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.

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.

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.

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.

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.

[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.

Projection and innervation patterns of individual thalamic reticular axons in the thalamus of the adult rat: a three-dimensional, graphic, and morphometric analysis

The gamma-aminobutyric acid-ergic thalamic reticular nucleus (Rt), which carries matching topographical maps of both the thalamus and cortex and in which constituent cells can synaptically communicate between each other, is the major extrinsic source of thalamic inhibitions and disinhibitions. Whether all the Rt axonal projections into the thalamus are similarly organized and have common projection and innervation patterns are questions of great interest to further our knowledge of the functioning of the Rt. The present study provides architectural and morphometric data of individual, anterogradely labeled axonal arbors that arose from distinct parts of the Rt. One hundred twenty-seven Rt neurons from all regions of Rt were marked juxtacellularly with biocytin or Neurobiotin in urethane-anesthetized adult rats. Eighteen two-dimensional and 14 three-dimensional reconstructions of single tracer-filled Rt neurons were made from serial, frontal, horizontal, or sagittal sections. Both the somatodendritic and axonal fields of tracer-filled Rt cells were mapped in three dimensions and illustrated to provide a complementary stereotaxic reference for future studies. Most marked units projected to a single nucleus of the anterior, dorsal, intralaminar, posterior, or ventral thalamus. Axons emerging from cells in distinct sectors of the Rt projected to distinct nuclei. Within a sector, neurons with separate dendritic fields innervated separate regions either in a single nucleus or into different but functionally related thalamic nuclei. Neurons with an overlap of their dendritic fields gave rise either to overlapping axonal arborizations or, more rarely, to distinct axonal arbors within two different thalamic nuclei implicated in the same function. In rare instances, an Rt axon could project within these two nuclei. Thalamic reticular axons commonly displayed a single well-circumscribed arbor containing a total of about 4,000 +/- 1,000 boutons. Every arbor was composed of a dense central core, which encompassed a thalamic volume of 5-63 x 10(6) microm3 and was made up of patches of maximal innervation density (10 +/- 4 boutons/tissue cube of 25 microm each side), surrounded by a sparse component. The metric relationships between the Rt axonal arbors and the dendrites of their target thalamocortical neurons were determined. Both the size and maximal innervation density of the axonal patches were found to fit in with the somatodendritic architecture of the target cells. The Rt axonal projections of adult rats are thus characterized by their (1) well-focused terminal field with a patchy distribution of boutons and (2) parallel organization with a certain degree of divergence. The role of the Rt-mediated thalamic inhibition and disinhibition may be to contrast significant with nonrelevant ongoing thalamocortical information.

Lack of relationship between preoperative measures of the severity of cirrhosis and short-term survival after liver transplantation

The purpose of this study was to evaluate the prognostic value of clinical measures of the severity of disease in cirrhotic patients who were candidates for liver transplantation at our institution. The records of the 132 cirrhotic patients who were candidates for a first transplantation between January 1, 1987, and December 31, 1994, were reviewed. One hundred nine patients (82.6%) received grafts, and 23 (17.4%) died while on the waiting list. The variables examined included level of medical urgency at the time of enlistment, date of transplantation, serum creatinine level, variables that constitute the Child-Pugh score and Shaw's risk score (serum bilirubin and albumin, prothrombin time, ascites, encephalopathy, nutritional status, age, and operative blood loss), and 6-month survival status after transplantation. The proportion of patients who died awaiting a graft increased as a function of the Child-Pugh score at enlistment (score 5-6, 0%, n = 6; score 7-9, 7%, n = 54; score 10-11, 18%, n = 33; score 12-15, 33%, n = 39; P = .01). Six-month survival rates after transplantation were similar irrespective of the Child-Pugh score or Shaw's risk score. Stepwise multiple logistic regression models identified the degree of ascites, serum bilirubin, and operative blood loss as significant variables for the prediction of overall mortality 6 months posttransplantation (model chi 2 = 12.8; P = .025; r = 0.32), but the model explained only 10% of the outcomes observed. We concluded that the Child-Pugh score is a valid prognostic index for survival up to the time of transplantation for cirrhotic patients on the waiting list; however, clinical measures of the severity of cirrhosis are poor predictors of 6-month survival after transplantation.

Intracortical axonal projections of lamina VI cells of the primary somatosensory cortex in the rat: a single-cell labeling study

A sample of 84 neurons in lamina VIa of rat somatosensory cortex (S1) was juxtacellularly labeled with biocytin, and the axons of the neurons were traced. Three classes of cells were identified as corticothalamic, corticocortical, and local circuit neurons. Corticothalamic cells (46%) are small, short pyramids projecting either to the ventral posteromedial nucleus alone or to the posterior group as well. The former are in upper lamina VI, have apical dendrites terminating in layer IV, and have intracortical collaterals ascending to layer IV as a narrow column about the size of a barrel. The latter are in the lower half of lamina VI, have apical dendrites terminating in layer V, and have a more extensive network of collaterals terminating in the upper part of lamina V. Corticothalamic cells do not project to distant cortical targets through branching axons. Corticocortical cells (44%) are small, short pyramids, inverted or modified pyramids, or bipolar spiny neurons. They send collaterals principally to infragranular layers of S1 and branches to the second somatosensory cortex, the motor cortex, or the corpus callosum. Local circuit neurons (10%) are basket cells, concentrated in upper lamina VI, having smooth, beaded dendrites and a rich collateral network densely covered with varicosities in layers V and VI. We conclude that (1) dendritic morphology and axonal arborizations of corticothalamic cells relate to the projection target; (2) many apparently diverse layer VI cells project to other cortical fields; and (3) lamina VI is a network for corticothalamic and corticocortical communication.

Dendrodendritic and axoaxonic synapses in the thalamic reticular nucleus of the adult rat

Currently, it is believed that cell-cell communications occur in the thalamic reticular nucleus (RT) during thalamocortical operations, but the anatomical substrate underlying these intrinsic interactions has not been characterized fully in the rat yet. To further our knowledge on this issue, we stained juxtacellularly rat RT neurons with biocytin or Neurobiotin and examined their intrinsic axon collaterals and "axon-like processes" at both light and electron microscopic levels. Of 111 tracer-filled RT cells for which the axon could be followed from its origin up to the thalamus, 12 displayed short-range, poorly ramifying varicose local axon collaterals, which remained undistinguishable from parent distal dendrites, raising the question as to whether their varicosities were presynaptic terminals. Correlated light and electron microscopic observations of the proximal part of these intrinsic varicose axonal segments revealed that their varicosities and intervaricose segments were, in fact, postsynaptic structures contacted by a large number of boutons that, for the most, formed asymmetric synapses and were nonimmunoreactive for GABA. Similarly, the so-called "axon-like processes" stemming from the soma or dendrites also were identified as postsynaptic structures. Two unexpected observations were made in the course of this analysis. First, the hillock and initial segment of some RT axons were found to receive asymmetric synaptic inputs from GABA-negative terminals. Second, examination of serial ultrathin sections of dendritic bundles cut in their longitudinal plane revealed the existence of several short symmetric dendrodendritic synapses and numerous puncta adhaerentia between component dendrites. In conclusion, dendrodendritic junctions might be a prominent anatomical substrate underlying interneuronal communications in the RT of the adult rat. Furthermore, excitatory axoaxonic synapses on the axon hillock, initial segment, and local axon collaterals might represent a powerful synaptic drive for synchronizing the firing of RT neurons. Future studies are essential to verify whether excitatory axoaxonic synapses with the axon hillock are a general feature in the RT.

A single-cell study of the axonal projections arising from the posterior intralaminar thalamic nuclei in the rat

Thalamostriatal projections arising from the posterior intralaminar nuclei (P1; the parafascicular nucleus and the adjacent caudalmost part of the posterior thalamic group) were studied in rats by tracing the axons of small pools of neurons labelled anterogradely with biocytin. Thirteen P1 cells were also stained by juxta cellular application of the tracer. Relay cells of P1 nuclei have a morphology that differs radically from the classical descriptions of the bushy cells which represent the main neuronal type of the sensory thalamic relay nuclei. P1 cells have ovoid or polygonal somata of approximately 20-25 microm, from which emerge four or five thick, long and poorly branched dendrites bearing spines and filamentous appendages; their dendritic domains extend for up to 1.5 mm. Before leaving the nucleus 20% of axons give off collaterals that ramify locally. All axons course through the thalamic reticular nucleus, where they also distribute collaterals, and arborize massively in the striatum and sparsely in the cerebral cortex. At the striatal level four or five collaterals leave the main axon and terminate in patches scattered dorsoventrally within a rostrocaudally oriented slab. As revealed by calbindin D-28k immunohistochemistry, only the matrix compartment receives terminations from P1 axons. The cortical branch form small terminal puffs centred upon layer VI of the motor cortex. Before entering the striatum some axons of the parafascicular nucleus give rise to descending collaterals that arborize in the entopeduncular nucleus, in the subthalamic nucleus and in the vicinity of the red nucleus. Other axons arising from the caudal part of the posterior group send descending branches only to the entopeduncular nucleus. These findings show that P1 cells belong to a distinct category of thalamic relay neurons which, beside their massive projection to the striatum, also distribute collaterals to other components of the basal ganglia. Moreover, these results provide the first direct evidence that virtually all P1 cells project to both striatum and cerebral cortex. Finally, it is proposed on the basis of morphological, histochemical and hodological criteria that the caudal part of the posterior thalamic group in the rat is homologous to the suprageniculate-limitans nuclei of cats and primates.

Two different types of thalamic fibers innervate the rat striatum

Thalamostriatal projections were studied in rats by tracing the axons of small pools of thalamic neurons labeled anterogradely with biocytin. Single-cell mapping of these projections revealed two types of thalamostriatal fibers. The first type arises from the bushy relay cells of the central lateral and associative thalamic nuclei which arborize sparsely in the striatum by means of long varicose axon collaterals. The second type of fiber arises from large, reticular-like, relay cells located in the parafascicular and ethmoid nuclei. These latter fibers form dense clusters of terminations within the striatum and they also send branches to other components of the basal ganglia. These different morphological features suggest that the two types of fibers subserve different functions.

Toxic megacolon complicating pseudomembranous enterocolitis

PURPOSE

Toxic megacolon is a rare complication of pseudomembranous enterocolitis. We reviewed our recent experience with this complication.

METHODS

The first five patients of the series were studied retrospectively, and six others were followed prospectively.

RESULTS

Between June 1992 and May 1994, 11 patients (8 male, 3 female) developed toxic megacolon secondary to pseudomembranous enterocolitis. Mean age was 60.7 +/- 11.8 (range, 40-79) years. Presenting symptoms and signs included diarrhea, 100 percent; malaise, 91 percent; abdominal pain, 82 percent; abdominal distention, 82 percent; abdominal tenderness, 72 percent; anemia less than 12 gm, 72 percent; albumin less than 3 gm, 64 percent; tachycardia greater than 100, 55 percent; fever greater than 38.5 degrees celsius, 45 percent; shock or hypotension, 45 percent. Predisposing factors included antibiotics, 64 percent; immunosuppressants or chemotherapy, 36 percent; antidiarrheals, 27 percent; and barium enema in one patient. Five patients (45 percent) had more than one predisposing factor. X-rays showed transverse colon dilation and loss of haustrations in eight patients (72 percent), with a mean diameter of 9.9 +/- 3.4 cm. Flexible proctosigmoidoscopy showed pseudomembranes in all scoped patients, and toxin assay for Clostridium difficile was positive in all patients. One patient had emergency surgery. Ten patients were initially treated medically with nasogastric suction and intravenous resuscitation (90 percent) and antibiotics (100 percent), usually in the intensive care unit (80 percent). Four patients did not respond and underwent surgery; two others improved, then deteriorated, and also underwent surgery. Altogether, 7 of 11 patients (64 percent) underwent surgery. Three patients (27 percent) responded well to medical treatment. One patient was deemed too ill to undergo surgery and died. Mean delay to surgery was 3.0 +/- 1.3 days. No sealed or overt perforation was found at laparotomy. All patients who underwent surgery had a subtotal colectomy, with either a Hartmann's stump (71 percent) or a mucous fistula (29 percent). Eventually, five of seven patients who were operated on and two of four medically treated patients died (overall mortality, 64 percent). Only one patient underwent closure of ileostomy and anastomosis.

CONCLUSION

Toxic megacolon complicating pseudomembranous enterocolitis is a serious problem that carries a high morbidity and mortality rate, regardless of treatment.

Corticothalamic projections from the primary visual cortex in rats: a single fiber study using biocytin as an anterograde tracer

This study investigates the pattern of axonal projections of single corticothalamic neurons from the rat primary visual cortex. Microiontophoretic injections of biocytin were made in cortical laminae V and VI to label small pools of corticothalamic cells and their intrathalamic axonal projections. After a survival period of 48 h, the animals were perfused and the tissue was processed for biocytin histochemistry. On the basis of the intrathalamic distribution of axonal fields and the types of terminations found in the thalamus, three types of corticothalamic projections were identified. (1) Cells of the upper part of lamina VI projected to the dorsal lateral geniculate nucleus where they arborized in rostrocaudally oriented bands or "rods" parallel to the lines of projection of retinal afferents. (2) Cells of the lower part of lamina VI projected to the lateral part of the lateral posterior nucleus and they also sent collaterals to the dorsal lateral geniculate nucleus where they participated in the formation of rods. (3) The corticothalamic projection of lamina V cells originated from collaterals of corticofugal cells whose main axons reached the tectum and/or the pontine nuclei. These collaterals never terminated within the dorsal lateral geniculate nucleus; they arborized in the lateral posterior, lateral dorsal and ventral lateral geniculate nuclei. All corticothalamic cells from lamina VI displayed the same type of axonal network made of long branches decorated by terminal boutons emitted "en passant" at the tip of fine stalks. Corticothalamic fibers arising from lamina V, however, generated varicose endings in restricted regions of their target nuclei. All corticothalamic axons derived from lamina VI cells, but not those derived from lamina V cells, gave off collaterals as they traversed the thalamic reticular complex. These results demonstrate that corticothalamic fibers arising from the rat primary visual cortex display a lamina-dependent projection pattern. In the light of previous studies on the topographical organization of corticothalamic projections, it is proposed that a similar organizational plan characterizes corticothalamic relationships in other sensory systems in the rat and in other species.

Thalamic reticular input to the rat visual thalamus: a single fiber study using biocytin as an anterograde tracer

This study describes the axonal projections of single thalamic reticular (TR) neurons within the visual thalamus in rats. Experiments were performed under urethane anesthesia and reticular cells were labeled by extracellular or juxtacellular microiontophoretic applications of biocytin. The axonal arborizations of 19 TR cells projecting to the dorsal lateral geniculate nucleus (DLG) or to the lateral dorsal/lateral posterior complex (LD/LP) were reconstructed from serial horizontal sections. It was found that single TR cells projected within the limits of a single thalamic nucleus, either the DLG or the LD/LP complex, where their terminal fields formed rostrocaudally oriented rods (length: approximately 800 microns; diameter: approximately 100 microns) densely packed with grape-like boutons and varicosities. In addition, none of the labeled TR cells possessed recurrent axonal collaterals that ramified within the reticular complex itself. The functional implications of these morphological data for the synchronization of thalamic oscillations are discussed.

The axonal arborization of single thalamic reticular neurons in the somatosensory thalamus of the rat

This study describes the axonal projections of single neurons of the thalamic reticular complex within the somatosensory thalamic nuclei in rats. Experiments were performed under urethane anaesthesia and reticular cells were labelled by extracellular microiontophoretic applications of biocytin. The axonal arborization of 25 thalamic reticular cells projecting to the ventrobasal (VB) nucleus and/or to the posterior thalamic (Po) complex were reconstructed from serial horizontal sections. Reticular cells labelled with biocytin display somatodendritic features similar to those reported previously. Their cell body is fusiform and their dendrites bear few spines and show a high degree of streaming along the horizontal curved axis of the nucleus. In most cells, axon-like beaded processes stem out from dendrites but, contrary to previous descriptions, no intrareticular axonal collateral was observed. The axonal arborization of most thalamic reticular cells is confined within the limits of a single thalamic nucleus; only two neurons were seen projecting to both the VB and the Po nuclei. In VB, termination fields form short rods (diameter approximately 150 microns, length approximately 200-300 microns) densely packed with grape-like boutons and varicosities; termination fields in Pro are larger, much less dense, and they are contained within a horizontal slab of tissue (thickness approximately 200 microns, mediolateral width approximately 400 microns, rostrocaudal length approximately 1 mm. By charting the position of all labelled cells within the thickness of the thalamic reticular complex, a strip-like arrangement was revealed. Cells projecting to Po occupy the innermost portion of the nucleus whereas those projecting to the ventral-posteromedial and ventral-posterolateral nuclei are located respectively in the middle and in the outer tiers of the nucleus. This strip-like reciprocity was confirmed by separate biocytin injections performed in VB and in Po. These results show that inhibition of reticular origin is distributed within the rat dorsal thalamus in a highly specific manner, most likely according to a principle of reciprocity within the somatotopic representation of the body.

Corticothalamic projections from the cortical barrel field to the somatosensory thalamus in rats: a single-fibre study using biocytin as an anterograde tracer

This study investigated the pattern of axonal projections of single corticothalamic neurons from the cortical barrel field representing the vibrissae in the rat. Microiontophoretic injections of biocytin were performed in cortical layers V and VI to label small pools of corticothalamic cells and their intrathalamic axonal projections. After a survival period of 48 h, the animals were perfused and the tissue was processed for biocytin histochemistry. On the basis of the intrathalamic distribution of axonal fields and of the types of terminations found in the thalamus, four types of corticothalamic projections were identified. (i) Cells of the upper part of layer VI projected exclusively to the ventral posteromedial (VPm) nucleus, where they arborized in long rostrocaudally oriented bands or 'rods'. (ii) All cells of the lower part of layer VI projected to the medial part of the thalamic posterior group (Pom) but the vast majority of them also collateralized in VPm where they participated in the formation of rods. (iii) A minority of corticothalamic cells in the lower portion of layer VI, possibly located under the interbarrel spaces (septae), arborized exclusively in Pom. (iv) The corticothalamic projection of layer V cells originated from collaterals of corticofugal cells whose main axons ran caudally towards the brainstem. These collaterals arborized exclusively in Pom or in the central lateral nucleus. All corticothalamic cells from layer VI displayed the same type of axonal network, made of long branches decorated by terminal buttons emitted en passant at the tip of fine stalks. Corticothalamic fibres arising from layer V pyramids, however, remained smooth as they ran across the lateral thalamus and they generated in Pom one or two clusters of large boutons. All corticothalamic axons derived from layer VI cells, but not those derived from layer V cells, gave off collaterals as they traversed the thalamic reticular complex. These observations are discussed in the light of previous studies bearing on the topological organization and function of corticothalamic projections to VPm and Pom in rats. The possibility that a similar cellular specificity and a similar organizational plan may characterize corticothalamic relationships in other sensory systems is also considered.

Corticothalamic projections from layer V cells in rat are collaterals of long-range corticofugal axons

The vast majority of corticothalamic (CT) axons projecting to sensory-specific thalamic nuclei arise from layer VI cells but intralaminar and associative thalamic nuclei also receive, to various degrees, a cortical input from layer V pyramidal cells. It is also well established that all long-range corticofugal projections reaching the brainstem and spinal cord arise exclusively from layer V neurons. These observations raise the possibility that the CT input from layer V cells may be collaterals of those long-range axons projecting below thalamic level. The thalamic projections of layer V cells were mapped at a single cell level following small microiontophoretic injections of biocytin performed in the motor, somatosensory and visual cortices in rats. Camera lucida reconstruction of these CT axons revealed that they are all collaterals of long-range corticofugal axons. These collaterals do not give off axonal branches within the thalamic reticular nucleus and they arborize exclusively within intralaminar and associative thalamic nuclei where they from small clusters of varicose endings. As layer V cells are involved in motor commands everywhere in the neocortex, these CT projections and their thalamic targets should be directly involved in the central organization of motor programs.

The behavior of mossy cells of the rat dentate gyrus during theta oscillations in vivo

Intracellular current clamp recordings were obtained from mossy cells (n = 6, identified by intracellular injection of biocytin) of the dorsal dentate gyrus from rats under ketamine-xylazine anesthesia. During electroencephalographic theta rhythm (4-6 Hz), recorded with a macroelectrode placed in the contralateral dorsal hippocampus near the fissure, mossy cells displayed intracellular membrane potential oscillations at low frequencies (4-6 Hz) which appeared to be phase locked to the electroencephalographic theta rhythm. The frequency of the intracellular theta rhythm was independent of the membrane potential. However, the phase difference between the intracellular and the electroencephalographic theta rhythms as well as the amplitude of the intracellular theta oscillations were voltage-dependent. These findings are consistent with the hypothesis that rhythmic GABAA receptor-mediated inhibitory postsynaptic potentials contribute to the genesis of the intracellular theta rhythm. Indeed, mossy cells displayed an early, fast inhibitory postsynaptic potential in response to electrical stimulation of the entorhinal cortex, which most likely represents a GABAA receptor-mediated event, indicating that mossy cells possess functional GABAA receptors. At the resting membrane potential, mossy cells did not fire at each cycle of the electroencephalographic theta rhythm but fired only rarely (< 1 Hz). However, when they did fire they did so preferentially in phase with the peak positivity of the electroencephalographic theta rhythm. Reconstruction of two mossy cells with axonal projections to the inner molecular layer showed that the spatial extent of the influence such weakly discharging mossy cells may have on other dentate gyrus neurons during theta oscillations can be several millimeters in the septotemporal direction. In conclusion, these findings show that mossy cells of the rat hilus during ketamine-xylazine anesthesia participate in theta oscillations of the hippocampal formation, during which their low-frequency firing may contribute to the phase-locking of a large number of spatially distributed postsynaptic neurons with postsynaptic sites in the inner molecular layer of the dentate gyrus.