to provide an alternative level of description to diagnostic systems. An analysis of therapeutic outcome in patients undergoing the biofeedback trial did not support the use of illness behaviour profiles as a prediction patients discussed here. Third is the Freudian mechanism of “conversion” which may account for pain syndromes where pathophysiological changes are not necessarily evident. These three concepts provide interlinking mechanism between adverse life experiences(with unpleasant affect) and musculoskeletal pain. These are part of an intrapersonal system which is potently influenced by the interpersonal and physical environment of the individual. Illness behaviour is at the social interface between intrapersonal and interpersonal systems. Research directions are suggested which may further elucidate the workings of this proposed psychosomatic formulation of chronic musculoskeletal pain

The constant battle between pathogen and host has led to substantial diversity and adaptability of the host immune system. Pathogens too, have evolved unique mechanisms to evade their hosts. The production of superantigens is one of these mechanisms. Superantigens are potent T cell mitogens that have the unique ability to bind simultaneously to major histocompatibility complex (MHC) class II molecules and T cell receptors (TCRs). The resulting uncontrolled activation of up to 20% of all T cells and the subsequent cytokine release, can lead to fever, shock and death. Superantigens are not processed intracellularly like conventional antigens but instead bind as intact proteins to MHC class II molecules expressed on the surface of professional antigen presenting cells. On the hypothesis that the unique properties of superantigens may serve useful for vaccine delivery, several bacterial superantigens were selectively mutated at their TCR-binding site with the ultimate goal of creating a safe, non-toxic carrier protein that could target antigen presenting cells by binding to MHC class II. Antigen presenting cells that expressed MHC class II were indeed targeted by the TCR-binding-deficient superantigens. Cellular internalisation of the superantigen into vesicles was observed as early as 30 min. These supcrantigens were also shown to traffic to, and be captured by, the lymph nodes of immunised mice. Using TCR-binding-deficicnt superantigens as vaccine carrier proteins, enhanced antigenicity and immunogenicity of the conjugated MHC class I-restricted peptide antigen. GP33, was observed in a mouse model. In vitro studies revealed up to 200-fold enhancement of antigenicity when GP33 was conjugated to superantigen. Enhanced immunogenicity was also observed in vivo, with conjugates providing protection against Lymphocytic choriomeningitis virus infection after only a single immunisation. These results indicate that modified superantigens are able to safely deliver peptides for cross-presentation, and may serve as a novel mechanism for vaccine delivery.

Perinatal asphyxia is thought to be a major cause of subsequent neurological deficits. Pathological studies suggest that many of these events occur before birth. However, the relationship between specific prenatal events and neurological outcome is not clear. This thesis tested the hypothesis that certain fetal factors play a role in determining the severity and distribution of neuronal loss following in utero asphyxia. Chronically instrumented fetal sheep at three different gestational ages; midgestation (90d), late-gestation (120-130d) or near term (> 135d) were subjected to either a single or repeated insult. The insult consisted of an episode of either systemic asphyxia (umbilical cord occlusion) or cerebral ischaemia (carotid artery occlusion). The fetal parietal cortical electroencephalogram (EEG), cortical impedance (CI) indicating intracellular edema, blood pressure (MAP), electrocardiogram (ECG) and frequent fetal blood gases and metabolites were measured. Three days after the insult, histopathological analysis or immunohistochemistry was performed to determine neuronal loss and specific neurotransmitters respectively. Transient (10min) occlusion of the umbilical cord in late-gestation fetuses, resulted in severe fetal asphyxia, hypotension (24±5mmHg, p<0.01), bradycardia (72±14bpm, p<0.001), depressed EEG activity (-17±2dB, p<0.001) and intracellular edema. The intracellular edema resolved within 27±6min, whereas the EEG activity was depressed for 5±2h, despite rapid recovery of pO2. Neither seizures or infarction were observed. The degree of hypotension, increase in CI, lactate and recovery of post-asphyxial EEG intensity were more marked in 135d fetuses compared with the midgestation fetus (p<0.01). Neuronal loss, which was only observed in the older group, was predominantly in the hippocampus and associated with the severity of hypotension during occlusion. Repeated episodes of cerebral ischaemia, altered the distribution of neuronal loss compared with single insults, inducing damage mainly in the striatum. The frequency of the insults determined the severity of the damage. Similarly, recurrent episodes of fetal asphyxia induced predominantly striatal neuronal loss. Each occlusion resulted in fetal hypoxia and bradycardia accompanied by increased T/QRS ratio as noted on the ECG. Progressively severe hypotension and lactic acidosis developed during successive occlusions. The EEG was depressed and CI increased with each occlusion. After the asphyxial episodes, blood pressure and heart rate returned to normal, while the T wave was inverted for 310±60min. The EEG remained depressed for 90±10min and intermittent seizures developed at 3.3±0.6h after the last occlusion. The extent of neuronal loss correlated with the degree of hypotension, increase in T/QRS ratio, duration of post-asphyxial EEG depression and number of seizures. Immunohistochemical analysis showed loss of striatal GABAergic projection neurons. These findings demonstrate that certain prenatal factors, such as neurological maturation, pattern of the insult and cardiovascular instability can influence neuronal outcome following fetal asphyxia. An isolated brief episode of asphyxia can lead to selective hippocampal neuronal loss, while repeated insults induce predominantly striatal damage. These distributions of neuronal loss may be associated with postnatal sequelae such as learning disorders and cerebral palsy.

The use of mental health legislation to determine involuntary treatment for people suffering from mental illness (civil commitment) is a controversial issue, centred on the ability of civil commitment to be coercive by limiting patients’ choice, autonomy and self-determination The intent of the New Zealand Mental Health (Compulsory Assessment and Treatment) Act 1992 was to limit coercion by emphasising informed consent (even if treatment can be administered without it); recognising the civil rights of patients subject to civil commitment; and encouraging involuntary treatment in the least restrictive environment (the community). However, there is no evaluative research that considers the extent to which patients subjected to the legislation perceive coercion. The aim of this thesis was to consider the extent to which mental health legal status equates with coercion, the factors that impact on patients’ perceptions of coercion and the factors that have the potential to ameliorate such perceptions. Empirical cross-sectional comparison studies, measuring perceived coercion using a validated psychometric measure, were undertaken at three points during the implementation of civil commitment. These involved a comparison between involuntary and voluntary patients admitted to acute inpatient psychiatric services, a comparison between involuntary patients admitted to acute psychiatric inpatient services and involuntary patients admitted to forensic psychiatric services, and a comparison between involuntary and voluntary outpatients. The studies found that legal status is only a broad index of the amount of coercion perceived by patients. Some voluntary patients feel coerced and some involuntary patients found the process non-coercive. Perceptions of coercion cannot be fully explained by socio-demographic and clinical characteristics, or by coercive incidents that occur throughout the process of civil commitment. Rather, the perceptions relate to the total experience of civil commitment, including the interactive processes with clinicians. In this regard, involving patients in proceedings that are experienced as fair and just (procedural justice) has a marked impact on reducing patients’ perceptions of coercion. In conclusion, the findings are underscored by legal requirements and ethics in order to provide clinical guidelines for implementing civil commitment.

The temporal and spatial relationships between altered vascular function and cardiac muscle cell injury at the margins of developing myocardial infarcts were investigated, because such knowledge might provide potential for intervention in the evolution of myocardial infarcts and limitation of their size. Regional myocardial ischaemia was modelled in isolated rabbit hearts subjected to ligation of the ventral interventricular branch of the left coronary artery (0,30,60,120 or 240 minutes duration), the remainder of the heart being continuously perfused with oxygenated Krebs-Henseleit buffer solution. After the experimental ischaemic period, the whole heart was fixed by perfusion with phosphate-buffered 2.5% glutaraldehyde which, in preliminary studies, was shown not only to preserve the morphological appearance of cardiac muscle cells, but also to stabilise the distribution of flow through the myocardial blood vessels in the pattern pertaining immediately prior to fixation. Polymerising acrylic resin (L.R. White) was then injected into the vessels of the ischaemic and non-ischaemic regions simultaneously at identical pressures. Resin injected into the ischaemic region contained lead dioxide whilst that injected into the other vessels contained Fat Red 7B dye to allow identification of the source of supply of blood vessels within the heart. Cryofracture, freeze-drying and imaging by scanning electron microscopy (SEM) with a backscattered electron detector and low vacuum specimen chamber conditions were used. This made possible examination of transmural segments of myocardium spanning the margins of the ischaemic and control ventricular myocardium containing blood vessels filled by resin. SEM showed severe injury of cardiac muscle cells after 60 minutes of ischaemia, as characterised by separation and swelling of some organelles. Earlier ischaemic changes in some cells (focal increase in prominence of t-tubules and sarcoplasmic reticulum) were seen after 30 minutes. There was a transmural progression in development of irreversible injury from the subendocardium to the epicardium between 60 and 120 minutes corresponding to the "wavefront phenonenon". The lateral margins did not show such marked progression and were typically sharply demarcated on a cell-to-cell basis after 60 minutes. An increase in the proportion of functional capillary pathways (from 55% to 85%) in early (30 minutes) ischaemia was succeeded by a profound perfusion defect, corresponding to the "no-reflow" phenomenon, which had a very close temporal and spatial association with severe injury of cardiac muscle cells. Loss of patency was associated with increased proportions of collapsed, compressed capillaries and swollen myocardial cells. This study demonstrated that there is a significant region of myocardium which for a period shows intermediate degrees of myocyte injury (and is thus potentially salvageable) in the subepicardial portion of the developing infarct. Contrary to the claims of various authors similar potentially salvageable lateral "border zones" were neither large nor non-existent. Within 150 microns of the typically abrupt boundary, small discontinuous areas (<20% of this region) showed intermediate degrees of injury, and there was also an increased proportion of non-functional capillaries which were not collapsed or compressed, resulting in a 'low-flow' zone. This narrow lateral zone requires further investigation to determine whether it is static, and thus of negligible size, or whether it moves in advance of infarction and is thus pathogenetically significant.

Testicular function is stimulated from the pituitary gland by the gonadotrophic hormones FSH and LH. The testis in turn regulates gonadotrophin secretion by negative feedback. The agents of feedback are steroids, and in addition, probably a protein hormone, which has been given the name inhibin. A method capable of detecting inhibin-like activity in bull seminal plasma (bSP) was developed. Administration of bSP at the time of castration to five-week old male rats inhibited the post-castration rise of serum concentrations of FSH and LH otherwise seen 24 h later. The degree of inhibition depended on the dose; 0.5 ml bSP or the equivalent amount of bSP-extract always suppressed FSH and LH to levels typical of intact rats. The rats' sensitivity to 0.2 ml bSP varied with the time of year, possibly reflecting seasonal changes in the onset of puberty. The time-course of action of bSP-extract was studied in intact rats. Serum FSH was suppressed 12, 24 and 48 h after a single injection, but not at 3 or 6 h. LH was suppressed at 6, 12, 24 and possibly 48 h.

A procedure was developed to purify ovine placental lactogen (oPL) from fetal cotyledonary tissue of late gestation. A prolactin radioreceptor assay using mammary tissue membranes from the late pregnant rabbit was established and used to monitor lactogenic activity throughout the purification.