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Biomedical subjects

D E Cochrane

Publications and source records attributed to D E Cochrane.

At least 19 recordsLinked to original sources
PubMed1992

Immunocytochemical and biochemical studies of histamine in the retina of the turtle Pseudemys scripta.

A combination of immunocytochemical and biochemical methods was used to study histamine in the turtle retina. Histamine-like immunoreactivity was localized within paraboloids of certain cone photoreceptors by use of two different antisera directed against histamine. Preincubation of eyecups in Ringer's containing 10 microM histamine selectively increased the immunoreactivity of these photoreceptor paraboloids. The present localization of histamine in paraboloids indicated that, although histamine is in photoreceptors of the turtle retina, it may play some metabolic or neuromodulatory role, and not function as a neurotransmitter.

Animals↗
PubMed1992

Formation of histamine-releasing activity from albumin by medium conditioned by endotoxin-stimulated rat peritoneal macrophages.

Incubation of bovine serum albumin (BSA), rat serum albumin or rat plasma with medium conditioned by endotoxin stimulated rat peritoneal macrophages produced an activity that released histamine from isolated rat serosal mast cells. The amount of histamine-releasing activity (HRA) produced increased with the length of the incubation period, with the concentration of albumin, with the number of macrophages stimulated, and with the duration of exposure of the macrophages to endotoxin. Moreover, the formation of the HRA showed a dependency on the pH of the incubation medium with an optimum at pH 4.5. Boiling the medium conditioned by stimulated macrophages before its incubation with albumin or including the acid protease inhibitor, pepstatin with the conditioned medium prevented the formation of HRA. The generation of HRA was not inhibited by pretreatment of the macrophages with the inhibitor of protein synthesis, cycloheximide. Media from macrophages not stimulated with endotoxin failed to generate HRA. Histamine release from mast cells in response to the HRA was inhibited by pretreatment of the cells with antimycin A and deoxyglucose or by preincubation in Ca-free Locke's solution containing a calcium chelating agent. When injected intradermally into anesthetized Evan's Blue treated rats, the generated HRA produced a change in vascular permeability that was prevented by the H1 antagonist, diphenhydramine. Treatment of the HRA with carboxypeptidase A reduced its ability to stimulate histamine release from mast cells. Histamine-Releasing Peptide (HRP), a neurotensin-related octapeptide, shown previously by us to be formed by the action of cathepsin D or pepsin on albumin, was identified by radioimmunoassay in acid:acetone extracts of the histamine-releasing activity. It is concluded that the formation of HRA is due to the actions of enzymes released from macrophages acting on albumin. It is suggested that such histamine-releasing activity could be formed during the later stages of the inflammatory response and that HRP is one of the peptides present.

Animals↗
PubMed1991

Generation of xenopsin-related peptides from tissue precursors by media conditioned by endotoxin-stimulated rat peritoneal macrophages.

Incubation of media conditioned by endotoxin-stimulated rat peritoneal macrophages generates immunoreactive xenopsin (iXP) when incubated with acid extracts of various tissues of the rat. The generation of iXP, as measured by specific radioimmunoassay and confirmed by HPLC analysis, increased as the length of the incubation period increased and was inhibited by pepstatin, prior boiling of the conditioned media, or by omitting either the tissue extract or the conditioned media. The pH optimum for the generation of iXP was 3.0. The generated iXP showed biological activity in that stimulated histamine secretion from isolated rat mast cells and this secretory response was prevented by metabolically poisoning the cells. In addition, the generated iXP stimulated contraction of the isolated guinea pig ileum. In this regard, it was similar to neurotensin (NT). Tissue precursor levels for iXP, as measured by this system of generation, were highest in kidney, liver, and skin and lowest in skeletal muscle and plasma. These results suggest to us that during the inflammatory response, the NT-related peptide, xenopsin, can be generated from tissue precursor(s) by enzymes secreted by invading macrophages. The generated XP may then affect the participating cells of inflammation.

Animals↗
PubMed1989

Structures of histamine-releasing peptides formed by the action of acid proteases on mammalian albumin(s).

The acid proteases, pepsin, rennin and cathepsin D, were shown to generate mast cell histamine releasing peptides (HRP) when incubated with the albumin fraction of mammalian plasmas. Significant histamine release was observed using less than 1 microliter equivalent of pepsin-treated plasma. Histamine release was rapid, dependent on calcium and energy, and accompanied by degranulation. The major HRP present in pepsin-treated human and canine plasma was identified as H-Ile-Ala-Arg-Arg-His-Pro-Tyr-Phe-OH whereas that from rat plasma had valine substituted for isoleucine. Cathepsin D-treated BSA gave rise to the human octapeptide (above) as well as to an extended decapeptide with H-Tyr-Glu- at the N-terminus. These peptides were apparently derived from one region of serum albumin, residues 139 to 149 of the human, canine, or bovine sequence. We hypothesize that cathepsin D, released from leukocyte lysosomes, might generate HRP during the delayed phase of an inflammatory response.

Amino Acid Sequence↗
PubMed1989

Generation of histamine-releasing activity from serum albumin by medium derived from stimulated neutrophils of rat.

1. Medium conditioned by rat neutrophils stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP) has been found to generate mast cell histamine-releasing activity (HRA) when incubated with bovine serum albumin (BSA). 2. Histamine release increased as the concentration of BSA used to generate HRA was increased from 0.25 to 10 mg ml-1, as the concentration of neurotrophil conditioned medium was increased and as the concentration of FMLP used to stimulate the neutrophils was increased. Histamine release was non-cytotoxic as it was inhibited by energy deprivation or by removal of calcium and it was accompanied by degranulation. 3. HRA was detectable after 30 min of incubation with BSA and its generation continued to increase over the 18 h of our measurements. 4. Generation of HRA was dependent upon the presence of medium from stimulated neutrophils and on the presence of BSA, although plasma could substitute for BSA. Likewise, HRA could be generated from gamma-globulin although to a lesser extent than with albumin. 5. Generation was optimum at acid pH and was inhibited by prior boiling of the neutrophil conditioned medium or by the addition of pepstatin. 6. It is suggested that an enzyme(s) released from the neutrophil during stimulation acts on an albumin-like substrate to generate HRA. It is proposed that HRA is peptide in nature and may be generated during an inflammatory response.

Animals↗
PubMed1988

Replenishment of the cellular calcium required for non-immunologic stimulation of mast cell histamine secretion: temperature sensitivity and inhibition by manganese and sodium-free conditions.

Mast cells depleted of cellular calcium (Ca) by a 3 hr exposure to Ca-free conditions and then bathed in Ca-free Locke failed to release histamine when stimulated by compound 48/80 or peptides. The cellular Ca required for histamine release could be replenished by a 5 sec exposure to extracellular Ca at 37 degrees C. To inhibit this replenished cellular Ca dependent histamine secretion required an additional 3 hr exposure to Ca-free conditions. When cellular Ca was replenished at 4 degrees C, an additional 2 min incubation at 37 degrees C was required to restore stimulated secretion to a maximum. During this 2 min incubation period the replenished cellular Ca is suggested to be "processed" so that it can be used for secretion. Manganese (Mn) or cobalt added during (but not after) this 2 min incubation period prevented the restoration of histamine release. Preincubation of cellular Ca depleted mast cells in Mn (0.1-1 mM) blocked the effect of subsequent Ca replenishment at 37 degrees C while cobalt and barium were less inhibitory. Neither magnesium nor strontium were inhibitory. Extracellular sodium (Na) was required for the restoration of cellular Ca dependent histamine secretion. Lithium could substitute for Na but rubidium and potassium were ineffective.

Animals↗
PubMed1988

Xenopsin-related peptide generated in avian gastric extracts.

Two avian counterparts to amphibian xenopsin have been identified as H-Phe-His-Pro-Lys-Arg-Pro-Trp-Ile-Leu-OH (XP-2) and its partial sequence H-His-Pro-Lys-Arg-Pro-Trp-Ile-Leu-OH (XP-1) isolated from extracts of turkey proventriculus and skin. Both peptides were shown to be present within these and other tissues primarily (99%) in precursor form(s), from which they were liberated by the action of endogenous enzyme(s) during extraction. Synthetic and native preparations of XP-2 increased vascular permeability in rats and released histamine from isolated rat mast cells at submicromolar concentrations. The ubiquitous distribution of this XP-related sequence and its pharmacologic capabilities suggest potential roles in the general regulation of tissue blood flow and fluid exchange.

Amino Acid Sequence↗
PubMed1988

Mast cell histamine-releasing activity from stimulated rat neutrophils.

Mast cell histamine-releasing activity (HRA) has been observed in medium derived from stimulated rat neutrophils pretreated with cytochalasin B. This HRA did not require cell-cell contact between mast cells and neutrophils, and its concentration was increased by increasing the number of neutrophils or by raising the concentration of chemotactic peptide used to stimulate the neutrophils. The HRA survived boiling for 5 min and storage overnight at -20 degrees C. In the absence of neutrophil stimulation, no HRA was observed.

Animals↗
PubMed1987

Isolation, structures, and biologic activity of neurotensin-related peptides generated in extracts of avian tissue.

Two immunoreactive neurotensin-related peptides generated by the action of endogenous protease(s) on protein substrates during acid extraction of avian tissues have been isolated from extracts of turkey skin and proventriculus. One was identified as the pentadecapeptide, H-Phe-Glu-Arg-Phe-Gln-Gly-Met-Arg-Thy-Arg-Gly-Pro-Tyr-Phe-Leu-OH and the other was its C-terminal octapeptide fragment. Each peptide showed partial homology to the C-terminal, biologically active region of avian neurotensin, and isolated preparations displayed pharmacologic activity at submicromolar concentrations. Synthetic preparations were shown to be indistinguishable from the native peptides during high pressure liquid chromatography (HPLC) and bioassay. Analysis by HPLC indicated that similar peptides could be generated in extracts of proventriculus, pancreas, small intestine, skin, heart, lung, and skeletal muscle. These results, establishing the presence of a neurotensin-related sequence which can be liberated from protein(s) by the action of tissue enzyme(s), suggest that peptide(s) similar to neurotensin may be rapidly formed in order to promote physiologic regulation in multiple tissue(s).

Amino Acid Sequence↗
PubMed1987

Structure of a biologically active neurotensin-related peptide obtained from pepsin-treated albumin(s).

Using a radioimmunoassay toward the COOH-terminal region of neurotensin, an immunoreactive and biologically active neurotensin-related peptide (NRP) has been isolated from pepsin-treated fractions of bovine, canine, human, and rat plasma. Bovine NRP was identified as H-Ile-Ala-Arg-Arg-His-Pro-Tyr-Phe-Leu-OH, which is similar in structure to both neurotensin and angiotensin I. Canine and human NRP also had the above amino acid composition, whereas that obtained from rat plasma had valine substituted for isoleucine. At their concentrations in pepsin-treated plasmas (2-6 microM) rat, human and canine NRP were shown to increase vascular permeability when injected intradermally into rats and to release histamine from rat mast cells in vitro. The pure peptides also cross-reacted very effectively at nanomolar concentrations in a radioreceptor assay for neurotensin. The protein(s) which liberated NRP upon pepsin treatment were purified about 7-fold and shown to behave like albumin during sodium dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, and high pressure liquid chromatography on muBondapak C4. In addition, the purified preparations were found to react with anti-albumin antisera during immunodiffusion. Although the amino acid sequence of NRP was not found in albumin, a partial sequence homology was noted for NRP and various segments of bovine albumin. Using V8 protease, glutamyl residues were shown to lie within 3-4 amino acids of each end of NRP, as also occurs for the related segments in albumin. These results suggest that a subset of albumin-related protein(s) could serve as precursor(s) to biologically active neurotensin-related peptide(s).

Amino Acid Sequence↗
PubMed1987

Viability and recovery from degranulation of isolated rat peritoneal mast cells.

Using a culture system that allows prolonged maintenance of purified populations of peritoneal mast cells, we have examined them following stimulation by non-immunologic or immunologic agents. Employing phase-contrast microscopy of living cells and various pharmacological manipulations, we have noted that the recovery process includes a reduction in cell size, the probable sealing of exocytotic cavities, a pronounced displacement of the cell nucleus and a resynthesis of histamine. During recovery, mast cells can entrap molecules from the extracellular fluid and later release these substances by a Ca-dependent mechanism. Our results suggest that microfilaments, calmodulin, Ca, and metabolic energy are necessary for recovery.

Animals↗
PubMed1986

Mast cell secretion: differences between immunologic and non-immunologic stimulation.

Non-immunologic and immunologic stimulation of mast cells have been compared. Non-immunologic stimulation relys heavily on cellular Ca, is unaffected by neuraminidase treatment, shows a rapid inactivation, and elicits no increase in the incorporation of 3H-methyl groups into the lipid fraction. In contrast, stimulation by immunologic agents relys primarily on extracellular Ca, is inhibited by neuraminidase treatment, shows a comparatively slow rate of inactivation, and causes a significant increase in the incorporation of 3H-methyl groups into the lipid fraction. We found no evidence of cross-inactivation or desensitization between immunologic and non-immunologic agents. However, pretreatment of mast cells with neurotensin desensitized them to subsequent stimulation by compound 48/80. Our results support the hypothesis that immunologic and non-immunologic agents activate exocytotic mast cell secretion via separate mechanisms.

Animals↗
PubMed1986

Neurotensin stimulates histamine release in in vivo skin 'blisters' in rats: an effect inhibited by cromolyn or somatostatin.

Histamine release was directly measured in in vivo skin blisters in rats in response to the intradermal injection of the peptide neurotensin (NT). Histamine release increased as the concentration of NT was raised from 10(-11) to 10(-5) M. This response was rapid in onset and was inhibited by disodium cromoglycate or the peptide somatostatin (SIRF). The inhibitory effect of SIRF was rapid and was evident from 10(-12) to 10(-8) M SIRF. A similar inhibition was observed on isolated peritoneal mast cells. Histamine release in response to substance P was not inhibited by SIRF.

Animals↗
PubMed1976

Histamine release by exocytosis from rat mast cells on reduction of extracellular sodium: a secretory response inhibited by calcium, strontium, barium or magnesium.

1. Histamine release from peritoneal mast cells of the rat was stimulated when the cells were exposed for 10 min to sodium-deficient media where all NaCl had been replaced by KC1, RbC1, glucose, sucrose, mannitol, or Tris, provided calcium was less than about 0-5 mM. 2. Light and electron microscopy showed the response to be exocytosis. 3. The chelating agents, EDTA and EGTA, abolished the response to sodium lack and their inhibitory effects were reversed by re-incubating cells with calcium but not magnesium. 4. The response was inhibited by dinitrophenol combined with glucose-deprivation. 5. The response was inversely related to the concentrations of sodium and calcium below 137-5 and 0-5 mM respectively. 6. The related alkaline earth metals, barium, strontium, and magnesium, resembled calcium in inhibiting the response to sodium lack. 7. No secretory response was seen when the cells were exposed for 10 min to calcium-free medium in which lithium replaced sodium. Exposure to this medium for 60 min, however, elicited secretion. 8. It is concluded that when extracellular calcium is low, a reduction in extracellular sodium induces a conventional exocytotic secretory response dependent on energy and cellular calcium. It is suggested that sodium lack may mobilize calcium from a cellular site possibly the inner aspect of the plasma membrane.

Animals↗
PubMed1975

Calcium and stimulus-secretion coupling in the adrenal medulla: contrasting stimulating effects of the ionophores X-537A and A23187 on catecholamine output.

1. The ionophores X-537A and A23187, which are known to transfer calcuim across cell membranes, stimulated catecholamine release from perfused cat adrenal glands. 2. These stimulant effects persisted in the presence of hexamethonium and atropine and are therefore attributable to direct actions of the ionophores on the adrenal chromaffin cells. 3. Perfusion with calcium-free Locke abolished responses to A23187 and reduced those to X-537A. 4. Responses to X-537A were consistently large and comparable with those produced by 56 mM potassium. By contrast, responses to A23177, over the wide range of concentrations tested, were variable and much smaller. 5. That the two ionophores can stimulate through calcium-dependent mechanisms is considered fresh support for the calcium hypothesis of stimulus-secretion coupling. That they differ in effectiveness may mean that factors besides calcium are important. The greater potency of the less specific ionophore, X-537A, may be attributable to its ability to depolarize as well as carry calcuim, while the relatively small effects of A23187, a generally more effective ionophore for calcuim, may indicate that inward movement of calcium without a background of membrane perturbation such as may be produced by depolarization, is insufficient to elicit strong secretory responses.

Adrenal Medulla↗