Search PubMed⌕ Search

Biomedical subjects

J A Cooper

Publications and source records attributed to J A Cooper.

At least 253 records · Page 14Linked to original sources
PubMed1991

Comparison of 6 and 8 hourly tobramycin dosing intervals in treatment of pulmonary exacerbations in cystic fibrosis patients.

The efficacy and toxicity of a shortened tobramycin dosing interval in the treatment of exacerbations of Pseudomonas aeruginosa pulmonary infection in cystic fibrosis patients were evaluated prospectively. Patients ages 13 to 30 years received 34 treatment courses and were randomized by pairs to receive tobramycin administered either every 6 or 8 hours. Peak serum concentrations were adjusted to 8 to 10 micrograms/ml; thus a larger total daily dosage was administered to patients receiving tobramycin every 6 hours. The shorter dosing interval was associated with better pulmonary function at follow-up and significantly longer time before next hospital admission for a pulmonary exacerbation. During the study hospitalization there were no differences in pulmonary function tests, clinical score, sputum carriage of P. aeruginosa, toxicity or necessary length of hospitalization. A 6-hour tobramycin dosing interval was more efficacious than an 8-hour dosing interval in the treatment of cystic fibrosis patients.

Adolescent↗
PubMed1991

Tyrosine phosphorylation and activation of homologous protein kinases during oocyte maturation and mitogenic activation of fibroblasts.

Meiotic maturation of Xenopus and sea star oocytes involves the activation of a number of protein-serine/threonine kinase activities, including a myelin basic protein (MBP) kinase. A 44-kDa MBP kinase (p44mpk) purified from mature sea star oocytes is shown here to be phosphorylated at tyrosine. Antiserum to purified sea star p44mpk was used to identify antigenically related proteins in Xenopus oocytes. Two tyrosine-phosphorylated 42-kDa proteins (p42) were detected with this antiserum in Xenopus eggs. Xenopus p42 chromatographs with MBP kinase activity on a Mono Q ion-exchange column. Tyrosine phosphorylation of Xenopus p42 approximately parallels MBP kinase activity during meiotic maturation. These results suggest that related MBP kinases are activated during meiotic maturation of Xenopus and sea star oocytes. Previous studies have suggested that Xenopus p42 is related to the mitogen-activated protein (MAP) kinases of culture mammalian cells. We have cloned a MAP kinase relative from a Xenopus ovary cDNA library and demonstrate that this clone encodes the Xenopus p42 that is tyrosine phosphorylated during oocyte maturation. Comparison of the sequences of Xenopus p42 and a rat MAP kinase (ERK1) and peptide sequences from sea star p44mpk indicates that these proteins are close relatives. The family members appear to be tyrosine phosphorylated, and activated, in different contexts, with the murine MAP kinase active during the transition from quiescence to the G1 stage of the mitotic cell cycle and the sea star and Xenopus kinases being active during M phase of the meiotic cell cycle.

Amino Acid Sequence↗
PubMed1991

Isolation of an inhibitor of neutrophil function from bronchial lavage of normal volunteers.

Bronchial inflammation is associated with a reduction in airway caliber. Factors that may dampen this inflammation are ill defined. We have developed a model of airway inflammation using an extract of cotton bracts (CBE). In the current study we characterize inhibitor(s) of polymorphonuclear neutrophil (PMN) function in bronchial lavage (BL) fluid and examine the relationship between inhibitor concentrations and induction of bronchial inflammation or bronchoconstriction by CBE. We report that BL obtained contains factors that inhibit PMN hydrogen peroxide production and chemotaxis to formylmethionylleucyl-phenylalanine (FMLP). In two different subject populations the relative degree of a one molecular mass inhibitor was greatest in BL from subjects that manifested little bronchoconstriction to CBE compared with other subjects. In one subject population the relative amount of this inhibitor correlated inversely with the bronchoconstricting response to CBE and a number of parameters of airway inflammation including PMN noted on bronchial biopsy after CBE instillation. Partial chemical characterization of one molecular mass BL-derived inhibitor reveals it is of low molecular mass (less than 1,000 Da), nonpolar, and sensitive to aminopeptidase digestion. The finding that the bronchial environment contains variable concentrations of an oligopeptide that inhibits PMN function has important implications for treatment of inflammatory airway diseases.

Aminopeptidases↗
PubMed1991

Effect of albumin on hydraulic conductivity of pulmonary artery endothelial monolayers.

We tested the hypothesis that albumin reduces the vascular wall hydraulic conductivity by an interaction with the endothelium. The system consisted of luminal and abluminal chambers separated by a microporous filter onto which was grown a confluent monolayer of ovine pulmonary artery endothelial cells. The abluminal chamber filtrate was collected for timed periods during increases in transendothelial pressures of 5, 10, 15, and 20 cmH2O. The transendothelial water flux was linearly related to the hydrostatic pressure. Hydraulic conductivity (Lp) was determined from the slope of this relationship per unit surface area. In the absence of albumin, Lp of the endothelium and the filter was 14.8 +/- 3.8 x 10(-5) cm.s-1.cmH2O-1. The addition of either 2.5 or 5.0 mg/ml ovine serum albumin to the medium reduced Lp values similarly to 2.0 +/- 0.3 x 10(-5) and 2.5 +/- 1.1 x 10(-5) cm.s-1.cmH2O-1, respectively. Removal of albumin from the media reversed the effect of albumin on Lp. The filter Lp value of 3.2 +/- 0.3 x 10(-3) cm.s-1.cmH2O-1 was unaffected by albumin. Endothelial Lp value did not decrease with 5.0 mg/ml of 70-kDa neutral dextran. Albumin decreased Lp in the presence of epsilon-amino-caproic acid to the same extent as albumin alone, suggesting that the positively charged lysine sites on albumin did not mediate the effect. The results indicate that albumin decreases Lp due to an interaction between albumin and the endothelial cell.

Animals↗
PubMed1991

Platelet-derived growth factor receptor sequences important for binding of src family tyrosine kinases.

We previously demonstrated that src family tyrosine kinases associate with activated platelet-derived growth factor receptors. We have now investigated the requirement for tyrosine phosphorylation sites in the human platelet-derived growth factor receptor for this binding. Tyrosine 857, but not tyrosine 751, is required for efficient association. Furthermore, even though src family tyrosine kinases associate with receptors lacking tyrosine 751, they are not activated, implying that association does not invariably lead to activation.

Animals↗
PubMed1990

Binding of GAP to activated PDGF receptors.

The ras proto-oncogene products appear to relay intracellular signals via the Ras guanosine triphosphatase (GTPase) activator protein, GAP. In dog epithelial cells expressing human platelet-derived growth factor (PDGF) receptors, binding of PDGF caused approximately one-tenth of the total GAP molecules to complex with the receptor. Studies with mutant PDGF receptors showed that maximum association required both receptor kinase activity and phosphorylatable tyrosine residues at both the identified sites of receptor autophosphorylation.

Animals↗
PubMed1990

Disruption of the actin cytoskeleton in yeast capping protein mutants.

Capping protein controls the addition of actin subunits to the barbed end of actin filaments and nucleates actin polymerization in vitro. Capping protein has been identified in all eukaryotic cells examined so far; it is a heterodimer with subunits of relative molecular masses 32,000-36,000 (alpha-subunit) and 28,000-32,000 (beta-subunit). In skeletal muscle, capping protein (CapZ) probably binds the barbed ends of actin filaments at the Z line. The in vivo role of this protein in non-muscle cells is not known. We report here the characterization of CAP2, the single gene encoding the beta-subunit of capping protein in Saccharomyces cerevisiae. Yeast cells in which the CAP2 gene was disrupted by an insertion or a deletion had an abnormal actin distribution, including the loss of actin cables. The mutant cells were round and large, with a heterogeneous size distribution, and, although viable, grew more slowly than congenic wild-type cells. Chitin, a cell wall component restricted to the mother-bud junction in wild-type budding yeast, was found on the entire mother cell surface in the mutants. The phenotype of CAP2 disruption resembled that of temperature-sensitive mutations in the yeast actin gene ACT1, indicating that capping protein regulates actin-filament distribution in vivo.

Actin Depolymerizing Factors↗
PubMed1990

Phosphorylation of the PDGF receptor beta subunit creates a tight binding site for phosphatidylinositol 3 kinase.

The beta subunit of the platelet derived growth factor receptor (PDGFR) coprecipitates with a phosphatidyl-inositol 3 kinase activity (PI3K) following stimulation of cells by PDGF. Mutagenesis of a tyrosine (Y) phosphorylation site, Y751, in the PDGFR, greatly reduces PI3K, consistent with the possibility that phosphorylation of Y751 signals association of PI3K. To test this we have reconstituted the binding of the PDGFR beta subunit and PI3K in vitro. Binding is rapid, saturable and requires phosphorylation of the PDGFR at Y751, but does not require PDGF-dependent phosphorylation of PI3K. To test which portions of the PDGFR are important for binding, we used an antibody to a small region of the receptor that includes Y751. This antibody blocked in vitro binding of PI3K to the receptor, while an antiserum to the C-terminus of the receptor had no effect on binding of PI3K. In addition, we found that PDGF stimulation of a cell results in the association of essentially all the PI3K activity with cellular PDGFRs. These data suggest that PI3K is a specific ligand for PDGF receptors that are phosphorylated at Y751.

Amino Acid Sequence↗
PubMed1990

Plasmodium falciparum: two antigens of similar size are located in different compartments of the rhoptry.

Two previously described antigens, AMA-1 and QF3, which are located in the rhoptries of Plasmodium falciparum merozoites have polypeptides of similar relative molecular masses. On immunoblots, antibodies to both antigens recognized polypeptides of relative molecular mass 80,000 and 62,000 in all isolates tested. Two-dimensional electrophoresis showed that the isoelectric points of the two antigens were different. QF3 being more basic than AMA-1. AMA-1 was soluble in Triton X-114 whereas QF3 partitioned into the aqueous phase after temperature-dependent phase separation. In immunoelectron microscopic studies. QF3 was found in the body of the rhoptry whereas AMA-1 was consistently found in the neck of the rhoptry. Both antigens gave a punctate double-dot pattern in mature schizonts and merozoites when visualized by fluorescence microscopy, but AMA-1 antibodies also appeared to label the merozoite surface. QF3 was also detected in ring-infected erythrocytes whereas AMA-1 was not. Synthesis of both antigens was first observed in mature trophozoites and immature schizonts. Pulse-chase experiments showed that the Mr 80,000 polypeptide of the AMA-1 gene was subject to immediate processing to the Mr 62,000 product. This cleavage pattern was not stage specific. The Mr 80,000 polypeptide of QF3 was derived from a short-lived Mr 84,000 precursor polypeptide. Processing of the Mr 80,000 polypeptide to an Mr 62,000 polypeptide was restricted to the period of merozoite maturation and reinvasion. Hence AMA-1 and QF3 are different antigens with polypeptides of similar size but located in different compartments of the merozoite rhoptries.

Animals↗
PubMed1990

Identification of peptides from autolysates of Saccharomyces cerevisiae that exhibit glucose tolerance factor activity in a yeast assay.

1. Cationic fractions were isolated from a low chromium (less than 0.2 ppm) commercial yeast extract in an attempt to purify the material responsible for glucose tolerance factor (GTF) activity observed in a standard yeast assay system. 2. Following previously described procedures a fraction with GTF activity but containing negligible chromium was isolated, which on further purification was found to be composed of many separate small basic peptides. 3. Much of the activity of the yeast GTF material in the yeast assay could be attributed to the presence of basic peptides and free amino acids acting as nitrogen sources for the yeast. 4. Additional activity was present in the yeast GTF sample, which was not due to a synergistic effect of the mixed amino acids and peptides although the component of the yeast extract responsible for this activity was not identified. 5. The results show that the GTF fractions isolated according to most previously published procedures are highly impure, and conclusions drawn about the nature of GTF based on these isolates must remain open to question. 6. The activity due to the presence of peptides and amino acids is a major cause of lack of specificity of the yeast systems as an assay for GTF.

Amino Acids↗
PubMed1990

Oncogenes and anti-oncogenes.

The study of oncogenes offers insights into many steps in signal transduction. Rapid progress is possible because of the combination of biochemistry and genetics--unique in vertebrate cell biology--the availability of specific clones and antibodies, sequence information, dominant mutants, and biochemical assays of function. The wealth of detail on oncogenes and proto-oncogenes continues to increase dramatically. Hopefully, in the next year or two some of the gaps will be filled in and all the steps along at least one pathway from the cell membrane to the nucleus will be understood.

Animals↗
PubMed1990

Atypical presentation of pulmonary embolism.

Today we have discussed an interesting patient with an atypical presentation of pulmonary embolism. We have outlined a suggested algorithm to aid in the diagnosis and management of this disease. References 8 through 24 in the reference section are suggested readings that offer further insight into the diagnosis and management of this entity.

Aged↗
PubMed1990

Hypoxia and hypercarbia of chronic lung disease: minimal effects on anterior pituitary function.

Previous studies have suggested that the hypoxia and/or hypercapnia associated with chronic lung diseases may lead to pituitary and gonadal dysfunction, with destruction of the sella turcica. It is unclear, however, whether these abnormalities were due to lung disease or to confounding factors. We studied the relationships between hormonal levels (triiodothyronine, thyroxine, T3 resin uptake, thyrotropin, prolactin, cortisol, and testosterone) and PaO2, PaCO2, pH, and alveolar-arterial gradient in 25 patients with chronic lung disease. These patients were highly homogeneous for diagnosis, age, sex, ambulatory status, lack of other illnesses, and minimal use of medications unrelated to lung disease, but did have various degrees of hypoxia and hypercarbia at the time of study. We found no relationship between hormonal levels and lung function, or evidence of major pituitary involvement on lateral roentgenograms of the skull, CT of the sella turcica, or stimulation of the pituitary. An inverse correlation did occur between serum levels of thyroxine and the daily dose of oral prednisone. We conclude that most of the endocrine dysfunction ascribed to chronic lung diseases is probably due to factors other than hypoxia or hypercarbia.

Analysis of Variance↗
PubMed1990

Macrophage colony-stimulating factor-induced tyrosine phosphorylation of c-fms proteins expressed in FDC-P1 and BALB/c 3T3 cells.

The c-fms protein is a receptor for macrophage colony-stimulating factor (M-CSF) with intrinsic protein-tyrosine kinase activity. We investigated the tyrosine phosphorylation of murine c-fms proteins expressed from a retroviral vector in factor-dependent myeloid FDC-P1 cells and in BALB/c 3T3 fibroblasts transformed by the expression of the c-fms gene. FDC-P1 cells expressing c-fms were able to grow and differentiate in response to M-CSF. Their c-fms proteins were normally phosphorylated on serine and became phosphorylated on tyrosine residues contained in five tryptic peptides when the cells were exposed to M-CSF. A subset of these peptides was constitutively phosphorylated in BALB/c cells expressing c-fms, consistent with the production of M-CSF by these cells. All the peptides detected in vivo were also phosphorylated in vitro. These peptides were analyzed by susceptibility to proteases, comparison with synthetic peptides, and site-directed mutagenesis. The identities of four of the tryptic peptides were determined; they arise from three unique tyrosine phosphorylation sites. One major site of tyrosine phosphorylation at residue 697 accounted for two of the tryptic peptides. A second major site was identified at tyrosine residue 706. These two tyrosine phosphorylation sites are located within the tyrosine kinase insert region. Tyrosine 807, which has homology to the major autophosphorylation site of the p60v-src tyrosine kinase, is a minor autophosphorylation site. Possible functional roles for these phosphorylations of the c-fms protein include interactions with substrate proteins, catalytic activity, and ligand-induced degradation.

Amino Acid Sequence↗
PubMed1990

Leukotriene B4 increases pulmonary transvascular filtration by a neutrophil-independent mechanism.

We examined the role of circulating granulocytes in the pulmonary microvascular response to leukotriene B4 (LTB4) by prior depletion of circulating granulocytes using hydroxyurea. LTB4 (2 micrograms/kg injection followed by infusion of 2 micrograms/kg over 15 min) produced transient increases in pulmonary arterial pressure and pulmonary vascular resistance, indicating that neutrophils were not required for the pulmonary hemodynamic effects of LTB4. Infusion of LTB4 in granulocyte-depleted sheep also resulted in transient increases in pulmonary lymph flow (QL) with no significant change in the lymph-to-plasma protein concentration ratio (L/P), findings similar to those in control animals. In vitro studies indicated that LTB4 (10(-7) or 10(-9) M) produced a transient adherence of neutrophils to cultured pulmonary artery endothelial monolayers. Maximal responses occurred at 10 min after the addition of LTB4 to the endothelial cell-neutrophil coculture system, and the adherence decreased to base line within 60 min. LTB4 infusion in sheep also produced a transient uptake of autologous 111In-oxine-labeled neutrophils. The results indicate that LTB4-mediated increase in pulmonary transvascular protein clearance (QL x L/P) is independent of circulating granulocytes.

Animals↗