Quantum magnetotransport theory for bound-state electrons in lateral surface superlattices.
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Journal Article↗
Biomedical subjects
D Huang
Publications and source records attributed to D Huang.
Reply to "Comment on 'Localization in a one-dimensional Thue-Morse chain' "
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Journal Article↗
Regulation of cAMP-responsive enhancer binding proteins during cell cycle progression in T lymphocytes stimulated by IL-2.
IL-2 stimulates the proliferative response of various lymphoid cells. Previous studies showed an increase in intracellular levels of cAMP concomitant with an increase in phosphorylation of discrete proteins by protein kinase A at late G1 phase in mitogen-stimulated lymphocytes. Thus, experiments were undertaken to study nuclear proteins that bind to the cAMP-responsive enhancer (CRE) in cloned T lymphocytes stimulated with IL-2. With the use of a 32P-labeled CRE consensus sequence in a DNA binding gel mobility shift assay, we showed that IL-2 stimulation resulted in the induction of two major DNA-protein complexes at late G1/S during the cell cycle. This binding was competed in a dose-dependent manner by a nonlabeled CRE oligonucleotide but was not competed by a nonlabeled AP-1 oligonucleotide. Rapamycin, a potent immunosuppressant, which arrests IL-2-stimulated T lymphocytes at G1/S, inhibited the IL-2-induced CRE binding activities concomitantly with inhibition of DNA synthesis. By using specific Abs in a gel mobility shift assay, we identified two known CREB/ATF transcription factors in the IL-2-induced CRE complexes: the CRE binding factor (CREB), and ATF1. The induction of CREB binding by IL-2 was not associated with an increase in its abundance but was associated with a major increase in CREB phosphorylation that was particularly prominent at late G1/S. However, we found that G1/S progression induced by IL-2 was not associated with an increase in the intracellular levels of cAMP. These results suggest that 1) the transcription factors CREB and ATF1 and possibly other CRE binding proteins may have an important role in the modulation of specific gene expression at G1/S during cell cycle progression induced by IL-2. 2) The involvement of these CRE binding transcription factors in IL-2-stimulated cells is regulated via a mechanism that is not cAMP dependent.
Activating Transcription Factor 1↗
Optical coherence tomography of the human retina.
OBJECTIVE: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. DESIGN: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. SETTING: Research laboratory. PARTICIPANTS: Convenience sample of normal human subjects. MAIN OUTCOME MEASURES: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. RESULTS: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10-microns depth resolution. CONCLUSION: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.
Fovea Centralis↗
Discoordinate gene expression of aggrecan and type II collagen in experimental osteoarthritis.
OBJECTIVE: To quantify the gene expression of aggrecan core protein and type II collagen in an experimental animal model of osteoarthritis (OA). METHODS: Total RNA was extracted from the articular cartilage of unoperated knee joints and from OA joints produced by anterior cruciate ligament transection. The relative amounts of type II collagen and aggrecan core protein messenger RNA (mRNA) were evaluated by Northern blot analysis. RESULTS: Total RNA was elevated 2.5 times, aggrecan mRNA was elevated 2 times, and type II collagen mRNA was elevated 8 times, in OA knees compared to unoperated controls. CONCLUSION: Chondrocytes are activated metabolically in response to joint injury. Discoordinate gene expression of aggrecan and type II collagen is characteristic of early experimental OA, and we speculate that it may contribute to its pathogenesis.
Aggrecans↗
Lengthening of the mesentery using the marginal vascular arcade of the right colon as the blood supply to the ileal pouch.
PURPOSE: Creation of a safe ileal pouch requires a tension-free anastomosis. The aim of this study was to evaluate a technical procedure that increases the length of the mesentery while preserving the blood supply to the ileal pouch. HYPOTHESIS: Preservation of the marginal vascular arcade (MVA) of the right colon will allow ligation of more mesenteric vessels and increase the mesenteric length. METHODS: Six fresh cadavers were dissected. Measurement of the apex of the terminal ileum was done in relation to the pubic symphysis. Measurements were taken after 1) complete mobilization of the terminal ileum, right colon, and hepatic flexure; 2) vascular ligation between colon wall and the MVA, preserving the latter from the right branch of the middle colic artery to the ileal branch of the ileocolic artery (ICA); 3) ligation of the distal third of the superior mesenteric artery; 4) ligation of the ICA at its origin; 5) ligation of the right colon artery; and 6) division of the terminal ileal mesentery. RESULTS: This technique enabled complete division of the terminal ileal mesentery, adding a mean additional 3.6 (range, 2.5 - 5.0) cm (36.5 +/- 16.5 percent) in length to the mesentery, compared with superior mesenteric artery, ICA, and right colic artery ligation. CONCLUSION: Patients who have a shorter mesentery and concern of excessive mesenteric tension should have colectomy performed, preserving the MVA from the middle colic artery to the ileal branch of the ICA. The preserved MVA can be a reliable alternative blood supply to the pouch if more mesenteric vessel ligations are necessary.
Anastomosis, Surgical↗
The action of philanthotoxin-343 and photolabile analogues on locust (Schistocerca gregaria) muscle.
The effects of philanthotoxin-343 (PhTX-343; tyrosyl-butanoyl-spermine) and photolabile analogues of this synthetic toxin on locust (Schistocerca gregaria) skeletal muscle have been investigated using whole muscle preparations (twitch contractions), single muscle fibres (excitatory postsynaptic currents (EPSCs)) and muscle membrane patches containing single quisqualate-sensitive glutamate receptors (qGluR). Analogues containing an azido group attached to either the butanoyl side-chain of PhTX-343 or as a substitute for the hydroxyl moiety of the tyrosyl residue were about 6 fold more potent antagonists than PhTX-343; those with an azido group located at the distal end of the toxin molecule were generally 2-3 fold less potent than PhTX-343. When these compounds were tested in subdued light, they were reversible antagonists of the muscle twitch, EPSC and qGluR. When a muscle was irradiated with U.V. during application of photolabile toxin combined with either neural stimulation of the muscle or L-glutamate application, antagonism of the twitch, EPSC and qGluR was complete and irreversible.
Animals↗
Theophylline attenuation of airway responses to allergen: comparison with cromolyn metered-dose inhaler.
BACKGROUND: The purpose of this study was to compare the protection afforded by individualized doses of theophylline and a cromolyn metered-dose inhaler (MDI) during allergen challenge. METHODS: The study design was randomized, double-blind, and crossover. Responses to inhaled allergen were measured in 16 subjects with allergic asthma (age range, 18 to 35 years) after 7 days of treatment with either placebo, once daily slow-release theophylline producing a mean +/- SD serum concentration of 16 +/- 5 micrograms/ml during the late phase, or 2 mg of cromolyn administered by MDI four times daily. Forced expiratory volume in 1 second was measured at frequent intervals, and airway responsiveness to histamine was measured before and 3 hours after allergen challenge. RESULTS: The mean +/- SD maximum decrease in forced expiratory volume in 1 second during the late phase was 30% +/- 14% during placebo treatment, 16% +/- 13% during theophylline treatment, and 13% +/- 14% during cromolyn treatment (placebo vs theophylline and cromolyn, p = 0.0001; theophylline vs cromolyn, p = 0.1). The geometric mean fold increase in airway responsiveness was 3.0 +/- 1.7 during placebo treatment, 1.7 +/- 1.7 during theophylline treatment, and 1.5 +/- 1.6 during cromolyn treatment (placebo vs theophylline and cromolyn, p = 0.0001; theophylline vs cromolyn, p = 0.1). CONCLUSIONS: Theophylline, when administered once daily as a slow-release formulation, was as effective as cromolyn, administered four times daily through an MDI, in attenuating airway responses to inhaled allergen. The protection afforded by both treatments, however, was modest when compared with the results of similar studies with inhaled corticosteroids or other cromolyn formulations that deliver more drug to the lungs than the MDI available in the United States.
Adolescent↗
Production of IgG autoantibodies to TCRs in mice infected with the retrovirus LP-BM5.
Autoantibodies (AAbs) directed against particular segments of the variable region of TCR beta chains occur in normal humans and in certain autoimmune diseases, but the factors regulating the appearance of such antibodies are unknown. We report that AAbs binding a peptide determinant corresponding to the CDR1 of the V beta domain are elevated in C57BL/6 mice following infection with the LP-BM5 murine leukemia retrovirus mixture, a treatment used to induce murine AIDS. The elevation of the level of these AAbs is an early event following retroviral infection which corresponds in part to the general polyclonal activation of the B cells, but a selectivity for particular V beta sequences is apparent later. This suggests that the appearance of these antibodies may play a part in the subsequent development of immunodeficiency. Since the antibodies studied are of the IgG isotype, both T cells and B cells are involved in their elaboration.
Amino Acid Sequence↗
Hyperacuity test to evaluate vision through dense cataracts; research preliminary to a clinical study. I. Studies conducted at the University of California at Berkeley before travel to India.
BACKGROUND. Patients with dense ocular media disorders retain the ability to project or point to an intense source of light. Using this response capability and high luminance points of light as stimuli, Vernier judgments (a hyperacuity test) can be made by these patients, even without the presence of a "window" through a leucoma, cataract, or bleed. Without coaching, these individuals are able to locate the centers of the individual degraded point images if the individual light sources are adequately separated (i.e., if sufficient "gaps" exist between the individual stimuli), and they can spatially align the degraded images. Advanced cataracts are the main cause of blindness in the developing world, and this is a treatable condition. In these nations, only a modest proportion of affected patients receive surgery, and only 5% or less of these individuals obtain treatment in two eyes. There are incredibly large and rapidly growing backlogs of advanced cataract patients requiring care (many millions). Because of the 20 to 30% failure rates that occur after treatment (all causes) in many developing world settings, a test performed before surgery, which offers a meaningful estimate of postsurgical visual outcome, can be valuable. Using the principle defined above, we seek to determine before surgery those individuals who will derive most benefit from cataract removal, and which of two cataractous eyes has the better postsurgical visual prognosis. EXPERIMENTAL. In Berkeley, we performed a series of preliminary studies on a Vernier acuity test before initiating a clinical study in a developing world setting. These studies were conducted upon young adult normal subjects wearing their usual vision corrections, with and without induced refractive errors, and/or with or without simulated dense nuclear cataracts. We sought (1) to determine the number of repeat trials necessary for reliable outcomes; (2) to compare a two-point and a three-point Vernier acuity display; (3) to determine the shape of the measured response function at large gap separations between test points; (4) to define optimal test distance and stimulus size; (5) to assess the effect(s) of a broad range of uncorrected refractive errors upon outcomes; and (6) to consider means to minimize refraction-based errors by using a pinhole, a refractive correction, and/or selective spatial filtering. We compared responses obtained using the current CRT/VDT-based, computer-driven (Berkeley) instrument with a new precision optical/mechanical computer-driven (India) instrument. The India instrument is needed to determine design parameters for a next stage simpler, cheaper, more rugged field instrument(s).(ABSTRACT TRUNCATED AT 400 WORDS)
Adult↗
Interband quantum coherence in intersubband coupled quantum wells.
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Journal Article↗
Identification of a silencer module which selectively represses cyclic AMP-responsive element-dependent gene expression.
The cyclic AMP (cAMP)-inducible promoter from the rat lactate dehydrogenase A subunit gene (LDH A) is associated with a distal negative regulatory element (LDH-NRE) that represses inherent basal and cAMP-inducible promoter activity. The element is of dyad symmetry, consisting of a palindromic sequence with two half-sites, 5'-TCTTG-3'. It represses the expression of an LDH A/chloramphenicol acetyltransferase (CAT) reporter gene in a dose-dependent, orientation- and position-independent fashion, suggesting that it is a true silencer element. Uniquely, it selectively represses cAMP-responsive element (CRE)-dependent transcription but has no effect on promoters lacking a CRE sequence. The repressing action of LDH-NRE could be overcome by cotransfection with LDH A/CAT vector oligonucleotides containing either the LDH-NRE or CRE sequence. This suggests that the reversal of repression was caused by the removal of functional active, limiting transacting factors which associate with LDH-NRE as well as with CRE. Gel mobility shift, footprinting, and Southwestern blotting assays demonstrated the presence of a 69-kDa protein with specific binding activity for LDH-NRE. Additionally, gel supershift assays with anti-CREB and anti-Fos antibodies indicate the presence of CREB and Fos or antigenically closely related proteins with the LDH-NRE/protein complex. We suggest that the LDH-NRE and CRE modules functionally interact to achieve negative modulation of cAMP-responsive LDH A transcriptional activity.
Animals↗
Requirement of the self-glucosylating initiator proteins Glg1p and Glg2p for glycogen accumulation in Saccharomyces cerevisiae.
Glycogen, a branched polymer of glucose, is a storage molecule whose accumulation is under rigorous nutritional control in many cells. We report the identification of two Saccharomyces cerevisiae genes, GLG1 and GLG2, whose products are implicated in the biogenesis of glycogen. These genes encode self-glucosylating proteins that in vitro can act as primers for the elongation reaction catalyzed by glycogen synthase. Over a region of 258 residues, the Glg proteins have 55% sequence identify to each other and approximately 33% identity to glycogenin, a mammalian protein postulated to have a role in the initiation of glycogen biosynthesis. Yeast cells defective in either GLG1 or GLG2 are similar to the wild type in their ability to accumulate glycogen. Disruption of both genes results in the inability of the cells to synthesize glycogen despite normal levels of glycogen synthase. These results suggest that a self-glucosylating protein is required for glycogen biosynthesis in a eukaryotic cell. The activation state of glycogen synthase in glg1 glg2 cells is suppressed, suggesting that the Glg proteins may additionally influence the phosphorylation state of glycogen synthase.
1,4-alpha-Glucan Branching Enzyme↗
Lactate dehydrogenase A subunit messenger RNA stability is synergistically regulated via the protein kinase A and C signal transduction pathways.
We have identified and studied a posttranscriptional mechanism of lactate dehydrogenase A (LDH) subunit gene expression at the level of mRNA stability. Using the well differentiated rat C6 glioma cell line as a model system, the effects of activators of the protein kinase A and C pathways on the half-life of LDH A mRNA were measured by two independent methods: 1) by the RNA synthesis inhibitor-chase method using actinomycin D, and 2) by analysis of decay of LDH A [3H]mRNA in [3H]uridine-labeled cells. By each method, the half-life of relatively short-lived LDH A mRNA was increased 5- to 7-fold in 8- (4-chloro-phenylthio) cAMP or forskolin-treated and about 3-fold in 12-0-tetradecanoylphorbol-13- acetate (TPA) or dioctanoylglycerol-treated cells. Forskolin acted synergistically with TPA to prolong LDH A mRNA half-life from 55 min to more than 20 h. The relatively rapid basal decay rate of LDH A mRNA was also considerably slowed in the presence of the protein phosphatase inhibitor okadaic acid, suggesting a functional role for protein phosphorylation in the stabilization process. In glioma cells stably transformed with a protein kinase A catalytic subunit expression vector, overexpression of the catalytic subunit stabilized LDH mRNA to the degree seen in forskolin-treated cells. In cells transfected with a protein kinase A inhibitor-expression vector, cAMP-mediated stabilization of LDH A mRNA half-life was prevented. Furthermore, both staurosporin and 3- [1-(3-dimethylaminopropyl)-indol-3-yl]-3-(indol- 3-yl)- maleimide, inhibitors of protein kinase C, prevented the TPA-induced stabilization of LDH A mRNA. We conclude from the experimental data that the protein kinase A and C signal pathways play an active functional role in regulating LDH A mRNA stability and act cooperatively to achieve LDH A mRNA stability regulation.
Animals↗
[Stability of amino acids and vitamins in total nutrient admixture].
We reported a formula of total nutrient admixture (TNA) used in our patients. During 24 hours of storage shaded from daylight at 4 degrees C and at room temperature (25 degrees C), the concentrations of 17 kinds of amino acids and vitamin A, E, B1, B2 in the TNA prepared in EVA plastic bag were not changed significantly. A patient who has been on this TNA for parenteral nutrition for more than 8.5 years is in a good nutritional status, with no clinical manifestations in difficiency of vitamins and proteins. 42 patients receiving this TNA on TPN for a period ranging from 31 to 93 days were improved significantly in their nutritional status.
Acute Disease↗
[Surveillance of diarrhea in children aged under five in Youxian county, Hunan].
Surveillance analysis of cases with diarrhea in children aged under five years, who visited and were treated at village clinics in rural areas of Youxian County during June 1992 to May 1993, was conducted. Children aged below five under surveillance averaged 1 346, and 223 cases of diarrhea were reported, with a reported incidence of 0.17 per person-year. Incidence was higher in 6-month and one-year groups with a peak during May to August. But no sex difference of diarrhea incidence existed. Use of oral rehydration solution (ORS) accounted for 87.89% of the cases, with an average of 1.56 packages (each package containing 500 ml) per case, and 95.52% of dehydrated cases used ORS, with average of 2.02 packages per case. Use of intravenous rehydration account for 1.79% of the cases, 58.74% of them used antibiotics and 16.03% of them used more than two kinds of antibiotics, and 47.98% of the cases used both ORS and antibiotics. Occurrence of blood, mucus and pus in stool accounted for 12.64% of the total cases. All indices of surveillance in 1993 improved, compared with those in September 1991.
Child, Preschool↗
Expression of proteoglycans and collagen in the hypertrophic phase of experimental osteoarthritis.
These studies seek to define the gene expression of proteoglycans and collagens in the developing hypertrophic phase of an experimental model of osteoarthritis (OA). Total RNA was extracted from articular cartilage of nonoperated and operated dog knees 10 weeks after induction of OA by transection of the anterior cruciate ligament. The relative amounts of mRNA for type II collagen and the core proteins for the aggrecan, biglycan, decorin, and fibromodulin were analyzed by Northern blotting. Total RNA in OA vs nonoperated knees was statistically significantly elevated 2.5x, the mRNA for type II collagen was elevated 8x, aggrecan 2x, biglycan 4x, fibromodulin 2x. The level for decorin was increased 1.6x, but this difference was not statistically significant. Chondrocytes respond actively to joint injury. Gene expression of proteoglycans and type II collagen is discoordinate in early experimental OA, and may contribute to the development of cartilage abnormalities.
Aggrecans↗