PubMed Health⌕ Search

Biomedical subjects

K B Helle

Publications and source records attributed to K B Helle.

At least 73 records · Page 4Linked to original sources
PubMed1982

Neurotensin-induced increase in intestinal blood flow in the anesthetized rat.

Cardiac output (CO) and blood flow to major organs were investigated in pentobarbital-anesthetized rats using 85Sr and 141Ce labelled microspheres (MS) of 15 microns diameter injected into the left ventricle. Changes in organ blood flow and CO were measured after intraventricular dextran (3.4 mumol/kg/min) and intravenous neurotensin (NT) at two different rates, 2.5 nmol/kg/min and 0.125 nmol/kg/min. Dextran, known to give anaphylactoid response in rats, reduced the mean arterial pressure (MAP) from 118 +/- 17 to 55 +/- 8 mmHg (p less than 0.001) concomitant with a 56% decline in CO and significant decreases in blood flow to most organs. At 2.5 nmol/kg/min, NT caused a pattern of changes in MAP, CO and organ blood flow similar to that obtained with dextran, and thus consistent with an indirect response via mast cell stimulation. NT injected at 0.125 nmol/kg/min resulted in a significant increase (30%) in blood flow to the small intestine (p less than 0.01) without changes in MAP or CO. Vascular resistance decreased by 30% in the small intestine (p less than 0.01) and by 20% in the large intestine (p less than 0.05). The results show that circulating NT, at concentrations below those eliciting hypotension, enhances intestinal blood flow without significant changes in other organs.

Animals↗
PubMed1981

An immunohistochemical study of the organization of catecholaminergic cells and terminal fields in the paraventricular and supraoptic nuclei of the hypothalamus.

The distribution of catecholaminergic fibers and cell bodies in the paraventricular and supraoptic nuclei of the hypothalamus was investigated with immunohistochemical methods in the adult albino rat. Sections through the nuclei were stained with antisera to the catecholamine synthesizing enzymes tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH), and phenylethanolamine-N-methyltransferase (PNMT). The results suggest that adrenergic (PNMT-stained) fibers innervate the entire parvocellular division of the paraventricular nucleus, although the highest density of fibers was found in the medial part of the division. Only widely scattered adrenergic fibers are found in the magnocellular division of the nucleus and in the supraoptic nucleus. Noradrenergic fibers appear to innervate the periventricular zone of the paraventricular nucleus and those parts of the paraventricular and supraoptic nuclei that contain predominantly vasopressinergic neurons in both the normal and in the homozygous Brattleboro rat. Significant numbers--somewhat more than 500--of dopaminergic (TH-stained) neurons are found in the paraventricular nucleus; the cells are distributed throughout the nucleus but are concentrated in the medial and periventricular parts of the parvocellular division. Double-labeling experiments with the retrogradely transported tracer true blue indicate that between 4% and 8% of the dopaminergic neurons in the paraventricular nucleus project to the region of the dorsal vagal complex and/or thoracic levels of the spinal cord. It is concluded that adrenergic inputs to the paraventricular nucleus may influence cells that project to the median eminence and to preganglionic autonomic cell groups in the medulla and spinal cord. Noradrenergic inputs to the supraoptic and paraventricular nuclei may influence primarily vasopressinergic cells that project to the posterior lobe of the pituitary, as well as cells in the periventricular part of the paraventricular nucleus that project to the median eminence.

Animals↗
PubMed1980

Heterogeneity in the adrenomedullary storage of catecholamines, ATP, calcium and releasable dopamine beta-hydroxylase activity.

Bovine adrenomedullary granules were separated into two subfractions by isopycnic density centrifugation. A small subfraction (approximately 10% of the total population) was sedimented into 2.2 M sucrose while the main population (80% of the total) was recovered at the interphase between 1.6 and 2.2 M sucrose. The concentrations of catecholamine (CA) and calcium showed marked seasonal variations for both subfractions, with lowest levels in the spring and highest levels in the winter. Throughout the year the concentrations of CA and calcium were 2-3 times higher in the minor subpopulation which also accounted for an abundance of noradrenaline (NA); on average 68% NA of total CA, 6.6 mumol CA and 225 nmol calcium/mg protein. The two subpopulations stored CA in similar ratios to ATP and calcium; i.e. 30 mol CA: 4 mol ATP: 1 mol Ca2+, indicating storage of CA largely independent of an equivalent amount of ATP, at least during winter when CA storage was 3.3 and 9.9 mumol/mg protein in the major and minor subpopulation respectively. The two subpopulations differed significantly in ratio of releasable dopamine beta-hydroxylase (DBH) activity per mole CA due to insignificant differences in specific activity of releasable DBH (0.4 unit/mg protein). The results show: (1) that the adrenomedullary granules are heterogeneous with respect to releasable activity of DBH per mole CA and subject to considerable seasonal variations; (2) a large portion of the NA-storing granules has a high concentration of releasable constituents; (3) both adrenaline (A)- and NA-storage are closely associated with that of calcium and occur in excess of that balanced by equivalent amounts of ATP.

Adenosine Triphosphate↗
PubMed1980

Neurotensin-induced contractions in venous smooth muscle.

Synthetic neurotensin was shown to be a powerful contractant of the isolated rat portal vein. Concentration-dependent increases in basal tension and frequency of spontaneous contractions were obtained in response to single dose (10-1000 nM, final bath concentrations). The responses reached maxima within 2 min and differed in this respect from comparable responses to angiotensin II, substance P and bradykinin, which were maximal after 2-4 min. The "apparent affinity" for neurotensin (pD2 = 7.5 +/- 0.3, S.D., n = 10) was about 10 times less than for angiotensin II while higher than for both the other peptides and for norepinephrine. The "intrinsic activity" was 0.75 (+/- 0.13, S.D., n = 6) relative to angiotensin II during the first 2 min of the response. A pronounced degree of tachyphylaxis was observed; repetition of the neurotensin dose at the lower range of concentrations (1-10 nM) within 2-4 min was completely ineffective. The results suggest that there is a specific neurotensin receptor in the tissue and that neurotensin-induced contractions may play a part in redistributing the blood flow in the gastrointestinal region following release of this peptide from the ileum into the portal circulation.

Angiotensin II↗
PubMed1980

Adrenal medullary responses to stimulation of the splanchnic nerve in the conscious calf.

1. Right adrenal medullary and various cardiovascular responses to stimulation of the peripheral end of the right splanchnic nerve have been investigated in conscious calves, 2--5 weeks after birth. 2. The output of both adrenaline and noradrenaline was linearly related to stimulus frequency over the range 2.0--10.0 Hz, 2 1/2 min after stimulation was initiated. Peak outputs of both amines were obtained in response to stimulation at 15.0 Hz. 3. The output of adrenaline invariably exceeded that of noradrenaline, roughly in the proportion 3:2. At all frequencies tested between 7.0 and 40.0 Hz this difference was statistically significant (P less than 0.1). 4. Continuous stimulation at either 4.0 or 10.0 Hz produced a small but significant rise in the output of dopamine-beta-monooxygenase (DBH) activity from the right adrenal gland. Mean maximal outputs were obtained after 10 min; the levels were closely similar at both 4.0 and 10.0 Hz and could not be related to stimulus frequency or to the output of either adrenaline or noradrenaline. 5. The results are discussed in relation to perfusion studies in vitro and experiments in anaesthetized animals. It is concluded that the levels of DBH in adrenal effluent plasma is an unreliable index of catecholamine exocytosis in the conscious calf.

Adrenal Medulla↗
PubMed1979

Immunochemically identical hydrophilic and amphiphilic forms of the bovine adrenomedullary dopamine beta-hydroxylase.

By means of a monospecific antibody, dopamine beta-hydroxylase was monitored immunoelectrophoretically in various extracts of chromaffin granules. Approximately one-third of the dopamine beta-hydroxylase present was located in the membrane fraction and could only be liberated with detergent. The dopamine beta-hydroxylases of the buffer and membrane fractions were antigenically identical, but differed in their amphiphilicity, as demonstrated by the change in precipitation patterns on removal of Triton X-100 from the gel, on charge-shift crossed immunoelectrophoresis and on crossed hydrophobic interaction immunoelectrophoresis with phenyl-Sepharose. Furthermore, immunoelectrophoretic analysis in the presence of Triton X-100 plus the cationic detergent cetyltrimethylammonium bromide indicates additional heterogeneity of the membrane-bound dopamine-beta-hydroxylase. By limited proteolysis with chymotrypsin and thermolysin the amphiphilic form could be convered into its hydrophilic counterpart.

Adrenal Medulla↗
PubMed1978

Complexes of chromogranin A and dopamine beta-hydroxylase among the chromogranins of the bovine adrenal medulla.

1. The core proteins of chromaffin granules have been examined by polyacrylamide gel electrophoresis and crossed immunoelectrophoresis against monospecific antisera. 2. Dopamine beta-hydroxylase (dopamine beta-monooxygenase, EC 1.14.17.1) appeared as the major immunogen of the core proteins and accounted for 4 and 8% by weight of the crude lysate and membrane-containing fractions, respectively. 3. The non-ionic detergent, Berol, solubilized dopamine beta-hydroxylase from the membranes in a form which was immunologically identical but of lower relative mobility by crossed immunoelectrophoresis. In the absence of detergent a difference in relative mobility was also noted between the purified enzyme and that contaminated by chromogranin A. These observations suggest that several molecular forms of dopamine beta-hydroxylase may occur which differ in size and/or charge due to interactions with the contaminants under the experimental conditions. 4. The main chromogranin in the crude lysate was absent from electropherograms of the acidic chromogranins (95--96% of total protein in lysate). These were obtained free of dopamine beta-hydroxylase by concanavalin A adsorption at high ionic strength or by acidification in 2 M acetic acid. The main band reappeared upon recombination with dopamine beta-hydroxylase, indicating the presence of some dopamine beta-hydroxylase, possibly as dimers, in this main, chromogranin A band. A protein concentration-dependent aggregate of dopamine beta-hydroxylase-free chromogranin A was detected, with a relative mobility slightly faster than the main band of the crude lysate.

Adrenal Medulla↗
PubMed1975

Granule containing cells and fibres in the sinus venosus of elasmobranchs.

The concentrations of catecholamines in the heart chambers of elasmobranchs were measured by the fluorimetric method of Bertler et al. (1958). Noradrenaline (NA) can be detected in all the chambers, but the sinus venosus is by far the richest in NA. This can either be due to the presence of storage sites for this amine in the sinus wall, or to a transport of amine to the sinus venosus from the anterior chromaffin bodies. The sinus wall contains large numbers of "granule containing cells" and axon-like processes, both with numerous dense-core vesicles of about 1800 A diameter. The dense-core vesicles contain a uranophilic matrix indicating the presence of protein, phospholipids and/or nucleic acid. The reactions failed to demonstrate amine, which may be due to a loss of amine by diffusion, to a relatively low intravesicular amine concentration, or, to the absence of amines in these granule-containing cells and processes. Heavy accumulations of granule-containing processes occur in the subendothelial area. The endothelium contains fenestrae and pores through which granule-containing fibres protrude into the venous cavity. Granule-containing cells are innervated by presumed cholinergic nerve endings. It is suggested that the granule-containing cells and fibres belong to the neurosecretory system with a cholinergic input, releasing the contents of the dense-core vesicles into the blood stream at the level of the venous cavity.

Acetylcholinesterase↗