Probing the (H3-H4)(2) histone tetramer structure using pulsed EPR spectroscopy combined with site-directed spin labelling

The (H3-H4)2 histone tetramer forms the central core of nucleosomes and, as such, plays a prominent role in assembly, disassembly and positioning of nucleosomes. Despite its fundamental role in chromatin, the tetramer has received little structural investigation. Here, through the use of pulsed electron-electron double resonance spectroscopy coupled with site-directed spin labelling, we survey the structure of the tetramer in solution. We find that tetramer is structurally more heterogeneous on its own than when sequestered in the octamer or nucleosome. In particular, while the central region including the H3-H3′ interface retains a structure similar to that observed in nucleosomes, other regions such as the H3 αN helix display increased structural heterogeneity. Flexibility of the H3 αN helix in the free tetramer also illustrates the potential for post-translational modifications to alter the structure of this region and mediate interactions with histone chaperones. The approach described here promises to prove a powerful system for investigating the structure of additional assemblies of histones with other important factors in chromatin assembly/fluidity

Significance of chromosome 9p status in renal cell carcinoma:a systematic review and quality of the reported studies

Defining the prognosis of renal cell carcinoma (RCC) using genetic tests is an evolving area. The prognostic significance of 9p status in RCC, although described in the literature, remains underutilised in clinical practice. The study explored the causes of this translational gap. A systematic review on the significance of 9p status in RCC was performed to assess its clinical applicability and impact on clinical decision-making. Medline, Embase, and other electronic searches were made for studies reporting on 9p status in RCC. We collected data on: genetic techniques, pathological parameters, clinical outcomes, and completeness of follow-up assessment. Eleven studies reporting on 1,431 patients using different genetic techniques were included. The most commonly used genetic technique for the assessment of 9p status in RCC was fluorescence in situ hybridization. Combined genomic hybridisation (CGH), microsatellite analysis, karyotyping, and sequencing were other reported techniques. Various thresholds and cut-off values were used for the diagnosis of 9p deletion in different studies. Standardization, interobserver agreement, and consensus on the interpretation of test remained poor. The studies lacked validation and had high risk of bias and poor clinical applicability as assessed by two independent reviewers using a modified quality assessment tool. Further protocol driven studies with standardised methodology including use of appropriate positive and negative controls, assessment of interobserver variations, and evidenced based follow-up protocols are needed to clarify the role of 9p status in predicting oncological outcomes in renal cell cancer

Effect of high fat and nutrient depleted diets on colon tumor formation in mice.

We investigated the effect of high fat and nutrient depleted diets on the formation of colon tumors in female Swiss mice treated with 1,2- dimethylhydrazine (DMH). Mice received the following diets: control diet (laboratory chow, 5.5% fat) or chow with added starch and/or corn oil so as to supply a fat level of 5.5% (diet F6) or 23% (diet F23), while reducing the level of nutrients and dietary fiber per. 100 calories to 61% of the level of the control diet. DMH was given as 5 weekly s.c. injections. Diets were given variously from 6 weeks before the first injection until 7 days after the last one (initiation period) or else for the subsequent 22 weeks until sacrifice of the mice (promotion period). A high fat diet (diet F23 vs. F6) tended to increase adenoma formation when fed during the initiation period but this requires further study. Feeding it in the promotion period increased the incidence of adenocarcinomas. A nutrient depleted diet (diet F6 vs. the control diet) caused a decreased incidence of adenocarcinomas

Cabbage and vitamin E: their effect on colon tumor formation in mice.

The effects of cabbage and vitamin E on colon carcinogenesis were investigated in Swiss mice treated with 1,2-dimethylhydrazine. Throughout the experiment the mice were fed a laboratory chow diet (46 mg vitamin E per kg) or chow containing 13 g cabbage per 100 g or 180 mg vitamin E per kg. Starting after 31 days of diet treatment the mice received 7 weekly s.c. injections of DMH. They were sacrificed 17 weeks after the first dose of DMH. While diet did not significantly alter colon tumor response, some trends were observed. Female mice given cabbage had a higher incidence. (percent of mice with a tumor) and multiplicity (tumors per tumor bearing mouse) of colon tumors. Males were little affected by cabbage apart from a lower incidence of adenocarcinomas. Compared with mice fed the control diet those given vitamin E had a higher colon tumor incidence, This effect, which was stronger in females, was due to an increased incidence of adenomas. Vitamin E had little apparent affect on tumor multiplicity apart from a reduction in adenocarcinomas in females and adenomas in males. The data do not support the view that cabbage and vitamin E are protective against colon cancer

Toxicity of 1,2-dimethlyhydrazine in mice: effect of diet and development of tolerance

The effect of diet on the lethality of 1, 2-dimethylhydrazine (DMH) injections was investigated using Swiss mice. Mortality was highest when mice were fed a nutrient-dilutealfhigh-fat diet, was intermediate with a nutrientdilutealflow- fat diet and was lowest with laboratory chow. Wheat bran was not protective. Mice developed tolerance to DMH after receiving several injections of progressively increasing dose

The histone chaperones Nap1 and Vps75 bind histones H3 and H4 in a tetrameric conformation

Histone chaperones physically interact with histones to direct proper assembly and disassembly of nucleosomes regulating diverse nuclear processes such as DNA replication, promoter remodeling, transcription elongation, DNA damage, and histone variant exchange. Currently, the best-characterized chaperone-histone interaction is that between the ubiquitous chaperone Asf1 and a dimer of H3 and H4. Nucleosome assembly proteins (Nap proteins) represent a distinct class of histone chaperone. Using pulsed electron double resonance (PELDOR) measurements and protein crosslinking, we show that two members of this class, Nap1 and Vps75, bind histones in the tetrameric conformation also observed when they are sequestered within the nucleosome. Furthermore, H3 and H4 trapped in their tetrameric state can be used as substrates in nucleosome assembly and chaperone-mediated lysine acetylation. This alternate mode of histone interaction provides a potential means of maintaining the integrity of the histone tetramer during cycles of nucleosome reassembly

Changes in pH and levels of B-glucosidase, B-glucuronidase and reducing activity as food residue passes along the mouse colon

The contents were collected from successive regions of the colon of Swiss mice. Ana(vses show that the pH rises by about 0.55 pH units between the cecum and the distal colon. The level of p-glucuronidase falls sharply, typically 2 to 3 fold;, as food residue leaves the cecum. This is followed by a large rise in the distal c%n, mvund 1.6 to 4 fold, about half of 1vhich is due to the concentrating ejlect caused by loss of water. lvleasurements were also made of nonspecific reducing activity, the level of which rises by about 74% along the colon mainly because of water loss. For each of the above parameters similar results were observed using old and young mice and with diets high and low in fat. Studies indicated that the reducing activity is nonenzymic

High-Fat Diets and Fecal Level of Reductase and Colon Mucosal Level of Ornithine Decarboxylase, B-Glucuronidase, 5'-Nucleotidase, ATPase, and Esterase in Mice.

In one experiment Swiss mice were maintained on a 16 or 23% fat diet (laboratory chow with added fat, principally corn on) or on laboratory chow alone (5.5% fat), In another experiment CS7BU1 mice were given a 23% fat diet (as above) or a low-fat diet (67% laboratory chow. 1.9% corn oil, and 31% starch; 5.5% fat). Colon mucosal samples were analyzed for several enzyme activities. In Swiss mice the analyses revealed the following: 1) Ouabain-insensitive ATPase was unaltered in male mice, but it rose significantly in females fed a high-fat diet (this effect was seen when a resuspended high-speed pellet was analyzed but not seen with the initial homogenate); 2) S'-nucleotidase activity showed a significant stepwise increase with dietary fat; 3) nonspecific esterase activity tended to rise with a high-fat diet (not significant); 4) fJ-glucuronidase levels were not altered by diet fat; and 5) ornithine decarboxylase levels were not altered by diet fat. In CS7BU1 mice analyse:;, were done on ouabaininsensitive ATPase, S'-nucleotidase, nonspecific esterase, and p-glucuronidase, but no diet effects were seen. Fecal reductase activity was measured with the use of 2-(p-iodophenyl)-3-(pnitrophenyl)- 5-phenyltetrazolium chloride hydrate). A high-fat diet did not affect the activity in CS7BU1 mice, but it caused a significant rise in Swiss mice

The prevalence of macrovascular complications among diabetic patients in the United Arab Emirates

<p>Abstract</p> <p>Background</p> <p>Diabetes Mellitus (DM) is a major public health problem in the UAE with a prevalence rate reaching 24% in national citizens and 17.4% in expatriates. The aim of this study was to determine the prevalence and risk factors of macrovascular complications among diabetic patients in the Al-Ain district of the United Arab Emirates (UAE).</p> <p>Methods</p> <p>The study was part of a general cross-sectional survey carried out to assess the prevalence of diabetes (DM) complications among known diabetic patients in Al-Ain District, UAE. Patients were randomly selected during 2003/2004. Patients completed an interviewer-administered questionnaire carried out by treating doctors and underwent a complete medical assessment including measurement of height, weight, blood pressure and examination for evidence of macrovascular complications. A standard ECG was recorded and blood samples were taken to document fasting blood sugar, glycosylated haemoglobin (HbA_1C) and lipid profile.</p> <p>Results</p> <p>A sample of 513 diabetic patients was selected with a mean age of 53 years (SD ± 13.01). Overall, 29.5% of DM patients had evidence of macrovascular complications: 11.6% (95% CI: 8.8–14.4) of patients had peripheral vascular disease (PVD), 14.4% (95% CI: 11.3–17.5) had a history of coronary artery disease (CAD) and 3.5% (95% CI: 1.9–5.1%) had cerebrovascular disease (CVD). Of the total population surveyed 35% (95%CI: 30.8–39) had hypertension. The analysis showed that macrovascular complications in diabetic patients were more common among males, increased with age, were more common among hypertensive patients and its prevalence increased steadily with duration of DM.</p> <p>Conclusion</p> <p>Our data revealed a significant association between hypertension and presence of macrovascular disease among diabetic patients. However, the risk of CAD in the UAE was relatively low compared to that seen in patients in other geographical settings. In addition, a lack of correlation between macrovascular disease and glycemic control among patients with DM was observed.</p