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At least 505 records · Page 28Linked to original sources
PubMed1978

[Radiocrystallographic study of 46 salivary calculi. Physiopathogenic hypotheses (author's transl)].

The radiocrystallographic study of 46 salivary calculi using the Debye and Scherrer powder methods showed that such stones, whether submaxillary, parotid or "accessory" consist essentially of hydroxyapatite with the frequent presence of tricalcium and octocalcium phosphates, Whitlockite and rarely Brushite and Calcite. In order for a stone to form, the following conditions would seem to be necessary; transient supersaturation of the saliva in Ca++ and PO4--, a pH greater than normal, intracellular precepitation of amorphous tricalcium phosphate which is transformed into crystalline hydroxyapatite and, then, the fixation of crystals on a "matrix" such as desquamated cells, fibrils and collagens.

Adolescent↗
PubMed1978

[Hydroxylapatite ceramics--a bone-like biomaterial. Preliminary report].

Inorganical materials are being increasingly tried out in surgery and periodontal surgery for reconstructing bone defects. This paper discusses the biocompatibility and biofunctionality of different implant materials and presents a new hydroxyapatite ceramic material, of which a good bioactive behaviour is expected.

Biocompatible Materials↗
PubMed1979

[Sialolithiasis].

Affections of the major salivary glands are relatively rare in stomatology; but according to the indications of several authors, the proportion of sialolithiasis to the total amount of affections of the salivary glands (ranging from 20.5 to 55.5%) is great. The concretions are, as a rule, located in the duct system of the submandibular gland where they may reach, circumstances permitting, considerable sizes. The author's own investigations evidence that these calculi have a partly regular, partly irregular shell-like structure around a non-calcified centre. Chemical analysis by means of X-ray diffractometry revealed hydroxyapatite varying in the degree of cristallinity as the major component. Precursors in the form of octacalcium phosphate and dicalcium phosphate dihydrate have been disclosed. Salivary calculi must be removed (most frequently by surgical intervention) to avoid secondary diseases of the duct system of the respective gland.

Crystallization↗
PubMed1978

Crystallographic studies on D-amino acid oxidase.

D-amino acid oxidase, a flavoprotein from hog kidneys, has been crystalized in two different forms. Orthorhombic prisms have been obtained from the enzyme.benzoate complex at pH 8.3; the space group is C2221 and the cell dimensions are a = 325A, b = 138.8 A, c = 200 A. At lower pH values, the enzyme crystallizes in trigonal prisms with a = b = 116.0 A, c = 399 A, space group P3112 or its enantiomorph. The two crystal forms have been obtained at 28 degrees C while at 4 degrees C only weak evidence of crystallization has been detected. In both crystalline modifications, the protein is highly associated.

D-Amino-Acid Oxidase↗
PubMed1977

The endocrine pancreas in early alloxan diabetes. Including study of the alloxan inhibitory effect of feeding and some hexoses.

Starved animals were sensitive to alloxan, whereas a more or less inhibitory effect towards alloxan was observed in fed animals, and in starved animals pretreated with glucose, mannose or fructose, but not in those pretreated with galactose. The islets of starved controls possessed larger B-cell mitochondria than those of fed ones. The earliest B-cell changes in the alloxan-treated animals were localized to the mitochondria which showed swelling, and disruption of inner and occasionally outer membranes. Later, many mitochondria were disintegrated, and the endoplasmic reticulum and Golgi complex disorganized. The secretory granules were preserved, although sometimes with atypical configuration, in degenerating but non-necrotic B-cells, suggesting that insulin stored in granules is not released until the cells are necrotic. Finally, frank necrosis was seen in some B-cells, whereas others were unaffected. The Ca2+-precipitation studied by pyroantimonate technique and x-ray analysis differed in the B-cells of the alloxan-treated animals from that in the controls; the former animals exhibited no or only sparse precipitation in mitochondria and secretory granules, but a rich precipitation in the cytoplasmic ground substance, whereas the precipitation in the controls mainly was localized to mitochondria and secretory granules. The primary site of alloxan action in the B-cells is believed to be localized to the mitochondria.

Animals↗
PubMedDate not supplied

[DNA complexes with lysozyme].

Sedimentation method has been used to study hen egg-white lysozyme binding to glucosylated (from T2 phage) and non-glucosylated (from calf thymus) DNA under conditions similar to physiological ones (pH 7,3--7,4, ionic strength 0.07--0.24). The results indicate that lysozyme binds cooperatively to both DNA's. Binding parameters have been obtained by applying the theory of one-dimensional adsorption of small molecules on a linear homopolymer. X-ray patterns of complexes with different protein content have been obtained.

Animals↗
PubMed1976

X-ray and functional studies of hemoglobins Nancy and Cochin-Port-Royal.

The mutations in hemoglobin Nancy beta145(HC2) Tyr leads to Asp and hemoglobin Cochin-Portal-Royal beta146(HC3) His leads to Arg involve residues which are thought to be essential for the full expression of allosteric action in hemoglobin. Relative to the structure of deoxyhemoglobin A, our x-ray study of deoxyhemoglobin Nancy shows severe disordering of the beta chain COOH-terminal tetrapeptide and a possible movement of the beta heme iron atom toward the plane of the porphyrin ring. These structural perturbations result in a high oxygen affinity, reduced Bohr effect, and lack of cooperatively in hemoglobin Nancy. In the presence of inositol hexaphosphate (IHP), the Hill constant for hemoglobin Nancy increases from 1.1 to 2.0. But relative to its action on hemoglobin A, IHP is much less effective in reducing the oxygen affinity and in increasing the Bohr effect of hemoglobin Nancy. This indicates that IHP does not influence the R in equilibrium T equilibrium as much in hemoglobin Nancy as in hemoglobin A, and this probably is due to the disordering of His 143beta which is known to be part of the IHP binding site. IHP is also known to produce large changes in the absorption spectrum of methemoglobin A, but we find that it has no effect on the spectrum of methemoglobin Nancy. In contrast to the large structural changes in deoxyhemoglobin Nancy, the structure of deoxyhemoglobin Cochin-Port-Royal differs from deoxyhemoglobin A only in the position of the side chain of residue 146beta. The intrasubunit salt bridge between His 146beta and Asp 94beta in deoxyhemoglobin A is lost in deoxyhemoglobin Cochin-Portal-Royal with the guanidinium ion of Arg 146beta floating freely in solution. This small difference in structure results in a reduced Bohr effect, but does not cause a change in the Hill coefficient, the response to 2,3-diphosphoglycerate, or the oxygen affinity at physiological pH.

Allosteric Site↗