Non-apoptotic signaling pathways activated by soluble Fas ligand in serum-starved human fibroblasts. Mitogen-activated protein kinases and NF-kappaB-dependent gene expression

Many Fas-expressing cells do not undergo cell death upon Fas stimulation. In the normal human diploid cell line GM6112, the addition of soluble Fas ligand (sFasL) leads to morphological signs of cell death in less than 1% of cells. Treatment of serum-starved GM6112 fibroblasts with sFasL resulted in a rapid and transient phosphorylation of ERK1/2 without a significant increase in JNK and p38 activities. Unless co-treated with the protein synthesis inhibitor anisomycin, sFasL did not show gene-inducing activity in cells maintained in complete medium. However, when cells were serum-starved for 4 days, treatment with sFasL alone induced interleukin-6 gene expression and, less strongly, interleukin-8 gene expression. Sensitization of the gene-inducing activity by serum starvation correlated with NF-kappaB activation by sFasL. Furthermore, we found that the expression of FADD and caspase-8 was significantly reduced in serum-starved cells, whereas the level of cFLIP remained unchanged. Transfection of GM6112 cells with the antisense caspase-8 expression construct sensitized cells toward sFasL-induced NF-kappaB-dependent reporter activation. Our results support the notion that a change in the ratio of cFLIP and caspase-8 may be responsible for turning on the Fas-activated NF-kappaB pathway, which otherwise is supplanted by the death-inducing pathway.

Expression of mucosal cyto-chemokine mRNAs in patients with Helicobacter pylori infection

BACKGROUND

Helicobacter pylori-induced destruction of the gastroduodenal mucosal barrier is initiated with mucosal infiltration of inflammatory cells. Cytokines and chemokines have been suggested to play important roles in the migration and activation of these inflammatory cells into the mucosa. The present study aimed to investigate expression rates of cyto-chemokine mRNAs using gastric mucosal biopsy specimens.

METHODS

In 98 patients infected with Helicobacter pylori, mucosal mRNA expression rates of cytokines (IL-1 beta, IL-6, and IL-10), C-C chemokines (macrophage inflammatory protein 1 alpha (MIP-1 alpha), and macrophage inflammatory protein 1 beta (MIP-1 beta), monocyte chemotactic and activating factor (MCAF), regulated on activation, normal T cell expressed and presumably secreted (RANTES)) and C-X-C chemokines (IL-8 and growth regulated a (GRO-alpha)) were examined using reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

The expression rates of mRNA for IL-8, GRO-alpha, MIP-1 alpha and RANTES were significantly more increased in H. pylori-positive patients than in H. pylori-negative patients. However, the expressions of IL-1 beta, IL-6 and IL-10 mRNA were statistically not different between two groups. After eradication of H. pylori, expressions of mRNA for three cytokines (IL-1 beta, IL-6 and IL-10), four C-C chemokines (MIP-1 alpha, MIP-1 beta, MCAF and RANTES) and two C-X-C chemokines (IL-8 and GRO-alpha) were significantly decreased.

CONCLUSION

These results suggest that C-X-C chemokines and some C-C chemokines play important roles in H. pylori-associated peptic ulcer diseases.

Is cholecystectomy necessary after ERCP for bile duct stones in patients with gallbladder in situ?

BACKGROUND

The requirement for subsequent cholecystectomy in patients with gallbladder in situ after endoscopic removal of stones from the common bile duct (CBD) is controversial. The aims of this study were to assess the requirement for subsequent cholecystectomy for gallbladder-related symptoms, and to identify the patients who develop symptoms after the endoscopic removal of CBD stones.

METHODS

Of 241 patients with gallbladder in situ following endoscopic removal of stones from the CBD, 146 patients (78 men and 68 women; mean age 69 +/- 13 years, range 20-93) with a follow-up time of more than three months without elective cholecystectomy were enrolled in the study. Fifty-nine patients had gallbladder stones (single stones in 27 and multiple stones in 32) and 87 patients had gallbladder in situ without stones. The time from entry to the occurrences of death or cholecystectomy was evaluated retrospectively. Cox regression analysis was used to evaluate the risk factors associated with these events.

RESULTS

The mean duration of follow-up was 24.1 +/- 18.0 months (range 3-70 months). During follow-up, seven patients (4.8%) underwent cholecystectomy, on average 18.4 months after CBD stone removal, as the result of acute cholecystitis in four cases, biliary pain in two cases and acute pancreatitis in one case. Laparoscopic cholecystectomy was performed in four patients and open cholecystectomy in three patients. Post-operative morbidity occurred in two patients, with improvement after conservative management. Nine patients (6.2%) died as the result of unrelated biliary disease. Age, sex, presence of gallbladder stones, multiplicity of gallbladder stones and underlying disease did not correlate with subsequent cholecystectomy by Cox regression analysis.

CONCLUSION

Elective cholecystectomy is not warranted in patients with bile duct stones when the common duct can be cleared of stones by endoscopic sphincterotomy. We could not find any clinical predictors of further symptoms or complications arising from the retained gallbladder.

BAPTA/AM, an intracellular calcium chelator, induces delayed necrosis by lipoxygenase-mediated free radicals in mouse cortical cultures

1. Disruption of calcium homeostasis during neurodegenerative diseases is known to trigger apoptotic or necrotic death in neuronal cells. Recently, the authors reported that intracellular calcium restriction by NMDA receptor antagonists induces apoptosis in cortical cultures. To evaluate whether further restriction of intracellular free calcium can induce apoptosis or necrosis, we examined the neurotoxic characterization of BAPTA/AM, a permeable free calcium chelator, in mouse cortical cultures. 2. Exposure of mixed (glia and neuron) cortical cultures (DIV 13-16) to 3-10 microM BAPTA/AM (non-toxic concentration for glial cells) for 24-48 hr resulted in delayed and necrotic neuronal death. The necrotic findings included swelling and loss of mitochondria and endoplasmic reticulum (ER) with neuronal membrane rupture 24 hr after treatment with BAPTA/AM. Simultaneously, we observed a few TUNEL-positive cells in the neuronal subpopulation of the same cultures. 3. The neurotoxicity evoked by BAPTA/AM (10 microM) was significantly attenuated by the addition of 0.5 microM cycloheximide (a protein synthesis inhibitor), 10 microM actinomycin D (an RNA transcription inhibitor), a high extracellular potassium concentration (total 15 mM KCl), 100 microM t-ACPD (a metabotrophic agonist), 100 microM alpha-tocopherol (a free radical scavenger), 100 microM deferoxamine (a ferric ion chelator), 100 microM L-NAME (a nitric oxide synthase (NOS) inhibitor), 50 microM DNQX (a non-NMDA receptor blocker), and 3-30 microM esculetin (a lipoxygenase inhibitor). However, 0.3-3 mM ASA (a cyclooxygenase inhibitor), 100 ng/ml nerve growth factor (NGF), 10 microM MK-801 (a NMDA receptor antagonist), 20 microM zVAD-fmk (caspase inhibitor) and 50 U/ml catalase failed to inhibit the injury. 4. However, NGF and catalase blocked the neurotoxicity induced by BAPTA/AM in young neuronal cells (DIV 6). BAPTA/AM (10 microM) did not alter the expression of inducible nitric oxide synthase (iNOS) on glial cells. 5. These results suggest that the feature of neuronal death induced by BAPTA/AM exhibits predominantly delayed necrosis mediated by lipoxygenase-dependent free radicals.

Genotyping CagA, VacA subtype, IceA1, and BabA of Helicobacter pylori isolates from Korean patients, and their association with gastroduodenal diseases

The genetic status of cagA, vacA subtype, iceA1, and babA, and the relationship to gastroduodenal diseases were assessed in Helicobacter pylori isolates in Korea. Seventy-six strains of H. pylori were isolated from the antrum and the corpus of 41 adult patients (22 with peptic ulcer and 19 with gastritis). The cagA, iceA1, and babA genes were assessed by polymerase chain reaction and the vacA subtypes were determined by reverse hybridization-line probe assay. The positive rates of 349-bp cagA, 208-bp cagA, iceA1, and babA genes were 97.4%, 96.1%, 84.2%, and 36.1%, respectively. The vacA s1a, s1b, s1c, and s2 variants were detected in 11.8%, 3.9%, 80.4%, and 1.3%, respectively. m1 (78.9%) is more prevalent than m2 (5.3%). The most common vacA genotype was s1c/m1 (61.9%), and 14 isolates (18.4%) contained mixed vacA genotypes from a single biopsy specimen. Twenty-one (60%) of 35 patients were infected with more than two strains of different cagA, iceA1, babA, and vacA genotypes. None of cagA, iceA1, babA, and vacA s1/m1 were associated with peptic ulcer. In conclusion, most H. pylori isolates in Korea carry cagA, iceA1, and vacA s1c/m1 genes, and reside with multiple strains. These genes do not correlate with the peptic ulcer in the Korean patients.

Characterization of a novel allele of glucose oxidase from a Korean wild type strain of Aspergillus niger

We have identified a novel allele of the glucose oxidase (GO, EC1.1.3.4) gene (GO) from a Korean wild type strain of Aspergillus niger, ACMO4, with an increased GO activity in culture filtrate. Southern blot analyses of GO from ACMO4 (GO-ACMO4) revealed that the gene was present as a single copy in the genome of A. niger. However, its sequence differs from that of GO from A. niger ATCC 9029 (GO-ATCC9029). GO-ACMO4 appears to be a functional gene based on the fact that it is enzymatically active when heterologously expressed in yeast. Sequence comparisons of the coding region of GO-ACMO4 revealed 16 nucleotide changes that resulted in four amino acid substitutions; T432D, G517D, G530S, and Q542R. The GO proteins from both ATCC 9029 and ACMO4 were heterologously expressed, purified, and compared biochemically. The two enzymes showed no difference in their apparent Km value for glucose (30 mM), but the Vmax of GO-ACMO4 (515.6 unit/mg) was 10% higher than that of GO-ATCC 9029, resulting in a 10% higher specific activity.

Relevance of vacA genotypes of Helicobacter pylori to cagA status and its clinical outcome

BACKGROUND

Determination of vacA mosaicism may be important because specific Helicobacter pylori vacA genotype can be used to predict different clinical outcome. The aim of this study was to assess the relationship of vacA genotypes of Helicobacter pylori to cagA status and its development of peptic ulcer diseases in Korean patients.

METHODS

Gastric biopsy specimens were obtained from 53 patients with gastric ulcer(GU), 57 with duodenal ulcer (DU) and 26 with chronic gastritis(CG) patients; all patients were infected with Helicobacter pylori. Bacterial mRNAs in the gastric mucosa were amplified by RT-PCR, using synthetic oligonucleotide primers specific for the vacA and the cagA gene. Patients with vacA s1 subtype were further examined to determine whether they had s1a or s1b subtype.

RESULTS

There was no correlation in frequency of vacA s1 and/or s1a genotype between CG and either GU or DU, as the vacA s1 and s1a/m1 were present in the majority of strains independent of clinical status(s1; 100.0% versus 94.3% or 93.0% and s1a/m1; 76.9% versus 62.3% or 64.9%, respectively). Likewise, there was no difference in the prevalence of the cagA gene between CG and either GU or DU patients (92.3% versus 90.6% or 98.2%, respectively). In addition, the cagA-negative status did not predict the presence of vacA s2 genotype.

CONCLUSION

These results strongly suggest that either cagA or vacA s1 and/or s1a is not proved to be a useful marker to distinguish disease-specific Helicobacter pylori strains for the development of peptic ulcer diseases in Korean patients.

Comparative study of Korean (Viscum album var. coloratum) and European mistletoes (Viscum album)

A lectin (agglutinin, VCA) from Korean mistletoe (Viscum album L. coloratum) was isolated by affinity chromatograpy on a asialofetuin-Sepharose 4B. The molecular weights of A- and B-chains of VCA were differenf from those of VAAS. The VCA recognized the antibody of VAAs in the Western blot analysis and ELLA system. We also investigated the synergistic effects of the components in mistletoe by dividing the extract into different molecular weight fractions.

High temperature stress resistance of Escherichia coli induced by a tobacco class I low molecular weight heat-shock protein

TLHS1 is a class I low molecular weight heat-shock protein (LMW HSP) of tobacco (Nicotiana tabacum). For a functional study of TLHS1, a recombinant DNA coding for TLHS1 with a hexahistidine tag at the amino-terminus was constructed and expressed in Escherichia coli. An expressed fusion protein, H6TLHS1, was purified using a Ni2+ affinity column and a Sephacryl S400 HR column. A polyclonal antibody against H6TLHS1 was produced to follow the fate of H6TLHS1 in E. coli. The fusion protein in E. coli maintained its solubility at a temperature of up to 90 degrees C and most of the proteins in the E. coli cell lysate with H6TLHS1 were prevented from thermally induced aggregation at up to 90 degrees C. We compared the viability of E. coli cells expressing H6TLHS1 to the E. coli cells without H6TLHS1 at a temperature of 50 degrees C. After 8 h of high temperature treatment, E. coli cells with H6TLHS1 survived about three thousand times more than the bacterial cells without H6TLHS1. These results showed that a plant class I LMW HSP, TLHS1, can protect proteins of E. coli from heat denaturation, which could lead to a higher survival rate of the bacterial cells at high temperature.

Pedunculated exogastric leiomyoblastoma presenting as a wandering abdominal mass

We report the imaging findings in a case of pedunculated exogastric leiomyoblastoma presenting as a wandering abdominal mass. Ultrasound and computed tomography showed a large, mixed solid and cystic mass in the peritoneal cavity. Computed tomography clearly showed that the mass was connected to the stomach by a narrow stalk. Small bowel follow-through showed subtle extrinsic indentation of the gastric body. The mass wandered from the right to the left side of the peritoneal cavity during various radiologic examinations.

Activation of the insulin-like growth factor II transcription by aflatoxin B1 induced p53 mutant 249 is caused by activation of transcription complexes; implications for a gain-of-function during the formation of hepatocellular carcinoma

Aflatoxin B1 (AFB1) induced mutation of the p53 gene at codon 249 (p53mt249) is critical during the formation of hepatocellular carcinoma (HCC) following hepatitis B virus (HBV) infection. p53mt249 markedly increases insulin-like growth factor II (IGF-II) transcription largely from promoter 4, accumulating the fetal form of IGF-II. Modulation of the transcription factor binding to IGF-II P4 by wild-type p53 and p53mt249 was identified. Wild-type p53 inhibited binding of transcription factors Sp1 and TBP on the P4 promoter, while p53mt249 enhanced the formation of transcriptional complexes through enhanced DNA-protein (Sp1 or TBP) and protein-protein (Sp1 and TBP) interactions. p53mt249 stimulates transcription factor Sp1 phosphorylation which might be a cause of increased transcription factor binding on the P4 promoter while wild-type p53 does not. Transfection of hepatocytes with p53mt249 impaired induction of apoptosis by the HBV-X protein and TNF-alpha. Therefore, the blocking of apoptosis through enhanced production of IGF-II should provide a favorable opportunity for the selection of transformed hepatocytes. These results explain the molecular basis for the genesis of HCC by p53mt249 which was found to be induced by a potent mutagen, AFB1.

Radicicol suppresses expression of inducible nitric-oxide synthase by blocking p38 kinase and nuclear factor-kappaB/Rel in lipopolysaccharide-stimulated macrophages

We show that radicicol, a fungal antibiotic, produces a marked inhibition of p38 kinase, nuclear factor-kappaB/Rel (NF-kappaB/Rel), and inducible nitric-oxide synthase (iNOS) transcription by the macrophage line RAW 264.7 in response to lipopolysaccharide (LPS). Treatment of RAW 264.7 with radicicol inhibited LPS-stimulated p38 kinase phosphorylation in a dose-related manner. iNOS transcription, which is regulated in part by the NF-kappaB/Rel family of transcription factors, has been shown to be under the control of the p38 kinase signaling cascade. Our data also show that the p38 kinase pathway is specifically involved in LPS-induced NF-kappaB/Rel activation and iNOS expression because NF-kappaB/Rel DNA binding and iNOS mRNA production in the presence of a specific inhibitor of p38 kinase, SB203580, were dramatically diminished. In contrast, PD98059, a specific inhibitor of mitogen-activated protein kinase/extracellular signal-regulated protein kinase kinase 1 had no effect on NF-kappaB/Rel activation and iNOS expression. LPS-induced loss of inhibitory proteins IkappaB-alpha and IkappaB-beta and translocation of p65, c-Rel, and p50 was inhibited by radicicol. Collectively, this series of experiments indicates that radicicol inhibits iNOS gene expression by blocking p38 kinase signaling. Due to the critical role that NO release plays in mediating inflammatory responses, the inhibitory effects of radicicol on iNOS suggest that this potent antifungal agent may represent a useful anti-inflammatory agent.

Cx43 gap junction gene expression and gap junctional communication in mouse neural crest cells

Although gap junctions are not known to be important in mediating cell-cell interactions amongst migratory cells, our studies showed that the connexin 43 (Cx43) gap junction gene is widely expressed in mouse neural crest cell lineages. Using in situ hybridization analysis, Cx43 expression was detected in presumptive neural crest cells emerging from the neural folds of the early postimplantation embryo. Neural crest expression of the Cx43 gap junction gene was also indicated by the analysis of transgenic mice containing a lacZ reporter construct driven by the Cx43 promoter. In neural tube explant cultures of these transgenic mice, lacZ expression was observed in the emerging neural crest outgrowths. Whole mount X-gal staining of these transgenic embryos at various stages of development showed lacZ expression in neural crest cells distributed along the entire craniocaudal axis, with expression found in both cranial and trunk neural crest cells contributing to a wide range of embryonic tissues. This included presumptive cardiac neural crest cells localized in the heart. In light of the widespread expression of Cx43 in neural crest cell lineages, dye injection studies, were carried out to determine if neural crest cells are functionally coupled via gap junctions. Such studies revealed extensive dye coupling among presumptive neural crest cells, thus demonstrating that these migratory cells are indeed gap junctional communication competent. In total, these observations suggest that gap junctions may play a role in mouse neural crest development. This possibility is particularly intriguing given the recent finding that the Cx43 knockout mice die of defects associated with the outflow tract [Reaume et al., 1995], a region of the heart in which neural crest cells are required for normal development.

Comparing MR imaging and CT in the staging of gastric carcinoma

OBJECTIVE

The purpose of this study was to assess the usefulness of breath-hold two-dimensional (2D) fast low-angle shot (FLASH) and T2-weighted turbo spin-echo fast MR imaging compared with helical CT in the staging of gastric carcinoma.

SUBJECTS AND METHODS

Thirty patients with gastric carcinoma underwent preoperative MR imaging and helical CT. MR imaging at 1.5 T was performed immediately after the intramuscular injection of scopolamine and the oral administration of water or effervescent granules. Breath-hold 2D FLASH T1-weighted images in all three planes, turbo spin-echo T2-weighted axial images, and gadolinium-enhanced fat-suppressed 2D FLASH axial images were included. Helical CT was performed 60 sec after initiation of i.v. contrast medium injection (2.5-3 ml/sec). Two groups of two radiologists each independently analyzed the MR and helical CT findings, and these results were compared with the pathologic findings.

RESULTS

For T staging, MR imaging accuracy was higher than that of helical CT (73.3% and 66.7%, respectively); however, the accuracies of the two methods were not significantly different from each other (McNemar test, p > 0.05). Overstaging was noted in 6.7% of cases with MR imaging and 10% with helical CT. Understaging was noted in 20% of cases with MR imaging and 23.3% with helical CT. For N staging, the accuracies of MR imaging and helical CT were 55% and 58.6%, respectively, with no statistical significance (overstaging, 10% and 6.9%; understaging, 34.5% and 34.5%, respectively).

CONCLUSION

MR imaging was comparable to helical CT in the T and N staging of gastric cancer.

Effect of extracellular cations on the chemotherapeutic efficacy of anticancer drugs

Cancer development and the efficiency of chemotherapy relies on the patients calcium-related pathological status such as hyper- or hypocalcemia. In the present study, we investigated the effect of extracellular cations such as calcium and magnesium on the therapeutic efficacy of antitumor drugs. The analytic parameters used were cellular drug uptake/excretion and the chemosensitivity of the human breast cancer cell lines, MCF7 and MCF7/ADR. Both calcium and magnesium ions decreased the membrane permeability of cancer cells, which was determined by cell size analysis. These divalent ions also lowered the drug uptake and the cytoplasmic levels of rhodamine 123 and adriamycin, suggesting that they might interfere with the diffusion of these drugs by modifying the physical properties of the cytoplasmic membrane. The acute cytotoxicity of adriamycin after a short period of incubation correlated with changes in its cytoplasmic level. Our results indicate that these extracellular cations might play an important role in the therapeutic activities of anticancer drugs in cancer patients. These results also provide insight a new aspect of chemotherapy, because they suggest that the therapeutic doses of anti-cancer drugs should be modified in cancer-bearing patients presenting with abnormal blood calcium levels.

Systemic mononuclear inflammatory vasculopathy associated with Sjögren's syndrome in a patient with primary biliary cirrhosis

We report a 46-year-old woman with primary biliary cirrhosis (PBC) presenting with Sjögren's syndrome and systemic mononuclear inflammatory vasculopathy. Biopsy specimens of sural nerve showed findings consistent with vasculitic neuropathy. Perivascular inflammatory mononuclear cell infiltration was observed on muscle biopsy specimen. The findings of abdominal computed tomography and brain magnetic resonance imaging were suggestive of vasculitis. Clinical manifestations and radiologic findings were improved after high dose prednisolone therapy.

Differential induction of cytokine genes and activation of mitogen-activated protein kinase family by soluble CD40 ligand and TNF in a human follicular dendritic cell line

Follicular dendritic cells (FDC)3 play crucial roles in germinal center (GC) formation and differentiation of GC B cells. Many aspects of FDC function are influenced by contact with B or T cells, and by cytokines produced in the GC, which involve stimulation of CD40 and TNF-alpha receptors on FDC. In this study, using an established FDC line, HK cells, we compared the effects of CD40 and TNF receptor triggering on cytokine induction and activation of mitogen-activated protein kinase family. We show that HK cells spontaneously produced IL-6, M-CSF, and G-CSF mRNA. Both the soluble form of CD40 ligand (sCD40L) and TNF increased the level of M-CSF and G-CSF mRNA. While TNF strongly induced IL-6 mRNA, its expression was not affected by sCD40L treatment, differing from the strong IL-6 induction in other cell types upon CD40 stimulation. In addition, sCD40L treatment resulted in activation of extracellular signal-related kinase 1 and 2 (ERK1/2) and p38 without significant increase in c-Jun N-terminal kinase (JNK) activity. Lack of JNK activation differs in that most B cells respond to CD40 stimulation by inducing JNK activity strongly, suggesting distinct characteristics of CD40 signaling in FDC. Compared with the effects of sCD40L, TNF was capable of inducing JNK activity in addition to the activation of ERK1/2 and p38. Furthermore, the proximal signaling elements activated by TNF differed from those activated by sCD40L, in that TNF did not require PMA-sensitive protein kinase C isoforms in the activation of ERK and p38, whereas sCD40L did. However, signals activated by these stimuli converged on cytokine gene expression in a synergistic manner, which may have implication in augmenting FDC function during GC reaction.

Assessment of body composition using dual energy x-ray absorptiometry in patients with liver cirrhosis: comparison with anthropometry

OBJECTIVES

The aim of this study was to evaluate changes of body composition in cirrhotic patients. Dual energy x-ray absorptiometry (DEXA) and anthropometry were used, and the values obtained were compared.

METHODS

Mid-arm fat and muscle areas were calculated by anthropometry in 66 cirrhotic patients and 94 healthy controls. In 37 of the cirrhotic patients and 39 of the controls, fat mass, lean soft tissue mass and bone mineral contents were measured with DEXA.

RESULTS

The number of cirrhotic patients with measured values below the fifth percentile of normal controls was 21 (31.8%) by mid-arm fat area, six (9.1%) by mid-arm muscle area, 15 (40.5%) by fat mass and 0 (0%) by lean soft tissue mass. The fat mass in cirrhotic patients was less than in controls, whereas lean soft tissue mass and bone mineral content were not different. Fat depletion was severe in Child-class C patients and with severe ascites. Mid-arm fat area and fat mass showed close correlation (r = 0.85, p < 0.01), but mid-arm muscle area and lean soft tissue mass showed poor correlation (r = 0.32, p < 0.05).

CONCLUSION

Cirrhotic patients showed lower fat component, with preserved lean soft tissue mass and bone mineral content. In clinical practice, the measurement of mid-arm fat area was useful for the assessment of fat mass.

Metabolite and isotopomer balancing in the analysis of metabolic cycles: II. Applications

In a previous paper (Klapa et al., 1999), we presented a model for the analysis of isotopomer distributions of the TCA cycle intermediates resulting from 13C (or 14C) labeling experiments. Results allow the rigorous determination of the degree of enrichment at specific carbon atoms of metabolites, of the molecular weight distribution of metabolite isotopomers, as well as of the fine structure of NMR spectra in terms of a small number of metabolic fluxes. In this paper we validate the model by comparing model predictions with experimental data and then apply it to the analysis of metabolic networks that have been investigated in previous studies. The results have allowed us to conclude that: (1) there is no evidence of propionyl-CoA carboxylase pathway in Escherichia coli; and (2) the possibility that acetone utilization in mammals occurs solely via the "lactate/methylglyoxal" pathway is consistent with available labeling data. The presented modeling framework provides additional constraints that must be satisfied by experimental data in a biochemical network structure and therefore enhances the power of labeling methods for resolving in vivo metabolic fluxes.

Metabolite and isotopomer balancing in the analysis of metabolic cycles: I. Theory

Proper analysis of label distribution in metabolic pathway intermediates is critical for correct interpretation of experimental data and strategic experimental design. While, for example, 13C nuclear magnetic resonance (NMR) spectroscopy is usually limited to the measurement of degrees of 13C enrichment, more information about metabolic fluxes can be extracted from the fine structure of NMR spectra, or molecular weight distributions of isotopomers of metabolic intermediates (measured by gas chromatography-mass spectrometry). For this purpose, rigorous accounting for the contribution of all pathways to label distribution is required, especially contributions resulting from multiple turns of metabolic cycles. In this paper we present a mathematical model developed to analyze isotopomer distributions of tricarboxylic acid cycle (TCA) intermediates following the administration of 13C (or 14C) labeled substrates. The theory presented provides the basis to analyze 13C NMR spectra and molecular weight distributions of metabolites. In a companion paper (Park et al., 1999), the theory is applied to the analysis of several cases of biological significance. Copyright 1999 John Wiley & Sons, Inc.

A novel parvovirus isolated from Manchurian chipmunks

A novel parvovirus was identified in Manchurian chipmunks inhabiting Korea. Hepatitis B surface antigen (HBsAg) was detected in sera from 4 animals among 62 apparently healthy chipmunks. Electron microscopic examination of the HBsAg-positive sera revealed virus-like spherical particles 20-22 nm in diameter. Extraction of nucleic acid under annealing conditions from the serum samples containing virus-like particles yielded a single species of DNA molecule with the electrophoretic mobility of 5.6-kb double-stranded DNA. Four overlapping clones that encompassed almost the full-length viral genome, except both ends, were obtained. By sequencing these clones, we determined the sequence of 5097 nucleotides of the viral DNA. Two open reading frames were identified, with the left side open reading frame encoding a putative nonstructural protein and the right side open reading frame encoding a putative capsid protein. The nucleotide and amino acid sequences showed significant homology to parvovirus B19 and simian parvovirus, but showed little homology to other mammalian autonomous parvoviruses or adeno-associated viruses. These observations indicate that the virus isolated from Manchurian chipmunks is a novel parvovirus and may be a potentially useful animal model of human B19 infection as a new member of the Erythrovirus genus of the Parvoviridae.

Effect of Helicobacter pylori infection on antral gastrin and somatostatin cells and on serum gastrin concentrations

OBJECTIVES

Helicobacter pylori infection induces selective reduction of the number of antral D-cells and results in abnormal regulation of serum gastrin secretion. The purpose of this study was to investigate the relationship between H. pylori infection and the numbers of G-cells and D-cells.

METHODS

The numbers of antral G-cells and D-cells, the ratio of G-cells to D-cells and fasting serum gastrin concentrations were compared between 37 patients with (29 with duodenal ulcers and 8 with gastric ulcers) and 33 without H. pylori infection (22 with duodenal ulcers and 11 with gastric ulcers). Serum gastrin concentrations were measured using the radioimmunoassay technique. Antral mucosal biopsy specimens were examined using immunohistochemical staining with antibodies specific for gastrin and somatostatin and the numbers of G-cells and D-cells per gastric gland were counted.

RESULTS

Fasting serum gastrin concentrations were significantly higher in patients with H. pylori infection compared to patients without infection (80.3 +/- 23.5 vs 47.6 +/- 14.1 pg/ml, p < 0.001). The number of G-cells per gastric gland was similar in infected and uninfected patients (7.1 +/- 3.1 vs 7.3 +/- 3.9, respectively, p > 0.5). The number of D-cells was significantly lower in patients with H. pylori infection than in uninfected patients in both duodenal and gastric ulcer patients (1.3 +/- 0.4 vs 2.5 +/- 1.6, respectively, p < 0.001). The ratio of G-cells to D-cells was also significantly higher in infected patients compared with uninfected patients for both gastric and duodenal ulcers (5.7 +/- 2.7 vs 3.5 +/- 1.9, respectively, p < 0.001).

CONCLUSIONS

These results strongly suggest that Helicobacter pylori infection induces reduction of the number of antral D-cells. The resulting relative hypofunction of the inhibitory action of D-cells against G-cells may be responsible for increased serum gastrin secretion.

Molecular characterization and regulation of an operon encoding a system for transport of arginine and ornithine and the ArgR regulatory protein in Pseudomonas aeruginosa

The complete nucleotide sequence for the aot operon of Pseudomonas aeruginosa PAO1 was determined. This operon contains six open reading frames. The derived sequences for four of these, aotJ, aotQ, aotM, and aotP, show high similarity to those of components of the periplasmic binding protein-dependent ABC (ATP binding cassette) transporters of enteric bacteria. Transport studies with deletion derivatives established that these four genes function in arginine-inducible uptake of arginine and ornithine but not lysine. The aotO gene, which encodes a polypeptide with no significant similarity to any known proteins, is not essential for arginine and ornithine uptake. The sixth and terminal gene in the operon encodes ArgR, which has been recently shown to function in regulation of arginine metabolism. Studies with an aotJ::lacZ translational fusion showed that expression of the aot operon is strongly induced by arginine and that this effect is mediated by ArgR. S1 nuclease and primer extension experiments showed the presence of two promoters, P1 and P2. The downstream promoter, P2, is induced by arginine and appears to be subject to carbon catabolite repression. The upstream promoter, P1, is induced by glutamate. Footprinting experiments established the presence of a 44-bp ArgR binding site that overlaps the -35 region for P2, as was shown to be the case for the arginine-inducible aru promoter, and the -10 region for P1, as was shown to be the case for arginine-repressible operons in P. aeruginosa. Sequence alignment confirms the architecture and the consensus sequence of the ArgR binding sites, as was previously reported.