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Biomedical subjects

G Dominguez

Publications and source records attributed to G Dominguez.

43 records · Page 3Linked to original sources
PubMed1986

Molecular cloning and sequencing of the region of the rubella virus genome coding for glycoprotein E1.

The sequence of the 1600 3' terminal nucleotides of the RNA of rubella virus was determined from cDNA synthesized from both virion and intracellular RNA using reverse transcriptase and an oligodeoxythymidine primer and cloned into a bacterial plasmid vector. This sequence contained the complete coding sequence for virion envelope protein E1 and a 57 nucleotide nontranslated region between the stop codon for E1 and the poly A tract. The predicted size for E1 was 481 amino acids and within this sequence were three potential N-linked glycosylation sites and a putative trans-membrane domain near the carboxy terminus. Immediately preceding the E1 coding region was a putative signal sequence. No homology was found at either the amino acid or nucleotide level between the region of the rubella virus genome sequenced and corresponding regions of the genomes of the alphaviruses, the other genus of the family Togaviridae for which sequence information has been obtained.

Amino Acid Sequence↗
PubMed1984

Evaluation of a system for serial biopsy of cerebral cortical tissue in an awake goat.

No techniques to date have been developed that allow investigators to obtain serial, rapidly frozen brain tissue samples in unanesthetized animals. The design and methods for implantation of cranial windows in goats are described in detail. The cranial window allows one direct and repeated access to the cerebral cortical surface. With each window, a parietal cortical area of 7.9 cm2 (minus the dura) is available for biopsy. Serial tissue samples are obtained using a suction-freezing system. Samples (100-250 mg) are frozen in less than 1 s. Up to six samples can be taken from each site. Goats were studied over a period of 2-5 days. No signs of sampling or immobilization stress were present as evidenced by a relatively constant level of arterial catecholamines and CO2 partial pressure (PCO2). Local cerebral blood flow (CBF) in the tissue under the window was of the same magnitude as that in other cerebral cortical regions and was unaffected by serial sampling. Levels of labile phosphates and of some glycolytic and tricarboxylic acid cycle-associated intermediates were minimally influenced by serial sampling. Greater variability in metabolite levels was seen for biopsies taken 2-5 days apart than for biopsies taken at 1- to 2-min intervals. However, variations within animals were less than variations among animals. This was especially true for acutely biopsied samples. The described methods provide a model for studies of cerebral metabolism in unstressed goats where anesthetic influences are avoided and where each animal can be utilized as its own control.

Animals↗
PubMed1979

Effect of stretch on conduction velocity and cable properties of cardiac Purkinje fibers.

Cardiac Purkinje fibers were studied before and after stretch to 30% and 50% in excess of their slack length, and membrane properties and conduction velocity were measured in relation to the stretch. Conduction velocity increased by 26% with 50% stretch. The resting potentials averaged -77 mV and did not change with stretch. In addition, the action potential height, maximal upstroke velocity, duration, and time constant of the foot did not change. These results suggested that the increase in conduction velocity was not due to a change in membrane excitability. Two geometric models of stretch, called unfolding and uncoiling, were considered. Cable analyses were performed to distinguish between these models. The effects were mixed, with about 2/3 of the length change resulting from unfolding and 1/3 from uncoiling. These results support the concept of redundancy of the surface membrane by folding. The changes are likely to be of importance in activation of the heart by the His-Purkinje system, especially in cardiac dilatation due to disease.

Action Potentials↗
PubMed1975

Effect of diameter on membrane capacity and conductance of sheep cardiac Purkinje fibers.

Membrane electrical properties were measured in sheep cardiac Purkinje fibers, having diameters ranging from 50 to 300 mum. Both membrane capacitance and conductance per unit area of apparent fiber surface varied fourfold over this range. Membrane time constant, and capacitance per unit apparent surface area calculated from the foot of the action potential were independent of fiber diameter, having average values of 18.8 +/- 0.7 ms, and 3.4 +/- 0.25 muF/cm2, respectively (mean +/- SEM). The conduction velocity and time constant of the foot of the action potential also appeared independent of diameter, having values of 3.0 +/- 0.1 m/s and 0.10 +/- 0.007 ms. These findings are consistent with earlier suggestions that in addition to membrane on the surface of the fiber, there exists a large fraction of membrane in continuity with the extracellular space but not directly on the surface of the fiber. Combining the electrical and morphological information, it was possible to predict a passive length constant for the internal membranes of about 100 mum and a time constant for chaning these membranes in a passive 100-mum fiber of 1.7 ms.

Action Potentials↗
PubMed1969

Effect of formaldehyde and glutaraldehyde on electrical properties of cardiac Purkinje fibers.

The effects of formaldehyde, glutaraldehyde, 1-fluoro-2,4-dinitrobenzene, and 1,5-difluoro-2,4-dinitrobenzene on the electrophysiological properties of cardiac Purkinje fibers were studied. At concentrations of 2.5 mM the aldehydes produced a transient hyperpolarization, lengthening of the plateau of the action potential, and an increase in action potential overshoot and upstroke velocity. If exposure to aldehyde was continued, the fiber failed to repolarize after an action potential and the membrane potential stabilized at about -30 mv. If exposure was terminated before this, recovery was usually complete. At the time the fibers were hyperpolarized the input resistance was increased without much change in length constant, leading to an increase in both calculated membrane resistance and calculated core resistance. Although it was anticipated that an effect of the aldehydes on the membrane was to increase fixed negative charge, it was difficult to explain all the electrophysiological changes on this basis. The major effects of the fluorobenzene compounds were not the same; they produced a shortening of the action potential and a rapid loss of excitability.

Action Potentials↗