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L Li

Publications and source records attributed to L Li.

At least 1,693 records · Page 94Linked to original sources
PubMed1993

Identification of a functional silencer element involved in neuron-specific expression of the synapsin I gene.

We have identified a functional silencer element (positions -231 to -211) in the human synapsin I gene that selectively represses its transcription in nonneuronal cells. Transfection experiments using synapsin I-luciferase constructs show that site-specific mutations or deletion of this silencer sequence results in expression of the reporter gene in nonneuronal cells. Moreover, the silencer element is capable of conferring repression on a heterologous promoter in nonneuronal cells. Gel-shift assays reveal the presence of a sequence-specific synapsin I silencer-binding protein in nonneuronal cell extracts but not in neuronal cell extracts. Mutagenesis studies of the silencer sequence demonstrate that formation of the specific silencer-protein complex in vitro correlates well with repression of transcription in vivo. These data indicate that the interaction between synapsin I silencer and its binding protein is involved in tissue-specific expression of the synapsin I gene. In addition, our results suggest the existence of at least one additional cis-acting element within the promoter-proximal region (positions -233 to +20) that also contributes to the neuron-specific expression of the synapsin I gene.

Animals↗
PubMed1993

Isolation of a cDNA for chicken liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase.

A chicken liver cDNA for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase was isolated from a Lambda ZAP2 phage library. The chicken liver cDNA codes for a protein that has 89.1, 88.4 and 88.0% amino acid identity with the human, rat and bovine liver isoforms, respectively. The kinetic properties of the rat and chicken liver enzymes, purified to homogeneity after expression in E. coli, were different including negative cooperativity for ATP binding and inhibition by Mg2+ for the chicken liver 6-phosphofructo-2-kinase but not for the rat liver kinase. Differences in the beta-loop ATP signature sequences in the chicken and rat liver kinase domains may explain the kinetic differences and represent the major divergence in the evolution of the enzyme from birds to mammals.

Adenosine Triphosphate↗
PubMed1993

Strontium induces murine keratinocyte differentiation in vitro in the presence of serum and calcium.

Primary mouse keratinocytes in culture are induced to terminally differentiate by increasing extracellular Ca2+ concentrations (Cao) from 0.05 mM to > or = 0.1 mM. The addition of Sr2+ (> or = 2.5 mM) to medium containing 0.05 mM Ca2+ induces focal stratification and terminal differentiation, which are similar to that found after increasing the Cao to 0.12 mM. Sr2+ in 0.05 mM Ca2+ medium induces the expression of the differentiation-specific keratins, keratin 1 (K1), keratin 10 (K10), and the granular cell marker, filaggrin, as determined by both immunoblotting and immunofluorescence. Sr2+ induces the expression of those differentiation markers in a dose dependent manner, with an optimal concentration of 5 mM. In the absence of Ca2+ in the medium, the Sr2+ effects are reduced, and Sr2+ is ineffective when both Ca2+ and serum are deleted from the medium. Sr2+ treatment increases the ratio of fluorescence intensity of the intracellular Ca2+ sensitive probe, fura-2, indicating an associated rise in the level of intracellular free Ca2+ and/or Sr2+. At doses sufficient to induce differentiation, Sr2+ also increases the level of inositol phosphates in primary keratinocytes within 30 min. The uptake curves of 85Sr2+ by primary keratinocytes are similar to those of 45Ca2+. At low concentrations, the initial uptake of both 45Ca2+ and 85Sr2+ reaches a plateau within 1 hr; at higher concentrations, the uptake of both 45Ca2+ and 85Sr2+ increases continuously for 12 hr. In keratinocytes pre-equilibrated with 45Ca2+ in 0.05 mM Ca2+ medium, Sr2+ causes an increase of 45Ca2+ uptake, which is dependent on the presence of serum. These results suggest that Sr2+ utilizes the same signalling pathway as Ca2+ to induce keratinocyte terminal differentiation and that Ca2+ may be required to exert these effects.

Animals↗
PubMed1993

Apparent diffusion coefficient mapping of experimental focal cerebral ischemia using diffusion-weighted echo-planar imaging.

Diffusion-weighted, echo-planar imaging (EPI) was used to map regional changes in the apparent diffusion coefficient (ADC) during experimental focal ischemia in the rat brain following permanent middle cerebral arterial occlusion (MCAO). Sixteen 64 x 64 diffusion-weighted EPIs were acquired in 32 s with successively increasing amplitudes of the diffusion-sensitive gradient pulses. A linear least-squares regression algorithm was used to fit 15 of the 16 two-dimensional matrices, on a pixel-by-pixel basis, to solve for the slope from which the ADC value was calculated. The correlation coefficient of the fit, R2, was used to filter the final ADC maps, and the ADCs were then scaled appropriately to be displayed in a 256 gray level format. Ranges (bins) of 0.05 x 10(-3) mm2/s were then grouped and color coded to qualify and quantify the evolution of ischemia in the MCA territory. The percentage of area in the ischemic and contralateral hemispheres in seven ADC bins were calculated at 30, 60, and 120 min after MCAO for 10 animals and demonstrated a significant increase in ADC bins below 0.45 x 10(-3) mm2/s and a decrease in bins above 0.50 x 10(-3) mm2/s over time. The postmortem infarct area, as measured by TTC staining, was highly correlated with the portion of the ischemic hemisphere falling below ADC values of 0.55 x 10(-3) mm2/s at 2 h after stroke onset. These studies suggest that focally ischemic brain tissue can be quantitatively subdivided according to ADC values and that ADC values below 0.55 x 10(-3) mm2/s 2 h following ischemia highly predict infarction in a rat permanent occlusion stroke model.

Algorithms↗
PubMed1993

Changing synaptic specificities in the nervous system of Caenorhabditis elegans: differentiation of the DD motoneurons.

During postembryonic development, the DD motoneurons in the nematode Caenorhabditis elegans completely reorganize their pattern of synapses. Ablation of a pair of embryonic precursors results in the absence of this entire class of motoneurons. In their absence animals exhibit two developmentally distinct locomotory defects. The transition period from one defect to the other is correlated with the synaptic reorganization of the DD mns. Mutations in a gene (unc-123) have been isolated that exhibit locomotory defects similar to those of the ablated adult animals. Genetic and cellular analyses of one of these alleles suggest that the unc-123 gene product may be involved in the reestablishment of functional synapses in these neurons.

Animals↗
PubMed1993

Effects of RPE age and culture conditions on support of photoreceptor cell survival in transplanted RCS dystrophic rats.

This study assessed the effects of transplants of freshly isolated or cultured (ie. passaged) retinal pigment epithelial (RPE) cells from neonatal and adult normal and RCS pigmented dystrophic rats on photoreceptor cell survival in retinas of 22-26-day-old pink-eyed RCS dystrophic rats. We determined that retinas of 2-month-old RCS rats transplanted at 26 days with RPE cells of adult RCS rats did not support photoreceptor cell survival above that seen in sham or nontreated control RCS retinas, as outer nuclear layer (ONL) thicknesses were not significantly different (10.0 +/- 1.31 microns, 11.7 +/- 4.04 microns and 9.42 +/- 1.88 microns, respectively). Surprisingly, in this same transplant group, RPE transplants from neonatal RCS dystrophic rats were able to promote photoreceptor cell survival similar to that seen in transplants of neonatal Long Evans rats, as evidenced by similar ONL thicknesses (34.4 +/- 3.16 microns and 33.6 +/- 6.03 microns, respectively), but the rescue effect quickly diminished. However, in retinas of 22-26-day-old RCS rats transplanted with RPE cells from adult Long Evans rats, the level of photoreceptor cell rescue was approximately 48% (ONL: 19.6 +/- 2.79 microns), when compared to retinas transplanted with RPE cells from neonatal Long Evans rats, but significantly greater than that caused by transplants of RPE cells from adult RCS rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

cDNA cloning and expression of human glutamyl aminopeptidase (aminopeptidase A).

The murine B-lymphocyte differentiation antigen BP-1/6C3 has been identified as glutamyl aminopeptidase (E-AP), formerly known as aminopeptidase A, the new gene symbol for which is ENPEP. In mice, the enzyme is found on early B-lineage cells and certain stromal cells of the bone marrow and thymus. This ectopeptidase is also expressed by capillary endothelial cells, placenta, and epithelial cells of the intestine and proximal renal tubules. Here we have used a mouse E-AP cDNA to identify the human counterpart in a kidney library. Sequence comparison of the human and mouse cDNAs reveals approximately 80% homology at both nucleotide and predicted amino acid levels. The nucleotide sequence of human E-AP predicts a type II integral membrane protein of 957 amino acids with an 18-amino-acid aminoterminal intracellular domain, and a 22-amino-acid transmembrane domain. The large extracellular carboxyterminal domain contains the zinc-binding motif typical of zinc-dependent metallohydrolases. When the human E-AP cDNA was placed downstream of the SR alpha promoter in an expression vector and transfected into COS-7 cells, the transfected cells exhibited cell surface E-AP activity. A 4.1-kb transcript could be detected in a variety of human tissues, including heart, brain, placenta, lung, liver, skeletal muscle, kidney, and pancreas. However, in representative lymphoid leukemias, E-AP transcripts were restricted to pre-B leukemia and were not found in T- and B-cell leukemias. The cDNA cloning and successful expression of human E-AP will allow more precise analysis of its physiological role(s).

Amino Acid Sequence↗
PubMed1993

Unmyelinated innervation of sinus hair follicles in rats.

Unmyelinated nerve fibres comprise approximately one third of the innervation of rodent sinus hair follicles but their function is unknown. They may play a role as high-threshold sensory fibres, or may be autonomic efferents controlling the vascular sinus. In the present experiments capsaicin and surgical sympathectomy were used to establish whether these unmyelinated fibres are afferent fibres or autonomic efferents. The deep vibrissal nerves of mystacial follicles (C1 and C4) and a non-mystacial follicle (the postero-orbital, PO) were assessed in normal adult animals (n = 6) and compared with those treated with neonatal capsaicin (n = 6) or bilateral superior cervical ganglionectomy (n = 7). In capsaicin-treated animals, counts of fibres in the deep vibrissal nerves from all follicles showed normal numbers of myelinated axons, but approximately 80% reduction in unmyelinated fibres (normal mean +/- SD: C1 94 +/- 10, C4 89 +/- 9, PO 85 +/- 6; after neonatal capsaicin: C1 17 +/- 8, C4 16 +/- 6, PO 18 +/- 6; n = 6, P < 0.001 for all follicles). After sympathectomy there was no significant reduction in myelinated or unmyelinated fibre numbers. Labelling of PO follicles with WGA-HRP showed minimal numbers of labelled cells (0-10) within the superior cervical ganglion, also suggesting minimal sympathetic innervation. This sparse sympathetic supply to the follicle was further demonstrated by a lack of tyrosine hydroxylase reactivity within the follicle complex; tissues outside the dermal capsule showed reactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

High degree of genetic polymorphism in apolipoprotein(a) associated with plasma lipoprotein(a) levels in Japanese and Chinese populations.

We have developed a sensitive, high-resolutin method for the analysis of the apolipoprotein(a) [apo(a)] isoforms using sodium dodecyl sulfate (SDS)-agarose/gradient polyacrylamide gel electrophoresis. In an analysis of the genetic polymorphism of apo(a) isoforms and their relationship with plasma lipoprotein(a) [Lp(a)] levels in Japanese and Chinese, this method identified 25 different apo(a) isoforms and detected one or two apo(a) isoforms in more than 99.5% of the individuals tested. The apparent molecular weights of the apo(a) isoforms ranged from 370 kDa to 950 kDa, and 22 of the 25 different apo(a) isoforms had a higher molecular weight than of apo B-100. Studies on Japanese families confirmed the autosomal codominant segregation of apo(a) isoforms and the existence of a null allele at the apo(a) locus. The observed frequency distribution of apo(a) isoform phenotypes fit the expectations of the Hardy-Weinberg equilibrium in both the Japanese and Chinese populations. Our data indicate the existence of at least 26 alleles, including a null allele, at the apo(a) locus. The frequency distribution patterns of the apo(a) isoform alleles in Japanese and Chinese were similar to each other and also similar to that of apo(a) gene sizes reported in Caucasian American individuals. The average heterozygosity at the apo(a) locus was 92% in Japanese and 93% in Chinese. A highly significant inverse correlation was observed between plasma Lp(a) levels and the size of apo(a) isoforms in both the Japanese (r = 0.677, P = 0.0001) and the Chinese (r = -0.703, P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1993

Vitamin D3 (soltriol) nuclear receptors in abdominal scent gland and skin of Siberian hamster (Phodopus sungorus) localized by autoradiography and immunohistochemistry.

In vivo autoradiography with [3H]1,25-dihydroxycholecalciferol (vitamin D, soltriol) and immunostaining with antibodies to vitamin D receptor were applied to identify specific binding sites in the abdominal scent gland of male Siberian hamster (Phodopus sungorus). Nuclear concentration of radiolabeled hormone and receptor antibodies was observed in the corresponding cell types including basal cells of sebaceous glands, cells of the outer hair sheaths and hair bulbs, and also keratinocytes in the epidermis. Cells of the hair dermal papillae and fibroblasts of the dermis did not show nuclear labeling. There was good correspondence between the autoradiographic and immunohistochemical data. The results indicate the presence of receptors for vitamin D-soltriol and suggest a seasonal regulation of scent gland marking activities by this steroid hormone of sunlight in cooperation with the sex steroid testosterone.

Animals↗
PubMed1993

Relationship between immunological parameters and survival of patients with liver metastases from breast cancer given immuno-chemotherapy.

We treated 33 patients with liver metastases from breast cancer by immuno-chemotherapy including adoptive cell transfer between 1987 and 1992. In this study, we examined the change of immunological parameters in the peripheral blood lymphocytes and interleukin-2 (IL-2)-cultured lymphocytes, in primary vs. metastatic breast cancer patients and before vs. after treatment. Moreover, we examined their correlation with therapeutic response and survival after treatment. The immunological parameters used were in vitro natural killer cell activity (% lysis of K562), in vitro autologous tumor-killing activity (% lysis against autologous freshly isolated tumor cells), and proliferation of lymphocytes stimulated with IL-2 and autologous sonicated tumor extract antigen in mixed culture (IL-2-enhanced MLTR). When compared with primary breast cancer patients, patients with liver metastases showed a significant decrease in % lysis of K562 and autologous tumor cells. After treatment, the stimulation index in IL-2-enhanced MLTR increased significantly from the pretreatment level and correlated with survival after treatment. Moreover, non-specific immunological parameters (performance status, lymphocyte count, and transferred cell count and proliferation rate of cultured lymphocytes) were significantly associated with response and prognosis.

Adult↗
PubMed1993

Diterpenoids from Caribbean gorgonians act as noncompetitive inhibitors of the nicotinic acetylcholine receptor.

1. Three cyclic diterpenoids isolated from gorgonians of the Eunicea genus and characterized as eupalmerin acetate (EUAC), 12,13-bisepieupalmerin (BEEP), and eunicin (EUNI) were found to be pharmacologically active on the nicotinic acetylcholine receptor (AChR). 2. The receptor from the BC3H-1 muscle cell line was expressed in Xenopus laevis oocytes and studied with a two-electrode voltage clamp apparatus. 3. All three compounds reversibly inhibited ACh-induced currents, with IC50's from 6 to 35 microM. ACh dose-response curves suggested that his inhibition was noncompetitive. The cembranoids also increased the rate of receptor desensitization. 4. Radioligand-binding studies using AChR-rich membranes from Torpedo electric organ indicated that all three cembranoids inhibited high-affinity [3H]phencyclidine binding, with IC50's of 0.8, 11.6, and 63.8 microM for EUNI, EUAC, and BEEP, respectively. The cembranoids at a 100 microM concentration did not inhibit [alpha-125I]bungarotoxin binding to either membrane-bound or solubilized AChR. 5. It is concluded that these compounds act as noncompetitive inhibitors of peripheral AChR.

Animals↗
PubMed1993

The ion channel of muscle and electric organ acetylcholine receptors: differing affinities for noncompetitive inhibitors.

1. Muscle and electric organ acetylcholine receptors (AChR's) were expressed in Xenopus laevis oocytes and differential effects of noncompetitive blockers on each type of receptor were analyzed using a two-electrode voltage clamp. 2. The positively charged channel blockers, phencyclidine (PCP) and tetracaine, displayed a much lower potency on muscle receptor than on the electric organ receptor. The IC50 for both blockers at the electrocyte receptor was close to 1 microM at -60 mV and even lower at more hyperpolarized voltages. In contrast, with muscle receptor IC50's were 20 to 40 microM at -60 or -80 mV. 3. Eupalmerin acetate, an uncharged noncompetitive inhibitor that displaces [3H]PCP from its high-affinity binding site, inhibited both receptors with a similar potency: IC50 of 4.9 and 6.4 microM for electrocyte and muscle receptors, respectively. However, eupalmerin acetate affected the desensitization process in each receptor type differently and triggered an unusual biphasic response in the muscle receptor. 4. These results are discussed with respect to differences in the amino acid sequences of the M2 regions of the two receptors. 5. A third type of noncompetitive inhibitor, Mg2+, was also examined and it inhibited both receptors with a similar potency (IC50, 0.5-1.0 mM). However, Mg2+ appeared to act at sites other than the PCP site.

Amino Acid Sequence↗
PubMed1993

Bone metastasis as a prognostic factor in breast cancer patients with liver metastasis given OK-432-combined adoptive immunotherapy via the hepatic artery.

The outcome in 31 patients with liver metastases from breast cancer given OK-432-combined adoptive immunotherapy via the hepatic artery was analyzed. Patients received intraarterial OK-432, a streptococcal preparation, followed by the transfer of autologous lymphocytes cultured with autologous tumor extract and interleukin-2 for 9-13 days. Liver lesions were evaluable in 11 of the 12 patients with bone metastasis (group A) and in 16 of the 19 patients without bone metastasis (group B). Complete response (CR) in the liver was attained in 8 patients in group A, but in only 1 in group B (p < 0.01). In group A, radiological features of all metastatic foci of bone improved after CR in the liver. Moreover, the median survival time (MST) of group A (20 months) was longer (p = 0.06) than that of group B patients with extra-hepatic metastasis (n = 12; MST = 6 months), while group B patients with liver metastasis alone (n = 7) showed a MST similar to that of group A. Thus, loco-regional immunotherapy via the hepatic artery was found to be useful in controlling both liver and bone metastasis from breast cancer. Moreover, in breast cancer patients with liver metastasis, bone metastasis appears to be a prognostic factor associated with good response to this immunotherapy.

Adult↗
PubMed1993

The induction of murine tumor infiltrating lymphocytes (TIL) by interleukin-2 or T cell growth factor.

Mice were injected in the foot pad with either 5 x 10(5) syngeneic plasmacytoma (MOPC104E) or fibrosarcoma cells (Meth A). Lymph nodes containing tumor cells were harvested 14 days later and cultured. In the presence of recombinant interleukin-2 (r-IL-2) predominantly tumor cells proliferated. Culture with T cell growth factor (TCGF) resulted in the growth of lymphoid cells. Concanavalin A (Con A) had only a modest effect on elimination of tumor cells in the culture. Tumor-infiltrating lymphocytes (TIL) prepared from the lymph nodes showed specific tumor-neutralizing activity when grown in the presence of TCGF. In vitro examination revealed that Meth A cells could not be lysed by TIL, while TIL from MOPC tumors showed tumor specific activity. This study may explain negative results in human trials with TIL induced by IL-2 alone.

Animals↗
PubMed1993

A simplified in vitro model of oxidant injury using vascular endothelial cells.

Oxidant injury of the vascular endothelium is considered an early event in the pathogenesis of atherosclerosis. The model of oxidant injury is crucial to the investigation of antioxidants. In the present study, a convenient in vitro model of oxidant injury induced by hydrogen peroxide (H2O2) was developed using bovine pulmonary artery endothelial cells (PAEC). Viability of PAEC grown in 96-well culture plates was determined with methylthiazol tetrazolium (MTT) colorimetric assay. Cell membrane integrity was measured by lactate dehydrogenase (LDH) release from PAEC grown in 24-well plates. Malondialdehyde (MDA, a product of lipid peroxidation) in PAEC grown in 6-well plates was detected by a thiobarbituric acid fluorometric assay. Incubation of H2O2 with PAEC caused a dose-dependent decrease of cell viability, an increase of LDH release, and an elevation of MDA production. MTT assay was convenient, quantitative, non-radioactive, and suitable for testing a large number of samples. The fluorometric assay for measuring MDA production in endothelial cells used 6-well plates instead of 80-cm2 flasks employed by previous investigators. The use of multiwell culture plates in these assays made it possible for more samples to be tested in any single experiment. The three assays are reproducible with low intraplate and interplate coefficients of variation. This in vitro model is suitable for screening antioxidants and for studying pharmacodynamics at the cellular level.

Animals↗