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J A Litwin

Publications and source records attributed to J A Litwin.

At least 55 records · Page 3Linked to original sources
PubMed1982

Transition metal-catalysed oxidation of 3,3'-diaminobenzidine [DAB] in a model system.

The oxidation of 3,3'-diaminobenzidine [DAB] by H2O2 catalysed by 4 transition metals, Cu++, Co++, Fe+++ and Mn++, was investigated spectrophotometrically in a model system. The velocity of the reactions was higher with higher concentrations of DAB, H2O2 and a metal as well as with higher temperature. Optimal pH found for reactions catalysed by different transition metals was pH = 7.0 for Cu++ and Co++, pH - 6.0 for Fe+++ and pH - 9.0 for Mn++. A rapid spontaneous DAB oxidation by H2O2 in the absence of any transition metal was observed at pH less than 5.0.

3,3'-Diaminobenzidine↗
PubMed1981

Ultrastructural demonstration of endogenous peroxidatic activity in mammalian arterial wall.

Endogenous peroxidatic activity has been demonstrated at the ultrastructural level in large arteries of rabbit and rat using diaminobenzidine. The reaction was positive in endothelial cells of both species and also in the smooth muscle cells of rat arteries. The reaction product was localized in the nuclear envelope and endoplasmic reticulum of the reactive cells. Since the enzymatic activity was extremely sensitive to fixation, best visualization was obtained in unfixed, directly incubated tissues in which additional mitochondrial staining occurred due to the activity of endogenous cytochrome c/cytochrome oxidase system. The peroxidatic activity was partially sensitive to cyanide and could be completely abolished by azide and aminotriazole. It has been suggested that the observed endogenous peroxidatic activity of the arterial wall components reflects the activity of prostaglandin endoperoxide synthetase and, indirectly, production of prostacyclin (PGI2).

Animals↗
PubMed1980

Cell membrane features of rabbit arterial smooth muscle. A freeze-fracture study.

The cell membrane of smooth muscle cells from four large arteries of rabbits was investigated by freeze-fracture. On the surface of the smooth muscle smooth zones could be distinguished arranged in an alternate manner with zones characterised by numerous openings of surface vesicles. Vesiculate zones formed bands of variable width, generally parallel to the long axis of the cell, or irregular patches of different size. The density of vesicles within bands and patches varied from a very loose packing to a dense, quasi-hexagonal array. Comparative morphometric studies of the cell membrane replicas showed differences in the ratio vesiculate area: smooth area and also different surface vesicle frequencies expressed either as mean values or as values for vesiculate zones, in the arteries investigated. Communicating junctions (nexuses, gap junctions) characterized by a random arrangement of particles on the P-face and a more ordered, rhomboidal array of pits on the E-face were the only type of intercellular junctions found between arterial smooth muscle cells.

Animals↗
PubMed1980

Application of colloidal iron method to semithin sections of epoxy embedded tissues.

Hale's colloidal iron reaction for acid mucopolysaccharides was applied to semithin sections of Epon-embedded tissues routinely processed for electron microscopy. The reaction was found to be positive only after partial removal of the resin in NaOH/absolute ethanol solution; its sensitivity, however, did not reach that obtained in paraffin or frozen sections. The duration of the Epon-removing procedure seems to be crucial for the specificity of staining.

Animals↗
PubMed1979

Histochemistry and cytochemistry of 3,3'-diaminobenzidine. A review.

The review presents applications of 3,3'-diaminobenzidine (DAB) to histochemistry and cytochemistry, including demonstration of oxidative enzymes and hemoproteins, tracer experiments, immunocytochemistry and methods based on non-enzymic DAB oxidation. A special attention is paid to methodological problems concerning the specifity and sensitivity of DAB reactions.

3,3'-Diaminobenzidine↗
PubMed1976

PAS reaction performed on semithin epon sections following removal of the resin by NaOH in absolute ethanol.

Different results of PAS reaction performed on semithin sections of Epon-embedded tissues were obtained when the sections were exposed for various time intervals to saturated solution of NaOH in absolute ethanol, the reagent known to dissolve the resin and facilitate staining. In the untreated sections only glycogen revealed strong PAS reaction, most mucosubstances reacted weakly or not at all. After 1 to 5 min of NaOH in absolute ethanol treatment results observed were in accordance with those usually seen in paraffin sections. When, however, the time of Epon-dissolving procedure was longer than 10 min, most tissue structures demonstrated positive, largely diffuse staining. The mechanism of the observed effect and its significance for the application of PAS reaction to Epon sections are discussed.

Animals↗
PubMed1975

Effect of stabilizers on diaminobenzidine reactions of mitochondria.

The effect of various stabilizers--0.9% NaCl, 7.5% sucrose and 7.5% polyvinyl pyrrolidone (PVP) on reactions of mitochondria with fresh and photooxidized diaminobenzidine (DAB) was investigated. NaCl and PVP abolished the DAB staining of mitochondria incubated without exogenous cytochrome c; NaCl, however, was ineffective when exogenous cytochrome c or oxidized DAB were present in the incubation medium. PVP considerably decreased the intensity of all reactions performed in the presence of exogenous cytochrome c or oxidized DAB. The mechanism of the observed effect is not likely to involve osmotic protection of mitochondria; extraction of endogenous cytochrome c from fresh frozen tissue by NaCl and greatly increased viscosity of PVP-containing media seem to be most probable explanations.

3,3'-Diaminobenzidine↗
PubMed1975

Light microscopic differential staining of epoxy-embedded adenohypophysis.

Light microscopic histochemical methods for differential staining of adenohypophysis glandular cells were applied to Epon-embedded tissue, after prior softening of resin with saturated solution of NaOH in absolute ethanol. All investigated staining procedures, i.e. carmoisin L-orange G, PAS-orange G, PAS-range G-methyl blue, Gabe's aldehyde fuchsin-Halmi counterstain, aldehyde thionin-PAS-orange G and performic acid-alcian blue-PAS-orange G were found to give satisfactory results and tissue structure showed no signs of damage caused by the Epon-dissolving reagent. The features of light microscopic image given by plastic-embedded semithin sections: nearly 2-dimensional picture as well as the highest possible resolving power provide the opportunity for much more precise and detailed examination of adenohypophysis prepared that way, as compared with conventionally paraffin-embedded gland. Moreover, the described technique permits to establish a direct connection between light microscopic differential histochemistry of adenohypophysis and the electron microscopy by means of adjacent sections.

Animals↗