[Effects of long-term exposure to lower concentration of carbon disulfide on cardiovascular system of workers in a viscose rayon factory]

An epidemiological cross-sectional study was conducted on 99 workers exposed to lower concentration of carbon disulfide in a viscose rayon factory for a long time and 28 non-exposed ones in the same factory. Blood pressure, serum lipoproteins and electrocardiograph were detected. The results showed that neither diastolic blood pressure nor systolic one between exposed group and control group was obviously different All indicators of serum lipids and lipoproteins were not significantly different except the lipoprotein(a) of exposed group was significantly higher than that of control group, and the risk of abnormal electrocardiogram in the workers exposed to carbon disulfide was 1.1 times of those non-exposed ones but with no statistical significance. The results suggest that lipoprotein(a) can be used as a sensitive indicator for the cardiotoxic effects of carbon disulfide.

Expression of the wild-type insulin-like growth factor II receptor gene suppresses growth and causes death in colorectal carcinoma cells

The insulin-like growth factor II receptor (IGFIIR) has been implicated as a tumor suppressor gene in human malignancy. Frequent mutation, loss of heterozygosity, and microsatellite instability (MSI) directly affecting the IGFIIR gene have been reported in several primary human tumor types. However, to our knowledge, dynamic functional evidence of a growth-suppressive role for IGFIIR has not yet been provided. We identified one MSI-positive colorectal carcinoma cell line, SW48, with monoallelic mutation in IGFIIR identical to that seen in primary colorectal carcinomas. A zinc-inducible construct containing the wild-type IGFIIR cDNA was stably transfected into SW48 cells. Growth rate and apoptosis were compared between zinc-treated, untreated, and untransfected cells. A twofold increase in IGFIIR protein expression was detected after zinc treatment in discrete clonal isolates of transfected SW48 cells. Moreover, zinc induction of exogenous wild-type IGFIIR expression reproducibly decreased growth rate and increased apoptosis. These data prove that wild-type IGFIIR functions as a growth suppressor gene in colorectal cancer cells and provide dynamic in vitro functional support for the hypothesis that IGFIIR is a human growth suppressor gene.

A mycobacterial extracytoplasmic sigma factor involved in survival following heat shock and oxidative stress

Extracytoplasmic function (ECF) sigma factors are a heterogeneous group of alternative sigma factors that regulate gene expression in response to a variety of conditions, including stress. We previously characterized a mycobacterial ECF sigma factor, SigE, that contributes to survival following several distinct stresses. A gene encoding a closely related sigma factor, sigH, was cloned from Mycobacterium tuberculosis and Mycobacterium smegmatis. A single copy of this gene is present in these and other fast- and slow-growing mycobacteria, including M. fortuitum and M. avium. While the M. tuberculosis and M. smegmatis sigH genes encode highly similar proteins, there are multiple differences in adjacent genes. The single in vivo transcriptional start site identified in M. smegmatis and one of two identified in M. bovis BCG were found to have -35 promoter sequences that match the ECF-dependent -35 promoter consensus. Expression from these promoters was strongly induced by 50 degrees C heat shock. In comparison to the wild type, an M. smegmatis sigH mutant was found to be more susceptible to cumene hydroperoxide stress but to be similar in logarithmic growth, stationary-phase survival, and survival following several other stresses. Survival of an M. smegmatis sigH sigE double mutant was found to be markedly decreased following 53 degrees C heat shock and following exposure to cumene hydroperoxide. Expression of the second gene in the sigH operon is required for complementation of the sigH stress phenotypes. SigH is an alternative sigma factor that plays a role in the mycobacterial stress response.

Low prevalence of the APC I1307K sequence in Jewish and non-Jewish patients with inflammatory bowel disease

A germline sequence alteration at codon 1307 of the APC gene (I1307K) has been reported in 6-7% of the Ashkenazi Jewish population in the United States. This alteration is believed to predispose the APC gene to a secondary mutation at the same locus, resulting in an increased risk of colorectal carcinoma. There is an increased risk of colorectal carcinoma in patients with inflammatory bowel disease (IBD), a relatively large proportion of whom are Ashkenazi Jews. We therefore sought to determine whether the I1307K sequence variant occurred in the germline DNA of IBD patients. To our surprise, we found this sequence in only two of 267 patients with IBD (0.7%), occurring in only 1.5% of Jewish IBD patients. The I1307K sequence variant was not found in 67 patients with esophageal cancer, 53 patients with gastric carcinoma (13 MSI-H and 44 MSI-negative), or ten patients with sporadic MSI-H colon cancer. These findings suggest that the I1307K sequence is relatively rare in the germline of Jewish as well as non-Jewish IBD patients. It does not appear to contribute to the increased colorectal cancer risk present in these patients.

PKC-dependent activation of p44/p42 MAPKs during myocardial ischemia-reperfusion in conscious rabbits

Using conscious rabbits, we examined the effect of ischemic preconditioning (PC) on p44 and p42 mitogen-activated protein kinases (MAPKs). We found that both isoforms contribute significantly to total MAPK activity in the heart (in-gel kinase assay: p44, 59 +/- 1%; p42, 41 +/- 1%). Ischemic PC (6 cycles of 4-min occlusion/4-min reperfusion) elicited a pronounced increase in total cellular MAPK activity (+89%). This increase, which occurred exclusively in the nuclear fraction, was contributed by both isoforms (in-gel kinase assay: p44, +97%; p42, +210%) and was accompanied by migration of the two proteins from the cytosolic to the nuclear compartment. In control rabbits, MAPK kinase (MEK)1 and MEK2, direct activators of p44 and p42 MAPKs, were located almost exclusively in the cytosolic fraction. Ischemic PC induced a marked increase in cytosolic MEK activity (+164%), whereas nuclear MEK activity did not change, indicating that MEK-induced activation of MAPKs occurred in the cytosolic compartment. Activation of MAPKs after ischemic PC was completely blocked by the protein kinase C (PKC) inhibitor chelerythrine. Selective overexpression of PKC-epsilon in adult rabbit cardiomyocytes induced activation of both p44 and p42 MAPKs and reduced lactate dehydrogenase release during simulated ischemia-reperfusion, which was abolished by the MEK inhibitor PD-98059. The results demonstrate that 1) ischemic PC induces a rapid activation of p44 and p42 MAPKs in hearts of conscious rabbits; 2) the mechanism of this phenomenon involves activation of p44 and p42 MAPKs in the cytosol and their subsequent translocation to the nucleus; and 3) it occurs via a PKC-mediated signaling pathway. The in vitro data implicate PKC-epsilon as the specific isoform responsible for PKC-induced MAPK activation and suggest that p44/p42 MAPKs contribute to PKC-epsilon-mediated protection against simulated ischemia. The results are compatible with the hypothesis that p44 and p42 MAPKs may play a role in myocardial adaptations to ischemic stress.

Synthesis, structural characterization and antitumor activity evaluations of copper complex with tetraazamacrocyclic ligand

Cu (II) complex with 1,4,7,10-tetrakis(2-cyanoethyl-)-1,4,7,10-tetraazacyclododecane was prepared and characterized by X-ray diffraction. Four nitrogen atoms of macrocyclic ligand and oxygen atom of water molecule defined a tetragonal pyramidal polyhedron surrounding the central copper atom. Preliminary pharmacological tests showed that it had antitumor activity against P388 and BEL-7404 cell lines in vitro. Also it exhibited perturbation effects to K562 tumor cell lines at G0-G1 stage and further studies showed that it can cleave supercoiled DNA (pBR 322) to nicked and linear DNA in aerobic condition.

Preparation of DNA-immobilized immunoadsorbent for treatment of systemic lupus erythematosus

A new DNA-immobilized immunoadsorbent was prepared to remove the pathogenic anti-DNA antibody from the serum of systemic lupus erythematosus (SLE) patients. A non-woven poly(ethylene terephthalate) (PET) fabric made of 3.5-microm diameter fibers was used as the support of the immunoadsorbent. A cationic monomer, N,N-dimethylaminoethyl methacrylate (DAM), was graft polymerized onto the PET fiber surface by UV irradiation or with a chemical initiator. Polyion complexation between the cationic groups of the graft chains and DNA molecules was employed to immobilize DNA onto the fiber surface. No DNA leaching was observed when the DNA-immobilized fabrics were placed in 0.9 and 2.0 wt% NaCl solution at 37 degrees C overnight. In vitro evaluation of this DNA-immobilized immunoadsorbent demonstrated that this adsorbent could selectively adsorb anti-DNA antibody from the serum of SLE patients.

Hypermethylation of the hMLH1 gene promoter in human gastric cancers with microsatellite instability

Human gastric carcinoma shows a higher prevalence of microsatellite instability (MSI) than does any other type of sporadic human cancer. The reasons for this high frequency of MSI are not yet known. In contrast to endometrial and colorectal carcinoma, mutations of the DNA mismatch repair (MMR) genes hMLH1 or hMSH2 have not been described in gastric carcinoma. However, hypermethylation of the hMLH1 MMR gene promoter is quite common in MSI-positive endometrial and colorectal cancers. This hypermethylation has been associated with hMLH1 transcriptional blockade, which is reversible with demethylation, suggesting that an epigenetic mechanism underlies hMLH1 gene inactivation and MMR deficiency. Therefore, we studied the prevalence of hMLH1 promoter hypermethylation in a total of 65 gastric tumors: 18 with frequent MSI (MSI-H), 8 with infrequent MSI (MSI-L), and 39 that were MSI negative. We found a striking association between hMLH1 promoter hypermethylation and MSI; of 18 MSI-H tumors, 14 (77.8%) showed hypermethylation, whereas 6 of 8 MSI-L tumors (75%) were hypermethylated at hMLH1. In contrast, only 1 of 39 (2.6%) MSI-negative tumors demonstrated hMLH1 hypermethylation (P<0.0001 for MSI-H or MSI-L versus MSI-negative). Moreover, hypermethylated cancers demonstrated diminished expression of hMLH1 protein by both immunohistochemistry and Western blotting, whereas nonhypermethylated tumors expressed abundant hMLH1 protein. These data indicate that hypermethylation of hMLH1 is strongly associated with MSI in gastric cancers and suggest an epigenetic mechanism by which defective MMR occurs in this group of cancers.

Sequence alterations of insulin-like growth factor binding protein 3 in neoplastic and normal gastrointestinal tissues

Insulin-like growth factor binding protein 3 (IGFBP-3) is an important regulator of normal and malignant cell growth. It modulates the mitogenic effects of insulin-like growth factors (IGFs) by inhibiting growth through mechanisms both dependent on and independent of IGF binding. IGF-I and IGF-II levels are regulated by binding to the IGF-II receptor, which is inactivated by mutation in human gastrointestinal (GI) tumors. We have previously demonstrated elevated IGF-II ligand expression in IGF-II receptor-mutant GI tumors, implicating the IGF signaling system in GI tumorigenesis. Therefore, to investigate the potential involvement of IGFBP-3 in human GI carcinogenesis, direct DNA sequencing of exons 1-4 and intron-exon boundaries of the IGFBP-3 gene was performed in 10 colorectal cancers, 10 gastric cancers, and 10 esophageal cancers. Four distinct sequence alterations were identified: (a) in one gastric and one esophageal tumor, an A to C transversion occurred at nucleotide 5795 (CAC-->CCC), leading to a His-->Pro substitution at codon 179; (b) a second esophageal tumor had a C to T transition at nucleotide 8291 (ACC-->ATC), leading to a Thr-->Ile substitution at codon 277 of IGFBP-3; (c) one alteration comprised a G to C transversion in exon 1 at nucleotide 2132 (GGG-->GCG), leading to a Gly-->Ala substitution at codon 32 in two gastric cancers, seven esophageal cancers, and nine colon cancers; and (d) a C to G transversion located 17 nucleotides from the 3' splice site in intron 1 was observed in three colon cancers and four esophageal cancers. All of these DNA sequence alterations were present in matched normal DNA from the same subjects, which suggests that some or all of them may represent polymorphisms. However, we cannot exclude the possibility that the germ-line nonconservative amino acid substitutions predicted to occur as a result of these alterations result in subtle changes to IGFBP-3 protein function and a predisposition to developing GI malignancy.

Mismatch cleavage detects base deletion in cystic fibrosis gene

The delta F508 is the most common defect in the cystic fibrosis (CF) gene; it involves in a 3-base deletion in codon 508 and results in the loss of a phenylalanine residue at amino acid position 508. Our previous results have shown the mismatch enzyme cleavage at the mismatch of a DNA duplex in identifying a specific DNA sequence or a point mutation. The assay is simple and reliable. By manipulating the melting temperature (Tm) for the hybrids of the DNA targets and the deoxynucleotide probes, the mismatch cleavage assays are able to detect the most common defective CF gene, delta F508. The assays with a delta F508 and a normal wild-type probe can differentiate the three genotypes, i.e., delta F508/delta F508, delta F508/normal and normal/normal. Furthermore, the addition of ammonium acetate amplifier to the assay for recycling the target DNA can increase the sensitivity to a level that is sufficient to detect the mutated target in a few micrograms of genomic DNA without the aid of PCR amplification. The detection of the base deletion, the amplification of sensitivity and the differentiation among the genotypes of normal, carrier delta F508 and mutant delta F508 suggest the useful application of mismatch cleavage in genetic diagnosis at the DNA level.

Development of a versatile computer integrated control system for bioprocess controls

A general approach is described for the implementation of a networked multi-unit computer integrated control system. The use of data acquisition hardware and graphical programming tools alleviates tedious programming and maintains potency and flexibility. One application of the control system, the control of a mammalian cell perfusion culture based on a key nutrient glucose concentration, was demonstrated. The control system offers customized user interface for all process control parameters and allows the flexibility for continued improvement and implementation of new tailored functions. The temperature, pH, dissolved oxygen and glucose level were accurately controlled.

Role of the acidic carboxyl-terminal domain of the single-stranded DNA-binding protein of bacteriophage T7 in specific protein-protein interactions

The gene 2.5 single-stranded DNA (ssDNA) binding protein of bacteriophage T7 is essential for T7 DNA replication and recombination. Earlier studies have shown that the COOH-terminal 21 amino acids of the gene 2.5 protein are essential for specific protein-protein interaction with T7 DNA polymerase and T7 DNA helicase/primase. A truncated gene 2.5 protein, in which the acidic COOH-terminal 21 amino acid residues are deleted no longer supports T7 growth, forms dimers, or interacts with either T7 DNA polymerase or T7 helicase/primase in vitro. The single-stranded DNA-binding protein encoded by Escherichia coli (SSB protein) and phage T4 (gene 32 protein) also have acidic COOH-terminal domains, but neither protein can substitute for T7 gene 2.5 protein in vivo. To determine if the specificity for the protein-protein interaction involving gene 2.5 protein resides in its COOH terminus, we replaced the COOH-terminal region of the gene 2.5 protein with the COOH-terminal region from either E. coli SSB protein or T4 gene 32 protein. Both of the two chimeric proteins can substitute for T7 gene 2.5 protein to support the growth of phage T7. The two chimeric proteins, like gene 2.5 protein, form dimers and interact with T7 DNA polymerase and helicase/primase to stimulate their activities. In contrast, chimeric proteins in which the COOH terminus of T7 gene 2.5 protein replaced the COOH terminus of E. coli SSB protein or T4 gene 32 protein cannot support the growth of phage T7. We conclude that an acidic COOH terminus of the gene 2.5 protein is essential for protein-protein interaction, but it alone cannot account for the specificity of the interaction.

Straw yields and nutrients of seventy-five Canadian barley cultivars

Straw, grain, and total yields were compared among 32 two-row and 43 six-row barley (Hordeum vulgare L.) cultivars registered in eastern and western Canada, that were grown at Charlottetown, Prince Edward Island in 1991 and 1992. Straw nutrients was determined in 1991. Two-row cultivars yielded more straw and less grain than six-row cultivars (P < 0.05). The total yield (i.e., total aboveground dry matter) of two-row cultivars was approximately equal to that of six-row cultivars. Straw of two-row cultivars contained more cell contents but less hemicellulose, total-N, Ca, Na, Mn, and Zn than six-row cultivars straw (P < 0.05). Straw yields were not different between eastern and western cultivars regardless of whether they were two-row or six-row types. Eastern two-row cultivars showed higher grain yield and higher total yield than western two-row, and their straws contained less lignin and P than those of western cultivars. Straw of eastern six-row cultivars contained less Ca, but more Na and Mg than that of western six-row cultivars. Hulless barleys showed less grain yield and their straw contained less cellulose than covered barleys regardless of whether they were two-row or six-row types. Two-row hulless cultivars yielded more straw than two-row covered barleys. Straw of six-row hulless barleys contained more cell contents, total-N, and minerals (except for Na and Mn) than that of six-row covered barleys. Key words: Barley cultivars, straw, yield, crude protein, fibre, minerals

Mutation of hMSH3 and hMSH6 mismatch repair genes in genetically unstable human colorectal and gastric carcinomas

Mutations within microsatellite sequences, consisting of additions or deletions of repeat units, are known as the replication/repair error positive (RER+) phenotype or micorsatellite instability (MI). Microsatellite instability has been demonstrated in hereditary and sporadic colorectal carcinomas and is usually observed in noncoding regions of genomic DNA. However, relatively few coding region targets of MI have been identified thus far. Using PCR, we amplified regions encompassing (A)8 and (C)8 microsatellite tracts within hMSH3 and hMSH6 from 31 RER+ sporadic colorectal tumors, 8 hereditary colon cancers, 23 RER+ gastric carcinomas, and 32 RER- gastric tumors. Mutations were found in 11 (36%) of 31 sporadic colon carcinomas, 4 (50%) of 8 hereditary colorectal cancers, and 5 (22%) of 23 RER+ gastric carcinomas, but in only 2 (6%) of 32 RER- gastric carcinomas. These frameshift mutations cause premature stop codons downstream that are predicted to abolish normal protein function. Our results and those of others suggest that DNA mismatch repair genes, such as hMSH3 and hMSH6, are targets for the mutagenic activity of upstream mismatch repair gene mutations and that this enhanced genomic instability may accelerate the accumulation of mutations in RER+ tumors.

FHIT gene alterations in esophageal cancer and ulcerative colitis (UC)

FHIT (fragile histidine triad gene), a candidate tumor suppressor gene, was recently identified and cloned at chromosome 3p14.2. Alterations of this gene have been reported in a number of primary human tumors, including colorectal, esophageal, gastric and lung carcinomas. However, some reports have found no abnormalities in this gene. We investigated a total of 63 primary esophageal tumors, nine esophageal cancer cell lines and 17 ulcerative colitis-associated neoplasms (UCANs) for alterations of FHIT. In 13 esophageal tumors, we employed overlapping reverse transcriptase-PCRs (RT-PCRs) to amplify and sequence the complete open reading frame of FHIT. One of 13 primary esophageal tumors analysed by RT-PCR expressed no detectable FHIT transcript; the remaining 12 expressed normal-sized transcripts with wild-type open reading frame sequences. In an additional 50 esophageal tumors, the polymorphic microsatellite loci D3S1300 and D3S1313 were used to evaluate loss of heterozygosity (LOH) at 3p14.2. Eleven of these 50 tumors showed LOH at one or both loci. In all these 11 tumors, genomic PCR and direct sequencing of FHIT exons 5-9 was performed. This analysis revealed that none of these 11 primary esophageal tumors contained any alterations in the FHIT open reading frame or adjacent intron sequences. Finally, among 17 UCANs, the in vitro synthesized protein (IVSP) assay detected no truncated protein products, nor were there any abnormalities in size or DNA sequence of FHIT RT-PCR products. However, in six of nine esophageal carcinoma cell lines, no FHIT RT-PCR product was detectable using either of the overlapping primer sets. Genomic PCR and direct sequencing of exons 5-9, also performed in these nine cell lines, revealed wild-type sequence in eight cell lines; however, one cell line contained no exon 5 PCR product. This cell line also lacked detectable FHIT transcript. These data suggest that the open reading frame of FHIT is not important in the development or progression of most primary esophageal carcinomas or UCANs, although lack of expression of the FHIT transcript may be common in esophageal cancer-derived cell lines. The possibility of an additional tumor suppressor gene at chromosome 3p14.2 remains to be evaluated.

Deficient transforming growth factor-beta1 activation and excessive insulin-like growth factor II (IGFII) expression in IGFII receptor-mutant tumors

The insulin-like growth factor II receptor (IGFIIR) gene has been identified as a coding region target of microsatellite instability in human gastrointestinal (GI) tumors. IGFIIR normally has two growth-suppressive functions: it binds and stimulates the plasmin-mediated cleavage and activation of the latent transforming growth factor-beta1 (LTGF-beta1) complex, and it mediates the internalization and degradation of IGFII ligand, a mitogen. We used an immunohistochemical approach to determine whether IGFIIR mutation affected expression of these proteins in GI tumors. Four highly specific antibodies were used: LC(1-30), which recognizes the active form of TGF-beta1; anti-LTGF-beta1, which detects the LTGF-beta1 precursor protein; anti-IGFIIR; and anti-IGFII ligand. Twenty GI tumors either with (6 of 20) or without (14 of 20) known IGFIIR mutation were examined, along with matching normal tissues. Results were statistically significant in the following categories: (a) decreased active TGF-beta1 protein expression in IGFIIR-mutant tumor tissues versus matching normal tissues or IGFIIR-wild-type tumor tissues; (b) increased LTGF-beta1 protein expression in IGFIIR-mutant tumor tissues versus matching normal tissues or IGFIIR-wild-type tumor tissues; and (c) increased IGFII ligand protein expression in IGFIIR-mutant tumor tissues versus matching normal tissues or IGFIIR-wild-type tumor tissues. These data suggest that in genetically unstable GI tumors, mutation of a microsatellite within the coding region of IGFIIR functionally inactivates this gene, causing both diminished growth suppression (via decreased activation of TGF-beta1) and augmented growth stimulation (via decreased degradation of the IGFII ligand).

A mycobacterial extracytoplasmic function sigma factor involved in survival following stress

The extracytoplasmic function (ECF) sigma factors constitute a diverse group of alternative sigma factors that have been demonstrated to regulate gene expression in response to environmental conditions in several bacterial species. Genes encoding an ECF sigma factor of Mycobacterium tuberculosis, Mycobacterium avium, and Mycobacterium smegmatis, designated sigE, were cloned and analyzed. Southern blot analysis demonstrated the presence of a single copy of this gene in these species and in Mycobacterium bovis BCG, Mycobacterium leprae, and Mycobacterium fortuitum. Sequence analysis showed the sigE gene to be highly conserved among M. tuberculosis, M. avium, M. smegmatis, and M. leprae. Recombinant M. tuberculosis SigE, when combined with core RNA polymerase from M. smegmatis, reconstituted specific RNA polymerase activity on sigE in vitro, demonstrating that this gene encodes a functional sigma factor. Two in vivo transcription start sites for sigE were also identified in M. smegmatis and M. bovis BCG. Comparison of wild-type M. smegmatis with a sigE mutant strain demonstrated decreased survival of the mutant under conditions of high-temperature heat shock, acidic pH, exposure to detergent, and oxidative stress. An inducible protective response to oxidative stress present in the wild type was absent in the mutant. The mycobacterial SigE protein, although nonessential for viability in vitro, appears to play a role in the ability of these organisms to withstand a variety of stresses.

Gene 4 helicase of bacteriophage T7 mediates strand transfer through pyrimidine dimers, mismatches, and nonhomologous regions

In bacteriophage T7 the gene 2.5 single-stranded DNA-binding protein and the gene 4 helicase together promote the annealing of homologous regions of two DNA partners to form a joint molecule and subsequent strand transfer. In this reaction T7 gene 2.5 protein is essential for joint molecule formation, but is not required for T7 gene 4 protein-mediated strand transfer. T7 gene 4 helicase alone is able to mediate strand transfer, provided that a joint molecule is available. The present paper shows that, in addition, strand transfer proceeds at a normal rate even when both DNA partners contain ultraviolet-induced pyrimidine dimers (0.6 dimer per 100 nt). An insert of a relatively long (842-nt) segment of nonhomologous DNA in the single-stranded DNA partner has no effect on strand transfer, whereas its presence in the double-stranded partner prevents strand transfer. A short insert (37 nt) can be tolerated in either partner. Thus, DNA helicase is able to participate in recombinational DNA repair through its role in strand exchange, providing a pathway distinct from nucleotide excision repair.

Role of the bacteriophage T7 and T4 single-stranded DNA-binding proteins in the formation of joint molecules and DNA helicase-catalyzed polar branch migration

Bacteriophage T7 gene 2.5 single-stranded DNA-binding protein and gene 4 DNA helicase together promote pairing of two homologous DNA molecules and subsequent polar branch migration (Kong, D., and Richardson, C. C. (1996) EMBO J. 15, 2010-2019). In this report, we show that gene 2.5 protein is not required for the initiation or propagation of strand transfer once a joint molecule has been formed between the two DNA partners, a reaction that is mediated by the gene 2.5 protein alone. A mutant gene 2.5 protein, gene 2.5-Delta21C protein, lacking 21 amino acid residues at its C terminus, cannot physically interact with gene 4 protein. Although it does bind to single-stranded DNA and promote the formation of joint molecule via homologous base pairing, subsequent strand transfer by gene 4 helicase is inhibited by the presence of the gene 2.5-Delta21C protein. Bacteriophage T4 gene 32 protein likewise inhibits T7 gene 4 protein-mediated strand transfer, whereas Escherichia coli single-stranded DNA-binding protein does not. The 63-kDa gene 4 protein of phage T7 is also a DNA primase in that it catalyzes the synthesis of oligonucleotides at specific sequences during translocation on single-stranded DNA. We find that neither the rate nor extent of strand transfer is significantly affected by concurrent primer synthesis. The bacteriophage T4 gene 41 helicase has been shown to catalyze polar branch migration after the T4 gene 59 helicase assembly protein loads the helicase onto joint molecules formed by the T4 UvsX and gene 32 proteins (Salinas, F., and Kodadek, T. (1995) Cell 82, 111-119). We find that gene 32 protein alone forms joint molecules between partially single-stranded homologous DNA partners and that subsequent branch migration requires this single-stranded DNA-binding protein in addition to the gene 41 helicase and the gene 59 helicase assembly protein. Similar to the strand transfer reaction, strand displacement DNA synthesis catalyzed by T4 DNA polymerase also requires the presence of gene 32 protein in addition to the gene 41 and 59 proteins.

Immunization of BALB/c mice with mIFN-gamma-secreting Mycobacterium bovis BCG provides early protection against Leishmania major infection

We developed and tested IFN-gamma-expressing Mycobacterium bovis, strain BCG, for the ability to activate macrophages and protect mice against a heterologous challenge with Leishmania major. One, 2 or 3 weeks after intraperitoneal immunization, mice were challenged with 10(6) L. major amastigotes injected into the right footpad. Recombinant BCG immunization for all 3 challenge time points initially showed greater protection compared to the BCG control, as judged by footpad thickness and number of parasites in the leishmanial lesion. However, at week 4 after challenge, while the 1- and 2-week immunization groups continued to show increased protection, the 3-week immunization group animals exhibited progressive disease. These data suggest that the IFN-gamma-expressing BCG initially activates macrophages more effectively than native BCG, but that late exacerbation of disease can occur, highlighting the complexity of the immune response against leishmaniasis.

Shanghai trial of nifedipine in the elderly (STONE)

OBJECTIVE

To assess the effectiveness of nifedipine treatment in elderly hypertensives.

METHODS

A single-blind trial was conducted under the direction of the Shanghai Institute of Hypertension in 1632 subjects aged 60-79 years alternatively allocated to either nifedipine or placebo after a 4-week placebo run-in period between 1987 and 1990 with mean follow-up of 30 months. Clinical events and risk modification were analysed in collaboration with the University of Montreal. Seventy-four patients with severe hypertension were reallocated to active nifedipine treatment after placebo run-in.

RESULTS

Cox's proportional hazards model accounting for covariates demonstrated a highly significant decrease in the probability of events: 'original treatment assignment' analysis indicated that 77 events occurred in the placebo and 32 in the nifedipine group. Similar significances were achieved with 'actual treatment' or 'changes excluded' (excluding reallocated subjects) analyses. A significant reduction in relative risk was observed for strokes and severe arrhythmia with an overall decrease from 1.0 to 0.41 (95% confidence interval 0.27-0.61).

CONCLUSION

Nifedipine treatment diminished the number of severe clinical outcomes in elderly hypertensives significantly.