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Biomedical subjects

S Rivera

Publications and source records attributed to S Rivera.

14 recordsLinked to original sources
PubMed1992

Increase in rat pup ultrasonic isolation calls induced by lindane.

The neurotoxic agent lindane was tested for its ability to alter the rate of ultrasonic isolation calls of suckling rats. Doses that did not produce any sign of convulsant activity significantly increased the number of calls and the cumulative time of calling in male pups. At days 10-13 of age after a single dose of 20 mg/kg lindane, animals showed more than twice the control call values. After daily dosing with 10 mg/kg during the first week of age call increases also appeared. It is suggested that lindane has an anxiogenic effect mediated through its action on the benzodiazepine-GABAA receptor-chloride channel complex.

Animals↗
PubMed1991

Regional effects on the cerebral concentration of noradrenaline, serotonin and dopamine in suckling rats after a single dose of lindane.

The effect of a low single dose of lindane (gamma-hexachlorocyclohexane) on monoaminergic neurotransmission during brain postnatal development was studied in 8-, 15-, 22- and 29-day-old suckling rats. Concentrations of noradrenaline, serotonin, dopamine and their metabolites were determined in eight cerebral regions 1 h after dosing (20 mg/kg lindane per os). All these aminergic systems were altered in a regional- and age-related pattern. Decreases of noradrenaline in regions rich with noradrenergic terminals together with increases of the ratio 5-HIAA/serotonin and DOPAC/dopamine suggest, as a whole, an enhanced release of the monoamines. This increased neuronal activity does not exclude an initial action of lindane on the inhibitory GABAergic system that would activate the neurotransmitter release in other systems shortly after a single administration of the neurotoxic agent.

Aging↗
PubMed1990

[Clinical use of chlorhexidine].

There is a wide variety of literature regarding chlorhexidine, so we have tried to put together the most recent studies in order to apply them to our clinical reality. Chlorhexidine is an excellent alternative which should be considered as the best chemical collaborator available in the market. In order to obtain the best therapeutic effects, chlorhexidine should always be used within a plaque control program administered by a professional. It's the best way to get the best advantages offered by this medicine.

Chlorhexidine↗
PubMed1989

The respiratory behavior of Lewis carcinoma cells--existence of a cyanide-resistant respiration.

The respiratory O2 consumption of vegetative, non-necrotic, Lewis lung carcinoma cells was found to be very low compared with that of non-tumor tissues and was highly resistant to cyanide. However, the resistant rate was inhibited by salicylhydroxamic acid (SHAM) in either isolated cells or tissue fragments. In addition, this compound did not affect their cytochrome-c oxidase activity. The results support the existence of an alternative oxidase system that significantly contributes to oxygen uptake in Lewis carcinoma cells. To our knowledge, this is the first report showing significant SHAM-sensitivity of tumor respiration and perhaps of higher animal cell respiration.

Animals↗
PubMed1988

Amino acid metabolism in tumour-bearing mice.

Mice bearing the Lewis lung carcinoma showed a high tumour glutaminase activity and significantly higher concentrations of most amino acids than in both the liver and the skeletal muscle of the host. Tumour tissue slices showed a marked preference for glutamine, especially for oxidation of its skeleton to CO2. It is proposed that the metabolism of this particular carcinoma is focused on amino acid degradation, glutamine being its preferred substrate.

Amino Acids↗
PubMed1988

The subcutaneous ventricular reservoir: an effective treatment for posthemorrhagic hydrocephalus.

Use of the subcutaneous ventricular reservoir in the treatment of posthemorrhagic hydrocephalus was studied in a series of 38 patients. All of the patients were considered to be medically labile. Additionally, all had failed conservative modes of therapy consisting of lumbar punctures with or without furosemide or acetazolamide. Management of the hydrocephalus consisted of reservoir placement. Subsequently, taps were performed at various intervals and amounts, depending upon the degree of ventricular dilatation as determined by sonography and signs of increased intracranial pressure. The majority of reservoirs were left in place for 1-2 months. There were no reservoir infections. Once the patients were medically stable, the reservoir was removed and a shunt placed. Eight patients died before shunt placement and 2 patients died after shunting, reflecting a 29% mortality. In no case was a death related to the shunt, but rather reflected the medical lability of the patient population. Four patients (15% of surviving patients) did not require shunting. The total shunt infection rate was 6.9% (among survivors with a shunt in place, 7.7%). These results support the use of the reservoir as an easy and effective means of protecting the cortical mantle while decreasing morbidity related to future shunt placement.

Catheterization↗
PubMed1987

Blood amino acid compartmentation in mice bearing Lewis lung carcinoma.

Blood amino acid compartmentation between plasma and red blood cells was studied in mice bearing the Lewis lung carcinoma. The animals showed a change in compartmentation with an increase in the concentration of most amino acids in the plasmatic fraction with the exception of glycine, glutamine, aspartate, asparagine, and taurine. This work focuses on the importance of studying the distribution of amino acids in both fractions when performing studies concerning amino acid metabolism in tumor-bearing animals.

Amino Acids↗
PubMed1985

Simplified techniques for the preparation and use of reversible hydrocolloid impression material.

The use of a simple technique with an inexpensive syringe loaded with heavy-body tray material resulted in a savings of preparation time and storage space in the conditioning unit. Only one type of material needs to be liquefied. The use of the heavy-body material in syringe and tray in conjunction with a hydrophilic technique have practically eliminated the annoying problem of tearing of the material in the gingival crevice on removal of the impression. Moisture control is no longer an aggravating problem.

Colloids↗
PubMedDate not supplied

Effect of lindane on the myelination process in the rat.

After lindane administration at several doses, brain myelin fractions of litters of male and female Wistar rats show a significant diminution of CNP (2',3'-cyclic nucleotide 3'-phosphodiesterase) activity. Furthermore, the immunohistochemical study of brains by means of a MBP (myelin basic protein) specific antibody reveals myelin deficits in some brain regions after lindane treatment. This loss of myelin protein is dose dependent. The deficit in myelin cannot be attributed to undernourishment of lindane-administered rats. This work shows the vulnerability of the developing central nervous system (CNS) to lindane and the correlation between a decrease in the CNPase activity and a deficit of MBP during the period of study of these animals.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMedDate not supplied

Behavioral changes induced in developing rats by an early postnatal exposure to lindane.

The purpose of this study was to determine whether the behavioral developmental pattern was altered by an early postnatal exposure to lindane. Male and female offspring of Wistar rats were daily orally administered with a nonconvulsant dose of lindane (10 mg/kg) during 7 days either the 1st or the 2nd postnatal week days. Effects on pups were evaluated with a reduced developmental neurotoxicological test battery. Body weight evolution, neuromotor reflexes (surface righting, cliff avoidance and tail hang reflex) and spontaneous motor activity were analyzed from day 1 after birth up to day 28. The body weight pattern was unaffected by treatment with lindane and no signs of overt toxicity were observed. Lindane-treated pups showed an increased positive response of the neuromotor reflexes. Furthermore, lindane produced hyperactivity, especially manifested between days 12 and 16. A peak of activity was reached at day 16 in lindane-treated group, while control animals had a maximum between days 20 and 24. These results suggest that low nonconvulsant doses of lindane may induce behavioral changes in developing rats.

Aging↗
PubMedDate not supplied

[Evaluation of a new medium using red-cell lysate for the isolation of Campylobacter jejuni and Campylobacter coli].

A semiprepared medium containing horse globular lysate was evaluated for the isolation of Campylobacter under two incubation atmospheres (5% O2 and candle jar). Studying 19 known strains of C. jejuni, 151 human and 230 animal fecal samples. They were seeded on conventional medium (MC) and on the new medium (MLG) and incubated at 42 degrees C for 24 and 48 h. Campylobacter strains grew better in 5% O2 atmosphere after 48 h of incubation. All the strains that grew or were isolated on MC, could also grow in MLG incubation in candle jar. Campylobacter was isolated from human fecal samples with the same frequency (5.3%) in MC and MLG, independently of the incubation atmosphere employed. These bacteria were isolated in 35.2% and 34.3% of the animal fecal samples seeded on Skirrow modified medium and MLG, respectively. The concordance proportion between both media was 99.13%.

Aerobiosis↗