Genome-wide prediction of disease variant effects with a deep protein language model

Predicting the effects of coding variants is a major challenge. While recent deep-learning models have improved variant effect prediction accuracy, they cannot analyze all coding variants due to dependency on close homologs or software limitations. Here we developed a workflow using ESM1b, a 650-million-parameter protein language model, to predict all ~450 million possible missense variant effects in the human genome, and made all predictions available on a web portal. ESM1b outperformed existing methods in classifying ~150,000 ClinVar/HGMD missense variants as pathogenic or benign and predicting measurements across 28 deep mutational scan datasets. We further annotated ~2 million variants as damaging only in specific protein isoforms, demonstrating the importance of considering all isoforms when predicting variant effects. Our approach also generalizes to more complex coding variants such as in-frame indels and stop-gains. Together, these results establish protein language models as an effective, accurate and general approach to predicting variant effects.

Polygenic prediction of educational attainment within and between families from genome-wide association analyses in 3 million individuals

We conduct a genome-wide association study (GWAS) of educational attainment (EA) in a sample of ~3 million individuals and identify 3,952 approximately uncorrelated genome-wide-significant single-nucleotide polymorphisms (SNPs). A genome-wide polygenic predictor, or polygenic index (PGI), explains 12-16% of EA variance and contributes to risk prediction for ten diseases. Direct effects (i.e., controlling for parental PGIs) explain roughly half the PGI's magnitude of association with EA and other phenotypes. The correlation between mate-pair PGIs is far too large to be consistent with phenotypic assortment alone, implying additional assortment on PGI-associated factors. In an additional GWAS of dominance deviations from the additive model, we identify no genome-wide-significant SNPs, and a separate X-chromosome additive GWAS identifies 57.

Resource profile and user guide of the Polygenic Index Repository

Polygenic indexes (PGIs) are DNA-based predictors. Their value for research in many scientific disciplines is growing rapidly. As a resource for researchers, we used a consistent methodology to construct PGIs for 47 phenotypes in 11 datasets. To maximize the PGIs' prediction accuracies, we constructed them using genome-wide association studies-some not previously published-from multiple data sources, including 23andMe and UK Biobank. We present a theoretical framework to help interpret analyses involving PGIs. A key insight is that a PGI can be understood as an unbiased but noisy measure of a latent variable we call the 'additive SNP factor'. Regressions in which the true regressor is this factor but the PGI is used as its proxy therefore suffer from errors-in-variables bias. We derive an estimator that corrects for the bias, illustrate the correction, and make a Python tool for implementing it publicly available.

Wound infection after ileostomy closure: a prospective randomized study comparing primary vs. delayed primary closure techniques

BACKGROUND

Closure of ileostomy is considered a contaminated operation. The infection rate of the stoma wound is > or = 30%. Several ileostomy-closure techniques intended to reduce the high rate of infection have been described in the literature. Among them, delayed primary closure of the stoma wound is a commonly used method that was reported to reduce the infection rate according to several retrospective studies. We therefore conducted the first prospective randomized trial comparing primary with delayed primary closure of a stoma wound.

METHODS

During 2003, 40 patients were admitted to our ward for closure of ileostomy. The ileostomies were taken down by the same team using the same surgical technique except for the technique of wound closure. We randomly divided the patients into two groups. In Group 1 (n = 20), the wound was left open for delayed primary closure and not closed until postoperative day 4. In Group 2, the wound was primarily closed at the end of the procedure.

RESULTS

The total wound infection rate was relatively low (15%). Infection occurred more frequently (4 cases, 20%) in Group 1 than in Group 2 (2 cases, 10%). The length of hospital stay was similar for both groups.

CONCLUSIONS

In this first prospective comparison of two techniques during ileostomy take down, primary closure unexpectedly produced less wound infection than delayed primary closure.

Extramammary Paget's disease of the perianal region

OBJECTIVE

Perianal Paget's disease (PPD) is a rare entity. The standard treatment for either in situ or invasive extra mammary Paget's disease (EMPD) is surgical excision. Local recurrence and morbidity from surgery, especially in the elderly, can, however, be high. The aim of this article is to review our experience with PPD and question the currently preferred treatment approaches in light of its histopathology and therapeutic outcome.

PATIENTS AND METHODS

A chart review of our patients with PPD from 1996 to 2002 was carried out to determine their outcome after treatment. Data from review of the literature are presented.

RESULTS

Five patients with in situ disease (four females, median age 68 years) were diagnosed as having PPD. A complete surgical excision was attempted in 4 patients and the fifth was treated by photodynamic therapy. At present, all patients are alive, two are free of disease, one has persistent disease and two have local recurrence.

CONCLUSION

Considering the significant rate of recurrence even after wide local excision, the extent of surgery needed and the good prognosis with long-term survival, we question whether nonsurgical modalities should be considered in place of surgery as primary treatment for noninvasive PPD, with radical surgery being reserved for failures or invasive disease.

Familial adenomatous polyposis at the Tel Aviv Medical Center: demographic and clinical features

Familial adenomatous polyposis (FAP) is an uncommon, but widespread genetic disorder that develops multiple colonic adenomatous polyps and, if untreated, can lead to large bowel cancer. Little is known about its occurrence and characteristics in the Israeli population.

AIMS

To evaluate FAP prevalence, phenotypic manifestations and compliance for diagnosis and follow-up in our registry.

METHODS

Since 1993 approximately one-half of FAP patients in Israel have been seen and followed-up by us before and/or after colectomy. They and their families were encouraged to have mutation analysis, genetic and/or endoscopic screening.

RESULTS

37 pedigrees were identified, including 2 non-Jewish. The Jewish ethnic distribution was similar to that of the general population and the point prevalence rate estimated as 28.4/one million Jewish inhabitants. There were 461 first-degree relatives at-risk for FAP. Genetic screening was completed and successful in 28 pedigrees (87.5%), and 73 FAP patients entered the registry. Marked intra- familial phenotypic variations with minimal disease manifestation were noted in 11 patients belonging to 4 pedigrees. Cancer occurred in 15.1% (11 patients), in 10 before FAP diagnosis or during follow- up elsewhere, but one non-compliant patient developed duodenal cancer. One other patient died from a massive, neglected, intra- abdominal desmoid. Compliance for evaluation and follow-up of pedigree members and individual FAP patients was inadequate in 29% and 27%, respectively.

CONCLUSIONS

FAP occurs in the Israeli Jewish population at the expected rate, but is inadequately recognized in non-Jews. The inadequate compliance for screening and post-surgical follow-up needs to be addressed by educating the public, health care workers and Health Insurers.

The correlation between quality of life and functional outcome in ulcerative colitis patients after proctocolectomy ileal pouch anal anastomosis

OBJECTIVE

The aim of this study was to evaluate functional outcome and quality of life (QOL) in patients undergoing proctocolectomy ileal pouch anal anastomosis (IPAA), to assess the correlation between functional outcome and QOL, and to identify factors influencing functional outcome and QOL in these patients.

BACKGROUND

IPAA is now considered the procedure of choice for ulcerative colitis. Functional outcome and QOL are important factors in evaluating operative outcome.

METHODS

All patients with UC who had undergone IPAA at our institute during the period 1990-2001 were included. QOL and functional outcome were evaluated by mailed questionnaires. QOL was scored using the Short Form 36 (SF-36). Global Assessment of Function Scale was used to evaluate functional outcome.

RESULTS

Data were obtained in 77 of 99 patients (78%), with the median age of 38 years. Median follow up time was 4.25 years. The QOL in patients after pelvic pouch procedure was excellent, with scores equal to published norms for the Israeli general population in most scales. Functional outcome and QOL scores correlated strongly (r > 0.5; P < 0.0001) in all dimensions. Older age was associated with lower scores in both functional outcome and QOL scales (P < 0.0001).

CONCLUSIONS

This study demonstrates a strong association between functional outcome and QOL in patients after IPAA. These patients, however, have a QOL that is comparable with the general population. Age at time of surgery strongly influences both functional outcome and QOL. This finding has to be taken into consideration in pre-operative counseling.

Tumour necrosis factor mediates bacterial translocation after haemorrhagic shock and endotoxaemia

OBJECTIVE

To assess the extent of bacterial translocation after haemorrhagic shock and reperfusion, and the involvement of tumour necrosis factor (TNF) in its mediation.

DESIGN

Controlled, randomised prospective experiment.

SUBJECTS

87 rats in 7 groups.

INTERVENTIONS

Haemorrhagic shock was induced in rats for 1 hour. Endotoxaemia was induced in a second group by the injection of lipopolysaccharide. A third group was injected with exogenous TNF. Some of the animals were further treated with anti-TNF.

MEASUREMENTS

After 24 hours, bacterial translocation in blood and in several remote organs, and serum TNF concentrations were measured.

RESULTS

High bacterial counts were found in all remote organs of rats with haemorrhagic shock or endotoxaemia. Their serum TNF concentrations were significantly higher than in the corresponding sham-operated controls. Anti-TNF significantly reduced the extent of bacterial translocation. Rats, the only treatment of which was exogenous TNF, developed substantial bacterial translocation.

CONCLUSION

Bacterial translocation is associated with increased serum TNF, and can be minimised by anti-TNF. This, and the triggering of translocation in unprovoked animals by TNF alone, suggest that TNF may be the stimulator, and not the consequence, of bacterial translocation.

Anal incontinence: prevalence among female patients attending a urogynecologic clinic

The present study prospectively surveyed the prevalence of anal incontinence among 283 consecutive female patients attending a urogynecologic outpatient clinic in a maternity hospital. Data concerning bowel habits, laxative use, previous anorectal surgery, and the presence, severity, and frequency of anal incontinence were collected by interviewing the patients. Anal incontinence was reported by 83 women, representing 29% of the study population. Of those reporting anal incontinence, 30% (9% of the study population) were incontinent to solid feces, 22% (6%) to liquid feces, and 48% (14%) to gas. Age distribution demonstrates progressive rise and a high prevalence of anal incontinence in patients older than 60 years. A significant higher rate of vacuum deliveries was found among patients with anal incontinence, compared with continent patients (9.6% vs. 2.5%; P = 0.01). Increased prevalence of anal incontinence was also found among patients with past history of hemorrhoidectomy and those with urodynamic diagnosis of combined genuine stress incontinence and detrusor instability/sensory urgency. In conclusion, in patients attending a urogynecologic clinic, anal incontinence is a frequent, although rarely volunteered, symptom.

Transanal endoscopic microsurgery: experience with 75 rectal neoplasms

PURPOSE

The aim of this study was to describe a single institution's experience with transanal endoscopic microsurgery in patients with benign and malignant rectal tumors.

PATIENTS

Between January 1992 and April 1998, 75 patients with a mean follow up of 38 months, underwent transanal endoscopic microsurgery excision of benign (46) or malignant (29) rectal tumors, located 3 to 18 cm from the dentate line.

RESULTS

A total of 3 of 46 (6.5 percent) patients with benign tumors underwent conversion to radical surgery owing to tumor size. During the follow-up period, benign tumor recurrence was observed in four (9 percent) patients, three of whom were managed by repeat transanal endoscopic microsurgery, whereas one required radical surgery. Histologic staging of malignant tumors was T1 (10), T2 (10), and T3 (9). Seven patients with either inadequate resection margins or T3 tumors were complimented with radical surgery. Of the remaining 22 patients, 11 received adjuvant radiation therapy whereas 11 had no further treatment. Four (18 percent) had recurrent disease, which was managed by repeat transanal endoscopic microsurgery in two, radical surgery in one, and laser ablation in one. No cancer-related deaths were observed during the follow-up period. There was one operative mortality in a cardiac-crippled patient. Postoperative complications were mainly of a minor character and included fever, urinary retention, and bleeding; none of which required reintervention. Rectourethral fistula developed in one patient who underwent repeat transanal endoscopic microsurgery excision for a T3 malignancy. Fecal soiling was transient in three patients and persisted in two.

CONCLUSION

Transanal endoscopic microsurgery excision is a safe and precise technique that is well tolerated even in high operative risk patients. Transanal endoscopic microsurgery may become a procedure of choice for benign rectal tumors and selected early malignant neoplasms.

Conservative management of ovarian cystic teratoma during pregnancy and labor

OBJECTIVE

Our goal was to evaluate the adequacy of conservative management during pregnancy and labor in women with an ultrasonographically diagnosed ovarian cystic teratoma.

STUDY DESIGN

Forty-nine women with ultrasonographically diagnosed ovarian cystic teratoma <6 cm were followed for detection of possible complications through pregnancy and labor. Serial ultrasonographic examinations before pregnancy, during pregnancy, and after delivery were performed to detect changes in the size of the cystic teratoma.

RESULTS

In a group of 49 women with dermoid cysts (mean age, 30 years), 68 pregnancies resulted. Of the 68 pregnancies, 4 ended in miscarriages, 1 was electively terminated, and in the remaining 63 pregnancies, a total of 64 healthy infants were delivered. Five patients needed treatment with assisted reproductive techniques. Fifty-five pregnancies ended in normal vaginal deliveries and 8 were delivered by cesarean (cesarean delivery rate of 16%). None of the classical complications attributed to dermoid cysts such as torsion, dystocia, or rupture occurred in the study group. In a follow-up of 56 dermoid cysts throughout pregnancy, cyst size remained unchanged.

CONCLUSIONS

Ovarian dermoid cysts <6 cm are not expected to grow during pregnancy or to cause complications in pregnancy and labor.

Model of implantation of tumor cells simulating recurrence in colonic anastomosis in mice

PURPOSE

Local recurrence after colorectal cancer surgery is usually perianastomotic. An experiment was designed to investigate whether free intraluminal cells can penetrate through a colonic anastomosis and thereby cause local recurrence.

METHODS

BALB/c and C57/BL mice underwent ascending colotomy followed by watertight anastomosis. Thereafter, CT-26 murine colon carcinoma cells were injected into the cecal lumen 2 cm proximal to the anastomosis of syngeneic BALB/c mice, whereas B-16 murine melanoma cells were injected in the same fashion into C57/BL mice. Control animals without anastomosis received similar injections. Animals were killed 24 hours, 72 hours, and 30 days after surgery and were checked for tumorigenesis.

RESULTS

Results of peritoneal fluid cytology were negative after 24 hours, whereas after 72 hours cancer cells were identified in the peritoneal fluid of 80 percent of mice with colotomy and anastomosis compared with 20 percent of control mice. Thirty days after surgery, 11.1 percent of the control BALB/c mice developed pericecal tumor growth, similar to the overall rate of murine melanoma in C57/BL. In mice with anastomoses, perianastomotic tumor growth was observed in 47.5 percent of BALB/c mice (P < 0.001) and was correlated with the number of injected cells. Tumor growth reached approximately 75 percent tumor take with high cell densities, whereas in C57/BL mice no difference was found between the experimental and control groups.

CONCLUSIONS

The findings suggest that free intraluminal cancer cells of colonic origin may penetrate through watertight anastomoses and implant on the anastomotic or peritoneal surface and initiate tumor growth. This anastomotic penetration is cell-mass dependent. The reported experimental model is simple, reproducible, and advantageous for studies of colonic anastomosis.

Three evaluation methods of a community health advocate program

The title Community Health Advocate (CHA) is one of thirty or more titles used throughout the world for an indigenous outreach worker who is trusted and respected in his or her community and who serves as a bridge between peers and health professionals. In 1992, the Center for Healthy Communities in Dayton, Ohio developed a program to train as Advocates people indigenous to the communities in which they would be working. Since the first CHAs began work in January 1993, the effectiveness of the program has been evaluated from three perspectives: the Community Health Advocates, the managers/directors of the community sites at which the CHAs work, and the clients with whom the CHAs work. Advocates indicated that the training program adequately prepared them for their roles and functions. They also identified systematic frustrations and barriers that made it more difficult for them to perform their job. Community site directors and community leaders indicated that the CHAs were considered a positive force in meeting client needs and facilitating independence, and were very effective in outreach and coordination of resources. A survey of CHA clients revealed an overwhelmingly positive response to the Advocate's work, validating the belief that CHAs can fill an important niche in the health care community. The three evaluation processes described in this paper helped to document the need for and the effectiveness of this program and can serve as a model for similar programs.

Development of vomeronasal receptor neuron subclasses and establishment of topographic projections to the accessory olfactory bulb

Previous studies of the adult vomeronasal system have shown that vomeronasal receptor neurons in the middle layer (expressing Gi alpha 2) and deep layers (expressing Go alpha) of the sensory epithelium project to the anterior and posterior parts of the accessory olfactory bulb (AOB), respectively. In the present study, the development of the two populations of vomeronasal receptor neurons and their segregated projections were investigated in the opossum, Monodelphis domestica. Antibodies to G proteins Gi alpha 2 and Go alpha were used to identify the two subpopulations of receptor neurons. The Gi alpha 2-immunoreactive (ir) cells and Go alpha-ir cells appeared between postnatal day 0 (P0) and postnatal day 3 (P3) and both types of cells increased in number during later development. The differential localization of Gi alpha 2-ir cells in the middle layer and Go alpha-ir cells in the deep layer of the VNO could be seen as early as P3 and became more prominent at later stages. The AOB was clearly identified at P10, and at this stage segregated projections of Gi alpha 2-ir fibers to the anterior part and Go alpha-ir fibers to the posterior part of the AOB were seen. The segregation of the two types of fibers in the AOB resemble that in the adult after P21. These results suggest that Gi alpha 2-ir and Go alpha-ir subpopulations of receptor neurons in the VNO develop in parallel, and that segregation of the two populations of receptor neurons in the VNO and the topographic projection to the AOB are established at very early stages during development.

Endotoxemia following enteral refeeding in children

Plasma endotoxin-like activity, tumor necrosis factor alpha (TNFalpha) concentrations, core body temperature, and liver functions were measured before and after enteral feeding in children who had been deprived of enteral feeding for 5 days because of their illness. Transient endotoxemia and elevations in plasma TNFalpha concentrations occurred. Core body temperature, aspartate aminotransferase, alamine aminotransferase, and bilirubin concentrations were normal in patients who had elevated plasma endotoxin-like activity. Transient endotoxemia following enteral feeding may be due to the translocation from the gastrointestinal (GI) tract as a result of increased mesenteric circulation and peristalsis. No clinical consequences were noted despite transient endotoxemia. The transient endotoxemia is not due to the immature GI tract; instead, it results from enteral feeding following the deprivation of enteral feeds.

Gut decontamination reduces bowel ischemia-induced lung injury in rats

OBJECTIVE

To evaluate the effects of gut decontamination on endotoxin, tumor necrosis factor (TNF) levels, and the associated lung injury in a rat model of bowel ischemia.

SUMMARY BACKGROUND DATA

Gut ischemia induces disruption of the intestinal mucosal barrier, allowing translocation of bacteria and endotoxin into the blood, which may trigger a systemic inflammatory response and lung injury.

METHODS

Thirty anesthetized rats were randomized into three groups: (1) ischemia-reperfusion (I/R) alone (a 60-min superior mesenteric artery occlusion and 4 h of reperfusion, n=10); (2) rats that underwent gut decontamination prior to ischemia (I/R+GD, n=10); and (3) control rats (sham operated, n=10). Serum levels of lipopolysaccharide (LPS) and TNF were measured at the end of the experiment. Lung permeability was measured using bovine serum albumin labeled with 125I, and organ injury was assessed histologically.

RESULTS

One hour of bowel ischemia and 4 h of reperfusion (I/R) led to elevations of blood LPS and TNF levels of 0.33+/-0.005 EU/mL and 173+/-56 pg/mL, which were higher than the sham group (p<0.01). Gut decontamination (I/R+GD) significantly attenuated the LPS and TNF generation, 0.09+/-0.005 and 56.2+/-6 pg/mL (p<0.01). Lung injury as assessed by pulmonary permeability index was also reduced by gut decontamination, 2.1+/-0.42 vs 5.3+/-0.82 in the control group (p<0.03). Surprisingly no difference was detected in the number of pulmonary neutrophils in sequestration between the groups.

CONCLUSIONS

Our data suggest that gut decontamination can reduce the generation of LPS, TNF, and the severity of lung damage that often follows ischemia and reperfusion of the intestine in rats.

Increased microvascular permeability induced by prolonged interleukin-2 administration is attenuated by the oxygen-free-radical scavenger dimethylthiourea

Effective use of interleukin (IL)-2 as an antineoplastic agent may be hindered by severe side-effects, in particular vascular leak syndrome, which leads to generalized, especially pulmonary, edema. The oxygen-free-radical scavenger dimethylthiourea (DMTU) was shown to attenuate IL-2-induced vascular leak syndrome in sheep receiving a single IL-2 injection. However, in the clinical setting multiple injections are necessary to gain a therapeutic effect. The present study tests whether DMTU attenuates IL-2-induced vascular leak syndrome following multiple IL-2 injections without affecting IL-2-induced cytotoxicity in peritoneal mononuclear cells. Mice were treated intraperitoneally with 1 x 10(5) units IL-2 three times daily for four consecutive days. DMTU (10 mg/0.5 ml) was administered to the study group once daily, prior to the first IL-2 injection. Comparing the wet/dry weight ratio of lungs, liver, and spleen showed that IL-2 caused a significant (P < 0.05) wet/dry increase in all three organs. DMTU attenuated the wet/dry increase in the lungs (P < 0.05), in the spleen (P < 0.05), and not at all in the liver. IL-2 induced a marked increase in peritoneal mononuclear cell counts, which was not attenuated by DMTU. The cytotoxic effect of IL-2-activated peritoneal mononuclear cells on target B16 cells was also unchanged in animals pretreated with DMTU. In conclusion, we have shown that DMTU ameliorates pulmonary permeability and vascular leak syndrome associated with multiple-dose IL-2 therapy, without eliciting an inhibitory effect on IL-2 induced-cytotoxicity.

[Restorative proctocolectomy for ulcerative colitis and familial polyposis]

From 1987-1994 we performed 35 proctocolectomies with ileal pouch anal anastomosis. The indication for operation was ulcerative colitis in 29 and familial polyposis in 6. The mean ages at operation were 35 and 25 years, respectively. The most common postoperative complication was small bowel obstruction in 25% of the patients, requiring re-operation in half of them. The incidence of this complication may be reduced by operating in only 1 stage when possible, without creating a protective ileostomy. The second serious complication was pouchitis, in 17%, which was controlled by antibiotics. There has been no mortality. All patients, except for 2 with an S-shaped pouch, evacuate spontaneously a mean of 5 bowel movements a day. Continence was mildly impaired (usually night-staining of a pad) in 30% of patients in whom the pouch-anal anastomosis was performed after stripping the mucosa of the rectal remnant. In those in whom the pouch-anal anastomosis was performed by means of the double stapling technique, continence was almost completely preserved. We therefore recommend that proctocolectomy with ileal pouch-anal anastomosis be performed in 1 stage when possible, using the double stapling technique. Staged operation should be reserved for severely ill patients, or when stripping of the rectal mucosa is performed for familial polyposis and ulcerative colitis with severe dysplasia.

Soluble tumor necrosis factor receptors reduce bowel ischemia-induced lung permeability and neutrophil sequestration

OBJECTIVES

To evaluate the possible role of tumor necrosis factor (TNF) in the development of lung injury after bowel ischemia, and the ability of TNF-soluble receptors to negate TNF toxicity, using a rat small bowel ischemia and reperfusion model.

DESIGN

Prospective, randomized, controlled laboratory study.

SETTING

Research laboratory.

SUBJECTS

Forty adult male Sprague-Dawley rats weighing approximately 300 g.

INTERVENTIONS

The rats were divided equally into four groups: a) ischemia and reperfusion alone; b) those animals receiving TNF antibodies (1 mL) before reperfusion; and c) those animals receiving 200 micrograms of human recombinant TNF soluble receptors. These 30 anesthetized rats underwent 60 mins of superior mesenteric artery occlusion per 4 hrs of reperfusion. The remaining ten animals were sham operated (laparotomy), serving as controls. Lung permeability was measured using bovine serum albumin labeled with 125I, and organ injury was assessed histologically.

MEASUREMENTS AND MAIN RESULTS

Thirty and 60 mins after declamping and reperfusion, plasma TNF concentrations increased to 830 +/- 66 and 173 +/- 56 pg/mL, respectively, compared with 10 pg/mL before ischemia (p < .001). In sham-operated control rats, TNF concentrations did not increase from baseline concentrations. Four hours after reperfusion, sequestration of neutrophils in the pulmonary microcirculation was noted (319 +/- 60 vs. 84 +/- 13 neutrophils/10 high-power fields in sham-operated rats [p < .04]). Pulmonary microvascular leak also occurred, as measured by translocation of radiolabeled albumin into the bronchoalveolar space and expressed as the ratio of bronchoalveolar lavage to blood concentrations. This ratio was 5.3 +/- 0.8 in ischemic control animals compared with 1.1 +/- 0.3 in sham animals (p < .03). Treatment with antibodies to TNF before reperfusion attenuated the pulmonary injury (75 +/- 6 neutrophils/10 high-power fields, permeability index 1.6 +/- 0.1) less than in ischemic controls (p < .005). A similar protection was achieved with soluble TNF receptors, which prevented bowel ischemia-induced lung neutrophil sequestration (117 +/- 35 neutrophils/10 high-power fields, pulmonary vascular leak ratio of 2.3 +/- 0.1, p < .05).

CONCLUSIONS

The results of this study show that ischemia and subsequent reperfusion of the intestine in rats produce lung injury. This injury is mediated, at least in part, by TNF. Soluble TNF receptors are an effective tool in preventing lung TNF injury after intestinal ischemia.

Neutrophil adhesion receptor CD18 mediates remote but not localized acid aspiration injury

BACKGROUND

Acid aspiration leads to lung polymorphonuclear neutrophil (PMN) sequestration and an associated increase in permeability. Although it is known that the neutrophil adhesion receptor (CD18) plays no role in determining PMN accumulations in the region aspirated, we postulated that this PMN adhesion receptor and its endothelial ligand, intercellular adhesion molecule-1 (ICAM-1), mediate remote neutrophil sequestration.

METHODS

Anesthetized rabbits underwent localized aspiration of either 0.1N HCl 0.1 ml/kg (n = 18) or saline solution (n = 18).

RESULTS

After 30 minutes leukopenia was noted, 2290 +/- 200 white blood cells/mm3 (p < 0.05). At 3 hours diapedesis occurred in the aspirated segment with accumulations in bronchoalveolar lavage fluid (X10(4)) of 87 +/- 6 PMN/ml versus control of 6 +/- 1 PMN/ml (p < 0.05). Histologic evidence of generalized lung leukosequestration occurred. The wet to dry weight ratio of the nonaspirated lung rose to 5.7 +/- 0.2 versus control of 3.9 +/- 0.1 (p < 0.05). Treatment (n = 18) with the CD18 monoclonal antibody (mAb) (R15.7, 1 mg/kg) had no effect on neutrophil accumulations in the aspirated segment. However, the mAb attenuated the remote inflammatory response: early leukopenia (5790 +/- 400 white blood cells/mm3); lung leukosequestration (24 +/- 4 PMN/10 high-power fields); protein leak in bronchoalveolar lavage fluid (570 +/- 50 micrograms/ml); and edema, wet to dry weight ratio (4.9 +/- 0.1) (all p < 0.05). Treatment with the ICAM-1 mAb (RR1/1, 1 mg/kg) (n = 9) did not reduce neutrophil accumulations in the aspirated segment but limited the remote inflammatory response.

CONCLUSIONS

Acid aspiration leads to neutrophil adhesion and edema in regions remote from those aspirated via neutrophil CD18 and endothelial ICAM-1.

Leukergy--a new diagnostic test for bone infection

This new blood test for infection is based on the phenomenon of leukergy in which white cells agglomerate in the peripheral blood of patients with inflammatory diseases. It was used in 26 patients with proven bone or joint infection and was positive in 25. The leukergy test was more accurate than the ESR, white cell count or blood culture. The percentage of cells agglomerated correlated with the clinical severity of the infection and the test detected reactivation of the septic process better than the other haematological tests. It is a rapid and inexpensive method which is useful in the diagnosis and management of bone and joint infections.

Factors influencing the practice of vaginal birth after cesarean section

OBJECTIVES

Vaginal birth after cesarean has been recommended for most women with previous cesarean sections for the past 10 years. This practice, however, has not yet been generalized because high variations can still be observed among countries, hospitals, and physicians.

METHODS

A case-control study involving 635 case patients and 2593 control patients was carried out to determine which characteristics of the physician, the patient, or the hospital were important in the adoption of this practice.

RESULTS

The results of the multiple stepwise logistic regression analysis indicate a higher likelihood that women will experience vaginal birth after cesarean if their physicians had cesarean rates under 20%, had less than 5% of their patients considered at risk, and were younger than 54 years old. Vaginal birth after cesarean was also favored by hospitals characterized by a high degree of neonatal and obstetrical specialization, and a patient population with a low level of education.

CONCLUSIONS

This policy is still in the developmental stage, as evidenced by the great variability between hospitals and physicians in rates of vaginal birth after cesarean. Further efforts are required for this policy to become the norm.

Leukocytes mediate acid aspiration-induced multiorgan edema

BACKGROUND

Acid aspiration leads to lung injury characterized by polymorphonuclear neutrophil leukocytes (PMN) sequestration and edema. This study investigates whether localized acid aspiration leads to activation of circulating PMN and triggers both local and remote PMN sequestration and whether these cells are responsible for increase in pulmonary permeability and systemic organ edema.

METHODS

Rats pretreated with intravenous saline solution or rendered neutropenic (nitrogen mustard or antineutrophil serum) underwent tracheostomy and insertion of a cannula into a lung segment. This was followed by instillation of either 0.1 N HCl or saline solution.

RESULTS

After 30 minutes leukopenia was noted (2650 white blood cells/mm3) in saline-treated, acid-lavaged rats, and circulating PMN produced H2O2 (20 femtomole dichlorofluorescein/PMN compared with 3 femtomole in control animals (both, p < 0.05). PMN were progressively sequestered in the nonaspirated lung, the heart, and kidney. Permeability and edema developed in the lungs and systemic organs. In neutropenic rats there was a reduction of aspiration-induced thromboxane B2 and leukotriene B4 synthesis (p < 0.05), decrease in lung wet to dry weight and protein level in bronchoalveolar lavage of the aspirated and nonaspirated lungs, and reduction in myeloperoxidase activity in the heart and kidney and in wet to dry weight of these organs (all, p < 0.05).

CONCLUSIONS

These data indicate that localized acid aspiration activates circulating neutrophils and promotes their sequestration in the lungs and systemic organs. These cells are largely responsible for the multisystem organ edema.

Lavage with leukotriene B4 induces lung generation of tumor necrosis factor-alpha that in turn mediates neutrophil diapedesis

In experimental models of acute respiratory failure, leukotriene (LT) B4 is generated in the lungs, followed by a 2- to 3-hour delay before there is substantial neutrophil (PMN) accumulation and increased permeability. This study tests whether lavage with LTB4 induces tumor necrosis factor (TNF) synthesis by the lungs that in turn mediates PMN diapedesis. Anesthetized rats underwent lavage with 0.1 ml LTB4 (10(-6) mol/L) into a lung segment. This led to localized TNF synthesis measured in bronchoalveolar lavage fluid with peak concentrations of 580 pg/ml after 1 1/2 hours and 120 pg/ml after 3 hours. These values were higher than after lavage with 0.1 ml saline solution: 0.7 and 4.3 pg/ml, respectively (both p < 0.05). There was a delay before PMN accumulated in bronchoalveolar lavage fluid (x 10(4)). After 30 minutes, the numbers were 2.2 PMN/ml, whereas at 4 hours there was a rise to 40 PMN/ml and at 5 hours 60 PMN/ml, higher than after saline lavage (all p < 0.05). Pretreatment of rats by lavage into airways with actinomycin D, 12 ng in 0.1 ml, minimized LTB4-induced TNF synthesis after 1 1/2 and 3 hours (38 and 51 pg/ml), as well as the delayed diapedesis after 4 hours (12 PMN/ml) (all p < 0.05). Similarly, pretreatment of other rats by lavage with TNF-alpha antiserum (rabbit antimurine), but not normal serum, limited LTB4-induced diapedesis (13 PMN/ml) (p < 0.05). Interestingly, administration of the protein synthesis inhibitor actinomycin D by lavage 10 minutes after LTB4 did not prevent TNF generation after 1 1/2 or 3 hours (490 and 440 pg/ml). However, this agent did limit PMN diapedesis after 4 hours (14 PMN/ml) (p < 0.05), an event possibly caused by limiting later synthesis of endothelial adhesion proteins, a thesis consistent with the findings that pretreatment of rats by lavage with actinomycin D was without any effect on N-formyl-methionyl-phenylalanine (10(-8) mol/L)-induced diapedesis. This agent is known to induce PMN migration without need for synthesis of endothelial adhesion proteins. The data indicate that lavage with LTB4 induces local TNF-alpha generation that in turn mediates a delayed PMN diapedesis. This event is likely regulated by endothelial synthesis of adhesion proteins.

Mast cells and leukotrienes mediate neutrophil sequestration and lung edema after remote ischemia in rodents

Reperfusion of ischemic hindlimbs leads to leukotriene B4 (LTB4) and polymorphonuclear neutrophil (PMN)-dependent lung injury. Pulmonary mast cells are capable of synthesizing LTB4 and are potential mediators of this inflammatory response. This study tests their role in PMN sequestration and pulmonary edema after hindlimb ischemia. Anesthetized, mast cell-sufficient mice (n = 8) or their congeneic mast cell-deficient strain (n = 8) were subjected to 3 hours of hindlimb ischemia. After another 3 hours of reperfusion, plasma LTB4 levels rose to 651 pg/ml, higher than sham ischemic control (n = 8) values of 202 pg/ml (p less than 0.05). At this time there was sequestration of neutrophils in the pulmonary microcirculation (54 PMN/10 high-power fields [HPF]) and an increase in lung wet/dry weight ratio (W/D) of 4.4. Both these values were higher (p less than 0.05) than those in sham ischemic animals that showed sequestration of 18 PMN/10 HPF and a lung W/D of 3.1. In contrast, mast cell-deficient mice showed an attenuation of ischemia- and reperfusion-induced rise in plasma LTB4 (507 pg/ml), fewer sequestered neutrophils (34 PMNs/10 HPF), and a reduction in lung W/D to 3.9 (all p less than 0.05). To test the role of lung LTB4 in determining PMN sequestration, rats (n = 78) were subjected to 3 hours of hindlimb ischemia. After 3 hours of reperfusion, plasma and bronchoalveolar lavage (BAL) LTB4 concentrations rose to 956 and 211 pg/ml, respectively--higher than sham values of 460 and 121 pg/ml (both p less than 0.05). After 4 hours, plasma LTB4 levels had returned to baseline, whereas BAL LTB4 had increased further to 658 pg/ml, indicating lung origin. Treatment of other rats by localized lung lavage of the lipoxygenase inhibitor diethylcarbamazine (80 mg/kg in 0.1 ml twice) prevented the ischemia- and reperfusion-induced rise in BAL LTB4 (267 pg/ml) and limited local neutrophil sequestration (from 51 PMN/10 HPF after saline aspiration to 36 PMN/10 HPF) and lung W/D (from 4.5 to 4.1) (all p less than 0.05). The data indicate that after hindlimb ischemia pulmonary mast cells and localized LTB4 synthesis mediate, in part, the lung inflammatory response.

Adherent neutrophils mediate permeability after atelectasis

Re-expansion of atelectatic lung is associated with increased permeability. This study tests whether neutrophils mediate this event. Right middle lobar atelectasis was induced in anesthesized rabbits (n = 18) by intraluminal obstruction of the bronchus after a 20-minute ventilation with 100% O2. After 1 hour of bronchial obstruction and 20 minutes after lobar re-expansion, leukopenia was noted, 2870 +/- 210 white blood cells (WBC)/mm3, relative to control animals treated with a noninflated balloon catheter, 6500 +/- 410 WBC/mm3 (p less than 0.05). Three hours after re-expansion, neutrophils were sequestered in the previously atelectatic region 78 +/- 7 polymorphonuclear leukocytes (PMN)/10 high-power field (HPF), as well as in nonatelectatic areas, 40 +/- 3 PMN/10 HPF, higher than control values of 26 +/- 3 PMN/10 HPF (p less than 0.05). In the atelectatic region, neutrophil sequestration was associated with increased protein concentration in lobar bronchoalveolar lavage (BAL) of 1370 +/- 100 micrograms/mL, higher than control values of 270 +/- 20 micrograms/mL (p less than 0.05). Reexpansion also induced increases in lung wet-to-dry weight ratio (W/d) of 6.2 +/- 0.2, higher than control values of 4.3 +/- 0.1 (p less than 0.05). Rendering rabbits neutropenic (n = 18) (0 to 4 PMN/mm3) limited the atelectasis-induced protein accumulations in BAL (520 +/- 60 micrograms/mL) and increase in lung W/d (5.2 +/- 0.1) (both p less than 0.05). Intravenous (I.V.; treatment of another group (n = 18) with an anti-CD 18 monoclonal antibody (R 15.7, 1 mg/kg) before balloon deflation prevented leukopenia (6550 +/- 560 WBC/mm3), minimized neutrophil sequestration (36 +/- 2 PMN/10 HPF), and attenuated protein leak (710 +/- 95 micrograms/mL) and the increased lung W/d (5.6 +/- 0.1) (all p less than 0.05). A final atelectatic group (n = 9) was treated I.V. with the anti-intercellular adhesion molecule-1 monoclonal antibody (RR 1/1, 1 mg/kg), which also prevented leukopenia and showed similar protection of microvascular barrier function. These data indicate that adherent neutrophils in large part mediate lung permeability and edema after atelectasis and re-expansion. Adhesion receptors of both neutrophils and endothelial cells regulate this event.

Reactive oxygen species and elastase mediate lung permeability after acid aspiration

Acid aspiration leads to increased neutrophil (PMN) oxidative metabolism, an event associated with lung leukosequestration and permeability increase. Neutropenia protected the vascular barrier function against acid injury. This study tests whether active oxygen species and elastase (which are presumably released by adherent PMNs) affect the microvascular barrier. Anesthetized rats underwent tracheostomy and insertion of a cannula into a lung segment. This was followed by localized instillation of 0.1 N HCl (n = 18) or saline (n = 18). Sequestration of PMNs in acid-aspirated and nonaspirated segments was 77 and 46 PMNs/high-power field (HPF), respectively, which was higher than control values of 11 and 8 PMNs/10 HPF in saline-aspirated and nonaspirated regions (P less than 0.05). Acid aspiration was associated with increased protein concentration in bronchoalveolar lavage (BAL) fluid to 3,550 and 2,900 micrograms/ml in the aspirated and nonaspirated lungs, respectively, which were higher than control values of 420 and 400 micrograms/ml (P less than 0.05). Acid aspiration also led to increased lung wet-to-dry weight ratios (W/D) of 6.6 and 5.4, which were higher than control values of 3.4 and 3.3 (P less than 0.05). Intravenous treatment of rats (n = 18) 90 min after aspiration with scavengers of reactive oxygen species, superoxide dismutase (1,500 U/kg), and catalase (5,000 U/kg), both conjugated to polyethylene glycol, did not reduce PMN sequestration but attenuated acid aspiration-induced increase in protein accumulation in BAL fluid in the aspirated and nonaspirated segments (990 and 610 micrograms/ml) as well as the increased lung W/D (4.6 and 4.0; all P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of neutrophil adherence receptors (CD 18) in lung permeability following lower torso ischemia

Ischemia and reperfusion of the lower torso lead to leukotriene- and neutrophil (PMN)-dependent lung injury characterized by lung PMN sequestration, increased permeability, and noncardiogenic edema. It is thought that PMNs require adhesion to endothelium to alter barrier function. This study tests the role of CD 18, the PMN adherence receptor, in mediating lung permeability after lower torso ischemia and reperfusion. Anesthetized rabbits (n = 9) underwent 3 hours of bilateral hind limb ischemia. Ten minutes after the release of the tourniquets, plasma leukotriene B4 levels increased to 395 +/- 85 pg/ml, higher than 129 +/- 35 pg/ml in controls (n = 9, p less than 0.01). At this time there was a reduction in circulating white blood cells (x 10(3)), 3.56 +/- 0.49/mm3 relative to 6.07 +/- 0.61/mm3 in controls (p less than 0.01). PMNs were sequestered in the hind limbs, indicated by increased myeloperoxidase activity of 1.06 +/- 0.19 units/g compared with 0.56 +/- 0.09 units/g in controls (p less than 0.05). Four hours after tourniquet release, PMNs were sequestered in the lungs, 52 +/- 4 PMNs per 10 high-power fields, a value higher than 31.5 +/- 3 PMNs per 10 high-power fields in controls; bronchoalveolar lavage fluid protein content increased to 554 +/- 90 micrograms/ml relative to 277 +/- 46 micrograms/ml in controls; and there was lung edema, measured by increased wet weight-to-dry weight ratios of 5.19 +/- 0.10, higher than 4.29 +/- 0.21 in controls (all p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Free fatty acids have nucleating effects in model biles

Nucleating factors are thought to be responsible for the more rapid nucleation of gallbladder bile from patients with gallstones as compared to controls. Biliary proteins and, in particular, mucus and non-mucus glycoproteins are the focus of current research. Non-protein nucleating factors were not extensively investigated. In this study we studied the role of free fatty acids (FFA) as possible nucleating factors. Palmitic, oleic and linoleic acid were added to model biles in increasing concentrations from 0 to 20 mu mol/ml. The nucleation time of model biles decreased to 45%-60% of the initial following the addition of 0.5 to 1 mu mol/ml of each of the three fatty acids. Only a small further decrease in the nucleation time was noted with higher concentrations of up to 20 mu mol/ml. The pronucleating effect of FFA added to whole model bile was also examined in the isolated vesicular and non-vesicular fractions. The decrease in the nucleation time at each concentration of the three fatty acids was in the following order of magnitude: whole bile greater than vesicular phase greater than non-vesicular phase. The addition of each of the three fatty acids resulted in a partial solubilization of vesicles, with transfer of their lipid contents to the non-vesicular fraction. The effect was more marked with oleic acid and least marked with linoleic acid. The vesicular cholesterol to phospholipid ratio did not change following the addition of exogenous free fatty acids. Studies with labeled FFA showed that they migrated with the non-vesicular fraction on gel chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxygen free radicals are required for ischemia-induced leukotriene B4 synthesis and diapedesis

Hind limb ischemia and reperfusion have been shown to result in high plasma levels of leukotriene B4 (LTB4) and polymorphonuclear neutrophil (PMN) sequestration in the pulmonary microvasculature. This study tests whether LTB4 is derived from PMNs and its role in mediating ischemic plasma-induced diapedesis. Plasma derived from rabbit hind limbs after 3 hours of tourniquet ischemia and 10 minutes of reperfusion (n = 6) showed an increased LTB4 level of 560 pg/ml, higher than sham plasma values of 106 pg/ml (p less than 0.05). Introduction of ischemic plasma in abraded skin chambers placed on the dorsum of normal rabbits (n = 6) led after 3 hours to PMN diapedesis of 1175 PMN/mm3, associated with a further increase in LTB4 levels to 820 pg/ml (both p less than 0.05). In contrast, ischemic plasma derived from neutropenic animals (n = 4; nitrogen mustard, 2 mg/kg; PMNs less than 30/mm3) contained lower levels of LTB4, 160 pg/ml (p less than 0.05). When introduced in skin chambers in normal rabbits (n = 4), this plasma induced accumulations of only 163 PMN/mm3, accompanied by a smaller increase in LTB4 levels in the blister fluid after 3 hours, 397 pg/ml (both p less than 0.05). A correlation was found between LTB4 levels in ischemic plasma and PMN accumulations in blister fluid (r = 0.92; p less than 0.05). Intravenous pretreatment of rabbits (n = 4) used in the blister chamber bioassay with the LT receptor antagonist FPL-55712, 40 micrograms/kg/hr, attenuated diapedesis induced by ischemic and ischemic-neutropenic plasma, 103 and 35 PMN/mm3, respectively (both p less than 0.05). Pretreatment with superoxide dismutase, 1500 units/kg, and catalase, 5000 units/kg, both conjugated to polyethylene glycol (n = 4), prevented ischemic plasma-induced LTB4 synthesis, as well as ischemic plasma-induced diapedesis, 12 PMN/mm3 (p less than 0.05). Finally, pretreatment with allopurinol, 25 mg/kg, was similarly effective in preventing LTB4 synthesis and PMN migration. These data suggest that oxygen free radicals are essential for ischemia-induced PMN synthesis of LTB4 that in turn mediates their diapedesis.

Prostaglandin E2 in duodenal ulcer complications

Prostaglandins are presumed to have cytoprotective properties and may play a role in the pathogenesis of duodenal ulcer and its complications. To evaluate this hypothesis, 35 patients with either duodenal ulcer bleeding (18 patients) or gastric outlet obstruction (17 patients) were investigated. Biopsies were taken from gastroduodenal tissues and secretions for prostaglandin E2 (PGE2) levels. These levels were compared to those taken from the same areas during a later endoscopy. A correlation was found between the severity of the clinical endoscopic findings and PGE2 levels. Increased levels of PGE2 were found in the quiescent phase and decreased levels found during the deteriorated phase. These differences of PGE2 levels were found to be of significant value (P less than 0.002). Furthermore, the patients in which the PGE2 levels were decreased at second endoscopy needed surgery. PGE2 may, thus, be a factor in duodenal ulcer pathogenesis and its complications, and be used as a prognostic marker and guide.

Synergism between leukotriene B4 and thromboxane A2 in mediating acid-aspiration injury

Acid aspiration leads to thromboxane-dependent lung neutrophil sequestration associated with microvascular permeability increase. Leukotriene B4 (LTB4) is postulated to be a cofactor in the thromboxane-induced inflammatory response. This study tests the interaction between LTB4 and thromboxane, focusing on LTB4 induction of thromboxane-dependent lung neutrophil sequestration after acid aspiration. Anesthetized rats underwent tracheostomy and insertion of a cannula in a left lung segment. This was followed by instillation of either 0.1 ml 0.1N hydrochloric acid (n = 18) or 0.1 ml saline in control rats (n = 18). When assayed at 3 hours, acid aspiration led to increased plasma levels of LTB4 and thromboxane B2 (TxB2), higher than control values (p less than 0.05). The rise in plasma LTB4 was correlated (p less than 0.05; r = 0.83) with sequestration of neutrophils in the nonaspirated lung. The entrapment of thromboxane-dependent lung neutrophil was associated with an increase in protein concentration in bronchoalveolar lavage of the aspirated and nonaspirated sides and an increase in lung wet to dry weight ratio. Pretreatment of other rats (n = 18) with the lipoxygenase inhibitor diethylcarbamazine IV prevented an aspiration-induced rise in plasma LTB4 and TxB2. Further, there was an attenuation of lung leukosequestration and protein leak in bronchoalveolar lavage and lung edema (all p less than 0.05). Pretreatment of other rats (n = 12) with the leukotriene receptor antagonist FPL 55712 IV did not prevent the aspiration-induced rise in LTB4 or TxB2, but otherwise was as effective as diethylcarbamazine in preventing injury. Finally, other hydrochloric acid-aspirated rats (n = 8) were pretreated intravenously with the thromboxane synthetase inhibitor OKY 046 or the thromboxane receptor antagonist SQ 29548. Both agents limited the aspiration-induced rise in plasma LTB4 (p less than 0.05). The data indicate that localized acid aspiration induces synthesis of LTB4 and thromboxane A2. Inhibition of either leukotriene or thromboxane will limit PMN adhesion and increased lung permeability.

Interleukin-2 induces early multisystem organ edema mediated by neutrophils

Interleukin-2 (IL-2), an agent known to activate neutrophils (PMN) with thromboxane (Tx)B2 release, produces pulmonary edema within 6 hours of intravenous infusion. This study tests the role of PMN in mediating the edema. Anesthetized rats received 10(6)U recombinant human IL-2 (n = 15) or vehicle (n = 14) as a constant intravenous infusion during a period of 1 hour. At this time there was leukopenia 3.63 +/- 0.43 (x10(3)/mm3) relative to vehicle-infused control rats 6.12 +/- 0.86 and a decline in PMN, 2.19 +/- 0.14 relative to control value of 3.33 +/- 0.05 (both p less than 0.05). After 6 hours edema, as measured by increase in the wet to dry weight (W/d) ratio, was present in the lungs (4.93 +/- 0.20 relative to control 4.06 +/- 0.10), heart (4.09 +/- 0.11 versus 3.76 +/- 0.08), liver (3.50 +/- 0.10 versus 3.18 +/- 0.10), and kidney (4.25 +/- 0.07 versus 4.00 +/- 0.07) (all p less than 0.05). There was increased lung permeability demonstrated by bronchoalveolar lavage fluid protein concentration of 1970 +/- 210 micrograms/mL relative to control 460 +/- 90 micrograms/mL (p less than 0.05). Interleukin-2 resulted in lung PMN sequestration of 53 +/- 7 PMN/10 high-power fields (HPF) relative to 23 +/- 2 PMN/10 HPF in controls (p less than 0.05) and increased plasma TxB2 levels to 1290 +/- 245 pg/mL relative to control 481 +/- 93 pg/mL (p less than 0.05). Pretreatment of other rats (n = 8) with selective anti-rat neutrophil antiserum 18 hours before the experiment led to a peripheral PMN count 10% of baseline and prevented edema in the lungs (W/d ratio 4.20 +/- 0.16) and heart (3.67 +/- 0.07) (both p less than 0.05) but not liver or kidney. Protein in lung lavage was reduced to 760 +/- 220 micrograms/mL (p less than 0.05). The protection afforded by leukopenia was associated with lack of PMN sequestration and prevention of the increase in plasma Tx levels (484 +/- 120 pg/mL, p less than 0.05). These data indicate that the rapid induction of lung and heart edema with a 1-hour infusion of IL-2 in the rat is mediated, in large part, by activated PMNs.

Role for tumor necrosis factor as mediator of lung injury following lower torso ischemia

Ischemia and reperfusion of the ischemic lower torso lead to a neutrophil- (PMN) dependent lung injury characterized by PMN sequestration and permeability edema. This mimics the injury seen after infusion of tumor necrosis factor alpha (TNF), a potent activator of PMN and endothelium. This study tests whether TNF is a mediator of the lung injury after lower torso ischemia. Anesthetized rats underwent 4 h of bilateral hindlimb tourniquet ischemia, followed by reperfusion for 10 min, 30 min, 1, 2, 3, and 4 h (n = 6 for each time point). Quantitative lung histology indicated progressive sequestration of PMN in the lungs, 25 +/- 3 (SE) PMN/10 high-power fields (HPF) 10 min after reperfusion vs. 20 +/- 2 PMN/10 HPF in sham animals (NS), increasing to 53 +/- 5 PMN/10 HPF after 4 h vs. 23 +/- 3 PMN/10 HPF in sham animals (P less than 0.01). There was lung permeability, shown by increasing protein accumulation in bronchoalveolar lavage (BAL) fluid, which 4 h after reperfusion was 599 +/- 91 vs. 214 +/- 35 micrograms/ml in sham animals (P less than 0.01). Similarly, there was edema, shown by the lung wet-to-dry weight ratio, which increased by 4 h to 4.70 +/- 0.12 vs. 4.02 +/- 0.17 in sham animals (P less than 0.01). There was generation of leukotriene B4 in BAL fluid (720 +/- 140 vs. 240 +/- 40 pg/ml, P less than 0.01), and in three of six rats tested at this time TNF was detected in plasma, with a mean value of 167 pg/ml. TNF was not detectable in any sham animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Pathophysiology of ischaemia reperfusion injury: central role of the neutrophil

Ischaemia is a common clinical event leading to local and remote injury. Evidence indicates that tissue damage is largely caused by activated neutrophils which accumulate when the tissue is reperfused. If the area of ischaemic tissue is large, neutrophils also sequester in the lungs, inducing non-cardiogenic pulmonary oedema. Ischaemia reperfusion injury is initiated by production of reactive oxygen species which initially appear responsible for the generation of chemotactic activity for neutrophils. Later, once adherent to endothelium, neutrophils mediate damage by secretion of additional reactive oxygen species as well as proteolytic enzymes, in particular elastase. Therapeutic options for limiting ischaemia reperfusion injury include inhibition of oxygen radical formation, pharmacological prevention of neutrophil activation and chemotaxis, and also the use of monoclonal antibodies which prevent neutrophil-endothelial adhesion, a prerequisite for injury.

Neutrophil elastase and oxygen radicals: synergism in lung injury after hindlimb ischemia

Hindlimb ischemia and reperfusion lead to lung injury dependent on activated polymorphonuclear neutrophils (PMN) adherence. This study tests whether elastase and oxygen radicals participate in PMN-induced injury once they have become sequestered in lungs. Anesthetized rats treated with saline (n = 9) or the specific elastase inhibitor methoxysuccinyl-L-Ala-L-Ala-L-Pro-L-Val-chloromethylketone (MAAPV, n = 6) underwent 4 h of bilateral hindlimb tourniquet ischemia followed by 4 h of reperfusion. At this time, in saline-treated rats, PMN were sequestered in lungs as assayed by myeloperoxidase activity [(MPO) 51 +/- 5 U/g tissue], higher than MPO in saline-treated sham rats (n = 9; 18 +/- 3 U/g MPO; P less than 0.01); bronchoalveolar lavage (BAL) fluid leukotriene (LT) B4 levels increased to 594 +/- 46 relative to 200 +/- 38 pg/ml in shams (P less than 0.01); increased permeability was documented by BAL fluid protein content of 599 +/- 91 compared with 214 +/- 35 micrograms/ml in sham animals (P less than 0.01); and edema was shown by increase in lung wet-to-dry weight ratio of 4.77 +/- 0.14 relative to 4.00 +/- 0.09 in sham rats (P less than 0.01). In MAAPV-treated animals, lung neutrophil sequestration (62 +/- 9 U/g MPO) and rise of LTB4 in BAL fluid (780 +/- 244 pg/ml) were not affected, but both BAL fluid protein (335 +/- 32 micrograms/ml) and lung wet-to-dry weight ratio (4.21 +/- 0.17) were reduced (both P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboxane-induced neutrophil adhesion to pulmonary microvascular and aortic endothelium is regulated by CD18

Thromboxane (Tx) A2 generation and subsequent selective pulmonary sequestration of neutrophils (PMNs) is characteristic of several forms of the adult respiratory distress syndrome (ARDS). Therefore, we examined PMN-dependent adhesion to cultured pulmonary microvessel and aortic endothelium (EC) in response to U46,619 (Tx mimic). Nonstimulated PMNs were two fold more adherent to pulmonary microvessel EC than to aortic EC (P less than 0.01). PMN pretreatment with Tx mimic (10(-6) M) increased adhesion to both types of EC (P less than 0.01). The Tx mimic-induced adhesion was blocked by receptor antagonists to Tx (SQ29,548) and to leukotrienes (FPL55,712), and by the anti-CD18 mAb TS1/18 (P less than 0.01, all cases). Baseline PMN adhesion also was modulated by Tx, leukotrienes, and CD18, for both EC types. These results indicate pulmonary microvessel EC is intrinsically more adhesive for both nonstimulated and stimulated PMNs than aortic EC and that Tx mediates PMN-dependent adhesion by coupled interaction of Tx and LT receptors via CD18 activation.

Thromboxane A2 induces leukotriene B4 synthesis that in turn mediates neutrophil diapedesis via CD 18 activation

Previous studies have indicated that thromboxane (Tx) and leukotriene (LT) B4 act synergistically to induce neutrophil (PMN) adhesion in the microvasculature. This study explores the ability of Tx to induce LTB4 synthesis, which then leads to activation of PMN and endothelial adhesion receptors. Tx-mimic (U46619, 1 microgram/ml) was administered into abraded skin chambers placed on the backs of rabbits (n = 6). After 3 hr LTB4 was synthesized in the blister fluid at 385 pg/ml, a value higher than levels in saline-treated blisters, 10 pg/ml (P less than 0.05). The LTB4 generation following Tx-mimic was correlated (P less than 0.05, r = 0.70) with neutrophil diapedesis. These averaged 645 PMN/mm3, values higher than saline values of 20 PMN/mm3 (P less than 0.05). Intravenous (iv) treatment of other rabbits (n = 4) with the lipoxygenase inhibitor diethylcarbamazine at 60 mg/kg, followed by 40 mg/kg/hr, prevented Tx-mimic-induced LTB4 synthesis (10 pg/ml) and diapedesis (19 PMN/mm3) (both P less than 0.05). Intravenous treatment of yet other rabbits (n = 4) with the anti-CD 18 monoclonal antibody R 15.7 at 1 mg/kg abolished Tx-induced diapedesis (3 PMN/mm3) (P less than 0.05). In contrast, local administration of 3 ng of the protein synthesis inhibitor actinomycin D, to prevent expression of endothelial adhesion proteins, limited TNF- but not Tx-induced diapedesis. The data indicate that Tx-induced diapedesis is mediated by the generation of LTB4 and the activation of neutrophil CD 18 but not endothelial adhesion proteins.

Modulation of pulmonary permeability in vivo with agents that affect the cytoskeleton

In vitro studies show that the cytoskeleton of the microvascular barrier moderates polymorphonuclear leukocyte (PMN) diapedesis and the transport of macromolecules. This in vivo study tests indirectly whether the cytoskeleton of the pulmonary microvasculature responds similarly to agents known to reorganize the cytoskeleton to alter diapedesis and permeability in vitro. One of four agents, saline solution, cytochalasin B (which promotes actin microfilament disassembly), leukotriene (LT) B4 (PMN chemoattractant), or phalloidin (which promotes and stabilizes F-actin polymerization) was introduced into the bronchus of the anterior segment of the left lung of anesthetized rats (n = 152) through a tracheostomy and fine-bore cannula. Twenty minutes later, saline solution, cytochalasin B, LTB4, or phalloidin was similarly introduced. PMN accumulations (x 10(4) cells/ml), protein concentration in bronchoalveolar lavage fluid, and lung wet/dry weight ratios were measured 3 hours later. When the initial and secondary treatments were saline solution, PMN accumulations were 3 +/- 1 cells/ml and the protein level was 274 +/- 48 micrograms/ml. Secondary treatment of the saline-treated group with cytochalasin B or LTB4 led to increases in PMN to 18 +/- 2 and 9 +/- 2 cells/ml and protein to 960 +/- 50 and 840 +/- 40 micrograms/ml (p less than 0.05); secondary treatment with phalloidin was similar to that with saline solution. With saline solution used for both treatments, the wet/dry ratio was 3.4 +/- 0.2. Primary saline solution and secondary treatments with either cytochalasin B or LTB4 led to a similar increase in wet/dry ratios to 3.9 +/- 0.1 (p less than 0.05), whereas phalloidin was without effect (3.5 +/- 0.3). Initial cytochalasin B treatment followed by LTB4 led to increased PMN diapedesis (43 +/- 6 cells/ml and wet/dry ratio 4.3 +/- 0.2) (p less than 0.05). Secondary phalloidin treatment attenuated the cytochalasin B effect with counts of 12 +/- 2 PMN/ml, protein levels of 460 +/- 30 micrograms/ml, and a lower wet/dry ratio of 3.7 +/- 0.1 (p less than 0.05). Even more striking, phalloidin as initial treatment further reduced the cytochalasin B effect to 7 +/- 1 PMN/ml, whereas protein level was 490 +/- 60 micrograms/ml and wet/dry ratio was 3.5 +/- 0.1 (p less than 0.05). Further, phalloidin, given initially, attenuated the effect of secondary treatment with LTB4, resulting in fewer cells (4 +/- 2 PMN/ml), a lower wet/dry ratio (3.4 +/- 0.1), and protein level of 650 +/- 20 micrograms/ml (p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Neutrophil accumulations due to pulmonary thromboxane synthesis mediate acid aspiration injury

Acid aspiration leads to lung injury associated with high levels of plasma thromboxane (Tx). This study tests the role of Tx synthesis by the aspirated lung segment in mediating local and remote neutrophil (PMN) sequestration, alveolar diapedesis, and permeability edema. Anesthetized rats underwent tracheostomy and insertion of a fine-bore cannula into the anterior segment of the left lung. This was followed by the installation of either 0.1 ml saline (n = 18) or the Tx synthase inhibitor OKY 046 (0.1 mg/kg in 0.1 ml, n = 18). Twenty minutes later either 0.1 ml 0.1 N HCL or 0.1 ml saline was similarly introduced (n = 18). Three hours later, in the saline-HCl group, the rise in Tx concentration in both plasma (1,340 pg/ml) and bronchoalveolar lavage (BAL) fluid (2,100 pg/ml) was higher than that in the saline-saline aspirated control group (350 and 115 pg/ml, respectively; both P less than 0.05). In the acid-aspirated lung PMN sequestration [87 PMN/10 high-power fields (HPF)] and diapedesis (96 x 10(4) PMN/ml in BAL) were higher than control values of 7 PMN/10 HPF and 3 x 10(4) PMN/ml (both P less than 0.05). Acid aspiration induced local permeability edema with a high protein concentration in BAL of 3,350 micrograms/ml and an increase in lung wet-to-dry weight ratio (W/D) of 6.6, both higher than control values of 482 micrograms/ml and 3.4, respectively (P less than 0.05). Leukosequestration in the aspirated side started at 30 min and was progressive over a 3-h monitoring period.(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboxane mediates diapedesis after ischemia by activation of neutrophil adhesion receptors interacting with basally expressed intercellular adhesion molecule-1

Ischemic injury is characterized by neutrophil (PMN)--endothelial cell adhesion and diapedesis associated with thromboxane (TX) generation. Neutrophil-endothelial cell interaction is regulated in part by the leukocyte adhesion receptor CD 18 glycoprotein complex and the endothelial intercellular adhesion molecule-1 (ICAM-1). This study tests the role of TX in ischemia-induced diapedesis and evaluates whether the diapedesis is regulated by neutrophil or endothelial adhesion receptors. Plasma derived from rabbit hind limbs made ischemic for 3 hours (n = 6) and reperfused for 10 minutes had increased levels of TXB2 3,450 pg/ml, which was higher than sham rabbit (n = 6) values of 653 pg/ml (p less than 0.05). When introduced into abraded skin chambers placed on the dorsum of other normal rabbits (n = 6), this ischemic plasma induced 1,000 pg/ml of new TX synthesis and diapedesis of 1,235 PMN/mm3. The total TX concentration and PMN accumulations in blister fluid were correlated (r = 0.88, p less than 0.05). In contrast, sham rabbit plasma induced no TX synthesis and diapedesis of only 77 PMN/mm3 (p less than 0.05). Administration of 50 ng/ml of authentic TXB2 into blisters induced an accumulation of 453 PMN/mm3, which was higher than that in saline controls (18 PMN/mm3) (p less than 0.05). Pretreatment of normal rabbits used for the diapedesis assay (n = 4) with the TX synthetase inhibitor OKY 046 (2 mg/kg/hr) limited ischemic plasma and authentic TXB2 induced diapedesis to 142 and 76 PMN/mm3, respectively (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)