[Aprospective study of detection and clinical significance of bone marrow tumor cells in small cell lung cancer].

Objective: To investigate the detection of bone marrow tumor cells in small cell lung cancer (SCLC) patients and their relationship with clinical features, treatment response and prognosis. Methods: A total of 113patients with newly diagnosed SCLC from January 2018 to October 2022 at Beijing Chest Hospital were prospectively enrolled. Before treatment, bone marrow was aspirated and separately submitted for tumor cells detection by liquid-based cytology and disseminated tumor cells (DTCs) detection by the substrction enrichment and immunostaining fluorescence in situ hybridization (SE-iFISH) platform. The correlation between the detection results of the two methods with patients' clinical features and treatment response was evaluated by Chi-square. Kaplan-Meier method was applied to create survival curves and the Cox regression model was used for multivariate analysis. Results: The positive rate of bone marrow liquid-based cytology in SCLC was 15.93% (18/113). The liver and bone metastases rates were significantly higher (55.56% vs 11.58% for liver metastasis, P＜0.001; 77.78% vs 16.84% for bone metastasis, P＜0.001) and thrombocytopenia was more common (16.67% vs 2.11%, P=0.033) in patients with tumor cells detected in liquid-based cytology than those without detected tumor cells. As for SE-iFISH, DTCs were detected in 92.92% of patients (105/113), the liver and bone metastasis rates were significantly higher (37.93% vs 11.90% for liver metastasis, P=0.002; 44.83% vs 20.23 % for bone metastasis, P=0.010), and the incidence of thrombocytopenia was significantly increased (13.79% vs 1.19%, P=0.020) in patients with DTCs≥111 per 3 ml than those with DTCs＜111 per 3 ml. The positive rates of bone marrow liquid-based cytology in the disease control group and the disease progression group were 12.00% (12/100) and 46.15% (6/13), respectively, and the difference was statistically significant (P=0.002). However, the result of SE-iFISH revealed the DTCs quantities of the above two groups were 29 (8,110) and 64 (15,257) per 3 ml, and there was no statistical difference between the two groups (P=0.329). Univariate analysis depicted that the median progression-free survival (PFS) and median overall survival (OS) of liquid-based cytology positive patients were significantly shorter than those of tumor cell negative patients (6.33 months vs 9.27 months for PFS, P=0.019; 8.03 months vs 19.50 months for OS, P=0.019, P=0.033). The median PFS and median OS in patients with DTCs≥111 per 3 ml decreased significantly than those with DTCs＜111 per 3 ml (6.83 months vs 9.50 months for PFS, P=0.004; 11.2 months vs 20.60 months for OS, P=0.019). Multivariate analysis showed that disease stage (HR=2.806, 95%CI:1.499-5.251, P=0.001) and DTCs quantity detected by SE-iFISH (HR=1.841, 95%CI:1.095-3.095, P=0.021) were independent factors of PFS, while disease stage was the independent factor of OS (HR=2.538, 95%CI:1.169-5.512, P=0.019). Conclusions: Both bone marrow liquid-based cytology and SE-iFISH are clinically feasible. The positive detection of liquid-based cytology or DTCs≥111 per 3 ml was correlated with distant metastasis, and DTCs≥111 per 3 ml was an independent prognostic factor of decreased PFS in SCLC.

Which of the fibrous layer is more important in the genesis of traumatic temporomanibular joint ankylosis: The mandibular condyle or the glenoid fossa?

INTRODUCTION: The aim of this experimental study was to investigate, under the premise of discectomy, whether damage to either the fibrous layer of the condyle or that of the glenoid fossa, could induce temporomanibular joint (TMJ) ankylosis. And if not, which of the fibrous layer was more important in the genesis of TMJ ankylosis. MATERIALS AND METHODS: Bilateral TMJ surgery was performed in 6 growing Xiao-wei Han sheep. Disk and condylar fibrous layer removal (DCFLR) was performed on the left TMJ, and disk and glenoid fibrous layer removal (DGFLR) was performed on the right TMJ. All animals were sacrificed at 3 months postoperatively. The TMJ complexes were examined by histological evaluation. RESULTS: Partial fibrous ankylosis was achieved on the DCFLR side in the 6 sheep at 3 months after surgery. On the DGFLR side, pathologic characteristics of TMJ osteoarthritis could be seen; however, no evidence of ankylosis was observed. The scores of TMJ ankylosis for the DGFLR side were significantly lower than those for the DCFLR side (P<0.05). CONCLUSION: This study demonstrated that removal of the condylar fibrous layer, not the glenoid fibrous layer, combined with discectomy could lead to traumatic TMJ ankylosis.

[Expression of FATS in non-small cell lung cancer and its relationship with prognosis].

Objective: To investigate the expression of fragile-site associated tumor suppressor (FATS) in non-small cell lung cancer and its relationship with clinicopathological features and prognosis. Methods: A total of 140 non-small cell lung cancer (NSCLC) cases and 30 adjacent normal tissues were used to detect the expression level of FATS protein, and to analyze the relationship of FATS protein expression and clinicopathological features and prognosis of NSCLC. Results: Western blot showed that the expression of FATS in adjacent normal tissues was significantly higher than that in non-small cell lung cancer tissues. The results of immunohistochemistry showed that the high expression rate of FATS in 140 cases of NSCLC was 40.0%, and the high expression rate of FATS in 30 cases of adjacent tissues was 73.3%. The difference was statistically significant (P=0.01). Further analysis showed that the TNM stage (P=0.044) and lymph node metastasis (P=0.022) were significant difference between FATS high expression group and low expression group. The 6-year overall survival (OS) rates of NSCLC patients with FATS high-expression and low-expression were 57.1% and 23.8%, respectively, and the 6-year disease-free survival (DFS) rates were 53.6% and 21.4%, respectively, with statistically significant differences (P=0.001). In Cox multivariate analysis, we found gender (HR=1.658, P=0.028; HR=1.684, P=0.023), TNM staging (HR=2.327, P=0.019; HR=2.332, P=0.013) and FATS expression (HR=0.532, P=0.010; HR=0.538, P=0.009) were independent prognostic factors for both OS and DFS of NSCLC patients. Conclusions: The expression of FATS protein is associated with the development and is an independent prognostic factor of NSCLC patients. The detection of FATS protein is expected to be a new biomarker for evaluating the prognosis of NSCLC patients.

[The diagnosis and treatment of traumatic optic nerve neuropathy combined with carotid artery injury].

Objective: To discuss the diagnosis and treatment strategy of traumatic optic nerve neuropathy (TON) combined with carotid artery injury. Methods: Retrospective analyses were performed 397 cases of TON at Neurosurgery department of Beijing Tongren Hospital, Capital Medical University (CMU), from January 2016 to December 2017.The clinical experience was concluded. Results: 9 cases of Traumatic Pseudo Aneurysm (TPA) and 16 cases of Traumatic Carotid Artery-Cavernous Sinus Fistula (TCCF) were found.7 cases of TPA were treated by covered stent, the other 2 cases were treated by detachable balloons.11 cases of TCCF were treated by detachable balloons, and 5 cases of fistulas were found spontaneously closed by DSA after 1-3 months.There was no disability rate and mortality in this study. Conclusion: TON combined with carotid artery injury was a critical situation, and sometime without obvious symptoms and sign, which was easily miss diagnosed.It should be with more concern in diagnosing and treating in such cases, to avoid disability rate and mortality.

[Antibody-based agents as experimental therapeutic interventions for corneal allograft rejection].

The corneal allograft rejection is the primary reason for graft failure, but the existing agents are of limited efficacy and may be accompanied by unacceptable morbidity. Recently, antibody-based agents have received great attention and have become an important part of therapeutic intervention for organ transplantation, which is also a research focus in the field of corneal transplantation. This review summarizes the history, current situation and mechanism of antibody-based agents in corneal transplantation.

High levels of phosphatase and tensin homolog expression predict favorable prognosis in patients with non-small cell lung cancer.

OBJECTIVE: The prognostic role of phosphatase and tensin homolog (PTEN) in non-small cell lung cancer (NSCLC) has been controversial. PATIENTS AND METHODS: In this study, levels of PTEN expression were investigated in NSCLC patients and their prognostic value in NSCLC was assessed. PTEN expression in tumor tissues from 68 NSCLC patients was analyzed using immunohistochemistry and confocal microscopy. Survival analysis was performed using the log-rank test and Cox proportional hazards regression analysis. RESULTS: NSCLC patients classified as expressers of high levels of PTEN (n = 46) had better prognoses than those classified as expressers of low levels (mean survival 17.1 versus 12.9 months, log-rank p = 0.038). In patients with adenocarcinoma (AC), high PTEN expression (n = 9) was associated with significantly longer survival than low PTEN expression (mean survival 23.50 versus 15.54 months, log-rank p = 0.043). High levels of PTEN expression resulted in 43% reduction in risk for all NSCLC patients (HR = 0.57, 95% CI: 0.33-0.98, p = 0.041). PTEN expression and clinical stage remained significantly associated with survival after adjustment for age, sex and tumor type (HR = 0.56, 95% CI: 0.32-0.99; p = 0.048; HR = 0.54, 95% CI: 0.36-0.97; p = 0.045). No significant difference in continuous PTEN expression levels was observed among groups with different clinical or pathological characteristics (p > 0.17). When levels of PTEN expression were binarized using the optimal cutpoint, higher levels of PTEN expression were observed in patients with T1/T2 than in those with T3/T4 (80% and 58% respectively, p = 0.049) and in patients with AC than in those with squamous-cell carcinoma (SCC) (78% and 58% respectively, p = 0.08). No significant difference in binarized PTEN expression levels was found among groups with any other clinical/pathologic characteristic (p > 0.28). CONCLUSIONS: Our results suggest that high levels of PTEN expression may be favorable prognostic marker in NSCLC patients.

Hyaluronic acid in combination with chondroitin sulfate and hyaluronic acid improved the degeneration of synovium and cartilage equally in rabbits with osteoarthritis.

The purpose of this study was to compare the chondroprotective effects of chondroitin sulfate (CS)-hyaluronic acid (HA) (CS-HA) injection and HA injection in an experimental model of osteoarthritis. After induction of osteoarthritis in rabbits, 28 rabbits were randomized into four groups: control group, 'HA' group, 'CS' group, and 'CS-HA' group. After 7 days, rabbits in the control group, 'HA' group, 'CS' group and 'CS-HA' group were respectively treated with normal saline, HA, CS, or CS-HA injection in the knees. All animals were treated once weekly. The animals were treated continuously for 5 weeks. Histological and biochemical evaluations were performed. As shown by histological observation, CS-HA injection treatment showed a chondroprotective effect on osteoarthritis. However, the histological scores of 'HA' group and 'CS-HA' group were not significantly different (p > 0.05). The results of biochemical evaluation showed that the expression levels of IL-1ß, TNF-α, TIMP-1 and NO in synovial fluid of treated groups were all different from the control group (p < 0.05). However, the expression levels of these biochemical molecules in three treated groups were not significantly different (p > 0.05). In conclusion, CS-HA injection showed no obvious advantage over HA injection in osteoarthritis treatment.

Use of induction promoters to regulate hyaluronan synthase and UDP-glucose-6-dehydrogenase of Streptococcus zooepidemicus expression in Lactococcus lactis: a case study of the regulation mechanism of hyaluronic acid polymer.

AIMS: To determine the effects of the ratios of hyaluronan synthase expression level to precursor sugar UDP-GlcA biosynthesis ability on the molecular weight (MW) of hyaluronic acid (HA) in recombinant Lactococcus lactis. METHODS AND RESULTS: The genes szHasA (hyaluronan synthase gene) and szHasB (UDP-glucose-6-dehydrogenase gene) of Streptococcus zooepidemicus were introduced into L. lactis under the control of nisA promoter and lacA promoter respectively, resulting in a dual-plasmid controlled expression system. The effects of the ratios of hyaluronan synthase expression level to the precursor sugar UDP-GlcA biosynthesis ability under different induction concentration collocations with nisin and lactose on the MW of HA in recombinant L. lactis were determined. The results showed that the final weight-average molecular weight () of HA correlated with the relative ratios of HasA (hyaluronan synthase) expression level to the concentration of UDP-GlcA. CONCLUSIONS: Regulating the relative ratios of HasA expression level to the precursor sugar biosynthesis ability was an efficient method to control the size of HA. SIGNIFICANCE AND IMPACT OF THE STUDY: This study put forward a guide to establish an efficacious way to control the size of HA in fermentation.

Effects of a hyaluronic acid and low molecular weight heparin injection on osteoarthritis in rabbits.

An osteoarthritis (OA) model was created in the knees of rabbits by injecting them with 0.3 mL of sterile papain solution in order to evaluate the effects of a hyaluronic acid (HA) and low molecular weight heparin (LMWH) injection on osteoarthritis. HA-LMWH, LMWH, and HA were injected into animals once weekly. After 5 weeks of treatment, the animals were sacrificed and the effects of the injections on osteoarthritis were evaluated by histological assessment. HA levels in cartilage and the levels of IL-1ß and TNF-α expression in synovial fluids were determined. As shown by histological observation, recovery of the synovium and cartilage of animals injected with HA-LMWH was better than that in animals injected with HA or LMWH. HA levels in cartilage of animals injected with HA-LMWH were much higher than those of the control group. The levels of IL-1ß expression in synovial fluids of animals injected with HA-LMWH were lower than those in other animals. The levels of TNF-α expression in synovial fluids of animals injected with HA-LMWH were much lower than those in the controls. In conclusion, HALMWH injection had a favorable anti-inflammatory and therapeutic effect on experimental OA.

Current knowledge and attitudes about organ donation and transplantation among Chinese university students.

Current attitudes toward organ donation among university students in mainland China and the differences in attitudes between Chinese students in mainland China versus overseas are unknown. To address these issues, we conducted a cross-sectional survey using questionnaires among 922 Chinese undergraduates from mainland China and overseas regions of the world. Data were analyzed by descriptive statistics, Student t tests, chi-square tests, and a logistic regression analysis. We found that blood donors showed significantly better awareness of heart, liver, lung, skin, and tendon donation among commonly transplanted organs/tissues. As to the willingness for cadaveric organ donation, 61.3% of respondents consented, 8.5% objected, and 30.3% answered "not sure." The percentage holding an organ donor card was 15.7% among students from Hong Kong; 3.0%, mainland China; 2.8%, Macau; 2.6%, Taiwan, and 4.0%, other regions of the world. In a logistic regression analysis, female students (odds ratio [OR], 2.24; 95% confidence interval [CI], 1.35 to 3.72) and blood donors (OR, 1.91; 95% CI, 1.10 to 3.32) did, but age and study specialty (medical vs nonmedical) did not show significantly more positive attitudes toward cadaveric organ donation. Compared with students from mainland China, overseas Chinese students from various regions did not show significantly different attitudes toward cadaveric organ donation. In summary, blood donors among university students have a greater knowledge of transplantation and a more positive attitude toward organ donation. Since university students are an important source of blood donors in China, they will be a potential pool of organ donors in the future.

Characterization and stability investigation of cu,zn-superoxide dismutase covalently modified by low molecular weight heparin.

Cu,Zn-superoxide dismutase (SOD) was chemically modified with low molecular weight heparin (LMWH). To characterize the conjugate, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis (native PAGE) with protein staining and polysaccharide staining were employed. The stabilities of the modified enzyme to heat, acid, alkali, and trypsin treatment were also investigated. SDS-PAGE of the conjugate presented two major bands, and native PAGE of the conjugate showed similar banding position with protein staining and polysaccharide staining, which was different from that of the unmodified SOD and LMWH/SOD mixture. Moreover, the conjugate migrated faster with increasing extent of the modification. Enhanced heat stability, acid resistance, alkali resistance, and anti-trypsin stability of the modified enzyme were observed compared with those of the unmodified enzyme. Results of the study suggest that covalent linkage in LMWH-SOD can be effectively characterized by electrophoretic techniques and the chemical modification of SOD with LMWH can enhance the stabilities of the enzyme. In addition, native PAGE with protein staining can be used to evaluate the extent of the modification.

Prevalence of human papillomavirus in cervical cancer: a multicenter study in China.

A large-scale epidemiologic survey on the prevalence of different types of human papillomavirus (HPV) in cervical cancer in China is indicated because of the implications for the development of diagnostic probes and vaccines against cervical cancer. A total of 809 cervical cancer specimens were collected from 5 regions in China including Shanghai, Guangzhou, Sichuan, Beijing and Hong Kong. HPV DNA was detected in 83.7% of the specimens. HPV-16 was present in 79.6%, HPV-18 in 7.5%, HPV-52 in 2.6% and HPV-58 in 3.8% of all HPV-positive specimens. The prevalences of HPV-16 and HPV-18 in Hong Kong were 61.7 and 14.8%, respectively, representing a lower HPV-16 and a higher HPV-18 proportion compared with the other regions. HPV-16 remained the most common HPV infection in both squamous cell carcinoma (SCC) and adenocarcinoma (AC). The proportion of HPV-18 infection was significantly higher in AC than in SCC.

Clinicopathological and molecular genetic analysis of 4 typical Chinese HNPCC families.

AIM: To study the clinicopathological and molecular genetic characteristics of typical Chinese hereditary nonpolyposis cotorectal cancer (HNPCC) families. METHODS: Four typical Chinese HNPCC families were analyzed using microdissection, microsatellite instability analysis, immunostaining of hMSH2 and hMLH1 proteins and direct DNA sequencing of hMSH2 and hMLH1 genes. RESULTS: All five tumor tissues of 4 probands from the 4 typical Chinese HNPCC families showed microsatellite instability at more than two loci (MSI-H or RER+ phenotype). Three out of the 4 cases lost hMSH2 protein expression and the other case showed no hMLH1 protein expression. Three pathological germline mutations (2 in hMSH2 and 1 in hMLH1), which had not been reported previously, were identified. The same mutations were also found in other affected members of two HNPCC families,respectively. CONCLUSION: Typical Chinese HNPCC families showed relatively frequent germline mutation of mismatch repair genes. High-level microsatellite instability and loss of expression of mismatch repair genes correlated closely with germline mutation of mismatch repair genes. Microsatellite instability analysis and immunostaining of mismatch repair gene might serve as effective screening methods before direct DNA sequencing. It is necessary to establish clinical criteria and molecular diagnostic strategies more suitable for Chinese HNPCC families.

Menadione reduced doxorubicin resistance in Ehrlich ascites carcinoma cells in vitro.

AIM: To study the effect of menadione (Men) reducing doxorubicin (Dox) resistance in Ehrlich ascites carcinoma (EAC) cells resistant to Dox (EAC/Dox cells). METHODS: Glutathione (GSH) content and membrane fluidity were measured by fluorometric assay and fluorescence depolarization assay, respectively. Glutathione S-transferase (GST) activity was measured with 1-chloro-2,4-dinitrobenzene as the substrate. Cell viability was determined by 3-(4, 5-dimethylthiazol)-2, 5-diphenyltetrazolium bromide assay. RESULTS: GSH content, GST activity, and membrane fluidity in EAC/Dox cells were higher than those in EAC cells (P < 0.01). The IC50 (95% confidence limits) for Dox on EAC/Dox cell was 22.3 (15.8-28.8) mg.L-1. Relative resistance of Dox in EAC/Dox cells was 42-fold. Pretreatment of EAC/Dox cells with Men 5 or 10 mg.L-1 decreased intracellular GSH content (P < 0.01). Men 1 mg.L-1 had no obvious effect on GSH content in EAC/Dox cells (P > 0.05), but decreased the elevated membrane fluidity efficiently (P < 0.05). Men had no obvious effect on GST activity in EAC/Dox cells (P > 0.05). IC50 of Dox was reduced to 9.6 (7.8-11.3), 6.0 (2.8-9.2), or 5.3 (3.9-6.7) mg.L-1 in EAC/Dox cells pretreated with Men 1, 5, or 10 mg.L-1. CONCLUSION: Men reduced Dox resistance effectively due in part to its depletion of GSH content in EAC/Dox cells.

Protective effects of succinic acid dimethyl ester infusion in experimental endotoxemia.

In rats injected with bacterial lipopolysaccharide (LPS; 5 gamma mg/g body weight [BWT]), the toxin provokes death within 24 h in 23% of the animals and, in surviving rats, causes a decrease in BWT, hyperlactacidemia, hyperlipacidemia, and hyperketonemia, as well as depletion of both liver and muscle glycogen content. In the liver, LPS severely lowers the ATP and total adenine nucleotide content, ATP/ADP ratio, and adenylate charge. In hepatocytes from LPS-injected rats, the oxidation of D-glucose is first increased 2 h after administration of the toxin, despite close-to-normal phosphorylation of the hexose. In hepatocytes prepared from rats killed 24 h after injection of LPS, the phosphorylation of D-glucose, its incorporation into glycogen, and its oxidation are all severely impaired. This sequence of changes, which coincides with a decreased ratio between pyruvate and lactate production from exogenous D-glucose, is comparable to that found with agents that uncouple oxidative phosphorylation. The injection of LPS also alters the metabolic response of hepatocytes to the dimethyl ester of succinic acid (SAD), in terms, for instance, of the sparing action of the ester upon both the production of 14CO2 by hepatocytes prelabeled with L-[U-14C] glutamine and the output of NH4+, and its inhibitory action on glycogenolysis and futile cycling in the reactions catalyzed by glucokinase and glucose-6-phosphatase. Nevertheless, the infusion of SAD protects the rats against the deleterious effect of LPS upon such variables as the plasma concentration of free fatty acids and beta-hydroxybutyrate, the liver ATP content, and the oxidation of D-glucose, as well as the pyruvate/lactate ratio, in hepatocytes prepared from the LPS-injected rats. The infusion of SAD also virtually suppresses lethality in the LPS-injected animals. It is proposed, therefore, that the infusion of succinic acid esters may represent a novel therapeutic approach in endotoxemia and multiple-organ failure.

In vivo stimulation of insulin release by the monoethyl, monopropyl, monoisopropyl, monoallyl and diallyl esters of succinic acid.

The methyl esters of succinic acid are potent insulin secretagogues, currently under investigation as possible tools in the treatment of non-insulin-dependent diabetes. The in vivo administration of these esters may result, however, in the undesirable generation of methanol. The present study reveals that other esters of succinic acid, such as the monoethyl, monopropyl, monoisopropyl, monoallyl and diallyl esters, stimulate insulin release when administered intravenously in a dose of 2 mumol/g body weight to anaesthetized fed rats. This indicates that several succinic acid esters, that are not susceptible to lead, through their intracellular hydrolysis, to the production of methanol remain efficient in vivo as insulin secretagogues.

D-glucose generation from [2-13C]pyruvate in rat hepatocytes: implications in terms of enzyme-to-enzyme channelling.

In rat hepatocytes exposed to [2-13C]pyruvate, newly formed glucose was more efficiently labeled in the carbon C5 than C2, as well as in the carbon C6 than C1, suggesting enzyme-to-enzyme channeling of D-glyceraldehyde 3-phosphate between glyceraldehyde-3-phosphate dehydrogenase and phosphofructoaldolase. Likewise the C1/C2 and C6/C5 ratios for 13C abundance in newly formed glucose, which largely exceeded the C3/C2 ratio of lactate or alanine and could reflect reversibility in the fumarase reaction, were compatible with the enzyme-to-enzyme tunneling of symmetrical Krebs cycle intermediates in the sequence of reactions catalyzed by succinyl-CoA synthetase, succinate dehydrogenase, and fumarase. This study further indicates that the major fraction of pyruvate is metabolized via pyruvate carboxylase rather than pyruvate dehydrogenase.

Enzyme-to-enzyme channelling of Krebs cycle metabolic intermediates in Caco-2 cells exposed to [2-13c]propionate.

The generation of 13C-labelled lactate by colon carcinoma cells of the Caco-2 line incubated for 120 min in the presence of [2-13C]propionate (10 mM) was assessed by 13C NMR. About 10% of the total amount of 13C-labelled lactate was recovered in the cell pellet and displayed a [2-13C]lactate/[3-13C]lactate isotopomer ratio of 1.18 +/- 0.01. An even higher isotopomer ratio of 1.53 +/- 0.14 was observed in the case of 13C-labelled lactate released by the cells into the incubation medium. These findings indicate that, in the Caco-2 cells, metabolic intermediates of the Krebs cycle undergo enzyme-to-enzyme channelling in the sequence of reactions catalysed by succinyl-CoA synthetase, succinate dehydrogenase and fumarase.

Enzyme-to-enzyme channelling of symmetric Krebs cycle intermediates in pancreatic islet cells.

Tumoural islet cells of the RINm5F line were incubated for 120 min in the presence of [2-13C]propionate (10 mmol/l), and the 13C enrichment of lactate released in the incubation medium was monitored by 13C nuclear magnetic resonance. The C3/C2 ratio of resonance areas was much lower than that found with naturally 13C-enriched lactate. This reveals that symmetric Krebs cycle intermediates undergo oriented transfer in the sequence of reactions catalysed by succinate thiokinase, succinate dehydrogenate and fumarase in the mitochondria of islet cells.