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Biomedical subjects

J Chang

Publications and source records attributed to J Chang.

At least 271 records · Page 15Linked to original sources
PubMed1997

Structural colocalisation of type VI collagen and fibronectin in agarose cultured chondrocytes and isolated chondrons extracted from adult canine tibial cartilage.

Cell-matrix and matrix-matrix interactions are of critical importance in regulating the development, maintenance and repair of articular cartilage. In this study, we examined the structural colocalisation of type VI collagen and fibronectin in isolated chondrons and long-term agarose cultured chondrocytes extracted from normal adult canine articular cartilage. Using double labelling immunohistochemistry in conjunction with dual channel confocal microscopy and digital image processing we demonstrate that type VI collagen and fibronectin are distributed in a similar staining pattern and are colocalised at the surface of cultured chondrocytes and isolated chondrons. The results suggest that type VI collagen and fibronectin may play a role in both cell-matrix adhesion and matrix-matrix cohesion in the pericellular microenvironment surrounding articular cartilage chondrocytes.

Animals↗
PubMed1997

Molecular analyses of human immunodeficiency virus type 1 V3 region quasispecies derived from plasma and peripheral blood mononuclear cells of the first long-term-nonprogressing mother and child pair.

Molecular analyses were done for the V3 region quasispecies of human immunodeficiency virus type 1 (HIV-1) strains from plasma and peripheral blood mononuclear cells of the first HIV-1-infected long-term-nonprogressing mother-child pair whose members have survived for >13 years with stable CD4 T cell counts. There was a predominance of lower V3 loop charge and the absence of genotypic changes that are critical in phenotypic determination and tropism during HIV-1 infection. The intrahost genetic diversity between HIV-1 strains from the mother-child pair compared with HIV-1 strains from slow and rapid progressors suggested that a high genetic heterogeneity in HIV-1 strains from this HIV-1-infected long-term-nonprogressing mother and child pair was directly proportional to the length of their immunocompetent period.

Amino Acid Sequence↗
PubMed1997

Gene expression of transforming growth factor beta-1 in rabbit zone II flexor tendon wound healing: evidence for dual mechanisms of repair.

The postoperative outcome of hand flexor tendon repair can be complicated by adhesions between the repair site and surrounding tissue. To date, the biology of hand flexor tendon wound healing remains controversial--both intrinsic (resident tenocyte) and extrinsic (tendon sheath fibroblast and inflammatory cell) processes may contribute to repair. Transforming growth factor beta-1 is a cytokine that plays multiple roles in wound healing but is also implicated in the pathogenesis of excessive scar formation. This study examines the activation of transforming growth factor beta-1 mRNA in a rabbit zone II flexor tendon wound-healing model. Forty New Zealand White rabbit forepaws underwent complete transection and repair of the middle digit flexor digitorum profundus tendon in zone II. Tendons were harvested at increasing time intervals (1, 3, 7, 14, 28, and 56 days) and analyzed by in situ hybridization and immunohistochemistry to determine the expression patterns of transforming growth factor beta-1. A small number of tenocytes exhibited expression of transforming growth factor beta-1 mRNA at baseline in nonwounded control tendon specimens. The surrounding tendon sheath in these control specimens also revealed low numbers of fibroblasts and inflammatory cells expressing transforming growth factor beta-1 mRNA. In contrast, flexor tendons subjected to transection and repair exhibited increased signal for transforming growth factor beta-1 mRNA in both resident tenocytes and infiltrating fibroblasts and inflammatory cells from the tendon sheath. These data demonstrate that (1) normal unwounded tenocytes and tendon sheath cells are capable of transforming growth factor beta-1 production, (2) this cytokine is activated in the tendon wound environment, as evidenced by mRNA upregulation, and (3) the upregulation of this cytokine in both "intrinsic" tenocytes and "extrinsic" tendon sheath fibroblasts and inflammatory cells supports dual mechanisms for tendon repair. Because transforming growth factor beta-1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that perioperative biochemical modulation of transforming growth factor beta-1 levels may help limit flexor tendon adhesion formation.

Animals↗
PubMed1997

Imaging of fluorescence in highly scattering media.

Two one-speed radiation transport equations coupled by a dynamic equation for the distribution of fluorophore electronic states are used to model the migration of excitation photons and emitted fluorescence photons. The conditions for producing appreciable levels of fluorophore in the excited state are studied, with the conclusion that minimal saturation occurs under the conditions applicable to tissue imaging. This simplifies the derivation of the frequency response and of the imaging operator for a time-harmonic excitation source. Several factors known to influence the fluorescence response-the concentration, mean lifetime and quantum yield of the fluorophore, and the modulation frequency of the excitatory source-are examined. Optimal sensitivity conditions are obtained by analyzing the fluorescence source strength as a function of the mean lifetime and modulation frequency. The dependence of demodulation of the fluorescent signal on the above factors is also examined. In complementary studies, transport-theory-based operators for imaging fluorophore distributions in a highly scattering medium are derived. Experimental data were collected by irradiating a cylindrical phantom containing one or two fluorophore-filled balloons with continuous wave laser light. The reconstruction results show that qualitatively and quantitatively good images can be obtained, with embedded objects accurately located and the fluorophore concentration correctly determined.

Algorithms↗
PubMed1997

Optical imaging of anatomical maps derived from magnetic resonance images using time-independent optical sources.

We present a model suitable for computing images of absorption cross sections of thick tissue structures illuminated at near infrared (NIR) wavelengths from tomographic projection data. Image reconstruction is accomplished by solving a system of linear equations derived from transport theory. Reconstruction results using different algebraic solvers are shown for anatomical maps of the breast, derived from magnetic resonance imaging data, containing two simulated pathologies, in which case qualitatively good reconstructions were obtained. Evaluation of magnetic resonance (MR) data to optimize NIR optical tomographic imaging methods and to assess the feasibility of a combined MR-optical measurement scheme is discussed.

Adipose Tissue↗
PubMed1997

Gene sequence and expression of an analog of proliferating cell nuclear antigen (PCNA) in the alga Tetraselmis chui and detection of the encoded protein with anti-rat PCNA monoclonal antibody.

To identify a phytoplankton cell cycle marker detected by a monoclonal antibody against mammalian proliferating cell nuclear antigen (PCNA) (S. Lin, J. Chang, and E. J. Carpenter, J. Phycol. 30:449-456, 1994), a PCNA gene fragment was isolated by reverse transcription-PCR from the marine unicellular alga Tetraselmis chui Butcher (Prasinophyceae). The gene fragment was 616 bp in length and contained an open reading frame of 205 amino acids. The deduced amino acid sequence showed 80 and 88% similarity to human and rice PCNA, respectively. Southern hybridization indicated that the isolated gene fragment was part of the T. chui genome, with up to three copies in each haploid nucleus. Northern hybridization was used to detect a PCNA mRNA with a size of 1.2 kb from an exponentially growing algal culture. The T. chui gene fragment has been cloned into an expression vector, and a fusion protein was subsequently generated. Anti-rat PCNA simultaneously recognized the PCNA fusion protein and a single 33-kDa band in T.chui total protein extract. Our results indicate that T. chui PCNA is highly similar to its mammalian counterpart and that anti-rat PCNA is a good tool for detecting phytoplankton PCNA in general.

Amino Acid Sequence↗
PubMed1997

Neonatal abstinence syndrome due to codeine.

The neonatal abstinence syndrome (NAS) is a potentially life threatening illness associated with significant morbidity especially in the neonatal period. A case of NAS due to codeine prescribed for pain relief during pregnancy is reported. Clinicians should be aware that narcotic derivatives prescribed in late pregnancy can give rise to this type of problem.

Acetaminophen↗
PubMed1997

Distribution and neuropeptide content of nitric oxide synthase-containing nerve fibers in arteries and conduction system of the rat heart.

The rat heart receives its blood supply not only from the coronary arteries but also from the accessory coronary arteries that supply mainly the atria. The distribution and chemical nature of nitric oxide synthase-containing nerve fibers in the conduction system as well as the coronary and accessory coronary arteries were investigated using immunohistochemistry and NADPH diaphorase (NADPH-d) histochemistry. A few NADPH-d-positive nerve fibers were observed mainly around the main trunk of the coronary arteries, while NADPH-d-positive fibers were found along the entire course of the accessory coronary arteries from their main branches to the arteriolar level. A double-staining method demonstrated that NADPH-d-positive fibers innervating both the coronary and accessory coronary arteries contained vasoactive intestinal polypeptide or neuropeptide Y. NADPH-d-positive fibers were relatively abundant in the sinus node and penetrating bundle but were very sparse in the atrioventricular node and right bundle branch. No NADPH-d-positive fibers were detected in the left bundle branch. Some of the NADPH-d-positive fibers innervating the penetrating bundle exhibited distinct immunoreactivity to calcitonin gene-related peptide. These results suggest that nitric oxide may play a role as a neurotransmitter and/or neuromodulator in the neural control of the cardiac blood flow and impulse conduction.

Animals↗
PubMed1997

Commentary: inaccurate data on the quality of care may do more harm than good--an alternative approach is required.

Recently the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) announced that it would integrate the use of clinical outcomes and other performance measures into the accreditation process through its new "ORYX" program. This JCAHO initiative represents a significant new development that will include more than 100 different performance measurement systems, most of which are available through commercial firms and outside organizations. However, we see some potential problems with this new initiative. This is because some indicators recommended by JCAHO may be questionable due to the fact they are based on flawed methodologies that could result in biased and confounded data. To illustrate some of the potential adverse effects that could result from using such data to compare health care providers and facilities, we discuss some common problems associated with several widely available performance measurement systems. We then suggest an alternative approach that could potentially avoid many of these problems in the future.

Bias↗
PubMed1997

Luminescence optical tomography of dense scattering media.

Using a set of coupled radiation transport equations, we derive image operators for luminescence optical tomography with which it is possible to reconstruct concentration and mean lifetime distribution from information obtained from dc and time-harmonic optical sources. Weight functions and detector readings were computed from analytic solutions of the diffusion equation and from numerical solutions of the transport equation by Monte Carlo methods. Detector readings were also obtained from experiments on vessels containing a balloon filled with dye embedded in an Intralipid suspension with dye in the background. Image reconstructions were performed by the conjugate gradient descent method and the simultaneous algebraic reconstruction technique with a positivity constraint. A concentration correction was developed in which the reconstructed concentration information is used in the mean-lifetime reconstruction. The results show that the target can be accurately located in both the simulated and the experimental cases, but quantitative inaccuracies are present. Observed errors include a shadowing effect in regions that have the lowest weight within the inclusion. Application of the concentration correction can significantly improve computational efficiency and reduce error in the mean-lifetime reconstructions.

Image Processing, Computer-Assisted↗
PubMed1997

Regularized progressive expansion algorithm for recovery of scattering media from time-resolved data.

Reconstructions of the absorption cross sections of dense scattering media from time-resolved data are presented. A progressive expansion (PE) algorithm, similar to a layer-stripping, is developed to circumvent the underdeterminedness of the inverse problem. An overlapping scheme, which used detector readings from several consecutive time intervals, is introduced to reduce the propagation of reconstruction errors that occur at shallower depths. To reduce the sensitivity of the PE algorithm to noise a regularized progressive expansion (RPE) algorithm is proposed, which incorporates regularization techniques into the PE algorithm. The PE and the RPE algorithms are applied to the problem of image reconstruction from time-resolved data. The test media were isotropically scattering slabs containing one or two compact absorbers at different depths below the surface. The data were corrupted by additive white Gaussian noise with various strengths. The reconstruction results show that the PE and the RPE algorithms, when they are combined by proper overlapping, can effectively overcome the underdeterminedness of the inverse problem. The RPE algorithm yields reconstructions that are more accurate and more stable under the same noise level.

Algorithms↗
PubMed1997

Iterative total least-squares image reconstruction algorithm for optical tomography by the conjugate gradient method.

We present an iterative total least-squares algorithm for computing images of the interior structure of highly scattering media by using the conjugate gradient method. For imaging the dense scattering media in optical tomography, a perturbation approach has been described previously [Y. Wang et al., Proc. SPIE 1641, 58 (1992); R. L. Barbour et al., in Medical Optical Tomography: Functional Imaging and Monitoring (Society of Photo-Optical Instrumentation Engineers, Bellingham, Wash., 1993), pp. 87-120], which solves a perturbation equation of the form W delta x = delta I. In order to solve this equation, least-squares or regularized least-squares solvers have been used in the past to determine best fits to the measurement data delta I while assuming that the operator matrix W is accurate. In practice, errors also occur in the operator matrix. Here we propose an iterative total least-squares (ITLS) method that minimizes the errors in both weights and detector readings. Theoretically, the total least-squares (TLS) solution is given by the singular vector of the matrix [W/ delta I] associated with the smallest singular value. The proposed ITLS method obtains this solution by using a conjugate gradient method that is particularly suitable for very large matrices. Simulation results have shown that the TLS method can yield a significantly more accurate result than the least-squares method.

Algorithms↗
PubMed1997

[Sequence analysis of 5' non-coding region of hepatitis G viruses and preliminary classification of genotypes].

For analyzing the structural characteristics of hepatitis G virus (HGV or GBV-C), 277 nucleic acids of 5' non-coding region of HGV were amplified using PCR from the sera of 2 paid donors, 2 chronic hepatitis patients and 2 patients with liver cirrohsis. The products were cloned and sequenced. The data were analyzed with the computer programs. The results indicated that the gene sequence homologies among 6 HGV isolates (G001-G006) obtained in this study were above 96.2%. The comparison of these 6 isolates and 3 foreign isolates reported previously showed that the sequence homologies were in the range from 86.9% to 91.6%. According to the variability of gene sequences, the preliminary division of genotypes of 6 Chinese HGV isolates (G001-G006) and 3 isolates reported abroad were classified into three distinct groups. The results suggest that the gene sequences of Chinese HGV isolates are highly homologous but have an obvious divergence with the foreign isolates. The 5' untranslated regions of all isolates analyzed probably contain a stable and similar secondary structure.

5' Untranslated Regions↗
PubMed1997

[Studies on the separation method with multiple injection of proteins].

An abrupt change of the eluting curve of proteins in the RPC and HIC was reported in the previous paper. Here, we present a new multi-injection method of proteins in which the sample may be injected for many times in the same chromatographic run. When the composition of mobile phase is far away from the position of the abrupt change, the multi-injection of proteins before and/or after starting a gradient elution for one chromatographic separation in the RPC and HIC can be performed. Thus we may obtain the same chromatogram and retention of proteins as the ordinary one. This method can be used to overcome the difficulty that the loop is too small for injection big volume of sample solution. A larger sample size can be injected by many times in one chromatographic run to save time and to decrease the consumption of the experimental material. If there exist some impure proteins of weak retention, the impure proteins may go through the column with the solution A when the selected concentration of mobile phase is suitable. Therefore, a fixed column size can adsorb more related proteins, that is the effective column capacity is relatively raised. This injection method has an important value in the preparative chromatography of proteins.

Chromatography↗
PubMed1997

[Studies on the packings of high performance strong cation exchange chromatography for the separation of proteins].

In this paper, the studies on the synthesis, chromatographic characteristics and application of new packings of high performance strong cation exchange chromatography with sulfonic group for the separation of proteins have been reported. The silica with the end hydroxyl group reacted with chlorosulfonic acid and thus packings for high performance strong cation exchange chromatography were obtained. The recovery of bioactivity for lysozyme of these high resolution packings is over 76%. The packings can be used for the separation of proteins and biotechnological products.

Animals↗
PubMed1997

Patients' associations and the control of leishmaniasis in Peru.

American mucocutaneous leishmaniasis is an important health problem in Peru, particularly in the mountainous Cuzco Region, where 25% of all new cases reported in 1989 were located. Cases have increased considerably since the beginning of the 1980s, when large-scale seasonal migration to endemic zones occurred, particularly the forest area of Madre de Dios, following the discovery of new gold deposits there, and the deterioration in the economic situation in Peru. Following the lack of official response from the Peruvian government, hundreds of people suffering from leishmaniasis in the Cuzco area formed self-help associations with the objective of obtaining the drugs needed to treat their disease. The major achievement of this spontaneous movement, which was supported by several public and private institutions, was to encourage sick people, particularly patients with mucosal lesions, to emerge from isolation. As a result, the prevalence and incidence of the disease have now considerably decreased in the region.

Animals↗
PubMed1997

Studies on the transmission potential of surviving microfilaremias after basic control of filariasis.

After filariasis was basically controlled (the microfilarial rate was lower than 1%) in Henan Province in 1987, longitudinal observation of the disease has been carried out in all the province in order to study the regular pattern of growth and decline or the transmission potential of the disease. According to the distribution of filaria species and original microfilarial rate, 7 administrative villages in 7 counties were selected as surveillance sites. From 1988 to 1995, etiological and mosquito vector surveys were made continuously in all sites where no control measure was conducted. 10 surviving microfilaremic individuals became negative gradually over the first 6 years and no new microfilaremia was found. Since then, the microfilarial rate was zero. During the 8 years, 19 vector mosquitos were positive, with a total of 33 filarial larva. Culex pipiens pallens was the predominant mosquito species inside human dwelling in all sites. The man-biting rate of mosquitos for outdoor sleepers fluctuated greatly, the highest was 360.60 mosquitos per man per night and the lowest 7.20. The man-biting rate of mosquitos for sleepers inside mosquito-nets was approximately 1. The proportion of multiparous mosquitos also fluctuated greatly, the highest was 88.10% and the lowest 27.27%. According to the data described above, the man-biting rate of mosquitos which contained filaria L3 was less than 1 mosquito per man per transmission season. It is suggested that after the microfilarial rate was lower than 1%, the surviving microfilaremias became negative gradually in 3-5 years, and the transmission of the disease was blocked. Therefore, in the districts where filariasis was basically controlled, elimination of the disease was attainable.

Animals↗