COMPLETE ABROGATION OF IMMUNE RESPONSE TO SKIN ALLOGRAFTS AND RABBIT ERYTHROCYTES IN THE EARLY THYMECTOMIZED XENOPUS

Larvae of the clawed toad, Xenopus laevis , were thymectomized at the N ieuwkoop -F aber stages 45–47 (4- to 7-day-old) and 51 (18-day-old), and raised beyond metamorphosis to study their immune reactivities. The toads thymectomized at stage 51 and the unoperated and sham-operated controls rejected allografted skins in 16–37 days. In contrast, the toads thymectomized at stages 45–47 did not reject the grafts at all, and there was no lymphoid invasion into the grafted area. The toads thymectomized at stage 51 produced antibodies against rabbit red blood cells (RRBC), as did the controls. However, those thymectomized at stages 45–47 did not produce specific antibodies. Electrophoresis on cellulose acetate membrane and immunoelectrophoretic analyses proved that in spite of the total lack of observed immune responses, the thymectomized toads do possess a certain level of immunoglobulins. It is concluded that the thymus exerts its decisive role in the establishment of immune competence when it is still in the initial state of differentiation. In relation to the immunoglobulins found in the early-thymectomized toads, a discussion was also offered of the presence of a thymus-independent humoral immune system.     

EVIDENCE FOR REGULATION OF PROTEIN SYNTHESIS AT THE TRANSLATION LEVEL IN RESPONSE TO DIETARY ALTERATIONS

Rats were maintained for several days on a protein-free diet which, approximately 14 hr before decapitation, was changed to a protein-rich diet. Microsomal subfractions of liver were obtained by sucrose density gradient centrifugation. The sedimentation patterns of the microsomal subfractions and of the polysomes were found to be unchanged after the alteration of the diet whereas the ability to incorporate amino acid was markedly enhanced. No significant differences in the RNA/protein ratio of the microsomal subfractions were observed. The changes in amino acid incorporation which were unrelated to concurrent changes in the amount of polysomes are discussed.     

METABOLIC AND ULTRASTRUCTURAL CHANGES IN THE FROG OVARIAN FOLLICLE IN RESPONSE TO PITUITARY STIMULATION

Frog ovarian fragments were prevented from ovulating in vitro by the addition of actinomycin D up to 3 hr following pituitary stimulation; but addition of Actinomycin D 6 hr after stimulation was far less effective. Puromycin, on the other hand, effectively inhibited ovulation when added as late as 6 hr after pituitary stimulation. Although actinomycin D reduced uptake of uridine-³H, and puromycin reduced uptake of leucine-³H and lysine-¹⁴ by pituitary-stimulated ovarian tissue minus oocytes (OTMO) in vitro, it was found that pituitary stimulation did not significantly increase uptake of these compounds by OTMO. Radioautographs of ovarian follicles fixed 6 hr after the addition of pituitary extract and uridine-³H in vitro revealed increased RNA synthesis in the peritoneal surface epithelium, compared with unstimulated controls, while the ovarian sac epithelium showed no increase. Gross ultrastructural changes occurred in the peritoneal area of ovarian follicles following pituitary stimulation in vivo, including loss of collagen fibrils, and general disorganization of the connective tissue theca. Changes in the rough endoplasmic reticulum of the peritoneal epithelial cells, while frequently encountered, were less pronounced. None of these changes was observed in the ovarian sac area, or in the interfollicular region. The above data are consistent with the hypothesis that pituitary stimulation of the frog ovary results in increased synthesis of RNA and protein by the peritoneal epithelial cells, and that the protein may be collagenase.     

急性低氧时的Starling效应及心包的影响

为确定 Starling效应在心泵急性低氧反应中的地位,以及心包对此反应的影响,把17条雄狗,分别在心包切开(A 组)和缝合(B 组)条件下进行实验。在连续、依次吸入空气、氧分压为89、70和55mmHg 的常压氧-氮混合气各30min,并最后吸入氮气时,分别记录不同低氧状况下的左室前后径超声图、左室压力,dp/dt,右室压力或主动脉压力和第二导联心电图。结果表明,重度低氧时,左室舒张期末直径显著增大,A组由对照值3.88±0.15cm(M±SE)增大至4.22±0.18cm(P<0.01);B组由3.53±0.13cm增至3.67±0.12cm(P<0.01),并伴以每搏直径变化的明显增大(A 组由对照值的4.4±0.2mm增至4.9±0.2mm P<0.05;B 组由3.2±0.1mm 增至3.8±0.2mm P<0.01)。左室压力-直径环在重度低氧时显著右移,环体面积不缩小。说明重度低氧时,Starling 效应对心脏搏血功能的调节具有重要作用。在严重低氧导致左室收缩压进行性降低时,迅速切开心包可有利于心泵功能的改善,提示,心包对 Starling 效应的充分发挥有限制作用。     

P-16DEFAULT FROM CYTOLOGICAL SURVEILLANCE OF LOW-GRADE SMEARS: LEVELS OF DEFAULT AND CHARACTERISTICS OF DEFAULTERS IN THE TRIAL OF MANAGEMENT OF BORDERLINE AND OTHER LOW-GRADE ABNORMAL SMEARS (TOMBOLA)

The problems encountered with a glass slide circulation are legion but timely circulation is a major problem and is an inherent deficiency of our Non-gynaecological EQA scheme. This applies not only to consultants but also to specialist registrars (SpRs) and technical staff that are not formally included in the circulation list. In 2005 only 7 technical staff and 4 out of 47 SpRs took part on a formal basis, their participation being dependant on access to slides during their cytology attachment. The results for the 2005 circulation have been analysed and despite the small numbers of participating technical staff and SpRs their answers concur with the consultant body. To address the issues of timeliness and circulation problems a pilot teaching set has been developed by SlidePath into a virtual microscope web based circulation and sent to all SpRs in our region. They have recorded their answers and been given immediate access to the consensus consultant opinion with illustrations of follow up histology. A questionnaire was completed to evaluate the scheme. The facility of immediate feedback of consultant consensus is particularly pertinent to the educational element of the scheme and use of virtual microscopy addresses the issue of timely circulation. If further funding was made available technical staff could also be given the opportunity to try this web-based circulation.     

BIOCHEMTCAL CHANGES IN THE BRAIN OF EXPERIMENTAL ANIMALS IN RESPONSE TO ELEVATED PLASMA HOMOCYSTINE AND METHIONINE

The effects of high plasma concentrations of homocystine and methionine on the free amino acids of brain have been examined. Incorporation of the label from [³⁵S]methionine into the free amino acid pools of rabbit brain was enhanced in response to high plasma homocystine or high plasma homocystine and mcthionine. Under comparable conditions a marked decrease in the incorporation of the label from [¹⁴C]glycine into the free pool was observed. The corresponding incorporation of ³⁵S and ¹⁴C into brain proteins parallelled the results obtained with incorporation into the free pools of amino acids. Amino acid analyses of the free amino acid pools of rabbit brain revealed a general decrease in the concentration of amino acids in response to high plasma homocystine or high plasma homocystine and methionine. Inhibition of protein synthesis which occurs under the above experimental conditions is a general phenomenon. myelin and other brain fractions being equally affected. The decrease in concentration of brain amino acids also results in a diminution in concentration of the neurotransmitters GABA, dopamine and noradrenaline. The possible relationship of the observed changes to homocystinuria is discussed.