Sixty-two newborn Holstein-Friesian calves were used to study the role of colostrokinin, serum cortisol, and serum thyroxine in the absorption of maternal immunoglobulin. Calves were removed from their dams prior to suckling and assigned one of four rations: colostrum, whole milk, milk plus colostral immunoglobulin, and milk plus immunoglobulin plus colostrokinin. Calves were fed their assigned ration either at birth or after twelve hours inanition. All calves were fed pooled colostrum at 24 hours postpartum. Blood samples were collected at seventeen times during the first 32 hours postpartum. Calves were born with high cortisol concentrations (88 ng/ml) which decreased (P < .05) within two hours postfeeding. Serum cortisol levels increased (P < .05) between two and three hours after calves ingested a colostral source of immunoglobulin. Time of initial feeding had no effect on the cortisol surge. No such increase was observed in neonates consuming an immunoglobulin-free milk ration. These results demonstrate that the immunoglobulin fraction of colostrum is responsible for initiating an increase in cortisol secretion by the adrenal cortex. Within four hours postpartum, serum thyroxine concentrations increased (P < .05) at least 50% in all treatment groups regardless of whether the calves were fed or fasted. After peaking at 18 μg/dL, the serum thyroxine concentrations fell gradually throughout the duration of the collection period. Colostrokinin exhibited a biphasic effect on serum immunoglobulin concentrations which was dependent on the initial time of feeding. Calves exposed to colostrokinin in 0 hour feedings had serum immunoglobulin G concentrations significantly higher (P < .05) after 16 hours postpartum than animals not fed colostrokinin. Fasted calves, exposed to colostrokinin at 12 hours postpartum, had no increase in serum immunoglobulin G concentrations following a colostrum feeding at 24 hours postpartum. Fasted calves fed a ration not containing colostrokinin exhibited a two-fold increase in serum immunoglobulin G concentrations after the 24 hour colostrum feeding. Colostrokinin did not have an immediate effect on serum immunoglobulin G concentrations, but required an approximate twelve hour period to manifest its regulatory function. The presence or absence of colostrokinin in the experimental rations did not have any effect on the cortisol or thyroxine profiles. The variable serum immunoglobulin G profiles suggest that colostrokinin is involved in the acquisition of passive immunity by the calf, but colostrokinin may have more than one physiological role.

Thesis (PhD (Biochemistry))--Stellenbosch University, 2008. / This study describes: • the cloning and sequencing of cytochrome P450 17 -hydroxylase/17,20 lyase (CYP17), 3 -hydroxysteroid dehydrogenase (3 HSD) and cytochrome b5 from the South African Angora goat; • the identification of two CYP17 genes encoding two unique CYP17 isoforms in the Angora goat; • the development of a UPLC-APCI-LC method for the separation and quantification of seven adrenal steroids; • the characterisation of the enzymatic activity of the two Angora CYP17 isoforms expressed in non-steroidogenic COS-1 cells. The Km and Vvalues for the metabolism of pregnenolone and progesterone were determined; • the development of a rapid and accurate real-time PCR genotyping test for CYP17 in Angora goats. Three unique genotypes were identified; • the determination of blood cortisol levels upon the stimulation of the HPAaxis by intravenous insulin injection in the three Angora goat genotypes.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study describes: • the comparison of the enzymatic activities of the two ovine cytochrome P450 17 - hydroxylase/17,20-lyase (CYP17) isoforms expressed in non-steroidogenic COS-1 cells. The Km and Vmax values for the metabolism of pregnenolone and progesterone were determined, while time-dependent metabolism of pregnenolone, 17-hydroxypregenolone, progesterone and 17-hydroxyprogesterone was also reported. The cloning and sequencing of ovine cytochrome b5 is reported and was co-expressed with CYP17. The results showed that the wild type 1 (WT1) isoform of ovine CYP17 produce more cortisol precursors than the wild type 2 (WT2) isoform; • the analysis of the frequency distribution of the CYP17 genotypes within a South African Merino population, which were divergently selected for (H-line) or against (L-line) the ability of a ewe to rear multiple offspring per birthing opportunity. It was observed that the CYP17 frequency distribution was the same within the H- and L-line, with 78.3 % heterozygous WT1/WT2 and 21.7 % homozygous WT1/WT1. No homozygous WT2/WT2 individuals were identified; • the development of a UPLC-MS/MS method for the separation and quantification of all thirteen adrenal steroids that are produced in the adrenal gland; • the relative contribution of the CYP17 genotypes in the total steroidogenic output in adult adrenocortical cells from the adrenal glands of H- and L-line sheep, with particular emphasis on cortisol production. The adrenocortical cells from the H-line sheep showed a marked higher cortisol production than the L-line, while adrenocortical cells from homozygous WT1/WT1 sheep also produced more cortisol than heterozygous WT1/WT2 sheep; • the blood cortisol responses upon the stimulation of the HPA axis by insulin induced hypoglycaemia of the H- and L-line sheep with known CYP17 genotypes. It was observed that the CYP17 genotype and selection line are important factors affecting the cortisol responses of sheep, where L-line heterozygous WT1/WT2 sheep showed the lowest cortisol response and glucose recovery; • the association of the CYP17 genotype with behavioural responses of H- and L-line sheep to flock isolation stress, as well as the association of the CYP17 genotype with ewe reproduction and lamb output. While reproduction seemed to be unaffected by the CYP17 genotype, the behavioural stress responses of sheep to flock isolation correlated with the CYP17 genotype, where the heterozygous WT1/WT2 genotype was associated with a wilder nature. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek: • die vergelyking van die ensiemaktiwiteite vir twee isoforme van skaap sitochroom P450 17 -hidroksilase/17,20-liase (CYP17), wat uitgedruk was in nie-steroïed genererende COS- 1 selle. Die Km and Vmax waardes was bepaal vir die metabolisme van pregnenoloon en progesteroon, terwyl die tyd-afhanklike metabolisme van pregnenoloon, 17- hidroksiepregnenoloon, progesteroon en 17-hidroksieprogesteroon ook gerapporteer word. Die klonering en volgorde bepaling van skaap sitochroom b5 was gedoen en gevolglik was sitochroom b5 saam met CYP17 uitgedruk in COS-1 selle. Die resultate het gewys dat wilde tipe 1 (WT1) meer voorlopers van kortisol produseer as wilde tipe 2 (WT2); • die frekwensie distrubusie van die CYP17 genotipes in ‘n Suid-Afrikaanse Merino populasie, waar skape in teenoorgestelde rigtings geselekteer was vir (H-lyn) of teen (L-lyn) die vermoë van ‘n ooi om geboorte te gee aan veelvoudige lammers per lamgeleentheid. Die frekwensie distrubusie van CYP17 was dieselfde in beide die H- en L-lyn, waar 78.3 % van die populasie heterosigoties WT1/WT2 en 21.7 % homosigoties WT1/WT1 was. Geen homosigote WT2/WT2 individue was geïdentifiseer nie; • die ontwikkeling van ‘n UPLC-MS/MS metode vir die skeiding en kwantifisering van al dertien steroïede wat natuurlik geproduseer word in die bynier van die skaap; • die relatiewe bydrae van die CYP17 isoforme tot die totale steroïedale uitsette vanuit die bynier kortex selle, vanaf die byniere van H- en L-lyn skape, waar klem geplaas word op die produksie van kortisol. Die bynierselle van die H-lyn skape het aansienlik meer kortisol produseer as die L-lyn, terwyl die bynierselle van die homosigotiese WT1/WT1 skape ook meer kortisol produseer het as heterosigotiese WT1/WT2 skape; • die bloed kortisol in reaksie tot die stimulering van die hipotalamus-hipofise-adrenale aksis, deur insulien geïnduseerde hipoglisemiese stress, in skape van die H- en L-lyne met bekende CYP17 genotipes. Dit was gevind dat die kortisol reaksie geaffekteer word deur beide die CYP17 genotipe en seleksie lyn, waar L-lyn heterosigotiese WT1/WT2 skape die minste kortisol geproduseer het en die stadigste herstel van glukose vlakke getoon het; • die assosiasie tussen die CYP17 genotipe en die gedrags reaksies op trop-isolasie, sowel as ooi-reproduksie en lamuitset, van die H- en L-lyn skape. Die reproduksie parameters was onafhanklik van die CYP17 genotipe, terwyl ‘n sterk assosiasie gevind was tussen die CYP17 genotipe en gedrags reaksies op trop-isolasie. Die heterosigotiese WT1/WT2 skape het ‘n wilder natuur getoon gedurende trop-isolasie in vergelyking met homosigotiese WT1/WT1 skape.

Over recent years the delivery of nanosized drug particles has shown potential in improving bioavailability. Drug nanosizing is achieved by 'top-down' and by 'bottom-up' approaches. Owing to limitations associated with the top-down techniques, such as high energy input, electrostatic effects, broad particle size distributions and contamination issues, great interest has been directed to alternative bottom up technologies. In this study, the hypothesis that microreactors can be used as a simple and cost-effective technique to generate organic nanosized products is tested using three steroids (hydrocortisone, prednisolone and budesonide). Arrested antisolvent nanoprecipitation using ethanol (solvent) and water (antisolvent) was conducted within the microreactors. To enable experimental design for the microreactor studies, solubility profiles in different ethanol-water combinations at 25 °C were explored. All three drugs' solubility increased with increasing ethanol concentration showing maxima at 80-90 % v/v ethanol-water mixtures. Because of the complex multivariate microfluidic process, artificial neural network modelling was then employed to identify the dominant relationships between the variables affecting nanoprecipitation (as inputs) and the drug particle size (as output). The antisolvent flow rate was found to have the major role in directing drug particle size. Based on these successful findings, the potential of preparing pharmaceutical nanosuspensions using microfluidic reactors was researched. A hydrocortisone (HC) nanosuspension (NS) was prepared by introducing the generated drug particles into an aqueous solution of stabilizers stirred at high speed with a propeller mixer. A tangential flow filtration system was then used to concentrate the prepared NS. Results showed that a stable narrow sized HC NS of amorphous spherical particles 500 ± 64 nm diameter and zeta potential -18 ± 2.84 mV could be produced. The ocular bioavailability of a microfluidic precipitated HC NS (300 nm) was assessed and compared to a similar sized, milled HC NS and HC solution as a control. The precipitated and the milled NS achieved comparable AUC0-9h of 28.06 ± 4.08 and 30.95 ± 2.2, respectively, significantly (P < 0.01) higher than HC solution (15.86 ± 2.7). These results illustrate the opportunity to design sustained release ophthalmic formulations. Going nano via microfluidic precipitation was also exploited to tailor budesonide (BD) NS for pulmonary administration. The in vitro aerosolization by nebulization of a BD NS was studied in comparison with a commercial BD microsuspension. Overall, the fine particle fraction generated from BD NS (56.88 ± 3.37) was significantly (P < 0.05) higher than the marketed BD (38.04 ± 7.81). The mean mass aerodynamic diameter of BD NS aerosol (3.9 ± 0.48 μm) was significantly smaller (P < 0.05) than the microsuspension (6.2 ± 1.09 μm) indicating improved performance for BD NS. In conclusion, findings of this study support the hypothesis of using microfluidic nanoprecipitation as a promising and economical technique of drug nanosizing.

O trabalho noturno e a alternância de turnos são identificados como fatores de maximização de efeitos negativos na saúde do trabalhador, como o estresse e a fadiga, por dificultarem a adaptação do ritmo circadiano do cortisol ao de trabalho. Objetivo: investigar o efeito do esquema de trabalho em turnos fixo e alternante e noturno de enfermeiros nos índices de estresse ocupacional e fadiga e na expressão circadiana do cortisol salivar. Método: estudo observacional de corte transversal e abordagem quantitativa dos dados estruturado com base no referencial teórico de Cooper. Realizado com 104 enfermeiros das Unidades de Emergência e Bloco Cirúrgico de hospital de ensino público do Estado de São Paulo e outro de Minas Gerais, no período de janeiro a março de 2017. Índices de estresse e fadiga foram mensurados por meio da aplicação de dois instrumentos: o Inventário de Estresse em Enfermeiros e a Escala de Avaliação de Fadiga, ambos validados para utilização no Brasil. A quantificação do cortisol salivar foi realizada por meio da técnica de ELISA. O projeto foi aprovado pelo Comitê de Ética em pesquisa sob protocolo. 55695416.7.0000.5393. Resultados: 66,67% dos enfermeiros trabalhavam em esquema de turnos alternantes e 39,39% eram fixos no turno matutino. Constatou-se 50,8% apresentaram alto índice de estresse e 46,03% fadiga. Não foram observadas associações estatisticamente significativas entre índices de cortisol salivar, turno de trabalho, esquema de turno fixo ou alternante, estresse e fadiga. Entretanto, profissionais de enfermagem de unidades críticas que trabalhavam em esquema de turnos alternante e matutino apresentaram tendência a mais altos índices de estresse e fadiga e menor secreção de cortisol ao longo do dia de trabalho do que aqueles dos turnos fixo e noturno. A fadiga mostrou-se significativa e positivamente correlacionada com a secreção total de cortisol no período da manhã. Conclusão: Os achados do presente estudo fornecem evidências de uma dessincronização do eixo HipotálamoHipófise-Adrenal em enfermeiros dos turnos alternante e matutino e, consequentemente, maior susceptibilidade destes ao desenvolvimento de doenças cardíacas, metabólicas e imunológicas / Night-work and shiftwork are identified as maximizing negative effects on worker health, such as stress and fatigue, by making it difficult to adapt the circadian rhythm of cortisol to work. Objective: to investigate the effect of the fixed and alternating and nocturnal shifts of nurses on the occupational stress index, fatigue and circadian expression of salivary cortisol. Method: observational, cross-sectional and quantitative study based on Cooper\'s theoretical framework. Performed with 104 nurses from the emergency units and surgical center of a public teaching hospital in the State of São Paulo and another from Minas Gerais, from January to March, 2017. Stress and fatigue indexes were measured using two instruments, the Nurses\' Stress Inventory and the Fatigue Assessment Scale, both of which were validated and salivary cortisol quantification was performed by ELISA assay. The project was approved by the Research Ethics Committee under protocol. 55695416.7.0000.5393. Results: 66.67% of the nurses worked on alternating shifts and 39.39% were fixed on the morning shift. It was found that 50.8% of the nurses had a high stress index and 46.03% presented fatigue. There were no statistically significant associations between salivary cortisol index, shiftwork, fixed or alternating shift scheme, stress and fatigue. However, nursing professionals from critical units who worked in an alternating and morning shift schedule showed a trend towards higher levels of stress and fatigue and lower cortisol secretion throughout the workday than fixed and night shift workers. Fatigue was significantly and positively correlated to overall morning cortisol. Conclusions: The findings of the present study provide evidence of a hypothalamic-pituitary-adrenal axis desynchronization in nurses of the alternating and morning shift and, consequently, a greater susceptibility of these to the development of cardiac, metabolic and immunological diseases

In the second part of our study, cDNA of AQP-1 and pro-vasotocin were cloned from the silver sea bream. An AQP-1 full clone was isolated from kidney and intestine and it consists of 904 bp with an open reading frame of 774 bp. The deduced amino sequence of sea bream AQP-1 shares highest identity with AQP-1a of gilthead sea bream (97.7%) and AQP-1a of other fish species (83.6% to 95.8%), however, considerably low identity was found between the silver sea bream AQP-1 and AQP-1b of gilthead sea bream (56%). The silver sea bream AQP-1 possesses basic features of a functional aquaporin and AQP-1, which includes two channel-forming asparagine-proline-alanine (NPA) signature motifs, six transmembrane domains, residues of the pore-forming region and a potential mercurial inhibiting site (Cys-178). The water channel was ubiquitously expressed in gills, liver, intestine, rectum, kidney, heart, urinary bladder and blood cells. A partial fragment of pro-vasotocin was isolated from hypothalamus of silver sea bream and consists of 184 bp, including encoding regions for the processing and amidation signal, vasotocin hormone and part of the neurophysin. / Lastly, single doses of cortisol (50 microg/g tissue) or vasotocin (1 microg/g tissue) were administered to seawater-acclimated sea bream with further three-day stabilizing period in seawater followed by an abrupt 6&permil; exposure or administered to seawater transfer controls for three days. Cortisol markedly stimulated intestinal expression of AQP-1 in both the seawater transfer control and abrupt 6&permil; transfer groups. Vasotocin treatment did not significantly modify AQP-1 expression in all tested organs. Hypothalamic pro-vasotocin expression levels were similar among different treatment groups. / Semi-quantitative RT-PCR analysis was used for studying the effect of salinity and hormones on expression of AQP-1 and pro-vasotocin. In the long-term salinity acclimation experiment, the sea bream were acclimated to six different salinity regimes (0&permil;, 6&permil;, 12&permil;, 33&permil;, 50&permil;, 70&permil;) for four weeks. The abundance of AQP-1 transcript was the highest in intestine of 70&permil;-acclimated fish among different salinity groups and there was also a statistically significant increase in 12&permil;-acclimated fish. Branchial AQP-1 expression was significantly upregulated in sea bream acclimated to freshwater. In contrast, the hypothalamic pro-vasotocin expression was significantly downregulated during freshwater acclimation. In addition, the sea bream were also subjected to an abrupt 6%o transfer at different time intervals (2, 6, 12, 72 and 168 hours). RT-PCR analysis revealed there was a transient decrease in branchial AQP-1 expression two hours after abrupt hypo-osmotic exposure and the expression levels subsequently returned to the seawater control levels. The expression levels of hypothalamic pro-vasotocin were not significantly altered by the abrupt exposure treatment. / The present experiments investigated the effects of salinity and hormones on the relative expression of hypothalamic pro-vasotocin, and aquaporin-1 (AQP-1) in intestine, gills and kidney of the silver sea bream Sparus sarba. With the use of immunohistochemical techniques, immunoreactivity of AQP-1 was detected at the basal side of enterocytes and gill chloride cells, and at the apical brush border of kidney tubules whereas AQP-3 was only localized in similar positions in the gills and intestines. AQP-1 was relatively more ubiquitous than AQP-3 and was localized with same cell types as the electrogenic Na+-K+-ATPase in gills and kidney. / The present study had demonstrated the responsiveness of intestinal and branchial AQP-1 expressions of the silver sea bream to environmental salinity perturbations. Further to this, cortisol was observed to upregulate the transcription of AQP-1 in the intestine. Pro-vasotocin expression was altered by long-term salinity adaptation, however, the linkage of this alteration to AQP-1 functioning in different osmoregulatory organs is yet to be elucidated. / Luk, Chun Yin. / Adviser: Norman Y. S. Woo. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 200-222). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Introduction: Diagnosed adrenal incidentalomas (AI) are increasing and dexamethasonesuppression test (DST) is gold standard for detection of excess cortisol production. Patients canbe categorized into three groups based on the DST level; non-functional adrenal adenomas(NFAA), possible autonomous cortisol secretion (PACS) and autonomous cortisol secretion(ACS), the latter two associated with increased risk of cardiovascular morbidity and mortality. Aim: The aim of this study was to compare cardiovascular morbidity and mortality in patientswith adrenal incidentalomas with and without hypercortisolemia defined by the EuropeanSociety of Endocrinology (2016) guidelines. Method: Retrospectively 160 consecutive patient charts between 2008 and 2015 were reviewedand 59 included. They were further categorized in NFAA (n = 37) or PACS (n = 22). Patientswith signs and symptoms of hormonal overproduction or AI found during malignancyinvestigations were excluded. Due to strict adherence to inclusion and exclusion criteria, onlyone case of ACS was found and excluded due to ethical reason. Results: Increased prevalence of type 2 diabetes in PACS group at baseline. No difference incardiovascular disease or mortality between the groups could be seen after mean follow up of7 years. Three (8%) patients in the NFAA group deceased, all of malignancy. In the PACSgroup, five (23%) deceased. Cause of death was cerebral infarction (n = 2), malignancy (n =1)and other causes (n =2). Conclusion: No significant difference of cardiovascular morbidity and mortality could be seenbetween NFAA and PACS during follow up. A prospective multicentre study is needed toidentify the long-term outcomes.

Low birth weight is associated with an increased risk of impaired glucose tolerance and type 2 diabetes and with signs of increased hypothalamic pituitary adrenal axis activity in later life (1, 2). Low birth usually weight reflects a reduction in fetal growth, which largely depends on an adequate supply of nutrients and oxygen. Variations in supply modify the metabolic and neuroendocrine characteristics of the fetus, which in turn modulate the pattern of functional development as well as growth (3). An adverse fetal environment, evident as low birth weight, is therefore proposed to alter functional development with long term effects for the function and risk of disease in the individual later in life (4, 5). Increased HPAA impairs metabolic homeostasis and could therefore mediate effect of prenatal challenge on later metabolic control (6). It was therefore hypothesised that restriction of fetal growth, increases circulating cortisol and/or alters sensitivity to cortisol, which increases fasting blood glucose, and impairs glucose tolerance in the young adult. Large litter size in the guinea pig is characterised by reduced placental and fetal growth, reduced size at birth and insulin resistance in offspring in later life, providing a suitable model to test this hypothesis. Spontaneous restriction of fetal growth in the guinea pig, evident as small size at birth, was associated with increased salivary cortisol, in both sexes but at different stages of postnatal life. In males, salivary cortisol was increased with small size at birth in early and adult life, but reduced later with ageing. In females however, salivary cortisol was increased in juveniles and in aged adults, possibly reflecting the impact of the oestrus cycle on cortisol production in mature cycling females. Altered activity of the HPGA, which can influence that of the HPAA, has also been reported to be programmed by prenatal restriction. In the guinea pig, salivary testosterone in males increased with age and small size at birth in juveniles, young and aged adults. In females, salivary progesterone increased with age up to 300 days, and decreased with size at birth in the young guinea pig. Although testosterone inhibits HPAA activity, in males, mean salivary cortisol correlated positively with mean salivary testosterone at 100 and 300 days of age. In contrast, progesterone may enhance HPAA activity, and consistent with this, in females, mean salivary progesterone correlated with mean salivary cortisol at 400 days of age. Therefore, salivary testosterone in the male and salivary progesterone in the female guinea pig changes with maturation and has previously reported in this or other species, but small size at birth increases salivary testosterone in males with modest effects in early life in females. This together with the unexpected positive associations of salivary cortisol with testosterone in males, suggests that programming of the HPAA makes little contribution to that of the HPAA as indicated by salivary cortisol. Here we show that low birth weight is associated with increased fasting blood glucose and impaired glucose tolerance in both male and female young adult guinea pigs aged 100 days. Fasting and mean (during IVGTT) plasma cortisol was reduced in low birth weight female adult guinea pigs, and is not vary with size at birth at this age in males. This suggests that circulating cortisol does not contribute to the impaired glycaemia associated with small size at birth in the guinea pig. Glucose tolerance was increasingly impaired in males but not females, as mean plasma cortisol increased. This is consistent with cortisol impairing glycaemia in the guinea pig as in other species, in males at least. To assess the role of cortisol in prentally programmed impairment of glycaemia directly, metyrapone or vehicle containing 24% ethanol was administered to young adult guinea pigs for 3 days. Treatment with the latter impaired fasting blood glucose and glucose tolerance in females and the latter in males compared to a previous IVGTT and this was exacerbated in low birth weight females. Metyrapone prevented this impairment of fasting glycaemia and glucose tolerance in the low birth weight adult female guinea pig and in the male guinea pig regardless of birth weight class. Neither vehicle or metyrapone altered plasma cortisol, before or during a second IVGTT. Limited numbers of animals, particularly females, limited this study however and additional investigation is required. Nevertheless this shows for the first time that inhibition of glucocorticoid synthesis in the guinea pig improves glucose control. Furthermore this suggests that the low birth weight guinea pig may be more sensitive to cortisol, have increased cortisol synthesis or reduced inactivation of cortisol in peripheral tissues, leading to increased local cortisol action. In conclusion, alterations in peripheral HPAA activity in the guinea pig due to restricted fetal growth may contribute to their prenatally programmed development of impaired glucose tolerance as young adults, but the extent of that contribution may vary with age and gender. / Thesis (Ph.D.) -- University of Adelaide, School of Paediatrics and Reproductive Health, 2008

Graduation date: 1993

The Hypothalamic Pituitary Adrenal (HPA) axis is the coordinator of adaptive responses to physical and psychological stress. The central nervous system plays a key role in modulation of both basal and adaptive HPA axis functions. In fact, since long ago, animal studies have shown that acute and chronic exposure to glucocorticoids (a stress hormone released due to HPA axis activation, cortisol in humans) affects the function and the morphology of brain areas such as the hippocampus and the cingulate cortex. This thesis is based on novel neuroimaging methodologies used to investigate the interactions of psychological stress, cortisol and the brain. It consists of three functional studies and a morphometric one. In the first functional study we show that the hippocampus (where glucocorticoid receptors are most abundant) plays a role in initiation of an HPA axis stress response. In the second study, we provide evidence that besides hippocampus, the neural activity in the so-called "default mode network" (DMN), especially the anterior cingulate cortex (ACC), relates to interindividual variations in HPA axis response to psychological stress. In the third study we have investigated the cortisol-modulation of the DMN. Again, we provide evidence for a role of the ACC and the orbitofrontal cortex in negative feedback inhibition of the HPA axis activity. Finally, we show a morphological link between the ACC and the cortisol response to awakening which is an index of basal HPA axis activity. Overall, our findings confirm the critical role of the ACC and mesolimbic system in HPA axis regulation. These findings also draw attention to the interactions between functional subregions of the medial prefrontal cortex and states of HPA axis function prior to stress onset---suggesting an interplay of the monitoring and the executive planning roles of the medial prefrontal cortex in behavioral adaptation to stress. Beyond stress research, our findings offer a framework for combining neuroimaging and neuroendocrinology to better understand the interindividual variances in behavior, and perhaps to better identify subgroups at risk of psychological disorders.