The Arabidopsis eer1 mutant has enhanced ethylene responses in the hypocotyl and stem

By screening for enhanced ethylene-response (eer) mutants in Arabidopsis, we isolated a novel recessive mutant, eer1, which displays increased ethylene sensitivity in the hypocotyl and stem. Dark-grown eer1 seedlings have short and thick hypocotyls even in the absence of added ethylene. This phenotype is suppressed, however, by the ethylene biosynthesis inhibitor 1-aminoethoxyvinyl-glycine. Following ethylene treatment, the dark-grown eer1 hypocotyl response is greatly exaggerated in comparison with the wild type, indicating that the eer1 phenotype is not simply due to ethylene overproduction. eer1 seedlings have significantly elevated levels of basic-chitinase expression, suggesting that eer1 may be highly sensitive to low levels of endogenous ethylene. Adult eer1 plants display exaggerated ethylene-dependent stem thickening, which is an ethylene response previously unreported in Arabidopsis. eer1 also has enhanced responsiveness to the ethylene agonists propylene and 2,5-norbornadiene. The eer1 phenotype is completely suppressed by the ethylene-insensitive mutation etr1-1, and is additive with the constitutive ethylene-response mutation ctr1-3. Our findings suggest that the wild-type EER1 product acts to oppose ethylene responses in the hypocotyl and stem.

[The evaluation of fetal cardiac function in diabetic pregnancies]

OBJECTIVE

To assess fetal cardiac hypertrophy and ventricular function in fetuses of diabetic mothers.

METHODS

Study group was consist of 23 fetuses of diabetic pregnancies. Control group was consist of 108 fetuses of normal pregnancies. Cardiac size was measured by ultrasound as inter-ventricular septal (IVS) thickness and ventricular diastolic and systolic (VD and VS) dimensions and perimeter. Cardiac function was expressed as ventricular shortening fraction 1 (VSF1) (ventricular diastolic perimeter-ventricular systolic perimeter/ventricular diastolic perimeter) and ventricular shortening fraction 2 (VSF2) (ventricular diastolic dimension-Ventricular systolic dimension/ventricular diastolic dimension). Fetal birth weight was recorded.

RESULTS

IVS of study group (6.1 +/- 0.7) mm, which was significantly thicker than IVS of control group (4.4 +/- 0.7) mm. Left ventricular diastolic dimension (LVDD) and Left ventricular systolic dimension (LVSD) of study group were (3.3 +/- 0.8) cm2 and (2.2 +/- 0.6) cm2, which were greater than those of control group (2.6 +/- 0.6) cm2 and (2.0 +/- 0.5) cm2. Right ventricular diastolic dimension (RVDD) and Right ventricular systolic dimension (RVSD) of study group were (3.9 +/- 0.7) cm2 and (2.6 +/- 0.7) cm2, which were also greater than those of control group (3.5 +/- 0.5) cm2 and (2.4 +/- 0.7) cm2. Left ventricular shortening fraction 1 of left ventricular (LVSF1) of study group was 0.20 +/- 0.07, which was greater than that of control group (0.12 +/- 0.04). LVSF2 of study group was 0.35 +/- 0.11, which was greater than that of control group too (0.23 +/- 0.10). Right ventricular shortening fraction 1 of left ventricular (RVSF1) of study group was 0.19 +/- 0.05, which was greater than that of control group (0.13 +/- 0.11). RVSF2 of study group was 0.33 +/- 0.09, which was greater than that of control group (0.23 +/- 0.14). Estimated fetal birth weight of study group was (4,076 +/- 608) g, which was greater than that of control group (3,440 +/- 377) g.

CONCLUSION

These findings showed that fetal hyperinsulinemia result in fetal weight increasing, global cardiac enlarger inter-ventricular septal thickness larger and revealed hypercontractilty of ventricle in fetuses of diabetes mothers.

Regulation of Smad degradation and activity by Smurf2, an E3 ubiquitin ligase

Smad proteins are key intracellular signaling effectors for the transforming growth factor-beta superfamily of peptide growth factors. Following receptor-induced activation, Smads move into the nucleus to activate transcription of a select set of target genes. The activity of Smad proteins must be tightly regulated to exert the biological effects of different ligands in a timely manner. Here, we report the identification of Smurf2, a new member of the Hect family of E3 ubiquitin ligases. Smurf2 selectively interacts with receptor-regulated Smads and preferentially targets Smad1 for ubiquitination and proteasome-mediated degradation. At higher expression levels, Smurf2 also decreases the protein levels of Smad2, but not Smad3. In Xenopus embryos, ectopic Smurf2 expression specifically inhibits Smad1 responses and thereby affects embryonic patterning by bone morphogenetic protein signals. These findings suggest that Smurf2 may regulate the competence of a cell to respond to transforming growth factor-beta/bone morphogenetic protein signaling through a distinct degradation pathway that is similar to, yet independent of, Smurf1.

Donor origin of neuroendocrine carcinoma in 2 transplant patients determined by molecular cytogenetics

Organ transplant recipients have an increased tumor incidence owing to their immunocompromised state. The origin of such tumors, whether donor or recipient, will have a clinical impact on decision-making concerning immunosuppressive therapy, retransplantation, and for recipients of other organs from the same donors. We report molecular cytogenetic determination of donor origin in 2 cases of small-cell neuroendocrine carcinoma developing in sex-mismatched transplant recipients (kidney and liver). Fluorescence in situ hybridization (FISH) analysis was performed on liver core needle biopsy material from the liver transplant patient and on liver fine needle aspiration cytopreparations from the kidney transplant patient. The results for the liver transplant patient were confirmed with microsatellite allelic analysis and with comparative genomic hybridization. In both cases, FISH showed the presence of only X chromosomes within the tumor cells, indicating the donor origin of the neoplasms. FISH is an excellent method to determine neoplastic origin in sex-mismatched transplant patients. HUM PATHOL 31:1425-1429.

Phosphorus accumulation in cultivated soils from long-term annual applications of cattle feedlot manure

Historically, manure has been recognized as an excellent soil amendment that can improve soil quality and provide nutrients for crop production. In areas of high animal density, however, the potential for water pollution resulting from improper storage or disposal of manure may be significant. The objective of this study was to determine the P balance of cultivated soils under barley (Hordeum vulgare L.) production that have received long-term annual manure amendments. Nonirrigated soils at the study site in Lethbridge, AB, Canada, have received 0, 30, 60, or 90 Mg manure ha(-1) (wet wt. basis) while irrigated plots received 0, 60, 120, and 180 Mg ha(-1) annually for 16 yr. The amount of P removed in barley grain and straw during the 16-yr period was between 5 and 18% of the cumulative manure P applied. There was a balance between P applied in manure and P recovered in crops and soils (to the 150-cm depth) of nonirrigated plots during the 16-yr study. In irrigated plots, as much as 1.4 Mg P ha(-1) added (180 Mg ha(-1) yr(-1) treatment) was not recovered over 16 yr, and was probably lost through leaching. The risk of ground water contamination with P from manure was greater in irrigated than nonirrigated plots that have received long-term annual manure amendments. Manure application rates should be reduced in nonirrigated and irrigated plots to more closely match manure P inputs to crop P requirements.

Quercetin cumulatively enhances copper induction of metallothionein in intestinal cells

Wilson's disease, a genetic copper-overload condition, is currently treated with zinc because of the ability of zinc to induce metallothionein. We are interested in nonmetal chemicals that may alter intestinal copper metabolism and thus help to alleviate copper toxicity. Previously, we have shown that quercetin, a dietary flavonoid, can chelate copper. This study further examined the interaction of quercetin and copper in intestinal epithelial cells. We found that quercetin enhanced metallothoinein induction by copper and the effect was dose dependent. Quercetin also exerted a cumulative effect after repeated exposure. Repeated low-dose treatment (3-10 microM) of cells with quercetin can lead to the same effect on metallothoinein as one higher concentration treatment (100 microM). This property of quercetin is distinct from its chemical interaction with copper, but both can contribute to a reduction of copper toxicity. Among other flavonoids tested, two other copper chelators, catechin and rutin, did not increase copper induction of metallothionein, whereas genistein, an isoflavone that does not interact with copper chemically, increased copper induction of metallothionein. The effect of quercetin on copper metabolism is unique. Quercetin decreased zinc-stimulated metallothionein expression and had no effect on the cadmium induction of metallothionein. The clinical application of our observation needs to be explored.

Anti-hepatitis B virus effects of wogonin isolated from Scutellaria baicalensis

By using an HBV-producing cell line (MS-G2) in vitro culture system, we found that wogonin isolated from Scutellaria baicalensis can suppress HBV surface antigen production (P < 0.001) without evidence of cytotoxicity. By assaying the endogenous HBV DNA polymerase activity, we found that both the relaxed circular and the linear forms of HBV DNA are significantly reduced in the wogonin-treated group. Wogonin deserves to be further evaluated for the treatment of human HBV infection.

Functional analysis of androgen receptor N-terminal and ligand binding domain interacting coregulators in prostate cancer

Several new androgen receptor (AR) coregulators, including ARA70, ARA55, ARA54, ARA160 and ARA24, associated with the N-terminal or the ligand-binding domain (LBD) of AR, have been identified by our group. We first identified the AR-LBD coregulators ARA70, ARA55, and ARA54. Our previous reports suggest that ARA70 can enhance the androgenic activity of 17 beta-estradiol (E2) and antiandrogens toward AR. It is of interest to compare and determine if the specificity of sex hormones and antiandrogens can be modulated by different coregulators. Our results indicate that, ARA70 is the best coregulator for increasing the androgenic activity of E2. Only ARA70 and ARA55 were able to significantly increase the androgenic activity of hydroxyflutamide, the active metabolite of a widely-used antiandrogen for the treatment of prostate cancer. Furthermore, our results suggest that among the LBD coregulators, ARA70 has a relatively high specificity for AR in the human prostate cancer cell line DU145. Together, our data suggest that the androgenic activity of some sex hormones and antiandrogens can be modulated by selective AR coactivators. In addition to the AR-LBD associated proteins, ARA24 and ARA160 have been identified as AR coregulators, interacting with the AR N-terminal instead of the LBD. Functional analysis revealed that the AR N-terminal coregulator ARA160 could cooperate with the AR LBD-associated coregulator ARA70. Our data indicate that ARA24 could also interact with AR, and that this binding is decreased by an expanding poly-glutamine (Q) length within AR. The length of the poly-Q stretch in the AR N-terminal domain is inversely correlated with the transcriptional activity of AR. Our data suggest that optimal AR transactivation may require interaction of AR with AR coregulators. The identification of factors or peptides that can interrupt androgen-mediated AR-ARA interactions may be useful in the development of better antiandrogens for treating androgen-related diseases, such as prostate cancer.

Nucleoside diphosphate kinase from the hyperthermophilic archaeon Methanococcus jannaschii: overexpression, crystallization and preliminary X-ray crystallographic analysis

Nucleoside diphosphate (NDP) kinase is a key enzyme in maintaining cellular pools of all nucleoside triphosphates. NDP kinase from the hyperthermophilic archaebacterium Methanococcus jannaschii has been overexpressed in Escherichia coli and crystallized at 297 K using polyethylene glycol 4000 as precipitant. The crystal is hexagonal, belonging to the space group P6(3), with unit-cell parameters a = b = 72.89, c = 100.87 A. The asymmetric unit contains two subunits of NDP kinase, with a corresponding crystal volume per protein mass (V(M)) of 2.38 A(3) Da(-1) and a solvent content of 48.3%. Native X-ray diffraction data to 2.30 A resolution have been collected using synchrotron X-rays.

Requirements of multiple domains of SLI-1, a Caenorhabditis elegans homologue of c-Cbl, and an inhibitory tyrosine in LET-23 in regulating vulval differentiation

SLI-1, a Caenorhabditis elegans homologue of the proto-oncogene product c-Cbl, is a negative regulator of LET-23-mediated vulval differentiation. Lack of SLI-1 activity can compensate for decreased function of the LET-23 epidermal growth factor receptor, the SEM-5 adaptor, but not the LET-60 RAS, suggesting that SLI-1 acts before RAS activation. SLI-1 and c-Cbl comprise an N-terminal region (termed SLI-1:N/Cbl-N, containing a four-helix bundle, an EF hand calcium-binding domain, and a divergent SH2 domain) followed by a RING finger domain and a proline-rich C-terminus. In a transgenic functional assay, the proline-rich C-terminal domain is not essential for sli-1(+) function. A protein lacking the SH2 and RING finger domains has no activity, but a chimeric protein with the SH2 and RING finger domains of SLI-1 replaced by the equivalent domains of c-Cbl has activity. The RING finger domain of c-Cbl has been shown recently to enhance ubiquitination of active RTKs by acting as an E3 ubiquitin-protein ligase. We find that the RING finger domain of SLI-1 is partially dispensable. Further, we identify an inhibitory tyrosine of LET-23 requiring sli-1(+) for its effects: removal of this tyrosine closely mimics the loss of sli-1 but not of another negative regulator, ark-1. Thus, we suggest that this inhibitory tyrosine mediates its effects through SLI-1, which in turn inhibits signaling upstream of LET-60 RAS in a manner not wholly dependent on the ubiquitin-ligase domain.

Increase of androgen-induced cell death and androgen receptor transactivation by BRCA1 in prostate cancer cells

Although mutations of the breast cancer susceptibility gene 1 (BRCA1) may play important roles in breast and prostate cancers, the detailed mechanism linking the functions of BRCA1 to these two hormone-related tumors remains to be elucidated. Here, we report that BRCA1 interacts with androgen receptor (AR) and enhances AR target genes, such as p21((WAF1/CIP1)), that may result in the increase of androgen-induced cell death in prostate cancer cells. The BRCA1-enhanced AR transactivation can be further induced synergistically with AR coregulators, such as CBP, ARA55, and ARA70. Together, these data suggest that the BRCA1 may function as an AR coregulator and play positive roles in androgen-induced cell death in prostate cancer cells and other androgen/AR target organs.

Epidemiologic study of type 2 diabetes in Taiwan

Diabetes mellitus (DM) in adults is a global health problem, although its prevalence varies widely between different populations and the rate has generally increased worldwide. In Taiwan, the mortality rate from DM has almost doubled over the past 10 years. The prevalence of DM in Taiwan was established between 1985 and 1996 and the rates were between 4.9 and 9.2%. The prevalence of impaired glucose tolerance (IGT) was 15.5% (men 15% and women 15.9%). The prevalence of DM and IGT increased significantly with age for both genders. The significant factors associated with newly diagnosed DM were age, BMI, family history of DM, systolic blood pressure (hypertension), physical activity and serum triglyceride levels. The prevalence of large vessel disease (LVD) in DM and non-diabetic subjects were 20.0 and 12.9%, respectively. Among diabetics, 15.8% had ischemic heart disease (IHD), 1.7% leg vessel disease (leg VD), and 2.5% stroke. In non-diabetics, the prevalence of the aforementioned macroangiopathies were 11.5, 0.2 and 1.2%, respectively. The diabetics had a significantly higher prevalence of macrovascular disease than non-diabetic subjects. The most significantly associated with the LVD was serum cholesterol levels. Serum cholesterol and HbA1(c) were significantly associated with the development of IHD. Cigarette smoking and female gender were significantly associated with the leg VD. The prevalence of diabetic retinopathy (DR) was 35.0%. (background DR 30%, preproliferative DR 2.8% and proliferative DR 2.2%, respectively.) The prevalence of DR for previously and newly diagnosed diabetics were 45.2 and 28.3% (men 42.8 vs. 33.3% and women 47.5 vs. 24.8%), respectively. From multiple logistic regression analysis, duration of DM was the most important risk factor related to DR. Diabetic subjects treated with insulin had a higher risk of developing retinopathy than those treated with dietary control. The prevalence of nephropathy and neuropathy were 12.9 and 23.5%, respectively. For those patients with and those without nephropathy and neuropathy, the duration of DM, percentage of insulin treatment, percentage of hypertension, and fasting plasma glucose were significantly different. Diabetic duration, hypertension, insulin treatment and glycemic control consistently correlated with nephropathy and neuropathy. In conclusion, the prevalence of DM in Taiwan was between 4.9 and 9.2%, and the prevalence of IGT was 15.5%. The possible risk factors of newly diagnosed diabetes were age, family history of DM, BMI, SBP (hypertension), physical activity and triglyceride levels. Diabetes in Chinese subjects share many characteristics similar to other Asian populations. The burden imposed by the chronic complications of diabetes is massive. In Taiwan, the mortality rates from DM have increased greatly over the past 10 years. Reduction of the modificable risk factors such as BMI, hypertenion and dyslipidemia, and increase of physical activity and good glycemic control through public health efforts may help to reduce the risk of DM and its chronic complications.

Uninsured under TennCare: a case study of public health clinic users

BACKGROUND

We characterized public health clinic users 4 years after implementation of a major public health insurance reform and identified barriers to health care access.

METHODS

We used face-to-face interviews and profile analysis of survey findings.

RESULTS

The typical public health client household is larger, poorer, and more likely to be black than the wider population. The health status of participants is generally good; the level of insurance coverage is preponderantly TennCare; and 90% of respondents are willing to pay some premium.

CONCLUSIONS

Lack of health insurance does not present a serious health care access barrier, nor do transportation or location; but taking time off from work with loss of wages is a problem for those employed. A cost-effective way to enroll uninsured children is to use the County Health Department clinics as a contact point.

Ligation-mediated PCR for quantitative in vivo footprinting

Ligation-mediated polymerase chain reaction (LM-PCR) is a genomic analysis technique for determination of (1) primary DNA nucleotide sequences (2) cytosine methylation patterns (3) DNA lesion formation and repair, and (4) in vivo protein-DNA footprints. However, LM-PCR can be limited by the multiple steps required and the relatively short stretch of sequence (usually <200 bp) that can be analyzed per reaction. We report here a simplified, one-day LM-PCR protocol in which all pipetting steps can be performed by a robotic workstation and which, moreover, provides longer reads (>350 bp) and enhanced signal quality by use of nonradioactive detection and a LI-COR DNA sequencing instrument. Sensitivity comparable to radiolabeling is achieved using oligonucleotide primers that are 5'-end labeled with infrared fluorochromes. We showed that the technique could be used for sensitive and reproducible in vivo photofootprinting of the human phosphoglycerate kinase 1 (PGK1) promoter, as well as providing good Maxam-Gilbert sequence information. The methods described here should allow high-throughput, high-resolution analysis of transcription factor binding and chromatin structure, and also may be useful for sequencing gaps that are refractory to cloning.

A computer-aided design mammography screening system for detection and classification of microcalcifications

This paper presents a prototype of a computer-aided design (CAD) diagnostic system for mammography screening to automatically detect and classify microcalcifications (MCCs) in mammograms. It comprises four modules. The first module, called the Mammogram Preprocessing Module, inputs and digitizes mammograms into 8-bit images of size 2048x2048, extracts the breast region from the background, enhances the extracted breast and stores the processed mammograms in a data base. Since only clustered MCCs are of interest in providing a sign of breast cancer, the second module, called the MCCs Finder Module, finds and locates suspicious areas of clustered MCCs, called regions of interest (ROIs). The third module, called the MCCs Detection Module, is a real time computer automated MCCs detection system that takes as inputs the ROIs provided by the MCCs Finder Module. It uses two different window sizes to automatically extract the microcalcifications from the ROIs. It begins with a large window of size 64x64 to quickly screen mammograms to find large calcified areas, this is followed by a smaller window of size 8x8 to extract tiny, isolated microcalcifications. Finally, the fourth module, called the MCCs Classification Module, classifies the detected clustered microcalcifications into five categories according to BI-RADS (Breast Imaging Reporting and Data System) format recommended by the American College of Radiology. One advantage of the designed system is that each module is a separate component that can be individually upgraded to improve the whole system. Despite that it is still is a prototype system a preliminary clinical evaluation at TaiChung Veterans General Hospital (TCVGH) has shown that the system is very flexible and can be integrated with the existing Picture Archiving and Communications System (PACS) currently implemented in the Department of Radiology at TCVGH.

Effects of genomic length on translocation of hepatitis B virus polymerase-linked oligomer

Accurate translocation of the polymerase-linked oligomer to the acceptor site (DR1*) in reverse transcription is crucial for maintaining the correct size of the hepatitis B virus (HBV) genome. Various sizes of foreign sequences were inserted at different sites of the HBV genome, and their effects on accurate translocation of polymerase-linked oligomer to DR1* were tested. Three types of replicate DNA products were observed in these insertion mutants: RC (relaxed circle) and type I and type II DL (duplex linear) DNA. Our results indicated that the minus strand of RC and type I DL form was elongated from DR1*, while the minus strand of the type II DL form was elongated from multiple internal acceptor sites (IAS), such as IAS2. These IASs were also found to be used by wild-type HBV but with a very low frequency. Mutation of IAS2 by base substitution abrogated polymerase-linked oligomer transferring to IAS2, demonstrating that base pairing also plays an important role in the function of IAS2 as a polymerase-linked oligomer acceptor site. Data obtained from our insertion mutants also demonstrate that the distance between the polymerase-linked oligomer priming site and the acceptor is important. The polymerase-linked oligomer prefers to translocate to an acceptor, DR1* or IAS2, which are ca. 3.2 kb apart. However, it will translocate to both DR1* and IAS2 if they are not located 3.2 kb apart. These results suggest that the polymerase-linked oligomer may be able to scan bidirectionally for appropriate acceptor sites at a distance of 3.2 kb. A model is proposed to discuss the possible mechanism of polymerase-linked oligomer translocation.

Fetal renal volume in normal gestation: a three-dimensional ultrasound study

To establish a reference chart of fetal kidneys in normal pregnancy, we performed a prospective and cross-sectional study. A total of 152 singleton fetuses ranging between 20 and 40 weeks' gestation and meeting the criteria of normal pregnancies were included. Three-dimensional ultrasound (3-D US) was used to measure the fetal renal volume. Our results revealed that both renal volumes are highly correlated with the fetal gestational age. Using gestational age (GA) as the independent variable and right renal volume (RRV) as the dependent variable, the best-fit regression equation was RRV (mL)=0.74053xGA (week)-13.318 (r = 0.89, p < 0.001). Similarly, the best-fit equation for the left renal volume (LRV) was LRV (mL)=0. 76093xGA (week)-13.421 (r = 0.86, p < 0.001). The normal growth centiles of both kidneys were established based on these two equations. There were no significant differences of the volumes between bilateral kidneys. In conclusion, our data of fetal renal volumes assessed by 3-D US may serve as a reference in evaluating fetal renal growth.

Identification and characterization of a structural protein of hepatitis B virus: a polymerase and surface fusion protein encoded by a spliced RNA

The hepatitis B virus (HBV) genome is known to contain four conserved and overlapped open reading frames (ORFs) encoding the viral core, polymerase (P), surface (S), and X proteins. Whether HBV encodes other proteins has long been a major interest in the field. Using (32)P-labeling of an introduced protein kinase A site attached to the N- or C-terminus of the HBV polymerase gene, a 43-kDa P-S fusion protein was detected in cell lysate, secreted virions, and 22-nm subviral particles. Immunobiochemical studies showed that the 43-kDa protein contains the epitopes of the N-terminus of polymerase and most parts of the surface proteins. This 43-kDa protein was shown to be a glycoprotein, similar to the surface protein. RT-PCR and sequence analyses identified a spliced mRNA which was derived from pregenomic RNA with a deletion of 454 nucleotides (nt) from nt 2447 to 2902. This splice event creates a P-S fusion ORF. This finding is consistent with the result obtained from an immunobiochemical study. Mutations at the splice donor or acceptor site on the HBV genome abrogated the production of the 43-kDa protein. These mutants had no effect on viral replication in transfected HuH-7 cells. However, this P-S fusion protein is able to substitute for the LS protein in virion maturation. On the basis of these results, we conclude that the 43-kDa protein is a polymerase-surface fusion protein encoded by a spliced RNA. Similar to the LS protein, the 43-kDa P-S fusion protein is a structural protein of HBV and might play a role in the HBV life cycle.

Polymorphic CAG and GGN repeat lengths in the androgen receptor gene and prostate cancer risk: a population-based case-control study in China

The length of the polymorphic CAG trinucleotide repeat in the polyglutamine region of the androgen receptor (AR) gene is inversely correlated with the transactivation function of the AR. Because increased androgenic activity has been linked to prostate cancer and because an ethnic variation exists in the CAG repeat length, this polymorphism has been suggested to explain part of the substantial racial difference in prostate cancer risk. We conducted a population-based case-control study in China to investigate whether CAG and other polymorphisms of the AR gene are associated with clinically significant prostate cancer in this low-risk population. Genomic DNA from 190 prostate cancer patients and 304 healthy controls was used for direct sequencing to evaluate the relationship of CAG and GGN (polyglycine) repeat length in the AR gene. Relative to western men, our study subjects had a longer CAG repeat length, with a median of 23 and only 10% of the subjects having a CAG repeat length shorter than 20. Men with a CAG repeat length shorter than 23 (median length) had a 65% increased risk of prostate cancer (odds ratio, 1.65; 95% confidence interval, 1.14-2.39), compared with men with a CAG repeat length of 23 or longer. For the GGN tract (GGT3GGG1GGT2GGCn), based on the sequencing results from 481 samples, we are the first to show that although GGC regions in the polyglycine tract are highly variable, there are no mutations or polymorphisms in the GGT and GGG regions. More than 72% of the subjects had a GGN repeat length of 23, and those with a GGN repeat length shorter than 23 had a 12% increased risk of prostate cancer (95% confidence interval, 0.71-1.78), compared with those with > or = 23 GGN repeats. Our study not only confirms that Chinese men do have a longer CAG repeat length than western men but also represents the first population-based study to show that even in a very low-risk population, a shorter CAG repeat length confers a higher risk of clinically significant prostate cancer. These results imply that CAG repeat length can potentially serve as a useful marker to identify a subset of individuals at higher risk of developing clinically significant prostate cancer. Larger studies are needed to evaluate the combined effect of CAG and GGN repeats. Because of the significance of AR in prostate cancer, investigation of factors that interact with the polyglutamine region of the AR gene to alter AR function and modulate prostate cancer risk is an important area for future research.

The p53/retinoblastoma-mediated repression of testicular orphan receptor-2 in the rhesus monkey with cryptorchidism

Whereas the linkage of infertility to cryptorchidism, the failure of the testis to descend into the scrotum at birth, has been well documented, the detailed molecular mechanism remains unclear. Here we report that the testicular orphan receptor-2 (TR2) expression, which modulates many signal pathways, was completely repressed in the surgery-induced cryptorchidism of the rhesus monkey. Further studies link TR2 repression to the induction of p53 and results suggest that induced p53 could repress TR2 expression via the p53-->p21-->CDK-->Rb-->E2F signal pathway. In return, TR2 could also control the expression of p53 and Rb through the regulation of human papillomavirus 16 E6/E7 genes. Together, our data suggest a feedback control mechanism between TR2 and p53/Rb tumor suppressors, which might play important roles in male infertility associated with cryptorchidism.

Expression of MHC class II in T cells is associated with increased HIV-1 expression

HIV-1 replicates in activated T cells at significantly higher levels than in resting cells. Thus, certain molecules up-regulated during T cell activation appear to be important for HIV-1 replication. In this study, we present evidence suggesting that expression of MHC class II (class II) molecules on CD4+ T cells facilitate HIV-1 replication. T cells that expressed class II supported greater virus replication than T cells lacking class II. The class II+ cells, when either infected with HIV-1 or transfected with an env-minus HIV-1 provirus plasmid, produced 10-20-fold greater virus expression than class II- cells. Anti-class II antibody markedly inhibited virus expression in class II+ cells (but not class II- cells) and also decreased the nuclear binding activity of AP-1, an inducible transcription factor important in T cell activation and HIV-1 expression. Most importantly, the induction of class II expression by transfection of the MHC class II transactivator (CIITA) stimulated HIV-1 replication in Jurkat T cells. Taken together, these data suggest that expression of MHC class II molecules and/or CIITA in T cells enhances HIV-1 transcription.

Caenorhabditis elegans SOS-1 is necessary for multiple RAS-mediated developmental signals

Vulval induction in Caenorhabditis elegans has helped define an evolutionarily conserved signal transduction pathway from receptor tyrosine kinases (RTKs) through the adaptor protein SEM-5 to RAS. One component present in other organisms, a guanine nucleotide exchange factor for Ras, has been missing in C.ELEGANS: To understand the regulation of this pathway it is crucial to have all positive-acting components in hand. Here we describe the identification, cloning and genetic characterization of C.ELEGANS: SOS-1, a putative guanine nucleotide exchanger for LET-60 RAS. RNA interference experiments suggest that SOS-1 participates in RAS-dependent signaling events downstream of LET-23 EGFR, EGL-15 FGFR and an unknown RTK. We demonstrate that the previously identified let-341 gene encodes SOS-1. Analyzing vulval development in a let-341 null mutant, we find an SOS-1-independent pathway involved in the activation of RAS signaling. This SOS-1-independent signaling is not inhibited by SLI-1/Cbl and is not mediated by PTP-2/SHP, raising the possibility that there could be another RasGEF.

Temporal changes of cerebral metabolites and striatal lesions in acute 3-nitropropionic acid intoxication in the rat

To investigate the mechanisms of neuronal death in neurodegeneration, in vivo localized proton magnetic resonance spectroscopy ((1)H-MRS) and diffusion-weighted MRI (DWI) were used to evaluate temporal changes in rat striata after administration of 3-nitropropionic acid. It was found that N-acetylaspartate (NAA) reduction, with nearly simultaneous evidence of striatal lesions in DWI, was preceded by a significant and progressive increase of acetate. Shortly before the NAA levels decreased to the lowest point, acetate levels peaked and began to gradually decline toward the control levels. These results suggest that acetate increase may arise from fatty acid degradation, inhibition of succinate dehydrogenase and possible NAA hydrolysis. The elevated acetate may provide a source of acetyl group for membrane repair during excitotoxic brain injury. Magn Reson Med 44:29-34, 2000.