The fine structure of the visual system of lycosa (Araneae: Lycosidae)

Summary The optic lobes of spiders contain a well differentiated synaptic region — the lame medullaire — in which the photoreceptor axon terminals synapse with the axons of the second order neurons.Each photoreceptor terminal has a very irregular outline and contains a great number of vesicles. It sends out collateral branches which end either in contact with other photoreceptor terminals or in contact with second order fibers. The second order fibers lie deeply recessed within folds of the photoreceptor terminal membrane. Frequently branches of the second order fibers can be seen as independent elements within the photoreceptor terminals. The synaptic loci are characterized by the presence of synaptic ribbons surrounded by cumuli of vesicles. These synaptic loci are always located at the intermembrane cleft between adjacent second order fibers.Synaptic structures have been found also within the second order fibers which in such cases appear as pre-synaptic elements in regard to the photoreceptor terminals.Research sponsored by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFOSR Grant Nr. 618-64.     

Rheological characterization of xanthan fermentation broths and their reconstituted solutions

Two strains of X. campestris from a collection and a wild strain isolated from infected cabbage were cultured in a defined medium in a 25 dm³ fermenter. The rheological characteristics of the broth were measured using a Weissenberg rheogoniometer. The rheological behaviour over a wide range of shear rates could be described with the power law model and a yield stress was obtained using the Herschel-Bulkley equation. As expected, the broth's flow behaviour is highly influenced by gum concentration. In general, the rheological parameters during the fermentations varied within the following ranges: K (2–210 dyn-sⁿ/cm²), n (0.2–0.9), τ _y (0.02–50 dyn/ cm²), with strain 1459 reaching the maximum values as well as the highest gum concentration. Differences in flow behaviour could be associated with different molecular configurations of the polymers produced by the different strains. Heat treatment of the broths change the rheological characteristics, increasing K and decreasing n. Reconstituted solutions of all sterilized gums exhibited similar rheological characteristics and, at low concentrations, also similar to those of a commercial xanthan.     

Subcellular localization of the major pneumococcal autolysin: a peculiar mechanism of secretion in Escherichia coli

The major pneumococcal autolysin (N-acetylmuramoyl-L-alanine amidase) has been localized in the cellular envelope of Streptococcus pneumoniae and Escherichia coli by using immunocytochemical labeling on ultrathin sections and whole-mounted cells. Cell fractionation experiments in E. coli confirmed the peripheral localization of the pneumococcal amidase and suggested that this enzyme is weakly bound to the outer face of the cytoplasmic membrane. This interaction does not depend on the presence of choline but represents an intrinsic property of the amidase. The autolysin, that is synthesized without any N-terminal signal sequence (García, P., García, J. L., García, E., and López, R. (1986) Gene (Amst.) 43, 265-272) was not processed during translocation. A new regulatory mechanism that might be specific for bacterial autolysins is discussed.     

Thymosin-beta 4 gene. Preliminary characterization and expression in tissues, thymic cells, and lymphocytes

A cDNA for rat thymosin-beta 4 was used to investigate the expression of this gene in different tissues, thymic cells, and lymphocytes. Hybridization analysis of total RNA from 13 rat tissues demonstrated the presence of an 800 nucleotides-long mRNA in all the tissues surveyed, with the highest levels in spleen, thymus, and lung. Examination of thymic cells showed that the thymosin-beta 4 gene is predominantly expressed in thymocytes. The thymosin-beta 4 mRNA was also studied in Ig+ and Ig- lymphocytes, being fourfold more abundant in Ig- than Ig+ splenic lymphocytes, whereas similar levels were found in both types of blood cells. The analysis of RNA from T cells at different maturation stages evidenced slight differences in their thymosin-beta 4 mRNA content, indicating that thymosin-beta 4 gene expression is not clearly related to the differentiation process of T cells. All these results do not support the roles for thymosin-beta 4 in cellular immunity and differentiation of lymphoid cells, suggesting a more general function for this peptide. Preliminary characterization of the human beta 4 gene by restriction analysis disclosed a complicated pattern consistent with multiple genes and/or introns. The analysis of genomic DNA from different species ranging from humans to Escherichia coli showed that this gene is only highly conserved in mammals.     

Photoperiodic variations in plasma concentration of testosterone in the rabbit

The photoperiodic variations of testosterone plasmatic levels in male rabbits have been studied. The animals were subjected to the influence of three circadian rhythms: 12/12, 14/10 and 10/14 h of light/darkness. The hormone assay was carried out using an enzymeimmunoassay method (Competitive ELISA). Blood samples were of two different types: seriated and non-seriated, to find if these might be any differences in the results. It is concluded that testosterone plasmatic levels are within physiologic values (0.3-10.0 ng/ml), although differences depending on the light/darkness cycle and on the type of blood extraction are remarkable; for this reason the selection of the circadian rhythm will depend on the experimentation that is to be carried out.     

Certain aspects of so-called post cholecystectomy syndrome

The study involved 126 patients with cholelithiasis. Set of biochemical, radiological, endoscopic, and ultrasound examinations was carried out in these patients. Potential coincidence of clinical symptoms and causes of so-called postcholecystectomy syndrome was the purpose of a 1-year follow-up studies. The significance of the results are discussed.     

Monotherapy with acebutolol in hypertensive diabetic patients

Monotherapy of hypertension with acebutolol in diabetics in daily dose of 200-400 mg for 6 weeks induced only non-significant and practically not acceptable hypotensive effect in groups of patients with hypertension and diabetes type I or type II without nephropathy. No therapeutical effect was observed in hypertension in diabetics type I with nephropathy. Administration of acebutolol to hypertensive diabetic patients with nephropathy resulted in tendency to increase in albuminuria. Values of creatinine clearance did not change at the same time. Also no effect of acebutolol on glycemic or lipid indices was observed. The lack of clear hypotensive effect under studied conditions of acebutolol in diabetic patients contrasted with its significant action in comparative group of hypertensive non-diabetic subjects.     

The role of insulin in the control of triacyglycerol (TG) in the rat skeletal muscles

The role of insulin in the control of triacyglycerol (TG) in different types of skeletal muscle has not been fully recognized so the aim of the present study was to fill this gap. The experiments were carried out on control rats, those fed with olive oil or fed with the oil and treated with insulin and on streptozotocin diabetic animals at rest and there after exercise till exhaustion. The level of TG was measured in the white and red layers of the vastus lateralis, the soleus and the diaphragm. It was found that acute feeding with olive oil had no effect on TG level in either muscle type examined. Insulin administered to rats fed with oil increased TG level in the red vastus. Streptozotocin diabetes caused an increase in TG level in muscles with high oxidative potential. Exercise lowered the level of TG only in the red vastus of the diabetic rats. It is concluded that insulin may increase muscle TG level. Accumulation of TG in muscles of rats with acute diabetes is likely to be a result of the high plasma free fatty acid concentration. Acute insulin deficiency did not affect the muscle TG response to exercise.     

Incomplete process of recombinant human platelet-derived growth factor produced in yeast and its effect on the biological activity.

Partially purified recombinant human Platelet-derived Growth Factor BB homodimer isolated from yeast culture media contains variable amounts of unprocessed PDGF-BB. This unprocessed PDGF-BB is found as a result of incomplete cleavage of the precursor to form the mature protein. Although the signal peptide is efficiently removed, a fraction of the PDGF secreted has an extended sequence corresponding to the truncated yeast alpha-factor leader. The data suggest that it is the amino acid chain from the truncated a-factor leader and not the sugar moiety attached to it that is responsible for the higher mitogenic activity found in this unprocessed molecule compared to highly purified PDGF-BB.     

A new spectrophotometric assay for dopachrome tautomerase

The existence of a new enzyme involved in mammalian melanogenesis has been recently reported. The names dopachrome oxidoreductase and dopachrome tautomerase have been proposed for the enzyme. So far, this enzyme has been assayed at 475 nm on the basis of its ability to catalyze dopachrome decoloration. This method presents two major problems, derived from the instability of the substrate (dopachrome): (1) dopachrome must be prepared immediately before use, and (2) the rate of dopachrome decoloration in the absence of the enzyme is not negligible, and, furthermore, is enhanced by non-enzymatic agents. In order to overcome these problems, we present a new procedure that combines: (1) a quantitative, fast and easy way to prepare dopachrome from L-dopa by sodium periodate oxidation; (2) a spectrophotometric method in the UV region, at 308 nm, based on following the absorbance increase due to the enzyme-specific tautomerization of dopachrome to 5,6-dihydroxyindole-2-carboxylic acid as opposed to the absorbance decrease due to the spontaneous decarboxylative transformation of dopachrome into 5,6-dihydroxyindole. The advantages of these methods as compared to the previously used procedures are discussed.