Validation of a nitrogen washout system to measure functional residual capacity in premature infants with hyaline membrane disease

A multiple-breath nitrogen washout system designed to measure lung volume in mechanically ventilated infants was validated by assessing three performance criteria: 1) accuracy of lung volume measurements in the presence of an endotracheal tube leak was assessed by comparing the measurements of functional residual capacity (FRC) in a mechanical lung model with and without airway leak; 2) in vivo accuracy was assessed in rabbits by comparing FRC measurements obtained by this system with measurements obtained by helium dilution; and 3) in vivo precision was assessed by analyzing measurements of FRC obtained in replicate measurements at different times in ventilator-dependent premature infants with hyaline membrane disease. The average difference between the measurements of FRC in a mechanical lung model with airway leak and without leak was 3.0 +/- 9.4% (mean +/- SD, P > 0.2), and no difference was greater than 20%. There was a significant correlation between the measurements of FRC in rabbits by nitrogen washout and by helium dilution (r = 0.93, P < 0.0001), and 65.4% of the paired measurements were within 20% of their average. The 95% limits of agreement within pairs of measurements by the two techniques ranged from -4.0 to + 6.5 mL/kg. FRC measured by helium dilution was slightly higher (1.3 +/- 2.7 mL/kg, P < 0.01) than FRC measured by nitrogen washout, and positive end-expiratory pressure was a significant predictor of this difference (P < 0.0001). The regression between the individual FRC measurements obtained in premature infants and the average of the other replicates was significant (r2 > 0.98, P < 0.0001). The coefficient of variation was 12.3%. These findings provide further validation of this multiple-breath nitrogen washout system for measuring FRC in premature infants during mechanical ventilation.

Cloning and expression of canine interleukin-10

We describe here the cloning of canine IL-10 cDNA (GenBank accession No. U33843) and the expression of recombinant IL-10 in a dog kidney cell line (DK6247) and Chinese hamster ovary cells (CHO). Canine IL-10 exhibits strong sequence homology to the known sequences of human, mouse, rat, and bovine genes at nucleotide and amino acid levels. The IL-10 gene, when introduced into DK and CHO cell lines, produces recombinant IL-10 that causes an inhibitory effect on allogeneic MHC-driven lymphoproliferative responses.

Late infections after allogeneic bone marrow transplantations: comparison of incidence in related and unrelated donor transplant recipients

Infectious complications are a major cause of morbidity and mortality after allogeneic bone marrow transplantation (BMT). We have evaluated the incidence of late infections (beyond day +50) in recipients of related (RD) and unrelated donor (URD) allogeneic BMT, factors associated with increased risks of infection, and the impact of the late infections on survival. Between 1989 and 1991, 249 patients received an RD (n = 151) or URD (n = 98) allogeneic BMT at the University of Minnesota and all late infections were investigated. Three hundred sixty-seven late infectious events developed in 162 patients between 50 days and 2 years after BMT. The incidence of any late infection was greater in URD versus RD recipients (84.7% v 68.2%, respectively; P = .009). In multivariate analysis, advanced graft-versus-host disease (GVHD) was significantly associated with late infections. The effect of GVHD was apparent only in RD recipients (relative risk [RR], 2.29; P = .003), whereas URD recipients, with or without GVHD, had more late infections compared with RD recipients without GVHD. Multivariate analysis showed that late posttransplantation infections were the dominant independent factor associated with increased nonrelapse mortality (RR, 5.5; P = .0001), resulting in improved 3-year survival for RD versus URD recipients (49.9% +/- 8% v 34.4% +/- 10%; P = .004). In this study, we observed that late infections are more frequent in URD recipients, resulting in substantially higher nonrelapse mortality. This prolonged period of increased infectious risk in URD recipients suggests the need for aggressive surveillance and therapy of late infections and perhaps prolonged antibiotic prophylaxis for all URD BMT recipients.

Overlapping stage models and reaction time additivity: effects of the activation equation

Many experimental factors have been found to affect mean reaction time (RT) additively in factorial experiments. What sorts of RT models are compatible with this fact? Sternberg (1969) showed that serial, discrete-stage models are consistent with additivity, and as a result additivity has sometimes been regarded as evidence in favor of such models. However, McClelland (1979) showed that an alternative "cascade" model, which violates crucial assumptions of discrete-stage models, also predicts RT additivity in many cases. This article examines various modified versions of the cascade model, and shows that mean RT additivity arises from many overlapping stage models, including some with thresholds, information quantization, and nonlinear activation transformations. This suggests that other aspects of the data besides mean RT additivity should be examined to distinguish between serial and overlapping stage models.

BPV E1 protein alters the kinetics of cell cycle entry of serum starved mouse fibroblasts

A stable bovine papillomavirus E1 expressing cell line (C2E1) was used to investigate the effects of E1 protein on the requirement for growth factors during serum-induced reentry from quiescence to proliferation. Flow cytometric bivariate DNA/PCNA analysis was utilized to study the expression of proliferating cell nuclear antigen (PCNA) concomitant with this transition. C2E1 cells, unlike the control cells (CNEO), were able to reenter the cell cycle when stimulated with low serum (1%). Stimulation with 10% serum revealed that C2E1 cells entered the first cell cycle faster than CNEO, indicating that E1 protein decreased the time of progression from G0 stage upon serum activation. It was also shown that PCNA expression started earlier in C2E1 cells than in CNEO cells after quiescent cells were stimulated with 10% serum. Addition of 1% serum was able to induce PCNA expression in C2E1 but not in CNEO cells in the first 24 h after stimulation. Using Triton X-100 treatment, it was found that the distribution between bound and unbound forms of PCNA was altered in E1-expressing cells compared to CNEO cells. Based on these results, it is suggested that E1 might possess mitogen-like properties.

Intercellular adhesion molecule-1 dimerization and its consequences for adhesion mediated by lymphocyte function associated-1

Intercellular adhesion molecule-1 (ICAM-1, CD54) is a ligand for the integrins lymphocyte function associated-1 (LFA-1, CD11a/CD18) and complement receptor-3 (Mac-1, CD11b/CD18) making it an important participant in many immune and inflammatory processes. Modified recombinant soluble ICAM-1 formed dimers. This result indicated that the ectodomain of ICAM-1 contains homophilic interaction sites. Soluble ICAM-1 dimers bind to solid-phase purified LFA-1 with high avidity (dissociation constant [Kd] = 8 nM) in contrast to soluble ICAM-1 monomers whose binding was not measurable. Cell surface ICAM-1 was found to be dimeric based on two distinct criteria. First, a monoclonal antibody specific for monomeric soluble ICAM-1, CA7, binds normal ICAM-1 poorly at the cell surface; this antibody, however, binds strongly to two mutant forms of ICAM-1 when expressed at the cell surface, thus identifying elements required for dimer formation. Second, chemical cross-linking of cell surface ICAM-1 on transfected cells and tumor necrosis factor-activated endothelial cells results in conversion of a portion of ICAM-1 to a covalent dimer. Cell surface ICAM-1 dimers are more potent ligands for LFA-1-dependent adhesion than ICAM-1 monomers. While many extracellular matrix-associated ligands of integrins are multimeric, this is the first evidence of specific, functionally important homodimerization of a cell surface integrin ligand.

Proteolysis of major histocompatibility complex class II-associated invariant chain is regulated by the alternatively spliced gene product, p41

Invariant chain (Ii) is an intracellular type II transmembrane glycoprotein that is associated with major histocompatibility complex class II molecules during biosynthesis. Ii exists in two alternatively spliced forms, p31 and p41. Both p31 and p41 facilitate folding of class II molecules, promote egress from the endoplasmic reticulum, prevent premature peptide binding, and enhance localization to proteolytic endosomal compartments that are thought to be the sites for Ii degradation, antigen processing, and class II-peptide association. In spite of the dramatic and apparently equivalent effects that p31 and p41 have on class II biosynthesis, the ability of invariant chain to enhance antigen presentation to T cells is mostly restricted to p41. Here we show that degradation of Ii leads to the generation of a 12-kDa amino-terminal fragment that in p41-positive, but not in p31-positive, cells remains associated with class II molecules for an extended time. Interestingly, we find that coexpression of the two isoforms results in a change in the pattern of p31 degradation such that endosomal processing of p31 also leads to extended association of a similar 12-kDa fragment with class II molecules. These data raise the possibility that p41 may have the ability to impart its pattern of proteolytic processing on p31 molecules expressed in the same cells. This would enable a small number of p41 molecules to modify the post-translational transport and/or processing of an entire cohort of class II-Ii complexes in a manner that could account for the unique ability of p41 to enhance antigen presentation.

Permethrin resistance in the head louse Pediculus capitis from Israel

Head lice, Pediculus capitis, were collected from children aged 3-12 years in Maale Adumin, a town near Jerusalem, after reports of control failure with the pyrethroid insecticide permethrin. A total of 1516 children were examined: living lice and eggs were found on 12.1% of the children; or another 22.8% of the children only nits were found. Twice as many girls as boys (8.1% v 4%) were infested with lice and or nits. Head lice collected from infested children were exposed to permethrin impregnated filter-papers. Log time probit mortality (ltp) regression lines were calculated for mortality data and compared to ltp lines for a similar collection of head lice made in 1989. The regression lines for the two years were significantly different, with a 4-fold decrease in susceptibility at the LT50 level between 1989 and 1994. The slopes of the lines also suggested that the 1994 population was more heterogenous in its response to permethrin than the 1989 population. In contrast, a laboratory population of body lice (Pediculus humanus) tested with the same batch of permethrin-impregnated papers showed a slight but non-significant increase in susceptibility between 1989 and 1994. The results suggest that resistance to pyrethroids has developed rapidly among head lice since permethrin was introduced in 1991 as a pediculicide in Israel.

Bicarbonate diffusion through mucus

The mucus layer overlying duodenal epithelium maintains a pH gradient against high luminal acid concentrations. Despite these adverse conditions, epithelial surface pH remains close to neutrality. The exact nature of the gradient-forming barrier remains unknown. The barrier consists of mucus into which HCO3- is secreted. Quantification of the ability of HCO3- to establish and maintain the gradient depends on accurate measurement of this ion's diffusion coefficient through mucus. We describe new experimental and mathematical methods for diffusion measurement and report diffusion coefficients for HCO3- diffusion through saline, 5% mucin solutions, and rat duodenal mucus. The diffusion coefficients were 20.2 +/- 0.10, 3.02 +/- 0.31, and 1.81 +/- 0.12 x 10(-6) cm2/s, respectively. Modeling of the mucobicarbonate layer with this latter value suggests that for conditions of high luminal acid strength the neutralization of acid by HCO3- occurs just above the epithelial surface. Under these conditions the model predicts that fluid convection toward the lumen could be important in maintaining the pH gradient. In support of this hypothesis we were able to demonstrate a net luminal fluid flux of 5 microliters.min-1.cm-2 after perfusion of 0.15 N HCl in the rat duodenum.

Early development of acute myelogenous leukemia following kidney transplantation: possible role of multiple serum cytokines

We report a patient who at the time of kidney transplantation for polycystic kidney disease was found to have an enlarged inguinal lymph node which later demonstrated evidence of extra medullary granulopoiesis. During the first two weeks following kidney transplantation, a striking leukemoid pattern developed and 2 months after transplant the patient was diagnosed with acute myelogenous leukemia (AML). Retrospective analysis of peripheral blood cytokines over this time revealed elevated levels of GMCSF and gamma IFN at the time of peak peripheral blood WBC with subsequent peaks in IL-4, IL-6 and IL-2 as the peripheral blood WBC fell. A rise in levels of TNF alpha also preceded the peripheral blood WBC rise (although these concentrations were at or below those following uncomplicated kidney transplants). The clinical course of AML in this patient was marked by relentless relapse despite chemotherapy. The possibility of cytokine facilitated tumor growth is discussed.

Nursing patients through 'Pathways of Care'

Pathways of Care can lead to standardised practice. Improved recordkeeping can save nursing time and improve continuity of care.

Potent effects of low levels of MHC class II-associated invariant chain on CD4+ T cell development

Invariant chain (Ii)-negative mice exhibit defects in MHC class II assembly and transport that results in reduced levels of surface class II, altered antigen presentation, and inefficient positive selection of CD4+ T cells. Many CD4+ T cells that do mature in Ii-negative mice express a cell surface phenotype consistent with aberrant positive selection or peripheral activation. Reconstitution of these mice with low levels of either the p31 or p41 form of Ii does not restore transport of the bulk of class II or class II surface expression, but surprisingly does restore positive selection as measured by numbers and surface phenotype of CD4+ T cells. Thus, an Ii-dependent process, independent of effects on class II surface density, appears to be required for normal positive selection of CD4+ T cells.

Heart retransplantation: the 25-year experience at a single institution

BACKGROUND

The current critical shortage of cardiac allograft donors means that the decision to offer a patient repeat heart transplantation must be carefully considered. Since 1968, a total of 66 heart retransplantation procedures (63 first-time and three second-time) have been performed in 63 patients at Stanford.

METHODS

There were 52 male and 11 female patients, ranging in age from 3 to 62 years with a mean age of 41 years. Indications for retransplantation were primary allograft failure in nine patients, acute rejection in 17, graft atherosclerosis in 37, and constrictive disease in three. Six of the seventeen patients (35%) who underwent retransplantation before 1981 died in the hospital, and none are currently alive. Of the 46 patients who underwent retransplantation since 1981 treated with cyclosporine-based immunosuppression, 11 (24%) died in the hospital. Actuarial survival estimates for the whole retransplantation group at 1, 5, and 10 years were 55% +/- 8%, 33% +/- 8%, and 22% +/- 7%, respectively.

RESULTS

This survival was significantly worse (p < 0.05) than that in patients undergoing primary heart transplantation (81% +/- 2%, 62% +/- 2%, 44% +/- 13% at 1, 5, and 10 years). Those patients who underwent retransplantation for graft atherosclerosis since 1981 had a significantly better 1-year survival (p < 0.05) than those who underwent retransplantation for allograft rejection (69% +/- 10% versus 33% +/- 16%), but the 5-year survival was similar in both groups (34% +/- 11% versus 33% +/- 16%). Since 1981, actuarial freedoms from infection and rejection were 22% +/- 8% and 41% +/- 9%, respectively, at 1 year, and 7% +/- 7% and 36% +/- 9% at 5 years. Patients with cyclosporine-induced renal dysfunction (serum creatinine level of greater than 2.0 mg/dl) had a high probability of requiring postoperative dialysis and also of death after retransplantation. Three patients with significant cyclosporine-induced renal dysfunction underwent simultaneous kidney transplantation and heart retransplantation, and all were alive and well at the time this article was written. Sixteen patients were also currently alive at a mean follow-up of 44 months, and 15 were in New York Heart Association functional class I.

CONCLUSIONS

We continue to list carefully selected candidates with good rehabilitation potential for heart retransplantation.