Influenza virus inhibits amiloride-sensitive Na+ channels in respiratory epithelia

Many pathogens causing diarrhea do so by modulating ion transport in the gut. Respiratory pathogens are similarly associated with disturbances of fluid balance in the respiratory tract, although it is not known whether they too act by altering epithelial ion transport. Here we show that influenza virus A/PR/8/34 inhibits the amiloride-sensitive Na(+) current across mouse tracheal epithelium with a half-time of about 60 min. We further show that the inhibitory effect of the influenza virus is caused by the binding of viral hemagglutinin to a cell-surface receptor, which then activates phospholipase C and protein kinase C. Given the importance of epithelial Na(+) channels in controlling the amount of fluid in the respiratory tract, we suggest that down-regulation of Na(+) channels induced by influenza virus may play a role in the fluid transport abnormalities that are associated with influenza infections.

Auditory and behavioral responses of bottlenose dolphins (Tursiops truncatus) and a beluga whale (Delphinapterus leucas) to impulsive sounds resembling distant signatures of underwater explosions

A behavioral response paradigm was used to measure masked underwater hearing thresholds in two bottlenose dolphins and one beluga whale before and after exposure to impulsive underwater sounds with waveforms resembling distant signatures of underwater explosions. An array of piezoelectric transducers was used to generate impulsive sounds with waveforms approximating those predicted from 5 or 500 kg HBX-1 charges at ranges from 1.5 to 55.6 km. At the conclusion of the study, no temporary shifts in masked-hearing thresholds (MTTSs), defined as a 6-dB or larger increase in threshold over pre-exposure levels, had been observed at the highest impulse level generated (500 kg at 1.7 km, peak pressure 70 kPa); however, disruptions of the animals' trained behaviors began to occur at exposures corresponding to 5 kg at 9.3 km and 5 kg at 1.5 km for the dolphins and 500 kg at 1.9 km for the beluga whale. These data are the first direct information regarding the effects of distant underwater explosion signatures on the hearing abilities of odontocetes.

Identification and characterization of a shared TNFR-related receptor for subgroup B, D, and E avian leukosis viruses reveal cysteine residues required specifically for subgroup E viral entry

Genetic and receptor interference data have indicated the presence of one or more cellular receptors for subgroup B, D, and E avian leukosis viruses (ALV) encoded by the s1 allele of the chicken tvb locus. Despite the prediction that these viruses use the same receptor, they exhibit a nonreciprocal receptor interference pattern: ALV-B and ALV-D can interfere with infection by all three viral subgroups, but ALV-E only interferes with infection by subgroup E viruses. We identified a tvb(s1) cDNA clone which encodes a tumor necrosis factor receptor-related receptor for ALV-B, -D, and -E. The nonreciprocal receptor interference pattern was reconstituted in transfected human 293 cells by coexpressing the cloned receptor with the envelope (Env) proteins of either ALV-B or ALV-E. This pattern of interference was also observed when soluble ALV surface (SU)-immunoglobulin fusion proteins were bound to this cellular receptor before viral challenge. These data demonstrate that viral Env-receptor interactions can account for the nonreciprocal interference between ALV subgroups B, D, and E. Furthermore, they indicate that a single chicken gene located at tvb(s1) encodes receptors for these three viral subgroups. The TVB(S1) protein differs exclusively at residue 62 from the published subgroup B- and D-specific receptor, encoded by the s3 allele of tvb. Residue 62 is a cysteine in TVB(S1) but is a serine in TVB(S3), giving TVB(S1) an even number of cysteines in the extracellular domain. We present evidence for a disulfide bond requirement in TVB(S1) for ALV-E infection but not for ALV-B infection. Thus, ALV-B and ALV-E interact in fundamentally different ways with this shared receptor, a finding that may account for the observed biological differences between these two ALV subgroups.

Response of the intact canine left ventricle to increased afterload and increased coronary perfusion pressure in the presence of coronary flow autoregulation

BACKGROUND

Increased left ventricular (LV) contractile force or oxygen consumption has been documented with increased coronary arterial pressure (CAP) and flow (Gregg phenomenon). We investigated whether the increase in contractile force with increased LV afterload might be mediated by the concomitant increase in CAP when coronary autoregulation is intact.

METHODS AND RESULTS

The LV of 6 autonomically blocked open-chest dogs was perfused through the left main coronary artery by a cannula with a side gate to the aortic root. With the gate open, CAP increased from 77+/-20 to 93+/-20 mm Hg (P<0.05) with aortic constriction (AC). With the gate closed, CAP was maintained at a constant level of 100 mm Hg. A small reduction in the slope of the preload recruitable stroke work (PRSW) relationship was observed with AC, but this response was not altered by the coronary perfusion gate position. The end-systolic pressure-volume (ESPV) relationship shifted upward significantly with AC (P<0.001), but this shift was not greater with open-gate perfusion than with closed-gate perfusion. Furthermore, with coronary autoregulation intact, wide changes in CAP (between 60 and 180 mm Hg, n=5) did not alter either the PRSW or ESPV relationship. In contrast, when autoregulation was abolished with intracoronary adenosine (n=6), both indexes of contractility increased progressively with increased CAP.

CONCLUSIONS

The concomitant increase in CAP with increased afterload in the intact canine LV does not contribute to the afterload-induced increase in contractile force. Coronary perfusion pressure per se does not influence LV contractile function. Coronary perfusion pressure influences contractility only when coronary flow changes.

Retroviral vectors preloaded with a viral receptor-ligand bridge protein are targeted to specific cell types

Successful targeting methods represent a major hurdle to the use of retroviral vectors in cell-specific gene-delivery applications. We recently described an approach for retroviral targeting with a retroviral receptor-ligand bridge protein that was bound to the cognate cell-surface ligand receptors before viral challenge. We now report a significant improvement made to this viral targeting method by using a related bridge protein, designated TVB-EGF, comprised of the extracellular domain of the TVB receptor for subgroup B avian leukosis virus fused to epidermal growth factor (EGF). The most important activity of TVB-EGF was that it allowed specific viral entry when preloaded onto virions. Furthermore, virions preloaded with TVB-EGF were thermostable and could be produced directly from virus- packaging cells. These data suggest an approach for targeting retroviral vectors to specific cell types by using virions preloaded with a retroviral receptor-ligand bridge protein and indicate that these types of bridge proteins may be useful reagents for studying the normal mechanism of retroviral entry.

Na(+)-H(+) exchange in salivary secretory cells is controlled by an intracellular Na(+) receptor

It recently has been shown that epithelial Na(+) channels are controlled by a receptor for intracellular Na(+), a G protein (G(o)), and a ubiquitin-protein ligase (Nedd4). Furthermore, mutations in the epithelial Na(+) channel that underlie the autosomal dominant form of hypertension known as Liddle's syndrome inhibit feedback control of Na(+) channels by intracellular Na(+). Because all epithelia, including those such as secretory epithelia, which do not express Na(+) channels, need to maintain a stable cytosolic Na(+) concentration ([Na(+)](i)) despite fluctuating rates of transepithelial Na(+) transport, these discoveries raise the question of whether other Na(+) transporting systems in epithelia also may be regulated by this feedback pathway. Here we show in mouse mandibular secretory (endpiece) cells that the Na(+)-H(+) exchanger, NHE1, which provides a major pathway for Na(+) transport in salivary secretory cells, is inhibited by raised [Na(+)](i) acting via a Na(+) receptor and G(o). This inhibition involves ubiquitination, but does not involve the ubiquitin protein ligase, Nedd4. We conclude that control of membrane transport systems by intracellular Na(+) receptors may provide a general mechanism for regulating intracellular Na(+) concentration.

Street talk: knowledge and attitudes about tuberculosis and tuberculosis control among homeless adults

OBJECTIVES

To measure knowledge and perceived susceptibility to tuberculosis among homeless adults in San Francisco and attitudes toward control measures used to improve adherence to treatment for tuberculosis.

DESIGN

A cross-sectional survey via interview of homeless shelter residents was done at five shelters.

RESULTS

Of 292 persons interviewed, 21.6% reported a positive skin test, and 57.1% of the positives had received preventive therapy. Over 60% had misconceptions about transmission, in particular confusion with transmission of the human immunodeficiency virus (HIV). Knowledge of skin testing procedures and symptoms was generally good, and most reported health care providers as the main source of information. Over half reported concern about catching tuberculosis and over 80% favored controls to ensure adherence, in particular directly observed therapy. Higher TB knowledge score (P = 0.0155) and male sex (P = 0.0357) were associated with a favorable attitude toward directly observed therapy.

CONCLUSIONS

Health care providers should expand educational messages beyond skin testing. Greater knowledge about tuberculosis may increase acceptance of control measures. Targeted education plus social norms favoring completion of therapy may improve screening and treatment outcomes in this population.

High-dose megestrol acetate in the treatment of patients with ovarian cancer who have undergone previous treatment: Eastern Cooperative Oncology Group Study PD884

High-dose megestrol acetate has been reported to be effective salvage therapy for women with ovarian carcinoma. The Eastern Cooperative Oncology Group performed this phase II study of oral megestrol acetate, 200 mg four times daily until disease progression, in 33 patients either with stage III or IV histologically confirmed ovarian carcinoma or with unresectable tumor in the pelvis with measurable or evaluable disease who progressed after treatment with one prior chemotherapy regimen. Thirty and 31 patients were evaluable for response and toxicity, respectively. No patient had an objective response and none had subjective improvement after a median treatment period of 1.4 months. Nausea or vomiting occurred in most patients, usually grade 1-2. Megestrol acetate is ineffective salvage therapy for patients with inoperable, previously treated ovarian carcinoma.

HIV-1: fifteen proteins and an RNA

Human immunodeficiency virus type 1 is a complex retrovirus encoding 15 distinct proteins. Substantial progress has been made toward understanding the function of each protein, and three-dimensional structures of many components, including portions of the RNA genome, have been determined. This review describes the function of each component in the context of the viral life cycle: the Gag and Env structural proteins MA (matrix), CA (capsid), NC (nucleocapsid), p6, SU (surface), and TM (transmembrane); the Pol enzymes PR (protease), RT (reverse transcriptase), and IN (integrase); the gene regulatory proteins Tat and Rev; and the accessory proteins Nef, Vif, Vpr, and Vpu. The review highlights recent biochemical and structural studies that help clarify the mechanisms of viral assembly, infection, and replication.

Control of Na+ transport in salivary duct epithelial cells by cytosolic Cl- and Na+

The duct cells of the mandibular glands of mice (and many other mammalian salivary glands) absorb NaCl from an isotonic, Na+-rich primary saliva, formed by the gland's secretory endpieces, utilising an amiloride-sensitive Na+ channel in the apical (luminal) domain of the plasma membranes. The present study focuses on the mechanisms whereby the apical membrane Na+ conductance is controlled so that the rate of Na+ influx from lumen to cytosol via the Na+ channels is matched to the rate of Na+ extrusion from cytosol to interstitium via the basolateral Na+-K+-ATPase (so called homocellular regulation or epithelial cross-talk). Our results show that the apical membrane Na+ conductance is not controlled by a sensor of extracellular (luminal) Na+, as has been previously believed, but by sensors of cytosolic Na+ and Cl- which down-regulate the Na+ channels when the cytosolic concentration of either ion increases. These effects of cytosolic Na+ and Cl- are mediated, respectively, by G proteins of the Gi and Go subclasses.

Nedd4 mediates control of an epithelial Na+ channel in salivary duct cells by cytosolic Na+

Epithelial Na+ channels are expressed widely in absorptive epithelia such as the renal collecting duct and the colon and play a critical role in fluid and electrolyte homeostasis. Recent studies have shown that these channels interact via PY motifs in the C terminals of their alpha, beta, and gamma subunits with the WW domains of the ubiquitin-protein ligase Nedd4. Mutation or deletion of these PY motifs (as occurs, for example, in the heritable form of hypertension known as Liddle's syndrome) leads to increased Na+ channel activity. Thus, binding of Nedd4 by the PY motifs would appear to be part of a physiological control system for down-regulation of Na+ channel activity. The nature of this control system is, however, unknown. In the present paper, we show that Nedd4 mediates the ubiquitin-dependent down-regulation of Na+ channel activity in response to increased intracellular Na+. We further show that Nedd4 operates downstream of Go in this feedback pathway. We find, however, that Nedd4 is not involved in the feedback control of Na+ channels by intracellular anions. Finally, we show that Nedd4 has no influence on Na+ channel activity when the Na+ and anion feedback systems are inactive. We conclude that Nedd4 normally mediates feedback control of epithelial Na+ channels by intracellular Na+, and we suggest that the increased Na+ channel activity observed in Liddle's syndrome is attributable to the loss of this regulatory feedback system.

Cell-specific viral targeting mediated by a soluble retroviral receptor-ligand fusion protein

TVA, the cellular receptor for subgroup A avian leukosis viruses (ALV-A) can mediate viral entry when expressed as a transmembrane protein or as a glycosylphosphatidylinositol-linked protein on the surfaces of transfected mammalian cells. To determine whether mammalian cells can be rendered susceptible to ALV-A infection by attaching a soluble form of TVA to their plasma membranes, the TVA-epidermal growth factor (EGF) fusion protein was generated. TVA-EGF is comprised of the extracellular domain of TVA linked to the mature form of human EGF. Flow cytometric analysis confirmed that TVA-EGF is a bifunctional reagent capable of binding simultaneously to cell surface EGF receptors and to an ALV-A surface envelope-Ig fusion protein. TVA-EGF prebound to transfected mouse fibroblasts expressing either wild-type or kinase-deficient human EGF receptors, rendered these cells highly susceptible to infection by ALV-A vectors. Viral infection was blocked specifically in the presence of a recombinant human EGF protein, demonstrating that the binding of TVA-EGF to EGF receptors was essential for infectivity. These studies have demonstrated that a soluble TVA-ligand fusion protein can mediate viral infection when attached to specific cell surfaces, suggesting an approach for targeting retroviral infection to specific cell types.

Activators of epithelial Na+ channels inhibit cytosolic feedback control. Evidence for the existence of a G protein-coupled receptor for cytosolic Na+

We have previously shown that epithelial Na+ channels in mouse mandibular gland duct cells are controlled by cytosolic Na+ and Cl-, acting, respectively, via Go and Gi proteins. Since we found no evidence for control of epithelial Na+ channels by extracellular Na+ ([Na+]o), our findings conflicted with the long-held belief that Na+ channel activators, such as sulfhydryl reagents, like para-chloromercuriphenylsulfonate (PCMPS), and amiloride analogues, like benzimidazolylguanidinium (BIG) and 5-N-dimethylamiloride (DMA), induce their effects by blocking an extracellular channel site which otherwise inhibits channel activity in response to increasing [Na+]o. Instead, we now show that PCMPS acts by rendering epithelial Na+ channels refractory to inhibition by activated G proteins, thereby eliminating the inhibitory effects of cytosolic Na+ and Cl- on Na+ channel activity. We also show that BIG, DMA, and amiloride itself, when applied from the cytosolic side of the plasma membrane, block feedback inhibition of Na+ channels by cytosolic Na+, while leaving inhibition by cytosolic Cl- unaffected. Since the inhibitory effects of BIG and amiloride are overcome by the inclusion of the activated alpha-subunit of Go in the pipette solution, we conclude that these agents act by blocking a previously unrecognized intracellular Na+ receptor.

The CAR1 gene encoding a cellular receptor specific for subgroup B and D avian leukosis viruses maps to the chicken tvb locus

Host susceptibility to subgroup B, D, and E avian leukosis viruses (ALV) is determined by specific alleles of the chicken tvb locus. Recently, a chicken gene that encodes a cellular receptor, designated CAR1, specific for subgroups B and D ALV was cloned, and it was proposed that this gene was the s3 allele of tvb (J. Brojatsch, J. Naughton, M. M. Rolls, K. Zingler, and J. A. T. Young, Cell 87:845-855, 1996). We now report that in a backcross derived from an F1 (Jungle Fowl x White Leghorn [WL]) male mated with inbred WL females, the cloned ALV receptor gene cosegregated with two markers linked to tvb. The two markers used were a tvb(s1)-specific antigen recognized by the chicken R2 alloantiserum and restriction fragment length polymorphisms associated with the expressed sequence tag com152e. With all three markers, no crossovers were observed among 52 backcross progeny tested and LOD linkage scores of 15.7 were obtained. These data demonstrate that CAR1 is the subgroup B and D ALV susceptibility gene located at tvb(s3).

Genetic mapping of the cloned subgroup A avian sarcoma and leukosis virus receptor gene to the TVA locus

A chicken gene conferring susceptibility to subgroup A avian sarcoma and leukosis viruses (ASLV-A) was recently identified by a gene transfer strategy. Classical genetic approaches had previously identified a locus, TVA, that controls susceptibility to ASLV-A. Using restriction fragment length polymorphism (RFLP) mapping in inbred susceptible (TVA*S) and resistant (TVA*R) chicken lines, we demonstrate that in 93 F2 progeny an RFLP for the cloned receptor gene segregates with TVA. From these analyses we calculate that the cloned receptor gene lies within 5 centimorgans of TVA, making it highly probable that the cloned gene is the previously identified locus TVA. The polymorphism that distinguishes the two alleles of TVA in these inbred lines affects the encoded amino acid sequence of the region of Tva that encompasses the viral binding domain. However, analysis of the genomic sequence encoding this region of Tva in randomly bred chickens suggests that the altered virus binding domain is not the basis for genetic resistance in the chicken lines analyzed.

Serological evidence for pneumovirus infections in pigs

A serological survey was carried out on pig sera from herds in Northern Ireland to investigate the incidence of reactivity to bovine respiratory syncytial virus (BRSV) antigens. A total of 529 pig sera from 61 herds were tested and 219 (41 per cent) were found to be reactive with BRSV-infected cell cultures in an indirect immunofluorescence test. None of the BRSV-reactive sera immunostained turkey rhinotracheitis virus-infected cell cultures, indicating specificity for BRSV epitopes. The specificity of this reactivity for BRSV antigen was confirmed by double immunolabelling, using monoclonal antibodies to BRSV and two pig sera with different reactivities to BRSV antigens. A longitudinal serological investigation of two litters of pigs indicated that BRSV-serum reactivity developed between six and 11 weeks after birth. The immunofluorescent staining pattern observed with the majority (73 per cent) of the BRSV-reactive pig sera was typical of that observed with known BRSV-reactive bovine sera. The other immunoreactive pig sera stained BRSV-infected cell cultures in an atypical staining pattern. These different reactivity patterns, combined with the results of the serum neutralisation tests, suggest that more than one serotype of a porcine pneumovirus may exist.

Activation of a retroviral membrane fusion protein: soluble receptor-induced liposome binding of the ALSV envelope glycoprotein

It is not known how membrane fusion proteins that function at neutral pH, for example the human immunodeficiency virus envelope (Env) glycoprotein and intracellular fusion machines, are activated for target bilayer binding. We have addressed this question using a soluble oligomeric form of an avian retroviral Env glycoprotein (API) and soluble forms of its receptor. Binding of soluble receptor to API induces API to bind to liposomes composed of phosphatidylcholine and cholesterol at neutral pH. Liposome binding only occurs at fusion permissive temperatures (T > 20 degrees C), is complete between 2 to 5 min at 37 degrees C, and is stable to high salt, carbonate, and urea. Liposome binding is mediated by the ectodomain of the transmembrane subunit of API, and a mutant with a Val to Glu substitution in the Env fusion peptide (located in the ectodomain of the transmembrane subunit) shows significantly reduced liposome binding. Moreover, under conditions of equivalent binding to API, a mutant receptor that does not support infection (Zingler, K., and J.A.T. Young. 1996. J. Virol. 70:7510-7516) does not induce significant liposome binding. Our results indicate that a highly specific interaction between an avian retroviral Env and its receptor activates the retroviral glycoprotein for target bilayer binding at neutral pH in much the same way as low pH activates the influenza hemagglutinin. Our findings are discussed in terms of the mechanisms of viral and cellular fusion proteins that function at neutral pH.

Identification of a cellular receptor for subgroup E avian leukosis virus

Genetic studies in chickens and receptor interference experiments have indicated that avian leukosis virus (ALV)-E may utilize a cellular receptor related to the receptor for ALV-B and ALV-D. Recently, we cloned CAR1, a tumor necrosis factor receptor (TNFR)-related protein, that serves as a cellular receptor for ALV-B and ALV-D. To determine whether the cellular receptor for ALV-E is a CAR1-like protein, a cDNA library was made from turkey embryo fibroblasts (TEFs), which are susceptible to ALV-E infection, but not to infection by ALV-B and ALV-D. The cDNA library was screened with a radioactively labeled CAR1 cDNA probe, and clones that hybridized with the probe were isolated. A 2.3-kb cDNA clone was identified that conferred susceptibility to ALV-E infection, but not to ALV-B infection, when expressed in transfected human 293 cells. The functional cDNA clone is predicted to encode a 368 amino acid protein with significant amino acid similarity to CAR1. Like CAR1, the TEF protein is predicted to have two extracellular TNFR-like cysteine-rich domains and a putative death domain similar to those of TNFR I and Fas. Flow cytometric analysis and immunoprecipitation experiments demonstrated specific binding between the TEF CAR1-related protein and an immunoadhesin composed of the surface (SU) envelope protein of subgroup E (RAV-0) virus fused to the constant region of a rabbit immunoglobulin. These two activities of the TEF CAR1-related protein, specific binding to ALV-E SU and permitting entry only of ALV-E, have unambiguously identified this protein as a cellular receptor specific for subgroup E ALV.

H+ transporters in the main excretory duct of the mouse mandibular salivary gland

1. We used microspectrofluorimetry with the pH-sensitive fluoroprobe 2',7'-bis(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF) to study the regulation of cytosolic pH (pHi) in the isolated, perfused main excretory duct of the mouse mandibular gland. 2. In nominally HCO3(-)-free solutions, removal of Na+ from the lumen alone caused pHi to decline whereas removing it from the bath alone did not. 3. Readmission of Na+ to the lumen of ducts studied under zero-Na+ conditions caused pHi to recover fully. This recovery was blocked by 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) with a half-maximum concentration of 0.5 mumol l-1, indicating the presence of an apical Na(+)-H+ exchanger. 4. Readmission of Na+ to the bath of ducts studied under zero-Na+ conditions also caused pHi to recover. This recovery was blocked by 100 mumol l-1 EIPA, indicating the presence of a basolateral Na(+)-H+ exchanger. 5. Measurements of H+ fluxes indicated that the apical Na(+)-H+ exchanger was approximately four times more active than the basolateral Na(+)-H+ exchanger. 6. In three sets of experiments (in the absence of Na+, in the presence of Na+, and in the presence of Na+ plus 100 mumol l-1 EIPA), the effects of changing luminal K+ concentration on pHi were examined. We found no evidence for the presence of K(+)-H+ exchange or Na(+)-coupled K(+)-H+ exchange in the apical membranes of duct cells. 7. pHi recovery under nominally HCO3(-)-free conditions following acidification with an NH4Cl pulse was abolished by removal of Na+ from the bath and luminal solutions, indicating that no Na(+)-independent systems such as H(+)-ATPases were present. 8. A repeat of the above experiments in the presence of 25 mmol l-1 HCO3- plus 5% CO2 did not reveal any additional H+ transport systems. The removal of luminal Cl-, however, caused a small rise in pHi. This latter effect was blocked by 500 mumol l-1 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulphonic acid (H2-DIDS), suggesting that a Cl(-)-HCO3- exchanger in the apical membrane might contribute in a minor way to pHi regulation. 9. We conclude that the predominant H+ transport systems in the mouse mandibular main excretory duct are Na(+)-H+ exchangers in the apical and the basolateral membranes. The model we postulate to account for electrolyte transport across the main duct in the mouse mandibular gland is quite different from that previously developed for the rat duct but is similar to that developed for the rabbit duct. The difference is in concordance with the known ability of the mandibular gland of the rat, but not the rabbit or the mouse, to secrete a HCO3(-)-rich final saliva.

Lung neutrophil retention and injury after intestinal ischemia/reperfusion

OBJECTIVE

To define the mechanisms responsible for the lung leukosequestration and injury elicited by intestinal ischemia/reperfusion (I/R).

METHODS

The effect of 120 minutes of superior mesenteric artery occlusion and 90 minutes of reperfusion on neutrophil deformability, lung neutrophil retention, and pulmonary microvascular permeability was determined.

RESULTS

Compared with control surgery, intestinal I/R resulted in a significant increase in neutrophil stiffness (mean yield pressure [Pyield], 1.533 +/- 0.075 and 2.302 +/- 0.288 cm H2O, respectively) and lung neutrophil content (6.3 +/- 1.4 and 31.5 +/- 6.4 U/g wet weight, respectively). These changes were not affected by inhibition of neutrophil adherence before gut reperfusion. However, the increased lung microvascular permeability elicited by gut I/R (0.111 +/- 0.020 [control surgery] and 0.255 +/- 0.041 [I/R] mL/min/cm H2O/100 g lung tissue) was significantly attenuated by administration of antibodies directed against neutrophil or endothelial determinants of leukocyte adhesion.

CONCLUSIONS

The results of this study suggest that intestinal I/R is a potent inflammatory stimulus that elicits an increase in neutrophil stiffness and lung neutrophil retention independent of neutrophil-endothelial cell adhesion. In contrast, the increased lung microvascular permeability elicited by gut I/R is attenuated by strategies that interfere with neutrophil-endothelial cell adhesion.

Intraperitoneal cisplatin plus intravenous cyclophosphamide versus intravenous cisplatin plus intravenous cyclophosphamide for stage III ovarian cancer

BACKGROUND

Intravenous platinum-based chemotherapy is the standard primary therapy for advanced ovarian cancer. We conducted a phase 3 trial to compare the effects of intraperitoneal and intravenous cisplatin on the survival of women with previously untreated, stage III, epithelial ovarian cancer.

METHODS

The patients underwent an initial exploratory laparotomy and resection of all tumor masses larger than 2 cm. Within four weeks after surgery, six courses of intravenous cyclophosphamide (600 mg per square meter of body-surface area per course) plus either intraperitoneal cisplatin (100 mg per square meter) or intravenous cisplatin (100 mg per square meter) were administered at three-week intervals.

RESULTS

Of 654 randomized patients, 546 were eligible for the study. The estimated median survival was significantly longer in the group receiving intraperitoneal cisplatin (49 months; 95 percent confidence interval, 42 to 56) than in the group receiving intravenous cisplatin (41 months; 95 percent confidence interval, 34 to 47). The risk of death was lower in the intraperitoneal group than in the intravenous group (hazard ratio, 0.76; 95 percent confidence interval, 0.61 to 0.96; P = 0.02). Moderate-to-severe tinnitus, clinical hearing loss, and neuromuscular toxic effects were significantly more frequent in the intravenous group.

CONCLUSIONS

As compared with intravenous cisplatin, intraperitoneal cisplatin significantly improves survival and has significantly fewer toxic effects in patients with stage III ovarian cancer and residual tumor masses of 2 cm or less.

CAR1, a TNFR-related protein, is a cellular receptor for cytopathic avian leukosis-sarcoma viruses and mediates apoptosis

Viral envelope (Env)-receptor interactions have been implicated in the cell death associated with infection by subgroups B and D avian leukosis-sarcoma viruses (ALVs). A chicken protein, CAR1, was identified that permitted infection of mammalian cells by these viral subgroups. CAR1 bound to a viral Env fusion protein, comprising an ALV-B surface Env protein and the Fc region of an immunoglobulin, indicating that it is a specific viral receptor. CAR1 contains two extracellular cysteine-rich domains characteristic of the TNFR family and a cytoplasmic region strikingly similar to the death domain of TNFR1 and Fas, implicating this receptor in cell killing. Chicken embryo fibroblasts susceptible to ALV-B infection and transfected quail QT6 cells expressing CAR1 underwent apoptosis in response to the Env-Ig fusion protein, demonstrating that this cytopathic ALV receptor can mediate cell death.

Residue Trp-48 of Tva is critical for viral entry but not for high-affinity binding to the SU glycoprotein of subgroup A avian leukosis and sarcoma viruses

Previously, mutant Tva receptors were classified as either partially or completely defective in mediating subgroup A avian leukosis and sarcoma virus (ALSV-A) entry (C. Bélanger, K. Zingler, and J. A. T. Young, J. Virol. 69:1019-1024, 1995; K. Zingler, C. Bélanger, R. Peters, D. Agard, and J. A. T. Young, J. Virol. 69:4261-4266, 1995). To specifically test the abilities of these mutant Tva proteins to bind ALSV-A surface (SU) protein, binding studies were performed with a subgroup A SU-immunoadhesin. This fusion protein is composed of the subgroup A Schmidt-Ruppin SU protein fused in frame to a rabbit immunoglobulin constant region. This reagent was conjugated to fluorescein isothiocyanate and used for flow cytometric analysis with transfected human 293 cells expressing different forms of Tva. The SU-immunoadhesin bound the wild-type Tva protein with a KD of approximately 1.5 nM. Amino acid substitutions that reduced viral entry at Asp-46 and at Cys-35 and Cys-50, which are predicted to form an intrachain disulfide bond in Tva, drastically reduced the binding affinity for the SU-immunoadhesin. Thus, the effects on viral entry of some mutations could be explained solely by changes in the binding affinity for ALSV-A SU. However, this was not true for other mutations tested, especially those with amino acid substitutions that replaced Trp-48. Compared with the wild-type receptor, these latter mutations led to approximately 43- to 200-fold reductions in viral infectivity but only to approximately 2.5- to 3.4-fold reductions in the binding affinity for the SU-immunoadhesin. These results support a role for Trp-48 of Tva in mediating steps of viral entry subsequent to binding ALSV-A SU.