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Biomedical subjects

L Hernandez

Publications and source records attributed to L Hernandez.

At least 163 records · Page 9Linked to original sources
PubMed1986

A small, removable microdialysis probe.

A miniaturized, concentric, microdialysis probe is described. It is constructed from 36 gauge stainless steel tubing inside of 26 gauge tubing, with a cellulose hollow fiber tip 0.2 mm in diameter and 2 mm long. It has a 6000 molecular weight cut off that excludes enzymes but collects monoamines, their metabolites, and other small neurochemicals. In vitro tests show relative recovery rates of 5-10%. Absolute recovery measured in picograms was independent of the perfusate flow rate inside the probe. Tests in awake rats with probes in the nucleus accumbens showed stable amounts of catecholamines and metabolites collected during repeated 20 min samples. After ip amphetamine, release of dopamine in the accumbens increased from 20 to 40 pg per sample while DOPAC and HVA decreased from about 1500 to 500 pg. Tests of multiple site sampling succeeded in obtaining norepinephrine and dopamine plus three metabolites (DOPAC, HVA and 5HIAA) from four probes simultaneously in four different brain sites in each rat. Five day continuous samples or monthly intermittent samples can be obtained with this microdialysis probe.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Lateral hypothalamic sites eliciting eating affect medullary taste neurons in rats.

A hypothetical functional relationship between the feeding area of the lateral hypothalamus and the medullary and pontine taste areas was assessed in rats. Multiple electrodes were implanted in the lateral hypothalamus and the animals which exhibited eating upon electrical stimulation were selected. Then under pentobarbital anesthesia, the hypothalamus was electrically stimulated while unit activity of medullary and pontine taste areas was recorded. Electrical stimulation of the hypothalamus at sites which elicited eating affected 22% of gustatory neurons, 13% of proprioceptive neurons sensitive to oropharyngeal stimuli but only 0.2% of the remaining nongustatory neurons. Electrical stimulation at nonfeeding sites affected 3% of the gustatory neurons. The electrical stimulation of the hypothalamus had the same inhibitory or excitatory effect on a given gustatory neuron as the sapid stimulation of the tongue did. These results are discussed in terms of the taste pathways and their possible role in electrically elicited feeding.

Action Potentials↗
PubMed1986

Abdominoscrotal hydrocele.

Abdominoscrotal hydrocele is a very rare finding, especially in infants. The authors describe the case of a 7-month-old boy presenting an abdominoscrotal mass, the diagnosis of which was made by sonography and which was excised totally through an extensive inguinal incision.

Abdomen↗
PubMed1985

"Forward" and "backward" flow mechanisms of portal hypertension. Relative contributions in the rat model of portal vein stenosis.

The contribution of "forward" and "backward" flow mechanisms to the increased portal pressure observed in the rat model of portal vein stenosis was evaluated using experimental and theoretical data. The experimental data indicate that portal venous inflow, portasystemic shunting, and portal venous pressure are increased after 10 days of portal vein stenosis when compared with sham-operated controls. Furthermore, portal vascular resistance was 40% higher in portal hypertensive animals than in control animals. The elevated portal vascular resistance in the rat with portal vein stenosis was attributed to the high resistance of the portal venous collaterals. Incorporation of the experimental data into a mathematical model that simulated the changes induced by chronic portal vein stenosis allowed for fractionation of the "forward" and "backward" flow components involved in the pathogenesis of portal hypertension. Model predictions indicate that the "forward" and "backward" flow mechanisms account for 40% and 60% of the increase in portal pressure, respectively.

Animals↗
PubMed1984

Effects of dehydration and renin on vasopressin concentration in the subfornical organ area.

The subfornical organ (SFO), one of the brain circumventricular organs, contains immuno-reactive arginine-vasopressin (AVP). AVP in the SFO area may originate in neurons of the hypothalamo-neurohypophysial system. If AVP in the SFO area is part of the magnocellular neuroendocrine system and is important in the regulation of hydration, then its concentration [(]) should change during prolonged dehydration. The SFO is also a target for angiotensin II when the peptide stimulates drinking and releases AVP from the hypothalamo-neurohypophysial system. For these reasons, it was reasoned that hormones of the renin-angiotensin system may also influence [AVP] in the SFO area. To test these hypotheses [AVP] was measured in the SFO area, hippocampal commissure-fornix (HC-F), neural lobe and plasma of rats after 24, 48 and 72 h of water deprivation and at various times after intracerebroventricular (i.v.t.) administration of 5 milli -Goldblatt Units of renin. Before examining the responsiveness of [AVP] in these brain regions to stimulation, we characterized the extraction and recovery of AVP from brain tissue and determined the variance of [AVP] in the SFO area and HC-F among different groups of animals. AVP was extracted from pooled brain tissue into 0.1 N HCl. The homogenate was centrifuged and AVP in the supernatant was quantified by radioimmunoassay either directly or after bentonite extraction. AVP extracted from the SFO area and HC-F displaced labelled antigen bound to antisera in a manner similar to that displaced by standard AVP. The recovery of AVP, added to the 0.1 N HCl extract and assayed directly, averaged 78-108%, whereas 51% was recovered after bentonite extraction. [AVP] in the SFO area from 47 or more groups of 2-6 organs each, averaged 16 +/- 5 pg/organ, 16 +/- 4 pg/mg wet wt, 153 +/- 31 pg/mg protein, and was not significantly different from that contained in the HC-F, 10 +/- 1 pg/mg wet wt and 111 +/- 16 pg/mg protein. A frequency histogram of these data revealed a normal (HC-F) and skewed distribution (SFO). Water deprivation for 24, 48 and 72 h stimulated drinking and increased plasma [AVP]. The elevation in plasma [AVP] plateaued after 48 and 72 h of water deprivation, whereas [AVP] in the neural lobe was reduced (P less than 0.05). Water deprivation increased [AVP] in the HC-F (control vs 72 h water deprivation), but did not alter hormone in the SFO area when expressed as pg/mg protein or pg/mg wet wt.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiotensin I↗
PubMed1984

Diminished amphetamine anorexia and enhanced fenfluramine anorexia after midbrain 6-hydroxydopamine.

Rats were made hyperphagic by 6-hydroxydopamine (6-OHDA) injected bilaterally into the ventral midbrain; then they were restricted to a 6 h/day feeding schedule and tested for appetite suppression with amphetamine and fenfluramine in randomized order. Amphetamine anorexia was diminished while fenfluramine anorexia was enhanced (both P less than 0.001). The opposite effect on fenfluramine anorexia shows that the effect of 6-OHDA on amphetamine anorexia was not due to hyperphagia masking the anorexia. Norepinephrine in the forebrain was 90% depleted, but DA and serotonin levels were within 9% of normal. These results demonstrate a new way to dissociate amphetamine and fenfluramine anorexia, as others have done with lateral hypothalamic lesions or DA depletion. The 6-OHDA injections, which were of a type that cause hyperphagia, apparently destroyed a substrate for amphetamine anorexia and also facilitated a substrate for fenfluramine anorexia.

Animals↗
PubMed1984

Utilization of market research in managing hospital pharmacy resources.

A market research survey of staff physicians and nurses was completed to obtain information on customer preference to be used in making planning and development decisions about the allocation of the pharmacy department's resources. Survey questionnaires were mailed to representative samples of each professional group and included the optimum mix of open-ended and closed-ended questions that would result in the highest response rate. The survey responses identified differences in wants and needs between the nurses and physicians that demonstrate the value of market research. Data obtained from the survey are being used by a staff advisory committee and management to develop departmental goals and objectives that will reduce costs and increase profit margins under the ever-increasing restrictions of prospective reimbursement.

Hospital Bed Capacity, 500 and over↗
PubMed1983

Self-injection of amphetamine directly into the brain.

Rats learned to self-administer d-amphetamine (10 micrograms/microliter) through a cannula implanted in the nucleus accumbens. They responded more frequently for 65 +/- 15 nl of amphetamine than for equal amounts of saline. When presented with two levers (one amphetamine, one blank) they responded more on the correct lever for amphetamine. They would also switch levers, when necessary, to maintain access to the drug. When half the usual drug intake was given automatically, animals reduced their response rate by half, thus self-regulating the total amount of amphetamine they received. In tests for leakage into the ventricles, eight rats that self-injected with an accumbens cannula showed response extinction when switched to a ventricular cannula. We conclude that amphetamine self-injected into the accumbens is a positive reinforcer. This localization of 'amphetamine reward' suggests that the nucleus accumbens contains a synaptic mechanism underlying amphetamine abuse and, perhaps, also natural reinforcement of behavior.

Animals↗
PubMed1983

Neurotransmitters extraction by local intracerebral dialysis in anesthetized rats.

A new technique for in vivo neurotransmitter extraction was developed. Perfusion U shaped cannulae were chronically implanted in the caudate or the thalamus of rats. A segment of the cannula was a piece of dialysis tube of molecular weight cut off 1000. Measurable amounts of dopamine and norepinephrine were recovered from the perfusion fluid. Intraperitoneal amphetamine 10 mg/kg increased dopamine output from the caudate but not from the thalamus. The potential applications of this technique are discussed.

Anesthesia↗
PubMed1983

Amphetamine-induced hyperphagia and obesity caused by intraventricular or lateral hypothalamic injections in rats.

Overeating and obesity relative to controls was produced by multiple bilateral injections of 0.5 mg of amphetamine in the lateral ventricles of female rats eating a palatable, high fat diet. This behavioral and physiological rebound following the expected period of anorexia was accompanied by long-term depletion of dopamine in the striatum and of norepinephrine in the hypothalamus. This suggested the next experiment in which 50 micrograms of amphetamine were injected repeatedly in the lateral hypothalamus; again a brief period of anorexia was followed by hyperphagia and chronic obesity. This suggests that amphetamine acts in the lateral hypothalamus not only to suppress feeding, but in high doses it may also have local neurotoxic effects that cause an upward shift in body weight maintained by overeating.

Amphetamine↗
PubMed1982

Overeating after midbrain 6-hydroxydopamine: prevention by central injection of selective catecholamine reuptake blockers.

Earlier research from this laboratory showed that 6-hydroxydopamine (6-OHDA) injected into the ventral midbrain of rats causes overeating and the gradual development of obesity in association with extensive depletion of forebrain norepinephrine. It was proposed that depletion of norepinephrine or epinephrine was the cause of the behavioral abnormality. This was questioned on the basis of experiments showing that 6-OHDA can cause non-selective lesions and also that non-selective neurotoxins can cause hyperphagia. To help resolve this question, the present experiments used 191 rats in 28 groups to test 3 doses of 6-OHDA and 3 different pretreatments with reuptake blockers, amphetamine, desmethylimipramine and benztropine. The result of midbrain 6-OHDA alone was hyperphagia that was highly correlated with the dose. Pretreatment with intraperitoneal desmethylimipramine (DMI) caused gastric distress, and systemic amphetamine caused delayed overeating, but these unwanted side effects were avoided by injecting the drugs directly into the midbrain 15 min before the 6-OHDA. DMI and amphetamine partially prevented catecholamine depletion in the forebrain and totally prevented subsequent hyperphagia and obesity. Benztropine prevented dopamine depletion, but had no effect on hyperphagia. We conclude that some of the neurons protected by local injection of amphetamine and DMI are probably norepinephrine or epinephrine fibers that ascend through the ventral midbrain and have as one of their functions the inhibition of food intake. These neurons could also play a role in the control of body weight.

Animals↗
PubMed1978

Effect of the anorectic drug, phenylpropanolamine, on blood glucose in rats.

Phenylpropanolamine hydrochloride (PPA) is a widely used decongestant and anorectic drug. The present study investigated the hypoglycemic effects of intraperitoneal PPA on rats to test the possibility that it might derive some of its anorectic properties through effects on glucostatic mechanisms. PPA tended to lower blood glucose levels in normal rats; the glycemia reducing effect was larger and statistically significant in rats made hyperglycemic by prior treatment with streptozocin to cause diabetes. This is the first evidence that PPA migh possibly reduce feeding by increasing blood sugar utilization.

Animals↗
PubMed1978

Cell DNA induction by human cytomegalovirus.

The studies presented indicate that in cells pretreated with IUDR: (1) a temporal relationship exists between CMV and cell DNA synthesis; (2) in cells pretreated with IUDR only a fraction of the cell genome is induced by the virus to replicate; and (3) cell DNA induced by the virus to replicate represents unique rather than repetitive DNA sequences.

Base Sequence↗