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Biomedical subjects

A Felix

Publications and source records attributed to A Felix.

At least 37 records · Page 2Linked to original sources
PubMed1990

Opioid control of growth hormone in the suckled sow is primarily mediated through growth hormone releasing factor.

Endogenous opioid peptides mediate the effect of suckling on LH and PRL in the domestic pig. However, the role of opioids in modulating GH during lactation in swine is not known. Primiparous sows that had been immunized against GRF(1-29) conjugated to human serum albumin (GRF-HSA, n = 5) or HSA (n = 4) were used to determine changes in GH after naloxone. Treatments were imposed in all sows on day 21 of lactation when antibody titers were 9100 +/- 1629. All sows received (i.v.) naloxone (0.25 mg/kg) or saline (0.0125 ml/kg) at 15 min intervals for 165 min. Active immunization against GRF-HSA during lactation decreased (P less than 0.05) mean concentration (4.8 +/- 0.2 vs 2.6 +/- 0.1 ng/ml) and frequency (1.5 +/- 0.3 vs 0.4 +/- 0.2 peaks/4 hr). Concentrations of LH and PRL were similar in GRF-HSA and HSA immunized sows. Naloxone suppressed (P less than 0.05) GH in all sows. In HSA sows, naloxone abolished episodic release of GH and decreased average, but not basal, concentrations of GH. In sows immunized against GRF-HSA, naloxone decreased (P less than 0.05) average and basal GH but failed to decrease frequency of GH release. Naloxone failed to alter frequency of LH release. Concentrations of PRL decreased (P less than 0.05) after naloxone in all sows. In conclusion, immunization against GRF-HSA blocked most of the effect of lactation on GH. Blocking opioid receptors with naloxone decreased GH and PRL in all sows. In contrast to previous findings naloxone had no effect on LH. Opioids alter concentrations of GH through a GRF dependent and GRF independent pathway.

Animals↗
PubMed1990

An evaluation of a mental health program for homeless men.

The authors report the results of a before-and-after evaluation of an on-site mental health day treatment program for homeless men. Thirty-two subjects were interviewed 6 or more months after placement from a crisis shelter to community housing in order to probe housing stability, aftercare treatment compliance, employment, rehospitalization, and criminal justice contacts. In the after phase, living on the street was virtually eliminated, use of shelters decreased sevenfold, aftercare utilization tripled, and contacts with the criminal justice system were halved. Psychiatric hospitalizations and unemployment were higher in the after phase. Findings are discussed in relation to the need to conduct controlled experiments of new psychosocial treatments for the homeless mentally ill.

Adult↗
PubMed1990

Active immunization of pigs against growth hormone-releasing factor: effect on concentrations of growth hormone and insulin-like growth factor 1.

Cyclic gilts (96 +/- 1 kg) were used to determine the effect of active immunization against growth hormone-releasing factor GRF(1-29)-NH2 on concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1). Gilts were immunized against GRF conjugated to human serum albumin (GRF-HSA, n = 5) or HSA alone at 180 d of age (wk 0). Booster doses were administered at wk 9 and 13. Seven days after the second booster (wk 14), blood samples were collected at 15-min intervals for 6 h before feeding and 30, 60, 120, 180 and 240 min after feeding. Eight days after the second booster, all gilts were administered a GRF analog, [desNH2Tyr1,Ala15]-GRF(1-29)-NH2, followed by an opioid agonist, FK33-824. Blood samples were collected at 15-min intervals from -30 to 240 min after injection. Immunization against GRF-HSA resulted in antibody titers, expressed as dilution required to bind 50% of [125I]GRF, ranging from 1:11,000 to 1:60,000 (wk 11 and 14); binding was not detectable or was less than 50% at 1:100 in HSA gilts (P less than .05). Episodic release of GH was abolished by immunization against GRF-HSA (P less than .05). Mean GH was decreased (P less than .07), but basal GH concentrations were not altered (P greater than .15) by immunization against GRF-HSA. Serum concentrations of IGF-1 were similar at wk 0, but concentrations were lower in GRF-HSA than in HSA gilts (P less than .05) at wk 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Structural determinants of the factor IX molecule mediating interaction with the endothelial cell binding site are distinct from those involved in phospholipid binding.

Previous studies have indicated that Factor IX/IXa interacts in a specific and high affinity manner with a binding site on the endothelial cell surface. In this study, the contributions of the gamma-carboxyglutamic acid-containing (GLA) and growth factor domains to the finding of Factor IX to the endothelium were assessed. While GLA-containing peptides from Factors IX, X, and prothrombin were inhibitors of 125I-Factor IX-endothelial cell binding, the GLA peptide from Factor IX was about 250-800-fold more effective than those from prothrombin and Factor X, respectively. In contrast to its relative efficacy as an inhibitor of Factor IX-cell surface interaction, the Factor IX-GLA peptide neither bound to lipid vesicles nor inhibited Factor IX-lipid interaction. A synthetic peptide comprising the entire first epidermal growth factor (EGF) exon was also an inhibitor of 125I-Factor IX-endothelial cell binding, although it did not interact with lipid vesicles. Experiments with synthetic peptides comprising each of the three loops of the first EGF domain or the entire first EGF region with specific substitutions indicated the importance of determinants in both the first and probably third loops for Factor IX-endothelial interaction. In contrast, the second loop of the first EGF domain and the first loop of the second EGF exon are probably not involved in Factor IX-endothelial interaction based on their inability to block 125I-Factor IX binding to cells. These results indicate that determinants in both the GLA and the first EGF domain contribute to the specific binding of Factor IX to the endothelial cell surface and that structural requirements for Factor IX-cell surface interaction are distinct from those for Factor IX binding to lipids.

Amino Acid Sequence↗
PubMed1989

Detection of transforming ras proteins containing leucine at position 61 by a new mouse monoclonal antibody, ras(53-69)Leu61.

A monoclonal antibody (mAb) was prepared after immunization of mice with a peptide that corresponds to amino acids 53 to 69 of a transforming ras protein. The amino acid sequence in this region is conserved among all members of the ras protooncogene family in rodent, rabbit, and human cells. The peptide used for immunization differs from the normal sequence by a single residue; Leu replaces Gln at a site corresponding to amino acid 61. A bacterial expression vector was constructed to synthesize H-ras transforming protein that contains this change (rasLeu61). In immunoblotting experiments, the affinity purified mAb, ras(53-69)Leu61, reacts specifically with the purified, bacterially produced rasLeu61 protein and does not react with bacterially produced normal H-ras protein. In immunoblotting experiments with cell lysates, the mAb recognizes the transforming protein in NIH3T3 cells transformed by the c-rasHLeu61 oncogene but fails to react with normal H-ras protein in the same cells or cells which produce 100 times more normal protein than NIH3T3. The mAb immunoprecipitates [35S]methionine-labeled H- and N-rasLeu61 proteins from transformed NIH3T3 cells under conditions in which the cells produce basal levels of the transforming protein, equivalent to the low amount of the normal protein ordinarily present in nontransformed NIH3T3 cells. The antibody fails to immunoprecipitate normal H-ras protein, even when present at high levels, or N-ras protein containing Lys as amino acid 61. Affinity purified mAb ras(53-69)Leu61 also recognizes the transforming ras protein specifically in immunohistochemical staining of tissue culture cells, and this staining is abolished by preincubating the antibody with the corresponding peptide. Staining was not observed with control NIH3T3 cells or cells that produce 100 times more normal H-ras protein than NIH3T3. However, in thin sections of normal human or rabbit skin the antibody reacted strongly with an unknown antigen, in cells of the basal layer of the epidermis, that is neither normal nor transforming ras protein. This new immunological reagent should be useful for the selective identification of Leu61 containing H-, K-, and N-ras transforming proteins in in vitro studies and analyses using rodent, rabbit, or human tissue culture cells. Its utility for direct staining of tissues may be limited to situations in which the presence of transforming protein can be verified by another method such as immunoblotting after gel electrophoresis.

Amino Acid Sequence↗
PubMed1988

Site-directed antibodies for probing the structure and biogenesis of phosphatidylinositol glycan-linked membrane proteins: application to placental alkaline phosphatase.

An immunological approach to the study of the structure and biogenesis of the phosphatidylinositol glycan (PI-G) membrane anchor at the carboxyl terminus of human placental alkaline phosphatase (PLAP) is described. Based on the protein sequence predicted from full length PLAP cDNA, two epitopes were chosen in the region of the carboxyl terminus for the production of site-directed antibodies. The exo site represents the last nine residues of preproPLAP, (res. 505-513), which is part of the sequence that is expected to be cleaved from the nascent protein during processing and addition of the PI-G tail. A second site, the endo sequence, was selected close to the expected carboxyl terminus in mature PI-G-tailed PLAP (res. 474-484 of proPLAP). The two peptides were synthesized, polyclonal antibodies to the conjugated peptides were prepared, and the antisera were characterized. Analytical methods for both synthetic peptides and proteins are presented. Preliminary applications to the isolation and characterization of the PI-G-linked carboxyl terminus of mature PLAP and to the characterization of nascent PLAP are described. The application of both carboxyl terminal-directed antibodies, and a third antibody directed to the amino terminus of mature PLAP, in studies employing mutant forms of PLAP and to the PI-G tailing process itself are discussed. The immunological approach used here for PLAP should be applicable generally to the study of other PI-G-tailed proteins.

Alkaline Phosphatase↗
PubMed1987

Antisera to the variable region of ras oncogene proteins, and specific detection of H-ras expression in an experimental model of chemical carcinogenesis.

Antisera were prepared in mice, rats and rabbits by immunization with peptides corresponding to regions of highest variability, located near the C-termini of four ras proteins. Two of these, H-ras (171-189) and K-rasB (171-186), react uniquely with H-ras and K-rasB gene products in immunoblots and immunoprecipitation reactions. Affinity-purified rabbit H-ras (171-189) antibody detects H-ras p21 in tissue culture cells and in tissue sections. Epithelial cells in normal mouse skin and cells in papillomas and carcinomas, in a mouse model system of chemical carcinogenesis in which mutational activation of H-ras occurs with high frequency, express high levels of H-ras p21 protein. These results suggest an hypothesis to explain the mechanism and preferential activation of particular ras loci in certain neoplasia.

Amino Acid Sequence↗
PubMed1986

[Not Available].

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Belgium↗
PubMed1985

Human placental alkaline phosphatase in liver and intestine.

Three distinct forms of human alkaline phosphatase, presumably isozymes, are known, each apparently associated with a specific tissue. These are placental, intestinal, and liver (kidney and bone). We have used a specific immunoassay and HPLC to show that placental alkaline phosphatase is also present in extracts of liver and intestine in appreciable amounts.

Alkaline Phosphatase↗
PubMed1982

Microbial Oxidation of Hydrocarbons: Properties of a Soluble Methane Monooxygenase from a Facultative Methane-Utilizing Organism, Methylobacterium sp. Strain CRL-26.

Methylobacterium sp. strain CRL-26 grown in a fermentor contained methane monooxygenase activity in soluble fractions. Soluble methane monooxygenase catalyzed the epoxidation/hydroxylation of a variety of hydrocarbons, including terminal alkenes, internal alkenes, substituted alkenes, branched-chain alkenes, alkanes (C(1) to C(8)), substituted alkanes, branched-chain alkanes, carbon monoxide, ethers, and cyclic and aromatic compounds. The optimum pH and temperature for the epoxidation of propylene by soluble methane monooxygenase were found to be 7.0 and 40 degrees C, respectively. Among various compounds tested, only NADH(2) or NADPH(2) could act as an electron donor. Formate and NAD (in the presence of formate dehydrogenase contained in the soluble fraction) or 2-butanol in the presence of NAD and secondary alcohol dehydrogenase generated the NADH(2) required for the methane monooxygenase. Epoxidation of propylene catalyzed by methane monooxygenase was not inhibited by a range of potential inhibitors, including metal-chelating compounds and potassium cyanide. Sulfhydryl agents and acriflavin inhibited monooxygenase activity. Soluble methane monooxygenase was resolved into three components by ion-exchange chromatography. All three compounds are required for the epoxidation and hydroxylation reactions.

Journal Article↗
PubMed1980

Microbial Oxidation of Gaseous Hydrocarbons: Production of Secondary Alcohols from Corresponding n-Alkanes by Methane-Utilizing Bacteria.

Over 20 new strains of methane-utilizing bacteria were isolated from lake water and soil samples. Cell suspensions of these and of other known strains of methane-utilizing bacteria oxidized n-alkanes (propane, butane, pentane, hexane) to their corresponding secondary alcohols (2-propanol, 2-butanol, 2-pentanol, 2-hexanol). The product secondary alcohols accumulated extracellularly. The rate of production of secondary alcohols varied with the organism used for oxidation. The average rate of 2-propanol, 2-butanol, 2-pentanol, and 2-hexanol production was 1.5, 1.0, 0.15, and 0.08 mumol/h per 5.0 mg of protein in cell suspensions, respectively. Secondary alcohols were slowly oxidized further to the corresponding methylketones. Primary alcohols and aldehydes were also detected in low amounts (rate of production were 0.05 to 0.08 mumol/h per 5.0 mg of protein in cell suspensions) as products of n-alkane (propane and butane) oxidation. However, primary alcohols and aldehydes were rapidly metabolized further by cell suspensions. Methanol-grown cells of methane-utilizing bacteria did not oxidize n-alkanes to their corresponding secondary alcohols, indicating that the enzymatic system required for oxidation of n-alkanes was induced only during growth on methane. The optimal conditions for in vivo secondary alcohol formation from n-alkanes were investigated in Methylosinus sp. (CRL-15). The rate of 2-propanol and 2-butanol production was linear for the 40-min incubation period and increased directly with cell protein concentration up to 12 mg/ml. The optimal temperature and pH for the production of 2-propanol and 2-butanol were 40 degrees C and pH 7.0. Metalchelating agents inhibited the production of secondary alcohols. The activities for the hydroxylation of n-alkanes in various methylotrophic bacteria were localized in the cell-free particulate fractions precipitated by centrifugation between 10,000 and 40,000 x g. Both oxygen and reduced nicotinamide adenine dinucleotide were required for hydroxylation activity. The metal-chelating agents inhibited hydroxylation of n-alkanes by the particulate fraction, indicating the involvement of a metal-containing enzyme system in the oxidation of n-alkanes. The production of 2-propanol from the corresponding n-alkane by the particulate fraction was inhibited in the presence of methane, suggesting that the subterminal hydroxylation of n-alkanes may be catalyzed by methane monooxygenase.

Journal Article↗
PubMed1980

Microbial Oxidation of Gaseous Hydrocarbons: Production of Methylketones from Corresponding n-Alkanes by Methane-Utilizing Bacteria.

Cell suspensions of methane-utilizing bacteria grown on methane oxidized n-alkanes (propane, butane, pentane, hexane) to their corresponding methylketones (acetone, 2-butanone, 2-pentanone, 2-hexanone). The product methylketones accumulated extracellularly. The rate of production of methylketones varied with the organism used for oxidation; however, the average rate of acetone, 2-butanone, 2-pentanone, and 2-hexanone production was 1.2, 1.0, 0.15, and 0.025 mumol/h per 5.0 mg of protein in cell suspensions. Primary alcohols and aldehydes were also detected in low amounts as products of n-alkane (propane and butane) oxidation, but were rapidly metabolized further by cell suspensions. The optimal conditions for in vivo methylketone formation from n-alkanes were compared in Methylococcus capsulatus (Texas strain), Methylosinus sp. (CRL-15), and Methylobacterium sp. (CRL-26). The rate of acetone and 2-butanone production was linear for the first 60 min of incubation and directly increased with cell concentration up to 10 mg of protein per ml for all three cultures tested. The optimal temperatures for the production of acetone and 2-butanone were 35 degrees C for Methylosinus trichosporium sp. (CRL-15) and Methylobacterium sp. (CRL-26) and 40 degrees C for Methylcoccus capsulatus (Texas). Metal-chelating agents inhibited the production of methylketones, suggesting the involvement of a metal-containing enzymatic system in the oxidation of n-alkanes to the corresponding methylketones. The soluble crude extracts derived from methane-utilizing bacteria contained an oxidized nicotinamide adenine dinucleotide-dependent dehydrogenase which catalyzed the oxidation of secondary alcohols.

Journal Article↗
PubMed1980

Effect of feeding isoacids with urea on growth and nutrient utilization by lactating cows.

In the growth study 10 g each of isobutyrate, isovalerate, 2-methylbutyrate, n-valerate, and phenylacetate were mixed with 80 g of urea, 50 g of molasses, and 270 g of ground hay and fed to nine dairy heifers for 90 days. The control group was fed the same diet minus isoacids and phenylacetate. All animals were fed ad libitum timothy hay as the sole roughage. In the digestion trial, two mixtures of isoacids and a control ration were fed to nine lactating cows in a 3 X 3 Latin square design with 28-day feeding periods. Corn silage was the sole roughage, and concentrate was fed in proportion to milk production. Collection of feces and urine was for the last 5 days of each period. Mixture 1 of isoacids contained on a molar basis 28, 24, 24, and 24% of isobutyrate, isovalerate, 2-methylbutyrate, and n-valerate, respectively. Corresponding for mixture 2 were 36, 17, 17, and 30%. Addition of isoacids increased growth rate of younger animals but not older ones. The isoacid mixtures improved utilization of nitrogen by lactating cows. Urinary nitrogen decreased, and retention of absorbed nitrogen increased. Digestibility of dry matter and nitrogen were not affected by isoacid additions.

Animals↗
PubMed1979

Microbial oxidation of methane and methanol: purification and properties of a heme-containing aldehyde dehydrogenase from Methylomonas methylovora.

Procedures for the purification of an aldehyde dehydrogenase from extracts of the obligate methylotroph, Methylomonas methylovora are described. The purified enzyme is homogeneous as judged from polyacrylamide gel electrophoresis. In the presence of an artificial electron acceptor (phenazine methosulfate), the purified enzyme catalyzes the oxidation of straight chain aldehydes (C1--C10 tested), aromatic aldehydes (benzaldehyde, salicylaldehyde), glyoxylate, and glyceraldehyde. Biological electron acceptors such as NAD+, NADP+, FAD, FMN, pyridoxal phosphate, and cytochrome c cannot act as electron carriers. The activity of the enzyme is inhibited by sulfhydryl agents [p-chloromercuribenzoate, N-ethylmaleimide and 5,5-dithiobis (2-nitrobenzoic acid)], cuprous chloride, and ferrour nitrate. The molecular weight of the enzyme as estimated by gel filtration is approximately 45000 and the subunit size determined by sodium dodecyl sulfate-gel electrophoresis is approximately 23000. The purified enzyme is light brown and has an absorption peak at 410 nm. Reduction of enzyme with sodium dithionite or aldehyde substrate resulted in the appearance of peaks at 523 nm and 552nm. These results suggest that the enzyme is a hemoprotein. There was no evidence that flavins were present as prosthetic group. The amino acid composition of the enzyme is also presented.

Aldehyde Oxidoreductases↗
PubMed1979

Microbial production of methyl ketones. Purification and properties of a secondary alcohol dehydrogenase from yeast.

Cell-free extracts derived from yeasts Candida utilis ATCC 26387, Hansenula polymorpha ATCC 26012, Pichia sp. NRRL-Y-11328 Torulopsis sp. strain A1 and Kloeckera sp. strain A2 catalyzed an NAD+-dependent oxidation of secondary alcohols (2-propanol, 2-butanol, 2-pentanol, 2-hexanol) to the corresponding methyl ketones (acetone, 2-butanone, 2-pentanone, 2-hexanone). We have purified a NAD+-specific secondary alcohol dehydrogenase from methanol-grown yeast, Pichia sp. The purified enzyme is homogenous as judged by polyacrylamide gel electrophoresis. The purified enzyme catalyzed the oxidation of secondary alcohols to the corresponding methyl ketones in the presence of NAD+ as an electron acceptor. Primary alcohols were not oxidized by the purified enzyme. The optimum pH for oxidation of secondary alcohols by the purified enzyme is 8.0. The molecular weight of the purified enzyme as determined by gel filtration is 98 000 and subunit size as determined by sodium dodecyl sulfate gel electrophoresis is 48 000. The activity of the purified secondary alcohol dehydrogenase was inhibited by sulfhydryl inhibitors and metal-binding agents.

Alcohol Oxidoreductases↗