[Mitochondrial DNA sequence variations of Shui ethnic group]

The mtDNA hypervariable segment I sequences (HVS I) were sequenced in 64 Shuis from Guizhou Province. 73 sites were polymorphic in the 495 bp fragment that sequenced, identified 48 different haplotypes. Phylogenetic analysis of the haplotypes suggested that there were some ancestral haplotypes in current Shuis, and these haplotypes were also present in Eurasia populations as well as in other ethnic groups. Demographic analysis of the Shuis demonstrated a unimodal distribution that is typical for a population undergone expansion in the past and with a high Tau value, which suggested that the Shui group might be a ancestral population. Combined with the analysis of the reported data, the Shui ethnic group showed a generally similar genetic component with the Zhuang from Guangxi, but it is also different from these typical south populations as Zhuang, Cantonese.

Comparative seven-day clinical evaluation of two tooth whitening products

A 1-week study was conducted to compare the tooth whitening efficacy of two carbamide peroxide-based products (one containing 5% carbamide peroxide and one containing 10% carbamide peroxide). In addition, the perception of transient tooth hypersensitivity associated with the use of these products was subjectively evaluated. Sixty participants took part in a double-blind, randomized, parallel clinical study. Change in tooth color was measured by chroma meter and Vita shade guide at the initiation of the study and after 7 days of product use. Color change (delta E) was calculated using the color-difference equation established by the Commission Internationale de L'Eclairage. Data concerning dental hypersensitivity was assessed by subjective panelist questionnaires administered after the day 7 recall examination. Results of the whitening data showed that there was no significant difference between the two products. After 1 week, the mean delta E for the product containing 5% carbamide peroxide was 4.43 +/- 1.89 and the mean delta E for the product containing 10% carbamide peroxide was 4.05 +/- 1.84. However, the subjective data collected on tooth hypersensitivity showed that the product containing 5% carbamide peroxide was associated with less discomfort. Of the group using the 5% carbamide peroxide product, 20% reported transient sensitivity of their teeth after product use for 1 week compared with 53% of the group using the product with 10% carbamide peroxide. Statistical analysis using a 2-tailed t test showed significant differences between the two groups (P < .05). The data suggest that these products are clinically equivalent for tooth whitening; however, the product containing 5% carbamide peroxide was associated with less tooth hypersensitivity after 1 week of application.

Molecular evolution of GH in primates: characterisation of the GH genes from slow loris and marmoset defines an episode of rapid evolutionary change

Pituitary growth hormone (GH), like several other protein hormones, shows an unusual episodic pattern of molecular evolution in which sustained bursts of rapid change are imposed on long periods of very slow evolution (near-stasis). A marked period of rapid change occurred in the evolution of GH in primates or a primate ancestor, and gave rise to the species specificity that is characteristic of human GH. We have defined more precisely the position of this burst by cloning and sequencing the GH genes for a prosimian, the slow loris (Nycticebus pygmaeus) and a New World monkey, marmoset (Callithrix jacchus). Slow loris GH is very similar in sequence to pig GH, demonstrating that the period of rapid change occurred during primate evolution, after the separation of lines leading to prosimians and higher primates. The putative marmoset GH is similar in sequence to human GH, demonstrating that the accelerated evolution occurred before divergence of New World monkeys and Old World monkeys/apes. The burst of change was confined largely to coding sequence for mature GH, and is not marked in other components of the gene sequence including signal peptide, 5' upstream region and introns. A number of factors support the idea that this episode of rapid change was due to positive adaptive selection. Thus (1) there is no apparent loss of function of GH in man compared with non-primates, (2) after the episode of rapid change the rate of evolution fell towards the slow basal level that is seen for most mammalian GHs, (3) the accelerated rate of substitution for the exons of the GH gene significantly exceeds that for introns, and (4) the amino acids contributing to the hydrophobic core of GH are strongly conserved when higher primate and other GH sequences are compared, and for coding sequences other than that coding for hydrophobic core residues the rate of substitution for non-synonymous sites (K(A)) is significantly greater than that for synonymous sites (K(S)). In slow loris, as in most non-primate mammals, there is no evidence for duplication of the GH gene, but in marmoset, as in rhesus monkey and man, the putative GH gene is one of a cluster of closely related genes.

[Studies of the origin of Chinese domestic fowls]

A total of 539 bases fragment of mitochondrial DNA D-loop region of six domestic chicken breeds (30 individuals) were sequenced and compared to that of red junglefowl, grey junglefowl, green junglefowl and Lafayette's junglefowl issued in GenBank, and the phylogenetic trees for the chickens constructed based on the D-loop sequences. The results indicated that the four species of genus Gallus had great differences between each other, the G. g. domesticus was the next of kin to red junglefowl in Thailand and its adjacent regions, and near of kin to red junglefowl in Indonesian, Lafayette's junglefowl, grey junglefowl and green junglefowl one by one in proper order, suggesting that the red junglefowl in Thailand and its neighbour areas sufficed as the matriarchic ancestor of Chinese domestic fowls. It was also discovered that the two subspecies of Thailand i.e. G. g. gallus and G. g. spadiceus should belong to one subspecies because of their far lower differentiation compared to that among the domestic breeds.

The enhanced anticaries efficacy of a sodium fluoride and dicalcium phosphate dihydrate dentifrice in a dual-chambered tube. A 2-year caries clinical study on children in the United States of America

PURPOSE

To clinically evaluate and compare a dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate (Test Dentifrice delivering 0.243% sodium fluoride), to a dentifrice containing 0.243% sodium fluoride in a silica base (Positive Control Dentifrice).

MATERIALS AND METHODS

This study was conducted in harmony with the published 1988 American Dental Association guidelines for studies geared toward the comparison of fluoride dentifrices. This 2-yr caries clinical study employed a double-blind, parallel-group design, and involved 5-17 yr-old children from the Central and South areas of Florida and from the Lares area of Puerto Rico. Qualifying subjects were stratified according to age and sex, and were randomly assigned to the two treatment groups, with multiple subjects in the same household all assigned to the dentifrice randomly allocated to the first among them. Caries examinations were conducted in accordance with U.S. Food and Drug Administration guidelines for the clinical evaluation of drugs to prevent dental caries. Two calibrated examiners performed all the measurements. After treatment assignment, study participants were instructed to brush their teeth at home with their assigned dentifrice at least twice daily. Brushing instructions were reinforced by indoctrination in proper oral hygiene techniques by dental professionals, supplemented by pamphlets supplied by the sponsor and yearly mailings to participants, emphasizing good oral hygiene and the need to enforce compliance with the study. Post-baseline examinations were performed after 1 yr of product use, and again after 2 yrs of product use.

RESULTS

Two thousand five hundred six (2,506) subjects completed this 2-yr study. For these subjects, the mean caries scores (DMFS, decayed, missing and filled tooth surfaces) at baseline were 2.29 for the Test Dentifrice group, and 2.47 for the Positive Control Dentifrice group. For caries increments after 1 yr, the respective means were 0.69 for the Test Dentifrice group and 0.81 for the Positive Control Dentifrice group. Finally, after 2 yrs, the mean caries increments were 1.25 for the Test Dentifrice group, and 1.46 for the Positive Control Dentifrice group. No statistically significant difference was indicated between the treatment groups at baseline or between the 1-yr caries increment scores. However, there was a statistically significant difference in the 2-yr caries increment scores between the treatment groups. Relative to the Positive Control Dentifrice group, the Test Dentifrice group presented a 14.38% reduction in caries increment scores at 2 yrs. In accordance with the procedures and standards provided by the published guidelines of the American Dental Association for the comparison of the anticaries efficacy of fluoride dentifrices, the results of this study support the conclusion that the dentifrice system in a dual-chambered tube, wherein one chamber contained sodium fluoride in a silica base and the other chamber contained dicalcium phosphate dihydrate, delivering 0.243% sodium fluoride, provided a superior level of anticaries efficacy than did the dentifrice containing 0.243% sodium fluoride in a silica base.

Incidence rates and populations at risk for spinal cord injury: A regional study

STUDY DESIGN

A 6 year retrospective study was conducted.

OBJECTIVES

The populations at risk for spinal cord injury (SCI) in the northwestern Kentucky (KY) and southern Indiana (IN) regions were identified following examination of the causes and factors associated with SCI.

SETTING

The database included patients primarily from the surrounding KY and IN counties admitted to the University of Louisville (U of L) Hospital.

METHOD

Specification of SCI patient demographics, injury causes and related factors was achieved utilizing the hospital's trauma institute database and an extensive review of patient medical records.

RESULTS

An adjusted average incidence rate of 27.1 cases per million per year was obtained for this region. A high rate of SCI was found for the youngest age group, 14-24 year olds, and for African Americans. A high frequency of injuries was also observed for adults between the ages of 25-39 years. Motor vehicle accidents (MVA) were the leading cause of SCI. Contributing factors included alcohol and widespread non-use of vehicle safety precautions.

CONCLUSIONS

In addition to the high proportion of youth at risk for SCI, a higher proportion of older adults with SCI was observed for this region compared to other studies. Because the primary source of transportation in this area is the use of private vehicles, rather than public transportation, greater effort is warranted in emphasizing the potential risks of combining driving with alcohol consumption and non-use of seatbelts.

[Molecular evolution of the Thr-Gly region of the period gene in Drosophila and some dipterans]

In this study, the molecular evolution of the Thr-Gly region of the period gene was characterized, using dipteran groups with close, medium, and long distance phylogenetic relationship. No sexual selection or other positive selection was found to be acting on the Thr-Gly region. The evolutionary rate of the Thr-Gly region in nasuta subgroup was 10.4 x 10(-9) synonymous substitution/site/year. The divergence time of the nasuta subgroup of Drosophila was estimated to be 1-3 mya. A phylogenetic tree of Drosophila genus was reconstructed, which is well supported by evidences from archaebiological and biogeographical studies, The molecular evolutionary pattern of Thr-Gly region was discussed.

Embryonic brain precursors transplanted into kainate lesioned rat spinal cord

Embryonic day 14 rat cerebral cortex-derived precursors were expanded with FGF2 and labeled with BrdU prior to being transplanted into the kainic acid-lesioned adult rat spinal cord. While these precursors give rise to cells with neuronal, astrocytic and oligodendroglial phenotypes vitro, they remained largely undifferentiated up to 12 weeks in vivo. Numerous BrdU-labeled cells were found in injured gray matter, and also lining the dilated central canal that sometimes accompanies these lesions. BrdU-labeled cells never co-expressed Map2ab, rarely co-expressed GFAP but often co-expressed nestin, even after 12 weeks in vivo. These observations suggest that the environment of the kainic acid-injured spinal cord is not hostile to transplanted embryonic cerebral cortex-derived precursors, but also is not conducive to their neuronal differentation.

Function and regulation of cholecystokinin octapeptide, β-endorp hin and gastrin in anorexic infantile rats treated with ErBao Granules

AIM: To study the role of cholecystokinin octapeptide (CCK-8), β-endorphin (β-EP), and gastrin in an anorexic infantile rat model and no subsequent regulation of nose peptides by the Yunpi complex prescription ErBao Granule.

METHODS: We fed infantile rats with special prepared forage. A liquid extract of ErBao Granule was administered to the rats daily for 3 weeks, CCK-8, β-EP, and gastrin concentrations in hypothalamus, gastric antrum, and plasma of the rats were measured by radioimmunoassay, and were compared with controls.

RESULTS: Treatment of rats with ErBao Granule inhibited CCK-8 secretion and increased β-EP and gastrin secretion. CCK-8 concentration in hypothalamus and plasma of model control group increased significantly and correlated negatively with food intake of models, respectively. β-EP concentration in gastric antrum and plasma of model control group decreased significantly and showed a positive correlation with food intake of models, respectively. Hypothalamus concentration of β-EP was similar in models and controls. Gastrin concentration in gastric antrum of models was lower than in the blank control group, and correlated positively to food intake of models. Finally, CCK-8 concentrations in plasma of rats showed a positive correlation with plasma β-EP (r = -0.68, P < 0.05).

CONCLUSION: The increased plasma and hypothalamus concentration of CCK-8, decreased gastric antrum and plasma level of β-EP, and decreased gastric antrum concentration of gastrin are associated significantly with the anorexia of infantile anorexic rat models produced by special forage. ErBao Granule can reverse these changes, which may be the major mechanisms of ErBao Granule simulating feeding.

[Effects of running armored car on dynamic posture equilibrium]

Objective. To study the effects of training in running armored car on dynamic posture equilibrium. Method. Dynamic posture was tested pre- and post running armored car in 56 healthy men. Result. Compared to pre-training, certain equilibrium scores of sensory organization test condition 1 (P<0.05), 2 (P< 0.001), and 3 (P< 0.001) decreased significantly, while those of condition 4 (P<0.001) and 6 (P< 0.001) increased significantly. The static proprioception score (SOT2/SOT1 x 100) (P< 0.01) decreased significantly, while visual sensory score (SOT4/SOT1 x 100, P <0.01) and dynamic proprioception (SOT (4+5+6)/SOT(1+2+3) x 100, P<0.001) increased significantly post-training. The motor strategy scores of sensory organization test condition 2 (P<0.01) and 3 (P<0.001) significantly decreased. Conclusion. The results demonstrated that training in a running armored car influenced postural equilibrium and sensory organization.

[Mitochondrial DNA sequence variations of Zhuang ethnic group in Guangxi]

The mtDNA hypervariable segment I sequences (515bp) were sequenced in 83 Zhuangs from Gunngxi Province, with the aim to learn more about the origin and genetic structure of the current Zhuangs. 66 haplotypes were identified in the samples, with 71 sites showing polymorphism. Phylogenetic analysis of the 66 haplotypes suggests that there are geographic differentiation in current Zhuangs, and those from the 4 geographic regions (Nanning, Hechi, Baise and Liuzhou) have different distribution frequencies in the cluster I, II and III in the tree. More than 50% individuals from Liuzhou and Hechi converge into cluster II, while those from Nanning and Baise have high frequency in cluster I. Combined with the analysis of the reported data, the Zhuang ethnic group shows remote affinity to those from North China, whereas it is close to those in South China. The frequencies of the radiation groups in Zhuangs, together with the phylogenetic relationship of the Zhuang ethnic group in the tree suggest that the Zhuang is a typical south population.

[Different evolution rule of SRY gene between hominoid and Old World monkey]

The complete SRY gene of P. nemaeus and M. arctiodes were amplified by using PCR and sequenced. Combined with the same regions of other primate animals, sequence analysis confirmed the conservation of HMGbox. In molecular phylogenetic tree constructed, we made the Ka/Ks value pairwise comparison of HMGbox flanking sequences both intra- and inter- Hominoid and the Old World monkey. To our interest, the pairwise comparison of species in Hominoid suggested a higher Ka/Ks ratio than that in the Old World monkey or between the Old World monkey and marmoset, which showed existent of different pattern of evolution. In addition, in Hominoid Ka/Ks ratio for HMGbox sequences was obviously on the increase. The rate of nonsynonymous substitutions per nonsynonymous site is faster than that of synonymous substitutions per synonymous site in Hominoid (driven by positive directional selection). Our analysis suggested that it might be resulted from functional change of this gene and the system error or the close relationship among Hominoid species. It is also supposed that the positive selection was functioned at the beginning of the divergence of Hominoid species.

[The development and application of HP-I closed thoracic cavity drainer]

The closed thoracic cavity drainer is equipped with a general standard infusion bottle as the drainage bottle, which can be easily supplied by all hospitals. Therefore, the new drainer is a very practical, cheap medical device of easy operation.

Melanocortin-1 receptor gene variants in four Chinese ethnic populations

There is strong relationship between melanocortin-1 receptor (MC1R) gene variants and human hair color and skin type. Based on a sequencing study of MC1R gene in 50 individuals from the Uygur, Tibetan, Wa and Dai ethnic populations, we discuss the occurrence of 7 mc1r variants consisting of 5 nonsynonymous sites (Val60Leu, Arg67Gln, Val92Met, Arg163Gln and Ala299Val) and 2 synonymous sites (C414T and A942G), among which C414T and Ala299Val were reported for the first time. Confirmation and analysis were also made of 122 individuals at three common point mutations (Val92Met, Arg163Gln, A942G) using PCR-SSCP. The frequency of Arg163Gln variant varies in the four ethnic populations, with percentage of 40%, 85.0%, 66.2% and 72.7%, respectively, while those of Val92Met and A942G are roughly similar in these four populations. The different environments, migration and admixture of various ethnic groups in China might have impact on the observed frequency of Arg163Gln.

A topical mixture for preventing, abolishing, and treating autophagia and self-mutilation in laboratory rats

The dysesthesia and paresthesia that occurs in laboratory rats after spinal cord injury and peripheral nerve injury results in autophagia and self-mutilation. This self-destructive behavior interferes with functional assessments in designed studies and jeopardizes the health of the injured rat. We developed a topical mixture that prevents, abolishes, and treats autophagia and self-mutilation. When the mixture is applied to the limb, its bitterness effectively prevents the rat from licking and biting the limb. In addition, the mixture has antiseptic properties.

[Chemokine and chemokine receptor gene families--a phylogenetic study]

In this study, the phylogenetic trees of chemokines and chemokine receptors are produced, based on distance parsimonious method, using available amino acid sequences from GenBank. The divergence of chemokine or chemokine receptors was earlier than the divergence of vertebrates. While the divergence of homologous genes from different species is in well congruent with phylogenetic relationship of those species. The molecular evolutionary rates of chemokine receptor genes are different, with CXCR4 gene scored the lowest. Chemokines and chemokine receptors originated from few ancient genes. The similarity between the virus encoded chemokines or chemokine receptors with those of host genes is a consequence of evolutionary mimicry.

[Phylogenetic relationships among Viperidae, Crotalinae based on mitochondrial 12S rRNA sequence variations]

This paper analyzed the phylogenetic relationships and classification of pit vipers (Viperidae, Crotalinae) based on mitochondrial 12S rRNA gene sequence variations. We have sequenced mtDNA 12S rRNA gene about 370 bp fragment from Gloydius saxatilis Emelianov, Gloydius shedaoensis Zhao, Gloydius ussurriensis (Emelianov), Trimeresurus stejnegeri Schmidt and Deinagkistrodon acutus, Gloydius brevicaudus (Stejneger) from two different localities, respectively. Combined with the sequence of Dinodon semicarinatus from GenBank, we have constructed two molecular phylogenetic trees using both Maximum-parsimony analysis and Neighbor-joining. Our results support the following conclusions: (1) Deinagkistrodon is a valid genus; (2) we also discussed the origin of Gloydius shedaoensis and showed it is a subspecies of Gloydius saxatilis; (3) Gloydius brevicaudsu and Gloydius ussurriensis are classified two species.

Molecular phylogenetics and the origins of placental mammals

The precise hierarchy of ancient divergence events that led to the present assemblage of modern placental mammals has been an area of controversy among morphologists, palaeontologists and molecular evolutionists. Here we address the potential weaknesses of limited character and taxon sampling in a comprehensive molecular phylogenetic analysis of 64 species sampled across all extant orders of placental mammals. We examined sequence variation in 18 homologous gene segments (including nearly 10,000 base pairs) that were selected for maximal phylogenetic informativeness in resolving the hierarchy of early mammalian divergence. Phylogenetic analyses identify four primary superordinal clades: (I) Afrotheria (elephants, manatees, hyraxes, tenrecs, aardvark and elephant shrews); (II) Xenarthra (sloths, anteaters and armadillos); (III) Glires (rodents and lagomorphs), as a sister taxon to primates, flying lemurs and tree shrews; and (IV) the remaining orders of placental mammals (cetaceans, artiodactyls, perissodactyls, carnivores, pangolins, bats and core insectivores). Our results provide new insight into the pattern of the early placental mammal radiation.

Peptide models of the helical hydrophobic transmembrane segments of membrane proteins: interactions of acetyl-K2-(LA)12-K2-amide with phosphatidylethanolamine bilayer membranes

High-sensitivity differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to study the interaction of a synthetic alpha-helical hydrophobic transmembrane peptide, acetyl-Lys(2)-(Leu-Ala)(12)-Lys(2)-amide [(LA)(12)], and members of a homologous series of n-saturated diacylphosphatidylethanolamines (PEs). In the lower range of peptide mole fractions, the DSC endotherms exhibited by the lipid/peptide mixtures consist of two components. The temperature and cooperativity of the sharper, higher temperature component are very similar to those of pure PE bilayers and are almost unaffected by variations in the protein/lipid ratio. However, the fractional contribution of this component to the total enthalpy changes decreases with increases in peptide concentration, and this component completely disappears at higher protein mole fractions. The other component, which is less cooperative and occurs at a lower temperature, predominates at higher protein concentrations. These two components of the DSC endotherm have been assigned to the chain-melting phase transitions of peptide-nonassociated and peptide-associated PE molecules, respectively. Although the temperature at which the peptide-associated PE molecules melt is progressively decreased by increases in (LA)(12) concentration, the magnitude of this downward shift is progressively greater as the length of the PE hydrocarbon chain decreases. As well, mixtures of (LA)(12) with the longer chain PEs exhibit unusual biomodal enthalpy variations, suggesting peptide immiscibility in thicker gel state bilayers. Moreover, the enthalpy of the chain-melting transition of the peptide-associated PE does not decrease to zero even at high peptide concentrations, indicating that (LA)(12) attenuates but does not abolish the cooperative gel/liquid-crystalline phase transition of the lipids with which it is in contact. Our FTIR spectroscopic data indicate that (LA)(12) remains in a predominantly alpha-helical conformation in liquid-crystalline PE bilayers of various hydrophobic thickness but that the helical conformation is altered in gel-state PE bilayers generally, probably due to peptide lateral aggregation. These data also suggest that (LA)(12) significantly disorders the hydrocarbon chains of adjacent PE molecules in both the gel and liquid-crystalline states, relatively independently of lipid hydrocarbon chain length. Many aspects of PE/(LA)(12) interactions exhibit a different dependence on the hydrophobic thickness of the host bilayer than was observed in our previous study of (LA)(12)-phosphatidylcholine (PC) model membranes [Zhang et al. (1995) Biochemistry 34, 2362-2371]. The differing effects of (LA)(12) incorporation on PE and PC bilayers is ascribed primarily to the much stronger lipid polar headgroup interactions characteristic of the former system. Finally, the considerable differences observed in the behavior of (LA)(12) and the related polyleucine-based peptide P(24) in both PC and PE bilayers indicate that the structure of the hydrophobic core of alpha-helical transmembrane peptides can affect their conformational plasticity and state of aggregation and thus the nature of their interactions with different phospholipid bilayers.

Pluripotent stem cells engrafted into the normal or lesioned adult rat spinal cord are restricted to a glial lineage

Proliferating populations of undifferentiated neural stem cells were isolated from the embryonic day 14 rat cerebral cortex or the adult rat subventricular zone. These cells were pluripotent through multiple passages, retaining the ability to differentiate in vitro into neurons, astrocytes, and oligodendrocytes. Two weeks to 2 months after engraftment of undifferentiated, BrdU-labeled stem cells into the normal adult spinal cord, large numbers of surviving cells were seen. The majority of the cells differentiated with astrocytic phenotype, although some oligodendrocytes and undifferentiated, nestin-positive cells were detected; NeuN-positive neurons were not seen. Labeled cells were also engrafted into the contused adult rat spinal cord (moderate NYU Impactor injury), either into the lesion cavity or into the white or gray matter both rostral and caudal to the injury epicenter. Up to 2 months postgrafting, the majority of cells either differentiated into GFAP-positive astrocytes or remained nestin positive. No BrdU-positive neurons or oligodendrocytes were observed. These results show robust survival of engrafted stem cells, but a differentiated phenotype restricted to glial lineages. We suggest that in vitro induction prior to transplantation will be necessary for these cells to differentiate into neurons or large numbers of oligodendrocytes.

Evolutionary history of the mtDNA 9-bp deletion in Chinese populations and its relevance to the peopling of east and southeast Asia

In total, 1218 Chinese from twelve ethnic groups and nine Han geographic groups were screened for the mtDNA 9-bp deletion motif. The frequency of the 9-bp deletion in all samples was 14.7% but ranged from 0% to 32% in the various ethnic groups. Three individuals had a triplication of the 9-bp segment. Phylogenetic and demographic analyses of the mtDNA hypervariable segment 1 (HVS 1) sequences suggest that the 9-bp deletion occurred more than once in China. The majority of the Chinese deletion haplotypes (about 90%) have a common origin as a mutational event following an initial expansion of modern humans in eastern Asia. Other deletion haplotypes and the three haplotypes with a 9-bp triplication may have arisen independently in the Chinese, presumably by replication error. HVS1 haplotype analysis suggests two possible migration routes of the 9-bp deletion in east and southeast Asia. Both migrations originated in China with one route leading to the Pacific Islands via Taiwan, the other to southeast Asia and possibly the Nicobar Islands. Along both routes of peopling, a decrease in HVSI diversity of the mtDNA haplotypes is observed. The "Polynesian motif (16217T/C, 16247A/G, and 16261C/T)" and the 16140T/C, 16266C/A, or C/G polymorphisms appear specific to each migration route.

Lasting paraplegia caused by loss of lumbar spinal cord interneurons in rats: no direct correlation with motor neuron loss

OBJECT

The aims of this study were to investigate further the role played by lumbar spinal cord interneurons in the generation of locomotor activity and to develop a model of spinal cord injury suitable for testing neuron replacement strategies.

METHODS

Adult rats received intraspinal injections of kainic acid (KA). Locomotion was assessed weekly for 4 weeks by using the Basso, Beattie, and Bresnahan (BBB) 21-point locomotor scale, and transcranial magnetic motor evoked potentials (MMEPs) were recorded in gastrocnemius and quadriceps muscles at 1 and 4 weeks. No changes in transcranial MMEP latency were noted following KA injection, indicating that the descending motor pathways responsible for these responses, including the alpha motor neurons, were not compromised. Rats in which KA injections included much of the L-2 segment (10 animals) showed severe locomotor deficits, with a mean BBB score of 4.5 +/- 3.6 (+/- standard deviation). Rats that received lesions rostral to the L-2 segment (four animals) were able to locomote and had a mean BBB score of 14.6 +/- 2.6. Three rats that received only one injection bilaterally centered at L-2 (three animals) had a mean BBB score of 3.2 +/- 2. Histological examination revealed variable loss of motor neurons limited to the injection site. There was no correlation between motor neuron loss and BBB score.

CONCLUSIONS

Interneuron loss centered on the L-2 segment induces lasting paraplegia independent of motor neuron loss and white matter damage, supporting earlier suggestions that circuitry critical to the generator of locomotor activity (the central pattern generator) resides in this area. This injury model may prove ideal for studies of neuron replacement strategies.