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Biomedical subjects

S L Shaw

Publications and source records attributed to S L Shaw.

14 recordsLinked to original sources
PubMed1998

Abnormalities detected on transvaginal ultrasonography in tamoxifen-treated postmenopausal breast cancer patients may represent endometrial cystic atrophy.

OBJECTIVE: This study was conducted to examine the histopathologic changes in tamoxifen-treated postmenopausal patients with endometrial thickness > or = 5 mm with transvaginal ultrasonography. STUDY DESIGN: Thirty-five tamoxifen-treated postmenopausal breast cancer patients underwent transvaginal pelvic ultrasonography with endometrial thickness > or = 5 mm followed by either curettage-hysteroscopy (n = 24), or hysterectomy (n = 11). Endometrial histopathologic findings were examined. RESULTS: Overall, endometrial polyps were the most common histopathologic finding (23 of 35 patients). Endometrial cystic atrophy was uncommonly detected in patients undergoing curettage-hysteroscopy (1 of 24 patients) compared with patients undergoing hysterectomy (9 of 11 patients). No cases of endometrial cancer or hyperplasia were detected. CONCLUSIONS: Endometrial polyps were a frequent finding in tamoxifen-treated postmenopausal women who had endometrial thickness > or = 5 mm with the use of transvaginal ultrasonography. Endometrial cystic atrophy may explain "thickened endometrium" on transvaginal ultrasonography in this patient population with no evidence of endometrial polyps, hyperplasia, or adenocarcinoma after surgical evaluation.

Adult↗
PubMed1997

Astral microtubule dynamics in yeast: a microtubule-based searching mechanism for spindle orientation and nuclear migration into the bud.

Localization of dynein-green fluorescent protein (GFP) to cytoplasmic microtubules allowed us to obtain one of the first views of the dynamic properties of astral microtubules in live budding yeast. Several novel aspects of microtubule function were revealed by time-lapse, three-dimensional fluorescence microscopy. Astral microtubules, about four to six in number for each pole, exhibited asynchronous dynamic instability throughout the cell cycle, growing at approximately 0.3-1.5 micron/min toward the cell surface then switching to shortening at similar velocities back to the spindle pole body (SPB). During interphase, a conical array of microtubules trailed the SPB as the nucleus traversed the cytoplasm. Microtubule disassembly by nocodozole inhibited these movements, indicating that the nucleus was pushed around the interior of the cell via dynamic astral microtubules. These forays were evident in unbudded G1 cells, as well as in late telophase cells after spindle disassembly. Nuclear movement and orientation to the bud neck in S/G2 or G2/M was dependent on dynamic astral microtubules growing into the bud. The SPB and nucleus were then pulled toward the bud neck, and further microtubule growth from that SPB was mainly oriented toward the bud. After SPB separation and central spindle formation, a temporal delay in the acquisition of cytoplasmic dynein at one of the spindle poles was evident. Stable microtubule interactions with the cell cortex were rarely observed during anaphase, and did not appear to contribute significantly to spindle alignment or elongation into the bud. Alterations of microtubule dynamics, as observed in cells overexpressing dynein-GFP, resulted in eventual spindle misalignment. These studies provide the first mechanistic basis for understanding how spindle orientation and nuclear positioning are established and are indicative of a microtubule-based searching mechanism that requires dynamic microtubules for nuclear migration into the bud.

Anaphase↗
PubMed1997

Imaging green fluorescent protein fusion proteins in Saccharomyces cerevisiae.

Tagging expressed proteins with the green fluorescent protein (GFP) from Aequorea victoria [1] is a highly specific and sensitive technique for studying the intracellular dynamics of proteins and organelles. We have developed, as a probe, a fusion protein of the carboxyl terminus of dynein and GFP (dynein-GFP), which fluorescently labels the astral microtubules of the budding yeast Saccharomyces cerevisiae. This paper describes the modifications to our multimode microscope imaging system [2,3], the acquisition of three-dimensional (3-D) data sets and the computer processing methods we have developed to obtain time-lapse recordings of fluorescent astral microtubule dynamics and nuclear movements over the complete duration of the 90-120 minute yeast cell cycle. This required low excitation light intensity to prevent GFP photobleaching and phototoxicity, efficient light collection by the microscope optics, a cooled charge-coupled device (CCD) camera with high quantum efficiency, and image reconstruction from serial optical sections through the 6 micron-wide yeast cell to see most or all of the astral molecules. Methods are also described for combining fluorescent images of the microtubules labeled with dynein-GFP with high resolution differential interference contrast (DIC) images of nuclear and cellular morphology [4], and fluorescent images of the chromosomes stained with 4,6-diamidino-2-phenylindole (DAPI) [5].

Dyneins↗
PubMed1996

The role of targeted secretion in the establishment of cell polarity and the orientation of the division plane in Fucus zygotes.

In this study, we investigate the role of polar secretion and the resulting asymmetry in the cell wall in establishing polarity in Fucus zygotes. We have utilized brefeldin-A to selectively interrupt secretion of Golgi-derived material into the cell wall as assayed by toluidine blue O staining of sulfated fucoidin. We show that the polar secretion of Golgi-derived material is targeted to a cortical site of the zygote identified by the localization of actin filaments and dihydropyridine receptors. The deposition of Golgi-derived material into the cell wall at this target site is temporally coincident with and required for polar axis fixation. We propose that local secretion of Golgi-derived material into the cell wall transforms the target site into the fixed site of polar growth. We also found that polar secretion of Golgi-derived material at the fixed site is essential for growth and differentiation of the rhizoid, as well as for the proper positioning of the first plane of cell division. We propose that the resulting asymmetry in the cell wall serves as positional information for the underlying cortex to initiate these polar events. Our data supports the hypothesis that cell wall factors in embryos, previously shown to be responsible for induction of rhizoid cell differentiation, are deposited simultaneously with and are responsible for polar axis fixation. Furthermore, the pattern of polar growth is attributable to a positional signal at the fixed site and appears to be independent of the orientation of the first cell division plane. Thus, the establishment of zygotic cell polarity and not the position of the first division plane, is critical for the formation of the initial embryonic pattern in Fucus.

Actins↗
PubMed1996

Polar localization of a dihydropyridine receptor on living Fucus zygotes.

We have used a fluorescently-labeled dihydropyridine (FL-DHP) to vitally stain living Fucus zygotes during the establishment of cell polarity. Localization of FL-DHP is primarily at the plasma membrane and FL-DHP binding is competitively blocked by an unlabeled dihydropyridine. Distribution of FL-DHP is initially symmetrical before fixation of the polar axis, but becomes asymmetrical in response to a unilateral light gradient. The distribution of FL-DHP receptors can be relocalized when the direction of the photopolarizing stimulus is changed. Treatment of cells with cytochalasin B prior to axis fixation reversibly prevents localization of FL-DHP receptors. Observation of FL-DHP labeling by time-lapse fluorescence microscopy indicates that the existing receptors are redistributed during polar axis formation. The asymmetric distribution of FL-DHP receptors coincides temporally and spatially with increased local intracellular calcium ion concentrations, as measured by calcium green dextran. Based on the site, timing, photo-reversibility, and actin dependence of the asymmetric localization of FL-DHP receptors, we conclude that FL-DHP is a vital probe for the later stage of polar axis formation in Fucus zygotes. Furthermore, we propose that FL-DHP receptors correspond to ion channels that are transported to the future site of polar growth to create the changes in local calcium concentration required for polarity establishment.

Calcium↗
PubMed1995

Digital photography for the light microscope: results with a gated, video-rate CCD camera and NIH-image software.

In this report, we describe a relatively inexpensive method for acquiring, storing and processing light microscope images that combines the advantages of video technology with the powerful medium now termed digital photography. Digital photography refers to the recording of images as digital files that are stored, manipulated and displayed using a computer. This report details the use of a gated video-rate charge-coupled device (CCD) camera and a frame grabber board for capturing 256 gray-level digital images from the light microscope. This camera gives high-resolution bright-field, phase contrast and differential interference contrast (DIC) images but, also, with gated on-chip integration, has the capability to record low-light level fluorescent images. The basic components of the digital photography system are described, and examples are presented of fluorescence and bright-field micrographs. Digital processing of images to remove noise, to enhance contrast and to prepare figures for printing is discussed.

Microscopy, Video↗
PubMed1985

Isolation and characterization of fibronectin from baboon plasma.

Fibronectin has been purified from baboon plasma by affinity chromatography on immobilized gelatin. Baboon fibronectin has subunit sizes, CNBr and thermolysin peptide patterns and an amino acid composition similar to human fibronectin. In Ouchterlony plates, baboon plasma fibronectin gives an immunological reaction of identity with human fibronectin, and a partial reaction with hamster fibronectin, using a goat antibody to human fibronectin. By radial immunodiffusion and rocket immunoelectrophoresis, using the same antibody, baboon fibronectin gives a dose response pattern similar to human fibronectin. Plasma concentrations of fibronectin in baboons are similar to those in humans. Fibronectin is thus another interesting protein that is closely related to its human counterpart and can be studied in subhuman primates using available antibodies to the human protein.

Amino Acids↗
PubMed1985

Studies on the elastolytic activity of chymotrypsin.

Chymotrypsin can completely solubilize insoluble [3H]-labeled ligamentum nuchae elastin. At similar enzyme levels, trypsin solubilizes only 5% of the elastin substrate whereas pancreatic elastase completely solubilizes the elastin at one-tenth the concentration required for chymotrypsin solubilization. The elastolytic activity of chymotrypsin is dependent on Ca+2, is enhanced by SDS, and is inhibited by NaCl at concentrations above 10 mM. The elastolytic activity of chymotrypsin is also inhibited by TPCK, a chymotrypsin specific inhibitor, but not by TLCK, a trypsin specific inhibitor. Neither TPCK nor TLCK abolish the elastolytic activity of pancreatic elastase. The sizes of [3H]elastin fragments produced by the elastolytic activity of chymotrypsin are similar to those produced by pancreatic elastase, and larger than those produced by trypsin.

Animals↗
PubMedDate not supplied

Rapid staining techniques employed in fine needle aspirations of the lung.

Fifty-two consecutive patients ranging in age from 22 to 90 years underwent percutaneous transthoracic fine needle aspiration biopsy under fluoroscopic guidance. A quick staining and rapid interpretation technique was used on samples from the 37 most recent cases. Rapid staining was accomplished within five minutes, and interpretation was available less than 15 minutes after obtaining the specimen. Successful diagnosis was obtained in 36 of 37 patients (97%). Standard methods utilizing a single aspiration sample yielded a successful diagnosis in 13 of 15 patients (86%). The improved rate of successful diagnosis following the rapid stain technique reflects the advantage of being able to determine the adequacy of specimens before releasing patients from the procedure room.

Adult↗