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Biomedical subjects

M Kos

Publications and source records attributed to M Kos.

At least 55 records · Page 3Linked to original sources
PubMed1997

Drug-induced apoptosis is associated with enhanced Fas (Apo-1/CD95) ligand expression but occurs independently of Fas (Apo-1/CD95) signaling in human T-acute lymphatic leukemia cells.

Induction of apoptosis is considered to be the underlying mechanism that accounts for the efficiency of chemotherapeutic drugs. It has recently been proposed that induction of Fas ligand (FasL) expression with subsequent autocrine and/or paracrine induction of cell death through binding to the Fas (Apo-1/CD95) membrane accounts for chemotherapy-associated apoptosis. In the present study, we analyzed the significance of FasL expression in the mediation of drug-induced apoptosis in the T-acute lymphatic leukemia model CEM. In particular, we examined the potential of the tumor drugs fludarabine, doxorubicin, and cisplatin to induce FasL expression. We also raised the question of whether apoptosis induced by these drugs occurs through the Fas pathway and hence can be blocked by the cowpox virus protein CrmA, a specific inhibitor of this pathway. All tumor drugs examined led to an increase in FasL protein. However, overexpression of CrmA had no effect on drug-induced apoptosis. Moreover, neither incubation with inhibitory monoclonal antibodies against Fas that completely prevented Fas-induced apoptosis in these cells nor pretreatment with a monoclonal antibody to FasL affected drug-induced cell death. Our observations suggest a Fas/FasL-independent mechanism for drug-induced apoptosis and exclude the involvement of caspase 1 and caspase 8 in this process in T-acute lymphatic leukemia cells.

Antineoplastic Agents↗
PubMed1997

Constitutive expression of Fas (Apo-1/CD95) ligand on multiple myeloma cells: a potential mechanism of tumor-induced suppression of immune surveillance.

The Fas (Apo-1/CD95) ligand (FasL) plays a central role in the elimination of target cells by effector T lymphocytes and in the suppression of cellular immune responses against nonmalignant and malignant cells. We show the expression of FasL on the surface of neoplastic plasma cells. We provide evidence that the FasL is functionally active because five of five neoplastic plasma cell lines tested killed CEM-C7H2 T-acute lymphoblastic leukemia (T-ALL) cells. The effect was mediated via the Fas (Apo-1/CD95) receptor molecule because blocking of Fas on the target cells or the FasL on the tumor cells by receptor- and ligand-specific monoclonal antibodies (MoAbs), respectively, protected T cells from being killed by myeloma cells. In addition, overexpression of the cowpox virus protein CrmA, a molecule with inhibitory potential on caspase-1 and caspase-8, specifically involved in Fas-induced signaling, protected T cells from being destroyed by the neoplastic cells or the agonistic anti-Fas MoAb. The potential of the malignant plasma cells to extinguish target T cells was independent of their own sensitivity to the agonistic anti-Fas MoAb, and FasL-positive (FasL+) CEM-C7H2 T cells were incapable of killing myeloma cells. Our results suggest that tumor cell-induced suppression of the immune system may be exerted via the FasL active on malignant plasma cells. Furthermore, loss of Fas expression or insensitivity to the agonistic anti-Fas MoAb do not seem to be prerequisites for myeloma cells to defeat T cells via Fas/FasL interaction.

Aged↗
PubMed1997

Expression of Apo-1/Fas (CD95), Bcl-2, Bax and Bcl-x in myeloma cell lines: relationship between responsiveness to anti-Fas mab and p53 functional status.

The down-regulation of apoptosis may be an essential mechanism for tumour cell expansion in slowly proliferating tumours such as multiple myeloma. We studied eight myeloma cell lines for the presence of Bcl-2, which inhibits apoptosis, of Bax, which counteracts Bcl-2, of Bcl-x(L) and Bcl-x(S), which act in an anti- and pro-apoptotic fashion, respectively, and of Apo-1/Fas, which induces programmed cell death, when activated by the Apo-1/Fas ligand or the relevant monoclonal antibody (mab). All cell lines constitutively expressed homogenous amounts of Bcl-2, but displayed different amounts of Bax and Bcl-x proteins. The Apo-1/Fas antigen could be detected in seven out of eight myeloma lines, but expression levels varied considerably. The relative expression levels of Apo-1/Fas correlated with that of Bax, but not with that of Bcl-2 or Bcl-x subtypes. Furthermore, the effectiveness of the Apo-1/Fas mab was associated with the relative expression levels of the Apo-1/Fas and with that of the Bax antigen, but not with that of the Bcl-2 and Bcl-x antigens. We further showed that wild-type p53 function is not required for Apo-1/Fas-induced apoptosis, nor is it necessary for the expression of Bax or Apo-1/Fas antigens in myeloma. In conclusion, our results suggest a p53-independent co-regulation of Apo-1/Fas and Bax, as well as a role for Bax in Apo-1/Fas-induced apoptosis in myeloma.

Apoptosis↗
PubMed1997

Conflicting data on intervillous circulation in early pregnancy.

According to classic embryological textbooks intervillous circulation is established early in the first trimester. This process starts with trophoblastic invasion of the decidua in which proteolytic enzymes facilitate the penetration and erosion of the adjacent maternal capillaries with formation of the lacunae. After the lacunar or previllous stage trophoblast invades deeper portions of endometrium with belonging spiral arteries. This gradual process finishes with direct opening of the spiral arteries in the intervillous space under the fully developed placenta. This classic concept of establishment of the intervillous circulation was challenged in 1987 and 1988 by the experiments of HUSTIN and SHAAPS. The authors believed that blood flow in the intervillous space is absent in incompletely development before 12 weeks of gestation. After the introduction of the new generation of far more sensitive color Doppler devices in the last few years, our group and several others reported a positive finding of intervillous circulation during the first trimester of pregnancy.

Chorionic Villi↗
PubMed1997

Intervillous circulation in all three trimesters of normal pregnancy assessed by color Doppler.

Our cross-sectional study included 115 healthy pregnant women in gestational age between 7 and 24 weeks. The aim of the study was to compare resistance (RI) and pulsatility (PI) indices, peak systolic velocity (PSV), end-diastolic velocity, and temporal averaged maximum velocity (TAMV) of the spiral arteries and vessels within the intervillous space in all three trimesters of pregnancy. The impedance to blood flow within the intervillous space significantly decreased towards the mid-pregnancy (p < 0.01) and then remained stable. Blood flow velocities within the intervillous space expressed by PSV, EDV and TAMV increased significantly (p < 0.01) towards the mid-pregnancy. After reaching the plateau between 16 and 22 weeks of gestation, these parameters remained almost constant until the 36th gestational week. Near the term low-significant decrease of blood flow velocities was noted: for PSV and TAMV p < 0.07, and for EDV p < 0.05. A significant increase in continuous intervillous blood flow velocity was noted from the 11th week onward (28 +/- 12 vs. 36 +/- 12) until the 36th week of gestation (36 +/- 12 cm/s). The first report of the haemodynamic changes within the intervillous space during pregnancy may have implication in better understanding of the metabolical interchange between maternal and fetal side.

Chorionic Villi↗
PubMed1997

Histopathologic findings of placenta and arcuate artery Doppler velociometry in preeclampsia and intrauterine growth retardation.

The aim was to analyze the histopathologic changes of placentas and to compare them to the results of arcuate artery color Doppler velocimetry. Fifty four placentas were from pregnancies complicated with pre-eclampsia that ranged from mild forms to convulsions (group 1), 42 from pregnancies complicated with intrauterine growth retardation (IUGR) (group 2) and 40 from uncomplicated pregnancies (group 3). The arcuate artery resistance index (AARI) was increased in 66.66% in group 1 and 59.52% in group 2 (NS). In all uncomplicated pregnancies (group 3) AARI was normal. In group 2, increased AARI was significantly more frequently associated with minimal hypoxic damage (MHD) of placental tissue than in group 1 (p < 0.005), whereas multiple infarcts were more common in group 1 than in group 2 (p < 0.005). At normal AARI multiple infarcts were significantly more frequently found in group 1 than in groups 2 and 3 (p < 0.005), whereas normal placental findings were significantly more common in group 3 than in groups 1 and 2 (p < 0.001). Hypoxic lesions were significantly more often associated with increased AARI (p < 0.01). The positive predictive value of arcuate artery color Doppler velocimetry for hypoxic placental lesions was 93%, and negative predictive value was 10%. Sensitivity and specificity of the method in the prediction of hypoxic placental lesions was 62% and 91%, respectively.

Blood Flow Velocity↗
PubMed1996

Constituents of autocrine IL-6 loops in myeloma cell lines and their targeting for suppression of neoplastic growth by antibody strategies.

We examined the constitution and biological relevance of an autocrine IL-6/IL6-receptor (r) loop in 7 multiple myeloma and plasma-cell leukemia lines in order to determine its biological role and potential therapeutic impact on antibody strategies. The expression and constitution of the IL-6r [i.e. membrane-bound gp-80, soluble (s)gp-55 and the gp-130 IL-6 signal-transducing element (str)], the binding capacity of the membrane-associated receptor(s) for IL-6, the production and secretion of IL-6 by neoplastic plasma cells, and the effect of IL-6 on tumor-cell proliferation were investigated. In the U-266 cell line, the growth-inhibitory effects of antibodies (Abs) against IL-6 and IL-6-binding subunit of its receptor were compared with each other. From our results the following conclusions may be drawn: (i) Substantial differences in the quantificative assembly of the IL-6r constituents and in the response to recombinant (r) human (h) IL-6 became evident in the 7 myeloma cell lines. (ii) The components of an autocrine IL-6 loop may be regulated in an independent and, in the case of IL-6 and sgp-55, probably counteractive manner. (iii) The level of endogenous IL-6 and the reservoir of recruitable sgp-55 were important for the response to exogenous rhIL-6. (iv) Apart from IL-6, other growth factors are important for the propagation of myeloma cells but at least some of them exert their effect through an IL-6-dependent pathway. Their growth-promoting activity, as well as that of IL-6, may be successfully targeted by immunological means, with Abs against the IL-6r being more efficient than those against the ligand.

Antibodies↗
PubMed1996

Modulation of Apo-1/Fas (CD95)-induced programmed cell death in myeloma cells by interferon-alpha 2.

The Apo-1/Fas (CD95) antigen is known to be involved in the process of T cell-mediated target cell killing and has recently been shown to be expressed on myeloma cell lines and native malignant plasma cells. Several cytokines have been reported to interfere with spontaneous and even Apo-1/Fas-induced apoptosis, but no attempt has been made yet to investigate these interactions and the possible underlying mechanisms in myeloma cells. Since in myeloma patients Interferon (IFN)-alpha2 displays a profound therapeutic effect in vivo, which is usually attributed to its growth inhibitory and/or immunomodulatory capacity, we set out to study the potential interference of IFN-alpha2 with Apo-1/Fas-induced apoptosis. Contrary to expectations, IFN-alpha2 reduced the degree of apoptosis caused by the treatment of five Apo-1/Fas-sensitive myeloma cell lines with a Fas monoclonal antibody (mAb). Simultaneous application of IFN-alpha2 and Fas mAb was superior to the prolonged (i.e. >8 h) preincubation with the cytokine as far as inhibition of Apo-1/Fas-induced apoptosis was concerned. This effect of IFN-alpha2 was neither explained by a down-regulation of the Apo-1/Fas receptor nor caused by modulation of the expression levels of c-myc, bcl-2-, bcl-xL, bax- or p53 genes. IFN-alpha2 did not alter the Apo-1/Fas-induced activity of Mitogen-activated protein kinase (MAPK) 1 and did not inhibit the Apo-1/Fas-mediated proteolytic cleavage of ADP-ribosyltransferase, a substrate of Interleukin-beta1 converting enzyme (ICE) and homologues. However, activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate (PMA) mimicked the effects of IFN-alpha2. Furthermore, the bis-indolylmaleimide GF 109203X, a specific inhibitor of PKC, inhibited the effect of PMA as well as that of IFN-alpha2 on Apo-1/Fas-induced apoptosis. These results point to a PKC-dependent mechanism of transient interaction between the intracellular signaling along the IFN-alpha2 and the Apo-1/Fas pathway (downstream of MAPK signaling as well as of ICE homologues), which becomes exhausted by prolonged stimulation with the cytokine. According to our data IFN-alpha2, applied continuously and in high doses resembling the therapeutic situation in vivo, inhibits myeloma growth. However, based on the observed inhibitory effect of IFN-alpha2 on Apo-1/Fas-induced apoptosis, a partial inhibition of the natural immune surveillance on myeloma cells by endogenous IFN-alpha2 present in the bone marrow microenvironment of this malignancy should be investigated.

Adjuvants, Immunologic↗
PubMed1996

Lamina propria of sex cords in human fetal testis: an immunohistological and stereological study.

Testicular peritubular cells are located in the lamina propria of seminiferous tubules. These cells, significantly contributing to the basal membrane of seminiferous epithelium, have been studied in a number of species. However, there is a lack of data on the development of the lamina propria in the human testis. The aim of our survey was to investigate the characteristics of the lamina propria and, in particular, peritubular cells in the fetal human testes by immunohistological and stereological methods. Therefore, testes (14-39 weeks of gestation, n = 45) were dissected and fixed in a 4% buffered paraformaldehyde solution. Several pieces of each testis were embedded in paraffin and processed for immunohistochemical and stereological analysis. All investigated testes have shown sex cords in the process of development and differentiation. Morphologically, peritubular cells in the lamina propria can be divided into two types: fibroblast-like (FL) and myoid-like (ML) type (cells which much resemble mature myoid cells). By immunohistochemistry, both FL and ML cells are found to be strongly positive for the intermediate filament desmin, but negative for alpha-smooth actin. While FL cells intensively express Ki-67 demonstrating proliferative activity, ML cells are found to be negative. The basement membrane of sex cords as well as the blood vessels of the interstitium show strong positivity to collagen IV and laminin. Concerning the correlation between the appearance of the investigated antigens with the gestational age, all antigens have been expressed (in the manner described above) already in the 14th week of gestation. The stereological analysis of the number (Nv) and volume (Vv) of peritubular cells indicates a pulsatile development of these cells in the lamina propria of the human fetal testis. While the stereological variables determined for FL cells show a gradual decrease, the same variables determined for ML cells demonstrate a successive increase. It appears that the lamina propria of the fetal human testes shares many of the properties previously discovered in rodents.

Cell Count↗
PubMed1996

Doppler information pertaining to the intrapartum period.

The aim of the study was to evaluate the use of color-Doppler velocimetry during the labor. 325 intrapartal measurements of the umbilical artery, fetal aorta, middle cerebral artery and arcuate arteries were performed in a group of 105 patients. The resistance index (RI) and pulsatility index (PI) were measured. During the active labor the RI and PI of the umbilical artery remained unchanged. The impedance in arcuate arteries have increased (p < 0.05). The RI and PI of the middle cerebral artery showed non significantly increased mean values when compared with the corresponding values during pregnancy. But, a short term, transitory decreased impedance is registered during the decrement slope of contraction. Since fetal outcome was normal in all newborns, these changes are considered as physiologic.

Aorta↗
PubMed1995

Medullary carcinoma of the thyroid: histomorphological, histochemical and immunohistochemical analysis of twenty cases.

Histomorphological patterns of twenty primary medullary carcinomas of the thyroid were studied by light and polarized microscopy in relation to the content of calcitonin and thyroglobulin determined by the immunoperoxidase method: Out of 20 tumors, 10 showed classical, 7 glandular and 3 insular histomorphological pattern. In 19/20 cases, the cytoplasm of tumor cells contained various amounts of calcitonin, and the intensity of Immunoreaction was strong in 2/19, moderate in 7/19 and weak in 10/19 cases. Tumor stroma contained calcitonin in 7/20 cases. In 1/20 case, which did not show calcitonin immunoreactivity in the cell cytoplasm, the stroma contained a considerable amount of calcitonin. Thyroglobulin immunoreactivity was found in 4/20 tumors, 2 of them with classic and 2 with glandular histomorphological picture only in the cytoplasm of tumor cells. These tumors are considered medullary carcinomas with thyroglobulin immunoreactivity, since they do not fulfil the WHO criteria for "mixed medullary-follicular carcinomas".

Adult↗
PubMed1994

The fetus as a patient.

This article highlights the concept, history and development of fetal medicine. The first attempts of fetal medicine date from the stone age and have continued throughout the medieval and modern ages. Attempts to influence fetal health and pregnancy outcome at first were purely theoretical and passive, limited by ignorance, fear, and religion. With the development of the medical sciences, the role of the obstetrician became more active. Today, not only obstetricians, but many other experts in the field of antenatal care as well, deal with the great number of medical and technological advances. The limitations arising today are mainly ethical. The main question that still has not been answered is to what extent the physician is allowed to interfere with the process of fetal development and pathology, based upon real fetal and maternal benefit. In order to answer this question and to coordinate many activities by different experts in this field, an international society antitled The Fetus as a Patient was formed in 1985. Croatian experts have played a leading role in this concept.

Ethics, Medical↗
PubMed1992

Assessment of dementia flow chart approach to clinical diagnosis.

With life spans increasing the number of demented people rises steeply which requires proper diagnosis, particularly in the early stage of the disease. Although the majority of patients suffering from dementia have Alzheimer's disease characterized by slowly progressive course, searching for treatable causes will enable effective support to a certain number of patients. Presence of only one clinical symptom and/or sign, like the memory impairment is not sufficient for diagnosing dementia owing to its nonspecificity. Proper diagnosis depends upon one's familiarity with the criteria, clinical features, associated symptoms and the natural course of the disease as well as a wide variety of different etiological factors manifested by the similar clinical picture. In spite of certain shortcomings, the flow chart system approach of diagnostic procedure is intended for more accurate and less time consuming assessment of the clinical diagnosis of dementia. Understanding and familiarity with different aspects of the clinical picture lie behind the rational approach and selection of various laboratory methods and techniques to confirm or exclude presence of the disease for the benefit of patients and to avoid unnecessary wasting of considerable amounts of financial resources.

Dementia↗
PubMed1990

NMR imaging in the earth's magnetic field.

The most important and very expensive part of a magnetic resonance imaging set-up is the magnet, which is capable of generating a constant and highly homogeneous magnetic field. Here a new MR imaging technique without the magnet is introduced. This technique uses the earth's magnetic field instead of a magnetic field created by a magnet. This new method has not yet reached the stage of medical application, but the first images obtained by MRIE (magnetic resonance imaging in the earth's field) show that the resolution is close to that expected based on sensitivity estimations.

Humans↗
PubMed1988

Recombinant alpha-interferon (alpha-IFN) for progressive hairy-cell leukemia (HCL): a study in previously untreated nonsplenectomized patients.

Ten nonsplenectomized patients (5 males, 5 females) with hairy-cell leukemia were treated with recombinant alpha-IFN. The median age of patients was 54 years (32-76 years). The time between diagnosis and onset of treatment ranged from 1-120 months. Initially the patients received 5 x 10(6) I.U. daily by intramuscular or subcutaneous injections for 10 weeks. Thereafter the dose of IFN was reduced to 5 x 10(6) I.U. 3 x weekly and after 6 months to 5 x 10(6) I.U. 2 x weekly for at least 6 months. The median time of patient follow-up is 23 months (4-28 months). Three complete remissions were achieved after 3-24 months and five partial remissions after 4-18 months. One patient showed improvement after 3 months, and one patient died from cerebral hemorrhage after 5 weeks. In eight of ten patients peripheral blood cell counts normalized after a median of 7 months (1.5-11 months). A marked reduction in spleen size was observed in all seven patients who had splenomegaly at study entry. Two of three patients who interrupted therapy have relapsed after 2 and 6 months. We conclude that alpha-interferon is an effective method of first-line treatment in patients with HCL.

Adult↗
PubMed1987

[Allogeneic bone marrow transplantation in acute myeloid leukemia (AML): results in 14 patients].

Between February 1982 and August 1986 14 patients with AML (median age 24 years, range 10-41) underwent allogeneic bone marrow transplantation. 9 patients were grafted in first complete remission, 4 in first relapse, 1 in second relapse and 1 patient with refractory AML. Conditioning consisted of cyclophosphamide (120 mg/kg) and total body irradiation (1000 rad). The patients received methotrexate (n = 12) or methotrexate and cyclosporine (n = 2) for prevention of graft versus host disease. Of the 14 patients, 7 are alive, 7 patients died. Causes of death were recurrence of leukaemia (n = 2), veno occlusive disease of the liver (n = 1), CMV-pneumonitis (n = 1), septicaemia (1), cerebral haemorrhage (1), acute graft versus host disease of the gut (1), necrotizing encephalopathy (n = 1). 7 patients are alive between 124 and 1784 days (median 671) in continuous complete remission. All patients but 1 have a Karnofsky-index of more than 80%.

Adolescent↗
PubMed1987

[Bone marrow transplantation in chronic myeloid leukemia--experiences in 16 patients].

Between January 1983 and December 1986 16 patients (8 f, 8 m, median age 31.5 years, 14-41) with chronic myelocytic leukaemia (CML) received bone marrow grafts from their HLA compatible sibling donors. 11 patients were in the chronic and 4 in the accelerated phase. 1 patient was in lymphatic blast crisis. The patients were pretreated with busulfan (n = 15, total dose: 100-1000 mg, median: 225), mitobromitol (1 pat.), hydroxyurea (2 pats.), pre-irradiation of the spleen with 800 rad (1 pat.) and one patient had received 3 cycles of vincristin and prednisolone. The conditioning regimen consisted of cyclophosphamide (120 mg/kg) and total body irradiation (1000 rad, lung 800 rad). The prophylaxis against graft versus host disease (GVH-D) consisted of methotrexate (MTX) in 14 patients and of MTX in combination with cyclosporin-A in 2. At present (January 15th 1987) 9 patients survive 30 to 1210 days (median 1009) post graft (6/11 grafted in chronic, 2 of 4 in accelerated phase and 1/1 grafted in blast crisis. The causes of death were interstitial pneumonitis (CMV-associated, 2 pats.), venoocclusive disease of the liver (2 pats.), acute GVH-D and septicemia (2 pat.) and relapse (1 pat.). The Karnovsky score of 8/9 survivors is 100%, one patient has a score of 70% due to chronic GVH-D. Bone marrow transplantation for CML bears a high risk of early mortality but offers the unique option of permanent eradication of leukaemic haemopoiesis with subsequent long term survival.

Adolescent↗