Antimicrobial use and stewardship practices on Australian beef feedlots

OBJECTIVE

Improving antimicrobial stewardship in the livestock sector requires an understanding of the motivations for antimicrobial use and the quantities consumed. However,detailed information on antimicrobial use in livestock sectors is lacking. This cross-sectional study aimed to better understand antimicrobial use in the beef feedlot sector in Australia.

DESIGN

A self-administered questionnaire asking about antimicrobial use and reasons for use was designed and mailed to beef feedlot operators in Australia. Respondents were asked to report the percentage of animals treated, purpose of use, and disease conditions targeted for 26antimicrobial agents.

RESULTS

In total, 83 of 517 (16.1%) beef feedlot operators completed the survey. Monensin (61.0%of respondents) and virginiamycin (19.5%of respondents) were the most commonly reported in-feed antimicrobials. In-feed antimicrobial agents were most frequently used by respondents for treatment of gastrointestinal diseases (52.8%). Antimicrobials were used for growth promotion by 42.1% of respondents, with most (85.7%) reporting the use of ionophores(a group of compounds not used in human medicine). Short-acting penicillin(69.1%), short-acting oxytetracycline, and tulathromycin (both 57.3%) werethe most common injectable antimicrobial agents used. Injectable antimicrobials were most frequently used to treat respiratory (72.3%) and musculoskeletal (67.5%) conditions.

CONCLUSION

Overall,the use of antimicrobials was appropriate for the purpose indicated, and there was a strong preference for drugs of low-importance in human medicine. The data described here stand to be a strong influence on the implementation of an antimicrobial stewardship program in the sector.

First Report of White Pine Blister Rust on Rocky Mountain Bristlecone Pine

White pine blister rust caused by Cronartium ribicola was introduced into North America in the early 20th century and is spreading throughout the range of five-needle pines. In northern Colorado, this pathogen was first observed in 1998 on limber pine (Pinus flexilis) (1). It has not been reported on Rocky Mountain or Great Basin bristlecone pine (Pinus aristata and P. longaeva, respectively) in nature. However, Rocky Mountain bristlecone pine is susceptible to the disease when artificially inoculated (2). In October 2003, a Rocky Mountain bristlecone pine was found infected with C. ribicola in the Great Sand Dunes National Monument, Alamosa County, Colorado. Seven branch cankers were observed on the tree. Cankers ranged in length from 15 to 41 cm and were estimated to be approximately 5 to 7 years old. Distinct C. ribicola branch symptoms were observed, including flagging, spindle-shaped swellings, and 6 mm long aecial scars. A branch was deposited at the Colorado State Herbarium. Microscopic examination of spores within remnant aecial blisters revealed aeciospores characteristic of C. ribicola (yellow-orange, ellipsoid, verrucose, and 19 × 25 μm). Cankers were only observed on one bristlecone pine. However, most limber pines in the area were infected with C. ribicola, including a limber pine less than 1 m from the infected bristlecone pine. To our knowledge, this is the first report that shows Rocky Mountain bristlecone pine can become infected naturally, and the pathogen is further south in Colorado on limber pine than previously reported. These observations suggest the need for a more complete investigation of this disease on bristlecone pines. References: (1) D. W. Johnson and W. R. Jacobi. Plant Dis. 84:595, 2000. (2) B. R. Stephan, Allg. Forst Z. 28:695, 1985.

CENP-A is phosphorylated by Aurora B kinase and plays an unexpected role in completion of cytokinesis

Aurora B is a mitotic protein kinase that phosphorylates histone H3, behaves as a chromosomal passenger protein, and functions in cytokinesis. We investigated a role for Aurora B with respect to human centromere protein A (CENP-A), a centromeric histone H3 homologue. Aurora B concentrates at centromeres in early G2, associates with histone H3 and centromeres at the times when histone H3 and CENP-A are phosphorylated, and phosphorylates histone H3 and CENP-A in vitro at a similar target serine residue. Dominant negative phosphorylation site mutants of CENP-A result in a delay at the terminal stage of cytokinesis (cell separation). The only molecular defects detected in analysis of 22 chromosomal, spindle, and regulatory proteins were disruptions in localization of inner centromere protein (INCENP), Aurora B, and a putative partner phosphatase, PP1gamma1. Our data support a model where CENP-A phosphorylation is involved in regulating Aurora B, INCENP, and PP1gamma1 targeting within the cell. These experiments identify an unexpected role for the kinetochore in regulation of cytokinesis.

Specification of kinetochore-forming chromatin by the histone H3 variant CENP-A

The mechanisms that specify precisely where mammalian kinetochores form within arrays of centromeric heterochromatin remain largely unknown. Localization of CENP-A exclusively beneath kinetochore plates suggests that this distinctive histone might direct kinetochore formation by altering the structure of heterochromatin within a sub-region of the centromere. To test this hypothesis, we experimentally mistargeted CENP-A to non-centromeric regions of chromatin and determined whether other centromere-kinetochore components were recruited. CENP-A-containing non-centromeric chromatin assembles a subset of centromere-kinetochore components, including CENP-C, hSMC1, and HZwint-1 by a mechanism that requires the unique CENP-A N-terminal tail. The sequence-specific DNA-binding protein CENP-B and the microtubule-associated proteins CENP-E and HZW10 were not recruited, and neocentromeric activity was not detected. Experimental mistargeting of CENP-A to inactive centromeres or to acentric double-minute chromosomes was also not sufficient to assemble complete kinetochore activity. The recruitment of centromere-kinetochore proteins to chromatin appears to be a unique function of CENP-A, as the mistargeting of other components was not sufficient for assembly of the same complex. Our results indicate at least two distinct steps in kinetochore assembly: (1) precise targeting of CENP-A, which is sufficient to assemble components of a centromere-prekinetochore scaffold; and (2) targeting of kinetochore microtubule-associated proteins by an additional mechanism present only at active centromeres.

Animal cytokinesis: breaking up is hard to do

Recent studies have shed new light on how the physical association between sister cells is severed at the end of cytokinesis while the membrane is resealed. Comparisons with yeast suggest that daughter cell shape may feed back to regulate cytokinesis through the Bub2 checkpoint system.

Large-scale chromatin fibers of living cells display a discontinuous functional organization

We investigated the chromatin organization of living cells with a combination of recently developed approaches for histone and DNA labeling. Nucleosomal DNA was labeled with a histone H2B-GFP (green fluorescent protein) fusion protein and the chromatin organization of living HeLa cells was analyzed by high resolution confocal microscopy. Within the perinuclear and perinucleolar regions chromatin was organized into large-scale fibers of 2 to 8 microm in length and 300 to 500 nm in diameter. Within the nuclear interior we observed similar large-scale fibers, but in addition focal as well as diffuse forms of organization. Comparison with standard labeling and detection procedures revealed major differences in the chromatin organization observed. Chromatin organization revealed by the distribution of histone H2B-GFP was directly compared with the functional organization of chromatin by Cy3-dUTP labeling of DNA replicating at a specific time. DNA regions replicating at a specific time display characteristic physical and functional properties. Analysis of Cy3-labeled foci revealed that they are associated with all three forms of chromatin organization (fibrillar, focal and diffuse). In particular, Cy3-labeled foci appeared as discontinuous regions of large-scale fibers. These results demonstrate that large-scale chromatin fibers have discontinuous functional characteristics.

A solid foundation: functional specialization of centromeric chromatin

Centromeres provide a distinctive mechanical function for the chromosomes as the site of kinetochore assembly and force generation in mitosis and meiosis. Recent studies show that a unique form of chromatin, based on the histone-H3-like protein CENP-A and homologues, provides a conserved foundation for this mechanical chromatin domain. CENP-A plays a role in templating kinetochore assembly and may be a central element in the epigenetic maintenance of centromere identity. Cohesion at the centromere, intimately linked to kinetochore assembly, is required for integrating spindle forces exerted across the centromere and for establishing the bipolar geometry of sister kinetochores.

Degradation of nucleosome-associated centromeric histone H3-like protein CENP-A induced by herpes simplex virus type 1 protein ICP0

Cells infected by herpes simplex virus type 1 in the G2 phase of the cell cycle become stalled at an unusual stage of mitosis defined as pseudoprometaphase. This block correlates with the viral immediate-early protein ICP0-induced degradation of the centromere protein CENP-C. However, the observed pseudoprometaphase phenotype of infected mitotic cells suggests that the stability of other centromere proteins may also be affected. Here, we demonstrate that ICP0 also induces the proteasome-dependent degradation of the centromere protein CENP-A. By a series of Western blot and immunofluorescence experiments we show that the endogenous 17-kDa CENP-A and an exogenous tagged version of CENP-A are lost from centromeres and degraded in infected and transfected cells as a result of ICP0 expression. CENP-A is a histone H3-like protein associated with nucleosome structures in the inner plate of the kinetochore. Unlike fully transcribed lytic viral DNA, the transcriptionally repressed latent herpes simplex virus type 1 genome has been reported to have a nucleosomal structure similar to that of cellular chromatin. Because ICP0 plays an essential part in controlling the balance between the lytic and latent outcomes of infection, the ICP0-induced degradation of CENP-A is an intriguing feature connecting different aspects of viral and/or cellular genome regulation.

Differential regulation of CENP-A and histone H3 phosphorylation in G2/M

After DNA replication, cells condense their chromosomes in order to segregate them during mitosis. The condensation process as well as subsequent segregation requires phosphorylation of histone H3 at serine 10. Histone H3 phosphorylation initiates during G2 in pericentric foci prior to H3 phosphorylation in the chromosome arms. Centromere protein A (CENP-A), a histone H3-like protein found uniquely at centromeres, contains a sequence motif similar to that around H3 Ser10, suggesting that CENP-A phosphorylation might be linked to pericentric initiation of histone H3 phosphorylation. To test this hypothesis, we generated peptide antibodies against the putative phosphorylation site of CENP-A. ELISA, western blot and immunocytochemical analyses show that CENP-A is phosphorylated at the shared motif. Simultaneous co-detection demonstrates that phosphorylation of CENP-A and histone H3 are separate events in G2/M. CENP-A phosphorylation occurs after both pericentric initiation and genome-wide stages of histone H3 phosphorylation. Quantitative immunocytochemistry reveals that CENP-A phosphorylation begins in prophase and reaches maximal levels in prometaphase. CENP-A phosphoepitope reactivity is lost during anaphase and becomes undetectable in telophase cells. Duplication of prekinetochores, detected as the doubling of CENP-A foci, occurs prior to complete histone H3 phosphorylation in G2. Mitotic phosphorylation of histone H3-family proteins shows tight spatial and temporal control, occurring in three phases: (1) pericentric H3 phosphorylation, (2) chromosome arm H3 phosphorylation and (3) CENP-A phosphorylation at kinetochores. These observations reveal new cytological landmarks characteristic of G2 progression.

Chromatin assembly at kinetochores is uncoupled from DNA replication

The specification of metazoan centromeres does not depend strictly on centromeric DNA sequences, but also requires epigenetic factors. The mechanistic basis for establishing a centromeric "state" on the DNA remains unclear. In this work, we have directly examined replication timing of the prekinetochore domain of human chromosomes. Kinetochores were labeled by expression of epitope-tagged CENP-A, which stably marks prekinetochore domains in human cells. By immunoprecipitating CENP-A mononucleosomes from synchronized cells pulsed with [(3)H]thymidine we demonstrate that CENP-A-associated DNA is replicated in mid-to-late S phase. Cytological analysis of DNA replication further demonstrated that centromeres replicate asynchronously in parallel with numerous other genomic regions. In contrast, quantitative Western blot analysis demonstrates that CENP-A protein synthesis occurs later, in G2. Quantitative fluorescence microscopy and transient transfection in the presence of aphidicolin, an inhibitor of DNA replication, show that CENP-A can assemble into centromeres in the absence of DNA replication. Thus, unlike most genomic chromatin, histone synthesis and assembly are uncoupled from DNA replication at the kinetochore. Uncoupling DNA replication from CENP-A synthesis suggests that regulated chromatin assembly or remodeling could play a role in epigenetic centromere propagation.

Annexation of the interchromosomal space during viral infection

The nucleus is known to be compartmentalized into units of function, but the processes leading to the spatial organization of chromosomes and nuclear compartments are not yet well defined. Here we report direct quantitative analysis of the global structural perturbations of interphase chromosome and interchromosome domain distribution caused by infection with herpes simplex virus-1 (HSV-1). Our results show that the peripheral displacement of host chromosomes that correlates with expansion of the viral replication compartment (VRC) is coupled to a twofold increase in nuclear volume. Live cell dynamic measurements suggest that viral compartment formation is driven by the functional activity of viral components and underscore the significance of spatial regulation of nuclear activities.

CENP-E forms a link between attachment of spindle microtubules to kinetochores and the mitotic checkpoint

Here we show that suppression of synthesis of the microtubule motor CENP-E (centromere-associated protein E), a component of the kinetochore corona fibres of mammalian centromeres, yields chromosomes that are chronically mono-orientated, with spindles that are flattened along the plane of the substrate. Despite apparently normal microtubule numbers and the continued presence at kinetochores of other microtubule motors, spindle poles fragment in the absence of CENP-E, which implicates this protein in delivery of components from kinetochores to poles. CENP-E represents a link between attachment of spindle microtubules and the mitotic checkpoint signalling cascade, as depletion of this motor leads to profound checkpoint activation, whereas immunoprecipitation reveals a nearly stoichiometric association of CENP-E with the checkpoint kinase BubR1 during mitosis.

First Report of White Pine Blister Rust in Nevada

White pine blister rust, caused by Cronartium ribicola Fisch., was found in 1997 infecting white pines (genus Pinus, subgenus Strobus) at two locations in the Carson Range of western Nevada. Rust incidence, infection age, damage to trees, rust phenology, and host distribution were evaluated at one of these locations and a nearby location in California in 1998. At the first location (39.3°N, 119.9°W), C. ribicola was found infecting 24 of 49 whitebark pines (P. albicaulis Engelm.) near Mt. Rose Summit on Highway 27 at 2,710 m elevation, ≈6 km northeast of Incline Village, Washoe County, NV. Among infected trees, 33% had only branch cankers, 54% had live stem cankers, and 12% had stem cankers that had killed portions of trees distal to cankers. No trees had died from infection. At the second location (39.1°N, 119.9°W), we found only 6 of 50 (12%) infected western white pines (P. monticola Dougl.) near Genoa Peak (≈2,750 m elevation), 3 km east of Lake Tahoe, Douglas County, NV; however, stem cankers occurred on 4 of the 6 infected trees. In September 1998, whitebark pines at Mt. Rose and Tahoe Meadows (2,550 m elevation, 1.5 km southwest of Mt. Rose Summit) were examined, and the following was observed: (i) aeciospore production was at its peak, indicating that sporulation can occur exceptionally late in the season in this region; (ii) signs of blister rust infection were absent on the telial hosts of C. ribicola (Ribes cereum, R. montigenum, and R. nevadense) at both locations; (iii) ≈80% of the cankers occurred on host wood produced in 1978 and 1979; and (iv) the oldest cankers originated on wood produced in 1968 and the youngest on wood produced in 1980. In October 1998, infected western white pines were examined at a location (2,650 m elevation) ≈30 km north of Lake Tahoe on Babbitt Peak, Sierra County, CA (39.6°N, 120.1°W). At this location, no trees had died from infection, fresh aeciospores were abundant on live cankers, R. montigenum and R. cereum were present but did not show signs of infection, and 19 of 20 cankers examined were on wood produced between 1978 and 1980. White pine blister rust was not found at any of 10 other locations examined throughout Nevada from 1995 to 1997. This is believed to be the first documented report of C. ribicola infecting white pines in Nevada and the easternmost extension of blister rust in the Sierra Nevada Region. These observations suggest that our understanding of blister rust spread and infection dynamics east of the Sierra Nevada crest is incomplete and that future surveys and research in this region must address, among other issues, timing of aeciospore production on pine, and the possibility of blister rust spread into the Great Basin.

The mammalian centromere: structural domains and the attenuation of chromatin modeling

The centromere-kinetochore complex can be divided into distinct domains based on structure and function. Previous work has used CREST auto-antibodies with various microscopic techniques to map the locations of proteins within the centromere-kinetochore complex and to analyze the maturation of prekinetochores before mitosis. Here we have focused on the centromere-specific histone Centromere Protein (CENP)-A and its spatial relationship to other histones and histone modifications found in condensed chromatin. We demonstrate that the phosphorylation of histone H3 is essentially excluded from a specific region of centromeric chromatin, defined by the presence of CENP-A. Interspersion of CENP-B with phosphorylated H3 in the inner centromere indicates that the exclusion of H3 modification is not a general property of alpha-satellite DNA. We also demonstrate that these regions are functionally distinct by fragmenting mitotic chromatin into motile centromere-kinetochore fragments that contain CENP-A with little or no phosphorylated H3 and nonmotile fragments that contain exclusively phosphorylated H3. The sequence of CENP-A diverges from H3 in a number of key residues involved in chromosome condensation and in transcription, potentially allowing a more specialized chromatin structure within centromeric heterochromatin, on which kinetochore plates may nucleate and mature. This specialized centromere subdomain would be predicted to have a very tight and static nucleosome structure as a result of the absence of H3 phosphorylation and acetylation.

CENP-A associated complex satellite DNA in the kinetochore of the Indian muntjac

The centromere/kinetochore complex is a chromosomal assembly that mediates chromosome motility and mitotic regulation by interacting with microtubules of the mitotic spindle apparatus. Centromere protein A (CENP-A) is a histone H3 homolog that is concentrated in the chromatin of the inner kinetochore plate of human chromosomes. To identify DNA sequences associated with the inner kinetochore plate, we used anticentromere autoantibodies to immunoprecipitate CENP-A associated chromatin selectively from Indian muntjac fibroblasts. DNA was cloned from immunoprecipitated CENP-A- associated chromatin and characterized by DNA sequence and hybridization analyses. A novel centromeric satellite DNA sequence was identified and shown by fluorescence in situ hybridization analysis to be present at all centromeres of the Indian muntjac. This satellite DNA constitutes a 972 bp monomer repeat and shows partial homology with satellite II DNA of the white-tailed deer. Southern blot analysis of muntjac genomic DNA suggests that this satellite DNA is present in repetitive tandem arrays and contains complex internal arrangements. In conjunction with previous work showing the association of CENP-A with human alpha-satellite DNA, we conclude that the mammalian inner kinetochore plate contains a unique form of chromatin that contains CENP-A in association with complex satellite DNA.

Using time-lapse confocal microscopy for analysis of centromere dynamics in human cells

Using these methods we have shown that the alpha-satellite domain of the human centromere behaves as an elastic element, stretching in response to spindle forces applied during prometaphase and metaphase (Shelby et al., 1996). These data complement previous observations of centromere stretching during mitosis (e.g., Skibbens et al., 1993) by demonstrating a specific molecular compartment within the centromere, the satellite heterochromatin domain, that supports this strain. Centromere stretching reports on the net force applied across the centromere during mitosis and the availability of a fluorescence-based assay system in human cells provides a robust assay system to complement the elegant DIC-based methods that have been perfected using marsupial and newt cell cultures (Cassimeris et al., 1990; Skibbens et al., 1993, 1995; Rieder et al., 1994). Current applications of this method are directed toward examining the relationship between centromere tension and microtubule dynamics using pharmacological approaches and the behavior of kinetochore-associated regulatory proteins, such as Mad2 and Bub1 (Li and Benezra, 1996; Chen et al., 1996; Taylor and McKeon, 1997), as a function of centromere distortion. In addition, GFP-labeled centromeres can be observed during interphase, providing a novel window into chromosome organization within the nucleus. Our observations show that centromeres distribute into the newly forming nucleus at telophase by what is apparently a uniform isometric expansion, with little evidence for directed motion of individual centromeres contributing to the formation of the G1 nucleus. During interphase, centromeres show very little movement in general, behaving as though embedded in a rigid matrix. Sustained movements of individual centromeres or groups of centromeres are occasionally observed, however, suggesting that chromosome position is subject to change during interphase (Shelby et al., 1996). These experiments complement those described by Belmont and colleagues, who have developed a method to mark specific chromosomal sites with GFP for analysis in vivo (see Chapter 13; Robinett et al., 1996; Straight et al., 1996). These new GFP-based techniques for direct observation of defined DNA sequence domains in vivo carry the logic of in situ hybridization analysis into living cells and, coupled with new methods for observing global chromatin architecture as well as functional nuclear protein domains (Huang et al., 1997; Misteli et al., 1997), promise significant progress toward understanding the dynamic organization of the genome within the living nucleus.

Isolation and comparison of natural and recombinant human CENP-A autoantigen

Anticentromere antibodies (ACA) are associated with systemic sclerosis (scleroderma) patients exhibiting the more benign or so called limited manifestation of the disease (lSSc). ACA reactivity is directed against multiple polypeptide targets, the smallest of which is designated CENP-A. CENP-A is not an abundant cellular constituent; therefore to maximize recovery, we developed a protocol with a minimum of steps to isolate CENP-A from a human cell line. The trace cellular amount of this protein clearly dictated the production of its recombinant counterpart to facilitate determination of the role of the CENP-A antigen in scleroderma pathogenesis. Here we describe the eukaryotic expression of CENP-A cDNA using baculovirus-mediated infection of insect cells. The non-fusion recombinant protein spans the natural residues of the human CENP-A protein and rCENP-A followed the same chromotographic sequence for purification as did the natural source. The availability of the bona fide antigen provided a critical standard upon which to document authenticity of the recombinant polypeptide. The two forms of this antigen have been compared and shown to exhibit similar physical and antigenic properties.

Histone-GFP fusion protein enables sensitive analysis of chromosome dynamics in living mammalian cells

BACKGROUND

The amplification of oncogenes in cancer cells is often mediated by paired acentric chromatin bodies called double minute chromosomes (DMs), which can accumulate to a high copy number because of their autonomous replication during the DNA synthesis phase of the cell cycle and their subsequent uneven distribution to daughter cells during mitosis. The mechanisms that control DM segregation have been difficult to investigate, however, as the direct visualization of DMs in living cells has been precluded because they are far smaller than normal chromosomes. We have visualized DMs by developing a highly sensitive method for observing chromosome dynamics in living cells.

RESULTS

The human histone H2B gene was fused to the gene encoding the green fluorescent protein (GFP) of Aequorea victoria and transfected into human HeLa cells to generate a stable line constitutively expressing H2B-GFP. The H2B-GFP fusion protein was incorporated into nucleosomes without affecting cell cycle progression. Using confocal microscopy, H2B-GFP allowed high-resolution imaging of both mitotic chromosomes and interphase chromatin, and the latter revealed various chromatin condensation states in live cells. Using H2B-GFP, we could directly observe DMs in living cancer cells; DMs often clustered during anaphase, and could form chromosomal 'bridges' between segregating daughter chromosomes. Cytokinesis severed DM bridges, resulting in the uneven distribution of DMs to daughter cells.

CONCLUSIONS

The H2B-GFP system allows the high-resolution imaging of chromosomes, including DMs, without compromising nuclear and chromosomal structures and has revealed the distinctive clustering behavior of DMs in mitotic cells which contributes to their asymmetric distribution to daughter cells.

Chromatin containing CENP-A and alpha-satellite DNA is a major component of the inner kinetochore plate

The pathway of molecular interactions leading to kinetochore assembly on mammalian chromosomes is unknown. Kinetochores could be specified by structural features of centromeric satellite DNA [1-3] or by specific DNA sequences, analogous to budding yeast centromeres, interspersed in centromeric satellite DNA arrays [4,5]. Alternatively, kinetochores could be epigenetic structures that replicate without strict dependence on DNA sequence [6-8]. We purified kinetochore-associated chromatin from human chromosomes by immunoprecipitation of CENP-A, a centromere-specific histone H3 homologue located in the inner plate of the kinetochore [6,9,10]. Hybridization and DNA sequence analyses of cloned kinetochore DNA fragments revealed alpha-satellite as the predominant sequence associated with CENP-A. A major site of micrococcal nuclease digestion was identified by mapping the termini of alpha-satellite clones, suggesting that the inner kinetochore plate contains phased arrays of CENP-A-alpha-satellite nucleosomes. These experiments demonstrate for the first time that complex satellite DNA is a structural component of the kinetochore. Further, because complex satellite DNA is evolutionarily unconserved, these results suggest that molecular recognition events necessary for kinetochore formation take place at the level of DNA conformation or epigenetic mechanisms rather than DNA sequence per se.

Immunolocalization of CENP-A suggests a distinct nucleosome structure at the inner kinetochore plate of active centromeres

The trilaminar kinetochore directs the segregation of chromosomes in mitosis and meiosis. Despite its importance, the molecular architecture of this structure remains poorly understood [1]. The best known component of the kinetochore plates is CENP-C, a protein that is required for kinetochore assembly [2], but whose molecular role in kinetochore structure and function is unknown. Here we have raised for the first time monospecific antisera to CENP-A [3], a 17 kD centromere-specific histone variant that is 62% identical to the carboxy-terminal domain of histone H3 [4,5] and that resembles the yeast centromeric component CSE4 [6]. We have found by simultaneous immunofluorescence with centromere antigens of known ultrastructural location that CENP-A is concentrated in the region of the inner kinetochore plate at active centromeres. Because CENP-A was previously shown to co-purify with nucleosomes [7], our data suggest a specific nucleosomal substructure for the kinetochore. In human cells, these kinetochore-specific nucleosomes are enriched in alpha-satellite DNA [8]. However, the association of CENP-A with neocentromeres lacking detectable alpha-satellite DNA, and the lack of CENP-A association with alpha-satellite-rich inactive centromeres of dicentric chromosomes together suggest that CENP-A association with kinetochores is unlikely to be determined solely by DNA sequence recognition. We speculate that CENP-A binding could be a consequence of epigenetic tagging of mammalian centromeres.

Assembly of CENP-A into centromeric chromatin requires a cooperative array of nucleosomal DNA contact sites

We investigated the requirements for targeting the centromeric histone H3 homologue CENP-A for assembly at centromeres in human cells by transfection of epitope-tagged CENP-A derivatives into HeLa cells. Centromeric targeting is driven solely by the conserved histone fold domain of CENP-A. Using the crystal structure of histone H3 as a guide, a series of CENP-A/histone H3 chimeras was constructed to test the role of discrete structural elements of the histone fold domain. Three elements were identified that are necessary for efficient targeting to centromeres. Two correspond to contact sites between histone H3 and nucleosomal DNA. The third maps to a homotypic H3-H3 interaction site important for assembly of the (H3/H4)2 heterotetramer. Immunoprecipitation confirms that CENP-A self-associates in vivo. In addition, targeting requires that CENP-A expression is uncoupled from histone H3 synthesis during S phase. CENP-A mRNA accumulates later in the cell cycle than histone H3, peaking in G2. Isolation of the gene for human CENP-A revealed a regulatory motif in the promoter region that directs the late S/G2 expression of other cell cycle-dependent transcripts such as cdc2, cdc25C, and cyclin A. Our data suggest a mechanism for molecular recognition of centromeric DNA at the nucleosomal level mediated by a cooperative series of differentiated CENP-A-DNA contact sites arrayed across the surface of a CENP-A nucleosome and a distinctive assembly pathway occurring late in the cell cycle.

Dynamic elastic behavior of alpha-satellite DNA domains visualized in situ in living human cells

We have constructed a fluorescent alpha-satellite DNA-binding protein to explore the motile and mechanical properties of human centromeres. A fusion protein consisting of human CENP-B coupled to the green fluorescent protein (GFP) of A. victoria specifically targets to centromeres when expressed in human cells. Morphometric analysis revealed that the alpha-satellite DNA domain bound by CENPB-GFP becomes elongated in mitosis in a microtubule-dependent fashion. Time lapse confocal microscopy in live mitotic cells revealed apparent elastic deformations of the central domain of the centromere that occurred during metaphase chromosome oscillations. These observations demonstrate that the interior region of the centromere behaves as an elastic element that could play a role in the mechanoregulatory mechanisms recently identified at centromeres. Fluorescent labeling of centromeres revealed that they disperse throughout the nucleus in a nearly isometric expansion during chromosome decondensation in telophase and early G1. During interphase, centromeres were primarily stationary, although motility of individual or small groups of centromeres was occasionally observed at very slow rates of 7-10 microns/h.

Persistent pulmonary hypertension of the newborn and smoking and aspirin and nonsteroidal antiinflammatory drug consumption during pregnancy

OBJECTIVE

Prenatal causation of persistent pulmonary hypertension of the newborn (PPHB) is suggested by a specific pattern of pulmonary vascular remodeling observed immediately after birth in some infants with fatal PPHN. The goal of this study was to determine whether PPHN is associated with fetal exposure to: (1) tobacco and marijuana smoking (ie, contributors to fetal hypoxemia), (2) consumption of aspirin and other nonsteroidal antiinflammatory drugs (ie, inhibitors of prostaglandin synthesis), and (3) cocaine use (ie, a contributor to vasospasm).

DESIGN

Case-control interview study.

SETTING

Two Harvard-affiliated newborn intensive care units.

PARTICIPANTS

Mothers of case infants who had PPHN or who met criteria for the referent group.

INTERVENTIONS

During July 1985 through April 1989, we interviewed mothers of 103 infants with PPHN and 298 control infants. Because of potential selection bias that might result from recruiting only inborn control infants even though two-thirds of cases were outborn, separate analyses compared the 103 total and 35 inborn infants with PPHN with the 298 inborn control infants. Multivariate analyses were used to adjust for potential confounding factors, including maternal education and Medicaid health insurance (ie, two markers of socioeconomic status), other antenatal factors found to be associated with PPHN (ie, maternal urinary tract infection and diabetes mellitus), and the infant's sex.

MAIN OUTCOME MEASURES

Self-reported use or consumption of tobacco, marijuana, cocaine, aspirin, and other nonsteroidal antiinflammatory drugs during pregnancy.

RESULTS

The adjusted odds ratios (and 95% confidence intervals) for maternal pregnancy exposures to the factors of principal interest among the total study population were: aspirin, 4.9 (1.6-15.3); and nonsteroidal antiinflammatory drugs, 6.2 (1.8-21.8); for the inborn group they were aspirin, 9.6 (2.4-39.0); and nonsteroidal antiinflammatory drugs, 17.5 (4.3-71.6). Although the association between tobacco smoking during pregnancy and PPHN was elevated in univariate analyses, with odds ratios (and 95% confidence intervals) of 2.0 (1.2-3.4) and 1.3 (0.6-3.3) for total and inborn populations, respectively, the relationship was not significant after adjustment for all other factors in the final logistic regression model. Acknowledged illicit drug use was too infrequent (3.2%) to evaluate.

CONCLUSION

Maternal consumption of nonsteroidal antiinflammatory drugs and aspirin during pregnancy or the reasons these drugs were ingested seem to contribute to an increased risk of PPHN.

Detection of anticentromere antibodies using recombinant human CENP-A protein

OBJECTIVE

To evaluate CENP-A reactivity with anticentromere antibodies (ACA) using recombinant protein (rCENP-A).

METHODS

Human CENP-A antigen was overexpressed in insect cells using the baculovirus system. We tested for ACA activity against the full-length recombinant polypeptide by immunoblot and by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Of the ACA+ sera studied (n = 38), 95% were positive when tested against the rCENP-A in the ELISA system. Of the ACA- sera (n = 100), only 2% gave false-positive results in the assay. There was good correlation between the recombinant and bona fide antigens in assaying for ACA reactivity.

CONCLUSION

CENP-A is a significant ACA target. The availability of the rCENP-A assay is a valuable adjunct to the previously described rCENP-B assay in analyses of the clinical significance of ACA.

Human CENP-A contains a histone H3 related histone fold domain that is required for targeting to the centromere

Centromeres are the differentiated chromosomal domains that specify the mitotic behavior of chromosomes. To examine the molecular basis for the specification of centromeric chromatin, we have cloned a human cDNA that encodes the 17-kD histone-like centromere antigen, CENP-A. Two domains are evident in the 140 aa CENP-A polypeptide: a unique NH2-terminal domain and a 93-amino acid COOH-terminal domain that shares 62% identity with nucleosomal core protein, histone H3. An epitope tagged derivative of CENP-A was faithfully targeted to centromeres when expressed in a variety of animal cells and this targeting activity was shown to reside in the histone-like COOH-terminal domain of CENP-A. These data clearly indicate that the assembly of centromeres is driven, at least in part, by the incorporation of a novel core histone into centromeric chromatin.

LKM-1 autoantibodies recognize a short linear sequence in P450IID6, a cytochrome P-450 monooxygenase

LKM-1 autoantibodies, which are associated with autoimmune chronic active hepatitis, recognize P450IID6, a cytochrome P-450 monooxygenase. The reactivities of 26 LKM-1 antisera were tested with a panel of deletion mutants of P450IID6 expressed in Escherichia coli. 22 sera recognize a 33-amino acid segment of P450IID6, and 11 of these recognize a shorter segment, DPAQPPRD. PAQPPR is also found in IE175 of herpes simplex virus type 1 (HSV-1). Antibodies for HSV-1 proteins were detected by ELISA in 17 of 20 LKM-1 sera tested. An immobilized, synthetic peptide, DPAQPPRDC, was used to purify LKM-1 antibodies. Affinity purified LKM-1 autoantibodies react on immunoblots with a protein in BHK cells after infection with HSV-1. 11 of 24 LKM-1 sera, including 3 that recognize DPAQPPRD, also exhibit antibodies to the hepatitis C virus (HCV) protein, C100-3. Affinity purified LKM-1 antibodies did not recognize C100-3. However, partial sequence identity was evident between portions of the immunopositive 33-amino acid segment of P450IID6 and other portions of the putative HCV polyprotein. Immune cross-recognition of P450IID6 and HCV or HSV-1 proteins may contribute to the occurrence of LKM-1 autoantibodies.

CENP-B is a highly conserved mammalian centromere protein with homology to the helix-loop-helix family of proteins

CENP-B is a centromere associated protein originally identified in human cells as an 80 kDa autoantigen recognized by sera from patients with anti-centromere antibodies (ACA). Recent evidence indicates that CENP-B interacts with centromeric heterochromatin in human chromosomes and may bind to a specific subset of human alphoid satellite DNA. CENP-B has not been unambiguously identified in non-primates and could, in principal, be a primate-specific alphoid DNA binding protein. In this work, a human genomic DNA segment containing the CENP-B gene was isolated and subjected to DNA sequence analysis. In vitro expression identified the site for translation initiation of CENP-B, demonstrating that it is encoded by an intronless open reading frame (ORF) in human DNA. A homologous mouse gene was also isolated and characterized. It was found to possess a high degree of homology with the human gene, containing an intronless ORF coding for a 599 residue polypeptide with 96% sequence similarity to human CENP-B. 5' and 3' flanking and untranslated sequences were conserved at a level of 94.6% and 82.7%, respectively, suggesting that the regulatory properties of CENP-B may be conserved as well. CENP-B mRNA was detected in mouse cells and tissues and an immunoreactive nuclear protein identical in size to human CENP-B was detected in mouse 3T3 cells using human ACA. Analysis of the sequence of CENP-B revealed a segment of significant similarity to a DNA binding motif identified for the helix-loop-helix (HLH) family of DNA binding proteins. These data demonstrate that CENP-B is a highly conserved mammalian protein that may be a member of the HLH protein family and suggest that it plays a role in a conserved aspect of centromere structure or function.

The epidemiology of germinal matrix hemorrhage during the first half-day of life

The personal and maternal characteristics of 27 babies with early-onset germinal matrix hemorrhage (EGMH) were compared with those of 280 babies with normal cranial ultrasonograms, studied in a separate clinical trial. None of the mothers of the babies with EGMH had high blood pressure or pre-eclampsia during pregnancy. Gestational age less than 30 weeks and initial pH less than 7.2 indicated increased risks of EGMH, and maternal receipt of steroids indicated reduced risk of EGMH. Thus prenatal and immediately perinatal factors appear to convey much of the information about the risk of EGMH.

Optimization of routine transformation of Escherichia coli with plasmid DNA

Methods to optimize resources and transformation efficiency of routine daily transformations of DH1 Escherichia coli prepared by three calcium chloride methods were investigated and compared with polyethylene glycol and Hanahan methods. The benefit of a heat-shock step, a preplating incubation step to allow expression of antibiotic resistance, use of log phase bacteria and prolonged storage of bacteria were investigated using pBR322 and pUC18 plasmid DNAs. Bacteria prepared by CaCl2 methods consistently gave efficiencies of 4 x 10(6) transformants/microgram of plasmid DNA or better and were overall the most labor- and resource-efficient methods. Use of log phase bacteria, a heat shock and an incubation step were found to be beneficial for freshly prepared bacteria for all methods. Prolonged storage of up to 30 days of bacteria prepared by the CaCl2 methods was beneficial, resulting in a sustained increase in transformation efficiency when selection was by ampicillin but not when by tetracycline resistance. Also found when using bacteria stored three days or longer was an increased transformation efficiency of stationary vs. log phase bacteria and an unchanged or even increased efficiency when the preplating incubation step was omitted. The Hanahan methods were the most labor and resource intensive and routinely gave efficiencies of 2 x 10(7). Higher efficiencies of 10(8) were obtained only with repeated trial and error and were not consistently reproducible. The polyethylene glycol method consistently gave efficiencies of 2 x 10(7), and bacteria could easily be prepared daily or frozen with a minimal decrease in efficiency.

Insights into native epitopes of proliferating cell nuclear antigen using recombinant DNA protein products

A cDNA clone encoding full-length human proliferating cell nuclear antigen (PCNA) was used to generate a panel of in vitro translated labeled protein products with COOH-terminal deletions and to construct a set of fusion proteins with COOH- and NH2-terminal deletions. A rabbit antiserum raised against an NH2-terminal peptide, a well-characterized murine monoclonal antibody (mAb), and 14 human lupus sera with autoantibody to PCNA were analyzed for their reactivity with the constructs using both immunoprecipitation and immunoblotting techniques. The rabbit antiserum reacted in immunoprecipitation and immunoblotting with constructs containing the appropriate NH2-terminal sequence and mAb reacted with a sequence from the midregion of PCNA. These experimentally induced antibodies also reacted with 15-mer synthetic peptides in enzyme-linked immunosorbent assay (ELISA). In contrast, none of the lupus sera reacted with synthetic peptides in ELISA. 9 of the 14 lupus sera also failed to react in Western immunoblotting with any recombinant fusion protein, although they all immunoprecipitated in vitro translated full-length protein. Four of the nine had variable patterns of immunoprecipitation with shorter constructs. The remaining five lupus sera were able to immunoprecipitate translation products as well as Western blot recombinant fusion proteins. From analysis of the patterns of reactivity of human lupus sera, it was deduced that the apparent heterogeneity of human autoantibodies to PCNA could be explained by immune response to highly conformational epitopes. These observations demonstrate that there might be special features in "native" epitopes of intranuclear antigens that are recognized by autoantibodies, and that these special features of native epitopes might not be present in prepared antigen used for experimental immunization. These features may be related to protein folding or to association of the antigen with other intranuclear proteins or nucleic acids, as might occur with antigens that are components of subcellular particles.

Patients with type II autoimmune hepatitis express functionally intact cytochrome P-450 db1 that is inhibited by LKM-1 autoantibodies in vitro but not in vivo

Liver-kidney microsomal-1 autoantibodies characterize a subgroup of autoimmune chronic active hepatitis. The liver antigen of liver-kidney microsomal-1 antibodies has been identified as cytochrome P450 db1, a microsomal enzyme catalyzing the oxidative metabolism of more than 20 drugs, including debrisoquine, sparteine and bufuralol. A genetic polymorphism (debrisoquin-sparteine polymorphism) is responsible for the lack of P450 db1 protein in the livers of 5% to 10% of Caucasians, leading to impaired drug metabolism and a distinct poor metabolizer phenotype. We investigated whether liver-kidney microsomal-1 positive autoimmune chronic active hepatitis patients express functionally intact P450 db1 in their livers. In four patients with liver-kidney microsomal-1 positive chronic active hepatitis, but not in five patients with various liver-kidney microsomal-1 negative liver diseases, the presence of circulating liver-kidney microsomal-1 antibodies was confirmed by immunofluorescence, radioimmunoassay and immunoblotting analysis using recombinant P450 db1. Moreover, only sera from liver-kidney microsomal-1 positive autoimmune chronic active hepatitis patients strongly inhibited the enzymatic activity of P450 db1 in human liver microsomes in vitro. Immunoblotting detected 50-kd P450 db1 protein in liver biopsy specimens from all patients. The in vivo function of P450 db1 was investigated by determining the metabolic ratio for sparteine and its 2-dehydro and 5-dehydro metabolites in 12-hr urine samples after oral administration of sparteine sulfate. In vivo P450 db1-mediated drug metabolism was of the extensive metabolizer phenotype and did not differ significantly between liver-kidney microsomal-1 positive (metabolic ratio = 1.15 +/- 0.32) and liver-kidney microsomal-1 negative (metabolic ratio = 1.18 +/- 0.48) patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Periventricular-intraventricular hemorrhage, sonographic localization, phenobarbital, and motor abnormalities in low birth weight infants

A total of 228 low birth weight (less than 1750 g), mechanically ventilated infants with and without periventricular-intraventricular hemorrhage were examined at 18 months corrected age to assess the relationship between cranial ultrasonographic findings and specific motor abnormalities. All infants were previously enrolled in a double-blind, randomized, prospective clinical trial of phenobarbital prophylaxis against periventricular-intraventricular hemorrhage. Ultrasonographic abnormalities on the scans performed between 7 and 13 days of life were categorized as germinal matrix hemorrhage, lateral ventricular hemorrhage, parenchymal hemorrhage, ventriculomegaly, and any hemorrhage. Regardless of anatomical location, periventricular-intraventricular hemorrhage was associated with an increased risk for developing motor abnormalities. Hypertonia and hyperreflexia/ankle clonus were most common. No abnormal motor findings distinguished unilateral from bilateral germinal matrix hemorrhage and lateral ventricular hemorrhage or between phenobarbital and placebo treatment. None of the 5 infants with parenchymal hemorrhage had spastic cerebral palsy. Ventriculomegaly was associated with a fivefold increase in risk for spastic cerebral palsy and delayed walking and a threefold increase for hypertonia and hyperreflexia/clonus. The results suggest that ventriculomegaly, observed even as early as the first week of life, might be a significant antecedent of later motor abnormalities among the survivors of periventricular-intraventricular hemorrhage.

In vitro posttranslational modification of lamin B cloned from a human T-cell line

Autoimmune diseases are characterized by spontaneously occurring autoantibodies which have proven to be useful reagents for the characterization of specific nuclear proteins. Using a monoclonal autoantibody (72B9) derived from a murine lupus strain, we have cloned a cDNA from the human T-cell line MOLT-4, which encodes nuclear lamin B. The identity of the encoded protein as lamin B was established by both biochemical and immunological criteria. Inspection of the deduced amino acid sequence of lamin B revealed the presence in coil 1B of the alpha-helical domain of a leucine heptad repeat region. Analysis of mRNA in HL60 and MOLT-4 cells, which express only lamin B, or HeLa cells, which express all three major lamins (A, B, and C), together with the comigration of in vitro-translated product with isolated HeLa cell lamin B by two-dimensional gel electrophoresis, suggests that a single lamin B is expressed in mammalian somatic cells. In vitro translation with the cDNA clone revealed an EDTA-sensitive posttranslational modification which resulted in an increase in the apparent molecular weight to that equivalent to the native in vivo-synthesized lamin B protein. This in vitro modification included incorporation of a product of mevalonolactone and required an intact carboxy terminus.

Sjögren's syndrome nuclear antigen B (La): cDNA cloning, structural domains, and autoepitopes

SS-B/La is a major antigenic target for autoantibodies in patients with Sjögren's syndrome. Its transient association with nascent RNA polymerase III transcripts in the cell nucleus suggest a functional role of SS-B/La in RNA processing and maturation. Human SS-B/La autoantibodies recognize at least two distinct epitopes on two separate structural domains of the SS-B/La protein and these epitopes are conserved among mammalian species. In contrast, murine monoclonal antibodies produced though immunization with purified bovine SS-B/La recognize different epitopes. To elucidate these differences, cDNA sequences of SS-B/La were cloned from several mammalian species including human, bovine, and rabbit. Complete human SS-B/La cDNAs including the coding sequence (1227bp) and untranslated sequences were isolated. The complete bovine sequence was determined from two overlapping partial cDNA clones. Comparison of the complete protein sequences encoded by the human and bovine cDNAs revealed a high degree of conservation of amino acid sequence showing only 26 substitutions/deletions out of 408 residues. RNA blot analysis indicated the presence of two size species of transcripts in bovine and rabbit cells, 1.8 kb and greater than 2.5 kb, in contrast to a single 1.8 kb mRNA species in human cells. The results of cDNA cloning support our previous finding of SS-B/La as a two-domain protein, and the RNA-binding site is confirmed to be located within N-terminal domain designated X. Epitope mapping using recombinant SS-B/La fusion proteins confirmed the findings of at least two autoepitopes located on different domains.

Isolation and characterization of a cDNA clone encoding the 60-kD component of the human SS-A/Ro ribonucleoprotein autoantigen

SS-A/Ro is a nucleocytoplasmic ribonucleoprotein (RNP) particle that is a common target of autoimmune response in Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE). Previously, SS-A/Ro has been shown to be composed of at least two polypeptide antigens of 60 and 52 kD noncovalently associated with a set of small RNAs, designated Y1-Y5. A serum from an SS patient was selected to screen a lambda gt11 cDNA library constructed from human T cell lymphoblastic leukemia (MOLT-4) mRNA. An immunoreactive clone was isolated that possessed a 1.8-kb cDNA insert. In vitro transcription and translation of the cDNA resulted in the synthesis of a 57.5-kD polypeptide which was specifically immunoprecipitated by SS-A/Ro antisera. The identity of the cDNA encoded protein as the 60-kD SS-A/Ro antigen was established by proteolytic peptide mapping of the cDNA-encoded protein and the 60-kD HeLa cell antigen. The sequence of the cDNA shows that the 60-kD SS-A/Ro protein possesses both RNA binding protein consensus sequences and a single zinc-finger motif. Recombinant SS-A/Ro antigen produced in bacteria proved to be a sensitive and specific reagent for detection of anti-SS-A/Ro antibodies in patient sera. The availability of the 60-kD SS-A/Ro cDNA will enable detailed analysis of the molecular structure and function of the SS-A/Ro RNP particle and its role in autoimmune pathology.

Ribonucleoprotein SS-B/La belongs to a protein family with consensus sequences for RNA-binding

Autoantibodies from systemic rheumatic disorders have become useful reagents in molecular biology. SS-B/La, a major target of autoantibodies in lupus and Sjogren's syndrome, has been identified as a 46 kDa protein component of a ribonucleoprotein (RNP) particle implicated in the maturation of RNA polymerase III transcripts. This report describes the complete sequences of human and bovine SS-B/La and the identification of RNA-binding protein consensus sequences RNP1 and RNP2 in the N-terminal region previously shown to be complexed with RNA in UV-crosslinking experiments. Segments of about 95 residues from the RNA-binding domain of SS-B/La and from 29 RNA-binding domains of several other proteins are analysed with respect to the frequency of amino acids and their hydrophobicity at each position. The data suggest that SS-B/La belongs to a large family of RNA-binding proteins which includes heterogeneous nuclear RNPs, nucleolin, mRNA polyadenylate binding protein, and small nuclear RNPs.

Major antigen of liver kidney microsomal autoantibodies in idiopathic autoimmune hepatitis is cytochrome P450db1

Type 1, liver kidney microsomal autoantibodies (LKM-1) are associated with a subgroup of idiopathic autoimmune type, chronic active hepatitis (CAH). The antigenic specificity of LKM-1 autoantibodies from 13 patients was investigated by immunoblot analysis of human liver microsomal proteins. Polypeptides of 50, 55, and 64 kD were detected with these antisera. A high titer LKM-1 serum was selected to screen a human liver lambda gt11 cDNA expression library, resulting in the isolation of several complementary (c)DNA clones. Autoantibodies affinity purified from proteins expressed by two of the immunopositive cDNA clones, HLD8.2 and HLD13.2, specifically react with a 50-kD protein of human liver microsomes and display immunofluorescence staining of the proximal renal tubular epithelia characteristic of LKM-1 sera. Determination of the sequence of HLD8.2 revealed that it encodes a recently described cytochrome P450db1. A bacterial fusion protein constructed from HLD8.2 proved to be a specific and sensitive diagnostic reagent. All sera from patients with LKM-1 positive liver disease react with this fusion protein. No reaction was seen, however, for sera from patients with other types of autoimmune liver diseases, viral hepatitis, systemic immunological disorders, or healthy controls.

Hemorrhage, phenobarbital, and fluctuating cerebral blood flow velocity in the neonate

Fifty-one sequential intubated babies with birth weights of less than 1,751 were evaluated by serial Doppler ultrasound during the first three days of life. These babies were part of a phenobarbital prophylaxis trial cohort study. Subependymal-intraventricular hemorrhage developed in 17 of the babies. Infants with subependymal-intraventricular hemorrhage, whether or not they received pancuronium or phenobarbital, had coefficients of variation comparable to those of babies without hemorrhage. Coefficient of variation values of the right were comparable to values obtained from the left anterior cerebral artery complex and did not appear to be consistently altered by the presence of subependymal-intraventricular hemorrhage. Coefficient of variation values appeared to be consistently greatest on day 1 and lowest on day 2. In addition, the values overall increased as the number of waves used to determine the coefficient of variation enlarged from five to 20. This phenomena, however, was not seen among pancuronium recipients and suggests that movement artifact may be a determinant of coefficient of variation values. We conclude that, when the best 20 waves are chosen to evaluate the coefficient of variation, no association exists between coefficient of variation values and development of subependymal-intraventricular hemorrhage or administration of phenobarbital.

Bilirubin, intraventricular hemorrhage, and phenobarbital in very low birth weight babies

The relationships among serum bilirubin concentration on days 5 and 7, birth weight, the presence of intraventricular hemorrhage, and the receipt of phenobarbital were examined in a group of 232 newborns weighing less than 1,751 g who were intubated, mechanically ventilated by 12 hours after birth, and whose parents had given permission for a randomized trial of phenobarbital prophylaxis of intraventricular hemorrhage. The ratio of serum bilirubin concentration to birth weight (the bilirubin divided by birth weight index [BBI]) was used to examine the impact of 25 variables on a clinical guideline for therapy of hyperbilirubinemia in newborn infants. A linear regression model was used; the most powerful covariate was a birth weight less than 1.0 kg. The only other variable that reduced the BBI was phenobarbital receipt. The presence of intraventricular hemorrhage and ecchymoses had a significant influence increasing the BBI.

A 52-kD protein is a novel component of the SS-A/Ro antigenic particle

Anti-SS-A/Ro autoantibodies are found in the sera of patients with Sjogren's syndrome (SS) and SLE. In the course of analyzing 61 SS patients for their autoantibody profiles, we found that 42 were positive for anti-SS-A by double diffusion in agarose and demonstrated precipitin lines identical to that produced by a prototype anti-SS-A serum. Further analysis of these SS-A antibody-positive sera by Western blotting of cell extracts revealed that 21 sera reacted with two proteins of 60 and 52 kD, 13 sera reacted with 52-kD protein, two detected only 60 kD, while six were nonreactive. Affinity-purified anti-60-kD and anti-52-kD antibodies reacted exclusively with their corresponding antigens. Partial proteolysis of these proteins did not reveal common degradation fragments. Thus the 52- and 60-kD proteins were found to be antigenically and apparently structurally distinct from each other. They were also distinct from 48-kD SS-B/La protein. In immunoprecipitation using labeled cell extracts, affinity-purified anti-52-kD antibodies brought down the 52-kD protein as well as the 60-kD band. In [32P]orthophosphate-labeled HeLa cell extract both antibodies precipitated the same spectrum of small RNAs (hYl-5). In indirect immunofluorescence, anti-52-kD and anti-60-kD antibodies immunolocalized in similar subcellular structures and showed similar punctate nuclear staining patterns. Western blot analysis revealed that both proteins were present in lymphocytic as well as epithelial human cell lines tested. The data above define a new antigen of 52 kD which is another component of the SS-A particle and is associated in complex formation with the previously reported 60-kD protein.

Antinuclear antibodies (ANAs): diagnostically specific immune markers and clues toward the understanding of systemic autoimmunity

The convergence of studies in the clinical and basic sciences has resulted in the definitive identification of many intracellular antigens which are the targets of autoantibodies in patients with systemic lupus erythematosus, scleroderma, dermatomyositis/polymyositis, Sjogren's syndrome, mixed connective tissue disease, and drug-induced autoimmunity. Some of this new knowledge includes the identification of the Sm and RNP antigens as ribonucleoprotein particles involved in splicing of precursor messenger RNA, Scl-70 as DNA topoisomerase I, proliferating cell nuclear antigen as auxiliary protein of DNA polymerase delta, and certain antigens in myositis as aminoacyl transfer RNA synthetases. This information confirms, at a molecular level, the presence of specific profiles of autoimmune responses so that autoantibodies can be used in clinical medicine as diagnostically useful immune markers. In addition the data give compelling reasons to consider that certain autoimmune diseases are antigen-driven. Many auto-antibodies have the interesting feature of recognizing epitopes on the antigens which are active or functional sites of the molecule. It is suggested that the data provide clues to the nature of the intracellular particle initiating the immune response and may help to elucidate some of the early mechanisms of the autoimmune process.

Arterial blood gas derangements associated with death and intracranial hemorrhage in premature babies

We evaluated to what extent acidosis and alkalosis and their respiratory and metabolic components during the first 12 hours of life occurred prior to early neonatal death and postnatal intracranial hemorrhage among 206 low birth weight, intubated premature babies participating in a clinical trial of phenobarbital prophylaxis for intracranial hemorrhage. Time-weighted indices included the time each baby spent with abnormal values of pH, PaCO2 and HCO3-. Babies whose birth weight was less than 1 kg suffered adversities associated with prolonged pH less than 7.35. Heavier birth weight babies were at increased risk of adversity if their pH fell below 7.2. Babies who were not severely acidotic initially, but became so within hours, were at prominently increased risk of death and hemorrhage. Babies who had a mild increase of PaCO2 between 45 and 60 mmHg were less likely to develop germinal matrix hemorrhage than their peers who had more severe hypercapnia. A time-weighted measure of metabolic deficit correlated with death, but not with hemorrhage. Prolonged exposure to pH greater than 7.55 was associated with reduced risk of subependymal/intraventricular hemorrhage and death, especially in babies below 1 kg birth weight. We conclude that acidosis is an antecedent of intracranial hemorrhage in low birth weight premature babies, that duration of exposure might convey important risk information, and that birth weight is a correlate of vulnerability to some pH disturbances.

Respiratory complications in low-birth-weight infants who received phenobarbital

We compared the ventilatory requirements of 127 infants who received phenobarbital for five days with those of 111 infants who received placebo. All infants were intubated, weighted less than 1750 g at birth, and survived the first ten days of life. Those infants who received phenobarbital did not require ventilatory assistance for more days than did placebo receivers. However, a pneumothorax or pulmonary interstitial emphysema was more likely to develop in infants who received phenobarbital than in infants who received placebo, even when adjustment was made for the presence of subependymal-intraventricular hemorrhage. We believe this is the first report of this relationship and recommend additional studies to test the hypothesis that phenobarbital contributes to the occurrence/recognition of pneumothorax or pulmonary interstitial emphysema in very-low-birth-weight infants if phenobarbital continues to be used routinely as prophylaxis or treatment.

Molecular cloning of cDNA for CENP-B, the major human centromere autoantigen

We have isolated a series of overlapping cDNA clones for approximately 95% of the mRNA that encodes CENP-B, the 80-kD human centromere autoantigen recognized by patients with anticentromere antibodies. The cloned sequences encode a polypeptide with an apparent molecular mass appropriate for CENP-B. This polypeptide and CENP-B share three non-overlapping epitopes. The first two are defined by monoclonal antibodies elicited by injection of cloned fusion protein. Epitope 1 corresponds to a major antigenic site recognized by the anticentromere autoantibody used to obtain the original clone. Epitope 2 is a novel one not recognized by the autoantibody. These epitopes were shown to be distinct both by competitive binding experiments and by their presence or absence on different subcloned portions of the fusion protein. The third independent epitope, recognized by a subset of anticentromere-positive patient sera, maps to a region substantially closer to the amino terminus of the fusion protein. DNA and RNA blot analyses indicate that CENP-B is unrelated to CENP-C, a 140-kD centromere antigen also recognized by these antisera. CENP-B is the product of a 2.9-kb mRNA that is encoded by a single genetic locus. This mRNA is far too short to encode a polypeptide the size of CENP-C. The carboxy terminus of CENP-B contains two long domains comprised almost entirely of glutamic and aspartic acid residues. These domains may be responsible for anomalous migration of CENP-B on SDS-polyacrylamide gels, since the true molecular mass of CENP-B is approximately 65 kD, 15 kD less than the apparent molecular mass deduced from gel electrophoresis. Quite unexpectedly, immunofluorescence analysis using antibodies specific for CENP-B reveals that the levels of antigen vary widely between chromosomes.

Sequence and expression of the chicken beta 5- and beta 4-tubulin genes define a pair of divergent beta-tubulins with complementary patterns of expression

We have determined the nucleotide sequence of the chicken beta 5 (c beta 5)-tubulin gene. The gene displayed the coding structure common to all previously studied vertebrate beta-tubulin genes and was divided into four exon sequences interrupted by three intervening sequences (located between codons 19 and 20, within codon 56, and within codon 93). Comparison of the predicted polypeptide sequence encoded by c beta 5 with those of four other available chicken beta-tubulin sequences revealed that c beta 5 encoded a highly divergent beta-tubulin polypeptide isotype which was distinguished from previously known sequences primarily by two discrete variable sequence domains. However, c beta 5 uniquely shared identity in 16 residue positions with another divergent chicken beta-tubulin gene, c beta 4. These common sequences distinguished c beta 4 and c beta 5 from the remaining three chicken beta-tubulin genes. Analysis of the expression of c beta 5 and c beta 4 revealed a strikingly complementary pattern of gene expression: c beta 5 was expressed in a wide variety of cell and tissue types but not in neurons, whereas c beta 4 expression was detected uniquely in neuronal cells. Overall, these findings suggest the existence of two divergent families of beta-tubulin sequences in the chicken and further raise the possibility that the complementary expression of the c beta 4 and c beta 5 genes may fulfill a requirement for the presence of a divergent beta-tubulin polypeptide isotype in all cell types.

Sequence and expression of the chicken beta 3 tubulin gene. A vertebrate testis beta-tubulin isotype

We report the determination of the complete DNA sequence for c beta 3, a chicken beta-tubulin gene which we show to be the dominant beta-tubulin expressed in testis. Like all previously studied vertebrate beta-tubulin genes, the gene is divided into four exon sequences interrupted by three intervening sequences (located between amino acids 19 and 20, within codon 56, and within codon 93). Analysis of the program of expression of this gene indicates that it encodes the dominant chicken testis beta-tubulin, although it is also expressed at lower levels in a wide variety of cell and tissue types. Comparison of the predicted polypeptide sequence for c beta 3 with four other available chicken beta-tubulin genes confirms our earlier suggestion that within an otherwise conserved framework, sequences within two variable region domains serve to define specific beta-tubulin polypeptide isotypes. The data indicate that the c beta 3 gene encodes a unique beta-tubulin isotype which diverges from the dominant neuronal beta-tubulin isotype in 18 of 445 residues (4%). Although the protein coding regions of the c beta 3 gene are highly homologous to the chicken c beta 1, c beta 2, c beta 4, and c beta 5 genes previously reported by us, no significant sequence homology with these previously analyzed genes is discernible in the 5'- or 3'-untranslated region sequences, in the intervening sequences, or in the presumptive transcriptional promoter sequences.