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Biomedical subjects

I Földes

Publications and source records attributed to I Földes.

At least 55 records · Page 3Linked to original sources
PubMed1987

Effect of poly I:C-activated peritoneal cells on the take of transplantable murine tumours.

The effect of syngeneic mouse peritoneal cells (PC) on the growth of four different transplantable tumours was studied in adoptive transfer experiments (Winn's test). PC from unstimulated mice did not influence the growth of a benzpyrene induced fibrosarcoma (BaF1) and a methylcholantrene induced mastocytoma (P815), but significantly enhanced the growth of a spontaneous adenocarcinoma (Sp4) and Lewis lung carcinoma (LL). PC induced by a single injection of thioglycollate did not influence, whereas PC elicited by proteose peptone markedly enhanced the growth of BaF1 fibrosarcoma. The enhancing effect of peptone induced PC was diminished by a single intraperitoneal dose (100 micrograms/mouse) of polyinosinic-polycytidylic acid (poly I:C) given after peptone injection. Transferring PC obtained after a single injection of poly I:C (100 micrograms intraperitoneally) resulted in retardation of growth of BaF1 fibrosarcoma and Sp4 adenocarcinoma or in a marked decrease in their take depending on the PC/tumour cell ratio. The effector cells involved in the protective effect proved to be different, using these two tumour models. Lewis lung carcinoma and P815 mastocytoma proved to be insensitive to poly I:C-stimulated PC.

Adenocarcinoma↗
PubMed1987

Morphological studies on the articular cartilage of old rats.

Age-dependent morphological alterations of the tibial articular cartilage were studied in 26-month-old Wistar rats of both sexes. Young and adult rats (6 and 10 months of age, respectively) served as a basis for comparison. Light microscopic histology, polarization optical analysis (toluidine-blue staining with or without the addition of 0.2, 0.4 or 0.8 M MgCl2, as well as after phenol reaction) as well as transmission electron microscopy were applied. The main observations are: (1) According to the histological findings, the proportion of the zones changes with age; the subchondral bone layer becomes wider and separated to a certain extent, while the fibres become demasked. (2) Polarization microscopy revealed a disorientation of both the proteoglycane (PG) and collagen molecules; considering the available biochemical data, this phenomenon involves both quantitative and structural changes, as well as differences in the localization of the PG and collagen molecules. (3) Electron microscopy also supports the structural alterations of the collagen (thin and thick, as well as non-striated, fragmented fibres). Cellular alterations are also observed parallel with the changes of the matrix (cell organelles occur less frequently, signs of degeneration and disintegration, rupture of the plasma membrane, as well as accumulation of lipid-bodies can be seen. On the basis of the findings, one can consider the articular cartilage in the old rats as a tissue which is still in equilibrium, however, aged chondrocytes with decreased function become predominant in it. This state can be modified into a pathological one by various mechanical, endocrinological, iatrogenic, post-traumatic, etc., influences through the alterations of the cell-matrix interactions.

Aging↗
PubMed1987

Factors of activation and stabilization of DNA-methylases from Shigella sonnei 47 and Mycobacterium smegmatis butyricum cells.

A comparative study of factors of activation and stabilization of individual DNA-methylases from two bacterial strains--Shigella sonnei 47 and Mycobacterium smegmatis butyricum--isolated by isoelectrofocusing in a pH gradient has been carried out. Storage of enzymes at +4 degrees C (pH 7.5) is accompanied by periodic changes in the methylating activity. No such changes are observed when the enzymes are stored at pI of the protein. In this case the methylases with alkaline or close to neutral values of pI remain stable over a period of at least two weeks, whereas acidic proteins are irreversibly inactivated by the end of a two-week period. A stabilizing effect of BSA on DNA-methylases of Sso 47 and Mbu strains has been demonstrated. A direct correlation between the stabilizing effect of BSA and the degree of enzyme purity has been established. Ca2+ appear to be a universal activator of methylases of the above strains; these cations produce a potent, although a short-term effect and can be used in the production of enzyme preparations with a high specific activity in DNA recombinant technology. Protease inhibitors do not exert any appreciable effect on the methylase activity upon storage. Storage at -20 degrees C and at neutral pH leads to complete inactivation of all DNA-methylases within 24 hours. In this case glycerol is fairly ineffective as a stabilizing agent.

Alkalies↗
PubMed1987

Radiological investigation of alterations in the rat femur after long-term immobilization.

The right hind limb of female rats was immobilized by plaster cast. Following 8 weeks of immobilization the alterations were compared with either the contralateral extremity of the same rat or with the extremities of non-immobilized animals. The femurs were investigated by microradioscopic, morphometric, densitometric and atom absorption methods. The results obtained have unequivocally shown that long-term immobilization by plaster cast leads to development of osteoporosis in the rat. Even though no considerable loss of calcium could be demonstrated when calculated in terms of unit layer thickness quantitative analysis of the bone revealed a high degree of osteopenia.

Animals↗
PubMed1987

Mouse peritoneal cells activated with a combination of indomethacin, poly I:C and Syncumar inhibit the take of Lewis lung carcinoma in adoptive transfer assay.

Effect of peritoneal cells (PC) from mice treated with a combination of drugs (indomethacin, poly I:C and Syncumar) on the take of Lewis lung (LL) carcinoma was studied in Winn-type adoptive transfer experiments. Transfer of PC from mice given a single intraperitoneal injection of polyinosinic-polycytidylic acid (poly I:C) or indomethacine or Syncumar (100 micrograms of each) per se did not suppress the take of Lewis lung carcinoma in the recipient mice. PC obtained from mice treated with a combination of indomethacin and poly I:C or poly I:C and Syncumar also failed to inhibit the take of the tumour. In contrast, PC collected from mice after a combined treatment with the three drugs (indomethacin + poly I:C + Syncumar) resulted in a 30-60% decrease in tumour take depending on the tumour cell/PC ratio. This effect could not be observed when a single intraperitoneal dose of cyclophosphamide was administered three days before starting of the combined treatment of the donor mice. The effector cells contributing to the tumour inhibitory effect proved to be nonadherent cells, probably large granular lymphocytes (LGL), as their suppressive effect was abrogated after treatment with the lysosomotrop vital dye neutral red.

Acenocoumarol↗
PubMed1986

Effect of heparin on the reactivity of SH-groups in the macrophage membrane.

The effect of heparin on macrophage (M phi) adherence and on the reactivity of membrane SH-groups to the specific SH-oxidizing agent 4,4'-dithiodipyridine (PDS) was studied. Various types of SH-reactive agents, except 5,5'-dithio-bis (2-nitrobenzoate) (DTNB), were found to inhibit adherence of mouse peritoneal M phi to serum-coated Falcon surfaces. Heparin inhibited M phi-adherence in serum containing medium and in higher concentrations stimulated the adherence inhibitory effect of PDS, especially in Ca-depleted medium. This effect of heparin may be due to its polyanionic character, as dextran sulphate but not dextran induced similar changes. The effect of heparin to increase the sensitivity of membrane SH-groups against SH-reactive agents was demonstrated also by cytotoxicity experiments. It is concluded that heparin makes the M phi-membrane unstable, by exposing some hidden SH-groups playing a role in membrane function.

Animals↗
PubMed1986

Effect of heat treatment on phage susceptibility of a Mycobacterium smegmatis strain.

Plating efficiency of mycobacteriophage butyricum (By) proved to be 10(-4)-10(-3) on Mycobacterium smegmatis strain Rabinowitz (M. sm. R.) cells being in the logarithmic phase. This increased to 10(-2)-10(-1) when the cells were held at 50-57 degrees C for 2 h before infection. After replacing the cells to 37 degrees C, plating efficiency of the phages returned to the starting values. This phenomenon could be inhibited by nalidixic acid (150 micrograms/ml) and chloramphenicol (10 micrograms/ml) but not by mitomycin C (0.05 microgram/ml). No return to the starting plating efficiency values were observed, if incubation of cells at 37 degrees C after heat treatment has been performed in buffer. The data suggest that By phage propagation in M. sm. R. cells is inhibited by a thermosensitive protein.

Chloramphenicol↗
PubMed1986

Growth of spontaneous BALB/c tumours excised from and retransplanted to autochtonous hosts.

Tumours of aged Balb/c mice developed without any conscious experimental interference were excised and retransplanted to the autochtonous hosts. The autotransplantation resulted in tumour take after a prolonged period of latency or in no take for an extended period of observation (more than 80 days) in 6 out of 19 cases. This can be regarded as a sign of antitumoural resistance, although it seems to be ineffective against development of recidives and metastases or second tumours. The sensitivity of the autotransplantation method in detecting antitumoural resistance was compared to that of the transplantation-excision-retransplantation assay using a benzpyrene induced Balb/c fibrosarcoma; the autotransplantation method proved to be less sensitive. According to these data the existence of some kind of resistance against spontaneous tumour cells cannot be excluded.

Animals↗
PubMed1986

Effect of plaster-cast immobilization on the bone.

Plaster-cast of the right hind limb resulted in immobilization osteoporosis in rats. The alteration was characterized by loss of the bony substance as well as by a partial transformation of lamellar bone to primordial osseous tissue. In the basis of histological and histomorphometric findings, an accelerated osteoclastic activity, an increased osteocytic osteolysis and a decreased ossification are responsible for the observed changes.

Animals↗
PubMed1985

Antiviral activity of phorbol myristate acetate and possible relationships with interferon action.

Signal-induced turnover of membrane phospholipids represents a fundamental transducing mechanism that induces a signal cascade resulting in mobilization of calcium, activation of protein kinase C by diacylglycerol, release of arachidonic acid and stimulation of cyclic GMP production. In this pathway tumor-promoting phorbol esters such as phorbol myristate acetate (PMA) may substitute for diacylglycerol. The interferon-like antiviral effect of PMA described here suggests that the inositol phospholipid-diacylglycerol-protein kinase C signal-transducing mechanism may be involved in interferon action.

Antiviral Agents↗
PubMed1985

Sequence specificity of isolated DNA-adenine methylases from Mycobacterium smegmatis (butyricum) and Shigella sonnei 47 cells.

A set of four individual DNA-adenine methylases differing in pI (isoelectric point) values (MMbu4.2, MMbu6.4, MMbu7.3, and MMbu8.7), and a sole methylating enzyme with the same base specificity (MSso9.5) are present in M. smegmatis (butyricum) and Sh. sonnei 47 cells, respectively. The sequence specificity of each of those was studied 'in vitro' by a combined approach that comprised isostich (purine tract) analysis and identification of the immediate neighbourhood of the methylated base within the sequence methylated. The MSso9.5 recognition site has been established as the hexanucleotide 'palindromic' 5'-G-A-A-T-T-C-3' sequence which is structurally similar to the analogous MEco RI recognition site. However, in contrast to MEco RI, MSso9.5 methylates the 5'-end adenine residue in the sequence and thus it appears to be an isometimer of MEco RI. By means of the same approach, the partial nucleotide sequences methylated by each of the four individual M. butyricum enzymes were determined. MMbu7.3 and MMbu8.7 exhibit the identical sequence specificity upon methylation of the degenerative trinucleotide 5'-Py-A-Py-3' sequence and thus these enzymes are assumed to represent the different molecular forms of the methylase. MMbu4.2 methylates the 5'-G-G-A-3' sequence and thus it is of a great value as the tool for negating effects of the RBam HI and RAva II-type restriction. MMbu6.4 is of a particular interest on account of its unique DNA methylation pattern which is distinguished in the pronounced clustering of purine bases in the 5'-Pu-Pu-Pu-Pu-Pu-3' sequence methylated.

Base Sequence↗
PubMed1984

Homologies between a brain-specific identifier (ID) sequence and regions of Harvey murine sarcoma virus and Rous sarcoma virus genomes. Putative role of identifier sequences in the tissue specificity of malignant transformation by RNA tumor viruses.

As a step toward understanding of the tissue specificity of cellular transformation by RNA tumor viruses were looked for the presence of a putative brain specific regulatory (identifier) sequence (C82B) in the genome of various oncornaviruses. The genomes of Harvey murine sarcoma virus and Rous sarcoma virus contain sequences flanking the viral oncogenes with greater than 80% and greater than 60% homology to C82B, respectively. We suggest that identifier sequences acquired by oncoviruses may determine the potential target cells of malignant transformation after virus penetration.

Animals↗
PubMed1984

Some characteristics of lysogens of Mycobacterium smegmatis.

By the use of radioactive labelling it was observed that mycobacteriophage butyricum (By) enter Mycobacterium smegmatis strain Rabinowitz (M. sm. R.) cells, lysogenise them but do not form plaques. Mycobacteriophage Rabinowitz (V72) and phage By proved to be heteroimmune; that is, they superinfect lysogens of one another productively. Spontaneous lysis frequencies of two different mycobacterium strains lysogenised by phage By [M. sm. R. (By); M. sm. b. (By)] and that of the double lysogenic M. sm. R. (V72, By) strain were compared. The spontaneous lysis frequency of the two monolysogenic strains was found to be similar (10(-4)-10(-2) indicating that transition into the vegetative replication cycle of By phages occurs also in M. sm. R. cells. Spontaneous lysis frequency of the double lysogenic strain was found to be influenced by the medium used.

DNA, Bacterial↗
PubMed1984

Take and growth of the transplantable MC29 hepatoma in allogeneic and xenogeneic hosts.

We report here the unexpected biological behaviour of the transplantable MC29 virus-induced hepatoma. This neoplasm, originating from an inbred white Leghorn (Duke) chicken, is maintained in our laboratory by serial in vivo passages in Hunnia hybrid chickens allogeneic to the original host. More than 80% of the tumours developing after subcutaneous inoculation of 3 x 10(6) hepatoma cells into newly hatched chickens grew progressively, while after injection of the same number of cells into 7 days old birds regressive tumour growth was observed. Transplantation from the allogeneic hosts into 7 days old inbred white Leghorn (Duke) chickens also resulted in regression of tumours in the great majority of cases. After inoculation to xenogeneic Japanese quails, progressor tumours developed in both two weeks old and adult birds with a dramatic increase of the frequency of liver metastases. Transplantation to another xenogeneic host, the turkey, revealed an age-related resistance similar to that of Hunnia hybrid chickens.

Animals↗