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Biomedical subjects

M Ryan

Publications and source records attributed to M Ryan.

At least 379 records · Page 21Linked to original sources
PubMed1976

Fetal hemopoiesis in diffusion chamber cultures. III. The effect of neutropenia.

Proliferation and differentiation of granulocytes, macrophages, and both myeloid committed (CFC) and pluripotent (CFU) stem cells in diffusion chamber (DC) cultures of fetal liver were studied in order to evaluate the role of circulating humoral factors in the control of fetal myelopoiesis. When DC with fetal liver cells were implanted into mice rendered neutropenic by pretreatment with cyclophosphamide, more granulocytes and CFC were produced through day 10 as compared to DC implanted into saline pretreated control hosts. A difference in CFU recovery from fetal liver suspensions grown in DC implanted into neutropenic and control hosts was not seen until day 10. Serum CSF concentrations were increased in neutropenic as compared to control host mice 2 and 3 days after implantation of DC. Levels of serum inhibitors of colony growth showed marked variability but, in general, were similar in both groups. These data provide evidence that fetal CFC and fetal myelopoiesis are influenced by a circulating humoral factor present in neutropenic serum. CSF may be the factor, although the data presented in this paper do not establish this with any certainty.

Agranulocytosis↗
PubMed1975

Comparison of ventricular ectopic activity during 24-hour monitoring and exercise testing in patients with coronary heart disease.

The exposure of ventricular ectopic activity (VEA) by maximal exercise testing and 24-hour ambulatory monitoring was compared in 100 unselected patients with coronary heart disease. The arrhythmia was noted with exercise in 56 patients and with monitoring in 88. Repetitive forms such as couplets and ventricular tachycardia were found to be twice as frequent (40 vs. 20) with monitoring than with exercise. Patients with prior myocardial infarction had more frequent ventricular ectopic activity of a more advanced grade with both exercise and monitoring than patients with angina pectoris. Exercise exposed the grades of ectopic activity that recurred during two or more hours of the monitoring session. Of seven patients with ventricular tachycardia on exercise only four exhibited this grade with monitoring. It may be that these two methods divulge different information regarding the electrophysiologic state of the myocardium.

Adult↗
PubMed1975

Tolerance to the granulocyte-releasing and colony-stimulating factor elevating effects of endotoxin.

Injection of Salmonella typhosa endotoxin into either CF1 or C57bl/6J mice leads to prompt increases in serum colony-stimulating factor (CSF). Repeated injections of endotoxin result in a dose-related hyporesponsiveness or tolerance to this effect. Tolerance is seen after either intravenous (i.v.) or intraperitoneal (i.p.) routes of administration or challenge and occurs after one to two preinjections. Cross-tolerance to heterologous endotoxin (Escherichia coli) was also shown. This cross-tolerance is complete immediately after cessation of preinjections, but partial at later time intervals. Levels of a serum inhibitor of colony growth were decreased in tolerant mice, although this decrease is not statistically significant. Tolerant mice injected with endotoxin release granulocytes from the bone marrow normally, in spite of the absence of a CSF response. This suggests that neutrophil releasing activity (NRA) and CSF are separate entities. A marked marrow granulocytic hyperplasia develops after 7 or 20 days of endotoxin injections, despite the tolerance to the CDF-elevating effect of endotoxin. This granulocytic hyperplasia could still be mediated by serum CSF increases. A negative medullary feed-back secondary to the repetitive release of marrow granulocytes, however, is an equally plausible mechanism for the stimulation of granulocyte production. It is also possible that the decrease in serum inhibitors played a role in the sustained increase in granulopoiesis seen here.

Animals↗
PubMed1975

Stimulus persistence in retarded and nonretarded children: a signal detection analysis.

Nine institutionalized EMR and 9 equal-CA nonretarded children were tested on a visual backward masking task. Signal detection analysis was used to separate the sensory and nonsensory aspects of behavior, and the presentation of stimuli was randomized to minimize the formation of effective strategies. Two sets of instructions, strict and lenient, and two stimulus durations, 10 and 30 msec, were used in a repeated measure design. No differences were found between the intelligence groups on interstimulus interval threshold or measures of stimulus sensitivity, criterion placement, and false positive rate. Retarded subjects showed significantly greater intersubject variability in criterion placement but failed to raise their criterion in response to strict instructions. The results suggest that (a) stimulus-trace concepts of retardation have been confounded by retarded subjects' inability to compete effectively with nonretarded subjects in the experimental situation, and (b) signal detection procedures are a useful alternative to traditional psychophysical techniques in such comparative research.

Adolescent↗
PubMed1975

Monitoring for serious arrhythmias and high risk of sudden death.

Ventricular premature beats (VPBs) are present in 85% of patients with coronary heart disease (CHD). A classification of VPBs based on frequency, multiformity, repetitive pattern, and degree of prematurity promises to aid in identifying patients at high risk of sudden death. Advanced grade or repetitive forms of VPBs are observed in 41% of patients with CHD who are monitored for 24 hours while ambulatory. Exercise stress is less effective than monitoring, but when advanced grades are exposed by exercise, they are likely to be persistent for two or more hours during monitoring. Such persistent and advanced grades characterize patients with multivessel coronary artery disease. Diurnal variations occur in VPB frequency and pattern with significant reduction during sleep. This as well as other facts suggest a primary role for neural activity in the genesis of ventricular ectopy. The relevance of these observations to sudden death is considered.

Aged↗
PubMed1970

An evaluation of the automated assay of urinary oestrogens in pregnant women.

An automated assay suitable for estimating urinary oestrogens in pregnant women has been investigated. Fluorimetry was found to have considerable advantages over colorimetry. The fluorimetric assay was simpler, more precise, more sensitive, and eliminated the need for correction for non-specific chromogens; in the assay of oestriol in pregnant women there was no need for correction for non-specific fluorescence. Spectrofluorimetric and photometric analyses, recoveries, and reproducibility show that the method offers a robust means of providing values for urinary oestrogen in pregnant women on a scale of up to 100 tests a day, the time of the assay being one and a half hours.

Autoanalysis↗