Functional compartmentalization of energy production in neural tissue

Previous work in our laboratory has shown that neural trauma results in a disparity between oxidative and glycolytic rates. In non-neural tissue, glycolysis and oxidative phosphorylation have been shown to work independently of one another, a phenomenon known as "energy compartmentalization". We believe that functional compartmentalization of energy production may also occur in the brain with glycolysis providing energy for membrane bound ionic pumps. Spreading depression, induced in rodent brain by topical KCl application, results in K+ shifts. The restoration of K+ gradients is accomplished by energy dependent Na(+)-K+ pumps. If these pumps depend upon glycolysis, blocking glycolysis should prevent reconstitution of normal [K+]e levels. The present series of experiments were designed to suggest that energy compartmentalization may also exist in brain, and that glycolytic energy production is preferentially used by Na(+)-K+ pumps to maintain normal ionic homeostasis by observing the dynamics of spreading depression induced K+ shifts before and after glycolytic blockade. Spreading depression was associated with increased K+ (48.6 +/- 16.6 mM over control) that normalized within 2.9 +/- 0.3 minutes. Following superfusion with a glycolytic blocking agent, spreading depression produced similar increases in [K+]e (40.6 +/- 12.0 mM over control) but time for reconstitution of the normal [K+]e was 400% longer than controls (2.9 +/- 0.3 to 14.9 +/- 2.1 minutes, P less than 0.001). Time required for recovery of EEG was identical pre- and post-blockade. We believe these data suggest that energy compartmentalization may exist in neural tissue and that glycolytic pathways of energy production are functionally tied to membrane Na(+)-K+ pumps.(ABSTRACT TRUNCATED AT 250 WORDS)     

The anaerobic recovery of frog muscle

Summary The muscle may undergo a partial recovery of its high energy phosphate stores in the absence of oxygen by the way of glycolysis (anaerobic recovery). This process has been studied in 41 pairs of frog gastrocnemii at different degrees of exhaustion induced by variable trains of supramaximal stimuli. Anaerobic recovery appears to be inadequate to replenish the fraction of muscle high energy phosphate stores (GP=ATP+PC) split as a consequence of the stimulation. The maximal amount of recovery (on the average about 5 Moles of GP per gram of fresh tissue) occurs when the muscle resting stores have been reduced to about 50%. This limitation in the extent of recovery is not a consequence of a reduced availability of glycogen but it is possibly related to the production of some metabolic intermediate, limiting the rate of the glycolytic sequence, likely the accumulation of lactic acid in the fiber. The time course of the anaerobic recovery process is characterized by at1/2 of about 2 min. The efficiency of the process, i.e. the number of the high energy phosphate bonds resynthesized by one Mole of lactic acid, appears to vary between 1.5 and 1.8, being of the same order of magnitude as the GP/L.A. ratio obtained from muscle extracts.     

The effects of repeated exposure to anoxia on intracellular calcium,glycogen and lactate in isolated ferret heart muscle

Isolated cardiac tissue from the ferret was repeatedly exposed to anoxia while perfused with glucose-containing Tyrode solution. In one series of experiments, papillary muscles were injected with aequorin to measure intracellular Ca²⁺. On the first exposure to anoxia, the Ca²⁺ transients often increased, but on subsequent exposures this increase disappeared and eventually the Ca²⁺ transients declined on exposure to anoxia. This decline in the Ca²⁺ transients could be converted back to an increase by a 1 h exposure to an elevated (×5) glucose concentration. Exposure of aerobic muscles to 10 mM lactic acid caused a similar increase in the Ca²⁺ transients to that seen in early exposures to anoxia. In a second series of experiments, performed on Langendorff-perfused hearts, measurements were made of glycogen concentration preceding, and lactate production during, exposures to anoxia. At a constant level of glucose, glycogen concentration and lactate production were found to decline on repeated exposures to anoxia, and both were increased after a period of elevated glucose and reduced stimulation frequency. These results suggest that the response of the Ca²⁺ transients to anoxia is dependent on the metabolic status of the muscle. The increase in the Ca²⁺ transients during an early eposure to anoxia may be a consequence of lactic acid production due to accelerated glycolysis. Repeated exposures to anoxia reduce glycogen concentration and lactate production and this reduces the rise in the Ca²⁺ transients.     

磷酸甘油酸脱氢酶基因与肿瘤

磷酸甘油酸脱氢酶(phosphoglycerate dehydrogenase,PHGDH)基因编码3-磷酸甘油酸脱氢酶,是糖酵解-丝氨酸生物合成途径中的第一个分支酶.PHGDH氧化糖酵解中间产物3-磷酸甘油酸为磷酸羟基丙酮酸,后通过一系列酶的作用最终合成丝氨酸.丝氨酸在蛋白和细胞增殖所需其他生物分子(如核苷酸、磷脂丝氨酸、鞘氨醇)的合成中起着重要的作用.最新研究发现PHGDH高表达于一系列肿瘤中,且与肿瘤细胞生长、凋亡相关.该文就PHGDH基因结构、功能及与肿瘤的关系作一综述.     

Nuclear PKM2 expression predicts poor prognosis in patients with esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common tumors worldwide, with a high malignant degree and poor prognosis. The present study aims to investigate the relationship between pyruvate kinase M2 (PKM2) expression and the prognosis of patients with ESCC. The expression of PKM2 in 86 cases of esophageal carcinoma tissues was tested using immunohistochemistry. The relationship between PKM2 expression and clinical pathological parameters, and their effects on the prognosis of patients with ESCC were analyzed. The expression levels of PKM2 in both cytoplasm and nucleus of ESCC tissues were significantly higher than those in paracancerous tissues (P = 6.73 × 10⁻⁹ and 4.32 × 10⁻⁶, respectively). The Kaplan–Meier analysis showed that nuclear PKM2 expression was closely related to the survival of patients with ESCC (P = 0.005). Patients with high PKM2 expression in the nucleus had significantly shorter survival times than those with low PKM2 expression in the nucleus (hazard ratio for death, 2.358; 95% confidence interval, 1.156–4.812; P = 0.018). No other significant difference was found between PMK2 expression and clinico-pathological features of ESCC patients (all P > 0.05). In conclusion, high PKM2 expression in the nucleus is essential in the pathogenic process of ESCC and may be used to predict the prognosis of patients with ESCC.     

Anti-SRBC Plaque-Forming Cells in Liver,Spleen and Hepatocyte Cell Suspensions of Rabbits and Mice

In a series of experiments in rabbits and mice, we have demonstrated that hepatocytes, isolated at a purity exceeding 98% from immunized animals, possess an immunological activity against the immunizing antigen, sheep red blood cells. Hepatocytes formed hemolyzing plaques as assayed by the Jerne technique, and hepatocyte culture fluids showed both hemagglutinating and hemolyzing activity as well as the presence of immunoglobulin components in immunoelectrophoretic patterns.     

Warburg effect in keloids: A unique feature different from other types of scars

Keloid fibroblasts (KFs) undergo reprogramming of the metabolic phenotype from oxidative phosphorylation to the Warburg effect. However, more studies are needed to demonstrate whether there is a Warburg effect in KFs and to determine whether there is a similar phenomenon in other types of scars or in the proliferative stage of scars. In our study, the mRNA and protein expression of key glycolytic enzymes, glucose consumption and lactate production in KFs, normal skin fibroblasts (NFs), atrophic scar fibroblasts (ASFs), proliferative stage scar fibroblasts (PSSFs), and hypertrophic scar fibroblasts (HSFs) were detected. In addition, the effects of 2-deoxy-d-glucose (2-DG, a glycolysis inhibitor) on cell proliferation in KFs and NFs were studied. We found that the mRNA and protein expression of key glycolytic enzymes in KFs were significantly upregulated compared with those in NFs. Glucose consumption and lactate production in KFs were also higher than that in NFs. However, we found no similar phenomenon in ASFs, PSSFs, or HSFs. When treated with 2 mmol/l 2-DG, the cell viability of KFs decreased more than that of NFs. What's more, treatment with increasing concentrations of 2-DG could inhibit cell viability and migration of KFs in a dose-dependent manner. In conclusion, the Warburg effect in KFs is a feature different from ASFs, PSSFs, or HSFs. Keloids are essentially different from other types of scars in terms of energy metabolism. This characteristic of KFs could provide new hope for the early diagnosis and treatment of keloids.     

PFKFB3基因在前列腺癌中的表达及其对前列腺癌细胞糖酵解及生长的影响

目的探讨6-磷酸果糖激酶-2/果糖双磷酸酶-2同工酶3（PFKFB3）基因在前列腺癌中的表达及其对前列腺癌细胞糖酵解及生长的影响。 方法收集我院病理科前列腺增生和前列腺癌蜡块组织,应用免疫组化技术检测PFKFB3的表达水平。通过荧光定量PCR和Western blot实验检测正常前列腺上皮细胞（RWPE-1）和四种前列腺癌细胞系（PC3、LNCaP、DU145、C4-2）中PFKFB3的表达。应用RNA干扰技术敲低PFKFB3表达,采用细胞糖酵解试剂盒、CCK-8和克隆形成实验检测PFKFB3对前列腺癌细胞的糖酵解和增殖活性的影响。 结果与前列腺增生组织相比,前列腺癌组织中的PFKFB3表达量明显增高[（59.7±0.25） vs （3.08±0.16）,P<0.05],且病理Gleason评分越高,PFKFB3表达量也越高。同样PFKFB3在不同前列腺癌细胞系中均明显高表达。抑制PFKFB3基因表达后,前列腺癌细胞的糖酵解和增殖能力显著降低。 结论PFKFB3基因在前列腺癌恶性进展中表达上调,促进肿瘤细胞的糖酵解和增殖,靶向PFKFB3可能为前列腺癌分子诊断和治疗提供潜在的应用价值。