Search PubMed⌕ Search

Biomedical subjects

M C Martin

Publications and source records attributed to M C Martin.

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

Insulin-like growth factor I (IGF-I) levels in follicular fluid from human preovulatory follicles: correlation with serum IGF-I levels.

Insulin-like growth factor I (IGF-I) levels were measured in both serum and fluid of preovulatory follicles (n = 156) in 43 women undergoing in vitro fertilization (IVF). The mean IGF-I level in follicular fluid (FF) was significantly lower than in serum (0.52 +/- 0.02 IU/L versus 0.66 +/- 0.23 IU/L), and FF levels were significantly correlated with individual serum IGF-I levels as well as with follicular size and FF volume but not with oocyte maturity, granulosa cell appearance, or IVF. This suggests that FF IGF-I levels cannot serve as a clinical indicator for the degree of oocyte/granulosa cell differentiation or a predictor for IVF. Serum IGF-I levels were inversely correlated with the number of human menopausal gonadotropin ampules administered during treatment, suggesting that IGF-I might enhance ovarian gonadotropic stimulation.

Estradiol↗
PubMed1990

Maintenance of cell proliferation and steroidogenesis in cultured human fetal adrenal cells chronically exposed to adrenocorticotropic hormone: rationalization of in vitro and in vivo findings.

Previous studies indicated that acute exposure of adrenal cells to adrenocorticotropic hormone (ACTH) markedly stimulates steroidogenic capacity in vitro but also inhibits cell proliferation. However, in vivo, ACTH is known to stimulate adrenal cell growth. To address this discrepancy, we determined the effect of long-term (9-11 days) continuous or intermittent exposure to ACTH on human fetal adrenal cell proliferation and steroidogenesis. Adrenal glands from fetuses 18-22 wk gestation were studied. Fetal zone cells were plated either on plastic or on an extracellular matrix (ECM) in the presence and absence of basic fibroblast growth factor (bFGF) (0.5 ng/ml) and 1 or 10 nM ACTH. As determined by cell counting, bFGF stimulated cell proliferation during 9 days in culture. In the presence of bFGF, the average doubling time decreased from 44 to 30 h on plastic and from 37 to 26 h on ECM. Under these conditions, ACTH did not inhibit cell proliferation. Proliferation of fetal adrenal corticosteroid-producing cells in the ACTH-treated cultures also was assessed by histochemical staining for 3 beta-hydroxysteroid dehydrogenase (3 beta HSD). The number of positive cells increased more than 4-fold between Days 5 and 9 in culture. Continuous treatment with 1 nM ACTH increased dehydroepiandrosterone sulfate (DHAS) production 5- to 10-fold during the first 5 days in culture. Thereafter, the stimulated hormone production decreased over time, although there was still a difference of almost 100-fold between the control and ACTH-treated cultures at the end of 9 days.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1990

Polypronuclear embryos after in vitro fertilization.

Triploidy occurs in 1% to 3% of recognized conceptions in vivo. In vitro fertilization (IVF), which places large numbers of sperm in proximity to the oocyte, may increase the risk of triploidy. The risk also could be influenced by stimulation protocols that differentially affect egg quality. We found no significant difference in triploidy when cycles were stimulated with clomiphene citrate/human menopausal gonadotropin (3.2%) compared with gonadotropin-releasing hormone analog/human menopausal gonadotropin stimulation (4.4%). Triploidy was less common with male factor infertility (0.7%) compared with other causes of infertility (3.4% to 3.8%). Triploid embryos can develop to cleavage stages indistinguishable from those generated by diploid embryos. Thus, identifying and discarding embryos with greater than 2 pronuclei is a vital function of an IVF laboratory.

Cell Nucleus↗
PubMed1989

Type II hyperprolinaemia in a pedigree of Irish travellers (nomads).

We describe a study of 312 subjects in 71 families near related to a proband with type II hyperprolinaemia. The subjects were Irish travellers (nomads) among whom consanguineous marriage and high fertility are common. Thirteen additional cases of type II hyperprolinaemia were discovered; all were offspring of consanguineous unions. A further 50 subjects were found to have mild hyperprolinaemia. We found a strong association between type II hyperprolinaemia and seizures during childhood but no significant association with mental handicap. Most adults with type II hyperprolinaemia enjoyed normal health and there was no evidence that maternal hyperprolinaemia compromised fetal development. The documented association between type II hyperprolinaemia and seizures may be related to the neuromodulatory or reducing-oxidising effects of proline and pyrroline-5-carboxylate, respectively, that has been shown in vitro. Alternatively, another genetic defect closely linked to the type II hyperprolinaemia allele could be the explanation.

1-Pyrroline-5-Carboxylate Dehydrogenase↗
PubMed1989

Pelvic endometriosis: MR imaging.

The value of magnetic resonance (MR) imaging at 0.35 T in detecting, characterizing, and staging pelvic endometriosis was prospectively investigated in 30 consecutive women in whom this disease was clinically suspected. MR findings were correlated with the results of laparoscopy (13 women) and laparotomy (17 women). Surgical examination revealed a normal pelvis in five patients and endometriosis in 25. Three of the five normal cases and 16 of the 25 cases of endometriosis were correctly identified with MR imaging (sensitivity, 64%; specificity, 60%; accuracy, 63%). MR imaging demonstrated seven of eight endometriomas but only 14 of 29 adhesions and only six of 45 endometrial implants. While MR imaging demonstrated endometriomas, ovarian adhesions, and extraperitoneal endometrial implants, it could not accurately depict extraovarian endometrial adhesions and intraperitoneal endometrial implants. In addition, MR imaging findings did not correlate with the surgically determined severity of the disease. These limitations indicate that MR imaging cannot be used as the primary modality in the detection, characterization, and staging of endometriosis; laparoscopy remains the procedure of choice.

Adult↗
PubMed1989

An enzyme-linked immunosorbent assay to study human relaxin in human pregnancy and in pregnant rhesus monkeys.

A sensitive and specific double-antibody enzyme-linked immunoassay, using a synthetic analogue of human relaxin for standard and immunogen, was developed for the measurement of human relaxin (hRLX) in serum and plasma. No cross-reactivity was observed for human insulin, human insulin-like growth factor-I, hGH, human chorionic gonadotropin, hFSH, hLH or human prolactin. The assay was used to monitor RLX concentrations in samples from men, non-pregnant and pregnant women, and in pregnant rhesus monkeys infused with hRLX. RLX was not detected in serum from men nor from non-pregnant women, while a concentration of 600 ng/l was measured in pooled sera from two pregnant women (pregnancies achieved by in-vitro fertilization). Immunoreactive RLX (1.1 micrograms/g) was found in human corpora lutea taken from ectopic pregnancies at 7 weeks. In an experiment with a pregnant rhesus monkey infused with human RLX analogue, less than 1.5% of the maternal concentration was measured in the fetal circulation. Even though preliminary, these data suggest a low level of transfer of human analogue relaxin across the placenta in a rhesus monkey. Further studies of the physiology of RLX in human pregnancy will be facilitated by the availability of this immunoassay.

Amino Acid Sequence↗
PubMed1988

Evaluating client autonomy in natural family planning.

A critical element for evaluation of natural family planning (NFP) methods is client autonomy. Autonomy in NFP refers to clients who can identify their fertile days and apply this method without teacher assistance. The results of this study show that clients who are autonomous have a 12-month continuation rate of 96.7% and a pregnancy rate of 1.7% after beginning charting. The non-autonomous clients had a 12-month continuation rate of 34.3% and a pregnancy rate of 24.8% after beginning charting, significantly different from the autonomous clients. Using a bivariate analysis, we found that women 30 years and older who had two children or more, and women in the same age group (30 years and older) who wanted to limit rather than space pregnancy were significantly more likely to become autonomous. These findings have implications for NFP programs and future evaluation efforts.

Adult↗
PubMed1988

Effect of preovulatory estradiol concentrations on luteinizing hormone diurnal secretory patterns: a hypothesis for the timing of the luteinizing hormone surge.

The effect of preovulatory estradiol concentrations on 24-hour patterns of luteinizing hormone secretion was studied in six women with normal menstrual cycles. Blood samples were collected every 15 minutes for 24 hours before and after 7 days of estradiol benzoate administration, which achieved mean (+/- SE) estradiol concentrations of 424 +/- 54 pg/ml. The luteinizing hormone pulse frequency decreased significantly during sleeping hours both before (p less than 0.05) and after (p less than 0.005) estradiol benzoate administration. After estradiol benzoate, there also was diurnal variation in overall mean luteinizing hormone concentrations, which markedly increased secretion in the morning hours. The diurnal changes in luteinizing hormone secretion varied inversely with those of prolactin. These findings are consonant with the observation that the onset of the preovulatory luteinizing hormone surge in women occurs most frequently in the early morning hours.

Adult↗
PubMed1988

Influence of preovulatory estradiol concentration on diurnal and pulsatile prolactin secretion patterns.

We evaluated the effect of preovulatory concentrations of estradiol on the 24-hour profile of prolactin secretion in women with regular menstrual cycles. An estradiol preparation was chosen to allow comparison with physiologic events. Estradiol benzoate, 1 mg intramuscularly, was administered for 7 days to achieve estradiol concentrations just above preovulatory levels (424 +/- 54 pg/ml); 24-hour mean prolactin concentrations increased threefold (14.0 +/- 2.1 to 40.6 +/- 7.1 ng/ml). Prolactin pulse frequency increased significantly (p less than 0.001) during waking hours after estradiol benzoate administration. The diurnal pattern of prolactin secretion was maintained with estradiol benzoate, although the sleep acrophase often reached high concentrations (86 +/- 11 ng/ml). These results suggest in women with regular menstrual cycles: (1) that estrogen administration that achieves slightly greater than preovulatory estradiol concentrations can stimulate prolactin release, (2) that estradiol may elevate prolactin by increasing its pulsatile secretion, (3) that estradiol does not alter the diurnal pattern of prolactin secretion, (4) that estradiol concentrations just above preovulatory levels can be associated with markedly elevated prolactin concentrations.

Adult↗
PubMed1988

Low-dose dopamine infusions do not ablate luteinizing hormone pulses in women.

The effect of dopamine on the secretion of luteinizing hormone in 15 euprolactinemic and 15 hyperprolactinemic women was investigated using infused doses of dopamine that achieved circulating levels from 2 to 100 times basal physiologic concentrations. The normal women were studied in the early follicular phase of the cycle. Different concentrations of dopamine were maintained at each dose level for 2 hours. Blood samples were obtained every 15 minutes and concentrations of dopamine, luteinizing hormone, follicle-stimulating hormone, and prolactin quantified. Mean basal concentrations of estradiol were 53 +/- 19 pg/ml in the euprolactinemic and 33 +/- 12 pg/ml in the hyperprolactinemic women; mean prolactin levels were 8.1 +/- 3.9 ng/ml in euprolactinemic and 183 +/- 174 ng/ml in hyperprolactinemic women; mean basal dopamine concentrations were 323 +/- 308 pg/ml in euprolactinemic and 337 +/- 232 pg/ml in hyperprolactinemic women. All doses of dopamine achieved some degree of prolactin suppression, but doses that achieved nanomolar circulating concentrations did not significantly affect luteinizing hormone secretion. Eight of the women in each group exhibited high-amplitude luteinizing hormone pulses, which persisted during the dopamine infusions. Neither the amplitude nor frequency of luteinizing hormone release correlated with basal estradiol, luteinizing hormone, or prolactin levels. We conclude that low doses of dopamine infused into the peripheral circulation do not achieve significant suppression of luteinizing hormone release. In some women during the early follicular phase of the menstrual cycle and in some amenorrheic hyperprolactinemic women, luteinizing hormone is secreted in a pulsatile manner characterized by high-amplitude low-frequency bursts. These bursts of luteinizing hormone were not influenced by elevations in circulating dopamine concentrations sufficient to suppress prolactin.

Adult↗
PubMed1988

Polyovular follicles associated with human in vitro fertilization.

Polyovular follicles were found in 61 (24%) of 251 laparoscopies performed for in vitro fertilization. Of 898 follicles that contained at least one oocyte, 76 (8%) were polyovular. When the oocytes from polyovular follicles were assessed by morphologic criteria, it was found that 46 of the follicles contained oocytes that were discordant in maturity. Thus, oocytes can develop at different rates even though they are exposed to the same follicular fluid. It is possible that the microenvironment provided by the cellular investments of oocytes may correlate more precisely with oocyte maturity.

Female↗
PubMed1987

The neuroendocrine mechanism responsible for sexual inversion of the gonad in the protandrous hermaphroditic mollusc, Crepidula fornicata L.

An in vitro investigation has clarified the neuroendocrine mechanism responsible for the differentiation of the female gonad in the protandrous hermaphrodite Crepidula fornicata. The male gonads were used as target organs; in some experiments they were brought to a uniform resting state by prior decerebration of donor animals. When isolated in culture, most of the male gonad degenerates, leaving only the stem cells lining the wall of the acini. No ovarian autodifferentiation has been observed. A masculinizing factor, released by the nervous ganglia during the male phase, controls spermatogonial mitosis and maintenance of male differentiation. A feminizing factor, secreted by the nervous ganglia during sex inversion and the female phase and present in the hemolymph, initiates oogonial mitosis and female differentiation in the male phase gonad.

Animals↗
PubMed1986

Audiological assessment in the selection of cochlear implant candidates.

In the UCH/RNID Cochlear Implant Programme, patients referred for further audiological assessment are all post-lingually deafened adults with bilateral hearing losses in excess of 90 dB HL in the frequency range 500 Hz to 4 kHz. The purpose of this assessment as part of the selection procedure for implant candidates is to ascertain whether or not the patient has any residual auditory function which can be aided by conventional means. The procedure includes measurement of thresholds of sensation (whether auditory or vibrotactile) for pure tones, and testing for Uncomfortable Loudness Levels up to 130 dB HL. It also includes measurements of frequency discrimination and abnormal adaptation, and assessment of the effect of acoustic stimulation on tinnitus if present. Those with measurable hearing are further tested for discrimination of simple sound patterns related to the perception of speech. Results of assessment, and criteria of suitability for a trial with a high-powered hearing aid are discussed in this paper. Of the 29 patients tested to date, 14 were judged to have sufficient residual auditory function to justify a hearing aid trial. In 10 cases the trial was successful and these people were then no longer considered to be potential candidates for cochlear implantation.

Acoustic Stimulation↗
PubMed1986

Total deafness: the need and possibility for a working definition.

There is an urgent need for a definition of total deafness or total hearing loss which would appear to be feasible in terms of audiometric threshold. Considerable care must be taken in providing appropriate instrumentation for measuring the hearing loss of profoundly deaf people, particularly with regard to sufficient acoustic output. Proposals are made for values for the maximum outputs of audiometers. The practical benefit in the management of profoundly deaf people that can be obtained by the introduction of an agreed definition is described.

Audiometry↗