Two-year outcomes with a bioinductive collagen implant used in augmentation of arthroscopic repair of full-thickness rotator cuff tears: final results of a prospective multicenter study

BACKGROUND

Full-thickness rotator cuff tears (FTRCTs) represent a common shoulder injury that, if untreated, can progress in size, become increasingly painful, and inhibit function. These lesions are often surgically repaired, with double-row arthroscopic repair often preferred for larger tears. Biological augmentation technologies have been developed to improve rates of postoperative radiographic retear and enhance patient-reported outcomes after surgical FTRCT repair. This study sought to confirm that augmented repair with a bioinductive bovine collagen implant results in favorable retear rates and patient outcomes with follow-up to 2 years.

METHODS

A prospective multicenter cohort study was undertaken to determine the efficacy and safety of augmenting single- or double-row arthroscopic repair of FTRCTs with a bioinductive bovine collagen implant. Of 115 adult patients participating, 66 (57.4%) had medium (1-3-cm) tears and 49 (42.6%) had large (3-5-cm) tears. Magnetic resonance imaging and patient-reported outcomes (American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form [ASES] and Constant-Murley Score [CMS]) were performed and recorded at baseline, 3 months, 1 year, and 2 years.

RESULTS

Mean duration of follow-up was 2.1 years (range, 1.5-2.9 years). Between baseline and 2-year follow-up, mean total thickness of the supraspinatus tendon increased by 12.5% for medium tears and by 17.1% for large tears. Radiographic retear was noted in 7 of 61 available patients (11.5%) with medium tears, and in 14 of 40 patients (35.0%) with large tears. In both groups, these tears primarily occurred before the 3-month follow-up visit (13 of 21 [61.9%]). Radiographic retear with the supplemented double-row (DR) repair technique was 13.2% overall (12 of 91 DR patients; 11.3% for medium tears and 15.8% for large tears). The minimal clinically important difference was achieved by >90% of patients with both medium and large tears for both ASES and CMS. There were 2 serious adverse events classified by the treating surgeon as being possibly related to the device and/or procedure (1 case of swelling/drainage and 1 case of intermittent pain). Nine patients (7.8%; 4 medium tears and 5 large tears) required reoperation of the index rotator cuff surgery.

CONCLUSION

Final 2-year data from this study confirm that using this implant in augmentation of arthroscopic double-row repair of FTRCTs provides favorable rates of radiographic retear and substantial functional recovery. The relative safety of the device is also further supported.

Specific Design of a Press Fit Humeral Stem Provides low Stress Shielding in Reverse Shoulder Arthroplasty at minimum 5 Years FU

Press fit fixation is becoming more popular in RSA to preserve, in theory, bone capital. Several studies report that bone resorption can be very high around humeral stems depending on their size, shape and mode of fixation. The aim of the current study is to mid-term follow-up clinical and radiological result of a press fit ovoid regular stem RSA in non acute trauma cases.

Retear rates and clinical outcomes at 1 year after repair of full-thickness rotator cuff tears augmented with a bioinductive collagen implant: a prospective multicenter study

Background

Biologic technologies can potentially augment existing arthroscopic rotator cuff repair to improve retear rates and postoperative outcomes. The purpose of this study was to evaluate healing rates and clinical outcomes of full-thickness rotator cuff repairs augmented with a bioinductive bovine collagen implant.

Methods

In this prospective multicenter study, investigators enrolled 115 patients (mean age, 60.4 years) with full-thickness rotator cuff tears. There were 66 (57.4%) medium (1-3 cm) tears and 49 (42.6%) large (3-5 cm) tears. Eligible patients consisted of those ≥21 years of age with chronic shoulder pain lasting longer than 3 months and unresponsive to conservative therapy. Patients underwent single- or double-row repair augmented with a bioinductive bovine collagen implant. At the baseline, 3 months, and 1 year, magnetic resonance imaging was performed and patients were assessed for American Shoulder and Elbow Surgeons (ASES) Shoulder Score and Constant-Murley Score (CMS). The primary failure end point was retear, classified as any new full-thickness defect observed on magnetic resonance imaging.

Results

There were 13 retears (11.3%) at 3 months, with an additional 6 (19 total [16.5%]) found at 1 year. In large tears, double-row repair had a significantly lower rate of retear at 3 months (P = .0004) and 1 year (P = .0001) compared with single-row repair. ASES and CMS scores significantly improved between the baseline and 1 year for medium and large tears. At 1 year, the minimally clinically important difference for ASES and CMS was met by 91.7% (95% CI: 84.9-96.1) and 86.4% (95% CI: 78.2-92.4) of patients, respectively. Patients without retear and those <65 years of age had significantly better CMS scores at 1 year when compared with those with retear and those ≥65 years (P < .05). There was no statistically significant difference in outcomes based on treatment of the biceps tendon. Of 9 reported reoperations in the operative shoulder, only 2 were considered potentially related to the collagen implant.

Conclusion

Interim results from this prospective study indicate a favorable rate of retear relative to the literature and improvement in clinical function at 1 year after adjunctive treatment with the study implant augmenting standard arthroscopic repair techniques.

Hernia prevention: practice patterns and surgeons' attitudes about abdominal wall closure and the use of prophylactic mesh

PURPOSE

The penetration of hernia prevention techniques into surgical practice remains unknown.

METHODS

A survey about knowledge/attitudes on hernia prevention was sent to the members of hernia societies.

RESULTS

The 497 respondents were mostly from the US (47%) or Europe (40%). Most reported practicing, but not measuring their suture-to-wound length closure of > 4:1 (63%) and practicing but not measuring the number of stitches (58%). Reasons for not using short stitch closure were: does not apply to patient population (19%), not familiar enough with methods to correctly execute (25%), takes too long (13%), not reimbursed (4%), concerned about closure-related complications (27%), and other (22%). Regarding prophylactic mesh, respondents stated they were not familiar with literature (11%), familiar with literature but would not use (24%), familiar with literature and interested in use (45%), familiar with literature and using (15%), and other (5%).

CONCLUSIONS

There appears to be some application of hernia prevention principles related to fascial closure; however, the use of prophylactic mesh still appears to be controversial.

Redox Sensing within the Genus Shewanella

A novel bacterial behavior called congregation was recently described in Shewanella oneidensis MR-1 as the accumulation of cells around insoluble electron acceptors (IEA). It is the result of a series of “run-and-reversal” events enabled by modulation of swimming speed and direction. The model proposed that the swimming cells constantly sense their surroundings with specialized outer membrane cytochromes capable of extracellular electron transport (EET). Up to this point, neither the congregation nor attachment behavior have been studied in any other strains. In this study, the wild type of S. oneidensis MR-1 and several deletion mutants as well as eight other Shewanella strains (Shewanella putrefaciens CN32, S. sp. ANA-3, S. sp. W3-18-1, Shewanella amazonensis SB2B, Shewanella loihica PV-4, Shewanella denitrificans OS217, Shewanella baltica OS155, and Shewanella frigidimarina NCIMB400) were screened for the ability to congregate. To monitor congregation and attachment, specialized cell-tracking techniques, as well as a novel cell accumulation after photo-bleaching (CAAP) confocal microscopy technique were utilized in this study. We found a strong correlation between the ability of strain MR-1 to accumulate on mineral surface and the presence of key EET genes such as mtrBC/omcA (SO_1778, SO_1776, and SO_1779) and gene coding for methyl-accepting protein (MCPs) with Ca⁺ channel chemotaxis receptor (Cache) domain (SO_2240). These EET and taxis genes were previously identified as essential for characteristic run and reversal swimming around IEA surfaces. CN32, ANA-3, and PV-4 congregated around both Fe(OH)₃ and MnO₂. Two other Shewanella spp. showed preferences for one oxide over the other: preferences that correlated with the metal content of the environments from which the strains were isolated: e.g., W3-18-1, which was isolated from an iron-rich habitat congregated and attached preferentially to Fe(OH)₃, while SB2B, which was isolated from a MnO₂-rich environment, preferred MnO₂.

A critical review of biologic mesh use in ventral hernia repairs under contaminated conditions

PURPOSE

We used an evidence-based approach to determine whether the promotions and claims of superiority of biologic mesh over synthetic mesh use in ventral hernia repairs (VHRs) under contaminated conditions were sound and valid.

METHODS

We searched the Medline database to specifically identify review articles relating to biologic mesh and VHR and critically reviewed these studies using an evidence-based approach.

RESULTS

For the past 45 years, four clinical reviews and one systematic review have included biologic meshes as part of a larger discussion on available prosthetics for VHR. All reviews supported biologic mesh use, especially in the setting of contaminated fields. Yet, the primary literature included in these reviews and served as the basis for these conclusions consisted entirely of case series and case reports, which have the lowest level of evidence in determining scientific validity. Furthermore, the FDA has neither cleared nor approved this particular use.

CONCLUSIONS

The cumulative data regarding biologic mesh use in VHRs under contaminated conditions does not support the claim that it is better than synthetic mesh used under the same conditions. The highly promoted and at least moderately utilized practice of placing biologic mesh in contamination is being done outside of the original intended use, and a re-evaluation of or possible moratorium on biologic mesh use in hernia surgery is seriously warranted. Alternatively, an industry-sponsored national registry of patients in whom ventral hernia repairs involved biologic mesh would substantively add to our understanding regarding how these intriguing biomaterials are being used and their overall clinical efficacy.

Failure analysis of rotator cuff repair: a comparison of three double-row techniques

BACKGROUND

The use of suture anchors has made arthroscopic repair of the torn rotator cuff possible. However, objective evaluations have demonstrated high failure rates. The goal of this study was to compare the modes and rates of failure of two double-row arthroscopic repair techniques and the mini-open double-row technique.

METHODS

Thirty pairs of fresh-frozen human shoulders were used in this study. The specimens were prepared to simulate a cuff defect, which was then repaired. The repairs were done with three different lateral row techniques (Mason-Allen sutures passed through transosseous tunnels, the knotless anchor method, and the corkscrew suture anchor method) with the same medial row technique (corkscrew suture anchors). Cyclic tests were conducted at 33 mm/s with a cyclic force of 10 to 180 N. Specimens were cycled to 5000 cycles or to failure as defined as formation of a 10-mm gap at the repair. Failure rates and failure modes of the suture, tendon, and bone-anchor interface were compared for the medial and lateral rows and among the three techniques.

RESULTS

Fourteen of the twenty repairs made with the transosseous technique, fifteen of the twenty repairs made with the knotless anchor technique, and ten of the twenty repairs made with the corkscrew anchor technique survived 5000 cycles. The failure rates for the medial row were not significantly different among the three repair techniques. For the lateral row, there was a significant difference (p < 0.01) in the rate of failure among individual transosseous tunnel-suture complexes (32%), knotless anchor-suture complexes (48%), and corkscrew anchor-suture complexes (75%), with a similar suture-tendon failure rate for all three techniques. The tendon and repair complexes with corkscrew suture anchors had the smallest displacement both at the first and the 5000th cycle.

CONCLUSIONS

Although repairs made with the anchor techniques had higher individual failure rates, the survival rates for the anchor techniques at the 5000th cycle were similar to that for the transosseous technique during cyclic tests. Suture failure was the main failure mode for the transosseous technique, whereas failure at the anchor-bone interface was the main failure mode for the anchor techniques.

Necrotizing pancreatitis: a surgical approach independent of documented infection

BACKGROUND

Strategies for the management of patients with necrotizing pancreatitis remain controversial. While consensus opinion supports operative necrosectomy for the treatment of infected pancreatic necrosis, the timing for surgical intervention is not completely resolved. Further, the indication for the surgical management of sterile pancreatic necrosis is also subject to debate.

METHODS

The objective of this study was to evaluate outcome measures for the surgical management of necrotizing pancreatitis, independent of documented infection. A retrospective review was undertaken between 1994 and 2002 at a single county hospital.

RESULTS

Twenty-one patients with CT-documented necrotizing pancreatitis underwent operative pancreatic necrosectomy with laparostomy within 21 days of initial diagnosis and had an average of three reoperations. Average length of stay (LOS) in the ICU was 36 days and in the hospital 67 days. Ten patients had documented infected necrosis based on initial intra-operative cultures, while I I had sterile necrosis. Overall, 95% (20/21) of the patients had a complication, with an average of three complications per patient. Common complications included ARDS (71%), sepsis (33%), renal failure (24%), and pneumonia (24%). The overall mortality rate was 14% (3/21), with a mean follow-up of 469 days.

DISCUSSION

The surgical management of acute necrotizing pancreatitis, independent of documented infection, can be undertaken within 3 weeks of diagnosis with an acceptable morbidity and a low mortality rate. Creation of a laparostomy to enable ready, atraumatic debridement of the retroperitoneum is a safe alternative to standard repeat laparotomies and thus represents a useful adjunct to the surgical management of necrotizing pancreatitis.

Intramedullary nailing of humeral shaft fractures with a locking flexible nail

BACKGROUND

Studies on intramedullary nailing of humeral shaft fractures in the orthopaedic literature have shown mixed results. The purpose of this investigation was to document the clinical outcome and complications associated with the use of a new flexible, locking intramedullary nail that can be implanted in the humerus in either a retrograde or an antegrade manner without violating the rotator cuff mechanism or damaging the articular surface of the humeral head.

METHODS

Fifty consecutive patients with fifty-one humeral shaft fractures were entered into our prospective clinical outcome study. The fracture was classified on the basis of the anatomic location and pattern. Implant positioning and fracture alignment were assessed postoperatively. Complications were recorded, and the time to union was measured. Shoulder function was evaluated with use of a combination of the Constant shoulder score, Short Form-36 (SF-36) clinical outcome data, range-of-motion measurements, and a subjective pain-rating scale.

RESULTS

Forty-one patients with forty-two fractures had an adequate duration of clinical follow-up (a mean of twenty-two months) for analysis. Thirty-nine fractures healed, with a mean time to clinical union of twelve weeks (range, four to fifty weeks). Thirty-eight of the forty-two shoulders had minimal or no pain. Thirty-six shoulders had a full range of motion. The mean Constant shoulder score was 90 points. Four patients had five complications, which included two nonunions, two hardware failures, and one wound infection. All four patients had been managed with a 7.5-mm nail. A multivariate analysis demonstrated that an age of more than fifty years was associated with a lower Constant score and that the occurrence of a complication was associated with a lower physical component score on the SF-36.

CONCLUSIONS

The flexible humeral nail allows both retrograde and antegrade implantation and static locking. Nail insertion can be accomplished without violating the rotator cuff or damaging the articular surface of the humeral head. Although the nail functioned well in most of our patients, the use of a small-diameter (7.5-mm) nail was associated with a higher complication rate. This implant should be used with caution in any patient with a medullary canal diameter of <or=8 mm.

Polyvalent cation receptor proteins (CaRs) are salinity sensors in fish

To determine whether calcium polyvalent cation-sensing receptors (CaRs) are salinity sensors in fish, we used a homology-based cloning strategy to isolate a 4.1-kb cDNA encoding a 1,027-aa dogfish shark (Squalus acanthias) kidney CaR. Expression studies in human embryonic kidney cells reveal that shark kidney senses combinations of Ca(2+), Mg(2+), and Na(+) ions at concentrations present in seawater and kidney tubules. Shark kidney is expressed in multiple shark osmoregulatory organs, including specific tubules of the kidney, rectal gland, stomach, intestine, olfactory lamellae, gill, and brain. Reverse transcriptase-PCR amplification using specific primers in two teleost fish, winter flounder (Pleuronectes americanus) and Atlantic salmon (Salmo salar), reveals a similar pattern of CaR tissue expression. Exposure of the lumen of winter flounder urinary bladder to the CaR agonists, Gd(3+) and neomycin, reversibly inhibit volume transport, which is important for euryhaline teleost survival in seawater. Within 24-72 hr after transfer of freshwater-adapted Atlantic salmon to seawater, there are increases in their plasma Ca(2+), Mg(2+), and Na(+) that likely serve as a signal for internal CaRs, i.e., brain, to sense alterations in salinity in the surrounding water. We conclude that CaRs act as salinity sensors in both teleost and elasmobranch fish. Their tissue expression patterns in fish provide insights into CaR functions in terrestrial animals including humans.

AQP2 is a substrate for endogenous PP2B activity within an inner medullary AKAP-signaling complex

We have demonstrated that inner medullary collecting duct (IMCD) heavy endosomes purified from rat kidney IMCD contain the type II protein kinase A (PKA) regulatory subunit (RII), protein phosphatase (PP)2B, PKCzeta, and an RII-binding protein (relative molecular mass ~90 kDa) representing a putative A kinase anchoring protein (AKAP). Affinity chromatography of detergent-solubilized endosomes on cAMP-agarose permits recovery of a protein complex consisting of the 90-kDa AKAP, RII, PP2B, and PKCzeta. With the use of small-particle flow cytometry, RII and PKCzeta were localized to an identical population of endosomes, suggesting that these proteins are components of an endosomal multiprotein complex. (32)P-labeled aquaporin-2 (AQP2) present in these PKA-phosphorylated endosomes was dephosphorylated in vitro by either addition of exogenous PP2B or by an endogenous endosomal phosphatase that was inhibited by the PP2B inhibitors EDTA and the cyclophilin-cyclosporin A complex. We conclude that IMCD heavy endosomes possess an AKAP multiprotein-signaling complex similar to that described previously in hippocampal neurons. This signaling complex potentially mediates the phosphorylation of AQP2 to regulate its trafficking into the IMCD apical membrane. In addition, the PP2B component of the AKAP-signaling complex could also dephosphorylate AQP2 in vivo.

The lipemia of sepsis: triglyceride-rich lipoproteins as agents of innate immunity

Bacterial endotoxin (LPS) elicits dramatic responses in the host including elevated plasma lipid levels due to the increased synthesis and secretion of triglyceride (TG)-rich lipoproteins by the liver, and the inhibition of lipoprotein lipase. This cytokine-induced hyperlipoproteinemia, clinically termed the "lipemia of sepsis", was customarily thought to represent the mobilization of lipid stores to fuel the host response to infection. However, since lipoproteins can also bind and neutralize LPS, we hypothesize that TG-rich lipoproteins (VLDL and chylomicrons) are also components of an innate, non-adaptive host immune response to infection. Herein we review data demonstrating the capacity of lipoproteins to bind LPS, protect against LPS-induced toxicity, and modulate the overall host response to this bacterial toxin. Lastly, we propose a pathway whereby lipoprotein-bound LPS may represent a novel, endogenous mechanism for regulating the hepatic acute phase response.

Necrotizing pancreatitis during pregnancy: a rare cause and review of the literature

Acute pancreatitis is an uncommon cause of abdominal pain during pregnancy, and rarely progresses to the necrotizing from of the disease in this clinical setting. Hyperlipidemia is an infrequent cause of acute pancreatitis. Whereas only 100 cases of hyperlipidemia-induced necrotizing pancreatitis have been reported in the literature to date, all of the cases were mild in severity and responsive to conservative medical management. Herein we present a case of life-threatening necrotizing pancreatitis, which developed in a hyperlipidemic pregnant woman and required multiple peripartum pancreatic necrosectomies. Additionally, we review the evaluation of pregnant patients with abdominal pain, the pathophysiology of hyperlipidemia-induced necrotizing pancreatitis, and the operative care of this challenging group of patients, revisiting an innovative technique for management of the retroperitoneum.

Pulmonary dysplasia, Denys-Drash syndrome and Wilms tumor 1 gene mutation in twins

While a genetic basis for the association of developmental lung and kidney defects has been suspected, the involvement of specific genes in this process is under active investigation. We report such a possible genetic linkage present in identical twins with a mutant Wilms tumor (WT1) gene. Twin girls, born at 35 weeks gestation, manifested symptoms of congenital nephrotic syndrome, renal failure, and severe respiratory abnormalities refractory to assisted ventilation. Both died at 1 month of age. Renal biopsies and autopsy kidney tissue from both the girls revealed diffuse mesangial sclerosis (DMS). Autopsy lung tissue revealed pulmonary dysplasia and hypoplasia in both twins. The WT1 gene from renal tissue in both twins was analyzed for mutations using polymerase chain reaction (PCR) amplification and the single-strand conformation polymorphism (SSCP) technique. Both twins possessed an identical missense mutation in exon 8 of the WT1 gene, resulting in replacement of arginine by histidine at amino acid 366 (arg366his) in the WTI protein. This mutation has previously been described in Denys-Drash syndrome. The WT1 gene plays a role in mesenchymal epithelial (ME) interactions in the developing urogenital system, and possibly has a similar role during lung morphogenesis. We propose that this WT1 gene mutation contributes to both DMS and developmental pulmonary abnormalities by altering ME interactions in both organs.

Cinematic nuclear scintigraphy reliably directs surgical intervention for patients with gastrointestinal bleeding

HYPOTHESIS

Cinematic technetium Tc 99m red blood cell ((99m)Tc-RBC) scans, in which real-time scanning is performed and analyzed, can accurately localize gastrointestinal bleeding and thus direct selective surgical intervention.

DESIGN

Retrospective medical record review with historical controls.

SETTING

Large, university-affiliated public hospital in urban setting.

PATIENTS

Twenty-six patients presenting with upper and lower gastrointestinal hemorrhage who underwent cinematic (99m)Tc-RBC scan examinations between 1990 and 1997 and required surgical intervention to control the bleeding.

INTERVENTIONS

All patients with gastrointestinal bleeding underwent open surgical procedures to provide cessation of bleeding and resection of appropriate abnormalities.

MAIN OUTCOME MEASURES

Patient outcome was based on correlation between preoperative RBC scans and intraoperative findings, surgical pathology, and postoperative clinical course.

RESULTS

Twenty-five (96%) of 26 scans were interpreted as positive for gastrointestinal bleeding. In 22 of these 25 scans, the site of bleeding was correctly identified for a sensitivity of 88%. One or more additional diagnostic tests were performed on 19 (73%) of 26 patients, and included angiography and flexible endoscopy. The most common operation performed to control bleeding was a hemicolectomy (14/26). Diverticulosis was the most prevalent diagnosis (46%). Two patients (8%) experienced rebleeding after operation. The overall mortality rate was 19% (5/26).

CONCLUSIONS

Cinematic (99m)Tc-RBC scintigraphy is a sensitive, noninvasive alternative to mesenteric angiography for accurately localizing the site of gastrointestinal hemorrhages. As such, this technique can be reliably used to direct selective surgical intervention.

Functional outcome of patients with femoral head fractures associated with hip dislocations

Fracture of the femoral head after hip dislocation is a relatively rare injury often associated with a poor functional outcome. Twenty-six patients who sustained femoral head fractures were evaluated using radiographs, clinical examinations, and a validated outcome scoring system. The Short Form-12 was used to assess functional outcome. Patients whose fractures were stabilized with 3-mm cannulated screws and washers had a poor functional outcome. When evaluated with an odds ratio analysis, the use of Kocher-Langenbeck posterior approach was associated with a 3.2 times higher incidence of the patients having avascular necrosis develop when compared with the Smith-Petersen approach. A literature review combined with the current series confirms that the principles of early reduction of hip dislocation, early stabilization, anatomic reduction of the fracture, and rigid fixation are critical principles to attain good results. The Brumback classification system provides superior differentiation of different fracture types when compared with the Pipkin classification. The Smith-Petersen anterior surgical approach is recommended for the majority of patients with femoral head fractures. Three-millimeter cannulated screws with threaded washers are contraindicated for use in stabilizing femoral head fractures, and should not be used in any joint because of dissociation between the screw and the washer.

Extracellular matrix regulates the hepatocellular heat shock response

BACKGROUND

Cirrhosis is characterized by the accumulation of collagen within the extracellular matrix (ECM) of the liver and progressive hepatocellular dysfunction. Since recent studies have shown that the ECM can modulate cellular function, we examined whether the ECM could contribute to hepatocellular dysfunction. To address this question we examined hepatocyte behavior in two different ECM environments.

MATERIALS AND METHODS

Primary rat hepatocytes were cultured as a monolayer on collagen or as multicellular aggregates (spheroids) within a laminin-rich ECM. Hepatocytes were then compared for viability, response to proinflammatory cytokines, and their capacity to activate a heat shock response and adopt a thermotolerant phenotype. In addition, we compared the ability of prior heat shock exposure to protect hepatocytes from tumor necrosis factor (TNF) alpha/actinomycin-D-induced apoptosis in the two different ECM environments.

RESULTS

Hepatocytes cultured as a monolayer on collagen exhibited decreased viability, underwent spontaneous apoptosis, and displayed an attenuated cytokine-stimulated nitric oxide production compared to hepatocytes cultured as spheroids. In response to heat, hepatocytes in both ECM environments expressed inducible heat shock protein 70 (hsp72). But, only the hepatocyte spheroids exhibited thermotolerance in response to a subsequent thermal challenge. In contrast to previous reports, induction of the heat shock response failed to protect hepatocytes against TNFalpha-induced apoptosis.

CONCLUSIONS

These data demonstrate that the ECM can play an integral role in specific hepatocellular behaviors. Furthermore, the progressive deposition of collagen within the ECM, which is characteristic of fibrotic liver diseases, may directly contribute to the progressive hepatocellular dysfunction observed in cirrhosis. Hepatocellular viability, response to proinflammatory cytokines, heat shock response, and thermotolerance were all altered depending on the composition of the ECM. In contrast, TNFalpha-induced apoptosis was independent of the composition of the ECM.

Substance P dependence of endosomal fusion during bladder inflammation

Urinary bladder instillation of ovalbumin into presensitized guinea pigs stimulates rapid development of local bladder inflammation. Substance P is an important mediator of this inflammatory response, as substance P antagonists largely reverse the process. Vacuolization of the subapical endosomal compartment of the transitional epithelial cells lining the bladder suggests that changes in endosomal trafficking and fusion are also part of the inflammatory response. To test directly for substance P mediation of changes in endosomal fusion, we reconstituted fusion of transitional cell endosomes in vitro using both cuvette-based and flow cytometry energy transfer assays. Bladders were loaded with fluorescent dyes by a hypotonic withdrawal protocol before endosomal isolation by gradient centrifugation. Endosomal fusion assayed by energy transfer during in vitro reconstitution was both cytosol and ATP dependent. Fusion was confirmed by the increase in vesicle size on electron micrographs of fused endosomal preparations compared with controls. In inflamed bladders, dye uptake was inhibited 20% and endosomal fusion was inhibited 50%. These changes are partly mediated by the neurokinin-1 (NK1) receptor (NK1R), as 4 mg/kg of CP-96,345, a highly selective NK1 antagonist, increased fusion in inflamed bladders but had no effect on control bladders. The receptor-mediated nature of this effect was demonstrated by the expression of substance P receptor mRNA in rat bladder lumen scrapings and by the detection of the NK1R message in guinea pig subapical endosomes by Western blot analysis. The NK1Rs were significantly upregulated following induction of an inflammatory response in the bladder. These results demonstrate that 1) in ovalbumin-induced inflammation in the guinea pig bladder, in vitro fusion of apical endosomes is inhibited, showing endocytotic processes are altered in inflammation; 2) pretreatment in vivo with an NK1R antagonist blocks this inhibition of in vitro fusion, demonstrating a role for NK1R in this process; and 3) the NK1R is present in higher amounts in apical endosomes of inflamed bladder, suggesting changes in translation or trafficking of the NK1R during the inflammatory process. This suggests that NK1R can change the fusion properties of membranes in which it resides.

Leukocytosis and free fluid are important indicators of isolated intestinal injury after blunt trauma

BACKGROUND

The detection of isolated intestinal injuries after blunt trauma can be difficult because of subtle signs and symptoms, often leading to delayed diagnosis. We hypothesized that specific clinical indicators could be identified to assist in the diagnosis of these injuries.

METHODS

Medical records of all patients with such injuries from 1988 to 1996 were reviewed. The patients were stratified into those operated on within 6 hours of presentation (apparent injury) and those operated on after 6 hours (occult injury), and the data were compared.

RESULTS

Forty-six patients with isolated intestinal injuries were identified. There were no differences in the rate of peritonitis or free fluid on abdominal computed tomography, blood loss, intraoperative findings, or morbidity and mortality between groups. Leukocytosis (sensitivity, 84.8%; specificity, 55.2%; p = 0.01) and free fluid on computed tomography were frequently present, however, and their significance was underappreciated in the occult injury group.

CONCLUSION

After blunt abdominal trauma in patients without obvious indications for invasive evaluation of the abdomen (e.g., peritoneal lavage, laparoscopy, laparotomy), leukocytosis can indicate an intestinal injury. Additionally, unexplained free fluid on abdominal computed tomography must be aggressively evaluated.

Diet-induced protection against lipopolysaccharide includes increased hepatic NO production

The host response to Gram-negative infection includes the elaboration of numerous proinflammatory agents, including tumor necrosis factor alpha (TNFalpha) and nitric oxide (NO). A component of the hepatic response to infection is an elevation in serum lipids, the so-called "lipemia of sepsis," which results from the increased production of triglyceride (TG)-rich lipoproteins by the liver. We have postulated that these lipoproteins are components of a nonadaptive, innate immune response to endotoxin [lipopolysaccharide (LPS)] and have previously demonstrated the capacity of TG-rich lipoproteins to protect against endotoxicity in rodent models of sepsis. Herein we report the capacity of a high-fructose diet to protect against LPS, most likely by inducing high circulating levels of endogenous TG-rich lipoproteins. The protective phenotype included the increased production of NO by hepatic endothelial cells. Rats, made hypertriglyceridemic by fructose feeding, experienced decreased LPS-induced mortality (P < 0.03) and systemic TNFalpha levels (P < 0.05) as compared with normolipidemic (chow-fed) controls. The increased survival was associated with elevated levels of inducible NO synthase (NOS2) mRNA levels and NO production (82 +/- 26 vs 3 +/- 3 nmol nitrite/10(6) cells, P < 0.001) by hepatic endothelial cells. Nonselective NOS inhibitors reversed the protective phenotype in vivo and readily decreased NO production by cultured endothelial cells from hypertriglyceridemic rats in vitro. This study suggests that a high-fructose diet can protect against endotoxicity in part through induction of endogenous TG-rich lipoproteins and hepatic endothelial cell NO production. This is the first report of diet-induced hyperlipoproteinemia and subsequent protection against endotoxemia.

Modulation of vasopressin-elicited water transport by trafficking of aquaporin2-containing vesicles

Vasopressin or AVP regulates water reabsorption by the kidney inner medullary collecting duct (IMCD) through the insertion and removal of aquaporin (AQP) 2 water channels into the IMCD apical membrane. AVP-elicited trafficking of AQP2 with the apical membrane occurs via a specialized population of vesicles that resemble synaptic vesicles in neurons. AQP2 vesicles and the IMCD apical membrane contain homologs of vesicle-targeting and signal transduction proteins found in neurons. Expression studies of AQP2, including human AQP2 mutants, suggest that the carboxyl-terminal domain of AQP2 is important in AQP2 trafficking, particularly as a site for cAMP-dependent protein kinase phosphorylation. These present data reveal that IMCD cells possess a complex integrated-signaling and vesicle-trafficking machinery that provides integration of AVP-elicited water transport with many other parameters within the IMCD cell as well as kidney.

Obstructive jaundice alters Kupffer cell function independent of bacterial translocation

BACKGROUND

There is a high incidence of perioperative morbidity and mortality in patients with obstructive jaundice. The absence of bile in the gastrointestinal tract promotes bacterial overgrowth and the increased translocation of bacteria and endotoxin to the liver which has been postulated to inhibit Kupffer cell function in these patients. But, biliary tract obstruction can directly damage liver cells and thus alter their function. Thus, we hypothesized that obstructive jaundice alone alters Kupffer cell function independent of the effects of bacterial translocation. This study was designed to evaluate the contribution of bacterial translocation to the altered Kupffer cell function observed in patients with obstructive jaundice.

METHODS

Sprague-Dawley rats were randomized to three groups of six animals each. Group 1 underwent common bile duct ligation with intestinal bile salt replacement (sodium taurocholate 100 mg/kg/day) via gastrostomy and an implantable osmotic pump (CBDL + bile salts), Group 2 underwent common bile duct ligation with normal saline replacement (CBDL + saline), and Group 3 underwent a sham operation (sham control). After 7 days, tissue and blood were collected for bacterial translocation and biochemical analyses. Examination of cultured Kupffer cell function included measuring the phagocytosis of heat-killed Candida albicans and endotoxin (LPS)-induced TNFalpha and nitric oxide production.

RESULTS

While bacterial translocation and cecal bacterial counts were significantly increased in the CBDL + saline group, these parameters were both reduced to control levels following intestinal bile salt replacement (CBDL + bile salts). Altered Kupffer cell function, as measured by the increased phagocytosis of C. albicans and LPS-induced NO production, and decreased LPS-induced TNFalpha production were observed in all animals with obstructive jaundice regardless of bile salt replacement.

CONCLUSION

Kupffer cell function appears to be differentially affected by obstructive jaundice and these altered functions can occur independent of bacterial translocation.

Recent insights into the coordinate regulation of body water and divalent mineral ion metabolism

Traditionally, arginine vasopressin modulation of renal water, sodium, and urea excretion has been considered somewhat in isolation from factors that control divalent mineral ion homeostasis. Similarly, previous considerations of divalent mineral ion metabolism have focused mainly on the role of hormones, eg, parathyroid hormone and various forms of vitamin D, as principal modifiers of renal calcium handling. Recent data, however, have now suggested the existence of novel linkages that coordinate control of water and divalent mineral ion homeostasis. This article summarizes these data and highlights the fundamental roles of the extracellular calcium polyvalent cation-sensing receptor (CaR) as an integrator of water and divalent mineral ion homeostasis on a cellular, organ-specific, and whole-body basis. Organs where CaRs may integrate water and divalent mineral ion metabolism include endocrine tissues that express CaRs, the brain, various nephron segments of the kidney, bone, and the gastrointestinal tract. These new data suggest that considerable regulatory overlap exists between water and divalent mineral ion homeostasis.

Membranous glomerulonephritis and nephrosis post factor IX infusions in hemophilia B

Children with hemophilia B who receive exogenous factor IX infusions may rarely develop inhibitors to the exogenous factor IX and require desensitization. Nephrotic syndrome has recently been described in some of these children. We report the renal clinicopathological findings in a child with severe factor IX deficiency, requiring induction of an immune tolerance protocol, who developed nephrotic syndrome. Renal biopsy revealed peripheral capillary wall thickening and a spike appearance consistent with membranous glomerulonephritis. Electron microscopy showed prominent deposits throughout the thickness of the basement membrane. Factor IX dose reduction was accompanied by reversal of the child's nephrotic syndrome without relapses.

Recurrent pyogenic cholangitis

BACKGROUND

Recurrent pyogenic cholangitis is a complex biliary tract disease characterized by intrahepatic pigment stones, endemic to Southeast Asia and seen with increasing frequency in the United States. The purpose of this study was to review the management of this disorder in a county hospital.

METHODS

A retrospective review of 45 patients with recurrent pyogenic cholangitis evaluated between 1984 and 1995. The clinical and surgical management of patients with localized versus bilateral hepatolithiasis were compared.

RESULTS

The prevalence of recurrent pyogenic cholangitis at our hospital has more than doubled since 1983. Fourteen of 45 patients (31%) had bilateral disease and required more abdominal computed tomography scans (P < 0.01), percutaneous cholangiograms (P < 0.05), endoscopies (P < 0.01), clinic visits (P < 0.05), and hospital admissions (P < 0.02) as compared with patients with localized disease.

CONCLUSIONS

The effective treatment of recurrent pyogenic cholangitis requires definition of the patients' intrahepatic distribution of disease, prior to surgical intervention, and the coordinated efforts of gastroenterologists, radiologists, and surgeons.

Disulfide bonds in the extracellular calcium-polyvalent cation-sensing receptor correlate with dimer formation and its response to divalent cations in vitro

Extracellular calcium/polyvalent cation-sensing receptors (CaR) couple to G proteins and contain highly conserved extracellular cysteine residues. Immunoblotting of proteins from rat kidney inner medullary collecting duct endosomes with CaR-specific antibodies reveals alterations in the apparent molecular mass of CaR depending on protein denaturation conditions. When denatured by SDS under nonreducing conditions, CaR migrates as a putative dimeric species of 240-310 kDa. This is twice the predicted molecular mass of the CaR monomer observed after SDS denaturation in the presence of sulfhydryl-reducing agents. In sucrose density gradients, Triton X-100-solubilized CaR sediments as a 220-kDa complex, not explainable by binding of G proteins to CaR monomers. Treatment of Triton-soluble CaR with divalent (Ca2+, Mg2+) and trivalent (Gd3+) metal ion CaR agonists, but not monovalent ions (Na+), partially shifts the electrophoretic mobility of CaR under reducing conditions from a predominantly monomeric to this putative dimeric species on immunoblots in a manner similar to their rank order of functional potency for CaR activation (Gd3+ >> Ca2+ > Mg2+). This Ca2+ effect is blocked by pretreatment with N-ethylmaleimide. We conclude that disulfide bonds present in CaRs mediate formation of dimers that are preserved in Triton X-100 solution. In addition, CaR exposure to Ca2+ induces formation of additional disulfide bonds within the Triton-soluble CaR complex.

Modulation of aquaporin 4 and the amiloride-inhibitable sodium channel in perinatal rat lung epithelial cells

During the perinatal period, a dramatic reversal of lung transepithelial ion and water transport occurs that involves the amiloride-inhibitable Na+ channel (ENaC). Aquaporin (AQP) water channel proteins facilitate cell membrane water transport. We now report that AQP-4, localized to basolateral membranes of airway epithelial cells, increases its mRNA expression in developing lung eightfold during the 2 days before birth to reach a peak on the first postnatal day in the lungs but not in brains or kidneys of neonatal rats. AQP-4 and the alpha-, beta-, and gamma-subunits of ENaC are both expressed by cultured rat fetal distal lung epithelial (FDLE) cells. AQP-4 and ENaC expression increase in FDLE cells cultured on uncoated permeant filters compared with matched control cells cultured on filters containing extracellular matrix derived from fetal lung epithelial cells. Similarly, AQP-4 expression increases in FDLE cells exposed to 21% O2 compared with cells exposed to 3% O2. These data demonstrate that AQP-4 expression is highest on the first day after birth in neonatal rat lungs. Exposure to ambient 21% O2 may contribute to increases in AQP-4 and ENaC expression to facilitate water transport across neonatal airway epithelia in the immediate postnatal period.

The perinatal expression of aquaporin-2 and aquaporin-3 in developing kidney

The kidney provides an important contribution to permit the fetus to successfully transition to an independent existence by production of urine with significantly different osmolality compared with plasma. Although recent work has uncovered many aspects of the maturation and regulation of the renal concentrating and diluting mechanism, understanding of how alterations in the expression of aquaporin (AQP) water channels contribute to the formation of urine in the perinatal period is incomplete. Here, we report that both AQP-2 and -3 are expressed during fetal life as early as embryonic d 18 in ureteric buds of rat kidneys, where each is localized to the apical and basolateral membranes of epithelial cells, respectively. Northern analyses demonstrate that the 1.9-kb AQP-2 transcript is present in fetal and postnatal rat kidneys similar to that observed in adults. AQP-2 mRNA expression increases after d 3 of postnatal life. Immunoblotting reveals an increase in total kidney AQP-2 protein particularly with respect to its glycosylated form after postnatal d 3. AQP-3 protein also exhibits a similar alteration likely due to a similar increase in its glycosylation state. Both AQP-2 and AQP-3 display a distribution in the collecting ducts of human postnatal infants and adults identical to that exhibited in rat kidneys. These data show that both AQP-2 and -3 are present in collecting duct epithelia of fetal and postnatal kidneys. Thus, the reduced AVP-responsiveness and decreased urinary concentrating ability of the kidney during the fetal and immediate postnatal period does not appear to be caused by lack of AQP-2 or AQP-3 proteins.

Vasopressin-elicited water and urea permeabilities are altered in IMCD in hypercalcemic rats

To investigate how hypercalcemia blunts renal concentrating ability, alterations in basal and arginine vasopressin (AVP)-elicited osmotic water (Pf) and urea (Purea) permeabilities were measured in isolated perfused terminal inner medullary collecting ducts (IMCD) from control and chronically hypercalcemic rats after dihydrotachysterol (DHT) (M. Levi, L. Peterson, and T. Berl. Kidney Int. 23: 489-497, 1983) treatment. The IMCD Pf of DHT-treated rats did not increase significantly after AVP and was accompanied by a significant 87 +/- 4% reduction in aquaporin-2 (AQP-2) protein but not mRNA. In contrast, both basal and AVP-elicited IMCD Purea from DHT rats were significantly increased and accompanied by a significant 41 +/- 11% increase in AVP-regulated urea transporter protein content. Immunoblotting with anti-calcium/polyvalent cation-sensing receptor protein (CaR) antiserum revealed specific alterations in CaR bands in endosomes purified from the apical membranes of inner medulla of DHT rats. These data are the first detailed analyses of hypercalcemia-induced alterations in AVP-regulated permeabilities and membrane transporters in IMCD. We conclude that selective alterations in IMCD transport occur in hypercalcemia, permitting the body to dispose of excess calcium without forming calcium-containing renal stones.

Chylomicrons alter the hepatic distribution and cellular response to endotoxin in rats

Chylomicrons (CM) can bind endotoxin (lipopolysaccharide [LPS]), forming CM-LPS complexes, and protect against endotoxic shock and death in rodent models of gram-negative sepsis. The liver appears to play a central role in this process, as demonstrated by the increased uptake of LPS by this organ. We examined the effect of CM on the uptake and cellular response to injected 125I-LPS by hepatocytes and hepatic nonparenchymal cells. Whereas CM increased the uptake of LPS by both hepatocytes and Kupffer cells, the increase was proportionately greater in hepatocytes than Kupffer cells. Importantly, CM-LPS complexes inhibited inducible nitric oxide synthase (iNOS) mRNA expression and NO production in Kupffer cells and endothelial cells, reducing mRNA levels by 45% to 50% as compared with LPS alone. CM-bound LPS also reduced NO production by hepatocytes in response to cytokine stimulation. Lastly, CM-LPS complexes yielded a concentration-dependent inhibition of LPS-induced tumor necrosis factor alpha (TNF-alpha) production by Kupffer cells in vitro. These data indicate that the mechanism by which CM protect against endotoxicity may involve an increased uptake of LPS by hepatocytes. Moreover, uptake of CM-bound LPS by liver cells attenuates the capacity of these cells to respond to proinflammatory stimulation. These results highlight important anti-inflammatory properties of CM.

Ciprofloxacin overdose: acute renal failure with prominent apoptotic changes

Acute renal failure due to ciprofloxacin has been well described. The previously reported cases have been consistent both clinically and pathologically with tubulointerstitial nephritis (TIN). We report a case of ciprofloxacin overdose leading to acute renal failure characterized by acute tubular necrosis (ATN). The outstanding features in the patient's renal biopsy were those of distal nephron apoptosis, best seen in plastic-embedded sections and electron microscopy. This report shows that the distal nephron can be singularly involved in acute renal failure and that electron microscopy or plastic-embedded sections may be necessary to define its involvement.

Changing management of gallstone disease during pregnancy

BACKGROUND

Symptomatic gallstones may be problematic during pregnancy. The advisability of laparoscopic cholecystectomy (LC) is uncertain. The objective of this study is to define the natural history of gallstone disease during pregnancy and evaluate the safety of LC during pregnancy.

METHODS

Review of medical records of all pregnant patients with gallstone disease at the University of California, San Francisco, from 1980 to 1996.

RESULTS

Of approximately 29,750 deliveries, 47 (0.16%) patients were treated for gallstone disease, including biliary colic in 33, acute cholecystitis in 12, and pancreatitis in two. Conservative treatment was attempted in all patients but failed in 17 (36%) cases. Two patients required combined preterm Cesarean-section cholecystectomy and 10 required surgery in the early postpartum period for persistent symptoms. Seventeen patients required cholecystectomy during pregnancy for biliary colic (10), acute cholecystitis (six), and pancreatitis (one). Three patients were treated with open cholecystectomy. Fourteen patients underwent LC at a mean gestational age of 18.6 weeks, mean OR time of 74 min, and mean length of stay of 1.2 days. Hasson cannulation was utilized in 11 patients. Reduced-pressure pneumoperitoneum (6-10 mmHg) was used in seven patients. Prophylactic tocolytics were used in seven patients, with transient postoperative preterm labor observed in one. There were no open conversions, preterm deliveries, fetal loss, teratogenicity, or maternal morbidity.

CONCLUSIONS

In past years, symptomatic gallstones during pregnancy were managed conservatively or with open cholecystectomy. LC is a feasible and safe method for treating severely symptomatic patients.

Renovascular hypertension in Marfan syndrome

A defect in fibrillin integrity predisposes patients with Marfan syndrome to vascular wall abnormalities, most notably aortic rupture and dissection. Renal vascular anomalies have not been described previously in children with Marfan syndrome. In this report, we detail data from a hypertensive 14-year-old girl with clinical stigmata of Marfan syndrome and a diagnostic evaluation significant for characteristic aortic root dilatation and aneurysm, as well as a disparity in renal size and function exacerbated by captopril administration. Renal arteriography confirmed a left main renal artery stenosis that was not amendable to balloon angioplasty. Surgical resection resulted in significant improvement in hypertension. Pathological examination of the resected renal artery segment revealed intimal proliferation, fragmentation of the elastic media, and inner medial dissection. This patient demonstrates that, in addition to the aorta, renal arteries can be affected with the characteristic vascular wall pathology of Marfan syndrome, resulting in systemic hypertension. These data suggest that children with Marfan syndrome and hypertension need to be evaluated carefully for the presence of renal anomalies.

Interactions of ultrapure bovine hemoglobin with renal epithelial cells in vivo and in vitro

Using an ultrapurified hemoglobin (Hb) solution, we investigated the physiological effects and cellular processing of Hb in rat kidneys and in cultured opossum kidney (OK) cells. Rats infused with < 5.0 g/kg Hb showed no change in baseline serum creatinine (SCr) values (0.58 +/- 0.05 mg/dl) over 48 h, whereas transient acute renal failure followed infusion of 7.5 g/kg Hb (SCr 3.4 +/- 1.02 mg/dl, P = 0.02). Histology of Hb-infused kidneys demonstrated tubular epithelial cell injury. Renal injury was not caused by volume or oncotic load, cardiovascular effect, or ATP depletion. After Hb infusion, heme oxygenase, the rate-limiting enzyme in Hb catabolism, was induced in an organ-specific fashion. Inhibiting heme oxygenase activity with cimetidine did not alter Hb renal injury. Using OK cells, we determined that renal epithelia process Hb by fluid-phase endocytosis. Proton permeability of fluorescein Hb endosomes was unaltered compared with fluorescein dextran controls, demonstrating that Hb does not alter endosomal membrane integrity. These data suggest that Hb renal injury in rats occurs following large doses of ultrapure Hb, does not alter early steps in Hb endosomal processing by renal epithelia, and involves a mechanism that is not heme oxygenase dependent.

Surgical risk assessment and management in patients with HIV disease

Determining the perioperative risks associated with surgical procedures performed in patients with HIV disease is a difficult and complex task. Because HIV is a contagious, blood-borne pathogen, it threatens the health and well-being of both patient and health care provider. Despite poor early results, there is now convincing evidence that HIV infection is not a significant, independent risk factor for major surgical procedures. In practice, the authors evaluate the risk of surgery in patients with HIV infection using the same basic tools and guidelines applied to the uninfected, with the best predictors of surgical morbidity and mortality stemming from a careful and accurate assessment of the patient's cardiopulmonary, renal, endocrine, and nutritional reserve. Although HIV disease provides a unique constellation of diagnoses and challenges to the health care provider, the risk of major surgery in this population is not unlike that for other immunocompromised or malnourished patients. The authors believe that members of the surgical team have a professional, moral, and ethical responsibility to provide the highest possible quality of care for their patients, regardless of their HIV status. If after weighing the risks and benefits to the patient the surgeon believes the procedure will have a positive effect on the patient's life, the surgeon must offer surgical treatment. To do less does a disservice to the patient, the provider, and the profession as a whole.

Apical extracellular calcium/polyvalent cation-sensing receptor regulates vasopressin-elicited water permeability in rat kidney inner medullary collecting duct

During antidiuresis, increases in vasopressin (AVP)-elicited osmotic water permeability in the terminal inner medullary collecting duct (tIMCD) raise luminal calcium concentrations to levels (> or = 5 mM) above those associated with the formation of calcium-containing precipitates in the urine. Calcium/polycation receptor proteins (CaRs) enable cells in the parathyroid gland and kidney thick ascending limb of Henle to sense and respond to alterations in serum calcium. We now report the presence of an apical CaR in rat kidney tIMCD that specifically reduces AVP-elicited osmotic water permeability when luminal calcium rises. Purified tIMCD apical membrane endosomes contain both the AVP-elicited water channel, aquaporin 2, and a CaR. In addition, aquaporin 2-containing endosomes also possess stimulatory (G(alpha q)/G(alpha 11) and inhibitory (G(alpha i1, 2, and 3)) GTP binding proteins reported previously to interact with CaRs as well as two specific isoforms (delta and zeta) of protein kinase C. Immunocytochemistry using anti-CaR antiserum reveals the presence of CaR protein in both rat and human collecting ducts. Together, these data provide support for a unique tIMCD apical membrane signaling mechanism linking calcium and water metabolism. Abnormalities in this mechanism could potentially play a role in the pathogenesis of renal stone formation.

The 17 kDa band identified by multiple anti-aquaporin 2 antisera in rat kidney medulla is a histone

The osmotic water permeability of epithelial cells of the inner medullary collecting duct of the kidney is regulated by antidiuretic hormone (ADH). ADH causes the insertion and removal of cytoplasmic vesicles containing the aquaporin (AQP-2) water channel protein which is recognized by multiple rabbit antipeptide antisera raised against amino acid sequences comprising its cytoplasmic carboxyl terminal. Immunoblots of rat kidney membrane fractions as well as human urine have all shown that AQP-2 is expressed exclusively by collecting duct cells and have identified a 29 kDa band (corresponding to the nonglycosylated AQP-2 protein), a broad 35-45 kDa band (corresponding to the mature glycosylated form of AQP-2 protein) and an additional immunoreactive 17 kDa band of unknown origin. We now report that the 17 kDa band identified by these anti-AQP-2 antisera is not an AQP-2 component but rather a denatured histone protein type H2A1. This binding of anti-AQP-2 antisera to denatured H2A1 present in protein samples derived from both kidney inner medulla and human urine is blocked specifically by preincubation of immunoblots with solutions containing the acidic protein gelatin.

Role of the Ca(2+)-sensing receptor in divalent mineral ion homeostasis

The divalent mineral cations Ca2+ and Mg2+ play many and diverse roles both in the function of cells and in extracellular processes. The metabolism of these cations is a complex process involving the coordinated function of several organ systems and endocrine glands. A recently cloned G-protein-coupled receptor responds to extracellular calcium concentration (Ca2+0-sensing receptor, CaSR) and mediates several of the known effects of Ca2+0 on parathyroid and renal function. The CaSR, which is also expressed in a number of other tissues including thyroidal C-cells, brain and gastrointestinal tract, may function as a Ca2+0 sensor in these tissues as well. Thus, Ca2+0 is a first messenger (or hormone) which, via CaSR-mediated activation of second messenger systems (e.g. phospholipases C and A2, cyclic AMP) leads to altered function of these cells. Several mutations in the human CaSR gene have been identified and shown to cause three inherited diseases of calcium homeostasis, clearly implicating the CaSR as an important component of the homeostatic mechanism for divalent mineral ions. Ca2+ and Mg2+ losses from the body are regulated by altering the urinary excretion of these divalent cations. The localization of the CaSR transcripts and protein in the kidney not only provides a basis for a direct Ca2+0 (or Mg2+0)-mediated regulation of Ca2+ (and Mg2+) excretion but also suggests a functional link between divalent mineral and water metabolism. In the kidney, the thick ascending limb of Henle (TAL) plays crucial roles in regulating both divalent mineral reabsorption and urine concentration. Recent studies have suggested models whereby extracellular Ca2+, via the CaSR expressed in the TAL as well as in the collecting duct system, modulates both Ca2+ 0 and Mg2+ 0 as well as water reabsorbtion. When taken together, these studies suggest that the CaSR not only provides the primary mechanism for Ca2+ 0-mediated regulation of parathyroid hormone secretion from parathyroid glands but also for direct modulation of renal divalent mineral excretion and urinary concentrating ability. These latter functions may furnish a mechanism for integrating and balancing water and divalent cation losses that minimizes the risk of urinary tract stone formation. This mechanism can explain hypercalcemia-mediated polyuria (diabetes insipidus).

Chronic morphine induces visible changes in the morphology of mesolimbic dopamine neurons

The mesolimbic dopamine system, which arises in the ventral tegmental area (VTA), is an important neural substrate for opiate reinforcement and addiction. Chronic exposure to opiates is known to produce biochemical adaptations in this brain region. We now show that these adaptations are associated with structural changes in VTA dopamine neurons. Individual VTA neurons in paraformaldehyde-fixed brain sections from control or morphine-treated rats were injected with the fluorescent dye Lucifer yellow. The identity of the injected cells as dopaminergic or nondopaminergic was determined by immunohistochemical labeling of the sections for tyrosine hydroxylase. Chronic morphine treatment resulted in a mean approximately 25% reduction in the area and perimeter of VTA dopamine neurons. This reduction in cell size was prevented by concomitant treatment of rats with naltrexone, an opioid receptor antagonist, as well as by intra-VTA infusion of brain-derived neurotrophic factor. In contrast, chronic morphine treatment did not alter the size of nondopaminergic neurons in the VTA, nor did it affect the total number of dopaminergic neurons in this brain region. The results of these studies provide direct evidence for structural alterations in VTA dopamine neurons as a consequence of chronic opiate exposure, which could contribute to changes in mesolimbic dopamine function associated with addiction.

Ontogeny of the extracellular calcium-sensing receptor in rat kidney

We recently cloned extracellular Ca(2+)-sensing receptors (CaRs) from bovine parathyroid and rat kidney that play key roles in Ca2+ homeostasis. Inactivating mutations of the CaR in the inherited human disorder, familial hypocalciuric hypercalcemia, cause reduced responsiveness of the parathyroid to extracellular Ca2+ (Cao2+), as well as abnormally avid renal tubular reabsorption of both Ca2+ and Mg2+ in the distal tubule, suggesting an important role for the CaR in regulating parathyroid hormone (PTH) secretion and renal handling of divalent cations. High Cao2+ also inhibits vasopressinstimulated adenosine 3',5'-cyclic monophosphate accumulation in the medullary thick ascending limb (MTAL) and water reabsorption in the collecting duct (CD) and modulates various other aspects of renal function. The relevance of the CaR to these processes, however, is uncertain. Reduced responsiveness of vasopressin-and PTH-mediated actions on the kidney have been described in the newborn that could potentially reflect effects of the CaR on these aspects of renal function. To define further the role of the CaR in regulating renal function, including the above-mentioned changes during the perinatal period, therefore, we have studied its ontogeny in rat kidney. Northern and Western blot analyses, as well as immunohistochemistry with CaR-specific probes, demonstrate that there is little prenatal expression of the extracellular Ca(2+)-sensing receptor, except in large tubules and branching ureteric buds of developing nephrons. Postnatally, CaR mRNA and protein increase markedly during the 1st wk, related principally to expression of the receptor in the developing TAL and, to a lesser extent, in the CD. The level of expression of the receptor remains nearly constant after postnatal day 14. These results demonstrate that the perinatal increases in expression of CaR mRNA and protein parallel its tissue-specific renal expression. Furthermore, it is possible that some of the previously described changes in renal handling of divalent cations and water in the perinatal and immediate postnatal period are related, in part, to the increasing levels of expression of the CaR and resultant inhibitory effects on the actions of PTH and antidiuretic hormone on the developing nephron.

Sepsis increases endocytosis of endotoxin into hepatocytes

BACKGROUND

Chylomicrons bind endotoxins and accelerate their clearance from plasma to the liver. This results in reduced mortality from septic shock in a rodent model. We hypothesized that the clearance of the LPS-chylomicron (LPS-CM) complex by hepatocytes is due to receptor-mediated endocytosis and that sepsis up-regulates this process.

METHODS

Three groups of Sprague-Dawley rats; (1) control; (2) pretreated with 10 micrograms/kg LPS 24 hours before treatment; and (3) pretreated with 17-alpha-ethinyl estradiol (EE, 5 mg/kg subcutaneously for 3 days), were infused with labeled I125-LPS alone or with I125-LPS bound to chylomicron. Livers were removed 2.5, 15, and 30 minutes after LPS injection, and hepatic endosomes were isolated from the liver homogenates by serial ultracentrifugation in sucrose gradients.

RESULTS

The injection of I125-LPS-CM complexes resulted in higher levels of endosomal I125-LPS in all groups, as compared with I125-LPS alone. In addition, the endosomal uptake of I125-LPS was markedly increased by both LPS and EE pretreatments.

CONCLUSIONS

These data strongly suggest a primary role for receptor-mediated endocytosis in the increased clearance of LPS when bound to chylomicron. In addition, exposure to LPS appears to increase the accumulation of LPS in endosomes by a mechanism similar to that of EE, which is known to up-regulate receptor-mediated lipoprotein uptake. This endogenous pathway for the catabolism of endotoxins may provide a teleological explanation for the hypertriglyceridemia observed during sepsis.

Phosphorylation of aquaporin-2 does not alter the membrane water permeability of rat papillary water channel-containing vesicles

Antidiuretic hormone modulates the water permeability (Pf) of epithelial cells in the rat kidney by vesicle-mediated insertion and removal of the aquaporin-2 (AQP-2) water channel. AQP-2 possesses a single consensus cAMP-dependent protein kinase A (PKA) phosphorylation site (Ser-256) hypothesized to regulate channel Pf(Kuwahara, M., Fushimi, K., Terada, Y., Bai, L., Sasaki, S., and Marumo, F. (1995) J. Biol. Chem. 270, 10384-10387). To test whether PKA phosphorylation of AQP-2 alters channel Pf, we compared the Pf values of purified AQP-2 endosomes after incubation with either PKA or alkaline phosphatase. Studies using [gamma-32P]ATP reveal that AQP-2 endosomes contain endogenous PKA and phosphatase activities that add and remove 32P label from AQP-2. However, the Pf (0.16 +/- 0.06 cm/s) of endosomes containing phosphorylated AQP-2 (0.7 +/- 0. 3 mol of PO4/mol of protein) is not significantly different from the same AQP-2 endosomes where 95 +/- 8% of the phosphate has been removed (Pf 0.14 +/- 0.06 cm/s). These data do not support a role for PKA phosphorylation in alteration of AQP-2's Pf. Instead, AQP-2 phosphorylation by PKA may modulate AQP-2's distribution between plasma membrane and intracellular vesicle compartments.

Immunohistochemical studies of mesolimbic dopaminergic neurons in Fischer 344 and Lewis rats

Previous work has shown that the inbred Lewis and Fischer 344 rat strains differ in several behavioral measures related to mesolimbic dopamine function. Moreover, the ventral tegmental area (VTA) of the Lewis rat has been shown to contain higher levels of tyrosine hydroxylase compared to that of the Fischer rat by blot immunolabeling procedures. To investigate structural correlates of this biochemical difference, an immunohistochemical study of VTA dopaminergic neurons in these two strains was undertaken. Results show that the density and total number of tyrosine hydroxylase-positive neurons in the VT 4 of the Lewis rat is about 50% of that found in the Fischer rat. In contrast, examination of the substantia nigra in the same sections revealed no differences in the density and number of tyrosine hydroxylase-positive cells between these strains. Fischer-Lewis strain differences were also evident for cholecystokinin immunoreactivity in the VTA, with much lower levels seen in the Lewis rat, consistent with the known colocalization of this neuropeptide in many VTA dopamine neurons. The finding of 50% fewer tyrosine hydroxylase-positive neurons in the VTA of the Lewis rat, along with our earlier results showing 45% higher levels of tyrosine hydroxylase by blot immunolabeling, would suggest much higher levels of tyrosine hydroxylase per VTA neuron in this strain. However, no obvious strain difference in the cellular intensity of tyrosine hydroxylase immunoreactivity could be detected by immunohistochemistry. Finally, the density of VTA dopamine neurons was assessed in 1-week-old Fischer and Lewis rats. In contrast to the results obtained for adult animals, no difference in the number of tyrosine hydroxylase-positive neurons was apparent in these young animals, indicating that the Fischer-Lewis strain difference in VTA dopamine neurons appears later in postnatal development. These anatomical findings shed new light on the differences in the mesolimbic dopamine system between Fischer and Lewis rats that may contribute to the behavioral differences exhibited by these animals.

Cloning of an aquaporin homologue present in water channel containing endosomes of toad urinary bladder

Regulation of total body water balance in amphibians by antidiuretic hormone (ADH) contributed to their successful colonization of terrestrial habitats approximately 200-300 million years ago. In the mammalian kidney, ADH modulates epithelial cell apical membrane water permeability (Pf) by fusion and retrieval of cytoplasmic vesicles containing water channel proteins called aquaporins (AQPs). To determine the role of AQPs in ADH-elicited Pf in amphibians, we have identified and characterized a unique AQP from Bufo marinus called AQP toad bladder (AQP-TB). AQP-TB possesses many structural features common to other AQPs, AQP-TB is expressed abundantly in ADH-responsive tissues, including toad urinary bladder and skin as well as lung, skeletal muscle, kidney, and brain. In a manner identical to that reported for the mammalian ADH-elicited water channel AQP2, AQP-TB expression is increased significantly by intervals of dehydration or chronic ADH stimulation. However, expression of AQP-TB protein in Xenopus laevis oocytes does not significantly increase oocyte Pf. The lack of expression of functional AQP-TB water channels in oocytes may result from intracellular sequestration of AQP-TB due to the presence of a YXRF sequence motif present in its carboxyterminal domain.