The identity of bovine liver "nothing dehydrogenase"

In situ determination of different dehydrogenase activity profiles in the linings of odontogenic keratocysts and radicular cysts

The levels of succinate, lactate, glutamate, glycerophosphate and glucose-6-phosphate dehydrogenases within the linings of keratinizing and non-keratinizing odontogenic cysts were investigated using static end-point and continuously monitored Nitroblue Tetrazolium-based histochemical methods. The use of TV image analysis for quantification of formazan final reaction products was validated by demonstrating significant relationships between the integrated absorbance at 585 nm and the amount of formazan in, and thickness of, gelatin films containing reduced tetrazolium salt (r = 1.0, p < 0.001). Absorbance readings of stained sections gave mean coefficients of variation of 1.8 +/- 0.9% between day of measurement, and of 5.65 +/- 1.32% between serial sections. End-point assays indicated that the linings of odontogenic keratocysts contained higher levels of glucose-6-phosphate dehydrogenases (p < 0.0002) and lower levels of lactate dehydrogenase (p < 0.002) than those of radicular cysts. Succinate, glutamate and glycerophosphate dehydrogenase activities were similar in both cyst types. Results from continuously monitored assays, performed for glucose-6-phosphate and succinate dehydrogenases, demonstrated linear reaction rates over the first 2.75 min of reaction. The calculated enzyme activities from continuous assays were between 1.49 and 3.49 times higher than those determined from end-point assays and confirmed that levels of glucose-6-phosphate dehydrogenase were significantly higher in the linings of odontogenic keratocysts than those of radicular cysts (p < 0.004). By contrast, succinate dehydrogenase activity was significantly higher in radicular cyst linings (p < 0.03). These results highlight the benefits of an approach to in situ determination of enzyme activity using image analysis and continuous monitoring methodologies. Overall, the high level of glucose-6-phosphate dehydrogenase found in keratocyst linings is consistent with their clinical behaviour and higher level of proliferation and synthetic activity whereas the level of lactate dehydrogenase in radicular cysts probably reflects the presence of local tissue damage within these inflammatory lesions.

Differential oxygen sensitivities in G6PDH activities of cultured keloid and normal skin dermis single cells

Cell cultures of excised keloids and biopsied normal skin were established from patients of the Plastic Surgery Department of Singapore General Hospital and their single cells quantitated for glucose-6-phosphate dehydrogenase (G6PDH) activity using microspectrophometry. G6PDH has been cited as a transformation-linked discriminant. Analysis of variance shows no difference in overall activity between skin and keloid cells, but under oxygen saturation conditions, keloid G6PDH activity was significantly higher than skin G6PDH activity, although they were almost identical under nitrogen saturation conditions. Differential oxygen sensitivity in G6PDH activities between malignant and non-malignant cells have been reported, but its occurrence between keloid and normal skin cells is novel, especially as the keloid is regarded as a benign tumor with a zero carcinogenicity rate.

In situ kinetic parameters of glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase in different areas of the rat liver acinus

The reaction velocity of glucose-6-phosphate dehydrogenase (G6PDH) and phosphogluconate dehydrogenase (PGDH) was quantified with a cytophotometer by continuous monitoring of the reaction product as it was formed in liver cryostat sections from normal, young mature female rats at 37 degrees C. Control incubations were performed in media lacking both substrate and coenzyme for G6PDH activity and lacking substrate for PGDH activity. All reaction rates were non-linear but test minus control reactions showed linearity with incubation time up to 5 min using Nitro BT as final electron acceptor. End point measurements after incubation for 5 min at 37 degrees C revealed that the highest specific activity of G6PDH was present in the intermediate area (Vmax = 7.79 +/- 1.76 mumol H2 cm-3 min-1) and of PGDH in the pericentral and intermediate areas (Vmax = 17.19 +/- 1.73 mumol H2 cm-3 min-1). In periportal and pericentral areas, Vmax values for G6PDH activity were 4.48 +/- 1.03 mumol H2 cm-3 min-1) and 3.47 +/- 0.78 mumol H2 cm-3 min-1), respectively. PGDH activity in periportal areas showed a Vmax of 10.84 +/- 0.33 mumol H2 cm3 min-1. Variation of the substrate concentration for G6PDH activity yielded similar KM values of 0.17 +/- 0.07 mM, 0.15 +/- 0.13 mM and 0.22 +/- 0.11 mM in periportal, pericentral and intermediate areas, respectively. KM values of 0.87 +/- 0.12 mM in periportal and of 1.36 +/- 0.10 mM in pericentral and intermediate areas were found for PGDH activity. The significant difference between KM values for PGDH in areas within the acinus support the hypothesis that PGDH is present in the cytoplasmic matrix and in the microsomes. A discrepancy existed between KM and Vmax values determined in cytochemical assays using cryostat sections and values calculated from biochemical assays using diluted homogenates. In cytochemical assays, the natural microenvironment for enzymes is kept for the demonstration of their activity and thus may give more accurate information on enzyme reactions as they take place in vivo.

An improved purification method for cytosolic malate dehydrogenase from several sources

A new purification method for cytosolic malate dehydrogenases from several sources has been developed. The procedure, employing chromatographies on 5'AMP-Sepharose, DEAE-Sephacel and Blue-Sepharose, allows for a rapid isolation of the enzyme (approximately 40 hours), in large quantities, with good yields (45-54%). The specific activity of final preparations were around 1300 I.U./mg and were judged homogeneous by polyacrylamide gradient gel and sodium dodecyl sulfate polyacrylamide gel electrophoresis, high performance size exclusion chromatography and isoelectric focusing.

On the nature of the 'nothing dehydrogenase' reaction

The biochemical mechanism underlying the 'nothing dehydrogenase' reaction during the histochemical demonstration of dehydrogenases using tetranitro BT as the final electron acceptor has been investigated in unfixed, frozen rat liver sections. The reaction is stronger with NAD+ than either with NADP+ or in the absence of coenzyme. As much as 50% of the reaction is due to lactate dehydrogenase converting endogenous lactate and is largely inhibited by pyruvate. No NAD+-dependent alcohol dehydrogenase activity was detected at pH 7.45, the pH used for the incubations. The coenzyme-independent activity may be caused by SH-groups present in proteins and compounds like glutathione and cysteine and can be inhibited by N-ethylmaleimide and p-chloromercuribenzoic acid. It was also found that the 'nothing dehydrogenase' reaction mainly occurs during the first few minutes of incubation, levelling off quickly to a slow rate. When studying the kinetics of dehydrogenase reactions with tetrazolium salts, it should be realized that the 'nothing dehydrogenase' reaction, which as a whole is nonlinear with time, can interfere seriously with the dehydrogenase reaction to be analysed and may yield initial reaction rates that are too high. The findings of the present study reveal the nature of the reactions used for detection of necrosis in tissues with tetrazolium salts.

Histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase

Histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase has found many applications in biomedical research. However, up to several years ago, the methods used often appeared to be unreliable because many artefacts occurred during processing and staining of tissue sections or cells. The development of histochemical methods preventing loss or redistribution of the enzyme by using either polyvinyl alcohol as a stabilizer or a semipermeable membrane interposed between tissue section and incubation medium, has lead to progress in the topochemical localization of glucose-6-phosphate dehydrogenase. Optimization of incubation conditions has further increased the precision of histochemical methods. Precise cytochemical methods have been developed either by the use of a polyacrylamide carrier in which individual cells have been incorporated before staining or by including polyvinyl alcohol in the incubation medium. In the present text, these methods for the histochemical and cytochemical localization of glucose-6-phosphate dehydrogenase for light microscopical and electron microscopical purposes are extensively discussed along with immunocytochemical techniques. Moreover, the validity of the staining methods is considered both for the localization of glucose-6-phosphate dehydrogenase activity in cells and tissues and for cytophotometric analysis. Finally, many applications of the methods are reviewed in the fields of functional heterogeneity of tissues, early diagnosis of carcinoma, effects of xenobiotics on cellular metabolism, diagnosis of inherited glucose-6-phosphate dehydrogenase deficiency, analysis of steroid-production in reproductive organs, and quality control of oocytes of mammals. It is concluded that the use of histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase is of highly significant value in the study of diseased tissues. In many cases, the first pathological change is an increase in glucose-6-phosphate dehydrogenase activity and detection of these early changes in a few cells by histochemical means only, enables prediction of other subsequent abnormal metabolic events. Analysis of glucose-6-phosphate dehydrogenase deficiency in erythrocytes has been improved as well by the development of cytochemical tools. Heterozygous deficiency can now be detected in a reliable way. Cell biological studies of development or maturation of various tissues or cells have profited from the use of histochemistry and cytochemistry of glucose-6-phosphate dehydrogenase activity.(ABSTRACT TRUNCATED AT 400 WORDS)