Transepidermal Water Loss and T-helper 2 (Th2)-Associated Inflammatory Markers in Two Pediatric Patients During the First Four Weeks of Treatment With the Oral Janus Kinase Inhibitor Upadacitinib

Few studies have evaluated the effects of upadacitinib on skin barrier function and T-helper 2 (Th2)-associated inflammatory biomarkers in severe atopic dermatitis (AD). In this study, we followed two pediatric patients with AD who had previously failed to respond to conventional treatment and measured their serum Th2-associated chemokine thymus and activation-regulated chemokine (TARC) and serine protease inhibitor squamous cell carcinoma antigen (SCCA) 2 levels and transepidermal water loss (TEWL) during the first four weeks of upadacitinib treatment. Both patients showed marked clinical improvement and decreased TEWL, blood eosinophil counts, and serum TARC and SCCA2 levels after four weeks of upadacitinib treatment. These findings suggest that upadacitinib attenuates Th2-associated inflammatory markers and promotes skin barrier integrity.

Predicting the Outcome of the Buckwheat Oral Challenge Test: A First Evaluation Assuming a Single Serving of Boiled Buckwheat Noodles

Summary

Background. Global increase in buckwheat consumption has led to a surge in buckwheat allergy reports. However, studies scrutinizing the predictive accuracy of buckwheat-specific immunoglobulin E (IgE) antibody levels in correlation with symptom manifestation remain limited. A critical concern is the discrepancy between the total buckwheat amount featured in prior studies and the quantity consumed per occasion. We aimed to determine open Oral Food Challenge (OFC) positivity rates with buckwheat, using a single serving of boiled buckwheat noodles, and assess the predictability of positive responses using buckwheat-specific IgE levels. Methods. Patients aged 20 years or younger, suspected of buckwheat allergy, were subjected to an OFC involving consumption of 100 g (4800 mg of protein) of boiled buckwheat noodles for those under six years, and 200 g (9600 mg of protein) for those six years or older. The predictive accuracy of the OFC, corresponding with buckwheat-specific IgE antibody levels, was evaluated using Receiver Operating Characteristic (ROC) analysis. Results. Our study involved 80 patients who undertook a buckwheat OFC. Among these, 14 (17.5%) tested positive for a buckwheat allergy, with 3 (3.8%) developing anaphylaxis. The comparative analysis of buckwheat-specific IgE antibody levels did not offer a reliable predictive measure for OFC outcomes. However, a past history of symptom manifestation following buckwheat consumption was significantly correlated with a positive OFC. Conclusions. Forecasting OFC outcomes based on buckwheat-specific IgE antibody levels poses a challenge, even when taking into account the total quantity of buckwheat that can be consumed in a single occasion.

Low-Dose Oral Challenge Test in Pediatric Patients With Peanut Allergy: Tolerance Assessment of a Trace 5 mg Peanut Test After Symptom Induction With a 500 mg Test

Introduction Peanut allergy (PA) represents a significant public health concern, particularly prevalent in Western countries. Children at high risk for PA may undergo a low-dose oral food challenge (OFC). However, if the result is positive, complete elimination of peanuts from the diet is recommended, and further trace OFC is typically not performed.  Material and methods This cross-sectional study retrospectively examined the rate of positive peanut OFC with a total peanut load of 5 mg in children who tested positive with a total peanut load of 500 mg. Patient information was gathered from medical records. The primary endpoint was the rate at which children who tested positive in the OFC with 500 mg of peanut butter also tested positive with 5 mg of peanut butter equivalent.  Results Among 32 children who underwent an OFC with a total peanut load of 500 mg, two were excluded for not meeting the criteria. Among the remaining 30 children, 14 (46.7%) had a positive 500 mg peanut OFC test, and three (10%) experienced an anaphylactic reaction. Those who tested positive for the OFC had higher peanut-specific and Ara h2-specific immunoglobulin E (IgE) antibodies. An OFC with 5 mg of peanuts performed on 10 of the 14 patients who tested positive for 500 mg of peanuts showed no positive results. Conclusion The results of this study suggest that children with severe PA who exhibit positive symptoms to a total peanut load of 500 mg can tolerate a 5 mg dose of peanuts and should be considered for an OFC.

Pranlukast treatment and the use of respiratory support in infants with respiratory syncytial virus infection

Background

In infants, respiratory syncytial virus (RSV) infection occasionally causes severe symptoms requiring respiratory support; however, supportive care is the primary treatment. This study compared the use of respiratory support among infants with RSV infection treated with or without pranlukast.

Methods

This retrospective cohort study included infants aged <10 months with RSV infection who were admitted to three secondary level hospitals in Japan between 2012 and 2019. The infants were divided into two groups depending on whether they were treated with pranlukast. The primary outcome was the receiving respiratory support (high-flow nasal cannula, nasal continuous positive airway pressure, or ventilator). The secondary outcomes were the length of hospital stay, and the Global Respiratory Severity Score (GRSS) on starting respiratory support or at the time of the worst signs during hospitalization. We performed a propensity score-matched analysis.

Results

A total of 492 infants, including 147 propensity score-matched pairs, were included in the analysis. The use of respiratory support was significantly lower in infants treated with pranlukast (3.4% [5/147]) than those treated without pranlukast (11.6% [17/147]; P = 0.01). In the propensity score-matched analysis, pranlukast use was associated with a significantly lower chance of needing respiratory support (odds ratio: 0.27, 95% confidence interval: 0.08–0.79; P = 0.01); however, the length of hospital stay (median: 4 days) and the GRSS (median: 2.804 and 2.869 for infants treated with and without pranlukast, respectively) did not differ significantly between propensity score-matched pairs.

Conclusions

Pranlukast use was associated with a reduced likelihood of requiring respiratory support in infants aged <10 months with RSV infection.

Susceptibility to serious skin and subcutaneous tissue disorders and skin tissue distribution of sodium-dependent glucose co-transporter type 2 (SGLT2) inhibitors

Objectives: In Japan, sodium-glucose co-transporter type 2 (SGLT2) inhibitors have been reported to be associated with serious skin and subcutaneous tissue disorders. A post-marketing surveillance (PMS) study suggested that the association was specific for ipragliflozin and, to a lesser extent for dapagliflozin. These studies were performed to confirm the association of 6 SGLT2 inhibitors with serious skin disorders in a clinical setting, to elucidate the role of melanin in serious skin disorders and to understand the underlying mechanisms. Methods: The latest PMS records were retrieved from the Japanese Adverse Drug Event Report (JADER) database, and the associations were analyzed by data mining techniques. In silico 3-D docking simulation of SGLT2 inhibitors with melanin was performed using the MOE software. The skin tissue distribution of SGLT2 inhibitors was evaluated using albino rats after oral administration at clinical doses. Results: The adjusted reporting odds ratio (95% confidential limit) was 1.667 (1.415, 1.963) for ipragliflozin, 0.514 (0.317, 0.835) for dapagliflozin, 0.149 (0.048, 0.465) for tofogliflozin, 0.624 (0.331, 1.177) for luseogliflozin, 0.590 (0.277, 1.257) for canagliflozin and 0.293 (0.073, 1.187) for empagliflozin, when drugs other than the SGLT2 inhibitors were referred, and the association was detected only for ipragliflozin in clinical use. In silico 3-D docking simulation suggested the influence of melanin in ipragliflozin-specific serious skin disorders. The skin tissue-to-plasma concentration ratio of ipragliflozin was 0.45 ± 0.20 (±SD) at 1 hr after administration and increased in a time-dependent manner to 5.82 ± 3.66 at 24 hr (p<0.05), but not in case of other SGLT2 inhibitors. Conclusions: Serious skin disorders were suggested to be specific for ipragliflozin. Interaction with melanin might be implicated in ipragliflozin-specific serious skin disorders. Ipragliflozin was retained in the skin tissue, which suggested its interaction with the skin tissue in serious skin disorders.

Molecular cloning and sequence analysis of the cyanobacterial gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase

Ribulose-1,5-bisphosphate carboxylase/oxygenase consists of large subunits (LS) and small subunits. In plants, the LS is encoded in chloroplast DNA and the small subunit, in nuclear DNA. In cyanobacteria, both subunits are thought to be encoded in chromosomal DNA because of prokaryotes. The gene for the LS of ribulose-1,5-bisphosphate carboxylase/oxygenase from a cyanobacterium, Anacystis nidulans 6301, has been cloned in pBR322 and subjected to sequence analysis. The coding region contains 1,416 base pairs (472 codons). The deduced amino acid sequence of A. nidulans LS protein shows 80% homology with sequences of maize, spinach, and tobacco LS proteins; the nucleotide sequence of A. nidulans LS gene shows 70% homology with sequences of the plant genes. Between A. nidulans LS and the plant LS proteins there is exact sequence homology around the lysine residue to which the activator CO(2) binds and around the two lysine residues to which ribulose 1,5-bisphosphate binds. The amino acid sequence where the LS binds to the small subunit is also highly conserved. From comparison of the LS proteins of A. nidulans and the three plants, the rate of amino acid substitution is estimated to be 0.25-0.5 x 10(-9) per year per site, which is far below the median value of various types of proteins (1.2 x 10(-9) for hemoglobin alpha). The LS protein is thus a conserved protein.

Genetic variability maintained in a finite population under mutation and autocorrelated random fluctuation of selection intensity

By using the diffusion equation method, the level of genetic variability maintained under mutation pressure in a finite population is investigated, assuming autocorrelated random fluctuation of selection intensity. An appropriate mathematical model was formulated to treat the change of gene frequencies, incorporating mutation pressure and fluctuating selection. Extensive Monte Carlo simulation experiments were also performed to supplement the theoretical treatments. Excellent agreement between the two results suggests the validity of the present diffusion model for the autocorrelated selection. One of the most important findings from the simulation studies is that mutations and random sampling drift largely determine the level of genetic variability, and that the presence of autocorrelated selection can significantly lower genetic variability only when its strength, as measured by the cumulative variance of selection intensity, is larger than about 10(3) times the mutation rate. It is pointed out that the effects of both mutations and random sampling drift have to be incorporated in order to assess the role of various factors for the maintenance of genetic variability in natural populations.

Gene Flow in Natural Populations of DROSOPHILA MELANOGASTER with Special Reference to Lethal Allelism Rates and Protein Variation

A simultaneous survey of 14 protein loci, together with frequencies and within- and between-population allelism rates of lethal chromosomes, was carried out in five (four Japanese and one Korean) natural populations and one cage population of Drosophila melanogaster. It was found that lethal allelism rates decrease rapidly as geographic distance between two populations increases, while variation at protein loci shows a remarkable similarity over all populations examined. These findings suggest that there are very high levels of gene flow in these natural populations and that selection at protein loci which can maintain substantial geographic variation, if present, is overshadowed by gene flow. There is no indication that invasion of D. melanogaster to the Far East occurred so recently that the frequencies of lethal chromosomes are still in nonequilibrium.

Analysis of mtDNA sequences shows Japanese native chickens have multiple origins

In this study, we analysed the mitochondrial DNA D-loop region of Japanese native chickens to clarify their phylogenetic relationships, possible maternal origin and routes of introduction into Japan. Seven haplogroups (Types A-G) were identified. Types A-C were observed in Jidori, Shokoku and related breeds. However, Type C was absent in Shokoku, which was introduced from China, while most Indonesian native chickens were included in the Type C haplogroup. Types D-G were observed in Shamo and related breeds. Type E had a close genetic relationship with Chinese native chickens. Our results indicate that some breeds were not introduced into Japan as suggested in conventional literature, based on low nucleotide diversity of certain chicken breeds. Sequences originating from China and Korea could be clearly distinguished from those originating from Southeast Asia. In each group, domestic chickens were divided into the Jidori-Shokoku and Shamo groups. These results indicate that Chinese and Korean chickens were derived from Southeast Asia. Following the domestication of red junglefowl, a non-game type chicken was developed, and it spread to China. A game type chicken was developed in each area. Both non-game and game chickens formed the foundation of Japanese native chickens.

Comparative analysis of human masculinity

To study rapidly evolving male specific Y (MSY) genes we retrieved and analyzed nine such genes. VCY, HSFY and RBMY were found to have functional X gametologs, but the rest did not. Using chimpanzee orthologs for XKRY, CDY, HSFY, PRY, and TSPY, the average silent substitution is estimated as 0.017 +/- 0.006/site and the substitution rate is 1.42 x 10(-9)/site/year. Except for VCY, all other loci possess two or more pseudogenes on the Y chromosome. Sequence differences from functional genes show that BPY2, DAZ, XKRY, and RBMY each have one pseudogene for each one that is human specific, while others were generated well before the human-chimpanzee split, by means of duplication, retro-transposition or translocation. Some functional MSY gene duplication of VCY, CDY and HSFY, as well as X-linked VCX and HSFX duplication, occurred in the lineage leading to humans; these duplicates have accumulated nucleotide substitutions that permit their identification.

The distribution of the ancestral haplotype in finite stepping-stone models with population expansion

Recent extensive analyses of human DNA polymorphism reveal that the ancestral haplotype at various genetic loci occurs almost exclusively in African samples. We develop a coalescence-based simulation method in stepping-stone models with population expansion and examine the probability (P(A)) that the ancestral haplotype is found in African samples and the probability (Q(A)) that the most recent common ancestor of sampled genes occurs in Africa. These probabilities and other summary statistics are used to infer the human demographic history. It is shown that the high observed P(A) value cannot be explained simply by sampling bias. Rather, it suggests that the African population has been more strongly subdivided and isolated from each other than the non-African population and that there must have been some African populations which were not directly involved in the Out-of-Africa expansion in the late Pleistocene.

Impairment of G(salpha) function in human brain cortex of Alzheimer's disease: comparison with normal aging

We examined the quantity and quality of G proteins in membrane preparations of post-mortem human brain, i.e. in parietal, temporal and occipital cortical regions, from normal subjects over age (17-89 years old) and with Alzheimer's disease (AD) in comparison with aged-matched controls. In normal aging, the immunoreactivities determined of G(ialpha), G(qalpha) and G(beta) were inversely correlated with age. The function of G proteins was examined by photoaffinity GTP analogue [azidoanilido GTP (AAGTP)] labelling. AAGTP labelling to G(salpha) and G(i/oalpha), and the ratio of G(salpha) to G(i/oalpha) AAGTP labelling showed no age-dependent changes. In AD compared to age-matched controls, there were no significant differences in the levels of G(sHalpha), G(sLalpha), G(ialpha), G(oalpha), G(qalpha) and G(beta) subunits. Functional effects of G proteins, however, as measured by AAGTP labelling to G(salpha), but not to G(i/oalpha), was significantly decreased in AD compared to controls in the parietal and temporal cortex, but not in the occipital cortex. These results suggest that the disturbances of post-receptor trans-membrane signalling in AD can be attributed to functional changes of G(salpha), and these are independent of alterations in the level for those proteins in normal aging.

Skew of mononucleotide frequencies, relative abundance of dinucleotides, and DNA strand asymmetry

Based on 152 mitochondrial genomes and 36 bacterial chromosomes that have been completely sequenced, as well as three long contigs for human chromosomes 6, 21, and 22, we examined skews of mononucleotide frequencies and the relative abundance of dinucleotides in one DNA strand. Each group of these genomes has its own characteristics. Regarding mitochondrial genomes, both CpG and GpT are underrepresented, while either GpG or CpC or both are overrepresented. The relative frequency of nucleotide T vs A and of nucleotide G vs C is strongly skewed, due presumably to strand asymmetry in replication errors and unidirectional DNA replication from single origins. Exceptions are found in the plant and yeast mitochondrial genomes, each of which may replicate from multiple origins. Regarding bacterial genomes, the "universal" rule of CpG deficiency is restricted to archaebacteria and some eubacteria. In other eubacteria, the most underrepresented dinucleotide is either TpA or GpT. In general, there are significant T vs A and G vs C skews in each half of the bacterial genome, although these are almost exactly canceled out over the whole genome. Regarding human chromosomes 6, 21, and 22, dinucleotide CpG tends to be avoided. The relative frequency of mononucleotides exhibits conspicuous local skews, suggesting that each of these chromosomal segments contains more than one DNA replication origin. It is concluded that, when there are several replicons in a genomic region, not only the number of DNA replication origins but also the directionality is important and that the observed patterns of nucleotide frequencies in the genome strongly support the hypothesis of strand asymmetry in replication errors.

Alu-mediated inactivation of the human CMP- N-acetylneuraminic acid hydroxylase gene

Inactivation of the CMP-N-acetylneuraminic acid hydroxylase gene has provided an example of human-specific genomic mutation that results in a widespread biochemical difference between human and nonhuman primates. We have found that, although a region containing a 92-bp exon and an AluSq element in the hydroxylase gene is intact in all nonhuman primates examined, the same region in the human genome is replaced by an AluY element that was disseminated at least one million years ago. We propose a mechanistic model for this Alu-mediated replacement event, which deleted the 92-bp exon and thus inactivated the human hydroxylase gene. It is suggested that Alu elements have played potentially important roles in genotypic and phenotypic evolution in the hominid lineage.

Integrative study on chromosome evolution of mammals, ants and wasps based on the minimum interaction theory

There is well-known evidence that in many eukaryotes, different species have different karyotypes (e.g. n=1-47 in ants and n=3-51 in mammals). Alternative (fusion and fission) hypotheses have been proposed to interpret this chromosomal diversity. Although the former has long been accepted, accumulating molecular genetics evidence seems to support the latter. We investigated this problem from a stochastic viewpoint using the Monte Carlo simulation method under the minimum interaction theory. We found that the results of simulations consistently interpreted the chromosomal diversity observed in mammals, ants and wasps, and concluded that chromosome evolution tends to evolve as a whole toward increasing chromosome numbers by centric fission. Accordingly, our results support the fission hypothesis. We discussed the process of chromosome evolution based on the latest theory of the molecular structure of chromosomes, and reconfirmed that the fission burst is the prime motive force in long-term chromosome evolution, and is effective in minimizing the genetic risks due to deleterious reciprocal translocations and in increasing the potential of genetic divergence. Centric fusion plays a biological role in eliminating heterochromatin (C-bands), but is only a local reverse flow in contrast to the previously held views.

Testing multiregionality of modern human origins

In order to examine the possibility of multiple founding populations of anatomically modern Homo sapiens, we collected DNA sequence data from 10 X-chromosomal regions, 5 autosomal regions, and 1 Y-chromosomal region, in addition to mitochondrial DNA. Except for five regions which are genealogically uninformative and two other regions for which chimpanzee orthologs are not available, the ancestral sequence and population for each of the remaining regions were successfully inferred. Of these 10 ancestral sequences, 9 occurred in Africa and only 1 occurred in Asia during the Pleistocene. Computer simulation was carried out to quantify the multiregional hypothesis based solely on the premise that there was more than one founding population in the Pleistocene. Allowing the breeding size to vary among the founding populations, the hypothesis may account for the observed African ancestry in 90% of the genomic regions. However, it is required that the founding population in Africa was much larger than that outside Africa. Likelihood estimates of the breeding sizes in the founding populations were more than 9,000 in Africa and less than 1,000 in outside of Africa, although these estimates can be much less biased at the 1% significance level. If the number of African ancestral sequences further increases as more data accumulate in other genomic regions, the conclusion of a single founding population of modern H. sapiens is inevitable.

Mhc class II B gene evolution in East African cichlid fishes

A distinctive feature of essential major histocompatibility complex (Mhc) loci is their polymorphism characterized by large genetic distances between alleles and long persistence times of allelic lineages. Since the lineages often span several successive speciations, we investigated the behavior of the Mhc alleles during or close to the speciation phase. We sequenced exon 2 of the class II B locus 4 from 232 East African cichlid fishes representing 32 related species. The divergence times of the (sub)species ranged from 6,000 to 8.4 million years. Two types of evolutionary analysis were used to elucidate the pattern of exon 2 sequence divergence. First, phylogenetic methods were applied to reconstruct the most likely evolutionary pathways leading from the last common ancestor of the set to the extant sequences, and to assess the probable mechanisms involved in allelic diversification. Second, pairwise comparisons of sequences were carried out to detect differences seemingly incompatible with origin by nonparallel point mutations. The analysis revealed point mutations to be the most important mechanism behind allelic divergences, with recombination playing only an auxiliary part. Comparison of sequences from related species revealed evidence of random allelic (lineage) losses apparently associated with speciation. Sharing of identical alleles could be demonstrated between species that diverged 2 million years ago. The phylogeny of the exon was incongruent with that of the flanking introns, indicating either a high degree of convergent evolution at the peptide-binding region-encoding sites, or intron homogenization.

The origin and age of haplochromine fishes in Lake Victoria, east Africa

According to a widely held view, the more than 300 species of haplochromine cichlid fishes in Lake Victoria (LV), East Africa, originated from a single founder species in less than 12,000 years. This view, however, does not follow from the published geological and molecular evidence. The former does indeed suggest that the LV basin dried out less than 15,000 years ago, but it does not provide any information about the species that re-colonized the new lake or that remained in the rivers draining the area. The molecular evidence is inconclusive with respect to the origin of the LV haplochromines because cichlids from critical regions around LV were not adequately sampled; and as far as the age of the LV haplochromines is concerned, it in fact led to an estimate of 250,000-750,000 years old. In the present study, mitochondrial DNA (control region) variation was determined by heteroduplex and sequencing analyses of more than 670 specimens collected at widely distributed East African riverine and lacustrine localities. The analyses revealed the existence of seven haplogroups (I-VII) distinguishable by characteristic substitutions. All endemic LV samples tested fell into one of these haplogroups (V) which, however, was also found to be present at various other localities, both riverine and lacustrine, outside LV. Within this haplogroup, four subgroups (VA through VD) could be distinguished, two of which (VB and VC) were represented in LV and at other localities. The great majority of the LV haplochromine species could be classified as belonging to the VC subgroup, which was found only in LV and in the rivers draining into it. Hence, while the endemic haplochromine species of LV could not have originated from a single founding population, the lake does harbour a large species flock which probably arose in situ.

Helium flux from a sedimentary basin

The tritium-3He ages of groundwaters collected from the Saijo Basin in Japan were measured. The ages vary between 11.7 and 16.3 years. The 4He flux of >3 x 10(4) atoms/cm2 s is calculated by the 4He concentrations and ages. In addition the helium flux of 8.3 x 10(5) atoms/cm2 s is calculated at the Higashi-Niigata gas field in Japan. The above two estimates are consistent with the continental helium flux reported in the literature, suggesting that helium flux on the Earth's crust is uniform.

DNA archives and our nearest relative: the trichotomy problem revisited

Ever since Thomas H. Huxley correctly identified the chimpanzee and the gorilla as the two closest relatives of the human, the problem of the relationship among the three species ("the trichotomy problem") has remained unresolved. Comparative morphology and other classical methods of biological investigation have failed to answer definitively whether the chimpanzee or the gorilla is the closest relative of the human species. DNA sequences, both mitochondrial and nuclear, too, have provided equivocal solutions, depending on the region of the genome analyzed. Random sorting of ancestral allelic lineages, sequence convergence, and sequence exchanges between alleles or duplicated loci have been identified as likely factors confounding the interpretation of the interrelationships among the three species. In the present study most of these difficulties are overcome by identifying evolutionary causes that might potentially provide misleading information. Altogether, 45 loci consisting of 46, 855 bp are analyzed. About 60% of the loci and approximately the same proportion of phylogenetically informative sites support the human-chimpanzee clade. The remaining 40% of loci and sites support the two alternatives equally. It is demonstrated that, while incompatibility between loci can be explained by random sorting of allelic lineages, incompatibility within loci must be attributed largely to the joint effect of recombination and genetic drift. The trichotomy problem can be properly addressed only within this framework.

Differential diagnosis between organic and inorganic mercury poisoning in human cases--the pathologic point of view

Differences in pathology were found between acute and chronic exposure to methylmercury, mercury vapor, and inorganic mercury. Characteristic pathologic changes produced by organic mercury in the brain have previously been described in patients with Minamata disease. The brains of patients who presented with acute onset of symptoms and died within 2-mo showed loss of neurons with reactive proliferation of glial cells, microcavitation, vascular congestion, petechial hemorrhage, and edema in the cerebral cortices, predominantly in the calcarine, pre- and postcentral, and transverse temporal cortices and in the cerebellar cortex. The neuropathologic changes in the patients with acute onset of symptoms who survived for a long period (>10 yr) were also included neuronal loss with reactive proliferation of glial cells in similar anatomic locations. The neuropathologic changes in patients with inorganic mercury poisoning are quite different. Autopsies performed on 3 individuals with fatal cases of acute inorganic mercury poisoning who were exposed to mercury vapor for about 2 wk revealed diffuse organized pneumonia, renal cortical necrosis, disseminated intravascular coagulopathy, and infarctions in the brain and kidneys. In 2 other patients who worked in mercury mines for about 10 yr and who suffered from chronic inorganic poisoning, no specific lesions were demonstrated in the brain. However, the assay and the histochemistry of mercury revealed that inorganic mercury was present in the brain in all 3 groups irrespective of the brain lesions and the duration of clinical signs.

Eye-head coordination abnormalities and regional cerebral blood flow in Alzheimer's disease

1. Three patients with Alzheimer's disease (AD) and three healthy controls (HC) were examined for eye-head coordination. Regional cerebral blood flow (rCBF) was measured in AD patients. 2. Eye-head coordination was analyzed using a Vision analyzer, and magnetic sensors. The authors measured the rCBF with 123I-IMP, and 99mTc-ECD SPECT. 3. AD reduced gaze accuracy and head movements, and prolonged the latency of saccade as compared to HC. AD patients had a tendency to focus on the target by using eye movements only. 4. AD reduced the rCBF in the inferior parietal part and the visual area, relative to the motor area. Damage of these areas may have caused the eye-head coordination disorders in the AD patients.

Paleo-demography of the Drosophila melanogaster subgroup: application of the maximum likelihood method

The species divergence times and demographic histories of Drosophila melanogaster and its three sibling species, D. mauritiana, D. simulans, and D. yakuba, were investigated using a maximum likelihood (ML) method. Thirty-nine orthologous loci for these four species were retrieved from DDBJ/EMBL/GenBank database. Both autosomal and X-linked loci were used in this study. A significant degree of rate heterogeneity across loci was observed for each pair of species. Most loci have the GC content greater than 50% at the third codon position. The codon usage bias in Drosophila loci is considered to result in the high GC content and the heterogenous rates across loci. The chi-square, G, and Fisher's exact tests indicated that data sets with 11, 23, and 9 pairs of DNA sequences for the comparison of D. melanogaster with D. mauritiana, D. simulans, and D. yakuba, respectively, retain homogeneous rates across loci. We applied the ML method to these data sets to estimate the DNA sequence divergences before and after speciation of each species pair along with their standard deviations. Using 1.6 x 10(-8) as the rate of nucleotide substitutions per silent site per year, our results indicate that the D. melanogaster lineage split from D. yakuba approximately 5.1 +/- 0.8 million years ago (mya), D. mauritiana 2.7 +/- 0.4 mya, and D. simulans 2.3 +/- 0.3 mya. It implies that D. melanogaster became distinct from D. mauritiana and D. simulans at approximately the same time and from D. yakuba no earlier than 10 mya. The effective ancestral population size of D. melanogaster appears to be stable over evolutionary time. Assuming 10 generations per year for Drosophila, the effective population size in the ancestral lineage immediately prior to the time of species divergence is approximately 3 x 10(6), which is close to that estimated for the extant D. melanogaster population. The D. melanogaster did not encounter any obvious bottleneck during the past 10 million years.

Evolution of Mhc-DRB introns: implications for the origin of primates

Introns are generally believed to evolve too rapidly and too erratically to be of much use in phylogenetic reconstructions. Few phylogenetically informative intron sequences are available, however, to ascertain the validity of this supposition. In the present study the supposition was tested on the example of the mammalian class II major histocompatibility complex (Mhc) genes of the DRB family. Since the Mhc genes evolve under balancing selection and are believed to recombine or rearrange frequently, the evolution of their introns could be expected to be particularly rapid and subject to scrambling. Sequences of intron 4 and 5 DRB genes were obtained from polymerase chain reaction-amplified fragments of genomic DNA from representatives of six eutherian orders-Primates, Scandentia, Chiroptera, Dermoptera, Lagomorpha, and Insectivora. Although short stretches of the introns have indeed proved to be unalignable, the bulk of the intron sequences from all six orders, spanning >85 million years (my) of evolution, could be aligned and used in a study of the tempo and mode of intron evolution. The analysis has revealed the Mhc introns to evolve at a rate similar to that of other genes and of synonymous sites of non-Mhc genes. No evidence of homogenization or large-scale scrambling of the intron sequences could be found. The Mhc introns apparently evolve largely by point mutations and insertions/deletions. The phylogenetic signals contained in the intron sequences could be used to identify Scandentia as the sister group of Primates, to support the existence of the Archonta superorder, and to confirm the monophyly of the Chiroptera.

Alterations of tubulin function caused by chronic antidepressant treatment in rat brain

1. Antidepressants have been used clinically for many years; however, the neurochemical mechanism for their therapeutic effect has not been clarified yet. Recent reports indicate that chronic antidepressant treatment directly affects the postsynaptic membrane to increase the coupling between the stimulatory GTP-binding (G) protein, Gs, and adenylyl cyclase. Tubulin, a cytoskeletal element, is involved in the stimulatory and inhibitory regulation of adenylyl cyclase in rat cerebral cortex via direct transfer of GTP to G proteins. In this study, we investigated whether the functional change of the adenylyl cyclase system caused by chronic antidepressant treatment involves an alteration of tubulin function in the regulation of adenylyl cyclase activity. 2. Male Sprague-Dawley rats were treated once daily with amitriptyline or saline by intraperitoneal injection (10 mg/kg) for 21 days, and their cerebral cortex membranes and GppNHp-liganded tubulin (tubulin-GppNHp) were prepared for what. 3. GppNHp-stimulated adenylyl cyclase activity in cortex membranes from amitriptyline-treated rats was significantly higher than that in control membranes. Furthermore, tubulin-GppNHp prepared from amitriptyline-treated rats was more potent than that from control rats in the stimulation of adenylyl cyclase activity in the cortex membranes of the controls. However, there was no significant difference in manganese-stimulated adenylyl cyclase activity between control and amitriptyline-treated rats. 4. The present results suggest that chronic antidepressant treatment enhances not only the coupling between Gs and the catalytic subunit of adenylyl cyclase but also tubulin interaction with Gs in the cerebral cortex of the rat.

Molecular clock and recombination in primate Mhc genes

To set an accurate chronological framework to the evolution of primate class I and II genes in the major histocompatibility complex (Mhc), the rate of silent nucleotide substitutions in exons and introns is examined for various cDNA and genome sequences currently available. The rate is sensitive to the GC content and correlates negatively with increased GC biases at the third codon positions of Mhc genes. The intergenic recombination rate in the HLA region is estimated from the synonymous nucleotide differences at 37 linked loci. Any HLA subregion is recombined more or less at the ordinary rate of 1 cM per 1 Mb, although the rate may be reduced in some subregions. This information is used to discuss HLA haplotypes when they are applied to studies of human demography. The unusual polymorphism in the alpha-helix of HLA-DRB1 is also revisited in relation to intragenic recombination, but the molecular mechanism and the evolutionary cause both remain enigmatic.

Persistence of neutral polymorphisms in Lake Victoria cichlid fish

Phylogenetic trees for groups of closely related species often have different topologies, depending on the genes used. One explanation for the discordant topologies is the persistence of polymorphisms through the speciation phase, followed by differential fixation of alleles in the resulting species. The existence of transspecies polymorphisms has been documented for alleles maintained by balancing selection but not for neutral alleles. In the present study, transspecific persistence of neutral polymorphisms was tested in the endemic haplochromine species flock of Lake Victoria cichlid fish. Putative noncoding region polymorphisms were identified at four randomly selected nuclear loci and tested on a collection of 12 Lake Victoria species and their putative riverine ancestors. At all loci, the same polymorphism was found to be present in nearly all the tested species, both lacustrine and riverine. Different polymorphisms at these loci were found in cichlids of other East African lakes (Malawi and Tanganyika). The Lake Victoria polymorphisms must have therefore arisen after the flocks now inhabiting the three great lakes diverged from one another, but before the riverine ancestors of the Lake Victoria flock colonized the Lake. Calculations based on the mtDNA clock suggest that the polymorphisms have persisted for about 1.4 million years. To maintain neutral polymorphisms for such a long time, the population size must have remained large throughout the entire period.

Selection, convergence, and intragenic recombination in HLA diversity

To account for high degrees of human leukocyte antigen (HLA) diversity, a method is proposed for detecting intragenic recombination or gene conversion separately from parallel substitutions or convergent evolution. An application of the method to HLA protein sequences suggests that intragenic recombination played important roles in HLA-B and DPB1, some in HLA-A and DRB1, and least in HLA-C and DQB1 diversity. However, the extent of diversity of these molecules does not necessarily correlate with the frequency of intragenic recombination, supporting the view that (balancing) selection is a primary agent of HLA diversity and often leads to convergent evolution. Computer simulation is carried out to examine two models of balancing selection under the coupled effect with mutation, intragenic recombination, and random drift in a diploid population. It is emphasized that break points by intragenic recombination need be specified to account for HLA diversity. Implications of HLA diversity in human evolution are briefly discussed.

Footprints of intragenic recombination at HLA loci

To evaluate the effect of balancing selection and intragenic recombination (or gene conversion) at six individual HLA loci, synonymous nucleotide diversity in different exon groups is examined within (pi w) and between (pi b) allelic lineages that may be defined by either serological or DNA sequence differences. Both pi values are high in exons which encode for the peptide binding region (PBR) and tend to decrease in other exons. The value of pi w is significantly smaller than that of pib in any exon of any locus. However, even pi w is much greater than nucleotide diversity at non-HLA loci. These observations provide additional strong evidence for the operation of balancing selection in PBR-encoding exons and its indirect effects on polymorphism at linked neighboring regions. It appears that allelic lineages have generally evolved in isolation but the linkage relationships within and between exons are incomplete throughout the long evolutionary history. To quantify intragenic recombination and account for the large discrepancy between the HLA and non-HLA diversity, a population genetics model is analyzed with special reference to the evolution of modern humans. The analysis suggests that the recombination rate between two sites 1000 base pairs apart is about 10(-5) per generation and that the effective size of human populations (equivalent roughly to the number of breeding individuals in a randomly mating population) has dropped from 10(5) to 10(4) in most of the Quaternary. One possibility for this reduction is discussed.

Evolutionary history and mechanism of the Drosophila cecropin gene family

Upon bacterial infection, insects secrete a set of synthesized antibacterial proteins into the hemolymph and initiate synergistic destruction of invaders. Cecropin is one such antibacterial protein which is also found in vertebrates. To study the evolutionary history and mechanism of the Cecropin gene family, we determined DNA sequences of one isogenic In(3R)C and six isofemale lines of Drosophila melanogaster as well as one line of D. simulans and of D. yakuba. The phylogenetic analysis of these sequences together with those published for D. virilis and Sarcophaga peregrina reveals frequent gene re-organization. It was also found that silent nucleotide differences within D. melanogaster are quite heterogeneous across the gene region of approximately 3 kilobases and the extent of polymorphism is unusually usually high. These data suggest that the Cecropin gene region of D. melanogaster underwent intragenic recombination as well as introgression from a closely related sibling species, D. simulans.

Reduced immunoreactivity of type I adenylyl cyclase in the postmortem brains of alcoholics

Reduced adenylyl cyclase activity after chronic ethanol exposure has been reported. In this study, we investigated by immunoblotting whether quantitative changes of adenylyl cyclase isoforms (type I, type II, and type V/VI adenylyl cyclases) exist in membrane preparations of the temporal cortex obtained from six alcoholics and six age-matched controls. The immunoreactivity of type I adenylyl cyclase decreased significantly in the temporal cortex of alcoholics when compared with controls (p < 0.05), whereas those of type II and type V/VI adenylyl cyclases showed no changes between the groups. These findings suggest that these isoform-specific afterations in the adenylyl cyclase system may be involved in the pathophysiology of alcoholism.

Differential alteration of adenylyl cyclase subtypes I, II, and V/VI in postmortem human brains of heroin addicts

In animal and culture cell experiments, the upregulation of cAMP-related signal transduction after chronic opioid administration has been hypothesized to be an adaptive change of the molecular mechanism to maintain homeostasis in intracellular signals downstream from opioid receptors. Herein, we have examined the quantitative changes of three adenylyl cyclase (AC) subtypes (I, II, and V/VI) in temporal cortex membranes from brains of heroin addicts and age-matched controls by immunoblotting. The immunoreactivity of AC-I decreased significantly (p < 0.05) in heroin addicts, compared with controls; whereas those of AC-II and AC-V/VI were not changed. The present findings indicate that differential regulation of AC subtypes occurs and that AC-I may play an important role in the signal transduction for opiate-induced tolerance and dependence mechanisms in human brain cortex.

The neutral theory and natural selection in the HLA region

Based on available DNA sequence data in the HLA region of 4 Mb, we review the degree of polymorphism at 39 loci of which most are involved in the immune system. The extent of nucleotide differences per silent site differs greatly from locus to locus. It is exceptionally high at classical MHC loci, intermediate at six MHC-related pseudogenes as well as at some loci in class I and II regions, and low in the class III region. Different exons of individual MHC loci show also different degrees of silent polymorphism; high in the exons encoding for the peptide binding region (PBR) and low in the exons encoding for trans-membranes and cytoplasmic tails. The degree of polymorphism within MHC allelic lineages is not much smaller than that between allelic lineages, contrary to the expectation where intra-allelic sequence exchanges are restricted. The observation that many allelic lineages at the HLA-DRB1 locus are combinations of distinct motifs in the beta pleated sheet and alpha helix of PBR indicates that sequence exchanges occur even within exon 2. Semi-quantitative analysis is presented about the rate of sequence exchanges between selected and linked neutral regions, although more sequence information is necessary to make definite conclusions. The extraordinary MHC polymorphism is viewed from the dual function of MHC molecules that controls the acquired immune system.

Evidence for presenilin-1 involvement in amyloid angiopathy in the Alzheimer's disease-affected brain

Presenilin-1 (PS-1) has been identified as the protein encoded by the chromosome 14 locus that, when mutated, leads to familial Alzheimer's disease (FAD). The role PS-1 plays in the pathogenesis of Alzheimer's disease (AD) remains unclear. Using a set of antibodies raised against PS-1 synthetic peptides, polyclonal antibody to amyloid beta protein (Abeta) and end-specific antibodies against Abeta40, and Abeta42, immunohistochemical studies were performed on brain sections obtained from AD cases and controls. The PS-1 antibodies clearly stained amyloid angiopathies in AD-affected brains, but no recognizable immunoreactions were observed in any other vessels free from amyloid involvement in either AD-affected brains or controls. Abeta antibodies and the end-specific antibody against Abeta40 also decorated amyloid angiopathies, showing localization similar to that of PS-1. Western blot analyses predominantly detected protein band polypeptide species of a 50 kDa, band, presumably full-length PS-1 protein with N-terminus antisera, since these antibodies turned out to recognize a 50-kDa full-length band in cell lysate of transfected HeLa cell overexpressing PS-1. In addition, we recognized 30, 27 and 25 kDa proteins in both AD and control brain homogenate with these antibodies. In microvessel fractions extracted from brain homogenates, the 50, and 27 kDa fragments were observed in AD-affected brains but not in those of controls. C-terminus rabbit antisera reacted strongly with the 33 and 27 kDa bands, and additionally detected a small amount of full-length PS-1 protein in extracts from AD and control brains. Our present data indicate that PS-1 might be involved in the pathogenesis of amyloid angiopathy in the AD brain.

Measurement of receptor-mediated functional activation of G proteins in postmortem human brain membranes

Guanine nucleotide-binding regulatory proteins (G proteins) play a pivotal role in receptor-mediated transmembrane signal transduction, and have been implicated in modes of action of psychotropic drugs as well as in pathogenesis of psychiatric disorders. In the present investigation, functional activation of G proteins coupled with several receptors, in particular with GABAB receptors, was assessed by agonist-induced stimulation of high-affinity GTPase, an enzyme that is intrinsic to alpha subunit of G protein, in postmortem human frontal cortical membranes. High-affinity GTPase activity was stimulated by GABA as well as (+/-)-baclofen, a selective GABAB receptor agonist, with EC50 values of 60-150 and 10-40 microM, respectively, in a Mg(2+)-dependent manner. The (+/-)-baclofen-stimulated response was antagonized by the selective GABAB receptor antagonist, 2-hydroxy-saclofen, in a competitive manner with a KB value of 59 microM. Although the maximal percent increase above basal value (% Emax) for GABAB receptor-mediated high-affinity GTPase activity was varied from subject to subject, % Emax values for both agonists were highly correlated with each other, and replicable and stable in a given subject, indicating that this measure is trustworthy as an index of functional coupling between receptors and G proteins in future studies at the aim of elucidating possible alteration of receptor/G protein interaction in psychiatric disorders. The % Emax values for GABAB receptor-mediated responses were correlated inversely with brain storage duration, which should be critically considered in postmortem studies. The increases in high-affinity GTPase activity stimulated by several agonists other than GABAB receptor agonists seemed too low to quantify for making a comparison in future studies.

Calcium mobilization evoked by amyloid beta-protein involves inositol 1,4,5-triphosphate production in human platelets

We examined the effects of amyloid beta-protein (A beta) on Ca2+ mobilization in human platelets. The addition of A beta fragments 25-35 (A beta 25-35) gradually increased the cytoplasmic free Ca2+ concentration ([Ca2+]i). After the maximum response, [Ca2+]i decreased and then reached a sustained, higher level of [Ca2+]i. Similar effects were also observed with A beta 1-40, whereas 1-28 , 12-28 and 31-35 did not affect the Ca2+ response. In the absence of extracellular Ca2+, A beta 25-35 caused a transient increase in [Ca2+]i, which returned to the resting level. U73122, a phospholipase C inhibitor, completely abolished Ca2+ mobilization induced by thrombin and A beta 25-35. Furthermore, A beta enhanced the production of inositol 1,4,5-trisphosphate (IP3) in platelets. These findings suggest that Ca2+ mobilization induced by A beta 25-35 is due to phospholipase C activation and IP3 production.

Differential effects of chronic administration of the antidepressants amitriptyline and rolipram on adenylyl cyclase activity

Significant increases were observed in guanylylimidodiphosphate- and fluoride-stimulated adenylyl cyclase activities in synaptic membrane preparations from rat cerebral cortex subsequent to the repeated administration of rolipram and amitriptyline. The potency of GppNHp-dependent inhibition of adenylyl cyclase was decreased by chronic treatment with rolipram but not by amitriptyline treatment. These findings suggest that chronically administered rolipram and amitriptyline share the augmentation of adenylyl cyclase activity by different actions on post-receptor signaling.

Ca2+/CaM-sensitive adenylyl cyclase activity is decreased in the Alzheimer's brain: possible relation to type I adenylyl cyclase

Immunoreactivities of four subtypes of adenylyl cyclase (AC) (types I, II, IV and V/VI), and basal, forskolin- and Mn(2+)-stimulated AC activities with or without calcium and calmodulin (Ca2+/CaM) were estimated in parietal cortex membranes from cases with dementia of the Alzheimer type (DAT) and age-matched controls. Immunoreactivities of AC-I and AC-II were significantly decreased, but those of AC-IV and AC-V/VI did not change in DAT brains. There was a significant correlation of AC-I immunoreactivity with Ca2+/CaM-sensitive AC activity, but not with the Ca2+/CaM-insensitive activity. Ca2+/CaM-sensitive AC activity was significantly lower in DAT than in the control, indicating that impairment of Ca2+/CaM-sensitive AC-I is clearly involved in the pathophysiology of DAT.

Potential antidepressant properties of forskolin and a novel water-soluble forskolin (NKH477) in the forced swimming test

The mechanisms of the antidepressant activity of forskolin and a novel water soluble forskolin analog (NKH477) were studied using the forced swimming method in rats. Forskolin (0.01-0.1 mg/kg) and NKH477 (0.01-0.1 mg/kg) dose-dependently decreased ratings of immobility, with effects similar to those of amitriptyline treatment. The maximum effects of forskolin and NKH477 were observed at 0.01 mg/kg dose which is 150 more times potent than that (15 mg/kg) of amitriptyline. At a high dose (1.0 mg/kg) of forskolin and NKH477, the duration of immobility was returned to control levels. Forskolin and NKH477 did not influence the spontaneous locomotor activity at intraperitoneal injection doses from 0.01 to 1 mg/kg. Furthermore chronic administration with NKH477 at oral dose from 0.5 to 1.5 mg/kg significantly decreases the duration of immobility. These data indicate that both forskolin and NKH477 have strong antidepressive potency, consistent with the hypothesis that elevation of the cAMP cascade system may have an important role in antidepressive effects.

Polymorphism of the HLA class II loci in Siberian populations

The populations that colonized Siberia diverged from one another in the Paleolithic and evolved in isolation until today. These populations are therefore a rich source of information about the conditions under which the initial divergence of modern humans occurred. In the present study we used the HLA system, first, to investigate the evolution of the human major histocompatibility complex (MHC) itself, and second, to reveal the relationships among Siberian populations. We determined allelic frequencies at five HLA class II loci (DRB1, DQA1, DQB1, DPA1, and DPB1) in seven Siberian populations (Ket, Evenk, Koryak, Chukchi, Nivkh, Udege, and Siberian Eskimo) by the combination of single-stranded conformational polymorphism and DNA sequencing analysis. We then used the gene frequency data to deduce the HLA class II haplotypes and their frequencies. Despite high polymorphism at four of the five loci, no new alleles could be detected. This finding is consistent with a conserved evolution of human class II MHC genes. We found a high number of HLA class II haplotypes in Siberian populations. More haplotypes have been found in Siberia than in any other population. Some of the haplotypes are shared with non-Siberian populations, but most of them are new, and some represent "forbidden" combinations of DQA1 and DQB1 alleles. We suggest that a set of "public" haplotypes was brought to Siberia with the colonizers but that most of the new haplotypes were generated in Siberia by recombination and are part of a haplotype pool that is turning over rapidly. The allelic frequencies at the DRB1 locus divide the Siberian populations into eastern and central Siberian branches; only the former shows a clear genealogical relationship to Amerinds.

Amino-terminus truncated apolipoprotein E is the major species in amyloid deposits in Alzheimer's disease-affected brains: a possible role for apolipoprotein E in Alzheimer's disease

Amyloid deposits in Alzheimer's disease (AD) are composed of amyloid beta protein (A beta) and many other components called amyloid-associated proteins. Apolipoprotein E (apoE) is one of the most important amyloid-associated proteins. The role apoE plays in AD, however, is yet to be determined. In this study, we present the biochemical and histochemical nature of apoE in AD-affected brains using four monoclonal antibodies (mAbs) against apoE and newly established antibodies against the amino-terminal (anti-apoE-N), and carboxyl-terminal regions (anti-apoE-C) of apoE. Competitive ELISA and Western-blot analysis combined with thrombolytic digestion of apoE indicated that our four mAbs recognized at least two different epitopes within a 22-kDa amino-terminal domain of apoE. Using these mAbs and an anti-A beta mAb, double immunostaining showed that the majority of amyloid deposits were stained by both anti-apoE and anti-A beta mAbs, but the minority of them were detected only by either anti-apoE or anti-A beta mAbs. Differences in staining properties between anti-apoE-N and anti-apoE-C were that anti-apoE-C recognized both amyloid deposits and astrocytes similar to anti-apoE mAbs, but anti-apoE-N strongly stained only astrocytes. Preliminary semi-quantitative determinations of apoE in CSF and brain homogenate showed that the amount of apoE increased in AD and Creutzfeldt-Jakob disease brains compared to normal samples. Our immunological data, using antibodies specific for the amino and carboxyl termini of apoE, suggest that apoE may, in some circumstances, initiate plaque formation, and that apoE in amyloid deposits has at least part of its amino termini cleaved out.

Amyloid precursor protein, A beta and amyloid-associated proteins involved in chloroquine retinopathy in rats--immunopathological studies

To understand the retinal changes in Alzheimer disease (AD) patients, pathological and immunocytochemical studies were performed on retinal cells in the chloroquine-treated rats at 0, 4, 8, 12, 16, 20, and 24 weeks after the initial injection, using anti-amyloid precursor protein (APP), -amyloid beta protein (A beta), -apolipoprotein E (apoE), -ubiquitin, and -cathepsin D antibodies. Pathological alterations consistent with chloroquine retinopathy were recognized in the ganglion cells of the ganglion cell layer (GCL) and the inner plexiform layer (IPL) 4 weeks after initial chloroquine injection. Rat retinal changes appear to have a direct relationship to the duration of chloroquine administration. Intense immunoreactivities for anti-APP, A beta, apoE (an associated protein), and ubiquitin co-localized in the swollen ganglion cells and Muller cells by 20-24 weeks together with the lysosomal enzyme cathepsin D. The present data indicate that the endosomal/lysosomal pathway plays an important role in the processing of APP in rat retina. This experimental model is considered to be a suitable neural model to understand retinal pathology and the processing of APP in terms of the pathogenesis of AD, whereas chloroquine-induced myopathy is a useful extra neuronal model.

Evolution of the primate lineage leading to modern humans: phylogenetic and demographic inferences from DNA sequences

To date major divergences that occurred in the primate lineage leading to modern humans and to infer a demographic parameter (effective population size) of the ancestral lineage that existed at each divergence, a maximum likelihood method was applied to autosomal DNA sequence data currently available for pairs of orthologous genes between the human and each of the chimpanzee, gorilla, Old World monkey (OWM), and New World monkey (NWM). A statistical test is carried out to support the assumption that silent substitutions have accumulated in a clock-like fashion over loci between primate taxa or even among sites within a locus. It is shown that the human ancestral lineage became distinct from the NWM 57.5 million years (Myr) ago, the OWM 31 Myr ago, the gorilla 8.0 Myr ago, and the chimpanzee 4.5 Myr ago, and that the effective population size at these divergences was generally much greater than that of modern humans. It is argued that the human ancestral lineage branched off from the NWM and OWM earlier than once thought and that significant demographic changes might have occurred at different evolutionary stages, particularly at the hominid stage.