Mechanism of age-dependent susceptibility and novel treatment strategy in glutaric acidemia type I

Glutaric acidemia type I (GA-I) is an inherited disorder of lysine and tryptophan metabolism presenting with striatal lesions anatomically and symptomatically similar to Huntington disease. Affected children commonly suffer acute brain injury in the context of a catabolic state associated with nonspecific illness. The mechanisms underlying injury and age-dependent susceptibility have been unknown, and lack of a diagnostic marker heralding brain injury has impeded intervention efforts. Using a mouse model of GA-I, we show that pathologic events began in the neuronal compartment while enhanced lysine accumulation in the immature brain allowed increased glutaric acid production resulting in age-dependent injury. Glutamate and GABA depletion correlated with brain glutaric acid accumulation and could be monitored in vivo by proton nuclear magnetic resonance (1H NMR) spectroscopy as a diagnostic marker. Blocking brain lysine uptake reduced glutaric acid levels and brain injury. These findings provide what we believe are new monitoring and treatment strategies that may translate for use in human GA-I.

High-throughput zebrafish histology

The morphological effects of mutation and disease are often critical to our understanding of normal and abnormal function. The power and popularity of zebrafish as a forward and reverse genetic vertebrate model system, combined with its small size, have made it an ideal model in which to study the genetics of histologically scorable phenotypes. The presence of multiple tissue types in this organism's small larvae also makes it a potentially important model for toxicological analysis. Studying histological phenotypes is greatly enhanced by high-throughput methods of histology. Here, we describe details of high-throughput histology of the zebrafish using larval arrays, along with recent advances in mold design and discussion of work in progress that will lead to easier ways for people in the field to more rapidly score phenotypes in arrays. These detailed descriptions, together with the troubleshooting guide, should enable any laboratory with ties to a histology facility to perform high-throughput histology of zebrafish.

Proteomic and bioinformatic characterization of the biogenesis and function of melanosomes

Melanin, which is responsible for virtually all visible skin, hair, and eye pigmentation in humans, is synthesized, deposited, and distributed in subcellular organelles termed melanosomes. A comprehensive determination of the protein composition of this organelle has been obstructed by the melanin present. Here, we report a novel method of removing melanin that includes in-solution digestion and immobilized metal affinity chromatography (IMAC). Together with in-gel digestion, this method has allowed us to characterize melanosome proteomes at various developmental stages by tandem mass spectrometry. Comparative profiling and functional characterization of the melanosome proteomes identified approximately 1500 proteins in melanosomes of all stages, with approximately 600 in any given stage. These proteins include 16 homologous to mouse coat color genes and many associated with human pigmentary diseases. Approximately 100 proteins shared by melanosomes from pigmented and nonpigmented melanocytes define the essential melanosome proteome. Proteins validated by confirming their intracellular localization include PEDF (pigment-epithelium derived factor) and SLC24A5 (sodium/potassium/calcium exchanger 5, NCKX5). The sharing of proteins between melanosomes and other lysosome-related organelles suggests a common evolutionary origin. This work represents a model for the study of the biogenesis of lysosome-related organelles.

Zebrafish genomic instability mutants and cancer susceptibility

Somatic loss of tumor suppressor gene function comprising the second hit of Knudson's two-hit hypothesis is important in human cancer. A genetic screen was performed in zebrafish (Danio rerio) to find mutations that cause genomic instability (gin), as scored by Streisinger's mosaic-eye assay that models this second hit. The assay, based on a visible test for loss of wild-type gene function at a single locus, golden, is representative of genomewide events. Twelve ENU-induced genomic instability (gin) mutations were isolated. Most mutations showed weak dominance in heterozygotes and all showed a stronger phenotype in homozygotes. Trans-heterozygosity for 7 of these mutations showed greatly enhanced instability. A variety of spontaneous tumors were found in heterozygous adults from all gin lines, consistent with the expectation that genomic instability (mutator) mutations can accelerate carcinogenesis. The incidence of spontaneous cancer at 30-34 months was increased 9.6-fold in heterozygotes for the mutant with the strongest phenotype, gin-10. Tumors were seen in skin, colon, kidney, liver, pancreas, ovary, testis, and neuronal tissues, with multiple tumors in some fish. The study of these mutants will add to our understanding of the mechanisms of somatic loss of gene function and how those mechanisms contribute to cancer susceptibility.

Separate Na,K-ATPase genes are required for otolith formation and semicircular canal development in zebrafish

We have investigated the role of Na,K-ATPase genes in zebrafish ear development. Six Na,K-ATPase genes are differentially expressed in the developing zebrafish inner ear. Antisense morpholino knockdown of Na,K-ATPase alpha1a.1 expression blocked formation of otoliths. This effect was phenocopied by treatment of embryos with ouabain, an inhibitor of Na,K-ATPase activity. The otolith defect produced by morpholinos was rescued by microinjection of zebrafish alpha1a.1 or rat alpha1 mRNA, while the ouabain-induced defect was rescued by expression of ouabain-resistant zebrafish alpha1a.1 or rat alpha1 mRNA. Knockdown of a second zebrafish alpha subunit, alpha1a.2, disrupted development of the semicircular canals. Knockdown of Na,K-ATPase beta2b expression also caused an otolith defect, suggesting that the beta2b subunit partners with the alpha1a.1 subunit to form a Na,K-ATPase required for otolith formation. These results reveal novel roles for Na,K-ATPase genes in vestibular system development and indicate that different isoforms play distinct functional roles in formation of inner ear structures. Our results highlight zebrafish gene knockdown-mRNA rescue as an approach that can be used to dissect the functional properties of zebrafish and mammalian Na,K-ATPase genes.

A diet-induced mouse model for glutaric aciduria type I

In the autosomal recessive human disease, glutaric aciduria type I (GA-1), glutaryl-CoA dehydrogenase (GCDH) deficiency disrupts the mitochondrial catabolism of lysine and tryptophan. Affected individuals accumulate glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) in the serum and often suffer acute striatal injury in childhood. Prior attempts to produce selective striatal vulnerability in an animal model have been unsuccessful. We hypothesized that acute striatal injury may be induced in GCDH-deficient (Gcdh-/-) mice by elevated dietary protein and lysine. Here, we show that high protein diets are lethal to 4-week-old and 8-week-old Gcdh-/- mice within 2-3 days and 7-8 days, respectively. High lysine alone resulted in vasogenic oedema and blood-brain barrier breakdown within the striatum, associated with serum and tissue GA accumulation, neuronal loss, haemorrhage, paralysis, seizures and death in 75% of 4-week-old Gcdh-/- mice after 3-12 days. In contrast, most 8-week-old Gcdh-/- mice survived on high lysine, but developed white matter lesions, reactive astrocytes and neuronal loss after 6 weeks. Thus, the Gcdh-/- mouse exposed to high protein or lysine may be a useful model of human GA-1 including developmentally dependent striatal vulnerability.

SLC24A5, a putative cation exchanger, affects pigmentation in zebrafish and humans

Lighter variations of pigmentation in humans are associated with diminished number, size, and density of melanosomes, the pigmented organelles of melanocytes. Here we show that zebrafish golden mutants share these melanosomal changes and that golden encodes a putative cation exchanger slc24a5 (nckx5) that localizes to an intracellular membrane, likely the melanosome or its precursor. The human ortholog is highly similar in sequence and functional in zebrafish. The evolutionarily conserved ancestral allele of a human coding polymorphism predominates in African and East Asian populations. In contrast, the variant allele is nearly fixed in European populations, is associated with a substantial reduction in regional heterozygosity, and correlates with lighter skin pigmentation in admixed populations, suggesting a key role for the SLC24A5 gene in human pigmentation.

Coordinate control of cell cycle regulatory genes in zebrafish development tested by cyclin D1 knockdown with morpholino phosphorodiamidates and hydroxyprolyl-phosphono peptide nucleic acids

During early zebrafish (Danio rerio) development zygotic transcription does not begin until the mid-blastula transition (MBT) ∼3 h after fertilization. MBT demarcates transition from synchronous short cell cycles of S and M phases exclusively to full cycles encompassing G₁ and G₂ phases. Transcriptional profiling and RT–PCR analyses during these phases enabled us to determine that this shift corresponds to decreased transcript levels of S/M phase cell cycle control genes (e.g. ccna2, ccnb1, ccnb2 and ccne) and increased transcript levels of ccnd1, encoding cyclin D1, and orthologs of p21 (p21-like) and retinoblastoma (Rb-like 1). To investigate the regulation of this process further, the translation of ccnd1 mRNA, a G₁/S checkpoint control element, was impaired by microinjection of ccnd1-specific morpholino phosphorodiamidate (MO) 20mer or hydroxyprolyl-phosphono peptide nucleic acid (HypNA-pPNA) 16mer antisense oligonucleotides. The resulting downregulation of cyclin D1 protein resulted in microophthalmia and microcephaly, but not lethality. The phenotypes were not seen with 3-mismatch MO 20mers or 1-mismatch HypNA-pPNA 16mers, and were rescued by an exogenous ccnd1 mRNA construct with five mismatches. Collectively, these results indicate that transcription of key molecular determinants of asynchronous cell cycle control in zebrafish embryos commences at MBT and that the reduction of cyclin D1 expression compromises zebrafish eye and head development.

Shark cartilage, cancer and the growing threat of pseudoscience

The promotion of crude shark cartilage extracts as a cure for cancer has contributed to at least two significant negative outcomes: a dramatic decline in shark populations and a diversion of patients from effective cancer treatments. An alleged lack of cancer in sharks constitutes a key justification for its use. Herein, both malignant and benign neoplasms of sharks and their relatives are described, including previously unreported cases from the Registry of Tumors in Lower Animals, and two sharks with two cancers each. Additional justifications for using shark cartilage are illogical extensions of the finding of antiangiogenic and anti-invasive substances in cartilage. Scientific evidence to date supports neither the efficacy of crude cartilage extracts nor the ability of effective components to reach and eradicate cancer cells. The fact that people think shark cartilage consumption can cure cancer illustrates the serious potential impacts of pseudoscience. Although components of shark cartilage may work as a cancer retardant, crude extracts are ineffective. Efficiencies of technology (e.g., fish harvesting), the power of mass media to reach the lay public, and the susceptibility of the public to pseudoscience amplifies the negative impacts of shark cartilage use. To facilitate the use of reason as the basis of public and private decision-making, the evidence-based mechanisms of evaluation used daily by the scientific community should be added to the training of media and governmental professionals. Increased use of logical, collaborative discussion will be necessary to ensure a sustainable future for man and the biosphere.

Histology-based screen for zebrafish mutants with abnormal cell differentiation

The power of histology to define states of cell differentiation was used as the basis of a mutagenesis screen in zebrafish. In this screen, 7-day-old parthenogenetic half-tetrad larvae from potential carrier females were screened for mutations affecting cell differentiation in hematoxylin and eosin-stained tissue sections. Seven, noncomplementing, recessive mutations were found. Two mutations affect only the retina: segmented photoreceptors (spr) show a discontinuous photoreceptor cell layer; vestigial outer segments (vos) has fewer photoreceptor cells and degenerated outer segments within this cell layer. Three mutants have gut-specific defects: the epithelial cells of kirby (kby) are replaced by ballooned cells; the intestines of stuffy (sfy) and stuffed (sfd) contain increased luminal mucus. Two mutations affect multiple organs: disordered neural retina (dnr) has disrupted retinal layering and mild nuclear abnormalities in the gut and liver; and in huli hutu (hht), the retinal cell layers are disorganized and multiple organs have mild to severe nuclear abnormalities that are reminiscent of the atypia of human neoplasia. Each mutation appears to be homozygous lethal. This screen is proof of principle for the feasibility of histologic screens to yield novel mutations, including potential models of human disease. The throughput for this type of screen may be enhanced by automation.

Functional genomic dissection of multimeric protein families in zebrafish

The study of multimeric protein function in the postgenomicera has become complicated by the discovery of multiple isoforms for each subunit of those proteins. A correspondingly large number of potential isoform combinations offer the multicellular organism a constellation of protein assemblies from which to generate a variety of functions across different cells, tissues, and organs. At the same time, the multiplicity of potential subunit isoform combinations presents a significant challenge when attempting to dissect the functions of particular isoform combinations. Biochemical and cell culture methods have brought us to a significant state of understanding of multimeric proteins but are unable to answer questions of function within the context of the many tissues and developmental stages of the multicellular organism. Answering those questions can be greatly facilitated in model systems in which expression can be determined over time, in the context of the whole organism, and in which hypomorphic function of each subunit can be studied individually and in combination. Fortunately, the potential for high-throughput in situ hybridization studies and antisense-based reverse genetic knockdowns in zebrafish offers exciting opportunities to meet this challenge. Some of these opportunities, along with cautions of interpretation and gaps in the existing technologies, are discussed in the context of ongoing investigations of the dimeric Na,K-ATPases and heterotrimeric G proteins.

Inhibition of N-acetyltransferase activity and gene expression in human colon cancer cell lines by diallyl sulfide

Diallyl sulfide (DAS) is one of the major components of garlic (Allium sativum) and is widely used in the world for food. In this study, DAS was selected for testing the inhibition of arylamine N-acetyltransferase (NAT) activity (N-acetylation of 2-aminofluorene) and gene expression (mRNA NAT) in human colon cancer cell lines (colo 205, colo 320 DM and colo 320 HSR). The NAT activity was examined by high performance liquid chromatography and indicated that a 24 h DAS treatment decreases N-acetylation of 2-aminofluorene in three colon (colo 205, 320 DM and colo 320 HSR) cancer cell lines. The NAT enzymes (protein) were analyzed by western blotting and flow cytometry and it indicated that DAS decreased the levels of NAT in three colon (colo 205, 320 DM and colo 320 HSR) cancer cell lines. The gene expression of NAT (mRNAT NAT) was determined by polymerase chain reaction (PCR), it was shown that DAS affect mRNA NAT expression in examined human colon cancer cell lines. This report is the first to demonstrate that DAS does inhibit human colon cancer cell NAT activity and gene expression.

Mosaic Eyes, Genomic Instability Mutants, and Cancer Susceptibility

We now know that genomic instability contributes to cancer. The zebrafish mosaic eye assay developed by George Streisinger takes advantage of the organism's transparency to provide an excellent assay for detecting somatic mutation. This assay allowed us to identify zebrafish mutants with increased frequencies of somatic mutation and spontaneous cancer. Here, we have described details of mutagenesis, the basis and practical use of the mosaic eye assay, and the histological methods used to study genomic instability mutants and cancer susceptibility. These techniques should prove useful to other zebrafish researchers, as they are broadly applicable to many other biological investigations of embryos, larvae, and adult zebrafish.

Patient effective dose from sentinel lymph node lymphoscintigraphy in breast cancer: a study using a female humanoid phantom and thermoluminescent dosemeters

The aim of this study was to measure the dose delivered to patients undergoing sentinel lymph node lymphoscintigraphy by taking into account both the transmission scan dose using a (57)Co flood source and the (99)Tc(m) internal emission dose. An adult female humanoid phantom and a set of thermoluminescent dosimeters were used in the measurements. The choice of measurement organs in the humanoid was guided by the recommendations described in the International Commission on Radiological Protection report number 60. A (57)Co flood source was used in external transmission to irradiate the humanoid at posterior, left lateral, left posterior oblique, right lateral and right posterior oblique positions. Four (99)Tc(m) deposits as internal emission sources were used to simulate patient peritumoural injection. The individual effective doses for external transmission and internal emission, normalized to the cumulated activity and expressed in micro Sv(MBq x h)(-1) were then calculated. The effective dose for a transmission scan was on average 0.061 micro Sv(MBq x h)(-1) for each (57)Co flood source position and for internal emission 0.312 micro Sv(MBq x h)(-1) and 0.291 micro Sv(MBq x h)(-1) for left and right breast injection, respectively. Using these results, the effective dose from both transmission and emission sources can be calculated according to the nuclear medicine scanning protocol and surgical procedure of the individual institution. For our protocols, the patient receives a maximum effective dose of 52 micro Sv for the 1 day protocol (18 MBq injection) and 204 micro Sv for the 2 day protocol (74 MBq injection) if only the sentinel lymph node is excised. If other tissues containing radioactivity are removed, the patient effective dose will be reduced by about 50% and 6%, respectively, for the 1 day protocol and 2 day protocol. Although the doses are low compared with other radiological examinations, the results are informative for patients concerned about radiation exposure for this new imaging technique.

Curcumin inhibited the arylamines N-acetyltransferase activity, gene expression and DNA adduct formation in human lung cancer cells (A549)

It is well known that N-acetyltransferase (NAT) plays an important role in the arylamine metabolism. We analysed the response of A549 human lung cancer cells for N-acetylation of 2-aminofluorene (AF) to curcumin. After curcumin treatment, the NAT activity was examined by HPLC, AF-DNA adduct formation was examined by HPLC, and NAT gene expression by polymerase chain reaction were detected. The NAT activity in the human A549 cells and cytosols was suppressed by curcumin in a dose-dependent manner. The results also demonstrated that gene expression (NAT1 mRNA) in human lung A549 tumor cells was inhibited and decreased by curcumin. After the incubation of human lung A549 tumor cells with AF with or without curcumin co-treatment, the cells were recovered and DNA was prepared and hydrolyzed to nucleotides. The adducted nucleotides were extracted into butanol and analyzation of AF-DNA adducts was done by HPLC. The results also demonstrated that curcumin decreases AF-DNA adduct formation in the human lung A549 tumor cells.

A call to fins! Zebrafish as a gerontological model

Among the wide variety of model organisms commonly used for studies on aging, such as worms, flies and rodents, a wide research gap exists between the invertebrate and vertebrate model systems. In developmental biology, a similar gap has been filled by the zebrafish (Danio rerio). We propose that the zebrafish is uniquely suited to serve as a bridge model for gerontology. With high fecundity and economical husbandry requirements, large populations of zebrafish may be generated quickly and cheaply, facilitating large-scale approaches including demographic studies and mutagenesis screens. A variety of mutants identified in such screens have led to modelling of human disease, including cardiac disorders and cancer. While zebrafish longevity is at least 50% longer than in commonly used mouse strains, as an ectothermic fish species, its life span may be readily modulated by caloric intake, ambient temperature and reproductive activity. These features, coupled with a growing abundance of biological resources, including an ongoing genome sequencing project, make the zebrafish a compelling model organism for studies on aging.

Life spans and senescent phenotypes in two strains of Zebrafish (Danio rerio)

Zebrafish have become a widely used model organism in developmental biology research. In order to initiate an experimental foundation for aging studies, we have determined some basic gerontological parameters for populations of outbred zebrafish, and the golden sparse strain. Outbred zebrafish manifested a mean life span of about 42 months, with the longest living individual surviving for 66 months. The golden sparse populations had a mean life span of 36 months and a maximum longevity of 58 months. Skeletal length at death increased with age, suggestive of indeterminate growth. A common age-related phenotype was spinal curvature. Radiographic analysis excluded bony changes as the cause of the spinal curvature, suggesting muscle abnormalities as a primary mechanism. These data and a growing abundance of related biological resources suggest that the zebrafish may be a compelling model organism for studies on aging.

Fixation and decalcification of adult zebrafish for histological, immunocytochemical, and genotypic analysis

To facilitate the molecular analysis of tissues in adult zebrafish, we tested eight different fixation and decalcification conditions for the ability to yield DNA suitable for PCR and tissue immunoreactivity, following paraffin embedding and sectioning. Although all conditions resulted in good tissue histology and immunocytochemistry, only two conditions left the DNA intact as seen by PCR. The results indicate that zebrafish fixed in either 10% neutral buffered formalin or 4% paraformaldehyde, followed by decalcification in 0.5 M EDTA, is an easy and reliable method that allows molecular experiments and histology to be performed on the same specimen. The fixation and decalcification by Dietrich's solution permitted the PCR amplification of DNA fragments of 250 but not 1000 bp. Therefore, a protocol of formalin or paraformaldehyde fixation followed by decalcification with EDTA is broadly applicable to a variety of vertebrate tissues when excellent histological, immunocytochemical, and genotypic analyses may be simultaneously required.

The repertoire of Na,K-ATPase alpha and beta subunit genes expressed in the zebrafish, Danio rerio

We have identified a cohort of zebrafish expressed sequence tags encoding eight Na,K-ATPase alpha subunits and five beta subunits. Sequence comparisons and phylogenetic analysis indicate that five of the zebrafish alpha subunit genes comprise an alpha1-like gene subfamily and two are orthologs of the mammalian alpha3 subunit gene. The remaining alpha subunit clone is most similar to the mammalian alpha2 subunit. Among the five beta subunit genes, two are orthologs of the mammalian beta1 isoform, one represents a beta2 ortholog, and two are orthologous to the mammalian beta3 subunit. Using zebrafish radiation hybrid and meiotic mapping panels, we determined linkage assignments for each alpha and beta subunit gene. Na,K-ATPase genes are dispersed in the zebrafish genome with the exception of four of the alpha1-like genes, which are tightly clustered on linkage group 1. Comparative mapping studies indicate that most of the zebrafish Na,K-ATPase genes localize to regions of conserved synteny between zebrafish and humans. The expression patterns of Na,K-ATPase alpha and beta subunit genes in zebrafish are quite distinctive. No two alpha or beta subunit genes exhibit the same expression profile. Together, our data imply a very high degree of Na,K-ATPase isoenzyme heterogeneity in zebrafish, with the potential for 40 structurally distinct alpha/beta subunit combinations. Differences in expression patterns of alpha and beta subunits suggest that many of the isoenzymes are also likely to exhibit differences in functional properties within specific cell and tissue types. Our studies form a framework for analyzing structure function relationships for sodium pump isoforms using reverse genetic approaches.

Oral administration of collagen conjugated with cholera toxin induces tolerance to type II collagen and suppresses chondritis in an animal model of autoimmune ear disease

B10.RIII (H-2r) mice were orally administered cyanogen bromide peptide 11 (CB11) or cholera toxin B (CTB)-conjugated CB11 to induce tolerance in collagen-induced autoimmune ear disease. Oral administration of a high dosage of CB11 provided partial protection from chondritis. However, administration of a tiny amount of CTB-CB11 conjugate effectively suppressed chondritis. Oral administration of CTB-CB11 conjugate did not alter the stimulation of T cells in vitro or the fine specificities of B cells. The oral administration of CTB-CB11 caused a higher level of type II collagen-specific IgG and its subclass. Interestingly, increases of TH1 cytokine (interferon-gamma) in Peyer's patches and of TH1/TH2 cytokines (interleukin-2 and interleukin-4) in lymph nodes were detected in mice that had been fed CTB-CB11. An increase of CD8+ T cells in the Peyer's patches with a decrease of CD8+ T cells in lymph nodes was seen in mice that had been fed CTB-CB11. These results suggest that protection from chondritis by oral administration of minute amounts of CTB-CB11 conjugate can be achieved by a mechanism distinct from that of conventional oral tolerance induction.

Proto-oncogene Raf-1 as an autoantigen in Meniere's disease

The 28 kd protein extracted from the guinea pig inner ear membranous fraction, which reacted with sera from patients with Meniere's disease, has been subjected to microsequencing. Nineteen amino acids were obtained (IVQQFGFQRRASDDGKLTQ). A protein data bank search showed that this sequence corresponded to residues 41 to 60 of human Raf-1 protein. Sera from 16 of 27 patients with Meniere's disease showed reactivity to the recombinant purified glutathione-S-transferase-Raf-1 protein. These results support the hypothesis that a subgroup of patients who suffer from Meniere's disease, as well as some other kinds of autoimmune inner ear diseases, have an autoantibody against Raf-1 protein.

Centromere-linked microsatellite markers for linkage groups 3, 4, 6, 7, 13, and 20 of zebrafish (Danio rerio)

A large number of interesting mutations affecting development and organogenesis have been identified through genetic screens in zebrafish. Mapping of these mutations to a chromosomal region can be rapidly accomplished using half-tetrad analysis. However, knowledge of centromere-linked markers on every chromosome is essential to this mapping method. Centromeres on all 25 linkage groups have been mapped on the RAPD zebrafish genetic map. However, species specificity and the lack of codominance make RAPD markers less practical for mapping than microsatellite-based markers. On the microsatellite-based genetic map, centromere-linked markers have been identified for 19 linkage groups. No direct evidence has been published linking microsatellite markers to the centromeres of linkage groups 3, 4, 6, 7, 13, and 20. Therefore, we compared the microsatellite-based genetic map with the RAPD map to identify markers most likely linked to the centromeres of these 6 linkage groups. These candidate markers were tested for potential centromere linkage using four panels of half-tetrad embryos derived by early-pressure treatment of eggs from four different female zebrafish. We have identified microsatellite markers for linkage groups 3, 4, 6, 7, 13, and 20 to within 1.7 cM of their centromeres. These markers will greatly facilitate the rapid mapping of mutations in zebrafish by half-tetrad analysis.

Ethylnitrosourea induces neoplasia in zebrafish (Danio rerio)

The zebrafish (Danio rerio) has been successfully used to discover hundreds of genes involved in development and organogenesis. To address the potential of zebrafish as a cancer model, it is important to determine the susceptibility of zebrafish to tumors. Germ line mutations are most commonly induced for zebrafish mutant screens by exposing adult male zebrafish to the alkylating agent, ethylnitrosourea (ENU). To determine whether ENU induces tumors, we compared the incidence of tumors in ENU-treated fish with untreated controls. Interestingly, 18 of 18 (100%) fish mutagenized with either 2.5 or 3.0 mM ENU developed epidermal papillomas, which numbered 1 to 22 per fish, within 1 year of treatment. The induced epidermal lesions included epidermal hyperplasia, flat papillomas (0.2 to 1.2 mm), and pedunculated papillomas (1.2 to 8 mm in greatest dimension), but no skin cancers. Angiogenesis was evident in papillomas larger than approximately 1 mm. All but two papillomas contained the three cell types (keratinocytes, club, and mucous cells) of normal zebrafish epidermis; histologic variants lacked either club cells or mucous cells. Two cavernous hemangiomas and a single malignant peripheral nerve sheath tumor were also found in the treated fish. None of five untreated controls developed tumors. These studies establish the feasibility of the zebrafish as an experimental model for the study of skin tumors.

Murine model of autoimmune hearing loss induced by myelin protein P0

Myelin protein P0 has been identified as an autoantigen in inner ear diseases. In order to study autoimmune hearing loss, we performed brain stem auditory-evoked potential (BAEP) studies on P0-sensitized mice. Two P0-sensitized mice showed hunched posture, poor coat, loss of body weight, and abnormal walking with a waddling gait. About 25% of the P0-sensitized mice developed hearing loss. In the BAEP study, peak latencies of waves I, III, and V and the interpeak latency I-III were prolonged in the P0-sensitized hearing loss group of mice. Hearing thresholds were elevated in this group of mice in comparison with the control mice. Inflammatory cell infiltration was observed in the cochlear nerve region, and a reduced number of spiral ganglion cells was also detected. These results suggest that P0-sensitized mice are a useful model for studying autoimmune inflammation of the peripheral portion of the auditory system.

Alternation of one-lung and two-lung ventilations with the same single-lumen endobronchial tube during thoracoscopic surgery--a case report

One-lung ventilation is sometimes necessary for procedures performed through thoracotomy. Single lumen endobronchial tube has been used purposefully for one lung ventilation since 1931. However, there are no reports on intra-operative alternation of one-lung and two-lung ventilations through the same single lumen endobronchial tube as it can only provide unilateral lung ventilation. We present a case in whom a tube exchanger was used to readjust tube position so as to provide alternation of one-lung and two-lung ventilations in a thoracoscopic procedure.

Successful prevention of retrocochlear hearing loss in murine experimental allergic encephalomyelitis with T cell receptor Vbeta8-specific antibody

Experimental allergic encephalomyelitis is an animal model of a T cell-mediated autoimmune disease -- for example, multiple sclerosis. We demonstrated that mice with experimental allergic encephalomyelitis developed retrocochlear hearing loss, and that the lesion of the auditory pathway might be related to T cell receptor Vbeta8-expressing T cells. To investigate whether anti-Vbeta8 antibody could prevent hearing loss, we carried out brain stem auditory evoked potential testing, histologic examinations, and flow cytometry in antibody-treated and control myelin basic protein-immunized B10.PL mice. The antibody was administered just before immunization of myelin basic protein. The disease incidence and severity were significantly reduced in the mice injected with the antibody. The results of brain stem auditory evoked potential testing, histologic examinations, and flow cytometry indicated that the depletion of Vbeta8-expressing T cells brings the prevention of hearing loss, as well as prevention of other neurologic deficits. The development of T cell receptor-specific antibody therapy might help treat retrocochlear hearing loss in multiple sclerosis.

Agarose-embedded tissue arrays for histologic and genetic analysis

To facilitate the histologic analysis of large numbers of 7-day-old zebrafish (Danio rerio), a method has been developed to process them in agarose-embedded arrays. Using thin tissue sections, the morphology of cells and tissues can be examined microscopically to investigate a variety of biologic processes. Because of their small size, precise arrangement of the larvae is necessary to section them simultaneously. A technique was designed to embed groups of zebrafish larvae in a single plane in agarose before sectioning. Stained tissue sections of thousands of larvae can be examined efficiently using this embedding method. In addition to histologic analysis, PCR-based genotypic analysis of DNA from individual larval sections is also possible. This technique can be modified to accommodate any study that requires the histologic examination of many pieces of tissue.

Clonal expansion of T-cell receptor beta gene segment in the retrocochlear lesions of EAE mice

It has been reported that the T cell receptor V beta 8.2 (TcrbV8.2) gene segment is predominantly expressed in encephalomyelitic T cells responding to myelin basic protein (MBP) in experimental allergic encephalomyelitis (EAE) mice. We have demonstrated retrocochlear hearing loss in EAE mice in previous studies. Administration of a monoclonal antibody specific to the T cell receptor V beta 8 (TcrbV8) subfamily prevented both this type of hearing loss and the central nerve disease. In this study, we examined the role of the TcrbV8.2 gene segment in the retrocochlear lesions of EAE mice. A clonal expression of T cell receptor beta chain gene segment (TcrbV8.2-TcrbD2-TcrbJ2.7) was identified in the retrocochlear lesions. The TcrbV8.2 gene segment appears to recombine only with TcrbJ2.1 (32.1%) and TcrbJ2.7 (67.9%) gene segments. The TcrbJ2.7 gene segment has also been previously identified as the dominant TcrbJ gene in the lymph nodes of EAE mice. Only TcrbD2, with a length of 4 amino acids, was observed recombining with these TcrbV8.2 sequences. G and C nucleotides are predominantly expressed at the N regions between the V-D and D-J junctions. This dominant TcrbV gene segment (TcrbV8.2-TcrbD2-TcrbJ2.7) observed in the retrocochlear lesions has been identified in the MBP-specific T cells from the lymph nodes of EAE mice. These results suggest that a small subset of antigen-specific T cells migrate to, and expand at, the retrocochlear lesions, which leads to hearing loss.

Transient bone marrow oedema: a variant pattern of sacral insufficiency fractures

A 71-year-old woman presenting with severe low back pain was found to have a large oval area of increased sacral uptake on Tc-99m MDP scan, with corresponding T1-hypointense and T2-hyperintense areas on magnetic resonance (MR) images, highly suggestive of malignancy. Open biopsies showed only callus formation. The patient responded clinically to conservative measures, with twice-repeated follow-up Tc-99m MDP and MR scans documenting resolution of transient bone marrow oedema. We suggest that this form of marrow oedema represents a variant pattern of sacral insufficiency fractures.

Genetic dissection of vertebrate processes in the zebrafish: a comparison of uniparental and two-generation screens

Genetic dissection is used to identify important genes in biological processes and is accomplished through the generation and study of mutations in model organisms. In diploid organisms, recessive mutations must be rendered hemizygous or homozygous for the mutant phenotype to be detected. In zebrafish (Danio rerio), this can be accomplished in two ways: (i) crosses between siblings who are potential carriers (in two-generation screens) and (ii) the generation of uniparental progeny. Two-generation screens have been the most productive to date but require substantial resources. However, uniparental screens involving haploids and half-tetrads (products of meiosis I) have also been productive, and require more modest resources. In genetic screens, the fraction of an average genome that is heterozygous (heterozygosity index) is inversely proportional to the likelihood that separate recessive mutations will be homozygous at the same time. Heterozygosity indices for haploid, half-tetrad, and two-generation screens are 0, 66, and 87.5%, respectively. Family sizes required to minimize bias in half-tetrad screens are also calculated. We conclude that gynogenetic half-tetrad screens are genetically robust and technically accessible to the independent researcher. The increasingly powerful genetic and experimental tools available for work with zebrafish can be used to address a broad range of questions in vertebrate biology.

House dust mite-induced sensitivity in mice

Sensitivity induced by house dust mite (HDM) extract in mice was investigated in this study. Sensitized B10.RIII mice (H-2r background) had T-cell proliferative responses to HDM extract in vitro and an HDM-specific IgE response. When mice were immunized by injection and intranasal inhalation with HDM extract, a histologic study showed eosinophils and mononuclear cell infiltration in the lung tissue and bronchial wall. Tcr alphabeta-positive cells were also found in the cell infiltration area of the lung lesions. In the control mice that were immunized by injection or intranasal inhalation (but not both), we did not observe cell accumulation in the lung tissue or in the bronchial wall. Epitope studies suggest that T cells recognize multiple epitopes. Molecular analysis of these HDM-specific T-cell hybridoma clones suggest that T-cell receptor use is restricted to members of the V alpha 8 and Vbeta 6 subfamilies.

TCRV and TCRJ gene usage in MBP responding T cells from (B10.PL x PL/J)F1 mice is biased towards that of B10.PL mice

We analyzed myelin basic protein (MBP) specific T cell hybridoma clones from (B10.PL x PL/J)F1 mice. MBP-reacting T cell hybridomas from F1 mice preferentially expressed B10.PL TcraV2.3 (53%) and B10.PL TcraV4.2 (13%) with minor expression of TcraV4.4 (13%) gene segments. A dominant expression of TcrbV8.2 (73%) accompanying with TcrbV8.1 (20%) and TcrbV13 (7%) gene segments have been identified in these MBP-reacting T cell hybridomas from F1 mice. There was less restrictive but non-random usage of the TcraJ and TcrbJ gene segments. Overall, the MBP-reacting T cell hybridomas from (B10.PL x PL/J)F1 mice were dominated by the MBP-reacting T cell pattern seen in B10.PL mice.

Genetic dissection of vertebrate processes in the zebrafish: a comparison of uniparental and two-generation screens

Genetic dissection is used to identify important genes in biological processes and is accomplished through the generation and study of mutations in model organisms. In diploid organisms, recessive mutations must be rendered hemizygous or homozygous for the mutant phenotype to be detected. In zebrafish (Danio rerio), this can be accomplished in two ways: (i) crosses between siblings who are potential carriers (in two-generation screens) and (ii) the generation of uniparental progeny. Two-generation screens have been the most productive to date but require substantial resources. However, uniparental screens involving haploids and half-tetrads (products of meiosis I) have also been productive, and require more modest resources. In genetic screens, the fraction of an average genome that is heterozygous (heterozygosity index) is inversely proportional to the likelihood that separate recessive mutations will be homozygous at the same time. Heterozygosity indices for haploid, half-tetrad, and two-generation screens are 0, 66, and 87.5%, respectively. Family sizes required to minimize bias in half-tetrad screens are also calculated. We conclude that gynogenetic half-tetrad screens are genetically robust and technically accessible to the independent researcher. The increasingly powerful genetic and experimental tools available for work with zebrafish can be used to address a broad range of questions in vertebrate biology.

Patient-ventilator flow dyssynchrony: flow-limited versus pressure-limited breaths

OBJECTIVES

Patient-ventilator flow dyssynchrony occurs when ventilator flow delivery is insufficient to meet patient demands. If sufficiently severe, flow dyssynchrony can produce significant imposed loads on ventilatory muscles. Flow dyssynchrony can be improved by increasing ventilator flow delivery. We hypothesized that the variable flow pressure-limited breath would be a better approach for matching patient flow demands than adjusting a set flow on a conventional volume-cycled breath.

DESIGN

Clinical interventional study.

SETTING

Medical intensive care unit.

PATIENTS

Sixteen stable, mechanically ventilated patients receiving volume-cycled assist-control ventilation.

INTERVENTIONS

Flow dyssynchrony was produced by reducing the set flow by 50%. Dyssynchrony was quantified by measuring the esophageal pressure time product during the assisted breath. Two strategies were then employed in an attempt to reduce the dyssynchrony. One strategy was to increase flow back to the initial set flow and then further increase flow by an additional 25% (VI strategy). The other strategy was to use a pressure-limited breath feature coupled to a volume assist breath (the P strategy). With the P strategy, the pressure limit was set at 75% and 100% of the static elastic recoil pressure at end-inspiration.

MEASUREMENTS AND MAIN RESULTS

Pressure time product, intrinsic positive end-expiratory pressure, and the ventilatory pattern were measured with each strategy and were analyzed by analysis of variance. Induced baseline flow dyssynchrony, as measured by the pressure time product, was > 5 cm H2O/sec in ten of 16 patients. This dyssynchrony was significantly reduced by both the VI strategy and the P strategy, although the P strategy appeared to be more effective in those patients with the greatest baseline dyssynchrony. Baseline inspiratory time was also shortened by both the VI strategy and the P strategy; the VI strategy shortened baseline inspiratory time more than the P strategy. Baseline tidal volume, frequency, and intrinsic positive end-expiratory pressure were only minimally affected by either strategy.

CONCLUSION

The pressure-limited, variable-flow approach to ventilator gas delivery appears to be more responsive to a vigorous patient effort than a fixed-flow approach.

Molecular basis of type II collagen autoimmune disease: observations of arthritis, auricular chondritis and tympanitis in mice

A type II collagen autoimmune response results in arthritis, auricular chondritis and tympanosclerosis in humans and animals. The purpose of this study is to further define the molecular and pathogenic events involved in these lesions in rodents. Type II collagen fragment CB11-specific monoclonal antibodies induced lesions in joints, ear lobes and tympanic membranes. In immunized mice, the thickness of tympanic membranes increased to two- to fourfold normal size. Electron micrography showed that the arrangement of collagen fibers is irregular in both radial and auricular layers, containing fibroblasts, a homogeneous material resembling low-density cholesterol crystals and cell infiltration. The mice with auricular chondritis had lymphocytes expressing V beta-8 T cell receptor (TCR) in arthritic joints and lymphocytes expressing V beta-6 TCR in ear lobe lesions. A monoclonal antibody specific to the TCR V beta-8 subfamily suppressed the onset of arthritis. Sequence analyses of the V beta structure of TCR involved in the lesions confirm the immunohistologic study.

Applied PEEP during pressure support reduces the inspiratory threshold load of intrinsic PEEP

OBJECTIVES

Mechanical ventilation in patients with obstructive airway disease (OAD) is associated with the development of dynamic hyperinflation and intrinsic positive end-expiratory pressure (PEEPi). One of the effects of this form of PEEPi is to act as an inspiratory threshold load that can produce ineffective breath triggering, dyspnea, and muscle fatigue. Recently it has been shown that applying PEEP in the ventilator circuit can reduce this imposed triggering load. We wished to investigate this further by studying patients with OAD being weaned with pressure support (PS) ventilation. Our first objective was to determine the prevalence and magnitude of this form of PEEPi in OAD patients who were clinically judged to be capable of triggering mechanical ventilatory breaths. Our second objective was to attempt to reduce the triggering load by applying circuit PEEP and then observe the response of patient-ventilator interactions during the patient-triggered, pressure-limited PS breath.

DESIGN

Thirteen random patients with OAD who were receiving PS ventilation were studied by measuring airway pressures, airway gas flow, baseline esophageal pressure, esophageal pressure time products (PTP), and esophageal pressure changes before ventilator gas delivery began (delta Pes taken to represent PEEPi). Measurements were made at baseline and after stepwise increases in circuit PEEP up to the PEEPi.

RESULTS

We found measurable PEEPi in all patients (average +/- SD of 9.54 +/- 4.3 cm H2O) and it was > 10 cm H2O in seven patients. As would be predicted, we observed progressive reductions in PEEPi as applied PEEP was given. We also observed that the component of patient effort (PTP) related to overcoming PEEPi also decreased, but the PTP related to tidal volume (VT) did not. The VT associated with the set PS thus did not change with application of PEEP, nor did the breathing frequency.

CONCLUSION

PEEPi is common in OAD patients receiving mechanical ventilatory support. The imposed triggering load from PEEPi can be offset to large extent by circuit PEEP approaching the baseline PEEPi. Although total patient effort substantially falls with applied PEEP, the patient effort that combine with PS to effect VT does not.

Antibodies against inner-ear proteins in the sera of patients with inner-ear diseases

Sera from patients with various inner-ear diseases, especially Ménière's disease, were investigated by Western blot against guinea pig inner-ear proteins. Of 45 patients, 24 (53%) with various inner-ear diseases had antibodies against inner-ear proteins, compared with 0 of 10 (0%) in control subjects without inner-ear diseases. Of the 10 proteins that showed a positive reaction with patient sera, the 28-kD band was unique in that it appeared only in the membranous fraction of the inner ear and was highly positive (28%) in reaction with Ménière's disease patient sera. The results in the present study with proteins extracted from guinea pig inner ear were consistent with our previous study using proteins from human inner ear, suggesting that the 28-kD protein may be a candidate for detecting autoimmune inner-ear disease.

Brain stem auditory-evoked potentials of mice with experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an experimental model for multiple sclerosis. In order to study autoimmune retrocochlear hearing loss, we performed brain stem auditory-evoked potential (BAEP) studies on EAE mice. The EAE was induced in B10.PL and (PL/J x SJL)F1 mice. In the BAEP study, all of the peak and interpeak latencies were prolonged significantly in the diseased mice. Hearing thresholds were slightly elevated in the immunized mice during the acute phase. Inflammatory and phagocytic cell infiltration, demyelination, and V beta 8.1, 8.2 T-cell receptor-positive cells were observed in the cochlear nerves or their proximity by histologic study. It is suggested that immunologic reactions identified with EAE also occurred in the cochlear nerve, and that these reactions were responsible for the hearing problems. It appears that EAE is a useful model system for studying autoimmune insults on the neural portion of the auditory system.

Factors affecting fidelity of DNA synthesis during PCR amplification of d(C-A)n.d(G-T)n microsatellite repeats

The susceptibility of microsatellite DNA sequences to insertions and deletions in vivo makes them useful for genetic mapping and for detecting genomic instability in tumors. An in vitro manifestation of this instability is the production of undesirable frameshift products during amplification of (dC-dA)n x (dG-dT)n microsatellites in the polymerase chain reaction (PCR). These products differ from the primary product by multiples of 2 nucleotides. We have tested the hypothesis that factors known to affect the fidelity of DNA synthesis may affect (dC-dA)n x (dG-dT)n frameshifting during the PCR. Neither modifications of pH, dNTP concentration, and Mg++ concentration using Amplitaq, nor the use of thermophilic DNA polymerases including UITma, Pfu, Vent and Deep Vent significantly decreased the production of frameshift products during amplification. However, 3'-->5' exonuclease activity in thermophilic DNA polymerases inhibited the accumulation of PCR products containing non-templated 3' terminal nucleotides. Most interestingly, extension temperatures of 37 degrees C during amplification using the thermolabile DNA polymerases Sequenase 1.0, Sequenase 2.0, and 3'-->5' exonuclease-deficient Klenow fragment greatly decreased the production of frameshift products. This method can improve the resolution of heterozygous or mutant (dC-dA)n x (dG-dT)n alleles differing in size by one or two repeat units.

Spontaneous cervical subcutaneous and mediastinal emphysema secondary to occult sigmoid diverticulitis

We present a case of spontaneous mediastinal and subcutaneous cervical emphysema due to perforation of an occult sigmoid diverticulitis. Mediastinal emphysema should alert the physician to the possibility of retroperitoneal gastrointestinal perforation, even in patients without signs of distinct peritoneal irritation.

Microsatellite-centromere mapping in the zebrafish (Danio rerio)

Ten (CA)n microsatellite simple sequence repeat (SSR) markers, 1, 2, 12, 14, 16, 18, 20, 22, 26, and 29, were used to show high chiasma interference and to determine centromere-marker map distances in the zebrafish (Danio rerio). Of these, SSR 12 exhibited no recombinant tetratypes among 175 half-tetrad embryos, placing this marker within 1 cM of the centromere of Linkage Group XVII. Fractions of heterozygous half-tetrads for the remaining nine markers ranged from 0.64 to 0.89. Of these, six recombinant fractions were more than 0.67 (P < 0.05), indicating strong chiasma interference during female meiosis in the zebrafish. Consistent with previous mapping data, SSRs 2 and 20 of Linkage Group VI were tightly linked. Half-tetrad analysis will allow the mapping of the remaining centromeres and may be useful in the mapping of new genes and mutations in the zebrafish.

Substrate specificity, gene structure, and tissue-specific distribution of multiple human 3 alpha-hydroxysteroid dehydrogenases

We have expressed in Escherichia coli functionally active proteins encoded by two human cDNAs that were isolated previously by using rat 3 alpha-hydroxysteroid dehydrogenase cDNA as the probe. The expressed proteins catalyzed the interconversion between 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha,17 beta-diol. Therefore, we name these two enzymes type I and type II 3 alpha-hydroxysteroid dehydrogenases. The type I enzyme has a high affinity for dihydrotestosterone, whereas the type II enzyme has a low affinity for the substrate. The tissue-specific distribution of these two enzymes was determined by reverse transcription polymerase chain reaction using gene-specific oligonucleotide primers. The mRNA transcript of the type I enzyme was found only in the liver, whereas that of the type II enzyme appeared in the brain, kidney, liver, lung, placenta, and testis. The structure and sequence of the genes encoding these two 3 alpha-hydroxysteroid dehydrogenases were determined by analysis of genomic clones that were isolated from a lambda EMBL3 SP6/T7 library. The genes coding for the type I and type II enzymes were found to span approximately 20 and 16 kilobase pairs, respectively, and to consist of 9 exons of the same sizes and boundaries. The exons range in size from 77 to 223 base pairs (bp), whereas the introns range in size from 375 bp to approximately 6 kilobase pairs. The type I gene contains a TATA box that is located 27 bp upstream of multiple transcription start sites. In contrast, the type II gene contains two tandem AP2 sequences juxtaposed to a single transcription start site.