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At least 307 records · Page 17Linked to original sources
PubMed2000

Kinematic analysis of total knee prosthesis designed for Asian population.

In designing a total knee replacement (TKR) prosthesis catering for the Asian population, 62 sets of femur were harvested and analyzed. The morphometrical data obtained were found to be in good agreement with dimensions typical of the Asian knee and has reaffirmed the fact that Caucasian knees are generally larger than Asian knees. Subsequently, these data when treated using a multivariate statistical technique resulted in the establishment of major design parameters for six different sizes of femoral implants. An extra-small implant size with established dimensions and geometrical shape has surfaced from the study. The differences between the Asian knees and the Caucasian knees are discussed. Employing the established femoral dimensions and motion path of the knee joint, the articulating tibia profile was generated. All the sizes of implants were modeled using a computer-aided software package. Thereupon, these models that accurately fits the local Asian knee were transported into a dynamic and kinematic analysis software package. The tibiofemoral joint was modeled successfully as a slide curve joint to study intuitively the motion of the femur when articulating on the tibia surface. An optimal tibia profile could be synthesized to mimic the natural knee path motion. Details of the analysis are presented and discussed.

Aged↗
PubMed1982

Paleoclimatic setting for Homo sapiens neanderthalensis.

A paleoclimatic hypothesis is presented to account for the evolution and eventual replacement of Homo sapiens neanderthalensis. Neandertal populations in the European Late Pleistocene were largely isolated by geographic barriers. Populations of modern Homo sapiens replaced Neandertals at 34000 years ago, near the end of the relatively cold oxygen isotope stage 3. These population were pushed into Europe by conditions brought on by increasing aridity affecting North Africa and southwestern Asia, and their dispersal was facilitated by lowered sea level.

Africa, Northern↗
PubMed2005

Comparing participants and nonparticipants recruited for an effectiveness study of nicotine replacement therapy.

BACKGROUND: Interventions for smoking cessation have been typically evaluated on reactively recruited samples in clinical trials (efficacy trials). However, to have an impact on smoking rates in a general population, the intervention should also be evaluated with proactively recruited representative samples (effectiveness trials). PURPOSE: The characteristics of participants and two groups of nonparticipants recruited for a population-based nicotine replacement therapy study were compared. METHODS: All members of a large New England Veterans' Administration Medical Center were contacted, and interviews were completed with 3,239 identified smokers (at least 10 cigarettes per day). At the end of the interview, all smokers were offered participation in a multiple intervention study. Of the interviewed smokers, 2,915 verbally agreed to participate in the study (90%). Of those who gave initial verbal consent, 2,054 returned the written informed consent form and became participants (70%). RESULTS: The participants (full consent group) differed significantly from both nonparticipant groups-that is, the smokers who were interviewed but declined participation by active refusal (survey only group) and those who gave verbal consent but passively refused participation by failing to return the written consent form (verbal consent only group). Participants were more likely to be married, younger, and female; to live with others; and to have previously used or considered using nicotine replacement therapy. The survey only group was also more likely to be in the precontemplation stage (54%), whereas the participants were more likely to be in the contemplation (46%) or preparation stage (35%). The verbal consent only group was intermediate of the other two groups in stage-of-change characteristics. CONCLUSIONS: An important finding was that it is possible to recruit a large proportion of a sample of identified smokers to an nicotine replacement therapy study. However, the participants are likely to differ in significant ways from those who either actively or passively decline participation.

Female↗
PubMed1985

Prosthetic heart valve replacement. Choice of prosthesis in a young, underdeveloped population group.

Despite recent advances in the perfection of cardiac valve prostheses, complications still bedevil the currently available models. To a degree, valve replacement is simply exchanging one disease for another. Mechanical prostheses are durable but associated with a high incidence of thrombo-embolic complications, while tissue valves are more resistant to thrombosis and thrombo-embolism but lack durability. The choice of prosthesis must be tailored to the individual patient's requirements, keeping in mind the social, economic and cultural characteristics of the population. Qualified support for conservative valve surgery (valvuloplasty) whenever reasonably possible would seem appropriate, even if it is later proved to have limited durability.

Adult↗
PubMed1988

Demography of dialysis and transplantation in Europe in 1985 and 1986: trends over the previous decade. Report from the European Dialysis and Transplant Association Registry.

The demography of renal replacement therapy for 1985 and 1986 is presented, based on returns of individual patient questionnaires to the EDTA Registry, supplemented by some data from the centre questionnaire. Patient questionnaires for 1985 were received from 83% of known centres and for 1986 from 79% of known centres in 33 countries. Of 244,497 individually registered patients, 116,892 were known to be alive on defined forms of renal replacement therapy on 31 December 1985 and 121,755 on 31 December 1986. Countries covered by the EDTA Registry include one-third of the world's population on renal replacement therapy. Individual countries exemplify different strategies with variable proportional contributions from home haemodialysis, CAPD and transplantation, and varying levels of achievement in numbers of patients on treatment. Trends in patient populations demonstrate that standard risk patients (aged under 55 and non-diabetic) are mostly receiving treatment in countries with advanced programmes, whereas the growth in numbers of new patients is due largely to increase in the acceptance of high-risk patients (aged over 55 or with diabetes mellitus). These trends have implications for the future; predictions must take account of the variable mixture of standard and high-risk patients, the different results achieved in these categories and the rates at which the mixture between them is changing.

Europe↗
PubMed1993

The importance of co-existent disease in the occurrence of postoperative complications and one-year recovery in patients undergoing total hip replacement. Comorbidity and outcomes after hip replacement.

Co-existent or comorbid diseases are appreciated as prognostic factors in studies of quality and effectiveness of care when mortality is the end point. The need to measure and adjust for comorbidity in studies of postoperative hospital complications or long-term recovery from surgery has not been documented. In this study, we determined the impact of co-existent disease on post-operative complications and 1-year health-related quality of life in patients hospitalized for a total hip replacement. The study population consisted of a cohort of 356 patients who were hospitalized in four teaching hospitals in California and Massachusetts for a total hip replacement. Patients' medical records were reviewed to collect information regarding severity of illness, co-existent disease, and postoperative complications. The kind and amount of baseline preoperative co-existent disease was measured from medical record information at admission using a four level Index of co-existent Disease (ICED). Approximately 12 months after hospital discharge, 283 (80%) of the patients were surveyed by questionnaire. The presence and amount of co-existent disease were significant predictors of postoperative complications. The complication rates ranged from 3% to 41% between the lowest and highest levels of the ICED. Patients treated at the four study hospitals differed in functional outcomes 1 year after surgery. Functional outcomes were strongly related to ICED scores: patients in Level 4 ICED scored 26.8 points lower in instrumental activities of daily living than patients in Level 1. After controlling for gender, age, education, and marital status, ICED remained a significant predictor of functional status at 1 year. Furthermore, differences among hospitals in functional outcomes disappeared when the ICED was included in the model to adjust for patient characteristics at the time of surgery. A measure of co-existent disease was crucial in explaining differences among hospitals in recovery from total hip replacement patients.

Activities of Daily Living↗
PubMed2006

Use of postmenopausal hormone replacement therapy and risk of non-Hodgkin's lymphoma: a Danish population-based cohort study.

Use of postmenopausal hormone replacement therapy (HRT) has been hypothesised to be associated with a reduced risk of non-Hodgkin's lymphoma (NHL), but the epidemiologic evidence is conflicting. To examine the risk of NHL in HRT users aged 40 and older, we conducted a cohort study in the County of North Jutland, Denmark (population 0.5 million) using data from population-based health registries for the period 1989-2002. We computed age-standardised NHL incidence rates and used Cox regression analysis to compute the relative risk (RR) and corresponding 95% confidence intervals (CI) of NHL among HRT users compared with non-users, adjusting for age and calendar period. The number of prescriptions redeemed (1, 2-4, 5-9, 10-19, or 20 or more prescriptions) was used as a proxy for duration of HRT. We identified 40 NHL cases among HRT users during 179 838 person-years of follow-up and 310 NHL cases among non-users during 1 247 302 person-years of follow-up. The age-standardised incidence rates of NHL were 25.7 per 100,000 among HRT users and 24.2 per 100,000 among non-users, yielding an adjusted RR of 0.99 (95% CI: 0.71-1.39). Our data did not support an association between HRT use and risk of NHL.

Adult↗
PubMedDate not supplied

Population extinction and recolonization in human demographic history.

For over 30 years, a debate has raged among anthropologists about the origins of anatomically modern humans. At first the debate centered on fossil evidence, but in the past 10-15 years population geneticists have entered the fray. One model, the multiregional evolution model, posits a gradual transition from Homo erectus to anatomically modern humans throughout the Old World. In contrast, the recent African origin model hypothesizes that anatomically modern humans arose from a small, isolated population in Africa, spread out of Africa, and replaced indigenous H. erectus populations in Eurasia and Australasia. A primary objection, from a population genetics perspective, to the multiregional model is that the genetic data suggest a small effective population size for humans. This effective size is on the order of 10,000. Effective population size has a complex relationship with census size, but it has been argued that, assuming that effective size is roughly equal to the number of breeding individuals in human populations under standard demographic conditions, 10,000 breeding individuals could not have occupied much of the Old World throughout the Pleistocene and remained a cohesive species via gene flow. However, this argument is not valid if one considers population extinction and recolonization, which might have played an important role in human history during the Pleistocene. With population extinction and recolonization, the inbreeding effective population size can be small and the census size extremely large. In this paper, I will show that under conditions of population extinction and recolonization, an effective population size of 10,000 suggested by genetic data is compatible with a large census size consistent with the multiregional model.

Animals↗
PubMed2002

Growth kinetics and fractal dimensions of casein particles during acidification.

Small angle static light scattering was used to study the effect of milk dilution in permeate on the mechanism of acid-induced aggregation of casein particles. Growth kinetics of casein aggregates during acidification was characterized by the succession of four populations of particles. The first one corresponded to casein particles ranging from 0.1 to 1 microm, with a mean value of 0.3 microm. The second population, from 1 to 10 microm, was quickly replaced by a third population, from 10 to 100 microm, which gave rise to the last population measurable, from 100 to 1000 microm. The angular dependence of static light scattering from about 0.01 to 50 degrees was used to determine the fractal dimension (D) of pH-induced casein aggregates. With the formation of about 10-microm aggregates, fractal structures appeared. The D values, determined from double logarithmic plots of intensity versus scatteringvector resulted in values between 1.85 and 2.03.

Animals↗
PubMed2002

Arthroscopic débridement of the knee for osteoarthritis in patients fifty years of age or older: utilization and outcomes in the Province of Ontario.

BACKGROUND: There is little available information regarding the effectiveness of arthroscopic knee débridement for the treatment of arthritis. The purpose of this study was to evaluate patterns of utilization of arthroscopic knee débridement and outcomes following that procedure for the treatment of degenerative arthritis in persons fifty years of age or older in the Province of Ontario. METHODS: All patients fifty years of age or older who underwent elective arthroscopic knee débridement for the treatment of degenerative arthritis between 1992 and 1996 were identified from administrative data sets. Surgical complications and subsequent knee replacements were noted. Population rates were compared across the sixteen District Health Council regions within Ontario. Outcomes were modeled as a function of patient age, gender, and comorbidity with use of multivariate regression analysis. RESULTS: We identified 14,391 eligible unilateral arthroscopic knee débridement procedures. There was a threefold difference in the population rate of arthroscopic débridement across geographic regions. Overall, 1330 (9.2%) of all patients required total knee arthroplasty within one year after the débridement. Of the 6212 patients with a minimum three-year follow-up, 1146 (18.4%) had undergone total knee replacement within three years following the débridement. Patients who were at least seventy years of age were 4.7 times more likely to have total knee arthroplasty within one year after the débridement than were those less than sixty years of age (19.0% compared with 4.0%; p < 0.05). Patients sixty years of age or older were more likely to have an early total knee replacement (within one year after the débridement) in District Health Council regions where the population rates of arthroscopic knee débridement were higher (p = 0.04). CONCLUSIONS: The higher rates of early total knee arthroplasty and the significant relationship between rates of early total knee arthroplasty and rates of utilization suggest that arthroscopic débridement for the treatment of osteoarthritis of the knee may be overutilized in elderly patients. Important clinical issues such as patient preference, risk perception, and functional outcome cannot be addressed just with the administrative data used for this study.

Age Factors↗
PubMed1997

Competition for cellobiose among three predominant ruminal cellulolytic bacteria under substrate-excess and substrate-limited conditions.

The ruminal cellulolytic bacteria Ruminococcus flavefaciens FD-1 and Fibrobacter succinogenes S85 coexisted in substrate-excess coculture with about equal population size, but R. flavefaciens outcompeted F. succinogenes for cellobiose in the substrate-limited cocultures whether the two strains were coinoculated or a steady-state culture of F. succinogenes was challenged by R. flavefaciens. This outcome of competition between these two strains is due to a classical pure and simple competition mechanism based on affinity for cellobiose. Although the population size of F. succinogenes was much higher (> 70%) than that of another cellulolytic species, Ruminococcus albus 7 in substrate-excess coculture, F. succinogenes was replaced by a population of R. albus in the substrate-limited coculture in both coinoculation and challenge experiments. R albus outcompeted F. succinogenes, apparently due to selection in the chemostat of a population of R. albus with a higher affinity for cellobiose. R. albus also outcompeted R. flavefaciens under substrate-limited conditions.

Animals↗
PubMedDate not supplied

Similar effects of aging and corticosterone treatment on mouse hippocampal function.

Cumulative exposure to corticosterone (CORT) during the lifespan plays an important role in the hippocampal aging process, and similar disturbances have been observed in chronic stress. However, there is little information on the electrophysiological changes observed in these two situations at the hippocampal level. The present study investigates the electrophysiological changes observed in control conditions and after a 10 microM CORT bath application on hippocampal slices taken from control adult BALB/c mice, from adult animals subjected to chronic overexposure to corticosterone (20 mg/kg/day during 3 months) and from aged animals. No electrophysiological difference was observed in the CA1 area of chronically CORT treated and aged groups compared to the control group. Conversely, the input/output curves from the dentate area showed a similar, statistically significant right shift in these two groups compared to the control group. Furthermore, in control subjects, a 10 microM CORT bath application produced the classical population spike amplitude decrease. However, in slices taken from chronically CORT-treated and aged mice, this effect did not occur in the CA1 while it was replaced by a population spike amplitude increase in the dentate. This increase was blocked by spironolactone. These electrophysiological alterations may indicate that a part of the aged-induced functional disturbances is mediated by glucocorticoids, and may progressively lead to impairment of neuroendocrine functions and behavioral adaptation.

Aging↗
PubMedDate not supplied

Testosterone replacement therapy and the risk of prostate cancer: a perspective view.

The topic of testosterone (T) and prostate cancer is timely and provocative. The Institute of Medicine report on testosterone and aging suggested that knowledge regarding T-replacement therapy in aging men was inadequate, urging a cautious approach to T replacement in this population. The Food and Drug Administration appears to support this cautionary stance. Counter arguments by Rhoden and Morgentaler in the New England Journal of Medicine suggest that T-replacement therapy in aging men may be safe under controlled settings. This perspective continues the debate, and offers a unique perspective from the vantage point of a uro-oncologist.

Aging↗
PubMed1971

Microbodies (Glyoxysomes and Peroxisomes) in Cucumber Cotyledons: Correlative Biochemical and Ultrastructural Study in Light- and Dark-grown Seedlings.

The changes in activities of glyoxysomal and peroxisomal enzymes have been correlated with the fine structure of microbodies in cotyledons of the cucumber (Cucumis sativus L.) during the transition from fat degradation to photosynthesis in light-grown plants, and in plants grown in the dark and then exposed to light. During early periods of development in the light (days 2 through 4), the microbodies (glyoxysomes) are interspersed among lipid bodies and contain relatively high activities of glyoxylate cycle enzymes involved in lipid degradation. Thereafter, these activities decrease rapidly as the cotyledons expand and become photosynthetic, and the activity of glycolate oxidase rises to a peak (day 7); concomitantly the microbodies (peroxisomes) become preferentially associated with chloroplasts.In seedlings grown in the dark for 10 days, the reserve lipid and the glyoxylate cycle enzyme activities persist for a longer time than in the light; correlated with this, there is a continued association of the microbodies with the lipid bodies. When these dark-grown seedlings are then exposed to 51 hours of the light-dark cycle, peroxisomal marker enzymes increase rapidly in activity, and the microbodies become appressed to chloroplasts. We conclude that the characteristic association observed between glyoxysomes and lipid bodies reflects their mutual involvement in net gluconeogenesis through the conversion of fatty acids to carbohydrate, while the close spatial relationship observed between peroxisomes and chloroplasts at later stages of development reflects their mutual involvement in glycolate metabolism.Although glyoxysomal enzyme activities are dropping rapidly while peroxisomal enzyme activities are increasing rapidly during the transition period in the light, the electron microscopic evidence does not indicate that glyoxysomes are being degraded or peroxisomes are being formed. Since in the dark-grown seedlings the activities of peroxisomal enzymes remain low and do not increase as they do in the light, an opportunity is afforded to compare quantitatively any changes in numbers of microbodies per cell with the changes in activities of glyoxysomal enzymes. It is found that the magnitude of the decrease in numbers of microbodies is considerably less than that of the decrease in glyoxysomal enzyme activities between days 4 and 10. When the cotyledons are exposed to light, peroxisomal enzyme activities increase greatly, but again there is no ultrastructural evidence for the synthesis of a new population of microbodies to accommodate this increase. These results allow us to conclude that the developmental transition from glyoxysomal to peroxisomal function almost certainly does not involve the actual replacement of one population of microbodies by another. Rather, the transition probably occurs within existing particles, either by a sequential functioning of two different kinds of microbodies or by a change in enzyme complement within a single population. Our findings with both light- and dark-grown cotyledons favor the latter possibility. The cytoplasmic invaginations into microbodies seen during greening of both light-grown cotyledons and etiolated cotyledons exposed to light may be morphological manifestations of the mechanism by which the microbodies lose or gain enzymes.

Journal Article↗
PubMed2000

Mature oligodendrocyte apoptosis precedes IGF-1 production and oligodendrocyte progenitor accumulation and differentiation during demyelination/remyelination.

We have documented changes in the oligodendrocyte population during demyelinating insult to the adult CNS. Feeding of cuprizone to adult mice led to apoptotic death of mature oligodendrocytes followed by profound demyelination of the corpus callosum. A regenerative response was initiated even during active demyelination. Oligodendrocyte progenitors have begun to proliferate and then accumulate within the lesion. Many of these cells may have migrated from the sub-ventricular zone and fornix before their accumulation in the demyelinating corpus callosum. The accumulation of differentiating oligodendrocyte progenitors was followed closely by the reappearance of mature oligodendrocytes and remyelination. Interestingly, an increase in IGF-1 mRNA was detected at Week 3 through Week 7, suggesting potential involvement in remyelination. Other factors, however, such as PDGF, NT3, FGF, jagged, and notch remained unchanged. These results suggest that the mature oligodendroglial population depleted by apoptosis is replaced by a newly formed oligodendroglial population derived from progenitors; these accumulate and seem to differentiate during remyelination.

Animals↗
PubMed1978

Erythroid stem cells in Friend-virus infected mice.

The erythropoietic stem cell compartment was studied in Friend-virus (polycythemic strain, FV-P) infected DBA/2 and NMRI mice with the CFUE and BFUE technique. Early after infection there was a depression in CFUE number in bone marrow and spleen, followed by an increase of the CFUE concentration, earlier and more pronounced in the spleen than in the marrow. Three days after FV-P infection an erythropoietin (Ep) independent CFUE population started to grow and replaced the normal Ep-dependent population within 8 to 12 days. The shift to Ep independency was not gradual. CFUE colonies of FV-P infected bone marrow cells were two to three times larger than control colonies after three days in vitro incubation. BFUE colonies increased in number during the first days of infection, but were totally lost after more than ten days. After velocity sedimentation of bone marrow cells of FV-P infected animals, however, the BFUE containing fractions showed normal BFUE colony growth and normal Ep sensitivity. In unfractionated bone marrow cell cultures BFUE colony growth could be observed later than ten days post infection when the cultures were refed with medium. It was therefore concluded that the loss of BFUE colony growth after FV-P infection was an in vitro artefact due to inadequate culture conditions.

Animals↗
PubMed2004

Chronic kidney disease and the risk for cardiovascular disease, renal replacement, and death in the United States Medicare population, 1998 to 1999.

Knowledge of the excess risk posed by specific cardiovascular syndromes could help in the development of strategies to reduce premature mortality among patients with chronic kidney disease (CKD). The rates of atherosclerotic vascular disease, congestive heart failure, renal replacement therapy, and death were compared in a 5% sample of the United States Medicare population in 1998 and 1999 (n = 1,091,201). Patients were divided into the following groups: 1, no diabetes, no CKD (79.7%); 2, diabetes, no CKD (16.5%); 3, CKD, no diabetes (2.2%); and 4, both CKD and diabetes (1.6%). During the 2 yr of follow-up, the rates (per 100 patient-years) in the four groups were as follows: atherosclerotic vascular disease, 14.1, 25.3, 35.7, and 49.1; congestive heart failure, 8.6, 18.5, 30.7, and 52.3; renal replacement therapy, 0.04, 0.2, 1.6, and 3.4; and death, 5.5, 8.1, 17.7, and 19.9, respectively (P < 0.0001). With use of Cox regression, the corresponding adjusted hazards ratios were as follows: atherosclerotic vascular disease, 1, 1.30, 1.16, and 1.41 (P < 0.0001); congestive heart failure, 1, 1.44, 1.28, and 1.79 (P < 0.0001); renal replacement therapy, 1, 2.52, 23.1, and 38.9 (P < 0.0001); and death, 1, 1.21, 1.38, and 1.56 (P < 0.0001). On a relative basis, patients with CKD were at a much greater risk for the least frequent study outcome, renal replacement therapy. On an absolute basis, however, the high death rates of patients with CKD may reflect accelerated rates of atherosclerotic vascular disease and congestive heart failure.

Age Distribution↗