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Biomedical subjects

L Hu

Publications and source records attributed to L Hu.

At least 199 records · Page 11Linked to original sources
PubMed1990

Cyclic AMP analogs and retinoic acid influence the expression of retinoic acid receptor alpha, beta, and gamma mRNAs in F9 teratocarcinoma cells.

Retinoic acid (RA) receptor alpha (RAR alpha) and RAR gamma steady-state mRNA levels remained relatively constant over time after the addition of RA to F9 teratocarcinoma stem cells. In contrast, the steady-state RAR beta mRNA level started to increase within 12 h after the addition of RA and reached a 20-fold-higher level by 48 h. This RA-associated RAR beta mRNA increase was not prevented by protein synthesis inhibitors but was prevented by the addition of cyclic AMP analogs. In the presence of RA, cyclic AMP analogs also greatly reduced the RAR alpha and RAR gamma mRNA levels, even though cyclic AMP analogs alone did not alter these mRNA levels. The addition of either RA or RA plus cyclic AMP analogs did not result in changes in the three RAR mRNA half-lives. These results suggest that agents which elevate the internal cyclic AMP concentration may also affect the cellular response to RA by altering the expression of the RARs.

Animals↗
PubMed1990

[Inhibiting effect of mitoxantrone on cell cycle progression of Chinese hamster ovary cells].

The effect of Mitoxantrone, a Potential anticancer chemotherapeutic agent, on the cell cycle progression of Chinese Hamster ovary (CHO) cells was investigated by microspectrophotometry. CHO cells incubated with the agent for either 30 min or 24 h were inhibited, to various degrees, from proliferation. The inhibition appeared in dose dependent fashion. A 10-fold dose of the drug was required for the 30 min group, as compared to the 24h group, to develop an equivalent inhibiting effect. When exponentially growing cells were treated with Mitoxantrone for 30 min, washed free of drug, and cultured in fresh medium for another 23.5 h a dose of 0.01 micrograms/ml had little or no effect on the distribution of CHO cells throughout the cell cycle at any point. However, a dose of 0.10-1.00 micrograms/ml was sufficient to cause a decrease of cells in G1 and an accumulation of cells in G2. Block cells had abnormally large nucleus.

Animals↗
PubMed1989

Identification of multiple repressor recognition sites in the hut system of Pseudomonas putida.

The hutC gene in Pseudomonas putida encodes a repressor protein that negatively regulates the expression of all hut genes. We have overexpressed this cloned hutC gene in Escherichia coli to identify P. putida hut regions that could specifically bind the repressor. Ten restriction fragments, some of which were partially overlapping and spanned the coding portions of the P. putida hut region, were labeled and tested for their ability to recognize repressor in a filter binding assay. This procedure identified three binding sites, thus supporting previous indications that there were multiple operons. A 1.0-kilobase-pair SalI restriction fragment contained the operator region for the hutUHIG operon, whereas a 1.9-kilobase-pair SmaI fragment contained the hutF operator. A 2.9-kilobase-pair XhoI segment appeared to contain the third operator, corresponding to a separate and perhaps little used control region for hutG expression only. The addition of urocanate, the normal inducer, caused dissociation of all operator-repressor complexes, whereas N-formylglutamate, capable of specifically inducing expression of the hutG gene, inhibited binding only of repressor to fragments containing that gene. Formylglutamate did not affect the action of urocanate on the repressor-hutUHIG operator complex, indicating that it binds to a site separate from urocanate on the repressor. DNA footprinting and gel retardation analyses were used to locate more precisely the operator for the hutUHIG operon. A roughly 40-base-pair portion was identified which contained a 16-base-pair region of dyad symmetry located near the transcription initiation site for this operon.

Base Sequence↗
PubMed1988

Organization and multiple regulation of histidine utilization genes in Pseudomonas putida.

The arrangement of the histidine utilization (hut) genes in Pseudomonas putida was established by examining the structure of a DNA segment that had been cloned into Escherichia coli via a cosmid vector. Southern blot analysis revealed that the restriction patterns of the hut genes cloned into E. coli and present in the P. putida genome were identical, indicating that no detectable DNA rearrangement took place during the cloning. Expression of the hut genes from a series of overlapping clones indicated the gene order to be hutG-hutI-hutH-hutU-hutC-hutF. The transcription directions of the different hut genes were determined by cloning the genes under control of the lambda pL promoter. This showed that hutF, encoding formiminoglutamate hydrolase, was transcribed in a direction opposite to that of the other genes. Inactivation of the cloned hut genes by Tn1000 insertion revealed that the hut genes were divided into three major transcriptional units (hutF, hutC [the repressor gene], and hut UHIG), but hutG may also be independently transcribed. When cloned individually with hutC on the same vector, hutF and hutU (which encodes urocanase) expression was induced by urocanate, indicating that these two genes each possess an operator-promoter element. Tn1000 insertions (in the cloned genes) or Tn5 insertions (in the P. putida genome) affecting the hutI or hutH gene only partially eliminated hutG expression. Furthermore, hutG, which specifies N-formylglutamate amidohydrolase, was regulated by the hutC product when the two genes were cloned on the same vector and expressed in E. coli. Therefore, hutG can be expressed independently from its own promoter, in keeping with earlier observations that N-formylglutamate amidohydrolase synthesis is not coordinated with that of urocanase and histidase and can be induced by N-formylglutamate or urocanate.

Cloning, Molecular↗
PubMed1987

Purification and properties of formylglutamate amidohydrolase from Pseudomonas putida.

Formylglutamate amidohydrolase (FGase) catalyzes the terminal reaction in the five-step pathway for histidine utilization in Pseudomonas putida. By this action, N-formyl-L-glutamate (FG) is hydrolyzed to produce L-glutamate plus formate. Urocanate, the first product in the pathway, induced all five enzymes, but FG was able to induce FGase alone, although less efficiently than urocanate did. This induction by FG resulted in the formation of an FGase with electrophoretic mobility identical to that of the FGase induced by urocanate. A 9.6-kilobase-pair HindIII DNA fragment containing the P. putida FGase gene was cloned into the corresponding site on plasmid pBEU1 maintained in Escherichia coli. Insertion of the fragment in either orientation on the vector resulted in expression, but a higher level was noted in one direction, suggesting that the FGase gene can be expressed from either of two vector promoters with different efficiencies or from a single vector promoter in addition to a less efficient Pseudomonas promoter. FGase was purified 1,110-fold from the higher-expression clone in a yield of 10% through six steps. Divalent metal ions stimulated activity, and among those tested (Co, Fe, Zn, Ca, Ni, Cd, Mn, and Mg), Co(II) was the best activator, followed by Fe(II). FGase exhibited a Km of 14 mM for FG and a specific activity of 100 mumol/min per mg of protein in the presence of 5 mM substrate and 0.8 mM CoCl2 at 30 degrees C. The enzyme was maximally active in the range of pH 7 to 8. FGase was found to be a monomer of molecular weight 50,000. N-Acetyl-L-glutamate was not a substrate for the enzyme, but both it and N-formyl-L-aspartate were competitive inhibitors of formylglutamate hydrolysis, exhibiting Ki values of 6 and 9 mM, respectively. The absence of FGase activity as an integral part of histidine breakdown in most other organisms and the somewhat uncoordinated regulation of FGase synthesis with that of the other hut enzymes in Pseudomonas suggest that the gene encoding its synthesis may have evolved separately from the remaining hut genes.

Amidohydrolases↗
PubMed1985

[Termination of mid- and late-term gestation with small dose of genkwaninol and rivanol: comparative clinical and pathological analysis].

This paper deals with a comparative study on the clinical aspects of 300 case of mid-late-term abortions induced by small dose and routine dose of alcoholic extract of Flos Genkwa and by rivanol and on 100 cases of fetal autopsies. Clinical aspects of 300 cases of abortions, the therapeutic effective rate, and the fetal mortality rate of the small doses of Flos Genkwa are similar to those of the routine doses of Flos Genkwa but with fewer side effects. As compared with the rivanol group, lower the time of induction of abortion is shorter, the rate of live fetuses and the cases with retention of part of the membranes and placenta are fewer. Pathologic aspects of 100 cases of fetal autopsies -- the predominant pathologic changes of the fetus in the Flos Genkwa group are congestion and hemorrhage in contrast with edema in the rivanol group. Degeneration and necrosis in visceral organs occurred in both groups, but they were severe in the Flos Genkwa group. The predominant pathologic changes of umbilical cord in the Flos Genkwa group were trauma and proliferation of intima, thrombosis, and pan-vesselitis. In the rivanol group, the predominant changes were diffuse infiltration of macrophages in the stroma. In both groups there was degeneration and necrosis of trophoblasts of placenta. In Flos Genkwa group, the vessels in the chorionic villi were highly contracted, even the lumen were closed, while in the rivanol group the vessels were dilated. The inflammation of placentas and decidua and the degeneration and necrosis of decidua were also thoroughly examined, analyzed, and compared.

Abortion, Induced↗
PubMed1983

Mechanism of action of an antiseptic, anti-odor mouthwash.

Inter-related determinants of oral malodor were measured over a three-hour period in 30 human subjects after mouthwash treatments. Re-odoration was important to mouthwash activity for 30 min. At post-treatment times of 60-180 min, the anti-odor activity of the product is due solely to its anti-microbial action.

Anti-Infective Agents, Local↗
PubMedDate not supplied

Association between IgE antibody against soluble egg antigen and resistance to reinfection with Schistosoma japonicum.

There is evidence that immunoglobulin (Ig) E antibody may be a critical component of protective immunity against Schistosoma mansoni and S. haematobium reinfection. In the present study, 555 individuals aged 3-67 years infected with S.japonicum received praziquantel treatment before the transmission season commenced; 45 d later, blood samples from 265 individuals who had no S. japonicum egg in their stool were examined by enzyme-linked immunosorbent assay for specific isotypic antibodies. Single, non-conditional logistic regression analysis showed that exposure intensity, age, soluble egg antigen (SEA)-IgE, SEA-IgM and soluble adult worm antigen-IgG4 were relevant to reinfection; multiple, non-conditional logistic regression analysis showed that exposure intensity was still a significant factor for reinfection while the SEA-IgE antibody level was associated with resistance to reinfection with S. japonicum, with a protective index of 2.00. It is suggested that this population in an area endemic for schistosomiasis japonica exhibits acquired immunity.

Adolescent↗
PubMedDate not supplied

Raccoon poxvirus live recombinant feline panleukopenia virus VP2 and rabies virus glycoprotein bivalent vaccine.

A raccoon poxvirus (RCNV) recombinant for immunizing against feline panleukopenia and rabies was developed by homologous recombination with a chimeric plasmid for insertional inactivation of the RCNV thymidine kinase gene. The recombinant, RCN-FPV/VP2-rabG, coexpressed the feline panleukopenia virus (FPV) VP2 protein and the rabies virus spike glycoprotein (rabG) under oppositely oriented vaccinia virus P11 promoters. Cats vaccinated subcutaneously with the recombinant showed relatively high neutralizing antibody responses against rabies virus and FPV, and protection against an otherwise virulent FPV challenge with no drop in white blood cell count. Because of containment constraints, no rabies virus challenges were done, but the high concentrations (> 8 IU) of rabies neutralizing antibodies were consistent with levels that usually indicate an ability to counter the infection.

Animals↗
PubMedDate not supplied

Evidence against a major role of PEG1/MEST in Silver-Russell syndrome.

Silver-Russell syndrome (SRS) is a heterogeneous disorder characterised by interauterine and postnatal growth retardation, with or without additional dysmorphic features. Most cases are sporadic but a few familial cases have been described. A subset of patients exhibit maternal uniparental disomy for chromosome 7 (mUPD7) strongly suggesting that genomic imprinting plays a role in the aetiology of the disease. We and others have recently characterised the human PEG1/MEST gene, the first imprinted gene known to be located on chromosome 7. Although the function of PEG1/MEST is unknown, the paternal-specific expression of this gene and its location at 7q32, render it a promising candidate for SRS. As a prerequisite for mutation screening in 49 patients with SRS and 9 with primordial growth retardation (PGR), we determined the complete genomic structure of the PEG1/MEST gene which consists of 12 exons. Apart from one silent mutation and two novel polymorphisms, nucleotide changes were not detected in any of these patients. Moreover, methylation patterns of the 5' region of PEG1/MEST were found to be normal in 35 SRS and 9 PGR patients and different from the pattern seen in patients with mUPD7. These findings strongly argue against a role of PEG1/MEST in the majority of Silver-Russell syndrome cases.

Abnormalities, Multiple↗
PubMedDate not supplied

A hypoxia-regulated adeno-associated virus vector for cancer-specific gene therapy.

The presence of hypoxic cells in human brain tumors is an important factor leading to resistance to radiation therapy. However, this physiological difference between normal tissues and tumors also provides the potential for designing cancer-specific gene therapy. We compared the increase of gene expression under anoxia (<0.01% oxygen) produced by 3, 6, and 9 copies of hypoxia-responsive elements (HRE) from the erythropoietin gene (Epo), which are activated through the transcriptional complex hypoxia-inducible factor 1 (HIF-1). Under anoxic conditions, nine copies of HRE (9XHRE) yielded 27- to 37-fold of increased gene expression in U-251 MG and U-87 MG human brain tumor cell lines. Under the less hypoxic conditions of 0.3% and 1% oxygen, gene activation by 9XHRE increased expression 11- to 18-fold in these cell lines. To generate a recombinant adeno-associated virus (rAAV) in which the transgene can be regulated by hypoxia, we inserted the DNA fragment containing 9XHRE and the LacZ reporter gene into an AAV vector. Under anoxic conditions, this vector produced 79- to 110-fold increase in gene expression. We believe this hypoxia-regulated rAAV vector will provide a useful delivery vehicle for cancer-specific gene therapy.

Adenoviridae↗
PubMedDate not supplied

SNAP-25 deficit and hippocampal connectivity in schizophrenia.

Regional abnormalities of brain connectivity may be an important substrate for the expression of schizophrenia, a severe form of mental illness. Brain imaging and postmortem morphometric studies indicate hippocampal structure is abnormal in schizophrenia. To study molecular components of hippocampal connectivity the presynaptic proteins SNAP-25 and synaptophysin were assayed in postmortem samples. Immunocytochemical studies indicated reduced SNAP-25 immunoreactivity in schizophrenia compared to controls, particularly in the terminal fields of entorhinal cortex projections. Although there were no overall changes in synaptophysin immunoreactivity, in the granule cell layer of the dentate gyrus synaptophysin immunoreactivity was increased in schizophrenia. These results indicate that disconnection of a subset of hippocampal circuitry from the entorhinal cortex, as well as intrinsic changes in hippocampal connectivity, may contribute to the mechanism of illness in schizophrenia.

Adult↗
PubMedDate not supplied

Prevalence of retinitis pigmentosa in urban and rural adult Chinese: The Beijing Eye Study.

PURPOSE: To determine the prevalence of retinitis pigmentosa in the elderly Chinese population. METHODS: The Beijing Eye Study is a population-based, cross-sectional cohort study and included 4439 subjects out of 5324 subjects invited to participate (response rate 83.4%) with an age of 40+ years. Readable fundus photographs were available for 4027 (90.7%) subjects. Diagnostic criteria for retinitis pigmentosa were visual field defects on frequency doubling perimetry, typical ophthalmoscopic abnormalities such as retinal pigment deposits, retinal arteriole attenuation, and pigment epithelial atrophy, and no other reason for perimetric defects and fundus abnormalities. RESULTS: Retinitis pigmentosa was diagnosed in four subjects (all men). Its prevalence was 0.099+/-3.15% (95% CI: 0.00, 0.2). CONCLUSIONS: Retinitis pigmentosa with typical fundus appearance and functional loss may be present in about 1 out of 1000 elderly Chinese in Northern China. Calculated for the whole population in China, the figure would be 1.3 million patients with retinitis pigmentosa.

Adult↗
PubMedDate not supplied

P53-independent apoptosis: a mechanism of radiation-induced cell death of glioblastoma cells.

PURPOSE: Radiation therapy, though routinely used in the treatment of patients with glioblastoma multiforme, is of limited efficacy in extending patients' lives. In this study we investigated the mechanism by which ionizing radiation causes death of glioblastoma cells in the hope of ultimately altering the intrinsic radioresistance of glioblastoma tumors. METHODS: Radiation survival in vitro was quantitated using linear quadratic and repair-saturation mathematical models. Radiation-induced apoptosis was assayed by fluorescence-activated cell sorter analysis, terminal deoxynucleotide transferase labeling technique, and chromatin morphology. Cellular distribution within the cell cycle was quantitated by dual labeling with propidium iodide and bromodeoxyuridine. RESULTS: We examined whether in vitro clonogenic radioresistance of glioblastoma would reflect their susceptibility to radiation-induced apoptosis and their ability to undergo a G1 arrest--two cellular functions associated with wild-type p53 expression. We demonstrated that apoptosis contributed to the cytocidal effect of ionizing radiation on glioblastoma cells. The apoptosis observed in glioblastoma cell lines occurred in the absence of wild-type p53 expression. We identified a glioblastoma cell line expressing wild-type p53 and found that it did not exhibit radiation-induced apoptosis but rather underwent a prolonged G1 arrest not observed in any glioblastoma cell line lacking wild-type p53 expression. CONCLUSION: Apoptosis is an important component of the lethal effect of ionizing radiation on glioblastoma cells and does not require wild-type p53 expression. Glioblastoma expressing wild-type p53 exhibited no apoptosis, even after high radiation doses, but rather underwent a prolonged G1 arrest. The observation of p53-independent apoptosis and p53-dependent Gi arrest in glioblastoma cells have important radiobiologic and clinical implications.

Apoptosis↗
PubMedDate not supplied

Radiation-induced damage in two human glioma cell lines as measured by the nucleoid assay.

We measured radiation-induced damage and repair in MO59J and MO59K human glioma cell lines using the nucleoid halo assay. Although these two cell lines have different radiosensitivities when assayed for colony forming efficiency, our results indicated that there was no significant difference between the two in terms of the unwinding and rewinding of DNA supercoils, radiation-induced changes in nucleoid halo size or the kinetics of nucleoid halo lysis. The only differences noted were in the kinetics of recovery of radiation-induced changes in nucleoid halo size, with the more sensitive cell line (MO59J) showing a slightly faster recovery than the more resistant cell line (MO59K). However, this difference was not statistically different. Our data indicate that the different cellular radiosensitivities of MO59J and MO59K cells are probably not due to any differences in their supercoiled DNA structure as measured by the nucleoid halo assay.

Cell Nucleus↗