bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanobiology of force transduction in dermal tissue
Authors: Silver Frederick H. , Siperko Lorraine M. , Seehra Gurinder P. 
Published: March 2003

Background/aims:The influence of mechanical forces on skin has been examined since 1861 when Langer first reported the existence of lines of tension in cadaver skin. Internal tension in the dermis is not only passively transferred to the epidermis but also gives rise to active cell‐extracellular matrix and cell–cell mechanical interactions that may be an important part of the homeostatic processes that are involved in normal skin metabolism. The purpose of this review is to analyse how internal and external mechanical loads are applied at the macromolecular and cellular levels in the epidermis and dermis.Methods:A review of the literature suggests that internal and external forces applied to dermal cells appear to be involved in mechanochemical transduction processes involving both cell–cell and cell–extra‐cellular matrix (ECM) interactions. Internal forces present in dermis are the result of passive tension that is incorporated into the collagen fiber network during development. Active tension generated by fibroblasts involves specific interactions between cell membrane integrins and macromolecules found in the ECM, especially collagen fibrils. Forces appear to be transduced at the cell–ECM interface via re‐arrangement of cytoskeletal elements, activation of stretch‐induced changes in ion channels, cell contraction at adherens junctions, activation of cell membrane‐associated secondary messenger pathways and through growth factor‐like activities that influence cellular proliferation and protein synthesis.Conclusions:Internal and external mechanical loading appears to affect skin biology through mechanochemical transduction processes. Further studies are needed to understand how mechanical forces, energy storage and conversion of mechanical energy into changes in chemical potential of small and large macromolecules may occur and influence the metabolism of dermal cells.
Changes in the prevalence of HIV‐associated mucosal disease at a dedicated clinic over 7 years
Authors: Greenwood I , Zakrzewska JM , Robinson PG 
Published: March 2003

OBJECTIVE: To investigate changes in the prevalence of mucosal disease in patients with HIV/AIDS.DESIGN: Retrospective analysis of clinic database.SETTING: An open‐access dental clinic dedicated to the dental treatment of patients infected with HIV in London, UK.SUBJECTS: Dental patients attending for routine assessment (check‐up).MAIN OUTCOME MEASURES: Prevalence of HIV associated oral lesions, diagnosed in accordance with EC classification criteria, in patients taking and not taking antiretroviral therapies (ARTs).RESULTS: Data were collected at 2789 dental examinations for 1590 patients between 1992 and 1998. More patients taking ART had one or more oral manifestations in the years up to 1996, after which the prevalence fell to a similar level to those not taking medications. The prevalence of mucosal disease in patients not taking ART was relatively constant over time. These trends were observed for oral hairy leukoplakia, pseudomembranous and erythematous candidiasis and Kaposi's sarcoma but not for oral papillomata.CONCLUSIONS: These data provide evidence that decreases in the prevalence of oral disease in people with HIV infection can be attributed to the effectiveness of ART.
A collaborative approach for improving information literacy skills of dental hygiene students
Authors: Cobban Sandra J. , Seale Linda N. 
Published: March 2003

Abstract Background: Evidence‐based practitioners need to develop proficiency in locating and evaluating necessary information from a variety of sources, a concept known as information literacy. One potential source of information is the World Wide Web; however, the wide range in the quality of information available through the Internet indicates a need for strong critical appraisal skills.Objectives:To facilitate development of these skills in dental hygiene students, dental hygiene faculty collaborated with a librarian to implement a project to improve information literacy skills and integrate the use of the Internet into dental hygiene course work.Methods:Students were required to develop a scenario about an aspect of dental hygiene practice, such as client health concern, practice management, or selection of an appropriate dental hygiene therapy. Students were to search the Internet, locate and evaluate a website that could address their scenario, and post this information and additional comments to a text‐based computer conferencing section of a class website. WebCT software, particularly the computer conferencing function, was used to support asynchronous online activities. Student evaluation of the assignment was conducted using a 5‐point Likert scale.Results:Mean ratings for structure variables ranged from 3.94 to 3.81. Slightly lower mean ratings for process variables, ranging from 3.74 to 3.21, suggest room for improvement to activities. Mean ratings for outcome variables, ranging from 4.42 to 3.29, suggest achievement of the desired learning outcomes.Conclusion:Evaluation results warrant the continued inclusion of asynchronous online activities in conjunction with face‐to‐face classroom instruction.
Value of Exercise Capacity and Heart Rate Recovery in Older People
Authors: Messinger‐Rapport Barbara , Snader Claire E. Pothier , Blackstone Eugene H. , Yu David , Lauer Michael S. 
Published: March 2003

OBJECTIVES:To evaluate the prognostic value in older adults of two predictors of mortality: impaired functional capacity and an attenuated heart rate recovery.SETTING:Academic medical center.DESIGN:Prospective study with mean 3.7 years follow‐up.PARTICIPANTS:Seven thousand three hundred fifty‐four adults aged 65 and older consecutively referred for exercise testing between 1990 and 1999. Patients with heart failure, valvular disease, atrial fibrillation, and pacemakers were excluded.MEASUREMENTS:The primary endpoint was all‐cause mortality. Impaired functional capacity was defined as the peak exercise workload in the lowest quintile of metabolic equivalents achieved according to prespecified strata of age and sex. Heart rate recovery was defined as the fall in heart rate during the first minute after exercise and was abnormal if 12 or fewer beats per minute, except for patients undergoing stress echocardiography, in which case 18 or fewer beats per minute was abnormal.RESULTS:There were 842 deaths. Patients with impaired functional capacity were at increased risk for death (23% vs 9%, hazard ratio (HR) = 2.7, 95% confidence interval (CI) = 2.2–3.1,P< .0001) as were patients with an abnormal heart rate recovery (17% vs 9%, HR = 2.0, 95% CI = 1.8–2.3,P< .0001). After adjusting for age, sex, coronary history, and other confounders, impaired functional capacity (adjusted HR = 2.1, 95% CI = 1.8–2.4) and an abnormal heart rate recovery (adjusted HR = 1.5, 95% CI = 1.3–1.7) independently predicted death. No interactions between these two variables with age were noted.CONCLUSIONS:In older patients, impaired functional capacity and heart rate recovery were independent predictors of death.
The MDS‐CHESS Scale: A New Measure to Predict Mortality in Institutionalized Older People
Authors: Hirdes John P. , Frijters Dinnus H. , Teare Gary F. 
Published: March 2003

OBJECTIVES: To develop a scale predicting mortality and other adverse outcomes associated with frailty.DESIGN: Observational study based on Minimum Data Set (MDS) 2.0 and mortality data.SETTING: Ontario chronic hospitals.PARTICIPANTS: All chronic hospital patients (N = 28,495) assessed with the MDS 2.0 after mandatory implementation in July 1996 followed until May 1999.MEASUREMENTS: MDS 2.0 assessments done as part of normal practice mainly by registered nurses or multidisciplinary teams in a chronic hospital. Mortality data are available from the accompanying discharge tracking form.RESULTS: The MDS‐Changes in Health, End‐stage disease and Symptoms and Signs (CHESS) score is a composite measure addressing changes in health, end‐stage disease, and symptoms and signs of medical problems. It is a strong predictor of mortality (P < .0001) independent of the effects of age, sex, activities of daily living impairment, cognition, and do‐not‐resuscitate orders. It is also strongly associated with physician activity, complex medical procedures, and pain (P < .001 for each dependent variable).CONCLUSIONS: The CHESS score provides a useful new MDS‐based test to predict mortality and to measure instability in health as a clinical outcome.
Testosterone Supplementation Therapy for Older Men: Potential Benefits and Risks
Authors: Gruenewald David A. , Matsumoto Alvin M. 
Published: March 2003

Serum testosterone levels decline gradually and progressively with aging in men. Many manifestations associated with aging in men, including muscle atrophy and weakness, osteoporosis, reduced sexual functioning, and increased fat mass, are similar to changes associated with testosterone deficiency in young men. These similarities suggest that testosterone supplementation may prevent or reverse the effects of aging. A MEDLINE search was performed to identify studies of testosterone supplementation therapy in older men. A structured, qualitative review was performed of placebo‐controlled trials that included men aged 60 and older and evaluated one or more physical, cognitive, affective, functional, or quality‐of‐life outcomes. Studies focusing on patients with severe systemic diseases and hormone deficiencies related to specific diseases were excluded.In healthy older men with low‐normal to mildly decreased testosterone levels, testosterone supplementation increased lean body mass and decreased fat mass. Upper and lower body strength, functional performance, sexual functioning, and mood were improved or unchanged with testosterone replacement. Variable effects on cognitive function were reported, with improvements in some cognitive domains (e.g., spatial, working, and verbal memory). Testosterone supplementation improved exercise‐induced coronary ischemia in men with coronary heart disease, whereas angina pectoris was improved or unchanged. In a few studies, men with low testosterone levels were more likely to experience improvements in lumbar bone mineral density, self‐perceived functional status, libido, erectile function, and exercise‐induced coronary ischemia with testosterone replacement than men with less marked testosterone deficiency. No major unfavorable effects on lipids were reported, but hematocrit and prostate specific antigen levels often increased.Based on these results, testosterone supplementation cannot be recommended at this time for older men with normal or low‐normal testosterone levels and no clinical manifestations of hypogonadism. However, testosterone replacement may be warranted in older men with markedly decreased testosterone levels, regardless of symptoms, and in men with mildly decreased testosterone levels and symptoms or signs suggesting hypogonadism. The long‐term safety and efficacy of testosterone supplementation remain uncertain. Establishment of evidence‐based indications will depend on further demonstrations of favorable clinical outcomes and symptomatic, functional, and quality‐of‐life benefits in carefully performed, long‐term, randomized, placebo‐controlled clinical trials. J Am Geriatr Soc 51:101–115, 2003.
Noradrenaline and Dopamine Regulation of Prolactin Secretion in Sheep: Role in Prolactin Homeostasis but not Photoperiodism
Authors: Lincoln G. A. , Clarke I. J. 
Published: March 2003

AbstractThe role of noradrenaline (NA) and dopamine (DA) in the hypothalamic control of prolactin (PRL) secretion was investigated in hypothalamic intact (control) and hypothalamo‐pituitary disconnected (HPD) Soay rams. The animals were exposed to alternating 16‐weekly periods of short (8 L : 16D) and long days (16 L : 8D) to induce marked cyclical changes in PRL secretion in both groups (as demonstrated previously). Selective NA and DA receptor antagonists (dose: 1.2 µmol/kg) were administered under short days (low endogenous PRL secretion), and agonists (dose: 0.0012–0.12 µmol/kg) were administered under long days (high endogenous PRL secretion). The acute changes in blood PRL concentrations were measured over 4 h as the index of responsiveness. Under short days, treatment with WB4101 (α‐1 adenoceptor antagonist), and rauwolscine (α‐2 antagonist), consistently increased PRL secretion in control, but not in HPD rams. The treatments produced similar acute, drug‐specific behavioural effects in both groups. Propranolol (β antagonist) had no effect on PRL secretion, while sulpiride (DA D‐2 antagonist) induced a marked increase in blood PRL concentrations in control rams (> 4 h), and a transient effect in HPD rams (15 min). Under long days, when endogenous PRL secretion was increased, phenylephrine (α‐1 agonist) produced no effects, while bromocriptine (DA D‐2 agonist) robustly decreased PRL concentrations in both control and HPD rams, even at the lowest treatment dose. Overall, the positive responses to the antagonists in the control rams, support the view that DA (acting via D‐2 receptors), and to a lesser extent NA (acting via α‐1/α‐2 receptors), negatively regulate PRL secretion. In contrast, the lack of responses to the antagonists in the HPD rams, support the view that neither DA, nor NA, mediate the photoperiodic control of PRL secretion.
Decreased Corticotropin‐Releasing Factor Receptor Expression and Adrenocorticotropic Hormone Responsiveness in Anterior Pituitary Cells of Wistar‐Kyoto Rats
Authors: Hauger R. L. , Shelat S. G. , Redei E. E. 
Published: March 2003

AbstractThe Wistar‐Kyoto (WKY) rat shows signs of persistent activation of the hypothalamic‐pituitary‐adrenal axis, but the cause and site of this activation is not yet known. Chronically activated corticotrophs generally show blunted adrenocorticotropic hormone (ACTH) response to corticotropin releasing factor (CRF); therefore, the anterior pituitary responsiveness to ACTH secretagogues, CRF and vasopressin, was compared in male WKY and Wistar rats. Anterior pituitary CRF binding and CRF receptor mRNA expression was significantly decreased in WKY rats. ACTH response to CRF or vasopressin was markedly impaired, and vasopressin failed to potentiate the CRF‐stimulated ACTH release in cultured WKY anterior pituitary cells. In contrast, CRF and vasopressin alone and in combination stimulated large, concentration‐dependent increases in ACTH release in Wistar anterior pituitary cells. By contrast to the decreased ACTH secretory responses, steady‐state anterior pituitary pro‐opiomelanocortin mRNA levels were approximately 12‐fold greater in WKY rats compared to Wistar rats, and they further increased in response to CRF stimulation. These findings suggest that, although the WKY rat corticotroph is under a chronic state of activation or disinhibition, the in vitro secretory responses to classic ACTH secretagogues are impaired.
Waterlogging tolerance in the tribe Triticeae: the adventitious roots ofCritesion marinumhave a relatively high porosity and a barrier to radial oxygen loss
Authors: Mcdonald M. P. , Galwey N. W. , Colmer T. D. 
Published: March 2003

AbstractNine species from the tribe Triticeae – three crop, three pasture and three ‘wild’ wetland species – were evaluated for tolerance to growth in stagnant deoxygenated nutrient solution and also for traits that enhance longitudinal O2movement within the roots.Critesion marinum(syn.Hordeum marinum) was the only species evaluated that had a strong barrier to radial O2loss (ROL) in the basal regions of its adventitious roots. Barriers to ROL have previously been documented in roots of several wetland species, although not in any close relatives of dryland crop species. Moreover, the porosity in adventitious roots ofC. marinumwas relatively high: 14% and 25% in plants grown in aerated and stagnant solutions, respectively. The porosity ofC. marinumroots in the aerated solution was 1·8–5·4‐fold greater, and in the stagnant solution 1·2–2·8‐fold greater, than in the eight other species when grown under the same conditions. These traits presumably contributed toC. marinumhaving a 1·4–3 times greater adventitious root length than the other species when grown in deoxygenated stagnant nutrient solution or in waterlogged soil. The length of the adventitious roots and ROL profiles ofC. marinumgrown in waterlogged soil were comparable to those of the extremely waterlogging‐tolerant speciesEchinochloa crus‐galliL. (P. Beauv.). The superior tolerance ofC. marinum, as compared toHordeum vulgare(the closest cultivated relative), was confirmed in pots of soil waterlogged for 21 d;H. vulgaresuffered severe reductions in shoot and adventitious root dry mass (81% and 67%, respectively), whereasC. marinumshoot mass was only reduced by 38% and adventitious root mass was not affected.
Photosynthesis, light and nitrogen relationships in a young deciduous forest canopy under open‐air CO2 enrichment
Authors: Takeuchi Y. , Kubiske M. E. , Isebrands J. G. , Pregtizer K.S. , Hendrey G. , Karnosky D. F. 
Published: March 2003

AbstractLeaf photosynthesis (Ps), nitrogen (N) and light environment were measured on Populus tremuloides trees in a developing canopy under free‐air CO2 enrichment in Wisconsin, USA. After 2 years of growth, the trees averaged 1·5 and 1·6 m tall under ambient and elevated CO2, respectively, at the beginning of the study period in 1999. They grew to 2·6 and 2·9 m, respectively, by the end of the 1999 growing season. Daily integrated photon flux from cloud‐free days (PPFDday,sat) around the lowermost branches was 16·8 ± 0·8 and 8·7 ± 0·2% of values at the top for the ambient and elevated CO2 canopies, respectively. Elevated CO2 significantly decreased leaf N on a mass, but not on an area, basis. N per unit leaf area was related linearly to PPFDday,sat throughout the canopies, and elevated CO2 did not affect that relationship. Leaf Ps light‐response curves responded differently to elevated CO2, depending upon canopy position. Elevated CO2 increased Pssat only in the upper (unshaded) canopy, whereas characteristics that would favour photosynthesis in shade were unaffected by elevated CO2. Consequently, estimated daily integrated Ps on cloud‐free days (Psday,sat) was stimulated by elevated CO2 only in the upper canopy. Psday,sat of the lowermost branches was actually lower with elevated CO2 because of the darker light environment. The lack of CO2 stimulation at the mid‐ and lower canopy was probably related to significant down‐regulation of photosynthetic capacity; there was no down‐regulation of Ps in the upper canopy. The relationship between Psday,sat and leaf N indicated that N was not optimally allocated within the canopy in a manner that would maximize whole‐canopy Ps or photosynthetic N use efficiency. Elevated CO2 had no effect on the optimization of canopy N allocation.
Acclimation of photosynthetic capacity to irradiance in tree canopies in relation to leaf nitrogen concentration and leaf mass per unit area
Authors: Meir P. , Kruijt B. , Broadmeadow M. , Barbosa E. , Kull O. , Carswell F. , Nobre A. , Jarvis P. G. 
Published: March 2003

AbstractThe observation of acclimation in leaf photosynthetic capacity to differences in growth irradiance has been widely used as support for a hypothesis that enables a simplification of some soil‐vegetation‐atmosphere transfer (SVAT) photosynthesis models. The acclimation hypothesis requires that relative leaf nitrogen concentration declines with relative irradiance from the top of a canopy to the bottom, in 1 : 1 proportion. In combination with a light transmission model it enables a simple estimate of the vertical profile in leaf nitrogen concentration (which is assumed to determine maximum carboxylation capacity), and in combination with estimates of the fraction of absorbed radiation it also leads to simple ‘big‐leaf’ analytical solutions for canopy photosynthesis. We tested how forests deviate from this condition in five tree canopies, including four broadleaf stands, and one needle‐leaf stand: a mixed‐species tropical rain forest, oak (Quercus petraea(Matt.) Liebl), birch (Betula pendulaRoth), beech (Fagus sylvaticaL.) and Sitka spruce (Picea sitchensis(Bong.) Carr). Each canopy was studied when fully developed (mid‐to‐late summer for temperate stands). Irradiance (Q,µmol m−2 s−1) was measured for 20 d using quantum sensors placed throughout the vertical canopy profile. Measurements were made to obtain parameters from leaves adjacent to the radiation sensors: maximum carboxylation and electron transfer capacity (Va,Ja,µmol m−2 s−1), day respiration (Rda,µmol m−2 s−1), leaf nitrogen concentration (Nm, mg g−1) and leaf mass per unit area (La, g m−2).Relative to upper‐canopy values,Vadeclined linearly in 1 : 1 proportion withNa. RelativeVaalso declined linearly with relativeQ, but with a significant intercept at zero irradiance (P < 0·01). This intercept was strongly related toLaof the lowest leaves in each canopy (P < 0·01,r2 = 0·98,n= 5). For each canopy, daily lnQwas also linearly related with lnVa(P < 0·05), and the intercept was correlated with the value for photosynthetic capacity per unit nitrogen (PUN:Va/Na,µmol g−1s−1) of the lowest leaves in each canopy (P < 0·05).Vawas linearly related withLaandNa(P < 0·01), but the slope of theVa : Narelationship varied widely among sites. Hence, whilst there was a uniqueVa : Naratio in each stand, acclimation inVatoQvaried predictably withLaof the lowest leaves in each canopy. The specific leaf area,Lm(cm2g−1), of the canopy‐bottom foliage was also found to predict carboxylation capacity (expressed on a mass basis;Vm,µmol g−1 s−1) at all sites (P < 0·01). These results invalidate the hypothesis of full acclimation to irradiance, but suggest thatLaandLmof the most light‐limited leaves in a canopy are widely applicable indicators of the distribution of photosynthetic capacity with height in forests.