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Biomedical subjects

B Johnson

Publications and source records attributed to B Johnson.

At least 325 records · Page 18Linked to original sources
PubMed1983

Selective protection of nonmalignant cells by a novel cell surface glycopeptide.

A novel glycopeptide inhibitor of cell division, isolated from bovine cerebral cortex cell surfaces, was shown to selectively protect nonmalignant cells from the cytoxic action of 5-bromo-2-deoxyuridine (5-BrdUrd). When mouse LM-22 cells (nonmalignant and devoid of gangliosides) were preincubated with GM1 ganglioside (3.0 micrograms/ml), the cell surface glycopeptide inhibitor effectively arrested cell division. In contrast to LM-22 cells, transformed mouse fibrosarcoma (No. 1316) cells were insensitive to the glycopeptide inhibitor whether or not they were preincubated with GM1 ganglioside. Mixed cultures of LM-22 cells preincubated with GM1 ganglioside and 1316 fibrosarcoma cells at an approximate ratio of 1:1 were established. Since LM-22 cells are resistant and 1316 fibrosarcoma cells are sensitive to 3.0 mM ouabain, the identity of surviving cells following BrdUrd treatment could easily be determined. Three hr after the establishment of the mixed cell population, 250 ng protein per ml of the purified bovine glycopeptide inhibitor was added to selectively arrest the mitosis of the LM-22 cells. After an additional 3 hr of incubation, 5-BrdUrd was added to a final concentration of 5.0 mM. Twelve hr later, cells were serially diluted and seeded into duplicate plates with and without 3.0 mM ouabain. LM-22 cells were effectively protected from the cytotoxic action of 5-BrdUrd (92 to 94% survival) while the majority of the 1316 fibrosarcoma cells were killed (21 to 30% survival). The selective protection of LM-22 cells was shown to be independent of differences in plating efficiency, cytotoxicity of 5-BrdUrd in the absence of the glycopeptide inhibitor, and the generation time of the two cell lines.

Animals↗
PubMed1982

A human skin window technique using micropore membranes.

A skin window technique using micropore membranes is described. Eight micrometre pore-size membranes are placed on abrasions made with a dental stone and covered with moist filter paper and impermeable film: adhesive tape is placed overall. The assembly is unobtrusive and stable and may be worn during normal activities. For clinical studies, a series of membranes used over 4-5 h gives information on distribution of leucocyte emigration sites, numbers and types of emigrant cells, their rate of locomotion in the membrane (solely under the influence of endogenous factors) and any difference in form, surface phenotype or function between cells at the dermal surface and those which have traversed the membrane. This system, using a 3-dimensional labyrinthine structured membrane, avoids errors inherent in previous techniques, e.g., differential adhesiveness, competition for space, no quantification of locomotion after emergence or indication of the productive area of the abrasion. Incidental findings include no major change in the nature of the emigrating population over 24 h, the presence of monocytoid cells from the earliest phase in normal subjects, the origin of emigrating cells in discrete foci, and an even distribution of cells in a fully infiltrated membrane. The skin window technique is capable of greater clinical precision and experimental elaboration than hitherto realised.

Cell Movement↗
PubMed1982

Identification of a T cell-derived b cell growth factor distinct from interleukin 2.

We report here a factor (B cell growth factor) found in induced supernatants of the mouse thymoma EL4 that co-stimulates with anti-IgM antibodies in short-term cultures of purified B lymphocytes to induce polyclonal B cell proliferation but not antibody-forming cell production. The factor is not mitogenic for resting B cells and interacts with anti-IgM-activated B cells in a non-H-2-restricted manner. Absorption studies and molecular weight analysis reveal the factor is distinct from interleukin 2. This factor synergises with antigen, interleukin 2, and an interleukin 2-free, B cell growth factor-free T cell supernatant that contains T cell-replacing factor to produce erythrocyte-specific plaque-forming cells in cultures of highly purified B cells.

Animals↗
PubMed1982

Colonometry, cystometry, and evoked potentials in multiple sclerosis.

The conditions of three patients with advanced-stage multiple sclerosis and symptoms related to bowel and bladder function were evaluated using colonometry, cystometry, and somatosensory evoked responses from the posterior tibial nerve. The colonometrograms and cystometrograms showed notable hyperreflexia and reduced filling capacity when compared with neurologically intact patients. The neurological lesions were localized to above the conus medullaris by recording normal somatosensory responses at L-1 and abnormal responses over the scalp. This combination of tests are important in the documentation of bowel and bladder dysfunction, the localization of the neurological lesion causing the symptoms, and the determination of treatment of bowel and bladder symptoms in patients with multiple sclerosis.

Brain↗
PubMed1982

Corneal transplantation in an infant with corneal dermoid.

A 1-month-old infant had a protuberant congenital corneal dermoid that extended into the anterior chamber. The dermoid was excised in two stages. A 12-mm lamellar keratectomy was followed three months later by a smaller (8-mm) penetrating keratoplasty. This technique minimized the complications associated with large corneal transplants and increased the chance of long-term success. The graft has remained transparent and the posterior segment appears to be normal. The infant can maintain constant fixation and recognize small objects and crawls without difficulty.

Anterior Chamber↗
PubMed1982

Ethanol kinetics during pregnancy. Study in ewes and their fetuses.

1. Kinetics of placental transfer and elimination of ethanol in maternal and fetal blood and amniotic fluid were studied after iv infusion of ethanol in 3 ewes in the third trimester of pregnancy. 2. Ethanol was transferred rapidly from the maternal to the fetal compartment, and more slowly from these to the amniotic fluid. 3. The kinetics of ethanol elimination from the maternal and fetal circulations were similar, indicating rapid bidirectional transfer between them and elimination from the former only. 4. There was significantly slower elimination of ethanol from the amniotic fluid, with increasing concentrations long after these had started to decline in the maternal and fetal blood. This suggests that the amniotic fluid can act as a reservoir for ethanol storage.

Amniotic Fluid↗
PubMed1982

Hepatic Injury following halothane, enflurane, and isoflurane anesthesia in rats.

Halothane anesthesia administered to enzyme-induced animals in a hypoxic atmosphere consistently produced hepatic necrosis. Rats pretreated with phenobarbital were exposed to hypoxia at varying intervals after administration of halothane, enflurane, or isoflurane anesthesia. Anesthetics were administered at 1 MAC for 2 h. For each agent, hypoxia consisting of 8 per cent oxygen-balance nitrogen for 1 h was imposed at the end of anesthesia. In other groups of rats, we also used a 15-, 30-, 60-, and 120-min interval of 100 per cent oxygen between 2 h of halothane anesthesia and the imposition of hypoxia. Controls included enzyme-induced animals with and without hypoxia, hypoxia alone, and cage controls. Hepatic injury was graded by histologic examination of the livers. Injury was greater when hypoxia followed halothane anesthesia than when it followed enflurane, isoflurane, or enzyme-induction alone. A difference in injury score existed between control animals and those anesthetized with halothane who received a 15-min interval of oxygen before hypoxia. Combined results from the 15- and 30-min delay groups also were different from control. There was no difference between control and halothane groups when the oxygen interval was 60 or 120 min. The injury score of the enflurane and isoflurane groups were comparable to that of controls. We conclude that the potential for hypoxia-induced liver injury during recovery exists after halothane anesthesia. Neither enflurane nor isoflurane anesthesia produced significant hepatic injury in this model.

Anesthetics↗
PubMed1982

Stereospecific lactate absorption during peritoneal dialysis.

Patients undergoing peritoneal dialysis were studied to determine if peritoneal absorption was selective. Dialysis was performed using dialysate exchange schedules similar to those for intermittent peritoneal dialysis and continuous ambulatory peritoneal dialysis. The clearance rate from the peritoneal cavity during hourly dialysate exchanges was 6.2 ml/min for D (-)-lactate and 8.7 ml/min for L(+)-lactate (p less than 0.01). L(+)-Lactate disappeared more rapidly from the dialysate during the long-cycle exchanges. Our results suggest that clearance of lactate from the peritoneal cavity is relatively stereospecific and raises the question of selective absorption for other organic anions.

Adult↗
PubMed1982

Stability of stored methacholine chloride solutions: clinically useful information.

Methacholine inhalation challenge (MIC) has been shown to be an extremely useful diagnostic test. Because a decrease in the time and expense involved in the preparation of methacholine chloride solutions might encourage more laboratories to perform MIC, we assessed the stability of several different concentrations of methacholine chloride in solution over a period of 4 months. We used and compared 2 different assay techniques: a high pressure liquid chromatography assay and a colorimetric assay. Comparable results were obtained by both assays and demonstrated that methacholine solutions stored either at room temperature or at 4 degrees C showed no significant decomposition over a period of 4 months. From our results, we conclude that: (1) methacholine chloride solutions are much more stable than stated in the Merck Manual, (2) the original data of MacDonald and coworkers on the stability of methacholine chloride solution are accurate, (3) our high pressure liquid chromatography method is an accurate and highly specific technique for measuring methacholine chloride solutions. The major clinical implication of our results is that the time and cost necessary to prepare methacholine chloride solutions is much less than previously thought. This should encourage a more widespread use of this important diagnostic technique for the demonstration of bronchial hyperreactivity.

Chromatography, High Pressure Liquid↗
PubMed1982

Detection of IgG bound within human trophoblast.

Previous studies have failed consistently to detect either binding sites for exogenous IgG or endogenous IgG on human trophoblast by using conventional immunohistologic methods. The present study demonstrates specific binding sites for exogenous IgG on all trophoblast-derived cells. The binding sites were detectable with monomeric IgG but not IgG aggregates. The binding sites were detected more easily if cells were washed at an acid pH (5.0). The level of binding activity was greater in younger placental tissue, although expression of binding sites on cells in extraplacental membranes was age-independent. Complexing of bound exogenous IgG resulted in its dissociation from tissue binding sites. Endogenous trophoblast-associated IgG was readily detectable when anti-IgG reagents that produced minimal complexing were used, e.g., Fab fragments of rabbit antihuman IgG. High levels of both Fc gamma binding sites and endogenous IgG were detected in placentae as late as 30 wk gestation, but both were present only in low levels at term. The results demonstrate that both binding sites for exogenous and endogenous IgG are associated with the human trophoblast and support the theory that IgG transport through the human trophoblast is dependent on Fc gamma receptors.

Female↗
PubMed1981

High pressure liquid chromatography on labetalol in serum or plasma.

A sensitive method for monitoring serum or plasma labetalol (2-hydroxy-5-[1- hydroxy-2-(1-methyl-3-phenylpropylamino) ethyl] benzamide hydrochloride) is described. The method is designed to study single dose kinetics and assess predose labetalol levels during chronic treatment. The applicable range of the assay is 10 to 400 ng/ml using 1 ml of plasma or serum. The method uses reverse-phase high pressure liquid chromatography (HPLC), a mobile phase of acetonitrile/pH 3.0 phosphate, and ultraviolet detection at 207 nm. The percentage recovery of labetalol and internal standard (propericiazine) (3-cyano-10-[3-4-hydroxypiperidino) propyl] phenothiazine from serum was 95.6% and 75.5%, respectively. Th precision of the method at labetalol serum concentrations of 400 and 50 ng/ml was indicated by a coefficient of variation of 4.3% and 6.9%, respectively. An approximate fourfold variation in plasma labetalol concentration, with plasma levels ranging from 20 to 93 ng/ml, was seen 10 to 11 hours after a dose in a group of patients taking 200 mg twice daily.

Chromatography, High Pressure Liquid↗