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Biomedical subjects

A T Kicman

Publications and source records attributed to A T Kicman.

At least 19 recordsLinked to original sources
PubMed2004

Depot testosterone with etonogestrel implants result in induction of azoospermia in all men for long-term contraception.

BACKGROUND: Combined testosterone and progestogen preparations are a promising approach to male hormonal contraception. We investigated the effect of s.c. etonogestrel with depot testosterone on spermatogenesis in normal men over a period of 48 weeks. METHODS: Fifteen healthy men received three s.c. 68 mg etonogestrel implants. Testosterone pellets (400 mg) were administered at 12 weekly intervals. RESULTS: Nine men completed 48 weeks of treatment. Four subjects chose to discontinue after 6 months, one man withdrew from the study early for personal reasons and one was withdrawn due to illness. Sperm concentrations of <1 x 10(6)/ml were achieved in all men by 16 weeks of treatment. All men became azoospermic, although the time to achieve this varied from 8 to 28 weeks. Azoospermia was maintained in eight of the nine men treated for 48 weeks, one subject showing partial recovery from 40 weeks. Testosterone levels remained in the physiological range throughout. Treatment did not result in weight gain, change in body composition or decline in high-density lipoprotein cholesterol concentrations. CONCLUSIONS: The combination of three etonogestrel implants with depot testosterone results in rapid and consistent suppression of spermatogenesis. This can be maintained for up to 1 year and may therefore be a suitable approach for a long-acting male hormonal contraceptive.

Adolescent↗
PubMed2003

Identification of post-translational modifications resulting from LHbeta polymorphisms by matrix-assisted laser desorption time-of-flight mass spectrometric analysis of pituitary LHbeta core fragment.

Metabolism of the human chorionic gonadotrophin (hCG)- and LHbeta-subunits (hCGbeta, LHbeta) terminates with the urinary excretion of core fragment (hCGbetacf, LHbetacf) molecules that retain antigenic shape and constituent N-linked carbohydrate moieties. We have previously demonstrated the resolved mass spectra of hCGbetacf, from which the carbohydrate moieties present at two N-linked glycosylation sites were identified. LHbetacf was subjected to the same mass spectrometric analysis. As LHbeta shares 82% homology with hCGbeta but possesses only one glycosylation consensus site a simpler spectral fingerprint of LHbetacf glycoforms was expected. LHbetacf was reduced with dithiothreitol and analysed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Glycoforms were predicted by subtracting the peptide mass from the m/z values of the observed peaks and then sequentially subtracting the masses of the monosaccharide residues of hCGbeta N-linked carbohydrates reported in the literature. The mass spectra of LHbetacf revealed a broad single peak ranging from m/z 8700 to 10 700. Following reduction, this peak was replaced by a set of partially resolved peaks between m/z 4130 and 5205 corresponding to glycosylated forms of the peptide LHbeta6-40. A peak at m/z 4252.2 corresponded to the non-glycosylated peptide LHbeta55-93. Remaining peaks indicated that the pooled sample comprised a wide set of glycoforms, contained LHbetacf with two N-linked carbohydrate moieties and indicated evidence of further glycosylation due to amino acid substitution in polymorphic variants. This is evidence that a single nucleotide polymorphism alters the post-translational modification of a protein and hence its structural phenotype.

Carbohydrate Conformation↗
PubMed2002

Oral desogestrel with testosterone pellets induces consistent suppression of spermatogenesis to azoospermia in both Caucasian and Chinese men.

BACKGROUND: Effective hormonal male contraception requires a high prevalence of spermatogenic suppression, which has proved particularly difficult in Caucasian populations. We have investigated the combination of oral desogestrel with depot testosterone in Caucasian and Chinese men. METHOD: Thirty men in Edinburgh and 36 men in Shanghai received 150 or 300 microg desogestrel p.o. daily for 24 weeks with 400 mg testosterone pellets s.c. on day 1 and at 12 weeks. RESULTS: Eight men withdrew before completing 24 weeks treatment. Testosterone concentrations remained within the normal range. Spermatogenesis was profoundly suppressed in all men. Azoospermia was achieved by a higher proportion of men in the 300 microg desogestrel group: 28/28 men versus 22/31 men (P < 0.05). All Caucasian men in the 150 microg group achieved sperm concentrations of < 1 x 10(6)/ml whereas three men in the Shanghai group maintained sperm concentrations of > 3 x 10(6)/ml. Fifteen men continued on this regimen for a subsequent 24 weeks: all remained azoospermic for the duration of treatment. High-density lipoprotein cholesterol fell by 15% in Caucasian men, but was unchanged in the Chinese men; both groups showed some weight gain. CONCLUSION: This combination of oral desogestrel with depot testosterone maintains physiological testosterone concentrations with consistent suppression of spermatogenesis to azoospermia in both Caucasian and Chinese men and therefore has many of the properties necessary for a contraceptive preparation for men.

Administration, Oral↗
PubMed2002

Action of MDMA (ecstasy) and its metabolites on arginine vasopressin release.

3,4-Methylenedioxymethamphetamine (MDMA) has been reported to cause hyponatraemia, which appears to result from inappropriate secretion of the antidiuretic hormone arginine vasopressin (AVP). After administration of a low dose of (R,S)-MDMA (40 mg) to eight healthy drug-free male volunteers, concentrations of AVP in plasma increased significantly at 1, 2, and 4 hours. Although no relation between plasma MDMA and AVP was found on an examination of the entire data set over the 24-hour study period, a statistically significant negative correlation was observed at 1 hour. As this occurred at a time when both AVP and MDMA concentrations were rising, it was postulated that a metabolite, or metabolites, could primarily be responsible for the increase in AVP. To test this hypothesis we examined the effect of MDMA and five of its metabolites, in the dose range 0.1-1,000 nM, on AVP release from the isolated rat hypothalamus. All compounds tested were found to increase AVP release (using 10 nM and 1,000 nM concentrations), with 4-hydroxy-3-methoxymethamphetamine (HMMA), the major metabolite of MDMA, being the most potent, and 3,4-dihydroxymethamphetamine (DHMA) the least potent. Each compound (1,000 nM), with the exception of DHMA, also enhanced the response to 40-mM potassium stimulation. Our findings confirm that metabolites of MDMA, in addition to the parent drug, contribute to AVP secretion in vitro. Further work will demonstrate whether this is also true in vivo.

Animals↗
PubMed2001

Arginine vasopressin release in response to the administration of 3,4-methylenedioxymethamphetamine ("ecstasy"): is metabolism a contributory factor?

The aim of this investigation was to examine the effect of 3,4-methylenedioxymethamphetamine (MDMA) administration on arginine vasopressin (AVP) release. (R,S)-MDMA (40 mg) was administered to eight normally hydrated healthy male volunteers (22-32 years) and blood samples were collected up to 24 h. Plasma was assayed for AVP and cortisol by radioimmunoassays, and for MDMA and the N-demethylated metabolite, MDA, by gas chromatography-mass spectrometry. Sodium concentrations and osmolality were also determined. Plasma AVP increased in all subjects after MDMA administration and a significant negative correlation was observed between concentrations of AVP and both single and total enantiomer MDMA at 1 h (r < -0.91, P < 0.01). This had disappeared by 2 h (P > 0.7). Compared with basal values, no significant change was observed for osmolality or cortisol at 1 h after drug administration. In conclusion, plasma AVP concentrations increase after MDMA administration, but the increase is not part of a generalized stress response since cortisol did not increase concurrently. A significant negative correlation between plasma MDMA and AVP was observed soon after administration. The possibility that a pharmacological effect of MDMA is primarily mediated via one or more metabolites, rather than by the parent drug, should be considered.

Adult↗
PubMed2000

Determination of the glycoforms of human chorionic gonadotropin beta-core fragment by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

BACKGROUND: Metabolism of human chorionic gonadotropin (hCG) in the serum and kidney yields the terminal urinary product hCG beta-core fragment (hCGbetacf), comprising two disulfide-linked peptides (beta6-beta40 and beta55-beta92) of which one (beta6-beta40) retains truncated N-linked sugars. Hyperglycosylated hCGbetacf may indicate choriocarcinoma or Down syndrome, but the glycosylation profile of hCGbetacf has not been thoroughly evaluated. METHODS: hCGbetacf, purified from pregnancy urine, was reduced by "on-target" dithiothreitol (DTT) reduction and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The mass ([M+H](+)) of the primary sequence of the glycosylated peptide beta6-beta40 was subtracted from the m/z values of the discrete peaks observed to give the masses of the carbohydrate moieties. Carbohydrate structure was predicted by sequentially subtracting the masses of the monosaccharide residues corresponding to N-linked carbohydrates of the hCG beta-subunit reported in the literature. RESULTS: Mass spectra of hCGbetacf revealed a broad triple peak at m/z 8700-11300. After reduction, the triple peak was replaced by a discrete set of peaks between m/z 4156 and 6354. A peak at m/z 4156.8 corresponded to the nonglycosylated peptide (beta55-beta92). The remaining nine peaks indicated that urinary hCGbetacf comprises a set of glycoforms smaller and larger than the trimannosyl core. CONCLUSIONS: hCGbetacf comprises a wider set of glycoforms than reported previously. Peaks of highest mass indicate evidence of hyperglycosylated carbohydrate moieties. The data support previous reports that hCGbetacf oligosaccharides lack sialic acid and galactose residues. No indication was found of a beta6-beta40 peptide that was entirely devoid of carbohydrate.

Carbohydrate Sequence↗
PubMed1999

Adrenal and gonadal contributions to urinary excretion and plasma concentration of epitestosterone in men--effect of adrenal stimulation and implications for detection of testosterone abuse.

OBJECTIVE: The ratio of urinary testosterone (T) to epitestosterone (EpiT) is used to detect T abuse in sport. Also, plasma or urinary concentrations of EpiT have been measured to assess testicular steroidogenesis during hormonal male contraception. Further investigations are required to evaluate the relative contributions of the testis and adrenal to EpiT production. To this purpose, we have compared basal urinary EpiT glucuronide and plasma EpiT and the response to synthetic adrenocorticotrophic hormone (ACTH) stimulation between eugonadal and hypogonadal men. DESIGN AND SUBJECTS: The basal urinary excretion rate of EpiT glucuronide was determined in 34 eugonadal men. Six men, clinically diagnosed as hypogonadal, and 6 out of the 34 eugonadal men previously described, received an intramuscular injection of synthetic ACTH depot (1 mg) at 0800 h on two consecutive days. Blood samples were collected prior to and then at 1.5, 8, 24, 25.5, 32 and 48 h with respect to the first administration (0 h). 24-h urine specimens were collected from 0800 h on days 1 and 2 (baseline) and 3 and 4 (stimulation). MEASUREMENTS: Plasma EpiT, T and cortisol were measured by RIA and urinary EpiT and T, following glucuronide hydrolysis, by gas chromatography-mass spectrometry (extract combines aglycones with a minor amount of urinary free steroids). RESULTS: Basal excretion rates of EpiT glucuronide in eugonadal men (range: 62-751 nmol/24 h) were considerably greater than in hypogonadal men (range: 3-34 nmol/24 h). Mean basal plasma EpiT in eugonadal men (1.32 +/- 0.08 nmol/l) were greater than in hypogonadal men (0.68 +/- 0.04 nmol/l). In each group, synthetic ACTH stimulation increased plasma cortisol 4-fold. In eugonadal men, plasma and urinary EpiT were unchanged whereas plasma and urinary T glucuronide decreased in response to ACTH. In hypogonadal patients, ACTH increased plasma and urinary EpiT while plasma T remained unchanged. CONCLUSION: The testes are the major source of epitestosterone, the adrenal contribution being relatively modest. Following adrenal stimulation, urinary epitestosterone glucuronide increases considerably in hypogonadal men but this increase is masked in eugonadal men because testicular production is probably suppressed by the ACTH-induced rise in cortisol. Activation of the adrenal cortex results in no change or only a small decrease in the urinary T/EpiT ratio in eugonadal men.

Adrenal Glands↗
PubMed1999

The beta-subunit of human chorionic gonadotrophin exists as a homodimer.

The free beta-subunit of human chorionic gonadotrophin (hCGbeta) is well recognised as a product of many epithelial tumours. Recently, it has been shown that this ectopic production may have a functional relationship to tumour growth. The growth-promoting activity of hCGbeta may be explained by its structural similarity to a family of growth factors which all contain the same distinct topological fold known as the cystine-knot motif. Since the other members of this family all exhibit their activities as homo- and heterodimers, it is possible that the same may be true for hCGbeta. Using size-exclusion chromatography, low stringency SDS-PAGE and matrix assisted laser desorption/ionisation (MALDI) time-of-flight (TOF) mass spectrometry (MS) we have shown that pure preparations of hCGbeta contain hCGbetabeta homodimers. Size-exclusion chromatography revealed asymmetric elution profiles with a forward peak corresponding to the size-exclusion characteristic of a globular protein with an approximate mass of 44-54 kDa and a late shoulder centered around an elution position expected for a globular protein of approximately 29 kDa. Two immunoreactive hCGbeta species, of approximately 32 and 64 kDa, were clearly resolved by SDS-PAGE and Western blotting. When analysed by MALDI-TOF MS a |mf23 kDa monomer and a |mf46 kDa dimer were identified. Formation of hCGbetabeta homodimers is consistent with the behaviour of other cystine-knot growth factors and strengthens the inclusion of the glycoprotein hormones within this superfamily. It has yet to be determined whether it is this dimeric molecular species that is responsible for growth-promoting activity of hCGbeta preparations in tumours.

Blotting, Western↗
PubMed1999

Stereospecific analysis and enantiomeric disposition of 3, 4-methylenedioxymethamphetamine (Ecstasy) in humans.

BACKGROUND: Little is known concerning the enantioselective disposition of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) in humans. In addition, the potential of utilizing the stereochemical composition of an analyte in biological media for forensic purposes requires investigation. METHODS: The enantiomers of MDMA and its demethylated metabolite, 3,4-methylenedioxyamphetamine (MDA), present in plasma and urine extracts were derivatized with (-)-(R)-alpha-methoxy-alpha-trifluoromethylphenylacetyl chloride and analyzed by gas chromatography-mass spectrometry and gas chromatography, respectively. The enantioselective disposition of MDMA and MDA was determined following oral administration of racemic MDMA (40 mg) to eight male volunteers. RESULTS: The plasma concentrations of (R)-MDMA exceeded those of the S-enantiomer [ratio R:S of the area under the curve (AUC), 2.4 +/- 0.3], and the plasma half-life of (R)-MDMA (5.8 +/- 2.2 h) was significantly longer than that of the S-enantiomer (3.6 +/- 0.9 h). The majority of the recovered material in urine was excreted within 24 h after dosing, with the recovery of (R)-MDMA (21.4% +/- 11.6%) being significantly greater than that of (S)-MDMA (9.3% +/- 4.9%), and with (S)- and (R)-MDA accounting for 1.4% +/- 0.5% and 1.0% +/- 0.3% of the dose, respectively. Mathematical modeling of plasma enantiomeric composition vs sampling time demonstrated the applicability of using stereochemical data for the prediction of time elapsed after drug administration. CONCLUSIONS: Analytical methods for determining the enantiomeric composition of MDMA and MDA in plasma and urine were developed. The disposition of MDMA in humans is stereoselective, with the more active S-enantiomer having a reduced AUC and shorter half-life than (R)-MDMA. The determination of stereochemical composition may be applicable for forensic purposes.

Administration, Oral↗
PubMed1998

Discrimination of mammalian growth hormones by peptide-mass mapping.

Recognition by the legal authorities that growth hormones (GHs) may be abused to improve sporting performance and/or physique has led to the implementation of controls that make it an offence to produce, supply, possess or import and export GHs, with intent to supply, without the authority to do so. A method is described for the discriminatory analysis of human, equine, porcine and bovine GHs for forensic purposes. Peptide-mass mapping by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry following tryptic digestion gave sequence coverages of 97.4%, 93.7%, 94.2% and 90.6% for human, equine, porcine and bovine GHs respectively. The tryptic-mass maps generated were sufficient to discriminate between the four hormones analysed and thus provide unambiguous identification of each individual GH. Identification of the N-terminal peptides of recombinant equine and porcine GHs, which possess additional methionine residues, within the tryptic-mass maps may provide the basis of a test to indicate exogeneous administration rather than endogenous secretion of GH in performance dogs and horses.

Amino Acid Sequence↗
PubMed1998

The measurement of testosterone in hair.

Trace metals and drugs have been measured in hair for a number of years but there are no published papers on the measurement of steroids in human hair. We report here the measurement of testosterone in hair samples taken from men, women and prepubertal children. This was a preliminary investigation to see whether testosterone was detectable in hair and whether concentrations between men and women, and men and prepubertal children were different in line with concentrations of testosterone in the blood. Hair was digested in sodium hydroxide and the testosterone extracted before measurement by radioimmuno- assay. There was a clear difference between testosterone concentrations found in heir collected from men (12.9-77.7 pmol/g) and those found in hair from women (<0.9-10.8 pmol/g). There was no significant difference between the concentrations found in women and children. The authenticity of the testosterone measured was confirmed with GCMS.

Adult↗
PubMed1997

Serum IGF-I and IGF binding proteins 2 and 3 as potential markers of doping with human GH.

OBJECTIVE: IGF-I and IGF binding protein (IGFBP)-3 levels in man are positively regulated by GH status; in contrast, evidence suggests an inverse relationship between GH status and IGFBP-2. We investigated the effects of somatropin administration on the serum concentrations of these analytes, together with serum and urinary concentrations of GH, to evaluate their potential as markers in the development of a test for detecting doping with GH in sports competitors. DESIGN: Somatropin was administered subcutaneously at a dose of 0.15 U/kg bodyweight/day at 1000 h for 3 days to eight healthy men (20-32 years old). MEASUREMENTS: Serum concentrations of GH, IGF-I, IGFBP-2 and -3 were determined in blood samples collected at 1600 h on the days prior to (day -1), during (days 0, 1 and 2), and following administration (days 3 and 7). Urine was collected continuously from days -2 to 3 and then on day 7. RESULTS: Serum and urinary concentrations of GH were only raised on the days of administration whereas, following cessation of somatropin, the increases in the serum concentrations of IGF-I and IGFBP-3 were sustained for at least 1 day (30 h). Serum IGFBP-2 decreased during the period of administration and was still suppressed on day 3. The concentration ratios of IGFBP-3 to IGFBP-2 and IGF-I to IGFBP-2 increased markedly with administration and both ratios were still significantly augmented compared with basal values 30 h after the last administration. CONCLUSION: With acute administration of somatropin to healthy men the serum concentration of IGFBP-2 decreases and the ratios of serum IGF-I/ IGFBP-2 and IGFBP-3/IGFBP-2 increase. These ratios should be considered in the development of a test for detecting somatropin administration in sport.

Adult↗
PubMed1997

Comparison between testosterone oenanthate-induced azoospermia and oligozoospermia in a male contraceptive study. IV. Suppression of endogenous testicular and adrenal androgens.

Administration of supraphysiological doses of testosterone to normal men causes inhibition of spermatogenesis, but while most become azoospermic, 30-55% maintain a low rate of spermatogenesis. We have investigated whether there are differences in endogenous androgen production, of testicular and adrenal origin, which may be related to the degree of suppression of spermatogenesis. Thirty-three healthy Caucasian men were given weekly i.m. injections of 200 mg testosterone oenanthate (TE), 18 became azoospermic, while 15 remained oligozoospermic. Urinary excretion of epitestosterone, a specific testicular product, was reduced to <10% of pretreatment values, with no differences between the groups. Similar results were obtained for other markers of testicular steroidogenesis. Urinary and plasma adrenal androgens were also reduced during TE treatment: a statistically significant decrease in both (P < 0.001 and P < 0.05 respectively) was seen in the azoospermic but not oligozoospermic responders. These results suggest that testicular steroidogenesis is decreased to <10% by the administration of supraphysiological doses of exogenous testosterone. Differences in the degree of ongoing steroidogenesis in the testis do not appear to account for incomplete suppression of spermatogenesis, thus differences in androgen metabolism may underlie this heterogeneous response. A small but significant reduction in secretion of adrenal androgens was also detectable, the relevance of which is unclear.

Adrenal Cortex Hormones↗
PubMed1997

Intramuscular administration of 5 alpha-dihydrotestosterone heptanoate: changes in urinary hormone profile.

A recommended confirmatory procedure for detecting 5 alpha-dihydrotestosterone (DHT) doping in male athletes proposed the use of the urinary concentration ratio of DHT to epitestosterone (EpiT) as the primary marker and those of 5 alpha-androstane-3 alpha,17 beta-diol (5 alpha-Adiol) to EpiT, luteinizing hormone (LH), and 5 beta-androstane-3 alpha,17 beta-diol (5 beta-Adiol) as secondary markers. Here we investigate the effects on these markers of intramuscular administration of DHT heptanoate (250 mg) to six healthy men. Within 24 h of administration all four markers greatly exceeded the published discrimination limits, remaining above these limits for 10-14 days. All ratios returned to basal values by day 28. In contrast to results after percutaneous administration, 5 beta-Adiol excretion decreased, probably as a consequence of greater suppression of testicular steroidogenesis. Results were largely in agreement with those obtained after percutaneous administration, although probably augmented by the larger dose and the different route of delivery.

Adult↗
PubMed1995

Tryptic mapping of human chorionic gonadotropin by matrix-assisted laser desorption/ionization mass spectrometry.

The potential of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry for use in the identification of human chorionic gonadotropin (hCG) seized by law enforcement agencies is investigated. Analysis of untreated hCG revealed signals corresponding to the molecular ions of the intact hCG heterodimer and both its non-covalently linked subunits. Unfortunately, due to carbohydrate heterogeneity, the peaks are broad which makes accurate mass assignment, and consequently identification, difficult. Peptide mapping by MALDI-TOF following tryptic digestion gave sequence coverage of 59% and 52% for the alpha- and beta-subunits respectively. Nevertheless, the tryptic map was considered to provide unambiguous identification of hCG. This was confirmed by searching peptide-mass databases with the experimentally determined masses. Our data suggest that peptide mapping by proteolytic digestion followed by MALDI-TOF mass spectrometry is a suitable analytical technique for the identification of hCG seized by the legal authorities.

Amino Acid Sequence↗