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Biomedical subjects

R Suarez

Publications and source records attributed to R Suarez.

At least 19 recordsLinked to original sources
PubMed1997

Honeybee flight muscle phosphoglucose isomerase: matching enzyme capacities to flux requirements at a near-equilibrium reaction

In honeybee flight muscle, there are close matches between physiological flux rates and the maximal activities (Vmax; determined using crude homogenates) of key enzymes catalyzing non-equilibrium reactions in carbohydrate oxidation. In contrast, phosphoglucose isomerase (PGI), which catalyzes a reaction believed to be close to equilibrium, occurs at Vmax values greatly in excess of glycolytic flux rates. In this study, we measure the Vmax of flight muscle PGI, the kinetic parameters of the purified enzyme, the apparent equilibrium constants for the reaction and the tissue concentrations of substrate and product. Using the Haldane equation, we estimate that the forward flux capacity (Vf) for PGI required to achieve physiological glycolytic flux rates is between 800 and 1070 units ml-1 cell water, approximately 45­60 % of the empirically measured Vmax of 1770 units ml-1 cell water at optimal pH (8.0) and low ionic strength (no added KCl). When measured at physiological pH (7.0) and ionic strength (120 mmol l-1 KCl) with saturating levels of substrate, PGI activity is 1130 units ml-1 cell water, a value close to the calculated Vf. These results reveal a very close match between predicted and measured PGI flux capacities, and support the concept of an economical design of muscle metabolism in systems working at very high metabolic rates.

Journal Article↗
PubMed1996

Estradiol effect on rate of proliferation of rat carotid segments: effect of gender and tamoxifen.

Using organ culture of carotid artery segments from sexually mature male and female rats, we examined the effect of estradiol 17 beta on proliferation. The index of cell proliferation was [3H]thymidine uptake. Estradiol 17 beta (0.18-0.36 microM) inhibited the uptake of thymidine in a concentration-dependent manner (p < 0.05). Estradiol 17 beta inhibited [3H]thymidine uptake only in the absence of the weak estrogen receptor agonist phenol red and in carotid artery segments from sexually mature female (p < 0.01) but not male rats. Tamoxifen (0.1 and 1 microM), a partial agonist of estrogen receptors, significantly inhibited thymidine uptake (p < 0.01). However, preincubation of the segments with tamoxifen (0.1 and 1.0 microM) for 4 h before the exposure to estradiol, blocked estradiol 17 beta-induced inhibition of thymidine uptake (p < 0.05 and p < 0.01 for 0.1 and 1.0 microM, respectively). The cyclooxygenase inhibitor indomethacin (5 microM) did not affect either the basal [3H]thymidine uptake or the estradiol 17 beta-induced inhibition of that uptake. This latter finding suggests that prostacyclin or prostaglandin E2 does not mediate the inhibitory response to estradiol 17 beta. The results of these experiments suggest that estradiol 17 beta-induced inhibition of proliferation of rat carotid artery segments is mediated through activation of estrogen receptors.

Animals↗
PubMed1996

Rapid assessment of drug consumption at Santa Cruz de la Sierra, Bolivia.

The present paper describes a rapid assessment carried out in 1996 at Santa Cruz de la Sierra, Bolivia, with a view to defining the sociocultural groups at risk and gaining insight, through the comments of those interviewed, into their perceptions of the phenomenon of drug abuse, their reasons for abusing drugs, the drugs most frequently abused and the psychological and social factors involved when they enter, remain in and finally leave drug-abusing circles. By using qualitative methodology and techniques it was possible to gain access to the typical world inhabited by the interviewees, and thus to characterize the subjects of the study in the light of their closest social reference points (family, peer group, education and work). Among the conclusions of the study are the following: drug abuse is a complex and dynamic phenomenon that has occurred throughout the society of Santa Cruz, fostered by cultural and economic factors; there is a need for society, and especially the Government, to devise a specific, focused and diversified range of services, both in prevention and in rehabilitation, with integration and participation being key features of such initiatives; and the mechanisms for controlling the production of drugs and drug trafficking need to be strengthened.

Adolescent↗
PubMed1984

Multiple primary tumors in association with prostatic cancer.

One hundred forty-six patients with clinically nonmetastatic carcinoma of the prostate were treated at Columbia-Presbyterian Medical Center from 1964 through 1976. Of these 146 patients, 24 (16.4%) had developed at least one additional primary cancer. This review contrasts the 122 patients who had a single primary prostate cancer only with the 24 patients who had additional primary carcinomas with respect to age, racial distribution, clinical stage, and prostate cancer histology including Gleason's score, patterns of failure of prostate cancer, and survival data. Local failure and distant failure were less in the multiple primary group. Patients with high Gleason's scores appear to be at greater risk for second primaries. Five-year observed survival (by actuarial life table method) for the single prostate primary group was 76.5%, and 5-year observed survival of the prostate multiple primary group where prostate cancer appeared first was 71%.

Adult↗
PubMed1984

Amiodarone-induced pulmonary fibrosis in hamsters.

Amiodarone, a cardiac antiarrhythmic agent, has been associated with the development of interstitial pulmonary fibrosis in patients receiving prolonged therapy with the drug. To further assess the toxic effects of amiodarone on lung tissue, Syrian hamsters were given a single intratracheal insufflation of the agent and evaluated for histologic evidence of lung injury. Control animals received intratracheal insufflations of the vehicle in which amiodarone was dissolved. After an initial, transient alveolitis in both experimental and control animals, the amiodarone-treated lungs developed increased interstitial thickening due to fibrinous exudates, alveolar epithelial hyperplasia, inflammatory cell infiltrates, and marked deposition of collagen manifested on trichrome staining. Controls, in contrast, showed nearly complete resolution of the initial alveolitis. An unusual feature of the amiodarone-induced lung injury was reemergence of the alveolitis between 5 and 14 days, which included a marked influx of eosinophils into the lung. Although the precise mechanism of the lung injury is not known, the persistence of the acute inflammatory cells as well as the presence of eosinophils suggests a hypersensitivity-type reaction. Furthermore, the progression of lung injury to fibrosis after a single insult with the drug suggests that mere discontinuation of amiodarone therapy in humans may not reverse the disease process, but that corticosteroid therapy may also be required. Amiodarone appears to be a useful agent to induce diffuse fibrotic reactions in the lung that morphologically resemble idiopathic pulmonary fibrosis in humans.

Amiodarone↗
PubMed1977

Clinical survey of the forms, number and localization of retinal tears in cases of relapses and recurrences in retinal detachment.

This study deals with the clinical observations of the different forms and shapes of retinal tears, their number and localizations in cases of relapses and recurrences in retinal detachement surgery. Two groups of patients were considered, the first belongs to our own centre and the second to referred patient operated in other hospitals. 45.1% of both groups account for relapses. We find 7.35% of undetected retinal breaks. The greater number of tears are mainly distributed in the temporal quandrants. The most common shapes of breaks are the punched-out hole, fingernail-tip-like tears, small and medium horseshoe tears, oval and 'pebbled'-like (cluster of microholes) holes. Approximately 25% of the breaks were seen in areas where thermotherapy had not been applied and 15% of them were found beside most probably overtreated areas.

Female↗
PubMedDate not supplied

Hamsters with coronary vasospasm are at increased risk from stress.

Results of earlier experiments suggested that hamsters with inherited heart disease were at a higher risk of succumbing to stress during the vasospastic, lesion-forming period of their lives rather than later when the process of congestive heart failure had begun. To test this hypothesis, we stressed cardiomyopathic hamsters (CMH) whose ages differed by about 3 months; the younger of the two groups of stressed hamsters was in the vasospastic phase of the disease. The stressor was cold immobilization in which stressor intensity was manipulated using two durations of cold exposure. Log rank survival curves revealed no difference in mortality with the more intense stressor. However, significantly fewer of the older hamsters succumbed to the less intense stressor (46% as compared with 85% of the younger CMHs). Examination of the hearts in the experiment where mortality rate was the same for both groups revealed evidence of cardiac dilatation, indicative of heart failure, only in the older hamsters following stress. Since the younger hamsters did not show these changes and since they, but not the older animals, have coronary microvascular spasm and an increased susceptibility to stress, it would appear that the process of coronary vasospasm should be viewed as an independent and additional risk factor in determining the consequences of stress. Because of the effects of stress in the younger cardiomyopathic hamster, we believe that a neural link--which can be activated by stress--may be involved in the pathogenetic process of coronary vasospasm.

Age Factors↗