Host genomic variation shapes gut microbiome diversity in threespine stickleback fish

IMPORTANCE

A major focus of host-microbe research is to understand how genetic differences, of various magnitudes, among hosts translate to differences in their microbiomes. This has been challenging for animal hosts, including humans, because it is difficult to control environmental variables tightly enough to isolate direct genetic effects on the microbiome. Our work in stickleback fish is a significant contribution because our experimental approach allowed strict control over environmental factors, including standardization of the microbiome from the earliest stage of development and unrestricted co-housing of fish in a truly common environment. Furthermore, we measured host genetic variation over 2,000 regions of the stickleback genome, comparing this information and microbiome composition data among fish from very similar and very different genetic backgrounds. Our findings highlight how differences in the host genome influence microbiome diversity and make a case for future manipulative microbiome experiments that use host systems with naturally occurring genetic variation.

Novel mitochondrial genome rearrangements including duplications and extensive heteroplasmy could underlie temperature adaptations in Antarctic notothenioid fishes

Mitochondrial genomes are known for their compact size and conserved gene order, however, recent studies employing long-read sequencing technologies have revealed the presence of atypical mitogenomes in some species. In this study, we assembled and annotated the mitogenomes of five Antarctic notothenioids, including four icefishes (Champsocephalus gunnari, C. esox, Chaenocephalus aceratus, and Pseudochaenichthys georgianus) and the cold-specialized Trematomus borchgrevinki. Antarctic notothenioids are known to harbor some rearrangements in their mt genomes, however the extensive duplications in icefishes observed in our study have never been reported before. In the icefishes, we observed duplications of the protein coding gene ND6, two transfer RNAs, and the control region with different copy number variants present within the same individuals and with some ND6 duplications appearing to follow the canonical Duplication-Degeneration-Complementation (DDC) model in C. esox and C. gunnari. In addition, using long-read sequencing and k-mer analysis, we were able to detect extensive heteroplasmy in C. aceratus and C. esox. We also observed a large inversion in the mitogenome of T. borchgrevinki, along with the presence of tandem repeats in its control region. This study is the first in using long-read sequencing to assemble and identify structural variants and heteroplasmy in notothenioid mitogenomes and signifies the importance of long-reads in resolving complex mitochondrial architectures. Identification of such wide-ranging structural variants in the mitogenomes of these fishes could provide insight into the genetic basis of the atypical icefish mitochondrial physiology and more generally may provide insights about their potential role in cold adaptation.

Genome-wide analysis facilitates estimation of the amount of male contribution in meiotic gynogenetic three-spined stickleback (Gasterosteus aculeatus)

Gynogenetic embryos - those inheriting only maternal DNA - can be experimentally created by fertilizing eggs with radiation-treated sperm containing inactivated paternal chromosomes. Diploidy in the zygotes can be maintained through prevention of the second meiosis or restored by preventing the first mitosis after the maternal chromosome complement has been replicated. These gynogenetic organisms are useful in many fields including aquaculture, evolutionary biology and genomics. Although gynogenetic organisms have been created in numerous species, the completeness of uni-parental inheritance has often been assumed rather than thoroughly quantified across the genome. Instead, when tests of uni-parental inheritance occur, they typically rely on well-studied genetically determined phenotypes that represent a very small sub-set of the genome. Only assessing small genomic regions for paternal inheritance leaves the question of whether some paternal contributions to offspring might still have occurred. In this study, the authors quantify the efficacy of creating gynogenetic diploid three-spined stickleback fish (Gasterosteus aculeatus). To this end, the authors mirrored previous assessments of paternal contribution using well-studied genetically determined phenotypes including sex and genetically dominant morphological traits but expanded on previous studies using dense restriction site-associated DNA sequencing (RAD-seq) markers in parents and offspring to assess paternal inheritance genome-wide. In the gynogenetic diploids, the authors found no male genotypes underlying their phenotypes of interest - sex and dominant phenotypic traits. Using genome-wide assessments of paternal contribution, nevertheless, the authors found evidence of a small, yet potentially important, amount of paternally "leaked" genetic material. The application of this genome-wide approach identifies the need for more widespread assessment of paternal contributions to gynogenetic animals and promises benefits for many aspects of aquaculture, evolutionary biology and genomics.

Extreme intraspecific divergence in mitochondrial haplotypes makes the threespine stickleback fish an emerging evolutionary mutant model for mito-nuclear interactions

Mitochondrial DNA is primarily maternally inherited in most animals and evolves about 10 times faster than biparentally inherited nuclear DNA. Mitochondrial dysfunction (mt-dys) arises when interactions between the co-evolving mitochondrial and nuclear genomes are perturbed in essential processes like oxidative phosphorylation (OXPHOS). Over time mt-dys can lead to mitochondrial diseases (mt-diseases), which are surprisingly prevalent and include common diseases such as Alzheimer’s, Parkinson’s, and diabetes. Unfortunately, the strong impact that intraspecific mitochondrial and nuclear genetic variation has on mt-disease complicates its study and the development of effective treatments. Animal models have advanced our understanding of mt-disease but their relevance to human conditions is often limited by their relatively low nuclear genetic diversity. Many traditional laboratory models also typically have a single mitochondrial haplotype (mitotype), in stark contrast to over 5,000 mitotypes in humans worldwide. The threespine stickleback fish has an evolutionary history that has made it a favorable evolutionary mutant model (EMM) for studying mito-nuclear interactions and possibly mt-diseases. EMMs are species with naturally evolved states that mimic maladaptive human diseases. In threespine stickleback, a period of isolation followed by introgression of the mitochondrial genome from a sister species resulted in the maintenance of two distinct mitochondrial haplotypes which continue to segregate within many populations of wild stickleback. The existence of two mitogenomes segregating in numerous genetically diverse populations provides a unique system for exploring complex mito-nuclear dynamics. Here we provide the first complete coding region analysis of the two threespine stickleback mitotypes, whose mitogenomic divergence exceeds that of other mammalian models for mitochondrial disease and even that between ancient and modern humans. We find that divergence is not uniform across the mitogenome, but primarily impacts protein coding genes, and significantly impacts proteins in Complex I of OXPHOS. The full characterization of these highly divergent intraspecific mitotypes provides a foundation for the development of threespine stickleback as an EMM for mito-nuclear interactions.

Effectiveness of a COVID-19 Testing Outreach Intervention for Latinx Communities: A Cluster Randomized Trial

Importance

Latinx individuals have been disproportionately affected during the COVID-19 pandemic caused by the spread of SARS-CoV-2. It is imperative to evaluate newly developed preventive interventions to assess their effect on COVID-19 health disparities.

Objective

To examine the effectiveness of a culturally tailored outreach intervention designed to increase SARS-CoV-2 testing rates among Latinx populations.

Design, Setting, and Participants

In this cluster randomized trial performed from February 1 to August 31, 2021, in community settings in 9 Oregon counties, 38 sites were randomized a priori (19 to the community health promoters intervention and 19 to outreach as usual wait-listed controls). Thirty-three sites were activated. A total of 394 SARS-CoV-2 testing events were held and 1851 diagnostic samples collected, of which 919 were from Latinx persons.

Interventions

A culturally informed outreach program was developed that made use of promotores de salud (community health promoters) to increase Latinx SARS-CoV-2 testing. Strategies addressed barriers by disseminating information on testing events in English and Spanish, mitigating misinformation, and increasing trust.

Main Outcomes and Measures

The primary outcomes were the count of sample tests from Latinx persons and the sampled proportion of the Latinx populace. Site-level covariates included census tract Latinx populace, nativity (number of US-born individuals per 100 population), median age, and income inequality. Time-varying covariates included number of new weekly SARS-CoV-2-positive cases and percentage of vaccine coverage at the county level.

Results

A total of 15 clusters (sites) were randomized to the control group and 18 to the community health promoters group. A total of 1851 test samples were collected, of which 995 (53.8%) were from female participants and 919 (49.6%) were from Latinx individuals. The intervention tested 3.84 (95% CI, 2.47-5.97) times more Latinx individuals per event than controls (incident rate ratio, 0.79; 95% CI, 0.46-1.34; Cohen d = 0.74; P < .001). The intervention was associated with a 0.28 increase in the proportion of Latinx populace being tested compared with control sites for the dependent variable scaled as the proportion of the Latinx populace ×100, or a 0.003 proportion of the raw populace count. The use of a standardized scaling of the proportion of Latinx individuals showed that the relative percentage increase was 0.53 (95% CI, 0.21-0.86) in the intervention sites compared with controls, representing a medium effect size.

Conclusions and Relevance

To our knowledge, this was the first randomized evaluation of an outreach intervention designed to increase SARS-CoV-2 testing among Latinx populations. Findings could be used to implement strategies to reduce other health disparities experienced by these groups.

Trial Registration

ClinicalTrials.gov Identifier: NCT04793464.

Advancing human disease research with fish evolutionary mutant models

Model organism research is essential to understand disease mechanisms. However, laboratory-induced genetic models can lack genetic variation and often fail to mimic the spectrum of disease severity. Evolutionary mutant models (EMMs) are species with evolved phenotypes that mimic human disease. EMMs complement traditional laboratory models by providing unique avenues to study gene-by-environment interactions, modular mutations in noncoding regions, and their evolved compensations. EMMs have improved our understanding of complex diseases, including cancer, diabetes, and aging, and illuminated mechanisms in many organs. Rapid advancements of sequencing and genome-editing technologies have catapulted the utility of EMMs, particularly in fish. Fish are the most diverse group of vertebrates, exhibiting a kaleidoscope of specialized phenotypes, many that would be pathogenic in humans but are adaptive in the species' specialized habitat. Importantly, evolved compensations can suggest avenues for novel disease therapies. This review summarizes current research using fish EMMs to advance our understanding of human disease.

Highly Reproducible 16S Sequencing Facilitates Measurement of Host Genetic Influences on the Stickleback Gut Microbiome

Multicellular organisms interact with resident microbes in important ways, and a better understanding of host-microbe interactions is aided by tools such as high-throughput 16S sequencing. However, rigorous evaluation of the veracity of these tools in a different context from which they were developed has often lagged behind. Our goal was to perform one such critical test by examining how variation in tissue preparation and DNA isolation could affect inferences about gut microbiome variation between two genetically divergent lines of threespine stickleback fish maintained in the same laboratory environment. Using careful experimental design and intensive sampling of individuals, we addressed technical and biological sources of variation in 16S-based estimates of microbial diversity. After employing a two-tiered bead beating approach that comprised tissue homogenization followed by microbial lysis in subsamples, we found an extremely minor effect of DNA isolation protocol relative to among-host microbial diversity differences. Abundance estimates for rare operational taxonomic units (OTUs), however, showed much lower reproducibility. Gut microbiome composition was highly variable across fish-even among cohoused siblings-relative to technical replicates, but a subtle effect of host genotype (stickleback line) was nevertheless detected for some microbial taxa.IMPORTANCE Our findings demonstrate the importance of appropriately quantifying biological and technical variance components when attempting to understand major influences on high-throughput microbiome data. Our focus was on understanding among-host (biological) variance in community metrics and its magnitude in relation to within-host (technical) variance, because meaningful comparisons among individuals are necessary in addressing major questions in host-microbe ecology and evolution, such as heritability of the microbiome. Our study design and insights should provide a useful example for others desiring to quantify microbiome variation at biological levels in the face of various technical factors in a variety of systems.

Development of an outbred disease model of Hermansky-Pudlak Syndrome in Threespine Stickleback

Mounting evidence shows that humans respond heterogeneously to diseases and treatments due to their genetic variation, leading to the growth of the field of personalized medicine. Research on model organisms is vital to seek scientific understandings of disease in this broader context, but current research in nonhuman disease models struggles to demonstrate the genetic variability of humans. One disease that exemplifies this issue is Hermansky-Pudlak Syndrome (HPS). HPS is a genetic syndrome resulting from mutations in one of ten HPS genes involved in endosome trafficking, which can result in oculocutaneous albinism, blood diathesis, pulmonary fibrosis, vision impairment, and granulomatous enterocolitis phenotypically indistinguishable from Crohn’s Disease. Currently no disease models for HPS exist that accurately demonstrate the variability of the human disease. Here we present an outbred mutant model of threespine stickleback (Gasterosteus aculeatus) fish exhibiting symptoms consistent with HPS. Using genetic mapping approaches we narrowed this mutation to a region of the genome containing hps4the causative disease gene of Hermansky-Pudlak Syndrome Type 4. Using histological staining and imaging we are confirming the presence of each symptom comprising the syndrome and hope to develop the first outbred system to tackle this disease. Ultimately, the application of outbred medical models in diverse organisms will be important for the advancement of personalized medicine, greatly enhancing our understanding of how genetic variation affects disease states.

Advancing threespine stickleback as an outbred immunogenetics model by pinpointing the onset of adaptive immunity

The development of an outbred immunogenetics model system is needed to understand how genetic variation impacts phenotypic variation of disease states in humans. Threespine stickleback fish (Gasterosteus aculeatus) provide just such a model. Stickleback are genetically tractable laboratory organisms with a well-annotated genome, but with lines drawn from populations inhabiting vastly different habitats. Individuals from different populations show high levels of genetic variation. The onset of the adaptive immune system is currently unknown in stickleback, a significant hindrance in studies of immunodeficiency diseases. To characterize the early development of adaptive immunity, we will analyze the expression of known early indicators of adaptive immunity maturation. These include recombination activating genes, rag1 and rag2, which are essential to the maturation of T and B lymphocytes, and T cell receptor genes, tcr-β and tcr-γ, which are expressed in mature T lymphocytes. To analyze the expression of rag1, rag2, tcr-β, and tcr-γ, we will perform whole mount in situ hybridization throughout a developmental time series to detect when and where the genes are first expressed, with special focus on the head kidney and the thymus, followed by qPCR to quantify the expression of the early adaptive immunity genes. Knowing when adaptive immunity onset occurs in threespine stickleback advances threespine stickleback as an outbred disease model in immunogenetics studies, allowing manipulative studies of immunological disease phenotypes in the context of genetic variation.

Interactions of Purified Rat Factor VIII/von Willebrand Factor with Rat and Human Platelets – Effect of Albumin and Ristocetin

Rat platelets do not respond to ristocetin in their own plasma nor do they aggregate in the presence of bovine or porcine factor VIII von Willebrand factor (F VIII R:WF) or human F VIII R:WF in presence of ristocetin. However, rat plasma supports ristocetin induced aggregation of washed human platelets. In this study we report on purification of rat F VIII R:WF from cryoprecipitate. Similarly to porcine or bovine material, purified rat F VIII R:WF induced aggregation of human washed fixed platelets. This effect was enhanced by addition of ristocetin and was not modified by addition of albumin. Rat washed platelets were aggregated by ristocetin in the presence of rat or human F VIII R:WF provided that high concentrations of ristocetin are added in a system essentially free of extraneous proteins. Increasing concentrations of albumin dramatically reduced the ability of ristocetin to aggregate rat platelets while human platelet aggregation by human or rat F VIII R:WF was only moderately affected.

These studies show that rat F VIII R:WF can interact with rat and human platelets. The lack of response of rat platelets to ristocetin in their own plasma is most likely due to a low sensitivity of rat platelets to this drug and to an inhibitory activity of plasma proteins on this reaction.

Reactivity of Small Molecular Forms of Human Factor VIII/von Willebrand Factor with Botrocetin and Anti-Factor VIII-Coated Latex Particles

Two recently developed tests for measurement of factor VIII/von Willebrand factor (FVIII/vWF), i.e. platetelet agglutination by botrocetin and a kinetic latex antigen assay, were compared with ristocetin cofactor and electroimmunoassay, in respect with FVIII/vWF size-distribution. FVIII/vWF was measured in six cases of atypical von Willebrand’s disease (type II), in gel-filtered fractions of normal cryoprecipitate and in the course of depolymerization of purified normal FVIII/vWF by disulfide reduction. Small molecular forms of FVIII/vWF from normal and variant type II plasma, and those derived by disulfide reduction of high-molecular weight FVIII/vWF, showed remarkably decreased reactivity in ristocetin-, botrocetin- and latex-assay. We conclude that for botrocetin-induced platelet agglutination, as well as for agglutination of antibody-coated latex particles, multiple interactions with repeating subunits of FVIII/vWF are required. As a practical consequence, the combined measurement of FVIII/vWF by the latex test and electroimmunoassay provides a simple tool for discriminating between the classical von Willebrand’s disease and its variants.

Three Abnormal Fibrinogen Variants with the Same Amino Acid Substitution (γ 275 Arg → His): Fibrinogens Bergamo II, Essen and Perugia

We report on three unrelated individuals with the same uncommon type of dysfibrinogenemia, originating from Bergamo, Essen and Perugia. None of them showed bleeding symptoms while the Bergamo patient and members of her family presented with a thrombotic tendency. The presence of a defective fibrinogen was suggested by prolonged thrombin and rep-tilase times. Furthermore, fibrinogen concentrations of less than 0.28 g/L were determined by the functional assay whereas values of 1.5-2.4 g/L were measured by heat precipitation or electroimmunoassay. Fibrinogen was isolated by affinity chromatography on insoluble fibrin monomer. The rate of fibrinopeptide release by thrombin was normal while the fibrin polymerization reaction was strongly delayed. An abnormal peptide (γ265-310) was isolated by high-performance liquid chromatography after cyanogen bromide cleavage of the purified γ-chain of fibrinogen Bergamo II and Essen. The same peptide was also isolated following cyanogen bromide treatment of the intact fibrinogen Perugia. Sequence analyses of these peptides demonstrated the same amino acid exchange in all three fibrinogens: γ275 arginine → histidine. The described fibrinogen variants appear to possess a molecular defect which has thus far only been observed in fibrinogen Haifa.

Fibrinogen Bergamo I (Aα16Arg → Cys): Susceptibility Towards Thrombin Following Aminoethylation, Methylation or Carboxamidomethylation of Cysteine Residues

An abnormal fibrinogen, denoted as “fibrinogen Bergamo I”, has been characterized. Its defect consists in an exchange of arginine by cysteine in position 16 of the Aα-chain, thus corresponding to that found in a number of other fibrinogen variants. The abnormal fibrinopeptide A cannot be split off by thrombin from intact fibrinogen Bergamo I. We describe three different chemical modifications of the cysteine Aαl6, i.e. aminoethylation, methylation and carboxamidomethylation, and their effects on the susceptibility of fibrinogen Bergamo I towards thrombin attack. S-aminoethylation of the Aαl6Cys renders the peptide bond Aαl6–17 cleavable by thrombin. Following methylation or carboxamidomethylation, the Aαl9-arginyl bond becomes accessible for thrombin. The chemically modified extended fibrinopeptide A can be readily separated from the normal fibrinopeptide A by HPLC. The latter two modifications are suitable alternative procedures for detecting the molecular defect Aαl6Arg → Cys of fibrinogen.

Effect of Calcium and Synthetic Peptides on Fibrin Polymerization

Human fibrinogen was subjected to limited proteolytic attack by thrombin, batroxobin or Agkistrodon contortrix thrombin-like enzyme, yielding desAB-, desA- or desB-fibrin monomers, respectively. Turbidity curves demonstrated that, with all three enzymes, the polymerization process was strongly accelerated by increasing the calcium concentration from 10−5 M to 10−4 M. Synthetic peptide Gly-His-Arg (5 mM), an analogue of the aminoterminal sequence of fibrin β-chain, inhibited aggregation of desB-fibrin monomers at physiological calcium concentration whereas it enhanced aggregation of desA- and desAB-fibrin monomers at calcium concentrations below 10−4 M. On the other hand, Gly-Pro-Arg (1 mM) corresponding to the amino-terminus of fibrin α-chain, dramatically inhibited aggregation of both desA- and desB-fibrins, but it only moderately affected the polymerization of thrombin-induced monomers. We conclude that the observed effects of Gly-Pro-Arg and Gly-His-Arg are not due solely to their competition with fibrin amino-termini for the respective binding sites in the D-domain, but rather reflect conformational changes in fibrin monomers which affect the polymerization process.

Gene flow between Drosophila yakuba and Drosophila santomea in subunit V of cytochrome c oxidase: A potential case of cytonuclear cointrogression

Introgression is the effective exchange of genetic information between species through natural hybridization. Previous genetic analyses of the Drosophila yakuba—D. santomea hybrid zone showed that the mitochondrial genome of D. yakuba had introgressed into D. santomea and completely replaced its native form. Since mitochondrial proteins work intimately with nuclear‐encoded proteins in the oxidative phosphorylation (OXPHOS) pathway, we hypothesized that some nuclear genes in OXPHOS cointrogressed along with the mitochondrial genome. We analyzed nucleotide variation in the 12 nuclear genes that form cytochrome c oxidase (COX) in 33 Drosophila lines. COX is an OXPHOS enzyme composed of both nuclear‐ and mitochondrial‐encoded proteins and shows evidence of cytonuclear coadaptation in some species. Using maximum‐likelihood methods, we detected significant gene flow from D. yakuba to D. santomea for the entire COX complex. Interestingly, the signal of introgression is concentrated in the three nuclear genes composing subunit V, which shows population migration rates significantly greater than the background level of introgression in these species. The detection of introgression in three proteins that work together, interact directly with the mitochondrial‐encoded core, and are critical for early COX assembly suggests this could be a case of cytonuclear cointrogression.

[A modified in vivo platelet retention test in the evaluation of primary hemostasis]

A simple assay system for measuring platelet retention in a standardized superficial skin wound is presented. Platelets were counted in the blood collected at the site of the wound 1, 2 and 3 minutes following incision. Per cent platelet retention was calculated from the difference between venous blood platelet count and wound blood platelet count, divided by venous count. The time course of platelet retention, measured in 20 healthy persons, reflected the sequence of primary and secondary platelet aggregation. Ten patients with congenital platelet defects already showed impaired platelet retention in the early stage of bleeding. On the other hand, administration of aspirin to 10 healthy subjects inhibited only the late stage of platelet retention. In comparison with the template bleeding time our platelet retention test provides additional information useful for evaluating congenital and drug-induced defects in platelet plug formation.

Monitoring of heparin therapy with the activated partial thromboplastin time and chromogenic substrate assays

Heparin therapy was monitored with the activated partial thromboplastin time (APTT) and with chromogenic substrate assays (factor Xa and factor IIa inhibition) in 100 plasma samples from 47 patients. Heparin concentrations were classified as being below, within or above a defined therapeutic range (TR; 0.2-0.55 units heparin/ml). In a first group of patients (A), all three assays allocated the plasma heparin levels to the same concentration interval with respect to the TR. The most frequent diagnoses in group A were uncomplicated arterial or venous thromboembolism, myocardial infarction with limited tissue necrosis, cardiac surgery without major complications and successfully treated infectious disease. In a second group of patients (B), the results of APTT suggested higher heparin concentrations with respect to the TR than the chromogenic assays. Predominant diagnoses were severe infectious diseases, severe liver disorders, extensive myocardial infarction and postoperative complications after cardiac surgery. The discrepancy between heparin concentrations determined by either APTT or the chromogenic substrate assays is most likely due to a non-heparin related prolongation of APTT caused by the underlying disease.

[Blood coagulation disorders]

Disorders of hemostasis are frequently encountered, and, if not recognised as early as possible, in particular prior to surgery, may lead to bleeding complications which are much more difficult to treat than those where exact diagnosis permits specific preventive therapy. A first case report on a woman with an acquired inhibitor against factor VIII illustrates that even minor injury may lead to hemorrhage necessitating blood transfusion. Furthermore, as long as the defect remains inaccessible to successful substitution therapy, wound healing will not take place. A second case report describes a patient with a congenital dysfunction of blood platelets, and serves as an example for similar disorders which, if unrecognised, lead to multiple, otherwise avoidable complications. Unfortunately there is no clearcut correlation between a given defect of hemostasis and bleeding manifestations, since psychological factors, among others, appear to influence the occurrence of "spontaneous" hemorrhage. Any unexpected and unexplained bleeding complication requires careful evaluation of the possible underlying causes, since such investigations often not only affect the future of the propositus himself but also that of his family members.

Exposure of platelet binding sites in von Willebrand factor by adsorption onto polystyrene latex particles

Von Willebrand factor molecules are flexible linear polymers composed of repeating protomeric polypeptide subunits. In the process of primary hemostasis, von Willebrand factor promotes platelet adhesion and platelet plug formation at the site of vascular injury. This biologic activity is apparently related to the multimeric size of von Willebrand factor. We simulated von Willebrand factor binding to the subendothelial surface by adsorbing purified human von Willebrand factor onto polystyrene latex particles of two different diameters, i.e., 0.312 micron and 2.02 micron. The rate and extent of 125I-labeled von Willebrand factor binding to polystyrene was similar with both size classes of latex particles. The von Willebrand factor-coated latex beads of 2.02 micron diameter, in contrast to the smaller size, induced rapid agglutination of formalin-fixed human platelets in the absence of any other aggregating agent. Von Willebrand factor was also adsorbed from human plasma onto latex particles coated with anti-von Willebrand factor antibodies. Again, only the large beads, carrying the von Willebrand factor-antibody complex, induced agglutination of fixed platelets. Shear stress promoted the rate of von Willebrand factor adsorption to latex particles. Our results suggest that adsorption to surface exposes binding sites in human von Willebrand factor for platelets.

Three abnormal fibrinogen variants with the same amino acid substitution (gamma 275 Arg----His): fibrinogens Bergamo II, Essen and Perugia

We report on three unrelated individuals with the same uncommon type of dysfibrinogenemia, originating from Bergamo, Essen and Perugia. None of them showed bleeding symptoms while the Bergamo patient and members of her family presented with a thrombotic tendency. The presence of a defective fibrinogen was suggested by prolonged thrombin and reptilase times. Furthermore, fibrinogen concentrations of less than 0.28 g/L were determined by the functional assay whereas values of 1.5-2.4 g/L were measured by heat precipitation or electroimmunoassay. Fibrinogen was isolated by affinity chromatography on insoluble fibrin monomer. The rate of fibrinopeptide release by thrombin was normal while the fibrin polymerization reaction was strongly delayed. An abnormal peptide (gamma 265-310) was isolated by high-performance liquid chromatography after cyanogen bromide cleavage of the purified gamma-chain of fibrinogen Bergamo II and Essen. The same peptide was also isolated following cyanogen bromide treatment of the intact fibrinogen Perugia. Sequence analyses of these peptides demonstrated the same amino acid exchange in all three fibrinogens: gamma 275 arginine----histidine. The described fibrinogen variants appear to possess a molecular defect which has thus far only been observed in fibrinogen Haifa.

[Monitoring heparin therapy by thrombin time and activated partial thromboplastin time--a comparison]

In 106 plasma samples obtained from patients on heparin therapy, monitoring by 2 methods (activated partial thromboplastin time and thrombin clotting time--APTT and TT) was compared. All patients in whom APTT indicated markedly higher plasma heparin concentrations than the TT were critically ill (group B): their main diagnoses included severe infectious disease, severe liver disease and extensive myocardial infarction. Patients with lesser discrepancies between the results of APTT and TT did not suffer from such severe conditions (group A). Cardiac surgery without major postoperative problems, limited myocardial infarction and uncomplicated thromboembolism were the main diagnoses in this group. In group B, non-heparin related prolongation of APTT was thought to be the main factor responsible for the overestimation of plasma heparin concentrations by this test. We conclude that in patients with severe infectious disease, liver disease or extensive tissue necroses (i.e. myocardial infarction), APTT cannot be recommended for laboratory monitoring of heparin therapy.

[A new test for evaluating the von Willebrand factor: collagen-induced agglutination of fixed thrombocytes]

In primary hemostasis von Willebrand factor (vWf) promotes the adhesion of platelets to subendothelial structures of the damaged blood vessel. A new test is described which measures the collagen binding affinity of vWf. Activities of vWf in plasmas of 51 patients were measured with either collagen (ColCof) or ristocetin (RCof). Regression-analysis showed a good correlation of both activities (r = 0.924). In a second group of 21 patients with a variant of von Willebrand's disease, ColCof activity was generally higher than RCof activity.

[Binding of the von Willebrand factor to solid surfaces: effect of shear strength]

Platelet adhesion onto subendothelium of a damaged blood vessel depends upon the presence of von Willebrand factor (vWf) only at high flow shear rate. Our results showed enhanced adsorption of vWf onto stainless steel and latex surfaces under conditions of high shear stress, thus suggesting that in the rapidly flowing blood the extremely long vWf molecules are stretched, thus accelerating their binding to a given surface.

Psychogenic purpura, idiopathic thrombocytopenic purpura, and platelet dysfunction in the same patient

A patient whose peculiar and painful purpura seemed to be strongly related to psychogenic factors is described. The skin bleeding pattern in this patient was consistent with the diagnosis of psychogenic purpura (autoerythrocyte sensitization). In addition, idiopathic thrombocytopenic purpura and platelet storage pool deficiency were present. These somatic conditions are considered to be of minor importance in the pathogenesis of this hemorrhagic syndrome. The association of these various types of bleeding disorders in the same patient has not been previously described.

Characterization of fibrinogen Milano I: amino acid exchange gamma 330 Asp----Val impairs fibrin polymerization

An abnormal fibrinogen was found in two asymptomatic members (father and daughter) of the same family, originating from northern Italy. Routine coagulation studies revealed prolonged thrombin and reptilase clotting times. Plasma fibrinogen levels, as determined by a functional assay, were markedly diminished, whereas the heat precipitation method indicated normal fibrinogen values. On the basis of these findings, a tentative diagnosis of dysfibrinogenemia was made, and according to the accepted nomenclature, this fibrinogen variant was called "fibrinogen Milano l." The time course of fibrinopeptide A and B release from fibrinogen Milano l was normal, but the aggregation of fibrin monomers was delayed. Two-dimensional electrophoresis of reduced variant fibrinogen chains showed a defective gamma-chain with increased cathodic mobility. An abnormal electrophoretic mobility was observed also for the gamma-chain remnants of fibrinogen fragments D1 and D2 derived from fibrinogen Milano l, whereas the charge anomaly was lost after a further digestion by plasmin to D3, suggesting that the structure abnormality of this variant is situated in the region gamma 303-356. An abnormal peptide was isolated after cyanogen bromide cleavage of intact fibrinogen Milano l. This fragment spans from position gamma 311 to gamma 336. Amino acid analysis of the abnormal peptide showed the presence of valine and a diminished content of aspartic acid. Sequence analysis demonstrated an amino acid exchange Asp----Val in the gamma-chain at position 330.

Von Willebrand factor-dependent agglutination of washed fixed human platelets by insoluble collagen isolated from bovine aorta

Adult bovine aortic tissue was homogenized in a neutral phosphate buffer containing proteinase inhibitors. The insoluble residue was rehomogenized in Tris-buffered 6 mol/L guanidinium chloride (pH 7.4). An insoluble fibrillar protein, floating above the main pellet after recentrifugation, was harvested. This material agglutinated washed fixed human platelets in the presence of either normal human plasma or purified von Willebrand factor (vWF). No such reaction was seen when either buffer or plasma from patients with severe von Willebrand's disease was added instead. The extent of platelet agglutination was measured photometrically, similarly to the ristocetin cofactor assay. The agglutination reaction was strongest at neutral pH and was impaired after either addition of EDTA or previous digestion of the fibrillar material by collagenase or pepsin. By light microscopy platelets were seen to adhere onto isolated fibers. Amino acid composition, subunit polypeptides, substrate properties, and interaction with fibronectin of this fibrillar protein were comparable to those of collagen. Therefore, we tentatively denote the induction of platelet agglutination by vWF protein in the described test system as "vWF-collagen cofactor" activity. Comparison of this activity in 65 plasma samples, containing various concentrations of vWF, with ristocetin cofactor activity showed good correlation between results obtained in both tests (r = 0.91).

[How can we improve long-term anticoagulation?]

Oral anticoagulation is sometimes unjustly referred to as a particularly difficult form of antithrombotic therapy. Apparent failures of this treatment may be caused by insufficient information on the part of either the physician or the patient himself, poor standardization of laboratory tests and/or inadequate dosage of vitamin K antagonists. Specialized centers for treatment of thrombosis have done pioneer work in standardizing and evaluating oral anticoagulant treatment with respect to various indications. Based on this experience, optimum long-term anticoagulant therapy is today possible even in a small hospital or in general medical practice, provided that the pharmacological peculiarities of vitamin K antagonists and international developments concerning standardization of the prothrombin time (Quick test) and its modifications (International Normalized Ratio, INR) are taken into consideration. Regular internal and external quality control of laboratory tests for monitoring of oral anticoagulation is of the utmost importance.

Reactivity of small molecular forms of human factor VIII/von Willebrand factor with botrocetin and anti-factor VIII-coated latex particles

Two recently developed tests for measurement of factor VIII/von Willebrand factor (FVIII/vWF), i.e. platelet agglutination by botrocetin and a kinetic latex antigen assay, were compared with ristocetin cofactor and electroimmunoassay, in respect with FVIII/vWF size-distribution. FVIII/vWF was measured in six cases of atypical von Willebrand's disease (type II), in gel-filtered fractions of normal cryoprecipitate and in the course of depolymerization of purified normal FVIII/vWF by disulfide reduction. Small molecular forms of FVIII/vWF from normal and variant type II plasma, and those derived by disulfide reduction of high-molecular weight FVIII/vWF, showed remarkably decreased reactivity in ristocetin-, botrocetin- and latex-assay. We conclude that for botrocetin-induced platelet agglutination, as well as for agglutination of antibody-coated latex particles, multiple interactions with repeating subunits of FVIII/vWF are required. As a practical consequence, the combined measurement of FVIII/vWF by the latex test and electroimmunoassay provides a simple tool for discriminating between the classical von Willebrand's disease and its variants.

Fibrinogen Bergamo I (A alpha 16Arg----Cys): susceptibility towards thrombin following aminoethylation, methylation or carboxamidomethylation of cysteine residues

An abnormal fibrinogen, denoted as "fibrinogen Bergamo I", has been characterized. Its defect consists in an exchange of arginine by cysteine in position 16 of the A alpha-chain, thus corresponding to that found in a number of other fibrinogen variants. The abnormal fibrinopeptide A cannot be split off by thrombin from intact fibrinogen Bergamo I. We describe three different chemical modifications of the cysteine A alpha 16, i.e. aminoethylation, methylation and carboxamidomethylation, and their effects on the susceptibility of fibrinogen Bergamo I towards thrombin attack. S-aminoethylation of the A alpha 16Cys renders the peptide bond A alpha 16-17 cleavable by thrombin. Following methylation or carboxamidomethylation, the A alpha 19-arginyl bond becomes accessible for thrombin. The chemically modified extended fibrinopeptide A can be readily separated from the normal fibrinopeptide A by HPLC. The latter two modifications are suitable alternative procedures for detecting the molecular defect A alpha 16Arg----Cys of fibrinogen.

Factors influencing hydrocarbon degradation in three freshwater lakes

The mixed microbial flora of 3 lakes in Ohio with differing histories of hydrocarbon pollution was examined in relation to the ability to use hydrocarbons. Weathered kerosene was spiked with naphthalene, pristane, 1,13-tetradecadiene, andn-hexadecane and added to water-sediment mixtures from the 3 lakes, and utilization of the 4 marker hydrocarbons was measured. Each of the marker hydrocarbons was metabolized; naphthalene was the most readily used and pristane was the most resistant. Values for dissolved oxygen suggest that oxygen did not limit hydrocarbon degradation in the water column at any site examined. Nutrient addition studies indicated that nitrogen and phosphorus limited hydrocarbon degradation at all sites examined. Maximum numbers of heterotrophic bacteria were detected when the water temperature was 10°C or higher. The data indicate that temperature limits hydrocarbon degradation in the winter, except at a site which had been impacted by an oil spill and which received chronic inputs of hydrocarbons and nutrients. In samples from that site, all 4 marker hydrocarbons were degraded at 0°C. Results of temperature and nutrient-addition experiments suggest that different seasonal populations of hydrocarbon users are selected at that site, but not at other lake sites.

Inhibition of human T lymphocyte proliferation in vitro by commercial factor VIII concentrates

Several investigators recently described a T lymphocyte subset abnormality (reversed helper/suppressor cell ratio) in haemophiliacs, especially following previous substitution therapy. We studied in vitro the potential effects of two commercial factor VIII concentrates on incorporation of 3H-thymidine by isolated human peripheral blood lymphocytes after stimulation with either phytohaemagglutinin or monoclonal antibody OKT3. Dose-related inhibition of thymidine incorporation was found for both concentrates but none using the purified main protein constituents, i.e. factor VIII, fibrinogen or fibronectin. Furthermore, the 'inhibitor' was completely removed by dialysis.

Pelvic and acetabular fractures: examination by angled CT scanning

A new technique of direct angled CT scanning of pelvic and acetabular fractures is presented that allows visualization of the entire ring on a single image or two adjacent images.

[Desamino-8-D-arginine vasopressin nose drops in the treatment of mild hemophilia A and von Willebrand's disease]

To permit home treatment in our patients we investigated the response to intranasal administration of 260 micrograms DDAVP in 28 patients with either mild hemophilia A or von Willebrand's disease. 6 patients with mild hemophilia A responded, and 6 did not. In the group with von Willebrand's disease 6 responded well, 4 responded partially and 6 did not respond. Knowledge of the severity of the disease did not allow us to predict the response, and therefore every patient should be tested individually. Intranasal DDAVP in our patients was used with success for bleeding into the knee joint, muscle hematoma and hematuria.

Interactions of purified rat factor VIII/von Willebrand factor with rat and human platelets--effect of albumin and ristocetin

Rat platelets do not respond to ristocetin in their own plasma nor do they aggregate in the presence of bovine or porcine factor VIII von Willebrand factor (F VIII R:WF) or human F VIII R:WF in presence of ristocetin. However, rat plasma supports ristocetin induced aggregation of washed human platelets. In this study we report on purification of rat F VIII R:WF from cryoprecipitate. Similarly to porcine or bovine material, purified rat F VIII R:WF induced aggregation of human washed fixed platelets. This effect was enhanced by addition of ristocetin and was not modified by addition of albumin. Rat washed platelets were aggregated by ristocetin in the presence of rat or human F VIII R:WF provided that high concentrations of ristocetin are added in a system essentially free of extraneous proteins. Increasing concentrations of albumin dramatically reduced the ability of ristocetin to aggregate rat platelets while human platelet aggregation by human or rat F VIII R:WF was only moderately affected. These studies show that rat F VIII R:WF can interact with rat and human platelets. The lack of response of rat platelets to ristocetin in their own plasma is most likely due to a low sensitivity of rat platelets to this drug and to an inhibitory activity of plasma proteins on this reaction.

Isolation of small molecular forms of Factor VIII/von Willebrand factor from plasma

Cryoprecipitated factor VIII/von Willebrand factor (FVIII/vWF), freed of fibrinogen by clotting with calcium and Defibrase, was chromatographed on Sepharose CL-2B. Fractions containing lower-molecular-weight forms of FVIII/vWF comprised coprecipitated plasma proteins of similar molecular weights. The major contaminants, fibronectin and IgM, were removed by affinity chromatography on gelatin- and anti-IgM-agarose, respectively. Finally, pure low-molecular-weight FVIII/vWF protein was harvested in the void volume fraction of a Sepharose CL-6B column. The smallest multimers had the size of the tetramer of the basic subunit chain of FVIII/vWF.

[Standardization problems in the monitoring of oral anticoagulants by Quick's thromboplastin time: an attempt to determine the state of the problem in Switzerland]

In comparison with British Comparative Thromboplastin, we examined 11 different reagents which are presently available in Switzerland for surveillance of oral anticoagulation. Frozen plasma samples obtained from 50 patients under oral anticoagulation for at least 6 weeks were used for comparison of the various reagents. From our results the following conclusions emerge: Our present results largely concur with those of a similar study which compared the therapeutic range of thromboplastin reagents available in Switzerland 6 years earlier; therefore, we assume that the reagents which were sold at that time and are now available in Switzerland have remained fairly constant. In contrast to this apparent agreement, the therapeutic ranges indicated by the producers of reagents are, at least in part, comparable neither with the therapeutic range established for the British Comparative Reagent nor among themselves. Thus, the intensity of the induced coagulation defect is obviously variable, depending on a given test system. The calculated "therapeutic range" for a given test system traditionally corresponds to an average risk of thrombosis or bleeding; this range is not of necessity identical with a target zone that has to be established either individually or for certain diseases. Once established, a target value defining the intensity of oral anticoagulation can be more conveniently reproduced by use of suitable control plasmas rather than with reference thromboplastins, at any rate by practitioners or non specialised hospital laboratories.(ABSTRACT TRUNCATED AT 250 WORDS)

[Fibrinogen Bern II: hereditary fibrinogen variant with amino acid substitution of arginine replaced by histidine in position 16 of the A alpha chain]

The number of described individuals with congenital dysfibrinogenemia continuously increases, but only a few fibrinogen variants have thus far been characterized with respect to their structural defect. Fibrinogen Bern II is a hereditary fibrinogen variant with impaired release of fibrinopeptide A (FPA) and a markedly prolonged coagulation time. It turned out that only half of the FPA was cleaved off at normal rate while the residual FPA was released much more slowly and incompletely, unless high thrombin concentrations were used. Amino acid analysis of normal and abnormal FPA revealed that the abnormal peptide, in contrast to the normal, contained histidine but hardly any arginine. It is therefore concluded that fibrinogen Bern II undergoes substitution of arginine in position 16 of the A alpha-chain by histidine. Thus, the structural alteration is identical with that of seven other recently described variants. The presence of 50% normal fibrinogen molecules provides the normal hemostasis in the heterozygous carriers of the Bern II-dysfibrinogenemia.

[Hemostasis disorders with reduced activity of the von Willebrand factor in myeloproliferative syndromes]

Splenectomy performed in a patient with polycythaemia vera and incipient osteomyelofibrosis was complicated by severe postoperative bleeding. A transient decrease of factor VIII/von Willebrand factor (VIIIR:WF) was detected as a possible cause of the bleeding tendency. As a result of this observation the VIIIR:WF system was investigated in all patients with myeloproliferative disorders who are presently followed by this laboratory. Subnormal VIIIR:WF activity was found in 5 of 9 prospectively investigated patients with polycythaemia vera and in one of 12 patients with chronic myeloid leukemia. These results suggest that acquired defects of the VIIIR:WF system are, in addition to the well known functional abnormalities of blood platelets, quite common in myeloproliferative disorders, especially polycythaemia vera, and must be reckoned with before surgery in particular. When specific antibodies directed against VIIIR:WF have been ruled out, the etiology of the VIIIR:WF defect found in our patients remains unclear.

Silver staining of high molecular weight proteins on large-pore polyacrylamide gels

A large-pore gel for electrophoresis in the presence of sodium dodecyl sulfate, composed of 2.55% polyacrylamide crosslinked with 2.75% methylenebisacrylamide, is described. This gel has a resolving power for very high molecular weight proteins and can be stained with silver. The gel is suitable for fractionation of factor VIII/von Willebrand factor directly from plasma samples. Visualization by silver staining revealed a series of covalently bound multimers with molecular weights of up to 8 X 10(6). The procedure described should be useful also for studies on other very high molecular weight proteins and nucleic acids.

Inhibition of fibrin polymerization by fragment d is affected by calcium, Gly-Pro-Arg and Gly-His-Arg

Fibrinopeptides A and B were removed from purified human fibrinogen by bovine thrombin, whereas the snake venom protease batroxobin only split fibrinopeptide A from fibrinogen. Aggregation of the resulting desAB- and desA-fibrin monomers was evaluated by recording the turbidity of incubation mixtures. Fibrin assembly was strongly accelerated by increasing the calcium concentration from 10(-5) to 10(-3) M. Fragment D was obtained from fibrinogen by proteolytic degradation with plasmin in the presence of Ca2+. At a 4-fold molar concentration relative to fibrinogen, fragment D dramatically inhibited fibrin polymerization at up to 10(-4) M Ca2+. This anticlotting activity was, however, much less pronounced at 10(-3) M Ca2+. The thrombin clotting time, measured on human plasma, was prolonged by fragment D in a dose-dependent manner. In citrate-containing plasma, the fibrinogen clotting was significantly delayed by an equimolar concentration of fragment D. In barium sulfate-adsorbed oxalated plasma, containing 2.5 mM Ca2+, the same amount of fragment D hardly affected fibrin polymerization. We conclude that fragment D has no important anticlotting effect under physiological conditions. The synthetic peptide Gly-Pro-Arg, corresponding to the amino-terminal sequence of the fibrin alpha-chain, inhibited aggregation of both desA-fibrin and desAB-fibrin at 10(-3) M Ca2+. The inhibition of desAB-fibrin polymerization by Gly-Pro-Arg was abolished at 10(-5) M Ca2+. In addition, Gly-Pro-Arg depressed the anticlotting activity of fragment D at low calcium concentration. An analogue of the amino-terminus of fibrin beta-chain, Gly-His-Arg, strongly accelerated aggregation of desA-fibrin monomers, but only moderately enhanced polymerization of desAB-fibrin monomers at 10(-5) M Ca2+, both in the presence and in the absence of fragment D. This activating effect of Gly-His-Arg was abolished at 10(-3) M Ca2+. It is suggested that the binding of calcium, Gly-His-Arg, and possibly also Gly-Pro-Arg, induces a conformational change in fibrin monomers and thus accelerates the polymerization process.

Effect of calcium and synthetic peptides on fibrin polymerization

Human fibrinogen was subjected to limited proteolytic attack by thrombin, batroxobin or Agkistrodon contortrix thrombin-like enzyme, yielding desAB-, desA- or desB-fibrin monomers, respectively. Turbidity curves demonstrated that, with all three enzymes, the polymerization process was strongly accelerated by increasing the calcium concentration from 10(-5) M to 10(-4) M. Synthetic peptide Gly-His-Arg (5 mM), an analogue of the aminoterminal sequence of fibrin beta-chain, inhibited aggregation of desB-fibrin monomers at physiological calcium concentration whereas it enhanced aggregation of desA- and desAB-fibrin monomers at calcium concentrations below 10(-4) M. On the other hand, Gly-Pro-Arg (1 mM) corresponding to the amino-terminus of fibrin alpha-chain, dramatically inhibited aggregation of both desA- and desB-fibrins, but it only moderately affected the polymerization of thrombin-induced monomers. We conclude that the observed effects of Gly-Pro-Arg and Gly-His-Arg are not due solely to their competition with fibrin amino-termini for the respective binding sites in the D-domain, but rather reflect conformational changes in fibrin monomers which affect the polymerization process.

[The 5q syndrome--a chromosome aberration with characteristic hematologic picture: preleukemia? Literature review and description of a personal case]

The case of a 74-year-old woman with macrocytic, refractory anemia, typical changes in the bone marrow and a 5q-chromosome in bone marrow cells is presented and the literature of this newly described hematological disorder is reviewed. The syndrome is characterized by partial deletion of the long arms of a chromosome No. 5 in bone marrow cells. The chromosomal anomaly is acquired and originates most probably from a pluripotent hematologic stem cell. Hematologic changes are (1) macrocytic, refractory anemia, (2) low to normal leukocyte counts, (3) normal to increased platelet number with marked anisocytosis and a high proportion of megathrombocytes, (4) normal to hypoplastic erythropoiesis and generally small megakaryocytes with nonlobulated nuclei in the bone marrow. In most of the reported cases (16 out of 19) with isolated 5q-anomaly, the clinical picture and laboratory findings remained stationary during a follow-up period of up to 6 years. In only 2 out of 19 cases did acute leukemia develop. In the presence of additional chromosomal abnormalities, all the cases developed acute leukemia and especially acute myelogenous leukemia. The diagnosis of 5q-syndrome in patients with refractory anemia is of prognostic significance, since it renders possible early recognition of a potentially malignant disorder and early detection of leukemic transformation.

Binding of bovine factor VIII-coated colloidal gold particles to receptors on platelet membranes

Bovine factor VIII/platelet aggregating factor was adsorbed into gold granules and the protein-gold complex added to either formalin-fixed or fresh washed human platelets. Following aggregation, binding of gold granules to the platelets was measured by monitoring the optical density of colloidal gold remaining in the supernatant. Scatchard analysis of binding data indicated that multiple classes of binding sites were present. The number of high affinity binding sites per formalin-fixed platelet depended on the concentration of ristocetin: 420 gold granules were calculated to bind at 1.4 mg/ml of ristocetin, 610 at 0.6 mg/ml of ristocetin and 875 when no ristocetin was added. Fresh washed platelets bound 1350 granules per cell in the absence of ristocetin. We conclude that during platelet aggregation, induced by bovine factor VIII, the binding sites on the platelet surface are only partially occupied.