A COMPARISON BETWEEN FLUOROMETRIC AND MASS FRAGMENTOGRAPHIC DETERMINATIONS OF HOMOVANILLIC ACID AND 5-HYDROXYINDOLEACETIC ACID IN HUMAN CEREBROSPINAL FLUID

HVA and 5-HIAA in human cerebrospinal fluid were quantitatively determined by both fluorometry and mass fragmentography. The homovanillic acid values obtained by fluorometry were significantly lower than those obtained by mass fragmentography (P < 0.05). The correlation coefficient between values for HVA obtained by the two methods was high, r= 0.90. For 5-HIAA the concentrations obtained by the two methods were not significantly different while the correlation coefficient was lower, r= 0.55.     

Alpha-1-antitrypsin deficiency and juvenile liver disease Ultrastructural observations compared with light microscopy and routine liver tests

Sixteen children (aged between 1 month and 20 years) with alpha-1-antitrypsin deficiency (PiZ) were investigated by liver biopsy on one or more occasions. Eight patients had suffered from neonatal cholestasis, and two of them were investigated during the cholestatic period as well. The clinical status and liver function tests were compared with the light and electron microscopical findings. According to the light microscopical analyses at the latest investigation, the cholestatic and noncholestatic patients were classified as healthy, fibrotic or cirrhotic cases. All livers displayed periodic acid-Schiff positive, diastase-resistant globules in some but not all periportally located hepatocytes. By electron microscopy accumulation of retained secretory material was found in all PiZ patients. This accumulation was most conspicuous in the smooth endoplasmic reticulum of hepatocytes. alpha-1-antitrypsin deficiency seems to affect some, but not all hepatocytes. In the affected cells disappearance or hypotrophy of the Golgi complex could be observed. The intracellular transport of very low density lipoproteins (VLDL) was apparently not affected. The migration block in alpha-1-antitrypsin deficiency seems to occur before transportation to the Golgi complex. The extent of the involvement was not strictly age-dependent. There was no ultrastructural evidence of subclinical cholestasis as a possible triggering factor in the development of cirrhosis.     

Selected ion monitoring for rapid differentiation of mycobacteria isolated from domestic animals

Gas chromatography/mass spectrometry adapted for selected ion monitoring was used to detect C₃₂ mycocerosic acid in short-term incubated cultures of procineand canine strains of mycobacteria. The method can be employed for rapid differentiation of Mycobacterium tuberculosis from M. avium-intracellulare.     

Cation specificity and modes of the Na+:CO3(2-):HCO3- cotransporter in renal basolateral membrane vesicles

The cation specificity and possible exchange modes of the Na+:CO3(2-):HCO3- cotransporter were evaluated by use of basolateral membrane vesicles isolated from rabbit renal cortex. External Li+ inhibited HCO3- gradient-stimulated 22Na uptake, indicating that Li+ interacts with the Na+:CO3(2-):HCO3- cotransporter. No interaction with K+, choline, Rb+, Cs+, or NH4+ could be similarly detected. Imposing an outward Li+ gradient caused quenching of acridine orange fluorescence in the presence but not in the absence of HCO3-, suggesting that Li+:base cotransport takes place via the Na+:CO3(2-):HCO3- cotransporter. Imposing an outward gradient of unlabeled Na+ stimulated the initial rate of 22Na uptake and induced its transient uphill accumulation, indicating Na(+)-Na+ exchange. Na(+)-Na+ exchange was observed in the presence but not in the absence of HCO3- and was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), suggesting that it occurs via the Na+:CO3(2-):HCO3- cotransporter. Similarly, an outward Li+ gradient stimulated uphill 22Na accumulation, indicating Na(+)-Li+ exchange. Na(+)-Li+ exchange was observed in the presence but not in the absence of HCO3-, and was inhibited by DIDS, suggesting that it also occurs via the Na+:CO3(2-):HCO3- cotransporter. Both Na(+)-Na+ and Li(+)-Na+ exchange modes were sensitive to inhibition by harmaline but not by amiloride. We conclude that Li+ is an alternative substrate for the renal Na+:CO3(2-):HCO3- cotransporter. Transport modes of the system include cation:base cotransport and HCO3-dependent cation-cation exchange.     

Stimulation of the insulin secretory mechanism following barium accumulation in pancreatic β-cells

Electrothermal atomic absorption spectroscopy was employed for measuring barium in β-cell-rich pancreatic islets microdissected from ob/ob-mice. Both the uptake and efflux of barium displayed two distinct phases. There was a 4-fold accumulation of barium into intracellular stores when its extracellular concentration was 0.26 mM. Unlike divalent cations with more extensive intracellular accumulation, the washout of Ba²⁺ was not inhibited by d-glucose. Ba²⁺ served as a substitute for Ca²⁺ both in maintaining the glucose metabolism after removal of extracellular Ca²⁺ and making it possible for glucose to stimulate insulin release. Furthermore, Ba²⁺ elicited insulin release in the absence of glucose and other secretagogues. The latter effect was reversible and was markedly potentiated under conditions known to increase the β-cell content of cyclic AMP. It is likely that the observed actions of Ba²⁺ are mediated by Ca²⁺, since Ca²⁺-dependent regulatory proteins, such as calmodulin, apparently cannot bind Ba²⁺ specifically.     

Norepinephrine Metabolism in Man Using Deuterium Labeling: Turnover of 4-Hydroxy-3-Methoxymandelic Acid

Abstract: 4-Hydroxy-3-methoxymandelic acid (HMMA; VMA) labeled with three deuterium atoms was used to study the turnover and fate of HMMA following intravenous injection. Five healthy men were given a pulse dose of 5.0 μmol of labeled HMMA. Plasma and urinary levels of both endogenous and labeled HMMA were subsequently followed by gas chromatography-mass spectrometry using selected ion detection. The kinetic parameters were determined both with and without compensation for the pool expansion caused by the injection of labeled HMMA. The urinary recovery of labeled HMMA was 85 × 10% (mean ± SD). No conversion of HMMA t o 4-hydroxy-3-methoxyphenyl glycol (HMPG) occurred. The biological half-life of HMMA was 0.54 ± 0.22 h. The apparent volume of distribution was 0.36 ± 0.11 L/kg. The production rate or body turnover was 1.27 ± 0.51 μmol HMM/h and urinary excretion rate was 0.82 ± 0.22 μmol/h. These results show that HMMA is turning over rapidly in a relatively small volume of distribution and that, unlike HMPG, it is an end metabolite of norepinephrine in man.     

Increased Salsolinol Levels in Rat Striatum and Limbic Forebrain Following Chronic Ethanol Treatment

Abstract: Endogenous levels of salsolinol and its methylated metabolite were measured by combined gas chromatography and mass spectrometry in rats chronically exposed to ethanol for 150 days. The chronic ethanol administration produced a significant increase of salsolinol concentrations in dopamine-rich brain areas, e.g., the striatum and the limbic forebrain. A negative correlation was observed between plasma ethanol concentration and the level of salsolinol in the brain. A possible role for salsolinol in the regulation of ethanol drinking and/or in the development of ethanol dependence is discussed.     

Glycosylation causes an apparent block in translation of immunoglobulin heavy chain

Analysis of nascent heavy chains isolated from MPC11 (gamma 2b heavy chains) and MOPC 21 (gamma 1 heavy chains) mouse myeloma cells demonstrates an accumulation of nascent heavy chains which are slightly smaller in mass (approximately 35,000 daltons) than nascent heavy chains which have just been glycosylated (approximately 38,000 daltons). The accumulation of 35,000-dalton nascent heavy chain appears to be a consequence of the glycosylation process since tunicamycin, an inhibitor of glycosylation, abolishes the apparent translational block manifested by the accumulation of 35,000-dalton nascent chains. Tunicamycin also causes a 15 to 25% increase n the relative rate of synthesis of heavy chain compared to the corresponding rate of synthesis of the nonglycosylated light chain synthesized by the same cell. These results suggest that the translation block, caused by the glycosylation process, of heavy chain synthesis contributes to the imbalance of heavy chain and light chain biosynthesis observed in malignant and normal lymphoid cells.     

Competitive Advantage Provided by Bacterial Motility in the Formation of Nodules by Rhizobium meliloti

The effect of motility on the competitive success of Rhizobium meliloti in nodule production was investigated. A motile strain formed more nodules than expected when mixed at various unfavorable ratios with either flagellated or nonflagellated nonmotile derivatives. We conclude that motility confers a selective advantage on rhizobia when competing with nonmotile strains.