Biomedical subjects

L A Foster

Publications and source records attributed to L A Foster.

33 records · Page 2Linked to original sources

PubMed1989

Glutamine- vs glucose-supported motor activity in Schistosoma mansoni: physiological relevance of aerobic metabolism.

The ability of Schistosoma mansoni to generate energy through aerobic metabolic processes was examined in adult parasites in vitro. Parasite catabolism of radiolabeled glucose, glutamine, and other amino acids to CO2 and Krebs cycle intermediates was measured under a variety of incubation conditions. L-Glutamine was metabolized to CO2 via the intermediates glutamate, alpha-ketoglutaramate, and alpha-ketoglutarate in worms incubated in a balanced salts solution containing this amino acid as the only organic constituent. Of the other amino acids tested, CO2 production was detected from L-glutamate and L-asparagine. The catabolism of L-glutamine to CO2 was reduced by the respiratory inhibitor antimycin A. The motility of schistosomes in culture was maintained for at least 24 hr when L-glutamine was the only carbon source available to the worms. Under these conditions, motility was reduced when parasites were exposed to a respiratory inhibitor such as KCN, antimycin A, rotenone, or oligomycin, but it was completely restored by the addition of glucose to the medium. These results suggest that while the schistosome is capable of limited aerobic energy-generating processes under certain conditions, survival is not contingent upon these processes in the presence of glucose.

Adenine Nucleotides↗

PubMed1989

Soluble proteins from Schistosoma mansoni and japonicum: a comparative biochemical and immunological analysis.

1. Soluble proteins were recovered from male Schistosoma mansoni after homogenization in Tris-HCl buffer containing 0.6 M KCl and 1.0% Triton X-100 followed by preparative electrophoresis on SDS-gel. 2. Polyclonal antibodies produced in mice against the soluble fraction were used in comparative analysis of S. mansoni and S. japonicum using immunoblots and immunoprecipitation of in vitro translated polypeptides. 3. Small molecular weight polypeptide (20-22 kdalton), identified by infected mouse serum (IMS) on immunoblots, was predominant in females and was not cross-reactive with heterologous IMS. 4. A 41-43 kdalton polypeptide which appeared as a doublet on immunoblots performed with polyclonal antiserum 4M, was predominant in males of both species although the polypeptides of S. mansoni showed slower electrophoretic mobility, and therefore the larger size (43 kdalton), than that of S. japonicum. 5. Comparison of fluorograms of the immunoprecipitates of in vitro translated polypeptides indicated that IMS of S. mansoni precipitated two, 30 and 94 kdalton, polypeptides while the IMS of S. japonicum identified at 72 kdalton polypeptide. Antisera 1M, 2M and 4M also showed similarities and differences in polypeptides of in vitro translation products of the two species of Schistosoma.

Animals↗

PubMed1989

Physiological role of HMG-CoA reductase in regulating egg production by Schistosoma mansoni.

Pathological lesions observed in humans infected with Schistosoma mansoni are due to the eggs produced by the female parasite. Mevinolin, a potent inhibitor of the enzyme hydroxymethylglutaryl-CoA (HMG-CoA) reductase, blocks egg production by this parasite. In this report, we demonstrate that cholesterol precursors, mevalonate and farnesol, stimulate egg production by the female parasite and that these precursors can reverse the mevinolin-induced inhibition of egg production. Because the parasite cannot synthesize cholesterol, we incubated parasites in a culture media containing radiolabeled acetate with and without mevinolin. We isolated nonsterol lipids from the parasite and observed that mevinolin dramatically reduced the conversion of acetate into the polyisoprenoid (dolichols) lipids of the parasite. Dolichols and other nonsterol lipids did not stimulate egg production. HMG-CoA reductase activity was observed in homogenates of the parasite and was inhibited by mevinolin (Ki = 52 nM), but its activity was tripled when the parasite was chronically exposed to low doses of the drug. Parasites with increased reductase activity produced five to six times more eggs. Lastly, chronic administration of large doses of mevinolin to infected mice resulted in a marked reduction of the pathology associated with the infection. These results suggest that egg production in S. mansoni is associated with the parasite's HMG-CoA reductase activity and that a nonsterol lipid produced in the biochemical pathway regulated by this enzyme stimulates egg production.

Animals↗

PubMed1989

Factors present when battered women kill.

Twelve women, imprisoned for killing their abusive male partners, were interviewed to determine factors present in battering relationships that end in homicide. Threats to kill made by the abuser, daily alcohol use by the man, and the presence of a firearm in the home existed in the majority of these relationships. Psychological abuse (e.g., enforced isolation, humiliation, and degradation) was perceived as more devastating than physical abuse. Although an escalation in the severity and frequency of violence, the occurrence of sexual abuse, and women's suicidal threats were also present, subjects indicated that these factors were less important reasons for taking lethal action. Knowledge of these factors may guide nurses as they assess and intervene in dangerous, potentially lethal, abusive situations.

Adult↗

PubMed1988

Light and electron microscopic demonstration of phospholipase B activity in the mouse eosinophil.

Phospholipase B (EC 3.1.1.5) which hydrolyzes phospholipids in the alpha and beta positions was demonstrated in murine leukocytes using light and electron microscopic histochemical techniques. Leukocytes (neutrophils, lymphocytes, macrophages, eosinophils) were harvested from peritoneal exudates of mice. Cells were fixed in 4% calcium-formol fixative for 10 min at 4 degrees C for light microscopy and 30 min at room temperature for electron microscopy, after which they were incubated at 37 degrees C in medium at pH 6.6 containing 2 microM lysolecithin and CaCl2. The fatty acids released during the hydrolytic reaction were trapped as a calcium precipitate and were converted to a cobalt precipitate for light microscopy by treatment with cobalt acetate or to a lead precipitate for electron microscopy by treatment with lead nitrate. The reaction products were observed to be present in eosinophils and absent in neutrophils, lymphocytes and macrophages. It is concluded that the eosinophilic leukocyte is the carrier cell for phospholipase B in inflammatory reactions.

Animals↗

PubMed1988

Clinical ketosis.

A diagnosis of primary ketosis is based on clinical signs, clinical pathology, and ruling-out disorders that cause secondary ketosis. Various treatments can be used alone or in combination during the management of clinical ketosis. A treatment should be based on drugs with a mechanism of action that will eliminate the pathogenesis of the clinical signs observed.

Acidosis↗

PubMed1987

Ascaris lumbricoides suum: morphological characterization of apparent cuticular pores by ionic permeability and electron microscopy.

The cuticle of the parasitic roundworm Ascaris lumbricoides suum has been found to contain apparent pores, using scanning and transmission electron microscopy. However, X-ray spectral analysis and dot mapping analysis of diffusing divalent cations in the cuticle found these ions to be randomly distributed on the pseudocoelomic surface of the cuticle. This indicates that the pores seen with the electron microscope were not true structural pores and that the cuticle is homogeneously permeable to ions.

Animals↗

PubMed1986

Utilization of the heme moiety of hemoglobin by Schistosoma mansoni schistosomules in vitro.

The hemoglobin in mouse reticulocytes was labeled in vitro with either [3H], [14C] aminolevulinic acid (ALA), or [3H] leucine. Specific labeling of the globin moiety with labeled leucine, and the heme moiety with labeled ALA, was confirmed by carboxymethylcellulose chromatography and cyclohexanone extraction. Most of the leucine label recovered from reticulocytes that were incubated for 4 hr was incorporated in hemoglobin. However, 2 hr incubation of reticulocytes in the presence of labeled ALA followed by 4 hr in cell incubation medium in the absence of ALA was required for sufficient incorporation of the radionuclide into reticulocyte hemoglobin. In all reticulocyte labeling experiments, regardless of the radionuclide used, label was also observed in non-hemoglobin heme-containing molecules. Schistosoma mansoni schistosomules fed reticulocytes in vitro in which the heme moiety of hemoglobin was labeled displayed radioactivity in the protein fraction of the organisms, as determined by TCA precipitation, and in the ethanol-soluble component. In comparison, schistosomules fed reticulocytes containing globin-labeled hemoglobin displayed radioactivity only in the protein component. Pre-incubation of the schistosomules in puromycin prior to exposure to lyophilized, [14C] ALA-labeled hemoglobin partially inhibited incorporation of label. These results suggest that the organism utilizes not only the globin moiety of hemoglobin in its nutritional requirements, but the heme moiety as well.

Animals↗

PubMed1978