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Biomedical subjects

L C Yu

Publications and source records attributed to L C Yu.

At least 91 records · Page 5Linked to original sources
PubMed1994

Successful treatment of multisystem Langerhans cell histiocytosis (histiocytosis X) with etoposide.

PURPOSE: Langerhans cell histiocytosis (LCH) in its disseminated form usually occurs in the very young, and has a fulminant, rapidly progressive, and fatal course despite different forms of therapy. PATIENTS AND METHODS: We treated two patients, who had failed on vinblastine treatment, with i.v. etoposide (VP-16) at a dose of 150 mg/kg/day for 3 days. Patient I, 8 months of age, presented with failure to thrive and huge bilateral granulomatous lesions of the external auditory canal with erosion and extensive destruction of the petrous pyramids and mastoid area. Patient II, 20 months of age, presented with widespread purpuric skin rash, hepatosplenomegaly, and bone marrow involvement. RESULTS: Both patients sustained complete remission (CR) following three to six courses of VP-16 and continued to be in unmaintained CR for > 48 months from diagnosis. No major toxicity was noted. CONCLUSIONS: Etoposide (VP-16), an epipodophyllotoxin known for its usefulness in the treatment of malignancies of the monocyte/macrophage lineage, appears to be an effective treatment for the severe multisystem (disseminated) LCH of childhood and should be strongly considered as front-line therapy for this subgroup of patients with poor prognostic factors.

Etoposide↗
PubMed1993

Primary structure and characterization of an androgen-stimulated autoantigen purified from mouse seminal-vesicle secretion.

A protein extract of mouse seminal-vesicle secretion was used to immunize mature mice (Balb/c) of both sexes. Results of Western-blot analyses for these secretory proteins indicated that only one minor protein component could be recognized by the autoantisera prepared from either autoimmunization of male mice or isoimmunization of female mice. The autoantigen was purified from seminal-vesicle secretion. The purified autoantigen retained the ability to induce autoantibody formation. The autoantigen has glycoprotein characteristics: the majority of the carbohydrate is N-linked and the remainder is O-linked. Rabbit antibodies to the autoantigen were used to isolate the corresponding cDNA from a mouse seminal-vesicle cDNA library. The primary structure deduced from the cDNA sequence was confirmed by direct amino acid sequence determination. The results indicate that the core protein consists of 131 amino acid residues. Analysis of the primary structure indicates that the autoantigen has two potential acceptor sites for the N-linked carbohydrate at Asn-12 and Asn-122, three potential phosphorylation sites for casein kinase II at Thr-55, Ser-68 and Thr-76, and three potential phosphorylation sites for protein kinase C at Thr-28, Thr-40 and Thr-124. The core protein and the carbohydrate portion together have a molecular mass of 19 kDa. Results from Western- and Northern-blot analyses for various tissues indicate that the seminal vesicle is the sole organ producing this autoantigen. Expression of this autoantigen gene was stimulated by testosterone.

Amino Acid Sequence↗
PubMed1993

The developmental profile of lactoferrin in mouse epididymis.

A sandwich e.l.i.s.a. method was developed to examine the distribution of lactoferrin in mouse reproductive tract. The lactoferrin concentration was found to be much higher in oviduct, uterus, vagina, vas deferens or epididymis than in serum, but the concentration in ovary, testis, seminal vesicle, prostate or coagulating gland was comparable with that in serum. The existence of lactoferrin in male sexual organs was confirmed by Western-blot analyses for tissue proteins. Lactoferrin in male sexual organs was shown to have a molecular mass similar to that of the deglycosylated form of lactoferrin purified from mouse uterine luminal fluid. Northern-blot analyses for total RNA prepared from male sexual organs indicated that only epididymis contained the lactoferrin mRNA. The lactoferrin mRNA was found in the prepubertal period and increased with the growth of epididymis. The mRNA level in prepubertal epididymis could be stimulated by 17 beta-oestradiol, but was not influenced by testosterone.

Aging↗
PubMed1993

Arousal following intra-preoptic area administration of naltrexone, ICI 174864 or nor-BNI in hibernating ground squirrels.

Experiments were performed from January 1 to 30 January, 1989. Drugs were administered to the preoptic area of hibernating ground squirrels through a chronically implanted cannula on the 2nd day of a torpor bout. When naltrexone (an antagonist of opioid receptor) was injected, part (naltrexone, 0.5 or 1 microgram/microliter/32 min) or all (naltrexone, 2 micrograms/microliters/32 min) of the animals' body temperature was increased and they aroused from hibernation within 20 h after the injection. Further experiments showed that intra-preoptic area perfusion of 1 nmol of ICI 174864 (an antagonist of delta receptor) or nor-BNI (an antagonist of kappa receptor), but not beta-FNA (an antagonist of mu receptor), were able to increase the body temperature of hibernating ground squirrels and arouse them from hibernation in 20 h after the injection. These results indicate that (1) opioid peptides in the preoptic area may be involved in the mechanisms of hibernation; (2) activation of delta and kappa receptors in the preoptic area is indispensable for the maintenance of hibernation in ground squirrels.

Animals↗
PubMed1993

Structural changes in the actomyosin cross-bridges associated with force generation.

It is generally thought that to generate active force in muscle, myosin heads (cross-bridges) that are attached to actin undergo large-scale conformational changes. However, evidence for conformational changes of the attached cross-bridges associated with force generation has been ambiguous. In this study, we took advantage of the recent observation that cross-bridges that are weakly attached to actin in a relaxed muscle are apparently in attached preforce-generating states. The experimental conditions were chosen such that there were large fractions of cross-bridges attached under relaxing and activating conditions, and high-resolution equatorial x-ray diffraction patterns obtained under these conditions were compared. Changes brought about by activation in the two innermost intensities, I10 and I11, did not follow the familiar reciprocal changes. Instead, there was almost no change in I11, whereas I10 decreased by 34%. Together with the changes found in the higher-order reflections, the results suggest that the structure of the attached force-generating cross-bridges differs from that of the weakly bound, preforce-generating cross-bridges and possibly also differs from that of the cross-bridges in rigor. These observations support the concept that force generation involves a transition between distinct structural states of the actomyosin cross-bridges.

Actomyosin↗
PubMed1993

Characterization of i(18p) in prenatal diagnosis by fluorescence in situ hybridization.

A case is presented in which chorionic villus direct preparation and cultured chorionic villus cells revealed a 47,XX+mar karyotype. The marker was a small metacentric chromosome and appeared to be i(18p)--isochromosome 18p. Follow-up studies in both amniotic fluid and fetal fibroblasts confirmed the karyotype. In order to characterize the marker, a panel of biotinylated DNA probes was used, including a whole chromosome 18 probe, chromosome 18-specific alpha satellite DNA, Yac clones, and a pan-telomeric probe. These studies show that the marker is a monocentric i(18p) in which about 80 per cent of chromosome 18 alpha satellite DNA has been lost.

Adult↗
PubMed1993

Evidence for structural changes in crossbridges during force generation.

During muscle contraction, it is generally thought that myosin heads undergo large scale conformational changes, such as an oar-like rotation between 90 degrees and 45 degrees while attached to actin. However, evidence for conformational changes of the attached crossbridges associated with force generation has been ambiguous. In this study, we compared the conformations of attached crossbridges in (i) the pre-force generating state, (ii) force generating state, (ii) rigor state. High resolution equatorial X-ray diffraction patterns have been obtained from single chemically skinned rabbit psoas fibers under relaxed, fully Ca(2+)-activated and rigor conditions. The experimental condition was chosen (ionic strength = 50 mM and temperature = 5 degrees C) such that there are large fractions (80-100%) of crossbridges attached in all the three states, and the attached crossbridges in the relaxed muscle represent the pre-force generating state. Upon activation, changes in the two innermost intensities I10 and I11 did not follow the familiar reciprocal changes. Instead, there was almost no change in I11 while I10 decreased by 30%. Similarly, greater changes were found in I10 as the fiber goes into rigor from the activate state. Changes were also found in the higher order reflections suggesting that the structure of the force generating crossbridges is not a mixture of those found in the weakly bound and rigor crossbridges. Therefore, our data provides evidence that the average conformation of the force generating crossbridges is different from the weakly attached and from rigor crossbridges.

Actins↗
PubMed1993

State-dependent radial elasticity of attached cross-bridges in single skinned fibres of rabbit psoas muscle.

1. In a single skinned fibre of rabbit psoas muscle, upon attachment of cross-bridges to actin in the presence of ADP or pyrophosphate (PP(i)), the separation between the contractile filaments, as determined by equatorial X-ray diffraction, is found to decrease, suggesting that force is generated in the radial direction.2. The single muscle fibres were subjected to compression by 0-8% of dextran T(500). The changes in lattice spacings by dextran compression were compared with changes induced by cross-bridge attachment to actin. Based on this comparison, the magnitude and the direction of the radial force generated by the attached cross-bridges were estimated. The radial cross-bridge force varied with filament separation, and the magnitude of the radial cross-bridge force reached as high as the maximal axial force produced during isometric contraction.3. One key parameter of the radial elasticity, i.e. the equilibrium spacing where the radial force is zero, was found to depend on the ligand bound to the myosin head. In the presence of ADP, the equilibrium spacing was 36 nm. In the presence of MgPP(i) the equilibrium spacing shifted to 35 nm and Ca(2+) had little effect on the equilibrium spacing.4. The equilibrium spacing was independent of the fraction of cross-bridges attached to actin. The fraction of cross-bridges attached in rigor was modulated from 100% to close to 0% by adding up to 10 mM of ATPgammaS in the rigor solution. The lattice spacing remained at 38 nm, the equilibrium spacing for nucleotide-free cross-bridges at mu = 170 mM.5. Radial force generated by cross-bridges in rigor at large lattice spacings (38 nm </= d(10) </= 46 nm) appeared to vary linearly with lattice spacing.6. The titration of ATPgammaS to fibres in rigor provided a correlation between the radial stiffness of the nucleotide-free cross-bridges and the equatorial intensities. The relation between the equatorial intensity ratio I(11)/I(10) and radial stiffness appeared to be approximately linear.7. The fibres under different conditions showed a wide range of radial stiffness, which was not proportional to the apparent axial stiffness of the fibre. If the apparent axial stiffness is a measure of the fraction of cross-bridges bound to actin, it follows that the radial elastic constant is state dependent; or vice versa.8. Differences in equilibrium lattice spacing and in radial elastic constant, most probably reflect differences in the molecular structure of the acto-myosin complex and there is more than one single conformation of the various strongly bound cross-bridge states.9. Determining equilibrium spacings of the radial elasticity appears to be an effective new approach in detecting structural differences among the attached cross-bridges, since this approach is independent of the fraction of cross-bridges attached, a factor that frequently encumbers the interpretation of structural studies of attached cross-bridge states.

Journal Article↗
PubMed1993

State-dependent radial elasticity of attached cross-bridges in single skinned fibres of rabbit psoas muscle.

1. In a single skinned fibre of rabbit psoas muscle, upon attachment of cross bridges to actin in the presence of ADP or pyrophosphate (PPi), the separation between the contractile filaments, as determined by equatorial X-ray diffraction, is found to decrease, suggesting that force is generated in the radial direction. 2. The single muscle fibres were subjected to compression by 0-8% of dextran T500. The changes in lattice spacings by dextran compression were compared with changes induced by cross-bridge attachment to actin. Based on this comparison, the magnitude and the direction of the radial force generated by the attached cross-bridges were estimated. The radial cross-bridge force varied with filament separation, and the magnitude of the radial cross-bridge force reached as high as the maximal axial force produced during isometric contraction. 3. One key parameter of the radial elasticity, i.e. the equilibrium spacing where the radial force is zero, was found to depend on the ligand bound to the myosin head. In the presence of ADP, the equilibrium spacing was 36 nm. In the presence of MgPPi the equilibrium spacing shifted to 35 nm and Ca2+ had little effect on the equilibrium spacing. 4. The equilibrium spacing was independent of the fraction of cross-bridges attached to actin. The fraction of cross-bridges attached in rigor was modulated from 100% to close to 0% by adding up to 10 mM of ATP gamma S in the rigor solution. The lattice spacing remained at 38 nm, the equilibrium spacing for nucleotide-free cross-bridges at mu = 170 mM. 5. Radial force generated by cross-bridges in rigor at large lattice spacings (38 nm < or = d10 < or = 46 nm) appeared to vary linearly with lattice spacing. 6. The titration of ATP gamma S to fibres in rigor provided a correlation between the radial stiffness of the nucleotide-free cross-bridges and the equatorial intensities. The relation between the equatorial intensity ratio I11/I10 and radial stiffness appeared to be approximately linear. 7. The fibres under different conditions showed a wide range of radial stiffness, which was not proportional to the apparent axial stiffness of the fibre. If the apparent axial stiffness is a measure of the fraction of cross-bridges bound to actin, it follows that the radial elastic constant is state dependent; or vice versa.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Diphosphate↗
PubMed1993

Acquisition of telomere repeat sequences by transfected DNA integrated at the site of a chromosome break.

Previous analysis of plasmid DNA transfected into 108 cell clones demonstrated extensive polymorphism near the integration site in one clone. This polymorphism was apparent by Southern blot analysis as diffuse bands that extended over 30 kb. In the present study, nucleotide sequence analysis of cloned DNA from the integration site revealed telomere repeat sequences at the ends of the integrated plasmid DNA. The telomere repeat sequences at one end were located at the junction between the plasmid and cell DNA. The telomere repeat sequences at the other end were located in the opposite orientation in the polymorphic region and were shown by digestion with BAL 31 to be at the end of the chromosome. Telomere repeat sequences were not found at this location in the plasmid or parent cell DNA. Although the repeat sequences may have been acquired by recombination, a more likely explanation is that they were added to the ends of the plasmid by telomerase before integration. Comparison of the cell DNA before and after integration revealed that a chromosome break had occurred at the integration site, which was shown by fluorescent in situ hybridization to be located near the telomere of chromosome 13. These results demonstrate that chromosome breakage and rearrangement can result in interstitial telomere repeat sequences within the human genome. These sequences could promote genomic instability, because short repeat sequences can be recombinational hotspots. The results also show that DNA rearrangements involving telomere repeat sequences can be associated with chromosome breaks. The introduction of telomere repeat sequences at spontaneous or ionizing radiation-induced DNA strand breaks may therefore also be a mechanism of chromosome fragmentation.

Animals↗
PubMed1993

PCR cloning of a repeated DNA fragment from Chinese hamster ovary (CHO) cell X chromosomes and mapping by fluorescence in situ hybridization.

Hamster chromosome-specific DNA sequences were amplified by primer directed DNA amplification using mixed base oligonucleotides in an arbitrarily primed polymerase chain reaction (AP-PCR) protocol. The template DNA was comprised of approximately 3000 chinese hamster ovary cell (CHO) chromosomes enriched by flow sorting from a human x hamster hybrid cell line. Labeling of the PCR product pool and fluorescence in situ hybridization (FISH) demonstrated preferential binding to the distal long arm of the CHO X chromosome. The PCR products were cloned, labeled by PCR and hybridized to metaphase spreads. Clones containing highly reiterated DNA were identified by FISH and sequenced. Here, we present the sequence and chromosomal location of one of the repeat clones that maps close to the secondary constriction on the long arm of the CHO X chromosome, pCAT2066-24.

Animals↗
PubMed1993

Effects of opioid receptors antagonists administration to suprachiasmatic nucleus on hibernation of ground squirrels Citellus dauricus.

1. Drugs were administered to a suprachiasmatic nucleus through a chronically implanted cannula at the second day of a torpor bout of hibernating ground squirrels. After naltrexone injection, the body temperature of the hibernating animals increased and they aroused from hibernation within 20 hr after the injection. 2. Further experiments show that intra-suprachiasmatic nucleus perfusion of 1 nmol of ICI 174864 or nor-BNI, not beta-FNA, were able to increase the body temperature of hibernating ground squirrels and aroused them from hibernation within 20 hr after the injection.

Animals↗
PubMed1993

Bone marrow transplantation: a children's hospital of New Orleans experience.

Bone marrow transplantation has become an important therapeutic strategy in the treatment of pediatric malignancies and certain congenital disorders. We initiated a bone marrow transplant program at Children's Hospital in New Orleans at the start of January 1989. Both allogeneic and autologous bone marrow transplantations have been performed. To date, a total of 20 children have received transplants for a variety of diseases. Their ages ranged from 17 months to 20 years. The overall 2-year survival is 40%. For the good-risk patients, the projected 2-year disease-free survival is 85%, compared to 30% for the poor-risk patients. Regimen-related mortality has been extremely low in our settings primarily due to improvement of available supportive care. We conclude that bone marrow transplantation offers a potential cure for these otherwise fatal diseases.

Adolescent↗
PubMed1993

Libraries for each human chromosome, constructed from sorter-enriched chromosomes by using linker-adaptor PCR.

We describe here the production of complex libraries enriched in sequences from each human chromosome type, starting with only a few thousand sorter-purified chromosomes. In this procedure, DNA is extracted from the sorted chromosomes, digested to completion by using the frequently cutting restriction endonuclease Sau3A1, and ligated, on each end, to an adaptor oligonucleotide. These fragments are then amplified using PCR with a sequence homologous to the adaptor oligonucleotide as a primer. We have used this procedure to produce PCR libraries for each of the 24 human chromosomes. These libraries were characterized by gel electrophoresis and found to be composed of a continuum of sequences ranging in size from a few hundred to approximately 1,000 bp. The libraries, when used as probes for fluorescence in situ hybridization, stained the target chromosomes more or less continuously, even after PCR amplification for more than 200 cycles. These libraries are useful as hybridization probes to facilitate molecular cytogenetic studies and as sources of probes either for identification of polymorphic short tandemly repeated sequences or for development of sequence-tagged sites.

Base Sequence↗
PubMed1992

Effect of Ca2+ on weak cross-bridge interaction with actin in the presence of adenosine 5'-[gamma-thio]triphosphate).

In the presence of the nucleotide analog adenosine 5'-[gamma-thio]triphosphate (ATP[gamma S]), effects of Ca2+ on stiffness and equatorial x-ray diffraction patterns of single skinned fibers of the rabbit psoas muscle were studied. It is shown that cross-bridges in the presence of ATP[gamma S] have properties of the weak-binding states of the ATP hydrolysis cycle. Raising the Ca2+ concentration up to pCa 4.5 has little effect on actin affinity of cross-bridges in the presence of ATP[gamma S]. However, the rate constants for cross-bridge dissociation and reassociation from and to actin are reduced by about 2 orders of magnitude. In addition, nucleotide affinity of the cross-bridge is much smaller at high Ca2+ concentrations. Implications for interpretation of fiber stiffness recorded during isotonic shortening and the rising phase of a tetanus are discussed.

Actins↗
PubMed1992

Directed isolation of human genes that escape X inactivation.

Existing methodologies have been combined to produce a directed approach to the isolation of human genes that escape X inactivation. A mouse-human somatic cell hybrid line was established that has an inactive X as its only human chromosome, and nuclear RNA from this cell line was used to construct a cDNA library. Transcribed human sequences were isolated by screening the library with labeled human DNA. The corresponding genomic sequences were isolated in phage or cosmid clones, and exons were identified by detection of transcripts on northern blots. By these means three human loci have been identified that contain genes expressed from an inactive X chromosome. Fluorescence in situ hybridization has been used to map these genes to Xp21.1-22.1, Xp22.1-22.2, and terminal Xp/Yp. One of the three genes (XE45) corresponds to the ZFX gene, while the other two genes (XE7 and XE59) represent novel cloned sequences. Physical and genetic evidence indicate that XE7 is a newly identified pseudoautosomal gene.

Animals↗
PubMed1992

Detection of retinoblastoma gene copy number in metaphase chromosomes and interphase nuclei by fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) was applied to detect the copy number of the retinoblastoma (RB1) tumor suppressor gene in metaphase chromosomes and interphase nuclei. We used 14 lambda phage clones spanning the whole RB1 gene region as a probe and obtained a specific hybridization signal in normal metaphase chromosomes at 13q14. Normal interphase nuclei showed two RB1 signals in about 90% of cases, whereas two cell lines with cytogenetically defined deletions involving the RB1 gene showed only one hybridization signal in about 80% of the nuclei. Analogous changes were detected in metaphase chromosomes. Multicolor FISH with subsets of the phage clones allowed visualization of subregions within the 200-kb gene in interphase nuclei. Analysis of clinical breast cancer samples showed that most of the cells contained two copies of the RB1 gene, even when restriction fragment length polymorphism analysis showed loss of heterozygosity (LOH) at the RB1 locus. This indicates that LOH at the RB1 locus in breast cancer cells probably involves mechanisms other than physical deletion.

Breast Neoplasms↗