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Biomedical subjects

M A Scott

Publications and source records attributed to M A Scott.

At least 55 records · Page 3Linked to original sources
PubMed1998

Optimal screening and diagnosis of microsporida in tissue sections: a comparison of polarization, special stains, and molecular techniques.

With improving therapeutic protocols, confirmation of microsporidiosis has become increasingly important. We designed a study to determine the best screening method(s) for microsporidian detection in biopsy specimens. Forty-two small intestinal biopsy specimens from 31 immunocompromised patients (68% AIDS) were stained (hematoxylin-eosin [H & E], modified trichrome, Warthin-Starry, and Brown-Brenn) and polarized. Polymerase chain reaction and Southern blot assays were performed on all positive cases. Microsporida were detected in nine cases (21%) by modified trichrome (all patients with AIDS). Of these, seven were Brown-Brenn positive, and five Warthin-Starry positive. Two cases polarized on H & E and three on special stains. Four of nine positive cases were confirmed by molecular studies. We found polarization to be the least sensitive screening method. The modified trichrome was the most sensitive when screening for microsporidiosis in paraffin-embedded biopsy specimens. Furthermore, combining Brown-Brenn or Warthin-Starry with the trichrome stain helps exclude false-positive results due to granular artifacts (eg, eosinophils, Paneth cells).

Adolescent↗
PubMed1997

Ductal carcinoma in situ of the breast: reproducibility of histological subtype analysis.

Historically, two major strata of ductal carcinoma in situ (DCIS) have been linked to outcome, the presence or absence of comedo type and size. Our initial approach in classification was dichotomous, often favoring the comedo type with most worrisome implications to foster agreement in diagnosis. We have now tested guidelines that foster agreement in the modified Lagios three-tiered system. Sixteen cases of DCIS were selected, reflecting a spectrum of histological subtypes, with specific inclusion of cases in which consensus in classification using a dichotomous (comedo/noncomedo) scheme would be difficult. Six independent observers reviewed a minimum of five color 35-mm slides from each case at two separate occasions. The aim was to subclassify each case based on architectural pattern, nuclear grade, and presence or absence of tumor necrosis (Modified Lagios Classification, Lagios et al, Cancer 1989). After initial review, emphasizing placement of each case into a high- or low-grade category, there was disagreement in seven cases (44%), confirming our aim to choose cases with uncertain cues for classification. Agreement was achieved in 94% of cases by allowing re-review with emphasis on inclusion of an intermediate-grade category. Our study also suggests that pure micropapillary DCIS and apocrine DCIS warrant independent classification as "special type" DCIS. Our small pilot study suggests that, with adherence to specific criteria, most DCIS cases can be easily and consistently classified into the following five categories: (1) high grade, (2) intermediate grade, (3) low grade, (4) pure or predominantly micropapillary, and (5) pure apocrine. Our six observers independently reached a final concordance of 94% despite selection of cases in which consensus in a dichotomous classification was difficult. This was achieved predominantly by accepting an intermediate category of DCIS with intermediate nuclear features and limited necrosis. Confirmation of the applicability of the Modified Lagios Classification awaits completion of a much larger multi-institutional study in which statistical significance and interobserver variation can be better defined.

Breast Neoplasms↗
PubMed1997

Staphylococcal protein A binding to canine IgG and IgM.

Staphylococcal protein A (SpA) binds with high affinity to immunoglobulins from many species, making it a useful reagent for immunoassays and immunoglobulin purification procedures. However, its use is limited by poor reactivity with some immunoglobulin subclasses including human IgG3 and murine IgG1. Reports of SpA's reactivity with canine immunoglobulins have been inconsistent. Because the most recent reports indicated a much greater reactivity of purified SpA with canine immunoglobulins than was suggested by our observations, we quantitatively reevaluated the binding of canine IgG and IgM to Cowan I strain SpA under the conditions of use in our laboratory. IgG and IgM were purified from pooled normal canine plasma by affinity chromatography with heavy chain specific polyclonal anti-IgG and anti-IgM antibodies. The purified IgG and IgM were assessed for SpA reactivity by affinity chromatography using a SpA-agarose column. The relative proportions of total chromatographed IgG or IgM in the flow-through (SpA-nonbindable) and eluate (SpA-bindable) fractions were determined by absorbance at 280 nm. The IgG and IgM in each immunoglobulin fraction were also nonspecifically adsorbed to microtitration plates and tested for reactivity with 125I-SpA using a solid phase immunoradiometric assay (IRMA). Approximately 18% of the affinity purified canine IgG and 33% of the affinity purified canine IgM did not bind to the SpA affinity column and were also unreactive with 125I-SpA using the IRMA. A second approach using a different polyclonal antibody to canine IgG yielded similar results: about 21% of the purified IgG was unreactive with SpA. Incomplete reactivity of SpA with canine IgG and IgM limits the usefulness of SpA in canine immunologic procedures.

Animals↗
PubMed1997

Biological properties of peripheral blood progenitor cells mobilized by cyclophosphamide and granulocyte colony-stimulating factor.

Patients transplanted with mobilized blood progenitor cells (PBPC) recover their neutrophil counts more rapidly than patients transplanted with bone marrow even when they receive the same dose/kg of granulocyte-macrophage colony-forming cells (CFU-GM). Here we have sought a biological explanation for this phenomenon. Most CD34-positive PBPC are quiescent (<1% in S phase) when they are collected from the bloodstream of patients treated with cyclophosphamide and granulocyte colony-stimulating factor (G-CSF), but we have shown that they are able to resume proliferation rapidly in vitro by measuring the kinetics of CFU-GM production by primitive plastic-adherent (Pdelta) cells. Also, Pdelta cells in PBPC harvests, unlike normal marrow Pdelta cells, were insensitive to cell-cycle restraint imposed by contact with marrow-derived stromal cells. We found that Pdelta cells in PBPC collections produce relatively more CFU-GM and relatively fewer BFU-E than Pdelta cells in bone marrow, indicating that granulopoiesis might occur at the expense of erythropoiesis, but we were unable to find any differences in the kinetics of granulocytic maturation between PBPC and bone marrow. Our interpretation of these findings is that transplanted PBPC rapidly enter the cell cycle and contact with stromal cells in the marrow does not reduce the proportion of progenitors participating in neutrophil production. Consequently. neutrophil recovery after PBPC infusion is more rapid than neutrophil recovery after marrow infusion. Granulopoiesis at the expense of erythropoiesis may also contribute to this effect.

Cell Cycle↗
PubMed1997

Expertise and the regulation of gait in the approach phase of the long jump.

In the approach phase of the long jump, athletes attempt to strike the take-off board accurately with minimum loss of speed, and in an optimum body position for take-off. Previous research has shown that skilled long jumpers demonstrate an ascending-descending trend of variability rather than a consistent pattern of foot placement over trials. The present study examined whether non-long jumpers showed a similar pattern of variability in footfall placement between trials to skilled long jumpers. Consistency of foot placement over trials for non-long jumpers (n = 11) was determined using a panned video camera. Digitization of the foot position provided toe-board distances during the run-up phase. Our results showed that non-long jumpers have a similar pattern of descending variability near to the take-off board to expert long jumpers, suggesting the use of visual regulation. However, in comparison to more skilled subjects, non-long jumpers accumulated a considerably larger maximum mean standard deviation in footfall placement between trials (58 cm). Since non-long jumpers had no previous task-specific training, these data extend our current understanding of the regulation of goal-directed gait.

Adult↗
PubMed1997

Reliability of drug utilization evaluation as an assessment of medication appropriateness.

OBJECTIVE: To test the reliability of drug utilization evaluation (DUE) applied to medications commonly used by the ambulatory elderly. METHODS: A DUE model was developed for four domains: (1) justification for use, (2) critical process indicators, (3) complications, and (4) clinical outcomes. DUE criteria specific to use in the elderly were developed for angiotensin-converting enzyme (ACE) inhibitors and histamine2 (H2)-antagonists, and consensus was reached by an external expert panel. After pilot testing, two clinical pharmacists independently evaluated these medications, applying the DUE criteria and rating each item as appropriate or inappropriate. Interrater and intrarater reliability was assessed by using kappa statistics. RESULTS: In a sample of 208 ambulatory elderly veterans, 42 (20.2%) were taking an ACE inhibitor and 56 (26.9%) an H2-antagonist. The interrater agreement for individual domains, represented by kappa statistics, were 0.10-0.58 and 0-0.83 for ACE inhibitors and H2-antagonists, respectively. The kappa statistic for overall agreement, which considered ratings from all criteria across all domains, was 0.24 for ACE inhibitors and 0.18 for H2-antagonists. Intrarater reliability was assessed 3 months later, and kappa statistics were 0.61-0.65 (0.49 overall) and 0-0.96 (0.81 overall) for ACE inhibitors and H2-antagonists, respectively. CONCLUSIONS: Intrarater reliability for DUE was good to excellent. However, interrater reliability exhibited only marginal reproducibility, particularly where evaluators were required to use subjective judgement (i.e., complications, clinical outcomes). DUE may not be a suitable standard for assessing medication appropriateness in ambulatory elderly patients.

Aged↗
PubMed1997

Disseminated toxoplasmosis. Unusual presentations in the immunocompromised host.

OBJECTIVE: Owing to the increasing number of patients with acquired immunodeficiency syndrome and immunosuppressed transplant patients, disseminated Toxoplasma gondii has emerged as a potentially fatal pathogen. Common presentations include encephalitis, pneumonia, and myocarditis. The objective of this report is to describe the clinical course, histologic features, and outcome in two immunocompromised patients with disseminated toxoplasmosis presenting with parasitemia and panniculitis. MATERIALS AND METHODS: Two cases of disseminated toxoplasmosis presenting with parasitemia (patient 1) and panniculitis (patient 2) were retrieved from the clinical, surgical, and autopsy pathology archives of Vanderbilt University Medical Center, Nashville, Tenn. The histology and diagnostic approaches used are reported. Charts were reviewed for primary diagnosis, therapy protocols, clinical presentation of infection, and outcome. RESULTS: Patient 1 developed a clinically unexplained sepsis syndrome shortly after heart transplantation; T gondii parasitemia was diagnosed by examination of peripheral blood smears. The diagnosis was confirmed at autopsy. Patient 2 was a child undergoing induction chemotherapy for lymphoma who developed rapidly progressive neurologic deterioration accompanied by a maculopapular skin rash; T gondii panniculitis was diagnosed retrospectively when histologic examination was combined with immunohistochemistry. Autopsies performed in both cases confirmed widely disseminated infection. CONCLUSIONS: Disseminated toxoplasmosis should be considered in the differential diagnosis of immunocompromised patients with culture-negative sepsis syndrome, particularly if combined with neurologic, respiratory, or unexplained skin lesions. Examination of Wright's-stained peripheral blood smears or antitoxoplasma immunoperoxidase studies of skin biopsies may be diagnostic and allow rapid initiation of antibiotic therapy. Autopsy findings contributed to both of our cases by documenting the wide-spread heavy parasite burden and demonstrating numerous diagnostic T gondii cyst forms.

Animals↗
PubMed1996

Microsatellite analysis of posttransplant lymphoproliferative disorders: determination of donor/recipient origin and identification of putative lymphomagenic mechanism.

The genetic mechanisms that give rise to posttransplant lymphoproliferative disorders (PTLDs) are not well established, yet previous studies have focused or) the role of immunosuppression and EBV infection. We investigated whether microsatellite analysis could: (a) determine the recipient/donor origin of the tumor; and (b) document novel genetic alterations in PTLDs, i.e., microsatellite instability. We characterized seven cases of PTLD (five B-cell and two T-cell non-Hodgkin's lymphomas) in which donor allograft tissue, normal recipient tissue, and tissue from the PTLDs were available. In each case, six microsatellite loci were analyzed. Five cases were of host origin (three B-cell and two T-cell lymphomas). The two cases of donor origin were B-cell lymphomas. Multiple loci showed microsatellite instability in two cases of host-derived T-cell non-Hodgkin's lymphomas (28% of PTLDs). These findings show that microsatellite analysis may be used to determine the host or donor origin of PTLDs and suggest for the first time that defective DNA mismatch repair may be an underlying genetic mechanism of lymphomagenesis in some cases of PTLD.

Adult↗
PubMed1996

Detection of chromosome 20q deletions in bone marrow metaphases but not peripheral blood granulocytes in patients with myeloproliferative disorders or myelodysplastic syndromes.

Myeloproliferative disorders and myelodysplastic syndromes arise in multipotent progenitors and may be associated with chromosomal deletions that can be detected in peripheral blood granulocytes. We present here seven patients with myeloproliferative disorders or myelodysplastic syndromes in whom a deletion of the long arm of chromosome 20 was detectable by G-banding and/or fluorescence in situ hybridization in most or all bone marrow metaphases. However, in each case, microsatellite polymerase chain reaction (PCR) using 15 primer pairs spanning the common deleted region on 20q showed that the deletion was absent from most peripheral blood granulocytes. The human androgen receptor clonality assay was used to show that the vast majority of peripheral blood granulocytes were clonal in all four female patients. This represents the first demonstration that the 20q deletion can arise as a second event in patients with pre-existing clonal granulopoiesis. Microsatellite PCR analysis of whole bone marrow from two patients was consistent with cytogenetic studies, a result that suggests that cytogenetic analysis was not merely selecting for a minor subclone of cells carrying the deletion. Furthermore, in one patient, the deletion was present in both erythroid and granulocyte/monocyte colonies. This implies that the absence of the deletion in most peripheral blood granulocytes did not reflect lineage restriction of the progenitors carrying the deletion but may instead result from other selective influences such as preferential retention/destruction within the bone marrow of granulocytes carrying the deletion.

Aged↗
PubMed1996

Thrombin is a distal mediator of lipopolysaccharide-induced liver injury in the rat.

Previous results demonstrated that rats given Escherichia coli lipopolysaccharide (LPS; 4 mg/kg, i.v.) experience hepatocellular necrosis that begins within 4 hr and that prior treatment with anticoagulants (e.g., heparin) which target thrombin prevents the liver injury. In this study, hepatocellular injury, as marked by increased plasma alanine aminotransferase (ALT) activity and histologic changes, was prevented when heparin or hirudin was administered to rats shortly before the onset of injury. These results suggest that thrombin is a critical mediator that acts distally in the series of inflammatory events that culminates in hepatocellular damage. To explore further this hypothesis, livers isolated from rats 2 hr after LPS administration were perfused with various media. Perfusion of livers with medium comprising diluted blood from heparin-treated donors resulted in no release of ALT activity. By contrast, perfusion with similar medium anticoagulated with ancrod, which prevents clotting by depleting fibrinogen but does not inhibit thrombin, resulted in hepatocellular injury evidenced as a time-dependent appearance of ALT activity in the medium. Moreover, when livers from rats treated 2 hr previously with LPS were perfused with buffer to which thrombin had been added, injury resulted. No injury resulted when thrombin was omitted from the buffer or when livers from saline-treated rats were used. These results indicate that thrombin is a critical and distal mediator of LPS-induced liver damage and contributes to hepatocellular injury through a mechanism that is independent of clot formation. Furthermore, inflammatory events triggered by LPS exposure are a prerequisite for thrombin-induced injury.

Alanine Transaminase↗
PubMed1996

Evaluation of "discordant maturation' in chronic myeloid leukaemia using cultures of primitive progenitor cells and their production of clonogenic progeny (CFU-GM).

The 'discordant maturation hypothesis' proposes that the most mature proliferating cells in chronic-phase chronic myeloid leukaemia (CML) are responsible for the expansion of the Ph-positive population. To evaluate this hypothesis we used a delta assay for primitive haemopoietic cells (P delta assay for P delta cells) which allows investigation of the kinetics of granulocyte-macrophage progenitor (CFU-GM) production. The frequencies of these primitive (P delta) cells were similar in CML blood (14.5/10(5) mononuclear cells), CML marrow (17.3/10(5)) and normal marrow (11.6/10(5)) The average frequency in normal blood is only 0.58/10(6). The absolute numbers of P delta cells in CML patients are therefore greatly increased. The average numbers of CFU-GM produced by individual P delta cells were reduced in CML blood (8.1) and marrow (11.6) compared with normal marrow (28.5). This is consistent with a reduced probability of differentiation at the single cell level in CML. Although the absolute number of CFU-GM produced by individual CML P delta cells was subnormal there was a relative increase in the number of day 7 CFU-GM compared with the number of day 14 and 21 CFU-GM, which agrees with the 'discordant maturation hypothesis'. This bias towards day 7 colony formation could reflect accelerated maturation by the CFU-GM produced by P delta cells or, alternatively, the production of CFU-GM with shorter than normal maturation pathways. Overall, these results suggest that discordant maturation does not by itself account for myeloid expansion in CML. It is more likely that myeloid expansion in CML is due mainly to an increase in the number of primitive haemopoietic progenitor cells.

Bone Marrow↗
PubMed1996

Bacterial contamination of peripheral blood progenitor cells for transplantation.

Peripheral blood progenitor cells (PBPC) were obtained from 128 apheresis harvests on 64 patients and were tested in duplicate for microbiological contamination (1) after collection and (2) after thawing, following processing and cryopreservation. In this study we have attempted to improve the monitoring of contamination in peripheral blood progenitor cell collections by identifying exogenous contamination that probably originated from the testing laboratory and is therefore not clinically significant. We found no contamination in 82% of harvests, 1.6% of harvests to be significantly contaminated and organisms were isolated from 16.4% that were assessed as clinically nonsignificant. Our experience indicates that the choice of microbiological methods will influence the results and their clinical relevance. No samples were positive by direct culture. We recommend that sampling should be performed at more than one stage during the procedure and that initially only the post-thaw samples be analysed. Testing should be performed by enrichment culture in duplicate only and if positive to aid interpretation the post-collection sample should then be cultured. No patient given nonsignificantly contaminated graft without antibiotic cover suffered infection from the identified organism. The incidence of significant contamination was low and we recommend that in these cases PBPC grafts can be infused safely provided prophylactic antibiotic cover is given.

Bacteriological Techniques↗