Recovery of function in cat visual cortex following prolonged deprivation

Summary Evidence that there is a critical period during which response characteristics of neurons in visual cortex of the cat may be influenced has been provided in several studies, which suggest that the period of influence is restricted to the first few months of life. Using a somewhat different experimental procedure, we have obtained evidence that cortical units retain plasticity long after the end of this period has passed. In our procedure prolonged visual deprivation was followed by exposure in a normal visual environment. The animals were maintained throughout the first year of life either in total darkness or in an enclosure illuminated intermittently by a strobe light. Following the period of deprivation, electrophysiologic recordings were taken from some of these animals. The remaining cats were permitted 6–12 months in a normally-illuminated environment prior to recording. Cats of the same age reared from birth in a normally lit environment were also recorded.Cortical neurons in cats deprived of any normal visual experience rarely show orientation selective responses. In animals allowed subsequent normal visual experience about one-half of the units studied exhibited this property. This level of response specificity is intermediate between that of normally-reared and recently-deprived animals. While most cortical units in normally-reared cats exhibit direction selectivity, this property is rarely observed in the recovery cats. A number of unit types which are rarely observed in either normal or totally deprived animals were encountered in cats that had normal exposure following prolonged deprivation. A convergent strabismus was observed, in contrast with the divergent strabismus often shown by cats immediately following prolonged visual deprivation. This shows that ocular alignment as well as cortical unit properties can remain plastic in the adult.Supported by NRC Grant No. A9939 and M.R.C. Grant No. MA5201 (to M.C.) and Grants from NIH and the Sloan Foundation (to A.H.).     

CR-lipped bearing is an adequate functional solution to patients with perioperative excessive laxity in cruciate retaining total knee arthroplasty

BackgroundThe cruciate retaining lipped (CR-lipped) bearing is designed to provide more anterior-posterior (AP) stability and could be employed to resolve excessive intraoperative laxity during the cruciate retaining TKA (CR-TKA). The aim of the study was to determine whether the CR-lipped bearing in CR-TKAs with a perioperative excessive laxity allows equivalent functional results as compared to the standard CR articulation.MethodsA cohort of 111 TKAs with CR-lipped bearings was matched to a cohort of conventional CR bearings regarding age and sex. The CR-lipped bearing was used in patients with excessive knee AP laxity and the regular CR bearing was used in patients without excessive AP laxity during TKA. Various PROMs (WOMAC, KSS, SF-36) were assessed preoperatively and at 5-years postoperative in combination with revision rate and Range of Motion (ROM).ResultsPROMs did not differ significantly between both groups 5-years postoperatively. Mean ROM (flexion) 5-years postoperatively was not significantly different. The implant survivorship was 100% for both cohorts with revision for any reason as end point.ConclusionBased on these results, the CR-lipped bearing is a safe and effective solution for mild interoperatively assessed PCL laxity during CR-TKA without loss of function or decreased survivorship at 5 years. Peroperative conversion to a PS-TKA in order to obtain satisfactory functional scores might therefore not be necessary when mild PCL laxity is observed during surgery. Further research should focus on verifying this approach and longer follow-up is needed to generate data on long term survivorship.Level of evidenceLevel IV therapeutic, retrospective, cohort study.     

广州市至灵学校167名学员智残原因的调查分析

本文以广州市至灵学校（智低）167名学员为研究对象，完成智力测验、体格检查和染色体分析．并且追溯围产期和出生后的种种异常．询查智力低下的家族史。综合分析有关资料，显示围产期的某些不利因素、遗传与先天疾病，以及婴幼儿中枢神经系统疾病是主要的发病原因。从而指出，加强优生咨询、重视围产期保健、提高产前诊断和产程中的监护水平、早期防治胎婴儿中枢神经系统损伤和疾病等，是降低智残儿发生率的重要措施。     

过敏性紫癜急性期血液流变性改变及其临床意义

为了研究过敏性紫癜（ＨＳＰ）急性期血液流变性改变及其临床意义，采用ＮＸＥ－Ｉ型锥板式粘度计，测定了２１例ＨＳＰ急性期血液流变学各项指标。结果表明，ＨＳＰ组全血粘度、血浆粘度、红细胞聚集性增多显著高于对照组；氧释放系数ＯＤ值较对照组明显降低；ＨＳＰ患儿红细胞压积、血小板计数、血清ＩｇＡ和ＩｇＭ呈明显升高。提示ＨＳＰ时存在明显的血液流变性异常，其发生与血液浓缩、高Ｉｇ血症等因素有关。及时治疗ＨＳＰ高粘滞血症对减轻症状、防止复发是十分有益的     

Pathogenesis of the low cardiac output syndrome in postresuscitation states

Acute hypervolemia induced in experiments on dogs by infusion of dextran, did not produce decompensation of the circulation in animals whose cardiac output was sharply depressed in the postresuscitation period after circulatory arrest lasting 15 min. The increase in the venous return and change in the conditions of the peripheral circulation as a result of dextran administration temporarily increased the central venous pressure, caused a lasting increase in the arterial pressure, cardiac output, stroke volume, work of the left ventricle, and total oxygen consumption by the body, and lowered the peripheral vascular resistance. In model experiments on dogs subjected to isolated compression ischemia of the brain for 20 min, a low cardiac output syndrome also developed.Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Fedorov.Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 7, pp. 787–789, July, 1976.     

Atrial fibrillation: a new explanation of the old phenomenon

We propose a new mechanism of atrial fibrillation basing on the results of 30 series of acute experiments on anesthetized cats. In brief, combination of two or more arrhythmogenic factors shortens the interval between the inward and outward ionic currents in cardiomyocytes to a critical value. Under these conditions repolarization of cardiomyocyte membrane reaches the excitation threshold before complete inactivation of the depolarizing currents. This inevitably results in autoexcitation of myocytes (or extrasystole), that in turn promotes repolarization. Once occurred, autoexcitation turns into self-triggering activity resembling tachyarrhythmia paroxysm.     

Case of postradiation osteosarcoma with a short latency period of 3 years

Osteosarcoma is one of the neoplasms that may occur following exposure to radiation. A case of osteosarcoma arising in the craniofacial bone with a short latency period of 3 years after radiotherapy for maxillary squamous cell carcinoma is described. A 64-year-old-man underwent right partial maxillectomy and chemoradiotherapy due to squamous cell carcinoma of his right maxillary sinus. Histologically, the tumor was composed of moderately differentiated squamous cell carcinoma with a component of spindle cell carcinoma. Three years later, osteosarcoma developed in the craniofacial bone within the irradiation field of the first tumor. Detailed histological examination demonstrated that there was no component of osteosarcoma in the first tumor or squamous cell carcinoma in the second tumor. Radiation-induced osteosarcoma usually occurs after a long latency period of more than 10 years after the radiotherapy. In this case, osteosarcoma was possibly a radiation-induced osteosarcoma with a short latency period of 3 years.     

Delayed responses to electrical stimuli reflect C-fiber responsiveness in human microneurography

The slowing of impulse conduction during the relative refractory period has often been used to assess activation of C-fibers, in particular, in human microneurography. This study aimed to evaluate the sensitivity of this method and the factors affecting it. Thirty cutaneous C-fibers were recorded from the peroneal nerves of healthy human subjects. Intracutaneous electrical stimulation in the receptive field at 4 s intervals, after some minutes of adaptation, induced spike discharges at constant latency. One or more conditioning stimulus pulses were interpolated at different intervals and the increase in latency after the subsequent regular pulse was assessed. The latency shift was found to depend on the number of interposed pulses, on the time interval between conditioning and conditioned stimulus, and on the conduction velocity of the C-unit. The increase in latency was larger with greater distance between stimulating and recording electrodes, indicating a contribution of the conductile membrane over its whole length. On the other hand, slowing was more pronounced, on average, in slower conducting C-units and conduction velocities were slower when recordings were performed more distally. These findings indicate that the slower terminal nerve branches contribute most to the latency increases. Even a single additional spike in between two regular pulses caused a reliable latency shift of 1.2±0.2 ms (mean ±SEM) and additional pulses lead to an approximately linear latency increase (2 pulses: 2.3±0.3 ms; 4 pulses: 5.9±0.7 ms). In contrast to the number of interposed stimuli, different intervals between interposed and regular stimuli had only a minor impact on the latency shifts. It is concluded that latency shifts are reliable indicators of C-fiber activation, being sensitive enough to detect even single spike responses. Furthermore, latency increases may be used as a relative measure of C-fiber activation, e.g., when comparing responses to stimuli of different strength.     

Maintained pregnancy levels of oestrogen afford complete protection from post-partum exacerbation of collagen-induced arthritis.

Pregnancy is known to influence the course of rheumatoid arthritis (RA) in women, as well as type II collagen-induced arthritis (CIA) in DBA/1 mice. A characteristic feature is the remission during gestation and the exacerbation of the diseases during the post-partum period. In the case of CIA in DBA 1 mice, two hormonal changes have been assumed to be critical for the induction of the post-partum flare: (i) the fall in steroid hormone levels from those present during pregnancy; and (ii) surges of prolactin (PRL) release at and after delivery. Our results show that treatment with oestradiol during a short period immediately after parturition protects the mouse from a post-partum flare of the disease, and that treatment with bromocriptine, a drug known to inhibit the endogenous PRL release, has a significant though less marked effect. Studies of lactating (i.e. animals with physiological stimulation of endogenous PRL release) and non-lactating arthritic mice revealed no clear-cut differences, indicating that PRL is of minor importance for the induction of the post-partum flare. Some steroids other than oestradiol, which may be implicated in the exacerbation of arthritis, namely progesterone and hydrocortisone, had no clinical effect. Analyses of agalactosyl IgG levels in mice with CIA, and anti-collagen II antibodies in sera collected at the end of the experiments revealed no significant differences between the oestradiol and the control groups. The successful oestradiol treatment of the mice indicates that the drop in endogenous oestradiol levels prior to delivery ends the oestrogen-mediated protection against arthritis during pregnancy.     

采用永磁悬浮的永久性左心室辅助装置

研制出一台采用永磁轴承的左心室辅助装置（LVAD）。该装置包括一个定子和一个转子，采用径向驱动方式；转子包括驱动磁钢和叶轮，电机定子线圈和泵壳组成定子。装置设计采用了一种特殊结构的永磁轴承。转子的位置测量表明，转子稳定悬浮的前提条件是必须有较高的转速（大于3250r／min）且流量大于1L/min。用猪血为介质所做的液动力测试表明，当转速达到3500r／min～4000r／min时，血泵输出流量达到4L/min～6L/min，输出压力达到100mmHg。该装置重200g，最大处直径为40mm。