Biomedical subjects

Y Y Zhong

Publications and source records attributed to Y Y Zhong.

5 recordsLinked to original sources

PubMed2006

Modeling biodegradation of toluene in rotating drum biofilter.

Rotating drum biofilters (RDBs) are cost-effective for control of emissions of volatile organic compounds (VOCs) from waste gas streams. In this paper, a dynamic mathematical model is presented which simulates and predicts the variation in performance of a multi-layer RDB with time on the basis of the two-film theory. The model takes into account factors including biofilm growth and biomass loss, and a changing biofilm surface area and thickness assuming quasi-steady-state conditions in the two-phase system and uniform bacterial population. Toluene was assumed to be the only rate-limiting substrate. The model equations for the gas-phase mass balance and biofilm growth were solved using MATLAB based on the fourth-fifth-order Runge-Kutta technique, and the concentration profiles in the biofilms were obtained using the method of orthogonal collocation. Simulation results showed that the toluene removal efficiency decreased with increased toluene loading or increased duration of operation of the biofilter. Calculation results were compared to the experimental results, which demonstrated that the dynamic model provided a good simulation of the performance of the biofilter.

Biodegradation, Environmental↗

PubMed1996

Evidence for the existence of a pseudoknot structure at the 3' terminus of the flavivirus genomic RNA.

The 3'-terminal nucleotides of the flavivirus genomic RNA form conserved secondary structures that may function as cis-acting signals for RNA replication. Here we provide evidence for the existence of a conserved pseudoknot structure at the 3' terminus of the flavivirus genomic RNA. A truncated version of the West Nile virus (WNV) 3'-terminal RNA sequence was used as the model for these studies. Circular dichroism spectra indicated the presence of a highly structured RNA conformation with a significant amount of A-form helix. Ribonuclease probing not only confirmed the presence of the predicted secondary structure, which consists of a long stem-loop (SL1) and a shorter stem-loop (SL2), but also suggested that base pairing occurs between nucleotides in the loop of SL2 and those in an internal loop strand located on the 5' side of SL1. Analysis of three mutant RNAs further supported the existence of pseudoknot interactions. UV-melting analysis of the WNV 3' model RNA showed three transitions with significant hyperchromicity at approximately 46, 62, and 79 degrees C. UV-melting analysis with either SL1 or SL2 RNA alone suggested that the 62 and 79 degree C transitions represent the unfolding of SL2 and SL1, respectively. The 46 degree C transition is most likely due to the opening of the proposed tertiary structure. A similar melting curve was obtained for another flavivirus (dengue-3 virus) 3'-terminal RNA, providing further support for the conservation of the structure among flaviviruses. Molecular modeling of the RNA indicated that a pseudoknot structure is a stereochemically and energetically reasonable model for the 3' terminus of flavivirus genomic RNA.

Base Sequence↗

PubMed1994

Sequence specific thermodynamic and structural properties for DNA.RNA duplexes.

DNA.RNA hybrid duplexes are found in many important biological processes and are involved in developing modes of disease treatment, such as antisense therapy, yet little is known about the sequence dependence of their structure and stability. The structure and thermodynamic stability of DNA.RNA hybrid model systems corresponding in composition and length and containing (1) all purine or all pyrimidine bases on each strand or (2) mixed purine and pyrimidine bases on each strand have been evaluated relative to pure RNA and DNA duplexes by thermal melting, CD, and electrophoresis analyses. The spread in free energies of denaturation of the homopurine.homopyrimidine systems covers over 14 kcal/mol of single strands, while the mixed sequence free energies vary by less than 4 kcal/mol. The RNA-homopurine.DNA-homopyrimidine hybrid resembles a corresponding pure RNA duplex in both structure and stability, whereas the DNA-homopurine.RNA-homopyrimidine hybrid resembles a corresponding pure DNA duplex. The mixed sequence hybrids show intermediate structure between the corresponding pure RNA and pure DNA duplexes and a stability closer to that of the pure DNA duplex. From these results and the evaluation of published hybrid data [Hall, K. B., & McLaughlin, L. W. (1991) Biochemistry 30, 10606-10613; Roberts, W. R., & Crothers, D. M. (1992) Science 258, 1463-1466], it can be predicted that a hybrid duplex containing more RNA purine bases will have a CD spectrum, and probably conformation, resembling that of A-form duplexes and will be more stable than a corresponding hybrid duplex with fewer RNA purine bases.

Base Sequence↗

PubMed1994

Induction of spermatogenesis with gonadotrophins in Chinese men with hypogonadotrophic hypogonadism.

The effects of gonadotrophin administration to 17 Chinese patients with hypogonadotrophic hypogonadism (HH) on testicular volume and induction of spermatogenesis were studied. Ten subjects had isolated HH and seven had hypopituitarism. Twelve of the subjects had prepubertal onset of HH and five of them had been treated previously with hCG for induction of puberty. None had a history of cryptorchidism. During hCG treatment for induction of spermatogenesis, all subjects had an increase in serum levels of testosterone into the normal adult male range and their testes increased in size from 3 (1-20) ml to 11.6 (5-20) ml [median(range), p < 0.02]. Six subjects required treatment with hCG alone. However, the remaining 11 subjects, after at least 6 months treatment with hCG, required the addition of human menopausal gonadotrophin (hMG) to induce spermatogenesis. Two subjects remained azoospermic. One had a history of mumps orchitis and the other had isolated elevation of blood FSH levels, suggestive of primary testicular failure in addition to HH. Excluding one subject with fertile eunuch syndrome, the mean duration for first appearance of spermatozoa was 13 (4-52) months. Twelve subjects became fertile and pregnancy was achieved in their partners after 20 (4-78) months. The weekly doses for hCG and hMG were 4000 (3000-10,000) IU and 225 (225-450) IU, respectively. Patients who responded to hCG alone had a significantly larger pretreatment testicular volume, suggesting that they had only partial gonadotrophin deficiency. Prepubertal onset of hypogonadism was not a determining factor for requirement of hMG treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Technology of the divalent engineered diarrhea vaccine (K88, K99) production by high cell density fermentation and the antigen overexpression.

This paper describes the production of divalent K88, K99 antigens by high cell density fermentation and gene overexpression. The cell density reached above 40 at A600nm and the antigens were at 2(12) level. The thousands dosage of the vaccine can be made by using 10 I broth of the fermentation. The stability of the plasmid showed that about 30 percent of the bacteria lost its plasmid after 20 h fermentation. It was found that the antigens were overexpressed and located in both the pili of E. coli and in the medium in equal quantities. It means that the expression and regulation of the genes of K88, K99 may be different from the wild type of enterotoxingenic E. coli. A large number of the vaccinated pregnant sow showed that the piglets were effectively protected from the infection of enterotoxingenic E. coli. The results indicated that the large quantities requirement of the vaccine could be provided by using a small fermenter. This vaccine consists of two forms of the antigen K88, K99 which, when present in the pili as well as the medium, is more favorable to stimulate the production of antibody in the colostrum of pregnant sow.

Animals↗