Biomedical subjects

X Liu

Publications and source records attributed to X Liu.

At least 829 records · Page 46Linked to original sources

PubMed1999

Distal versus proximal arm tremor in multiple sclerosis assessed by visually guided tracking tasks.

OBJECTIVES: To compare action tremor (AT) during manual tracking in normal subjects and patients with multiple sclerosis with tremor (MS-tremor group) and without tremor (MS-no tremor group), and to differentiate tremor occurring predominantly around the distal joint from that involving the proximal joints of the arm. METHODS: Subjects performed both a visually guided ramp tracking task using wrist flexion/extension and a whole arm circle tracking task using shoulder movement. Action tremor at the wrist or shoulder was computed as the SD of the tracking velocity. The ratio of wrist:arm tremor was then calculated to differentiate distal from proximal tremor in the tested arm. Frequency spectra of the records were also examined. RESULTS: During wrist tracking, AT in patients with multiple sclerosis contained a major frequency component at 4-5 Hz; the frequency was slightly lower during whole arm tracking. The ratio of wrist:arm tremor was significantly higher in the MS-tremor group. Of 12 tested arms, eight had tremor significantly weighted towards the distal joint, only one towards the proximal joint, and three had a ratio inside the control range. CONCLUSIONS: AT in the arms of patients with multiple sclerosis can be effectively differentiated into proximal or distal using these two different tracking tasks. Despite the variability of the effects of multiple sclerosis, most of the AT was distal rather than proximal in this group of patients. Possibly conduction block along the corticocerebellocortical pathways caused this distal tremor.

Adult↗

PubMed1999

Changes in cardiac protein kinase C activities and isozymes in streptozotocin-induced diabetes.

To understand cardiac dysfunction in diabetes, the activity of protein kinase C (PKC) and protein contents of its isozymes (PKC-alpha, -beta, -epsilon, and -zeta) were examined in diabetic rats upon injection of streptozotocin (65 mg/kg iv). The hearts were removed at 1, 2, 4, and 8 wk, and some of the 6-wk diabetic animals had been injected with insulin (3 U/day) for 2 wk. The Ca(2+)-dependent PKC activity was increased by 43 and 51% in the homogenate fraction and 31 and 70% in the cytosolic fraction from the 4- and 8-wk diabetic hearts, respectively, in comparison with control values. The Ca(2+)-independent PKC activity was increased by 24 and 32% in the homogenate fraction and 52 and 89% in the cytosolic fraction from the 4- and 8-wk diabetic hearts, respectively, in comparison with control values. The relative protein contents of PKC-alpha, -beta, -epsilon, and -zeta isozymes were increased by 43, 31, 48, and 38%, respectively, in the homogenate fraction and by 126, 119, 148, and 129%, respectively, in the cytosolic fraction of the 8-wk diabetic heart. The observed changes in heart homogenate and cytosolic fractions were partially reversible upon treatment of the diabetic rats with insulin. The results suggest that the increased myocardial PKC activity and increased protein contents of the cytosolic PKC isozymes are associated with subcellular alterations and cardiac dysfunction in the diabetic heart.

Animals↗

PubMed1999

Biliary excretion in primary rat hepatocytes cultured in a collagen-sandwich configuration.

The objective of the present investigation was to examine the functional reestablishment of polarity in freshly isolated hepatocytes cultured between 2 layers of gelled collagen (sandwich configuration). Immunoblot analysis demonstrated that the canalicular multispecific organic anion transport protein (multidrug resistance-associated protein, Mrp2) was partially maintained in day 5 hepatocytes cultured in a sandwich configuration. Fluorescein-labeled taurocholate and carboxydichlorofluorescein were excreted into and concentrated in the bile canalicular lumen of day 5 sandwich-cultured hepatocytes, resulting in formation of fluorescent networks in standard buffer (intact bile canaliculi). Confocal microscopy studies demonstrated that 1) carboxydichlorofluorescein that had concentrated in the canalicular lumen was released into the incubation buffer in the presence of Ca(2+)-free buffer (disrupted bile canaliculi), and 2) rhodamine-dextran, an extracellular space marker, was only able to diffuse into the canalicular lumen in the presence of Ca(2+)-free buffer. The cumulative uptake of [(3)H]taurocholate in day 5 sandwich-cultured hepatocytes was significantly higher in standard buffer compared with Ca(2+)-free buffer, due to accumulation of taurocholate in canalicular spaces. When [(3)H]taurocholate was preloaded in the day 5 sandwich-cultured hepatocytes, taurocholate efflux was greater in Ca(2+)-free compared with standard buffer. The biliary excretion index of taurocholate, equivalent to the percentage of retained taurocholate in the canalicular networks, increased from approximately 8% at day 0 to approximately 60% at day 5 in sandwich-cultured hepatocytes. In summary, hepatocytes cultured in a collagen-sandwich configuration for up to 5 days establish intact canalicular networks, maintain Mrp2, reestablish polarized excretion of organic anions and bile acids, and represent a useful in vitro model system to investigate the hepatobiliary disposition of substrates.

Animals↗

PubMed1999

Receptor subtype mediating the adrenergic sensitivity of pain behavior and ectopic discharges in neuropathic Lewis rats.

Receptor subtype mediating the adrenergic sensitivity of pain behavior and ectopic discharges in neuropathic Lewis rats. We attempted to identify the subtype of alpha-adrenergic receptor (alpha-AR) that is responsible for the sympathetic (adrenergic) dependency of neuropathic pain in the segmental spinal injury (SSI) model in the Lewis strain of rat. This model was chosen because our previous study showed that pain behaviors in this condition are particularly sensitive to systemic injection of phentolamine (PTL), a general alpha-AR blocker. We examined the effects of specific alpha1- and alpha2-AR blockers on 1) behavioral signs of mechanical allodynia, 2) ectopic discharges recorded in the in vivo condition, and 3) ectopic discharges recorded in an in vitro setup. One week after tight ligation of the L5 and L6 spinal nerves, mechanical thresholds of the paw for foot withdrawals were drastically lowered; we interpreted this change as a sign of mechanical allodynia. Signs of mechanical allodynia were significantly relieved by a systemic injection of PTL (a mixed alpha1- and alpha2-AR antagonist) or terazosin (TRZ, an alpha1-AR antagonist) but not by various alpha2-AR antagonists (idazoxan, rauwolscine, or yohimbine), suggesting that the alpha1-AR is in part the mediator of the signs of mechanical allodynia. Ongoing ectopic discharges were recorded from injured afferents in fascicles of the L5 dorsal root of the neuropathic rat with an in vivo recording setup. Ongoing discharge rate was significantly reduced after intraperitoneal injection of PTL or TRZ but not by idazoxan. In addition, by using an in vitro recording setup, spontaneous activity was recorded from teased dorsal root fibers in a segment in which the spinal nerve was previously ligated. Application of epinephrine to the perfusion bath enhanced ongoing discharges. This evoked activity was blocked by pretreatment with TRZ but not with idazoxan. This study demonstrated that both behavioral signs of mechanical allodynia and ectopic discharges of injured afferents in the Lewis neuropathic rat are in part mediated by mechanisms involving alpha1-ARs. These results suggest that the sympathetic dependency of neuropathic pain in the Lewis strain of the rat is mediated by the alpha1 subtype of AR.

Adrenergic alpha-Agonists↗

PubMed1999

Changing properties of GABA(A) receptor-mediated signaling during early neocortical development.

Evidence from several brain regions suggests gamma-aminobutyric acid (GABA) can exert a trophic influence during development, expanding the role of this amino acid beyond its function as an inhibitory neurotransmitter. Proliferating precursor cells in the neocortical ventricular zone (VZ) express functional GABA(A) receptors as do immature postmigratory neurons in the developing cortical plate (CP); however, GABA(A) receptor properties in these distinct cell populations have not been compared. Using electrophysiological techniques in embryonic and early postnatal neocortex, we find that GABA(A) receptors expressed by VZ cells have a higher apparent affinity for GABA and are relatively insensitive to receptor desensitization compared with neurons in the CP. GABA-induced current magnitude increases with maturation with the smallest responses found in recordings from precursor cells in the VZ. No evidence was found that GABA(A) receptors on VZ cells are activated synaptically, consistent with previous data suggesting that these receptors are activated in a paracrine fashion by nonsynaptically released ligand. After neurons are born and migrate to the CP, they begin to demonstrate spontaneous synaptic activity, the majority of which is GABA(A) mediated. These spontaneous GABA(A) postsynaptic currents (sPSCs) first were detected at embryonic day 18 (E18). At birth, approximately 50% of recordings from cortical neurons demonstrated GABA(A)-mediated sPSCs, and this value increased with age. GABA(A)-mediated sPSCs were action potential dependent and arose from local GABAergic interneurons. GABA application could evoke action potential-dependent PSCs in neonatal cortical neurons, suggesting that during the first few postnatal days, GABA can act as an excitatory neurotransmitter. Finally, N-methyl-D-aspartate (NMDA)- but not non-NMDA-mediated sPSCs were also present in early postnatal neurons. These events were not observed in cells voltage clamped at negative holding potentials (-60 to -70 mV) but were evident when the holding potential was set at positive values (+30 to +60 mV). Together these results provide evidence for the early maturation of GABAergic communication in the neocortex and a functional change in GABA(A)-receptor properties between precursor cells and early postmitotic neurons. The change in GABA(A)-receptor properties may reflect the shift from paracrine to synaptic receptor activation.

Animals↗

PubMed1999

Synapse density related to cerebral blood flow and symptomatology in frontal lobe degeneration and Alzheimer's disease.

In order to evaluate the functional significance of synaptic pathology, synaptic density was quantitated and related to clinical symptomatology and regional cerebral blood flow (rCBF) in 8 patients with frontal lobe degeneration of non-Alzheimer type (FLD) and 19 patients with Alzheimer's disease (AD). Synaptic density was measured in all layers of prefrontal and parietal cortex. The clinical picture of FLD was dominated by a frontal lobe syndrome with changes in personality and behavior, while AD was dominated by temporoparietal symptoms. This parallels the finding of frontal rCBF reductions in FLD patients and temporoparietal reductions in AD patients. Synaptic density was significantly decreased in both FLD and AD, with a regional severity which closely correlated with that of the degeneration, symptomatology and rCBF deficit. The results suggest that synaptic pathology is a likely cause of clinical symptoms and regional metabolic decrement in dementia.

Adult↗

PubMed1999

Human neutrophil elastase augments fibroblast-mediated contraction of released collagen gels.

In the present study, we tested the hypothesis that neutrophil elastase (NE) might mediate remodeling of extracellular matrix by affecting fibroblast-mediated contraction of three-dimensional collagen gels. Human lung fibroblasts were cast into type I collagen gels containing NE. After gelation, the gels were released into medium and the area was measured by image analyzer. NE augmented gel contraction (p < 0.001). This was not due to cell proliferation or to degradation to soluble collagen fragments because the amounts of DNA and hydroxyproline were not altered. alpha1-Protease inhibitor and the synthetic inhibitor of NE, L-680,833, when added in sufficient amount to inhibit free elastase activity, blocked the contraction induced by NE. Furthermore, neutrophil granulocytes (PMN) in coculture, as well as conditioned media from PMN, resulted in an increased contractility (p < 0.001 for both). Bronchoalveolar lavage fluid (BALF) from patients with increased PMN in their lower respiratory tract and free elastase activity had augmentive activity for gel contraction which could be partially blocked by the inhibitors. We conclude that NE augments fibroblast-mediated contraction of collagen gels. The findings support the notion that products secreted by PMN in inflammatory disorders may lead to rearrangement of extracellular matrix and could subsequently lead to tissue dysfunction.

Adult↗

PubMed1999

Activin from secondary follicles causes small preantral follicles to remain dormant at the resting stage.

The purpose of the present study was to investigate 1) whether activin A can cause primary follicles to become dormant at the resting stage, and 2) the role of the secondary follicle on follicular growth of primary follicles. Preantral follicles (100-120 microm in diameter) harvested from adult mice and cultured in in vitro follicle culture system showed a significant increase in size and estrogen and inhibin secretion in response to FSH, but the administration of activin A blocked the effect of FSH. Withdrawal of activin A not only restored the follicular response to FSH but also enhanced the effect of FSH, indicating that the action of activin A is to cause small preantral follicles to become dormant at the preantral stage. To investigate the role of secondary follicles in early folliculogenesis, small preantral follicles were cocultured with secondary follicle (300-350 microm in diameter) in the presence of FSH. The secondary follicle showed a significant increase in follicular diameter as a result of stimulation by FSH, but the small preantral follicles did not increase in size. After removal of the secondary follicle, however, the small preantral follicles commenced follicular growth, indicating that the growth of small preantral follicles is suppressed by the secondary follicle. Administration of the activin binding protein follistatin caused a significant increase in follicular diameter of both small preantral and secondary follicles as a result of stimulation by FSH. These results have suggested that secondary follicles cause primary follicles to become dormant at the resting stage by secreting activin.

Activins↗

PubMed1999

Multiple elements and protein factors coordinate the basal and cyclic adenosine 3',5'-monophosphate-induced transcription of the lutropin receptor gene in rat granulosa cells.

The expression of the lutropin receptor (LHR) in granulosa cells is a complex phenomenon under the hormonal control of FSH and estradiol. Using primary cultures of granulosa cells from immature female rats pretreated with diethylstilbestrol (a compound with estrogen-like activity), the role of FSH in LHR induction was studied. Previous studies from our laboratory have shown that FSH or 8-bromo-cAMP addition to these cells causes a marked increase in the rate of transcription of the rat LHR (rLHR) gene. The present studies were undertaken to compare the properties of the rLHR gene in undifferentiated vs. differentiated rat granulosa cells as a means of determining those elements that confer basal activity and cAMP responsiveness. Our studies show that the proximal 155 bp (relative to the translational initiation codon) of the 5'-flanking region of rLHR gene represent a minimal promoter that accounts for the basal expression of this receptor in rat granulosa cells. A major domain located between nucleotides (nt) -90 and -120, with another one possibly being between nt -120 and -155, induced activation of basal transcriptional activity. An inhibitory domain was observed to lie between nt -186 and -1375. Our data further show that multiple elements within the 2.1 kb of the 5'-flanking region of the rLHR gene are involved in the 8-bromo-cAMP-induced expression of the LHR gene. Of these, the three Sp1-binding sites within the proximal portion of the 5'-flanking region appear to be important for both basal as well as cAMP-induced rLHR gene transcription.

Animals↗

PubMed1999

A comparative study on transforming growth factor-beta and activin A for preantral follicles from adult, immature, and diethylstilbestrol-primed immature mice.

Both transformation growth factor-beta (TGFbeta) and activin belong to the TGFbeta superfamily, and each receptor is structurally related. We have shown that the action of activin A on folliculogenesis is different in immature and adult mice, so it is of interest to study whether TGFbeta has such an action on follicular development. The effect of TGFbeta on folliculogenesis was studied in isolated preantral follicles from immature, adult, and diethylstilbestrol (DES)-primed immature mice and was compared with that of activin A. TGFbeta caused a significant increase in follicular diameter and estradiol and immunoreactive inhibin secretion in adult mice in a dose-related manner, but did not affect the size of preantral follicles from immature mice. Activin A, on the other hand, caused a significant increase in the size of follicles from immature mice, but did not change the size of preantral follicles from adult mice. TGFbeta enhanced the effect of FSH, whereas activin A completely blocked the action of FSH on preantral follicles from adult mice. Such a specific action of TGFbeta and activin A was age dependent because preantral follicles obtained from 28-day-old mice, compared with those from 11- and 56-day-old mice, showed an intermediate reaction to TGFbeta and activin A. DES pretreatment of 11- and 28-day-old mice caused an enhanced response to FSH, but this response was completely inhibited by TGFbeta. These results indicate that both TGFbeta and activin A have proliferative action and cytodifferentiative action on granulosa cells, but the action of each is age dependent and opposite in direction. In conclusion, although both TGFbeta and activin A belong to the same family, and each receptor is structurally related, both share a specific role in early folliculogenesis before and after puberty.

Activins↗

PubMed1999

Role of G protein-coupled receptor kinases on the agonist-induced phosphorylation and internalization of the follitropin receptor.

The experiments presented herein were designed to identify members of the G protein-coupled receptor kinase (GRK) family that participate in the agonist-induced phosphorylation and internalization of the rat FSH receptor (rFSHR). Western blots of human kidney 293 cells (the cell line used in transfection experiments) and MSC-1 cells (a cell line derived from Sertoli cells that displays many of the differentiated functions of their normal counterparts) reveal the presence of GRK2 and GRK6 in both cell lines as well as GRK4 in MSC-1 cells. Cotransfection of 293 cells with the rFSHR and GRK2, GRK4alpha, or GRK6 resulted in an increase in the agonist-induced phosphorylation of the rFSHR. Cotransfections of the rFSHR with GRKs or arrestin-3 enhanced the agonist-induced internalization of the rFHSR, and combinations of GRKs and arrestin-3 were more effective than the individual components. To characterize the involvement of endogenous GRKs on phosphorylation and internalization, we inhibited endogenous GRK2 by overexpression of a kinase-deficient mutant of GRK2 or G alpha t, a scavenger of G betagamma. We also inhibited endogenous GRK6 by overexpression of a kinase-deficient mutant of GKR6. All three constructs were effective inhibitors of phosphorylation, but only the kinase-deficient mutant of GRK2 and G alpha t inhibited internalization. The inhibition of internalization induced by these two constructs was less pronounced than that induced by a dominant-negative mutant of the nonvisual arrrestins, however. The finding that inhibitors of GRK2 and GRK6 impair phosphorylation, but only the inhibitors of GRK2 impair internalization, suggests that different GRKs have differential effects on receptor internalization.

Animals↗

PubMed1999

Inactivation of erythropoietin leads to defects in cardiac morphogenesis.

Erythropoietin is an essential growth factor that promotes survival, proliferation, and differentiation of mammalian erythroid progenitor cells. Erythropoietin(-/-) and erythropoietin receptor(-/-) mouse embryos die around embryonic day 13.5 due, in part, to failure of erythropoiesis in the fetal liver. In this study, we demonstrated a novel role of erythropoietin and erythropoietin receptor in cardiac development in vivo. We found that erythropoietin receptor is expressed in the developing murine heart in a temporal and cell type-specific manner: it is initially detected by embryonic day 10.5 and persists until day 14.5. Both erythropoietin(-/-) and erythropoietin receptor(-/-) embryos suffered from ventricular hypoplasia at day 12-13 of gestation. This defect appears to be independent from the general state of hypoxia and is likely due to a reduction in the number of proliferating cardiac myocytes in the ventricular myocardium. Cell proliferation assays revealed that erythropoietin acts as a mitogen in cells isolated from erythropoietin(-/-) mice, while it has no effect in hearts from erythropoietin receptor(-/-) animals. Erythropoietin(-/-) and erythropoietin receptor(-/-) embryos also suffered from epicardium detachment and abnormalities in the vascular network. Finally, through a series of chimeric analysis, we provided evidence that erythropoietin acts in a manner which is non-cell-autonomous. Our results elucidate a novel role of erythropoietin in cardiac morphogenesis and suggest a combination of anemia and cardiac failure as the cause of embryonic lethality in the erythropoietin(-/-) and erythropoietin receptor(-/-) animals.

Animals↗

PubMed1999

Brain-derived neurotrophic factor improves blood glucose control and alleviates fasting hyperglycemia in C57BLKS-Lepr(db)/lepr(db) mice.

Systemic administration of brain-derived neurotrophic factor (BDNF) decreases nonfasted blood glucose in obese, non-insulin-dependent diabetic C57BLKS-Lepr(db)/lepr(db) (db/db) mice, with a concomitant decrease in body weight. By measuring percent HbA1c in BDNF-treated and pair-fed animals, we show that the effects of BDNF on nonfasted blood glucose levels are not caused by decreased food intake but reflect a significant improvement in blood glucose control. Furthermore, once established, this effect can persist for weeks after cessation of BDNF treatment. Oral glucose tolerance tests were performed to examine the effects of BDNF on blood glucose control in the fasted state and after an oral glucose challenge. BDNF treatment normalized fasting blood glucose from initially hyperglycemic levels and also showed evidence for beneficial, although less marked, effects on the ability to remove exogenous glucose from blood. One means to lower fasting blood glucose is to reduce the glucose output of peripheral tissues that normally play a part in the maintenance of fasting hyperglycemia. Because the liver is the major endogenous source of glucose in blood during fasting, and because hepatic weight and glucose output are increased in type 2 diabetes, we evaluated the effects of BDNF on liver tissue. BDNF reduced the hepatomegaly present in db/db mice, in association with reduced liver glycogen and reduced liver enzyme activity in serum, supporting the possible involvement of liver tissue in the mechanism of action for BDNF.

Animals↗

PubMed1999

Advances in glaucoma diagnosis and therapy for the next millennium: new drugs for trabecular and uveoscleral outflow.

Advances in our understanding of the physiology and molecular biology of the trabecular and uveoscleral outflow pathways of the eye will lead to the development of new approaches for glaucoma therapy. Therapies of the future will target the structures and enzymes involved in maintaining cell shape and cell-cell and cell-extracellular matrix interactions. Altering the extracellular matrix in the ciliary muscle has been important in the intraocular pressure lowering effects of prostaglandins and will be developed further as an approach to enhancing outflow through the trabecular meshwork. Gene therapy may be used to enhance or suppress the endogenous targets that are ultimately responsible for the outflow enhancement triggered by these agents.

Animals↗

PubMed1999

Isolation of cDNAs encoding gibbon and monkey platelet and T cell activation antigen 1 (PTA1).

Human platelet and T cell activation antigen 1 (PTA1) is a 67kDa type I transmembrane glycoprotein mainly expressed on the surface of activated T cells and platelets, and is involved in the development of human cytotoxic T cell (CTL) as well as platelet activation and aggregation. We have cloned and sequenced gibbon PTA1 (gPTA1) and monkey PTA1 (mPTA1) cDNAs by RT-PCR from gibbon leukemic cell line MLA 144 and PHA-induced Rhesus monkey PBMC respectively. The mature proteins of gPTA1, mPTA1 and human PTA1 (hPTA1) share 93-95% amino acid similarity with the highest similarity in domain 1 of extracellular region. All the important features of PTA1 molecule are conserved among these Primates: (1) the ORF encoding 336 amino acid residues including signal sequence (18aa), extracellular region (232aa), transmembrane sequence (25aa) and cytoplasmic region (61aa); (2) two conserved pairs of Cys (Cys19 to Cys90 and Cys134 to Cys204) forming disulfide bonds stabilizing the two immunoglobulin superfamily V-like domains; (3) eight putative N-linked glycosylation sites (except gPTA1 with nine sites) and three O-linked glycosylation sites in extracellular region; and (4) predicated protein kinase C phosphorylation sites (Thr275 and Ser311), casein kinase II sites (Ser295 and The299) and the potential tyrosine phosphorylation site (Tyr304). These data indicate that PTA1 molecule is highly conserved among the Primates and may play important roles in immune response.

Amino Acid Sequence↗

PubMed1999

Safety of implantable coronary stents during 1H-magnetic resonance imaging at 1.0 and 1.5 T.

The safety of most available implantable intracoronary stents during magnetic resonance imaging (MRI) has not been sufficiently tested. Minor, but possibly clinically significant, increases in temperature have not been excluded. We measured temperature changes of 14 different stents clinically in use or currently tested for release on the world market. Stents were examined in 1.0- and 1.5-T MR scanners with multiple sequences used in routine cardiac and thoracic MRI examinations ("clinical worst case") and after implantation of the stents into the coronary arteries of excised pig hearts (1.5-T scanner only). We used a highly sensitive infrared camera with a thermal resolution of 10 mK and did not see significant heating of any stent during the examinations. We conclude that MRI is safe in patients with the currently available intracoronary stents.

Animals↗

PubMed1999

High O6-methylguanine methyl transferase activity is frequently found in human oral cancer cells with p53 inactivation.

Many studies have indicated that cancer cells expressing mutant (mt) p53 are resistant to genotoxic stress such as chemotherapy and radiation therapy. Inasmuch as most human oral cancer cells either express mt p53 or are infected with human papillomavirus (HPV), we determined the sensitivity to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a genotoxic chemical carcinogen, the activity of a DNA repair enzyme O6-methylguanine methyl transferase (MGMT) and the status of p53 in 11 human oral cancer cell lines, 2 HPV-immortalized human oral keratinocytes and 3 normal human oral keratinocyte (NHOK) cultures. Ten cancer cell lines demonstrated significantly higher level of MGMT activities compared to normal or immortalized non-tumorigenic cells, while one cancer cell line showed negligible MGMT activity. All immortalized cells and NHOK showed very low MGMT activity. Interestingly, all cancer cells with high MGMT activity expressed either mt p53 or harbored HPV DNA. However, infection of one cancer cell line (that does not demonstrate the MGMT activity) with retrovirus expressing an mt p53 protein did not alter the sensitivity of cells to MNNG and the enzyme activity. These data indicate that most human oral cancer cells contain moderately high DNA repair enzyme activity, and in doing so may be resistant to genotoxic stress, but the association of p53 with MGMT activities should further be investigated.

Blotting, Western↗

PubMed1999

Improved fusion partners transfected with DNA fragment encoding IL-11 on generation of human B lymphocyte hybridomas.

IL-11, a less identified cytokine, possesses some overlapping functions with IL-6 that are able to facilitate the growth and antibody secretion of B lymphocyte hybridomas. In this report, a DNA fragment encoding human IL-11 was transduced into fusion partners (mouse myelomas Ag8.653 and SP2/0, and human lymphoblastoid cell line HF2) mediated by lipofection. The transfected cells selected with G418 secreted IL-11 constitutively over the range of 32.4 +/- 10.5 units/ml to 76.6 +/- 18.4 units/ml, which could be inhibited by an IL-11 neutralizing MAb up to 80%. The fusion frequency of PBMC doubled, while that of LCLs displayed a 2.4- or 3.3-fold increase, when fused with the transfected fusion partners, respectively. The derived hybridomas from IL-11 secreting fusion partner secreted 3 or 4 times as many immunoglobulins as that from its ancestor. Our data indicate that IL-11 gene transfected fusion partners are improved cell lines for generation of human B lymphocyte hybridomas, and IL-11 may contribute to the increased fusion frequency and antibody secretion of B lymphocyte hybridomas.

Animals↗