Biomedical subjects

R R Ramirez

Publications and source records attributed to R R Ramirez.

4 recordsLinked to original sources

PubMed1999

Interactive contributions of intracellular calcium and protein phosphatases to massed-trials learning deficits in Hermissenda.

Using Hermissenda as subjects, massed-trials training deficits were examined. Associative pairings of light and rotation induced a progressively greater conditioned foot contraction in response to light as the intertrial interval (ITI) was extended (up to 8 min). In contrast, a short ITI (30 s) produced no evidence of learning. In a corresponding in vitro conditioning experiment that mimicked training of the intact animal, facilitation of neuronal excitability in the animal's B photoreceptors paralleled the results obtained in vivo. Imaging of intracellular Ca2+ using Fura-2 indicated that Ca2+ levels remained elevated during short ITIs. This Ca2+ accumulation appears to induce activation of protein phosphatases because normal facilitation of the B photoreceptors was induced with a short ITI if training occurred in the presence of a phosphatase inhibitor. These results suggest that intracellular Ca2+ and protein phosphatases contribute interactively to the kinetics of memory formation and provide evidence that an accumulation of intracellular Ca2+ across training trials may impede memory formation.

Animals↗

PubMed1998

Bienestar: a diabetes risk-factor prevention program.

The Bienester Health Program, a diabetes risk-factor prevention pilot program, targeted fourth grade Mexican American children. The primary goals are to decrease the two established risk factors for diabetes--overweight and dietary fats. Since the health program is based on Social Cognitive Theory, on social systems structure, and on culturally relevant material, it considers the child's social systems on both its health program and process evaluation. Learning activities were developed for four social systems that potentially influence children's health behaviors (parent, classroom, school cafeteria, and after-school care). Preliminary results show that the Bienestar Health Program significantly decreased dietary fat, increased fruit and vegetable servings, and increased diabetes health knowledge.

Attitude to Health↗

PubMed1996

Health care access among Mexican Americans with different health insurance coverage.

This study describes the rates of health care access among Mexican Americans with different health insurance coverage. An interview questionnaire was used to collect information regarding sociodemographics, perceived health status, health insurance coverage, and sources of health care from a random sample of 501 Mexican Americans from San Antonio, Texas. Health care access was determined more by having health insurance coverage than by health care needs. Poor Mexican Americans with health insurance had higher health care access rates than did poor Mexican Americans without health insurance. Health care access may improve health care outcomes, but more comprehensive community-based campaigns to promote health and better use of health services in underprivileged populations should be developed.

Adult↗

PubMedDate not supplied

Protein synthesis-dependent memory and neuronal enhancement in Hermissenda are contingent on parameters of training and retention.

Following contiguous pairings of light and rotation, light alone elicits a conditioned contraction of Hermissenda's foot, indicative of an associative memory. After a 5-min retention interval, this conditioned response was evident following two or nine (but not one) conditioning trials but persisted for 90 min only after nine trials. In vivo incubation of animals in the protein synthesis inhibitor anisomycin (ANI; 1 microM) did not affect the conditioned response at the 5-min retention interval but significantly attenuated conditioned responding at the 90-min interval even following nine training trials. Deacetylanisomycin (DANI; 1 microM; an inactive form of anisomycin) had no effect on either 5- or 90-min retention. In a companion procedure, groups of isolated nervous systems were exposed to comparable light and rotation pairings, and the B photoreceptors (considered a site of storage for the associative memory) underwent electrophysiological analysis. An increase in neuronal excitability (indexed by depolarizing voltage responses to injected current) in the B photoreceptors paralleled the expression of conditioned responding in intact animals, that is, two training trials produced a short-term increase in excitability that dissipated within 45 min, whereas nine trials produced a persistent (at least 90-min) increase in excitability. In a fmal experiment, isolated nervous systems were exposed to nine training trials, and ANI or DANI was either present in the bathing medium before and during training or was introduced 5 min after training. Following training in ANI, a short-term (5- to 45-min) but not persistent (90-min) increase in excitability in the B photoreceptors was observed. ANI had no effect on either the short-term or persistent increase in excitability if the drug was applied 5 min after the last (ninth) training trial, and DANI had no effect on training-induced increases in excitability at any retention intervals. These results suggest that short-term retention in Hermissenda is protein synthesis independent but that new protein synthesis initiated during or shortly after the training event is necessary for even 90-min retention. Moreover, these results indicate that under some conditions, a critical threshold of training must be exceeded to initiate protein synthesis-dependent retention.

Animals↗