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Biomedical subjects

M McClelland

Publications and source records attributed to M McClelland.

At least 55 records · Page 3Linked to original sources
PubMed1997

Evaluation of artecoll polymethylmethacrylate implant for soft-tissue augmentation: biocompatibility and chemical characterization.

Artecoll polymethylmethacrylate implant (Artecoll) is a combination of polymethylmethacrylate beads suspended in 3.5% atelocollagen and has been designed for use in soft-tissue augmentation applications. The biocompatibility and immunogenicity of Artecoll were evaluated to assess the safety of this product for use in the dermis. To characterize the collagen component, chemical analysis was performed including trypsin sensitivity, differential scanning calorimetry, and pepsin content. Particle size analysis was also performed on the polymethylmethacrylate beads. The ability of this material to elicit an immunologic response was measured in a sensitized and nonsensitized guinea pig intradermal model. In these studies, 24 guinea pigs were injected intradermally with either Artecoll or Zyderm, a bovine collagen product for soft-tissue augmentation. Six sites were evaluated for each material at 3, 7, and 28 days after injection. In the sensitized model, 60 guinea pigs were divided into five groups, and each group received a sensitizing dose (in conjunction with Freund's adjuvant) of Zyderm, Artecoll, or a nonsensitizing dose of the same materials. The fifth group served as a nontreatment control. After the animals were sensitized, they were challenged with intradermal injections of various antigens to evaluate delayed type hypersensitivity reactions. Chemical characterization indicated polymethylmethacrylate beads of varying sizes, including many less than 35 microns, and a vehicle of extensively denatured and impure collagen. In vivo evaluations indicated that Artecoll elicited an immune response in guinea pigs, including delayed type hypersensitivity and antibody reactions. Histological assessment demonstrated particle phagocytosis and transepidermal elimination. Following immunization with Artecoll, guinea pigs were also found to be sensitized to pepsin, an impurity found in the collagen carrier. The biocompatibility of this material was compared with that of bovine dermal collagen (Zyderm collagen implant), which is widely used and accepted as biocompatible. The results of this evaluation indicate that Artecoll polymethylmethacrylate implant has the potential to elicit an immune response in humans, and polymethylmethacrylate beads are susceptible to phagocytosis and elimination.

Adjuvants, Immunologic↗
PubMed1996

DNA rehybridization during PCR: the 'Cot effect' and its consequences.

The rate of amplification of abundant PCR products generally declines faster than that of less abundant products in the same tube in the later cycles of PCR. As a consequence, differences in product abundance diminish as the number of PCR cycles increases. Rehybridization of PCR products which may interfere with primer binding or extension can explain this significant feature in late cycles. Rehybridization occurs with a half-time dependent on the reciprocal of the DNA concentration. Thus, if multiple PCR products are amplified in the same tube, reannealing occurs faster for the more abundant PCR products. In RT-PCR using an internal control, this results in a systematic bias against the more abundant of the two PCR products. In RNA fingerprinting by arbitrarily primed PCR (or differentially display of cDNAs), very large or absolute differences in the expression of a transcript between samples are preserved but smaller real differences may be gradually erased as the PCR reaction proceeds. Thus, this 'Cot effect' may systematically cause an underestimate of the true difference in starting template concentrations. However, differences in starting template concentrations will be better preserved in the less abundant PCR products. Furthermore, the slow down in amplification of abundant products will allow these rarer products to become more visible in the fingerprint which may, in turn, allow rarer cDNAs to be sampled more efficiently. In some applications, where the object is to stochiometrically amplify a mixture of nucleic acids, the bias against abundant PCR products can be partly overcome by limiting the number of PCR cycles and, thus, the concentration of the products. In other cases, abundance normalization at later cycles may be useful, such as in the production of normalized libraries.

Animals↗
PubMed1996

Screening of differentially amplified cDNA products from RNA arbitrarily primed PCR fingerprints using single strand conformation polymorphism (SSCP) gels.

Arbitrarily primed PCR fingerprinting of RNA and differential display resolved on an acrylamide gel has been extensively used to detect differentially expressed RNAs. However, after a differentially amplified product is detected the next steps are labor-intensive: a small portion of the fingerprinting gel that contains the differentially amplified product is cut out, reamplified and the correct product is determined, typically by cloning and sequencing what is often a mixture of products of similar size. Here we use a native acrylamide gel to separate DNAs in the reamplified mixture based on single-stranded conformation polymorphisms. Reamplifications are performed for the region carrying the differentially amplified product and a corresponding region from an adjacent lane where the product is less prominent or not visible. Denaturation of the reamplified DNA followed by side-by-side comparison on an SSCP gel allows the classification of reamplified material into (i) those that can be directly cloned because the differentially amplified product is relatively pure, (ii) those that need to be reamplified from the SSCP gel before cloning and (iii) those that are too complex for further study. This screen should save considerable effort now wasted on directly cloning unsuitable products from RNA fingerprinting experiments. An example is presented of cloning a gene differentially expressed in Trypanosoma brucei life cycle.

Acrylic Resins↗
PubMed1996

Evaluation of antibody class in response to bovine collagen treatment in patients with urinary incontinence.

PURPOSE: Contigen Bard Collagen Implant (CI), made of highly purified bovine dermal type I collagen (BDC), is used as a bulking agent for the treatment of urinary stress incontinence. The humoral immune response to placement of this material in the urinary sphincter was evaluated. MATERIALS AND METHODS: In a prospective clinical study, patients were treated with CI in the urinary sphincter, and blood was collected at various timepoints following injection. Approximately 28% of the patients treated with BDC demonstrated specific antibodies against bovine type I collagen. Serum samples from 27 patients from this cohort were evaluated. The class specificity of circulating antibodies against bovine collagen was characterized by an indirect enzyme-linked immunosorbent assay. RESULTS: In all patients demonstrating an antibody response to bovine collagen, the predominant immunoglobulin class was IgG, found in 100% of sera samples. Immunoglobulin A was produced in approximately 40% of these patients, and IgM was seen in approximately 0.6%. No specific IgE was detected against bovine collagen in any serum sample. The highest concentrations of IgG and IgA antibody classes were observed 4 to 5 months after the initial treatment with CI. In the multicenter clinical trial, adverse events were reported in approximately 40% of all patients treated with CI (19). There was no correlation found between the production of a specific immunoglobulin class and the onset of any clinical adverse events. CONCLUSIONS: In all sera from patients treated with CI for urinary stress incontinence, antibodies to bovine dermal collagen always were predominantly IgG. Immunoglobulin A was seen in less than half of the sera samples, and IgE was not observed. In addition, no change in the humoral response to CI over time was noted in patients demonstrating presensitization to bovine dermal collagen at the time of initial treatment. Clinical adverse events reported for patients demonstrating pretreatment antibodies against bovine dermal collagen did not differ in type or number when compared with patients having no presensitization.

Animals↗
PubMed1996

Prevalence, reliability and bias of adolescents' reports of smoking and quitting.

A follow-up of smoking behaviour to age 18 in a longitudinal study of a birth cohort enabled an assessment of the prevalence of smoking and quitting among adolescents approaching adulthood. There was a dramatic increase in number of daily smokers (15% at age 15 years to 31% at age 18 years), and in a climate of expected decreases in smoking, a history of never smoking to age 15 years was not as protective against future smoking as anticipated. Among 15-year-olds who had experimented with smoking, only 11% per year stopped by age 18 years. Cessation rates for adolescent daily smokers were low (3% had not smoked in the last year at age 18 years), and previously have not been widely reported. We also examined some methodological issues related to self-reported prevalence rates, in particular reliability, validity and sources of bias, finding confirmation of the accuracy of information from prospective longitudinal studies and supporting the conclusion that adolescents' recall for information beyond a 1-year period is inconsistent.

Adolescent↗
PubMed1995

Gastric carcinoma.

Explore the source record for details and available documents.

Adenocarcinoma↗
PubMed1995

Genetic variability of Paecilomyces fumosoroseus isolates revealed by molecular markers.

Paecilomyces fumosoroseus (Deuteromycotina:Hyphomycetes) is a fungus that is potentially useful for the bio-control of economically important agricultural pests, such as whitefly (Bemisia tabaci). Arbitrarily primed PCR and PCR with tRNA consensus primers were used to analyze genetic variability among 27 P. fumosoroseus isolates, 15 of which came from the same host, B. tabaci, one P. lilacinus isolate, used as an outgroup, 9 previously unidentified Paecilomyces isolates. Fifteen 10-mer oligonucleotide primers of arbitrary sequence revealed 322 scorable binary characters. Principal coordinates and cluster analysis of characters showed that most of the P. fumosoroseus and Paecilomyces sp. isolates were in three phenetic groups with > 65% internal similarity. Two of the three arbitrary phenetic groups were closely related (76% similarity) with the third group quite different (only 14% similarity) from the first two. The phenetic groups did not correlate with geographical origin or host species. Genetic variability of isolates infecting whitefly in Florida was detected. Isolates from B. tabaci were represented in two of the three groups, and different genotypes were identified even when they were isolated from an epizootic population in India and Pakistan. There was no evidence of host-specific selection of genotypes, as has been shown in other entomopathogenic fungi. Three isolates morphologically classified as P. fumosoroseus were clustered in a phenetic group which displayed only 14% similarity to the other isolates of this species. Seven isolated that presented problems for morphological classification were found to be similar or, in three cases, identical to other P. fumosoroseus isolates that dit not present problems for morphological classification.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Fingerprinting of DNA and RNA by arbitrarily primed polymerase chain reaction: applications in cancer research.

RNA fingerprinting by RAP-PCR is a powerful tool for the temporal and spatial analysis of differential gene expression. Many biological situations exist where differential gene expression results in distinguishable phenotypes, including, for example, tissue and cell types, responses to hormones, growth factors, stress, and the heterologous expression of certain genes. There are several methods for detecting differential gene expression and cloning differentially expressed genes that do not rely on a biological assay of phenotype. Most of these methods fall into two general categories: subtractive hybridization and differential screening. RAP-PCR offers numerous advantages over these methods, including its simplicity and its ability to compare the fluctuations in gene expression between multiple samples simultaneously using minute amounts of RNA. In addition, RAP-PCR can yield information on the overall patterns of gene expression between different cell types or between different physiological conditions of the same cell type. Comparison of the RAP-PCR fingerprints from these different experimental groups permits one to draw inferences regarding the overall cellular states of gene expression and the interrelation between gene transcripts belonging to the same or different regulatory pathways. Hypotheses regarding signal transduction pathways can be obtained using this information. RAP-PCR offers applications in cancer research in the detection of tumor-specific alterations in gene expression, providing a bountiful source of tumor markers. The pleiotropic impact of oncogene activation, tumor suppressor gene inactivation, and mutator mutations, in gene regulation, can be readily assessed by RAP-PCR in model systems both in vitro and in vivo.

Base Sequence↗
PubMed1995

Genetic diversity and population structure of Trypanosoma brucei: clonality versus sexuality.

Genomic fingerprinting by arbitrarily primed PCR was used to analyze the genetic variability among 59 Trypanosoma brucei stocks representing the three T. brucei subspecies isolated from various hosts and different countries in Africa. 14 oligonucleotide primers revealed 355 polymorphic binary characters which were used for phenetic and phylogenetic analysis and to perform recombination tests exploring the linkage disequilibrium in the sample. There was good concordance between arbitrarily primed PCR polymorphisms and isoenzyme data previously collected for many of the same strains [1]. However, the arbitrarily primed PCR typing was more discerning than multilocus enzyme electrophoresis typing. Phenetic and phylogenetic analysis using arbitrarily primed PCR markers did not confirm T. brucei brucei and T. brucei rhodesiense as separate subspecies, but T. brucei gambiense group I was monophyletic, confirming this group as suitable for the subspecies status. With this exception, there were no clear lineages among the sample, other than clustering of East African stocks and clustering of West African stocks. Some features of the phylogenetic analysis suggested that the population structure was not strictly clonal though recombination tests showed linkage disequilibrium, even in the absence of repeated genotypes. While genotypes appear stable enough for tracking in applied studies, sexuality will impact at the evolutionary time scale, and may be more frequent under some ecological conditions. The arbitrarily primed PCR approach should be an effective and simple approach to follow epidemics and to quantify the role of sexuality in T. brucei populations.

Africa↗
PubMed1995

Nucleic acid fingerprinting by PCR-based methods: applications to problems in aging and mutagenesis.

There are many methods of inference in common use in biology that are based on population sampling, including such diverse areas as sampling organisms to determine the population structure of an ecosystem, sampling a set of DNA sequences to infer evolutionary history, sampling genetic loci to build a genetic map, sampling differentially expressed genes to find phenotypic markers, and many others. Recently developed PCR-based methods for nucleic acid fingerprinting can be used as sampling tools with general applicability in molecular biology, evolution and genetics. These methods include arbitrarily primed PCR (AP-PCR; Welsh and McClelland, 1990) and random amplified polymorphic DNA (RAPD; Williams et al., 1990) for the fingerprinting of DNA, and RNA arbitrarily primed PCR (RAP-PCR; Welsh et al., 1992a) and differential display (DD; Liang and Pardee, 1992) for the fingerprinting of RNA. Novel ways of looking at genetic control are facilitated by the high data-acquisition capabilities of the fingerprinting methods. In this article, we review some of the applications of DNA fingerprinting to the study of mutagenesis, and of RNA fingerprinting to the study of normal and abnormal signal transduction. We propose that these fingerprinting approaches may also have applications in the study of senescence and aging.

Aging↗
PubMed1995

RNA fingerprinting and differential display using arbitrarily primed PCR.

RNA fingerprinting by arbitrarily primed PCR can be used to detect and clone transcripts that are differentially expressed between cells that have been subject to different environments or developmental programs. The method also allows an estimate of the number of genes that are differentially expressed under various circumstances. When many experimental treatments are compared in parallel, intersecting regulatory pathways are reflected in genes that are perturbed by more than one treatment.

Animals↗
PubMed1995

Arbitrarily primed DNA fingerprinting for phylogenetic reconstruction in vertebrates: the Xiphophorus model.

Arbitrarily primed PCR (AP-PCR or RAPD) is a technique for producing species-specific DNA fingerprints. We tested the utility of AP-PCR as a source of phylogenetically informative characters in three separate experiments, using fishes of the genus Xiphophorus. We chose Xiphophorus as a standard of comparison, because evolutionary relationships within the genus have been studied repeatedly using a variety of techniques. We compared our results to a "classical" phylogenetic hypothesis synthesized from studies using morphological, pigmentation, and allozyme characters, and to a recent conflicting hypothesis constructed from DNA sequence data. The sequence-based hypothesis places the southern swordtail Xiphophorus clemenciae squarely within the platyfish, whereas the classical hypothesis separates the two groups. In addition, the two hypotheses differ in their clustering of species of northern swordtails. Our findings are in close accord with the classical hypothesis. Our results allow the strongest phylogenetic hypothesis yet for Xiphophorus and demonstrate the utility of AP-PCR for studying species relationships within vertebrate genera.

Animals↗
PubMed1995

Continuous midazolam/atracurium infusions for the management of increased intracranial pressure.

Maintaining the pressure/volume balance in the brain is a challenging goal for the neuroscience team caring for patients with traumatic brain insults. Often, standard therapies are not effective in controlling increased intracranial pressure (ICP). Four severe traumatic brain injury patients given continuous infusions of midazolam and atracurium showed control of otherwise unstable ICPs. Midazolam and atracurium infusions are now considered an acceptable form of therapeutic intervention for our patients requiring such treatment. Intensive nursing care considerations for patients using the combined pharmacologic therapy are essential.

Adult↗
PubMed1995

Genetic and phenotypic analysis of Borrelia miyamotoi sp. nov., isolated from the ixodid tick Ixodes persulcatus, the vector for Lyme disease in Japan.

The ixodid tick Ixodes persulcatus is the most important vector of Lyme disease in Japan. Most spirochete isolates obtained from I. persulcatus ticks have been classified as Borrelia burgdorferi sensu lato because of their genetic, biological, and immunological characteristics. However, we found that a small number of isolates obtained from I. persulcatus contained a smaller 38-kDa endoflagellar protein and single 23S-5S rRNA gene unit. Representative isolate HT31T (T = type strain) had the same 23S rRNA gene physical map as Borrelia turicatae. The DNA base composition of strain HT31T was 28.6 mol% G+C. DNA-DNA hybridization experiments revealed that strain HT31T exhibited moderate levels of DNA relatedness (24 to 51%) with Borrelia hermsii, B. turicatae, Borrelia parkeri, and Borrelia coriaceae. However, the levels of DNA reassociation with the previously described Lyme disease borreliae (B. burgdorferi, Borrelia garinii, and Borrelia afzelii) were only 8 to 13%. None of the previously described species examined exhibited a high level of DNA relatedness with strain HT31T. In addition, the 16S rRNA gene sequence (length, 1,368 nucleotides) of strain HT31T was determined and aligned with the 16S rRNA sequences of other Borrelia species. Distance matrix analyses were performed, and a phylogenetic tree was constructed. The results showed that isolate HT31T is only distantly related to both previously described Lyme disease borreliae and relapsing fever borreliae. Thus, the spirochetes isolated from I. persulcatus and closely related isolates should be classified as members of a new Borrelia species. We propose the name Borrelia miyamotoi sp. nov. for this spirochete; strain HT31 is the type strain.

Animals↗
PubMed1995

tRNA intergenic spacers reveal polymorphisms diagnostic for Xanthomonas albilineans.

A PCR-based detection system was developed for Xanthomonas albilineans, a pathogen of sugarcane, and other related xanthomonads, using the conserved sequence of two adjacent tRNA genes and the variable length and sequence of the spacer region between them. An appropriate region was identified as follows: tRNA genes with the same anticodon from a wide variety of bacteria were aligned and the most frequent base at each position was chosen to derive primers that would anneal to the gene in either orientation. Pairs of such primers were screened against various Xanthomonas species and members of related genera using PCR at low to moderate annealing stringency. A subset of these pairs of tRNA consensus primers gave one or more PCR products which generally displayed interspecific length variability. The primer pair 5'-3' tRNA(ala) and 3'-5' tRNA(ile) showed interspecific length polymorphisms between X. albilineans and all other Xanthomonas species examined. These PCR products were cloned and sequenced from four isolates of X. albilineans and four isolates from different pathovars of X. campestris, and the spacer length variation confirmed. Specific tRNA gene primers were derived from the tRNA gene sequences. These primers yielded a PCR product of a characteristic length within most Xanthomonas species and pathovars tested. When a primer that projected from tRNA(ala) into the 3' end of the variable intergenic spacer was used with a tRNA(ile)-specific primer, PCR was a very sensitive diagnostic test for X. albilineans-infected sugarcane and gave no product or only a faint product with other species of bacteria. The specificity of this PCR-based detection system was further enhanced by a nested PCR reaction that took advantage of the fact that the tRNA(ala)-tRNA(ile) region was found to be embedded in a 16S rRNA-23S rRNA gene spacer. By amplifying the region between the 16S rRNA gene and tRNA(ile) or between the tRNA(ala) and the 23S rRNA gene, the subsequent nested PCR product was shown to be X. albilineans-specific.

Base Sequence↗
PubMed1994

Interactions among regulators of RNA abundance characterized using RNA fingerprinting by arbitrarily primed PCR.

Using RNA fingerprinting by arbitrarily primed PCR it is possible to infer convergent transcript regulatory pathways from the coordinate behavior of subsets of anonymous transcripts without cloning any genes. The number of transcripts in each response category can be estimated. The same may be true for differential display. We demonstrate these claims by treating a cell line with two known modulators of RNA abundance, transforming growth factor-beta (TGF beta) and cycloheximide (CX), used together and alone. The responses of over 1700 anonymous transcripts were monitored under these three conditions and in an untreated control. Eight of the twenty-seven [3(3)] possible transcript response categories were observed among 86 differentially expressed transcripts. For example, CX stabilizes or induces as many as 2.7% of transcripts of which about one third do not accumulate when TGF beta is also present. This intersection may reflect CX stabilization or induction of an important class of RNAs that otherwise usually have short half-lives. We predict that RNAs in this class constitute the majority of transcripts targeted for rapid down regulation in response to TGF beta and perhaps most other natural transcriptional modulators.

Animals↗
PubMed1994

Transfusion of one HLA-DR antigen-matched blood to potential recipients of a renal allograft.

Patients awaiting a renal transplant were given 1 HLA-DR antigen-matched blood in order to compare the sensitization and graft outcome of these patients with those of control patients, who had been given random blood before transplantation. No differences in sensitization, measured by the formation of HLA antibodies, or in graft survival were found between the 2 groups. However, the incidence of rejection episodes was significantly reduced in the patients who received blood matched for 1 HLA-DR antigen compared with the patients who received random blood.

Blood Grouping and Crossmatching↗