The Lurcher mutation identifies delta 2 as an AMPA/kainate receptor-like channel that is potentiated by Ca(2+)

Neurodegeneration in Lurcher (Lc) mice results from constitutive activation of delta 2, a subunit of ionotropic glutamate receptors (GluRs) with unknown natural ligands and channel properties. Homo-oligomeric channels of GluR-delta2 with the Lurcher mutation (GluR-delta 2(Lc)) expressed in human embryonic kidney 293 cells showed a doubly rectifying current-voltage relation reminiscent of the block by intracellular polyamines in AMPA/kainate channels. Similarly, the fraction of the total current carried by Ca(2+) was approximately 2-3%, comparable with that found in Ca(2+)-permeable AMPA/kainate channels. Currents through GluR-delta 2(Lc) channels were also potentiated by extracellular Ca(2+) in a biphasic manner, with maximal potentiation occurring at physiological concentrations of Ca(2+). We examined the functional role of the Q/R site in GluR-delta 2(Lc) by replacing glutamine with arginine. Analogous to AMPA/kainate receptors, GluR-delta 2(Lc)(R) channels showed no voltage-dependent block by intracellular polyamines and were nominally impermeable to Ca(2+). The potentiation by Ca(2+), however, remained intact. Hence, GluR-delta 2(Lc) channels are functionally similar to the AMPA/kainate receptor channels, consistent with the high-sequence identity shared by these subunits within the channel-lining M2 and M3 segments. Furthermore, potentiation by Ca(2+) and a permeability to Ca(2+) comparable with that of AMPA/kainate receptors provide a possible cause for cell death in Lurcher mice and may contribute to cerebellar long-term depression under physiological conditions.

[Screening the trans-action factors binding to the enhancer element of rat GST-P by yeast one-hybrid system]

OBJECTIVE

To investigate the diversity of the mechanisms of rat glutathione S-transferase P (GST-P) gene expression regulation and the relation between rat GST-P gene expression and carcinogenesis. To search the trans-action factors binding to the enhancer element of rat GST-P (glutathione S-transferase P enhancer, GPE I).

METHODS

We searched the trans-action factors binding to GPE I using yeast one-hybrid system, and analyzed the DNA sequence by sequencing and computer search.

RESULTS

Two positive clones pYGPE1 and pYGPE2 were obtained. The homologies of the insert sequence of pYGPE1 nucleotide and amino acid sequences with rat c-jun cDNA were 99% and 100% respectively; the homologies of the insert sequence of pYGPE2 nucleotide and amino acid sequences with rat mitochondrial adenine nucleotide translocase cDNA were 99% and 100% respectively.

CONCLUSIONS

Rat c-Jun and mitochondrial adenine nucleotide translocase can bind to the GPE I core sequence, and they perhaps are the trans-action factors of GPE I.

[Dynamic observation and clinical significance of integrated traditional Chinese and Western medicine on interleukin-2 system, T cell and erythrocyte immune system in patients of lung cancer]

OBJECTIVE

To study the dynamic changes and its clinical significance of integrated traditional Chinese and western medicine (TCM-WM) on IL-2 system, T cell and erythrocyte immune system in patients of lung cancer.

METHODS

Forty-eight cases with lung cancer were randomly divided into two groups: TCM-WM group (group I) and the chemotherapy group (group II); and 20 healthy subjects were simultaneously compared. The relevant immune indices, clinical symptoms and signs, changes of solid tumor and living quality were dynamically observed.

RESULTS

(1) The serum IL-2 level of lung cancer patients were significantly lower, while sIL-2R level higher than that of the healthy subjects. And they were raised and lowered respectively after treatment, especially in the group I, but different from the control group yet. And there were highly negative correlation between IL-2 and sIL-2R levels. (2) The percentage of CD3, CD4 and the ratio CD4/CD8 were decreased markedly in both groups, except CD8 which was increased markedly. And the percentage of RBC-C3b RR was obviously lower, while that of RBC-ICR was obviously higher. But the above-mentioned indices could be improved after treatment, especially in the group I, and there were highly positive correlation between CD4/CD8 ratio and RBC-C3bRR. (3) After treatment, all above-mentioned indices were changed significantly to their corresponding opposites. However, in regard to the degree of improvement, the patients of group I were in a better position than those of group II. At the same time, improvement of their clinical symptoms and signs, change of solid tumor and living quality also showed advantageous.

CONCLUSION

The therapeutic superiority of TCM-WM on lung cancer may be related with the modulation on immune function. Thus we can say that the effect of TCM-WM is better than that of chemotherapy alone.

KORRIGAN, an Arabidopsis endo-1,4-beta-glucanase, localizes to the cell plate by polarized targeting and is essential for cytokinesis

The formation of the cell plate, a unique structure in dividing plant cells, is pivotal for cytokinesis. A mutation in the Arabidopsis KORRIGAN (KOR) gene causes the formation of aberrant cell plates, incomplete cell walls, and multinucleated cells, leading to severely abnormal seedling morphology. The mutant, designed kor1-2, was identified as a stronger allele than the previously identified kor1-1, which appears to be defective only in cell elongation. KOR1 encodes an endo-1,4-beta-d-glucanase with a transmembrane domain and two putative polarized targeting signals in the cytosolic tail. When expressed in tobacco BY2 cells, a KOR1-GFP (green fluorescence protein) fusion protein was localized to growing cell plates. Substitution mutations in the polarized targeting motifs of KOR1 caused the fusion proteins to localize to the plasma membrane as well. Expression of these mutant genes in kor1-2 plants complemented only the cell elongation defect but not the cytokinesis defect, indicating that polarized targeting of KOR1 to forming cell plates is essential for cytokinesis. Our results suggest that KOR1 plays a critical role during cytokinesis.

KORRIGAN, an Arabidopsis endo-1,4-beta-glucanase, localizes to the cell plate by polarized targeting and is essential for cytokinesis

The formation of the cell plate, a unique structure in dividing plant cells, is pivotal for cytokinesis. A mutation in the Arabidopsis KORRIGAN (KOR) gene causes the formation of aberrant cell plates, incomplete cell walls, and multinucleated cells, leading to severely abnormal seedling morphology. The mutant, designed kor1-2, was identified as a stronger allele than the previously identified kor1-1, which appears to be defective only in cell elongation. KOR1 encodes an endo-1,4-beta-d-glucanase with a transmembrane domain and two putative polarized targeting signals in the cytosolic tail. When expressed in tobacco BY2 cells, a KOR1-GFP (green fluorescence protein) fusion protein was localized to growing cell plates. Substitution mutations in the polarized targeting motifs of KOR1 caused the fusion proteins to localize to the plasma membrane as well. Expression of these mutant genes in kor1-2 plants complemented only the cell elongation defect but not the cytokinesis defect, indicating that polarized targeting of KOR1 to forming cell plates is essential for cytokinesis. Our results suggest that KOR1 plays a critical role during cytokinesis.

Maintenance of CD8(+) T-cell memory following infection with recombinant sindbis and vaccinia viruses

CD8(+) T-cell memory is critical for protection against pathogens poorly controlled by humoral immunity. To characterize two distinct vaccine vectors, the acute and memory CD8(+) T-cell responses to an HIV-1 epitope (p18) expressed by recombinant vaccinia (vp18) and Sindbis (SINp18) viruses were compared. Whereas 9 to 13% of CD8(+) splenocytes were p18 specific during the acute response to vp18, 4% were induced by SINp18 as revealed by class I tetramer staining. Increased T-cell activation by vp18 was confirmed by higher numbers of both p18-specific IFN-gamma-secreting splenocytes and activated CD8(+) and CD4(+) T cells. Although higher frequencies of p18-specific CD8(+) T cells during primary responses correlated with higher frequencies during memory, the overall decline was only two- to threefold during the transition to memory, demonstrating equally efficient maintenance of memory in SINp18- as in vp18-immune mice. Despite modest in vivo activation, SINp18-induced CD4(+) T cells secreted substantial amounts of IFN-gamma and IL-2, potentially contributing to sustained CD8(+) memory. Collectively the data indicate that Sindbis virus recombinants provide effective vaccines for inducing protective memory CD8(+) T cells in the absence of the extensive inflammation and replication associated with vaccinia virus.

Chemical-inducible systems for regulated expression of plant genes

Chemical regulation of transgene expression presents a powerful tool for basic research in plant biology and biotechnological applications. Various chemical-inducible systems based on de-repression, activation and inactivation of the target gene have been described. The utility of inducible promoters has been successfully demonstrated by the development of a marker-free transformation system and large-scale gene profiling. In addition, field applications appear to be promising through the use of registered agrochemicals (e.g. RH5992) as inducers.

[HLA-DQ molecules associated with myasthenia gravis in Chinese patients]

Myasthenia Gravis (MG) is an autoimmune disease which is a neuromuscular disorder of autoimmune origin. MG in different races or ethnic groups has different genetic susceptibility. To search for the associations of MG in the Chinese patients with HLA-DQ molecules, PCR-RFLP method was employed for genotyping HLA-DQA1 and -DQB1 genes of MG patients and the normal Chinese. The distributions of alleles of DQA1 and DQB1 in the normal Chinese and the MG patients were listed. The DQB allele, DQB1 * 0302 was positively associated with MG (RR = 2.990, Pc = 0.0307), and a negative association was found for DQA1 * 0501 (RR = 0.4166, Pc = 0.0315). DQ haplotype DQA1 * 0301-DQB1 * 0302 was significantly increased in patients when compared to controls (RR = 7.727, Pc = 0.0109).

[Study on GMA-DNA adducts in vivo]

OBJECTIVE

To investigate whether glycidly mechacrylate (GMA-DNA) adducts can be produced in various organs of rat in vivo.

METHODS

Rats divided into 5 groups were orally administrated with mutagen, GMA 31.25, 62.5, 125, 250 mg/kg respectively for 14 days. DNA adducts produced in liver, kidney, white blood cells and testis had been analyzed by nuclease P1 mediated 32P-postlabelling method.

RESULTS

Several GMA-DNA adducts were formed in various organs (in white blood cells, 4 types, liver and kidney, 3 types and testis 1 type). The amount of GMA-DNA adducts increased with GMA dosage within 0-125 mg/kg dosages, degree of the overall level of GMA-DNA adducts in various organs were kidney > liver > white blood cells > testis. N3-methacrylate-2-hdroxypropyl-deoxycytidine monophosphate was found in kidney, liver and white blood cells.

CONCLUSIONS

GMA with electrophilic group could react with negatively charged centers on DNA and form GMA-DNA adducts.

Visualization of alpha9 acetylcholine receptor expression in hair cells of transgenic mice containing a modified bacterial artificial chromosome

The alpha9 acetylcholine receptor (alpha9 AChR) is specifically expressed in hair cells of the inner ear and is believed to be involved in synaptic transmission between efferent nerves and hair cells. Using a recently developed method, we modified a bacterial artificial chromosome containing the mouse alpha9 AChR gene with a reporter gene encoding green fluorescent protein (GFP) to generate transgenic mice. GFP expression in transgenic mice recapitulated the known temporal and spatial expression of alpha9 AChR. However, we observed previously unidentified dynamic changes in alpha9 AChR expression in cochlear and vestibular sensory epithelia during neonatal development. In the cochlea, inner hair cells persistently expressed high levels of alpha9 AChR in both the apical and middle turns, whereas both outer and inner hair cells displayed dynamic changes of alpha9 AChR expression in the basal turn. In the utricle, we observed high levels of alpha9 AChR expression in the striolar region during early neonatal development and high levels of alpha9 AChR in the extrastriolar region in adult mice. Further, simultaneous visualization of efferent innervation and alpha9 AChR expression showed that dynamic expression of alpha9 AChR in developing hair cells was independent of efferent contacts. We propose that alpha9 AChR expression in developing auditory and vestibular sensory epithelia correlates with maturation of hair cells and is hair-cell autonomous.

[Role of glutathione S-transferase pi in tumor drug resistance]

OBJECTIVE

To establish the cytologic expressing system for the glutathione S-transferase pi (GST-pi) cDNA.

METHODS

The pSV-GT, a recombinant plasmid containing rat GST-pi cDNA and the pSV-neo, a vector plasmid, were transfected the HeLa cells respectively and then G418 resistant colonies were isolated. The degree of the expression of GST-pi mRNA in the resultant cell lines was estimated by in situ hybridization using Digoxin-labelled probe cDNA. Cytotoxicity of variant anticancer drugs on the transfected cells were estimated by MTT assays.

RESULTS

Two subclones, HeLa/pSV-GT, and HeLa/pSV-neo, which transfected respectively by pSV-GT and pSV-neo, were established. HeLa/pSV-GT expressed significantly high degree of the GST-pi mRNA, where as both the HeLa/pSV-neo and the HeLa cell lines showed the similar but negligible degree of the GST-pi mRNA expression. Moreover, HeLa/pSV-GT cells were insensitive to adriamycin, mitomycin C, and cisplatinum as compared to HeLa/pSV-neo. Concentrations of adriamycin producing 50% inhibition (IC50) to HeLa/pSV-GT was 70.13 micrograms/ml, highly elevated 6.78-fold of that of HeLa/pSV-neo, to which IC50 was 10.34 micrograms/ml.IC50 of mitomycin and cisplatinum to HeLa/pSV-GT were 10.95 and 16.52 micrograms/ml respectively, slightly but significantly higher than those to HeLa/pSV-neo, which were 7.48 and 13.70 micrograms/ml. But the cytotoxicity of vincristine on the two cell lines were not significantly different.

CONCLUSIONS

These findings suggeste that HeLa/pSV-GT cell line, after being transfected with GST-pi cDNA, acquired drug-resistance property and the overexpression of GST-pi mRNA may contribute to the multidrug resistance of HeLa/pSV-GT cells. This cell line, as a stable cytogenetic system, will contribute more for the observation of GST-pi and drug resistance.

Mutations in a novel retina-specific gene cause autosomal dominant retinitis pigmentosa

Inherited retinal diseases are a common cause of visual impairment in children and young adults, often resulting in severe loss of vision in later life. The most frequent form of inherited retinopathy is retinitis pigmentosa (RP), with an approximate incidence of 1 in 3,500 individuals worldwide. RP is characterized by night blindness and progressive degeneration of the midperipheral retina, accompanied by bone spicule-like pigmentary deposits and a reduced or absent electroretinogram (ERG). The disease process culminates in severe reduction of visual fields or blindness. RP is genetically heterogeneous, with autosomal dominant, autosomal recessive and X-linked forms. Here we have identified two mutations in a novel retina-specific gene from chromosome 8q that cause the RP1 form of autosomal dominant RP in three unrelated families. The protein encoded by this gene is 2,156 amino acids and its function is currently unknown, although the amino terminus has similarity to that of the doublecortin protein, whose gene (DCX) has been implicated in lissencephaly in humans. Two families have a nonsense mutation in codon 677 of this gene (Arg677stop), whereas the third family has a nonsense mutation in codon 679 (Gln679stop). In one family, two individuals homozygous for the mutant gene have more severe retinal disease compared with heterozygotes.

Formation of glycidyl methacrylate-DNA adducts in vivo

In in vivo test, rats were orally administrated with glycidyl methacrylate (GMA) at respective doses of 250 mg/kg, 125 mg/kg and 62.5 mg/kg, 31.25 mg/kg and solvent as control for 14 days. DNA adducts produced in the liver, kidney, blood and testis were analyzed by RP-HPLC and nuclease P1 mediated 32P-postlabelling method. Results showed that several potential GMA-DNA adducts were formed in various organs (4 adducts in blood, 3 adducts in liver and kidney, 1 adduct in testis). A linear dose-response relationship was observed within certain dose levels. The relative adduct labeling values failed to further increase any more when the concentration went up to 125 mg/kg. The order of adduct level with GMA was kidney, liver, blood and testis. The GMA adduct N3-methacrylate-2-hydroxypropyl-dCMP was found in kidney, liver and blood. These results indicated that GMA could react with negatively charged centers on DNA and form GMA-DNA adducts. If carcinogen induced DNA damage exceeds the ability of repair systems, gene mutation is induced. Therefore, study on molecular mechanism of gene mutation induced by DNA adducts is not only an important part of chemical-carcinogenesis, but also provides information on critical biomarkers for monitoring human exposure to genetic toxins.

Degradation of chondroitin sulfate proteoglycan enhances the neurite-promoting potential of spinal cord tissue

The contribution of chondroitin sulfate proteoglycan (CSPG) in the suppression of axonal growth in rat spinal cord has been examined by means of an in vitro bioassay in which regenerating neurons are grown on tissue section substrata. Dissociated embryonic chick dorsal root ganglionic neurons were grown on normal and injured adult spinal cord tissue sections treated with chondroitinases. Neuritic growth on normal spinal cord tissue was meager. However, both the percentage of neurons with neurites and the average neurite length were substantially greater on sections treated with chondroitinase ABC. Enzymes that specifically degraded dermatan sulfate or hyaluronan were ineffective. Neuritic growth was significantly greater on injured (compared to normal) spinal cord and a further dramatic increase resulted from chondroitinase ABC treatment. Neurites grew equally within white and gray matter regions after chondroitinase treatment. Observed increases in neurite outgrowth on chondroitinase-treated tissues were largely inhibited in the presence of function-blocking laminin antibodies. These findings indicate that inhibitory CSPG is widely distributed and predominant in both normal and injured spinal cord tissues. Additionally, inhibitory CSPG is implicated in negating the potential stimulatory effects of laminin that might otherwise support spinal cord regeneration.

Role of dNTPs in mutagenesis

The induced mutation frequency by alkylating mutagen glycidyl methacrylate (GMA) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was investigated with or without perturbation of deoxyribonucleoside triphosphate (dNTP) pools; the influence of short treatment at different concentrations of GMA or MNNG on dNTP pools was also explored. The results indicated that the induced mutation frequency increased greatly at high dosages of mutagen (GMA approximately 64 micrograms/ml, MNNG approximately 8 micrograms/ml) and the perturbation on dNTP pools was carried out before the treatment of mutagen; the short treatment with mutagen could induce distinct fluctuations of dNTP pools, but different mutagen might have different effects on dNTP pools. According to the results of the present study and other reports in literature, we conclude that dNTP pools may be the targets of alkylating mutagens and the fluctuations of dNTP pools are closely associated with mutagenesis.

Neuronal matrix metalloproteinase-2 degrades and inactivates a neurite-inhibiting chondroitin sulfate proteoglycan

Chondroitin sulfate proteoglycans (CSPGs) are implicated in the regulation of axonal growth. We previously reported that the neurite-promoting activity of laminin is inhibited by association with a Schwann cell-derived CSPG and that endoneurial laminin may be inhibited by this CSPG as well [Zuo J, Hernandez YJ, Muir D (1998) Chondroitin sulfate proteoglycan with neurite-inhibiting activity is upregulated after peripheral nerve injury. J Neurobiol 34:41-54]. Mechanisms regulating axonal growth were studied by using an in vitro bioassay in which regenerating embryonic dorsal root ganglionic neurons (DRGn) were grown on sections of normal adult nerve. DRGn achieved slow neuritic growth on sections of normal nerve, which was reduced significantly by treatment with metalloproteinase inhibitors. Similar results were obtained on a synthetic substratum composed of laminin and inhibitory CSPG. DRGn expressed the matrix metalloproteinase, MMP-2, which was transported to the growth cone. Recombinant MMP-2 inactivated the neurite-inhibiting CSPG without hindering the neurite-promoting potential of laminin. Similarly, neuritic growth by DRGn cultured on normal nerve sections was increased markedly by first treating the nerve sections with MMP-2. The proteolytic deinhibition by MMP-2 was equivalent to and nonadditive with that achieved by chondroitinase, suggesting that both enzymes inactivated inhibitory CSPG. Additionally, the increases in neuritic growth resulting from treating nerve sections with MMP-2 or chondroitinase were blocked by anti-laminin antibodies. From these results we conclude that MMP-2 provides a mechanism for the deinhibition of laminin in the endoneurial basal lamina and may play an important role in the regeneration of peripheral nerve.

Transcriptional activation of heat shock factor HSF1 probed by phosphopeptide analysis of factor 32P-labeled in vivo

Mapping of tryptic phosphopeptides of heat shock factor 1 (HSF1) from non-stressed or moderately heat-stressed HeLa cells, labeled in vivo by [32P]orthophosphate, revealed four major phosphopeptides A to D. Heat stress drastically increased phosphopeptide signals. To identify target peptides and amino acids and to correlate phosphorylation and transactivation function, phosphopeptide maps were produced of LexA-human HSF1 chimeras and mutant derivatives thereof, and transactivation activities of original and mutant chimeras were compared. LexA-HSF1 chimeras were previously shown to be regulated identically to HSF1, except that they transactivate promoters with LexA-binding sites instead of hsp promoters. The patterns of phosphopeptides of LexA-HSF1 and endogenous HSF1 were similar. Analysis of single residue substitutions suggested that phosphopeptide C is peptide VKEEPPSPPQSPR (297-309) phosphorylated on Ser-307 but not Ser-303. Substitution of Ser-307 but not Ser-303 caused deregulation of factor activity. Mapping of several constitutively active chimeras associated unphosphorylated peptide C with the transcriptionally active HSF1 conformation, suggesting that dephosphorylation of this peptide (at Ser-307) may either be an integral step in the activation process or serve to maintain the active conformation of HSF1. Exploiting this correlation, indirect evidence was obtained that activation domains of HSF1 interact with the distantly located regulatory domain to maintain the factor in an inactive state.

A high-resolution genetic map of the nervous locus on mouse chromosome 8

The nervous (nr) mutant mouse displays two gross recessive traits: both an exaggeration of juvenile hyperactivity and a pronounced ataxia become apparent during the third and fourth postnatal weeks. Using an intersubspecific intercross, we have established a high-resolution map of a segment of mouse chromosome 8 that places the nr locus in a genomic segment defined by D8Rck1 on the centromeric end and D8Mit3 on the telomeric end. This map position places the nr locus within the BALB/cGr congenic region of the C3HeB/ FeJ-nr strain, confirming the accuracy of our study. We used this map position to identify and evaluate three genes-ankyrin 1, cortexin, and farnesyltransferase-as candidates for the nr gene. These three genes were eliminated from consideration but allowed us to establish the conservation of synteny between the region containing the nr locus and a segment of the short arm of human chromosome 8 (8p21-p11.2). Finally, the incomplete penetrance of the nr phenotype led us to perform a screen for modifier loci, and we present evidence that such a nervous modifier locus may exist on mouse chromosome 5.

The human glutamate receptor delta 2 gene (GRID2) maps to chromosome 4q22

We isolated the human glutamate receptor delta 2 (GRID2) gene, which has 97.0% identity in amino acid sequence to the mouse glutamate receptor delta 2 (Grid2) gene. We subsequently mapped this gene to human chromosome 4q22 by radiation hybrid mapping and by hybridization to two overlapping human yeast artificial chromosomes that are located in 4q22. The Grid2 gene, which is mutated in lurcher (Lc) mice, maps to mouse chromosome 6. Thus, the mapping of the GRID2 gene to human chromosome 4q22 confirms and refines a region of synteny between mouse and human genomes.

Chondroitin sulfate proteoglycan with neurite-inhibiting activity is up-regulated following peripheral nerve injury

Numerous findings support the possibility that highly sulfated proteoglycans are inhibitory molecules which, at high concentration relative to growth-promoting signals, may regulate or guide axonal growth. Although most studies implicate sulfated proteoglycans in the poor regenerative capacity of the central nervous system, inhibitory proteoglycans also may play an important role in the successful regeneration of axons within peripheral nerve. Cultured rat schwannoma and Schwann cells produce chondroitin sulfate proteoglycan (CSPG) which binds to and inhibits the neurite-promoting activity of laminin [Muir et al. (1989) J. Cell Biol. 109:2353]. In the present study, we found a similar neurite-inhibiting activity associated with CSPG isolated from normal adult rat sciatic nerve. Following nerve crush injury, this inhibitory activity was increased sevenfold in regenerating nerve distal to the injury. This increase was largely attenuated by in vivo administration of the proteoglycan synthesis inhibitor beta-D-xyloside. In normal adult nerve, immunolabeling for CSPG core protein was concentrated in slender bands surrounding axon-Schwann cell units and within nodes of Ranvier. Following nerve crush injury, immunolabeling of CSPG and laminin became more intense in distal nerve and CSPG increased within endoneurium and surrounding nerve sheaths. Embryonic dorsal root ganglionic neurons cultured on longitudinal nerve sections extended neurites along the exposed surfaces of Schwann cell basal lamina. The length of neurites was increased 58% on normal nerve sections pretreated with chondroitinase. Even though laminin levels were elevated in basal lamina of injured nerve, neuritic growth on sections of injured nerve was not significant increased unless sections were pretreated with chondroitinase. These results indicate that inhibitory CSPG is up-regulated in injured nerve and plays a role in regulating axonal regeneration.

[The Raman scatting of carbon nanotubes]

Raman scattering measurements of the cathode deposite produced by carbon arc discharge method and graphite was repotred. The results indicate that the inner core of the deposite containing large quantities of carbon nanotubes undergoing crystallization process. Carbon nanotube is one kind of micro-crystal of quasi-graphite.

Development of 11 beta-hydroxysteroid dehydrogenase expression in the rat cochlea

11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) catalyzes the transformation of active glucocorticoid (GC) steroids to inactive 11-oxosteroids, as well as the reverse reaction. 11 beta-HSD was previously demonstrated specifically in the spiral ligament of the lateral cochlear wall where it was co-localized with adrenal steroid receptors. These findings imply that 11 beta-HSD regulates binding of corticoids to their inner ear receptors. The GC receptor expression initially occurs around the critical maturation period of the cochlear duct. 11 beta-HSD, which is an integral part of the cochlear steroid receptor system, could indirectly affect glucocorticoid-mediated induction processes. In this study the expression of 11 beta-HSD was studied in the postnatal rat cochlea from the 3rd to 30th postnatal day. Bouin's fixed, paraffin-embedded cochlear sections were processed for immunocytochemical detection of 11 beta-HSD using polyclonal antibodies against 11 beta-HSD. 11 beta-HSD expression appeared at the 12th postnatal day at low levels in spiral ligament tissues. From the 15th postnatal day, 11 beta-HSD expression was stronger and similar to that of the adult cochlea. No additional inner ear tissue region expressed 11 beta-HSD enzyme during the observed period. 11 beta-HSD expression coincides with the onset of functional maturity of the rat cochlear duct. The expression of 11 beta-HSD is preceded by the expression of GC receptors which appeared at the 7th postnatal day in the rat cochlea. These results further suggest an integrative role of the cochlear steroid receptor system in the homeostasis and functional maturation of the cochlea.

A new allele of the lurcher gene, lurcherJ

A new neurological mouse mutation that arose spontaneously in a BALB/cByJ stock displays a semidominant pattern of inheritance. In the heterozygote, this mutation results in an early loss of Purkinje cells in the cerebellum, which is followed by the overt symptom of an ataxic gait first observed at postnatal day 13 (P13). A portion of animals homozygous for the mutation die within P0; the remaining homozygotes die by P25. The mutation maps to mouse Chromosome (Chr) 6 between markers D6Rck314 and D6Rck361, a chromosomal segment that contains the lurcher (Lc) locus. The Lc mutation is also semidominant and has a strikingly similar phenotype. A cross between a new mutant (Nm) heterozygote and an Lc heterozygote yields double heterozygotes, animals that carry both mutations, with a phenotype similar to that of both Nm and Lc homozygotes. The similarity in phenotype, the colocalization of the two loci on mouse Chr 6, and the positive result of the allelism test demonstrate that the new mutation is an allele of the Lc gene.

Neurodegeneration in Lurcher mice caused by mutation in delta2 glutamate receptor gene

Lurcher (Lc) is a spontaneous, semidominant mouse neurological mutation. Heterozygous Lurcher mice (Lc/+) display ataxia as a result of a selective, cell-autonomous and apoptotic death of cerebellar Purkinje cells during postnatal development. Homozygous Lurcher mice (Lc/Lc) die shortly after birth because of a massive loss of mid- and hindbrain neurons during late embryogenesis. We have used positional cloning to identify the mutations responsible for neurodegeneration in two independent Lc alleles as G-to-A transitions that change a highly conserved alanine to a threonine residue in transmembrane domain III of the mouse delta2 glutamate receptor gene (GluR delta2). Lc/+ Purkinje cells have a very high membrane conductance and a depolarized resting potential, indicating the presence of a large, constitutive inward current. Expression of the mutant GluR delta2(Lc) protein in Xenopus oocytes confirmed these results, demonstrating that Lc is inherited as a neurodegenerative disorder resulting from a gain-of-function mutation in a glutamate receptor gene. Thus the activation of apoptotic neuronal death in Lurcher mice may provide a physiologically relevant model for excitotoxic cell death.