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Tablets have been prepared from previously characterized microcrystalline cellulose (Avicel) powders, using an instrumented single station tablet machine. The regenerated particle size was found to increase in compaction pressure. Compaction caused a slight initial decrease in B.E.T. surface area, followed by an increase mainly as a result of elastic recovery of the particles. The intra-particulate pore size distribution showed no change throughout the range of compaction pressures studied, demonstrating that the internal pores did not collapse. Measurement of the interparticulate porosity by mercury porosimetry, liquid penetration techniques and scanning electron microscopy showed a decrease in this parameter with increase in compaction pressure. The dissolution behaviour from the compacts showed in general a decreased rate with increase in compaction pressure, that from the cellulose grade PH 105 being slower than from the remaining grades.
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PMID:The effect of compression on some physical properties of microcrystalline cellulose powders. 1 79

We present four cases of heavy metal poisoning (mercury, lead, bismuth and arsenic) in which plain chest and/or abdominal assisted in the differential diagnosis of the clinical picture manifested upon admission at our Emergency Department. The patients suffering from mercury, lead, and bismuth poisoning recovered some weeks after treatment was started. However, the patient with arsenic trioxide poisoning developed cardio-circulatory collapse leading to death three days after admission.
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PMID:[The radiological findings in poisonings by metals]. 156 22

Voltaire, the leading French intellect of the 18th century, was a notorious hypochondriac. His numerous letters contain hundreds of references to his medical and dental disorders, as well as to those of close friends. Voltaire lived to be 84 years old, but not without suffering from several systemic medical disorders and from periodontal disease that left him nearly edentulous by his mid-50s. His dental condition was diagnosed as a scorbutic condition, requiring systemic medication. As a result of neglect and possible mercury intoxication, his condition worsened, and he lost most of his teeth and suffered facial collapse because he did not wear a dental prosthesis. This paper recounts events in Voltaire's life that were connected to his medical and dental history, and in so doing provides a glance at medical and dental practice in 18th-century France.
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PMID:Voltaire, medicine, and dentistry. 192 96

Echocardiographic and hemodynamic data were measured in closed-chest dogs during graded cardiac tamponade (pericardial pressure 5, 10, and 15 mm Hg) before and after production of diffuse ischemic left ventricular dysfunction. Left ventricular dysfunction was produced by intracoronary injection of nonradioactive microspheres (54 +/- 3.9 mm diameter). Changes in left atrial pressure with cardiac tamponade were influenced by coexisting left ventricular dysfunction. Left atrial pressure increased with tamponade and was equal to pericardial pressure before left ventricular dysfunction was produced. However, after left ventricular dysfunction was produced, left atrial pressure was significantly higher than pericardial pressure before tamponade, but it fell toward pericardial pressure when tamponade was produced. Pulsus paradoxus (greater than 10 mm Hg) was present in all animals with cardiac tamponade before left ventricular dysfunction but in only one animal afterward. During each level of tamponade, the inspiratory fall of aortic systolic pressure was greater before than with left ventricular dysfunction. The slope of the linear regression between pericardial pressure and millimeters of mercury of inspiratory fall in aortic systolic pressure was significantly greater before than with left ventricular dysfunction (0.74 +/- 0.12 versus 0.32 +/- 0.12, p less than 0.05). Left ventricular dysfunction caused a leftward and upward shift of the pericardial pressure-volume relation. As a result, right atrial and ventricular collapse occurred with significantly smaller volumes of pericardial fluid after than before left ventricular dysfunction. We conclude that pulsus paradoxus may be absent in cardiac tamponade with coexisting left ventricular dysfunction and unequal filling pressures. Echocardiographic signs of cardiac tamponade may occur with small effusions in the presence of left ventricular dysfunction.
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PMID:Cardiac tamponade in left ventricular dysfunction. 240 Oct 70

Arterial blood nitrogen tensions of free-diving Weddell seals (Leptonychotes weddelli) were measured by attaching a microprocessor-controlled blood pump and drawing samples at depth to determine how these marine mammals dive to great depths and ascend rapidly without developing decompression sickness. Forty-seven samples of arterial blood were obtained from four Weddell seals during free dives lasting up to 23 minutes to depths of 230 meters beneath the sea ice of McMurdo Sound, Antarctica. Peak arterial blood nitrogen tensions of between 2000 and 2500 millimeters of mercury were recorded at depths of 40 to 80 meters during descent, indicating that the seal's lung collapses by 25 to 50 meters. Then arterial blood nitrogen tensions slowly decreased to about 1500 millimeters of mercury at the surface. In a single dive, alveolar collapse and redistribution of blood nitrogen allow the seal to avoid nitrogen narcosis and decompression sickness.
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PMID:Seal lungs collapse during free diving: evidence from arterial nitrogen tensions. 402

Exposing (soluble) calf thymus chromatin and, as reference, protein-free native calf thymus DNA (both in 0.01 M Na+, pH 6.8, 25 degrees C) to increasing concentrations of CH3HgOh produces cooperative transitions in their CD spectra. In the case of chromatin, and there especially at low concentrations of methylmercury, they are due to reactions affecting the relative orientation of the bases in the constituent DNA, without disrupting base-pairing. In the case of protein-free DNA, and with chromatin at higher methylmercury concentrations, the CD changes signal collapse of the DNA secondary structure. Primary data (molar ellipticities [theta], zero-ellipticity points, and rotational strengths R) are presented as a function of methylmercury concentration and wavelength. The results are discussed in relation to previous findings of this laboratory regarding methylmercury-DNA and methylmercury-chromatin interactions, and it is pointed out that the structural alterations observed with chromatin at low levels of methylmercury may very well be the primary events in a chain that is responsible for the teratogenic and clastogenic damages caused by organic mercury.
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PMID:Circular dichroism of micrococcal nuclease-treated calf thymus chromatin (soluble chromatin) in presence of CH3HgOH. 405 87

It is generally accepted that multi-ring basins are the consequence of very large impacts, but the mechanism by which they form is still a matter of contention. Most of what is currently known about multi-ring basins is based on remote studies of the Moon and, to a lesser extent, Mars and Mercury. But at least two multi-ring impact basins have been recognized on Earth--the Sudbury (Canada) and Vredefort (South Africa) impact structures--providing an opportunity to study their properties directly. Here we describe the distribution of friction melt (pseudotachylyte) in the floor of the Sudbury impact basin. Although the veins and dykes of pseudotachylyte decrease in both thickness and frequency of occurrence towards the basin periphery, the greatest volumes of friction melt appear to define four rings around the central impact melt sheet. Field evidence indicates that the rings originated as zones of large displacement, which facilitated localized frictional melting of the basin floor during the modification (collapse) stage of the cratering process. By analogy, we argue that the rings of other multi-ring impact basins are also likely to be the remnants of such large-displacement fault zones.
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PMID:Friction melt distribution in a multi-ring impact basin. 781 86

The right atrium and the right ventricle of fifty-five patients were imaged with transesophageal echocardiography during fifty-nine total knee arthroplasties performed with cement and the use of general anesthesia. The patients ranged in age from thirty-two to eighty-three years (mean, 65.5 years). Cardiopulmonary parameters were measured with use of hemodynamic monitoring systems, such as pulse oximeters, pulmonary artery catheters, and radial artery catheters. In addition, a femoral vein catheter was inserted on the side of the operation in ten of the fifty-five patients. Showers of echogenic material traversing the right atrium, the right ventricle, and the pulmonary artery after the tourniquet was deflated were observed to various degrees in all patients and lasted three to fifteen minutes. The mean peak intensity occurred within thirty seconds (range, twenty-four to forty-five seconds) after the tourniquet was released. The mean mixed venous oxygen saturation (and standard error of the mean) decreased (from 83+/-0.9 to 72+/-1.5 per cent) and the mean pulmonary arterial pressure increased (from 20+/-1.0 to 27+/-1.0 millimeters of mercury [2.67+/-0.13 to 3.60+/-0.13 kilopascals]), compared with the values before the tourniquet was released, in all patients. The pulmonary vascular resistance index increased after release of the tourniquet (to a maximum of 328+/-29 dyne.s.cm(-5).m2; p = 0.00002) only in the patients who had echogenic material that was at least 0.5 centimeter in diameter. Clinical pulmonary embolism developed postoperatively in three patients; all three had had echogenic particles that were more than 0.5 centimeter in maximum diameter on imaging. Blood aspirated from one of the pulmonary artery catheters and from five of the ten femoral vein catheters demonstrated fresh venous thrombus. Histological evaluation of the aspirates failed to demonstrate fat, marrow, or particles of polymethylmethacrylate. Surgeons should consider acute pulmonary embolism as a diagnosis when evaluating a patient who has hemodynamic collapse during total knee arthroplasty performed with cement.
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PMID:Emboli observed with use of transesophageal echocardiography immediately after tourniquet release during total knee arthroplasty with cement. 953 Dec 7

Hot, humid conditions in tropical regions generally rule out any risk of hypothermia due to cold exposure. In this report, we describe a case of severe hypothermia involving a core temperature of 26 degrees C in a 61-year-old man living in Gabon. Parkinson's disease and chronic alcoholism may have been predisposing factors. The patient was treated by active and passive rewarming (intestinal irrigation with warm water). Sudden circulatory collapse occurred during treatment but the final outcome was successful. This case demonstrates that hypothermia can occur in tropical areas. Emergency diagnosis may be difficult in Black Africa where adequate temperature monitoring equipment is rarely available. Standard mercury thermometers do not allow measurement of temperatures lower than 34 degrees C. African physicians should be aware of the possibility of potentially life-threatening hypothermia and be prepared to initiate proper treatment and surveillance in intensive care.
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PMID:[Severe hypothermia in a tropical setting]. 979 96

Poly(DL-lactic-co-glycolic acid) (PLGA) foams are an osteoconductive support that holds promise for the development of bone tissue in vitro and implantation into orthopedic defects. Because it is desirable that foams maintain their shape and size, we examined a variety of foams cultured in vitro with osteoblastic cells. Foams were prepared with different porosities and pore sizes by the method of solvent casting/porogen leaching using 80, 85, and 90 wt% NaCl sieved with particle sizes of 150-300 and 300-500 microm and characterized by mercury intrusion porosimetry. Foams seeded with cells were found to have volumes after 7 days in static culture that decreased with increasing porosity: the least porous exhibited no change in volume while the most porous foams decreased by 39 +/- 10%. In addition, a correlation was observed between decreasing foam volume after 7 days in culture and decreasing internal surface area of the foams prior to seeding. Furthermore, foams prepared with the 300-500 microm porogen had lower porosities, greater mean wall thicknesses between adjacent pores, and larger volumes after 7 days in culture than those prepared with the smaller porogen. Two culture conditions for maintaining cells, static and agitated (in a rotary vessel), were found to have similar influences on foam size, cell density, and osteoblastic function for 7 and 14 days in culture. Finally, we examined unseeded foams in aqueous solutions of pH 3.0, 5.0, and 7.4 and found no significant decrease in foam size with degradation. This study demonstrates that adherent osteoblastic cells may collapse very porous PLGA foams prepared by solvent casting/particulate leaching: a potentially undesirable property for repair of orthopedic defects.
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PMID:Effect of osteoblastic culture conditions on the structure of poly(DL-lactic-co-glycolic acid) foam scaffolds. 1058 98


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