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F Liu

Publications and source records attributed to F Liu.

At least 505 records · Page 28Linked to original sources
PubMed1996

Initial processing of human proenkephalin in bovine chromaffin cells.

The opioid peptide precursor preproenkephalin (PPE) contains seven enkephalin sequences and is synthesized by epinephrine-producing adrenal chromaffin cells and various peripheral and central neurons. After removal of its signal peptide, PPE undergoes processing at dibasic amino acid sites to yield its final opioid products-Met-enkephalin, Leu-enkephalin, and various larger, enkephalin-containing peptides. Processing of PPE was examined in bovine chromaffin cells using a plasmid containing the human PPE (hPPE) cDNA under the control of the cytomegalovirus immediate early enhancer/promoter. Following transfection of this hPPE-containing plasmid into bovine chromaffin cells, several proenkephalin-immunoreactive bands were observed on western blots with monoclonal antibodies that recognize human, but not bovine, proenkephalin sequences. The pattern of hPPE-derived peptides observed was similar to that of bovine PPE processing products. A series of recombinant plasmids containing mutations in the hPPE sequence at putative processing sites was then constructed. Conversion of Lys-Lys and Lys-Arg sequences to Lys-Gln and of Arg-Arg to Arg-Gln altered initial hPPE processing at only three of the putative processing sites. When hPPE cDNA containing mutations at all of these initially processed sites was expressed, one or more alternative processing sites were revealed. These data suggest the importance of structural features in addition to the dibasic sequences that limit the processing of proenkephalin.

Adrenal Cortex↗
PubMed1996

Urban ozone plumes and population distribution by income and race: a case study of New York and Philadelphia.

Who lives in the downwind areas of urban ozone plumes? Location theory suggests that the poor should disaproportionately populate the downwind area, while the rich are most likely to live outside urban ozone plumes. Dynamically, we would expect that the downwind area would become poorer over time because the rich would "vote with their feet" under the serious impacts of urban ozone plumes. However, the importance of urban ozone pollution could be discounted due to the public's risk perception. According to risk and air quality perception literature, one would expect that the public would likely perceive ozone air pollution as a relatively low risk, compared with other environmental risks and social concerns. Therefore, actual population distribution might not follow what location theory suggests. Who actually does live in the downwind areas of urban ozone plumes? The results from a case study of New York and Philadelphia show that the ozone downwind areas are currently populated by a considerably larger proportion of upper income households and whites than the source areas. Furthermore, the population dynamics data do not provide any evidence for the "vote with their feet" hypothesis. While these findings deviate from the hypotheses prescribed by location theory, they are consistent with what we could expect from theories of risk perception.

Air Pollutants↗
PubMed1996

Inhibition of high K+ and norepinephrine-induced free intracellular calcium by tetrandrine in dissociated rabbit retina cells.

The effect of tetrandrine (Tet) on the changes of intracellular free Ca2+ concentration ([Ca2+]i) induced by high concentration of K+ and norepinephrine is dissociated rabbit retina cells were studied. The changes of [Ca2+]i were reflected by the fluorescent indicator, Fura-2/AM, employed. The resting [Ca2+]i was 223 +/- 27 nM in Hank's solution containing 1.3 mM Ca2+. Tet at 30 microM did not affect the resting [Ca2+]i when the extracellular Ca2+ concentration was in the range of 0-2 mM. Tet at 1-100 microM suppressed the [Ca2+]i elevation induced by high concentration of K+ in a concentration-dependent manner. When the concentration of K+ was 50 mM IC50 for Tet was 10.9 microM. Although Tet at high concentration (30 microM) suppressed the [Ca2+]i increases induced by norepinephrine (0.1-100 nM) in the presence of Ca2+ at 1.3 mM, failed to do the same at lower concentration of Tet (1-10 microM), however, Tet at 30 microM did not effect the release of intracellular Ca2+ stored in the sarcoplasmic reticulum in the Ca(2+)-free Hank's solution. These results indicate that Tet is able to block Ca2+ influx from extracellular site via voltage-sensitive ionic channels and at high concentration via receptor-operated ionic channels in retina cells.

Adrenergic alpha-Agonists↗
PubMed1996

Inhibitory effects of tetrandrine on intracellular free Ca2+ increase induced by glutamate, serotonin and histamine in dissociated retina cells.

The effects of tetrandrine (Tet) on the elevation of intracellular free Ca2+ concentration ([Ca2+]i) induced by glutamate, serotonin and histamine in dissociated rabbit retina cells were studied. The changes of [Ca2+]i were reflected by the fluorescent indicator, Fura-2/AM, employed. In the presence of extracellular Ca2+ (1.3 mM), glutamate, serotonin and histamine significantly increased the [Ca2+]i in a dose-dependent manner. Glutamate (100 microM), serotonin (100 microM) and histamine (200 microM) markedly increased the [Ca2+]i of retina cells by 165%, 126% and 58%, respectively. Tet 30 microM significantly inhibited the increase of [Ca2+]i induced by glutamate (100 microM), serotonin (100 microM) and histamine (200 microM) by 28.0%, 46.8% and 29.0%, respectively. A lower concentration (10 microM) of Tet also produced an inhibitory effect on the increase of [Ca2+]i but was less effective than the Tet 30 microM. In Ca(2+)-free Hank's solution, Tet did not produce a significant inhibitory effect on the increase of [Ca2+]i caused by serotonin and histamine. These results indicate that Tet exercises blocking Ca2+ influx from the extracellular site via NMDA, 5-HT2 and H1-receptor operated Ca2+ channels and has no obvious effect on the Ca2+ release from intracellular Ca2+ stores.

Alkaloids↗
PubMed1996

The effect of growth hormone treatment on the insulin-like growth factor axis in a child with nonislet cell tumor hypoglycemia.

We have previously described a case of tumor-associated hypoglycemia secondary to the production of high molecular weight insulin-line growth factor (IGF)-II in a child with congenital neuroblastoma. The child's hypoglycemia resolved with GH therapy and has continued to be well controlled for 1 yr. This represents one of the first cases of nonislet cell tumor hypoglycemia (NICTH) treated successfully with long-term exogenous GH. We now present an in-depth analysis of the IGF axis in this patient, before and after GH treatment. Although IGF-II levels at presentation were in the normal range, they were inappropriate for the patient's low GH state. Furthermore, the percentage of "big" IGF-II was elevated, as was the level of the IGF-IIE peptide, which is normally cleaved in the processing of the mature peptide. On the initial evaluation, GH levels failed to rise in response to hypoglycemia, IGF-I levels were low, IGF binding protein-3 (IGFBP-3) levels were suppressed, and IGFBP-2 levels were elevated. We have shown that baseline IGFBP-3 levels were low by RIA and immunoblotting and have demonstrated that this decrease was not associated with IGFBP protease activity. We have also demonstrated the baseline suppression of the acid labile subunit (ALS) of the 150K ternary complex by a novel immunoblot assay. The ratio of IGFs to IGFBP-3 was dramatically elevated, presumably leading to hypoglycemia. Furthermore, the percentage of serum IGF-I and IGF-II present as part of a binary (50K) complex with IGFBPs was also increased. GH therapy resulted in a normalization of the levels of blood sugars, IGFBP-3, ALS, IGFBP-2, and IGF-I, as well as the IGF/IGFBP-3 ratio. In summary, we have presented evidence that the hypoglycemia in this patient resulted from tumor production of high molecular weight IGF-II, which suppressed GH secretion, leading to the described derangements in the IGF binding proteins. We speculate that as a result of the decreased IGFBP-3 and ALS levels, the IGF population was shifted from the stable 150K complex to lower molecular weight complexes with IGF binding proteins, increasing IGF availability to tissues due to rapid turnover of these low molecular weight complexes. We demonstrated the reversal of the abnormalities in the IGFBP levels with GH treatment, corresponding to the clinical response of euglycemia.

Adenoma, Islet Cell↗
PubMed1996

A homologous radioimmunoassay for rat insulin-like growth factor-I (IGF-I): implications for studies of human IGF-I physiology.

We report the development of a unique radioimmunoassay (RIA) for rat insulin-like growth factor-I (rIGF-I) which does not recognize human IGF-I (hIGF-I). The rIGF RIA uses a specific anti-rIGF-I antiserum with rIGF-I standards and radioligand. Rat sera were extracted by either an abbreviated acid/ethanol procedure or by acid-chromatography with virtually identical results. Assay sensitivity is congruent to 0.5 ng/tube and inter- and intra-assay coefficients of variation were 3.4-7.6% and 4.8-9.2%, respectively. Comparisons of the rIGF-I RIA with a typical heterologous RIA shows that the latter underestimates rIGF-I levels congruent to of 3-fold. Sera from rats treated with hIGF-I were also studied using the rIGF-I RIA and a hIGF-I- specific immunoradiometric assay (IRMA), and results indicate poor correlation between the actual total IGF-I levels (rIGF-I RIA + hIGF-IRMA) and the heterologous RIA estimates. The availability of both rIGF-I and hIGF-I specific immunoassays facilitates more precise studies of hIGF-I in the rat model.

Animals↗
PubMed1996

The frequency of homozygous deletion of a developmentally regulated Vh gene (Humhv3005) is increased in patients with chronic idiopathic thrombocytopenic purpura.

Little is known of the genetic factors that may contribute to the development of chronic idiopathic thrombocytopenic purpura (cITP). We have previously shown that a developmentally regulated Vh gene (Humhv3005) is absent in 10/41 (24%) of patients with systemic lupus erythematosus while it is absent in only 7/88 (8%) of normal controls. This finding suggests that a homozygous deletion of an Ig variable (V) gene may alter the immune system and thus predispose the host to an autoimmune disorder. We have analyzed the same gene in 44 patients with cITP and found that Humhv3005 and like genes were absent in a higher percentage of patients (14 of 44, 31.8%) than they were absent in either normals (7/88, 8%, p = 0.002) or thrombocytopenic patients without cITP (6/53, 11.3%, p = 0.042); the hv3005 deletion frequency in the latter group did not differ from that in normals (P = 0.74). These data suggest that deletions of Humhv3005 and/or highly homologous Vh genes may predispose individuals to the development of cITP, and may contribute toward production of pathogenic antiplatelet antibodies.

Chronic Disease↗
PubMed1996

[Normalization of myocardial perfusion reserve after coronary stent implantation in comparison with balloon angioplasty alone].

Stents scaffold coronary arteries after angioplastic treatment and inhibit elastic recoil resulting in a larger and more circular focal lumen. In 25 patients with significant stenoses of the left anterior descending coronary artery, presenting no collaterals or myocardial infarction, EKG-gated digital subtraction angiograms were recorded at baseline and during hyperemia induced by intracoronary injection of 12 mg papaverine before and after balloon angioplasty, and after adjunct implantation of a single Palmaz-Schatz stent. Densitometric evaluation revealed the time parameters contrast medium appearance time (MCAT) rise time (RT) and mean transit time (MTT) and maximum intensity (Imax). Myocardial perfusion reserve (MPR1) was calculated as the ratio of baseline MCAT and hyperemic MCAT multiplied by the ratio of hyperemic Imax and baseline Imax while MPR2 was calculated as the ratio of baseline RT and hyperemic RT. Maximum flow ratio (MaxFR) was calculated as the ratio of preprocedural hyperemic MTT and postprocedural hyperemic MTT. Post-stenotic MPR1 increased from 1.36 +/- 0.28 to 2.50 +/- 1.20 and to 3.40 +/- 0.58 (ANOVA p < 0.05), while reference MPR1 remained unchanged with 3.40 +/- 0.60. Post-stenotic MPR2 increased from 1.57 +/- 0.14 to 2.59 +/- 0.86 after balloon angioplasty and to 3.10 +/- 0.41 after stenting (ANOVA p < 0.05), while reference MPR2 remained unchanged with 3.10 +/- 0.40. MaxFR was 2.13 +/- 0.53 after balloon angioplasty and 2.83 +/- 0.35 after stenting (p < 0.05). A good correlation was found between minimal stenosis diameter and MPR1 or MPR2 (MPR1: r = 0.94; MPR2: r = 0.87) and between luminal gain and MaxFR (r = 0.75). A negative correlation was measured between recoil, defined as the difference between inflated balloon diameter and resulting minimal stenosis diameter, and MPR1 and MPR2 and MaxFR (MPR1: r = -0.86; MPR2 r = -0.80; MaxFR r = -0.83). In conclusion, adjunct coronary stent implantation normalized post-stenotic myocardial perfusion immediately in contrast to balloon angioplasty alone resulting from a larger postprocedural lumen and a more pronounced inhibition of elastic recoil.

Adult↗
PubMed1996

[The effect of nimodipine and papaverine on delayed cerebral vasospasm in dogs].

OBJECTIVE: To evaluate the effect of nimodipine and papaverine (Pap) on the spastic arteries with delayed cerebral vasospasm (DCVS) in dogs. METHODS: A model of DCVS in dogs was induced by the cisterna magna injections of fresh autologous blood twice. The diameter of the basilar arteries with and without DCVS was measured with the aid of a JVC operative microes cope in vivo after nimodipine and Pap were directly placed around the arteries. RESULTS: The dilation of the basilar arteries was obviously induced by application of nimodipine and Pap in the dogs without DCVS no dilation was induced by application of nimodipine and slight dilation by application of Pap but in those with DCVS. CONCLUSION: The cerebral blood flow is improved by the effect of nimodipine on non-spastic arteries. Pap has been found to reverse slightly the narrowing of the basilar arteries with DCVS and to dilate the arteries without DCVS, but the vasodilation effect is transient.

Animals↗
PubMed1996

[High frequency rotational angioplasty].

High-speed rotational coronary atherectomy is an alternative method to treat complex, especially calcified coronary stenoses. A rotating burr tip removes the occlusive plaque tissue. The applied rotating frequency is between 160 000 to 190 000 rpm. The primary technical success-rate for high frequency rotational atherectomy alone yields between 50 to 60% on average. Associated with consecutive additional balloon angioplasty, the success rate is between 80 and 95% when treating complex type B II or C stenoses. Today, the usage of a single burr tip size with adjunctive balloon angioplasty has become a standard procedure. The occurrence of serious complications such as extensive dissections or thrombotic vessel occlusion is a rare phenomenon after high-speed rotational atherectomy compared to coronary balloon angioplasty, whereas coronary spasm is more common after high-speed rotational atherectomy. According to the actual results, high-speed rotational angioplasty did not lower the rate of long-term restenosis, compared to the results achieved by balloon angioplasty alone. The rate of long-term restenosis is reported to be between 40 to 50% after highspeed rotational angioplasty with or without adjunctive balloon angioplasty.

Atherectomy, Coronary↗
PubMed1996

[The significance of intravascular ultrasound in differential diagnosis and therapy of coronary stenoses].

Intravascular ultrasound (IVUS) has emerged from being a research tool to becoming an important aspect in invasive cardiology, because it offers the possibility to obtain "in vivo" histology, including the vessel wall, while angiography allows for lumenograms only. The reasons for performing IVUS can be divided into either diagnostic or intervention associated indications. Diagnostic strength of IVUS is the ability to monitor compensatory coronary artery enlargement as a response to arteriosclerosis, to reveal occult left main stem disease, and angiographically "silent" arteriosclerosis. The peri-interventional potentials of IVUS are the ability to allow optimal device selection, i.e., rotablators in calcified lesions or atherectomy devices in large plaque burden. The effects of PTCA on vessel wall morphology can be studied in great detail and the effect on true luminal gain assessed almost on-line. Several groups showed that the residual plaque area after angiographically successful PTCA lies in the range of 60%. A significant reduction of this number may influence long-term outcome after PTCA. Minimal luminal areas after PTCA seem to be an indicator of restenosis, while the morphological appearance alone seems to be less predictive. Intravascular monitoring of stent implantation led to high-pressure stent deployment with significant increase in postprocedural luminal diameters and, finally, the ability to withold anticoagulation in patients with optimal stent deployment. Furthermore, integrated devices, like balloons on IVUS catheters, steerable catheters, integrated flow measurements and pressure transducers will further increase the usefulness of IVUS.

Angioplasty, Balloon, Coronary↗
PubMed1996

Expression of G1 cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors in androgen-induced prostate proliferation in castrated rats.

Androgen induces prostate cell proliferation in the castrated rat. We hypothesized that G1 cyclins, cyclin-dependent kinases (cdk), and cdk inhibitors mediate this cellular response to mitogenic signals. In this study, induction of cyclins D1, D2, D3, E, and cdks 2, 4, and 6 expression was observed at various time points during testosterone replacement in the ventral prostate of castrated rats. The induction followed prostate epithelium proliferation, which peaked at 48 h and decreased at 120 h during the treatment. The study of cyclin/cdk complex formation revealed that more cyclin D1/cdk4 and cyclin D1/cdk6 complexes were formed at 48 h than at 120 h of treatment, but cyclin D1/cdk2 complexes remained the same. Furthermore, both hyperphosphorylated and hypophosphorylated forms of Rb were detected at 48 h, but only the hypophosphorylated form was detected at 120 h of treatment. p21Cip1, which was very abundant in the ventral prostate of castrated and intact rats, was not detected when the prostate started proliferation and increased gradually as proliferation decreased during the androgen treatment. Meanwhile, p27Kip1 dramatically increased after androgen treatment, and the induction levels were less at the peak of prostate proliferation and higher when proliferation was low. The results presented here suggest that expression of G1 cyclins and their related kinases and kinase inhibitors are well regulated after androgen replacement in the ventral prostate of castrated rats. The cooperation between these cell cycle regulators leads to a well-controlled prostate regeneration.

Animals↗
PubMed1996

Development of arithmetical competencies in Chinese and American children: influence of age, language, and schooling.

The arithmetical competencies of more than 200 Chinese or American kindergarten, first-, second-, or third-grade children were assessed toward the beginning and toward the end of the U.S. school year. All children were administered a paper-and-pencil test of addition skills, a digit span measure, and an addition strategy assessment. The addition strategy assessment provided information on the types of strategies the children used to solve simple addition problems as well as information on the speed and accuracy of their strategy use. Information on the number of math instruction periods across times of measurement was also obtained for each of the first-, second-, and third-grade children. The pattern of arithmetical development across the academic year and across the Chinese and American children suggests that a mix of cultural and maturational factors influence the emergence of early arithmetical competencies and that the Chinese advantage in early mathematical development is related to a combination of language- and school-related factors.

Achievement↗
PubMed1996

[The PCR amplification, cloning, sequencing, expression in E. coli of gene encoding endoflagella subunit protein (fla B) from Leptospira interrogans serovar lai].

A pair of oligonucleotide primers were designed by ourselves to amplify the endoflagella gene of L. interrogans serovar lai. A fragment about 840 bp was generated with PCR and inserted into plasmid pUC8 after the fragment and pUC8 were digested respectively with Bam HI and Pst I. A recombinant plasmid (designated as pLF1) was obtained. SDS-PAGE analysis indicated that a 33 kd was expressed in E. coli JM103 harboring pLF1 and the expression level of the protein was 11% of total bacterial soluble proteins. Western blot analysis showed that the protein band could be recognized by the antiserum against the endoflagella (Axiall filament) of Leptospira interrogans serovar lai. Nucleotide seguence data showed an open reading frame encoding 282 aminoacids residues, corresponding to a protein of molecular weight 33.6 kd. The G + C content of endoflagella subunit protein gene was 48 mol%. Therefore, the G + C content of the leptospiral fla B Gene is significantly higher than the reported 39 mol% G + C content of leptospiral genome of L.interrogans serovar lai but similar to the G + C of the Treponema pallidum genome. Comparison of the deduced endoflagellar subunit protein (fla B) amino acid sequence with flagellins from other bacteria revealed a high level of identity with the Treponema pallidum fla B proteins. Immunization/protection experiment was performed on the model of BALB/c mice and showed that the survival rate in the group JM103-pLF1 was higher than that in the group JM103-pUC8, but statistically the difference between them was significant (P < 0.05) and pLF1 did not induce significant levels of agglutinating antibodies against L.interrogans serovar lai.

Amino Acid Sequence↗
PubMed1996

[Systematic analysis of basic drugs in plasma using X-5 solid-phase extraction GC-FID and GC-MS].

A systematic determination method for 34 basic drugs in human plasma is described. Drugs were extracted from plasma at pH 10 using X-5 resin as adsorbent, then identified and quantitated by capillary GC-FID and GC-MS. The detection limits for most drugs are in the range of 0.5-2.0 micrograms.ml-1. Precision and linearity of the method are satisfactory for clinical toxicological applications.

Analgesics, Opioid↗
PubMed1996

[Morphological changes in intracranial and extracranial arteries of autopsy cases of cerebrovascular diseases].

OBJECTIVE: To determine the distribution and severity of arterial lesions of intracranial and extracranial arteries in stroke patients in Chinese. METHODS: We studied 120 consecutive autopsy cases including 100 cases of stroke (50-80 years) and 20 cases of cancer as controls (50-80 years). Medium intracranial arteries and their primary branches, small intracerebral arteries, arterioles and extracranial carotid arteries (from 16 cases only) were examined with light microscopy. RESULTS: The stroke patients had significantly lower mean LA-VA ratios of the medium sized intracranial arteries and their primary branches, small intracerebral arteries and arterioles than the controls (P < 0.001). The stroke patients had higher mean VW-VR ratios of these arteries than the controls (P < 0.001). Atherosclerotic narrowing of the medium sized intracranial arteries and their primary branch were more severe than those of the extracranial caotid arteries. Moreover, the proximal portion of the primary branch arteries was much more severe than that of extracranial caotid arteries (P < 0.01, P < 0.05) in the stroke patients. CONCLUSION: Stroke patients had atherosclerotic lesions of the intracranial medium sized arteries and their primary branches and sclerotic lesions of the small intracerebral arteries and arterioles. These pathological changes resulted in thickening arterial walls and narrowing arterial lumens.

Aged↗
PubMed1996

[Detection and clinical pathological significance of the expression of P21, P185, p53 proteins and mutation of ras, p53 genes in transitional cell carcinoma of the bladder].

In order to find the significance of gene changes in the development of transitional cell carcinoma of bladder, immunohistochemical and PCR-RFLP methods were used to study the expression of P21, P185, p53 proteins and mutations in ras and p53 genes. The results showed that the P21, P185 and p53 positive rates were 59.3%, 55.3% and 29.3% respectively. Positive rates for P21 and P185 decreased with the progression of the pathological grade (P < 0.05). p53 positive rates decreased with the progression of pathological grade (P < 0.01). Positive expression of P21, P53 were significantly correlated with prognosis. Expression of more than two kinds of oncogene proteins were present in 73 cases of bladder transitional cell carcinoma. The rate of point mutation in codon 12 of Ha-ras gene of bladder transitional cell carcinoma was 32%. The p53 gene mutation rate of bladder transitional cell carcinoma was 18%, all mutations occurred at codon 248. The point mutation in codon 12 of Ha-ras gene increased with the progression of pathological grade (P < 0.05). The ras and p53 gene mutations were significantly correlated with prognosis (P < 0.05). The mortality of patients with ras and p53 gene mutation were higher than patients without mutations. 4 cases of bladder transitional cell carcinoma contained both ras and p53 gene mutations.

Adult↗