Showing papers by "Université catholique de Louvain published in 1969"

Lactoferrin, an iron-binbing protein ni neutrophilic leukocytes

Abstract: Lactoferrin, an iron-binding protein previously shown to occur in many external secretions, is identified as one of the major proteins present in human and guinea pig neutrophilic polymorphonuclear leukocytes. The identification of this protein in leukocyte extracts was based upon a comparison of its electrophoretic, antigenic, and iron-combining properties with the corresponding properties of the same protein isolated from human and guinea pig milk. Immunochemical quantitations showed that lactoferrin occurs in human neutrophilic leukocytes at the concentration of 3 µg per 106 cells. Tissue cultures from guinea pig bone marrow and spleen actively synthesized the protein, as shown both by net production of lactoferrin and incorporation of labeled amino acids into the protein. Immunohistochemical data indicate that lactoferrin first appears in myeloid cells at the stage of the promyelocyte.

ANTIBODIES OF THE IgA TYPE IN INTESTINAL PLASMA CELLS OF GERMFREE MICE AFTER ORAL OR PARENTERAL IMMUNIZATION WITH FERRITIN

Abstract: In adult germfree C3H mice immunized with horse spleen ferritin, either subcutaneously or intraperitoneally, plasma cells containing specific antibodies were found in lymph nodes and spleen and, in smaller numbers, also in the lamina propria of the intestine. In extraintestinal sites, these antiferritin-containing plasma cells were mainly of the IgM class after a single stimulation, and of the IgG1 class after repeated stimulation. In the intestine, all the anti-ferritin-containing cells appeared to be of the IgA class. Circulating antibodies, after repeated stimulation, were for the major part IgG1 and IgG2. In germfree mice given ferritin in their drinking water, antiferritin-containing cells were abundant in the intestinal mucosa, much less numerous in the mesenteric lymph nodes, and extremely scarce in other lymphoid tissues. All these cells, whatever their location, appeared to belong exclusively to the IgA class. Similarly, all the circulating antibody in these animals was found to be IgA. These findings illustrate the role of the gut as a site of antibody synthesis, as well as its selective commitment to the production of antibodies of the IgA class.

Circadian variations of blood sugar and plasma insulin levels in man.

Abstract: Blood sugar, plasma insulin, non-esterified fatty acids (NEFA), plasma cortisol, and urinary catecholamines were measured for 24 h in seven normal subjects receiving a standard diet. During the night, blood sugar and plasma insulin remained low, NEFA decreased progressively, and the excretion of catecholamines diminished. During the day, the insulin response appeared particularly important after the morning meal. This last observation was also made when normal subjects were given three identical meals at intervals of four and a half hours. Under these conditions, the postprandial elevations of blood sugar were not statistically different, but the plasma insulin rose significantly higher after the morning meal. These observations may be explained by the existence of a periodicity which would regulate the insulin secretion. It is also possible that the insulin liberated postprandially conserves a certain activity at the moment of the next meal, and still intervenes in the maintaining of blood sugar homeostasis. Later in the day, however, blood sugar homeostasis would necessitate a new synthesis of insulin, which would explain the delayed plasma insulin response to the evening meal.

The association of cholesterol, 5'-nucleotidase, and alkaline phosphodiesterase i with a distinct group of microsomal particles

Abstract: 5,aminopyrine demethylase, cytochrome P450 ),and 40-50% of the homogenate content in cholesterol, 5'-nucleotidase, and alkaline phosphodiesterase I (acting on p-nitrophenyl 5'-thymidylate) . The latter three components exhibit a "nucleo-microsomal distribution" in the sense that the amount recovered in the nuclear fraction is much higher than that expected for particles of microsome size or observed for typical microsomal constituents . Since the high activity of 5'-nucleotidase and the abundance of cholesterol are characteristic properties of purified plasma membrane preparations isolated from low speed sediments (for a review see ref . 5), the obvious interpretation for the presence of these components in the nuclear fraction is that they belong to plasma membrane fragments of large size that sediment together with the nuclei and large cell debris . In line with this interpretation, which is widely accepted, it is tempting to assume that small fragments of plasma membrane sedimenting together with the fragments of the endoplasmic reticulum are responsible for the microsomal localization of most of the remaining cholesterol, 5'-nucleotidase, and alkaline phosphodiesterase I

Structural organization in amorphous silico-aluminas

Abstract: A structure model for amorphous hydrated or dehydrated silico-aluminas with composition varying between 0 < Al: Al + Si < 1 is presented. A central core made from a tetrahedral network in which silicon is partially substituted by aluminium carries a net negative electrical charge. This charge is balanced by more or less polymerized hydroxyaluminium cations forming a coating around the core.

Liver peroxisomes, cytology and function

Abstract: Since the occurrence of a special type of cytoplasmic particle containing hydrogen peroxide-producing oxidases and catalase was first reported some nine years ago,l this new type of organelle has been extensively investigated and characterized, both biochemically and morphologically. It is the aim of this article to provide a summary of the information presently available on the properties of mammalian liver peroxisomes and to discuss some of the still unanswered problems. Emphasis will be mostly on rat liver particles, since peroxisomes have been most extensively studied in this species; some of the differences occurring between liver peroxisomes of various sources will, however, be mentioned.

The hydrolysis of the naturally occurring alpha-glucosides by the human intestinal mucosa.

Abstract: An extract of human intestinal mucosa can degrade glycogen, isomaltose, sucrose and maltose through the action of several hydrolytic enzymes, which have been identified by experiments of competition between substrates and by some other properties. Besides an α-amylase, which is soluble and probably of pancreatic origin, three truly intestinal α-glucosidases are bound to cellular structures: a glucoamylase forms glucose from glycogen (Km= 0.65 mg/ml) and maltose (Km= 2 mM), a maltase-isomaltase, from maltose (Km= 1 mM) and isomaltose (Km= 7 mM) and a maltase-sucrase, from maltose (Km= 7 mM) and sucrose (Km= 17 mM).

Heterogeneity in silicon-iron mixed hydroxides

Abstract: Summary Several mixed hydroxides obtained by co-precipitation of FeCl2 or FeCl2 with Na2SiO2 followed by ageing and purification were studied by X-ray diffraction, infra-red spectroscopy, and surface-area measurements. The compounds with molecular ratios SiO2/Fe2O3 ranging from 0·1 to 1·17 are essentially amorphous. Silica, which is not to be considered as an integral part of the gel, is chemi-sorbed on the ferric or‘ferrosic’ phase. The good agreement between IR, DTA, and surface-area measurements with increasing molecular ratios permits the distinction between two ranges of silica contents. In the first range, MR 0·1 range, silica polymerizes as a separate phase growing upon the‘ferrosic’ or‘ferric’ phase.

[Influence of arousal on the size of the visual receptive fields of suprageniculate and geniculate neurons in the intact alert cat and in the "cerveau isole" cat].

Abstract: In alert cat, geniculate cells respond more strongly to visual stimulus when preceeded by somatic stimulation. Moreover, the somatic stimulation can enlarge the visual receptive field of these neurons which then even discharge when the light stimulus is applied outside and near to the border of the field as previously determined without any somatic stimulation.

The Sedimentation Properties of the Intestinal α-Glucosidases of Normal Human Subjects and of Patients with Sucrose Intolerance

Abstract: The maltase-isomaltase, maltase-sucrase and glucoamylase of the human intestinal mucosa have been solubilized by Triton X-100 and submitted to centrifugation in a mannitol gradient. Under these conditions, the three enzymes sediment together in a 10 S fraction; with one normal mucosa out of 10 which were investigated a supplementary 13 S peak of both glucoamylase and maltase-isomaltase was observed. Several experimental conditions, like treatment of the extracts at 45° or solubilization of the α-glucosidases by papain in the absence of potassium ions, induced an important inactivation of the maltase-isomaltase and deep alterations in the sedimentation profile of the 3 glucosidases: the glucoamylase and the residual maltase-isomaltase were distributed in 3 fractions with 13 S, 10 S and 6–7 S sedimentation coefficient, whereas the maltase-sucrase was mostly present as a 7 S structure. In sucrose intolerance, the maltase-sucrase is absent and the activities of the maltase-isomaltase and glucoamylase are significantly reduced. The residual enzymes were -recovered as 13 S and 6 S structures instead of the normal 10 S species. These observations allow the conclusion that the three α-glucosidases are naturally linked to each other in the normal mucosa and that the alteration of one of them induces a structural rearrangement of the 3 enzymes. The absence of maltase-sucrase in patients with congenital intolerance to sucrose can be regarded as the result of a single mutation of the corresponding structural gene and as the cause of a reorganization of the two other α-glucosidases; this reorganization can explain a partial loss of the enzymatic activity.

The fine structure of frozen etched nitrobacter cells.

Abstract: 1. The ultrastructure of frozen etched Nitrobacter winogradskyi cells was examined and compared with thin sections of chemically fixed cells. 2. Frozen etched cells showed two equally thick wall layers interconnected by short strands. This connection was weakened by a chemical prefixation treatment explaining the appearance of an intermediate electron-transparent layer in thin sections of chemically fixed cells. 3. Freeze etching revealed membrane surfaces carrying particles with an approximate diameter of 100 A. Cytomembranes were also observed and showed a spatial arrangement similar to that described in chemically fixed cells. 4. In frozen etched cells the cytoplasm had an uniform granular appearance. When the cells were chemically prefixed the uniform granularity was disturbed by a partial coagulation of the cytoplasm. The same enclosures were identified in the cytoplasm of frozen etched cells as those reported in chemically fixed cells, i. e. PHB and polyphosphate storage granules.

[Influence of the somato-sensory stimulation on the visual receptive fields of suprageniculate and geniculate neurons in the chloralose anesthetized cat].

Abstract: In dark adapted cat under deep chloralose anaesthesia, a somatic stimulation enlarges the size of the visual field of geniculate neurons, which then even discharge when a light stimulus is applied outside and near to the border of the visual field which has been outlined before without any somatic stimulation; moreover, the discharge rate upon visual stimulation inside the visual field also increases. This was also demonstrated in photopic conditions. Above the L G N, some units, which could be cells of the Nucleus Reticularis Thalami, exhibit unusual large receptive fields (30°–90°), and their responses appear to be fatigable. In a very few cases, paw stimulation enhances their visual response; but generally, after somatic stimulation, these units become unresponsive to the light stimulus.

Subfractionation of rat liver microsomes

Abstract: The microsome fraction isolated from rat liver homogenates by differential centrifugation was subfractionated by centrifuging in four different density gradients under conditions sufficient to bring the particles close to their equilibrium positions The gradients were made up by means of a linearly increasing concentration of sucrose with either H2O or D2O as solvent, or of Ficoll with either 025 or 05 M sucrose as solvent Some 15 subfractions were separated and analyzed for a number of enzymes and chemical constituents The distribution patterns observed in these experiments allow the assayed components to be classified into four distinct groups of increasing median density: (a) Monoamine oxidase, 5′-nucleotidase (assayed on AMP), and cholesterol The two enzymes in this group behaved somewhat differently in different gradients and could be associated with distinct components (b) NADH-cytochrome c reductase, NADPH-cytochrome c reductase, aminopyrine demethylase, and phospholipids (c) Glucose-6-phosphatase, esterase, nucleoside diphosphatase (assayed on IDP, UDP, or GDP), and proteins (d) Fumarase, aldolase, glutamine synthetase, and RNA The enzymes in group (d) all occur in significant amounts in the soluble fraction; their partial attachment to the RNA of ribosomes may be due to an adsorption artifact On the other hand, the enzymes of group (a) are sufficiently dissociated from the others to suggest association with distinct membrane components present in small amounts in the preparation Those bearing 5′-nucleotidase could be related to the plasma membrane, those containing monoamine oxidase to the outer mitrochondrial membrane From the shape of their distributions, the enzymes of groups (b) and (c) all appear to belong largely or entirely to the main component of the preparation, ie to endoplasmic reticulum vesicles of both the smooth and the rough variety The slight but significant differences in distribution between the two groups could reflect the existence either of a moderate degree of enzymic heterogeneity within a single membrane component, or of two distinct components each of which could be biochemically homogeneous

La Vision Daniélique Du Fils D'Homme

Abstract: Un article recent de M. A. CAQUOT nous invite a revenir une fois de plus a l'explication de la vision danielique du Fils d'homme, et cela d'autant plus que le professeur de Paris ne se contente pas d'etudier cette figure enigmatique mais s'applique aussi a interpreter le cadre ou elle apparait, c'est-a-dire la vision des quatre empires dont la destruction precede la venue du personnage mysterieux 1 ). Nous voudrions donc, en dialogue avec l'auteur cite, examiner successivement le cadre de la vision, les origines du symbole et sa signification.

Note sur l'innervation des branchies chez Anguilla anguilla L.

Abstract: Maillet's technique demonstrated the innervation of pillar cells of the secondary gill lamellae inAnguilla anguilla L. Nervous control may work in conjunction with an humoral regulation which would make clearer the understanding of the in- and outflux of blood in the respiratory organs.

On the Minimal Initial Size of an Explosive Reaction Center

Abstract: In connection with the explosive reaction center (e.r.c.) put forward to explain the appearance of sharp ignition process in flammable mixtures, a criterion is proposed for its minimal initial size. Different approaches of the problem are suggested. The analysis based primarily on a chain branched mechanism of the reaction provides a formula which depends explicitly on the initial conditions of pressure, temperature and mixture composition. Diffusion coefficient of radicals and geometrical factor of the e.r.c. are taken into account. Some numerical computations of the critical size are carried out to exemplify the dependence on several parameters.