Isolation of a mutant that changes genomic packaging specificity in phi6

Bacteriophage phi6 has a genome of three segments of double-stranded RNA enclosed in a polyhedral procapsid. Plus strand transcripts of the segments are packaged in a serially dependent fashion in which S can package alone, M depends on S, and L depends on S and M. We have isolated a mutant form of the virus in the carrier state that has lost segment S. This finding presented an apparent anomaly with respect to the packaging program. Sequencing of gene 1 of segment L in this virus showed a translational change of arginine to glycine at the 14th position. Procapsids prepared from cDNA containing this mutation show behavior in in vitro packaging that is consistent with the phenotype of the mutant virus. The procapsids are able to package segment S alone, but this RNA is present in reduced amounts when the other segments are present. Segments M and L package without dependence on segment S. The mutant virus appears to produce procapsids that are at the second stage of the packaging program.

Cerebellar brain-derived neurotrophic factor-TrkB defect associated with impairment of eyeblink conditioning in Stargazer mutant mice

In the spontaneous ataxic mutant mouse stargazer, there is a selective reduction of brain-derived neurotrophic factor (BDNF) mRNA expression in the cerebellum. BDNF protein levels in the cerebellum are reduced by 70%. Despite normal levels of full-length and truncated TrkB receptor, constitutive and neurotrophin-4/5-induced tyrosine phosphorylation was significantly reduced in several signal transduction molecules, including phospholipase-Cgamma1, erk1, and erk2. Morphological examination revealed an increased number of external granule cells at postnatal day 15 and the presence of abnormal neurons resembling immature granule cells in the adult. These abnormalities are associated with a severe impairment in the acquisition of classical eyeblink conditioning, indicating cerebellar malfunction. Our data suggest that normal BDNF expression and TrkB signal transduction in the cerebellum are necessary for learning and plasticity in this model.

Impaired eye-blink conditioning in waggler, a mutant mouse with cerebellar BDNF deficiency

In addition to their trophic functions, neurotrophins are also implicated in synaptic modulation and learning and memory. Although gene knockout techniques have been used widely in studying the roles of neurotrophins at molecular and cellular levels, behavioral studies using neurotrophin knockouts are limited by the early-onset lethality and various sensory deficits associated with the gene knockout mice. In the present study, we found that in a spontaneous mutant mouse, waggler, the expression of brain-derived neurotrophic factor (BDNF) was selectively absent in the cerebellar granule cells. The cytoarchitecture of the waggler cerebellum appeared to be normal at the light microscope level. The mutant mice exhibited no sensory deficits to auditory stimuli or heat-induced pain. However, they were massively impaired in classic eye-blink conditioning. These results suggest that BDNF may have a role in normal cerebellar neuronal function, which, in turn, is essential for classic eye-blink conditioning.

Mutation in AP-3 delta in the mocha mouse links endosomal transport to storage deficiency in platelets, melanosomes, and synaptic vesicles

The mouse mutant mocha, a model for the Hermansky-Pudlak storage pool deficiency syndrome, is characterized by defective platelets, coat and eye color dilution, lysosomal abnormalities, inner ear degeneration, and neurological deficits. Here, we show that mocha is a null allele of the delta subunit of the adaptor-like protein complex AP-3, which is associated with coated vesicles budding from the trans-Golgi network, and that AP-3 is missing in mocha tissues. In mocha brain, the ZnT-3 transporter is reduced, resulting in a lack of zinc-associated Timm historeactivity in hippocampal mossy fibers. Our results demonstrate that the AP-3 complex is responsible for cargo selection to lysosome-related organelles such as melanosomes and platelet dense granules as well as to neurotransmitter vesicles.

Directed changes in the number of double-stranded RNA genomic segments in bacteriophage phi6

Bacteriophage Phi6 has a genome of three segments of double-stranded RNA. The segments are designated S, M, and L. Each segment has a unique packaging site, pac, near the 5' end of the plus strand. The plus strands of the segments are normally packaged in the order S, M, L. Chimeras of segment M and S in which segment M is at the 5' end of the plus strand can be stably incorporated into the virion; however, an independent segment S must be included along with normal segment L, even if it contains no active genes. A chimera of segment M and S in which segment S is at the 5' end of the plus strand can be stably incorporated into the virion along with normal segment L to form a two-segment genome. A chimera of segments S, M, and L in which the packaging sequence is that of S can also form a stable nonsegmented genome. These findings are consistent with a model that we have proposed for the packaging of the Phi6 genome.

Neutrophil maturation of CD34+ cells from peripheral blood and bone marrow in serum-free culture medium with PIXY321 and granulocyte-colony stimulating factor (G-CSF)

Bone marrow (BM) or peripheral blood (PB) CD34+ cells were cultured for 12 days in serum-free culture medium containing PIXY321 (IL-3/ GM-CSF fusion protein) with or without periodic supplements of granulocyte-colony stimulating factor (G-CSF). The cultures were evaluated at day 12 for total cell proliferation (fold increase from day 0), neutrophil differentiation by flow cytometry, using dual staining with CD15-FITC and CD11b-PE, and morphology using Wright-Giemsa and granule staining. In cultures containing PIXY321 where 6000 U/ml of G-CSF was added days 0 and 6, there was no significant difference (p > or = 0.05) in cell proliferation or the percent of CD15+/CD11b+ cells when compared with cultures with PIXY321 alone. ELISA analysis showed G-CSF levels had declined by 90% after 3 days of culture. Further studies were performed to assess the benefit of supplementing lower concentrations of G-CSF (600 U/ml) at more frequent intervals. A significant increase (p < or = 0.05) in cell proliferation and percent CD15+/CD11b+ was observed when G-CSF was added on days 0, 3, 6, and 9 (every 3 days) as compared with those cultures with PIXY321 alone. CD34+ cell proliferation without G-CSF was 19.6 +/- 4.8-fold, with G-CSF added on days 0 and 6 was 28.7 +/- 6.4-fold, and with G-CSF added on days 0, 3, 6, and 9 was 45.9 +/- 10.6-fold. Percent of CD15+/CD11b+ cells was 19.0 +/- 4.6%, 38.2 +/- 7.2%, and 58.5 +/- 6.5%, respectively, in these cultures. We observed more CD15+/CD11b+ cells, myelocytes/metamyelocytes, and secondary granule staining in cultures with G-CSF added on day, 0, 3, 6, and 9 as compared with cultures with G-CSF added on days 0 and 6 or no G-CSF added. We conclude that PIXY321 and G-CSF act synergistically on the in vitro proliferation and neutrophil differentiation of BM and PB CD34+ cells and that frequent supplements of G-CSF facilitate neutrophil differentiation.

Elevated mRNA expression of brain-derived neurotrophic factor in retinal ganglion cell layer after optic nerve injury

PURPOSE

Recent studies show that exogenous brain-derived neurotrophic factor (BDNF) can promote retinal ganglion cell survival in vivo and in vitro. BDNF is expressed by a subpopulation of cells in the ganglion cell layer (GCL). To investigate whether endogenous BDNF may play a role in neuronal protection after ganglion cell trauma, BDNF expression in the retina was examined after optic nerve (ON) injury.

METHODS

The optic nerve in Sprague-Dawley rats was crushed intraorbitally posterior to the optic disc. For controls, the optic nerve on the opposite side in each animal was similarly exposed but was not crushed. After intervals of 6 hours to 6 weeks, eye tissues were processed for in situ hybridization, Northern blot, and RNase protection assay using radiolabeled rat riboprobes.

RESULTS

After ON injury, BDNF expression was significantly elevated in cells restricted to the GCL, and more cells demonstrated expression of BDNF than were observed in the controls. Elevated BDNF expression was first observed at 24 hours, peaked at 48 hours, and declined to the basal level 2 weeks after ON injury. Quantitative analysis showed a fivefold to sixfold increase in the number of BDNF-positive cells and a 54% increase in BDNF signal intensity in individual cells in the GCL 48 hours after ON injury. In control retinas without ON injury, BDNF expression was localized to some cells in the GCL, as was observed in normal eyes without surgery. Northern blot and RNase protection assay demonstrated a 38% elevation in BDNF expression above control levels 48 hours after ON injury.

CONCLUSIONS

These results indicate that cells in the GCL can upregulate gene expression of BDNF in response to ganglion cell axonal injury and suggest that endogenous BDNF may contribute to a natural neuroprotective process after ON injury.

Stoichiometric packaging of the three genomic segments of double-stranded RNA bacteriophage phi6

A model that explains the stoichiometric packaging of the chromosomes of phi6, a bacteriophage with a genome of three unique double-stranded RNA segments, is proposed and supported. Ordered switches in packaging specificity and RNA synthesis are determined by the amount of RNA within the procapsid. The plus strand of segment S binds to one of several sites on the outside of the empty procapsid. The RNA enters and the procapsid expands so that the S sites are lost and M sites appear. Packaging of segment M results in the loss of the M sites and the appearance of the L sites. Packaging of L readies the particle for minus-strand synthesis. If any of the segments is less than normal size, packaging of that class of segments continues until the normal content of RNA for that segment is packaged and the binding sites then change.

Lead exposure at an early age substantially increases lead retention in the rat

It has been hypothesized that the high rate of bone remodeling during childhood and the consequent high calcium and lead turnover result in a substantial reduction in bone lead stores so that much of the lead incorporated in bone during childhood does not persist into adulthood. We studied the effect of age at lead exposure on blood and organ concentrations of lead, calcium, and zinc 1-5 months after termination of lead ingestion. Blood and organ lead concentrations and contents 4 weeks after lead exposure ceased were significantly higher in the rats exposed beginning at 5 weeks of age than in those exposed beginning at 10 or 15 weeks old. Bone lead declined as the time since exposure increased. Despite this trend, the rats exposed when youngest had bone lead concentrations at 20 weeks after the termination of lead exposure that were higher than those of the other rats only 4 weeks after cessation of lead ingestion. Multiple regression analysis demonstrated that age at lead exposure remained a significant predictor of blood and organ lead concentrations and contents even after the inclusion of total lead consumed, body weight, and age at organ harvesting in the regression analysis. There were only small differences in organ calcium and zinc concentrations among treatment groups except for kidney calcium. The results do not support the hypothesis of rapid depletion of bone lead stores in young animals, but rather suggest that younger age at lead exposure is associated with greater lead retention and toxicity even in the absence of continued lead exposure.

An in vitro system for the investigation of heterologous RNA recombination

Bacteriophage Phi6 has a genome of three segments of double-stranded RNA enclosed in a polyhedral procapsid. Purified procapsids are capable of the specific packaging of viral plus strands and the synthesis of their complementary minus strands. The genomic segments of Phi6 are capable of heterologous recombination. We have prepared an in vitro system containing purified procapsids that is capable of packaging plus strands of the genomic segments and synthesizing minus strands on these templates. The system generates heterologous recombination products when stimulated by having one of the plus strands incapable of serving as a template for minus strand synthesis. Recombinants were produced upon transfection of spheroplasts with the in vitro packaged and replicated RNA. Sites of recombination were not found to be localized in particular regions of either the donor or the recipient strands.

[Preparation and characterization of sinopak-s-DEAE weak-anion exchange packing for high performance liquid chromatography]

High-performance ion exchange chromatography (HPIEC) is extensively used in the separation of peptides and proteins, especially in the biotechnology process. The principle of separation of proteins is based on the changes of pH and salt concentration in the mobile phase for the chromatographic model. A new synthetic method with the help of a catalyst for the bounding of diethylaminoethyl group on a home-made macro-pore silica sphere (the trade mark is Sinopak-s, with sphere size of 5 microm and pore diameter of 100 nm) was developed in our laboratory for the application of the scale-up separation of biotechnological target products in China. The Sinopak-s-DEAE weak anion ion exchange matrix for HPLC was prepared and characterized with various proteins. The pH value and reaction time were discussed for the reaction efficiency of ligand to the silica sphere. The coverage of the DEAE ligand on the silica surface were among 1.6 to 2.1 micromol/m2 for six batches of packings. The influences of the pH value and the salt concentration in mobile phase upon the retention of proteins on the DEAE column were also discussed. A bio-activity recovery up to 98% for trypsin was arrived after purification with the DEAE column under the chosen chromatographic conditions. The capacity of matrix for BSA was 80 mg/g. The column was successfully applied to separate a mixture of several standard proteins in a linear gradient elution condition from 0 to 0.4 mol/L of NaCl in a 50 mmol/L of Tris/HCl buffer (pH 7.0) at 1.0 mL/min flow rate and detected at 280 nm wavelength.

[Determination of elemental sulfur in liquefied gas by high performance liquid chromatography]

A method for the determination of elemental sulfur in liquefied gas has been developed in this work. First, the elemental sulfur existed in the liquefied gas was extracted by chloroform and the volatile petroleum hydrocarbons vaporized with a rate of ca. 500mL/min at low temperature in an ice water bath. The elemental sulfur dissolved in chloroform was then determined by high performance liquid chromatography. The operating conditions were: 300 x 4mm i.d. mu-Bondapak C18 column; 0.8mL/min methanol-water, 95/5 (V/V), as eluent and UV-254nm detector. The average recovery of elemental sulfur was 98.3% and the minimum detectable limit was 0.1ng/g.

Large-scale selection of CD34+ peripheral blood progenitors and expansion of neutrophil precursors for clinical applications

Hematopoietic recovery after high-dose chemotherapy is characterized by an obligate period of neutropenia of approximately 8-10 days. It is postulated that if a pool of neutrophil precursors and progenitors were expanded in vitro and reinfused, the duration of neutropenia may be substantially shortened by these cells capable of providing mature neutrophils within days of reinfusion. In this study, peripheral blood progenitor cell products were obtained from six normal donors mobilized with rhG-CSF and two patients mobilized with cyclophosphamide and rhG-CSF. CD34+ cells were isolated using the Isolex immunomagnetic bead method. A mean of 8.26 x 10(7) CD34+ cells with a mean purity of 74.5% were seeded at a concentration of 1 x 10(5)/ml into a 12 day stroma-free liquid culture using gas-permeable bags. A serum-free growth medium supplemented with PIXY321 was used. On day 7, there was a mean cellular expansion of fourfold, at which time the cells were resuspended at the initial concentration, yielding a mean culture volume of 3L (1-6 L). On day 12, there was an additional mean fold cellular expansion of 10 x, achieving an overall mean fold expansion of 41 +/- 16. Cellular characterization of the expanded cells revealed predominantly neutrophil precursors by morphology (mean 70.1%) and flow cytometric analysis. A mean of 52.3% of the expanded cells expressed CD15. Immunohistochemical staining revealed a mean of 7.1% CD41a+ megakaryocytic progenitors in the final cultured cell product. Detectable CD34+ cells were maintained only in those cultures initiated with greater than 90% CD34+ cells. Colony-forming units-granulocyte-macrophage (CFU-GM) were maintained in the 12 day culture at a level similar to the preculture number, whereas CFU mixed were depleted in all samples. On day 0, there were few CFU clusters (colonies containing fewer than 50 cells) identified, but by day 12, a mean total of 8.3 x 10(6) CFU clusters were identified. On day 12, the expanded cells were harvested and pooled using the Fenwal CS3000 Plus blood cell separator and resuspended in Plasma-Lyte-A with 1% human serum albumin. The mean harvest recovery of expanded progenitors was 91%, with a mean viability of 86%.

Immunocytochemistry and flow cytometry evaluation of human megakaryocytes in fresh samples and cultures of CD34+ cells

Adhering platelets on the cell surface can give misleading results when doing flow cytometry analysis of platelet/megakaryocyte-specific glycoprotein (GP) antigens to enumerate megakaryocytes (MK) in mobilized peripheral blood (PB), apheresis products, or normal bone marrow (BM). For adequate quantification and characterization of human MK, we examined samples with parallel flow cytometry and immunocytochemistry. MK expression of GP IIb/IIIa (CD41a), GP Ib (CD42b), GP IIIa (CD61), CD45, CD33, and CD11b, and their light scatter properties were evaluated. Fresh samples of low density mononuclear cells (MNC) or purified CD34+ cells contained 10-45% of platelet-coated cells. Platelet-coated cells decreased dramatically after several days of incubation in a serum-free medium supplemented with stem cell factor, IL-3, IL-6, and/or GM-CSF. Between d 9-12, flow cytometry detected a distinct CD41a+ MK population, 8.3 +/- 1.3% in BM CD34 cell cultures (n = 7) and 13.1 +/- 2.1% in PB CD34 cell cultures (n = 14), comparable to immunocytochemistry data (7.8 +/- 1.9% and 16.4 +/- 2.6%, respectively). CD41a stained a higher proportion of MK than CD42b or CD61, while CD42b+ or CD61+ cells contained more morphologically mature MK than CD41a+ cells in cultures containing aplastic serum. When fluorescence emission of CD41a was plotted against forward-light scatter (FSC), subpopulations of small and large MK were observed. Such subpopulations overlapped in CD41a intensity and side-light scatter (SSC) property. Most MK co-expressed CD45 (98.8% positive) but not CD33 (80.7% negative) or CD11b (88.9% negative). Our data indicate that flow cytometry can be used effectively to identify MK. However, caution should be taken with samples containing adherent platelets.

NT-4/5 protects against adrenalectomy-induced apoptosis of rat hippocampal granule cells

Adrenalectomy (ADX) in rats has been shown to induce apoptosis of hippocampal granule cells. We tested whether neurotrophins are able to protect hippocampal neurons in this neurodegeneration model. Acid fucshsin stain was used to identify pyknotic cells in ADX rats treated for 4 days with NT-3, NT-4-5 or cytochrome-C, as a control protein. Cytochrome-C injections slightly decreased cell death on the ipsilateral side. NT-3 did not further promote this effect. Significantly less cell death was observed bilaterally in hippocampus treated with NT-4/5. TUNEL end labeling also confirmed the results. Our results demonstrated that NT-4/5, but not NT-3, promotes hippocampal neuron survival in adrenalectomized rats. They further show that injections of a control solution can induce a local protective effect.

Selective failure of brain-derived neurotrophic factor mRNA expression in the cerebellum of stargazer, a mutant mouse with ataxia

In search of the possible involvement of neurotrophic factors in inherited neurological disease, we examined brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3) mRNA expression patterns in the ataxic mutant mouse stargazer (stg). Using in situ hybridization, we found a selective and near total reduction in BDNF mRNA in the cerebellar granule cell layer. NT-3 or NGF mRNA expression in the cerebellum was normal. Northern blot analysis demonstrated a 70% reduction in BDNF mRNA in the whole cerebellum. BDNF mRNA levels in other mutant brain regions were unchanged. Absence of BDNF mRNA in granule cells was observed at postnatal age (P15), coincident with the onset of ataxia, and expression levels failed to follow the developmental increase found in the wild type at later ages (P20 and P30). Despite the severe BDNF reduction, in situ hybridization patterns for both the full-length and the truncated BDNF TrkB receptor mRNA were unaltered. No major cytoarchitectural abnormalities were apparent in the stg/stg cerebellum. BDNF expression in a related ataxic mutant, tottering, was unaltered. These data show that BDNF can be regulated selectively in distinct brain regions, possibly by differential activation of its multiple promoters. Absence of cerebellar granule cell BDNF mRNA in stg/stg mice demonstrates that sustained expression of this neurotrophin is not required for cell survival in the developing cerebellar cortex. Our data, in contrast, suggest a role of BDNF in maturation of specific cerebellar neurons and pathways. Early failure of cerebellar BDNF expression may be related to the ataxic phenotype in stg mice.

Weight loss alters organ concentrations and contents of lead and some essential divalent metals in rats previously exposed to lead

The loss of adipose tissue during energy restriction may be accompanied by a loss of lean body mass, including bone mass. Because most of the body lead burden is in the skeleton, we studied the effects of weight loss on the concentrations of lead in bone, blood and several organs in rats with prior but not current lead exposure. Concentrations of the essential divalent metals calcium, copper, iron, magnesium and zinc were also determined for comparison with lead. Lead-exposed rats (n = 25) were randomly assigned to one of three treatment groups: weight maintenance (WM), moderate weight loss (MWL) or substantial weight loss (SWL). For the two last-named groups, food intake was restricted for 4 wk to 70 and 40% of that of the WM group. Lead concentrations did not differ significantly (ANOVA, P > 0.05) among the three groups for blood, brain and bone. Significantly higher liver lead concentrations were observed in the SWL rats than in the WM and MWL groups. In general, organ concentrations of calcium, copper, magnesium and zinc were either lower or did not differ in the groups losing weight compared with the WM group. In contrast, organ Iron concentrations of the SWL group were higher than those of the other groups except in brain where there were no significant differences. The total liver content of lead was highest in the SWL group, but the lead content of other organs did not differ among the treatment groups. The contents of calcium, copper, magnesium and zinc generally were lower in the MWL and SWL groups than in the WM group in the liver and some of the other organs. The results demonstrate that weight loss can increase the quantity and concentration of lead in the liver, even in the absence of continued lead exposure. The data also demonstrate considerable differences among organ divalent metals in response to weight loss.

Acquisition of a fourth genomic segment in bacteriophage phi 6, a bacteriophage with a genome of three segments of dsRNA

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a polyhedral procapsid. Packaging of individual segments is dependent upon unique packaging sequences near the 5' ends of the segments. We have prepared deletions in segments L and M that decrease their size by half. Phages with these deletions can be propagated on host strains carrying plasmids with complementing genes. The deletion segments are present in two copies per virion. Phage carrying a deletion segment can acquire the transcript of the complementing plasmid if the latter has a packaging sequence. If the packaging sequence is homologous to that of the deletion segment, acquisition occurs at high frequency. If it is heterologous, then recombination exchanges the heterologous packaging sequence for a homologous one or it attaches the transcript to one of the other genomic segments.

Packaging of multiple copies of reduced-size genomic segments by bacteriophage phi 6

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a polyhedral procapsid. The preformed procapsid is capable of packaging plus-strand transcripts of the genomic segments in an in vitro reaction. Packaging of individual segments is dependent upon unique packaging sequences of about 300 nucleotides near the 5' ends of the segments. We have prepared segments L, M, and S with internal deletions that decrease their size by as much as sixfold without affecting either their packaging sequences or their 3' ends. Although packaging of genomic segments is normally very precise, with only one of each in a procapsid, these smaller segments are packaged in multiples such that the total number of nucleotides for each segment class approaches that of the normal genomic segment.

Interference with bacteriophage phi 6 genomic RNA packaging by hairpin structures

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a procapsid composed of four different proteins. The preformed procapsid is capable of packaging plus-strand transcripts of the genomic segments in an in vitro reaction. Minus-strand synthesis within the procapsid then results in the production of the double-stranded RNA genome. When plus-strand transcripts contain strong hairpin structures near the 3' ends, they are subject to heterologous recombination to remove the hairpins. We now find that the sequences bounded by the hairpins as well as those 3' to them are excluded from particles in packaging reactions. This finding implies that packaging occurs from the 5' end and that the explanation for the facilitation of recombination by the hairpin structures is the lack of entry of the 3' ends rather than a difficulty of progressing through the hairpin by the phage polymerase. Packaging of segment M is dependent on the packaging of segment S. An S segment containing a strong hairpin is able to facilitate the packaging of segment M. This result implies that there is more than one entry pore into the procapsid.

[Detection of serum procollagen III peptide in tuberculous patients]

The serum procollagen peptide (PIIIP) levels of 132 cases of tuberculosis and 37 healthy persons have been detected with RIA. The results showed that the serum PIIIP level in tuberculous patients is significantly higher than that of healthy persons (P < 0.001) and strongly related to the severe degree of activity and the size of pathological change of tuberculosis and patient condition. It suggests that there might be some significance in assessing serum PIIIP in tuberculous patients for evaluating the severity and prognosis of the illness.

In vitro packaging of individual genomic segments of bacteriophage phi 6 RNA: serial dependence relationships

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a procapsid composed of four different proteins. The preformed procapsid is capable of packaging plus-strand transcripts of the genomic segments in an in vitro reaction. The packaging of the three segments shows a strong order of dependence in that segment S packages alone, but segment M requires S and and segment L requires S and M for efficient packaging. Packaging of individual segments is dependent on unique packaging sequences of about 200 nucleotides near the 5' ends of the segments. Deletions that invade these regions destroy packaging competence for the particular segment and for the dependent segments as well. In the presence of 2 mM phosphate and at magnesium ion concentrations above 4 mM, packaging becomes progressively more independent and ultimately nonspecific with respect to phi 6 sequences.

Reconstitution of active replicase in procapsids of the segmented dsRNA bacteriophage phi 6

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a procapsid composed of four different proteins. The preformed procapsid is capable of packaging plus strand transcripts of the genomic segments in an in vitro reaction. The plus strands then serve as templates for in vitro minus strand synthesis. Procapsids that are missing protein P2 are incapable of minus strand synthesis. In this report we show that incubation with a cell extract containing P2 results in particles with normal amounts of attached P2 and with packaging and replicase activity. Particles lacking P7 have reduced replicase activity which can be augmented by incubation with extracts containing P7, but the amount of attached P7 is small.

RNA structural requirements for stability and minus-strand synthesis in the dsRNA bacteriophage phi 6

Bacteriophage phi 6 has a genome consisting of three segments of double-stranded RNA designated L, M, and S. Each virion contains one of each genomic segment. Empty procapsids can package plus-strand transcripts of the genomic segments if the 5' regions are intact. Minus-strand synthesis takes place if all three segments are packaged and if the 3' end of the segment is intact. The 3' ends of the segments contain four hairpin structures within a region of high sequence conservation. We now show that removal of parts of this region leads to progressive but limited loss of ability to support minus-strand synthesis. The defective 3' ends can be corrected by heterologous recombination with the termini of other segments. Segments that have small deletions in the conserved region and that support apparently normal minus-strand synthesis are highly recombinogenic.

Effects of smoking and drinking habits on urinary o-cresol excretion after occupational exposure to toluene vapor among Chinese workers

The relationship between the time-weighted average intensity of exposure to toluene and o-cresol concentration in shift-end urine was investigated in nearly 500 factory workers of both sexes in China, together with a similar number of nonexposed control subjects. Toluene concentration (25 ppm as geometric mean and 550 ppm as the maximum) was monitored by diffusive sampling using carbon cloth as adsorbent followed by gas chromatographic (GC) analysis. o-Cresol (up to 7 mg/l) was measured by GC after acid hydrolysis of samples. Urinary o-cresol levels correlated significantly (r = 0.69-0.77; p < 0.01) with toluene exposure in men, women and the two sexes in combination, regardless of correction for urine density. When compared with hippuric acid, however, o-cresol was less sensitive as an indicator of exposure to toluene and is not a suitable biological marker for detecting low level toluene exposure. Since urinary o-cresol level was significantly reduced by smoking, drinking, and the two habits combined, it cannot be considered reliable as an indicator of exposure to toluene.

Identification of the packaging regions within the genomic RNA segments of bacteriophage phi 6

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a procapsid composed of four different proteins. The preformed procapsid is capable of packaging plus-strand transcripts of the genomic segments in an in vitro reaction. The packaging-specific sequences on the RNA molecules are located near the 5' ends. In this study we show that the packaging sequences are different for each of the three segments and that they are of about 250 nucleotides in length. Although these sequences are consistent with some secondary structure, there is no clear structural similarity between the packaging regions of the three segments.

Localization and modulatory actions of zinc in vertebrate retina

Zinc ions are colocalized with glutamatergic synaptic vesicles in vertebrate photoreceptors and may act as a diffusible molecular switch regulating neurotransmitter signaling at two distinct sites in the outer retina. In the dark, extracellular zinc acts presynaptically at rods and cones to minimize the depletion of tonically released glutamate, and selectively reduces GABA-mediated depolarization in horizontal cells, accelerating the response kinetics of the second-order cells. The discovery of zinc ions in photoreceptors provides a mechanism for gain control, kinetics modulation, and the balance of rod vs cone output at the first synapse in the visual system.

Developmental analysis of hippocampal mossy fiber outgrowth in a mutant mouse with inherited spike-wave seizures

Neural firing patterns are an essential determinant of normal axon terminal growth and synaptic connectivity in developing afferent pathways, but the trophic role of synchronous activity in associative neural networks is less well defined. We examined the ontogeny of inherited synchronous hippocampal network discharges and mossy fiber innervation patterns at sequential stages of development in the stargazer (stg) mutant, a single-locus mouse mutation expressing generalized spike-wave epilepsy. Brief bursts of 6/sec repetitive discharges arise spontaneously on postnatal days 17-18 and persistently activate neocortical and hippocampal networks throughout adulthood. We found a striking pattern of mossy fiber recurrent axon collateral sprouting in the inner molecular layer of dentate gyrus in the adult stg hippocampus. Sprouting is not apparent until 4-6 weeks following seizure onset, but then steadily intensifies with continued synchronous activation. In the adult mutant, axon outgrowth is accompanied by a mild selective loss of hilar interneurons without gliosis. These data indicate that hypersynchronous stimulation during late postnatal brain development is linked, following a prolonged latent period, to significant fiber outgrowth and synaptic reorganization within the hippocampal formation. Since the pattern of synchronous activation in the stg mutant strongly resembles that seen in human spike-wave absence epilepsy, the synaptic plasticity described in this model has important implications for normal brain development in this common disorder.

RNA structure and heterologous recombination in the double-stranded RNA bacteriophage phi 6

Bacteriophage phi 6 has a genome of three segments of double-stranded RNA, designated L, M, and S. A 1.2-kbp kanamycin resistance gene was inserted into segment M but was shown to be genetically unstable because of a high recombination rate between segment M and the 3' ends of segments S and L. The high rate of recombination is due to complementary homopolymer tracts bounding the kan gene. Removal of one arm of this potential hairpin stabilizes the insertion. The insertion of a 241- or 427-bp lacZ' gene into segment M leads to a stable Lac+ phage. The insertion of the same genes bounded by complementary homopolymer arms leads to recombinational instability. A stable derivative of this phage was shown to have lost one of the homopolymer arms. Several other conditions foster recombination. The truncation of a genomic segment at the 3' end prevents replication, but such a damaged molecule can be rescued by recombination. Similarly, insertion of the entire 3-kb lacZ gene prevents normal formation of virus, but the viral genes can be rescued by recombination. It appears that conditions leading to the retardation or absence of replication of a particular genomic segment facilitate recombinational rescue.

[The applicability of a new stable fluorescence reagent CGE (N) for TLC measurements and spectrofluorimetry]

A new stable fluorescent reagent, CGE (N), was designed and synthesized in our laboratory. This paper presents the results of using it to detect a compound having aminogroup. Glycine as an example was derived by using CGE (N), the best condition of derivatisation reaction was pH8, T 50 +/- 1 degree C, and time 3-5 h. Spread agent was CHCl3: CH3OH:CH3COOC2H5: iceHAc (1:3:5:1). Rf of glycine-CGE (N) was 0.45, of which fluorescent spectrum Em was 356nm (at Ex = 277nm). The correlation coefficient between the fluorescent scanning area and quantity was over 0.99, the linear relation retained for 24 h, the detection limit 0.24 microgram, and the linear range 0.24-19.2 micrograms. The data revealed that stability, sensitivity and reproducibility were good. These indicate that CGE(N) is a fine fluorescent reagent for compounds having primary amino-group and this method is reliable.

Dose-dependent increase in subjective symptoms among toluene-exposed workers

A factory survey on dose-response relationship in toluene toxicity was conducted in 1985-1989 in four cities in China. The examination items consisted of personal diffusive sampling for TWA exposure measurement, questionnaires on subjective symptoms, hematology and serum biochemistry, and clinical examination including simple neurology tests. Hippuric acid was also determined in urine samples collected at the end of the shift. With selection criteria that (1) complete results were available on all study items and (2) valid toluene exposure data (i.e., toluene shared 90% or more of the exposure) were obtained for the exposed, 452 toluene-exposed workers (206 men and 246 women; toluene exposure at 24.7 ppm as GM) and 517 nonexposed controls (246 men and 271 women) were selected. The subjective symptoms increased in close association with the intensity of exposure to toluene; the threshold concentration appeared to exist at 100 ppm in the case of symptoms during work, and it might be at 50-100 ppm when symptoms off work were evaluated. During the work with exposure at higher concentrations, various symptoms possibly related to CNS or local effects (e.g., eyes, nose, and throat) were complained, and dizziness and floating sensations were identified as typical symptoms with significant dose-response relationship. Several symptoms persisted off work, most of which were apparently related but not necessarily limited to CNS effects. Hematology and serum biochemistry were essentially negative.

[Alpha 2 megaloglobulin inhibits the activation of rabbit platelet by Chinese Agkistrodon acutus venom]

An in vitro study of alpha 2-mengaloglobulin (alpha 2MG) in the inhibition of the activation of washed rabbit platelet by Chinese Agkistrodon acutus venom (CAAV) was reported. Results showed that CAAV induced aggregation rate of washed rabbit platelet was positively related to the CAAV concentration, and the maximal aggregation rate was 43.8 +/- 9.9% at the concentration of 100 micrograms/ml. Meanwhile the release of serotonin (5-HT) and platelet factor 4(PF4) from the platelet reached maximum at the CAAV concentrations of 0.81 +/- 0.07 microgram/ml and 39.08 +/- 2.78%, respectively. Platelet aggregation and the release of 5-HT and PF4 induced by CAAV could be inhibited by the addition of 0.25% alpha 2 MG into the platelets both 1 minute before and 1 minute after the addition of CAAV. When alpha 2 MG was added to the platelets 1 minute prior to the addition of CAAV, the platelet aggregation and the ultrastructural changes which could be induced by CAAV were not observed, and the morphology of the rabbit platelets was the same as that of the normal counterparts.

In vitro packaging and replication of individual genomic segments of bacteriophage phi 6 RNA

The genome of bacteriophage phi 6 contains three segments of double-stranded RNA. Procapsid structures whose formation was directed by cDNA copies of the large genomic segment are capable of packaging the three viral message sense RNAs in the presence of ATP. Addition of UTP, CTP, and GTP results in the synthesis of minus strands to form double-stranded RNA. In this report, we show that procapsids are capable of taking up any of the three plus-strand single-stranded RNA segments independently of the others. In manganese-containing buffers, synthesis of the corresponding minus strand takes place. In magnesium-containing buffers, individual message sense viral RNA segments were packaged, but minus-strand replication did not take place unless all three viral single-stranded RNA segments were packaged. Since the conditions of packaging in magnesium buffer more closely resemble those in vivo, these results indicated that there is no specific order or dependence in packaging and that replication is regulated so that it does not begin until all segments are in place.

Heterologous recombination in the double-stranded RNA bacteriophage phi 6

Bacteriophage phi 6 contains three double-stranded RNA genomic segments. We have constructed a virus with an insertion of a kanamycin resistance gene in genomic RNA segment M. The virus forms small, turbid plaques, and its genome is unstable. Virus from a single plaque contained from about 0.1 to 10% large clear-plaque forms of the virus; these were usually missing the kanamycin resistance gene, and in many cases, the resulting segment M was larger or smaller than its normal size. Sequence analysis of the genomic RNA of the apparent deletions showed that they were formed by recombination events between segment M and either segment S or L. These heterologous recombination events resulted in the loss of the kanamycin resistance gene from segment M and the replacement of the 3' end of segment M with the 3' end of segment S or L. Although the 3' ends of the single-stranded RNA transcripts of the genomic segments appear to have extensive secondary structure, the sequences at the 3' ends are not involved in the specificity of genomic packaging.

The quality of family planning services in rural China

This article provides a preliminary analysis of three aspects of service quality in four rural counties in China--the availability of contraceptive methods, information given to users, and provider knowledge about methods. Contraceptive choice and characteristics of contraceptive use by women in the study areas are also examined. The data are derived from a survey carried out by the authors during 1987, under the auspices of China's State Family Planning Commission. The survey was conducted in four rural counties located in Fujian and Heilongjiang provinces. A total of 318 married women of reproductive age were randomly selected and interviewed. All family planning service sites serving the women were visited and a sample of service providers was interviewed. No shortage of contraceptives existed in any of the counties, but variations in community wealth and local procurement practices have resulted in the acquisition of an IUD with high failure rates. Although providers believe they inform women about method choices and side effects, women were poorly informed about the methods they selected. Not all providers who insert IUDs and distribute pills were knowledgeable about contraindications and side effects of the methods. Ever-use of contraception was nearly 100 percent, but most women, especially in Heilongjiang, have only used one method: the IUD or sterilization. Improvements in quality, especially in method mix, providers' level of knowledge, and the quality and quantity of information provided to users will likely improve contraceptive continuation, client satisfaction, and women's health.

[The qualitative and quantitative analyses of protein with a novel fluorescence agent (EPQS) by fluorescent scanning on solid substrate]

We synthesized a new fluorescence agent, EPQS, which could be soluble in water and was stable in the analytical process. It was characteristic of good fluorescence parameters. Human serum albumin (HSA) was marked with EPQS and purified by the paper electrophoresis dialysis. We determined the fluorescent spectra and excitation spectra of the marked HSA, or EPQS on the cellulose acetate paper by RF-510 fluorescence spectrophotometer-thin-layer chromatoscanner. The former lambda ex = 370nm lambda em = 470nm; the latter lambda ex = 382nm lambda em = 476 nm. Then we touched different quantity of EPQS-HSA upon the cellulose acetate. The fluorescent scanning on the paper disclosed that the relationship between the quantity adopted and the fluorescence intensity is linear. These showed that the protein could be quickly determined qualitatively and quantitatively by this simple method, and EPQS was useful.

Stargazer: a new neurological mutant on chromosome 15 in the mouse with prolonged cortical seizures

We report here the initial description of the inheritance pattern, linkage mapping, and electroclinical phenotype of a recessive mutation on mouse Chromosome 15, stargazer (stg), that produces epilepsy. The salient epileptic phenotype is a syndrome of spontaneous, prolonged, generalized spike-wave cortical discharges with behavioral arrest. A second, complex, seizure pattern featuring movements during the discharge can also appear. The stg/stg mutant phenotype confirms the general principal that inherited epilepsies sharing similar cortical excitability patterns can be transmitted by single gene loci residing on different chromosomes and provides new evidence that the severity of seizure expression depends on the specific mutant gene affected.

[States of dentine surface and interface between dentine and coupling agent]

In order to research the states of dentine surface and dentine surface primed with coupling agent, we used microscope, transmission electron microscope (TEM) and solid fluorescence method. Observed under microscope, patterning of dentinal tubules and their poles was very explicit; through the view of interface between coupling agent adsorbed and human dentine powder by TEM, it was revealed that the coupling agent was adsorbed onto the dentine surface as if it "grew out" of the dentine surface; through examination of interface between the coupling agent adsorbed and dentine surface by fluorescence spectrum, which differed from that of the coupling agent or dentine surface, i.e., this fluorescence spectrum of interface changed obviously (red shift). This phenomenon indicated that there was a chemical reaction occurring between tooth surface and adsorbed coupling agent. Therefore we can conclude that the three examinations are necessary to provide the argument for establishment of chemical bonding mechanism between dentine and coupling agent.