Search PubMed⌕ Search

Biomedical subjects

G R Pearson

Publications and source records attributed to G R Pearson.

At least 163 records · Page 9Linked to original sources
PubMed1978

Solubilization and characterization of Herpesvirus saimiri-induced membrane antigens.

Treatment of Herpesvirus saimiri (HVS)-infected owl monkey cells by limited papain digestion removed the HVS-induced membrane antigen (MA) as determined by membrane immunofluorescence and antibody-dependent lymphocyte cytotoxicity (ADLC). Soluble antigenically active HVSMA was detected by inhibition of ADLC and by the decreased binding of 125I-labeled staphylococcus protein A to HVS-infected cells after absorption of an anti-MA-positive serum with papain extracts. Approximately 38% of the inhibitory activity of the papain extracts was sedimentable at 100,000 X g, indicating that the released MA was heterogeneous in size. Preliminary investigations by gel filtration chromatography identified a major peak of MA with a molecular weight between 20,000 and 50,000.

Animals↗
PubMed1978

Papain solubilization of the Epstein-Barr virus-induced membrane antigen.

The Epstein-Barr virus (EBV)-induced membrane antigen (MA) was successfully solubilized from the membranes of viable EBV-infected Raji cells by treatment with papain (5 to 6 U per 1 X 10(7) to 2 X 10(7) cells). The loss of MA from viable cells was monitored by membrane immunofluorescence and antibody-dependent cellular cytotoxicity. Soluble MA was demonstrated in papain digests through inhibition of antibody-dependent cellular cytotoxicity and by inhibition of the binding of anti-MA antibodies to cells as detected by use of 125I-labeled staphylococcal protein A. Approximately 75% of the MA activity in the extracts was not sedimentable at 100,000 X g,, indicating that the majority of EBV MA activity that was released by this procedure was associated with small-molecular-weight material. Antiserum prepared from an owl monkey immunized with these papain extracts contained antibody to MA and neutralizing antibodies, but lacked detectable antibodies against viral capsid antigens and EBV-induced early antigens.

Animals↗
PubMed1978

Pathological changes in the small intestine of neonatal calves with enteric colibacillosis.

Three neonatal calves, protected from colisepticaemia by intravenously administered immunoglobulin M, were infected orally with Escherichia coli type 0101 K?(A). All calves developed severe enteric colibacillosis. When they were 4 days old stunting and fusion of villi were seen in the distal half of the small intestine and were associated with adhesion of the challenge organism to the mucosa. Two uninfected control calves kept under similar conditions, did not develop diarrhoea and had no lesions.

Animals↗
PubMed1978

Clinical evaluation of EBV serology in American patients with nasopharyngeal carcinoma.

There is now extensive immunological, biological and biochemical evidence to support a possible etiological relationship between EBV and NPC in patients from different geographical locations. Besides providing information on the question of etiology, the results from immunological investigations suggest that antibodies to some of the EBV-associated antigens might also be of clinical importance in the diagnosis and prognosis of NPC. To determine the possible clinical application of EBV serology to American NPC, sera from patients seen at the Mayo Clinic and the National Institutes of Health were examined for antibodies to EBV-associated antigens in an effort to identify those parameters which most reliably distinguish NPC from other types of cancer. The results show that high antibody titres to EBV-induced EA and the presence of antibody to EBV antigens in the IgA immunoglobulin fraction were the two most specific discriminating parameters, although neither was infallible. These findings are discussed in relation to future studies that are needed in order to determine the potential clinical value of EBV serology to the diagnosis and prognosis of NPC.

Antibodies, Viral↗
PubMed1978

Potential for immunization against herpesvirus infections with plasma membrane vesicles.

Virus-free, membrane antigen (MA)-positive plasma membrane vesicles produced from herpesvirus saimiri-infected owl monkey cells were used as immunogens in cotton-top marmosets. Neutralizing antibodies as well as antibodies to MA and HVS-induced LA were induced following immunization of marmosets with these vesicles. Preliminary findings demonstrated that immunized marmosets were significantly less susceptible to tumour induction by HVS than control animals.

Animals↗
PubMed1978

The distribution of immunoglobulins in the intestine of the neonatal calf.

The distribution of immunoglobulins G, M and A in the small intestine of colostrum fed calves was monitored using immunofluorescent techniques. Colostral immunoglobulins were located in villous region of the small intestine where they were found either in the lamina propria, in the epithelial cells or on the mucosal surface of the epithelial cells. The distribution varied according to the age of calf examined. In very young calves, the villous epithelial cells were seen to be absorbing immunoglobulin of all 3 classes, whereas in 4 day old calves, the epithelial cells were generally devoid of immunoglobulin. In unsuckled calves, the intestinal immunoglobulins were synthesised in the Peyers patches and crypt region of the mucosa of the small intestine and immunoglobulin was found in the crypt epithelial cells and in plasma cells in the surrounding lamina propria.

Animals↗
PubMed1978

The rate of development of postmortem artefact in the small intestine of neonatal calves.

The rate of development of postmortem artefacts was investigated in the mucosa of the small intestine of a calf dually infected with an enteropathogenic strain of Esch. coli and rotavirus, and an uninfected control calf. Samples were removed under general anaesthesia from the proximal, middle and distal small intestine and compared with those taken from adjacent sites 1-30 min after severing the major blood vessels of the neck. In the challenged calf, changes occurred in the villous mucosa by 3 min after severance, whilst in the control calf good fixation was obtained until 10 min after severance.

Anesthesia, General↗
PubMed1977

Studies on the immunity of the calf to colibacillosis--VII: the experimental reproduction of enteric colibacillosis in colostrum-fed calves.

Eight newborn calves were challenged orally with a known enteropathogenic strain of Escherichia coli 0101 K?(A) and two to six hours later each calf was fed a minimum of three pints colostrum. All calves suffered from acute diarrhoea of varying severity within 24 to 48 hours of infection. Immunofluorescent and histological examination of the small intestine demonstrated adherence of the challenge organism to the epithelium and the presence of pathological lesions similar to those seen in colostrum-deprived calves with enteric colibacillosis. It was concluded that in order to be effective prophylactically, colostrum must be fed prior to infection.

Animals↗
PubMed1977

Isolation of virus-free Herpesvirus saimiri antigen-positive plasma membrane vesicles.

Experiments were undertaken to determine whether virus-free, antigen-positive plasma membrane vesicles could be isolated from owl monkey kidney cells infected with Herpesvirus saimiri. The results demonstrate that vesicles can be produced by using a vesiculation fluid containing 25 mM formaldehyde/2 mM dithiothreitol. Electron microscopy revealed that these vesicles were free of detectable virus particles. Vesicles prepared from the infected cells contained virus-induced membrane antigens as shown by membrane immunofluorescence and by inhibition of antibody-dependent lymphocyte cytotoxicity. Nonhuman primates immunized with vesicles produced antibodies to these membrane antigens, late cytoplasmic antigens, and neutralizing antibodies. Infectious virus was not demonstrated in these vesicles by cocultivation with owl monkey kidney cells or by the inoculation of cottontop marmosets. Furthermore, no DNA could be demonstrated in vesicles prepared from Herpesvirus-infected owl monkey kidney cells. The implication of these findings in relation to the question of a virus-free membrane vaccine against Herpesvirus infections is discussed.

Animals↗
PubMed1977

Inhibition of Herpesvirus saimiri replication by phosphonoacetic acid, benzo(a)pyrene, and methylcholanthrene.

The present investigations were undertaken to determine the possible effects of two carcinogenic polycyclic aromatic hydrocarbons, benzo(a)pyrene and 3-methylcholanthrene on Herpesvirus saimiri replication. The results from these experiments were compared with the effects of phosphonoacetic acid on the virus replication cycle. Phosphonoacetic acid inhibited the synthesis of virus-induced intracellular late antigens, membrane antigens and infectious virus but not the synthesis of the early antigens induced by H. saimiri. In contrast, benzo(a)pyrene and 3-methylcholanthrene inhibited primarily membrane antigen expression and infectious virus production. Benzo(a)pyrene was the most effective of the two compounds, with significant inhibition occurring with 2 mug/ml, whereas a minimum concentration of 10 mug/ml was required with 3-methylcholanthrene. Both compounds were most effective when present continuously during the 4-day infection process. However, exposure of infected cultures to a 3-hr pulse with each chemical also inhibited membrane antigen expression. Furthermore, pretreatment of cells for 48 hr before virus infection resulted in the inhibition of membrane antigen expression but not that of early or late antigens. These result demonstrate that some carcinogenic chemicals are capable of altering the H. saimiri replication cycle, primarily by inhibiting some but not all late events.

Acetates↗
PubMed1976

Antibody responses to membrane antigens in monkeys infected with Herpesvirus saimiri.

The antibody response to Herpesvirus saimiri (HSV)-induced membrane antigens (MA) was followed in HSV-infected owl monkeys using the membrane immunofluorescence (MF) and antibody-dependent lymphocyte cytotoxicity (ADLC) assays. These responses were correlated with the loss of T-cell responsiveness to general mitogens. Antibody titers to MA as determined by ADLC but not MF increased to remarkably high titers in those monkeys that developed malignant disease following virus infection, while remaining at relatively low and constant levels in those monkeys that developed a chronic virus infection in the absence of malignant disease. This disease-related antibody response pattern was paralleled by the loss of T-cell function in diseased animals. The development of leukemia in HVS-infected owl monkeys did not suppress the ability of peripheral blood lymphocytes to act as effector cells in the ADLC assay. The relationship of these immune response patterns to the development of malignant disease in this system is discussed.

Animals↗
PubMed1976

Antibody-dependent lymphocyte cytotoxicity against cells expressing Epstein-Barr virus antigens.

Antibody-dependent lymphocyte cytotoxicity (ADLC) was demonstrated against Epstein-Barr virus (EBV)-infected RAJI cells with peripheral with peripheral blood lymphocytes from EBV-infected donors. No cytotoxic activity was detected against unifected RAJl cells. The results indicated that this antibody-mediated cytotoxic reaction was directed against the same EBV-induced membrane antigens (MA) previously defined by the membrane immunofluorescence (MF) assay. Antibody to EBV-associated early antigens did not participate in this in vitro reaction. Antibody titers to EBV-induced MA were significantly higher by the ADLC assay in comparison with the MF test. A preliminary study showed no relationship between high antibody titers and the presence of EBV-associated malignancies. The possible in vivo significance of this immune reaction was discussed.

Antibodies, Viral↗
PubMed1976

Chronic Herpesvirus saimiri infection in an owl monkey.

An adult owl monkey (Aotus tricirgatus) used for immunologic studies of Herpesvirus saimiri (HVS) developed early, late, membrane, and neutralizing antibodies to HVS approximately 3 weeks after the beginning of the experiment. HVS was isolated by the cocultivation of peripheral blood for over 1 year. No clinical, gross, or histopathologic findings of malignancy were exhibited by the animal. The HVS isolate from the animal was indistinguishable biologically and serologically from the original HVS strain of Meléndez and from an isolate of an experimentally HVS-induced tumor. Inoculation of this isolate into 2 young white-lipped marmosets (Saguinus fuscicollis) produced typical malignant lymphoma and lymphocytic leukemia. Our findings suggested that the virus from the chronically infected animal was oncogenic and that host factors were primarily responsible for determining the disease manifestation of the virus infection. Another owl monkey chronically infected with HVS for over 2 years has remained asymptomatic.

Animals↗
PubMed1976

Persistent herpes simplex virus infections established in two Burkitt lymphoma derived cell lines.

Examination of P3HR-I cells (Epstein-Barr virus [EBV] producer) persistently infected with the MAL strain of herpes simplex virus type I (HSV-I) suggested that only a few cells were actively producing a virus indistinguishable from HSV-I (MAL) despite the presence of immunofluorescent HSV-I antigens associated with the majority of cells. EBV-specific immunofluorescence was not altered in HSV-I persistently infected P3HR-I cells. HSV-I persistently infected cells, labelled for 72 h with 14C-thymidine, incorporated approx. 8% of the label into cell associated HSV-I DNA as resolved by caesium chloride gradients. Values greater than 8% of the total were suggested by hybridization of gradient fractions with 3H-HSV-I DNA. To determine whether the establishment of HSV persistent infections in Burkitt lymphoma derived cells was a general phenomenon, six strains of HSV-I (MAL, KOS, Patton, Syn R, BF and SYN V) and two strains of type 2 (333 and MS) were used to infect the P3HR-I and Raji (EBV non-producer) cell lines derived from Burkitt lymphomas. In P3HR-I cells, persistent infections were established with all strains of HSV-I but not with HSV-2. In Raji cells, persistent infections were established with all strains of HSV-I, except Syn V, and with both strains of HSV-2. No external support was required to maintain these infections.

Adsorption↗