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Biomedical subjects

H Huang

Publications and source records attributed to H Huang.

At least 433 records · Page 24Linked to original sources
PubMed1996

Preparation, cloning, and high level expression in E. coli of interleukin 2-pseudomonas exotoxin fusion genes.

Using PCR and oligonucleotide-directed mutagenesis, recombinant plasmids which express IL2-PE fusion genes, e.g., IL2-PE40, IL2-PE40 KDEL, IL2-PE66(4Glu), and IL2-PE66(4Glu) KDEL, were constructed and expressed in E. coli at a high level. The fusion proteins were 20-30% of the total soluble bacterial proteins, existing as inclusion bodies in the host cell. In addition, there are single EcoRI, PstI, and SmaI restriction sites at the 5', 3' terminals and the linking region of the fusion genes, respectively, in the constructed expression plasmids so that these vectors could be conveniently converted to other expression vectors containing other cytokines or toxins.

ADP Ribose Transferases↗
PubMed1996

[A study on complicated chromosome translocation by fluorescence in situ hybridization (FISH) of G-banded chromosomes].

An experimental method of fluorescence in situ hybridization (FISH) with conventionally G-band chromosomes was developed to analyze the complex chromosome rearrangements of patients. In order to obtain optimal results of both G-banding and fluorescence signals, it was essential that G-banded chromosomes were fixed with formaldehyde prior to fluorescence in situ hybridization. The karyotype of a patient with spontaneous abortion might be described as 46, XX, t(1; 5; 12) (1pter-->1q25 : : 12q24-->12qter; 5qter-->5p11 : : 1q25-->1qter; 12pter-->12q24 : : 5p11-->5pter) by the analysis of conventional cytogenetics. However, her karyotype should be identified as 46, XX, t(1; 5; 12) (1pter-->1q23 : : 12q22-->12qter; 5qter-->5p11 : : 1q25-->1qter; 12pter-->12q22 : : 1q23-->1q25 : : 5p11-->5pter) with this newly established method. This investigation indicates that this technique described above is a powerful tool to detect complex chromosome rearrangements of patients.

Adult↗
PubMed1996

T7-promoter-based Escherichia coli expression system induced with bacteriophage M13HEP.

The bacteriophage M13HEP was constructed by cloning the T7 RNA polymerase gene into phage M13mp18 RF DNA to express T7 RNA polymerase under the control of the lac promoter. Through M13HEP phage infection, T7 RNA polymerase could be introduced into an expression strain and heterologous genes under the control of the T7 promoter can be induced to express. Using this phage M13HEP induction system, many heterologous genes, especially some genes whose products are toxic to the host strain, were successfully expressed. By transferring F' pilli from E. coli XL1-blue to E. coli HMS174, a new E. coli strain HMS174F' was obtained to make the construction, expression, and single-stranded DNA rescue of the T7 expression plasmid be conveniently performed in the same strain.

Bacteriophage M13↗
PubMed1996

[A dynamic study of the cytotoxic effects of hyperthermia combined with cis-diaminedichlorolplatinum (DDP) on human gastric cancer cell lines MKN28 and MKN45 in vitro].

Cytotoxic effects of hyperthermia combined with DDP on MKN28 and MKN45 cells were studied by MTT assay according to a nested design. The rusults showed: hyperthermia alone above 43 degrees C for 30 min was cytotoxic; hyperthermia at temperature lower than 43 degrees C for 30 min could increase sensitivity of cancer cells to DDP. The cytotoxic effect of simultaneous use of hyperthermia and DDP was more marked than that of sequential use of the 2 treatments. Hyperthermia combined with DDP could inhibit growth of human gastric adenocarcinoma cells regardless of their degree of differentiation.

Adenocarcinoma↗
PubMed1996

Management of ovarian endodermal sinus tumor.

OBJECTIVE: To evaluate the role of combination chemotherapy and the optimal cycles of treatment in improving the prognosis of ovarian endodermal sinus tumor, and to study the relationship between the type of surgical management and the outcome of the disease. PATIENTS AND METHOD: Sixty-three patients with ovarian endodermal sinus tumor were divided into 3 groups according to the postoperative chemotherapy they had received. Group 1 (37 patients) patients were treated with at least 6 cycles of VAC (vincristine, actinomycin-D and cytoxan) or 4 cycles of PVB (cysplatin, vincristine and bleomycin). Group 2 (17 patients) patients were treated with VAC in less than 6 cycles or PVB in less than 4 cycles. Group 3 (9 patients) patients received no VAC or PVB but some other drugs like TSPA, 5FU, MTX and cytoxan in various combinations. The sustained remission rates and survivals were compared among these 3 groups. For patients with full courses of treatment with VAC or PVB (Group 1), different types of surgical management were studied about their relationship with the outcome of the disease. RESULTS: The persistent remission rates are 81.8%, 23.5% and 11.8% for group 1, group 2 and group 3 patients respectively (P < 0.001). The survival curve of group 1 is very much different from that of group 2 and group 3 patients. With full courses of chemotherapy with VAC or PVB, it appears that the different types of surgical managements (unilateral vs bilateral adenectomy; with vs without systemic lymphadenectomy; residual tumor < 2 cm vs > 2 cm) did not show definite relationship with the outcome of the disease. CONCLUSION: Combination chemotherapy with VAC or PVB dramatically improved the prognosis of ovarian endodermal sinus tumor but it should be emphasized that the favorable results could be obtained only when the treatment is given on time and in optimal cycles. Although ovarian endodermal sinus tumor is chemosensitive, appropriate surgical treatment is still important, however, the surgical techniques need some further studies.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

[Effects of clomiphene citrate treatment on endometrial estrogen and progesterone receptors expressions].

OBJECTIVE: To assess the effects of clomiphene citrate (CC) on estrogen receptors (ER) and progesterone receptors (PR) expressions in glandular, epithelial and stromal cells of endometrium. METHODS: Endometrium samples of 16 normal ovulatory women (11 with unexplained and 5 female infertility) were taken in the late proliferative phase (12th day) and late secretory phase (10 days after ovulation), both in spontaneous and CC-induced cycles. ER and PR in glandular, epithelial and stromal cells of endometrium were localized and their histological score (H-score) were measured semi-quantitatively by monoclonal antibodies immunohistochemical analysis. RESULTS: The H-score of ER and PR contents were significantly lower in late proliferative phase and secretory phase of CC cycles when compared with that in spontaneous cycles (P < 0.01, P < 0.05). The decrease of receptor contents in glandular cells was significantly pronounced than that in stromal cells (P < 0.05). In late proliferative phase the decrease of ER was significantly severe than that of PR. On the contrary in late secretory phase the decline of PR was more significant. CONCLUSIONS: Based on these data, we suggested that CC inhibited the ER and PR induction in endometrium and affected endometrial development. These may be one of the causes of low pregnancy rate in CC-induced cycles.

Adult↗
PubMed1996

[The protective effects of dichloroacetate on cerebral ischemia after reperfusion of fed rats].

OBJECTIVE: To study the brain protective mechanisms of dichloroacetate (DCA) by observing the influence of DCA on the biochemical and pathological changes in ischemic brain tissues in different periods of reperfusion. METHODS: The FED-RAT cerebral ischemic model induced by 4-vessel occlusion was applied. 55 mature male Sprague-Dawley rats were divided into the control group, normal saline and DCA-treated groups before ischemia, normal saline and DCA-treated groups after ischemia equally and randomly. RESULTS: DCA could significantly lower the brain lactic acid, water content, and the diameter of cortical neurons, and protect the pathological damage of the membranaceous structure, before or after ischemia at a dose of 25 mg/kg, compared with the normal saline treated groups. CONCLUSION: Lowering brain lactate, resisting brain edema and protecting the membranaceous structures are the main brain protective mechanisms of DCA in biochemistry and ultrastructure.

Animals↗
PubMed1996

[Mandibular ridge augmentation with hydroxylapatite and its extension].

The results of 5 years follow-up of 84 cases of mandibular residual ridge augmented with hydroxlapatite (HA), followed by ridge extension, are reported. The first surgical procedures, subperiosteal HA insertion, and the second stage of total lowering of the floow of the mouth, vestibuloplasty and skin graft are detailedly described. The ridge is augmented by the first surgery, disturbance of the fraenums of the lip, buccal and tongue and muscles are eliminated by the second surgery, to increase denture retention and stability, improve wear resisting of tissue covered over the artifical ridge and eliminate pain and uncomfort when wearing denture. The results of five years follow-up show that two stages reconstruction are better than HA insertion only. HA is a kind of ideal material of bone replacement, which is not resorbed in most cases.

Adult↗
PubMed1996

[Reappraisal of the pathological criteria for uterine leiomyosarcoma].

In order to study the pathologic criteria for uterine Leiomyosarcoma, 42 cases of morphologically malignant or uncertain malignant potential uterine smooth muscle tumors which exhibited recurrences or metastasis, or were followed for a minimum of 2 years clinically, were analysed and reappraised. The results showed that in comparison with the leiomyoma group, active mitosis (mitotic index, MI > or = 10/10HPF), significant cytologic atypia and coagulative tumor cell necrosis (CTCN) were more common in the leiomyosarcoma group (71.4%, 92.9% and 71.4% respectively). Whereas 4 of the 14 leiomyosarcomas had MI < or = 4/10HPF, developed recurrences or metastasis, and 7 of the 28 leiomyomas had MI > or = 5/10HPF, including 2 with MI > 10/10HPF were alive and well 5.5-23.0 years after operation; hence a mitotic count is an unreliable prognostic criterion for uterine smooth muscle tumors. The data suggest that a trivariate rule using MI, the degree of atypia and CTCN best identifies the aggressive potential of uterine smooth muscle tumors.

Adult↗
PubMed1996

[Metastatic potential correlates with cell surface carbohydrate profiles of nasopharyngeal carcinoma].

In order to investigate the changes in glycoprotein structure between non-metastatic and metastatic cells of nasopharyngerl carcinoma (NPC), peanut agglutinin (PNA), ulex europeaus (UEA-I) and concanavalin ensifomis agglutinin (ConA) staining were used to examine 102 nasopharyngeal carcinoma tissues (84 primary tumors and 18 metastatic lymph nodes) with the avidin-biotinperoxidase complex method. PNA reaction was positive in most cells of nasopharyngeal carcinomas regardles of in histopathologic type, the degree of differentiation and metastasis. The levels of UEA-I receptors apparently increased during nasopharyngeal carcinoma progression from non-metastatic to metastatic tumors. The binding to ConA clearly decreased in the cells of metastatic cases and metastatic lymph node. So, the increased expression of UEA-I receptors and decrease of ConA receptors on tumor cells might have been implicated in the expression of metastatic potential.

Arachis↗
PubMed1995

Membrane thinning caused by magainin 2.

Magainin 2 is a 23-residue antibiotic peptide found in the skin of Xeonpus laevis (African clawed frog). It belongs to a broad class of alpha-helical peptides which interact directly with the lipid bilayer. Very little is presently known about the nature of this peptide/lipid interaction on the molecular level. We have performed a sequence of lamellar X-ray diffraction experiments to provide some insight into the nature of this interaction. We have found that, at concentrations below the critical concentration for lysis, the peptide causes the membrane thickness to decrease roughly in proportion to the peptide concentration. We further show that this thinning is consistent with a model where the peptide adsorbs within the headgroup region of the lipid bilayer at these concentrations. The energy cost of this thinning may also explain why the peptide inserts at high concentrations. We have already shown that a similar interaction exists for alamethicin interacting with diphytanoylphosphatidylcholine, and it should hold for a wide variety of peptide/lipid systems.

Amino Acid Sequence↗
PubMed1995

Solution structure of a cisplatin-induced DNA interstrand cross-link.

The widely used antitumor drug cis-diamminedichloroplatinum(II) (cisplatin or cis-DDP) reacts with DNA, cross-linking two purine residues through the N7 atoms, which reside in the major groove in B-form DNA. The solution structure of the short duplex [d(CAT-AGCTATG)]2 cross-linked at the GC:GC site was determined by nuclear magnetic resonance (NMR). The deoxyguanosine-bridging cis-diammineplatinum(II) lies in the minor groove, and the complementary deoxycytidines are extrahelical. The double helix is locally reversed to a left-handed form, and the helix is unwound and bent toward the minor groove. These findings were independently confirmed by results from a phase-sensitive gel electrophoresis bending assay. The NMR structure differs markedly from previously proposed models but accounts for the chemical reactivity, the unwinding, and the bending of cis-DDP interstrand cross-linked DNA and may be important in the formation and repair of these cross-links in chromatin.

Antineoplastic Agents↗
PubMed1995

Role of the carboxyl terminal MATEE sequence of spermidine/spermine N1-acetyltransferase in the activity and stabilization by the polyamine analog N1,N12-bis(ethyl)spermine.

Purified recombinant spermidine/spermine N1-acetyltransferase (SSAT) was found to be unstable in the absence of polyamines, but the loss of activity could be prevented or reversed by the addition of the polyamine analog and potential antitumor agent N1,N12-bis(ethyl)spermine (BE-3-4-3), which is known to be a potent inducer of SSAT in mammalian cells. Addition of BE-3-4-3 prevented the loss of SSAT activity and the digestion of the protein by the proteases trypsin, Lys-C, or Glu-C. In the absence of BE-3-4-3, this digestion occurred at the sequence Lys141Arg142Arg143 for trypsin or Lys-C and at the sequence Glu151Glu152 for Glu-C. When these sites were altered by mutation to residues which are not substrates for these proteases, cleavage in the absence of BE-3-4-3 occurred at residues Lys161, Lys166, and Glu162. These results indicate that the structure of SSAT contains a region that binds to the polyamine analog, BE-3-4-3, and that binding alters the configuration of the protein to prevent protease access to the region from amino acid residue 141 to the carboxyl terminal end (residue 171) of the SSAT. In order to determine the nature of the regulatory sites, specific mutations were made in the SSAT amino acid sequence, and the activity of the resulting SSAT protein and the sensitivity to proteases in the presence and absence of BE-3-4-3 was determined. The results indicate that the carboxyl terminal domain, MATEE, is critical for activity and for protection by BE-3-4-3.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyltransferases↗
PubMed1995

The Arabidopsis MADS-box gene AGL3 is widely expressed and encodes a sequence-specific DNA-binding protein.

The Arabidopsis AGL3 gene was previously identified on the basis of sequence similarity to the floral homeotic gene AGAMOUS (AG), which encodes a protein with a conserved MADS domain that is also found in human and yeast transcription factors (SRF and MCM1, respectively). Analysis of newly isolated full-length cDNA clones as well as genomic clones indicates that AGL3 is indeed a MADS-box gene with a general intron-exon structure similar to other plant MADS-box genes. However, unlike the others, which are expressed specifically in flowers, AGL3 is expressed in all above-ground vegetative organs, as well as in flowers, but not in roots. Furthermore, since AGL3 is MADS-domain protein, it is likely that it is also a DNA-binding protein regulating transcription. To characterize AGL3 as a DNA-binding protein in vitro, we expressed the AGL3 protein in Escherichia coli, and characterized its DNA-binding properties. We show that AGL3 binds to sequences which resemble the target sequences of SRF and MCM1, and have determined the consensus sequence to which AGL3 binds using random oligonucleotides. These results suggest that AGL3 is a widely distributed DNA-binding protein, which may be involved the transcriptional regulation of genes in many cells.

Amino Acid Sequence↗
PubMed1995

Evidence for coupling between Na+ pump activity and TEA-sensitive K+ currents in Xenopus laevis oocytes.

Using the two-microelectrode voltage clamp technique in Xenopus laevis oocytes, we estimated Na(+)-K(+)-ATPase activity from the dihydroouabain-sensitive current (IDHO) in the presence of increasing concentrations of tetraethylammonium (TEA+; 0, 5, 10, 20, 40 mM), a well-known blocker of K+ channels. The effects of TEA+ on the total oocyte currents could be separated into two distinct parts: generation of a nonsaturating inward current increasing with negative membrane potentials (VM) and a saturable inhibitory component affecting an outward current easily detectable at positive VM. The nonsaturating component appears to be a barium-sensitive electrodiffusion of TEA+ which can be described by the Goldman-Hodgkin-Katz equation, while the saturating component is consistent with the expected blocking effect of TEA+ on K+ channels. Interestingly, this latter component disappears when the Na(+)-K(+)-ATPase is inhibited by 10 microM DHO. Conversely, TEA+ inhibits a component of IDHO with a KD of 25 +/- 4 mM at +50 mV. As the TEA(+)-sensitive current present in IDHO reversed at -75 mV, we hypothesized that it could come from an inhibition of K+ channels whose activity varies in parallel with the Na(+)-K(+)-ATPase activity. Supporting this hypothesis, the inward portion of this TEA(+)-sensitive current can be completely abolished by the addition of 1 mM Ba2+ to the bath. This study suggests that, in X. laevis oocytes, a close link exists between the Na-K-ATPase activity and TEA(+)-sensitive K+ currents and indicates that, in the absence of effective K+ channel inhibitors, IDHO does not exclusively represent the Na(+)-K(+)-ATPase-generated current.

Animals↗
PubMed1995

The adoption of preventive care practice guidelines by primary care physicians: do actions match intentions?

OBJECTIVE: To measure primary care physicians' familiarity with, attitudes toward, and confidence in preventive care practice guidelines for the elderly and to determine whether their attitudes are associated with implementation of guidelines into clinical practice. DESIGN: A self-administered survey of physicians employed by a health maintenance organization (HMO) and of patients cared for by those physicians. Medical records were also reviewed to assess compliance with practice guidelines. SETTING: An HMO in Southern California. PARTICIPANTS: Forty-eight primary care physicians completed the survey (100% response rate). The medical records of 3,249 randomly selected elderly patients (65 to 75 years old) were studied. Of these patients, 2,799 completed a preventive care survey (response rate 86.1%). MEASUREMENT AND RESULTS: Most HMO primary care physicians agreed or strongly agreed that guidelines will improve quality of medical care (88%) and that guidelines have caused them to change their care of patients (73%). Although the physicians' general attitudes about guidelines did not often correlate with their use of preventive care guidelines, the physicians who stated that practice guidelines had changed their practices were more likely to offer their patients clinical breast examinations (75.9% vs 67.2%, p = 0.04) and to counsel their patients to exercise (70% vs 58%, p = 0.01) than were the physicians who did not. There was a significant association between physicians' support for and adoption of specific practice guidelines regarding mammography (r = 0.34, p = 0.02) and immunizations against influenza (r = 0.42, p < 0.005), pneumococcal pneumonia (r = 0.47, p < 0.001), and tetanus (r = 0.31, p = 0.03). CONCLUSIONS: Physicians employed by an HMO were familiar with and hopeful about the role of guidelines for improving patient care. Physicians' attitudes toward specific preventive care guidelines and admission that guidelines had caused them to change their practice did at times, but not always, correlate with their implementation of guidelines into clinical practice.

Adult↗