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Biomedical subjects

R G Johnson

Publications and source records attributed to R G Johnson.

234 records · Page 13Linked to original sources
PubMed1971

Junctions between cancer cells in culture: ultrastructure and permeability.

Cell junctions between Novikoff hepatoma cells (N1S1-67) growing as small clumps or chains in suspension culture have been studied with ultrastructural, electrophysiological, and dye-injection techniques. Cells within clumps are commonly electrically coupled and can exchange dyes with a molecular weight of 332 to 500. Gap junctions and intermediate junctions are present, whereas true tight junctions and desmosomes are absent or very rare. This system should provide a useful model for studying the properties of "communicating" junctions.

Biological Transport↗
PubMed1968

Ten-armed fossil cephalopod from the Pennsylvanian of Illinois.

Jeletzkya douglassae Johnson and Richardson is described as the oldest known representative of an extant squid group. The species is known from a single specimen from the Middle Pennsylvanian of Illinois. This very unusual fossil consists of the complete tentacular crown and a fragile shell. The arms bear hooks in double rows.

Animals↗
PubMedDate not supplied

Effects of TPA on dye transfer and dye leakage in fibroblasts transfected with a connexin 43 mutation at ser368.

In order to investigate the site of active phosphorylation under treatment with TPA, both wild type (WT) fibroblasts and fibroblasts from Cx43-knockout mice transfected with Cx43 mutated at ser368 were used to study the effects of TPA on dye leakage and gap junction assembly. Results showed that in control conditions with or without EGTA, no significant differences in dye leakage were observed between these two kinds of cells. However, under TPA treatment, non-leakage cases in the mutant cells were much less than those in WT cells. In the two types of reaggregated cells, there was a marked difference in the capacity for dye transfer. Dye transfer in WT cells was 4-fold stronger than in mutant cells. While under TPA treatment, the difference between WT and mutant cells was diminished suggesting that ser368 was probably the most important phosphorylation site under treatment with TPA.

Alanine↗
PubMedDate not supplied

The preparation of an acceptable placebo for NPH insulin.

A suitable placebo for NPH insulin has not previously been available for clinical investigation. A series of organic and inorganic compounds were formulated as insulin placebos and analyzed according to the following criteria: (1) degree of visual similarity to insulin, (2) stability, (3) absence of local side effects, and (4) clinical safety. Dilute suspensions of cortisone acetate (1.25-2.5 mg/ml) were found to fulfill the criteria as acceptable insulin placebos. Placebo-controlled studies with NPH insulin can now be performed.

Clinical Trials as Topic↗
PubMedDate not supplied

Localization of symptomatic lumbar pseudarthroses by use of discography.

Twenty-four patients with lumbar pseudarthroses following attempted fusion were investigated by preoperative discography. The pseudarthroses were confirmed at surgical exploration. In 19 patients, discography at the level of a pseudarthrosis reproduced typical back pain, and in two patients the level above the fusion reproduced typical pain. Discography is not indicated when the major symptoms are leg or buttock pain. Technical errors included injection into the annulus fibrosis and impingement of the needle into the vertebral endplate. The latter may produce a false-positive result. Previous posterior fusions and very narrow disc spaces prevented insertion of the needle in some patients. Not all lumbar pseudarthroses were symptomatic, and two frequently occurred in the same patient. Discography is a useful adjunct to the traditional investigation of lumbar pseudarthroses.

Adult↗
PubMedDate not supplied

Biochemical analysis of rabbit articular cartilage using an amino acid analyzer.

The automated amino acid analyzer has been used to provide a simple, rapid and accurate means of assaying the glycosaminoglycan (GAG) and collagen content, and collagen type of connective tissues. The analysis of rabbit articular cartilage using this method is reported. Cartilage slices taken from the tibial plateaus of rabbits were dried and weighed. A comparison study showed that oven-drying (110 degrees C for 24 hours) was more effective in dehydrating cartilage than vacuum dessication for 96 hours. This drying temperature could be maintained for 24 hours without destroying hexosamine. The dried samples were hydrolyzed for 4 hours in 4 N HCl at 100 degrees C; these conditions were shown to give virtually 100% release of galactosamine from purified chondroitin-6-sulphate with minimal degradation of the hexosamine. The 4-hour hydrolysates were assayed for galactosamine and glucosamine using the amino acid analyzer. From these values the amount of chondroitin sulphate and keratan sulphate were calculated. An aliquot of the 4-hour hydrolysate was hydrolyzed further in 6 N HCl for 24 hours. This destroyed hexosamine but permitted the quantitation of hydroxyproline and hydroxylysine using the amino acid analyzer. Collagen content was calculated from the hydroxyproline value and the hydroxylysine to hydroxyproline ratio was used to determine the collagen type.

Amino Acids↗
PubMedDate not supplied

Intracellular lucifer yellow leakage from Novikoff cells in the presence of ATP or low extracellular Ca: evidence for hemi-gap junction channels.

Lucifer Yellow was microinjected into Novikoff hepatoma cells and leakage was investigated under treatment with ATP (5 mM) and EGTA (5 mM) in the culture medium. In control conditions, there was no leakage in single or paired cells, except a few cases which showed very slow leakage (defined as slope < -0.0007/sec). Slow leakage rate (slope > -0.0008 but < -0.009/sec) and quick leakage rate (slope > -0.01) of intracellular dye were not seen. Dye transfer between cell pairs after Lucifer Yellow was injected into one cell was divided into two groups: quick transfer rates (4 cases, slope = -0.151 +0.0032) and slow transfer rates (15 cases, slope = -0.041 +0.0018). Under ATP treatment the intracellular dye leakage was observed in single cells (16 of 31 cases) and in cell pairs (20 of 57 cases). Extracellular low Ca2+ (EGTA treatment) enhanced the dye leakage much more: 30 of 40 cases in single cells and 21 of 36 cases in cell pairs. The leakage rates of intracellular dye under these treatments were similar to the transfer rates of the dye between cell pairs with quick and slow rates. It is suggested that the dye leakage from Novikoff cells under treatment with ATP or low [Ca2+]o shares the same mechanism as dye transfer through gap junctions, suggesting that the hemichannels in the plasma membrane can be opened under certain conditions.

Adenosine Triphosphate↗