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Biomedical subjects

Q Fan

Publications and source records attributed to Q Fan.

At least 19 recordsLinked to original sources
PubMed2000

A long stringent sequence signal for programmed chromosome breakage in Tetrahymena thermophila.

Programmed chromosome breakage occurs at 50-200 specific sites in the genome of Tetrahymena thermo-phila during somatic nuclear (macronuclear) differentiation. Previous studies have identified a 15 bp sequence, the Cbs (for chromosome breakage sequence), that is necessary and sufficient to specify these sites. In this study we determined the effects of mutations in the Cbs on its ability to specify the chromosome breakage site and promote new telomere formation in conjugating cells. Twenty-one constructs with single nucleotide substitutions covering all 15 positions of the Cbs were made and tested. Fourteen of them (covering 11 positions) abolished breakage entirely, six (covering six positions, including the remaining four) caused partial loss of breakage function and one showed no detectable effect. This result indicates that the Cbs has an exceptionally long and stringent sequence requirement. It offers no evidence that the Cbs contains a separate domain for promoting new telomere formation. In addition, we found that a partially functional Cbs retained in the macronucleus does not induce chromosome breakage during vegetative growth and that excess copies of this germline-specific sequence in the somatic nucleus have little deleterious effect on cell growth.

Animals↗
PubMed2000

Antigenic cross-reactivity among Porphyromonas gingivalis serotypes.

The goal of our research program is to develop a Porphyromonas gingivalis vaccine. Vaccine development requires identification of antigenic components shared by the many clonal types of P. gingivalis. The purpose of the present study was to evaluate the extent and nature of antigenic cross-reactivity among serotypes of P. gingivalis and to identify shared antigenic components. Strains selected to represent serotypes A-D were 33277, A7A1-28 W50 and 381, respectively. Using intact cells, antibodies were raised in rabbits. Titers were assessed by enzyme-linked immunosorbent assay (ELISA) using intact cells as antigen, Western blots were prepared and biologic activity was measured as opsonization (chemiluminescence expressed as mV) and enhancement of phagocytosis and killing by polymorphonuclear leukocytes. Extensive cross-reactivity that varied greatly among serotypes was observed by ELISA. The Western blots showed an even greater extent of cross-reactivity, with shared protein components at approximately 140, 130, 37, 32 and 28 kDa and a shared variable molecular mass smear considered to be lipopolysaccharide and other carbohydrate. Additional protein components at 110, 85, 35 and 20 kDa appeared to be shared by some but not all serotypes. In the functional assays, strains 33277 and 381 were equally well opsonized by anti-33277 and anti-381 (500-650 mV) but opsonized to a much lesser extent by anti-A7A1-28 and anti-W50 (roughly 125 mV and 350 mV respectively). A7A1-28 and W50 were opsonized by all four immune sera almost equally but to a much lower extent (roughly 400 mV and 250 mV respectively). Enhancement of phagocytosis and killing in the presence of active complement mirrored opsonization with the exception that 381 was reasonably well opsonized by anti-A7A1-28 (400 mV) and anti-W50 (350 mV), but poorly killed. The protein components at 140, 130, 37 and 28 kDa shared by all of the four serotypes appear to have potential as vaccine candidate antigens.

Animals↗
PubMed2000

[Cloning and sequencing of the maize ribosome-inactivating protein gene].

A gene encoding maize Ribosome-inactivating protein was amplified by means of PCR using mRNA of maize leaves as a template, and cloned into pUC19 vector. The amplified DNA sequence has been determined, which consists of 828 bp and encodes 275 amino acid residues. Comparison with previously reported sequence shows 98.4% homologies in nucleotide sequence and 97.4% in amino acid sequence, respectively.

Amino Acid Sequence↗
PubMed1999

In vivo animal studies with gadolinium (III) texaphyrin as a radiation enhancer.

PURPOSE: Gadolinium texaphyrin (Gd-Tex, PCI-0120) is an expanded porphyrin that has demonstrated radiation enhancement. In this study, we evaluated the radiation enhancement and biolocalization of Gd-Tex in three animal tumor models. METHODS AND MATERIALS: EMT6, SMT-F, and MCa tumors were established intramuscularly or subcutaneously. Gd-Tex and other metallotexaphyrins were administered prior to single or multiple fractions of radiation. 14C-labeled Gd-Tex was used for biolocalization studies. RESULTS: Gd-Tex, in combination with radiation, produced significant tumor growth delay compared to irradiated control groups in both single and multifraction radiation studies. Gd-Tex radiation enhancement was observed only when the drug was given before, but not after irradiation. Several metallotexaphyrins, identical except for the metal ion, were studied in the EMT6 tumor model including gadolinium (Gd), lutetium (Lu), europium (Eu), yttrium (Y), and cadmium (Cd) texaphyrin complexes. Only Gd-Tex produced radiation enhancement. Biodistribution studies using 14C-labeled Gd-Tex demonstrated drug selectivity and retention in tumors growing intramuscularly compared to uninvolved muscle and plasma. CONCLUSIONS: Gd-Tex produces reproducible radiation enhancement in a variety of in vivo tumor models. This drug's unique radiochemistry, tumor selectivity, and in vivo activity suggests possible mechanisms of action not addressed by in vitro assay methods.

Animals↗
PubMed1999

Divergence of smooth muscle target and sympathetic pathway cell phenotypes in the orbit of the developing rat.

The periorbital sheath serves as a major pathway for sympathetic nerves traveling to distal orbital targets in the rat. This tissue accommodates sympathetic fiber sprouting in the neonate but becomes impassable by postnatal day 30 (PND 30). In contrast, smooth muscle target remains receptive to sympathetic ingrowth. To determine the attributes of receptive and nonreceptive tissues, we compared periorbital pathway and target tissue phenotypes prior to (PND 5 and PND 15) and after (PND 30 and PND 60) the period when pathway receptivity is lost. Both pathway cells and superior tarsal smooth muscle cells expressed alpha-smooth muscle actin and smooth muscle myosin heavy chain throughout development. At PND 5-15, both tissues also expressed vimentin, collagen IV, laminin 1 and laminin beta2, whereas fibronectin was detected only in pathway tissue. At PND 30, vimentin, collagen IV, and fibronectin were absent in tarsal muscle but were robust in pathway tissue. Laminin 1 and laminin beta2 expression was maintained in muscle; however, in pathway cells, laminin 1 declined modestly, and laminin beta2 decreased precipitously to barely detectable levels. Quantitative competitive polymerase chain reaction showed that nerve growth factor mRNA was present in the pathway throughout development at levels that were greater than both surrounding connective tissue and tarsal muscle. We conclude that the loss of pathway receptivity to sympathetic nerve ingrowth is associated with a transition from a phenotype similar to fetal smooth muscle cells to one that is more consistent with myofibroblast-like cells.

Animals↗
PubMed1999

Relationships between nerves and myofibroblasts during cutaneous wound healing in the developing rat.

Contraction of skin excision wounds is affected by age and the presence of peripheral nerves. The present study examined relationships between peripheral innervation, wound contractile cells, and rate of wound closure to determine whether these are altered during development. Full-thickness 4-mm-diameter circular flaps were excised from the interscapular skin of rats on postnatal day (PND) 5, PND 12, or PND 60. Wounds of PND 5 and PND 12 rats contracted 45% between post-wound days (WD) 3 and 5 and more slowly thereafter, with a scar 9-14% of the original wound size by WD 21. In contrast, PND 60 wounds contracted only 22% between WD 3 and 5, and the residual scar at WD 21 was 40% of the original wound size. In younger rats, alpha-smooth muscle actin-immunoreactive myofibroblasts first appeared on WD 2 and attained maximum density at WD 5. Innervation, as assessed by protein gene product 9.5 immunoreactivity, appeared by WD 3 and increased rapidly through WD 7 in younger rats. In PND 60 wounds, myofibroblasts did not appear until WD 5 and did not attain a maximum until day 10. Nerve ingrowth was not significant until WD 10 and was depressed relative to younger rats throughout the healing phase. Wound nerves were predominantly immunoreactive to calcitonin gene-related peptide, and synaptophysin-immunostaining revealed close associations between varicosities and myofibroblasts. These findings suggest that wound myofibroblasts may be a target of peripheral nerves, and delayed wound closure in mature rats is associated with deficiencies in both myofibroblasts and innervation.

Aging↗
PubMed1999

Maximal stimulation of meiotic recombination by a yeast transcription factor requires the transcription activation domain and a DNA-binding domain.

The DNA sequences located upstream of the yeast HIS4 represent a very strong meiotic recombination hotspot. Although the activity of this hotspot requires the transcription activator Rap1p, the level of HIS4 transcription is not directly related to the level of recombination. We find that the recombination-stimulating activity of Rap1p requires the transcription activation domain of the protein. We show that a hybrid protein with the Gal4p DNA-binding domain and the Rap1p activation domain can stimulate recombination in a strain in which Gal4p-binding sites are inserted upstream of HIS4. In addition, we find recombination hotspot activity associated with the Gal4p DNA-binding sites that is independent of known transcription factors. We suggest that yeast cells have two types of recombination hotspots, alpha (transcription factor dependent) and beta (transcription factor independent).

Actins↗
PubMed1999

Effect of recombinant human fibronectin polypeptide CH50 on growth and metastasis of melanoma.

AIM: To study the effect of recombinant human fibronectin polypeptide CH50 on murine melanoma growth and metastasis, and its antitumor mechanism. METHODS: Mouse and melanoma B16 cell tests were used to observe antitumor effect and mechanism of CH50. RESULTS: CH50 markedly inhibited melanoma growth and experimental lung metastasis. The melanoma weight was reduced from (2.3 +/- 1.2) g of control group to (0.7 +/- 0.8) g of test group (P < 0.05). CH50 at 0.125, 0.25, 0.5 mg/mouse reduced melanoma lung metastatic colonies from 87 +/- 49 of control group to 34 +/- 6, 14 +/- 12, 4 +/- 2, respectively. CH50 adhered to melanoma B16 cells and inhibited adhesion of B16 cells to laminin. CH50 enhanced the cytotoxicity of macrophages to melanoma B16 cells. CONCLUSION: CH50 inhibited tumor growth and metastasis of murine melanoma. The antitumor effect of CH50 is related to its adhesion ability to melanoma B16 cells and enhancing macrophage cytotoxicity.

Animals↗
PubMed1998

An SP1-like 5'-GACCACGCC-3' sequence is critical for activity of the inflammatory phospholipase A2 promoter and binds several non-zinc finger proteins.

We have previously shown that the promoter of the type IIa secreted phospholipase A2 gene contains a strong positive regulatory proximal element [-125 to -85] element B. Mutation of this element abolishes the activation of the phospholipase A2 promoter by C/EBPbeta in HepG2 cells. Liver nuclear proteins form three major and two minor complexes with this element. The [-107 to -99] 5'-GACCACGCC-3' sequence is critical for the formation of these complexes and the activity of the promoter. Although the sequence of element B is highly similar to those of Sp1 binding sites, it does not bind Sp1 or other zinc-finger proteins. Each major complex contains a single protein, the molecular masses of these proteins being 100, 90 and 75 kDa. These proteins have the same nucleotide requirements for binding, with the cytosines at positions -102, -100, -99 and the adenosine at -103 being the most important nucleotides. The activity of the phospholipase A2 promoter in HeLa cells was lower than in HepG2 cells, and was correlated with the absence of complex 3 in HeLa cell nuclear extracts. Our results suggest different roles for the proteins bound to the 5'-GACCACGCC-3' sequence. In particular, the 75-kDa protein which forms the third complex is critical for the activity of the promoter of the secretory phospholipase A2 gene.

Animals↗
PubMed1998

Cellular terrain surrounding sympathetic nerve pathways in the rat orbit: comparisons of orbital connective tissue and smooth muscle cell phenotypes.

Sympathetic axons are abundant within some orbital tissues but are absent from others. This study investigated cellular phenotypes of tissues containing sympathetic nerves en passage and compared these with phenotypes in regions devoid of sympathetic nerves and with smooth muscle targets. Two primary orbital smooth muscle targets, the tarsal muscle and orbital muscle, contained many synaptophysin-immunoreactive nerves. Target cells had ultrastructural features typical of smooth muscle and were immunoreactive for alpha-smooth muscle actin, smooth muscle myosin heavy chain, desmin, vinculin, and laminin, but not non-muscle myosin, vimentin, fibronectin, or type IV collagen; nerve growth factor (NGF) mRNA was detected by reverse transcription-polymerase chain reaction. Periorbital sheath devoid of sympathetic nerves contained elongated fibroblasts that were immunoreactive for vimentin, non-muscle myosin, and fibronectin, but not for alpha-smooth muscle actin, smooth muscle myosin heavy chain, vinculin, desmin, laminin, or type IV collagen, and did not express NGF mRNA. Regions of periorbital sheath containing sympathetic nerves had few synaptophysin-immunoreactive varicosities. Cells in this region contained myofilaments, ribosomes, and rough endoplasmic reticulum and were larger than tarsal muscle cells. They expressed NGF mRNA and showed a unique immunophenotype, reacting for vimentin, alpha-smooth muscle actin and myosin heavy chain, desmin, vinculin, laminin, and type IV collagen. This phenotype reflects both fibroblast and smooth muscle features similar to myofibroblasts or transdifferentiated smooth muscle described in other tissues. The spatial association between these cells and sympathetic nerves suggests that they may be involved in axon guidance or maintenance.

Animals↗
PubMed1998

Variations in uterine innervation during the estrous cycle in rat.

Uterine innervation undergoes profound remodeling during puberty, pregnancy, and after parturition. However, the extent to which uterine innervation may change during the estrous cycle is uncertain. The objective of the present study was to determine whether nerve fiber density of the uterine horn is altered during the estrous cycle and, if so, which subpopulations are affected. Immunostaining for the pan-neuronal marker protein gene product (PGP) 9.5 revealed fibers within the vascular zone, myometrium, and endometrium, with greater density in the ovarian and cervical regions than in the middle. In most structures, nerve density was reduced during estrus. This could not be accounted for by increased target volume, as the reduction in longitudinal muscle innervation persisted after correction for changes in target size. Immunostaining for vasoactive intestinal polypeptide-immunoreactive parasympathetic nerves revealed fibers associated predominantly with the vascular zone and circular muscle within the cervical region. No cyclical variation was detected. Calcitonin gene-related peptide-immunoreactive nerves were present within all structures, and density was highest at the ovarian end. These fibers also did not vary significantly through estrous. Dopamine beta-hydroxylase-immunoreactive sympathetic nerves innervated all structures, with greater density in the ovarian end. These fibers were reduced substantially during estrus, but the decline was also significant in proestrus, thus preceding that detected by using the pan-neuronal marker. We conclude that the estrous cycle in rat is accompanied by structural remodeling of sympathetic nerves by way of retraction or degeneration of terminal fibers during estrus. The structural loss of the terminal axon apparently is preceded by depletion of catecholamine-synthesizing enzyme.

Animals↗
PubMed1998

Antisense in abundance: the ribosome as a vehicle for antisense RNA.

Insertions at some sites within rRNA variable regions can be tolerated without affecting rRNA function. Antisense RNAs inserted at such sites in the T. thermophila rRNA can eliminate phenotypically or immunologically detectable gene expression of three genes tested. This unusually effective antisense activity is probably due to the abundance, stability and favourable intracellular localization of these antisense rRNAs with respect to mRNAs. Since antisense RNAs function very well as a part of the rRNA, rRNA might also be useful as a vehicle for other RNAs that might affect cell function such as protein binding sites or trans-acting ribozymes. The robust function of the antisense ribosome system in T. thermophila should allow the use of this system to specifically suppress gene expression and to clone genes by their null or hypomorphic phenotypes. The use of the antisense ribosome in other eukaryotes has yet to be explored, but the realization of this goal is well within the realm of possibility.

Animals↗
PubMed1998

Augmentation of recombinant fibronectin polypeptide CH50 on the antitumor function of macrophages.

We prepared an anti-metastatic polypeptide, recombinant fibronectin polypeptide CH50, and finished the preliminary identification of its functions. In this paper, we studied the effect of this polypeptide on the function of macrophages. CH50 can significantly augment the production of nitric oxide(NO) by macrophages in a dose-dependent manner. The continuous presence of CH50 had a much stronger effect. In the presence of CH50, the cytotoxicity of macrophages to melanoma B16/F1 cells was significantly enhanced, and a stronger effect was obtained if CH50 was present continuously. CH50 polypeptide and IFN-gamma have a synergistic effect on the production of NO by macrophages and the cytotoxicity of macrophages on tumor cells. In the in vivo experiments, CH50 can inhibit the growth of tumor cells, and have a better effect in the presence of IFN-gamma. Our results suggest that recombinant fibronectin polypeptide CH50 has two functions: one is to inhibit the metastasis of tumor cells, and the other one is to augment the function of macrophages. And this polypeptide will be potentially useful in tumor therapy.

Animals↗
PubMed1998

Effect of fragment Asp1961-Glu1978 in fibronectin on the expression of triple-domain polypeptide in E. coli.

Two plasmids were constructed and used to express two triple-domain recombinant polypeptide of human fibronectin (FN). The cDNAs in plasmids code for two polypeptides, CH62 (Pro1239-Ser1515 of FN linked with Ala1690-Val2049 through Met) and CH63 (CH62 without Ile1850-Glu1978). The expression level of CH62 in E. coli was very low, but that of CH63 was very high. The results suggests that Asp1961-Glu1978 in FN is a key sequence influencing the expression of triple-domain polypeptide in E. Coli. After being dissolved and renatured, CH63 can be purified by heparin-agarose affinity chromatography. Both of the cell-binding domains in the recombinant polypeptide were functional. The production of CH63 provides a fundamental basis for further study of recombinant products with better anti-metastasis function.

Animals↗
PubMed1998

Photodynamic therapy of B16F10 murine melanoma with lutetium texaphyrin.

Photodynamic therapy (PDT) of pigmented melanoma has generally been unsuccessful because of insufficient light penetration in such tissues. In this study, the responsiveness of the heavily pigmented B16F10 murine melanoma to lutetium texaphyrin (PCI-0123), a water-soluble sensitizer with strong absorbance in the near infrared (700-760 nm), was examined. These studies were carried out in both normal and ApoE deficient C57BL/6 mice. The latter strain exhibits a lipoprotein profile more like humans (low density lipoprotein > high density lipoprotein) than rodents (high density lipoprotein >> low density lipoprotein). Under optimal conditions of drug dose, light dose, and interval between drug administration and irradiation--the median survival time of C57BL/6 tumor bearing mice was approximately doubled (29 d) compared with tumor bearing control animals (13 d). The life-span of the ApoE knockout mice was greater (33 d) than the C57BL/6 animals (23 d) when irradiation occurred 3 h after administration of a 10 micromol per kg drug dose. The greater efficacy of PDT in the ApoE deficient mice was associated with more rapid clearance of drug from the blood, greater accumulation of sensitizer in tumor tissue, and substantially greater drug binding to the very low density lipoprotein/low density lipoprotein plasma fraction. Confocal laser scanning microscopy showed that the predominant subcellular site of photosensitizer binding was to melanosomes; costaining was performed with Mel-5. Melanosomes are susceptible to oxidative stress. Photo-oxidation, mediated by PCI-0123 PDT, could potentially overload an already highly oxidized stressed state leading to cell death. The good tissue penetration depth achieved by PCI-0213 mediated PDT and the activation of melanosomes makes PDT of pigmented melanoma, for the first time, clinically relevant.

Animals↗
PubMed1998

[Microsurgical repair of the defect with large area of bare tibia].

OBJECTIVE: To study the best method in repairing the defect with a large area of bare tibia. METHOD: Three hundred and twenty-two cases of large bare tibia defects were treated by three microsurgical methods. RESULTS: The bare tibiae in the 322 cases ranging from 12 x 3 cm to 24.0 x 3.5 cm were covered with myocutaneous flaps. Primary wound healing was achieved in 300 cases and delayed healing in 22 cases. All the cases were followed-up for 1 to 5 years. The function of the lower limbs was evidently improved. None of them was amputated due to deficit of skin coverage. The patients were all satisfied with the operative results. CONCLUSION: Transposition of the bridging skin flap pedicaled with the contralateral posterior tibial blood vessels can cover extensive bare tibia to avoid amputation. Other myocutaneous flaps from thoraco-umbilical, tensor muscle of fascia lata and scapular-lateral chest areas are good options too.

Accidents, Traffic↗
PubMed1997

Decreased neuronal nitric oxide synthase-immunoreactivity and NADPH-diaphorase activity in rat pterygopalatine ganglion parasympathetic neurons and cerebrovascular innervation following long-term sympathectomy.

Neural control of tissue perfusion is mediated predominantly by sympathetic vasoconstrictor and, in some tissues, parasympathetic vasodilator systems. The objective of this study was to determine if changes occur within parasympathetic vasodilator neurons supplying cranial vessels after sympathectomy. Cranial sympathetic innervation was excised unilaterally, and 6 weeks later pterygopalatine ganglion neurons were evaluated for expression of neuronal nitric oxide synthase immunoreactivity (NOS-ir) and NADPH-diaphorase activity. Relative to the unoperated side, the number of parasympathetic neurons staining densely either for NOS or for NADPH-diaphorase decreased by 37% and 47%, respectively, whereas unstained somata increased by 51% and 48%. Internal carotid artery NOS-ir innervation density was reduced by 35%. These findings are consistent with a down-regulation of nitrergic properties in some cranial parasympathetic neurons after sympathectomy.

Animals↗