Predictive Model for Positive Video Capsule Endoscopy in Iron Deficiency Anemia

BACKGROUND AND AIMS

Bleeding from the gastrointestinal tract can contribute to the development of iron deficiency anemia (IDA) among individuals without another obvious source of bleeding. In order to identify patients most likely to benefit from examination of the small bowel, our aim was to create a risk score for positive video capsule endoscopy (VCE) in IDA utilizing a multicenter collection of studies.

METHODS

We performed a retrospective multicenter study utilizing VCE studies performed for an indication of IDA between 1/1/2005 and 7/31/2018. VCE findings were graded based on the P0-P2 grading system. The primary outcome of interest was a positive (P2) VCE. Data were analyzed with Student's t test for continuous variables and the Fisher's exact test for categorical variables. Logistic regression was used to identify independent associations with positive VCE.

RESULTS

In total, 765 VCE procedures were included with 355 (46.5%) male subjects and a median age of 63.2 (SD 15.3) years. One hundred ninety studies (24.8%) were positive (P2) for small bowel bleeding. Four variables associated with positive VCE which were incorporated into a point scoring system: (+) 1 for age ≥ 66 years, active smoking and cardiac arrythmia and (-) 1 for preceding hemoglobin level ≥ 8.5. The risk probabilities for positive VCE-assigned scores - 1, 0, 1, and 2 + were 12.3% (95% CI 7.3-17.3%), 20% (14.9-25.1%), 34.8% (28.6-41%), and 39% (30-47.8%).

CONCLUSION

In order to improve the diagnostic yield of capsule examinations, risk factors should be applied to clinical decision-making. We created a risk score for positive VCE in IDA, including the risk factors of age, smoking, history of cardiac arrythmia, and preceding hemoglobin level.

Intracranial Hemorrhage in Term and Late-Preterm Neonates: An Institutional Perspective

BACKGROUND AND PURPOSE

Distribution of intracranial hemorrhage in term and late-preterm neonates is relatively unexplored. This descriptive study examines the MR imaging-detectable spectrum of intracranial hemorrhage in this population and potential risk factors.

MATERIALS AND METHODS

Prevalence and distribution of intracranial hemorrhage in consecutive term/late-preterm neonates who underwent brain MR imaging between January 2011 to August 2018 were assessed. MRIs were analyzed to determine intracranial hemorrhage distribution (intraventricular, subarachnoid, subdural, intraparenchymal, and subpial/leptomeningeal), and chart review was performed for potential clinical risk factors.

RESULTS

Of 725 term/late-preterm neonates who underwent brain MR imaging, intracranial hemorrhage occurred in 63 (9%). Fifty-two (83%) had multicompartment intracranial hemorrhage. Intraventricular and subdural were the most common hemorrhage locations, found in 41 (65%) and 39 (62%) neonates, respectively. Intraparenchymal hemorrhage occurred in 33 (52%); subpial, in 19 (30%); subarachnoid, in 12 (19%); and epidural, in 2 (3%) neonates. Twenty infants (32%) were delivered via cesarean delivery, and 5 (8%), via instrumented delivery. Cortical vein thromboses were present in 34 (54%); periventricular or medullary vein thromboses, in 37 (59%); and cerebral venous sinus thrombosis, in 5 (8%). Thirty-seven (59%) had elevated markers of coagulopathy (international normalized ratio > 1.2, fibrinogen level < 234), 9 (14%) had a clinically meaningful elevation in the international normalized ratio (>1.4), and 3 (5%) had a clinically meaningful decrease in the fibrinogen level (<150). Three (5%) neonates had thrombocytopenia (platelet count < 100 × 103/μL).

CONCLUSIONS

While relatively infrequent, there was a wide distribution of intracranial hemorrhage in term and late-preterm infants; intraventricular and subdural hemorrhages were the most common types. We report a high prevalence of venous congestion or thromboses accompanying neonatal intracranial hemorrhage.

Surveillance Recommendation for Colonoscopy after Polypectomy

The incidence and mortality of colorectal cancer (CRC) have declined over the past several decades, largely due to improvement and uptake in screening, particularly with colonoscopy. The US Multi-Society Task Force on CRC published guidelines for surveillance after polypectomy in 2012, which were updated in 2020 with some important changes, and this review will provide an updated overview of evidence and outcomes of surveillance after polypectomy. Notable modifications to surveillance guidelines include increasing interval time between colonoscopies from 5 to 7 to 10 years for 1 to 2 low-risk adenomas (<10 mm) and from 3 years to 3 to 5 years when 3 to 4 low-risk adenomas are identified.

Analysis of Speaker Introduction Formality by Gender at the American College of Gastroenterology 2020 Annual Scientific Meeting

BACKGROUND

Gender-based differences in the use of professional titles during speaker introductions have been described in other medical specialties.

AIMS

Our primary aim was to assess gender-based differences in the formality of speaker introductions at the American College of Gastroenterology 2020 Virtual Annual Scientific Meeting. Our secondary aim was to assess gender-based differences in the formality of speaker self-introductions.

METHODS

Reviewed presentations from the American College of Gastroenterology Annual Meeting for gender-based differences in professional title use during speaker introductions and self-introductions.

RESULTS

Speakers included 29 women (37.2%) and 49 men (62.8%). We found no significant gender differences in the use of professional titles by introducers (t(67) = -  0.775, p = 0.441) or in self-introductions (36.4% of women vs. 41.9% of men, t(63) = 0.422, p = 0.674).

CONCLUSION

The lack of gender differences in professional title use may represent a novel advantage of virtual meeting formats or suggest increased attention to gender bias in introductions.

Upregulation of polycistronic microRNA-143 and microRNA-145 in colonocytes suppresses colitis and inflammation-associated colon cancer

Because ADAM17 promotes colonic tumorigenesis, we investigated potential miRNAs regulating ADAM17; and examined effects of diet and tumorigenesis on these miRNAs. We also examined pre-miRNA processing and tumour suppressor roles of several of these miRNAs in experimental colon cancer. Using TargetScan, miR-145, miR-148a, and miR-152 were predicted to regulate ADAM17. miR-143 was also investigated as miR-143 and miR-145 are co-transcribed and associated with decreased tumour growth. HCT116 colon cancer cells (CCC) were co-transfected with predicted ADAM17-regulating miRNAs and luciferase reporters controlled by ADAM17-3'UTR. Separately, pre-miR-143 processing by colonic cells was measured. miRNAs were quantified by RT-PCR. Tumours were induced with AOM/DSS in WT and transgenic mice (Tg) expressing pre-miR-143/miR-145 under villin promoter. HCT116 transfection with miR-145, -148a or -152, but not scrambled miRNA inhibited ADAM17 expression and luciferase activity. The latter was suppressed by mutations in ADAM17-3'UTR. Lysates from colonocytes, but not CCC, processed pre-miR-143 and mixing experiments suggested CCC lacked a competency factor. Colonic miR-143, miR-145, miR-148a, and miR-152 were downregulated in tumours and more moderately by feeding mice a Western diet. Tg mice were resistant to DSS colitis and had significantly lower cancer incidence and tumour multiplicity. Tg expression blocked up-regulation of putative targets of miR-143 and miR-145, including ADAM17, K-Ras, XPO5, and SET. miR-145, miR-148a, and miR-152 directly suppress colonocyte ADAM17 and are down-regulated in colon cancer. This is the first direct demonstration of tumour suppressor roles for miR-143 and miR-145 in an in vivo model of colonic tumorigenesis.

Management of code status in the periendoscopic period: a national survey of current practices and beliefs of U.S. gastroenterologists

BACKGROUND AND AIMS

This study aims to assess current practices and perspectives of gastroenterologists on approaches to code status before inpatient endoscopy.

METHODS

Self-reported data were obtained through a voluntary, anonymous survey of gastroenterologists and gastroenterology trainees in the United States. The survey assessed respondents' approach to, beliefs, and knowledge regarding inpatient periprocedural code status discussions.

RESULTS

Four hundred thirty-six gastroenterologists and 83 trainees completed the survey. For patients with an existing do not resuscitate (DNR) order, respondents reversed the code status before endoscopy either all (40.8%, n = 212) or most of the time (18.3%, n = 95). When asked their personal opinion, 32.6% (n =169) supported automatic DNR reversal to full resuscitation attempt during a procedure, 18.5% (n = 96) supported that DNR orders could be sustained, and 48.7% (n = 253) supported offering limited resuscitation. Many gastroenterologists were unaware of institutional (40.7%, n = 211) or national (80.7%, n = 419) policies, and a majority reported that a gastroenterology-specific guideline would be helpful (88.6%, n = 460).

CONCLUSIONS

Although most of the gastroenterologists reverse DNR orders more than 75% of the time before endoscopy, many also believe patients should be allowed to remain DNR during a procedure and supported a third option for limited resuscitation. Most gastroenterologists were unaware of institutional policies or existing national guidelines. These findings suggest considerable variation in knowledge and current approaches regarding periendoscopic code status reversal.

Celiac Disease and Its Role in the Development of Metabolic Bone Disease

Celiac disease (CD) is an immune-mediated enteropathy that occurs in genetically susceptible hosts with the ingestion of gluten-containing products. Ongoing gluten consumption leads to intestinal damage, characterized by villous blunting and increased intraepithelial lymphocytes, resulting in malabsorption. Pertinent to the development of bone disease, malabsorption of calcium and vitamin D leads to secondary hyperparathyroidism and metabolic bone disease among individuals with CD. In this article, we review the pathogenesis of CD and the effects of malabsorption on bone health. Imbalances in bone resorption and formation particularly in individuals with CD and persistent disease activity ultimately lead to a state of bone loss and impaired mineralization. Initiation of a gluten-free diet is critical in the management of CD-related metabolic bone disease, demonstrating improvements in bone mineral density within the first year of dietary adherence.

Predictors of mortality and endoscopic intervention in patients with upper gastrointestinal bleeding in the intensive care unit

Background

The outcomes of patients undergoing esophagogastroduodenoscopy (EGD) in the intensive care unit (ICU) for upper gastrointestinal bleeding (UGIB) are not well described. Our aims were to determine predictors of 30-day mortality and endoscopic intervention, and assess the utility of existing clinical-prediction tools for UGIB in this population.

Methods

Patients hospitalized in an ICU between 2008 and 2015 who underwent EGD were identified using a validated, machine-learning algorithm. Logistic regression was used to determine factors associated with 30-day mortality and endoscopic intervention. Area under receiver-operating characteristics (AUROC) analysis was used to evaluate established UGIB scoring systems in predicting mortality and endoscopic intervention in patients who presented to the hospital with UGIB.

Results

A total of 606 patients underwent EGD for UGIB while admitted to an ICU. The median age of the cohort was 62 years and 55.9% were male. Multivariate analysis revealed that predictors associated with 30-day mortality included American Society of Anesthesiologists (ASA) class (odds ratio [OR] 4.1, 95% confidence interval [CI] 2.2-7.9), Charlson score (OR 1.2, 95% CI 1.0-1.3), and duration from hospital admission to EGD (OR 1.04, 95% CI 1.01-1.07). Rockall, Glasgow-Blatchford, and AIMS65 scores were poorly predictive of endoscopic intervention (AUROC: 0.521, 0.514, and 0.540, respectively) and in-hospital mortality (AUROC: 0.510, 0.568, and 0.506, respectively).

Conclusions

Predictors associated with 30-day mortality include ASA classification, Charlson score, and duration in the hospital prior to EGD. Existing risk tools are poorly predictive of clinical outcomes, which highlights the need for a more accurate risk-stratification tool to predict the benefit of intervention within the ICU population.

Can reporting more lead to less? The role of metrics in assessing liver transplant program performance

Appropriate metrics for performance analysis is an active topic of debate within the transplant community. This study explores current proposals on metric expansion as well as potential metrics and prospective collaborations that have not received widespread discussion within the transplant community. The premature introduction of additional, nonvalidated metrics risks behaviors that may undermine donor utilization and patient access to transplantation.

Risk factors for small bowel bleeding in an overt gastrointestinal bleeding presentation after negative upper and lower endoscopy

INTRODUCTION

A small bowel source is suspected when evaluation of overt gastrointestinal (GI) bleeding with upper and lower endoscopy is negative. Video capsule endoscopy (VCE) is the recommended next diagnostic test for small bowel bleeding sources. However, clinical or endoscopic predictive factors for small bowel bleeding in the setting of an overt bleeding presentation are unknown. We aimed to define predictive factors for positive VCE among individuals presenting with overt bleeding and a suspected small bowel source.

METHODS

We included consecutive inpatient VCE performed between September 1, 2012 to September 1, 2015 for melena or hematochezia at two tertiary centers. All patients had EGD and colonoscopy performed prior to VCE. Patient demographics, medication use, and endoscopic findings were retrospectively recorded. VCE findings were graded based on the P0-P2 grading system. The primary outcome of interest was a positive (P2) VCE. The secondary outcome of interest was the performance of a therapeutic intervention. Data were analyzed with the Fisher exact test for dichotomous variables and logistic regression.

RESULTS

Two hundred forty-three VCE were reviewed, and 117 were included in the final analysis. A positive VCE (P2) was identified in 35 (29.9%) cases. In univariate analysis, a positive VCE was inversely associated with presence of diverticula on preceding colonoscopy (OR: 0.44, 95% CI: 0.2-0.99), while identification of blood on terminal ileal examination was associated with a positive VCE (OR: 5.18, 95% CI: 1.51-17.76). In multivariate analysis, only blood identified on terminal ileal examination remained a significant risk factor for positive VCE (OR: 6.13, 95% CI: 1.57-23.81). Blood on terminal ileal examination was also predictive of therapeutic intervention in both univariate (OR: 4.46, 95% CI: 1.3-15.2) and multivariate analysis (OR: 5.04, 95% CI: 1.25-20.32).

CONCLUSION

Among patients presenting with overt bleeding but negative upper and lower endoscopy, the presence of blood on examination of the terminal ileum is strongly associated with a small bowel bleeding source as well as with small bowel therapeutic intervention. Presence of diverticula on colonoscopy is inversely associated with a positive VCE and therapeutic intervention in univariate analysis.

Risk Factors for Clostridium difficile Isolation in Inflammatory Bowel Disease: A Prospective Study

INTRODUCTION

Clostridium difficile is the most commonly isolated stool pathogen in inflammatory bowel disease (IBD). Traditional risk factors for C. difficile may not exist in patients with IBD, and no prior studies have assessed the risk factors for the isolation of C. difficile in both symptomatic and asymptomatic IBD outpatients.

METHODS

We prospectively recruited consecutive IBD patients presenting to our outpatient clinic between April 2015 and February 2016. We excluded patients with a diverting ostomy or ileoanal pouch. Demographics, healthcare exposures, medical therapies and disease activity were recorded from medical charts or surveys. A rectal swab was performed from which toxigenic culture and PCR analysis for the presence of toxin and fluorescent PCR ribotyping were performed. The primary outcome of interest was isolation of toxigenic C. difficile.

RESULTS

A total of 190 patients were enrolled in this prospective study including 137 (72%) with Crohn's disease and 53 (28%) with ulcerative colitis. At the time of enrollment, 69 (36%) had clinically active disease. Sixteen (8.4%) patients had toxigenic C. difficile isolated on rectal swab at enrollment and four (2.1%) patients had non-toxigenic C. difficile cultured. Mixed infection with more than one toxigenic isolate was present in 5/16 (31.3%) individuals. Patients with CD with a toxin positive isolate were more likely to have a history of CDI in the past 12 months (40 vs. 11.02%, p = 0.027) and an emergency department visit in the past 12 weeks (50 vs. 20.63%, p = 0.048). In UC, individuals with isolation of C. difficile were more likely to be hospitalized within the past 12 months (66.6 vs. 8.51%, p = 0.003). C. difficile isolation at the time of presentation was not associated with a subsequent disease relapse over a 6-month period in CD (p = 0.557) or UC (p = 0.131).

CONCLUSION

Healthcare exposures remain a significant risk factor for C. difficile isolation in the IBD population; however, this was not associated with relapse of disease. Further studies assessing the clinical significance of C. difficile isolation is warranted in IBD.

Vedolizumab in patients with concurrent primary sclerosing cholangitis and inflammatory bowel disease does not improve liver biochemistry but is safe and effective for the bowel disease

BACKGROUND

Blocking of lymphocyte trafficking to bile ducts is a potential mechanism to alter the disease course of patients with primary sclerosing cholangitis (PSC).

AIM

To describe the effect of the α₄ β₇ integrin antibody, vedolizumab, on liver biochemistry and disease activity in patients with PSC and inflammatory bowel disease (IBD).

METHODS

This is a retrospective multi-centre study of adult patients with a diagnosis of both IBD and PSC. The primary outcome was change in serum alkaline phosphatase level at weeks 14 and 30. Secondary outcomes included changes in other liver biochemistries and in clinical outcomes for the bowel disease. A safety analysis for adverse events was performed.

RESULTS

Thirty-four patients (16 Crohn's disease, 18 ulcerative colitis) were included. Nine (26%) had a history of liver transplant. Median follow-up on vedolizumab was 9 months (IQR: 7-16). There was no overall change in serum alkaline phosphatase level with vedolizumab therapy (median 268 [IQR: 105-551] IU/L at baseline versus 249 [IQR: 183-634] IU/L, P = 0.99 at week 30). No significant changes in other liver biochemistries or the Mayo PSC Risk Score were demonstrated at week 30. Clinical remission was achieved at week 30 in 55% of Crohn's disease and 29% of ulcerative colitis patients. Seven (21%) patients ceased vedolizumab; six patients stopped therapy due to persistent IBD activity and one for worsening of liver biochemistries.

CONCLUSION

Vedolizumab treatment in patients with PSC and IBD did not improve liver biochemistry but was associated with improvement in bowel disease and a favourable safety profile.

Rhizophorin A, a novel secolabdane diterpenoid from the Indian mangrove plant Rhizophora mucronata

The ethyl acetate extract of Rhizophora mucronata furnished rhizophorin A, a novel secolabdane diterpenoid, (6R,11S,13S)-6,11,13-trihydroxy-2,3-seco-14-labden-2,8-olide-3-oic acid (1).

GeneChip analysis after acute spinal cord injury in rat

Spinal cord injury (SCI) leads to induction and/or suppression of several genes, the interplay of which governs the neuronal death and subsequent loss of motor function. Using GeneChip, the present study analyzed changes in the mRNA abundance at 3 and 24 h after SCI in adult rats. SCI was induced at T9 level by the New York University impactor by dropping a 10-g weight from a height of 25 mm. Several transcription factors, immediate early genes, heat-shock proteins, pro-inflammatory genes were up-regulated by 3 h, and persisted at 24 h, after SCI. On the other hand, some neurotransmitter receptors and transporters, ion channels, kinases and structural proteins were down-regulated by 3 h, and persisted at 24 h, after SCI. Several genes that play a role in growth/differentiation, survival and neuroprotection were up-regulated at 24 h after SCI. Using real-time quantitative PCR, the changes observed by GeneChip were confirmed for seven up-regulated (interleukin-6, heat-shock protein-70, heme oxygenase-1, suppressor of cytokine signaling 2, suppressor of cytokine signaling 3, interferon regulatory factor-1, neuropeptide Y), two down-regulated (vesicular GABA transporter and cholecystokinin precursor) and two unchanged (Cu/Zn-superoxide dismutase and phosphatidyl inositol-3-kinase) genes. The present study shows that inflammation, neurotransmitter dysfunction, increased transcription, ionic imbalance and cytoskeletal damage starts as early as 3 h after SCI. In addition to these effects, 24 h after SCI the repair and regeneration process begins in an attempt to stabilize the injured spinal cord.

Protective effects of glial cell line-derived neurotrophic factor on hippocampal neurons after traumatic brain injury in rats

OBJECT

The purpose of this study was to evaluate whether glial cell line-derived neurotrophic factor (GDNF) can protect against hippocampal neuronal death after traumatic brain injury (TBI).

METHODS

Male Sprague-Dawley rats were subjected to moderate TBI with a controlled cortical impact device while in a state of halothane-induced anesthesia. Then, GDNF or artificial cerebrospinal fluid ([aCSF]; vehicle) was infused into the frontal horn of the left lateral ventricle. In eight brain-injured and eight sham-operated rats, GDNF was infused continuously for 7 days (200 ng/day intracerebroventricularly at a rate of 8.35 ng/0.5 microl/hour). An equal volume of vehicle was infused at the same rate into the remaining eight brain-injured and eight sham-operated rats. Seven days post-injury, all rats were killed. Their brains were sectioned and stained with cresyl violet, and the hippocampal neuronal loss was evaluated in the CA2 and CA3 regions with the aid of microscopy. A parallel set of sections from each brain was subjected to immunoreaction with antibodies against glial fibrillary acidic protein (GFAP; astroglia marker). In the aCSF-treated group, TBI resulted in a significant neuronal loss in the CA2 (60%, p < 0.05) and CA3 regions (68%, p < 0.05) compared with the sham-operated control animals. Compared with control rats infused with aCSF, GDNF infusion significantly decreased the TBI-induced neuronal loss in both the CA2 (58%, p < 0.05) and CA3 regions (51%, p < 0.05). There was no difference in the number of GFAP-positive astroglial cells in the GDNF-infused rats in the TBI and sham-operated groups compared with the respective vehicle-treated groups.

CONCLUSIONS

The authors found that GDNF treatment following TBI is neuroprotective.

Neuroprotection by memantine, a non-competitive NMDA receptor antagonist after traumatic brain injury in rats

This study investigated whether memantine, a non-competitive NMDA receptor antagonist is neuroprotective after traumatic brain injury (TBI) induced in adult rats with a controlled cortical impact device. TBI led to significant neuronal death in the hippocampal CA2 and CA3 regions (by 50 and 59%, respectively), by 7 days after the injury. Treatment of rats with memantine (10 and 20 mg/Kg, i.p.) immediately after the injury significantly prevented the neuronal loss in both CA2 and CA3 regions. This is the first study showing the neuroprotective potential of memantine to prevent the TBI-induced neuronal damage.

Up-regulation of the peripheral-type benzodiazepine receptor expression and [(3)H]PK11195 binding in gerbil hippocampus after transient forebrain ischemia

In mammalian CNS, the peripheral-type benzodiazepine receptor (PTBR) is localized on the outer mitochondrial membrane within the astrocytes and microglia. The main function of PTBR is to transport cholesterol across the mitochondrial membrane to the site of neurosteroid biosynthesis. The present study evaluated the changes in the PTBR density, gene expression and immunoreactivity in gerbil hippocampus as a function of reperfusion time after transient forebrain ischemia. Between 3 to 7 days of reperfusion, there was a significant increase in the maximal binding site density (B(max)) of the PTBR antagonist [(3)H]PK11195 (by 94-156%; P < 0.01) and PTBR mRNA levels (by 1.8- to 2.9-fold; P < 0.01). At 7 days of reperfusion, in the hippocampal CA1 (the brain region manifesting selective neuronal death), PTBR immunoreactivity increased significantly. Increased PTBR expression after transient forebrain ischemia may lead to increased neurosteroid biosynthesis, and thus may play a role in the ischemic pathophysiology.

Transient focal cerebral ischemia down-regulates glutamate transporters GLT-1 and EAAC1 expression in rat brain

Transient focal cerebral ischemia leads to extensive excitotoxic neuronal damage in rat cerebral cortex. Efficient reuptake of the released glutamate is essential for preventing glutamate receptor over-stimulation and neuronal death. Present study evaluated the expression of the glial (GLT-1 and GLAST) and neuronal (EAAC1) subtypes of glutamate transporters after transient middle cerebral artery occlusion (MCAO) induced focal cerebral ischemia in rats. Between 24h to 72h of reperfusion after transient MCAO, GLT-1 and EAAC1 protein levels decreased significantly (by 36% to 56%, p < 0.05) in the ipsilateral cortex compared with the contralateral cortex or sham control. GLT-1 and EAAC1 mRNA expression also decreased in the ipsilateral cortex of ischemic rats at both 24h and 72h of reperfusion, compared with the contralateral cortex or sham control. Glutamate transporter down-regulation may disrupt the normal clearance of the synaptically-released glutamate and may contribute to the ischemic neuronal death.

Antisense knockdown of the glial glutamate transporter GLT-1, but not the neuronal glutamate transporter EAAC1, exacerbates transient focal cerebral ischemia-induced neuronal damage in rat brain

Transient focal cerebral ischemia leads to extensive neuronal damage in cerebral cortex and striatum. Normal functioning of glutamate transporters clears the synaptically released glutamate to prevent excitotoxic neuronal death. This study evaluated the functional role of the glial (GLT-1) and neuronal (EAAC1) glutamate transporters in mediating ischemic neuronal damage after transient middle cerebral artery occlusion (MCAO). Transient MCAO in rats infused with GLT-1 antisense oligodeoxynucleotides (ODNs) led to increased infarct volume (45 +/- 8%; p < 0.05), worsened neurological status, and increased mortality rate, compared with GLT-1 sense/random ODN-infused controls. Transient MCAO in rats infused with EAAC1 antisense ODNs had no significant effect on any of these parameters. This study suggests that GLT-1, but not EAAC1, knockdown exacerbates the neuronal death and thus neurological deficit after stroke.

Antisense knockdown of the glial glutamate transporter GLT-1 exacerbates hippocampal neuronal damage following traumatic injury to rat brain

Traumatic injury to rat brain induced by controlled cortical impact (CCI) results in chronic neuronal death in the hippocampus. In the normal brain, glutamate transporters actively clear the glutamate released synaptically to prevent receptor overactivation and excitotoxicity. Glutamate transporter 1 (GLT-1) is the most abundant and active glutamate transporter, which mediates the bulk of glutamate uptake. CCI injury significantly decreased GLT-1 mRNA (by 49-66%, P < 0.05) and protein (by 29-44%, P < 0.05) levels in the ipsilateral hippocampus, compared with either the respective contralateral hippocampus or the sham-operated control, 24-72 h after the injury. CCI injury in rats infused with GLT-1 antisense oligodeoxynucleotides (ODNs) exacerbated the hippocampal neuronal death and mortality, compared with the GLT-1 sense/random ODN-infused controls. At 7 days after the injury, hippocampal neuronal numbers were significantly lower in the CA1 (reduced by 32%, P < 0.05), CA2 (by 45%, P < 0.01), CA3 (by 68%, P < 0.01) and dentate gyrus (by 31%, P < 0.05) in GLT-1 antisense ODN-infused rats, compared with the GLT-1 sense/random ODN-infused controls. This study suggested a role for GLT-1 dysfunction in promoting the hippocampal neuronal death after traumatic brain injury.

Five diterpenoids (agallochins A-E) from the mangrove plant Excoecaria agallocha Linn

Chemical examination of the hexane extract of the roots of Excoecaria agallocha Linn collected from the Godavari estuary resulted in the isolation of altogether eleven diterpenoids of which five (1-5) are new. The structures of the new diterpenoids have been elucidated by a study of their physical and spectral (UV, IR, 1H, 13C, DEPT, 1H-1H COSY, NOESY, HMQC, HMBC and MASS) data as 3-oxo-ent-13epi-8(13)-epoxy-15-chloro-14-hydroxylabdane (1), ent-15-chloro-13,14-dihydroxylabd-8(9)-en-3-one (2), ent-15-chloro-labd-8(9)ene-3alpha,13,14-triol (3), ent-11beta-hydroxy-8(14),15-isopimaradien-3-one (4), 8,13-epoxy-3-nor-2,3-seco-14-epilabden-2,4-olide (5). The six known diterpenoids have been characterised respectively as ent-3-oxo-13-epi-manoyl oxide (6), ent-3beta-hydroxy-13-epi-manoyl oxide (7), (13R,14S)-ent-8alpha,13;14,15-diepoxy-13-epi-labdan-3-one (8), ent-16-hydroxy-3-oxo-13-epimanoyl oxide (9), ent-15-hydroxylabda-8(17),13E-dien-3-one (10), labda-8(17),13E-diene-3beta,15-diol (11) by a comparative study of their spectral data with the literature values.

Protective effects of memantine against ischemia-reperfusion injury in spontaneously hypertensive rats

Memantine, an uncompetitive NMDA open-channel blocker, has been shown to be effective in preventing neuronal damage after permanent focal cerebral ischemia. Reperfusion after a long period of ischemia may aggravate the progression of neuronal damage. Those drugs that show protective effects after permanent cerebral ischemia, therefore, might fail to do so against ischemia-reperfusion injury. In this study we evaluated the effects of memantine on brain edema formation and ischemic injury volume after transient cerebral ischemia. Male Spontaneously Hypertensive Rats (SHR) weighing 250-300 g were anesthetized with halothane and subjected to 1 hour of temporary middle cerebral artery occlusion by an intraluminal suture. 20 mg/kg of memantine or saline were injected intraperitoneally 5 min. after the induction of ischemia. Physiological parameters and regional cerebral blood flow were monitored during the surgical procedure. Brain water content and ischemic injury volume were measured with the wet dry method and 2,3,5-triphenyl tetrazolium chloride monohydrate (TTC) staining, respectively, at 24 hours after occlusion. There were no statistically significant differences between the groups regarding physiological parameters during the procedure. Memantine treatment (n=9) reduced the brain water content significantly in the cortex compared to saline treatment (n=8; 83. 1+/-0.7% vs. 84.5+/-1.5%, respectively, p<0.05). The total volume of ischemic brain injury was 300+/-49 mm(3) in the animals treated with saline (n=13). Treatment with 20 mg/kg memantine (n=14) reduced the ischemic injury volume to 233+/-61 mm(3) (P<0.01). These results demonstrate that the harmful effects of recirculation after a period of ischemia can be attenuated by the treatment of memantine, perhaps by its action at the NMDA receptors.

Portacaval anastomosis causes selective alterations of peripheral-type benzodiazepine receptor expression in rat brain and peripheral tissues

There is a growing body of evidence to suggest that peripheral-type benzodiazepine receptors (PTBRs) and their endogenous ligands are implicated in the pathogenesis of end-organ failure in chronic liver disease. Portal-systemic encephalopathy, a major neuropsychiatric complication associated with chronic liver disease, results in activation of brain PTBR and probably in peripheral organs. In order to address these issues, PTBR mRNA was measured using semi-quantitative RT-PCR in extracts of cerebral cortex, kidney and testis of rats four weeks after end-to-side portacaval anastomosis and sham-operation (controls). Densities of PTBR sites were measured concomitantly by in vitro receptor binding using the selective PTBR ligand [3H]PK11195. Portacaval shunting resulted in a 2 to 3-fold increase in expression of PTBR in brain and kidney and a 37% reduction in expression in testis. Densities of [3H]PK11195 sites changed in parallel with the alterations of gene expression. These findings suggest that selective alterations of PTBR expression are implicated in the pathogenesis of peripheral tissue hypertrophy (kidney) and/or atrophy (testis) which accompanies portal-systemic shunting in chronic liver failure. In brain, activation of PTBR could result in an increase in the production of neurosteroids with potent inhibitory action in the CNS, which could contribute to the pathogenesis of portal-systemic encephalopathy.

Traumatic injury to rat brain upregulates neuronal nitric oxide synthase expression and L-[3H]nitroarginine binding

Overstimulation of N-methyl-D-aspartate (NMDA) receptors is felt to precipitate the neuronal damage following traumatic brain injury (TBI). NMDA receptor-mediated, glutamate-induced excitotoxicity is thought to be mediated via nitric oxide (NO) formed by neuronal nitric oxide synthase (nNOS). The present study examined the mRNA and protein levels of nNOS in the ipsilateral and contralateral cortex of rats as a function of time (5 minutes to 1 week) after controlled cortical impact (CCI) brain injury. Sham-operated rats served as controls. TBI resulted in a significant increase in the levels of nNOS mRNA (1.5- to 2.8-fold, p < .05) between 2 and 4 hours after the injury. There was also a significant increase in the levels of nNOS protein (by 55% to 90%, p < .05) and binding densities of the nNOS-specific ligand L-[3H]nitroarginine (L-[3H]NOARG) (by 35% to 59%, p < .05) between 2 and 12 hours after the injury. Increased nNOS expression and function may contribute to the concomitant excitotoxic neuronal death after TBI.

Contribution of polyamine oxidase to brain injury after trauma

OBJECT

The possible role of the polyamine interconversion pathway on edema formation, traumatic injury volume, and tissue polyamine levels after traumatic brain injury (TBI) was studied using an inhibitor of the interconversion pathway enzyme, polyamine oxidase.

METHODS

Experimental TBI was induced in Sprague-Dawley rats by using a controlled cortical impact device at a velocity of 3 m/second, resulting in a 2-mm deformation. Immediately after TBI was induced, 100 mg/kg of N1,N4-bis(2,3-butadienyl)-1,4-butanediamine 2HCl (MDL 72527) or saline was injected intraperitoneally. Brain water content and tissue polyamine levels were measured at 24 hours after TBI. Traumatic injury volume was evaluated using 2% cresyl violet solution 7 days after TBI occurred. The MDL 72527 treatment significantly reduced brain edema (80.4+/-0.8% compared with 81.2+/-1.2%, p < 0.05) and injury volume (30.1+/-6.6 mm3 compared with 42.7+/-13.3 mm3, p < 0.05) compared with the saline treatment. The TBI caused a significant increase in tissue putrescine levels at the traumatized site (65.5+/-26.5 nmol/g [corrected] in the cortex and 70.9+/-22.4 nmol/g [corrected] in the hippocampus) compared with the nontraumatized site (7+/-2.4 nmol/g [corrected] in the cortex and 11.4+/-6.4 nmol/g [corrected] in the hippocampus). The increase in putrescine levels in both the traumatized and nontraumatized cortex and hippocampus was reduced by a mean of 60% with MDL 72527 treatment.

CONCLUSIONS

These results demonstrate, for the first time, that the polyamine interconversion pathway has an important role in the increase of putrescine levels after TBI and that the polyamine oxidase inhibitors, blockers of the interconversion pathway, can be neuroprotective against edema formation and necrotic cavitation after TBI.

Effects of MDL 72527, a specific inhibitor of polyamine oxidase, on brain edema, ischemic injury volume, and tissue polyamine levels in rats after temporary middle cerebral artery occlusion

The possible effects of the polyamine interconversion pathway on tissue polyamine levels, brain edema formation, and ischemic injury volume were studied by using a selective irreversible inhibitor, MDL 72527, of the interconversion pathway enzyme, polyamine oxidase. In an intraluminal suture occlusion model of middle cerebral artery in spontaneously hypertensive rats, 100 mg/kg MDL 72527 changed the brain edema formation from 85.7 +/- 0.3 to 84.5 +/- 0.9% in cortex (p < 0.05) and from 79.9 +/- 1.7 to 78.4 +/- 2.0% in subcortex (difference not significant). Ischemic injury volume was reduced by 22% in the cortex (p < 0.05) and 17% in the subcortex (p < 0.05) after inhibition of polyamine oxidase by MDL 72527. There was an increase in tissue putrescine levels together with a decrease in spermine and spermidine levels at the ischemic site compared with the nonischemic site after ischemia-reperfusion injury. The increase in putrescine levels at the ischemic cortical and subcortical region was reduced by a mean of 45% with MDL 72527 treatment. These results suggest that the polyamine interconversion pathway has an important role in the postischemic increase in putrescine levels and that blocking of this pathway can be neuroprotective against neuronal cell damage after temporary focal cerebral ischemia.

Traumatic brain injury down-regulates glial glutamate transporter (GLT-1 and GLAST) proteins in rat brain

Excess activation of NMDA receptors is felt to participate in secondary neuronal damage after traumatic brain injury (TBI). Increased extracellular glutamate is active in this process and may result from either increased release or decreased reuptake. The two high-affinity sodium-dependent glial transporters [glutamate transporter 1 (GLT-1) and glutamate aspartate transporter (GLAST)] mediate the bulk of glutamate transport. We studied the protein levels of GLT-1 and GLAST in the brains of rats after controlled cortical impact-induced TBI. With use of subtype-specific antibodies, GLT-1 and GLAST proteins were quantitated by immunoblotting in the ipsilateral and contralateral cortex at 2, 6, 24, 72, and 168 h after the injury. Sham-operated rats served as control. TBI resulted in a significant decrease in GLT-1 (by 20-45%; p < 0.05) and GLAST (by 30-50%; p < 0.05) protein levels between 6 and 72 h after the injury. D-[3H]Aspartate binding also decreased significantly (by 30-50%; p < 0.05) between 6 and 72 h after the injury. Decreased glial glutamate transporter function may contribute to the increased extracellular glutamate that may mediate the excitotoxic neuronal damage after TBI. This is a first report showing altered levels of glutamate transporter proteins after TBI.

Intraluminal suture occlusion of the middle cerebral artery in Spontaneously Hypertensive rats

In models of middle cerebral artery occlusion using intraluminal suture, the size and the distribution of ischemic injury vary considerably among laboratories. In transcranial models of cerebral ischemia, a more consistent cerebral ischemic lesion is seen in Spontaneously Hypertensive rats (SHR). In the present study, we performed intraluminal suture occlusion of the MCA in SHR and compared its reproducibility with those in Sprague-Dawley (SD) rats. Male SHR and SD rats were anesthetized with halothane and subjected to 2 h of temporary middle cerebral artery occlusion by an intraluminal suture. Comparisons of regional cerebral blood flow figures taken throughout the experiment and lesion volume figures taken at 24 h after occlusion were made between the two groups. Total lesion volume in the SHR group was 263.6+/-30.5 mm3 (mean +/- SD), significantly larger and less variable than that in the SD group (145.4+/-123.7 mm3, p < 0.02). Throughout the ischemic period there was a tendency for rCBF to be lower in the SHR group than in the SD group. In some animals of both groups, recirculation could not be produced by withdrawal of the suture from the ICA. The mortality rate was 9% in the SD group and 17% in the SHR group. Intraluminal MCA occlusion in SHRs is associated with a more consistent, reliable and reproducible volume of ischemic injury. In the studies of temporary focal cerebral ischemia, this model must be accompanied by the monitoring of regional cerebral blood flow so as to obtain more reliable results.

Characterization of binding sites for the omega3 receptor ligands [3H]PK11195 and [3H]RO5-4864 in human brain

The kinetics and pharmacology of the isoquinoline and benzodiazepine binding sites of the omega3 or peripheral-type benzodiazepine receptors were studied using the specific ligands [3H] 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin -2-one ([3H]PK11195) and [3H]1-(2-Chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarb oxamide ([3H]RO5-4864), respectively. Binding of both ligands was saturable, reversible, displayed nanomolar affinity, and best fit to a single site model. Occipital cortex and cerebellum displayed highest and lowest densities of binding sites respectively; for both ligands. Bmax values of [3H]PK11195 were several-fold higher than that of [3H]RO5-4864 in all regions studied consistent with their binding to distinct subunits of the human peripheral-type benzodiazepine receptor heteromeric complex. However, the isoquinoline and benzodiazepine ligands were found to be mutually competitive at nanomolar concentrations suggesting allosteric interactions between these two sites. Competition binding experiments showed that the binding of both ligands was displaced by diazepam with Ki values in the nM range, and by clonazepam in the microM range. The novel peripheral-type benzodiazepine receptor ligand 2-(4-fluorophenyl)-N,N-di-n-hexyl-1H-indole-3-acetamide (FGIN1-27) displaced only [3H]PK11195 binding with high potency. Heterogeneity of the two sites is observed, manifested by their differential susceptibility towards detergents and alcohols. Histidine residue modification by diethylpyrocarbonate treatment abolished only [3H]PK11195 binding but had no effect on [3H]RO5-4864 binding. These studies demonstrate that the isoquinoline and benzodiazepine sites on the peripheral-type benzodiazepine receptor in human brain manifest many pharmacological characteristics that are distinct from each other and from rodent brain peripheral-type benzodiazepine receptors.

Effects of ifenprodil, a polyamine site NMDA receptor antagonist, on reperfusion injury after transient focal cerebral ischemia

Polyamines and N-methyl-D-aspartate (NMDA) receptors are both thought to play an important role in secondary neuronal injury after cerebral ischemia. Ifenprodil, known as a noncompetitive inhibitor of polyamine sites at the NMDA receptor, was studied after transient focal cerebral ischemia occurred. Spontaneously hypertensive male rats, each weighing between 250 and 350 g, underwent 3 hours of tandem middle cerebral artery (MCA) and common carotid artery occlusion followed by reperfusion for a period of 3 hours or 21 hours. Intravenous ifenprodil (10 microg/kg/minute) or saline infusion was started immediately after the onset of MCA occlusion and continued throughout the ischemic period. Physiological parameters including blood pressure, blood gas levels, blood glucose, hemoglobin, and rectal and temporal muscle temperatures were monitored. Six rats from each group were evaluated at 6 hours postocclusion for brain water content, an indicator of brain edema, and Evans blue dye extravasation for blood-brain barrier breakdown. Infarct volume was also measured in six rats from each group at 6 and 24 hours postocclusion. Ifenprodil treatment significantly reduced brain edema (82.5 +/- 0.4% vs. 83.5 +/- 0.4%, p < 0.05) and infarct volume (132 +/- 14 mm3 vs. 168 +/- 25 mm3, p < 0.05) compared with saline treatment, with no alterations in temporal muscle (brain) or rectal (body) temperature (35.9 +/- 0.4 degrees C vs. 36.2 +/- 0.2 degrees C; 37.7 +/- 0.4 degrees C vs. 37.6 +/- 0.6 degrees C; not significant). These results demonstrate that ifenprodil has neuroprotective properties after ischemia/reperfusion injury in the absence of hypothermia. This indicates that antagonists selective for the polyamine site of the NMDA receptors may be a viable treatment option and helps to explain some of the pathophysiological mechanisms involved in secondary injury after transient focal cerebral ischemia has occurred.

Increased neuronal nitric oxide synthase expression in brain following portacaval anastomosis

It has previously been suggested that increases of L-arginine uptake into brain following portacaval shunting may result in increased activities of constitutive neuronal nitric oxide synthase (nNOS). In order to further address this issue, nNOS protein and gene expression were studied by Western blot analysis using a monoclonal nNOS antibody and RT-PCR respectively in the brains of rats following portacaval shunting or sham operation. Portacaval shunting resulted in a 2-fold increase (P < 0.01) in nNOS protein and a concomitant 2.4-fold increase (P < 0.01) in nNOS mRNA. Increased nNOS activity in brain and the resulting increase in nitric oxide production could contribute to the increased cerebral blood flow and to the pathogenesis of hepatic encephalopathy in chronic liver disease.

Portacaval shunting and hyperammonemia stimulate the uptake of L-[3H] arginine but not of L-[3H]nitroarginine into rat brain synaptosomes

Elevated activities of nitric oxide synthase (NOS) have been reported previously in the brains of portacaval-shunted (PCS) rats, a model of chronic hepatic encephalopathy (HE). As L-arginine availability for nitric oxide synthesis depends on a specific uptake mechanism in neurons, we studied the kinetics of L-[3H]-arginine uptake into synaptosomes prepared from the brains of PCS rats. Results demonstrate that L-arginine uptake is significantly increased in cerebellum (60%; p < 0.01), cerebral cortex (42%; p < 0.01), hippocampus (56%; p < 0.01), and striatum (51%; p < 0.01) of PCS rats compared with sham-operated controls. Hyperammonemia in the absence of portacaval shunting also stimulated the transport of L-[3H]arginine; kinetic analysis revealed that the elevated uptake was due to increased uptake capacity (Vmax) without any change in affinity (Km). Incubation of cerebellar synaptosomes with ammonium acetate for 10 min caused a dose-dependent stimulation of L-[3H]arginine uptake. Neither portacaval shunting nor hyperammonemia had any significant effect on the synaptosomal uptake of NG-nitro-L-[3H]arginine. These studies demonstrate that increased NOS activity observed in experimental HE may result from increased availability of L-arginine resulting from a direct stimulatory effect of ammonia on L-arginine transport.

Vesicular dysfunction during experimental thiamine deficiency is indicated by alterations in dopamine metabolism

Experimental and clinical studies indicate that catecholamines play an important role in the neurobehavioural symptomatology of thiamine deficiency. Given the cerebral region-selective vulnerability and the behavioural impairment commonly encountered in thiamine deficiency, we undertook to investigate regional catecholamine metabolism in the brains of pyrithiamine-induced thiamine-deficient rats. Dopamine metabolism was unaffected in the striatum. In contrast, other regions also known to be involved in sensory processing and intellectual function (e.g., frontal cortex, hypothalamus, thalamus), but having a greater noradrenergic input, had increased levels of 3,4-dihydroxyphenylacetic acid (DOPAC) and decreased levels of other dopaminergic metabolites including noradrenaline. In these regions levels of the vesicular amine transporter, defined by tetrabenazine-sensitive [3H]ketanserin binding, were also decreased. Our data suggest a region-selective vesicular dysfunction resulting in intraneuronal release, and subsequent degradation, of dopamine. These disruptions of dopamine and consequently noradrenaline metabolism may account for certain neurobehavioural deficits commonly encountered in thiamine deficiency.

Alterations in serotonin parameters in brain of thiamine-deficient rats are evident prior to the appearance of neurological symptoms

Biochemical alterations of serotoninergic parameters have been demonstrated in experimental thiamine deficiency. In addition, hypophagia and hypothermia, two physiological processes associated with changes in the serotonin [5-hydroxytryptamine (5-HT)] system, are manifest early during the progression of thiamine deficiency. The binding of selected 5-HT radioligands was therefore investigated in discrete brain regions of pyrithiamine-induced thiamine-deficient rats. Using quantitative receptor autoradiography, the binding of 8-hydroxy-2-(di-n-[3H]propylamino) tetralin, a ligand used to label the somatodendritic 5-HT1A autoreceptor of the dorsal raphe nucleus, was found to be unaffected in this region, suggesting that the structural integrity of the 5-HT cell bodies is maintained throughout the course of pyrithiamine treatment. Increased binding of [3H]-ketanserin was observed in regions considered vulnerable as well as in some considered to be nonvulnerable during the course of thiamine deficiency. These binding changes, which appear to represent changes in the density of the postsynaptic 5-HT2A receptor population rather than the "tetrabenazine-sensitive" vesicular monoamine transporter, are evident before the appearance of histopathologic lesions and coincide with altered tissue concentrations of 5-HT. These data suggest that 5-HT neurons, although structurally intact, are functionally affected early during the progression of thiamine deficiency. These alterations, which are likely a part of adaptive neuronal change consequent to thiamine dysfunction, may be important in the physiological manifestations and the learning deficits commonly encountered in experimental thiamine deficiency.

L-[3H]nitroarginine and L-[3H]arginine uptake into rat cerebellar synaptosomes: kinetics and pharmacology

Characteristics of the transport of the nitric oxide synthase substrate L-arginine and its inhibitor, NG-nitro-L-arginine (L-NOARG), into rat cerebellar synaptosomes were studied. Uptake of both L-arginine and L-NOARG was linear with increasing amount of protein (up to 40 micrograms) and time of incubation (up to 5 min) at 37 degrees C. Uptake of both compounds reached a steady state by 20 min. Maximal uptake of L-NOARG (650 pmol/mg of protein) was three to four times higher than that of L-arginine (170 pmol/mg of protein). L-NOARG uptake showed biphasic kinetics (Km1 = 0.72 mM, Vmax 1 = 0.98 nmol/min/mg of protein; Km2 = 2.57 mM, Vmax2 = 16.25 nmol/min/mg of protein). L-Arginine uptake was monophasic with a Km of 106 microM and a Vmax of 0.33 nmol/min/mg of protein. L-NOARG uptake was selectively inhibited by L-NOARG, NG-nitro-L-arginine methyl ester, and branched-chain and aromatic amino acids. L-Alanine and L-serine also inhibited L-NOARG uptake but with less potency. Uptake of L-arginine was selectively inhibited by NG-monomethyl-L-arginine acetate and basic amino acids. These studies suggest that in rat cerebellar synaptosomes, L-NOARG is transported by the neutral amino acid carrier systems T and L with high affinity, whereas L-arginine is transported by the basic amino acid carrier system y+ with high affinity. These data indicate that the concentration of competing amino acids is an important factor in determining the rates of uptake of L-NOARG and L-arginine into synaptosomes and, in this way, may control the activity of nitric oxide synthase.

Nitric oxide synthase activities are selectively decreased in vulnerable brain regions in thiamine deficiency

Pyrithiamine-induced thiamine deficiency in the rat exhibits many neuropathological and biochemical similarities to Wernicke's Encephalopathy in human. Activities of constitutive nitric oxide synthase (NOS) were measured in vulnerable (thalamus and cerebellum) and non-vulnerable (hippocampus and striatum) brain regions of pyrithiamine-induced thiamine-deficient rats. NOS activities were significantly decreased in the thalamus (by 26%, P < 0.05) of presymptomatic thiamine-deficient rats compared to pair-fed controls. Following onset of symptoms, in addition to thalamus (-38%, P < 0.01), cerebellum (-50%, P < 0.01) also manifested significantly decreased activities of NOS. Hippocampal and striatal activities of NOS were unchanged at both presymptomatic and symptomatic stages of thiamine deficiency. Selectively decreased activities of neuronal NOS in the thalamus and the cerebellum extends the previous observations of region-selective metabolic changes and, ultimately, neuronal cell loss observed in thiamine deficiency.

Na+,K(+)-ATPase activity is selectively increased in thalamus in thiamine deficiency prior to the appearance of neurological symptoms

The relationship between progression of neurological status and the activities of both Na+,K(+)- and Mg(2+)-dependent-ATPase (adenosine 5'-triphosphate phosphohydrolase) was investigated in brain regions of pyrithiamine-induced thiamine deficient rats. Thalamic Na+,K(+)-ATPase activity was selectively increased by 200% (P < 0.01) prior to the appearance of symptoms of thiamine deficiency and normalized in symptomatic rats. This selective transitory activation precludes a mediation by brain soluble fraction Na+,K(+)-ATPase modifiers as does the unaltered distribution in regional high-affinity [3H]ouabain binding densities observed throughout the time-course used in these experiments. Na+,K(+)-ATPase maintains cellular ionic gradients and has been implicated in neurotransmitter uptake and release mechanisms. The fact that the increased thalamic Na+,K(+)-ATPase activity coincides with the early alterations in serotonin metabolism observed in similarly treated animals and the concomitantly early increase in glucose utilization previously observed in the thalamus of thiamine-deficient rats is discussed.

Regional distribution of binding sites for the nitric oxide synthase inhibitor L-[3H]nitroarginine in rat brain

The regional distribution of NG-nitro-L-[(3)H]arginine (L-[(3)H]NOARG) binding to different regions of rat brain was studied by quantitative autoradiography. These studies revealed highest density of binding sites in cerebellum, anterior olfactory nucleus, islands of Calleja and substantia nigra with appreciable binding site densities in inferior colliculus, superior colliculus, olfactory tubercle and dorsal tegmental nucleus. The regional distribution of L-[(3)H]NOARG binding, is in good agreement with the distribution of nitric oxide synthase studied previously by NADPH-diaphorase staining and immunohistochemistry using antibodies against neuronal nitric oxide synthase. The kinetics of L-[(3)H]NOARG binding to the cytosolic preparations of cerebral cortex, cerebellum, hippocampus and striatum was studied using an in vitro binding technique. Specific L-[(3)H]NOARG binding was of nanomolar affinity, saturable, and best fit to a single-site model in all four brain regions. These studies support the potential use of L-[(3)H]NOARG binding as a tool for further elucidation of the regional distribution and functional properties of NOS in the central nervous system.