Search PubMed⌕ Search

Biomedical subjects

S Chang

Publications and source records attributed to S Chang.

At least 253 records · Page 14Linked to original sources
PubMed1994

The long-term follow-up of severely malnourished children who participated in an intervention program.

18 severely malnourished children (IM) who participated in a 3-year home-visiting program were compared with 2 other comparison groups comprising 17 severely malnourished (NIM) and 19 adequately nourished children (controls). On enrollment, all the groups were in the same hospital, and both malnourished groups had lower developmental levels than the controls. The IM group received intervention for 3 years after hospitalization, consisting of weekly or 2 weekly home visits with toy demonstrations. At 7, 8, 9, and 14 years after leaving the hospital, the 3 groups were compared on tests of school achievement and IQ. The NIM group showed no sign of reducing their deficits, and at the 14-year follow-up they had markedly lower scores on the WISC verbal and performance scales, the Wide Range Achievement Test (WRAT), and the Peabody Picture Vocabulary Test (PPVT), than the controls. Throughout the follow-up the IM group's scores were intermediate between the NIM and the controls in every test. At the 14-year follow-up, their scores were significantly higher than those of the NIM group in the WISC verbal scale, and the difference approached significance in the WRAT. We conclude that psychosocial intervention should be an integral part of treatment for severely malnourished children.

Adolescent↗
PubMed1994

Identical twins with Ollier's disease and intracranial gliomas: case report.

Sarcomatous transformation of the enchondromas is a well-known complication of Ollier's disease, and nonsarcomatous malignancies have usually been associated with Maffucci's syndrome. Only 13 cases of multiple enchondromatosis associated with intracranial gliomas have been described, 5 of which were in patients with Ollier's disease. We describe three patients, including identical twins, who had both Ollier's disease and primary brain tumors. This is the first report of Ollier's disease in identical twins. These three cases support the theory that Ollier's disease and Maffucci's syndrome may represent a spectrum of the same disease process rather than two distinct diseases.

Adult↗
PubMed1994

Phase II trial of Virulizin in patients with pancreatic cancer.

Twenty-two patients were enrolled in a clinical trial to determine the toxicity and efficacy of the novel immunomodulator Virulizin in patients with measurable, biopsy-proven pancreatic cancer. The dose was 0.11 ml/kg (minimum 7.5 ml) 3 times weekly for the first week, then twice weekly until disease progression. No toxicity was encountered. In the 17 evaluable patients there was no evidence of tumour regression. Six patients (35%) had disease stabilization for more than 3 months, and 2 are still alive with progressive disease, having had disease stabilization for 15 and 17 months. While the results do not suggest any cytotoxic activity at this dose and schedule, the possibility of an antiproliferative effect warrants further study of this agent.

Adenocarcinoma↗
PubMed1993

Prebiotic ammonia from reduction of nitrite by iron (II) on the early Earth.

Theories for the origin of life require the availability of reduced (or 'fixed') nitrogen-containing compounds, in particular ammonia. In reducing atmospheres, such compounds are readily formed by electrical discharges, but geochemical evidence suggests that the early Earth had a non-reducing atmosphere, in which discharges would have instead produced NO. This would have been converted into nitric and nitrous acids and delivered to the early oceans as acid rain. It is known, however, that Fe(II) was present in the early oceans at much higher concentrations than are found today, and thus the oxidation of Fe(II) to Fe(III) provides a possible means for reducing nitrites and nitrates to ammonia. Here we explore this possibility in a series of experiments which mimic a broad range of prebiotic seawater conditions (the actual conditions on the early Earth remain poorly constrained). We find that the reduction by Fe(II) of nitrites and nitrates to ammonia could have been a significant source of reduced nitrogen on the early Earth, provided that the ocean pH exceeded 7.3 and is favoured for temperatures greater than about 25 degrees C.

Ammonia↗
PubMed1993

Hepatic lipase function and the accumulation of beta-very-low-density lipoproteins in the plasma of cholesterol-fed rabbits.

The accumulation of cholesterol-rich beta-very-low-density lipoproteins (beta-VLDL) in the plasma of rabbits fed on a high-fat high-cholesterol diet is due to a defect in the clearance of these lipoprotein remnants from circulation by the liver. In view of the evidence that hepatic lipase participates in the process of rapid removal of remnants from circulation, and considering that rabbits are naturally deficient in hepatic lipase, we examined whether this defect in the clearance of beta-VLDL could be reversed by exogenous hepatic lipase. We report that treatment in vitro of [3H]cholesterol-labelled beta-VLDL, or rat chylomicrons, with hepatic lipase resulted in the formation of particles that were rapidly cleared from circulation by the liver when injected intravenously into hypercholesterolaemic rabbits. These results are consistent with the notion that, in addition to the well-established requirement for lipoprotein lipase activity, the generation of remnants capable of being efficiently taken up by the liver also requires the action of hepatic lipase. Lipoprotein lipase acts on triacylglycerol-rich lipoproteins to transform them into particles (remnants) which bind to the surface of liver cells, where they become accessible to hepatic lipase. Hepatocyte endocytosis of these remnants occurs only after further modification by hepatic lipase. According to this scheme, the results presented suggest that the accumulation of beta-VLDL in the circulation of rabbits fed on a high-fat high-cholesterol diet is the result of the saturation of the available hepatic lipase by abnormally high levels of lipoprotein-lipase-generated chylomicron remnants.

Animals↗
PubMed1993

AgSK1, a novel carcinoma associated antigen.

An IgM human monoclonal antibody (HuMAb) SK1 was generated from mesenteric nodal lymphocytes of a colon cancer patient that were fused with a human B-lymphoblastoid cell line SHFP-1. The reactivities of HuMAb SK1 to various human cell lines were screened by cell enzyme linked immunosorbent assay and immunocytochemical staining. The HuMAb SK1 reacted strongly with all 11 human carcinoma cell lines that were tested and had no detectable binding with noncarcinoma cell lines of the following origins: fibroblast; fetal lung; melanoma; soft tissue sarcoma; neuroblastoma; and glioblastoma. Carcinoma preferred reactivity of HuMAb SK1 was further confirmed by immunoperoxidase staining of a large number of frozen tissues, both malignant and benign. The antigen SK1 (AgSK1) in human carcinoma detected by immunoperoxidase staining was also identified biochemically as a sialoglycoprotein that migrated at M(r) 42,000 with an isoelectric point (pI) of approximately 5.9. A preferential staining by HuMAb SK1 was seen among colorectal, gastric, pancreatic, and lung cancers. Competitive inhibition study in solid-phase immunoassay suggested that the HuMAb SK1 did not cross-react with other antibodies specific for CEA, CA 19-9, and TAG 72. The AgSK1 appears to be a novel carcinoma associated antigen which may be a useful tumor marker in cancer diagnosis and treatment.

Animals↗
PubMed1993

Rheumatoid factor expression and complement activation in children congenitally infected with human immunodeficiency virus.

Rheumatic disease manifestations and autoimmune phenomena are common in adults infected with human immunodeficiency virus (HIV). On the other hand, rheumatic disease manifestations are rare in children congenitally infected with HIV. We studied the relationship between autoimmune phenomena and rheumatic diseases by examining HIV-infected children for the presence of rheumatoid factors (RFs), immune complexes, and complement activation fragments. RFs (principally IgA) were detected in 12 of the 24 HIV-infected patients (50%) and in none of the uninfected (HIV-exposed, seroreverted) controls (n = 22). Mean levels of complement activation fragments C3a and Bb were elevated in the HIV-infected children compared with the controls. A correlation was seen between the presence of IgA RF and alternative complement pathway activation as measured by plasma levels of Bb. None of the children had clinical or laboratory evidence of rheumatic disease.

Antigen-Antibody Complex↗
PubMed1993

A search for C60 in carbonaceous chondrites.

Analysis of interior samples of the Murchison meteorite by two routes yielded an upper limit of 2 ppb for its C60 content, as compared to parts per million levels for individual polycyclic aromatic hydrocarbons (PAHs). Provided the samples contain an interstellar component, which is probable since Murchison hydrocarbons contain excess deuterium, this result argues against the ubiquitous presence of C60 in the interstellar medium. A possible explanation for the absence of C60 was found in experiments showing how PAHs replace fullerenes as stable end products when hydrogen is present during carbon condensation. As a secondary result we found high molecular weight PAHs in the Murchison and Allende meteorites. Coronene and its methyl derivatives are especially interesting since features in the coronene spectrum have been shown to match some of the unidentified interstellar infrared emission bands.

Carbon↗
PubMed1993

The Strecker synthesis as a source of amino acids in carbonaceous chondrites: deuterium retention during synthesis.

Deuterium-enriched amino acids occur in the Murchison carbonaceous chondrite. Synthesis from D-enriched interstellar precursors by Strecker reactions during aqueous alteration of the parent body has been proposed. To test this hypothesis, we have measured the retention of deuterium in amino acids produced from HCN, NH3, and formaldehyde-D2, acetaldehyde-D4, and acetone-D6 in H2O. The isotopic label is 50% to 98% retained, with variations in retentivity depending on the amino acid and the reaction conditions. If amino acids, once formed on the parent body by the Strecker synthesis, lose no deuterium by subsequent exchange with water or H-bearing minerals, then the observed deuterium isotopic composition of Murchison amino acids represents as much as 50% or more of the enrichments inherited from their interstellar precursors. Imino diacids are prominent side products of the Strecker synthesis which have not been reported in carbonaceous chondrites. Under the conditions of the Strecker reaction using deuterium labeled aldehydes and ketones, unlabeled amino acids are also formed by an HCN polymerization route indicating multiple pathways for the synthesis of amino acids in meteorites.

Acetaldehyde↗
PubMed1993

Retinal tolerance to intravitreal perfluoroethylcyclohexane liquid in the rabbit.

To evaluate the use of perfluoroethylcyclohexane (PFE) liquid during vitreoretinal surgery, retinal tolerance was tested by electroretinographic (ERG) and histologic study of rabbit eyes undergoing intravitreal placement of PFE for 48 hours. When PFE occupied the vitreous cavity, ERG amplitudes were decreased, probably because of electrical insulation by the liquid. Immediately after removal of the liquid, elevations of a and b waves occurred. Further improvements in the waveforms were recorded when tested between 5 days and 2 months after PFE removal, such that the eyes injected with PFE exhibited ERG amplitudes comparable to contralateral control eyes and preoperative eyes. Histologic examination of the eyes 2 months after PFE removal also revealed normal morphologic features. Small residual amounts of PFE produced no adverse histologic changes after 6 months. When PFE remained intravitreally for longer than 1 week, dispersion of the liquid and preretinal accumulation of macrophages occurred, and in inferior retina, distortions of photoreceptor outer segments and narrowing of outer plexiform layer were observed in the rabbit model.

Animals↗
PubMed1993

Perfluorocarbon effects on rabbit blood-retinal barrier permeability.

Studies have been made of the effects of intravitreal perfluoro-n-octane on the permeability to fluorescein of the blood-retinal barrier in rabbits. At day 1 after injection, there is increased aqueous humor fluorescence that reflects the physical disturbance to the eye following injection. From that time through 7 weeks, there is no evidence of any overt toxicity to the blood-retinal barrier. The retention in the vitreous of a small volume of perfluoro-n-octane following its intraoperative use would not be expected to induce a toxic response. Some effect on an already compromised retina cannot, however, be excluded.

Animals↗
PubMed1993

A comparison of immunoglobulin G-containing high-molecular-weight complexes isolated from children with juvenile rheumatoid arthritis and congenital human immunodeficiency virus infection.

Circulating immune complexes have been described in both juvenile rheumatoid arthritis and in AIDS. We isolated high-molecular-weight complexes from plasma of children with juvenile rheumatoid arthritis and congenital human immunodeficiency virus infection by sequential gel filtration followed by affinity chromatography on protein A-Sepharose. We demonstrate that 1) mixed IgG-, IgM-, and IgA-bearing immune complexes can be found in both juvenile rheumatoid arthritis and congenital human immunodeficiency virus infection and 2) complexes isolated via affinity chromatography on protein A-Sepharose do not have detectable C4 but activate the classic complement pathway in vitro.

Adolescent↗
PubMed1993

5-Bromo-2-deoxyuridine regulates invasiveness and expression of integrins and matrix-degrading proteinases in a differentiated hamster melanoma cell.

Cell interactions with the extracellular matrix play a critical role in regulating complex processes such as terminal differentiation and tumor progression. In these studies we describe a melanoma cell system that should be useful in addressing the regulation of cell-matrix interactions and the roles they play in regulating differentiation and cell invasiveness. CS (suspension)-1 melanoma cells are relatively well differentiated: they are melanotic, responsive to melanocyte-stimulating hormone, and express TA99, a melanosome membrane differentiation marker. Their repertoire of integrin receptors for extracellular matrix ligands is limited; in particular, they lack receptors for vitronectin, accounting for the observation that they are nonadherent when cultured in the presence of serum. CS-1 cells are noninvasive as well, and express low levels of both metalloproteinases and activated plasminogen activators. Treatment of these cells with melanocyte-stimulating hormone causes them to increase melanin production and assume an arborized phenotype, suggesting that it promotes their further differentiation. In contrast, treatment of CS-1 with the thymidine analog 5-bromodeoxyuridine, converts them to a highly invasive cell population (termed BCS-1) that loses its differentiated properties and responsiveness to melanocyte-stimulating hormone, acquires a broad integrin repertoire (including vitronectin receptors), and expresses elevated levels of metalloproteinases and activated urokinase. From these observations and findings of others on BrdU treatment of other developmental lineages, we hypothesize that BrdU both suppresses differentiation and promotes invasiveness of CS-1 cells. The demonstrated manipulability of CS-1 cells should make them extremely useful for studying the regulation of both terminal differentiation and tumor progression in the melanocyte lineage.

Animals↗
PubMed1992

Two gap junction genes, connexin 31.1 and 30.3, are closely linked on mouse chromosome 4 and preferentially expressed in skin.

Two new gap junction genes isolated from the mouse genome code for connexin homologues of 271 and 266 amino acids, designated here Cx31.1 and Cx30.3, respectively. The two open reading frames, oriented in the same direction, are only 3.4 kb apart on mouse chromosome 4. Within the connexin family, these two proteins are most closely related to one another (70% amino acid sequence identity) and to Cx31 (65 and 68% identity, respectively). Comparison of the Cx31.1 mouse gene with a Cx31.1 cDNA showed a similar genomic organization to that found with other members of the connexin gene family, i.e. the coding and 3'-untranslated regions are contained within a single exon, which is preceded by an intron, less than 25 bases upstream of the ATG start codon. Northern blot hybridization revealed highly tissue-specific coexpression of the 1.6-kb Cx31.1 mRNA and two Cx30.3 transcripts of 1.9- and 3.2-kb size, predominantly in skin and two related mouse keratinocyte cell lines. Minor levels of Cx31.1 mRNA were detected in testis. Microinjection of Cx30.3, but not Cx31.1 cRNA, into Xenopus oocyte pairs induced formation of functional gap junction channels with unique voltage-gated parameters compared to other connexins expressed similarly.

Amino Acid Sequence↗