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Biomedical subjects

A Hu

Publications and source records attributed to A Hu.

47 records · Page 3Linked to original sources
PubMed1993

The mumps virus V protein is unstable in virus infected cells.

The mumps virus (MuV) V protein was characterized in virus infected cells by the use of antipeptide sera. In radioimmune precipitation assay (RIPA), the sera reacted with the V protein and also immunoprecipitated the nucleocapsid (NP) and phospho (P) proteins. However, by depletion RIPA (in which either the NP and P proteins or the V protein were removed) and Western immunoblotting, it was demonstrated that the V protein was not associated with the NP and P proteins, but that the anti-V sera cross-reacted with the NP protein. Pulse-chase experiments demonstrated that the V protein was gradually decreased during the chase period and could not be detected by antibodies raised against peptides representing three different regions of the protein at the end of the chase, while the NP and P proteins were relatively stable during the chase period. These results suggest that the V protein is unstable and degraded gradually in virus infected cells.

Amino Acid Sequence↗
PubMed1993

Putative determinants of the cellular response to hyperthermia.

Recently, it has been demonstrated that two different thermal resistant states found in Chinese hamster cells, one transient, associated with thermotolerance, and the other permanent, associated with the increased expression of the cognate member of the hsp 70 family, are characterized by faster recovery from heat-induced perturbations in several cellular processes (Laszlo 1992b). These processes include total cellular protein and RNA synthesis, the localization of hsp70, the organization of vimentin, and the protein composition of the nucleus. In the present study, the recovery from heat-induced perturbations in cellular physiology was extended further to two more types of Chinese hamster cells: permanently heat resistant cells in which thermoresistance is associated with the overexpression of hsp27 and heat-sensitive cell lines. When the heat-resistant hsp27 transfected cell lines were compared with the control wild-type cell line, the recovery of protein synthesis from heat-induced inhibition was similar in the normal and hsp27 transfected cells, while the recovery from heat-induced inhibition of total RNA synthesis and the recovery from heat-induced increased association of hsp70 with nuclei were both more rapid in the hsp27 transfected cell lines. In the permanently heat-sensitive cell lines, the kinetics of recovery from heat-induced inhibition of protein synthesis did not correlate with the heat sensitive state. However, delays in the recovery from heat-induced alterations in total cellular RNA synthesis and from heat-induced excess nuclear association of hsp70 were associated with the heat-sensitive state. Overall, these results suggest that the kinetics of recovery from heat-induced alterations in total cellular RNA synthesis and the localization of hsp 70 are putative candidates for being determinants of the cellular response to hyperthermia, and thus have the potential to form the basis of predictive assays for use in conjunction with clinical hyperthermia.

Adaptation, Physiological↗
PubMed1993

Effect of age on the expressed B cell repertoire: role of B cell subsets.

Aged humans and experimental animals are impaired in their responses to most foreign antigens although they produce greater amounts of autoantibodies. We have examined the effect of age on the production of antibodies to a prototypic foreign antigen, sheep erythrocytes (SRBC), and to a prototypic autoantigen, bromelain-treated mouse erythrocytes (BrMRBC), in young and old mice before and after immunization with SRBC. Old mice express more anti-BrMRBC plaque-forming cell (PFC) antibodies before and an even greater number after immunization with SRBC than young mice. Conversely, old mice produce far fewer anti-SRBC PFC than young mice following immunization with SRBC. We hypothesized that the differences in the responses of old mice to BrMRBC and SRBC reflects differences in the activity of CD5+ and CD5- B cells. To test this hypothesis we immunized young and old mice with foreign antigens reported (and confirmed in our studies) to stimulate CD5+ B cells [TNP-ficoll and phosphorylcholine-keyhole limpet hemocyanin (KLH)] or CD5- B cells (SRBC and TNP-KLH). We found that the PFC response of old mice to antigens mediated by CD5+ B cells was equal to or greater than that of young mice. In contrast the PFC response of old mice induced by antigens mediated by CD5- B cells was only 10% that of young mice. Thus it appears that the immune response of old mice is well maintained for antigens which elicit a CD5+ B cell response but not for those which elicit a CD5- B cell response.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1992

Sequence analysis of the genes encoding the nucleocapsid protein and phosphoprotein (P) of phocid distemper virus, and editing of the P gene transcript.

The nucleotide and deduced amino acid sequences of two genes of phocid distemper virus (PDV) were determined by cDNA cloning and sequencing. The long open reading frame of the gene encoding the nucleocapsid (N) protein is presented. As with other morbilliviruses, the phosphoprotein (P) gene of PDV was found to be located after the 5' end of the N gene and before the 3' end of the matrix protein gene. The P gene was shown to have the capacity to encode three distinct proteins, P, V and C, in analogy to other morbilliviruses. The results presented provide evidence for editing of the PDV P mRNA transcript by insertion of G residues. When the nucleotide and deduced amino acid sequences of the N, P, V and C genes were aligned with corresponding sequences of other established members of the morbillivirus genus, compelling homology was found between PDV and canine distemper virus (CDV), whereas there was markedly less similarity between PDV and measles virus or rinderpest virus. On the basis of the alignments presented, the estimated amino acid sequence similarity between the N and P genes of PDV and CDV was 84% and 76%, respectively. These differences at the genomic level indicate that the viruses are two separate entities.

Amino Acid Sequence↗
PubMed1992

[The preparation and identification of anti-idiotypic antibody against Plasmodium vivax at erythrocytic stages].

Through hypotonic dialyzing and gel filtration on Sephadex G200, 6H7G11 McAb-IgM (Mouse IgM) was successfully purified. Anti-6H7G11Id (Ab2) was induced in rabbit. This Ab2 was identified by agar diffusion, ELISA and competitive assays. The results showed that the Ab2 was able to combine respective Ab1 (6H7G11McAb), and the binding between Ab2 and Ab1 could be inhibited by Plasmodium vivax (P.v) antigen. Meantime, by using Ab2 thus prepared to immunize BALB/c mice, the anti-6H7G11Id (Ab3 or Ab1') was obtained with specificity of Ab1. It was revealed that the Ab2 thus prepared could mimic the antigenic determinant of P.v, and it belongs to the cross-reacted idiotype.

Animals↗
PubMed1980

Activation of lecithin:cholesterol acyltransferase by a synthetic model lipid-associating peptide.

We have synthesized a model lipid-associating peptide of 20 residues (LAP-20) and studied its association with the phospholipid dimyristoyl phosphatidylcholine (DMPC) and its activation of the plasma enzyme lecithin:cholesterol acyl-transferase (EC 2.3.1.43). The lipid-associating behavior of LAP-20 is similar to that of well-characterized native plasma apolipoproteins after which it was modeled. Upon forming an isolated complex with DMPC, LAP-20 exhibits a large blue-shift in its intrinsic fluorescence, converts from a random coil to an alpha -helix, and changes turbid multilamellar structures of DMPC into small complexes that are optically clear. Addition of 2 mol % cholesterol does not detectably alter the structure or properties of the complex. The cholesterol-containing complexes of LAP-20 and DMPC are substrates for LCAT, having an activity 65% of that of complexes composed of DMPC, cholesterol, and the natural activator, apolipoprotein A-I. These findings suggest that the LCAT-activating regions of apoA-I may be confined to relatively short sequences that contain a lipid-binding determinant.

Apolipoprotein A-I↗
PubMed1978

Isotopic (18O) shift in 31P nuclear magnetic resonance applied to a study of enzyme-catalyzed phosphate--phosphate exchange and phosphate (oxygen)--water exchange reactions.

An isotopic shift of the (31)P nuclear magnetic resonance due to (18)O bonded to phosphorus of 0.0206 ppm has been observed in inorganic orthophosphate and adenine nucleotides. Thus, the separation between the resonances of (31)P(18)O(4) and (31)P(16)O(4) at 145.7 MHz is 12 Hz and, in a randomized sample containing approximately 50% (18)O, all five (16)O-(18)O species are resolved and separated from each other by 3 Hz. Not only does this yield the (18)O/(16)O ratio of the phosphate but, more important, the (18)O-labeled phosphate in effect can serve as a double label in following phosphate reactions, for oxygen in all cases and for phosphorus, provided the oxygen does not exchange with solvent water. Thus, it becomes possible to follow labeled phosphorus or labeled oxygen continuously as reactions proceed. Rate studies involving (i) phosphorus and (ii) oxygen are illustrated by continuous monitoring of the exchange reactions between (i) the beta phosphate of ADP and inorganic phosphate catalyzed by polynucleotide phosphorylase and (ii) inorganic orthophosphate and water catalyzed by yeast inorganic pyrophosphatase. In the ADP-P(i) exchange, the P(i) ((18)O(4)) yielded an alpha P((16)O(3) (18)O) and a beta P((18)O(4)), proving that bond cleavage occurs between the alpha P and the alpha-beta bridge oxygen. Among the many additional potential uses of this labeling technique and its spectroscopic observation are: (i) different labeling of each phosphate group of ATP, (ii) to follow rate of transfer of (18)O from a nonphosphate compound such as a carboxylic acid to a phosphate compound, and (iii) to follow the rate of scrambling (for example, of the beta-gamma bridge oxygen of ATP to nonbridge beta P positions) and simultaneously the rate of exchange of the gamma P nonbridge oxygens with solvent water in various ATPase reactions.

Adenosine Diphosphate↗
PubMedDate not supplied

Delayed hemolytic transfusion reaction caused by the second example of anti-K19.

A second example of anti-K19 has been identified in the serum of a black patient immunized by blood transfusions. The antibody was responsible for delayed hemolysis of transfused incompatible red blood cells. The patient's red blood cells are K:--19 but are otherwise of common Kell phenotype. The K19 antigen is closely associated with the Kell blood group although there is, as yet, no pedigree information to confirm that it is produced by the Kell gene. Tests on 10,757 group O blood donors have not revealed any further examples of the K:--19 phenotype.

Anemia, Hemolytic, Autoimmune↗