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Biomedical subjects

D L Williams

Publications and source records attributed to D L Williams.

At least 145 records · Page 8Linked to original sources
PubMed1995

Relapse of Mycobacterium leprae infection with ocular manifestations.

A case of ocular leprosy as the manifestation of persistent or relapsed Mycobacterium leprae infection approximately 20 years following treatment is reported. The clinical and pathological features of this case are described, and the molecular methods needed to arrive at the definitive diagnosis are examined. If blindness is to be averted, clinicians must have a high index of suspicion for the diagnosis of ocular leprosy when anterior segment changes are noted during ophthalmologic examination of a patient from an area in which M. leprae is endemic. The indolent nature of ocular leprosy may require lifelong surveillance and therapy to insure sight preservation.

Adult↗
PubMed1995

Rapid identification of a point mutation of the Mycobacterium tuberculosis catalase-peroxidase (katG) gene associated with isoniazid resistance.

The complete catalase-peroxidase (katG) gene DNA sequence was determined for 15 strains of Mycobacterium tuberculosis with a wide range of susceptibility to isoniazid. Five of 9 strains with isoniazid MICs > or = 1.0 microgram/mL had one or more missense mutations and all 5 strains had a common G-->T transversion in codon 463, causing the replacement of arginine with leucine and the loss of an NciI or MspI restriction site. None of 6 strains with an isoniazid MIC < 1.0 microgram/mL had mutations affecting codon 463. Restriction analysis of 43 strains with isoniazid MICs > or = 1.0 microgram/mL showed that 19 (44.2%) had lost the NciI-MspI restriction site at the locus of codon 463 while only 1 of 32 strains with isoniazid MICs < or = 1.0 microgram/L had this restriction polymorphism. These results indicate that the mutation arginine-->leucine in codon 463 of the catalase-peroxidase gene occurs in a significant fraction (44.2%) of M. tuberculosis strains with isoniazid MICs > or = 1.0 microgram/mL.

Bacterial Proteins↗
PubMed1995

Partial characterization of chitinolytic enzymes from Streptomyces albidoflavus.

Streptomyces albidoflavus NRRL B-16746 secreted three types of chitinolytic enzymes: N-acetyl-glucosaminidase, chitobiosidase and endochitinase. Optimal activity for all three types of enzymes occurred at pH 4-6; however 55-74% of the chitobiosidase and endochitinase activity was detectable at pH 8-10. Chitobiosidase activity originated from two strongly acidic (pI < 3.0) proteins with molecular mass of 27 kDa and 34 kDa, while endochitinase activity originated from five major acidic proteins (pI 5.1, 5.3, 5.75, 5.8-5.9 and 6.4) with molecular mass of 59, 45, 38.5, 27 and 25.5 kDa. Purified chitobiosidases significantly reduced spore germination and germ tube elongation of Botrytis cinerea and Fusarium oxysporum. Chitinolytic enzymes with significant activity at pH 4-10 may be used, transgenically, to reduce the growth and/or development of a broad spectrum of insects and fungi that are major economic pests.

Acetylglucosaminidase↗
PubMed1995

Direct genotypic detection of Mycobacterium tuberculosis rifampin resistance in clinical specimens by using single-tube heminested PCR.

Recent analysis of the gene encoding the beta subunit of Mycobacterium tuberculosis RNA polymerase (rpoB) has demonstrated a small region that harbors the mutations most frequently associated with rifampin resistance. Earlier reports have described a high degree of sequence conservation of rpoB among mycobacteria other than M. tuberculosis and other GC-rich bacteria that can lead to false-positive amplification when applied directly to clinical specimens. We developed reagents for PCR amplification that are based on signature nucleotides discovered by comparative sequence analysis of the rpoB genes of organisms phylogenetically related to M. tuberculosis. The specificities of the reagents were challenged with 20 isolates of multiple-drug-resistant M. tuberculosis and more than 20 species of mycobacteria other than M. tuberculosis and other GC-rich organisms. A single-tube heminested PCR protocol was devised to obtain sensitivity equal to those of an IS6110-based PCR assay and culture in spiked sputum experiments. The assay correctly identified 21 of 24 (87.5%) culture-positive specimens, 13 of which were acid-fast smear-negative, in a panel of 51 clinical specimens. Three specimens that were false-positive initially were negative upon repeat testing when the assay was modified to eliminate the potential for aerosol carryover of the first-round amplification product during the open-tube addition of the second set of reaction reagents. This assay is the most sensitive and specific test to date for the direct detection of M. tuberculosis rpoB in clinical specimens. This rapid PCR-based assay can be used for the simultaneous identification of M. tuberculosis and its rifampin susceptibility genotype.

Amino Acid Sequence↗
PubMed1995

Ethanol fixation of sputum sediments for DNA-based detection of Mycobacterium tuberculosis.

The effect of ethanol fixation on PCR detection and viability of Mycobacterium tuberculosis in human sputum sediments was evaluated. M. tuberculosis seeded into sputum sediments was efficiently killed when treated for 1 h with 50, 70, or 95% ethanol. PCR amplification of a 123-bp fragment of the M. tuberculosis-specific IS6110 was not affected in ethanol-treated samples even when fixation was extended to 24 h. Ethanol fixation of sputum sediments did not affect the PCR detection of M. tuberculosis in clinical samples. PCR results from ethanol-treated clinical samples containing M. tuberculosis (smear positive and smear negative) or other respiratory pathogens correlated directly with the results by conventional detection methods for M. tuberculosis. Our results show that ethanol fixation of human sputum sediments containing M. tuberculosis significantly reduces the potential exposure of workers to viable M. tuberculosis without affecting DNA analysis by PCR. Also, ethanol fixation of sputum sediments provides a simple and inexpensive way to store and transport clinical specimens identified for DNA-based diagnostics without refrigeration.

Bacteriological Techniques↗
PubMed1995

Evolution of rifampin resistance in human immunodeficiency virus-associated tuberculosis.

Acquired rifampin resistance without preexisting isoniazid resistance is highly unusual in patients with tuberculosis. The purpose of this report is to describe and characterize that unusual pattern of acquired drug resistance in three patients with human immunodeficiency virus (HIV) infection. The patients originally had Mycobacterium tuberculosis strains that were susceptible to isoniazid and rifampin. During treatment in two patients and after completion of therapy in the remaining one, each patient developed active, rifampin-resistant, isoniazid-susceptible tuberculosis. One patient subsequently developed isoniazid resistance also. Studies on patients' M. tuberculosis isolates using IS6110 restriction fragment length polymorphism typing and rpoB gene sequencing indicated that rifampin resistance in each patient arose during therapy by an rpoB gene mutation in the original M. tuberculosis isolate. Detection of this unusual drug-resistance phenotype in three patients with HIV infection suggests that acquired rifampin resistance is somehow associated with co-infection due to HIV and tuberculosis.

AIDS-Related Opportunistic Infections↗
PubMed1995

Influence of roughage and grain processing in high-concentrate diets on the performance of long-fed Holstein steers.

The effects of roughage source and timing of inclusion in high-concentrate diets on feedlot performance were evaluated in each of 2 yr with 144 and 120 long-fed Holstein steers, respectively. Roughage, when included in the diet, was delivered in a built-in-roughage (BIR) pellet supplying 15 and 6% roughage (percentage of DM) or hay crop silage (HCS) supplying 7 and 10% roughage (percentage of DM) for the growing and finishing periods, respectively. The six dietary treatments (two pens each) investigated were continuous whole corn and pelleted supplement (no added roughage; WSC-PEL); BIR with cracked corn either in the growing (BIR-G) or finishing (BIR-F) period with whole corn being fed with pelleted supplement when BIR was not part of the diet; BIR and cracked corn fed continuously (BIR-CONT); and two HCS treatments in which the corn was fed either whole (HCS-WSC) or cracked (HCS-CSC) for the entire feeding period. Replicates were slaughtered 4 and 3 wk apart for yr 1 and 2, respectively. Pooled daily gains (yr 1 and 2) for the entire trial (1.39 to 1.45 kg/d) were not different (P > .05). Daily DM and concentrate intakes were lower (P < .001) and gain efficiency was higher (P < .001) for the WSC-PEL than for the other treatments. Carcass characteristics were similar among treatments except for an improved yield grade (P < .02) for the HCS treatments over the BIR treatments. The WSC-PEL treatment was the most profitable (+/steer) and the BIR-CONT diet was the least profitable. The HCS treatments were the most profitable of the roughage treatments. A newly proposed intake prediction equation for feedlot cattle performed similarly to the 1984 NRC equation with long-fed Holstein steer calves.

Animal Feed↗
PubMed1995

Cell surface "blanket" of apolipoprotein E on rat adrenocortical cells.

Apolipoprotein (apo) E is expressed at high levels by adrenocortical cells. In the present study, an affinity-purified antibody to rat apoE was used in combination with immunogold visualization at both the light and electron microscopic levels to determine the cellular and subcellular distribution of apoE within the rat adrenal cortex. At the light microscopic level, apoE was found primarily in z. fasciculata and z. reticularis with little or none detected in z. glomerulosa and medulla. Within the z. fasciculata and z. reticularis, apoE was present in the cytoplasm of all parenchymal cells. ApoE also was found on the cell surface both on the sinusoidal front and in regions well removed from the subendothelial space. Electron microscopic examination of the z. fasciculata showed that apoE on the sinusoidal front was on the parenchymal cell surface but not the endothelial cell. Cell surface apoE was prominent on microvilli as well as non-microvillar regions of plasma membrane in the subendothelial space. ApoE was also associated with the cell surface in intercellular spaces continuous with but well removed from the subendothelial space. These findings at the light and electron microscopic levels suggest that the z. fasciculata cell is encircled or covered with apoE on all faces of the cell. These results are consistent with the idea that this cell surface "blanket" of apoE participates in the uptake of lipoprotein cholesterol by either the endocytic or selective uptake pathways.

Adrenal Glands↗
PubMed1995

Pharmacology of L-754,142, a highly potent, orally active, nonpeptidyl endothelin antagonist.

L-754,142, (-)-N-(4-iso-propylbenzenesulfonyl)-alpha-(4-carboxyl-2-n-propy lphenoxy)-3,4- methylenedioxyphenylacetamide, is a potent nonpeptidyl endothelin antagonist (e.g., Ki: cloned human ETA = 0.062 nM: cloned human ETB = 2.25 nM), with high specificity for endothelin receptors. In vitro, L-754,142 is a potent antagonist of ET-1-induced phosphatidyl inositol hydrolysis in Chinese hamster ovary cells expressing cloned human endothelin receptors (IC50: hETA = 0.35 nM; hETB = 26 nM) and of ET-1 induced contractions in rabbit iliac artery rings (pA2 = 7.74) and rat aortic rings (pA2 = 8.7). In vivo, L-754,142 is a potent and specific antagonist of exogenously administered ET-1 or big ET-1, L-754,142 fully protects against ET-1-induced lethality in mice (AD50 = 0.26 mg/kg i.v.). The pressor response to big ET-1 in the anesthetized ferret is blocked by this compound with an ED50 value of 0.019 mg/kg i.v. L-754,142 also blocks the pressor response to big ET-1 in the conscious rat with ED50 values of 0.30 mg/kg i.v. and 0.56 mg/kg p.o. The duration of action of L-754,142 in this rat model is more than 12 hr after an oral dose of 3 mg/kg. In summary, L-754,142 is a potent, orally active ET antagonist with a long duration of action in several in vivo models.

Acetamides↗
PubMed1994

Apolipoprotein E expression in Y1 adrenal cells is associated with increased intracellular cholesterol content and reduced free cholesterol efflux.

The expression of apoE mRNA in the adrenal gland is inversely correlated to steroidogenesis and directly correlated to the level of cholesteryl ester stores. To further investigate the relationship between apoE and cellular cholesterol homeostasis, several parameters of cholesterol metabolism in the murine Y1 adrenal cell line engineered to constitutively express human apoE (Y1-E cells) have been studied. It is reported here that Y1-E cells have increased cellular cholesterol content and markedly reduced efflux of free cholesterol as compared to control Y1 cells that do not express apoE. Y1-E cells have increases in both free and esterified cholesterol. However, Y1 and Y1-E cells incorporate [14C]oleate into cholesteryl ester at similar rates and have similar levels of maximal ACAT activity in isolated microsomes. Turnover of cholesteryl ester stores prelabeled with [14C]oleate occurred at similar rates in Y1-E and control Y1 cells, suggesting that increased cholesteryl ester stores in Y1-E cells do not result from reduced cholesteryl ester hydrolysis. Y1-E cells showed reduced cholesterol efflux as compared to control Y1 cells with either native high-density lipoprotein or cholesterol-free reconstituted particles as extracellular acceptors. Cholesterol efflux was not altered by inhibition of ACAT, suggesting that cholesterol esterification in Y1-E cells is not inhibiting efflux. These results suggest that reduced cholesterol efflux is responsible, at least in part, for the cholesterol accumulation in Y1-E cells. In comparison to the rat adrenal gland in vivo, Y1-E cells resemble adrenocortical cells under conditions where steroidogenesis is suppressed and apoE expression and cholesteryl ester storage are increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1994

Cloning and characterization of the gene encoding Schistosoma mansoni glutathione peroxidase.

Antioxidant enzymes are thought to play a crucial role in the survival of the parasite, Schistosoma mansoni, during its migration through the tissues of the definitive host. We recently cloned the cDNA encoding one such enzyme, glutathione peroxidase (Gpx). In order to elucidate the regulation of expression of this gene, we describe the cloning and characterization of a Gpx gene of S. mansoni. An initial screen of a lambda EMBL4 genomic library using the corresponding cDNA sequence as a probe yielded 14 positive clones, two of which have so far been analyzed in detail. The complete Gpx gene contains five introns, four of which, located at the 5' end, are extremely short (30-51 bp) and the last of which is approximately 6 kb long. We present the sequence of the gene including 73 bp at the 5' end, the complete sequence to 137 bp downstream from the penultimate exon, 164 bp upstream and 131 bp downstream from the last 3' exon. The potential mRNA cap site is situated 219 bp upstream from the ATG start codon. All intron/exon junctions correspond to the conventional eukaryotic splice signal. Analysis of the 5' flanking region revealed the presence of a potential TATA box at--26 bp from the cap site, but no CAAT-like element is present. Southern blot analysis showed a unique Gpx gene organisation in the S. mansoni genome.

Amino Acid Sequence↗
PubMed1994

Apolipoprotein (apo) B and apoII gene expression are both estrogen-responsive in chick embryo liver but only apoII is estrogen-responsive in kidney.

Estrogen regulates the hepatic synthesis of a variety of proteins required for egg yolk production in oviparous vertebrates. In chickens, two of these proteins, apolipoprotein (apo) B and apoII, comprise the major protein components of specialized very low density lipoprotein particles that transport triacylglycerols and cholesterol to the developing egg yolk. In the adult, apoB is synthesized constitutively in liver, small intestine, and kidney but is estrogen-responsive only in the liver. In this work we have examined the embryonic expression of the apoB and apoII genes in yolk sac, liver, kidney, and small intestine. The 14 kb apoB mRNA was first detected at day 3 of development in vascular yolk sac, a tissue involved in the transfer of yolk lipids into the embryonic circulation. Constitutive apoB mRNA expression was detectable in liver at day 6.5 and in kidney at day 7.5, but in intestine was barely detectable before hatching. The hepatic apoB gene acquired estrogen-responsiveness at day 6.5 and its hormone-dependent expression increased throughout development in concert with the estrogen-responsive expression of the apoII gene. In contrast, the constitutively expressed apoB gene in kidney remained unresponsive to estrogen. Surprisingly, the apoII gene was found to be responsive to estrogen in both the embryonic kidney and small intestine. ApoII mRNA induction by estrogen in kidney at day 11 was at 10% of the level in the liver but estrogen-responsiveness decreased later in development and was low in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Ambient noise levels in industrial audiometric test rooms.

In 1983 the Occupational Safety and Health Administration (OSHA) specified maximum permissible ambient noise levels (MPANLs) that would allow valid hearing threshold measurements in an audiometric test room. However, ambient noise sound pressure levels (SPLs) in rooms used for industrial hearing tests are unknown. The present study reports octave band (125 to 8000 Hz) ambient noise SPLs measured in 490 single-walled prefabricated audiometric test rooms located in industrial settings that were obtained from eight sources. The ambient noise SPLs were highest in the lower frequencies and decreased as frequency increased. All 490 rooms met the OSHA MPANLs. Fortunately, the ambient noise SPLs were considerably lower than the OSHA MPANLs, since previous research has demonstrated that hearing thresholds cannot be obtained down to 0-dB HL in a test room having ambient noise levels equal to the OSHA MPANLs. In fact, 33%, or 162 of the 490 test rooms, met the more stringent MPANLs recently specified by the American National Standards Institute (ANSI) for industrial hearing testing. Given that the OSHA MPANLs are too high and that the test room ambient noise SPLs were considerably less than the OSHA MPANLs, that authors recommend that the OSHA MPANLs be revised to the more stringent ANSI 1991 MPANLs so that hearing thresholds for baseline and annual audiograms can be measured down to 0-dB HL.

Audiometry↗