Neuron-specific deficits of bioenergetic processes in the dorsolateral prefrontal cortex in schizophrenia.

Schizophrenia is a devastating illness that affects over 2 million people in the United States and costs society billions of dollars annually. New insights into the pathophysiology of schizophrenia are needed to provide the conceptual framework to facilitate development of new treatment strategies. We examined bioenergetic pathways in the dorsolateral prefrontal cortex (DLPFC) of subjects with schizophrenia and control subjects using western blot analysis, quantitative real-time polymerase chain reaction, and enzyme/substrate assays. Laser-capture microdissection-quantitative polymerase chain reaction was used to examine these pathways at the cellular level. We found decreases in hexokinase (HXK) and phosphofructokinase (PFK) activity in the DLPFC, as well as decreased PFK1 mRNA expression. In pyramidal neurons, we found an increase in monocarboxylate transporter 1 mRNA expression, and decreases in HXK1, PFK1, glucose transporter 1 (GLUT1), and GLUT3 mRNA expression. These results suggest abnormal bioenergetic function, as well as a neuron-specific defect in glucose utilization, in the DLPFC in schizophrenia.

A continuous microtiter plate assay for screening nucleotide sugar-synthesizing nucleotidyltransferases.

A continuous microtiter plate nucleotidyltransferase substrate screening assay (NUSSA) is described which allows the identification of nucleotide sugar-synthesizing enzyme activities. The assay is accomplished by the determination of the common product of these enzymes PPi with a PPi-dependent phosphofructokinase. A subsequent enzyme reaction cascade leads to the production of 2 mol NAD per mol PPi. PPi-dependent phosphofructokinase was purified from potato with respect to contaminating enzyme activities which would disturb NUSSA performance. NUSSA allows the quick, simultaneous, and comprehensive check of different sugar 1-phosphate and nucleoside triphosphate substrates using purified pyrophosphorylases or crude extracts of plants, microorganisms, and mammalian tissues. Moreover, NUSSA will assist to evaluate these enzymes for the synthesis of important nucleotide sugars which serve as substrates of glycosyltransferases in carbohydrate syntheses.

Carbohydrate utilization and digestibility by tilapia, Oreochromis niloticus x O. aureus, are affected by chromic oxide inclusion in the diet.

A 12-wk feeding trial was conducted to study the influence of chromic oxide (Cr2O3) on carbohydrate utilization and digestibility by tilapia, Oreochromis niloticus x O. aureus. Two levels of chromic oxide (0.5 and 2%) were each incorporated into diets containing glucose or starch. Chromic oxide was added at 0 or 8 wk. The diets were fed to triplicate groups of fish weighing 1.11 +/- 0.05 g. Fish fed the starch diet had greater (P < 0.05) weight gain, feed efficiency ratio, protein efficiency ratio, protein deposition and digestibility of protein, lipid, carbohydrate and dry matter than fish fed the glucose diet irrespective of the time and level of chromic oxide supplementation. Fish fed the glucose diet with 0.5% chromic oxide had higher weight gain, feed efficiency ratio, protein efficiency ratio and protein deposition than fish fed the glucose diet with 2% chromic oxide. The ingredient digestibility estimated using 0.5% chromic oxide as the marker was greater than that estimated with 2% chromic oxide. Higher phosphofructokinase and lower glucose-6-phosphatase activity was found in fish fed the starch diet than in fish fed the glucose diet regardless of the time and level of chromic oxide inclusion. Fish fed the glucose diet with 0.5% chromic oxide had higher phosphofructokinase activity and lower tissue chromium concentration than fish fed the glucose diet with 2% chromic oxide irrespective of chromic oxide inclusion time. These data suggest that the level of chromic oxide in the diet alters glucose utilization by tilapia and affects nutrient digestibility by tilapia. The time of chromic oxide inclusion had no effect on carbohydrate utilization and digestibility.

Hyperbaric oxygenation treatments and metabolic enzymes in the heart and diaphragm.

We previously found that intermittent hyperbaric oxygen exposure increases metabolic enzyme activity in soleus muscle. Since the metabolic enzyme activities of the heart and diaphragm of healthy animals are difficult to alter, we questioned whether intermittent hyperbaric oxygenation would provide a stimulus sufficient to increase metabolic enzyme activity. Therefore, we exposed 36 rabbits (4 groups of 9) twice daily for 90 min 5 days/wk to either 100% O2 at 243 kPa, 8.5% O2, and 91.5% N2 at 243 kPa, 100% O2 at 101 kPa, or 21% O2 at 101 kPa. After 4 wk of treatment, the activities of citrate synthase, succinate dehydrogenase, alpha-glycerophosphate dehydrogenase, phosphofructokinase, and glyceraldehyde-3-phosphate dehydrogenase were measured. In both the heart and the diaphragm, none of the treatments significantly altered the mean enzyme activities for any of the enzymes measured. Therefore, it seems that the hyperbaric oxygenation treatment protocols used do not induce an increase in metabolic enzyme activity in the heart and diaphragm in healthy animals.

Drug effects on certain enzymes of carbohydrate metabolism in MCF-7 cells in culture.

The effects of treatments with ethinyl-estradiol, tamoxifen, prednisolone, cyclophosphamide, methotrexate, 5-fluorouracil and Adriamycin on the activities of PFK, 6PGDH, alpha-GPDH and alpha-GPDH/6PGDH ratios were investigated in MCF-7 cells in monolayer cultures. The following findings are recorded. Both ethinyl-estradiol and prednisolone failed to induce alterations in the activities of these enzymes. Tamoxifen increased the activities of PFK, alpha-GPDH and alpha-GPDH/6PGDH ratios whereas ethinyl-estradiol inhibited the tamoxifen-induced rise in the activity of PFK. Treatment with cyclophosphamide alone was without any effect but in combination with either methotrexate or 5-fluorouracil induced increases in the activities of 6PGDH and alpha-GPDH. Adriamycin at a lower dose increased the activities of 6PGDH and alpha-GPDH and the alpha-GPDH/6PGDH ratio and decreased the activity of PFK. At a higher dose level it reduced the activities of all the enzymes whilst increasing the alpha-GPDH/6PGDH ratio. These data encourage us to undertake a project to test the sensitivity of individual tumours to these drugs in vitro thereby enabling the selection of appropriate drugs for adjuvant therapy.

Supplementing glucose metabolism in human senile cataracts.

Assay of the activities of hexokinase, phosphofructokinase, and pyruvate kinase showed that the first two declined in aging human lens cortex and all three enzymes retained constant activities in the epithelium throughout life. Moreover, both clear and cataractous aging lenses contained the same enzyme activities. ATP contents in cataracts, however, were lower than in clear lenses; in fact, after incubation at 37.5 degrees C in isotonic (290 to 300 mOsm), glucose-containing media, ATP was rapidly lost from cataracts (but not from clear lenses), suggesting excessive ATP expenditure in cataracts for osmotic balance. Cataracts incubated in media containing either glucose-6-phosphate or fructose-1, 6-diphosphate produced significantly higher ATP than with glucose in the media, indicating that glucose metabolism in human senile cataracts could be supplemented with hexose phosphates. Fructose-1, 6-diphosphate appeared to be more efficient than glucose-6-phosphate in preventing lens swelling during incubation.

Quantitative histochemical studies of the hypothalamus. Control point enzymes during the estrous cycle.

Three control point enzymes of the Embden-Meyerhof pathway, hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK), have been measured in individual hypothalamic nuclei during the 5-day estrous cycle of adult rats by quantitative histochemical methods. PK levels, low during proestrus, rise to maximum activity during estrus; this rise is significantly greater than on all other days of the cycle in the lateral preoptic area (LP), ventromedial pars medialis (VMM) and pars lateralis (VML) and posterior hypothalamic (Post) nuclei. HK activity also rises from low proestrous levels during the cycle but, in contrast to PK, reaches maximum activity during diestrus-1 (D-1) or diestrus-2 (D-2). PFK showed variable changes during the estrous cycle with peaks occurring during estrus in some nuclei and during diestrus in others, but these changes were not significantly different. These metabolic changes occur in specific hypothalamic nuclei which have been shown by electrical stimulation, lesion production, stereotaxic hormone implantation and localization of luteinizing hormone-releasing factor experiments to have an important role in reproductive physiology and sexual behavior.