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Biomedical subjects

D C Lewis

Publications and source records attributed to D C Lewis.

At least 37 records · Page 2Linked to original sources
PubMed1995

Detection of platelet-bound and serum platelet-bindable antibodies for diagnosis of idiopathic thrombocytopenic purpura in dogs.

The sensitivity and specificity of 2 antibody tests for diagnosis of idiopathic thrombocytopenic purpura (ITP) in dogs were investigated prospectively. An ELISA to detect antibodies bound to the surface of platelets from affected dogs (direct test) was performed in 34 dogs with a clinical diagnosis of ITP and in 21 dogs with thrombocytopenia attributable to other causes. An ELISA to detect platelet-bindable antibodies in serum from affected dogs (indirect test) was performed in 32 dogs with ITP and in 15 dogs with other causes of thrombocytopenia. The direct test was positive in 32 of 34 dogs with ITP (sensitivity, 94%) and negative in 13 of 21 dogs with other causes of thrombocytopenia (specificity, 62%). Positive direct test results were obtained in 2 dogs with systemic lupus erythematosus, and in 1 dog each with concurrent Ehrlichia canis and Babesia canis infections, dirofilariasis, myelodysplasia, disseminated intravascular coagulation (of unknown cause), and thrombocytopenia subsequent to administration of trimethoprim/sulfadiazine, as well as in 1 dog with thrombocytopenia 14 days after a whole blood transfusion. The indirect test had positive results in 11 of 32 dogs with ITP (sensitivity, 34%) and negative results in 12 of 15 dogs with other causes of thrombocytopenia (specificity, 80%). Positive indirect test results were obtained in 1 dog each with systemic lupus erythematosus, concurrent E canis and B canis infections, and thrombocytopenia subsequent to administration of trimethoprim/sulfadiazine. Detection of platelet-bound antibodies was more sensitive than detection of serum-platelet bindable antibodies in confirming a diagnosis of ITP in dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Detection and differentiation of antigenically distinct small round-structured viruses (Norwalk-like viruses) by reverse transcription-PCR and southern hybridization.

Application of reverse transcription (RT)-PCR to detect small round-structured viruses (SRSVs) from fecal specimens of patients with gastroenteritis has been insensitive because of the tremendous sequence heterogeneity between strains. We have designed two RT-PCR primer sets (G-1 and G-2) based on the nucleotide sequence diversity in the RNA polymerase gene of SRSVs belonging to two distinct genogroups represented by Norwalk virus (primers G-1) and Snow Mountain agent (primers G-2). All 22 SRSV strains examined that had been classified previously by solid-phase immune electron microscopy into four antigenic types (UK1, UK2, UK3, and UK4) could be detected by RT-PCR with these two primer sets. The G-1 primer set detected 6 UK2 strains, and the G-2 primers detected 16 strains, including 7 UK1, 5 UK3, and 4 UK4 strains. On the basis of nucleotide sequences of 81-bp fragments of the RT-PCR products from 13 strains determined in this study, together with those previously reported for 17 SRSV strains, we designed four sets of internal oligonucleotide probes (P1-A, P1-B, P2-A, and P2-B) for Southern hybridization, using chemiluminescent detection. The P1-A probe hybridized with PCR products from the UK2 strains; the P1-B probe, with products from two of the seven UK1 strains; the P2-A probe, with four of the remaining five UK1 strains; and the P2-B probe, with products from both UK3 and UK4 strains, as well as with one strain originally typed as UK1 which showed cross-reactivity with UK4 upon retesting by solid-phase immune electron microscopy. RT-PCR with both the G-1 and the G-2 primer sets can increase the detection rate of the many antigenically distinct SRSVs and, when combined with Southern hybridization, may predict the antigenic type of the SRSV associated with infection.

Adult↗
PubMed1995

Development and characterization of a flow cytometric assay for detection of platelet-bound immunoglobulin G in dogs.

OBJECTIVE: To develop a flow cytometric assay for detection of platelet-bound IgG in dogs. SAMPLE POPULATION: Negative-control platelets were obtained from 5 clinically normal Greyhounds. Positive-control platelets were platelets from 1 clinically normal dog, sensitized with dog anti-canine platelet alloantibodies. PROCEDURE: Washed platelets were incubated with mouse anti-canine IgG conjugated to fluorescein isothiocyanate and analyzed by flow cytometry. Optimal dilution of antibody reagent and dose-response were determined, as were effects on platelet-bound IgG detection of storage time and temperature of K3EDTA-anticoagulated blood samples, variable platelet numbers, and variable filling of K3EDTA evacuated tubes. RESULTS: A 1:128 dilution of antibody reagent was optimal. There was a linear increase in platelet-bound IgG when normal canine platelets were incubated with increasing concentrations of positive-control serum. Variable numbers of positive-control platelets tested and variable filling of K3EDTA evacuated tubes had no significant effect on platelet-bound IgG concentration. Platelet-bound IgG concentration increased with storage time at room temperature (P = 0.0003), but not when blood was kept cool. Sufficient platelets for assay were able to be isolated from 3 ml of blood from 5 dogs with < 10,000 platelets/microliters. CONCLUSIONS: This assay for platelet-bound IgG in dogs is simple, repeatable, and practical. The assay is not affected by platelet count or variable filling of evacuated tubes, and requires only 3 ml of K3EDTA-anticoagulated blood. Blood samples for testing require packaging on ice and overnight delivery but, after arrival at the laboratory, can be refrigerated and analyzed within 72 hours of collection. CLINICAL RELEVANCE: Assays for platelet-bound IgG may help in assessing causes and treatment of thrombocytopenia.

Animals↗
PubMed1994

Comparison of the polymerase region of small round structured virus strains previously classified in three antigenic types by solid-phase immune electron microscopy.

We have used a reverse transcription-polymerase chain reaction with nested sets of primers to determine the nucleotide sequences of a 166 base pair segment of the RNA polymerase region of seven strains of small round structured viruses (SRSVs) from the United Kingdom. These SRSV strains were previously classified by solid-phase immune electron microscopy into three antigenic types--UK2, UK3 and UK4, which are comparable to the prototype strains Norwalk virus, Hawaii agent, and Snow Mountain agents, respectively. Based on their sequences, the seven strains from the United Kingdom could be divided into two groups. The first group included two strains of the UK2 type along with Norwalk virus and Southampton virus and the second group included three strains of UK3 and two strains of UK4 types. Viruses in the first group showed 75.3%-77.1% nucleotide and 89.1%-94.6% amino acid identity with Norwalk virus while those of the second group showed 60.8%-63.3% nucleotide and 67.3%-69.1% amino acid identity. Nucleotide and amino acid identity within the second group ranged between 91.6%-99.4% and 96.4%-100%, respectively. These results suggest that the SRSVs antigenically related with Norwalk virus, Hawaii agent, and Snow Mountain agent, can be classified into two genotypes on the basis of their sequences in the RNA polymerase region.

Adult↗
PubMed1994

Characterization of a variant strain of Norwalk virus from a food-borne outbreak of gastroenteritis on a cruise ship in Hawaii.

A gastroenteritis outbreak affecting at least 217 (41%) of 527 passengers on a cruise ship was caused by a variant strain of Norwalk virus (NV) that is related to but distinct from the prototype NV strain. Consumption of fresh-cut fruit served at two buffets was significantly associated with illness (P < or = 0.01), and a significant dose-response relationship was evident between illness and the number of various fresh-cut fruit items eaten. Seven (58%) of 12 paired serum specimens from ill persons demonstrated at least fourfold rises in antibody response to recombinant NV capsid antigen. A 32-nm small round-structured virus was visualized by electron microscopy in 4 (29%) of 14 fecal specimens, but none of the 8 specimens that were examined by an enzyme immunoassay for NV antigen demonstrated antigen. Four (40%) of 10 fecal specimens were positive by reverse transcriptase-PCR by using primer pairs selected from the polymerase region of NV. In a 145-bp region, the PCR product shared only 72% nucleotide sequence identity with the reference NV strain and 77% nucleotide sequence identity with Southampton virus but shared 95% nucleotide sequence identity with UK2 virus, a United Kingdom reference virus strain. In addition, the outbreak virus was serotyped as UK2 virus by solid-phase immune electron microscopy. The genetic and antigenic divergence of the outbreak strain from the reference NV strain highlights the need for more broadly reactive diagnostic assays and for improved understanding of the relatedness of the NV group of agents.

Antigenic Variation↗
PubMed1994

Effect of anticoagulant and blood storage time on platelet-bound antibody concentrations in clinically normal dogs.

A solid-phase ELISA to detect antibodies bound to the surface of canine platelets (platelet-bound antibodies) is described. Using this assay, the effect of anticoagulant and storage time of anticoagulant blood on the concentration of antibodies bound to the surface of platelets from clinically normal dogs was investigated. Blood from 3 clinically normal dogs was anticoagulated with acid citrate dextrose, Na3 citrate, and aqueous K3 EDTA and stored on ice for up to 48 hours. Platelet-bound antibody concentration was measured on platelets isolated from anticoagulated blood immediately after venipuncture and subsequent to storage of blood for 24 and 48 hours. Differences in platelet-bound antibody concentrations were investigated among dogs, anticoagulants, and storage times by ANOVA and Bonferroni pair-wise comparison of means. There was no effect of dog on platelet-bound antibody concentration. The effect of time was significant (P < 0.0001), with higher concentration of platelet-bound antibodies detected with increasing storage time. Effect of anticoagulant on platelet-bound antibody concentration was not statistically significant; however, there was a trend to increasing concentration of antibodies bound to platelets isolated from Na3 citrate- and K3 EDTA-anticoagulated blood. Moreover, there was significant (P = 0.02) interaction between anticoagulant and time. Platelet-bound antibody concentration increased with storage of anticoagulated blood prior to platelet isolation and with use of Na3 citrate and K3 EDTA anticoagulants. The preferred anticoagulant for platelet-bound antibody measurement is acid citrate dextrose. Platelet-bound antibody concentration should be determined not longer than 24 hours after blood collection.

Analysis of Variance↗
PubMed1993

Pneumothorax in polysubstance-abusing marijuana and tobacco smokers: three cases.

Three patients are reported who suffered spontaneous pneumothorax, each of whom also had a history of daily marijuana and tobacco use. The patients ranged in age from 24 to 37 years, had smoked marijuana on a daily basis for 10 to 14 years, and had 11 to 50 pack-year tobacco-smoking histories. Marijuana may predispose to pneumothorax both by accelerating tobacco-induced lung disease, and by the frequent performance of the Valsalva maneuver during marijuana smoking. Although there is an association between pneumothorax and heavy tobacco use, an association with chronic daily marijuana use has not previously been reported.

Adult↗
PubMed1993

Estimation of potential health effects from acute exposure to hydrogen fluoride using a "benchmark dose" approach.

Communities across the United States are examining the manufacture, use, transport, and storage of hydrogen fluoride (HF) near residential areas as a consequence of a major release of HF in Texas in 1987. Reference exposure levels for routine and accidental HF emissions are calculated using existing animal and human data. The approach employs a log-probit extrapolation of concentration-response data to the 95% lower confidence limit on the toxic concentration producing a "benchmark dose" of 1% response (TC01), called a practical threshold. Species-specific and chemical-specific adjustment factors are applied to develop exposure levels applicable to the general public. Using this method, the 1-hr reference exposure level to protect the public against any irritation from a routine emission (REL-1) is 0.7 ppm and the level to protect against severe irritation from a once-in-a-lifetime (REL-2) release is 2 ppm. This approach is compared to a modified "uncertainty factor" approach.

Air Pollutants↗
PubMed1992

Open or transurethral surgery for the large prostate gland.

A comparative study of transurethral (TUR) and open prostatectomy for the large prostate gland has been carried out. Over a 5-year period 94 transurethral resections and 73 open procedures were performed for prostate glands weighing more than 50 g. There was a single death in each group, giving relative mortality rates of 1.1% TUR and 1.4% open. The post-operative hospital stay was significantly shorter in the TUR group. The open group suffered significantly more complications in the first week but the TUR patients, although having fewer immediate postoperative complications, had significantly more in the first year, so that overall complication rates were similar (35% vs 36%). Patient satisfaction was equal in both groups.

Aged↗