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Biomedical subjects

S M Green

Publications and source records attributed to S M Green.

At least 127 records · Page 7Linked to original sources
PubMed1991

Plain abdominal radiography in the detection of acute medical and surgical disease in children: a retrospective analysis.

A retrospective review was performed to determine the utility of plain abdominal radiographs in evaluating children presenting to the emergency department. Clinical features, radiographic interpretation, and final diagnoses of 431 patients seen over one year were recorded. One hundred three (24%) patients had major diseases (ventriculoperitoneal shunt malfunction, foreign body ingestion, appendicitis, intussusception, bowel obstruction, necrotizing enterocolitis, toxic megacolon, blunt abdominal trauma, pyloric stenosis, and Hirschsprung's disease), while the remaining 328 (76%) had minor diseases. Radiographs were categorized as diagnostic, suggestive, normal, incidental, or misleading, with respect to the patient's final diagnosis. No single clinical feature was able to detect all diagnostic radiographs in patients with major diseases. Limiting radiographs to patients with prior abdominal surgery, suspected foreign body ingestion, abnormal bowel sounds, abdominal distention, or peritoneal signs identified all patients with radiographs diagnostic of a major disease while eliminating 48% of studies ordered. Our results suggest that restricting abdominal roentgenograms to patients with at least one of these features will detect most diagnostic radiographs in children with acute abdominal diseases.

Abdomen, Acute↗
PubMed1991

Silicone rubber arthroplasty of the proximal interphalangeal joint: dorsal and lateral approaches.

Although arthrodesis of an arthritic proximal interphalangeal joint provides excellent relief of pain, it does so at the expense of mobility. Silicone rubber implant arthroplasty also provides predictable relief of pain and approximately 60 degrees of motion. Insertion of the implant through a dorsal extensor-splitting approach is preferred when a tendon reconstruction is necessary, as in cases of boutonniére deformity. If tendon reconstruction is not necessary, the lateral approach is an excellent alternative because it does not disturb the extensor mechanism and therefore permits earlier rehabilitation exercises. The following article outlines the dorsal and lateral techniques and postoperative rehabilitation of silicone rubber arthroplasty.

Arthritis↗
PubMed1990

Steady-state fluorescence and time-resolved fluorescence monitor changes in tryptophan environment in arginase from Saccharomyces cerevisiae upon removal of catalytic and structural metal ions.

Yeast arginase is a trimeric protein of identical subunits, each containing three tryptophans. Time-resolved fluorescence and steady-state fluorescence were employed to monitor the effects of removing the weakly bound catalytic Mn2+ as well as the tightly bound structural Zn2+/Mn2+. Resolution of the total native emission spectrum into decay-associated spectra (DAS) yielded components with lifetimes of 0.1, 1.2, and 4.0 ns. Upon removal of the catalytic metal, the intensities increased approximately 20% while the lifetimes increased less than 10%, and the DAS were unchanged except in intensity. The two major components are well resolved, but the 0.1-ns term is small and dominated by scattered excitation. In contrast, removal of the structural metal increased decay times to 0.2, 1.8, and 5.3 ns. More important, both native DAS red-shifted and became indistinguishable. These data suggest that removal of the catalytic metal does little to change the microenvironments of the individual tryptophans while removal of the structural metal causes partial unfolding of the protein. The excitation spectra for the active and inactive trimers were resolved into their excitation DAS (IEDAS), suggesting ground-state heterogeneity of the fluorescent species. In contrast, the excitation spectra of arginase without the structural metal could not be resolved due to the indistinguishable DAS. The tryptophans are quenched by acrylamide but not by cesium or iodide. Global analysis of the acrylamide quenching data resulted in two quenching decay-associated spectra (QDAS) which correlated well with the DAS. Since the apoenzyme does not exhibit tryptophan accessibility to either positive or negative ionic quenchers, one must assume that the "unfolded" monomeric protein retains considerable tertiary structure.

Apoenzymes↗
PubMed1990

HIV-1 regulator of virion expression (Rev) protein binds to an RNA stem-loop structure located within the Rev response element region.

HIV-1 Rev protein, purified from E. coli, binds specifically to an RNA transcript containing the 223 nucleotide long Rev response element (RRE) sequence. Rev binds to RRE in vitro with an apparent dissociation constant of 1 to 3 nM as determined by filter binding, gel mobility shift assays, or an immunoprecipitation assay using a monoclonal antibody specific for the Rev C-terminus. Antisense RRE sequences are bound by Rev with a 20-fold lower affinity than wild-type RRE sequences. The Rev-RRE complex forms even in the presence of a 10,000-fold molar excess of 16S rRNA, whereas formation of the low affinity antisense RRE-Rev complex is efficiently blocked by addition of excess 16S rRNA. A approximately 33 nucleotide fragment is protected from ribonuclease T1 digestion by the binding of Rev to RRE RNA, suggesting that Rev binds with high affinity to only a restricted region of the RRE. This protected fragment is unable to rebind Rev protein but has been mapped to a 71 nucleotide long Rev binding domain sequence that overlaps the protected fragment.

Amino Acid Sequence↗
PubMed1990

The purification and characterization of arginase from Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, ornithine transcarbamoylase and arginase form a regulatory multienzyme complex (Hensley, P. (1988) Curr. Top. Cell. Regul. 29, 35-75). In this complex, arginase acts as a negative allosteric effector for ornithine transcarbamoylase. Before an analysis of the factors which promote and stabilize complex formation, arginase was purified in milligram quantities from a plasmid-containing, enzyme-overproducing, protease-deficient yeast strain and its physical characterization undertaken. The purified enzyme has a specific activity of 885 mumol urea min-1 mg-1 and a Km for arginine of 15.7 mM. The ultraviolet spectrum has a maximum absorbance at 279 nm, and the steady-state fluorescence emission spectrum has a maximum intensity at 337 nm, suggesting that the 3 tryptophans/polypeptide chain are in a relatively hydrophobic environment. Arginase has a weakly bound manganese responsible for the maintenance of the catalytic activity and is known to be heat activated in the presence of manganese. This effect is half-maximal at 12.1 microM manganese. In addition to a catalytic requirement for manganese, the presence of a more tightly bound metal is suggested from sedimentation studies. The native trimeric enzyme has a sedimentation coefficient of 5.95 S. Removal of the weakly associated metal results in no change in the sedimentation coefficient. However, dialysis with EDTA causes the s-value to decrease to 4.65 S, suggesting that under these conditions, the trimeric enzyme may partially dissociate. An analysis of CD spectra shows that significant spectral changes result from the removal of both the weakly bound metal and dialysis against EDTA.

Arginase↗
PubMed1990

HIV-1 tat protein stimulates transcription by binding to a U-rich bulge in the stem of the TAR RNA structure.

The HIV-1 trans-activator protein, tat, is an RNA binding protein with a high affinity for a U-rich bulge near the tip of the stem in the RNA stem-loop structure encoded by the trans-activation responsive region (TAR). A Scatchard analysis of tat binding has shown that the purified protein forms a one-to-one complex with HIV-1 TAR RNA with a dissociation constant of Kd = 12 nM. Deletion of the uridine residues in the bulge or substitution with guanine residues produced RNAs with a 6- to 8-fold lower affinity than wild-type TAR. Introduction of a point mutation expected to destabilize base pairing in nearby residues of the TAR stem-loop structure reduced tat binding 10-fold. In contrast, mutations that alter the sequence of the six nucleotide long loop at the tip of TAR RNA structure, and mutations which alter the sequence of the stem whilst preserving Watson-Crick base pairing, do not affect tat binding significantly. There is a direct correlation between the ability of tat to bind to TAR RNA and to activate HIV transcription. Viral LTRs carrying TAR sequences encoding any of the mutations known to produce transcripts which bind tat weakly, are not stimulated efficiently by tat in vivo.

Base Sequence↗
PubMed1990

Ketamine sedation for pediatric procedures: Part 1, A prospective series.

Emergency physicians frequently perform painful but necessary procedures on frightened children. We conducted a prospective, uncontrolled clinical trial of ketamine sedation (4 mg/kg IM) to facilitate a variety of procedures in 108 children aged 14 months to 13 years. Acceptable conditions were achieved with a single injection in 97% of the patients, and adjunctive restraint or local anesthesia was not required in 86%. Full sedation was produced within five minutes in 83%. Mean duration from injection to dischargeable recovery was 82 minutes (range, 30 to 175 minutes). One 18-month-old child vomited shortly after injection and experienced transient laryngospasm with cyanosis; intubation was not required, and there were no adverse sequelae. Airway patency and independent respirations were fully maintained in all other patients; no hemodynamic instability occurred at any time. There were no other clinically significant complications. Emesis well into the recovery phase was noted in 6% of the patients. Nightmares were not observed. Response from parents and physicians was strongly positive. Ketamine can be effectively used by emergency physicians to facilitate procedural sedation, yet equipment and expertise for advanced airway management are mandatory due to the rare occurrence of laryngospasm.

Adolescent↗
PubMed1990

Ketamine sedation for pediatric procedures: Part 2, Review and implications.

Ketamine produces rapid and consistent pediatric sedation with a predictable onset and recovery time. A wide margin of safety is afforded without the respiratory and cardiovascular depression commonly seen with alternative agents. The efficacy of ketamine is well established in anesthesia and dentistry and has extensive applications in other specialties. Ketamine sedation facilitates superior technical and cosmetic results while minimizing emotional trauma to distraught children. The much-feared complications of aspiration and laryngospasm are extremely rare when ketamine is used with proper precautions. Ketamine deserves increased use in the ED, and we advocate additional clinical investigation in this setting.

Child↗
PubMed1990

Expression of v-fms and c-fms in the hemopoietic cell line FDC-P1.

A hemopoietic cell line FDC-P1 that requires either IL-3 or GM-CSF to survive and proliferate was infected with retroviruses that expressed either c-fms, which encodes the receptor for M-CSF, or v-fms, which is an oncogenic derivative of c-fms. The expression of c-fms allowed FDC-P1 to grow in the absence of IL-3 or GM-CSF provided that M-CSF was present. The M-CSF did not, however, induce macrophage differentiation. The expression of v-fms allowed FDC-P1 to grow in the absence of any added hemopoietic growth factors, including M-CSF, although the addition of M-CSF enhanced v-fms activity. V-fms cell lines grew to a higher cell density in suspension and were tumorigenic.

Animals↗
PubMed1989

Pacemaker electrode perforation of the myocardium: an unusual etiology for recurrent abdominal pain.

A 79-year-old man with a permanent pacemaker presented on five separate occasions to the emergency department with recurrent episodes of crampy abdominal pain. Extensive radiographic studies and repetitive labwork were nondiagnostic. Shortly after hospital admission on the fifth visit he experienced cardiac arrest and was successfully resuscitated. Poor pacemaker capture and paced clonic contractions of the diaphragm and abdominal wall were noted, suggesting myocardial perforation by the pacemaker electrode. A new lead and pulse generator were implanted and the patient was discharged without further abdominal discomfort. Implications of pacemaker electrode perforation of the myocardium are discussed.

Abdomen↗
PubMed1989

Human immunodeficiency virus 1 tat protein binds trans-activation-responsive region (TAR) RNA in vitro.

tat, the trans-activator protein for human immunodeficiency virus 1 (HIV-1), has been expressed in Escherichia coli from synthetic genes. Purified tat binds specifically to HIV-1 trans-activation-responsive region (TAR) RNA in gel-retardation, filter-binding, and immunoprecipitation assays. tat does not bind detectably to antisense TAR RNA sequences, cellular mRNA sequences, variant TAR RNA sequences with altered stem-loop structures, or TAR DNA.

Base Sequence↗
PubMed1989

Transformation of growth factor-dependent myeloid stem cells with retroviral vectors carrying c-myc.

Myeloid progenitor cells and macrophages derived from bone marrow and spleen were efficiently transformed in vitro by infection with Moloney-based retroviral vectors carrying a human c-myc gene. Infected cells were plated in agar in the presence of combinations of the murine lymphokines CSF-1, IL-3, GM-CSF and IL-1. Between 20% and 100% of the colony-forming cells in the initial bone marrow or spleen population could be infected and gave rise to drug-resistant colonies. A large fraction of the infected cells showed continued proliferation after transfer to liquid media and we have derived over 200 growth factor-dependent cell lines. These include adherent and non-adherent CSF-1 or GM-CSF dependent macrophages and macrophage precursors and cell lines which require complex combinations of growth factors for optimal growth. Each of the cell lines displays a unique pattern of expression of surface markers specific for the myeloid lineage including the Mac-1, Mac-2, Mac-3, Ser-4 and F4/80 antigens. Surface markers not specifically associated with the myeloid lineage such as the MHC class II antigens and the Fc-receptor; and surface markers normally associated with the B-cell and T-cell lineages such as B220, L3T4 and Thy1.2 are also found on these cell lines.

Animals↗
PubMed1989

Regulation of cell cycle duration by c-myc levels.

Early passage murine fibroblasts infected with retroviral vectors carrying human c-myc 'minigenes' express high levels of c-myc and have a dramatically shortened G1-phase of the cell cycle. Cells infected with viruses where c-myc is expressed from the viral LTR (MSN-4 virus) express more c-myc protein than cells infected with viruses where c-myc is expressed from the SV40 early promoter (NSM-7 virus). Populations of cells were infected with high titre viruses, selected for drug-resistance, pulse labelled with bromodeoxyuridine (BrdUrd) and chased in BrdUrd free media. This allows accurate, simultaneous, measurement of the rate of exit of unlabelled cells from G1 and progression of BrdUrd-labelled cells through S-phase. The length of the G1-phase in cell populations infected with the MSN-4 virus is 4.65 h, a reduction of nearly 30% compared to the G1-phase length of 6.50 h seen in cells infected with the VSN-2 control virus. Cells infected with NSM-7 virus show an intermediate phenotype and have a G1-phase of 5.25 h. The lengths of the S-phase (4.50 to 4.75 h) and G2 + M phases (2.75 h) were not significantly altered by exogenous c-myc expression. When chases are performed in growth-factor free media, the G1-phase of infected and non-infected cells is extended by approximately 2 h. Cells infected with the c-myc viruses continue to cycle more rapidly than uninfected cells. Growth factor-deprived cells, restimulated with serum, show similar alterations of the cell cycle kinetics. MSN-4 and NSM-7 infected cells, expressing high levels of c-myc, enter S-phase 2 to 4 h earlier, but less synchronously, than control cells, and sustain subsequent rounds of DNA synthesis, while control cells do not. However, cells carrying activated c-myc genes have nearly-normal morphologies and are not tumourgenic in syngenic mice. These results demonstrate that c-myc levels are rate limiting for events in G1, and the length of G1 varies proportionally with the level of exogenous c-myc expression.

Animals↗
PubMed1986

The quaternary structure of ornithine transcarbamoylase and arginase from Saccharomyces cerevisiae.

Electron microscopic studies employing negative staining, rotary shadowing, and unidirectional shadowing have revealed the subunit architecture of ornithine transcarbamoylase and arginase from Saccharomyces cerevisiae. These techniques have confirmed the quaternary structure of these enzymes, and have permitted an estimate of the shape and dimensions of each of the individual enzymes as well as those of the corresponding subunits to be determined. Both enzymes are trimers exhibiting 3-fold rotational symmetry with subunits which are oblate ellipsoids of revolution. The overall dimensions determined for ornithine transcarbamoylase are a height of 39 A and a width of 102 A. The consequent subunit dimensions are 59 X 59 X 39 A, yielding a subunit axial ratio of 1.51. Arginase has a height of 42 A and a width of 97 A. The subunit dimensions are 56 X 56 X 42 A, yielding a subunit axial ratio of 1.33. The hydrodynamic behavior of the two enzymes is fully consistent with this molecular architecture, suggesting that the structures proposed here are similar to those of the proteins in aqueous solution.

Arginase↗
PubMed1986

The locked metacarpophalangeal joint: diagnosis and treatment.

The locked metacarpophalangeal joint of a finger is an unusual condition frequently confused with a "trigger finger." The causes can be classified into degenerative and spontaneous groups. Ten cases are presented. The cause of locking of one patient in the degenerative group was gouty arthritis, a cause not previously reported in the literature. Although surgery is usually necessary, joint mobility was restored in 30% of the cases by distending the joint capsule with an intraarticular injection of a local anesthetic followed by gentle manipulation. In addition to routine x-ray films, arthrotomography was found to be a useful diagnostic technique in determining the cause of locking.

Adult↗