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Biomedical subjects

M Wong

Publications and source records attributed to M Wong.

At least 325 records · Page 18Linked to original sources
PubMed1983

Degenerative calcific valvular disease and systolic murmurs in the elderly.

By use of echocardiographic and radiologic imaging, a prospective study was made of 98 elderly men, 65 to 102 years old, to define degenerative calcific valvular disease (DCVD)--its prevalence, morphologic features, functional significance, and relationship to systolic murmurs in the elderly. DCVD was diagnosed in 74 per cent of the group and murmurs were detected in 55 per cent, the incidences increasing with age. Fibrotic and calcific change of the aortic valve was the most common abnormality, occurring alone or together with alteration of the mitral valve. The murmurs were characteristically early systolic, of low intensity and medium pitch, and heard at more than one area. Of the group with valve degeneration, only 7 per cent was judged to be functionally significant and no more than moderate. It was concluded that DCVD is the cause of most systolic murmurs in the elderly and is usually hemodynamically unimportant. Echocardiographic criteria are important in identifying those subjects with possibly significant valvular dysfunction requiring invasive study.

Aged↗
PubMed1983

Sensitivity and specificity of two-dimensional echocardiography in the detection of valvular calcification.

To test the ultrasonic method for detecting valvular calcifications, two-dimensional echocardiograms and 35-mm cinefluorograms recorded in 113 elderly men were compared. Four views of the heart were filmed with image intensification. Valvular opacifications 1.5 mm or more in diameter were considered to be calcium and served as the standards. From parasternal views the brightness of valvular echoes was compared to echoes of the aortic wall by incremental rejection. Valvular echoes persisting as long as or beyond suppression of aortic root echoes were called positive for calcium. In half of the subjects, fluorographic studies disclosed valvular calcium, of which 67 percent was graded minimum. Echocardiographic sensitivity for detecting calcium in both the mitral anulus and aortic valve was 76 percent; specificity was 89 to 94 percent. Detection in the mitral leaflets was low and due to the smallness of the target and high sensitivity of the standard. Thus, an easily performed ultrasonic technique can screen moderate calcification of the mitral annulus and aortic valve with a predictive accuracy of 80 percent.

Aged↗
PubMed1983

Fine resolution of the poly ADP-ribosylated domains of polynucleosomal chromatin: DNA gene and integrity analysis; mechanism of histone H1 modification.

The focus of our laboratory has been to ascertain how the poly(ADP-ribosyl)ation reaction influences the structure and biological function of nucleosomal chromatin. Antibody to poly(ADP-ribose (ADP-Rib] was coupled to Sepharose to prepare an immunoaffinity column. The following new information concerning poly(ADP-Rib) and chromatin was obtained with this column: 1) those limiting domains of nucleosomal chromatin undergoing the modification (circa 10%) could be isolated in the "bound" fraction, 2) antibody-bound nucleosomes contained all the poly ADP-ribosylated acceptors and polymerase activity of the bulk chromatin, 3) bound nucleosomes contain significant numbers of internal DNA strand breaks, and [3H]-thymidine (TdR) repair incorporation from in vivo "DNA repair label," compared to the unbound, bulk of the chromatin, 4) the presence of actively transcribed genes in "bound" nucleosomes is being investigated, 5) the acetylation modification of histones occurs in the same domains of chromatin as does poly(ADP-ribosyl)ation, and 6) poly ADP-ribosylated histone H1 can be selectively purified by the immunoaffinity method. These same histone H1 molecules appear to be equally accessible to the histone kinase, phosphorylation modification. In addition, new information has been obtained concerning histone H1 cross-linking by poly(ADP-ribosyl)ation, and on polymerase binding sites to chromatin. We have reconstituted histone H1-depleted chromatin with intact H1 and peptide domains of H1, and subsequently studied H1-poly(ADP-Rib)-complex synthesis. The data indicate that elongation of poly(ADP-Rib) proceeds on the amino terminal region of this histone. By utilizing the new techniques of DNA technology, huge advances in our understanding of the programmed structure of the eukaryotic genome have been accomplished in a relatively short time. To complement this explosion of information, it is important to ascertain how these recently appreciated properties of eukaryotic DNA are packaged within extended and condensed domains of chromatin. The research to be discussed is directed, in part, at this latter topic. We have initiated a program aimed at furthering our comprehension of chromatin structure by studying one specific, enzymatically active chromosomal protein.

Chemical Phenomena↗
PubMed1982

Organization of the glycosphingolipid asialo-GM1 in phosphatidylcholine bilayers.

An affinity purified monovalent ferritin conjugate of Ricinus communis agglutinin (RCA 60) is used with freeze-etch electron microscopy to study the ultrastructural localization of the glycosphingolipid asialo-GM1 in multilamellar phosphatidylcholine liposomes. Dimyristoylphosphatidylcholine (DMPC) liposomes containing up to 20 mol% asialo-GM1 and quenched below the main transition temperature show a striking linear localization of ferritin-RCA 60 between phospholipid ridges. The glycosphingolipid localization is similar to that postulated for up to 20 mol% cholesterol in pure phosphatidylcholine bilayers by Copeland, B.R. and McConnell, H.M. (Biochim. Biophys. Acta, 599, 95-109 (1980)). Above the main phase transition temperature, asialo-GM1 appears to be organized into clusters, especially in palmitoyloleoylphosphatidylcholine (POPC) liposomes. This clustered distribution of glycosphingolipids seen above the phase transition temperature suggests that this type of lipid may exhibit compositional domain structure in biological membranes.

Chemical Phenomena↗
PubMed1982

Fusion of dipalmitoylphosphatidylcholine vesicles at 4 degrees C.

Small sonicated dipalmitoylphosphatidylcholine vesicles when incubated at 4 degrees C and high concentrations are shown to fuse completely to vesicles about 700-A diameter in 7 days, and these further fuse to about 950 A diameter vesicles after 3-4 weeks. The 950 A diameter vesicles are spherical, homogeneous, mostly unilamellar, have an internal aqueous space about 10 times that of small vesicles, and are stable for at least 6 months. The 950-A vesicles are characterized by agarose gel chromatography, freeze-fracturing electron microscopy, trapped volume measurements, differential scanning calorimetry, and diphenylhexatriene fluorescence polarization.

Chemical Phenomena↗
PubMed1982

Aggregation of dipalmitoylphosphatidylcholine vesicles.

Quasi-elastic and 90 degrees light scattering were used to study the aggregation of dipalmitoylphosphatidylcholine vesicles at temperatures below the gel-liquid-crystalline phase transition as a function of concentration, temperature, and size. Increased vesicle concentration did not appreciably change aggregate size but did change the total number of aggregates in a manner consistent with a bimolecular collisional mechanism for the conversion of aggregates to fused vesicles. Increased temperature decreased aggregation, indicating that the disaggregation rate constant increased faster than the aggregation rate constant. As a function of size, aggregation decreased slightly from small to 700 A diameter vesicles and increased considerably for 950 A diameter vesicles. A model of the interaction of small vesicles below the gel-liquid-crystalline phase transition is presented in which aggregation precedes fusion and collision between aggregates triggers fusion.

Chemical Phenomena↗
PubMed1982

The correlates of an abnormal first heart sound in mitral-valve-prolapse syndromes.

In 52 patients with mitral-valve prolapse we studied the intensity of the first heart sound (S1) in relation to the timing of the prolapse and to the presence of leaflet tip coaptation. Sixteen normal subjects served as controls. With two-dimensional echocardiography, three distinct groups were identified. Sixteen patients had early systolic mitral prolapse coincident with initial mitral-leaflet coaptation at the S wave on electrocardiography. Twenty-one had middle to late systolic mitral prolapse. Fifteen had flail mitral leaflet without normal leaflet coaptation at the free margins. The intensity of S1 was expressed as the ratio of the S1 amplitude to that of the aortic component of the second heart sound. This ratio was greater in the patients with early prolapse (6.2 +/- 3.1, mean +/- S.D.) than in the controls (1.4 +/- 0.7) (P less than 0.01). The ratio was reduced in patients with flail valves (0.3 +/- 0.5) (P less than 0.01) and did not differ between patients with middle to late prolapse (1.3 +/- 0.6) and controls. We conclude that the amplitude of S1 may provide a clue to the type and timing of mitral-valve prolapse.

Adolescent↗
PubMed1982

Saxitoxin binding sites in frog-myocardial cytosol.

Cytosolic fractions of frog heart homogenates contain large amounts of a soluble, large molecular weight protein that binds the specific neurotoxin saxitoxin with the same high affinity as does the plasma membrane. Another neurotoxin, tetrodotoxin, which ordinarily is competitive with saxitoxin, does not displace saxitoxin from the cytosolic sites or from plasma membrane-enriched vesicular fractions even when its concentration exceeds that of saxitoxin by a factor of 1000. Thus, cytosolic sites are similar to membrane sites in this respect. The vesicular fraction accounts quantitatively for the amount of saxitoxin bound by whole ventricles, so that no appreciable losses seem to occur. Therefore, the cytosolic site probably is a membrane site precursor, although other possibilities cannot be ruled out. In any case, the occurrence of a soluble molecule closely related to the sodium channel provides opportunities for further study of the structure of the sodium channel.

Animals↗
PubMed1982

The participation of poly(ADP-ribosyl)ated histone H1 in oligonucleosomal condensation.

The chromatin-associated enzyme poly(ADP-Rib) polymerase causes an NAD-dependent crosslinking of modified oligonucleosomes, as demonstrated by electrophoretic and sedimentation analysis [Butt, T. R. and Smulson, M. (1980) Biochemistry, 19, 5235-5242]. It was speculated that poly(ADP-ribosyl)ation of histone H1 and subsequent formation through crosslinking to an H1 dimer may be an important component of this phenomenon. To study this process, a method of complexing histone H1 to chromatin was required that promoted the restoration of accurate poly(ADP-ribosyl)ation of this histone. Previously we have established that two histone H1 molecules are crosslinked by a chain of poly(ADP-Rib) 15 or 16 units in length. In the current study, we made use of the ability of oligonucleosomes, reconstituted with H1, to carry out the synthesis of the poly(ADP-Rib)-H1 complex in order to monitor the accuracy of reconstitution. It appears that a specific distance and juxtaposition of adjacent H1 molecules along the polynucleosome fiber is required for the enzymatic synthesis of this modified histone complex. We established that a controlled trypsin digestion of oligonucleosomes removed H1 histone with minimal perturbation of other nuclear proteins associated with chromatin. In addition, poly(ADP-Rib) polymerase was partially removed from chromatin by this procedure. Subsequently, methods utilizing gradient salt dialysis have been employed to reconstitute both the polymerase and histone H1 to the depleted oligonucleosomes. The reassociation of H1 (and polymerase) to specific binding sites within oligonucleosomes was accomplished by the above procedures. Poly(ADP-Rib)--H1-dimer synthesis was not observed in depleted oligonucleosomes, but this capacity was found to be partially restored in the reconstituted chromatin. Similarly, the ability of NAD to promote crosslinking of nucleosomes was restored in the reconstituted samples. These results provide a basis for further studies on how the poly(ADP-ribosyl)ation of histones alters the structure of chromatin.

Binding Sites↗
PubMed1982

Properties of oxaloacetate decarboxylase from Veillonella parvula.

Oxaloacetate decarboxylase was purified to 136-fold from the oral anaerobe Veillonella parvula. The purified enzyme was substantially free of contaminating enzymes or proteins. Maximum activity of the enzyme was exhibited at pH 7.0 for both carboxylation and decarboxylation. At this pH, the Km values for oxaloacetate and Mg2+ were at 0.06 and 0.17 mM, respectively, whereas the Km values for pyruvate, CO2, and Mg2+ were 3.3, 1.74, and 1.85 mM, respectively. Hyperbolic kinetics were observed with all of the aforementioned compounds. The Keq' was 2.13 X 10(-3) mM-1 favoring the decarboxylation of oxaloacetate. In the carboxylation step, avidin, acetyl coenzyme A, biotin, and coenzyme A were not required. ADP and NADH had no effect on either the carboxylation or decarboxylation step, but ATP inhibited the carboxylation step competitively and the decarboxylation step noncompetitively. These types of inhibition fitted well with the overall lactate metabolism of the non-carbohydrate-fermenting anaerobe.

Adenosine Triphosphate↗
PubMed1982

The tricuspid valve annulus: study of size and motion in normal subjects and in patients with tricuspid regurgitation.

The tricuspid valve leaflets and their annular attachments were recorded by two-dimensional echocardiography from a view of the right ventricular inflow tract obtained by placing the transducer at an intermediate position between the left ventricular apex and the left lower sternal border. The transducer was rotated, and recordings were made at 30 degrees rotational intervals around the circumference of the tricuspid valve annulus. The cyclical pattern of variations in tricuspid annular size was studied with 12 measurements made during the cardiac cycle in five normal subjects. Annular areas and circumferences were measured. The overall motion pattern was similar to that reported in normal mitral valve annular study. Subsequently, in 16 normal subjects and 18 patients with tricuspid regurgitation, the maximum and minimum tricuspid annular sizes and their percent reduction were measured. The mean maximum annular circumference and area were 11.9 +/- 0.9 cm (mean +/- SD) and 11.3 +/- 1.8 cm2 in normal subjects. They were significantly greater in tricuspid regurgitation (14.0 +/- 0.7 cm and 15.8 +/- 1.8 cm2, respectively). The mean minimum annular sizes were much larger in tricuspid regurgitation (12.5 +/- 0.6 cm and 13.0 +/- 1.4 cm2) than in normal subjects (9.6 +/- 0.9 cm, 7.6 +/- 1.4 cm2). Thus, the percent reduction of annular circumference and area were significantly decreased in tricuspid regurgitation. For anatomic correlations, measurements of the tricuspid annular circumference were made at autopsy in 18 hearts without underlying valvular disease. The annular circumference was measured in the fresh and fixed states. The measurement in the fresh state was 13.5 +/- 0.8 cm and in the fixed state was 12.0 +/- 0.8 cm. The values measured in the fixed hearts were more similar to measurements obtained by echocardiography in a group of normal subjects. Thus, tricuspid annular reconstruction by the new two-dimensional echocardiographic method provides additional information about normal and abnormal size and function of the tricuspid valve annulus.

Adult↗