Effect of different framework materials of resin-bonded bridges on load to fracture values and stress distribution

Purpose

The aim of this study was to compare in vitro fracture strengths (FSs) of metal- and fiber-reinforced frameworks of resin-bonded bridges and to evaluate stress distribution with finite element analysis (FEA).

Materials and Methods

Totally 80 extracted maxillary central and maxillary canine teeth were used for in vitro part of this study as two groups; metal-reinforced framework (n = 20) [(metal-supported resin-bonded bridge (MR-RB)] and fiber-reinforced frameworks (n = 20) [fiber-reinforced resin-bonded bridge (FR-RB) were prepared for three unit resin-bonded bridges. All bridges were loaded from lateral pontic at 1 mm/min crosshead speed and fracture values were recorded. Mann-Whitney U-test was used for statistical analysis, and fracture patterns were evaluated visually. FEA was carried out in the second part of the study, and stress distribution of MR-RB and FR-RB structures was analyzed using one of the models from in vitro specimens as main model.

Results

The mean FSs of MR-RB and FR-RB were 637.47 ± 151.91 N and 224.86 ± 80.97 N, respectively. Fiber-reinforced specimens were found to distribute stress more homogeneous and connectors in each framework were the regions where stress concentrated mostly.

Conclusion

In vitro FSs of MR-RB and the stress concentration of the point that the forces were applied were higher as compared to other parts of the restoration. Furthermore, in contrast to FR-RB specimens, retainer tooth fractures were observed in MR-RB specimens.

Evaluation of arterial stiffness and cardiac function in patients with vascular erectile dysfunction: acute effects of phosphodiesterase-5 inhibitor tadalafil

This study aimed to detect endothelial dysfunction in erectile dysfunction (ED) patients free from cardiovascular diseases or atherosclerotic risk factors and to evaluate acute effects of phosphodiesterase-5 inhibitor tadalafil on endothelial dysfunction and cardiac function. Thirty ED patients and 20 healthy male subjects (mean ages: 48.7±11.7 and 48.3±8.7 years, respectively) were enrolled. Endothelium functions were assessed by applanation tonometry. Aortic stiffness and cardiac function were evaluated by transthoracic echocardiography. Pulse pressure was greater in the ED group (P<0.05), whereas aortic strain and aortic distensibility were significantly lower (P<0.001). Treatment with tadalafil reduced pulse pressure (P=0.0179), systolic blood pressure (P=0.001) and diastolic blood pressure (P=0.054) and increased aortic distensibility (P=0.001) and aortic strain (P=0.003) in the ED group. Tadalafil administration also increased large artery and small artery elasticity indices that were reduced in the ED group at baseline (P=0.02 and 0.003, respectively). Systemic vascular disease and compromised left ventricular diastolic function (LVDF) were present in ED patients with no known atherosclerotic risk factors and cardiac diseases. Tadalafil positively affected arterial stiffness and LVDF.

Tissue Doppler Echocardiography and Myocardial Performance Index in Patients with Scleroderma

In this study, left and right ventricular functions were examined echocardiographically in 22 patients with scleroderma and 22 healthy volunteers. Conventional and tissue Doppler echocardiography and myocardial performance indexes were used as measures of right and left ventricular global functions. Mitral early diastolic E wave deceleration time, isovolumetric contraction time and left ventricular myocardial performance index and peak tricuspid A wave velocity were significantly higher in the scleroderma group compared with the control group. Mitral and tricuspid E/A ratios were significantly lower in patients with scleroderma. In addition, mitral annular and tricuspid annular isovolumetric relaxation times and the tricuspid E/E' ratio were significantly increased in scleroderma patients compared with the control group. In conclusion, in scleroderma patients the global left ventricular functions were depressed and diastolic function abnormalities were seen in both right and left ventricles. In addition, longitudinal muscle functions of the ventricles were depressed in scleroderma patients, as shown by tissue Doppler imaging parameters.

Prognostic Value of Viable Myocardium in Patients with Non-Q-wave and Q-wave Myocardial Infarction

This study assessed the amount and prognostic value of myocardial viability in patients with non-Q-wave myocardial infarction (NQMI) and Q-wave myocardial infarction (QMI). A total of 175 patients with MI and an ejection fraction ≤ 45% underwent dobutamine stress echocardiography. On the basis of clinical criteria and myocardial viability, 110 patients were revascularized. The amount of viable myocardium and the clinical outcome were compared in the NQMI and QMI groups. Patients with NQMI exhibited a larger amount of viable myocardium compared with those with QMI. The mortality rate was 6% in patients with NQMI with viable myocardium and subsequent revascularization, 33% in patients with NQMI without viable myocardium or revascularization, 27% in patients with QMI with viable myocardium and subsequent revascularization, and 33% in patients with QMI without viable myocardium or revascularization. In conclusion, our data suggest that patients with NQMI and viable myocardium have the best prognosis after revascularization.

Spread of carbapenem-resistant international clones of Acinetobacter baumannii in Turkey and Azerbaijan: a collaborative study

Epidemic clones of Acinetobacter baumannii, described as European clones I, II, and III, are associated with hospital epidemics throughout the world. We aimed to determine the molecular characteristics and genetic diversity between European clones I, II, and III from Turkey and Azerbaijan. In this study, a total of 112 bloodstream isolates of carbapenem-resistant Acinetobacter spp. were collected from 11 hospitals across Turkey and Azerbaijan. The identification of Acinetobacter spp. using conventional and sensitivity tests was performed by standard criteria. Multiplex polymerase chain reaction (PCR) was used to detect OXA carbapenemase-encoding genes (bla OXA-23-like, bla OXA-24-like, bla OXA-51-like, and bla OXA-58-like). Pulsed-field gel electrophoresis (PFGE) typing was used to investigate genetic diversity. The bla OXA-51-like gene was present in all 112 isolates, 75 (67 %) carried bla OXA-23-like, 7 (6.2 %) carried bla OXA-58-like genes, and 5 (4.5 %) carried bla OXA-24-like genes. With a 90 % similarity cut-off value, 15 clones and eight unique isolates were identified. The largest clone was cluster D, with six subtypes. Isolates from clusters D and I were widely spread in seven different geographical regions throughout Turkey. However, F cluster was found in the northern and eastern regions of Turkey. EU clone I was grouped within J cluster with three isolates found in Antalya, Istanbul, and Erzurum. EU clone II was grouped in the U cluster with 15 isolates and found in Kayseri and Diyarbakır. The bla OXA-24-like gene in carbapenemases was identified rarely in Turkey and has been reported for the first time from Azerbaijan. Furthermore, this is the first multicenter study in Turkey and Azerbaijan to identify several major clusters belonging to European clones I and II of A. baumannii.

Comparison between dexmedetomidine and remifentanil infusion in emergence agitation during recovery after nasal surgery: A randomized double-blind trial

BACKGROUND

Postoperative emergency agitation (EA) is a common problem. Dexmedetomidine and remifentanil may be used to prevent this problem. Our primary aim was to compare dexmedetomidine, remifentanil, and placebo with respect to their effectiveness in preventing postoperative EA.

MATERIAL AND METHODS

Ninety patients undergoing nasal surgery were randomized into three groups. The dexmedetomidine group (group D, n = 30) received dexmedetomidine infusion at a rate of 0.4 μg kg(-1 ) h(-1); the remifentanil group (group R, n = 30) received remifentanil infusion at a rate of 0.05 μg kg(-1) min(-1) from induction of anesthesia until extubation; and the control group (group S, n = 30) received a volume-matched normal saline infusion as a placebo. Propofol (1.5-2 mg kg(-1)) and fentanyl (1 μg kg(-1)) were used to initiate anesthesia, and desflurane was used to maintain anesthesia. The incidence of agitation, hemodynamic parameters, and recovery characteristics were evaluated during emergence.

RESULTS

The incidence of EA was significantly higher in group S (46.7%) compared with groups R and D (3.3 and 20%, respectively; p < 0.001). The lowest incidence of EA was detected in group R (p = 0.046). Residual sedation in the post-anesthesia care unit (PACU) was similar in all groups (p = 0.947). The incidence of nausea or vomiting was significantly lower in group D than in groups R and S (p = 0.043). Administration of analgesics in the PACU was higher in group R than in groups S and D (p = 0.015).

CONCLUSION

Anesthetic maintenance with either remifentanil or dexmedetomidine infusion until extubation provided a more smooth and hemodynamically stable emergence, without complications after nasal surgery. While remifentanil was superior to dexmedetomidine with regard to avoiding EA, dexmedetomidine was more effective than remifentanil regarding vomiting and pain.

A possible association of idiopathic osteosclerosis with excessive occlusal forces

OBJECTIVES

The aim of the study was to determine the relationship between idiopathic osteosclerotic lesions and occlusal forces using the T-Scan II computerized occlusal analysis device, and to test the sensitivity of the system in occlusal analysis.

METHOD AND MATERIALS

The study was conducted with 21 volunteers with idiopathic osteosclerosis (IO; 14 women, 7 men) aged between 17 and 62 years (mean 29.95). For every patient, seven or eight recordings were made with the T-Scan II occlusal analysis device in maximum intercuspation, and the last two (excluding any with technical problems) were chosen for evaluation. For each lesion-related area, the distribution of high occlusal forces from two different movies was analyzed.

RESULTS

In 18 patients (85.71%), lesions were observed in an area of high occlusal force, and in 13 patients (61.9%), the lesions were located at the first area subjected to high occlusal forces. The percentage distribution of high forces at a lesion related area ranged from 0% to 88%. On average, the high forces at an osteosclerotic lesion area accounted for 20% of the maximum total force. No statistical differences were observed between the measurements of the two selected recordings (P > .05).

CONCLUSION

The findings of this study suggest a possible relationship between IO and occlusal forces and primary contacts. T-Scan II was found to be a successful diagnostic device for detecting primary contacts and excessive occlusal forces.

Dyskeratosis congenita: clinical report and review of the literature

Dyskeratosis congenita (DKC) is an inherited disorder that usually presents in males, consisting of the triad of leukoplakia of the mucous membranes, nails dystrophy and skin pigmentation. Oral and dental abnormalities may also be present. Most cases are X-linked autosomal dominant, but recessive forms have also been reported. This study describes herein a case in which the classic triad of signs was present, along with the development of leukoplakia in the buccal mucosa. Our patient, a 25-year-old man, presented with several characteristic systemic features of this condition, together with the following oral features: hypodontia, delayed dental eruption, short blunt roots, extensive caries, gingival inflammation and bleeding, loss of alveolar bone and buccal mucosa with leukoplakia and irregular ulcers. The patient was given full preventive care. The primary teeth were extracted under local anaesthesia. After establishing optimal oral health, oral hygiene instructions were given to the patient and he was rehabilitated with fixed and removable partial denture. Prosthetic treatments were carried out after establishing optimal oral health. This treatment option appears beneficial in this patient, resulting in rehabilitation of occlusion and less mechanical irritation to the oral mucosa.

Effects of Origanum onites on endothelial function and serum biochemical markers in hyperlipidaemic patients

The effects of Origanum onites on endothelial function and antioxidative status were investigated in 48 patients with mild hyperlipidaemia who required no drug therapy. All participants were given lifestyle and low-fat dietary advice, however 32 of the patients (study group) were also prescribed 25 ml of aqueous distillate of Origanum onites to be taken after each meal for 3 months. The remaining 16 patients were the control group. Various biochemical markers and endothelial function parameters were measured at baseline and after 3 months. A significantly greater increase in high density lipoprotein-cholesterol and significantly greater decreases in low density lipoprotein-cholesterol, apolipoprotein B, lipoprotein(a) and high sensitivity C-reactive protein occurred in the study group compared with the control group over the 3-month study period. Paraoxonase and arylesterase activities, and flow- and nitroglycerine-mediated dilatation of the brachial artery showed significantly greater increases in the study group compared with the changes in the control group. In conclusion, consumption of Origanum onites distillate had beneficial effects on lipid profiles, antioxidant status and endothelial function in patients with mild hyperlipidaemia.

Self-reported denture hygiene habits and oral tissue conditions of complete denture wearers

The aim of the study was to examine the influence of denture hygiene on the development and intensity of denture stomatitis and traumatic ulcers and their relationship to age, gender, educational level, smoking status, age of the denture, denture hygiene habits and denture-wearing behavior. The study population comprised 310 complete denture (CD) wearers (159 males and 151 females) aged 60-85 living in Kirikkale, Turkey. Denture hygiene habits were assessed and recorded, and any relationships between denture hygiene habits and the condition of oral tissue were assessed. The majority (48.4%) of participants reported cleaning their dentures with a toothbrush and toothpaste and 45.2% with a toothbrush only. Less than half (44.8%) removed their dentures overnight. Stomatitis was observed in 35.8% and traumatic ulcers in 29% of patients. A positive relationship was observed between poor denture hygiene habits and the presence of denture-related stomatitis and traumatic ulcers. The degree of denture hygiene was significantly associated with age, sex, education, general health status, smoking status, self-perception of halitosis, overnight denture removal and denture immersion habits.

Factors associated with self-reported halitosis (SRH) and perceived taste disturbance (PTD) in elderly

The aim of this study was to estimate the prevalence of self-reported halitosis (SRH) and perceived taste disturbance (PTD) and analyze their association with age, gender, subjective oral dryness, burning mouth, tongue coating, number of teeth remaining, and type of dentures and wear duration in healthy elderly. Subjects who neither reported systemic disorders nor medication use were included in the study. The participants of this study were 254 healthy subjects, 116 males (mean age: 63.2+/-7.2 years) and 138 females (mean age: 61.9+/-6.8 years), all aged 55 years and above. A self-administered structured questionnaire on SRH and PTD was given to the participants. Each subject underwent a comprehensive dental examination by one of the examiners. The number of carious teeth, number of restorations, type of dentures (fixed-partial, removable-partial or complete dentures) and wear duration, and tongue coating status were recorded. Associations of the categorical background variables (age, gender, smoking status, tooth brushing frequency) with SRH and PTD were examined using the chi(2)-test. Spearman's rho correlation coefficient was used to analyze the relationship between taste disturbance and SRH with relevant variables (p<0.05). The prevalence of SRH was 28.3% and the prevalence of PTD was 8.3%. Use of the toothbrush less than once daily was the factor most strongly associated with SRH. Of the individuals with SRH, 73.6% reported subjective oral dryness (p<0.001) and 9.7% had burning mouth (p=0.008). Of the individuals with PTD, 71.4% reported subjective oral dryness (p=0.003) and 14.3% had burning mouth (p=0.019). Age (p<0.05), denture type (p<0.001), tongue coating (p<0.001), frequency of tooth brushing (p<0.000 for SRH and p<0.05 for PTD) were significantly associated with SRH and PTD. Educational level of the participants was significantly different for SRH (p<0.05). Gender was not found to be associated with either SRH or PTD (p>0.05). We concluded that the factors most strongly associated with SRH and PTD were subjective oral dryness, tongue coating, inadequate oral hygiene practice and partial and/or complete denture wear. Other factors with significant associations included older age and lower education levels. Smoking was found to be associated with SRH.

Evaluation of the oral health status of the people aged 65 years and over living in near rural district of Middle Anatolia, Turkey

The aim of this study was to assess the oral health status of aged 65 years and over, and evaluate the level of edentulousness and study the factors that could have an influence on edentulism. The participants of this study were 215 patients; 94 males (47.3%) and 121 females (56.3%), aged 65 years and over. Each subject underwent a comprehensive dental and radiographic examination by one examiner. Periodontal attachment loss observed in the panoramic radiographs was divided into three diagnostic categories: infrabony defects, horizontal bone loss, and furcation lesions. The number of teeth with apical periodontitis lesions, the number of carious teeth, and restorations, type of dentures and wear duration, intrabony root remains, impacted teeth, smoking status, educational level and self-reported medical history of the participants were recorded. Extent of tooth loss was significantly higher in females than males and increased with increasing age (p<0.05). Tooth loss was significantly associated with educational levels; lower literacy level was found to be associated with a higher number of missing teeth (p<0.01). Also, as the educational levels of the participants increased, the number of infrabony defects, furcation lesions and number of carious teeth decreased (p<0.05). Low literacy level and female gender are found to be high-risk groups for tooth loss. Community-based oral disease prevention programs should be implemented to reduce the risk for tooth loss in this population.

Distortion of symmetrical introgression in a hybrid zone: evidence for locus-specific selection and uni-directional range expansion

The fate of species integrity upon natural hybridization depends on the interaction between selection and dispersal. The relative significance of these processes may be studied in the initial phase of contact before selection and gene flow reach equilibrium. Here we study a hybrid zone of two salamander species, Lyciasalamandra antalyana and Lyciasalamandra billae, at the initial phase of hybridization. We quantify the degree and mode of introgression using nuclear and mtDNA markers. The hybrid zone can be characterized as an abrupt transition zone, the central hybrid zone being only c. 400 m, but introgressed genes were traced up to 3 km. Introgression was traced in both sexes but gene flow may be slightly male-biased. Indirect evidence suggests that hybrid males are less viable than females. Introgression occurred at two levels: (1) locus-specific selection led to different allelic introgression patterns independent of species, while (2) asymmetrical species-level introgression occurred predominately from L. antalyana to L. billae due to range expansion of the former. This indicates that foreign genes can be incorporated into novel genomic environments, which in turn may contribute to the great diversity of morphological variants in Lyciasalamandra.

Palaeoclimatic changes explain Anatolian mountain frog evolution: a test for alternating vicariance and dispersal events

Holarctic biodiversity has been influenced by climatic fluctuations since the Pliocene. Asia Minor was one of the major corridors for postglacial invasions in the Palearctic. Today this area is characterized by an extraordinarily rich fauna with close affiliation to European, Asian and Indo-African biota. However, exact scenarios of range expansion and contraction are lacking. Using a phylogeographical approach we (i). identify monophyletic lineages among Anatolian mountain frogs and (ii). derive a spatio-temporal hypothesis for the invasion process in Anatolia. We sequenced 540 bp of the mitochondrial 16S rRNA gene from 40 populations of mountain frogs from Anatolia, the Elburz Mountains and the Caucasus. Our samples comprise all known species and subspecies: Rana macrocnemis macrocnemis, R. m. tavasensis, R. m. pseudodalmatina, R. camerani and R. holtzi. They include the type localities of four of these taxa. We used a nested clade analysis (NCA) to infer historical and recurrent events that account for the observed geographical distribution of haplotypes. None of the extant species is monophyletic. Based on a molecular clock calibration using homologous sequences of Western Palearctic water frogs of the same genus, we estimated that a basic radiation into three lineages c. 2 Mya was followed by several dispersal and fragmentation events. The geographical distribution of resident and widespread haplotypes allows us to infer and date scenarios of range expansion and fragmentation that are aligned with dramatic climatic oscillations that have occurred during the last 600000 years. Consequently, Pliocene and Pleistocene climatic oscillations triggered the evolution of Anatolian mountain frogs through an interplay of vicariance and dispersal events.

Evaluation of diastolic dysfunction and repolarization dispersion in Behcet's disease

Behcet's disease is a generalized chronic inflammatory disease characterized by genital, ocular, and cardiovascular involvement. Recently, left ventricular diastolic dysfunction, ventricular arrhythmia and sudden cardiac death have been documented in Behcet's disease. From January 1996 to May 1998, we investigated left ventricular systolic and diastolic function, valvular heart disease, ischemic heart disease and repolarization dispersion in 71 cases, 40 men and 31 women (mean age, 36.8+/-10.3 years) with Behcet's disease. All of the results were compared with the control group of 33 men and 22 women (mean age, 37.9+/-9.6 years). Exercise stress test or myocardial perfusion scintigraphy was performed for the documentation of ischemia. All the patients and the controls were recorded by M-mode, 2-D and Doppler echocardiography. Ventricular wall thickness, valvular apparatus, left ventricular systolic and diastolic parameters were evaluated. Repolarization dispersion parameters were calculated as the difference between maximal and minimal values of QT from 12-lead electrocardiogram recording at baseline, immediate and end of recovery from the exercise stress tests. The measured parameters were compared with the control group by using statistical methods. In the Behcet's group of 22 patients (31%) E/A ratio was <1. In the control group of five cases (10%) E/A ratio was <1 (P=0.003). In the Behcet's group isovolumic relaxation time (IRT) and mitral deceleration time (MDT) were longer than the control group (P=0.002, P=0.041, respectively). A mean QT of 368+/-30 ms and mean QT dispersion of 73+/-14 ms in the patient group compared with a mean QT of 395+/-39 ms and mean QT dispersion of 38+/-12 ms in the controls. There was no statistical difference between the mean QT values of the patient and control groups however, ventricular dispersion parameters in the Behcet's patients were longer than in the controls (P<0.001). There was also statistical significance for the QT dispersion between the Behcet's patients with and without diastolic dysfunction (P<0.01). In conclusion, the study reveals that the patients with Behcet's disease have a high incidence of increased diastolic dysfunction and repolarization dispersion. A positive correlation may exist between diastolic dysfunction and QT dispersion.

Percutaneous treatment of hepatic hydatid cysts: an alternative to surgery

OBJECTIVE

Percutaneous treatment of hydatid cysts is relatively new, and the data related to it are limited. The purpose of this study was to provide additional data to strengthen the proof of its effectiveness.

SUBJECTS AND METHODS

One hundred sixty-eight hepatic cysts in 111 patients were treated using a percutaneous approach under sonographic and fluoroscopic guidance. Cysts smaller than 5 cm in diameter were treated with a one-stage procedure that consisted of puncture of the cyst, aspiration of fluid, and injection and reaspiration of hypertonic saline solution. Larger cysts were treated with a two-stage procedure that consisted of the one-stage procedure followed by catheterization and sclerotherapy with alcohol.

RESULTS

The mean observation time was 19 months (range, 1-48 months). Follow-up examinations showed progressive shrinkage and solidification of the cysts. Early complications occurred in 32 (28.8%) of the 111 patients, including fatal anaphylaxis in one patient, biliary fistula in seven, infection of the cyst in four, persistent serous drainage from the cyst in two, intraperitoneal leakage of cyst fluid in two, urticaria in seven, fever without evidence of infection in seven, and pleural effusion in two. Late complications occurred in four (3.8%) of the 104 patients who underwent follow-up examinations, including local recurrence in three patients and intrabiliary rupture of a cyst in one patient.

CONCLUSION

Our experience indicates that percutaneous treatment is efficient in the management of hepatic hydatid cysts and that this technique should be considered an alternative to surgery.

Palliation of malignant obstructive jaundice. Use of self-expandable metal stents

PURPOSE

The aim of this study was to analyze the clinical efficacy of metal stents in the palliation of malignant obstructive jaundice.

MATERIAL AND METHODS

Fifty patients with malignant biliary obstruction were palliated by means of drainage with a metallic self-expandable stent (Wallstent). Nineteen patients had pancreatic carcinoma, 22 cholangiocarcinoma, 4 hepatocellular carcinoma, and the remaining 5 metastatic carcinoma from a variety of primary sites. The obstruction was at the level of the liver hilum in 19 cases, in the middle common bile duct in 11, and in the lower common bile duct in 20.

RESULTS

The patients were followed over a period of 1-17 months. A total of 36 patients (72%) died; 14 (28%) survived. The mean observation time for the whole group of 50 patients was 3.3 months. The 30-day mortality rate was 14% (7 patients). Short-term complications occurred in 6 patients (12%). Long-term complications included stent occlusion requiring a 2nd intervention in 2 patients (4%), and cholangitis in 2 patients (4%). Excellent palliation was achieved in most of the patients. No stent migration was observed.

CONCLUSION

The metallic stent provides good palliative drainage, and the percutaneous insertion of metallic stents is well tolerated by the patients. The procedure is simple and safe to use and can be executed in one stage. The one-stage procedure, compared to the 2-stage procedure, may reduce hospital stays.

Calcium and cell cycle progression: possible effects of external perturbations on cell proliferation

Exit from the phase of cellular division appears to be driven by a calcium signal that triggers a cascade of events leading to the completion of mitosis. Here we propose a model that relates the dynamics of cytosolic calcium to progression through mitosis, G1 and G2 phases of the cell cycle. To this end, the assumption has been made that the transient rise ir cytosolic calcium concentration during mitosis is induced by inositol(1,4,5)triphosphate (IP3), which in turn is released at high levels of mitosis-promoting factor (MPF). On this basis, a system of ordinary differential equations is proposed to simulate the evolution of ten cell-cycle-specific molecular species, including cyclins A and B, MPF, IP3, Ca2+, the CaMKII holoenzyme, and the ubiquitination complex. The influence on the cell proliferation capacity exerted by external perturbations, like calcium microinjections, depletion of intracellular calcium stores, electromagnetic fields, or stimulation/inhibition of different calcium currents through the plasma membrane, can be studied by appropriate modulation of the parameters involved in the signal transduction pathway.

Exit from mitosis induced by a calcium transient: the relation to the MPF and InsP3 dynamics

Cells divide only after passing through a control point in late G1. This passage is followed by the accumulation of the mitotic cyclin which binds to p34cdc2, allowing for the subsequent phosphorylation and dephosphorylation of the latter protein. It is the active MPF, i.e. the phosphorylated mitotic cyclin-p34cdc2 kinase complex that triggers entry into mitosis. MPF becomes increasingly active as the cell forwards to anaphase, when a sudden increase in InsP3 takes place. This in turn induces a large Ca2+ release in cytosol from internal calcium stores and a calcium-dependent positive feedback control on InsP3-induced calcium release enhances the effect on InsP3-mediated Ca2+ transient. Meanwhile, empty calcium stores signal to plasma membrane for a constant calcium influx at high InsP3 levels. The cytosolic calcium excess is assumed to activate the CaMKll holloenzyme which involves the production of the ubiquitination complex necessary for cyclin degradation and MPF inactivation. Accordingly, a mathematical model was proposed by means of an eight-dimensional dynamical system that yields the time dependence of the main cellular quantities in a picture of the mitosis specific events.

Rediscovery of the Bolkar viper: morphological variation and systematic implications on the 'Vipera xanthina complex'

Abstract

There are no morphological characters which allow a distinction between V. xanthina and V bulgardaghica. There are only minor differences between populations from the Near East (V. bornmuelleri) and the Anatolian xanthina, with the Bolkar specimens being intermediate between these two forms. V albizona is identical with bulgardaghica. These four nominal species (albizona, bornmuelleri, bulgardaghica and xanthina, respectively) are conspecific. The systematic status of V wagneri remains uncertain. The three "species" of the 'raddei group' (incl. albicornuta and latifii) are merely distinguishable on the basis of certain characters of the dorsal colour pattern. The distribution patterns and zoogeographical considerations do not argue in favour of a Tertiary 'vicariance model' for 'mountain vipers' proposed by Nilson and Andrén (1986b). Rather the actual distribution has been poorly investigated in eastern Anatolia and adjacent areas.