Clinicopathological correlates of cardiac myxomas: a 30-year experience

Between 1961 and 1991, 23 patients (eight men and 15 women, with a mean age of 50 (range 25-72) years) with cardiac myxomas were managed at the Alfred Hospital, Prahran, Victoria, Australia. Symptoms of mitral valve obstruction were present in 13 patients and of systemic embolism in nine. In the patients, 21 myxomas were confined to the left atrium. In the other two patients, one myxoma was confined to the right atrium and the other was a dumb-bell-shaped biatrial myxoma. Most tumours were diagnosed with echocardiography. Removal was achieved via a median sternotomy and by entering the involved chamber. Those myxomas presenting with systemic embolism were always soft and friable, whereas those with obstructive symptoms were large and of variable consistency. There was one operative death early in the series. The 22 surviving patients have been assessed as functional class I of the New York Heart Association at follow-up, ranging from 2 months to 23 years (mean 9 years). There were no episodes of tumour recurrence. Excellent short, intermediate and long-term results can be achieved by excision of cardiac myxomas.

The inhibition of human duodenal adenylate cyclase activity by Ca2+ and the effects of EGTA

This study demonstrates that the inhibition of adenylate cyclase activity by Ca2+ is enhanced in the presence of increasing [EGTA] (0, 0.3, 1, 2.5 mM) by 2 orders of magnitude. It has been established that this effect is not because of poor Ca2+ buffering by low [EGTA] or high Ca2+ binding by the membrane preparation. It is present irrespective of stimulus. We suggest the enhanced sensitivity of adenylate cyclase to Ca2+ induced by EGTA is caused by the Ca-EGTA complex being a more inhibitory species than Ca2+. Thus consideration of the effects of the Ca-EGTA complex should be made when interpreting the results from experiments involving Ca2+ and EGTA.

Hypercholesterolaemia severely impairs EDRF-dependent collateral perfusion following acute arterial occlusion in rabbit isolated ear

1. We have used a rabbit isolated buffer-perfused ear as a model of acute arterial occlusion to investigate the effects of dietary-induced hypercholesterolaemia on EDRF-dependent collateral perfusion. The effects of hypercholesterolaemia on endothelium-dependent relaxations to acetylcholine were also investigated in the unligated isolated buffer-perfused ear of the rabbit. 2. In rabbits receiving a high cholesterol diet (1%) for 4 weeks, blood cholesterol levels were significantly (P < 0.001) increased (26.0 +/- 3.6 vs. 2.6 +/- 0.6 mmol l-1), EDRF-dependent collateral perfusion was similar to that in age-matched controls for the first 15 min after occlusion but then decreased and was significantly (P < 0.01) less than control during the maintenance phase of collateral perfusion. 3. Cholesterol feeding for 8 weeks (blood cholesterol = 56.2 +/- 3.8 vs. 1.3 +/- 0.1 mmol l-1) was associated with almost complete impairment of collateral perfusion, an effect previously observed following inhibition of EDRF synthesis. 4. Endothelium-dependent relaxations to acetylcholine in isolated perfused ears were impaired in the rabbits fed the diet for 8 weeks but not those fed for 4 weeks. In the 8 week group, the maximum relaxation of tone was 32.6 +/- 11.6% and was significantly (P < 0.01) less than that in the controls (77.9 +/- 5.7%). 5. We conclude that EDRF-dependent collateral perfusion is severely impaired in hypercholesterolaemia and that the level of impairment is related to the duration of feeding.

Ectopic production of heparin-binding growth factors and receptors for basic fibroblast growth factor by rat mammary epithelial cell lines derived from malignant metastatic tumours

A rat mammary (Rama) epithelial cell line, Rama 704, derived from normal rat mammary gland does not possess any detectable cell-surface receptors for basic fibroblast growth factor (bFGF), produces a barely detectable level of bFGF mRNA and does not contain detectable levels of bFGF-like activity. Similar results have been obtained with the Rama 37 epithelial cells derived from benign tumours. However, 4 independently isolated epithelial cell lines derived from malignant rat mammary tumours and their metastases possess receptors for bFGF and contain between 2 ng and 9 ng heparin-binding, growth-stimulatory activity per 10(6) cells. The weakly metastatic Rama 600 cells possess high- and low-affinity receptors for bFGF, (KD 20 pM and 8 nM, respectively), while the moderately metastatic Rama 800 cells possess only high-affinity receptors (KD 40 pM). The moderately metastatic C18PLN and 267LU cells, derived from metastases arising from benign Rama 37 cells which had been transfected with DNA from the malignant Rama 800 cells, also possess only high-affinity receptors (KD 36 pM and 80 pM, respectively). Our results show that within the Rama system there is a correlation between the appearance of heparin-binding growth factors and of high-affinity but not low-affinity receptors for bFGF with the malignant phenotype.

Further characterization of the neutrophil oxidative burst by flow cytometry

The ability to generate reactive oxygen species is essential for neutrophils to kill infectious micro-organisms. We have investigated the 'oxidative burst' in human neutrophils stimulated in vitro with either opsonized zymosan (OZ) or phorbol myristate acetate (PMA) at the single cell level by flow cytometry using dichlorofluorescein diacetate (DCFH-DA) and dihydrorhodamine 123 (DHR) as oxidative probes. These responses have been compared to results obtained with chemiluminescence and spectrophotometric assays. DHR was the most sensitive oxidative probe and PMA the more potent stimulus. The magnitude of the intracellular fluorescence generated with both probes was increased substantially by inhibiting the activities of H2O2-consuming enzymes with a relatively low concentration of azide, which also influenced the distribution of neutrophil subpopulations that expressed fluorescence differentially. Positive correlations between the DCFH-DA and DHR assays were found with both stimuli, and between these assays and ferricytochrome c reduction with OZ-stimulated cells only. We conclude that the DHR flow cytometric assay is the most sensitive technique available for investigating changes that may occur in the oxidative activities and distribution patterns of active neutrophil subpopulations in response to a variety of physiological and pathological conditions.

Inhibition of insulin-degrading enzyme increases translocation of insulin to the nucleus in H35 rat hepatoma cells: evidence of a cytosolic pathway

We previously demonstrated the translocation of insulin to the nucleus in several cell types and partially characterized the uptake mechanisms and pathways in H35 rat hepatoma cells. Nuclear accumulation of insulin was energy independent, time and temperature dependent, and apparently was not saturable at insulin concentrations which resulted in full receptor occupancy. We also have shown insulin could be internalized by both receptor-mediated and fluid-phase endocytosis. This study investigated subsequent steps involved in the nuclear accumulation of insulin following internalization. We examined the effects of inhibiting insulin degrading enzyme (IDE) with 1,10-phenanthroline on the nuclear accumulation of insulin in H35 cells. 1,10-phenanthroline (2 mM) which markedly inhibited insulin degradation, significantly increased nuclear accumulation of insulin without having any effects on total cell-associated and intracellular insulin. This reagent increased 125I-insulin on the cellular membrane and decreased 125iodine (125I-insulin and 125I-insulin degradation products) in the cytosolic fractions. Chemical extraction and Sephadex G-50 chromatography revealed the insulin associated with the nucleus in 1,10-phenanthroline-treated cells formed the same complex(es) with the nuclear matrix as in control cells. These results suggested that inhibition of cytosolic IDE activity resulted in increased insulin translocation from the cytosol to the nucleus. Furthermore, when IDE activity was inhibited by high cytosolic insulin concentrations, the amount of 125I-insulin in the nucleus was significantly increased. Our study suggests internalized insulin is probably released from endosomes into the cytosol where modulation of IDE activity could have significant effects on the accumulation of insulin, or insulin-cytoplasmic protein complexes, in nuclei. The IDE regulatory mechanism, by controlling the translocation of insulin to the cell nucleus, could play a crucial role in insulin's regulation of gene expression and cell proliferation.

Metastasis of pineal germinoma via ventriculoperitoneal shunt

The case of a 13 year old boy with pineal germinoma and subsequent metastasis 3 years later via ventriculoperitoneal shunt to the abdominal cavity is presented. The abdominal disease was managed with chemotherapy and subsequent surgical resection. He remains free of disease 2 years following the resection. The literature regarding this rare complication is reviewed.

Anesthetic pollution and waste anesthetic gas scavenging

The significance of chronic exposure to anesthetic pollution for veterinarians and their associates is not well defined, but one cannot ignore the evidence that a potential occupational health hazard exists. Installation of a scavenging system can reduce anesthetic pollution and personnel exposure to waste gases significantly. However, it is important to realize that these systems are not a replacement for safe anesthetic practices and are only effective when used correctly and maintained properly.

Activation and inhibition of insulin receptor autophosphorylation by trypsin treatment of intact H35 cells

1. Treatment of intact cultured H35 cells with trypsin (1 mg/ml) for 15 min at low temperature (4 degrees C) or for 30 sec at 37 degrees C causes activation of the insulin receptor subsequently isolated from the cells. 2. Receptor activation was assessed by increased phosphotyrosine content of the beta-subunit of the receptor, and increased autophosphorylation using [32P]-ATP. 3. Treatment of the cells for 15 min at 37 degrees C however completely abolished insulin binding and all insulin receptor kinase activity. 4. These data demonstrate that proteolytic damage of the extracellular domain of the insulin receptor can render the receptor kinase inactive and lead to a cell which is unresponsive to insulin.

Long-term follow-up after two coronary repair of anomalous left coronary artery from the pulmonary artery

A retrospective analysis of ten patients with anomalous left coronary artery arising from the pulmonary artery operated between 1979 and 1990 was undertaken. All presented with evidence of left ventricular dysfunction and "ischemic" mitral regurgitation. Surgical repair consisted of an aortopulmonary tunnel (Takeuchi) procedure in eight and direct left coronary artery reimplantation in two. Two patients required postoperative support with a left ventricular assist device. There were no operative or late deaths (CL 0% to 17%) for a follow-up of over 670 patient months. All patients are in New York Heart Association Class I or II, though two patients are still receiving anticongestive medications. One patient has required further surgery for pulmonary artery stenosis, and another has had a mitral valve replacement because of severe mitral regurgitation. One additional patient has moderate-to-severe residual mitral regurgitation and two have a trivial left coronary to main pulmonary artery fistula. All have a patent, nonstenotic left coronary artery and much improved left ventricular function and perfusion as assessed by echocardiography, thallium scan, gated blood pool scan, and angiography. There have been no documented arrhythmias, clinically or on Holter monitoring. The ECGs have shown resolution or improvement of the initial changes of ischemia/infarction in all patients. Chest X-rays have shown normalization of cardiothoracic ratio in eight of ten patients. Excellent early and late results can be achieved following timely surgical repair. Marked improvement in left ventricular function has been observed in patients with poor preoperative left ventricular function, even in the presence of extensive ischemia/infarction.

Adverse effects of administration of propofol with various preanesthetic regimens in dogs

The effects of propofol on anesthetic induction were evaluated in 40 dogs anesthetized with isoflurane. Propofol is a rapidly acting, nonbarbiturate drug that induces anesthesia of ultrashort duration with IV administration. Four preanesthetic regimens were used: anesthesia without preanesthetic drugs; or with preanesthetic administration of acepromazine (0.1 mg/kg of body weight, IM), diazepam (0.2 mg/kg, IV), or acepromazine (0.02 mg/kg) and butorphanol (0.4 mg/kg) IM. Heart rate, systolic arterial blood pressure (SAP), respiration, quality of induction and recovery, and adverse effects were induction and recovery, and adverse effects were recorded. Intravenous propofol administration induced a variable period of apnea in 34 of 40 dogs. Cyanosis (in 2 dogs) and signs of pain on injection (in 3 dogs) were infrequently observed during induction. One dog developed ventricular premature depolarizations after propofol administration. Venous CO2 tension increased and pH decreased immediately after propofol administration, regardless of preanesthetic regimen. The SAP significantly (P < 0.05) decreased after propofol administration in dogs treated with acepromazine (SAP, 178 mm of Hg before vs 128 mm of Hg after propofol) and with acepromazine/butorphanol (SAP, 184 mm of Hg before vs 98 mm of Hg after propofol). When used for induction, propofol induces anesthetic-related adverse effects, some of which can be minimized by preanesthetic medication. Recovery characteristics varied with preanesthetic medication, independent of propofol administration.

Porcine ventricular endocardial cells in culture express the inducible form of nitric oxide synthase

1. We have investigated whether porcine endocardial cells in culture express the inducible, Ca(2+)-independent form of nitric oxide (NO) synthase. 2. NO synthase activity in cytosolic extracts of endocardial cells was measured by estimation of the rate of formation of L-[14C]-citrulline from L-[14C]-arginine. 3. Treatment of the cells in culture with lipopolysaccharide or cytokines induced a Ca(2+)-independent NO synthase activity in the cell cytosol. The combination of tumour necrosis factor (TNF alpha, 10 ng ml-1) and interleukin-1 beta (IL-1 beta, 10 ng ml-1) induced the greatest enzyme activity. 4. The increased Ca(2+)-independent NO synthase activity following exposure to cytokines was paralleled by an increase in guanosine 3':5'-cyclic monophosphate (cyclic GMP) levels in the endocardial cell cytosol. 5. Simultaneous addition of dexamethasone (0.01-1 microM) or cycloheximide (0.03-3 microM) inhibited in a concentration-dependent manner TNF alpha- and IL-1 beta-induced expression of Ca(2+)-independent NO synthase activity. Neither dexamethasone (1 microM) nor cycloheximide (3 microM) had any effect on the activity of the constitutive NO synthase. 6. The possible pathophysiological consequences of endocardial expression of the inducible NO synthase are discussed.

Respiratory arrest following intramuscular ketamine injection in a 4-year-old child

A healthy 4-year-old boy presented to the pediatric emergency department after inserting a black-eyed pea into his right external ear canal. Initial attempts at removal of this foreign body were unsuccessful, resulting in patient agitation. After administration of intramuscular ketamine for sedation, the patient was observed to experience one ineffective respiration followed by a period of apnea. No excessive oropharyngeal secretions or laryngospasm were noted. Spontaneous respirations resumed after 40 seconds, and the child recovered with no apparent ill effects. This case illustrates the need for adequate monitoring and preparation for emergency airway management when using ketamine for sedation in the ED.

Cardiorespiratory effects of combined midazolam and butorphanol in isoflurane-anesthetized cats

The cardiorespiratory effects of midazolam (0.1 mg/kg) and butorphanol (0.4 mg/kg) were evaluated in seven cats. Cats were induced in a chamber, removed and intubated, and maintained with isoflurane in 100% oxygen. Cardiorespiratory data were recorded before and 3, 10, 20, 30, 40, 50, and 60 minutes after intravenous injection of midazolam-butorphanol. Heart rate, mean arterial pressure, and respiration rate were significantly (p < .05) decreased below baseline at various times throughout the study. Tidal volume and minute ventilation were unchanged. End-tidal carbon dioxide was significantly (p < .05) increased above baseline for 30 minutes. Midazolam-butorphanol administered intravenously induced significant alterations in several cardiorespiratory parameters in isoflurane-anesthetized cats.

Induction of a calcium-independent NO synthase by hypercholesterolaemia in the rabbit

Endothelium-dependent and -independent relaxation of aortic ring preparations was assessed and nitric oxide (NO) synthase activity measured in the lung, and cerebellum of cholesterol-fed and normal rabbits. Endothelium-dependent relaxation of acetylcholine and ATP was depressed while that to the calcium ionophore, A23187, was unaltered in the cholesterol-fed group. Relaxation to sodium nitroprusside was however greater in aortae from the cholesterol-fed animals. Neither Ca(2+)-dependent nor Ca(2+)-independent NO synthase activity could be detected in aortae or hearts taken from either group of animals. Activity of both enzymes was unaltered in cerebellae from both groups of animals. Activity of the Ca(2+)-independent enzyme was however significantly greater (ca. 2 fold) in lungs from the cholesterol-fed rabbits though the activity of the Ca(2+)-dependent NO synthase was not significantly altered. This finding may account for the increased production of nitrogen oxides previously observed in this model of hypercholesterolaemia.

Emery-Dreifuss muscular dystrophy: linkage to markers in distal Xq28

Emery-Dreifuss muscular dystrophy (EMD) is characterised by (1) early contractures of the Achilles tendons, elbows, and postcervical muscles, (2) slowly progressive muscle wasting and weakness with a predominantly humeroperoneal distribution in the early stages, and (3) cardiomyopathy with conduction defects and risk of sudden death. Inheritance is usually X linked recessive but can be autosomal dominant. Family linkage studies have mapped X linked EMD to the distal long arm of the X chromosome but precise genetic localisation has been hampered by the rarity of this condition. We report three new families with X linked Emery-Dreifuss muscular dystrophy studied with DNA markers from Xq27-qter and three previously published families typed for additional markers. No recombination was observed with the red/green cone pigment locus, RGCP (lod score, Z = 2.46), the factor VIII coagulant gene locus, F8C (Z = 6.39), or with DXS115 (Z = 4.94). Two recombinants were observed which mapped EMD distal to DXS15 (DX13) and DXS52 (St14) respectively. Multipoint linkage analysis gave odds exceeding 200:1 for EMD being distal to these markers. A multipoint analysis incorporating published data gave the map cen-DXS304-9cM-DXS15-3cM-DXS52-2 cM-(RGCP,EMD)-3cM-F8C-2cM-DXS115 with odds of 120:1 in favour of a location for EMD between DXS52 and F8C as compared to the next best position distal to F8C.

Alteration in the modulatory role of respiratory epithelium after exposure of guinea pigs to respirable cotton dust

Chest tightness may occur after inhalation of cotton dust. To understand the origins of this symptom of byssinosis, we exposed guinea pigs to respirable cotton dust and determined whether the resulting pulmonary obstruction was associated with alterations in the in vitro reactivity of the trachea to methacholine. The isolated, perfused trachea preparation was utilized because it allows a comparison of airway smooth muscle responses to drugs after they are applied separately to the mucosal or serosal surfaces. In epithelium-containing control tracheae, mucosally applied methacholine was less potent and elicited smaller maximum contractile responses than those obtained when it was applied to the serosal compartment. After a 6-h inhalation exposure to 30 mg/m3 respirable cotton dust, the mucosal maximum response to methacholine was substantially increased immediately (0 h) after the end of the exposure, but it was decreased 18 h postexposure. A dust level of 10 mg/m3 produced modest increases in the mucosal maximum responses at both postexposure periods, elevating them to the magnitude of the extraluminal maximum response. The potency of serosally applied methacholine was not affected by any cotton dust exposure. Mechanical epithelium removal increased mucosal reactivity to the serosal level in both control and cotton (30 mg/m3)-exposed groups, and abolished the effects of dust on mucosal reactivity to methacholine. Our findings suggest that the modulatory effect of the epithelium may be inhibitory or excitatory. The balance between the two influences may be altered by inhaled cotton dust.