Nano-micro structured superhydrophobic zinc coating on steel for prevention of corrosion and ice adhesion.

Thin films of zinc have been deposited on steel substrates by electrodeposition process and further functionalized with ultra-thin films of commercial silicone rubber, in order to obtain superhydrophobic properties. Morphological feature, by scanning electron microscope (SEM), shows that the electrodeposited zinc films are composed of micro-nano rough patterns. Furthermore, chemical compositions of these films have been analyzed by X-ray diffraction (XRD) and infra-red (IRRAS). An optimum electrodeposition condition, based on electrical potential and deposition time, has been obtained which provides superhydrophobic properties with a water contact angle of 155±1°. The corrosion resistance properties, in artificial seawater, of the superhydrophobic zinc coated steel are found to be superior to bare steel. Similarly, the measured ice adhesion strength on superhydrophobic surfaces, using the centrifugal adhesion test (CAT), is found to be 6.3 times lower as compared to bare steel. This coating has promising applications in offshore environment, to mitigate corrosion and reduce ice adhesion.

Bacteria, viruses, and parasites in an intermittent stream protected from and exposed to pasturing cattle: prevalence, densities, and quantitative microbial risk assessment.

Over 3500 individual water samples, for 131 sampling times, targeting waterborne pathogens/fecal indicator bacteria were collected during a 7-year period from 4 sites along an intermittent stream running through a small livestock pasture system with and without cattle access-to-stream restriction measures. The study assessed the impact of cattle pasturing/riparian zone protection on: pathogen (bacterial, viral, parasite) occurrence, concentrations of fecal indicators, and quantitative microbial risk assessments (QMRA) of the risk of Cryptosporidium, Giardia and Escherichia coli O157:H7 infection in humans. Methodologies were developed to compute QMRA mean risks on the basis of water samples exhibiting potentially human infectious Cryptosporidium and E. coli based on genotyping Crytosporidium, and E. coli O157:H7 presence/absence information paired with enumerated E. coli. All Giardia spp. were considered infectious. No significant pasturing treatment effects were observed among pathogens, with the exception of Campylobacter spp. and E. coli O157:H7. Campylobacter spp. prevalence significantly decreased downstream through pasture treatments and E. coli O157:H7 was observed in a few instances in the middle of the unrestricted pasture. Densities of total coliform, fecal coliform, and E. coli reduced significantly downstream in the restricted pasture system, but not in the unrestricted system. Seasonal and flow conditions were associated with greater indicator bacteria densities, especially in the summer. Norovirus GII was detected at rates of 7-22% of samples for all monitoring sites, and rotavirus in 0-7% of samples for all monitoring sites; pasture treatment trends were not evident, however. Seasonal and stream flow variables (and their interactions) were relatively more important than pasture treatments for initially stratifying pathogen occurrence and higher fecal indicator bacteria densities. Significant positive associations among fecal indicator bacteria and Campylobacter spp. detection were observed. For QMRA, adjusting for the proportion of Cryptosporidium spp. detected that are infectious for humans reduces downstream risk estimates by roughly one order of magnitude. Using QMRA in this manner provides a more refined estimate of beneficial management practice effects on pathogen exposure risks to humans.

Comparison of different RT-qPCR assays for the detection of human and bovine group A rotaviruses and characterization by sequences analysis of genes encoding VP4 and VP7 capsid proteins.

AIMS: The aim of this study was to compare the performance of four RT-qPCR assays for the detection of human and bovine group A rotaviruses and to characterize the positive samples by sequence analysis of VP4 and VP7 genes. METHODS AND RESULTS: RNA extracted from eight human rotavirus strains, and a panel of 33 human and 25 bovine faecal samples was subjected to different RT-qPCR detection systems. Among these assays, only RT-qPCR primers and probe systems B and C were able to detect all human rotavirus strains from cell culture solutions and faecal samples. However, the results showed that the system C was generally more sensitive by one or two logs than the other RT-qPCR assays tested. With the bovine faecal samples, the most efficient RT-qPCR systems were B and A with the detection in 100 and 92% of samples tested, respectively. Human group A rotavirus G1P[8] and bovine G6P[11] were the most frequently used strains identified in this study. A G3P[9] strain, closely related to a feline rotavirus isolated in the USA, was also discovered in a human rotavirus infection. CONCLUSION: The RT-qPCR system B was the only TaqMan assay evaluated in this study able to detect rotavirus RNA in all positive human and bovine faecal samples. SIGNIFICANCE AND IMPACT OF THE STUDY: Utilization of only one RT-qPCR for the detection of human and bovine group A rotaviruses and the possibility of human infection by a feline rotavirus strain.

Development of a real-time TaqMan PCR assay for the detection of porcine and bovine Torque teno virus.

AIMS: The goal of this study was to develop and to optimize molecular tools to detect the presence of Torque teno virus (TTV) in swine and cattle. A novel real-time polymerase chain reaction (PCR) using a TaqMan probe was developed to detect both genogroups of TTV strains. METHODS AND RESULTS: Oligonucleotide primers and hybridization probes were designed based on sequence analysis of the noncoding region, a highly conserved part of the genome. The real-time PCR assay specifically detected bovine and porcine TTV DNA without cross-amplification of other common pathogens. The assay was compared with conventional PCR and nested-PCR assays for the detection of porcine genogroups 1 and 2 and bovine TTV on plasma and faecal samples, and the assay was found faster, more reliable and reduced the risk of false positive results. CONCLUSIONS: The real-time PCR assay provided better detection results for the two TTV genogroups in both swine and cattle compared to the conventional PCR assays. SIGNIFICANCE AND IMPACT OF THE STUDY: This new TaqMan PCR assay will be a useful tool for the detection of animal TTV strains, to evaluate the viral load from animal host and finally to identify the presence of these viruses in the agri-food continuum.

The effect of pre-treatment and sonication of centrifugal ultrafiltration devices on virus recovery.

Enteric viruses such as norovirus (NV) and hepatitis A (HAV) are responsible for a large proportion of food and water-borne illnesses. Most human pathogenic enteric viruses cannot be cultured so they must be detected by molecular techniques. Male specific (F(+)) RNA coliphages, a potential surrogate for human enteric viruses, can be detected by culture and molecular assays. Numbers of viruses and F-RNA coliphages in contaminated food or water may be too low for direct detection. Ultrafiltration is a general concentration method for all virus types but there is little information on the recovery efficiency of F-RNA coliphages and enteric viruses. The recovery of F-RNA coliphage MS2 was only 25% by plaque assay in initial trials. The objective was to optimize the recovery of concentrated MS2 from Microsep 100K ultrafiltration devices. The mean recovery of MS2 increased significantly to 85% by plaque assay and 65% by real-time RT-PCR when ultrafiltration devices were treated with 1% BSA before concentration and then ultrasonicated after concentration. The method was validated with MS2, HAV, NV and feline calicivirus (FCV) in water and spinach eluate. The recovery of MS2, HAV and NV was significantly higher from concentrates obtained from water with treated devices than untreated devices but not significantly different for FCV or from spinach eluate. To our knowledge, this is the first study to use ultrasonication as a post-treatment step to increase recovery of viruses from ultrafiltration devices.

Comparative analysis of different TaqMan real-time RT-PCR assays for the detection of swine Hepatitis E virus and integration of Feline calicivirus as internal control.

AIMS: The aim of this study was to compare the performance of four TaqMan RT-PCR assays with a commonly used nested RT-PCR and to include the Feline calicivirus (FCV) as an internal control. METHODS AND RESULTS: RNA extracted from 87 swine faecal samples and 103 swine blood samples was subjected to different detection systems. Faecal samples naturally contaminated with Hepatitis E virus (HEV) and negative samples were artificially inoculated with 3.2 x 10(3) PFU of FCV. Detection results obtained on faecal and plasma samples were 35.6% and 4.9% with the nested RT-PCR assay, 8.0% and 0%, 0% and 0%, 13.8% and 0% and 36.8% and 3.9% with TaqMan systems A, B, C and D respectively. The Ct means obtained with the multiplex TaqMan assay were 30.11 and 30.43 for the detection of FCV with HEV contaminated samples and negative samples. CONCLUSIONS: The TaqMan system D was more suitable for the detection of swine HEV strains than the three others and FCV was integrated successfully as an internal control. SIGNIFICANCE AND IMPACT OF THE STUDY: FCV was demonstrated as an efficient control to monitor the RNA extraction process and HEV amplification procedure in a multiplex HEV/FCV TaqMan assay. This control would be helpful in limiting false negative results.

Molecular detection of bovine and porcine Torque teno virus in plasma and feces.

Torque teno virus (TTV) is frequently detected in humans, livestock and some companion animals. Very little is known about presence of TTV in Canadian livestock and the goal of this study was to evaluate the presence of TTV in swine and cattle using molecular tools. TTV DNA was detected and confirmed by sequencing in the plasma of 90.5% and in the feces of 60.3% of the animals tested in a single swine herd as well as 80.9% and 1.1% in the plasma of individuals from general Quebec swine and cattle populations, respectively. The impact of the TTV presence in livestock population for the agri-food chain should be further investigated.

Decrease of the adhesion of Streptococcus suis serotype 2 mutants to embryonic bovine tracheal cells and porcine tracheal rings.

Streptococcus suis is an important swine pathogen that may be present in the tonsils of pigs that show no signs of illness. Because adhesion to host cells may be important in the carrier state, this study was undertaken to investigate adhesion to host cells by S. suis mutant strains defective in expression of a 39-kDa protein. Mutant strains of S. suis were generated by transposon Tn916 mutagenesis and were tested for adhesion to embryonic bovine tracheal cells and porcine tracheal rings. Compared with the parent strain, there was a significant reduction in adherence of 3 mutant strains to both bovine tracheal cells and porcine tracheal rings.

Expression and characterization of von Willebrand factor dimerization defects in different types of von Willebrand disease.

Dimerization defects of von Willebrand factor (vWF) protomers underlie von Willebrand disease (vWD) type 2A, subtype IID (vWD 2A/IID), and corresponding mutations have been identified at the 3' end of the vWF gene in exon 52. This study identified and expressed 2 additional mutations in this region, a homozygous defect in a patient with vWD type 3 (C2754W) and a heterozygous frameshift mutation (8566delC) in a patient with vWD type 2A, subtype IIE. Both mutations involve cysteine residues that we propose are possibly essential for dimerization. To prove this hypothesis, transient recombinant expression of each of the 2 mutations introduced in the carboxy-terminal vWF fragment II and in the complete vWF complementary DNA, respectively, were carried out in COS-7 cells and compared with expression of vWD 2A/IID mutation C2773R and the wild-type (WT) sequence in COS-7 cells. Recombinant WT vWF fragment II assembled correctly into a dimer, whereas recombinant mutant fragments were monomeric. Homozygous expression of recombinant mutant full-length vWF resulted in additional dimers, probably through disulfide bonding at the amino-terminal multimerization site, whereas recombinant WT vWF correctly assembled into multimers. Coexpression of recombinant mutant and recombinant WT vWF reproduced the multimer patterns observed in heterozygous individuals. Our results suggest that a common defect of vWF biosynthesis--lack of vWF dimerization--may cause diverse types and subtypes of vWD. We also confirmed previous studies that found that disulfide bonding at the vWF amino-terminal is independent of dimerization at the vWF carboxy-terminal. (Blood. 2001;97:2059-2066)

Incubation time of acute human immunodeficiency virus (HIV) infection and duration of acute HIV infection are independent prognostic factors of progression to AIDS.

The severity and the duration of acute human immunodeficiency virus (HIV) infection (AHI) are associated with a faster rate of progression to AIDS, but the prognostic value of the length of incubation time of AHI (IncAHI), defined as the time between HIV infection and AHI, on progression to AIDS has not been assessed. We explored this issue prospectively in 70 individuals with documented AHI and a known date of HIV infection. The median IncAHI was 21.5 days (range, 5-70 days), and the median duration of AHI was 15.5 days (range, 3-67 days). The adjusted relative hazard of progression to AIDS or to a CD4(+) count <200x103/mL was 4.23 (95% confidence interval [CI], 1.40-12.73; P=.01) for the patients with an IncAHI <21.5 days, compared with those with longer IncAHI, and was 3.53 (95% CI, 1.09-11.36; P=.03) for the patients with a duration of AHI >15.5 days, compared with those with shorter duration. Both IncAHI and duration of AHI were independent predictors of progression. This suggests that early pathogenic events before the onset of AHI influence the rate of HIV disease progression.

Allergic contact dermatitis to epoxy resin in microscopy immersion oil: cases from Canada.

The presence of epoxy resin in a reformulated immersion oil for microscopy has caused an epidemic of occupational contact dermatitis in laboratory technicians from some European centers. We report 6 additional cases, the mode of presentation of which was similar to the European patients. All patients were patch tested to the undiluted oil, and some were tested to the European or North American standard series and to an extensive series of glues and adhesives allergens. At 96 hours, all 6 patients displayed a strong 2+ to 3+ reaction to the undiluted oil. Two patients were not further tested, but in the remaining 4, positive reactions were seen to epoxy resin from the standard tray. One patient reacted to cycloaliphatic epoxy resin, and 2 displayed positive tests to the reactive diluents phenyl glycidyl ether and cresyl glycidyl ether. These further cases confirm the strong sensitizing properties of this particular immersion oil. The product, manufactured by Leica Microsystems (Wetzlar, Germany), since has been withdrawn from sale.

Interspecies differences in renal localization of cyclooxygenase isoforms: implications in nonsteroidal antiinflammatory drug-related nephrotoxicity.

Cyclooxygenase (COX) exists in 2 related but unique isoforms: one is constitutive (COX-1) and functions in normal cell physiology, and the other is inducible (COX-2) and is expressed in response to inflammatory stimuli. Nonsteroidal antiinflammatory drugs (NSAIDs) cause renal toxicity following inhibition of renal cyclooxygenases. Humans and animals exhibit differences in susceptibility to NSAID-related renal toxicity, which may be associated with differences in expression of 1 or both isoforms of COX in the kidney. In this study, we evaluated COX-1 and COX-2 expression in the kidneys of mixed-breed dogs, Sprague-Dawley rats, cynomolgus monkeys, and humans. In addition, the effect of volume depletion on renal COX expression was investigated in rats, dogs, and monkeys. COX expression was evaluated using 1 or more of the following procedures: reverse transcriptase polymerase chain reaction, in situ hybridization, and immunohistochemistry. We demonstrated that both COX isoforms are expressed in the kidneys of all species examined, with differences in the localization and level of basal expression. COX-1 is expressed at high levels in the collecting ducts and renal vasculature of all species and in a small number of papillary interstitial cells in rats, monkeys, and humans. Basal levels of COX-2 are present in the maculae densa, thick ascending limbs, and papillary interstitial cells in rats and dogs and in glomerular podocytes and small blood vessels in monkeys and humans. COX-2 expression is markedly increased in volume-depleted rats and dogs but not monkeys. These results indicate that significant interspecies differences exist in the presence and distribution of COX isoforms, which may help explain the difference in species susceptibility to NSAID-related renal toxicity.

Varicella vaccination for healthcare workers at a university hospital: an analysis of costs and benefits.

OBJECTIVE: To demonstrate the costs and benefits of vaccinating varicella-susceptible healthcare workers at a university hospital with live, attenuated varicella-zoster virus vaccine. DESIGN: Retrospective review of employee medical records and data on the cost of special paid absence for susceptible healthcare workers after exposure to varicella or herpes zoster. SETTING: A 988-bed tertiary-care university hospital. RESULTS: In 1994, 224 hospital employees (3.4%) were susceptible to the varicella-zoster virus. There were 40 exposures to varicella and herpes zoster in that year, involving 29 of the susceptible employees. Nine (31%) of the exposed susceptibles became varicella immune by indirect fluorescent antibody testing subsequent to exposure. Seventeen (59%) have had multiple varicella exposures and special paid absences while employed by the hospital. In 1994, wages paid to healthcare workers while furloughed for the communicable period following varicella exposure totaled $38,463.93. An additional $24,748.74 was paid to replacement workers during that same time. Varicella vaccine to immunize all 224 susceptibles in 1994 would have cost $17,920. Absences due to varicella and herpes zoster exposure also result in disruptions to patient care. CONCLUSIONS: Varicella vaccination for varicella-susceptible healthcare workers at a university hospital would result in financial savings and improved patient care. We recommend that other institutions consider the costs and benefits of adopting a varicella immunization program for their susceptible employees.

Temporal variation and factors affecting measurement of canine von Willebrand factor.

OBJECTIVE: To determine whether canine plasma von Willebrand factor (vWf) varies between and within individuals over time and with different blood sample collection and processing procedures. ANIMALS: 26 adult dogs and 6 pups. PROCEDURE: Blood was obtained from the jugular or cephalic vein daily for 8 to 19 days and weekly for 9 to 23 weeks in adult dogs and periodically up to 180 days of age in pups. Temporal variation in vWf concentration and the effect of vascular occlusion, venipuncture site, lipemia, hemolysis, anticoagulant, storage time, freeze-thawing, and centrifugation speed on plasma vWf concentration, measured by ELISA, were determined. RESULTS: Plasma vWf concentration varied over time. In dogs with mean vWf concentration > or = 79 U/dl, the largest intraindividual range in vWf spanned 64 U/dl with daily and 53 U/dl with weekly sample collection. In dogs with mean vWf concentration < or = 24 U/dl, the largest individual variation was 12 U/dl with daily and weekly sample collection. In dogs with mean vWf concentration > or = 53 and < or = 74 U/dl, the largest intraindividual range spanned 35 U/ dl. Mean vWf concentration of pups from 3 to 180 days of age did not change. Sample hemolysis decreased mean vWf by 37%. Mean vWf concentration was 9% higher in cephalic than jugular vein samples (P = 0.056). Other sample collection/preparation procedures did not affect vWf concentration. CONCLUSION: There was substantial temporal variation in vWf concentration within individual dogs. CLINICAL RELEVANCE: Multiple tests may be necessary to obtain a reliable estimate of vWf concentration in dogs.

Altered expression of basement membrane proteins and their integrin receptors in lichen planus: possible pathogenetic role of gelatinases A and B.

Lichenoid lesions of the skin are characterized by a band-like dermal inflammatory infiltrate and structural alterations of the basement membrane (BM). The etiopathogenesis of these lesions, of which lichen planus (LP) is perhaps the prototypic example, is unknown. Acute cases of LP are accompanied by the destruction of epidermal BM, degeneration of basal keratinocytes with loss of tonofilaments and hemidesmosomes, vesicular alterations, and even blister formation. Chronic LP is characterized by hyperkeratosis and acanthosis in the epidermis, fibrosis, and dense infiltrate in dermis. We found that acute LP lesions are characterized by uneven or absent immunostaining for laminin-5, laminin-1, and collagen type IV. Distribution and activity of gelatinases matrix metalloproteinase (MMP)-9 and MMP-2, and a specific inhibitor of MMP-2, tissue inhibitor of metalloprotein-2, were analyzed. The expression and activity of MMP-2 were increased, whereas tissue inhibitor of metalloprotein-2 expression was weak in the involved areas during the acute phase of LP. Moreover, we demonstrated in vitro that MMP-2 is directly capable of digesting laminin-5 gamma 2 chains to yield a 80-kd fragment. We also observed a weak or absent staining of all examined integrin receptors in the acute LP lesions. In chronic lesions, the staining of BM components was similar to normal controls. In these sections, normal expression of gelatinases and inhibitor was observed. There was, however, up-regulation and altered polarity of integrin receptors. These results indicate a link between overexpression of gelatinases, BM disruption, and altered integrin expression. In LP, the digestion of BM by MMP-2 may contribute to the pathogenesis by inducing altered integrin expression in basal keratinocytes and ultimately blister formation.

Defective dimerization of von Willebrand factor subunits due to a Cys-> Arg mutation in type IID von Willebrand disease.

The same heterozygous T -> C transition at nt 8567 of the von Willebrand factor (vWF) transcript was found in two unrelated patients with type III) von Willebrand disease, with no other apparent abnormality. In one family, both alleles were normal in the parents and one sister; thus, the mutation originated de novo in the proposita. The second patient also had asymptomatic parents who, however, were not available for study. The structural consequences of the identified mutation, resulting in the CyS2010 -> Arg substitution, were evaluated by expression of the vWF carboxyl-terminal domain containing residues 1366-2050. Insect cells infected with recombinant baculovirus expressing normal vWF sequence secreted a disulfide linked dimeric molecule with an apparent molecular mass of 150 kDa before reduction, yielding a single band of 80 kDa after disulfide bond reduction. In contrast, cells expressing the mutant fragment secreted a monomeric molecule of apparent molecular mass of 80 kDa, which remained unchanged after reduction. We conclude that CyS2010 is essential for normal dimerization of vWF subunits through disulfide bonding of carboxyl-terminal domains and that a heterozygous mutation in the corresponding codon is responsible for defective multimer formation in type III) von Willebrand disease.

Two antipeptide monoclonal antibodies that recognize adhesive sequences in fibrinogen: identification of antigenic determinants and unrelated sequences using synthetic combinatorial libraries.

The fine specificity of two different monoclonal antibodies raised against synthetic peptides, each representing one of the two Arg-Gly-Asp (RGD) sequences in fibrinogen, was examined using synthetic combinatorial libraries (SCLs). The monoclonal antibodies (mAb), mAb LJ-134B/29 and mAb LJ-155B/16, recognize both the immunogenic peptide and native fibrinogen. The specificity of mAb LJ-134B29 was mapped using hexa- and decapeptide positional scanning SCLs (PS-SCLs) and competitive ELISA. The most active amino acids at each position of the two libraries were identified from a single screening. Individual hexa- and decapeptides were synthesized and assayed to determine their binding affinities. The 16 individual hexapeptides represented single and multiple substitutions of the antigenic determinant sequence, -GDSTFE-, eight of which had affinities less than 10nM. Four of the twelve individual decapeptides were found to have binding affinities of approximately 300nM, or nearly three-fold less than the peptide immunogen. A dual-defined hexapeptide library was screened against mAb LJ-155B/16, and individual peptides were obtained through an iterative selection and synthesis process. Surprisingly, one of the most active sequences was Ac-WWYESW-NH2 (IC50 = 40nM), which showed no similarity to the sequence of the immunizing peptide. Further mapping of the specificity of this antibody revealed that the antigenic determinant within the peptide immunogen was not completely linear. Recognition of this unrelated sequence by mAb LJ-155B/16 was confirmed in a direct binding assay using biotinylated peptide. The use of SCLs for the elucidation of high affinity peptides recognized by these two antibodies may provide additional information on the molecular mechanisms of fibrinogen binding to different integrin receptors.

Effects of hyperoxia on rat diaphragm function.

The association of oxygen radical generation with impaired diaphragm performance has previously been reported after inspiratory resistive loading (IRL). We hypothesized that exposure of rats to normobaric hyperoxia (O2) could produce impaired diaphragm function because of free radical production. Sprague-Dawley rats were divided into four groups: 1) room air (control), 2) > 95% O2 for 24 h, 3) > 95% O2 for 48 h, and 4) > 95% O2 for 60 h. Each group was studied at rest after the O2 exposure and then after IRL. During IRL, the animals breathed through an inspiratory resistor until they were unable to sustain > 70% of the maximum airway pressure. Diaphragm samples were obtained for analysis of glutathione (GSH) and glutathione disulfide (GSSG) concentrations. In vitro isometric contractile properties were also determined, including maximal tetanic tension (Po) and maximal twitch tension (Pt), in GSSG content and in GSSG-to-GSH ratios. Hyperoxia for > 48 h resulted in significant decreases in Po and Pt and an increase in GSSG content and in GSSG-to-GSH ratios compared with other groups. Those same animals subjected to IRL showed a further decrease in Po and Pt. These data suggest that free radical generation may occur in the diaphragm during a hyperoxia exposure associated with activation of the GSH redox cycle and impairment of diaphragm function.

Experimentally induced renal failure in the dog as an animal model of uremic bleeding.

Experimental canine renal failure was studied as a potential animal model for human uremic bleeding. Renal failure accompanied by hemostatic alterations was induced in eight dogs by means of two surgical techniques of renal mass reduction. The hemostatic deficits consisted of immediate and marked reduction of the platelet glass bead retention (PR) to less than 10% of normal and gradual prolongation of the buccal mucosal bleeding time (BMBT) to approximately four times the normal value. Platelet count, volume, aggregation responses, and coagulation were normal. A packed cell volume (PCV) of less than 30% was observed in three dogs. Elevation of the PCV normalized the BMBT in two dogs, but because the PR was unchanged and the BMBT effect was temporary, anemia was not considered the primary cause of the prolonged bleeding time. There was a significant, positive correlation between BMBT and BUN, suggesting that the altered hemostasis may be related to the accumulation of urea or other uremic toxins of protein origin. The finding of a defect in PR and BMBT--tests that require normal platelet adhesion and aggregation--in azotemic dogs were platelet numbers and aggregation are normal indirectly implicates platelet adhesion as the primary hemostatic defect.

von Willebrand factor is not altered in azotemic dogs with prolonged bleeding time.

The effects of azotemia on von Willebrand factor (vWf) plasma concentration, structure, and function were studied by utilizing canine models for both uremic bleeding and type I vWf deficiency (vWd). Seventy-five percent to 80% renal mass reduction in eight mixed-breed dogs induced marked azotemia (blood urea nitrogen [BUN] 103 +/- 7 mg/dl [mean +/- SEM]; creatinine 5.8 +/- 1 mg/dl) and prolonged mean buccal mucosal bleeding time (BMBT) from 1.8 +/- 0.2 minutes to 7.0 +/- 0.4 minutes. The mean vWf plasma concentration increased from 0.88 +/- 0.11 U/ml to 1.26 +/- 0.14 U/ml. The pre- and postsurgical sodium dodecyl sulfate-agarose gel electrophoresis multimeric patterns were similar in all dogs. Administration of cryoprecipitate from pooled azotemic mixed-breed dog plasma to five Doberman pinschers with type I vWd increased the mean plasma vWf from 0.14 +/- 0.01 U/ml to 0.48 +/- 0.04 U/ml and decreased the BMBT from 7.1 +/- 0.6 minutes to 3.14 +/- 0.09 minutes. After renal mass reduction, five type I vWd Dobermans developed marked azotemia (BUN 79 +/- 8.6 mg/dl; creatinine 3.7 +/- 0.6 mg/dl) and prolonged BMBT (16.1 +/- 3.6 minutes). Findings in the eight azotemic mixed-breed dogs indicated that (1) vWf plasma levels were normal to increased in azotemic dogs; (2) vWf structure and multimeric distribution were not altered in canine azotemia; and (3) vWf was functional when placed in a non-azotemic environment. The prolongation of the BMBT in azotemic vWd dogs indicated that factors other than alteration of vWf function were responsible for the prolonged BMBT in canine azotemia.