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Biomedical subjects

C L Smith

Publications and source records attributed to C L Smith.

At least 163 records · Page 9Linked to original sources
PubMed1994

Critical incident stress debriefings for crisis management in post-traumatic stress disorders.

Critical incident stress debriefings (CISDs) are a form of crisis management for rescuers such as police officers, fire-fighters and others involved in rescue efforts during natural disasters. This article describes a qualitative evaluation study of one police department's CISD implementation. Participant observation and semi-structured interviews were conducted with ten police officers involved in violent incidents. Results indicated that CISD was perceived as helpful by the officers in alleviating the symptoms of post-traumatic stress disorder they experienced after the violent incidents.

Adult↗
PubMed1994

Cytoskeletal movements and substrate interactions during initiation of neurite outgrowth by sympathetic neurons in vitro.

The initial outgrowth of neurites from chick sympathetic neurons grown in vitro was investigated by time-lapse microscopy with laser-scanning and conventional light microscopes. Video-enhanced contrast, differential interference contrast optics (VECDIC) were used to monitor movements of neuronal cytoplasm, as well as the movements of small beads attached to the surface membrane, and interference reflection microscopy (IRM) was used to determine the concomitant pattern of attachment to the growth substrate (polyornithine or laminin). Related changes in the distributions of actin filaments, microtubules, and neurofilaments were determined by fluorescence labeling methods. Neurite formation on both substrates entailed invasion of the actin cores of filopodia by cytoplasm containing microtubules and neurofilaments. Small beads attached to the surface membrane surrounding the cytoplasm moved outward simultaneously with the cytoplasm. Cytoplasm invaded filopodia of neurons plated on laminin soon after attachment to the substrate or, for neurons generated in vitro, within as little as 3 min after cytokinesis. However, cytoplasm invaded filopodia of neurons grown on polyornithine only when they contacted a three-dimensional object such as another cell or a large, polyornithine-coated polystyrene bead. The observation that adhesion of filopodia to polyornithine-coated beads can initiate neurite formation is inconsistent with the commonly held view that neurite formation requires adhesion mediated by specific cell adhesion molecules. Simultaneous IRM and DIC imaging showed that cytoplasm invaded filopodia when only their tips were closely apposed to a substrate but not when they were closely apposed to a substrate along their entire lengths. These findings help to elucidate the mechanisms by which interactions between the cytoskeleton and the growth substrate initiate and produce the neuronal movements that lead to the formation of neurites.

Actins↗
PubMed1993

Newly expressed progesterone receptor cannot activate stable, replicated mouse mammary tumor virus templates but acquires transactivation potential upon continuous expression.

During development and differentiation, the expression of transcription factors is regulated in a temporal fashion. Newly expressed transcription factors must interact productively with target genes organized in chromatin. Although the mechanisms governing factor binding to chromatin templates are not well understood, it is now clear that template access can be dramatically influenced by nucleoprotein structure. We have examined the ability of a well characterized transactivator, the progesterone receptor (PR), to activate the mouse mammary tumor virus (MMTV) promoter organized either in stable, replicating templates that have a highly ordered nucleosome structure or as transiently transfected DNA, which adopts a less-defined structure. If the PR is transiently expressed in cells harboring both replicated and transient MMTV receptor constructs, it cannot significantly activate the stable replicated MMTV template. In contrast, when PR cDNA is stably inserted into the same cells and constitutively expressed, it gains the ability to activate both chromosomal and transiently introduced templates. These results demonstrate that newly expressed PR is not competent to activate the MMTV template in its native nucleoprotein conformation but acquires this ability upon prolonged expression in replicating cells.

3T3 Cells↗
PubMed1993

Modulation of the ligand-independent activation of the human estrogen receptor by hormone and antihormone.

It has been previously demonstrated that several members of the steroid receptor superfamily may be activated by the neurotransmitter dopamine in the apparent absence of cognate ligand. We have examined wild-type and mutant human estrogen receptors (ERs, [Gly400]ER and [Val400]ER, respectively) for their abilities to activate ER-dependent transcription of a transgene in a ligand-independent manner. In cells expressing the wild-type ER, dopamine was nearly as effective as 17 beta-estradiol at inducing the chloramphenicol acetyltransferase activity of the reporter gene in a dose-dependent manner; simultaneous addition of suboptimal concentrations of 17 beta-estradiol and dopamine stimulated transcription more than either compound alone. Dopamine alone was unable to induce gene expression in cells expressing [Val400]ER mutant receptors, but concomitant treatment with 17 beta-estradiol produced a synergistic increase in transcription, suggesting that the ligand may alter the mutant receptor's conformation such that it can be activated subsequently by a dopaminergic signaling mechanism. In the presence of the antiestrogen ICI 164,384, dopamine-stimulated gene expression was undetectable in cells expressing either form of ER. However, simultaneous treatment of cells expressing wild-type ER with trans-4-hydroxytamoxifen and dopamine resulted in transgene expression that was additive in nature compared to either compound alone; similar treatment of cells expressing [Val400]ER produced a synergistic increase. Our results suggest that ligand and ligand-independent activation of the ER initiate from distinct pathways and that the latter may occur in a variety of target tissues subject to modulation by receptor ligands.

Chloramphenicol O-Acetyltransferase↗
PubMed1993

Atomic force microscopy of biochemically tagged DNA.

Small fragments of DNA of known length were made with the polymerase chain reaction. These fragments had biotin molecules covalently attached at their ends. They were subsequently labeled with a chimeric protein fusion between streptavidin and two immunoglobulin G-binding domains of staphylococcal protein A. This tetrameric species was expected to bind up to four DNA molecules via their attached biotin moieties. The DNA-protein complex was deposited on mica and imaged with an atomic force microscope. The images revealed the protein chimera at the expected location at the ends of the strands of DNA as well as the expected dimers, trimers, and tetramers of DNA bound to a single protein.

Bacterial Proteins↗
PubMed1993

Oncogene ect2 is related to regulators of small GTP-binding proteins.

We have developed an efficient expression cloning system that allows rapid isolation of complementary DNAs able to induce the transformed phenotype. We searched for molecules expressed in epithelial cells and possessing transforming potential to fibroblasts, and cloned a cDNA for the normal receptor of a growth factor secreted by NIH/3T3 cells. Here we report a second novel transforming gene, ect2. The isolated cDNA is activated by amino-terminal truncation of the normal product. The Ect2 protein has sequence similarity within a central core of 255 amino acids with the products of the breakpoint cluster gene, bcr (ref. 5), the yeast cell cycle gene, CDC24 (ref. 6), and the dbl oncogene. Each of these genes encodes regulatory molecules or effectors for Rho-like small GTP-binding proteins. The baculovirus-expressed Ect2 protein could bind highly specifically to Rho and Rac proteins, whereas the dbl product showed broader binding specificity to Rho family proteins. Thus ect2 is a new member of an expanding family, whose products have transforming properties and interact with Rho-like proteins of the Ras superfamily.

3T3 Cells↗
PubMed1993

The 0.7 to 3.3 megabase chromosomes from Candida, Kluyveromyces, and Pichia provide accurate size standards for pulsed field gel electrophoresis.

Pulsed field gel electrophoresis was used to size intact chromosomal DNAs from Candida albicans, Kluyveromyces lactis, Pichia scolyti, and Pichia mississippiensis by optimization methods using, as size standards, concatenated bacteriophage lambda DNA, and intact and NotI digestion products of Schizosaccharomyces pombe chromosomal DNAs. These newly sized fungal DNAs can now serve as convenient and accurate size standards for DNA molecules between 0.7 and 3.3 megabases (Mb). These size standards are valid over a wide range of different electrophoretic conditions.

Candida↗
PubMed1993

Cloning and characterization of EagI YACs from human chromosome 21.

Yeast artificial chromosomes (YACs) were made from a total EagI digest of DNA from a mouse-human chromosome 21 hybrid cell line. Approximately 3750 YACs, corresponding to 75-125 human YACs, with an average size of approximately 100 kb were recovered. Southern hybridization indicates that the chimera frequency in this library may be less than 3%. Thirty-four of the human EagI YACs were regionally assigned by a number of methods. Some YACs were regionally assigned to one of six chromosome regions by hybridization of Alu-PCR products from the YAC against Alu-PCR-amplified DNA from a panel of hybrid cell lines that contain various parts of chromosome 21. Additional YACs were regionally assigned by fluorescence in situ hybridization using either biotinylated Alu-PCR products or yeast genomic DNA from the YAC-containing strains as probes. The regionally assigned EagI YACs are located preferentially in two regions of the chromosome: near the q telomere and in the p-arm ribosomal gene region.

Animals↗
PubMed1993

DNA sequence analysis of human chromosome 21 notI linking clones.

Portions of 16 chromosome 21 NotI linking clones were sequenced. These linking clone sequences represent sequence-tagged restriction sites that are potentially useful for finding genes and for finer genome mapping and sequencing. All of the clones were G+C rich (54 to 83%). CpG and GpC dinucleotide frequencies were very close to the expected values based on base composition and were very similar in 15 of the clones. Most of the NotI linking clones were derived from CpG islands, which are often associated with genes. Five NotI linking clones had a high potential for coding regions; 7 additional clones may also contain coding regions. The NotI linking clones had many short homologous regions, but no extensive homologies either with each other or with GenBank sequences.

Base Composition↗
PubMed1993

A streptavidin mutant containing a cysteine stretch that facilitates production of a variety of specific streptavidin conjugates.

The ability to produce specific streptavidin conjugates has been considerably enhanced by using a streptavidin mutant containing a cysteine stretch, in which sulfhydryl groups serve as unique conjugation sites. A streptavidin molecule containing five cysteine residues at its C-terminus, referred to as Stv-28, was efficiently expressed in Escherichia coli, and purified to homogeneity. Purified Stv-28 had full biotin-binding ability and formed a subunit tetramer. Reactive sulfhydryl groups of Stv-28, derived solely from the cysteine stretch, greatly facilitate the specific conjugation of partner molecules to streptavidin by simple sulfhydryl chemistry. In this manner, S-[14C]carboxymethylated streptavidin and a streptavidin-fluorescein conjugate were prepared. These conjugates contain almost twenty [14C]carboxymethyl groups and fluorescein molecules, respectively, per subunit tetramer, indicating that the sulfhydryl groups of the cysteine stretch are fully reactive. More importantly, these conjugates retain full biotin-binding ability and form subunit tetramers, suggesting that the fundamental properties of streptavidin would be unaffected by the conjugation of other partner molecules to the C-terminal cysteine stretch.

Amino Acid Sequence↗
PubMed1993

Extracting dynamic parameters from speech movement data.

A quantitative characterization of articulatory movements, using the parameter values of a linear second-order dynamical system, was developed in order to compare classes of movements, in particular, classes defined by linguistic factors such as syllable position, stress, and vowel quality. Movements of the lower lip in utterances such as ['bibebib] and [babe'bab] were partitioned into sections ("windows") in two ways: at successive displacement peaks and valleys, and at the right edge of plateau regions around such extreme values. The linguistic factors affected natural frequency in similar ways regardless of whether damping ratio was permitted to vary or held fixed at one of several different values. Damping ratio was generally unaffected by the linguistic factors. For the most part, the type of partition or window did not affect the patterns of the results, with the exception of the closing gesture out of the reduced syllable.

Adult↗
PubMed1993

Spatial and temporal distribution of corticosteroid-binding globulin and its messenger ribonucleic acid in embryonic and fetal mice.

Glucocorticoids influence fetal development, and their actions are regulated by plasma corticosteroid-binding globulin (CBG). Immunohistochemistry and in situ hybridization were, therefore, used to localize CBG and its mRNA in sections of embryonic and fetal mice and their associated placental tissues from day 5 of gestation until term (day 19). In the fetus, CBG mRNA was first detectable in the hepatocytes on day 11 of gestation. The amount of CBG mRNA in these cells increased transiently to a maximum on days 15-16 of gestation and was negligible by day 19. In hepatocytes, CBG immunoreactivity correlated with the distribution and relative abundance of CBG mRNA. The fetal exocrine pancreas also contained CBG mRNA, but this was only present on days 15-16 of gestation, while immunoreactive CBG persisted in these cells until term. Immunoreactive CBG was detected in the tubular cells of the developing fetal kidney as early as day 13, but CBG mRNA was never found in the fetal kidney, suggesting that the protein is probably sequestered from fetal blood directly or via the glomerular filtrate. The placenta contained immunoreactive CBG throughout gestation, even before its detection in fetal tissues, and it was most abundant in the spongiotrophoblasts and the extracellular matrix surrounding fetal and maternal capillaries. However, CBG mRNA was not detected in the placenta at any gestational age. Therefore, CBG present in the placenta is most likely of maternal origin and may influence the activities of steroid hormones that control placental development and/or function. The presence of smaller immunoreactive polypeptides in placental extracts, compared to CBG in corresponding maternal serum samples, suggests that this process may involve an interaction between maternal CBG and placental proteinases. The results presented here suggest that temporal and spatial changes in the localization of CBG and its mRNA in the fetus may influence the effects of steroid hormones on developing tissues.

Amino Acid Sequence↗
PubMed1993

Reduced sensitivity to intra-oesophageal acid in patients with reflux-induced strictures.

Patients presenting with benign reflux-induced oesophageal strictures often have no antecedent symptoms of reflux, which might be a consequence of decreased oesophageal sensitivity. This has been investigated in 36 patients with strictures and 30 patients with uncomplicated oesophagitis by means of a visual analogue scale (0 to 10) to assess preceding symptoms and acid perfusion tests to assess oesophageal sensitivity. Patients with strictures had lower symptom scores (median, 2.7) than those with uncomplicated oesophagitis (median, 4.85) and were more likely to have a negative acid perfusion test (18 of 28 compared with 6 of 23, respectively; p < 0.05). Furthermore, the volumes of acid perfused at the onset of symptoms in the stricture group (median, 80 ml) were greater than in the oesophagitis group (median, 40; p < 0.05). These results support the hypothesis that patients who develop reflux-induced strictures have decreased sensitivity to intra-oesophageal acid. This may be a factor in the pathogenesis of reflux-induced strictures.

Adult↗
PubMed1993

Myelodysplasia, vasculitis and anti-neutrophil cytoplasm antibodies.

A cutaneous or systemic vasculitis occurs in myelodysplasia as well as in myeloproliferative and lymphoproliferative disorders. The most common lesion is a leucocytoclastic vasculitis, with neurological or joint involvement occurring less often. The vasculitis may appear contemporaneously with or precede the clinical onset of the blood dyscrasia. Occasionally the lesions respond dramatically to the use of steroids but in general, patients with vasculitis have a worse prognosis than those with uncomplicated myelodysplasia. Vasculitis and myelodysplasia appear together too often for the association to be coincidental and the vasculitis in most cases cannot be attributed to intercurrent infections, therapeutic agents or a pre-existing rheumatological disorder. While autoantibodies are frequently present in myelodysplasia, and ANA and anti-neutrophil cytoplasm antibodies (ANCA) are found in other vasculitides, neither of these antibodies is associated with the vasculitis of myelodysplasia. There has however been one report of ANCA in Sweet's syndrome a non-vasculitic skin condition that also occurs in the myelodysplastic syndromes.

Adult↗