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C J Kenyon

Publications and source records attributed to C J Kenyon.

At least 37 records · Page 2Linked to original sources
PubMed1998

Glucocorticoid receptor polymorphism, skin vasoconstriction, and other metabolic intermediate phenotypes in normal human subjects.

Genetic variation of the glucocorticoid receptor (GR) locus is associated with differences in blood pressure. To define the intermediate phenotypes associated with this variation, we investigated the biochemical and clinical significance of a BclI restriction fragment length polymorphism of the GR locus in 64 normal male volunteers. Blood samples were genotyped as either AA (homozygous large allele; n = 6), Aa (heterozygous; n = 51), or aa (homozygous small allele, n = 7). Four primary glucocorticoid variables were measured including GR binding characteristics and glucocorticoid-sensitive lysozyme release of leukocytes in vitro and the blanching response of forearm skin to budesonide. A large number of secondary variables (urinary and plasma steroid measurements, blood pressure and indices of body fat metabolism, and routine biochemical and hematological measurements) were also considered. In vivo sensitivity to budesonide was greater in AA than aa individuals (mean +/- SE EC50 values: 13 +/- 5 and 42 +/- 10 ng; P < 0.01). In contrast, leukocytes of AA subjects tended to have lower affinity and reduced sensitivity for dexamethasone, although these effects were not statistically significant. Based on urinary steroid measurements, 11 beta-hydroxysteroid dehydrogenase activity [ratio of tetrahydrocortisol (THF) to tetrahydrocortisone (THE) metabolites] was not affected by genotype. The relative activities of 5 alpha- and 5 beta-reductase activity (allo-THF/THF + THE) appeared lower in AA than aa subjects (0.22 +/- 0.04 cf. 0.33 +/- 0.06; P < 0.005) but were not judged to be significantly different when corrected for multiple comparisons. Single and multivariate analyses were carried out to determine which variables influence GR binding characteristics and glucocorticoid responsiveness and to see whether cardiovascular risk factors (blood pressure and body fat) were influenced by glucocorticoid-dependent functions. Only 15-20% of the variations in the dissociation constant (Kd) and maximum binding capacity (Bmax) were influenced by other variables; plasma cholesterol was the most important for affinity and plasma sodium concentration for binding capacity. Multivariate analysis showed that several factors including GR genotype and urinary cortisol account for 10% of the variation of in vivo responses to glucocorticoid hormones; plasma calcium concentration was the only variable that contributed to in vitro sensitivity of leukocytes to dexamethasone. Glucocorticoid-dependent responses were of negligible importance in determining blood pressure or percentage body fat within the narrow physiological ranges of the present study. We conclude that GR genotype affects steroid sensitivity in a tissue-specific manner because of altered GR function or possibly because of linkage to a locus that controls hormone access to the receptor by influencing steroid metabolism.

Adipose Tissue↗
PubMed1998

Glucocorticoid receptor polymorphism in genetic hypertension.

The Milan hypertensive strain of rat (MHS) displays abnormalities in both renal function and adrenocortical activity. While the pressor role of the former has been studied in detail, the role of the latter has not yet been clearly evaluated. In the present study, glucocorticoid receptor (GR) binding characteristics in liver cytosol from adult MHS and Milan normotensive controls (MNS) have been investigated. Dexamethasone, aldosterone and corticosterone were bound with lower affinity to cytosol of MHS rats compared with that of MNS rats. This pattern of binding could explain the raised plasma corticosterone concentrations and adrenocortical hypertrophy previously noted in MHS. The coding sequence of MHS and MNS GR genes have been determined. The MHS gene differed in four respects from that of MNS: three silent point mutations and a polymorphic microsatellite region in exon 2. The latter polymorphism has been used in cosegregation studies of F2 hybrids of MHS x MNS. The MHS GR genotype was associated with hypercalciuria and lower blood pressure in female rats and lower body weight in male rats. Although the effect on blood pressure is small, it is consistent with the affinity data. MHS GR genotype cosegregated with lower blood pressure in F2 rats and displayed a lower affinity in binding studies. In conclusion, GR polymorphism may be responsible for differences of adrenocortical function between MHS and MNS. This may lead to a reduction in the blood pressure difference between the two strains.

Animals↗
PubMed1998

The effects of static charge in spacer devices on glucocorticosteroid aerosol deposition in asthmatic patients.

Electrostatic charge in plastic spacer devices has been shown in vitro to reduce delivery of asthma medications intended for inhalation, but the effect of static charge on in vivo drug deposition is unknown. A six-way randomized crossover study was conducted in 10 mild asthmatic patients. Two plastic spacers (Nebuhaler and Volumatic) and one metal spacer (Nebuchamber) were tested. The spacers were used either "primed" or "unprimed". Priming was performed by firing 20 doses of placebo aerosol into a new spacer, hence coating the inner surface with surfactant and minimizing static charge. Unprimed spacers were new and were not treated. Pressurized aerosol canisters delivering budesonide (200 microg Pulmicort) were radiolabelled with the radionuclide 99mTc and lung deposition was measured by gamma scintigraphy. The radiolabel was shown to be a valid marker for the drug substance prior to the clinical phase of the study. Priming significantly increased mean whole lung deposition following inhalation from plastic spacers (Nebuhaler primed 37.7% and unprimed 26.7%, p=0.01; Volumatic primed 32.0% and unprimed 22.1%, p=0.02). Priming had no effect on the mean whole lung deposition following inhalation from the Nebuchamber (primed 33.5% and unprimed 32.9%). Lung deposition in vivo from plastic spacer devices will vary according to the electrostatic charge on the spacer walls. Priming reduces retention of drug on plastic spacer devices and increases lung deposition. Metal spacers are not susceptible to static charge, which should result in more predictable lung deposition.

Administration, Inhalation↗
PubMed1997

Role of a new Rho family member in cell migration and axon guidance in C. elegans.

Rho family GTPases are thought to regulate actin-dependent processes, but their functions in vivo are still poorly understood. We have investigated the function of a new, widely expressed Rho family member in C. elegans by analyzing mutations in the endogenous gene. Activated and null alleles all inhibit cell migration, demonstrating that this protein is required for cell migration in vivo. Only a small subset of the migrations inhibited by activating mutations are inhibited by null mutations, suggesting that considerable functional redundancy exists within this system. Our findings support this conclusion and show that mig-2 functions redundantly with another pathway to regulate nuclear migration. Surprisingly, activated alleles also cause misguided axon growth, suggesting that Rho family GTPases may couple guidance cues to process outgrowth.

Alleles↗
PubMed1997

In vivo and in vitro effects of carbenoxolone on glucocorticoid receptor binding and glucocorticoid activity.

Carbenoxolone potentiates the mineralocorticoid activity of endogenous glucocorticoid hormones by inhibiting the enzyme 11 beta-hydroxysteroid dehydrogenase, which converts cortisol and corticosterone to inactive 11-oxo-derivatives. We addressed the question of whether glucocorticoid activity is also affected by carbenoxolone. Using a rat model involving low dose corticosterone treatment, we found that carbenoxolone neither potentiated nor inhibited the modest increases in blood pressure or reductions in weight gain caused by steroid treatment. Other indices of glucocorticoid activity including white blood cell number, thymus weight, and down regulation of the glucocorticoid receptor were unaffected. In vitro studies with liver and kidney cytosol preparations indicated that carbenoxolone did compete for 3H-dexamethasone binding sites. Carbenoxolone was 5-10 times more effective than glycyrrhetinic acid, 20-30 thousand times less effective than dexamethasone, and is therefore, approximately 1000 times less effective than corticosterone. Analysis of dexamethasone-binding curves indicated a single class of receptor. We conclude that carbenoxolone at the dose tested does not have intrinsic glucocorticoid activity in vivo, nor does it modulate the activities of corticosterone. Carbenoxolone binds weakly to the glucocorticoid receptor. It is not clear whether this weak affinity accounts for some or any of the direct in vitro effects of high concentrations of carbenoxolone that others have described.

Animals↗
PubMed1997

The use of scintigraphy to provide "proof of concept" for novel polysaccharide preparations designed for colonic drug delivery.

PURPOSE: The aim of the present study was to provide "proof of concept" data in man for novel polysaccharide preparations designed for colonic drug delivery using gamma scintigraphy. METHODS: Two placebo calcium pectinate matrix tablet formulations were studied: one contained calcium pectinate and pectin (CaP/P) and was designed to rapidly disintegrate in the ascending colon, the other contained calcium pectinate and guar gum (CaP/GG) and was designed to disintegrate more slowly, releasing its contents throughout the ascending and transverse colon. Both formulations were enteric coated in order to protect them from the stomach. Ten healthy volunteers received either a CaP/P or CaP/GG tablet, in a randomised cross-over study. Transit and disintegration of the radiolabelled formulations was followed by gamma scintigraphy. Rat studies were conducted in order to verify that the expected colonic degradation of the polysaccharide formulations was as a consequence of bacterial enzyme attack. RESULTS: The in vivo clinical study confirmed the results obtained in the rat and bench in vitro fermentation models; complete tablet disintegration for Formulation CaP/GG appeared to be slower than that of Formulation CaP/P and the time and the location of complete tablet disintegration was more reproducible with Formulation CaP/P compared to Formulation CaP/GG. CONCLUSIONS: These results provide "proof of concept" data for the use of calcium pectinate preparations for drug delivery to the colon and highlight the value of scintigraphy in focusing the development strategy for colonic targeting preparations.

Adult↗
PubMed1997

Spreading and retention of vaginal formulations in post-menopausal women as assessed by gamma scintigraphy.

PURPOSE: In this paper we report on the first scintigraphic evaluation of vaginal dosage forms in post-menopausal women. To date, almost nothing is known about the in vivo performance of pharmaceutical formulations in the human vagina, which is a major deficiency in the rational design of drug delivery systems for both existing and new indications. METHODS: The vaginal spreading and clearance of a radiolabelled pessary formulation and Replens (polycarbophil) gel, was assessed in six healthy, post-menopausal female volunteers over a six hour period using the technique of gamma scintigraphy. RESULTS: In five out of the six subjects studied, clearance of the two formulations exhibited very little intra-subject variation. However, there was considerable inter-subject variability in clearance; in Subject 5 circa 80% of the products were retained whilst in Subject 2 less than 2% was present at the end of the six hour imaging period. Importantly, there was no evidence to suggest that either of the formulations dispersed material beyond the cervix, into the uterus, in any of the subjects studied. CONCLUSIONS: The lack of significant retention of these products in most of the volunteers has obvious implications for the delivery of therapeutic agents. This study shows that gamma scintigraphy is an invaluable technique with which to assess novel formulations aimed at optimising retention in the vagina for topical or systemic drug delivery.

Administration, Intravaginal↗
PubMed1997

Platelet sodium/hydrogen ion exchange in normal pregnancy and non-proteinuric pre-eclampsia.

In non-pregnant individuals, abnormalities in cation transport in vascular tissues have been linked to essential hypertension. In the present study, we consider whether Na+/H+ exchange (NHE) is affected in non-proteinuric pre-eclampsia (NPP). Platelet NHE characteristics and plasma cholesterol were measured in a cross-sectional study of normal primigravidae at 14 +/- 0.5 (n = 9), 29 +/- 0.7 (n = 7), 39 +/- 0.4 (n = 8) weeks gestation, in women with NPP (n = 15) and in non-pregnant women (n = 8). Amiloride-sensitive 22Na uptake was measured in platelets which had been acid loaded, to stimulate NHE, by suspension in isotonic potassium propionate buffer (pH 6.7). Intraplatelet radioactivity was used to calculate the affinity (Km) and the capacity (Vmax) of Na+ uptake. In normotensive women, Vmax (mean +/- s.e.) at 14, 29, 39 weeks gestation and 6 weeks postpartum were 452 +/- 46, 469 +/- 33, 713 +/- 101 and 562 +/- 77 pmolNa+/10(6) cells/min respectively; the third trimester values were higher (P < 0.05) than those in the first and second trimester and were also higher than those of non-pregnant women (415 +/- 20). Vmax of patients with NPP in the third trimester (712 +/- 44) was not different from gestational age-matched controls. Km values were not affected by gestational age or NPP. Plasma cholesterol concentration was positively correlated with Vmax values during normotensive pregnancy (r = 0.493, P < 0.05). In conclusion, the capacity for amiloride-sensitive Na+ uptake by platelets correlates positively with gestational age during normal pregnancy. However, neither the capacity nor affinity for Na+ was altered in NPP platelets suggesting that NHE is not implicated in the pathophysiology of this condition.

Adult↗
PubMed1997

Colonic delivery of dexamethasone: a pharmacoscintigraphic evaluation.

BACKGROUND: Colonic delivery of corticosteroids may reduce the side-effects commonly associated with their use. Therefore, we tested the ability of the naturally occurring polysaccharide guar gum to deliver a corticosteroid, dexamethasone, to the colon using pharmacoscintigraphy. Guar gum is metabolized in the colon by resident bacterial enzymes to trigger drug release. MATERIALS: Each subject (eight per group, parallel study design) was administered one of four dexamethasone (9 mg) tablet formulations, radiolabelled with 153Sm using neutron activation, under fasted conditions. One formulation was designed to release drug rapidly following ingestion while the other three formulations were designed to delay release of dexamethasone to varying degrees. Progression of the formulations down the gastrointestinal tract was followed by gamma scintigraphy. Serum concentrations were measured over time to relate disintegration profiles of the tablets with pharmacokinetic observations. RESULTS: The immediate release formulation disintegrated in the stomach, on average, within 20 min of dosing. One of the three delayed release preparations (CD1) began to disintegrate in the small intestine 1.7 +/- 1.0 h after dosing. The second and third delayed release preparations (CD2 and CD3) did not begin to disintegrate until 5.8 +/- 2.3 and 3.6 +/- 1.6 h after dosing, respectively. All three colonic delivery preparations completely disintegrated in the colon ranging from 7.8 +/- 2.7 h (CD1) to 12.4 +/- 3.2 h (CD2) following oral administration. Pharmacoscintigraphic data indicated that 72-82% of the dexamethasone was delivered into the colon although not all the dexamethasone delivered into the colon was absorbed. CONCLUSIONS: Simple guar gum formulations are capable of delivering the corticosteroid dexamethasone to the colon of normal subjects. Locally delivered corticosteroids may be useful in the treatment of ulcerative colitis and Crohn's disease. Pharmacoscintigraphic evaluation is a useful method to discriminate between the in vivo behaviour of colonic delivery systems.

Adult↗
PubMed1997

Analysis of phenotypic consequences of renin gene polymorphism in Lyon rats.

OBJECTIVE: To investigate phenotypic consequences of renin gene polymorphism between Lyon hypertensive (LH) and normotensive (LN) rats because previously we demonstrated cosegregation of the LH allele with increased blood pressure in a cross of LH with LN rats. DESIGN: Two studies were conducted. Study 1 used a cohort of male F2 rats from a LH x LN cross. Eighty-two rats homozygous for the hypertensive (HH) renin gene allele were compared with 82 rats homozygous for the normotensive (NN) allele. Urinary steroid excretion was measured in 24 h urine samples collected from rats aged 6 weeks. The direct aortic blood pressure was recorded in 30-week-old rats and, after they had been killed, their kidney renin concentration (KRC) was measured. In study 2, renin, angiotensinogen and angiotensin converting enzyme plasma concentrations and renin messenger RNA (mRNA) levels were measured in renal and extra-renal tissues from 6- and 25-week-old LH and LN parental and HH and NN F2 male rats. METHODS: Urinary steroids and plasma components of the renin-angiotensin system (RAS) were measured using specific radioimmunoassays. mRNA levels were quantified by northern blotting. RESULTS: In study 1, HH F2 rats had a higher blood pressure (151.5 +/- 8.2 versus 146.0 +/- 7.4 mmHg, P < 0.001) and a lower KRC (514 +/- 203 versus 666 +/- 304 micrograms A1/h per g cortex, P < 0.01) than did NN rats aged 30 weeks. In covariate analysis the decrease in KRC in HH rats was attributable to their increased blood pressure rather than to the renin genotype. The renin genotype of rats aged 6 weeks was not associated with a change in the urinary excretion of aldosterone, desoxycorticosterone, corticosterone or 18-hydroxy desoxycorticosterone. In study 2, we found no difference either in plasma levels of RAS components or in renal or extrarenal renin mRNA levels either between parental LH and LN rats or between HH and NN F2 rats apart from a higher plasma renin concentration in LH rats aged 6 weeks. Renal, but not extra-renal, renin mRNA levels declined with age. CONCLUSIONS: We found no evidence of a renin genotype-dependent phenotypic difference in the RAS that could account for the effect of the renin locus on blood pressure in Lyon rats. Our findings suggest that the effect of the locus on blood pressure might be due to an as yet unidentified gene linked to renin.

Animals↗
PubMed1997

Impaired cortisol binding to glucocorticoid receptors in hypertensive patients.

We compared glucocorticoid receptor binding characteristics and glucocorticoid responsiveness of human mononuclear leukocytes (HML) from hypertensive patients and matched normotensive volunteers. We also considered associations of these variables with plasma renin activity, aldosterone, cortisol, corticotropin, and electrolyte concentrations. We calculated binding affinity (Kd; nmol/L) and capacity (Bmax; sites/cell) for dexamethasone and cortisol from homologous and heterologous competition curves for specific [3H]dexamethasone binding sites on HML isolated from the blood of normotensive volunteers and subjects with essential hypertension. Glucocorticoid responsiveness of HML was evaluated as IC50 values (nmol/L) for dexamethasone and cortisol for the inhibition of lysozyme release. We measured plasma hormones by radioimmunoassay. Kd values (mean+/-SE) for cortisol in HML of hypertensive patients were higher than in control subjects (24.6+/-2.4 versus 17.5+/-1.7 nmol/L, P<.04). Binding capacity (4978+/-391 versus 4131+/-321 sites/cell), Kd values for dexamethasone (6.7+/-0.5 versus 5.7+/-0.3 nmol/L), and IC50 values for dexamethasone (3.4+/-0.3 versus 3.1+/-0.2 nmol/L) and cortisol (12.2+/-1.6 versus 9.5+/-0.3 nmol/L) were not significantly different. Patients with renin values less than 0.13 ng angiotensin I/L per second were markedly less sensitive to cortisol than those with higher values. Both Kd (30.3+/-2.5 versus 19.2+/-2.4 nmol/L) and IC50 values (15.5+/-1.8 versus 8.9+/-1.2 nmol/L) for cortisol were significantly higher in patients with lower renin values (P<.03). Other variables, including plasma hormone and electrolyte values and binding characteristics for dexamethasone, were not different. These data suggest that cortisol binding to glucocorticoid receptor is slightly impaired in patients with essential hypertension. In vivo, this could lead to inappropriate binding of cortisol to mineralocorticoid receptors. Hence, decreased sensitivity to cortisol is associated with renin suppression. This hypothesis is supported by evidence of hypertension and low renin activity, which others have described in patients with primary glucocorticoid resistance due to mutations of the glucocorticoid receptor.

Adult↗
PubMed1997

The role of lin-22, a hairy/enhancer of split homolog, in patterning the peripheral nervous system of C. elegans.

In C. elegans, six lateral epidermal stem cells, the seam cells V1-V6, are located in a row along the anterior-posterior (A/P) body axis. Anterior seam cells (V1-V4) undergo a fairly simple sequence of stem cell divisions and generate only epidermal cells. Posterior seam cells (V5 and V6) undergo a more complicated sequence of cell divisions that include additional rounds of stem cell proliferation and the production of neural as well as epidermal cells. In the wild type, activity of the gene lin-22 allows V1-V4 to generate their normal epidermal lineages rather than V5-like lineages. lin-22 activity is also required to prevent additional neurons from being produced by one branch of the V5 lineage. We find that the lin-22 gene exhibits homology to the Drosophila gene hairy, and that lin-22 activity represses neural development within the V5 lineage by blocking expression of the posterior-specific Hox gene mab-5 in specific cells. In addition, in order to prevent anterior V cells from generating V5-like lineages, wild-type lin-22 gene activity must inhibit (directly or indirectly) at least five downstream regulatory gene activities. In anterior body regions, lin-22(+) inhibits expression of the Hox gene mab-5. It also inhibits the activity of the achaete-scute homolog lin-32 and an unidentified gene that we postulate regulates stem cell division. Each of these three genes is required for the expression of a different piece of the ectopic V5-like lineages generated in lin-22 mutants. In addition, lin-22 activity prevents two other Hox genes, lin-39 and egl-5, from acquiring new activities within their normal domains of function along the A/P body axis. Some, but not all, of the patterning activities of lin-22 in C. elegans resemble those of hairy in Drosophila.

Amino Acid Sequence↗
PubMed1996

Genes affecting sensitivity to serotonin in Caenorhabditis elegans.

Regulating the response of a postsynaptic cell to neurotransmitter is an important mechanism for controlling synaptic strength, a process critical to learning. We have begun to define and characterize genes that may control sensitivity to the neurotransmitter serotonin in the nematode Caenorhabditis elegans by identifying serotonin-hypersensitive mutants. We reported previously that mutations in the gene unc-2, which encodes a putative calcium channel subunit, result in hypersensitivity to serotonin. Here we report that mutants defective in the unc-36 gene, which encodes a homologue of a calcium channel auxiliary subunit, are also serotonin-hypersensitive. Moreover, the unc-36 gene appears to be required in the same cells as unc-2 for control of the same behaviors. Mutations in several other genes, including unc-8, unc-10, unc-20, unc-35, unc-75, unc-77, and snt-1 also result in hypersensitivity to serotonin. Several of these mutations have previously been shown to confer resistance to acetylcholinesterase inhibitors, suggesting that they may affect acetylcholine release. Moreover, we found that mutations that decrease acetylcholine synthesis cause defective egg-laying and serotonin hypersensitivity. Thus, acetylcholine appears to negatively regulate the response to serotonin and may participate in the process of serotonin desensitization.

Acetylcholine↗
PubMed1996

Corticosteroids in essential hypertension: multiple candidate loci and phenotypic variation.

1. The role of genetically determined changes in adrenal steroid production, metabolism and action in the pathogenesis of cardiovascular disease in man is considered by studying three loci that are important in corticosteroid function. 2. Variation at the glucocorticoid receptor locus can be identified as a biallelic restriction fragment length polymorphism (Bcl1); subjects with contrasting genotypes show altered skin vasoconstrictor responses to topically applied budesonide without any significant change in leucocyte receptor binding characteristics. 3. In a case control study of patients with essential hypertension, we have shown evidence of reduced 11 beta-hydroxysteroid dehydrogenase activity, with an elevated ratio of cortisol to cortisone metabolites in urine. 4. The genes encoding 11 beta-hydroxylase and aldosterone synthase are highly homologous. Studies in the Milan hypertensive rat show variation at this locus, which may account for the increased steroid synthesis noted in the hypertensive strain; in man, a chimaeric gene comprising 5' regulatory regions from 11 beta-hydroxylase and 3' coding sequence from aldosterone synthase accounts for the autosomal dominant condition Dexamethasone Suppressible Hyperaldosteronism. Variation in the precise location of the crossover site between the two genes does not account for the observed phenotypic heterogeneity in this condition. 5. Measurement of basal plasma steroid levels in subjects with essential hypertension show an increased ratio of 11-deoxycortisol/cortisol, consistent with reduced activity of 11 beta-hydroxylase in the zona fasciculata. 6. In summary, three loci involved in corticosteroid synthesis, metabolism and action can independently affect cardiovascular phenotypes; their roles in determining pathophysiological changes, including hypertension, remain to be studied.

Adrenal Cortex Hormones↗
PubMed1996

Control of cell proliferation in the rat adrenal gland in vivo by the renin-angiotensin system.

Adrenal cytogenesis was investigated in response to 1) subcutaneous infusions of angiotensin (ANG) II (200 ng.kg-1.min-1); 2) high and low sodium intake; and 3) captopril treatment (10 mg.kg-1.day-1). Cell proliferation was assessed as uptake of 5-bromo-2'-deoxyuridine (BrdUrd) into nuclei. BrdUrd, infused continuously throughout 2 wk of treatment, was detected immunocytochemically. ANG II and sodium restriction caused hypertrophy of the zona glomerulosa with two- to threefold increases in BrdUrd indexes. After captopril, the glomerulosa appeared atrophied with pyknotic nuclei, but the BrdUrd index was unchanged. Zonae intermedia and fasciculata were unaffected by any treatment. Zona reticularis epithelial cells proliferated in response to ANG II and sodium restriction but were unaffected by captopril. In the medulla, captopril increased BrdUrd uptake, whereas ANG II, but not low sodium, caused a decrease. In conclusion, 1) proliferation of the glomerulosa and reticularis cells is specifically controlled by ANG II, 2) captopril may cause glomerulosa cells to die, and 3) blood pressure may control proliferation of the medulla.

Adrenal Glands↗