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Biomedical subjects

D Rivero

Publications and source records attributed to D Rivero.

7 recordsLinked to original sources
PubMed2001

Effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults.

BACKGROUND: The amount of limb-length discrepancy necessary to adversely affect gait parameters in older adults is unknown, with information being largely anecdotal. This investigation was conducted to determine the effects of limb-length discrepancy on gait economy and lower-extremity muscle activity in older adults. METHODS: Forty-four men and women ranging in age from fifty-five to eighty-six years with no evidence of limb-length discrepancy of >1 cm participated in the study. Subjects walked on a treadmill at a self-selected normal walking pace with artificial limb-length discrepancies of 0, 2, 3, and 4 cm applied in a randomly selected order. Indirect calorimetry was used to measure oxygen consumption and minute ventilation. Electromyography was used to measure muscle activity of the right and left quadriceps femoris, plantar flexors, gluteus maximus, and gluteus medius. Heart rate, the rating of perceived exertion, and frequency of gait compensation patterns were also measured. RESULTS: There was a significant increase in oxygen consumption and the rating of perceived exertion with 2, 3, and 4-cm artificial limb-length discrepancies; a significant increase in heart rate, minute ventilation, and quadriceps activity in the longer limb with 3 and 4-cm artificial limb-length discrepancies; and a significant increase in plantar flexor activity in the shorter limb with a 4-cm artificial limb-length discrepancy compared with the same parameters with no artificial limb-length discrepancy. CONCLUSIONS: Both oxygen consumption and the rating of perceived exertion were greater with a 2-cm artificial limb-length discrepancy than they were with no artificial limb-length discrepancy. There appears to be a breakpoint between 2 and 3 cm of artificial limb-length discrepancy in older adults with regard to the effects on most other physiological parameters. A 3-cm artificial limb-length discrepancy is likely to induce significant quadriceps fatigue in the longer limb. Elderly patients with substantial pulmonary, cardiac, or neuromuscular disease may have difficulty walking with a limb-length discrepancy as small as 2 cm.

Aged↗
PubMed1996

Heterotopic ossification.

Heterotopic ossification is a well-recognized condition frequently encountered by the orthopedic surgeon. Although typically asymptomatic, heterotopic ossification can be a complication of extreme severity. This article is a review of literature and attempts to clarify the definition, and delineates the etiology, incidence, risk factors, and current modes of prophylaxis and treatment of various types of heterotopic ossification.

Aged↗
PubMed1992

Epidemiology and long-term consequences of hepatitis delta virus infection in the Yucpa Indians of Venezuela.

To define better the epidemiology and clinical impact of hepatitis delta virus (HDV) infection among hepatitis B virus (HBV) carriers in less developed countries, the authors prospectively studied a cohort of 216 Yucpa Indian HBV carriers in Venezuela. HBV carriers were followed regularly between 1983 and 1988 by physical examination, laboratory testing for liver enzymes and HBV and HDV markers, and epidemiologic history. Among the cohort, 74 (34%) were initially positive for HDV infection, and 35 additional persons became infected during the study. Risk factors for new HDV infection included living in southern Yucpa villages; being young adults (15-19 years) or young children (1-9 years), and living in a household with a person with acute HDV infection. Persons with HDV infection were at high risk of developing chronic liver disease; 56% of HDV-infected persons had moderate-to-severe chronic liver disease at the end of the study compared with none of the HBV carriers without HDV infection. Mortality rates were 6.9% and 8.8% per year, respectively, among initially HDV-positive HBV carriers and those with new HDV infection, because of rapidly progressive chronic liver disease and fulminant hepatitis; mortality was significantly lower in HBV carriers without HDV infection and in non-HBV carriers. HDV superinfection is a devastating disease in HBV carriers in tropical South America. Prevention of HBV infection with hepatitis B vaccine is the best available tool to reduce the impact of this problem.

Acute Disease↗
PubMed1991

[Cost-benefits of vaccination against hepatitis B in hospital personnel in Venezuela].

A cost-benefit study for hepatitis B vaccination in Venezuelan hospital workers was performed through a decision tree analysis model, which includes the probabilities for the different outcomes of the hepatitis B virus infection (HBV). The current average cost of HBV infection to the Venezuelan Government was estimated at US$ 1,759 per patient. Implementation of selective vaccination or a mass vaccination campaign for the hospital workers would reduce the total cost of HBV infection to 51% or 28%, respectively, saving $17 to $26 million. This type of economic analysis may influence the distribution of the resources to be allocated for the control of HBV infection in Venezuela.

Carrier State↗
PubMed1985

Phorbol myristate acetate induces endocytosis as well as exocytosis and hydroosmosis in toad urinary bladder.

The induction of the hydroosmotic response in the toad urinary bladder is considered to be associated with membrane addition mediated by exocytosis at the affected luminal membrane and reversed by endocytic retrieval at that surface. The permeability, exocytosis and endocytosis are initiated by antidiuretic hormone (ADH) receptor interaction on the basolateral membrane. In other hormone responsive systems, phorbol ester (phorbol myristate acetate, PMA), a tumor promoter, has been implicated in the regulation of various transport processes through the activation of protein kinase C and cytoskeletal protein phosphorylation. We found that addition of 10(-6) M PMA to the mucosa induces an hydroosmotic response which is gradual and which reaches a maximum within 60 min, equal to about 1/3 the maximal ADH response. Morphologically, PMA causes rapid exocytosis of the granules, endocytosis of horseradish peroxidase from the mucosal medium into tubules and multivesicular bodies and elongation of apical microvilli. Controls treated with mucosal 0.1% dimethylsulfoxide (DMSO) or an inactive PMA isomer on the mucosal surface, or PMA on the serosal surface lack the hydroosmotic, exocytic, endocytic and cytoskeletal changes. Addition of serosal ADH to PMA-treated bladders results in a precocious hydroosmotic and exocytic ADH response, but a lowering of the maximal response. Also pretreatment of bladders with PMA prevented the ADH-induced increase in transepithelial potential difference. Thus, apical events mediating the PMA hydroosmotic response are correlated with exo- and endocytosis and elongation of apical microvilli.

Animals↗
PubMed1984

Delta virus infection and severe hepatitis. An epidemic in the Yucpa Indians of Venezuela.

Over a 3-year period, 149 Yucpa Indians in Venezuela developed hepatitis; 34 persons died and at least 22 developed chronic hepatitis. Children and young adults were primarily affected, especially males. Serologic testing showed that hepatitis B virus infection was highly endemic in this population, but also that 65% of patients had hepatitis B virus surface antigen (HBsAg) during or after illness. Most patients had evidence of delta-agent superinfection; 86% of HBsAg-positive patients had delta antibody, and delta antigen was found in specimens taken during autopsies on 7 of 9 patients. Serologic data suggested that most infections were due to delta superinfection of hepatitis B carriers, and that more than 60% of these infections progressed to chronic disease. Delta agent infection, and particularly delta superinfection of hepatitis B carriers, appears to be an ominous occurrence that may develop in populations among whom hepatitis B virus infection is endemic, and who have no other risk factor for delta infection.

Adolescent↗