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Biomedical subjects

J Klimek

Publications and source records attributed to J Klimek.

At least 19 recordsLinked to original sources
PubMed2006

Pharmacological doses of triiodothyronine upregulate lipogenic enzyme gene expression in rat white adipose tissue.

Triiodothyronine (T (3)) is known to increase liver lipogenic enzyme gene expression both in vivo and in tissue culture. Conflicting results have been reported on the effect of T (3) on lipogenic enzyme gene expression in white adipose tissue. The results presented in this paper indicate that administration of pharmacological doses of T (3) in rats leads to increased fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), ATP-citrate lyase (ACL) and malic enzyme (ME) activity in white adipose tissue. The increase in lipogenic enzyme activity was associated with increased FAS, ACC, ACL and ME mRNA levels. The response was dose-dependent. Activity of lipogenic enzyme and the lipogenic enzyme mRNA levels were positively correlated to serum T (3) concentration. The in vivo effect of T (3) on lipogenic enzyme gene expression could be reproduced in primary white rat adipocyte culture. In conclusion, the results presented in this paper indicate that T (3) exerts a stimulatory effect on lipogenic enzyme gene expression in white adipose tissue both in vivo and in tissue culture. Significant effects of T (3) on lipogenic enzyme gene expression were only observed in the presence of relatively high (pharmacological) concentrations of the hormone.

Adipocytes↗
PubMed2006

Accuracy and consistency of the visual diagnosis of exposed dentine on worn occlusal/incisal surfaces.

Most indices for the assessment of wear of various aetiologies include the distinction between 'enamel still present' and 'dentine exposed' for grading. Since the visual diagnosis of exposed dentine has not yet been validated, the present study is a first attempt to investigate its accuracy and consistency. Sixty-one examiners (23 scientists, 18 university dentists and 20 dental students) were asked to diagnose 49 tooth areas with different grades of wear and to decide whether dentine was exposed (positive test) or not (negative test). Afterwards, the teeth were histologically evaluated. In 44 areas, dentine (also in all cases with minor wear) was exposed, and in 5 areas enamel was present. Overall sensitivity was 0.65, specificity 0.88 and the proportion of correct diagnoses was 0.67. The diagnosis 'dentine is exposed' was about 5 times as likely and the diagnosis 'dentine is not exposed' half as likely to come from an area with exposed dentine than from an enamel-covered area. The closeness of the visual diagnosis to the histological findings was only fair (kappa=0.27), no significant impact of professional experience was found. For inter- and intra-examiner agreement, kappa was 0.28 and 0.55, respectively. It was concluded that the diagnosis of exposed dentine is difficult.

Dental Enamel↗
PubMed2005

The imaging of root canal obturation using micro-CT.

AIM: To examine the potential and accuracy of micro-computed tomography (micro-CT) for imaging of filled root canals. METHODOLOGY: The root canals of five extracted maxillary teeth were shaped manually with K-files. After irrigation and drying, the root canals were filled by lateral condensation using gutta-percha cones and AH plus (Dentsply Maillefer, Ballaigues, Switzerland) as sealer. The filled root canals were examined by micro-CT at resolutions <11 microm. Three-dimensional reconstructions of the root canal fillings were made. The roots were sectioned histologically and standard photographs of the sectioned surfaces were taken. Digitized photographic images and the corresponding micro-CT sections were correlated qualitatively by superimposition. Quantitative morphometric data were obtained with respect to the surface area of the root canal filling and the individual gutta-percha points of the histological and the micro-CT sections. Pearson correlation coefficients were calculated. RESULTS: There was a good qualitative correlation between the images from the histological and the micro-CT sections. The fillings were clearly differentiated from the root canal walls. Individual gutta-percha cones and sealer were discernable. Pearson correlation coefficients showed a highly significant correlation between the two methods (P < 0.001) with respect to the area of the complete root canal filling (r = 0.992) and the gutta-percha cones (r = 0.968). CONCLUSIONS: The micro-CT technique was a highly accurate and nondestructive method for the evaluation of root canal fillings and its constituents. Qualitative and quantitative correlation between histological and micro-CT examination of root canal fillings was high.

Dental Pulp Cavity↗
PubMed2005

Mimicking of glutathione peroxidase deficiency by exposition of JAR cells to increased level of synthetic hydroperoxide.

A short chain synthetic analogue of lipid hydroperoxides was used to overload glutathione peroxidase (GPx) in human choriocarcinoma cell line JAR cells. Cells exposed to 100 microM tBuOOH displayed a 40% reduction in ATP level and significantly increased in membrane permeability, visualised by the lactate dehydrogenase (LDH) release into the extracellular medium. The intracellular level of oxygen free radicals measured as an oxidation of the dichlorodihydro-fluorescein diacetate (H2DCF-DA) significantly increased after 2 hours of cell exposition to 100 microM tBuOOH. Concomitantly MDA, 4-HNE level increased to 2 nmol/mg of cell protein after 2 hours. Mitochondria stained with MitoTracker Red CMXRos displayed a filamentous appearance in control cells but changed into granular less energised organelles after exposition to tBuOOH. Collectively, the above results indicate the importance of the contribution of oxidative stress in the development of pre-eclampsia.

Adenosine Triphosphate↗
PubMed2001

Dental erosion in children and adolescents--a cross-sectional and longitudinal investigation using study models.

OBJECTIVE: To investigate the prevalence and incidence of dental erosion in children and adolescents. METHODS: Lesions were registered for all tooth surfaces of primary and permanent teeth using pre-orthodontic study models. A total of 1,000 individuals (mean age 11.4+/-3.3 years) were included; 265 of them were followed over a 5-year period using their final orthodontic casts. RESULTS: In the primary teeth, 26.4% of the individuals had no erosive lesions, 70.6% had at least one tooth with grade 1 erosion and 26.4% had grade 2 erosion. Grade 1 erosion was found in 44% of the occlusal surfaces of molars (36% of the incisal surfaces of the canines) and grade 2 erosion in 11% (9%). Lesions affecting oral or vestibular surfaces were negligible. In the permanent teeth, 11.6% of individuals had at least one tooth with grade 1 erosion but only 0.2% had at least one tooth with grade 2 erosion. The most affected teeth were the mandibular first molars (7% with grade 1 lesions). Lesions affecting oral or vestibular surfaces were negligible. Mandibular first molars were identified as possible marker teeth for the onset of erosive lesions. Within the last two decades, the percentage of subjects with at least one tooth with a grade 1 or 2 erosive lesion significantly increased for primary and with grade 1 for permanent teeth (P< or =0.001). The longitudinal observation revealed that subjects with erosive lesions in their primary dentition had a significantly increased risk for erosion in their permanent teeth (P< or =0.001). CONCLUSION: In Germany, dental erosion seems to be a significant, but not a serious, problem for dental health in adolescents.

Adolescent↗
PubMed2000

Relation between mercury concentrations in saliva, blood, and urine in subjects with amalgam restorations.

The aim was to determine the relationship between mercury content of resting and stimulated saliva, and blood and urine. Eighty subjects participated; 40 of them attributed their self-reported complaints to dental amalgam (patients), the others were matched with respect to age, sex and amalgam restorations (controls). Serum, 24-h urine, resting and chewing stimulated saliva were analyzed for mercury using the ASS-technique. Quality, number, surfaces and total area of amalgam fillings were recorded clinically and using study models. Median (range) mercury levels in serum were 0.67 (0.1-1.52) microgram/l for patients and 0.60 (0.1-1.3) for controls. In urine levels were found to be 0.77 (0.11-5.16) and 0.94 (0.17-3.01) microgram/g creatinine respectively. No significant differences were found between the groups. Resting saliva contained 2.97 (0.10-45.46) micrograms/l in patients and 3.69 (0.34-55.41) in controls (not significant). Chewing mobilized an additional amount of 16.78 (-6.97 to 149.78) micrograms/l in patients and 49.49 (-1.36 to 504.63) in controls (P < or = 0.01). Only a weak correlation was found between mobilized mercury in saliva and serum (r = 0.27; P < or = 0.05) or urine (r = 0.47; P < or = 0.001). For resting saliva the respective values were r = 0.45 (P < or = 0.001) and r = 0.60 (P < or = 0.001). Saliva testing is not an appropriate measure for estimating the mercury burden derived from dental amalgam.

Adult↗
PubMed2000

A comparative profilometric in vitro study of the susceptibility of polished and natural human enamel and dentine surfaces to erosive demineralization.

This study sought to compare the depths of erosive lesions in samples from different tooth sides as well as from enamel, dentine and root surfaces, and to examine the effect of preparation and polishing of specimens on erosive demineralization. From 30 impacted human third molars, two enamel samples from the mesial, distal, buccal and oral aspects, and similar samples from the radicular dentine, were prepared. One of each pair of samples was polished whereas the other was left untreated. Four samples were also prepared from the coronal dentine. For erosive demineralization, all samples were immersed in 0.05 M citric acid for 3 h and the erosion depth was calculated profilometrically. In general, natural surfaces showed significantly smaller erosion depths than polished surfaces (p< or =0.001) and enamel samples showed greater depths than coronal dentine (not significant) and root dentine (p< or =0.001). The erosion depths of the four tooth sides correlated significantly for polished enamel and coronal dentine samples but not for natural enamel specimens. There was no correlation between erosion depths for enamel and coronal dentine, and only a weak correlation between enamel and root dentine.

Citric Acid↗
PubMed2000

The effects of ascorbate and alpha-tocopherol on the NADPH-dependent lipid peroxidation in human placental mitochondria.

The effects of ascorbate and alpha-tocopherol as antioxidants and as co-operative factors against NADPH-dependent lipid peroxidation in human placental mitochondria have been studied. The addition of ascorbate at low concentration (up to 50 microM) to the NADPH-generating system resulted in increasing lipid peroxidation and Fe3+ to Fe2+ reduction. High concentration of ascorbate (150 microM), which produced maximal rate of ascorbate-dependent lipid peroxidation, was found to inhibit almost completely NADPH-dependent lipid peroxidation by maintaining too much iron in its reduced form. Either stimulatory or inhibitory effect of ascorbate on NADPH-dependent lipid peroxidation depends on the appropriate Fe3+/Fe2+ ratio. Alpha-tocopherol caused a decrease of NADPH-dependent lipid peroxidation, inhibiting completely this process at 150 microM concentration. The inhibitory effect of alpha-tocopherol increased rapidly with the increasing ascorbate concentration, almost complete inhibition of NADPH-dependent lipid peroxidation being obtained at 25 microM alpha-tocopherol and 50 microM ascorbate. This strong inhibitory combined effect of alpha-tocopherol and ascorbate was independent of the Fe3+/Fe2+ ratio, as alpha-tocopherol is not able to reduce Fe3+ to Fe2+ under the conditions employed. These findings suggest that antioxidant effects of ascorbate in placental mitochondria are mediated by recycling of alpha-tocopherol rather than by strong reduction of Fe3+ to Fe2+. On the basis of the results obtained, we assume that adequate concentrations of alpha-tocopherol and ascorbate in placental tissue may prevent the release of lipid peroxide from placental mitochondria and therefore could be protective against the development of preeclampsia.

Antioxidants↗
PubMed2000

[A grid pattern type of photocoagulation in treatment of diabetic maculopathy--personal experience].

PURPOSE: The aim of the present study was the evaluation of visual outcome of 425 eyes in 283 patients treated by focal and grid pattern photocoagulation for clinically significant macular edema according to the recommendations of the Early Treatment Diabetic Retinopathy Study (ETDRS). MATERIAL AND METHODS: On the basis of baseline status of macula, eyes were classified into three groups: group I--eyes treated by focal photocoagulation (39 eyes), group II--eyes treated by focal photocoagulation and/or modified grid (84 eyes), group III--eyes treated by focal photocoagulation and/or grid pattern (302 eyes). Eligibility criteria for this retrospective study included a diagnosis of clinically significant macular edema according to the ETDRS scale. The baseline examination for all patients presented in this review included: the best corrected visual acuity (VA), slit lamp with contact lens indirect ophthalmoscopy, fundus color photography and fluorescein angiography. All patients were treated with argon green by grid with Nidek 2300 laser. Modified grid or focal photocoagulation according to the ETDRS recommendations were performed. Patients with proliferative diabetic retinopathy (PDR) were transferred to panretinal photocoagulation (PRP) after treatment of maculopathy. Development of VA from the baseline to last checkup in treated eyes was reported and compared. Follow-up ranged widely from 6 to 45 months. RESULTS: General stabilization was achieved in 51.3%, improvement in 10.1% and deterioration in 38.6% of eyes. The best results were achieved after selective and focal and/or modified grid treatment: in the Ist group stabilization of VA was achieved in 43.6% and improvement in 41% of eyes; in the IInd group: stabilization in 60.7% and improvement in 21.4% were stated; in the IIIrd group: stabilization in 49.7% and improvement only in 3.0%. In 164 (38.6%) cases supplemental treatment was administered. CONCLUSION: Photocoagulation has proved effective in the treatment of diabetic clinically significant macular edema.

Adult↗
PubMed1999

One year clinical evaluation of the retention and quality of two fluoride releasing sealants.

In this prospective, double-blind, split-mouth-designed study, sealant retention rate and quality of two light-cured, fluoride-releasing sealants (Helioseal F, Fissurit F) were compared. Additionally the influence of the isolation method was evaluated. Fifty-eight subjects participated; 1 year later 54 of these (mean age 13.7 +/- 3.6 years) were reexamined. Sealants were applied to 203 tooth pairs (168 conventional and 25 invasive sealants). After 1 year, 193 tooth pairs were available for study; 82 were applied using rubber dam and 111 using cotton roll isolation. Retention rate and sealant quality were judged clinically and with photographs. The initial sealant quality was comparable for both materials. After 1 year, 53.4% of the Helioseal F sealants (44.6% of the Fissurit F sealants) were fully intact, 43.1% (51.8%) partially intact and 3.6% (3.6%) completely lost (P < 0.001). Placement under rubber dam resulted in significantly higher retention rates for both sealants (P < 0.001) as well as in an improved sealant quality. Cases of complete loss only occurred in teeth isolated with cotton rolls. The findings suggest that placement under rubber dam increases retention rate and sealant quality and may reduce material dependent factors that are considered a cause of sealant failures.

Adolescent↗
PubMed1999

Surface roughness and bond strength of enamel to composite.

OBJECTIVES: The aim of the study was to assess the influence of pretreating enamel by different rotary instruments on shear-bond strength of composite to enamel after the acid etch technique. METHODS: Ninety human enamel specimens with transversely and longitudinally sectioned prisms were ground flat, and half of the enamel area of each specimen was prepared with one of the eight different rotary instruments: a 120 microns diamond bur, three finishing diamonds (30, 15 and 8 microns), two tungsten carbide finishing instruments (8- and 30-fluted) and two stones (Dura green and Dura white). The other half of the enamel area was left untreated. Enamel roughness was measured by laser-stylus profilometry. Two cylinders filled with the hybrid composite Pertac were adhesively fixed on each enamel surface, one on the prepared side and the other on the untreated side. After seven days of water storage, shear-bond strength was measured with a Universal testing machine. RESULTS: Rz values of the treated enamel surfaces were between 4.14 and 17.75 microns. The shear-bond strength data varied between 16.8 and 29.4 MPa and were similar for transversely and longitudinally orientated prisms. The different roughness data had no significant influence on shear-bond strength of composite to enamel. Additional SEM investigation showed that the surface geometry caused by the rotary instruments largely persisted after acid etching. SIGNIFICANCE: With regard to shear-bond strength, there was no advantage in using a special bur for finishing enamel surfaces prior to the acid etch technique. Burs causing extreme roughness should not be used for this purpose.

Acid Etching, Dental↗
PubMed1999

Dental erosions in subjects living on a raw food diet.

The aim of the study was to investigate the frequency and severity of dental erosions and its association with nutritional and oral hygiene factors in subjects living on a raw food diet. As part of a larger dietary study 130 subjects whose ingestion of raw food was more than 95% of the total food intake were examined. The median duration of the diet was 39 (minimum 17, maximum 418) months. Before the clinical examination, the participants answered questionnaires and recorded their food intake during a 7-day period. Dental erosions were registered using study models. As a control 76 sex- and age-matched patients from our clinic were randomly selected. The raw food diet records showed the median daily frequency of ingesting citrus fruit to be 4.8 (minimum 0.5, maximum 16.1). The median intake of fruit was 62% (minimum 25%, maximum 96%) of the total, corresponding to an average consumption of 9.5 kg of fruit (minimum 1.5, maximum 23.7) per week. Compared to the control group subjects living on a raw food diet had significantly (p</=0.001) more dental erosions. Only 2.3% of the raw food group (13.2% of the controls) had no erosive defects, whereas 37.2% had at least one tooth with a moderate erosion (55.2% of the controls) and 60.5% had at least one tooth with a severe erosion (31.6% of the controls). Within the raw food group no significant correlation was found between nutrition or oral health data and the prevalence of erosions. Nevertheless, the results showed that a raw food diet bears an increased risk of dental erosion compared to conventional nutrition.

Adolescent↗
PubMed1998

Inhibitory effect of free radicals derived from organic hydroperoxide on progesterone synthesis in human term placental mitochondria.

Different natural and synthetic organic hydroperoxides have been found to stimulate TBARS formation in human term placental mitochondria. The levels of TBARS were lower than arising from NADPH-dependent lipid peroxidation. BHT, Mn2+ and DMPO counteracted TBARS formation in the presence of cumene hydroperoxide implicating involvement of free radicals in this process. On the other hand superoxide dismutase, catalase and EDTA while being inhibitory in NADPH-dependent lipid peroxidation did not inhibit cumene hydroperoxide-dependent TBARS formation. Amphenone B and SKF-525A, inhibitors of cytochrome P-450, strongly inhibit both NADPH- and cumene hydroperoxide-dependent lipid peroxidation. These data provide evidence that cytochrome P-450SCC is involved in both these processes. However NADPH-dependent lipid peroxidation and the cumene hydroperoxide have been found to inactivate placental mitochondrial cytochrome P-450SCC. The presence of cumene hydroperoxide resulted in a more rapid inactivation of cytochrome P-450SCC and consequently inhibited NADPH-dependent lipid peroxidation. It has been observed for the first time that progesterone biosynthesis can be inhibited by cumene hydroperoxide. Protective effect of Mn2+ and DMPO on progesterone biosynthesis indicates the importance of free radicals as transient products of cytochrome P-450SCC-dependent cumene hydroperoxide metabolism. In contrast to progesterone formation from cholesterol, the conversion of pregnenolone to progesterone was not affected by cumene hydroperoxide. This suggests that inhibition of progesterone synthesis from cholesterol by hydroperoxide may be ascribed to its effect on the desmolase activity of cytochrome P-450SCC in placental mitochondria. On the basis of the results obtained, we propose that the inhibition of progesterone biosynthesis by naturally occurring hydroperoxides may contribute to the development of preeclampsia.

Benzene Derivatives↗
PubMed1997

Effectiveness of diamond-impregnated felt wheels for polishing a hybrid composite.

The effectiveness of diamond-impregnated felt wheels for polishing the surfaces of a fine-particle hybrid composite was studied in relation to different finishing methods. Standardised composite specimens were finished with one or a series of two or three finishing diamonds (particle size 30, 15 and 8 microns), one or two tungsten carbide finishing burs (12- and 30-fluted) or with a finishing diamond followed by a tungsten carbide bur. The final polishing of all specimens was done with the diamond-impregnated felt wheel Diafix alpha. Treatment with Sof-Lex discs after the use of a finishing diamond served as a polishing standard for comparison. Evaluation of the final surfaces was done with profilometry and by scanning electron microscopy. The profilometric results showed that the type of pretreatment was decisive for the quality of the final polishing. Nearly all surfaces polished by the diamond-impregnated felt wheels were smoother than those treated by the flexible discs (P < 0.01). The lowest roughness data were recorded following a pretreatment with a finishing diamond and a tungsten carbide finishing bur. After appropriate pretreatment, the hybrid composite surface was sufficiently polished with the diamond-impregnated felt wheels.

Analysis of Variance↗
PubMed1997

Interindividual differences in degradation of sodium monofluorophosphate by saliva in relation to oral health status.

The enzymatic degradation of sodium monofluorophosphate by whole saliva in patients with differing oral health status was compared Ten patients each with good or poor oral health were selected. Assessment of oral health status included indices of the amount of dental plaque, caries experience and counts of Streptococcus mutans and lactobacilli. Whole-saliva samples were collected under standardized conditions and monofluorophosphatase (MFPase) activity was measured in 2-ml saliva samples during 2 h of incubation at 37 C with 1 ml of monofluorophosphate solution (equivalent 31.5 mmol/1 F). MFPase activity was found in all the saliva samples. The values ranged from 0.6 to 17.8 nmol F/ml saliva per min. High MFPase activities correlated well with large amounts of plaque with the D component of the DMFT index and with high counts of salivary S. mutans and lactobacilli. The results show a wide range of MFPase activity in individuals and a statistically significant correlation (p < 0.05) between high MFPase activity and poor oral health status.

Adolescent↗
PubMed1992

The influence of NADPH-dependent lipid peroxidation on the progesterone biosynthesis in human placental mitochondria.

In an in vitro system consisting of human term placental mitochondria and an NADPH-generating system plus Fe2+, significant lipid peroxidation was observed along with a concomitant inhibition of progesterone biosynthesis. This inhibition could be markedly blocked by Mn2+, superoxide dismutase and dimethylfuran, inhibitors of NADPH-dependent lipid peroxidation. In addition, it has been found that malondialdehyde formation is accompanied by a corresponding decrease in placental mitochondrial cytochrome P-450 content. Inhibitors of lipid peroxidation also prevent the loss of cytochrome P-450, further demonstrating a direct relationship between NADPH-dependent lipid peroxidation and degradation of cytochrome P-450 in cell-free systems. These measurements provide the first evidence that the inhibition of progesterone biosynthesis by a NADPH-dependent lipid peroxidation in placental mitochondria is a consequence of cytochrome P-450 degradation due to lipid peroxidation.

Cytochrome P-450 Enzyme System↗
PubMed1991

[Primary accuracy of fit of composite inlays produced according to the indirect method].

The primary accuracy of fit of three composite inlay systems was evaluated comparatively. Control inlays were made of a phantom metal. In the proximal-cervical surfaces the resulting median widths of the open margins showing luting agent were as follows: EOS (74.1 microns) greater than Ful-Fil (59.5 microns) greater than Brilliant (43.13 microns) greater than Phantom metal (18.6 microns). Even though, under clinical conditions, composite inlays are attached by means of adhesives, the primary accuracy of fit achieved should be comparable to that of cast restorations, because the long-term stability of the material used for fasting the inlays cannot be warranted.

Composite Resins↗