Biomedical subjects

Y Chang

Publications and source records attributed to Y Chang.

At least 181 records · Page 10Linked to original sources

PubMed1997

The effect of enforcing tobacco-sales laws on adolescents' access to tobacco and smoking behavior.

BACKGROUND: Enforcing laws banning tobacco sales to minors is widely advocated as a way to reduce young people's access to tobacco and tobacco use. Whether this approach is successful is not known. METHODS: In a two-year controlled study, we assessed sales of tobacco to minors and young people's access to and use of tobacco in six Massachusetts communities. Three communities (the intervention group) enforced tobacco-sales laws, whereas three matched communities (the control group) did not. To assess compliance with the law, minors working for the study investigators attempted to purchase tobacco from all retail vendors in each community every six months. Three annual anonymous surveys of a total of 22,021 students in grades 9 through 12 (response rate, 84 percent) measured access to tobacco and smoking behavior. RESULTS: At base line, 68 percent of 487 vendors sold tobacco to minors. Compliance with the law improved significantly faster in the intervention communities than in the controls (P<0.001). By the study's end, 82 percent of the merchants in the intervention communities complied with the law, as compared with 45 percent in the control communities (P<0.001). However, adolescents under 18 years old reported only a small drop in their ability to purchase tobacco and no decline in its use. Communities with and those without enforcement programs did not differ with respect to these outcomes. CONCLUSIONS: Enforcing tobacco-sales laws improved merchants' compliance and reduced illegal sales to minors but did not alter adolescents' perceived access to tobacco or their smoking. Test purchases of tobacco do not accurately reflect adolescents' self-reported access to tobacco, and reducing illegal sales to less than 20 percent of attempts -- the goal of a new federal law-- may not decrease young people's access to or use of tobacco.

Adolescent↗

PubMed1997

Loss of heterozygosity analysis in primary mammary tumors and lung metastases of MMTV-MTAg and MMTV-neu transgenic mice.

Loss of heterozygosity (LOH) analysis has been used in many types of human cancer to localize putative tumor suppressor genes important in carcinogenesis. However, this approach has only recently been applied to transgenic mouse tumor models, which offer greater opportunity for detailed molecular genetic analysis of tumor initiation and progression. To explore the possible role of secondary genetic events in transgenic mouse mammary tumor development, we performed microsatellite-based allelotypes on primary mammary adenocarcinomas and lung metastases arising in mice transgenic for the polyomavirus middle T antigen under the control of the mouse mammary tumor virus promoter/enhancer (MMTV-MTAg mice) and on primary mammary adenocarcinomas arising in mice transgenic for the neu proto-oncogene (MMTV-neu mice). We examined a total of 80 microsatellite loci distributed throughout the mouse genome for LOH and observed high rates of specific chromosomal loss but very low rates of background allelic loss in these tumors. For the MMTV-MTAg mice, no individual chromosomes showed rates of LOH significantly above the background rates. For MMTV-neu mice, markers on chromosome 4 showed LOH in 82% of mammary tumors, whereas markers on chromosome 3 showed loss in 29% of tumors. These data suggest that the middle T antigen transgenic mice do not undergo whole chromosome loss or large genomic deletions as common mechanisms of tumor formation and that chromosomes 3 and 4 may contain tumor suppressor gene loci that play important roles in the development of neu-mediated mouse mammary tumors.

Adenocarcinoma↗

PubMed1997

A Kaposi's sarcoma-associated herpesvirus-encoded cytokine homolog (vIL-6) activates signaling through the shared gp130 receptor subunit.

The present studies analyzed the biologic activity of a gene product (vIL-6) encoded by the recently discovered Kaposi's sarcoma-associated herpesvirus (KSHV) bearing 24.8% amino acid identity with human interleukin-6 (huIL-6). Based on this similarity, we hypothesized that this viral homolog might trigger the JAK/STAT pathway, which typically is engaged by IL-6 and other cytokines. Activation of receptor-associated Janus tyrosine kinases (JAKs) results in the subsequent phosphorylation of signal transducers and activators of transcription (STATs) leading to nuclear entry and transcriptional regulation of target genes. Treatment of HepG2 cells with culture medium containing recombinant KSHV-encoded vIL-6 led to rapid induction of JAK1 phosphorylation and a nuclear DNA-binding activity found to contain STAT1 and STAT3. An antibody to the IL-6 receptor (IL-6R) alpha subunit effectively neutralized the response to huIL-6 but failed to block STAT activation by vIL-6. In contrast, an antibody reactive with the gp130 subunit of IL-6R abrogated signaling of both responses. Moreover, a transfected cell line expressing human gp130 without IL-6Ralpha exhibited a robust response to vIL-6 but not to huIL-6. These results demonstrate that KSHV encodes a cytokine that activates specific JAK/STAT signaling via interactions with the gp130 signal transducing subunit independently of the IL-6Ralpha chain. This activity may have an impact on gp130-mediated signaling in response to native cytokines and thereby influence disease pathogenesis upon KSHV infection.

Antigens, CD↗

PubMed1997

Role of tryptophan-63 of the kringle 2 domain of tissue-type plasminogen activator in its thermal stability, folding, and ligand binding properties.

Conservative (F and Y) and radical (H and S) mutations have been engineered at a rigidly conserved aromatic residue, W63, of the isolated recombinant kringle 2 domain of tissue-type plasminogen activator (r-K2tPA), an amino acid residue predicted from the X-ray crystal structure to be important in the ligand binding properties of this isolated protein domain. The variants were expressed in Pichia pastoris cells. The binding constants of epsilon-aminocaproic acid (EACA), 7-aminoheptanoic acid (7-AHpA), and trans-(aminomethyl)cyclohexanecarboxylic acid (AMCHA) to each of these mutant polypeptides were determined by titrations of the alterations in intrinsic fluorescence of the variant kringles with the ligands. As compared to wild-type r-K2tPA, increases in the Kd (dissociation) values of approximately 15-fold and 20-200-fold were found for the W63F and W63Y mutants, respectively, toward these three ligands. Neither the W63H nor the W63S variant interacted with these same ligands. Differential scanning calorimetric analyses were also performed on each of the peptides to determine whether the alterations affected the conformational stability of wtr-K2tPA. The data demonstrated that all of these mutants were thermally destabilized, possessing temperatures of maximum heat capacity (Tm) values that were 12-20 degrees C lower than that of wtr-K2tPA. Addition of EACA resulted in increases (approximately 12 degrees C) in the Tm values of r-[W63F]-K2tPA and r-[W63Y]K2tPA, a result showing that EACA stabilized the native conformations adopted by these kringle domains. As expected from its greatly diminished binding to r-[W63H]K2tPA and r-[W63S]-K2tPA, high concentrations of EACA had little effect on the Tm of thermal denaturation of these latter mutants. 1H-NMR analysis of the two aromatic mutant kringles was employed to assess their overall comparative folding properties. The high upfield chemical shifts (-0.98 ppm) of the CH3(delta') protons of L47, a major signal of proper kringle folding, were slightly lowered to -0.83 to -0.86 ppm in the cases of all of the mutants. This is due to alterations in the W25-L47 side-chain spatial orientations, possibly the result of slight conformational alterations that affect the distance relationships of these two amino acid side chains. Assignments of nearly all of the protons of the aromatic residues in the W63F and W63Y mutants were accomplished, and few additional differences from their wild-type counterpart were noted. Reactivities of the mutants against four different monoclonal antibodies directed to wtr-K2tPA revealed the possibility that some small local conformational alterations might have resulted from the residues that have replaced the W63. We conclude that W63 possesses an important direct role in the ligand binding properties of r-K2tPA. This residue also contributes significantly to the stability of the native conformation of this kringle domain and perhaps to maintenance of local conformations.

Cell Line↗

PubMed1997

Impaired host defense, hematopoiesis, granulomatous inflammation and type 1-type 2 cytokine balance in mice lacking CC chemokine receptor 1.

CC chemokine receptor 1 (CCR1) is expressed in neutrophils, monocytes, lymphocytes, and eosinophils, and binds the leukocyte chemoattractant and hematopoiesis regulator macrophage inflammatory protein (MIP)-1alpha, as well as several related CC chemokines. Four other CCR subtypes are known; their leukocyte and chemokine specificities overlap with, but are not identical to, CCR1, suggesting that CCR1 has both redundant and specific biologic roles. To test this, we have developed CCR1-deficient mice (-/-) by targeted gene disruption. Although the distribution of mature leukocytes was normal, steady state and induced trafficking and proliferation of myeloid progenitor cells were disordered in -/- mice. Moreover, mature neutrophils from -/- mice failed to chemotax in vitro and failed to mobilize into peripheral blood in vivo in response to MIP-1alpha. Consistent with this, -/- mice had accelerated mortality when challenged with Aspergillus fumigatus, a fungus controlled principally by neutrophils. To test the role of CCR1 in granuloma formation, we injected Schistosoma mansoni eggs intravenously, and observed a 40% reduction in the size of lung granulomas in -/- mice compared to +/+ littermates. This was associated with increased interferon-gamma and decreased interleukin-4 production in -/- versus +/+ lung lymph node cells stimulated with egg-specific antigen, suggesting that CCR1 influences the inflammatory response not only through direct effects on leukocyte chemotaxis, but also through effects on the type 1-type 2 cytokine balance. Thus CCR1 has nonredundant functions in hematopoiesis, host defense, and inflammation.

Animals↗

PubMed1997

Prevalence of antineutrophil cytoplasmic antibodies in a large inception cohort of patients with connective tissue disease.

BACKGROUND: Two types of antineutrophil cytoplasmic antibodies (ANCA), antiproteinase 3 antibodies (anti-PR3) and antimyeloperoxidase antibodies (anti-MPO), are useful in the diagnosis of such types of vasculitis as Wegener granulomatosis and microscopic polyangiitis. Connective tissue diseases frequently appear in the differential diagnosis of this spectrum of vasculitis. OBJECTIVE: To determine the prevalence of ANCA in patients with connective tissue disease. DESIGN: Blinded, controlled study of a 5-year inception cohort. SETTING: Tertiary-care university teaching hospitals. PATIENTS: 70 patients with rheumatoid arthritis, 70 patients with systemic lupus erythematosus, 45 patients with scleroderma, 36 patients with inflammatory myositis, 44 patients with the sjögren syndrome, 33 patients with the antiphospholipid syndrome, and 165 patients with early undifferentiated connective tissue disease (EUCTD). Serum was taken from 200 blood donors and 52 patients who had known vasculitis and positive results on tests for anti-PR3 or anti-MPO; these patients served as controls. MEASUREMENTS: The presence of anti-PR3 and anti-MPO was determined by combining the results of indirect immunofluorescence tests for cytoplasmic (C-ANCA) and perinuclear (P-ANCA) patterns with the results of enzymelinked immunosorbent assays (ELISAs) directed to measure antigen. RESULTS: Cytoplasmic ANCA was not detected in any study or control patient. Perinuclear ANCA was commonly detected among patients with lupus (31%) but was uncommon among patients in other groups (0% to 5%). In all cases, P-ANCA was associated with the presence of antinuclear antibodies. Atypical ANCA immunofluorescence patterns were fairly common in all groups (11% to 39%). Antiproteinase 3 was detected by ELISA in study patients (1 patient with rheumatoid arthritis, 1 with lupus, 1 with polymyositis, and 6 with EUCTD). Antimyeloperoxidase was detected by ELISA in 2 study patients (1 with rheumatoid arthritis and 1 with lupus). None of the patients with positive ELISA results had evidence of renal vasculitis during follow-up. When an ANCA scoring system that combines immunofluorescence and ELISA was used, the test specificity for vasculitis was 99.5% among patients with connective tissue disease. CONCLUSIONS: Patients with connective tissue disease are known to develop multiple autoantibodies; positivity for anti-PR3 and anti-MPO ANCA in such patients is highly specific for anti-PR3. However, P-ANCA immunofluorescence, which may have positive results because of the presence of antinuclear antibodies, is not a specific marker of anti-MPO. A rigorous ANCA testing system that combines the results of immunofluorescence with those of ELISA is highly specific for Wegener granulomatosis and related vasculitides even in patients with connective tissue disease.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed1997

XTT-colorimetric assay as a marker of viability in cryoprocessed cardiac valve.

This study sought to evaluate the use of tetrazolium salt XTT reduction as an indicator of valvular viability in a cryoprocessed porcine cardiac homograft model. The XTT tetrazolium assays was based on the metabolic reduction of Sodium 3'-[1-(phenylamino-carbonyl)-3,4-Tetrazolium]-bis(4-methoxy-6-nitro) benzene sulfonic acid hydrate. The relationship between XTT reduction and: (1) leaflet tissue with various weight (n = 24); (2) morphometric evaluation (n = 30); (3) cadaveric ischemic intervals (n = 30); (4) freeze-thawing (n = 30) has been studied. The measurement of XTT reduction were significantly correlated with the weight of cardiac leaflets, in the range of 30 to 180mg (y=0.015x-0.063; r=0.99). Compared to morphometry of valvular damage, the reduction of mitochondrial enzymatic activity in cardiac leaflets was correlated with matrix cells without irreversible damage (r=0.89, P<0.005). The depletion of XTT reduction occurred dependent of ischemic time intervals. In general, freeze-thawing reduced more than 20% activity of mitochondrial dehydrogenase. We concluded that XTT tetrazolium assay is highly sensitive to determine valvular injury. The study demonstrated its potential for testing of cryopreserved cardiac valve.

Animals↗

PubMed1997

Dimensional stability of thermosensitive gutta-percha.

The expansion and shrinkage of four commercial brands of endodontic thermosensitive gutta-percha were evaluated. A modified volume dilatometry technique was used; the dilatometric system (DS) consisted of Pyrex glass capillary tubes and a specimen chamber. Each sample was weighed to 10(-4) mg, placed in the specimen chamber, and subjected to vacuum for 45 min to eliminate moisture or gases. The DS was gradually heated from 24 degrees C to 80 degrees C and then cooled to 24 degrees C using a well-agitated temperature-controlled water bath. In a parallel set of experiments, the DS was heated in the same manner but cooled to body temperature (37 degrees C) in the water bath and the temperature kept stable at 37 degrees C for 24 h. The level of the mercury meniscus within the DS was monitored to determine the percent volume change of each sample at 2 degrees C intervals. All samples expanded as the temperature was elevated and shrank during cooling. The percent volume change for each of the four gutta-percha products, as the temperature was raised to 80 degrees C, ranged from an expansion of +11.62 to +12.25. As the temperature was lowered from 80 degrees C to 24 degrees C, the percent volume change representing shrinkage ranged from -2.22 to -3.53. When the temperature was lowered from 80 degrees C to 37 degrees C, the products continued to exhibit shrinkage for a range of time between 45 min and 10 h before stabilizing at a fixed volume. The final percent volume change for each experiment, with each product, was positive, ranging from +5.50 to +7.20, with discernible differences between products.

Drug Stability↗

PubMed1997

Outcome of IVF in DES-exposed daughters: experience in the 90s.

PURPOSE: The outcome of in vitro fertilization (IVF) in a group of infertile women with a history of in utero exposure to diethylstilbestrol (DES) was analyzed. Records from an academic IVF program were retrospectively reviewed. METHODS: Seventeen infertile women with a self-reported history of exposure to DES in utero, attending the IVF unit at Massachusetts General Hospital (MGH) for assisted reproductive technology (ART), underwent 27 IVF cycles. Analysis of the outcome of IVF including implantation and ongoing pregnancy rates was performed. The data were compared with results from a group of 20 infertile patients with idiopathic infertility undergoing 27 IVF cycles at MGH during the same period. The patients in the two groups were matched for age, basal day 3 levels of follicle stimulating hormone and serum estradiol, and the number and quality of embryos transferred. RESULTS: The response to controlled ovarian hyperstimulation was comparable in the two groups. Significantly lower implantation and ongoing pregnancy rates following IVF and embryo transfer were seen in the utero DES-exposed group compared to the control patients. CONCLUSIONS: Infertile patients with a history of in utero exposure to DES exhibit a significantly impaired implantation rate following IVF, and the outcome of ART remains poor.

Adult↗

PubMed1997

Kaposi's sarcoma-associated herpesvirus encodes a functional bcl-2 homologue.

Kaposi's sarcoma-associated herpesvirus (KSHV) is a newly discovered herpesvirus etiologically associated with Kaposi's sarcoma (KS) and two lymphoproliferative disorders. We describe a KSHV vbcl-2 gene with homology to the proto-oncogene bcl-2. It is expressed in KS lesions and in cell lines derived from primary effusion lymphomas. Using yeast and human cells we demonstrate the ability of KSHV vBcl-2 protein to suppress Bax toxicity. We show that KSHV vBcl-2 heterodimerizes with human Bcl-2 in a yeast two-hybrid system. These results suggest that KSHV vBcl-2 plays an anti-apoptotic role in virus infected cells.

Amino Acid Sequence↗

PubMed1997

Effect of different Ig transgenes on B cell differentiation in scid mice.

In this study we show that the ability of bone marrow pre-B cells to differentiate into B cells in H/L chain transgenic scid mice correlates with the ability of the transgenes to inhibit initiation of endogenous kappa gene rearrangement. Initiation of rearrangement was scored by assaying for DNA double-strand breaks (DSB) at the recombination signal/coding borders of J kappa 1 and J kappa 2. In H/L chain transgenic scid mice that develop B cells, we found little or no DSB; whereas in H chain only transgenic scid mice, in which pre-B cells are unable to give rise to B cells, we found a normal level of DSB but no VJ kappa coding joints. As scid mice are deficient in the repair of DSB, we suggest that initiation of kappa gene rearrangement in H chain transgenic scid mice causes B lineage cells to die at the late pre-B stage. In one transgenic scid line (Y-Sp6), which falls to generate B cells despite containing a H and L chain transgene, we found evidence for loss of B lineage cells at two stages of development: the pro-B to pre-B transitional stage and the late pre-B stage.

Animals↗

PubMed1997

Characterization of intrafollicular steroid hormones, inhibin, and follistatin in women with and without polycystic ovarian syndrome following gonadotropin hyperstimulation.

The etiology of polycystic ovary syndrome (PCOS) is unexplained. Since no major deficiencies are reported in serum FSH or inhibin, we hypothesized that abnormal levels of a paracrine modulator of FSH action within the ovary may be associated with the arrest of follicular growth seen in the PCOS ovary. Follicular fluid aspirates were collected from women with (n = 7) or without (n = 17) PCOS during oocyte retrieval for in vitro fertilization. Aspirates were assayed for total inhibin, inhibin A (InhA), inhibin B (InhB), and follistatin (FS), as well as for estradiol, progesterone (P4), androstenedione, and total protein. Hormone levels were compared between women with and without PCOS using all aspirates (some of which were collected from multiple follicles at once) and also between aspirates containing fluid from a single follicle only (PCOS, n = 30; non-PCOS, n = 107). P4 levels were significantly (p < 0.01) reduced in PCOS versus non-PCOS women as evidenced by analysis of all follicles as well as in single-follicle aspirates only. In addition, InhA, P4, and FS increased with follicle volume, and InhB decreased significantly in non-PCOS, but not in PCOS, follicles. Therefore, although follicular development can be induced in PCOS patients with gonadotropins, hormonal responses within the ovary appear inappropriate in terms of concentrations or patterns of secretion. These data support the concept that PCOS is associated with a deficit in the paracrine control of folliculogenesis.

Adult↗

PubMed1997

The impact of choice of muscle relaxant on postoperative recovery time: a retrospective study.

UNLABELLED: To test the hypothesis that the use of long-acting muscle relaxants is associated with prolonged postoperative recovery when compared with the use of shorter-acting relaxants, we undertook a retrospective study of 270 patients with induced paralysis recovering from general anesthesia. We calculated the mean recovery time associated with each muscle relaxant used. Regression analyses were performed to control for potential confounding of the results by length and type of surgery, as well as age and sex. Taking these into account, the adjusted difference in mean recovery time between patients receiving short- and intermediate-acting relaxants (mivacurium, atracurium, and vecuronium) versus those receiving long-acting relaxants (d-tubocurarine, pancuronium, and pancuronium and d-tubocurarine combination) was 30 min (95% confidence interval [CI] 8-53). The adjusted difference in mean recovery time between patients receiving vecuronium and those receiving pancuronium (i.e., the single most frequently used drug in each category) was 33 min (95% CI 1-66). Shortened recovery time accounted for an estimated average $37.95 decrease in recovery room charge per patient when vecuronium was used instead of pancuronium, versus a $22.84 increase in drug cost. Our data and analyses support the hypothesis that the use of long-acting muscle relaxants is associated with prolonged recovery after surgery and provide preliminary evidence that restricting the use of the more expensive, shorter-acting muscle relaxants may represent a false economy. IMPLICATIONS: In this retrospective study, the use of old-fashioned, inexpensive, long-acting paralyzing drugs was found to be associated with prolonged postoperative recovery. This has implications when deciding whether, as an economic measure, to restrict the use of the more expensive, shorter-acting paralyzing drugs, because prolonged recovery also has a price.

Adolescent↗

PubMed1997

Unusual intramedullary vascular lesion: report of two cases.

OBJECTIVE AND IMPORTANCE: Spinal arteriovenous malformations have been divided by location into dural (Type I), intramedullary glomus (Type II), juvenile (Type III), and perimedullary direct arteriovenous fistulae (Type IV). We report two cases of an unusual intramedullary proliferation of hyalinized capillaries that do not fit into any of these categories. CLINICAL PRESENTATION: A 27-year-old woman and a 62-year-old man presented with subacute progressive caudal myelopathy. Magnetic resonance imaging revealed focal spinal cord enlargement, high signal on T2-weighted images, and patchy enhancement with gadolinium consistent with tumor. No serpentine flow voids were visualized on the surface of the spinal cord. Spinal angiography revealed nothing abnormal. No abnormal vasculature was grossly visible on open biopsy. Histological examination of the tissue specimens revealed a proliferation of capillary-sized vessels with varying degrees of vascular wall changes ranging from endothelial hyperplasia to concentric hyalinization, suggesting ongoing evolution of the lesion. Surrounding neural tissue demonstrated ischemic changes characterized by myelin and axonal loss and astrocytosis but no necrosis. INTERVENTION: Patients were treated with chronic anticoagulation, which seemed to slow, but not halt, symptomatic disease progression. CONCLUSION: Although the pathological substrate seems to be an acquired intramedullary vascular lesion characterized primarily by capillary proliferation, the cause of this lesion is unknown. This disease differs from Foix-Alajouanine syndrome and subacute necrotizing myelopathy by an absence of abnormal surface vessels and a lack of intramedullary necrosis. The histological findings are reminiscent of the process that occurs in the kidney and various end organs from long-standing mild to moderate elevations in blood pressure or chronic diabetes. Tissue ischemia may result from luminal obstruction by severe hyalinization and thrombosis. Because the natural history of this disease is unknown, it is unclear whether anticoagulation slowed disease progression.

Adult↗

PubMed1997

Fixation of various porcine arteries with an epoxy compound.

The clinical results of biological vascular grafts have been unsatisfactory. The poor results of these vascular grafts may be attributed to the fixatives, aldehydes, used in fixing tissues. In an attempt to overcome this problem, a new fixative, epoxy compound, has recently been used to fix biological vascular grafts. The study was undertaken to investigate the crosslinking characteristics, fixation index and denaturation temperature, of various porcine arteries fixed with an epoxy compound. The porcine arteries investigated in the study were the common carotid artery, internal thoracic artery, abdominal aorta, and saphenous artery. In addition, the effects of sonication on the porcine arteries before fixation on their crosslinking characteristics were analyzed. The fresh and glutaraldehyde-fixed arteries were used as controls. It was noted that glycine, proline, and alanine were the most abundant amino acids found in the porcine internal thoracic artery. In the amino acid analysis, it was observed that the amino acids in the porcine arteries reacted with epoxy compound or glutaraldehyde were lysine, hydroxylysine, histidine, and arginine. Of these amino acids, lysine was the most reactive. In general, the fixed arteries were relatively stiffer than their fresh counterparts. The fixation indices and denaturation temperatures of various porcine arteries were comparable throughout the entire fixation process. The amounts of free amino groups of the sonicated arteries were significantly lower than those of their unsonicated counterparts (p < 0.05). It is speculated that the diminishing free amino groups of the sonicated arteries may be attributed to the removal of the destroyed cell debris and adherent proteins of the arteries after sonication. However, it was learned that sonication on the porcine arteries before fixation did not seem to affect their fixation indices and denaturation temperatures. The results obtained in this study may help one in selecting the raw materials for developing a small-diameter biological vascular graft

Analysis of Variance↗

PubMed1997

Selective switch between latency and lytic replication of Kaposi's sarcoma herpesvirus and Epstein-Barr virus in dually infected body cavity lymphoma cells.

The BC-1 cell line, derived from a body cavity-based, B-cell lymphoma, is dually infected with Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV). In these studies, the relationships between these two gammaherpesviruses and BC-1 cells were characterized and compared. Single-cell cloning experiments suggested that all BC-1 cells contain both genomes. In more than 98% of cells, both viruses were latent. The two viruses could be differentially induced into their lytic cycles by chemicals. EBV was activated into DNA replication and late-gene expression by the phorbol ester tetradecanoyl phorbol acetate (TPA). KSHV was induced into DNA replication and late-gene expression by n-butyrate. Amplification of both EBV and KSHV DNAs was inhibited by phosphonoacetic acid. Induction of the KSHV lytic cycle by n-butyrate was accompanied by the disappearance of host-cell beta-actin mRNA. Induction of EBV by TPA was not accompanied by such an effect on host-cell gene expression. Induction of the KSHV lytic cycle by n-butyrate was associated with the expression of several novel polypeptides. Recognition of one of these, p40, served as the basis of development of an assay for antibodies to KSHV in the sera of infected patients. BC-1 cells released infectious EBV; however, there was no evidence for the release of encapsidated KSHV genomes by BC-1 cells, even though n-butyrate-treated cells contained numerous intranuclear nucleocapsids. The differential inducibility of these two herpesviruses in the same cell line points to the importance of viral factors in the switch from latency to lytic cycle.

Animals↗

PubMed1997

The cyclin encoded by Kaposi's sarcoma-associated herpesvirus stimulates cdk6 to phosphorylate the retinoblastoma protein and histone H1.

Kaposi's sarcoma-associated herpesvirus (KSHV or human herpesvirus 8) is a novel gammaherpesvirus implicated in the cause of Kaposi's sarcoma and certain malignancies of lymphatic origin. One of the candidate genes possibly involved in promoting tumor development is an open reading frame (ORF) with sequence similarity to human type D cyclin genes. This cyclin-like gene, when expressed in tissue culture cells, promotes phosphorylation and inactivation of the retinoblastoma tumor suppressor protein and thereby may result in deregulation of cell division control. We report here the biochemical characterization of this cyclin (KSHV-cyc) and the kinase activity that it elicits upon expression in tissue culture cells. We demonstrate that the kinase activity associated with KSHV-cyc is sensitive to the cdk inhibitor p27 (KIP) and due to activation of cdk6. However, in contrast to cdk6 activated by cellular type D cyclins, the cdk6 activated by KSHV-cyc is capable of phosphorylating not only the retinoblastoma protein but also histone H1. This finding implies that activation by KSHV-cyc alters the substrate preference of this cdk. This may have important physiological consequences in that the kinase activity triggered by this viral cyclin may abrogate cell cycle checkpoints in addition to those targeted by cellular cyclin D-cdk6 kinase.

Animals↗

PubMed1997

Delayed posthypoxic demyelination. Association with arylsulfatase A deficiency and lactic acidosis on proton MR spectroscopy.

Delayed demyelination is a rare and poorly understood complication of hypoxic brain injury. A previous case report has suggested an association with mild-to-moderate deficiency of arylsulfatase A. We describe a 36-year-old man who recovered completely from an episode of hypoxia related to drug overdose, and 2 weeks later progressed from a confusional state to deep coma. MRI showed diffuse white matter signal changes, and brain biopsy demonstrated a noninflammatory demyelinating process. Proton magnetic resonance spectroscopy revealed elevated choline and lactate and reduced N-acetyl aspartate signal in the affected white matter, consistent with demyelination and a shift to anaerobic metabolism. Arylsulfatase A activity from peripheral leukocytes was approximately 50% of normal, consistent with a "pseudodeficiency" phenotype. These findings confirm the hypothesis that relative arylsulfatase A deficiency predisposes susceptible individuals to delayed posthypoxic leukoencephalopathy and implicates lactic acidosis in the pathogenesis of this disorder.

Acidosis, Lactic↗