Structure Of Globules Research Articles

Composition and molecular structure of chromoplast globules of Viola tricolor

Plastoglobules have been isolated in pure form from petals of the pansy, Viola tricolor L. Their chemical composition has been determined up to a recovery of 96% dry weight. Triacyl glycerols (57%) as well as carotenoids and their esters (23%) are the main constituents. Polar lipids, proteins, alkanes, phytyl esters, plastid quinones, and steryl esters have been detected in smaller amounts (cf. Table 1). The mean diameter of chromoplast globules is 280±70 nm (corresponding to a volume of 11.7×10(6) nm(3)), their buoyant density 0.93 g cm(-3). The plastoglobules are devoid of a surrounding unit membrane. However, electron microscopical evidence and analytical data are consistent with a structural model envisaging the globules to consist mainly of an apolar core, covered by a 'half unit membrane' of polar constituents.

Chemical and morphological changes of rat plasma lipoproteins after a prolonged administration of diets containing olive oil and cholesterol

1. (1) The long-term effect of the administration of a diet containing olive oil and cholesterol on the chemical composition and structure of plasma lipoproteins was studied in 3 groups of rats receiving respectively 2% olive oil plus 2% cholesterol (group 1), 2% olive oil (group II) and normal laboratory chow (group III). 2. (2) The administration of 2% olive oil for 6 weeks caused an increased concentration of VLDL and LDL 1, whereas the addition of 2% cholesterol to this diet led to a further increase of both VLDL and LDL 1 and a reduction of HDL 2. 3. (3) In the rats of groups I and II, VLDL, LDL 1 and LDL 2 contained more hydrophobic lipids (cholesteryl esters and triglycerides) and less protein than the normal counterparts. 4. (4) Agarose gel chromatography showed that LDL 2 of both groups I and II contained 3 different subfractions. Subfractions A and B were rich in cholesteryl esters and had a low protein content, whereas subfraction C had a composition fairly similar to that of normal LDL 2. 5. (5) The plasma of the rats of both groups I and II contained large polymorphous globules (30.0–350.0 nm in diameter) which showed a low affinity for the negative stain and differed from the chylomicrons and VLDL in that their shape was irregular and they had a strong tendency to coalesce into larger complexes. 6. (6) These polymorphous globules were present together with normal particles in all lipoprotein fractions of the rats of both groups I and II, but they were more numerous in the lipoprotein classes of density less than 1.050 g/ml. 7. (7) The structure of the polymorphous globules was greatly affected by the different negative staining procedures we used which did not alter the structure of the normal lipoprotein particles. 8. (8) The ultrastructure of the polymorphous globules strongly resembled that of an artificially prepared emulsion of fat having a high content of neutral lipids.

Investigation of the protecting envelopes of natural and synthetic emulsions

The fine structure of fatty globules in artificial emulsion, in crude human milk and in the cells of mammary glands of both virgin and nursing albino rats were studied. The envelopes of milk fatty globules have been shown to consist of a diffuse protein layer bordering upon fat followed by a trilaminar unit membrane. The envelope of the artificial fatty globule posseses only the diffuse protein layer. The spatial interrelationships of the envelopes of the milk fatty globules are discussed in relation to the mode of lactic fat formation inside the cells of the mammary gland.

The reactivity of imidazole derivatives on their being acylated in the surface layer of cationic micelles

The imidazole group, which is a part of the active centre of many enzymes, often dieplays an unusual reactivity '. It is intereeting to find out which role in this phenomenon is played by the effects of the microenvironment. It is known that there are certain analogiee between the structure of protein globules and aurfactant micellee 2-4 . Hence we believed it feasible to elucidate how the reactivity of imidazole derivative6 ie affected by the environment of the surface layer of cetyltrimethylammonium bromide (CTAB) micelles. We have meaeured the liberation of p-nitrophenate ion on acylation of a series of imidazole derivatives (see legend to the figure) by p-nitrophenylheptanoate, under conditions when the concentration of the nucleophile greatly exceeds that of the ester. The true rate constanta for this reaction in micellee were calculated from the observed reaction rate va. CTAB concentration profilee. To this end we used the kinetic method 5-7 developed previouely for other reactions. It should be emphasized that thie approach to the analyaie of the overall kinetic data makes it possible to estimate the contribution to the micellar effect of the partition of the reagents between the bulk end micellar phaeee. The second order rate constant8 found reflect the true reactivity of the reagente in the micellar environment. Study of the pH dependence allowed

Composition and Structure of Cytoplasmic Globules in Leukemic Lymphocytes

AbstractThe hypothesis of undue susceptibility to leukemia or lymphoma in individuals with autoimmune disease is evaluated by an analysis of case reports and an analysis of the mortality experience of series of patients with systemic lupus erythematosus or rheumatoid arthritis. No direct support for the hypothesis is found. The difficulty in accumulating a sufficient number of person years at risk in series of individuals with autoimmune disease is noted and alternative approaches to validating this hypothesis are discussed.

Royal Academy of Medicine, Paris: M. Mandl on the Structure of Milk Globules

Royal Academy of Medicine, Paris: M. Mandl on the Structure of Milk Globules