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At least 469 records · Page 26Linked to original sources
PubMed1993

Regulation of epithelial shunt conductance by the peptide leucokinin.

Isolated Malpighian tubules of the yellow fever mosquito Aedes aegypti spontaneously secrete NaCl, KCl and water across an epithelium of modest transepithelial resistance (40-80 omega cm2) and high transepithelial voltage (30-70 mV, lumen positive). Transepithelial electrochemical potentials indicate that Na and K are secreted by active and Cl by passive transport mechanisms. The addition of synthetic leucokinin-VIII (LK-VIII, insect myotropic peptide) to the peritubular bath significantly increases the rates of transepithelial NaCl, KCl and water secretion. In parallel, LK-VIII depolarizes the transepithelial voltage from 59.3 to 5.7 mV, decreases the transepithelial resistance from 57.7 to 9.9 omega cm2, and renders the basolateral and apical membrane voltages nearly equipotential (approximately -90 mV). Unilateral step changes of the [Cl] in the peritubular bath or tubule lumen elicit small transepithelial Cl diffusion potentials in the absence of LK-VIII but large transepithelial Cl diffusion potentials, up to 85% of Nernst equilibrium potentials, in the presence of LK-VIII. In Malpighian tubules treated with dinitrophenol for estimates of the shunt resistance Rsh, LK-VIII reduces Rsh from 52.5 to 5.8 omega cm2. Bilateral reductions of the Cl concentration in tubule lumen and peritubular bath fully restore Rsh to 55.8 omega cm2 in the presence of LK-VIII. LK-VIII has no effects when presented from the luminal side. These results suggest that LK-VIII increases the Cl conductance of the epithelial shunt via a receptor located at the basolateral side of the epithelium.

Aedes↗
PubMed1992

Segmental peptidergic innervation of abdominal targets in larval and adult dipteran insects revealed with an antiserum against leucokinin I.

An antiserum against the cockroach neuropeptide leucokinin I (LKI) was used to study peptidergic neurons and their innervation patterns in larvae and adults of three species of higher dipteran insects, the flies Drosophila melanogaster, Calliphora vomitoria, and Phormia terraenovae, as well as larvae of a primitive dipteran insect, the crane fly Phalacrocera replicata. In the larvae of the higher dipteran flies, the antiserum revealed three pairs of cells in the brain, three pairs of ventro-medial cells in the subesophageal ganglion, and seven pairs of ventro-lateral cells in the abdominal ganglia. Each of these 14 abdominal leucokinin-immunoreactive (LKIR) neurons innervates a single muscle of the abdominal body wall (muscle 8), which is known to degenerate shortly after adult emergence. Conventional electron microscopy demonstrates that this muscle is innervated by at least one axon containing clear vesicles and two axons containing dense-cored vesicles. Electron-microscopical immunocytochemistry shows that the LKIR axon is one of these two axons with dense-cored vesicles and that it forms terminals on the sarcolemma of its target muscle. The abdominal LKIR neurons appear to survive metamorphosis. In the adult fly, the efferent abdominal LKIR neurons innervate the spiracles, the heart, and neurohemal regions of the abdominal wall. In the crane fly larva, dorso-medial and ventrolateral LKIR cell bodies are located in both thoracic and abdominal ganglia of the ventral nerve cord. As in the larvae of the other flies, the abdominal ventrolateral LKIR neurons form efferent axons. However, in the crane fly larva there are two pairs of efferent LKIR neurons in each of the abdominal ganglia and their peripheral targets include neurohemal regions of the dorsal transverse nerves. An additional difference is that in the crane fly, a caudal pair of LKIR axons originating from the penultimate pair of dorso-median LKIR cells in the terminal ganglion innervate the hind-gut.

Abdominal Muscles↗
PubMed1992

Postembryonic development of leucokinin I-immunoreactive neurons innervating a neurohemal organ in the turnip moth Agrotis segetum.

In the abdominal ganglia of the turnip moth Agrotis segetum, an antibody against the cockroach neuropeptide leucokinin I recognizes neurons with varicose fibers and terminals innervating the perisympathetic neurohemal organs. In the larva, the abdominal perisympathetic organs consist of a segmental series of discrete neurohemal swellings on the dorsal unpaired nerve and the transverse nerves originating at its bifurcation. These neurohemal structures are innervated by varicose terminals of leucokinin I-immunoreactive (LKIR) fibers originating from neuronal cell bodies located in the preceding segment. In the adult, the abdominal segmental neurohemal units are more or less fused into a plexus that extends over almost the whole abdominal nerve cord. The adult plexus consists of peripheral nerve branches and superficial nerve fibers beneath the basal lamina of the neural sheath of the nerve cord. During metamorphosis, the LKIR fibers closely follow the restructuration of the perisympathetic organs. In both larvae and adults the LKIR fibers in the neurohemal structures originate from the same cell bodies, which are distributed as ventrolateral bilateral pairs in all abdominal ganglia. The transformation of the series of separated and relatively simple larval neurohemal organs into the larger, continuous and more complex adult neurohemal areas occurs during the first of the two weeks of pupal life. The efferent abdominal LKIR neurons of the moth Agrotis segetum thus belong to the class of larval neurons which persist into adult life with substantial peripheral reorganization occurring during metamorphosis.

Animals↗
PubMed1979

Effect of leukocyte hydrolases on bacteria. XV. Inhibition by antibiotics, metabolic inhibitors, and ultraviolet irradiation of the release by leukocyte extracts, trypsin, and lysozyme of lipopolysaccharide from gram-negative bacteria.

Leukocyte extracts, trypsin, and lysozyme are all capable of releasing the bulk of the LPS from S. typhi, S. typhimurium, and E. coli. Bacteria which have been killed by heat, ultraviolet irradiation, or by a variety of metabolic inhibitors and antibiotics which affect protein, DNA, RNA, and cell wall synthesis no longer yield soluble LPS following treatment with the releasing agents. On the other hand, bacteria which are resistant to certain of the antibiotics yield nearly the full amount of soluble LPS following treatment, suggesting that certain heatlabile endogenous metabolic pathways collaborate with the releasing agents in the release of LPS from the bacteria. It is suggested that some of the beneficial effects of antibiotics on infections with gram-negative bacteria may be the prevention of massive release of endotoxin by leukocyte enzymes in inflammatory sites.

Anti-Bacterial Agents↗
PubMedDate not supplied

Peptidergic modulation of learning a motoric food-procuring conditioned reflex skill.

Experimental data are presented which were obtained during an investigation of the influence of various doses of a synthetic heptapeptide based on tafcine on the learning of a complex instrumental skill in dogs. The effectiveness of the intranasal application of the peptide in the early stages of learning was demonstrated, as was its capacity to restore the lost skill. The vegetative support of the motoric reactions during the modulation of the learning by the peptide was investigated.

Acoustic Stimulation↗
PubMed1975

[Granulocyte dysfunction. I. Inborn defects (author's transl)].

The insight in the function and dysfunction of granulocytes lately arouses more and more interest. This report summarises our present knowledge. In the first of two chapters the authors review the molecular basis of granulocyte function and the inborn defects of chemotaxis, opsonisation, phagocytosis and intracellular killing of bacteria and fungi.

Agranulocytosis↗
PubMed1976

Proline endopeptidase and exopeptidase activity in polymorphonuclear granulocytes.

Peptidases capable of releasing proline residues from polypeptides are present in the cytoplasmic fraction of rabbit polymorphonuclear granulocytes. This was shown with peptide substrates where proline is present either at the carboxy-terminal or within the polypeptide chain. Lysosomal and plasma membrane enzymes were inactive towards such polypeptides. The proline residue was hydrolyzed at either its amino end or its carboxy end. It is noteworthy that a Pro:Pro bond was cleaved both in the pentapeptide Thr-Lys-Pro-Arg and the dipeptide Pro:Pro.

Animals↗
PubMed1984

Effects of protizinic acid on leukokinin generation and its physiological action.

The effect of protizinic acid (PRT), a non-steroidal antiinflammatory drug, on the in vivo leukokinin (LK) generation system using feline acute ischemia model, in vitro LK generation system and the LK-induced contraction of the isolated smooth muscle was investigated. When 3 mg/kg PRT was injected twice intravenously to cats with acute cardiac ischemia, increased blood acid protease activity was inhibited and significant inhibitory action on the decrease of leukokininogen, the precursor of LK, was observed. Simultaneously, ST-segment elevation on the electrocardiogram tended to be suppressed and the lowered mean aortic blood pressure was significantly restored. On the LK generation induced by rabbit kininogen and acid protease derived from mouse L-1210 leukemic cells or rabbit polymorphonuclear leukocytes, PRT showed a dose-dependent inhibition while indomethacin (IM) and ibuprofen (IB) at a concentration of 3 X 10(-4) M showed no effect. However, potencies of the inhibitory actions of PRT, IM and IB on the LK generation induced by bovine spleen cathepsin D were almost the same at a concentration of 3 X 10(-4) M. Furthermore, PRT as well as IM showed antagonistic action on the isolated rat uterine contraction induced by LK. These results suggest that PRT not only inhibits the in vitro and in vivo generation of LK but also antagonizes to it on the receptor site of LK.

Animals↗
PubMed1984

Colonic surgery. The splenic connection.

Colonic resections, particularly those that require mobilization of the splenic flexure, occasionally will lead to injury of the spleen. Under these circumstances, the abdominal surgeon has traditionally considered incidental splenectomy to be the only safe alternative. Currently, a better understanding of splenic physiology and its role in sepsis prevention has reversed this trend. These efforts to preserve splenic function have resulted in various options available to the surgeon, herein reviewed. The results obtained in 36 general surgical patients with splenic injuries suggest that the salvage of the spleen is a safe alternative. In situations where salvage is impossible, the surgeon can resort to omental autotransplantation of the removed spleen, a recently described technique of appealing simplicity. The results obtained with this procedure in 23 other patients are presented.

Colon↗