A breathing lung phantom for 81mKr lung ventilation studies its use in dosimetry and quality control

The construction of a breathing lung phantom that can be used to measure the amount of radioactive gas in the lungs as well as to determine the absorbed dose is described. For a lung ventilation study that consists of 6 views of 300 kents each, an effective dose equivalent of 50 Sv was calculated. The phantom is also suitable for comparison of different generator systems.     

Analgesic dose-response relation in cervical epidural block

The relationship between the age and the spread of analgesia from different epidural anesthetic doses was examined by studying analgesic dose responses in cervical epidural analgesia. Two different anesthetic doses (5ml or 10ml) of 2% mepivacaine were injected into the cervical epidural space at a constant pressure (80mmHg) using an intravenous apparatus, and the spread of analgesia to pinprick was assessed. The significant correlation was found between the patients age and the number of spinal segments blocked (5ml:r = 0.8498, P < 0.01, 10ml:r = 0.5988, P < 0.01). The inverse linear relationship was found between the patients age and the segmental dose requirement (5ml:r = –0.6754, P < 0.01, 10ml:r = –0.5784, P < 0.01). Patients under 39 years of age showed a direct relationship between the dose injected and the number of spinal segments blocked, enabling prediction of the number of segments blocked with a given dose of local anesthetic. Doubling the epidural dose approximately doubled the number of spinal segments blocked. The analgesic dose-response relation in patients over 60 years of age differed from that in patients under 39 years of age and doubling the epidural dose did not double the number of spinal segments blocked. Progressively more extensive analgesia was obtained from a given dose of local anesthetic with advancing age. It was difficult to limit the extent of analgesia by injecting a smaller dose of local anaesthetic in the elderly.(Hirabayashi Y, Matsuda I, Inoue S et al.: Analgesic dose-response relation in cervical epidural block. J Anesth 2: 22–27, 1988)     

2022年欧洲临床营养与代谢学会和欧洲肥胖研究学会《肌肉减少性肥胖的定义和诊断标准共识》解读及启示

近年来,欧洲临床营养与代谢学会（ESPEN）和欧洲肥胖研究学会（EASO）的专家组成员对肌肉减少性肥胖（SO）的相关研究进行了系统地评价。2022年2月,ESPEN和EASO共同发布了《肌肉减少性肥胖的定义和诊断标准共识》,该共识对SO的定义和诊断进行了详细的阐述,旨在就SO的定义和诊断达成共识,为研究人员和临床工作者提供参考依据,以推进SO预防和治疗的发展。本文主要对《肌肉减少性肥胖的定义和诊断标准共识》中SO的定义,诊断流程包括筛查、诊断和分期标准,拟采用的方法和相关的参数等主要内容进行梳理和解读,旨在为国内医务工作者提供更多参考。     

Pharmacokinetics and tolerance of a new penem antibiotic,FCE 22101, in healthy volunteers after a single intravenous dose

Summary The clinical tolerance and pharmacokinetics of FCE 22101 (sodium (5R, 6S)-6-[(1R)-hydroxyethyl]-2-carbamoyloxymethyl-2-penem-3-carboxylate), a new penem antibiotic, have been studied after giving a single i.v. dose of 4 mg·kg^–1 to ten healthy male volunteers. The pharmacokinetics was estimated according to a two-compartment open model. The peak plasma concentration (C_max) was 15.5 (1.08) µg·ml^–1, mean (SEM). FCE 22101 was rapidly cleared from the systemic circulation [ =44.2 (4.2) min; CL=7.21 (0.47) ml·kg^–1·min^–1]. The mean apparent volume of distribution at steady-state was 246 (16.9) ml·kg^–1. The mean residence time relative to the 10 min infusion was 39.4 (1.5)min. Urinary recovery of FCE 22101 showed wide inter-subject variation, ranging from 10.2 to 53.6% of the dose. No subject complained of adverse effects.     

Lactic dehydrogenase virus (LDV) impairs the antigen-presenting capacity of macrophages yet fails to affect their phagocytic activity

The effect of acute infection of mice with lactic dehydrogenase virus (LDV) on two major functions of peritoneal macrophages was tested. Using a macrophage-dependent T cell proliferative assay to test the antigen-presenting capacity of LDV-infected macrophages we found that LDV impairs the capacity of antigen-presenting cells to trigger memory T lymphocytes. Endocytosis of antigen by LDV-infected macrophages was similar to that of uninfected cells. In addition, the proportion of intracellular antigen versus membrane-bound antigen in LDV-infected cells were similar to that observed in uninfected mice. It appears therefore, that the impaired immunogenic effect of LDV-infected macrophages results from reduced immunogenicity of the membrane-bound antigen.Testing the phagocytic activity of peritoneal macrophages we found that the uptake of radiolabeled antibody-coated sheep erythrocytes or bacteria (E. coli) by infected cells was similar to that by uninfected macrophages. In addition, LDV failed to affect the ability of peritoneal macrophages in a nitroblue tetrazolium reduction reaction which serves as an alternative parameter for measuring phagocytic activity. Our results support the assumption that LDV, which probably propagates in the cells of the reticuloendothelial system, impairs some of the immunogenic functions of macrophages and thereby affects macrophage-dependent immune responses.     

A natriuresis receptor at the carotid bifurcation specifically activated by oxytocin

Summary Rats anaesthetised with Inactin, body temp. maintained at 37°C, were infused with mannitol-saline until both urine flow rate and conductivity reached a balanced state. In separate experiments under analogous conditions cardiac output was measured by dye dilution and organ flow rates by⁸⁶Rb distribution. Doses of oxytocin of 3 ng or less, injected at or just below the carotid bifurcation, caused a highly significant natriuresis with increased tubular rejection, but no measureable haemodynamic changes. The same oxytocin dose given into the internal or external carotid artery above the bifurcation caused neither haemodynamic changes nor natriuresis. Injection of vasopressin, angiotensin and -MSH at the sensitive site did not result in natriuresis in the same dosage range. Section of the sinus nerve significantly decreased the natriuretic response to oxytocin. It is suggested that the carotid body contains a specific oxytocin receptor capable of eliciting natriuresis in the rat.     

A Field-Compatible Method for Interpolating Biopotentials

Mapping of bioelectric potentials over a given surface (e.g., the torso surface, the scalp) often requires interpolation of potentials into regions of missing data. Existing interpolation methods introduce significant errors when interpolating into large regions of high potential gradients, due mostly to their incompatibility with the properties of the three-dimensional (3D) potential field. In this paper, an interpolation method, inverse-forward (IF) interpolation, was developed to be consistent with Laplace's equation that governs the 3D field in the volume conductor bounded by the mapped surface. This method is evaluated in an experimental heart–torso preparation in the context of electrocardiographic body surface potential mapping. Results demonstrate that IF interpolation is able to recreate major potential features such as a potential minimum and high potential gradients within a large region of missing data. Other commonly used interpolation methods failed to reconstruct major potential features or preserve high potential gradients. An example of IF interpolation with patient data is provided to illustrate its applicability in the actual clinical setting. Application of IF interpolation in the context of noninvasive reconstruction of epicardial potentials (the inverse problem) is also examined. © 1998 Biomedical Engineering Society. PAC98: 8710+e, 0260Ed     

Low plasma glutamine in combination with high glutamate levels indicate risk for loss of body cell mass in healthy individuals: the effect of N-acetyl-cysteine

Skeletal muscle catabolism, low plasma glutamine, and high venous glutamate levels are common among patients with cancer or human immunodeficiency virus infection. In addition, a high glycolytic activity is commonly found in muscle tissue of cachectic cancer patients, suggesting insufficient mitochondrial energy metabolism. We therefore investigated (a) whether an anaerobic physical exercise program causes similar changes in plasma amino acid levels, and (b) whether low plasma glutamine or high glutamate levels are risk factors for loss of body cell mass (BCM) in healthy human subjects, i.e., in the absence of a tumor or virus infection. Longitudinal measurements from healthy subjects over longer periods suggest that the age-related loss of BCM occur mainly during episodes with high venous glutamate levels, indicative of decreased muscular transport activity for glutamate. A significant increase in venous glutamate levels from 25 to about 40 M was seen after a program of anaerobic physical exercise. This was associated with changes in T lymphocyte numbers. Under these conditions persons with low baseline levels of plasma glutamine, arginine, and cystine levels also showed a loss of BCM. This loss of BCM was correlated not only with the amino acid levels at baseline examination, but also with an increase in plasma glutamine, arginine, and cystine levels during the observation period, suggesting that a loss of BCM in healthy individuals terminates itself by adjusting these amino acids to higher levels that stabilize BCM. To test a possible regulatory role of cysteine in this context we determined the effect of N-acetyl-cysteine on BCM in a group of subjects with relatively low glutamine levels. The placebo group of this study showed a loss of BCM and an increase in body fat, suggesting that body protein had been converted into other forms of chemical energy. The decrease in mean BCM/body fat ratios was prevented by N-acetyl-cysteine, indicating that cysteine indeed plays a regulatory role in the physiological control of BCM.Abbreviations BCM Body cell mass - HIV Human immunodeficiency virus type 1 - NAC N-Acetyl-cysteine     

Central and peripheral contributions to control of heart rate during heat acclimation

The contributions of the autonomic nervous system and the cardiac pacing cells in the development of heat-acclimation-induced bradycardia were analyzed, and the effect of heat acclimation on the chronotropic response of the heart to heat stress (40° C) was studied. Rats were acclimated at 34° C for 0, 5, 14, 30 and 60 days. Heart rate (HR) was measured in conscious animals, using chronic subcutaneous electrodes. Sympathetic and parasympathetic influences were studied by IP administration of 0.1 and 1 mg/100 g body weight atropine and propranolol respectively, while intrinsic HR (HR_i) was measured following administration of both drugs simultaneously. The effects of carbamylcholine and norepinephrine on the beating rate of isolated rat atria were investigated to study pacemaker responsiveness to neutrotransmitters. Up to day 14 of heat acclimation, bradycardia was attained by tonic parasympathetic acceleration (18%) and temporal sympathetic withdrawal (0.8% on day 14), to compensate for the gradually augmented HR_i (2.5% and 8% on days 5 and 14, respectively). Following long-term acclimation HR_i declined below pre-acclimation rate. This was associated with resumed sympathetic activity (16% and 10% on days 30 and 60 respectively) while parasympathetic activity continued to be high (18%). Tachycardia, known to occur with severe uncontrolled body hyperthermia, was attenuated following heat acclimation by 42%. It was concluded that during the initial phase of heat acclimation bradycardia is achieved primarily by changes in autonomic influences, while following long-term acclimation, changes in the intrinsic properties of the pacing cells (HR_i) and the autonomic system both play a role.     

The immune response of healthy adults to a reduced dose of hepatitis B vaccine

Three hundred thirty-six medical personnel from hemodialysis centers were treated with three doses, 20 μg each, of the Merck hepatitis B vaccine (at 0, 1, and 6 months). Within 1 month after the first injection, 41% converted to anti-HBs positivity; after the second injection the conversion rate rose to 80–90%; and after the booster, to 96–98%. The later rate remained unchanged during the 18-month follow-up period. Only 2.8% of those vaccinated did not respond to the vaccine. The patterns of immune responses to 20-μg doses were found to be exactly the same as to 40-μg doses. It is suggested that reduced doses of vaccine should be as efficacious as the larger ones.