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Biomedical subjects

M Gross

Publications and source records attributed to M Gross.

At least 271 records · Page 15Linked to original sources
PubMed1996

The quantitation of metabolites of quercetin flavonols in human urine.

The flavonoid quercetin, or its metabolites, inhibit chemical carcinogenesis in rodents and may have a role in the prevention of human cancers. Quercetin exposure in human populations results from the dietary intake of various plant foods; high concentrations of quercetin are found in apples, onions, tea, and red wine. Determination of the relationship between dietary intake and cancer risk depends on the characterization of quercetin intake. The development and use of biomarkers for quercetin intake may provide a basis for the objective classification of this exposure. One possible biomarker is metabolic products of quercetin. We report the development of a high-performance liquid chromatography (HPLC)-based assay for quantitation of quercetin metabolites in human urine. The metabolites include 3,4-dihydroxyphenylacetic acid (homoprotocatechuic acid), metahydroxyphenylacetic acid, and 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid). The assay has only two major steps, ether extraction and HPLC analysis, and is suitable for analysis of large sample numbers. Analytical characteristics of the assay include a sensitivity of less than 1 microgram, precision with coefficients of variation < 10%, and metabolite recoveries > 90%. The mean concentrations of 3,4-dihydroxyphenylacetic acid, metahydroxyphenylacetic acid, and homovanillic acid in two human urine samples are approximately 0.7, 4.8, and 2.8 micrograms/ml, respectively. The identification of each metabolite is confirmed by HPLC, UV absorbance scans, and gas chromatography-mass spectrometry analysis. These results verify the occurrence of quercetin metabolites in human urine and the feasibility of quercetin metabolite quantitation, by the assay described herein, for epidemiological studies. Development of the analytical procedure is an essential first step for validation of the metabolites as biomarkers of quercetin intake.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

[Avian yolk antibodies in diagnosis and research].

Hens were immunized with bacterial polysaccharide (alginate), Hepatitis B surface antigen (HBsAg), and potato viruses (PVA, PVS, PVM, PVX, and PVY). The antibodies were isolated noninvasively from the yolks of laid eggs. The purified yolk immunoglobulins (IgY) were tested in an array of various assays and diagnostic techniques. The methods employed were precipitation reactions, immun-electrophoresis, ELISA (after biotinylation of IgY), immuno-gold electron microscopy, and western and immuno blotting. Some of these methods had to be modified according to the special requirements of avian antibodies. The special handling of this animal system is described in regard to antibody production. The results demonstrate that IgY derived from hens can replace IgG produced by traditional methods in mammals. The advantages of this alternate animal system are emphasized in respect to animal care, high productivity, and special suitability of avian antibodies for certain diagnostic purposes.

Animals↗
PubMed1996

Retrievable cemented crown options on implant-supported angled abutments: a case report.

Nonaxial implant alignment often predicates the use of cemented of screw-retained angled abutments with inherent disadvantages, including reduced retrievability on screw loosening. The purposes of this article are to review the relative merits of cemented and screw-retained angled abutments and to present a method of ensuring retrievability of cemented angled abutments.

Cementation↗
PubMed1995

Association of a M(r) 90,000 phosphoprotein with protein kinase PKR in cells exhibiting enhanced phosphorylation of translation initiation factor eIF-2 alpha and premature shutoff of protein synthesis after infection with gamma 134.5- mutants of herpes simplex virus 1.

The protein encoded by the gamma 134.5 gene of herpes simplex virus precludes premature shutoff of protein synthesis in human cells triggered by stress associated with onset of viral DNA synthesis. The carboxyl terminus of the protein is essential for this function. This report indicates that the shutoff of protein synthesis is not due to mRNA degration because mRNA from wild-type or gamma 134.5- virus-infected cells directs protein synthesis. Analyses of the posttranslational modifications of translation initiation factor eIF-2 showed the following: (i) eIF-2 alpha was selectively phosphorylated by a kinase present in ribosome-enriched fraction of cells infected with gamma 134.5- virus. (ii) Endogenous eIF-2 alpha was totally phosphorylated in cells infected with gamma 134.5- virus or a virus lacking the 3' coding domain of the gamma 134.5 gene but was not phosphorylated in mock-infected or wild-type virus-infected cells. (iii) Immune precipitates of the PKR kinase that is responsible for regulation of protein synthesis of some cells by phosphorylation of eIF-2 alpha yielded several phosphorylated polypeptides. Of particular significance were two observations. First, phosphorylation of PKR kinase was elevated in all infected cells relative to the levels in mock-infected cells. Second, the precipitates from lysates of cells infected with gamma 134.5- virus or a virus lacking the 3' coding domain of the gamma 134.5 gene contained an additional labeled phosphoprotein of M(r) 90,000 (p90). This phosphoprotein was present in only trace amounts in the immunoprecipitate from cells infected with wild-type virus or mutants lacking a portion of the 5' domain of gamma 134.5. We conclude that in the absence of gamma 134.5 protein, PKR kinase complexes with the p90 phosphoprotein and shuts off protein synthesis by phosphorylation of the alpha subunit of translation initiation factor eIF-2.

Animals↗
PubMed1995

Multiple-state equilibrium unfolding of guanidino kinases.

The denaturant-induced equilibrium unfolding of octameric mitochondrial creatine kinase, dimeric cytosolic muscle-type creatine kinase, and monomeric arginine kinase was investigated. Stable unfolding intermediates for all three enzymes were manifested by a strongly biphasic red shift of intrinsic protein fluorescence upon increasing denaturant concentrations. In the intermediate state, all proteins were monomeric and enzymatically inactive, but still retained a globular shape. Native tertiary structure interactions were largely disrupted, while at least 50% of the secondary structures were conserved, as suggested by near- and far-UV circular dichroism, respectively. A significantly increased surface hydrophobicity of the intermediate conformation, compared to both the native and the fully unfolded states, was observed by the binding of the hydrophobic fluorescent dye ANS. The observed properties agree formally with the definition of the molten globule state, but can be alternatively explained by a sequential unfolding of individual domains, involving a transient exposure of domain interfaces. Very similar unfolding profiles for all three proteins suggest that the formation of stable unfolding intermediates is not a consequence of the specific oligomeric structures of the CKs but rather due to a common, probably two-domain architecture of the guanidino kinase protomers.

Animals↗
PubMed1995

Dimer-dimer interactions in octameric mitochondrial creatine kinase.

Mitochondrial creatine kinase (Mi-CK) forms octamers and dimers, which are readily interconvertible in vitro. The kinetic and thermodynamic octamer stability of wild-type and two mutant, octamer-destabilized forms of chicken sarcomeric Mi-CK was investigated at varying temperatures, pHs, and salt and substrate concentrations, in order to identify parameters which might regulate the octamer/dimer ratio in vivo and to assess the nature of octamer-stabilizing interactions. For wild-type Mi-CK, the rate of the transition state analogue complex (TSAC)-induced octamer decay increased with increasing temperature up to 28 degrees C; increasing pH markedly accelerated the decay in a biphasic manner. The substrate-dependent decay data suggest that also the productive enzymatic transition state of Mi-CK induces an octamer-destabilizing conformation. Thermodynamically, the octamers are stabilized by a combination of hydrophobic and polar contributions. Van't Hoff analysis showed that hydrophobic interactions dominate both in the absence of substrates and in the TSAC conformation, since the equilibrium octamer fractions increased with increasing temperatures, in spite of the accelerated decay kinetics. For the Mi-CK mutant E4Q, a similar temperature dependence was found; in contrast, mutant W264C exhibited an inverted temperature dependence, suggesting that hydrophobic interactions might be largely abolished in this mutant. Both the kinetic and the thermodynamic data seem to suggest that the octamer-dimer transitions of Mi-CK might not play a major role in a fast regulation of mitochondrial energy metabolism, but could rather be involved in slow long-term modulations.

Adenosine Diphosphate↗
PubMed1995

Differential selenium-dependent expression of type I 5'-deiodinase and glutathione peroxidase in the porcine epithelial kidney cell line LLC-PK1.

The Se-dependent expression of two selenoproteins, cytosolic glutathione peroxidase (cGPx) and type I iodothyronine-5'-deiodinase (5'DI), was investigated in the porcine epithelial kidney cell line LLC-PK1 in serum-free medium. The selenite-dependent expression of cGPx and 5'DI was revealed by enzyme-activity measurements, affinity labelling of 5'DI, metabolic labelling of proteins with 75Se and steady-state mRNA analysis. The expression of the two enzymes strongly depended on selenite concentrations of the culture medium. cGPx required 2-fold higher selenite levels than 5'DI to reach half-maximal activity. The Se-dependent enzyme activities were approximately paralleled by the corresponding steady-state mRNA levels. The response of the two enzymes to Se supply was further characterized by kinetic Se-depletion and -repletion experiments. Upon removal of medium selenite, cGPx activity decreased exponentially, whereas after an initial decrease over 1-2 days, 5'DI levels completely recovered during a further 2 days. These data indicate a differential Se-dependent regulation of the two selenoproteins, with 5'DI being preferentially supplied with the trace element Se, thus ensuring a continuous cellular capacity for thyroid-hormone activation, even under Se-deficient conditions. The abundant cGPx in cells with sufficient Se supply might serve as a cellular Se store which can be mobilized for the synthesis of more vital selenoproteins such as 5'DI under shortage conditions. Thus, a cellular hierarchy of selenoprotein expression, reflected by different individual regulation mechanisms at the transcriptional and post-transcriptional level, adds to the previously recognized tissue-specific hierarchy of Se retention.

Animals↗
PubMed1995

Capillary electrophoresis for screening of adenylosuccinate lyase deficiency.

We report a new screening method for adenylosuccinate lyase (ASase) deficiency using capillary electrophoresis (CE). This enzyme defect causes secondary autism and psychomotor retardation in early childhood. In all body fluids of these patients, two succinylpurine metabolites can be found that are normally not detectable: succinyladenosine and succinylaminoimidazole carboxamide (SAICA) riboside. A Beckman P/ACE 2050 capillary electrophoresis system was used with a 47.1 cm capillary, 75 microns ID, and the P/ACE Beckman UV absorbance detector. Untreated urine, injected for 1 s, was separated in a pH 8.63 borate buffer at 20 kV. The two succinylpurines (migration times 13.36 and 13.60 min) were detected at 254 nm only in urine of patients with ASase deficiency but not in control samples.

Adenosine↗
PubMed1995

Occlusion and stability of synthetic femoral canal plugs used in cemented hip arthroplasty.

The occlusion and stability of five synthetic plugs used to restrict the femoral canal prior to cemented arthroplasty was assessed. A model was employed consisting of a hollow wooden dowel to simulate the canal, with adapters fixed to both ends to accommodate cement insertion and pressurization, and to produce a closed distal cavity. Three different canal diameters within the range accommodated by the plug selected were employed to assess insertion force, distal pressure during both insertion and pressurization of acrylic cement, and plug migration and leakage for each device. There was a wide variation among plugs in the magnitudes of the force and distal pressure upon plug insertion. During cement pressurization, cement leakage and/or plug migration was noted in all trials, and either of these events resulted in pressure rises in the distal cavity. Most notably, differences of only 0.5 mm in the diameter of the canal resulted in marked changes in the occlusion and stability achieved. It is concluded that for the range of canal sizes anticipated intraoperatively, these synthetic plugs appear deficient to varying extents in their ability to occlude or remain stable in the intramedullary canal.

Cementation↗
PubMed1995

Critical steps in total knee arthroplasty. A method of analyzing operative procedures.

We have analyzed the operation of knee arthroplasty using the Whiteside Mark II prosthesis, and found that it could be broken down into 42 steps, some of which are more important than others and can be considered as critical. We have identified 4 criteria to evaluate a critical step: 1) it must be necessary to complete the procedure, 2) it must take a significantly longer time to perform than other steps, 3) it must be revised significantly more frequently than other steps and 4) it must take significantly longer to revise than other steps. Two steps have been found to which all 4 criteria applied, namely placement of the femoral cutting jig and the first femoral saw cuts.

Analysis of Variance↗
PubMed1995

Some basic biomechanical characteristics of medullary pressure generation during reaming of the femur.

We measured femoral intramedullary pressures and applied axial thrust force generated in vitro during reaming with the AO and Zimmer systems. Six pairs of cadaver femora were instrumented with pressure taps midshaft and in the distal diaphysis, a load cell distally to measure force, and a displacement transducer to monitor reamer position. Following initial hand reaming, intramedullary power reaming was conducted utilizing a 9-mm reamer initially, with subsequent increases in steps of 0.5 mm. All femora were maintained at 37 degrees C and albumin was used to maintain a fluid-filled canal. The highest pressures consistently occurred during initial power reaming, with peak pressures ranging from 270 to 1500 mmHg amongst femora with the AO system. No significant differences were found in the peak pressures generated for the two systems (P = 0.10). The pressure measurements at the two locations in the femur were consistently similar, indicating that pressures are continuous throughout this aspect of the femur. The pressures were not correlated with instantaneous applied axial thrust (R2 = 0.191), and this could be attributed chiefly to the additional friction force of cutting. While pressure generation in the medullary canal upon reaming is likely governed by the rate of clearance of canal content, this is a highly variable response produced by characteristics of the femur which are still not fully understood.

Aged↗
PubMed1995

Effect of carotenoids on in vitro immunoglobulin production by human peripheral blood mononuclear cells: astaxanthin, a carotenoid without vitamin A activity, enhances in vitro immunoglobulin production in response to a T-dependent stimulant and antigen.

The effect of carotenoids on in vitro immunoglobulin (Ig) production by peripheral blood mononuclear cells (PBMNC) was examined by employing blood samples from adult volunteers and full-term newborn babies (umbilical cord blood). Under carotenoid-supplemented culture conditions, cells were stimulated by polyclonal stimulants, neoantigens, and a recall antigen (Ag), and IgM, IgA, and IgG levels in the culture supernatant were measured. Beta-carotene and astaxanthin were used as representatives of carotenoids with and without vitamin A activity, respectively. Astaxanthin enhanced IgM production in response to T-dependent Ag (TD-Ag) and a T-dependent polyclonal stimulant. Astaxanthin also augmented IgG production in response to a recall Ag. IgA production without supplemental carotenoids was negligible for all stimuli. However, in carotenoid-supplemented cultures, IgA production was significantly higher in response to a T-dependent polyclonal stimulant than in unsupplemented cultures. IgM and IgA production was augmented at 10(-8) mol/l astaxanthin, whereas astaxanthin enhanced IgG production in response to a recall Ag at 10(-10)-10(-9) mol/l. Similar enhancing actions of astaxanthin on IgM production were observed in cord blood mononuclear cells (CBMNC), although CBMNC produced less IgM than adult PBMNC. Beta-carotene did not have a significant effect on human Ig production. The carotenoid actions were not demonstrated under serum-free culture conditions; serum is essential for solubilization of carotenoids. In summary, this study has shown for the first time that astaxanthin, a carotenoid without vitamin A activity, enhances human Ig production in response to T-dependent stimuli.

Adult↗