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Biomedical subjects

M R Brown

Publications and source records attributed to M R Brown.

At least 271 records · Page 15Linked to original sources
PubMed1984

Corticotropin-releasing factor and angiotensin II: comparison of CNS actions to influence neuroendocrine and cardiovascular function.

The cardiovascular and hormonal responses to intracerebroventricular administration of corticotropin-releasing factor (CRF) and angiotensin II (AII) were compared in conscious, freely moving rats. CRF elevated mean arterial pressure (MAP) and heart rate (HR), increased plasma catecholamine levels and had no effect on plasma vasopressin levels. AII increased MAP and decreased HR, had no effect on plasma catecholamine levels and elevated plasma vasopressin levels. Ganglionic blockade with chlorisondamine blocked the cardiovascular effects of CRF but failed to antagonize the pressor response to AII. The vasopressin antagonist, [1-deaminopenicillamine, 2-(0-methyl)tyrosine]-AVP, did not modify CRF-induced cardiovascular changes but greatly attenuated AII's effects on blood pressure. These results suggest that CRF and AII have different central actions on hormonal and cardiovascular systems.

Angiotensin II↗
PubMed1984

Effectiveness of phosphocitrate and N-sulpho-2-amino tricarballylate, a new analogue of phosphocitrate, in blocking hydroxyapatite induced crystal growth and calcium accumulation by matrix vesicles.

Phosphocitrate and its analogue N-sulpho-2-amino tricarballylate were compared with ethane-1-hydroxy-1,1-diphosphonate for inhibition of calcium phosphate crystallization in hydroxyapatite induced crystal growth and 45Ca uptake by matrix vesicles. Phosphocitrate (1 microM) was the most potent inhibitor followed by ethane-1-hydroxy-1,1-diphosphonate and N-sulpho-2-amino tricarballylate, the latter requiring a high concentration (100 microM) to be equally effective as an inhibitor.

Animals↗
PubMed1984

Bombesin-induced stimulation of cardiac parasympathetic innervation.

The central nervous system effects of bombesin on cardiovascular function were examined in conscious, freely-moving rats. Intracerebroventricular administration of bombesin elevated mean arterial pressure, reduced heart rate and inhibited cold-induced tachycardia. Adrenalectomy prevented bombesin-induced elevations of mean arterial pressure. In contrast, bombesin-induced bradycardia was neither adrenal-dependent nor a baroreceptor-mediated reflex response to increased arterial pressure. Systemic atropine methyl nitrate treatment attenuated bombesin-induced bradycardia, suggesting that bombesin acts within the central nervous system to stimulate cardiac vagal activity.

Adrenalectomy↗
PubMed1984

Calcitonin gene-related peptide acts within the central nervous system to inhibit gastric acid secretion.

The central nervous system effect of calcitonin gene-related peptide (CGRP) on gastric acid secretion was studied in conscious freely moving rats. CGRP (220 fmol to 2.2 nmol) injected into the lateral cerebral ventricle or intravenously inhibited gastric acid secretion. Intravenous passive immunization with CGRP antiserum prevented the inhibitory effect of CGRP following intravenous but not intracerebroventricular administration. Adrenalectomy and noradrenergic blockade with bretylium tosylate did not significantly alter the inhibitory action of CGRP given intracerebroventricularly on gastric secretion. These studies indicate that CGRP acts within the central nervous system to potently decrease gastric acid secretion by mechanism(s) not dependent on intact sympathetic nervous function.

Adrenalectomy↗
PubMed1984

Effect of iron deprivation on the production of siderophores and outer membrane proteins in Klebsiella aerogenes.

The outer membrane (OM) protein profile of Klebsiella aerogenes grown in an iron rich chemically defined medium (Fe + CDM) showed three major proteins of 32.5, 35.5 and 39.0 kDal. The 35.5 and 39.0 kDal proteins were non-covalently associated with peptidoglycan. At least six new iron regulated outer membrane proteins (IRMP) of 69, 70, 73, 75, 78 and 83 kDal, which were not peptidoglycan associated, were apparent in the OM of K. aerogenes grown in iron restricted (serum) or iron deficient (Fe-CDM) media. An 18.5 kDal protein was also present in the OM of stationary phase K. aerogenes following growth in Fe + CDM, in iron saturated serum and in citrate supplemented CDM but was repressed in Fe-CDM or in serum. Enterochelin but not aerobactin was detected in the spent supernates of iron deficient K. aerogenes. Inoculation of iron replete K. aerogenes into low iron CDM (less than 17 X 10(-7) M-Fe3+) produced IRMP and enterochelin within two generations, and several generations before the end of exponential phase. Inoculation of iron depleted cells into Fe + CDM resulted in dilution rather than active excretion from the OM of the IRMP, 1.5 generations being required for the initial level to decrease by one-half and 4 generations for it to return to that observed after growth to stationary phase in Fe + CDM. The appearance of the IRMP of K. aerogenes grown under iron depletion was unaffected by prior growth of the inoculum in a gross excess of iron which suggested that whether or not K. aerogenes was capable of storing iron, it rapidly responded to the extracellular iron concentration.

Bacterial Outer Membrane Proteins↗
PubMed1984

Brain peptide regulation of adrenal epinephrine secretion.

The studies described in this paper support the hypothesis that specific brain peptides may act as neurochemical substrates for the differential patterns of sympathetic nervous system and adrenomedullary responses to various provocative stimuli. Different treatments, e.g., exposure to ether vapor or cold, hemorrhage or hypoglycemia, elicit stimulus-specific changes in plasma concentrations of epinephrine and norepinephrine. Likewise, several neuropeptides, e.g., bombesin, corticotropin-releasing factor, thyrotropin-releasing factor, and somatostatin-related peptides, act within the central nervous system to produce differential changes in the relative concentrations of epinephrine and norepinephrine in plasma. The possibility that these peptides may be involved in generating stimulus-specific changes in plasma catecholamine concentrations following various physiological and pharmacological treatments is discussed.

Adrenal Medulla↗
PubMed1984

Central nervous system regulation of adrenocorticotropin secretion: role of somatostatins.

Somatostatin-28 (SS-28) and desAA1,2,4,5,12,13[D-Trp8]somatostatin (ODT8-SS), but not somatostatin-14, given intracerebroventricularly, but not when given iv, inhibit stress-induced pituitary ACTH and adrenomedullary epinephrine secretion in rats. The elevation of ACTH after tail-suspension stress is totally prevented by iv administration of antisera raised against corticotropin-releasing factor (CRF). SS-28 and ODT8-SS do not inhibit CRF-induced ACTH secretion in vivo or in vitro. These results are consistent with the hypothesis that SS-28 and ODT8-SS prevent stress-induced ACTH secretion by inhibition of CRF release.

Adrenocorticotropic Hormone↗
PubMed1984

Neuropeptide modulation of photosensitivity. I. Presence, distribution, and characterization of a substance P-like peptide in the lateral eye of Limulus.

The lateral eye of Limulus is innervated by an efferent system of fibers containing a substance P-like peptide. They were detected and their distribution was studied using indirect immunocytochemical techniques and monoclonal and serum antibodies. These thin, efferent fibers travel up the optic nerve, cross the lateral plexus, and branch out profusely when reaching the ommatidial layer. Innervation is extended to more than one component of the ommatidia, including the pigment, retinular, and eccentric cells. Immunoreactive staining could be abolished by absorbing the antisera with as little as 1 microM synthetic substance P. The efferent character of the fibers was established by means of ligation experiments, a technique also used to determine their origin in the circumesophageal connectives. Radioimmunoassay with two different C-terminal serum antibodies confirmed the presence of substance P-like material in the eye in the amounts of 61.44 pg/micrograms of protein, or up to 18 ng/eye. Gel filtration chromatography of crude extracts of the lateral eye, followed by radioimmunoassay, revealed an elution pattern extremely similar but not identical to that of synthetic substance P. These results show that a system of efferent fibers containing a substance P-like peptide originates in cells in the circumesophageal ring and innervates the ommatidia of the lateral eye. Their distribution and origin suggest an involvement in the modulation of photosensitivity, as part of a larger, generalized, level-setting regulator that is driven by a circadian clock but can also be activated by other systems.

Animals↗
PubMed1984

Effect of breast-feeding on morbidity in rotavirus gastroenteritis.

Fifty infants less than 1 year of age with rotavirus gastroenteritis were studied with regard to the protective effect of breast-feeding. The initial incidence of breast-feeding was 64% in the patients infected with rotavirus and 70% in a matched control population. Seven patients were breast-fed at the time of infection, 25 patients had stopped breast-feeding prior to infection, and 18 patients were exclusively formula-fed. There were no significant differences between groups in the average age of infection, mean duration of diarrhea, mean number of bowel movements in 24 hours, or in the frequency of fever or irritability. The only apparent difference between groups was that the frequency of vomiting was significantly decreased in the breast-fed children. The results of this study suggest that breast-feeding offers little protection against rotavirus gastroenteritis.

Age Factors↗
PubMed1984

Esophageal function after repair of esophageal atresia.

The results of this study demonstrate that there is abnormal esophageal function in patients who have undergone repair of esophageal atresia. The diagnostic tests used may be too sensitive as the abnormalities demonstrated have little clinical relevance. In addition, there was an inverse relationship between signs and symptoms of esophageal dysfunction and the age of the child. The abnormalities are probably intrinsic and only secondarily affected by surgical treatment. Increased tension at the gastroesophageal junction is a likely factor in the production of gastroesophageal reflux. Esophageal dysfunction does not necessarily lead to detrimental gastroesophageal reflux with the sequela of repeated respiratory infections, failure to gain weight or esophageal stricture. Only patients who have such signs or symptoms need to undergo evaluation of esophageal function to determine if there is an abnormality. The results of the studies then document the need for an antireflux procedure.

Child↗
PubMed1983

Influence of sodium dodecyl sulphate quality on the electrophoretic mobility of the outer membrane proteins of mucoid and non-mucoid Pseudomonas aeruginosa.

The electrophoretic mobilities of proteins F and H1 from the outer membrane of Pseudomonas aeruginosa (mucoid and non-mucoid) in polyacrylamide gel electrophoresis were affected by the quality of sodium dodecyl sulphate (SDS) used. In particular, the sodium tetradecyl sulphate impurity present in crude SDS influenced the mobilities of F and H1. These observations explain conflicting reports on changes in outer membrane proteins with strain and growth conditions. Synthesis of H1 was induced by growth in magnesium depleted medium but repressed when calcium or manganese were added to magnesium depleted medium.

Bacterial Outer Membrane Proteins↗
PubMed1983

Central nervous system effects of corticotropin releasing factor in the dog.

UNLABELLED: Corticotropin releasing factor (CRF) given intracerebroventricularly (i.c.v.) increases mean arterial pressure (MAP) and heart rate (HR), while CRF given intravenously decreases MAP and increases HR. CRF given i.c.v. elevates plasma concentrations of vasopressin and catecholamines. Ganglionic blockade with chlorisondamine prevents CRF-induced increases in MAP; the vasopressin antagonist, [1-deaminopenicillamine,2-(O-methyl)tyrosine]-vasopressin does not alter CRF-induced increases in MAP. In contrast to CRF, angiotensin II (A-II) given i.c.v. increases MAP but decreases HR. IN CONCLUSION: (1) CRF elevation of MAP and HR in dogs is dependent on an intact sympathetic nervous system, and (2) CRF and A-II have different CNS effects on cardiovascular function.

Angiotensin II↗
PubMed1983

Central nervous system sites of action of bombesin and somatostatin to influence plasma epinephrine levels.

Bombesin acts within dog brain to increase plasma concentrations of glucose and epinephrine. Microinjection of bombesin into a variety of brain regions demonstrates that this peptide's site of action is within the dorsal hypothalamic area. Microinjection of the somatostatin analog, desAA1,2,4,5,12,13 [D-Trp8]-somatostatin (ODT8-SS) into the dorsal hypothalamic area but not into other brain areas prevents bombesin-induced elevation of plasma glucose and epinephrine. Thus bombesin and ODT8-SS act within specific brain areas to influence plasma concentrations of glucose and epinephrine.

Animals↗
PubMed1983

The synthesis and characterization of N-sulfo-2-amino tricarballylate: an analog of phosphocitrate and inhibitor of calcification.

The synthesis of N-sulfo-2-amino tricarballylate, a sulfamate analog of phosphocitrate, is described using pyridine-sulfur trioxide to sulfonate 2-amino tricarballylate. The product was purified using selective precipitation and chromatographic techniques and characterized by a variety of physical and chemical means. In particular, its ability to inhibit hydroxyapatite formation and calcium oxalate crystallization was assessed by comparison with known inhibitors including phosphocitrate and pyrophosphate. On the basis of these results, this new compound may ultimately have a role in preventing abnormal biological calcification.

Calcium↗
PubMed1983

Effect of nutrient depletion on the sensitivity of Pseudomonas cepacia to antimicrobial agents.

Pseudomonas cepacia depleted of various nutrients showed marked variation in sensitivity to cetrimide, chlorhexidine, and benzalkonium chloride. In all cases cells depleted of magnesium were the most resistant. It is proposed that these observations may be due to alterations of the envelope of P. cepacia in response to changes in the growth environment. This may have profound implications for investigations of the resistance of this organism both in vivo and in vitro.

Anti-Infective Agents, Local↗
PubMed1983

Corticotropin-releasing factor (CRF): mechanism to elevate mean arterial pressure and heart rate.

The efferent mechanisms by which central administration of corticotropin-releasing factor (CRF) elevates mean arterial pressure and heart rate were assessed in unanesthetized, unrestrained rats. CRF increased blood pressure and heart rate by stimulating noradrenergic sympathetic nervous outflow. CRF-induced cardiovascular changes were not dependent on anterior pituitary hormone release, adrenomedullary epinephrine secretion, the renin-angiotensin system or circulating vasopressin.

Adrenal Glands↗
PubMed1983

Biological effects of cysteamine: relationship to somatostatin depletion.

Cysteamine given subcutaneously to rats decreases brain concentrations of somatostatin-like immunoactivity (SLI) but does not affect vasopressin-like immunoactivity as determined by radioimmunoassay and immunocytochemistry. Since somatostatin-related peptides act within the central nervous system (CNS) to increase body temperature and decrease adrenal epinephrine secretion, changes in these parameters were assessed following cysteamine administration. Cysteamine administration lowers oxygen consumption and body temperature, and elevates plasma concentrations of epinephrine, glucose, insulin and glucagon. The lowering of body temperature and elevation of plasma epinephrine is prevented by CNS administration of the CNS-selective somatostatin analog desAA1,2,4,5,12,13[D-Trp8 ))somatostatin. The CNS actions of somatostatin-related peptides are opposite to the effects of cysteamine. The observations are consistent with the possibility that brain somatostatin-related peptides are involved in regulation of body temperature and adrenal epinephrine secretion.

Animals↗