Effects of missense mutations in sortase A gene on enzyme activity in Streptococcus mutans

Background

Streptococcus mutans (S. mutans) is the major aetiological agent of dental caries, and the transpeptidase Sortase A (SrtA) plays a major role in cariogenicity. The T168G and G470A missense mutations in the srtA gene may be linked to caries susceptibility, as demonstrated in our previous studies. This study aimed to investigate the effects of these missense mutations of the srtA gene on SrtA enzyme activity in S. mutans.

Methods

The point mutated recombinant S.mutans T168G and G470A sortases were expressed in expression plasmid pET32a. S. mutans UA159 sortase coding gene srtA was used as the template for point mutation. Enzymatic activity was assessed by quantifying increases in the fluorescence intensity generated when a substrate Dabcyl-QALPNTGEE-Edans was cleaved by SrtA. The kinetic constants were calculated based on the curve fit for the Michaelis-Menten equation.

Results

SrtA_{△N40(UA159)} and the mutant enzymes, SrtA_△N40(D56E) and SrtA_{△N40(R157H)}, were expressed and purified. A kinetic analysis showed that the affinity of SrtA_△N40(D56E) and SrtA_{△N40(R157H)} remained approximately equal to the affinity of SrtA_{△N40(UA159)}, as determined by the Michaelis constant (K_m). However, the catalytic rate constant (k_cat) and catalytic efficiency (k_cat/K_m) of SrtA_△N40(D56E) were reduced compared with those of SrtA_{△N40(R157H)} and SrtA_{△N40(UA159)}, whereas the k_cat and k_cat/K_m values of SrtA_{△N40(R157H)} were slightly lower than those of SrtA_{△N40(UA159)}.

Conclusions

The findings of this study indicate that the T168G missense mutation of the srtA gene results in a significant reduction in enzymatic activity compared with S. mutans UA159, suggesting that the T168G missense mutation of the srtA gene may be related to low cariogenicity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12903-016-0204-1) contains supplementary material, which is available to authorized users.

Peptide Glycosylation Generates Supramolecular Assemblies from Glycopeptides as Biomimetic Scaffolds for Cell Adhesion and Proliferation

Glycopeptide-based hydrogelators with well-defined molecular structures and varied contents of sugar moieties were prepared via in vitro peptide glycosylation reactions. With systematic glucose modification, these glycopeptide hydrogelators exhibited diverse self-assembling behaviors in water and formed supramolecular hydrogels with enhanced thermostability and biostability, in comparison with their peptide analogue. Moreover, because of high water content and similar structural morphology and composition to extracellular matrixes (ECM) in tissues, these self-assembled hydrogels also exhibited great potential to act as new biomimetic scaffolds for mammalian cell growth. Therefore, peptide glycosylation proved to be an effective means for peptide modification and generation of novel supramolecular hydrogelators/hydrogels with improved biophysical properties (e.g., high biostability, increased thermostability, and cell adhesion) which could promise potential applications in regenerative medicine.

[Outcome of treatment of Y chromosome AZFc microdeletion patients]

OBJECTIVE

To discuss the treatment options for patients with azoospermia factor (AZF) c microdeletion on Y chromosome.

METHODS

One hundred and eighty three patients, who were diagnosed as AZFc microdeletion on Y chromosome in Peking University Third Hospital, were recruited in our study. In order to get better treatment option for this kind of patients, we retrospectively analyzed their clinic data including the treatment process and pregnancy outcome and found out the characteristics of their semen.

RESULTS

Among the 183 patients, sperms can be found in ejaculated semen in 105 patients (57.4%, 105/183). One hundred and three patients (98.1%, 103/105) were diagnosed as severe or extremely severe oligospermia. Regular medication was given to 98 patients, 6 patients (6.1%, 6/98) of which got natural pregnancy. The other 99 patients who have sperms in their semen received intracytoplasmic sperm injection (ICSI), 68 patients (68.7%, 68/99) of which got pregnancy. Seventy eight patients were diagnosed as azoospermia among all the 183 patients. Forty nine patients received testicular sperm aspiration (TESA), and 21 patients choose to receive micro-TESE directly. Among the 49 patients with TESA, sperms were retrieved in 17 patients (34.7%, 17/49), and sperms were not retrieved in 32 patients (65.3%, 32/49), of which 12 patients (37.5%, 12/32) gave up treatment and 20 patients (62.5%, 20/32) choose micro-TESE. Among the 41 patients who choose to receive micro-TESE, operation has been done on 19 patients, of which 11 patients (57.9%, 11/19) got sperms. Among the 11 patients, TESA has been done on 6 patients before micro-TESE, of which 4 patients (66.6%, 4/6) got sperms. ICSI has already been done on 7 azoospermia AZFc microdeletion patients who underwent micro-TESE, of which 4 patients (57.1%, 4/7) get pregnancy.

CONCLUSION

AZFc microdeletion patients who had sperms were always diagnosed as severe or extremely severe oligospermia. ICSI was their first choice instead of drug therapy. For AZFc microdeletion patients who were diagnosed as azoospermia, TESA was one of their choices, however, the success rate is not high. Micro-TESE is still possible to get sperms even after the failure of TESA. Therefore, we may choose micro-TESE instead of TESA in some azoospermia patients in order to reduce surgical trauma on patients.

A supramolecular gel based on a glycosylated amino acid derivative with the properties of gel to crystal transition

Here we report the generation of a novel gelator from a glycosylated amino acid derivative, which contained three structural units, an aromatic residue, a carbohydrate moiety and a tert-butyl group in a single molecule. These structural units can promote the supramolecular self-assembly of this gelator in both aprotic and protic solvents via coordinated π-π stacking, multiple hydrogen binding and van der Waals interactions. More importantly, due to their non-equilibrium natures, the organogels formed in DCM, chloroform and ethanol can undergo gel to crystal transition in storage, driven by unbalanced gelator-gelator and solvent-gelator interactions. In this process, the gelators were firstly trapped in a kinetically favorable gel state, and then transferred into a more thermodynamically stable crystal state upon ageing, with the generation of microcrystals in different morphologies.

No increased risk of coronary heart disease for patients receiving androgen deprivation therapy for prostate cancer in Chinese/Taiwanese men

The relationship between androgen deprivation therapy (ADT) and coronary heart disease (CHD) remains controversial. Furthermore, the majority of such studies focused on Caucasian populations, and there is still a paucity of studies among Asian populations. This population-based study aimed to investigate the relationship between ADT and CHD in an ethnic Chinese (i.e., Taiwanese) population. We used data sourced from the Taiwan 'Longitudinal Health Insurance Database'. This study included 1278 patients with prostate cancer in the study group and 1278 subjects without prostate cancer in the comparison group. Each patient was individually tracked for a 3-year period to identify those who had subsequently received a diagnosis of CHD. The results showed that the incidence rate of CHD during the 3-year follow-up period was 4.69 (95% CI: 2.99-5.48) per 100 person-years and 2.67 (95% CI: 2.15-3.27) per 100 person-years for the study and comparison cohort, respectively. The Cox proportional hazard regression showed that the hazard ratio for CHD during the 3-year follow-up period for prostate cancer patients was 1.65 (95% confidence interval (CI) = 1.25-2.16) compared with comparison subjects after adjusting for patients' geographic location, monthly income, urbanization level, hypertension, diabetes, hyperlipidemia, and stroke. However, we failed to find a significant difference in the adjusted hazard of CHD during the 3-year follow-up period between prostate cancer patients who did and those who did not receive ADT (hazard ratio = 1.12, 95% CI = 0.79-1.59). We concluded that prostate cancer but not ADT was significantly associated with CHD. In addition, a common cause of prostate cancer and coronary heart disease could exist.

Molecular epidemiology of invasive Candida albicans at a tertiary hospital in northern Taiwan from 2003 to 2011

Candida albicans is a common cause of bloodstream fungal infections in hospitalized patients. To investigate its epidemiology, multilocus sequence typing (MLST) was performed on 285 C. albicans bloodstream isolates from patients in Chang Gung Memorial Hospital at Linkou (CGMHL), Taiwan from 2003 to 2011. Among these isolates, the three major diploid sequence types (DSTs) were 693, 659, and 443 with 19, 16, and 13 isolates, respectively. The 179 DSTs were classified into 16 clades by unweighted pair-group method using arithmetic averages (UPGMA). The major ones were clades 1, 4, 3, and 17 (54, 49, 31, and 31 isolates, respectively). Further analyses with eBURST clustered the 285 isolates into 28 clonal complexes (CC). The most common complexes were CC8, CC20, and CC9. DST 693 that had the highest number of isolates was determined to be the cluster founder of CC20, which belonged to clade 3. So far, 33 isolates worldwide including 29 from Taiwan and 4 from Korea, are CC20, suggesting that CC20 is an Asian cluster. Two fluconazole-resistant isolates belonging to CC12 and CC19 were detected. All other CGMHL isolates were susceptible to 5-flucytosine, amphotericin B, anidulfungin, caspofungin, fluconazole, itraconazole, micafungin, posaconazole, and voriconazole. However, CC20 isolates exhibited significantly lower susceptibility to fluconazole. In conclusion, the 285 CGMHL C. albicans isolates displayed geographically clustering with Asian isolates, and most of them are susceptible to common antifungal drugs. Isolates of DST 693, a Taiwanese major genotype belonging to MLST clade 3, were more resistant to fluconazole than other isolates.

Benign prostatic enlargement is not associated with diabetes: a population-based study

The association between diabetes and benign prostatic hyperplasia remains inconclusive. In this case-control study, we examined the association of diabetes with benign prostatic enlargement (BPE) using the Longitudinal Health Insurance Database 2000 in Taiwan. In total, 20 152 patients with BPE as cases and 20 152 age-matched patients without BPE were included as controls. Conditional logistic regression analyses were performed to calculate the odds ratio (OR) and corresponding 95% CI for having been previously diagnosed with diabetes between cases and controls. We found that of the 40 304 sampled patients, 9492 (23.6%) had a history of diabetes before the index date. This mean age for the sampled patients was 65.9 with a standard deviation of 12.0 years. A Chi-squared test revealed that there was a significant difference in the prevalence of prior diabetes between cases and controls (25.3% vs. 21.8%, p < 0.001). The conditional logistic regression found that the OR of prior diabetes for cases was 1.21 (95% CI = 1.15-1.27) compared with controls. However, after adjusting for geographic region, monthly income, urbanization level, hypertension, coronary heart disease (CHD), hyperlipidemia, tobacco use disorder, and obesity, the association between prior diabetes and BPE did not reach a statistically significant level (OR = 1.03, 95% CI = 0.98-1.08). In addition, it was noteworthy that hypertension (OR = 1.25, 95% CI = 1.20-1.31), CHD (OR = 1.40, 95% CI = 1.32-1.48), and hyperlipidemia (OR = 1.30, 95% CI = 1.24-1.36) were all significantly associated with BPE. We found that men with a diagnosis of diabetes were not significantly associated with BPE after adjusting for patient's sociodemographic characteristics and comorbidities.

Statin Use Is Associated with Bladder Pain Syndrome/Interstitial Cystitis: A Population-Based Case-Control Study

INTRODUCTION

Statin may induce epithelial dysfunction of the bladder urothelium. Epithelial dysfunction was proposed as one of the major potential etiologies for bladder pain syndrome/interstitial cystitis (BPS/IC). In this study, we examined the association between statin use and BPS/IC using a population-based study.

SUBJECTS AND METHODS

This case-control study used the Taiwan Longitudinal Health Insurance Database. In total, 815 female subjects with BPS/IC and 4075 randomly selected female controls were included. We used a conditional logistic regression to compute the odds ratio (OR) for having previously used statins between cases and controls.

RESULTS

A conditional logistic regression analysis showed that the OR of prior statin users for cases was 1.52 (95% confidence interval (CI): 1.19-1.94) compared to controls after adjusting for diabetes, hypertension, coronary heart disease, obesity, chronic pelvic pain, irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, depression, panic disorder, migraines, sicca syndrome, allergies, endometriosis, and asthma. Furthermore, adjusted ORs of regular and irregular statin use for cases were 1.58 (95% CI: 1.20-2.08) and 1.53 (95% CI: 1.02-2.31), respectively, compared to controls.

CONCLUSION

We concluded that there was an association between statin use and BPS/IC.

Dementia is associated with open-angle glaucoma: a population-based study

PURPOSE

Previous epidemiologic studies that focused on the association between open-angle glaucoma (OAG) and dementia showed inconsistent results. In the present study, we explored the association between OAG and dementia in an ethnic Chinese (i.e., Taiwanese) population using a population-based data set.

METHODS

We retrieved data on study subjects for this case-control study from the Longitudinal Health Insurance Database 2000. We identified 7770 patients who had a diagnosis of dementia as cases, and 7770 subjects matched in terms of sex and age, which were randomly extracted as controls. A conditional logistic regression conditioned on age group, sex, and index year was used to assess the association of dementia with previously diagnosed OAG among the sampled patients.

RESULTS

Of 15,540 patients, 1.70% had prior OAG, including 2.02% of the dementia group and 1.38% of the controls. After adjusting for patient socioeconomic characteristics and comorbid medical disorders, dementia patients were more likely to have had prior OAG than controls (odds ratio (OR): 1.44; 95% confidence interval (CI): 1.12-1.85; P<0.01). In addition, female dementia patients were more likely to have had prior OAG than controls (OR: 1.93; 95% CI: 1.35-2.77; P<0.001), whereas no statistical difference in prior OAG between male dementia patients and controls was found.

CONCLUSIONS

Female dementia patients were associated with a higher proportion of prior OAG than were the controls.

Impact of early childhood caries on oral health-related quality of life of preschool children

AIM

Child oral health-related quality of life (COHRQoL) has been assessed in developed areas; however, it remains unstudied in mainland China. Studies on COHRQoL would benefit a large number of children in China suffering from oral health problems such as dental caries. This study explored the relationship between COHRQoL and early childhood caries, adjusted by socioeconomic factors, in 3- to 4-year-old children in a region of southern China.

MATERIALS AND METHODS

In this study, 1062 children aged 3-4 years were recruited by cluster sampling and their oral health statuses were examined by a trained dentist. The Chinese version of the Early Childhood Oral Health Impact Scale (ECOHIS) and questions about the children's socioeconomic conditions were completed by the children's parents. A negative binomial regression analysis was used to assess the prevalence of early childhood caries among the children and its influence on COHRQoL.

RESULTS

The total ECOHIS scores of the returned scale sets ranged from 0 to 31, and their average scores was 3.1±5.1. The negative binomial analysis showed that the dmfs indices were significantly associated with the ECOHIS score and subscale scores (P<0.05). The multivariate adjusted model showed that a higher dmft index was associated with greater negative impact on COHRQoL (RR = 1.10; 95% CI = 1.07, 1.13; P < 0.05). However, demographic and socioeconomic factors were not associated with COHRQoL (P>0.05).

CONCLUSION

The severity of early childhood caries has a negative impact on the oral health-related quality of life of preschool children and their parents.

Self-assembly and hydrogelation from multicomponent coassembly of pentafluorobenzyl-phenylalanine and pentafluorobenzyl-diphenylalanine

To screen the possibility of forming self-assembled hydrogels under physiological pH, various molar ratios of the hydrogelators based on pentafluorobenzyl-phenylalanine (PFB-F) and pentafluorobenzyl-diphenylalanine (PFB-FF) were studied.

Nanofibrous hydrogels self-assembled from naphthalene diimide (NDI)/amino acid conjugates

A new approach is proposed for the design of NDI-capped supramolecular hydrogels.

A supramolecular hydrogel self-assembled from pentafluorobenzyl-dipeptide

We report a new aromatic-capped peptide amphiphile which is able to form a supramolecular hydrogel under neutral pH.

Remarkable influence of alkyl chain lengths on supramolecular hydrogelation of naphthalene diimide-capped dipeptides

The influence of aliphatic chain lengths on supramolecular hydrogelation of naphthalene diimide-capped dipeptides is described.

The effect of fluorine on supramolecular hydrogelation of 4-fluorobenzyl-capped diphenylalanine

Due to the replacement of only one hydrogen atom by fluorine, 4-fluorobenzyl-diphenylalanine molecules self-assemble to form a transparent hydrogel.

An unexpected route for otolaryngology bacterial contamination with a Venturi atomizer

BACKGROUND

The Venturi-principle atomizer is a commonly used device in otolaryngology practices. The purpose of this study is to evaluate the possible route of bacterial contamination from the nasal vestibule to the atomizer tip through the jet airflow created during the use of the Venturi atomizer.

METHODS

Thirty nostrils from 15 enrolled volunteers were tested. The aerosols generated by spraying sterilized saline into the nostrils were collected using a specially made aerosol-collecting nozzle cap. The collected samples were sent for bacterial culture, and nasal vestibular swab cultures were performed for comparison.

RESULTS

In the aerosol-exposed group, 18 out of 30 samples (60%) were positive for bacterial growth, confirming the bacterial contamination from the nasal vestibule to the atomizer tip through the reverse jet airflow. The bacteria species in 8 of the 18 positive samples were identical to those from the nasal swab culture results from the same nostril.

CONCLUSION

In ordinary otolaryngology practices, there are significant risks for bacterial contamination from the nasal vestibule to the tip of the Venturi atomizer even without direct contact. Clinicians must be more aware of this pattern of contamination, which has not been reported in the existing literature.

Factors associated with colonization of Streptococcus mutans in 8- to 32-month-old children: a cohort study

BACKGROUND

The factors involved in Streptococcus mutans colonization in young children are not clear. The aim of this study was to determine the factors associated with S. mutans colonization in 8- to 32-month-old children.

METHODS

A group of 225 caries-free 8-month-old children was recruited for the study. They were examined every six months until they were 32 months old to investigate their environmental factors, host factors and bacterial transmission factors. At baseline and during each examination, their teeth were checked for the presence of dental plaque and developmental defects of enamel, and S. mutans plaque status was assessed using a real-time PCR test.

RESULTS

Eight children (3.6%) showed S. mutans colonization by the age of 8 months. The percentages of colonization were 6.0% at 14 months, 16.2% at 20 months, 26.7% at 26 months, and 33.5% at 32 months. The results showed that females (p = 0.006), children with enamel hypoplasia (p = 0.024), children with low birth weights (p = 0.005), those who consume more sweets (p < 0.001), and those with a higher proportion of visible plaque (p = 0.020 and p = 0.041) were more likely to be colonized by S. mutans.

CONCLUSIONS

Streptococcus mutans colonization in young children was associated with gender, tooth enamel hypoplasia, low birth weight, frequent consumption of sweets and poor oral hygiene.

Dose effect of thiazolidinedione on cancer risk in type 2 diabetes mellitus patients: a six-year population-based cohort study

WHAT IS KNOWN AND OBJECTIVE

Prior studies found that thiazolidinediones (TZDs) might have tumour-suppressor activity mediated through cell-cycle arrest, induction of apoptosis and inhibition of cell invasion. The main objective of this study was to investigate the effects of TZDs on the risk of cancer among patients with type 2 diabetes mellitus (DM).

METHODS

Patients diagnosed with DM between 1 January 1998 and 31 December 2002 were identified from the Longitudinal Health Insurance Database (LHID) within the Taiwan National Health Insurance (NHI) programme. Using Cox regression models, we assessed the association between prescribed TZDs and cancer risk, TZDs' dose effect and the association between TZDs and specific cancer types. Hazard ratios (HR) were adjusted for potential confounders (age, gender, income, Charlson score index, metformin and insulin use).

RESULTS AND DISCUSSION

The adjusted HRs for those prescribed TZD were 0·74 (95% CI 0·43-1·26, P = 0·27), 0·39 (95% CI 0·33-0·45, P < 0·001) and 0·49 (95% CI 0·27-0·89, P = 0·02), respectively, relative to non-DM patients, DM patients prescribed other anti-DM drugs besides TZDs and DM patients not prescribed any anti-DM drugs. In addition, the effects of TZDs were shown to be significantly dose dependent (P for trend < 0·001). The risk of breast, brain, colorectal, ear-nose-throat, kidney, liver, lung, lymphatic, prostate, stomach, and uterus cancer was significantly lower in those prescribed TZDs.

WHAT IS NEW AND CONCLUSIONS

The results showed a decrease in cancer risk in diabetic patients using TZD, and the association was dose dependent.