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Biomedical subjects

T H Oh

Publications and source records attributed to T H Oh.

At least 55 records · Page 3Linked to original sources
PubMed1988

Perioperative considerations in esophageal replacement for epidermolysis bullosa: report of two cases successfully treated by colon interposition.

Esophageal stricture commonly occurs in patients with epidermolysis bullosa dystrophica recessive (EBDR), but esophageal replacement is considered a high risk procedure because of limited exposure of the airway, malnutrition, and postoperative skin bullae to secondary infection. Recent innovations in care, including preoperative parenteral nutrition, topical care for bullae and skin ulceration, fiberoptic tracheal intubation, electrocardiogram monitoring with metallic pacer leads, and an overall concern to protect the fragile intact skin, have improved the results of esophageal replacement. Utilizing these adjunctive measures, ileocolonic substernal interposition has been successfully performed in a 26-yr-old male and a 19-yr-old female at our institution. Despite cervical anastomotic stricture requiring resection in one, and an obstructive cervical esophageal bullous developing acutely 5 yr after operation in the second, both patients now gum or chew a solid diet. The first patient also benefited from total esophagectomy for squamous dysplasia detected at the time of esophageal replacement. Multidisciplinary management by the surgeon, gastroenterologist, anesthesiologist, and dermatologist makes esophageal replacement available for younger patients with epidermolysis bullosa dystrophica recessive and esophageal strictures.

Adult↗
PubMed1987

Transferrin: assay of myotrophic effects and method for immunocytochemical localization.

1. Primary cultures of dissociated embryonic chicken skeletal muscle cells provide an ideal model for investigating the effects of growth factors such as Tf because these cells undergo a highly integrated pattern of differentiation and maturation. 2. The trophic effects of a growth factor such as Tf can be assessed on muscle cultures by the determination of such parameters as acetylcholinesterase and acetylcholine receptors. These proteins are specific to the cultured myotubes, appear in high levels following fusion of myoblasts into myotubes, and are relatively easy to assay. 3. Tf and other growth factors are internalized by a receptor-mediated mechanism (see Trowbridge et al. and Seligman and Allen, this volume). These growth factors can be localized to specific tissues by immunocytochemistry at the light or electron microscopic level. This information on cellular distribution could be very useful in assessing the pattern of growth and differentiation with regard to the particular growth factor under study.

Acetylcholinesterase↗
PubMed1986

Immunocytochemical distribution of transferrin and its receptor in the developing chicken nervous system.

Transferrin is the plasma protein responsible for iron transport in all vertebrates. While transferrin is known to have growth-promoting activity on a variety of cells in culture, the role of transferrin and its membrane receptor in neuronal development is unknown. Using antibodies to transferrin and transferrin receptors, we studied the immunocytochemical localization of transferrin and its receptor in developing chicken neural tissues by the peroxidase-antiperoxidase method. In 5-day-old embryonic brain, germinal cells of the ventricular zone showed a positive reaction for transferrin receptors but were negative for transferrin. By 6-7 days, transferrin-positive cells were seen in the inner layer of the ventricular zone and a few 'patches' of transferrin-positive cells were also seen in the adjacent area. By 10 days, large neurons throughout the brain were strongly positive for transferrin. By 11-16 days, all neurons in the brain showed a strong positive reaction for the protein. Thereafter, the transferrin-positive reaction became gradually weaker in neurons whereas the walls of blood capillaries showed a positive reaction for transferrin. In the adult brain, neurons showed very weak or negative staining. A similar staining pattern for transferrin was observed in the developing spinal cord and dorsal root ganglia (DRG). By 10-12 days, both spinal cord neurons and DRG neurons showed strong reactions for transferrin. Thereafter, the transferrin-positive reaction gradually diminished in older spinal cord neurons and completely disappeared from DRG neurons. Cultured cerebral hemisphere, spinal cord, and DRG neurons showed positive staining reactions for both transferrin and its receptor. Our results suggest that: transferrin is initially taken up by developing neurons from cerebrospinal fluid via receptor-mediated endocytosis; the accumulation of transferrin ultimately reaches a maximum level within immunoreactive neurons and then declines just prior to hatching; in contrast to other CNS neurons, DRG neurons accumulate transferrin only briefly and then become negative for transferrin by immunocytochemistry; and after closure of the blood-brain barrier, transferrin may reach neurons by transport across capillaries into the 'paravascular' spaces. In view of these results, transferrin may play some important but unrecognized role in early neuronal development in vivo as well as in vitro.

Animals↗
PubMed1986

Changes in heart rate and rhythm after intramuscular succinylcholine with or without atropine in anesthetized children.

The effects of intramuscular injections of succinylcholine with or without atropine on heart rate and rhythm were studied in 50 unpremedicated children 6-18 months of age. All had anesthesia induced with N2O-O2 and halothane 2% by face mask. Sixty seconds later, one of four study drugs or drug combinations was injected into the deltoid muscle of patients in groups 1-4. Following injection, halothane concentration was reduced to 1%, and ventilation was controlled. Patients given atropine only (0.02 mg/kg), succinylcholine only (4 mg/kg), or a combination of both (4 mg/kg succinylcholine plus 0.02 mg/kg atropine) showed transient increases in heart rate to 106 +/- 7.5%, 113 +/- 11.8%, and 109 +/- 10.1% (mean +/- SD) of control, followed by a decrease to 78 +/- 6.7%, 79 +/- 9.4%, and 80 +/- 10.5%, respectively, in 2-3 min after injection. Patients given a combination of succinylcholine (4 mg/kg) plus a higher dose of atropine (0.03 mg/kg) also had a transient increase in heart rate to 107 +/- 7.5%, followed by a decrease to 82 +/- 11.8% 2 min after injection. However, this group differed from the other three groups in presenting a second, prolonged increase in heart rate to 115 +/- 9.0% of preinjection levels. Patients in group 5 (controls) received no injections. Their heart rate decreased to 76 +/- 10.78% of preinduction level within 90 sec of induction, and remained unchanged thereafter. We conclude that succinylcholine (4 mg/kg) can be used intramuscularly with or without atropine (0.02 mg/kg) in lightly anesthetized young children without producing severe bradycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1985

Synthesis of the transferrin receptor by cultures of embryonic chicken spinal neurons.

We have purified a glycoprotein from chicken sciatic nerves, sciatin, which has pronounced trophic effects on avian skeletal muscle cells in culture. Recent studies have shown that sciatin is identical to the iron-transport protein, transferrin, in terms of its physicochemical structure, immunological reactivity, and biological activity. To determine whether transferrin is synthesized and released by neuronal tissue, we incubated cultures of dissociated chicken spinal neurons in a medium free of L-leucine containing either L-3H-amino acids or L-[14C]leucine and immunoprecipitated transferrin with highly specific antibodies. The radiolabeled protein precipitated by rabbit heteroclonal, goat heteroclonal, or mouse monoclonal antitransferrin antibodies increased in specific activity in a linear manner for at least 30 min. Synthesis of this protein was abolished by the presence of puromycin (20 micrograms/ml) or cycloheximide (10(-5) M). The disappearance of the radiolabeled protein from cells was linear with a half-life (t 1/2) of 8-10 h. When immunoprecipitates were separated by SDS gel electrophoresis, a prominent band corresponding to transferrin (Mr 84,000) was visualized by staining with Coomassie Blue. However, when such gels were fluorographed, no radioactivity was apparent in the transferrin region of the gel although a prominent radioactive band was visualized at an Mr of 56,000. The protein of Mr 56,000 was not simply a degradation product of transferrin because this particular protein band was not generated by incubating radiolabeled transferrin with unlabeled neuronal homogenates. The protein of Mr 56,000 was purified from embryonic chicken brain and spinal cord by immunoabsorption chromatography on mouse monoclonal antitransferrin IgG conjugated to Sepharose 4B followed by affinity chromatography on immobilized transferrin. The purified protein bound radioiodinated transferrin and was precipitated by rabbit anti-chicken transferrin-receptor antibodies. Furthermore, this receptor protein was found to be localized on the plasma membrane of dorsal root ganglion neurons by immunocytochemistry using the peroxidase-antiperoxidase technique, and by blocking experiments, which showed that antitransferrin receptor IgG could inhibit the binding of fluorescein-conjugated transferrin at 4 degrees C to cultured neurons in vitro. From these data, we conclude that transferrin is not synthesized by cultures of chicken spinal cord neurons, but that the receptor for transferrin is synthesized by these cultures and is precipitated by antitransferrin antibodies as an antigen-receptor complex.

Animals↗
PubMed1984

Tracheal tube cuff pressure. Changes during nitrous oxide anaesthesia following inflation of cuffs with air and saline.

The volume and pressure of a tracheal tube cuff inflated with air increases during nitrous oxide anaesthesia. The study was designed to investigate the changes of tracheal tube cuff pressure during nitrous oxide anaesthesia following inflation of the cuff with air or saline in 10 mongrel dogs who were anaesthetised with nitrous oxide and their lungs artificially ventilated. At the end of 6 hours there was no change in cuff pressure when saline had been used for inflation, but was six times the initial pressure when air had been used. On microscopic examination of the trachea, only the air group had glandular inflammation, dilatation and destruction. Therefore, it appears that if saline is used to inflate tracheal tube cuffs, there will not be an increase in cuff volume and pressure during nitrous oxide anaesthesia.

Anesthesia↗
PubMed1982

Chicken serum transferrin duplicates the myotrophic effects of sciatin on cultured muscle cells.

Sciatin, a glycoprotein purified from chicken sciatic nerves, has been shown to have trophic effects on chicken skeletal muscle cells in culture. Since we recently observed pronounced structural similarities between sciatin and chicken serum transferrin [Markelonis et al, 1982a], we decided to investigate the muscle growth-promoting activity of transferrin on cultured muscle cells. Serum transferrin was isolated by the same protocol used to purify sciatin, viz., affinity chromatography on concanavalin A-agarose followed by ion-exchange chromatography on DEAE cellulose. The serum protein recovered by this purification scheme was indistinguishable immunologically from sciatin as evidenced by a positive precipitin reaction against goat anti-sciatin serum on double immunodiffusion in agar. Purified serum transferrin had myotrophic effects identical to those of sciatin when added to skeletal muscle cells in vitro. For example, even when chicken embryo extract--a constituent normally required for chicken muscle cell differentiation in vitro--was omitted from culture medium, either serum transferrin or sciatin promoted myogenesis in culture as measured by a stimulation of the fusion index. Furthermore, both proteins caused a significant increase in the level of protein synthesis, the number of acetylcholine receptors and the activity of acetylcholinesterase in treated muscle cultures. By contrast, commercially obtained ovotransferrin (conalbumin) or FeSO4 (100 microM) were unable to fully support myogenesis of skeletal muscle in vitro if embryo extract was omitted from the culture medium. From these data, we conclude that the neuronal myotrophic protein sciatin is both structurally and biologically related to serum transferrin. Furthermore, we suggest that sciatin may represent a neuronal form of this iron-transport protein.

Animals↗
PubMed1982

An ultrastructural and immunocytochemical study of astrocytic differentiation in vitro: changes in the composition and distribution of the cellular cytoskeleton.

Astroglia in cultures of dissociated neonatal rat optic nerves were studied by light microscopy, immunocytochemistry and electron microscopy to determine whether intermediate filaments play a role in defining the multipolar morphology of the mature astrocyte. Immature, polygonal astroblasts contained few glial filaments, in spite of exhibiting positive staining with antiserum against glial fibrillary acidic (GFA) protein. Microtubules were the most prominent cytoskeletal component at early stages of cytodifferentiation, but these were progressively reduced in number at later intervals and were gradually replaced by intermediate filaments. These observations suggest that microtubules are involved in the initial establishment of cytoplasmic asymmetry and process development. Subsequently, glial filaments may play a role in maintaining and stabilizing the overall geometry of the mature astrocyte.

Animals↗
PubMed1982

Sciatin is a transferrin-like polypeptide.

Sciatin, an acidic glycoprotein from chicken sciatic nerve, the myotrophic effects on avian skeletal muscle cells in culture. As sciatin was found to have certain structural similarities to transferrin, we further investigated the physiochemical characteristics of sciatin in order to determine the relationship between these two proteins. Sciatin was found to be strikingly similar to ovotransferrin in amino acid composition. In addition, amino acid sequence analysis revealed that sciatin and ovotransferrin and identical amino-terminal sequences for a t least the first 20 amino acid residues. Chicken ovotransferrin, but not human serum transferrin, cross-reacted with rabbit antisciatin antibodies upon rocket immunoelectrophoresis and double immunodiffusion in agar. In addition, in the presence of bicarbonate, sciatin bound approximately 2 mol ferrous iron/mol protein. Using the purification procedure developed for sciatin, we purified a protein from chicken serum that cross-reacted with antisciatin serum, migrated at a position identical to that of sciatin or ovotransferrin on two-dimensional gel electrophoresis, had an amino composition very similar to ovotransferrin and sciatin, and had myotropic effects on cultured muscle cells. From these data, we conclude that sciatin is a growth-promoting polypeptide closely related in structure to transferrin.

Amino Acid Sequence↗
PubMed1981

Purification of sciatin using affinity chromatography on concanavalin A-Agarose.

A glycoprotein from chicken sciatic nerves, sciatin, has been shown to have trophic effects on the maturation and maintenance of skeletal muscle cells in culture. This protein was purified 24-fold from sciatic nerve extracts by affinity chromatography on concanavalin A-agarose followed by ion-exchange on diethylaminoethyl cellulose. The purity of sciatin obtained by this procedure was greater than 97% as estimated by densitometric integration of sodium dodecyl sulfate gels, and represented 33% of the sciatin present in sciatic nerve extracts as determined by rocket immunoelectrophoresis. Sciatin purified by this technique retained full biological activity since (1) addition of the protein to embryonic chicken skeletal muscle cells in culture enhanced the morphological development of the cells, and (2) the protein increased the number of acetylcholine receptors as measured by binding of 125I-alpha-bungarotoxin to 261% of the control value after 4 days in vitro. The purification procedure described in the present communication provides a more rapid and convenient method for the isolation of this trophic protein.

Animals↗
PubMed1981

Sciatin: immunocytochemical localization of a myotrophic protein in chicken neural tissues.

A mytotrophic protein (sciatin) purified from chicken sciatic nerves has "trophic" or "maintenance" effects on cultured muscle. We have elicited a specific antiserum against purified sciatin in rabbits. Using this antiserum, we investigated the distribution of sciatin in embryonic and adult chicken tissues by an unlabeled peroxidase-an-tiperoxidase method at the light microscopic level. The antiserum stained adult chicken neural tissues in situ and cultured embryonic chick neurons. Staining was intense in the cell bodies of spinal cord neurons and the axoplasm of sciatic nerves. These was reaction product seen in the outer margins of myelin sheaths that corresponded to the Schwann cell cytoplasm. Cerebral cortical neurons were weakly stained by the antiserum. No staining was apparent in oligodendrocytes or astrocytes. Nonneural tissues, such as skeletal, smooth and cardiac muscle, kidney, and liver, were also unstained by the antiserum. Cultured spinal cord neurons, cerebral cortical neurons, and sensory neurons were stained immunocytochemically by the antiserum. There was no reaction product seen in the glial cells that are usually present in neuronal cultures or cultured cells from liver, kidney, skeletal muscle, smooth muscle, and cardiac muscle. Our results thus show that the myotrophic protein is localized in neuronal perikarya and their processes in vivo as well as in vitro.

Animals↗