Characteristics of neuronal systems in the visual cortex

The coupling complexity of cortical areas makes it very difficult to analyse them experimentally. Studies of model systems provide the possibility of adapting the analysis to the available data base and elaborating the fundamental properties that depend on the structure of the system. We propose a model system of variable complexity that is spatially two-dimensional and time-dependent, uses feedback for iteration and smoothing, includes the mapping of the cortical networks and can be nonlinear as the case requires. Combining such elementary systems on the basis of neuroanatomical findings enables us to simulate cortical mappings and to interpret neurophysiological data. The decisive factor is that the dynamics of the system and the neuroanatomically based spatial coupling are closely connected with each other.     

Tranexamic acid as an aid to reducing blood transfusion requirements in gastric and duodenal bleeding.

A prospective randomised double blind study examined the effect of the antifibrinolytic drug tranexamic acid compared with placebo in 154 patients bleeding from verified benign lesions in the stomach or duodenum or both. Three out of 72 patients receiving tranexamic acid underwent emergency surgery compared with 15 out of 82 given placebo (p = 0.010). Nineteen patients receiving placebo rebled during their admission as compared with 10 in the active treatment group (p = 0.097). Blood transfusion requirements were significantly reduced by tranexamic acid (p = 0.018). Side effects occurred in six patients, of which an uncomplicated deep venous thrombosis was the most severe. Tranexamic acid reduces the blood transfusion requirement and need for emergency surgery in patients bleeding from a benign gastric or duodenal lesion.     

Effect of bromocriptine and progesterone on the length of the ovarian cycle in 4- and 5-day estrous cyclic rats

To study the effect of prolactin and progesterone on the length of the reproductive cycle in the rat, rats of different estrous cycle length (four and five days, respectively) were injected daily (09.00 h) with either bromocriptine (1 mg/rat) or 70% ethanol vehicle (0.25 ml) from the day of estrus onward, up to the appearance of the next ovulation. Each group of rats was then (16.00, metestrus) also injected with either progesterone (4 mg/rat) or 0.2 ml of olive oil. The effects of these treatments on the length of the estrous cycle was studied by both the recording of vaginal smears daily and by direct visualization of oocyte-cumulus complexes on the ensuing day of estrus (10.00 h-12.00 h). Bromocriptine treatment shortened the length of the cycle by one day in 5-day but not in 4-day cyclic rats, while progesterone treatment lengthened estrous cycles by one day in both groups of rats. Treatment with both bromocriptine and progesterone had no effect on the estrous cycle length of 5-day cyclic rats, but did prolong in one day the cycle of 4-day cyclic rats. These facts suggest that prolactin regulates the length of the ovarian reproductive cycle in the rat through its action on the secretion of progesterone by the corpus luteum.     

Role of phospholipase A2 in the stimulation of sponge cell proliferation by homologous lectin

Using the Geodia cydonium system, we showed that after incubation of competent sponge cells in the presence of lectin, phospholipase A2 was released from the cells. The substrates for this enzyme, phosphatidylethanolamine and phosphatidylcholine, were identified in the extracellular material of sponge tissue. In addition, the phospholipase A2 inhibitor calelectrin was identified by immunobiochemical techniques; this molecule was associated with the aggregation factor. Reconstitution experiments strongly suggested that phospholipase A2 catalyzed the release of arachidonic acid, which is then taken up by the cells. Intracellularly, arachidonic acid was metabolized primarily to prostaglandin E2. Inhibition studies revealed that prostaglandin E2 is involved in the ultimate increase of DNA synthesis. These findings suggest that the phospholipase A2-arachidonic acid system is involved in the matrix-initiated signal transduction pathway in sponges.     

Analysis of the HLA-A10-crossreacting group of antigens by one-dimensional isoelectric focusing

The antigens belonging to the HLA-A10 group, HLA-A25, -A26, -Aw34, and -Aw66, have been characterized serologically during the International Histocompatibility Workshops. However, it remains difficult to discriminate between the HLA-A26 antigen on the one hand and the HLA-Aw34 and -Aw66 antigens on the other on the basis of serology. In this paper, we compare the serologically defined antigens with the data obtained by one-dimensional isoelectric focusing. The results indicate that the serologically well-defined HLA-A25 antigen cannot be discriminated from the HLA-A26 antigen by one-dimensional isoelectric focusing. In contrast, this technique can indeed be used to discriminate between HLA-A26, -Aw34 and -Aw66 antigens. In addition, the biochemical analysis suggests further heterogeneity of the HLA-Aw34 antigen. This antigen can be subdivided into three variants.     

Significance of myocardial eicosanoid production

Summary The precise role of eicosanoids in the development of myocardial injury during ischemia and reperfusion is still a matter of debate. Enhanced local production of these bioactive compounds appears to be a common response to tissue injury. Most likely, the cardiac tissue has the capacity to generate prostaglandins, thromboxanes as well as leukotrienes. Prostacyclin (PGI,) is the major eicosanoid produced by the jeopardized myocardium. In addition, at sites of tissue injury activation of platelets and infiltrating leukocytes results in the formation of considerable amounts of thromboxanes and leukotrienes. The production of eicosanoids requires prior release of arachidonic acid (AA) from phospholipids. Both ischemia and reperfusion are associated with a rise in the tissue level of AA. The absence of a proportional relationship between the tissue level of AA and the amounts of PGI, produced suggests that the sites of AA accumulation and PGI₂ formation are different. It is conceivable that AA accumulation is mainly confined to myocytes, whereas the capacity to synthesize PGI, mainly resides in vascular cells. Both beneficial and detrimental effects of eicosanoids on cardiac tissue have been described. Prostaglandins act as vasodilators. Besides, some of the prostaglandins, especially PGI,, are thought to possess cyto-protective properties. Thromboxanes and leukotrienes may impede blood supply by increasing smooth muscle tone. Besides, leukotrienes augment vascular permeability. Experimental studies, designed to evaluate the effect of pharmacological agents, like PGI₂-analogues and lipoxygenase and cyclo-oxygenase inhibitors, indicat that eicosanoids influence the outcome of myocardial injury. However, the delineation of the physiological significance of the locally produced eicosanoids is complicated by such factors as the wide variety of AA derivatives produced and the dose-dependency of their effects.     

Early and late effects in the bone marrow of mice following 2 Gy (6 MeV) neutron irradiation

Summary Following 5 Gy gamma irradiation, residual damage in bone marrow persisted up to one year and was ascribed to genetic defects in hemopoietic stem cells (von Wangenheim et al. 1986). To see whether high LET radiation is more efficient in inducing late effects, mice were whole-body irradiated with a single dose of 2 Gy neutrons ( = 6 MeV) and femoral cellularity, CFU-S number, proliferation ability of bone marrow cells (PF) and the compartment ratio (CR), i.e. the splenic 125-iodo-deoxyuridine incorporation per transfused CFU-S were measured up to one year after the radiation insult. Within 12 weeks, femoral cellularity, PF and CR recovered to control or near-control level, whereas CFU-S numbers remained significantly below control. No further recovery was observed. On the contrary, PF and CR deteriorated again after 12 and 26 weeks, respectively. CFU-S per femur tended to decrease as well. Thus it is demonstrated that a single dose of 2 Gy 6 MeV neutrons causes significant injury in function (PF) and structure (CFU-S numbers, CR) of bone marrow which persisted up to one year. While this residual injury can be attributed to genetic defects in hemopoietic stem cells, its increasing expression is probably due to late evolving damage in microenvironmental cells. The RBE of 6 MeV neutrons for the introduction of late effects in the bone marrow is in the range of 3.