Brain glutamate decarboxylase and pyrroloquinoline quinone

Porcine brain glutamate decarboxylase was examined for the presence of covalently bound pyrroloquinoline quinone (PQQ). HPLC analysis of pure glutamate decarboxylase subjected to the hexanol extraction procedure gave negative results when monitored at 320 nm, the maximum of absorbance of 4-hydroxy-5-hexoxy-PQQ. Resolved glutamate decarboxylase exhibits a structureless absorption band at wavelengths longer than 300 nm which cannot be attributed to PQQ. The holoenzyme is not a pyridoxal-quinoprotein; its catalytic mechanism involves the participation of only one cofactor, i.e. pyridoxal-5-P. Free PQQ is a strong inhibitor of the decarboxylase (Ki = 13 microM) and the reaction with the protein results in spectral changes resembling those of polylysine treated with PQQ. If the concentration of free PQQ in some regions of the brain reaches the micromolar level, then PQQ might play a role in the regulation of glutamate decarboxylase activity.

Effect of cigarette smoking and alcohol consumption in the aetiology of cancer of the oral cavity, pharynx and larynx

This study presents a comparative risk pattern for cancer of the oral cavity, pharynx and larynx, in relation to cigarette smoking and alcohol consumption based on data from case-control studies conducted in Korea Cancer Center Hospital, Seoul, Korea. The risk of cancer of the oral cavity, pharynx and larynx rose for current smokers and declined for ex-smokers. In males the odds ratios (ORs) for these sites rose with duration of smoking and number of cigarettes smoked per day. The relationship is strongest for laryngeal cancer. The risk for all sites was elevated linearly as amount and frequency of alcohol intake increased. Heavy drinkers, i.e. males who drank 90 g ethanol daily had an approximately 15-fold risk of cancer of the oral cavity, an 11-fold risk of pharyngeal cancer and an 11-fold risk of laryngeal cancer compared with non-drinkers. Alcohol drinking was a much stronger risk factor for cancer of the oral cavity than cancer of the pharynx and larynx. Alcohol was a much weaker risk factor for laryngeal cancer than cigarette smoking. Cancer of the oral cavity, pharynx and larynx also showed an interaction between smoking and alcohol, suggesting a synergistic effect.

Absorption of short-chain fatty acids from the rat cecum in vivo

Absorption of the short-chain fatty acids (SCFA), acetate, propionate and butyrate, was studied in vivo by measuring their disappearance from the washed cecum of anesthetized rats. The SCFA seemed to be absorbed predominantly by simple passive diffusion, because there was linear absorption over a wide concentration range, and no evidence of competition or enhancement of absorption when more than one SCFA was present in the lumen. Absorption of these three SCFA was independent of chain length. Their absorption was clearly limited by the lipid membrane, because permeability through the unstirred water layers was much greater than through the lipid membrane. Absorption was unaffected by altering the pH of the luminal infusate between 5.4 and 7.4. Based on our observation that, during absorption, there were increases in pH, total CO2 and HCO3- but no change in pCO2, we suggest that SCFA are absorbed primarily via diffusion involving anionic exchange with HCO3-.

Use of an anti-low density lipoprotein receptor antibody to quantify the role of the LDL receptor in the removal of chylomicron remnants in the mouse in vivo

Lipoproteins are removed from the plasma by LDL receptor-dependent and -independent pathways. The relative contribution of these has been established for LDL by using modified lipoproteins, but this has not been possible for apoE-rich lipoproteins, such as chylomicron remnants. To do this, we used a monospecific antibody to the rat LDL receptor. The antibody was injected intravenously into mice followed by 125I-lipoproteins. Blood samples were obtained sequentially and radioactivity measured to determine the plasma clearance of the lipoproteins. The animals were then sacrificed and the tissues removed, dried, and the radioactivity measured to determine tissue uptake. An albumin space was also measured to correct for blood trapping. With 125I-human LDL, approximately 50% of the injected dose was cleared in 180 min. This was reduced to 30% by the antibody and this was identical to the disappearance of reductively methylated LDL. This is a lower estimate of LDL-mediated uptake (40%) than in other species. LDL uptake per gram tissue was similar for the liver and the adrenal gland and was approximately 50% LDL receptor-dependent in both tissues. With 125I-chylomicron remnants, clearance was much more rapid with approximately 50% cleared in 5 min. By agarose gel electrophoresis, radioactivity was not transferred from chylomicron remnants to other lipoprotein classes. Chylomicron remnants with label on only apoB or in 3H-cholesterol esters showed a similar pattern. Combining the estimates of the three labeling procedures, approximately 35% of the 30 s and 25% of the 5 min chylomicron remnant disappearance was LDL receptor dependent. The liver, per gram tissue, took up five times as much radioactivity as the adrenal gland. At 5 min, at least 50% of this was LDL receptor-dependent in liver and 65% in adrenal gland. We conclude that the LDL receptor plays a major, and somewhat similar quantitative role in the clearance of both LDL and chylomicron remnants in the mouse. However, at least in the mouse, non-LDL receptor-mediated lipoprotein clearance is quantitatively important and is also very rapid for chylomicron remnants. Thus, for chylomicron remnants, it can easily compensate for LDL receptors if they are blocked or absent. Further, the tissue distribution of lipoprotein uptake may be directed by factors other than LDL receptor density.

Effect of cigarette smoking and alcohol consumption in the etiology of cancers of the digestive tract

This study presents the comparative patterns of risk of selected digestive tract cancers (esophagus, stomach, colon, rectum and liver) for males in relation to cigarette smoking and alcohol drinking, based on the data from case-control studies conducted in the Korea Cancer Center Hospital (KCCH). There was strong positive association between cigarette smoking and esophageal cancer, but none of the other sites was significantly related to cigarette smoking. In esophageal cancer, a dose-dependent effect for cigarette smoking was observed, with the odds ratio ranging from 1.29 for ever smoking up to 1 pack daily to 3.17 for smokers of more than 2 packs per day. The risk declined markedly following cessation of smoking. Cancers of the esophagus, rectum and liver were strongly related to alcohol consumption. Compared with non-drinkers, the OR for heavy drinkers was 9.14 in esophageal cancer, 4.75 in rectal cancer and 2.46 in liver cancer. In cancer of the stomach and colon, however, there was no association with alcohol drinking.

The mitochondrial ATP synthase of Trypanosoma brucei: developmental regulation through the life cycle

The mitochondrial H(+)-ATPase of the parasitic protozoan Trypanosoma brucei is shown to be developmentally regulated through the T. brucei life cycle as has been shown for components of the mitochondrial electron transport chain. We have substantiated our results by assaying not only for oligomycin-sensitive ATPase activity but also by determining the level of ATP synthetic activity. These results show that the level of ATPase present in the procyclic form of T. brucei is increased by at least threefold from that of the early bloodstream form while the ATPase activity in the late bloodstream form is only about twofold higher than the early form. ATP synthesis activity shows these same results. We have determined the level of ATP synthase protein present in the life cycle stages by Western analysis employing the antibodies that we have raised against both the water soluble F1 and the membrane-associated F0 moieties which we have purified from T. brucei. The Western blots of the procyclic form show strong reactivity with both the F0 and F1 antibodies. The other two life cycle stages, the early and the late bloodstream forms, show considerably less reactivity, paralleling the activity results. Electron micrographs of the sonicated mitochondrial fraction show inverted vesicles which are studded with knobby H(+)-ATPase in the procyclic form. The early bloodstream vesicles show very few of these characteristic structures, while the late bloodstream form shows a range of vesicles from nearly nude to partially studded.

Hepatocellular carcinoma in extrahepatic bile ducts

An elongated solid lesion observed on ultrasonography and CT in the biliary tree causing a smooth filling defect on cholangiography was observed in 2 patients. No tumor was observed in the liver parenchyma either on radiography or at operation. Histopathology showed hepatocellular carcinoma. After removal of the intraductal tumors, recurrence was observed in 2 and 6 months, respectively.

Overproduction of glutamate racemase of Pediococcus pentosaceus in Escherichia coli clone cells and its purification

We previously isolated a 6.0-kb DNA fragment that specifies glutamate racemase activity from the chromosomal DNA of Pediococcus pentosaceus by digestion with HindIII (N. Nakajima, K. Tanizawa, H. Tanaka, and K. Soda, 1986), Agric. Biol. Chem. 50, 2823-2830). We digested it further with EcoRI to obtain a fragment of 1.8 kb, which was blunt-ended and ligated into the SmaI site of vector plasmid pKK223-3. The recombinant plasmid showed a high glutamate racemase activity upon transformation of Escherichia coli W3110 cells with it; the plasmid was named pICR223. Glutamate racemase was overproduced in the clone cells and occurred in inclusion bodies in the cells. The enzyme was solubilized with 6 M urea, renatured by dialysis to remove urea, and purified to homogeneity with an overall yield of about 70% after a single DEAE-cellulose column chromatography. The amount of enzyme produced by the clone cells corresponded to about 38% of the total insoluble protein.

A case-control study of ginseng intake and cancer

The effect of ginseng consumption on the risk of cancer was investigated by interviewing 905 pairs of cases and controls matched by age, sex, and date of admission to the Korea Cancer Center Hospital, Seoul, Korea. Of the 905 cases 562 (62%) had a history of ginseng intake compared to 674 of the 905 controls (75%) a statistically significant difference (p less than 0.01). The odds ratio (OR) of cancer in relation to ginseng intake was 0.56 (95% confidence interval (CI), 0.45-0.69). Ginseng extract and powder were shown to be more effective than fresh sliced ginseng, the juice, or tea in reducing the OR. Odds ratios for decreasing levels of ginseng intake were 1.00, 0.58, 0.43 and 0.25 for males and 1.00, 0.81, 0.56 and 0.52 for females. A trend test showed a significant decrease in proportion of cancer cases with increasing frequency of intake for males (p less than 10(-5)) as well as for females (p less than 0.05). Chi-square homogeneity tests also confirmed significant differences between cases and controls for both sexes (p less than 10(-3)). The reliability of recall for ginseng use was assessed by interviewing 180 randomly-selected subjects twice using the same questionnaire. The overall agreement in reported ginseng use between the two interviews was 0.85, and the Kappa value was 0.71 (p less than 0.01). These results strongly support the hypothesis of preventive effects of ginseng on cancer suggested by earlier animal studies.

Brain pyridoxine-5-phosphate oxidase. Modulation of its catalytic activity by reaction with pyridoxal 5-phosphate and analogs

Pyridoxine-5-P oxidase, the flavoprotein involved in the oxidation of pyridoxamine-5-P and pyridoxine-5-P to pyridoxal-5-P, has been isolated and purified to homogeneity using sheep brain tissues. Inactivation of the oxidase by bis-pyridoxal-5-P results in binding of the inhibitor to specific lysyl residues. After NaBH4 reduction of the inactivated enzyme, it was found that 1 P-pyridoxyl-pyridoxine-P residue was incorporated per enzyme dimer. After trypsin digestion of the bis-PLP modified enzyme, only one peptide absorbing at 320 nm, was separated by reverse-phase high performance liquid chromatography. The amino acid sequence of the labeled peptide was determined by automated Edman degradation. The observations reported in this paper are relevant to the mechanisms underlying the regulation of the catalytic function of pyridoxines-5-P oxidase by the product pyridoxal-5-P. It is postulated that the catalytic function of the oxidase is modulated by binding of pyridoxal-5-P to a specific lysyl residue of the dimeric structure of the protein.

Biosynthesis of 4-aminobutyrate aminotransferase

Mitochondrial 4-aminobutyrate aminotransferase was synthesized in a cell-free reticulocyte lysate using polysomal RNA isolated from pig brain. Its primary translation product has a higher molecular mass than the mature enzyme. The difference in relative molecular mass is approximately 2000 as revealed by SDS/polyacrylamide gel electrophoresis. The precursor of 4-aminobutyrate aminotransferase recognizes polyvalent antibodies raised against the mature enzyme. The precursor of 4-aminobutyrate aminotransferase binds pyridoxal-5-P and displays catalytic activity. Enzymatic activity was detected using a sensitive fluorimetric method, which is based on the formation of condensation products between succinic semialdehyde and cyclohexane-1,3-dione. It is concluded that removal of an extra peptide from the precursor is not an obligatory first step in the production of biological active species.

Glutamate decarboxylase side reactions catalyzed by the enzyme

A homogeneous glutamate decarboxylase isolated from pig brain contains 0.8 mol of tightly bound pyridoxal 5-phosphate/enzyme dimer. Upon addition of exogenous pyridoxal 5-phosphate (pyridoxal-5-P), the enzyme acquires maximum catalytic activity. Preincubation of the enzyme with L-glutamate (10 mM) brings about changes in the absorption spectrum of bound pyridoxal-5-P with the concomitant formation of succinic semialdehyde. However, the rate of this slow secondary reaction, i.e. decarboxylative transamination, is 10(-4) times the rate of normal decarboxylation. It is postulated that under physiological conditions enzymatically inactive species of glutamate decarboxylase, generated by the process of decarboxylative transamination, are reconstituted by pyridoxal-5-P produced by the cytosolic enzymes pyridoxal kinase and pyridoxine-5-P oxidase. The catalytic activity of resolved glutamate decarboxylase is recovered by preincubation with phospho-pyridoxyl-ethanolamine phosphate. The experimental evidence is consistent with the interpretation that the resolved enzyme binds the P-pyridoxyl analog, reduces the stability of the covalent bond of the phospho-pyridoxyl moiety, and catalyzes the formation of pyridoxal-5-P.

4-Aminobutyrate aminotransferase. Conformational changes induced by reduction of pyridoxal 5-phosphate

Conformational changes induced in 4-aminobutyrate aminotransferase (4-aminobutyrate:2-oxoglutarate aminotransferase, EC 2.6.1.19) by conversion of pyridoxal-5-P to pyridoxyl-5-P were examined by two independent methods. The reactivity of the SH groups of the reduced enzyme is increased by chemical modification of the cofactor. 1.8 SH per dimer of modified enzyme react with DTNB, whereas 1.2 SH per dimer of the native enzyme react with the attacking reagent under identical experimental conditions. The modified and native forms of the enzyme bind the fluorescent probe ANS, but the number of binding sites for ANS is increased as result of conversion of P-pyridoxal to P-pyridoxyl. After the conformational changes onset by reduction of the cofactor, the modified enzyme binds one molecule of pyridoxal-5-P with a Kd of 0.1 microM to become catalytically competent. The catalytic site of the reduce enzyme was probed with P-pyridoxal analogs. Like resolved 4-aminobutyrate aminotransferase, the reduced species recognize the phosphorothioate analog and regain 40% of the total enzymatic activity. Since the catalytic parameters of reduced and native 4-aminobutyrate aminotransferase are indistinguishable, it is concluded that the additional catalytic site of the reduced enzyme is functionally identical to that of the native enzyme.

Binding of new PLP analogs to the catalytic domain of GABA transaminase

The binding site of Pyridoxal-5-P in 4-aminobutyrate aminotransferase was studied by using analogs of the cofactor. A phosphorothioate analog (PLP(S] recognizes the catalytic site; it forms a stable complex with the apoenzyme (KD = 1nM) and serves as cofactor during catalysis. Replacement of a non-bridged oxygen by sulfur in the phosphate side chain renders a compound which preserves the negative charges needed for correct alignment of the cofactor at the catalytic site. This phosphorothioate analog of PLP can be used to investigate the catalytic site of vitamin B6 dependent enzymes by means of 31P NMR spectroscopy. A bulky P-pyridoxamine derivative, ie, N-4-azido-2-nitrophenyl pyridoxyl-5-P (NANP) competes with natural cofactor for its binding site. Upon illumination, the arylazide of P-pyridoxamine acts as an efficient photolabeling reagent of the protein. A characteristic feature of this photolabeling reagent, ie, its ability to recognize the cofactor binding site, can be exploited to ascertain the chemical nature of amino acid residues at the catalytic site.

4-Aminobutyrate aminotransferase reaction of sulfhydryl residues connected with catalytic activity

4-Aminobutyrate aminotransferase is inactivated by preincubation with N-(1-pyrene)maleimide (mixing molar ratio 10:1) at pH 7. The reaction with N-(1-pyrene)maleimide was monitored by fluorescence spectroscopy and the degree of labeling of the enzyme determined by absorption spectroscopy. The blocking of 2 cysteinyl residues/enzyme dimer is needed for inactivation of the aminotransferase. The time course of the reaction is significantly affected by the substrate alpha-ketoglutarate, which afforded complete protection against the loss of catalytic activity. Trypsin digestion of pyrene-labeled aminotransferase, followed by gel filtration and "fingerprint" analysis, revealed the presence of only one peptide tagged with the fluorescent probe. The reaction of approximately 1.9 SH residues/dimer with iodosobenzoate resulted in enzyme inactivation together with a formation of an oligomeric species of Mr = 100,000 detectable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The cross-linked subunits are dissociated by addition of 2-mercaptoethanol which also restores full catalytic activity. Altogether, these observations are consistent with the concept that inactivation of 4-aminobutyrate aminotransferase by iodosobenzoate proceeds through disulfide bond formation between vicinal cysteinyl residues of the protein. It is postulated that the critical sulfhydryl groups of the enzyme are situated on opposite sides of the dimeric structure at the subunit interfaces.

The ontogeny of a natural food aversion in domestic rats (Rattus norvegicus) and house mice (Mus musculus)

During a 1-hr feeding test, hungry domestic rats (Rattus norvegicus) that had been reared individually from weaning with a domestic house mouse (Mus musculus) were less likely (p less than .05) to feed on the intact carcass of a freshly sacrificed mouse than were rats that had been reared individually with another rat. Likewise, hungry mice that had been reared individually with a rat were less likely (p less than .01) to feed on a dead rat than were mice that had been reared individually with another mouse. Regardless of the social conditions during rearing, hungry mice were more likely to feed on a dead mouse than were hungry rats to feed on a dead rat. Taken together, the present and other findings suggest that the tendency by rats to reject conspecific flesh stems, at least in part, from prior experience with conspecifics and with their own bodies. The experiential factors mediating the tendency by mice to reject conspecific flesh remain unclear.

Historical review of small and microvascular vessel surgery

The history of small and microvessel surgery is reviewed to aid the beginning microvascular surgeon in gaining a perspective of the surgical techniques used on vessels less than 3 mm in diameter. Although microvascular surgery uses sophisticated microscopes, instruments, and sutures, the fundamental operative procedures are similar to those first worked out on larger vessels. The trial and error methods of past surgeons from many different disciplines have led to ever-expanding possibilities for treatment of sick and injured patients and to laboratory investigation of disease processes. We have tried to highlight the major steps in the development of vascular surgery leading up to our present core of microvascular techniques. We recognize that many of these will become obsolete tomorrow; however, in developing the new it is wise to avoid the mistakes of the past.

Visual attention and neuronal firing patterns in the feline pulvinar nucleus of thalamus

In behaving cats, temporal patterns of neuronal firing were studied during slow wave sleep (SWS), motionless quiet wakefulness (QW) coupled with specific direction of the animal's attention, and during bar pressing performance (BP) for milk reward. The analysis was based on relative relations between sequential spike intervals. The strength of the method is based on the fact that the probabilities of occurrence of patterns are determined by the history of a spike train. During SWS, the neuronal firing modes closely followed the theoretical model of independent distribution of intervals, whereas during QW and BP specific for each neuron departures from the model, i.e., patterning was observed. Most importantly, in seven chronically studied neurons idiosyncratic patterns were related to direction of the animal's attention, and, very likely, to the visual forms the animals gazed at, because the patterns disappeared in the dark and during SWS without major changes in the mean firing rate. The replications of patterns upon recurrence of a particular direction of attention was proven statistically. The constancy and idiosyncrasy of these patterns were apparent even though the comparable episodes occurred several hours apart, and the animals slept and/or ate in between, and the distance, i.e., the retinal size of visual forms varied from one episode to another. On the basis of correlative evidence, it was argued that, compared to more abstract modes of information processing, the identification and quantification of patterns based on relative relations between intervals require the least amount of storage of intermediate results. Hence, these patterns are likely to represent a simple and phylogenetically old principle of communication between neurons. It was postulated that the idiosyncrasy and invariance of patterns may play a role in constancy of feature extraction and Gestalt perception.

Death in young alcoholics

Homicide, accidents and heart disease were the leading causes of death among young alcoholics treated at an outpatient alcoholism clinic over a 3-year period. Ways of preventing early death in alcoholics are suggested.