Effects and mechanisms of PCB ecotoxicity in food chains: Algae  fish  seal  polar bear 1

Wildlife populations are adversely affected in polluted environments. Nevertheless, a cause‐and‐effect relationship between excessive exposure to chlorinated hydrocarbons and induction of pathologic disorders in animals, is difficult to demonstrate without verification from experiments following the rationale of Koch's postulates. Deleterious effects of chlorinated chemicals such as DDT on songbird reproduction, as demonstrated by the clutch size of eggs in a nest, however, is an example, where exposure and causation are apparent. With amelioration of DDT pollution, clutch size increases, and the cause‐and‐effect relationship is established. Similar examples of exposure to DDT and PCBs inducing reproductive disorders and endocrine disruption among marine mammals have been documented in industrialized nations of northern Europe and in the upper latitudes of the Northern Hemisphere. Population declines in ringed, grey and harbor seals are apparently due to a rapid decrease in their rates of reproduction¹. These latter observations are best interpreted in light of experiments conducted by Reijnders². Reijnders exposed harbor seals to relatively high dietary levels of PCBs and induced PCB‐blood‐lipids among seals to an average of 25 mg/kg compared to 10 mg/kg among controls. The treated seals had a significantly reduced reproductive rate. A relationship between increased PCB‐blood‐levels in vivo and the decrease in reproductive rates in this experiment is highly instructive for interpreting the decline of fertility in seal populations in polluted Baltic Sea waters. These linked observations are dependent upon demonstration of pathologic mechanisms associated with occlusion and stenosis of the uterine lumen among affected females in seal populations.

PCB congeners apparently disrupt endocrine‐system‐functions leading to, or associated with, increases in endometriosis, fetal abortion, glomerulonephropathies and osteoporosis. This observation is further highlighted by Reijnders experiment, which closely replicated the range of PCB concentrations found in seal populations living in a variety of PCB polluted waters.

Various PCB congeners differentially accumulate in brain, liver and adipose tissues in young and old seals. Further research of PCB toxic effects on organ systems of these animals and other species is thus indicated.

This report, then, examines the process of PCB bioaccumulation within the marine food chain from fish to seals, whales, other marine mammals and to polar bears. Environmental toxic pollutants affect animals within the food chain in different ways but ultimately they affect humans as well.     

复方盐酸伪麻黄碱缓释胶囊治疗季节性变应性鼻炎的临床研究

目的　观察复方盐酸伪麻黄碱缓释胶囊治疗季节性变应性鼻炎患者的临床疗效和安全性。方法　采用开放、多中心临床研究设计。患者每次口服 1粒复方盐酸伪麻黄碱缓释胶囊、每日 2次、间隔 12h ,连服 7d ,然后观察患者症状和体征的改善情况。结果　本研究最终有 370例患者可供疗效分析 ,371例患者可供安全性分析。与服药前相比 ,患者服药第 1～ 7天各临床症状 (包括鼻塞、流涕、鼻痒、打喷嚏、流泪、眼痒、耳 /腭痒 )及体征 (包括鼻甲、鼻黏膜情况和眼部充血 )评分的改善均有统计学意义 (P <0 0 0 1)。复方盐酸伪麻黄碱缓释胶囊治疗季节性变应性鼻炎症状和体征的显效率分别为 70 %和 6 8% ,总有效率分别为 89%和 80 %。在用药过程中共有 5 4例患者报告了 6 1例次不良反应 ,主要为轻、中度困倦和口干。未出现严重不良反应。结论　复方盐酸伪麻黄碱缓释胶囊可持续有效控制季节性变应性鼻炎患者的症状和体征 ,疗效较高 ,耐受性较好     

Effect of short-term use of oral smokeless tobacco on random- pattern skin flap survival in rats.

We investigated the effects of smokeless tobacco on the survival of random-pattern skin flaps in rats. Twenty rats were divided into two groups (n=10 each). In the experimental group 200 mg smokeless tobacco (Maras powder) (1 mg nicotine) was inserted intraorally once a day for seven days under general anaesthesia. It was not given to the control group, but the rats were similarly anaesthetised with ketamine. On day 8, plasma cotinine concentrations were measured. The random-pattern dorsal skin flaps measuring 3 x 10 cm were then raised and resutured. Percentage survival area was assessed after a further eight days. The mean (SD) survival was 39 (7)% in the experimental, and 65 (8.9)% in the control, groups (p=0.0001). The mean (SD) plasma cotinine concentrations were 124.4 (73) ng/ml and <10 ng/ml, respectively. Smokeless tobacco use increased the incidence of flap necrosis in random-pattern skin flaps in rats.     

Production of lactic acid by respiratory muscles

We measured blood lactate in normal subjects after 10 minutes of sustained maximum voluntary ventilation (SMVV) with end-tidal Pco₂ kept constant and after breathing against a big added respiratory load for 200 breaths. With SMVV subjects sustained on average 68% of the predicted maximum breathing capacity and achieved final lactate concentrations of 1·9 mmol/l (17·1 mg/100 ml), representing an average increase of about 1·0 mmol/l (9·0 mg/100 ml) over resting values. There was a wide range between individuals, from no increase at all to 2·7 mmol/l, despite similar levels of ventilation. Breathing against added loads produced much smaller changes in blood lactate.     

Doppler sonographic evaluation of cerebral blood flow in anemia resulting from chronic renal failure.

OBJECTIVE: This study was undertaken to describe Doppler sonographic measurement of cerebral blood flow in anemia secondary to chronic renal failure and to compare the results with data gathered from healthy control subjects. We also aimed to compare vertebral and internal carotid artery blood flows to see whether any alteration of dominance in cerebral blood supply would occur. METHODS: We studied 27 predialytic patients with chronic anemia resulting from chronic renal failure and 20 healthy control subjects by means of extracranial Doppler sonography. In these patients, blood flows of bilateral internal carotid and vertebral arteries were measured, and net vertebral artery, net internal carotid artery, and total cerebral blood flows were estimated. Statistical significance was observed between groups, and the data were correlated with hemoglobin level. Variation of the difference of the Doppler measurements between case and control groups by side (left or right) or disease status (patient or control subject) was analyzed. RESULTS: From the assessed Doppler parameters, only cerebral blood flow and right and net vertebral artery blood flows had a significant difference between groups (P < .05) and showed a negative correlation with hemoglobin level. Vertebral artery blood flow was found to have significant interactions with disease status (P = .009) and side (P = .054). CONCLUSIONS: Right vertebral artery blood flow is most prone to increase in chronic anemia of chronic renal failure. This effect also appears as increasing net vertebral artery blood flow and cerebral blood flow.     

Doppler sonography evaluation of flow velocity and volume of the extracranial internal carotid and vertebral arteries in healthy adults

PURPOSE: To measure with Doppler sonography the velocity and volume of blood flow in the extracranial internal carotid artery (ICA) and vertebral artery (VA) of healthy adults and to calculate total cerebral blood flow volume (tCBFV). METHODS: Bilateral ICA and VA were examined sonographically in 180 healthy adults. Angle-corrected peak systolic (Vps), end-diastolic (Ved), and time-averaged maximum blood flow velocity (TAV) were measured in pulsed Doppler mode, and the resistance index (RI) and pulsatility index (PI) were calculated. The cross-sectional area (A) was measured on gray-scale images. Volume flow was calculated as FV = TAV x A, and tCBFV was calculated as the sum of the right and left ICA and VA volume flow. RESULTS: tCBFV was 651 +/- 96 ml/min for the entire population. There was a significant decrease in Vps, Ved, TAV, and tCBFV with age in all arteries. RI and PI values initially declined and then increased with age. Cross-sectional area increased with age in ICA but not in VA. PI and RI were higher in men than in women. Blood flow velocity and volume were higher, and RI was lower in the left than in the right VA. CONCLUSION: The Doppler sonographic assessment of extracranial ICA and VA blood flow volume may be useful for the study of cerebral hemodynamic changes in patients with cerebrovascular disorders. Age-dependent changes should be considered, for instance, in the management of intensive care patients with impaired cerebral perfusion.     

Dedicated MR receiver coils: a simple design and construction method

We describe a simple method for design and construction of dedicated receiver coils for use in magnetic resonance imaging. We have been successful in constructing dedicated coils for multiple regions of the body using this method.