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Biomedical subjects

W D Warren

Publications and source records attributed to W D Warren.

At least 19 recordsLinked to original sources
PubMed1995

Induction of germ-line gamma 1 and epsilon Ig gene expression in murine B cells. IL-4 and the CD40 ligand-CD40 interaction provide distinct but synergistic signals.

The interaction between B cell CD40 and its ligand (CD40L) on activated Th cells provides a critical signal necessary for T cell-dependent isotype switching. Previous studies suggest that this signal might be important in regulating isotype switching at the level of germ-line Ig transcription. To assess the effects of the CD40L-CD40 interaction on germ-line Ig transcript expression in murine B cells, a membrane-bound form of mouse CD40L was expressed in the baculovirus system. We show that stimulation of resting splenic B cells with CD40L-expressing Sf9 cells induces germ-line gamma 1 and epsilon transcripts independently of cytokines. The CD40-mediated induction cannot be blocked by anti-IL-4 Ab and is not mediated by other cytokines secreted endogenously in response to CD40 stimulation. Importantly, stimulation with CD40L and IL-4 together has a significant synergistic effect on germ-line transcript expression. Stimulation of CD40 does not activate the NF-IL-4-gamma 1 DNA binding factor believed to be required for IL-4-dependent germ-line gamma 1 transcription. Moreover, mutation of the NF-IL-4-gamma 1 DNA binding site in a germ-line gamma 1 promoter-luciferase reporter gene construct completely ablates IL-4 responsiveness but has no effect on responsiveness to CD40L in transient transfection assays. These results demonstrate that the CD40L-CD40 interaction and IL-4 activate germ-line Ig gene transcription by distinct but synergistic mechanisms and suggest that multiple signals may be required to induce sufficient germ-line transcription and/or germ-line transcript levels necessary to target switch recombination.

Animals↗
PubMed1995

The transposable element mariner can excise in non-drosophilid insects.

Plasmid-based excision assays performed in embryos of two non-drosophilid species using the mariner transposable element from Drosophila mauritiana resulted in empty excision sites identical to those observed after the excision of mariner from D. mauritiana chromosomes. In the presence of the autonomous mariner element Mos1, excision products were recovered from D. melanogaster, D. mauritiana and the blowfly Lucilia cuprina. When a hsp82 heat shock promoter-Mos1 construct was used to supply mariner transposase, excision products were also recovered from the Queensland fruitfly Bactrocera tryoni. Analysis of DNA sequences at empty excision sites led us to hypothesise that the mariner excision/repair process involves the formation of a heteroduplex at the excision breakpoint. The success of these assays suggests that they will provide a valuable tool for assessing the ability of mariner and mariner-like elements to function in non-drosophilid insects and for investigating the basic mechanisms of mariner excision and repair.

Animals↗
PubMed1995

Signaling via major histocompatibility complex class II molecules and antigen receptors enhances the B cell response to gp39/CD40 ligand.

Activated T cells induce proliferation and differentiation of resting B cells in vitro through their CD40 molecules and lymphokine receptors. However, despite constitutive B cell expression of CD40 and lymphokine receptors, widespread nonspecific polyclonal B cell activation by activated T cells is seldom observed in vivo. The present study was designed to test the hypothesis that signals delivered via the B cell antigen (Ag) receptor (membrane immunoglobulin, mIg) and major histocompatibility complex (MHC) class II molecules enhance B cell responsiveness to CD40-mediated signals, providing specificity to the Ag-nonspecific, MHC-unrestricted CD40 signal. To test this hypothesis, both an Ag-specific mouse B cell clone CH12.LX, and freshly isolated resting splenic B cells were cultured with either soluble or membrane-bound forms of the T cell ligand for CD40 (CD40L), in the presence or absence of additional signals provided by Ag or anti-IgM, interleukin-4, and class II-specific monoclonal antibody (mAb). Differentiation of CH12.LX cells and proliferation of splenic B cells in response to both forms of CD40L was greatly enhanced by exposure to mIg-mediated signals, with greatest enhancement seen when cells were cultured with Ag prior to receiving other signals. Response to CD40L was further enhanced by concurrent culture with class II-specific, but not class I-specific mAb. Enhancement was greatest at limiting concentrations of CD40L. The ability of class II MHC-mediated signals to enhance Ag-specific B cell responsiveness to CD40-mediated signaling may selectively promote the activation of B cell clones capable of cognate interactions with helper T cells.

Animals↗
PubMed1994

Interplasmid transposition of Drosophila hobo elements in non-drosophilid insects.

A modified hobo element from Drosophila melanogaster was introduced into embryos of the housefly, Musca domestica (family Muscidae) and the Queensland fruitfly, Bactrocera tryoni (family Tephritidae) to assess its ability to transpose. Hobo was capable of transposition in these species and transposition products had all of the hallmarks of hobo transposition products recovered from D. melanogaster, including the movement only of sequences precisely delimited by the inverted terminal repeats of hobo, the creation of an 8 bp duplication of the insertion site and an absolute requirement for hobo-encoded transposase. Transposition of hobo into the target gene resulted in a non-random distribution of insertion sites, with 10 of 38 independent insertions into the same nucleotide position. The results indicate that hobo can transpose in heterologous species, further demonstrating the similarity of hobo to Ac (Activator) of Zea mays and Tam3 of Antirrhinum majus. Hobo has excellent potential to act as a gene vector or gene tagging agent in nondrosophilid insects.

Animals↗
PubMed1994

The Hermes transposable element from the house fly, Musca domestica, is a short inverted repeat-type element of the hobo, Ac, and Tam3 (hAT) element family.

The genome of the house fly, Musca domestica, contains an active transposable element system, called Hermes. Using PCR and inverse PCR we amplified and sequenced overlapping segments of several Hermes elements and from these data we have constructed a 2749 bp consensus Hermes DNA sequence. Hermes termini are composed of 17 bp imperfect inverted repeats that are almost identical to the inverted terminal repeats of the hobo element of Drosophila melanogaster. Full length Hermes elements contain a single long ORF capable of encoding a protein of 612 amino acids which is 55% identical to the amino acid sequence of the hobo transposase. Comparison of the ends of the Hermes and hobo elements to those of the Ac element of Zea mays, and the Tam3 element of Antirrhinum majus, as well as several other plant and insect elements, revealed a conserved terminal sequence motif. Thus Hermes is clearly a member of the hobo, Ac and Tam3 (hAT) transposable element family, other members of which include the Tag1 element from Arabidopsis thaliana and the Bg element from Zea mays. The evolution of this class of transposable elements and the potential utility of Hermes as a genetic tool in M. domestica and related species are discussed.

Amino Acid Sequence↗
PubMed1990

Endoscopic variceal sclerosis compared with distal splenorenal shunt to prevent recurrent variceal bleeding in cirrhosis. A prospective, randomized trial.

STUDY OBJECTIVE: To define the roles of endoscopic variceal sclerosis and distal splenorenal shunt in the prevention of recurrent variceal bleeding in patients with cirrhosis. DESIGN: A prospective, randomized clinical trial with crossover for those failing therapy. The median follow-up was 61 months. SETTING: A private, tertiary-referral university hospital. PATIENTS: Seventy-two patients fulfilling inclusion criteria were drawn from a total of 420 patients treated during a 4.5-year interval. TREATMENTS: Endoscopic variceal sclerosis or distal splenorenal shunt. MEASUREMENTS AND MAIN RESULTS: Survival was significantly (P = 0.02) improved in patients randomly assigned to receive sclerotherapy: 13 of these 37 (35%) patients failed sclerotherapy and required surgical rescue. A survival advantage (P = 0.01) was seen in patients with alcoholic cirrhosis who had this combined therapy; however, in patients with nonalcoholic cirrhosis, survival for those receiving sclerotherapy and surgical rescue was not significantly (P = 0.36) different from that of patients receiving distal splenorenal shunt. Control of variceal bleeding was significantly (P less than 0.001) better in the distal splenorenal shunt group (34 of 35 [97%] compared with 15 of 37 [41%] in the sclerotherapy group). Using death, uncontrolled rebleeding, or shunt thrombosis as the endpoints resulted in no significant difference between treatment groups. Hepatocyte function and portal perfusion were significantly better maintained in patients with alcoholic cirrhosis who were managed by sclerotherapy rather than shunt (P = 0.01 and P = 0.001, respectively). CONCLUSIONS: Endoscopic sclerotherapy with surgical rescue for uncontrolled bleeding is the optimum therapy for patients with alcoholic cirrhosis and variceal bleeding. Survival is similar in nonalcoholic patients treated with either distal splenorenal shunt or endoscopic sclerotherapy, but shunting provides better control of variceal bleeding.

Endoscopy↗
PubMed1990

A hypercoagulable state follows orthotopic liver transplantation.

Orthotopic liver transplantation may be associated during the postoperative period with hepatic artery thrombosis, a catastrophic occurrence generally necessitating emergency retransplantation. To assess the contribution of the coagulation mechanism to this complication, the levels of procoagulant and anticoagulant proteins were followed in 41 liver transplant patients during the first 10 postoperative days. The mean activities of all procoagulant factors reach normal values on day 1 except for factors V and VII, which achieve normal activity by day 3. Supernormal levels of factor VIII activity and antigen are noted (peak values on day 5 of 334% +/- 113% and 481% +/- 260%, respectively). The anticoagulant proteins show delayed recovery, with deficient antithrombin III levels seen in 81% of patients on day 3 and 57% on day 5. Similarly, proteins C and S are subnormal in 24% and 21%, respectively on day 3, and 20% and 10%, respectively, on day 5. During this period, elevated levels of thrombin/antithrombin complexes are encountered, reflecting in vivo activation of the coagulation mechanism. Activated thrombin is, therefore, being generated at a time when a decrease in the major regulatory anticoagulant proteins exists. These data suggest an imbalance between the hemostatic and thrombotic mechanisms and indicate a sustained prothrombotic state that may contribute to the risk for hepatic artery thrombosis. Using a regimen of low-dose heparin and fresh frozen plasma infusion, no thromboses have been seen in 65 consecutive liver transplants.

Blood Coagulation Disorders↗
PubMed1990

Surgical options, hematologic evaluation, and pathologic changes in Budd-Chiari syndrome.

This article presents a scheme of management for Budd-Chiari syndrome based on experience with 33 patients. Therapy in acute Budd-Chiari syndrome is dictated by the liver biopsy, with hepatocyte necrosis indicating the need for placement of a decompressive shunt. The type of shunt was determined by intrahepatic vena cava obstruction; a higher morbidity rate was associated with the mesoatrial shunt in 11 patients than with a portacaval shunt in 10 patients. Successful shunt placement allowed stabilization of the liver biopsy and maintenance of good hepatocyte function [galactose elimination capacity (preoperative: 349 +/- 40 mg/minute; 20 months: 344 +/- 60 mg/minute)]. Severe fibrosis and reduced galactose elimination capacity (264 +/- 43 mg/minute) indicated advanced disease--chronic Budd-Chiari syndrome--and were indications for liver transplant. Hematologic evaluation documented a myeloproliferative disorder in 8 of the last 13 patients evaluated; perioperative and late anticoagulation and/or chemotherapy reduced recurrent thrombosis. We conclude that the Budd-Chiari syndrome requires different therapies depending on the stage of disease. If no hepatocyte injury is present on biopsy, therapy may not be needed. Acute, reversible injury can be managed by placement of a decompressive shunt. Irreversible damage requires transplantation. Selection of the right therapy requires a complete evaluation.

Budd-Chiari Syndrome↗
PubMed1990

The relative role of sclerotherapy vs. surgical procedures in portal hypertension.

This review is a discussion of the evolution of different modes of therapy to treat variceal bleeding. At the present time, endoscopic sclerosis represents the mainstay of therapy for most patients with chronic cirrhosis. In patients who fail sclerotherapy, selective shunt surgery is indicated in patients with good hepatic reserve, and liver transplantation for those who have chronic liver failure.

Humans↗
PubMed1989

Increased galactose clearance after liver transplantation: a measure of increased blood flow through the denervated liver?

This study measured the liver blood flow-dependent index of galactose clearance in patients after liver transplantation, to test the hypothesis that liver blood flow is increased in the denervated liver. Eight normal subjects and 16 patients 1 to 8 months after liver transplant were studied. All patients were stable with no evidence of severe rejection at the time of study. Galactose clearance was measured at steady state during continuous infusion of 75 mg per min of 5% galactose. The results show a statistically significant (p less than 0.01) higher average galactose clearance in the transplant patients (1,187 +/- 316 ml per min per m2) compared to the control group (709 +/- 121 ml per min per m2). The major limiting factor in galactose clearance at low concentrations is liver blood flow, and we interpret these data as evidence for increased blood flow in the transplanted liver. Possible mechanisms for the increased galactose clearance are (i) loss of normal vasomotor tone in the denervated liver, or (ii) persistence of abnormal systemic hemodynamics after transplantation. Elucidation of these mechanisms awaits further study.

Adult↗
PubMed1989

Change in hepatic function, hemodynamics, and morphology after liver transplant. Physiological effect of therapy.

Orthotopic liver transplantation (OLT) has become standard therapy for patients with acute hepatic necrosis and end-stage liver disease. This study measured change in hepatic function (galactose elimination capacity [GEC]), liver blood flow (low dose galactose clearance: flow), hepatic volume (CT scan; volume) and morphology after OLT. The aim was to measure the physiologic response after OLT and compare this response with that after selective shunt (SS) and sclerotherapy (ES) to determine which patients should receive specific therapy. Between January 1987 and November 1988, 37 patients underwent OLT. Operative mortality was 18%, which was similar to that of SS in Child's C cirrhotics. GEC and volume were less in transplant patients than in cirrhotics treated with SS or ES. GEC, flow, and volume normalized after OLT; GEC was preserved after ES and SS, but volume decreased. Three preoperative patterns were observed that can aid in selection of OLT candidates. Patients with chronic cirrhosis (chronic active hepatitis; cryptogenic) need OLT when GEC is less than or equal to 225 mg/min and volume is less than or equal to 50% normal. Patients with Budd-Chiari Syndrome require OLT if cirrhosis has evolved. Patients with sclerosing cholangitis and primary biliary cirrhosis qualify for transplants when complications of the portal hypertensive syndrome develop. The studies can also direct therapy for ES failures. Selective shunt is indicated in those patients with stable disease whose GEC is greater than or equal to 300 mg/min and liver volume is greater than 75% normal; OLT is indicated for cirrhotics with GEC that is less than 225 mg/min and liver volume that is less than 50% predicted normal.

Adult↗
PubMed1989

Distal splenorenal shunt with splenopancreatic disconnection. A 4-year assessment.

The aims of distal splenorenal shunt with splenopancreatic disconnection (DSRS-SPD) were to improve maintenance of portal flow and prevent siphoning of hepatotrophic factors from the pancreas, as occurs after standard DSRS. The main patient population targeted for improvement were alcoholic cirrhotics, who have poorer survival than nonalcoholic cirrhotics and greater loss of portal flow (60%) after standard DSRS. Seventy-eight patients had DSRS-SPD during the study period 1983 to 1987: thirty-two patients were Child's A, 25 were Child's B, and 21 were Child's C. The 35 patients with alcoholic cirrhosis were a significantly poorer risk group by Child's class and galactose elimination capacity (GEC) than the 39 patients with nonalcoholic cirrhosis. Four patients had portal vein thrombosis. At 4-year follow-up, portal perfusion is maintained in 84% alcoholic and 90% nonalcoholic patients, with hepatic and systemic hemodynamics showing identical patterns for both groups. Hepatic function measured by GEC was maintained in alcoholic patients (290 +/- 68 mg/min to 303 +/- 74 mg/min) and nonalcoholics patients (342 +/- 92 to 320 +/- 118 mg/min). Gastric variceal rebleeding occurred in 10 patients--4 early (less than 2 months) and 6 late (18 to 54 months), leading to operation in 4 and transhepatic embolization in 4 patients: 2 of these patients died from this complication. Survival data show an operative mortality rate of 6.4% and overall mortality rate of 30%, with no significant difference between alcoholic and nonalcoholic cirrhotics. DSRS-SPD has significantly improved maintenance of portal perfusion and survival in patients with alcoholic cirrhosis requiring selective shunt for variceal bleeding when compared to standard DSRS. In this population DSRS-SPD is the operation of choice. In patients with nonalcoholic cirrhosis, the current data have not shown DSRS-SPD to have advantage over standard DSRS.

Angiography↗
PubMed1989

Two-stage surgical management of Budd-Chiari syndrome with obstruction of the inferior vena cava.

A two-stage approach to the surgical management of acute Budd-Chiari syndrome complicated by inferior vena caval obstruction was advocated by our group in 1984. This entailed initial hepatic decompression by suprahepatic, mesoatrial shunt, with subsequent takedown of the mesoatrial shunt combined with conversion to a short infrahepatic, portacaval shunt. We report herein the late follow-up results for two patients managed in this manner. While both patients are alive and doing well, both of the courses have been complicated by stenosis of the inferior vena cava. The cause is unclear but probably relates to fibrosis at the hepatic venous orifices. Management was by percutaneous balloon dilation, which relieved the recurrent hepatic congestion. This cautions others considering this approach to provide careful longitudinal follow-up study for such patients.

Acute Disease↗
PubMed1988

Management of variceal bleeding in patients with noncirrhotic portal vein thrombosis.

Since 1971, 70 patients have been seen at Emory University Hospital with gastroesophageal varices secondary to extrahepatic portal vein thrombosis (PVT). Thirty-seven of these patients had had prior major operative therapy. In only three patients (8%) was shunt surgery successful, and there was a high incidence of rebleeding, other morbidity, and mortality. Of especial note are the serious consequences of simple splenectomy; splenomegaly and thrombycytopenia should rarely, if ever, be used as indication for splenectomy in portal hypertension. In 1977, the use of selective distal splenorenal shunt (DSRS) was begun at Emory in this population and a selective shunt has been possible in 24 of 29 patients (83%) who had had no prior operative therapy. Results have been excellent with a greater than 90% patency rate, long-term portal perfusion in all, no encephalopathy, and late rebleeding in one patient. Quantitative studies at 3-6 years show stability of liver function, significant decrease in spleen size, and rise in platelet count. However, long-term follow-up (greater than 15 years) is required in PVT patients before definitive assessment can be obtained. A specific problem of the PVT patient is late shunt stenosis which requires close observation; dilatation of the shunt was performed in six of the 24 patients with a patent shunt. Poor results with non-shunt operative procedures in PVT were again documented. The proper role of endoscopic variceal sclerotherapy is not yet clear, but appears to be an excellent addition to the therapeutic options. In conclusion, for patients with a patent splenic vein, initial therapy should be a selective shunt; for patients without a patent splenic venous system, endoscopic sclerotherapy is the procedure of choice.

Adult↗
PubMed1988

Bleeding due to portal hypertension: the role of surgery.

Several therapeutic options are available to stop acute variceal bleeding or prevent its recurrence. Sclerotherapy has emerged as the optimal method for stopping acute bleeding, and as primary therapy for preventing recurrence. Surgery is required for the 30% to 40% in whom sclerotherapy fails. Selective variceal decompression has emerged as the best surgical option to balance bleeding control and maintenance of liver function. Survival is significantly improved at five years in nonalcoholic (75%) compared with alcoholic (45%) cirrhotic patients. Recent advances have modified the operative technique to better maintain portal perfusion. Total shunts stop bleeding, and may be used in emergencies. Devascularization procedures have a 20% to 40% rebleeding rate, but do not accelerate liver failure. Liver transplantation, which is increasingly indicated for patients with end-stage liver disease and variceal bleeding, is dictated by the degree of hepatic failure. To provide optimal patient care, a center should be able to offer all of the treatment methods.

Esophageal and Gastric Varices↗