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M Stevenson

Publications and source records attributed to M Stevenson.

At least 181 records · Page 10Linked to original sources
PubMed1986

Transfection of lymphoblastoid cells using DNA-loaded reconstituted Sendai virus envelopes: expression of transfected DNA and selection of transfected cells.

The American Burkitt's lymphoma cell line Loukes was cotransfected with cloned BamHI K fragment of EBV DNA and a vector pSV2neo. Reconstituted Sendai virus envelopes (RSVE) loaded with DNA were used for efficient gene transfer. Two cell lines have been obtained following culture in the presence of geneticin sulfate (G-418). Messenger RNA from both transfected DNAs was expressed during the whole period of observation, 42 days after transfection. This method provides a relatively simple and efficient means for selection of lymphoblastoid cells expressing a transfected gene.

Burkitt Lymphoma↗
PubMed1986

Activated v-myc and v-ras oncogenes do not transform normal human lymphocytes.

Activated v-myc (pSV v-myc) and v-Ha-ras (GT10) oncogenes were introduced into normal human lymphocytes, NIH 3T3 fibroblasts, B-lymphoblastoid cells, and human epithelial cells, using a reconstituted Sendai virus envelope-mediated gene transfer technique. Efficient transfer of the plasmid in each cell type was demonstrable within 1.5 h of transfection by Southern blotting of extrachromosomal DNA extracts, which unexpectedly revealed that v-myc plasmid DNA was unstable in normal lymphocytes but not in the other cell types. The v-myc plasmid was stabilized when cotransfected into lymphocytes together with v-Ha-ras. The transfected v-Ha-ras plasmid was stable in all the cell types tested. v-myc plasmid expression was clearly detectable by 5 h in all cell types except human lymphocytes. Lymphocytes expressed v-myc when transfected together with v-Ha-ras. Transfected ras oncogene was efficiently expressed in all the cell types tested. Expression of the transfected genes increased at 24 and 48 h after transfection. Even though plasmid stability and expression were achieved in myc-ras-cotransfected lymphocytes, no effects on cellular DNA synthesis or immortalization were observed, in contrast to efficient transformation of NIH 3T3 fibroblasts by the same procedure. Our data suggest that efficient expression of transfected myc and ras oncogenes in normal quiescent human lymphocytes is not sufficient for the induction of cell growth and immortalization.

Animals↗
PubMed1986

Retroviral etiology of the acquired immune deficiency syndrome (AIDS).

The acquired immune deficiency syndrome (AIDS) is characterized by severe immunological defects resulting in opportunistic infections and malignancies. A novel human retrovirus, known under the terms of LAV, HTLV-III, ARV or as a human immunodeficiency virus (HIV), has been defined as the infectious agent responsible for the induction of the immunologic disorders in AIDS. However, two recent lines of evidence, reviewed in this article, complicate the etiological picture of AIDS: the HIV family appears to consist of a great number of diverse, and perhaps diversifying in vivo, members that exhibit different molecular and biological properties; the human retrovirus family may contain yet another distinct class of member viruses that resemble HIV morphologically and structurally but may differ in their pathogenicity. Our understanding of the retroviral etiology of AIDS may be far from complete.

Acquired Immunodeficiency Syndrome↗
PubMed1984

Genetic control of resistance to murine malaria.

Strain variation in the level of resistance to malaria was investigated in inbred mice after infection with Plasmodium chabaudi. Following intraperitoneal infection with the typing dose of parasitized erythrocytes, mice of 11 inbred strains could be separated using survival time as the criterium into resistant and susceptible groups. Genetic analysis of F1 hybrid and backcross progeny derived from one of the most resistant (B10.A) and from the most susceptible (A/J) strains as parents suggested that host resistance in this strain combination was genetically controlled by a dominant, non-H-2-linked, autosomal gene or closely linked genes. Analysis of the mechanisms of resistance to P chabaudi showed (1) phenotypic expression of the resistance gene was apparent within 6 days of infection as a significant difference between resistant and susceptible mice in the level of parasitemia; (2) the level of host NK cell activity was not related to the level of host resistance to malaria; (3) compared with susceptible A/J mice, resistant B10.A hosts had an augmented erythropoietic response during the course of malaria as well as during phenylhydrazine-induced anemia and (4) treatment with BCG or P acnes resulted in an equal degree of protection, measured by parasitemia and survival, in both resistant and susceptible mice.

Animals↗
PubMed1984

Sleep apnea in cluster headache.

The impetus to study sleep changes in a cluster population arose from a recent hypothesis that predicted the finding of sleep apnea in this disorder. It holds that cluster attacks may occur in response to oxygen desaturation. Proposed mechanisms involve impairment of carotid body activity secondary to hypothalamic-vasomotor regulatory dysfunction. Five chronic and five episodic cluster patients underwent nocturnal polysomnography, utilizing standard equipment for monitoring sleep status, cardiac activity, nasal and buccal air flow change, chest and abdominal breathing, muscle activity and oxygen saturation. All episodic patients and one of five chronic patients were found to have sleep apnea (60%). Mean apneas per hour during NREM sleep were similar to that of REM sleep; 26.7 and 28.2, respectively. Six patients with sleep apnea experienced 14 cluster headache attacks during the study period. Eight attacks (57%) followed episodes of oxygen desaturation ranging from 65% to 85%. In the sleep apnea group, 8 out of 14 attacks (57%) were associated with REM; three without, and five following oxygen desaturation. Of the non-apnea group, all of whom had chronic cluster headache, none of 5 attacks were associated with oxygen desaturation, and only 2/5 attacks occurred in relation to REM. Thus, our study showed that sleep apnea was a common finding in a randomly selected group of episodic cluster patients; and most nocturnal attacks were preceded by oxyhemoglobin desaturation and REM-related. These findings were uncommon in the chronic cluster group.

Adult↗
PubMed1984

An in-vitro model of intracellular bacterial infection using the murine macrophage cell line J774.2.

A simple model of intracellular bacterial infection based on the ability of the macrophage cell line J774.2 to phagocytose Escherichia coli in a reproducible manner is described. Viable counting of intracellular bacteria and microscopic examination of infected macrophage cultures after treatment with fluorescent E. coli antibody showed that the bacteria multiplied within the J774.2 cells. Viable intracellular bacteria may be used to study the activity of bactericidal and bacteriostatic drugs within the macrophage. The low apparent intracellular bactericidal activity of streptomycin, which was time- and concentration-dependent, accords with a low permeability of the J774.2 macrophages to this antibiotic. An exclusively intracellular infection could be achieved by inactivation of non-phagocytosed extracellular bacteria by streptomycin treatment of infected macrophage cultures. Under appropriate conditions intracellular bacterial viability was unaffected.

Animals↗
PubMed1984

Quantification of uptake of liposomal carboxyfluorescein by professional phagocytes in-vitro. A flow microfluorimetric study on the J774 murine macrophage cell line.

Unilamellar egg phosphatidylcholine/cholesterol liposomes containing carboxyfluorescein were prepared by an ether injection method. The ability of cells of the J774.2 murine macrophage cell line to incorporate the liposomal fluorophore during incubation at 37 degrees C was measured by flow microfluorimetry. Liposomes incorporating additional phosphatidylserine or phosphatidic acid were taken up much more avidly than those lacking these phospholipids and the greatest uptake of carboxyfluorescein was observed with the phosphatidylserine species. Calculation of the number of liposomes taken up, greater than or equal to 0.2% of the number given, showed that this was an inefficient process. However these uptake data support previous findings based on the intracellular bactericidal activity of liposomal antibiotics determined in an identical in-vitro system.

Animals↗
PubMed1984

Genetic control of resistance to Listeria monocytogenes: regulation of leukocyte inflammatory responses by the Hc locus.

The control mechanisms responsible for the innate resistance of C57BL/6J (B) mice and for the innate susceptibility of A/J (A) mice to infection with Listeria monocytogenes were studied by typing the recombinant inbred (RI) strains derived from these two progenitors for the trait of Listeria resistance/susceptibility. The strain distribution pattern (SDP) of this trait obtained in the 13 AXB/BXA RI strains studied suggests that an allelic difference at a major locus (Lr-1) is responsible for the trait of resistance/susceptibility to Listeria. In addition, another putative gene (Lr-2) unlinked to Lr-1 is postulated to control the level of bacterial load within the group of susceptible strains. The SDP of A and B alleles at the Lr-1 locus was fully concordant with that observed for the Hc locus (controlling the level of the C5 component of complement). This suggests that the genetic susceptibility of A strains of mice to Listeria infection is either directly due to or related to the C5 deficiency found in that strain. This conclusion is enhanced by the observation of a significant protection of A mice from listeriosis by the infusion of C5-rich serum. A survey of RI strains for the magnitude of PMN and macrophage inflammatory responses showed that the expression of both traits co-segregated and that the C5 deficiency was the major factor responsible for the defective inflammatory response of A strain mice. We conclude that a defect in the phagocyte inflammatory responses caused by C5 deficiency is the major reason for the extreme susceptibility of A mice to Listeria.

Animals↗
PubMed1983

Sexing penguins by cloacal examination.

Cloacal examination to determine sex was carried out in 145 penguins of five species. The birds were from four of the major collections in the British Isles. Differences in the appearance of the urodaeum were sufficient to differentiate between the sexes in the species examined.

Animals↗
PubMed1983

Enhanced activity of streptomycin and chloramphenicol against intracellular Escherichia coli in the J774 macrophage cell line mediated by liposome delivery.

Streptomycin and chloramphenicol were entrapped within large neutral or anionic unilamellar vesicles of egg phosphatidylcholine prepared by an ether injection method. Both antibiotics in liposomal form were inactive against Escherichia coli in a simple tube dilution assay. A comparison was made of the activities of the free and liposomal forms of the antibiotics against E. coli located within the macrophages of the J774.2 murine cell line. The apparent intracellular antibacterial activity of both antibiotics was increased more than 10-fold by entrapment in neutral liposomes and in the case of chloramphenicol in anionic liposomes containing phosphatidylserine. Anionic liposomes containing phosphatidic acid were much less effective carriers than neutral liposomes for either antibiotic in this in vitro system. Incubation at 4 degrees C of cells with liposomes containing antibiotic or carboxyfluorescein inhibited intracellular antibacterial activity and cell-associated fluorescence. The high intracellular activity of the liposomal antibiotics is consistent with their phagocytic uptake by the macrophages followed by intracellular liposomal degradation and antibiotic release. Liposomal modification of cellular uptake and intracellular distribution of antibiotics may be used to extend the activity of existing and new agents against intracellular infection of the reticuloendothelial system.

Animals↗
PubMed1983

Patients--a virtue?

Explore the source record for details and available documents.

History, 15th Century↗
PubMed1979

Comparison of sickle cell-beta0 thalassaemia with homozygous sickle cell disease.

Clinical and haematological features in 41 patients with sickle cell-beta0 thalassaemia (Sbeta0 thalassemia) and in 123 age--sex matched controls with homozygous sickle cell (SS) disease were compared. Persistence of splenomegaly was more common and fetal loss less common in Sbeta0 thalassemia but other clinical features were similar in the two genotypes. Total haemoglobin, Hb A2, PCV, CCV, and red cell count were significantly higher and MCV, MCH, MCHC, and ISC counts significantly lower in Sbeta0 thalassaemia. Proportional reticulocyte counts were significantly lower in Sbeta0 thalassaemia but there was no difference in absolute reticulocyte counts. Persistence of splenomegaly and low ISC counts are compatible with decreased intravascular sickling which may result from the lower mean cell haemoglobin S concentration in Sbeta0 thalassaemia. If beneficial effects of a low MCHC can be confirmed then a carefully monitored trial of iron deficiency in SS disease may be a logical experimental procedure.

Adolescent↗
PubMed1979

Sleep apnea in normal kittens.

Apneic episodes in normal 10-, 20-, and 40-day-old kittens were assessed with polygraphic recordings. End expiratory apneas, usually preceded by somatic activity and/or augmented breaths, with durations less than 10 sec were observed in quiet sleep, active sleep, and transitions between states in all age groups. The highest apnea density was found at state transitions. Heart rate decelerations occurred before, during, and following apneas, but decelerations were not related to apnea duration. Combined central and obstructive components were associated with 9% of apneas in normal kittens.

Age Factors↗
PubMed1978

Polygraphic studies of kitten development: respiratory rate and variability during sleep-waking states.

The developmental course of respiration rate and variability during sleep states and waking was measured in chronically prepared kittens. Kittens had higher respiration rates during active sleep (AS) as compared to quiet sleep (QS) at all ages, with rates declining developmentally in both sleep states. Compared to waking, respiration rate and variability were decreased during sleep. The decrease was greatest in the youngest animals and during QS. Minute-to-minute respiratory variability declined from 10 to 40 days of age for each state, whereas breath-to-breath variability declined during the same period only during QS. Respiratory variability was higher in AS than QS in older kittens. Heart rate and variability were found to be correlated with respiratory parameters only during QS. These observations support the hypothesis that the control and development of respiration during sleep is achieved by different processes in QS and AS.

Age Factors↗