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Biomedical subjects

M J Gibson

Publications and source records attributed to M J Gibson.

At least 91 records · Page 5Linked to original sources
PubMed1985

A technique for the long term measurement of intra-compartmental pressure in the lower leg.

The early diagnosis of an acute compartmental pressure syndrome is often difficult, but can be facilitated by long term, up to several days, measurement of intra-compartmental pressures. A measuring system has been developed, together with its associated surgical and operational procedures, which may be applied in a variety of situations, including an immobile patient or a patient mobilized following surgery. If the technique is adopted as soon as the patient enters hospital, or immediately postoperatively, an acute compartmental syndrome may be recognized early and measures taken to alleviate its consequences.

Biomedical Engineering↗
PubMed1985

Implantation of normal fetal preoptic area into hypogonadal mutant mice: temporal relationships of the growth of gonadotropin-releasing hormone neurons and the development of the pituitary/testicular axis.

Central nervous system tissue which included the preoptic area (an area rich in gonadotropin-releasing hormone neurons) was taken from normal 17-day fetal mice and transplanted into the infundibular recess of the third ventricle of the hypothalamus of 90-day male mutant hypogonadal mouse hosts that are unable to synthesize the neurohormone, gonadotropin-releasing hormone. The growth and development of gonadotropin-releasing hormone neurons and fibers in the donor and host tissue as well as recovery of the pituitary-testicular axis were followed from 10 to 120 days post-implantation. Testicular growth was evident in 94% of the hypogonadal animals within 30 days post-implantation, continued for 90 days but showed no further increase during the remainder of the experiment. Increases in seminal vesicle weight, an index of testosterone secretion, were measurable at 30 days and continued through to the end of the experiment. Pituitary concentrations of gonadotropins were doubled at 30 days over that seen in the control mutant mouse and were maintained thereafter at normal or supranormal concentrations. In contrast plasma levels of gonadotropins, although above baseline at 30 days, never reached normal circulating levels. Nevertheless, it appeared that the concentration of luteinizing hormone achieved was sufficient to initiate and maintain testicular growth and testosterone secretion for the entire duration of the experiment. Immunocytochemical analysis of brain tissue was used to determine the presence and numbers of gonadotropin-releasing hormone neurons in the transplant and the distribution of their fibers in the donor and host tissue. The numbers of immunoreactive gonadotropin-releasing hormone neurons present at the time of sacrifice ranged from 3 to 140. Fiber outgrowth from the donor cells into the host was noted as early as 10 days post-implantation and the density of outgrowth continued to increase over the course of the experiment. Positive fibers tended to accumulate over the tuberoinfundibular sulci as they do in normal animals. In those instances where the transplant was placed a long distance from the median eminence, the gonadotropin-releasing hormone axons grew on the internal surface of the third ventricle until they reached these specific exit zones. These studies indicate that in the mutant hypogonadal mouse, central nervous system transplants from normal fetal mice can maintain the function of the pituitary-gonadal axis for periods of up to 120 days post-implantation. Outgrowth of the neurosecretory fibers begins very soon after implantation and the axons tend to follow pathways seen in normal tissue.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1985

Streptozotocin-induced diabetes is associated with reduced immunoreactive beta-endorphin concentrations in neurointermediate pituitary lobe and with disrupted circadian periodicity of plasma corticosterone levels.

Lower concentrations of immunoreactive (IR) beta-endorphin were present in the neurointermediate pituitary lobes of streptozocin-induced diabetic versus control animals at both 2 and 4 weeks after the onset of diabetes. The forms of beta-endorphin-like material present appeared to be similar in both groups when studied with cation-exchange chromatography. Insulin therapy via minipump for 2 weeks did not alter this finding of lowered beta-endorphin concentrations in diabetic animals, despite normalization of blood glucose levels and body weight gain. Lower IR beta-endorphin levels were also found in neurointermediate lobes of weight-restricted rats, but this group had increased plasma IR beta-endorphin concentrations compared to diabetic animals. Concentrations of IR beta-endorphin in microdissected brain regions and in anterior pituitaries of the diabetic animals failed to show consistent changes; in addition, ACTH concentrations in pituitary lobes and plasma did not differ among groups. Circadian rhythmicity of plasma insulin and corticosterone concentrations was absent in the diabetic animals, although food and water intake, while elevated, showed the normal nocturnal pattern of increased ingestion. Furthermore, adrenal hypertrophy was present in the diabetic animals and was accompanied by an elevation of mean plasma corticosterone levels. The present findings indicate that diabetes is associated with a decrease of neurointermediate pituitary lobe synthesis of beta-endorphin, while not affecting the processing of the peptide in this lobe, and confirm previous reports of altered adrenal function in diabetic animals.

Adrenocorticotropic Hormone↗
PubMed1984

Mating and pregnancy can occur in genetically hypogonadal mice with preoptic area brain grafts.

Adult female hypogonadal mice, in whom hypogonadism is secondary to a genetic deficiency in hypothalamic gonadotropin-releasing hormone (GnRH), are infertile. Mating, pregnancy, and delivery of healthy litters were achieved after transplantation of normal fetal preoptic area tissue, a major site of GnRH-containing cell bodies, into the third ventricle of adult female hypogonadal mice. Immunocytochemistry revealed GnRH-containing neurons in the grafts and GnRH-containing processes extending to the lateral median eminence of the host brains.

Animals↗
PubMed1984

Preoptic area brain grafts in hypogonadal (hpg) female mice abolish effects of congenital hypothalamic gonadotropin-releasing hormone (GnRH) deficiency.

Normal fetal preoptic area (POA), a site of GnRH production, was implanted into the third ventricle of adult female hypogonadal (hpg) mice. When the grafts were successful, the mice (genetically deficient in hypothalamic GnRH) responded with vaginal opening, cornified vaginal cells, ovarian and uterine development, and increased pituitary FSH content and plasma LH concentrations. Similar results were obtained with fetal POA tissue, whether derived from males or females. Two of four hpg mice with POA grafts mated when caged overnight with males. Hpg females that received cortical tissue from fetuses or from 16-day-old pups, or POA tissue from 16-day-old pups, showed none of these changes, remaining similar to untreated hpg females.

Animals↗
PubMed1983

Brain tissue grafts in the central nervous system: reversal of hypogonadism.

Transplantation of brain tissue from normal donors into the central nervous system of animals with specific central neurochemical deficiencies has been used to remedy such defects. The present studies demonstrate that the hypogonadism present in the adult male hypogonadal (hpg) mouse that is secondary to hypothalamic gonadotropin releasing hormone (GnRH) deficiency can be corrected by grafts into the anterior third ventricle of fetal preoptic area (p.o.a.) tissue. The p.o.a. is a primary site of localization of GnRH neurones in rodents. As compared with untreated hpg males, or with hpg males that had received control cortical tissue implants, the hpg animals with p.o.a. grafts showed measurable levels of GnRH within the hypothalamus. Immunocytochemical studies revealed GnRH within the transplants. Increased pituitary and plasma LH and FSH, and testicular growth with full spermatogenesis, were also evident in the hpg males that had received p.o.a. implants.

Animals↗
PubMed1982

Brain grafts reverse hypogonadism of gonadotropin releasing hormone deficiency.

Hypogonadism in the mutant hpg mouse is characterized by a deficiency of hypothalamic gonadotropin releasing hormone (GnRH). Affected male mice exhibit immature reproductive organs, small abdominal testes and low pituitary and plasma gonadotropin concentrations. Recent studies have demonstrated the potential of fetal brain transplants to establish functional connections with host tissues. We therefore sought to use this approach to correct the hpg deficit. Fetal preoptic area (POA) (a site of GnRH production) from unaffected animals of the hpg strain was transplanted into the anterior third ventricle of adult hpg mice. We report that in such implanted animals, killed 2 months post-implantation, the POA grafts contained GnRH neurones, from which GnRH-positive fibres could be traced to capillaries of the median eminence. Hypothalamic GnRH and pituitary and plasma gonadotropin concentrations were increased compared with levels in untreated (hpg) animals. The testes were enlarged and had descended into the scrotum. Evidence of full spermatogenesis and interstitial cell development was present in testicular sections. No such effects were seen with transplants of cortical tissue.

Animals↗
PubMed1982

Primary colo-rectal linitis plastica type of carcinoma: report of two cases and review of the literature.

Linitis Plastica type of carcinoma can arise primarily in the colon or rectum. Fifty-two cases have been reported in the English medical literature over a 50-yr period. Two new cases are described. One patient had primary linitis plastica of the ascending colon, the other being in the rectum. Both patients died of widespread malignancy within 10 mth of diagnosis, the fate of most of the reported cases. This rare manifestation of colo-rectal carcinoma carries an ominous prognosis.

Adenocarcinoma, Scirrhous↗
PubMed1981

Bacterial survival in a dilute environment.

Bacteria were isolated from lake water, and their ability to remain viable in a dilute, nutrient-deficient environment was tested by a method that permits suspension of test bacteria between two appressed microporous membranes in an aqueous environment. This approach permitted separation of the lake isolates into two categories. Members of the tribe Klebsielleae were shown to have a prolonged survival rate of 40% or better after 24 h, whereas nonsurvivors were not viable for much longer than 24 h. These nonsurvivors belonged to the genera Acinetobacter, Aeromonas, Alcaligenes, Erwinia, Escherichia, Flavobacterium, and Pseudomonas. Differences in ribonuclease and adenosine triphosphatase levels between Escherichia coli (nonsurvivor) and Klebsiella (survivor) cells were detected. At pH 7.5, stressed E. coli cells contained 14% of the adenosine triphosphatase activity detected in the control, whereas at pH 5.5, in the presence of calcium ions, these same cells contained 50% of the control adenosine triphosphatase levels. At pH 7.2, E. coli cells were strongly inhibited by an adenosine triphosphatase inhibitor, bathophenanthroline (88%); oligomycin (64%); and the proton ionophore carbonyl- cyanide-m-chlorophenyl hydrazone (67%). Both sodium azide and valinomycin were only moderately inhibitory (15 and 28%, respectively). Although the ability to scavenge internal endogenous reserves seems important, we postulate that certain enteric bacteria are capable of utilizing acidic conditions (pH 5.5) as an electrochemical gradient to generate necessary high-energy intermediates for prolongation of survival beyond that possible in environments of near-neutraL pH.

Adenosine Triphosphatases↗
PubMed1981

Circadian corticosterone rhythm and stress response in rats with adrenal autotransplants.

A significant circadian variation in plasma corticosterone concentrations as determined by sequential sampling was observed in rats with adrenals autotransplanted (ADT) to the inguinal region as well as in sham-operated controls when studied 3 wk after surgery. Phase shifting of plasma corticosterone concentrations was observed in a second ADT group placed in reverse photoperiod (D12:L12, lights on 1900) for 2 wk. Intravenous injections of ACTH in dexamethasone-suppressed animals resulted in significant increments in plasma corticosterone concentrations in sham-operated but not in ADT animals. ADT and sham groups both showed elevated plasma corticosterone concentrations after ether or 30-min immobilization stress, although greater responses were present in the sham group. It appears that direct innervation of the adrenal is unnecessary for the maintenance of circadian plasma corticosterone concentrations or certain stress responses.

Adrenal Glands↗
PubMed1980

The plain abdominal radiograph in acute pancreatitis.

The radiographs of 100 patients with acute pancreatitis were reviewed and compared with 100 controls by two radiologists and a surgeon. Our aim was to assess the frequency and usefulness of the signs described in the literature. Calcification of the pancreas was seen in one case only. Abnormalities of the biliary tree (visible gallbaldder, biliary gas and gallstones) were seen in 10%. The left psoas shadow was more frequently absent in the pancreatitis series. Paucity of gastrointestinal gas although observed in 12 cases was ascribed to vomiting. A more important sign was the gaseous outline of an adynamic duodenal loop which was seen in half of the patients examined in the left lateral decubitus position. Dilated jejunum was seen in 31 cases, associated with sentinel loops in 10 and multiple fluid levels in 25 patients. Dilatation of thet ransverse colon was the most constant colonic sign (18%), but the colon 'cut-off' sign was not seen. It was concluded that the most prominent signs in order of importance are a gaseous distension of the duodenal loop, gas in the duodenal cap, a dilated transverse colon and the sentinel loop. The gasless abdomen is a striking but rare sign and in our series was always associated with severe pancreatitis.

Acute Disease↗
PubMed1978

U.S. medical students in Nepal.

A formal course in Human Ecology in the Himalayas proved to be a powerful educational innovation partly because of its international setting. The six students in the medical part of this course experienced a profound affective impact on their career goals, a totally new orientation toward the problems of poverty in the United States, and a changed appreciation of the need for preventive measures and a community approach. The effect was far greater than that usually associated with individualized international experiences because of careful preparatory seminars, group activities which included surveys and research, and abundant opportunity for interpretive discussions as cultural and health care shock was being experienced. Clinical work was kept in perspective and provided opportunities for learning, not only about exotic diseases but also about what could be done under the simplest of conditions.

Attitude to Health↗