Nucleotide binding and autophosphorylation of the clock protein KaiC as a circadian timing process of cyanobacteria

A negative feedback control of kaiC expression by KaiC protein has been proposed to generate a basic oscillation of the circadian clock in the cyanobacterium Synechococcus sp. PCC 7942. KaiC has two P loops or Walker's motif As, that are potential ATP-/GTP-binding motifs and DXXG motifs conserved in various GTP-binding proteins. Herein, we demonstrate that in vitro KaiC binds ATP and, with lower affinity, GTP. Point mutation by site-directed mutagenesis of P loop 1 completely nullified the circadian rhythm of kaiBC expression and markedly reduced ATP-binding activity. Moreover, KaiC can be autophosphorylated in vitro. These results suggest that the nucleotide-binding activity of KaiC plays important roles in the generation of circadian oscillation in cyanobacteria.

Retrovirus vectors designed for efficient transduction of cytotoxic or cytostatic genes

It is difficult to establish stable packaging cell lines producing retrovirus vectors for the expression of anti-oncogenes with cytotoxic or cytostatic potential, because these genes would also affect the growth of the packaging cell lines. To overcome this problem, we designed a transcriptional unit pBabeLPL for vector RNA production, in which the transcription of the exogenous genes is completely suppressed by the presence of a preceding insertion containing the puromycin resistance gene (puro) and a poly(A) addition signal. This insertion is flanked by a tandem pair of loxP, and is designed to be excised after the introduction of Cre recombinase, when transcription of the exogenous gene will be started from the 5'-LTR. The transcriptional unit car- rying LacZ or p53 as the exogenous gene was introduced into a previously constructed prepackaging cell lines PtG-S2, in which the expression of VSV-G is also designed to be initiated by the introduction of Cre recombinase, while the gag-pol gene is expressed continuously. After the introduction of Cre recombinase by an adenovirus vector, LacZ- or p53-expressing VSV-G-pseudotyped retrovirus vectors with the designed structure were produced at high virus titers. The p53 virus was shown to be able to transduce p53 into the entire population of several human cancer cell lines and to induce their growth arrest at the G1 phase, indicating that this vector-producing system will be advantageous for human gene therapy.

Significant differences in the frequency of transcriptional units, types and numbers of repetitive elements, GC content, and the number of CpG islands between a 1010-kb G-band genomic segment on chromosome 9q31.3 and a 1200-kb R-band genomic segment on chromosome 3p21.3

We determined the nucleotide sequence of the entire 1,010,525-bp insert contained in CEPH YAC clone 867e8. This human genomic segment was derived from chromosome 9q31.3 and corresponds to a G-band region. We compared this segment, in terms of structure, with a previously characterized 1,201,033-bp sequence in CEPH YAC936c1 that had come from a portion of human chromosome 3p21.3 corresponding to an R-band region. The two segments were significantly different with respect to the frequency of transcriptional units, the types and numbers of repetitive elements present, their GC content, and the number of CpG islands. Alu elements, GC content, and CpG islands all showed positive correlations with the abundance of exons, but the distribution of LINE1s did not. These observations might reflect an influence of the first three of these features on the functions or expression of genes in the respective regions. In addition to a novel gene (F36) lying at the centromeric end of the 9q segment, we found a cluster of placenta-specific genes within a small section (about 400 kb) on the telomeric side of YAC867e8. This cluster consisted of four apparently unrelated ESTs and two genes, pregnancy-associated plasma protein-A (PAPP-A) and a novel gene (tentatively named EST-YD1). Our characterization of the two chromosomal regions provided evidence that genes are not evenly distributed throughout the human genome, and that gene richness is correlated with the GC content and with the frequency of either Alu elements or CpG islands.

Isolation and characterization of a human cDNA homologous to the Xenopus laevis XCAP-C gene belonging to the structural maintenance of chromosomes (SMC) family

We have isolated a human cDNA encoding a protein of 1288 amino acids that shows 77% identity in amino acid sequence to XCAP-C, Xenopus chromosome-associated polypeptide-C, belonging to the family of structural maintenance of chromosomes (SMC), which is known to play a crucial role in the proper condensation and segregation of mitotic chromosomes. In particular, an almost 200-amino-acid domain in the N-terminal, including an NTP-binding motif and that in the C-terminal domain, including a DA-box, were well conserved and showed 95% identity between human and frog, indicating that these two domains are functionally very important. The transcript of this gene was expressed ubiquitously in various human tissues, but thymus, testis, and colon seemed to express this gene more abundantly. We also determined its chromosomal location at 3q26.1 by fluorescence in situ hybridization.

Molecular cloning of a candidate tumor suppressor gene, DLC1, from chromosome 3p21.3

The short arm of chromosome 3 is thought to contain multiple tumor suppressor genes, because one copy of this chromosomal arm frequently is missing in carcinomas that have arisen in a variety of tissues. We have isolated a novel gene encoding a 1755-amino acid polypeptide, through large-scale sequencing of genomic DNA at 3p21.3. Mutational analysis of this gene by reverse transcription-PCR revealed the lack of functional transcripts and an increase of nonfunctional RNA transcripts in a significant proportion (33%) of cancer cell lines and primary cancers (4 of 14 esophageal cancer cell lines, 2 of 2 renal cancer cell lines, 11 of 30 primary non-small cell lung cancers, and 3 of 10 primary squamous cell carcinomas of the esophagus). However, no alterations of the gene itself were detected in any of the cancers examined. Introduction of the cDNA significantly suppressed the growth of four different cancer cell lines, two of which produced no normal transcript on their own. No such effect occurred when antisense cDNA, cDNA corresponding to an aberrant transcript, or the vector DNA alone were transfected. These data suggest that aberrant transcription of this gene, designated DLC1 (deleted in lung cancer 1), may be involved in carcinogenesis of the lung, esophagus, and kidney.

Characterization of a 1200-kb genomic segment of chromosome 3p22-p21.3

We previously determined the nucleotide sequence and characterized the 685-kb proximal half of CEPH YAC936c1, which corresponds to a portion of human chromosome 3p21.3. In the study reported here, we characterized the remaining 515-kb of this YAC clone corresponding to the telomeric half of its human insert. The newly sequenced region contained a total of ten genes including six reported previously: phospholipase C delta 1 (PLCD1), human activin receptor type IIB (hActR-IIB), organic cation transporter-like 1 (OCTL1), organic cation transporter-like 2 (OCTL2), oxidative stress response 1 (OSR1), and human xylulokinase-like protein (XYLB). The remaining four genes present in the telomeric region included two known genes, MyD88 and ACAA, and two novel genes. One (designated ENGL) of the novel sequences was found to encode an amino-acid sequence homologous to the family of DNA/RNA endonucleases, especially endonuclease G. The other gene F56 revealed no significant homology to any known genes. These results disclosed complete physical and transcriptional maps of the 1200-kb region of 3p present in YAC 936c1.

Characterization and developmental regulation of proteoglycan-type protein tyrosine phosphatase zeta/RPTPbeta isoforms

Protein tyrosine phosphatase zeta (PTPzeta/RPTPbeta) is a receptor-like protein tyrosine phosphatase specifically expressed in the brain. Alternative splicing produces three isoforms of this molecule: PTPzeta-A, the full-length form of PTPzeta; PTPzeta-B, the short form of PTPzeta; and PTPzeta-S, an extracellular variant. Here, we identified all these isoforms, including PTPzeta-B, as chondroitin sulfate proteoglycans, and characterized their carbohydrate modification and expression profiles in the rat brain. The level of PTPzeta-A expression was maintained during the prenatal period and decreased rapidly after birth. PTPzeta-S was expressed in a similar manner, although the postnatal decrease was gradual. In contrast, relatively constant amounts of PTPzeta-B were observed from embryonic day 13 (E13) through adulthood. PTPzeta-A and -S were constantly expressed only as proteoglycans during development, but a substantial amount of PTPzeta-B was detected in a non-proteoglycan form at E13-15. Moreover, PTPzeta-B did not contain LeX, HNK-1 carbohydrate, or keratan sulfate, although PTPzeta-A and -S were generally modified with these carbohydrates. L cells transfected with PTPzeta-A and -B cDNAs expressed these proteins as enzymatically active chondroitin sulfate proteoglycans. The PTPzeta-A and -B in L cells showed essentially similar localizations in cell cortical structures on immunofluorescence microscopy, although immature or processed forms of PTPzeta-A were accumulated additively in intracellular patchy structures. These results show that the three isoforms of PTPzeta are differentially regulated during development, and that the extracellular deleted region in PTPzeta-B is important for determination of carbohydrate modification.

Hypoxia stimulates ecNOS mRNA expression by differentiated human trophoblasts

Cytotrophoblasts isolated from normal human placenta cultured under normoxic conditions (20% O2, pO2 = 130 mmHg) for 48-72 h differentiate to a form which expresses high levels of hCG and which morphologically resembles syncytiotrophoblast. We had previously shown that hypoxia (0-1% O2, pO2 = 12-14 mmHg) blocks this differentiation process, although trophoblasts exposed to hypoxia for up to 96 h were completely viable. In this article we showed that trophoblast responds to hypoxia by expressing the hypoxia-sensitive DNA binding protein HIF-1. We also showed that in trophoblast cultured under normoxic conditions, expression of endothelial cell nitric oxide synthase (ecNOS) mRNA increases with time, reaching a maximum in 48-72 h. However, in trophoblast maintained under hypoxic conditions for 48 h (after an initial 24 h in normoxia), expression of ecNOS mRNA is greatly reduced. These observations are consistent with the expression of ecNOS by syncytiotrophoblast but not by cytotrophoblast. In contrast, exposure of differentiated trophoblasts to hypoxia for 24 h (after 48-72 h in normoxia) significantly stimulates expression of ecNoS mRNA over that of cells maintained continuously in normoxia. These results suggest that in differentiated trophoblast hypoxia can stimulate ecNOS expression.

Characterization of rat receptor-like protein tyrosine phosphatase gamma isoforms

We identified four isoforms of receptor-like protein tyrosine phosphatase gamma (RPTPgamma) from rat brain by cDNA cloning. We designated these molecules RPTPgamma-A, -B, -C, and -S. RPTPgamma-A was the longest form and had the same structure as human and mouse RPTPgamma. RPTPgamma-B lacked the intracellular juxtamembrane 29 amino acids of RPTPgamma-A. RPTPgamma-C had a single phosphatase domain. RPTPgamma-S is an extracellular variant of RPTPgamma. mRNAs of the four isoforms were expressed in the brain, kidney, lung, and heart. Transfection of RPTPgamma-A and -S expression plasmids into COS7 cells resulted in the expression of membrane-bound 190-kDa proteins and secreted 120-kDa proteins, respectively. These molecules were similar to PTPzeta/RPTPbeta with regard not only to structure but also to the presence of both secretory and transmembrane forms. However, RPTPgamma isoforms were not expressed as proteoglycans.

6B4 proteoglycan/phosphacan, an extracellular variant of receptor-like protein-tyrosine phosphatase zeta/RPTPbeta, binds pleiotrophin/heparin-binding growth-associated molecule (HB-GAM)

A major chondroitin sulfate proteoglycan in the brain, 6B4 proteoglycan/phosphacan, corresponds to the extracellular region of a receptor-like protein-tyrosine phosphatase, PTPzeta/RPTPbeta. Here, we purified and characterized 6B4 proteoglycan-binding proteins from rat brain. From the CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid) extract of brain microsomal fractions, 18-, 28-, and 40-kDa proteins were specifically isolated using 6B4 proteoglycan-Sepharose. N-terminal amino acid sequencing identified the 18-kDa protein as pleiotrophin/heparin-binding growth-associated molecule (HB-GAM). Scatchard analysis of 6B4 proteoglycan-pleiotrophin binding revealed low (Kd = 3 nM) and high (Kd = 0.25 nM) affinity binding sites. Chondroitinase ABC digestion of the proteoglycan decreased the binding affinities to a single value (Kd = 13 nM) without changing the number of binding sites. This suggested the presence of two subpopulations of the proteoglycan with different chondroitin sulfate structures. Heparin potently inhibited binding of 6B4 proteoglycan to pleiotrophin (IC50 = 3.5 ng/ml). Heparan sulfate and chondroitin sulfate C inhibited moderately (IC50 = 150 and 400 ng/ml, respectively), but, in contrast, chondroitin sulfate A and keratan sulfate were poor inhibitors (IC50 > 100 microg/ml). Immunofluorescence and immunoblotting analyses indicated that both 6B4 proteoglycan and PTPzeta are located on cortical neurons. Anti-6B4 proteoglycan antibody added to the culture medium suppressed pleiotrophin-induced neurite outgrowth of cortical neurons. These results suggested that interaction between 6B4 proteoglycan and pleiotrophin is required for the action of pleiotrophin, and chondroitin sulfate chains on 6B4 proteoglycan play regulatory roles in its binding.

Intravenous immunoglobulin replacement therapy for common variable immunodeficiency during pregnancy

Patients with common variable immunodeficiency (CVID), characterized by impaired antibody production, have a high susceptibility to bacterial infections and need supplements of immunoglobulin G (IgG). We report two pregnancies in a woman with CVID. Differences in the outcome of the two pregnancies suggest the need for adjustment of replacement therapy during pregnancy.

Differences of somatostatin mRNA in the rat suprachiasmatic nucleus under light-dark and constant dark conditions: an analysis by in situ hybridization

Daily profiles of somatostatin mRNA expression were investigated in the rat suprachiasmatic nucleus (SCN) by semiquantitative in situ hybridization histochemistry. Under 12 h light/12 h dark conditions, somatostatin mRNA signals were higher during the day time (Zeitgeber time (ZT) 1) than during the night time (ZT 16). This day-night difference was still maintained in constant darkness where the somatostatin mRNA was higher in the subjective day (circadian time (CT) 1) than in the subjective night (CT 16). Together with previous Northern blot hybridization studies, the present observation suggests that the level of somatostatin mRNA in SCN neurons is controlled by the circadian clock, independent of photic environment.

Circadian change of VIP mRNA in the rat suprachiasmatic nucleus following p-chlorophenylalanine (PCPA) treatment in constant darkness

Neuronal activity of the suprachiasmatic nucleus (SCN) is known to be regulated by two major extrinsic factors conveyed by three anatomically distinct pathways to the SCN: photic stimulus by the direct retinohypothalamic tract (RHT) and the indirect geniculohypothalamic tract (GHT), and information from the brainstem by ascending forebrain serotonergic (5-hydroxytryptamine: 5-HT) tract. It has been shown that VIP mRNA level in neurons of the SCN is altered by external light, but remains stable in constant darkness. In the present study, by using the in situ hybridization technique combined with computer-assisted image analysis, we examined VIP mRNA expression in the SCN of rats in which the two major factors were eliminated, i.e. photic stimulus by exposing animals in total darkness and 5-HT transmission by three-day successive administration of p-chlorophenyl-alanine methylester (an inhibitor of tryptophan hydroxylase, 200 mg/kg, daily). In saline-treated controls, VIP mRNA levels remained almost constant throughout the day. In contrast, in PCPA-treated rats, a significant rhythm of VIP mRNA was observed with a peak at CT 4 and a trough at CT 20. These observations suggest that the removal of photic and 5-HT influence induces VIP mRNA rhythm in the SCN, indicating that VIP mRNA is controlled not only by photic information but also by the circadian clock.

Multiple receptor-like protein tyrosine phosphatases in the form of chondroitin sulfate proteoglycan

The possibility that some of the brain proteoglycans are receptor-like protein tyrosine phosphatases (PTPases) was investigated. Membrane-bound proteoglycan fractions were prepared from the postnuclear membrane fraction of 8-day-old rat brain by DEAE ion-exchange chromatography and CsCl density gradient centrifugation. The isolated proteoglycan fractions showed high PTPase specific activities together with the typical PTPase characteristics. Renaturation experiments indicated that chondroitin sulfate proteoglycans with 380- and 170-kDa core proteins carried the PTPase activity. The proteoglycan with 380-kDa core protein was identified as RPTP beta/zeta bearing HNK-1 carbohydrate.

Emergence of VIP rhythmicity following somatostatin depletion in the rat suprachiasmatic nucleus

Administration of a somatostatin (SS) depletor, cysteamine, markedly reduced SS levels in rat suprachiasmatic nucleus (SCN). At the same time, cysteamine administration induced a circadian rhythm of vasoactive intestinal polypeptide (VIP) content in the SCN, which otherwise remains constant under constant environmental conditions. These results suggest that the stable level of VIP in the SCN under constant conditions is not an intrinsic property of VIP neurons but a consequence of interactions with other components in the SCN.

[Effects of volatile anesthetics on crossbridge mechanism of skeletal muscle--effects on the crossbridge in contraction]

The suppressive effect of enflurane on the maximal activated force in skinned muscle fiber at high Ca2+ concentration was determined in our previous report. This result suggests that the acto-myosin system might be inhibited in the presence of enflurane. Therefore, the present study was performed to identify the sites and to clarify the mechanism of the above mentioned action. For this purpose, the stiffness during Ca2+ contraction was measured using mechanically-skinned frog muscle fiber. The force oscillation was given by high frequently sinusoidal length perturbation. The maximum shortening speed, which is considered to be a parameter of crossbridge kinetics, was also measured using the slack method on frog and rat muscle fibers. The results of this study are summarized as follows: 1. The total force was decreased when enflurane or halothane was present, while the stiffness, which is a parameter of the number of attachments (crossbridges), was decreased only by enflurane. Furthermore, the stiffness over force ratio, which is a parameter of the individual force generated by each crossbridge, was increased when enflurane or halothane was present. These results initially seem contradictory. However, the contradiction seems far smaller in light of our assumption that the amplitude of reduction of the force generated by each crossbridge was much higher in the presence of halothane than in the presence of enflurane. 2. The maximum shortening speed was also decreased when enflurane or halothane was present. Therefore, it was suggested that enflurane and halothane have a potentiality to decrease the rate of crossbridge cycling.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of enflurane on the elastic properties of frog skinned skeletal muscle fiber under relaxed and rigor conditions]

We studied the effects of enflurane on the elastic property of the mechanical skinned fiber prepared from M. Semitendinosus of bullfrog. Longitudinal and lateral elastic properties of the skinned fibers were measured under relaxed and rigor conditions to clarify the effects of enflurane on actomyosin complex. Under the rigor condition, enflurane did not change the lateral elasticity of the fibers, but enflurane decreased the longitudinal elasticity. On the other hand, under the relaxed condition, enflurane did not change the elasticity. The results suggest that enflurane probably decreases the force of binding of cross-bridges to actin, which is one of the factors to reduce the maximal force.

[Clinical study on serum immunosuppressive factors in gastric cancer patients--with special reference to preoperative ferritin levels and influence of surgical stress]

Serum ferritin values were measured preoperatively in 83 patients with gastric cancer and were found to be significantly higher than in normal subjects and mammary cancer patients. They were also significantly higher in healthy men than in women and in gastric cancer patients at stages I and IV than in those at stage III. There was no significant correlation between the serum ferritin value and various immunologic parameters. OK-432 serially administered pre- and postoperatively (A) and only postoperatively (B). The ferritin value increased markedly at one week postoperatively, reaching a peak at two weeks; at four weeks, it was reduced toward the value at one week. However, these changes in ferritin value showed no significant difference between groups A and B.

[Experimental study on quantitative evaluation of fatty liver by computed tomography]

Biochemical, histological and CT examinations of the liver were performed in 32 rabbits on significance of measuring CT values in the diagnosis of fatty liver. In 2 groups of rabbits, in which 2g/kg/day and 4g/kg/day of fat emulsion were administered intravenously for 4 weeks respectively, post-treatment reduction in CT value of light degree was observed. In a group, in which 8g/kg/day were given, there was a sufficient reduction in CT value for giving diagnosis of fatty liver of moderate degree. Significant correlation was found between changes in CT value of the liver on the one hand and contents of triglyceride, total cholesterol and cholesterol ester in the liver on the other hand, while there was, no significant correlation between changes in CT value and contents of phospholipid, protein and water. Significant correlation was found between changes in CT value of the liver and degrees of histological fat accumulation in the liver cells. It has been evidenced experimentally that prolonged administration of fat emulsion may cause fatty liver, and that measurement of CT values of the liver is a non-aggressive method of diagnosing fatty liver.

[Seven-year follow-up studies on asymptomatic HBs Ag carriers]

This report covers 7-year follow-up studies on 35 HBs Ag carriers whose anti-HBc titer levels were 10 (log 2) or more and who had normal liver functions at the start of the studies, when 9 of them (25.7%) were HBe Ag positive, 24 (68.6%) anti-HBe positive and 2 (5.7%) negative to both. 1. There was no significant difference in the incidence of abnormal SGPT levels as a whole between HBe Ag positives and anti-HBe positives. But abnormally high SGPT levels of 100 KU or more were observed at a higher percentage among HBe Ag positives (4/9. 44.4%) than among anti-HBe positives (1/24. 4.2%. p less than 0.02). 2. Based on the results of the 7-year studies, all cases were classified into six clinical stages. HBe Ag positives were divided into three groups by the stage with different SGPT levels: 5 cases (15.2%) whose SGPT leves never rose above 50 KU were classified as Stage 1; 3 cases with chronic active hepatitis (9.6%) whose highest SGPT levels were over 200 KU (2 new cases and 1 case with a relapse of chronic inactive hepatitis) as Stage 2 and 1 case (3.0%) seroconverted to anti-HBe positive following an acute relapse of chronic inactive hepatitis as Stage 3. Anti-HBe positives were divided into another three groups similarly according to their mean HBs Ag titer levels: 6 cases (18.2%) whose mean HBs Ag titer levels ranged from 10 to 13 (log 2) were classified as Stage 4; 13 cases (39.4%) whose mean HBs Ag titer levels ranged from 6 to 9 as Stage 5 and 5 cases (15.2%), including 2 cases turned negative to HBs Ag, whose mean HBs Ag titer levels were below 5 as Stage 6. The average age of each group increased wth its clinical stage, namely, 32.6 in Stage 1, 34.3 in Stage 2, 33.0 in Stage 3, 34.5 in Stage 4 and 37.0 in Stage 5, but the average age in Stage 6 was 29.0. 3. All HBe Ag positives showed fluctuations in HBs Ag titer levels. The fluctuations were particularly noteworthy among cases with chronic active hepatitis in Stage 2 during an acute relapse. The HBs Ag titers rose just before the acute relapses in a case of chronic active hepatitis when SGPT levels went over 200 KU. This suggested a proliferation of the virus. On the other hand, in anti-HBe positives, a decrement of the virus was suggested by the fact that an increasing proportion of cases showed their HBs Ag titer levels to fluctuate or to become lower with the progress of stages (p less than 0.05) and two cases turned negative to HBs Ag as plotted in Stage 6. And the proportion of cases with abnormal SGPT levels decreased with the progress of stages (p less than 0.05). One case whose SGPT level was 125 KU, highest among anti-HBe positives, followed the clinical course of chronic inactive hepatitis and lowered in HBs Ag titer. 4. Between HBe Ag and anti-HBe cases, there were considerable differences in the occurrence of liver disturbances and their clinical courses...