Tufts University

About: Tufts University is a education organization based out in Medford, Massachusetts, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 32800 authors who have published 66881 publications receiving 3451152 citations. The organization is also known as: Tufts College & Universitatis Tuftensis.

Gravitational particle creation and inflation

Abstract: Particle creation due to the changing spacetime metric at the end of an inflationary era in the early Universe is discussed. The Universe is assumed to make a transition from de Sitter space to either a radiation-dominated or matter-dominated universe. A perturbation approach is used to calculate the number density and energy density of massless, nonconformally coupled particles created by this transition. It is found that their energy density is typically of the order of ${\ensuremath{\rho}}_{v}$${\mathrm{}}^{2}$/${\ensuremath{\rho}}_{\mathrm{Pl}}$, where ${\ensuremath{\rho}}_{v}$ is the value of the cosmological constant in the de Sitter phase and ${\ensuremath{\rho}}_{\mathrm{Pl}}$ is the Planck energy density. This is approximately the energy density of a thermal bath at the Gibbons-Hawking temperature of de Sitter space. The possible applications of this effect to inflationary models is discussed. It is shown that gravitational particle creation is capable of reheating the Universe after inflation and of being the source of the matter in the Universe. This effect makes it possible to avoid the difficulty with reheating which inflationary models with weakly coupled scalar fields otherwise encounter.

Variations in Resource Utilization Among Medical Specialties and Systems of Care: Results From the Medical Outcomes Study

Abstract: Objective. —To examine whether specialty and system of care exert independent effects on resource utilization. Study Design. —Cross-sectional analysis of just over 20 000 patients (≥18 years of age) who visited providers' offices during 9-day periods in 1986. Patient- and physician-provided information was obtained by self-administered questionnaires. Setting. —Offices of 349 physicians practicing family medicine, internal medicine, endocrinology, and cardiology within health maintenance organizations, large multispecialty groups, and solo practices or small single-specialty group practices in three major US cities. Outcome Measures. —Indicators of the intensity of resource utilization were examined among four medical specialties (family practice, general internal medicine, cardiology, and endocrinology) and five systems of care (health maintenance organization, multispecialty group—fee-for-service, multispecialty group—prepaid; solo practice and single-specialty group—fee-for-service, and solo practice and single-specialty group—prepaid) before and after controlling for the mix of patients seen in these offices. The indicators of resource utilization were hospitalizations, annual office visits, prescription drugs, and common tests and procedures, with rates estimated on both a per-visit and per-year basis. Results. —Variation in patient mix was a major determinant of the large variations in resource use. However, increased utilization was also independently related to specialty (cardiology and endocrinology), fee-for-service payment plan, and solo and single-specialty group practice arrangements. After adjusting for patient mix, solo practice/single-specialty groups—fee-for-service had 41% more hospitalizations than health maintenance organizations. General internists had utilization rates somewhat greater than family physicians on some indicators. Conclusion. —Although variations in patient mix should be a major determinant of variations in resource use, the independent effects of specialty training, payment system, and practice organization on utilization rates need further explication. The 2- and 4-year outcomes now being analyzed will provide information critical to interpretation of the variations reported herein. ( JAMA . 1992;267:1624-1630)

Vascular Endothelial Growth Factor/Vascular Permeability Factor Enhances Vascular Permeability Via Nitric Oxide and Prostacyclin

Abstract: Background—Vascular endothelial growth factor (VEGF), an endothelial cell mitogen that promotes angiogenesis, was initially identified as a vascular permeability factor (VPF). Abundant evidence suggests that angiogenesis is preceded and/or accompanied by enhanced microvascular permeability. The mechanism by which VEGF/VPF increases vascular permeability (VP), however, has remained enigmatic. Accordingly, we used an in vivo assay of VP (Miles assay) to study the putative mediators of VEGF/VPF-induced permeability. Methods and Results—VEGF/VPF and positive controls (platelet-activating factor [PAF], histamine, and bradykinin) all increased vascular permeability. Prior administration of the tyrosine kinase inhibitors genistein or herbimycin A prevented VEGF/VPF-induced permeability. Placenta growth factor, which binds to Flt-1/VEGF-R1 but not Flk-1/KDR/VEGF-R2 receptor tyrosine kinase, failed to increase permeability. Other growth factors such as basic fibroblast growth factor (FGF), acidic FGF, platelet-der...

Anthocyanins in aged blueberry-fed rats are found centrally and may enhance memory.

Abstract: Research has shown that fruits and vegetables containing high levels of polyphenolics (flavonoids) display high total antioxidant activity. Our laboratory found that various fruit and vegetable extracts, particularly blueberry (BB), were effective in reversing age-related deficits in neuronal signaling and behavioral parameters following 8 weeks of feeding, possibly due to their polyphenolic content. However, it was unclear if these phytonutrients were able to directly access the brain from dietary BB supplementation (BBS). The present study examined whether different classes of polyphenols could be found in brain areas associated with cognitive performance following BBS. Thus, 19 month old F344 rats were fed a control or 2% BB diet for 8-10 weeks and tested in the Morris water maze (MWM), a measure of spatial learning and memory. LC-MS analyses of anthocyanins in the diet and subsequently in different brain regions of BBS and control rats were carried out. Several anthocyanins (cyanidin-3-O-beta-galactoside, cyanidin-3-O-beta-glucoside, cyanidin-3-O-beta-arabinose, malvidin-3-O-beta-galactoside, malvidin-3-O-beta-glucoside, malvidin-3-O-beta-arabinose, peonidin-3-O-beta-arabinose and delphinidin-3-O-beta-galactoside) were found in the cerebellum, cortex, hippocampus or striatum of the BBS rats, but not the controls. These findings are the first to suggest that polyphenolic compounds are able to cross the blood brain barrier and localize in various brain regions important for learning and memory. Correlational analyses revealed a relationship between MWM performance in BBS rats and the total number of anthocyanin compounds found in the cortex. These findings suggest that these compounds may deliver their antioxidant and signaling modifying capabilities centrally.

Sarcopenia and Age-Related Changes in Body Composition and Functional Capacity

Abstract: Advancing adult age is associated with profound changes in body composition. One of the most prominent of these changes is sarcopenia, defined as the age-related loss in skeletal muscle mass, which results in decreased strength and aerobic capacity and thus functional capacity. Sarcopenia is also closely linked to age-related losses in bone mineral, basal metabolic rate and increased body fat content. Through physical exercise and training, especially resistance training, it may be possible to prevent sarcopenia and the remarkable array of associated abnormalities, such as type II diabetes, coronary artery disease, hypertension, osteoporosis and obesity. Using an exercise program of sufficient frequency, intensity and duration, it is quite possible to increase muscle strength and endurance at any age. There is no pharmacological intervention that holds a greater promise of improving health and promoting independence in the elderly than does exercise.