Search PubMed⌕ Search

Biomedical subjects

D Lawson

Publications and source records attributed to D Lawson.

At least 145 records · Page 8Linked to original sources
PubMed1983

Analysis and purification of the blood-sinusoidal domain of rat liver plasma membrane.

Methods are described for the analysis and purification of the blood-sinusoidal domains of rat liver plasma membranes using a combination of sucrose and Ficoll density gradient centrifugation. Use has been made of 125I-labelled wheat-germ agglutinin and hormone-stimulated adenylate cyclase to identify the blood sinusoidal fraction, which may be resolved from Golgi and endoplasmic reticulum markers on Ficoll gradients.

Animals↗
PubMed1983

Epinemin: a new protein associated with vimentin filaments in non-neural cells.

In this report I describe a new protein, defined by a monoclonal antibody, which is associated with vimentin filaments in a variety of cultured cells and in skeletal muscle. By immunofluorescence it is absent in smooth muscle, in cells without vimentin, and in neural vimentin containing cells. This protein has a molecular weight of 44,500, a pl of 5, a two-dimensional tryptic peptide fingerprint pattern different from vimentin, is unrelated to actin by Cleveland peptide analysis and by light and electron microscopy, and is not recognized by either a polyclonal antivimentin antibody (Frank, E.D., and L. Warren, 1981, Proc. Natl. Acad. Sci. USA, 78:3020-3024) or a monoclonal antibody against all classes of intermediate filaments (Pruss, R.M., R. Mirsky, M.C. Raff, R. Thorpe, A.J. Dowding, and B.H. Anderton, 1981, Cell, 27:419-428). The protein is resistant to nonionic detergent extraction, is soluble in high salt and can thus be removed from vimentin filaments, but fragments with vimentin in either low salt or anionic detergent and collapses with vimentin in colchicine-treated cells. By light microscopy, the distribution of the protein is indistinguishable from vimentin filaments and appears uniform along them. In contrast, immunoferritin electron microscopy reveals that the molecule is distributed in an intermittent pattern on vimentin filaments. Adopting the terminology of Granger and Lazarides (1980, Cell, 30:263-275), the molecule is called epinemin, meaning "upon filaments."

Animals↗
PubMed1980

The place of bone-marrow transplantation in acute myelogenous leukaemia.

28 patients with acute myeloid leukaemia (AML) in first remission were maintained on chemotherapy, consisting of courses of cytosine arabinoside and daunorubicin, and immunotherapy with irradiated AML cells and BCG. The relapse rate and survival rate of these patients were compared with those of a simultaneously treated group of 22 patients in first remission who received sibling bone-marrow transplants after cyclophosphamide (60 mg/kg) given for 2 days and followed by a single dose of 1000 rads total body irradiation. Substantially fewer transplanted patients (4 out of 22) than chemo-immunotherapy patients (19 out of 28) relapsed (p less than 0.005) and 14 (64%) transplanted patients remain alive, well, and disease-free. Survival curves of the two groups of patients show that the transplanted patients never fared worse than the chemo-immunotherapy patients. We suggest that when possible young AML patients in remission should be offered transplantation as an alternative form of treatment.

Adolescent↗
PubMed1980

Cyclosporin A to prevent graft-versus-host disease in man after allogeneic bone-marrow transplantation.

Cyclosporin A has been used in conjunction with allogeneic bone-marrow transplantation in the treatment of 23 patients--21 with acute leukaemia, 1 with chronic granulocytic leukaemia, and 1 with aplastic anaemia. The drug was given twice daily from the day before transplant. At the start of the study cyclosporin prophylaxis was stopped in 3 patients within 44 days of transplantation because of non-specific rashes and/or deteriorating renal function. All 3 patients had acute graft-versus-host disease (GVHD) and died. Thereafter the drug was not stopped because of possible toxic manifestations, and 20 patients have been studied (median follow-up 7 months; maximum 13 months). 2 patients have acquired GVHD; 1 patient died of acute GVHD and 1 has chronic mild disease. 3 other patients have died, 2 of recurrent leukaemia and a third of staphylococcal pneumonia with renal failure. Of the remaining patients, 1 has recurrent leukaemia and 1 has moderately severe renal failure. Several toxic effects of cyclosporin A have been observed but they are mostly reversible and no second malignant neoplasm has developed.

Adolescent↗
PubMed1980

Rat peritoneal mast cells: a model system for studying membrane fusion.

We used the mast cell as a model system for studying some of the membrane events which occur during exocytosis. Our observations indicate that the maximum cluster size of IgE molecules necessary for the "on" signal to activate a mast cell is 10 or less and that the "off" signal is not associated with the gross patching or pinocytosis of IgE and its Fc receptors. Furthermore, the use of Con A-Sepharose beads to stimulate mast cells has shown that such signaling is localized to the areas of stimulus, but this localization is not a function of desensitization over the rest of the cell since the subsequent addition of soluble Con A to locally released cells induced generalized degranulation. Ca2+ influx therefore acts in a localized manner to initiate degranulation. Following receptor cross-linking, most of the membrane proteins and the layer of intervening cytoplasm are laterally displaced away from the areas of membrane interaction. This displacement may act as the signal for fusion to occur. The resulting fused bilayers are predominantly lipid, a situation which may be common in all transient membrane fusion. The mechanism of exposing histamine-containing granules to the extracellular space by blebbing is discussed.

Animals↗
PubMed1980

An evaluation of hexamethylmelamine, cis-diamminedichloroplatinum, and mitomycin-C in advanced breast cancer. A pilot study of the Southeastern Cancer Study Group.

Eleven patients with metastatic breast cancer refractory to conventional therapy were treated with a combination of hexamethylmelamine 250 mg/m2 p.o. days 1-14, repeated at 4-week intervals; cis-platinum 30 mg/m2 I.V. q 28 days; and mitomycin-C 7.5-10 mg/m2 I.V. q 56 days. There were no complete responders and three partial responders for a response rate of 27%. Two patients (18%) had stabilization of disease for brief periods. The gastrointestinal toxicity of hexamethylmelamine was unacceptable. Recent reports that cis-platinum and hexamethylmelamine lack activity in breast cancer suggest that the activity of the combination was due to mitomycin-C alone.

Altretamine↗
PubMed1979

Some membrane events occurring during fusion and exocytosis in rat peritoneal mast cells.

We have used the mast cell as a model system for studying some of the membrane events which occur during exocytosis. Our observations indicate that the maximum cluster size of IgE molecules necessary for the 'on' signal to activate a mast cell is ten or less, and that the 'off' signal is not associated with the gross patching or pinocytosis of IgE and its Fc receptors. Furthermore, the use of Con A-Sepharose beads to stimulate mast cells has shown that such signalling is localized to the areas of stimulus, but this localization is not a function of desensitization over the rest of the cell since the subsequent addition of soluble Con A to locally released cells induced generalized degranulation. Ca2+ influx therefore acts in a localized manner to initiate degranulation. Following receptor cross-linking, most of the membrane proteins and the layer of intervening cytoplasm are laterally displaced away from the areas of membrane interaction. This displacement may act as the signal for fusion to occur. The resulting fused bilayers are predominantly lipid, a situation which may be common in all transient membrane fusion.

Animals↗
PubMed1978

Localized mast cell degranulation induced by concanavalin A-sepharose beads. Implications for the Ca2+ hypothesis of stimulus-secretion coupling.

Concanavalin A (Con A) covalently linked to Sepharose 4B beads induced localized degranulation of sensitized rat peritoneal mast cells in regions of contact between beads and cells. This degranulation was Ca2+ dependent and was not seen when sensitized mast cells bound to beads conjugated with a nonstimulating lectin, wheat germ agglutinin, or when unsensitized mast cells bound to Con A-Sepharose. The finding that sensitized mast cells which had adhered to Con A-Sepharose beads degranulated in regions of the cell away from the area of bead contact if exposed to soluble Con A excluded the possibility that the localized release was due to a redistribution of the IgE receptors or putative Ca2+ channels to the region of bead contact. The results suggest that, if an influx of Ca2+ is the mechanism for initiating mast cell degranulation, then the opening of Ca2+ channels in the plasma membrane of activated mast cells is a localized event and that Ca2+ acts locally within the cell to initiate exocytosis.

Animals↗
PubMed1977

Molecular events during membrane fusion. A study of exocytosis in rat peritoneal mast cells.

We have used thin section and freeze-fracture electron microscopy to study membrane changes occurring during exocytosis in rat peritoneal mast cells. By labeling degranulating mast cells with ferritin-conjugated lectins and anti-immunoglobulin antibodies, we demonstrate that these ligands do not bind to areas of plasma membrane or granule membrane which have fused with, or are interacting with, granule membrane. Moreover, intramembrane particles are also largely absent from both protoplasmic and external fracture faces of plasma and granule membranes in regions where these membranes appear to be interacting. Both the externally applied ligands and intramembrane particles are sometimes concentrated at the edges of fusion sites. The results indicate that membrane proteins are displaced laterally into adjacent membrane regions before the fusion process and that fusion occurs between protein-depleted lipid bilayers. The finding of protein-depleted blebs in regions of plasma and granule membrane interaction raises the interesting possibility that blebbing may be a process for exposing the granule contents to the extracellular space and for the elimination of excess lipid while conserving membrane proteins.

Antibodies↗
PubMed1977

Urea synthesis in Novikoff and Morris hepatomas.

The rates of urea synthesis in rat liver and in a series of rat liver neoplasms with widely different growth rates and degree of differentiation were investigated using tissue slices incubated in a Krebs-Ringer bicarbonate buffer. Urea synthesis did not occur in fast-growing, poorly differentiated Novikoff and Morris 3924A hepatomas, but it did occur in slow-growing, well- and highly differentiated hepatomas; however, there was no correlation with growth rate or degree of differentiation. Urea synthesis was comparable with normal liver, at about 32 mumoles/hr/g tissue, in the slow-growing Morris hepatomas 21, 28A, 47C, and 44; but it was very low in two other slow-growing, highly differentiated hepatomas, 9618A and 20. The well-differentiated Morris hepatoma 5123C had intermediate levels of urea synthesis. This pattern of urea synthesis closely paralleled the previously reported activity of carbamyl phosphate synthetase in these tumors. The rate of urea synthesis was normal in livers of Buffalo rats bearing fast- or slow-growing hepatomas in low urea synthesis rates, but it was markedly lowered in the livers of rats bearing large, slow-growing tumors with high urea synthesis rates. Urea synthesis in liver declined as the tumors increased in size. The total rate of urea synthesis in liver and tumor, as well as the concentrations of urea in the serum and urine of tumor-bearing animals, remained remarkably constant throughout the period of tumor growth, suggesting the existence of a homeostatic mechanism that controls the urea cycle activity in accordance with the synthetic activity of the tumor. In parabiotic animals, carbamyl phosphate synthetase activity and urea synthesis were lowered in the host livers of partners bearing tumors with high carbamyl phosphate synthetase- and urea-synthetic activity, but there was no significant effect on urea cycle activity in the normal partners. This result discounts the likelihood of a circulating humoral factor that controls hepatic urea cycle activity.

Animals↗
PubMed1976

Polyamine concentrations in bone marrow aspirates of children with leukemia and other malignancies.

High-pressure liquid chromatography analysis of polyamines in bone narrow from leukemic and nonleukemic subjects demonstrated increased concentrations of putrescine, spermidine, and spermine associated with increased cellularity. The most striking abnormality was the marked elevation of putrescine. Bone marrow polyamine analysis may be an adjunct for evaluation of leukemia patients.

Bone Marrow↗
PubMed1975

Anti-immunoglobulin-induced histamine secretion by rat peritoneal mast cells studied by immunoferritin electron microscopy.

We have used ferritin-conjugated divalent and monovalent anti-Ig antibodies to study simultaneously, histamine secretion and the ultrastructural distribution and redistribution of Ig receptors on rat peritoneal mast cells. We conclude that (a) divalent anti-Ig is required for both receptor redistribution and for calcium-dependent degranulation and histamine release, (b) divalent anti-Ig induces patching and pinocytosis but not capping of Ig molecules, (c) neither capping nor pinocytosis are required for triggering and if clustering is necessary, then less than 10 Ig molecules are required per cluster, and (d) degranulation (and histamine release) is not an all or none response of the mast cell.

Animals↗
PubMed1975

Carbamyl phosphate synthetases in rat liver neoplasms.

Isozymes of carbamyl phosphate synthetase (CPS), CPS I, a mitochondrial enzyme found exclusively in liver and involved in urea synthesis, and of CPS II, a soluble cytoplasmic enzyme widely distributed in animal tissues, were assayed in rat liver and in a series of rat liver neoplasms ranging widely in growth rate and degree of differentiation. CPS I was absent from fast-growing, poorly differentiated hepatomas, such as the Novikoff hepatoma and Morris hepatomas 3924A and 9098F, but was present in slow-growing, well- and highly differentiated Morris hepatomas. However, there was no close correlation between the growth rate or degree of differentiation and the CPS I activity. Activity was very high, at levels comparable with normal liver at about 9 UNITS/G, IN SLOW-GROWING, HEPATOMAS 21, 47C, and 28A but was very low in other slow-growing highly differentiated hepatomas 9618A, 66, and 16. CPS II activity was present in normal liver and all hepatomas examined, but with very low activity, of the order of 1% or less of that of CPS I activity, with maximal values at 5 to 70 milliunits/g. Again, there was no clear correlation with growth rate; the activity was lowest in fast-growing, poorly differentiated hepatomas. A striking observation was a marked lowering of CPS I activity in livers of rats bearing large, slow-growing tumors that have high CPS I activity. As the tumors grew larger and the liver CPS I decreased, a relatively constant total CPS I activity was maintained, suggesting the existence of a homeostatic mechanism. The effect was not observed in rats bearing either fast-growing hepatomas or slow-growing hepatomas with low CPS I activity and was not due to some specific nutritional effects of the tumor on the host.

Animals↗