Oxygen sensing by the carotid body: mechanisms and role in adaptation to hypoxia.

Oxygen (O2) is fundamental for cell and whole-body homeostasis. Our understanding of the adaptive processes that take place in response to a lack of O2(hypoxia) has progressed significantly in recent years. The carotid body (CB) is the main arterial chemoreceptor that mediates the acute cardiorespiratory reflexes (hyperventilation and sympathetic activation) triggered by hypoxia. The CB is composed of clusters of cells (glomeruli) in close contact with blood vessels and nerve fibers. Glomus cells, the O2-sensitive elements in the CB, are neuron-like cells that contain O2-sensitive K(+)channels, which are inhibited by hypoxia. This leads to cell depolarization, Ca(2+)entry, and the release of transmitters to activate sensory fibers terminating at the respiratory center. The mechanism whereby O2modulates K(+)channels has remained elusive, although several appealing hypotheses have been postulated. Recent data suggest that mitochondria complex I signaling to membrane K(+)channels plays a fundamental role in acute O2sensing. CB activation during exposure to low Po2is also necessary for acclimatization to chronic hypoxia. CB growth during sustained hypoxia depends on the activation of a resident population of stem cells, which are also activated by transmitters released from the O2-sensitive glomus cells. These advances should foster further studies on the role of CB dysfunction in the pathogenesis of highly prevalent human diseases.

Onco-neural antibodies and tumour type determine survival and neurological symptoms in paraneoplastic neurological syndromes with Hu or CV2/CRMP5 antibodies.

OBJECTIVE: Anti-Hu antibodies (Hu-Ab) and anti-CV2/CRMP5 antibodies (CV2/CRMP5-Ab) have been identified in association with paraneoplastic neurological disorders. However, it is not clear whether these antibodies are associated with specific neurological symptoms or are only markers of anti-cancer immune reaction. METHODS: To address this question, 37 patients with CV2/CRMP5-Ab and 324 patients with Hu-Ab were compared. RESULTS: Whereas the age and sex ratio were the same between the two groups, the distribution of neurological symptoms was not. Patients with CV2/CRMP5-Ab presented more frequently cerebellar ataxia, chorea, uveo/retinal symptoms and myasthenic syndrome (Lambert-Eaton myasthenic syndrome LEMS or myasthenia gravis). They also had a better Rankin score. In contrast, dysautonomia, brainstem encephalitis and peripheral neuropathy were more frequent in patients with Hu-Ab. Limbic encephalitis occurred similarly in both groups. Small-cell lung cancer was the most frequently associated tumour in both groups of patients, while malignant thymoma was observed only in patients with CV2/CRMP5-Ab. In particular, patients with CV2/CRMP5-Ab and thymoma developed myasthenic syndrome more frequently, while patients with SCLC developed neuropathies more frequently. Chorea and myasthenic syndrome were only seen in patients with CV2/CRMP5-Ab. The median survival time was significantly longer in patients with CV2/CRMP5-Ab, and this effect was not dependent on the type of tumour. INTERPRETATION: The data demonstrate that in patients with paraneoplastic neurological syndromes, the neurological symptoms and survival vary with both the type of associated onco-neural antibody and the type of tumour.

Influence of Pre-renal Transplant Secondary Hyperparathyroidism on Later Evolution After Transplantation.

Persistence of secondary hyperparathyroidism (SHPT) is common after renal transplantation. Good diagnosis and treatment are important to avoid complications. The objective of our work was to perform a retrospective analysis of the evolution of SHPT after renal transplantation. We selected patients who had received a kidney transplant at our hospital between 2000 and 2014. The biochemical variables of chronic kidney disease-metabolic bone disorders (CKD-MBD) were collected at pretransplantation and at 3, 6, 12, and 24 months post-transplantation. Treatments related to SHPT were also analyzed. Five hundred forty-three renal transplants were included. The average preoperative parathyroid hormone (PTH) was 241.14 pg/mL, 115.7 pg/mL at 3 months, and at 12 and 24 months postoperatively, PTH levels stabilized to 112 pg/mL. Treatment related to SHPT was present in 27.3% of patients during the preoperative period, 40.4% at 3 months postoperatively, 24.2% at 12 months postoperatively, and 23.2% at 24 months postoperatively. There was a significant association between requiring some type of treatment preoperatively and the rest of the postoperative periods (P < .005). The sample was later divided into 3 groups based on preoperative PTH (1: <150 pg/mL, n = 223 [41.1%]; 2: 150-300 pg/mL, n = 173 [31.9%]; 3: >300 pg/mL, n = 147 [27.1%]) and their evolutions were compared. Higher levels of postoperative PTH in group pre-PTH 3 were observed. Group 3 also presented with greater need for treatment in the postoperative periods, with significant association (P < .05). A regression analysis was performed and found that postoperative PTH were dependent on preoperative PTH adjusted by glomerular filtration. In conclusion, parameters related to CKD-MBD (mainly PTH) after kidney transplant, dependent on preoperative levels and glomerular filtration. Patients with a greater grade of SHPT presented with higher levels of postoperative PTH despite receiving more intensive treatment.

Cancer incidence and survival in kidney transplant patients.

Immunosuppression after organ transplantation is associated with a markedly increased risk of nonmelanoma skin cancer (NMSC) and malignancies, including posttransplant lymphoproliferative disorder (PTLD) and solid organ cancer. This study sought to investigate the incidence of malignancies and the clinical characteristics and risk factors of the renal transplant patients with solid organ tumors and NMSC. We included 1017 patients who received a kidney transplant in our hospital from 1979 to 2007. Results were contrasted with a cohort of patients from the same center without malignancies. The mean follow-up of patients in our series was 10 years. The mean age at presentation of the malignancy was 61 +/- 5 years. The malignancy and NMSC incidences were 6% and 5%, respectively. Patients with malignancy had a longer posttransplant time and greater recipient and donor age. In the multivariate analysis, independent risk factors for developing NMSC were: male sex (hazard ratio [HR] 3.1, P = .004); greater patient age (HR 1.09, P < .001), longer posttransplant time (HR 1.2, P = .004) and tacrolimus treatment (HR 4.4, P = .001). Risk factors associated with developing any malignancy were: patient age (HR 1.06, P < .001), number of grafts (HR 3.2, P = .019), tacrolimus treatment (HR 2.5, P = .035), and time posttransplantation (HR 1.2, P = .011). The mean times to development of an NMSC, solid organ malignancy, on PTLD were 7.5, 6.1, or 3.9 years, respectively. The mean survival time from the diagnosis of any malignancy was 9.6 months (95% confidence interval, 0.12-30) for solid organ malignancies and 1 month (95% confidence interval, 0.24-1.87) for PTLD.

24-Hour Proteinuria Versus Spot Protein-Creatinine Ratio for Kidney Transplant Management in Clinical Practice.

BACKGROUND: 24-hour proteinuria (24h-P) has been the most widespread test for clinical follow-up of proteinuria after kidney transplantation (KT), but urine collection is often not properly collected. Spot protein-creatinine ratio (P/Cr) has become the alternative to 24h-P for proteinuria evaluation in many KT units. However, its reliability, equivalence to 24h-P, and prognostic value regarding allograft outcome remain unknown. Therefore, the aim of this study was to evaluate the correlation and agreement between both methods for assessing proteinuria and to analyze which of them is a better predictor of graft survival. METHODS: We collected proteinuria measurements from KT patients in our center. 24h-P was adjusted for body surface area. Pearson correlation test and the Bland-Altman method were used to analyze correlation and agreement. Survival analysis was performed with the use of the Kaplan-Meier method and multivariate Cox proportional hazard model. RESULTS: A total of 8,549 urine samples were analyzed from 472 patients in whom 24h-P and P/Cr were simultaneously measured. A significant correlation was observed between 24h-P and P/Cr (r = .76; P < .001); however, the agreement between methods showed that P/Cr overestimated proteinuria compared with 24h-P, particularly when the latter was >1 g/24 h. The Cox regression multivariate model showed an increased risk of graft loss associated with proteinuria when assessed by either 24h-P (hazard ratio [HR] 6.53, 95% confidence interval [CI] 2.49-17.1) or P/Cr (HR 3.34, 95% CI 1.04-10.7). CONCLUSIONS: P/Cr is an method interchangeable with 24h-P for detecting proteinuria after KT. When proteinuria increases, the P/Cr overestimates 24h-P, even though it also has a significant and similar prognostic value for predicting graft survival.

Prevalence and Survival of Cancer After Pancreas-Kidney Transplantation.

BACKGROUND: Malignancy is an important cause of mortality in solid organ transplantation. There have been few studies of de novo solid organ malignancy (NSOM) after pancreas-kidney transplantation (PKT). The aim of this study was analyze the prevalence of NSOM and transplant outcomes. METHODS: We studied the development of NSOM after PKT in our center from May 1990 to February 2017. We analyzed demographic characteristics, prevalence of cancer, and survival after cancer diagnosis. We excluded nonmelanoma skin cancer and patients with history of malignancy before transplantation. RESULTS: We included 194 patients who received 206 PKTs (184 simultaneous PKTs and 22 pancreas after kidney transplants) with triple immunosuppressive therapy and basiliximab in more than 95%. The mean age at transplantation was 39 ± 7 years and 74% were male patients. Twelve patients developed malignancies (6.1%). Median time from transplant to NSOM was 6.6 (interquartile range [IQR] 0.2-11.7) years. The malignancies were 2 cecal appendix tumors, 2 hematologic tumors, 2 breast tumors, 1 melanoma, 1 native kidney tumor, 1 brain tumor, 1 bladder tumor, 1 prostate tumor, and 1 leiomyosarcoma. Thirty-five of the 194 patients of the whole cohort died throughout the follow-up, 4 of whom died after NSOM diagnosis (11.4%). Patient and grafts survivals were lower in recipients with tumor compared with recipients without tumor, but the difference was not statistically significant: renal graft survival was 80% vs 90% at 10 years (P = .86); and pancreatic graft survival was 45% vs 70% at 10 years (P = .15), respectively. The mean patient survival time from the diagnosis of cancer was 36.6 (IQR 18-54) months. Patient survival after NSOM diagnosis was 90% at 1 year and 50% at 5 years. CONCLUSION: The prevalence of NSOM in our PKT recipients is low, despite the scarce series of published data for comparison. Also hematologic tumors rate is very low, possibly influenced by age and type of induction.

Phosphate control in reducing FGF23 levels in hemodialysis patients.

BACKGROUND: In hemodialysis patients, high levels of Fibroblast Growth Factor 23 (FGF23) predict mortality. Our study was designed to test whether the control of serum phosphate is associated with a reduction in serum FGF23 levels. Additionally other variables with a potential effect on FGF23 levels were evaluated. MATERIAL AND METHODS: The effect of sustained (40-weeks) control of serum phosphate on FGF23 levels (intact and c-terminal) was evaluated in 21 stable hemodialysis patients that were not receiving calcimimetics or active vitamin D. Patients received non-calcium phosphate binders to maintain serum phosphate below 4.5 mg/dl. In an additional analysis, values of intact-FGF23 (iFGF23) and c-terminal FGF23 (cFGF23) from 150 hemodialysis patients were correlated with parameters of mineral metabolism and inflammation. Linear mixed models and linear regression were performed to evaluate longitudinal trajectories of variables and the association between FGF23 and the other variables examined. RESULTS: During the 40-week treatment, 12 of 21 patients achieved the target of serum phosphate <4.5 mg/dl. In these 12 patients, iFGF23 decreased to less than half whereas cFGF23 did not reduce significantly. In patients with serum phosphate >4.5 mg, iFGF23 and cFGF23 increased two and four-fold respectively as compared with baseline. Furthermore, changes in serum phosphate correlated with changes in C-reactive protein (hs-CRP). In our 150 hemodialysis patients, those in the higher tertile of serum phosphate also showed increased hs-CRP, iPTH, iFGF23 and cFGF23. Multiple regression analysis revealed that iFGF23 levels directly correlated with both serum phosphate and calcium, whereas cFGF23 correlated with serum phosphate and hs-CRP but not with calcium. CONCLUSIONS: The control of serum phosphate reduced iFGF23. This reduction was also associated with a decreased in inflammatory parameters. Considering the entire cohort of hemodialysis patients, iFGF23 levels correlated directly with serum phosphate levels and also correlated inversely with serum calcium concentration. The levels of cFGF23 were closely related to serum phosphate and parameters of inflammation.

Acute O2 Sensing: Role of Coenzyme QH2/Q Ratio and Mitochondrial ROS Compartmentalization.

Acute O2 sensing by peripheral chemoreceptors is essential for mammalian homeostasis. Carotid body glomus cells contain O2-sensitive ion channels, which trigger fast adaptive cardiorespiratory reflexes in response to hypoxia. O2-sensitive cells have unique metabolic characteristics that favor the hypoxic generation of mitochondrial complex I (MCI) signaling molecules, NADH and reactive oxygen species (ROS), which modulate membrane ion channels. We show that responsiveness to hypoxia progressively disappears after inducible deletion of the Ndufs2 gene, which encodes the 49 kDa subunit forming the coenzyme Q binding site in MCI, even in the presence of MCII substrates and chemical NAD+ regeneration. We also show contrasting effects of physiological hypoxia on mitochondrial ROS production (increased in the intermembrane space and decreased in the matrix) and a marked effect of succinate dehydrogenase activity on acute O2 sensing. Our results suggest that acute responsiveness to hypoxia depends on coenzyme QH2/Q ratio-controlled ROS production in MCI.

Donor-Specific Antibodies After Starting Hemodialysis in Nonrenal Solid Organ Transplant Recipients: Role of TH17.

BACKGROUND: Nonrenal transplantation could cause a progressive deterioration in renal function until need dialysis. It is important to know if these patients increased their risk to develop de novo donor-specific anti-HLA antibody (DSA) after starting hemodialysis (HD) and if so, try to find the mechanism. MATERIAL AND METHODS: In this double-phase study, we first analyzed the incidence of development DSA in nonrenal transplant recipients after starting HD by a retrospective study. Secondly, a prospective study was designed to analyze the pharmacokinetics of immunosuppressive drugs and the cytokine profile of these patients. RESULTS: Of 179 pancreas transplant recipients, 16 needed to start HD, and 62.5% of these patients developed de novo DSA after starting HD, with 80% of them class I DSA. In the second phase of the study, the plasma levels of the immunosuppressive drugs as measured by a limited sampling strategy of 3 sample time points (C0, C2, and C4) were stable. The cytokine profile showed that there was an increase in Th1 cytokine (interferon gamma of 0.045 ng/mL) and also in Th17 cytokines (transforming growth factor ß >10 ng/mL). CONCLUSION: Our data suggest that the development of DSA after starting HD in nonrenal transplant recipients could be mediated by Th17 immune response mechanisms.

Short-Term Outcome of Untreated Versus Treated Asymptomatic Bacteriuria in Renal Transplant Patients.

BACKGROUND: Infection of the urinary tract (UTI) is the most common form of bacterial infection in renal transplant patients, but its management is still controversial. We compared symptomatic and asymptomatic bacteriuria, treated or untreated, during two different months (summer or winter). METHODS: This longitudinal, prospective study involved routine urine cultures collected during September 2014 or March 2015. Demographic, clinical, and microbiological characteristics from the patients with positive urine cultures were described. The main outcomes were the need of hospitalization, the bacterial clearance, and the selection of the resistant pathogen. RESULTS: From the 538 urine cultures collected, only 61 were positive urine cultures. Twenty were untreated asymptomatic bacteriuria (AB), 28 were treated AB, and 13 were treated symptomatic bacteriuria. The more prevalent micro-organisms were E coli (27%), K pneumoniae (11%), and E faecalis (7%). There were no differences in the demographic, clinical, and microbiological characteristics depending on the month when the urine cultures were collected. Only 10 patients required hospitalization during follow-up, and all of them belonged to the treated group. Bacterial clearance after the treatment occurred in 20 patients of the 41 treated (48.9%) and spontaneously in 14 of the 20 patients untreated (70%). Of the treated patients, 47.6% developed a new resistance to another antibiotic. CONCLUSIONS: Only 7.6% of the routine urine cultures on renal transplant were positive. Untreated AB did not require hospitalization, and 70% had spontaneous bacterial clearance.

Oxygen-sensing by arterial chemoreceptors: Mechanisms and medical translation.

Acute O2 sensing is necessary for the activation of cardiorespiratory reflexes (hyperventilation and sympathetic activation), which permit the survival of individuals under hypoxic environments (e.g. high altitude) or medical conditions presenting with reduced capacity for gas exchange between the lung alveoli and the blood. Changes in blood O2 tension are detected by the arterial chemoreceptors, in particular the carotid body (CB), which act in concert with the adrenal medulla (AM) to facilitate rapid adaptations to hypoxia. The field of arterial chemoreception has undergone a considerable expansion in recent years, with many of the fundamental observations made at the molecular and cellular levels serving to improve our understanding of the pathogenesis of numerous medical disorders, and even to propose advances in the treatment strategies. In this review, after a short historical preface, we describe the current model of chemosensory transduction based on the modulation of membrane K(+) channels by O2 in specialized chemoreceptor cells. Recent progress in elucidating the molecular mechanisms underlying the modulation of ion channels by O2 tension, which involves mitochondrial complex I, is also discussed. The discovery in the last few years of a specific population of neural crest-derived stem cells in the CB explains the reversible growth of this organ, an intriguing and unusual property of this type of neuronal tissue that contributes to acclimatization under chronic hypoxia. The essential homeostatic role of the CB-AM axis is clearly evident in newly generated mouse models that reach adulthood, albeit with CB and AM atrophy. These animals exhibit a marked intolerance to even mild hypoxia. CB inhibition or over-activation can have important medical consequences. Respiratory depression by general anesthetics or by opioid use is a common clinical condition that frequently causes death in susceptible individuals. An exaggerated sympathetic outflow due to over-activation of the CB-AM axis may contribute to the pathogenesis of several highly prevalent medical conditions, such as chronic heart failure, obstructive sleep apnea, obesity, metabolic syndrome, and diabetes. A detailed understanding of the molecular mechanisms underlying acute O2 sensing may help in the design of more efficient therapeutic approaches to combat these disorders.

Isolation and expression pattern of human Unc-33-like phosphoprotein 6/collapsin response mediator protein 5 (Ulip6/CRMP5): coexistence with Ulip2/CRMP2 in Sema3a- sensitive oligodendrocytes.

The Unc-33-like phosphoprotein/collapsin response mediator protein (Ulip/CRMP) family consists of four homologous phosphoproteins considered crucial for brain development. Autoantibodies produced against member(s) of this family by patients with paraneoplastic neurological diseases have made it possible to clone a fifth human Ulip/CRMP and characterize its cellular and anatomical distribution in developing brain. This protein, referred to as Ulip6/CRMP5, is highly expressed during rat brain development in postmitotic neural precursors and in the fasciculi of fibers, suggesting its involvement in neuronal migration/differentiation and axonal growth. In the adult, Ulip6/CRMP5 is still expressed in some neurons, namely in areas that retain neurogenesis and in oligodendrocytes in the midbrain, hindbrain, and spinal cord. Ulip2/CRMP2 and Ulip6/CRMP5 are coexpressed in postmitotic neural precursors at certain times during development and in oligodendrocytes in the adult. Because Ulip2/CRMP2 has been reported to mediate semaphorin-3A (Sema3A) signal in developing neurons, in studies to understand the function of Ulip6/CRMP5 and Ulip2/CRMP2 in the adult, purified adult rat brain oligodendrocytes were cultured in a Sema3A-conditioned medium. Oligodendrocytes were found to have Sema3A binding sites and to express neuropilin-1, the major Sema3A receptor component. In the presence of Sema3A, these oligodendrocytes displayed a dramatic reduction in process extension, which was reversed by removal of Sema3A and prevented by anti-neuropilin-1, anti-Ulip6/CRMP5, anti-Ulip2/CRMP2 antibodies, or VEGF-165, another neuropilin-1 ligand. These results indicate the existence in the adult brain of a Sema3A signaling pathway that modulates oligodendrocyte process extension mediated by neuropilin-1, Ulip6/CRMP5, and Ulip2/CRMP2, and they open new fields of investigation of neuron/oligodendrocyte interactions in the normal and pathological brain.

Development of Donor-Specific Anti-HLA Antibodies After Restarting Hemodialysis Due to Graft Failure.

BACKGROUND: Incidents of renal replacement therapy (RRT) from renal transplants are on the rise. Some authors have associated the development of donor-specific anti-HLA antibodies (DSA) with the end of immunosuppression treatment (IS) and/or the performing of a transplantectomy. The objective of this study was to analyze the characteristics of transplant patients having high immunological risk who restarted RRT and the subsequent development of DSA. METHODS: We selected incidents on RRT carried out between 1980 and 2012 in our center: 146 cases; they presented non-DSA cytotoxic antibodies prior to returning to RRT. Survival time for the graft was 77.2 months; the average follow-up period for DSA development was 131.9 months. DSA in 76 cases (52.1%). Of 146 grafts, 72 underwent transplantectomy and 41 presented DSA after returning to RRT. In 17 of these cases (41.5%), the development of DSA occurred prior to the transplantectomy. Fifty-one cases of DSA were registered at the date of completion of the IS treatment, and 40 appeared after discontinuation (median 36 weeks) and 11 with previous appearance. IS was completed, with a median of 13 weeks after the return to RRT. RESULTS: No association was found between DSA development and order of graft, transplantectomy, or premature loss of the graft (≤15 months) after the return to RRT. There were significant differences between the number of HLA incompatibilities of the donor and the development of DSA. CONCLUSIONS: The development of DSA in high-immunological risk patients after restarting RRT is not related to transplantectomy.

Impact of Asystolic Donations in Kidney Transplant Activity From Cadaveric Donors in Andalusia.

BACKGROUND: Kidneys from donors after brain death (DBD) cannot meet the demand for renal transplants in Andalusia. METHODS: We analyzed the impact of using non-heart-beating donors (NHBD) in Andalusia from the start of this program to the present. RESULTS: From 2010 to 2014, brain-death kidney donations remained at a standstill (1,635 in total) although NHBD increased from 2.4% to 16% annually, to 5% of the total (n = 164: 83 type II Maastricht [NHBD-T2] and 81 type III Maastricht [NHBD-T3]). The donors were more frequently men (T2 80.5% and T3 76.5% vs DBD 58.2%; P < .001). NHBD were younger (48.9 ± 10.8 y vs DBD 53.3 ± 16 y; P < .001); 11.6% of NHBD were >60 and 0% >70 years old, versus 39.4% and 15.2% of DBD, respectively; this is mostly explained by NHBD-T2 (48.9 ± 10.8 y vs DBD 53.3 ± 16 y). NHBD were used much less frequently than DBD in recipients over the age of 65 years or for retransplanted or hyperimmunized patients and never on priority recipients (children and combined transplant patients). Blood groups differed significantly among different donor types (A, O, B, AB): NHBD-T2 65.1%, 27.7%, 7.2%, and 0%, respectively; NHBD-T3 45.7%, 45.7%, 8.6%, and 0%; and DBD 46.5%, 39.4%, 10.2 %, and 3.9% (P = .01). The immediate output of the graft also differed in the proportion of primary nonfunction and delayed graft function: NHBD-T2 9.8% and 70.7%, respectively; NHBD-T3 5.0% and 65.0%; and DBD 5.9% and 28.7%. CONCLUSIONS: The development of an NHBD program allows us to maintain and even increase transplants in our region. The impact on transplant access for O group recipients without priority will depend on the type of NHBD (low proportion of O group in NHBD-T2).

Tyrosine-phosphatase and glutamate-decarboxylase antibodies after simultaneous pancreas kidney transplantation: do they have an impact on pancreas graft survival?

INTRODUCTION: The pathogenesis of type 1 diabetes mellitus (T1DM) is associated with auto-antibodies. These auto-antibodies contribute to pancreatic ß-cell destruction. Tyrosine-phosphatases (IA-2) and glutamic acid decarboxylase (GAD65) are the most frequently used by clinicians. When T1DM patients develops advanced chronic kidney disease, simultaneous pancreas-kidney (SPK) transplantation becomes the best option. However, pancreatic graft survival is limited. The role of the auto-antibodies on pancreas graft survival remains controversial. OBJECTIVE: The aim of this study was to assess pancreas graft survival according to the presence of GAD65 and IA-2 auto-antibodies after SPK transplantation. METHODS: We analyzed all SPK transplantations performed in our hospital since January 1990 to December 2013 with at least 30 days of pancreas graft survival. We collected demographic and clinical variables from donors and recipients. Graft failure was defined as complete insulin independence after transplantation. Pancreatic graft survival was analyzed using the Kaplan-Meier method. RESULTS: Overall, 152 SPK transplantations were performed during the period. One hundred sixteen were accessed for de novo post-transplantation auto-antibodies. Also, 17.8% (n = 27) were positive for anti-GAD65, 13.8% (n = 20) for IA-2, 3.9% (n = 6) were positive for both, and the rest were negative for any auto-antibody (n = 63). Kaplan-Meier survival curves estimated a worst pancreas graft survival for patients with positive IA-2 antibodies versus those patients with negative auto-antibodies and GAD65+auto-antibodies (P = .003 and .022, respectively, by log-rank). Mean pancreas graft survival rates at first and fifth year were 72% and 64%, respectively, for those patients with positive IA-2. CONCLUSIONS: IA-2 antibodies after SPK transplantation are associated with long-term graft lost compared with the rest of the groups. Monitoring of these auto-antibodies after SPK may help to identify patients with a higher risk of graft failure.

Oxygen Sensing by Arterial Chemoreceptors Depends on Mitochondrial Complex I Signaling.

O2 sensing is essential for mammalian homeostasis. Peripheral chemoreceptors such as the carotid body (CB) contain cells with O2-sensitive K(+) channels, which are inhibited by hypoxia to trigger fast adaptive cardiorespiratory reflexes. How variations of O2 tension (PO2) are detected and the mechanisms whereby these changes are conveyed to membrane ion channels have remained elusive. We have studied acute O2 sensing in conditional knockout mice lacking mitochondrial complex I (MCI) genes. We inactivated Ndufs2, which encodes a protein that participates in ubiquinone binding. Ndufs2-null mice lose the hyperventilatory response to hypoxia, although they respond to hypercapnia. Ndufs2-deficient CB cells have normal functions and ATP content but are insensitive to changes in PO2. Our data suggest that chemoreceptor cells have a specialized succinate-dependent metabolism that induces an MCI state during hypoxia, characterized by the production of reactive oxygen species and accumulation of reduced pyridine nucleotides, which signal neighboring K(+) channels.

POP66, a paraneoplastic encephalomyelitis-related antigen, is a marker of adult oligodendrocytes.

Paraneoplastic neurological diseases are disorders of the central nervous system, associated with neuronal degeneration in patients with systemic cancer, but are not a direct result of the tumor mass or metastasis. The biological diagnosis of these syndromes is based mainly on the detection, in the patient's serum and cerebrospinal fluid, of autoantibodies (anti-Hu, anti-Yo, for example), suggesting an autoimmune origin for these disorders. Recently, we described novel autoantibodies (anti-CV2 autoantibodies) associated with paraneoplastic neurological disease, which recognize a 66 kDa brain protein. We named this antigen POP66, for Paraneoplastic Oligodendrocyte Protein of 66 kDa molecular weight, as in the adult human, rat, and mouse brain, it is specifically expressed by a subpopulation of oligodendrocytes. This cell type specificity was surprising given the fact that the cell loss in the brains of patients with anti-CV2 autoantibodies is neuronal. POP66-expressing oligodendrocytes are distributed along the longitudinal axis of the brain according to an increasing rostro-caudal gradient, with no positive oligodendrocytes being found in the forebrain and the greatest number found in the spinal cord. In addition, in transverse sections of the spinal cord, the distribution of POP66-positive oligodendrocytes follows an increasing dorsal-to-ventral gradient, which may be related to different oligodendrocyte precursor pools. In addition, the neuronal loss without demyelination seen in the brains of patients with anti-CV2 autoantibodies, together with the exclusive oligodendroglial expression of POP66 in the adult brain, raises the question of the possible involvement of POP66 in neuron survival via neuron/oligodendrocyte interactions.

Specific potentialities of embryonic rat serotonergic neurons to innervate different periventricular targets in the adult brain.

During the development of the central nervous system, neurons are directed by both genetic and environmental factors to differentiate and form connections with their targets. We took advantage of the abundant homogeneous serotonergic innervations of the ependyma forming the supra- and subependymal plexuses to investigate possible commitment of embryonic neurons to innervate specific targets during axogenesis in the rat. The origin of the supraependymal innervation was determined by retrograde transport of cholera toxin (CT) from the ventricles. The supraependymal plexuses of the fourth ventricle mainly originated from neurons in the dorsocaudal region of the raphe dorsalis (DRN), while the rostral DRN and raphe centralis (CRN) contained perikarya projecting into the third ventricle. This suggested the existence, along the rostrocaudal axis of the raphe, of different neuronal subsets able to form distinct supraependymal plexuses in the third or fourth ventricle. To determine whether serotonergic neurons were committed to innervate specific areas of the ependyma, different embryonic metencephalic segments (rostral, median, or caudal) from 14-day-old rat embryos were independently grafted into the third or fourth ventricle of an adult brain in which the serotonergic neurons had been previously destroyed. The distinctive patterns of re-innervation specific to each of grafted segments indicate that subsets of embryonic serotonergic neurons are indeed committed to innervate certain restricted ependymal areas of the adult brain, presumably in response to different neurotropic and/or neurotrophic cues.

Autoantibodies to glutamate decarboxylase in a patient with cerebellar cortical atrophy, peripheral neuropathy, and slow eye movements.

OBJECTIVE: To study the existence of autoimmunity against the cerebellum in patients with sporadic cortical cerebellar atrophy. DESIGN: The presence of autoantibodies against the cerebellum in the serum and cerebrospinal fluid samples that were obtained from patients with sporadic cortical cerebellar atrophy and control patients was investigated by using immunohistochemical techniques. SETTING: University hospital and research laboratory in Lyons, France. PATIENTS: Eight patients with cortical cerebellar atrophy that was associated with or without other neurological symptoms; 350 patients with various neurological diseases; and 33 normal, healthy subjects. OUTCOME MEASURES: Serum and cerebrospinal fluid anti-cerebellar autoantibodies were investigated by using indirect immunofluorescence techniques in rat cerebellum. To characterize antigen labeled by patient's serum, we used an immunotrapping enzyme activity assay of glutamate decarboxylase. RESULTS: Serum and cerebrospinal fluid samples that were taken from one patient with sporadic cortical cerebellar atrophy associated with peripheral neuropathy and slow eye movements contained anti-glutamate decarboxylase autoantibodies. CONCLUSIONS: These results suggest a participation of autoimmunity in the pathogenesis of some cases of sporadic cerebellar cortical atrophy and the involvement of the cerebellar gamma-aminobutyric acid-ergic system in the pathogenesis of this disease.

gamma-Aminobutyric acid and 5-hydroxytryptamine interrelationship in the rat nucleus raphe dorsalis: combination of radioautographic and immunocytochemical techniques at light and electron microscopy levels.

Serotonin and gamma-aminobutyric acid (GABA) neurons in the nucleus raphe dorsalis were identified by immunocytochemistry using antibodies to 5-hydroxytryptamine or GABA. The pattern of the 5-hydroxytryptamine and GABA immunostaining presented similar features: 5-hydroxytryptamine or GABA immunoreactive somata were fusiform or ovoid (15-20 micron) and positive dendritic profiles were found either without any connection with other nerve elements or in contact with one or several terminals. In addition, some 5-hydroxytryptamine nerve endings were apposed to 5-hydroxytryptamine immunoreactive cell bodies or dendrites; also some GABA-immunopositive terminals were in contact with GABA-immunopositive nerve cell bodies. On the other hand, GABA and 5-hydroxytryptamine patterns may be differentiated in several respects: the 5-hydroxytryptamine-reactive nerve cell bodies were more numerous than the GABA ones. Some small, round (8-10 micron) nerve cell bodies were reactive with GABA antiserum, but no neurons of this type were reactive with a 5-hydroxytryptamine antiserum; finally, GABA nerve terminals were more numerous than 5-hydroxytryptamine ones. In order to understand the relationship between GABA and 5-hydroxytryptamine neurons, radioautographic and immunocytochemical procedures were combined: 5-hydroxytryptamine and GABA immunocytochemistry was combined with radioautography of [3H]GABA and [3H]5-hydroxytryptamine uptake, respectively. Some nerve cell bodies, dendrites or terminals, which were 5-hydroxytryptamine-immunopositive, were also capable of accumulating [3H]GABA and, conversely, some GABA-immunopositive elements were capable of accumulating [3H]5-hydroxytryptamine. Moreover, several nerve elements were reactive with both glutamate decarboxylase and 5-hydroxytryptamine antisera. These data confirm in electron microscopy previous studies suggesting the coexistence of both GABA and 5-hydroxytryptamine in the same neurons. The presence of uptake mechanisms for GABA and 5-hydroxytryptamine may indicate the action of both neurotransmitters in the same neuron. On the other hand, the [3H]GABA-labelled nerve endings in contact with 5-hydroxytryptamine-positive dendrites or nerve cell bodies indicate the possibility of a GABAergic control of the activity of some 5-hydroxytryptamine neurons; this corroborates biochemical and electrophysiological studies whereby a trans-synaptic control of the 5-hydroxytryptamine neurons by GABA may be envisaged.