Binding of vinyl polymers to anionic model membranes.

The association of poly2-vinylpyridine (P2VPy) and poly4-vinylpyridine (P4VPy) to dimyristoylphosphatidic acid (DMPA) small unilamellar vesicles (SUVs) was studied as a function of pH, ionic strength (I), polymer concentration and temperature using spectrofluorimetry. Poly(vinylpyridine) (PVPy) data were transformed into association isotherms and analyzed in terms of binding and partition models. In the case of polyions, the inclusion of the activity coefficient in both models was essential. Moreover, a relating equation was proposed to compare parameters based on both theoretical approaches. On the basis of the results obtained, a model was developed to analyze polymer adsorption at the surface level, in which the length of the hydrophobic chain and the position of the N atom in the pyridinium ring play an important role. Transition temperature (Tc) for DMPA (ca. 55 degrees C) is decreased between 15 degrees C-19 degrees C in the presence of PVPy. Van't Hoff isochore showed that the binding constant (KA) accounted for average PVPy-DMPA two-dimensional solid and liquid interactions. KA decreased with I in the presence of both polymers, but was more sensitive to I in the case of P2VPy. Likewise, the number of phospholipid heads (N) involved in the binding process decreased with I in the presence of PVPy. The influence of I was more significant on N than on KA.     

Experimental tendon repair: glycosaminoglycan arrangement in newly synthesized collagen fibers.

Changes in the macromolecular orientation and metachromasy of glycosaminoglycans (GAG) in newly synthesized and assembled collagen fibers in rat Achilles tendon after tendon excision were investigated in toluidine blue (TB)-stained preparations, based in the selective absorption of polarized light (= linear dichroism, LD) and of absorption of unpolarized light in situ. Extrinsic LD was observed microspectrophotometrically from the early phases of tendon repair onwards, although the absorption peaks in both parallel and perpendicular directions with respect to the plane of polarized light and the long axis of the collagen fibers occurred at the same wavelength, and thus differed from the pattern situation in normal adult controls. Compared to normal adult tendons, the pattern of LD in newly synthesized and assembled fibers was still not fully attained 110 days after surgical tendon removal. This incomplete recovery possibly reflected the influence of aging during the repair process. There was no correlation between LD and metachromasy. The highest absorption values for metachromatic staining occurred on the 7th day after tendon removal, at a time when LD was not intense. Treatment with hyaluronidase showed that the LD in the early stages of tendon repair was mostly due to hyaluronate whereas the LD in the later stages was due to chondroitin sulfates. The changes in LD during Achilles tendon repair were attributed to gradual modifications in the composition and macromolecular orientation of GAGs relative to the long axis of the collagen fibers.     

In vitro micropropagation of the macarronesian evergreen treePersea indica (L.) K. Spreng

Summary Shoot propagation ofPersea indica (L.) K. Spreng was achieved using seedling axillary buds cultured on MS (Murashige and Skoog, 1962) medium with 1 mg/l (2.8 μM) N⁶-benzyladenine (BA). Forty percent of the obtained shoots did not elongate, but showed bud proliferation, which was maximal (three axillary buds per shoot) at the end of the seventh subculture. Sixty percent of the shoots elongated, did not show bud proliferation, and formed calluses at their base. Successful rooting (84.6%) was achieved dipping the base of each elongated shoot in 3 g/l (16.11 mM) indolebutyric acid (IBA) for 1–2 s, and transferring to half strength MS medium without growth regulators. These shoots presented an acclimatization success of 100%. Results suggest that micropropagated elongated shoots ofP. indica can be adequately used in reforestation programs.     

The complete amino acid sequence of the major alpha subunit of the lectin from the seeds of Dioclea grandiflora (Mart)

The complete amino acid sequence of the major alpha subunit of the lectin from seeds of Dioclea grandiflora was determined. The sequence was deduced from analysis of peptides derived from the native alpha subunit by digestion with trypsin, chymotrypsin, the Staphylococcus aureus V8 protease, and pepsin; and from larger peptides produced by digestion of the citraconylated protein with trypsin. The alpha subunit consists of a single polypeptide chain of 237 amino acids which differs from the sequence of concanavalin in 53 positions. Significant levels of heterogeneity were observed in five positions in the sequence.     

Distribution of the genus Ancylostoma (Dubini, 1843) along the digestive tube of the dog (author's transl)

The A. A. studied the distribution of nematodes of the genus Ancylostoma (Dubini, 1843) along the digestive tube of 45 dogs. For the collection of the worms they used the method developed by Mello and Campos. The distribution found was: 97,5% in the jejunum, 1,2% in the ileon, 0,7% in the duodenum, 0,3% in the colon, 0,2% in the cecum and 0,1% in the stomach.     

Pulmonary maturation in the hypophysectomised ovine fetus. Differential responses to adrenocorticotrophin and cortisol

Pulmonary maturation in six ovine fetuses hypophysectomised by a cryosurgical method at 0.7-0.8 of pregnancy and delivered by hysterotomy at 152.2 +/- 2.9 (SD) days was compared with that in seven control fetuses delivered at 144.5 +/- 3.5 days. Both the wet and the dry weight of the lungs was less in the hypophysectomised fetuses but total DNA did not differ. Lung volumes at 40 cm of H2O and at 5 cm of H2O on deflation in hypophysectomised fetuses were less than one-third that of controls. Saturated phosphatidylcholine, as an estimate of surfactant, was lower in both lung tissue and lavage fluid. A further group of hypophysectomised fetuses was infused intravenously either with cortisol at 1 mg/h for 72 h (n = 6), or with ACTH1-24 at 5 microgram/h for 84 h (n = 6) before delivery at 155.0 +/- 2.1 days and 154.2 +/- 3.9 days respectively. None of the indices of pulmonary maturation in the cortisol-treated fetuses differed from those in untreated hypophysectomised fetuses whereas values for lung volumes at 40 and 5 cm of H2O in ACTH-treated fetuses were more than twice those of untreated hypophysectomised fetuses and did not differ significantly from controls. In addition, the amount of saturated phosphatidylcholine in lavage fluid was greater in ACTH-treated fetuses (0.13 +/- 0.10 mg/g) than in untreated hypophysectomised fetuses (0.04 +/- 0.48 mg/g). Lung volume at 40 cm of H2O in four fetuses that were thyroidectomised at the time of hypophysectomy responded to ACTH as in hypophysectomised fetuses with intact thyroids but other indices were unaffected. We conclude that hypophysectomy retards pulmonary maturation in fetal sheep. Since ACTH restores distensibility and increases alveolar surfactant in the absence of other pituitary hormones it is likely that ACTH has a major role in lung maturation. The lack of response to cortisol suggests that the effect of ACTH is not mediated only by circulating cortisol.     

Modified oscillation behavior and decreased D-3-hydroxybutyrate dehydrogenase activity in diabetic rat liver mitochondria

One month after induction of diabetes in adult white rats with streptozotocin or 4–10 months after its induction by pancreatectomy (in every case glycemia was over 3 g/liter), the following alterations were observed in liver mitochondria: (a) a decrease of amplitude and an increase of the damping factor of volume oscillations induced by potassium ions and valinomycin; (b) a 50% decrease of d-3-hydroxybutyrate dehydrogenase (HBD) activity in mitochondria disrupted by repeated freeze-thawing; (c) a similar decrease in the rate of d-3-hydroxybutyrate oxidation by intact mitochondria; (d) a significant increase of cytochrome oxidase activity and cytochrome aa₃ content. Measurement of succinate dehydrogenase and NADH dehydrogenase activity, the cytochrome b, c₁, and c content, and the P:O ratio for mitochondria oxidizing d-3-hydroxybutyrate did not reveal significant differences between control and diabetic rat mitochondria. In the streptozotocin-injected rats, the variation of HBD activity and the modification of the mitochondrial oscillation pattern were time-dependent phenomena, both effects reaching their maximal expression about 1 month after the onset of diabetes. The variation of HBD activity followed a biphasic course, since it rose to above the control level during the first 2 weeks of diabetes, then fell progressively to about half the control value after the third week. Treatment of diabetic rats with NPH insulin (5 IU twice daily, for 3 days, reinforced by the same dose 45 min before sacrifice) restored the mitochondrial oscillation pattern, HBD activity, and rate of d-3-hydroxybutyrate oxidation by intact mitochondria to their normal values.     

A limnological reconnaissance of Lake Tebenquiche,Salar de Atacama,Chile

A number of expeditions to the area of Salar de Atacama, Chile, 68° 15'W, 20° 30'S, have involved studies of the biological and chemical features of Lake Tebenquiche, situated in the interior of the salar. Chemically, Tebenquiche is hypersaline, with practically anoxic waters dominated by sodium and chloride ions but with high concentrations of sulphate also. The lake is surrounded and invaded by macrophytes, dominated by Scirpus olmeyi and Juncus, which provide organic material for the formation of bacterial mats. The fauna of limnetic crustaceans is almost exclusively of Artemia salina. The most important genera of bacteria are: Marinomonas, Halobacterium, Acinetobacter and the sulphur reductors Vibrio and Bacillus. The Cyanobacteria are represented exclusively by Oscillatoria.     

Fine needle aspiration of retroperitoneal human dirofilariasis with a pseudotumoral presentation

The accidental finding of a pseudotumoral para-aortic mass in a 60-year-old woman led to the performance of a fine needle aspiration (FNA) biopsy under ultrasonographic guidance. The milky aspirate was centrifuged and processed as a cell block. The examination of sections confirmed the lymphatic origin of the sample, but also revealed some unexpected parasitic structures. While a complete identification could not be made on a few sections, the morphologic and epidemiologic evidence suggested Dirofilaria repens. The mass was surgically removed and identified as an adenolymphocele, which appears to be a new localization of dirofilariasis in humans. This case emphasizes the utility of FNA in diagnosing such unexpected findings without the use for exploratory surgery.