Superovulation of Beef Heifers with Follicle Stimulating Hormone or Human Menopausal Gonadotropin: Acute Effects on Hormone Secretion

The effects of superovulatory treatment (follicle stimulating hormone [FSH] versus human menopausal gonadotropin [HMG]) and of route of administration (intramuscular versus intravenous) of prostaglandin F2a (PGF2a) on hormonal profiles were determined in 32 Angus x Hereford heifers for breeding and subsequent embryo collection and transfer. Heifers were superstimulated either with FSH (total of 26 milligrams) or HMG (total of 1,050 international units) beginning on days 9 to 12 of an estrous cycle and PGF2a (40 milligrams) was administered at 60 and 72 hours after the beginning of superovulatory treatments. Heifers were artificially inseminated three times at 12-hour intervals beginning 48 hours after PGF2a treatment. Blood serum samples were collected immediately before treatments began and at frequent intervals until embryo collection 288 hours later. Concentrations of luteinizing hormone (LH) and FSH were not affected by hormone treatments, route of PGF2a injection, or interactions between them. Estradiol-17ß (E2-17ß) levels were higher in HMG- than in FSH-treated heifers 60 hours after gonadotropin treatment. Peak concentration of E2-17ß occurred earlier in HMGthan in FSH-treated heifers and earlier in heifers injected with PGF2a intramuscularly than those injected intravenously. Progesterone concentrations were not influenced by treatment or route of PGF2a administration. The progesterone:E2-17ß ratio was higher in FSH- than in HMG-treated heifers 24 hours after the LH peak. The high steroid hormone concentrations in superovulated beef heifers before and after ovulation may lead to asynchrony between stages of embryonic development, a situation that may interfere with the pregnancy outcome of superovulated embryos in recipient animals.

Effects of Novel Growth Hormone Secretagogues on Growth Hormone Secretion in Farm Animals

The requirement for growth hormone (GH) secretion by the anterior pituitary gland in beef calves is demonstrated by a complete lack of long bone-growth and muscle accretion after hypophysectomy (surgical removal of the pituitary gland). When the connecting link (hypophyseal stalk) to the basal region (hypothalamus) of the brain is surgically severed, long bone growth and body weight gain are greatly limited compared with sham-operated controls. This limited growth results from obliteration of episodic GH secretion and reduced basal blood concentration of the hormone compared with sham-operated controls. Thus, the hypophyseal stalk-transected (HST) calf provides an appropriate model to determine mechanisms by which hypothalamic neuropeptides from the brain regulate GH secretion, and thereby growth in the young calf. Neuropeptides have been isolated and characterized in bovine hypothalamus that stimulate GH secretion (GH-releasing hormone [GHRH]) or factor [GHRF] and inhibit GH secretion (GH release-inhibiting hormone [GHRIH] or somatostatin [SRIH]). A dose of .067 micrograms of GHRF per kilogram of body weight injected intravenously in HST calves abruptly increased plasma GH concentration to 55 nanograms per milliliter from the control period mean of 5 nanograms per milliliter. HST calves then were infused intravenously with .033 and .067 microgram somatostatin per kilogram of body weight, during which a pulse injection of .067 microgram of GHRF was administered. GH increase was limited to 9 and 5 micrograms per kilogram body weight during the .033- and .067 microgram SRIH infusions after GHRF; no GH rebound was observed after the SRIH was discontinued. GHRF from humans contains 40 to 44 amino acids. Rat hypothalamic GHRF analogs containing 29 to 32 amino acids elicited dose-dependent GH peak release in these HST calves. In 1977, Bowers and Monomy isolated novel GH releasing peptides consisting of only six amino acids; they caused GH release by isolated pituitary cells in culture and acute GH release when administered intravenously. We recently have utilized a novel nonpeptidyl GH secretagogue of low molecular weight in the pig to determine its mechanisms of action within the central nervous system.

Kinetics of maternally acquired anti-hepatitis A antibodies: prediction of waning based on maternal or cord blood antibody levels

BACKGROUND Timing is critical for efficient hepatitis A vaccination in high endemic areas as high levels of maternal IgG antibodies against the hepatitis A virus (HAV) present in the first year of life may impede the vaccine response. OBJECTIVES To describe the kinetics of the decline of anti-HAV maternal antibodies, and to estimate the time of complete loss of maternal antibodies in infants in León, Nicaragua, a region in which almost all mothers are anti-HAV seropositive. METHODS We collected cord blood samples from 99 healthy newborns together with 49 corresponding maternal blood samples, as well as further blood samples at 2 and 7 months of age. Anti-HAV IgG antibody levels were measured by enzyme immunoassay (EIA). We predicted the time when antibodies would fall below 10 mIU/ml, the presumed lowest level of seroprotection. RESULTS Seroprevalence was 100% at birth (GMC 8392 mIU/ml); maternal and cord blood antibody concentrations were similar. The maternal antibody levels of the infants decreased exponentially with age and the half-life of the maternal antibody was estimated to be 40 days. The relationship between the antibody concentration at birth and time until full waning was described as: critical age (months)=3.355+1.969 × log(10)(Ab-level at birth). The survival model estimated that loss of passive immunity will have occurred in 95% of infants by the age of 13.2 months. CONCLUSIONS Complete waning of maternal anti-HAV antibodies may take until early in the second year of life. The here-derived formula relating maternal or cord blood antibody concentrations to the age at which passive immunity is lost may be used to determine the optimal age of childhood HAV vaccination.

Does single use of an autologous transfusion system in TKA reduce the need for allogenic blood?: a prospective randomized trial

BACKGROUND Mechanical autotransfusion systems for washed shed blood (WSB) were introduced to reduce the need for postoperative allogenic blood transfusions (ABTs). Although some authors have postulated decreased requirements for ABT by using autologous retransfusion devices, other trials, mostly evaluating retransfusion devices for unwashed shed blood (USB), verified a small or no benefit in reducing the need for postoperative ABT. Because of these contradictory findings it is still unclear whether autologous retransfusion systems for WSB can reduce transfusion requirements. QUESTIONS/PURPOSES We therefore asked whether one such autologous transfusion system for WSB can reduce the requirements for postoperative ABT. METHODS In a prospective, randomized, controlled study, we enrolled 151 patients undergoing TKA. In Group A (n=76 patients), the autotransfusion system was used for a total of 6 hours (intraoperatively and postoperatively) and the WSB was retransfused after processing. In Control Group B (n=75 patients), a regular drain without suction was used. We used signs of anemia and/or a hemoglobin value less than 8 g/dL as indications for transfusion. If necessary, we administered one or two units of allogenic blood. RESULTS Twenty-three patients (33%) in Group A, who received an average of 283 mL (range, 160-406 mL) of salvaged blood, needed a mean of 2.1 units of allogenic blood, compared with 23 patients (33%) in Control Group B who needed a mean of 2.1 units of allogenic blood. CONCLUSIONS We found the use of an autotransfusion system did not reduce the rate of postoperative ABTs. LEVEL OF EVIDENCE Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Early follicular testosterone level predicts preference for masculinity in male faces — But not for women taking hormonal contraception

It has been shown that women’s preference for masculinity in male faces changes across the menstrual cycle. Preference for masculinity is stronger when conception probability is high than when it is low. These findings have been linked to cyclic fluctuations of hormone levels. The purpose of the present study is to further investigate the link between gonadal steroids (i.e. testosterone, estradiol, and progesterone) and masculinity preference in women, while holding the cycle phase constant. Sixty-two female participants were tested in their early follicular cycle phase, when conception probability is low. Participants were shown face pairs and where asked to choose the more attractive face. Face pairs consisted of a masculinized and feminized version of the same face. For naturally cycling women we found a positive relationship between saliva testosterone levels and masculinity preference, but there was no link between any hormones and masculinity preference for women taking hormonal contraception. We conclude that in naturally cycling women early follicular testosterone levels are associated with masculinity preference. However, these hormonal links were not found for women with artificially modified hormonal levels, that is, for women taking hormonal contraception.

Growth hormone response to catecholamine depletion in unmedicated, remitted subjects with major depressive disorder and healthy controls

We investigated whether the human growth hormone (HGH) response to catecholamine depletion differs between fully remitted patients with major depressive disorder and healthy control subjects. Fourteen unmedicated subjects with remitted major depressive disorder (RMDD) and 11 healthy control subjects underwent catecholamine depletion with oral α-methylparatyrosine (AMPT) in a randomized, placebo-controlled, double-blind crossover study. The main outcome measure was the serum level of HGH. The diagnosis × drug interaction for HGH serum concentration was significant (F₁,₂₃ = 7.66, P < 0.02). This interaction was attributable to the HGH level increasing after AMPT administration in the RMDD subjects but not in the healthy subjects. In the RMDD sample, the AMPT-induced increase in HGH concentration correlated inversely with AMPT-induced anxiety symptoms as assessed using the Beck Anxiety Inventory (r = -0.63, P < 0.02). There was a trend toward an inverse correlation of the AMPT-induced HGH concentration changes with AMPT-induced depressive symptoms as measured by the BDI (r = -0.53, P = 0.05). Following catecholamine depletion, the RMDD subjects were differentiated from control subjects by their HGH responses. This finding, together with the negative correlation between HGH response and AMPT-induced anxiety symptoms in RMDD subjects, suggests that AMPT administration results in a deeper nadir in central catecholaminergic transmission, as reflected by a greater disinhibition of HGH secretion, in RMDD subjects versus control subjects.

EGFR exon-level biomarkers of the response to bevacizumab/erlotinib in non-small cell lung cancer

Activating epidermal growth factor receptor (EGFR) mutations are recognized biomarkers for patients with metastatic non-small cell lung cancer (NSCLC) treated with EGFR tyrosine kinase inhibitors (TKIs). EGFR TKIs can also have activity against NSCLC without EGFR mutations, requiring the identification of additional relevant biomarkers. Previous studies on tumor EGFR protein levels and EGFR gene copy number revealed inconsistent results. The aim of the study was to identify novel biomarkers of the response to TKIs in NSCLC by investigating whole genome expression at the exon-level. We used exon arrays and clinical samples from a previous trial (SAKK19/05) to investigate the expression variations at the exon-level of 3 genes potentially playing a key role in modulating treatment response: EGFR, V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) and vascular endothelial growth factor (VEGFA). We identified the expression of EGFR exon 18 as a new predictive marker for patients with untreated metastatic NSCLC treated with bevacizumab and erlotinib in the first line setting. The overexpression of EGFR exon 18 in tumor was significantly associated with tumor shrinkage, independently of EGFR mutation status. A similar significant association could be found in blood samples. In conclusion, exonic EGFR expression particularly in exon 18 was found to be a relevant predictive biomarker for response to bevacizumab and erlotinib. Based on these results, we propose a new model of EGFR testing in tumor and blood.

Differential regulation of human 3β-hydroxysteroid dehydrogenase type 2 for steroid hormone biosynthesis by starvation and cyclic AMP stimulation: studies in the human adrenal NCI-H295R cell model

Human steroid biosynthesis depends on a specifically regulated cascade of enzymes including 3β-hydroxysteroid dehydrogenases (HSD3Bs). Type 2 HSD3B catalyzes the conversion of pregnenolone, 17α-hydroxypregnenolone and dehydroepiandrosterone to progesterone, 17α-hydroxyprogesterone and androstenedione in the human adrenal cortex and the gonads but the exact regulation of this enzyme is unknown. Therefore, specific downregulation of HSD3B2 at adrenarche around age 6-8 years and characteristic upregulation of HSD3B2 in the ovaries of women suffering from the polycystic ovary syndrome remain unexplained prompting us to study the regulation of HSD3B2 in adrenal NCI-H295R cells. Our studies confirm that the HSD3B2 promoter is regulated by transcription factors GATA, Nur77 and SF1/LRH1 in concert and that the NBRE/Nur77 site is crucial for hormonal stimulation with cAMP. In fact, these three transcription factors together were able to transactivate the HSD3B2 promoter in placental JEG3 cells which normally do not express HSD3B2. By contrast, epigenetic mechanisms such as methylation and acetylation seem not involved in controlling HSD3B2 expression. Cyclic AMP was found to exert differential effects on HSD3B2 when comparing short (acute) versus long-term (chronic) stimulation. Short cAMP stimulation inhibited HSD3B2 activity directly possibly due to regulation at co-factor or substrate level or posttranslational modification of the protein. Long cAMP stimulation attenuated HSD3B2 inhibition and increased HSD3B2 expression through transcriptional regulation. Although PKA and MAPK pathways are obvious candidates for possibly transmitting the cAMP signal to HSD3B2, our studies using PKA and MEK1/2 inhibitors revealed no such downstream signaling of cAMP. However, both signaling pathways were clearly regulating HSD3B2 expression.

Botulinum toxin A and B raise blood flow and increase survival of critically ischemic skin flaps

BACKGROUND Botulinum toxin (BTX) A and B are commonly used for aesthetic indications and in neuromuscular disorders. New concepts seek to prove efficacy of BTX for critical tissue perfusion. Our aim was to evaluate BTX A and B in a mouse model of critical flap ischemia for preoperative and intraoperative application. METHODS BTX A and B were applied on the vascular pedicle of an axial pattern flap in mice preoperatively or intraoperatively. Blood flow, tissue oxygenation, tissue metabolism, flap necrosis rate, apoptosis assay, and RhoA and eNOS expression were endpoints. RESULTS Blood-flow measurements 1 d after the flap operation revealed a significant reduction to 53% in the control group, while flow was maintained or increased in all BTX groups (103%-129%). Over 5 d all BTX groups showed significant increase in blood flow to 166-187% (P < 0.01). Microdialysis revealed an increase of glucose and reduced lactate/pyruvate ratio and glycerol levels in the flap tissue of all BTX groups. This resulted in significantly improved tissue survival in all BTX groups compared with the control group (62% ± 10%; all P < 0.01): BTX A preconditioning (84% ± 5%), BTX A application intraoperatively (88% ± 4%), BTX B preconditioning (91% ± 4%), and intraoperative BTX B treatment (92% ± 5%). This was confirmed by TUNEL assay. Immunofluorescence demonstrated RhoA and eNOS expression in BTX groups. All BTX applications were similarly effective, despite pharmacologic dissimilarities and different timing. CONCLUSIONS In conclusion, we were able to show on a vascular, tissue, cell, and molecular level that BTX injection to the feeding arteries supports flap survival through ameliorated blood flow and oxygen delivery.

Comprehensive MicroRNA expression profiling identifies novel markers in follicular variant of papillary thyroid carcinoma

BACKGROUND Follicular variant of papillary thyroid carcinoma (FVPTC) shares features of papillary (PTC) and follicular (FTC) thyroid carcinomas on a clinical, morphological, and genetic level. MicroRNA (miRNA) deregulation was extensively studied in PTCs and FTCs. However, very limited information is available for FVPTC. The aim of this study was to assess miRNA expression in FVPTC with the most comprehensive miRNA array panel and to correlate it with the clinicopathological data. METHODS Forty-four papillary thyroid carcinomas (17 FVPTC, 27 classic PTC) and eight normal thyroid tissue samples were analyzed for expression of 748 miRNAs using Human Microarray Assays on the ABI 7900 platform (Life Technologies, Carlsbad, CA). In addition, an independent set of 61 tumor and normal samples was studied for expression of novel miRNA markers detected in this study. RESULTS Overall, the miRNA expression profile demonstrated similar trends between FVPTC and classic PTC. Fourteen miRNAs were deregulated in FVPTC with a fold change of more than five (up/down), including miRNAs known to be upregulated in PTC (miR-146b-3p, -146-5p, -221, -222 and miR-222-5p) and novel miRNAs (miR-375, -551b, 181-2-3p, 99b-3p). However, the levels of miRNA expression were different between these tumor types and some miRNAs were uniquely dysregulated in FVPTC allowing separation of these tumors on the unsupervised hierarchical clustering analysis. Upregulation of novel miR-375 was confirmed in a large independent set of follicular cell derived neoplasms and benign nodules and demonstrated specific upregulation for PTC. Two miRNAs (miR-181a-2-3p, miR-99b-3p) were associated with an adverse outcome in FVPTC patients by a Kaplan-Meier (p < 0.05) and multivariate Cox regression analysis (p < 0.05). CONCLUSIONS Despite high similarity in miRNA expression between FVPTC and classic PTC, several miRNAs were uniquely expressed in each tumor type, supporting their histopathologic differences. Highly upregulated miRNA identified in this study (miR-375) can serve as a novel marker of papillary thyroid carcinoma, and miR-181a-2-3p and miR-99b-3p can predict relapse-free survival in patients with FVPTC thus potentially providing important diagnostic and predictive value.

Impact of changes in haematocrit level and platelet count on thromboelastometry parameters

INTRODUCTION To what extent haematocrit levels (Hct) and platelet counts (PLT) influence the measurement of parameters of thromboelastometry when assessed with the ROTEM® device is unclear. We investigated to what extent thromboelastometry measurements depend on Hct and PLT. MATERIALS AND METHODS Whole blood samples were taken for in-vitro preparations of mixtures with three different levels of PLT and a varying Hct. Maximum clot firmness (MCF), clotting time (CT), clot formation time (CFT) and alpha angle (α) for INTEM, EXTEM, FIBTEM and APTEM was recorded. RESULTS Measurements depended substantially on Hct and PLT. MCF readings were systematically lower with increasing Hct (0.2 vs. 0.4: -7.8 (-8.3 to -7.2); p<0.001, 0.2 vs. 0.55: -14.5 (-17.3 to -14.3); p<0.001) but higher with increasing PLT (50 vs. 125×10(9)/l: 8.2 (4.2 to 12.3); p=0.005, 50 vs. 250×10(9)/l: 12.0 (7.2 to 16.8); p=0.002). CT readings were systematically higher with increasing Hct (0.2 vs. 0.4: 9.2 (6.2 to 12.1); p=0.001, 0.2 vs. 0.55: 38.2 (21.5 to 54.9); p=0.003) while increasing PLT had no influence. CFT readings were also systematically higher with increasing Hct (0.2 vs. 0.4: 83.8 (40.2 to 127.6); p=0.006, 0.2 vs. 0.55: 226.2 (110.7 to 341.7); p=0.006) but systematically lower with increasing PLT (50 vs. 125×10(9)/l: -144.0 (-272.3 to -15.6); p=0.036, 50 vs. 250×10(9)/l: -189.2 (-330.4 to -48.0); p=0.02); readings of the alpha angle showed a similar pattern. CONCLUSIONS Our results suggest that readings of thromboelastometry parameters need to be adjusted by Hct and PLT to avoid potential confounding and miss-interpretations in clinical practice.

Analysis of Pressure Head-Flow Loops of Pulsatile Rotodynamic Blood Pumps

The clinical importance of pulsatility is a recurring topic of debate in mechanical circulatory support. Lack of pulsatility has been identified as a possible factor responsible for adverse events and has also demonstrated a role in myocardial perfusion and cardiac recovery. A commonly used method for restoring pulsatility with rotodynamic blood pumps (RBPs) is to modulate the speed profile, synchronized to the cardiac cycle. This introduces additional parameters that influence the (un)loading of the heart, including the timing (phase shift) between the native cardiac cycle and the pump pulses, and the amplitude of speed modulation. In this study, the impact of these parameters upon the heart-RBP interaction was examined in terms of the pressure head-flow (HQ) diagram. The measurements were conducted using a rotodynamic Deltastream DP2 pump in a validated hybrid mock circulation with baroreflex function. The pump was operated with a sinusoidal speed profile, synchronized to the native cardiac cycle. The simulated ventriculo-aortic cannulation showed that the level of (un)loading and the shape of the HQ loops strongly depend on the phase shift. The HQ loops displayed characteristic shapes depending on the phase shift. Increased contribution of native contraction (increased ventricular stroke work [WS ]) resulted in a broadening of the loops. It was found that the previously described linear relationship between WS and the area of the HQ loop for constant pump speeds becomes a family of linear relationships, whose slope depends on the phase shift.

Human placental lactogen enhancer: Tissue specificity and binding with specific proteins

Human placental lactogen (hPL) is a 22,000 dalton protein hormone produced in the placenta. The physiological actions of hPL are not well understood but its major activity is to regulate both maternal and fetal metabolism. hPL stimulates maternal lipolysis increasing free fatty acids in the maternal blood, allowing their use as an energy source by the mother, and sparing glucose for the fetus. It may also act as a growth promoting hormone for the fetus. hPL is produced in increasing amounts as pregnancy progresses. At term, hPL accounts for 10% of protein and 5% of total RNA in the placenta. This high level of hPL production is tissue-specific, as hPL is only produced in the placenta by syncytiotrophoblast cells.^ The objective of this work was to understand the mechanism by which such high levels of hPL are produced in a tissue-specific manner. A transcriptional enhancer found 2.2 kb 3$\sp\prime$ to one of the hPL genes (hPL$\sb3$) may explain the regulation of hPL expression. Transient transfection experiments using the hPL-producing human choriocarcinoma cell line JEG-3 localized the hPL enhancer to a 138 bp core element. This 138 bp sequence was found to be tissue specific in its actions as it did not promote transcription in heterologous cell lines. Gel mobility shift assays showed the hPL enhancer interacts specifically with nuclear proteins unique to hPL-producing cells. Within the 138 bp enhancer a 22 bp region was shown to be protected from DNase I digestion due to binding of proteins derived from placental nuclear extracts. Proteins binding this region of the enhancer may be instrumental in the tissue specific activity of the hPL enhancer. ^

Analysis of endogenous retinoic acid receptor expression and function in murine melanoma cells

There have been numerous reports over the past several years on the ability of vitamin A analogs (retinoids) to modulate cell proliferation, malignant transformation, morphogenesis, and differentiation in a wide variety of cell types and organisms. Two families of nuclear retinoid-inducible, trans-acting, transcription-enhancing receptors that bear strong DNA sequence homology to thyroid and steroid hormone receptors have recently been discovered. The retinoic acid receptors (RARs) and retinoid X receptors (RXRs) each have at least three types designated $\alpha,$ $\beta,$ and $\gamma,$ which are encoded by separate genes and expressed in a tissue and cell type-specific manner. We have been interested in the mechanism by which retinoids inhibit tumor cell proliferation and induce differentiation. As a model system we have employed several murine melanoma cell lines (S91-C2, K1735P, and B16-F1), which are sensitive to the growth-inhibitory and differentiation-inducing effects of RA, as well as a RA-resistant subclone of one of the cell lines (S91-C154), in order to study the role of the nuclear RARs in these effects. The initial phase of this project consisted of the characterization of the expression pattern of the three known RAR and RXR types in the murine melanoma cell lines in order to determine whether any differences exist which may elucidate a role for any of the receptors in RA-induced growth inhibition and differentiation. The novel finding was made that the RAR-$\beta$ gene is rapidly induced from undetectable levels by RA treatment at the mRNA and protein level, and that the induction of RAR-$\beta$ by other biologically active retinoids correlated with their ability to inhibit the growth of the highly RA-sensitive S91-C2 cell line. This suggests a role for RAR-$\beta$ in the growth inhibiting effect of retinoids. The second phase of this project involves the stable expression of RAR-$\beta$ in the S91-C2 cells and the RAR-$\beta$ receptor-null cell line, K1735P. These studies have indicated an inverse correlation between RAR-$\beta$ expression and proliferation rate. ^

Genes to blood pressure: The effects of variation in genes of the renin-angiotensin system on the hormonal and renal control of blood pressure

Objective. Essential hypertension affects 25% of the US adult population and is a leading contributor to morbidity and mortality. Because BP is a multifactorial phenotype that resists simple genetic analysis, intermediate phenotypes within the complex network of BP regulatory systems may be more accessible to genetic dissection. The Renin-Angiotensin System (RAS) is known to influence intermediate and long-term blood pressure regulation through alterations in vascular tone and renal sodium and fluid resorption. This dissertation examines associations between renin (REN), angiotensinogen (AGT), angiotensin-converting enzyme (ACE) and angiotensin II type 1 receptor (AT1) gene variation and interindividual differences in plasma hormone levels, renal hemodynamics, and BP homeostasis.^ Methods. A total of 150 unrelated men and 150 unrelated women, between 20.0 and 49.9 years of age and free of acute or chronic illness except for a history of hypertension (11 men and 7 women, all off medications), were studied after one week on a controlled sodium diet. RAS plasma hormone levels, renal hemodynamics and BP were determined prior to and during angiotensin II (Ang II) infusion. Individuals were genotyped by PCR for a variable number tandem repeat (VNTR) polymorphism in REN, and for the following restriction fragment length polymorphisms (RFLP): AGT M235T, ACE I/D, and AT1 A1166C. Associations between clinical measurements and allelic variation were examined using multiple linear regression statistical models.^ Results. Women homozygous for the AT1 1166C allele demonstrated higher intracellular levels of sodium (p = 0.044). Men homozygous for the AGT T235 allele demonstrated a blunted decrement in renal plasma flow in response to Ang II infusion (p = 0.0002). There were no significant associations between RAS gene variation and interindividual variation in RAS plasma hormone levels or BP.^ Conclusions. Rather than identifying new BP controlling genes or alleles, the study paradigm employed in this thesis (i.e., measured genes, controlled environments and interventions) may provide mechanistic insight into how candidate genes affect BP homeostasis. ^