Search PubMed⌕ Search

Biomedical subjects

M K Estes

Publications and source records attributed to M K Estes.

261 records · Page 15Linked to original sources
PubMed1975

Structural proteins of simian virus 40. I. Histone characteristics of low-molecular-weight polypeptides.

The DNA-associated polypeptides of simian virus 40 (SV40), VP4 (mol wt 14,000), VP5 (mol wt 12,000), and VP6 (mol wt 11,000), have several properties characteristic of cell histones. After extraction from purified SV40 with dilute acids, these three polypeptides co-electrophoresed on low pH polyacrylamide gels with monkey-kidney cell histones F3, F2b, and F2a1. No virus polypeptide co-electrophoresed with histone F1. Polypeptides VP4, 5, and 6 lacked tryptophan, and only VP4 contained cysteine, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis of virus labeled in vivo with (3H)lysine and either (14C)tryptophan or (35S)cystine. All of the capsid polypeptides VP1, 2, and 3 contained tryptophan whereas only VP1 and 2 contained cysteine. In addition, VP4, 5, and 6 are rich in arginine and lysine when compared with virus labeled with a mixture of amino acids. Analysis of virus grown in cells labeled prior to infection showed that VP4, 5 and 6 were labeled fivefold greater than the major capsid polypeptide, VP1, which indicates that they were partially derived from preexisting cell histones. Based on these data and on previously determined molecular weight estimates, we conclude that VP4, 5, and 6 are histones F3, F2b, and F2a1, respectively, although the possibility that SV40 contains a small amount of F2a2 could not be excluded.

Amino Acids↗
PubMed1974

Papovavirus structural polypeptides: comparison of human and rabbit papilloma viruses with simian virus 40.

A comparative study of the structural polypeptides of purified human papilloma virus, rabbit papilloma virus, and simian virus 40 (SV40) was performed by electrophoretic analysis on 10% polyacrylamide gels containing sodium dodecyl sulfate either by Coomassie blue staining or by electrophoresing purified virus preparations labeled with radioactive iodine. Analysis of human papilloma virus on stained gels revealed 6 bands with a major polypeptide of molecular weight 63,000 daltons comprising 60% of the virion protein. Analysis of rabbit papilloma virus on stained gels revealed 5 bands with a major polypeptide of molecular weight 60,000 daltons comprising 48% of the virion protein. Under conditions which yielded 6 polypeptides for SV40, in agreement with published data, 4 and 7 polypeptides were regularly detected in iodinated preparations of human and rabbit papilloma viruses, respectively. Isoelectrofocusing of iodinated virions revealed isoelectric points of pH 3.7 for SV40 and pH 4.0 for both rabbit and human papilloma viruses.

Animals↗
PubMed1972

Structure and function of the polypeptides in simian virus 40. I. Existence of subviral deoxynucleoprotein complexes.

Velocity sedimentation analysis of simian virus 40 degraded in alkaline buffers, pH 10.5, yields two components: soluble protein containing the largest polypeptides, VP1 and VP2, of the virion, and a deoxynucleoprotein complex (DNP-I) containing the viral deoxyribonucleic acid (DNA) and the small polypeptides, VP4, 5, and 6, and all or part of VP3. Dissociation of DNP-I by equilibrium centrifugation in CsCl yields a complex (DNP-II) of the viral DNA and residual, tightly bound polypeptide; VP4, 5, and 6, but not VP3, are recovered after separation from DNP-II. Treatment of the virus with beta-mercaptoethanol and iodination experiments suggest that VP1 and VP2 might exist as compact structures cross-linked with disulfide bonds, perhaps forming the capsid. VP4, 5, and 6 form a relatively stable complex with the viral DNA and are supposed to be the internal proteins. The location of VP3 is not well defined; at least a portion of it is tightly bound to the viral DNA.

Acetates↗
PubMed1971

Structural polypeptides of simian virus 40.

To determine the number and molecular weights of the structural polypeptides of simian virus 40, we have analyzed purified virus by electrophoresis on 14% polyacrylamide gels containing sodium dodecyl sulfate. Full virus purified by several different methods showed six distinct bands with molecular weights of approximately 43,000 (VP1, containing 70% of virion protein), 32,000 (VP2, 9%), 23,000 (VP3, 10%), 14,000 (VP4, 6%), 12,500 (VP5, 4%), and 11,000 (VP6, 3%) both by analysis of radioactively labeled virions and by visualization of the polypeptide bands after staining. "Empty" virions contain decreased amounts of VP4, 5, and 6. The approximate molecular ratios of the polypeptides were 6.0, 1.0, 1.5, 1.5, 1.1, and 1.0. When virus degraded in an alkaline buffer was analyzed by velocity centrifugation in sucrose gradients, the two larger polypeptides (VP1 and VP2) remained at the top of the gradient, whereas the three smallest polypeptides (VP4, 5, and 6) sedimented as a complex with the viral deoxyribonucleic acid. VP3 was found in association with either VP1 and 2 or VP4, 5, and 6, depending on the conditions of degradation. Presumably, VP1 and VP2, comprising about 80% of the protein, form the capsid of the virus. VP4, 5, and 6 may form a nucleoprotein in the virion, and VP3 may serve as an intermediate structural component.

Alkalies↗
PubMedDate not supplied

Properties of cells transformed by DNA tumor viruses.

Transformation by the papovaviruses, SV40 and polyoma, is reviewed briefly, including factors that affect the frequency of transformation. Virus markers useful in the determination of the etiology of virus-free tumors are described, including viral DNA, viral mRNA, virus-induced antigens, and the rescue of infectious virus. Finally, the evidence that viral genes are involved in the maintenance of transformation is presented.

Cell Transformation, Neoplastic↗
PubMedDate not supplied

Molecular biology and immunology of rotavirus infections.

Rotaviruses were first recognized about 15 years ago in association with diarrhea in children and animals. Since then, rotaviruses have been determined to be the most important viral agent that causes clinically significant diarrhea in children and a need for an effective vaccination program has been recognized. This article reviews the progress which has been made in understanding the molecular biology of rotaviruses and summarizes information on the immune responses to rotavirus infections obtained in a new animal model in rabbits. This model is useful to systematically evaluate active protective immunity following infection of seronegative animals.

Animals↗
PubMedDate not supplied

Intussusception in southern Indian children: lack of association with diarrheal disease and oral polio vaccine immunization.

BACKGROUND: Intussusception is the most common cause of intestinal obstruction in young children and has been reported as a complication of a recently withdrawn tetravalent reassortant rotavirus vaccine. METHODS: We studied the history, clinical presentation, management and outcome of intussusception presenting to a tertiary care hospital in southern India over a 10-year period, in order to assess potential association with diarrheal disease and immunization. RESULTS: Data from 137 index cases and 280 control subjects indicated that the risk of diarrheal disease or oral polio vaccine administration in the month prior to presentation was similar in the index cases and controls. Mean time to presentation to hospital after developing symptoms was 1.8 days, and 77.3% of patients required surgery, with 47.4% undergoing intestinal resection. Mortality was 0.006%. CONCLUSIONS: No association could be demonstrated between gastroenteritis or oral poliovirus vaccine immunization and intussusception in southern Indian children. These children presented later and required operative intervention more frequently than has been reported in other studies, but had a good outcome with low mortality.

Case-Control Studies↗