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Biomedical subjects

M F Johnston

Publications and source records attributed to M F Johnston.

29 records · Page 2Linked to original sources
PubMed1976

Vitamin K-dependent synthesis and modification of precursor prothrombin in cultured H-35 hepatoma cells.

The ability of confluent monolayers of H-35 cells, originally obtained from a rat hepatoma, to synthesize prothrombin in response to vitamin K1 (phylloquinone) was studied. As demonstrated by radioimmunoassay, selective barium salt adsorption, and two coagulation assays which discriminate between precursor- and mature-prothrombin, these cells retained their ability to synthesize precursor prothrombin (preprothrombin) in the absence of exogenous phylloquinone (vitamin K). When phylloquinone was added to the medium (100 ng/ml), the existing intracellular concentration of preprothrombin was reduced to 50% within 1 hr after exposure to the vitamin and slowly declined thereafter to approximately 30% of control levels by 36 hr. Concomitant with the rapid loss of intracellular preprothrombin was the appearance of mature prothrombin in the medium. The appearance of prothrombin was biphasic: occurring during the initial 0-6 hr interval, and again at an increased rate during the next 18-24 hr interval. The amount of prothrombin appearing in the medium exceeded by severalfold the amount of precursor mobilized. These data demonstrate that monolayer cultures of H-35 hepatoma cells retain their ability to synthesize preprothrombin and other enzymes, responsible for post-translational modification of prothrombin and its subsequent secretion, under the influence of vitamin K.

Biological Assay↗
PubMed1976

Mechanism of inhibition of adoptive transfer of tuberculin sensitivity in acute uremia.

Cell-mediated immunity is reduced in uremia, but the mechanism of this inhibition is poorly understood. To determine the site of inhibition a study of adoptive transfer of cell-mediated immunity was undertaken. Strain 13 guinea pigs were made uremic by ureteral ligation. Lymph node cells were isolated and transferred in the following three ways: Group 1: tuberculin sensitive nonuremic donors to nonimmune nonuremic recipients; Group 2: tuberculin sensitive nonuremic donors to nonimmune uremic recipients; Group 3: tuberculin sensitive uremic donors to nonimmune nonuremic recipients. There was no difference in the skin test responses of the transfer recipients in Groups 1 and 3, even though the uremic donors in Group 3 had lost their skin test reactivity. Transfer of tuberculin sensitivity was not successful in Group 2. These results indicate that the uremic state inhibits previously established skin test reactivity but does not prevent sensitized T lymphocytes from transferring cellular immunity.

Acute Disease↗
PubMed1976

Cross-reactions between 2, 4-dinitrophenyl and menadione (vitamin K3) and the general problem of antibody specificity.

Early and late antisera to 2, 4-dinitrophenyl (DNP) and to menadione (K3)4 were compared for reactivity with diverse DNP and K3 ligands. Late antisera were generally more reactive (higher affinity) than early antibodies. Nevertheless, the early antibodies had higher affinity for homologous ligands than late antibodies had for heterologous ligands; the exception, a small (ca. 5%) and possibly heteroclitic subset from late anti-DNP sera, had higher affinity for K3-butyrate than for DNP-lysine. Early antisera appeared to be more specific than late antisera by one criterion (the precipitin reaction), but less specific by a more fundamental criterion (KO/KX, the ratio of intrinsic affinities for homologous and cross-reacting ligands). By several methods (precipitation, binding to heterologous immunoadsorbants) 25 to 75% of the antibodies in both anti-DNP and anti-K3 sera were cross-reactive; even more cross-reactivity was evident by equilibrium dialysis, where it appeared that virtually all anti-DNP antibodies can bind K3 and that virtually all anti-K3 can bind DNP. This extreme level of cross-reaction is not as "strange" as was once thought, it seems unwarranted to regard this cross-reaction as support for the view that antibodies in general are multispecific.

Animals↗
PubMedDate not supplied

Intraoperative autologous blood salvage with cardiac surgery: an analysis of five years' experience in more than 3,000 patients.

STUDY OBJECTIVE: To analyze intraoperative autologous salvage of shed mediastinal blood and subsequent transfusion in cardiac surgery. DESIGN: Retrospective statistical analysis. SETTING: University hospital. PATIENTS: Three thousand twenty two patients undergoing cardiac surgery from 1984 to 1988. INTERVENTIONS: A review of anesthesia and transfusion records of all patients who underwent intraoperative salvage of shed blood and autologous transfusion using the Sorenson Receptal Auto Transfusion System (ATS) with saline wash prior to reinfusion in cardiac surgery. MEASUREMENTS AND MAIN RESULTS: The salvaged blood volume ranged from 36 to 2,795 ml, with a mean of 321 +/- 222 ml (SD). Eighteen percent of patients did not receive any homologous blood products during their hospitalization. Patients who received only salvaged autologous transfusion were younger, had higher preoperative hemoglobin and hematocrit values, had a larger body surface area, and had shorter surgeries compared with patients who received only homologous blood or both autologous and homologous blood. More blood products were given to patients who received salvaged autologous blood compared with those who did not. Patients who underwent normovolemic hemodilution prior to extracorporeal circulation with subsequent reinfusion received significantly fewer blood products. Ten preoperative and four intraoperative variables significantly influenced the salvaged volume. Previous cardiac surgery was the most significant preoperative variable, and repair of ventricular septal defect produced by myocardial ischemia was the most significant intraoperative variable. CONCLUSION: Considering the average salvaged volume and its current autologous transfusion-related expense, autologous blood salvage is potentially an economic benefit. Perioperative blood conservation requires a considerable commitment from surgeons, anesthesiologists, perfusionists, and intensive care physicians to be effective.

Blood Substitutes↗
PubMedDate not supplied

Immunodetection of hepatic peroxisomal PMP70 as an indicator of peroxisomal proliferation in the mummichog, Fundulus heteroclitus.

Peroxisomes are important sites for beta-oxidative fatty acid metabolism and peroxidative detoxification. Agents causing peroxisomal proliferation have been associated with reproductive and developmental toxicity and hepatocarcinogenesis. Female mummichog (Fundulus heteroclitus) were exposed to waterborne 2,4-dichlorophenoxyacetic acid (2,4-D), a model peroxisome proliferator, at sublethal concentrations of 0.01, 0.10, and 1.00 ppm or dimethyl sulfoxide (DMSO) vehicle for 7, 14, or 21 days. A polyclonal antibody to rat PMP70 protein (70 kDa peroxisomal membrane protein, a major component of peroxisomes and member of the ABC transporter superfamily) was used for Western blotting after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to determine possible peroxisome proliferation. Significant increases of an approximately 70-kDa protein band recognized by anti-PMP70 were observed on all days, especially at the highest exposure concentration. The data suggest that immunoassay of PMP70 is a useful biomarker assay for peroxisome proliferation, and may be applicable to a wide range of species. The response also suggests that this assay could be used for measuring chronic exposures to environmental peroxisome proliferating agents.

2,4-Dichlorophenoxyacetic Acid↗