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Biomedical subjects

M A Lopez

Publications and source records attributed to M A Lopez.

48 records · Page 3Linked to original sources
PubMed1984

Circadian rhythmicity in the 'basal' pancreatic secretion of the domestic fowl.

The interdigestive pancreatic exocrine secretion of the domestic fowl has been studied following the cosine-vector analysis. For the flow of pancreatic juice the crest phase was at 1040 and the sample amplitude was 2.26 microliter/min. For the amylase output the crest phase was at 1128 and the sample amplitude was 0.297 U.A.A./min. Both parameters are characterized by a phase-and frequency-synchronized rhythm whose period must be close to 24 hr.

Amylases↗
PubMed1983

Effect of biliverdin and bilirubin on the hepatic excretion of bile pigments in the rabbit.

1. A study has been carried out on the effect of i.v. infusion of biliverdin and bilirubin at four different dose strengths in sodium pentobarbital-anaesthetized rabbits. 2. Both pigments show similar values for the maximum excretion rate in bile. 3. At doses of 0.45 and 0.60 mg/kg/min, the infusion of biliverdin does not affect bile flow in the resting state, contrary to the negative effect on flow induced by bilirubin. 4. This negative effect induced by bilirubin on bile flow is explained on the basis of its inhibitory action on the bile salt independent fraction (BSIF).

Animals↗
PubMed1982

Death anxiety among nursing home residents: a comparison of the young-old and the old-old.

The purpose of this research was (a) to determine whether there is a comparative difference in the level of conscious death anxiety between young-old and the old-old nursing home residents and (b) to assess the predictive value of educational attainment, gender, subjective health, functional ability, social support, and length of stay on the conscious death anxiety of the persons in the two age groups. A discriminant analysis of 228 residents from three nursing homes revealed that among the 103 young-old subjects poor subjective health, poor functional ability, poor social support, and extended stays in the facilities were indicative of high death anxiety. Among the 125 old-old subjects, high death anxiety was associated with poor subjective health, poor functional ability, and higher educational attainment. Further, it was found that age was an important variable. A significantly greater proportion of the older residents compared to the younger residents had higher conscious death anxiety. The results may direct practitioners and planners in program development for the elderly nursing home patient.

Aged↗
PubMed1981

The effects of perceived control on the paired-associate learning of elderly persons.

Forty-five elderly subjects performed a modified paired-associate learning task under two conditions designed to enhance their perception of control. Subjects in enhanced control conditions chose their own response items ("choice" subjects) or were allowed to manually control response interval duration ("self-paced"). Yoked controls learned the same items selected by choice subjects, or experienced pacing conditions under which they were allowed comparable amounts of response time. The design was an incomplete 2 x 3 x 6 factorial with two types of item selection (choice vs. force), three types of pacing (self-paced, yoked item-by-item, yoke by trial median time), and six trials. There was no "choice" group in the "item yoked" pacing condition. As predicted, subjects experiencing either or both of the control-enhancing conditions performed better than yoked controls. Experiencing both item choice and self-pacing did not result in performance which was significantly better than that of subjects experiencing only one or the other. Results are discussed in light of previous work with young persons, and recommendations are offered to researchers.

Aged↗
PubMed1981

Biliary secretion in conscious rabbits: role of the enterohepatic circulation of bile salts and of the gall bladder.

The role of enterohepatic circulation of bile salts in biliary secretion in conscious rabbits has been investigated before and after cholecystectomy. Bile flow was higher and bile salt concentration lower in cholecystectomized than in intact rabbits: this could have been caused by a negative feed-back effect on bile salt synthesis as the circulating bile salt pool increased. The effects of cholecystectomy on flow and bile salt concentration balanced each other. Bile flow and bile salt concentration declined after interruption of the enterohepatic circulation in both cholecystectomized and intact rabbits. Furthermore, the percentage of the flow of bile independent of bile salt secretion increased, while that independent of total analysed solutes decreased after the enterohepatic circulation was broken. These results confirm that the decrease in bile flow after interruption of the enterohepatic circulation is due to loss of bile salts and not of electrolytes.

Animals↗
PubMed1981

Biliary response to food in rabbits: role of the gall bladder and the enterohepatic circulation of bile salts.

The biliary response to feeding has been investigated in intact and cholecystectomized rabbits, with and without interruption of the enterohepatic circulation of bile salts. The relative contribution of the different secretory mechanisms involved in this process has been examined. Feeding induced an increase in the flow and bicarbonate concentration of the bile and a slight decrease in the bile salt content in rabbits with gall bladders and the enterohepatic circulation intact. Feeding with the enterohepatic circulation interrupted elicited a drop in bile flow and the bile salt concentration, but an increase in bicarbonate concentration. Interruption of the enterohepatic circulation thus dramatically modifies the feeding response: a response to food is still detectable after interruption, but is masked by the negative effects of drainage of the bile away from the duodenum.

Animals↗
PubMed1980

Effects of overlearning and incentive on the acquisition and transfer of interpersonal skills with institutionalized elderly.

Structured Learning Therapy, a skill training program consisting of modeling, role playing, social reinforcement, and transfer of training was used to teach 56 elderly inpatients (mean age = 65.74) the interpersonal skill of "Starting a Conversation." The effects of three levels of overlearning and the addition of concrete (monetary) reinforcement on skill acquisition and transfer were also assessed. All patients acquired the target skill, and there was some evidence of transfer of skill training. Individuals not receiving concrete reinforcement during training showed greater skill transfer compared to those individuals receiving additional incentive. A transfer-enhancing effect of overlearning was found on the Structured Post-test, but no effect was obtained for the other post-test transfer measures.

Aged↗
PubMed1977

The effect of secretin and cholecystokinin-pancreozymin on the secretion of bile in the anaesthetized rabbit.

Effects of secretin and Cholecystokinin-Pancreozymin (CCK-PZ) on the secretion of bile in anaesthetized rabbits have been studied. Single injections of secretin (5.0 u.kg(-1) significantly increased the flow of bile irrespectively of whether the cystic duct was free or had been tied. A sustained increase in bile flow could be obtained by the continuous infusion of secretin. Cholecystokinin-Pancreozymin was effective in increasing the bile flow in doses of 1.0 u.kg(-1). Much of the effect could be attributed to contraction of the gallbladder but a significant increase in flow could still be elicited after ligation of the cystic duct. Our findings strongly suggest that the biliary secretion in rabbits is not as different from the general pattern as has previously been suggested.

Animals↗
PubMedDate not supplied

Effect of secretin on pancreatic juice proteins in caerulein-induced acute pancreatitis in the rat.

Nine hours after the start of treatment with caerulein in rats, an increase in the weight of the pancreas and an increase in serum amylase levels were observed. Likewise, a significant increase in endogenous secretin occurred in rats with acute pancreatitis. A dramatic reduction in the secretion of total protein and amylase was also observed. A partial recovery of this latter effect was achieved after an infusion of high doses of secretin. Under our experimental conditions, the volume of secretion did not vary in caerulein-treated rats wtih respect to controls, either in resting conditions or under secretin stimulation, which indicates that the ductular cells were not significantly affected. Isoelectrofocusing (IEF) and crossed-immunoelectrophoresis (CIE) studies revealed important alterations in the proteins of the pancreatic juice of rats with caerulein-induced acute pancreatitis. Trypsinogen appeared to be particularly affected, showing an increase in the T2 acidic form with an IEP of 4.4 and a decrease in the basic form T3 with an IEP of 8.0, which splits in other forms with a clear antigenic community. A hydrolase was also observed with an IEP of 6.2. In this sense, secretin administration may also be said to induce a significant improvement in established acute pancreatitis, since it tended to normalize the structure and proportion of the proteins secreted.

Acute Disease↗
PubMedDate not supplied

Exocrine pancreatic response to CCK in rats after long-term hydrocortisone administration.

The effects of prolonged administration of hydrocortisone (10 mg/kg/day) on exocrine pancreatic secretion were examined, analyzing the quantitative and qualitative variations in secretion at 7, 18 and 30 days of treatment. The weight of the pancreata was found to increase during the period of hydrocortisone treatment. After the 7th day of treatment the hormone significantly decreases basal exocrine pancreatic secretion, maintaining similar values up to the 30th day of treatment. Hydrocortisone enhances the pancreatic response to CCK since the percent increase in acinar secretion under stimulation compared to basal secretion surpassed control levels in all cases. However, the inhibitory effect on secretion shown by hydrocortisone opposes and surpasses the stimulatory effect of the secretagogue, secretion being reduced in the treated animals. Hydrocortisone especially affected the amylase fraction of the juice, to a larger extent inhibiting the isoenzyme A1, with an IEP of 8.5 when the animals were treated over 30 days; thus, a considerable reduction was observed in the amylase secreted both in resting conditions and under stimulation with CCK. There is a possibility that chronic treatment with glucocorticoids may sensitize the acinar cells, alter the composition of the pancreatic juice and inhibit secretion, effects that may involve pancreatic dysfunction.

Analysis of Variance↗