Teresa M. Landers

Induction of Alzheimer-like β-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.

Increased incidence of neurofibrillary tangles (NFT) in non-demented individuals with hypertension.

The incidence rates and numerical densities of argryophilic neurofibrillary tangles (NFT) and senile plaques (SP) were determined in non-demented individuals and subjects with Alzheimers disease (AD). The non-AD subjects were grouped according to cardiac status; those individuals with critical coronary artery disease (cCAD), those hypertensive individuals without cCAD (HyperT), and those without heart disease (non-HD). The incidence and densities of SP and NFT were significantly greater in AD than any of the non-demented groups. The prevalence of SP was increased in both HyperT and cCAD compared to non-HD controls, while NFT occurrence was accentuated in non-demented HyperT subjects only. The densities of SP and NFT in HyperT were elevated compared to cCAD or both cCAD and non-HD controls; NFT densities were similar in cCAD and non-HD. NFT density increased with increasing age in only the non-HD and cCAD groups, suggesting a possible relationship between disease process and NFT formation in the AD and HyperT populations.

Truncation releases olfactory receptors from the endoplasmic reticulum of heterologous cells.

Abstract: Olfactory receptors are difficult to express functionally in heterologous cells. We found that olfactory receptors traffic poorly to the plasma membrane even in cells with neuronal phenotypes, including cell lines derived from the olfactory epithelium. Other than mature olfactory receptor neurons, few cells appear able to traffic olfactory receptors to the plasma membrane. In human embryonic kidney 293 cells and Xenopus fibroblasts, olfactory receptor immunoreactivity overlapped with a marker for the endoplasmic reticulum (ER) but not with markers for the Golgi apparatus or endosomes. Except for the ER, olfactory receptors were therefore absent from organelles normally involved in the plasma membrane trafficking of receptors. Olfactory receptors truncated prior to transmembrane domain VI were expressed in the plasma membrane, however. Co‐expression of the missing C‐terminal fragment with these truncated receptors prvented their expression in the plasma membrane. Intramolecular interactions between N‐ and C‐terminal domains joined by the third cytoplasmic loop appear to be responsible for retention of olfactory receptors in the ER of heterologous cells. Our results are consistent with misfolding of the receptors but could also be explained by altered trafficking of the receptors.

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.

Molecular Cloning of a Lobster Gαq Protein Expressed in Neurons of Olfactory Organ and Brain

Abstract: We have isolated from an American lobster (Homarus americanus) olfactory organ cDNA library a clone, hGαq, with >80% identity to mammalian and arthropod Gαq sequences. In brain and olfactory organ, hGαq mRNA was expressed predominantly in neurons, including virtually all the neuronal cell body clusters of the brain. Gαq protein was also expressed broadly, appearing on western blots as a single band of 46 kDa in brain, eyestalk, pereiopod, dactyl, tail muscle, olfactory organ, and aesthetasc hairs. These results suggest that hGαq plays a role in a wide variety of signal transduction events. Its presence in the olfactory aesthetasc hairs, which are almost pure preparations of the outer dendrites of the olfactory receptor neurons, the expression of a single hGαq mRNA species (6 kb) in the olfactory organ, and the localization of hGαq mRNA predominantly in the olfactory receptor neurons of the olfactory organ strongly suggest that one function of hGαq is to mediate olfactory transduction.

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 Picks patients. This case strongly suggests that chemical dysfunction and neuropathological features of Picks disease occur in advance of overt clinical manifestations of the disorder

Molecular Cloning and Characterization of a Lobster Gαs Protein Expressed in Neurons of Olfactory Organ and Brain

Abstract: We have isolated from an American lobster (Homarus americanus) olfactory organ cDNA library a clone, lobGαs, with >70% identity to mammalian and arthropod Gαs sequences. In genomic Southern blots, a fragment of lobGαs detected only one band, suggesting the lobsters have a single Gαs gene. In brain and olfactory organ, lobGαs mRNA was expressed predominantly in neurons, including many of the neuronal cell body clusters of the brain. Gαs protein was also expressed broadly, appearing on western blots as a band of 51.8 kDa in brain, eyestalk, pereiopod, dactyl, tail muscle, olfactory organ, and aesthetasc hairs. These results suggest that lobGαs plays a role in a wide variety of signal transduction events. Its presence in the olfactory aesthetasc hairs, which are almost pure preparations of the outer dendrites of the olfactory receptor neurons, and the expression of lobGαs mRNA in the olfactory receptor neurons of the olfactory organ indicate that lobGαs may mediate olfactory transduction. That virtually all ORNs express lobGαs mRNA equally predicts that hyperpolarizing odor responses mediated by cyclic AMP are a property of all lobster olfactory receptor neurons.

MOLECULAR CLONING OF A LOBSTER GBETA SUBUNIT AND GBETA EXPRESSION IN OLFACTORY RECEPTOR NEURON DENDRITES AND BRAIN NEUROPIL

We have isolated from the olfactory organ of the American lobster (Homarus americanus) two cDNA clones with homology to beta subunits of G proteins. LobGbeta1 contained a complete open reading frame that predicted an amino acid sequence with >80% identity to Gbeta sequences from other species. LobGbeta2 was a fragment of an open reading frame whose predicted amino acid sequence had 65-69% identity to other Gbeta sequences. LobGbeta2 mRNA was not detectable in the brain, eye plus eyestalk, leg, dactyl, olfactory organ, or tail muscle. In contrast, lobGbeta1 was expressed in all these tissues as a single mRNA species of 6.4 kb and a protein of 37 kD. In the brain and olfactory organ, Gbeta immunoreactivity was almost exclusively confined to neurites: the neuropil regions of the brain and the outer dendrites of the olfactory receptor neurons. Coimmunoprecipitation revealed that lobster Gbeta interacted with both Galpha s and Galpha q. LobGbeta1 is likely to be involved in a wide range of signaling events including olfactory transduction and synaptic transmission in the brain.