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Biomedical subjects

M J Ryan

Publications and source records attributed to M J Ryan.

At least 109 records · Page 6Linked to original sources
PubMed1986

Gastrointestinal bleeding in competitive runners.

Competitive runners have been shown to develop previously undescribed clinical conditions, including "runner's anemia." This has been shown to be an iron-deficiency anemia of several etiologies including gastrointestinal bleeding. Although 8-23% of runners have been shown to have guaiac-positive stools after a marathon, the incidence of significant and prolonged bleeding is unknown. We report four cases of competitive runners with iron-deficiency anemia, gastrointestinal bleeding coinciding with running, and no definitive gastrointestinal pathology despite extensive evaluation.

Adult↗
PubMed1986

Neuroanatomy influences speciation rates among anurans.

Evolutionary divergence among animal courtship signals is an important component of the speciation process. In anurans, the preferential response of females to the mating call of conspecific males often maintains reproductive isolation among populations. Much of the information in the call is initially processed in the inner ear, and there is considerable variation in the structure of this organ among lineages of frogs. This variation is responsible for differences in the frequency range to which frog species are sensitive and thus influences the frequency range over which mating calls can effectively diverge. Data suggest that this influence of neuroanatomy on mating call divergence is partly responsible for the different rates of speciation among lineages of frogs.

Journal Article↗
PubMed1986

Synchronized calling in a treefrog (Smilisca sila). Short behavioral latencies and implications for neural pathways involved in call perception and production.

A neotropical treefrog, Smilisca sila, exhibits an unusual ability to synchronize its calling with that of neighbors such that calls often overlap temporally. Call playback experiments measured the latency to evoked calling in response to one-note and two-note mating calls. Approximately one-half of the responses overlapped the one-note stimulus call, while 20% overlapped the two-note stimulus call. Minimum response latencies were 55 ms and 78 ms in response to the one-note and two-note calls, respectively. These data were used to evaluate the efficacy of proposed neural pathways involved in call recognition and production. Based on neural and behavioral latencies presented in those studies, it is suggested that the proposed pathways for call recognition and production might not accommodate the short behavioral latencies in S. sila. One possible explanation for this discrepancy is that call detection is decoupled from call recognition, the former requiring a shorter neural pathway thus permitting a shorter behavioral latency.

Animals↗
PubMed1986

Factors influencing the evolution of acoustic communication: biological constraints.

Numerous studies have investigated selective forces that appear to influence the evolution of acoustic communication systems. I review a number of constraints on evolution in these systems. A species' history is of undeniable importance in the analysis of any trait. However, studies have given little or no attention to phylogenetic patterns of acoustic signals. This precludes the identification of phylogenetic constraints, and should be viewed as a serious constraint on our ability to understand how communication systems evolve. Morphological constraints influence the energetic efficiency of acoustic communication. To maximize transmission distance of signals used in long-range communication, the animal's morphology favors signals with high frequencies. Thus morphology acts in opposition to properties of the environment, which favor low frequencies for use in long-range communication. Sensory receptors also play an important role in the evolution of acoustic signals. There is significant variation in the frequency range to which an inner-ear organ of the frog is sensitive. Different lineages of frogs are characterized by ear organs with different ranges of sensitivity. This variation should influence the frequency range over which calls evolved and, as a consequence, might have influenced the rate at which different lineages of anurans speciate.

Acoustics↗
PubMed1986

CI-926 (3-[4-[4-(3-methylphenyl)-1-piperazinyl]butyl]-2,4-imidazolinedione): antihypertensive profile and pharmacology.

CI-926 (10(-7)-10(-6) M) selectively antagonized the contraction of isolated rabbit aortae to phenylephrine and displaced the alpha-1 adrenoceptor ligand WB4101 (IC50: 82 nM) in rat brain. In the spontaneously hypertensive rat, single oral doses of either CI-926 (0.3-10 mg/kg) or prazosin (0.3-100 mg/kg) caused dose-related reductions in blood pressure; however, CI-926 was more efficacious. The maximal antihypertensive response to CI-926 was unchanged with three consecutive days of oral dosing in the spontaneously hypertensive rat, whereas a first dose effect was noted with prazosin. In two-kidney, one-clip, renal hypertensive rats, CI-926 and prazosin (1-10 mg/kg) lowered blood pressure; however, prazosin was more efficacious. In perinephritic hypertensive dogs, CI-926 (10 mg/kg) lowered blood pressure 20%. In anesthetized dogs, CI-926 in the presence of supermaximal blood pressure-lowering doses of prazosin caused an additional reduction in pressure. With equivalent alpha-1 blockade in anesthetized rats, CI-926 tended to have greater hypotensive activity than prazosin. These results demonstrate that CI-926 is a potent, orally active antihypertensive agent in renin-dependent and -independent hypertension. The profile of CI-926 suggests that it lowers blood pressure in part by interacting with peripheral alpha-1 adrenoceptors and in part via an additional mechanism(s). Although weak relative to its affinity for alpha-1 adrenoceptors, CI-926 was found in preliminary experiments to interact with alpha-2 adrenoceptors, serotonergic receptors and dopaminergic receptors. The importance of these interactions to the blood pressure response of CI-926 remains to be elucidated.

Adrenergic alpha-Antagonists↗
PubMed1985

Changes in hormone levels in relation to breeding behavior in male bullfrogs (Rana catesbeiana) at the individual and population levels.

Fluctuations in plasma androgen (testosterone and 5 alpha-dihydrotestosterone), corticosterone (B), and luteinizing hormone (LH) of male bullfrogs in central California were measured during the spring mating season. Androgen and LH levels generally increased in the population prior to the initiation of chorusing and establishment of territories, whereas plasma B peaked in a 2-week period at the start of heavy chorusing; this coincided with a transitory, 1 week decline in androgen. Individual males showed fluctuations in plasma androgen and LH levels throughout the breeding season, often within 1 day, but there was no clear correlation between changes in the two hormones. No time of day effect was apparent on any of the hormones. B and androgen levels were significantly but weakly correlated, (r = 0.35) but LH and androgen were not. Although the seasonal trend of increasing androgen corresponded with the start of intense chorusing (and presumably sexual activity) by the population, behavior of individuals and their circulating androgen levels did not correlate. After acquiring territories, males showed no overall trend of increased plasma androgen. Moreover, males that showed no vocal or territorial behavior had significantly higher androgen and lower B levels than calling males. Increased B levels suggest that territorial behavior and especially direct agonistic encounters represent stresses that could have an inhibitory effect on androgen secretion.

Androgens↗
PubMed1984

Antihypertensive effects of CI-907 (indolapril): a novel nonsulfhydryl angiotensin converting enzyme inhibitor.

CI-907 is a new orally active nonsulfhydryl angiotensin converting enzyme (ACE) inhibitor. Monoester (prodrug) and diacid forms produced concentration related ACE inhibition in guinea-pig serum (IC50 for monoester, 1.7 X 10(-7) M and for diacid, 2.6 X 10(-9) M). In isolated rabbit aortic rings and in rat and dog autonomic studies, CI-907 is highly specific in suppressing the contractile or pressor responses to angiotensin I. In two-kidney, one-clip Goldblatt hypertensive rats, single daily doses (0.03-30 mg/kg p.o.) produced dose-dependent decreases in blood pressure; 3 mg/kg lowered blood pressure to normotensive levels. In the spontaneously hypertensive rat, subacute administration of CI-907 (30 mg/kg/day for 5 days) produced the same decrease in blood pressure as that obtained in the renal hypertensive rat. In diuretic-pretreated renal hypertensive dogs, 10 mg/kg normalized blood pressure. For equivalent drops in blood pressure, heart rate increases were less in CI-907 than in enalapril-treated renal hypertensive dogs. No side effects were observed with CI-907 in any of the conscious animals. The antihypertensive response to CI-907 (0.03-1.0 mg/kg p.o.) was found to correlate with inhibition of vascular tissue ACE, but not plasma or brain ACE in two-kidney, one-clip renal hypertensive rats. These studies indicate that CI-907 is a potent antihypertensive agent with a heart rate profile different from enalapril.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1984

CI-906 and CI-907: new orally active nonsulfhydryl angiotensin-converting enzyme inhibitors.

CI-906, [3S-[2[R*(R*)]], 3R*]-2-[2-[[1-(ethoxycarbonyl)-3-phenylpropyl]-amino]-1-oxopropyl] 1,2,3,4-tetrahydro-3-isoquinolinecarboxylic acid, monohydrochloride, and CI-907, [2S-[1[R*(R*)]], 2 alpha, 3a beta, 7a 7a beta]-1-[2-[[1-(ethoxycarbonyl)-3-phenylpropyl]amino] 1-oxopropyl]octahydro-1H-indole-2-carboxylic acid, monohydrochloride, are two new nonsulfhydryl-type angiotensin-converting enzyme (ACE) inhibitors. Monoester (prodrug) and diacid forms produced concentration-related ACE inhibition in guinea pig serum (IC50 for CI-906 = 8.3 X 10(-9) M, diacid = 2.8 X 10(-9) M; CI-907 = 1.0 X 10(-7) M, diacid = 2.6 X 10(-9) M). In isolated rabbit aortic rings and in in vivo rat and dog autonomic studies, both compounds were highly specific in suppressing the contractile or pressor responses to angiotensin I. In two-kidney, one-clip Goldblatt (renin-dependent) hypertensive rats there was a good correlation between the inhibition of vascular converting enzyme and blood pressure lowering and a poor correlation between blood pressure lowering and plasma and brain converting enzyme inhibition. Cardiovascular, pulmonary, and central nervous system performance evaluations showed no side effects or gross toxicity. The preclinical profile shows CI-906 and CI-907 to be specific, potent, orally active ACE inhibitors. They are expected to have therapeutic utility in hypertension and in any other condition where converting enzyme inhibition would be useful.

Angiotensin I↗
PubMed1984

Antihypertensive profile of the angiotensin-converting enzyme inhibitors CI-906 and CI-907.

CI-906 and CI-907, new orally active nonsulfhydryl angiotensin-converting enzyme inhibitors, were examined for antihypertensive effects in unanesthetized hypertensive rats and dogs. In two-kidney, one-clip Goldblatt hypertensive rats, single oral daily doses (0.03-30 mg/kg) produced dose-dependent decreases in blood pressure; a single 3 mg/kg oral dose lowered blood pressure to normotensive levels. In spontaneously hypertensive rats, 30 mg/(kg X day) orally administered for 5 consecutive days achieved the same blood pressure decrease as that obtained on the first day in the renal hypertensive rats. In diuretic-pretreated renal hypertensive dogs, a 10 mg/kg oral dose decreased blood pressure by 25%. No adverse side effects were observed with CI-906 and CI-907 in any of the conscious animals. These studies indicate that CI-906 and CI-907 are potent, orally active antihypertensive agents without any apparent limiting side effects.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1983

The classification of feline colitis.

Clinical and pathological features of a variety of forms of feline colitis or enterocolitis were examined and classified into 9 separate entities: Salmonella enterocolitis, the colitis of feline infectious peritonitis, mycotic enterocolitis, acute angiopathic colitis, acute angiopathic colitis with ischaemic ulcers, feline granulomatous colitis, the colitis of feline panleucopenia, feline histiocytic colitis, and feline ulcerative, lymphocytic mucosal-submucosal colitis.

Animals↗
PubMed1983

Morphologic changes following intraarticular inoculation of Mycoplasma bovis in calves.

Intraarticular inoculation of Mycoplasma bovis into the joints of six-week-old calves caused severe arthritis in five inoculates and mild arthritis in a sixth. Intraarticular inoculation of killed M. bovis did not cause arthritis. Arthritic calves had fever, joint swelling, lameness, neutrophilia, and intercurrent pneumonia from which M. bovis could not be recovered. Gross lesions were massive fibrinosuppurative synovitis and tenosynovitis, erosion of cartilage, and its replacement by polypoid granulation tissue. Histologic lesions were extensive ulceration of synovial membranes, leukocytic infiltration of the subsynovium, congestion, hyperemia, and thrombosis of the subsynovial vessels. Cartilage erosion was accompanied by chronic osteomyelitis and formation of pannus tissue. The presence of thrombi and platelet aggregates suggests that the inflammatory process in the synovium may arise from the interaction of M. bovis with the vasculature and the coagulation process of the host.

Animals↗