Lipid balance in HepG2 cells: active synthesis and impaired mobilization

The human hepatoma cell line HepG2 in culture medium synthesized fatty acids de novo (144 +/- 9 nmol fatty acid/mg protein per 24 h) at a rate similar to that observed in freshly prepared rat hepatocytes (192 +/- 8 nmol/mg per 24 h) and in primary cultures of rat hepatocytes (165.4 +/- 29.3 nmol/mg per 24 h). In HepG2 cells, fatty acid synthesis was inhibited by extracellular oleate (0.75 mM), and, to a lesser extent, by glucagon (10(-7) M). Insulin (7.8 x 10(-8) M) had a mild stimulatory effect. Fatty acid synthesis was not influenced by lipogenic precursors (lactate plus pyruvate), substances which, in rat hepatocytes, had pronounced stimulatory effects. Fatty acid synthesis rates were also unchanged in the presence of prostaglandin E2 (PGE2). In general, compared to rat hepatocytes, fatty acid synthesis in HepG2 cells was less sensitive to manipulation of the culture medium in vitro. HepG2 cells had a high capacity for triacylglycerol synthesis from extracellular oleate (469 +/- 43 nmol triacylglycerol/mg protein per 24 h) but phospholipid synthesis was relatively low (15.8 +/- 0.4% of total glycerolipids). Very little of the above newly synthesized triacylglycerol was secreted as lipoprotein (4.62 +/- 0.88 nmol triacylglycerol/mg protein per 24 h) resulting in a large intracellular accumulation of triacylglycerol. This was exacerbated by the absence of any detectable ketogenesis. The secretion of triacylglycerol produced from de novo synthesized fatty acids was also very low in HepG2 compared to that observed in primary cultures of rat hapatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tolerance and sensitization to the behavioral effects of cocaine in rats: relationship to benzodiazepine receptors

Tolerance and sensitization to the behavioral effects of cocaine were investigated in rats responding under a fixed-consecutive-number eight schedule of food reinforcement. The development of tolerance or sensitization was induced by delivering the drug either immediately before or after each behavioral session during chronic administration. Chronic cocaine administered before each session resulted in tolerance, as indicated by the shift to the right in the cocaine dose response curve. This tolerance was more likely to develop in the presence of an external discriminative stimulus. On the other hand, when cocaine was delivered after each session, the injections did not disrupt responding and sensitization or increased sensitivity rather than tolerance developed. This sensitization was more likely to occur when the external discriminative stimulus was not present. These data suggest that either tolerance or sensitization to the behavioral effects of cocaine can occur following the same number of chronic injections, with the effect dependent on the context under which the drug is delivered. Significant differences in benzodiazepine receptor binding measured autoradiographically using [3H]flumazenil were observed between rats that received cocaine before or after each session, suggesting that the development of tolerance and sensitization may be mediated through changes in benzodiazepine receptors in discrete brain regions.     

Surgery in the management of small cell lung cancer

OBJECTIVE: We analyzed our experience in the period January 1975-December 1995 aiming to confirm the role of surgery in the multimodality treatment of small cell lung cancer (SCLC). METHODS: 127 patients (5.28% of the overall lung resections for carcinoma) underwent surgery for SCLC. The median age was 60 years (range 34-73). In 87 patients (68.5%) a pre-operative tissue diagnosis was effected and those patients underwent a complete staging procedure. Fifteen patients received up to six complete courses of neoadjuvant and adjuvant chemotherapy. The surgical procedures included: 50 pneumonectomies, 71 lobectomies and six wedge resections. Two patients experienced a local recurrence and a completion pneumonectomy was performed. RESULTS: The median follow-up is 66 months (range 6-214). The 5-year actuarial survival rate is 22.6% (median 18 months). Twenty-three patients are still alive, 21 of them being disease-free. Considering the most conspicuous group of patients (n = 92) treated by surgery and adjuvant chemotherapy, the survival data were 47.2, 14.8 and 14.4% for Stage I, II and III, respectively (P = 0.001). NO patients had a significantly better survival than N1 and N2 patients (P = 0.035). CONCLUSIONS: Surgery and adjuvant chemotherapy might represent an effective form of treatment of limited SCLC without lymph-node involvement. The role of surgery is yet to be verified as regards N1 and N2 status, where even neoadjuvant chemotherapy has not achieved the hoped-for results (no patient reaching a 2-year survival).     

Are head and neck specific quality of life measures necessary?

BACKGROUND: The purpose of this study was to determine whether head and neck-specific health status domains are distinct from those assessed by general measures of quality-of-life (QOL). METHODS: Cross-sectional study of 55 head and neck cancer patients in tertiary academic center was made. Three head and neck-specific measures,-including the Head & Neck Survey (H&NS); a brief, multi-item test which generates domain scores; and a general health measure,-were administered. RESULTS: The H&NS was highly reliable and more strongly correlated to the specific measures than to the general measure. Eating/swallowing (ES) and speech/communication (SC) were not well correlated with general health domains. Head and neck pain was highly correlated to general bodily pain (0.88, p < .0001). Despite correlations to some general health domains, appearance (AP) was not fully reflected by any other domain. CONCLUSIONS: Head and neck-specific QOL measures are necessary and should include domains that reflect ES, SC, and AP.     

In vivo 13C NMR measurements of cerebral glutamine synthesis as evidence for glutamate-glutamine cycling

The cerebral tricarboxylic acid (TCA) cycle rate and the rate of glutamine synthesis were measured in rats in vivo under normal physiological and hyperammonemic conditions using 13C NMR spectroscopy. In the hyperammonemic animals, blood ammonia levels were raised from control values of approximately 0.05 mM to approximately 0.35 mM by an intravenous ammonium acetate infusion. Once a steady-state of cerebral metabolites was established, a [1-13C]glucose infusion was initiated, and 13C NMR spectra acquired continuously on a 7-tesla spectrometer to monitor 13C labeling of cerebral metabolites. The time courses of glutamate and glutamine C-4 labeling were fitted to a mathematical model to yield TCA cycle rate (V(TCA)) and the flux from glutamate to glutamine through the glutamine synthetase pathway (V(gln)). Under hyperammonemia the value of V(TCA) was 0.57 +/- 0.16 micromol/min per g (mean +/- SD, n = 6) and was not significantly different (unpaired t test; P > 0.10) from that measured in the control animals (0.46 +/- 0.12 micromol/min per g, n = 5). Therefore, the TCA cycle rate was not significantly altered by hyperammonemia. The measured rate of glutamine synthesis under hyperammonemia was 0.43 +/- 0.14 micromol/min per g (mean +/- SD, n = 6), which was significantly higher (unpaired t test; P < 0.01) than that measured in the control group (0.21 +/- 0.04 micromol/ min per g, n = 5). We propose that the majority of the glutamine synthetase flux under normal physiological conditions results from neurotransmitter substrate cycling between neurons and glia. Under hyperammonemia the observed increase in glutamine synthesis is comparable to the expected increase in ammonia transport into the brain and reported measurements of glutamine efflux under such conditions. Thus, under conditions of elevated plasma ammonia an increase in the rate of glutamine synthesis occurs as a means of ammonia detoxification, and this is superimposed on the constant rate of neurotransmitter cycling through glutamine synthetase.     

Schizophrenia, psychosis, and the basal ganglia

Schizophrenia is one of the most common and perhaps the most disabling of mental disorders, for which effective forms of treatment have not yet been established definitively. The findings reviewed in this article strongly suggest that basal ganglia abnormalities are involved in the pathophysiology of psychotic syndromes in general, and schizophrenia in particular.