Robert W. Guynn

Effects of acute alcohol intoxication on cerebral blood flow measured with PET

Regional distribution of cerebral blood flow was assessed in a group of 13 normal social drinkers under baseline conditions and after acute alcohol intoxication. Blood flow measurements were done using 15O-labeled water and positron emission tomography (PET). Each subject underwent two control sessions under baseline conditions and two sessions after alcohol. Seven of the subjects were given 0.5 g/kg of alcohol and six were given 1 g/kg of alcohol p.o. The first and second post-alcohol scans were done 40 and 60 min after alcohol ingestion. The studies revealed that both the high and the low doses of alcohol reduced blood flow to the cerebellum. This effect was significant only for the high doses of alcohol, which also increased blood flow to the right temporal and the prefrontal cortex. The decrease in blood flow of the cerebellum could account for the muscular incoordination induced by alcohol.

Enzymic determination of inorganic phosphate in the presence of creatine phosphate

Abstract A method is presented for the enzymic determination of inorganic phosphate in the presence of labile organic phosphates. The procedure, based on the reaction of glyceraldehydephosphate dehydrogenase, is simple and accurate over a wide range of phosphate concentrations. Commercially available reagents can be used for the assay without purification, making the method suitable for routine use. Methods are also described for extraction of inorganic phosphate from tissues without significant hydrolysis of labile phosphate esters.

Is Schizoaffective Disorder a Stable Diagnostic Category: A Retrospective Examination

Debate continues about whether clear nosologic boundaries can be drawn between schizoaffective disorder (SA), schizophrenia (SP), and bipolar disorder (BPD). This study attempted to clarify these boundaries. A retrospective review of the records of adult psychiatric inpatients with DSM-IV diagnoses of SA (n=96), SP (n=245), and BPD (n=203) was conducted. Patients were assessed at admission and discharge using standardized rating scales (completed by physicians and nurses) and self-report inventories. Differential improvement over time also was examined. Significant differences were found for gender, legal status at admission, age, LOS, episode number, and ethnicity. Overall, SA was rated by clinicians as intermediate between SP and BPD, although SA rated themselves as the most severe. SA was similar to SP on positive symptoms, intermediate on negative symptoms, and similar to BPD on mood- and distress-related symptoms. Independent of diagnosis, differences in change scores from admission to discharge were related to severity level at admission. Although several differences were found in symptom severity across domains, no syndrome was identifiable associated with the diagnosis of SA and the diagnosis was unstable over time, thereby bringing into question the validity of SA as a diagnostic entity.

Recent Trends in American Board of Psychiatry and Neurology Psychiatric Subspecialties

ObjectiveThis article reviews the current status and recent trends in the American Board of Psychiatry and Neurology (ABPN) psychiatric subspecialties and discusses the implications of those trends as well as several key questions whose answers may well determine subspecialty viability.MethodsData are presented on specialty and subspecialty programs; graduates; and ABPN certification candidates and diplomates drawn from several sources, including the records of the ABPN, the websites of the Accreditation Council for Graduate Medical Education and the American Medical Association, and the annual medical education issues of JAMA.ResultsFewer than half of psychiatry graduates pursue sub-specialty training. While most recent specialty graduates attempt to become certified by the ABPN, many subspecialists elect not to do so. There have been recent decreases in the number of fellowship programs and trainees in geriatric psychiatry and addiction psychiatry. The pass rates for fellowship graduates are superior to those for the “grandfathers” in all of the newer psychiatric subspecialties. Lower percentages of subspecialists than specialists participate in maintenance of certification, and maintenance of certification pass rates are high.ConclusionThe initial interest in training and certification in some of the ABPN subspecialties appears to have slowed, and the long-term viability of those subspecialties may well depend on the answers to a number of complicated social, economic, and political questions in the new health care era.

Evidence for a Tetrahydrobiopterin Deficit in Schizophrenia

Tetrahydrobiopterin (BH4) is a vital cofactor maintaining availability of the amine neurotransmitters [dopamine (DA), noradrenaline (NA), and serotonin (5-HT)], regulating the synthesis of nitric oxide (NO) by nitric oxide synthase (NOS), and stimulating and modulating the glutamatergic system (directly and indirectly). These BH4 properties and their potential relevance to schizophrenia led us to investigate the hypothesis of a study group (healthy controls, n = 37; schizophrenics, n = 154) effect on fasting plasma total biopterin levels (a measure of BH4). Study analysis showed a highly significant deficit of total biopterins for the schizophrenic sample after partialling out the effects of potential confounds of gender, age, ethnicity, neuroleptic use history and dose of current use, 24-hour dietary phenylalanine/protein ratio (a dietary variable relevant to BH4 synthesis), and plasma phenylalanine (which stimulates BH4 synthesis). A mean decrement of 34% in plasma total biopterins for schizophrenics from control values supports clinical relevance for the finding. In a subsample (21 controls and 23 schizophrenics), sequence analysis was done of the GTP cyclohydrolase I feedback regulatory gene and no mutations were found in the coding region of the gene. A deficiency of BH4 could lead to hypofunction of the systems of DA, NA, 5-HT, NOS/NO, and glutamate, all of which have been independently implicated in schizophrenia psychopathology. Further, evidence has been accumulating which implicates the critical interdependence of these neurotransmitter systems in schizophrenia; this concept, along with the present study finding of a biopterin deficit, suggests that further study of the BH4 system in schizophrenia is warranted and desirable.

Substrate specificity of choline kinase.

The substrate specificity of choline kinase (ATP:choline phosphotransferase, EC 2.7.1.32) from brewers yeast has been examined using multiple analogs of choline, most of which have been reported to be a substrate of one or another choline-using system from other sources. In contrast to many such systems, choline kinase from brewers yeast has been found to have relatively stringent and straight-forward structural requirements for its substrates. It is hypothesized that there are at least four points of interaction of the substrate with the enzyme--one for the hydroxyalkyl side chain and one for each of the three substituents on the quaternary nitrogen. Of the latter, one site seems relatively more sterically hindered than the other two. Short, single or double alkyl substitutions on the quaternary nitrogen are possible without a large loss of substrate capacity of the analog. Thus N,N-dimethyl-N-propylethanolamine had a relative Vmax of 116% and a relative Vmax 96% that of choline and a Km of 68 +/- 15 microM [nearly four times that of choline itself (18 microM)]. However, N-butyl-N,N-dimethylethanolamine and N,N,N-triethylethanolamine were very poor substrates. Analogs with substituents on the quaternary nitrogen of longer chain length were without activity as were aromatic derivatives. None of the bisquaternary compounds of the general structure HOCH2CH2N+(CH3)2-(CH2)n-N+(CH3)2CH2CH2OH (n = 2-10) showed any substrate capacity, as well. Restrictions on the hydroxyethyl side chain were also severe. One additional methylene group in this chain greatly reduced substrate capacity of the analog and two additional ones eliminated it entirely, as did almost any substituent on the beta carbon. A single (but not a double) substituent on the alpha carbon was moderately tolerated, however. Thus alpha-methylcholine and N-methyl-2-hydroxymethylpiperidine were substrates (although the latter one was a poor one) but beta-methylcholine and N-methyl-3-hydroxypiperidine were not. Such information may be of use toward designing cholinergic probes targeting specific enzyme or metabolic functions.

The reactions of the phosphorylated pathway of L-serine biosynthesis: thermodynamic relationships in rabbit liver in vivo.

The thermodynamic relationships among the reactions of the phosphorylated pathway of L-serine biosynthesis have been determined in rabbit liver in vivo in different dietary states. The mass action ratios of the reactions involved were calculated from the concentrations of appropriate metabolites in freeze-clamped liver and compared with the equilibrium constants of the same reactions previously determined under physiological conditions. Toward this goal, a new, highly specific enzymatic assay for L-phosphoserine was developed to allow the accurate measurement of this intermediate in biological material. The level of L-phosphoserine, the immediate precursor of L-serine, varied significantly with diet, being 0.81, 0.38, and 0.21 mumol/g wet wt in the fed, and 24 h and 48 h fasted states, respectively. The tissue content of L-phosphoserine was also sensitive to anoxia, falling almost fivefold within 5 min after the liver was removed. Values of for the combined reactions of the first two steps of the pathway of L-serine biosynthesis [D-3-phosphoglycerate dehydrogenase (EC 1.1.1.95) and L-phosphoserine aminotransferase (EC 2.6.1.52)] in livers from animals in different dietary states were calculated to be 1.2 X 10(-4) (fed), 1.4 X 10(-4) (24 h starved), and 0.70 X 10(-4) (48 h starved), all being very close to the value of the combined equilibrium constant of the same reactions (2.44 X 10(-4). Even when there were major changes in the individual components of, such as a fivefold drop in L-phosphoserine and a sevenfold fall in alpha-ketoglutarate following 5 min of anoxia, remained relatively unchanged (2.7 X 10(-4). Thus, it has been concluded that, in rabbit liver under most normal conditions, the combined reactions of D-3-phosphoglycerate dehydrogenase and L-phosphoserine aminotransferase remain very near equilibrium, and that almost all of the disequilibrium of the pathway, amounting to a delta G of -5.5 kcal/mol in the fed state, is at the last step, the L-phosphoserine phosphatase reaction (EC 3.1.3.3).

High-affinity hemicholinium-3 binding to brain membranes: reduction by treatment witphysostigmine in vivo

We examined high-affinity, sodium-dependent binding of hemicholinium-3 to brain membranes. Binding, with Kd of about 3 nM, was highest in corpus striatum, intermediate in cerebral cortex and hippocampus, and low in cerebellum. Treatment with physostigmine in vivo reduced binding in all regions without affecting apparent affinity.

[37] Enzymatic determination of acetate

Publisher Summary This chapter presents the enzymatic determination of acetate. The assay depends on the conversion of acetate to acetyl-CoA and the measurement of the acetyl-CoA by a coupled system of malate dehydrogenase and citrate synthase. The assay is specific as citrate synthase is specific for acetyl-CoA. The spectrophotometric assay is designed for either a dual or single beam instrument holding cuvettes of 1 cm light path. The fluorimetric procedure is designed for an instrument capable of handling 1.0 ml volumes. For the fluorimetric assay quinine sulfate in sulfuric acid is used as the reference standard; however, for each assay a standard curve of potassium acetate is run simultaneously. The fluorimetric procedure is usually less precise than the spectrophotometric assay. The standard error of the mean of triplicate tissue samples is 3–5%. The higher standard error of the mean in the fluorimetric procedure reflects the relatively greater significance of the acetate contaminations of the reagent cocktail at these very low concentrations of acetate.

Effect of ethanol on brain CoA and acetyl-CoA.

BKAIN, lacking as it does significant amounts of alcohol dehydrogenase. [EC 1.1.1.1] ( R A S K I N & SOKOLOtF. 1972). seems relatively immune (VELOSO er d., 1972) from the major metabolic disturbances that have come to be associated with ethanol metabolism in liver (KKEBS, 1968: WII.LIAMSON PI a/.. 1969; Lrsu~os. 1970: VFECH of d., 1072). There is evidence. however, that acetaldehyde, the bloodborne product of hepatic ethanol oxidation. can affect some aspects of brain metabolism. In particular, several studics have suggested that ethanol (presumably \ia its metabolic product acetaldehyde) can produce significant decreases in the concentrations of CoA i n brain as well as liver (AMMON et a/.. 1967: AMWOK P I u/.. 1969: RAWAT. 1074). Such ohscrvations are of interest especially i n brain since CoA and acetyl-CoA arc inbolved in the synthcsis of the neurotransmitter acctyl-cholinc through the reaction of choline acetyltransferase [EC 2.3. I .6]. Unfortunately all the previous studies of the interaction of ethanol with CoA have used quite non-specific assays for CoA making the results uncertain and difficult to interpret. Recausc of the key position of CoA and its derivatives in intermediary metabolism including the synthesis of acetylcholine and because of the importance of understanding the interaction of ethanol with hrain. the eNcct of ethanol on brain CoA and acetyl-CoA has been rc-examined using specific assay procedures (ALLRED & GL,Y, 1969). I,:nfortunatelg by using specific methods, we hake been unable to conlirm that cthanol has a significant effect on brain CoA or acctyl-CoA 111 cico.