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Biomedical subjects

M Ryba

Publications and source records attributed to M Ryba.

At least 19 recordsLinked to original sources
PubMed1998

The application of microspheres from the copolymers of lactide and epsilon-caprolactone to the controlled release of steroids.

The microspheres made of the copolymers of lactide and epsilon-caprolactone were used for the controlled release of progesterone and beta-estradiol. The copolymers contained 83-94% of l or d,l-lactide. The influence of the microstructure of lactidyl blocks in the copolymer chains on the drug release rate was studied. More uniform release rate was observed in the case of the copolymer derived from d,l-lactide as composed to l-lactide. For the copolymer containing 83-94% of d,l-lactide units the progesterone and beta-estradiol release rate in vitro was found to be practically constant within over 40 days. The in vivo studies performed on rats revealed that the period of constant release rate of beta-estradiol can be prolonged to about 70 days. The microspheres made of the applied poly-(d,l-lactide-co-epsilon-caprolactone) are the convenient system for long time release of steroids.

Animals↗
PubMed1996

Mitochondrial damage following exposure of organotypic cultures of human malignant gliomas to 2-chloro- and 2-bromo-2'-deoxyadenosine.

The effects of 2-chloro-2'-deoxyadenosine (cladribine, 2-CdA) and a closely related compound 2-bromo-2'-deoxyadenosine (2-BdA) on organotypic cultures of human malignant gliomas were studied with the use of electron microscopy. The cultures grown from surgical biopsies included six glioblastomas, three anaplastic astrocytomas and low-grade fibrillary astrocytoma. After 6 to 10 days of the in vitro growth the cultures were exposed to 0.3-10 microM 2-CdA or 2-BdA for 1 to 10 days. Mitochondrial swelling and disappearance of cristae following exposure to the tested substances were observed, but only in highly anaplastic (low-differentiated) tumor cells. The mitochondrial toxicity was dose- and time-dependent, and no difference was found between the effect of 2-CdA and 2-BdA.

Antineoplastic Agents↗
PubMed1996

2-chloro- and 2-bromo-2'-deoxyadenosine have no effect on the morphology of rat neural and glial cells in organotypic culture.

Organotypic cultures of hippocampus and cerebellum, established from brains of 1-3 days old rats, were exposed at different stages of development (3, 14 and 21 DIV) to 2-chloro-2'-deoxyadenosine (cladribine, 2-CdA) and 2-bromo-2'-deoxyadenosine (2-BdA) at concentrations up to 10 microM, for up to 10 days. Normal pattern and dynamics of differentiation and maturation of both neurons and glial cells was found with the use of light and electron microscopy. No ultrastructural abnormalities were induced by the substances tested. We conclude that 2-CdA and its sister compound 2-BdA do not exert cytotoxic effects toward normal rat central nervous system tissues in organotypic culture.

Animals↗
PubMed1995

Survival and maturation of heterotopic fetal brain stem xenografts after treatment with 2-chlorodeoxyadenosine and cyclosporine A.

Brain stem halves from fetal rabbits were transplanted to the caudate nucleus area of adult rats. The animals were treated postoperatively with cyclosporine A (CsA) and 2-chlorodeoxyadenosine (CdA) for three days, and with CdA alone for the next 13 days. The treatment started at the day of implantation, and in some animals it was repeated starting at day 36 after grafting (at the time when signs of a light inflammatory reaction appeared in some grafts). Grafts survived and matured histologically, and no signs of acute rejection were observed up to the 90th day. In some grafts we recorded phasic neuronal activities similar to the respiratory-related neural activities characteristic for the adult brain stem. Immunosuppressive with CdA and CsA deserves further evaluation in fetal brain grafting.

Animals↗
PubMed1995

DNA protein flow cytometry of dissociated cultures of human anaplastic gliomas. Pattern of proliferation and differentiation, and the effect of a new cytostatic drug cladribine (2-CdA).

A technique of protein-DNA flow cytometry was applied to characterize cell cycling, and to assess the cytotoxicity of cladribine (2-chloro-2'deoxyadenosine) toward seven dissociated cultures of human primary brain tumors (anaplastic astrocytoma and glioblastoma multiforme) grown in vitro from surgical biopsies. Control cytograms were suggestive of that a clonogeneic fraction of the cell population consists mainly of cells with low protein content, which do not require increase in protein content before entering the S phase of the cell cycle. Following 24 or 48 hours exposure to cladribine, 1 nM approximately 1 microM, no cytotoxic effect was evident in 4 cultures, whereas in two cases dose-dependent progressive block of the phase of the cell cycle was noted. In one case a massive cytotoxic effect resulted in disintegration of culture exposed to 100 nM of the drug. However, the treatment with cladribine was ineffective in a patient bearing the tumor which was the source for the last culture, suggesting that cytotoxicity in vitro may not be predictive of clinical response.

Antineoplastic Agents↗
PubMed1995

Effect of repeated treatments with cladribine (2-chlorodeoxyadenosine) on blood counts in multiple sclerosis patients.

We report the results of blood morphology monitoring of 11 remitting-relapsing multiple sclerosis patients who received repeated treatments with cladribine (2-chlorodeoxyadenosine). The drug was given once, daily, subcutaneously (5 mg) or orally (10 mg) for 5 consecutive days, as 6 monthly courses followed by one or two additional courses at 3 or 6 month intervals. The treatments were well tolerated, although many patients suffered from incidental upper respiratory tract infections, most of which occurred during the last 6 months of the observation period. One patient had recurrent infections, including an episode of urosepsis. All infections responded to standard therapy with antibiotics. Progressive lymphocyte reduction to 1000/microliters on average, and clear, but clinically insignificant drop in thrombocytes, was observed. Granulocyte counts were sometimes markedly elevated. A few patients developed macrocytosis, but none required transfusion. With our dosing and schedule, cladribine seems relatively safe in multiple sclerosis patients.

Adult↗
PubMed1994

Depressed immune surveillance against cancer: role of deficient T cell: extracellular matrix interactions.

Although T cells infiltrate malignant tumors, the local immune response is usually inefficient and tumors escape destruction. While extracellular matrix proteins strongly costimulate T cell responses in normal individuals, our studies indicate that peripheral blood T cells from cancer patients and tumor infiltrating cells respond poorly or are resistant to stimulative signals mediated by collagen I and IV and fibronectin. Moreover, the adhesive properties of cancer T cells are markedly depressed. Those functional deficiencies are paralleled by variable deficits in integrin and non-integrin T cell receptors for extracellular matrix. Immunotherapy with BCG causes a dramatic but transient increase in T cell: ECM interactions.

BCG Vaccine↗
PubMed1994

2-Chloro-2'-deoxyadenosine (2-CdA) combined with cyclosporine A successfully prevents rejection of fetal brain stem allograft in rabbits.

Allografts of brain stem from 20-day-old fetuses to nucleus caudatus of adult rabbits were performed. To prevent graft rejection immunosuppression with 2-CdA and cyclosporine A was transiently induced. Graft survival were assessed by histological and electrophysiological techniques. Both morphological (synaptogenesis, myelinization) and functional (generation of rhythmic neuronal activity) signs of graft maturation were found after nine weeks. The data suggest that transient immunosuppression used is sufficient to induce tolerance to neural graft, and no interference with maturation of implanted fetal tissue occurs.

Animals↗
PubMed1994

Modulation of lymphocyte-fibroblast interactions by 2-chloro-2'-deoxyadenosine (2-CdA) in subarachnoid hemorrhage.

The adherence to monolayers of human fibroblasts of chromium-51 labelled peripheral blood mononuclear cells (PBMC) from normal subjects, and from patients after single or multiple subarachnoid hemorrhage (SAH), and the effect of 2-CdA on cell adhesion have been quantified. The fraction of cells adhering to fibroblasts were the lowest for multiple SAH patients and the highest for normal subjects, which can be explained by depletion of activated lymphocytes from peripheral blood of SAH patients. 2-CdA decreased the fraction of adhering cells isolated from normal subjects, did not change the adherence of cells from single SAH patients and increased the fraction of adhering cells isolated from multiple SAH patients. We conclude that the influence of 2-CdA on the adherence of PBMC to fibroblasts is inversely related to the degree of immune system activation.

Autoimmunity↗
PubMed1994

Determination of 2-bromo and 2-chloro derivatives of 2'-deoxyadenosine in human blood serum by high performance liquid chromatography.

The aim of this study was to determine 2-chloro, and 2-bromo derivatives of 2'-deoxyadenosine (2-CdA and 2-BdA respectively) in the serum of human blood by high performance liquid chromatography (HPLC). 2-CdA is a substance with anticancer and immunosuppressive activity. Caffeine or 5,6-dimethylbenzo-1,2,4-triazole-1-beta-D-ribofuranoside was added to 1 cm3 of serum as internal standard. 2-CdA and 2-BdA were isolated from serum using acetone as deproteinizing reagent. LiChrosorb Si 60 column was used for the separation of drugs and the internal standard from endogenous compounds in the sample. A mixture of potassium dihydrophosphate-methanol was used as a mobile phase.

Chromatography, High Pressure Liquid↗
PubMed1993

Successful prevention of neurological deficit in SAH patients with 2-chlorodeoxyadenosine.

Twenty patients suffering from subarachnoid haemorrhage due to ruptured intracranial aneurysm and operated on within 72 h after SAH were treated with an experimental immunosuppressive drug 2-chlorodeoxyadenosine (2-CDA), dose 0.05 mg/kg/day i.v. for 7 days. The 2-CDA treatment was started immediately after angiographic confirmation of ruptured aneurysm, and the standard pharmacological treatment (nimodipine and steroids) was also given. 50% of patients were severely threatened by "delayed vasospasm" or late neurological deficit (Fisher's score 3 or 4). The neurological outcome (assessed 8-12 weeks after SAH) was good (GOS = 1) in 70%, and fair (moderate disability, GOS = 2) in 25%. A single case of severe disability (GOS = 3), as well as two cases of less than perfect outcome (GOS = 2), were related to unusual pre- or intraoperative complications. We conclude that the low doses of 2-CDA can be considered as a valuable adjunct to the standard pharmacotherapy of SAH patients operated on early.

Adult↗
PubMed1993

A strategy for analyzing multiple parameters with application to aneurysmal SAH patients all of them clipped but treated with and without cyclosporine.

The study evaluated the effectiveness of the combination of nimodipine and cyclosporine A vs nimodipine alone in the prevention of delayed neurologic deficit in 82 (31 plus 51) patients in whom intracranial aneurysms were clipped within 72 h after subarachnoid haemorrhage. The tests performed included examination of the neurological condition before and after operation, angiography of cerebral arteries to visualize vasospasm, and analysis of the distribution and amount of blood in the brain fluids and/or tissue according to Fisher's scale. Inclusion of cyclosporine A in the treatment was clearly beneficial for the neurological condition. While cyclosporine A did not appear to produce a statistically significant improvement as evaluated by the chi-square test, a positive result was obtained following analysis of the correlation coefficients after Pearson in combination with the logistic log-linear regression analysis. The results argue against the utility of the chi-square test for verifying clinical data obtained in a limited number of patients.

Adult↗
PubMed1993

Impaired in vitro proliferative response of suppressor lymphocytes in patients with subarachnoid haemorrhage from ruptured intracranial aneurysm.

Proliferative response to mitogens concanavalin A, phytohemagglutinin and pokeweed mitogen, and other chosen indicators of the activity of the immune system were assayed in peripheral blood mononuclear cells isolated from blood of patients with subarachnoid haemorrhage from ruptured aneurysm. Healthy blood donors served as control group. The SAH group displayed impaired response to concanavalin A, which is a mitogen specific for suppressor cells. It is suggested that the impaired activity of suppressor cells pre-existed in patients with subarachnoid haemorrhage, and after intracranial bleeding it might have contributed to the development of late neurological deficits.

Adult↗
PubMed1993

2-Chloro-2' deoxyadenosine prevents angiopathic changes in cerebral arteries in experimental SAH in rabbits.

We compared the morphology of the basilar artery walls in rabbits with experimental subarachnoid haemorrhage (SAH) without and with concomitant treatment with a novel immunosuppressive drug, 2-chloro-2'-deoxyadenosine (2 CdA). The treatment was successful in the prevention of the angiopathic changes, most likely due to its ability to inhibit lymphocyte activation in response to mitogenic signals. Since lymphocyte (and monocyte?) activation may play an important role in the development of the delayed neurological deficits in patients following SAH, the use of 2 CdA to prevent these deficits shall be considered.

Animals↗
PubMed1992

Is vascular angiopathy following intracranial aneurysm rupture immunologically mediated?

Immunofluorescence studies showed the presence of IgM and/or C3 in the endothelium of intracranial aneurysms in 5 out of 6 patients with subarachnoid haemorrhage (SAH). In none of them were the immune deposits found in the gyrus rectus. Cortical tissue of 4 epileptic patients which served as a control give negative results. Serum studies on femoral artery wall used as an antigenic substrate did not reveal circulating antibodies of the IgM or IgG class. Our studies strongly suggest that the IgM and/or C3 immune deposits located in the endothelium of intracranial arteries may play a role in post SAH neurological complications.

Adult↗