胎儿耳廓弹性软骨及其组织的发生

用９周－３９周引产胎儿标本７２例，取右耳廓石蜡切片，ＨＥ和Ｗｅｉｔｅｒｔ弹性纤维染色，光镜观察其弹性软骨、弹性纤维、耳廓肌和结缔组织的发生。     

Continuing professional development for radiographers

Purpose: The purposes of this survey were to identify the current participation in Continuing Professional Development (CPD) of radiographers in the South and West Regional Health Authority (SWRHA), and to invite them to comment on issues related to CPD activities.Methods: A questionnaire was sent to 1686 diagnostic and therapy radiographers in the SWRHA. This was designed to gain a profile of those radiographers currently practising and their participation in, and comments on, CPD activities.Results: A response rate of 51% was achieved, although only 634 questionnaires were used for the final analysis. The population of radiographers who responded were predominantly diagnostic, in the age range 26–45 years, female and employed on a full-time basis. Most respondents did not hold any post-registration qualifications, and only 149 respondents were involved in formal studies. Most respondents were involved in statutory CPD activities such as resuscitation and manual lifting, and fewer, although a majority, were involved in activities associated with changing roles and developing new competencies. Other CPD activities which respondents considered as benefiting their professional role were wide ranging. Most of the issues raised concerning CPD related to provision, support and funding.Conclusions: The challenge for the future is to develop a coherent, progressive and affordable scheme of CPD to meet the needs of individual radiographers, the health services, the patient and the profession.     

Preselection Thymocytes Are More Sensitive to T Cell Receptor Stimulation Than Mature T Cells

During T cell development, thymocytes which are tolerant to self-peptides but reactive to foreign peptides are selected. The current model for thymocyte selection proposes that self-peptide–major histocompatibility complex (MHC) complexes that bind the T cell receptor with low affinity will promote positive selection while those with high affinity will result in negative selection. Upon thymocyte maturation, such low affinity self-peptide–MHC ligands no longer provoke a response, but foreign peptides can incidentally be high affinity ligands and can therefore stimulate T cells. For this model to work, thymocytes must be more sensitive to ligand than mature T cells. Contrary to this expectation, several groups have shown that thymocytes are less responsive than mature T cells to anti-T cell receptor for antigen (TCR)/CD3 mAb stimulation. Additionally, the lower TCR levels on thymocytes, compared with T cells, would potentially correlate with decreased thymocyte sensitivity. Here we compared preselection thymocytes and mature T cells for early activation events in response to peptide–MHC ligands. Remarkably, the preselection thymocytes were more responsive than mature T cells when stimulated with low affinity peptide variants, while both populations responded equally well to the antigenic peptide. This directly demonstrates the increased sensitivity of thymocytes compared with T cells for TCR engagement by peptide–MHC complexes.     

MANIPULATION OF CHILDREN'S EATING PREFERENCES

Giving foods as rewards can enhance consumption of those foods, while giving rewards to induce consumption of foods can decrease subsequent consumption of those foods.     

Patterns of angiogenesis in neural transplant models: I. Autonomic tissue transplants

Functional vascular connections must form rapidly to prevent ischemic damage to grafted neural tissues. The temporal sequence by which transplant circulation is re-established provides information about the angiogenic capacity of either intact or damaged CNS blood vessels. This study compares the time course and mechanism of vascular reperfusion in allografts of superior cervical ganglia or adrenal medulla inserted either into the fourth ventricle or directly into the parietal cortex of perinatal rats. Tritiated thymidine was administered to recipients to determine angiogenic patterns at various postoperative time periods. After processing for light microscopic autoradiography, host and graft endothelial labelling indices were determined in order to establish the temporal sequence and location of vascular proliferation. Correlative electron microscopy depicted the morphological changes in transplant vasculature. Some recipients were prelabelled with 3H thymidine prior to transplantation to determine if host vessels invaded the grafts. Intraventricular graft vessels initially collapsed but sustained minimal ischemic damage and were completely reperfused by 24 hours postoperative. Adjacent intact host vessels attained peak 3H thymidine incorporation at 20 hours. Intrinsic graft vessels were radioactively labelled only after 48 hours. Intraparenchymal transplants surrounded by minimal trauma exhibited a similar temporal sequence of reperfusion and host endothelial proliferation. Intrinsic graft vessels in intraparenchymal grafts sustained more severe damage. With increased trauma, a concomitant delay in graft reperfusion time was observed. Grafts within prelabelled hosts rarely contained any labelled endothelium, indicating that anastomotic connections were made between original, intrinsic graft vessels and nearby host vascular sprouts. This study demonstrates that mature autonomic tissue stimulates the growth of adjacent host vessels when transplanted to undamaged brain surfaces. The anastomosis of nascent host vessels with pre-existing graft vessels is responsible for the rapid re-establishment of circulation within the transplants. A similar mechanism occurs within intraparenchymal grafts, although the rapidity of reperfusion appears to be predicated on the amount of trauma present at the graft site.     

Deleterious effects of the prone position in the full-term infant throughout the first year of life

Summary Seventy-one first-born infants who had been nursed in prone position since birth, were referred for motor assessment at 3 months, 5 months and 9 months. All infants were administered the same checklist of motor items, based on the Amiel-Tison Infant Neurological Evaluation and on the Brunet-Lézine Developmental Psychomotor Scale. Abnormalities in muscular shortening and delay in motor skills were found. These findings are critical as regards environmental influences on postural development, continuities in motor development and issues of early primary prevention. Early identification and follow-up programmes, including frequent changes in posture, are suggested in order to avoid abnormalities of motor behaviour and subsequently in postural patterns.     

Morphometric analysis of the great vessels in early fetal life

Pathological examination of the heart and great vessels wasperformed in 61 specimens obtained after surgical terminationof pregnancy for psychosocial indications at 9–18 weeksof gestation. The aorta and pulmonary trunk were identifiedand external diameters were measured at the level of, and distalto the aortic valve and pulmonary valve, the level of the aorticisthmus and thoracic aorta, and the proximal and distal ductusarteriosus. All eight vessel diameters increased linearly withgestational age and the ratio of the diameter of the aorticisthmus to that of the aortic valve or the distal ductus arteriosusalso increased with gestation. Early pregnancy is characterizedby rapid growth of the fetal head and this may well be the consequenceof a preferential distribution of left ventricular output infavour of the head due to relative narrowing of the aortic isthmusat this gestation.     

Position of growth cones within the retinal nerve fibre layer of fetal ferrets.

Optic axons are added to the retinal nerve fibre layer of fish along its vitreal border in a chronotopic manner. Likewise, the optic tract of all vertebrate species acquires axons preferentially along the superficial surface of the pathway. We have examined the developing retina of fetal ferrets (Mustela putorius furo) aged between embryonic day 27 (E27) and E34 to see whether a similar segregation of growth cones is apparent within the mammalian retinal nerve fibre layer. The distributions of growth cone, "wrist" (thick trailing portion of the growth cone), axonal, and glial profiles were determined from electron micrographs, and expressed as a percentage of neural profiles for several retinal locations. The retinal nerve fibre layer of fetal ferrets contains radially elongated bundles of fibres composed of axonal, wrist, and growth cone profiles. Glial processes of varying density divide the adjacent bundles, occasionally subdividing them in the plane of the retina, and give rise to endfeet lining the basal lamina and separating the optic axons from the latter. Growth cones within the developing fibre layer represented about 2.4% of profiles at E28, while at later developmental stages (E34), this value fell to about 0.6%. During this period of axonal outgrowth, growth cones were not preferentially segregated toward the vitreal basal lamina or the glial endfeet within the nerve fibre layer. Rather, they were found scattered throughout the axon bundles of the fibre layer. While there were differences in the proportion of immature profiles found within the vitreal half compared to the scleral half of the fibre layer, such that more growth cones and wrists were found vitreally, there was no clear accumulation of them in association with features of the vitreal margin. The present results show that young and old optic axons course together throughout the depth of the nerve fibre layer. A chronotopic mode of pathway genesis such as seen in the optic fibre layer of fish or in the optic tract of mammals is not present in the nerve fibre layer of ferrets. Differences in growth cone behaviour in the optic fibre layer and tract indicate that the mechanisms governing pathway formation differ along its course.