Influence of dietary protein intake on whole-body protein turnover in humans.

Methods for measuring rates of protein synthesis and degradation in the whole body of humans with isotopes of carbon and nitrogen are described and attention is drawn to their relative merits and drawbacks for studying the nutritional control of protein metabolism. A review of published work on dietary protein and protein metabolism leads to the conclusion that protein is the major dietary determinant of whole-body protein turnover rates, and that energy intake is comparatively unimportant. Dietary protein affects protein turnover at two levels: an immediate response to the intake of protein in meals and a longer-term adaptation after a change in protein intake. An increase in the level of dietary protein enhances the response to meals, which mainly consists of a decrease in the rate of protein degradation. The adaptation to higher protein intakes involves an increase in the basal (postabsorptive) rates of both synthesis and degradation. Suggestions for future investigation include more detailed studies of the acute and adaptive responses, to facilitate understanding of dietary protein requirements, and the effects of very-high-protein intakes with continued development of techniques for studying protein turnover in individual tissues in humans.     

长期运动对十二指肠黏膜一氧化氮合成和铁贮存的调控效应

目的:观察长期运动对十二指肠黏膜一氧化氮合成和铁贮存的影响及一氧化氮对铁贮存的调节作用。方法:实验于2004-04/09在江苏大学医学院铁代谢研究室完成。①健康雌性SD大鼠40只,随机分为静息组、静息并应用一氧化氮抑制剂组、运动组、运动并应用一氧化氮抑制剂组,每组10只。②静息并应用一氧化氮抑制剂组和运动并应用一氧化氮抑制剂组饮用水中含有一氧化氮抑制剂(1g/L),运动组和运动并应用一氧化氮抑制剂组的大鼠游泳3个月。③3个月后分析各组大鼠血浆铁饱和度,一氧化氮浓度以及十二指肠黏膜一氧化氮含量和非血红素铁含量。结果:实验过程中死亡11只,进入结果分析29只(静息组8只、静息并应用一氧化氮抑制剂组5只、运动组8只、运动并应用一氧化氮抑制剂组8只)。①运动及一氧化氮抑制剂对大鼠血浆铁饱和度和一氧化氮浓度的影响:运动组的血浆铁饱和度低于静息组(P<0.01);运动并应用一氧化氮抑制剂组的血浆铁饱和度低于静息并应用一氧化氮抑制剂组(P<0.05),并且高于运动组(P<0.05)。运动组血浆一氧化氮浓度显著高于静息组(P<0.01);运动并应用一氧化氮抑制剂组的血浆一氧化氮浓度低于运动组(P<0.01),与静息并应用一氧化氮抑制剂组差别不显著(P>0.05)。②运动及一氧化氮抑制剂对大鼠十二指肠黏膜一氧化氮和非血红素铁含量的影响:运动组的十二指肠一氧化氮含量高于静息组(P<0.01);静息并应用一氧化氮抑制剂组的一氧化氮含量低于静息组(P<0.01);运动并应用一氧化氮抑制剂组的一氧化氮含量低于运动组(P<0.01),但高于静息并应用一氧化氮抑制剂组(P<0.01),与静息组差别不显著。与静息组比较,运动组和静息并应用一氧化氮抑制剂组的十二指肠黏膜非血红素铁含量均降低(P<0.05)。结论:静息状态下十二指肠黏膜细胞一氧化氮合成具有较高的紧张性,可能参与维持非血红素铁含量。长期运动可刺激十二指肠黏膜一氧化氮合成,降低铁贮存。但其机制是否涉及运动诱导的一氧化氮的直接作用以及是否参与铁吸收的调节有待于进一步研究。     

DIGITAL ISCHAEMIA: AN UNUSUAL PRESENTATION OF DYSBARISM

SUMMARY Dysbaric symptoms following ascent from a scuba dive are due to symptomatic nitrogen or air emboli with clear patterns of associated injury. This case report highlights an unusual presentation of dysbaric injury treated successfully with a prostacyclin analogue.     

Impact of Body Mass Index on Left Ventricular Function

Background

Obesity is associated with increased cardiovascular morbidity and mortality. A direct effect of isolated obesity on cardiac function is not well established. The study was designed to determine the direct effect of various grades of isolated obesity on echocardiographic indices of systolic and diastolic left ventricular function.

Methods

Fifty one obese and 25 normal weight, serving personnel without any other pathological condition were studied. Group I (n=25) consisted of subjects with normal weight and body mass index (BMI <25kg/m²), Group II (n=34) of overweight subjects (BMI 25-29.9 kg/m²) and Group III (n=17) of obese subjects (BMI >30 kg/m²). Echocardiographic indices of systolic and diastolic function were obtained and dysfunction was assumed when at least two values differed by ≥ 2 SD from the normal weight group.

Result

Ejection fraction, fractional shortening were increased (p<0.05) in Group II and III. Left ventricular dimensions were increased (p< 0.001) but relative wall thickness was unchanged. Systolic dysfunction was not observed in any of the obese patients. The mitral valve pressure half time (p< 0.01), left atrial diameter (p < 0.01) and the deceleration time were increased (p< 0.01) in obese subjects, while other diastolic variables were unchanged. No difference were found between obesity subgroups. Subclinical diastolic dysfunction was more prevalent among obese subjects. BMI correlated significantly with indices of left ventricular systolic and diastolic function.

Conclusion

Subclinical left ventricular diastolic dysfunction was noted in all grades of obesity which correlates with BMI.Key Words: Obesity, Systolic function, Diastolic function, Echocardiography     

Biofunctionalized electrospun silk mats as a topical bioactive dressing for accelerated wound healing

Materials able to deliver topically bioactive molecules represent a new generation of biomaterials. In this article, we describe the use of silk mats, made of electrospun nanoscale silk fibers containing epidermal growth factor (EGF), for the promotion of wound healing processes. In our experiments, we demonstrated that EGF is incorporated into the silk mats and slowly released in a time-dependent manner (25% EGF release in 170 h). We tested these materials using a new model of wounded human skin-equivalents displaying the same structure as human skin and able to heal using the same molecular and cellular mechanisms found in vivo. This human three-dimensional model allows us to demonstrate that the biofunctionalized silk mats, when placed on the wounds as a dressing, aid the healing by increasing the time of wound closure by the epidermal tongue by 90%. The preservation of the structure of the mats during the healing period as demonstrated by electronic microscopy, the biological action of the dressing, as well as the biocompatibility of the silk demonstrate that this biomaterial is a new and very promising material for medical applications, especially for patients suffering from chronic wounds.     

Growth hormone does not affect albumin synthesis in the critically ill

OBJECTIVE: To study the effect of growth hormone (GH) on albumin synthesis in critically ill patients. DESIGN: Prospective randomized controlled study. SETTING: Two intensive care units, university hospital and county hospital, respectively. PATIENTS: Twenty-two critically ill patients in the intensive care unit. INTERVENTIONS: Albumin synthesis was measured twice in each patient, with a 5-day interval. The patients in the control group (n = 11) received standard intensive care unit (ICU) treatment between measurements, whereas those in the GH group (n = 11) also received 0.3 U/kg daily of human recombinant GH. MEASUREMENTS AND RESULTS: Albumin synthesis was measured by labeling with L-[2H5]phenylalanine. In the control group, the fractional synthesis rate (FSR) of albumin was 16.3+/-4.1%/day (mean and SD) in the first measurement and 15.7+/-4.2%/day 5 days later (NS), whereas in the GH group the corresponding values were 17.0+/-4.7%/day and 16.7+/-5.5%/day (NS). The calculated absolute synthesis rates of albumin, based on FSR and intravascular albumin mass, also showed no effect of GH. CONCLUSION: Albumin synthesis rates were consistently higher in the two groups of critically ill patients than previously reported values in healthy subjects. However, GH treatment for 5 days neither stimulated nor inhibited albumin synthesis rates in these critically ill patients.     

Evidence that mitochondrial phosphate is visible in 31P NMR spectra of isolated, perfused rat hearts.

We have previously found (P. B. Garlick, T. R. Brown, R. H. Sullivan and K. Ugurbil, J. Mol. Cell Cardiol. 15, 855-858 (1983)) that two peaks could be observed in the phosphate region of NMR spectra of isolated, perfused rat hearts. Upon valinomycin treatment, an increase in the peak at 2.8 ppm in the phosphate region (phosphocreatine set at -2.52 ppm) had been observed. We have now confirmed our hypothesis that this peak originates from the mitochondrial phosphate by: (i) determination of myocardial mitochondrial phosphate contents using density gradient centrifugation in non-aqueous solvents; and (ii) quantitative electron microscopy of the heart tissue. Thus, we conclude that mitochondrial and cytosolic phosphate can be distinguished from each other in 31P NMR spectra of isolated, perfused rat hearts.     

运动对铁吸收的影响及其作用途径

目的:综合分析运动对铁吸收的影响及其作用途径。资料来源:检索Pubmed1950-01/2006-04有关运动对铁吸收的影响及其作用途径的文献,检索词为“iron absorption,iron metabolism,exercise”。同时检索万方数据库1994-01/2006-03有关运动对铁吸收的影响及其作用途径的文献,检索词为“铁吸收,铁代谢,运动”。资料选择:初选后,有关铁吸收、运动对铁吸收影响及其调节机制的文献被选中。发表于2002年后的文献被优先选择,排除重复实验和Meta分析。资料提炼:检索到9000篇文献,大部分是关于铁吸收调节机制的文献,其中40篇有关运动和铁吸收及其调节机制,30篇作为代表性研究文献被引用。资料综合:运动可导致低铁状态,影响运动能力,这种低铁状态的形成及其调节与铁吸收相关。但是,对于运动如何影响铁吸收存在两种截然相反的观点,一种观点认为运动促进铁吸收;另一种观点认为运动降低铁吸收。最近的研究已经显示运动可能通过机体铁水平、一氧化氮、Hepcidin、促红细胞生成素、低氧以及基因突变(如HFE突变)调节铁吸收。结论:有关运动影响铁吸收的研究仍是初步的,在运动情况下如何调节铁吸收尚有待研究,这对于进一步分析运动诱导的低铁状态的本质以及运动员和运动健身人群是否需要以及如何补充铁具有重要意义。