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Biomedical subjects

J Jacob

Publications and source records attributed to J Jacob.

At least 253 records · Page 14Linked to original sources
PubMed1976

Molecular hybridization of RNA and DNA in situ" visualization at the electron microscope level.

Electron microscopic visualization of molecular hybrids formed in situ is feasible at the present time. It can be accomplished by two alternative approaches. In one, the in situ hybridization is carried out on ultrathin sections of target embedded in glycol methacrylate. In the other, whole cells are used for hybridization and they are subsequently prepared for electron microscopy. The choice of the method to be adopted depends on the type of target tissue. When there is a choice, the second approach seems preferable. Some of the important technical steps in the hybridization procedure, such as DNA denaturation in ultrathin sections, have been discussed and attention has been drawn to practical problems that may arise during the preparatory steps. Our light microscope experiments demonstrate that preparations made after glutaraldehyde fixation have a lower hybridization efficiency than those fixed with 3 : 1 methanol-acetic acid. Attempts are therefore being made to explore the possibility of using methanol-acetic acid for electron microscope in situ hybridization. First results of straight-forward fixation show that the preservation of nuclear structure may be fairly satisfactory for the purpose. However, the cumultative effects of subsequent treatments in the procedure still remain to be examined. For electron microscope autoradiograph (EM ARG) of hybridized preparations, the most suitable emulsion at present appears to be Ilford L4. Various factors conductive to optimum resolution consistent with maximum efficiency in this emulsion have been pointed out. Practical problems that may arise in autoradiographs of hybridized preparations such as background and variation of grain density in adjacent sections have also been considered.

Acetates↗
PubMed1976

The permeability to cytochalasin B of the new unpigmented surface in the first cleavage furrow of the newt's egg.

Two of 10 mug/ml cytochalasin B (CB) caused retraction of the first cleavage furrow in Triturus eggs, a spreading of the unpigmented surface from the furrow region and a flattening of the whole egg. CB appears to act against the contractility of the microfilamentous band at mid-cleavage so as to relax the furrow and also to weaken unpigmented surface to allow the egg to flatten. Uncleaved eggs and the initial formation of the cleavage groove were unaffected by CB. A fully-retracted first cleavage furrow reformed itself on transfer of the egg to normal medium but only at the time of second cleavage. Initiation of second cleavage depended upon there being sufficient of the original pigmented surface on the animal hemisphere. Tritium-labelled CB of high specific activty was prepared and used to study its ability to penetrate the surface of newt eggs during cleavage. Scintillation couting of whole eggs showed that CB was not taken into the newt egg until mid-cleavage (about 17 min after the double stripe stage) when new surface began to spread in the cleavage furrow. Fixation in glutaraldehyde and osmium tetroxide retained radioactivity in the egg, but more CB was retained after fixation in osmium tetroxide alone than after double fixation. Most of the retained radioactivity was in yolk platelets. Autoradiographs were prepared to sectioned eggs which had been fixed at late cleavage after [3H]CB had flattend the furrow. These showed that CB entered the egg through the unpigmented surface which formed in the furrow but it could not enter through the pigmented surface. The impermeability of the pigmented surface explains the observations that CB does not prevent initial furrowing at cleavage. Once inside the egg CB is transported slowly. CB penetrates to a limited extent beneath the pigmented surface from its border with the unpigmented surface in the first cleavage furrow and this seems insufficient in some circumstances to suppress the contractile phase of second cleavage.

Animals↗
PubMed1976

Abnormalities in the differentiation and cellular properties of hyperplastic lens epithelium from strains of chickens selected for high growth rate.

Similar morphological abnormalities of the lens of the eye of two unrelated strains of chicks, both of which had been selected for high growth rate, were found to be associated with epithelial cells showing marked deviations from the normal in cell surface properties, mitotic rate, capacity for differentiation, and in DNA, RNA and protein metabolism. The relationship between these modified properties and the observed morphology is discussed.

Animals↗
PubMed1976

Antibody coated red cells with and without hemolysis in chronic ulcerative colitis.

A young female with ulcerative colitis associated with positive direct and indirect Coombs reaction and severe autoimmune hemolytic anemia is reported. Cortisone was beneficial and total colectomy was promptly followed by subsidence of the hematologic defects. Review of the literature suggests that this complication of ulcerative colitis is uncommon. It basis is unclear. It seems to be expressed through the presence of a "warm" auto-antibody. Colectomy should be strongly considered when severe hemolysis is present but not when the Coombs test is positive alone without significant hemolysis.

Adult↗
PubMed1976

Incorporation of tritiated cytochalasin B into ectodermal explants of the amphibian gastrula.

Ectodermal explants from gastrulae of Triturus alpestris were exposed to tritiated cytochalasin B (5 and 10 mug/ml) for 1/2-2 1/2 h. The flat explants failed to heal into compact spheres and the component cells gradually rounded up. Radioactivity in the fixed and sectioned material was analysed by light and electron microscopic autoradiography. Silver grains were found predominantly over the yolk platelets, but were also scattered over other cellular components. Areas containing pigment granules or the feltwork material, present in the apices of dissociating cells of the superficial layer, exhibited higher activity than areas containing mitochondria or cytoplasmic matrix. Lipid droplets and nuclei showed comparatively little activity. The results are discussed in relation to previous findings on the uptake of tritiated cytochalasin D by cell fractions.

Animals↗
PubMed1975

Composition of uropygial gland secretions of birds of prey.

The chemical composition of the uropygial gland secretion of five species of birds of prey was investigated by gas liquid chromatography-mass spectroscopy technique, and the results are discussed from the chemotaxonomical point of view. The secretion is a complex mixture of monoester waxes, the fatty acids of which are mainly dimethyl-branched, with the first substituent in 2 position and the other near the methyl end of the molecule. Mono-, trimethyl-, and unbrached fatty acids also are observed. The wax alcohols are mainly mono- and dimethyl-substituted. Unbranched alcohols and traces of trimethyl-substituted alcohols also were detected. Chemotaxonomically, the birds of prey differ from all orders hitherto investigated. The degree of substitution increases from the Falconidae to the Accipitridae.

Animals↗
PubMed1975

TLC, GLC and MS of complex lipid mixtures from uropygial secretions.

A general technique of investigation of uropygial gland secretions is described including sample collection and extraction as well as partition, TLC and column chromatography of the crude lipids. The main components, generally ester waxes, are cleaved by CH3OH/HCl followed by conversion into fractions ready for GLC. Some GLC and MS details are reported.

Animals↗