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Biomedical subjects

D Tran

Publications and source records attributed to D Tran.

106 records · Page 6Linked to original sources
PubMed1984

Production of anti-Müllerian hormone: another homology between Sertoli and granulosa cells.

Anti-Müllerian hormone (AMH) has been detected by RIA in the follicular fluid of mature bovine ovaries and in incubation medium of bovine granulosa cells. Purification of AMH from two independent batches of follicular fluid was achieved with a yield of 11% and 15% respectively. Both ovarian and control testicular AMH produced near-complete regression of fetal rat Müllerian ducts exposed to it in culture at a final concentration of 200-300 mU/ml and were recognized by the same monoclonal and polyclonal antibodies. These findings indicate that adult mammalian granulosa cells are capable of producing immunoreactive and bioactive AMH at a rate apparently similar to that already demonstrated for mature Sertoli cells and add yet another item to the homologies reported between male and female somatic gonadal cells.

Animals↗
PubMed1984

Origin of anti-Müllerian hormone in bovine freemartin fetuses.

The origin of AMH responsible for Müllerian duct regression in bovine freemartins has been reinvestigated, using a sensitive RIA for this hormone. Between 50 and 80 days, Müllerian duct regression occurs simultaneously in males and freemartins. Both twins exhibited high and positively correlated serum AMH concentrations, whereas gonadal in-vitro production of AMH and biological anti-Müllerian activity were detectable at a low level only in 2 out of 13 freemartins. In the gonads of approximately half the freemartins after 80 days, seminiferous tubules differentiated and the gonads produced AMH, but the output was very low compared to that of the male twin. These data suggest that regression of Müllerian duct in freemartins is essentially mediated by AMH produced by the testes of the male twin.

Animals↗
PubMed1983

Use of monoclonal antibody techniques to study the ontogeny of bovine anti-Müllerian hormone.

Monoclonal antibodies against bovine anti-Müllerian hormone (AMH) were used to study the hormone in cattle. Anti-Müllerian activity of testicular tissue, immunoreactive testicular AMH, serum AMH concentration and AMH production by incubated testicular tissue were detectable from 42 days, i.e. at the time of seminiferous tubule differentiation, and peaked between 50 and 80 days, when the Müllerian ducts regress in the male fetus. All the values stabilized at a lower level until 30 days after birth and then slowly decreased. At 18 months, only traces of AMH immunoreactivity were detectable in testicular tissue and serum concentration and AMH production by incubated testicular tissue were negligible; the main source of AMH in the adult animal was the rete testis fluid. Study of the disappearance rate of AMH from the serum of castrated calves gave a half-life of approximately 2 days for bovine AMH.

Aging↗
PubMed1983

[Persistence of Mullerian ducts in the male rabbit by passive immunization against anti-mullerian hormone during fetal life].

A female Rabbit immunized against bovine anti-Müllerian hormone (AMH) was mated and gave birth to 3 litters, containing a total of 13 males. Ten of these presented with Müllerian derivatives, of variable development. Testicular position and structure, Wolffian development and virilization of the urogenital sinus were apparently normal in males with persistent Müllerian ducts.

Animals↗
PubMed1978

Biosynthesis of labelled anti-müllerian hormone by fetal testes: evidence for the glycoprotein nature of the hormone and for its disulfide-bonded structure.

Tritiated fucose incorporated into proteins released by fetal calf tests into incubation medium proved to be a marker for anti-müllerian hormone (AMH) once non-specific glycoproteins had been eliminated by partial purification. When partially purified incubation medium from fetal calf teste s was fractionated by gel filtration, sucrose density gradient sedimentation or preparative electrofocusing, a single radioactive protein peak co-purified with anti-müllerian activity. Partially purified medium from bull testes--which are devoid of anti-müllerian activity--has a much lower fucose content than that derived from fetal testes. Antisera directed against 'fetal'--but not 'bull'--partially purified incubation medium, and capable of blocking anti-müllerian activity, precipitated the radioactive protein peak. The molecular weight of labelled AMH was 215,000 when determined by gel filtration and 124,000 when determined by density gradient sedimentation. By SDS-PAGE the molecular weight of labelled AMH was 123,000 and dissociation into a 72,000 subunit was demonstrated under conditions which reduce disulfide bonds.

Animals↗
PubMed1977

The anti-Müllerian hormone.

Müllerian regression in the male fetus is mediated by a discrete fetal testicular hormone, different from testosterone and synthetized by Sertoli cells. Secretion of AMH begins shortly after testicular differentiation and lasts into the perinatal period; however, the müllerian duct is responsive to AMH only during a short "critical" period at the end of the ambisexual stage. Species-specificity has not been demonstrated in mammals, but avian müllerian ducts do not respond to mammalian AMH, although the mammalian müllerian ducts to respond to avian AMH. Investigations concerning the biochemical nature of AMH have been carried out on incubation media of calf fetal testes. Anti-müllerian activity of the incubation medium is not affected by dialysis, is enhanced by concentration by ultrafiltration and is not correlated with the testosterone content of the medium. Gel filtration of the incubation medium on Sephadex G 200 and Biogel A-5m indicates that the anti-müllerian hormone is a protein of relatively high molecular weight, between 200,000 and 320,000 daltons.

Animals↗
PubMedDate not supplied

An electronic menstrual cycle calendar: comparison of data quality with a paper version.

OBJECTIVES: This pilot study compared a prototype electronic menstrual calendar on a handheld computer with a paper calendar for data quality and participants' perceptions. DESIGN: Twenty-three women completed identical information about menstrual bleeding and symptoms using paper and electronic calendars for 1 month each. RESULTS: Use of the paper calendar resulted in more missing data than the electronic calendar for bleeding characteristics (13% vs. 4%) and symptoms (35% vs. 4%). The electronic calendar's ability to log data entries revealed retrospective entry for 61% of the data. Total data entry and cleaning time was reduced by 81% with the electronic calendar. Overall, participants preferred the electronic (70%) to the paper (22%) calendar. CONCLUSIONS: Data quality with conventional paper calendars may be poorer than recognized. The data-logging feature, unique to the electronic calendar, is critical for assessing data quality. Electronic menstrual calendars can be useful data collection tools for research in women's health.

Computers↗
PubMedDate not supplied

[Calcium and liver].

Cells expand energy to lower the concentration of free calcium in the cytosol ([Ca2+]i) to a very low level. Extracellular Ca2+ entering via channels situated in the plasma membrane is expelled into the extracellular medium by a Ca(2+)-Mg(2+)-ATPase or by Na(+)-Ca2+ exchangers. The Ca2+ that enters the cell is sequestered, once inside the cytosol, by a Ca(2+)-Mg(2+)-ATPase, which concentrates Ca2+ in specialized domains of the endoplasmic reticulum. The nucleus and the mitochondria also concentrate Ca2+, but less efficiently. The stimulation of numerous receptors by hormones, growth factors and neurotransmitters coupled to GTP-binding proteins provokes a rapid increase in [Ca2+]i by mobilizing Ca2+ from intra- and extracellular compartments. Membrane coupling is ensured by the activation of a phospholipase C-beta, which hydrolyses a doubly phosphorylated phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). The inositol (1,4,5)-trisphosphate (InsP3) consequently formed binds to a receptor consisting in 4 homologous of 250 kDa each. The InsP3 receptor has been localized to a specialized region, rich in Ca2+, of the endoplasmic reticulum. The receptor has been purified and its sequence obtained. Reincorporated into planar bilayers, it displays the properties of a channel. In the cell, opening of the InsP3 receptor-channel provokes the release of the Ca2+ accumulated within the endoplasmic reticulum. Analyzing the kinetics of channel opening by the methods of rapid mixing, rapid filtration or flash photolysis of caged InsP3 has revealed that InsP3 opens the channel within a very short time, probably less than 30 msec. The InsP3 receptor-channel is autoregenerative. With the sustained stimulation of a Ca2+ influx the release of Ca2+ leads to an augmentation of [Ca2+]i, which is responsible for triggering cellular responses. The complexity of Ca2+ signals produced by stimulated cells has been revealed by studies in which highly effective techniques have been used to detect Ca2+ ions in the cytosol, such as bioluminescent proteins, fluorescent indicators or ionic currents sensitive to Ca2+. It appears that variations in [Ca2+]i induced by stimulation consist of oscillations of which the frequency, but not the amplitude, depends on the concentration of the hormone. Moreover, by summing the images picked up with a video recorder, it has been possible to demonstrate the changes in [Ca2+]i at the subcellular level and the waves of Ca2+ in stimulated cells.

Animals↗
PubMedDate not supplied

[Anti-mullerian hormone : a new glycoprotein (author's transl)].

The hypothesis that anti-müllerian hormone might be a glycoprotein was suggested by the discrepancy between various methods of evaluation of the molecular weight of the substance responsible for anti-müllerian activity. Incorporation of radioactive fucose to the proteins synthesised by the fetal calf testis in vitro resulted in specific labelling of bioactive molecules, once labelled contaminants had been removed by prior partial purification.

Aging↗