Chemical differentiation, cold storage and remobilization of magma in the Earth's crust.

The formation, storage and chemical differentiation of magma in the Earth's crust is of fundamental importance in igneous geology and volcanology. Recent data are challenging the high-melt-fraction 'magma chamber' paradigm that has underpinned models of crustal magmatism for over a century, suggesting instead that magma is normally stored in low-melt-fraction 'mush reservoirs'1-9. A mush reservoir comprises a porous and permeable framework of closely packed crystals with melt present in the pore space1,10. However, many common features of crustal magmatism have not yet been explained by either the 'chamber' or 'mush reservoir' concepts1,11. Here we show that reactive melt flow is a critical, but hitherto neglected, process in crustal mush reservoirs, caused by buoyant melt percolating upwards through, and reacting with, the crystals10. Reactive melt flow in mush reservoirs produces the low-crystallinity, chemically differentiated (silicic) magmas that ascend to form shallower intrusions or erupt to the surface11-13. These magmas can host much older crystals, stored at low and even sub-solidus temperatures, consistent with crystal chemistry data6-9. Changes in local bulk composition caused by reactive melt flow, rather than large increases in temperature, produce the rapid increase in melt fraction that remobilizes these cool- or cold-stored crystals. Reactive flow can also produce bimodality in magma compositions sourced from mid- to lower-crustal reservoirs14,15. Trace-element profiles generated by reactive flow are similar to those observed in a well studied reservoir now exposed at the surface16. We propose that magma storage and differentiation primarily occurs by reactive melt flow in long-lived mush reservoirs, rather than by the commonly invoked process of fractional crystallization in magma chambers14.

Formation and dynamics of magma reservoirs.

The emerging concept of a magma reservoir is one in which regions containing melt extend from the source of magma generation to the surface. The reservoir may contain regions of very low fraction intergranular melt, partially molten rock (mush) and melt lenses (or magma chambers) containing high melt fraction eruptible magma, as well as pockets of exsolved magmatic fluids. The various parts of the system may be separated by a sub-solidus rock or be connected and continuous. Magma reservoirs and their wall rocks span a vast array of rheological properties, covering as much as 25 orders of magnitude from high viscosity, sub-solidus crustal rocks to magmatic fluids. Time scales of processes within magma reservoirs range from very slow melt and fluid segregation within mush and magma chambers and deformation of surrounding host rocks to very rapid development of magma and fluid instability, transport and eruption. Developing a comprehensive model of these systems is a grand challenge that will require close collaboration between modellers, geophysicists, geochemists, geologists, volcanologists and petrologists. This article is part of the Theo Murphy meeting issue 'Magma reservoir architecture and dynamics'.

Body mass index and prostate specific antigen levels in Jamaican men.

OBJECTIVE: To investigate the relationship between body mass index (BMI) and prostate specific antigen (PSA) levels in Jamaican men. METHODS: Men, 40-79 years old, attending public and private urology clinics in Kingston, Jamaica were recruited to a case-control study on the role of dietary and lifestyle factors on prostate cancer. Trained interviewers administered questionnaires and measured weight and height using standardized techniques. Blood samples for PSA were measured at a central laboratory using a micro-particle enzyme immunoassay method. Prostate biopsy was used to confirm prostate cancer. Multivariable linear regression was used to examine the relationship between BMI and PSA separately in the cases and controls. RESULTS: Data from 501 men (233 cases and 263 controls) were assessed. Thirty-five per cent of subjects were overweight and 13% were obese. Among cases, the median PSA was 35.3 ng/dL in normal weight, 26.1 ng/dL in overweight and 14.5 ng/dL in obese men (p = 0.02). For controls, median PSA was 2.0 ng/dL in normal weight, 1.3 ng/dL in overweight and 1.1ng/dl in obese men (p = 0.01). Among cases, BMI was negatively associated with PSA (B(SE) per 5 kg/m2 (BMI difference = -0.51 (0.13); p < 0.01) and remained significant after adjustment for age, sexual activity, smoking, use of statins and tumour grade. For controls, the BMI was also inversely related to the PSA (B(SE) per 5 kg/m2 difference -0.17 (0.07)) but the effect became of borderline significance after adjusting for age. CONCLUSIONS: Prostate specific antigen was inversely related to body mass index in Jamaican men with prostate cancer. Clinicians should consider this association when interpreting PSA results.

Processing determinants of reading speed.

Two groups of university undergraduates differing in reading ability were tested on a number of reaction-time tasks designed to determine the speed of encoding visual information at several different levels. In addition, the subjects were given tests of sensory functions, verbal and quantitative reasoning ability, short-term auditory memory span, and ability to comprehend spoken text. The groups did not differ on the sensory tests. However, the faster reader group had faster reaction times on all of the reaction-time tasks, and the size of the fast-reader advantage increased with the mean reaction time. Faster readers also performed more accurately in verbal and quantitative reasoning, short-term auditory memory, and speech comprehension. Regression analyses suggested that the ability to comprehend spoken material and speed of accessing overlearned memory codes for visually presented letters represented two important independent correlates of reading ability in our sample of subjects. Two variables reflecting these abilities--the percentage of correct answers to a listening comprehension test and the reaction time for correct responses in a letter-matching task--accounted for nearly all of the variance in reading ability tapped by both of our reading tests. In a second experiment, no reaction-time difference was found between fast and average readers in a matching task requiring no long-term memory code access but considerable visual information processing as indexed by overall mean reaction time. The results supported the conclusion that one skill allowing fast readers to capture more information from each reading fixation is faster access to letter codes from print.

Chronic disease and exercise.

With current trends in health consciousness, physicians are being asked to counsel individuals with chronic diseases who are involved in exercise programs. To accomplish this goal, health care providers should understand the effects of exercise on these individuals. Previously, epileptics were precluded from physical activity. Recent data reveals that exercise can be beneficial for epileptics. Therefore, in most cases, these individuals should be encouraged to participate in exercise programs. Asthmatics should be encouraged to participate in regular exercise to improve cardiovascular and respiratory fitness levels. For asthmatics, a proper exercise program can lead to an increased threshold before the stimulation of exercise-induced asthma occurs. The benefits of exercise for diabetics have been recognized for many decades. Exercise should be combined with appropriate diabetic education. Hypertrophic cardiomyopathy (HCM) is the number one cause of sudden death in young adults. HCM is a contraindication to strenuous exercise, but with proper medical management low-intensity exercise may be safely accomplished.

Graphical analysis and visualization of three-dimensional properties of molecules and solids.

A simple approach is presented for visualizing three-dimensional properties of molecular and crystalline systems by using PC-based molecular drawing software. This allows a scientist with lower-cost PC-graphics capability to carry out analysis of data, such as wave functions and electron density, which would otherwise require a dedicated graphics workstation and expensive specialized software. In this approach, a data set [x,y,z,f1(x,y,z)] is transformed to a new set of data [x,y,z] for values of f1 meeting specified requirements. The function f1, which varies throughout a chemical system is difficult to visualize. However, a more manageable data set is obtained if the set of Cartesian coordinates corresponding to locations in the system where f1 has a specified value are used. This set of points can then be visualized and plotted with standard graphics software or PC-based molecular modeling programs. In addition, the use of PC-based molecular graphics permits one to superimpose the data describing molecular properties on drawings of the molecular geometry. The entire object can then be rotated to facilitate a clear analysis of the property of the molecule.

Gastroparesis following traumatic brain injury and response to metoclopramide therapy.

Most studies on nutrition in patients with traumatic brain injury (TBI) have focused on the hypermetabolic state immediately after trauma, or the swallowing disorders that frequently follow acute TBI. A less well-known sequela, however, is gastroparesis, which generally manifests itself when patients have advanced from nasogastric to oral feeding programs. Case histories of four patients are reported, all of whom responded to therapeutic intervention with metoclopramide. Results of a radionuclide gastric emptying study, before and after metoclopramide therapy, are presented. The etiologic and physiologic mechanisms behind this disorder are unclear, but demonstration of this disorder and other clinical trials with metoclopramide appear to deserve further consideration in the nutritionally compromised TBI patient.

Insecticide movement following application to crevices in rooms.

The movement of chlorpyrifos and diazinon from cracks and crevices in empty dormitory rooms with and without forced air movement to houseflies and plates in non-target areas was studied. Aluminum pie plates in rooms with the high concentrations of an insecticide, no forced air movement, and at the earlier sampling interals contained more insecticide. Insecticides were not detectable at 48 hr. Increased housefly movement occurred simultaneously with the initiation of insecticide application in rooms with forced air and 1 min later in rooms with no forced air. Mortality of houseflies exposed during and at 5 hr after insecticide application was greater for males than females in all tests except one; at the high insecticide concentrations; and at successive time intervals through the 24-hr interval after their transfer from the treated rooms to holding rooms. Houseflies in cages near the ceiling, exposed to an insecticide, and forced air movement, exhibited greater mortality than those in cages on the floor, while the reverse was true for houseflies in rooms with no forced air movement.

Environmental and biological effects of propoxur-impregnated strips within a laboratory animal room.

Rats were exposed to propoxur-impregnated strips in a conventional laboratory animal room. The air in the room was monitored for the pesticide, and erythrocyte acetylcholinesterase activity was determined periodically. Air concentration of the pesticide never exceeded 0.8 microgram/m3, and no significant change in enzyme activity was observed.

Environmental and biological effects following application of diazinon impregnated strips within a laboratory animal room.

Rats were exposed to diazinon impregnated strips in a conventional laboratory animal room. The air in the room was monitored for the pesticide. Erythrocyte acetylcholinesterase and plasma pseudocholinesterase activities were determined periodically. Air concentration of the pesticide never exceeded 1.34 microgram/m3. No significant change in enzyme activities were observed.

Magnetic resonance imaging of avascular necrosis of the lunate.

Avascular necrosis (AVN) of carpal bones, particularly the lunate, is often an elusive cause of wrist pain. Physical examination can be indistinguishable from that of a simple wrist sprain, and standard radiographic evaluations are frequently normal. Early diagnosis is critical, since late treatment is often simple observation of the natural history of the disease, which includes progressive collapse of the lunate and derangement of the carpal architecture. Magnetic resonance imaging (MRI) produces images of high contrast, demarcating necrotic from normal bone. We present a case of lunate AVN ("Kienböck's disease") to illustrate the ability of MRI to identify necrotic bone in the wrist. We suggest that MRI is useful in diagnosing AVN in the wrist and that it may allow an earlier diagnosis of lunate AVN than is possible with standard radiographs.

Rocky mountain spotted fever: hepatic lesions in childhood cases.

We studied 16 fatal childhood cases of Rocky Mountain spotted fever (RMSF). Hepatic histologic lesions with statistically significant differences from age- and sex-matched controls were portal triaditis consisting of polymorphonuclear leukocytes and large mononuclear cells, portal vasculitis, sinusoidal leukocytosis, erythrophagocytosis by Kupffer cells, and gross hepatic weight. Hepatocellular necrosis, cholestasis, and congestion were not more frequent in RMSF than in controls. Using immunofluorescence microscopy, we were able to demonstrate rickettsial organisms in portal blood vessels and sinusoidal lining cells of 7 cases.

Factors affecting the sensitivity and specificity of the three-phase technetium bone scan in the diagnosis of reflex sympathetic dystrophy syndrome in the upper extremity.

The three-phase technetium bone scan has been recommended for use in the diagnosis of the reflex sympathetic dystrophy syndrome with a sensitivity and specificity of greater than 90%. A retrospective chart review was conducted of 63 patients who had three-phase technetium bone scan as part of a work-up for unexplained upper extremity pain, to determine the predictive value of the three-phase technetium bone scan in reflex sympathetic dystrophy syndrome, and what factors might affect it. The prevalence of definite or probable reflex sympathetic dystrophy syndrome, as assessed by Kozin's criteria, was 26% in this sample. The 3-hour delayed image demonstrated a sensitivity = 50%; specificity = 92%; positive predictive value = 67%, and negative predictive value = 84%. This was not improved using the data from the blood flow or pool phase. The sensitivity of 50% is lower than previous reports. The predictive value of the three-phase technetium bone scan was affected by the duration of symptoms and the age of the patient. Duration of symptoms less than 6 months, or ages more than 50 years substantially increased the sensitivity and positive predictive value of the three-phase technetium bone scan.

Comparison of Ca2+, Sr2+, and Mn2+ fluxes in mitochondria of the perfused rat heart.

The amount of readily exchangeable Ca2+ in mitochondria of an isolated working rat heart is less than 10 ng-ions/g heart. We therefore conclude that either no Ca2+ enters mitochondria or that the Ca+ which does enter is removed continuously. Using Sr2+ and Mn2+, we obtained evidence that the mitochondrial Na+-Ca2+ exchanger was indeed operational in releasing metal from mitochondria of the heart. When Ca2+ in the perfusate was replaced by Sr2+, we found that a significant amount of Sr2+ (approximately 100 ng-ions/g heart) entered mitochondria. When the heart then was returned to a Ca2+-containing perfusate, over 80% of the Sr2+ was washed out of mitochondria within 30 seconds. When low levels of Mn2+ were added to the perfusate, we found that Mn2+ accumulated in mitochondria irreversibly. This is evidence for the operation of the Na+-Ca2+ exchanger because Na+ was found to release Ca2+ and Sr2+ but not Mn2+ from isolated rat heart mitochondria. Our estimates indicate that when the Na+-Ca2+ exchanger is maximally operative, as in the Sr2+-perfused heart, the flux of Sr2+ through mitochondria is at most 10% of the total flux needed for the activation of contraction. The low level of Ca2+ in the mitochondria of Ca2+-perfused hearts suggests a much smaller flux of Ca2+ through the mitochondria in this case. We therefore conclude that mitochondria play little if any role in the beat-to-beat regulation of normal Ca2+ fluxes in the rat heart.

Pulmonary blastoma: an ultrastructural and histochemical study.

We present a unique case of pulmonary blastoma and describe its histology and ultrastructure. The stromal component exhibited bizarre multinucleated giant cells containing previously undescribed granules. These membrane-limited granules were eosinophilic, periodic acid-Schiff positive, diastase resistant, acid phosphatase and nonspecific esterase negative, immunohistologically negative for lysozyme, albumin, and gamma globulin, and often homogeneously electron dense. A similar electron-dense material accumulated in the rough endoplasmic reticulum of these stromal giant cells, suggesting that the material in the granules is synthetic. The material appeared to be a glycoprotein but was not alpha1-antitrypsin, alpha-fetoprotein, or human chorionic gonadotropin by immunohistologic techniques. These stromal cell granules differ from granules described in epithelial cells of other pulmonary blastomas but resemble granules found in some sarcomas.