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Biomedical subjects

M Knezević

Publications and source records attributed to M Knezević.

At least 19 recordsLinked to original sources
PubMed2003

Phagocytic functions of salivary neutrophils in oral mucous membrane diseases.

BACKGROUND AND PURPOSE: Phagocytic functions of salivary polymorphonuclear neutrophils (sPMNs) have not been comprehensively studied in patients with oral mucous membrane diseases, although available data suggest the role of immunity in their pathogenesis. SUBJECTS AND METHODS: Phagocytic functions of sPMN were determined in 15 patients with acute recurrent aphthous ulceration (RAU), 11 patients with oral lichen planus (OLP) and 20 healthy volunteers. In healthy subjects, the same parameters were also determined in peripheral blood polymorphonuclear neutrophils (bPMNs). Phagocytic activity (proportion of ingesting cells, PA), ingestion ability (number of ingested targets per 100 phagocytes, IA) and intracellular microbicidity (proportion of killed targets, IM) of PMNs separated from peripheral blood and the whole unstimulated saliva were determined by acridine orange method with living yeast cells as targets. RESULTS: Salivary PMNs in healthy individuals showed significant reduction in PA (33% vs. 76%; P < 0.009) and IA (0.47% vs. 2.93%; P < 0.009) and significant increase in IM (12.0% vs. 5.5%; P = 0.011) in comparison with bPMNs. In RAU patients, reduced PA (27% vs. 37%; P = 0.035) and IA (0.25% vs. 0.47%; P = 0.05) were detected, while in OLP patients enhanced IM was detected (12% vs. 19%; P = 0.033) in comparison with healthy controls. CONCLUSION: Salivary PMNs present functional features distinct from those in peripheral blood. Some phagocytic functions of sPMNs are reduced in RAU and enhanced in OLP, indicating their role in pathogenesis or reflecting clinical changes in these conditions.

Adult↗
PubMed2001

Immunogenicity of dendritic cells pulsed with cartilage derived soluble alloantigens.

Investigation of allo- and autoreactivity of cartilage components is useful not only for the potential allogeneneic transplantation but also for the treatment of tissue specific degenerative autoimmune diseases. We generated dendritic cells (DCs) to study articular cartilage immunogenicity, by using human peripheral blood mononuclear cells. Dendritic cells are extremely efficient antigen-presenting cells that initiate and modulate T-cell dependant immune responses. After isolation by density centrifugation, GM-CSF and IL-4 were added to adherent mononuclear cells. After 7 days of cultivation the cells in cell culture were: HLA-DR+, CD86+, CD14-, CD80-, CD83, CD19-, CD56-, CD3-. Dendritic cells were then pulsed with a supernatant taken from primary monolayer cell cultures of human allogeneic chondrocytes. The stimulating capacity of antigen-pulsed DCs was measured in a classical proliferation assay using tritium labelled thymidine as a marker of mitosis. Proliferative responses were significantly strong but became much stronger when DCs were concomitantly incubated with soluble antigens and human recombinant TNF-alpha and used subsequently as stimulators. Although TNF-alpha positively influenced the stimulating capacity of pulsed DCs, we were unable to detect major differences in expression of specific DCs' phenotype markers assessed by flow cytometry in the absence or presence of this cytokine.

Antigen Presentation↗
PubMed2001

Protein synthesis of human articular chondrocytes cultured in vitro for autologous transplantation.

Chondrocytes in hyaline cartilage produce typical matrix proteins, the most abundant of them being collagen type II and aggrecan. Chondrocytes in monolayer cell culture dedifferentiate and gain fibroblastic phenotype. The cells gradually start to produce collagen type I while the production of collagen type II and aggrecan decreases. Transplantation of autologous chondrocytes cultured in vitro is used for treatment of aseptic articular cartilage lesions. For this purpose, cartilage biopsy is taken and isolated cells are subsequently proliferated in a monolayer cell culture. When implanted, the cells start to produce specific cartilaginous matrix that fills the defect. Prior to surgical procedure the cells can also be cryopreserved for longer periods of time after reaching appropriate numbers. We tested the influence of cultivation time and number of continuous culture passages as well as the influence of cryopreservation on the matrix protein synthesis of human articular chondrocytes. The ability of dedifferentiated chondrocytes to redifferentiate has been monitored by measuring matrix protein synthesis of the cells, re-seeded in agarose suspension culture. The results obtained show progressive dedifferentiation during monolayer cell culture procedures, facilitated by cryopreservation. Successful redifferentiation of cells re-seeded in suspension cultures was observed regardless of the previous level of chondrocyte dediferentiation.

Cartilage, Articular↗
PubMed2001

Determination of optimal transport conditions for biopsies of human articular cartilage as well as for suspensions of cultured chondrocytes used in autologous transplantation.

Autologous transplantation of chondrocytes is currently being promoted as a novel approach for the treatment of deep cartilage lesions. Briefly, the method involves enzyme-mediated release of chondrocytes from cartilage biopsies, the expansion of cells by in vitro cultivation and their re-implantation into the defect. The success of this technique depends on many factors including transport conditions for both, cartilage biopsies from the operating hall to the laboratory and the return transport of final suspension of cultured chondrocytes. To determine the extent of cellular damage in biopsies, chondrocytes were enzymatically isolated following a few days of tissue preservation in different tissue culture media. The proportion of dead cells was assessed by Trypan blue staining and counting. The viability was not dependant of the type of the medium used and remained approximately 50% in all samples, even after 72 h. To develop optimal conditions for transport of final chondrocyte suspension, isolated cells were firstly grown in monolayer cultures. Cell suspensions in media with different additives were injected into special glass containers used for the transport and left at 4 degrees C or 25 degrees C for up to 3 days. During this period every 24 h the samples were taken and viability as well as apoptosis levels were assessed. Viability of cells in suspensions at 25 degrees C decreased significantly and became inadequate already after 48 h. In contrast to that, the proportion of viable cells at 4 degrees C remained above 80% even after 48 h. In the majority of the samples, culture medium containing serum and vitamin C provided the best conditions for long-term preservation of chondrocytes.

Apoptosis↗
PubMed2000

In vitro functional tests for evaluation of stimulating capacity of cultured human dendritic cells.

Basic functional test for evaluation of in vitro cultured human dendritic cells (DC) is primary allogeneic one-way mixed lymphocyte reaction (MLR). In this way, one can evaluate stimulating capacity, which is a basic characteristic of DC. The proliferation of cells is measured through incorporation of 3H-thymidine. Normally proliferation is measured at days 5-7. We studied kinetics of proliferative responses initiated with different stimulating cell suspensions to evaluate differences and possibly reduce time needed to perform this test. Gradual increase in response from days 1 to 7 and a significant difference from controls (peripheral blood mononuclear cells) seen from day 4 was noted if macrophages were used as stimulators. A consistently higher proliferation, compared to controls, was always found already on day 2 when mature DC were used as stimulators. The reaction peaked 2 to 3 days earlier and was also more than two times more intense. This maximal and significantly higher response, consistently seen already after 48 hours, allows us to confirm the presence of mature DC in stimulating suspensions much earlier than previously.

Cells, Cultured↗
PubMed1999

Oscillatory behavior of critical amplitudes of the Gaussian model on a hierarchical structure.

We studied oscillatory behavior of critical amplitudes for the Gaussian model on a hierarchical structure presented by a modified Sierpinski gasket lattice. This model is known to display nonstandard critical behavior on the lattice under study. The leading singular behavior of the correlation length xi near the critical coupling K=K(c) is modulated by a function which is periodic in ln/ln(K(c)-K)/. We have also shown that the common finite-size scaling hypothesis, according to which for a finite system at criticality xi should be of the order of the size of the system, is not applicable in this case. As a consequence of this, the exact form of the leading singular behavior of xi differs from the one described earlier (which was based on the finite-size scaling assumption).

Journal Article↗
PubMed1999

Transfection of mammalian cells by the methods of receptor mediated gene transfer and particle bombardment.

The efficacy of currently developed methods for gene transfer into mammalian cells depends primarily on the transfection technique, and also on the type of targeted cells. Considering the importance of gene transfer in the creation of gene therapies, our study was aimed at the assessment of transfection capacity of receptor mediated gene transfer method (RMGT), and method of particle bombardment (helios gene gun system--HGG) in different normal and malignant mammalian cells ex vivo. In addition, the HGG was also assessed for its ability to transfect tumor cells of subcutaneous (s.c.) tumors in C57Bl/6 mice in vivo. Using RMGT an average ex vivo transfection rate of 35.7%, and 20.4% was achieved in malignant melanoma B-16, and human breast adenocarcinoma MCF7, respectively. However, in normal fibroblast L929 cells the transfection by RMGT succeeded only in 2.1% of the cells. On the other hand, the transfection efficacy of HGG was comparable in both malignant cell lines resulting in an average gene transfer to 9.6% of B-16 and 10.5% of MCF7 cells, while only 3.9% of normal fibroblasts were successfully transfected. Application of HGG for an in vivo gene transfer into s.c. B-16 melanoma tumors in C57Bl/6 mice resulted in a successful but limited transfection of the epithelium as well as of the superficially sited tumor cells. Taking into consideration both methods, RMGT is more appropriate for ex vivo transfection of cells, under the condition that target cells express a specific receptor for the molecule attached to the carrier. On the other hand, HGG is not complicated to use, no requirements for specific structures on target cells are necessary (potentially usable in different cells), and it has applicability in direct in vivo transfection processes.

Adenocarcinoma↗
PubMed1997

Changing the stereotypes of "counsellors".

Stereotypes, as a relatively inflexible form of cognitive organization, serve in the organization of personal experience. They are relatively difficult to change and take a relatively long time. In our study we have tried to examine whether some traditional stereotypes of "counsellors" have altered during more than three years of work by members of the Croatian Psychiatrists Association with displaced persons in a camp in Zagreb. The statistical analysis of the information indicated that stereotypes have changed and in such a way that positive stereotypes have become more positive while the negative have become less negative among those displaced persons who had continued counseling from psychiatrists, psychologists and social workers from our Association. In the long-term, these results can be considered even more positive than the actual process of psychological assistance because the change in stereotypes is likely to be reflected in a larger number of future clients and through future generations.

Adolescent↗
PubMed1996

Human interleukin-2 (IL-2) expressed by transfected mammalian cells.

cDNA for human interleukin-2 (IL-2) was cloned into the pRc/RSV vector for expression in animal cells. Baby hamster kidney (BHK-21) cells and Chinese hamster ovary (CHO) cells were transfected several times using calcium phosphate and electroporation methods with the construct pRc/RSV SIGIL2. Different transfection efficiencies were obtained. The biological test on CTLL-2 (mouse cytotoxic lymphocytes) showed that the kinetics of cell proliferation were different from those of rIL-2 (recombinant IL-2) expressed in bacteria and in BHK cells. When high concentrations of rIL-2 were applied, an inhibitory effect on CTLL-2 was observed when bacterial product was used, whilst rBHK interleukin caused no inhibition. Recombinant BHK IL2 induced a slower response of CTLL-2 cells at the beginning of the cultivation, however, prolonged activity was detected at the later stage of the experiment.

Animals↗
PubMed1996

Cultivation of mouse-mouse hybridomas producing IgM monoclonal antibodies.

The mouse-mouse hybridomas producing monoclonal antibodies (MAbs) for ABO blood group determination were cultivated for 10 days in 25 cm2 Roux bottles using standard cultivation medium (DMEM) with different foetal-calf serum (FCS) concentrations (2-13%). The highest specific production rates (200-1100 micrograms/10(6) cells/day) for MAbs were measured at the end of the cultivation: this phenomenon could be explained by advanced cell death and liberating the content of the cells into the medium.

ABO Blood-Group System↗
PubMed1993

[A compound odontoma].

Compound odontoma is a malformation manifested as a localized lesion before a non-erupted or displaced tooth consisting of numerous small tooth-like components. The lesion develops asymptomatically. The recognition of its clinical features helps the prevention of deformities and caries in the adjacent teeth by an on time and adequate surgical treatment.

Adult↗
PubMed1993

[Ultrastructure of pigmented skin nevi].

Nevus cells are biologically significant because they are associated with epidermal melanocytes, while their clinical malignant melanomas. Apart from many other ultrastructural features their mutual characteristic is that they are exceptionally diverged. The main feature distinguishing nevus cells from melanocytes is the presence of big binuclear cells as well as frequent occurrence of grouped melanosomes in their cytoplasm.

Humans↗
PubMed1993

[Large dermoid cysts of the mouth floor].

Dermoid cysts of the mouth floor are very rare. The incidence of these cysts is up to 3.6% of all cysts in the oral cavity. The article presents the material from the Clinic of Maxillofacial Surgery MMA. Eleven cases of large dermoid cyst are discussed. All of them were removed completely and no recurrence developed in longer period of time postoperatively.

Adult↗
PubMed1993

[Use of the modified Warthin-Starry method in pigmented nevi of the skin].

Warthin-Starry method is an argyrophilic method, performed at ph 3.2. It is a very efficient method for demonstration of melanin pigment granules in the nevus tissue and in malignant melanoma. We have concluded that it is highly specific for demonstration of melanin pigment granules, and more efficient than the Fontan-Masson method. The Fontan-Mason method reduces other pigments in the cell, apart from melanin. Modified Warthin-Starry method at ph 3.2 in the nevus tissue reduces only melanin pigment granules.

Histocytochemistry↗
PubMed1993

[Idiopathic histiocytosis of the jaw].

Principal features of Idiopathic Histiocytosis (IH) are discussed in relation to five cases treated in the Department of Maxillofacial Surgery VMA. Clinical symptoms of the disease are known. Radiology of the bones and bone scintiscans are of most importance for evaluation of extension of the disease. Surgery is treatment of choice. The major problem with IH in the jaws is, however, progressive mutilation of dental apparatus.

Adolescent↗
PubMed1991

Basal cell carcinoma treated with interferon.

Human natural leukocytic interferon (HNLI) and recombinant interferon (rIFN) alpha 2c can be used in the therapy of basal cell carcinoma. Seventy-two patients were treated for 3 to 6 weeks with a single dose of 400,000 to 1,200,000 units (HNLI) and 2,000,000 to 5,000,000 units (rIFN alpha 2c). According to histopathologic and clinical findings, 52 patients were cured, and cancer cells were not found in the biopsy material taken after HNLI treatment for the second biopsy. In nine of 72 patients the cancer lesion was reduced 25% to 90%. In 11 patients it was not reduced or was reduced less than 25%. With rIFN alpha 2c therapy given five times per week for 4 weeks, histopathologic and clinical findings showed that five patients out of 12 were cured, and cancer cells were not found in the biopsy material taken after treatment. In seven patients out of 12 the cancer lesion was reduced 25% to 90%. Both types of interferons are effective in the treatment of basal cell carcinoma. Side effects were mild.

Adult↗
PubMed1991

Treatment of squamous cell carcinoma with interferon.

Human natural leukocytic interferon and recombinant HulFN alpha 2c can be used in the therapy of squamous cell carcinoma. The duration of treatment was 3-6 weeks. A single dose was 400,000-5,000,000 units given weekly for 3-6 weeks. Clinically and histologically 19 of 32 patients were cured and tumor cells were not found in the material taken after interferon treatment for the second biopsy. In ten patients tumor size was reduced 25-90%, and in three patients tumor size was not reduced according to clinical findings. With recombinant HulFN alpha 2c therapy given 5 times per week for 4 weeks. Four of ten patients with similar tumors were cured clinically and histologically clinical findings. In five patients tumor size was reduced 25-90%, while in one patient there was no reduction in tumor size. Both types of interferons are effective in the treatment of squamous cell carcinoma. Side reactions were mild.

Adult↗