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Biomedical subjects

N F Taylor

Publications and source records attributed to N F Taylor.

At least 55 records · Page 3Linked to original sources
PubMed1990

5 alpha-reductase deficiency without hypospadias.

A boy aged 4 with penoscrotal hypospadias and his brother aged 12 with micropenis had typical changes of homozygous 5 alpha-reductase deficiency. After three injections of chorionic gonadotrophin there was a trivial rise in plasma dihydrotestosterone with a normal increase in plasma testosterone. Urine steroid chromatography showed abnormally high 5 beta: 5 alpha ratios and 5 alpha-reductase activity was appreciably reduced in genital skin fibroblasts. The results indicate that 5 alpha-reductase deficiency is not invariably associated with genital ambiguity.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1988

Steroid profiling in the study of rat testicular steroidogenesis.

Twenty authentic steroids, derivatized as O-methyl oximes (MO), trimethylsilyl (TMS) ethers or as MO-TMS ethers have been subjected to capillary gas chromatography using two different columns. Virtually all of the steroid derivatives have been resolved, one difficult pair to separate being 5,16-androstadien-3 beta-ol and 5 alpha-androst-16-en-3 beta-ol on the non-selective phase OV-1. Where syn and anti forms of MO derivatives arose, these were also resolved under the conditions utilised. This technique of 'steroid profiling' has been applied to the separation and quantification of metabolites of pregnenolone which were formed during incubations of the microsomal and cytosolic fractions from rat testes. The majority of the metabolites were found in the microsomal incubation. These compounds included some odorous 16-androstenes as well as other C21 and C19 steroids, the formation of which was consistent with the 5-ene and 4-ene pathways of testosterone biosynthesis being operative. In addition, evidence was obtained for 16 alpha-hydroxylation of C21 steroids. Very much less metabolic activity was found in the cytosolic fraction of rat testes. Metabolic pathways have been proposed which both confirm and extend earlier work. We conclude that the rat testis can only form some of the odorous, possibly pheromonal, 16-androstenes and that these are quantitatively less important than in the porcine testis.

Animals↗
PubMed1987

Lesch-Nyhan syndrome: growth delay, testicular atrophy and a partial failure of the 11 beta-hydroxylation of steroids.

There is a failure of growth in hypoxanthine guanine phosphoribosyltransferase deficiency; slow weight gain is marked after the second year of age but is apparent in the birth weights of all eight of our patients for whom we have data. However, head growth and bone development are less affected than weight. A partial defect in the adrenocortical 11 beta-hydroxylation of steroids was demonstrated after ACTH stimulation in all four patients studied. This hydroxylation takes place in mitochondria the function of which is modulated by purine nucleotide concentrations; this may be the link with the enzyme defect. Testicular atrophy at autopsy was found in two pubertal age boys and seven patients aged 12-17 years had no signs of puberty. All five boys aged 3-11 years showed less than the normal mean response of plasma testosterone concentration to human chorionic gonadotrophin despite the normal histological appearance of the testes of one 6-year-old-boy. Follicle stimulating hormone responses to gonadotrophin releasing hormone are probably less than in normal in at least three of the seven prepubertal boys. The absence of the normally high activities of hypoxanthine guanine phosphoribosyltransferase in testes appears to inhibit their ability to respond to gonadotrophin.

Adolescent↗
PubMed1987

Adrenal status during the first month of life in mature and premature human infants.

Measurements of 17-hydroxyprogesterone (17-OHP) in blood collected onto filter paper after heel puncture by lancet and steroid metabolites in random collections of urine, were made in human infants born from 25 weeks of gestation onwards. The concentration of 17-OHP in blood eluted from filter paper samples was inversely related to both gestational age and birth weight. In mature infants, 17-OHP concentrations fell rapidly soon after birth, whereas concentrations remained high over the first month of life in infants born earlier than 33 weeks of gestation. Sulphated urinary steroids were identified as having a 3 beta-hydroxy-5-ene structure and although the pattern of excretion was similar in mature and premature infants, significantly higher concentrations were found in the premature group. Steroid metabolites normally present when concentrations of circulating 17-OHP are increased due to 21-hydroxylase deficiency were not detectable in urine samples collected from infants born prematurely. Where direct comparison of 17-OHP in blood spots and urinary steroid metabolites was possible, the concentrations of 17-OHP in blood samples paralleled 3 beta-hydroxy-5-ene steroid metabolites in urine. The results suggest that a circulating cross-reacting 3 beta-hydroxy-5-ene steroid may be responsible for increased concentrations of 17-OHP in infants born prematurely. Increased concentrations of both 17-OHP in blood spots and steroid sulphates in urine were associated with stress in premature, but not in more mature, infants suggesting that in infants born prematurely postnatal stress may delay adrenal maturation.

17-alpha-Hydroxyprogesterone↗
PubMed1986

Incorporation of 3-deoxy-3-fluoro-D-glucose into glycogen and trehalose in fat body and flight muscle in Locusta migratoria.

Flight muscle and fat body extracts from Locusta migratoria were incubated with D-[U-14C]-glucose or D-[3-3H]-3-deoxy-3-fluoroglucose and the products were analyzed. In the case of the latter compound, radio-chromatographic analysis yielded glycogen and trehalose fractions that were shown by 19F nuclear magnetic resonance to contain fluorine. Acid hydrolysis of these fractions liberated tritium labelled 3-deoxy-3-fluoro-D-glucose. In addition to the formation of "fluoroglycogen" and "fluorotrehalose" in these tissue extracts, there was an accumulation of tritium labelled fructose.

Adipose Tissue↗
PubMed1986

Abnormal steroid excretion in gestational trophoblastic disease complicated by ovarian theca-lutein cysts.

Serum and urine steroids were examined in two subjects with trophoblastic disease accompanied by large ovarian theca-lutein cysts and compared with those from 10 patients with trophoblastic disease but without palpable cysts. In the patients without cysts normal values were obtained for serum oestradiol, progesterone, 17 alpha-hydroxyprogesterone and androstenedione, and for urinary total oestrogens, pregnanediol, pregnanetriol, and 17-oxosteroids. Nineteen urinary steroid metabolites, quantified by capillary gas-liquid chromatography, were either within reference limits or marginally raised. In several cases relatively minor increases in serum testosterone and cortisol and urinary free cortisol were observed. In contrast, the subjects with cysts showed pronounced excesses of androgen metabolites, 17 alpha-hydroxypregnenolone, pregnanediol, and pregnanetriol, and both exhibited a similar pattern of unusual additional metabolites. The profiles superficially resembled those seen in 21-hydroxylase deficiency adrenogenital syndrome, but there were important discrepancies reflecting known differences in ovarian and adrenal steroid metabolism. Chemotherapy led to decline of human chorionic gonadotrophin concentrations, regression of the cysts, and return to normal of the steroid profile. Excess steroids in the patients with cysts may have originated in the ovary rather than in the trophoblastic tissue.

Adult↗
PubMed1986

L-malate transport and proton symport in vesicles prepared from Pseudomonas putida.

In vesicles from glucose-grown Pseudomonas putida, L-malate is transported by nonspecific physical diffusion. L-Malate also acts as an electron donor and generates a proton motive force (delta p) of 129 mV which is composed of a membrane potential (delta psi) of 60 mV and a delta pH of 69 mV. In contrast, vesicles from succinate-grown cells transport L-malate by a carrier-mediated system with a Km value of 14.3 mM and a Vmax of 313 nmol X mg protein-1 X min-1, generate no delta psi, delta pH, or delta p when L-malate is the electron donor, and produce an extravesicular alkaline pH during the transport of L-malate. A kinetic analysis of this L-malate-induced proton transport gives a Km value of 16 mM and a Vmax of 667 nmol H+ X mg protein-1 X min-1. This corresponds to a H+/L-malate ratio of 2.1. The failure to generate a delta p in these vesicles is considered, therefore, to be consistent with the induction in succinate-grown cells of an electrogenic proton symport L-malate transport system.

Biological Transport↗
PubMed1985

The active transport of 2-keto-D-gluconate in vesicles prepared from Pseudomonas purida.

The transport of 2-keto-D-gluconate (alpha-D-arabino-2-hexulopyranosonic acid; 2KGA) in vesicles prepared from glucose-grown Pseudomonas putida occurs by a saturable process with a Km of 110.0 +/- 2.9 microM and a Vmax. of 0.55 +/- 0.04 nmol X min-1 X (mg of protein)-1. The provision of phenazine methosulphate/ascorbate or L-malate leads to an accumulation of intravescular 2KGA, a decrease in the Km value to 50 +/- 2.1 microM and 35 +/- 2.9 microM respectively and no change in the Vmax. In the presence of electron donors the transport of 2KGA is inhibited by the respiratory poisons antimycin A, rotenone and the uncoupler 2,4-dinitrophenol. 2KGA transport is also competitively inhibited by 4-deoxy-4-fluoro-2-keto- or 3-deoxy-3-fluoro-2-keto-D-gluconate with Ki values of 50 microM and 160 microM respectively. The carrier system for 2KGA is repressed in vesicles from cells grown on succinate. Such vesicles transport 2KGA by non-specific physical diffusion with a Km value of infinity in the absence or presence of electron donors. Vesicles from glucose or succinate grown cells, in the presence of phenazine methosulphate/ascorbate at pH 6.6, generate a proton-motive force (delta p) of approx. 140 mV. The delta p, composed of proton gradient (delta pH) and a membrane potential (delta psi), is collapsed in the presence of dinitrophenol. Based on the results obtained with valinomycin, nigericin and carbonyl cyanide m-chlorophenylhydrazone, the active transport of 2KGA at pH 6.6 is coupled predominately to the delta pH component of delta p.

2,4-Dinitrophenol↗
PubMed1985

Gas chromatographic-mass spectrometric study of metabolites of C21 and C19 steroids in neonatal porcine testicular microsomes.

Microsomal fractions obtained from testes of 3-week-old piglets have been incubated, separately, with progesterone, 17-hydroxyprogesterone, 5-pregnene-3 beta,20 beta-diol, 16 alpha-hydroxypregnenolone, 5-androstene-3 beta,17 alpha-diol and dehydro-epiandrosterone. The metabolites, after derivatization, have been separated by capillary gas chromatography and identified by mass spectrometry. Quantification was by selected ion monitoring. Progesterone was shown to be 17-hydroxylated and also converted into 4,16-androstadien-3-one (androstadienone). The major metabolite of 17-hydroxyprogesterone was 4-androstene-3,17-dione (4-androstenedione), but little, if any, androstadienone was formed, indicating that this particular biosynthesis did not require 17-hydroxylation. The metabolites of 5-pregnene-3 beta, 20 beta-diol were found to be 17-hydroxypregnenolone, 3 beta-hydroxy-5,16-pregnadien-20-one (16-dehydropregnenolone) and 5,16-androstadien-3 beta-ol. Dehydroepiandrosterone and 5-androstene-3 beta,17 alpha-diol were interconvertible but neither steroid acted as a substrate for 16-androstene formation. However, dehydroepiandrosterone was metabolized to a small quantity of 4-androstenedione. Under the conditions used, no metabolites of 16 alpha-hydroxypregnenolone could be detected. The present results, together with those obtained earlier, indicate that the neonatal porcine testis has the capacity to synthesize weak androgens, mainly by the 4-en-3-oxo steroid pathway. Although 16-androstenes cannot be formed from C19 steroids, progesterone served as a substrate and may be converted directly to androstadienone, without being 17-hydroxylated first. The pathway to 5,16-androstadien-3 beta-ol, however, involves 17-hydroxypregnenolone and 16-dehydropregnenolone as intermediates.

17-alpha-Hydroxypregnenolone↗
PubMed1985

Prenatal diagnosis and variable presentation of recessive X-linked ichthyosis.

Three infants with X-linked ichthyosis have been observed following pregnancies in which placental sulphatase deficiency (PSD) was suggested prenatally by low oestrogen excretion and an abnormal urinary steroid excretion pattern. This was confirmed in two cases by the absence of placental enzyme activity. In one case labour was spontaneous but all deliveries required Caesarean section. At 8 months the first infant showed an eczema in an atopic distribution but when seen at 5 years had typical X-linked ichthyosis. The skin of the second child peeled extensively at the age of 2 days but was not troublesome for 2 years, when ichthyosis vulgaris was diagnosed on clinical grounds. This pattern has persisted for 3 years. The third infant showed a mildly scaly skin in the neonatal period but at 3 months the features and distribution of X-linked ichthyosis were apparent. X-linked ichthyosis may have a variable presentation which is not always apparent at birth.

Adult↗
PubMed1984

The use of steroid profiling in the resolution of pregnenolone metabolites from porcine testicular preparations.

The behaviour of 22 steroids has been examined by capillary gas chromatographic profiling, and the identities of the steroids confirmed by mass spectrometry and their relative retention times. Five pairs of steroids have been separated: 5 alpha-androstane-3 alpha,17 beta- and -3 beta,17 beta-diols; 5-androstene-3 beta,17 alpha- and -3 beta,17 beta-diols; pregnenolone and 3 beta-hydroxy-5,16-pregnadien-20-one; progesterone and 4,16-pregnadiene-3,20-dione; 17-hydroxypregnenolone and 5-pregnene-3 beta,20 beta-diol. 5 alpha-Androst-16-en-3 beta-ol and 5,16-androstadien-3 beta-ol (as trimethylsilyl-, tert.-butyl-dimethylsilyl- and chloromethyldimethylsilyl ethers) were only partially resolved but could be well separated on thin-layer plates of Kieselgel that had previously been dipped in AgNO3 solution. The profiling method was successfully applied to the separation of pregnenolone and its metabolites in porcine testicular incubation extracts.

Animals↗
PubMed1984

Identification of 16-dehydropregnenolone as an intermediate in 16-androstene biosynthesis in neonatal porcine testicular microsomes.

The biosynthesis of 16-androstenes has been studied in neonatal porcine testicular microsomes using 17-hydroxypregnenolone and 16-dehydropregnenolone, separately, as substrates. The metabolites formed after microsomal incubation with these substrates were purified, derivatized as O-methyloxime-trimethylsilyl ethers and analysed by capillary gas chromatography-mass spectrometry. In the incubation of 17-hydroxypregnenolone with microsomes, 16-dehydropregnenolone was identified as an intermediate in the biosynthesis of 16-androstenes. Further microsomal incubation of 16-dehydropregnenolone has established the intermediary role of this steroid in the production of 16-androstenes.

17-alpha-Hydroxypregnenolone↗
PubMed1984

Intermediates in 16-androstene biosynthesis in neonatal porcine testis.

The metabolism of pregnenolone has been studied in microsomal preparations of testes from 3-week old piglets. Metabolites identified after derivatization by capillary gas-chromatography and further by combined gas chromatography-mass spectrometry were: 17-hydroxy- and 16 alpha-hydroxypregnenolone, dehydroepiandrosterone, 5-androstenediols, 5-pregnenediol and andien-beta. Pregnenolone and 16-dehydro-pregnenolone, previously not separable by other methods, were successfully resolved as methyl oximetrimethylsilyl ethers using capillary column gas-chromatography.

Androstenes↗
PubMed1984

Steroid biochemistry of virilising adrenal tumours in childhood.

Steroid excretion in urine of 12 infants with virilising adrenal tumours has been determined using gas chromatography. In six children, (Group A, five female, one male) aged 2.8-5.3 years, very high urinary excretions of 17 oxosteroids (greater than 40 mumol/24 h) were largely accounted for by dehydroepiandrosterone (DHA). In one of the girls, the pattern of steroids excreted in urine was similar to that of newborn infants, with high excretions of 16-oxygenated derivatives of DHA. The histology of this tumour suggested a neoplasia of fetal-type adrenocortical cells. Very large tumours were found in three of the infants, two of whom have died and one has multiple metastases. From the other three children, small, well-encapsulated adenomas were successfully removed. Six children (Group B), had moderately elevated 17-oxosteroid excretions (8-17 mumol/24 h). In five of these cases (four female, one male) aged 0.8-5 years, 11 beta-hydroxyandrosterone was a consistently prominent urinary steroid. In one boy, aged 7.7 years, 17-oxosteroid excretion was 15 mumol/24 h and the major steroids in urine were metabolites of pregnenolone. These six children have survived with no clinical evidence of recurrent tumour. The in vivo functional activities of the tumours can be deduced from the different profiles of steroids in urine. These have revealed heterogeneous patterns of steroid biosynthesis.

17-Ketosteroids↗
PubMed1984

A simple DHEAS loading test in the antepartum diagnosis of placental sulphatase deficiency.

The accurate antenatal diagnosis of placental sulphatase deficiency (PSD) is essential if this condition is to be distinguished from others in which levels of oestrogen are low. In this study we have evaluated a simple protocol determining the serum oestradiol response to 50 mg of dehydroepiandrosterone sulphate (DHEAS) given intravenously to twelve women with low serum or urinary oestrogens. Seven of the women had PSD confirmed by other means, the remaining five had other reasons for the low oestrogen levels. In affected pregnancies the rise in oestradiol was lower, the peak occurred earlier and the level fell towards baseline at 60 min. In the unaffected women, timing of the peak value was not consistent and there was no trend towards basal values at 60 min. There was clear discrimination between the two groups at all times after the injection, but the separation was greater at 60 min.

Dehydroepiandrosterone↗
PubMed1983

The fetus determines circadian oscillation of myometrial electromyographic activity in the pregnant rhesus monkey.

Uterine electromyographic activity in the pregnant rhesus monkey showed two types of episodic electrical events, defined on the basis of duration of the episodes. One of these (designated type I in this report) was characterized by frequent bursts of electrical activity that lasted from 0.5 to 1.2 minutes (mean duration, 0.64 +/- 0.007 [SE] minutes) and occurred at frequencies of 10 to 45 per hour. The other type of electromyographic activity observed (type II) consisted of fragmented series of discharges that lasted 2 to 15 minutes (mean duration, 5.45 +/- 0.12 [SE] minutes) and occurred at frequencies of 0 to 6 per hour. The frequency of type I electromyographic events showed a circadian pattern of low amplitude with a maximum at night in animals with minimal uterine manipulation (electrodes only). This daily pattern was amplified during the 8 to 10 days that preceded delivery. Hysterotomy and fetal catheterization induced a circadian increase in the frequency of type I electromyographic events akin to that observed during the predelivery period. Fetal death abolished the high-amplitude circadian variation of type I electromyographic events both postoperatively and in the predelivery period. These data indicate that the fetus plays a role in the regulation of uterine type I electromyographic activity in the rhesus monkey.

Amnion↗