Simultaneous radioenzymatic assay of dopamine and dihydroxyphenylacetic acid: an index of in vivo dopamine release

The relative brain tissue concentrations of dopamine (DA) and its deaminated metabolite, dihydroxyphenylacetic acid (DOPAC), appears to be a reliable index of the functional activity of dopaminergic neurons. In order to apply this approach to the assessment of dopaminergic neuronal activity in small regions of brain, we have developed a sensitive radioenzymatic assay for simultaneous measurement of DA and DOPAC. The sensitivity of the assay for DA is approximately 10 pg and for DOPAC 100 pg. In addition, the assay is highly specific, simple, and relatively inexpensive. The concurrent estimation of tissue DA and DOPAC concentrations seems to be a reliable means of evaluating the rate of DA turnover or release in behavioral, electrical stimulation, and certain drug paradigms. However, the release or turnover of DA as induced by D-amphetamine (and perhaps other indirectly-acting dopaminemimetic drugs) cannot be meaningfully assessed by measurement of DA and DOPAC alone.

Radioimmunoreactivity and receptor-binding activity of the recombined molecule obtained by complementation of two fibrinolysin fragments of ovine prolactin

The recombined molecule obtained by complementation of two fibrinolysin fragments of ovine prolactin (oPRL) has been characterized by radioimmunoassay and radioreceptor assay. The recombinant alone exhibits very low radioimmunoreactivity and radioreceptor activity. However, in the presence of excess fragment oPRL-(1-53), which does not compete with oPRL in either assay, the recombinant has 101% of the radioimmunoreactivity and only 13% of the radioreceptor activity. The result shows that the low activity of the recombinant when assayed alone is due to dissociation of the molecule. When the molecule is completely in the recombined form in the presence of excess oPRL-(1-53), it retains full immunoreactivity but only part of the radioreceptor activity.

The inactivation of rat adipocyte Mg2+-dependent phosphatidate phosphohydrolase by noradrenaline

The inactivation of rat adipocyte Mg2+-dependent phosphatidate phosphohydrolase by noradrenaline [Cheng & Saggerson (1978) FEBS Lett. 87, 65--68; Cheng & Saggerson (1978) FEBS Lett. 93, 120--124] persists for at least 40 min in crude defatted homogenates kept at 0 degrees C or 20 degrees C, but is diminished at 37 degrees C. The effect of noradrenaline persists through the isolation of post-105000 g supernatants and is then stable in these preparations at 0 degrees C and 37 degrees C. Inclusion of albumin (10--20 mg/ml) in homogenization buffers abolishes the effect of noradrenaline. The effect of noradrenaline is not removed by dialysis of extracts or by raising the concentrations of Mg2+ or phosphatidate in assays.

Subcellular distribution and some properties of N-ethylmaleimide-sensitive and-insensitive forms of glycerol phosphate acyltransferase in rat adipocytes

1. Glycerol phosphate acyltransferase (GPAT) activities were measured in subcellular fractions obtained from rat epididymal adipocytes. These contained both N-ethylmaleimide-sensitive and N-ethylmaleimide-insensitive forms of the enzyme. 2. As shown by parallel measurements of marker enzymes, N-ethylmaleimide-insensitive GPAT is most probably a mitochondrial activity, whereas N-ethylmaleimide-sensitive GPAT is the microsomal enzyme. 3. Subcellular distributions are also reported for dihydroxyacetone phosphate acyltransferase (DHAPAT) (assayed with and without N-ethylmaleimide), monoacylglycerol phosphate acyltransferase (MGPAT) and Mg2+-dependent and Mg2+-independent forms of phosphatidate phosphohydrolase (PPH).

A highly sensitive radioenzymatic assay for simultaneous estimation of norepinephrine, dopamine, and epinephrine

We have developed a radioenzymatic assay for simultaneous estimation of norepinephrine (NE), dopamine (DA), and epinephrine (E) that was the result of the integration of several unique features of previously described assay procedures. Catecholamines in sera or tissue homogenates were enzymatically O-methylated in the presence of partially purified catechol-O-methyltransferase with S-[methyl-3H] adenosyl methionine serving as the methyl donor. The O-methylated products were then separated by thin-layer chromatography, eluted from the gel, and their tritium content determined. The assay allows measurement of catecholamines with a sensitivity in the ranges of 15-20 pg. In addition, the assay is highly specific, reproducible, relatively rapid and simple, and inexpensive.

Genetic analysis of Escherichia coli mutants defective in adenylate kinase and sn-glycerol 3-phosphate acyltransferase

Complementation analysis with independently isolated plA and adk (adenylate kinase) mutants of Escherichia coli showed that all the mutants belong to the same complementation group. The results suggest that the adk (plsA) locus is the structural gene for adenylate kinase.

Membranous lipodystrophy: a clinicopathological study of six cases

Membranous lipodystrophy apparently is a new disease, first reported and named by Nasu and associates 31 in 1971. We have collected six cases of this disease. The initial manifestation was articular pain at adolescence. Symmetrical changes in the bones of the extremities then appeared and the disease seemed to progress slowly with age. The younger patients exhibited only skeletal pain or fractures, while the older patients had some neuropsychiatric changes. Three of the patients died in middle age. The cystic bone lesions contained a yellow, lipid-like substance which histologically showed a characteristic membranocystic appearance. Electron microscopic study showed unique features, but biochemical analysis of the substance did not reveal a definable abnormality.

Moonquakes: Mechanisms and Relation to Tidal Stresses

Observed features of moonquakes are combined with theoretical calculations of the tidal stresses to interpret the moonquake mechanisms. Tidal stresses, together with a postulated ambient tectonic stress, are sufficient to explain the depth, periodicity, and polarity reversal of moonquakes. Both of these stresses are small (on the order of 1 bar) and consistent with the small magnitudes of moonquakes.

Leukocyte transketolase activity as an indicator of thiamin nutriture in rats

The purpose of this study was to evaluate the possibility of using leukocyte transketolase activity (TKA) as an index of thiamin status. It was shown previously that hepatic TKA in rats is altered by changes in the type and amounts of carbohydrate, protein, and fat in the diet. It was, therefore, essential to determine whether leukocyte TKA in rats is affected by dietary factors other than thiamin intake. Hepatic TKA and leukocyte TKA both varied with dietary thiamin intake; maximum activity was attained when the diet contained 3 to 4 mg thiamin/kg diet. Administration of oxythiamin resulted in decreases in TKA in both liver and leukocytes. The changes in leukocyte and hepatic TKA induced by varying degrees of thiamin deficiency were closely correlated. The responses of thiamin content were also closely correlated in liver and leukocytes. However, only hepatic TKA was altered by increasing the fat or protein content of the diet or by substituting fructose for glucose. None of the dietary manipulations studied except the production of thiamin deficiency had any effect on leukocyte TKA. We conclude from our results that leukocyte TKA is a sensitive and specific indicator of thiamin nutriture in rats.