Showing papers by "Université de Montréal published in 1970"

Generalized Diffusion Equation for Superconducting Alloys

Abstract: Eilenberger's transportlike equations for a superconductor of type II can be simplified very much in the dirty limit. In this limit a diffusionlike equation is derived which is the generalization of the de Gennes-Maki theory for dirty superconductors to arbitrary values of the order parameter.

Steroid production from plasma cholesterol. I. Conversion of plasma cholesterol to placental progesterone in humans.

Abstract: Cholesterol-7α-3H was administered via the antecubital vein to 2 mothers bearing term anencephalic fetuses, 8 and 3 days prior to delivery, respectively. Blood and urine samples were collected daily, as well as fetal blood, fetal liver and placenta at delivery. A corpus luteum was excised the day after delivery in one case. The specific activity (SA) of cholesterol was measured in all tissues. At delivery, the SA (dpm/μmole) of placental progesterone was equal to the SA of the corresponding free maternal plasma cholesterol and the SA of the urinary pregnanediol in both cases. Fetal cholesterol as well as placental cholesterol had a SA which was lower than placental progesterone. These data indicate that, in pregnancies without a functioning fetal adrenal, virtually all placental progesterone is derived from maternal plasma cholesterol.

Crystallite Size in Natural Cellulose

Abstract: NATURALLY occurring long thin threads of cellulose, the so-called microfibrils, vary in width from about 100 A in bacterial, most algal and all higher plants, to more than 200 A in some marine algae (for example, Valonia and the Cladophorales). Two schools of thought have developed concerning the internal structure of microfibrils. Ranby1, Preston2 and Ellefsen et al.3 conclude from electron microscopy, qualitative X-ray analysis and various chemical treatments that each microfibril contains a single crystalline core, the same order of size as the microfibril. Although the smaller microfibrils, for example of higher plants, may well fasciate to give broader structures, the broad microfibrils of the exceptional seaweeds are not multiples of narrower fibrillar bodies. Frey-Wyssling and Muhlethaler4–6 and Manley7, on the other hand, maintain that electron microscopical evidence points to the presence in microfibrils of linear bodies 35 A wide which they call “elementary fibrils”. They conclude that the thickness of microfibrils differs in steps of 35 A, dependent on the number of included elementary fibrils. The reliability of this evidence has already been called into question by Colvin8. We have attempted to resolve the controversy by determining crystal dimensions in a variety of microfibrils of different sizes in conditions closely resembling those in the living organism. Our findings, mostly using the method of X-ray high-angle line-broadening, but supported by low-angle scattering and electron microscopy, are presented here, and the details will be published elsewhere.

Geochemistry of the volcanics of central Mexico

Abstract: The Tertiary and Recent volcanics of Mexico occur in two provinces. The Cordillera Province is made up of about 1700 m of ignimbrite sheets overlain and intercalated in the upper part by olivine basalt and basaltic andesite. The Rio Lerma Province extends transversely across Mexico and in the Valley of Mexico the lavas consist mainly of andesite and dacite, 68 % of those analysed having 62 | 4.7 % SiO2. A total of 108 chemical analyses were made for the major elements, 90 of these including determinations of Cr, Ni, Cu, Zn, Rb, Sr, Ba, Th and Pb for two areas, the Valley of Mexico in the Rio Lerma Province and the Guadalajara region which lies at the intersection of the two provinces. Computer constructions of normative components in the basalt tetrahedron and other projections support an origin of partial melting of tholeiitic to pyrolitic material for the production of andesite. The Guadalajara lavas have consistently higher K/SiO2 and K/Rb ratios and lower Mg/SiO2 ratio than the Valley of Mexico rocks suggesting generation at greater depth.

Effects of beryllium on deoxyribonucleic acid-synthesizing enzymes in regenerating rat liver

Abstract: 1. The incorporation of thymidine into DNA of regenerating rat liver was measured at various times after partial hepatectomy. A single intravenous injection of 30μmol of beryllium/kg given immediately after the operation inhibited DNA synthesis 12, 16, 20, 24 and 28h later. 2. The activity of several enzymes critical to DNA synthesis (thymidine kinase, thymidylate kinase, thymidylate synthetase, deoxycytidylate deaminase and DNA polymerase) increased in control rats 20–24h after partial hepatectomy severalfold over the activity found in resting livers. After beryllium treatment this rise in activity was much less and it seemed as if beryllium would partially block the induction of DNA-synthesizing enzymes after partial hepatectomy. 3. Enzymes whose activities do not rise during liver regeneration were not affected by beryllium (aspartate transcarbamoylase, carbamoyl phosphate synthetase, uridine kinase and glucose 6-phosphatase). 4. No evidence was found in vitro that beryllium would specifically inhibit thymidine kinase or DNA polymerase. 5. The time–effect relationship between beryllium administration and thymidine kinase activity in vivo was examined. Measured 24h after partial hepatectomy, thymidine kinase activity was only affected if beryllium was given within the first 9–12h after partial hepatectomy. Beryllium given later, even in greatly increased doses, failed to have any effect on thymidine kinase. The possibility is discussed that beryllium inhibits enzyme induction at the transcriptional level.

Stress and aging

Abstract: The experimental “aging” exemplified in the progeria-like syndrome (induced by dihydrotachysterol, DHT, in rats) is not the cause but the consequence of disturbed calcium metabolism. Certain anabolic steroids can prevent the loss of body weight (protein) and the abnormal tissue calcification. Moreover, steroidal substances designated “catatoxic” have been found to play a role in adaptive reactions, particularly the maintenance of resistance to stress. Thus the anti-DHT effect of the steroids is not due to their antimineralocorticoid or anabolic action, but to their catatoxic (antitoxic) potency. An experimental biochemical disease model—the “Electrolyte-Steroid-Cardiopathy with Necrosis” (ESCN)—was developed to demonstrate a typical pluricausal disease in which several factors operate conjointly to produce a lesion. Glucomineralo-corticoids plus sodium salts were outstanding factors in the production of cardiac necrosis. This experimental necrosis could be prevented by KCl or MgCl2. However, oral administration of KCl has many drawbacks for the prophylaxis or treatment of myocardial infarction; more convenient and lasting methods of providing potassium are needed. Certain catatoxic steroids also were found to be efficacious in preventing ESCN. These data may eventually help in finding ways to combat spontaneous aging. Aging has no specific cause. Body hormones and numerous other factors play decisive roles.

Geochemistry of an oceanite-ankaramite-basalt suite from East Island, Crozet Archipelago

Abstract: The petrology and geochemistry of East Island have been investigated for the first time. The island is a deeply dissected remnant of a Pleistocene shield volcano, one of several emerging from an oceanic rise forming part of the southwest branch of the Indian Ocean ridge system. The lavas form a flat-lying sequence of oceanites, ankaramites, olivine basalts and feldsparphyric basalts, the ankaramites containing 1 cm phenocrysts of diopsidic clinopyroxene. X-Ray fluorescence analyses were made of 43 lavas for the major elements plus Cr, Ni, Rb, Sr, Ba, Pb, and Th and the minerals were analysed by electron microprobe. The elements Mg, Cr, and Ni are strongly concentrated in spinel, olivine and clinopyroxene phases and in the ankaramites and oceanite lavas with maximum concentrations of 18% MgO, 1,000 ppm Cr, 380 ppm Ni, while Al, Ti, K, Rb, Ba, Th, Na, P, Sr concentrate in the groundmass and in the feldspathic and aphyric basalts. The elements Si, Ca, Fe and Mn remain virtually constant throughout the series.

Hemin-deficient mutants of Salmonella typhimurium.

Abstract: Nine hemin-deficient mutants of Salmonella typhimurium LT2 were isolated as neomycin-resistant colonies. Five of these mutants could be stimulated by Δ-aminolevulinic acid (Δ-ALA), thus representing hemA mutants. Since S. typhimurium LT2 is not able to incorporate hemin, the identification of the mutants not stimulated by Δ-ALA was made on the basis of the simultaneous loss of catalase activity and cytochromes. The hemA gene was mapped by conjugation in the trp region, probably in the order purB-pyrD-hemA-trp; the episome FT71trp does not carry the hemA gene. Transductional intercrosses by phage P22 indicate that hemA 11, 12, 13, and 37 are at very closely linked sites, whereas hemA14 is at a more distant site in the same or an adjacent gene. No joint transduction was detected between hemA and trp or pyrF. The loci affected in the other hemin-deficient mutants were linked in conjugation to the pro+ marker (frequency of linkage, 88 to 97%), but cotransduction of the two markers could not be obtained. The episome F lac hem purE, which originates from Escherichia coli K-12, could complement these hemin-deficient mutants of S. typhimurium LT2. As a result, the sequence of the markers on the chromosome of S. typhimurium LT2 is probably pro heme purE, analogous to the sequence found in E. coli K-12. Thus, the chromosome of S. typhimurium also possesses two hem regions, with a location similar to that described in E. coli K-12.

Mercury poisoning: prevention by spironolactone.

Abstract: The renal tubular necrosis and calcification as well as the mortality induced by mercuric chloride in the rat are readily prevented by prior treatment with well-tolerated amounts of spironolactone.

Geochemistry of the Steens Mountain Basalts, Oregon

Abstract: Major and trace element analyses have been made for 63 of 70 successive basaltic lavas from Steens Mountain in southeastern Oregon The section was extruded 151 ± 03 my ago, during a period when the geomagnetic field was changing from reversed to normal polarity This indicates that the entire 1000-m section accumulated in no more than 50,000 years, and perhaps as little as 2000 years Groups of 3 to 12 successive lavas possessing related within-group chemistry characterize the sequence These major lava-groups are separable mainly on their pyroxene/plagioclase ratio which ranges from 46 to 76 percent by weight Within certain lava groups, the TiO2 and total Fe contents systematically decrease with decreasing age by as much as 30 percent in sequences of as many as 12 successive lavas, with, in some cases, sharp reversals back to the composition of the parental magma type taking place at the boundaries of the major groups Two geochemical trends are present, those dominated by plagioclase fractionation, and those due to olivine fractionation This is expressed in the following facts: (a) Elements virtually absent in plagioclase are diluted in concentration with increase in feldspar content, compared with the presumed parental magma These include Fe, Ti, Mn, and Cu Ratios between pairs of these elements remain essentially constant Ratios involving these elements and elements that are included in plagioclase (such as Al/Ti or Ca/Fe) show, however, a great range of variation (b) Elements present in approximate equal amount in feldspar and parental magma (such as Si and Na) remain nearly constant in amount throughout (c) Homologous element pairs with markedly different distribution coefficients between plagioclase and magma show strong fractionation between high and low feldspar rocks; for example, K and Rb The K/Rb ratio has a range of 500 to 750 (d) Accumulation and subtraction of olivine has resulted in a Mg/Ni ratio increasing from 300 to 1000 with decreasing olivine content Superimposed on this Mg/Ni distribution is the concentration-dilution trend due to plagioclase variation (e) Enrichment of K, Ba, Rb and P is found in lavas affected either by plagioclase or olivine removal The limitations which the paleomagnetic data place on the time span of the section suggests that systematic changes (as described above) occupying sequences of as many as 12 successive lavas took place in a time perhaps as short as 200 years This provides an estimate of the maximum rate of change of TiO2 of the order of 1 percent absolute per thousand years for some of the sequences

Total Precedence Relations

Abstract: A description is given of a method of syntact ical analysis based on the use of precedence relations which are defined over the whole vocabulary of the context-free grammar under investigation. These relations are defined in such a way tha t t r ial-and-error is avoided whenever possible. To the same end, the customary restr ict ion tha t analysis will be lefttoright is not imposed. The results are formulated in such a way tha t all relations can be computed by simple operations on Boolean matrices. This s tudy reveals the existence of an interest ing subset of context-free languages, which is then compared with other well-known subsets.

Role of the Sinus Node in the Mechanism of Cholinergic Atrial Fibrillation

Abstract: The effect of suppressing sinus rhythm on initiation and maintenance of atrial fibrillation was studied in 17 thoracotomized and artificially ventilated dogs. Atrial fibrillation was evoked by methacholine chloride applied to the right atrium followed by light mechanical stimulation. Episodes of fibrillation were compared before and after sinus rhythm had been suppressed by injection of absolute alcohol or concentrated sodium pentobarbital into the sinus node artery. Sixty-nine control episodes of atrial fibrillation lasting 6.00 ± 0.36 (SE) minutes were easily initiated while the heart was in sinus rhythm. The response to methacholine application plus mechanical stimulation depended on the type of escape rhythm obtained after suppression of sinus rhythm. In ten dogs with no sign of supra A-V junctional pacemaker activity, only 50% of the attempts to initiate fibrillation were successful. The 26 episodes of atrial fibrillation observed in this group of animals lasted 0.65 ± 0.23 (SE) minutes. In seven other dogs, supra A-V junctional pacemaker activity persisted after injection into the sinus node artery. In these seven dogs, 60% of the attempts at initiating fibrillation were successful, and the 18 episodes of fibrillation lasted 4.44 ± 0.30 (SE) minutes. In dogs showing no supra A-V junctional pacemaker activity, a more sustained arrhythmia was obtained after recovery of sinus node activity or during electrical pacing of the right atrial appendage. These observations suggest that the sinus node participates in the mechanism of cholinergic atrial fibrillation and that an equivalent role can be played by a natural or artificial supra A-V junctional pacemaker.

Spironolactone-induced proliferation of smooth-surfaced endoplasmic reticulum in the liver of rats.

Abstract: Electron microscopic studies revealed that spironolactone, given orally to rats, causes a marked proliferation of smooth-surfaced endoplasmic reticulum in hepatocytes. The characteristic fine structural alterations in the liver may represent the morphologic equivalent of stimulation or induction of drug metabolizing microsomal enzymes and may explain why spironolactone protects rats against the injurious effects of different compounds.

Fine structure of a third epithelial component of the thyroid gland of the rat

Abstract: Duct-like structures made of cells different from follicular or light cells were observed with the electron microscope in the thyroid glands of 16 rats. The wall of most of the ducts was made of two types of cells: (1) the lumen-bordering cells, mostly cuboidal or columnar, with short microvilli, and (2) the subjacent squamous cells, arranged in one or several layers of cells displaying numerous desmosomes and dense bundles of tonofilaments. Both cell types showed intricate folding of the plasma membrane at sites of cell-to-cell contact, an abundance of free ribosomes and nuclear indentations. In one occasion mucous-like cells were found. The lumen contained a finely granular homogeneous material as well as cell remnants. The ducts were located among the follicles, and were ususally discrete from them; but on four occasions the epithelium of the duct was seen in direct continuity with that of a thyroid follicle. Only one case of a light cell associated with a duct was observed while many of these cells were associated with thyroid follicles.

Histochemical study on rat liver glycogen during dab carcinogenesis

Abstract: The distribution of glycogen in livers of DAB-fed rats has been examined by the PAS reaction. At early stages of DAB feeding, a loss of glycogen was observed in cells of centrolobular areas undergoing a degenerative process. Intense glycogen staining was shown, on the other hand, by the hyperplastic nodules which develop from cells of periportal areas. At later stages, the formation of hyperbasophilic foci was found to be accompanied by a loss of glycogen, and the hepatomas, which apparently arise from such foci, were PAS-negative. It thus seems that a radical change in glycogen metabolism is associated with the neoplastic transformation. Alterations inglycogen metabolism being considered irrelevant to neoplasia per se, these results suggest that hyperbasophilic foci are the sites not only of modifications in the regulation of the cell cycle that initiate neoplastic growth but also of parallel changes responsible for secondary features of tumors.

The ultrastructural localization of adenosinetriphosphatase and alkaline phosphatase activity in eosinophil leukocytes.

Abstract: The previously undescribed localization of reaction products of adenosinetriphosphatase and of alkaline phosphatase in eosinophil leukocytes was demonstrated by cytochemical studies of the rat intestine. Alkaline phosphatase reaction product was found only in minimal amounts on the plasma membrane but was distinct on the nuclear membranes and outer compartment of mitochondria but not on the cristae. The Golgi membranes and the endoplasmic reticulum reacted but less intensely. The specific granules showed no alkaline phosphatase activity.

Transplantation Antigens in the Central Nervous System

Abstract: INVESTIGATIONS into the presence of histocompatibility antigens in mouse brain have given apparently conflicting results. Haemagglutinin1,2 and cytotoxin3 inhibition studies have revealed that the brain has an extremely small capacity for absorbing H-2 antibodies, compared with lymphoid tissues. Brain tissue, however, induces transplantation immunity4 and histocompatibility antigens are detected in neurones of the cerebral cortex by immuno-fluorescence5. The selective localization of the specific fluorescence to the neurones can explain these conflicting results, for the number of stained cells represents only a small proportion of the total brain tissue. This will be reflected by a very low absorptive capacity in quantitative inhibition studies.

Studies in the mechanism of metal-induced soft tissue calcification.

Abstract: Many metallic salts (e.g., Pbcl2, HoCl3, FeCl2 CrCl3) favor the precipitation of apatite when added to a calcifying solution; however, only some of them (e.g., PbCl2, HoCl3) have the same actionin vivo. FeCl2 injected subcutaneously is deposited mostly on the surface of well-formed collagen fibrils; it increases the local concentrations of calcium and phosphorus but does not produce apatite. On the other hand, lead acetate (administered by the same route) produces an early accumulation of a crystalline material (probably lead triphosphate); it is deposited around collagen bundles and has, a more damaging effect on the cellular components of connective tissue than FeCl2. Eventually, it gives way to apatite formation.