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At least 1,099 records · Page 61Linked to original sources
PubMed2001

Collagen synthesis and collagenase activity of cryopreserved heart valves.

OBJECTIVE: Durability of the valve seems to be dependent on the remodeling ability of the valve itself, which is controlled by both collagen synthesis and collagenolytic activity of valvular fibroblasts and endothelial cells. However, the balance of collagen synthesis and collagenolysis of the cryopreserved valve has not yet been clearly revealed. Thus, we assessed the collagen synthesis and collagenolysis ability of the cryopreserved valve. METHODS: Twelve valves were divided into 2 groups: freshly harvested valves (n = 6) and cryopreserved valves (n = 6). We measured the collagen content using Sirius red, a dye selective to the collagen. Collagen synthesis was evaluated by means of the tritiated proline incorporation method. Noncollagenase-digestible counts, which represent protein synthesis, and collagenase-digestible counts, which represent collagen synthesis, were estimated. Collagenase activity of the valves was assessed by gelatin zymography. RESULTS: The collagen content of the cryopreserved group was maintained. The noncollagenase-digestible counts of the cryopreserved group decreased from 3862 +/- 1180 counts/mg to 1174 +/- 1362 counts/mg, and the collagenase-digestible counts of the cryopreserved group were 831 +/- 762 counts/mg compared with the value of 1062 +/- 136 counts/mg for the freshly harvested group. The collagenase activity of the cryopreserved group was observed at the same level as that of the freshly harvested group, despite the serious endothelial damage of the cryopreserved valves. CONCLUSIONS: Although the collagen synthesis of cryopreserved valves was relatively maintained, the protein synthesis was highly diminished, and the collagenolysis ability was activated immediately after the thawing process. These results imply that the cryopreservation procedure itself may cause the collagen metabolism to be on the degradable side, which will lead to valve failure.

Animals↗
PubMed1980

Community life and the development of avoidance reaction in the laboratory rat.

The development of learning of active avoidance reaction in laboratory rats was studied in the course of the juvenile period, sexual maturation and in adulthood. The ability of acquiring and extinguishing an active avoidance reaction during the juvenile period is determined by the way of life: life in a community, at least during the suckling, weaning, or juvenile period positively influenced the ability of the animals to extinguish the reaction while the rate of acquisition slowed down. During learning a balance was thus reached between the rate of acquisition and extinction. In the young reared exclusively in presence of their mother and siblings, the rate of acquisition of this reaction was higher, and the ability of extinguishing was both qualitatively and quantitatively worsened. Thus the relation between the process of excitation and inhibition became unbalanced. In the period of sexual maturation and in adulthood community life had no effect on acquisition and extinction. It had, however, a late effect in those animals which were reared until weaning in a community: in the adulthood a positive correlation was detected between their rate of acquisition and extinction. In contrast, in adult animals reared until weaning in the presence of their mother and siblings, the correlation was found to be negative.

Age Factors↗
PubMed2003

A community-based group exercise program for persons with chronic stroke.

PURPOSE: The purpose of this study was to evaluate the physical and psychosocial effects of an 8-wk community-based functional exercise program in a group of individuals with chronic stroke. METHODS: Twenty-five subjects (mean age 63 yr) participated in a repeated measures design that evaluated the subjects with two baseline assessments 1 month apart, one postintervention assessment, and one retention assessment 1 month postintervention. Physical outcome measures assessed were the Berg Balance Test, 12-Minute Walk Test distance, gait speed, and stair climbing speed. Psychosocial measures assessed were the Reintegration to Normal Living Index (RNL) and Canadian Occupational Performance Measure (COPM). The 8-wk training consisted of a 60-min, 3 x wk-1 group program that focused on balance, mobility, functional strength, and functional capacity. The program was designed to be accessible by reducing the need for costly one-on-one supervision, specialized settings, and expensive equipment. RESULTS: Improvements from the exercise program were found for all physical measures and these effects were retained 1-month postintervention. Subjects with lower function improved the most relative to their initial physical status. Significant effects were found for the COPM, but not the RNL Index; however, subjects with lower RNL improved the most relative to their initial RNL Score. CONCLUSION: A short-term community-based exercise program can improve and retain mobility, functional capacity, and balance and result in a demonstrable impact upon the performance of activities and abilities that were considered meaningful to the subjects. Implementation of such community-based programs has potential for improving activity tolerance and reducing the risk for secondary complications common to stroke (e.g., falls resulting in fractures and cardiac events).

Activities of Daily Living↗
PubMed2003

Effects of a physical activity program. The study of selected physical abilities among elderly women.

This study evaluated the effects of a 12-week exercise program on the physical abilities of 55 sedentary women ages 60 to 75. The variables tested were dynamic balances, muscular endurance, sit and reach flexibility, and muscular coordination. Participants were grouped into three exercise groups (n = 45) and one control group (n = 10). Exercise was performed for 1 hour, once, twice, and three times a week for the three experimental groups. Participants were pre- and post-tested for the selected variables. Significant differences (p < .05) were found between exercise and non-exercise groups. The main effects of the training program were significant for all four variables examined, indicating that even those who participated in an exercise group once a week had a significantly higher levels of physical abilities than the control group. The improvement of the experimental groups was proportional to the frequency of the training program applied.

Activities of Daily Living↗
PubMed2004

A comparison of instrument-centering ability within the root canal for three contemporary instrumentation techniques.

AIM: To study and compare Great Taper (GT) hand files using a reversed balanced force technique, nickel-titanium (NiTi)flex files with a balanced force technique and stainless steel (SS) K-type files using a step-back technique. METHODOLOGY: Forty-eight extracted mandibular premolar teeth with single root canals having curvatures between 15 and 45 degrees were prepared using a modified Bramante model and randomly divided into three groups. The teeth were cross-sectioned at 2, 6 and 10 mm from the working length. Preoperative images of canals at three levels were captured at 20x magnification using a stereomicroscope. Canals in each group were, respectively, prepared to an apical size.10 GT file with 0.2 mm tip diameter, size 30 NiTiflex file and size 30 SS K-file. The GT file was used in a reversed balanced force technique, the NiTiflex file was used in a balanced force technique, and the SS K-file was used in a step-back technique. Postoperative canals were imaged under the conditions same as those for the preoperative canals. The postoperative images were superimposed over the preoperative images using software photoshop 6.0. The ability to maintain the instrument in the central axis of the canal and the deviation from the central canal axis were determined and compared by statistical analysis, along with the assessment of the amount of dentine removed. RESULTS: At apical level, the centering ratio, the distance of transportation and the dentine removed in GT and NiTiflex groups were significantly less than those in SS group (P < 0.01), but no statistical differences were found between the two NiTi groups. At other levels, there were no substantial differences amongst the groups. CONCLUSIONS: Compared with SS K-files, GT hand files and NiTiflex files remain better centered and produce significantly less transportation in curved canals.

Bicuspid↗
PubMed2004

Use of energy reserves in fighting hermit crabs.

When animals engage in fights they face a series of decisions, which are based on the value of the contested resource and either their relative or their absolute fighting ability. Certain correlates of fighting ability or 'resource holding potential' such as body size are fixed but physiological correlates are expected to vary during the encounter. We examine the role of energy reserves in determining fight outcomes and parameters during 'shell fighting' in hermit crabs. During these fights, the two contestants perform very different roles of attacker and defender. We show that the balance of the total energy pool, in the form of glucose and glycogen, determines the ability of defenders to resist eviction from their shells. Low glucose in evicted defenders is not caused by depletion of energy reserves, rather mobilization of glycogen appears to be the result of a strategic decision about whether to resist effectively, based on the perceived fighting ability of the attacker. Attackers, however, always initiate the fight so such a decision for this role appears unlikely. In addition to influencing decisions and ability during fights, physiological correlates of fighting ability can in turn be influenced by strategic decisions.

Agonistic Behavior↗
PubMed2005

The effect of hormone replacement on physical performance in community-dwelling elderly women.

PURPOSE: Our aim was to determine the effect of hormone replacement on physical performance measures, functional ability, physical activity, falls, and cognitive function in elderly women. SUBJECTS AND METHODS: Following a 3-month, open-label, run-in phase, we randomized 373 community-dwelling women aged 65 years and older to receive conjugated equine estrogen 0.625 mg/day plus or minus medroxyprogesterone 2.5 mg/day vs placebo for 3 years in a double-blind fashion. We assessed time to rise from a chair, timed walking, balance, Instrumental Activities of Daily Living, Physical Activity Scale of the Elderly, Folstein Mini-Mental State Examination, and falls. RESULTS: Over 3 years, except for balance scores, performance measures declined significantly (all P<.05). There were no significant mean differences between women on hormone replacement versus placebo for rising time (0.1, -0.5 to 0.7 seconds [mean, 95% confidence interval]), walking normal (0.0, -0.4 to 0.4 seconds), and walking fast (0.2, -0.1 to 0.6 seconds). There were no significant mean differences between the two groups for the Instrumental Activities of Daily Living (0.1, -0.1 to 0.3 points), Physical Activity Scale of the Elderly (-3, -15 to 8 points), Folstein Mini-Mental State Examination (-0.1, -0.3 to 0.3 points), or the proportion of participants reporting falls (-1, -11 to 9%). CONCLUSION: In elderly women, hormone replacement had no statistically significant effect on cognition or balance, nor did it prevent the age-related decline in physical measures of mobility, ability to rise from a chair, self-reported activities of daily living, physical activity scores, or falls.

Accidental Falls↗
PubMed2006

Leptin: nourishment for the immune system.

Leptin, a protein produced by adipocytes, exerts several functions, including modulation of the immune response. A report in this issue of the European Journal of Immunology describes for the first time the effect of either leptin receptor deficiency or blockade on murine dendritic cell (DC) maturation, survival and function. The study describes how leptin receptor deficiency/blockade delays DC maturation and promotes apoptosis, shifts the balance between pro- and anti-inflammatory cytokine production, and reduces the ability of DC to stimulate CD4(+) lymphocytes. These exciting novel data add an important piece of evidence to the picture of the role of leptin in immunity and inflammation and generate the possibility that many of the effects of leptin on T lymphocytes might be mediated through DC.

Animals↗
PubMed1995

Mathematical models for tumour angiogenesis: numerical simulations and nonlinear wave solutions.

To ensure its sustained growth, a tumour may secrete chemical compounds which cause neighbouring capillaries to form sprouts which then migrate towards it, furnishing the tumour with an increased supply of nutrients. In this paper a mathematical model is presented which describes the migration of capillary sprouts in response to a chemoattractant field set up by a tumour-released angiogenic factor, sometimes termed a tumour angiogenesis factor (TAF). The resulting model admits travelling wave solutions which correspond either to successful neovascularization of the tumour or failure of the tumour to secure a vascular network, and which exhibit many of the characteristic features of angiogenesis. For example, the increasing speed of the vascular front, and the evolution of an increasingly developed vascular network behind the leading capillary tip front (the brush-border effect) are both discernible from the numerical simulations. Through the development and analysis of a simplified caricature model, valuable insight is gained into how the balance between chemotaxis, tip proliferation and tip death affects the tumour's ability to induce a vascular response from neighbouring blood vessels. In particular, it is possible to define the success of angiogenesis in terms of known parameters, thereby providing a potential framework for assessing the viability of tumour neovascularization in terms of measurable quantities.

Animals↗
PubMed2003

Lymphocyte subsets and T(h)1/T(h)2 immune responses in patients with adenocarcinoma of the oesophagus or oesophagogastric junction: relation to pTNM stage and clinical outcome.

INTRODUCTION: Recent studies have indicated that the cytokines produced by CD4(+) T helper type 1 (T(h)1) and type 2 (T(h)2) cells are critically important in antitumour immunity and perhaps clinical outcome. From this perspective, we investigated the immunocompetence of patients with previously untreated cancer of the oesophagus or oesophagogastric junction (OGJ) in relation to stage of disease and postoperative survival. METHODS: Blood samples were taken prior to surgery from 32 patients with adenocarcinoma of the oesophagus or OGJ. Ten healthy volunteers served as normal controls. T-cell and monocyte subpopulations were determined using flow cytometry. Monocyte as well as T(h)1- and T(h)2-lymphocyte cytokine levels were assessed in stimulated whole blood cultures. RESULTS: Absolute T-cell and monocyte (subset) counts as well as monocyte cytokine levels were similar among patients and controls. Production of T(h)1-type cytokines was higher in patients than in controls (IFN-gamma, p=0.01; IL-2, p=0.05), whereas T(h)2-type cytokine levels were comparable (IL-4, p=0.5; IL-13, p=0.3). T-cell CD4(+)/CD8(+) ratios decreased as pTNM stage worsened (stage I/II vs stage III/IV, p=0.009). Of all measured immunological parameters, only IL-2 production significantly affected both overall survival ( p=0.015) and disease-free survival ( p=0.0062). High IL-2 levels corresponded with a favourable prognosis. CONCLUSIONS: Patients awaiting surgery for adenocarcinoma of the oesophagus or oesophagogastric junction demonstrated a shift in the T(h)1/T(h)2 balance-in favour of T(h)1-compared with healthy volunteers. The ability of T cells to produce IL-2 was related to survival indicating a crucial role of T(h)1-type cells in antitumour immunosurveillance.

Adenocarcinoma↗
PubMed2004

Grassland management activity data: current sources and future needs.

Estimates of potential and actual C sequestration require areal information about various types of management activities. Forest surveys, land use data, and agricultural statistics contribute information enabling calculation of the impacts of current and historical land management on C sequestration in biomass (in forests) or in soil (in agricultural systems). Unfortunately little information exists on the distribution of various management activities that can impact soil C content in grassland systems. Limited information of this type restricts our ability to carry out bottom-up estimates of the current C balance of grasslands or to assess the potential for grasslands to act as C sinks with changes in management. Here we review currently available information about grassland management, how that information could be related to information about the impacts of management on soil C stocks, information that may be available in the future, and needs that remain to be filled before in-depth assessments may be carried out. We also evaluate constraints induced by variability in information sources within and between countries. It is readily apparent that activity data for grassland management is collected less frequently and on a coarser scale than data for forest or agricultural inventories and that grassland activity data cannot be directly translated into IPCC-type factors as is done for IPCC inventories of agricultural soils. However, those management data that are available can serve to delineate broad-scale differences in management activities within regions in which soil C is likely to change in response to changes in management. This, coupled with the distinct possibility of more intensive surveys planned in the future, may enable more accurate assessments of grassland C dynamics with higher resolution both spatially and in the number management activities.

Agriculture↗
PubMed2000

Digestive performance and digesta passage in the omnivorous greater bilby, Macrotis lagotis (Marsupialia: Peramelidae).

Omnivores such as the greater bilby (Macrotis lagotis) consume a variety of dietary items and often are faced with large changes in the nutrient composition of their food. This paper explores the basis for the dietary flexibility of the bilby by comparing digestive performance and digesta retention patterns of captive bilbies fed either an insect diet (mealworm larvae) or a plant diet (mixed seeds). Mean retention times (MRTs) of particle and solute markers in the gastrointestinal tract did not differ significantly between the two diets, but MRT of the particle marker was significantly longer than that of the solute marker on both the mealworm (particle: 23.5 h; solute: 17.9 h) and mixed seed (particle 33.0 h; solute: 30.2 h) diets. Lack of selective retention of solutes and small particles in the bilby gastrointestinal tract probably restricts them to relatively low-fibre diets, such as those based on seeds rather than leaves and stems of plants. It was observed radiographically that the major sites of digesta retention were the caecum, proximal colon and distal colon, and thus the hindgut is probably the principal site of microbial fermentation. The mealworms were more digestible than the mixed seeds, but digestible energy intake (mealworm: 939 kJ x kg(-0.75) x d(-1); mixed seed: 629 kJ x kg(-0.75) x d(-1)) was high enough for maintenance of body mass and positive nitrogen balance on both diets. Thus, although bilbies may be limited in their ability to utilize high-fibre diets by a lack of selective retention of solutes and small particles in their hindgut, their digestive strategy is flexible enough to accommodate at least some diets of both animal and plant origin. Such a strategy should benefit an animal inhabiting environments in which food resources are unpredictable in their relative abundance.

Animal Nutritional Physiological Phenomena↗
PubMed2006

A dual color ELISPOT method for the simultaneous detection of IL-2 and IFN-gamma HIV-specific immune responses.

The single color IFN-gamma ELISPOT assay has become a standard for assessing HIV-specific immune responses in HIV-infected subjects. However, recent data suggests that single cytokine detection for immune monitoring of HIV-infected individuals may not be sufficient to fully describe virus-specific immune responses. Here, we have designed and validated a dual color ELISPOT assay capable of detecting both IL-2 and IFN-gamma secreting cells simultaneously in response to HIV antigens. We found that a cell input number of 200,000 cells/well provided a good balance between limited availability of cells due to blood volume restrictions and ability to detect all cytokine secretion patterns. The simultaneous detection of IL-2 and IFN-gamma resulted in a decreased magnitude of IFN-gamma but not IL-2 responses. Measures of intra- and inter-assay variability for the dual color ELISPOT assay were comparable to that seen for single cytokine ELISPOT assay with coefficients of variation below 20% for IL-2, IFN-gamma and dual secretion. Although CD8+ T cells mediated most HIV-specific responses in infected subjects, CD4+ T cells mediated responses to HIV were also detected. Features of this assay such as high throughput, cell number requirement and cytokine choice should make this assay a valuable tool for screening for HIV-specific immune responses in several clinically relevant settings.

Cells, Cultured↗
PubMed2005

Electrophysiological and behavioral phenotype of insulin receptor defective mice.

The olfactory bulb expresses one of the highest levels of insulin found in the brain. A high level of expression of the concomitant insulin receptor (IR) kinase is also retained in this brain region, even in the adult. We have previously demonstrated in a heterologous system that insulin modulates the voltage-dependent potassium channel, Kv1.3, through tyrosine phosphorylation of three key residues in the amino and carboxyl terminus of the channel protein. Phosphorylation also induces current suppression of the Kv1.3-contributed current in cultured olfactory bulb neurons (OBNs) of rodents. In order to explore the behavioral importance of this kinase-induced modulation of the channel for the olfactory ability of the animal, mice with a targeted-gene deletion of the insulin receptor were electrophysiologically and behaviorally characterized. Mice heterozygous for the insulin receptor kinase (IR+/-) gene performed the same as wild-type (+/+) mice when challenged with a traditional, non-learning-based task to test gross anosmia. There was also no significant difference across the two genotypes in tests designed to measure exploratory behavior or in a battery of systems physiology experiments designed to assess metabolic energy usage (locomotion, ingestive behaviors, weight, oxygen consumption, and respiratory quotient). Object memory recognition tests suggest that IR+/- mice have an impairment in recognition of familiarized objects; IR+/- mice demonstrate poor performance for both short-term (1 h) and long-term (24 h) memory tests in comparison to that of wild-type mice. Electrophysiological experiments indicate that mitral cell neurons cultured from both heterozygous and homozygous-null mice (IR+/- and IR-/-) have an decreased peak current amplitude compared with that recorded for wild-type (+/+) animals matched for days in vitro (DIV). These data indicate that the loss of one allele of the IR kinase gene modifies the electrical phenotype of the mitral cell neurons in the olfactory bulb without a change in gross olfactory ability. Given our findings that there are no significant changes in metabolic balance of the IR (+/-) mice but some impairment in memory retention, future experiments testing for specific olfactory behaviors or functional deficits in IR-/+ mice models of diabetes will need to either be tasks that do not require learning or will require a different model (such as diet-induced diabetes) that may evoke a stronger phenotype.

Animals↗
PubMed2004

Upregulation of transforming growth factor-beta and interleukin-10 in cows with clinical Johne's disease.

Johne's disease progresses through distinct stages including a protracted subclinical stage in which the infection appears to be controlled; followed by a more acute stage in which the host animal demonstrates clinical signs such as diarrhea and weight loss. Little is known about the dynamics of the host immune response during these two phases of disease, however, it is possible that immune modulation in the early stages of disease may play an important role in disease progression. We hypothesized that the clinical stage of Johne's disease is mediated by the expression of cytokines such as transforming growth factor-beta (TGF-beta) and interleukin-10 (IL-10) that may be accompanied by the downregulation of IFN-gamma gene expression. In the present study, tissue samples were collected from the ileum, ileocecal junction, ileocecal lymph node, and mesenteric lymph nodes of healthy, subclinically or clinically infected cows. The expression of TGF-beta, IL-10, and IFN-gamma genes in these tissues was determined by quantitative competitive RT-PCR. The results demonstrate that TGF-beta and IL-10 mRNA levels are higher in cows that have progressed to the clinical stage of disease compared to subclinically infected or healthy cows. In contrast, IFN-gamma gene expression was significantly higher in subclinically infected cows. These results suggest that a change in the balance of cytokines at the site of infection may contribute to the ability of the host to control Mycobacterium avium subsp. paratuberculosis infection.

Animals↗
PubMed1999

Expression of angiogenesis stimulators and inhibitors in human thyroid tumors and correlation with clinical pathological features.

Experimental evidence has shown, both in vitro and in animal models, that neoplastic growth and subsequent metastasis formation depend on the tumor's ability to induce an angiogenic switch. This requires a change in the balance of angiogenic stimulators and inhibitors. To assess the potential role of angiogenesis factors in human thyroid tumor growth and spread, we analyzed their expression by semiquantitative RT-PCR and immunohistochemistry in normal thyroid tissues, benign lesions, and different thyroid carcinomas. Compared to normal tissues, in thyroid neoplasias we observed a consistent increase in vascular endothelial growth factor (VEGF), VEGF-C, and angiopoietin-2 and in their tyrosine kinase receptors KDR, Flt-4, and Tek. In particular, we report the overexpression of angiopoietin-2 and VEGF in thyroid tumor progression from a prevascular to a vascular phase. In fact, we found a strong association between tumor size and high levels of VEGF and angiopoietin-2. Furthermore, our results show an increased expression of VEGF-C in lymph node invasive thyroid tumors and, on the other hand, a decrease of thrombospondin-1, an angioinhibitory factor, in thyroid malignancies capable of hematic spread. These results suggest that, in human thyroid tumors, angiogenesis factors seem involved in neoplastic growth and aggressiveness. Moreover, our findings are in keeping with a recent hypothesis that in the presence of VEGF, angiopoietin-2 may collaborate at the front of invading vascular sprouts, serving as an initial angiogenic signal that accompanies tumor growth.

Angiogenesis Inducing Agents↗
PubMed2002

The hypoxic core: a possible answer to the cancer paradox.

There are many differences, at all levels of organization, between cancerous and normal cells. Two of these (oxygen delivery and glucose metabolism) are related and manifest as low intercellular oxygen tensions (pO(2)) and a glycolytic metabolic profile in tumours and/or cancer cells. It is becoming increasingly apparent that these characteristics of cancer combine to enhance both the survival and aggressiveness of cancer cells, and that they can adversely impact on some forms of treatment. But they are also exploited in current strategies of detection and monitoring of cancers. These are therefore characteristics with important implications for the crucial balance between the aggression and growth characteristics of a tumour, and our ability to detect and treat it. The interactions and the hierarchy of events leading to these manifestations are complex, not fully understood, and involve a pivotal and intriguing paradox. This paradox results in a seemingly contradictory state in which the most dangerous tumours are those that are the most hypoxic, but also those that are the most angiogenic. This review is a synthesis of the available data into a feasible hypothesis which offers a possible resolution of this paradox and provides a testable paradigm for tumour behaviour.

Cell Hypoxia↗