RESUMEN
BACKGROUND: Sexual violence is a prevalent issue in contemporary society requiring a robust forensic healthcare response. It is critically important that forensic examiners put clinical examination findings into an appropriate evidence-based context. The presence of genital injuries has been shown to increase the likelihood of successful criminal prosecution and report the crime. However, the reported rates of genital injury vary widely in published studies. AIMS AND OBJECTIVES: We aim to critically evaluate and synthesize existing literature on the prevalence of genital injuries in post-pubertal females, examined following sexual violence, with a view to describing the prevalence and characteristics of genital injuries as well as the range of forensic practices employed. METHODS: Three online databases (PubMed, Embase, and Scopus) were systematically searched with key terms. RESULTS: Of the 1224 studies screened, 141 full-text publications met the inclusion criteria. Reported injury prevalence rates varied widely. Details pertaining to forensic examinations included in each study, such as grade of the examiner, type of examination, location of examination, and time interval from assault to examination also varied widely. Injury prevalence was highest in studies where enhanced visualization techniques were utilized. CONCLUSIONS: This systematic review demonstrates that there is no universally agreed standard for documenting genital injuries in cases of sexual violence and highlights the need for standardized approaches and guidelines for assessing, documenting, and reporting these injuries. The review provides robust evidence to support a call for establishing consistent context, terminology, classification systems, and data collection methods to improve the comparability and reliability of future research findings.
Asunto(s)
Víctimas de Crimen , Violación , Delitos Sexuales , Femenino , Humanos , Prevalencia , Reproducibilidad de los Resultados , Genitales/lesionesRESUMEN
BACKGROUND: The COVID-19 pandemic constitutes a social crisis that will have long-term health consequences for much of the global population, especially for adolescents. Adolescents are triply affected as they: 1) are experiencing its immediate, direct effects, 2) will carry forward health habits they develop now into adulthood, and 3) as future parents, will shape the early life health of the next generation. It is therefore imperative to assess how the pandemic is influencing adolescent wellbeing, identify sources of resilience, and outline strategies for attenuating its negative impacts. METHODS: We report the results of longitudinal analyses of qualitative data from 28 focus group discussions (FGDs) with 39 Canadian adolescents and of cross-sectional analyses of survey data from 482 Canadian adolescents gathered between September 2020 and August 2021. FGD participants and survey respondents reported on their: socio-demographic characteristics; mental health and wellbeing before and during the pandemic; pre- and during-pandemic health behaviours; experiences living through a crisis; current perceptions of their school, work, social, media, and governmental environments; and ideas about pandemic coping and mutual aid. We plotted themes emerging from FGDs along a pandemic timeline, noting socio-demographic variations. Following assessment for internal reliability and dimension reduction, quantitative health/wellbeing indicators were analyzed as functions of composite socio-demographic, health-behavioural, and health-environmental indicators. RESULTS: Our mixed methods analyses indicate that adolescents faced considerable mental and physical health challenges due to the pandemic, and were generally in poorer health than expected in non-crisis times. Nevertheless, some participants showed significantly better outcomes than others, specifically those who: got more exercise; slept better; were food secure; had clearer routines; spent more time in nature, deep in-person social relationships, and leisure; and spent less time on social media. CONCLUSIONS: Support for youth during times of crisis is essential to future population health because adolescence is a period in the life course which shapes the health behaviours, socio-economic capacities, and neurophysiology of these future parents/carers and leaders. Efforts to promote resilience in adolescents should leverage the factors identified above: helping them find structure and senses of purpose through strong social connections, well-supported work and leisure environments, and opportunities to engage with nature.
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COVID-19 , Humanos , Adolescente , COVID-19/epidemiología , Pandemias , Estudios Transversales , Reproducibilidad de los Resultados , Canadá/epidemiologíaRESUMEN
Understanding nutrient utilization and partitioning is essential for advancing the efficiency of dairy cattle. Our objective was to determine if dairy cows exposed to a 24-h fasting period differ in heat production (HP) and macronutrient oxidation at different stages of lactation. Twelve primiparous, lactating German Holstein dairy cows were used in a longitudinal study design spanning from 2013 to 2014. Dairy cows were housed in respiration chambers during 3 stages of the lactation cycle: early (mean ± SD; 28.8 ± 6.42 d), mid- (89.4 ± 4.52 d), and late (293 ± 7.76 d) lactation. Individual CO2, O2, and CH4 gas exchanges were measured every 6 min for two 24-h periods, an ad libitum period and fasting period (RES). Blood was sampled at the start and end of the RES period. Gas measurements were used to calculate HP, net carbohydrate oxidation (COX), and net fat oxidation (FOX). Measurements were corrected with metabolic BW (kg of BW0.75; cBW). The RES period for each stage of lactation was further subdivided into the start (RESstart) and end (RESend) by averaging the first and last 2 h of the RES period. The net change was calculated as RESend - RESstart. All energy variables differed among lactation stage within the RES period except for HP/cBW. As expected, COX, COX/cBW, COX/HP, HP, and HP/cBW, were greater at the RESstart compared with RESend, whereas FOX, FOX/cBW, and FOX/HP were greater at the RESend except for FOX and FOX/cBW during mid lactation, which was only a tendency for a difference. The net change for COX, COX/cBW, HP, HP/cBW, and FOX/cBW did not differ among stages of lactation. Despite detecting a tendency for a difference among stage of lactation for FOX, pairwise analysis revealed no differences. Plasma triglyceride, urea, and nonesterified fatty acid concentrations were greater at RESend than RESstart. The net change for plasma glucose, urea, ß-hydroxybutyrate, and nonesterified fatty acid concentrations were greater in early than late lactation. Our results demonstrate that despite differences in absolute measurements of energy variables and plasma metabolites, the change in whole-body macronutrient oxidation and HP as cows' transition from a fed-like state to a starvation-like state during a 24-h fasting period is consistent throughout lactation.
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Metabolismo Energético , Lactancia , Femenino , Bovinos , Animales , Lactancia/metabolismo , Estudios Longitudinales , Ayuno , Nutrientes , Ácidos Grasos no Esterificados , Termogénesis , Dieta/veterinaria , Leche/metabolismoRESUMEN
Improving feed utilization efficiency in dairy cattle could have positive economic and environmental effects that would support the sustainability of the dairy industry. Identifying key differences in metabolism between high and low feed-efficient animals is vital to enhancing feed conversion efficiency. Therefore, our objectives were (1) to determine whether cows grouped by either high or low feed efficiency have measurable differences in net fat and carbohydrate metabolism that account for differences in heat production (HP), and if so, whether these differences also exists under conditions of feed withdrawal when the effect of feeding on HP is minimized, and (2) to determine whether the abundance of mitochondria in the liver can be related to the high or low feed-efficient groups. Ten dairy cows from a herd of 15 (parity = 2) were retrospectively grouped into either a high (H) or a low (L) feed-efficient group (n = 5 per group) based on weekly energy-corrected milk (ECM) divided by dry mater intake (DMI) from wk 4 through 30 of lactation. Livers were biopsied at wk -4, 2, and 12, and blood was sampled weekly from wk -3 to 12 relative to parturition. Blood was subset to be analyzed for the transition period (wk -3 to 3) and from wk 4 to 12. In wk 5.70 ± 0.82 (mean ± SD) postpartum (PP), cows spent 2 d in respiration chambers (RC), in which CO2, O2, and CH4 gases were measured every 6 min for 24 h. Fatty acid oxidation (FOX), carbohydrate oxidation (COX), metabolic respiratory quotient (RQ), and HP were calculated from gas measurements for 23 h. Cows were fed ad libitum (AD-LIB) on d 1 and had feed withdrawn (RES, restricted diet) on d 2. Additional blood samples were taken at the end of the AD-LIB and RES feeding periods in the RC. During wk 4 to 30 PP, H had greater DMI/kg of metabolic body weight (BW0.75), ECM per kilogram of BW0.75 yield, and ECM/DMI ratio, compared with L, but a lower body condition score between wk 4 and 12 PP. In the RC period, we detected no differences in BW, DMI, or milk yield between groups. We also detected no significant group or group by feeding period interactions for plasma metabolites except for Revised Quantitative Insulin Sensitivity Check Index, which tended to have a group by feeding period interaction. The H group had lower HP and HP per kilogram of BW0.75 compared with L. Additionally, H had lower FOX and FOX per kilogram of BW0.75 compared with L during the AD-LIB period. Methane, CH4 per kilogram of BW0.75, and CH4 per kilogram of milk yield were lower in H compared with L, but, when adjusted for DMI, CH4/DMI did not differ between groups, nor did HP/DMI. Relative mitochondrial DNA copy numbers in the liver were lower in the L than in the H group. These results suggest that lower feed efficiency in dairy cows may result from fewer mitochondria per liver cell as well as a greater whole-body HP, which likely partially results from higher net fat oxidation.
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Alimentación Animal , ADN Mitocondrial , Animales , Bovinos , Variaciones en el Número de Copia de ADN , Dieta/veterinaria , Metabolismo Energético , Femenino , Lactancia , Hígado , Leche/metabolismo , Mitocondrias , Embarazo , Estudios Retrospectivos , TermogénesisRESUMEN
Little is known about the spatial origins of auditory nerve (AN) compound action potentials (CAPs) evoked by moderate to intense sounds. We studied the spatial origins of AN CAPs evoked by 2- to 16-kHz tone bursts at several sound levels by slowly injecting kainic acid solution into the cochlear apex of anesthetized guinea pigs. As the solution flowed from apex to base, it sequentially reduced CAP responses from low- to high-frequency cochlear regions. The times at which CAPs were reduced, combined with the cochlear location traversed by the solution at that time, showed the cochlear origin of the removed CAP component. For low-level tone bursts, the CAP origin along the cochlea was centered at the characteristic frequency (CF). As sound level increased, the CAP center shifted basally for low-frequency tone bursts but apically for high-frequency tone bursts. The apical shift was surprising because it is opposite the shift expected from AN tuning curve and basilar membrane motion asymmetries. For almost all high-level tone bursts, CAP spatial origins extended over 2 octaves along the cochlea. Surprisingly, CAPs evoked by high-level low-frequency (including 2 kHz) tone bursts showed little CAP contribution from CF regions ≤ 2 kHz. Our results can be mostly explained by spectral splatter from the tone-burst rise times, excitation in AN tuning-curve "tails," and asynchronous AN responses to high-level energy ≤ 2 kHz. This is the first time CAP origins have been identified by a spatially specific technique. Our results show the need for revising the interpretation of the cochlear origins of high-level CAPs-ABR wave 1. NEW & NOTEWORTHY Cochlear compound action potentials (CAPs) and auditory brain stem responses (ABRs) are routinely used in laboratories and clinics. They are typically interpreted as arising from the cochlear region tuned to the stimulus frequency. However, as sound level is increased, the cochlear origins of CAPs from tone bursts of all frequencies become very wide and their centers shift toward the most sensitive cochlear region. The standard interpretation of CAPs and ABRs from moderate to intense stimuli needs revision.
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Potenciales de Acción , Núcleo Coclear/fisiología , Potenciales Evocados Auditivos del Tronco Encefálico , Animales , Femenino , Cobayas , Masculino , Percepción de la Altura TonalRESUMEN
BACKGROUND: Rural-urban differences and spatial navigation deficits have received much attention in Alzheimer's Disease research. While individual environmental and neighborhood factors have been independently investigated, their integrative, multifactorial effects on Alzheimer's diagnosis have not. Here we explore this "environmental complexity" for predictive power in classifying Alzheimer's from cognitively-normal status. METHODS: We utilized data from the National Alzheimer's Coordinating Center (NACC) uniform data set containing annual visits since 2005 and selected individuals with multiple visits and who remained in their zipcode (N = 22,553). We georeferenced each subject with 3-digit zipcodes of their residences since entering the program. We calculated environmental complexity measures using geospatial tools from street networks and landmarks for spatial navigation in subjects' zipcode zones. Zipcode zones were grouped into two cognitive classes (Cognitively-Normal and Alzheimer's-inclined) based on the ratios of AD and dementia subjects to all subjects in an individual zipcode zone. We randomly selected 80% of the data to train a neural network classifier model on environmental complexity measures to predict the cognitive class for each zone, controlling for salient demographic variables. The remaining 20% served as the test set for performance evaluation. RESULTS: Our proposed model reached excellent classification ability on the testing data: 83.87% accuracy, 95.23% precision, 83.33% recall, and 0.8889 F1-score (F1-score=1 for perfect prediction). The most salient features of "Alzheimer's-inclined" zipcode zones included longer street-length average, higher circuity, and slightly fewer points of interest. Most "cognitively-normal" zipcode zones appeared in or near urban areas with high environmental complexity measures. CONCLUSION: Environmental complexity, reflected in frequency and density of street networks and landmarks features, predicted with high precision the cognitive status of 3-digit zipcode zones based on the etiologic diagnoses and observed cognitive impairment of NACC subjects residing in these zones. The zipcode zones vary widely in size (1.6 km2 to 35,241 km2), and large zipcode zones suffer high spatial heterogeneity. Other proven AD risk factors, such as PM2.5, disperse across zones, and so do individual's activities, leading to spatial uncertainty. Nevertheless, the model classifies diagnosis well, establishing the need for prospective experiments to quantify effects of environmental complexity on Alzheimer's development.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Humanos , Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/psicología , Estudios Prospectivos , Disfunción Cognitiva/diagnóstico , Disfunción Cognitiva/psicología , Aprendizaje AutomáticoRESUMEN
We have suggested recently that the fall in plasma CRF-binding protein (BP) during the last few weeks of pregnancy is a direct effect of association with its ligand because of the rapid decrease in plasma BP concentration seen in normal males reaching a nadir some 15 min after a bolus injection of synthetic CRF. In the present study, we have investigated the physicochemical properties of both natural and recombinant BP by gel filtration under physiological conditions and have shown that association of human CRF to this BP results in an increase in molecular weight consistent with the formation of a dimer form of the BP ligand complex. The dimer is more stable when the interaction occurs in the presence of serum or if a peptide with a higher affinity for the BP is substituted as ligand. Experimental evidence would also suggest that the dimer BP has a higher affinity for ligand than the monomeric form. We suggest that this dimerization occurs in vivo when CRF is released into the bloodstream and provides the trigger that causes the uptake of the complex at specific receptor sites.
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Proteínas Portadoras/química , Proteínas Portadoras/metabolismo , Hormona Liberadora de Corticotropina/metabolismo , Animales , Anticuerpos/farmacología , Sangre , Cromatografía en Gel , Hormona Liberadora de Corticotropina/inmunología , Hormona Liberadora de Corticotropina/farmacología , Ácido Edético/farmacología , Electroforesis en Gel de Poliacrilamida , Humanos , Yodoacetamida/farmacología , Sustancias Macromoleculares , Peso Molecular , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Ovinos , Urotensinas/farmacologíaRESUMEN
This study investigated the effects of tone bursts (1000 Hz, 2000 Hz, and 4000 Hz) in quiet, notch noise, highpass noise, and broadband noise on the identifiability, latency, and amplitude of the auditory brainstem response (wave V). Normal listeners were presented with 40 dB and 80 dB nHL tone bursts having rise-plateau-fall times of 1 msec. Wave V was observed in all subjects at 40 dB and 80 dB nHL for the quiet and noise conditions. The latency findings suggest that responses elicited by the 80 dB nHL tone bursts in quiet were, in part, mediated by regions on the basilar membrane that did not correspond to the center frequency of the tone burst. To increase frequency-specificity, high-level tone bursts (e.g., 80 dB nHL) should be mixed with notch, highpass, or broadband noise. The use of noise conditions for low intensity levels (e.g., 40 dB nHL) does not appear necessary for isolating the response because both the notch and the highpass conditions yielded latencies similar to the quiet condition. Although similar wave V amplitudes were found at all frequencies, amplitudes were smaller for the broadband noise than for the quiet, notch, and highpass conditions. Thus, the latter conditions seem preferred.
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Potenciales Evocados Auditivos del Tronco Encefálico , Audición/fisiología , Ruido , Estimulación Acústica , Adulto , Audiometría , Umbral Auditivo , Femenino , Humanos , MasculinoRESUMEN
The 1990s have seen many health care organizations attempting to merge, acquire, or affiliate with physician groups. Many have failed to provide physicians a stake in the success of the newly formed enterprise, frequently resulting in declining physician productivity, poor morale, and large operating losses. These problems warrant a reexamination of the traditional acquisition model of growth in favor of structures that retain a physician ownership component. This article examines three models of health care organization in which physicians share in the success of the enterprise and compares them in terms of ownership structure, governance, and funds flow.
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Prestación Integrada de Atención de Salud/organización & administración , Modelos Organizacionales , Propiedad , Administración de la Práctica Médica/organización & administración , Prestación Integrada de Atención de Salud/economía , Estudios de Evaluación como Asunto , Consejo Directivo , Sector de Atención de Salud , Convenios Médico-Hospital/economía , Convenios Médico-Hospital/organización & administración , Humanos , Fondos de Seguro , Administración de la Práctica Médica/economía , Corporaciones Profesionales/economía , Corporaciones Profesionales/organización & administración , Estados UnidosRESUMEN
Evaluating the financial terms of capitation contracts and negotiating their nonfinancial provisions are becoming increasingly important responsibilities for healthcare financial managers. To evaluate the financial terms of a contract, financial managers must understand both incremental and replacement pricing strategies. They also must understand when strategic positioning objectives make a capitated plan attractive despite limited financial rewards. Before a contract is accepted, financial managers can take steps to increase its potential profitability by negotiating the nonfinancial provisions that can help control contract expenses. These provisions are related to services to be provided, payment terms, withholds and risk pools, access to data, provision of eligibility data, utilization review and quality assurance procedures, filing of grievances, contract renewal terms, and contract termination.
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Capitación/normas , Administración Financiera de Hospitales/métodos , Programas Controlados de Atención en Salud/economía , Negociación , Servicios Contratados/economía , Toma de Decisiones en la Organización , Estudios de Evaluación como Asunto , Planes de Aranceles por Servicios/economía , Modelos Organizacionales , Estados UnidosRESUMEN
As managed care penetration increases, physician compensation plans need to reflect the current transition from fee-for-service to capitated payment. In choosing the compensation structure that will be most beneficial to the success of the group practice and secure physician buy-in, practices need to assess their mission, goals, and corporate culture. They also need to assess their percentage of capitation to total revenues and develop, when necessary, new compensation pools that reward physicians for a variety of behaviors, such as increased productivity and utilization control. Compensation plans should be fair, flexible, and simple to understand and administer.
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Capitación , Práctica de Grupo/economía , Planes de Incentivos para los Médicos/economía , Salarios y Beneficios/clasificación , Eficiencia Organizacional/economía , Planes de Aranceles por Servicios , Administración Financiera/métodos , Cultura Organizacional , Objetivos Organizacionales , Estados UnidosRESUMEN
To improve the profitability of group practice ownership, some healthcare organizations have structured arrangements to include a form of physician equity. An equity incentive is designed to encourage physician behavior that supports business operations by tying financial reward to overall organizational performance. Three physician-equity models--third-party integration, joint venture management services organization (MSO), and physician-owned practice management company--have used the physician equity incentive with varying degrees of success. The experiences of three healthcare systems that implemented these models demonstrates that strategies often cannot be executed as planned, growth should not be assumed, and the changing healthcare marketplace is unpredictable.
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Práctica de Grupo/economía , Reestructuración Hospitalaria/organización & administración , Modelos Organizacionales , Propiedad , Planes de Incentivos para los Médicos , Connecticut , Práctica de Grupo/organización & administración , Convenios Médico-Hospital , Oregon , Gestión de la Práctica Profesional , Texas , Estados UnidosRESUMEN
Risk arrangements typically fall into one of three categories: primary care capitation, professional services capitation, and global, or full-risk, capitation. Yet, in light of various disadvantages associated with these three methods, such as high administrative costs and inappropriate levels of risk assumed by providers, many healthcare payers and providers are experimenting with alternative payment plans. These alternatives include contact capitation arrangements, under which specialists receive a capitation payment on a per referral basis; open-access arrangements, under which patients do not need a gatekeeper referral to see specialists; and capitation arrangements with quality and hospital utilization bonuses, under which specialists and primary care physicians receive a capitation payment plus the potential for bonuses based on quality and utilization criteria.
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Capitación/clasificación , Programas Controlados de Atención en Salud/economía , Modelos Económicos , Administración de la Práctica Médica/economía , Capitación/tendencias , Programas Controlados de Atención en Salud/organización & administración , Planes de Incentivos para los Médicos , Administración de la Práctica Médica/organización & administración , Calidad de la Atención de Salud , Derivación y Consulta , Mecanismo de Reembolso , Gestión de Riesgos/economía , Gestión de Riesgos/métodos , Estados Unidos , Revisión de Utilización de RecursosRESUMEN
Medical practitioners are occasionally requested to provide opinions on people's ability to make a valid will. Moreover, if a will is challenged subsequent to the death of the testator, the evidence of a medical practitioner may be pivotal to a decision by the courts on the validity of the will. Litigation can be avoided if a well-founded expert opinion, based on thorough medical assessment, is available. The combination of an aging population, a consequent increase in the prevalence of dementia, an increase in per capita wealth, and more complex family structures with increasing rates of divorce and remarriage, is likely to result in a greatly increased frequency of demands on medical practitioners to provide opinion in this regard. In order for the result of a medical assessment of testamentary capacity to be legally valid, it is imperative that medical practitioners have adequate guidance on what is expected of them in their assessment. As there is no standardised tool for medical practitioners to which to refer, a synthesis of relevant literature is presented to guide medical practitioners in the assessment of testamentary capacity. Medical practitioners' roles in this medico-legal process are elaborated and elucidated.
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Competencia Mental/legislación & jurisprudencia , Rol del Médico , Testamentos/legislación & jurisprudencia , Intoxicación Alcohólica/psicología , Coerción , Toma de Decisiones , Deluciones/psicología , Demencia/psicología , Función Ejecutiva , Humanos , Trastornos Mentales/psicología , Pruebas NeuropsicológicasRESUMEN
OBJECTIVE: Several lines of evidence suggest that pathologic changes underlying Alzheimer disease (AD) begin years prior to the clinical expression of the disease, underscoring the need for studies of cognitively healthy adults to capture these early changes. The overall goal of the current study was to map the cortical distribution of ß-amyloid (Aß) in a healthy adult lifespan sample (aged 30-89), and to assess the relationship between elevated amyloid and cognitive performance across multiple domains. METHODS: A total of 137 well-screened and cognitively normal adults underwent Aß PET imaging with radiotracer (18)F-florbetapir. Aß load was estimated from 8 cortical regions. Participants were genotyped for APOE and tested for processing speed, working memory, fluid reasoning, episodic memory, and verbal ability. RESULTS: Aß deposition is distributed differentially across the cortex and progresses at varying rates with age across cortical brain regions. A subset of cognitively normal adults aged 60 and over show markedly elevated deposition, and also had a higher rate of APOE ε4 (38%) than nonelevated adults (19%). Aß burden was linked to poorer cognitive performance on measures of processing speed, working memory, and reasoning. CONCLUSIONS: Even in a highly selected lifespan sample of adults, Aß deposition is apparent in some adults and is influenced by APOE status. Greater amyloid burden was related to deleterious effects on cognition, suggesting that subtle cognitive changes accrue as amyloid progresses.
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Envejecimiento/metabolismo , Péptidos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Cognición , Adulto , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/metabolismo , Encéfalo/diagnóstico por imagen , Trastornos del Conocimiento/diagnóstico por imagen , Trastornos del Conocimiento/metabolismo , Femenino , Humanos , Masculino , Memoria , Persona de Mediana Edad , Pruebas Neuropsicológicas , CintigrafíaRESUMEN
Immunization rates among the very poor are critically low. The solution to improving rates requires technological tracking of immunizations linked to extensive home visiting outreach services as well as physician and member support services to increase compliance with recommended immunization schedules. This paper describes the development and implementation of a comprehensive immunization program which incorporates these strategies for members of a Medicaid managed care organization. Analysis of preliminary data provides some indication of the value of the tracking system and the effectiveness of incentives and home visiting on member compliance with immunizations.
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Programas de Inmunización/organización & administración , Asociaciones de Práctica Independiente/organización & administración , Medicaid/organización & administración , Cooperación del Paciente , Contabilidad , Preescolar , Accesibilidad a los Servicios de Salud , Humanos , Programas de Inmunización/economía , Programas de Inmunización/estadística & datos numéricos , Asociaciones de Práctica Independiente/economía , Lactante , Sistemas de Información Administrativa , Philadelphia , Técnicas de Planificación , Pobreza , Desarrollo de Programa , Sistemas Recordatorios , Estados UnidosRESUMEN
Neurotransmission at chemically transmitting synapses requires calcium-mediated fusion of synaptic vesicles with the presynaptic membrane. Utilizing ultrastructural information available for the crustacean excitatory neuromuscular junction, we developed a model that employs the Monte Carlo simulation technique to follow the entry and movement of Ca2+ ions at a presynaptic active zone, where synaptic vesicles are preferentially docked for release. The model includes interaction of Ca2+ with an intracellular buffer, and variable separation between calcium channels and vesicle-associated Ca(2+)-binding targets that react with Ca2+ to trigger vesicle fusion. The end point for vesicle recruitment for release was binding of four Ca2+ ions to the target controlling release. The results of the modeling experiments showed that intracellular structures that interfere with Ca2+ diffusion (in particular synaptic vesicles) influence recruitment or priming of vesicles for release. Vesicular recruitment is strongly influenced by the separation distance between an opened calcium channel and the target controlling release, and by the concentration and binding properties of the intracellular buffers, as in previous models. When a single opened calcium channel is very close to the target, a single synaptic vesicle can be recruited. However, many of the single-channel openings actuated by a nerve impulse are likely to be ineffective for release, although they contribute to the buildup of total intracellular Ca2+. Thus, the overall effectiveness of single calcium channels in causing vesicles to undergo exocytosis is likely quite low.
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Método de Montecarlo , Unión Neuromuscular/fisiología , Vesículas Sinápticas/fisiología , Animales , Astacoidea , Calcio/metabolismo , Canales de Calcio/fisiología , PermeabilidadRESUMEN
OBJECTIVE: To test the hypothesis that entorhinal cortex (EC) volume decreases at a slower rate than the hippocampal (HC) volume in healthy adults, and to examine whether the rate of shrinkage increases with age. METHODS: Volumes of the HC and EC were measured twice on MRI scans of 54 healthy adults (aged 26 to 82 years), with an average interval of 5 years. RESULTS: Markedly different age trends were noted in the examined regions. The EC showed no age-related differences on both occasions and only minimal age-related change (0.33%/y). By contrast, the HC exhibited significant age-related differences at baseline and at follow-up evaluation and decreased at a faster pace of 0.86%/y. Older participants (aged > or = 50 years) showed increased annual shrinkage of the HC (1.18%) and EC shrinkage (0.53%/y). The rate of HC volume loss significantly exceeded that of the EC. No EC shrinkage and modest HC volume reduction were observed in people aged <50 years. CONCLUSIONS: Age-related shrinkage occurs in the medial temporal lobes of healthy adults, with significant hippocampal decline and minimal entorhinal changes. In both regions, the rate of decline accelerates with age, although the role of pathologic factors in age-related increase of volume loss merits further investigation.