Biomedical subjects

E L Holder

Publications and source records attributed to E L Holder.

10 recordsLinked to original sources

PubMed1998

Microtubules modulate cardiomyocyte beta-adrenergic response in cardiac hypertrophy.

The role of microtubules in modulating cardiomyocyte beta-adrenergic response was investigated in rats with cardiac hypertrophy. Male Sprague-Dawley rats underwent stenosis of the abdominal aorta (hypertensive, HT) or sham operation (normotensive, NT). Echocardiography and isolated left ventricular cardiomyocyte dimensions demonstrated cardiac hypertrophy in the HT rats after 30 wk. Cardiomyocyte microtubule fraction was assayed by high-speed centrifugation and Western blot. In contrast to previous reports of increased microtubules after acute pressure overload, microtubule fraction for HT was significantly lower than that for NT. Cardiomyocytes were exposed to either 1 microM colchicine, 10 microM taxol, or equivalent volume of vehicle. Colchicine decreased microtubules, and taxol increased microtubules in both groups. Cardiomyocyte cytosolic calcium ([Ca2+]c) and shortening/relaxation dynamics were assessed during exposure to increasing isoproterenol concentrations. The beta-adrenergic response for these variables in the HT group was blunted compared with NT. However, increased microtubule assembly by taxol partially recovered the normal beta-adrenergic response for time to peak [Ca2+]c, time to peak shortening, and mechanical relaxation variables. Microtubule assembly may play a significant role in determining cardiomyocyte beta-adrenergic response in chronic cardiac hypertrophy.

Animals↗

PubMed1996

Measurement of hydrocarbon-degrading microbial populations by a 96-well plate most-probable-number procedure.

A 96-well microtiter plate most-probable-number (MPN) procedure was developed to enumerate hydrocarbon-degrading microorganisms. The performance of this method, which uses number 2 fuel oil (F2) as the selective growth substrate and reduction of iodonitrotetrazolium violet (INT) to detect positive wells, was evaluated by comparison with an established 24-well microtiter plate MPN procedure (the Sheen Screen), which uses weathered North Slope crude oil as the selective substrate and detects positive wells by emulsification or dispersion of the oil. Both procedures gave similar estimates of the hydrocarbon-degrader population densities in several oil-degrading enrichment cultures and sand samples from a variety of coastal sites. Although several oils were effective substrates for the 96-well procedure, the combination of F2 with INT was best, because the color change associated with INT reduction was more easily detected in the small wells than was disruption of the crude oil slick. The method's accuracy was evaluated by comparing hydrocarbon-degrader MPNs with heterotrophic plate counts for several pure and mixed cultures. For some organisms, it seems likely that a single cell cannot initiate sufficient growth to produce a positive result. Thus, this and other hydrocarbon-degrader MPN procedures might underestimate the hydrocarbon-degrading population, even for culturable organisms.

Bacteria↗

PubMed1995

Molecular remodelling in hypertrophied hearts from polyomavirus large T-antigen transgenic mice.

Polyomavirus large T-antigen transgenic mice develop cardiac hypertrophy characterized by an increase in atrial natriuretic factor and beta-myosin heavy chain isoform expression. The aim of this study was to examine changes in proto-oncogene expression in hypertrophied hearts from the transgenic mice. Expression of early growth response-1 (Egr-1) mRNA was detected in hearts from all 15 transgenic mice, but was not detectable in 13 control mice. Reverse transcriptase-polymerase chain reaction experiments using Egr-1-specific primers confirmed the increase in Egr-1 mRNA in enlarged hearts from the transgenic mice. Expression of c-jun, junD and Ha-ras mRNAs was increased in the transgenic hearts 3, 17 and 2.8-fold respectively. Western blots showed an increase in c-myc, c-jun and ras protein in hypertrophied transgenic hearts. Immunofluorescence analyses confirmed an increase in Egr-1 and c-jun protein in transgenic cardiomyocytes. Proliferating cell nuclear antigen, Ki-ras and HSP 90 mRNAs were decreased 22, 2.7 and 3-fold, respectively in the transgenic hearts. Not altered in most hypertrophied hearts was expression of c-fos, junB, p53, c-neu, c-myc, HSP70, HSP27, TGF-beta or IGF 1 mRNAs. Proto-oncogene and growth factor gene expression in hypertrophy induced by PVLT expression is modulated with some proto-oncogenes increased and others decreased in expression.

Animals↗

PubMed1994

A method for analysis of gene expression patterns.

mRNA can be copied into cDNA with the use of reverse transcriptase so that the relative abundance of individual mRNAs is reflected in the cDNA product. With further manipulation a replica of the mRNA expression pattern can be duplicated into a radioactive double-stranded DNA probe. DNA from a series of genes inserted into plasmids can be fixed to a membrane using a slot blot manifold and probed with the RNA-derived DNA probe. The intensity of the hybridization signal for a given gene is a result of its relative abundance in the RNA-derived DNA probe. Quantitation can be achieved through the use of housekeeping genes as baseline monitors. Inclusion of vector sequences can negate any spurious hybridization to vector rather than insert sequences. We have successfully used this method to obtain gene expression patterns for RNA isolated from diverse sources including rodent tissues, various cell lines, and Drosophila and Caenorhabditis elegans samples. Northern blots have verified the results obtained. The pattern of expression of many genes can be determined from as little as 10 micrograms of total RNA, making this method ideally suited for studies in which RNA is rare or in short supply.

Base Sequence↗

PubMed1991