The NAP prism

The optics of the NAP prism are described. This is a prism that is produced commercially in "NAP glasses," which are marketed by the Sakura Company of Japan. It deflects a beam through about 90 degrees while keeping the image erect. Rays are both reflected and refracted, leading to some color fringing. The condition for zero color fringing is explored and the corresponding angle of deviation is calculated. The effects of prism apex angles on beam deviation angle and field of view are also investigated. The results show that the requirement for zero color fringing gives a small field of view but if some color fringing is tolerated, a larger field of view can be obtained.     

A comparison of the haemodynamic and hormonal effects of low and conventional dose cyclopenthiazide in normal volunteers

Summary In this study we compared low (125 g) and conventional (500 g) doses of cyclopenthiazide on the renin angiotensin system, plasma and extracellular fluid volumes and the pressor responsiveness to angiotensin II since we have previously shown that the two doses have the same antihypertensive effect but different effects on plasma renin activity.Following a two week placebo run-in period, 8 healthy male volunteers received 125 g or 500 g of cyclopenthiazide for 2 treatment periods of 4 weeks as part of a double blind, 2-part crossover study with treatment periods separated by a 4-week placebo washout phase. Measurements were made on two study days at the beginning and end of the active treatment periods. On the first day serum potassium, plasma renin activity and plasma angiotensin II levels were measured after a 1 h period of supine rest. Plasma and extracellular fluid volumes were also measured after appropriate equilibration times. The blood pressure responses to angiotensin II were assessed on day 2.The 500 g dose of cyclopenthiazide had a greater effect than the 125 g dose on plasma renin activity, serum potassium, angiotensin II levels and extracellular fluid volumes. Neither drug had any effect on plasma volume or the responsiveness to infused angiotensin II.Low dose cyclopenthiazide failed to increase angiotensin II levels, contract body fluid volumes or attenuate vascular reactivity in normotensive volunteers.     

Auditing the effect of experience and change on home parenteral nutrition related complications

A prospective record of all patients receiving home parenteral nutrition (HPN) in Tayside since 1980 has been used to audit the effect of experience and specific policy changes on HPN related complications. Total HPN related complications fell significantly over the years from 1.59 complications per treatment year during the initial 5 years of HPN experience to the current rate of 0.36 complications per treatment year. Specific policy changes, such as modification of the glucose concentration of feed, could also be shown to produce a significant benefit in the reduction of complications. Increasing experience with HPN results in a fall in complication rates, however, continuous audit of HPN is essential to determine the effect of policy changes on complication rates.     

Polymeric Microspheres Prepared by Spraying into Compressed Carbon Dioxide

Purpose. The objective was to prepare polymeric microparticles by atomizing organic polymer solutions into a spray chamber containing compressed CO₂ (PCA-process) and to study the influence of various process parameters on their morphological characteristics. Methods. The swelling of various pharmaceutically acceptable polymers [ethyl cellulose, poly(methyl methacrylate), poly(-caprolactone), poly(dl-lactide), poly(l-lactide) and poly(dl-lactide-glycolide) copolymers] in CO₂ was investigated in order to find polymers which did not agglomerate during the spraying process. Poly(l-lactide) (L-PLA) microparticles were prepared by spraying the organic polymer solution into CO₂ in a specially designed spraying apparatus. The effect of various process (pressure and temperature of the CO₂ phase, flow rate) and formulation (polymer concentration) variables on the morphology and particle size of L-PLA-microparticles was investigated. Results. Polymers with low glass transition temperatures agglomerated even at low temperatures. The formation of microparticles was favored at moderate temperatures, low polymer concentrations, high pressures and high flow rates of CO₂. High polymer concentrations and low flow rates resulted in the formation of polymeric fibers. Colloidal L-PLA particles could also be prepared with this technique in a surfactant-free environment. Initial studies on the microencapsulation of drugs resulted in low encapsulation efficiencies. Conclusions. The PCA method is a promising technique for the preparation of drug-containing microparticles. Potential advantages of this method include the flexibility of preparing microparticles of different size and morphology, the elimination of surfactants, the minimization of residual organic solvents, low to moderate processing temperatures and the potential for scale-up.     

Effect of cold exposure, exercise and high altitude on plasma endothelin-1 and endothelial cell markers in man

The aims were to examine the effect of cold exposure, exercise and high altitude on plasma concentrations of big endothelin-1, endothelin-1, von Willebrand factor and serum e-selectin in twenty five healthy male volunteers. Clinical evaluation and venesection were performed before and after 24 hours of low altitude mountaineering, exposure to temperatures of -18 degrees C and +4 degrees C and whilst ascending from sea level to an altitude of 5000 m in the Karakoram. Plasma big endothelin-1, plasma endothelin-1 and serum soluble e-selectin concentrations were significantly elevated after two hours at -18 degrees C (p < 0.05, p < 0.05 and p < 0.01 respectively). At +4 degrees C, plasma big endothelin-1 and endothelin-1 concentrations rose significantly after 5 hours (p < 0.005 for both) but not after 2.5 hours. Low altitude mountaineering did not alter circulating marker concentrations. At high altitude, big endothelin-1 and endothelin-1 (p < 0.01 for both) rose significantly at 2500 m and initially at 5000 m but returned to sea level values after prolonged exposure to 5000 m. Serum e-selectin rose at all altitudes greater than sea level (p < 0.05). In conclusion, exposure to high altitude, moderate cold or freezing temperatures, but not exercise, selectively activates endothelial cells increasing endothelin-1 production. Cold exposure may contribute to the observed increase in plasma endothelin-1 in mountaineers at high altitude.     

Surgeons' assessment of symptoms suggesting extrathoracic metastases in patients with lung cancer. Canadian Lung Oncology Group.

BACKGROUND: In patients with apparently operable non-small cell lung cancer (NSCLC), clinicians often omit investigation for M disease in asymptomatic patients. Previous investigations have not specified in detail what is meant by "symptomatic," and this could differ between surgeons. We have investigated the extent to which surgeons' criteria differ for presence of symptoms. METHODS: Participating surgeons from seven centers, enrolled patients they judged "asymptomatic" in a randomized trial of investigational strategies for NSCLC. Patients completed a structured questionnaire describing symptoms of the central nervous system (CNS). In 685 patients, we documented CNS symptom recurrence after resectional surgery over 1 year of follow-up. RESULTS: Two centers enrolled only patients without even the mildest symptoms. Three centers took an intermediate approach, occasionally classifying patients with mild symptoms as "asymptomatic" and thus enrolling them in the trial. Two centers classified an appreciable number of patients with minimal symptoms, and occasionally with more than minimal symptoms, as "asymptomatic." Patients with even mild CNS symptoms were more likely to subsequently present with CNS metastases. CONCLUSIONS: Thoracic surgeons differ in their ideas of what may constitute the symptoms of M disease. Patients with structured questionnaire results that suggest symptoms of CNS disease are more likely to have CNS symptom recurrence after resectional surgery.     

Increased intracerebral excitatory amino acids and nitric oxide after hypothermic circulatory arrest

BACKGROUND: Prolonged hypothermic circulatory arrest (HCA) results in neurologic injury, but the mechanism of this injury is unknown. This study was undertaken to measure quantitatively intracerebral excitatory amino acids and citrulline, an equal coproduct of nitric oxide, during HCA. We hypothesized that HCA resulted in higher levels of glutamate, aspartate, glycine, causing increased intracellular calcium, and therefore, nitric oxide and citrulline. METHODS: Ten dogs underwent intracerebral microdialysis and 2 hours of HCA at 18 degrees C. Effluent was analyzed by high performance liquid chromatography with electrochemical detection. Five dogs each were sacrificed at 8 and 20 hours after HCA. Neuronal apoptosis was scored from 0 (no injury) to 100 (severe injury). RESULTS: Time course of HCA was divided into six periods. Peak levels of amino acids in each period were compared with those at baseline. Glutamate, coagonist glycine, and citrulline, an equal coproduct of nitric oxide, increased significantly over baseline during HCA, cardiopulmonary bypass, and 2 to 8 hours after HCA. Aspartate increased significantly during HCA and 8 to 20 hours after HCA. Apoptosis score was 65.56 +/- 5.67 at 8 hours and 30.63 +/- 14.96 at 20 hours after HCA. CONCLUSIONS: Our results provide direct evidence that HCA causes increased intracerebral glutamate and aspartate, along with coagonist glycine. We conclude that HCA causes glutamate excitotoxicity with subsequent nitric oxide production resulting in neurologic injury, which begins during arrest and continues until 20 hours after hypothermic circulation arrest. To provide effective cerebral protection, pharmacologic strategies to reduce glutamate excitotoxicity require intervention beyond the initial ischemic insult.