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Biomedical subjects

S Chang

Publications and source records attributed to S Chang.

At least 217 records · Page 12Linked to original sources
PubMed1995

Uptake of chylomicron remnants and hepatic lipase-treated chylomicrons by a non-transformed murine hepatocyte cell line in culture.

AML 12 is a recently established differentiated, non-transformed hepatocyte cell line derived from mice transgenic for transforming growth factor alpha (Wu et al. (1994) Proc. Natl. Acad. Sci. 91, 674-678). The ability of these cells to take up [3H]cholesterol-labeled in vivo-generated chylomicron remnants, as well as [3H]cholesterol-labeled chylomicrons treated with hepatic lipase in vitro was investigated. Both types of lipoprotein particles were taken up by the AML hepatocytes at a much faster rate than intact chylomicrons, and in a saturable and specific manner. Chylomicrons treated with hepatic lipase in vitro competed with in vivo-generated chylomicron remnants for uptake by the AML hepatocytes, and the uptake of both types of lipoproteins was inhibited by lactoferrin, suggesting that they share the same process of cellular recognition and uptake. It is suggested that hepatic lipase-treated chylomicrons may be valuable in studies aimed at gaining a better understanding of the processes involved in the hepatic recognition and uptake of chylomicron remnants. AML hepatocytes, which can be maintained as replicating, untransformed, and differentiated under standard culture conditions, may be useful and practical for such studies.

Animals↗
PubMed1995

Native and recombinant DM-GRASP selectively support neurite extension from neurons that express GRASP.

DM-GRASP (GRASP) is an integral membrane glycoprotein expressed on a restricted set of axons in the developing chick nervous system. We demonstrate that purified GRASP supports neurite extension from the subpopulation of neurons that express GRASP. Sensory, sympathetic, and ciliary neurons express GRASP and extend neurites on a GRASP substrate. In contrast, tectal, diencephalic, and retinal cells express GRASP at a very low level, if at all, and do not extend neurites on a GRASP substrate. Moreover, as GRASP is downregulated on sensory neurons during development, they lose the capacity to extend neurites on a GRASP substrate. Recombinant GRASP produced in a baculovirus expression system is biochemically and functionally identical to GRASP purified from embryonic chick brain. The finding that GRASP selectively supports neurite extension supports the hypothesis that it mediates selective fasciculation via a homophilic binding mechanism.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed1995

Communication between the subretinal space and the vitreous cavity in the morning glory syndrome.

BACKGROUND: The aim was to describe a pathogenic mechanism for a rhegmatogenous retinal detachment in a 69-year-old man with the morning glory syndrome. METHODS: During vitreous surgery for a retinal detachment, a membrane was removed that covered the optic disc anomaly and produced traction on the peripapillary retina. A retinal hole was found in tissue lying within the optic cup, and the hole was sealed using a autologous plasma-thrombin mixture. Silicone oil was used for retinal tamponade. RESULTS: A retinal hole in tissue lying within the optic cup provided a fluid pathway between the vitreous cavity and the subretinal space. Following vitrectomy surgery, bubbles of silicone oil passed through the retinal hole into the subretinal space of the macula. CONCLUSION: This case demonstrates that a retinal hole in tissue lying within the optic disc anomaly of the morning glory syndrome provides a communication for fluid between the subretinal space and the vitreous cavity, resulting in a rhegmatogenous retinal detachment. Vitreous replacement with silicone oil resulted in the migration of silicone bubbles into the subretinal space.

Aged↗
PubMed1995

The synthesis of glutamic acid in the absence of enzymes: implications for biogenesis.

This paper reports on the non-enzymatic aqueous phase synthesis of amino acids from keto acids, ammonia and reducing agents. The facile synthesis of key metabolic intermediates, particularly in the glycolytic pathway, the citric acid cycle, and the first step of amino acid synthesis, lead to new ways of looking at the problem of biogenesis.

Alanine↗
PubMed1995

Mutation spectrum of 2-chloroethyl methanesulfonate in Drosophila melanogaster premeiotic germ cells.

The 2-chloroethyl methanesulfonate (2ClEMS)-induced alcohol dehydrogenase (Adh) null germline mutation frequency in treated Drosophila melanogaster second instar larval gonia was two orders of magnitude greater than the spontaneous mutation frequency. DNA sequence analysis of 83 Adh null mutations showed that 40 mutations of independent origin were at 23 sites in the Adh gene. The mutation spectrum contained only GC-->AT transitions with 35 mutations (87.5%) at the middle or 3' guanine. In addition, characteristics of glutathione (GSH)-mediated bioactivation were determined for 2ClEMS in vitro. Rates of GSH-mediated conjugation, catalyzed by purified rat liver glutathione-S-transferase (GST), and binding of [35S]GSH-mediated conjugation products to calf thymus DNA were determined for 2ClEMS, 1,2-dichloroethane (EDC) and 1,2-dibromoethane (EDB). The relative rates of GSH-mediated conjugation were the following: 5 mM EDB > 40 mM 2ClEMS > 40 mM EDC. A similar trend was observed for DNA binding of the [35S]GSH-mediated conjugation products when differences in mutagen concentration were considered: EDB > 2ClEMS > EDC. The ratios of DNA binding to GSH conjugation calculated for EDB, EDC and 2ClEMS were 6.8 x 10(-5), 9.3 x 10(-5) and 19.1 x 10(-5), respectively. A narrow range, less than a 3-fold difference, in the ratios of DNA binding to GSH conjugation indicates that the bioactivation of 2ClEMS is mediated by the same mechanism as EDB and EDC. Consequently, 2ClEMS, EDC and EDB may induce a specific mutation in premeiotic germ cells.

Alcohol Dehydrogenase↗
PubMed1995

NGFI-C expression is affected by physiological stimulation and seizures in the somatosensory cortex.

NGFI-C is an early response gene which encodes a Cys2/His2 zinc finger protein. NGFI-C has previously been demonstrated to be inducible in PC12 cells after NGF stimulation. This study sought to localize this gene in somatosensory cortex, and investigate its possible induction by physiological and seizure stimuli. To determine if NGFI-C message levels are affected by stimulation, RT-PCR was performed on mRNA extracts from somatosensory cortex. NGFI-C mRNA levels were increased to levels four-fold over baseline after a seizure. In a paradigm used as a model of experience-dependent plasticity, vibrissae stimulation also increased the level of NGFI-C expression in the contralateral barrel cortex to 180% of control levels. In situ analysis using digoxigenin-labelled cRNA probes demonstrated NGFI-C containing neurons throughout layers 2 through 6 in somatosensory cortex. A higher cell density was seen after stimulation. Qualitatively, staining was more intense in post-seizure and post-stimulus cortex than in control cortex. Analysis of related zinc finger expression in serial sections revealed that NGFI-C is expressed in a distinct but overlapping cell populations relative to NGFI-A, Krox 20, and Egr-3. These studies demonstrate the inducible nature of NGFI-C message in response to a physiological vibrissae stimulus, as well as to seizures. However, the levels and pattern of expression differ between these two stimuli.

Animals↗
PubMed1995

A family of molecules related to collapsin in the embryonic chick nervous system.

Signaling molecules with either attractive or repulsive effects on specific growth cones are likely to play a role in guiding axons to their appropriate targets. A chick brain glycoprotein, collapsin, has been shown to be a good candidate for a repulsive guidance cue. We report here the discovery of four new molecules related to collapsin in chick brains. All contain a semaphorin domain. One is structurally very similar to collapsin but is only 50% identical in its amino acid sequence. We have named it collapsin-2. The collapsin-related genes exhibit distinct but overlapping patterns of mRNA expression in the developing spinal cord and the developing visual system. This family of collapsin-related molecules could potentially act as repulsive cues toward specific neuronal populations.

Amino Acid Sequence↗
PubMed1995

Surgical techniques for repositioning a dislocated intraocular lens, repair of iridodialysis, and secondary intraocular lens implantation using innovative 25-gauge forceps.

PURPOSE: We developed surgical techniques for the sulcus fixation of a posteriorly dislocated or secondarily implanted posterior chamber intraocular lens, repair of an iridodialysis, and the management of a decentered intraocular lens during vitreous surgery using innovative 25-gauge forceps. METHODS: The 25-gauge forceps have a curved shaft, a tip with a distal platform for grasping a suture, and a proximal groove for gripping a haptic. The forceps are inserted through a grooved scleral incision into the plane of the ciliary sulcus, facilitating manipulations such as fastening a suture loop around a haptic, repositing an intraocular lens at the ciliary sulcus, and grasping sutures during repair of a iridodialysis or implantation of a secondary intraocular lens. Seven patients underwent vitreous surgery using the new forceps. RESULTS: In all seven patients the surgical objectives were accomplished with the 25-gauge forceps without postoperative complications such as hemorrhage, hypotony, or lens decentration. CONCLUSIONS: The 25-gauge forceps are innovative instrumentation designed specifically for anterior segment applications during vitreous surgery.

Adolescent↗
PubMed1995

Perfluorocarbon liquid in the management of retinal detachment with proliferative vitreoretinopathy.

PURPOSE: To describe the techniques and results of perfluoro-N-octane used during vitrectomy for managing retinal detachment with severe proliferative vitreoretinopathy (PVR). METHODS: The authors retrospectively studied 223 consecutive patients who underwent vitreoretinal surgery for severe PVR (93% D1-D3). Patients underwent an average of 1.72 prior vitreoretinal surgeries. Perfluoro-N-octane was used intraoperatively to flatten the retina, avoiding posterior drainage retinotomy, to identify areas of residual retinal traction and periretinal membranes, to stabilize the peripheral retina during dissection of anterior PVR, and to help determine the extent and location of relaxing retinotomies. Extended-term gas tamponade was used in 91% of eyes. All patients were followed for a minimum of 6 months. RESULTS: Seventy-eight percent of the retinas were reattached posterior to the scleral buckle after a single vitreoretinal surgery and 96% were reattached after multiple surgeries. An average of 1.24 vitrectomy surgeries were required. The final visual acuity was 20/400 or better in 74% of eyes and 20/80 or better in 30% (P = 0.004). Preoperative hypotony (intraocular pressure < or = 5 mmHg) and multiple prior vitreoretinal surgeries were associated with a poor final visual acuity (P = 0.01 and 0.02, respectively). Preoperative hypotony (intraocular pressure < or = 5 mmHg) was associated with a greater frequency of relaxing retinotomies (P = 0.02). Retained perfluoro-N-octane was observed postoperatively in the vitreous cavity in 1.3% and subretinal perfluoro-N-octane in 0.9%. CONCLUSION: Experience with perfluoro-N-octane has demonstrated its usefulness both diagnostically and therapeutically as an intraoperative tool and improved the anatomic and visual outcome for retinal detachment complicated by severe PVR.

Adolescent↗
PubMed1995

Lens-sparing vitrectomy with perfluorocarbon liquid for the primary treatment of giant retinal tears.

PURPOSE: To evaluate the surgical success of vitrectomy without initial lensectomy in the primary treatment of retinal detachment associated with giant tears without proliferative vitreoretinopathy. METHODS: Thirty-four consecutive phakic eyes with idiopathic giant retinal tears underwent vitrectomy, injection of perfluorocarbon liquid, endolaser, and gas tamponade. Encircling scleral buckling was performed in 14 of 34 patients. Preoperative visual acuity ranged from 20/25 to hand motions. Giant tear size ranged from 90 degrees to 330 degrees. Follow-up ranged from 10 to 64 months. RESULTS: Anatomic retinal re-attachment was achieved intraoperatively in all eyes. The re-operation rate was 14% for eyes that underwent scleral buckling with the initial vitrectomy and 45% in eyes without primary scleral buckling. In 59% of eyes with cataract formation, 32% underwent cataract surgery with or without intraocular lens implantation. Best-corrected final visual acuity ranged from 20/15 to 20/400. CONCLUSION: Most phakic eyes with giant retinal tear not associated with proliferative vitreoretinopathy can be re-attached successfully with initial preservation of the lens.

Adolescent↗
PubMed1995

Effect of intravitreal tissue plasminogen activator on experimental subretinal hemorrhage.

PURPOSE: To study the effect of intravitreally injected tissue plasminogen activator (tPA) in an experimental model of subretinal hemorrhage. METHODS: Autologous blood was transsclerally injected into the subretinal space in 34 albino rabbits. One day later tPA was injected into the posterior vitreous in 24 eyes and saline was injected into 10 control eyes. Lysis of the subretinal blood was assessed ophthalmoscopically and retinal function was evaluated electroretinographically. RESULTS: In all eyes in which tPA was injected intravitreally 1 day after subretinal injection of blood, the formed subretinal clots was not visible within 24 hours of treatment. Liquefied subretinal blood that formed from clot lysis disappeared within 6 days. Conversely, in all saline-injected control animals, the subretinal clots were unchanged at 24 hours and were observed for at least 3 days after injection. As a result of the presence of subretinal blood, scotopic electroretinogram amplitudes were markedly reduced in the tPA and saline-injected groups. In many eyes, blood migrated from the subretinal space into the vitreous, but it was detected later, was less severe, and cleared more rapidly after tPA injection. CONCLUSION: Intravitreal injection of tPA 1 day after subretinal injection of blood in rabbits facilitated more rapid lysis of the clotted blood, however, retinal damage was not prevented.

Animals↗