The public health impact of Lyme disease in Maryland

The purpose of this study was to estimate the health burden imposed by Lyme disease (LD) in Maryland during 1992 and 1993. A cross-sectional 1-in-15 survey of physicians (total, 1200) in Maryland was conducted to estimate the incidence of diagnosed LD, presumptive cases of LD, patients with tick bites, and diagnostic tests ordered for LD. Results show that LD is underreported by 10- to 12-fold in Maryland, that 80% of cases are managed by primary care physicians, and that there is discordance between the actual clinical treatment of patients and the recommended approach. In addition, the much greater numbers of patients treated for presumptive LD, seen and given prophylaxis for tick bites, and having diagnostic tests indicate that real and perceived LD is a far greater public health problem and uses more medical resources than official surveillance data suggest.

p53 mutations in esophageal tumors from high-incidence areas of China

Carcinomas of the upper digestive tract (squamous-cell carcinoma of the esophagus, adenocarcinoma of the cardia) from 24 patients residing in Linxian (China) and near-by high-incidence areas were analyzed for mutations in exons 5-8 of the p53 tumor-suppressor gene. Mutations were identified by polymerase chain reaction amplification and direct sequencing in 50% of the specimens. Eleven tumors harbored a single base-pair substitution leading to either an amino-acid substitution (8 tumors) or a chain-termination signal (3 tumors), and one tumor revealed a 15-bp deletion in exon 7 with a silent base substitution adjacent to the deletion site. Mutations occurred in all 4 exons examined, with a preponderance in exon 5. Of the 6 mutations identified among the 14 adenocarcinomas examined, 3 were G to T transversions, a mutation that has thus far been absent from reported mutations in Barrett's esophageal adenocarcinomas and dysplasias from patients residing in Europe and North America.

[Alterations of oncogenes in human fetal esophageal epithelium induced by N-methylbenzylnitrosamine (NMBzA)]

Epidemiological investigation showed that N-methylbenzylnitrosamine (NMBzA) has been associated with increased incidence of esophageal cancer (EC) in Linxian county, a high incidence area. In present study, our results indicate that NMBzA can induce amplification and over-expression of EGFr gene in human fetal esophageal epithelium (HFE) treated with NMBzA for 24 hours as shown by southern blot assay and immunohistochemistry. The papillary hyperplasia was induced in HFEs that cultured with NMBzA for 1 to 3 weeks. Amplification of c-myc and int-2 gene in HFEs treated by NMBzA for 1 week and 3 weeks was found, respectively. Deletions of p53 and Rb gene were found in human fetal esophageal carcinomas induced by NMBzA. Overexpression of p53 protein in human fetal esophageal carcinomas detected by immunohistochemical methods indicates that p53 gene mutation(s) may be occured. The HFE explants treated in vitro with NMBzA for 3 weeks were inoculated subcutanously into balb/c nude mice. No tumor was found in 5 months after inoculation, suggesting that only changes of oncogene(s) are insufficient to induce full transformation. Other genetic alterations (such as functional inactivation of Rb or/and p53 tumor suppressor genes) may be necessary in the further progression of malignant lesions.

[Effect of dimercaptosuccinic acid per os on distribution and excretion of 210Pb and 203Hg in mice]

Sodium dimercaptosuccinate (Na-DMS) ip 1 g.kg-1, dimercaptosuccinic acid (DMSA) ig 1 g.kg-1, DMSA ig 1 g.kg-1 with NaHCO3 or Na-citrate ig 3 g.kg-1 was given to mice, separately. It enhanced the excretion of 210Pb in urine about 3.4, 3.8, 3.6, and 2.3 times vs control, respectively within 24 h. It enhanced the excretion of 203Hg in urine about 2.4, 2.3, 3.3, and 2.7 times, respectively within 24 h. Fecal excretion was not significantly elevated vs control. Tissue radioactivities showed a remarkable decrease in the levels of 210Pb and 203Hg in most organs, but DMSA increase the 210Pb content in kidney. The therapeutic effect of ig DMSA was similar to that of ip sodium dimercaptosuccinate.

[Whole-body autoradiographic localization of catecholamic acid in mice]

Catecholamic acid [catechol-3,6-bis-(methyleneimino diacetic acid)] is a chelating agent synthesized in our institute. Whole-body autoradiographic study was carried out to determine the distribution of [14C]catecholamic acid in 5 adult male mice. Each mouse was injected i.v. 370 kBq. After various times the mice, under ether anesthesia, were immersed in a mixture of dry ice and hexane. Whole-body sections were made at -20 C, 20 microns in thickness. Results showed: (1) At 5 min, higher radioactivities appeared in blood, kidneys, gastrointestinal mucosa, bone, skin, and hair; moderate concentrations in liver, lungs, spleen, and salivary glands. (2) During 20 min and 3 h, the radioactivities decreased (gradually) in all tissues except the bone. (3) Intense radioactivity persisted in the bone, while only traces remained in the kidneys and intestinal mucosa throughout the 24 h period of observation.

[Effects of dimercaptosuccinic acid per os on copper excretion in rat]

After dimercaptosuccinic acid (DMSA) was given intragastrically by gavage (ig) 0, 250, or 500 mg.kg-1 following in CuSO4 30 mg.kg-1 daily x 3 d in rats, the Cu contents of serum increased markedly within 1-12 h. When ig DMSA daily x 3 d, the excretion of Cu in urine per 24 h in the treated group was greatly promoted vs the control (P < 0.01), that in the 250 or 500 mg.kg-1 group were enhanced 2.4-3.8 and 5.8-7.8 times, respectively. That the excretion of Cu was increased in bile but not in feces suggested the plausible existence an enterohepatic circulation.

[Multiple gene alterations in human esophageal squamous cell carcinoma]

In 45 human esophageal squamous cell carcinomas, 29 showed alterations of EGFr, c-myc, int-2, Rb and p53 gene by Southern blot hybridization, a frequency of 15.6%, 31.1%, 35.6%, 22.2%, 6.7%, respectively. Among these cases, 16 cases showed two or multiple gene changes, and most of them were of II-III stage. The results suggest that gene alterations may be related to pathological stages of the disease. The poorer the differentiation of the tumor, the more gene changes were accumulated. We did not find association between the presence of metastasis in lymph nodes and the gene alterations.

[Study on the relationship between two second-messenger pathways on the regulation of proliferation and differentiation in MGc 80-3 cells]

By using an inducer of differentiation (HMBA) and blockers of signal pathways, the relationship between two second-messenger pathways (DG-PKC, cAMP-PKA) in inducer-mediated MGc80-3 cell differentiation was studied. Cells were treated with HMBA for 24 h, levels of DG decreased by 64.7%, activity of PKC decreased by 28.7%, while levels of cAMP and rate of it's protein binding increased by 62% and 32.6% respectively (after treated for 48 h, the result was more remarkable). PKA-R II distributed in nuclei. H7 (PKC inhibitor) was used to substitute for HMBA to block the DG-PKC pathway. After treatment for 24 h, the levels of DG and activity of PCK both decreased, while the levels of cAMP increased 1.04 times. On the contrary, PKA inhibitor was added while HMBA was used to induce cell differentiation, cAMP-PKA pathway was blocked, levels of cAMP and rate of it's protein binding decreased. But levels of DG and activity of PKC both increased to the levels of control cells. At this time, PKA-R II distributed only in cytoplasm. These results suggest that harmonious relations of the positive and negative regulation of cAMP-PKA and DG-PKC systems in cells during the proliferation and differentiation of cells. It also showed that positive regulation of PI system may play a leading role in MGc80-3 cells. It let to normal regulation of two signal pathway out of control to remain malignant phenotype of these cells.

Characterization of the ntrBC genes of Azospirillum brasilense Sp7: their involvement in the regulation of nitrogenase synthesis and activity

A 7.1 kb EcoRI fragment from Azospirillum brasilense, that hybridized with a probe carrying the ntrBC genes from Bradyrhizobium japonicum, was cloned. The nucleotide sequence of a 3.8 kb subfragment was established. This led to the identification of two open reading frames, encoding polypeptides of 401 and 481 amino acids, that were similar to NtrB and NtrC, respectively. A broad host range plasmid containing the putative Azospirillum ntrC gene was shown to restore nitrogen fixation under free-living conditions to a ntrC-Tn5 mutant of Azorhizobium caulinodans. Several Tn5 insertion mutants were isolated in the ntrBC coding region in A brasilense. These mutants were prototrophic and Nif+. However, their nitrogenase activity was slightly lower than in the wild type and they were unable to grow on nitrate as sole nitrogen source. Under microaerobiosis and in the absence of ammonia, a nifA-lacZ fusion was expressed in the mutants at about 60% of the level in the wild type. In the presence of ammonia, the fusion was similarly expressed (60% of the maximum) both in the wild type and mutants. Addition of ammonia to a nitrogen-fixing culture of ntrBC mutants did not abolish nitrogenase activity, in contrast with the wild type. It thus appears that in Azospirillum the ntrBC genes are not essential for nitrogen fixation, although NtrC controls nifA expression to some extent. They are, however, required for the switch-off of nitrogenase activity.

Regulation of nitrogen fixation inAzospirillum brasilenseSp7: Involvement ofnifA, glnAandglnBgene products

The expression of nifA-, niH- and nifB-lacZ fusions was examined in different mutants of Azospirillum brasilense. Mutations in nifA, glnA and glnB severely impaired the expression of nifH- and nifB-lacZ fusions. By contrast, a nifA-lacZ fusion was not affected in a nifA or a glnB background and was only partially impaired in glnA mutants. It is proposed that in A. brasilense, the PII protein and glutamine synthetase are involved in a post-translational modification of NifA.

A study on a family with high incidence of leukemia

A family with a high incidence of leukemia was investigated and followed up for 10 years. Up to now, 7 of 48 members in this family had acute nonlymphocytic leukemia. Chromosomal aberration was found in 3 healthy members, 2 of whom were found to have 47, XX, +5, -8, +Mar, del (7) (q22-qter) and 45, XO, -Y chromosomes and developed this disease 5 and 7 years later respectively. Pedigree analysis suggested that the hereditary defect in the family should rest on the maternal lineage. It is considered that hereditary factors play an important part in the pathogenesis of leukemia in the family.

The ouabain-dependent Na(+)-K+ pump and the brain renin-angiotensin system

The present study investigated the role of ouabain-dependent inhibition of the Na(+)-K+ pump and stimulation of the brain renin-angiotensin system by looking at 1) the short-term and long-term effects of ouabain on arterial blood pressure, and 2) the acute and chronic effects of angiotensin II (ANG II) intraventricularly (i.c.v.) on the release of an endogenous inhibitor of the Na(+)-K+ pump. Ouabain infused subcutaneously in a dose of 1.5 mg.kg-1. 24 h-1 for 7 days did not affect arterial blood pressure in rats, whereas increases in both blood pressure and weight were observed in rats infused with ouabain at the same dose for a 4-week period. Plasma supernate obtained from pentobarbital-anesthetized dogs acutely treated with ANG II (1 microgram i.c.v. every 30 min for 2 h) induced a 44% decrease in the ouabain-sensitive 86Rb uptake by the rat tail artery which was prevented by pretreatment with saralasin i.c.v. Plasma supernate obtained from dogs that were infused for 4 days with ANG II (20 ng/min i.c.v.) and received saline as the drinking fluid also reduced by 34% the ouabain-sensitive 86Rb uptake by the rat tail artery. The present study provides evidence that chronic inhibition of the Na(+)-K+ pump for 4 weeks leads to the development of hypertension and that the release of an endogenous inhibitor of the Na(+)-K+ pump is implicated in the hypertension resulting from chronic stimulation of the brain angiotensin-system and an increase in sodium chloride intake.

Identification of a nifA-like regulatory gene of Azospirillum brasilense Sp7 expressed under conditions of nitrogen fixation and in the presence of air and ammonia

A gene bank of Azospirillum lipoferum Br17 constructed in the vector lambda GEM11 was screened with a Bradyrhizobium japonicum nifA gene probe. A 7.3 kb EcoRI fragment carrying a nifA-like gene was thereby isolated and subsequently used to screen a gene bank of Azospirillum brasilense Sp7 constructed in pUC18. Two EcoRI fragments of 5.6 kb and 3.6 kb covering the nifA-homology region were found. Mutants with Nif- phenotype were obtained by site-directed Tn5 mutagenesis of the 5.6 kb fragment and subsequent recombination into the A. brasilense Sp7 genome. The mutations were clustered into two loci located at each extremity of the fragment. One of these loci corresponded to nifA and the other to nifB. The nucleotide sequence of nifA of A. brasilense Sp7 was determined. Comparison of the deduced amino acid sequences of NifA of A. brasilense Sp7 and NifA of B. japonicum, Rhizobium leguminosarum biovar trifolii and Klebsiella pneumoniae confirmed that it was a nifA-like gene. Construction of a nifA-lacZ fusion and mapping of the RNA transcriptional start site showed that the nifA-like gene was expressed from an unidentified promoter, under conditions of nitrogen fixation and in the presence of oxygen and ammonia.

[Scavenging effects of dimercaptosuccinic acid per os on nickel in mice and rats]

In mice and rats given iv or im 63NiCl2 148-370 kBq, radioactivity was present in highest concentrations in kidney, lung, and liver. After given ig dimercaptosuccinic acid (DMSA) 1 g.kg-1, radioactivity decreased remarkably in kidney, lung, and blood. The excretion of 63Ni via urine and feces within 24 h, respectively 13.0 +/- 2.4% and 0.6 +/- 0.4%, was similar to that in the control group in mice. But radioactivity increased markedly in bone. The Ni content of bone decreased on d 7. In rats given im 63NiCl2 370 kBq, two different nickel complex peaks appeared in the gel chromatograms of serum, kidney, and lung. DMSA reduced the contents of protein-bound Ni in serum, kidney, and lung. The results showed that DMSA detoxified the Ni by forming a low toxicity Ni-DMSA complex to redistribute in the body.

[Expression of c-myc and HER-1 genes in the development of human esophageal cancer]

To understand the possible role of oncogenes in the development of human esophageal cancer, the expression of c-myc and HER-1 genes was studied by in situ hybridization. The results showed that: (a) The c-myc and HER-1 protooncogenes were transcriptionally activated (b) Activation of c-myc gene was observed in hyperplastic cells and carcinoma cells. (c) The degree of pathological changes of the esophageal epithelium was related to the level of c-myc transcription, the highest level of c-myc expression was seen in invasive carcinoma cells. (d) Expression of HER-1 gene in carcinoma cells is higher than that in normal and adjacent non-tumor cells, but its frequency is lower than that of c-myc gene.

[Whole body autoradiographic localization of dimercaptosuccinic acid per os in mice]

Dimercapto [14C]succinic acid ([14C]DMSA) was given to male mice by ig 233 kBq. The mice were sacrificed by immersion in dry ice/hexane at 1, 3, 9 and 24 h. The distribution and concentration of [14C]DMSA were observed and analysed by whole-body autoradiograph. Higher concentration appeared in oral cavity, esophagus, gastrointestinal contents, liver, kidney and urine at 1 or 3 h. A moderate concentration was seen in blood, bone and skin. A remarkable reduction of radioactivity was found in liver at 9 h, but GI contents, Harderian gland, kidney and urine retained intense distribution. The results indicated that DMSA absorbed rapidly per os and was eliminated by kidney within 24 h. No tissue had a pronounced retention of the [14C]DMSA.

Antidotal effects of dimercaptosuccinic acid

Dimercaptosuccinic acid (DMS), HOOC-CH(SH)-CH(SH)-COOH, was first developed in China as an effective antidote for poisoning from many heavy metals, such as Pb, Hg, As, Cd, Sb, Tl, Au, Zn, Ni, Pt, Ag, Co and Sn. DMS increases the excretion of Ce, Pm, Sr and Po from the body. Hundreds of patients suffering from hepatolenticular degeneration (Wilson's disease) have been treated successfully with DMS. Recently, DMS was found to be effective also in treating certain non-metallic intoxications, like some of the new non-phosphate pesticides and mushroom poisonings.

The antisense c-Ha-ras oligodeoxynucleotides inhibit the proliferation of the gastrocarcinoma-DNA-transformed rat 3-3 cells and reduce the p21 expression of the cells

The Rat 3-3 is a secondary transformant of the rat fibroblast cell line (Rat-1) transfected with total DNA of a gastrocarcinoma cell line BGC-823. The cells over-express the c-Ha-ras oncogene which contains point mutation at the 12th codon. In order to determine how the activated c-Ha-ras oncogene expression governs the cell's transformation, two pentadecadeoxy-nucleotides AS-1 and AS-2 were synthesized. AS-1 was complementary to the single strand of the first three codons and the upstream sequence close to the ribosome binding site of c-Ha-ras mRNA. AS-2 was complementary to the 3' end of the first intron and the 5' end of the second exon of c-Ha-ras unripe RNA enclosed in the nucleus. The oligonucleotides could block either the translation of c-Ha-ras mRNA or the splicing of c-Ha-ras unripe RNA, thus inhibiting the expression of the activated c-Ha-ras oncogene and the proliferation of the transformed cells Rat 3-3. The inhibitory effect increased with a growing concentration of the antisense oligodeoxynucleotide (from 4-10 mumol/L) and reached its peak at 12 h after Rat 3-3 was treated with AS-1 and AS-2. This effect became weaker afterwards. The p21 level, product of c-Ha-ras, in the Rat 3-3, was examined by ELISA method. The result shows that the amount of p21 in the growth-inhibited cells is about 30% of that of the control cells.

Effect of gender in centrally induced angiotensin II hypertension in dogs

This study was designed to investigate the relation between gender, an endogenous inhibitor of the Na+-K+ pump, and volume-dependent hypertension induced by stimulation of the brain renin-angiotensin system and increased salt intake. Angiotensin II (20 ng/min i.c.v.) was infused for 4 weeks in five dogs of each sex with saline as the drinking fluid. In male dogs, angiotensin II induced parallel pressor (30%) and dipsogenic responses (70%), whereas no hypertension and no increase in fluid intake were observed in females. In contrast, the activity of the Na+-K+ pump as assessed by 86Rb uptake was independent of gender. Our data provide novel evidence that gender plays a determining role in the physiological properties of centrally administered angiotensin II.

[Biological effect of HPD photosensitivity on human stomach cancer cells (MGC-803) in mitotic phase and interphase]

Photodynamic effect of HPD plus light on human stomach cancer cells (MGC-803) in the mitotic phase and interphase was studied. The synchronized mitotic cells were selected from the monolayer of asynchronous growing cells by shaking the culture flask. It was found that the killing frequency of HPD photosensitization was markedly different in the mitotic phase and interphase of synchronous growing MGC-803 cells, but a very small difference was found in HPD alone or light alone groups. The results show that, for adhesive cells in the two phases, there was a marked difference in damage pattern and recovery rate of mitosis 36 hr, 60 hr and 108 hr after photoradiation. The tolerance of mitotic cells to HPD plus light was much greater than that of the interphase cells. In the interphase, a great many of nude nuclei were seen and in the mitotic phase, cytokinesis was arrested resulting in many binucleated or multinucleated cells.

Disposition of [14C]dimercaptosuccinic acid in mice

Dimercaptosuccinic acid labeled with 14C ([14C]DMSA) was administered to mice iv; the mice were frozen by immersion in dry ice/hexane at 6 and 20 min and 1, 3, 9, and 24 hr after injection. The frozen mice were sectioned and processed for whole-body autoradiography for soluble substances. The radioactivity was highly localized in extracellular fluids such as the subcutaneous, intrapleural, intraperitoneal, and periosteal spaces. There was a pronounced accumulation in the periosteal fluid above that in other fluids during the first hour after injection. Most of the radioactivity was eliminated by the kidney and liver. Pretreatment of a mouse with HgCl2 subcutaneously 1 hr before [14C]DMSA produced an increase in radioactivity in the liver and decrease in lung. A high concentration of radioactivity was seen at the subcutaneous site of injection of the HgCl2. The results are interpreted to indicate that most of the DMSA is in the extracellular space but that it can cross cellular membranes to some extent. The pronounced accumulation in periosteal fluid may be an interaction of DMSA with Ca2+ in this space. No tissue had a pronounced retention of the compound, but lung retained more than most other tissues.