Transfer of the E6 and E7 genes of human papillomavirus type 18 into human epithelial cells via recombinant retrovirus infection

A retroviral vector carrying the E6 and E7 genes of HPV type 18 was transfected into a packaging cell line, Ampho psi 2. Thirteen recombinant viruses carrying the E6 and E7 genes were obtained. The titers of these recombinant viruses were estimated by infecting BALB/c3T3 cells and then counting the number of G418r colonies. Presence of HPV E6/E7 genes was confirmed by the PCR method and sequence-specific primers. The expression of E7 gene was examined by RT-PCR method. Results showed that the titers were ranged between 0.2 and 1.2 x 10(3) CFU/ml and the E7 transcripts were detected in all 13 cell clones. These E6 and E7-containing cell clones were able to grow in soft agar, indicating the E6/E7 delivered by the recombinant retroviruses retained their transformation function. These recombinant viruses were then used to infect human NPC cell lines, NPC-TW076 and -TW039 and cell clones resistant to G418 were obtained. Using Western blot analysis and HPV type 18 E6-specific monoclonal antibody, HPV-CIP5, these cells were shown to contain a protein with a molecular mass of 18 kDa. Our data indicated that the HPV E6/E7-containing recombinant retroviruses were capable of infecting human cell lines. The potential of using these recombinant retroviruses to immortalize human primary epithelial cells was discussed.

Physiological transport properties of cultured retinal microvascular endothelial cell monolayers

PURPOSE

To characterize baseline transport properties: hydraulic conductivity (Lp), albumin permeability (Pe), and transendothelial electrical resistance (TER) of bovine retinal microvascular endothelial cells (RMEC) in the development of an in vitro model of the blood-retinal barrier (BRB).

METHODS

RMEC were grown on porous, polycarbonate filters for determination of the number of days required to achieve minimal transport rates. Lp, Pe, and TER were measured by utilizing a bubble tracking spectrophotometer, by quantifying the diffusional movement of fluorescein isothiocyanate-labeled albumin, and by utilizing a Millipore electrical resistance meter, respectively.

RESULTS

Lp decreased significantly from 7.82 +/- 0.85 x 10(-7) (mean +/- SEM) cm/sec/cm H2O at post-plating Day 5 to 1.44 +/- 0.26 x 10(-7) cm/sec/cm H2O at Day 9. Pe of the monolayer also decreased progressively with days post-plating from 3.44 +/- 0.53 x 10(-6) cm/sec at Day 7 to a minimum of 1.95 +/- 0.29 x 10(-6) cm/sec at Day II. Peak TER fluctuated until Day 7, when it began to steadily increase from 17.14 ohm-cm2 to a peak value of 25.42 ohm-cm2 at Day 10, decreasing from then on to 22.24 ohm.cm2 on Day 12. Known disrupters of the BRB, NECA and VEGF, elicited significant increase in RMEC Lp showing the sensitivity of this model to pharmacological alterations.

CONCLUSIONS

Our data indicate that RMEC grown on polycarbonate filters form a restrictive monolayer of cells, which exhibit dynamic alterations in response to pharmacological agents, thus demonstrating an in vitro model of the BRB. Future studies with the model may offer insights into the pathogenesis of retinal vascular diseases and allow convenient testing of pharmacological interventions.

Identification of a promoter for the latent membrane protein 1 gene of Epstein-Barr virus that is specifically activated in human epithelial cells

Latent membrane protein 1 (LMP 1) is one of two Epstein-Barr virus (EBV)-encoded proteins that expressed in nasopharyngeal carcinoma (NPC) cells. Previous studies showed that a 3.5-kb transcript of the LMP 1 gene, in addition to the 2.8-kb transcript, was detected in a B95-8-EBV-containing, nude mice-passaged NPC tumor, C15. This indicated that a transcript was initiated from a region 5' to the putative promoter, ED-L1. We have isolated an EBV variant from a NPC tissue, and this virus strain contained a more pathogenic LMP 1 gene. DNA sequence analysis of the 5'-upstream region showed distinct variations as compared to that of B95-8 strain. To test if the LMP 1 gene of the NPC strain also contained an upstream promoter, we generated a series of deletion plasmids encompassing positions -1,030 to +20 of the LMP 1 promoter and tested for their abilities to drive the expression of the reporter gene in human epithelial cell lines, C-33A and NPC-TW076. We found that the region between -643 and -496 contained a promoter activity that was approximately five-fold higher than the putative promoter, ED-L1. This region between -643 and -496 was designated as ED-L1E. C-33A cells containing the genomic clone pT7(E) or the clone that had deleted a 94-bp ED-L1 sequence (delta94) was used to determine the transcription initiation sites by RNase protection assay. Results showed that a transcription initiation site was located at nucleotide 170,099 ("A") of EBV genome. The transcript was expressed in NPC biopsies and in human primary normal epithelial cells transfected with pT7(E) and delta94, respectively, as examined by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Furthermore, the ED-L1E was not regulated by the EBV-encoded nuclear antigen 1-mediated transcriptional enhancer family of repeats (FR) in C-33A cells. Our results suggested that the ED-L1E was specifically activated in epithelial cells. The biological significance of the selective usage of the ED-L1E promoter was discussed.

Comparison of two enzyme-linked immunosorbent assay tests for diagnosis of Helicobacter pylori infection in China

An ELISA based on a pool of United States strains of Helicobacter pylori was compared with a newly developed ELISA based on a pool of Chinese strains. Both assays were tested using sera from 132 Chinese study subjects with biopsy-proven H. pylori infection. Using cutpoints designed to yield equal specificities of 94.9% in an uninfected control population, the sensitivity of the Chinese assay was 100.0%, compared to 97.7% for the United States assay (P = 0.25 by McNemar test). These results suggest that a H. pylori assay based on pooled antigens from United States strains will perform as well in the rural Chinese population as one based on antigens from Chinese strains.

Construction and characterization of a biotin-regulated gene expression system in Escherichia coli

An autoregulated gene expression system in Escherichia coli was designed such that the cloned genes on the vector were not expressed until biotin was depleted during cell growth. The expression vectors were constructed by assembling the DNA fragments containing the regulatory region of the E. coli biotin operon (bio operon), the universal ribosome-binding site (RBS) and the strong transcription terminator rrnBT1T2. The promoter region was further modified by site-directed mutagenesis to create promoters of varied strength. The feasibility of this system was examined in E. coli strain R901 (with bio operon deleted) using various marker genes, including the E. coli birA gene, T7 RNA polymerase gene and yellowfin-porgy growth-hormone gene. The results demonstrated that the induction of marker-gene expression can be triggered as the biotin concentration drops to a threshold value of approximately 2 ng/mL by metabolic utilization.

Prevalence and heterogeneity of Helicobacter pylori in gastric biopsies of patients with gastroduodenal diseases

Helicobacter pylori is a risk factor for development of peptic ulcers and adenocarcinoma of distal stomach. There are several highly specialized virulence factors, such as the production of sialic acid-specific hemagglutinins, cytotoxins and enzymes. This study was designed to study the in vivo prevalence of H. pylori in patients with gastroduodenal diseases, the in vivo correlation between H. pylori infection and blood group O, and the heterogeneity of H. pylori isolates in central Taiwan. We enrolled 776 symptomatic patients residing in the central Taiwan area. The age-specific in vivo prevalence of H. pylori in patients with gastroduodenal diseases increased from 11.1% in those between the ages of 1 to 20, 73.1% in those between the ages of 21 and 30, and to 79.8% in those between the ages of 51 and 60. In conclusion, H. pylori was present in 70% of biopsied specimens of symptomatic patients with gastroduodenal diseases and had the highest incidence (86%) in patients with peptic ulcers. The prevalence of H. pylori cag A expression positive strains in central Taiwan was 92.5%. This study has also demonstrated the high correlation between H. pylori and the blood group O-positive patients with gastroduodenal diseases. The prevalence of H. pylori infection in blood O-positive patients in central Taiwan was 86.4%.

Effect of population density on the early post-implantation mouse embryo growth in vitro

OBJECTIVES

To investigate the relationship between embryo population density and embryo development in vitro.

METHODS

Swiss Webster albino mice were used and blastocysts were flushed from the uterine horns. Various numbers of blastocysts were randomly assigned to separate 35 mm dishes and cultured for 9 days.

RESULTS

The effect of duration of culture to the mean success rates was different as the number of embryos in the dish was changed. In early egg cylinder (EEC) stage, the mean success rate was a flat function of the number of embryos. But the mean success rate was a decreasing function in late egg cylinder (LEC) stage and the decreasing rate was faster in early somite (ES) stage. Interestingly, the mean success rate to ES stage was nearly constant when more than 10 embryos were cultured in one dish.

CONCLUSION

The success rate to each developmental stage in vitro decreased as the number of embryos in the dish and the duration of cultured increased.

Molecular cloning, structural analysis, and expression of carp ZP2 gene

The cDNAs encoding carp ZP2 homologous to winter flounder and mammalian ZP2 were cloned. Carp ZP2 contains a tandemly repetitive domain and a nonrepetitive domain. A repeat is composed of 13 amino-acid residues whose consensus sequence is QQTSQQFQPQKPA/V. The length of the repetitive domain is highly variable, but that of the nonrepetitive domain is fairly constant among various cDNAs. The termination codons of various cDNAs appear at three different positions. Three groups of cDNAs were therefore categorized. Groups I-III encode a nonrepetitive domain of 356, 255, and 10 residues, respectively. A carp ZP2 gene corresponding to group II cDNA was cloned. It spans 2.4 kb and consists of eight exons and seven introns. Carp ZP2 mRNA was detected only in oocytes but not in other tissues. Carp ZP2 is heterogenous in size. The molecular weight ranges from 40-80 kDa. It is present in vitellogenic but not in previtellogenic oocytes, nor in other tissues. Carp ZP2 content in oocytes increases as vitellogenesis proceeds.

Evaluation of acute renal failure in bacterial allograft pyelonephritis using abdominal CT and graft biopsy

The causes of acute renal failure in bacterial allograft pyelonephritis were evaluated using abdominal CT and graft biopsy. Twenty-one recipients, who showed a poor response to antibiotic therapy, comprised this study group. The diagnostic approach taken with this poor responder group was first to perform abdominal CT. If a focal lesion was identified on abdominal CT, a diagnosis of acute focal bacterial nephritis or renal abscess was made. If no focal lesion was found, a graft biopsy was performed for diagnosis. Abdominal CT revealed focal lesions in 9 of the 21 recipients, and renal biopsy showed superimposed acute rejection in 8 of the 12 recipients biopsied. In conclusion, acute renal failure in allograft pyelonephritis is associated with not only severe infection but also a superimposed acute rejection process. Therefore, imaging study and graft biopsy are recommended in the poor responder group.

Distance and velocity measurements by the use of an orthogonal Michelson interferometer

A novel signal processing scheme for detecting distance and velocity signals simultaneously is demonstrated. In this method, a frequency-modulated diode laser is used to illuminate a dual-channel Michelson interferometer with two orthogonal output signals. The distance and the velocity signals then exist on the beat frequencies of the output interferometric signal. Two interferometric output signals with a quadrature phase shift are used to adjust the gating time period of frequency counters for beat-frequency measurement. The distance and velocity signals can thus be obtained from the counting number within the gated-in time period.

Serum and urine soluble HLA class I antigen concentrations are increased in patients with hemorrhagic fever with renal syndrome

OBJECTIVES

In order to evaluate the association between the Hantaan virus-induced cellular-immune response and clinical severity in patients with hemorrhagic fever with renal syndrome (HFRS).

METHODS

We serially measured the serum (n = 16) and urine (n = 6) concentrations of soluble HLA class 1 antigen (sHLA-l) and clinical powameters in patients with HFRS.

RESULTS

Serum sHLA-I concentrations in patients with HFRS were significantly higher than those in controls throughout all clinical phases (p < 0.01). The highly elevated Serum sHLA-I concentrations peaked in the oliguric phase and declined gradually through the phases of HFRS. Serum sHLA-l concentrations in patients with hypotensive episode were higher than in those without the episode (5,85 +/-2,184 vs. 2,389 +/- 860 ng/ml in oliguric phase, 4.11 +/- 1,952 vs. 1,502 +/- 592 ng/ml in diuretic phase, p < 0.05), and serum sHLA-l levels showed a significant correlation with blood WBC count (r = 0.75 in the febrile and hypotensive phase, p < 0.01) and serum creatinine concentrations (r = 0.64 in the oliguric phase, p < 0.01), respectively, Urine sHLA-I levels in the oliguric phase were significantly higher than those in the diuretic phase (390 +/- 155 vs. 214 +/- 45 ng/mg Cr, p < 0.05) and urine sHLA-I levels are associated with severe illness in patients with HFRS. The higher serum sHLA-I are associated with severe illness in patients with HFRS. The persistent elevation of serum sHLA-I during all phases of HFRS might be related to increased production due to prolonged cellular immunologic stimulation by the Hantaan virus rather than decreased excretion of sHLA-I through the kidney.

CONCLUSION

We suggest that the serum and urine sHLA-I concentrations can be used as a stable and objective parameter for monitoring clinical severity and renal dysfunction in patients with HFRS.

Factors on graft survival of living donor kidney transplantation in a single center

We analyzed the potential factors that could influence the survival of graft, focused on primary graft living-donor kidney transplantation with cyclosporine (CsA) therapy. 680 cases were enrolled in this study. Patients and graft survival rates were calculated by a Kaplan-Meier product limit estimate with a 1-day time interval. The analyzed variables were donor relationship, HLA matching, recipient age and sex, donor age and sex, ABO blood type compatibility, diabetic status, hepatitis virus infection, donor specific or non-specific blood transfusion and acute rejection episode. The results suggested that acute rejection episode was the most prognostic factor in graft survival. An HLA-matched donor and a young male donor, i.e. a greater donor nephron mass for less recipient body mass, will show better long-term survival. Diabetes and hepatitis B infection have some negative effects on the long-term survival of graft kidney, but age of recipient, donor-specific transfusion and donor-recipient relationship have little effect.

Simultaneous program of natural-cycle in vitro fertilization and cryopreserved-thawed embryo transfer

PURPOSE

This clinical study was designed to identify and compare the pregnancy rates of simultaneous program of natural-cycle IVF and cryopreserved-thawed ET (NICE) with those of natural-cycle IVF and cryopreserved-thawed ET.

METHODS

All three groups comprised spontaneously ovulating infertile women under the age of 40 and without any male factor present. The NICE program was performed in 36 patients (47 cycles) who had previously undergone IVF-ET resulting in cryopreserved embryos. As control groups, the natural-cycle IVF was performed in 45 patients (80 cycles), and the cryopreserved-thawed ET alone in 29 patients (40 cycles).

RESULTS

The cancellation rate of the initiated cycles prior to ET was 19.1% (9/47) in the NICE group, 23.8% (19/80) in the natural-cycle IVF group, and 2.5% (1/40) in the cryopreserved-thawed ET group. The mean number of embryos transferred was 4.0 +/- 1.1 (2-5) in the NICE group, 1.0 in the natural-cycle IVF group, and 4.2 +/- 1.8 (1-5) in the cryopreserved-thawed ET group. The clinical pregnancy rates per aspiration cycle (32.5%) and per ET cycle (34.2%) in the NICE group were significantly higher than those (14.9, 16.4%) in the natural-cycle IVF group. The clinical and delivered pregnancy rates per ET (34.2, 26.3%) in the NICE group were higher than those (20.5, 15.4%) in the cryopreserved-thawed ET group, without statistical significance.

CONCLUSIONS

Since the NICE program results in saving the fresh oocyte for patients participating in cryopreserved-thawed ET, more favorable pregnancy rates may be obtained from NICE cycles in women ovulating normally who had previously undergone IVF-ET with embryo cryopreservation.

Effects of Gastrodia elata and its active constituents on scopolamine-induced amnesia in rats

The effects of the rhizome of Gastrodia elata Blume (Orchidaceae) (abbreviated as GE) and its active constituents on learning and memory by using the one-trial passive avoidance task were studied in rats. At the 1.0 g/kg dose administered for one week, the methanol extract of GE significantly prolonged the shortened step-through latency induced by scopolamine in the passive avoidance task. Furthermore, at the 50.0 mg/kg dose administered for one week, the ethyl acetate and n-butanol fractions of the methanol extract prolonged the shortened step-through latency induced by scopolamine in rats. Gastrodin, isolated from the n-butanol fraction of the methanol extract, and p-hydroxybenzyl alcohol, isolated from the ethyl acetate fraction of the methanol extract, also significantly prolonged the shortened step-through latency induced by scopolamine on the passive avoidance task. These results suggested that gastrodin and p-hydroxybenzyl alcohol may be the active constituents of GE.

Helicobacter pylori antibodies in relation to precancerous gastric lesions in a high-risk Chinese population

Helicobacter pylori infection is a major cause of gastritis and may be a key risk factor for stomach cancer, but its role in the process of gastric carcinogenesis is not well understood. Herein, we examine H. pylori prevalence in relation to demographic and lifestyle factors and to severity of precancerous lesions in an area of China with one of the highest rates of stomach cancer in the world. H. pylori serum IgG antibody positivity was assayed among 2646 adults, ages 35-64, participating in a population-based gastroscopic screening survey in the high-risk area. The prevalence of positivity was evaluated according to gastric histology, environmental and lifestyle variables determined by interviews during the screening, and level of serum pepsinogens. The odds of advanced precancerous lesions (intestinal metaplasia and dysplasia) of the stomach among those with antibody positivity were estimated by logistic regression. Seventy-two % of the population was H. pylori antibody-positive, with nonsignificant variation by sex, age, income, education, family size, and cigarette smoking habits. H. pylori positivity was higher among those who ate sour pancakes, a fermented indigenous staple that is a risk factor for gastric dysplasia and stomach cancer in this population. The prevalence of H. pylori varied most notably, however, with gastric pathology. The percent of H. pylori positivity increased from 55 to 60 to 87% among those with superficial (nonatrophic) gastritis, mild chronic atrophic gastritis, and severe chronic atrophic gastritis, respectively, before falling to 78% among those with intestinal metaplasia or dysplasia. H. pylori antibody positivity also was strongly correlated with serum pepsinogen concentrations, particularly pepsinogen II, but knowledge of H. pylori status did not markedly improve serological identification of advanced precancerous lesions above that provided by pepsinogen ratios alone. The findings suggest that H. pylori infection contributes to the process of gastric carcinogenesis, particularly during the early stages, in this high-risk area.

Current status of assisted reproductive technology in Asia and Oceania

OBJECTIVE

To summarize the procedures and outcomes of assisted reproductive technology (ART) initiated in Asia-Oceanic region in 1992 and 1993.

DESIGN

Data were collected on an annual summary form and submitted to the Reproductive Biology Committee of AOFOG.

PARTICIPANTS

Twelve member countries of AOFOG submitted data on ART procedures performed in 1992 and 1993-Australia, Egypt, Hong Kong, India, Indonesia, Japan, Korea, New Zealand, Pakistan, Singapore, Taiwan, and Thailand. Data were collected in 1995 so that the outcomes of all pregnancies established would be known.

MAIN OUTCOME MEASURES

Clinical characteristics of patients, causes of infertility, protocols and outcomes of controlled ovarian hyperstimulation (COH), and outcomes of clinical pregnancy including abortion, ectopic pregnancy, multiple pregnancy, and congenital malformation were measured in each ART procedure.

RESULTS

In 1992, 23,872 cycles of IVF-ET were performed with 21.8% clinical pregnancy rate (PR) per ET, 4,840 cycles of GIFT with 29.5% PR per transfer, 1,136 cycles of simultaneous IVF-ET and GIFT with 29.9% PR, and 1,563 cycles of ZIFT with 23.1% PR. Total 575 clinical pregnancies were achieved in cryopreserved ET program, 96 pregnancies in oocyte donation program, and 87 pregnancies in microassisted fertilization (MAF) program. In 1993, 24,571 cycles of IVF-ET were performed with 21.6% clinical PR per ET, 5,240 cycles of GIFT with 28.2% PR per transfer, 1,063 cycles of simultaneous IVF-ET and GIFT with 32.0% PR, 1,005 cycles of ZIFT with 21.6% PR, 5,562 cycles of cryopreserved ET program with 12.8% PR, and 2,198 cycles of MAF program with 11.6% PR. Total 117 clinical pregnancies were achieved in oocyte donation program.

CONCLUSIONS

Although the concepts as well as the status and results of ART are continuously changing, this report may be helpful in planning the future of ART in Asia-Oceania by analyzing the past history.

Molecular cloning and functional expression of mouse connexin-30,a gap junction gene highly expressed in adult brain and skin

A new gap junction gene isolated from the mouse genome codes for a connexin protein of 261 amino acids. Because of its theoretical molecular mass of 30.366 kDa, it is named connexin-30. Within the connexin gene family, this protein is most closely related to connexin-26 (77% amino acid sequence identity). The coding region of mouse connexin-30 is uninterrupted by introns and is detected in the mouse genome as a single copy gene that is assigned to mouse chromosome 14 by analysis of mouse x hamster somatic cell hybrids. Abundant amounts of connexin-30 mRNA (two transcripts of 2.0 and 2.3 kilobase pairs) were found after 4 weeks of postnatal development in mouse brain and skin. Microinjection of connexin-30 cRNA into Xenopus oocytes induced formation of functional gap junction channels that gated somewhat asymmetrically in response to transjunctional voltage and at significantly lower voltage (Vo = +38 and -46 mV) than the closely homologous connexin-26 channels (Vo = 89 mV). Heterotypic pairings of connexin-30 with connexin-26 and connexin-32 produced channels with highly asymmetric and rectifying voltage gating, respectively. This suggests that the polarity of voltage gating and the cationic selectivity of connexin-30 are similar to those of its closest homologue, connexin-26.

Shear stress-induced release of PGE2 and PGI2 by vascular smooth muscle cells

This study addresses the direct effect of fluid flow shear stress on production of the vascular mediators, PGE2 and PGI2 by vascular smooth muscle cells (SMC). Results indicate that shear stress increases PGE2 and PGI2 release in SMC. The production patterns, however, differ between PGE2 and PGI2. For PGE2, the rate of production is moderate for the first three hours after the onset of shear stress, then dramatically increases between the fourth and fifth hours, returning to basal levels in the sixth hour. On the other hand, the rate for PGI2 production is maximal right after the onset of shear and remains elevated for the first three hours. The rate then plateaus and remains at a moderate level during the next three hours. The results also indicate that SMC production of PGI2 is more sensitive to shear stress than PGE2 production since a level of 0.5 dynes/cm2 produces a maximal PGI2 release whereas 1 dyne/cm2 produces only 1/4 the response seen at 20 dynes/cm2 for PGE2. The physiological implications of fluid shear stress regulation of SMC are discussed.

Molecular cloning, structural analysis, and expression of carp ZP3 gene

Two types of cDNAs coding for a major component of carp egg membrane were clones from a carp ovarian cDNA library. They encode polypeptides of 422-424 amino acid residues whose sequences are homologous to those of medaka and mammalian ZP3. Similar to the mammalian ZP3 genes, carp ZP3 gene also consists of eight exons and seven introns. Carp ZP3 genes are 2.9 kb in length and present in multiple forms. Carp ZP3 is a glycoprotein of 45 kDa. It was transcribed and translated exclusively in oocytes, in contrast with medaka ZP3, which was synthesized in liver. The transcription of carp ZP3 starts very early in oogenesis, but translation occurs during vitellogenesis, as it is present in vitellogenic but not in previtellogenic oocytes. ZP3 content in oocytes increases as vitellogenesis proceeds.

Significance of interstitial bone ingrowth under load-bearing conditions: a comparison between solid and porous implant materials

Interstitial bone ingrowth is extremely important for optimum fixation of implanted materials under load-bearing conditions. In this study, three types of biomaterial test piece were manufactured in solid and open-pore structures, and implanted into dog femoral condyles. Bone formation and remodelling were observed histologically and roentgenologically for 24 weeks thereafter. The study demonstrated that, 24 weeks after implantation, thick fibrous tissue surrounded by corticalized bone formed around both solid smooth-surfaced alumina and titanium implants. On the other hand, however, with an implant made of an artificial osteochondral composite material, thickening of ingrown trabeculae could be observed as early as 4 weeks. Bone ingrowth into the titanium fibre mesh was ambundant and increased with time after implantation. This interstitial bone ingrowth resulted in the complete integration of this implant and the viable host bone. Our findings suggest that interstitial bone ingrowth has great significance, even though new bone formation and remodelling follows Wolff's law after the completion of the bonding between the bone and implanted material under load-bearing conditions. The artificial osteochondral composite material could lead to complete integration of the implant and viable bone, suggesting that it is a promising material for joint replacements. Moreover, the tibial joint surface which bore against the polyvinyl alcohol hydrogel surface of this implant remained intact, which suggests that this composite is a very promising biomaterial for use in joint prostheses.

Effect of exogenous glycine on peptidoglycan composition and resistance in a methicillin-resistant Staphylococcus aureus strain

A highly homogeneously methicillin-resistant Staphylococcus aureus strain was grown in the presence of various concentrations of exogenous glycine. Increasing concentrations of glycine in the medium resulted in a decrease in methicillin resistance and the appearance of a heterogeneous resistance phenotype. Parallel to the gradual changes in resistance was an alteration in the muropeptide composition of peptidoglycan. Increasing concentrations of glycine in the medium resulted in peptidoglycan in which muropeptides with a D-alanyl-D-alanine terminus were replaced with D-alanyl-glycine-terminating muropeptides. The disappearance of D-alanyl-D-alanine-terminating muropeptides in peptidoglycan and the concomitant decrease in resistance indicate a central role for D-alanyl-D-alanine-terminating precursors in methicillin resistance.

Effect of a 10-amino acid deletion on the oncogenic activity of latent membrane protein 1 of Epstein-Barr virus

A previous study has shown that the BNLF1 of Epstein-Barr virus (EBV), isolated from a nasopharyngeal carcinoma biopsy (BNLF1-1510), was able to transform Balb/3T3 cells. On the other hand, BNLF1 of a prototype virus B95-8 (BNLF1-958) was not transforming unless the gene was transcribed from a strong promoter. In this study, we have generated chimeric BNLF1 by exchanging the DNA fragments between BNLF1-1510 and BNLF1-958 and examined their expression and transformation ability in Balb/3T3 cells. Results showed that transformation of Balb/3T3 cells by BNLF1-1510 was not due to the excessive expression of the gene. Transfection of Balb/3T3 cells with chimeric BNLF1 showed that the genes with 3' 453 bp sequence of BNLF1-1510 were oncogenic to the cells. Study also revealed that changing the numbers of the 33 bp repeats in the 3' region of the two BNLF1s did not affect the transformation characteristics. On the other hand, deletion of a 30 bp sequence of BNLF1-958, which is absent in BNLF1-1510, changed the gene from non-oncogenic to oncogenic and insertion of this 30 bp sequence into BNLF1-1510 abolished the transformation ability. BNLF1 without this 30 bp sequence was also found in the tumours of other EBV-related neoplastic disease, suggesting that absence of this 30 bp sequence in BNLF1 may be associated with the oncogenesis of these diseases.

Characterization of the replicon of plasmid pSW500 of Erwinia stewartii

A 1.6-kb DNA region required for the replication of pSW500 from Erwinia stewartii SW2 has been identified. DNA sequencing analysis revealed that this DNA fragment consists of a DnaA box, seven 16-bp direct repeats, and a 1005-bp open reading frame. The seven direct repeats have been demonstrated to mediate the incompatibility function of the plasmid. Primer extension analysis showed that the 1005-bp ORF is transcribed in vivo and the +1 site of the transcript is located 113 bp upstream from the translation initiation codon of the ORF. Complementation studies showed that this ORF is required for the replication of the plasmid and may encode a replication protein, RepA. Gene fusion studies revealed that the expression of repA is autoregulated by RepA. We also found that the pSW500 replicon has a copy number of approximately two and that the plasmid is stably maintained in Escherichia coli, thus demonstrating that the replicon contains all the elements required for copy number control and plasmid stability in E. coli. Curing of pSW500 from E. stewartii SW2 revealed that loss of pSW500 did not have any obvious effect on morphology or physiology of the cells, suggesting that pSW500 does not encode a function that is indispensable for the survival of the organism.