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Biomedical subjects

M A Stein

Publications and source records attributed to M A Stein.

17 recordsLinked to original sources
PubMed1992

Molecular and cellular characterization of the 29-kilodalton peripheral membrane protein of Entamoeba histolytica: differentiation between pathogenic and nonpathogenic isolates.

To further characterize the 29-kDa surface antigen of Entamoeba histolytica, we analyzed the complete nucleotide sequence and compared the immunoreactivity of this antigen in pathogenic and nonpathogenic strains. Five cDNA clones (one 1.0-kb full-length clone, designated p13, and four partial-length clones) encoding the antigen were analyzed for allelic variation. Comparison of the nucleotide sequences revealed several single-nucleotide substitutions in all five cDNAs, two of which resulted in amino acid differences. Localization of the antigen to the amebic surface in a previous report (B. E. Torian, B. M. Flores, V. L. Stroeher, F. S. Hagen, and W. E. Stamm, Proc. Natl. Acad. Sci. USA 87:6358-6362, 1990) was corroborated by transmission electron microscopy showing colloidal gold particles on the surface of the trophozoites. Computer analysis of the deduced amino acid sequence predicted that the protein encoded by p13 was a hydrophilic peripheral membrane protein, and these data were confirmed by a Triton X-114 membrane extraction showing the presence of the 29-kDa antigen primarily in the aqueous phase of the detergent partition. Monoclonal antibodies to a fusion peptide differentiated between pathogenic and nonpathogenic clinical strains of E. histolytica in immunoblots. Although no immunoreactive epitopes were detected on nonpathogenic strains, Northern (RNA) analysis and DNA-DNA hybridization with a 700-bp cDNA probe demonstrated that mRNA and the gene encoding the 29-kDa surface antigen were present in both pathogenic and nonpathogenic clinical isolates.

Amino Acid Sequence↗
PubMed1992

Role of the rfaG and rfaP genes in determining the lipopolysaccharide core structure and cell surface properties of Escherichia coli K-12.

Deletions which removed rfa genes involved in lipopolysaccharide (LPS) core synthesis were constructed in vitro and inserted into the chromosome by linear transformation. The deletion delta rfa1, which removed rfaGPBI, resulted in a truncated LPS core containing two heptose residues but no hexose and a deep rought phenotype including decreased expression of major outer membrane proteins, hypersensitivity to novobiocin, and resistance to phage U3. In addition, delta rfa1 resulted in the loss of flagella and pili and a mucoid colony morphology. Measurement of the synthesis of beta-galactosidase from a cps-lacZ fusion showed that the mucoid phenotype was due to rcsC-dependent induction of colanic acid capsular polysaccharide synthesis. Complementation of delta rfa1 with rfaG+ DNA fragments resulted in a larger core and restored the synthesis of flagella and pili but did not reverse the deep rough phenotype or the induction of cps-lacZ, while complementation with a fragment carrying only rfaP+ reversed the deep rough phenotype but not the loss of flagella and pili. A longer deletion which removed rfaQGPBIJ was also constructed, and complementation studies with this deletion showed that the product of rfaQ was not required for the functions of rfaG and rfaP. Thus, the function of rfaQ remains unknown. Tandem mass spectrometric analysis of LPS core oligosaccharides from complemented delta rfa1 strains indicated that rfaP+ was necessary for the addition of either phosphoryl (P) or pyrophosphorylethanolamine (PPEA) substituents to the heptose I residue, as well as for the partial branch substitution of heptose II by heptose III. The substitution of heptose II is independent of the type of P substituent present on heptose I, and this results in four different core structures. A model is presented which relates the deep rough phenotype to the loss of heptose-linked P and PPEA.

Carbohydrate Sequence↗
PubMed1992

Acquisition of apparently intact and unmodified lipopolysaccharides from Escherichia coli by Bdellovibrio bacteriovorus.

The ability of Bdellovibrio bacteriovorus to relocalize the OmpF major outer membrane porins from its Escherichia coli prey to its own outer membranes is diminished in prey expressing smooth lipopolysaccharide (S-LPS). Since porins exist in the membrane complexed with LPS, we examined the LPS associated with relocalized porin to determine whether it had been acquired intact, mixed or replaced with Bdellovibrio LPS, or derivatized by the bdellovibrios. The relocalized trimers were found associated with the same LPS originally bound to them in the E. coli. The bulk-phase LPS from bdellovibrios grown on various chemotypes of rough prey was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to determine whether more than the trimer-bound LPS was acquired by the bdellovibrios. This analysis revealed bands of Bdellovibrio LPS matching the LPS chemotype of the prey. One or two other bands were identical in migration to the LPS of prey-independent mutants of B. bacteriovorus and represented bdellovibrio-synthesized LPS. The LPS of bdellovibrios grown on prey with radiolabeled lipid A showed radioactivity only in gel band positions identical with those of the prey's LPS. The amount of this prey-derived LPS was shown by enzyme-linked immunosorbent assay to reach a constant value during the purification of the bdellovibrios, and it represented approximately 25% of the total Bdellovibrio LPS. Immunoelectron microscopy confirmed the presence of prey-derived LPS on the cell surface of bdellovibrios, and no evidence could be found for bdellovibrio-induced modifications of the relocalized prey LPS.

Bacterial Outer Membrane Proteins↗
PubMed1991

Immediate postoperative mammogram for failed surgical excision of breast lesions.

In a series of 200 consecutive preoperative needle localizations of non-palpable breast lesions, 128 lesions (64%) were calcified and 72 lesions (36%) were noncalcified on preoperative mammograms. Radiographs of the surgical specimen failed to confirm excision of 11 lesions (5.5%), seven calcified and four noncalcified. These 11 patients were taken directly from the surgical suite to the radiology suite, where an immediate postoperative mammogram was obtained. In five patients (2.5%), immediate postoperative mammograms showed surgical failure with the lesion still present. In six patients (3.0%), immediate postoperative mammograms showed that the lesion had been removed, even though the lesion had not been identified on surgical-specimen radiographs. No errors occurred in the interpretation of immediate postoperative mammograms, a fact corroborated by examination of surgical specimens obtained at repeat surgery in three patients and identification of skin calcifications in two patients, and with follow-up mammograms in six patients. Whenever a discrepancy between preoperative localization radiographs and surgical-specimen radiographs exists, the authors suggest immediate postoperative mammography to improve the diagnostic process.

Aged↗
PubMed1991

Calcifications in breast biopsy specimens: discrepancies in radiologic-pathologic identification.

To analyze the effectiveness and accuracy of the diagnostic process from screening mammography to final diagnosis at pathologic examination, the authors conducted a prospective study of 277 consecutive patients who underwent 291 mammographically directed biopsies of nonpalpable lesions. Of the 170 lesions that demonstrated findings consistent with calcification on preoperative mammograms and radiographs of specimens, 12 (7.1%) were not described by the pathologist as being calcified. These discrepancies were due to inadequate sampling in three cases (25%), lack of explicit description by the pathologist in four (33%), presence of oxalate crystals that required examination with polarizing lenses in two (17%), and unexplained loss of tissue probably related to processing in three (25%). Of the 121 lesions that did not demonstrate findings consistent with calcification at radiography, eight (6.6%) were described as calcified by the pathologist. The authors recommend a protocol for avoiding these discrepancies that involves performance of a more comprehensive examination of histologic sections by the pathologist, including the use of polarizing lenses, if necessary, and radiographic reexamination of paraffin-embedded tissue blocks with subsequent step sectioning by the pathologist when results are positive.

Biopsy↗
PubMed1990

Detection of lipopolysaccharides blotted to polyvinylidene difluoride membranes.

Bacterial lipopolysaccharide (LPS) blotted to polyvinylidene difluoride (PVDF) membranes was detected by a technique adapted from current methodologies used to detect glycoproteins. PVDF-bound LPS was coupled to a hapten and localized on the membrane by Western blotting with an antibody-alkaline phosphatase conjugate specific for the hapten. Immobilon blots could be made reversibly transparent for photography and densitometry.

Alkaline Phosphatase↗
PubMed1990

Associations of Escherichia coli K-12 OmpF trimers with rough and smooth lipopolysaccharides.

The associations of both rough and smooth lipopolysaccharides (LPS) with the OmpF porin of Escherichia coli K-12 were examined in galE strains deleted for ompC. Transformation with pSS37 and growth with galactose conferred the ability to assemble a Shigella dysenteriae O antigen onto the core oligosaccharide of E. coli K-12 LPS. The association of LPS with OmpF trimers was assessed by staining, autoradiography of LPS specifically labeled with [1-14C]galactose, and Western immunoblotting with a monoclonal antibody specific for OmpF trimers. These techniques revealed that the migration distances and multiple banding patterns of OmpF porin trimers in sodium dodecyl sulfate-polyacrylamide gels were dictated by the chemotype of associated LPS. Expression of smooth LPS caused almost all of the trimeric OmpF to run in gels with a slower mobility than trimers from rough strains. The LPS associated with trimers from a smooth strain differed from the bulk-phase LPS by consisting almost exclusively of molecules with O antigen.

Autoradiography↗
PubMed1986

Cold lesions: enhanced contrast using asymmetric photopeak windows.

Cold-lesion contrast resolution was measured as a function of photopeak window position, photon energy, and scatter configuration using a clinical scintillation camera capable of asymmetric photopeak imaging. Two radionuclide solutions, technetium-99m and thallium-201, were studied at five photopeak window positions: the symmetric setting and window settings that were 5%, 10%, 20%, and 30% asymmetrically high (asymmetry was defined here by the intrinsic percentage of count loss relative to the symmetric window setting). Low contrast was examined with small cold-sphere phantoms and large cold-cube phantoms to produce high- and low-scatter conditions, respectively. High contrast was examined with a Hine cylindrical step phantom. Lesion contrast improved markedly with small degrees of window asymmetry but showed less dramatic improvement when positions at the higher degrees of asymmetry were studied. For the high-scatter and low-contrast situations, the maximum improvement in lesion contrast tended to be inversely proportional to lesion size. The maximum improvement in contrast resolution ranged from 10% to 45%, depending on lesion size, scatter configuration, and the radionuclide solution used.

Humans↗
PubMed1986

Effects of asymmetric photopeak windows on flood field uniformity and spatial resolution of scintillation cameras.

Pulse height analyzer windows that are set on the high side of the photopeak are known to improve spatial resolution and contrast when used for scintillation camera imaging. Asymmetric windows can be used with some scintillation cameras that have energy correction circuitry. In this study the improvement in spatial resolution and loss of field uniformity for 99mTc, 201Tl, and 131I were measured as a function of window asymmetry (up to 30%, defined relative to the loss of counts as compared to a symmetric window under intrinsic conditions). Flood field uniformity was inversely related to the degree of window asymmetry. With 10 cm of scatter the 99mTc integral uniformity deteriorated from 7.9% with a symmetric window to 11.5% for a 30% asymmetric window. The corresponding values for 201Tl were 9.9 and 10.9%. Even without additional scatter, the values for 131I were 23.0 and 26.5%. Spatial resolution, as measured by the full width at half maximum in 10 cm of scatter improved by only 5% for 99mTc and 7% for 201Tl. However, the full width at tenth maximum increased by as much as 20% for 99mTc and 201Tl. A large percentage of this improvement was attained with small degrees of asymmetry. This study demonstrates that 10% or less asymmetry can provide most of the benefit in spatial resolution and contrast that is to be gained without significant losses in field uniformity and count rate.

Image Enhancement↗
PubMed1985

Classification of children's behavior problems: clinical and quantitative approaches.

Children diagnosed Conduct Disorder, Attention Deficit Disorder, or Anxiety Disorder by DSM-III criteria were compared to contrast groups of Physically Disabled and Normal children using the Conners Teacher Rating Scale (CTRS). Discriminant function analyses of the CTRS ratings yielded accurate classification (67% correct) only when Conduct was combined with Attention Deficit and Normals were combined with Physically Disabled. The teacher raters seemed to be describing the children as behaviorally disordered with and without hyperactivity. The data also suggest that Attention Deficit Disorder is part of a broader Conduct Problems dimension.

Anxiety Disorders↗
PubMed1985

Ocular massage before cataract surgery.

We used the Honan intraocular pressure reducer, a balloon that applies a constant force, to the eyes in ten subjects with senile cataracts. An initially significant decrease in intraocular pressure after removal disappeared exponentially with a half-time of 9.6 minutes, indicating that the benefits derived from the Honan balloon do not result from a sustained reduction in intraocular pressure. Measurements made on a phantom eye showed both marked variability and unexpectedly high intraocular pressure during typical preoperative digital massage by a group of ophthalmic surgeons. Measurements made on a cadaver eye after application of the Honan balloon showed that very high intraocular pressures may be achieved under some conditions.

Cataract Extraction↗
PubMed1977

Omental band: new sign of metastasis.

Lymphomatouscellular infiltration of the greater omentum has been visualized by ultrasound as a uniformly thick, hyposonic, band-shaped structure adjacent to the anterior and lateral walls of the abdomen, following the contour of the abdominal convexity, and containing low-level, nonstructured internal echoes. From this finding, diffuse metastatic disease to the omentum can probably be inferred with a high degree of reliability.

Female↗
PubMed1975

The value of the pulmonary-artery-seeking catheter in percutaneous selective pulmonary arteriography.

Selective catheterization of the main pulmonary artery via the percutaneous route using a pulmonary-artery-seeking catheter was successful in 98.4% of 122 consecutive pulmonary angiographic studies in 114 patients. Complications were comparable to those encountered in other studies. Myocardial perforation, a frequently reported complication, did not occur, a factor attributed to the "pigtail" design of the catheter. This catheter was found to offer a distinct advantage in performing percutaneous selective pulmonary arteriography.

Adult↗