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Biomedical subjects

R Martin

Publications and source records attributed to R Martin.

At least 613 records · Page 34Linked to original sources
PubMed1983

Co-occurrence of immunoreactive corticotropin-like and alpha-melanotropin-like material in pituitary cells: differences between young and adult rats.

We examined to which extent adrenocorticotropin (ACTH)-like substances are cleavable into alpha-melanotropin (MSH)-like material by application of exogenous enzymes on pituitary sections prior to immunocytochemical stainings. In pro-opiomelanocortin (POMC) cells of the anterior lobe from developing rats (1 to 21 postnatal days) at least one of two cells contained alpha-MSH-like immunoreactivity besides ACTH-like immunostaining. Pretreatment of these tissue sections with tryptic enzymes enhanced remarkably alpha-MSH-like immunostaining. In contrast, alpha-MSH-like immunoreactivity was almost not detectable in anterior lobes from adult rats, also after treatment with enzymes. After adrenalectomy (ax) POMC cells in anterior lobes behaved similarly: a few days after the operation almost all ACTH cells contained also alpha-MSH immunostaining, whereas after more than two weeks alpha-MSH immunostaining was nearly absent, also after application of enzymes. In contrast to rats, in young and adult guinea pig pituitaries all ACTH-like immunoreactivity was prevented by treatment with tryptic enzymes. These observations are consistent with the assumption that occurrence of ACTH- and alpha-MSH-like substances in rat pituitaries is regulated by a protection mechanism against proteolytic cleavage in the ACTH sequence which appears with delay in differentiating and maturing cells.

Adrenocorticotropic Hormone↗
PubMed1983

The significance of surface changes on explanted polyurethane pacemaker leads.

Although over 140,000 polyurethane leads have been implanted in humans, a controversy has recently arisen dealing with the significance of frequently detected irregularities on explanted insulator surfaces by scanning electron microscopy (SEM), and their relationship with lead failure. We therefore implanted ten, 6 Fr atrial polyurethane leads and an equal number of 4 Fr ventricular leads in dogs for a mean 26 +/- 2 and 29 +/- 2 weeks, respectively. Fourteen leads were removed utilizing metered force. The remaining leads were removed surgically without force at the termination of the study. Specimens were stored in saline prior to physical testing (tensile strength and elongation) of intravascular and extravascular lead segments. Similarly stored samples were prepared for SEM analysis. The polyurethane insulator disconnected from the electrode on forcible removal in three atrial and two ventricular leads (concordant connected from the electrode on forcible removal in three atrial and two ventricular leads (concordant for two pairs). There was no significant relationship between the results of physical testing and extraction force, lead size, integrity on removal, sample location or SEM scores. Chemical analysis of surface changes employing both x-ray and electron emission spectroscopy failed to reveal evidence of protein adsorption or liquid impregnation. Samples soaked in sodium hydroxide displayed the same SEM irregularities. The combined effects of fissuring and fluid absorption by polyurethane did not affect chronic anodal or cathodal thresholds. In conclusion, a clear relationship between chronic surface irregularities and the insulator function of polyurethane, its relationship between chronic surface irregularities and the insulator function of polyurethane, its integrity in situ, or its strength at explant has not been established by this relatively short-term study. On the other hand, a potential time-dependent impact of these changes on lead performance has not been excluded. Moreover, only a single species of medical grade polyurethane has been clinically evaluated. Thus, the ultimate place of polyurethane leads in pacing systems has yet to be determined.

Animals↗
PubMed1983

Bone density in amenorrheic women with and without hyperprolactinemia.

To determine whether decreased bone density in patients with PRL-secreting pituitary tumors is specifically related to hyperprolactinemia or is a consequence of disordered pituitary-gonadal function common to all amenorrheic states, we measured the bone mineral content of the radius by photon absorptiometry in normal subjects, in women with amenorrhea and normal serum PRL levels, and in women with PRL-secreting pituitary tumors. The women did not differ significantly in mean age, height, weight, or serum calcium, phosphorous, gonadotropin, testosterone, vitamin D, or PTH concentrations, and all had normal renal and thyroid function. The bone mineral content in women with amenorrhea and normal serum PRL levels (0.91 +/- 0.02 g/cm) was not significantly different from that in control subjects (0.88 +/- 0.01 g/cm). Patients with PRL-secreting tumors studied 2-5 yr after transsphenoidal surgery had significantly diminished bone mineral content whether they were cured (0.82 +/- 0.02 g/cm) or had persistent amenorrhea and hyperprolactinemia (0.81 +/- 0.02 g/cm). Serum estradiol concentrations did not differ significantly in the four groups, and there was no correlation between estradiol concentration and bone mineral content or between PRL concentration and bone mineral content in the amenorrheic women. The presence of decreased bone mineral content in hyperprolactinemic patients suggests that PRL may have a direct effect on bone and may be another indication for early treatment of PRL-secreting pituitary tumors.

Adult↗
PubMed1982

Maternal prostaglandin levels after vaginal examination in two pregnancy.

Plasma 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) levels were measured in patients with twin pregnancies in come of whom the cervix was dilated and effaced. Significant rises in PGF M values were observed 5 and 10 minutes after vaginal examination in those patients who had a negative cervical score; these changes were abolished by prophylactic oral use of the beta-sympathomimetic drug fenoterol (Berotec; Boehringer Ingelheim). Patients who went into labour within 72 hours of examination had a greater percentage rise in PGFM levels than those in whom the onset of labour was delayed. Beta-sympathomimetic drugs such as fenoterol may be of value in preventing prostaglandin release and delaying the onset of labour.

Cervix Uteri↗
PubMed1982

Enzymatic cleavage prior to antibody incubation as a method for neuropeptide immunocytochemistry.

When deplasticized Epon sections were treated with endo- and/or exopeptidases prior to incubation with antibodies, the neuropeptide immuno-reactivity of secretory nerves was often altered in a predictable way. Cleavage of neurosecretory material in octopus nerves by trypsin and carboxypeptidase-B enhanced enkephalin-like immunoreactivity, while Molluscan neuropeptide-like immunoreactivity was prevented by tryptic cleavage. The enzyme effects indicated the occurrence of a heptapeptide (Tyr-Gly-Gly-Phe-Met/Leu-Arg-Phe) that contains both the enkephalin and the Molluscan neuropeptide sequence. Vasopressin terminals of the rat neurohypophysis, which presumably contain enkephalin precursor sequences, exhibited enkephalin-like immunostaining after tryptic cleavage. ACTH/beta-endorphin cells of the rat intermediate pituitary, which synthesize the enkephalin sequence at the N-terminus of Beta-endorphin, exhibited enkephalin=like immunoreactivity when sections were treated with alpha-chymotrypsin or trypsin, but not after incubation with leucine-aminopeptidase or carboxypeptidase-B. Enkephalin-like immunostaining could not be induced in any way in ACTH/beta-endorphin cells of the anterior pituitary. Enzymatic cleavage may give additional information in immunocytochemical localization studies on neuropeptide sequences in secretory nerves and hormonal granules.

Adrenocorticotropic Hormone↗
PubMed1982

Epidural morphine for postoperative pain relief: a dose-response curve.

Different doses of epidural morphine were studied in order to determine their effectiveness in providing postoperative pain relief after surgery of the lower extremities and their relationship to the incidence of untoward reactions. The study was carried out in a double-blind fashion using five dosages of epidural morphine (0.5, 1.0, 2.0, 4.0, and 8.0 mg) and included 60 patients. The higher doses of morphine (2.0, 4.0, and 8.0 mg) were equally effective and more effective than the lower doses (0.5 and 1.0 mg) in providing postoperative analgesia. Nausea and vomiting were encountered more frequently with the highest dose (8.0 mg) and this finding was statistically significant (P less than 0.03). No statistically significant difference was found between the doses studied with regard to itching, urinary retention, and respiratory depression; the latter was evaluated in a subgroup of 20 patients. These data suggest that effective postoperative pain relief after surgery of the lower extremities can be achieved with relatively low doses of morphine sulfate and with minimal side effects. For the type of surgery studied, 2 mg morphine sulfate appeared to be the optimum dose.

Carbon Dioxide↗
PubMed1982

Bradycardia during sleep apnea. Characteristics and mechanism.

To determine the characteristics of and mechanisms causing the bradycardia during sleep apnea (SA), both patients with SA and normals were studied. Evaluation of six consecutive SA patients demonstrated that bradycardia occurred during 95% of all apneas (central, obstructive, and mixed) and became marked with increased apnea length (P less than 0.01) and increased oxyhemoglobin desaturation (P less than 0.01). Heart rate slowed 9.5 beats per minute (bpm) during apneas of 10-19 s in duration, 11.4 bpm during 20-39s apneas, and 16.6 bpm during 40-59-s apneas. Sleep stage had no effect unexplained by apnea length or degree of desaturation. Oxygen administration to four SA patients completely prevented the bradycardia although apneas lengthened (P less than 0.05) in three. Sleeping normal subjects did not develop bradycardia during hypoxic hyperpnea but, instead, HR increased with hypoxia in all sleep stages, although the increase in HR was not as great as that which occurred while awake. Breath holding in awake normals did not result in bradycardia during hyperoxia (SaO2 = 99%), but was consistently (P less than 0.01) associated with heart rate slowing during room air breath-holds (-6 bpm) at SaO2 = 93%, with more striking slowing (-20 bpm) during hypoxic breath-holds (P less than 0.01) at SaO2 = 78%. Breath holding during hyperoxic hypercapnia had no significant effect on rate. Breath holding in awake SA subjects demonstrated similar findings. We conclude that the bradycardia of SA is a consistent feature of apnea and results from the combined effect of cessation of breathing plus hypoxemia.

Adult↗
PubMed1982

Multiple cellular forms of corticotrophs in surgically removed pituitary adenomas and periadenomatous tissue in Cushing's disease.

Transsphenoidally removed samples of pituitary adenomas from 14 patients with Cushing's disease and 5 patients with Nelson's syndrome always contained groups of uniform small ACTH-cells. Antibodies against the pro-opiocortin precursor fragments beta-endorphin, ACTH, and 16k-peptide recognized material in typical adenoma cells. A subpopulation of these cells, varying in number from sample to sample, specifically exhibited alpha-melanotropin immunoreactivity. Most periadenomatous samples showed signs of severe degeneration. Typical Crooke cells only occurred in samples from patients with Cushing's syndrome, but, with this exception, no clear differences between pituitaries of patients with Cushing's and Nelson's syndromes could be discerned. Two other forms of ACTH-immunoreactive cells were observed: rare, single, highly immunoreactive cells, with characteristics of both normal and Crooke cells, and numerous syncytial groups of cells in an advanced state of disintegration, presumably the remnants of hyperplastic follicles. The four different corticotrophs are characterized according to their fine structure and immunoreactivity in this study.

Adenoma↗