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Z Q Lu

Publications and source records attributed to Z Q Lu.

17 recordsLinked to original sources
PubMed1992

Cleavage of concatemeric DNA at the internal junction of "translocation" mutants of pseudorabies virus and inversion of their L component appear to be linked.

When pseudorabies virus (PrV) strains are grown in chicken embryo fibroblasts (CEF), variants ("translocation" mutants) arise in which there is a duplication of the leftmost sequences of the genome and their translocation in inverted orientation next to the internal inverted repeat bracketing the S component. In these variants, the UL becomes bracketed by inverted repeats and is found in two orientations relative to the Us. To study the cis-functions involved in cleavage of concatemeric DNA as well as those involved in inversion of the L component and to ascertain whether the two events are linked in the "translocation" mutants, a viral mutant (vLD68) was constructed in which the terminal 64 bp of the L component (that include sequences with homology to the pac 2 site of HSV) and the 4 terminal bp of the S component were deleted from the internal junction. Although revertants that have acquired the 68 bp at the internal junction emerge rapidly in populations of vLD68, analysis of the characteristics of this mutant revealed that: (1) the termini derived from both orientations of the L component include the 64 bp that have been deleted from the internal junction of vLD68; (2) in contrast to other "translocation" mutants, the internal junction of the vLD68 genome is not a good substrate for cleavage; (3) inversion of the L component of true vLD68 DNA does not occur or is rare; a good correlation exists in the populations of vLD68 between the proportion of revertants that have acquired an intact internal junction and the proportion of genomes with an L component that inverts. These results show that an intact internal junction in "translocation" mutants is necessary for both inversion of their L components and cleavage at their alternative internal junction. Since cleavage at the alternative junction will result in inversion of the L component, we conclude that inversion of the L component of "translocation" mutants of PrV can be attributed to cleavage of concatemeric DNA at the internal alternative junction.

Animals↗
PubMed1992

[Antidotal effects of 2,3-dimercaptopropane-1-sulfonate sodium (DMPS) and combined with diazepam on acute poisoning caused by sodium ammonium dimethyl-2-propano-1,3-dithiosulfate monohydrate (SCD)].

In mice, DMPS (250 mg/kg, i.v.) combined with diazepam (1.25 mg/kg, i.p.) could increase LD50 of p. o. SCD 5.3 times. DMPS (62.5 mg/kg, i.v.) antagonized completely the respiratory depression and neuromuscular blockade caused by SCD(7.5 mg/kg, i.v.) in rabbits. SCD (15 mg/kg, i.v.) caused tremor, tonic convulsion and the abnormal paroxysmal discharges in EEG in rabbits. DMPS (0.5 mg/kg, i.c.v) could not eliminate the abnormal paroxysmal discharges in EEG of rabbits. DMPS (62.5 mg/kg, i.v.) combined with diazepam (5 mg/kg, i.v.) completely and rapidly antagonize these toxic symptoms and the abnormal changes in EEG.

Animals↗
PubMed1991

Analysis of an origin of DNA replication located at the L terminus of the genome of pseudorabies virus.

We have localized an origin of DNA replication at the L terminus of the pseudorabies virus genome. This origin differs in location as well as in general structure from the origins of replication of other herpesviruses that have been identified. The 600 leftmost nucleotides of the genome that were found to include origin function have been analyzed. This sequence is composed of an 82-bp palindrome whose center of symmetry is separated by 352 unique bp (UL2). Within the UL2, a sequence that fits the consensus sequence of the NF1 binding site, as well as one that has partial homology to the binding site of UL9 of herpes simplex virus, is present. Using truncated fragments of DNA, sequences essential for minimal origin function were delimited to within a fragment that includes the terminal 104 bp of the left end of the genome. Within these 104 bp, two elements essential to origin function have been identified. One of these elements is present within the terminal 64 bp of the L component (within one of the palindromic arms). The other is present within the 22 bp of the UL2 adjacent to this palindromic arm. Other auxiliary elements, although not essential for origin function, contribute to more efficient replication. The NF1 and UL9 binding site homologies were found to be nonessential to origin function.

Animals↗
PubMed1991

Acquisition of an additional internal cleavage site differentially affects the ability of pseudorabies virus to multiply in different host cells.

The translocation of the 325 leftmost bp of the genome of pseudorabies virus (PrV) to the internal junction between the L and S components confers upon the virus a growth advantage relative to wild-type PrV in chicken embryo fibroblasts (CEFs) and chickens and a growth disadvantage in rabbit kidney (RK) cells and mice. To clarify the molecular basis for the species-specific growth characteristics of the translocation mutants, we have compared several parameters of the virus growth cycle in CEFs and RK cells infected with wild-type PrV and with translocation mutants. The salient findings are as follows. (i) The synthesis of early-late and late proteins is not as effective in CEFs as it is in RK cells, and these proteins, in particular, the major capsid proteins, accumulate less abundantly in CEFs than in RK cells. (ii) Cleavage of concatemeric DNA to genome-size molecules is also not as effective in CEFs as it is in RK cells. (iii) The internal junction present in translocation mutants is a functional cleavage site. (iv) In RK cells, translocation mutants are hypercleaved and a significant proportion of the total viral DNA is cleaved into subgenomic fragments. (v) In CEFs infected with translocation mutants, subgenomic fragments also accumulate but most of the viral DNA remains in concatemeric form. A model which postulates that the cell-specific growth advantage or disadvantage of the translocation mutants is related to the presence of a second cleavage site within their genomes and is affected by the efficiency of cleavage of concatemeric DNA in particular infected cell types is presented. The significance of these findings as they relate to the evolution of herpesviruses with class 2- and class 3-like genomes is discussed.

Animals↗
PubMed1991

Inhibition of methyl methanesulfonate-induced unscheduled DNA synthesis in spermatozoa of mice by Poly I-C.

Methyl methanesulfonate (MMS 75 mg.kg-1)-induced unscheduled DNA synthesis (UDS) was inhibited significantly in the spermatozoa of mice injected with Poly I-C (0.05, 0.50, and 5.00 mg.kg-1) at 4 h prior to ip MMS. Radioactivity was reduced from 53 +/- 3 to 50, 45 +/- 5, and 34 +/- 6 dpm/million sperms respectively. The effects of Poly I-C were dose-dependent (r = 0.9498, P less than 0.05) in inhibition of MMS-induced UDS. The effect of serum collected from the mice injected with Poly I-C (0.50 mg.kg-1) had similar effects as that of Poly I-C. Our findings suggest that both Poly I-C alone and mouse serum induced with Poly I-C may prevent the DNA damage produced by MMS.

Animals↗
PubMed1990

Structural organization of the termini of the L and S components of the genome of pseudorabies virus.

The sequences of several hundred nucleotides around the junctions between the L and S components in concatemeric DNA and in mature virion DNA were ascertained. The two ends of the mature genome (which are joined in concatemeric DNA) show no sequence homology. Several directly repeated elements are present near both ends of the genome. Furthermore, the last 82 nucleotides at the left end of the L component (and of the genome) are repeated in inverted form (inverted repeat within the L component [IRL]) approximately 350 to 600 nucleotides downstream (depending on the virus isolate) bracketing the UL2 component. A comparison between the sequences at the right and left ends of the L component of the genome showed patchy homology, probably representing a vestigial inverted repeat bracketing the L component (IRL). Furthermore, less than 5% of the genomes have an L component that is in the orientation opposite to that of most of the viral genomes, indicating that the vestigial IRL that brackets the UL sequence may be sufficient to mediate inversion of the L component in some of the genomes. On the other hand, the UL2 component, which is bracketed by a perfect IRL, does not invert to a greater extent than does the L component (if it inverts at all). Analysis of the nucleotide sequence at the concatemeric junction of three different pseudorabies virus isolates showed almost complete sequence conservation. The sequence and organization of the repeated elements in the different isolates were almost identical, despite their different histories and origins. The high degree of conservation of these repeated elements implies that they may fulfill an essential function in the life cycle of the virus.

Animals↗
PubMed1990

[Effects of nicardipine and chlorpromazine on proliferation and intracellular calmodulin in cultured aortic smooth muscle cells].

Effects of Ca2+ and calcium antagonists nicardipine (Nic) and chlorpromazine (CPZ) on the proliferation, DNA synthesis and intracellular calmodulin (CaM) levels in cultured rabbit aortic smooth muscle cells were investigated. Maximal response of cell to Ca2+ stimulation occurred in the normal medium with CaCl2 1.4 mmol/L, whereas CaCl2 0.02-0.6 mmol/L, Nic (2.5-40.0 mumol/L) and CPZ (5.0-20.0 mumol/L) inhibited the cell proliferation in a concentration-dependent manner. The additive effects of Nic and CPZ were observed. There was a transient surge of intracellular soluble CaM level at 9h in late G1 phase of the cell cycle just before the initiation of DNA synthesis. Not only the initiation of DNA synthesis but also the CaM surge were prevented by adding Nic or CPZ (20-40 mumol/L) to media. These results suggest that an appropriate extracellular Ca2+ concentration was required for aortic smooth muscle cells to grow normally. Since calcium antagonists influenced the intracellular Ca2+ pool by blockade of calcium channel and they inhibited the CaM function directly by anticalmodulin activity or indirectly through altered intracellular Ca2+ metabolism, intracellular Ca2+ and CaM levels may be involved in the effects of Nic and CPZ on the proliferation and DNA synthesis.

Animals↗
PubMed1990

[An observation of the effect of sulfur dioxide on rat nasal mucosa].

This paper reports the effect of SO2 on rat nasal mucosa. The rats were forced to inhale SO2 and the effect on the nasal mucosa observed. The rats were divided into four groups. The first group inhaled 10ppm SO2; the second group 20ppm; the third group 40 ppm and the fourth group served as control. The observation lasted for 6 months. It was found that the nasal mucosa in the control group remained columnar ciliated. In the experimental groups, during the early stage (groups I, II) of exposure, there was no significant morphological change in epithelium. Then (groups I, II) the epithelium changed into cuboidal with complete disappearance of cilia, only some short and slender microvilli remained. While in the late stage (group III), the epithelium had transformed into squamous stratified and the amount of mucosal glands reduced.

Animals↗
PubMed1989

Nucleotide sequences at recombinational junctions present in pseudorabies virus variants with an invertible L component.

The genome of pseudorabies virus (PrV) consists of two components--a noninvertible long (L) and an invertible short (S) component. The S component is bracketed by inverted repeats. In some variant strains of PrV (which have a selective growth advantage in certain cell lines), a sequence normally present at the left end of the L component has been translocated to the right end of the L component next to the inverted repeat. Consequently, these strains have acquired a genome with an L component that is bracketed by inverted repeats and that also inverts. We have determined the restriction maps and have analyzed the nucleotide sequences of those parts of the genome of three strains with invertible L components that contain the translocated segment of DNA. The results were as follows. The translocated fragments were derived in all cases from the extreme left end of the L component only. The sizes of the translocated fragments were similar, ranging from 1.3 to 1.4 kilobase pairs. The junction between the L and S components in these strains was the same as that in standard viral concatemeric DNA. The translocation of sequences from the left end of the genome next to the inverted repeats was always accompanied by a deletion of sequences from the right end of the L component. The sizes of the deleted fragments varied considerably, ranging from 0.8 to 2.3 kilobase pairs. Sequence homology at the points of recombination, i.e., at the junction between the right end and the left end of the L component, existed sometimes but not always. A model depicting how a virus with a class 2 genome (such as PrV) may acquire a genome with characteristics of a class 3 genome (such as herpes simplex virus) is presented.

Animals↗
PubMed1985

Ginseng extract inhibits protein degradation and stimulates protein synthesis in human fibroblasts.

Aqueous extracts of Panax ginseng inhibit intracellular protein degradation in confluent cultures of IMR-90 human diploid fibroblasts. The magnitude of the inhibition is similar to that observed with insulin and polypeptide growth factors. Furthermore, the inhibition of proteolysis by ginseng, like that produced by insulin and growth factors, is selective in that it applies to long-lived proteins but not to short-lived proteins. Ginseng also stimulates protein synthesis in human fibroblasts indicating that components of ginseng extract are capable of acting directly on human cells to promote protein accumulation.

Cell Line↗
PubMed1984

Diffraction tomography using beam waves: z-average reconstruction.

This paper discusses the problem of diffraction tomography, when a general beam wave is used as the excitation and the three-dimensional structure of the object is considered. The special case of a zero-order beam wave with measurements of the average of the scattered field in the z direction is detailed. It is shown that in this case a reconstruction algorithm identical to the two-dimensional geometry yields a z-averaged tomogram of the inhomogeneity.

Fourier Analysis↗