In vivo expression of a nonselected gene transferred into murine hematopoietic stem cells by electroporation

Mouse bone marrow cells were subjected to electroporation in the presence of RSVCAT and SV2NEO plasmids. CAT activity was detected in the G-418 resistant granulocyte-macrophage colonies. RSVCAT electroporated into primary bone marrow cells, repopulated lethally irradiated mice as demonstrated by the persistence of CAT activity in the hematopoietic tissues showing that electroporation can offer a powerful mode of gene transfer into bone marrow cells.

Development of an assay system for the detection and classification of methotrexate resistance in fresh human leukemic cells

An assay system was developed for the detection and classification of methotrexate resistance in fresh human leukemic cells. Mechanisms of resistance to be identified were: overexpression of dihydrofolate reductase, decreased cellular uptake of methotrexate, decreased affinity of dihydrofolate reductase for methotrexate, decreased polyglutamylation of methotrexate, and low thymidylate synthase activity. The initial screening procedure utilizes 3H release after addition of [5-3H]-2'-deoxyuridine as a measure of intracellular activity of thymidylate synthase and of DNA synthesis; 3H release is assayed after 3-h incubations with methotrexate, trimetrexate, or gamma-fluoromethotrexate and after 4-h incubations with these agents followed by a 6-h incubation in drug free medium. The pattern of DNA synthesis inhibition and recovery under these two sets of conditions establishes the presence or absence of methotrexate resistance and allows a tentative classification of the resistance mechanism involved. In combination with determinations of dihydrofolate reductase activity, methotrexate titration studies, and the determination of intracellular drug accumulations in vitro, the system is readily able to classify CCRF-CEM human leukemia cell lines possessing well defined mechanisms of resistance. The findings in seven leukemia patients are also reported. Applying tentative reference values, four patients showed biochemical evidence of methotrexate resistance: two patients had only a transport defect, one patient had evidence of both a transport defect and low thymidylate synthase activity, and one patient appeared to have decreased methotrexate polyglutamylation. Application of the assay system in larger numbers of patients is feasible and is required to establish adequate reference values for the evaluation of biochemical-clinical correlates.

Introduction of deoxyribonucleoside triphosphates into intact cells by electroporation

A simple method, employing high-voltage electric discharge (electroporation), was developed to introduce phosphorylated nucleosides into the cytoplasm of viable cells. HL-60 leukemia cells permeabilized by this technique remained viable and incorporated deoxyribonucleoside triphosphates into nuclear DNA. Furthermore, DNA synthesis was depressed for at least 24 h in HL-60 cells made permeable to 1-beta-D-arabinosylcytosine 5'-triphosphate by this methodology. Electroporation was found to be applicable to the permeabilization of a wide variety of cell lines in culture to nucleotides, suggesting that this methodology may be useful for the introduction into intact cells of a wide variety of molecules that are not normally transported effectively.

DNA-mediated gene transfer into epidermal cells using electroporation

A reliable method for the introduction of foreign DNA into epidermal cells is described. Electroporation of murine BALB/c MK-1 epidermal cells with pSV2-CAT resulted in the transient expression of chloramphenicol-acetyltransferase (0.03 to 0.05 nmoles acetylchloramphenicol per mg protein per min) in the transfected cells. Transfection of MK-1 cells with pSV2-neo led to the appearance of approximately eight G418 resistant clones per 10(-6) cells per microgram of plasmid DNA. Distinct patterns of integration of SV2-neo were detected in three different resistant clones.

Development of an amphotropic, high-titer retrovirus vector expressing the dihydrofolate reductase gene and conferring methotrexate resistance

Altered mouse dihydrofolate reductase gene (DHFRR) was expressed in murine cells using Abelson murine leukemia provirus genome as a prototype vector. A cDNA clone of DHFRR was inserted into a plasmid structure containing retroviral transcriptional as well as packaging signals. The recombinant plasmid was transfected into psi-2 ecotropic cells and the transient virus was used to infect amphotropic PA-12 cells. Recombinant virus (ABL-DHFRR) was detected in the culture medium of transfected PA-12 cells and was free of helper virus. The ABL-DHFRR was capable of conferring methotrexate (MTX) resistance to a variety of cells in culture. The titer of ABL-DHFRR virus was at least tenfold higher than other DHFR retroviruses. The ABL-DHFRR virus titer was increased by selection at increasing concentrations of MTX. The presence of the DHFRR in the virus-infected cells was confirmed by assays which showed reduced inhibition of enzyme activity by MTX. A helper-virus-free, amphotropic, high-titer retrovirus containing the altered DHFR was obtained which may be of use as a dominant selectable marker in infecting hematopoietic progenitor cells.

Isolation and characterization of a human T cell leukemia virus type II from a hemophilia-A patient with pancytopenia

Human T cell leukemia virus (HTLV) type I has been isolated from the cultured T cells of several patients with adult T cell leukemia (ATL) and has been etiologically linked to ATL. However, HTLV-type II has been isolated only once, from the T cells of a patient with a T cell variant of hairy-cell leukemia. We report here the isolation of HTLV-II-related virus from the cultured T cells of a hemophilia-A patient with pancytopenia. The T cell line (CM) grows in the absence of T cell growth factor. Cord blood T cells were rapidly transformed when co-cultivated with irradiated CM cells. Heterologous competition radioimmunoassays using purified HTLV-I p24 showed the expression of HTLV-IIMO-related protein in these cells. Electron microscopy of the CM cells showed the presence of intracellular and extracellular type C viral particles. Comparison of the proviral genome in the CM cell line and the prototype HTLV-IIMO-containing cell line (MO) by molecular hybridization with probes specific for HTLV-IIMO indicated that restriction cleavage sites were identical. The fresh peripheral blood leukocytes of the patient contained two complete copies of the proviral genome, despite the lack of HTLV-II p24 expression. The virus from the cell line CM is designated as HTLV-IICM to distinguish it from the original HTLV-IIMO isolate.

Sequences in the long terminal repeats of the Moloney murine sarcoma virus-124 genome which control transforming gene function

The role of long terminal repeat (LTR) sequences in the efficient expression of Moloney murine sarcoma virus (MSV-124) transforming gene function was investigated. Recombinant plasmids containing a single LTR positioned 3' of v-mos were subjected to sequential deletions, and the relative transforming efficiency of these recombinants was analyzed in the NIH/3T3 transfection assay. Recombinants lacking CAAT, TATA, and poly(A) signals within the LTR were able to transform with an efficiency comparable to that of the wild-type MSV-124 genome. Deletion of one of the two 74-bp tandem repeat units within the LTR did not abolish v-mos gene function, whereas removal of both 74-bp repeat units completely eliminated transforming activity. The addition of a fragment containing only a single 74-bp unit and 29-bp downstream sequences derived from the LTR to a position 3' of v-mos led to efficient activation of v-mos transforming function. Residual potentiating activity for v-mos expression was retained even when the distance between v-mos and the 3' LTR was increased by several kilobase pairs. All these findings are consistent with the concept that the potentiating action of the LTR in its 3' position is due to activator/enhancer sequences localized to one of its 74-bp repeats. A permuted MSV-124 molecule, whose single LTR was localized 5' of v-mos, was very inefficient at transformation. However, its transforming activity could be increased by approximately 1000-fold by tandemization of the molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies to the core protein of lymphadenopathy-associated virus (LAV) in patients with AIDS

Lymphadenopathy-associated virus ( LAV ), a human T- lymphotrophic retrovirus isolated from a homosexual man with lymphadenopathy, has been causally associated with acquired immunodeficiency syndrome (AIDS). A sensitive and specific radioimmunoprecipitation test was developed for the detection of antibodies to the major core protein of LAV , p25 (molecular weight 25,000). Antibody to LAV p25 was found in the serum of 51 of 125 AIDS patients, 81 of 113 patients with lymphadenopathy syndrome, 0 of 70 workers at the Centers for Disease Control (some of whom had handled specimens from AIDS patients), and 0 of 189 random blood donors. Of a group of 100 homosexual men from San Francisco whose serum was obtained in 1978, only one had antibody to LAV p25; in contrast, of a group of 50 homosexual men in the same community whose serum was obtained in 1984, 12 had antibodies to LAV p25.

Late laminectomy in traumatic paraplegia

Long-term observation in cases of spinal injury with subarachnoid block, treated by laminectomy and removal of compressing elements, shows worthwhile results in a good percentage. Twenty-seven cases of fractures of the spine at the dorsolumbar and lumbar levels with conus and cauda equina injury were treated by laminectomy and decompression from 6 to 12 weeks after the injury, and have been followed for periods of 3-27 years. Surgical intervention was offered only in those cases in which myelography demonstrated a subarachnoid block. Most of the cases were operated on at 6-12 weeks after the injury. Displaced laminae, thickened ligamentum flavum, and arachnoidal adhesions were the common causes of compression. In six cases there was also an arachnoid cyst. Long-term follow-up showed improvement in bladder function in 14 of 27 patients, and in motor function in 8 of 27. In dorsolumbar and lumbar injuries in which there is a subarachnoid block, decompressive laminectomy is a worthwhile procedure.

Accuracy of a rapid carbohydrate oxidation microtube method for identification of nonfermentative gram-negative bacilli

A rapid carbohydrate oxidation microtube system (Carr Microbiologicals, Wichita, Kans.), designed for detecting the saccharolytic activity of gram-negative, nonfermenting bacilli, was evaluated and compared with the conventional oxidation-fermentation method. The oxidation of glucose, maltose, lactose, and xylose was tested with 430 strains of Pseudomonas, Acinetobacter, Achromobacter, Alcaligenes, Moraxella, Flavobacterium, and Bordetella species. More than 95% of the isolates tested gave correct oxidation reactions within 4 h in the rapid carbohydrate oxidation microtubes, whereas oxidation-fermentation media required 24 h to achieve the same sensitivity. The microtube system was found to be simple, accurate, rapid, and economical.

Fluorescence and N.M.R. studies of the binding of cholinergic fluorescent probes to horse serum cholinesterase

The interaction of the cholinergic fluorescent probes, 1-(5-dimethyl-aminoaphthalene-1-sulfonamido) ethane-2-trimethylammonium perchlorate, 1-(5-dimethylaminoaphthalene-1-sulfonamido) pentane-5-trimethylammonium tartarate and 1-(5-dimethylaminonaphthalene-1-sulfonamido) decane-10- trimethylammonium tartarate with horse serum cholinesterase has been examined by fluorescence and n.m.r. methods. Fluorescence titrations show binding of the decane derivative to two sites on the protein whereas the lower homologs bind largely to one site. Active site inhibitors like carbamylcholine and decamethonium abolish binding of the decane derivative to the high affinity site. The inhibitors are largely without effect on the binding of the lower homologs. N.m.r. studies clearly establish immobilization of both ends of the molecule on binding in the case of the decane derivative, whereas in the lower homologs the dimethylamino group on the naphthalene ring is significantly more affected in the presence of enzyme. The probes are effective inhibitors of the enzyme with the decane derivative being two orders of magnitude more effective than its lower homologs. Based on the n.m.r., fluorescence and inhibition studies, a model for probe binding to the enzyme is advanced. It appears that the decane derivative binds with high affinity to the catalytic anionic site while the lower affinity site is assigned to a peripheral anionic site. The lower homologs probe only the peripheral site. A comparison of fluorescence, n.m.r. and inhibition studies with acetylcholinesterases from electric eel and bovine erythrocytes is presented.

Incidence of postoperative venous thromboembolism in South India

The development of postoperative deep vein thrombosis (DVT) was determined in 50 South Indian patients aged 50 years or more using the 125I-fibrinogen uptake technique. The overall incidence was 28 per cent. In patients with malignancy the incidence was 47.6 per cent. Predisposing factors such as varicose veins, oral contraceptives and obesity did not appear important. A retrospective analysis of post-mortem examinations performed on 432 patients dying after operation showed major pulmonary embolism to have occurred in only 1.9 per cent. The disproportion between the frequent occurrence of postoperative DVT and the infrequence of fatal pulmonary embolism warrants further study.

Fluorescent probe studies of mixed micelles of phospholipids and bile salts. Effect of cholesterol incorporation

The binding of the fluorescent alkylamines, N-(2-aminoethyl)-5-dimethyl-amino-1-naphthalene sulfonamide, N-(5-aminopentyl)-5-dimethylamino-1-naphthalene sulfonamide (dansyl cadaverine) and N-(10-aminodecyl)-5-dimethylamino-1-napthalene sulfonamide with phospholipid and phospholipid-deoxycholate micelles, has been shown to increase with the length of the alkyl spacer chain. The probes bind more effectively to micelles containing unsaturated phospholipids and do not interact strongly with bile salt solutions at low concentrations. Cholesterol incorporation into mixed micelles results in a quenching of probe fluorescence due to displacement of probe molecules. The enhanced rigidity of the mixed micelles on solubilizing cholesterol is established by a decrease in pyrene excimer fluorescence and by the less effective perturbation of the micellar structure by 1-anilino-8-naphthalene sulfonate. The anionic probe 1-anilino-8-naphthalene sulfonate is also displaced from the mixed micelles when cholesterol is incorporated, suggesting a dominant role for packing and hydrophobic effects in binding both positively and negatively charged probes.