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Biomedical subjects

L Morgan

Publications and source records attributed to L Morgan.

At least 145 records · Page 8Linked to original sources
PubMed1987

Axonal signals regulate the differentiation of non-myelin-forming Schwann cells: an immunohistochemical study of galactocerebroside in transected and regenerating nerves.

Little is known about the factors involved in directing and maintaining the divergent differentiation of the 2 major Schwann cell variants, myelin and non-myelin-forming cells, in peripheral nerves. There is strong evidence that the differentiation of myelin-forming cells depends critically on cell-cell signaling through contact with appropriate axons. In this paper we ask whether this remarkable dependence of the Schwann cell on axonal contact for full differentiation is unique to those cells that form myelin or whether axonal signaling is also an important factor in the differentiation of non-myelin-forming Schwann cells. Sciatic nerves or cervical sympathetic trunks of adult rats were either transected or crushed and the axons allowed to degenerate and, in the case of crushed nerves, to regenerate into the distal stump for periods of time varying from 2 d to 9 weeks. The distal stump of the nerve was excised at specific times, the Schwann cells dissociated and immunolabeled with antibodies to galactocerebroside. In the sciatic nerve, which contains a mixture of non-myelin-forming and myelin-forming Schwann cells, transection resulted in a loss of galactocerebroside expression from the surface of all the Schwann cells in the distal stump over a 9 week period, irrespective of their original phenotype. In crushed sciatic nerves, where axons were allowed to regrow into the distal stumps, the number of Schwann cells expressing immunohistochemically detectable quantities of galactocerebroside in the stump declined over the first 3 weeks, but by 9 weeks after crush the total percentage of galactocerebroside-positive cells in the nerve had risen to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Models for respiratory cancer in nickel refinery workers.

Lung and nasal sinus cancer death rates among employees of a nickel refinery in South Wales were examined from the standpoint of quantifying the relationship between exposure and the risk of these two cancers. Areas in the refinery associated with high risk were identified by using a matched case-control approach, and a simple index of exposure for each man was constructed accordingly based on the duration of time spent in these areas. The dependence of relative risk and absolute excess risk for lung and nasal sinus cancers on age at first employment, calendar period of first employment, time since first employment, and duration of exposure in high-risk areas was then analyzed. The relative risk for nasal sinus cancer increased sharply with increasing age at first exposure but remained roughly constant throughout the period of follow-up, while that for lung cancer was independent of age at first exposure and dropped sharply with increasing time since first employment. The implications and limitations of these analyses are discussed in relation to the multistage theory of carcinogenesis and occupational risk assessment.

Adult↗
PubMed1985

Forskolin and 12-0-tetradecanoylphorbol-13-acetate mimic thyrotropin-stimulated protein iodination in mouse thyroid.

In the present study, the capacity of the diterpene, forskolin, and the phorbol ester, 12-0-tetradecanoylphorbol-13-acetate (TPA), to stimulate protein iodination in freshly dispersed mouse thyroid open follicles was assessed. Although both agents stimulated 125I incorporation into TCA precipitable material, dose response curves (0.1 - 25 microM) showed that maximal concentrations of either agonist alone failed to reproduce the stimulatory effect of a maximal concentration of thyrotropin (TSH; 50 mU/ml). When a maximal concentration of forskolin (20 microM) and TPA (10 microM) were added in combination, the stimulatory effect was additive and mimicked the effect of TSH. TPA had no significant effect on either basal or forskolin-stimulated cyclic-AMP production. We conclude that the regulation of protein iodination by TSH may involve both the adenylate cyclase-cyclic-AMP-dependent protein kinase system and the diacylglycerol-activated calcium/phospholipid-dependent protein kinase C pathway.

Adenylyl Cyclases↗
PubMed1985

Use of anti-inflammatory drugs by patients admitted with small or large bowel perforations and haemorrhage.

The intake of anti-inflammatory drugs by 268 patients with colonic or small bowel perforation or haemorrhage was compared with that by a group of patients, matched for age and sex, with uncomplicated lower bowel disease. Patients with perforation or haemorrhage were more than twice as likely to be takers of anti-inflammatory drugs, but no association was detected with the intake of other types of drugs, particularly cardiovascular drugs. The association between complicated lower bowel disease and intake of anti-inflammatory drugs may be causal.

Adrenal Cortex Hormones↗
PubMed1985

Concomitant use of activated charcoal and N-acetylcysteine.

Activated charcoal is a safe, effective, inexpensive adjunct in the management of most toxic ingestions. It has the ability to adsorb a wide variety of drugs and chemicals, one of which is acetaminophen. N-acetylcysteine (NAC) is the specific antidote available for serious overdoses of acetaminophen. Current management of acetaminophen overdose, however, does not recommend the concomitant oral administration of these two useful agents because adsorption and inactivation of NAC by charcoal is believed to occur. Our study was designed to help evaluate the effect of activated charcoal on N-acetylcysteine absorption. Ten healthy male volunteers were each given in the first, or control, phase of the study an oral dose of 140 mg/kg NAC, and venous blood samples were obtained. In the second phase, after a washout period, each subject received 60 g activated charcoal orally followed immediately by 140 mg/kg NAC. NAC serum levels were measured using gas-liquid chromatography, and levels were compared with and without the concomitant administration of charcoal. Although only a small number of the subjects completed the study, the results showed that in both phases there were no significant differences in the peak NAC levels, the plasma half-life of NAC, or the calculated area under the curve. We recommend that NAC and activated charcoal not be used clinically until further studies are completed.

Absorption↗
PubMed1985

Galactocerebroside is expressed by non-myelin-forming Schwann cells in situ.

Interest in the glycosphingolipid galactocerebroside (GC) is based on the consensus that in the nervous system it is expressed only by myelin-forming Schwann cells and oligodendrocytes, and that it has a specific role in the elaboration of myelin sheaths. We have investigated GC distribution in two rat nerves--the sciatic, containing a mixture of myelinated and non-myelinated axons, and the cervical sympathetic trunk, in which greater than 99% of axons are non-myelinated. Immunohistochemical experiments using mono- and polyclonal GC antibodies were carried out on teased nerves and cultured Schwann cells, and GC synthesis was assayed biochemically. Unexpectedly, we found that mature non-myelin-forming Schwann cells in situ and in short-term cultures express unambiguous GC immunoreactivity, comparable in intensity to that of myelinated fibers or myelin-forming cells in short-term cultures. GC synthesis was also detected in both sympathetic trunks and sciatic nerves. In the developing sympathetic trunk, GC was first seen at day 19 in utero, the number of GC-positive cells rising to approximately 95% at postnatal day 10. In contrast, the time course of GC appearance in the sciatic nerve shows two separate phases of increase, between day 18 in utero and postnatal day 1, and between postnatal days 20 and 35, at which stage approximately 94% of the cells express GC. These time courses suggest that Schwann cells, irrespective of subsequent differentiation pathway, start expressing GC at about the same time as cell division stops. We suggest that GC is a ubiquitous component of mature Schwann cell membranes in situ. Therefore, the role of GC needs to be reevaluated, since its function is clearly not restricted to events involved in myelination.

Animals↗
PubMed1985

Magnetic resonance imaging of the pelvis: evaluation of ovarian masses at 0.15 T.

Seventeen patients with suspected ovarian masses were evaluated by magnetic resonance imaging (MRI). MRI findings were confirmed by surgery (13 patients) or sonography and clinical follow-up (four). The study evaluated MRI characteristics of ovarian lesions using recently developed multislice and multiecho pulse techniques for a 0.15-T system. T1 and T2 relaxation times were calculated in 12 patients and although a range of values was obtained in several disease categories, diagnostic accuracy was frequently improved. MRI appearances tended to vary considerably with different pulse sequences and were particularly complex in patients with endometriosis and cystic ovarian tumors. Shortest calculated T1 and T2 values were found in hemorrhagic cysts in patients with endometriosis. Benign tumors with thick fibrous pseudocapsules had longer T1 values. Inflammatory masses and malignant ovarian tumors had significantly longer T1 and T2 values and relaxation times in a patient with mucinous cystadenoma varied within the complex mass.

Cystadenoma↗
PubMed1984

Infants of adolescent mothers. Maternal characteristics and developmental status at 1 year of age.

The Bayley Scales of Infant Development were administered at 1 year of age to 54 healthy infants of adolescent mothers. Information was obtained regarding maternal cognitive and emotional maturity, child-rearing attitudes, attitudes toward the infant, and psychosocial status at one year. The average Bayley Mental Scale score was 113, and the average Bayley Motor Scale score was 105. There was a negative correlation between the Bayley Mental Scale score and maternal age and education. Bayley Motor Scale scores were predictable from a combination of maternal authoritarian attitudes, abuse potential, and infant's birth weight. Although high authoritarian attitudes in mothers have been associated with poor cognitive development at later ages, they may represent an important strength in adolescent mothers during the first year.

Adolescent↗
PubMed1984

Elective ilioinguinal lymph node irradiation.

Most radiologists accept that modest doses of irradiation (4500-5000 rad/4 1/2-5 weeks) can control subclinical regional lymph node metastases from squamous cell carcinomas of the head and neck and adenocarcinomas of the breast. There have been few reports concerning elective irradiation of the ilioinguinal region. Between October 1964 and March 1980, 91 patients whose primary cancers placed the ilioinguinal lymph nodes at risk received elective irradiation at the University of Florida. Included are patients with cancers of the vulva, penis, urethra, anus and lower anal canal, and cervix or vaginal cancers that involved the distal one-third of the vagina. In 81 patients, both inguinal areas were clinically negative; in 10 patients, one inguinal area was positive and the other negative by clinical examination. Tumor doses most commonly used were 4500-5000 rad/5 weeks (180 rad to 200 rad per fraction). With a minimum two-year follow-up, there were only two regional failures in patients whose primaries were controlled; both failures occurred outside of the radiation fields. The single significant complication was a bilateral femoral neck fracture. The inguinal areas of four patients developed mild to moderate fibrosis. One patient with moderate fibrosis had bilateral mild leg edema that was questionably related to irradiation. No other instances of leg or genital edema were noted. Complications were dose-related. The advantages and disadvantages of elective ilioinguinal node irradiation versus elective inguinal lymph node dissection or no elective treatment are discussed.

Adenocarcinoma↗
PubMed1984

Proteinase inhibitory function in inflammatory lung disease. I. Acute bacterial pneumonia.

This study examines the bronchial alveolar lavage (BAL) samples from a group of patients with acute bacterial pneumonia (n = 13) and makes a comparison with a control group (n = 5). The proteinase inhibitory capacity was examined and found to be composed primarily of alpha 1-proteinase inhibitor (PI, alpha 1-antitrypsin) and, to a lesser extent, bronchial mucosal inhibitor. Although the average PI concentration was elevated approximately 5-fold in the pneumonia group, its inhibitory function against elastase was decreased 15-fold when compared with that in the control group. The pneumonia group showed an increased concentration of immunologically identified elastin-derived peptides. Some of the BAL fluid from patients with pneumonia showed elastolytic activity against amorphous insoluble lung elastin. The majority of the elastase appears to be of neutrophil origin. Bronchial mucosal inhibitor is shown to be a component of both normal and pneumonia BAL fluids by both immunologic quantitation and by its resistance to perchloric acid inactivation. Compared with those from control subjects, BAL samples from patients with acute bacterial pneumonia showed a decreased proteinase inhibitor function and both increased elastolytic activity and elastin-derived peptide concentration.

Acute Disease↗
PubMed1984

Effects of physical training on insulin, connecting peptide (C-peptide), gastric inhibitory polypeptide (GIP) and pancreatic polypeptide (PP) levels in obese subjects.

Ten severely obese women were subjected to physical training for three months on ad libitum diet. Under metabolic ward conditions oral glucose tolerance test was performed before and after the training period with the same energy intake quantitatively and qualitatively, and glucose, insulin, connecting (C)-peptide, gastric inhibitory polypeptide (GIP) and pancreatic polypeptide (PP) were determined. In confirmation of previous work, physical training caused no decrease in body fat in these severely obese subjects, and no change in body cell mass or glucose tolerance, while insulin and blood pressure decreased. The control of dietary conditions demonstrated that the latter phenomena were not due to quantitative or qualitative changes in the diet. C-peptide concentrations decreased also, indicating effects of physical training in obesity on insulin production. GIP is believed to be a gastrointestinal factor facilitating insulin secretion (Incretin). Previous work has indicated that gastrointestinal factor(s) are involved in the insulin lowering effect seen after physical training. It is possible that GIP is contributing to this phenomenon.

Adipose Tissue↗
PubMed1983

Effects of physical training on adrenergic sensitivity in obesity.

To examine the possibility that the decrease of hyperinsulinemia and blood pressure in obesity associated with physical training is mediated via adaptations in the adrenergic nervous system, a pure beta-adrenergic agonist (isoproterenol) or an alpha-adrenergic antagonist (phentolamine) was infused before and during an oral glucose tolerance test before and after physical training. A number of circulatory, metabolic, and endocrine factors under adrenergic control were followed. Physical training was associated with an augmented beta-agonist response in blood pressure, heart rate, blood glucose, plasma insulin, connecting (C) peptide, and pancreatic polypeptide (PP) but not in plasma glucagon and gastric inhibitory polypeptide. Physical training also resulted in higher values of C-peptide and PP values after alpha-adrenergic blockade. It was concluded that physical training probably is associated with an augmented sensitivity of the beta-adrenergic nervous system. This might also be the case with the alpha-adrenergic system. It was suggested that this in turn might be due to a decreased firing in the adrenergic nervous system leading secondarily to an increased sensitivity in the effector cells. It was hypothesized that such decreased firing could provide a background to explain lower blood pressure and plasma insulin after physical training.

Adult↗
PubMed1982

Plasma and serum concentrations of DNA in pulmonary thromboembolism.

The value of circulating DNA concentrations in the diagnosis of pulmonary embolism (PE) was assessed in 68 consecutive patients, of which 36 (Group 1) had clinical symptoms suggesting PE. The diagnosis of PE was established in 13 patients on the basis of pulmonary angiography (PA) (8 patients) and high probability ventilation-perfusion lung scanning (VPS) (5 patients). Pulmonary embolism was ruled out in 23 patients (by PA, 9 patients; by VPS, 14 patients). We found abnormally high DNA concentrations in 26 of the 36 patients (72%) with suggested PE, but there was no significant differences between patients with and patients without PE (p less than 0.05). The results were compared with the DNA concentrations in the remaining 32 patients (16 medical and 16 surgical cases) who had no clinical evidence of PE (Group 2). Increased DNA concentrations were found in 21 of these (66%). There was no significant difference in mean DNA concentrations between Group 1 and Group 2 (p less than 0.05). We conclude that pulmonary angiography and high probability ventilation-perfusion scanning remain the most reliable methods for the diagnosis of PE.

Adrenal Cortex Hormones↗