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Biomedical subjects

R Zhao

Publications and source records attributed to R Zhao.

At least 163 records · Page 9Linked to original sources
PubMed1994

Oral toxicity of boric acid and other boron compounds to immature cat fleas (Siphonaptera: Pulicidae).

Oral toxicity was characterized in first-instar cat fleas, Ctenocephalides felis felis (Bouché), feeding on dried blood treated with boric acid. LC50 values ranged from 2.11% after 24 h to 0.21% after 7 d. In carpet tests with five different boron compounds and a number of different formulations, significant mortality for first instars was observed in all cases. In similar tests with prepupae and cocoons, there was no significant effect on mortality. The importance of these results is discussed in light of current application procedures for boron compounds, and suggestions are made for future research.

Administration, Oral↗
PubMed1994

Products, genetic linkage and limb patterning activity of a murine hedgehog gene.

The hedgehog (hh) segmentation gene of Drosophila melanogaster encodes a secreted signaling protein that functions in the patterning of larval and adult structures. Using low stringency hybridization and degenerate PCR primers, we have isolated complete or partial hh-like sequences from a range of invertebrate species including other insects, leech and sea urchin. We have also isolated three mouse and two human DNA fragments encoding distinct hh-like sequences. Our studies have focused upon Hhg-1, a mouse gene encoding a protein with 46% amino acid identity to hh. The Hhg-1 gene, which corresponds to the previously described vhh-1 or sonic class, is expressed in the notochord, ventral neural tube, lung bud, hindgut and posterior margin of the limb bud in developing mouse embryos. By segregation analysis the Hhg-1 gene has been localized to a region in proximal chromosome 5, where two mutations affecting mouse limb development previously have been mapped. In Drosophila embryos, ubiquitous expression of the Hhg-1 gene yields effects upon gene expression and cuticle pattern similar to those observed for the Drosophila hh gene. We also find that cultured quail cells transfected with a Hhg-1 expression construct can induce digit duplications when grafted to anterior or mid-distal but not posterior borders within the developing chick limb; more proximal limb element duplications are induced exclusively by mid-distal grafts. Both in transgenic Drosophila embryos and in transfected quail cells, the Hhg-1 protein product is cleaved to yield two stable fragments from a single larger precursor. The significance of Hhg-1 genetic linkage, patterning activity and proteolytic processing in Drosophila and chick embryos is discussed.

Animals↗
PubMed1994

[Direct determination of tin in water by oscillopolarography].

Sn(IV) has a sensitive polarographic wave in the system of H2SO4-KI-VitC-V (IV). We examined the factors influencing the polarographic wave and found that the concentration of sulfuric acid and temperature were critical factors for the determination. The sensitivity of the method was increased nearly 50-fold by decreasing the concentration of sulfuric acid from 0.8 mol/L to 0.1 mol/L. The coefficient of variation (CV) percentages of the method were less than 5% and 8% for 6-7 determinations of Sn (IV) standard and sample respectively. The recovery ranged from 97.3% to 101%. The proposed method is suitable for direct determination of trace Sn (IV) in most natural water samples.

Polarography↗
PubMed1994

[The effect of acupuncture on the function of macrophages in rats of immunodepression].

The immunodepression model was established by means of intraperitoneal injection of cyclophosphamide in rats. Their phagocytic percentage and phagocytic index of peritoneal macrophages (PM phi) as well as serum lysozyme (LSZ) decreased obviously; After 6 days of acupuncture at "Zusanli" points (ST 36), PM phi phagocytic percentage and phagocytic index increased significantly, Serum LSZ showed no significant change. These results indicate that acupuncture can increase the phagocytic function of M phi in rats of immunodepression, but Serum LSZ level does not synchronously increase with the phagocytic function of M phi.

Acupuncture Therapy↗
PubMed1994

[The experimental study of prevention and treatment of the side-effects of chemotherapy with acupuncture (comparison among the effect of acupuncture at different acupoint)].

After an intraperitoneal injection of cyclophosphamide in rats, there was pathologic changes in hemopoietic, immune and visceral function. Acupuncture respectively at Zusanli, Dazhui and Shenshu points could decrease the above mentioned harms in the rats, the effect of acupuncture on hemopoietic function: Dazhui more than or equal to Zusanli, Zusanli more than Shenshu; the effect of acupuncture on immune function: Zusanli more than Dazhui, Dazhui more than or equal to Shenshu; the effect of acupuncture on the function of the liver and the kidney: Shenshu more than or equal to Zusanli, Zusanli more than Dazhui. The effect of acupuncture at all three points, i.e. Zusanli. Dazhui and Shenshu was more than that at any single point due to their coordination. There was no obvious effect when acupuncture at non-acupoints on tail.

Acupuncture Points↗
PubMed1993

The structure of human rhinovirus 16.

BACKGROUND: Rhinoviruses and the homologous polioviruses have hydrophobic pockets below their receptor-binding sites, which often contain unidentified electron density ('pocket factors'). Certain antiviral compounds also bind in the pocket, displacing the pocket factor and inhibiting uncoating. However, human rhinovirus (HRV)14, which belongs to the major group of rhinoviruses that use intercellular adhesion molecule-1 (ICAM-1) as a receptor, has an empty pocket. When antiviral compounds bind into the empty pocket of HRV14, the roof of the pocket, which is also the floor of the receptor binding site (the canyon), is deformed, preventing receptor attachment. The role of the pocket in viral infectivity is not known. RESULTS: We have determined the structure of HRV16, another major receptor group rhinovirus serotype, to atomic resolution. Unlike HRV14, the pockets contain electron density resembling a fatty acid, eight or more carbon atoms long. Binding of the antiviral compound WIN 56291 does not cause deformation of the pocket, although it does prevent receptor attachment. CONCLUSIONS: We conjecture that the binding of the receptor to HRV16 can occur only when the pocket is temporarily empty, when it is possible for the canyon floor to be deformed downwards into the pocket. We further propose that the role of the pocket factor is to stabilize virus in transit from one host cell to the next, and that binding of ICAM-1 traps the pocket in the empty state, destabilizing the virus as required for uncoating.

Amino Acid Sequence↗
PubMed1993

Fluorescence HPLC methods for detecting benzo[a]pyrene-7,8-dihydrodiol 9,10-oxide-deoxyadenosine adducts in enzyme-digests of modified DNA: improved sensitivity.

The fluorescence of mononucleoside adducts derived from the binding of anti-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene (BPDE I) to N6-deoxyadenosine (BPDE-dA adducts) is 10-100 times stronger (depending on the methanol/water solvent composition) than the fluorescence of adducts derived from the binding of this diol epoxide derivative to N2-deoxyguanosine. It is shown here that these fluorescence characteristics can be used to quantitate the relatively low yields of BPDE-dA adducts by fluorescence detection when BPDE-modified DNA is subjected to enzymatic degradation to the mononucleoside levels, followed by HPLC analysis of the digests.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1993

Mechanisms of quenching of the fluorescence of a benzo[a]pyrene tetraol metabolite model compound by 2'-deoxynucleosides.

The hydrophobic interactions of bulky polycyclic aromatic hydrocarbons with nucleic acid bases and the formation of noncovalent complexes with DNA are important in the expressions of the mutagenic and carcinogenic potentials of this class of compounds. The fluorescence of the polycyclic aromatic residues can be employed as a probe of these interactions. In this work, the interactions of the (+)-trans stereoisomer of the tetraol 7,8,9,10-tetrahydroxytetrahydrobenzo[a]pyrene (BPT), a hydrolysis product of a highly mutagenic and carcinogenic diol epoxide derivative of benzo[a]pyrene, were studied with 2'-deoxynucleosides in aqueous solution by fluorescence and UV spectroscopic techniques. Ground-state complexes between BPT and the purine derivatives 2'-deoxyguanosine (dG), 2'-deoxyadenosine (dA), and 2'-deoxyinosine (dI) are formed with association constants in the range of approximately 40-130 M(-1). Complex formation with the pyrimidine derivatives 2'-deoxythymidine (dT), 2'-deoxycytidine (dC), and 2'-deoxyuridine (dU) is significantly weaker. Whereas dG is a strong quencher of the fluorescence of BPT by both static and dynamic mechanisms (dynamic quenching rate constant k(DYN) = [2.5 +/- 0.4] x 10(9) M(-1)s(-1), which is close to the estimated diffusion-controlled value of approximately 5 x 10(9) M(-1)s(-1), both dA and dI are weak quenchers and form fluorescence-emitting complexes with BPT. The pyrimidine derivatives dC, dU, and dT are efficient dynamic fluorescence quenchers (k(DYN) approximately [1.5-3.0] x 10(9) M (-1)s(-1), with a small static quenching component due to complex formation evident only in the case of dT. None of the four nucleosides dG, dA, dC and dT are dynamic quenchers of BPT in the triplet excited state; the observed lower yields of triplets are attributed to the quenching of single excited states of BPT by 2'-deoxynucleosides without passing through the triplet manifold of BPT. Possible fluorescence quenching mechanisms involving photoinduced electron transfer are discussed. The strong quenching of the fluorescence of BPT by dG, dC and dT accounts for the low fluorescence yields of BPT-native DNA and of pyrene-DNA complexes.

Benzo(a)pyrene↗
PubMed1992

Identification and quantitative detection of isomeric benzo[a]pyrene diolepoxide--DNA adducts by low-temperature conventional fluorescence methods.

The pyrene-like fluorescence of adducts derived from the covalent binding of (+/-)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene [+/-]-anti-BPDE] to DNA increases in intensity by factors of 20 or more as the temperature is lowered from ambient to approximately 100 K. This effect is primarily associated with the strong quenching of the pyrene-like fluorescence of BPDE-deoxyguanosyl adducts at room temperature, and the suppression of the electron-transfer quenching mechanism at 100 K. In contrast, the fluorescence of BPDE-deoxyadenosyl adducts is not quenched at ambient temperatures, and the fluorescence yields of (+/-)-anti-BPDE-poly(dA-dT).(dA-dT) adducts increases by only a factor of 2 in this same temperature range. Utilizing an internal fluorescein fluorescence standard to correct for differences in light scattering and variations in instrumental factors, a fluorescence method is described for quantitatively determining the levels of benzo[a]pyrene diolepoxide derivatives covalently bound to cellular DNA at 100 K. The method is illustrated with (+/-)-reverse-BPDE [(+/-)-trans-9,10-dihydroxy-anti-7, 8-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene]. Adduct levels as low as 10 pmol in a 400 microliters sample volume can be detected and identified from their excitation and fluorescence emission spectra using a conventional and commercially available fluorometer. In the case of modified DNA extracted from BPDE-treated Chinese hamster ovary cells or from mouse skin (approximately 1 BPDE residue/20,000 bases), such an analysis requires only 100 micrograms of DNA. Conformationally different adducts derived from the binding of the isomeric (+/-)-anti-BPDE, (+/-)-reverse-BPDE or (+/-)-syn-BPDE to cellular DNA can be distinguished by their low-temperature fluorescence excitation spectra. Specifically, the quasi-intercalated site I BPDE adducts (believed to be associated with cis-addition stereochemistry) can be distinguished from site II adducts situated at external BPDE binding sites (trans-addition stereochemistry). These results suggest that the fates of these conformationally different BPDE-DNA adducts, e.g. due to enzymatic repair, can be monitored as a function of time in DNA extracted from intact, functioning cells.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1992

[Pasting acupoints with Chinese herbs applying in infant acute bronchitis and effect on humoral immune substances].

This report described the clinical observation of pasting acupuncture with Chinese herbs applying in 72 infant acute bronchitis cases and regarding to the humoral immune substances such as IgA, IgM, IgG, Complement C3 The result shows high cure and improve rate. The curative effect of infantile group is higher than that of childhood one (x2 = 6.501, 0.05 > p > 0.025). All indexes of humoral immune substances, especially IgA, were increased after treatment (t = 10.50, p < 0.01).

Acupuncture Points↗
PubMed1992

[Diagnostic value of stroboscopy in early glottic carcinoma].

Stroboscopic evaluation was conducted on 34 cases with glottic T1 carcinomas, and the relationship was studied between the area, thickness and volume of the lesion and the amplitude as well as mucosal wave of vibration. In all cases the mucosal wave of the lesion (WAVL) was abolished. The amplitude of the lesion (AMPL) was decreased in 17 and abolished in another 17 cases. There were significant relationship between the area of the lesion and the mucosal wave of the entire vocal fold (WAVE), the thickness of the lesion and AMPL, and the volume of the lesion and WAVE, AMPL, and the amplitude of the entire vocal fold (AMPE). The present paper suggested that if WAVL is reserved, the lesion is not invasive carcinoma, nor is it if any one of AMPE, AMPL, WAVE or WAVL is normal (except for lesions confined to the cartigenous vocal fold).

Aged↗
PubMed1991

Pathological changes of hyperphonated cat vocal folds.

To investigate the pathological changes of hyperphonated vocal folds 15 cats were used and over-cry was induced by mechanical stimuli. The longest experiment time was 15 weeks. All of the larynges were taken and the vocal folds were examined grossly and microscopically. The results were as follows: 1) liquid exudate accumulation beneath the epithelium developed in all of the experimental animals; 2) thickening of the epithelium was noticed in cats which had hyperphonated for more than 4 weeks; 3) acute laryngitis occurred in three cats.

Acute Disease↗
PubMed1991

[A logistic regression analysis of relations between juvenile myopia and TV-watching, trace elements, and psychological characteristics].

With a paired study, 23 factors were investigated in 204 school children aged 9-14 in Taiyuan. The results of analysis of logistic regression showed that there was a close relationship between juvenile myopia and TV-watching distance, myopia in parents, Zn: Cu ratio in hair, N score of EPQ, Pscore of EPQ, and verbal IQ. The relations between myopia and some factors were discussed.

Adolescent↗
PubMed1991

[Medicinal Polygonatum in northwest China].

This paper reports 16 species of medicinal plants of Polygonatum found in northwest China, along with their distribution, ecological conditions, infraspecies variations and clinical applications. A key to the species is provided.

China↗
PubMed1991

[The study of standard of classroom temperature for middle and primary schools in freezing and cold regions in winter].

In order to study the standard of appropriate temperature for classroom in freezing and cold regions, field and laboratory research were conducted. The results indicated: the appropriate temperature for classroom was 16-18 degrees C or 15-20 degrees C, according to the children's sense of cold and hot at different classroom temperature. The most appropriate classroom temperature was 18-20 degrees C, according to the changes of certain physiological indexes of children. 16-18 degrees C is recommended to be the standard of temperature for the middle and primary school classrooms in the cold regions in China.

Adolescent↗
PubMed1989

[Cell line of hybridoma secreting monoclonal antibodies against Echinococcus granulosus antigens].

In order to produce specific monoclonal antibodies for immunodiagnosis and immunoprophylaxis in hydatid disease, a monoclonal antibody cell line NIA2 secreting specific antibodies was established, through fusion of myeloma cells SP2/0 and spleen cells of BALB/c mice immunized with hydatid fluid from a local (Ningxia) patient and repeated screenings and clonings. The specificity was assayed via ELISA, immunoprecipitating and ultramicroscopy. Antibody titer of 1:2,560 was obtained in the supernatant of the culture medium by ELISA and a high titer of 1:163,840 in seeded ascitic fluid of mice of the same isolate. Immunoglobulin subclass of the NIA2 secreting antibody was determined to be IgG1 which showed no cross reaction to Cysticercus cellulosae. Cloned cell lines from the hybridomas were found consistent in secreting anti-Echinococcus granulosus antibody through serial passage in tissue culture for ten months.

Animals↗