Amyloid beta protein in rat soleus muscle in chloroquine-induced myopathy using end-specific antibodies for A beta 40 and A beta 42: immunohistochemical evidence for amyloid beta protein

Previous immunohistochemical studies from this laboratory demonstrated that monoclonal antibodies raised against various regions of amyloid precursor protein (APP) (i.e., N-terminus, amyloid beta protein (A beta), and C-terminus) strongly labeled vacuoles in chloroquine-induced myopathy-affected muscle in rats. In this study, we used antibodies end specific for the A beta 40 and A beta 42 species, and a monoclonal antibody to A beta 1-9 which reacts with APP and A beta. Most vacuoles clearly reacted with anti-A beta 1-9, while about half reacted with anti-A beta 42, and only a few reacted with anti-A beta 40. These results demonstrate that vacuoles in chloroquine-induced myopathy-affected muscle contain cleaved A beta, and that distribution of the two major A beta species is similar to what is observed in A beta deposition in Alzheimer's disease (AD)-affected brain. This provides further evidence that chloroquine-induced myopathy in rats provides a suitable model to understand APP processing into A beta, and the role of APP in terms of the pathogenesis of AD.

Co-localization of amyloid-associated proteins with amyloid beta in rat soleus muscle in chloroquine-induced myopathy: a possible model for amyloid beta formation in Alzheimer's disease

Chloroquine, a potent lysosomotropic agent, induces myopathy in experimental animals similar to rimmed vacuole (RV) myopathy in humans. The abnormal accumulation of amyloid beta protein (A beta), which is the invariable pathological alterations in the brains affected by Alzheimer's disease (AD), has been demonstrated in denervated soleus muscle fibers in chloroquine-induced myopathy in rats. In AD affected brains, a variety of additional proteins are associated with the extracellular deposition of A beta, which leads to the intracellular accumulation of neurofibrillary tangles and finally to neuronal death. In this study, we demonstrate that amyloid-associated proteins, alpha 1-antichymotrypsin, apolipoprotein E, SP-40,40 and ubiquitin co-localize with A beta in vacuolated muscle fibers in chloroquine-induced myopathy. There are striking similarities in immunopathology between experimental RV myopathy and AD. Chloroquine-induced myopathy in rats provides a suitable model not only to obtain insight into the basic mechanisms underlying RV formation in muscle, but also to understand amyloid precursor protein processing into A beta, and the role of amyloid-associated proteins in terms of the pathogenesis of AD.

Divergence time and population size in the lineage leading to modern humans

We have developed maximum likelihood (ML) methods for comparisons of nucleotide sequences from unlinked genomic regions. In the case of a single species, the ML method primarily estimates the effective population size (Ne) under both constant size and abrupt expansion conditions. In the case of two or three species, the ML method simultaneously estimates the species divergence time and the effective size of ancestral populations. This allows us to trace the evolutionary history of the human population over the past several million years (my). Available sequences at human autosomal loci indicate Ne = 10,000 in the Late Pleistocene, a figure concordant with the results obtained from mitochondrial DNA sequence and allele-frequency data analysis, and there is no indication of population expansion. The ML analysis of two species shows that humans diverged from chimpanzees 4.6 my ago and that the human and chimpanzee clade diverged from the gorilla 7.2 my ago. Furthermore, the effective population size of humans more than 4.6 my ago is nearly 10 times larger than Ne of modern humans. The effective population size in the human lineage does not seem to have remained constant over the past several million years. The ML model for three species predicts slightly different, but consistent results to those obtained by the two-species analysis.

[Changes in GABAA/benzodiazepine receptor complex function in the pentobarbital-dependent rat. II: Strain differences between Lewis and Wistar-Kyoto rats]

We studied the differences in alterations of GABAAergic receptor function between pentobarbital (PB)-dependent female Lewis (LEW) and Wistar-Kyoto (WKY) rats. The 36Cl- influx induced by 10 microM GABA in the PB-dependent WKY was significantly lower than that in the control, while there was no significant 36Cl- influx change in both PB-dependent and control LEW. The additions of PB, flunitrazepam (FZ) and ethanol (EtOH) enhanced the GABA-dependent 36Cl- influx in control rats of both strains. However, the enhancements of 36Cl- influx by PB, FZ, EtOH were not recognized in PB-dependent WKY. On the other hand, the enhancement of GABA-dependent 36Cl- influx was observed only with the addition of PB in PB-dependent LEW. The additions of bicuculline (BIC) and picrotoxin (PIC) inhibited GABA-dependent 36Cl- influx in control rats of both strains. However, inhibition of 36Cl- influx by BIC and PIC was not recognized in the PB-dependent WKY. These results suggest that physical dependence on PB in WKY may cause greater functional alterations of the GABA/benzodiazepine receptor complex than those in LEW, and that these changes in this receptor complex may relate to the difference in the development of physical dependence on PB between the two strains.

Ground-Water Radon Anomaly Before the Kobe Earthquake in Japan

Radon concentration in ground water increased for several months before the 1995 southern Hyogo Prefecture (Kobe) earthquake on 17 January 1995. From late October 1994, the beginning of the observation, to the end of December 1994, radon concentration increased about fourfold. On 8 January, 9 days before the earthquake, the radon concentration reached a peak of more than 10 times that at the beginning of the observation, before starting to decrease. These radon changes are likely to be precursory phenomena of the disastrous earthquake.

[Changes in GABAA/benzodiazepine receptor complex function in the pentobarbital-dependent rat]

Changes in GABAA receptor function were studied in pentobarbital (PB)-dependent rats. Physical dependence on PB in male Lewis rats was induced by the drug-admixed food method. The 36Cl- influx into cerebral cortical synaptoneurosomes induced by 10 microM GABA in the PB-dependent rat was significantly decreased compared with the control. The enhancement of GABA-dependent 36Cl- influx by the addition of PB, ethanol (EtOH) and flunitrazepam (FZ) was not recognized in the PB-dependent group. The addition of picrotoxin and bicuculline had no effect on GABA-dependent 36Cl- influx in PB-dependent rats. In the [3H]muscimol binding assay of low affinity sites of the GABAA receptor, Kd was significantly increased and Bmax was significantly decreased in PB-dependent rats compared with the control. However, these values were similar between PB-dependent and control rats in the study of [3H]FZ binding to benzodiazepine (BZ) receptors. The present study indicates that GABAergic transmission involving GABA-dependent chloride channels was altered in PB dependent rats. This alteration of the GABAA/BZ/chloride channel complex function may be related to the cross-tolerance among barbiturates, BZ and EtOH.

Recent African origin of modern humans revealed by complete sequences of hominoid mitochondrial DNAs

We analyzed the complete mitochondrial DNA (mtDNA) sequences of three humans (African, European, and Japanese), three African apes (common and pygmy chimpanzees, and gorilla), and one orangutan in an attempt to estimate most accurately the substitution rates and divergence times of hominoid mtDNAs. Nonsynonymous substitutions and substitutions in RNA genes have accumulated with an approximately clock-like regularity. From these substitutions and under the assumption that the orangutan and African apes diverged 13 million years ago, we obtained a divergence time for humans and chimpanzees of 4.9 million years. This divergence time permitted calibration of the synonymous substitution rate (3.89 x 10(-8)/site per year). To obtain the substitution rate in the displacement (D)-loop region, we compared the three human mtDNAs and measured the relative abundance of substitutions in the D-loop region and at synonymous sites. The estimated substitution rate in the D-loop region was 7.00 x 10(-8)/site per year. Using both synonymous and D-loop substitutions, we inferred the age of the last common ancestor of the human mtDNAs as 143,000 +/- 18,000 years. The shallow ancestry of human mtDNAs, together with the observation that the African sequence is the most diverged among humans, strongly supports the recent African origin of modern humans, Homo sapiens sapiens.

Immunohistochemical evidence for amyloid beta in rat soleus muscle in chloroquine-induced myopathy

Deposition of amyloid beta (A beta) is one of the pathological hallmarks of brains affected with Alzheimer's disease (AD). The accumulation of A beta have been observed in human myopathies with rimmed vacuoles (RVs) which might involve lysosomal function. Chloroquine, a potent lysosomotropic agent, induces muscle pathology in experimental animals similar to myopathy with RV. In this study, we demonstrate, for the first time, immunohistochemical evidence that A beta and cathepsin D, a lysosomal enzyme, accumulate in vacuolated rat soleus muscle due to chloroquine-induced myopathy. These data indicate that lysosomes are important in the metabolism of amyloid precursor protein to generate A beta. This experimental system seems to be useful not only to study basic mechanisms underlying RV myopathy but also to understand processing of amyloid precursor protein to A beta in AD.

Potentially amyloidogenic fragment of 50 kDa and intracellular processing of amyloid precursor protein in cells cultured under leupeptin

The principal neuropathological feature of Alzheimer's disease is extracellular deposition of approximately 4-kDa proteinous fragment, designated as beta-amyloid peptides (beta/A4 peptides) derived by proteolytic cleavage from amyloid precursor protein (APP), a large cell-surface receptor-like protein. There has been evidence that APP is proteolytically degraded in the secretory and endosomal/lysosomal pathways. The pathway in which APP is cleaved to generate beta/A4 peptides is still not identified. To clarify the intracellular processing of APP into the generation of beta/A4 peptides, we detected and characterized potentially amyloidogenic or non-amyloidogenic fragments using newly established monoclonal and polyclonal antibodies in the cultured cells with or without leupeptin, potent lysosomal protease inhibitor of lysosome. APP fragments of 50 and 20 kDa containing full-length beta/A4 peptides were identified in the cultured cells. Immunoblot analysis, biochemical study for specific marker enzyme activity of the fractions obtained from subcellular fractionation, sucrose density gradient centrifugation indicated that the 50-kDa APP fragment was produced in the compartment closely related to endosomal/lysosomal system. Our data suggest that the endosomal/lysosomal pathway is involved in the processing and generation of beta/A4 peptides.

Intensity of natural selection at the major histocompatibility complex loci

Long persistence of allelic lineages, prevalence of nonsynonymous over synonymous substitutions in the peptide-binding region (PBR), and deviation from neutrality of the expected gene identity parameter F all indicate indirectly that balancing selection is operating at functional major histocompatibility complex (MHC) loci. Direct demonstrations of the existence of balancing selection at MHC loci are, however, either lacking or not fully convincing. To define the conditions under which balancing selection could be demonstrated, we estimated its intensity from the mean number of nonsynonymous substitutions, KB, at the PBR and the mutation rate mu. We compared the five available methods for estimating KB by computer simulation and chose the most reliable ones for estimation of selection intensity. For the human MHC, the selection coefficients of the HLA-A, -B, -C, -DRB1, -DQB1, -DQA1, and -DPB1 loci are 0.015, 0.042, 0.0026, 0.019, 0.0085, 0.0028, and 0.0007, respectively. This low selection intensity places severe restrictions on the possibility of measuring selection directly in vertebrate populations.

Structure, function, and evolution of mouse TL genes, nonclassical class I genes of the major histocompatibility complex

In contrast to well-studied "classical" class I genes of the major histocompatibility complex (MHC), the biology of nonclassical class I genes remains largely unexamined. The mouse TL genes constitute one of the best defined systems among nonclassical class I genes in the T region of the MHC. To elucidate the function and the evolution of TL genes and their relationship to classical class I genes, seven TL DNA sequences, including one from a Japanese wild mouse, were examined and compared with those of several mouse and human classical class I genes. The TL genes differ from either classical class I genes or pseudogenes in the extent and pattern of nucleotide substitutions. Natural selection appears to have operated so as to preserve the function of TL, which might have been acquired in an early stage of its evolution. In a putative peptide-binding region encoded by TL genes, the rate of nonsynonymous (amino acid replacing) substitution is considerably lower than that of synonymous substitution. This conservation is completely opposite that in classical class I genes, in which the peptide-binding region has evolved to diversify amino acid sequences so as to recognize a variety of antigens. Thus, it is suggested that the function of TL antigens is distinct from that of classical class I antigens and is related to the recognition of a relatively restricted repertoire of antigens and their presentation to T-cell receptors.

[A case of Wernicke's encephalopathy which accompanied a passing blindness]

The case of a chronic alcoholic patient with Wernicke's encephalopathy accompanied by passing blindness is reported and the alcoholic amblyopia is discussed in this study. The patient was a 39 year-old male who had been a heavy drinker for 13 years, and was habitually inebriated for the last one year. Disturbance of consciousness ataxia of gait, nystagmus and blindness were manifested on admission. Decreased level of serum vitamin B1 was also recognized at admission. The symptoms diminished from about a month after admission except for horizontal nystagmus. Since the patient had racket-like scotoma in his central visual field, his blindness was thought to be alcoholic amblyopia. Although alcohol dependence is associated with many physical disabilities, there are few reports about Wernicke's encephalopathy with alcoholic amblyopia. This case demonstrates the importance of careful physical examination for understanding alcohol-related disabilities and alcohol dependence.

Reduced sensitivity to ethanol of Gs alpha and Gi/o alpha in the cerebral cortex of alcoholic patients

In this study, we examined the quantity and quality of G proteins in membrane preparations from cortical regions (frontal, parietal, temporal and occipital cortex) in post-mortem brains obtained from subjects with chronic alcoholism and controls matched with respect to age and post-mortem delay (PMDT). Immunoblot analysis showed that the level of GsH alpha (52 kDa) was significantly decreased in temporal cortical membranes from alcoholics compared with controls, while no differences were observed in the amount of any G protein in frontal, parietal and occipital regions. Additionally, ethanol enhanced photoaffinity guanine nucleotide binding to both G alpha and Gi/o alpha in human cortical membranes. The percentage of increase in ethanol-stimulated photoaffinity GTP labeling of Gs alpha and Gi/o alpha was decreased in alcoholic patients in all cortical regions. These observations indicated that subsensitivities to ethanol-induced stimulation in G protein may contribute to impaired trans-signaling in cortical membranes of chronic alcoholics.