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Biomedical subjects

J Lawrence

Publications and source records attributed to J Lawrence.

At least 163 records · Page 9Linked to original sources
PubMed1986

Radioimmunoassays for fish tail neuropeptides: I. Development of assay and measurement of immunoreactive urotensin I in Catostomus commersoni brain, pituitary, and plasma.

Antisera were raised in rabbits using highly purified urotensin I (UI) or UI (4-41) conjugated with high-molecular-weight proteins. Antiserum 2U4, at a final dilution of 1:300,000, gave 50% binding to iodinated UI (specific activity 40-120 microCi/micrograms). Carp (Cyprinus carpio) and sucker (Catostomus commersoni) UI peptides cross-reacted completely with the antiserum. Results from cross-reactivity tests using various tryptic and Staphylococcus aureus protease fragments of UI indicated that the antigenic sites of the main antibody(ies) are directed against a part sequence in the C-terminal region of the peptide although antibodies with lower concentration or affinity, recognizing N-terminal region(s) of the peptide, are also present. No cross-reactivity was seen with insulin, secretin, vasoactive intestinal peptide or a structural UI-homolog, the ovine hypothalamic corticotropin-releasing factor, up to molar concentrations. Sauvagine, another structurally homologous peptide from frog skin, showed only 0.1% cross-reactivity. The urophysis-specific proteins, urophysins B and D, showed a low degree of cross-reactivity. Assays of serial dilutions of urophysis extracts from teleostean species yielded parallel displacement curves, except in the case of the pacific goby, Gillichthys mirabilis. Varying concentrations of immunoreactive UI were present in different regions of C. commersoni brain, spinal cord, and pituitary, and also in plasma. The measurement of 17.5 +/- 2.1 fmol UI/ml of plasma indicates that this assay may be used for the study of circulating UI peptide(s).

Amino Acid Sequence↗
PubMed1986

Endemic canine and feline histoplasmosis in El Paso, Texas.

Seventeen cases of histoplasmosis involving 2 dogs and 15 cats have occurred in the Upper Rio Grande Valley of El Paso since 1978. The diagnosis, based on clinical signs and radiographic findings, was confirmed by one or more of the following laboratory procedures: demonstration of intracellular Histoplasma capsulatum yeast cells in tissue, positive serology, or isolation of H. capsulatum from various organs of necropsied animals. H. capsulatum was isolated also from a bat cave and soil in the vicinity of some of the houses where the affected animals had resided. Skin-tests of 97 persons for histoplasmosis indicated a 14% positive prevalance in this locale.

Animals↗
PubMed1986

Clinical trial comparing bacitracin with Strep-A-Chek for accuracy and turnaround time in the presumptive identification of Streptococcus pyogenes.

In a clinical trial, Strep-A-Chek (a 10-min chromogenic test) was compared with the bacitracin disk susceptibility test for accuracy and turnaround time in the presumptive identification of Streptococcus pyogenes. Among 461 isolates of beta-hemolytic streptococci (344 throat isolates and 117 isolates from other sites), 303 group A S. pyogenes isolates were found. The sensitivities of the Strep-A-Chek and bacitracin tests were high (96.4 and 100%, respectively), but the bacitracin test had a lower specificity (84.2%) than the Strep-A-Chek test (98.7%). The predictive values for positive and negative test results were 99.3 and 93.4%, respectively, for Strep-A-Chek and 92.4 and 100%, respectively, for bacitracin. Strep-A-Chek correctly identified all isolates upon repeat testing. All bacitracin tests were performed on subcultures of isolates from the primary plate. Strep-A-Chek testing was performed on colonies from the primary plate when isolated colonies were available. This shortened the turnaround time for Strep-A-Chek compared with bacitracin by at least 24 h on nearly one-half (45%) of the isolates. A peripheral finding of this study was that sulfamethoxazole-trimethoprim blood agar offered no advantage over conventional blood agar with regard to the number of false-positive bacitracin tests obtained from each medium.

Bacitracin↗
PubMed1985

Translocations that highlight chromosomal regions of differentiated activity.

The frequent translocation of the c-myc oncogene into the immunoglobulin loci in tumors of B lymphocytes prompted us to ask whether or not disease-associated chromosomal translocations specific for other disorders in different cell types would also involve regions of the genome encoding important differentiation-specific products made by these cells. We have studied the karyotypes of two patients with erythroleukemia and an established erythroleukemia cell line, K562 (late passages), and find translocations within the chromosomal regions to which the genes that encode alpha and beta globin have been assigned. Additionally, we have analyzed the karyotype of cloned B-lymphocytes, including both kappa and lambda producing cells, from a patient with ataxia telangiectasia (AT) and find a translocation between the regions encoding immunoglobulin (Ig) light and heavy chain genes whereas a different translocation not involving these regions is seen in T-lymphocytes from the same patient. These examples provide insight into the mechanism of chromosomal translocation in both cancerous and noncancerous conditions and lead to the speculation that genomic activity is a necessary factor in the generation of some chromosomal translocations.

Adult↗
PubMed1985

Incidence and characterization of beta-hemolytic Streptococcus milleri and differentiation from S. pyogenes (group A), S. equisimilis (group C), and large-colony group G streptococci.

The biochemical characteristics of 172 clinical isolates of group A, C, F, or G or "nongroupable" beta-hemolytic streptococci were examined. Among these isolates, 91 were identified as beta-hemolytic strains of Streptococcus milleri. The remaining isolates included 20 Streptococcus pyogenes, 21 Streptococcus equisimilis, 37 large-colony group G streptococci, and 3 unidentified nongroupable isolates. A majority (84%) of the S. milleri strains possessed Lancefield group antigen (3 A, 27 C, 41 F, and 5 G), whereas 15 S. milleri strains (16%) were nongroupable. Serological tests did not differentiate S. milleri isolates with group A, C, or G antigen from S. pyogenes (group A), S. equisimilis (group C), or large-colony group G streptococci. Biochemical tests which were found useful for differentiation included the Voges-Proskauer test, hydrolysis of pyroglutamic acid and beta-D-glucuronide, bacitracin susceptibility, and acid production from ribose. S. milleri represented 56% of the group C, 100% of the group F, and 83% of the nongroupable beta-hemolytic streptococci isolated in our clinical laboratory, whereas the incidence of S. milleri among group A and group G streptococci was estimated to be low. The role of beta-hemolytic S. milleri as a cause of human infection remains obscured by the failure to routinely differentiate S. milleri from other beta-hemolytic streptococci.

Hemolysis↗
PubMed1984

Carboxylic ionophores enhance the cytotoxic potency of ligand- and antibody-delivered ricin A chain.

The highly selective cytotoxicity of site-directed ricin A chain conjugates can be potentiated by membrane-active carboxylic ionophores. The combined use of the two agents results in much faster inactivation of ribosomes and subsequent cell death and lysis. The potency of A chain cytotoxins is correspondingly increased by several orders of magnitude and cells that sparsely express the target antigen or receptor can be killed.

Animals↗
PubMed1984

Role of actin binding protein phosphorylation in platelet cytoskeleton assembly.

Actin binding protein from human blood platelets is shown to exist in the resting platelet as a phosphorylated protein and contains two residues of phosphate per 260,000 kd. Removal of one-half of these residues with E. coli alkaline phosphatase results in the loss of its ability to crosslink F-actin into a low speed sedimentable complex (its cytoskeleton) and to bind to an F-actin affinity column. Thus, phosphorylation-dephosphorylation of ABP may be an important regulatory mechanism by which the platelet regulates its shape via its cytoskeletal structure.

Actins↗
PubMed1983

Penbutolol in hypertension, alone and in combination with furosemide. A long-term multicentre study.

Penbutolol is a new, potent and long-acting non-cardioselective beta-adrenergic blocker which has been evaluated in a 6-month open study of patients with moderate essential or renal hypertension. Eighty-two patients entered the study and 69 completed at least 3 months of treatment. Two-thirds of these showed a good response to penbutolol given alone as a single daily dose of either 40 mg or 80 mg. The major reduction in blood pressure occurred within the first 2 weeks of active therapy. This response was maintained for the entire study period. Blood pressure reduction after penbutolol did not correlate wtih the small reduction in heart rate observed. The remaining patients were treated with a combination of penbutolol and furosemide and most had achieved satisfactory control of their blood pressure by the end of the study. Penbutolol was well tolerated and produced no serious adverse effects. Some patients developed gastro-intestinal side-effects at the beginning of treatment which subsequently resolved. One patient with chronic glomerulonephritis showed a marked deterioration in renal function during the study. This may well have been related to disease progression. No other significant changes in biochemical or haematological parameters were observed.

Adult↗
PubMed1982

Effect of various extraction solutions and thrombin activation on the composition of the platelet cytoskeleton.

When human blood platelets were immersed in an ice-cold solution containing 1% Triton X-1200, 40 mM KCl, 10 mM EGTA, 10 mM imidazole-HCl, and 2 mM NaN3 pH 7.0, a flocculent precipitate appeared immediately in the tube. This precipitate was collected at 3,000g and SDS-polyacrylamide gel analysis showed it to consist mainly of actin, alpha-actinin, actin-binding protein (ABP), and varying amounts of myosin. Any modifications of this solution used to isolate the platelets' Triton-insoluble cytoskeleton caused profound changes in the nature of the cytoskeleton isolated. Increasing the KCl concentration resulted in a lower yield of cytoskeletal actin and ABP. Inclusion of EDTA in the solution resulted in an increased amount of myosin associated with the cytoskeleton, whereas including MgATP decreased the myosin yield. Experiments with the purified proteins showed that ABP and myosin can each protect the actin from depolymerizing when dialyzed into the Triton solubilization solution. In addition, it was found that when platelets were stimulated with thrombin for 2 min prior to the addition of the Triton solution, 3-4 times more myosin was associated with the cytoskeletal precipitate. The results suggest, therefore, that any variations in solution conditions used for isolating the cytoskeleton from resting platelets, which results in alterations in the amount of ABP, may have profound effects on the state of actin polymerization. Likewise, in thrombin-activated platelets, it is suggested that the increased association of myosin with the cytoskeleton results in a greater stabilization of the F-actin associated with the cytoskeleton. These factors must be considered when interpreting the results regarding the nature of actin transformations in the resting and activated platelet.

Actinin↗