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Biomedical subjects

C W Adams

Publications and source records attributed to C W Adams.

At least 37 records · Page 2Linked to original sources
PubMed1987

Biological consequences of segmental alterations in mRNA stability: effects of deletion of the intercistronic hairpin loop region of the Rhodobacter capsulatus puf operon.

It has been proposed that intercistronic stem and loop structures located in the puf operon of the photosynthetic bacterium Rhodobacter capsulatus account for segmental differences in transcript stability and consequently, the differential expression of the B870 and reaction center (RC) proteins encoded by puf. We report here that deletion of these structures leads to a failure to detect as discrete fragments the B870-encoding 0.49 kb and 0.50 kb mRNA segments located upstream from the site of the hairpins. The absence of these stable transcript fragments is associated with altered stoichiometry of the B870 and RC pigment-protein complexes in the bacterial intracytoplasmic membrane and a decreased rate of cell growth under photosynthetic conditions. These results support the view that the hairpin loop structures of the puf intercistronic region function in vivo to impede exoribonucleolytic degradation of upstream mRNA and establish that segmental variations in mRNA stability have a biologically important role in regulating the expression of puf operon genes.

Base Sequence↗
PubMed1987

Renal arterial pathology after percutaneous transluminal angioplasty.

Percutaneous transluminal angioplasty (PTA) has been shown to cause cracking of the intimo and atherosclerotic plaque in the renal arteries of two cases, who died from incidental causes about a week after the procedure. In addition, movement or redistribution of atheromatous gruel was seen into the cracks and dissections at the intima-medial junction and media. Thus, enlargement of the lumen by redistribution of the lipid mass by 'warm flow' may be an important beneficial result of angioplasty. One case also showed severe fragmentation of medial elastic fibres at the orifice, with rupture of the internal elastic membrane.

Aged↗
PubMed1987

Two promoters, one inducible and one constitutive, control transcription of the Streptomyces lividans galactose operon.

Galactose utilization in Streptomyces lividans was shown to be controlled by an operon that is induced in the presence of galactose and repressed by glucose. Two promoters, galP1 and galP2, which direct transcription of two distinct polycistronic transcripts, have been identified. galP1 is located immediately upstream of the operon and is induced in the presence of galactose. This promoter directs transcription of the galT, galE, and galK genes. The second promoter, galP2, is located within the operon just upstream of the galE gene. This promoter is responsible for constitutive transcription of the galE and galK genes. Comparison of the S. lividans gal operon to the Escherichia coli gal operon indicates the presence of a constitutive promoter positioned upstream of galE in both operons. We suggest that coupling the operon's constitutive promoter to the galE gene fulfills a physiological requirement for constitutive UDPgalactose 4-epimerase expression in Streptomyces.

Base Sequence↗
PubMed1987

A simple inexpensive technique for placing drainage catheters through the skin.

A simple, inexpensive technique for placement of the T tube or Jackson-Pratt closed suction drainage catheter through the skin is described herein. This is an ideal procedure to use when treating a patient who has underlying ascites and is at a higher risk of having a leak develop through the standard procedures of placing drains.

Catheterization↗
PubMed1985

Analysis of in vivo RNA transcription products of the ilvGEDA attenuator region of Escherichia coli K12.

The precise points of in vivo transcription initiation and termination in the leader region of the ilvGEDA operon of Escherichia coli K12 have been determined. Leader RNA transcription products from either side of the attenuator have been identified and quantitated by T1 fingerprint analyses under growth conditions which affect operon expression. The results provide in vivo confirmation of the ilvGEDA attenuation model. Previous DNA sequence and in vitro transcription analyses have demonstrated that this operon is preceded by two strong in vitro promotors. The studies reported here show that transcription is initiated in vivo only from the downstream promotor and that no detectable in vivo expression from the upstream promotor is observed under conditions which affect operon regulation.

DNA Restriction Enzymes↗
PubMed1985

Inflammatory vasculitis in multiple sclerosis.

Fifty-two plaque or lesion areas were examined from 25 cases of multiple sclerosis. Twenty-four of these showed acute features, whereas the rest were more chronic in nature. The acute lesions showed lymphocytic infiltration (79%), fibrinous exudation (63%), lymphocytic meningitis (50%) and venulitis (58%). Of the chronic lesions, there were only 21% with lymphocytic infiltration, 11% with fibrinous exudates, none with meningitis, 29% with organising endovenulitis, 36% with fibrosed vein walls. The finding of a fibrinous inflammatory exudate in the acute lesion is a new observation in multiple sclerosis. Likewise, the observation of an inflammatory infiltrate confined to the vein wall (and often present at a distance from the plaque) has not been previously recorded in the disease. The chronic lesion, by contrast, showed relatively little fibrin, but there was considerable reparative thickening of the walls of the involved veins. The evidence provides new humoral and cellular evidence of an inflammatory process in multiple sclerosis which precedes or is not directly associated with the demyelinating process.

Brain↗
PubMed1985

Differential expression of photosynthesis genes in R. capsulata results from segmental differences in stability within the polycistronic rxcA transcript.

We report that the light-harvesting and reaction center genes in the rxcA locus of R. capsulata are contained within a single operon and that their differential expression results predominantly from marked segmental differences in stability within the polycistronic rxcA transcript. The 3' portion of this transcript is rapidly degraded to give rise to either of two slowly decaying mRNA remnants, both of which encode only the light-harvesting polypeptides. The greater stability of these remnants accounts for nearly all of the difference between the concentrations of the light-harvesting and reaction center proteins. The unstable 3' portion of the transcript is delimited by two alternative stem-and-loop structures, which apparently act as barriers to 3' exoribonucleases and thereby protect the upstream RNA segment. When a DNA fragment containing the rxcA locus was fused to a plasmid promoter and transcribed in E. coli, the long precursor transcript was processed to two short messages of greater stability, as in R. capsulata.

Bacterial Proteins↗
PubMed1985

Lymph-vessel embolism in a case of Whipple's disease.

A case of Whipple's disease is described where the lymphatics in the regional lymph nodes appear to be obstructed by embolized macrophages, containing the characteristic PAS positive bacillary material. It is suggested that the regional lymphangiectasia in Whipple's disease may in part result from such cellular embolism.

Biopsy↗
PubMed1984

Effects of promoter strengths and growth conditions on copy number of transcription-fusion vectors.

Promoters with widely different transcriptional activities have been fused to the galactokinase gene contained in a multicopy plasmid ( McKenny , K., Shimatake , H., Court, D., Schmeissner , U., Brady, C., and Rosenberg, M. (1982) in Gene Amplification and Analysis: Analysis of Nucleic Acids ( Chirkjian , J. G., and Papas , T., eds) pp. 383-415, Elsevier /North-Holland Biomedical Press, Netherlands). Assay methods which allow determination of galactokinase-specific activity (nanomoles of galactose 1-phosphate/min/mg of protein) and plasmid-specific number (femtomoles of plasmid/mg of protein) in the same sonicated cellular extract are described. These methods provide a way to accurately measure and compare the promoter activities (nanomoles of galactose 1-phosphate/min/fmol of plasmid) of different plasmid constructions which exhibit different in vivo plasmid copy numbers. It is demonstrated that in vivo, copy number fluctuations are correlated with such parameters as promoter strength and cellular growth conditions. The ability to account for these uncontrolled in vivo copy number variations when comparing the transcriptional activities of different DNA inserts in multicopy transcription-fusion plasmids greatly facilitates the utility of these systems.

Base Sequence↗
PubMed1984

Pathological principles involved in regression of atherosclerosis.

The view is advanced that regression of atherosclerosis depends on normal pathological principles, namely the process of organization. On account of the hypoxic milieu of the arterial wall and lack of capillary ingrowths into it, the hypoxia-resistant arterial smooth muscle cell subserves the functions of both phagocyte and fibroblast in organization. The proliferation of smooth muscle in atherosclerosis is, thus, attributed to a variant of a basic pathological mechanism, and does not require more a complex explanation, such as the action of a somatotropin, mitogen or mutagen. Moderate dilatation of the arterial wall, caused by the basic pathological mechanisms of either atrophy or hypertrophy would, within definite limits, offset inward encroachment by atherosclerosis and, thus, could constitute another type of regression, or at least a failure of lumen calibre to get worse.

Adult↗
PubMed1984

Myocardial and renal arteriolar thickening in cigarette smokers.

Arteriolar wall thickness was measured in cigarette smokers by means of eyepiece micrometry, paper planimetry and computerized planimetry. Myocardial and renal arterioles in such smokers showed significant thickening of their walls. This thickening was mainly attributable to an increase in collagen and smooth muscle. The adventitia of small to medium-sized intramyocardial coronary arteries showed an increase in collagen. Platelets are known to be more adhesive to the vessel wall in smokers. It is suggested that platelet-derived growth factor, released in the vessel wall, may promote proliferation of connective tissues, thus leading to the vascular thickening described.

Arterial Occlusive Diseases↗
PubMed1982

Lipoprotein levels and tissue lipids in fatty-fibrous atherosclerosis induced in rabbits by two years' cholesterol feeding at a low level.

A group of 12 young NZW rabbits of the same breeding strain were fed a diet enriched with 0.1% cholesterol by weight. The resulting modest hypercholesterolaemia resolved after 4-5 months. Two animals that died during this period showed no gross or microscopic atherosclerosis. After 6 months, the dietary cholesterol was increased to 0.2%. In some animals this resulted in moderate hypercholesterolaemia. One animal that died at this time showed no atherosclerosis with a mean serum cholesterol level of 224 mg/dl. Just after one year, dietary cholesterol was increased to 0.3%. This resulted in definite hypercholesterolaemia in some animals, but a few resisted the treatment with mean serum cholesterol levels around 40-60 mg/dl. In general, animals with established hypercholesterolaemia showed severe atherosclerosis, but often of a more fibrous and less cellular nature than is usual in the rabbit. Aortic wall cholesterol content (on a weight basis) correlated positively with serum cholesterol concentration (r = + 0.69, P approximately 0.05) and negatively with the ratio of HDL cholesterol to (LDL plus VLDL) cholesterol (double log plot: r = -0.79, P less than 0.025).

Animals↗
PubMed1982

Connective tissue responses to oxysterols.

We studied the effect of sterols and oxidized sterols on promoting tissue inflammation and necrosis, and on causing cell death in tissue culture. The cells studied were mouse fibroblasts and macrophages, and pig vascular smooth muscle. The lipid preparations were dibromide-purified cholesterol, air-oxidized cholesterol, 25-hydroxycholesterol, cholesterol-5alpha, 6 beta-epoxide and cholestane 3 beta, 5 alpha, 6 beta-triol. Of these, the triol was most active in its cytopathic effect on cells in culture, in size of granuloma formation and in producing necrosis. The epoxide, 25-hydroxycholesterol and air-oxidized cholesterol produced rather less effect on tissues and cultures than the triol, but more than purified cholesterol and the control. The results are considered in relation to the presence of oxysterols in stored foodstuffs and their possible presence over the surface of cholesterol crystals in the tissues.

Animals↗