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Biomedical subjects

M C Martin

Publications and source records attributed to M C Martin.

At least 73 records · Page 4Linked to original sources
PubMed1985

Ablation of folliculogenesis in women by a single dose of gonadotropin-releasing hormone agonist: significance of time in cycle.

Effects of single subcutaneous doses (1, 5, 20, and 100 micrograms) of nafarelin, a potent gonadotropin-releasing hormone agonist, on the physiologic events of the human menstrual cycle were studied in 28 normal women. Nafarelin entered the circulation rapidly after injection. Peak concentrations were observed within 1 hour, and the plasma half-life was 4 to 5 hours. Maximal concentrations of luteinizing hormone and follicle-stimulating hormone were reached 3 to 4 hours after nafarelin administration. The magnitude of the gonadotropin responses depended both on the phase of the menstrual cycle (smallest responses during the early follicular phase) and the dose of nafarelin. Nafarelin administration during the early follicular phase delayed ovulation by 4.6 +/- 1.7 (standard deviation) days and prolonged the duration of the menstrual cycle from a pretreatment length of 29.2 +/- 2.1 days to 33.4 +/- 4.0 days (P less than 0.001). When nafarelin was administered shortly before or after ovulation, cycle length was not altered consistently. Administration 5 to 10 days after ovulation resulted in a truncated luteal phase. These observations suggest that the hormonal events triggered by nafarelin during the early follicular phase temporarily arrest the process of selection of the dominant follicle. Repeated intermittent administration of nafarelin or other gonadotropin-releasing hormone agonists in the early follicular phase may prevent follicular maturation and ovulation and may be a practical approach to contraceptive development.

Adult↗
PubMed1985

Effect on corpus luteum function of luteal phase administration of a potent gonadotropin-releasing hormone analog (nafarelin).

Fourteen women with ovulatory menstrual cycles were treated with a superactive agonistic analog of gonadotropin-releasing hormone (6-D-[2-naphthyl]-alanyl)-GnRH (nafarelin). Eight of the women received a single subcutaneous injection of nafarelin during the luteal phase at a dosage of 2, 5, or 100 micrograms for determination of the dose-response and pharmacokinetic characteristics of the drug. All doses stimulated the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Maximal release was obtained with the 5-micrograms dose (mean +/- standard deviation: delta LH = 297 +/- 75 mIU/ml; delta FSH = 29 +/- 7 mIU/ml), and there was no greater release of gonadotropin with the 100-micrograms dose. To investigate the contraceptive potential of nafarelin as a luteolytic agent, six of the women were treated with 100 micrograms of analog by daily injection for 10 days, beginning either 2 to 3 days or 5 to 7 days after ovulation. Gonadotroph desensitization or down-regulation developed within 24 hours, but serum concentrations of LH and FSH did not fall below normal values during treatment. There were no significant changes in mean estradiol or progesterone concentrations. There also was no change in mean length of the luteal phase (13.7 +/- 2.1 days [control] versus 13.6 +/- 1.4 days). Thus, nafarelin, like other superactive analogs of GnRH, does not appear to be clinically useful as a luteolytic agent in contraceptive development.

Corpus Luteum↗
PubMed1985

Polycystic ovarian disease.

Polycystic ovarian disease represents a poorly defined spectrum of clinical disorders having oligo-ovulation or anovulation as a common feature. There is no single, universally accepted biochemical or clinical definition. Clinical findings usually include anovulation resulting in irregular uterine bleeding and infertility, androgen excess resulting in hirsutism and acne, and obesity. The patho-physiology involves altered functions of the hypothalamus, pituitary, ovary and adrenal glands, resulting in failure of folliculogenesis to regularly proceed to ovulation. The cause of the initiating event in this disease process remains enigmatic. Therapy for the various abnormalities in polycystic ovarian disease is tailored to a patient's needs and may include preventing endometrial hyperplasia, controlling irregular uterine bleeding, controlling hirsutism and inducing ovulation.

Female↗
PubMed1985

Benign cystic teratoma of the ovary: a 6-year review.

Benign cystic teratoma of the ovary was diagnosed histologically in 118 patients over 6 years at the Sir Mortimer B. Davis-Jewish General Hospital in Montreal. The charts were reviewed with respect to population distribution, symptomatology, diagnostic procedures and treatment. Of the 118 patients, 85.6% were younger than 40 years. Only 3.4% had documented recurrence and 6.8% were pregnant. Roentgenograms of the pelvis revealed calcification in 64.1% of cases. Ultrasonography of the pelvis failed to make the diagnosis in 19.4%. The majority of patients had a Pfannenstiel incision (78.8%) and underwent oophorectomy (55.3%). In half the patients the contralateral ovary was only palpated.

Adolescent↗
PubMed1984

Decreased spinal mineral content in amenorrheic women.

Premenopausal amenorrheic women may be at risk for the development of osteoporosis. In hyperprolactinemia, cortical bone mass is decreased and the magnitude of the decrease correlates with the severity of the estrogen deficiency. However, bone loss in women with amenorrhea from other causes has not been assessed. We have studied women with hypothalamic and hyperprolactinemic amenorrhea and premature ovarian failure. Bone mass in the peripheral cortical bone was only slightly decreased from age-matched controls, but spinal trabecular bone was decreased 20% to 30%. Estradiol levels were 20 to 80 pg/mL in these women, not different from normal early follicular levels. The decrease in bone mass in the spine did not correlate with serum estradiol at these levels. The hypothalamic amenorrhea group was made up of athletes in whom the bone mass decrease was an unexpected finding.

Adolescent↗
PubMed1984

Serum neuronal growth factor levels in von Recklinghausen's neurofibromatosis.

A single neuronal cell biological assay was used to quantitate neuronal growth factors in 87 serum samples from 69 patients in 48 families with von Recklinghausen's neurofibromatosis, plus 16 samples from 16 comparison subjects. Mouse nerve growth factor was used as a standard for the bioassay, and results of serum assays were expressed as nerve growth factor equivalents. Antiserum to mouse nerve growth factor inhibited fractionally serum-induced neurite outgrowth, while kinetics of neurite outgrowth and maximal cellular response to serum differed from those induced by mouse nerve growth factor. The mean values (+/- SD) of neuronal growth factors for the patients were 20.5 +/- 15.7 pg/mg serum protein, while mean values for the comparison group as a whole were 22.3 +/- 15.6 pg/mg serum protein. Sex, race/ethnicity, patient age, and date of sample collection did not significantly influence serum levels among patients or comparison subjects. Three to six serial samples taken from women before pregnancy, during the course of pregnancy, during delivery, and in the postpartum period did not show significant differences from one period to another. These data suggest that human serum does contain non-nerve-growth-factor neuronal growth factors, but that levels of the factors do not contribute to the identification of patients with von Recklinghausen's neurofibromatosis.

Adolescent↗
PubMed1984

Prolactin-secreting adenomas in women. VII. Dopamine regulation of prolactin secretion.

Previous studies demonstrated that high doses of dopamine administered as a constant infusion were capable of suppressing PRL secretion in both normal and hyperprolactinemic individuals. The present study was designed to examine the dose-response relationship of PRL suppression to low doses of dopamine (between 0.06 and 4 micrograms/kg X min) infused in a step-wise fashion. Ten hyperprolactinemic patients with PRL-secreting pituitary adenomas and 10 normally menstruating women in the early follicular phase of a cycle were studied. For hyperprolactinemic women, the mean (+/- SD) serum PRL level (by RIA) was 112 +/- 101 ng/ml, with a range of 26-386 ng/ml, the mean estradiol level (by RIA) was 28 +/- 8 pg/ml, and the mean baseline dopamine level by carboxy-o-methyl transferase assay (COMT) was 357 +/- 237 pg/ml (2.33 +/- 1.54 X 10(-9) M). The normal women had a mean PRL of 8.1 +/- 3.5 ng/ml, a mean estradiol level of 42 +/- 12 pg/ml, and a mean baseline dopamine level of 317 +/- 223 pg/ml (2.07 +/- 1.45 X 10(-9) M). Concentrations of dopamine achieved at the lowest doses infused were less than 10 times baseline levels and were in the nanomolar range. The measured IC50 (the concentration of dopamine required to achieve 50% of maximal suppression) was 6 +/- 3 X 10(-9) M for normal women and 14 +/- 4 X 10(-9) M for hyperprolactinemic patients. The apparent inhibition constant determined by a nonlinear least squares procedure, was 3 +/- 3 X 10(-9) M for normal women and 11 +/- 12 X 10(-9) M for women with hyperprolactinemia. Both groups exhibited dose-dependent suppression of PRL to about 80% of initial values. Under these experimental conditions, the data do not support the hypothesis that there is a marked loss in sensitivity to dopamine in patients with PRL-secreting adenomas.

Adenoma↗
PubMed1984

Is AGC beneficial in hearing aids?

Three different functions of Automatic Gain Control (AGC) circuits in hearing aids are distinguished and the evidence for their benefits is considered. The value of AGC's function as a relatively distortion-free means of limiting output has been well established. With regard to compression, the benefit of short-term or 'syllabic' compression has not been demonstrated convincingly. Most evaluations of this type of AGC have looked for increase in speech intelligibility, but theoretical predictions of its effect do not appear to take account of the acoustic cues to consonant contrasts actually used by hearing impaired people, and empirical studies have often used listening conditions which do not give a realistic test of benefit. Relatively little attention has been paid to long-term compression, or to the effect of AGC on comfort rather than intelligibility. Listening tests carried out at the RNID and reported here have shown that AGC can benefit hearing aid users by allowing them to listen to a wider range of sound levels without either strain or discomfort, and, if time constants are well chosen, without adverse effects on speech intelligibility in quiet or in noise.

Amplifiers, Electronic↗
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↗
PubMed1983

Aids to hearing of a different kind.

Apart from personal hearing aids, there are a wide range of devices available for the hearing impaired. Most are not technically sophisticated but can make a considerable impact on their users. The major problem, however, is to ensure that they are used to the best advantage by as many people as possible. This paper describes the varieties of devices available and the settings in which they can be used.

Amplifiers, Electronic↗
PubMed1983

Prolactin-secreting pituitary adenomas.

Prolactin-secreting pituitary adenoma is a common cause of gynecologic problems that include oligomenorrhea, infertility, amenorrhea and galactorrhea. Diagnosis requires a combination of endocrine testing and radiologic evaluation. The diagnosis of macroadenomas is usually straightforward and these large tumors may be associated with mass effects such as severe headache, nerve palsies or visual changes. Microadenomas may be more subtle in presentation, and the diagnosis of hyperprolactinemia without radiologic evidence of a tumor frequently is problematic. The management of prolactin-secreting adenoma remains controversial, with no clear consensus or indication for surgical versus medical treatment. Surgical intervention is a realistic option for those patients who have access to an experienced neurosurgeon and who have tumor characteristics that offer a reasonable hope for cure. Many questions remain to be answered, including the cause, natural history of development and the optimum treatment for individual cases.

Adenoma↗
PubMed1982

A feasibility trial of a bureau-based telephone service for the deaf.

In the autumn of 1980, a 6-week experimental trial of a telephone service for deaf people was carried out with the financial support of NRD, British Telecom, RNID and in collaboration with the Electronics Department at Southampton University. The trial involved 25 deaf people with speech who were supplied with Prestel TV sets which allowed them to receive text from an operator at the bureau who set up the call connections and transcribed the speech of the hearing caller into text. The text was transmitted via the telephone network and displayed on the participant's Prestel receiver. The deaf callers used their telephones in the normal fashion to make their replies. Although the trial had its fair measure of problems, particularly at the start, the experiment proved to be successful. This paper describes the system used for the trial, the trial itself and also attempts to evaluate the requirements of a bureau-based telephone service for the deaf.

Activities of Daily Living↗