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Biomedical subjects

T Landers

Publications and source records attributed to T Landers.

10 recordsLinked to original sources

Increased density of senile plaques (SP), but not neurofibrillary tangles (NFT), in non-demented individuals with the apolipoprotein E4 allele: comparison to confirmed Alzheimer's disease patients.

The apolipoprotein E genotype and cortical senile plaque (SP) and cortical and hippocampal neurofibrillary tangle (NFT) densities were determined in non-demented individuals and neuropathologically confirmed AD patients. The non-demented population was further subdivided according to presence or absence of pathologically established critical coronary artery disease (cCAD), hypertension (HyperT), or neither (non-heart disease; non-HD). The apolipoprotein E4 (APOE4) allele incidence and dose frequencies were increased in the AD, cCAD and HyperT groups compared to the non-HD controls. The mean number of SP and NFT was significantly increased with the presence of the APOE4 allele within the entire population. After grouping the non-demented subjects according to cardiac status, SP but not NFT density was increased among those individuals with the APOE4 genotype. In HyperT, the increased density of SP also correlated to the APOE4 allele dose frequency. The density of SP and NFT was increased in all regions of AD brain compared to all other non-demented groups, but no significant difference was found between AD patients with or without an APOE4 allele. These two AD groups were age-matched, but could not be matched for disease duration. The data suggest a relationship between heart disease, APOE4 genotype and the presence of SP regardless of cognitive status.

Aged↗

Medicaid managed care: a brief analysis.

Many states have begun to implement Medicaid managed care programs as a means of reducing costs and improving access for Medicaid recipients. This paper presents a review of the debate surrounding Medicaid managed care programs gathered from the literature, professional meetings, and correspondence.

Humans↗

Induction of Alzheimer-like beta-amyloid immunoreactivity in the brains of rabbits with dietary cholesterol.

beta-amyloid and ALZ-50 immunocytochemical reactivity were determined in the brains of rabbits fed either a control or 2% cholesterol diet. Control rabbits demonstrated no accumulation of intracellular immunolabeled beta-amyloid within 3 min after death. In animals fed the experimental diet for 4, 6, and 8 weeks (postmortem interval < 3 min), there was an increasingly mild-to-moderate-to-severe accumulation of intracellular immunolabeled beta-amyloid. Whether or not beta-amyloid is causally linked to processes leading to dementia, it is related in some way to the prime cause of human death; heart disease. Hypercholesterolemic rabbits may provide an animal model to study altered beta-APP metabolism leading to Alzheimer-like beta-amyloid accumulation xe03and extracellular deposition in brain.

Amyloid beta-Peptides↗

Neurochemical and histopathologic alterations characteristic of Pick's disease in a non-demented individual.

In the course of investigating a large number of non-demented subjects, a 68 year old female dying of coronary artery disease was found to have Pick bodies in her grossly normal brain. Although only mild subcortical gliosis and no neuron loss were observed. Pick bodies were found throughout the brain and occasional balloon cells were noted. Pick bodies and numerous neurons were also ALZ-50 and Tau-1 immunoreactive. Retrospective studies indicated a lack of overt intellectual decline or depression in this individual. Frontal, temporal and occipital poles, amygdala, hypothalamus and nucleus basalis of Meynert (nbM) were analyzed for ChAT, AChE and MAO-A and -B enzymatic activities and for the binding of 5HT and imipramine. Cholinergic decreases were found only in subcortical structures. Serotonin binding decreases were widespread, excluding the nbM. Altered MAO-B activity was regionally variable, and no differences in MAO-A activity or imipramine binding were observed. Few differences in neurochemical alterations were observed in the current non-demented subject with abundant Pick bodies compared to previous studies of demented Pick's patients. This case strongly suggests that chemical dysfunction and neuropathological features of Pick's disease occur in advance of overt clinical manifestations of the disorder.

Acetylcholinesterase↗

Prefrontal cortex lesions differentially disrupt cocaine-reinforced conditioned place preference but not conditioned taste aversion.

The reinforcing efficacy of cocaine is thought to involve, at least in part, mesocortical dopaminergic (DA) neurons. Rats will self-administer cocaine applied directly into the medial prefrontal cortex but not into nucleus accumbens or the ventral tegmental area (Goeders & Smith, 1983). The present experiments were conducted to assess whether lesions of prefrontal cortex (mesocortical DA target regions) attenuate the reinforcing properties of systemically administered cocaine. Male Sprague-Dawley rats were anesthetized, and one of three subfields (medial, orbital, or precentral) of the prefrontal cortex was removed by aspiration or no brain injury was done (sham operates). In four experiments the rats were tested on conditioned place preference (CPP), conditioned taste aversion (saccharin conditioned stimulus, cocaine unconditioned stimulus), general activity in the running wheel and open field, and food-reinforced spatial alternation in the T-maze. Sham operates demonstrated a cocaine-induced place preference, rats with medial frontal lesions showed a cocaine-induced place aversion, and other operates showed neither a conditioned place preference nor an aversion. The results of this experiment suggest that lesions of the DA projection fields of the prefrontal cortex in the rat reduce the positive reinforcing properties of systemically injected cocaine. In the second experiment, all subjects showed a conditioned taste aversion of equal magnitude. This suggests that whereas the positive reinforcing properties were affected differentially by prefrontal cortex lesions, the aversive properties were not affected. In Experiment 3 there were no lesion-induced differences in activity in either the running wheel or the open field. Therefore, changes in motor activity cannot account for the CPP data. In the final experiment, the medial frontal operates were impaired relative to the precentral and sham operates on learning to alternate choices in the T-maze, but the orbital frontal operates' performance was not different from that of any other group. This suggests that a general disruption of all reinforcement mechanisms did not occur following these lesions. Instead, these results indicate that mesocortical DA projection regions are involved with mediating the reinforcing properties of cocaine and that there is a separate system mediating the aversive properties of cocaine.

Animals↗

Characterization of components released by alkali disruption of simian virus 40.

Treatment of simian virus 40 (SV40) particles at pH 9.8 in the presence of 1 mM dithiothreitol for 5 min at 37 degrees C disrupted the virions into a 60S DNA-protein complex and DNA-free 7S protein particles. The DNA-protein complex contained approximately equal amounts of DNA and protein, and appeared by electron microscopy to be relaxed circular structures with an average of 21 beads joined by short, thin bridges. The major protein components in the complex were host cell histones, but SV40-specific proteins VP3 and VP2 were also present. The 7S protein particles were almost exclusively VP1 and, in negatively stained samples, resembled the capsomer structures of intact virions.

DNA, Circular↗

Physical and genetic characterization of deletion mutants of simian virus 40 constructed in vitro.

Mutants of simian virus 40 (SV40), with deletions ranging in size from fewer than 3 to 750 base pairs located throughout the SV40 genome, were obtained by infecting CV-1P cells with linear SV40 DNA and DNA of an appropriate helper virus. The linear DNA was obtained by complete cleavage of closed circular DNA with Hae II or Bam HI endonuclease or partial cleavage with either Hae III endonuclease or nuclease S1, followed, in some cases, by mild digestion with phage lambda 5' -exonuclease. The following mutants with deletions in the late region of the SV40 genome were obtained and characterized. Ten, containing deletions at the Hae II endonuclease site (map location 0.83), define a new genetic complementation group, E, grow extremely slowly without helper virus, and cause alterations only in VP2. Two mutants with deletions in the region 0.92 to 0.945 affect both VP2 and VP3, demonstrating that VP3 shares sequences with the C-terminal portion of VP2. The mutant with a deletion at 0.93 is the first deletion mutant in the D complementation group and is also temperature sensitive; the mutant with a deletion at 0.94 is viable and grows normally. Three mutants with deletions at the EcoRI endonuclease site (0/1.0) and eleven with deletions at the BamHI endonuclease site (0.15) fall into the B/C complementation group. Six additional mutants with deletions at the BamHI endonuclease site are viable, growing more slowly than wild type. VP1 is the only polypeptide affected by mutants in the B/C group. A mutant with a deletion of the region 0.72 to 0.80 has a polar effect, failing to express the E, D, and B/C genes. Mutants with deletions in the early region (0.67 counterclockwise to 0.17) at 0.66 to 0.59, 0.48, 0.47, 0.33, and 0.285 to 0.205 are all members of the A complementation group. Thus, the A gene is the only viral gene in the early region whose expression is necessary for productive infection of permissive cells. Since mutants with deletions in the region 0.59 to 0.54 are viable, two separate regions are essential for expression of the gene A function: 0.66 to 0.59 and 0.54 to 0.21. Mutants with deletions at 0.21 and 0.18 are viable. Approximate map locations of SV40 genes and possible models for their regulation are discussed.

Cell Line↗