The Interaction of Compliance and Activation on the Force-Length Operating Range and Force Generating Capacity of Skeletal Muscle: A Computational Study using a Guinea Fowl Musculoskeletal Model.

A muscle's performance is influenced by where it operates on its force-length (F-L) curve. Here we explore how activation and tendon compliance interact to influence muscle operating lengths and force-generating capacity. To study this, we built a musculoskeletal model of the lower limb of the guinea fowl and simulated the F-L operating range during fixed-end fixed-posture contractions for 39 actuators under thousands of combinations of activation and posture using three different muscle models: Muscles with non-compliant tendons, muscles with compliant tendons but no activation-dependent shift in optimal fiber length (L0), and muscles with both compliant tendons and activation-dependent shifts in L0. We found that activation-dependent effects altered muscle fiber lengths up to 40% and increased or decreased force capacity by up to 50% during fixed-end contractions. Typically, activation-compliance effects reduce muscle force and are dominated by the effects of tendon compliance at high activations. At low activation, however, activation-dependent shifts in L0 are equally important and can result in relative force changes for low compliance muscles of up to 60%. There are regions of the F-L curve in which muscles are most sensitive to compliance and there are troughs of influence where these factors have little effect. These regions are hard to predict, though, because the magnitude and location of these areas of high and low sensitivity shift with compliance level. In this study we provide a map for when these effects will meaningfully influence force capacity and an example of their contributions to force production during a static task, namely standing.

A Interação de Conformidade e Ativação na Faixa de Operação Força-Comprimento e Capacidade de Geração de Força do Músculo Esquelético: Um Estudo Computacional Usando um Modelo Musculoesquelético de Galinhas-D'angola O desempenho muscular é influenciado por onde ele opera na sua curva de força-comprimento. Aqui, exploramos como a ativação e a conformidade do tendão interagem para influenciar os comprimentos musculares e a capacidade de geração de força. Para estudar isso, construímos um modelo musculoesquelético do membro inferior da galinha-d'angola e simulamos a faixa de operação força-comprimento durante contrações fixas de postura e extremidade para 39 atuadores sob milhares de combinações de ativação e postura usando três modelos musculares diferentes: músculos com tendões não-complacentes, músculos com tendões complacentes, mas sem desvio dependente de ativação no comprimento ideal de fibra (L0), e músculos com tendões complacentes e desvios dependentes de ativação em L0. Descobrimos que os efeitos dependentes da ativação alteraram os comprimentos da fibra muscular em até 40% e aumentaram ou diminuíram a capacidade de força em até 50% durante as contrações de extremidade fixas. Normalmente, os efeitos de ativação e conformidade reduzem a força muscular e são dominados pelos efeitos de complacência do tendão em altas ativações. Em baixa ativação, no entanto, desvios dependentes de ativação em L0 são igualmente importantes e podem resultar em mudanças de força relativas de até 60% para músculos de baixa complacência. Existem regiões da curva de força-comprimento em que os músculos são mais sensíveis à complacência e há baixas de influência onde esses fatores têm pouco efeito. Essas regiões são difíceis de prever porque a magnitude e a localização dessas áreas de alta e baixa sensibilidade mudam com o nível de conformidade. Neste estudo, fornecemos um mapa para quando esses efeitos influenciarão significativamente a capacidade de força e um exemplo de suas contribuições para a produção de forças durante uma tarefa estática, ou seja, em pé. Translated to Portuguese by G. Sobral (gabisobral@gmail.com).

Accurate transcription of a cloned gene from Babesia bovis in Saccharomyces cerevisiae.

Two cloned chromosomal segments of the hemoprotozoan Babesa bovis bearing genes from the polymorphic locus designated BabR were inserted into plasmid vector YCp19, cloned in Escherichia coli and then introduced into Saccharomyces cerevisiae. Both genes were transcribed producing poly(A+) RNAs. In at least one case, the transcript was very similar if not identical to that produced in B. bovis. It is therefore possible that S. cerevisiae can recognize at least some hemoprotozoan promoter and poly(A+)-addition signals.

Failure of halo vest to prevent in vivo motion in patients with injured cervical spines.

Forty-two patients with cervical spine injuries immobilized in halo vests were studied prospectively to determine in vivo vertebral segmental motion. Lateral radiographs taken in the supine and upright positions within 5 days of injury demonstrated intervertebral motion. At noninjured levels, the positional change accounted for an average 3.9 degrees of angulation with the greatest motion occurring between the occiput and C1 (8.0 degrees). At the injured levels, sagittal plane angulation averaged 7.0 degrees and translation averaged 1.7 mm between the two positions. Fracture site motion did not correlate with either the fracture type or the injury level. Fracture site motion greater than 3 degrees of angulation or 1 mm of translation was observed at 35 (77%) of 45 injured levels. When treating patients who have unstable cervical injuries with halo vests, supine and upright radiographs should be obtained. If excessive motion is present, alternative methods of treatment should be considered.

Avoiding common pitfalls in qualitative data collection and transcription.

The subjective nature of qualitative research necessitates scrupulous scientific methods to ensure valid results. Although qualitative methods such as grounded theory, phenomenology, and ethnography yield rich data, consumers of research need to be able to trust the findings reported in such studies. Researchers are responsible for establishing the trustworthiness of qualitative research through a variety of ways. Specific challenges faced in the field can seriously threaten the dependability of the data. However, by minimizing potential errors that can occur when doing fieldwork, researchers can increase the trustworthiness of the study. The purpose of this article is to present three of the pitfalls that can occur in qualitative research during data collection and transcription: equipment failure, environmental hazards, and transcription errors. Specific strategies to minimize the risk for avoidable errors will be discussed.

An outbreak of cysticercosis in feedlot cattle.

An outbreak of cysticercosis (infestation with the larvae of Taenia saginata) occurred in feedlot cattle in Ontario in 1986. Two hundred and thirty-three of 271 steers were confirmed histologically to be positive for cysticerci. Nineteen (8.2%) animals had viable cysticerci, 87 (37.3%) had degenerated cysticerci, 77 (33.0%) had mineralized cysticerci, and 50 (21.5%) steers had lymphoid granulomas consistent with cysticercosis. Three viable cysticerci were partly evaginated and one degenerate cysticercus was fully evaginated.

Defining the concept of self-care.

Self-care is a concept frequently referred to in both the theory and the clinical practice of nursing. This article presents an overview of self-care theory as described by Henderson, Hall, and Orem. Self-care theory operates on the assumption that all individuals have a need to care for themselves. While this premise may be true, it poses difficult questions for the nurse who must intervene with patients who refuse to achieve their maximum level of independence. When a disease process occurs that alters self-image, some patients (particularly elderly females who have cared for others most of their adult lives) may consciously opt to become the ones cared for. This choice gives them a temporary sense of control over a situation in which they feel helpless. When nursing care is directed toward returning control of the situation to the patient, the process of self-care and healing can begin.

Using focus groups in rehabilitation nursing.

The purpose of this paper is to describe the research method of focus groups and give an example of how it could be used to advance rehabilitation nursing in the area of poststroke adaptation or recovery. Stroke is a leading cause of death and disability in elderly Americans. Although much is known about the physical effects and treatments of stroke, little has been published on the adaptive behaviors or recovery process of stroke survivors. The focus-group technique can provide an "insider's" view of the adaptive behaviors of stroke survivors and is a cost-effective way to generate rich qualitative data to guide nursing practice.

The roles of the pastor in the interdisciplinary rehabilitation team.

People with chronic illnesses and functional limitations may face a lifetime of changes and adjustments. Often, the onset of a long-term illness or disease requires a person to rethink values and develop new coping strategies in order to adapt to a life-changing event. At such times, people may draw on sources of spiritual support, finding comfort from a pastor or other clergy. This article describes key roles taken by the clergy who provide these services. Patients discharged from inpatient rehabilitation units have reported using faith and prayer as effective coping strategies. Religious faith can have a positive influence on emotions and may be directly related to improved functional ability. Disciplines of faith, such as solitude, silence, and meditation, may promote mental health. Although this article presents information from a Christian church perspective, readers should note that services should be considered from a wide range of spiritual representatives.

Developing and implementing a stroke education series for patients and families.

Stroke is the third leading cause of death and the major reason for disability in American adults (Sullivan, 1992). Stroke can be a recurrent disease, but most strokes are preventable. Patient and family education about stroke is a vital link in eliminating the knowledge deficit that can help lead to stroke. This article describes the process of developing and implementing a stroke education program that involves both patients and their significant others. In 1990, rehabilitation nurses at St. Margaret Mercy Healthcare Centers in Hammond, IN, identified 11 essential areas for education and grouped them into six 1-hour teaching sessions. A program was developed and held weekly for a trial period of 3 months. It was so well received that it continues to be a permanent part of the rehabilitation program. Such structured teaching in a relaxed atmosphere better prepares patients for discharge and eases the transition to the home environment.

Effectiveness of a nurse-managed follow-up program for rehabilitation patients after discharge.

Former patients in a rehabilitation unit at a large Midwestern hospital continued to actively seek services provided by the inpatient nursing staff, primarily through telephone contact, long after their discharge. A proactive formal follow-up program managed by an advanced practice nurse in rehabilitation was proposed as a better means of providing continuing care for rehabilitation patients after discharge. To examine the efficacy of the nurse-managed follow-up program, a randomized clinical trial was conducted. One hundred patients were randomly assigned to either the intervention group or the control group. Comparisons were made between the two groups on several outcome measures at 4 months after discharge. Outcomes included Functional Independence Measure (FIM) instrument scores, complication rates, rehospitalizations, and anxiety levels. The organizational outcomes included number and types of calls to staff, as well as time spent by staff nurses and social workers. The results indicated significant differences between the intervention and control groups in terms of anxiety levels, the number of calls made to the unit, and the amount of time spent by staff nurses and social workers.

Psychoanalytic principles in psychosocial rehabilitation.

Major mental symptomology in schizophrenic patients is alleviated when isolation and withdrawal are replaced by improved object relationships. This can best be accomplished through the enhancement of social, emotional, and environmental support systems. Psychosocial rehabilitation, that is, the establishment of a corrective living situation for emotionally isolated individuals, is a dynamic process. Staff in psychosocial centers are presented with unusual challenges and opportunities for helping people. Freudian psychoanalytic theory helps explain the causation of major mental symptomatology in schizophrenics as well as the mechanisms for the alleviation of those symptoms. It is postulated that the basic defect is exaggerated narcissistic libido and deficient cathexis of libido onto objects, which is accompanied by dammed-up libido. Like a festering boil, the dammed-up libido continues to exert noxious and deleterious effects, ultimately by way of chemical and neuronal pathways presently not well understood. The release of the dammed-up libido through improved object relationships is accompanied by lessening symptomatology and improved functioning. Indiscriminate and prolonged utilization of psychotropic medication is antitherapeutic in that it prevents delabeling, interferes with the resocialization process, and inhibits ego growth and development.