Renal tubular injury in hyperbilirubinemia: Bile cast nephropathy

The toxic renal accumulation of bile pigment sparked clinical intrigue almost a century ago. More recently, however, the identification of bile casts within renal tubules in patients with liver dysfunction has been largely overlooked. We have reviewed the literature, including natural history, pathophysiology, and potential treatment of bile cast nephropathy (BCN). We report two cases of acute kidney injury (AKI) associated with acute-on-chronic liver failure in which prolonged hyperbilirubinemia and bile cast identification on renal biopsy evoked the diagnosis of BCN.

A205 PEMBROLIZUMAB ASSOCIATED SCLEROSING CHOLANGITIS RESPONDS TO COMBINATION OF STEROIDS AND MYCOPHENOLIC ACID: A CASE REPORT

Background

Pembrolizumab is a check point inhibitor that targets programmed cell death receptor ligand 1 (PD-L1). However, check-point inhibitors are associated with its characteristic adverse event know as immune related adverse events that can affect a myriad of organ systems. In the hepatobiliary system, the most commonly described iRAE is hepatitis/hepatotoxicity and latest oncology guidelines offer recommendations on treatment and followup of immunotherapy related hepatitis (1). However, a more rare presentation of iRAE, that have only been described as case reports or case series, is secondary cholangitis. We report one of such a case.

Aims

Case report

Methods

Case report

Results

The patient is a 55 year-old Caucasian female know for lung adenocarcinoma presented to the emergency room on May 5th, 2020, having received her 8th cycle of pembrolizumab. Her blood works mildly elevated transaminitis; ALT 78 U/L, AST 11 U/L, alkaline phosphate of 130 U/L, and total bilirubin of 3.5 umol/L.

MRI of the abdomen showed a normal appearing liver without focal parenchymal lesion, no biliary stones or obstructing masses, dilated common bile duct at 11 mm with small pericholecystic free fluid, and normal gall badder thickness of 2 mm. There was also notion of minimally prominent intrahepatic biliary radicles seen within the CBD.

Etiology workup of cholestatic transaminitis was negative. A diagnosis of immunotherapy related sclerosing cholangitis was posed and the patient was treated with MMF and prednisone with good response.

Conclusions

Discussion

This patient seems to have developed immunotherapy mediated cholangitis. Liver biopsy when performed in liver injury tend to show lobular hepatitis, with liver parenchyma infiltrated with lymphocytes and focal necrosis with acidophilic bodies. However, there seems to be another, less frequent pattern of injury described with pembrolizumab and associated with cholangiopathy, resembling primary biliary cholangitis. It is characterized with portal tracts enlarged with fibrosis and inflammatory cells infiltration; infiltrating cells are lymphocytes (2). Biliary epithelium with fibrosis with CD8+ T cells infiltration seem to be recurrently reported in case reports. (3, 4).

Other cases have been describe in the literature. In many cases, steroid therapy was attempted, but response rates seem to be inconsistent. Nivolumab related cholangitis have been also been described and characterized by extra hepatic bile duct dilatation along with negative immunological markers such as ANA and IgG4 in patients with non-small cell lung cancer, and seems to respond only moderately to steroid therapy (6). Retrospective data of nivolumab related cholangiopathy seems to suggest that there is favourable response to the combination of MMF and steroid therapy (7).

Funding Agencies

None

Navigating the perfect [data] storm

Bioscience has recently undergone a series of knowledge-based and technological revolutions. A critical consequence has been increasing recognition of the need to invest in infrastructure. Good access to data (and samples) from multiple studies is axiomatic to the value of this infrastructure. Access must be streamlined, secure, and based upon transparent and ‘fair’ decision making. It must be clear who has created and who has used which data. Ethico-legal policies and guidelines, which reflect dominant local cultural and societal norms, must take account of the increasingly global nature of bioscience research. A robust data infrastructure must also be attentive to the translational aims and social impact of its knowledge generation. In order to maintain the trust of its constituency – the general public as well as professional, political, commercial stakeholders – it must develop mechanisms to take account of all of these perspectives. These considerations form the basis of an emerging data economy. Building on extant achievements and pursuing the ideas outlined here could revolutionise the way we use and manage large-scale data. They have critical implications for biomedical and public health research communities and will be of central relevance for healthcare managers and policy makers, governments and industry. However, if the major challenges are to be met we must continue to invest,both nationally and internationally, in developing the cooperative infrastructures that provide a complementary foil to competitive resourcing mechanisms that drive hypothesis-driven science.

The utility of Xenon-133 liver scan in the diagnosis and management of nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is an important and common condition affecting approximately 20% of the general population. Given the limitation of radiological investigations, diagnosis often requires a liver biopsy.

OBJECTIVE

To compare Xenon-133 (Xe-133) liver scanning with ultrasonography in the diagnosis of NAFLD.

METHODS

From January 2003 to February 2007, 258 consecutive patients with suspected NAFLD underwent Xe-133 liver scanning at Royal Victoria Hospital (Montreal, Quebec). Of these, 43 patients underwent ultrasonography and liver biopsy for the evaluation of NAFLD. Patients with other liver diseases and significant alcohol consumption were excluded. Two nuclear medicine physicians assessed liver Xe-133 uptake and measured the grade of steatosis using a standardized protocol. The degree of steatosis was determined from biopsy specimens assessed by two hepatopathologists.

RESULTS

NAFLD was identified by liver biopsy in 35 of 43 patients (81.4%). Xe-133 scan demonstrated 94.3% sensitivity (95% CI 81.4% to 98.4%) and 87.5% specificity (95% CI 52.9% to 99.4%) for the presence of NAFLD. The positive and negative predictive values for detection of steatosis by Xe-133 scan were 97.1% (95% CI 85.1% to 99.8%) and 77.8% (95% CI 45.3% to 93.7%), respectively. The positive and negative likelihood ratios were 7.54 (95% CI 1.20 to 47.26) and 0.07 (95% CI 0.02 to 0.26), respectively. Two patients with NAFLD (5.7%) who had a negative Xe-133 scan result had histologically mild steatosis (<10%). The grade of steatosis on liver biopsy was highly correlated with the results of the Xe-133 scan (r=0.87; P<0.001). The sensitivity and specificity of ultrasound in diagnosing steatosis were 62.9% and 75%, respectively.

CONCLUSION

Xe-133 liver scan proved to be a safe, reliable, noninvasive method for diagnosing and quantifying hepatic steatosis, and was superior to ultrasound.

A European survey on biobanks: trends and issues

Biobanks have recently gained great significance for research and personalised medicine, being recognised as a crucial infrastructure. At the same time, the widely varied practices in biobanking may also pose a barrier to cross-border research and collaboration by limiting access to samples and data. Nevertheless, the extent of the actual activities and the impact of the level of networking and harmonisation have not been fully assessed. To address these issues and to obtain missing knowledge on the extent of biobanking in Europe, the Institute for Prospective Technological Studies (IPTS) of the European Commission's Joint Research Centre, in collaboration with the European Science and Technology Observatory (ESTO), conducted a survey among European biobanks. In total, 126 biobanks from 23 countries responded to the survey. Most of them are small or medium-sized public collections set up either for population-based or disease-specific research purposes. The survey indicated a limited networking among the infrastructures. The large majority of them are stand-alone collections and only about half indicated to have a policy for cross-border sharing of samples. Yet, scientific collaborations based on the use of each biobank appear to be prominent. Significant variability was found in terms of consent requirements and related procedures as well as for privacy and data protection issues among the biobanks surveyed. To help promote networking of biobanks and thus maximise public health benefits, at least some degree of harmonisation should be achieved.

Evaluating cimetidine for GFR estimation in liver transplant recipients

Background. Serum creatinine (Scr)-based equations lack accuracy in predicting glomerular filtration rate (GFR) in patients with liver disease. Cimetidine has been shown to improve the performance of Scr-based GFR formulae. Methods. We evaluated the use of cimetidine on the performance of GFR-estimating equations in 39 liver transplant recipients. The patients received oral cimetidine (800 mg tid) during a 24-h urine collection. The next day, the patients underwent radionucleotide GFR (rGFR) determination and Scr was measured for creatinine clearance (CrCl) and GFR estimation using the Cockcroft-Gault, Nankivell and modified diet in renal disease (MDRD) equations. Data were analysed using the Pearson correlation statistic and Bland-Altman plots. Results. The mean rGFR was 65 +/- 26.4 mL/min. The use of cimetidine increased the bias between rGFR and the Nankivell and MDRD equations. The combined root mean square error for the CrCl, Cockcroft-Gault, Nankivell and MDRD equations without cimetidine were 20.2, 15.6, 17.0 and 15.5 and cimetidine-aided were 28.2, 23.2, 23.7 and 24.3, respectively. Conclusions. All the tested equations without using cimetidine predicted GFR with modest accuracy. The addition of cimetidine decreased the precision and increased the bias of all the GFR-estimating equations. In the absence of accurate GFR-estimating equations, rGFR should be used to monitor kidney function in liver transplant recipients.

Clinical trial: exposure to ribavirin predicts EVR and SVR in patients with HCV genotype 1 infection treated with peginterferon alpha-2a plus ribavirin

BACKGROUND

The impact of reduced drug exposure on outcomes in patients with chronic hepatitis C has not been determined in routine clinical practice.

AIM

To examine the impact of exposure to peginterferon alpha-2a and ribavirin on early virological response (EVR) and sustained virological response (SVR) in treatment-naive patients with HCV genotype 1 infection enrolled in a large expanded access programme.

METHODS

Eight hundred and ninety-one patients treated for 48 weeks with an initial ribavirin dose of 800 or 1000/1200 mg/day were evaluated. Ribavirin 1000 mg/day (<75 kg) or 1200 mg/day (>or=75 kg) and peginterferon alpha-2a 180 microg/week were considered optimal. The impact of reduced drug exposure (expressed as a percentage of optimal) on EVR and SVR was evaluated.

RESULTS

Mean ribavirin exposure in week 0-12 was 70% and 96% in patients assigned to ribavirin 800 and 1000/1200 mg/day, respectively. EVR and SVR rates were lower in patients assigned to ribavirin 800 than 1000/1200 mg/day (EVR, 75% vs. 84%, respectively, P < 0.001; SVR, 45% vs. 54%, respectively, P = 0.011). Furthermore, there was a strong correlation between achievement of EVR and SVR and ribavirin dose over the first 12 weeks expressed either as absolute dose or proportion of optimal dose received (P < 0.001 for both).

CONCLUSIONS

Ribavirin exposure to week 12 is significantly associated with EVR and SVR in genotype 1 patients. Maintenance of an optimal ribavirin dose is the most important modifiable factor during combination therapy for chronic hepatitis C.

Caregivers attitudes for very premature infants: what if they knew?

BACKGROUND

Decisions about resuscitation of extremely premature babies are controversial. Such decisions may reflect poor understanding of outcomes.

OBJECTIVE

To compare caregivers' attitudes towards the resuscitation of a premature infant if they are only told the infant's gestational age or if they are only given prognostic information for infants at that gestational age.

DESIGN/METHODS

Residents and nurses involved in perinatal care were asked whether they would resuscitate a depressed AGA 24-week gestation infant at birth. In another question they were asked whether they would resuscitate a depressed preterm infant with a 50% chance of survival, knowing that of those who survived, 50% would have a development 'within normal limits', 20-25% a serious handicap and 40% with behavioural and/or learning disability.

RESULTS

Two hundred and seventy-nine caregivers responded (91% response rate). In the scenario that only presented gestational age, 21% of respondents would resuscitate. In the scenario that only presented prognostic statistics, 51% of respondents would resuscitate (p<0.05).

CONCLUSIONS

Providers of perinatal health care respond to vignettes differently depending upon the format in which information is provided. The relative unwillingness to resuscitate a baby of 24-week gestation is surprising since outcomes for such babies are the same or better than those we described in the scenario that provided only outcome data without specifying gestational age. Two explanations are possible: (1) respondents have irrational negative associations with low gestational ages or (2) respondents are unaware of actual outcomes.

The effect of information level and coping style on pain and anxiety in needle liver biopsy

Biopsy of the liver is an important diagnostic procedure. The procedure is invasive and may be painful for patients. Sedative drugs are not used because the associated drop in blood pressure mimics hemorrhage, a major complication of the procedure. Cognitive and behavioural techniques have been used to decrease stress in patients undergoing other medical procedures. In the present study, it is postulated that providing procedural and sensory information may reduce patient anxiety levels. Patient coping styles were evaluated and anxiety and pain levels were assessed by using a visual analogue scale. Subjects were randomly assigned to one of two groups. The control group received basic information about the procedure. The experimental group received the same basic information followed by more detailed educational information. Subjects also filled out the Krantz Health Opinion Survey, a short questionnaire used to classify coping styles as either information-seeking or information-avoiding. Seventy-five subjects (38 control and 37 experimental) with similar demographics were included in the present study. No significant differences were found in anxiety levels or pain levels 30 min and 6 h post-biopsy. There was also no significant difference between groups once coping style was added into the analysis. The study failed to show any advantage in providing additional information to subjects before liver biopsy, regardless of coping style.

Management of chronic hepatitis B: consensus guidelines

The present document presents the proceedings of the consensus development conference on the management of viral hepatitis held in January 2007 under the auspices of the Canadian Association for the Study of the Liver and the Association of Medical Microbiology and Infectious Disease Canada. Several new agents have become available since the last such document was published in 2004, and new information has become available to help assess risk of adverse outcomes and who should be treated. In addition, the participants at the meeting identified a number of structural barriers that exist uniquely in Canada and that prevent physicians from properly managing their patients. The conference discussed the selection of patients for treatment and the drugs that can be used to treat these patients, as well as the treatment of hepatitis B in special populations. The present document should be read in conjunction with the companion document on the management of chronic hepatitis C.

Management of chronic hepatitis C: consensus guidelines

Since the last consensus conference on the management of chronic viral hepatitis, a number of studies looking at modifications of the standard course of treatment have been published. These changes have been sufficiently substantive to warrant review to determine whether any changes in the recommended treatment algorithms are needed. A consensus development conference was held in January 2007, and the present document highlights the results of the presentations and discussion about these issues. It reviews the epidemiology of hepatitis C in Canada, treatment of acute hepatitis C and new algorithms in chronic hepatitis C, including retreatment of previous treatment failures. In addition, sections on management of hepatitis C in special populations have been updated. There is also a section on the use of hematopoietic growth factors to help manage patients on therapy. The document should be read in conjunction with the previous document to identify changes. Some recommendations made in the previous document remain and are not discussed here.

Preoperative alpha-fetoprotein slope is predictive of hepatocellular carcinoma recurrence after liver transplantation

BACKGROUND

Liver transplantation (LT) offers a possible cure for patients with hepatocellular carcinoma (HCC) and cirrhosis. However, tumour progression while on the waiting list and tumour recurrence after LT are common. The prognostic significance of various pre- and postoperative variables were investigated in regard to tumour recurrence, with an emphasis on the slope of preoperative serum alpha-fetoprotein (AFP) levels. patients and

METHODS

Data from 48 patients who had HCC diagnosed preoperatively and underwent LT at the McGill University Health Centre (Montreal, Quebec) were reviewed retrospectively, and possible risk factors for tumour recurrence were examined.

RESULTS

Univariate analysis revealed a positive correlation between the preoperative AFP slope and vascular invasion (P = 0.045), total tumour diameter at explant (P = 0.040), Cancer of the Liver Italian Program score (P = 0.017) and recurrence-free survival (P = 0.028). Of the preoperative variables examined, only the preoperative AFP slope was identified as an independent predictor of tumour recurrence by multivariate analysis. Receiver operating characteristic analysis showed that the best discriminant cut-off value, calculated as the value of the maximized likelihood ratio, was preoperative AFP slope greater than 50 microg/L per month. At this cut-off, sensitivity was 36%, and specificity was 97%. Patients with a preoperative AFP slope greater than 50 microg/L per month had a much worse one-year recurrence-free survival rate than those with a preoperative AFP slope 50 microg/L per month or less (40% versus 90%, P < 0.001).

CONCLUSIONS

These results suggest that the preoperative AFP slope is an important predictor of HCC recurrence after LT and should be examined in future studies of patients receiving LT for HCC.

Moral distress in the neonatal intensive care unit: caregiver's experience

BACKGROUND

The Neonatal Intensive Care Unit (NICU) can be ethically charged, which can create challenges for health-care workers.

OBJECTIVE

To determine the frequency with which nurses and residents have experienced ethical confrontations and what factors are associated with increased frequency.

DESIGN/METHODS

An anonymous questionnaire was distributed to nurses in a university center, a high-risk obstetric service, a maternity hospital NICU with 85% in-born patients and an outborn NICU, most of whose preterm admissions are those with surgical complications. Obstetric and pediatric residents in the four universities of the province also received the questionnaire, which included demographics, opinions regarding the gestational age threshold at which resuscitation of a premature infant with bradycardia was appropriate, knowledge of cerebral palsy (CP) outcomes (as an indicator of knowledge about long-term sequelae of prematurity) and questions about ethical confrontation in the NICU.

RESULTS

Two hundred and seventy-nine caregivers participated (115 full time nurses and 164 residents). All the distributed questionnaires were completed. Frequent ethical confrontation was reported by 35% of the nurses and 19% of the residents. Among the nurses, moral distress differed significantly between work environments. Nurses working in an out-born NICU and obstetric nurses were more likely to overestimate CP prevalence (P<0.05). Nurses who overestimated CP rates had higher thresholds for resuscitation and were more likely to experience ethical confrontations. Of the residents, 60% were pediatric and 40% obstetric. All groups of residents frequently overestimated the prevalence of CP, and knowledge differed significantly by residency program (P<0.05). The residents who overestimated CP rates had higher thresholds for resuscitation, had more incorrect answers regarding prematurity outcomes and were less likely to have ethical confrontations.

CONCLUSIONS

A large proportion of nurses and residents report frequent ethical confrontations. Many residents and nurses have limited knowledge of outcomes and high threshold for resuscitation. Ethical confrontation is more common among nurses with poor knowledge about outcomes, and less common in residents with poor knowledge about outcomes.

Use of sequence analysis of the NS5B region for routine genotyping of hepatitis C virus with reference to C/E1 and 5' untranslated region sequences

Nucleotide sequence analysis of the NS5B region was performed to identify genotypes of 8,479 hepatitis C virus (HCV) RNA-positive patient samples collected in the Canadian province of Quebec. Genotypes could be determined for 97.3% of patients. Genotypes 1 to 6 were found in 59.4, 9.0, 25.7, 3.6, 0.6, and 1.8% of patients, respectively. Two isolates did not classify within the six genotypes. The subtype 1 distribution was 76.7% 1a, 22.6% 1b, and 0.7% others, while the subtype 2 distribution was 31.8% 2a, 47.6% 2b, 10.9% 2c, 4.1% 2i, and 5.6% others. Subtype 3a accounted for 99.1% of genotype 3 strains, while all genotype 5 samples were of subtype 5a. The subtype 4 distribution was 39.2% 4a, 15.4% 4k, 11.6% 4d, 10.2% 4r, and 23.6% others. The subtype 6 distribution was 40.4% 6e, 20.5% 6a, and 39.1% others. The 5' untranslated region (5'UTR) sequences of subtype 6e were indistinguishable from those of genotype 1. All samples that did not classify within the established subtypes were also sequenced in C/E1 and 5'UTR. C/E1 phylogenetic reconstructions were analogous to those of NS5B. The sequences identified in this study allowed the provisional assignments of subtypes 1j, 1k, 2m, 2r, 3i, 4q, 6q, 6r, and 6s. Sixty-four (0.8%) isolates classifying within genotypes 1 to 6 could not be assigned to one of the recognized subtypes. Our results show that genotyping of HCV by nucleotide sequence analysis of NS5B is efficient, allows the accurate discrimination of subtypes, and is an effective tool for studying the molecular epidemiology of HCV.

Recurrent hepatitis C post-transplantation: where are we now and where do we go from here? A report from the Canadian transplant hepatology workshop

Approximately 400 liver transplants are performed in Canada every year and close to 6000 per year in the United States. Forty per cent to 45% of all liver transplants are performed for patients with underlying hepatitis C virus (HCV)-related liver disease. These patients have a different natural history, new complication risks and different treatment efficacy than nontransplant HCV patients. Every effort must be made to identify those patients at highest risk for progressive liver disease post-transplant. Recurrent HCV is an Achilles' heel to transplant hepatology. The true natural history of this disease is only starting to unravel and many questions remain unanswered on the optimal management of these patients after liver transplantation. The present report summarizes the literature and ongoing research needs that are specific to HCV-related liver transplantation.

Elderly patients are at greater risk of cytopenia during antiviral therapy for hepatitis C

The results of antiviral therapy for hepatitis C virus (HCV) have improved recently with the use of pegylated interferon (PEG-IFN)/ribavirin (RBV) combination therapy. At this point, most patients with chronic HCV remain untreated. Thus, it is anticipated that therapy will be more appealing and prescribed more broadly than in the past, including in patients considered marginal.

AIM

To examine the effects of PEG-IFN-based antiviral therapy in elderly patients with chronic HCV.

METHODS

The charts of patients treated with chronic HCV were reviewed. Patients were defined as elderly if they were 60 years of age or older. The control group consisted of patients younger than 60 years of age who were matched to the treated elderly patients based on sex, treating physician, prescribed treatment and intended prescribed treatment duration. The data recorded included end of treatment response, sustained virological response (SVR), adverse events, dose modification and withdrawal of therapy.

RESULTS

Thirty of 147 (20.4%) elderly patients attending a hepatitis C clinic were treated. The average age of the elderly patients was 65+/-4 years. Forty-three per cent were men and 57% were women. Ten per cent received IFN monotherapy, 70% received a combination of IFN/RBV therapy and 20% received a combination of PEG-IFN/RBV therapy. The overall response rates in the elderly patients compared with the younger patients was 46.7% versus 65.8% (P=0.11) for end of treatment response and 33.3% versus 51.2% (P=0.13) for SVR. The rate of dose modification was 50% in the elderly patients compared with 29% in the control group (P=0.08). Therapy was discontinued in 53% of the elderly compared with 34% of younger patients (P=0.17). The younger patients reported more side effects than elderly patients; although, there were more laboratory abnormalities (anemia, thrombocytopenia and neutropenia) in the elderly patients during therapy than in the younger group (0.93 per patient versus 0.49 per patient, P=0.01).

CONCLUSION

Elderly patients with chronic HCV can be treated successfully. However, they are more at risk to develop cytopenias while on treatment. In such patients, the close monitoring of blood counts is necessary. Larger studies are needed to confirm these findings and to determine whether SVR differs in this population.

Liver transplantation for metastases from a bile duct carcinoid

BACKGROUND

A 29-year-old woman who presented with fatigue and jaundice was found to have an obstructing mass at the bifurcation of the bile duct. The patient underwent a successful left hepatectomy with resection of the bile duct bifurcation and a reconstruction with a right hepaticojejunostomy. Pathology revealed an atypical carcinoid tumour of the left extrahepatic bile duct, with perineural and lymphatic invasion. The patient subsequently developed multiple metastases in the remaining liver.

METHODS

In the absence of extrahepatic disease, the patient underwent a successful liver transplant.

RESULTS

Two years later she remains disease-free.

DISCUSSION

To our knowledge this is the first report of a biliary carcinoid treated with hepatectomy and finally with liver transplantation, with excellent results. The biological behaviour of these rare tumours mandates aggressive surgical management.

Liver transplantation for incidental cholangiocarcinoma: analysis of the Canadian experience

Cholangiocarcinoma is a biliary tumor, which not infrequently complicates primary sclerosing cholangitis. It carries a poor prognosis and, with the exception of carefully selected individuals in research protocols, contraindicates orthotopic liver transplantation. There has been some suggestion that cholangiocarcinomas incidentally discovered at the time of transplantation carry a better prognosis. The goal of this retrospective study was to perform a national review of outcomes after liver transplantation in Canadian recipients found to have incidental cholangiocarcinoma in their explanted native liver. Six of the seven liver transplant centers in Canada provided clinical and follow-up information on all liver transplant recipients found to have incidental cholangiocarcinoma in their explants. The diagnosis or suspicion of cholangiocarcinoma prior to transplantation were exclusion criteria for this study. Ten individuals with cholangiocarcinoma were transplanted between 1996 and 2003. The median duration of follow-up was 28 months. Eight of the 10 had PSC. All of the tumors were stage I or II. The 3-year survival for these patients was 30%. The median time to recurrence was 26 months (95% confidence interval 13-37), and the median time to death was 30 months (95% confidence interval 28-53). In conclusion, although early survival of patients transplanted for incidental cholangiocarcinoma appears good, intermediate- and long-term survival rates are not better than for individuals historically transplanted with known cholangiocarcinoma. Aggressive investigation for cholangiocarcinoma is mandated. Incidentally found tumours remain a difficult treatment problem, and prospective adjuvant chemo-, radio-, and immunotherapies should be investigated.

[Rapid antigen detection tests for diagnosis of group A streptococcal pharyngitis: comparative evaluation of sensitivity and practicability of 16 in vitro diagnostics medical devices performed in July 2002 by the French health products safety agency (Afssaps) as part of its market control mission]

Within the scope of its health products control mission, the French Health Products Safety Agency (Afssaps) collaborating with two expert's sites, has assessed the 16 tests available on the French market in 2002 for rapid diagnosis of the Streptococcus A tonsillitis. The purpose of this study was to verify the reliability and rapidity of these tests and to give some information to the users about their analytical criteria and practicability characteristics. The analytical study has been performed on a same panel of four reference strains of Streptococcus pyogenes dilutions to determine the limit of detection of all the reagents in the same condition of methodology. The limit of detection has been calculated with the results expressed in colony forming unit by ml (CFU/ml). The practicability study has permitted to analyze the quality of the presentation, the easiness of the final reading and of performing tests. A score has been established for each rapid test. A classification of the analytical sensitivity (limit of detection) and practicability (score) of these 16 devices has been established. The limit of detection of the reagents giving the best results allows the detection of the lowest bacterial concentration of the panel which is 10(5) CFU/ml. Regarding practicability, the results suggest that, the immunochromatographic strip methods have the best score in a view with the use by a non medical laboratory.

Do biliary endoprostheses decrease biliary complications after liver transplantation?

AIM

Most technical complications after orthotopic liver transplantation (OLT) are related to the biliary tree. This report reviews the role of routine intraoperative placement of stents to reduce biliary complications.

METHODS

We retrospectively analyzed 396 consecutive OLTs. We reviewed rates of biliary complications after hepaticojejunostomy (HJA) as well as following choledochocholedochostomy (CCA) groups: "experimental" group (routine intraoperative biliary stenting, last 10 months), "recent" control group (nonstented, previous 10 months), "historical" control group (prior to that period of time).

RESULTS

All groups were matched for donor/recipient characteristics and for graft cold/warm ischemia time. The overall prevalence of biliary complications was 30.7% after CCA versus 35% after HJA. In the experimental group 21 patients had a 4.8% biliary complication rate compared to the recent control and historical groups, where biliary complication rates were 30% and 32.6%, respectively (P <.05).

CONCLUSIONS

The intraoperative use of biliary stents is feasible and appears to decrease the rate of biliary complications. These results support the need for a prospective randomized trial.

Efficacy of mycophenolate mofetil combined with very low-dose cyclosporine microemulsion in long-term liver-transplant patients with renal dysfunction

BACKGROUND

Cyclosporine (CsA)-induced renal dysfunction is common after liver transplantation. We evaluated the efficacy of tapering CsA to a very low dose and introducing mycophenolate mofetil (MMF) in long-term liver-transplant recipients with renal dysfunction. In addition, we assessed the impact of this strategy on calcineurin inhibition and on transforming growth factor (TGF)-beta levels.

METHODS

We prospectively enrolled 19 adult, long-term (>1 year) liver-transplant recipients with a decreased creatinine clearance greater than 25% compared with the first month posttransplant. MMF was introduced, and CsA was tapered to 25 mg twice daily. Calcineurin inhibition and TGF-beta were measured at baseline and 3 months thereafter.

RESULTS

The CsA dose was tapered over 13+/-3 weeks. At 1-year follow-up, serum creatinine decreased from 141+/-24 to 105+/-22 micromol/L (P=0.002), creatinine clearance increased from 53+/-9 to 71+/-19 ml/min (P=0.02), and glomerular filtration rate increased from 40+/-13 to 64+/-18 mL/min (P=0.002). The incidence of acute rejection was 29%. Antihypertensive medications were discontinued in 71% of the patients. Although CsA levels decreased significantly, serum TGF-beta did not differ from normal controls, and calcineurin inhibition remained stable. The incidence of gastrointestinal side-effects and leukopenia was 18% and 24%, respectively.

CONCLUSION

In long-term liver-transplant recipients with renal dysfunction, the introduction of MMF followed by tapering of CsA to a very low dose resulted in a significant improvement in renal function. However, this strategy maybe associated with a risk of acute rejection. The clinical pertinence of measuring serum TGF-beta levels and calcineurin inhibition remains to be determined.

Elevation of CA-125 level is due to abdominal distension in liver transplantation candidates

BACKGROUND

CA (cancer antigen) 125 is a serologic marker used in the monitoring of ovarian cancer. Elevated levels are also reported in cirrhosis. We evaluated the range of serum CA 125 levels seen before and after liver transplantation, and examined possible factors associated with CA 125 elevation.

METHODS

We examined prospectively 57 consecutive patients with cirrhosis who underwent liver transplantation. CA 125 levels were also measured in two patients with polycystic liver disease.

RESULTS

The mean serum CA 125 level before transplantation was 352+/-549 u/ml, compared with 46+/-49 u/ml after transplantation (P<0.001). Multivariate analysis identified the degree of ascites as the only significant predictive variable of preoperative CA 125 level. In five patients who underwent abdominal paracentesis, the mean ascites CA 125 level (951+/-322 u/ml) was higher than that of the serum (619+/-290 u/ml) (P<0.003). In 16 hepatectomy specimens, the grade of staining for CA 125 was 0.8+/-1.4 for the mesothelium of patients with a normal serum CA 125 level, compared with 1.5+/-1.1 in patients with elevated serum levels (P=0.37). Two patients with severe abdominal distension due to polycystic liver disease but without ascites had elevated serum CA 125 levels.

DISCUSSION

CA 125 concentration is elevated in the majority of patients with cirrhosis and normalizes after liver transplantation. It is a reflection of the abdominal distention seen in these patients. Therefore, an elevation in CA 125 should not be considered a contraindication to liver transplantation in the absence of evidence of malignancy.

Relationship between pre-TIPS liver perfusion by the portal vein and the incidence of post-TIPS chronic hepatic encephalopathy

OBJECTIVE

In the present study we evaluated the predictive value of pretransjugular intrahepatic portosystemic shunt (TIPS) portal perfusion as assessed by Doppler ultrasonography for the onset of chronic encephalopathy after TIPS.

METHODS

A total of 231 cirrhotic patients were followed-up prospectively after TIPS placement. The pattern of intrahepatic portal flow was assessed before TIPS. Patients were divided into two groups according to Doppler findings. Group 1 comprised patients with prograde portal flow (n = 200), whereas group 2 comprised those with loss of portal perfusion (hepatofugal or back-and-forth flow or portal vein thrombosis; n = 31). The presence of chronic encephalopathy during a median follow-up of 32 months was prospectively recorded. The prognostic value of the following parameters for the onset of chronic recurrent encephalopathy after TIPS was evaluated: age, presence of encephalopathy before TIPS, alcoholism, Pugh score, and loss of portal perfusion before TIPS. The independent prognostic value of each variable was tested with a multiple logistic regression analysis.

RESULTS

The two groups were comparable in terms of age, incidence of prior episodes of hepatic encephalopathy, and portacaval gradient before and after the procedure; however, liver failure was more severe in patients in group 2 (Pugh score: 9.2 +/- 1.9 vs 10.3 +/- 1.7). The 3-yr survival was identical for both groups; 25% of the 200 patients in group 1 developed chronic encephalopathy as compared to 6% of the 31 patients in group 2 (p = 0.03). Multiple logistic regression analysis demonstrated that loss of portal perfusion and age >65 yr were the only independent predictors of the onset of post-TIPS chronic encephalopathy (odds ratios 0.24 and 1.98, respectively).

CONCLUSIONS

Cirrhotic patients with loss of portal perfusion before TIPS were protected against post-TIPS chronic hepatic encephalopathy despite a more severe liver dysfunction at baseline. The only other independent predictive factor for the onset of this complication was age.

Transjugular intrahepatic portosystemic shunt (TIPS) versus endoscopic variceal ligation in the prevention of variceal rebleeding in patients with cirrhosis: a randomised trial

BACKGROUND AND AIMS

The transjugular intrahepatic portosystemic shunt (TIPS) is a new therapeutic modality for variceal bleeding. In this study we compared the two year survival and rebleeding rates in cirrhotic patients treated by either variceal band ligation or TIPS for variceal bleeding.

METHODS

Eighty cirrhotic patients (Pugh score 7-12) with variceal bleeding were randomly allocated to TIPS (n=41) or ligation (n=39), 24 hours after control of bleeding.

RESULTS

Mean follow up was 581 days in the ligation group and 678 days in the TIPS group. The two year survival rate was 57% in the TIPS group and 56% in the ligation group (NS); the incidence of variceal rebleeding after two years was 18% in the TIPS group and 66% in the ligation group (p<0.001). Uncontrolled rebleeding occurred in 11 patients in the ligation group (eight were rescued by emergency TIPS) but in none of the TIPS group. The incidence of encephalopathy at two years was 47% in the TIPS group and 44% in the ligation group (NS).

CONCLUSIONS

TIPS did not increase the two year survival rate compared with variceal band ligation after variceal bleeding in cirrhotic patients with moderate or severe liver failure. It significantly reduced the incidence of variceal rebleeding without increasing the rate of encephalopathy.

Parallel streams for the relay of vibrissal information through thalamic barreloids

This study investigated the organization of a vibrissal pathway that arises from the interpolar division of the spinal trigeminal complex (SP5i), transits through the ventral posterior medial nucleus (VPM), and innervates the somatosensory cortical areas in the rat. Using Fluoro-Gold and biotinylated dextran amine, respectively, as retrograde and anterograde tracers, the following organization plan was disclosed. The SP5i projection arises from a population of small-sized neurons that selectively innervate the ventral lateral part of VPM. In cytochrome oxidase-stained material, this region does not display any barreloid arrangement, but Fluoro-Gold injections in single barrel columns labeled rods of cells that extend caudally into the ventral lateral division of VPM. Thus, on the basis of retrograde labeling, barreloids were divided into core and tail compartments, which correspond to the rod segments running across the dorsal and ventral lateral parts of VPM, respectively. Double-labeling experiments revealed that SP5i afferents innervate the tail of barreloids. The anterograde labeling of thalamocortical axons show that most "core cells" project to a single barrel column, whereas some "tail cells" give rise to branching axons that innervate the second somatosensory area and the dysgranular zone of the barrel field. Injections that straddled the transition zone between the core and tail regions disclosed cells projecting to a single barrel column and to the surrounding dysgranular zone. These results suggest that the projection of "barreloids cells" to the granular and/or dysgranular zones relates to the class of prethalamic input(s) they receive.

Corticothalamic projections from layer 5 of the vibrissal barrel cortex in the rat

This study bears on the projections of layer 5 cells of the vibrissal sensory cortex to the somatosensory thalamus in rats. Small groups of cells were labeled with biotinylated dextran amine (BDA), and their axonal arborizations were individually reconstructed from horizontal sections counterstained for cytochrome oxidase. Results show that the vast majority ( approximately 95%) of layer 5 axons that innervate the somatosensory thalamus are collaterals of corticofugal fibers that project to the brainstem. The anterior pretectal nucleus, the deep layers of the superior colliculus, and the pontine nuclei are among the structures most often coinnervated. In the thalamus, layer 5 axons terminate exclusively in the dorsal part of the posterior group (Po), where they form clusters of large terminations. Because dorsal Po projects to multiple cortical areas, we sought to determine whether all recipient areas return a layer 5 projection to this part of the thalamus. Additional experiments using fluoro-gold and BDA injections provided evidence that the primary somatosensory area is the sole source of layer 5 projections to dorsal Po but that this thalamic region receives convergent layer 6 projections from the primary and second somatosensory areas and from the motor and insular cortices. These results show that layer 5 projections do not overlap in associative thalamic nuclei, thus defining area-related subdivisions. Furthermore, the coinnervation of brainstem nuclei by layer 5 CT axons suggests that this pathway conveys to the thalamus a copy of the cortical output aimed at brainstem structures.

Thalamic projections from the whisker-sensitive regions of the spinal trigeminal complex in the rat

This study investigated the axonal projections of whisker-sensitive cells of the spinal trigeminal subnuclei (SP5) in rat oral, interpolar, and caudal divisions (SP5o, SP5i, and SP5c, respectively). The labeling of small groups of trigeminothalamic axons with biotinylated dextran amine disclosed the following classes of axons. 1) Few SP5o cells project to the thalamus: They innervate the caudal part of the posterior group (Po) and the region intercalated between the anterior pretectal and the medial geniculate nuclei. These fibers also branch profusely in the tectum. 2) Two types of ascending fibers arise from SP5i: Type I fibers are thick and distribute to the Po and to other regions of the midbrain, i.e., the prerubral field, the deep layers of the superior colliculus, the anterior pretectal nucleus, and the ventral part of the zona incerta. Type II fibers are thin; branch sparsely in the tectum; and form small-sized, bushy arbors in the ventral posterior medial nucleus (VPM). Accordingly, a statistical analysis of the distribution of antidromic invasion latencies of 96 SP5i cells to thalamic stimulation disclosed two populations of neurons: fast-conducting cells, which invaded at a mean latency of 1.23 +/- 0. 62 msec, and slow-conducting cells, which invaded at a mean latency of 2.97 +/- 0.62 msec. 3) The rostral part of SP5c contains cells with thalamic projections similar to that of type II SP5i neurons, whereas the caudal part did not label thalamic fibers in this study. A comparison of SP5i projections and PR5 projections in the VPM revealed that the former are restricted to ventral-lateral tier of the nucleus, whereas the latter terminate principally in the upper two tiers of the VPM. These results suggest a functional compartmentation of thalamic barreloids that is defined by the topographic distribution of PR5 and type II SP5i afferents.

Use of older donor livers is associated with more extensive ischemic damage on intraoperative biopsies during liver transplantation

Initial poor graft function is associated with increased morbidity and graft loss after liver transplantation. Donor age is a risk factor for the development of initial poor function. The severity of ischemic damage on intraoperative postreperfusion (0Post) allograft biopsy specimens is predictive of subsequent initial poor function. This study was performed to assess whether donor age is a risk factor for the development of ischemic damage on 0Post biopsy specimens. The records of 94 liver transplantations were reviewed. 0Post biopsy specimens were obtained after complete allograft revascularization. The severity of ischemic damage was graded as follows: 0, none; 1, minimal; 2, mild; 3, moderate; and 4, severe. Grafts were defined as older when donor age was 50 years or older. Other independent variables examined included donor cause of death, length of hospital stay, acidosis, serum alanine aminotransferase level, graft cold ischemia time, and degree of steatosis. Older grafts were associated with higher grades of ischemic damage than younger grafts (2.3 +/- 1.0 v 1.3 +/- 1.1; P =.003). Univariate and multivariate analysis identified donor age of 50 years or older as the only significant predictive variable of the severity of ischemic damage. In 16 transplantations involving older grafts, there was no statistically significant association between the severity of ischemic damage and incidence of initial poor function and graft loss. The use of older liver grafts is associated with more extensive ischemic damage immediately after graft reperfusion. Whether this early lesion identifies among older graft recipients those at risk for a worst outcome remains to be determined.

Risk factors for the development of bacterial infections in hospitalized patients with cirrhosis

OBJECTIVE

Bacterial infection is a frequent and severe complication of cirrhosis. Cirrhotic patients admitted for gastrointestinal bleeding are at high risk of such a complication and have been targeted in trials of antibiotic prophylaxis. However, it has not been shown that these patients are at a higher risk than cirrhotic patients hospitalized for other reasons. This prospective study was performed to assess the risk of bacterial infection in unselected hospitalized cirrhotic patients and to evaluate possible risk factors for this complication.

METHODS

One hundred-forty hospitalized cirrhotic patients without clinical evidence of infection at the time of initial presentation were followed-up prospectively for manifestations of infection.

RESULTS

Twenty-eight (20%) patients developed an infection during their hospitalization. Infections without a specific site (39%) and spontaneous bacterial peritonitis (32%) were the most common diagnoses. Univariate analysis showed that patients who developed an infection were more likely to have a low serum albumin level, to be admitted for gastrointestinal bleeding, to stay in the intensive care unit, and to undergo therapeutic endoscopy. Logistic regression identified admission for gastrointestinal bleeding (odds ratio (OR) = 4.3, 95% confidence interval (CI) = 1.7-10.9) and a low serum albumin (OR = 1.3, 95% CI = 1.03-1.22) as the only two variables independently associated with the development of an infection.

CONCLUSION

The present study indicates that patients with severe cirrhosis who are admitted for gastrointestinal bleeding have a higher risk of developing a bacterial infection during their hospitalization than other cirrhotic patients.

Single- and multi-whisker channels in the ascending projections from the principal trigeminal nucleus in the rat

This study investigated the relationship between axonal projections and receptive field properties of whisker-sensitive cells in the principal trigeminal sensory nucleus of the rat. The labeling of small groups of trigeminothalamic axons with biotinylated dextran amine disclosed two broad classes of axons; a majority of fibers (68%; n = 107) project to a single barreloid of the ventral posteromedial nucleus, and the remaining group includes axons that innervate both the posterior group of the thalamus and the tectum. Additional terminal sites for axons of this latter group may include the pretectum, the zona incerta, the medial part of the medial geniculate nucleus, and the ventral posteromedial nucleus. Corresponding to these two classes of fibers, 67% of the cells in the principal trigeminal nucleus (n = 313) have single-whisker receptive fields, whereas the rest of the population have receptive fields composed of multiple whiskers. The tonic or phasic properties of the responses apparently bear no relation to the axonal projection patterns. Solid retrograde labeling of cells that project to the ventral posteromedial nucleus and intracellular staining revealed that single-whisker cells have small somata and narrow, barrelette-bounded dendritic trees. In contrast, multi-whisker neurons have large multipolar somata, expansive dendritic trees, and many respond antidromically to stimulation of the superior colliculus. Together, these results provide evidence for two main channels of vibrissal information: a single-whisker channel that links trigeminal barrelettes to their corresponding barreloids, and a multi-whisker channel that distributes principally in the posterior group and tectum.

Predictors of clinical response to transjugular intrahepatic portosystemic shunt (TIPS) in cirrhotic patients with refractory ascites

OBJECTIVE

Transjugular intrahepatic portosystemic shunt (TIPS) is used increasingly as a treatment for refractory ascites. The aim of the present study was to determine the prognostic value of different parameters in predicting a favorable evolution following TIPS in a cohort of 53 cirrhotic patients without organic renal disease and with refractory ascites.

METHODS

Patients were classified as good responders if they survived more than 6 months, without severe chronic hepatic encephalopathy and with good control of ascites. The prognostic value for a good outcome was evaluated using age, creatinine clearance, plasma renin activity, plasma aldosterone, and Pugh score.

RESULTS

Good control of ascites was obtained in 90%. The cumulative survival rate was 54% at 6 months, 48% at 1 yr, and 39% at 2 yr. The vast majority of patients died of complications of hepatic insufficiency. Severe chronic hepatic encephalopathy developed in 26%. Overall, a good clinical response was observed in 47%. Creatinine clearance was identified as the only pre-TIPS factor to be significantly and independently associated with a good clinical response to TIPS for refractory ascites. A good clinical response was observed in 57% of patients with a creatinine clearance >36 ml/min compared to 9% of those with a clearance <36 ml/min (p < 0.01). This cutoff point in creatinine clearance had a sensitivity of 96% and a specificity of 36%; positive predictive and negative predictive values were 57% and 90%, respectively.

CONCLUSIONS

TIPS might be useful for the treatment of refractory ascites in cirrhotic patients without severe renal function impairment. However, the TIPS usefulness still has to be demonstrated compared to large volume paracentesis or Leveen shunt. In patients with poor renal function or with liver failure after TIPS, liver transplantation should be considered.

Hepatitis C virus is related to progressive liver disease in human immunodeficiency virus-positive hemophiliacs and should be treated as an opportunistic infection

The hypothesis was investigated that hepatitis C virus (HCV) infection behaves like an opportunistic infection in which progressive liver disease (PLD) is the principal manifestation. PLD in 81 hemophiliacs coinfected with HCV and human immunodeficiency virus (HIV) was compared with 53 HIV-seronegative HCV-infected hemophiliacs. Progression to AIDS and death in 22 HCV/HIV-coinfected hemophiliacs with PLD was also compared with 59 coinfected hemophiliacs who did not develop PLD. The risk of PLD occurrence associated with an HIV-positive status was 7.4 (95% confidence interval [CI], 2.2-25.5; Cox model). In the coinfected group, the risk of PLD occurrence was higher in subjects with severe AIDS-defining immunodeficiency than in those without (odds ratio, 3. 6; 95% CI, 1.3-10). Persons with PLD also had a faster progression to AIDS (P=.03, log rank test) than those without PLD. Thus, as with other chronic resident human viruses, HCV should be considered another opportunistic pathogen in HIV disease.

The organization of corticothalamic projections: reciprocity versus parity

All neocortical areas receive inputs from and project back to the thalamus. It is often said that the corticothalamic projections are organized in a way that reciprocates the spatial distribution of thalamocortical pathways. The present review examines to what extent this rule of reciprocity is actually supported by the most recent neuroanatomical data, particularly those relating to the central organization of the vibrissal sensory system in the rat. A critical survey of previous studies is made and new results are presented concerning the fine-grained organization of corticothalamic projections in this sensory system. Together, prior results and the present set of new data confirm the existence of both, reciprocal and nonreciprocal patterns of corticothalamic connectivity. This conclusion leads us to propose that the spatial organization of corticothalamic connections complies with a more fundamental rule, the rule of parity, from which reciprocity follows as a general, but not obligatory consequence. The rule of parity states that the distribution of corticothalamic projections across and within the thalamic nuclei is determined by the branching patterns of the different classes of prethalamic afferents. The anatomical, developmental and physiological consequences of this rule are discussed. The rule of parity suggests that, according to the behavioral context, both prethalamic and corticothalamic pathways may function in a feedback mode.

Anatomical evidence for a mechanism of lateral inhibition in the rat thalamus

The aim of this study was to determine whether or not thalamic reticular nucleus (Rt) neurons form synaptic connections with the thalamocortical (TC) neurons from which they receive synaptic contacts. Therefore, we examined, in adult rats, the relationships between single TC and Rt neurons, which had been marked simultaneously with an anterograde/retrograde tracer (biocytin or Neurobiotin), using the extracellular or juxtacellular technique. (i) From 30 successful extracellular microapplications of marker into the Rt, 22 gave retrogradely marked TC somatodendritic arbors at the fringe of or clear outside the anterogradely darkly stained Rt axon terminal fields. Following biocytin application into the thalamus, few cells were retrogradely stained in the Rt at the periphery of the anterogradely labelled axon terminal field. (ii) The juxtacellular filling of a single Rt cell was accompanied by the back-filling of a single TC neuron (n = 4 pairs), which presumably formed synaptic contacts with the former cell. The somatodendritic complex of the back-filled TC neuron was located outside the Rt cell's axonal arbor. These anatomical data provide clear evidence that Rt and thalamic neurons predominantly form between themselves open rather than closed loop connections. Because TC neurons make glutamatergic synapses onto Rt cells, which are GABAergic, and are the first elements synaptically activated by prethalamic afferents into the TC-Rt network, the present results strongly support the hypothesis that Rt neurons principally generate a mechanism of lateral inhibition in the thalamus.

Early allograft dysfunction after liver transplantation: a definition and predictors of outcome. National Institute of Diabetes and Digestive and Kidney Diseases Liver Transplantation Database

BACKGROUND

Poor graft function early after liver transplantation is an important cause of morbidity and mortality. We defined early allograft dysfunction (EAD) using readily available indices of function and identified donor, graft, and pretransplant recipient factors associated with this outcome.

METHODS

This study examined 710 adult recipients of a first, single-organ liver transplantation for non-fulminant liver disease at three United States centers. EAD was defined by the presence of at least one of the following between 2 and 7 days after liver transplantation: serum bilirubin >10 mg/dl, prothrombin time (PT) > or =17 sec, and hepatic encephalopathy.

RESULTS

EAD incidence was 23%. Median intensive care unit (ICU) and hospital stays were longer for recipients with EAD than those without (4 days vs. 3 days, P = 0.0001; 24 vs. 15 days, P = 0.0001, respectively). Three-year recipient and graft survival were worse in those with EAD than in those without (68% vs. 83%, P = .0001; 61% vs. 79%, P = 0.0001). A logistic regression model combining donor, graft, and recipient factors predicted EAD better than models examining these factors in isolation. Pretransplant recipient elevations in PT and bilirubin, awaiting a graft in hospital or ICU, donor age > or =50 years, donor hospital stay >3 days, preprocurement acidosis, and cold ischemia time > or =15 hr were independently associated with EAD.

CONCLUSION

Recipients who develop EAD have longer ICU and hospital stays and greater mortality than those without. Donor, graft, and recipient risk factors all contribute to the development of EAD. Results of these analyses identify factors that, if modified, may alter the risk of EAD.

Projections to layer VI of the posteromedial barrel field in the rat: a reappraisal of the role of corticothalamic pathways

The present study bears on afferents that terminate in layer VI of the posteromedial barrel field in the rat. Their origin was determined by the retrograde transport of cholera toxin, and their axonal arborizations were revealed by targeting injections of biotinylated dextran amine in regions that contained retrogradely labeled neurons. Afferents to lamina VI arise from the thalamus (the ventral posteromedial, the posterior group and the intralaminar nuclei), the claustrum and the infragranular layers of other somatomotor regions of the neocortex (the motor, second somatosensory and perirhinal cortices). Among these afferent systems, corticocortical axons, particularly those issuing from the motor cortex, give rise to the most profuse projections in layer VI, whereas thalamic and claustral afferents form sparse terminal fields. Because corticothalamic cells represent approximately 50% of the neuronal population in lamina VI and 73% of their dendritic processes are deployed locally, it seems likely that afferents arising from the infragranular layers of the motor cortex may directly influence the firing of these neurons. These anatomical data suggest that the role of corticothalamic pathways should be studied from the viewpoint that sensory perception is an active process which operates under the guidance of motor activities.