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Biomedical subjects

J M Mason

Publications and source records attributed to J M Mason.

At least 127 records · Page 7Linked to original sources
PubMed1982

Fibronectin-mediated binding of group A streptococci to human polymorphonuclear leukocytes.

Human plasma was shown to promote the attachment of an avirulent strain of Streptococcus pyogenes to human polymorphonuclear leukocytes. Removal of the fibronectin by absorption of the plasma with agarose-immobilized gelatin abolished the attachment-promoting activity. The activity of the absorbed plasma was restored with purified human serum fibronectin. The fibronectin was found to promote the attachment of three M protein-negative, but not of three M protein-positive, strains of streptococci. Radiolabeled fibronectin was shown to bind in various degrees to all strains of S. pyogenes tested. Thus, in the absence of streptococci surface M protein, fibronectin promotes the association of group A streptococci with human polymorphonuclear leukocytes.

Antigens, Bacterial↗
PubMed1981

Genetic analysis of X-linked mutagen-sensitive mutants of Drosophila melanogaster.

Mutants at 2 new loci which control mutagen-sensitivity are described. Mutants of both foci are female-sterile and are hypersensitive to killing by MMS; neither increases the frequency of sex-linked recessive lethals. A screen of previously described female-sterile and meiotic mutants has revealed that a number of these are also sensitive to mutagens. In addition, several new mutants have been identified on the basis of sensitivity to either HN2 or MMS. An analysis of complementation data suggests that all of the X-linked genes controlling sensitivity to MMS may now have been identified. Among the new mei-41 alleles are mutants which show very little meiotic nondisjunction or loss. Cytogenetic mapping of previously known mutants is also described. The mutants mus(1)104D1 and mei-41D5 are located in the region 14B13+/- -14D1,2 on the polytene chromosome map, and they map very close to each other genetically. Cytogenetically mus(1)101D1 is between salivary chromosome bands 12A6,7 and 12D3, mus(1)103D1 is between bands 12A1,2 and 12A6,7 and mus(1)109A1 is in section 8F3--9A2.

Animals↗
PubMed1980

Sudden death due to spontaneous rupture of the spleen from infectious mononucleosis.

An 18-year-old white male showing no external signs of trauma was discovered dead in his bathroom. A ten-day history of illness resulting in symptomatic treatment for viremia one day before death was elicited. Autopsy revealed splenic rupture, massive peritoneal hemorrhage, and atypical lymphocytes. Laboratory tests on postmortem samples confirmed the diagnosis of infectious mononucleosis.

Adolescent↗
PubMed1979

Sleep apnea and Q-T interval prolongation--a particularly lethal combination.

We have discovered a 20-day-old infant who possessed anatomic evidence of chronic hypoxemia with right ventricular hypertrophy and who died in hypoxic hypoxemia with a postmortem PO2 of 4 mm. Hg. Subsequently, and ECG was discovered which had been obtained at one day of age and showed Q-T interval prolongation along with T-wave alternation. We believe this case to be one of the first to substantiate the mechanism for SIDS as proposed by Schwartz, 26 with hypoxia acting synergistically with a prolonged Q-T interval causing sudden unexpected death in this infant--providing a link between cardiac and respiratory mechanisms of death.

Adult↗
PubMed1979

Prolongation of the Q-T interval in a victim of sudden infant death syndrome: cause or effect?

A 3-week-old infant died of sudden infant death syndrome (crib death, cot death). Although prolongation of the Q-T interval was found on an electrocardiogram taken at birth, this child appeared to have died of terminal respiratory failure as judged by a postmortem arterial oxygen tension of 4 mm Hg. The heart showed right ventricular hypertrophy, a finding consistent with chronic hypoxemia. The prolongation of the Q-T interval may have contributed to the death of this child with hypoxia predisposing to a fatal episode of ventricular fibrillation.

Cardiomegaly↗
PubMed1978

Role of strategy in reading by mentally retarded persons.

Mentally retarded individuals who could read were tested on their ability to pronounce words and produce meaningful associates. Analyses of their responses indicated an overuse of a strategy of memorizing works as a way to recognize words in print and an inability to consider work meanings in terms of abstract referents. A comparison of these results with responses given by nonretarded children suggests that retarded persons use cognitive strategies that lead to inefficient reading and even interfere with the development of effective reading skills.

Adolescent↗
PubMed1977

T-lymphocytes and survival of head and neck squamous cell carcinoma.

The thymus-dependent lymphocytes (T cells) were enumerated in the peripheral circulation of 38 patients with histologically demonstrated squamous cell carcinoma of the head and neck. We have previously shown that this "total" T-cell count correlates well with degree of tumor involvement. A lower percentage of T cells were shown in patients with more advanced malignant neoplasms. Here we present follow-up data on these patients to evaluate the efficiency of the T-cell test in determining survival prognoses. We found no evidence that results of this test can extend prognostic abilities above those based on clinical staging. The survival data from six patients treated with a chemoimmunotherapy regimen of BCG vaccine, methotrexate sodium, and isoniazid did not demonstrate an increased survival time compared to patients at similar clinical stages who were treated by conventional use of surgery and irradiation.

Adult↗
PubMed1977

Inhibition of epidermal cell migration by concanavalin A in skin wounds of the adult newt.

Pigment cell migration was used as an indicator to study the effects of the plant lectin, concanavalin A (con A), on epidermal cell closure of skin wounds. Continuous immersion of wounded animals in 10-100 microng/ml of con A greatly slowed but did not stop epidermal cell migration. Thus, untreated animals closed wounds in 12 to 24 hours while some treated wounds were still open after three days. Removal from con A after 24 hours, allowed inhibited wounds to close faster than those left in con A. Brief (30-minute) immersion of wounded animals in con A, either before or after migration had begun, suppressed closure for four to eight hours, demonstrating that the affinity for con A persists as epidermal cells migrate. When the left forelimb of bilaterally wounded animals was immersed in con A, it caused suppression of migration only on the immersed side, indicating a local rather than systemic site of action. Mixture with its competing sugar, alpha methyl D mannoside, abolished the effects of con A. The mechanism by which this lectin suppresses epidermal cell migration is unknown but clearly involves binding of the molecule to glycoprotein or glycolipid receptors on the cell surface.

Animals↗
PubMed1977

Concanavalin A induced inhibition of cell migration in African green monkey kidney cell cultures.

The effect of concanavalin A (con A) on the mobility of Vero cells into cell free gaps is examined. The movement of cells into these wounds is inhibited by a 30 minute exposure of con A at a concentration of 12.5 ug/ml. The effects of con A on the mobility are dependent on the concentration of the lectin used for treatment as well as the total amount of time the cells are exposed to a given concentration. The con A inhibition is abrogated by alpha-methyl-mannose. The competitive effects of con A inhibition and serum migration stimulation factors are examined. Treatment of the monolayer prior to wounding inhibits as effectively as treatment after wounding, indicating that residual con A on the bed of the wound which the cells cross is not responsible for the demonstrated inhibition.

Cell Line↗
PubMed1976

T-cell rosette test in squamous cell carcinoma of the head and neck.

The percentage of total T-lymphocytes was measured in 38 patients with histologically diagnosed squamous cell carcinoma of the head and neck. This measure of cellular immunity, which appears to be important in tumor-cell destruction, is demonstrably lowered in advanced stages of this disease. With the use of this test, the effect of a combined chemoimmunotherapeutic regimen consisting of methotrexate sodium, isoniazid, and BCG vaccine was sutdied. In this small series, no decrease of the T-cell count following treatment by methotrexate was demonstrated, except when a high dosage followed by leucovorin calcium was used. The BCG vaccine appeared to enhance T-cell counts, and one patient who was treated with cryosurgery had a dramatic increase in circulating T-lymphocytes. The T-cell test may be of clinical importance in the development of treatment sequences that provide maximum reduction of tumor cell mass while preserving host T cells.

Adult↗
PubMed1976

X-ray induced inhibition of DNA synthesis and mitosis in internal tissues during the initiation of limb regeneration in the adult newt.

Left front limbs of adult male newts were given 2000r of X-irradiation at least four weeks prior to amputation of both forelimbs. Internal stump tissues were evaluated for the ability to incorporate 3H-thymidine and accumulate colchicine-blocked mitotic figures. In otherwise uninjured limbs, irradiation stimulated low levels of DNA synthesis which did not increase significantly after amputation. Thus, as soon as DNA synthesis increased significantly in normal limbs as a result of amputation, it was demonstrably higher than in X-rayed limbs. In general, mitotic activity in both groups reflected the DNA synthetic rates. Since others have shown that denervation at the time of amputation blocks subsequent mitosis in internal stump tissues yet allows normal levels of DNA synthesis for eight days, we conclude that X-irradiation and denervation prevent cell division in potential blastema cells by different mechanisms.

Animals↗
PubMed1976

Orientation disruptor (ord): a recombination-defective and disjunction-defective meiotic mutant in Drosophila melanogaster.

The effects of a semidominant autosomal meiotic mutant, orientation disruptor (symbol: ord), located at 2-103.5 on the genetic map and in region 59B-D of the salivary map, have been examined genetically and cytologically. The results are as follows. (1) Crossing over in homozygous females is reduced to about seven percent of controls on all chromosomes, with the reduction greatest in distal regions. (2) Crossing over on different chromosomes is independent. (3) Reductional nondisjunction of any given chromosome is increased to about thirty percent of gametes from homozygous females. The probability of such nondisjunction is the same among exchange and nonexchange tetrads with the exception that a very proximal exchange tends to regularize segregation. (4) Equational nondisjunction of each chromosome is increased to about ten percent of gametes in homozygous females; this nondisjunction is independent of exchange. (5) The distributive pairing system is operative in homozygous females. (6) In homozygous males, reductional nondisjunction of each chromosome is increased to about ten percent, and equational nondisjunction to about twenty percent, of all gametes. (7) Cytologically, two distinct meiotic divisions occur in spermatocytes of homozygous males. The first division looks normal although occasional univalents are present at prophase I and a few lagging chromosomes are seen at anaphase I. However, sister chromatids of most chromosomes have precociously separated by metaphase II. Possible functions of the ord(+) gene are considered.

Animals↗