Prostaglandin biosynthesis in the epidermis and dermis of young mouse skin, and the effects of calcium and cyclic nucleotides.

Homogenates of skin from 2- to 3-day old mice converted labeled eicosa-8,11,14-trienoic acid to prostaglandins (PGs) PGE1, D1, and F1alpha. For several reasons PGD2 has been overlooked as a possible major PG in skin. The relative formation of each PG was modified by the presence of reduced glutathione (GSH), chelating agents (EDTA, EGTA), and L-epinephrine. Chelating agents and l-epinephrine increased conversion, espeicially to PGE1 but this effect was not due to inactivation of Ca++ which was shown to have no control over the reaction. Cyclic nucleotides including cyclic AMP (cAMP) and cyclic GMP (cGMP) were also ineffective. The conversion occurred mostly in the epidermis. Epidermal preparations were more efficient in the conversion than those from whole skin. Indomethacin (0.2 mM) completely inhibited the reaction.

Naloxone and focal epilepsy: a study with depth electrodes.

Intravenous injections of naloxone (0.8 to 2.4 mg) were given to patients with focal epilepsy who had had electrodes implanted in cortical and subcortical structures. There were no changes in interictal spike activity, responses to electrical stimulation, of frequency of spontaneous seizures. These data do not support the hypothesis that opiate peptides are involved in human focal epilepsy.

Evaluation of an index of peripheral vascular resistance in human subjects.

Based on evidence in animal studies, an index of resistance in man has been evaluated. In 10 human subjects, ranging in age from 31 to 60 years, direct brachial arterial pressure was measured, and a computer program using linear regression calculated the index of resistance from the slope of the logarithm of the pressure versus time during the second half of diastole. Resistance was independently calculated from 20-s averages of pressure and cardiac output obtained by thermodilution. Resistance was varied by infusion of phenylephrine and nitroprusside. The values of the index of resistance were compared with independently calculated resistance by linear regression and correlation. The index of resistance was variably correlated with independently calculated resistance. However, when the comparison was limited to points with a model correlation coefficient greater than or equal to 0.98 (i.e. a good fit of a straight line to the logarithm of pressure versus time), the correlation of the index of resistance with calculated resistance approached or exceeded 0.9 in eight of 10 subjects. In the two subjects showing poor correlation of the index with calculated resistance, estimated compliance from the same model was much lower than in the other subjects. In the same two subjects pressure dependence of estimated compliance was much higher than in the other subjects, suggesting the presence of significant atherosclerosis. We concluded that the diastolic decay of pressure may be used to calculate a useful index of resistance, provided that a single exponential decay fits the observed diastolic waveform well, and arterial compliance is not significantly reduced by atherosclerosis.

An index of peripheral vascular resistance.

An index of peripheral vascular resistance, derived from directly measured arterial pressure, has been developed and tested in an animal model. Assuming a mono-exponential character for diastole, the time constant for direct arterial pressure decay in the central aorta was obtained with high-fidelity recording techniques from six anaesthetized dogs. Changes in peripheral resistance were induced by infusion of phenylephrine or nitroprusside. The time constant correlated well with resistance determined from 1-min averages of pressure divided by integrated electromagnetic flow (r = 0.845). A portable system used for direct arterial pressure recording in ambulant outpatients yielded a mean correlation of 0.822 with resistance. In a study of patients undergoing cardiac catheterization, a time constant obtained from the brachial artery (the site of pressure recording in the ambulant subjects) correlated well with the aortic time constant (n = 6, r = 0.964). The results of the present work suggest that the time constant derived from direct arterial pressure waveform may be a useful index in the evaluation of the peripheral vascular resistance. Furthermore, with the help of the portable system it might be used for the continuous monitoring of resistance changes in ambulatory subjects.

Pulmonary capillary wedge pressure in mitral stenosis accurately reflects mean left atrial pressure but overestimates transmitral gradient.

Current opinion varies as to whether pulmonary capillary wedge pressure assessment of transmitral gradient in mitral stenosis is accurate; we therefore compared transmitral gradient in 36 patients awaiting balloon valvuloplasty using both pulmonary capillary wedge pressure and direct left atrial pressure. Mean pulmonary capillary wedge pressure correlated well with mean left atrial pressure (limits of agreement -1.5 to +3.7 mm Hg), but mean diastolic mitral gradient calculated using pulmonary capillary wedge pressure differed significantly from that calculated using left atrial pressure (limits of agreement -1.2 to +9.8 mm Hg): wedge pressure-assessed transmitral gradient is therefore misleading, routinely overestimating stenosis severity.

Relation of daily activity levels in patients with chronic heart failure to long-term prognosis.

Symptom-limited, laboratory-based exercise tests are often used to define prognosis in patients with chronic heart failure, but they do not relate to measures of normal daily activity. Invasive measures of central hemodynamics similarly relate poorly to outcome. Pedometer scores of weekly walking are markedly reduced in patients with heart failure, but whether this less artificial measure of exercise capacity is important in predicting prognosis is not known. Eighty-four patients with chronic heart failure were followed for a mean of 710 days during which 44 died and 3 underwent cardiac transplantation. Symptom-limited treadmill exercise capacity using 2 different protocols did not predict survival, whereas reduced weekly pedometer scores were strong predictors of death (p < 0.001). Other variables that predicted death included resting cardiac output, arterial blood pressure, diuretic requirements, New York Heart Association class, increased bilirubin, and hyponatremia (all p < 0.01). Reduced levels of daily activity are strong predictors of death in chronic heart failure and appear more powerful than laboratory-based exercise tests. This type of assessment is valuable in identifying patients at high risk and provides an objective measure of incapacity during normal daily life. The exercise capacity of patients unable to exercise in the laboratory could also be assessed using this technique. This may prove invaluable in clinical and mortality trials.

Comparison of central venous and inferior vena caval pressures.

Inferior vena caval pressures were measured in 60 patients undergoing cardiac catheterization and compared with central venous pressure from within the right atrium. Mean pressures within the abdominal inferior vena cava were essentially the same as mean right atrial pressure, suggesting that the inferior vena cava provides a useful safe alternative for measuring central venous pressure.

Comparison of radial versus brachial approaches for diagnostic coronary angiography when the femoral approach is contraindicated.

One hundred patients with contraindications to the femoral approach were randomized to undergo diagnostic coronary angiography via percutaneous radial puncture or brachial artery cutdown. Procedure duration, fluoroscopy time, and total radiation dose were significantly less via the radial route, whereas procedural success, complication rates, and pain scores were comparable; we conclude that the radial technique should be the arm approach of choice for new trainees, although there will be occasions when radial access fails and a brachial approach is required.

Evidence of gene amplification in the form of double minute chromosomes is frequently observed in lung cancer.

Amplification of cellular proto-oncogenes, important in tumor progression, has been correlated with a poor clinical outcome in a variety of human tumor types. Amplified genes are observed in two cytogenetically distinct entities, double minutes (DMs) and homogeneously staining regions (HSR). We examined 54 fresh lung tumor specimens obtained from patients with non-small cell lung cancer for cytogenetic evidence of gene amplification in the form of DMs. The majority of these patients had received no prior treatment. The cells were harvested within 24 hours after receiving the specimens, and the slides were stained with Giemsa to specifically look for DMs. We found DMs in 24 of 31 (77%) specimens that exhibited metaphase spreads. Similar incidences of DMs were found when histologic cell types, primary vs. non-primary tumors, and specimens from patients with prior treatment vs. no prior treatment were compared. Therefore, DMs occur frequently in non cultured lung tumor cells, providing evidence that gene amplification may be an important aspect of tumor behavior in patients with non-small cell lung carcinoma. Further investigation is warranted to identify the specific tumor-related genes located on these abnormal chromosomes. This also suggests that ongoing efforts to eliminate amplified drug-resistant genes or oncogenes contained on DMs in tumor cells may be relevant in patients with non-small cell lung cancer.

Double minutes are frequently found in ovarian carcinomas.

Double minutes (dmins) are acentric chromosomal-like entities that are important in the etiology of cancer because they are known to harbor amplified oncogenes and drug resistance genes. Because dmins can be unequally partitioned at mitosis they have the ability to confer genetic diversification rapidly. Selective pressures operative in vitro may be quite different than those in vivo; therefore, tumor cells which harbor dmins could be selected against during short-term in vitro propagation. We wanted to determine the incidence of dmins in human ovarian cancer cells obtained from fresh ovarian specimens with an absolute minimum of culture time (6-24 hours). In "direct" chromosomal preparations obtained from these clinical specimens we found dmins present in 88% of these samples. This remarkable finding that dmins are found so frequently in ovarian cancers underscores the importance of gene amplification in human tumor biology. Therefore, the presence of dmins in patient specimens indicates that these unstable genetic elements may play a significant role in the maintenance or progression of malignancy.

Abnormalities of skeletal muscle metabolism in patients with chronic heart failure: evidence that they are present at rest.

OBJECTIVE: To investigate abnormalities of skeletal muscle metabolism in patients with congestive heart failure. SETTING: A university teaching hospital. METHODS: 43 patients (22 New York Heart Association (NYHA) grade II, 21 grade III) and 10 controls were studied. A forearm model of muscle metabolism was used, with a cannula inserted retrogradely into an antecubital vein of the dominant forearm. Maximum voluntary contraction (MVC) was measured using handgrip dynamometry. Subjects performed handgrip exercise, 5 s contraction followed by 5 s rest for 5 min at 25%, 50%, and 75% of MVC or until exhaustion. Blood was taken at rest and 0 and 2 min after exercise for measurement of lactate and ammonia. After 30 min the procedure was repeated with fixed workloads of 7 kg, 14 kg, and 21 kg. RESULTS: MVC (kg, mean (SEM)) was lower in patients than in controls (control 42.45 (2.3); NYHA II 34.13 (1.3), P = 0.003; NYHA III 33.13 (1.94), P = 0.008). Resting lactate (mmol/l) was higher in patients than controls (control 0.65 (0.06); NYHA II 0.84 (0.08), P = 0.13; NYHA III 1.18 (0.1), P = 0.002). Resting ammonia (mumol/l) was higher in NYHA III (65.7 (6.0)) than in NYHA II (48.0 (3.7), P = 0.016); no difference was found between controls (48.0 (7.1)) and patients. The overall lactate and ammonia response to exercise was greater in NYHA III than in NYHA II and controls (P < 0.05). At volitional exhaustion, peak lactate (mmol/l: NYHA III 3.31 (0.26); NYHA II 2.56 (0.16); controls 2.71 (0.22); P = 0.022 NYHA III v NYHA II) and ammonia (mumol/l: NYHA III) 126.4 (8.97); NYHA II 92.9 (7.23); controls 109 (16.3); P = 0.006 NYHA III v NYHA II) were higher in severe congestive heart failure. CONCLUSIONS: Skeletal muscle metabolism is abnormal at rest in congestive heart failure. During exercise, the degree of metabolic abnormality is related to the symptomatic status of the patient.

Inspiratory muscle endurance in patients with chronic heart failure.

OBJECTIVE: To assess the significance of changes in respiratory muscle endurance in relation to respiratory and limb muscle strength in patients with mild to moderate chronic heart failure using a threshold loading technique. SUBJECTS: 20 patients with chronic heart failure (17 male) aged 63.8 (SD 7.4) years and 10 healthy men aged 63.1 (5.6) years. Heart failure severity was New York Heart Association (NYHA) grade II (n = 11) and NYHA grade III/IV (n = 9). METHODS: Respiratory muscle strength was measured from mouth pressures during maximum inspiratory effort (MIP) at functional residual capacity (FRC) and limb muscle strength was measured using a hand grip dynamometer. Inspiratory muscle endurance was measured using a threshold loading technique. The total endurance duration, the maximum threshold pressure achieved (P-Max), and the inspiratory load (% ratio of P-Max/MIP) were recorded in all subjects. RESULTS: Inspiratory muscles were weaker in patients with heart failure than in the controls [MIP 53.6 (16.5) v 70.9 (20.2) cm H2O, P < 0.05]. Hand grip strength was similar in both subject groups [31.6 (SD) v 36.1 (15.9) dynes]. Total endurance duration was significantly reduced in the patient group [494 (223) v 996 (267) s, P < 0.01], as was the maximal threshold pressure achieved [P-Max 18.5 (6.4) v 30.7 (6.6) cm H2O, P < 0.01]. When expressed as a percentage of MIP, P-Max was also lower in the patients [35.2 (11.8) v 44.8 (11.4)%, P < 0.05]. There was no significant correlation between any measure of endurance and limb muscle strength. CONCLUSIONS: Respiratory muscle endurance is reduced in patients with chronic heart failure. These changes probably reflect a generalised skeletal myopathy and provide further evidence of respiratory muscle dysfunction in patients with this disease. Respiratory muscle endurance needs now to be related to symptoms and the effects of treatment and respiratory muscle training should also be explored.

Ventricular dilatation in the absence of ACE inhibitors: influence of haemodynamic and neurohormonal variables following myocardial infarction.

OBJECTIVE: To examine the relation between patterns of ventricular remodelling and haemodynamic and neurohormonal variables, at rest and during symptom limited exercise, in the year following acute myocardial infarction in patients not receiving angiotensin converting enzyme (ACE) inhibitors. DESIGN: A prospective observational study. PATIENTS: 65 patients recruited following hospital admission with a transmural anterior myocardial infarction. METHODS: Central haemodynamics and neurohormonal activation at rest and during symptom limited treadmill exercise were measured at baseline before hospital discharge, one month later, and at three monthly intervals thereafter. PATIENTS were classified according to individual patterns of change in left ventricular end diastolic volumes at rest, assessed at each visit using transthoracic echocardiography. RESULTS: In most patients (n = 43, 66%) ventricular volumes were unchanged or reduced. Mean (SEM) treadmill exercise capacity and peak exercise cardiac index increased at month 12 by 200 (24) seconds (p < 0.001 v baseline) and by 0.8 (0.4) l/min/m2 (p<0.05 v baseline), respectively, in this group. In patients with limited ventricular dilatation (n = 11, 17%) exercise capacity increased by 259 (52) seconds (p < 0.001 v baseline) and peak exercise cardiac index improved by 0.8 (0.7) l/min/m2 (NS). In the remaining 11 patients with progressive left ventricular dilatation, exercise capacity increased by 308 (53) seconds (p< 0. 001 v baseline) and peak exercise cardiac index similarly improved by 1.3 (0.7) l/min/m2 (NS). There were trends towards increased atrial natriuretic factor (ANF) secretion at rest and at peak exercise in this group. CONCLUSIONS: Ventricular dilatation after acute myocardial infarction is a heterogeneous process that is progressive in only a minority of patients. Compensatory mechanisms, including ANF release, appear capable of maintaining and improving exercise capacity in most patients for at least 12 months, even in those with a progressive increase in ventricular size.

Shear strength of composite bonded to Er:YAG laser-prepared dentin.

An Er:YAG laser coupled with a cooling stream of water effectively removes dental hard tissues. However, before such a system can be deemed clinically viable, some safety and efficacy issues must be addressed. We compared the bonding of composite to dentin following the preparation of the dentinal surface with either an Er:YAG laser (lambda = 2.94 microns) or a standard dental bur and with and without a subsequent acid-etching treatment. The crowns of extracted human molars were removed, revealing the underlying dentin. We removed an additional thickness of material with either a dental handpiece or an Er:YAG laser (350 mJ/pulse at 6 Hz) by raster-scanning the samples under a fixed handpiece or laser. Comparable surface roughnesses were obtained. Several samples from each group received an acid-conditioning treatment. A cylinder of composite was bonded onto the prepared surfaces. The dentin-composite bond was then shear-stressed to failure on a universal testing apparatus. The results indicate that laser-irradiated samples had improved bond strengths compared with acid-etched and handpiece controls. SEM photographs of the surfaces show exposed tubules following the laser treatment: tubules could also be exposed with acid etching. We conclude that Er:YAG laser preparation of dentin leaves a suitable surface for strong bonding or an applied composite material.

Dye-assisted laser skin closure with pulsed radiation: an in vitro study of weld strength and thermal damage.

Previous laser skin welding studies have used continuous wave delivery of radiation. However, heat diffusion during irradiation prevents strong welds from being achieved without creating large zones of thermal damage. Previously published results indicate that a thermal damage zone in skin greater than 200 µm may prevent normal wound healing. We propose that both strong welds and minimal thermal damage can be achieved by introducing a dye and delivering the radiation in a series of sufficiently short pulses. Two-cm-long incisions were made in guinea pig skin, in vitro. India ink and egg white (albumin) were applied to the wound edges to enhance radiation absorption and to close the wound, respectively. Continuous wave (cw), 1.06 µm, Nd:yttrium-aluminum-garnet laser radiation was scanned over the weld producing ∼100 ms pulses. The cooling time between scans and the number of scans was varied. The thermal damage zone at the weld edges was measured using a transmission polarizing light microscope. The tensile strength of the welds was measured using a tensiometer. For pulsed welding and long cooling times between pulses (8 s), weld strengths of 2.4±0.9 kg/cm2 were measured, and lateral thermal damage at the epidermis was limited to 500±150 µm. With cw welding, comparable weld strengths produced 2700±300 µm of lateral thermal damage. The cw weld strengths were only 0.6±0.3 kg/cm2 for thermal damage zones comparable to pulsed welding. © 1998 Society of Photo-Optical Instrumentation Engineers.

Birefringence measurement of rapid structural changes during collagen denaturation.

Linear birefringence, an optical property that results from a material's structure and composition, can be used to study dynamic changes in tissue structure. Single, 200 microseconds-long pulses from a Ho:YAG laser emitting 2.1 microns radiation were used to induce changes in the linear birefringence of rat tail tendon. Such changes were measured on a millisecond timescale. The measured rate coefficients describing the denaturation are not predicted by previous studies of collagen denaturation induced by slower, lower-temperature heating. Two types of laser-induced collagen denaturation can be differentiated: thermal denaturation, which appears rate-limited, and thermomechanical denaturation, which is observed at higher laser radiant exposures. Neither process is described by standard Arrhenius-type kinetic models.

Cryogen spray cooling during laser tissue welding.

Cryogen cooling during laser tissue welding was explored as a means of reducing lateral thermal damage near the tissue surface and shortening operative time. Two centimetre long full-thickness incisions were made on the epilated backs of guinea pigs, in vivo. India ink was applied to the incision edges then clamps were used to appose the edges. A 4 mm diameter beam of 16 W, continuous-wave, 1.06 microm, Nd:YAG laser radiation was scanned over the incisions, producing approximately 100 ms pulses. There was a delay of 2 s between scans. The total irradiation time was varied from 1-2 min. Cryogen was delivered to the weld site through a solenoid valve in spurt durations of 20, 60 and 100 ms. The time between spurts was either 2 or 4 s, corresponding to one spurt every one or two laser scans. Histology and tensile strength measurements were used to evaluate laser welds. Total irradiation times were reduced from 10 min without surface cooling to under 1 min with surface cooling. The thermal denaturation profile showed less denaturation in the papillary dermis than in the mid-dermis. Welds created using optimized irradiation and cooling parameters had significantly higher tensile strengths (1.7 +/- 0.4 kg cm(-2)) than measured in the control studies without cryogen cooling (1.0 +/- 0.2 kg cm(-2)) (p < 0.05). Cryogen cooling of the tissue surface during laser welding results in increased weld strengths while reducing thermal damage and operative times. Long-term studies will be necessary to determine weld strengths and the amount of scarring during wound healing.

Unruptured aneurysm of the left sinus of Valsalva presenting with atrial fibrillation.

Congenital aneurysms arising from the left sinus of Valsalva are extremely uncommon, and when unruptured often asymptomatic. Abnormalities of rhythm are more commonly associated with dilatation of the right coronary sinus although the reason for this is unclear. We report the first case of an unruptured aneurysm involving the left sinus of Valsalva presenting with paroxysmal atrial fibrillation. Two-dimensional echocardiography confirmed the diagnosis.

Coronary angiography from the radial artery--experience, complications and limitations.

AIMS: to assess the outcomes, complications and limitations of coronary angiography performed via percutaneous radial artery puncture. METHODS AND RESULTS: two hundred and fifty patients underwent diagnostic coronary angiography from the radial artery, 182 (72.8%) of whom had contraindications to the femoral approach, for example due to peripheral vascular disease (n=85), therapeutic anticoagulation (29), or failed femoral approach (17). Procedural success in this high-risk population was achieved in 231 patients (92.4%). Principle reasons for failure were unsuccessful radial access (5) and arterial spasm (5). Procedure duration (SD) for an operator's first 20 cases compared with cases thereafter (min) was 47.7 (16.7) vs. 41.5 (14.6), P=0.0004; fluoroscopy time (min) 9.7 (7.1) vs. 6.6 (5.1), P=0.0001 and procedural success 89.6% vs. 94.1%, P=ns. Complications included two deaths associated temporally with catheterisation, three cases of arterial dissection without ischaemic sequelae and one transient ischaemic attack. CONCLUSIONS: coronary angiography can be performed successfully from the radial artery, but this approach has limitations, which include the need to demonstrate dual palmar vascular supply, the prolonged learning phase, the procedural failure rate, patient discomfort and a demonstrable incidence of vascular and haemodynamic complications. We believe that radial coronary angiography should only be undertaken when there is a contraindication to the femoral approach.

Pulsed CO2 laser ablation of tissue: effect of mechanical properties.

The ablation rate of guinea pig skin and bovine aorta, myocardium, and liver by a CO2 laser emitting 2-microseconds-long pulses was quantified. Ablation efficiency was found to be strongly dependent upon the ultimate tensile strength of the tissue; the ablation efficiency of liver is seven times that of skin. Gluteraldehyde cross linking of skin, which is known to greatly increase tissue stiffness but not significantly affect ultimate tensile strength, did not change the ablation rate. The water content of the tissues, which largely determines the optical and thermal properties, was measured and found to vary only slightly. The results demonstrate that tissue mechanical properties are important in the interpretation and modeling of pulsed laser ablation of tissue and that variations in these mechanical properties can lead to drastically different cutting rates for different tissues.