Biomedical subjects

X Lin

Publications and source records attributed to X Lin.

At least 127 records · Page 7Linked to original sources

PubMed2000

SSeCKS, a major protein kinase C substrate with tumor suppressor activity, regulates G(1)-->S progression by controlling the expression and cellular compartmentalization of cyclin D.

SSeCKS, first isolated as a G(1)-->S inhibitor that is downregulated in src- and ras-transformed cells, is a major cytoskeleton-associated PKC substrate with tumor suppressor and kinase-scaffolding activities. Previous attempts at constitutive expression resulted in cell variants with truncated ectopic SSeCKS products. Here, we show that tetracycline-regulated SSeCKS expression in NIH 3T3 cells induces G(1) arrest marked by extracellular signal-regulated kinase 2-dependent decreases in cyclin D1 expression and pRb phosphorylation. Unexpectedly, the forced reexpression of cyclin D1 failed to rescue SSeCKS-induced G(1) arrest. Confocal microscopy analysis revealed cytoplasmic colocalization of cyclin D1 with SSeCKS. Because the SSeCKS gene encodes two potential cyclin-binding motifs (CY) flanking major in vivo protein kinase C (PKC) phosphorylation sites (Ser(507/515)), we addressed whether SSeCKS encodes a phosphorylation-dependent cyclin scaffolding function. Bacterially expressed SSeCKS-CY bound cyclins D1 and E, whereas K-->S mutations within either CY motif ablated binding. Activation of PKC in vivo caused a rapid translocation of cyclin D1 to the nucleus. Cell permeable, penetratin-linked peptides encoding wild-type SSeCKS-CY, but not K-->S or phospho-Ser(507/515) variants, released cyclin D1 from its cytoplasmic sequestration and induced higher saturation density in cyclin D1-overexpressor cells or rat embryo fibroblasts. Our data suggest that SSeCKS controls G(1)-->S progression by regulating the expression and localization of cyclin D1. These data suggest that downregulation of SSeCKS in tumor cells removes gating checkpoints for saturation density, an effect that may promote contact independence.

3T3 Cells↗

PubMed2000

Activation of the heterodimeric IkappaB kinase alpha (IKKalpha)-IKKbeta complex is directional: IKKalpha regulates IKKbeta under both basal and stimulated conditions.

Signal-induced nuclear expression of the eukaryotic NF-kappaB transcription factor involves the stimulatory action of select mitogen-activated protein kinase kinase kinases on the IkappaB kinases (IKKalpha and IKKbeta) which reside in a macromolecular signaling complex termed the signalsome. While genetic studies indicate that IKKbeta is the principal kinase involved in proinflammatory cytokine-induced IkappaB phosphorylation, the function of the equivalently expressed IKKalpha is less clear. Here we demonstrate that assembly of IKKalpha with IKKbeta in the heterodimeric signalsome serves two important functions: (i) in unstimulated cells, IKKalpha inhibits the constitutive IkappaB kinase activity of IKKbeta; (ii) in activated cells, IKKalpha kinase activity is required for the induction of IKKbeta. The introduction of kinase-inactive IKKalpha, activation loop mutants of IKKalpha, or IKKalpha antisense RNA into 293 or HeLa cells blocks NIK (NF-kappaB-inducing kinase)-induced phosphorylation of the IKKbeta activation loop occurring in functional signalsomes. In contrast, catalytically inactive mutants of IKKbeta do not block NIK-mediated phosphorylation of IKKalpha in these macromolecular signaling complexes. This requirement for kinase-proficient IKKalpha to activate IKKbeta in heterodimeric IKK signalsomes is also observed with other NF-kappaB inducers, including tumor necrosis factor alpha, human T-cell leukemia virus type 1 Tax, Cot, and MEKK1. Conversely, the theta isoform of protein kinase C, which also induces NF-kappaB/Rel, directly targets IKKbeta for phosphorylation and activation, possibly acting through homodimeric IKKbeta complexes. Together, our findings indicate that activation of the heterodimeric IKK complex by a variety of different inducers proceeds in a directional manner and is dependent on the kinase activity of IKKalpha to activate IKKbeta.

Cell Line↗

PubMed2000

Protein kinase C-theta participates in NF-kappaB activation induced by CD3-CD28 costimulation through selective activation of IkappaB kinase beta.

The NF-kappaB/Rel family of eukaryotic transcription factors plays an essential role in the regulation of inflammatory, antiapoptotic, and immune responses. NF-kappaB is activated by many stimuli including costimulation of T cells with ligands specific for the T-cell receptor (TCR)-CD3 complex and CD28 receptors. However, the signaling intermediates that transduce these costimulatory signals from the TCR-CD3 and CD28 surface receptors leading to nuclear NF-kappaB expression are not well defined. We now show that protein kinase C-theta (PKC-theta), a novel PKC isoform, plays a central role in a signaling pathway induced by CD3-CD28 costimulation leading to activation of NF-kappaB in Jurkat T cells. We find that expression of a constitutively active mutant of PKC-theta potently induces NF-kappaB activation and stimulates the RE/AP composite enhancer from the interleukin-2 gene. Conversely, expression of a kinase-deficient mutant or antisense PKC-theta selectively inhibits CD3-CD28 costimulation, but not tumor necrosis factor alpha-induced activation of NF-kappaB in Jurkat T cells. The induction of NF-kappaB by PKC-theta is mediated through the activation of IkappaB kinase beta (IKKbeta) in the absence of detectable IKKalpha stimulation. PKC-theta acts directly or indirectly to stimulate phosphorylation of IKKbeta, leading to activation of this enzyme. Together, these results implicate PKC-theta in one pathway of CD3-CD28 costimulation leading to NF-kappaB activation that is apparently distinct from that involving Cot and NF-kappaB-inducing kinase (NIK). PKC-theta activation of NF-kappaB is mediated through the selective induction of IKKbeta, while the Cot- and NIK-dependent pathway involves induction of both IKKalpha and IKKbeta.

CD28 Antigens↗

PubMed2000

Relation of weight gain and weight loss on subsequent diabetes risk in overweight adults.

STUDY OBJECTIVE: To determine whether long term weight gain and weight loss are associated with subsequent risk of type 2 diabetes in overweight, non-diabetic adults. DESIGN: Prospective cohort. Baseline overweight was defined as BMI>/=27.3 for women and BMI>/=27. 8 for men. Annual weight change (kg/year) over 10 years was calculated using measured weight at subjects' baseline and first follow up examinations. In the 10 years after measurement of weight change, incident cases of diabetes were ascertained by self report, hospital discharge records, and death certificates. SETTING: Community. PARTICIPANTS: 1929 overweight, non-diabetic adults. MAIN RESULTS: Incident diabetes was ascertained in 251 subjects. Age adjusted cumulative incidence increased from 9.6% for BMI<29 to 26. 2% for BMI>/=37. Annual weight change over 10 years was higher in subjects who become diabetic compared with those who did not for all BMI<35. Relative to overweight people with stable weight, each kg of weight gained annually over 10 years was associated with a 49% increase in risk of developing diabetes in the subsequent 10 years. Each kg of weight lost annually over 10 years was associated with a 33% lower risk of diabetes in the subsequent 10 years. CONCLUSIONS: Weight gain was associated with substantially increased risk of diabetes among overweight adults, and even modest weight loss was associated with significantly reduced diabetes risk. Minor weight reductions may have major beneficial effects on subsequent diabetes risk in overweight adults at high risk of developing diabetes.

Adult↗

PubMed2000

Regulation of food intake by neuropeptide Y in goldfish.

In mammals, neuropeptide Y (NPY) is a potent orexigenic factor. In the present study, third brain ventricle (intracerebroventricular) injection of goldfish NPY (gNPY) caused a dose-dependent increase in food intake in goldfish, and intracerebroventricular administration of NPY Y1-receptor antagonist BIBP-3226 decreased food intake; the actions of gNPY were blocked by simultaneous injection of BIBP-3226. Goldfish maintained on a daily scheduled feeding regimen display an increase in NPY mRNA levels in the telencephalon-preoptic area and hypothalamus shortly before feeding; however, a decrease occured in optic tectum-thalamus. In both fed and unfed fish, brain NPY mRNA levels decreased after scheduled feeding. Restriction in daily food ration intake for 1 wk or food deprivation for 72 h resulted in increased brain NPY mRNA levels. Results from these studies demonstrate that NPY is a physiological brain signal involved in feeding behavior in goldfish, mediating its effects, at least in part, through Y1-like receptors in the brain.

Animals↗

PubMed2000

Paradoxical effects of iodine-125 decays in parent and daughter DNA: a new target model for radiation damage.

Chinese hamster ovary cells were synchronized at the G(1)/S-phase boundary of the cell cycle and were pulse-labeled with (125)I-iododeoxyuridine 30 min after they entered the S phase. Cell samples were harvested and frozen for accumulation of (125)I decays during the first and second G(2) phase after labeling. Cell aliquots that had accumulated the desired number of decays were thawed and plated for evaluation micronucleus formation and cell death. Cells subjected to (125)I decays during the first G(2) phase after labeling exhibited single-hit kinetics of cell killing (n = 1, D(0) 41 decays/cell). In contrast, decays accumulated during the second G(2) phase killed cells with dual-hit kinetics (n = 1.9, D(0) 81 decays/cell). A similar divergence in the action of (125)I was noted for micronucleus formation. These findings indicate that the effects of (125)I varied depending on whether the decays occurred in daughter DNA (first G(2) phase) or parent DNA (second G(2) phase). Control studies with external X rays showed no such divergence of the action of radiation. To account for this paradox, a model is proposed that invokes higher-order chromatin structures as radiation targets. This model implies differential spatial arrangements for parent and daughter DNA in the genome, with DNA strands organized such that a single (125)I decay originating in daughter DNA damages two targets during the first G(2) phase, but identical decays occurring during the second G(2) phase damage only one of the targets.

Animals↗

PubMed2000

SIK (Salt-inducible kinase): regulation of ACTH-mediated steroidogenic gene expression and nuclear/cytosol redistribution.

Possible involvement of salt-inducible kinase (SIK), a serine/threonine protein kinase first cloned from high K+-diet treated rat adrenal glands, in the regulation of steroidogenesis was investigated. Y-1 cells, when treated with ACTH, underwent a rapid change in SIK's mRNA content. It reached the maximum within a few hours and returned to the base after 8 h. In contrast, the levels of mRNAs for CYP11A and StAR protein reached the maxima after 8 h. The SIK's mRNA induction failed to occur in ACTH-, forskolin- or 8-Br-cAMP-treated Kin-7 cells, a mutant cell line of Y-1 with defective cAMP-dependent protein kinase A (PKA). Y-1 cells that overexpress SIK, when treated with ACTH, had significantly repressed levels of mRNAs for CYP11A and StAR protein. Therefore, SIK might have a negative effect on the CYP11A- and StAR protein-gene expression in the early phase of ACTH-mediated steroidogenesis. To further explore the mechanisms underlying this phenomenon, we examined intracellular distribution of the green fluorescence protein (GFP)-tagged SIK. When GFP-SIK was introduced into HeLa cells, the fluorescent signals were detected in the nucleus. In Y-1 cells GFP-SIK was detected both in the nucleus and cytosol, and the signal in the former moved to the latter after ACTH-treatment. The nuclear/cytosol re-distribution of GFP-SIK was also observed in forskolin- or 8-Br-cAMP-treated Y-1 cells, but not in Kin-7 cells. These results suggest that the intracellular re-distribution of SIK in Y-1 cells may depend on the cAMP/PKA signaling pathway and has an important regulatory role in the ACTH-mediated steroidogenic gene expression.

Adrenal Cortex↗

PubMed2000

GSTP1 CpG island DNA hypermethylation in hepatocellular carcinomas.

Glutathione S-transferases, enzymes that defend cells against damage mediated by oxidant and electrophilic carcinogens, may be critical determinants of cancer pathogenesis. We report here that the pathogenesis of hepatocellular carcinoma (HCC), one of the most common cancers in the world, frequently involves an accumulation of somatic DNA methylation changes at GSTP1, the gene encoding the pi-class glutathione S-transferase. For our study, Hep3B HCC cells and a cohort of 20 HCC tissue specimens were subjected to analysis for GSTP1 expression and for somatic GSTP1 alterations. GSTP1 DNA hypermethylation in HCC DNA was assessed by Southern blot analysis, via a polymerase chain reaction (PCR) assay, and by using a genomic sequencing approach. Hep3B HCC cells failed to express GSTP1 mRNA or GSTP1 polypeptides. Similarly, HCC cells in 19 of 20 HCC cases were devoid of GSTP1 polypeptides. By Southern blot analysis, DNA from Hep3B HCC cells displayed abnormal GSTP1 hypermethylation. Treatment of Hep3B HCC cells in vitro with the DNA methyltransferase inhibitor 5-aza-deoxycytidine both reversed GSTP1 DNA hypermethylation and restored GSTP1 expression. Using a PCR assay, somatic GSTP1 DNA hypermethylation was also detected in HCC DNA from 17 of 20 HCC cases. Genomic sequencing analyses, undertaken to map 5-methyldeoxycytidine nucleotides located at the GSTP1 transcriptional regulatory region, frequently detected somatic DNA hypermethylation near the gene promoter in HCC DNA. The data indicate that GSTP1 DNA hypermethylation changes appear frequently in human HCC. In addition, the data raise the possibility that somatic GSTP1 inactivation, via hypermethylation, may contribute to the pathogenesis of HCC.

Adult↗

PubMed2000

Somatostatin family of peptides and its receptors in fish.

Somatostatin (SRIF or SS) is a phylogenetically ancient, multigene family of peptides. SRIF-14 is conserved with identical primary structure in species of all classes of vertebrates. The presence of multiple SRIF genes has been demonstrated in a number of fish species and could extend to tetrapods. Three distinct SRIF genes have been identified in goldfish. One of these genes, which encodes [Pro2]SRIF-14, is also present in sturgeon and African lungfish, and is closely associated with amphibian [Pro2,Met13]SRIF-14 gene and mammalian cortistatin gene. The post-translational processing of SRIF precursors could result in multiple forms of mature SRIF peptides, with differential abundance and tissue- or cell type-specific patterns. The main neuroendocrine role of SRIF-14 peptide that has been determined in fish is the inhibition of pituitary growth hormone secretion. The functions of SRIF-14 variant or larger forms of SRIF peptide and the regulation of SRIF gene expression remain to be explored. Type 1 and type 2 SRIF receptors have been identified from goldfish and a type 3 SRIF receptor has been identified from an electric fish. Fish SRIF receptors display considerable homology with mammalian counterparts in terms of primary structure and negative coupling to adenylate cyclase. Although additional types of receptors remain to be determined, identification of the multiple gene family of SRIF peptides and multiple types of SRIF receptors opens a new avenue for the study of physiological roles of SRIF, and the molecular and cellular mechanisms of SRIF action in fish.

Amino Acid Sequence↗

PubMed2000

Timing patterns of cluster headaches and association with symptoms of obstructive sleep apnea.

Cluster headaches (CH) frequently recur at the same point in the circadian cycle, often during sleep. They may, in some cases, represent a susceptible individual's response to hypoxemia or other physiological changes induced by obstructive sleep apnea (OSA). If and when this mechanism exists, timing of CH close to the onset of sleep-and therefore OSA-might be expected. We questioned 36 subjects with CH about the times at which their CH usually occurred and about several symptoms known to be predictive of OSA, including habitual snoring, loud snoring, observed apneas and excessive daytime sleepiness. We then used logistic regression to determine whether occurrence of CH in each of six time periods was associated with OSA symptoms. The 23 subjects (64%) who reported CH in the first half of a typical night's sleep also tended to report headaches during the midday/afternoon period. Symptoms of OSA, and in particular habitual snoring, were predictive of both first-half-of-the-night and midday/afternoon CH (p<.05). Thirty-one subjects (86%) reported that their CH were sleep-related, usually occurring during any part of the night or on awakening, but symptoms of OSA were not predictive of this timing pattern. In short, several OSA symptoms showed an association with CH occurrence in the first half of the night but not with sleep-related CH in general. These findings suggest that in some patients, physiological consequences of OSA may trigger CH during the first few hours of sleep and thereby influence the timing of subsequent daytime headaches.

Adult↗

PubMed2000

Comparative study of D2 receptors and dopamine content in striatum before and after electro-acupuncture treatment in rats.

OBJECTIVE: To evaluate the change in D2 receptors and their relationship with dopamine (DA) content in experimental hemi-parkinsonism rats before and after electro-acupuncture (EA) treatment. METHODS: 125I-IBZM D2 receptor cerebral autoradiographic analysis, HPLC-ECD detection of DA and its metabolites, homovanillic acid (HVA), 3, 4-dihydroxyphenylacetic acid (DOPAC) were used to study their levels in striatum in pre-EA, EA and EA control group. RESULTS: The DA, HVA and DOPAC levels in striatum of the lesioned side in the EA group were elevated compared to the pre-EA and EA control group (P < 0.05). For the EA group, the striatum/cerebellum 125I-IBZM uptake ratio of the lesioned side was 8.04 +/- 0.71, (29.34% +/- 4.83%) more than that of the contralateral side (P < 0.05), while no significant difference was observed as compared with that in the pre-EA group (8.09 +/- 0.52, 30.12% +/- 4.53%, higher than that of the intact side P > 0.05). It was lower than the EA control group (8.61 +/- 0.63, P < 0.05), and the latter was (38.63% +/- 3.71%) higher than that in its contralateral side (P < 0.05). CONCLUSION: 6-OH-DA lesions in the substantia nigra and ventral tegmental areas induce an up-regulation of striatal D2 binding sites. EA treatment could elevate the DA level of the lesioned side striatum and prevent D2 receptor up-regulation in rats with experimental hemiparkinsonism.

Animals↗

PubMed2000

Effect of preoperative transcatheter arterial chemoembolization on tumor cell activity in hepatocellular carcinoma.

OBJECTIVE: To evaluate the role of preoperative transcatheter arterial chemoembolization (TACE) as a palliative approach in hepatocellular carcinoma (HCC). METHODS: From January 1992 to December 1998, 279 patients with HCC underwent curative liver resection. One to five courses of TACE prior to liver resection were performed in 117 patients (TACE group), while the other 162 patients received only liver resection (control group). All 279 specimens of resected tumors were submitted to the following assessments: PCNA and expression of P53 protein. All specimens from the TACE group were examined for downstaging or necrosis of tumors. RESULTS: In the TACE group, gross inspection revealed downstaging or necrosis of tumor in all cases. Total necrosis (100%) of tumor was observed in 11.1% of 117 patients, > 90% but incomplete necrosis in 15.4%, 50%-90% necrosis in 46.2% and < 50% necrosis in 27.3%. Microscopically, extensive and homogenous coagulative necrosis was observed. Viable cancer cells were also present within and outside the tumor capsule in 111 cases. In the remaining 6 cases, the tumor necrosed completely. In control group, necrosis was observed in 8.0% of 162 cases and reduction of tumor size was < 20%. Microscopically, viable HCC cells were noted in all cases. There was no statistical difference in expression of P53 protein between the TACE and control group. High labeling index of PCNA was significantly higher in the TACE group. CONCLUSIONS: TACE has a marked antitumor effect resulting in various degree of tumor necrosis, but only a small proportion of tumors show complete necrosis. Since the residual tumor cells following preoperative TACE may have more aggressive behavior, we conclude that sequential liver resection is the preferred therapy whenever feasible and preoperative TACE should be avoided in resectable HCC.

Adult↗

PubMed2000

[Study on treatment of eczema by Chinese herbal medicine with anti-type IV allergic activity].

OBJECTIVE: To study Chinese herbal prescription for treatment of eczema based on the suppressive effect of Chinese herbal medicine on type IV allergic reaction. METHODS: Various formulae composed of Chinese herbal medicines possessing suppressive effect on allergic contact dermatitis were formed based on the therapeutic principles of traditional Chinese medicine in treating eczema, and their effect on murine ear swelling, ear flake weight, dermal inflammatory infiltration cell count and plasma level of calcitonin gene related peptide (CGRP) were examined in mice with dinitrofluorobenzene induced dermatitis. A prescription, Composite Poria Decoction was formulated and made into granule form, which was used to treat 63 cases of eczema (atopic dermatitis was excluded), and compared with 59 cases treated with antihistamine that was aimed at the type I allergic reaction. RESULTS: Experimental study showed that all the 4 Chinese prescriptions had the effect of anti-type IV allergic reaction, among them, the formula for cooling blood, remove Heat, Wind and Dampness evil possessed the most potent effect in suppressing murine dermatitis, and it was also able to up-regulate the plasma CGRP concentration. The clinical cure rate of Composite Poria Granule treatment was 47.6%, and that of control was 22.0%, the difference was significant between the two groups (u = 2.9555, P < 0.01). CONCLUSIONS: Chinese herbal medicine has effect of anti-type IV allergic reaction. Composite Poria Granule has good effect in treating eczema.

Animals↗

PubMed2000

[A study on general status and affecting factors on infant intellectual development in Changsha city].

OBJECTIVE: To evaluate the intellectual level of infants in Changsha city and analyze the main factors that affect infant intellectual development. METHODS: Two hundred and sixty infants were measured by Fagan Test of Infant Intelligence, who were randomly selected from Changsha city. RESULTS: The general intellectual level of infants in Changsha city was good; stepwise regression analysis revealed the main possible risk factors affecting intellectual development of infants in Changsha city were newborn asphyxiated at birth (B = -17.162), perinatal fever in the first trimester (B = -8.084), infant with abnormal temper (B = -6.295) and poor appetite (B = -3.103). Parental care (B = 4.622) possibly benefit the infant intellectual development. CONCLUSION: These data suggested that the main measures to promote infant intellectual development were more attention need to be paid to health care for women and children, prevention of perinatal disease and infant rearing in a scientific way.

Asphyxia Neonatorum↗

PubMed2000

[Study on effect of spine surgery on gastric function and its efficacy of relevant treatments].

OBJECTIVE: To study the effect of spine surgery (SpS) on gastric function and the efficacy of relevant treatments. METHODS: Sixty patients in the spine surgery group, 20 patients in the extremity surgery (ES) group and 20 healthy subjects in the control group were observed. Electrogastrography (EGG) was used to observe gastroelectric activity before and after operation. Twenty patients among the SpS group were examined with barium meal under actinoscopy to observe the gastric peristaltic waves before and after operation. The SpS group was randomly subdivided into 3 groups, and treated by Xiangsha Yangwei pill (XSYW), moxibustion and motilium respectively. At the same time, the EGG of various groups was observed and the change of preoperative and postoperative EGG were compared. RESULTS: The gastroelectric rhythm of SpS group was remarkably abnormal, both frequency and amplitude of EGG were significantly different from the other two groups (P < 0.05, P < 0.01). The gastric peristaltic waves were reduced, and the emptying time was obviously prolonged. EGG was significantly improved after either of the three treatments statistically (P < 0.05), the effect of XSYW was the best, but in comparing with the other two, the difference was not significant (P > 0.05). CONCLUSION: SpS could change the gastroelectric rhythm to cause the gastric functional disorder and induce gastroparesis, EGG can get satisfactory results in the diagnosis of these illnesses. XSYW, moxibustion and motilium all have significant effects on the gastric function after SpS.

Acupuncture↗

PubMed2000

[Otogenic hypertrophic cranial pachymeningitis associated with edema of the temporal lobe and organic mental disorder-case report].

OBJECTIVE: Hypertrophic cranial pachymeningitis(HCP) is a rare disease which might be misdiagnosed. One typical case of otogenic hypertrophic cranial pachymeningitis (HCP) associated with edema of the temporal lobe and organic mental disorder was reported. Literatures associated with HCP were reviewed for reference. METHODS: In July, 1997, a 26-year-old man was admitted for right-sided severe headache, dizziness, nausea, vomiting, facial and abducens nerve palsy. MRI and CT revealed inflammation in the temporal bone and locally thickened dura mater with obvious enhancement as a band in the petrous apex and nearby tentorium cerebellum. The patient then underwent operation including decompression of the facial nerve, labyrinthectomy, and eradication of the inflammatory cells in the mastoid and petrous portion. Postoperatively, the clinical signs disappeared except hearing loss. Seven months later, the patient suffered from mental disorder with interrupted excitement to hit and abuse the family members. He was then treated in a psychosis hospital but no improvement could be seen. On May 13, 1998, MRI and the enhanced MRI demonstrated diffuse thickened tentorium cerebellum and dura mater in the middle cranial fossa. The inferior portion of the temporal lobe was obvious edema. The internal carotid artery was partially occluded due to the thickened wall of cavernous sinus. RESULTS: Hence, the diagnosis of HCP associated with edema of temporal lobe and organic mental disorder was established. The patient was cured by high dosage of penicillin. CONCLUSION: MRI is an essential method for diagnosis of HCP. Antibiotic was an effective treatment.

Adult↗

PubMed2000

[IR and Raman studies of inorganic nano giant cluster compounds].

The syntheses, IR and Raman spectra of four nanosize giant cluster compounds were reported in this paper. These compounds show similar IR and Raman spectra because they were assembled by the similar building blocks. The bands with frequencies in IR spectra in the range from 980 to 550 cm-1 and those absorptions under 970 cm-1 in Raman spectra have to be attributed to the absorptions of Mo-O bonds including Mo = O, Mo-O-Mo and mu 3-O-Mo bonds.

English Abstract↗

PubMed1999

Genetic definition and sequence analysis of Arabidopsis centromeres.

High-precision genetic mapping was used to define the regions that contain centromere functions on each natural chromosome in Arabidopsis thaliana. These regions exhibited dramatic recombinational repression and contained complex DNA surrounding large arrays of 180-base pair repeats. Unexpectedly, the DNA within the centromeres was not merely structural but also encoded several expressed genes. The regions flanking the centromeres were densely populated by repetitive elements yet experienced normal levels of recombination. The genetically defined centromeres were well conserved among Arabidopsis ecotypes but displayed limited sequence homology between different chromosomes, excluding repetitive DNA. This investigation provides a platform for dissecting the role of individual sequences in centromeres in higher eukaryotes.

Arabidopsis↗