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Biomedical subjects

D Huang

Publications and source records attributed to D Huang.

287 records · Page 16Linked to original sources
PubMed1975

Insulin-induced reduction of membrane receptor concentrations in isolated fat cells and lymphocytes. Independence from receptor occupation and possible relation to proteolytic activity of insulin.

Incubation of cultured human lymphocytes or isolated rat fat cells at 37 degrees with insulin results in a time-dependent fall in the ability of the thoroughly washed cells to bind 125I-labeled insulin. Although this effect is dependent on the concentration of insulin used in the preincubation period, the concentration dependence pattern varies directly with the length of this incubation, and kinetically (i.e. at early times) it is virtually impossible to demonstrate saturability with respect to insulin concentration. Significant effects are demonstrable at very early times (e.g. 1 to 3 hours) provided sufficiently high insulin concentration (i.e. 5 mug/ml or more) are used...

Adipose Tissue↗
PubMedDate not supplied

Mechanisms and dynamics of mechanical strengthening in ligament-equivalent fibroblast-populated collagen matrices.

We have measured the dynamics of extracellular matrix consolidation and strengthening by human dermal fibroblasts in hydrated collagen gels. Constraining matrix consolidation between two porous polyethylene posts held rigidly apart set up the mechanical stress which led to the formation of uniaxially oriented fibroblast-populated collagen matrices with a histology resembling a ligament. We measured the mechanical stiffness and tensile strength of these ligament equivalents (LEs) as a function of age at biweekly intervals up to 12 weeks in culture using a mechanical spectrometer customized for performing experiments under physiologic conditions. The LE load-strain curve changed as a function of LE age, increasing in stiffness and exhibiting less plastic-like behavior. At 12 weeks, LEs had acquired up to 30 times the breaking strength of 1-week-old LEs. Matrix strengthening occurred primarily through the formation of BAPN-sensitive, lysyl oxidase catalyzed crosslinks. Sulfated glycosaminoglycan (GAG) content increased monotonically with LE age, reaching levels that are characteristic of ligaments. Cells in the LEs actively incorporated [3H]proline and [35S]sulfate into the extracellular matrix. Over the first three weeks, DNA content increased rapidly but thereafter remained constant. This data represent the first documentation of strengthening kinetics for cell-assembled biopolymer gels and the results suggest that this LE tissue may be a valuable model for studying the cellular processes responsible for tissue growth, repair, and remodeling.

Age Factors↗
PubMedDate not supplied

Binding of IgG to amyloid beta A4 peptide via the heavy-chain hinge region with preservation of antigen binding.

Amyloid beta A4 peptide is found in the extracellular region of the senile plaque and in the angiopathy of Alzheimer's disease. Several other proteins, including IgG, also reside in these abnormal structures. In an attempt to understand how these structures are assembled and to determine how proteins are recruited, interactions of various proteins with synthetic beta A4 peptide have been examined in vitro. Purified IgG binds directly to synthetic beta A4 peptide with high avidity. The domain between amino acids 12-28 of beta A4 binds IgG. beta A4 peptide binds the hinge region of the immunoglobulin heavy chain, and preserves the ability of the immunoglobulin to bind antigen. A protein which does not bind directly to beta A4 peptide can be targetted to the senile plaque and angiopathy by binding to IgG, which avidly binds beta A4 peptide.

Amyloid beta-Peptides↗
PubMedDate not supplied

A new candidate region for the positional cloning of the XLP gene.

X-linked lymphoproliferative disease (XLP) is an inherited immunodeficiency characterised by selective susceptibility to Epstein-Barr virus and frequent association with malignant lymphomas chiefly located in the ileocecal region, liver, kidney and CNS. Taking advantage of a large bacterial clone contig, we obtained a genomic sequence of 197620 bp encompassing a deletion (XLP-D) of 116 kb in an XLP family, whose breakpoints were identified. The study of potential exons from this region in 40 unrelated XLP patients did not reveal any mutation. To define the critical region for XLP and investigate the role of the XLP-D deletion, detailed haplotypes in a region of approximately 20 cM were reconstructed in a total of 87 individuals from 7 families with recurrence of XLP. Two recombination events in a North American family and a new microdeletion (XLP-G) in an Italian family indicate that the XLP gene maps in the interval between DXS1001 and DXS8057, approximately 800 kb centromeric to the previously reported familial microdeletion XLP-D.

Base Sequence↗
PubMedDate not supplied

Dose parameters of 125I and 192Ir seed sources.

As mandated by an NCI brachytherapy contract, we measured dosimetric parameters for 192Ir seeds and two models of 125I seeds. Measurements were with LiF powder in a water-equivalent phantom. Data were corrected for background, sample mass, and finite detector volume. Selected parameters were also investigated through Monte Carlo calculations. Results are presented in terms of a dose parametrization that is described in detail, and are compared to published data. Our results agreed well with published data for relative quantities such as radial and angular dose dependence. Our measured value for the 192Ir dose factor was 4.55 cGy(H2O) cm2 mCi-1 h-1, also in good agreement with commonly used values. However, the measured dose factors for 125I seed models 6702 and 6711 were 1.18 and 1.06 cGy(H2O) cm2 mCi-1 h-1, values well below those in general use.

Brachytherapy↗
PubMedDate not supplied

The change of C-fos expression in ovariectomized rats following electroacupuncture treatment--an immunohistochemistry study.

The roles of electroacupuncture (EA) in regulating the function of ovulation in rat have been investigated; however, the systematic study for the involvement of neural population of central nervous system (CNS) in acupuncturing the ovariectomized rat for promoting functional recovery has not been well understood. The present research was designed to examine, by C-fos immunocytochemistry, the distribution of Fos labelled neuron in CNS after acupuncturing the point of "Zhong-Ji (RN3)", "Guan-Yuan (RN4)", "San-Ying-Jiao (SP6)" and "Zi-Gong (EXCA1)" in ovariectomized rat. The area occupied by Fos protein labelled neuron, two hours after ovariotomy, was detected in medial preoptic nucleus (MPN), lateral preoptic nucleus (LPN), suprachiasmatic nucleus (SCN), paraventricular nucleus of the hypothalamus (PANH), medial amygdala nucleus (MAN), periventricular nucleus of the hypothalamus (PVNH), ventromedial nucleus of the hypothalamus (VNH), and arcuate nucleus (AR). The C-fos immunoreactive labelled neurons disappeared two weeks later following ovariotomy. The rat, recovering for two weeks after ovariotomy, received EA, and many specific Fos labelled cell were observed in LPN, PVNH, VNH, SCN and especially in AR, PANH and MPN, but not any labelled neuron could be found in MAN. No obvious C-fos expression was shown in these areas in the control group and EA group without ovariotomy. These results indicate that the above structures involved in regulating the function of hypothalamus-pituitary-ovarian axis and EA could modulate this function through effects on the above nuclei.

Animals↗
PubMedDate not supplied

Multiple regression and vector analyses of laser in situ keratomileusis for myopia and astigmatism.

PURPOSE: To construct a quantitative model relating refractive results to laser settings and other factors. METHODS: A prospective clinical trial was performed, including 14 surgeons and 523 eyes of 278 patients who desired correction of myopia from -1.00 to -16.00 D (mean, -6.20 D) and astigmatism up to 6.00 D (mean, 1.10 D). Myopia and astigmatism were corrected by laser in situ keratomileusis (LASIK) with sequential spherical and cylindrical ablations using a 5.5-mm ablation zone and a transition zone to 7.0 mm. The Nidek EC-5000 excimer laser and the Chiron Automated Corneal Shaper were used. RESULTS: Surgically induced refractive changes 3 months after surgery were measured. Spherical ablation by LASIK produced a 19% greater refractive change than that predicted by the Nidek PRK algorithm. The laser setting needed to achieve each 1.00 D of cylinder correction induced 1.30 D change in spherical equivalent refraction (0.80 D more than expected). Patient age and nonlinear effects had small but statistically significant influences on refractive outcome. Sex, left/right eye, and surgeon were not significant factors. Residual variations in spherical equivalent refraction included a 0.50-D constant plus 9% of the predicted spherical equivlanet change. Residual variations in the parallel and orthogonal components of cylinder correction were, respectively, 28% and 13% of the predicted cylinder change plus a 0.30-D constant component. The standard deviation of axis alignment error for cylinder ablation was 3.7 degrees. CONCLUSIONS: Cylindrical ablation produced a spherical change that was larger than expected. To compensate for this, spherical ablation should be reduced in eyes with astigmatism. Variability in the correction of astigmatism was proportionally larger than that for spherical correction and was primarily due to magnitude rather than axis error.

Adult↗
PubMedDate not supplied

Surgically-induced astigmatism after laser in situ keratomileusis for spherical myopia.

PURPOSE: To characterize the surgically-induced-astigmatism (SIA) associated with spherical LASIK. METHODS: Refractive outcomes in 70 eyes that underwent primary myopic LASIK with purely spherical ablation were analyzed. The Summit Apex Plus excimer laser was used. The Bausch & Lomb Hansatome with the 180-microm plate was used to produce superiorly hinged flaps. The relationship between refractive astigmatism and corneal topographic astigmatism was analyzed using linear regression and vector analysis. RESULTS: There was a statistically significant negative correlation (slope = -0.21) between refractive surgically-induced astigmatism and preoperative topographic cylinder. A 0.24-D with-the-rule shift was also found. Surgically-induced astigmatism was not correlated with the magnitude of laser ablation. CONCLUSION: The lamellar keratotomy portion of LASIK reduces pre-existing corneal astigmatism and produces a relative steepening of the hinge meridian.

Adult↗
PubMedDate not supplied

Spot size and quality of scanning laser correction of higher order wavefront aberrations.

PURPOSE: To investigate the effect of laser spot size on the outcome of aberration correction with scanning laser corneal ablation. METHODS: Numerical simulation of ablation outcome. RESULTS: Correction of wavefront aberrations of Zernike modes from second to eighth order were simulated. Gaussian and top-hat beams of 0.6 to 2.0-mm full-width-half-maximum diameters were modeled. The fractional correction and secondary aberration (distortion) were evaluated. Using a distortion/correction ratio of less than 0.5 as a cutoff for adequate performance, we found that a 2 mm or smaller beam is adequate for spherocylindrical correction (Zernike second order), a 1 mm or smaller beam is adequate for correction of up to fourth order Zernike modes, and a 0.6 mm or smaller beam is adequate for correction of up to sixth order Zernike modes. CONCLUSIONS: Since ocular aberrations above Zernike fourth order are relatively insignificant, current scanning lasers with a beam diameter of 1 mm or less are theoretically capable of eliminating most of the higher order aberrations of the eye.

Computer Simulation↗
PubMedDate not supplied

Laser in situ keratomileusis for hyperopia and hyperopic astigmatism with the Nidek EC-5000 Excimer laser.

PURPOSE: We evaluated the efficacy, predictability, stability, and safety of laser in situ keratomileusis (LASIK) for hyperopia and hyperopic astigmatism. METHODS: A retrospective study was performed for 92 eyes of 62 consecutive patients to evaluate uncorrected (UCVA) and best spectacle-corrected visual acuity (BSCVA) and manifest refraction before and 3 and 6 months after LASIK (Moria LSK-ONE microkeratome, Nidek EC-5000 excimer laser). Eyes were divided into groups: Group 1 (low hyperopia) for spherical correction of +1.00 to +3.00 D (22 eyes), Group 2 (low hyperopic astigmatism) for toric correction with spherical equivalent refraction of +1.00 to +3.00 D (18 eyes), Group 3 (moderate hyperopia) for spherical correction of +3.25 to +6.00 D (10 eyes), and Group 4 (moderate hyperopic astigmatism) for toric correction with spherical equivalent refraction between +3.25 and +6.00 D (18 eyes). RESULTS: At 3 and 6 months after LASIK, 68 eyes (73.9%) were available for follow-up examination. Percentage of eyes with a spherical equivalent refraction within +/-0.50 D of emmetropia for Group 1 was 54.5% (12 eyes); Group 2, 50% (9 eyes); Group 3, 40% (4 eyes), and Group 4, 38.8% (7 eyes). UCVA > or =20/20 in Group 1 was 14% and in Groups 2, 3, and 4, 0%. One eye (5.5%) lost two lines of BSCVA. CONCLUSION: LASIK with the Moria LSK-ONE microkeratome and the Nidek EC-5000 excimer laser reduced low and moderate hyperopia and was within +/-0.50 D of target outcome in approximately 50% of eyes. Undercorrection was evident in all groups. The procedure was safe.

Adult↗
PubMedDate not supplied

Extracellular matrix-cell interactions and chondrogenesis.

Extracellular matrix macromolecules are capable of complex interactions. Recent studies demonstrate that extracellular matrix macromolecules can regulate the synthesis of chrondroitin sulfate by chondrocytes. Extracellular chondroitin sulfate stimulates chondroitin sulfate synthesis, whereas external hyaluronic acid inhibits chondroitin sulfate production. Other matrix macromolecule-cell interactions are reviewed. An hypothesis is proposed to account for the interaction between the cell and its extracellular matrix macromolecules.

Cartilage↗
PubMedDate not supplied

Regulation of LDH-A gene expression by transcriptional and posttranscriptional signal transduction mechanisms.

The lactate dehydrogenase-A (LDH-A) gene, whose product plays a pivotal role in normal anaerobic glycolysis and is frequently increased in human cancers, is highly regulated at the transcriptional and posttranscriptional levels. Our laboratory has carried out extensive studies concerning the regulation of LDH-A subunit expression. We have elucidated complex regulatory mechanisms by identifying multiple cis-acting promoter elements including functional sites for Sp1 and c-Myc interactions as well as sites that interact with the protein kinase A and protein kinase C substrates, CREB and AP1, respectively. Furthermore, we have reported the existence of a CRE-dependent silencer element in the LDH-A promoter. LDH-A expression is additionally regulated through the protein kinase A and C signal pathways at the posttranscriptional level, specifically mRNA stability.

Humans↗