Ostreopsis Schmidt and Coolia Meunier (Dinophyceae, Gonyaulacales) from Cook Islands and Niue (South Pacific Ocean), including description of Ostreopsis tairoto sp. nov

It is important to decipher the diversity and distribution of benthic dinoflagellates, as there are many morphologically indistinct taxa that differ from one another in production of potent toxins. To date, the genus Ostreopsis comprises twelve described species, of which seven are potentially toxic and produce compounds presenting a threat to human and environmental health. In this study, isolates previously identified as "Ostreopsis sp. 3" were sampled from the area where it was first reported, Rarotonga, Cook Islands, and have been taxonomically and phylogenetically characterised as Ostreopsis tairoto sp. nov. Phylogenetically, the species is closely related to "Ostreopsis sp. 8", O. mascarenensis, "O. sp. 4", O. fattorussoi, O. rhodesiae and O. cf. siamensis. Previously, it was considered a part of the O. cf. ovata complex but can be distinguished from O. cf. ovata based on the small pores identified on this study, and from O. fattorussoi and O. rhodesiae based on relative lengths of the 2' plates. No known palytoxin -like compounds were detected in strains investigated in this study. Strains of O. lenticularis, Coolia malayensis and C. tropicalis were also identified and described. This study advances our knowledge of biogeography, distribution, and toxins of Ostreopsis and Coolia species.

Apparent oliguria following urological surgery

Oliguria is a common feature of acute kidney injury (AKI), but should be interpreted in the context of other biochemical markers when diagnosing and monitoring AKI or considering the need for renal support. We report an unusual case of apparent severe oliguria arising as a result of complex urological pathology and discuss how an understanding of creatinine kinetics raised suspicions of an alternative diagnosis. We discuss the problems caused by an over-reliance on urine output or serum creatinine alone when diagnosing and staging AKI and highlight the need for a more holistic approach.

Theory and practical application of blood-based renal replacement therapy

The term renal replacement therapy incorporates three modalities that control or correct biochemical and fluid disturbances of renal failure. Peritoneal dialysis and renal transplantation are two forms of renal replacement therapy that are outside the remit of this article. This review focuses upon the third group which are blood-based and involve direct treatment of a patient's blood in a closed, extracorporeal circuit. They provide renal replacement for end-stage renal failure and during periods of severe acute kidney injury, and also for non-renal indications such as the management of drug overdoses. Blood-based renal replacement therapies are often loosely referred to as 'haemodialysis', although this is only one of a range of treatments. This article outlines the theory and practical applications of these treatments.

Catalytic Hydrodeoxygenation of Methyl-Substituted Phenols: Correlations of Kinetic Parameters with Molecular Properties

The hydrodeoxygenation of methyl-substituted phenols was carried out in a flow microreactor at 300 degrees C and 2.85 MPa hydrogen pressure over a sulfided CoMo/Al(2)O(3) catalyst. The primary reaction products were methyl-substituted benzene, cyclohexene, cyclohexane, and H(2)O. Analysis of the results suggests that two independent reaction paths are operative, one leading to aromatics and the other to partially or completely hydrogenated cyclohexanes. The reaction data were analyzed using Langmuir-Hinshelwood kinetics to extract the values of the reactant-to-catalyst adsorption constant and of the rate constants characterizing the two reaction paths. The adsorption constant was found to be the same for both reactions, suggesting that a single catalytic site center is operative in both reactions. Ab initio electronic structure calculations were used to evaluate the electrostatic potentials and valence orbital ionization potentials for all of the substituted phenol reactants. Correlations were observed between (a) the adsorption constant and the two reaction rate constants measured for various methyl-substitutions and (b) certain moments of the electrostatic potentials and certain orbitals' ionization potentials of the isolated phenol molecules. On the basis of these correlations to intrinsic reactant-molecule properties, a reaction mechanism is proposed for each pathway, and it is suggested that the dependencies of adsorption and reaction rates upon methyl-group substitution are a result of the substituents' effects on the electrostatic potential and orbitals rather than geometric (steric) effects.

Modeling alternative binding registers of a minimal immunogenic peptide on two class II major histocompatibility complex (MHC II) molecules predicts polarized T-cell receptor (TCR) contact positions

Several major histocompatibility complex class II (MHC II) complexes with known minimal immunogenic peptides have now been solved by X-ray crystallography. Specificity pockets within the MHC II binding groove provide distinct peptide contacts that influence peptide conformation and define the binding register within different allelic MHC II molecules. Altering peptide ligands with respect to the residues that contact the T-cell receptor (TCR) can drastically change the nature of the ensuing immune response. Here, we provide an example of how MHC II (I-A) molecules may indirectly effect TCR contacts with a peptide and drive functionally distinct immune responses. We modeled the same immunogenic 12-amino acid peptide into the binding grooves of two allelic MHC II molecules linked to distinct cytokine responses against the peptide. Surprisingly, the favored conformation of the peptide in each molecule was distinct with respect to the exposure of the N- or C-terminus of the peptide above the MHC II binding groove. T-cell clones derived from each allelic MHC II genotype were found to be allele-restricted with respect to the recognition of these N- vs. C-terminal residues on the bound peptide. Taken together, these data suggest that MHC II alleles may influence T-cell functions by restricting TCR access to specific residues of the I-A-bound peptide. Thus, these data are of significance to diseases that display genetic linkage to specific MHC II alleles, e.g. type 1 diabetes and rheumatoid arthritis.

Comparison of quantum chemical parameters and Hammett constants in correlating pK(a) values of substituted anilines

Historically, Hammett constants have been extremely effective in describing the influence of substituents on chemical reactivity and other physical and chemical properties, whereas variables derived from quantum chemical calculations have generally been less effective. Taking the experimental pK(a)s of substituted anilines as a representative physicochemical property, five ab initio quantum chemical indices are compared for effectiveness as one-parameter regression descriptors for pK(a). All of the tested descriptors performed well for a set of 19 mono-, 13 di-, and 4 trisubstituted anilines, and two performed somewhat better than the traditional Hammett sigma constants. Among the calculated quantities, the best representation of the aniline pK(a)s is produced by the minimum average local ionization energy on the molecular surface.

Social support for school-aged siblings of children with cancer: a comparison between parent and sibling perceptions

This descriptive, exploratory study investigated the social support interventions received by school-aged siblings of children with cancer and which of those interventions are perceived as being helpful. A comparison between the siblings' and parents' perceptions was made. The conceptual framework was guided by House's (1981) work on social support, which includes major categories of support variables including emotional, informational, instrumental, and appraisal support. A nonprobability purposive sample consisted of 50 school-aged siblings of children with cancer and their parents. Subjects completed either the sibling or parent version of the Nurse-Sibling Social Support Questionnaire (NSSSQ). Descriptive statistical analyses were performed to examine NSSSQ helpfulness and frequency scores for both siblings and parents. Paired t tests were used to test the difference between the responses given by siblings and by their parents on the NSSSQ helpfulness and frequency scales. Results demonstrated that siblings perceive interventions aimed at providing emotional and instrumental support as the most helpful. Parents perceived interventions aimed at meeting the siblings' need for emotional and informational support the most beneficial. Parents reported that siblings receive emotional, informational, and appraisal support more frequently than siblings did.

Self-concept of siblings of children with cancer

Childhood cancer can have detrimental effects on the psychosocial well-being of healthy siblings of children with cancer. The limited research done over the past 40 years has identified adjustment difficulties such as poor self-concept, depression, sorrow, anxiety, and feelings of loneliness in children who have a sibling with cancer. To date, clinical research investigating self-concept is scarce as it relates to siblings of children with cancer. The purpose of this study was to examine self-concept in siblings of children with cancer who attended summer camp. A nonprobability purposive sample consisted of 50 school-age siblings of children with cancer. Using the Personal Attribute Inventory for Children (PAIC) to measure children's self-concept, the researcher found that healthy siblings who attended summer camp scored higher on the PAIC than healthy siblings who did not attend camp. This research suggests that social support such as a camp experience may play an important function in coping with having a brother or sister with childhood cancer.

Development of two instruments measuring social support for siblings of children with cancer

The literature on childhood cancer provides a very limited understanding of healthy siblings' perceptions of supportive interventions during the childhood cancer experience. The purpose of this article is to discuss the development of the Nurse-Sibling Social Support Questionnaire (NSSSQ). Instrument methodology for the study involved item development, face and content validation, and internal consistency reliability as described by Hockenberry-Eaton, Manteuffel, and Bottomley (1997). Item development for the research instrument evolved from an extensive review of the literature and clinical experience of the principal investigator. Content validity of the instrument was accomplished by five experienced pediatric oncology nurses according to the methodology described by Lynn (1986). Using the content validity index, each nurse rated each item as either 4 or 5, indicating 100% agreement among experts that these items measured the concept of social support. Readability for the instrument was determined by using a computerized program. Results showed that readability was concordant with the grade school level for all items. Twenty-five school-age siblings of children with cancer and their mothers were asked to complete the questionnaire. Instrument completion was accomplished in less than 1 hour. The NSSSQ showed high internal consistencies (alpha coefficients >.90). Results indicated that siblings' perceptions of social support differed from those of their mothers. Siblings perceive emotional and instrumental support as greater in importance, whereas mothers perceive emotional and informational support as more beneficial to siblings. Support issues for siblings of children with cancer have been difficult to assess because of the lack of appropriate instruments. This study finding provides exploratory evidence to suggest that the new instrument can help measure siblings' perceptions of social support during the childhood cancer experience.

A concept analysis of social support as experienced by siblings of children with cancer

Social support is a complex phenomenon. The concept is variably defined by multiple disciplines. This article analyzes the concept of social support by using the methods outlined in the nursing literature. The concept analysis focuses on psychosocial support of siblings of children with cancer. Each step in the concept analysis is presented to show the relevance of the concept with siblings of children with cancer.

Conducting psychosocial research with children and adolescents: a developmental perspective

In the past 10 years, childhood has become a focal point of concern. Children are viewed as symbolizing an investment in the future of societies around the world. In the past, knowledge about children's views was realized through objective measures or from representative accounts by adults (e.g., parents and teachers) who were thought to know the child best. Current research suggests that most adult representations and interpretations are only attempts to describe something that more or less represents the child's world. The literature suggests that in the past, children have been perceived mainly as objects rather than subjects of research interest. This perhaps reflects the viewpoint held by many that children are unable to comprehend and describe their world and life experiences because of developmental immaturity and/or that there are intrinsic difficulties in researching children. The purpose of this article is to describe how a child's developmental level affects the research process. Specifically discussed are developmental differences in responses to research including psychosocial research methods, assent, and consent with children.

The role of resistance testing in clinical trial design and product labelling: a regulatory perspective

Assays that attempt to characterize HIV susceptibility or resistance are among the latest technologies that are likely to impact HIV clinical trial design, antiretroviral drug development and patient management. However, at present the Food and Drug Administration (FDA) have yet to approve any phenotypic or genotypic HIV resistance assay and the role of resistance testing in clinical management of patients and in drug development is ill defined. In November 1999, the Division of Antiviral Drug Products at the FDA convened a meeting of its advisory committee to consider the available information about HIV resistance testing, and to generate some recommendations about how these assays could be utilized in antiretroviral drug development. In addition, the committee was presented with several hypothetical regulatory scenarios in order to illustrate how HIV resistance testing might be incorporated in antiretroviral drug development and drug labelling. In this article, we discuss the regulatory history of resistance testing in antimicrobial drug development, the current use of resistance testing for antiretrovirals, as well as a summary of the hypothetical scenarios that were presented to the committee and the discussion of the committee members regarding those scenarios.

Attachment theory and adjustment difficulties in siblings of children with cancer

The demands of the childhood cancer experience on children and their parents has been investigated for a number of years. Despite this research, very little emphasis has been placed on well siblings. In the health care profession today, there is a growing perception that the psychosocial needs of the healthy siblings of children with cancer are less sufficiently met than those of other members of the family system. Previous research proposes that well siblings are especially susceptible to a number of adjustment difficulties (such as depression, anger, anxiety, feelings of guilt, and social isolation) (Murray, 1999). Given these findings, the question arises as to whether the adjustment difficulties seen in siblings are a result of the loss of, or separation from, the attachment figure--the mother who is busy caring for the child with cancer. The purpose of this article is to use attachment theory as a conceptual framework to try to understand the effects of the childhood cancer experience on siblings. Recent findings regarding siblings of children with cancer and some speculations regarding clinical implications are provided.

Detection and Partial Characterization of Tenuiviruses from Black Spruce

Filamentous viral ribonucleoproteins (RNPs) 12 to 16 nm in diameter and 100 to 1,260 nm in length, and characteristic of the genus Tenuivirus, were detected by transmission electron microscopy in purified extracts of needles collected from two mature, asymptomatic black spruce (Picea mariana) trees in New York, but not in extracts of needles from nursery seedlings. Purified RNPs from one tree had a buoyant density in CsCl = 1.39 g/cm³ and an A _260/280 = 1.436. Four ssRNA segments of 1.3, 2.1, 2.3, and 3.5 kb, but not the 8- to 9-kb fragment characteristic of most tenuiviruses, were detected in purified RNA extracts. Amplification products of the expected size were observed when RNA extracts from the two spruce trees and Maize stripe tenuivirus (MStpV), but not from tobacco, Chenopodium quinoa, or spruce seedlings were subjected to reverse transcription-polymerase chain reaction (RT-PCR) using primers to the p3 open reading frame (ORF) of MStpV vRNA 3. However, only MStpV amplified when primers to the nucleocapsid ORF (pc3 ORF on vcRNA 3) were used. Similarly, only MStpV amplified by immunocapture polymerase chain reaction (PCR) using antiserum to MStpV and primers to the p3 ORF. Sequence comparisons suggest that two distinct tenuiviruses occur in black spruce, one more closely related to MStpV than the other. One of these tenuiviruses was detected in one of 10 additional black spruce trees tested, but not in trees of six other coniferous species sampled in the Adirondack Mountains of New York.

Understanding sibling adaptation to childhood cancer

Clinical research conducted over the past 40 years has described adjustment difficulties healthy siblings face when they have a brother or sister with childhood cancer. Research on healthy siblings of children with pediatric malignancies has advanced over the past few years and has broadened from distinguishing psychosocial problems following the patient's death to identifying stressors during the illness experience. More recent research endeavors have focused on recognizing what behaviors or interventions health care providers understand to be most significant in promoting the patient's, parents', and siblings' coping efforts with childhood cancer and its treatment. In addition, descriptive research is exploring interventions used by pediatric oncology health care providers to render social support to siblings of children with cancer (Murray, 1999). Despite the growing body of literature on sibling adaptation to childhood cancer, an understanding of this experience from a developmental perspective is lacking. This lack of theoretical understanding may contribute to inadequate care of siblings of children with cancer. Understanding the meaning cancer has for well siblings is critical. This article discusses the theoretical framework of child development in relation to understanding sibling adaptation to the childhood cancer experience.

Methodological triangulation in a study of social support for siblings of children with cancer

Triangulation is an approach to research that is becoming increasingly popular among nurse researchers. Five types of triangulation are used in nursing research: data, methodological, theoretical, researcher, and analytical triangulation. Methodological triangulation is an attempt to improve validity by combining various techniques in one study. In this article, an example of quantitative and qualitative triangulation is discussed to illustrate the procedures used and the results achieved. The secondary data used as an example are from a previous study that was conducted by the researcher and investigated nursing interventions used by pediatric oncology nurses to provide social support to siblings of children with cancer. Results show that methodological triangulation was beneficial in this study for three reasons. First, the careful comparison of quantitative and qualitative data added support for the social support variables under investigation. Second, the comparison showed more in-depth dimensions about pediatric oncology nurses providing social support to siblings of children with cancer. Finally, the use of methodological triangulation provided insight into revisions for the quantitative instrument.

Pediatric nursing health care delivery plan for humanitarian missions in developing countries

In today's health care environment, pediatric nurses are being called upon to perform humanitarian missions in tropical developing countries. During these missions, pediatric nurses often are faced with providing short-term health care to children in the villages of the developing countries visited. These efforts involve a group of pediatric health care personnel traveling to a poor, medically underserved area; establishing provisional clinics; and seeing a large number of children over several days. Usually only the most necessary resources are taken along, including varying amounts of medications and supplies and possibly minimal laboratory capabilities. To date, health care delivery plans for pediatric nurses as part of an interdisciplinary team on these missions are unavailable. This article provides literature and experience-based guidance for pediatric nurses performing humanitarian missions around the world in tropical developing countries to provide care in a manner that is safe, appropriate, and offers the greatest likelihood of benefit to the children in these countries.

The use of plasma HIV RNA as a study endpoint in efficacy trials of antiretroviral drugs

OBJECTIVES

To evaluate the utility of HIV RNA as an endpoint in antiretroviral efficacy studies.

DESIGN

Data collected from antiretroviral efficacy trials were analyzed to explore relationships between clinical progression and the magnitude, nadir and duration of HIV RNA reductions. The proportion of patients suppressing HIV RNA below assay quantification, time to maximal virologic response, and loss of virologic response in relation to pretreatment characteristics were also analyzed.

METHODS

Analyses were conducted using data from individual antiretoviral efficacy trials or groups of trials that studied similar types of drug regimens and used similar HIV RNA assays. Treatment regimens were pooled for most analyses. Clinical progression was defined as the occurrence of an AIDS-defining event (essentially Centers of Disease Control criteria) or death.

RESULTS

Treatment-induced reductions in HIV RNA approximating total assay variability of about 0.5 log10 copies/ml were associated with decreases in the risk of clinical progression. Larger and more sustained reductions in HIV RNA were directly associated with lower risks for disease progression. Lower initial HIV RNA reductions were associated with more durable HIV RNA suppression.

CONCLUSIONS

For antiretoviral efficacy studies, plasma HIV RNA is a suitable study endpoint that is likely to predict a decreased risk for AIDS progression and death. Because greater and more sustained reductions in HIV RNA appear to confer greater reductions in clinical risk, maintaining maximal suppression of plasma HIV RNA, particularly below the limits of assay quantification, appears to be a rigorous benchmark for assessing the efficacy of antiretroviral regimens.

Siblings of children with cancer: a review of the literature

Research on siblings of children with cancer during the past 40 years has clearly shown that the childhood cancer experience is a stressor that may increase subjective feelings of stress by well siblings and in some cases lead to decreased psychosocial competencies and increased psychopathologies. Research has expanded from identifying psychosocial problems experienced by the sibling after the patient's death to identifying stressors during the illness experience. More recent studies have been targeted at identifying what action siblings take to cope with the stressors imposed since the cancer diagnosis and have addressed what interventions pediatric oncology nurses use in clinical practice to provide support to siblings of children with cancer. The current state of this body of literature, a review of 18 studies, is presented in this article along with a critique of the research studies and suggestions for future research.

The lived experience of childhood cancer: one sibling's perspective

The demands of cancer on children and their parents have been studied and understood for many years now. However, very little focus has been placed on one other very important part of the family system--the siblings. In the health care profession today, there is a growing awareness that the psychosocial needs of siblings of children with cancer are less adequately met than those of other family members. Research suggests that siblings are particularly vulnerable to adjustment difficulties (depression, anger, anxiety, feelings of guilt, and social isolation), and they experience similar stress to that of the ill child Siblings have been identified as the most emotionally neglected and unhappy of all family members during serious childhood illnesses. The purpose of this study was to gain a better understanding of the lived experience of one 14-year-old sibling's experience with childhood cancer. Through the qualitative research process of phenomenology, the researcher gained a greater understanding of the participant's experience and how the childhood cancer experiences affected her and her family. Themes that emerged through the process of content analysis included emotional intensity, increased empathy for others, personal growth, need for support, and desire to help others.

How the MHC selects Th1/Th2 immunity

While the effects of cytokines on T helper 1 (Th1)/Th2 differentiation are well documented, it is less clear why a dichotomy of effector cytokine production would initiate from antigen-specific lymphocytes. Nevertheless, in defined experimental systems, the interaction between T-cell receptor (TCR), peptide and major histocompatibility complex (MHC) can determine Th1/Th2 dominance. Here, Joseph Murray discusses how TCR affinity and ligand density might interface with innate forces in the selection of CD4+ T-cell functions.

MHC genotype controls the capacity of ligand density to switch T helper (Th)-1/Th-2 priming in vivo

A quantitative mechanism for the differentiation of CD4 T cells into recognized subsets of Th1 and Th2 effectors is controversial. Here, we define the Ag dose more precisely to the density of a minimal immunogenic peptide presented on the surface of a specific APC type. Th1 and Th2 responder MHC genotypes differ by as much as an order of magnitude in the density of this peptide displayed on B7-2+ B cells. We asked whether such B cells presenting a low ligand density primed Th2 effectors in an MHC genotype with predisposed high-density presentation and Th1-type immunity, and whether high ligand density B cells primed Th1 effectors in an MHC genotype that normally presents a low density and the Th2 phenotype. While low ligand density had the capacity to switch phenotype in the Th1 responder, high-density presentation did not alter genetically determined Th2 responder status.

MHC genotype controls the capacity of ligand density to switch T helper (Th)-1/Th-2 priming in vivo

A quantitative mechanism for the differentiation of CD4 T cells into recognized subsets of Th1 and Th2 effectors is controversial. Here, we define the Ag dose more precisely to the density of a minimal immunogenic peptide presented on the surface of a specific APC type. Th1 and Th2 responder MHC genotypes differ by as much as an order of magnitude in the density of this peptide displayed on B7-2+ B cells. We asked whether such B cells presenting a low ligand density primed Th2 effectors in an MHC genotype with predisposed high-density presentation and Th1-type immunity, and whether high ligand density B cells primed Th1 effectors in an MHC genotype that normally presents a low density and the Th2 phenotype. While low ligand density had the capacity to switch phenotype in the Th1 responder, high-density presentation did not alter genetically determined Th2 responder status.

Unique T cell antagonist properties of the exact self-correlate of a peptide antigen revealed by self-substitution of non-self-positions in the peptide sequence

The role of self-peptides in shaping the T cell receptor (TCR) repertoire remains to be established. While TCR reactive to certain self-peptides are thought to be depleted in the thymus, the selection of TCR specificity for foreign peptide reactivity appears to require recognition of self-peptide(s) bound to the groove of thymic major histocompatibility complex (MHC) molecules. This dichotomy suggests that different TCR affinities, accessory signals, and/or different sets of self-peptides dictate the eventual fate of any given TCR-bearing clone. Recently, it has been established for several T cell epitopes that derivatives with substitutions in TCR-contact residues can antagonize the proliferation of T cell clones against the wild-type peptide antigen. Moreover, these altered peptide ligands have demonstrated activity in the positive selection of thymocytes with TCR reactive to the wild-type peptide antigen. We have investigated the specificity of T cell antagonism with step-wise substitution of self-amino acids into each nonconserved position of a 12-amino-acid foreign peptide antigen. Our data demonstrate that the ability to antagonize proliferation without competition for MHC binding is unique to the exact self-derivative, where all five of the self-substitutions are inserted. These properties may specifically allow certain self-peptides to downregulate T cell activation to the foreign ligand and/or provide a source of stimulation for immunologic memory.

High-density presentation of an immunodominant minimal peptide on B cells is MHC-linked to Th1-like immunity

Ligand-directed differences in the amount of peptide presented on a specific APC subset could influence the functional outcome of any given immune response. We have investigated this issue with a biochemically determined immunodominant peptide that is presented at a higher density on the APC of Th1 responders (I-As genotypes) than on the APC of Th2 responders (I-Ab genotypes). MHC-linked high peptide density is expressed on B lymphocytes, predominantly those that bear the B7-2 activation marker/costimulatory ligand. We further investigated the role of I-As-specific polymorphism with transfected cells bearing an R-->Q change at position-70 of A beta (found only in the I-As allele). Strikingly, I-Ab-restricted Th1 and Th2 clones proliferate at a peptide dose 10- to 100-fold lower than wild-type on transfected fibroblasts bearing this single s-like substitution in A beta b. Moreover, the shift in the clone dose response is sensitive to the peptide's C-terminus, as is MHC-linked Th1-like immunity to this peptide in vivo. Together, these data suggest that ligand-density can dictate Th1/Th2 selection via a single MHC polymorphism that determines the level of peptide presented to a given TCR on activated B cells.

Social support for siblings of children with cancer

This descriptive study investigated nursing interventions used by pediatric oncology nurses to provide social support to siblings of children with cancer. The study was guided by House's conceptualization of social support which includes components of emotional, instrumental, informational, and appraisal support. A sample of 250 randomly selected pediatric oncology nurses were mailed the Sibling Social Support Questionnaire (SSSQ), developed by the researcher, to determine what interventions they use in clinical practice to provide social support to siblings of children with cancer. With 134 nurse respondents, the SSSQ demonstrated high internal consistency (Cronbach's alpha of .95). Results indicated that the two most frequently used nursing interventions to provide social support to siblings are: (1) encouraging parents to spend time with their other children and (2) providing honest responses to questions asked by siblings.

Isolation, characterization and expression of the gene that encodes D-arabinitol dehydrogenase in Candida tropicalis

The gene (ARD) that encodes NAD-dependent D-arabinitol dehydrogenase (ArDH) in the pathogenic fungus Candida tropicalis (Ct) was cloned by transforming Escherichia coli (Ec) BW31M (araCc) with a plasmid library of Ct genomic DNA and selecting for D-arabinitol-utilizing (D-arab+) clones. Plasmid DNA from a D-arab+ clone retransformed fresh Ec BW31M cells to D-arab+; these cells produced both ArDH catalytic activity and a 31-kDa protein recognized by antibodies to native Ct ArDH. The plasmid contained an 846-bp open reading frame (ORF) that encoded a deduced protein of 282 amino acids (aa) (30,748 Da). Four partial aa sequences from Ct ArDH were present in the deduced aa sequence, thus verifying that Ct ARD had been cloned. Ct ArDH was 95% identical to ArDH from Candida albicans (Ca), 85% identical to a xylitol dehydrogenase (XDH) from Pichia stipitis (Ps) and 20-25% identical to many other short-chain dehydrogenases. Ct ArDH, Ca ArDH and Ps XDH were typical short-chain dehydrogenases except that they lacked an N-terminal Gly that is conserved in other members of this family. Thus, these enzymes may represent a subclass of closely-related fungal pentitol dehydrogenases. Large amounts of recombinant ArDH (re-ArDH) were produced in Ec and purified by dye ligand affinity chromatography. The physical and catalytic properties of re-ArDH were similar to those of native Ct ArDH, and re-ArDH and native ArDH performed similarly in an automated enzymatic assay for D-arabinitol in human serum.

Major histocompatibility complex regulation of T helper functions mapped to a peptide C terminus that controls ligand density

The functional status (Th1- versus Th2-like) of CD4 T cells primed against human collagen type IV (hCol IV) or a single 30mer peptide from the alpha 2 chain of this molecule is predicted by the major histocompatibility complex (MHC) class II (I-A) genotype of the responding mice. H-2s mice elicit Th1-like cell-mediated responses to these antigens, whereas Th2-like humoral responses are primed in H-2b,d,k mice. We now report that the ability of MHC to dictate T helper function in this system depends upon a single amino acid of the minimal alpha 2(IV) peptide. The C terminus of this minimal (12mer) peptide is -G-G-P-K, which is predicted to form a beta-turn. The present data demonstrate that the terminal lysine (K) stabilizes the immunogens full biological effects necessary for exclusive cell-mediated responses in H-2s mice. The lysine-truncated (11mer) peptide with otherwise identical sequence effectively primes T helper function in both H-2b and H-2s genotypes. Most importantly, our direct analysis of these peptides' presentation by live antigen-presenting cells (APC) reveals that the 12mer is bound at a log higher density on H-2s APC than on H-2b APC, and that the 11mer is presented at an equally low relative density on APC from both genotypes. In vitro analyses of 12mer/11mer cross-reactive Th clones demonstrate that I-As restricted clones require about 1-2 log lower doses of 12mer peptide than 11mer peptide to stimulate equivalent thymidine incorporation and cytokine release. By contrast, I-Ab-restricted (12mer/11mer cross-reactive) Th clones show no preference for the 12mer and require relatively high peptide doses similar to those required to stimulate the I-As clones with the 11mer peptide. Thus, the peptide dose requirements of Th clones reflect the high density of presentation associated with the 12mer: I-As ligand. Taken together, the results directly support the role of ligand density as an important control point in the functional decision of CD4 T cells.

Calculated surface electrostatic potentials of molecular sieve models containing SiO4, AlO4, and PO4 units

Surface electrostatic potentials have been computed at the ab initio HF/STO-5G* level for two model systems: a fragment of a zeolite channel wall; and a fragment composed of SiO4, AlO4 and PO4 units. The potential above the SiO4 network is negative everywhere, despite these units commonly being regarded as electrically neutral. In marked contrast, the AlO4 and PO4 units introduce strongly negative and positive regions, respectively, giving rise to a much more heterogeneous surface potential.

D-arabitol metabolism in Candida albicans: studies of the biosynthetic pathway and the gene that encodes NAD-dependent D-arabitol dehydrogenase

Candida albicans produces large amounts of the pentitol D-arabitol in culture and in infected mammalian hosts, but the functional and pathogenic significance of D-arabitol in C. albicans is not known. In this study, we sought to elucidate the pathway by which C. albicans synthesizes D-arabitol and to identify and characterize key enzymes in this pathway. C. albicans B311 produced D-[14C-1]arabitol from [14C-2]glucose; this finding implies on structural grounds that D-ribulose-5-PO4 from the pentose pathway is the major metabolic precursor of D-arabitol. NAD- or NADP-dependent pentitol dehydrogenases catalyze the final steps in D-arabitol biosynthesis in other fungi; therefore, lysates of C. albicans B311 were tested for enzymes of this class and were found to contain a previously unknown NAD-dependent D-arabitol dehydrogenase (ArDH). The ArDH structural gene was cloned by constructing a new D-arabitol utilization pathway in Escherichia coli. The C. albicans ArDH gene expressed in E. coli and Saccharomyces cerevisiae an enzyme that catalyzes the reaction D-arabitol + NAD <-->D-ribulose + NADH; this gene was present as a single copy per haploid genome, and its deduced peptide sequence was homologous with sequences of several members of the short-chain dehydrogenase family of enzymes. These results suggest that (i) C. albicans synthesizes D-arabitol by dephosphorylating and reducing the pentose pathway intermediate D-ribulose-5-PO4 and (ii) ArDH catalyzes the final step in this pathway.

Functional CD4 T cell subset interplay in an intact immune system

Immunization with human collagen IV has been shown to lead to the selective activation of Th-1 and Th-2-like cells in vivo depending on the I-A genotype of the mice. Mice expressing I-As generate Th-1 cells, and mice expressing I-Ab generate Th-2 cells after immunization. We examined the response of (bxs)F1 hybrid mice to determine the types of CD4 T cell activated. We found that Th-1-like responses dominated, in that CD4 T cells from human collagen IV-primed mice displayed good proliferative responses and little ability to induce antibody formation, and secreted IFN-gamma and not IL-5. Most of the Th-1-like activity of F1 hybrid T cells was I-As restricted. Inhibition of Th-1 cell priming using anti-I-As antibody administered with the priming Ag in vivo revealed Th-2-like activity, in that the CD4 T cells now secreted IL-5 and not IFN-gamma and induced antibody formation. Additional studies indicated that anti-IFN-gamma treatment in vivo also revealed Th-2 cells, suggesting that I-As-restricted CD4 T cells producing or controlling the production of IFN-gamma suppress Th-2 priming.

Functional CD4 T cell subset interplay in an intact immune system

Immunization with human collagen IV has been shown to lead to the selective activation of Th-1 and Th-2-like cells in vivo depending on the I-A genotype of the mice. Mice expressing I-As generate Th-1 cells, and mice expressing I-Ab generate Th-2 cells after immunization. We examined the response of (bxs)F1 hybrid mice to determine the types of CD4 T cell activated. We found that Th-1-like responses dominated, in that CD4 T cells from human collagen IV-primed mice displayed good proliferative responses and little ability to induce antibody formation, and secreted IFN-gamma and not IL-5. Most of the Th-1-like activity of F1 hybrid T cells was I-As restricted. Inhibition of Th-1 cell priming using anti-I-As antibody administered with the priming Ag in vivo revealed Th-2-like activity, in that the CD4 T cells now secreted IL-5 and not IFN-gamma and induced antibody formation. Additional studies indicated that anti-IFN-gamma treatment in vivo also revealed Th-2 cells, suggesting that I-As-restricted CD4 T cells producing or controlling the production of IFN-gamma suppress Th-2 priming.

Major histocompatibility complex (MHC) control of CD4 T cell subset activation. II. A single peptide induces either humoral or cell-mediated responses in mice of distinct MHC genotype

CD4 T cells activated in vivo in response to human collagen type IV (hCol IV) resemble either T helper type 1 (Th1) or Th2 cells depending on the major histocompatibility complex (MHC) class II genotype of the responding mice. H-2s mice were shown to selectively activate Th1-like cells, releasing interleukin (IL 2 and interferon-gamma in response to hCol IV, whereas H-2b.d mice were shown to selectively activate Th2-like cells, releasing IL 4 and IL 5 in response to hCol IV. These results suggested that MHC class II regulated the type of effector function observed during an immune response. It was of interest to determine if the functional difference observed between the CD4 T cells of the two strains was due to the presentation of different peptides of the hCol IV molecule by the two MHC class II molecules. The present results demonstrate that a single peptide of the collagen IV molecule will elicit a Th1-like response in H-2s strains and Th2-like responses in H-2b.d strains, as was observed when using the intact hCol IV molecule. Furthermore, the failure to generate Th1-like responses in H-2b.d could be overcome by increasing the dose of this peptide in vitro. Compared to H-2s, the Th1-like response in H-2b required 100 times the amount of peptide to reelicit an equivalent response. These data suggest that a single peptide of hCol IV can control the type of effector response observed.

Evidence that the Fc region of autologous rabbit IgG isolated before and after hyperimmunization is structurally different: recognition by rheumatoid factor and monoclonal antibodies

Autologous hyperimmune (HI) and pre-inoculation (PI) rabbit Fc gamma populations were found to be conformationally different by spectroscopic measurements, and antigenically different by measurements which examined rheumatoid factor (RF) and monoclonal antibody (MoAb) binding specificity for both populations in ELISA. Circular dichroism spectra of HI rabbit Fc gamma (prepared from animals after hyperimmunization with streptococcal vaccine) were both qualitatively and quantitatively different, particularly in the 225-228 nm range, in comparison to both homologous normal and autologous PI Fc gamma. Binding studies in ELISA showed that affinity constants obtained for reactions of both rabbit RF and various murine MoAb with HI IgG and Fc were approximately 10-fold higher relative to those observed for PI IgG and Fc. Enzymatic deglycosylation of HI and PI Fc gamma led to elimination of CD spectral differences. Further, association constants obtained for RF and MoAb reactions with deglycosylated (sialic acid and galactose removed) PI Fc gamma were equivalent to those obtained in the presence of untreated HI Fc gamma. Together, these results suggest the complex oligosaccharide structure of rabbit IgG may play a significant role in the expression of Fc gamma determinants, and alteration of this structure under hyperimmune or other conditions may be related to induction of an RF response.

The use of the electrostatic potential at the molecular surface in recognition interactions: dibenzo-p-dioxins and related systems

An ab initio self-consistent-field molecular orbital approach was used to compute the electrostatic potentials of dibenzo-p-dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), two analogues of the latter, and two isomeric benzoflavones on a three-dimensional molecular surface corresponding to the contour of constant electronic density equal to 0.002 electrons/bohr3. The results are discussed in relation to the biological activities of the respective molecules. It is shown that the electrostatic potential graphically depicted on the molecular surface is well suited for the study of recognition interactions, such as are believed to be involved in the initial receptor-mediated step leading to toxicity in the dibenzo-p-dioxins. The surface potential has the advantage of clearly showing steric features that may play a role in understanding the recognition process being investigated.

Measurement of association constants in ELISA. Reactions between solid-phase antibody and fluid-phase biotinylated antigen

An ELISA procedure which utilized an avidin-peroxidase amplification reaction to detect and quantify the amount of fluid-phase biotinylated antigen bound to solid-phase antibody was developed to determine antibody association constants. The methodology required is uncomplicated, avoids the use of radioisotopes, and is theoretically amenable for use with any protein which can be biotinylated, and any receptor protein which can be immobilized on plastic wells. A plot of known immobilized biotinylated antigen concentrations, which ranged from approximately 100 ng/ml to 1000 ng/ml, versus avidin-peroxidase conjugate product formation, was used to establish a standard curve from which the amount of antibody-associated antigen in binding assays could be determined. Antibody association constants obtained with this method ranged from 10(5) to 10(9) M-1.

MHC control of CD4+ T cell subset activation

The present results demonstrate that CD4+ T cells activated in the primary in vivo response to antigen produce distinct patterns of cytokines depending upon the MHC class II haplotype of the responding mice. I-As mice were found to selectively activate IL-2/IFN-gamma-producing CD4+ T cells, whereas I-Ab mice exhibited selective activation of IL-4-producing CD4+ T cells in response to collagen IV. The effector response phenotype was found to correlate with the cytokine phenotype of CD4+ T cells activated in vivo; IL-2/IFN-gamma-producing cells giving rise to proliferative (cell-mediated) responses, IL-4-producing cells leading to secondary IgG (humoral) responses. Together the data support the notion that the outcome of a given immune response (e.g., protection vs. onset, tolerance vs. autoimmunity) may be determined in part by the type of CD4+ T cells initially activated by antigen. Moreover, the present experiments demonstrate for the first time that polymorphism in class II MHC can determine such selective activation of different cytokine-producing CD4+ T cell phenotypes.

Hyperimmunization alters Fc gamma antigenicity. Linkage to glycosylation

Rabbits were hyperimmunized with streptococcal vaccine to produce hyperimmune (HI) IgG, and both HI IgG and autologous preinoculation (PI) IgG were used to prepare Fc gamma. mAb raised against these, and deglycosylated PI Fc gamma preparations were subsequently used to determine if antigenic differences existed between autologous HI and PI Fc gamma. Although the majority of mAb examined did not discriminate between the two sources of Fc gamma, several mAb exhibited remarkable specificity for autologous HI Fc gamma. We did not detect any mAb which exhibited the converse specificity. Of the mAb chosen for study, all except one appeared specific for determinants located in C gamma 2; the exception specifically reacted with pFc', and did not discriminate between the two Fc preparations. Importantly, partial deglycosylation of autologous PI Fc gamma led to equivalent reactivity with previously HI-specific mAb. The results of this study provide immunologic evidence that abnormal C gamma 2 structures exist prior to and reach serologically detectable levels during the hyperimmune response in these animals, apparently as a result of glycosylation pattern alterations within the Fc region. Such autoantigenic differences could account for the induction of RF under these conditions, and perhaps in certain human arthritic diseases as well.

Hyperimmunization alters Fc gamma antigenicity. Linkage to glycosylation

Rabbits were hyperimmunized with streptococcal vaccine to produce hyperimmune (HI) IgG, and both HI IgG and autologous preinoculation (PI) IgG were used to prepare Fc gamma. mAb raised against these, and deglycosylated PI Fc gamma preparations were subsequently used to determine if antigenic differences existed between autologous HI and PI Fc gamma. Although the majority of mAb examined did not discriminate between the two sources of Fc gamma, several mAb exhibited remarkable specificity for autologous HI Fc gamma. We did not detect any mAb which exhibited the converse specificity. Of the mAb chosen for study, all except one appeared specific for determinants located in C gamma 2; the exception specifically reacted with pFc', and did not discriminate between the two Fc preparations. Importantly, partial deglycosylation of autologous PI Fc gamma led to equivalent reactivity with previously HI-specific mAb. The results of this study provide immunologic evidence that abnormal C gamma 2 structures exist prior to and reach serologically detectable levels during the hyperimmune response in these animals, apparently as a result of glycosylation pattern alterations within the Fc region. Such autoantigenic differences could account for the induction of RF under these conditions, and perhaps in certain human arthritic diseases as well.

Halogenated hydrocarbon epoxides: some predictive methods for carcinogenic activity based on electronic mechanisms

We summarize some of our computational studies (involving an ab initio self-consistent-field molecular orbital procedure) of the reactive properties of halogenated hydrocarbon epoxides. Two of the factors that are believed to determine the carcinogenicities of halogenated olefins and their metabolically produced epoxides are discussed in detail. These are the epoxide's tendency toward oxygen protonation, and its subsequent reactivity. The first of these provides a means for identifying suspect carcinogens, on the basis of our earlier observation that epoxide carcinogenicities are associated with relatively strong negative electrostatic potentials near the oxygens (the protonation sites). With regard to the epoxide's reactivity, optimum carcinogenicity appears to require that this be at an intermediate level. We have investigated the feasibility of using calculated C-O bond orders as measures of reactivity, with encouraging initial results, which suggest that this reactivity requirement may provide a means for ranking the activities of carcinogens.

Teratogenic effects of vitamin A palmitate in Fischer 344 rats

Prior to employing the Fischer 344 rat in teratology studies, it was considered necessary to establish the responsiveness of this strain to teratogenic agents. Bred Fischer 344 rats were administered 0, 3.2, 32, or 128 mg/kg/day (approximately 1,000, 10,000, or 40,000 USP units per animal) of vitamin A palmitate by gavage on days 6 through 15 of gestation. Maternal toxicity, as evidenced by decreased body weight gain, and decreased food and water consumption, was observed at the 128 mg/kg/day dose level. This dosage level was embryolethal and teratogenic in the Fischer 344 rat. The incidence of fetal resorptions was statistically significantly increased as compared to controls. Among the surviving fetuses, malformations observed included cleft palate, exencephaly, microphthalmia, anophthalmia, hydronephrosis, brachygnathia, pinna anomalies, and great vessel and heart anomalies. Based on these findings, it is concluded that the Fischer 344 rat responded to a known teratogenic agent and hence is appropriate for use in studies designed to evaluate the teratogenic potential of test agents.

Triethylenemelamine (TEM): dominant lethal effects in Fischer 344 rats

Male Fischer 344 rats were administered triethylenemelamine orally at dose levels of 0, 0.5 or 1.0 mg TEM/kg/day, five days per week for four weeks. A separate group of males was administered TEM as a single intraperitoneal injection of 0.3 mg/kg. Following treatment, males were mated with two groups of untreated females for a period of one week each. The uterine contents of untreated females were examined for evidence of a dominant lethal effect as manifested in an increase in the average resorption rate. Significant increases in the resorption rate were seen at 0.5 mg/kg/day for the second breeding period, and at 1.0 mg/kg/day for both breeding periods following oral administration. Significant decreases in the number of implantations, and increases in the average pre-implantation loss and resorption rate were observed following intraperitoneal administration. These effects seen in Fischer 344 rats were comparable to results obtained with other strains following a similar treatment regimen.