Biomedical subjects
Publications and source records attributed to L Zhong.
The sole, as the body weight-bearing region, is characterized with the skin of thick stratum corneum. Wound in the region is difficult to cure. Based on the blood supply of the foot, a fibular skin flap of the great toe was designed and used to treat the defect of the planta pedis. Clinical applications in 6 cases were successful. The operation results were satisfactory.
The mice used in this study were of the in-bred strains C57BL/6 and Balb/c which differ at the major histocompatibility complex (MHC). The immunogenicity of tooth allografts was studied in vitro by means of detecting the response of Antibody-Complement Mediated Cytotoxity (ACMC) and Cell Mediated Cytotoxity (CMC) of the host. We found that there was significant difference for both ACMC and CMC activity between the allogenic and isogenic tooth transplantation (P < 0.01). The results indicate that tooth allografts are immunogens and do evoke the immune response of recipients.
This paper introduce a novel comprehensive system of visual electrophysiological information processing. The weak-light stimulator and surface-electrode are used to overcome the subject's unfitted sense led by Ganzifield stimulator and the cornea-touch electrode. Based on two computers which are interconnected, this system can work on pan-character picture stimulating mode. While working on line, it can dynamically display the process of test in real-time. It also offers a clear interface and integrated modules of information processing and analysis.
Expression of the A. niger T21 and 3.795 glaA gene was investigated with respect to the growth of mycelia, producing of glucoamylase, copy number of glaA gene as well as glucoamylase mRNA level and its stability. Both A. niger T21 and 3.795 produced substantial glucoamylase at the stable phase when their biomass were the same. After incubating for 72 hours, while the biomass remained the same, the glucoamylase produced by T21 was 10-17 times higher than that by 3.795. Northern analysis showed that in the total RNA from T21 4.3-4.4 fold as much glucoamylase mRNA as from 3.795 was determined. This result along with results with regard to copy number of glaA gene and stability of glucoamylase mRNA supported the suggestion that the increased mRNA level of glucoamylase was contributed by the increasing at transcription level. The inconsistancy between the difference of enzyme production (10-17 fold) and that of the mRNA level (4.3-4.4 fold) revealed that some difference at translation exist probably. Furthermore, expression of both T21 and 3.795 glaA gene was regulated by carbon sources, this regulation occurred at transcription level in the same manner and also probably occurred at translation level.
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Mutational analysis of several amino acids in the transmembrane region of the sarcoplasmic reticulum ATPase was performed by expressing wild type ATPase and 32 site-directed mutants in COS-1 cells followed by functional characterization of the microsomal fraction. Four different phenotype characteristics were observed in the mutants: (a) functions similar to those sustained by the wild type ATPase; (b) Ca2+ transport inhibited to a greater extent than ATPase hydrolytic activity; (c) inhibition of transport and hydrolytic activity in the presence of high levels of phosphorylated enzyme intermediate; and (d) total inhibition of ATP utilization by the enzyme while retaining the ability to form phosphoenzyme by utilization of P(i). Analysis of experimental observations and molecular models revealed short and long range functions of several amino acids within the transmembrane region. Short range functions include: (a) direct involvement of five amino acids in Ca2+ binding within a channel formed by clustered transmembrane helices M4, M5, M6, and M8; (b) roles of several amino acids in structural stabilization of the helical cluster for optimal channel function; and (c) a specific role of Lys297 in sealing the distal end of the channel, suggesting that the M4 helix rotates to allow vectorial flux of Ca2+ upon enzyme phosphorylation. Long range functions are related to the influence of several transmembrane amino acids on phosphorylation reactions with ATP or P(i), transmitted to the extramembranous region of the ATPase in the presence or in the absence of Ca2+.
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Toxoplasma gondii tachyzoites were loaded with the fluorescent indicator fura 2 to investigate the transport mechanisms involved in maintaining their intracellular Ca2+ homoeostasis. The mitochondrial ATPase inhibitor oligomycin and the endoplasmic-reticulum Ca(2+)-ATPase inhibitor thapsigargin increased the intracellular Ca2+ concentration ([Ca2+]i), thus indicating the requirement for ATP and the involvement of the endoplasmic reticulum in maintaining intracellular Ca2+ homoeostasis. The effect of thapsigargin was more accentuated in the presence of extracellular Ca2+, clearly showing that, as occurs with other eukaryotic cells, depletion of intracellular Ca2+ pools led to an increase in the uptake of Ca2+ from the extracellular medium. In addition to these results, we found evidence that, in contrast with what occurs in mammalian cells, T. gondii tachyzoites possess a significant amount of Ca2+ stored in an acidic compartment, termed the acidocalcisome, as indicated by: (1) the increase in [Ca2+]i induced by bafilomycin A1 (a specific inhibitor of H(+)-ATPases), nigericin (a K+/H+ exchanger) or the weak base NH4Cl, in the nominal absence of extracellular Ca2+ to preclude Ca2+ entry; and (2) the effect of ionomycin, a Ca(2+)-releasing ionophore that cannot take Ca2+ out of acidic organelles and that was more effective after alkalinization of these compartments by addition of bafilomycin A1, nigericin or NH4Cl. Considering the relative importance of the ionomycin-releasable and the ionomycin + NH4Cl-releasable Ca2+ pools, it is apparent that T. gondii tachyzoites contain a significant amount of Ca2+ stored in acidocalcisomes.
A 850 bp fragment of the 5' flanking region of the glucoamylase gene (glaA) was synthesized from A. niger T21 genome using PCR. The function detection vector was constructed by fusing this fragment to E. coli hygromycin B phosphotransferase gene (hph) and was used to transform A. niger. The high hygromycin resistance transformants thus obtained verified that the synthesized fragment functioned as a promoter in filamentous fungi. Southern blot analysis showed the hph gene has been integrated into genomic DNA of A. niger transformant.
The brewing yeast having glucoamylase activity was constructed by integrating glucoamylase cDNA from Asapergillus niger into the genome of brewing yeast B48. The integration was achieved by cotransformation of YEP type plasmid pKG1 carrying glucoamylase expression-secretion element and was verified by Southern blot analysis. The engineered yeast was stable, and the fermentation test demonstrated that the lower residual dextrin level was obtained compared with control strain B48. Thus the fermentation rate was raised to 80.5%. No alteration of growth and brewing properties was observed. Beer quality was judged to be good.
A large proportion of antimicrobial peptides share a common structural feature that is critical to their antimicrobial activity, i.e. amphipathic alpha-helices. The amphipathy of a polypeptide chain can be quantitated through the value of the hydrophobic moment. Generally, antimicrobial peptides are characterized by high hydrophobic moment and low hydrophobicity values. Using these criteria we have identified two short segments that possess hydrophobic moment properties associated with known antimicrobial peptides. Using in vitro assays the segment derived from the protein perforin displays no antifungal or antibacterial activity and, while showing no alpha-helicity in buffer or liposomes, exhibits a modest degree of alpha-helical structure in the presence of the alpha-helical inducer, 2,2,2-trifluoroethanol. However, rational modifications result in a derivative which assumes an alpha-helical conformation in the presence of liposomes, exhibits potent antifungal activity against plant fungal pathogens, has significant antibacterial activity, effects leakage of a fluorescent dye from acidic liposomes and is devoid of hemolytic activity. Results are also presented for a segment derived from the human immunodeficiency virus envelope protein. We suggest that the identification of putative amphipathic structures in proteins may provide a useful starting strategy in the design and synthesis of antimicrobial peptides.
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Leishmaniasis remains endemic in China, especially in the west and northwest frontier regions in central Asia. Epidemic outbreaks of both visceral and cutaneous forms of the disease have become a serious concern in view of such events occurring in neighboring countries. In the present study, we have begun to characterize available parasites as an initial step in understanding the epidemiology of leishmaniasis in central Asia. Nineteen Leishmania isolates collected since the 1950s from epidemiologically different foci in China were separated into five genotypes (Groups I-V) based on their polymorphisms in both kinetoplast (kDNA) and nuclear (nDNA) DNAs. Both kDNA and nDNA are conserved in Group I, which consists of six isolates, i.e., five cases of human kala-azar and one case of canine leishmaniasis isolated from three distant foci more than 30 years apart. In contrast, both kDNA and nDNA are heterogeneous in Group II, consisting of 10 isolates scattered in the plain area from the eastern coast to the western desert. This group includes five kala-azar cases, one post-kala-azar dermal leishmaniasis case, two sand fly isolates, and two canine isolates. The remaining three groups (III-V), two from great gerbils (Rhombomys opimus) and one from a kala-azar case, differ among themselves and from the aforementioned groups. Groups I, II/III, IV, and V contain isolates that have been recognized epidemiologically or typed isoenzymatically as L. donovani s.l., L. infantum s.l., L. turinica, and L. gerbilli, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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Phlebotomus major wui, an anthropophilic species, was predominant among sandflies in Karamay, Xinjiang of China. The females of this species collected in the wild and houses were detected to be infected with promastigotes. Three isolates of promastigotes obtained from P. major wui were inoculated intraperitoneally and subcutaneously into normal hamsters or BALB/c mice which developed visceral leishmaniasis later. The mean size of amastigotes in hamster viscera (smear observation) artificially inoculated with the cultured parasite originated from sandfly was significantly smaller than those in control hamster inoculated with the cultured Leishmania turanica from great gerbils in situ. The promastigotes from P. major wui hardly grew in NNN medium. In addition, 32P labeled gene gp63 was used as probe to hybridize DNA prepared from L. infantum, L. turanica and Leishmania from this sandfly showed that marked homogeneity existed between the isolates from P. major wui and L. infantum. At the present time, visceral leishmaniasis did not occur in Karamay but cutaneous leishmaniasis (CL) has been evidenced. Thus, what is the source of natural infection of P. major wui? Whether L. turanica or L. infantum is the pathogen of human CL in this area? These are interesting aspects to deal with in the further study.
Glucoamylase cDNA synthesized from A. niger mutant T21 was modified at 5' and 3' ends in order to clone it into yeast shuttle plasmid YFD18 and to cause fusion between cDNA and the leader region of the yeast-mating pheromone alpha-factor. The modified cDNA was then inserted into YFD18 at HindIII site. Saccharomyces cerevisiae Y33 was transformed with the resultant recombinant plasmid YFD18HH6. Analysis of transformants including halo formation on starch medium plate, SDS-PAGE of culture filtration and determination of glucoamylase activity showed that the yeast transformed with plasmid containing glucoamylase cDNA efficiently secreted glucoamylase into the medium. This fact indicated that yeast alpha-factor was able to direct the synthesis and secretion of functional glucoamylase of Aspergillus. In addition the protolytic cleavage site involved in the maturation of glucoamylase in A. niger also worked in S. cerevisiae.