PubMed Health⌕ Search

Biomedical subjects

M Kovacević

Publications and source records attributed to M Kovacević.

At least 19 recordsLinked to original sources
PubMed2000

Detection of a transitional ion concentration zone during electronic measurement of root canal length: a study in vitro.

AIM: The aim of this study was to examine the importance of a transitional ion concentration zone at the apical foramen during electronic root canal length measurement (ERCLM). METHODOLOGY: The model comprised 21 extracted single-rooted human teeth, divided into two experimental groups and one control group, each of seven teeth. The anatomical tooth length was determined from the site of reference on the tooth crown to the canal orifice and was measured using an endodontic file and a vernier caliper. Two aqueous solutions of various NaCl, KCl and CaCl2 concentrations were mixed with agar. The Na+, K+ and Ca++ concentrations corresponded to the average value of each group as determined by atomic spectrophotometry evaluation of the extirpated human pulps. The agar containing cations was injected into the root canals after their preparation to a foramen diameter of 0.70 mm. The control teeth were then completely immersed in agar having the same concentration of cations as the agar inside the canal. In the first experimental group (group 1), the teeth were immersed in agar so that the ion concentration was higher inside the canal; in the second experimental group (group 2), the concentrations were reversed. In all three groups, ERCLM was performed by an EED 11--resistance type device. Length d1 was defined as the length of the root when measured to a value one degree less than the test value. Length d2 was defined as the length of the root inducted by the test value, which corresponded to the resistance of the periapical agar. RESULTS: In group 1 the average d1 length was 0.44 +/- 1.05 shorter than the anatomical foramen (AF), and in group 2, 1.11 +/- 0.43 mm longer than AF. In the control group the d1 length was on average--3.02 +/- 3.72 mm from the AF. The d1 values of all groups were not statistically significantly different from the anatomical length (AL). In all three experimental groups the d2 length was statistically significantly different from the AL (P < 0.05, t-test); group 1 d2 = AL + 6.32 +/- 1.38 mm; group 2 d2 = AL + 6.27 +/- 1.47; control group d2 = AL + 9.15 +/- 1.00 mm. CONCLUSIONS: The results of this study indicated that when the electroconductive medium in the canal had a different ion concentration than the periapex, and the canal orifice had a wide diameter (0.70 mm), the transitional concentration zone influenced the accuracy of measurement during ERCLM with a resistance type device. When ion concentrations inside and outside the canal were identical, in teeth with a wide foramen diameter (0.70 mm or more) the lack of a transitional ion concentration zone meant that the length of the root canal could not be determined by ERCLM.

Agar↗
PubMed1999

Erythroid progenitor cells from pig bone marrow and peripheral blood.

With the intention of using the pig as a large animal model in haematopoietic research, a clonal assay in methylcellulose was developed and the optimal conditions for raising erythroid progenitors from adult pig bone marrow (BM) and peripheral blood (PB) have been established. Progenitor cells were stimulated to proliferate and differentiate in vitro by growth factors containing leucocyte condition medium (LCM), and with recombinant human erythropoietin (rhEpo). The number of PB BFU-E (burst forming units - erythroid) directly depended on the concentration of LCM, but BM BFU-E were not dependent on LCM. Both CFU-E (colony forming units - erythroid) and BFU-E were rhEpo dependent. Despite relatively high but expected individual variations, the mean number of colonies, as well as the functional characteristics of progenitor cells investigated, were similar to those of miniature pigs and some other mammals.

Animals↗
PubMed1999

Water phantom backscatter factors for x-rays in the 60 kV to 300 kV region.

Experimentally determined values of x-ray backscatter factors are presented in this paper. Measurements were made for x-rays generated at voltages between 60 kV and 300 kV and three water phantoms different in shape and size. To study the influence of the irradiation geometry on the backscatter factors, the measurements were performed for different photon beam field diameters at the phantom front face, at a fixed source-to-phantom distance of 1 m. An ionization chamber of volume 1 cm3 was used for dose measurement. Measured results are analysed and discussed in comparison with measured and calculated values given in the cited references.

Phantoms, Imaging↗
PubMed1999

Radiosensitivity of human lymphocytes in vitro correlates more with proliferative ability of cells than with the incidence of radiation-induced damages of the genome.

The purpose of this study was the estimate the extent of individual variability in radioresponse of human lymphocytes in vitro and to establish the reasons of variability. Individual variability in radiation-response was evaluated using the cytochalasin B micronucleus test among 82 healthy individuals (36 men and 46 women), of mean age 38 (range 30-48). Blood samples were irradiated with gamma (60Co) rays at a dose of 2 Gy in vitro. The yield of radiation-induced micronuclei (MN), cytochalasin blocked proliferation index (CBPI), fraction of micronucleated binucleate (BN) cells and mean incidence of MN per micronucleated BN cells at a sampling time of 72 hours were scored. Our results brought out a significant effect of gender on the level of spontaneously occurring micronuclei, the lack of statistical differences between gender in the yield of radiation-induced micronuclei and marked variability in radiation response among individuals. Likelihood of expressing hypersensitivity was correlated with ability of cells to proliferate in vitro (beta = 0.41, p < 0.000) more than with the incidence of radiation-induced micronuclei per micronucleated cell (beta = 0.20, p < 0.000).

Adult↗
PubMed1998

Influence of the concentration of ions and foramen diameter on the accuracy of electronic root canal length measurement--an experimental study.

Investigations on the concentration of cations in human pulp have shown that pathological changes in the pulp lead to changes in the concentration of ions in the tissue. Consequently, its electrophysiological characteristics are changed, which affects the accuracy of electronic root canal length measurements (ERCLMs). The aim of this study was to examine the effect of concentrations of Na+, K+, and Ca2+ cations in medium within the canal and around the tooth, and also foramen diameter, on the accuracy of ERCLMs. The model comprised 21 extracted single-rooted human teeth divided into two experimental groups and one control group, with seven teeth each. Two aqueous solutions of different concentrations of NaCl, KCl, and CaCl2 were mixed with agar. The concentrations of Na+, K+, and Ca2+ corresponded to the results of analyses performed by atomic spectrophotometry on the extirpated human pulps. Agar containing cations was injected into the root canal prepared with a foramen diameter of 0.25 mm. In the control group, the teeth were then completely immersed in agar of the same concentration of cations as the agar inside the canal. In the first experimental group (group 1), the concentration of ions was higher inside the canal, compared with the concentration outside the canal. In the second experimental group (group 2), the order of concentrations was inverse. In all three groups, ERCLMs was performed in the previously described model. Then, the size of the apical foramens was enlarged and ERCLMs repeated at foramen diameters of 0.45 mm and 0.70 mm diameters, respectively. Results indicate that at 0.25 diameters, the most accurate measurements were taken when the concentrations of ions inside the canal were higher than outside the canal (Xdif = 1.39 +/- 1.21 mm) (group 1). At diameters of 0.45 and 0.70 mm, no significant differences were found (p < 0.05) between the experimental groups (error amounted to Xdif = 6.27 +/- 1.47 mm). In the control group measurement, error increased with enlargement of the foramen.

Calcium↗
PubMed1995

The anatomical basis for the cerebellar infarcts.

BACKGROUND: Very little can be found in the literature concerning the variation of the irrigation area of the cerebellar arteries, as well as the characteristics of anastomoses among these vessels. The anatomical features may determine certain features of cerebellar infarcts. Consequently, we examined the irrigation area of and the anastomoses among the cerebellar arteries. METHODS: The anatomical features of the posterior inferior cerebellar artery (PICA), the anterior inferior cerebellar artery (AICA), and the superior cerebellar artery (SCA) were studied in 26 cerebella injected with india ink, while their irrigation areas and anastomoses were examined in 8 of these cerebella. RESULTS: The PICA, which most often (82%) arose from the vertebral artery, was found most commonly (81.3%) to supply the largest part of the occipital surface of the cerebellar hemisphere, the caudal or caudomedial part of the tentorial surface, and the inferior vermis. The AICA, which usually (92%) arose from the basilar artery, commonly (68.8%) supplied most of the petrosal surface of the hemisphere and the flocculus. The SCA, which divided into the medial and the lateral trunks, always irrigated most of the tentorial surface of the cerebellum, the superior vermis, and the dentate nucleus. The PICA, AICA, and SCA were always interconnected by anastomoses, which ranged from 40 microns to 420 microns in diameter. CONCLUSIONS: Cerebellar infarcts were documented by computed tomography (CT) or magnetic resonance imaging (MRI) examinations in 10 patients. The infarcts were located in the PICA territory (60%) or the SCA region (40%). The authors compared the obtained anatomic data to the features of the cerebellar infarcts in these patients.

Adult↗
PubMed1993

[Investigational methods in Lyme disease].

After the first clinical case of Lyme disease had been recorded in Belgrade in 1987 a multi-level research of the disease was undertaken in our country. The research was organized on the team basis and was systematized. Ever since the beginning epidemiological method has been applied. Professional approach was provided by guidelines, while methods and research stages have been provided and further developed during seminars and symposiums dealing with lyme disease. Research team was comprised of experts from Institute of Public Health of Belgrade, Institute for Preventive Medicine of the Medical Military Academy and clinicians--specialists in the relevant areas. The team gathered its own precious experience in Lyme borreliosis, the disease with precisely defined features and well-described manifestations and characteristics. This work describes methodology applied in the research of Lyme disease in our country.

Animals↗
PubMed1993

[Epidemiologic characteristics and serologic findings in erythema migrans].

Our three-year research covered 417 patients with erythema migrans, of both sexes and all age groups. Among them 87.3% had a history of tick bite. Average attachment of tick to a patients skin was two days. Diameter of erythematous lesions was 1-50 cm (with an average of 15.1 cm). Magnitude of the lesion does not correlate with the further development of the Lyme disease. IFA test detected antibodies against Borreliae burgdorferi in 27.0% of our patients.

Adult↗
PubMed1993

[Rheumatic manifestations in Lyme borreliosis: personal experience in patients with oligoarthritis of "unknown" origin].

Lyme borreliosis is an infectious illness caused by the spirochete Borrelia burgdorferi and is transmitted by tick vectors. A prospective study was performed from January 1990, to investigate whether Lyme arthritis might have been undetected among patients with (unclassified arthritis) oligoarthritis of "unknown" aetiology. 210 patients were tested for antibodies to Borrelia burgdorferi: 82 patients with oligoarthritis of "unknown" aetiology; 52 patients with Reiter's syndrome; 20 patients with seronegative, B-27 positive oligoarthritis and 56 controls. Serological testing for Borrelia burgdorferi was performed by indirect immunofluorescence assay. The occurrence of positive antibodies (1:80) in 11 (13.4%) patients with arthritis of "unknown" aetiology was significantly different from the combined control group (1.6%) (p < 0.05). Four out of 11 patients remembered a tick bite, two out of 11 patients developed erythema migrans after 3 to 10 days. Six weeks later 2 patients developed oligoarthritis and one patient after a month. In the remaining 8 patients arthritis was the first sign of the disease. Knees were most commonly affected (90%). Radiographic abnormalities (osteoporosis, soft tissue swelling) were noted in 3 patients. The synovial fluid findings were typical for inflammatory arthritides in 6 patients. The diagnosis of Lyme borreliosis was made according to following data: origin from an area endemic for Lyme borreliosis, tick bite, erythema migrans, significant levels of the antibodies to the Borrelia burgdorferi and oligoarthritis. It can be concluded that arthritis may be the main manifestation of Borrelia burgdorferi infection.

Adult↗
PubMed1993

[Lyme borreliosis in Belgrade].

In the period 1990-1992 in Belgrade area a diagnosis of Lyme disease was registered in 487 patients. There were 195 men and 292 women. The disease was registered in all ages groups, median age 38 y. The tick bite has been confirmed in 379 (77.8%) patients. Erythema migrans was the first sign of illness in 387 (84.6%) patients. The disease resoted in neurologic symptoms in 1.8%, joint manifestation in 4.8% and cardiac involvement in 0.9%. Antibodies to Borrelia burgdorferi have been detected by indirect immunofluorescence microscopy in 23.4%. Lyme disease has been registered in all districts of Belgrade. Acarological investigations have detected an infection by Borrelia burgdorferi in 29.0% of investigated ticks.

Adolescent↗
PubMed1991

[Microsurgical treatment of tubal factors in sterility].

In the period from 1982-1988, 164 patients were operated due to the tubal factor sterility. Indications for operations were based on HSG and laparoscopy. Microsurgical process was applied. 57 (34.75%) of 164 operated patients conceived. There were 41 (25.90%) intrauterine and 16 (9.14%) ectopic pregnancies. The most frequently pregnancies happened in the patients who had been treated by fimbroplasty and isolated adhesiolysis. The patients, who had been treated by salpingostomy terminalis and tubal implantation had lower pregnancy percentages.

Adult↗
PubMed1989

[Free forearm flap in the reconstruction of mucosal defects of the oral cavity and oropharynx after radical removal of a tumor].

In the Department of Surgery, Clinical Hospital Center Rijeka in cooperation with ENT Department and the Department of Maxillofacial Surgery, fifty patients with the mouth and the throat tumor were operated since 1985. The defects were covered with free radial forearm flaps. In seven cases flap did not survived due to thrombosis of the anastomosis. The arterial anastomosis were usually made on the external carotid artery branches. Seven anastomosis were made on the opposite side of the neck because homolateral carotid artery was ligated. In three cases terminolateral anastomosis with common carotid artery was made. In eight patients the bone defect of the lower jaw was reconstructed with vascularized radial bone graft. Irradiation and/or cytostatic therapy was mostly applied two weeks after surgery. The donor site defect has no functional nor aesthetic implications.

Forearm↗
PubMed1989

Hypoplasia of the proximal segment of the anterior cerebral artery.

Hypoplasia of the proximal (A1) segment of the anterior cerebral artery (ACA) has been examined in 50 human brains and on 8 selected carotid arteriograms. Hypoplasia has been found in 22% of the cases. Two types of this phenomenon exist, namely the mild and extreme hypoplasia. Mild hypoplasia has been noticed in 14% of the specimens. The hypoplastic vessel has ranged from 1.3 to 1.9 mm in diameter (average 1.6 mm) and it was from 0.6 to 0.9 mm smaller than the opposite A1 portion. Extremely hypoplastic proximal segment has been present in 8% of the cases. It has varied from 0.3 to 1.1 mm in size (average 0.9 mm) and has been more than 1 mm smaller than the opposite proximal segment. Both mild and extreme hypoplasia have been associated in 81.8% of the cases with the corresponding variations or malformations of the anterior cerebral, posterior cerebral, posterior communicating and basilar arteries.

Adult↗
PubMed1986

Oculomotor, trochlear, and abducens nerves penetrated by cerebral vessels. Microanatomy and possible clinical significance.

Twenty formaldehyde-fixed brains were examined under the stereoscopic microscope. In 12 brains (60%), the oculomotor nerves were penetrated by the circumflex mesencephalic artery or by a branch of the perforating vessels of the posterior cerebral artery, either on one side (40%) or on both (20%). In one brain (5%), a particular relationship was noticed between the trochlear nerve and the superior cerebellar artery. The abducens nerves were penetrated by the corresponding pontine veins in three brains (15%). These anatomical findings might have important clinical implications.

Abducens Nerve↗
PubMed1986

Anatomical bases for surgical approach to the initial segment of the anterior cerebral artery. Microanatomy of Heubner's artery and perforating branches of the anterior cerebral artery.

Both the Heubner's artery and the perforating branches of the anterior cerebral artery (ACA) were present in all thirty-three examined brains. Heubner's arteries varied in number from 1 to 3. They originated from the distal (A2) segment of the ACA in 34% of the cases, from the proximal (A1) segment of the ACA in 17%, at the level of the anterior communicating artery in 21%, from the fenestration of the ACA in 8%, and in all the other cases (20%) from the azygous anterior cerebral artery, accessory middle cerebral artery, frontopolar artery and, finally, by the common stem with the medial orbitofrontal artery. Heubner's artery most commonly terminated dorsal and lateral to the carotid bifurcation, at an average distance of 4.8 mm. The mean diameter of Heubner's artery was 662 microns, that of its extracerebral collateral branches 205 microns, of the terminal branches 462 microns, and of the intracerebral segments 354 microns. Perforating branches varied in number from 1 to 12 with an average of 6.6. The majority of the branches originated from the initial 6.1 mm of the A1 segment. These vessels terminated close to the carotid bifurcation, at an average distance of 3.8 mm. All the perforating branches were divided into small (average 122 microns in diameter) and large (average 325 microns). The mean diameter of intracerebral segments was 276 microns, and that of terminal branches 259 microns. It was concluded that the anatomical characteristics of both the recurrent artery and the perforating branches can be of a great significance in cerebrovascular diseases.

Adult↗