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Biomedical subjects

S A Green

Publications and source records attributed to S A Green.

At least 19 recordsLinked to original sources
PubMed1992

Experimental reproduction of ELEM. A study to determine the minimum toxic dose in ponies.

An experiment to gain insight into the minimum toxic dose of fumonisins was conducted by feeding ponies rations with known fumonisin concentrations. Naturally contaminated corn screenings (CS) were blended with pellets, corn, and molasses to formulate individual daily diets. One group of 4 ponies was fed a ration with fumonisin B1 (FB1) varying from less than 1 ppm to 22 ppm. A second group of 5 ponies was fed a ration at varying rates containing 8 ppm FB1 for 180 days. A panel of clinical chemistry parameters was evaluated twice weekly for both groups. One pony in the first group died of equine leukoencephalomalacia (ELEM) after 225 days of which the final 55 days' diet contained 22 ppm FB1. Approximately 9 days prior to death, this animal experienced elevated liver chemistry values. All 5 ponies in the second group experienced mild, transient, clinical signs; were euthanized at 180 days; and had mild, histopathological brain lesions.

Animal Feed↗
PubMed1992

Low density lipoprotein receptor and cation-independent mannose 6-phosphate receptor are transported from the cell surface to the Golgi apparatus at equal rates in PC12 cells.

Efficient transport of cell surface glycoproteins to the Golgi apparatus has been previously demonstrated for a limited number of proteins, and has been proposed to require selective sorting in the endocytic pathway after internalization. We have studied the endocytic fate of several glycoproteins that accumulate in different organelles in a variant clone of PC12, a regulated secretory cell line. The cation-independent mannose 6-phosphate receptor and the low density lipoprotein receptor, both rapidly internalized from the cell surface, and the synaptic vesicle membrane protein synaptophysin, were transported to the Golgi apparatus with equivalent, nonlinear kinetics. Transport to the Golgi apparatus (t1/2 = 2.5-3.0 h) was several times faster than turnover of these proteins (t1/2 greater than or equal to 20 h), indicating that transport of these proteins to the Golgi apparatus occurred on average several times for each protein. In contrast, Thy-1, a protein anchored in the membrane by a glycosylphosphoinositide group, was internalized and transported to the Golgi apparatus more slowly than the three transmembrane proteins. Since each of the transmembrane proteins studied showed the same t1/2 for transport to the Golgi apparatus, we conclude that transport of these proteins from the cell surface to the Golgi apparatus does not require sorting information specific to any one of these proteins. These results suggest that one of the functions of late endosomes is constitutive recycling of cell surface receptors through the Golgi apparatus if they fail to recycle to the cell surface directly from early endosomes, and that the late endosome recycling pathway is followed frequently by many rapidly internalized proteins.

Animals↗
PubMed1992

Beta 1- and beta 2-adrenergic receptors display subtype-selective coupling to Gs.

beta-Adrenergic receptor (beta AR) subtypes differ in their affinities for some agonists and antagonists and thus may potentially impart different cellular effects based on this ligand-binding specificity. However, the possibility that there may be subtype-specific events subsequent to ligand binding has not been evaluated extensively. In particular, although beta ARs stimulate adenylyl cyclase by coupling to the guanine nucleotide-binding protein Gs, no studies have directly assessed the coupling efficiencies among isolated beta AR subtypes. We, therefore, permanently transfected the mammalian fibroblast cell line CHW-1102 with beta 1- or beta 2AR cDNAs and studied the coupling characteristics of these two receptor subtypes, each expressed at approximately 335 fmol/mg of protein. Both receptors mediated equivalent maximal increases in adenylyl cyclase activities (6.63 +/- 1.85-fold for beta 1AR versus 6.10 +/- 0.53-fold for beta 2AR; p = not significant). However, the isoproterenol dose-response curves for the beta 2AR were shifted to the left, compared with those for the beta 1AR (EC50 of 52.3 +/- 2.87 nM and 191 +/- 10.5 nM, respectively; p less than 0.05), resulting in an approximately 4-fold greater potency for the beta 2AR versus the beta 1AR. Thus, at the submaximal isoproterenol concentration of 30 nM, the beta 2AR stimulated adenylyl cyclase approximately 50% more than did the beta 1AR. This finding was not due to a difference in the affinities of isoproterenol for these receptors, which were found to be the same, as determined by competition binding studies with 125I-cyanopindolol in the presence of GTP. The ability of beta 1- and beta 2ARs to form the high affinity ternary complex was assessed in agonist competition studies without guanine nucleotide. We found that, whereas the proportion of receptors in the high affinity state was equivalent between the two receptor subtypes, the affinity of this state for isoproterenol was approximately 5-fold greater for the beta 2AR, compared with the beta 1AR (KH for beta 2AR, 11.8 +/- 3.1 nM; KH for beta 1AR, 61.7 +/- 18.3 nM; p less than 0.05). In addition, we examined physical and functional coupling of beta 1- and beta 2ARs to Gs using the agonist epinephrine, which also has equal binding affinity for both receptor subtypes. As with isoproterenol, epinephrine was more potent in stimulating adenylyl cyclase and promoted a higher affinity ternary complex for the beta 2AR. Thus, a greater degree of both physical and functional agonist-promoted coupling occurs between Gs and beta 2AR, compared with beta 1AR. We conclude that coupling to Gs by beta 1- and beta 2ARs is subtype selective and is a potentially important distinguishing feature among these members of the beta AR family.

Adrenergic beta-Agonists↗
PubMed1992

The Rancho mounting technique for the Ilizarov method. A preliminary report.

To improve implant tolerance and muscle function associated with circular external fixation, the authors substituted divergent titanium pins for the tensioned steel wires used to mount the Ilizarov apparatus on a limb. The first ten patients treated with half-pins were compared to the last ten patients managed with tensioned wires. While the conditions were not exactly comparable, the half-pin group showed improvement over the wire group in categories including time in fixation, implant-site sepsis, range of joint motion, pain medication requirements, and ambulatory capacity. Half-pin mountings require special techniques for a successful application.

Adolescent↗
PubMed1992

Management of segmental defects by the Ilizarov intercalary bone transport method.

Seventeen patients with segmental skeletal defects were managed with the Ilizarov intercalary bone transport method, whereby an osseous defect is eliminated by elongating one fragment. On average, the regenerate new bone length measured 5.14 cm, corresponding to the creation of new osseous tissue equaling 13.7% of the bone's original length (range, 4.2%-35%). The average time in fixation was 9.6 months, including 4.8 months to transport the bone fragment throughout the limb. Numerous complications were encountered, most commonly wire-site sepsis and fixator instability. No serous nerve or vessel complications occurred. All but one patient eventually healed, although six patients required bone grafts, five at the target site and one at the level of the regenerate. Most of the difficulties encountered were due to a lack of technical knowledge with the method.

Adolescent↗
PubMed1992

Ilizarov method.

Explore the source record for details and available documents.

Bone Lengthening↗
PubMed1991

Osteomyelitis. The Ilizarov perspective.

It is evident that Professor Ilizarov has devised some remarkable strategies for dealing with chronic osteomyelitis. In summary, his methods include: Extensive debridement and intercalary bone transport. Oblique osteotomy through multiloculated cavitary osteomyelitis in intact bone. Elimination of large cavities by gradual displacement of one cortical wall. The role that these techniques will play in the future of osteomyelitis surgery remains to be determined by careful clinical and experimental research.

Bone Lengthening↗
PubMed1991

The Ilizarov method: Rancho technique.

Ilizarov's methods of creating new bone within a widening distraction gap have been modified at a number of centers around the world. The Rancho technique substitutes divergent titanium half pins for Ilizarov's tension wires (in most locations), while retaining the rings, hinges, posts, and functional assemblies of the Ilizarov apparatus. In this way, the versatility of the Ilizarov system has been maintained, yet with less muscle impalement and greater functional capacity of the limb. The unique biocompatibility of titanium lessens implant site sepsis.

Bone Lengthening↗
PubMed1991

Postoperative management during limb lengthening.

The postoperative management of a patient having his or her limb lengthened requires frequent contact and close monitoring by the surgeon. Deformities and contractures cannot be allowed to persist or progress. The patient must be encouraged to bear weight on the lengthening limb, lest the newly formed bone fail to mature and corticalize properly. Pin- or wire-site sepsis should be treated aggressively; osteolysis around an implant suggests that additional transosseous fixation is needed. By following the principles outlined here, a surgeon will have the gratifying experience of elongating a stunted or deformed limb to an amount never before thought possible, and without undue problems or residual complications.

Bone Lengthening↗
PubMed1990

Endocytic membrane traffic to the Golgi apparatus in a regulated secretory cell line.

We have established a ricin-resistant glycosylation-defective PC12 pheochromocytoma cell line to study biochemically glycoprotein traffic from the cell surface to the Golgi apparatus in regulated secretory cells. The strategy employed in this study is a modification of that used previously (Duncan, J. R., and Kornfeld, S. (1988) J. Cell Biol. 106, 617-628) to demonstrate transport of the cation-independent and -dependent mannose 6-phosphate receptors from the cell surface to the trans-Golgi network in nonsecretory cell types. In ricin-resistant PC12 cells, radiolabeled galactose was incorporated enzymatically into surface glycoconjugates, primarily glycoproteins. Resistance to beta-galactosidase was acquired upon reculture at 37 degrees C due to further terminal glycosylation of the galactose residues. Treatment of N-linked oligosaccharides isolated from recultured cells with a variety of glycosidases in conjunction with beta-galactosidase demonstrated the addition of sialic acid N-acetylglucosamine and fucose residues to the galactose residues in recultured cells. Resistance to beta-galactosidase was not acquired in cells recultured at 19 degrees C, indicating that subsequent glycosylation of galactose residues did not occur at the cell surface or in endosomes. While glycosylation of galactose incorporated into asparagine oligosaccharides in Chinese hamster ovary clone 13 cells was not significant (less than 1%) after 6 h of reculture, approximately 10% of the galactose incorporated into surface oligosaccharides was further glycosylated in PC12 cells in this time. Analysis of total labeled versus beta-galactosidase-resistant proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that endocytic traffic to the site of glycosylation activity in mutant PC12 cells was highly selective, but included a much greater number of proteins than were detected in Chinese hamster ovary clone 13 fibroblasts.

Adrenal Gland Neoplasms↗
PubMed1990

Characterization and cloning of lgp110, a lysosomal membrane glycoprotein from mouse and rat cells.

lgp110 is a heavily glycosylated intrinsic protein of lysosomal membranes. Initially defined by monoclonal antibodies against mouse liver lysosomes, it consists of a 45-kilodalton core polypeptide with O-linked and 17 asparagine-linked oligosaccharide side chains in mouse cells. Sialic acid residues make the mature protein extremely acidic, with an isoelectric point of between 2 and 4 in both normal tissues and most cultured cell lines. Partial sequencing of mouse lgp110 allowed oligonucleotide probes to be constructed for the screening of several mouse cDNA libraries. A partial cDNA clone for mouse lgp110 was found and used for additional library screening, generating a cDNA clone covering all of the coding sequence of mature rat lgp110 as well as genomic clones covering most of the mouse gene. These new clones bring to seven the number of lysosomal membrane proteins whose amino acid sequences can be deduced, and two distinct but highly similar groups (designated lgp-A and lgp-B) can now be defined. Sequence comparisons suggest that differences within each group reflect species variations of the same protein and that lgp-A and lgp-B probably diverged from a common ancestor prior to the evolup4f1ary divergence of birds and mammals. Individual cells and individual lysosomes possess both lgp-A and lgp-B, suggesting that these two proteins have different functions. Mouse lgp110 is encoded by at least seven exons; intron positions suggest that the two homologous ectodomains of each lgp arose through gene duplication.

Amino Acid Sequence↗
PubMed1989

The process of reviewing peers.

Drawing on experiences as a Physician Advisor to the Office of Quality Assurance of the American Psychiatric Association, the author discusses process interactions endemic to peer review and presents recommendations for facilitating this necessary professional activity.

Clinical Competence↗
PubMed1989

Severe trauma to the lower extremity: long-term sequelae.

Limb salvage after major traumatic injury to the lower extremity has become commonplace in modern trauma centers. Despite initial successful limb salvage, however, long-term complications often occur. We present 121 patients who were treated for complications after major injuries to the lower limb at Rancho Los Amigos Medical Center. In general, these patients required a total of 224 surgical procedures over an average of approximately three years after injury to achieve a successful outcome. Final limb function, however, was often impaired.

Adult↗
PubMed1988

Derived protein sequence, oligosaccharides, and membrane insertion of the 120-kDa lysosomal membrane glycoprotein (lgp120): identification of a highly conserved family of lysosomal membrane glycoproteins.

The 120-kDa lysosomal membrane glycoprotein (lgp120) is an acidic, heavily glycosylated membrane protein enriched in the lysosomal membrane. To determine the basis for its selective transport to and stability in lysosomes, we have investigated the structure of lgp120. By using an oligonucleotide probe corresponding to the amino terminus of rat lgp120, we isolated and characterized cDNA clones containing the entire coding region. The deduced amino acid sequence demonstrates that lgp120 contains a putative signal peptide, 18 sites for N-linked glycosylation, a single membrane-spanning segment, and a short (11 amino acid) cytosolic tail. The sequence suggests a distinct domain organization, with two luminal glycosylated regions separated by a nonglycosylated proline-rich region. Proteolysis in detergent showed that the protein was not intrinsically resistant to exogenous or endogenous proteases. The N-linked oligosaccharides on lgp120, tetraantennary structures with two lactosamine repeats on one of the branches, were not different from those of glycoproteins on the plasma membrane. lgp120 was similar in its domain organization and portions of its amino acid sequence to the avian 100-kDa lysosomal membrane protein LEP100 [Fambrough, D. M., Takeyasu, K., Lippincott-Schwartz, J., Siegel, N. R. & Somerville, D. (1988) J. Cell Biol. 106, 61-67], and to a distinct 110-kDa lysosomal membrane protein (lgp110) that colocalizes with lgp120. The similarities between lysosomal membrane glycoproteins from diverse species, coupled with the fact that at least two distinct lysosomal membrane glycoproteins are expressed in a single species, indicate the existence of a conserved family of glycoproteins enriched in the lysosomal membrane.

Amino Acid Sequence↗
PubMed1988

Ilizarov external fixation. Technical and anatomic considerations.

The Ilizarov external fixator can be safely applied if the surgeon is alert to the "danger areas" where the transfixion wires might penetrate a neurovascular structure. The basic principle of frame assembly and application require that the wires are never bent to reach the support rings; instead, the Ilizarov hardware is used to build up to the wires from the rings. The wires are then tensioned axially.

Blood Vessels↗