In Vivo Confocal Microscopy of Keratic Precipitates

OBJECTIVE

To evaluate the heterogeneity of keratic precipitates (KP) in varying subtypes of uveitis by in vivo confocal microscopy (IVCM).

METHODS

The KP were viewed with a scanning confocal microscope in patients (n = 33) who sought care at a tertiary referral uveitis service for immune-mediated and infectious forms of uveitis, including HLA-B27-associated uveitis, sarcoidosis, Vogt-Koyanagi-Harada syndrome, juvenile chronic arthritis, Fuchs heterochromic iridocyclitis, cytomegalovirus retinitis, herpes zoster ophthalmicus, ocular toxoplasmosis, and idiopathic uveitis. Images were captured and digitalized in real time.

RESULTS

Forty-two eyes of 33 patients were examined in this study. Patient age ranged from 22 to 84 years, with a mean age of 49.4 years. Seventeen (52%) of the patients were women, and 16 patients (48%) were men. The KP ranged in diameter from 10 to 350 mum. We observed the following absolute and speculative outcomes: KP are markedly heterogeneous and variable as documented by IVCM; KP in individual patients are consistent throughout the cornea; the morphologic features of KP change across time; infectious vs noninfectious causes of uveitis seem to be readily distinguishable by using IVCM; and KP may have consistency for specific disease states and therefore may have diagnostic importance.

CONCLUSIONS

To our knowledge, this is the first time that IVCM has been used to describe the architecture and heterogeneity of KP in uveitis. Such observations reveal a heterogeneity that could not be appreciated by conventional slitlamp microscopy and may have diagnostic relevance.

HLA-B27-associated uveitis: overview and current perspectives

PURPOSE OF REVIEW

To review current knowledge about the pathogenesis, clinical presentation, and treatment of HLA-B27-associated uveitis, which is the most commonly identified cause of uveitis in community-based practice and an important cause of ocular morbidity.

RECENT FINDINGS

Significant advances have been made in understanding the pathogenesis of HLA-B27-associated ocular and systemic disease, especially with regard to the genetic underpinning of these diseases. Increasing attention has also been focused on the use of alternative therapies in the treatment of HLA-B27-associated uveitis, with special attention to sulfa class antibiotics, historically have been used to treat the articular manifestations of the spondyloarthritides, and newer drugs that inhibit tumor necrosis factor-alpha.

SUMMARY

The next several years promise to yield exciting new advances in understanding of the genetic epidemiology and treatment of HLA-B27-associated uveitis.

Genetics of uveitis

Uveitis phenotypes can differ substantially, and most uveitis diseases are considered polygenic with complex inheritance patterns. When considering the genetics of these diseases, common threads can be identified. For example, in virtually every polygenic disease studied, there exists an HLA genetic association. This association can be strong, such as the associations of HLA-B27 with AAU and HLA-A29 with BSCR; or it can be more subtle, involving several HLA genes or a combination of HLA genes that compose specific haplotypes. In many of these conditions, it is hypothesized that genes other than classic MHC genes but located at the MHC locus may be important susceptibility genes. Genome-wide scans and other genetic methods are becoming increasingly successful in identifying genetic loci and candidate genes in many inflammatory disorders that have an uveitic component. It will be important to test these findings as uveitis-specific genetic factors. Therefore, the burgeoning understanding of the human genome promises to result in new insight into the pathogenesis of uveitis.

Genetic studies in familial ankylosing spondylitis susceptibility

OBJECTIVE

To define the genetic basis of susceptibility to ankylosing spondylitis (AS), especially non-major histocompatibility complex (MHC) genes.

METHODS

The study group comprised 244 affected sibling pairs from 180 pedigrees of primarily European ancestry. Sibling pairs were concordant for AS by the modified New York criteria and had available sacroiliac radiographs. The subjects were genotyped for 400 markers in ABI PRISM linkage map MD-10 and for 17 additional markers on chromosomes 6p, 6q, and 11q (including HLA-B, DRB1, DQA1, DQB1, and DPB1 alleles). Two-point and multipoint nonparametric linkage (NPL) analyses were conducted using the NPL statistic and 1-parameter allele-sharing model logarithm of odds (LOD) scores, calculated using the Allele-Sharing Model (ASM) computer program.

RESULTS

Linkage of the MHC region was supported by both 2-point and multipoint analyses, with the strongest peak (45.90 cM) in the MHC at the HLA-DRB1 locus (NPL score 8.720, ASM LOD score 20.49; P = 6.8 x 10(-20) for 2-point analysis). A second region was found to have positive linkage at the q arm of chromosome 6 (D6S441) in 2-point analysis; this was supported by a 39.13-cM region (135.58-174.71 cM) in multipoint analysis, with the smallest P value (4.2 x 10(-3)) at 166.39 cM. A third region was found on chromosome 11q, with the strongest evidence for linkage for D11S4094 at 123 cM (NPL score 2.235, ASM LOD score 1.939) and, on transmission disequilibrium test analysis, D11S4090 at 105.74 cM (P = 6.2 x 10(-5)). Linkage in this area was supported by multipoint analysis, spanning 22.19 cM continuously from 101.68 cM to 123.87 cM, with the strongest peak at 112.33 cM (P = 0.014); this was confirmed by subsequent fine mapping studies.

CONCLUSION

Thus, this genome-wide scan implicates, in addition to the MHC, regions outside the MHC in AS susceptibility, especially on chromosomes 6q and 11q.

Uveitis in patients with sarcoidosis is not associated with mutations in NOD2 (CARD15)

PURPOSE

Mutations in NOD2 are responsible for Blau syndrome, a systemic disease triad involving the uvea, joints, and skin. NOD2 mutations are also associated with Crohn disease. Both Blau syndrome and Crohn disease involve granulomatous inflammation and uveitis, as does sarcoidosis. We sought to determine if NOD2 mutations were present in patients with sarcoidosis, especially those with uveitis.

METHODS

NOD2 gene exons were sequenced from DNA obtained from sarcoidosis patients. The diagnoses of sarcoidosis and uveitis were verified from clinical records.

RESULTS

NOD2 polymorphisms were found in 26 patients with sarcoidosis (13 with uveitis). There was no significant difference in allele frequencies between patients with and without uveitis.

CONCLUSIONS

Despite the strikingly similar pathologies of Blau syndrome and sarcoidosis, no mutations were found to be associated with sarcoidosis in a group of patients, regardless of the presence of uveitis.

Analysis of the ARMD1 locus: evidence that a mutation in HEMICENTIN-1 is associated with age-related macular degeneration in a large family

Age-related macular degeneration (AMD) is a common cause of severe vision loss. Identification of the genes involved in AMD will lead to a better understanding of this disease at the molecular level, which will eventually lead to early detection, prevention and treatment. Previously, we mapped the ARMD1 gene to 1q25-31 in a large family with AMD. Here, we narrow the ARMD1 locus to 14.9 Mb between LAMB2 and D1S3469, a region containing 50 known genes. Twenty candidate genes within this region were screened for mutations. Only one DNA variation, an A16,263G transition in exon 104 of HEMICENTIN-1, was found to segregate exclusively with the disease haplotype in members of this large family with AMD. This variation produces a non-conservative substitution of arginine for glutamine at amino acid position 5345 (Gln5345Arg). It was also identified in 11 other individuals, all of whom share a haplotype, which envelops HEMICENTIN-1, with the large AMD family. The affected status of all but one of those individuals conforms to the age-dependent penetrance observed in AMD. The amino acid at position 5345 of HEMICENTIN-1 was conserved as glutamine in eight species analyzed. RT-PCR analysis demonstrated that exon 104 of HEMICENTIN-1 is alternatively spliced in various cell types. Exclusive segregation of Gln5345Arg with the disease haplotype in this large family, amino acid conservation of glutamine at this position among mammals, the non-conservative nature of the substitution and similarities to EFEMP1 support the conclusion that HEMICENTIN-1 is the ARMD1 gene.

With a mere nod, uveitis enters a new era

PURPOSE

To advance the knowledge of the ophthalmologist with regard to new developments in the genetics and pathologic mechanisms of uveitis.

DESIGN

A review of recently published literature exploring the relationship between the nucleotide oligomerization domain (NOD2) gene and uveitis.

RESULTS

Mutations in the nucleotide-binding region of NOD2 were found to be responsible for familial juvenile systemic granulomatosis (Blau syndrome or Jabs disease), a rare form of uveitis, arthritis, and dermatitis. The NOD2 gene is thought to be involved in the innate immune response to pathogens. Currently, the pathologic mechanisms behind Blau syndrome in familial juvenile systemic granulomatosis are unknown, but the interactions of NOD2 with caspases, nuclear factor kappaB, and other pathways are slowly being revealed.

CONCLUSIONS

A single amino acid change in NOD2 can lead to a chronic granulomatous uveitis. By studying NOD2 and the proteins that interact with NOD2, we should gain a better understanding of the pathogenic mechanisms of uveitis and identify novel ways to halt its destructive consequences.

Cloning, sequencing and expression analysis of the mouse NOD2/CARD15 gene

BACKGROUND

Mutations in the human NOD2/CARD15 gene have been associated with Crohn's disease and Blau syndrome. The objective of the present study was to clone the murine form of NOD2 and characterize its tissue distribution, function and response to inflammatory stimuli.

METHODS

Murine NOD2 was isolated using anchored polymerize chain reaction (PCR). Sequence analysis confirmed the identification of full-length cDNA representing the murine NOD2 gene. Using this sequence to search a Mus musculus supercontig database, NOD2 genomic DNA was identified. NOD2 was transfected into human embryonic kidney (HEK) cells and nuclear factor kappa B (NF-kappaB) activation was measured using a reporter assay. Tissue distribution and changes in transcription in mouse monocytes in response to inflammatory stimuli was determined by real time PCR.

RESULTS

The NOD2 gene spans 39 KB and contains 12 coding exons on chromosome 8. Expression of mouse NOD2 into HEK cells resulted in NF-kappaB activation. NOD2 was found to be expressed in all mouse tissues analyzed except skin, with highest levels in lung, thymus and spleen. NOD2 mRNA levels increased greater than two-fold in a monocyte cell line in response to lipopolysaccharide, lipoteichoic acid, interferon-g and tumor necrosis factor-alpha.

CONCLUSIONS

Common structural and functional features between human and mouse NOD2 were identified. This should allow for development of relevant animal models to evaluate the role of NOD2 in chronic inflammatory disorders.

Immunohistology of antigen-presenting cells in vivo: a novel method for serial observation of fluorescently labeled cells

PURPOSE

Dendritic cells and macrophages are phagocytic antigen-presenting cells that bridge the innate and acquired immune systems. The coexistence of subtypes of dendritic cells and macrophages with overlapping properties complicates resolution of their precise roles in an immune response within a given tissue. This report documents a method to identify and observe these cells over time in a living animal and thereby to visualize them during a dynamic immune response.

METHODS

To label potential antigen-presenting cells, fluorescently tagged ovalbumin was injected into the anterior chambers of mouse eyes. Fluorescently tagged antibodies to cell surface proteins were injected to label specific cell types. Intravital fluorescence microscopy with digital image recording was used to visualize the labeled cells in the irises at various times after the injection.

RESULTS

The pattern and density (116-148 cells/mm(2)) of cells labeled in vivo by fluorescent ovalbumin or F4/80 antibodies were similar to that identified by conventional wholemount immunostaining for macrophages and dendritic cells. Fluorescent antibodies specific for CD11b, CD11c, CD80, CD86, or major histocompatibility complex (MHC) class II protein each labeled selective populations of cells in vivo. In contrast to conventional histology, in vivo immunohistology permitted serial observations. The phenotype of cells labeled by fluorescent ovalbumin was not the same at 6 (95% CD11c(+)) and 24 hours (24% CD11c(+)) after injection.

CONCLUSIONS

This method of in vivo immunohistology provides a tool for studying cell kinetics and dynamic interactions that cannot be assessed by conventional immunohistology. Furthermore, it avoids potential artifacts from tissue fixation and may work with antibodies that label cells poorly in vitro.

Restoration of Ig secretion: mutation of germline-encoded residues in T15L chains leads to secretion of free light chains and assembled antibody complexes bearing secretion-impaired heavy chains

We previously described T15H chain mutants that were impaired in assembly with L chain and in ability to be secreted from the cell. The unmutated T15L chain is unusual in that it is secretion-impaired in the absence of assembly with H chain. The T15L chain preferentially pairs with T15H in vivo, suggesting that if we introduced mutations that would allow secretion of free T15L chain, they might also lead to the secretion of the complex with the defective H chain. We mutated four positions in the germline T15L that had amino acids infrequently found in other kappa-chains. Mutation to the most frequently occurring amino acid at three of the four positions allowed secretion of free L chain, while the combination of two secretion-restoring mutations was synergistic. Coexpression of secretion-restored mutant L chains with the secretion-defective mutant H chains rescued secretion of the assembled H(2)L(2) complex, suggesting that during somatic hypermutation in vivo, deleterious mutations at the H chain may be compensated by mutations on the L chain. To our knowledge, this is the first example of mutations in IgL chains that are able to restore secretion-defective H chains to secretion competence in mammalian cells.

Strong associations between specific HLA-DQ and HLA-DR alleles and the tubulointerstitial nephritis and uveitis syndrome

PURPOSE

To identify genetic markers for the tubulointerstitial nephritis and uveitis (TINU) syndrome by using human leukocyte antigen (HLA) genotyping.

METHODS

Eighteen patients who had TINU syndrome were evaluated at three institutions. Typing of class I and II genes was performed by using DNA-based techniques.

RESULTS

Significant associations were found with HLA-B14 (6/18 patients, 33.3%; control subjects, 5.5%; P = 0.0003; relative risk [RR] = 8.5), HLA-DQA1*01 (17/18 patients, 94.4%; control subjects, 46.6%, P = 0.0001; RR = 19.5), HLA-DQA1*0101 (14/18 patients, 77.8%; control subjects 22.2%; P < 0.0001; RR = 12.2), HLA-DQB1*05 (14/18 patients, 77.8%; control subjects 17.7%; P < 0.0001; RR = 16.3), HLA-DQB1*0501 (13/18 patients, 72.2%; control subjects 12.9%; P < 0.0001; RR = 17.6), HLA-DRB1*01 (14/18 patients, 77.8%; control subjects, 12.1%; P < 0.0001; RR = 25.5), and HLA-DRB1*0102 (13/18 patients, 72.2%; control subjects, 1.6%; P < 0.0001, RR = 167.1). The HLA haplotype most frequently identified in the study patients was HLA-DQA1*01/DQB1*05/DRB1*01 (13/18 patients, 72.2%).

CONCLUSIONS

TINU syndrome is strongly associated with HLA-DQA1*01, HLA-DQB1*05, and HLA-DRB1*01. The association with HLA-DRB1*0102 is one of the highest reported for any disease. Because these genes are in linkage disequilibrium, the role of the individual alleles is difficult to assess. Based on the results of the present study and on previously reported HLA associations in patients with TINU syndrome, the alphabeta dimer encoded by HLA-DQA1*01/DQB1*05 may be particularly important in conferring risk for development of this disease.

Immune mechanisms in uveitis. What can be learned from in vivo imaging?

In many aspects, in vivo imaging is superior to other techniques, such as conventional histology, because it allows the stepwise process of leukocyte migration to be dissected. The potential uses of the in vivo imaging techniques have yet to be achieved. The transfer of lymphocytes with fluorescent dyes can be marked. APCs that ingest fluorescent antigen and use fluorescent antibodies specifically to label different types of APCs in the anterior segment can be identified. Combining these techniques could result in more exciting insights into uveitis and the mechanisms of the immune system. For example, one can confidently expect to be able to observe the extravasation of CFSE-marked DO11.10 T cells and their subsequent interaction with APCs containing red fluorescent OVA. The use of green fluorescent protein to measure the expression of various proteins has occurred in a variety of in vitro and in vivo models. To identify activated T cells specifically, heterozygous knock-in mice have been generated that have a cDNA for enhanced green fluorescent protein substituted for the IL-2 coding region on one allele [91]. Activated T cells from these IL-2-green fluorescent protein mice up-regulate the expression of the IL-2 gene and consequently synthesize the green fluorescent protein marker. The authors recently demonstrated the presence of these activated cells in vivo in the mouse iris [16]. With both the green fluorescent protein and the brighter yellow fluorescent protein the authors anticipate being able to detect in vivo the expression of various cytokines, such as IL-2, the Th1 cytokine IFN-gamma, or the Th2 cytokine IL-4, in T cells infiltrating the eye. First steps have been undertaken to establish in vivo imaging in human eyes. Toxicity of fluorescent dyes currently used for animal research and movement artifacts of the tissue under investigation amplified by the high magnification necessary for cell research, however, remain the major challenges to study leukocyte migration in human uveitis.

Anterior uveitis: current concepts of pathogenesis and interactions with the spondyloarthropathies

Anterior uveitis describes inflammation that involves the iris or ciliary body. Anterior uveitis may be part of a systemic illness such as a spondyloarthropathy. It may also arise from an infection such as herpes simplex; be part of an ocular syndrome, such as Fuchs' heterochromic iridocyclitis; be part of trauma, as in cataract surgery; or result from an idiopathic eye disease with a presumed immune pathogenesis. During 2001, progress has been made understanding uveitis in general, as well as specifically, in association with spondyloarthropathy. Here, we review recent insights into anterior uveitis with regard to clinical presentation, immune mechanisms, genetics, and anti-tumor necrosis factor therapy.

Imaging ocular immune responses by intravital microscopy

The eye offers excellent opportunities to observe cellular interactions in vivo. This applies especially to the immune response in which discrete events can be studied, including cell trafficking, transendothelial migration, adhesion, antigen presentation, and T cell activation. Intravital microscopy has allowed study of immune cell interactions in tissues such as the conjunctiva, the inflamed cornea, and the iris. Thus the realtime observation of presentation of antigen injected into the anterior chamber of the eye can be imaged using fluorescently labelled antigen and cells. Application of the scanning laser ophthalmoscope to the rat and mouse eye allows analysis of leukocyte-endothelial interactions in the retinal and choroidal circulations. These studies have provided important information on rolling and adhesion of leukocytes in real time in different microvascular beds that have not been manipulated in any way and has, for instance, provided quantitation to the effects of shear stress on leukocyte-endothelial adhesion. In addition, the model permits an accurate analysis of the timing of trafficking of T cells into the eye and the possibility of determining which cells, if any, may be responsible for antigen presentation in the tissues as opposed to the secondary lymphoid organs. Finally, these experimental methods are now being applied to the human eye and should prove valuable in determining the nature of tissue damage events in the eye as well as evaluating the response to treatments.

Prediction of the acute toxicity (96-h LC50) of organic compounds to the fathead minnow (Pimephales promelas) using a group contribution method

A group contribution method has been developed to correlate the acute toxicity (96-h LC50) to the fathead minnow (Pimephales promelas) for 397 organic chemicals. Multilinear regression and computational neural networks (CNNs) were used for model building. The models were able to achieve a fairly good correlation of the data (r2 > 0.9). The linear model, which included four specific interaction terms, provided a rapid means of predicting the toxicity of a compound. The CNN model was able to yield virtually the same predictions with or without the four interaction terms that were included in the multilinear model.

Intraocular in vivo imaging of activated T-lymphocytes expressing green-fluorescent protein after stimulation with endotoxin

BACKGROUND

Intravital microscopy allows imaging of specific cell populations in vivo. The value of this technique is well established, but would be enhanced if one could distinguish functional states of cells in vivo. Interleukin-2 (IL-2) is expressed upon stimulation of T-cells and is a commonly used marker for T-cell activation. This study tests the use of enhanced green fluorescent protein (GFP) as a reporter gene for interleukin-2 (IL-2) expression in vivo.

METHODS

Characterization of mice that have the GFP gene under the control of IL-2 regulatory sequences has previously been published. Uveitis was induced by injection of E. coli endotoxin into the vitreous of these IL-2/GFPki transgenic mice. Four hours later, 3 microg of recombinant mouse IL-2 was injected into the anterior chambers of one group of mice. In vivo imaging of infiltrating cells in the iris stroma was performed with fluorescence microscopy at 6, 24, 48, and 72 h after endotoxin injection. The absolute number of fluorescent cells per mm2 was evaluated.

RESULTS

Eyes with endotoxin-induced uveitis had cells that expressed GFP and were identifiable by intravital microscopy. The fluorescent cells were exclusively seen in the subset of cells that had infiltrated the iris stroma or arrested along the vascular endothelium. The number of GFP-positive infiltrating cells in the iris increased from undetectable at baseline to 0.5 cells/mm2 at 6 h and 1.3 cells/mm2 at 72 h. The animals that received endotoxin as well as IL-2 tended to have more GFP-positive cells at the 48-h and 72-h time points, but these differences were not statistically significant

CONCLUSIONS

GFP is commonly used as a reporter gene for in vitro expression assays. The results presented here document that transgenic mice with GFP under the control of IL-2 regulatory elements can be used with intravital microscopy for in vivo expression assays that allow detection of activated T-cells at multiple time points within the same animal. This provides a novel method for temporal and spatial studies on the state of cell activation in inflammatory responses.

Inefficient Assembly and Intracellular Accumulation of Antibodies with Mutations in VH CDR2

We previously described secretion defects in four mutants of the murine anti-phosphocholine Ab, T15. The mutant heavy (H) chains had amino acid replacements in the VH complementarity-determining region 2 (HCDR2) and were expressed at normal intracellular levels. Here, the intracellular fate of the secretion-defective mutant heavy chains was investigated. Metabolic labeling demonstrated that the T15 wild-type Ab was secreted within a 4-h chase. In contrast, the mutant H chains accumulated with intracellular t1/2 values ranging from 10 to 24 h. The mutant H chains were associated with increased levels of the molecular chaperones BiP and GRP94, and remained endoglycosidase H sensitive, suggesting retention in the endoplasmic reticulum. Assembly of the mutant H chains with T15 light (L) chain was arrested at the H2 and H2L intermediate stages of the T15 wild-type pathway (H2 → H2L → H2L2). Even though some assembly with L chain occurred, it was not as a secretion-competent H2L2 Ig moiety. The T15 L chains coexpressed with mutant H chains were degraded efficiently except for a minor L chain population with a long t1/2 that was apparently protected at the H2L stage. To our knowledge, this is the first study demonstrating that intracellular half-lives of Ig H and L chains can be influenced by somatic mutations in HCDR2.

Inefficient assembly and intracellular accumulation of antibodies with mutations in V(H) CDR2

We previously described secretion defects in four mutants of the murine anti-phosphocholine Ab, T15. The mutant heavy (H) chains had amino acid replacements in the V(H) complementarity-determining region 2 (HCDR2) and were expressed at normal intracellular levels. Here, the intracellular fate of the secretion-defective mutant heavy chains was investigated. Metabolic labeling demonstrated that the T15 wild-type Ab was secreted within a 4-h chase. In contrast, the mutant H chains accumulated with intracellular t(1/2) values ranging from 10 to 24 h. The mutant H chains were associated with increased levels of the molecular chaperones BiP and GRP94, and remained endoglycosidase H sensitive, suggesting retention in the endoplasmic reticulum. Assembly of the mutant H chains with T15 light (L) chain was arrested at the H2 and H2L intermediate stages of the T15 wild-type pathway (H2 --> H2L --> H2L2). Even though some assembly with L chain occurred, it was not as a secretion-competent H2L2 Ig moiety. The T15 L chains coexpressed with mutant H chains were degraded efficiently except for a minor L chain population with a long t(1/2) that was apparently protected at the H2L stage. To our knowledge, this is the first study demonstrating that intracellular half-lives of Ig H and L chains can be influenced by somatic mutations in HCDR2.

Comparison of cuffed and uncuffed endotracheal tubes in young children during general anesthesia

BACKGROUND

Uncuffed endotracheal tubes are routinely used in young children. This study tests a formula for selecting appropriately sized cuffed endotracheal tubes and compares the use of cuffed versus uncuffed endotracheal tubes for patients whose lungs are mechanically ventilated during anesthesia.

METHODS

Full-term newborns and children (n = 488) through 8 yr of age who required general anesthesia and tracheal intubation were assigned randomly to receive either a cuffed tube sized by a new formula [size(mm internal diameter) = (age/4) + 3], or an uncuffed tube sized by the modified Cole's formula [size(mm internal diameter) = (age/4) + 4]. The number of intubations required to achieve an appropriately sized tube, the need to use more than 21.min-1 fresh gas flow, the concentration of nitrous oxide in the operating room, and the incidence of croup were compared.

RESULTS

Cuffed tubes selected by our formula were appropriate for 99% of patients. Uncuffed tubes selected by Cole's formula were appropriate for 77% of patients (P < 0.001). The lungs of patients with cuffed tubes were adequately ventilated with 2 1.min-1 fresh gas flow, whereas 11% of those with uncuffed tubes needed greater fresh gas flow (P < 0.001). Ambient nitrous oxide concentration exceeded 25 parts per million in 37% of cases with uncuffed tubes and in 0% of cases with cuffed tubes (P < 0.001). Three patients in each group were treated for croup symptoms (1.2% cuffed; 1.3% uncuffed).

CONCLUSIONS

Our formula for cuffed tube selection is appropriate for young children. Advantages of cuffed endotracheal tubes include avoidance of repeated laryngoscopy, use of low fresh gas flow, and reduction of the concentration of anesthetics detectable in the operating room. We conclude that cuffed endotracheal tubes may be used routinely during controlled ventilation in full-term newborns and children during anesthesia.

Deletion in HCDR3 rescues T15 antibody mutants from a secretion defect caused by mutations in HCDR2

We recently described mutants of the murine anti-phosphocholine Ab T15, with changes in heavy chain complementarity determining region 2 (HCDR2) that caused loss of secretion. Surprisingly, the T15 HCDR2 mutations did not alter secretion when placed into the related anti-phosphocholine Ab D16, which differs from T15 only in HCDR3 and light (L) chain. Here, we exploit the differences between these two Abs to assess the basis of the secretion defect. The T15 L chain is not secreted in the absence of heavy (H) chain. In contrast, D16 L chain is secreted in the absence of H chain, as are most L chains. We co-expressed the T15 wild-type (wt) and mutant H chains with the D16 L chain, as well as with another secreted L chain, J558L. The mutant H chains were not secreted when expressed with either heterologous L chain. These results establish that the T15 L chain is not uniquely associated with the defect. The T15 and D16 Abs also differ in HCDR3 length in that D16 lacks four amino acid residues (Ser99, Ser100, Tyr100a, Trp100b) present in T15. We deleted these four residues from T15 wt and mutant H chains. Secretion of T15 wt was unaffected by the deletion, but shortening HCDR3 restored secretion in the HCDR2 mutants regardless of L chain association. Together these data demonstrate that both the HCDR2 and HCDR3 domains contain structural information that may affect the secretion competence of Abs.

Deletion in HCDR3 rescues T15 antibody mutants from a secretion defect caused by mutations in HCDR2

We recently described mutants of the murine anti-phosphocholine Ab T15, with changes in heavy chain complementarity determining region 2 (HCDR2) that caused loss of secretion. Surprisingly, the T15 HCDR2 mutations did not alter secretion when placed into the related anti-phosphocholine Ab D16, which differs from T15 only in HCDR3 and light (L) chain. Here, we exploit the differences between these two Abs to assess the basis of the secretion defect. The T15 L chain is not secreted in the absence of heavy (H) chain. In contrast, D16 L chain is secreted in the absence of H chain, as are most L chains. We co-expressed the T15 wild-type (wt) and mutant H chains with the D16 L chain, as well as with another secreted L chain, J558L. The mutant H chains were not secreted when expressed with either heterologous L chain. These results establish that the T15 L chain is not uniquely associated with the defect. The T15 and D16 Abs also differ in HCDR3 length in that D16 lacks four amino acid residues (Ser99, Ser100, Tyr100a, Trp100b) present in T15. We deleted these four residues from T15 wt and mutant H chains. Secretion of T15 wt was unaffected by the deletion, but shortening HCDR3 restored secretion in the HCDR2 mutants regardless of L chain association. Together these data demonstrate that both the HCDR2 and HCDR3 domains contain structural information that may affect the secretion competence of Abs.

Binding of phenylphosphocholine-carrier conjugates to the combining site of antibodies maintains a conformation of the hapten

The structural basis of the binding of phenylphosphocholine haptens to antibodies was studied. This was done by preparing antibodies and testing binding to conjugates of phenylphosphocholine. The choice of haptens was made in order to evaluate the contribution of the carrier to binding, and its effect on hapten conformation in the active site. Thus, phosphocholine (PC) was diazophenyl-linked to tyrosine or histidine as single amino acid carriers and to tripeptides or octapeptides containing tyrosine or histidine as central amino acids to which PC was attached. Relative affinity was assessed by inhibition enzyme-linked immunosorbent assay (ELISA) and binding constants were determined by fluorescence quenching. Fluorinated haptens were used to determine the kinetics of binding using 19F nuclear magnetic resonance. The transferred nuclear Overhauser effect was used to characterize conformation of the bound hapten. We had previously shown that nitrophenylphosphocholine unlinked to carrier is bound in the active site as a bent structure [Bruderer, U., Peyton, D. H., Barbar, E., Fellman, J. H., & Rittenberg, M. B. (1992) Biochemistry 31, 584-589]. We show here that this same bent conformation is retained in the active site regardless of the neighboring carrier or the conformation of the hapten in the unbound conjugate. The presence of the carrier residues in the bound state does, however, influence affinity.

Posttonsillectomy vomiting. Ondansetron or metoclopramide during paediatric tonsillectomy: are two doses better than one?

This randomized, double blinded, placebo controlled, prospective study compared the anti-emetic efficacy of one preoperative dose of metoclopramide 0.25 mg.kg-1 intravenously or ondansetron 0.15 mg.kg-1 intravenously with two doses of the same drugs (second dose administered one h postoperatively) in 200 preadolescent children undergoing tonsillectomy with either isoflurane or propofol anaesthesia. The incidence of posttonsillectomy vomiting was significantly reduced (P < 0.005) by two doses of either metoclopramide or ondansetron (18% and 8%, respectively) compared with placebo (50%). No difference in posttonsillectomy vomiting exists between the children who received isoflurane and those who received a propofol infusion. Our results suggest that two doses of metoclopramide 0.25 mg.kg-1 intravenously, like two doses of ondansetron 0.15 mg.kg-1, are effective in reducing vomiting after tonsillectomy in children who have received either isoflurane or propofol anaesthesia.

Ondansetron reduces the incidence and severity of poststrabismus repair vomiting in children

This prospective, randomized, placebo-controlled, double-blinded study evaluated the antiemetic efficacy of ondansetron and metoclopramide in 90 ASA physical status I or II children, 2-17 yr of age, undergoing strabismus repair. After anesthetic induction and prior to eye muscle manipulation, subjects received normal saline 0.3 mL/kg (Group 1), metoclopramide 0.25 mg/kg (Group 2), or ondansetron 0.15 mg/kg (Group 3), intravenously. There were no differences between groups with respect to age, weight, gender, fluids received, number of eye muscles repaired, anesthetic technique, or time in the operating room. The incidence of vomiting in Groups 1, 2, and 3 was 50%, 27%, and 10% prior to discharge, and 67%, 53%, and 30% during the 24 h after surgery, respectively. The number of children vomiting prior to discharge and within 24 h of surgery was significantly reduced in Group 3 compared with Group 1 (P < 0.003 and P < 0.015, respectively). The number of vomiting episodes per patient in Groups 1, 2, and 3 was 1.1, 0.5, and 0.1 prior to discharge, and 4.5, 2.6, and 1.2 during the 24 h after surgery (P < 0.0005 and P < 0.004, respectively). Ondansetron 0.15 mg/kg intravenously after the induction of anesthesia reduces the incidence and severity of vomiting after strabismus repair both prior to discharge from the hospital and during the 24 h after surgery.

Defective secretion of an immunoglobulin caused by mutations in the heavy chain complementarity determining region 2

We have investigated four secretion-deficient antibodies (Abs) derived from a panel of 46 mutant T15 anti-phosphocholine Abs, all of which have point mutations in the heavy chain (H) complementarity determining region 2 (CDR2). The level of secretion for these four Abs was < 10% of wild type when expressed together with the T15 light chain (L) in either SP2/0 or P3X63Ag8.653 myeloma cells although normal levels of H and L chain mRNA were produced. Moreover, abundant intracellular H and L chain proteins were detected. Three of the four mutants had little or no assembled H and L complexes intracellularly whereas one had a significant amount of intracellular immunoglobulin (Ig) which was shown to be capable of binding Ag. Thus, we demonstrate for the first time that point mutations confined to CDR2 of the H chain variable (V) region can impede Ab assembly and secretion. We then introduced the same CDR2 mutations into a related H chain which is encoded by the same T15 VH gene but different diversity (D) and joining (J) genes. When these H chains were expressed with a non-T15 L chain, the resulting Abs were secreted normally. The results thus suggest that the effects of the CDR2 mutations on Ab secretion are dependent on their interactions with L and/or H chain D-J sequences. These results also reveal a novel mechanism that could contribute to B cell wastage.

PKA-dependent regulation of mKv1.1, a mouse Shaker-like potassium channel gene, when stably expressed in CHO cells

Potassium (K) channels are important regulators of cellular physiology and can themselves be modulated by phosphorylation. We have investigated the potential protein kinase A (PKA) regulation of mKv1.1, a mouse Shaker-like K channel gene, when it is expressed in stably transfected Chinese hamster ovary (CHO) cell lines. Whole-cell patch-clamp records show that expression of mKv1.1 gives rise to a rapidly activating, sustained K+ current, referred to classically as a delayed rectifier-type current. In order to study the effects of PKA, we compared cell lines transfected with mKv1.1 alone with lines cotransfected with both mKv1.1 and a plasmid encoding a dominant negative mutation in the regulatory subunit of PKA. These mutant regulatory subunits bind to endogenous catalytic subunits of PKA but do not respond to cAMP, thereby causing a chronic reduction in the basal PKA activity in these cells. We found that mKv1.1 current kinetics are unaltered but current density is 3.4-fold higher in the cell lines expressing mutant regulatory subunit than in lines expressing only mKv1.1. RNase protection assays indicate that levels of the specific RNA for mKv1.1 are increased almost twofold in the lines expressing mutant regulatory subunit over the lines expressing mKv1.1 only. Further, the levels of mKv1.1 protein, assayed using an mKv1.1 channel-specific antibody, are increased by almost a factor of 3 between the two types of cell lines. These results suggest that PKA can regulate mKv1.1 channel expression by changing steady-state levels of RNA and by other posttranscriptional mechanisms.

Heteromultimeric K+ channels in terminal and juxtaparanodal regions of neurons

Voltage-gated potassium (K+) channels display a wide variety of conductances and gating properties in vivo. This diversity can be attributed not only to the presence of many K(+)-channel gene products, but also to the possibility that different K(+)-channel subunits co-assemble to form heteromultimeric channels in vivo. When expressed in Xenopus oocytes or transfected cells, K(+)-channel polypeptides assemble to form tetramers. Certain combinations of Shaker-like subunits have been shown to co-assemble, forming heteromultimeric channels with distinct properties. It is not known, however, whether K(+)-channel polypeptides form heteromultimeric channels in vivo. Here we describe the co-localization of two Shaker-like voltage-gated K(+)-channel proteins, mKv1.1 and mKv1.2, in the juxtaparanodal regions of nodes of Ranvier in myelinated axons, and in terminal fields of basket cells in mouse cerebellum. We also show that mKv1.1 and mKv1.2 can be coimmunoprecipitated with specific antibodies that recognize only one of them. These data indicate that the two polypeptides occur in subcellular regions where rapid membrane repolarization may be important and that they form heteromultimeric channels in vivo.

Propofol anesthesia reduces emesis and airway obstruction in pediatric outpatients

This study was an authors comparison of the effects of and recovery from anesthesia in healthy, premedicated pediatric outpatients who received either inhaled anesthetics (group 1) or propofol (group 2). Group 1 (n = 68) averaged 3.8 +/- 0.2 yr and weighed 17.7 +/- 0.8 kg, whereas group 2 (n = 75) averaged 3.3 +/- 0.2 yr and weighed 16.3 +/- 0.6 kg. The incidence of vomiting in the Postanesthetic Care Unit (PACU) and from discharge to the first postoperative morning was lower in the group receiving propofol (0% and 18%) than in the group receiving volatile agents (7% and 34%, P < 0.05). The incidence of airway obstruction during induction of anesthesia was higher (34% vs 10%, P < 0.01) in children receiving inhaled agent. Withdrawal of the extremity with propofol injection occurred in 14 (19%) patients. Arterial blood pressure was higher at loss of consciousness, laryngoscopy, and tracheal intubation in group 2 (P < 0.01). The length of time from the end of surgery to extubation of the trachea, recovery scores, and length of time spent in the PACU and the Day Surgery Unit were the same in the two groups. Pain scores obtained in the PACU were not different. The data indicate that propofol can be used safely to induce and maintain anesthesia in healthy pediatric outpatients. This coupled with the low incidence of vomiting and airway obstruction in the propofol group suggests distinct and compelling reasons to consider using the drug in this patient population.