Segmental dynamics in polymers: from cold melts to ageing and stressed glasses

Recent progress in developing statistical mechanical theories of supercooled polymer melts and glasses is reviewed. The focus is on those approaches that are either explicitly formulated for polymers, or are applications of more generic theories to interpret polymeric phenomena. These include two configurational entropy theories, a percolated free volume distribution model, and the activated barrier hopping nonlinear Langevin theory. Both chemically-specific and universal aspects are discussed. After a brief summary of classic phenomenological approaches, a discussion of the relevant length scales and key experimental phenomena in both the supercooled liquid and glassy solid state is presented including ageing and nonlinear mechanical response. The central concepts that underlie the theories in the molten state are then summarized and key predictions discussed, including the glass transition in oriented polymer liquids and deformed rubber networks. Physical ageing occurs in the nonequilibrium glass, and theories for its consequences on the alpha relaxation are discussed. Very recent progress in developing a segment scale theory for the dramatic effects of external stress on polymer glasses, including acceleration of relaxation, yielding, plastic flow and strain hardening, is summarized. The article concludes with a discussion of outstanding theoretical challenges.

Meta- and pooled analyses of the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and colorectal cancer: a HuGE-GSEC review

Worldwide, over 1 million cases of colorectal cancer (CRC) were reported in 2002, with a 50% mortality rate, making CRC the second most common cancer in adults. Certain racial/ethnic populations continue to experience a disproportionate burden of CRC. A common polymorphism in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene has been associated with a lower risk of CRC. The authors performed both a meta-analysis (29 studies; 11,936 cases, 18,714 controls) and a pooled analysis (14 studies; 5,068 cases, 7,876 controls) of the C677T MTHFR polymorphism and CRC, with stratification by racial/ethnic population and behavioral risk factors. There were few studies on different racial/ethnic populations. The overall meta-analysis odds ratio for CRC for persons with the TT genotype was 0.83 (95% confidence interval (CI): 0.77, 0.90). An inverse association was observed in whites (odds ratio = 0.83, 95% CI: 0.74, 0.94) and Asians (odds ratio = 0.80, 95% CI: 0.67, 0.96) but not in Latinos or blacks. Similar results were observed for Asians, Latinos, and blacks in the pooled analysis. The inverse association between the MTHFR 677TT polymorphism and CRC was not significantly modified by smoking status or body mass index; however, it was present in regular alcohol users only. The MTHFR 677TT polymorphism seems to be associated with a reduced risk of CRC, but this may not hold true for all populations.

Association of human papillomavirus 7 with warts in toe webs

BACKGROUND

There have been no studies on the prevalence of types of human papillomavirus (HPV) in cutaneous warts that focus on warts in toe webs (WTW). There is no documented association between HPV 7 and WTW.

OBJECTIVES

To explore the clinical and histopathological features of WTW, and the distribution of HPV genotypes in patients with WTW.

METHODS

The study group consisted of 20 patients with WTW; 31 patients with typical verruca vulgaris (VV) were enrolled as the disease control group, and 53 patients with tinea pedis and 48 healthy volunteers were enrolled as the disease-negative control group. Tissue specimens were analysed for clinical and histological features and distribution of HPV genotypes. Polymerase chain reaction (PCR)-based direct sequencing, TA cloning and type-specific PCR (TS-PCR) were performed in the WTW and VV groups. Interdigital scale specimens from patients with tinea pedis and from healthy volunteers were analysed for HPV DNA by nested PCR and TS-PCR (HPV 7).

RESULTS

All the patients with WTW were male and nearly all were immunocompetent; their mean age was 41 +/- 10 years. The lesions presented mainly as soft, friable and vegetating clusters. HPV 7 was the predominant genotype in WTW with a frequency of 80% (16/20). Fourteen specimens were taken for histopathological examination. The most frequent histological results (seven out of 14) revealed characteristics of HPV 7 infections such as heavily stained cells containing medium-sized keratohyaline granules and a pronounced hyperkeratosis with parakeratosis. TA cloning showed that the sequence shared 90% or more homology with the HPV genotype in direct sequencing. No HPV 7 DNA was found in the scales taken from toe webs without warts.

CONCLUSIONS

This is the first study evaluating the prevalence of HPV types in WTW and the first report of the association between HPV 7 and specific subgroups of patients with warts.

Dietary sodium deprivation evokes activation of brain regional neurons and down-regulation of angiotensin II type 1 receptor and angiotensin-convertion enzyme mRNA expression

Previous studies have indicated that the renin-angiotensin-aldosterone system (RAAS) is implicated in the induction of sodium appetite in rats and that different dietary sodium intakes influence the mRNA expression of central and peripheral RAAS components. To determine whether dietary sodium deprivation activates regional brain neurons related to sodium appetite, and changes their gene expression of RAAS components of rats, the present study examined the c-Fos expression after chronic exposure to low sodium diet, and determined the relationship between plasma and brain angiotensin I (ANG I), angiotensin II (ANG II) and aldosterone (ALD) levels and the sodium ingestive behavior variations, as well as the effects of prolonged dietary sodium deprivation on ANG II type 1 (AT1) and ANG II type 2 (AT2) receptors and angiotensin-convertion enzyme (ACE) mRNA levels in the involved brain regions using the method of real-time polymerase chain reaction (PCR). Results showed that the Fos immunoreactivity (Fos-ir) expression in forebrain areas such as subfornical organ (SFO), paraventricular hypothalamic nuclei (PVN), supraoptic nucleus (SON) and organum vasculosum laminae terminalis (OVLT) all increased significantly and that the levels of ANG I, ANG II and ALD also increased in plasma and forebrain in rats fed with low sodium diet. In contrast, AT1, ACE mRNA in PVN, SON and OVLT decreased significantly in dietary sodium depleted rats, while AT2 mRNA expression did not change in the examined areas. These results suggest that many brain areas are activated by increased levels of plasma and/or brain ANG II and ALD, which underlies the elevated preference for hypertonic salt solution after prolonged exposure to low sodium diet, and that the regional AT1 and ACE mRNA are down-regulated after dietary sodium deprivation, which may be mediated by increased ANG II in plasma and/or brain tissue.

Lessons from the diagnosis and treatment of spontaneous vertebral arterial dissection. Case report

SUMMARY

A 36-year-old man presented a sudden left occipital headache and right limb weakness after tooth-brushing. Conventional catheter digital subtraction angiography (DSA) showed a left VA occlusion at the crotch of the posterior inferior cerebellar artery. Four days later, the patient got worse. The angiogram showed the left vertebral artery had reopened and the basilar trunk occluded above the AICA. He died two days later and autopsy demonstrated a dissection of the basilar arteries. Based on the autopsy data from the patient in this study, we suggest that the BA dissection might be due to left VA dissection, and placing a stent on the juncture between the uninjured VA and the basilar trunk might be an effective method to prevent fatal BA occlusion.

Type 2 diabetes mellitus associated with increased risk for colorectal cancer: evidence from an international ecological study and population-based risk analysis in China

OBJECTIVE

To study the association between type 2 diabetes mellitus (T2DM) and colorectal cancer (CRC).

STUDY DESIGN

An international ecological study and a population-based risk analysis.

METHODS

Prevalence data for T2DM and incidence data for CRC were collected from 170 countries, and Spearman's correlation was calculated between T2DM and CRC. In the Nan-Hu district of Jia-Xing city, Zhejiang province, China, the incidence of CRC among T2DM patients between 1 January 2002 and 30 June 2002 was identified through record linkage between the Diabetic Surveillance and Registry Database with the Cancer Surveillance and Registry Database. Standardized incidence ratios (SIRs) and 95% confidence intervals were used to estimate the risk of CRC among T2DM patients.

RESULTS

Significant positive correlations (r(s)=0.534 and 0.597 in males and females, respectively) were found between the prevalence of T2DM and the incidence of CRC. Sixty-four cases of CRC were found among 7938 T2DM patients. The SIR for CRC among T2DM patients was 1.588 (95% CI 1.199-1.977). For male T2DM patients, the SIR for CRC was 1.821 (95% CI 1.234-2.408), compared with 1.364 (95% CI 0.85-1.879) among female T2DM patients. Significant increased risks for colon cancer were found, with an SIR of 1.899 (95% CI 1.139-2.658) in male T2DM patients. Female T2DM patients showed a borderline significant risk for colon cancer, with an SIR of 1.687 (95% CI 0.948-2.426). However, no significant associations were found between T2DM and risk for rectal cancer among males (SIR 1.723, 95% CI 0.786-2.66) or females (SIR 0.906, 95% CI 0.235-1.578) (all P>0.05).

CONCLUSIONS

T2DM was associated with increased risk for CRC, and this association was more evident for colon cancer and among male diabetic patients.

A genome-wide survey on basic helix-loop-helix transcription factors in rat and mouse

The basic helix-loop-helix (bHLH) proteins play essential roles in a wide range of developmental processes in higher organisms. bHLH family members have been identified in over 20 organisms, including nematode, fruit fly, and human. Our study identified 114 rat and 14 additional mouse bHLH members in rat and mouse genomes, respectively. Phylogenetic analyses revealed that both rat and mouse had 49, 26, 15, 4, 12, and 4 bHLH members in groups A, B, C, D, E, and F, respectively. Only the rat Mxi1 gene has two copies in the genome. All other rat bHLH genes and all mouse bHLH genes are single-copy genes. The chromosomal distribution pattern of mouse, rat, and human bHLH genes suggests the emergence of some bHLH genes through gene duplication, which probably happened at least before the divergence of vertebrates from invertebrates. The present study provides useful information for future studies using rat as a model animal for mammalian development.

Renoprotective effect of rosiglitazone through the suppression of renal intercellular adhesion molecule-1 expression in streptozotocin-induced diabetic rats

OBJECTIVE

To observe the effect of rosiglitazone on serum intercellular adhesion molecule-1 (SICAM-1) level, urinary excretion of ICAM-1, and renal expression of ICAM-1, and investigate its possible renoprotective mechanisms in diabetic rats.

METHOD

Twenty-four Wistar Rats were divided into 3 groups: non-diabetic control rats (group A, no.=8), streptozotocin-induced diabetic rats (group B, no.=8), and diabetic rats treated with rosiglitazone (group C, no.=8). Rats in group C were treated with rosiglitazone (5 mg x kg(-1) x d(-1)) 1 week after the establishment of diabetic model, group A and B were treated with corresponding sodium chloride. Peripheral blood glucose was tested weekly. Glycosylated hemoglobin (HbA1c) and SICAM-1 as well as urinary albumin excretion rate (UAER), urinary retinol binding-protein (URBP) excretion rate, and urinary ICAM-1 (UICAM- 1) excretion rate were tested at the 8th week, and the renal tissues of all rats were obtained for evaluating kidney/body weight ratio, observing pathologic change via electron microscope, and for examining the expression of ICAM-1 mRNA by reverse transcriptase-PCR.

RESULTS

At the 8th week, the blood glucose, HbA1c levels, UAER, URBP excretion rate, kidney/body weight ratio and serum, urinary ICAM-1 levels all increased significantly in group B and group C in comparison with group A; however, the above-mentioned parameters in group C (except the blood glucose and HbA1c levels) were much lower than those in group B. In addition, both SICAM-1 and UICAM-1 were highly correlated with the UAER, URBP level, and kidney/body weight ratio in all rats; renal pathological lesions observed by electron microscope in group C were much lighter than those of group B; compared with group A, the expression of ICAM-1 mRNA was markedly up-regulated in group B and group C, and rosiglitazone was able to decrease the expression of ICAM-1 mRNA in the renal tissue.

CONCLUSION

Rosiglitazone could definitely protect against the renal injury of diabetic rats, which may be partly associated with decreasing the expression of ICAM-1 in the renal tissue, reducing ICAM-1 productions in both serum and urine.