ICK1, a cyclin-dependent protein kinase inhibitor from Arabidopsis thaliana interacts with both Cdc2a and CycD3, and its expression is induced by abscisic acid

Cyclin-dependent kinase (CDK) inhibitor genes encode low molecular weight proteins which have important functions in cell cycle regulation, development and perhaps also in tumorigenesis. The first plant CDK inhibitor gene ICK1 was recently identified from Arabidopsis thaliana. Although the C-terminal domain of ICK1 contained an important consensus sequence with the mammalian CDK inhibitor p27Kip1, the remainder of the deduced ICK1 sequence showed little similarity to any known CDK inhibitors. In vitro assays showed that recombinant ICK1 exhibited unique kinase inhibitory properties. In the present study we characterized ICK1 in terms of its gene structure, its interaction with both A. thaliana Cdc2a and CycD3, and its induction by the plant growth regulator, abscisic acid (ABA). ICK1 was expressed at a relatively low level in the tissues surveyed. However, ICK1 was induced by ABA, and along with ICK1 induction there was a decrease in Cdc2-like histone H1 kinase activity. These results suggest a molecular mechanism by which plant cell division might be inhibited by ABA. ICK1 clones were also identified from independent yeast two-hybrid screens using the CycD3 construct. The implication that ICK1 protein could interact with both Cdc2a and CycD3 was confirmed by in vitro binding assays. Furthermore, deletion analysis indicated that different regions of ICK1 are required for the interactions with Cdc2a and CycD3. These results provide a mechanistic basis for understanding the role of CDK inhibitors in cell cycle regulation in plant cells.

Predictive value of serum parathyroid hormone levels for bone turnover in patients on chronic maintenance dialysis

With the increasing occurrence of adynamic bone disease, it is essential to determine the level of bone turnover in chronically dialyzed patients before instituting vitamin D therapy. To assess the value of serum parathyroid hormone (PTH) levels for prediction of bone turnover, we determined sensitivity, specificity, and predictive value positive of serum PTH, alone or in combination with other variables, in 79 patients who underwent one or two bone biopsies. Serum PTH levels were determined by a radioimmunometric assay and were obtained at the time of bone biopsies. Patients were classified into (1) low or normal and (2) high bone turnover according to the value of activation frequency of bone. There were 57 biopsy specimens taken from hemodialysis patients and 39 specimens from continuous ambulatory peritoneal dialysis patients (CAPD). All patients with serum PTH levels within or below the normal range had low or normal bone turnover. Values of serum PTH above 450 pg/mL were 100% and 95.5% specific for high bone turnover in hemodialysis and CAPD patients, respectively. Values of serum PTH between 65 and 450 pg/mL had worse predictive value positive in CAPD patients (48.6% to 78.6%) than in hemodialysis patients (67.3% to 87.1%). When other characteristics of the patients were taken into consideration, only age in hemodialysis patients and serum ionized calcium in CAPD patients improved the predictive value of serum PTH. All hemodialysis patients younger than 45 years of age with serum PTH levels above 65 pg/mL (n = 15) had high bone turnover, and CAPD patients with low or normal bone turnover had higher serum ionized calcium. However, overall, bone turnover could not be predicted by serum PTH measurements in 30% of hemodialysis and 51.3% of CAPD patients. The data suggest that for patients with serum PTH levels between 65 and 450 pg/mL, bone biopsies are indicated to precisely assess bone turnover prior to initiation of vitamin D therapy.

Autoantibodies and neuropsychiatric events at the time of systemic lupus erythematosus diagnosis: results from an international inception cohort study

OBJECTIVE

To examine, in an inception cohort of systemic lupus erythematosus (SLE) patients, the association between neuropsychiatric (NP) events and anti-ribosomal P (anti-P), antiphospholipid (lupus anticoagulant [LAC], anticardiolipin), anti-beta2-glycoprotein I, and anti-NR2 glutamate receptor antibodies.

METHODS

NP events were identified using the American College of Rheumatology case definitions and clustered into central/peripheral and diffuse/focal events. Attribution of NP events to SLE was determined using decision rules of differing stringency. Autoantibodies were measured without knowledge of NP events or their attribution.

RESULTS

Four hundred twelve patients were studied (87.4% female; mean +/- SD age 34.9 +/- 13.5 years, mean +/- SD disease duration 5.0 +/- 4.2 months). There were 214 NP events in 133 patients (32.3%). The proportion of NP events attributed to SLE varied from 15% to 36%. There was no association between autoantibodies and NP events overall. However, the frequency of anti-P antibodies in patients with central NP events attributed to SLE was 4 of 20 (20%), versus 3 of 107 (2.8%) in patients with other NP events and 24 of 279 (8.6%) in those with no NP events (P = 0.04). Among patients with diffuse NP events, 3 of 11 had anti-P antibodies (27%), compared with 4 of 111 patients with other NP events (3.6%) and 24 of 279 of those with no NP events (8.6%) (P = 0.02). Specific clinical-serologic associations were found between anti-P and psychosis attributed to SLE (P = 0.02) and between LAC and cerebrovascular disease attributed to SLE (P = 0.038). There was no significant association between other autoantibodies and NP events.

CONCLUSION

Clinically distinct NP events attributed to SLE and occurring around the time of diagnosis were found to be associated with anti-P antibodies and LAC. This suggests that there are different autoimmune pathogenetic mechanisms, although low sensitivity limits the clinical application of testing for these antibodies.

Prognostic nutritional index predicts survival and correlates with systemic inflammatory response in advanced pancreatic cancer

BACKGROUND

Recent studies have implied a prognostic value of the prognostic nutritional index (PNI) in certain types of human cancers. However, the value of PNI for predicting survival in patients with pancreatic cancer remains unknown. The goal of this study was to investigate the predictive significance of PNI in patients with advanced pancreatic cancer.

METHODS

A total of 321 consecutive patients with pathologically-confirmed locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC) were retrospectively recruited between January 2011 and August 2013. The patients were divided into a test set (n = 110) and a validation set (n = 211). We evaluated the association between PNI and overall survival (OS). The relationship between PNI and systemic inflammatory response markers, including the neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and lymphocyte/monocyte ratio (LMR) was also assessed. In addition, the associations between PNI and the TNF-α were analyzed.

RESULTS

Kaplan-Meier analyses showed that a low PNI correlated significantly with a shorter OS in patients with advanced pancreatic cancer (190 days for patients with a low PNI vs. 290 days for patients with a high PNI, log-rank = 12.566, P < 0.001). Multivariate analysis identified PNI as an independent prognostic factor for OS (hazard ratio [HR]: 0.627, 95% confidence interval [CI]: 0.453-0.868, P = 0.003). PNI also correlated positively with NLR and PLR and negatively with LMR. Additionally, patients with a low PNI exhibited high levels of TNF-α.

CONCLUSIONS

Our results confirm that PNI is associated with the systemic inflammatory response and can be used to predict survival in advanced pancreatic cancer.

Synthesis of poly(3-hydroxyalkanoates) in Escherichia coli expressing the PHA synthase gene phaC2 from Pseudomonas aeruginosa: comparison of PhaC1 and PhaC2

In order to obtain functional expression of PHA synthase gene phaC2 from Pseudomonas aeruginosa in Escherichia coli, the coding region of phaC2 was subcloned, including the ribosomal binding site, into pBluescript SK- collinear to the lac promoter. This plasmid pBHR71-C2 enabled functional expression of phaC2 in E. coli LS1298 (fadB) under lac promoter control, leading to PHA accumulation, when grown in LB medium containing 0.5% (w/v) of various fatty acids (C8-C14). The strongest accumulation of PHA was observed, when dodecanoate was provided as carbon source, and PHA contributed to 15% of cell dry weight, which was composed of 35 mol% 3-hydroxydodecanoate, 60 mol% 3-hydroxydecanoate and 5 mol% 3-hydroxyoctanoate. Plasmid pBHR78, which contained both genes phaC1 and phaC2 from P. aeruginosa under lac promoter control in pBluescript SK- led in E. coli LS1298 to PHA accumulation, which contributed to 13% of cell dry weight, when cells were grown on decanoate. Only slight differences in PHA composition compared with either PhaC1 or PhaC2 were obtained. The weight average molecular masses of PHA purified from decanoate-grown cells of E. coli LS1298 expressing PhaC1 or PhaC2 alone or both PHA synthases, were 106 x 10(3), 70 x 10(3) or 67 x 10(3), respectively. This study clearly demonstrated that both PHA synthases from P. aeruginosa exhibit very similar properties resulting in similar extent of PHA accumulation, similar composition and molecular mass, when expressed in E. coli and that fatty acid beta-oxidation provides substrates for both PHA synthases.

Clinical implications of systemic inflammatory response markers as independent prognostic factors for advanced pancreatic cancer

BACKGROUND

Cancer-associated inflammation is a key molecular feature of pancreatic ductal adenocarcinoma. In this study, we systematically evaluated the prognostic relevance of systemic inflammatory response (SIR) markers in patients with advanced pancreatic cancer.

METHODS

A total of 321 consecutive patients with pathologically-confirmed locally advanced or metastatic pancreatic adenocarcinoma were retrospectively recruited. The patients were divided into a test set (n = 110) and a validation set (n = 211). The associations between overall survival (OS) and clinically available SIR markers including white blood cell (WBC) count, absolute neutrophil count, absolute lymphocyte count, absolute monocyte count, platelet count, neutrophil-lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR) and lymphocyte/monocyte ratio (LMR) were analyzed using Kaplan-Meier curves and multivariate Cox proportional models.

RESULTS

High WBC count, neutrophil count, monocyte count, NLR, PLR and low LMR were significantly associated with decreased OS in the test set. Using the validation set for confirmation, we found also in multivariate analysis an independent value of WBC count (hazard ratio (HR): 2.176, 95% confidence interval (CI): 1.560-3.035, P < 0.001), neutrophil count (HR: 2.807, 95% CI: 2.000-3.940, P < 0.001), monocyte count (HR: 1.848, 95% CI: 1.315-2.598, P < 0.001), NLR (HR: 2.204, 95% CI: 1.590-3.055, P < 0.001), PLR (HR: 1.537, 95% CI: 1.114-2.122, P = 0.009) and LMR (HR: 0.569, 95% CI: 0.412-0.784, P = 0.001) for OS in patients with advanced pancreatic cancer.

CONCLUSIONS

Our study confirmed that SIR markers can be used to determine optimal therapeutic strategies for individual patients and to predict pancreatic cancer prognosis.

Intermittent and continuous administration of the bisphosphonate ibandronate in ovariohysterectomized beagle dogs: effects on bone morphometry and mineral properties

Bisphosphonates have emerged as a valuable treatment for postmenopausal osteoporosis. Bisphosphonate treatment is usually accompanied by a 3-6% gain in bone mineral density (BMD) during the first year of treatment and by a decrease in bone turnover. Despite low bone turnover, BMD continues to increase slowly beyond the first year of treatment. There is evidence that bisphosphonates not only increase bone volume but also enhance secondary mineralization. The present study was conducted to address this issue and to compare the effects of continuous and intermittent bisphosphonate therapy on static and dynamic parameters of bone structure, formation, and resorption and on mineral properties of bone. Sixty dogs were ovariohysterectomized (OHX) and 10 animals were sham-operated (Sham). Four months after surgery, OHX dogs were divided in six groups (n = 10 each). They received for 1 year ibandronate daily (5 out of 7 days) at a dose of 0, 0.8, 1.2, 4.1, and 14 microg/kg/day or intermittently (65 microg/kg/day, 2 weeks on, 11 weeks off). Sham dogs received vehicle daily. At month 4, there was a significant decrease in bone volume in OHX animals (p < 0.05). Doses of ibandronate >/= 4.1 microg/kg/day stopped or completely reversed bone loss. Bone turnover (activation frequency) was significantly depressed in OHX dogs given ibandronate at the dose of 14 microg/kg/day. This was accompanied by significantly higher crystal size, a higher mineral-to-matrix ratio, and a more uniformly mineralized bone matrix than in control dogs. This finding lends support to the hypothesis that an increase in secondary mineralization plays a role in gain in BMD associated with bisphosphonate treatment. Moreover, intermittent and continuous therapies had a similar effect on bone volume. However, intermittent therapy was more sparing on bone turnover and bone mineral properties. Intermittent therapy could therefore represent an attractive alternative approach to continuous therapy.

Polyhydroxybutyrate biosynthesis in Caulobacter crescentus: molecular characterization of the polyhydroxybutyrate synthase

Caulobacter crescentus was investigated with respect to polyhydroxybutyrate (PHB) biosynthesis. Polyhydroxyalkanoate (PHA) accumulation contributing to approximately 18% of the cell dry weight was obtained in the presence of glucose. Gas chromatography-mass spectrometry and gel permeation chromatography of the purified PHA showed that this polyester was solely composed of 3-hydroxybutyrate and had a weight average molar mass of 5.5 x 10(5) g mol(-1) and a polydispersity of 1.6. An ORF encoding a conserved, hypothetical protein which shared approximately 47% identity with the PHB synthase from Azorhizobium caulinodans was identified within the complete C. crescentus genomic sequence. This putative C. crescentus PHB synthase gene, phaC, consisted of a 2019 nt stretch of DNA (encoding 673 aa residues), which encoded a PHB synthase with a molecular mass of approximately 73 kDa. This is currently the largest PHA synthase identified. The phaC coding region was subcloned into vector pBBR1-JO2 under lac promoter control. The resulting plasmid, pQQ4, mediated PHB accumulation in the mutant Ralstonia eutropha PHB(-)4 and recombinant Escherichia coli JM109(pBHR69), which produced the beta-ketothiolase and acetoacetyl-CoA reductase from R. eutropha, contributing to approximately 62% and 6% of cell dry weight, respectively. Functional expression of the coding region of phaC was confirmed by immunoblotting and in vitro PHB synthase activity.

In vitro synthesis of poly(3-hydroxydecanoate): purification and enzymatic characterization of type II polyhydroxyalkanoate synthases PhaC1 and PhaC2 from Pseudomonas aeruginosa

For the first time, the purification has been achieved of the type II polyhydroxyalkanoate (PHA) synthases PhaC1 and PhaC2 from Pseudomonas aeruginosa applying N-terminal His6-tag fusions and metal chelate affinity chromatography. In vivo His6-tagged PHA synthase activity was confirmed by functional expression of the corresponding genes in Escherichia coli, and PHA synthase activity could also be measured in vitro with the enzymes. The specific enzyme activity of PHA synthases PhaC1 and PhaC2 was 0.039 U mg(-1) and 0.035 U mg(-1) protein, respectively. Kinetic studies showed a lag phase for both PHA synthases using (R,S)-3-hydroxydecanoyl-CoA as substrate. Specific enzyme activity was increased to 0.055 U mg(-1) when the phasin GA24 from Ralstonia eutropha was added to the assay. CoA inhibited PHA synthase activity, and a Ki of 85 microM was determined. A two-enzyme system was established, employing commercially available acyl-CoA synthetase and PHA synthase, which allowed the in vitro de novo PHA granule formation and the in vitro synthesis of poly(3-hydroxydecanoate) exhibiting a weight average molar mass of 9.8 x 10(4) g mol(-1), and which occurred independently of pre-existing PHA granules.

(+)-Abscisic acid metabolism, 3-ketoacyl-coenzyme A synthase gene expression, and very-long-chain monounsaturated fatty acid biosynthesis in brassica napus embryos

Microspore-derived embryos of Brassica napus cv Reston were used to examine the effects of exogenous (+)-abscisic acid (ABA) and related compounds on the accumulation of very-long-chain monounsaturated fatty acids (VLCMFAs), VLCMFA elongase complex activity, and induction of the 3-ketoacyl-coenzyme A synthase (KCS) gene encoding the condensing enzyme of the VLCMFA elongation system. Of the concentrations tested, (+)-ABA at 10 &mgr;M showed the strongest effect. Maximum activity of the elongase complex, observed 6 h after 10 &mgr;M (+)-ABA treatment, was 60% higher than that of the untreated embryos at 24 h. The transcript of the KCS gene was induced by 10 &mgr;M (+)-ABA within 1 h and further increased up to 6 h. The VLCMFAs eicosenoic acid (20:1) and erucoic acid (22:1) increased by 1.5- to 2-fold in embryos treated with (+)-ABA for 72 h. Also, (+)-8'-methylene ABA, which is metabolized more slowly than ABA, had a stronger ABA-like effect on the KCS gene transcription, elongase complex activity (28% higher), and level of VLCMFAs (25-30% higher) than ABA. After 24 h approximately 60% of the added (+)-[3H]ABA (10 &mgr;M) was metabolized, yielding labeled phaseic and dihydrophaseic acid. This study demonstrates that (+)-ABA promotes VLCMFA biosynthesis via increased expression of the KCS gene and that reducing ABA catabolism would increase VLCMFAs in microspore-derived embryos.

Molecular cloning, genomic organization, and biochemical characterization of myristoyl-CoA:protein N-myristoyltransferase from Arabidopsis thaliana

Myristoyl-CoA:protein N-myristoyltransferase (NMT, EC 2.3.1.97) catalyzes the co-translational addition of myristic acid to the amino-terminal glycine residue of a number of important proteins of diverse functions. We have isolated a full-length Arabidopsis thaliana cDNA encoding NMT (AtNMT1), the first described from a higher plant. This AtNMT1 cDNA clone has an open reading frame of 434 amino acids and a predicted molecular mass of 48,706 Da. The primary structure is 50% identical to the mammalian NMTs. Analyses of Southern blots, genomic clones, and database sequences suggested that the A. thaliana genome contains two copies of NMT gene, which are present on different chromosomes and have distinct genomic organizations. The recombinant AtNMT1 expressed in Escherichia coli exhibited a high catalytic efficiency for the peptides derived from putative plant myristoylated proteins AtCDPK6 and Fen kinase. The AtNMT was similar to the mammalian NMTs with respect to a relative specificity for myristoyl CoA among the acyl CoA donors and also inhibition by the bovine brain NMT inhibitor NIP(71). The AtNMT1 expression profile indicated ubiquity in roots, stem, leaves, flowers, and siliques (approximately 1.7 kb transcript and approximately 50 kDa immunoreactive polypeptide) but a greater level in the younger tissue, which are developmentally very active. NMT activity was also evident in all these tissues. Subcellular distribution studies indicated that, in leaf extracts, approximately 60% of AtNMT activity was associated with the ribosomal fractions, whereas approximately 30% of the activity was observed in the cytosolic fractions. The NMT is biologically important to plants, as noted from the stunted development when the AtNMT1 was down-regulated in transgenic Arabidopsis under the control of an enhanced CaMV 35S promoter. The results presented in this study provide the first direct molecular evidence for plant protein N-myristoylation and a mechanistic basis for understanding the role of this protein modification in plants.

Association of GCKR rs780094, alone or in combination with GCK rs1799884, with type 2 diabetes and related traits in a Han Chinese population

AIMS/HYPOTHESIS

The GCKR rs780094 and GCK rs1799884 polymorphisms have been reported to be associated with dyslipidaemia and type 2 diabetes in white Europeans. The aim of this study was to replicate these associations in Han Chinese individuals and to identify the potential mechanisms underlying these associations.

METHODS

The single nucleotide polymorphisms rs780094 and rs1799884 were genotyped in a population-based sample of Han Chinese individuals (n = 3,210) and tested for association with risk of type 2 diabetes and related phenotypes.

RESULTS

The GCKR rs780094 A allele was marginally associated with reduced risk of type 2 diabetes (OR 0.85, 95% CI 0.73-1.00, p value under an additive model [p((add))] = 0.05) and significantly associated with reduced risk of impaired fasting glucose (IFG) or type 2 diabetes (OR 0.86, 95% CI 0.77-0.96, p([add]) = 0.0032). It was also significantly associated with decreased fasting glucose and increased HOMA of beta cell function (HOMA-B) and fasting triacylglycerol levels (p([add]) = 0.0169-5.3 x 10(-6)), but not with HOMA of insulin sensitivity (HOMA-S). The associations with type 2 diabetes and IFG remained significant after adjustment for BMI, while adjustment for HOMA-B abolished the associations. The GCKR rs780094 was also associated with obesity and BMI, independently of its association with type 2 diabetes. The GCK rs1799884 A allele was significantly associated with decreased HOMA-B (p([add]) = 0.0005), but not with type 2 diabetes or IFG. Individuals with increasing numbers of risk alleles for both variants had significantly lower HOMA-B (p([add]) = 5.8 x 10(-5)) in the combined analysis.

CONCLUSIONS/INTERPRETATION

Consistent with observations in white Europeans, the GCKR rs780094 polymorphism contributes to the risk of type 2 diabetes and dyslipidaemia in Han Chinese individuals. In addition, we showed that the effect on type 2 diabetes is probably mediated through impaired beta cell function rather than through obesity.

22-oxacalcitriol suppresses secondary hyperparathyroidism without inducing low bone turnover in dogs with renal failure

BACKGROUND

Calcitriol therapy suppresses serum levels of parathyroid hormone (PTH) in patients with renal failure but has several drawbacks, including hypercalcemia and/or marked suppression of bone turnover, which may lead to adynamic bone disease. A new vitamin D analogue, 22-oxacalcitriol (OCT), has been shown to have promising characteristics. This study was undertaken to determine the effects of OCT on serum PTH levels and bone turnover in states of normal or impaired renal function.

METHODS

Sixty dogs were either nephrectomized (Nx, N = 38) or sham-operated (Sham, N = 22). The animals received supplemental phosphate to enhance PTH secretion. Fourteen weeks after the start of phosphate supplementation, half of the Nx and Sham dogs received doses of OCT (three times per week); the other half were given vehicle for 60 weeks. Thereafter, the treatment modalities for a subset of animals were crossed over for an additional eight months. Biochemical and hormonal indices of calcium and bone metabolism were measured throughout the study, and bone biopsies were done at baseline, 60 weeks after OCT or vehicle treatment, and at the end of the crossover period.

RESULTS

In Nx dogs, OCT significantly decreased serum PTH levels soon after the induction of renal insufficiency. In long-standing secondary hyperparathyroidism, OCT (0.03 microg/kg) stabilized serum PTH levels during the first months. Serum PTH levels rose thereafter, but the rise was less pronounced compared with baseline than the rise seen in Nx control. These effects were accompanied by episodes of hypercalcemia and hyperphosphatemia. In animals with normal renal function, OCT induced a transient decrease in serum PTH levels at a dose of 0.1 microg/kg, which was not sustained with lowering of the doses. In Nx dogs, OCT reversed abnormal bone formation, such as woven osteoid and fibrosis, but did not significantly alter the level of bone turnover. In addition, OCT improved mineralization lag time, (that is, the rate at which osteoid mineralizes) in both Nx and Sham dogs.

CONCLUSIONS

These results indicate that even though OCT does not completely prevent the occurrence of hypercalcemia in experimental dogs with renal insufficiency, it may be of use in the management of secondary hyperparathyroidism because it does not induce low bone turnover and, therefore, does not increase the risk of adynamic bone disease.

Parathyroid hormone/parathyroid hormone-related peptide type 1 receptor in human bone

The parathyroid hormone/parathyroid hormone-related peptide (PTH/PTHrP) receptor (denoted as PTH-1R) is a key signaling factor through which calcium-regulating hormones PTH and PTHrP exert their effects on bone. There are contradictory reports regarding the capability of osteoclasts to express PTH-1R. To address this issue in humans, bone biopsy specimen samples from 9 normal controls and 16 patients with moderate to severe secondary renal hyperparathyroid bone disease (2 degrees HPT) with elevated PTH levels were studied to determine whether osteoclasts in the bone microenvironment express PTH-1R messenger RNA (mRNA) and protein. We report that osteoclasts express the PTH-1R mRNA but the protein is detected only in patients with 2 degrees HPT. The PTH-1R mRNA and protein also were found in osteoblasts, osteocytes, and bone marrow cells. Receptor expression was higher in osteoclasts and osteoblasts of patients with 2 degrees HPT than normal controls (98.0 +/- 1.1% vs. 65.7 +/- 14.3% and 65.8 +/- 3.4% vs. 39.1 +/- 6.2%; p < 0.01, respectively). Approximately half of osteoclasts found in bone of patients with 2 degrees HPT have the PTH-1R protein. In patients with 2 degrees HPT, a positive relationship exists between erosion depth, a parameter of osteoclastic activity, and the percentage of osteoclasts with PTH-1R protein (r = 0.58; p < 0.05). In normal controls, an inverse relationship exists between the percentage of osteoblasts with receptor mRNA, mRNA signals/cell, and serum PTH levels (r = -0.82 and p < 0.05 and r = -0.78 and p < 0.01, respectively). The results provide the novel evidence of PTH-1R in human osteoclasts and suggest a functional role for the receptors in 2 degrees HPT.

Effects of antisense repression of an Arabidopsis thaliana pyruvate dehydrogenase kinase cDNA on plant development

Pyruvate dehydrogenase kinase (PDHK), a negative regulator of the mitochondrial pyruvate dehydrogenase (PDH) complex (mtPDC), plays a pivotal role in controlling mtPDC activity, and hence, the TCA cycle and cell respiration. This report describes the cloning of a pyruvate dehydrogenase kinase cDNA (AtPDHK) from Arabidopsis thaliana and focuses on the effects of antisense down-regulation of its expression on plant growth and development. The deduced amino acid sequence of AtPDHK exhibits extensive similarity to other plant and mammalian PDHKs, containing conserved domains typical of two-component histidine protein kinases. The Escherichia coli expressed AtPDHK specifically phosphorylated mammalian PDH E1 in a time-dependent manner. Antisense expression of the AtPDHK cDNA led to marked elevation of mtPDC activity in transgenic plants with increases ranging from 137% to 330% compared to control plants. Immunoblot analyses performed with a monoclonal antibody to the E1alpha mtPDH component (the subunit phosphorylated by PDHK) indicated that the increased mtPDC activity was not the result of an increase in the level of PDH protein. MtPDC from transgenic plants showed a reduced sensitivity to ATP-dependent inactivation compared to that observed in wild-type plants. Collectively, these data suggest that the antisense partial silencing of the negative regulator, PDHK, was responsible for the increased mtPDC activity observed in the antisense PDHK plants. Transgenic plants with partially repressed AtPDHK also displayed altered vegetative growth with reduced accumulation of vegetative tissues, early flower development and shorter generation time. The potential role for AtPDHK gene manipulation in crop improvement is discussed.

Non-invasive prenatal testing for fetal aneuploidies in the first trimester of pregnancy

OBJECTIVES

To evaluate the feasibility of non-invasive prenatal testing (NIPT) of maternal plasma samples collected from pregnant Chinese women in early gestation, between 8 + 0 and 12 + 6 weeks' gestation.

METHODS

In this pilot study, 212 women with high-risk pregnancies were recruited at a single Chinese Hospital. Fetal aneuploidies associated with chromosomes 21, 18, 13, X and Y were detected by massively parallel sequencing of maternal plasma DNA samples. Invasive prenatal diagnosis by either chorionic villus sampling or amniocentesis and then karyotyping was offered to all women to confirm both positive and negative NIPT results. Fetal DNA fraction was also determined in male pregnancies, by the relative percentage of Y-chromosome sequences. All confirmed NIPT-negative pregnancies were followed up to birth and neonates were clinically evaluated for any symptoms of chromosomal disease.

RESULTS

Autosomal aneuploidies trisomy 21 (n = 2), 18 (n = 1) and 13 (n = 1) were detected by NIPT and confirmed by amniocentesis and karyotyping. There were one false-positive 45,X sample and two false-negative samples associated with fetal karyotypes 47,XXY and 45,X[16]/47,XXX[14]. In the 100 male pregnancies, the median fetal DNA fraction was 8.54% and there was a trend towards an increasing fetal fraction from 8 + 0 to 12 + 6 weeks' gestation. The majority (95%) of pregnancies had a fetal DNA fraction > 4%, which is generally the limit for accurate aneuploidy detection by NIPT. Across this early gestational time period, there was a weak inverse relationship (R(2)  = 0.186) between fetal DNA fraction and maternal weight.

CONCLUSIONS

NIPT is highly reliable and accurate when applied to maternal DNA samples collected from pregnant women in the first trimester between 8 + 0 and 12 + 6 weeks.

Matrix-assisted in vitro refolding of Pseudomonas aeruginosa class II polyhydroxyalkanoate synthase from inclusion bodies produced in recombinant Escherichia coli

In order to facilitate the large-scale preparation of active class II polyhydroxyalkanoate (PHA) synthase, we constructed a vector pT7-7 derivative that contains a modified phaC1 gene encoding a PHA synthase from Pseudomonas aeruginosa possessing six N-terminally fused histidine residues. Overexpression of this phaC1 gene under control of the strong Ø10 promoter was achieved in Escherichia coli BL21(DE3). The fusion protein was deposited as inactive inclusion bodies in recombinant E. coli, and contributed approx. 30% of total protein. The inclusion bodies were purified by selective solubilization, resulting in approx. 70-80% pure PHA synthase, then dissolved and denatured by 6 M guanidine hydrochloride. The denatured PHA synthase was reversibly immobilized on a Ni(2+)-nitrilotriacetate-agarose matrix. The matrix-bound fusion protein was refolded by gradual removal of the chaotropic reagent. This procedure avoided the aggregation of folding intermediates which often decreases the efficiency of refolding experiments. Finally, the refolded fusion protein was eluted with imidazole. The purified and refolded PHA synthase protein showed a specific enzyme activity of 10.8 m-units/mg employing (R/S)-3-hydroxydecanoyl-CoA as substrate, which corresponds to 27% of the maximum specific activity of the native enzyme. The refolding of the enzyme was confirmed by CD spectroscopy. Deconvolution of the spectrum resulted in the following secondary structure prediction: 10% alpha-helix, 50% beta-sheet and 40% random coil. Gel filtration chromatography indicated an apparent molecular mass of 69 kDa for the refolded PHA synthase. However, light-scattering analysis of a 10-fold concentrated sample indicated a molecular mass of 128 kDa. These data suggest that the class II PHA synthase is present in an equilibrium of monomer and dimer.

Long-term expression of the 35,000 mol. wt fos-related antigen in rat brain after kainic acid treatment

Systemic injection of kainic acid, a rigid analogue of glutamate, induces both the short-term and the long-term expression of activator protein-1 transcription factors. The short-term responses of activator protein-1 factors such as c-fos and fos-related antigens have been well studied. However, the long-term expression of activator protein-1 factor(s) induced by kainic acid is poorly understood. The present study was designed to document the long-term expression (up to seven months) of the fos-related antigens and to map their distributions in the rat brain after systemic treatment with kainic acid. A single dose of kainic acid (8 mg/kg) was injected i.p. into Fischer 344 rats and their epileptic seizure behaviour was monitored. The rats with full limbic seizures were chosen for long-term study. By using immunocytochemistry with an antibody that cross-reacts with all known fos-related antigens, western blot analysis and a gel mobility-shift assay, we have now shown that a 35,000 mol. wt fos-related antigen was induced by kainic acid treatment and expressed at high levels for up to five months. This fos-related antigen still maintains the activator protein-1 DNA binding activity in the rat brain seven months after kainic acid treatment. The fos-related antigens and activator protein-1 binding activity were continuously expressed at high levels throughout the experimental period in the dentate granule cells where mossy fibre collateral sprouting occurred after kainic acid treatment. Our results suggested that long-term expression of fos-related antigen may reflect the pathophysiological changes after kainic acid administration.

Combined effects of 17 common genetic variants on type 2 diabetes risk in a Han Chinese population

AIMS/HYPOTHESIS

The recent advent of genome-wide association studies has considerably accelerated the identification of type 2 diabetes loci. We aimed to investigate the combined effects of multiple genetic variants, alone or in combination with conventional risk factors, on type 2 diabetes and diabetes-related traits in Han Chinese.

METHODS

We genotyped 17 variants in 17 loci in a population-based Han Chinese cohort including 3,210 unrelated individuals. A genetic risk score (GRS) was calculated on the basis of these variants. The discriminatory ability was assessed by the area under the receiver operating characteristics curve.

RESULTS

The odds ratio for type 2 diabetes and hyperglycaemia with each GRS point (per risk allele) was 1.18 (95% CI 1.12-1.23, p = 1.3 x 10(-12)) and 1.12 (95% CI 1.09-1.16, p = 7.5 x 10(-14)), respectively. Compared with participants with GRS < or =11.0 (7.63%), those with GRS > or =19.0 (8.87%) had a 4.58-fold higher risk (95% CI 2.49-8.42) of type 2 diabetes. The GRS also showed a significant association with lower beta cell function estimated by HOMA of beta cell function (p = 8.4 x 10(-10)). In addition, we observed significant interactive effects between GRS and BMI on fasting glucose and HbA(1c) levels (p = 0.04 and p = 0.03 for interaction, respectively). Discrimination of diabetes risk was improved (p < 0.001) when the GRS was added to a model including clinical risk factors. The AUCs were 0.62 and 0.77, respectively, for the GRS and conventional clinic risk factors alone, and 0.79 when the GRS was added.

CONCLUSIONS/INTERPRETATION

In this Han Chinese population, the GRS of 17 combined variants modestly but significantly improved discrimination of the conventional risk factors for type 2 diabetes.

Secondary hyperparathyroidism and vitamin D receptor binding to vitamin D response elements in rats with incipient renal failure

The pathogenesis of secondary hyperparathyroidism in early renal failure is poorly understood. In the study presented here, parathyroid hormone and GFR in rats with mild renal failure of various durations are evaluated. Parathyroid hormone increased significantly 3 days after nephrectomy and peaked at 2 wk, despite reduction in GFR of < 50%. Parathyroid hormone remained elevated, but there was no difference in serum levels of calcium, phosphorus, and calcitriol between the nephrectomized and sham-operated rats. There were also no differences in both intestinal and kidney vitamin D receptor concentrations between the two groups. Histomorphometric analysis of bone at 6 wk revealed significant increase in osteoid thickness, osteoblast number, erosion surface with osteoclasts, and erosion depth. Employing electrophoretic mobility shift assay, we consistently observed a significant reduction in kidney calcitriol-receptor complex binding to mouse osteopontin vitamin D response element (-70.2 +/- 4.9%, P < 0.001). Western blot analysis also revealed a significant reduction in at least one retinoid X receptor isoform. In conclusion, biochemical and histological evidence of secondary hyperparathyroidism develops in rats with mild renal failure, despite normal calcium, phosphorus, calcitriol, and vitamin D receptor concentrations. These rats also have evidence of reduced renal vitamin D receptor binding to nuclear response elements. This finding, possibly an important early factor in the pathogenesis of secondary hyperparathyroidism, could also play a role in the development of compensatory renal growth of the remnant kidney.

Detection of Hong Kong 97-like H5N1 influenza viruses from eggs of Vietnamese waterfowl

Three H5N1 influenza viruses were isolated from shell washes of duck and goose eggs confiscated from travelers coming from Vietnam. All eight gene segments of these viruses share high sequence identity with the H5N1 avian influenza viruses that caused outbreaks in poultry and humans in Hong Kong in 1997. Animal studies indicate that these isolated viruses are able to replicate in mouse lung and could be found in the organs of ducks without causing any clinical signs or death. However, the viruses are highly pathogenic for chickens. Although the source of these recently isolated Hong Kong 97-like H5N1 viruses is undetermined, their detection in the egg shell of duck and goose suggests that this particular genotype of H5N1 virus may have re-emerged in nature or may have been circulating continuously.

Metabolic routing towards polyhydroxyalkanoic acid synthesis in recombinant Escherichia coli (fadR): inhibition of fatty acid beta-oxidation by acrylic acid

Heterologous expression of the phaC1 gene from Pseudomonas aeruginosa, which encodes one of the polyhydroxyalkanoic acid synthases, in Escherichia coli impaired in fatty acid beta-oxidation results in polyhydroxyalkanoic acid accumulation when cells were cultivated on fatty acids. We evaluated the application of the fatty acid beta-oxidation inhibitor acrylic acid as a tool to channel intermediates of beta-oxidation to polyhydroxyalkanoic acid synthesis. Various E. coli strains affected in fatty acid metabolism and the wild-type strain harboring plasmid pBHR71 were analyzed with respect to polyhydroxyalkanoic acid accumulation in the presence of acrylic acid. The E. coli fadR mutant RS3097 revealed the strongest polyhydroxyalkanoic acid accumulation. The optimum inhibitory concentration of acrylic acid was 0.24 mg ml-1 and caused efficient channeling of intermediates of beta-oxidation to polyhydroxyalkanoic acid synthesis. Under these conditions and grown on decanoate E. coli RS3097 harboring plasmid pBHR71 revealed a polyhydroxyalkanoic acid accumulation contributing to about 60% of cellular dry weight.

Long-term expression of Fos-related antigen and transient expression of delta FosB associated with seizures in the rat hippocampus and striatum

Systemic administration of kainic acid (KA), an analogue of glutamic acid, causes limbic seizures and pathophysiological changes in adult rats that are very similar to human temporal lobe epilepsy. One of the earliest changes in gene expression after treatment with KA is the induction of immediate-early genes. The fos and jun families are frequently studied immediate-early genes that are induced by KA. Several groups, including ours, have recently reported that a 35-kDa Fos-related antigen (FRA) is induced for a protracted time by various stimuli. It has been suggested that this FRA is delta FosB, which has a molecular mass of approximately 35 kDa. The present study characterizes the long-term expression of FRA and delta FosB after systemic treatment with KA. Immunocytochemistry and western blot analysis using an antibody that cross-reacts with all known FRAs showed that a 35-kDa FRA was induced at high levels in both the hippocampus and striatum for up to 1 month by KA. A semiquantitative PCR analysis showed that delta FosB was induced by KA, but its expression lasted for only 6 h. This result was also verified by northern blot analysis. These results suggested that the 35-kDa FRA with long-term elevated levels seen with western blot analysis and immunocytochemistry is a new species of the FRA and not delta FosB. The long-term expression of FRA in both the hippocampus and striatum may be associated with the pathophysiological changes after KA administration.

The Utilization of Glycolytic Intermediates as Precursors for Fatty Acid Biosynthesis by Pea Root Plastids

Radiolabeled pyruvate, glucose, glucose-6-phosphate, acetate, and malate are all variously utilized for fatty acid and glycerolipid biosynthesis by isolated pea (Pisum sativum L.) root plastids. At the highest concentrations tested (3-5mM), the rates of incorporation of these precursors into fatty acids were 183, 154, 125, 99 and 57 nmol h-1 mg-1 protein, respectively. In all cases, cold pyruvate consistently caused the greatest reduction, whereas cold acetate consistently caused the least reduction, in the amounts of each of the other radioactive precursors utilized for fatty acid biosynthesis. Acetate incorporation into fatty acids was approximately 55% dependent on exogenously supplied reduced nucleotides (NADH and NADPH), whereas the utilization of the remaining precursors was only approximately 10 and 20% dependent on added NAD(P)H. In contrast, the utilization of all precursors was greatly dependent (85-95%) on exogenously supplied ATP. Palmitate, stearate, and oleate were the only fatty acids synthesized from radioactive precursors. Higher concentrations of each precursor caused increased proportions of oleate and decreased proportions of palmitate synthesized. Radioactive fatty acids from all precursors were incorporated into glycerolipids. The data presented indicate that the entire pathway from glucose, including glycolysis, to fatty acids and glycerolipids is operating in pea root plastids. This pathway can supply both carbon and reduced nucleotides required for fatty acid biosynthesis but only a small portion of the ATP required

Calcitonin prevents bone loss but decreases osteoblastic activity in ovariohysterectomized beagle dogs

The antiresorptive effects of calcitonin are well documented. Recent in vitro and in vivo evidence points to an anabolic effect of calcitonin on osteoblasts. To assess the value of calcitonin in preventing the rapid and early bone loss after cessation of ovarian function and to investigate its effects on osteoblasts in vivo, 32 dogs were ovariohysterectomized (OHX) and 32 dogs were sham-operated (Sham). After the surgeries, half of the OHX and Sham dogs received every-other-day subcutaneous injections of human calcitonin (0.25 mg/dog/d), and the remaining dogs were given vehicle. Half of the animals had a bone biopsy at week 2 and were euthanized thereafter; the other half of the animals underwent a bone biopsy at month 1 and were euthanized at month 4. Blood drawings were done at baseline and at the time of each bone biopsy. Calcitonin prevented the increase in erosion depth seen in OHX animals and prevented the cancellous bone loss observed at 2 weeks and at 1 and 4 months. Calcitonin did not affect bone volume in Sham dogs. However, treatment with calcitonin induced a decrease in mineralizing surfaces and bone formation rates at the bone surface and cell level and an increase in mineralization lag time in both Sham and OHX animals without significantly affecting osteoblast number. This finding indicates that the negative effect of calcitonin on bone mineralization is not solely the result of a decrease in bone turnover. The data show that calcitonin, because of its antiresorptive effects, can prevent bone loss after cessation of ovarian function. However, short-term treatment with calcitonin does not stimulate osteoblast activity; on the contrary, it exerts a negative effect on osteoblastic bone formation and mineralization. Long-term studies are needed to investigate whether this unwanted effect of calcitonin on osteoblasts in vivo represents a transitory or persistent phenomenon.