Determining the bistability parameter ranges of artificially induced lac operon using the root locus method.

This paper employs the root locus method to conduct a detailed investigation of the parameter regions that ensure bistability in a well-studied gene regulatory network namely, lac operon of Escherichia coli (E. coli). In contrast to previous works, the parametric bistability conditions observed in this study constitute a complete set of necessary and sufficient conditions. These conditions were derived by applying the root locus method to the polynomial equilibrium equation of the lac operon model to determine the parameter values yielding the multiple real roots necessary for bistability. The lac operon model used was defined as an ordinary differential equation system in a state equation form with a rational right hand side, and it was compatible with the Hill and Michaelis-Menten approaches of enzyme kinetics used to describe biochemical reactions that govern lactose metabolism. The developed root locus method can be used to study the steady-state behavior of any type of convergent biological system model based on mass action kinetics. This method provides a solution to the problem of analyzing gene regulatory networks under parameter uncertainties because the root locus method considers the model parameters as variable, rather than fixed. The obtained bistability ranges for the lac operon model parameters have the potential to elucidate the appearance of bistability for E. coli cells in in vivo experiments, and they could also be used to design robust hysteretic switches in synthetic biology.

Can dental pulp calcification serve as a diagnostic marker for carotid artery calcification in patients with renal diseases?

OBJECTIVES: The aim of this study was to determine the relationship between the presence of pulp calcification and carotid artery calcification on dental panoramic radiographs in end-stage renal disease (ESRD) patients on haemodialysis and renal transplant recipients. METHODS: A total of 60 nephrology patients (29 haemodialysis patients and 31 renal transplant recipients) participated in this study. For all patients, both panoramic and periapical radiographs were evaluated twice by three examiners to determine the presence or absence of narrowing of the dental pulps and pulp stones in pulp chambers and canals. The kappa coefficient was used for intervariable agreement, and interexaminer reliability was evaluated by the intraclass correlation coefficient. Panoramic radiographs were also evaluated to determine carotid calcification. Ultrasound examination confirmed radiographic findings of carotid calcification on panoramic radiographs. RESULTS: Carotid calcifications were detected in 11 patients (6 haemodialysis patients and 5 transplant recipients). 48 patients (22 haemodialysis patients, 26 transplanted recipients) had dental pulp narrowing, and 8 patients (5 haemodialysis patients, 3 transplant recipients) had pulp stones. There was no statistical relation between pulp narrowing and carotid artery calcification (CAC) in the haemodialysis patient group and renal transplant recipients. There was also no statistical relation between pulp stones and CAC in haemodialysis patients and renal transplant recipients. CONCLUSION: In our study, no relationship was found between the presence of pulpal calcification and CAC in ESRD patients on haemodialysis and renal transplant recipients. Therefore, the presence of pulp calcification does not seem to serve as a diagnostic marker for carotid atherosclerosis.

Effect of turban use on temporomandibular joint problems.

The aim of this study was to evaluate the effects of daily turban wear on temporomandibular joint (TMJ) problems. This cross-sectional study was carried out on 249 female patients. Of these, 119 patients were using turban daily, while 130 patients did not use. Patients were asked questions to ascertain the signs of TMJ problems. Thereafter, the TMJ region was examined clinically. Cross-tabulations and Chi-square statistics were computed in accordance with Bonferroni correction for multiple comparisons. To investigate the association between continuous turban wear and temporomandibular disorder symptoms, logistic regression analysis was performed. Limited mouth opening, deviation, pain on TMJ palpation and mouth opening were not affected with turban usage. However, turban users more frequently demonstrated pain during palpation of the masticatory muscles than non-users (P = 0.001). Duration of the turban usage did not affect clinical examination findings except pain on masticatory muscles during palpation (P = 0.001). Complaint of pain on masticatory muscles are more frequently seen among the turban users.

Gingival health status in renal transplant recipients: relationship between systemic inflammation and atherosclerosis.

Cardiovascular disease (CVD) is the leading cause of mortality in renal transplant recipients (RTR). Systemic and periodontal inflammation has been suggested to have a possible role in the development of atherosclerosis. In the present study, we aimed to investigate the relationship between gingival health status, inflammation and atherosclerosis in RTRs. Eighty-three RTR (50 male, 33 female) were enrolled in the study. Routine biochemical analyses, serum lipoproteins, C-reactive protein, fibrinogen, homocystein, parathyroid hormone (PTH) and cyclosporin A (CsA) trough levels were studied. All patients had 24-h ambulatory blood pressure monitoring and B-mode ultrasound of the common carotid arteries. Gingival status was evaluated by the Löe and Silness gingival index (GI). Mean GI value was 2.3 +/- 0.5. Fifty patients (60.3%) had GI value >or= 2.1 (severe gingivitis; group A). Thirty-three patients (39.7%) had GI value < 2.1 (no or moderate gingivitis; group B). Age, carotid intima-media thickness (CIMT) and mean time on dialysis before transplantation were significantly higher in group A than in B. Systemic inflammation markers were not different between group A and group B. Mean CIMT was positively correlated with GI (r = 0.425; p = 0.001) and negatively correlated with high-density lipoprotein cholesterol (r = -0.256; p = 0.023). After the correction for confounding variables, mean CIMT was still significantly correlated with GI (r = 0.376, p = 0.02). In RTR, gingival inflammation seems to be associated with CIMT in the absence of systemic inflammation. Thus, gingivitis may, in part, play a role in the development of systemic atherosclerosis without causing any aggravation in systemic inflammatory response.

The prevalence of carotid artery calcification on the panoramic radiographs of patients with renal disease.

OBJECTIVES: To determine the prevalence of carotid calcification on dental panoramic radiographs in end-stage renal disease (ESRD) patients on haemodialysis and renal transplant recipients. METHODS: Panoramic radiographs of 69 adult patients with renal disease (34 with haemodialysis and 35 with renal transplantations) (age range 17-74 years; mean age 39.45 years) and 50 controls (age-match, free of systemic disease) were examined on panoramic radiographs for any unusual radiopacity adjacent to or just below the intervertebral space between C3 and C4. Patients with such calcifications were referred to ultrasound examination. Using Chi-squared tests, calcification prevalence rates were statistically compared. RESULTS: The statistical difference between renal disease patients and control group was significant (chi2 = 17.91, P < 0.001). On comparison of haemodialysis patients and renal transplant recipients with controls, statistical difference (P=0.007) was found to be significant. CONCLUSION: Carotid artery calcification was higher in haemodialysis patients and renal transplant recipients. These patients with such calcifications should be referred for further evaluation and treatment of carotid arteries, coronary arteries and vascular risk factors.

Bilateral bifid mandibular condyle.

Bilateral bifid mandibular condyles are rare and may appear as a congenital or developmental anomaly. A case of bilateral bifid mandibular condyles is reported. The patient had no history of trauma and no link was apparent with respect to the patient's medical history. In this case, the condition was an incidental panoramic radiographic finding. Magnetic resonance imaging findings revealed bilateral anterior disc displacement without reduction. The radiographic appearance of this anomaly and the literature on bilateral bifid condyles are reviewed.

The prevalence of tongue lesions in 5150 Turkish dental outpatients.

OBJECTIVE: The aim of this study was to assess the prevalence of nine tongue conditions and relate to data obtained about oral hygiene or habits in Turkish dental outpatients. SUBJECTS: A total of 5150 subjects (2837 women, 2313 men) were included in this study. RESULTS: Of the 5150 subjects, 2690 subjects were detected as having tongue lesions with a prevalence of 44.2 and 62.0% for women and men, respectively. The difference was found to be statistically significant (P < 0.0001). There was a strong correlation between tongue lesions and increasing age. There was also a strong association between tongue lesions and smoking, black tea drinking, and fair or poor oral hygiene. Hairy and coated tongue was significantly higher in males. Contrary to this, papillary atrophy was more prominent in women. CONCLUSION: A strong correlation was found between tongue lesions and age, sex, oral hygiene and habits in Turkish dental outpatients. An efficient oral health program such as the elimination of risk habits and attention to cultural practices may improve tongue hygiene.

The relationship between gastric-oral Helicobacter pylori and oral hygiene in patients with vitamin B12-deficiency anemia.

OBJECTIVE: The aim of this study was to determine whether a relationship exists between gastric and oral Helicobacter pylori and oral hygiene in patients with vitamin B12 deficiency. STUDY DESIGN: One hundred eight patients with vitamin B12 deficiency who were H pylori -positive in their gastric mucosa were enrolled in the study. These patients were divided into 3 groups determined by Oral Hygiene Index (OHI) scores of good, fair, or poor. H pylori was detected in the dental plaque with camphylobacter-like organism test gels. All patients were treated with a combination regimen to eradicate H pylori. RESULTS: H pylori positivity in dental plaque was correlated with OHI scores; the positivity was 28.5%, 90.2%, or 100% in patients with good, fair, or poor OHI scores, respectively. The eradication of H pylori was associated with recovery from anemia and increased serum vitamin B12 level (P <.0001 and P <.0001). The patients with poor OHI scores had the most frequent gastric recurrence of H pylori (58.3%) compared with those with fair OHI scores (41.2%) and good OHI scores (4.8%). CONCLUSIONS: H pylori seems to be an etiologic factor in vitamin B12 deficiency, since anemia was cured and the level of vitamin B12 in the serum increased as a result of its eradication. However, eradication of H pylori from gastric mucosa alone is not enough to prevent gastric recurrence of the bacteria. Proper oral hygiene must be established to eliminate H pylori in dental plaque. Therefore, we suggest that control of H pylori in dental plaque is necessary to control recurrence of H pylori.