Certified Reference Material for Analytical Quality Assurance of Minor and Trace Elements in Food and Related Matrixes Based on a Typical Japanese Diet: Interlaboratory Study

A Certified Reference Material (CRM) was prepared at the National Institute for Environmental Studies (NIES), Japan, in collaboration with the National Institute of Radiological Sciences (NIRS), Japan, for the analytical quality assurance of minor and trace elements in food and related matrixes. The starting material for the CRM was all food served in 29 households in Japan over two 3-day periods in 1997–1998, and thus the CRM represented a typical Japanese diet. All foods (meals, snacks, and beverages) were homogenized, freeze-dried, pulverized, blended, dispensed into 1100 bottles, and sterilized. The within- and between-bottle homogeneity of the prepared CRM was satisfactory for most of the elements. The concentrations of 14 elements (Na, Mg, K, Ca, Mn, Cu, Zn, As, Se, Sr, Cd, Sn, Ba, and U) were certified based on a collaborative analysis involving NIES, NIRS, and 20 other laboratories. Reference values were given for the concentrations of 12 additional elements (P, Cl, Fe, Co, Ni, Br, Rb, Mo, I, Cs, Pb, and Th). The elements certified and those given reference values include minerals, essential trace elements, contaminant elements, and long-lived radionuclides. Thus, this CRM is of practical value in the quality assurance of element analysis of foods and diets in nutritional, environmental, and radiological research.

Electronic Structure of Ce-Doped and -Undoped Nd_{2}CuO_{4} Superconducting Thin Films Studied by Hard X-Ray Photoemission and Soft X-Ray Absorption Spectroscopy

In order to realize superconductivity in cuprates with the T^{'}-type structure, not only chemical substitution (Ce doping) but also postgrowth reduction annealing is necessary. In the case of thin films, however, well-designed reduction annealing alone without Ce doping can induce superconductivity in the T^{'}-type cuprates. In order to unveil the origin of superconductivity in the Ce-undoped T^{'}-type cuprates, we have performed bulk-sensitive hard x-ray photoemission and soft x-ray absorption spectroscopy on superconducting and nonsuperconducting Nd_{2-x}Ce_{x}CuO_{4} (x=0, 0.15, and 0.19) thin films. By postgrowth annealing, core-level spectra exhibited dramatic changes, which we attributed to the enhancement of core-hole screening in the CuO_{2} plane and the shift of chemical potential along with changes in the band filling. The result suggests that the superconducting Nd_{2}CuO_{4} film is doped with electrons despite the absence of the Ce substitution.

Direct k-space mapping of the electronic structure in an oxide-oxide interface

The interface between LaAlO(3) and SrTiO(3) hosts a two-dimensional electron system of itinerant carriers, although both oxides are band insulators. Interface ferromagnetism coexisting with superconductivity has been found and attributed to local moments. Experimentally, it has been established that Ti 3d electrons are confined to the interface. Using soft x-ray angle-resolved resonant photoelectron spectroscopy we have directly mapped the interface states in k space. Our data demonstrate a charge dichotomy. A mobile fraction contributes to Fermi surface sheets, whereas a localized portion at higher binding energies is tentatively attributed to electrons trapped by O vacancies in the SrTiO(3). While photovoltage effects in the polar LaAlO(3) layers cannot be excluded, the apparent absence of surface-related Fermi surface sheets could also be fully reconciled in a recently proposed electronic reconstruction picture where the built-in potential in the LaAlO(3) is compensated by surface O vacancies serving also as a charge reservoir.

Histone acetylation by CBP and p300 at double-strand break sites facilitates SWI/SNF chromatin remodeling and the recruitment of non-homologous end joining factors

Non-homologous end joining (NHEJ) is a major repair pathway for DNA double-strand breaks (DSBs) generated by ionizing radiation (IR) and anti-cancer drugs. Therefore, inhibiting the activity of proteins involved in this pathway is a promising way of sensitizing cancer cells to both radiotherapy and chemotherapy. In this study, we developed an assay for evaluating NHEJ activity against DSBs in chromosomal DNA in human cells to identify the chromatin modification/remodeling proteins involved in NHEJ. We showed that ablating the activity of the homologous histone acetyltransferases, CBP and p300, using inhibitors or small interfering RNAs-suppressed NHEJ. Ablation of CBP or p300 impaired IR-induced DSB repair and sensitized lung cancer cells to IR and the anti-cancer drug, etoposide, which induces DSBs that are repaired by NHEJ. The CBP/p300 proteins were recruited to sites of DSBs and their ablation suppressed acetylation of lysine 18 within histone H3, and lysines 5, 8, 12, and 16 within histone H4, at the DSB sites. This then suppressed the recruitment of KU70 and KU80, both key proteins for NHEJ, to the DSB sites. Ablation of CBP/p300 also impaired the recruitment of BRM, a catalytic subunit of the SWI/SNF complex involved in chromatin remodeling at DSB sites. These results indicate that CBP and p300 function as histone H3 and H4 acetyltransferases at DSB sites in NHEJ and facilitate chromatin relaxation. Therefore, inhibition CBP and p300 activity may sensitize cancer cells to radiotherapy and chemotherapy.

Histone acetylation by CBP and p300 at double-strand break sites facilitates SWI/SNF chromatin remodeling and the recruitment of non-homologous end joining factors

Non-homologous end joining (NHEJ) is a major repair pathway for DNA double-strand breaks (DSBs) generated by ionizing radiation (IR) and anti-cancer drugs. Therefore, inhibiting the activity of proteins involved in this pathway is a promising way of sensitizing cancer cells to both radiotherapy and chemotherapy. In this study, we developed an assay for evaluating NHEJ activity against DSBs in chromosomal DNA in human cells to identify the chromatin modification/remodeling proteins involved in NHEJ. We showed that ablating the activity of the homologous histone acetyltransferases, CBP and p300, using inhibitors or small interfering RNAs-suppressed NHEJ. Ablation of CBP or p300 impaired IR-induced DSB repair and sensitized lung cancer cells to IR and the anti-cancer drug, etoposide, which induces DSBs that are repaired by NHEJ. The CBP/p300 proteins were recruited to sites of DSBs and their ablation suppressed acetylation of lysine 18 within histone H3, and lysines 5, 8, 12, and 16 within histone H4, at the DSB sites. This then suppressed the recruitment of KU70 and KU80, both key proteins for NHEJ, to the DSB sites. Ablation of CBP/p300 also impaired the recruitment of BRM, a catalytic subunit of the SWI/SNF complex involved in chromatin remodeling at DSB sites. These results indicate that CBP and p300 function as histone H3 and H4 acetyltransferases at DSB sites in NHEJ and facilitate chromatin relaxation. Therefore, inhibition CBP and p300 activity may sensitize cancer cells to radiotherapy and chemotherapy.

4f-derived Fermi surfaces of CeRu2(Si1-xGex)2 near the quantum critical point: resonant soft-X-ray ARPES study

Angle-resolved photoelectron spectroscopy in the Ce 3d-->4f excitation region was measured for the paramagnetic state of CeRu2Si2, CeRu2(Si0.82Ge0.18)2, and LaRu2Si2 to investigate the changes of the 4f electron Fermi surfaces around the quantum critical point. While the difference of the Fermi surfaces between CeRu2Si2 and LaRu2Si2 was experimentally confirmed, a strong 4f-electron character was observed in the band structures and the Fermi surfaces of CeRu2Si2 and CeRu2(Si0.82Ge0.18)2, consequently indicating a delocalized nature of the 4f electrons in both compounds. The absence of Fermi surface reconstruction across the critical composition suggests that SDW quantum criticality is more appropriate than local quantum criticality in CeRu2(Si1-xGex)2.

Direct observation of dispersive Kondo resonance peaks in a heavy-fermion system

Ce 4d-4f resonant angle-resolved photoemission spectroscopy was carried out to study the electronic structure of strongly correlated Ce 4f electrons in a quasi-two-dimensional nonmagnetic heavy-fermion system CeCoGe1.2Si0.8. For the first time, dispersive coherent peaks of an f state crossing the Fermi level, the so-called Kondo resonance, are directly observed together with the hybridized conduction band. Moreover, the experimental band dispersion is quantitatively in good agreement with a simple hybridization-band picture based on the periodic Anderson model. The obtained physical quantities, i.e., coherent temperature, Kondo temperature, and mass enhancement, are comparable to the results of thermodynamic measurements. These results manifest an itinerant nature of Ce 4f electrons in heavy-fermion systems and clarify their microscopic hybridization mechanism.

Blockade of Angiotensin II type-1 receptor reduces oxidative stress in adipose tissue and ameliorates adipocytokine dysregulation

Dysregulated production of adipocytokines may be involved in the development of atherosclerotic cardiovascular disease in metabolic syndrome and chronic kidney disease (CKD) associated with metabolic syndrome. The aim of this study was to determine the effects of treatment with angiotensin II (Ang II) type-1 receptor blocker (ARB) on the regulation of adipocytokines. Olmesartan, an ARB, significantly blunted the age- and body weight-associated falls in plasma adiponectin both in genetically and diet-induced obese mice, without affecting body weight, but had no effect on plasma adiponectin levels in lean mice. Olmesartan also ameliorated dysregulation of adipocytokines in obesity, such as tumor necrosis factor-alpha, plasminogen activator inhibitor-1, monocyte chemotactic protein-1, and serum amyloid A3. Olmesartan significantly reduced reactive oxygen species originating from accumulated fat and attenuated the expression of nicotinamide adenine dinucleotide phospho hydrogenase oxidase subunits in adipose tissue. In cultured adipocytes, olmesartan acted as an antioxidant and improved adipocytokine dysregulation. Our results indicate that blockade of Ang II receptor ameliorates adipocytokine dysregulation and that such action is mediated, at least in part, by targeting oxidative stress in obese adipose tissue. Ang II signaling and subsequent oxidative stress in adipose tissue may be potential targets for the prevention of atherosclerotic cardiovascular disease in metabolic syndrome and also in metabolic syndrome-based CKD.

Mouse soluble CD14 truncated at amino acid 71 in transgenic mice: preventive effect on endotoxin-mediated toxic shock

Mouse soluble CD14 truncated at amino acid 71 (N71) contains the lipopolysaccharide (LPS)-binding sequence. Transgenic mice carrying alpha1-antitrypsin (AT) promoter-N71 fusion genes, designated AT363-1 and AT363-2, were produced. These mice constitutively produced elevated levels of N71. The concentration of LPS in sera after intraperitoneal LPS injection was lower in AT363-1 mice than in nontransgenic mice. The expression of N71 mRNA was enhanced by subcutaneous turpentine oil injection. The levels of serum LPS and tumor necrosis factor-alpha (TNF-alpha) after intraperitoneal LPS injections were lower in AT363-1 mice than in nontransgenic mice. Cell surface TNF-alpha and CD14 expression in exudate peritoneal macrophages prepared by intraperitoneal injection of proteose peptone and then LPS were higher in AT363-1 mice than in nontransgenic mice. Neutrophil infiltration in the liver after induction of the generalized Shwartzman reaction was lower in AT363-1 mice than in nontransgenic mice. Lethality of the Shwartzman reaction was significantly lower in AT363-1 than in nontransgenic mice. These findings suggest that the endotoxin-binding protein (N71) from CD14 prevents endotoxin-mediated toxic shock.

Photorepair of RNA polymerase arrest and apoptosis after ultraviolet irradiation in normal and XPB deficient rodent cells

Cyclobutane pyrimidine dimers (CPDs) are directly involved in signaling for UV-induced apoptosis in mammalian cells. Failure to remove these lesions, specially those located at actively expressing genes, is critical, as cells defective in transcription coupled repair have increased apoptotic levels. Thus, the blockage of RNA synthesis by lesions is an important candidate event triggering off active cell death. In this work, wild-type and XPB mutated Chinese hamster ovary (CHO) cells expressing a marsupial photolyase, that removes specifically CPDs from the damaged DNA, were generated, in order to investigate the importance of this lesion in both RNA transcription blockage and apoptotic induction. Photorepair strongly recovers RNA synthesis in wild-type CHO cell line, although the resumption of transcription is decreased in XPB deficient cells. This recovery is accompanied by the prevention of cells entering into apoptosis. These results demonstrate that marsupial photolyase has access to CPDs blocking RNA synthesis in vivo, and this may be affected by the presence of a mutated XPB protein.

Cyclobutane pyrimidine dimers are responsible for the vast majority of mutations induced by UVB irradiation in mammalian cells

The most prevalent DNA lesions induced by UVB are the cyclobutane pyrimidine dimers (CPDs) and the pyrimidine (6-4) pyrimidone photoproducts ((6-4)PPs). It has been a long standing controversy as to which of these photoproduct is responsible for mutations in mammalian cells. Here we have introduced photoproduct-specific DNA photolyases into a mouse cell line carrying the transgenic mutation reporter genes lacI and cII. Exposure of the photolyase-expressing cell lines to photoreactivating light resulted in almost complete repair of either CPDs or (6-4)PPs within less than 3 h. The mutations produced by the remaining, nonrepaired photoproducts were scored. The mutant frequency in the cII gene after photoreactivation by CPD photolyase was reduced from 127 x 10(-5) to 34 x 10(-5) (background, 8-10 x 10(-5)). Photoreactivation with (6-4) photolyase did not lower the mutant frequency appreciably. In the lacI gene the mutant frequency after photoreactivation repair of CPDs was reduced from 148 x 10(-5) to 28 x 10(-5) (background, 6-10 x 10(-5)). Mutation spectra obtained with and without photoreactivation by CPD photolyase indicated that the remaining mutations were derived from background mutations, unrepaired CPDs, and other DNA photopoducts including perhaps a small contribution from (6-4)PPs. We conclude that CPDs are responsible for at least 80% of the UVB-induced mutations in this mammalian cell model.

Elevated gastrin secretion by in vivo gene electroporation in skeletal muscle

Whether or not in vivo gene transfer of gastrin gene into skeletal muscle by electroporation could modify gastrin secretion was examined. The expression plasmid vector, either pMEPrGaspA encoding the rat gastrin gene or pEGFP-N1 encoding the GFP reporter gene was injected into M. rectus abdominis of rats or M. biceps formis of mice. Subsequently, square electric pulses of direct current were applied six times at 25 V with a loading period of 100 msec per pulse. Clear foreign gene expression in the skeletal muscle was demonstrated by both GFP fluorescence and immunostaining of rat gastrin. Time course changes in plasma gastrin levels after transfection revealed that in rats, gastrin gene transfer significantly increased the plasma gastrin level for 4 weeks post-transfection (P<0.05), but the difference diminished at the end of the 10-week period. In mice, plasma gastrin level elevated similarly for 3 weeks, and pH of gastric contents decreased in the gastrin gene transfected group compared with the control counterpart (P<0.05). These findings suggest that localized in vivo gene transfer by electroporation allows skeletal muscle to become an artificial endocrine tissue for hormonal manipulation of animals.

Postoperative delirium and melatonin levels in elderly patients

BACKGROUND

Melatonin, a hormone produced in the pineal gland, is involved in circadian rhythms and the sleep-wake cycle. Postoperative delirium is encountered frequently in elderly patients after major surgery; whether changes in the pattern of melatonin secretion are associated is unclear.

METHODS

Plasma samples were obtained every 2 hours from 19 patients without delirium and 10 with delirium after major abdominal surgery. Postoperative delirium was determined using the Confusion Assessment Method in the Practice Guideline of the American Psychiatric Association.

RESULTS

All patients without delirium showed nearly identical preoperative and postoperative melatonin secretion for 24 hours, although peak values were significantly lower in patients more than 80 years old (7.2 +/- 2.3 pg/mL) than in patients younger than 80 years (24.4 +/- 4.1 pg/mL, P = 0.022). Patients with delirium showed two different abnormal postoperative patterns: in 5 patients without complications, melatonin levels were lower than preoperative values (11.0 +/- 5.8 versus 6.5 +/- 4.2 pg/mL, P = 0.079); and in 5 patients with complications, melatonin levels were markedly increased (21.1 +/- 4.5 versus 58.8 +/- 12.4 pg/mL, P = 0.043).

CONCLUSIONS

Abnormal melatonin secretion may be involved in postoperative sleep disturbances, which triggered delirium in elderly patients.

Escherichia coli Nth and human hNTH1 DNA glycosylases are involved in removal of 8-oxoguanine from 8-oxoguanine/guanine mispairs in DNA

The spectrum of DNA damage caused by reactive oxygen species includes a wide variety of modifications of purine and pyrimidine bases. Among these modified bases, 7,8-dihydro-8-oxoguanine (8-oxoG) is an important mutagenic lesion. Base excision repair is a critical mechanism for preventing mutations by removing the oxidative lesion from the DNA. That the spontaneous mutation frequency of the Escherichia coli mutT mutant is much higher than that of the mutM or mutY mutant indicates a significant potential for mutation due to 8-oxoG incorporation opposite A and G during DNA replication. In fact, the removal of A and G in such a situation by MutY protein would fix rather than prevent mutation. This suggests the need for differential removal of 8-oxoG when incorporated into DNA, versus being generated in situ. In this study we demonstrate that E.coli Nth protein (endonuclease III) has an 8-oxoG DNA glycosylase/AP lyase activity which removes 8-oxoG preferentially from 8-oxoG/G mispairs. The MutM and Nei proteins are also capable of removing 8-oxoG from mispairs. The frequency of spontaneous G:C-->C:G transversions was significantly increased in E.coli CC103mutMnthnei mutants compared with wild-type, mutM, nth, nei, mutMnei, mutMnth and nthnei strains. From these results it is concluded that Nth protein, together with the MutM and Nei proteins, is involved in the repair of 8-oxoG when it is incorporated opposite G. Furthermore, we found that human hNTH1 protein, a homolog of E.coli Nth protein, has similar DNA glycosylase/AP lyase activity that removes 8-oxoG from 8-oxoG/G mispairs.

Clinicopathological features of superficial spreading and nonspreading squamous cell carcinoma of the esophagus

OBJECTIVES

Superficially spreading carcinoma of the esophagus, consisting mainly of intraepithelial carcinoma, is not as rare as was previously thought. Despite the surgical significance of this entity, no general definition has been established, and the clinical features of this disease remain to be clarified.

METHODS

A total of 54 patients with superficial carcinoma of the esophagus (defined as carcinoma limited to the epithelium or superficially invading the lamina propria or submucosa) were classified into two groups according to the longitudinal extent of the lesion. A total of 13 patients with superficially spreading carcinoma (defined as a superficial carcinoma measuring >5 cm and consisting mainly of intraepithelial carcinoma) were compared to 41 patients with nonspreading esophageal carcinoma.

RESULTS

One patient with superficially spreading carcinoma had a positive resection margin because of multiple cancerous lesions. The only significant difference in the clinical and pathological features of the two groups was a higher prevalence of associated multiple cancerous lesions in patients with the superficially spreading type.

CONCLUSIONS

Superficially spreading carcinoma of the esophagus is often associated with multiple cancerous lesions. For endoscopists and esophageal surgeons, it is important to define the proximal extent of intraepithelial cancer and the presence of multiple cancerous lesions to perform curative resection.

Highly elevated ultraviolet-induced mutation frequency in isolated Chinese hamster cell lines defective in nucleotide excision repair and mismatch repair proteins

We have isolated N-methyl-N'-nitro-N-nitrosoguanidine-resistant cell lines from 43-3B Chinese hamster ovary cells, which are deficient in the ERCC1 gene involved in nucleotide excision repair. By Western blotting analysis, we found cell lines that are deficient or decreased in the amount of MSH6, or PMS2, or MSH2 proteins. Cell extracts of these cell lines show reduced efficiency of G:T mismatch repair activity. Compared with 43-3B, these cell lines exhibit highly elevated UV-induced mutation rates, indicating that mammalian mismatch repair can suppress UV-induced mutagenesis and may play a role in the fidelity of DNA replication at the sites of UV damage.

Cellular responses and repair of single-strand breaks introduced by UV damage endonuclease in mammalian cells

Although single-strand breaks (SSBs) occur frequently, the cellular responses and repair of SSB are not well understood. To address this, we established mammalian cell lines expressing Neurospora crassa UV damage endonuclease (UVDE), which introduces a SSB with a 3'-OH immediately 5' to UV-induced cyclobutane pyrimidine dimers or 6-4 photoproducts and initiates an alternative excision repair process. Xeroderma pigmentosum group A cells expressing UVDE show UV resistance of almost the wild-type level. In these cells SSBs are produced upon UV irradiation and then efficiently repaired. The repair patch size is about seven nucleotides, and repair synthesis is decreased to 30% by aphidicolin, suggesting the involvement of a DNA polymerase delta/epsilon-dependent long-patch repair. Immediately after UV irradiation, cellular proteins are poly(ADP-ribosyl)ated. The UV resistance of the cells is decreased in the presence of 3-aminobenzamide, an inhibitor of poly(ADP-ribose) polymerase. Expression of UVDE in XRCC1-defective EM9, a Chinese hamster ovary cell line, greatly sensitizes the host cells to UV, and addition of 3-aminobenzamide results in almost no further sensitization of the cells to UV. Thus, we show that XRCC1 and PARP are involved in the same pathway for the repair of SSBs.

Identification and characterization of human DNA polymerase beta 2, a DNA polymerase beta -related enzyme

The BRCA1 COOH terminus (BRCT) motif is present in many nuclear proteins that contribute to cell cycle regulation or DNA repair. Polymerase chain reaction-based screening with degenerate primers targeted to the BRCT motif resulted in the isolation of a human cDNA for a previously unidentified DNA polymerase (designated DNA polymerase beta2) that is closely related to DNA polymerase beta (Pol beta). The predicted Pol beta2 protein contains a BRCT motif in its NH(2)-terminal region; its COOH-terminal region exhibits 33% sequence identity to a corresponding region of human Pol beta. The Pol beta2 gene is expressed in a tissue-specific manner, with transcripts being most abundant in testis. A fusion construct comprising Pol beta2 and green fluorescent protein exhibited a predominantly nuclear localization in transfected HeLa cells. Recombinant human Pol beta2 from insect cells exhibited substantial DNA polymerase activity, but it did not possess terminal deoxyribonucleotidyl transferase activity. A truncated Pol beta2 mutant lacking the BRCT motif retained substantial DNA polymerase activity, whereas a mutant Pol beta2 with two alanine point mutations within the DNA polymerase active site did not. These results indicate that Pol beta2 is a Pol beta-related DNA polymerase with a BRCT motif that is dispensable for its polymerase activity.

Repair of UV damage in the fission yeast Schizosaccharomyces pombe

This review is concerned with repair and tolerance of UV damage in the fission yeast, Schizosaccharomyces pombe and with the differences between Sch. pombe and budding yeast, Saccharomyces cerevisiae in their response to UV irradiation. Sch. pombe is not as sensitive to ultra-violet radiation as Sac. cerevisiae nor are any of its mutants as sensitive as the most sensitive Sac. cerevisiae mutants. This can be explained in part by the fact that Sch. pombe, unlike budding yeast or mammalian cells, has an extra pathway (UVER) for excision of UV photoproducts in addition to nucleotide excision repair (NER). However, even in mutants lacking this additional pathway, there are significant differences between the two yeasts. Sch. pombe mutants that lack the alternative pathway are still more UV-resistant than wild-type Sac. cerevisiae; recombination mutants are significantly UV sensitive (unlike their Sac. cerevisiae equivalents); mutants lacking the second pathway are sensitized to UV by caffeine; and checkpoint mutants are relatively more sensitive than the budding yeast equivalents. In addition, Sch. pombe has no photolyase. Thus, the response to UV in the two yeasts has a number of significant differences, which are not accounted for entirely by the existence of two alternative excision repair pathways. The long G2 in Sch. pombe, its well-developed recombination pathways and efficient cell cycle checkpoints are all significant components in survival of UV damage.

The DNA damage spectrum produced by simulated sunlight

The mutagenic effects of ultraviolet and solar irradiation are thought to be due to the formation of DNA photoproducts, most notably cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)PPs). Experimental systems for determining the levels and sequence dependence of photoproduct formation in DNA have often used high doses of short-wave (UVC) irradiation. We have re-assessed this issue by using DNA sequencing technologies and different doses of UVC as well as more physiologically relevant doses of solar irradiation emitted from a solar UV simulator. It has been questioned whether hot alkali treatment can detect (6-4)PPs at all sequence positions. With high UVC doses, the sequence distribution of (6-4)PPs was virtually identical when hot alkali or UV damage endonuclease (UVDE) were used for detection, which appears to validate both methods. The (6-4)PPs form at 5'-TpC and 5'CpC sequences but very low levels are seen at all other dipyrimidines including 5'-TpT. Contrary to expectation, we find that (6-4) photoproducts form at almost undetectable levels under conditions of irradiation for up to five hours with the solar UV simulator. The same treatment produces high levels of CPDs. In addition, DNA glycosylases, which recognize oxidized and ring-opened bases, did not produce significant cleavage of sunlight-irradiated DNA. From these data, we conclude that cyclobutane pyrimidine dimers are at least 20 to 40 times more frequent than any other DNA photoproduct when DNA or cells are irradiated with simulated sunlight.

Dimerization and nuclear entry of mPER proteins in mammalian cells

Nuclear entry of circadian oscillatory gene products is a key step for the generation of a 24-hr cycle of the biological clock. We have examined nuclear import of clock proteins of the mammalian period gene family and the effect of serum shock, which induces a synchronous clock in cultured cells. Previously, mCRY1 and mCRY2 have been found to complex with PER proteins leading to nuclear import. Here we report that nuclear translocation of mPER1 and mPER2 (1) involves physical interactions with mPER3, (2) is accelerated by serum treatment, and (3) still occurs in mCry1/mCry2 double-deficient cells lacking a functional biological clock. Moreover, nuclear localization of endogenous mPER1 was observed in cultured mCry1/mCry2 double-deficient cells as well as in the liver and the suprachiasmatic nuclei (SCN) of mCry1/mCry2 double-mutant mice. This indicates that nuclear translocation of at least mPER1 also can occur under physiological conditions (i.e., in the intact mouse) in the absence of any CRY protein. The mPER3 amino acid sequence predicts the presence of a cytoplasmic localization domain (CLD) and a nuclear localization signal (NLS). Deletion analysis suggests that the interplay of the CLD and NLS proposed to regulate nuclear entry of PER in Drosophila is conserved in mammals, but with the novel twist that mPER3 can act as the dimerizing partner.

Photorepair prevents ultraviolet-induced apoptosis in human cells expressing the marsupial photolyase gene

Photolyase absorbs blue light and employs the energy to remove UV-induced DNA damage, cyclobutane pyrimidine dimers, or pyrimidine pyrimidone (6-4) lesions. These enzymes have been found in many living organisms ranging from bacteria to aplacental mammals, but their photoreactivation effect, such as survival increase of UV-irradiated cells by light-illumination, has not been identified in placental mammals, including humans. Therefore, we introduced a photolyase gene derived from the marsupial rat kangaroo, Potorous tridactylus, into HeLa cells and established the first human cell line capable of photorepairing UV-induced pyrimidine dimers. Several clones were found to increase cell survival after UV irradiation when illuminated by fluorescent light. The induction of apoptosis by UV irradiation was investigated in these photoreactivation-proficient cells. Several typical features of the programmed cell death, such as internucleosomal DNA degradation, presence of subdiploid cells, loss of membrane integrity, and chromosomal condensation, were found to be induced by UV in the HeLa cells, but they can be reduced by photorepair. This implicates that cyclobutane pyrimidine dimers cause UV-induced apoptosis in human cells.

Alternative excision repair pathway of UV-damaged DNA in Schizosaccharomyces pombe operates both in nucleus and in mitochondria

The fission yeast, Schizosaccharomyces pombe, possesses a UV-damaged DNA endonuclease-dependent excision repair (UVER) pathway in addition to nucleotide excision repair pathway for UV-induced DNA damage. We examined cyclobutane pyrimidine dimer removal from the myo2 locus on the nuclear genome and the coI locus on the mitochondrial genome by the two repair pathways. While nucleotide excision repair repairs damage only on the nuclear genome, UVER efficiently removes cyclobutane pyrimidine dimers on both nuclear and mitochondrial genomes. The ectopically expressed wild type UV-damaged DNA endonuclease was localized to both nucleus and mitochondria, while modifications of N-terminal methionine codons restricted its localization to either of two organelles, suggesting an alternative usage of multiple translation initiation sites for targeting the protein to different organelles. By introducing the same mutations into the chromosomal copy of the uvde(+) gene, we selectively inactivated UVER in either the nucleus or the mitochondria. The results of UV survival experiments indicate that although UVER efficiently removes damage on the mitochondrial genome, UVER in the mitochondria hardly contributes to UV resistance of S. pombe cells. We suggest a possible UVER function in mitochondria as a backup system for other UV damage tolerance mechanisms.

Pancreas-sparing duodenectomy for a huge leiomyosarcoma in the third portion of the duodenum

A duodenal leiomyosarcoma which was resected by pancreas-sparing duodenectomy is reported. The tumor arose in the third portion of the duodenum and grew in an extraluminal direction. The tumor was huge (13 cm x 9 cm x 8 cm) but did not involve the pancreas, and there were no findings of periduodenal lymph node metastases. Because the possibility of metastasis to the lymph nodes around the root of the superior mesenteric artery (which are removed only in a pancreatoduodenectomy) was judged to be low, pancreas-sparing duodenectomy was performed, with dissection of the pancreaticoduodenal lymph nodes. The proximal duodenum was transected between the second and third portions of the duodenum, and the distal end was cut in the jejunum at the portion of the first jejunal artery. Reconstruction was performed by end-to-side anastomosis between the duodenum and jejunum, using an end-to-end anastomosis instrument. Since the incidence of lymph node metastasis of leiomyosarcoma is low, resection of the head of the pancreas for extensive lymph node dissection does not always seem necessary. Pancreas-sparing duodenectomy can be a good option for a leiomyosarcoma in the third and fourth portions of the duodenum which does not invade the pancreas and is not accompanied by any apparent periduodenal lymph node metastases.

Photic induction of mPer1 and mPer2 in cry-deficient mice lacking a biological clock

Mice lacking mCry1 and mCry2 are behaviorally arrhythmic. As shown here, cyclic expression of the clock genes mPer1 and mPer2 (mammalian Period genes 1 and 2) in the suprachiasmatic nucleus and peripheral tissues is abolished and mPer1 and mPer2 mRNA levels are constitutively high. These findings indicate that the biological clock is eliminated in the absence of both mCRY1 and mCRY2 (mammalian cryptochromes 1 and 2) and support the idea that mammalian CRY proteins act in the negative limb of the circadian feedback loop. The mCry double-mutant mice retain the ability to have mPer1 and mPer2 expression induced by a brief light stimulus known to phase-shift the biological clock in wild-type animals. Thus, mCRY1 and mCRY2 are dispensable for light-induced phase shifting of the biological clock.

Characterization of a Neurospora crassa photolyase-deficient mutant generated by repeat induced point mutation of the phr gene

We produced a photolyase-deficient mutant by repeat induced point mutation using the Neurospora crassa photolyase gene cloned previously. This mutation identified a new gene, phr, which was mapped on the right arm of linkage group I by both RFLP mapping and conventional mapping. To investigate the relationship between photoreactivation and dark repair processes, especially excision repair, double mutants of phr with representative repair-defective mutants of different types were constructed and tested for UV sensitivity and photoreactivation. The results show that the phr mutation has no influence on dark repair. Tests with CPD and TC(6-4) photoproduct-specific antibodies demonstrated that the phr mutant is defective in CPD photolyase and confirmed that there is no TC(6-4) photolyase activity in N. crassa. Furthermore, N. crassa photolyase is not a blue light receptor in the signal transduction that induces carotenoid biosynthesis.

Transcription dependence and the roles of two excision repair pathways for UV damage in fission yeast Schizosaccharomyces pombe

Fission yeasts Schizosaccharomyces pombe possess two types of excision repair systems for UV-induced DNA damage, nucleotide excision repair (NER) and UV-damaged DNA endonuclease (UVDE)-dependent excision repair (UVER). Despite its high efficiency in damage removal, UVER defects have less effect on UV survival than NER defects. To understand the differential roles of two pathways, we examined strand-specific damage removal at the myo2 and rpb2 loci. Although NER removes cyclobutane pyrimidine dimers from the transcribed strand more rapidly than from the nontranscribed strand, UVER repairs cyclobutane pyrimidine dimers equally on both strands and at a much higher rate than NER. The low rate of damage removal from the nontranscribed strand in the absence of UVER indicates inefficient global genome repair (GGR) in this organism and a possible function of UVER as an alternative to GGR. Disruption of rhp26, the S. pombe homolog of CSB/RAD26, eliminated the strand bias of NER almost completely and resulted in a significant increase of UV sensitivity of cells in a uvdeDelta background. We suggest that the combination of transcription-coupled repair of NER and rapid UVER contributes to UV survival in growing S. pombe cells, which is accomplished by transcription-coupled repair and GGR in other organisms.

Differential subcellular localization of human MutY homolog (hMYH) and the functional activity of adenine:8-oxoguanine DNA glycosylase

The post-replicative adenine:8-oxo-7,8-dihydroguanine (GO) mismatch is crucial for G:C to T:A transversion. This mismatch is corrected by Escherichia coli MutY which excises the adenine from A:GO. A candidate gene coding for the human counterpart of MutY has been cloned as hMYH. However, the function and enzyme activities of the gene product have not been identified. We previously demonstrated that an epitope-tagged hMYH protein behaves as a mitochondrial protein. In the present study, we have identified an alternative hMYH transcript, termed type 2, which differs in the exon 1 sequence of the known transcript (type 1). A nuclear localization for the type 2 protein was revealed by detection of epitope-tagged protein in COS-7 cells. Expression of both type 1 and type 2 transcripts was reduced in post-mitotic tissues. hMYH cDNA suppressed the mutator phenotype of E.coli mutY. In vitro expressed hMYH showed adenine DNA glycosylase activity toward the A:GO substrate. The protein can bind to A:GO, and to T:GO and G:GO without apparent catalysis. These results represent the first demonstration of the function of the hMYH gene product which is differentially transported into the nucleus or the mitochondria by alternative splicing

Repair of apurinic/apyrimidinic sites by UV damage endonuclease; a repair protein for UV and oxidative damage

UV damage endonuclease (UVDE) initiates a novel form of excision repair by introducing a nick imme-diately 5" to UV-induced cyclobutane pyrimidine dimers or 6-4 photoproducts. Here, we report that apurinic/apyrimidinic (AP) sites are also nicked by Neurospora crassa and Schizosaccharomyces pombe UVDE. UVDE introduces a nick immediately 5" to the AP site leaving a 3"-OH and a 5"-phosphate AP. Apyrimidinic sites are more effectively nicked by UVDE than apurinic sites. UVDE also possesses 3"-repair activities for AP sites nicked by AP lyase and for 3"-phosphoglycolate produced by bleomycin. The Uvde gene introduced into Escherichia coli cells lacking two types of AP endonuclease, Exo III and Endo IV, gave the host cells resistance to methylmethane sulfonate and t-butyl hydroperoxide. We identified two AP endonuclease activities in S.pombe cell extracts. Besides cyclobutane pyrimidine dimers and 6-4 photoproducts, N. crassa UVDE also nicks Dewar photoproducts. Thus, UVDE is able to repair both of the major forms of DNA damage in living organisms: UV-induced DNA lesions and AP sites.

Mammalian Cry1 and Cry2 are essential for maintenance of circadian rhythms

Many biochemical, physiological and behavioural processes show circadian rhythms which are generated by an internal time-keeping mechanism referred to as the biological clock. According to rapidly developing models, the core oscillator driving this clock is composed of an autoregulatory transcription-(post) translation-based feedback loop involving a set of 'dock' genes. Molecular clocks do not oscillate with an exact 24-hour rhythmicity but are entrained to solar day/night rhythms by light. The mammalian proteins Cryl and Cry2, which are members of the family of plant blue-light receptors (cryptochromes) and photolyases, have been proposed as candidate light receptors for photoentrainment of the biological clock. Here we show that mice lacking the Cryl or Cry2 protein display accelerated and delayed free-running periodicity of locomotor activity, respectively. Strikingly, in the absence of both proteins, an instantaneous and complete loss of free-running rhythmicity is observed. This suggests that, in addition to a possible photoreceptor and antagonistic clock-adjusting function, both proteins are essential for the maintenance of circadian rhythmicity.

Processing of UV damage in vitro by FEN-1 proteins as part of an alternative DNA excision repair pathway

Ultraviolet (UV) irradiation induces predominantly cyclobutane and (6-4) pyrimidine dimer photoproducts in DNA. Several mechanisms for repairing these mutagenic UV-induced DNA lesions have been identified. Nucleotide excision repair is a major pathway, but mechanisms involving photolyases and DNA glycosylases have also been characterized. Recently, a novel UV damage endonuclease (UVDE) was identified that initiates an excision repair pathway different from previously established repair mechanisms. Homologues of UVDE have been found in eukaryotes as well as in bacteria. In this report, we have used oligonucleotide substrates containing site-specific cyclobutane pyrimidine dimers and (6-4) photoproducts for the characterization of this UV damage repair pathway. After introduction of single-strand breaks at the 5' sides of the photolesions by UVDE, these intermediates became substrates for cleavage by flap endonucleases (FEN-1 proteins). FEN-1 homologues from humans, Saccharomyces cerevisiae, and Schizosaccharomyces pombe all cleaved the UVDE-nicked substrates at similar positions 3' to the photolesions. T4 endonuclease V-incised DNA was processed in the same way. Both nicked and flapped DNA substrates with photolesions (the latter may be intermediates in DNA polymerase-catalyzed strand displacement synthesis) were cleaved by FEN-1. The data suggest that the two enzymatic activities, UVDE and FEN-1, are part of an alternative excision repair pathway for repair of UV photoproducts.

Influence of vagal pyloric branches on gastric acid secretion and gastrointestinal motility in patients following a pylorus preserving pancreatoduodenectomy

BACKGROUND/AIMS

The authors evaluated the influence of the vagal pyloric branches on the gastrointestinal function in patients who underwent a pylorus preserving pancreatoduodenectomy (PPPD).

METHODOLOGY

Twenty-seven patients with pancreatobiliary and duodenal diseases underwent a PPPD between 1991 and 1994. We analyzed several variables including the daily volume of gastric juice, days of gastric suctioning, start of diet, gastric acid, and gastrin levels. In addition, a gastric emptying scintigram and gastrointestinal manometry were measured. These variables were compared between two groups, namely, those with retained superior pyloric branches of the vagus nerve (preserved group: n = 14), and those without these branches (non-preserved group: n = 13).

RESULTS

There were no significant differences in basal acid output, maximum acid output, or plasma gastrin levels between the preserved group and the non-preserved group. In addition, a gastric emptying scintigram demonstrated no difference between the two groups. Finally, on gastrointestinal manometry, there was no significant difference between the two groups during gastric and jejunal phase III activity of migrating motor complex.

CONCLUSIONS

Preservation of the vagal pyloric branches did not influence gastric exocrine and endocrine secretion, nor did it effect the gastric emptying of patients who underwent a PPPD.

A putative blue-light receptor from Drosophila melanogaster

A gene encoding a 62.5 kDa homolog of Drosophila melanogaster photolyase was isolated. Purified recombinant protein contained a flavin adenine dinucleotide chromophore. The recombinant protein did not show photolyase activity for either cyclobutane pyrimidine dimers or 6-4 photoproducts in vitro as well as in vivo in Escherichia coli host cells, suggesting that the protein is not a DNA repair enzyme but a blue-light photoreceptor. Reverse transcription polymerase chain reaction analysis showed that the gene is more expressed in head than in body and that it is more expressed in antennae than in legs, wings and mouth appendages. In a phylogenetic tree of the photolyase family, the Drosophila photolyase homolog is located in a cluster containing 6-4 photolyases and mammalian photolyase homologs, which is only distantly related to the clade of higher plant blue-light photoreceptors. The mammalian photolyase homologs are more closely related to Drosophila 6-4 photolyase than to the Drosophila photolyase homolog, suggesting different roles of the photolyase homologs.

Characterization of photolyase/blue-light receptor homologs in mouse and human cells

We isolated and characterized mouse photolyase-like genes, mCRY1 (mPHLL1) and mCRY2 (mPHLL2), which belong to the photolyase family including plant blue-light receptors. The mCRY1 and mCRY2 genes are located on chromosome 10C and 2E, respectively, and are expressed in all mouse organs examined. We raised antibodies specific against each gene product using its C-terminal sequence, which differs completely between the genes. Immunofluorescent staining of cultured mouse cells revealed that mCRY1 is localized in mitochondria whereas mCRY2 was found mainly in the nucleus. The subcellular distribution of CRY proteins was confirmed by immunoblot analysis of fractionated mouse liver cell extracts. Using green fluorescent protein fused peptides we showed that the C-terminal region of the mouse CRY2 protein contains a unique nuclear localization signal, which is absent in the CRY1 protein. The N-terminal region of CRY1 was shown to contain the mitochondrial transport signal. Recombinant as well as native CRY1 proteins from mouse and human cells showed a tight binding activity to DNA Sepharose, while CRY2 protein did not bind to DNA Sepharose at all under the same condition as CRY1. The different cellular localization and DNA binding properties of the mammalian photolyase homologs suggest that despite the similarity in the sequence the two proteins have distinct function(s).

Cloning and characterization of a mouse homologue (mNthl1) of Escherichia coli endonuclease III

Endonuclease III (endoIII; nth gene product) of Escherichia coli is known to be a DNA repair enzyme having a relatively broad specificity for damaged pyrimidine bases of DNA. Here, we describe the cloning and characterization of the cDNA and the gene for a mouse homologue (mNthl1/mNth1) of endoIII. The cDNA was cloned from a mouse T-cell cDNA library with a probe prepared by PCR using the library and specific PCR primers synthesized based on the reported information of partial amino acid sequences of bovine NTHL1/NTH1 and of EST Data Bases. The cDNA is 1025 nucleotides long and encodes a protein consisting of 300 amino acids with a predicted molecular mass of 33.6 kDa. The amino acid sequence exhibits significant homologies to those of endoIII and its prokaryotic and eukaryotic homologues. The recombinant mNthl1 with a hexahistidine tag was overexpressed in a nth::cmr nei::Kmr double mutant of E. coli, and purified to apparent homogeneity. The enzyme showed thymine glycol DNA glycosylase, urea DNA glycosylase and AP lyase activities. Northern blot analysis indicated that mNthl1 mRNA is about 1 kb and is expressed ubiquitously. A 15 kb DNA fragment containing the mNthl1 gene was cloned from a mouse genomic library and sequenced. The gene consists of six exons and five introns spanning 6.09 kb. The sequenced 5' flanking region lacks a typical TATA box, but contains a CAAT box and putative binding sites for several transcription factors such as Ets, Sp1, AP-1 and AP-2. The mNthl1 gene was shown to lie immediately adjacent to the tuberous sclerosis 2 (Tsc2) gene in a 5'-to-5' orientation by sequence analysis and was assigned to chromosome 17A3 by in situ hybridization.

Dihydropyridine type calcium channel blocker-induced turbid dialysate in patients undergoing peritoneal dialysis

We previously reported that manidipine, a new dihydropyridine type calcium channel blocker, produced chylous peritoneal dialysate being visually indistinguishable from infective peritonitis in 5 patients undergoing continuous ambulatory peritoneal dialysis (CAPD) [Yoshimoto et al. 1993]. To study whether such an adverse drug reaction would also be elicited by other commonly prescribed calcium channel blockers in CAPD patients, we have conducted postal inquiry to 15 collaborating hospitals and an institutional survey in International Medical Center of Japan as to the possible occurrence of calcium channel blocker-associated non-infective, turbid peritoneal dialysate in CAPD patients. Our diagnostic criteria for drug-induced turbidity of dialysate as a) it developed within 48 h after the administration of a newly introduced calcium channel blocker to the therapeutic regimen, b) absence of clinical symptoms of peritoneal inflammation (i.e., pyrexia, abdominal pain, nausea or vomiting), c) the fluid containing normal leukocyte counts and being negative for bacterial and fungal culture of the fluid, and d) it disappeared shortly after the withdrawal of the assumed causative agent. Results showed that 19 out of 251 CAPD patients given one of the calcium channel blockers developed non-infective turbid peritoneal dialysis that fulfilled all the above criteria. Four calcium channel blockers were suspected to be associated with the events: benidipine [2 out of 2 (100%) patients given the drug], manidipine [15 out of 36 (42%) patients], nisoldipine [1 out of 11 (9%) patients] and nifedipine [1 out of 159 (0.6%)] in descending order of frequency. None of the patients who received nicardipine, nilvadipine, nitrendipine, barnidipine and diltiazem (25, 7, 2, 1 and 8 patients, respectively) exhibited turbid dialysate. In conclusion, we consider that certain dihydropyridine type calcium channel blockers would cause turbid peritoneal dialysate being similar to that observed in patients developing infective peritonitis. To avoid unnecessary antibiotic therapy the possibility of this adverse reaction should be ruled out whenever a CAPD patient receiving a dihydropyridine type calcium channel blocker develops turbid dialysate.

Mitochondrial targeting of human DNA glycosylases for repair of oxidative DNA damage

Oxidative damage to mitochondrial DNA has been implicated in human degenerative diseases and aging. Although removal of oxidative lesions from mitochondrial DNA occurs, the responsible DNA repair enzymes are poorly understood. By expressing the epitope-tagged proteins in COS-7 cells, we examined subcellular localizations of gene products of human DNA glycosylases: hOGG1, hMYH and hNTH1. A gene encoding for hOGG1 which excises 7,8-dihydro-8-oxoguanine (8-oxoG) from DNA generates four isoforms by alternative splicing (types 1a, 1b, 1c and 2). Three tagged isoforms (types 1b, 1c and 2) were localized in the mitochondria. Type 1a protein, which exclusively contains a putative nuclear localization signal, was sorted to the nucleus and lesser amount to the mitochondria. hMYH, a human homolog gene product of Escherichia coli mutY was mainly transported into the mitochondria. hNTH1 protein excising several pyrimidine lesions was transported into both the nucleus and mitochondria. In contrast to the three DNA glycosylases, translocation of the human major AP endonuclease (hAPE) into the mitochondria was hardly observed in COS-7 cells. These results suggest that the previously observed removal of oxidative base lesions in mitochondrial DNA is initiated by the above DNA glycosylases.

ERCC1 mutations in UV-sensitive Chinese hamster ovary (CHO) cell lines

In mammalian nucleotide excision repair (NER), the ERCC1 protein is known to act as a complex with ERCC4 (XPF) protein, which is necessary for stability of ERCC1, and this complex introduces an incision on the 5' side of a damaged site in DNA. ERCC1 also binds to XPA protein to make a large protein complex at the site of DNA damage. Since no human disease associated with ERCC1 has been identified, Chinese hamster ovary (CHO) cell lines defective in ERCC1 are a unique source for characterization of ERCC1 deficiency in mammalian cells. We have isolated the full length ERCC1 cDNA from a wild-type CHO cell line and analyzed mutations in two CHO cell lines which fall into complementation group 1 of UV-sensitive rodent cell lines. One cell line, 43-3B, has a missense mutation at the 98th residue (V98E). The in vitro translated mutant protein of 43-3B is unable to bind to XPA protein. Although the mutant protein is able to bind to XPF protein in vitro, the mutant protein is highly unstable in vivo. These defects presumably cause the NER deficiency of this cell line. Another mutant, UV-4, has an insertion mutation in the middle of the coding sequence, resulting in a truncated protein due to a nonsense codon arising from the frameshift. Thus, these two mutant cell lines are deficient in the function of the ERCC1 gene for NER.

Short report: An imported case of cystic echinococcosis in Japan diagnosed by imaging and serology with confirmation of Echinococcus granulosus-specific DNA sequences

We report one case of cystic echinococcosis (CE) in Japan in a native of Nepal. Ultrasonography and computed tomography scan of the liver revealed unique cystic lesions with or without daughter cysts of Echinococcus granulosus. Immunoblot analysis using crude antigens of E. multilocularis and cyst fluid of E. granulosus, without reference to these image analyses, strongly suggested this was a case of CE. We found protoscoleces in surgically removed hepatic lesions and analyzed the mitochondrial cytochrome c oxidase subunit I (COI) gene by the polymerase chain reaction. Based on the similarity in DNA sequences of the COI gene of this Echinococcus spp. with that of previously reported sheep-dog strain (GI), the parasite was considered to be the so-called common sheep strain of E. granulosus.

Alternative repair pathways for UV-induced DNA damage

Ultraviolet light (UV) is thought to have had a major impact on the early evolution of life. UV is absorbed by nucleic acids and produces several types of DNA damage, which interfere with DNA replication and transcription. This damage can result in mutagenesis and cell killing. Several mechanisms for repairing UV-induced DNA damage have been identified. Besides the widely distributed nucleotide excision repair, two alternative repair mechanisms for specific lesions in UV-damaged DNA are known, involving photolyases and DNA glycosylases. Recently, a novel endonuclease for UV-induced DNA damage was identified that initiates an excision repair pathway completely different from previously established repair mechanisms. The finding of this "alternative excision repair" suggests the presence of a new category of DNA repair, initiated by single-strand breaks in DNA. Homologues of the UVDE enzyme have been found in eukaryotic microorganisms, as well as in bacteria, indicating that the enzyme originated early in evolution, and suggesting the existence of multirepair systems for UV-induced DNA damage during early evolution.

Cloning and characterization of the guinea pig C5a anaphylatoxin receptor: interspecies diversity among the C5a receptors

The anaphylatoxin C5a receptor (C5aR, CD88 in man) plays a prominent role in mediating inflammatory and host defense processes. Direct evidence of C5aR involvement in host defense mechanisms was demonstrated recently using C5aR knockout mice. Mice deficient in C5aR were unable to clear intrapulmonary-instilled bacteria. The guinea pig system is perhaps unique for exhibiting cross-reactivity with human complement components and its high sensitivity to anaphylatoxins. Therefore, we cloned the guinea pig C5aR from a megakaryocyte cDNA library. The deduced amino acid sequence of guinea pig C5aR is 67% identical to human, 61.6% to dog, 60.2% to mouse and 63.6% to rat C5aR. Transient expression of guinea pig C5aR in COS-7 cells and stable expression on L cell fibroblasts were confirmed by FACS analysis. Competitive binding studies using [125I]C5a and stimulation of calcium mobilization by C5a proved that functional C5aR was expressed on these stably transfected L cells. The N-terminal extracellular region of guinea pig C5aR was five to seven residues shorter than the same region in C5aR from other species and sequence homology was limited to 11%. Other outer membrane loops were also poorly conserved (8-33%) when compared across five species. Transmembrane segments were highly conserved between these various species (46-86%). Guinea pig C5aR binds human C5a, therefore residues critical for C5a binding have been conserved between these species. Sequence comparison of C5aR from multiple species permits conserved elements of the ligand binding sites to be elucidated.

Gastrointestinal cancer metastasis and lymphogenous spread: viewpoint of animal models of lymphatic obstruction

Primary gastrointestinal cancer frequently spreads to the mesentery, omentum and other parts of the peritoneum and these deposits are generally considered to be induced by intraperitoneal seeding from the primary lesion. In this work, we examined the spread of gastrointestinal cancer from the viewpoint of lymphogenous metastasis using a rat model of mesenteric lymph vessel obstruction. With these models, we carried out mesenteric lymphangiography on the fourth and sixth postoperative days (five animals each) to examine morphological changes in the lymph vessels and lymph flow. In model animals with mesenteric lymph vessel obstruction, re-celiotomy, performed on the fourth postoperative day, revealed marked mesenteric edema and enlargement of the mesenteric lymph nodes, suggestive of lymph retention. We also carried out mesenteric lymphangiography and obtained images of extensive mesenteric lymph vessels and reflux of lymph distal to the obstruction point in all five animals. On the sixth postoperative day, we obtained lymphangiographic images of lymphatico-venous communication in the mesentery in all five animals. Thus in animals with lymph vessel obstruction, the lymph flow appeared to change to lymphatico-venous communication or reverse lateral flow. In clinical cases, it is conceivable that lymph retention and reflux of lymph induced by lymph vessel obstruction sometimes play a role in the mechanism of intraperitoneal cancer dissemination and hematogenous metastasis.