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Biomedical subjects

M S Johnson

Publications and source records attributed to M S Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1998

Characterization and chromosomal localization of rat scavenger receptor class B type I, a high density lipoprotein receptor with a putative leucine zipper domain and peroxisomal targeting sequence.

High density lipoprotein (HDL) participates in reverse cholesterol transport and in the delivery of cholesterol to steroid-producing tissues. Scavenger receptor class B type I (SR-BI) was recently shown to bind HDL and mediate internalization of its cholesterol content. We have cloned the rat homolog of this receptor, determined its chromosomal location, and examined its expression in rat tissues and in a model of follicular development, ovulation, and luteinization. The predicted protein contained two transmembrane domains, a leucine zipper motif, and a peroxisomal targeting sequence. The rat and human SR-BI genes were mapped to a region previously linked between rat and human chromosomes 12. SR-BI gene expression was detected in several rat tissues, with high levels in ovarian tissue, liver, and adrenal cortex, as determined by ribonuclease protection assay and in situ hybridization. A significant increase in SR-BI gene expression was detected in the late phase of corpus luteum formation, and transcripts were abundant in corpus luteum and in thecal cells at all stages of follicular development. In conclusion, the rat SR-BI complementary DNA predicted a protein with several conserved motifs, including a putative leucine zipper and a peroxisomal targeting sequence. The chromosomal locations of the rat and human SR-BI homologs suggest that this gene is a new member of a previously reported, conserved synteny group. SR-BI gene expression was high in steroid-producing tissues and in the liver, consistent with a role of this receptor in the uptake of HDL cholesterol.

Amino Acid Sequence↗
PubMed1998

Maximum intensity projection images in the detection of simulated pulmonary nodules by spiral CT.

This study was undertaken to investigate the use of maximum intensity projection (MIP) images in the detection of pulmonary nodules by spiral CT (SCT). 40 pulmonary nodules of high density were created by endobronchial deployment of 2 and 4 mm beads in the peripheral airways of five anesthetized dogs. Standard SCT was performed with 5 mm collimation, pitch 2 and reconstruction of contiguous slices. MIP images were generated from overlapped slabs of seven consecutive 3 mm slices, reconstructed at 2 mm intervals and acquired at pitch 2. Scans were reviewed by six radiologists. The data were modelled using ordinal logistic regression for repeated measures, and the Wald chi 2 statistic used to test if there was a difference in nodule detection and reader confidence level between the two techniques. MIP imaging increased the odds of nodule detection by 2.18 (p = 0.0002). Reader confidence level for nodule detection was significantly higher with MIP images (p < 0.00001). MIP images improve the detection rate for small high density pulmonary nodules and increase reader confidence level, when compared with standard SCT.

Animals↗
PubMed1998

Carbon dioxide angiography of the transplanted kidney: technical considerations and imaging findings.

OBJECTIVE: We evaluated the usefulness of carbon dioxide as the primary contrast material for renal transplant arteriography. CONCLUSION: Carbon dioxide accurately showed artery pathology including anastomotic and intrarenal stenoses, arteriovenous shunting, and diffuse arterial disease from chronic transplant rejection. Using carbon dioxide as a contrast agent reduced the volume of iodinated contrast material that needed to be used. There was no procedure-associated nephrotoxicity.

Adult↗
PubMed1997

The Aer protein and the serine chemoreceptor Tsr independently sense intracellular energy levels and transduce oxygen, redox, and energy signals for Escherichia coli behavior.

We identified a protein, Aer, as a signal transducer that senses intracellular energy levels rather than the external environment and that transduces signals for aerotaxis (taxis to oxygen) and other energy-dependent behavioral responses in Escherichia coli. Domains in Aer are similar to the signaling domain in chemotaxis receptors and the putative oxygen-sensing domain of some transcriptional activators. A putative FAD-binding site in the N-terminal domain of Aer shares a consensus sequence with the NifL, Bat, and Wc-1 signal-transducing proteins that regulate gene expression in response to redox changes, oxygen, and blue light, respectively. A double mutant deficient in aer and tsr, which codes for the serine chemoreceptor, was negative for aerotaxis, redox taxis, and glycerol taxis, each of which requires the proton motive force and/or electron transport system for signaling. We propose that Aer and Tsr sense the proton motive force or cellular redox state and thereby integrate diverse signals that guide E. coli to environments where maximal energy is available for growth.

Amino Acid Sequence↗
PubMed1997

The three-dimensional structure at 2.4 A resolution of glycosylated proteinase A from the lysosome-like vacuole of Saccharomyces cerevisiae.

The crystal structures of glycosylated native proteinase A, an aspartic proteinase found in the vacuole of Saccharomyces cerevisiae, and its complex with a difluorostatone-containing tripeptide have been determined by molecular replacement to 3.5 A and 2.4 A resolutions, respectively. Superposition of the bound and native forms gave an r.m.s. difference of 0.6 A largely reflecting the poor resolution of the native crystal structure. The secondary and tertiary structures are highly similar to those found in porcine pepsin and lysosomal cathepsin D; superposition of the structure of proteinase A bound to the difluorostatone inhibitor on those of pepsin and cathepsin D gave pairwise r.m.s. differences for C(alpha) atoms of 1.36 A and 0.88 A. Most differences occur in loop regions. Comparison of the structure of the proteinase A-difluorostatone complex with that of endothiapepsin bound with the same inhibitor shows that the conformation and hydrogen bond interactions of the inhibitor in the active site are very similar, even though the enzymes have only 27% sequence identity. Electron density for the crystal structure of the proteinase A complex reveals five residues of the oligosaccharide structure attached to Asn67: Man-(1 --> 2)-alpha-Man-(1 --> 3)-beta-Man-(1 --> 4)-beta-GlcNAc-(1 --> 4)-beta-GlcNAc-Asn-67. The first three residues of the oligosaccharide cover the same region of the protein surface as those of the oligosaccharide attached to the equivalent position in cathepsin D. The second carbohydrate attachment site is disordered beyond the first carbohydrate residue in both enzymes.

Aspartic Acid Endopeptidases↗
PubMed1997

Acute oral toxicity study of pyridostigmine bromide, permethrin, and DEET in the laboratory rat.

This study investigated the lethal interaction of pyridostigmine bromide (PB), permethrin, and DEET when given to adult male rats by gavage and was separated into two phases. Phase I determined the acute oral lethal dose-response relationship of each compound with the vehicle, propylene glycol. Phase II was divided into two portions: a dose-response study using probit units obtained from phase I [lethal dose (LD) 16, 30, 50, 70, and 84], and an interaction study that contained low levels (calculated LD16, additive LD32) of the two compounds while the concentration of the third compound was varied. Rats were fasted overnight, dosed, and observed for 14 d. A significant increase in lethality occurred when PB, permethrin, and DEET were given concurrently when compared to expected additive values. Furthermore, solutions containing PB and permethrin or PB and DEET also caused a significant increase in lethality when compared to expected additive values. This information suggests that lethality in this study was more than an additive effect.

Animals↗
PubMed1997

Fluoride-induced lesions in the teeth of the short-tailed field vole (Microtus agrestis): a description of the dental pathology.

The effect of fluoride on the appearance of the teeth of the short-tailed field vole, Microtus agrestis, was investigated in both wild animals collected from field sites affected by different levels of industrial fluoride contamination and laboratory-reared animals consuming experimental grass diets of known fluoride concentration or with known fluoride concentrations in drinking water. The extent and severity of lesions on the surface and structure of both incisors and molars are described as six lesion types and related to the amount of biologically available orally ingested fluoride. In the incisors of voles consuming relatively low fluoride diets, lesions are mainly confined to those resulting from disruption of enamel pigmentation expressing itself as concentric bands of pigmentation-free areas on incisor surfaces. The visible effects on molars at low fluoride levels are confined to minor alterations in surface appearance. At higher levels of available dietary fluoride, effects on enamel pigmentation are superseded by alterations in the formation, composition, and strength of both enamel and dentine. The incisors exhibit a marked to severe increase in the cutting tip erosion rates with comparable increases in the extent of abnormal surface changes (enamel hypoplasia) and the loss of enamel pigmentation. The grinding surfaces of molars from animals exposed to high levels of dietary fluoride exhibit increasingly severe erosion of outer enamel regions, combined with cavitation and staining of the exposed central dentine. The mechanisms through which fluoride elicits increasingly visible and pathological alterations to the surface and subsurfaces of rodent teeth are discussed.

Animals↗
PubMed1997

Isolation and characterization of five actin cDNAs from the cestode Diphyllobothrium dendriticum: a phylogenetic study of the multigene family.

Five cDNAs (pDidact2-pDidact6), representing different actin genes, were isolated from a Diphyllobothrium dendriticum cDNA library, and the DNA as well as the putative amino acid sequences were determined. The corresponding Didact2 and Didact4 genes code for peptides 376 amino acids long, with molecular weights 41,772 and 41,744 Da, respectively, while the deduced Didact3 protein is 377 amino acids long and weighs 41,912 Da. The pDidact5 and -6 cDNAs lack nucleotides corresponding to three to six amino acids at the amino-terminus. Two of the five cDNAs contain the conventional AATAAA as the putative polyadenylation signal, one has the common variant ATTAAA, whereas the hexanucleotide AATAGA is found 15 and 18 nucleotides, respectively, upstream of the poly(A) site in two of the cDNAs. Phylogenetic studies including 102 actin protein sequences revealed that there are at least four different types of cestode actins. In this study three of these types were found to be expressed in the adult D. dendriticum tapeworm. Structurally the cestode actin groupings differ from each other to an extent seen only among the metazoan actins between the vertebrate muscle and cytoplasmic isoforms. In the phylogenetic trees constructed, cestode actins were seen to map to two different regions, one on the border of the metazoan actins and the other within this group. It is, however, difficult to say whether the cestode actins branched off early in the metazoan evolution or if this position in the phylogenetic tree only reflects upon differences in evolutionary rate.

Actins↗
PubMed1997

Successful treatment of an iatrogenic infrarenal aortic dissection with serial Wallstents.

We report a patient who presented with acute lower extremity ischemia 13 days following removal of an intraaortic balloon pump. Dissection of the infrarenal aorta, extending into the left iliac artery, was found at operation. The patient's recent myocardial infarction, prolonged ischemia with compartment syndrome, otherwise normal aortoiliac and infrainguinal arteries and the necessity for suprarenal aortic clamping for surgical repair, were all factors in the decision for endovascular repair of the dissection. Infrarenal aortic and left iliac Wallstents, placed intraoperatively, successfully occluded the false lumen of the dissection. The patient was discharged after an uncomplicated recovery and is asymptomatic with palpable pedal pulses and triphasic pedal Doppler waveforms 1 year following the procedure.

Aortic Dissection↗
PubMed1997

Magneto-aerotaxis in marine coccoid bacteria.

Magnetotactic cocci swim persistently along local magnetic field lines in a preferred direction that corresponds to downward migration along geomagnetic field lines. Recently, high cell concentrations of magnetotactic cocci have been found in the water columns of chemically stratified, marine and brackish habitats, and not always in the sediments, as would be expected for persistent, downward-migrating bacteria. Here we report that cells of a pure culture of a marine magnetotactic coccus, designated strain MC-1, formed microaerophilic bands in capillary tubes and used aerotaxis to migrate to a preferred oxygen concentration in an oxygen gradient. Cells were able to swim in either direction along the local magnetic field and used magnetotaxis in conjunction with aerotaxis, i.e., magnetically assisted aerotaxis, or magneto-aerotaxis, to more efficiently migrate to and maintain position at their preferred oxygen concentration. Cells of strain MC-1 had a novel, aerotactic sensory mechanism that appeared to function as a two-way switch, rather than the temporal sensory mechanism used by other bacteria, including Magnetospirillum megnetotacticum, in aerotaxis. The cells also exhibited a response to short-wavelength light (< or = 500 nm), which caused them to swim persistently parallel to the magnetic field during illumination.

Cell Movement↗
PubMed1997

Methylated hexachlorocyclohexane in blue mussels (Mytilus edulis) from the Mersey and Dee Estuaries.

Blue mussels (Mytilus edulis) from the Mersey and Dee Estuaries have been found to contain high concentrations of alpha-MHCH (methyl hexachlorocyclohexane) and gamma-MHCH (methyl lindane), and a series of other methylated isomers of MHCH. Mean values for SigmaMHCH in mussels declined serially from Rock Ferry (81.4 +/- 19.3 microg kg(-1)), the innermost site in the Mersey Estuary, to Egremont (49.0 +/- 8.6 microg kg(-1)) and New Brighton (11.1 +/- 3.8 microg kg(-1)); but the value for Crosby (67.0 +/- 10.2 microg kg(-1)) on the Liverpool shoreline was surprisingly high. Concentrations of alpha-HCH and gamma-HCH in M. edulis were consistently low, at <3.0 microg kg(-1). Comparisons between MHCH data for M. edulis and muscle tissue of both dab (Limanda limanda) and plaice (Pleuronectes platessa) give some evidence of food chain biomagnification of MHCH compounds, with adult plaice caught within the Mersey Estuary, where they feed on shellfish, showing very high levels of gamma-MHCH (18 +/- 9 microg kg(-1)) and MHCH (169 +/- 76 microg kg(-1)). Methylated analogues of HCH in biota are of potential regulatory interest and of substantial importance to the environmental management of the Mersey and Dee Estuaries.

Journal Article↗
PubMed1997

How do bacteria avoid high oxygen concentrations?

Bacteria, such as Escherichia coli and Azospirillum brasilense, avoid microenvironments with elevated oxygen concentrations, not by sensing reactive oxygen derivatives, but by sensing a metabolic down-shift that results from elevated oxygen levels. A novel protein, Aer, and the chemotaxis serine receptor, Tsr, have recently been identified as transducers for aerotaxis which monitor internal energy levels in the bacteria.

Bacterial Physiological Phenomena↗
PubMed1997

Alaska's statewide trauma registry: a useful surveillance tool for injury prevention planning and evaluation.

The state of Alaska is unique because it is one of a small number of states with a surveillance system that collects trauma information from every hospital in the state. The Alaska Trauma Registry (ATR) collects up to 144 data elements for every injured patient. Information from the ATR is useful as an injury surveillance tool for federal, state, and local governments and other agencies and organizations when planning and evaluating injury prevention programs. Combining trauma registry data with Bureau of Vital Statistics cause of death data provides complete, statewide, population-based data on all injuries serious enough to result in death or hospitalization.

Adolescent↗
PubMed1997

Glycerol elicits energy taxis of Escherichia coli and Salmonella typhimurium.

Escherichia coli and Salmonella typhimurium show positive chemotaxis to glycerol, a chemical previously reported to be a repellent for E. coli. The threshold of the attractant response in both species was 10(-6) M glycerol. Glycerol chemotaxis was energy dependent and coincident with an increase in membrane potential. Metabolism of glycerol was required for chemotaxis, and when lactate was present to maintain energy production in the absence of glycerol, the increases in membrane potential and chemotactic response upon addition of glycerol were abolished. Methylation of a chemotaxis receptor was not required for positive glycerol chemotaxis in E. coli or S. typhimurium but is involved in the negative chemotaxis of E. coli to high concentrations of glycerol. We propose that positive chemotaxis to glycerol in E. coli and S. typhimurium is an example of energy taxis mediated via a signal transduction pathway that responds to changes in the cellular energy level.

Bacterial Proteins↗
PubMed1997

Oxygen-dependent growth of the obligate anaerobe Desulfovibrio vulgaris Hildenborough.

Desulfovibrio vulgaris Hildenborough, a sulfate-reducing bacterium classified as an obligate anaerobe, swam to a preferred oxygen concentration of 0.02 to 0.04% (0.24 to 0.48 microM), a level which also supported growth. Oxygen concentrations of 0.08% and higher arrested growth. We propose that in zones of transition from an oxic to an anoxic environment, D. vulgaris protects anoxic microenvironments from intrusion of oxygen.

Aerobiosis↗
PubMed1997

Outcome of tunneled hemodialysis catheters placed via the right internal jugular vein by interventional radiologists.

PURPOSE: To assess the outcome of interventional radiologic placement of tunneled hemodialysis catheters via the right internal jugular vein. MATERIALS AND METHODS: In 194 patients, the catheter was placed via the right internal jugular vein unless thrombosis was present. Real-time ultrasound-guided puncture and fluoroscopic guidance were used. Patients were followed up until catheter removal or death. Outcomes evaluated included infection, thrombosis, and catheter malfunction. RESULTS: In 175 patients, 250 consecutive catheters were placed via the right internal jugular vein with 100% success. All catheters functioned immediately after placement. Procedural complications were limited to clinically unimportant air embolus (n = 2). No instances of pneumothorax, hemothorax, or substantial bleeding complications occurred. Follow-up was available in 173 (99%) patients. Mean and median "catheter duration" were 87 and 56 days, respectively. Catheter-related symptomatic venous thrombosis or stenosis was not observed. The rate of infection was 0.08 per 100 catheter days, and the rate of malfunction that necessitated removal was 0.22 per 100 catheter days. Definite or possible catheter thrombosis that necessitated removal occurred at a rate of 0.16 per 100 catheter days. CONCLUSION: Interventional radiologic placement of tunneled hemodialysis catheters via the right internal jugular vein showed equal or better long-term results than those reported for surgical placement. Interventional radiologic placement should be the method of choice.

Catheterization↗