Search PubMed⌕ Search

Biomedical subjects

C W Adams

Publications and source records attributed to C W Adams.

At least 19 recordsLinked to original sources
PubMed1992

DNA topology-mediated regulation of transcription initiation from the tandem promoters of the ilvGMEDA operon of Escherichia coli.

It is becoming increasingly clear that the intrinsic and protein-induced topological properties of the DNA helix influence transcriptional efficiency. In this report we describe the properties of two upstream activating regions that influence transcription from the non-overlapping tandem promoters of the ilvGMEDA operon of Escherichia coli. One 20 base-pair region between the promoter sites contains an intrinsic DNA bend that activates transcription from the downstream promoter. The other region contains an integration host factor (IHF) binding site that overlaps the upstream promoter site. IHF binding at this site represses transcription from the upstream promoter and enhances transcription from the downstream promoter. IHF also induces a severe bend in the DNA at its target binding site in the upstream promoter region. The activating property of the 20 base-pair DNA sequence located between the promoters is dependent upon the helical phasing of the sequence-directed DNA bend that it encodes. However, the IHF-mediated activation of transcription is not dependent upon the helical phasing (spatial orientation) of the upstream IHF and downstream promoter sites. The IHF-mediated activation of transcription is also uninfluenced by the presence or absence of the intrinsic DNA bend between its binding site and the downstream promoter site. These results suggest the interesting possibility that IHF activates transcription from the nearby downstream promoter simply by bending the DNA helix in the absence of specific IHF-RNA polymerase or upstream DNA-RNA polymerase interactions.

Bacterial Proteins↗
PubMed1991

Carcinosarcoma of the lung with hypertrophic pulmonary osteoarthropathy.

Carcinosarcoma of the lung is a rare malignancy. Endobronchial and parenchymal variants are classically described. Clinicopathological features are often related to anatomical location, as is the case for most lung neoplasms. This case report details the surgical management of a carcinosarcoma in a patient seen with pulmonary osteoarthropathy.

Carcinosarcoma↗
PubMed1991

Steady-state and dynamic response properties of the Mandelbaum effect.

The Mandelbaum effect refers to an inadvertent accommodation response to an intervening surface (e.g. a window screen) while attempting to focus a distant object of interest. Previous research has attributed the Mandelbaum effect to a tendency for the accommodation mechanism to preferentially focus the stimulus nearest the dark (resting) focus position. The present study extends this work by examining dynamic accommodation response properties for different distances and stimulus separations. Accommodation measurements of nine young, emmetropic subjects were obtained with an infrared optometer while they viewed superimposed horizontal and vertical square-wave gratings at various dioptric separations. Three subjects demonstrated a strong focussing preference for the target located nearest their dark focus position for all stimulus conditions, while two other subjects showed a similar, but weaker, preference. Conversely, two subjects primarily focussed the nearer of the two targets, and two subjects tended to focus the vertical target (regardless of whether it was near or far, or was closet to the dark focus). For all subjects, accommodation rarely fluctuated from one target to the other, and was seldom focussed midway between the two targets. Our findings indicate that the influence of the dark focus on the Mandelbaum effect varies among individuals, and plays little or no role in some individuals. Thus, accommodation responses to competing stimuli are more complex than previous findings would suggest.

Accommodation, Ocular↗
PubMed1990

Macrophage histology in paraffin-embedded multiple sclerosis plaques is demonstrated by the monoclonal pan-macrophage marker HAM-56: correlation with chronicity of the lesion.

Using the monoclonal antibody HAM-56 with the avidin-biotin method on recent or archival paraffin-embedded tissue from multiple sclerosis brains, we have been able to distinguish between acute, chronic active and inactive lesions. HAM-56 stains all macrophages, monocytes and at least some microglia; it is the only pan-macrophage marker to our knowledge that can be satisfactorily used on conventional paraffin sections. A much narrower range of mainly perivascular macrophages in acute plaques of multiple sclerosis is stained with MAC-387, anti-muramidase and anti-alpha1-anti-trypsin. The acute plaques show HAM-56-stained macrophages throughout the lesion, and these macrophages exhibit profiles of phospholipid-rich myelinic bodies, which are also usually stainable with Luxol fast blue. Active ongoing lesions show a rim of macrophages at the edge of the lesion. These macrophages show profiles of large vacuoles, thought to represent the sudanophilic esterified cholesterol formed during demyelination. Inactive cases show none of these features; the few perivascular macrophages present often contain the end product of lipid peroxidation, ceroidlipofuscin.

Antibodies, Monoclonal↗
PubMed1990

Isolation and characterization of Rhodobacter capsulatus mutants defective in oxygen regulation of the puf operon.

cis-acting mutations that affect regulation of the Rhodobacter capsulatus puf operon by oxygen were isolated by placing the mutagenized puf regulatory region 5' to a promoterless Tn5 neo gene, which encodes resistance to kanamycin (Kmr). R. capsulatus mutants that failed to show wild-type repression of KMr by oxygen were selected and analyzed. Four independent clones contained point mutations, three of which were identical, in a region of dyad symmetry located between puf operon nucleotide positions 177 and 207, approximately 45 base pairs 5' to the site of initiation of puf transcripts. The phenotypic effects of the aerobically selected mutations were duplicated by single and double point mutations introduced site specifically into the region of dyad symmetry by oligonucleotide-directed mutagenesis. Determinations of the bacterial 50% lethal dose of kanamycin, of aminoglycoside phosphotransferase activity in cell sonicates, and of neo-specific mRNA confirmed the diminished responsiveness of the mutants to oxygen and consequently implicated the mutated region in O2-mediated transcriptional regulation.

Base Sequence↗
PubMed1989

Pathology, histochemistry and immunocytochemistry of lesions in acute multiple sclerosis.

Twenty cases of acute or early multiple sclerosis have been examined using staining, histochemical or immunocytochemical methods. They had died within 6 months after initial clinical onset (12) or commencement of an "anatomically-remote" acute relapse (8). Plaques in these acute cases showed the following characteristics: lymphocytic perivascular infiltration, plaque hypercellularity, plaque macrophage infiltration and intra-macrophage myelin debris. In most cases of clinical duration of less than 12 weeks, some macrophages showed characteristic formaldehyde-resistant markers for haematogenous macrophages (muramidase, anti-alpha 11-antitrypsin, MAC and HAM56) but, with the exception of the last, these markers subsequently declined indicating a haematogenous origin for macrophages in the early lesion. Lymphocytes were prominent in perivascular (perivenous) regions but, except in one case, were only scanty in or at the demyelinating edge of plaques. Oligodendroglial hyperplasia, indicative of remyelinating activity, was seen at the edge of plaques in one quarter of these acute cases (7 times the rate seen in chronic lesions). Astrocytic activation was not apparent in the earliest stages but was usually seen from about 6 weeks onwards. The conclusion from these observations is that the prime inflammatory process is around blood vessels with usually only scanty initial inflammatory activity in the parenchyma of the brain. Macrophages emigrating from blood vessels digest myelin either as a response to inflammatory damage to the myelin or as a response to activation signals produced in either the perivascular region or plaque.

Adolescent↗
PubMed1989

Structural and functional analysis of transcriptional control of the Rhodobacter capsulatus puf operon.

We report data indicating that the Rhodobacter capsulatus puf operon promoter and the site for its oxygen regulation are located more than 700 base pairs upstream from the previously identified puf genes and have identified the nucleotide sequences that constitute these control signals. A model is proposed in which a polycistronic transcript at least 3.4 kilobases in length is initiated near the O2-regulated promoter and is processed posttranscriptionally by endonucleolytic cleavage at multiple sites, yielding discrete mRNA segments that are degraded at different rates. A newly identified gene (pufQ), which includes a hydrophobic domain having some similarity to domains of the products of the pufL and pufM genes, begins 313 nucleotides into the puf transcript and is located entirely within the most rapidly degraded segment of the transcript. A previously identified puf transcript segment encoding structural proteins for photosynthetic membrane complexes persists after degradation of the most 5' region of the transcript and is itself subject to segmentally specific degradation. Our results suggest a model in which differential expression of the multiple genes encoded by the puf operon is at least in part attributable to major differences in the rates of decay of the various segments of puf mRNA.

Amino Acid Sequence↗
PubMed1989

The cerebral vasculature in dementia pugilistica.

The brains of 22 ex-boxers were examined histologically to determine the frequency of recent or old haemorrhage. Four boxers had died from an acute intracerebral bleed, usually soon after a boxing bout. Seven of the other 18 showed evidence of previous perivascular haemorrhage, as detected by Perls' ferrocyanide test for iron, and a similar number showed minor degrees of meningeal or subpial siderosis, consistent with previous meningeal bleeding; cerebellar siderosis was present in six cases. Seventeen of the 22 boxers showed evidence of recent or past haemorrhage. Control material showed an incidence of 11% for perivascular iron deposition and only 4% for minor degrees of meningeal siderosis.

Aged↗
PubMed1988

Coronary arterial dimensions and cell populations in ageing man.

A combined computerised morphometric and immunocytochemical study on the ageing human coronary arterial wall shows that dilatation of the vessel is related to age but is less related to the degree of atherosclerosis. Loss of medial smooth muscle is not related to either atherosclerosis or dilatation of the artery. Occasional cases with severe medial and adventitial infiltrates of inflammatory cells (mainly T-cells and macrophages) do develop marked ectasia, but this arteritis is rather rare and, thus, an infrequent cause of dilatation.

Aged↗
PubMed1988

The use of colostomy bags for chest tube drainage.

Occasionally patients require long-term chest tube drainage. We describe a method whereby a short chest tube may be drained into a colostomy bag to alleviate the necessity of keeping the patient attached to a bulky drainage system. The colostomy bag allows greater mobility, and the patient can be discharged with the bag.

Colostomy↗
PubMed1988

Gene organization and structure of the Streptomyces lividans gal operon.

We present the gene organization and DNA sequence of the Streptomyces lividans galactose utilization genes. Complementation of Escherichia coli galE, galT, or galK mutants and DNA sequence analysis were used to demonstrate that the galactose utilization genes are organized within an operon with the gene order galT, galE, and galK. Comparison of the inferred protein sequences for the S. lividans gal gene products to the corresponding E. coli and Saccharomyces carlbergensis sequences identified regions of structural homology within each of the galactose utilization enzymes. Finally, we discuss a potential relationship between the gene organization of the operon and the functional roles of the gal enzymes in cellular metabolism.

Amino Acid Sequence↗
PubMed1988

Perivascular iron deposition and other vascular damage in multiple sclerosis.

Evidence of damage to cerebral vein walls was sought in 70 cases of multiple sclerosis. Seventy control cases were also examined. The multiple sclerosis cases showed venous intramural fibrinoid deposition (7%), recent haemorrhages (17%), old haemorrhages revealed by haemosiderin deposition (30%), thrombosis (6%) and thickened veins (19%). In all, 41% of all multiple sclerosis cases showed some evidence of vein damage. Occasional control cases showed haemosiderin deposition in the brain but, unlike the multiple sclerosis cases, these were diffuse and almost entirely related to coexistent cardiovascular or cerebrovascular disease. Haemosiderin deposition was common in the substantia nigra and other pigmented nuclei in all cases. It is concluded that the cerebral vein wall in multiple sclerosis is subject to chronic inflammatory damage, which promotes haemorrhage and increased permeability, and constitutes a form of vasculitis.

Cerebral Hemorrhage↗
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↗