Lateral and protrusive contact schemes and occlusal wear: a correlational study in a young adult Saudi population.

This study investigated the influence of occlusal contacts on the location and severity of occlusal wear during various mandibular movements. The study population consisted of 80 dental students with a mean age of 22 years, within the age range of 19 to 25 years. A dentition wear index--in addition to anterior, canine, and posterior subindexes--was derived from a tooth-by-tooth evaluation of casts.

Possible role of an iron-oxygen complex in 4(S)-4-hydroxyochratoxin a formation by rat liver microsomes.

Rat liver microsomes were examined for their ability to oxidize the mycotoxin ochratoxin A (OTA) to 4(R)-4-hydroxyochratoxin A [(R)-4-OH-OTA] and 4(S)-4-hydroxyochratoxin A [(S)-4-OH-OTA] and to induce OTA-dependent lipid peroxidation. Microsomes isolated from rats pretreated with pregnenolone-16 alpha-carbonitrile greatly induced both (R)-4-OH-OTA and (S)-4-OH-OTA formation whereas isoniazid pretreatment primarily induced (S)-4-OH-OTA. (R)-4-OH-OTA and (S)-4-OH-OTA formation showed significant differences with respect to pH optima, effect of antioxidants, and iron chelators.

An investigation of some factors associated with occlusal tooth wear in a selected high-wear sample.

The aim of the present study was to investigate the influence of some factors associated with occlusal tooth wear in a selected high-wear Swedish sample. The material comprised 59 persons having a mean age of 35 yr within the range 16-70 yr, the criteria for selection being a full or near-full complement of natural teeth, and the presence of definite clinical signs of occlusal wear. A dentition wear index, in addition to anterior, posterior, and arch subindices, was derived from a tooth-by-tooth evaluation of casts.

Covariation of some factors associated with occlusal tooth wear in a selected high-wear sample.

The aim of the present study was to investigate the significance of some factors associated with occlusal tooth wear in a selected high-wear Swedish sample. The material comprised 59 subjects having a mean age of 35 yr within the range 16-70 yr, the criteria for selection being a full or nearly full complement of natural teeth, and the presence of definite clinical signs of occlusal wear. A dentition wear index was derived from a tooth-by-tooth evaluation of casts.

Extramedullary plasmacytomas of the head and neck.

Extramedullary plasmacytomas are solitary tumors consisting of neoplastic plasma cell proliferations that occur in locations other than bone. On initial presentation they must be differentiated from multiple myeloma. This may prove to be difficult because a varying percentage may be associated at a later date with the development of multiple myeloma.

Comparison of the prevalence, severity and possible causes of occlusal tooth wear in two young adult populations.

Most reports of the prevalence and severity of tooth wear in contemporary Western populations claim that advanced wear in uncommon by comparison with certain non-Western populations. Differing methods of wear evaluation in the various studies, however, preclude accurate comparisons from being made. This study records mean total and segmental wear indices obtained from the casts of a selected Swedish patient population sample, and age- and sex-matched Saudi high-wear and random samples.

A system for assessing the severity and progression of occlusal tooth wear.

This study represents an attempt to introduce a system for the longitudinal evaluation of the severity and the rate of progression of tooth wear. The material comprised a selected group of 10 males and 10 females, examined twice within an 18-month period. The subjects were predisposed to advanced occlusal wear and had a mean age of 32 years within the range of 16-56 years.

Acid phosphatase activity in senile plaques and cerebrospinal fluid of patients with Alzheimer's disease.

The origin of the various components of senile plaques in Alzheimer's disease (AD) continues to be a focus of intense research scrutiny. Lysosomal enzyme activity within the plaques is of particular interest because of its possible relevance to a presumed abnormal processing of precursor molecules that may lead to the formation of plaque amyloid. Histochemical evidence of acid phosphatase (ACP), a lysosomal hydrolase, activity in senile plaques has been documented long before many of the current biochemical data regarding plaque pathogenesis became available.

Oxygen free radicals as inducers of heat shock protein synthesis in cultured human neuroblastoma cells: relevance to neurodegenerative disease.

We studied heat shock protein (HSP) synthesis by cultured human neuroblastoma cells in response to either hyperthermia or high levels of superoxide anion (oxygen free radical). Both treatment modalities resulted in induced synthesis of the same major HSP species with an additive effect on the latter and on cell growth inhibition upon combined treatments. Exposure to superoxide anion in the presence of the free radical scavenging enzymes, superoxide dismutase and catalase improved cell survival and prevented HSP induction.

The genesis of the senile plaque. Further evidence in support of its neuronal origin.

Senile plaques are among the most conspicuous neuropathologic changes found in the brains of elderly individuals and patients with Alzheimer's disease (AD). The origin of the amyloid beta protein (A beta P) that accumulates in senile plaques continues to be highly controversial. Recently, using quantitative immunohistochemistry and computerized image analysis, we obtained evidence that at least a subset of early ("diffuse") senile plaques originate from neurons.

Properties of an endogenous arachidonic acid--elicited relaxing mechanism in human placental vessels.

Objective: Our objective was to examine the action of arachidonic acid on tone in isolated human placental arteries and veins (1 to 2 mm diameter) for mechanisms involving endothelium-derived mediators, the stimulation of guanylate cyclase, and prostaglandin and cytochrome P450 metabolites.

Study Design: Pharmacologic probes and endothelium-removal were used to examine the mechanism of relaxation to arachidonic acid (10 nmol/L to 10 mumol/L) observed in placental arteries and veins obtained after delivery from uncomplicated term pregnancies and precontracted with prostaglandin F2 alpha.

Results: Neither removal of the endothelium nor inhibition of prostaglandin biosynthesis with 10 mumol/L indomethacin, arginine-derived nitric oxide formation with 30 mumol/L nitro-L-arginine, or guanylate cyclase stimulation with 10 mumol/L LY83583 altered the observed relaxation to arachidonic acid in either preparation.

Hydrogen peroxide and reoxygenation cause prostaglandin-mediated contraction of human placental arteries and veins.

Objective: Because our previous studies in several vascular preparations suggest that posthypoxic reoxygenation elicits tone responses by generation of hydrogen peroxide we compared the actions of reoxygenation and hydrogen peroxide on isolated human placental arteries and veins.

Study Design: Endothelium-intact and denuded arteries and veins (1 to 2 mm diameter, from normal term deliveries), incubated under 95% oxygen/5% carbon dioxide or 5% oxygen/5% carbon dioxide (balance nitrogen) and precontracted with 1 to 10 nmol/L U46619, were exposed to hypoxia (95% nitrogen/5% carbon dioxide, PO2 8 to 10 torr) followed by reoxygenation and to 1 to 100 mumol/L hydrogen peroxide in the presence and absence of the inhibitor of prostaglandin biosynthesis, 10 mumol/L indomethacin.

Results: In both arteries and veins posthypoxic reoxygenation or exposure to hydrogen peroxide produced vascular contraction that was eliminated or reversed to a modest relaxation by indomethacin, consistent with mediation by prostaglandins.

Immunohistochemical evidence of oxidative [corrected] stress in Alzheimer's disease.

Membrane and cytoskeletal structures are known targets of oxidative injury. Brains from patients with Alzheimer's disease have cytoskeletal abnormalities and platelet and possible neuronal membrane lesions. The authors have recently demonstrated that superoxide anion is a powerful inducer of heat-shock protein synthesis, and have also shown that in response to oxidative stress or hyperthermia, intracellular levels of antioxidant enzymes increase to several folds.

Image analysis microspectroscopy shows that neurons participate in the genesis of a subset of early primitive (diffuse) senile plaques.

Amyloid is a component of the senile plaques that characterize one of the major neuropathologic changes in patients with Alzheimer's disease (AD). The sequence of events leading to the accumulation of amyloid precursors in senile plaques is unknown. In previous studies, the authors have shown that congophilic deposits in a subset of mature amyloid plaques are angiocentric.

Analysis of possible factors influencing the occurrence of occlusal tooth wear in a young Saudi population.

The purpose of this study was to attempt to correlate possible etiologic factors with the occurrence of occlusal tooth wear in a young Saudi population. The material comprised 90 individuals with a mean age of 22 years within a range of 19-25 years. A dentition wear index, in addition to anterior and posterior wear subindices were derived from tooth-by-tooth evaluations of casts.

The outcome of patients with acute bronchial asthma presenting to the emergency room.

We collected data on patients above the age of 5 years with acute bronchial asthma who presented to the emergency room of Hospital Sains Universiti Sains Malaysia during the period between 1 January to 31 March 1990. Two hundred and twelve patients (57% males and 43% females) who made a total of 271 visits were recorded. This constitutes 16.

Two distinct types of intraneuronal neurofibrillary tangles highlighted by polarized light after silver impregnation with a modified Bielschowsky method.

Neurofibrillary tangles (NFTs) are one of the morphological hallmarks of Alzheimer's disease. The birefringency and dichroism of NFTs following congo red staining have long been known. Herein, we report the observation that a subset of NFTs show distinct birefringency induced by a modified Bielschowsky silver impregnation method.

A "Pap" test for men? Male urethral smears as screening tool for detecting subclinical human papillomavirus infection.

We have explored the potential of using immunoperoxidase staining and in situ DNA hybridization techniques to detect the HPV common antigen and HPV DNA (subtypes 6/11 and 16/18) in urethral smears obtained from men with no grossly visible urethral lesions, with or without HPV-related clinical history. A total of 91 such smears were studied of which 25 (27.5%) were positive for HPV antigen.

In vitro inhibition of rat platelet aggregation by ochratoxin A.

The mycotoxin ochratoxin A (OA) consists of 5-chloro-3-methyl-3,4-dihydro-8-hydroxyisocoumarin moiety linked by an amide bond to beta-L-phenylalanine. When added to washed rat platelets in vitro, OA caused a dose-dependent inhibition of aggregation induced by agonists such as adenosine diphosphate (ADP) or thrombin. The aggregatory response induced by prior addition of an agonist was also reversed in a dose-dependent manner by OA.

Role of cytochrome P-450 in ochratoxin A-stimulated lipid peroxidation.

The role of cytochrome P-450 in the stimulation of lipid peroxidation by the nephrotoxic mycotoxin ochratoxin A has been investigated. Ochratoxin A was previously shown to markedly stimulate lipid peroxidation in a reconstituted system consisting of phospholipid vesicles, NADPH-cytochrome P-450 reductase, Fe3+, ethylenediaminetetraacetic acid (EDTA), and reduced nicotinamide adenine dinucleotide phosphate (NADPH). We now show that purified cytochrome P-450IIB1 could effectively replace EDTA in stimulating lipid peroxidation suggesting that it could mediate the transfer of electrons from NADPH to Fe3+.

NADPH-cytochrome-P-450 reductase promoted hydroxyl radical production by the iron(III)-ochratoxin A complex.

The Fe3+ complex of ochratoxin A has been shown to produce hydroxyl radicals in the presence of NADPH and NADPH-cytochrome-P-450 reductase. ESR spin-trapping experiments carried out in the presence of the hydroxyl radical scavenger ethanol and the spin trap DMPO (5,5-dimethyl-1-pyrroline-1-oxide) produced ESR spectra characteristic of the hydroxyl radial-derived carbon-centered DMPO-alkoxyl radical adduct. Thus hydroxyl radicals produced by the Fe3(+)-ochratoxin A complex in the presence of an enzymatic reductase may be be partly responsible for ochratoxin A toxicity.

Mechanism of ochratoxin A stimulated lipid peroxidation.

Lipid peroxidation, measured as malondialdehyde formation or by oxygen uptake, was stimulated markedly by the mycotoxin ochratoxin A (OTA) in a reconstituted system consisting of phospholipid vesicles, the flavoprotein NADPH-cytochrome P450 reductase, Fe3+, EDTA and NADPH. Deletion of EDTA lowered the extent of lipid peroxidation but did not eliminate it. Fluorometric and spectrophotometric studies demonstrated the formation of a 1:1 Fe3(+)-OTA complex.

Prevalence and severity of occlusal tooth wear in a young Saudi population.

An epidemiologic investigation of the prevalence and severity of occlusal wear was carried out in a young Saudi population. Occlusal wear was evaluated on a tooth-by-tooth basis on study casts made for 206 dental students, using an ordinal scale. The reliability of the scale was assessed by percentage inter- and intra-observer concordance.

Immunocytochemical detection of the 70-kd heat shock protein in alcoholic liver disease.

Exposure of cells to physical (eg, heat) or chemical (eg, alcohol) stress results in increased synthesis of a set of highly conserved polypeptides termed heat shock proteins (HSPs), among which the 70-kd protein (HSP 70) is one of the most consistently inducible and highly conserved. This HSP has adenosine triphosphate-binding properties and is known to associate strongly with cytoskeletal structures that are usually disrupted on injury by heat or alcohol. Some HSPs apparently function as accessories to a nonlysosomal, adenosine triphosphate-dependent proteolytic system that binds and digests away stress-generated abnormal or denatured proteins after their conjugation with ubiquitin, a small HSP.

The "normal" brain. "Abnormal" ubiquitinilated deposits highlight an age-related protein change.

Known morphologic changes that characterize "normal" brain senescence are insufficient to explain the widespread, age-related decline of psychomotor functions. We report that the heavily ubiquitinilated deposits can be consistently detected by immunohistochemistry in the normal senescent brain. Immunostaining of hippocampal sections from aged brains with an anti-ubiquitin antibody was unrelated to neurofibrillary degeneration or senile plaque formation.