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Biomedical subjects

W Yu

Publications and source records attributed to W Yu.

At least 343 records · Page 19Linked to original sources
PubMed1994

Heterotopic liver transplantation in rats: effect of intrahepatic islet isografts and split portal blood flow on liver integrity after auxiliary liver isotransplantation.

BACKGROUND: Auxiliary heterotopic liver grafts atrophy in the absence of portal venous inflow; evidence suggests that an islet-derived hepatotrophic factor may exist in the portal drainage. Here we examine the effects of intrahepatic islet isografts in maintaining hepatocyte integrity in Wistar Furth rats with one of several types of arterialized auxiliary liver isografts. METHODS: In type 1 procedures the auxiliary liver was interposed into the recipient infrarenal vena cava and perfused through the graft portal vein with caval blood. In type 2 procedures the donor infrahepatic vena cava was anastomosed end-to-side to the recipient vena cava and the recipient portal vein was diverted to the graft portal vein. Both types of auxiliary grafts were arterialized; bile duct drainage was through the duodenum. Syngeneic islets were isolated and embolized into the portal veins of one half of the donor type 1 or native type 2 livers (1500 to 1700 islets). Finally, we performed six type 3 procedures in which a type 2 procedure was performed except that the portal blood flow was split so that the portal vein receiving the splenic, gastric, pancreatic, and duodenal drainage supplied the native liver and that the common mesenteric vein supplied the auxiliary graft with equivalent portal blood flow. Atrophy in heterotopic and native livers were compared for the three models after 3 months. RESULTS: Intrahepatic islets in type 1 auxiliary liver isografts without portal venous inflow did not prevent graft atrophy. Conversely, native livers deprived of portal venous inflow in our type 2 procedures, regardless of the presence of intrahepatic islet isografts, atrophied relative to auxiliary liver grafts in which portal venous inflow was provided by diverting the recipient's portal vein to the graft. In type 3 recipients atrophy was greater in the native livers than in the grafts. CONCLUSIONS: The results of our study suggest that islet-derived factors are not sufficient to prevent hepatocellular atrophy in auxiliary rat liver transplantation models and that a potent hepatotrophic factor may exist in the venous drainage of the bowel distal to the duodenum.

Animals↗
PubMed1993

Identification of the facile gas-phase cleavage of the Asp-Pro and Asp-Xxx peptide bonds in matrix-assisted laser desorption time-of-flight mass spectrometry.

Abundant ions corresponding to the gas-phase cleavage of the Asp-Pro and Asp-Xxx bonds of peptides in the process of matrix-assisted laser desorption were observed using a time-of-flight mass spectrometer equipped with both linear and reflector mass analyzers. Peptides containing the N-terminal sequence, Asp-Pro ... from an endoproteinase Asp-N digest yielded one peak in the molecular ion region in the linear mode and two equally abundant peaks in the reflector mode TOF mass spectra. The lower molecular masses in the reflector mode mass spectra could be eliminated by removing the Asp residue or derivatizing its side-chain carboxyl group. The observed mass differences did not correspond to any amino acid; however, by lowering the potential of the reflector to correct for the energy loss the mass difference was determined to be 115 Da, i.e., Asp. The extent and rate of this decomposition was compared with that obtained using a four-sector tandem mass spectrometer in the MS/MS mode of operation without and with a collision gas at collision cell potentials of 3.0 and 9.86 kV. These data suggest the Asp-Pro peptide bond is more labile than other peptide bonds in the gas phase. Abundant metastable decomposition of internal Asp-Pro bonds was also observed in larger peptides and proteins. Based on these latter data, a mechanism for this gas-phase cleavage is proposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Site-specific carbohydrate identification in recombinant proteins using MALD-TOF MS.

The utility of matrix-assisted laser desorption time-of-flight (MALD-TOF) mass spectrometry for the analysis of recombinant glycopeptides is discussed and compared to information which may be obtained by fast atom bombardment mass spectrometry (FABMS) and tandem mass spectrometry (MS/MS). MALD-TOF appears to be 10-100 times more sensitive than FAB MS for the analysis of underivatized glycopeptides, providing qualitative site-specific information regarding the carbohydrate microheterogeneity without the extensive isolation and derivatization procedures required to obtain similar information by FAB MS. Analysis of a digest mixture in the positive and negative ion mode of MALD-TOF indicated that, in mixtures, sialylated glycopeptides are preferentially detected in the negative ion mode. The determination of the molecular masses of a glycopeptide with MALD-TOF prior to and after treatment with a variety of specific glycosidases, often without removal of the buffers, coupled to a comparison of molecular mass information available from a carbohydrate database facilitates the assignment of a carbohydrate composition. The vast majority of the molecular ion signal observed in the linear mode for sialylated glycopeptides are metastable ions. Reflector mass spectra reveal a shift to lower mass consistent with the loss of most of the neuraminic acid residues. The loss of Hex and HexNAc residues is also observed. Sequential lowering of the reflector potential reveals structurally significant fragment ions representing the carbohydrate and peptide portions of the molecule.

Amino Acid Sequence↗
PubMed1993

Protein dynamics in minimyoglobin: is the central core of myoglobin the conformational domain?

The kinetics of CO binding to the horse myoglobin fragment Mb-(32-139), the so-called "mini-Mb," were investigated by laser flash photolysis in 0.1 M phosphate buffer and in buffer with 75% (vol/vol) glycerol. The reaction displays complex time courses that can be approximated satisfactorily only with a sum of five exponentials. The features of the kinetic components and a comparison of the deoxy-minus-carbonyl difference spectra of mini-Mb and horse Mb obtained under equilibrium conditions, with the kinetic difference spectra resulting from the global analysis of the traces recorded between 400 and 450 nm, show that CO binding to mini-Mb is accompanied by large structural changes. In view of the fact that mini-Mb is an approximation of the Mb-(31-105) fragment encoded by the central exon of the Mb gene, this finding is particularly relevant. On the basis of our data and previous reports [De Sanctis, G., Falcioni, G., Giardina, B., Ascoli, F. & Brunori, M. (1988) J. Mol. Biol. 200, 725-733; De Sanctis, G., Falcioni, G., Grelloni, F., Desideri, A., Polizo, F., Giardina, B., Ascoli, F. & Brunori, M. (1992) J. Mol. Biol. 222, 637-643], we propose that the protein fragment encoded by the central exon of the Mb gene is the domain responsible for ligand-linked conformational transitions, while the two terminal fragments dampen the amplitude of the structural changes that accompany ligand binding, thus rendering the protein stable and kinetically more efficient in its physiological function.

Animals↗
PubMed1993

Structure-dynamics-function relationships in Asian elephant (Elephas maximus) myoglobin. An optical spectroscopy and flash photolysis study on functionally important motions.

In this work we report the thermal behavior (10-300 K) of the Soret band lineshape of deoxy and carbonmonoxy derivatives of Asian elephant (Elephas maximus) and horse myoglobins together with their carbon monoxide recombination kinetics after flash photolysis; the results are compared to analogous data relative to sperm whale myoglobin. The Soret band profile is modeled as a Voigt function that accounts for the coupling with high and low frequency vibrational modes, while inhomogeneous broadening is taken into account with suitable distributions of purely electronic transition frequencies. This analysis makes it possible to isolate the various contributions to the overall lineshape that; in turn, give information on structural and dynamic properties of the systems studied. The optical spectroscopy data point out sizable differences between elephant myoglobin on one hand and horse and sperm whale myoglobins on the other. These differences, more pronounced in deoxy derivatives, involve both the structure and dynamics of the heme pocket; in particular, elephant myoglobin appears to be characterized by larger anharmonic contributions to soft modes than the other two proteins. Flash photolysis data are analyzed as sums of kinetic processes with temperature-dependent fractional amplitudes, characterized by discrete pre-exponentials and either discrete or distributed activation enthalpies. In the whole temperature range investigated the behavior of elephant myoglobin appears to be more complex than that of horse and sperm whale myoglobins, which is in agreement with the increased anharmonic contributions to soft modes found in the former protein. Thus, to satisfactorily fit the time courses for CO recombination to elephant myoglobin five distinct processes are needed, only one of which is populated over the whole temperature range investigated. The remarkable convergence and complementarity between optical spectroscopy and flash photolysis data confirms the utility of combining these two experimental techniques in order to gain new and deeper insights into the functional relevance of protein fluctuations.

Animals↗
PubMed1993

Microtubule nucleation and release from the neuronal centrosome.

We have proposed that microtubules (MTs) destined for axons and dendrites are nucleated at the centrosome within the cell body of the neuron, and are then released for translocation into these neurites (Baas, P. W., and H. C. Joshi. 1992. J. Cell Biol. 119:171-178). In the present study, we have tested the capacity of the neuronal centrosome to act as a generator of MTs for relocation into other regions of the neuron. In cultured sympathetic neurons undergoing active axonal outgrowth, MTs are present throughout the cell body including the region around the centrosome, but very few (< 10) are directly attached to the centrosome. These results indicate either that the neuronal centrosome is relatively inactive with regard to MT nucleation, or that most of the MTs nucleated at the centrosome are rapidly released. Treatment for 6 h with 10 micrograms/ml nocodazole results in the depolymerization of greater than 97% of the MT polymer in the cell body. Within 5 min after removal of the drug, hundreds of MTs have assembled in the region of the centrosome, and most of these MTs are clearly attached to the centrosome. A portion of the MTs are not attached to the centrosome, but are aligned side-by-side with the attached MTs, suggesting that the unattached MTs were released from the centrosome after nucleation. In addition, unattached MTs are present in the cell body at decreasing levels with increasing distance from the centrosome. By 30 min, the MT array of the cell body is indistinguishable from that of controls. The number of MTs attached to the centrosome is once again diminished to fewer than 10, suggesting that the hundreds of MTs nucleated from the centrosome after 5 min were subsequently released and translocated away from the centrosome. These results indicate that the neuronal centrosome is a highly potent MT-nucleating structure, and provide strong indirect evidence that MTs nucleated from the centrosome are released for translocation into other regions of the neuron.

Animals↗
PubMed1993

An observation on flash evoked cortical potentials and Qigong meditation.

The purpose of this study was to investigate the functional state of the cerebral cortex during Qigong meditation with flash visual evoked potentials (F-VEPs) recorded from the occipital scalp in four groups of adults. The first group included 14 subjects who had exercised in Neiyang Gong for 0.5-5.5 years. The second group was composed of 12 subjects who had practiced Neiyang Gong for only 0.5-3 months. Eleven subjects who had never practiced Qigong before made up the third group and served as control. Eleven Qigong practitioners constituted the fourth group. It was found that F-VEP amplitudes were increased in the first group and decreased in the fourth group with the exception of one subject during Qigong meditation. No significant changes were found in the second group and controls. The results were discussed and it is shown that Qigong mediation may have either facilitative or inhibitory effects on the visual cortex depending on the Qigong methods practiced by different individuals.

Adult↗
PubMed1993

[Immunohistochemical localization of CEA,EMA and keratin in salivary mucoepidermal carcinoma]

Localizations of CEA,EMA and keration in 19 cases of mucoepidermal carcinomas were investigated using the indirect immunoperoxidase technique.The results showed CEA was negative in normal salivary glands and showed faint reaction in glands near carcinoma tissue.Keratin and EMA were localized in some myoepithelial cells.The positive rates in carcinoma tissue were 78.9%,89.5% and 84.2%,respectively.The positive rates and staining intensity of CEA and EMA in carcinoma tissue gradually decreased with the decline of tumor differentitation,but that of keratin showed no variation.the author consider that CEA and EMA could become good indices in clinically diagnosing mucoepithelial carcinoma and determining tumor differentiation type cell in mucoepidermal carcinoma and have a potential to multiply express the tumor elements of epithelium and/or mesenchyma.

Journal Article↗
PubMed1993

High level expression of human prourokinase cDNA in Chinese hamster ovary cells.

We have used Chinese hamster ovary (CHO) cells to express high levels of human prourokinase gene cDNA with recourse to construction of good expression vector, the improvement of transfection technique and gene coamplification. First, we constructed expression plasmid pMG10102 by placing pro-UK cDNA under the control of SR alpha promoter/SV40 polyadenylation signals and expressed it transiently in COS-7 cells. Expression level was about 5 times higher than with SV40 early promoter. Linear plasmids pMG10102 and pSV2-dhfr were then cotransfected into CHO-dhfr cells by calcium phosphorate coprecipitation and cells were cultured in selective medium. Twenty transformants expressing pro-UK were picked, the range of expression levels was 12.5-100IU/10(6) cells/day. When subjected to stepwise selection of methotrexate (MTX), the stable cell lines were obtained that secreted up to 400-500IU/10(6) cells/day. Western blot analysis showed that molecular weight of secreted recombinant pro-UK was the same as that of natural pro-UK, which is 52 kDa, and more than 60% of expression production was single chain urokinase (rscUK) without protease inhibitor in medium.

Animals↗
PubMed1993

[The influences of acupuncture on the cortical evoked potentials in rabbits].

In this work the visual, auditory, somatosensory evoked cortical potentials as well as raw EEGs were observed in 31 rabbits either anesthetized with urethane or conscious. The effects of acupuncture on them were as follows: 1) The main components of the evoked potentials were significantly depressed; 2) The raw EEGs were desynchronized while the animals appeared to be slightly activated; 3) Both the integral values of raw EEGs and the powers of lower frequency waves (1-3.99 Hz) were decreased and positively correlated well with the amplitudes of the main components of the evoked potentials. Therefore, It could not be ruled out that the effects of acupuncture on the evoked potentials are secondary to the changes of EEGs, and it is suggested that the inhibition of evoked potentials during acupuncture does not necessarily mean that the cerebral cortex is in an inhibitory state.

Animals↗
PubMed1993

Cloning of human prourokinase cDNA without the signal peptide and expression in Escherichia coli.

Human prourokinase (pro-UK) cDNA without the signal peptide was obtained using synthetic oligonucleotide and DNA recombination techniques and was successfully expressed in E. coli. The plasmid pMMUK which contained pro-UK cDNA (including both the entire coding sequence and the sequence for signal peptide) was digested with Hind III and PstI, so that the N-terminal 371-bp fragment could be recovered. A 304-bp fragment was collected from the 371-bp fragment after partial digestion with Fnu4HI in order to remove the signal peptide sequence. An intermediate plasmid was formed after this 304-bp fragment and the synthetic oligonucleotide was ligated with pUC18. Correctness of the ligation was confirmed by enzyme digestion and sequencing. By joining the PstI-PstI fragment of pro-UK to the plasmid we obtained the final plasmid which contained the entire coding sequence of pro-UK without the signal peptide. The coding sequence with correct orientation was inserted into pBV220 under the control of the temperature-induced promoter PRPL, and mature pro-UK was expressed in E. coli at 42 degrees C. Both sonicated supernatant and inclusion bodies of the bacterial host JM101 showed positive results by ELISA and FAPA assays. After renaturation, the biological activity of the expressed product was increased from 500-1000IU/L to about 60,000IU/L. The bacterial pro-UK showed a molecular weight of about 47,000 daltons by Western blot analysis. It can be completely inhibited by UK antiserum but not by t-PA antiserum nor by normal rabbit serum.

Base Sequence↗
PubMed1993

CT detection of wrist bone erosion in rheumatoid arthritis.

A correlative radiographic and CT study of the wrists of 30 patients with rheumatoid arthritis (RA) was reported. The results showed that sensitivity of CT in detecting wrist erosion is superior to that of conventional radiograph. Accordingly, wrist CT scanning is useful for early diagnosis of RA.

Adult↗
PubMed1993

Transluminal placement of a prosthetic graft-stent device for treatment of subclavian artery aneurysm.

A 78-year-old man was seen with an expanding 5 cm false aneurysm of the right subclavian artery. This was treated by an intraluminal graft-stent device introduced through the brachial artery via a 16 F sheath. The graft was constructed from two polytetrafluoroethylene patches of 0.4 mm thickness and anchored in the subclavian artery by an 8 mm stainless steel stent. The procedure was monitored by an image intensifier. Completion arteriography and postoperative duplex scanning confirmed normal flow through the subclavian artery with no communication between the lumen and the aneurysmal sac. The patient recovered without complication.

Aged↗