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Biomedical subjects

T Hernandez

Publications and source records attributed to T Hernandez.

At least 19 recordsLinked to original sources
PubMed1992

Intracranial tuberculosis in AIDS: CT and MRI findings.

CT and MRI findings in 35 patients with the acquired immune deficiency syndrome (AIDS) and proven intracranial tuberculosis (TB) are presented. Over 90% of the patients were intravenous drug abusers and in two-thirds TB was the first manifestation of AIDS. CT was normal in one quarter, the most frequent findings being hydrocephalus (51%) and meningeal enhancement (41%), commonly seen together (31.5%). Meningeal enhancement was seen in 48% of the CT studies with intravenous contrast medium and in 3 cases studied with MRI and i.v. gadolinium DTPA, in 2 of which CT was negative. Parenchymal involvement was found in 37% of cases; MRI was more sensitive than CT for its detection. One quarter of the patients had ischaemic lesions, mainly in the basal ganglia. We confirm the usefulness of CT and the superiority of MRI in the diagnosis of intracranial TB and in differential diagnosis from other conditions likely to be found in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Decreased oxygen consumption after catecholamine-induced glycolysis in the alligator.

Anaerobic glycolysis was stimulated by forcing alligators to work to exhaustion, or by injecting them with epinephrine or norepinephrine. In all three groups, plasma lactate increased to above 20 mM. In the work group, oxygen consumption increased three-fold. In the catecholamine experiments, oxygen consumption dropped almost to zero immediately and stayed at zero from 45 min to over 2 hr. Gradually oxygen consumption resumed, finally exceeding the control value, but only by 50%. It was concluded that catecholamine-induced glycolysis produced phosphate-bond energy greatly in excess of immediate need, and that this energy was stored until it was used by the tissue. No oxygen was used until the store was depleted.

Alligators and Crocodiles↗
PubMed1984

Improved intrinsic resolution: does it make a difference? Concise communication.

The purpose of this study was to determine what effect further improvement in an Anger camera's intrinsic resolution has on lesion detection. We studied 52 patients undergoing bone imaging and 58 undergoing liver imaging. All patients had images performed in rapid sequence on ZLC -75 and ZLC -37 Anger cameras, both by Siemens. The two imaging systems are virtually identical except for the number of photomultiplier tubes and crystal thickness; these resulted in differences in intrinsic resolution ( ZLC -75 less than 3.8 mm FWHM at 140 keV, ZLC -37 less than 4.9 mm) and sensitivity ( ZLC -75 approximately 0.91 of ZLC -37 at 140 keV). Observer performance, measured by ROC curves, for detection of abnormalities was virtually identical with the two instruments. Subjectively, there was a trend toward preference of the ZLC -75 images, but this was not associated with any significant improvement in lesion detectability even in the subgroup in which a preference for one or the other instrument was noted.

Bone and Bones↗
PubMed1983

Amino acid transport in the intestine of the caiman.

Seventeen amino acids were fed singly to small caimans and the rates of their disappearance from the gut lumen, and of their appearance in intestinal mucosa, whole intestine, whole stomach, and plasma were determined. The results were compared with those in which massive amounts of protein were fed. When single amino acids were fed, only traces of arginine, ornithine, lysine, aspartate and asparagine were absorbed intact. Glycine, alanine and serine were absorbed rapidly reaching mucosal concentrations as high as 40 mM. The others were not concentrated as highly and most were absorbed by the mucosa more slowly than the glycine group. Protein feeding did not result in high amino acid concentrations in the mucosa. Whether amino acids were ingested as protein or in the free state, glycine, alanine and glutamine increased in the mucosa, suggesting these three incorporate nitrogen released from the others. It appeared that several transport systems operate if amino acids are given singly, and that a different more efficient transport system operates during protein digestion.

Alligators and Crocodiles↗
PubMed1982

Adult toxicity and dominant lethals induced by ozone at specific stages in spermatogenesis in Drosophila virilis.

Ozone, a highly reactive three-atom allotrope of oxygen, is formed in high concentrations in various kinds of microenvironments, including electron microscopes, office copy machines, and X-ray devices. Mutagenicity and action modus operandi of ozone suggest its radiomimetic property. In order to test for ozone-induced dominant lethals in Drosophila virilis, we determined that four-hr and longer exposures to 30 +/- 2 ppm ozone were lethal on or before day 25 postexposure. Accordingly, we used a three-hr ozone exposure to investigate dominant lethals induced at specific spermatogenic stages. Ozone increased the percentage of dominant lethals in the stages of spermatogenesis which were investigated. Under the conditions of this experiment, the sperm-sperm bundle stage showed the greatest percentage of dominant lethals induced by ozone. Meiotic cells were the least sensitive to ozone mutagenicity. The induction of dominant lethals is discussed on the basis of chemical reactions from the molecular decomposition of water by radiations and/or ozone. Alternative explanations are presented due to the definition of induced dominant lethals and to associated modifications from ozone exposure.

Animals↗
PubMed1982

Posttranscriptional control of bacteriophage lambda gene expression from a site distal to the gene.

The bacteriophage lambda int gene product, integrase, recombines the phage DNA with the host DNA at specific sites on each to accomplish lysogeny. The int gene is transcribed from two promoters, PL and PI, each regulated positively by lambda proteins. The expression of integrase is also controlled from a site, sib, in the b region of the phage genome. This is a unique regulatory site because it is located distal to the structural gene in relation to the promoters. The expression of int from the PL promoter is inhibited when sib is present. This effect appears to be specific for PL because sib does not cause inhibition of PI-dependent int synthesis. lambda mutants that contain alterations in the site have been isolated. Sequence analyses of the mutations reveal single base changes, spanning 37 base pairs (bp) in the b region, some 240 bp beyond the int gene. Another mutant, hef13, which has a phenotype similar to that of sib, introduces a nucleotide change within the same 37-bp region. The sib and hef mutations cluster within a region of dyad symmetry. Regulation of int synthesis by sib occurs after transcription of the int gene. There is no difference in the rate of PL-promoted int mRNA synthesis in either sib+ or sib- phage infections, yet int mRNA is less stable in the sib+ infection. Because RNase III host mutants are defective in sib regulation, processing of the PL mRNA at sib by this endoribonuclease may cause int mRNA decay and decrease int synthesis.

Bacteriophage lambda↗
PubMed1981

Circadian rhythm in pineal N-acetyltransferase activity: phase shifting by light pulses (I).

N-Acetyltransferase activity (NAT) in the pineal gland has a circadian rhythm which is responsive to environmental light-dark cycles. The rhythm entrains to (synchronizes with or is phased by) light-dark cycles. To assess the means by which phase resetting is accomplished, the phase response of the pineal NAT rhythm to light pulses was examined using chicks (Gallus domesticus). When 4-h light pulses were imposed on chicks at intervals over a 24-h period of darkness and the time of the next rise in NAT was determined in darkness, it was found that: (1) pulses early in the subjective dark time delayed the rise in NAT, (2) pulses late in the subjective dark time advanced the rise in NAT, and (3) pulses in the subjective light time were relatively ineffective. These results are typical of a circadian phase response curve and show that an enzyme with a circadian rhythm is similar to other circadian rhythms studied.

Acetyltransferases↗
PubMed1979

Increase in metabolic rate of the alligator fed proteins or amino acids.

Energy required for protein digestion, amino acid absorption and transport, and for protein synthesis in the alligator was estimated by determining oxygen consumption following feeding of single amino acids, various amino acid mixtures, fish, casein, gelatin, zein, and a gelatin hydrolysate. Results suggested a low energy requirement for protein digestion, for absorption of the released amino acids, and for amino acid transport, and a high energy requirement for protein synthesis. Little energy was needed for absorption and transport of neutral single amino acids but absorption of single ionic amino acids appeared to require energy. The alligator's metabolic rate is so low that processes requiring extra energy increased oxygen consumption as much as 300%. Peptide bond synthesis seems to have been responsible for the 3-fold increase in metabolic rate after feeding protein. Whether that phenomenon should be called "specific dynamic action" is problematical.

Absorption↗