Fluorescence studies on aged and young erythrocyte populations

Structural changes in red blood cell (RBC) membrane are investigated by fluorescence techniques. Results obtained with three probes (DPH, 3-PM and fluorescamine) indicate a significant increase in membrane rigidity associated with aging of RBCs. Discrepancies between our observations and published data could arise from utilization of experimental conditions closer to physiological conditions in our study. Use of intact RBCs continuously manipulated in a 37 degrees C environment could represent experimental conditions favourable to the identification of rheologic membrane changes in senescent RBCs.     

A neural cocktail-party processor

Sensory segmentation is an outstanding unsolved problem of theoretical, practical and technical importance. The basic idea of a solution is described in the form of a model. The response of neurons within the sensory field is temporally unstable. Segmentation is expressed by synchronization within segments and desynchronization between segments. Correlations are generated by an autonomous pattern formation process. Neuronal coupling is the result both of peripheral evidence (similarity of local quality) and of central evidence (common membership in a stored pattern). The model is consistent with known anatomy and physiology. However, a new physiological function, synaptic modulation, has to be postulated. The present paper restricts explicit treatment to the peripheral evidence represented by amplitude modulations globally present in all components of a sound spectrum. Generalization to arbitrary sensory qualities will be the subject of a later paper. The model is an application and illustration of the Correlation Theory of brain function.This work has been supported by Grant I/37-821 of the Stiftung Volkswagenwerk.     

Histochemical studies on the lipids in the epithelium of the fetal colon

Summary Large intestines from 30 fetuses with crown-rump lengths ranging from 26 to 180 mm have been studied histochemically as to their epithelial content of lipids. These lipids have been localized intracellularly and basally in the cells, and comparative studies of the colon and the small intestine have demonstrated that there are considerable amounts of lipids in the colon as compared with the small intestine.It is concluded that the main part of the lipids consist of saturated and unsaturated constituents.The possible explanations of the lipids as absorbed material, biological active material synthetized de novo or as material involved in the metabolism of fetal surface cells are discussed.This work was supported by a grant from the Aid of the Crippled Children, New York.     

Zur Verbreitung der ABO-Blutgruppen in der Bevölkerung Nordthailands

2048 subjects in North Thailand were examined for AB0 blood groups. A control group representative of the population of the provinces of Chiengmai and Lampun was formed of 382 examinees and 3403 blood donors.The distribution of AB0 groups in this population is similar to that of Central Thailand. Some ethnic groups show significant deviations: The Miao tribe, originating in South China, has a much higher frequency of B. There was a significant reduction in gene A and B in the younger generation of this tribe. The Thai Yong, people who migrated to North Thailand from Yunnan in the 19th century, show an AB0 distribution similar to Chinese in Yunnan. They differ significantly from the Northern Thai. There is also a difference in the distribution of -thalassaemia and hemoglobin E between these two groups.Male leprosy patients showed an excess of group A which was not present in female patients. The percentage of severely ill patients was much higher in the males. Differentiation into lepromatous and tuberculid forms is not available. Among 108 people who had suffered from smallpox approximately 20 years ago there was an excess of groups 0 an B in comparison to the control group.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Effects of isoniazid (INH) on the oogenesis of mice

Summary Mutagenic damages in female germ, cells of mice have been tested with the dominant, lethal assay and the cytogenetic analysis of unfertilized M II-oocytes. Concluding one can say that from the experimental data presented here do not show any mutagenic effect of INH on oogenesis of different strains of mice can be stated.     

The spatial distribution of currents in the receptor layer of the frog retina

Steady state patterns of currents flowing extracellularly in the receptor layer of the frog retina are used to work out an electrical model of vertebrate rods. The model can be thought of as a linear network consisting of resitances and current sources. The model predicts the axial spread of currents along the outside of the receptors. In addition, it predicts membrane voltages in light and darkness. If the dark-adapted receptors are assumed to have a uniform membrane with a specific resistance of 500 ·cm², a single rod gives rise to an extracellular dark current of about 200 pa.     

Angiotensin-like activity in resistance vessels

Summary Angiotensin II (ANG II) was localized immunocytochemically in kidney and various other organs of the chinese hamster. In the kidney ANG II-like activity was found in the epitheloid cells of the juxtaglomerular apparatus as well as in the media i.e. the smooth muscle cells of arcuate and interlobular arteries and afferent arterioles. ANG II-like activity was also observed in the medial muscle cells of resistance vessels in other organs and tissues such as submandibular gland and brown adipose tissue. The site of synthesis of ANG II needs to be investigated but the data point to the possibility of an intracellular function of ANG II in smooth muscle cells of blood vessels.These studies were supported by the Deutsche Forschungsgemeinschaft within the SFB 90 Cardiovasculäres System     

Bisexual behavior in the male rat: Influence of masculine sexual activity on the display of lordosis behavior

Sexually inexperienced male Wistar rats (strain WI in our colony) known to very infrequently display spontaneous lordosis behavior (Schaeffer et al., 1990b) were used. A first group was tested four times at 5-day intervals for lordosis with vigorous stimulus males (heterotypic sexual behavior), immediately following testing for masculine sexual activity with highly receptive females (homotypic sexual behavior). A small number of animals displayed lordosis during the first test, but more and more animals displayed this behavior from the first to the fourth test. There was no relationship between the degree of masculine sexual activity--intromission without ejaculation or ejaculation--and the occurrence of lordosis behavior. A second group was tested only once for both masculine sexual activity and lordosis behavior as above and afterwards three times at 5-day intervals for lordosis behavior in the absence of any previous testing for masculine sexual activity. A few animals displayed lordosis during their first test. As compared to the first group, the animals which had not displayed lordosis in the first test never showed lordosis responses in the following tests. It is concluded that both homotypic and heterotypic sexual interactions are required for the display of lordosis behavior in the strain of Wistar rats used in this study.     

Mutation of asparagine 111 of rubisco from Rhodospirillum rubrum alters the carboxylase/oxygenase specificity.

The conserved asparagine 111 of ribulose-1,5-bisphosphate carboxylase/oxygenase from the photosynthetic bacteria Rhodospirillum rubrum was identified as a candidate for a side-chain that might be involved in the carboxylase/oxygenase specificity. It was replaced by site-directed mutagenesis with aspartic acid, leucine, glutamine or glycine residues. The mutant enzymes exhibit a very low carboxylase activity compared with the wild-type enzyme. The values of Km(RuBP) and kcat for Asn111----Gly, the most active mutant, are 420 microM and 0.034 s-1, compared with 13 microM and 3.0 s-1 for wild-type. The mutation of Asn111----Gly causes a more than tenfold decrease in the CO2/O2 specificity factor, tau, tau Asn111----Gly = 0.56 and tau wild-type = 6.7. This is the first reported change in rubisco specificity by a single site-directed mutation alone and suggests a target for future protein engineering studies.