Alteration of membrane permeability by amphotericin B

Amphotericin B (AmB) increased unidirectional Na transport and net transcellular sodium movements across the skin of the frog, Rana pipiens, when added to the solution bathing the corium side, but not from the outer epidermal surface. The AmB response was prevented with pretreatment with amiloride, ouabain and mucosal sodium substitution. Alteration in pH markedly reduced the permeability changes induced by AmB. AmB did not interfere with the increase in sodium transport induced by antidiuretic hormone. The present study demonstrates that AmB interacts with the skin of the frog, Rana pipiens, from the corium side specifically increasing transepithelial sodium transport. The increase in transport apparently occurs through the existing sodium pathway.     

Vers une approche physiopathologique des troubles de l’éjaculation

Seminal emission and sperm expulsion are under the control of both the sympathetic and parasympathetic outflows and also of the somatic innervation conveyed by the pudendal nerve. The 2 phases of ejaculation are reflexive with the reflexes handled at the thoraco-lumbar and sacral levels of the spinal cord. Such a spinal organization remains widely unknown. The role of various peripheral neurotransmitters has been evidenced including norepinephrine and acetylcholine and also peptidergic, purinergic i.e. ATP and nitric oxide. Stimulation of the seminal tract afferents play a crucial in the onset of ejaculatory mechanisms. Except for the dorsal nerve of the penis, there is a lack of information concerning these afferents. Several supraspinal centers i.e. hypothalamus, medial amygdala, pons and nucleus paragigantocellularis exert descending and ascending inhibitory and excitatory influences on spinal nuclei controlling emission and expulsion of sperm. Central neurotransmission responsible for this supraspinal control could involve serotonin, oxytocin and norepinephrine. In the light of the available anatomical and neurophysiological data, pathophysiological aspects of ejaculatory disorders are futher discussed. Premature ejaculation could be related to a periheral and central hypersentivity. Most of the other ejaculation abnormalities are likely mainly related to an impairment of the central mechanisms.     

Comparative effects of four surfactants on growth,contraction and adhesion of cultured human fibroblasts

A range of surfactants, including the anionic sodium dodecyl sulfate, the cationic cetyltrimethylammonium bromide and the nonionics octylphenoxy polyethoxyethanol (Triton X100) and polyoxyethylene 20 sorbitan monoleate (Tween 80) was studied for effects on proliferation, contractibility and attachment of cultured human fibroblasts. Only ionic surfactants exhibited a stimulatory effect on fibroblast proliferation, whereas all the surfactants tested increased the contraction of collagen gels containing fibroblasts, with the greatest effect from the non-ionic surfactants. This activity was not correlated with an increase of cell population or cell attachment within the collagenous matrix. The activity of the surfactants was seen only at levels close to their LD₅₀ values and in a narrow range of concentrations. Thus, we consider that they are the result of the so-called hormesis phenomenon.Abbreviations CTAB cetyltrimethyl-ammonium bromide - FCS fetal calf serum - LD₁₀₀ dose lethal to 100% of exposed - MCD maximal contraction dose - PDL population doubling level - SDS sodium dodecyl sulfate     

Subculture of rabbit articular chondrocytes within a collagen gel: growth and analysis of differentiation

Primary cultures of rabbit articular chondrocytes have been subcultured within three-dimensional (3D) collagen gels. Under these conditions, the cells remained viable and divided, but with a lower proliferation rate than that observed in control monolayer cultures. Flow cytometric analysis of progression of the cells into the cell cycle has confirmed and extended these findings. Also the cellular volume was decreased in 3D-culture, being in the same range as thein vivo size of cartilage cells. Specific staining for proteoglycans and type II collagen immunolocalization on sections of gels showed the expression of differentiated phenotypes and revealed the accumulation of these matrix components in the immediate surroundings of the cells. The use of Ultroser G (a serum substitute) improved the conditions for 3D- culture of rabbit articular chondrocytes.     

Existence of very weak level of residual multiple innervation of Purkinje cells through climbing fibers in the cerebellum of the normal adult rat

Extra- or intracellular unit responses of Purkinje cells to the activation of climbing fibres were recorded in the cerebellum of adult rats. Out of 1.719 cels studied, only 4 were found to be innervated by more than one climbing fibre. This very small rate of residual multiple innervation in the normal adult illustrates the accuracy of the synaptic elimination process which leads to the innervation of each Purkinje cell through only one climbing fibre during normal development in the rat.     

Anaerobic Degradation of Cyanuric Acid, Cysteine, and Atrazine by a Facultative Anaerobic Bacterium

A facultative anaerobic bacterium that rapidly degrades cyanuric acid (CA) was isolated from the sediment of a stream that received industrial wastewater effluent. CA decomposition was measured throughout the growth cycle by using a high-performance liquid chromatography assay, and the concomitant production of ammonia was also measured. The bacterium used CA or cysteine as a major, if not the sole, carbon and energy source under anaerobic, but not aerobic, conditions in a defined medium. The cell yield was greatly enhanced by the simultaneous presence of cysteine and CA in the medium. Cysteine was preferentially used rather than CA early in the growth cycle, but all of the CA was used without an apparent lag after the cysteine was metabolized. Atrazine was also degraded by this bacterium under anaerobic conditions in a defined medium.     

Chicken erythrocyte membranes: comparison of nuclear and plasma membranes from adults and embryos

These experiments were designed to determine whether the migration of RNA molecules from an implanted nucleus to the host cytoplasm and from there into the host cell nucleus against a concentration gradient might reflect an artefact induced by the process of nuclear transplantation. That is, are RNA molecules, as previously shown for certain nuclear proteins, caused to artefactually leave a manipulated nucleus and then move into the host cell nucleus (as well as return to the grafted nucleus) during the recovery period?A variety of experiments involving different kinds of manipulative sequences and different numbers of nuclear transplantations suggest—but do not prove—that no artefact is involved in the migration of RNA from one nucleus to another but two experiments strongly support the view that the shuttling activity is a normal physiological process. One of the latter involved a determination of the rate of egress of ³H-RNA from an implanted nucleus and reveals that that rate, in contrast with the equivalent rate of egress for labeled proteins which is clearly abnormal after micromanipulation, is totally consonant with the rate of movement of RNA from nucleus to cytoplasm established from experiments that do not involve micromanipulation. The other experiment involves comparison of (1) the amount of radioactivity acquired by an unlabeled nucleus present in the cell at the time a labeled nucleus is implanted with (2) the amount of radioactivity acquired by an unlabeled nucleus implanted after a labeled nucleus had been implanted and had time to recover from any possible operation-induced trauma. With ³H-protein nuclei the host nuclei of (1) acquired much more label than the host nuclei of (2) because in (1) the host nuclei were able to acquire much of the artefactually-released ³H-protein. For the ³H-RNA experiments, however, little difference was found between (1) and (2) in the amount of label acquired by the host cell nuclei. It can be concluded that little, if any, of the non-random shuttling activity of RNA molecules can be a reflection of an artefact.     

Activation and germination of Bacillus thuringiensis spores in Manduca sexta larval gut fluid

Incubation of Bacillus thuringiensis HD-1 spores in the larval gut fluid of Manduca sexta (tobacco hornworm) resulted in increased viable counts, conversion to phase-dark spores, and a loss of absorbance in spore suspensions, indicative of spore germination. Heat-activated and untreated spores incubated in water did not exhibit these changes. Only when spores were heat activated and incubated in germinants L-alanine and adenosine did changes in the spores approximate those observed in gut fluid. These data suggest that M. sexta larval gut fluid induces the activation and germination of B. thuringiensis spores.