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Biomedical subjects

J Pitha

Publications and source records attributed to J Pitha.

At least 127 records · Page 7Linked to original sources
PubMed1981

Progressive nodular histiocytoma.

Progressive nodular histiocytoma is a clinically distinct variant in the general group of normolipemic histiocytic proliferations. Its cardinal feature is the presence of two different lesions--a superficial yellow-brown papule and a deep nodule. We describe herein a 29-year-old man with such lesions. Histologically, a variety of fibrous and cellular patterns were seen, mimicking the wide spectrum of findings in ordinary dermatofibromas. On ultrastructural examination, the most striking feature of the preponderant cell was lipid phagocytosis.

Adult↗
PubMed1980

Age-related decrease in repair of oxidative damage to surface sulfhydryl groups on rat adipocytes.

Adipocytes were isolated from the Wistar and Sprague-Dawley strains of rats of different ages. An impermeable reagent, mercury-[3H] dextran, was used to quantitate the sulfhydryl groups on the surface of these cells. The application of this reagent after the pre-reduction of cells with 2-mercaptoethanol yielded a measure of the total sulfhydryl and disulfide groups located there. Aging was found to significantly decrease the ratio of the number of exofacial sulfhydryl groups to the total number of exofacial sulfhydryl and disulfide groups.

Adipose Tissue↗
PubMed1980

Macromolecular beta-adrenergic antagonists discriminating between receptor and antibody.

The beta-adrenergic antagonist, alprenolol, was attached in an irreversible manner to macromolecular dextran via side arms that differed in length. The ability of these macromolecules to bind to the beta-adrenergic receptor of frog erythrocytes and to catecholamine-binding antibodies raised against partially purified receptors was studied. Compared to the parent drug the potency of binding of macromolecular alprenolol to the receptor decreased about 1/10, 1/600, and 1/8000 when the length of the arm separating alprenolol from the dextran moiety was 13, 8, and 4 atoms, respectively. In contrast, the binding potencies of the parent drug and of all its macromolecular derivatives for the antibody were within the same order of magnitude. Thus, conversion of a drug to a macromolecular form may not only sustain its binding activity but may also lead in a higher selectivity. The macromolecular derivatives described here may be suitable probes for investigation of the location and of the molecular properties of the binding sites for beta-adrenergic drugs.

Alprenolol↗
PubMed1980

Water-soluble, dextran-linked retinal: preparation, vitamin A-like activity in rats, and effects on melanoma cells.

A new, water-soluble, polymer-linked form of retinal was synthesized and tested for its ability to support the growth of vitamin A-deficient noninbred Holtzman rats and to inhibit the proliferation of melanoma cells in culture. Retinal was conjugated to the hydrazide of carboxymethyldextran in the presence of alpha-and beta-cyclodextrins. The aqueous solutions of the product contained between 200 and 1,000 micrograms retinal/ml as opposed to the low water solubility (< 0.01 micrograms/ml) of retinal itself. The retinal-dextran complex, although barely resorbed from the gastrointestinal tract, supported the growth of rats fed a vitamin A-deficient diet when administered ip at 2.3 mumol of retinal equivalent/kg body weight. Retinal and the retinal-dextran complex exhibited differential cytotoxicity toward S91 melanoma cells and caused cell lysis at 10 and 500 microM (retinal residue), respectively. At noncytotoxic doses both free retinal and its dextran-linked derivative reduced the cell proliferation rate in a time- and dose-dependent fashion with median inhibitory doses of 1 and 4 microM (retinal residue), respectively. These data demonstrated that the water-soluble retinal-dextran complex retained certain biologic activities of retinal and was less cytotoxic.

Animals↗
PubMed1979

Mechanism of enhancement of polynucleotide binding to cells by mutagens.

The binding of polyuridylate to cells is substantially increased by proflavine. This enhanced binding is saturable with respect to time and to the concentration of both proflavine and polyuridylate. Enhancement is observed only when cells are exposed to both proflavine and polyuridylate together and depends cooperatively on the proflavine concentration. The resulting complex formed between the cell, proflavine, and polyuridylate can be dissociated with salt but not with sucrose solutions. An increase in the binding of polyuridylate to cells similar to that observed with proflavine was also obtained with cationic dyes such as acridine orange, 9-aminoacridine, and Hoechst 33258, while the introduction of a bulky polysaccharide residue, dextran, into the dyes cancels these effects. Similarly, cationic aromatic compounds such as primaquine and quinacrine which carry bulky nonplanar substituents or aliphatic cationic compounds like ethylenediamine do not enhance binding. Proflavine is unable to augment the binding of a basic macromolecule, diethylaminoethylaminoethyldextran, to cells. The model proposed for the enhanced binding of polyuridylate is based on the cooperative formation of stacked complexes of cationic dye located between the cell surface and the bound polyuridylate.

Cell Line↗
PubMed1979

Adenocarcinoma of rete testis.

Adenocarcinoma of the rete testis is a rare tumor of the genital tract. An advanced case of adenocarcinoma thought to arise from the rete testis is presented. We believe this is the eighteenth reported case.

Adenocarcinoma, Papillary↗
PubMed1979

Opposite effects of dextrans substituted with sulfhydryls or mercury on tumor growth.

Macromolecular dextrans carrying substituents terminated by sulfhydryl groups or terminated by aromatic amines effectively inhibit the growth of a fibrosarcoma and of a mammary adenocarcinoma in a syngeneic mouse model. These compounds have no or very low toxicity to animals and are nontoxic to fibrosarcoma cells in vitro. Small-molecular-weight compounds carrying the same substituents as the above dextrans are without any effect on the growth of these tumors. A dextran substituted with mercury-containing side chains is growth promoting for the same fibrosarcoma in mice at doses which are nontoxic for these animals. However, the mercury-containing compound is toxic to fibrosarcoma cells in vitro. It is hypothesized that these nonpermeating macromolecules do not directly influence the tumor cells in animals but modulate the natural system of defense against tumors; cells of that system are stimulated or poisoned by the substituted dextrans.

Animals↗
PubMed1978

Binding of polynucleotides to fibroblasts. Effects of complex formation with vinyl analogs of nucleic acids.

The binding of polynucleotides or of their vinyl analogs to human fibroblasts is changed when complexes are formed between these compounds. The following polymers have been studied: poly(1-vinylcytosine), poly(1-vinyluracil, poly(9-vinyladenine), polyuridylate, polyadenylate and polyinosinate. Only that complex formation (between poly(1-vinylcytosine) and polyinosinate) which is accompanied by aggregation leads to a considerable increase (30 fold) in binding to cells; all the other complex formations have only moderate effects (0.2-3 fold). Furthermore, a comparison of unordered complexes containing polyinosinate whows that enhanced binding to cells is paralleled by an increased cellular resistance to viral infection.

Cell Line↗
PubMed1978

Reagents specific for cell surface components.

Mercury, diazonium ions and dyes which bind nucleic acids were covalently linked to dextrans using methods that resulted in non-hydrolyzable reagent-dextran bonds without impairing the binding abilities of the reagents, i.e. these dextran derivatives reacted with thiols, phenols/imidazoles and nucleic acids respectively. Since these dextran derivatives cannot penetrate into cells and since dextran itself does not bind to cells, these compounds represent reagents specific for the cell surface. They may be used both to evaluate cell surface constituents of intact cells and to affect viable cells via an interaction with those constituents. Mercury-dextran was found to bind to cells; the amount of mercury thus attached to the cells was about ten times smaller than when an equivalent concentration of free mercury ions was used. Mercury-dextran, bound to cells after a 30-min exposure at room temperature, was localized on the surface of these cells, as sodium borohydride reduced this complex giving rise to the intact cells, elementary mercury and free dextran which was released into medium. When cells were constantly exposed to the mercury-dextran, its toxic effects were comparable to that of free mercury ions. Diazonium-dextran, which also binds tightly to the cell surface, was also considerably toxic. Dextrans substituted with dyes which bind to nucleic acids were less toxic than the parent dyes themselves; it was shown that the attachment of such a dye to dextran decreased the binding of dye to cells under detection limits.

Aniline Compounds↗
PubMed1978

Template specific inhibitors of E. coli RNA polymerase.

Electroneutral analogs of polynucleotides, poly-9-vinyladenine and poly-1-vinyluracil inhibit E. coli RNA polymerase in all combinations where the single stranded polynucleotides are used as templates and the vinyl analogs are complementary to them. As templates both the ribo- and deoxyribopolynucleotides were tested; variation of the template concentration in the presence of vinyl analogs produced a competitive pattern of inhibition. The electroneutral analogs do not inhibit the enzyme activity when non-complementary single stranded polynucleotides or double stranded polynucleotides are used as templates; the latter fully supports transcription even when one of the strands is complementary to the analog.

DNA↗