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Biomedical subjects

D G Johnson

Publications and source records attributed to D G Johnson.

At least 217 records · Page 12Linked to original sources
PubMed1977

Immunocytochemical localization of a gastric imhibitory polypeptide-like material within A-cells of the endocrine pancreas.

In rat pancreatic islets, the glucagon-producing A-cells also contain a GIP-like material as revealed by the peroxidase-antiperoxidase immunocytochemical technique. Control studies showed that this dual staining was not due to the cross-reactivity of anti-GIP with glucagon. It is concluded either that the A-cells synthesize a GIP-like peptide or that it is taken up from the circulation.

Animals↗
PubMed1977

Neonatal small left colon syndrome.

Neonatal small left colon syndrome is a functional disease of the lower colon which produces typical signs and symptoms of intestinal obstruction. It is manifest in the first 24-48 hours of life, particularly in infants of diabetic mothers and, if detected early, it can be fully cured by radiographic contrast enemas, not unlike meconium plug syndrome. Intestinal perforation and death may occur, however. The etiology of the disease is unknown but it may relate to neurohumoral imbalances between the autonomic nervous system and glucagon.

Colonic Diseases↗
PubMed1977

Study of U.S. medical school applicants, 1975-76.

This annual descriptive study provides statistics on the demographic and background characteristics, academic ability, and career plans of applicants to the 1975--76 first-year class. Comparisons with the preceding year's applicant pool, traditionally the focus of the applicant study series, show a slight decline in the size of the pool, a continued increase in the number of women applicants and acceptees, and a slightly higher acceptance rate for all applicants. The study has been expanded by reinstating data on the socioeconomic background of applicants and by providing general summaries on topics such as career plan preferences of applicants. New to the series is an analysis of "in-phase" applicants, that is, undergraduate college seniors applying to medical school for the first time. The conclusion outlines those activities of the Association of American Medical Colleges over the past year that are related to the medical school admissions process.

Adult↗
PubMed1977

Role of glucagon in mediating metabolic effects of epinephrine.

In order to separate direct effects of epinephrine on fuel metabolism from those mediated by glucagon, epinephrine (0.1 microng/kg-min) was infused for 120 min in 18- and 65-h fasted, nonanesthetized baboons with and without a concomitant somatostatin infusion. At both stages of fasting, epinephrine stimulated glucagon, secretion, and this was blocked by somatostatin. At 18 h, with epinephrine alone, glucose rose early and remained elevated throughout the infusion. In the glycogen-depleted 65-h fasted animals, there was attenuation of the early glucose rise, with glucose reaching a maximum level at 100-120 min. With somatostatin blockade of glucagon release in the 18-h fasted animals, a pattern of attenuated early glucose rise similar to that of the 65-h fasted animals occurred. Somatostatin also inhibited this early glycogenolytic response when the epinephrine dose was increased fivefold. The behavior of FFA, glycerol, and beta-hydroxybutyrate was unchanged by the addition of somatostatin to epinephrine at either stage of fasting. Thus, glucagon mediates the early glycogenolytic response to epinephrine, but not the delayed hyperglycemia and probably not the lipolysis.

Animals↗
PubMed1977

Plasma norepinephrine responses of man in cold water.

The hypothermic stress of immersion in cold water stimulates release of norepinephrine from the sympathetic nervous system. The speed and pattern of this response was studied in six healthy men by serial measurements of plasma norepinephrine concentrations before, during, and after 60 min of immersion in 10 degrees C water. After immersion for 2 min, the mean norepinephrine concentration was increased from 359+/-32 (basal) to 642+/-138 pg/ml and rose gradually to a maximum of 1.171+/-226 pg/ml after 45 min of immersion. Metabolic rate increased approximately threefold during the immersion period. After rewarming in warm water (40 degrees C), the subjects showed a transient peak in plasma norepinephrine followed by a rapid decrease to basal levels after 30 min. The fall in plasma norepinephrine after approximately 8 min of rewarming occurred despite persistent depression of the core temperature and coincided with a sudden decrease in metabolic rate and cessation of body shivering. These results suggest that the sympathetic nervous response to cold can be activated or suppressed very quickly and is dependent on the skin temperature.

Adult↗
PubMed1977

Glucagon and catecholamine secretion during hypoglycemia in normal and diabetic man.

To examine the role of catecholamines in glucopenia-induced glucagon secretion, urinary epinephrine and norepinephrine and plasma immunoreactive glucagon (IRG) were measured during insulin-induced hypoglycemia in normal and insulin-dependent diabetic-man. Despite equivalent levels of hypoglycemia the mean plasma IRG increment in diabetes was only 15% of normals. The increases in epinephrine and norepinephrine were comparable in diabetics and normals; thus, the blunted response in plasma IRG to the stimulus of low blood sugar in diabetics cannot be explained by a generalized defect in catecholamine secretion. It is suggested that an alpha-cell glucoreceptor defect may account for the abnormal response to glucopenia in diabetics. To evaluate the possibility that impaired sensitivity to circulating catecholamines could explain the alpha cell dysfunction in diabetics, exogenous epinephrine was infused in normals and insulin-dependent diabetics. Elevated plasma IRG during epinephrine infusion was observed in only 50% of normals. The diabetics were hyperresponsive; mean increment in plasma IRG 3 times that of normals. The data demonstrate enhanced rather than impaired sensitivity to catecholamines in diabetes mellitus.

Adolescent↗
PubMed1977

Evaluation of gastroesophageal reflux surgery in children.

Fifty-five infants and children with complications of gastroesophageal reflux required operative management for control of symptoms. All patients, except those with severe esophageal stricture, received a six-week trial with 60-degree constant elevation before an operation was considered necessary. The operation was performed to control (1) persistent vomiting, (2) vomiting with growth retardation, (3) esophagitis, (4) esophagitis with stricture, and (5) recurrent aspiration pneumonia. Preoperative and postoperative evaluation involved both X-ray fluoroscopy and esophageal manometry with pH studies. A good surgical result was not dependent upon an increase in the lower esophageal pressure following operation. The Boerema anterior gastropexy is simple and effective for controlling gastroesophageal reflux for cases uncomplicated by esophagitis, stricture, or previous operation. Complex cases with inflammatory or operative changes in the lower esophagus are more effectively treated by Nissen fundoplication.

Child, Preschool↗
PubMed1976

Hormonal regulation of pancreatic islet adenyl cyclase.

Adenyl cyclase activity of rat pancreatic islet membrane was increased by secretin, pancreozymin, and isoproterenol, while ACTH, glucagon, growth hormone, and insulin had no effect. Both secretin and isoproterenol activations were enhanced by prostaglandin E1 (PGE1) and GTP. Isoproterenol activation was additive with PGE1, as was that of secretin with PGE1, but only in the presence of GTP. Secretin activation in the presence of PGE1 and GTP was equivalent to NaF stimulation. Kinetic analysis indicated that secretin and GTP increased the maximum velocity of the adenyl cyclase and tended to decrease the apparent affinity of the enzyme for ATP. Glucagon activation of islet membrane adenyl cyclase was dependent upon prior treatment of the membrane preparation with EGTA and the use of inhibitors of proteolytic enzymes during the collagenase digestion phase of islet preparation. These results suggest that hormonal regulation of insulin secretion may be affected by PGE1 and guanine nucleotide modulation of the adenyl cyclase activation process.

Adenylyl Cyclases↗
PubMed1976

Gastroesophageal reflux with protein-losing enteropathy and finger clubbing.

Finger clubbing, protein-losing enteropathy, and iron deficiency were documented in three children with severe gastroesophageal reflux. One patient had Sandifer syndrome and the other two had the rumination syndrome. In each case, surgical repair of the gastroesophageal reflux resulted in immediate clearing of signs of the Sandifer syndrome, gastroesophageal reflux, and anemia and the return of serum protein levels to normal. There was definite regression of the finger clubbing during the ensuing year. It is suggested that finger clubbing, protein-losing enteropathy, Sandifer syndrome, and rumination be viewed as parts of an extended syndrome of unusual presentations of gastroesophageal reflux.

Anemia, Hypochromic↗
PubMed1976

Surgical aspects of airway management in infants and children.

The surgical management of the upper airway in infants and children varies in many important details from the principles of airway management usually applied to adults. Recent technical adaptations and innovations have improved our ability to deal with upper airway obstruction effectively. Advances in respiratory support for sick infants have saved thousands of lives and at the same time produced a new spectrum of airway problems which must be dealt with effectively. The surgeon who takes on such problems should be specially trained and dedicated to the unique requirements of infants and children.

Adolescent↗
PubMed1976

Study of U.S. medical school applicants, 1974-75.

The applicant activity for the 1974-75 first-year class in U.S. medical schools presents an unusual combination of statistics. There were more applicants than ever before, but the annual growth rate showed a decline, a trend that began in 1973-74; the national acceptance average remained unchanged; and the average application frequency per individual was accelerated. Most of the traditional tables cover five years of historical data (1970-71 through 1974-75), while the new features--acceptance success for first-time and repeat applicants and ability levels by acceptance success and application frequency--depict data for one year (1974-75). As in past studies, the conclusion enumerates major efforts instituted by the Association of American Medical Colleges to assist medical schools with admission problems. The most important innovations among these were two new task forces--one for minority admissions and one for financial aid.

Achievement↗
PubMed1976

Glucagon response to hypoglycemia in sympathectomized man.

Hypoglycemia stimulates immunoreactive glucagon (IRG) secretion and increases the activity of the sympathetic nervous system. To ascertain if the augmented alpha cell activity evoked by glucopenia is mediated by the adrenergic nervous system, the glucagon response to insulin-induced hypoglycemia of five subjects with neurologically complete cervical transections resulting from trauma, thereby disrupting their hypothalamic sympathetic outflow, was compared to six healthy volunteers. In addition to clinical neurological evaluation, completeness of sympathectomy was verified by failure to raise plasma norepinephrine levels during hypoglycemia compared to the two- and threefold increase observed in controls. Total IRG response (IRG area above basal 0-90 min) and peak IRG levels achieved were the same in the quadriplegics and the controls. Although the glucagon rise tended to be slower, and the peak levels attained occurred later in the quadriplegic patients than in the controls, this response was appropriate for their sugar decline, which was slower and reached the nadir later than in the control subjects. These observations that the glucagon release during insulin-induced hypoglycemia is normal in subjects whose hypothalamic sympathetic outflow has been interrupted provide strong evidence that the sympathetic nervous system does not mediate the glucagon response to hypoglycemia.

Adult↗
PubMed1976

Inhibition of insulin rlease by scorpion toxin in rat pancreatic islets.

Toxin purified from venom of the scorpion Leiurus quinquestriatus was used to release the norepinephrine from adrenergic nerve terminals in isolated pancreatic islets perifused in vitro. Addition of toxin (10 mug./ml) to the perifusion medium caused a sixfold increase in release of norepinephrine in the presence or absence of 3 X 10(-5) M phenoxybenzamine. During 20 minutes of stimulation with toxin, the pancreatic islets released an average of 15 pg. of norepinephrine per islet, which represented 20 per cent of the normal content of norepinephrine in islets. Insulin secretory rates in response to either 1.0 or 3.0 mg./ml. glucose were inhibited similarly by scorpion toxin. Addition of phenoxybenzamine abolished the inhibition of insulin release caused by scorpion toxin. Phenoxybenzamine alone did not affect release of insulin. Neither the enhanced release of norepinephrine nor the decreased release of insulin was reversed by a 20-minute wash-out period after infusion of toxin. These results indicate that the sympathetic nerve terminals in the rat pancreatic islet contain considerable amounts of norepinephrine that can be released by scorpion toxin. The norepinephrine released from sympathetic nerve endings in the pancreatic islet can inhibit release of insulin through an alpha-adrenergic action that is blocked by phenoxybenzamine.

Animals↗
PubMed1976

Stimulation of glucagon secretion by scorpion toxin in the perfused rat pancreas.

Toxin from the scorpion Leiurus quinquestriatus was used to release norepinephrine from sympathetic nerve endings in the perfused rat pancrease. Addition of toxin, 10 mug./ml., to perfusate containing 0.3 mg./ml. glucose caused a large increase in release of norepinephrine and glucagon. Glucagon secretion was suppressed by perfusate containing 3.0 mg./ml. glucose but still responded to stimulation with scorpion toxin. Atropine, 10 muM, had no effect on either norepinephrine or glucagon release in response to scorpion toxin. The release of glucagon was blocked by 100 muM propranolol, 10 muM phentolamine, or 30 muM phenoxybenzamine. Somatostatin, 55nM, did not affect the release of norepinephrine by scorpion toxin but totally inhibited the glucagon response. These results suggest that pharmacologic stimulation of the adrenergic nerve endings in the rat pancreas can elicit a rapid release of glucagon. This response can be prevented by appropriate concentrations of either alpha or beta adrenergic blocking agents or somatostatin.

Animals↗
PubMed1976

Corn grain preserved with ammonium isobutyrate for lactating dairy cattle.

Twenty-four lactating cows were fed one of three complete rations containing dry corn, ensiled corn, or corn treated with ammonium isobutyrate in a Latin square arrangement of treatments. Two weeks were used for adjustments to rations and 3 wk for collection of data. There were no differences in average daily yield of milk or fat-corrected milk, but fat percentage of milk from cows fed ensiled corn was lower than that of those given dry corn. Fat test of cows fed treated corn was intermediate and not different from the other groups. Molar proportions of volatile fatty acids and concentrations of rumen ammonia were not different among treatments.

Ammonia↗