汞对人体必需元素干扰的研究

对42例汞吸收、2例汞中毒者(尿汞>99.7nmol/L),采用原子吸收光谱法,检测了汞对人体必需五种金属元素代谢的干扰。研究发现,汞时人体必需元素镁、铜具有拮抗作用。汞吸收者血清镁极显著低于对照组(P>0.01)。经驱汞治疗后,血清镁、铜自然上升与对照组无统计学差异(P>0.05),镁离子低下,可出现神经肌纤维兴奋性增高。由此推测,汞引起肌肉震颤的毒理,可能由汞拮抗镁离子低下引起。设想,对汞中毒者采用补镁制剂治疗,是否具有驱汞作用值得探讨。     

The effect of ionic strength on the kinetics of rigor development in skinned fast-twitch skeletal muscle fibres

 Recent atomic 3-D reconstructions of the acto-myosin interface suggest that electrostatic interactions are important in the initial phase of cross-bridge formation. Earlier biochemical studies had also given strong evidence for the ionic strength dependence of this step in the cross-bridge cycle. We have probed these interactions by altering the ionic strength (Γ/2) of the medium mainly with K⁺, imidazole⁺ and EGTA^2– to vary charge shielding. We examined the effect of ionic strength on the kinetics of rigor development at low Ca²⁺ (experimental temperature 18–22°C) in chemically skinned single fast-twitch fibres of mouse extensor digitorum longus (EDL) muscle. On average the delay before rigor onset was 10 times longer, the maximum rate of rigor tension development was 10 times slower, the steady-state rigor tension was 3 times lower and the in-phase stiffness was 2 times lower at high (230 mM) compared to low (60 mM) ionic strength. These results were modelled by calculating ATP depletion in the fibre due to diffusional loss of ATP and acto-myosin Mg.ATPase activity. The difference in delay before rigor onset at low and high ionic strength could be explained in our model by assuming a 15 times higher Mg.ATPase activity and a threefold increase in K _m in relaxing conditions at low ionic strength. Activation by Ca²⁺ induced at different time points before and during onset of rigor confirmed the calculated time course of ATP depletion. We have also investigated ionic strength effects on rigor development with the activated troponin/tropomyosin complex. ATP withdrawl at maximum activation by Ca²⁺ induced force transients which led into a ”high rigor” state. The peak forces of these force transients were very similar at low and high ionic strength. The subsequent decrease in tension was only 10% slower and steady-state ”high rigor” tension was reduced by only 27% at high compared to low ionic strength. Addition of 10 mM phosphate to lower cross-bridge attachment strongly suppressed the transient increases in force at high ionic strength and reduced the steady-state rigor tension by 17%. A qualitatively similar but smaller effect of phosphate was observed at low ionic strength where steady-state rigor force was reduced by 10%. The data presented in this study show a very strong effect of ionic strength on rigor development in relaxed fibres whereas the ionic strength dependence of rigor development after thin filament activation was much less. The data confirm the importance of electrostatic interactions in cross-bridge attachment and cross-bridge-attachment-induced activation of thin filaments. Received: 3 September 1997 / Received after revision and accepted: 12 December 1997     

Chemical and enzymatic treatment of endothelin

Endothelin-1 (ET), the most potent vasoconstrictor yet discovered, is a peptide containirig 21 amino acids with two intrachain disulfide bridges. With the aim of obtaining two-chain derivatives, Et was submitted to chemical and enzymatic treatments. Reaction of ET with CNBr in 70% HCOOH gave, in addition to the expected [Hse⁷ lactone]-7,8-seco-ET and unreacted material, a by-product whose molecular weight was 25 m.u. greater than that of ET. When the reaction mixture, after lyophilisation, was immediately quenched with NH3-saturated dry MeOH, two products could be recovered in a 5:1 ratio, both obtained by nucleophilic attack of the homoserine lactone: the expected [Hse⁷-NH₂]-7,8-seco-ET and [Hse⁷]ET, resulting from competitive intramolecular reaction of the deprotonated α-amino group of the Asp⁸ residue. The Lys⁹-Glu¹⁰ bond turned out to be very resistant to enzymatic attack both by Lys-C-endopeptidase and trypsin. The 9,10-seco-ET derivative could be obtained by treatment with Lys-C-endopeptidase only by using a high enzyme/ET ratio and after a prolonged incubation time. Cleavage of the Lys⁹-Glu¹⁰ bond could not be achieved by treatment with trypsin, even with a high enzyme/substrate ratio. The main product was 13, 14-seco-ET, deriving from the action of chymotripsin (present as an impurity in the trypsin preparation) on Tyr¹³. The structure of these peptides was confirmed by amino-acid sequence analysis and fast atom bombardment mass spectrometry (FAB-MS). Nicking of the ET structure at different positions had different impact on the biological properties of the resulting derivatives. © Munksgaard 1995.     

Plastic surgical treatment of a chronic thoracic duct fistula using a sternocleidomastoid muscle flap — a case report

Thoracic duct fistula is a rare but potentially serious complication of head and neck surgery. Such fistulae may be difficult to treat, and several techniques, both operative and non-operative, have been advocated. A case of successful surgical treatment of a chronic thoracic duct fistula is presented. The fistula occurred in a 51-year-old female following treatment of a solitary supraclavicular breast metastasis by local excision and radiotherapy. The divided duct was ligated and the area was covered with the clavicular head of the sternocleidomastoid muscle.     

贵阳市婴幼儿和青少年发育调查研究 Ⅰ．骨龄研究

对贵阳市１５００名健康婴幼儿童和青少年进行骨发育的调查，根据手腕部骨Ｘ线解剖变化规律，观察每块骨从出现至成熟的过程中，骨化点的出现顺序、数量、形态和密度的改变等指标的系列变化，提出了骨发育评价标准。可供我省运动员选材、儿童少年发育咨询和临床治疗参考。     

阻塞性睡眠呼吸暂停与缓慢性心律失常的关系

Objective To analyze the relations between obstructive sleep apnea and bradyarrhythmia.Methods From 1999 to 2005,203 patients who came from Bering Tongren Hospital and Fuwai Hospital were found to have sleep apnea in an ambulatory study. A Hoher electrecardiogram was recorded for 24 hours within 2 weeks after patients were diagnosed as obstructive sleep apnem Results Nocturnal episodes of bradyarrhythmia were identified in 12(5.9%)of 203 patients.Body mass index and respiratory disturbance index in patients with bradyarrhythmia(n=12)were higher than those in patientswithour bradyarrhymia(n=191)(34±5 735.24±6 and 63±15 vs.25±5,respectively,both P<0.01).There was a significant difference in end-apneic oxygen saturation in apnea/hypopnea episodes with and without bradyarrhythmia(63%±15% vs.75%±11%,P<0.05).A linear relation between end-apneic oxygen saturation and number of sinus arrests and heart blocks was not found.Conclusions Patients with apnea-associated bradyarrhythmia have higher body mflgB index and higher respiratory disturbance index than patients without bradyarrhythmi&Bradyarrhythmia occurres independently from decrease in oxygen saturation.     

Can a Single Muscle Fiber Model the Features of Myocardial Stunning?

The exact mechanisms that cause myocardial stunning are still unclear. We previously utilized a computer model of the ventricle that was effective in modeling the dominant observable features of stunning, but it was not simple to implement. This led to the design of a single muscle fiber model. The mathematical model of a muscle fiber consisted of three elements: a contractile element, a series elastic element, and a parallel elastic element. The model created length waveforms based on time-dependent force and contractile stiffness functions. This model was initially evaluated by entering the same regional parameter values used in the global dual region ventricular model. First a reduction of the contractile stiffness function was applied by reducing the peak stiffness by 30%, and then the rates of activation and deactivation were reduced by 20% while maintaining the peak values constant. The three-element model produced results very similar to the canine and ventricular model. Thus, it is concluded that the simpler three-element model provides an accurate model of the myocardial tissue and its deficiencies during stunning.     

Presynaptic α2-adrenoceptor-mediated modulation of norepinephrine release from vascular adrenergic neurons in reduced renal mass salt hypertensive rats

The present study was designed to investigate the presynaptic alpha 2-adrenoceptor function to inhibit norepinephrine (NE) release in blood vessels of reduced renal mass salt hypertensive rats (Na-loaded HT). Isolated perfused mesenteric vasculatures were prepared from Na-loaded HT and normotensive control rats (NT-control), and the NE release and vascular responsiveness were examined. Periarterial nerve stimulation caused a significantly greater release of NE and pressor responses in Na-loaded HT than in NT-control. Yohimbine, a potent alpha 2-adrenoceptor antagonist, demonstrated the facilitatory effects on NE release during nerve stimulation. The effects were significantly attenuated in Na-loaded HT compared with NT-control. These results demonstrate that vascular sympathetic nervous activity might be enhanced in Na-loaded HT. Furthermore, the increased NE release from vascular adrenergic neurons in Na-loaded HT could partially depend on impaired presynaptic alpha 2-adrenoceptor-mediated modulation, which might contribute to the pathogenesis and maintenance of this form of salt-dependent hypertension.     

Chest Wall Implants: Their Use for Pectus Excavatum,Pectoralis Muscle Tears,Poland's Syndrome,and Muscular Insufficiency

Solid customized and prefabricated silicone implants have been used by the author for 15 years in a wide range of chest wall deformities. Chest wall implants are often used in males seeking to augment a muscularly deficient or underdeveloped chest; however, their greatest use has come in a variety of deformities both congenital and acquired, such as pectus excavatum, Poland's Syndrome, and pectoralis muscle tears. The implants can be either customized using a moulage technique or are prefabricated, manufactured implants which can be modified on the operating table to repair the contour deformity. The immediate postoperative problem of seroma and subcutaneous implant ``show' has been minimized by careful planning, gentle technique, deep insertion, improved patient positioning on the operating room table, and the use of oral anti-inflammatory medications. The long-term results of these implants seem very satisfactory. The patients are usualy physically active, and the implants show no long-term sequelae such as seroma, infection, displacement, or rupture.     

Mass Screening for Neuroblastoma and Estimation of Costs

ABSTRACT. On the basis of epidemiological data and medical costs for patients with neuroblastoma, we have calculated the cost of mass screening for neuroblastoma with high performance liquid chromatography (HPLC) compared to the cost when it is not performed. If the sensitivity of the mass screening is 80 % and 22 000 infants are screened annually the cost will be 27809000 yen ($191800). If mass screening is not performed, the cost will be 28 446 000 yen ($196 200). The difference in cost (637 000 yen or $4 400) is fairly small. If the sensitivity is 75 % and 16 500 infants are screened, the difference is also small (174000 yen or $1 200). Therefore, mass screening with the HPLC method will not be an undue financial burden. But re-screening at an older age will be done with less financially favorable results, considering that the sensitivity may not be as high as that of the first screening and that mothers are somewhat reluctant about re-screening. The balance of the cost of mass screening by qualitative methods may also be less favorable, since the detection rate is low.