Bacteriophage T4 self-assembly: in vitro reconstitution of recombinant gp2 into infectious phage

T4 gene 2 mutants have a pleiotropic phenotype: degradation of injected phage DNA by exonuclease V (ExoV) in the recBCD(+) host cell cytoplasm and a low burst size due, at least in part, to a decreased ability for head-to-tail (H-T) joining. The more N terminal the mutation, the more pronounced is the H-T joining defect. We have overexpressed and purified the recombinant gene 2 product (rgp2) to homogeneity in order to test its role in H-T joining, during in vitro reconstitution. When we mix extracts of heads from a gp2(+) phage infection (H(+)) with tails from a gp2(+) or gp2(-) phage infection (T(+) or T(-)), the H-T joining is fast and all of the reconstituted phage grow equally well on cells with or without ExoV activity. When heads from gene 2 amber mutants (H(-)) are used, addition of rgp2 is required for H-T joining. In this case, H-T joining is slow and only about 10% of the reconstituted phage can form plaques on ExoV(+) cells. When extracts of heads with different gene 2 amber mutations are mixed with extracts of tails (with a gene 2 amber mutation) in the presence of rgp2, we find that the size of the gp2 amber peptide of the head extract is inversely related to the fraction of reconstituted phage with a 2(+) phenotype. We conclude that free rgp2 is biologically active and has a direct role in H-T joining but that the process is different from H-T joining promoted by natural gp2 that is incorporated into the head in vivo. Furthermore, it seems that gp2 has a domain which binds it to the head. Thus, the presence of the longer gp2am mutants (with this domain) inhibits their replacement by full-length rgp2.

The effect of allergen immunotherapy on in vitro IL-4 and IFN-gamma production by peripheral mononuclear cells in house dust-sensitive Chinese patients with bronchial asthma

The IFN-gamma produced by Th1 cells and IL-4 produced by Th2 cells are two most important cytokines in the regulation of IgE production. House dust immunotherapy has been tried in the treatment of house dust-sensitive Chinese asthmatic patients with good results. We examined the influence of such treatment on in vitro IL-4 and IFN-gamma production by peripheral blood mononuclear cells in house dust-sensitive asthmatic patients. Allergen immunotherapy in house-dust sensitive asthmatic patients can significantly decrease IL-4 production from peripheral mononuclear cells (p<0.05). The production levels of IL-4 in patients without treatment had higher levels than those in patients with hyposensitization (p<0.01). Such therapy also have some effect on promotion of IFN-gamma production in asthmatic patients. In conclusion, immunotherapy with house dust may have the potential ability to shift the Th1/Th2 balance of immune response to allergens and to create a favorable cytokine microenvironment to suppress the allergic reaction in the asthmatic airway.

The epidemiology of Japanese encephalitis on Taiwan during 1966-1997

Japanese encephalitis (JE) is an endemic disease in Taiwan. A mass vaccination program of children against JE was first implemented in 1968. Along with general improvements in various aspects of living conditions over the years, the program has brought JE well under control. The main characteristics of JE epidemiology in Taiwan in the past 3 decades are as follows. The transmission mode remains unchanged-that is, the amplification stage of the virus in pigs is followed by a human epidemic each year. The frequency of JE incidence has dropped significantly. The incidence rate of confirmed cases was 2.05 per 100,000 in 1967, the highest in record, and merely 0.03 per 100,000 in 1997. Confirmed cases occur sporadically all over the island. The peak of the epidemic season has shifted from August in the 1960s to June since the 1980s. The age distribution of confirmed cases has shifted gradually from mainly children to adults. Vaccine efficacy for those having received more than 2 doses of the vaccine is estimated to be about 85%.

Preliminary studies on target antigens for the diagnosis of Trichomonas vaginalis infection

Trichomonas vaginalis, a parasitic protozoa residing in the human urogenital tract, causes one of the most common sexually transmitted diseases, trichomoniasis. Clinical diagnosis of T. vaginalis infection mainly involves a wet-mount microscopic examination, and a culture method, and both of which are either laborious or time-consuming. An immunodiagnostic strategy is under development, which is based on the fact that T. vaginalis releases various protein factors, notably proteinases, into the culture medium, some of which can also be detected in vaginal washes. These factors are closely related to the clinical presentation of trichomonad vaginitis, and thusly may serve as potential earmarks for diagnosis. We have attempted to identify the most appropriate target antigen(s) by screening and analyzing the profile of T. vaginalis antigens existing in patient's vaginal secretion, using the antiserum raised against the total secretory antigens from T. vaginalis cultures. Two T. vaginalis antigens with molecular weights near 110 KDa have been demonstrated to be useful antigens as the diagnostic markers.

[Molecular typing of Taiwanese Orientia tsutsugamushi isolates by restriction fragment profile]

Scrub typhus, which is caused by Orientia tsutsugamushi, is one of the reportable diseases in Taiwan, ROC. Positive cases seemed to be increasing in recent years and our laboratory had confirmed a total of 247 cases in 1997. In this study, 71 strains of O. tsutsugamushi were isolated from heparinized blood of the patients by cell culture, and their DNA was isolated. Two-step polymerase chain reaction was then used to amplify a specific sequence from the DNA, which was digested with restriction enzymes, Hha I and Sfa NI, for typing. With this technique, 34 strains gave rise to the same profile as that of the Kuroki type, 6 as the Karp type and 2 as the Gilliam type. The remaining 28 strains produced fragment profiles different from those of types Karp, Kato, Kawasaki, Kuroki, Gilliam and Shimokoshi and, therefore, were classified as 6 new types designated Taiwan A to Taiwan F, respectively. These strains with profiles different from those of the standard Japanese strains may represent the local mutant strains.

Anti-GD1a antibody is associated with axonal but not demyelinating forms of Guillain-Barré syndrome

Immunopathological studies suggest that the target of immune attack is different in the subtypes of Guillain-Barré syndrome (GBS). In acute motor axonal neuropathy (AMAN), the attack appears directed against the axolemma and nodes of Ranvier. In acute inflammatory demyelinating polyneuropathy (AIDP), the attack appears directed against a component of the Schwann cell. However, the nature of the antigenic targets is still not clear. We prospectively studied 138 Chinese GBS patients and found that IgG anti-GD1a antibodies were closely associated with AMAN but not AIDP. With a cutoff titer of greater than 1:100, 60% of AMAN versus 4% of AIDP patients had IgG anti-GD1a antibodies; with a cutoff titer of greater than 1:1,000, 24% of AMAN patients and none of the AIDP patients had IgG anti-GD1a antibodies. In contrast, low levels of IgG anti-GM1 antibodies (> 1:100) were detected in both the AMAN and the AIDP forms (57% vs 35%, NS). High titers of IgG anti-GM1 (>1:1,000) were more common in the AMAN form (24% vs 8%, NS). Serological evidence of recent Campylobacter infection was detected in 81% of AMAN and 50% of AIDP patients, and anti-ganglioside antibodies were common in both Campylobacter-infected and noninfected patients. Our results suggest that IgG anti-GD1a antibodies may be involved in the pathogenesis of AMAN.

Enterovirus 71 from fatal and nonfatal cases of hand, foot and mouth disease epidemics in Malaysia, Japan and Taiwan in 1997-1998

Enterovirus 71 (EV71), one of the major causative agents for hand, foot and mouth disease (HFMD), is sometimes associated with severe central nervous system diseases. In 1997, in Malaysia and Japan, and in 1998 in Taiwan, there were HFMD epidemics involving sudden deaths among young children, and EV71 was isolated from the HFMD patients, including the fatal cases. The nucleotide sequences of each EV71 isolate were determined and compared by phylogenetical analysis. EV71 strains from previously reported epidemics belonged to genotype A-1, while those from recent epidemics could be divided into two genotypes, A-2 and B. In Malaysia, genotype A-2 was more prevalent, while in Japan and Taiwan, B genotype was more prevalent. Two isolates from fatal cases in Malaysia and one isolate from a fatal case in Japan were genotype A-2. However, all isolates from three fatal cases in Taiwan belonged to genotype B. The severity of the HFMD did not link directly to certain genotypes of EV71.

Mechanism of platelet inhibition by nitric oxide: in vivo phosphorylation of thromboxane receptor by cyclic GMP-dependent protein kinase

Nitric oxide (NO) is a potent vasodilator and inhibitor of platelet activation. NO stimulates production of cGMP and activates cGMP-dependent protein kinase (G kinase), which by an unknown mechanism leads to inhibition of Galphaq-phospholipase C-inositol 1, 4,5-triphosphate signaling and intracellular calcium mobilization for several important agonists, including thromboxane A2 (TXA2). To explore the mechanism of platelet inhibition by NO, activation of platelet TXA2 receptors in the presence of cGMP was studied. The nonhydrolyzable analog 8-bromo-cyclic GMP (8-Br-cGMP) potently inhibited activation of the TXA2-specific GTPase in platelet membranes in a concentration-dependent fashion, suggesting that G kinase catalyzes the phosphorylation of some proximal component of the receptor-G protein signaling pathway. Nanomolar concentrations of G kinase were found to catalyze the phosphorylation of platelet TXA2 receptors in vitro, but not Galphaq copurifying with the TXA2 receptors in these experiments. Using immunoaffinity methods, in vivo phosphorylation of TXA2 receptors by cyclic GMP was demonstrated from 32P-labeled cells treated with 8-Br-cGMP. Peptide mapping studies of in vivo phosphorylated TXA2 receptors demonstrated cGMP mediates phosphorylation of the carboxyl terminus of the TXA2 receptor. G kinase also catalyzed the phosphorylation of peptides corresponding to the cytoplasmic tails of both alpha and beta forms of the receptor but not control peptide or a peptide corresponding to the third intracytoplasmic loop of the TXA2 receptor. These data identify TXA2 receptors as cGMP-dependent protein kinase substrates and support a novel mechanism for the inhibition of cell function by NO in which activation of G kinase inhibits signaling by G protein-coupled receptors by catalyzing their phosphorylation.

Surveillance of anti-hantavirus antibodies among certain high-risk groups in Taiwan

Hemorrhagic fever with renal syndrome is a serious health concern in neighboring countries of Taiwan, such as mainland China and Korea. In Taiwan, only two suspected cases were recorded before 1994. The first confirmed case was reported in 1995, but this proved to be imported. To study hantavirus infection in Taiwan, we tested blood collected from garbage collectors, animal handlers, patients with febrile illness of unknown origin, and field rats, the host of hantavirus, for the presence of antibody against hantavirus using an indirect immunofluorescent antibody technique. The positive rates were 1.55% (3/193), 3.45% (1/29), 1.42% (3/211), and 5.56% (9/162), respectively. The subtypes of hantavirus involved were either Hantaan-like or Seoul-like. These results showed that hantavirus may have already invaded Taiwan without our knowledge and physicians should be aware of this.

Identification of a measles virus isolate from a recent outbreak in northern Taiwan

Specimens were collected during a recent outbreak. Those specimens displaying both CPE positive in B95-8 lymphocyte cell culture and positive by IFA were checked by a RT-PCR with a specific set of measles virus primers derived from the C-terminal of the nucleoprotein. Such RT-PCR method was found ideal for routine diagnostic purposes. Product from this RT-PCR was treated for plasmid construction before transformed into E. coli. One of those transformed clones, i. e. T94, was further studied for its DNA sequence. Since T94 is found to bear several evident different characteristics from those ever published, we conclude that this isolate is neither a vaccine derived strain nor one of those reported previously with specific amino acid residues, but unique in its own right. This isolate can well be a local lineage of wild measles virus in Taiwan.

Temperature effect on the sensitivity of ELISA, PA and WB to detect anti-HIV-1 antibody and infectivity of HIV-1

BACKGROUND

This study is designed to resolve the problem of whether temperature or freeze/thaw cycle will have any impact on the sensitivity for detection of anti-HIV-1 antibody by particle agglutination (PA), enzyme-linked immunosorbent assay (ELISA) and western blotting (WB). To reduce potential risk for laboratory personnel exposed to HIV-infection, it will be useful to determine the temperature effect on HIV infectivity.

METHODS

Testing sera were incubated at different temperatures or treated with several cycles of freeze and thaw. PA, ELISA and WB were used to detect anti-HIV-antibodies, whereas syncytia formation assay and polymerase chain reaction (PCR) were applied to detect HIV-infection.

RESULTS

The data showed that certain temperature points (no treatment, 25 degrees C for 1 hr, 2 hrs and 4 hrs, 37 degrees C for 30 minutes and 60 minutes, 56 degrees C for 30 minutes and 60 minutes, 65 degrees C for 15 minutes and 30 minutes) had no impact on the testing results of ELISA, PA and WB in detection of anti-HIV-1 antibody. In addition, testing results of 50 normal human serum samples which had been heated to 56 degrees C for 30 minutes were still negative by ELISA and PA. Only the samples incubated at 65 degrees C for 60 minutes had slight differences in results. Freeze and thaw treatments of the serum did not alter anti-HIV testing results, either. Treatments of supernatant of HTLV-IIIB culture at 56 degrees C for 30 minutes and 60 minutes, 65 degrees C for 15 minutes and 30 minutes could eliminate the syncytia formation caused by HIV-infection. Further analysis of the samples by PCR was able to detect HIV-specific sequences in all the treatments.

CONCLUSIONS

Anti-HIV antibody is quite stable in serum, even when it is pre-heated to 56 degrees C for 30 minutes. Freeze and thaw treatment of serum samples up to seven cycles did not change the results, either. In addition, to minimize the potential risk of laboratory personnel exposed to HIV infection, pre-treatment of serum samples with heat at 56 degrees C for 30 minutes or 60 minutes can reduce HIV infectivity. However, laboratories still must emphasize the importance of universal precautions rather than heat-inactivation of serum to prevent occupational transmission of HIV.

[Primary surveillance of spotted fever group antibodies on rats in the Kinmen area]

The positive rate of rickettsial antibodies of 107 rats in the Kinmen area by indirect immunofluorescent antibody (IFA) technique was 0% (0/107) in typhus fever, 38.3% (41/107) in scrub typhus and 66.4% (71/107) in spotted fever group; the positive rate (42.9%) of spotted fever group of 21 rats in Taiwan island also higher than scrub typhus (19.0). It suggests that spotted fever group patients may be present in our country but have not been discovered.

Force measurement on fracture site with external fixation

A force measurement device has been designed to monitor the mechanical properties of fracture site with external fixation. Forces are measured through electric resistance strain gauges mounted on fixation framework and the measurement results are displayed on an LCD screen. The device features a force range of 0-10 kg with linearity and repeatability less than 1% and accuracy less than 0.1 kg.

Characterization of four outer membrane proteins that play a role in utilization of starch by Bacteroides thetaiotaomicron

Results of earlier work had suggested that utilization of polysaccharides by Bacteroides spp. did not proceed via breakdown by extracellular polysaccharide-degrading enzymes. Rather, it appeared that the polysaccharide was first bound to a putative outer membrane receptor complex and then translocated into the periplasm, where the degradative enzymes were located. In a recent article, we reported the cloning and sequencing of susC, a gene from Bacteroides thetaiotaomicron that encoded a 115-kDa outer membrane protein. SusC protein proved to be essential for utilization not only of starch but also of intermediate-sized maltooligosaccharides (maltose to maltoheptaose). In this paper, we report the sequencing of a 7-kbp region of the B. thetaiotaomicron chromosome that lies immediately downstream of susC. We found four genes in this region (susD, susE, susF, and susG). Transcription of these genes was maltose inducible, and the genes appeared to be part of the same operon as susC. Western blot (immunoblot) analysis using antisera raised against proteins encoded by each of the four genes showed that all four were outer membrane proteins. Protein database searches revealed that SusE had limited similarity to a glucanohydrolase from Clostridium acetobutylicum and SusG had high similarity to amylases from a variety of sources. SusD and SusF had no significant similarity to any proteins in the databases. Results of 14C-starch binding assays suggested that SusD makes a major contribution to binding. SusE and SusF also appear to contribute to binding but not to the same extent as SusD. SusG is essential for growth on starch but appears to contribute little to starch binding. Our results demonstrate that the binding of starch to the B. thetaiotaomicron surface involves at least four outer membrane proteins (SusC, SusD, SusE, and SusF), which may form a surface receptor complex. The role of SusG in binding is still unclear.

Immunopotentiating activity of Clostridium butyricum in mice

Bacterial vaccine, as generated by heat-inactivated Clostridium butyricum cells, displayed antitumor activity against sarcoma 180 in DDY mice and antimetastatic activity against B16-F10 melanoma in BDF1 mice. According to our results, the vaccine has no direct growth inhibitory effect toward the tumor cell lines tested in this study. The vaccine increased gamma-interferon production, elicited delayed type hypersensitivity reaction, and enhanced IgM antibody formation and mitogenicity. The phagocytic activity of macrophage and killing activity of NK cells from mice were enhanced in a dose-dependent manner by stimulating with the heat-inactivated vaccine. Among those responses in the mice treated with CB, elevated NK cell activity may play a prominent role in manifesting antitumor activity in the B16-F10 metastasis experiment.

NBU1, a mobilizable site-specific integrated element from Bacteroides spp., can integrate nonspecifically in Escherichia coli

NBU1 is an integrated Bacteroides element that can he mobilized from Bacteroides donors to Bacteroides recipients. Previous studies have shown that a plasmid carrying the internal mobilization region of NBU1 could be transferred by conjugation from Bacteroides thetaiotaomicron to Escherichia coli. In this report, we show that NBU1 can integrate in E. coli. Whereas integration of NBU1 in B. thetaiotaomicron is site specific, integration of NBU1 in E. coli was relatively random, and the insertion frequency of NBU1 into the E. coli chromosome was 100 to 1,000 times lower than the frequency of integration in B. thetaiotaomicron. The frequency of NBU1 integration in E. coli could be increased about 10- to 70-fold, to a value close to that seen with B. thetaiotaomicron, if the primary integration site from B. thetaiotaomicron, BT1-1, was provided on a plasmid in the E. coli recipient or the NBU1 integrase gene, intN1, was provided on a high-copy-number plasmid to increase the amount of integrase available in the recipient. When the primary integration site was available in the recipient, NBU1 integrated site specifically in E. coli. Our results show that NBUs have a very broad host range and are capable of moving from Bacteroides spp. to distantly related species such as E. coli. Moreover, sequence analysis of NBU1 integration sites provided by integration events in E. coli has helped to identify some regions of the NBU1 attachment site that may play a role in the integration process.

The Bacteroides mobilizable insertion element, NBU1, integrates into the 3' end of a Leu-tRNA gene and has an integrase that is a member of the lambda integrase family

NBU1 is a 10.3-kbp integrated Bacteroides element that can be induced to excise from the chromosome and can be mobilized to a recipient by trans-acting functions provided by certain Bacteroides conjugative transposons. The NBU1 transfer intermediate is a covalently closed circle, which is presumed to be the form that integrates into the recipient genome. We report here that a 2.4-kbp segment of NBU1 was all that was required for site-specific integration into the chromosome of Bacteroides thetaiotaomicron 5482. This 2.4-kbp region included the joined ends of the NBU1 circular form (attN1) and a single open reading frame, intN1, which encoded the integrase. Previously, we had found that NBU1 integrates preferentially into a single site in B. thetaiotaomicron 5482. We have now shown that the NBU1 target site is located at the 3' end of a Leu-tRNA gene. The NBU1 integrase gene, intN1, was sequenced. The predicted protein had little overall amino acid sequence similarity to any proteins in the databases but had limited carboxy-terminal similarity to the integrases of lambdoid phages and to the integrases of the gram-positive conjugative transposons Tn916 and Tn1545. We also report that the intN1 gene is expressed constitutively.

Identification of serotypes of Rickettsia tsutsugamushi by nested polymerase chain reaction

Nested polymerase chain reaction (PCR) was applied to identify the serotypes of Rickettsia tsutsugamushi isolated from patients. The primers used for PCR were based on the nucleotide sequences encoding a 56 kDa antigen of rickettsiae. Comparing to the conventional immunofluorescence assay (IFA), which displays a considerable degree of cross-reactivity among different species, the result obtained suggests that the polymerase chain reaction method is much more reliable than IFA.

Improved fluorometric quantification of urinary xanthurenic acid

Measurement of urinary xanthurenic acid (XA) has been used clinically to study a variety of disorders caused by vitamin B6 deficiency. To obviate some cumbersome steps of current methods for measuring XA in human urine, we have developed a simple fluorometric method. We apply the urine sample to a solid-phase extraction column containing trimethylaminopropyl group bound to silica, which enables us to purify and concentrate the XA from the urine without contamination from various tryptophan metabolites. The XA in the acidic eluate can then be quantified fluorometrically. The linearity of the proposed method extends from 0.2 to 10.0 mg/L. The method is precise, yielding day-to-day CVs for two pooled control specimens (1.08 and 1.90 mg/L) of 1.2% and 2.6%, respectively. Correlation studies with an established HPLC method and with a spectrophotometric procedure showed correlation coefficients of 0.99 and 0.98, respectively. Interference from vitamin C, uric acid, salicylate, acetaminophen, vanillylmandelic acid, and homovanillic acid was insignificant. The proposed method for urinary XA is rapid, simple, and suitable for routine use in the clinical laboratory.

Improved fluorometric quantification of urinary xanthurenic acid

Measurement of urinary xanthurenic acid (XA) has been used clinically to study a variety of disorders caused by vitamin B6 deficiency. To obviate some cumbersome steps of current methods for measuring XA in human urine, we have developed a simple fluorometric method. We apply the urine sample to a solid-phase extraction column containing trimethylaminopropyl group bound to silica, which enables us to purify and concentrate the XA from the urine without contamination from various tryptophan metabolites. The XA in the acidic eluate can then be quantified fluorometrically. The linearity of the proposed method extends from 0.2 to 10.0 mg/L. The method is precise, yielding day-to-day CVs for two pooled control specimens (1.08 and 1.90 mg/L) of 1.2% and 2.6%, respectively. Correlation studies with an established HPLC method and with a spectrophotometric procedure showed correlation coefficients of 0.99 and 0.98, respectively. Interference from vitamin C, uric acid, salicylate, acetaminophen, vanillylmandelic acid, and homovanillic acid was insignificant. The proposed method for urinary XA is rapid, simple, and suitable for routine use in the clinical laboratory.

ELISA-based colorimetric detection of Rickettsia tsutsugamushi DNA from patient sera by nested polymerase chain reaction

A rapid diagnostic system for scrub typhus was established using colorimetric detection of nested polymerase chain reaction (PCR). This system relied on binding the amplified DNA via a sequence in one of oligodeoxyribonucleotide to the DNA-binding protein GCN4 coated on the well of a micotiter dish. The primer pairs used for the nested PCR were designed on the basis of the homologous nucleotide sequence of the gene that encodes the 56 kDa antigen of serovariants. With this colorimetric PCR, diagnosis can be performed easily from serum samples of patients before the antibody titer increases or in the early stage of the disease. Furthermore, these positive results are able to be confirmed by pathogenic isolation.

Use of a modified Bacteroides-Prevotella shuttle vector to transfer a reconstructed beta-1,4-D-endoglucanase gene into Bacteroides uniformis and Prevotella ruminicola B(1)4

A carboxymethyl cellulase (CMCase) gene from Prevotella ruminicola B(1)4 was reconstructed by adding a cellulose binding domain from a Thermomonospora fusca cellulase and was conjugally transferred from Escherichia coli to Bacteroides uniformis 0061 by using a chloramphenicol and tetracycline resistance shuttle vector (pTC-COW). pTC-COW was specifically constructed to facilitate conjugal transfer of vectors from B. uniformis donors to P. ruminicola recipients. B. uniformis transconjugants containing CMCase constructs cloned into pTC-COW expressed Cmr, but they did not produce the reconstructed CMCase until a xylanase promoter from P. ruminicola 23 was added upstream of the CMCase (pTC-XRCMC). The xylanase promoter allowed the B. uniformis transconjugants to produce large amounts of the reconstructed CMCase, which was present on the outside surface of the cells. Although the reconstructed CMCase alone did not allow B. uniformis to grow on acid-swollen cellulose, rapid growth was observed when two exocellulases were added to the culture supernatant. Under these conditions, the reconstructed CMCase permitted faster growth than the wild-type CMCase. The frequency of transfer of pTC-XRCMC from B. uniformis to P. ruminicola B(1)4 was increased 100-fold when strictly anaerobic conditions, nitrocelluose filters (cell immobilization), and more stringent selections were employed. Although the P. ruminicola B(1)4 (pTC-XRCMC) transconjugates expressed Tcr and had DNA that hybridized with a probe to the shuttle vector, these transconjugants did not produce detectable levels of the reconstructed CMCase even when xylan was the carbon source. On the basis of these results, it appears that not all of the promoters recognized by B. uniformis and P. ruminicola 23 are functional in P. ruminicola B(1)4. However, the results with B. uniformis suggest that the introduction of a P. ruminicola B(1)4 promoter should allow expression of the reconstructed CMCase in P. ruminicola B(1)4.

Some altered concentrations of elements in semen of workers exposed to trinitrotoluene

OBJECTIVES

A cross sectional study was performed to find the concentrations of elements contained in the semen of workers exposed to trinitrotoluene (TNT).

SUBJECTS AND METHODS

Semen of exposed workers in two TNT plants located in He-Nan Province in 1992 were examined.

RESULTS

The average TNT concentrations in the workplace, except the packing site, were found to have exceeded the maximal allowable concentration (MAC, 1 mg/m3); skin contaminations of male workers exposed to TNT were higher after a shift than in controls, and correlated with the total blood concentrations of TNT, 4-amino-2, 6-dinitrotoluene (4A), and 2-amino-4, 6-dinitrotoluene (2A). Cu, Zn, Na, Mg, and Se concentrations were significantly decreased, but K, Ca, Co, Mn and Li contents were not significantly changed in the semen of workers exposed to TNT. Compared with the control group, the percentage of liquifying time of semen, the sperm malformation incidence, and viability in the men exposed to TNT were all significantly changed.

CONCLUSIONS

Men exposed to TNT have decreased concentrations of some elements is semen and altered semen physiology.

The mobilization regions of two integrated Bacteroides elements, NBU1 and NBU2, have only a single mobilization protein and may be on a cassette

Bacteroides conjugative transposons can act in trans to excise, circularize, and transfer unlinked integrated elements called NBUs (for nonreplicating Bacteroides units). Previously, we localized and sequenced the mobilization region of one NBU, NBU1, and showed that this mobilization region was recognized by the IncP plasmids RP4 and R751, as well as by the Bacteroides conjugative transposons. We report here that the single mobilization protein carried by NBU1 appears to be a bifunctional protein that binds to the oriT region and catalyzes the nicking reaction that initiates the transfer process. We have also localized and sequenced the mobilization region of a second NBU, NBU2. The NBU2 mobilization region was 86 to 90% identical at the DNA sequence to the oriT-mob region of NBU1. The high sequence similarity between NBU1 and NBU2 ended abruptly after the stop codon of the mob gene and about 1 kbp upstream of the oriT region, indicating that the oriT-mob regions of NBU1 and NBU2 may be on some sort of cassette. A region on NBU1 and NBU2 which lies immediately upstream of the oriT region had 66% sequence identity to a region upstream of the oriT region on a mobilizable transposon, Tn4399, an element that had previously appeared to be completely unrelated to the NBUs.