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Biomedical subjects

J F Ryan

Publications and source records attributed to J F Ryan.

At least 37 records · Page 2Linked to original sources
PubMed1990

The effects of extracellular magnesium on myoplasmic [Ca2+] in malignant hyperthermia susceptible swine.

It is now well established that the pathophysiology of the malignant hyperthermia (MH) syndrome is related to a malfunction of intracellular calcium homeostasis. Magnesium plays important roles in the basic contractile properties of muscle, and many of its actions are antagonistic to those of calcium. The aim of this study was to determine the effectiveness of magnesium sulphate to prevent the MH episode in susceptible animals and correlate this with its effects on the intracellular free calcium [( Ca2+]i). The experiments were carried out using six control (Yorkshire) and ten MH-susceptible crossbred swine (Poland China X Pietrain). After determination of resting concentrations of [Ca2+]i and [Mg2+]i, each animal was given either two iv bolus doses of 50 mg/kg or one iv bolus of 100 mg/kg of MgSO4. The resting [Ca2+]i and [Mg2+]i were determined by means of ion-selective microelectrodes. The resting [Ca2+]i in normal muscle fibers was 0.11 +/- 0.01 microM (mean +/- SEM), whereas in the MH muscles the resting [Ca2+]i was 0.36 +/- 0.01 microM. In neither group was the resting [Ca2+]i modified by MgSO4. This cumulative dose of MgSO4 (100 mg/kg) was not able to prevent the induction of an MH episode by 2% halothane. Although MgSO4 did not directly decrease [Ca2+]i, it did attenuate the increase in [Ca2+]i associated with the syndrome from 7.29 +/- 0.43 microM in untreated animals to 0.84 +/- 0.03 microM in MgSO4 pretreated swine. In addition, the limb rigidity that accompanies this increase in calcium was prevented by MgSO4 pretreatment. Baseline measurements of [Mg2+]i were not different in control and MH-susceptible muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Parosteal osteogenic sarcoma of the hand.

Osteosarcomas of the tubular bones of the hands and feet are rare tumours and the initial biopsies are frequently misdiagnosed. We report a case of parosteal osteosarcoma arising in the metacarpal of a female patient aged 53 at first presentation. The tumour recurred three times over two decades and eventually metastasized to the lungs. The differential diagnosis includes florid reactive mesenchymal proliferation and bizarre parosteal osteochondromatous proliferations of the tubular bones of the hand.

Bone Neoplasms↗
PubMed1989

Ketamine does not trigger malignant hyperthermia in susceptible swine.

The use of ketamine in individuals susceptible to malignant hyperthermia (MH) is controversial. We describe our experience with ketamine used for induction and/or maintenance of anesthesia in our herd of swine inbred for susceptibility to MH. A total of 76 MH-susceptible swine were given a total of 112 general anesthetics using ketamine as the induction drug. In 34 of these anesthetics, anesthesia was also maintained with ketamine. Signs of MH did not develop in response to ketamine in any of the pigs.

Animals↗
PubMed1988

A single-blind study of pulse oximetry in children.

Oxygen saturation determined by pulse oximetry was monitored in 152 pediatric surgical patients divided into two groups. In one group, the oximeter data and alarms were available (N = 76) to the anesthesia team, and, in the other group, these data were unavailable (N = 76). A trained observer recorded all intraoperative hypoxic episodes and informed the anesthesia team of all major events (i.e., oxygen saturation less than or equal to 85% for greater than or equal to 30 s) (PaO2 approximately 52 mmHg). Thirty-five major events occurred: 24 in the unavailable group, and 11 in the available group (P = 0.021). A greater number of major events occurred in children less than or equal to 2 yr of age (P = 0.013). Hypoxic events diagnosed by the oximeter, but not by the anesthesiologist, were more frequent in the unavailable group (13) than in the available group (5) (P = 0.0495). ASA Physical Status 3 and 4 patients were more likely to suffer a major event (P = 0.009 available, 0.006 unavailable). The pulse oximeter diagnosed hypoxemia before the signs and symptoms of hypoxemia were apparent (i.e., prior to observed cyanosis or bradycardia). Major hypoxic events were unrelated to duration of anesthesia. Major events were evenly distributed among induction, maintenance, and awakening from anesthesia; a greater number of hypoxic events occurred during induction in the unavailable group (P = 0.031). No morbidity was documented in any patient who suffered an hypoxic event.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Dantrolene prevents the malignant hyperthermic syndrome by reducing free intracellular calcium concentration in skeletal muscle of susceptible swine.

Malignant hyperthermia (MH) is a pharmacogenetic disorder of skeletal muscle triggered when susceptible subjects are exposed to volatile anesthetic agents and/or depolarizing muscle relaxants. We have used Ca2+ selective microelectrodes to measure in vivo the intracellular free [Ca2+] in skeletal muscle of MH susceptible swine before and after the administration of dantrolene. We have investigated the effectiveness of this muscle relaxant in preventing clinical MH and the relationship between the resting intracellular free [Ca2+] and the probability of inducing the MH syndrome. The resting intracellular free [Ca2+] was 0.41 +/- 0.01 microM (M +/- SEM), which agrees with our previous measurements in susceptible swine. The administration of 0.5, 1, 2, 2.5 and 3 mg/Kg Dantrolene, reduced the intracellular free [Ca2+] to 0.31, 0.21, 0.09, 0.08, 0.08 microM respectively. The 0.5 mg/Kg dose induced a moderate decrease of [Ca2+]i and failed to prevent the MH syndrome after exposure to halothane (2%). The 1 mg/Kg dose produced a further reduction in [Ca2+]i and was sufficient to prevent the clinical syndrome in 2 out of 3 animals. The 2.5 mg/Kg dose was uniformly protective in all animals. These results suggest that the mechanism by which dantrolene protects susceptible animals exposed to triggering agents is by reducing the intracellular free [Ca2+] in skeletal muscle.

Anesthetics↗
PubMed1987

Case mix of public patients in skilled nursing facilities in Connecticut.

The case mix of publicly funded residents in 73 skilled nursing facilities (SNFs) in two Connecticut counties was examined. Data collected in 1980-1981 for utilization review by a professional standards review organization were used for the analysis. The findings indicate that considerable variation exists in case mix across the SNFs. Medicaid per diem rates, which are based on historic costs, have a low and negative correlation with case mix. Case mix indices are significantly higher for rural facilities, with a for-profit type of ownership, and with less than 75% of the bed days devoted to Medicaid residents.

Connecticut↗
PubMed1986

Malignant hyperthermia.

The increasing use of intravenous and inhalation sedation in the dental office has the potential of increasing the incidence of malignant hyperthermia (MH) in susceptible subjects. The object of this article is to present two cases of MH and to discuss its pathophysiology, its clinical picture, and its management in the light of the current literature. Stringent screening procedures should be adopted and maintained in order to channel suspected cases to appropriate centers for expert consultation and management. It is further advocated that a program of education for patients and their families be instituted, as it is an essential prerequisite of effective prophylaxis.

Child↗
PubMed1986

Malignant eccrine poroma: report of three cases.

The characteristic clinical and histological features of three cases of malignant eccrine poroma are discussed, in addition to the metastatic disease that had occurred in two cases. These cases were compared with previously reported cases of malignant eccrine poroma that had metastasised, and it is suggested that a strict classification of malignant eccrine sweat gland tumours should be made.

Adenoma, Sweat Gland↗
PubMed1986

Immunohistochemical analysis of mononuclear cell subsets in inflammatory and non-inflammatory myopathies.

Immunohistochemical procedures were used to analyse the subpopulations of mononuclear cells in muscle biopsies from 24 patients with polymyositis. The character of the cellular infiltrate was similar at the perivascular, perimysial, and endomysial sites, with cytotoxic-suppressor T lymphocytes (T8+) and macrophages being the dominant elements. Helper T lymphocytes (T4+) and B lymphocytes were present in smaller numbers. A control series of 17 muscle biopsies from normal subjects and patients with non-inflammatory myopathies and neurogenic conditions was also studied: the numbers of mononuclear cells present were much smaller than in polymyositis, but the ratio of T4:T8 lymphocytes was similar to that found in biopsies affected by polymyositis. We conclude that both cytotoxic-suppressor T lymphocytes and macrophages are important in the pathogenesis of inflammatory myopathy.

Adolescent↗
PubMed1985

Concomitant angiosarcoma and carcinoma of the breast: a case report.

A case of concomitant angiosarcoma and carcinoma of the left breast in a forty-three year old woman is described. Following a diagnosis of angiosarcoma she was treated by simple mastectomy. Five months later, left axillary lymph node biopsy showed metastatic adenocarcinoma. Retrospective examination of the mastectomy specimen disclosed a concomitant but separate adenocarcinoma. The patient remains well after 3 years. The implications of this rare association are discussed and the long survival gives an opportunity to review the prognosis in breast angiosarcomas.

Adult↗
PubMed1984

Kinetic studies of Ca2+ release from sarcoplasmic reticulum of normal and malignant hyperthermia susceptible pig muscles.

The time-course of Ca2+ release from sarcoplasmic reticulum isolated from muscles of normal pigs and those of pigs susceptible to malignant hyperthermia were investigated using stopped-flow spectrophotometry and arsenazo III as a Ca2+ indicator. Several methods were used to trigger Ca2+ release: (a) addition of halothane (e.g., 0.2 mM); (b) an increase of extravesicular Ca2+ concentration ([Ca2+0]); (c) a combination of (a) and (b), and (d) replacement of ions (potassium gluconate with choline chloride) to produce membrane depolarization. The initial rates of Ca2+ release induced by either halothane or Ca2+ alone, or both, are at least 70% higher in malignant hyperthermic sarcoplasmic reticulum than in normal. The amount of Ca2+ released by halothane at low [Ca2+0] in malignant hyperthermic sarcoplasmic reticulum is about twice as large as in normal sarcoplasmic reticulum. Membrane depolarization led to biphasic Ca2+ release in both malignant hyperthermic and normal sarcoplasmic reticulum, the rate constant of the rapid phase of Ca2+ release induced by membrane depolarization being significantly higher in malignant hyperthermic sarcoplasmic reticulum (k = 83 s-1) than in normal (k = 37 s-1). Thus, all types of Ca2+ release investigated (a, b, c and d) have higher rates in malignant hyperthermic sarcoplasmic reticulum than normal sarcoplasmic reticulum. These results suggest that the putative Ca2+ release channels located in the sarcoplasmic reticulum are altered in malignant hyperthermic sarcoplasmic reticulum.

Animals↗