Changes in evoked cortico-motor responses in the rat during aging and after partial decortication

Some changes of the organization of cortical motor representations, which were revealed by means of the intracortical microstimulation (ICMS) in aged rats after unilateral partial decortication, were true consequences of the decortication, but had no significant relationship to the aging. Distributions of latent periods of contralateral hind-leg EMG-responses to the ICMS had no significant shifts both during aging and after the surgery. Values of short-latency responses of ipsilateral proximal and axial muscles to the ICMS were in late time periods, from 8 to 16 months after surgery, significantly lower than ones of contralateral homonymous muscles. It is supposed, that ipsi- and bilateral short-latency responses to the ICMS in proximal and axial muscles of operated rats during late time periods are relayed through some pathways from the brain stem to the spinal cord.     

Changes in the parameters of locomotion following partial extirpation of the motor cortex in white rats

Quantitative locomotion changes have been studied in the norm and in different periods after local ablation of motor projection of hind paw in the right hemisphere of 5-16 weeks white rats. The length and width of step gradually increase with the age, and coefficients of gait asymmetry reflecting individual characteristics, are relatively stable in intact animals. Local decortication is accompanied by significant shifts of all locomotion parameters clearly expressed in the first days after ablation. The most sensitive characteristic of gait anomaly is the standard deviation of half-step. In 5 weeks after ablation a lag is observed of operated rats behind the control ones in all parameters. Load application contributes to revealing of locomotion parameters shifts from the norm in later periods after decortication. In 9 and 11 weeks after surgery, the signs of supercompensation are observed in a number of parameters.     

Patterns of DNA Barcode Variation in Canadian Marine Molluscs

Background

Molluscs are the most diverse marine phylum and this high diversity has resulted in considerable taxonomic problems. Because the number of species in Canadian oceans remains uncertain, there is a need to incorporate molecular methods into species identifications. A 648 base pair segment of the cytochrome c oxidase subunit I gene has proven useful for the identification and discovery of species in many animal lineages. While the utility of DNA barcoding in molluscs has been demonstrated in other studies, this is the first effort to construct a DNA barcode registry for marine molluscs across such a large geographic area.

Methodology/Principal Findings

This study examines patterns of DNA barcode variation in 227 species of Canadian marine molluscs. Intraspecific sequence divergences ranged from 0–26.4% and a barcode gap existed for most taxa. Eleven cases of relatively deep (>2%) intraspecific divergence were detected, suggesting the possible presence of overlooked species. Structural variation was detected in COI with indels found in 37 species, mostly bivalves. Some indels were present in divergent lineages, primarily in the region of the first external loop, suggesting certain areas are hotspots for change. Lastly, mean GC content varied substantially among orders (24.5%–46.5%), and showed a significant positive correlation with nearest neighbour distances.

Conclusions/Significance

DNA barcoding is an effective tool for the identification of Canadian marine molluscs and for revealing possible cases of overlooked species. Some species with deep intraspecific divergence showed a biogeographic partition between lineages on the Atlantic, Arctic and Pacific coasts, suggesting the role of Pleistocene glaciations in the subdivision of their populations. Indels were prevalent in the barcode region of the COI gene in bivalves and gastropods. This study highlights the efficacy of DNA barcoding for providing insights into sequence variation across a broad taxonomic group on a large geographic scale.     

Expression of miRNAs in ovine fetal gonads: potential role in gonadal differentiation

Background  

Gonadal differentiation in the mammalian fetus involves a complex dose-dependent genetic network. Initiation and progression of fetal ovarian and testicular pathways are accompanied by dynamic expression patterns of thousands of genes. We postulate these expression patterns are regulated by small non-coding RNAs called microRNAs (miRNAs). The aim of this study was to identify the expression of miRNAs in mammalian fetal gonads using sheep as a model.     

Molecular evolution of mitochondrial 12S RNA and cytochrome b sequences in the pantherine lineage of Felidae

DNA sequence comparisons of two mitochondrial DNA genes were used to infer phylogenetic relationships among 17 Felidae species, notably 15 in the previously described pantherine lineage. The polymerase chain reaction (PCR) was used to generate sequences of 358 base pairs of the mitochondrial 12S RNA gene and 289 base pairs of the cytochrome b protein coding gene. DNA sequences were compared within and between 17 felid and five nonfelid carnivore species. Evolutionary trees were constructed using phenetic, cladistic, and maximum likelihood algorithms. The combined results suggested several phylogenetic relationships including (1) the recognition of a recently evolved monophyletic genus Panthera consisting of Panthera leo, P. pardus, P. onca, P. uncia, P. tigris, and Neofelis nebulosa; (2) the recent common ancestry of Acinonyx jubatus, the African cheetah, and Puma concolor, the American puma; and (3) two golden cat species, Profelis temmincki and Profelis aurata, are not sister species, and the latter is strongly associated with Caracal caracal. These data add to the growing database of vertebrate mtDNA sequences and, given the relatively recent divergence among the felids represented here (1-10 Myr), allow 12S and cytochrome b sequence evolution to be addressed over a time scale different from those addressed in most work on vertebrate mtDNA.      

Changes in synaptic vesicles of axon terminals of the cat motor cortex after stimulation

The relationship between the size of synaptic vesicles and their distance from the active zone of the synapse was investigated quantitatively in axon terminals on dendritic spines and branches of neurons of the cat motor cortex in a resting state (moderate barbiturate anesthesia) and after prolonged repetitive stimulation of somatosensory area SII. The dimensions of the vesicles belonging to each of the three layers distinguishable in transverse section through the terminals on electron micrographs were recorded as a diminishing variance series. They were characterized by the value of a special rank statistic. Predominance of vesicles of the smallest sizes in layer I, next to the active zone of the synapse, in both the control and the experimental material was established by statistical analysis (using, in particular, the criterion of signs and ²). After stimulation of cortico-cortical projections a significant gradient of decrease in the mean size of the vesicles from peripheral layer III to layer I developed in the terminals studied. Compared with the control, the size of the vesicles decreased both in layer I and in the intermediate layer II. The functional significance of the phenomenon is discussed.A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 7, No. 6, pp. 639–646, November–December, 1975.     

Experience with the use of horseradish peroxidase for light and electron microscope studies of interneuronal connections]

By the method based on a retrograde axonal transport of exogenous horseradish peroxidase (HRP), the origins of afferentation of the motor cortex of adult cats, kittens and albino rats were studied. HRP-positive neurons were found by light and electron microscopy in the somatosensory cortex (C1) of the ipsilateral hemisphere and in the portions of the cortex of the contralateral hemisphere which were symmetrical to the site of injection of HRP. The disposition of neurons, marked by HRP, in the Vth layer of the motor cortex suggest that these neurons may send their axons into the bundles of comissural fibres going to the motor cortex of the opposite hemisphere. This method considerably expands possibilities of revealing the origins of afferentation of the investigated portion of the nervous system and allows more complete and reliable investigation of interneuronal connections.     

Plutella australiana (Lepidoptera,Plutellidae), an overlooked diamondback moth revealed?by?DNA?barcodes

The genus Plutella was thought to be represented in Australia by a single introduced species, Plutella xylostella (Linnaeus), the diamondback moth. Its status as a major pest of cruciferous crops, and the difficulty in developing control strategies has motivated broad-ranging studies on its biology. Prior genetic work has generally supported the conclusion that populations of this migratory species are connected by substantial gene flow. However, the present study reveals the presence of two genetically divergent lineages of this taxonin Australia. One shows close genetic and morphological similarity with the nearly cosmopolitan Plutella xylostella. The second lineage possesses a similar external morphology, but marked sequence divergence in the barcode region of the cytochrome c oxidase I gene, coupled with clear differences in genitalia. As a consequence, members of this lineage are described as a new species, Plutella australiana Landry & Hebert, which is broadly distributed in the eastern half of Australia.