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Biomedical subjects

W Wallace

Publications and source records attributed to W Wallace.

At least 37 records · Page 2Linked to original sources
PubMed1992

Transplacental genotoxicity of triethylenemelamine, benzene, and vinblastine in mice.

Transplacental cytogenetic effects of triethylenemelamine (TEM), benzene, and vinblastine on maternal mice and their fetuses have been investigated using micronucleus and sister chromatid exchange (SCE) as genetic endpoints. CD-1 mice were treated on day 14 and 15 of gestation with TEM (0.125, 0.25, and 0.5 mg/kg), benzene (439,878, and 1,318 mg/kg), and vinblastine (0.5, 1, and 2 mg/kg) by intraperitoneal injection at 24 hr intervals, and sacrificed 40 hr after the first injection. Erythrocytic precursor cells in maternal bone marrow and fetal livers (2-4) from each pregnant mouse were used for the micronucleus and/or the SCE analyses. Significant dose-related increases in both micronuclei and SCE were found in maternal bone marrow and fetal liver following TEM treatment. Benzene at the highest dose (1,318 mg/kg) also caused a significant increase in micronuclei and SCE in both maternal bone marrow and fetal liver cells. The embryonic genotoxic effect of TEM was much higher than that of benzene for both genetic endpoints, and the frequency of micronuclei induced by benzene was higher in fetal liver than in maternal bone marrow cells. Vinblastine, a spindle poison, induced micronuclei but not SCE. Micronuclei induction by vinblastine was 7 fold greater in maternal bone marrow than in fetal liver cells. All three chemicals were cytotoxic in maternal bone marrow cells, but not in fetal liver cells except for TEM, which showed a weak cytotoxicity in fetal liver cells in the micronucleus assay. These results indicate that TEM, benzene, and vinblastine are transplacental genotoxicants in mice.

Animals↗
PubMed1992

Increased phosphorylation of elongation factor 2 in Alzheimer's disease.

Elongation factor 2 (EF-2) is a phosphoprotein that mediates the translocation step of elongation during protein synthesis. We investigated its phosphorylation to characterize translational regulation of gene expression in Alzheimer's disease. EF-2 was identified on two-dimensional (2D) gels of brain homogenates by analyzing immunoblots with EF-2-specific antibody (M(r) 96,000; pI 6.8). Four distinct charge variant isoforms were observed. We identified the two most acidic isoforms as being the phosphorylated forms by incorporation of radiolabeled phosphate. The phosphorylation of EF-2 in control and Alzheimer's disease (AD) brain was directly measured as the distribution of the four polypeptides on silver stained 2D gels. The ratio of the phosphorylated forms to unphosphorylated forms was elevated 45% in AD homogenates compared to controls (1.07 +/- 0.18; n = 9 vs 0.73 +/- 0.20; n = 6; P less than 0.004) which indicated an increased phosphorylation of AD EF-2. The phosphorylation exhibited specificity to the disease in that it was observed in affected areas (cortex and hippocampus) but not in an unaffected area (thalamus) of the same brains. Because phosphorylation of EF-2 inhibits protein synthesis, the observed AD-associated phosphorylation of EF-2 is consistent with the reduced in vitro activity of polysomes isolated from AD tissues that we have previously reported.

Adenosine Diphosphate Ribose↗
PubMed1992

Evidence for 4-chlorobenzoic acid dehalogenation mediated by plasmids related to pSS50.

The biodegradation of 4-chlorobiphenyl usually proceeds through the intermediate 4-chlorobenzoate. Few bacterial strains can degrade 4-chlorobiphenyl to 4-chlorobenzoate and 4-chlorobenzoate to CO2. This study demonstrates that the 4-chlorobiphenyl-degrading Alcaligenes sp. strain ALP83 can degrade 4-chlorobenzoate to 4-hydroxybenzoate. The dehalogenase activity is correlated with a 10-kb fragment carried on plasmid pSS70.

Alcaligenes↗
PubMed1991

Increased synthesis and accumulation of heat shock 70 proteins in Alzheimer's disease.

Postmortem cortical tissues from Alzheimer's disease cases were found to contain significantly higher levels of the heat shock proteins hsp 72 and hsp 73 than control cortical tissues. This elevation was associated with the disease pathology in that it was not observed in Alzheimer's disease cerebella and was not correlated with perimortem characteristics such as age or cause of death of the patient or postmortem interval of the brain tissue. Examination of polysome translation products on two dimensional gels and by immunoprecipitation indicated that the syntheses of hsp 72/73 were increased in Alzheimer's disease tissues. In addition, immunoprecipitation of newly synthesized hsp 72 showed that numerous other nascent polypeptides were co-precipitated, which indicates an irreversible cotranslational association with the hsp 72. These results indicate that induction of specific heat shock proteins is associated with Alzheimer's disease and that cotranslational processes are affected by this induction.

Aged↗
PubMed1991

Expression of the Alzheimer amyloid precursor in brain tissue and effects of NGF and EGF on its metabolism.

Alzheimer's disease (AD) is the major cause of serious dementia and memory loss in several million elderly Americans. The most prominent lesions in the brains of these patients are the depositions of two types of abnormal filaments: the predominantly intraneuronal neurofibrillary tangles (NFT), which consist of paired helical filaments (PHF), and the extracellular amyloid fibers. These changes are characteristic of AD, and a final diagnosis of this disease is based on the presence of large numbers of these abnormal filamentous structures in the patient's brain. The amyloid fibers consist of a peptide subunit termed beta-protein or A4 peptide, which derives from a larger precursor protein. In this study we review the structural characteristics, regulation of expression, and metabolism of the Alzheimer amyloid precursor in brain tissue and cell cultures.

Aged↗
PubMed1991

Changes in dental caries prevalence in upstate New York schoolchildren.

A survey of second and fifth grade children was conducted in upstate New York to determine recent trends in dental caries prevalence. Clinical examinations were conducted on 960 second grade and 837 fifth grade children in 51 schools. A single examiner derived the findings on a uniform basis using a standard protocol. An examination of changes in the percent of caries-free children and mean DMFS/dfs indices revealed that caries prevalence has continued to decline. Although the low SES group in this survey had consistently higher caries levels and a higher treatment need compared to the high SES group, the magnitude of the difference was much smaller compared to the previous survey. Because the sampling was restricted to young children in upstate New York, the trends observed should not be applied to a similar New York City population, to older children throughout New York State, or to children in other states.

Adolescent↗
PubMed1991

The relationship of residents' autonomy and use of a teaching hospital's resources.

This 1990 study examines the relationship between the degree of use of patient care resources and the degree of supervision of residents by attending physicians (as perceived by residents) at a large midwestern teaching hospital. Ratings of the degree of clinical autonomy allowed residents by 65 attending physicians--each of whom had a general internal medicine practice with a significant hospital component--were provided by 23 former internal medicine chief residents and 17 internal medicine residents who were in their third year at the time of the study. A regression model was used to test the association between hospital resource use (as shown by total hospital charges to patients and their lengths of stay) and the residents' mean ratings of the degrees of autonomy the attending physicians permitted residents, for 7,169 of these physicians' patients discharged between 1986 and 1989 in 28 diagnosis-related groups. The analysis was controlled for patients' insurance status and chronic disease comorbidities. The patients whose attending physicians were rated as allowing substantial clinical autonomy had significantly lower total charges and lengths of stay (p less than .0001). These results suggest that internal medicine residents have an inherently conservative practice style that values low-intensity workups and rapid discharge of patients.

Aged↗
PubMed1989

Differential brain expression of the Alzheimer's amyloid precursor protein.

The expression of the Alzheimer amyloid protein precursor (AAPP) was examined in human, monkey, dog and rat brains. Two proteins, one identified as AAPP695 and the other as AAPP751, were immunoprecipitated from the in vitro translation of human, dog and rat brain polysomes. The AAPP751 to AAPP695 ratio was highest in human, intermediate in dog and lowest in rat brain polysomes. Human cerebral cortex contained higher levels of the AAPP751 mRNA than either dog or rat cortex. AAPP695 was detected in both cerebral cortex and cerebellum of all species examined. In contrast, AAPP751 was detected predominantly in the cortex of human, monkey and to a lesser extent dog brains while it was not detected in rat brain. These findings indicate that the amyloid precursors are differentially expressed in different mammalian brains and suggest that AAPP751 is mainly expressed in the brain regions involved in plaque formation.

Aged↗
PubMed1989

Cellular forms of the rat and human beta-amyloid precursor protein (BAPP).

Using synthetic peptide antisera generated against beta-amyloid precursor protein (BAPP) sequences we demonstrate that the newly synthesized BAPP appears as a 94 kDa peptide in rat brain RNA cell-free translates or polysome runoffs, while from similar human brain material we see two bands at 94 and 120 kDa. Immunoblots reveal likely post-translational modification of BAPP, and possibly an age-dependent, endogenous proteolysis of the protein in rat brain. On human brain immunoblots an unusual post-translational modification or possibly oligomerization of BAPP is seen, particularly in cortical regions.

Aging↗
PubMed1989

Translational control of gene expression in the human brain.

1. Translational control is the regulation of protein synthesis as an alteration in the efficiency of mRNA translation and is a common mechanism by which cells regulate gene expression. 2. Alternations of total protein synthesis are often the responses of cells to various stress stimuli including starvation, viral infection, and heat shock. 3. Numerous specific genes including ferritin heavy chain, tubulin, vimentin and the lck proto-oncogene have also been shown to be under translational control. 4. Unlike cultured cells or intact organisms, the investigation of translational control in the human brain requires the measurement of components of protein synthesis, especially polysomes. Therefore, we have purified and characterized polysomes from human postmortem brain tissues and compared them to polysomes purified from the adult rat brain. 5. The yield (as A260 units per gram brain tissue), size (as number of ribosomes per message), translational efficiency (as amount protein synthesized per A260 unit), and ability to reinitiate (as amount of protein synthesis prevented by initiation inhibitors) were all significantly lower as exhibited by the human polysomes compared with the rat polysomes. However, the human and rat polysomes synthesized similar polypeptides. 6. Thus, the human polysomes differed from the rat polysomes principally in the efficiency of mRNA translation which is likely due to the greatly reduced ability of the human polysomes to initiate protein synthesis.

Animals↗
PubMed1989

Trends in dental fluorosis and dental caries prevalences in Newburgh and Kingston, NY.

A study was undertaken in New York State to determine the changes in dental fluorosis prevalence from 1955 to 1986 in fluoridated Newburgh and non-fluoridated Kingston children. The frequency and severity of dental fluorosis among 884 7-14-year-old children were measured by two dentists utilizing Dean's Index. Data regarding residential and fluoride history were obtained from the parents of participants. Among the Newburgh residents, the prevalence of dental fluorosis (very mild to moderate) varied from a low of 5 per cent for the 9-10-year-old group to a high of 9.4 per cent for 11-12-year-olds. Except for the 13-14-year-old group, children in non-fluoridated Kingston had the lowest dental fluorosis prevalence rates. A comparison of Dean's Community Fluorosis Indices to the 1955 baseline data obtained from studies conducted after 10 years of fluoridation in Newburgh revealed no changes of consequence among Newburgh residents. However, the changes are apparent for Kingston residents, indicating the availability of fluorides in non-fluoridated areas. The increased risk for dental fluorosis for Kingston residents appears to be from the use of fluoride tablets. An analysis of dental caries data revealed that caries prevalence declined substantially in both fluoridated and non-fluoridated areas.

Adolescent↗
PubMed1988

A new A4 amyloid mRNA contains a domain homologous to serine proteinase inhibitors.

The amyloid proteins isolated from neuritic plaques and the cerebrovasculature of Alzheimer's disease are self-aggregating moieties termed A4 protein and beta-protein, respectively. A putative A4 amyloid precursor (herein termed A4(695] has been characterized by analysis of a human brain complementary DNA. We report here the sequence of a closely related amyloid cDNA, A4(751), distinguished from A4(695) by the presence of a 168 base-pair (bp) sequence which adds 57 amino acids to, and removes one residue from, the predicted A4(695) protein. The peptide predicted from this insert is very similar to the Kunitz family of serine proteinase inhibitors. The two A4-specific messenger RNAs are differentially expressed: in a limited survey, A4(751) mRNA appears to be ubiquitous, whereas A4(695) mRNA has a restricted pattern of expression which includes cells from neuronal tissue. These data may have significant implications for understanding amyloid deposition in Alzheimer's disease.

Alzheimer Disease↗
PubMed1986

Towards a molecular genetic approach to Alzheimer's disease.

The current observations of a familial form of Alzheimer's disease and the alterations in the neurochemistry of Alzheimer tissue including neurotransmitter deficits, paired helical filament and RNA degradation suggest that the modification of specific genes may be responsible for the disease. These genes may be identified with the use of complementary DNA probes synthesized from normal and Alzheimer mRNA. In characterizing the gene expression in demented tissue, we have found that RNA from Alzheimer frontal cortex and hippocampus was partially degraded compared to RNA isolated from control. However, the polyadenylated RNA exhibited no obvious degradation. Similarly, polysome content of the Alzheimer tissue was lower than in control tissues. In addition, the Alzheimer polysomes were much less efficient in protein synthesis.

Alzheimer Disease↗
PubMed1984

Relationship between preferred orientation and receptive field position of neurons in extrastriate cortex (area 19) in the cat.

Orientation sensitivity is a characteristic of most retinal ganglion cells (Levick and Thibos, '82), most relay cells in the dorsal lateral geniculate nucleus (Vidyasagar and Urbas, '82), and most neurons in the visual cortex (Hubel and Wiesel, '62) in the cat. In the retina there is a systematic relationship between receptive field position (polar angle) and preferred orientation. Outside of the area centralis most retinal ganglion cells respond best to stimuli oriented radially, i.e., oriented parallel to the line connecting their receptive fields to the area centralis (Levick and Thibos, '82). This relationship is strongest along the horizontal meridian (the visual streak) and appears to reflect the innate, radial orientation of retinal ganglion cell dendritic fields (Leventhal and Schall, '83). A relationship between preferred orientation and polar angle also exists in cat striate cortex; outside of the area centralis representation most cells respond best to lines oriented radially. This relationship is strongest for S-type cells, the most orientation-selective cells, and cells in regions representing the horizontal meridian (Leventhal, '83). To determine if similar relationships exist in cat extrastriate cortex, the preferred orientations and receptive field positions of 226 neurons in area 19 were studied. We find that, as in area 17, most area 19 cells outside of the representation of the area centralis respond best to lines oriented radially; this relationship is strongest for the cells having the narrowest receptive fields and in regions subserving the horizontal meridian. Unlike in striate cortex, in area 19 the relationship between preferred orientation and polar angle is not dependent upon cell type (S or C) or to the degree of orientation sensitivity exhibited. Also, in area 19, but not in area 17, the relationship between preferred orientation and polar angle fails for the cells having the widest receptive fields.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Rapid Accumulation of gamma-Aminobutyric Acid and Alanine in Soybean Leaves in Response to an Abrupt Transfer to Lower Temperature, Darkness, or Mechanical Manipulation.

Soybean (Glycine max [L.] Merr) leaves contain a low level (0.05 micromole per gram fresh weight) of gamma-aminobutyric acid (Gaba) but the concentration of this non-protein amino acid increased to 1 to 2 micromoles per gram fresh weight within 5 minutes after transfer of plants or detached leaves from 33 degrees C to 22 degrees C or lower temperatures. A parallel decrease occurred in the concentration of glutamate. Accumulation of Gaba was also triggered by mechanical damage to the soybean leaves, but in plants subjected to a gradual reduction in temperature (2 degrees C per minute) only a small increase in Gaba occurred. A rapid increase in the concentration of alanine and decrease in glycine occurred upon transfer of the soybean plants to darkness and was not influenced by temperature. When plants were returned to normal growing conditions, all changes in amino acid concentrations were fully reversed in 1 hour.In soybean leaf discs incubated with [(14)C]glutamate, a rapid accumulation of [(14)C]Gaba was detected, and glutamate decarboxylase activity of the soybean leaf considerably exceeded (>30-fold) that of Gaba pyruvate transaminase. Part of the transaminase was localized in the mitochondria, but glutamate decarboxylase was not associated with any organelle or membrane component of the leaf cell. We consider that Gaba accumulation results from some change in intracellular compartmentation of the cell triggered by low temperature shock or mechanical damage. The accumulation of alanine due to a light-dark transition could be accounted for by transamination. [(14)C]Alanine formation was demonstrated when soybean leaf extracts were incubated with glutamate, aspartate, or serine and [(14)C]pyruvate.The changes in amino acid concentrations described for soybean leaves were demonstrated for all the vegetative tissues of the soybean plant and at variable rates in the leaves of a range of plant species. The response in detached tomato (Lycopersicon esculentum Mill.) leaves was of a similar magnitude to soybean. Thus, precautions are necessary to minimize changes in amino acid composition induced by manipulation and extraction of plant material.

Journal Article↗
PubMed1983

Reversible Inactivation of Nitrate Reductase by NADH and the Occurrence of Partially Inactive Enzyme in the Wheat Leaf.

Nitrate reductase from wheat (Triticum aestivum L. cv Bindawarra) leaves is inactivated by pretreatment with NADH, in the absence of nitrate, a 50% loss of activity occurring in 30 minutes at 25 degrees C with 10 micromolar NADH. Nitrate (50 micromolar) prevented inactivation by 10 micromolar NADH while cyanide (1 micromolar) markedly enhanced the degree of inactivation.A rapid reactivation of NADH-inactivated nitrate reductase occurred after treatment with 0.3 millimolar ferricyanide or exposure to light (230 milliwatts per square centimeter) plus 20 micromolar flavin adenine dinucleotide. When excess NADH was removed, the enzyme was also reactivated by autoxidation. Nitrate did not influence the rate of reactivation.Leaf nitrate reductase, from plants grown for 12 days on 1 millimolar nitrate, isolated in the late photoperiod or dark period, was activated by ferricyanide or light treatment. This suggests that, at these times of the day, the nitrate reductase in the leaves of the low nitrate plants is in a partially inactive state (NADH-inactivated). The nitrate reductase from moisture-stressed plants showed a greater degree of activation after light treatment, and inactive enzyme in them was detected earlier in the photoperiod.

Journal Article↗