Revue canadienne de biologie experimentale最新文献

The observations of a previous work on the architecture of the rat node suggested that the organ is divided into "physiological compartments". Each compartment corresponds to a node portion stimulated by the immunogenic content poured by an opening of an afferent lymphatic or a branch of it. The same study also investigated the lymph flow in the organ sinuses by analysing the distribution, in draining nodes, of a locally injected small dose of China ink. It was found that the ink, pouring into a node from a lymphatic opening, had spread in a restricted portion of its subcapsular sinus corresponding to that of a compartment. The finding thus supported the proposal on the physiological compartmentation of the organ. However, the question arose as to whether such restricted ink distribution in the sinus did not result from the non-diffusible and unphysiological nature of the ink. We, therefore, repeated the latter analysis with a diffusible and physiological tracer: uridine-3H. The similarity of the results of the latter analysis, with those of the preceeding one, indicate that the observations witness the physiological modalities of the pattern of lymph flow in the organ sinuses. It, therefore, confirms that the node is divided into physiological compartments. Additional observations of present work, further demonstrate that small sized lymph substances diffuse from the subcapsular sinus into the cortex. The process is maximal under a lymphatic opening and decreases along the sinus with distance from the opening.

Since it is known that the metabolism of acetaminophen is involved in its hepatotoxicity and that drug metabolizing enzyme activity is decreased in tumor bearing animals, it was of interest to study the influence of L-1210 leukaemia on acetaminophen hepatotoxicity in BDF-1 male mice. A single oral dose of acetaminophen, 125 mg/kg, was given at the fifth day of the mice survival period (7.7 days) and the animals killed twenty-four hours later. As revealed by serum glutamic-pyruvic transaminase, serum glutamic-oxaloacetic transaminase and lactic dehydrogenase, acetaminophen was less hepatotoxic in leukaemic mice than in control mice by comparison with their own saline group; on the other hand the difference between control and leukaemic mice treated with acetaminophen was significant only for glutamic-pyruvic transaminase. Moreover, we found higher unchanged acetaminophen concentrations in plasma, liver, kidneys, brain and fat of the leukaemic mice as compared to controls, less conjugated metabolites in plasma and liver, decreased in vitro aniline hydroxylation and ethylmorphine N-demethylation. Finally, following acetaminophen administration, reduced hepatic glutathione was depleted to a much lesser extent in the tumor bearing animals than in controls. In conclusion, the L-1210 leukaemia seems to modify the acetaminophen hepatotoxicity and this effect might be explained by decreased acetaminophen biotransformation into toxic metabolites or intermediates.

The thickness of two layers of the retina (the inner plexiform layer and the inner nuclear layer), together with the density of cells in the ganglion cell layer, were measured in a sample of mice from a population segregating for albinism and retinal degeneration. The expression of retinal degeneration was found to involve not only the disappearance of retinal receptors but also a reduction in thickness of the inner plexiform layer and a reduction of cell density in the ganglion cell layer: these changes were found to be associated with a reduction of neuronal density in the lateral geniculate nucleus, but not in the superior colliculus. The expression of retinal degeneration was also found to be unaffected either by albinism or by dark-rearing.

Sites of aldosterone-induced hyperplasia along the nephron and collecting ducts. The mitotic activity was separately measured in 12 segments of the nephron and collecting ducts in intact and adrenalectomized rats, injected with aldosterone for two or five days, with daily doses of 0, 10, 20, 40 and 80 micrograms. Stimulation of the mitotic activity was observed in the proximal convoluted tubules, the deep straight distal tubules and in the collecting ducts in the same layer as that containing deep straight tubules (medulla externa interna). Adrenalectomy depressed the mitotic activity in the straight distal tubules and, after 6 days, stimulated it in the proximal convoluted tubules. Adrenalectomy also induced morphological change in these two segments. Apart from the collecting ducts, which have already been recognized as a target for aldosterone, this paper points to another probable target for this hormone: namely the straight distal tubule.

Recent major advances in our knowledge of the biology of collagen considerably facilitated an understanding of the structure, function and pathology of connective tissues. This short review is designed as an introduction to current concepts and findings in collagen polymorphism, its biosynthesis, degradation, and interaction with the ground substance. Such a discussion will serve as a basis for a review of the current concepts and advances regarding the tissue distribution, and specific functional roles, of the different types of collagen, as well as the disorders of the connective tissue that involve collagen. We hope that this article will serve to grant the reader an opportunity to gain an overview of the developments in the research related to this fascinating protein. It was also our intention to show how much more remains to be learnt about the biology of collagen.

Light measurements were made at seven sites in the Amazon river system near Manaus. It was found that very little light penetrates into the white water of the Solimões because of the large amount of suspended material it contains. In lakes off the Solimões the suspended material settles out, and light penetration is increased. The black waters of the Rio Negro contain dissolved material but little suspended matter, and the penetrating light is mainly of long wavelength. Fishes were also collected from these areas, and the spectral characteristics of their visual pigments, lenses and corneas measured. The visual pigments of the different species vary considerably, fishes from clearer water having pigments absorbing at shorter wavelengths on average than those inhabiting more coloured or turbid waters, and the characins having pigments absorbing at longer wavelengths on average than the cichlids. Yellow lenses and corneas are common among cichlids, but rare in other groups and fishes with such filters were, with one exception, absent from the Solimões where the light levels are especially low. The exception was Colomesus asellus which has an occlusable yellow cornea, which while coloured in the light loses its colour at low levels of illumination. Using the date on light penetration and visual pigments it was calculated that vision would be impossible below 2.3 m in the Solimões, but should be possible at depths up to about 9 m in the clearest waters studied.

Differences in the in vitro adhesion of Staphylococcus strains on rabbit tissues were evaluated by viable unit counts and radio-labeling. Among coagulase-positive strains, two freshly isolated strains and the Cowan I strain adhered much more than the Wood 46 strain especially to peritoneum. In addition, the Smith strain, which is coagulase-positive and encapsulated, showed on rabbit peritoneum a degree of adhesion smaller than that of the Cowan I strain and similar to that of the Wood 46 strain. These quantitative results were corroborated by examination of the bacteria on thin sections of peritoneum or on whole mesentery samples with fluorescence microscopy. With fluorochroming either with acridine orange or fluorescent homologous antibodies, we could detect a preferential localization of the bacteria on the epithelium and also on fibers of the mesentery. Even if the Cowan I strain produces Protein A, this substance does not seem to have been involved in the adhesion of this strain to rabbit tissues, since IgG did not affect the degree of its adhesion. Treatment by Na metaperiodate of the peritoneum had an inhibitory effect of about 50% on the degree of adhesion; several other known inhibitors had no effect. The higher affinity of the Cowan I strain for the peritoneum or the mesentery, when compared with the Wood 46 strain, is an observation which could contribute to the study and understanding of adhesion, presumably an element of the experimental pathogenicity of Staphylococcus.

In contrast to conventional membranes prepared from a mixture of glyceryl-monooleate (GMO) and decane (GMO-D) which still contain decane in the final state, the membranes formed from a mixture of GMO and squalene (GMO-S) or triolein (GMO-T) contain finally only GMO and are said to be "solventless". The use of the electric current relaxation technique following a voltage jump has allowed us to characterize the effect of the absence of solvent on the various steps of ion transport induced by nonactin. We have measured the rates of formation (kri) of dissociation (kDi) and of translocation (kis) of the ion-ionophore complex as well as the rate of translocation of the ionophore (ks). With the GMO-S and GMO-T membranes, kis is about ten times higher, ks, twice as high, and kDi twice as small than with the GMO-D membranes. The observed effects are always more prominent with the GMO-T membranes. These results can be interpreted in terms of modifications of the energy barriers in the membrane due to the absence of solvent.

This paper reviews results of a study of various factors altering 5-phosphoribosyl-1-pyrophosphate (PRPP) availability in freshly isolated rat liver cells. Total PRPP availability is not changed in the presence of allopurinol but in the competition for available PRPP is increased. Changes of PRPP availability due to phosphate, electron acceptors, or glycerol are usually accompanied by similar changes in the rate of purines synthesis de novo.

Solubility of narcotics in lipids has promoted the quest for non-aqueous and lipidic models of cell membranes. Artificial phosphatidic bilayers have been proposed. They display ionic conductance and excitability only if they are in contact with cyclic ion-carrier or specific substances, such as the protein fraction EIM. However many lipidic substances form non-bilayer membranes ion-conducting and excitable, without any specific additive. Only a small amount of free fatty acid is necessary. This is the condition for penetration through cation exchange. Coloured cations and cationic drugs undergo large exchange. Cu++, Hg++, emetine ++ cations have very high exchange coefficients which can be experimentally measured and which explain their respective antifungal, antibacterial and antiamoebian actions. The possible processes of membrane excitation are discussed. First the classical pores, specific of K+ and Na+ transfers and their "gating" mechanisms, because cell membranes are bi-ionic systems. Artificial membranes, are mono-ionic systems. But recent work shows that the axon membrane can be transformed into a monoionic system with Co++ as the only cations inside and outside the axon. Suggestions for the excitation processes are proposed. a) The assumption of a single energy barrier corresponding to minor conformational changes of structure. b) The membrane may be thixotropic. An outside cation penetrating the membrane would leave behind itself a wake of fluidity into which the next cations could penetrate if they follow each other closely. If they progress widely apart (under a small field), the ionic current would soon stop as the structure solidifies. c) The most promising suggestion is that anionic fixed charges in the membranes and cations form electrostatically bound ion-pairs. Dissociation of such pairs, that is conductance, augments markedly when dielectric constant increases. This process could be produced by water carried by incoming cations, that is by electro osmosis. This is exactly what occurs in Teorell's membrane oscillator in which a model membrane of fritted glass displays, under a weak current, oscillations of water flux and of potentials. The calculations pertaining to this model can be generalised if the electroosmotic water flux is assumed in increase the dielectric constant of the lipidic membrane. Thus the notion of an electroosmotic increase upon the dielectric constant of the membrane offers an alternative to the pore theory. Besides other phenomena show the role of low dielectric constants. The conductance of lipids containing coloured cations increase when subjected to illumination. The radiant energy absorbed then surpasses the association energy of ion pairs.