A case of encephalitis in central Australia due to Ross River virus?
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Adult↗
Biomedical subjects
M Qiao
Publications and source records attributed to M Qiao.
Mouse chromosome classification by radial basis function network with fast orthogonal search.
This paper provides the results of our study on automatic classification of mouse chromosomes. A radial basis function neural network was compared with a multi-layer perceptron and a probabilistic neural network. The networks were trained and tested with 3723 chromosomes presented to each network as 30-point banding profiles. The radial basis function classifier trained with the fast orthogonal search learning rule provided the best unconstrained classification error rate of 12.7% which was obtained with a training set of 2250 chromosomes.
Journal Article↗
Spread of influenza A virus infection in hospitalised patients with cancer.
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Adult↗
Hepatitis G virus infection detected in a woman with intrahepatic cholestasis of pregnancy.
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Adult↗
Protective efficacy of DNA vaccines against duck hepatitis B virus infection.
The efficacy of DNA vaccines encoding the duck hepatitis B virus (DHBV) pre-S/S and S proteins were tested in Pekin ducks. Plasmid pcDNA I/Amp DNA containing the DHBV pre-S/S or S genes was injected intramuscularly three times, at 3-week intervals. All pre-S/S and S-vaccinated ducks developed total anti-DHBs and specific anti-S antibodies with similar titers reaching 1/10,000 to 1/50,000 and 1/2,500 to 1/4,000, respectively, after the third vaccination. However, following virus challenge, significant differences in the rate of virus removal from the bloodstream and the presence of virus replication in the liver were found between the groups. In three of four S-vaccinated ducks, 90% of the inoculum was removed between <5 and 15 min postchallenge (p.c.) and no virus replication was detected in the liver at 4 days p.c. In contrast, in all four pre-S/S-vaccinated ducks, 90% of the inoculum was removed between 60 and 90 min p.c. and DHBsAg was detected in 10 to 40% of hepatocytes. Anti-S serum abolished virus infectivity when preincubated with DHBV before inoculation into 1-day-old ducklings and primary duck hepatocyte cultures, while anti-pre-S/S serum showed very limited capacity to neutralize virus infectivity in these two systems. Thus, although both DNA vaccines induced high titers of anti-DHBs antibodies, anti-S antibodies induced by the S-DNA construct were highly effective in neutralizing virus infectivity while similar levels of anti-S induced by the pre-S/S-DNA construct conferred only very limited protection. This phenomenon requires further clarification, particularly in light of the development of newer HBV vaccines containing pre-S proteins and a possible discrepancy between anti-HBs titers and protective efficacy.
Animals↗
Mice lacking 5-lipoxygenase have increased cortical bone thickness.
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Animals↗
Hepatitis B virus binding to leucocyte plasma membranes utilizes a different region of the preS1 domain to the hepatocyte receptor binding site and does not require receptors for opsonins.
A quantitative assay of hepatitis B virus (HBV) binding to hepatocyte plasma membranes was adapted to show that leucocyte plasma membranes bind serum-derived HBV saturably, and that this binding is inhibited using synthetic peptides representative of the large envelope protein of HBV. Using a panel of ligand-blocking monoclonal antibodies (mAb) to opsonin receptors, it was shown that the three classes of Fc gamma R and CR3 are not major receptors for HBV on leucocytes or hepatocytes. It was also shown that HBV does not utilize the receptor for IgA, Fc alpha R, for attachment to leucocytes, despite reported sequence homology between the large envelope protein of HBV and the Fc portion of human IgA. Evidence is presented that the receptor for HBV on leucocytes may differ from the hepatocyte receptor(s), based on synthetic peptide inhibition assays of HBV binding. Furthermore, it was observed that glycosaminoglycans influence the HBV-liver and leucocyte interactions, providing evidence that HBV attachment may be a multi-stage process.
Adult↗
[Beneficial effect and mechanism of 764-3 on cognitive deficit induced by brain damage in rats].
Animal model of excitotoxic cognitive deficit induced by kainic acid bilaterally injection into caudate nucleus was successfully established in rats. Based on this model, chronic administration of 764-3 (8 mg/(kg.d), i.p.), an extract from Chinese traditional medicine, markedly improved the learning and memory impairment in the injured caudate nucleus rats. Moreover, attenuation of the neuronal loss in caudate nucleus following excitotoxic damage was observed after 764-3 treatment. In addition, results indicated that the mechanism of the effect of 764-3 may be related to the antagonism against the decline of Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activity in synaptic membrane resulted from excitotoxicity.
Animals↗
Evidence for a role of NisT in transport of the lantibiotic nisin produced by Lactococcus lactis N8.
The biosynthesis, immunity and regulation of nisin, a lanthionine-containing antimicrobial peptide produced by Lactococcus lactis, is encoded by two gene clusters, nisA/ZBTCIPRK and nisFEG. The mutant strain LAC46 with a deletion in the translocator gene nisT could not secrete nisin but nisin activity was detected from cell lysates. The nisT mutation was complemented by a NisT-expression plasmid resulting in restored capacity to secrete nisin. These results demonstrate that NisT is the transport protein dedicated to translocate nisin and that dehydration and lanthionine formation in nisin maturation can occur independently of transport.
Anti-Bacterial Agents↗
Effects of synthetic peptido-leukotrienes on bone resorption in vitro.
Peptido-leukotrienes are short-lived organic molecules known to have potent biological effects as mediators of inflammation, hypersensitivity and respiratory disorders. However, little is known concerning their effects on bone cells. We have shown previously that stromal cells isolated from a human giant cell tumor secrete 5-HETE (5-hydroxyeicosatetraenoic acid) and the peptido-leukotrienes, also known as the cysteinyl leukotrienes LTC4, LTD4, and LTE4. These eicosanoids were shown to stimulate the multinucleated giant cells obtained from these tumors to form resorption lacunae on sperm whale dentine. Here, we show that the peptido-leukotrienes also stimulate isolated avian osteoclast-like cells to form resorption lacunae and to increase their content of tartrate-resistant acid phosphatase. LTD4 increased 45Ca release from murine calvarial bone organ cultures, but not from fetal rat long bone cultures. Isolated avian osteoclast-like cells were chosen to perform receptor binding studies, as this population is the most homogeneous source of osteoclasts available. After the precursors had fused to form multinucleated cells, receptor binding assays were performed. Scatchard analysis of saturation binding data showed a single class of binding sites, with a dissociation constant (Kd) of 0.53 nM and a receptor density of 5,200 receptors per cell. Competition binding studies showed receptor specificity using a specific LTD4 receptor antagonist ZM 198,615. These data show that the peptido-leukotrienes activate highly enriched populations of isolated avian osteoclast-like cells, and also that specific LTD4 receptors are present in this cell population.
Animals↗
Leukotriene B4 stimulates osteoclastic bone resorption both in vitro and in vivo.
Upon activation, the enzyme 5-lipoxygenase converts arachidonic acid into principally three products, the peptidoleukotrienes, 5-hydroperoxyeicosatetraenoic acid (5-HETE) or the leukotriene B4. We have shown that the peptido-leukotrienes (known as LTC4, LTD4, or LTE4) and 5-HETE induce osteoclastic bone resorption and that receptors for LTD4 are present on isolated avian osteoclast-like cells. Here, we show the effects of the third metabolic product of the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism, the leukotriene LTB4, on osteoclastic bone resorption both in vivo and in vitro. Because LTB4 production is increased in a number of inflammatory conditions, it may be an important contributor to the bone loss which occurs in these disorders. LTB4 increased osteoclastic bone resorption in vivo following local administration over the calvariae of normal mice and in vitro in organ cultures of neonatal mouse calvariae. When LTB4 was injected over the calvaria of mice, there was a significant increase in bone resorption, osteoclast numbers, and eroded surfaces. LTB4 also increased the formation of resorption lacunae by isolated neonatal rat osteoclasts. Greater potency was observed with LTB4 compared with the peptido-leukotriene LTD4. This is in contrast to prostaglandins of the E series, which are reported to inhibit isolated osteoclasts. Experiments using marrow cultures suggest that LTB4 stimulates bone resorption in part by enhancing the formation of osteoclasts.
Analysis of Variance↗
Regulation of the nisin operons in Lactococcus lactis N8.
The antibiotic peptide nisin produced by Lactococcus lactis is used as a food preservative due to its activity against spores and vegetative cells of Gram-positive bacteria. The post-translational maturation of this secreted peptide includes dehydration of serine and threonine residues, lanthionine formation and a proteolytic processing of 23 amino acids from the N-terminus. Mutations in the nisZ, nisB and nisP genes of the biosynthetic nisZBTCIPRK nisin operon were made by gene replacement or integration of a plasmid. The mutations caused a drastic decrease of the transcription from the promoters upstream of the nisZBTCIPRK and nisFEG operons resulting in loss of nisin production and nisin immunity. The transcription of the nisin operons and nisin immunity could be partially restored by adding nisin to the growth medium of the cells. Nisin induction of the mutant strains also increased the level of the putative immunity NisI protein. These results showed that the nisZBTCIPRK operon is positively autoregulated and that the nisFEG operon is in the same regulon.
Cloning, Molecular↗
The cellular location and effect on nisin immunity of the NisI protein from Lactococcus lactis N8 expressed in Escherichia coli and L. lactis.
Lactococcus lactis cells secreting the lantibiotic nisin, commercially used for food preservation, must protect their cell membrane against the pore-forming activity of extracellular nisin. The nisI gene product has been suggested to be a lipoprotein, which due to the location on the extracellular surface would be an ideal candidate for an immunity protein. In vivo labelling of NisI from L. lactis N8 expressed in Escherichia coli proved that NisI is a lipoprotein. Expression of nisI in the nisin-sensitive L. lactis MG1614 strain resulted in immunologically active protein on the cytoplasmic membrane in comparable amounts to the immune strain L. lactis N8, but only to slightly increased nisin immunity, suggesting that additional proteins are needed for full immunity.
Bacterial Proteins↗
NisP is related to nisin precursor processing and possibly to immunity in Lactococcus lactis.
In this study, a plasmid was integrated into nisP, creating the first defined mutation in a nisin biosynthetic gene. The mutant strain secreted fully modified nisin with the N-terminal leader still attached. The presence of the leader was confirmed by N-terminal sequencing of the purified precursor. The dehydration and lanthionine formation of the precursor were already completed as active nisin could be formed by cleaving the leader from the inactive precursor by a trypsin treatment or by incubation with wild type cells. Nisin immunity of the NisP mutant strain was lowered to about 10% of the wild type immunity. The results show that NisP is needed fro precursor processing and for development of high immunity of nisin.
Base Sequence↗
The codon usage of the nisZ operon in Lactococcus lactis N8 suggests a non-lactococcal origin of the conjugative nisin-sucrose transposon.
An 11.6 kb area downstream from the structural gene of nisin Z in the conjugative nisin-sucrose transposon of Lactococcus lactis subsp. lactis N8 was cloned and sequenced. Analysis of the sequence revealed eight open reading frames, nisZBTClPRK, followed by a putative rho-independent terminator (delta G degrees = -4.7 kcal/mol). The C-terminal hydrophilic domain of the NisK protein is homologous to the C-termini of several histidine kinases of bacterial two-component regulator systems, such as SpaK from Bacillus subtilis and KdpD and RcsC of Escherichia coli. The nisin Z biosynthetic genes were highly similar with the genes of the nisin A operons having, however, a 0-3% difference in the amino acid sequences of the individual proteins. The codon usage of eleven genes within the same conjugative transposon was calculated and found to be strikingly different from that of other lactococcal genes. This, together with the low GC-content (32%) compared to the 38% (G+C) of the lactococcal chromosome in general strongly suggests a non-lactococcal origin of this transposon.
Amino Acid Sequence↗
Adsorption and penetration of hepatitis B virus in a nonpermissive cell line.
A cell monolayer radioimmunoassay was established to detect hepatitis B virus (HBV)-binding activity. HBV was shown to bind to HepG2 and HuH7 cells, but not to LTK- and HeLa cells. The binding activity was inhibited by peptide 21-47 from the large hepatitis B surface antigen (L-HBsAg) region, but not by other peptides from the L- and middle-HBsAg. A monoclonal antibody to L-HBsAg (MA18/7) and a polyclonal antibody to HBsAg (anti-HBs) also inhibited the binding. However, only the Fab fragment of MA18/7 showed blocking activity, suggesting that these two antibodies may neutralize virus by different mechanisms. Excess HBV was able to saturate the binding activity of HepG2 cells. The virus was also shown to be internalized; virus DNA was detected in the cytoplasmic fraction 1-2 hr postadsorption and was associated with the nuclear fraction 2 hr later. Furthermore, immunoprecipitation experiments showed that the virus DNA remained encapsidated 48 hr after internalization. Nuclear fractionation experiments showed that the encapsidated HBV DNA remained associated with the nuclear membrane. Trypsinization of intact nuclei resulted in disassociation of the nucleocapsid from the nuclear membranes, suggesting that the nuclear membrane presents a barrier to intact HBV virions or nucleocapsids. This may explain why HepG2 cells are refractile to infection although permissive for HBV replication after transfection of viral DNA.
Antibodies, Monoclonal↗
Matrix vesicles produced by osteoblast-like cells in culture become significantly enriched in proteoglycan-degrading metalloproteinases after addition of beta-glycerophosphate and ascorbic acid.
Matrix vesicles, media vesicles, and plasma membranes from three well-characterized, osteoblast-like cells (ROS 17/2.8, MG-63, and MC-3T3-E1) were evaluated for their content of enzymes capable of processing the extracellular matrix. Matrix vesicles were enriched in alkaline phosphatase specific activity over the plasma membrane and contained fully active neutral, but not acid, metalloproteinases capable of digesting proteoglycans, potential inhibitors of matrix calcification. Matrix vesicle enrichment in neutral metalloproteinase varied with the cell line, whereas collagenase, lysozyme, hyaluronidase, and tissue inhibitor of metalloproteinases (TIMP) were not found in any of the membrane fractions examined. MC-3T3-E1 cells were cultured for 32 days in the presence of ascorbic acid (100 micrograms/ml), beta-glycerophosphate (5 mM), or a combination of the two, to assess changes in matrix vesicle enzymes during calcification. Ascorbate or beta-glycerophosphate alone had no effect, but in combination produced significant increases in both active and total neutral metalloproteinase in matrix vesicles and plasma membranes, with the change seen in matrix vesicles being the most dramatic. This correlated with an increase in the formation of von Kossa-positive nodules. The results of the present study indicate that osteoblast-like cells produce matrix vesicles enriched in proteoglycan-degrading metalloproteinases. In addition, the observation that matrix vesicles contain significantly increased metalloproteinases under conditions favorable for mineralization in vitro lends support to the hypothesis that matrix vesicles play an important role in extracellular matrix processing and calcification in bone.
3T3 Cells↗
5-Lipoxygenase metabolites of arachidonic acid stimulate isolated osteoclasts to resorb calcified matrices.
Bone resorption requires cooperation between osteoclasts and mononuclear accessory cells by mechanisms which have not been elucidated. Since multinucleated cells in giant cell tumors of bone have many phenotypic and functional characteristics of normal osteoclasts, we have examined the interaction between the bone-resorbing multinucleated cells and the distinct mononuclear stromal cells from these tumors. We have found that these mononuclear cells produce an activity which stimulates both giant cells from giant cell tumors and rodent osteoclasts to resorb bone in vitro. We have identified the activity and found that it represents several products of the 5-lipoxygenase pathway of arachidonic acid metabolism, namely 5-hydroxyeicosatetraenoic acid and the leukotrienes. These data indicate that 5-lipoxygenase metabolites stimulate isolated osteoclasts to resorb bone in vitro and may represent a mechanism by which mononuclear stromal cells in human giant cell tumors communicate with the giant cells. In addition, these results may explain a possible mechanism for communication between accessory cells and osteoclasts involved in normal bone resorption.
Acid Phosphatase↗