Acceleration Mechanism of Steel Slag Hydration Using THEED

In this paper, the strength development of a pure steel slag (SS) system with various concentrations of N,N,N',N'-Tetrakis-(2-hydroxyethyl) ethylenediamine (THEED) was investigated. The hydration kinetics, pore structure and microstructure of SS pastes with and without THEED were characterized to underscore the working mechanism of THEED. Results show that THEED additions significantly increase the 3, 7 and 28 days compressive strength of hardened SS pastes. The enhancement effect increases with the dosage of THEED. At a concentration of 2000 ppm, THEED increased the compressive strength by 733%, 665%, and 545% at 3, 7 and 28 days, respectively. It is confirmed that THEED additions improve the hydration degree of SS by accelerating hydration of the aluminum phase (C3A, PDF-38-1429; C12A7, PDF-48-1882) and C2F,( PDF 38-0408) to generate Mc (PDF-41-0219) and Pa (PDF-30-0222) in the presence of CaCO3. Also, the hydration degree of silicates is increased by THEED. In this way, THEED additions refine the pore structure of hardened SS paste by increasing the pore volume with a diameter below 300 nm to achieve enhancement. The chelating effect of THEED results in promoting dissolution of SS, which provides the driving force for accelerating SS hydration.

Improvements in Air Quality and Health Outcomes Among California Medicaid Enrollees Due to Goods Movement Actions

INTRODUCTION

In 2006, the California Air Resources Board (CARB) and local air quality management districts implemented an Emission Reduction Plan for Ports and Goods Movement program (referred to hereinafter as GM policy actions) (CARB 2006). The GM policy actions comprise approximately 200 actions with an estimated investment value of $6 to $10 billion. These actions targeted the major sources and polluters related to goods movements, such as highways; ports and railyard trucks; ship fuel and shore power; cargo equipment; and locomotives. These actions aimed to reduce total statewide domestic GM emissions to 2001 levels or lower by the year 2010; to reduce the statewide diesel particulate matter (DPM) health risk from GM by 85% by the year 2020; and to reduce the nitrogen oxides (NOx) emissions from international GM in the South Coast Air Basin by 30% from projected 2015 levels and 50% from projected 2020 levels. The years 2006 and 2007 marked an important milestone in starting to regulate GM polluters and adopting stricter standards for traffic-related air pollution.

This project aimed to examine the impact of the GM policy actions on reductions in ambient air pollution and subsequent improvements in health outcomes of Medi-Cal fee-for-service (FFS) beneficiaries with chronic conditions in 10 counties in California. Specifically, we examined whether the GM policy actions reduced air pollution near GMC corridors more than in control areas. We subsequently assessed whether there were greater decreases in emergency room (ER) visits and hospitalizations for enrollees with chronic conditions who lived in the GM corridors (GMCs) than for those who lived in other areas.

METHODS

The study used a quasi-experimental design. We defined areas within 500 m of truck-permitted freeways and ports as GMCs. We further defined non-goods movement corridors (NGMCs) as locations within 500 m of truck-prohibited freeways or 300 m of a connecting roadway, and areas out of GMCs and NGMCs as controls (CTRLs). We defined years 2004-2007 as the pre-policy period and years 2008-2010 as the post-policy period. We developed linear mixed-effects land use regression models and created annual air pollution surfaces for nitrogen dioxide (NO2), fine particulate matter (PM2.5), and ozone (O3) across California for years 2004-2010 at a spatial resolution of 30 m, then assigned them to enrollees' home addresses.

We used a retrospective cohort of 23,000 California Medicaid (Medi-Cal) FFS adult beneficiaries living in 10 California counties with six years of data (September 1, 2004, to August 31, 2010). Cohort beneficiaries had at least one of four chronic conditions, including asthma, chronic obstructive pulmonary disease (COPD), diabetes, and heart disease.

We used a difference-in-differences (DiD) model to assess whether air pollutant concentration and health care utilization (ER visits and hospitalizations) for cohort beneficiaries declined more for those living in intervention corridors (GMCs, NGMCs) than those living in CTRLs. All the models controlled for age, sex, language spoken, race/ethnicity, number of comorbidities in baseline years, county, time-varying health indicator variables, and several neighborhood variables.

To facilitate interpretation, we calculated the DiD estimates in each of the three years after the policy intervention. The DiD was used to assess the causal impact of regulatory policy on reductions of air pollution, as well as for the improvements in health outcomes.

We explored whether improvements in health outcomes were due to the air pollution reduction by using a multi- level mediation model, in which the effect of GM actions on health outcomes was mediated through the effect of actual air pollution reductions in the post-policy years. We used the Generalized Structural Equation Models for the estimation and combined the effects of NO2 and PM2.5 in the model. To further verify the causal inferences of the GM actions on reductions of exposures and improvements in health outcomes, we performed sensitivity analyses with propensity score weighting.

RESULTS

We observed statistically significant reductions in pollutant NO2 and PM2.5 concentrations for enrollees in all 10 counties. The enrollees in GMCs experienced greater reductions in NO2 and PM2.5 from the pre- to the post-policy periods than those in CTRLs. Greater reductions were also observed among beneficiaries living in NGMCs versus those in CTRLs, but those reductions were smaller than among beneficiaries living in GMCs. For O3 concentrations, an opposite trend was observed.

Furthermore, we observed significantly greater reductions in ER visits for patients with asthma and COPD living in GMCs than those in CTRLS in the post-policy years. For example, we saw in the DiD modeling results there were 170 fewer ER visits for 1,000 beneficiaries with asthma per year in GMCs if the regionwide trend in the CTRL group was considered not related to the GM policy. Similarly, among the beneficiaries with COPD, there were 180 fewer ER visits per 1,000 patients estimated in the GMCs for the third year after the implementation of the policy.

We also observed greater reductions in ER visits among those with asthma, when comparing NGMCs with CTRLs, but reductions were smaller than comparisons between GMCs and CTRLs. The ER visits for those with COPD, diabetes, and the total sample in NGMCs also had downward trends in the post-policy year in comparison with those in CTRLs but the differences were not statistically significant; similar phenomena were also observed for the ER visits among those with diabetes and heart diseases and in the total sample when GMCs versus CTRLs and GMCs versus NGMCs were compared. Although hospitalizations also decreased more in GMCs than in NGMCs and more in NGMCs than in CTRLs in the post-policy period, results were not statistically significant.

Using the mediation models, we observed 0.129 more reductions in the expected number of ER visits among individuals with asthma for a composite reduction in one unit NO2 and one unit PM2.5 (DiD = -0.129, P < 0.05) from the pre-policy years to the post-policy years. The reductions in NO2 and PM2.5 due to policy change estimated by the mediation model are essentially the same as shown in the respective DiD models. Mediation analyses suggested that the effects of GM policy interventions on health improvements were largely due to exposure reductions. Finally, sensitivity analyses with propensity scores produced similar DiD results.

CONCLUSIONS

This project has produced empirical evidence that air pollution control actions reduced pollution exposures among disadvantaged and susceptible populations. More importantly, our findings suggest that the reductions in air pollution led to health outcome improvements among low-income people with chronic conditions. Our investigation also contributed to scientific methods for assessing the health effects of long-term, large-scale, and complex regulatory actions with routinely collected pollutants and medical claims data. Therefore, the results strongly support both short-term and long-term efforts to improve air quality for all members of society and future studies on the impact of air pollution control policies.

IL6 derived from cancer-associated fibroblasts promotes chemoresistance via CXCR7 in esophageal squamous cell carcinoma

Various factors and cellular components in the tumor microenvironment are key drivers associated with drug resistance in many cancers. Here, we analyzed the factors and molecular mechanisms involved in chemoresistance in patients with esophageal squamous cell carcinoma (ESCC). We found that interleukin 6 (IL6) derived mainly from cancer-associated fibroblasts played the most important role in chemoresistance by upregulating C-X-C motif chemokine receptor 7 (CXCR7) expression through signal transducer and activator of transcription 3/nuclear factor-κB pathway. CXCR7 knockdown resulted in the inhibition of IL6-induced proliferation and chemoresistance. In addition, CXCR7 silencing significantly decreased gene expression associated with stemness, chemoresistance and epithelial-mesenchymal transition and suppressed the proliferation ability of ESCC cells in three-dimensional culture systems and angiogenesis assay. In clinical samples, ESCC patients with high expression of CXCR7 and IL6 presented a significantly worse overall survival and progression-free survival upon receiving cisplatin after operation. These results suggest that the IL6-CXCR7 axis may provide a promising target for the treatment of ESCC.

Portobiliary fistula following laparoscopic cholecystectomy

The laparoscopic approach has replaced open surgery as the gold standard for cholecystectomy. This technique is, however, associated with a greater incidence of bile duct injuries (BDIs). We report a case of portobiliary fistula (PBF), a rare complication of BDI, occurring post laparoscopic cholecystectomy (LC). PBF has been reported after procedures such as endoscopic retrograde cholangiopancreatography and pathologies such as liver abscesses, but only once previously in the setting of LC. We discuss the management of this patient with apparent dual pathology, and summarise other aetiologies that may give rise to this condition.

Triple assessment is not necessary in most young women referred with breast symptoms

INTRODUCTION

A palpable lesion in the breast is usually subjected to triple assessment (clinical examination [CE], imaging and core biopsy [CB] or fine needle aspiration [FNA]) to minimise the risk of missing breast cancer. However, breast cancer is rare in young women, and triple assessment (especially CB) is invasive and expensive. Our aim was to see whether CB/FNA could be avoided in young women with benign findings on CE and imaging.

METHODS

This study analysed data from a prospectively entered database on female patients aged under 25 years who attended a rapid diagnosis breast clinic over a 68-month period.

RESULTS

Among 10,301 patients seen, 955 females (9.3%) were aged <25 years. The most common presenting complaint was a lump, followed by pain and nipple discharge. CE was normal or revealed benign findings in all except 15 patients, in whom it was indeterminate. Ultrasonography was performed in 692 patients (72%) and was normal (n=289) or benign (n=382) in all except 21 patients, in whom it was indeterminate. In six patients, both were indeterminate. A total of 317 patients (35%) had triple assessment: FNA in 106, CB in 239 and both in 9 cases. No cancers were diagnosed.

CONCLUSIONS

It would appear safe to omit FNA/CB in patients aged under 25 years when clinical and ultrasonography findings are normal or benign. This approach would have avoided needle biopsies in all but 30 patients (3%) in the study.

Efficacy and safety of canagliflozin over 52 weeks in patients with type 2 diabetes mellitus and chronic kidney disease

AIM

This study evaluated the efficacy and safety of canagliflozin, a sodium glucose co-transporter 2 inhibitor, in patients with type 2 diabetes mellitus (T2DM) and within a subset of Stage 3 chronic kidney disease (CKD; estimated glomerular filtration rate [eGFR] ≥ 30 and <50 ml/min/1.73 m(2)).

METHODS

In this 52-week, randomized, double-blind, placebo-controlled study, patients (N = 269; mean eGFR, 39.4 ml/min/1.73 m(2)) received canagliflozin 100 or 300 mg and placebo once daily. Efficacy endpoints included changes in glycated haemoglobin (HbA1c), fasting plasma glucose (FPG), body weight and systolic blood pressure (BP); adverse events (AEs) were also recorded.

RESULTS

At week 52, canagliflozin 100 and 300 mg reduced HbA1c compared with placebo (-0.19, -0.33 and 0.07%, respectively); placebo-subtracted differences (95% confidence interval) were -0.27% (-0.53, 0.001) and -0.41% (-0.68, -0.14). Canagliflozin also lowered FPG, body weight and BP versus placebo. Overall AE incidence was 85.6, 80.9, and 86.7% with canagliflozin 100 and 300 mg and placebo, respectively. Osmotic diuresis-related AEs were more common with both canagliflozin doses, and incidences of urinary tract infections and volume depletion-related AEs were higher with canagliflozin 300 mg versus placebo. Decreases in eGFR (-2.1, -4.0 and -1.6 ml/min/1.73 m(2)) were seen with canagliflozin 100 and 300 mg compared with placebo. Canagliflozin 100 and 300 mg provided median percent reductions in urine albumin to creatinine ratio versus placebo (-16.4, -28.0 and 19.7%).

CONCLUSIONS

Canagliflozin improved glycaemic control and was generally well tolerated in patients with T2DM and within a subset of Stage 3 CKD over 52 weeks.

Prognostic value of magnetic resonance imaging-detected cranial nerve invasion in nasopharyngeal carcinoma

Background:

We previously reported that magnetic resonance imaging evidence of cranial nerve invasion was an unfavourable prognostic factor in nasopharyngeal carcinoma. However, the prognostic value of this evidence in nasopharyngeal carcinoma treated with intensity-modulated radiotherapy remains unknown.

Methods:

We retrospectively analysed 749 nasopharyngeal carcinoma patients who underwent intensity-modulated radiotherapy.

Results:

Cranial nerve invasion was observed in 299 (39.9%) patients with T3–4 disease. In T3–4 nasopharyngeal carcinoma, magnetic resonance imaging-detected cranial nerve invasion was associated with inferior 5-year overall survival, distant metastasis-free survival, and locoregional relapse-free survival (P=0.002, 0.003, and 0.012, respectively). Multivariate analyses confirmed that cranial nerve invasion was an independent prognostic factor for distant metastasis-free survival (hazard ratio, 1.927; P=0.019) and locoregional relapse-free survival (hazard ratio, 2.605; P=0.032). Furthermore, the receiver-operating characteristic curves verified that the predictive validity of T classifications was significantly improved when combined with magnetic resonance imaging-detected cranial nerve invasion in terms of death, distant metastasis, and locoregional recurrence (P=0.015, 0.021 and 0.008, respectively).

Conclusions:

Magnetic resonance imaging-detected cranial nerve invasion is an independent adverse prognostic factor in nasopharyngeal carcinoma treated with intensity-modulated radiotherapy.

Efficacy and safety of canagliflozin in subjects with type 2 diabetes and chronic kidney disease

AIMS

Canagliflozin is a sodium glucose co-transporter 2 inhibitor in development for treatment of type 2 diabetes mellitus (T2DM). This study evaluated the efficacy and safety of canagliflozin in subjects with T2DM and stage 3 chronic kidney disease [CKD; estimated glomerular filtration rate (eGFR) ≥30 and <50 ml/min/1.73 m(2)].

METHODS

In this randomized, double-blind, placebo-controlled, phase 3 trial, subjects (N = 269) received canagliflozin 100 or 300 mg or placebo daily. The primary efficacy endpoint was change from baseline in HbA1c at week 26. Prespecified secondary endpoints were change in fasting plasma glucose (FPG) and proportion of subjects reaching HbA1c <7.0%. Safety was assessed based on adverse event (AE) reports; renal safety parameters (e.g. eGFR, blood urea nitrogen and albumin/creatinine ratio) were also evaluated.

RESULTS

Both canagliflozin 100 and 300 mg reduced HbA1c from baseline compared with placebo at week 26 (-0.33, -0.44 and -0.03%; p < 0.05). Numerical reductions in FPG and higher proportions of subjects reaching HbA1c < 7.0% were observed with canagliflozin 100 and 300 mg versus placebo (27.3, 32.6 and 17.2%). Overall AE rates were similar for canagliflozin 100 and 300 mg and placebo (78.9, 74.2 and 74.4%). Slightly higher rates of urinary tract infections and AEs related to osmotic diuresis and reduced intravascular volume were observed with canagliflozin 300 mg compared with other groups. Transient changes in renal function parameters that trended towards baseline over 26 weeks were observed with canagliflozin.

CONCLUSION

Canagliflozin improved glycaemic control and was generally well tolerated in subjects with T2DM and Stage 3 CKD.

Attenuation of massive cytokine response to the staphylococcal enterotoxin B superantigen by the innate immunomodulatory protein lactoferrin

Staphylococcal enterotoxin B (SEB) is a pyrogenic exotoxin and a potent superantigen which causes massive T cell activation and cytokine secretion, leading to profound immunosuppression and morbidity. The inhibition of SEB-induced responses is thus considered a goal in the management of certain types of staphylococcal infections. Lactoferrin (LF) is a multi-functional glycoprotein with both bacteriostatic and bactericidal activities. In addition, LF is known to have potent immunomodulatory properties. Given the anti-microbial and anti-inflammatory properties of this protein, we hypothesized that LF can modulate T cell responses to SEB. Here, we report that bovine LF (bLF) was indeed able to attenuate SEB-induced proliferation, interleukin-2 production and CD25 expression by human leucocyte antigen (HLA)-DR4 transgenic mouse T cells. This inhibition was not due to bLF's iron-binding capacity, and could be mimicked by the bLF-derived peptide lactoferricin. Cytokine secretion by an engineered SEB-responsive human Jurkat T cell line and by peripheral blood mononuclear cells from healthy donors was also inhibited by bLF. These findings reveal a previously unrecognized property of LF in modulation of SEB-triggered immune activation and suggest a therapeutic potential for this naturally occurring protein during toxic shock syndrome.

Strong family history predicts a younger age of onset for subjects diagnosed with type 2 diabetes

AIMS

Age of onset of type 2 diabetes is becoming earlier and with it there is an increase in the development of chronic complications. This study examined the relationship between the strength of family history of diabetes on (i) age of diabetes onset and (ii) prevalence of diabetic complications.

RESEARCH DESIGN AND METHODS

Data on family history of diabetes and age of diabetes onset were prospectively collected on 5193 subjects. Family members were deemed to include grandparents, parents, siblings, aunts/uncles and children. To adjust for family size and to assess effects of pathway to diagnosis, we also contacted a subset of 180 patients selected on the basis of the strength of family histories of diabetes. A full assessment for diabetic complications including retinopathy, neuropathy and renal and macrovascular status was performed for the total cohort.

RESULTS

The more cases of diabetes found in a family, the younger the age of onset of type 2 diabetes. This phenomenon does not appear to be due to patients with strong family history of diabetes being more concerned about the possibility of having diabetes. The effect of strong family history is also evident in many ethnic groups when examined individually, although they differ from each other in their characteristic age of onset of diabetes. Once adjusted for duration of diabetes, strength of family history does not appear to affect metabolic profiles or prevalence of chronic complications.

CONCLUSIONS

There is a strong relationship between the number of affected family members with diabetes and age of developing diabetes. The genetic and environmental factors underlying this phenomenon remain to be elucidated. However, it may be one of the reasons explaining why type 2 diabetes is affecting younger people worldwide.

Clustering of cardiovascular risk factors with diabetes in Chinese patients: the effects of sex and hyperinsulinaemia

OBJECTIVE

This study was designed to investigate factors which affect the clustering of cardiovascular risk factors with diabetes in Chinese patients.

RESEARCH DESIGN AND METHODS

Six hundred and fifty-four patients with diabetes were assessed comprehensively for diabetes complications and cardiovascular risk factors in a metropolitan hospital in Beijing, China. Insulin resistance and secretion were also evaluated by measurement of glucose and insulin levels before and after a meal tolerance test. Results were analysed according to patient groups stratified by the number of cardiovascular risk factors coexisting with diabetes.

RESULTS

Cardiovascular risk factors were common in Chinese diabetic patients. The clustering of three or more of these factors with diabetes occurred more often than by chance alone and was associated with postprandial hyperinsulinaemia. Patients with a high number of risk factors were more prone to macrovascular events but did not have higher albuminuria. Using the commonly adopted lower threshold for diagnosing obesity and central obesity in women, there were more women with multiple risk factors. However, this disappeared if the same criteria were used for men and women. Even in the presence of diabetes, cardiovascular risk factors were inadequately controlled in most patients.

CONCLUSIONS

The concurrence of diabetes and other cardiovascular risk factors which constitute the metabolic syndrome is a common phenomenon in urban Chinese diabetic patients. It is associated with hyperinsulinaemia and possibly the female sex. This study emphasises the importance of public health measures to control cardiovascular risk factors in patients with diabetes.

Synthetase recognition determinants of E. coli valine transfer RNA

We have studied the interactions between Escherichia coli tRNAVal and valyl-tRNA synthetase (ValRS) by enzymatic footprinting with nuclease S1 and ribonuclease V1, and by analysis of the aminoacylation kinetics of mutant tRNAVal transcripts. Valyl-tRNA synthetase specifically protects the anticodon loop, the 3' side of the stacked T-stem/acceptor-stem helix, and the 5' side of the anticodon stem of tRNAVal against cleavage by double- and single-strand-specific nucleases. Increased nuclease susceptibility at the ends of the anticodon- and T-stems in the tRNAVal.ValRS complex is indicative of enzyme-induced conformational changes in the tRNA. The most important synthetase recognition determinants are the middle and 3' anticodon nucleotides (A35 and C36, respectively); G20, in the variable pocket, and G45, in the tRNA central core, are minor recognition elements. The discriminator base, position 73, and the anticodon stem also are recognized by ValRS. Replacing wild-type A73 with G73 reduces the aminoacylation efficiency more than 40-fold. However, the C73 and U73 mutants remain good substrates for ValRS, suggesting that guanosine at position 73 acts as a negative determinant. The amino acid acceptor arm of tRNAVal contains no other synthetase recognition nucleotides, but regular A-type RNA helix geometry in the acceptor stem is essential [Liu, M., et al. (1997) Nucleic Acids Res. 25, 4883-4890]. In the anticodon stem, converting the U29:A41 base pair to C29:G41 reduces the aminoacylation efficiency 50-fold. This is apparently due to the rigidity of the anticodon stem caused by the presence of five consecutive C:G base pairs, since the A29:U41 mutant is readily aminoacylated. Identity switch experiments provide additional evidence for a role of the anticodon stem in synthetase recognition. The valine recognition determinants, A35, C36, A73, G20, G45, and a regular A-RNA acceptor helix are insufficient to transform E. coli tRNAPhe into an effective valine acceptor. Replacing the anticodon stem of tRNAPhe with that of tRNAVal, however, converts the tRNA into a good substrate for ValRS. These experiments confirm G45 as a minor ValRS recognition element.

A new psychotherapy training program : description and preliminary results

Psychotherapy training programs require a uniform introduction to psychotherapy that presents the basic, generic concepts common to the major schools in a time-efficient manner. The program described in this article fits these criteria. The program has been initiated at seven residency training programs in the United States. The authors describe the six modules comprising the program-verbal response modes and intentions, working alliance, inducing patterns, change, resistance, and transference and countertransference. The authors also report preliminary results of the program evaluation (N = 15) from the University of Missouri-Columbia. By using a well-researched measure of trainee self-confidence as psychotherapist (The Counselor Self-Estimate Inventory), the authors report a statistically significant increase in trainee self-confidence beginning and maintained after Module 4. The authors conclude that this training shows promise as a standard introduction to psychotherapy for psychiatric residents.

Diabetic retinopathy and nephropathy in Fiji: comparison with data from an Australian diabetes centre

BACKGROUND

As part of a project to improve diabetes care in Fiji, we assessed the magnitude of problems posed by diabetic retinopathy in that country and compared the findings with those from an Australian diabetes centre. The relationship between diabetic retinopathy and nephropathy was also examined in a subset of patients.

METHODS

A medical team from Australia screened a total of 446 type 2 diabetic patients (ethnicity: Fijian/Indian 16/84%) for diabetic retinopathy in five towns from the Division of Viti Levu, Fiji. The findings were compared with data obtained from 1659 type 2 diabetic patients who had attended an Australian diabetes centre (ethnicity Indian/ Anglo-Celtic 12/88%). In both cohorts, retinopathy was assessed by direct fundoscopy and a spot urine sample was collected for determination of albuminuria (defined as a concentration > 50 mg/L).

RESULTS

The prevalence of diabetic retinopathy increased linearly with duration of diabetes. It was higher in Fiji, even when cases from the same ethnicity (i.e. Indians) and duration were compared (P < 0.05). Extrapolation of the data points suggests a delay in the diagnosis of diabetes in Fiji. Of those patients with retinopathy in Fiji, more than half had moderate to severe non-proliferative diabetic retinopathy or proliferative diabetic retinopathy, significantly higher than patients in the Australian cohort (chi2 = 29.2; P < 0.0001). Retinopathy was not a predictor of albuminuria in Fijian Indians (chi2 = 0.4; P = 0.5). In contrast, Australian Indians with retinopathy had significantly more albuminuria (chi2 = 10.2; P = 0.001).

CONCLUSIONS

Severe diabetic retinopathy is common in both ethnic groups in Fiji. A delay in the diagnosis of diabetes as well as poor glycaemic control are possible factors. The availability of laser therapy is important to prevent loss of vision, but it is also essential that appropriate training of health professionals is integrated with a programme of diabetic complication screening to support this form of therapy.

The CCA-adding enzyme has a single active site

The CCA-adding enzyme (tRNA nucleotidyltransferase) synthesizes and repairs the 3'-terminal CCA sequence of tRNA. The eubacterial, eukaryotic, and archaeal CCA-adding enzymes all share a single active-site signature motif, which identifies these enzymes as belonging to the nucleotidyltransferase superfamily. Here we show that mutations at Asp-53 or Asp-55 of the Sulfolobus shibatae signature sequence abolish addition of both C and A, demonstrating that a single active site is responsible for addition of both nucleotides. Mutations at Asp-106 (and to a lesser extent, at Glu-173 and Asp-215) selectively impaired addition of A, but not C. We have previously demonstrated that the tRNA acceptor stem remains fixed on the surface of the CCA-adding enzyme during C and A addition (Shi, P.-Y., Maizels, N., and Weiner, A. M. (1998) EMBO J. 17, 3197-3206). Taken together with this new evidence that there is a single active site for catalysis, our data suggest that specificity of nucleotide addition is determined by a process of collaborative templating: as the single active site catalyzes addition of each nucleotide, the growing 3'-end of the tRNA would progressively refold to create a binding pocket for addition of the next nucleotide.

Identification of candidate target genes for EVI-1, a zinc finger oncoprotein, using a novel selection strategy

We have sought to identify and isolate target genes for the zinc finger protein, EVI-1, which has been implicated in the genesis of myelogenous leukemia both in mouse and human. We have approached this with a two-step selection: we first selected for genomic fragments of mouse DNA that bind to the protein with high affinity; second, we employed cDNA hybrid selection to identify gene sequences contained within these fragments. We show that we have constructed a sublibrary of genomic fragments that contains a significant fraction of the EVI-1-binding sites in the mouse genome. Our data has allowed us to estimate that there are approximately 4300 binding sites per haploid genome in the mouse. We further demonstrate that by using cDNA hybrid selection, it is relatively straightforward to isolate cDNAs that correspond to genes embedded in the EVI-1-binding sublibrary. Several of these are novel, but are represented in databases of anonymous human or mouse cDNAs (expressed sequence tags). One selected gene is Itpr2, encoding the inositol trisphosphate type two receptor, which is transcriptionally regulated during myelopoiesis. Finally, using a chimeric EVI-1-VP16-fusion protein under the control of a tetracycline-regulated system, we have shown that this chimeric activator can directly regulate Itpr2.

Changes of extracellular matrix in a baboon (Papio hamadryas) model of insulin dependent diabetes: studies using electron microscopy and X-ray diffraction techniques

Extracellular matrix plays an important role in many physiological functions and its abnormalities are thought to play a key role in the pathogenesis of diabetic complications. In this paper we used the techniques of electron microscopy, immunostaining and X-ray diffraction to document some of the early events in the changes of extracellular matrix in a model of insulin dependent diabetes in baboons. Our results show that thickening of basement membrane and enlargement of mesangium are demonstrable in the glomeruli of prepubertal diabetic baboons within 2 years from the onset of diabetes. Concomitant with this was the accumulation of type IV collagen and laminin in the mesangium. By contrast, even the very sensitive technique of X-ray diffraction failed to demonstrate changes in the equatorial direction of collagen molecules of the skin and tendon. We conclude that changes of glomerular extracellular matrix are demonstrable early in insulin dependent diabetes even in prepubertal baboons. These can be used as endpoints in evaluating the efficacy of pharmacological agents such as aminoguanidine in preventing diabetic complications.

CCA-adding enzymes and poly(A) polymerases are all members of the same nucleotidyltransferase superfamily: characterization of the CCA-adding enzyme from the archaeal hyperthermophile Sulfolobus shibatae

We describe the purification, cloning, and characterization of the CCA-adding enzyme [ATP(CTP):tRNA nucleotidyl transferase] from the thermophilic archaebacterium, Sulfolobus shibatae. Characterization of an archaeal CCA-adding enzyme provides formal proof that the CCA-adding activity is present in all three contemporary kingdoms. Antibodies raised against recombinant, expressed Sulfolobus CCA-adding enzyme reacted specifically with the 48-kDa protein and fully depleted all CCA-adding activity from S. shibatae crude extract. Thus, the cloned cca gene encodes the only CCA-adding activity in S. shibatae. Remarkably, the archaeal CCA-adding enzyme exhibits no strong homology to either the eubacterial or eukaryotic CCA-adding enzymes. Nonetheless, it does possess the active site signature G[SG][LIVMFY]xR[GQ]x5,6D[LIVM][CLIVMFY]3-5 of the nucleotidyltransferase superfamily identified by Holm and Sander (1995, Trends Biochem Sci 20:345-347) and sequence comparisons show that all known CCA-adding enzymes and poly(A) polymerases are contained within this superfamily. Moreover, we propose that the superfamily can now be divided into two (and possibly three) subfamilies: class I, which contains the archaeal CCA-adding enzyme, eukaryotic poly(A) polymerases, and DNA polymerase beta; class II, which contains eubacterial and eukaryotic CCA-adding enzymes, and eubacterial poly(A) polymerases; and possibly a third class containing eubacterial polynucleotide phosphorylases. One implication of these data is that there may have been intraconversion of CCA-adding and poly(A) polymerase activities early in evolution.

[Experimental steroid osteonecrosis in rabbits and pathologic findings]

Osteonecrosis of femoral head was experimentally induced in adult rabbits by employing a combined protocol of hypersensitive vasculitis and administration of high dose corticosteroids. By using India ink introartery infusion microangiography and pathologic examination, we found that the damage of terminal arterioles and interruption of blood supply of terminal arteriole was causative pathogenesis. In the early phase, the haemopoietic necrosis and enlargement of fat cell in the bone marrow occurred. The perfused arterioles decreased, especially in the subchondrol bone. In the later phase, the osteocytes showed necrotic fibrosis in bone marrow. The perfused arterioles increased gradually and repairtive changes began.

A baboon (Papio hamadryas) model of insulin-dependent diabetes

Over a period of four years, streptozocin has been used to induce diabetes in 10 baboons, all of whom are insulin dependent. We describe our experience with their husbandry, induction of diabetes, insulin therapy, metabolic control and growth rate. Streptozocin dosage of 60 mg/kg readily induces hyperglycemia with minimal hepatic or renal toxicity. Using a once daily injection of mixed short and intermediate acting insulins at a dosage of 2-4 U/kg, it is possible to maintain a degree of metabolic control similar to that attained in patients.

Nucleoside modifications stabilize Mg2+ binding in Escherichia coli tRNA(Val): an imino proton NMR investigation

The structures of in vitro transcribed Escherichia coli tRNA(Val), which lacks base modifications, and the native tRNA, which contains them, are very similar in the presence of excess Mg2+ (Kintanar, Yue, and Horowitz, unpublished results). To further probe the effects of base modifications on the structure of tRNA, the Mg2+ ion dependence of the downfield region of the 1H NMR spectrum of in vitro transcribed E. coli tRNA(Val) in aqueous phosphate buffer was investigated. The spectra indicate a remarkable conformational change in unmodified E. coli tRNA(Val) coincident with binding or release of Mg2+. Assignment of the imino proton resonances in the low Mg2+ form of the tRNA transcript allows a detailed description of the conformational change. There is near total disruption of the D stem and tertiary interactions in the absence of bound Mg2+. A new strong interaction between the U67-A6 base pair and the G50-U64 wobble pair is observed, indicating a substantial structural rearrangement at the junction of the acceptor and T stems. The binding constants of the strong Mg2+ binding sites in the D loop and near the D stem in unmodified tRNA(Val) are at least 2 orders of magnitude less than in tRNAVal containing base modifications. The metal ion binding site in the anticodon loop is somewhat stronger than metal ion binding sites in the D loop and stem in unmodified tRNA(Val), but it is still weaker than all strong Mg2+ binding sites in native tRNA(Val). Thus, one role of the base modifications found in tRNA is to stabilize or strengthen the Mg2+ binding sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of nucleoside modifications on the structure and thermal stability of Escherichia coli valine tRNA

Transfer RNA transcribed in vitro lacks the base modifications found in native tRNA. To understand the effect of base modifications on the structure of tRNA, the downfield region of the 1H NMR spectrum of in vitro transcribed E coli tRNAVal in aqueous phosphate buffer in the presence of excess Mg2+ was investigated. The resonances of all imino protons involved in hydrogen bonds in the helical stem regions and in tertiary interactions were assigned using two-dimensional nuclear Overhauser enhancement spectroscopy (NOESY) and one-dimensional difference nuclear Overhauser effect (NOE) methods. In addition, some aromatic C2 and C8 proton resonances as well as one amino proton resonance were assigned. The chemical shifts of the assigned resonances of unmodified E coli tRNAVal were compared with those of the native tRNA molecule under similar solution conditions. The similarity of the NMR data for unmodified and modified tRNA indicates that the in vitro transcribed tRNA has nearly the same solution structure as the native molecule in the presence of excess Mg2+. The only significant differences were the chemical shifts of resonances corresponding to protons in (or interacting with) bases, indicating the possibility of local structural perturbations. The thermal stability of E coli modified and unmodified tRNAVal in the presence of Mg2+ was also investigated by analyzing the temperature dependence of the imino proton spectra. Several tertiary interactions involving modified nucleosides in native E coli tRNAVal are less stable in the absence of base modifications.