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Biomedical subjects

G A Neil

Publications and source records attributed to G A Neil.

31 records · Page 2Linked to original sources
PubMed1992

Immunization of SCID-Hu mice and generation of anti-hepatitis B surface antigen-specific hybridomas by electrofusion.

Human hybridomas with specificity for recombinant hepatitis B surface antigen (HBSAg) were produced by adoptive transfer of human peripheral blood mononuclear cells prepared from HBSAg-immune donors to CB.17 mice bearing the severe combined immunodeficiency (SCID) phenotype. A total of ten SCID-Hu mice were immunized with recombinant HBSAg. Eight SCID-Hu mice found to have human HBSAg antibody in their serum were sacrificed, and single-cell suspensions were made from their spleens. The SCID-Hu spleen cells were electrofused to the mouse-human fusion partner H7. HBSAg-specific hybridomas were recovered from all fusions. This method may provide the means for the production of other human hybridomas and may, in some cases, circumvent the need for in vitro immunization or Epstein-Barr virus transformation of human B lymphocytes.

Adult↗
PubMed1992

Microscale production of hybridomas by hypo-osmolar electrofusion.

We have developed and tested a novel electrofusion chamber, the adjustable plate microchamber, that permits the successful electrofusion and production of hybridomas in a hanging droplet from as few as 1,000 B lymphocytes. Cell suspension volumes of 10 microliters may be used without excessive difficulty in aseptically recovering fused cells. With a modification of the hypo-osmolar electrofusion protocol with this microchamber, fusion efficiencies of the order of 10(-3) may be attained. These efficiencies are comparable to those attained with standard hardware and much higher numbers of input B lymphocytes. This technology should permit high efficiency hybridoma production using a variety of hitherto inaccessible B lymphocyte populations such as B cells isolated from human organ biopsies.

Animals↗
PubMed1991

Substance P but not vasoactive intestinal peptide modulates immunoglobulin secretion in murine schistosomiasis.

Neuropeptides including SP and VIP modulate Ig secretion by in vitro stimulated lymphocyte cultures. It is not known whether these neuropeptides effect the B cell directly, or if they significantly alter humoral immune responses to pathogens. We have previously shown that granulomas derived from schistosome-infected mice contain immunoglobulin secreting B cells (ISC) as well as eosinophils that secrete substance P (SP) and vasoactive intestinal peptide (VIP). It therefore seemed plausible that B cells derived from infected animals might respond to these neuropeptides, and that such responses might effect immunoregulatory signals. In this study, we addressed these issues in the murine Schistosoma mansoni model, at the level of immunoglobulin secretion in single B cells. Spontaneous ISC were observed in both splenic and granuloma cell preparations. The addition of SP resulted in a dose-dependent reduction in the number and size of plaques (a 50% reduction was observed at 10(-9) M). This effect was blocked with SP antagonists. Similar results were observed in T cell-depleted cell cultures. VIP had no effect on ISC number or plaque size. We conclude that SP, but not VIP, decreases spontaneous ISC number and Ig secretion in short-term cultures of spleen and granuloma cells. SP appears to exert its effects at the level of single B cells through a receptor-mediated mechanism and may thus play an immunoregulatory role in schistosomiasis.

Animals↗
PubMed1990

Electrofused mammalian cells analyzed by free-flow electrophoresis.

Somatic cell fusion is a powerful and widely used technique. In recent years, electrofusion has become increasingly popular because it is a gentle process that can be optically controlled and carefully monitored using appropriate fusion chambers and because it permits the efficient fusion of smaller cell numbers. However, damage of the cell membrane and cell lysis occurs during application of the electrical field and is accompanied by changes in surface charge which can be detected by free-flow electrophoresis. In this study, we evaluated free-flow electrophoresis to detect changes in cell viability after application of electric-field conditions employed in mammalian cell electrofusion and to separate dead cells and cell debris from intact unfused or fused cells.

Animals↗
PubMed1989

Efficient generation of stable antibody forming hybridoma cells by electrofusion.

A variety of modified electrofusion protocols designed to improve the efficiency of hybridoma production have recently appeared in the literature. We undertook to maximize the number of antibody secreting murine hybridomas by optimizing the temperature and fusion strength parameters of the conventional electrofusion technique. Anti-DNP secreting hybridomas were generated by fusing SP2/0 to immunized mouse splenic lymphocytes using an unmodified electrofusion protocol consisting of washing in a weakly conducting sorbitol fusion medium supplemented with bovine serum albumin, calcium and magnesium ions. This was followed by dielectrophoretic alignment and application of 3 short duration, high intensity field pulses in helical chambers. Optimal efficiencies of hybridomas were generated by the application of 2000 V/cm pulses at 25 degrees C (2.45 hybridomas x 10(-4) splenocytes) and as many as 63% of resulting hybridomas secreted anti-DNP monoclonal antibodies, the majority of which were IgG's. These data show that modification of the electrofusion protocol by pretreatment of fusion partners with proteolytic enzymes or the use of antigen bridging is not required for the successful and efficient production of specific monoclonal antibodies by electrofusion.

Animals↗
PubMed1988

Increased efficiency of transfection of murine hybridoma cells with DNA by electropermeabilization.

Dispase-treated murine hybridoma cells (SP2/0-Ag14) were transfected with the G418 resistance gene bearing plasmid pSV2-neo by electropermeabilization with a high degree of efficiency. The cells were subjected to intermittent multiple high-voltage short duration (5 microsecond) DC pulses at intervals of 1 min in a weakly conducting medium followed by selection in G418-containing medium. The transfection medium, temperature, pulse duration, and voltage were empirically determined by preliminary electropermeabilization experiments. Increasing the number of pulses resulted in a higher percentage of transfected cells, but a decrease in the number of viable cells, with the optimal transfectant yield resulting when five pulses of 10 kV/cm were administered. This method allows the rapid and efficient injection of DNA into mammalian cells, and permits the rapid production of stable, drug resistant hybridoma cell lines for use in subsequent fusion experiments.

Animals↗
PubMed1988

Experimental approaches to colon cancer prevention in humans.

Colorectal cancer is a major illness in the Western world. International and migrant studies suggest that environmental causes, notably a fat- and calorie-dense diet (even if adopted in adulthood), are associated with the disease. Case-control studies have not conclusively identified specific etiologic dietary factors, however. In addition, the emphasis placed on migrant studies has led many to overlook potentially important genetic factors that might help to explain some of the discrepancies in the epidemiologic data. Thus, the cause(s) of colorectal cancer remain unclear and hence effective preventive strategies are not presently available. Numerous tenable hypotheses have been generated as a consequence of observational and analytical epidemiologic studies, as well as rodent experiments. Controlled trials to test these hypotheses using colorectal cancer as an endpoint are not justifiable at present. It is possible, however, that "intermediate markers" (such as epithelial cell proliferation rates and others) that are associated with colorectal cancer in both humans and experimental animal systems might provide the means for hypothesis testing in short-term clinical trials. Despite the fact that this approach has several caveats, consistent results obtained in short-term studies would more readily justify the undertaking of a large-scale, long-term controlled study using colon cancer or adenomatous polyp recurrence as an endpoint.

Colorectal Neoplasms↗
PubMed1987

The mechanism of anti-Lyt-2 inhibition of antibody-directed lysis by cytotoxic T lymphocytes.

Bifunctional antibodies specific for a determinant within the T cell receptor (TcR) complex of cytotoxic T lymphocytes (CTL) and a determinant expressed on the surface of the target cell will effectively mediate cytolysis. In such a lytic system anti-Lyt-2 antibody can block cytolysis. We have observed that the amount of inhibition varies considerably from clone to clone and surprisingly correlates well with inhibition of conjugate formation as mediated by bifunctional antibody. This implies that inhibition of antibody-mediated killing occurs as the result of reduction of the avidity of the effector cell for its target, the same mechanism responsible for inhibition of receptor-mediated lysis by anti-Lyt-2. In light of the similarity between the mechanism of inhibition by anti-Lyt-2 of receptor-mediated and antibody-mediated cytolysis, we compared the ability of anti-Lyt-2 to inhibit cytolysis in these two different assay systems by using a number of different CTL clones. Whereas the majority of secondary CTL clones (presumed to have high affinity TcR) are inhibited equally in both assay systems, most primary CTL (presumed to have low affinity TcR) are more susceptible to inhibition by anti-Lyt-2 in their receptor-specific than their antibody-directed cytolysis. These results, taken together with an apparent correlation between the amount of Lyt-2 expressed on the cell surface and susceptibility to inhibition, suggest anti-Lyt-2 may block CTL function by sterically inhibiting mobility of the TcR complex.

Animals↗
PubMed1986

Lymphocytic interstitial pneumonia and abdominal lymphoma complicating celiac sprue.

We report the development of lymphocytic interstitial pneumonia followed later by abdominal lymphoma in a 62-year-old woman with celiac sprue. She presented with dyspnea, cough, weight loss, and bibasilar pulmonary infiltrates. Lung biopsy demonstrated lymphocytic interstitial pneumonia and corticosteroid therapy resulted in clinical and radiological improvement. She remained well for just over a year until abdominal pain developed and investigation revealed an abdominal lymphoma. Chemotherapy effectively controlled the lymphoma while the lymphocytic interstitial pneumonia was satisfactorily managed by corticosteroid therapy. Although lymphoma is a well-recognized complication of celiac sprue, it is not associated with lymphocytic interstitial pneumonia, despite a number of other reports describing the occurrence of pulmonary disease in this disorder.

Abdominal Neoplasms↗
PubMed1983

A clinical approach to common electrolyte problems: 2. Potassium imbalances.

A clinical approach to potassium imbalances is presented. Hypokalemia is rarely due solely to a reduced intake of potassium; instead, it usually results from a potassium flux into the cells or increased loss of the element, at times combined with a decreased intake. The clinician must seek the cause of the intracellular flux or the source of the gastrointestinal or renal loss. The causes of gastrointestinal losses are generally self evident. Renal potassium wasting, though, generally results from increased mineralocorticoid activity, an increased rate of urinary flow or of sodium delivery to the distal nephron, or both, hypomagnesemia or a combination of these factors. Hyperkalemia may be factitious, but usually it is caused by a flux of potassium from the cells or a decrease in the renal loss of potassium, the latter being mediated by a reduction in renal function, mineralocorticoid activity, or the rate of urinary flow or sodium delivery, or both. In both hypokalemia and hyperkalemia, treatment must be guided by the specific clinical circumstances.

Calcium↗
PubMed1983

A clinical approach to common electrolyte problems. 1. Hyponatremia.

The clinical approach to hyponatremia described in this paper involves identification of the hyponatremia as iso-osmolar (factitious), hyperosmolar (mediated by osmotically induced flux of water from cells) or hypo-osmolar. Hypo-osmolar hyponatremia results from decreased renal excretion of dilute urine. This may be caused by renal failure through decreased delivery of filtrate to or function of the ascending limb of the loop of Henle, where dilute urine is made, or through increased water reabsorption in the collecting duct, either independent of antidiuretic hormone or related to a physiologic, drug-induced or pathologic increase in the bioactivity of antidiuretic hormone. The treatment of hyponatremia must be individualized.

Absorption↗
PubMedDate not supplied

Drainage of the gallbladder in patients with acute acalculous cholecystitis by transpapillary endoscopic cholecystotomy.

The mortality associated with acute acalculous cholecystitis approaches 50%. Removal or decompression of the gallbladder in these patients may prevent gallbladder rupture and may be lifesaving. This is usually accomplished by cholecystectomy, cholecystotomy, or percutaneous gallbladder drainage. We describe a novel transpapillary endoscopic approach to gallbladder drainage in patients at high surgical risk. A total of seven high surgical risk patients were treated with transpapillary endoscopic cholecystotomy. Cannulation of the cystic duct was accomplished by using standard hourglass-tipped catheters in two patients. A new "selector" catheter was developed for selective cannulation of the cystic duct and used in the other five patients. Five of the seven patients showed evidence of clinical, radiographic, and laboratory improvement after treatment. We conclude that transpapillary endoscopic cholecystotomy may be an effective treatment alternative for high surgical risk patients with acalculous cholecystitis.

Acetylcysteine↗