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Biomedical subjects

X Lin

Publications and source records attributed to X Lin.

At least 325 records · Page 18Linked to original sources
PubMed1996

A novel gene selectively expressed in the cerebellum.

A cDNA clone encoding a novel protein (Cer-1) was isolated from a mouse cerebellar cDNA library. The deduced amino acid sequence of Cer-1 is not homologous to other sequences in the protein sequence data base. RNA blot analysis suggests that expression of Cer-1 RNA occurs selectively in the adult cerebellum and in purified cultures of cerebellar granule neurons. An increase in its expression correlates with the timing of granule neuron differentiation in the cerebellum. Thus, the expression of Cer-1 may provide a selective marker for terminal differentiation of cerebellar granule neurons.

Amino Acid Sequence↗
PubMed1996

Mechanism of taxadiene synthase, a diterpene cyclase that catalyzes the first step of taxol biosynthesis in Pacific yew.

The first committed step in the formation of taxol has been shown to involve the cyclization of geranylgeranyl diphosphate to taxa-4(5),11(12)-diene. The formation of this endocyclic diterpene olefin isomer as the precursor of taxol was unexpected, since the exocyclic isomer, taxa-4(20),11(12)-diene, had been predicted as the initial product of the taxol pathway on the basis of metabolite co-occurrence. [1-2H2,20-2H3] and [20-2H3]geranylgeranyl diphosphates were employed as substrates with the partially purified taxadiene synthase from Pacific yew (Taxus brevifolia) stems to examine the possibility of a preliminary cyclization to taxa-4(20),11(12)-diene followed by isomerization to the more stable endocyclic double bond isomer. GLC-MS analysis of the derived taxa-4(5),11(12)-diene, via selected ion monitoring of the parent ion and the P-15 and C-ring fragment ions, compared to those of unlabeled standard, showed the olefin product to possess a deuterium enrichment essentially identical to that of the acyclic precursor, thus ruling out the putative isomerization step. With [4-2H2]geranylgeranyl diphosphate as substrate, similar product analysis established the enzymatically derived taxa-4(5),11(12)-diene to contain only one deuterium atom, consistent with direct formation from a taxenyl cation by deprotonation at C5. (+/-)-Casbene, (+/-)-verticillene, and (+/-)-taxa-4(20),11(12)-diene were tested as possible olefinic intermediates in taxa-4(5),11(12)-diene formation by a series of inhibition, trapping, and direct conversion experiments; no evidence was obtained that these exogenous olefins could serve as intermediates of the cyclization reaction. However, GLC-MS analysis of the taxadiene product derived by enzymatic cyclization of [1-3H]geranylgeranyl diphosphate in 2H2O indicated little incorporation of deuterium from the medium and suggested a rapid internal proton transfer in a tightly bound olefinic intermediate. Analysis of the enzymatic product generated from [10-2H1]geranylgeranyl diphosphate confirmed the intramolecular hydrogen transfer from C11 of a verticillyl intermediate to the C-ring of taxa-4(5),11(12)-diene. From these results, a stereochemical mechanism is proposed for the taxadiene synthase reaction involving the initial cyclization of geranylgeranyl diphosphate to a transient verticillyl cation intermediate, with transfer of the C11 alpha-proton to C7 to initiate transannular B/C-ring closure to the taxenyl cation, followed by deprotonation at C5 to yield the taxa-4(5),11(12)-diene product directly.

Isomerases↗
PubMed1996

Characterization and sequence analysis of the human homeobox-containing gene GBX2.

Polymerase chain reaction (PCR) was used to amplify portion of homeobox genes present in a human 11-week fetal brain cDNA library. One of these PCR products was determined by sequencing to be the Gastrulation and brain specific-2 gene (GBX2). Screening this human fetal brain cDNA library with probes specific for GBX2 led to the identification of a 2151-bp cDNA clone. The nucleotide sequence of the cDNA clone encodes for a protein of 347 amino acid residues. The amino acid sequence of the GBX2 homeodomain is identical (100%) to the that of homologous gene, Gbx2, expressed in the developing mouse embryo and virtually identical (97%) to a gene expressed in the developing chicken embryo, CHox7. The 5' end of the GBX2 gene contains a CpG island in the untranslated region and a trinucleotide (CCG)8 repeat in the coding region. The amino-terminal end of the GBX2 protein is proline-rich, with 30 proline residues in one stretch of 120 amino acids. A single 2.2-kb transcript was detected by Northern analysis in the developing human CNS as well as in other tissues. The human genomic clone for GBX2 was also isolated, characterized, and mapped to 2q36(d)-q37 by somatic cell hybrid analysis and fluorescence in situ hybridization. These studies provide a framework for designing future experiments that are needed to determine the functional significance of this gene in CNS development.

Amino Acid Sequence↗
PubMed1996

Comparison of the grignard deacylation TLC and HPLC methods and high resolution 13C-NMR for the sn-2 positional analysis of triacylglycerols containing gamma-linolenic acid.

There is increasing evidence that the fatty acid, gamma-linolenic acid (GLA) is the effective component found in evening primrose oil (EPO) which has been shown to bring about clinical improvement in a number of disease conditions. The two major triacylglycerols (TAGs) in EPO are trilinolein (LLL) and a TAG species containing one GLA and two linoleic (LA) fatty acid chains. This latter TAG, called dilinoleoyl-mono-gamma-linolenin (DLMG or Oenotheral), makes up about 15% by weight of EPO and accounts for over one-half of the total amount of GLA present in EPO. Although DLMG is comprised of three possible isomers, the abbreviation is used to represent the naturally occurring mixture of these isomers. We have isolated DLMG from EPO and also prepared its three possible isomers, sn-GLL, sn-LGL and sn-LLG, and carried out the sn-2 positional analysis using three different approaches, namely, Grignard deacylation TLC and HPLC methods and high resolution 13C-NMR spectroscopy. The results of the sn-2 positional analysis for both the natural and synthetic TAGs containing LA and GLA in this study using the three approaches are all in very good agreement. This indicates that the three positional analysis methods are valid within their acceptable error margin and can be used with confidence in determining the fatty acid composition of the sn-2 position. Given the increased availability of NMR spectrometers this method might prove to be the easiest and most convenient in determining the sn-2 position for oil or TAG samples that contain a small number of different fatty acids providing all the 13C-NMR carbonyl resonances are well resolved.

Anti-Inflammatory Agents↗
PubMed1996

Covalent binding of peptides to the N-terminal hydrophobic region of cardiac troponin C has limited effects on function.

Exposure of an N-terminal hydrophobic region in troponin C is thought to be important for the regulation of contraction in striated muscle. To test this hypothesis, single Cys residues were engineered at positions 45, 81, 84, or 85 in the N-terminal hydrophobic region of cardiac troponin C (cTnC) to provide specific sites for attachment of blocking groups. A synthetic peptide, Ac-Val-Arg-Ala-Ile-Gly-Lys-Leu-Ser-Ser, or biotin was coupled to these Cys residues, and the covalent adducts were tested for activity in TnC-extracted myofibrils. Covalent modification of cTnC(C45) had no effect on maximal myofibril ATPase activity. Greatly decreased myofibril ATPase activity (70-80% inhibited) resulted when the peptide was conjugated to Cys-81 in cTnC(C81), while a lesser degree of inhibition (10-25% inhibited) resulted from covalent modification of cTnC(C84) and cTnC(C85). Inhibition was not due to an altered affinity of the cTnC(C81)/peptide conjugate for the myofibrils, and the Ca2+ dependence of ATPase activity was essentially identical to the unmodified protein. Thus, a subregion of the N-terminal hydrophobic region in cTnC is sensitive to disruption, while other regions are less important or can adapt to rather bulky blocking groups. The data suggest that Ca(2+)-sensitizing drugs may bind to the N-terminal hydrophobic region on cTnC but not interfere with transmission of the Ca2+ signal.

Amino Acid Sequence↗
PubMed1996

The expression of MEF2 genes is implicated in CNS neuronal differentiation.

The myocyte enhancer factor-2 (MEF2) proteins are transcription factors required for muscle differentiation. In the present study we examined MEF2 expression in developing cerebellar granule neurons. In the developing postnatal cerebellum, RNA blot analysis revealed that MEF2A and MEF2D RNA levels increase after birth. The majority of this increase occurs around postnatal day 9 reaching a peak at postnatal day 15-18 which is maintained in adults. This time course of expression coincides with the expression of GABA(A) receptor alpha6 subunit RNA, a marker for the differentiation of the mature cerebellar granule neurons. We further observed, using the polyclonal antibody generated against an MEF2A peptide, that MEF2 protein expression occurs primarily in the internal granule cell layer of the developing cerebellum. Thus, MEF2 expression increases as granule neurons differentiate and mature. Experiments also indicated that MEF2 expression not only occurs in the cerebellum but also in other regions of the CNS. In adult mice, expression of RNA for the MEF2 isoforms A, C and D occurs throughout the CNS. MEF2A and D expression occurs at highest levels in the olfactory bulb, hippocampus and cerebellum. The expression of MEF2C differs with low levels of expression in the cerebellum and hindbrain. Using the MEF2A polyclonal antibody, we observed a similar adult pattern of expression for the MEF2 protein with high level of expression in the olfactory bulb, cortex, hippocampus, thalamus and cerebellum. These observations suggest that MEF2 molecules may be an important factor involved in CNS neuron differentiation similar to their role in muscle differentiation.

Amino Acid Sequence↗
PubMed1996

Preliminary studies on the role of plasminogen activator in seminal plasma of human and rhesus monkey.

Two types of plasminogen activators (PA), tissue type (tPA) and urokinase type (uPA), were identified in the seminal plasma of both the human and the rhesus monkey. We studied the possible relationship between PA activities in the seminal plasma and the sperm counts and motility and demonstrated that: (i) PA activity in human seminal plasma from infertile patients was associated with immotile spermatozoa; (ii) the treatment of fertile men with testosterone enanthate (TE) to induce azoospermia was accompanied by an increase in seminal PA activity; (iii) when monomer T4 (isolated from multiglycosides of Tripterygium wilforddi) was administered to fertile male rhesus monkeys to induce azoospermia, PA activities in seminal plasma increased considerably; and (iv) immunocytochemistry studies showed that both uPA and PAI-1 antigens were localized on the surface of human spermatozoa, indicating that human spermatozoa were capable of binding uPA and PAI-1 through their receptors or forming a complex. These data demonstrate that seminal PA activity may be related to azoospermia, and possibly, to the fertilizing capability of spermatozoa in primates.

Adult↗
PubMed1996

Isolation and characterization of a diverse set of genes from carrot somatic embryos.

The early events in plant embryogenesis are critical for pattern formation, since it is during this process that the primary apical meristems and the embryo polarity axis are established. However, little is known about the molecular events that are unique to the early stages of embryogenesis. This study of gene expression during plant embryogenesis is focused on identifying molecular markers from carrot (Daucus carota) somatic embryos and characterizing the expression and regulation of these genes through embryo development. A cDNA library, prepared from polysomal mRNA of globular embryos, was screened using a subtracted probe; 49 clones were isolated and preliminarily characterized. Sequence analysis revealed a large set of genes, including many new genes, that are expressed in a variety of patterns during embryogenesis and may be regulated by different molecular mechanisms. To our knowledge, this group of clones represents the largest collection of embryo-enhanced genes isolated thus far, and demonstrates the utility of the subtracted-probe approach to the somatic embryo system. It is anticipated that many of these genes may serve as useful molecular markers for early embryo development.

Animals↗
PubMed1996

Effects of active warm-down and carbohydrate feeding on free fatty acid concentrations after prolonged submaximal exercise.

We examined the effects of active warm-down (AWD) and carbohydrate ingestion on plasma levels of free fatty acids (FFAs) and glucose changes into recovery following prolonged submaximal exercise. Subjects in Group 1 cycled at 70% of maximal oxygen uptake (VO2max); carbohydrate (CHO) or placebo (PLA) was ingested 15 min before and 45 min during exercise. In the AWD experiment, exercise was followed immediately by an AWD and subjects were given a placebo solution. Group 2 subjects consumed CHO or PLA at 75 min during and after exercise at 70% VO2max. ANOVA revealed a significant decrease in blood glucose levels only in Group 1, with a concomitant increase in FFA concentrations during exercise in both groups. Carbohydrate ingestion in Groups 1 and 2 significantly decreased the normal response of FFAs during exercise and markedly reduced the normal elevation of FFAs in recovery. AWD following submaximal exercise had no effect on plasma FFA elevations in recovery. These results suggest that carbohydrate ingestion, but not active warm-down, attenuates FFA elevations in recovery.

Adult↗
PubMed1996

Hydrolysis of feather keratin by immobilized keratinase.

Keratinase isolated from Bacillus licheniformis PWD-1 was immobilized on controlled-pore glass beads. The immobilized keratinase demonstrated proteolytic activities against both insoluble feather keratin and soluble casein. It also displayed a higher level of heat stability and an increased tolerance toward acidic pHs compared with the free keratinase. During a continuous reaction at 50(deg)C, the immobilized keratinase retained 40% of the original enzyme activity after 7 days. The immobilized keratinase exhibits improved stability, thereby increasing its potential for use in numerous applications.

Journal Article↗
PubMed1996

Theiler's virus persistence and demyelination in major histocompatibility complex class II-deficient mice.

Mice with targeted disruption of the A beta gene of major histocompatibility complex class II molecules (Abo) were used to investigate the role of class II gene products in resistance or susceptibility to virus-induced chronic demyelination in the central nervous system (CNS). Class-II-deficient mice from the resistant H-2b [H-2b(Abo)] and nonmutant H-2b backgrounds were infected with Theiler's murine encephalomyelitis virus intracerebrally and examined for CNS virus persistence, demyelination, and neurologic clinical signs. Virus titers measured by plaque assays showed that 8 of 10 normally resistant nonmutant H-2b mice had cleared the virus within 21 days, whereas the other 2 mice had low titers. In contrast, all class II-deficient Abo mice had high virus titers for up to 90 days after infection (4.30 log10 PFU per g of CNS tissue). Virus antigens and RNA were localized to the brains (cortex, hippocampus, thalamus, and brain stem) and spinal cords of Abo mice. Colocalization identified persistent Theiler's murine encephalomyelitis virus in oligodendrocytes and astrocytes but not in macrophages. There was demyelination in 11 of 23 and 6 of 9 Abo mice 45 and 90 days after virus infection, respectively, whereas no demyelination was observed in infected nonmutant H-2b mice. Demyelinating lesions in Abo mice showed virus-specific CD8+ T cells and macrophages but no CD4+ T cells. Spasticity and paralysis were observed in chronically infected Abo mice but not in the nonmutant H-2b mice. These findings demonstrate that class II gene products are required for virus clearance from the CNS but not for demyelination and neurologic disease.

Animals↗
PubMed1996

DNA damage, micronucleus formation, and cell death from 125I decays in DNA.

CHO cells were pulse-labeled with 125I-iododeoxyuridine, harvested 30 min or 5 h after labeling, and stored at -196 degrees C for accumulation of 125I decays. The 30- min groups yielded low-LET survival curves (large shoulder, D0 136 decays/cell); 5-h groups showed a high-LET pattern of cell killing (no shoulder, D0 45 decay/cell). Surprisingly, the shift in 125I action was abolished in cells exposed to HAT medium; both 30-min and 5-h cell groups exhibited high-LET-type killing (no shoulder, D0 52 decays/cell). The striking difference in cell death was not accompanied by any change in induction or repair of DNA DSBs, but the pattern of micronucleus formation (and by implication chromosome damage) did parallel 125I-induced cell death. These findings suggest that cell killing may not be directly linked to the absolute number of DNA DSBs and that damage to higher-order genome structures may be an important factor in radiation-induced cell death.

Animals↗
PubMed1996

[A clinical analysis of 30 cases of sympathetic ophthalmia].

PURPOSE: To study the clinical characteristics of 30 patients with sympathetic ophthalmia in order to find out the valuable clues for future investigation. METHODS: The incidence, cause, location of injury, and prognosis of the 30 patients were analyzed retrospectively. RESULTS: Patients with sympathetic ophthalmia occupied 0.72% of the in-patients with eye trauma in our hospital between 1982 and 1997. In most cases the disease related with perforating injury at the limbus or the sclera, but in a few cases it may be associated with blunt trauma, tumors or even intraocular operation. Diffuse uveitis in sympathizing eye happened in 63.3% of the patients. CONCLUSION: Development of sympathetic ophthalmia always related to the damaged ocular structure. Association of sympathetic ophthalmia with hereditary background and the melanin-protein may be worthy of study in future.

Adolescent↗
PubMed1996

Proliferation kinetics of chorionic villi in chromosomally normal and abnormal spontaneous abortions analyzed by premature chromosome condensation and northern blot.

The activity of cell proliferation in human chorionic villi (CV) obtained from early spontaneous abortions (SAB) and from elective abortions (EAB) was determined by means of premature chromosome condensation (PCC), and by Northern blot analysis of expression of proliferation antigens Ki67 and PCNA. The rate of chromosome aberrations among the SABs was 57%, while the EABs, taken as controls, were shown to be chromosomally normal. PCCs were induced by fusion of the chorionic interphase cells with mitotic Chinese hamster ovary (CHO) cells. To analyze the proliferation stages of the chorionic G1-interphases, the potential proliferation index (PPI) was ascertained. The PPI values found in SABs ranged from 36% to 97% as described for intensely proliferating tissues. They did not differ from the values found in the controls (34-90%), indicating maintenance of proliferation activity of CV cells even after death of the embryo in missed abortions. No significant PPI differences were observed between the abortion groups with different cytogenetic results. The expression of proliferation associated antigens Ki67 and PCNA showed no significant differences between mean values of the total of SABs and of the controls. However, the comparison of mean values of chromosomally abnormal with chromosomally normal SABs revealed a significantly reduced Ki67 activity in the SABs with chromosome aberrations. A similar results was obtained when comparing mean values of Ki67 and PCNA expression from trisomic SABs with those of the controls. By further subdivision of chromosome aberrations a decrease for the expression of both antigens in chorionic villi from early lethal trisomies, and a significantly increased Ki67- and PCNA-expression in triploidies became evident.

Abortion, Induced↗
PubMed1996

[Limb-preserving segmental bone resection for malignant bone tumors of the extremities: a report of 27 cases].

Segmental bone resection with preservation of the affected limb was performed in 27 patients with malignant bone tumors. Diagnosis as confirmed by histopathology was: osteosarcoma (n = 8), chondrosarcoma (n = 3), fibrosarcoma (n = 2), malignant fibrous histiocytoma (n = 2), giant cell tumor (n = 6), reticulum cell sarcoma (n = 1), myeloma (n = 1) and metastatic bone tumor (n = 4). Four different kinds of operative procedure were used: enbloc resection of shoulder girdle in 13 cases, segmental resection and replantation of distal forearm in 1, partial hemipelvisection in 6 and segmental resection of the lower thigh with leg rotation plasty in 7. Twenty four patients were followed up from 16 months to more then 12 years. Twenty patients survived for more than 2 years, 9 patients survived over 5 years with functional limbs. The 2- and 5-year survival rate was 83.3% and 37.5%, respectively.

Adolescent↗
PubMed1996

[Influence of different needling methods on fever caused by E. bacillus coli injection in rabbit].

The theory of reinforcement and reduction with acupuncture is one of the important contents of the needling techniques in acupuncture. In order to verify the theory, experimental fever caused by venous injection of E. Bacillus coll in rabbits were treated by acupuncture at Quchi(LI 11) with different needling methods (reinforcing or reducing) and stimulations (acupuncture or electroacupuncture). The results showed that each of the three reducing techniques with simple rotating of needle, rotation with lifting-thrusting needle and electroacupuncture presented the fever-subduing effects, especially obtaining the immediate effect and lowering the peak of fever. Among them, the former two had the better result than electroacupuncture. The reinforcing technique with rotating needle did not give rise to the significant effect on lowering fever. The result indicates that there exist significant differences in the effect on fever-subduing between reinforcing and reducing methods with acupuncture and between acupuncture and electroacupuncture. The simple reducing needling technique share the same therapeutic result with compound one. The work provides avaluable example for further laboratory study of reinforcing-reducing theory of acupuncture.

Acupuncture Therapy↗
PubMed1996

An observation on combined use of chemotherapy and traditional Chinese medicine to relieve cancer pain.

We have treated 50 patients with stage III, VI malignant tumors confirmed by pathology. The patients were divided into two groups. One group was treated by combination of chemotherapy and traditional Chinese medicine (treatment group); the other only by chemotherapy (control group). The effect of cancer treatment was evaluated according to the criteria of WHO. The results showed that the effective rate was 80% in treatment group and 52% in control group. The pain relieving rate was 68% in treatment group and 40% in control group (P < 0.01). This fact demonstrates that the application of traditional Chinese medicine can invigorate blood circulation, eliminate blood stasis, soften hardness and dissolve the mass, nourish blood and increase vigor. This kind of application can not only enhance the effect of cancer treatment but also increase the cancer pain relieving rate.

Adult↗