Increased insufflation pressure enhances the development of liver metastasis in a mouse laparoscopy model: possible mechanisms

BACKGROUND

The effect of different insufflation pressures and durations of CO2 pneumoperitoneum on the growth of liver metastasis was investigated in a mouse model. The possible mechanisms involved in the pressure-related enhancement of liver metastasis were also examined.

METHODS

Mice inoculated intraportally with colon 26 cells underwent CO2 pneumoperitoneum at different pressures (5,10, or 15 mmHg) for 30 or 60 min, or received no treatment other than tumor cell inoculation (control). The subsequent growth of liver metastases was examined. Mice injected intraportally with 111In-oxine-labeled colon 26 cells underwent pneumoperitoneum at three different pressures or served as controls. The radioactivity of the liver was determined to evaluate tumor accumulation in the liver. Mice received pneumoperitoneum at three different pressures or received trocar placement alone. Changes in plasma interleukin-6 levels were determined.

RESULTS

The growth of liver metastases on day 14 was influenced by increased insufflation pressures (p < 0.05) rather than the prolonged duration of pneumoperitoneum without significant interaction. The 15-mmHg pneumoperitoneum group showed a higher (p < 0.05) accumulation of radioactivity in the liver compared with the 5-mmHg pneumoperitoneum group and controls. Pneumoperitoneum groups with 5 and 10 mmHg showed higher (p < 0.05) peak levels of IL-6 compared with controls.

CONCLUSIONS

An elevated insufflation pressure plays an important role in the enhancement of liver metastases, and this pressure-related adverse effect may be partly relevant to facilitating accumulation of tumor cells in the liver.

FHIT alterations in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in rats

Alteration of the FHIT gene was investigated in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl) amine (BHP) in male Wistar rats. Animals at 6 weeks of age were given 2000 p.p.m. of BHP in drinking water for 12 weeks, then maintained without further treatment until killed at the end of week 25. A total of 25 lung adenocarcinomas were obtained and total RNAs were extracted from each for assessment of aberrant transcription of the FHIT gene by reverse transcription (RT)-polymerase chain reaction (PCR) analysis. Aberrant transcripts were detected in 15 adenocarcinomas (60%) as absence in the regions of nucleotides (nt) -9 to 279, -98 to 279, -98 to 348 or -98 to 447. Genomic DNAs were also extracted from all 25 adenocarcinomas and exons 5-9 were examined for mutations, using PCR-single strand conformation polymorphism (SSCP) analysis and sequencing. A mutation was detected in only one adenocarcinoma (4%), an ACC to ATC (Thr to IIe) transition at codon 76. Southern blot analysis of eight tumors did not show any evidence of gross rearrangement or deletion of the FHIT gene. Western blot analysis revealed reduced expression of Fhit protein in six out of 10 adenocarcinomas (60%). These results suggest that alteration of the FHIT gene may be involved in the development of lung adenocarcinomas induced by BHP in rats.

Increased insufflation pressure enhances the development of liver metastasis in a mouse laparoscopy model

Despite the widespread use of laparoscopic techniques for colorectal cancer surgery, little is known about the potential risk of liver metastasis following CO2 pneumoperitoneum. We investigated the effect of different insufflation pressures and durations of CO2 pneumoperitoneum on the growth of liver metastasis in a mouse model. Six- to 7-week old male BALB/C mice were intraportally inoculated with 2 x 10(4) Colon 26 cells and randomly allocated to receive either CO2 pneumoperitoneum at different pressures (5 mmHg, 10 mmHg, or 15 mmHg), xiphoid-pubic laparotomy, or no treatment other than tumor cell inoculation. Mice undergoing pneumoperitoneum or laparotomy were then subdivided by the duration of treatment (30 minutes or 60 minutes). Cancer nodules on the liver surface from a total of 122 mice were evaluated on the 14th postoperative day. Similar to full laparotomy, CO2 pneumoperitoneum at 10 mmHg and 15 mmHg for 60 minutes, and pneumoperitoneum at 15 mmHg for 30 minutes significantly promoted the growth of cancer nodules on the liver surface. Enhancement of tumor growth was influenced by increased insufflation pressures (p < 0.05) rather than the prolonged length of pneumoperitoneum (p = 0.53) without significant interaction (p = 0.49). These results suggest that an increased insufflation pressure promotes the growth of liver metastases as well as laparotomy in this animal model. growth of liver metastases in a mouse laparoscopy model, following different pressures and durations of CO2 pneumoperitoneum, which is used most often in laparoscopic procedures.

Analysis of the structure, substrate specificity, and mechanism of squash glycerol-3-phosphate (1)-acyltransferase

BACKGROUND

Glycerol-3-phosphate (1)-acyltransferase(G3PAT) catalyzes the incorporation of an acyl group from either acyl-acyl carrier proteins (acylACPs) or acyl-CoAs into the sn-1 position of glycerol 3-phosphate to yield 1-acylglycerol-3-phosphate. G3PATs can either be selective, preferentially using the unsaturated fatty acid, oleate (C18:1), as the acyl donor, or nonselective, using either oleate or the saturated fatty acid, palmitate (C16:0), at comparable rates. The differential substrate specificity for saturated versus unsaturated fatty acids seen within this enzyme family has been implicated in the sensitivity of plants to chilling temperatures.

RESULTS

The three-dimensional structure of recombinant G3PAT from squash chloroplast has been determined to 1.9 A resolution by X-ray crystallography using the technique of multiple isomorphous replacement and provides the first representative structure of an enzyme of this class.

CONCLUSIONS

The tertiary structure of G3PAT comprises two domains, the larger of which, domain II, features an extensive cleft lined by hydrophobic residues and contains at one end a cluster of positively charged residues flanked by a H(X)(4)D motif, which is conserved amongst many glycerolipid acyltransferases. We predict that these hydrophobic and positively charged residues represent the binding sites for the fatty acyl substrate and the phosphate moiety of the glycerol 3-phosphate, respectively, and that the H(X)(4)D motif is a critical component of the enzyme's catalytic machinery.

Matrix metalloproteinase-2 and -9 in bile as a marker of liver metastasis in colorectal cancer

Matrix metallproteinases (MMP)-2 and -9 are associated with cancer invasion and metastasis. MMP-2 and MMP-9 activities have never been assayed in bile. In the present study we investigated whether MMP-2 and -9 activities in the bile could be a marker for evaluation of liver metastasis in colorectal cancer. Fifty-three patients underwent colorectal resection for histologically verified adenocarcinoma. Twenty-six patients had colorectal cancer without liver metastasis and 27 patients had metastatic liver tumor. Six patients were studied as carcinoma-free control. MMP-2 and MMP-9 activities were assayed in bile using gelatin zymography and quantitated. Active MMP-2 activity of colorectal cancer with liver metastasis group (24.1 +/- 2.5 pixel count) was significantly higher than that of colorectal cancer without liver metastasis group (11.4 +/- 1.3 pixel count) (P < 0.001) or of control group (6.4 +/- 1.0 pixel count) (P < 0.001). Active MMP-9 was not detected in bile. ProMMP-9 activity of colorectal cancer with liver metastasis group (530.3 +/- 127.5 pixel count) was significantly higher than that of colorectal cancer without liver metastasis group (213.9 +/- 33.2 pixel count) (P = 0.008). This is the first report showing that the levels of active MMP-2 and proMMP-9 in bile were significantly higher in liver metastasis of colorectal cancer than in metastasis-free colorectal cancer. The results suggest that activities of active MMP-2 and proMMP-9 in the bile may be useful markers for predicting liver metastasis in colorectal cancer.

[Histological evaluation of liver metastasis of colorectal cancer following hepatic arterial infusion with degradable starch microspheres and adriamycin/mitomycin C]

Little is known about the histological effect of hepatic arterial infusion with degradable starch microspheres (DSM), adriamycin (ADM), and mitomycin C (MMC) on liver metastasis of colorectal cancer. We histologically examined hepatic metastases resected following this therapy and investigated their relation to macroscopic changes in size. Neither a histological nor macroscopic effect was found in 2 patients receiving this therapy only one time. A 57-year-old woman with a solitary liver metastasis who received this therapy repeatedly (five times every 3 to 4 weeks) subsequently showed a partial response. She underwent hepatic metastasectomy 5 months after the end of the therapy. Histological examination showed that the greater part of the metastatic lesion was composed of fibrous tissues without any viable cancer cells. In conclusion, it should be noted that repeated infusions of DSM.ADM.MMC for liver metastases of colorectal cancer can have a marked histological effect even though the lesion does not show a complete response.

[A case of pseudomyxoma peritonei with a pancreatic cancer treated by the intraperitoneal administration of cisplatinum]

A 55-year-old woman underwent laparotomy with a diagnosis of pseudomyxoma peritonei associated with a pancreatic cancer. The peritoneal cavity was filled with much gelatinous material, which was removed as much as possible by suction and by hand. Distal pancreatectomy, appendectomy and bilateral oophorectomy were performed. The peritoneal cavity was washed by saline and 5% glucose solution followed by dispersion of 100 mg of cisplatinum. The intraperitoneal chemotherapy was performed once every two weeks after the operation through an indwelling catheter. Histological examination revealed a mucinous cystadenocarcinoma of the pancreas, causing pseudomyxoma peritonei. The patient is in a good health 4 years after the operation.

Two new variants of the Rhodococcus equi virulence plasmid, 90 kb type III and type IV, recovered from a foal in Japan

This report describes the discovery of two new virulence plasmid types from a crossbred foal with Rhodococcus equi pneumonia in Kumamoto died with severe R. equi pneumonia and ulcerative enteritis. R. equi was isolated in large numbers and isolates from the foal were investigated for the presence of virulence-associated 15-17 kDa antigens (VapA) by colony blotting, using the monoclonal antibody 10G5, and by gene coding for VapA by PCR. Plasmid DNAs extracted from the isolates were digested with restriction endonucleases BamHI, EcoRI, EcoT22I, and HindIII. The digestion patterns that resulted divided the plasmids of these isolates into two closely related types. The digestion patterns were then compared with eight representative virulence plasmid types (85 kb types I, II, III and IV, 87 kb types I and II, 90 kb types I and II), which have already been reported. None of the EcoRI and EcoT22I digestion patterns of the eight representative plasmids matched those of the two plasmid types. We tentatively designated these new plasmid types as 90 kb type III and type IV, since HindIII and BamHI digestion patterns of the two plasmid types were identical with those of a 90 kb type I plasmid. This study, demonstrated that there are at least 10 distinct but closely related plasmids present in isolates from horses in the world.

[Effect of peroral doxifluridine plus hepatic arterial infusion for synchronous liver metastasis of colorectal cancer--correlation with the expression of thymidine phosphorylase and dihydropyrimidine dehydrogenase in primary colorectal cancer lesions]

We investigated whether the efficacy of peroral doxifluridine and hepatic arterial 5-FU infusion on synchronous liver metastasis of colorectal cancer could be predicted based on the expression of thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) in the primary colorectal lesions. Ten patients with synchronous liver metastasis of colorectal cancer were given doxifluridine (600-800 mg/body/day) orally and 5-FU (500 mg/body, once or twice a week) through the hepatic artery following resection of the primary lesions between June 1996 and July 2001. The levels of TP and DPD in the primary lesions were determined by an enzyme-linked immunosorbent assay. The level of TP, DPD, and the ratio of TP/DPD in patients with partial response (n = 4) were 89.8 +/- 30.0 U/mg protein, 23.5 +/- 25.7 U/mg protein, and 3.8 +/- 1.4, respectively, while those in patients with no response or progressive disease (n = 6) were 41.8 +/- 9.7 U/mg protein, 25.8 +/- 15.8 U/mg protein, and 2.2 +/- 1.6, showing significant difference (p < 0.01) in the level of TP between the groups. These results indicate that determining the level of TS in primary colorectal lesions may be useful for predicting the efficacy of this regimen for patients with synchronous liver metastasis of colorectal cancer.

Elevated expression of transforming growth factor betas and the tumor necrosis factor family in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine in rats

Expression of transforming growth factor betas (TGF betas), tumor necrosis factor (TNF) family members, interferons (IFNs), macrophage migration inhibitory factor (MIF) and granulocyte macrophage colony stimulating factor (GM-CSF) in lung adenocarcinomas induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats was investigated using a multiprobe RNase protection assay (RPA) followed by densitometric quantification. Male Wistar rats, 6 weeks of age, were given 2,000 ppm BHP in their drinking water for 12 weeks and maintained without further treatment until killed at week 25. Total RNAs were extracted from 15 adenocarcinomas. Four samples of normal lung tissue from untreated rats served as controls. The expression of TGFbeta1, TGFbeta2, TGFbeta3, TNFalpha, TNFbeta and lymphotoxin beta (Ltbeta) was significantly higher in adenocarcinomas than in normal lung tissues. In contrast, MIF was expressed at the same level in neoplasms and normal tissue and no expression of IFNbeta, IFNgamma and GM-CSF was apparent in either adenocarcinomas or normal lung tissues. These results suggest that elevated expression of TGFbetas and TNF family members may contribute to the development and progression of lung adenocarcinomas induced by BHP in rats.

Preferential and persistent activation of the STAT1 pathway in rheumatoid synovial fluid cells

OBJECTIVE

Inflammatory cytokines such as interleukin 1 (IL-1), IL-6, and tumor necrosis factor-alpha are produced in great quantities in inflamed rheumatoid joints. However, little is known about the pathogenic significance of each cytokine in the proliferative synovitis and destruction of bone and joint. We investigated the role of cytokine receptor signals transduced into cells at the foci of rheumatoid inflammation.

METHODS

Synovial fluid (SF) cells from patients with rheumatoid arthritis (RA) and osteoarthritis (OA) were examined for the activation of a group of cytokine receptor signaling molecules, signal transducers and activators of transcription (STAT).

RESULTS

DNA binding of STAT1 in SF cells was observed in 8 out of 14 patients with RA, but in none of the 10 patients with OA studied, and this was prevented by preincubation of these cells with neutralizing anti-IL-6 antibody. IL-6 activated both STAT1 and STAT3 in normal peripheral blood (PB) leukocytes, and preferentially STAT1 in rheumatoid SF cells. Moreover, STAT1 activation in rheumatoid SF cells appeared to be continuous, in contrast to the transient activation in normal PB leukocytes.

CONCLUSION

STAT1 and STAT3 are differentially regulated in response to IL-6 in different cell types. The continuous STAT1 activation may be of pathogenic significance in the progression and persistence of RA.

Absence of beta-catenin gene mutations in pancreatic duct lesions induced by N-nitrosobis(2-oxopropyl)amine in hamsters

The involvement of beta-catenin gene alterations in pancreatic duct carcinogenesis induced by N-nitrosobis(2-oxopropyl)amine (BOP) in hamsters was examined by polymerase chain reaction-single strand conformation polymorphism analysis and the expression of beta-catenin protein was examined by immunohistochemistry. No mutations of the beta-catenin gene were detected in 20 pancreatic duct adenocarcinomas (PDAs). Immunohistochemical staining showed the beta-catenin protein to be ubiquitously localized in the cell membranes. beta-Catenin accumulation was not identified in the cytoplasm and/or nucleus in any of 102 hyperplasias, 35 atypical hyperplasias, and 73 PDAs, as well as normal pancreatic duct cells. These results suggest that the Wnt/beta-catenin signaling pathway may not play an important role in pancreatic duct carcinogenesis induced by BOP in hamsters.

Intra-articular injection of hyaluronate (SI-6601D) improves joint pain and synovial fluid prostaglandin E2 levels in rheumatoid arthritis: a multicenter clinical trial

OBJECTIVE

The relationship between clinicalfeatures and biochemical parameters of synovialfluid after serial intra-articular injections of sodium hyaluronate (SI-6601D) was investigated.

METHODS

SI-6601D (sodium hyaluronate with an average molecular weight of 8.4 x 10(5); 25mg/2.5ml/syringe) was injected intra-articularly into the knees of 25 patients with rheumatoid arthritis (RA) every week for 5 consecutive weeks. Clinical and biochemical parameters were monitored before and after injection. Clinicalfindings included pain, as a summation of 3 categories (pain at rest, pain in motion and pain in passive motion, each assessed on a 4-step rating scale), and inflammation, also as a summation of 3 categories (swelling, patellar ballotement and local warmth, each assessed on a 4-step rating scale). Pain on walking of patient was qualitatively assessed by visual analogue scale (VAS). The aspirated volume of synovialfluid (SFV) was recorded and levels of prostaglandin (PG) E2, transforming growth factor beta-1, tumor necrosis factor alpha, interleukin I receptor antagonist, chondroitin 4-sulfate (C4S) and chondroitin 6-sulfate were measured.

RESULTS

Significant improvement in pain symptoms (p < 0.0001), inflammation (p < 0.0001), VAS pain (p < 0.001) and SFV (p < 0.05) were observed after the 5 injections. Levels of PGE2 (p < 0.05) and C4S (p < 0.05) in the synovialfluid were significantly decreased.

DISCUSSION

SI-6601D improved local clinical symptoms in RA patients by suppressing PGE2 and, therefore, may be a useful treatment for local inflammation in RA.

[Tumoral levels of thymidine phosphorylase and dihydropyrimidine dehydrogenase in elderly colorectal cancer patients]

Fluoropyrimidine therapy for elderly colorectal cancer patients remains controversial. Tumoral levels of thymidine phosphorylase (TP), dihydropyrimidine dehydrogenase (DPD), and the ratio of TP to DPD determined by an enzyme-linked immunosorbent assay were compared between colorectal cancer patients aged 75 or over (elderly group, n = 25) and those 74 years or less (control group, n = 87), in order to examine the characteristics of colorectal cancers in the elderly from the viewpoint of metabolic and anabolic pathways of fluoropyrimidines. The level of TP was 78.4 +/- 47.0 unit/mg protein in the elderly group and 82.4 +/- 70.9 unit/mg protein in the control group (p = 0.86). The level of DPD was 53.7 +/- 43.1 unit/mg protein in the elderly group and 52.6 +/- 37.7 unit/mg protein in the control group (p = 0.73). The ratio of TP to DPD was 2.0 +/- 1.2 in the elderly group and 1.8 +/- 0.9 in the control group (p = 0.44). These three parameters did not differ between the groups when divided according to Dukes' stage (Dukes' A.B versus Dukes' C.D). These results suggest that there are no age-specific characteristics in relation to conversion of fluoropyrimidines such as capecitabine and doxifluridine to 5-fluorouracil (FU) and degradation of 5-FU in colorectal cancers.

Bioenergetic responses of Synechocystis 6803 fatty acid desaturase mutants at low temperatures

Fatty acid composition of the membrane lipids in the mesophilic cyanobacterium Synechocystis sp. PCC 6803 was altered in earlier work by targeted mutagenesis of genes for fatty acid desaturases. In this work, cells of several mutant strains, depleted in the unsaturated fatty acids in membrane lipids, were grown at 34 degrees C. Spheroplasts (permeabilized cells) were prepared by lysozyme digestion of the cell wall followed by gentle osmotic shock. The bioenergetic parameters ATP formation, electron transport, and H+ uptake were measured at various temperatures. All three bioenergetic parameters for spheroplasts from wild-type cells (which had abundant polyunsaturated fatty acids) were active down to the lowest temperatures used (1 degrees - 2 degrees C). In two strains, which lacked the capacity to desaturate fatty acids at the A 12 position and at the A 12 and A6 positions (designated as desA- and desA-/desD-, respectively), the spheroplasts lost the capacity to form ATP (measured as phenazine methosulfate cyclic phosphorylation) at about 5 degrees C but retained electron transport (water oxidation-dependent ferricyanide reduction) and H+ uptake linked to phenazine methosulfate cyclic electron transport. It appears that the absence of the unsaturation of fatty acids in the A 12 and A6 positions blocks the ability of the photosynthetic membranes to couple a bioenergetically competent proton-motive force to the ATP formation mechanism at temperatures below 5 degrees C. It remains to be determined whether the loss of ATP formation in the mutant strains is the failure of available protons to properly flow into the CF0CF1-ATP synthase or a failure in the CF1 part of the complex in coupling the dissipative H+ flow to the enzyme mechanism of the synthase.

Cold-regulated genes under control of the cold sensor Hik33 in Synechocystis

A histidine kinase, Hik33, appears to sense decreases in temperature and to regulate the expression of certain cold-inducible genes in the cyanobacterium Synechocystis sp. PCC6803. To examine the role of Hik33 in the regulation of gene expression, we analysed a DeltaHik33 mutant using the DNA microarray technique. In wild-type cells, genes that were strongly induced at low temperature encoded proteins that were predominantly subunits of the transcriptional and translational machinery. Most cold-repressible genes encoded components of the photosynthetic machinery. Mutation of the hik33 gene suppressed the expression of some of these cold-regulated genes, which could be divided into three groups according to the effect of the mutation of hik33. In the first group, regulation of gene expression by low temperature was totally abolished; in the second group, the extent of such regulation was reduced by half; and, in the third group, such regulation was totally unaffected. These results suggest that expression of the genes in the first group is regulated solely by Hik33, expression of genes in the third group is regulated by an as yet unidentified cold sensor, and expression of genes in the second group is regulated by both these cold sensors.

Unsaturated fatty acids in membrane lipids protect the photosynthetic machinery against salt-induced damage in Synechococcus

In this study, the tolerance to salt stress of the photosynthetic machinery was examined in relation to the effects of the genetic enhancement of the unsaturation of fatty acids in membrane lipids in wild-type and desA+ cells of Synechococcus sp. PCC 7942. Wild-type cells synthesized saturated and mono-unsaturated fatty acids, whereas desA+ cells, which had been transformed with the desA gene for the Delta12 acyl-lipid desaturase of Synechocystis sp. PCC 6803, also synthesized di-unsaturated fatty acids. Incubation of wild-type and desA+ cells with 0.5 M NaCl resulted in the rapid loss of the activities of photosystem I, photosystem II, and the Na+/H+ antiport system both in light and in darkness. However, desA+ cells were more tolerant to salt stress and osmotic stress than the wild-type cells. The extent of the recovery of the various photosynthetic activities from the effects of 0.5 M NaCl was much greater in desA+ cells than in wild-type cells. The photosystem II activity of thylakoid membranes from desA+ cells was more resistant to 0.5 M NaCl than that of membranes from wild-type cells. These results demonstrated that the genetically engineered increase in unsaturation of fatty acids in membrane lipids significantly enhanced the tolerance of the photosynthetic machinery to salt stress. The enhanced tolerance was due both to the increased resistance of the photosynthetic machinery to the salt-induced damage and to the increased ability of desA+ cells to repair the photosynthetic and Na+/H+ antiport systems.

Crystallization and preliminary X-ray analysis of the glycerol-3-phosphate 1-acyltransferase from squash (Cucurbita moschata)

Glycerol-3-phosphate 1-acyltransferase (E.C. 2.3.1.15; G3PAT) catalyses the incorporation of an acyl group from either acyl-acyl carrier proteins (acylACPs) or acylCoAs into the sn-1 position of glycerol 3-phosphate to yield 1-acylglycerol 3-phosphate. Crystals of squash G3PAT have been obtained by the hanging-drop method of vapour diffusion using PEG 4000 as the precipitant. These crystals are most likely to belong to space group P2(1)2(1)2(1), with approximate unit-cell parameters a = 61.1, b = 65.1, c = 103.3 A, alpha = beta = gamma = 90 degrees and a monomer in the asymmetric unit. X-ray diffraction data to 1.9 A resolution have been collected in-house using a MAR 345 imaging-plate system.

Liver metastasis following pneumoperitoneum with different gases in a mouse model

BACKGROUND

The validity of using CO2 in laparoscopic tumor surgery has not yet been established. To address this question, we investigated the growth of liver metastases following insufflation with different gases in a mouse laparoscopy model.

METHODS

Male BALB/C mice inoculated intraportally with colon 26 cells were randomized to undergo pneumoperitoneum with CO2 (n = 16), helium (n = 16), argon (n = 16), or air (n = 17), or to act as controls without insufflation (n = 17).

RESULTS

The growth of cancer nodules on the liver 14 days after surgery was greater in mice following insufflation with CO2 (p < 0.01), helium (p < 0.01), argon (p = 0.01), and air (p = 0.07) than in control mice. No significant differences were found between the four insufflation groups in the growth of liver metastases.

CONCLUSION

These results suggest that insufflation plays an important role in the development of liver metastases but that the choice of gas may not affect their growth.

Functional expression in Escherichia coli of low-affinity and high-affinity Na(+)(Li(+))/H(+) antiporters of Synechocystis

Synechocystis sp. strain PCC 6803 has five genes for putative Na(+)/H(+) antiporters (designated nhaS1, nhaS2, nhaS3, nhaS4, and nhaS5). The deduced amino acid sequences of NhaS1 and NhaS2 are similar to that of NhaP, the Na(+)/H(+) antiporter of Pseudomonas aeruginosa, whereas those of NhaS3, NhaS4, and NhaS5 resemble that of NapA, the Na(+)/H(+) antiporter of Enterococcus hirae. We successfully induced the expression of nhaS1, nhaS3, and nhaS4 under control of an Na(+)-dependent promoter in Escherichia coli TO114, a strain that is deficient in Na(+)/H(+) antiport activity. Inverted membrane vesicles prepared from TO114 nhaS1 and TO114 nhaS3 cells exhibited Na(+)(Li(+))/H(+) antiport activity. Kinetic analysis of this activity revealed that nhaS1 encodes a low-affinity Na(+)/H(+) antiporter with a K(m) of 7.7 mM for Na(+) ions and a K(m) of 2.5 mM for Li(+) ions, while nhaS3 encodes a high-affinity Na(+)/H(+) antiporter with a K(m) of 0.7 mM for Na(+) ions and a K(m) of 0.01 mM for Li(+) ions. Transformation of E. coli TO114 with the nhaS1 and nhaS3 genes increased cellular tolerance to high concentrations of Na(+) and Li(+) ions, as well as to depletion of K(+) ions during cell growth. To our knowledge, this is the first functional characterization of Na(+)/H(+) antiporters from a cyanobacterium. Inverted membrane vesicles prepared from TO114 nhaS4 cells did not have Na(+)/H(+) antiport activity, and the cells themselves were as sensitive to Na(+) and Li(+) ions as the original TO114 cells. However, the TO114 nhaS4 cells were tolerant to depletion of K(+) ions. Taking into account these results and the growth characteristics of Synechocystis mutants in which nhaS genes had been inactivated by targeted disruption, we discuss possible roles of NhaS1, NhaS3, and NhaS4 in Synechocystis.

Optical study of cytochrome cM formation in Synechocystis

The expression of the cytM gene, which encodes cytochrome cM in Synechocystis sp. PCC 6803, is induced under stress conditions such as low temperature. Results of spectrophotometric studies revealed that cytochrome cM was oxidized by light absorbed by photosystem I in cells that had acclimatized to a low temperature. However, no similar light-induced oxidation of cytochrome cM was observed in delta cytM mutant cells. The kinetics of the oxidation and reduction of P700 before and after acclimation of Synechocystis cells to low temperature suggested that cytochrome cM might donate electrons to photooxidized P700. Our observations indicate that cytochrome cM is synthesized under low-temperature stress and that it might carry electrons directly to P700+ in photosystem I.

Alterations of the transforming growth factor-beta signaling pathway in hepatocellular carcinomas induced endogenously and exogenously in rats

To elucidate involvement of the transforming growth factor-beta (TGF-beta) signaling pathway in endogenous and exogenous liver carcinogenesis, we investigated mutations of TGF-beta receptor type II (TGF-betaRII), Smad2 and Smad4 genes, and expression of TGF-betaRII in hepatocellular carcinomas (HCCs) induced by a choline-deficient L-amino acid-defined (CDAA) diet and by N-nitrosodiethylamine (DEN). Male Fischer 344 rats received a CDAA diet continuously and HCCs were sampled after 75 weeks. Administration of DEN was followed by partial hepatectomy (PH), with colchicine to induce cell cycle disturbance and a selection pressure regimen, HCCs being obtained after 42 weeks. Total RNAs were extracted from individual HCCs and mutations in TGF-betaRII, Smad2 and Smad4 were investigated by reverse transcription (RT)-polymerase chain reaction (PCR)-restriction-single-strand conformation polymorphism (SSCP) analysis followed by sequencing analysis. Mutations of Smad2 were detected in 2 out of 12 HCCs (16.7%) induced by the CDAA diet, a GGT-to-GGC transition (Gly to Gly) at codon 30 and a TCT-to-GCT (Ser to Ala) transversion at codon 118, without any TGF-betaRII or Smad4 alterations. No mutations of TGF-betaRII, Smad2 and Smad4 were encountered in eleven HCCs induced by the exogenous carcinogen. Semi-quantitative RT-PCR revealed reduced expression of TGF-betaRII in 2 HCCs (16.7%) without Smad2 mutations out of 12 HCCs induced by the CDAA diet and none of 11 induced by DEN. These results suggest that the TGF-beta signaling pathway may be disturbed in endogenous liver carcinogenesis in rats.

Characterization of a two-component signal transduction system involved in the induction of alkaline phosphatase under phosphate-limiting conditions in Synechocystis sp. PCC 6803

The gene products of sll0337 and slr0081 in Synechocystis sp. PCC 6803 have been identified as the homologues of the Escherichia coli phosphate-sensing histidine kinase PhoR and response regulator PhoB, respectively. Interruption of sll0337, the gene encoding the histidine protein kinase, by a spectinomycin-resistance cassette blocked the induction of alkaline phosphatase activity under phosphate-limiting conditions. A similar result was obtained when slr0081, the gene encoding the response regulator, was interrupted with a cassette conferring resistance to kanamycin. In addition, the phosphate-specific transport system was not up-regulated in our mutants when phosphate was limiting. Unlike other genes for bacterial phosphate-sensing two-component systems, sll0337 and slr0081 are not present in the same operon. Although there are three assignments for putative alkaline phosphatase genes in the Synechocystis sp. PCC 6803 genome, only sll0654 expression was detected by northern analysis under phosphate limitation. This gene codes for a 149 kDa protein that is homologous to the cyanobacterial alkaline phosphatase reported in Synechococcus sp. PCC 7942 [Ray, J.M., Bhaya, D., Block, M.A. and Grossman, A.R. (1991) J. Bact. 173: 4297-4309]. An alignment identified a conserved 177 amino acid domain that was found at the N-terminus of the protein encoded by sll0654 but at the C-terminus of the protein in Synechococcus sp. PCC 7942.