The chromosomes of the two species of field mouse occurring in Britain, A. sylvaticus (L.) and A. flavicollis (Melchior) have not been widely studied. An investigation was therefore initiated to analyze the chromosomes of these species from different localities on the mainland of Britain. The chromosome characteristics studied at mitotic metaphase include the relative length of the chromosomes, G-banding, the presence and pattern of heterochromatic regions in the chromosomes (C-banding) and the position of the nucleolus organizers. In meiosis the type of association between the x and y and the mode of their segregation has been discussed. Species comparisons based on these chromosomal data showed a chromosomal difference between A. sylvaticus and A. flavicollis which support the separate identities of these two species. Intraspecific variation between different populations of A. sylvaticus has been reported. Chromosomal polymorphism due to B chromosomes has been detected in all the populations studied. Four classes of B chromosome have been identified in nine populations of A. sylvaticus from the mainland of Britain. They are distinguished by shape and size and according to their euchromatic or heterochromatic composition. Inter- and intra-individual variation (mosaicism) as well as interpopulational variation of the number and the nature of B chromosomes has been studied. Polymorphism resulting by a deletion, that is the loss of chromosomes or parts of chromosomes, has been found in the X chromosome of two females from different populations; one of them had XO and the other Xx. Intraspecific karyotype homology, as judged by G- and C-banding has been demonstrated between populations of the bank vole Clethrionomys qlareolus (Schreber) from different localities on the British mainland and from Skomer Island. In conclusion, the results of this investigation clearly indicate that studying karyotype evolution and variation between species, G- and C-banding and nucleolar organizer regions (NORs) are essential tools without which erroneous conclusions may be reached.

No description available.

The basic reproductive physiology of the vole has been little studied in the past, although its population dynamics have been extensively investigated. In this thesis the reproductive physiology of the adult female is considered. The work was stimulated by a hypothesis put forward by Chitty and Austin (1957); that 3-4 day oestrous cycles (vaginal and behavioural) occurred in females living apart from strangers, but constant cornification and heat was present if strangers were mixed together - the former implied spontaneous ovulation every few days; the latter implied induced ovulation. The results of Chitty and Austin could not be reproduced, however; no regular 3-4 day vaginal smear changes were found in any females. Once vaginal perforation had become established, just over half the individuals had no leucocytes present in the smears; a smear that was predominantly cornified and/or nucleated was present for most of the time. No corpora lutea were found in the ovaries of any females. It thus became apparent that, regardless of the social environment, a state of induced ovulation was probably present. Seven out of 11 adult females ovulated when placed, for 24 hours, with a vasectomised male - this confirmed that ovulation could be induced by the male, presumably by coitus, (mounting of 6 out of the 7 females that ovulated was seen during the 60-90 minute period of observation). Neither sexual excitement in females tested, that were not mounted, nor stimulation of the cervix with a glass rod, caused ovulation. From analysis of smears taken from females just prior to testing with males, it was found that mating could occur if either nucleated and/or cornified cells were present, but not in the presence of leucocytes. Other environmental factors were investigated to ascertain whether or not spontaneous ovulation occurred under other conditions. Neither reduced light regimes, nor a known balanced diet permitted spontaneous ovulation. Light, however, greatly affected reproductive development and function, as shown by uterine weight, time of perforation, and follicle size - complete gonad development took place when animals were subjected to 14 or more hours of light; but there seemed to be more or less complete inhibition when subjected to 12 or less hours light per day. Food collected from the natural environment, given to laboratory animals, did not permit normal reproductive organ or body growth. After environmental factors thought most likely to affect ovulation had been tested, an investigation of females in the natural environment was undertaken. Two groups of wild animals were caught, and caged in the wild for 1 month - one group was caged from late July to late August; the second, from late August to late September, No healthy corpora lutea were found in any individuals killed one month after capture. Thus, no evidence of spontaneous ovulation occurring in wild animals was obtained. All evidence indicated that the vole never ovulated under normal circumstances unless coitus occurred. Smear patterns (and mating tests) implied that virgin voles remained on heat for long periods of time. In order to obtain some insight into whether uterine weights and smear patterns were related in any way to ovarian hormonal levels, voles were ovariectomised and given either no hormone replacement therapy, or variable doses of oestrogen, or a combination of oestrogen and progesterone. After ovariectomy vaginal closure took place within a few days, a marked drop in uterine weight also resulted. Oestrogen replacement appeared to inhibit these effects. Females given 0.01 andmu;gs. of oestrogen per day had variable smears although cornified cells were normally present; 1 andmu;g. of oestrogen per day invariably resulted in smears with nucleated epithelial cells. The mean uterine weight of the latter females was greater than that of females given 0.01 andmu;gs. of oestrogen. Thus, it appeared that nucleated epithelial smears and heavier uteri were related to higher oestrogen levels. Progesterone invariably induced a leucocytic invasion, followed by thin smears, and mucification of the vaginal epithelium; the size of the vaginal opening was also reduced. Once it had been established that the vole was an induced ovulator, a reinvestigation of ovarian histology was considered to be necessary, as this had previously been likened to that of the mouse. It seemed plausible that if the vole's ovarian physiology differed from the mouse, so would its morphology. A Graafian follicle and various stages of atresia were described. By killing groups of voles at approximate 2-hour intervals up to 18-20 hours after mating, morphological changes before and after ovulation were determined. Ovulation occurred about 9 hours after coitus; the latter appeared to affect all Graafian follicles and most, but not all of these, ovulated. There did not appear to be any marked preovulatory swelling. Ovarian changes during pregnancy and pseudopregnancy were then studied. There were two waves of corpora luteal growth during pregnancy; the first took place within the first 3 days and the second during the latter half of pregnancy. Graafian follicles had reappeared by day 3 of pregnancy and were present throughout its length. Corpora lutea of pseudopregnancy were initially similar to those of pregnancy, but by day 8 some signs of degeneration were seen. Degenerative changes were very marked by day 10. Concurrent with luteal regression, there was a marked increase in Graafian follicle size. The vaginal smears of pregnant and pseudopregnant animals were initially leucocytic. A thin smear then developed and mucification of the vaginal epithelium took place at about the same time. Thin smears remained until term in the pregnant animals, but disappeared after day 8 or 9 in the pseudopregnant females; this, therefore, indicated the length of pseudopregnancy in the vole. No spontaneous ovulation occurred postpartum; thus no corpora lutea of lactation were formed. During this period, the corpora lutea of pregnancy degenerated quickly; the smears were variable but nucleated cells were usually predominant. It was found that mating could occur throughout the lactation period. No marked delay in implantation, following mating, took place at this time. In the final chapter some aspects of the hypothalamo-hypophyseal control of ovulation were considered. Electrophysiological studies indicated that the anterior hypothalamus was most intimately concerned with the ovulatory response; electrical stimulation above or posterior to the pituitary region resulted in ovulation in very few individuals. Intravenous injections of a crude sheep median eminence extract invariably resulted in some ovarian stimulation, ovulation occurred in most individuals; intraperitoneal injections did not appear to have such potent effects. Intraperitoneal injections of 0.6 andmu;gs. or more of luteinizing hormone resulted in ovulation in most individuals; 0.3 andmu;gs. of N.I.H. - LH - S or less had no effect. Intravenous injections of LH had a similar dose/response result. Ovulation occurred between 8 and 12 hours after a 2.5 andmu;g LH intraperitoneal injection. This study has shown, therefore, that the vole, M.agrestis, appears to be a typical induced ovulator - no corpora lutea were ever found in virgin females subjected to various external environmental conditions, nor did ovulation occur spontaneously postpartum. Smear patterns suggested that the vole remained constantly on heat for long periods of time. Coitus usually occurred when perforate adult females were tested with virile males; this almost invariably resulted in ovulation. Electrical stimulation of the anterior hypothalamus, intravenous injection of extracts of median eminence, and 0.5 - 0.6 andmu;gs. or above of LH given either intravenously or intraperitoneally, to adult perforate virgin voles, usually brought about ovulation.

This thesis examines how rats represent relationships in their environment. There are currently two broad classes of account of how animals learn about such relationships: The associative account offers a relatively simple mechanistic account of behaviour; while the second account proposes that animal behaviour, like human behaviour, is underpinned by the processes of causal and deductive reasoning, that are beyond associative analyses. Chapter 1 identifies three domains in which these two classes of account provide quite different analyses of animal behaviour, which are experimentally investigated in Chapters 2, 3 and 4. Chapter 2 reports three experiments that investigated the accuracy of predictions derived from the claim that rats are capable of forming and using causal models involving their own interactions with their environment (interventions) and external events (Blaisdell, Sawa, Leising, & Waldmann, 2006). The results failed to confirm these predictions and were instead more consistent with the operation of simpler processes. The results from Chapter 2 left open two interpretations: either rats can represent causality but do not use such representations to reason, or they do not represent cause per se. Chapter 3 investigated these alternatives in three experiments using a timing task, which should be sensitive to whether rats are more likely to represent their actions as causal than external events (Buehner & Humphreys, 2009). The results provided no support for the view that causal binding occurs in rats. Chapter 3 examined the possibility that sensory preconditioning might reflect a form of deductive reasoning (Hall, 1990). However, taken together, the results from four experiments provided no support for such an analysis; but instead helped to inform the nature of the associative processes that underlie sensory preconditioning. In summary, while the results reported in this thesis provide no support for analyses of animal behaviour that rely on the processes of causal or deductive reasoning, they do help to inform the nature of the associative processes involved.

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Glyoxalase 1 (Glo1) of the glyoxalase system catalyses the metabolism of the reactive dicarbonyl metabolite, methylglyoxal, and thereby prevents potentially damaging glycation of protein and DNA. Glo1 is hypothesised to be a potential factor in the development of vascular complication of diabetes, such as diabetic nephropathy. The induction of diabetes in mice deficient in Glo1 provides a pre-clinical in vivo model to test this hypothesis. Glo1 mutant mice with putative Glo1 deficiency produced by the International Mouse Knockout Consortium (IMKC) were acquired from the European Mutant Mouse Archive. The initial aim of this study was to study the exacerbation of diabetic nephropathy by Glo1 deficiency in streptozotocin-induced diabetic mice, with an initial objective to confirm Glo1 deficiency in the IMKC Glo1 mutant mouse and subsequent objectives contingent on this. The preliminary studies were unable to confirm Glo1 deficiency in this mouse model and so a revised aim was to characterise the mechanism of compensatory Glo1 expression in the mutant mouse and explore similar occurrence in similar precursor mouse embryonic stem cells (ESCs) and related clinical application. Genotyping of Glo1 mutant mouse offspring by PCR revealed only heterozygotes and wild-type (WT) littermates, and no homozygotes without Glo1 wild-type alleles. Studies of the Glo1 mutant mouse revealed levels of Glo1 activity, protein and mRNA identical to those of wild-type control siblings. Other components of the glyoxalase system were also analysed – activity of glyoxalase 2, concentrations of methylglyoxal (MG) and D-lactate, and tissue protein content and urinary excretion of MG-derived glycation adduct MG-H1 and found no significant change in Glo1 mutant mice, with respect to WT controls. This suggested a functionally normal Glo1 and glyoxalase system in Glo1 mutant mice. Therefore, Glo1 mutant mice have a mutated Glo1 gene but with compensatory Glo1 expression identical to that of WT control. This provided a possible explanation for the unexpected normal phenotype of Glo1 mutant mice reported in the IMKC project. To explore the mechanism of compensatory Glo1 expression, Glo1 copy number was quantified by Taqman® method, normalizing response to transferrin receptor protein-1 (Tfrc). Glo1 mutant mice had 3 copies of Glo1 in all tissues analysed with amplification extending from 3’-end of exon 1 to the 5’-end of exon 6. Taqman copy number assay was established to detect and quantify mutant Glo1Gt(..)Lex and WT alleles. Most mutant mice contained two copies of Glo1 and one mutant copy of Glo1Gt(..)Lex – Glo1(+/+)Gt(..)1Lex. In some cases, however, 2 copies of both Glo1 and mutated Glo1Gt(..)Lex – Glo1(+/+)Gt(..)2Lex were found. Inheritance studies suggested a simple Mendelian inheritance with a WT allele accompanying the Glo1Gt(..)Lex mutant allele on arms of chromosome 17 such that Glo1 deficiency was prevented. This was indeed observed throughout the all breeding of the Glo1 mutant mice. I hypothesised that Glo1 copy number increase may have arisen in the mutant mice during gene trapping by copy number alteration (CNA) induced by increased methylglyoxal concentration, or dicarbonyl stress, in mouse ESCs. To explore and model this, mouse ESCs were cultured with exogenous 200 μM MG under atmospheres containing 20% oxygen - typical of most cell culture conditions, and 3% oxygen - typical of ESCs oxygen exposure in vivo. Incubation of ESCs for 12 days with MG induced CNV increase of Glo1 by up to 16% in both 20% and 3% oxygen atmospheres. Increase in Glo1 CNV at day 12 with MG treatment was associated with an increase in Glo1 protein. Therefore, functional low level CNA of Glo1 was induced by exposure to high levels of exogenous MG. No evidence was found for Glo1 CNA with dicarbonyl stress induced by Glo1 silencing or cell permeable Glo1 inhibitor. Finally, I hypothesised that GLO1 CNA may occur in clinical dicarbonyl stress, a severe example of which is patients with renal failure receiving haemodialysis - associated with ca. 5-fold increase in plasma MG concentration. DNA of peripheral mononuclear cells from healthy subjects and patients with renal failure receiving hemodialysis renal replacement therapy were examined. Human GLO1 copy number was not significantly different between the patients and the control subjects. This requires further investigation in this case and other examples of clinical dicarbonyl stress. From these studies I conclude that the IMKC Glo1 mutant mouse does not exhibit the Glo1 deficiency; rather, it maintains wild-type levels of Glo1 expression through Glo1 copy increase likely induced during gene trapping. Dicarbonyl stress in mouse ESCs in vitro induced low level Glo1 copy number increase – a model of Glo1 CNA in putative gene trapping associated dicarbonyl stress. It is unclear if GLO1 CNA occurs clinically. These findings reveal that focussed copy number alternation of GLO1 may provide a protective response to dicarbonyl stress in some circumstances.

Considerable progress has been made in determining the factors in the environment which are responsible for the control of seasonal breeding in mammals and birds. There is less information available about how these factors produce their physiological effects. Light has been shown to be very important in the control of vole breeding seasons. Temperature may also have some effect. How these factors act is not known. As part of an attempt to understand how the breeding season of the vole is controlled, an investigation of some of its endocrine organs has been undertaken. Animals have been collected from the field in mid-summer (at the height of the breeding season) and in mid-winter (during the non-breeding period). A total of 174 adult field animals has been studied. As an approximate indication of the reproductive and endocrinological state of the animals, measurements have been made of the weights of their bodies, adrenals, thyroids, gonads and also certain accessory organs (the uteri of females in winter and the seminal vesicles and ventral prostates of males in both summer and winter). From the examination of this data it is clear that there are considerable endocrine changes with season. Furthermore, within both winter and summer populations reproductive sub-groups which show endocrine differences can be recognized. More detailed study of these endocrine differences has involved the use of cytological and histological methods. Because of the trophic control which the adenohypophysis exercises over the other endocrine organs, it may be presumed to be important in bringing about seasonal changes. It has, therefore, received particular study. The adenohypophyses of field animals have been examined by the methods of cytology, histochemistry and bioassay. In order to identify the cells responsible for the production of gonadotrophin and thyrotrophin, the pituitary function of laboratory bred animals has been altered by castration and the administration of goitrogens. In the adenohypophysis of the vole five cell types have been recognized. Oval basophils which are periodic acid-Schiff (PAS) positive and aldehyde fuchsin (AF) negative. They react to castration by degranulation and the subsequent formation of colloid filled castration cells. They are considered to secrete gonadotrophins. In field animals it has been found that the gonadotrophin producing cells (gonadotrophs) of winter animals are markedly different from those of summer animals. The gonadotrophin content of the pituitaries of male voles in winter and in summer has been studied by means of bioassay. In the summer the vole pituitary contains well granulated gonadotrophs and gonadotrophic hormone can be detected. In winter the gonadotrophs are vesiculated and no gonadotrophic hormone can be detected. This indicates that the granulated gonadotrophs contain hormone, but that the vesiculated cells are depleted of active gonadotrophic principles. Angular basophils which are PAS positive and AF positive. They react to the administration of goitrogen by the formation of colloid filled thyroidectomy cells. They are considered to secrete thyrotrophin. They show no marked changes with season, as would be anticipated from the lack of marked change in the thyroid itself. Round acidophils which show no marked change with season. This study provides no indication as to their function. A second type of acidophil which is numerous and well developed only in females which are pregnant or show signs of mammary development. It is suggested that they may be the source of prolactin. The adenohypophysis also contains a few large cells with poor staining qualities. They do not show any marked changes with season or in response to either castration or the administration of goitrogens. Their function is not known. The gonads were, in general, found to exhibit the expected seasonal change in activity. Sexually inactive males in winter may be divided into two groups on the basis of the structure of the tunica albuginea. It is suggested that these two groups represent, respectively, regressed males, which were sexually active in the preceding summer, and inhibited males, which were born late in the season and have never been sexually active. Similarly, on the basis of uterine weight, female voles in winter can be divided into two groups, parous and non-parous. The pituitary cytology of regressed and inhibited males, parous and non-parous females in winter is similar. In one winter collection the males show considerable evidence of being sexually active. This suggests the operation of a factor or factors other than light and temperature in the control of vole breeding seasons. These males were distinguished from the males in other winters by differences in pituitary cytology. The study of the pituitary suggests that gonadal changes at the end of the breeding season are secondary to changes in the pituitary. The alternative possibility, that the gonads are not competent to respond to pituitary hormones, was tested experimentally. Commercial gonadotrophins were injected into winter field animals and into laboratory bred animals whose sexual development had been inhibited by maintaining them on short days in the cold. The results suggest that the gonads of such animals are able to respond to gonadotrophins. The adrenal has been found to undergo marked changes in weight with season. In summer there is also a sex difference in adrenal weight. These weight changes can be correlated with striking histological differences in the inner regions of the adrenal cortex. In winter voles the adrenal cortex possesses a juxtamedullary zone. It is similar in cytological appearance to the X zone of mice and the two zones are seemingly homologous. The zone is present in all winter field voles, whether regressed or inhibited males, parous or non-parous females. The zone is small or absent in the adrenals of sexually active males. It must, therefore, be formed secondarily in the adrenals of regressed males. It also reappears in a similar, though not identical, form in males after castration. The zone can also disappear from females, but is present in an especially well developed form in all pregnant and lactating animals. Multipara and primipara differ in the details of the structure of the juxtamedullary zone. These changes are clearly related to sexual activity, but their significance is not known. The epithelium lining the ventral prostate is the site of marked stimulation in winter field males and in castrated laboratory animals. It is possible that the adrenal is the source of the hormone responsible for this stimulation. The zona glomerulosa and zona fasciculata of the adrenal cortex also show cytological and histological change with season. Their structure in the winter males which may have been sexually active suggests that these changes are not primarily related to sexual activity. The principal conclusions which can be drawn from this study are: That in the vole there is functional differentiation of adenohypophyseal cells. Two cell, types have been recognized which are clearly related to the production and secretion of gonadotrophic and thyrotrophic hormones, respectively. A third cell type is probably the source of prolactin. There is no evidence available on the function of the other two cell types which have been recognized. That the cessation of breeding in winter in the vole is apparently brought about by a cessation of both the synthesis and the secretion of gonadotrophin. That there are striking changes in the juxtamedullary region of the vole adrenal which appear to be related to sexual activity.

No description available.

Evaluation of aerial photographs, LiDAR imagery and GPS survey points was conducted to characterise water vole habitat at Grains in the Water and Swains Greave, in the Peak District. Justification for the study is to explore an affective way to monitor water vole habitat in relation to water vole signs utilising GIS. The water vole is a rapidly declining native species (Strachan and Strachan, 2003). The geospatial data was evaluated in terms of integration and extraction. The aerial photography provided a basis for vegetation mapping after visual interpretation. The aerial photograph required geometric correction and an average control point RMSE of 4.17m for the Grains in the Water site, using a 2nd order polynomial model was achieved. Extraction of slope, aspect, stream proximity and elevation were achieved using LiDAR imagery. Pearson’s product moment correlation coefficient highlighted a significant relationship between water vole latrine density with slope at the 0.01 significance level for 4m and 6m resolution data (Grains in the Water). The Swains Greave site supported this result with a 0.01 significance level for 6m resolution slope data. Elevation and aspect did not show a significant correlation with latrine density at Grains in the Water. The main conclusion is that water vole habitat cannot be solely characterised by aerial photography and LiDAR data, as other habitat variables could affect water vole distributions, which cannot be extracted from these geospatial data e.g. pH, bank exposure and stream depth.

Thesis (PH.D. (Medical Sciences)) --University of Limpopo, 2010 / Refere to document