Ca2+ and Sr2+ activation: Comparison of cardiac and skeletal muscle contraction models

The mechanism of contraction in rabbit fast-twitch, and bovine and rabbit cardiac muscle was examined using functionally skinned fibers, ATPase activity of myofibrils, and cardiac or skeletal troponintropomyosin regulated actin heavy meromyosin. The Ca²⁺ and Sr²⁺ activation properties for the different measures of contraction were evaluated. (1) Tension in rabbit and bovine cardiac skinned fibers and rabbit cardiac myofibrillar ATPase were activated equally well by either Ca²⁺ or Sr²⁺. By contrast, rabbit adductor magnus (fast-twitch) skinned fibers required substantially higher [Sr²⁺] than [Ca²⁺] for activation, as did rabbit myofibrils from back muscle (fast-twitch). (2) Substantially more Sr²⁺ than Ca²⁺ was also required for activation of skeletal muscle actin heavy meromyosin ATPase, controlled by either the skeletal or cardiac troponin-tropomyosin complex, similar to the activation of fast-twitch muscle. (3) The absence of correlation between the divalent cation selectivity properties of actin heavy meromyosin ATPase controlled by cardiac troponin-tropomyosin and cardiac muscle tension or myofibrillar ATPase activation by Ca²⁺ and Sr²⁺ suggests that troponin, if primarily responsible for the activation of cardiac muscle, has very different in vivo and in vitro binding properties. (4) The close correlation between percentage of maximal Ca²⁺- and Sr²⁺-activated myofibrillar ATPase and tension in skinned fibers strongly justifies the use of myofibrillar ATPase, in contrast to a reconstituted troponin-tropomyosin actin heavy meromyosin ATPase system, as a biochemical measure of contraction.     

Differential effects of neonatal denervation on intrafusal muscle fibers in the rat

The response of developing muscle spindles to denervation was studied by sectioning the nerve to the medial gastrocnemius muscle of rats at birth. The denervated spindles were examined daily throughout the first postnatal week for changes in ultrastructure and expression of several isoforms of myosin heavy chain (MHC). Each of the three different types of intrafusal muscle fiber exhibited a different response to denervation. Within 5 days after the nerve section nuclear bag₂ fibers degenerated completely; nuclear bag₁ fibers persisted, but ceased to express the spindle-specific slow-tonic MHC isoform and thereby could not be differentiated from extrafusal fibers; nuclear chain fibers did not form. The capsules of spindles disassembled, hence spindles or their remnants could no longer be identified 1 week after denervation. Neonatal deefferentation has little effect on these features of developing spindles, so removal of afferent innervation is presumably the factor that induces the loss of spindles in denervated muscles. Degeneration of the bag₂ fiber, but not bag₁ or extrafusal fibers, reflects a greater dependence of the bag₂ fiber than the bag₁ fiber on afferent innervation for maintenance of its structural integrity. This difference in response of the two types of immature bag fiber to denervation might reflect an origin of the bag₂ fibers from a lineage of myogenic cells distinct from that giving rise to bag₁ or extrafusal fibers, or a difference in the length of contact with afferents between the two types of bag fiber prior to nerve section.     

Mutational Analysis of the Rhodopsin Gene in Sector Retinitis Pigmentosa

Background: To determine the role of rhodopsin (RHO) gene mutations in patients with sector retinitis pigmentosa (RP) from Northern Ireland.

Design: A case series of sector RP in a tertiary ocular genetics clinic.

Participants: Four patients with sector RP were recruited from the Royal Victoria Hospital (Belfast, Northern Ireland) and Altnagelvin Hospital (Londonderry, Northern Ireland) following informed consent.

Methods: The diagnosis of sector RP was based on clinical examination, International Society for Clinical Electrophysiology of Vision (ISCEV) standard electrophysiology, and visual field analysis. DNA was extracted from peripheral blood leucocytes and the coding regions and adjacent flanking intronic sequences of the RHO gene were polymerase chain reaction (PCR) amplified and cycle sequenced.

Main Outcome Measure: Rhodopsin mutational status.

Results: A heterozygous missense mutation in RHO (c.173C?>?T) resulting in a non-conservative substitution of threonine to methionine (p. Thr58Met) was identified in one patient and was absent from 360 control individuals. This non-conservative substitution (p.Thr58Met) replaces a highly evolutionary conserved polar hydrophilic threonine residue with a non-polar hydrophobic methionine residue at position 58 near the cytoplasmic border of helix A of RHO.

Conclusions: The study identified a RHO gene mutation (p.Thr58Met) not previously reported in RP in a patient with sector RP. These findings outline the phenotypic variability associated with RHO mutations. It has been proposed that the regional effects of RHO mutations are likely to result from interplay between mutant alleles and other genetic, epigenetic and environmental factors.     

Harmony in health sector: a requirement for effective healthcare delivery in Nigeria

Harmony is defined as the pleasing combination of elements of a system to form an all-inclusive, all involving and more productive team. The aim of this present review was to investigate the factors militating against harmony among healthcare professional in the Nigerian healthcare delivery system. This review was carried out by searching through literature on the topic that bother on harmony among health professions in the health sector. Literature search and reports from previous studies indicates that harmony among health workers is pivotal to improving the health indices. However, available evidence suggests that unlike in the developed world, health care professionals do not collaborate well together in Nigeria because of the claim of superiority of a particular health professional over others. This has often resulted in inter-professional conflict which is threatening to tear the health sector apart to the detriment of the patients. The Nigeria health system should be based on team work. Health professionals from a variety of disciplines should work together to deliver the best possible healthcare services to all Nigerians. All members of the team are equally valuable and essential to the smooth running of hospitals. Hospitals should ideally be headed by health administrators or by a qualified member of any of the professions in the health sector.     

A型肉毒素内括约肌侧方注射+病灶扇形小切口切扩引流术治疗Ⅱ、Ⅲ期肛裂的临床研究

目的评价A型肉毒素内括约肌侧方注射+病灶扇形小切口切扩引流术治疗Ⅱ、Ⅲ期肛裂的安全性和有效性,探索其手术操作步骤及要点,介绍一种治疗肛裂的新手术方式。方法采用随机、平行、对照的临床试验方法,将纳入病例随机分为试验组和对照组,试验组行A型肉毒素内括约肌侧方注射+病灶扇形小切口切扩引流术,对照组行肛裂切除扩创术加部分内括约肌侧方切断术。将2组安全性指标(包括肛门狭窄、肛门失禁、急性尿潴留、术后疼痛的发生及直肠肛管测压结果)和有效性指标(包括痊愈率、手术时间、切口创面愈合时间、切口愈合分级、切口愈合后瘢痕面积大小)进行比较。结果 2组均无肛门狭窄和急性尿潴留发生;对照组肛门失禁评分高于试验组,但差异无统计学意义(P>0.05)。试验组术后(术后24 h、术后第1次排便及术后1周)疼痛评分明显低于对照组(P<0.01)。术前、术后直肠肛管测压结果 2组间比较差异无统计学意义(P>0.05)。试验组痊愈率高于对照组(P<0.05),手术时间及切口创面愈合时间均明显短于对照组(P<0.01),切口愈合优于对照组(P<0.05),切口愈合后瘢痕面积小于对照组(P<0.01)。结论 A型肉毒素内括约肌侧方注射+病灶扇形小切口切扩引流术具有治愈率高、切口愈合时间短、切口愈合后瘢痕面积小、操作快捷、手术微创化等优点;且在肛门外形和功能保护方面优于对照组,本术式具有较好的临床疗效和安全性。     

Outcomes of Donation After Circulatory Death Heart Transplantation in Australia

Background

Transplantation of hearts retrieved from donation after circulatory death (DCD) donors is an evolving clinical practice.

Trends in Binge and Heavy Drinking,Alcohol-Related Problems,and Combat Exposure in the U.S. Military

Population-based Department of Defense health behavior surveys were examined for binge and heavy drinking among U.S. active duty personnel. From 1998–2008, personnel showed significant increases in heavy drinking (15% to 20%) and binge drinking (35% to 47%). The rate of alcohol-related serious consequences was 4% for nonbinge drinkers, 9% for binge drinkers, and 19% for heavy drinkers. Personnel with high combat exposure had significantly higher rates of heavy (26.8%) and binge (54.8%) drinking than their counterparts (17% and 45%, respectively). Heavy and binge drinking put service members at high risk for problems that diminish force readiness and psychological fitness.     

Treatment adherence following national antiretroviral rollout in South Africa

The national antiretroviral (ARV) programme in South Africa commenced in 2004. ARV drugs became readily available to all South Africans due to the concerted efforts of ‘access to all’ campaigns. This study investigates medication adherence among a sample of South Africans after the ARV rollout in order to gain insight into the adherence challenges they face. A semi-structured questionnaire was completed by 439 participants from across the country. The results show that only 40% of the respondents were able to reach the optimum adherence level of 90% or above. The patients who displayed below-optimum adherence often had not been part of an ARV-preparation programme, did not have HIV-treatment supporters, lacked general knowledge about drug adherence, and felt unsupported by healthcare providers in their day-to-day effort to adhere to their medications. They often had no money for food or transportation, ran out of ARVs for various reasons, suffered from HIV-treatment fatigue, battled with depression, abused alcohol, could not disclose to sexual partners that they were on ARVs, and often had to hide or skip ARV dosages because they feared stigma and discrimination. Suggestions to assist patients to adhere to their ARV medications are made.     

Characterization of Printed Circuit Boards for Metal and Energy Recovery after Milling and Mechanical Separation

The proper disposal of electrical and electronic waste is currently a concern of researchers and environmental managers not only because of the large volume of such waste generated, but also because of the heavy metals and toxic substances it contains. This study analyzed printed circuit boards (PCBs) from discarded computers to determine their metal content and characterized them as solid waste and fuel. The analysis showed that PCBs consist of approximately 26% metal, made up mainly of copper, lead, aluminum, iron and tin, as well as other heavy metals such as cadmium and nickel. Comparison with the results of other studies indicated that the concentration of precious metals (gold and silver) has declined over time. Analysis of the leachate revealed high concentrations of cadmium and lead, giving the residue the characteristics of hazardous waste. After milling the PCBs, we found that larger amounts of metal were concentrated in smaller fractions, while the lightest fraction, obtained by density separation, had a gross calorific value of approximately 11 MJ/kg, although with a high ash content. Milling followed by density separation proved potentially useful for recovery of metals and energy-rich fractions.