Use of an optical fiber scope to confirm endotracheal tube placement in pediatric patients

OBJECTIVE

To determine the efficacy of a portable optical fiber scope to confirm endotracheal tube (ETT) placement.

DESIGN

A prospective, nonrandomized, blinded study.

SETTING

Pediatric intensive care unit in a children's hospital.

PATIENTS

Thirty mechanically ventilated patients with an ETT in place.

INTERVENTIONS

Patients entered into the study underwent ETT placement determination by chest roentgenogram (CXR) and by the optical fiber scope.

MEASUREMENTS AND MAIN RESULTS

Thirty patients were entered into the study, for a total of 46 measurements (n = 46). ETT size ranged from 3.0 to 6.0 mm internal diameter. Distance from the ETT and the carina was determined by the scope and compared with the distance measured on the CXR. No statistical difference was found between the two methods. None of the patients experienced clinically significant side effects from the procedure. On three occasions, the presence of secretions in the ETT did not allow for the visualization of the carina by the scope.

CONCLUSION

The use of a flexible optical fiber scope is an accurate, fast, and practical method to determine ETT placement in pediatric patients on mechanical ventilation.

Phenotypic analysis and virulence of Candida albicans LIG4 mutants

In previous studies, we reported the isolation and preliminary characterization of a DNA ligase-encoding gene of Candida albicans. This gene (LIG4) is the structural and functional homologue of both yeast and human ligase IV, which is involved in nonhomologous end joining (NHEJ) of DNA double-strand breaks. In the present study, we have shown that there are no other LIG4 homologues in C. albicans. In order to study the function of LIG4 in morphogenesis and virulence, we constructed gene deletions. LIG4 transcript levels were reduced in the heterozygote and were completely absent in null strains. Concomitantly, the heterozygote showed a pronounced defect in myceliation, which was slightly greater in the null strain. This was true with several solid and liquid media, such as Spider medium, medium 199, and 2% glucose-1% yeast extract-2% Bacto Peptone, at several pHs. Reintroduction of the wild-type allele into the null mutant partially restored the ability of cells to form hyphae. In agreement with the positive role of LIG4 in morphogenesis, we detected a significant rise in mRNA levels during the morphological transition. LIG4 is not essential for DNA replication or for the repair of DNA damage induced by ionizing radiation or UV light, indicating that these lesions are repaired primarily by homologous recombination. However, our data show that the NHEJ apparatus of C. albicans may control morphogenesis in this diploid organism. In addition, deletion of one or both copies of LIG4 resulted in attenuation of virulence in a murine model of candidiasis.

High-frequency oscillatory ventilation in pediatric respiratory failure: a multicenter experience

OBJECTIVE

The use of high-frequency oscillatory ventilation (HFOV) has increased dramatically in the management of respiratory failure in pediatric patients. We surveyed ten pediatric centers that frequently use high-frequency oscillation to describe current clinical practice and to examine factors related to improved outcomes.

DESIGN

Retrospective, observational questionnaire study.

SETTING

Ten tertiary care pediatric intensive care units.

PATIENTS

Two hundred ninety patients managed with HFOV between January 1997 and June 1998.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were classified according to presence or absence of preexisting lung disease, symptomatic respiratory syncytial virus infection, or presence of cyanotic heart disease or residual right-to-left intracardiac shunt. In addition, patients for whom HFOV acutely failed were analyzed separately. Those patients with preexisting lung disease were significantly smaller, had a significantly higher incidence of pulmonary infection as the triggering etiology, and had a significantly greater duration of conventional ventilation before institution of HFOV compared with patients without preexisting lung disease. Stepwise logistic regression was used to predict mortality and the occurrence of chronic lung disease in survivors. In patients without preexisting lung disease, the model predicted a 70% probability of death when the oxygenation index (OI) after 24 hrs was 28 in the immunocompromised patients and 64 in the patients without immunocompromise. In the immunocompromised patients, the model predicted a 90% probability of death when the OI after 24 hrs was 58. In survivors without preexisting lung disease, the model predicted a 70% probability of developing chronic lung disease when the OI at 24 hrs was 31 in the patients with sepsis syndrome and 50 in the patients without sepsis syndrome. In the patients with sepsis syndrome, the model predicted a 90% probability of developing chronic lung disease when the OI at 24 hrs was 45.

CONCLUSIONS

Given the number of centers involved and the size of the database, we feel that our results broadly reflect current practice in the use of HFOV in pediatric patients. These results may help in deciding which patients are most likely to benefit from aggressive intervention by using extracorporeal techniques and may help identify high-risk populations appropriate for prospective study of innovative modes of supporting gas exchange (e.g., partial liquid breathing or intratracheal pulmonary ventilation).

In vivo therapy of malignant melanoma by means of antagonists of alphav integrins

Integrin alphavbeta3 (vitronectin receptor) has been implicated in human malignant melanoma progression and angiogenesis as a receptor that provides survival signals. However, little is known about the therapeutic potential of antagonists of alphavbeta3. In this report, we characterize the activities of 2 antagonists of alphavbeta3 integrins: a human specific monoclonal antibody (MAb), 17E6, and a cyclic RGD peptide that blocked cell adhesion and induced detachment of previously substrate-attached cells in vitro. In vivo, alphavbeta3 antagonists behaved as anti-tumor drugs in a dose- and time-dependent manner. Moreover, different therapeutic treatments proved to be effective even in the therapy of established macroscopic tumor masses, thus supporting the use of these antagonists in clinical therapy. Using a panel of 6 human melanomas and 5 carcinomas, MAb 17E6 efficiently blocked the in vivo tumor growth of melanomas expressing alphavbeta3 as xenografts but did not affect the alphavbeta3-negative (although alphav integrin-positive) tumors. This demonstrated that alphavbeta3 is a pivotal integrin for the growth of human melanomas. Furthermore, since MAb 17E6 does not recognize murine alphavbeta3, the effect is due only to the direct anti-tumor activity and not to the well-known anti-angiogenic activity of alphav-integrin antagonists. Taken together, our results confirm the essential role of alphavbeta3 integrin in the growth of human malignant melanoma in vivo and provide strong evidence of the therapeutic potential of alphav-integrin antagonists for the treatment of such tumors.

Histamine alters endothelial barrier function at cell-cell and cell-matrix sites

To determine how histamine regulates endothelial barrier function through an integrative cytoskeletal network, we mathematically modeled the resistance across an endothelial cell-covered electrode as a function of cell-cell, cell-matrix, and transcellular resistances. Based on this approach, histamine initiated a rapid decrease in transendothelial resistance predominantly through decreases in cell-cell resistance in confluent cultured human umbilical vein endothelial cells (HUVECs). Restoration of resistance was characterized by initially increasing cell-matrix resistance, with later increases in cell-cell resistance. Thus histamine disrupts barrier function by specifically disrupting cell-cell adhesion and restores barrier function in part through direct effects on cell-matrix adhesion. To validate the precision of our technique, histamine increased the resistance in subconfluent HUVECs in which there was no cell-cell contact. Exposure of confluent monolayers to an antibody against cadherin-5 caused a predominant decrease in cell-cell resistance, whereas the resistance was unaffected by the antibody to cadherin-5 in subconfluent cells. Furthermore, we observed an increase predominantly in cell-cell resistance in ECV304 cells that were transfected with a plasmid containing a glucocorticoid-inducible promoter controlling expression of E-cadherin. Transmission electron microscopy confirmed tens of nanometer displacements between adjacent cells at a time point in which histamine maximally decreased cell-cell resistance.

A head-on comparison of the in vitro antifungal activity of conventional and lipid-based amphotericin B: a multicenter study

A comparative study of conventional amphotericin B, Abelcet and AmBisome was performed using a microdilution format of the NCCLS M27-A methodology for susceptibility testing against 300 fungal isolates (152 yeasts, 148 filamentous fungi) in both RPMI-1640 and antibiotic medium #3 (AB3). The clinical isolates included Candida albicans (n=54), Candida glabrata (n=25), Candida parapsilosis (n=23), Candida krusei (n=19), Candida lusitaniae (n=14), Cryptococcus neoformans (n=5), Candida tropicalis (n=12), Aspergillus flavus (n=34), Aspergillus fumigatus (n=46) and 68 other filamentous fungi encompassing 22 different genera. The minimal inhibitory concentrations (MIC) for all drugs were defined as the lowest concentrations in which there was no visible growth. MICs were determined after 48 h for yeasts and 72 h for filamentous fungi. The mean MICs +/- standard error (microg/ml) for yeasts and filamentous fungi, respectively, were: Abelcet, 0.51+/-0.21, 4.34+/-0.61; AmBisome, 1.28+/-0.24, 5.68+/-0.57; amphotericin B, 0.29+/-0.11, 1.12+/-0.19, respectively. Overall, against both yeasts and filamentous fungi Abelcet proved to have more potent antifungal activity than AmBisome. Using AB3 as opposed to RPMI-1640 generally produced lower MIC values but did not have any effect on the order of relative activity with all of the antifungal agents tested. In conclusion, our data shows that Abelcet is more active than AmBisome against pathogenic yeast and filamentous fungi when assayed in AB3 in vitro. Comparison of the activities of these antifungals in experimental animal models is necessary to determine whether these in vitro findings are correlated with in vivo efficacy.

DCC and SMAD4 alterations in human colorectal and pancreatic tumor dissemination

Chromosome 18q is lost a high proportion of colorectal and pancreatic cancers. Three candidate tumor suppressor genes, DCC, Smad4 and Smad2 have been identified in this chromosome region. DCC and Smad4 aberrations have been previously identified in pancreatic and colorectal tumors. The aim of this study was to compare the presence of concurrent genetic aberrations in DCC and neighboring Smad4 and Smad2 genes during colorectal and pancreatic distal dissemination. We have used a panel of orthotopically implanted colorectal and pancreatic xenografts and corresponding metastases. We have shown that while LOH at DCC locus occurred at a similar frequency in both tumors, diminished DCC protein expression was exclusively present in colorectal tumors harboring intragenic DCC LOH. In contrast, in pancreatic xenografts loss of DCC protein and mRNA expression was restricted to metastases. Smad4 gene aberrations were detected at a similar frequency in both tumors and were selected for during distal dissemination. Acquisition of alterations in both genes occurred independently. Our results suggest that both DCC and Smad4 contribute to pancreatic and colorectal distal dissemination. However, the role of DCC may differ between both tumor types.

Histological characteristics of the intestinal mucosa of the rat during the first year of life

In spite of the widespread use of rats in gastrointestinal research, there is a lack of information on the qualitative and quantitative histological characteristics. Therefore, a study was performed in 69 male Wistar rats with ages ranging from one day to one year old. The features studied included: height and number of villi in the duodenum, jejunum and ileum, and depth and number of crypts in the duodenum, jejunum, ileum, colon and rectum. Morphometric observations were expressed in a mathematical logarithmic curve that showed a normal, pattern of intestinal growth for each intestinal level. The number of villi in the small intestine decreased from 1 to 35 days of age, whereas the other intestinal parameters all increased during the same period. After 35 days the rates of increase or decrease were lower. The quantification of these intestinal changes provides a new complementary pattern as a reference for research as indicators of normality or malfunction in the rat intestine.

Effects of voriconazole on Candida glabrata in vitro

The effects of voriconazole on the growth, morphology and lipids of Candida glabrata were studied. MIC data showed that voriconazole was up to 32- to 64-fold more active than fluconazole in its ability to inhibit various C. glabrata strains. Voriconazole inhibited the growth of C. glabrata in a dose-dependent fashion. Electron microscope examination showed that voriconazole treatment affected the external and internal morphology of C. glabrata. Treatment of C. glabrata with voriconazole inhibited ergosterol synthesis and led to accumulation of methylated sterols. In contrast, no significant difference in phospholipid composition was observed between treated and untreated cells.

Orthotopic models of human pancreatic cancer

Orthotopic transplantation of solid tumor fragments of human tumors in nude mice reproduces their pattern of local growth and distal dissemination. While lymphatic, hepatic or peritoneal dissemination can be reproduced, perineural invasion is absent. Early passages (less than 3) of xenografts show a high degree of stability regarding K-ras, p53 and p16 gene status. On the other hand, advanced passages of tumors acquire additional alterations in the p15 and Smad4 genes. Mutations in K-ras, p53, p15 and Smad4 genes can be acquired, in this model system, in the more advanced stages of pancreatic tumor dissemination. Finally, it is also possible to standardize local growth of these tumors as well as its dissemination pattern giving us a preclinical tool to evaluate the anticancer activity of new drugs.

p53 and K-ras gene mutations correlate with tumor aggressiveness but are not of routine prognostic value in colorectal cancer

PURPOSE

p53 gene and K-ras mutations are among the most common genetic alterations present in colorectal cancer. The prognostic utility of such mutations remains controversial. The purpose of this study was to prospectively evaluate the prognostic significance of p53 and K-ras gene mutations in colorectal cancer.

PATIENTS AND METHODS

One hundred forty patients were analyzed. Tumors belonging to the microsatellite mutator phenotype were excluded (n = 8). Mutations at the K-ras and p53 genes were detected and characterized by restriction fragment length polymorphism, single-strand conformation polymorphism, and sequencing, as appropriate.

RESULTS

p53 mutations were detected in 66 (50%) and K-ras mutations were detected in 54 (41%) of the 132 patients. In 26 cases (20%), ras and p53 mutations coexisted; in 38 cases (29%), neither mutation was found. Multivariate analysis of the whole population analyzed (n = 132) showed that survival was strongly correlated with the presence of p53 mutations alone or in combination with K-ras mutations (P = .002; log-rank test). When only patients undergoing a radical resection were considered (R0; n = 101), p53 mutations were no longer of prognostic significance.

CONCLUSION

p53 mutations alone or in combination with K-ras mutations are correlated with a worse outcome. However, the routine use of these mutations as prognostic markers in the clinical setting is not recommended.

Congenital diaphragmatic hernia: mortality determinants in a Hispanic population

OBJECTIVES

Determine which factors were associated with mortality in our patients, specifically whether ventilatory parameters and arterial blood gas could be used to predict outcome. The role of delaying surgery and the presence of contra lateral pneumothorax were also assessed.

BACKGROUND

Mortality among babies born with congenital diaphragmatic hernia remains high. The associated pulmonary hypoplasia and hypertension account for most of the overall mortality. There is no uniform consensus as to which parameters predict outcome.

METHOD

Study population consisted of thirty-two patients with CDH managed during a ten-year period. Retrospective data obtained included: perinatal data, postnatal complications, ventilatory parameter data, arterial blood gas, type and age of surgery. Ventilatory index, oxygenation index and arterial to alveolar oxygen difference (A-aDO2) within the first 24 hours of life and after surgical correction were compared among the 23 patients who underwent surgical correction. Timing of surgery and frequency of pneumothorax were compared between survivors and non-survivors. Epi-Info Software Package was used for statistic analysis.

RESULTS

Overall survival was 40%. Survival of surgically corrected infants was 61%. Non-survivors had significantly higher A-aDO2 than survivors (p < 0.05). No significant differences in pCO2, ventilatory index, or oxygenation index were identified between survivors and non survivors. Surgical repair performed after the first twenty-four hours of life, was associated with a higher survival rate (p < 0.05). Fourteen patients (39%) developed contralateral pneumothorax, eleven (79%) of these died.

CONCLUSIONS

(1) contralateral pneumothorax was associated with higher mortality, 2) A-aDO2 was a better prognostic indicator than pCO2, ventilatory index, or oxygenation index, 3) delaying surgical repair was associated with better survival rate.

Disruption of the antiproliferative TGF-beta signaling pathways in human pancreatic cancer cells

Resistance to TGF-beta1 occurred in pancreatic cancer cells suggesting that inactivation of TGF-beta inhibitory signaling pathways may play an important role in human pancreatic cancer. The aim of our study was to determine the presence of alterations in the main putative components of the TGF-beta inhibitory signaling pathways (p15, Smad4, Smad2, TGFbeta-RII, CDC25A). A panel of human carcinomas of the exocrine pancreas orthotopically implanted and perpetuated in nude mice and pancreatic cancer cell lines were studied. p15 gene alterations, mainly homozygous deletions that involved exons 1 and/or 2, were found in the 62.5% (5 of 8) of pancreatic xenografts whereas Smad4 gene aberrations were found in one of eight xenografts and in two of seven cell lines. Additional aberrations in these genes were acquired during in vivo perpetuation and distal dissemination. Paradoxically, TGFbeta-RII overexpression and a decrease in CDC25A protein levels were found in all tumors and cell lines. In one cell line, resistance to TGF-beta1 occurred in the absence of alterations in the genes analysed so far. We conclude that all human pancreatic tumor cells analysed herein have non-functional TGF-beta pathways. The majority of cells harbor alterations in at least one of the putative components of TGF-beta pathways, mainly in p15 and Smad4 genes. These results suggest that inactivation of TGF-beta signaling pathways plays an important role in human pancreatic tumorigenesis.

Pharmacokinetics of Catecholamines During Hemofiltration in Pediatric Patients

BACKGROUND: Continuous hemofiltration is used in pediatric patients with acute renal failure. Many of these patients are treated with catecholamines for hemodynamic instability. The authors studied the pharmacokinetics of dopamine and dobutamine on patients undergoing continuous venovenous hemofiltration. METHODS AND RESULTS: Three critically ill pediatric patients with acute renal failure and cardiovascular instability treated with hemofiltration and intravenous infusion of dopamine and/or dobutamine were entered into the study. Blood samples were drawn at steady-state levels from the arterial port (inflow) of the hemofilter, from the venous port (outflow) of the hemofilter, and from the ultrafilter. Sixteen (n = 16) pharmacokinetic measurements were made, six (n = 6) for dopamine and 10 (n = 10) for dobutamine. The clearance of dopamine by the hemofilter was 0.078 +/- 0.011 mL/kg/min, and for dobutamine it was 0.036 +/- 0.008 mL/kg/min. On the average, 0.56% of the dopamine dose and 0.13% of the dobutamine dose was removed by the hemofilter. CONCLUSIONS: The pharmacokinetics of dopamine and dobutamine at the dosage range of 5-25 µg/kg/min are not altered by continuous hemofiltration. Relative to total plasma clearance, negligible amounts of the drug were removed. The dosage of these catecholamines need not be adjusted during continuous hemofiltration.

Isometric tension of cultured endothelial cells: new technical aspects

In this paper new technical aspects are discussed in the measurement of the low amount of force typically expressed in cultured endothelial cells. We illustrate how potential background noises interfere with signal acquisition. We present a new generation prototype that measures isometric tension in vitro in multiple samples and in more than on isometric vector. We report that thrombin increases isometric tension in at least two separate vectors that are directed in opposite directions. We also report that phorbol ester dibutyrate can randomly mediate a false relaxation (anisotropic contraction) in cultured PPAEC, when the force vector is directed opposite to the referenced isometric vector of the transducer. In contrast, stimulation of cultured HUVEC with the cAMP agonists, theophylline and forskolin, decreased isometric force in both vectors. Thus direction of the force vector needs to be considered when interpreting isometric tension in cultured endothelial cells.

Effect of prenatal T4 treatment in neonatal morbidity: preliminary findings

We report our experience with the use of intra-amniotic thyroxine to accelerate fetal maturation in preterm delivered infants. One hundred and fourteen infants who had received 500 micrograms of thyroxine weekly prenatally until an L/S ratio greater or equal to 2.0 was achieved, were compared to 113 premature infants who had not been given thyroxine or steroids prenatally. After stratification by weight, the relative incidence of respiratory distress syndrome (RDS), patent ductus arteriosus (PDA), necrotizing enterocolitis (NEC) and intraventricular hemorrhage (IVH) were compared. A decrease in the incidence of RDS was observed in the infants with birth weight between 1000 and 1500 g who had received more than one dose of intra-amniotic thyroxine. No difference in the incidence of RDS was observed in infants with birth weight of less than 1000 g or over 1500 g. One dose of thyroxine had no effect in decreasing the incidence of RDS, PDA, NEC, and IVH in any of the groups. We conclude intra-amniotic thyroxine seems to decreases the incidence of RDS in very low birth weight infants.

Orthotopic xenografts of human pancreatic carcinomas acquire genetic aberrations during dissemination in nude mice

Orthotopic transplantation of human tumors in nude mice reproduces the pattern of local growth and distal dissemination. The aim of our study was to determine the pattern of genetic alterations in human carcinomas of the exocrine pancreas orthotopically implanted and perpetuated in nude mice. Eight of the sixteen orthoimplanted human pancreatic carcinomas were perpetuated through several passages. Four perpetuated tumors followed distinct patterns of distal dissemination. Point mutations in the K-ras gene, genetic aberrations in the p53 and p16 genes, and allelic losses at retinoblastoma, adenomatous polyposis coli, and deleted in colorectal cancer loci were analyzed. Perpetuated tumors maintained the pattern of genetic alterations present in primary tumors. Five perpetuated tumors contained K-ras mutations, and all tumors contained p53 and/or p16 genetic aberrations. Allelic losses were present in four of the perpetuated tumors. Additional genetic alterations were detected in 6 of 35 metastases analyzed. Five of 9 peritoneal metastases or malignant ascitic cells acquired either K-ras or second p53 mutations. In contrast, only 1 of 25 liver metastases and none of the lymph node metastases acquired additional mutations. No additional p16 gene aberrations or other allelic losses were evidenced during tumor dissemination. We conclude that orthotopically implanted pancreatic carcinomas xenografted in nude mice show a high degree of genetic stability. Mutations in K-ras and p53 genes can occur in this model system in the more advanced stages of pancreatic tumor progression, mainly during peritoneal dissemination.

Earth-Based Observations of the Galileo Probe Entry Site

Earth-based observations of Jupiter indicate that the Galileo probe probably entered Jupiter's atmosphere just inside a region that has less cloud cover and drier conditions than more than 99 percent of the rest of the planet. The visual appearance of the clouds at the site was generally dark at longer wavelengths. The tropospheric and stratospheric temperature fields have a strong longitudinal wave structure that is expected to manifest itself in the vertical temperature profile.

Morphogenesis of the epithelial cell transporting phenotype: synthesis and distribution of ion channels

The exchange of substances between higher organisms and the environment takes place across epithelia consisting of one or more cell layers. To perform this function, epithelial cells have two basic differentiated properties: 1) they form tight junctions (TJs) that seal the extracellular space, and 2) they are polarized into an apical and a basolateral domain, with entirely different structural, biochemical and physiological properties. Our understanding of the mechanisms involved in the expression of these properties has been greatly enhanced by the availability of epithelial cell lines that form TJs and polarize in vitro under conditions suitable for experimental control. In this article we summarize our studies on the synthesis and polarized expression of ion channels in epithelial cells. MDCK cells have four types of K+ channels in the apical domain, and a fifth one in the basolateral domain. The basolateral side also has a population of CI- channels. Each type of channel is absolutely polarized. Harvesting with trypsin-EDTA reduces the area of the plasma membrane by 50% and the channel population by 90%. Upon plating, these channels are recovered within a few hours. We describe here the main extracellular and intracellular mechanisms involved in these phenomena.

Diagnostic utility of K-ras mutations in fine-needle aspirates of pancreatic masses

BACKGROUND & AIMS

Mutations at codon 12 of the K-ras gene are present in 65%-100% of carcinomas of human exocrine pancreas and could be used as a potential tumor marker at the tissue level. The purpose of this study was to assess, in large series of patients, the utility of K-ras mutation analysis to evaluate fine-needle aspirates of pancreatic masses.

METHODS

One hundred fifteen fine-needle aspirates obtained from 93 patients were evaluated retrospectively. Cytological analysis was based on the review of cell blocks. Mutations were detected by using artificial restriction fragment length polymorphisms using the Hphl and BstNl approaches.

RESULTS

The sensitivity and specificity of cell block cytology was 64% and 100%, respectively, for the diagnosis of pancreatic carcinoma. K-ras mutations were detected in 41 pancreatic carcinomas (sensitivity, 59%) and in one mucinous cystic tumor; specificity of ras analysis alone was 100%. The sensitivity of cytology combined with K-ras mutations were 77.6% and 100%, respectively.

CONCLUSIONS

The detection of K-ras mutations would have suggested the diagnosis of pancreatic cancer in 14 cases otherwise not detected by cytology alone. K-ras mutation analysis should be restricted to cell blocks containing suspicious, normal-appearing duct cells, or insufficient material in the cytological examination.

Hypoxia attenuates metabolism of platelet activating factor by fetal and newborn lamb lungs

The metabolism of platelet activating factor (PAF) by lungs of near-term fetal and 5- to 9-day-old lambs was studied during normoxia and hypoxia at 37 degrees C in 30 mM Tris buffer. PAF synthesis was studied in lung cytosol and membrane using 250 microM [3H]acetyl CoA, 40 microM lyso-PAF, and 50 micrograms protein. PAF catabolism was studied in lung homogenate (LH) using 50 microM [3H]alkyl-PAF. PAF was extracted and assayed by thin-layer chromatography (TLC) and liquid scintillation spectrometry. Levels of PAF synthesized (nmol/min per mg protein) by fetal lung membrane versus cytosol were 1.35 +/- 0.07 versus 0.61 +/- 0.08, which were greater than those by newborn which were 0.33 +/- 0.07 versus 0.17 +/- 0.03. Hypoxia did not alter PAF synthesis by the lungs. PAF catabolism (nmol lyso-PAF/min per mg protein) by fetal LH was 0.07 +/- 0.01, which increased to 0.24 +/- 0.02 during normoxia. In newborn LH, the rate was 0.24 +/- 0.04 and increased to 0.33 +/- 0.01 during normoxia. PAF catabolism was higher in newborn than in fetal LH. An increase in pO2 augmented PAF catabolism, more in fetal than in newborn LH. Thus rate of PAF synthesis decreases from fetus to newborn, but PAF catabolism increases from fetus to newborn. The higher rate of PAF synthesis coupled with a low rate of PAF catabolism in the hypoxic environment of fetal lungs may predispose the fetus to a high PAF level, which may contribute to the high basal vasomotor tone in fetal lungs. A fall in PAF level with oxygenation, due to increased PAF catabolism, may facilitate the normal fall in pulmonary vascular resistance at birth.

Benzodiazepine-insensitive mice generated by targeted disruption of the gamma 2 subunit gene of gamma-aminobutyric acid type A receptors

Vigilance, anxiety, epileptic activity, and muscle tone can be modulated by drugs acting at the benzodiazepine (BZ) site of gamma-aminobutyric acid type A (GABAA) receptors. In vivo, BZ sites are potential targets for endogenous ligands regulating the corresponding central nervous system states. To assess the physiological relevance of BZ sites, mice were generated containing GABAA receptors devoid of BZ sites. Following targeted disruption of the gamma 2 subunit gene, 94% of the BZ sites were absent in brain of neonatal mice, while the number of GABA sites was only slightly reduced. Except for the gamma 2 subunit, the level of expression and the regional and cellular distribution of the major GABAA receptor subunits were unaltered. The single channel main conductance level and the Hill coefficient were reduced to values consistent with recombinant GABAA receptors composed of alpha and beta subunits. The GABA response was potentiated by pentobarbital but not by flunitrazepam. Diazepam was inactive behaviorally. Thus, the gamma 2 subunit is dispensable for the assembly of functional GABAA receptors but is required for normal channel conductance and the formation of BZ sites in vivo. BZ sites are not essential for embryonic development, as suggested by the normal body weight and histology of newborn mice. Postnatally, however, the reduced GABAA receptor function is associated with retarded growth, sensorimotor dysfunction, and drastically reduced life-span. The lack of postnatal GABAA receptor regulation by endogenous ligands of BZ sites might contribute to this phenotype.

Characterization of adhesion plates induced by the interaction of Entamoeba histolytica trophozoites with fibronectin

Entamoeba histolytica trophozoites are pleiomorphic and highly motile cells. Although scarce fibrous material can be identified in the cytoplasm as elements of an organized cytoskeleton, clearly defined actin-containing structures are formed at the site of cell-matrix contact upon the interaction of trophozoites with fibronectin (FN) and other cellular matrix substrates. The structures are reminiscent of the adhesion plaques or focal contacts found in higher eukaryotic cells, where actin filament bundles insert into specialized regions of the plasma membrane and function as signal transduction organelles. Thus, the formation of adhesion plates in this parasitic ameba could be related to the specific signaling responses involved in its invasive behavior. Here, we report the isolation of amebic adhesion plates and the results of their structural and molecular analyses. Filaments, with the characteristic diameter of F-actin, radiating from an electron-dense matrix, are the main feature. Actin is one of the main protein components of the plate; other proteins identified are a FN-binding protein--previously reported as a "putative" FN receptor--the actin-binding proteins myosin II, myosin I, alpha-actinin, vinculin, and tropomyosin. The presence of the isolated plates of several proteases and protein kinases, in particular pp125FAK, is also demonstrated. our results suggest that adhesion plates in amebas are dynamic membrane-cytoskeletal complexes participating not only in the attachment to FN substrates but also providing the structural basis for their involvement in parasite locomotion and invasiveness.

Predictive factors in the genesis of intraventricular hemorrhage in premature infants

Intraventricular hemorrhage of the newborn (IVH) is a common complication of prematurity, especially of those infants with birth weights of less than 1500 grams. It may be associated with neurodevelopmental impairment and even death. We did a retrospective study of infants born with birth weights of less than 1500 grams during the period of January 1989 to January 1990 who had head sonograms done during the newborn period. A total of 37 patients were identified. The purpose of the study was to identify risk factors associated to IVH. Risk factors considered were those related to pregnancy and delivery complications and perinatal and postnatal events. Patients were classified according to type of IVH into mild and severe. The overall incidence of IVH was 43% (16/37). The incidence of severe IVH was 30%. Pregnancy and delivery complications were not related to the development of IVH. None of the perinatal factors were associated with IVH. Of the neonatal factors, hypertension per se was not associated with severe IVH, but the fluctuations in mean blood pressure (MAP) during the first 72 hours of life were significantly different in infants with mild IVH as compared to infant with severe IVH, 25mmHg and 40mmHg respectively.

Bedside management of lung collapse in children on mechanical ventilation: saline lavage--simulated cough technique proves simple, effective

We report a simple, four-step procedure for bedside treatment of infants on mechanical ventilation who have various degree of lung collapse unresponsive to conventional instillation of saline followed by chest percussion with endotracheal suctioning. The technique involves hyperoxygenation by bagging with 100% oxygen, deep endotracheal instillation of 0.25-0.5 mL/kg sterile saline, bagging with momentary inspiratory hold, followed by release of the hold and simultaneous forced exhalation and vibration to simulate cough, and endotracheal suctioning. This procedure was repeated three to five times on the affected side and at least once on the unaffected side; it resulted in notably improved lung expansion in 48 of 57 infants, documented by chest radiographs. The 57 infants included 48 (84%) whose chest radiographs showed airways occluded by mucus ("no air bronchograms") and 7 (16%) whose chest radiographs showed patent airways ("air bronchograms"). The technique is less successful in the latter group of patients in whom material obstructing proximal and intermediate airways has already been removed or displaced to distal airways, or a parenchymal infection has developed.

Prepyloric antrectomy, truncal vagotomy, and front pylorotomy for the treatment of duodenal ulcer

We have performed a suprapyloric antrectomy with anterior pylorotomy and truncal vagotomy in 106 patients with chronic duodenal ulcer between 1975 and 1990. Follow-up was carried out in 94 patients, during a mean time of 6 years. We have had no postoperative mortality and no long-term recurrence. The percentage of Visick I patients is similar to that after truncal vagotomy and antrectomy. We, therefore, believe that this procedure is safe and can be performed when an antrectomy is mandatory to avoid the operative morbidity and mortality of classic antrectomy.

Ultrasound characteristics of renal cryosurgery

The ability to visualize renal cryosurgery using ultrasound was tested in an animal model. Five dogs underwent open laparotomy and ultrasound-monitored cryosurgery of both kidneys. On each kidney two cryolesions were made. The borders of the frozen region were identified on ultrasound as a hyperechoic rim created by the interface between frozen and unfrozen tissue. The thawed cryolesion appeared hyperechoic compared with the unfrozen kidney. Excellent correlation between the ultrasound and autopsy measurements of the cryolesions was obtained. Knowing this, renal cryosurgery under ultrasound monitoring may be possible.

Isotypic and IgG subclass restriction of the humoral immune responses to human T-lymphotropic virus type-I

We have investigated the isotypic and IgG subclass profile of the antibody response to HTLV-I structural proteins (gag and env) in patients with HTLV-I-associated myelopathy (HAM; n = 20), adult T-cell leukemia (ATL; n = 15), and HTLV-I-positive asymptomatic carriers (ASY; n = 21). IgG, IgM, and IgA were the predominant antibody responses in all HTLV-I-infected individuals; minimal IgE response was detectable in the HAM and ATL groups. Among the IgG subclasses, IgG1 was the most predominant antibody detected in responses to HTLV-I antigens, followed by IgG3 and IgG2; IgG4 could not be detected in any patient group. Levels of both IgG1 and IgG3 were significantly higher in patients with HAM, when compared to ATL and ASY (P < 0.01 for both comparisons). In addition, Ig isotypes and IgG subclass antibody in patient sera reactive with purified viral proteins and several immunodominant epitopes, represented by synthetic peptides, Gag-1a102-117, Env-1(191-214), Env-5(242-257), and recombinant proteins, MTA-1(162-209) and r21e303-440, were examined to delineate specific epitopes responsible for inducing the host immune responses of each isotype and subclass to the structural proteins of HTLV-I. IgG, IgM, and IgA responses were directed against both the gag and env gene products. Among IgG subclasses, the IgG1 and IgG3 responses were directed against both the gag (p53, p24, p19, and Gag-1a) and env (recombinant MTA-1, r21e, and synthetic Env-1, Env-5) proteins; IgG2 responses were mainly restricted to gag proteins. The frequency profile of HTLV-I-specific antigen recognition in all four IgG subclasses were similar in all of the clinical groups. These results further define the fine specificity of anti-HTLV-I immune reaction for understanding the mechanism of pathogenesis in these individuals and suggest that factors other than the humoral immune responses may be associated with the clinical manifestation of the disease.