Differential presentation of the same MHC class I epitopes by fibroblasts and dendritic cells

Ag is presented to CTL as peptide associated with MHC class I molecules, which are present on most types of cells. We have investigated the presentation of Db-restricted lymphocytic choriomeningitis virus (LCMV) peptides by a fibroblast line (MC57) and a dendritic cell line (JawsII) to splenocytes from LCMV-immune C57BL/6 mice. We found that when LCMV-infected MC57 were used to restimulate the spleen cells, the resulting CTL line lost its ability to respond to the two dominant epitopes of the immune response to LCMV glycoprotein (gp)33 and nucleoprotein (np)396 but remained strongly lytic for targets coated with the subdominant gp276 epitope. In contrast, when LCMV-infected JawsII cells were used to restimulate the splenocytes, the resulting line continued to target gp33 and np396 but lost reactivity to gp276. When uninfected JawsII or MC57 cells were coated with peptides and used as stimulators, the resulting CTL lines continued to recognize all three epitopes, indicating that costimulatory or other potential innate differences in Ag presentation between the two cell lines are unlikely to account for the selective expansion of CTL specificities. When infected, both cell types produce similar levels of infectious LCMV, have similar levels of the NP and GP proteins from which np396 and gp33 are derived, and can be recognized by CTL specific for each of the three epitopes. These data indicate that in the generation of peptides for MHC-I binding and presentation to CTL, MC57 and JawsII process the same set of virus proteins in quantitatively different ways.     

Substrate binding and catalytic mechanism of a barley beta-D-Glucosidase/(1,4)-beta-D-glucan exohydrolase

A beta-glucosidase, designated isoenzyme betaII, from germinated barley (Hordeum vulgare L.) hydrolyzes aryl-beta-glucosides and shares a high level of amino acid sequence similarity with beta-glucosidases of diverse origin. It releases glucose from the non-reducing termini of cellodextrins with catalytic efficiency factors, kcat/Km, that increase approximately 9-fold as the degree of polymerization of these substrates increases from 2 to 6. Thus, the enzyme has a specificity and action pattern characteristic of both beta-glucosidases (EC 3.2.1.21) and the polysaccharide exohydrolase, (1,4)-beta-glucan glucohydrolase (EC 3.2.1.74). At high concentrations (100 mM) of 4-nitrophenyl beta-glucoside, beta-glucosidase isoenzyme betaII catalyzes glycosyl transfer reactions, which generate 4-nitrophenyl-beta-laminaribioside, -cellobioside, and -gentiobioside. Subsite mapping with cellooligosaccharides indicates that the barley beta-glucosidase isoenzyme betaII has six substrate-binding subsites, each of which binds an individual beta-glucosyl residue. Amino acid residues Glu181 and Glu391 are identified as the probable catalytic acid and catalytic nucleophile, respectively. The enzyme is a family 1 glycoside hydrolase that is likely to adopt a (beta/alpha)8 barrel fold and in which the catalytic amino acid residues appear to be located at the bottom of a funnel-shaped pocket in the enzyme.     

Response to dopamine vs norepinephrine in tricyclic antidepressant-induced hypotension

OBJECTIVE: To compare the efficacy of dopamine (DA) with that of norepinephrine (NE) in the treatment of refractory hypotension caused by tricyclic antidepressants (TCAs). METHODS: A retrospective analysis was used to compare blood pressure responses in concurrent case series of patients treated with vasopressors for TCA-associated hypotension. The patients were adults (aged > or = 16 years) treated at 2 urban teaching hospitals from 1983 to 1994. All patients were diagnosed as having TCA ingestion (positive serum toxicologic assay), were hypotensive [systolic blood pressures (SBPs) < or = 90 mm Hg], and required vasopressor therapy. The patients were grouped by initial vasopressor treatment (i.e., NE vs DA). RESULTS: There were 26 hypotensive adult patients who met study criteria. All 26 patients remained hypotensive after initial treatment of their TCA-associated hypotension with crystalloid infusion and alkalinization. The NE and DA groups were similar in age, sex, and proportion of patients with single and co-drug ingestion. The NE group, however, had a significantly lower average SBP at study entry (56 vs 74 mm Hg, p = 0.04). Nine of 15 (60%) patients responded to DA (5-10 micrograms/kg/min) and 11/11 (100%) patients responded to NE (5-53 micrograms/min). The difference in response rates was statistically significant (p = 0.02). Six patients in whom DA (max rate 10-50 micrograms/min/kg) failed to raise the SBP subsequently responded to NE (max rate 5-74 micrograms/ min) when this drug was later used. One patient receiving NE (12 micrograms/min) developed ventricular ectopy, successfully treated with lidocaine. There were no ischemic complications from either NE or DA. Patients who failed DA therapy tended to be older (39 vs 30 years, p = 0.08), to be more hypotensive at study entry (64 vs 81 mm Hg, p = 0.008), and to remain hypotensive even at higher doses of DA (24 vs 7 micrograms/min/kg, p = 0.002). CONCLUSION: While this was not a prospective randomized study, NE appears advantageous over DA as the first-line vasopressor agent for those patients who require vasopressor support in the setting of TCA-induced hypotension that is refractory to IV fluid and serum alkalinization.     

Assessment of protein synthesis and secretion by rat seminiferous and epididymal tubules in vivo

In vivo microperifusion and micropuncture were used to study tubule protein synthesis and proluminal secretion by the male reproductive tract in vivo. Seminiferous and caput and cauda epididymal tubules were perifused for 3 h. with [35S]-methionine. Perifused interstitial fluid (IF), lumen fluid (LF), and tubule extract (TE) were collected. Proteins were separated by SDS-PAGE, and autoradiograms were developed. Trichloroacetic acid precipitable proteins in each fluid were determined and a protein synthesis index (PSI) was calculated. PSI values demonstrated that the cauda epididymis synthesized less protein in vivo than did either seminiferous or caput tubules. Seminiferous tubules synthesized and secreted into the tubule lumen a relatively constant panel of proteins. Epididymal tubules synthesized and secreted proteins in a region-specific manner. In the caput epididymis the most prominent secreted bands were consistent with the heavy and light chains of epididymal clusterin. In the cauda epididymis, the most prominent synthesized and secreted protein was a 25 kDa protein consistent with the protein D. The above approach to studying protein synthesis and secretion will allow direct study of the physiological and pathophysiological effects on this important epithelial function in vivo.     

Evaluation of acute physiology and chronic health evaluation III predictions of hospital mortality in an independent database

OBJECTIVE: To assess the accuracy and validity of Acute Physiology and Chronic Health Evaluation (APACHE) III hospital mortality predictions in an independent sample of U.S. intensive care unit (ICU) admissions. DESIGN: Nonrandomized, observational, cohort study. SETTING: Two hundred eighty-five ICUs in 161 U.S. hospitals, including 65 members of the Council of Teaching Hospitals and 64 nonteaching hospitals. PATIENTS: A consecutive sample of 37,668 ICU admissions during 1993 to 1996; including 25,448 admissions at hospitals with >400 beds and 1,074 admissions at hospitals with <200 beds. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: We used demographic, clinical, and physiologic information recorded during ICU day 1 and the APACHE III equation to predict the probability of hospital mortality for each patient. We compared observed and predicted mortality for all admissions and across patient subgroups and assessed predictive accuracy using tests of discrimination and calibration. Aggregate hospital death rate was 12.35% and predicted hospital death rate was 12.27% (p =.541). The model discriminated between survivors and nonsurvivors well (area under receiver operating curve = 0.89). A calibration curve showed that the observed number of hospital deaths was close to the number of deaths predicted by the model, but when tested across deciles of risk, goodness-of-fit (Hosmer-Lemeshow statistic, chi-square = 48.71, 8 degrees of freedom, p< .0001) was not perfect. Observed and predicted hospital mortality rates were not significantly (p < .01) different for 55 (84.6%) of APACHE III's 65 specific ICU admission diagnoses and for 11 (84.6%) of the 13 residual organ system-related categories. The most frequent diagnoses with significant (p < .01) differences between observed and predicted hospital mortality rates included acute myocardial infarction, drug overdose, nonoperative head trauma, and nonoperative multiple trauma. CONCLUSIONS: APACHE III accurately predicted aggregate hospital mortality in an independent sample of U.S. ICU admissions. Further improvements in calibration can be achieved by more precise disease labeling, improved acquisition and weighting of neurologic abnormalities, adjustments that reflect changes in treatment outcomes over time, and a larger national database.     

Is adverse pregnancy outcome predictable after blunt abdominal trauma?

OBJECTIVE: The aim of the study was to evaluate the following: (1) pregnancy outcome after blunt abdominal trauma and (2) factors that may predict preterm birth and adverse peripartum outcomes. STUDY DESIGN: All women who had noncatastrophic abdominal trauma and came to the labor and delivery suite July 1994-August 1997 were prospectively evaluated and admitted for continuous uterine and fetal monitoring. A complete blood cell count, coagulation profile, and Kleihauer-Betke stain were performed. Ultrasonographic examination was performed to rule out hematoma. Tocolytic agents were administrated in cases with persistent contractions. Pregnancy outcomes and risk factors were compared between those with preterm birth before 37 weeks' gestation and those who were delivered after 37 weeks' gestation. RESULTS: Delivery information was available for 85 women with blunt abdominal trauma from motor vehicle accident (28), falls (27), and direct assault (30, which included 17 cases of domestic abuse). Four women, 3 of whom were exposed to domestic abuse, were hospitalized twice. Thirteen patients had preterm birth and 72 patients were delivered at term. In all cases the results of Kleihauer-Betke stains, maternal vital signs, blood cell count, coagulation profile, and placental ultrasonographic examinations were normal. The differences between the 2 groups with respect to gestational age at the time of trauma, length of hospital stay, subjective reports of abdominal pain, objective findings of abdominal tenderness, patterns of uterine contractions, interval between trauma and delivery, and Apgar scores were not statistically significant. However, the preterm birth group received magnesium sulfate tocolysis more frequently (31% vs 7%) and had a significantly greater rate of peripartum complications, such as rupture of membranes and abruptio placentae, than the group of patients who delivered at term (46.2% vs 12.5%, P <.05). Women with domestic abuse had increased uterine contractions at the time of abdominal trauma (52.9% vs 19.1%, P =.01) but did not require increased use of tocolysis. Women with domestic abuse had more peripartum complications (41.8% vs 11.8%, P <.01). CONCLUSIONS: Women with noncatastrophic blunt abdominal trauma in pregnancy tend to have favorable neonatal outcomes. Findings or reports of abdominal tenderness and uterine contractions are not predictive of preterm birth. Preterm birth was associated with increased peripartum complications. However, domestic abuse was associated with repeated trauma in the index pregnancy and increased peripartum complications.     

Diagnosing breast implant rupture with MR imaging, US, and mammography

A total of 135 symptomatic women with 262 breast implants were examined with magnetic resonance (MR) imaging performed with a body coil, ultrasound (US), or both to determine imaging features of implant rupture. Surgical proof was available for 33 women with 62 implants; 24 were ruptured and 38 were intact. Complicated internal structure was the most reliable predictor of implant rupture: Diffuse low-level echoes were seen on sonograms in 56% of ruptured implants; internal membranes (which correspond to the collapsed implant shell) were seen on MR images in 58% of ruptured implants. Fluid droplets were seen within the silicone in 26% of ruptured implants on MR images. Irregular implant contour can be a sign of rupture but is unreliable. Fluid collections around silicone implants are not a sign of rupture. At present, neither US nor conventional MR imaging with a body coil is sufficiently reliable to advocate routine screening of asymptomatic women with breast implants. Evaluation with MR imaging performed with a surface coil is more reliable.     

Polymeric composite materials incorporating an elastomeric interphase: A mathematical assessment

A mathematical model based upon the method of cells is extended in order to describe three-phase composite materials containing an interphase. A parametric study is performed wherein the effective properties of the composites are determined as a function of interphase material properties, interphase thickness and fiber volume fraction. The simulation is designed in particular towards describing the behavior of model composites which incorporate elastomeric polymers as an interphase to bond carbon fibers chemically to a polymeric matrix. Two hypothetical interphases are considered: one whose properties are representative of elastomers (Young's modulus less than fiber and matrix) and one whose properties are intermediate with respect to the fiber and matrix. The two cases provide a broad assessment of how the interphase properties influence the effective composite properties.     

Blood donation and patterns of use in southeastern Nigeria

A retrospective study of donor blood availability and patterns of use from 1984 through 1988 was conducted in a 400-bed university teaching hospital in Nigeria by extraction of data from the master registers for blood donors and recipients. Blood transfusion requests, number of persons who underwent phlebotomy, number of crossmatches performed, and blood use increased each year during the period of study. Average wastage rate and crossmatch-to-transfusion ratio were 3.5 percent and 1.61, respectively. Replacement blood donation constituted 98 percent of available donor blood. Obstetrics and gynecology and surgery patients used 70.4 percent of the donor blood. The donor blood units were used as whole blood (81%) because of a lack of infrastructure such as a refrigerated centrifuge. Less than 5 percent of the donors were females. It is concluded that the levels of voluntary blood donation and general blood supply are unacceptably low. The need for a functional National Blood Transfusion Service is highlighted.