Validation of carbon isotopologue distribution measurements by GC-MS and application to 13C-metabolic flux analysis of the tricarboxylic acid cycle in Brassica napus leaves

The estimation of metabolic fluxes in photosynthetic organisms represents an important challenge that has gained interest over the last decade with the development of ¹³C-Metabolic Flux Analysis at isotopically non-stationary steady-state. This approach requires a high level of accuracy for the measurement of Carbon Isotopologue Distribution in plant metabolites. But this accuracy has still not been evaluated at the isotopologue level for GC-MS, leading to uncertainties for the metabolic fluxes calculated based on these fragments. Here, we developed a workflow to validate the measurements of CIDs from plant metabolites with GC-MS by producing tailor-made E. coli standard extracts harboring a predictable binomial CID for some organic and amino acids. Overall, most of our TMS-derivatives mass fragments were validated with these standards and at natural isotope abundance in plant matrices. Then, we applied this validated MS method to investigate the light/dark regulation of plant TCA cycle by incorporating U-¹³C-pyruvate to Brassica napus leaf discs. We took advantage of pathway-specific isotopologues/isotopomers observed between two and six hours of labeling to show that the TCA cycle can operate in a cyclic manner under both light and dark conditions. Interestingly, this forward cyclic flux mode has a nearly four-fold higher contribution for pyruvate-to-citrate and pyruvate-to-malate fluxes than the phosphoenolpyruvate carboxylase (PEPc) flux reassimilating carbon derived from some mitochondrial enzymes. The contribution of stored citrate to the mitochondrial TCA cycle activity was also questioned based on dynamics of ¹³C-enrichment in citrate, glutamate and succinate and variations of citrate total amounts under light and dark conditions. Interestingly, there was a light-dependent ¹³C-incorporation into glycine and serine showing that decarboxylations from pyruvate dehydrogenase complex and TCA cycle enzymes were actively reassimilated and could represent up to 5% to net photosynthesis.

Intraoperative facial nerve monitoring in posterior fossa surgery: prognostic value

A retrospective study was done of 43 patients operated on for acoustic neuroma by a translabyrinthine approach with intraoperative facial nerve monitoring. Direct stimulation of the facial nerve at the level of the cerebellopontine angle (CPA) and the internal auditory canal (IAC) permits the calculation of a R ratio that has a predictive value for postoperative facial function: R = R'/R'', where R' is the ratio of the minimal intensity (I) of stimulation capable of inducing a response after direct stimulation of the facial nerve at the level of the CPA over the electromyographic response amplitude (A): R' = I(CPA)/A(CPA), R'' being equal to the ratio of these same measurements after stimulation at the IAC: R'' = I(IAC)/A(IAC). Statistical analysis has shown that an R ratio </= 2 has a favorable prognostic value on facial mobility whereas an R ratio > 2 permits the supposition of an alteration of facial function. This prognostic value is more precise if the R ratio is co-related to the macroscopic aspect of the facial nerve at the end of surgery.

Effectiveness of conservative management of acoustic neuromas

OBJECTIVE

The goal of this study was to assess the effectiveness of the conservative management in patients with acoustic neuroma (vestibular schwannoma).

STUDY DESIGN

This retrospective study was performed in a university hospital.

PATIENTS

Patients were selected for this wait-and-see policy on the basis of age, general condition, audiometric results, tumor size, and patient preference. The study group included 97 patients, 87 of whom had at least two neuroradiologic examinations. The mean age of this population was 63 years (29 to 89 years). The mean length of follow-up of this population was 31 months. Eighty-seven of these patients had at least two radiologic examinations (magnetic resonance imaging or computed tomography). The mean interval between the initial and follow-up radiologic examinations was 15 months.

MAIN OUTCOME MEASURES

Tumor size was measured by use of two-dimensional data in all patients. The mean tumor size was 12 mm. The growth rate of the tumor was estimated by comparison of the results of the measurements from the initial and follow-up neuroradiologic examinations.

RESULTS

Of the 97 patients studied, 6 patients required surgery and 6 required radiotherapy. Sixty patients (62%) were still being treated conservatively at the end of the study period. Three patients of 28 who were classified as candidates for hearing preservation surgery lost their candidacy during the observation period. The mean annual tumor growth rate was 1.52 mm/year. The tumor was stable in size in 36% of patients, regressed in 11% of patients, or grew in 53% of patients. The growth patterns of the acoustic neuroma fell into five categories: continuous growth in 15% of patients, negative growth in 5%, growth followed by negative growth in 40%, negative growth followed by growth in 20%, and no variation of tumor size in 20%.

CONCLUSION

Conservative management of acoustic neuromas carries difficulties: long-term follow-up of the patients and unpredictability of the tumor growth pattern. A reliable and reproducible radiologic method for evaluating tumor size is of great importance.

Functional magnetic resonance imaging may avoid misdiagnosis of cochleovestibular nerve aplasia in congenital deafness

OBJECTIVE

To investigate a narrow internal auditory canal (IAC) syndrome using functional magnetic resonance imaging (fMRI) of the auditory cortex.

STUDY DESIGN

The study design was a case report. The follow-up period lasted 18 months.

SETTING

The study was carried out in the audiology clinic of an ear, nose, and throat department and in the department of pediatric neuroradiology at a university hospital.

MAIN OUTCOME MEASURES

Age-appropriate observational audiometry, objective audiovestibular tests, computed tomography (CT), magnetic resonance imaging (MRI), and (fMRI) of the auditory cortex were performed to analyze in detail the profound deafness of a young child.

RESULTS

Audiovestibular examination demonstrated both measurable hearing and normal vestibulo-ocular reflex, and CT showed narrow IACs combined with normal labyrinths. Axial MR images completed by sagittal sections perpendicular to the IAC delineated a single nerve that was initially supposed to be the facial nerve. No cochleovestibular nerve was identified. However, fMRI performed with the patient under general anesthesia demonstrated activation of the primary auditory cortex during 1-kHz monaural stimulation on the left side.

CONCLUSIONS

The absence of cochleovestibular nerve on MR studies cannot exclude connections between the inner ear and the central auditory pathways. This might be caused by a lack of spatial resolution of anatomical MR studies. The single nerve delineated within the IAC might also carry both facial and cochleovestibular fibers. Functional MRI can assess the cortical response to acoustic stimuli when aplasia of the cochleovestibular nerve is suspected. This case study illustrates a novel and atypical presentation of cochlear nerve dysplasia.

Minimal number of circulating CD34+ cells to ensure successful leukapheresis and engraftment in autologous peripheral blood progenitor cell transplantation

BACKGROUND

The number of peripheral blood (PB) CD34+ cells has been widely used to monitor the timing of leukapheresis for autologous transplantation. However, no cutoff value for CD34+ cells in PB has been defined as a guideline for the identification of patients in whom the harvest would be effective and those in whom there was a high probability of failure.

STUDY DESIGN AND METHODS

The present study investigated the best threshold of CD34+ cells in PB for successful harvesting and engraftment, using 263 PB samples with their corresponding leukapheresis components. In addition, that measure has been compared to other commonly used criteria such as the white cell count, the number of mononuclear cells, and the number of colony-forming units-granulocyte macrophage in PB.

RESULTS

Time to engraftment of both granulocytes and platelets was significantly influenced by the number of CD34+ cells transfused, but all patients receiving > or = 0.75 x 10(6) CD34+ cells per kg achieved engraftment within a reasonable number of days (> 0.5 x 10(9)/L granulocytes by Day 11 and > 20 x 10(9)/L platelets by Day 13). A clear correlation between the number of CD34+ cells per microL in PB and of CD34+ cells per kg collected was found at each apheresis (r = 0.9, p < 0.0001). Moreover, the number of CD34+ cells per microL measured in PB the day the first leukapheresis was initiated displayed an excellent correlation with the total amount of CD34+ cells per kg finally collected (r = 0.81, p < 0.0001). On the basis of the regression curve obtained and the clinical engraftment results, it was found that the presence of > 5 CD34+ cells per microL in PB ensured a good yield from the harvest in 95 percent of patients and would avoid an unsuccessful harvest in 81 percent of cases.

CONCLUSION

A dose of only 0.75 x 10(6) CD34+ cells per kg guarantees hematopoietic recovery within a reasonable number of days. To initiate a leukapheresis from which enough progenitor cells may confidently be obtained, a minimum of 5 CD34+ cells per microL in PB is required.

Expression of fatty acid binding protein in the liver during pregnancy and lactation in the rat

Expression of the liver fatty acid binding protein (L-FABP) has been studied in the liver of pregnant and lactating rats. The L-FABP concentration found in the cytosol by immuno-enzymatic assay (ELISA) was consistently higher in the dams during the pregnancy and the lactation than in the age-matched virgin females. Paradoxically, a decrease in the L-FABP mRNA level occurred in the maternal liver during the last days of the gestation. This level remained low on days 7 and 14 of the lactation. Since the transcription rate of the L-FABP gene was unchanged in the maternal liver, these data suggest a post-transcriptional regulation of the L-FABP during pregnancy and lactation in the rat. The nutritional adaptations occurring during pregnancy and lactation are not involved in this regulation since a chronic maternal food-restriction failed to correct these modifications. The mechanism of this regulation is presently unknown, but possibilities include hormonally mediated effects.

The heterogeneity of type IIA von Willebrand's disease: studies with protease inhibitors

The absence of large von Willebrand factor (vWF) multimers from plasma is a characteristic of Type IIA von Willebrand's disease (vWD) and is thought to contribute to the clinical expression of this disorder. Recently, three IIA patients have been reported in whom intermediate and large multimers could be restored if blood were collected in 5 mm EDTA, 6 mmol/L N-ethylmaleimide, and 1 mmol/L leupeptin. This suggested that absence of large multimers resulted from in vitro proteolysis. We have now collected blood from ten Type IIA vWD patients in these inhibitors but were not able to detect large multimers in the plasma of any of them. In addition, intermediate-sized multimers were reduced or completely absent in all. The inclusion of inhibitors in the citrate anticoagulant, as compared to citrate alone, was found to increase the relative proportion of intermediate multimers in some patients but had no effect in others, and in none did it restore large multimers to plasma. The results with platelet vWF were more varied. Four patients showed an absence or decrease of large multimers, whereas in seven patients large multimers were present. When compared with citrate anticoagulant alone, the inclusion of inhibitors in the anticoagulant had little or no effect on the platelet multimeric pattern. 1-Deamino-8-D-Arginine Vasopressin (DDAVP) was administered to six patients from five families. Two patients from one family showed complete correction and a third patient showed almost complete correction of her bleeding time. Two patients showed minimal correction and one showed no detectable correction. An increase in multimer size after DDAVP tended to be associated with correction of the bleeding time. However, in no case did the largest multimers appear in plasma even in patients with complete bleeding time correction. The presence or absence of inhibitors in the anticoagulant had little or no effect on the multimeric pattern after DDAVP. These results indicate that Type IIA vWD is a heterogeneous disorder in which absence of largest and intermediate multimers is an in vivo phenomenon.

[A review of ten cases of aldosteronoma. Diagnostic and therapeutic conclusions (author's transl)]

Ten patients with primary hyperaldosteronism resulting from a functioning adrenocortical adenoma were studied. The high incidence of hypertension and/or renal disease in the families of these patients suggests that hereditary factors play a part in the genesis of aldosteronomas. In patients with hypertension and hypokalemia the diagnosis of primary hyperaldosteronism is established by measurements of serum renin activity and serum aldosterone concentrations under normal conditions and during pharmacodynamic tests. The adenoma is demonstrated by radioactive iodocholesterol scintigraphy and computerized tomography. In nearly two-thirds of the patients, unilateral adrenalectomy is followed by complete definitive recovery.