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.     

Blockage of tropoelastin secretion by monensin represses tropoelastin synthesis at a pretranslational level in rat smooth muscle cells.

The blockage of protein secretion in the R22 cultured rat aortic smooth muscle cell strain with monensin repressed tropoelastin gene expression at the mRNA level by ca. 50-fold as measured by biosynthetic pulse-labeling, in vitro translation, and hybridization with a tropoelastin genomic DNA probe. These results suggest that tropoelastin gene expression is autoregulated, and they represent the first reported effect of monensin on gene expression.     

Inflammatory atypia and the false-negative smear in cervical intraepithelial neoplasia

The effectiveness of cervical cytologic screening is compromised by the increasingly recognized prevalence of false-negative smears. Our previous studies suggested that some false-negative cytologies can be accounted for by smears showing cervical intraepithelial neoplasia (CIN) reported as inflammatory atypia; we found that at least 4% of 5,752 consecutive smears had been underreported in this manner. In the present study, that data was reanalyzed to derive 95% confidence limits for the number of CIN smears reported as inflammatory atypia. Using several differing estimates of cytologic screening sensitivity, it is speculated that, under certain testable assumptions, colposcopy of patients with cytologic diagnoses of inflammatory atypia may be one cost-effective approach to finding CIN cases missed by screening. If confirmed, these findings imply that laboratory quality assurance efforts, traditionally directed to the most serious cytologic diagnoses, should also focus in part on nondysplastic atypia.     

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     

Fatness, menarche, and female fertility

It is hypothesized that a particular ratio of fat to lean mass is required for menarche and the maintenance of regular menstrual cycles. Females who lose 10-15% of normal weight for height, equivalent to a loss of 1/3 of body fat, become amenorrheic, presumably due to hypothalamic dysfunction. Adipose tissue may provide signals to the central nervous system and gonadotropin regulatory areas either directly, by estrogen production, or indirectly, by the effects of relative fatness on temperature control and metabolic rate, or by both means. Women with hypothalamic dysfunction experience changes in the secretion of gonadotropins, luteinizing hormone, follicle-stimulating hormone, and estrogen. Weight gain restores postmenarcheal secretion patterns. This approach suggests that the secular trend toward earlier age at menarche reflects earlier attainment of critical weight as a result of improved nutrition and child care. In many societies, subnutrition may explain the observed submaximum fertility. This suggests a need to integrate family planning programs with nutrition programs in many developing countries. It is important to note that the prediction of the minimum weight for height for onset and maintenance of ovulatory cycles is from total water as percentage of body weight. Although the percentage of fat in the body is inversely related to the percent of body water, only the latter is predictive. Successful prediction of the minimum weights for height is related to a lean mass/fat ratio represented by about 17% fat of body weight at menarche and 22% of body weight at the completion of growth at age 18 years.     

On the stationary state analysis of reaction-diffusion mechanisms for biological pattern formation

We present a biologically plausible two-variable reaction-diffusion model for the developing vertebrate limb, for which we postulate the existence of a stationary solution. A consequence of this assumption is that the stationary state depends on only a single concentration-variable. Under these circumstances, features of potential biological significance, such as the dependence of the steady-state concentration profile of this variable on parameters such as tissue size and shape, can be studied without detailed information about the rate functions. As the existence and stability of stationary solutions, which must be assumed for any biochemical system governing morphogenesis, cannot be investigated without such information, an analysis is made of the minimal requirements for stable, stationary non-uniform solutions in a general class of reaction-diffusion systems. We discuss the strategy of studying stationary-state properties of systems that are incompletely specified. Where abrupt transitions between successive compartment-sizes occur, as in the developing limb, we argue that it is reasonable to model pattern reorganization as a sequence of independent stationary states.     

The Ll.LtrB intron from Lactococcus lactis excises as circles in vivo: insights into the group II intron circularization pathway

Group II introns are large ribozymes that require the assistance of intron-encoded or free-standing maturases to splice from their pre-mRNAs in vivo. They mainly splice through the classical branching pathway, being released as RNA lariats. However, group II introns can also splice through secondary pathways like hydrolysis and circularization leading to the release of linear and circular introns, respectively. Here, we assessed in vivo splicing of various constructs of the Ll.LtrB group II intron from the Gram-positive bacterium Lactococcus lactis. The study of excised intron junctions revealed, in addition to branched intron lariats, the presence of perfect end-to-end intron circles and alternatively circularized introns. Removal of the branch point A residue prevented Ll.LtrB excision through the branching pathway but did not hinder intron circle formation. Complete intron RNA circles were found associated with the intron-encoded protein LtrA forming nevertheless inactive RNPs. Traces of double-stranded head-to-tail intron DNA junctions were also detected in L. lactis RNA and nucleic acid extracts. Some intron circles and alternatively circularized introns harbored variable number of non-encoded nucleotides at their splice junction. The presence of mRNA fragments at the splice junction of some intron RNA circles provides insights into the group II intron circularization pathway in bacteria.     

CML9, a multifunctional Arabidopsis thaliana calmodulin-like protein involved in stress responses and plant growth?

Plants have evolved complex signaling networks to respond to their fluctuating environment and adapt their growth and development. Calcium-dependent signaling pathways play key role in the onset of these adaptive responses. In plant cells, the intracellular calcium transients are triggered by numerous stimuli and it is supposed that the large repertory of calcium sensors present in higher plants could contribute to integrate these signals in physiological responses. Here, we present data on CML9, a calmodulin-like protein that appears to be involved in plant responses to both biotic and abiotic stress. Using a reverse genetic approach based on gain and loss of function mutants, we present here data indicating that this CML might also be involved in root growth control in response to the flagellin, a pathogen-associated molecular pattern (PAMP) also involved in plant immunity.