Partitioning of niches among four species of orb-weaving spiders in a grassland habitat.

Partitioning of niches can play an important role in structuring faunal communities. We tested the hypothesis that differences between four species of orb-weaving spiders (Araneidae) in body size and the structure and position of their webs resulted in their partitioning the available prey. The study species are sympatric in a grassland habitat and included Argiope trifasciata (Forskål), Cyclosa turbinata (Walckenaer), Mangora gibberosa (Hentz), and Neoscona arabesca (Walckenaer). The spider species differed in body size, web diameter, height of web above the ground, spacing of mesh within webs, and the type of plant to which the web was attached. The spider species had a generalist diet and captured prey of multiple trophic levels. Nevertheless, the hypothesis was supported: the spider species differed in the types of prey that they captured. Partitioning of the available prey was influenced by body size, with larger spiders capturing larger prey, but not by the structure or position of their webs. Differences between spider species in niche may reduce competitive interactions and allow them to coexist in sympatry.

Thermal History of CBb Chondrules and Cooling Rate Distributions of Ejecta Plumes.

It has been proposed that some meteorites, CB and CH chondrites, contain material formed as a result of a protoplanetary collision during accretion. Their melt droplets (chondrules) and FeNi metal are proposed to have formed by evaporation and condensation in the resulting impact plume. We observe that the skeletal olivine (SO) chondrules in CBb chondrites have a blebby texture and an enrichment in refractory elements not found in normal chondrules. Because the texture requires complete melting, their maximum liquidus temperature of 1928 K represents a minimum temperature for the putative plume. Dynamic crystallization experiments show that the SO texture can be created only by brief reheating episodes during crystallization, giving a partial dissolution of olivine. The ejecta plume formed in a smoothed particle hydrodynamics simulation served as the basis for 3D modeling with the adaptive mesh refinement code FLASH4.3. Tracer particles that move with the fluid cells are used to measure the in situ cooling rates. Their cooling rates are ~10,000 K hr-1 briefly at peak temperature and, in the densest regions of the plume, ~100 K hr-1 for 1400-1600 K. A small fraction of cells is seen to be heating at any one time, with heating spikes explained by the compression of parcels of gas in a heterogeneous patchy plume. These temperature fluctuations are comparable to those required in crystallization experiments. For the first time, we find an agreement between experiments and models that supports the plume model specifically for the formation of CBb chondrules.

Blends of Pheromones, With and Without Host Plant Volatiles, Can Attract Multiple Species of Cerambycid Beetles Simultaneously.

Pheromone components of cerambycid beetles are often conserved, with a given compound serving as a pheromone component for multiple related species, including species native to different continents. Consequently, a single synthesized compound may attract multiple species to a trap simultaneously. Furthermore, our previous research in east-central Illinois had demonstrated that pheromones of different species can be combined to attract an even greater diversity of species. Here, we describe the results of field bioassays in the northeastern, midwestern, southeastern, south-central, and southwestern United States that assessed attraction of cerambycids to a 'generic' pheromone blend containing six known cerambycid pheromone components, versus the individual components of the blend, and how attraction was influenced by plant volatiles. Nineteen species were attracted in significant numbers, with the pheromone blend attracting about twice as many species as any of the individual components. The blend attracted species of three subfamilies, whereas individual components attracted species within one subfamily. However, some antagonistic interactions between blend components were identified. The plant volatiles ethanol and α-pinene usually enhanced attraction to the blend. Taken together, these experiments suggest that blends of cerambycid pheromones, if selected carefully to minimize inhibitory effects, can be effective for sampling a diversity of species, and that plant volatiles generally enhance attraction. Such generic pheromone blends may serve as an effective and economical method of detecting incursions of exotic, potentially invasive species.

A DPA technique for simultaneously measuring bone, soft tissue, and fat content.

Although conventional dual photon absorptiometry (DPA) techniques can be used to estimate fat and soft tissue content, such estimates are not possible where bone is present. We propose a method that can make these estimates in the presence of bone in the extremities of the body. The combination of this method with the conventional method should yield fat and soft tissue composition from most points within the body. The proposed technique simultaneously measures thicknesses of bone, soft tissue, and fat. These thicknesses are determined of bone, soft tissue, and fat. These thicknesses are determined from a combination of gamma-ray transmission data at two energies and a measurement of total tissue thickness. To test the technique, a feasibility study was performed with known thicknesses of aluminum (simulating bone), lucite (simulating tissue), and polyethylene (simulating fat). A variety of thicknesses of each material were employed (Al: 0-1.3 cm, lucite: 0-5 cm, polyethylene: 0-5 cm). The accuracies (standard errors of the estimates) of the calculated versus true thicknesses of aluminum, lucite, and polyethylene were 0.6%, 2.6%, and 2.5%, respectively. The estimates of "bone" thickness were insensitive to the presence of varying thicknesses of "fat." (In contrast, application of the conventional DPA method to the same gamma-ray transmission data yielded underestimates in "bone" thickness due to "fat" by as much as 11%.) For a 60 minute (whole body) scan time, the reproducibility of the measurements of the thicknesses of aluminum, lucite, and polyethylene were 0.4%, 1.0%, and 1.3%, respectively. All of these values are in a clinically useful range.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnostic performance of magnetic resonance imaging for the diagnosis of rotator cuff tears using supplemental images in the oblique sagittal plane.

RATIONALE AND OBJECTIVES: The authors evaluated the diagnostic utility of supplemental imaging in the oblique sagittal (OS) plane for the magnetic resonance imaging (MRI) diagnosis of rotator cuff tears. METHODS: Two radiologists with varying levels of MRI experience blindly reviewed shoulder MR examinations of 50 patients for rotator cuff tears. Shoulder examinations were interpreted twice, initially using only double-echo spin-echo images obtained in the oblique coronal (OC) plane and later using double-echo spin-echo images obtained in the both the OC and OS planes. Tears were characterized according to size, location, and extent, and levels of diagnostic confidence were evaluated. RESULTS: Sensitivity and specificity of MR for the diagnosis of rotator cuff tear was 85% and 80%, respectively, with the OC series increasing to 95% and 93%, respectively with OCOS scans. However, these increases were not statistically significant. Receiver operating characteristic (ROC) curves suggest a trend toward increased diagnostic confidence when supplemental OS scans are available, especially for the less experienced reader. Characterization of rotator cuff tears was not improved with additional OS images. CONCLUSIONS: Supplemental OS scans did not demonstrate a definite improvement in diagnostic accuracy for rotator cuff tears compared to OC scans alone. Estimations based on sample size calculations indicate that a much larger population of patients would be needed to show a statistically significant difference.

Gallstone susceptibility to in vitro fragmentation by a 480-nm pulsed dye laser. Correlation with computed tomography characteristics.

The object of this investigation was to determine gallstone susceptibility to laser lithotripsy and to discover whether this susceptibility is related to the computed tomography (CT) appearance of gallstones. Gallstones collected from surgery were scanned by CT and classified as homogeneously dense (greater than 90 Hounsfield units [HU]), homogeneously faint (30-60 HU), or rimmed. Sixty stones were subjected to laser energy at 20, 40, 60, 80, or 100 mJ. Fracture and fragmentation (all particles less than 2 mm) were assessed in relation to the energy level setting and number of laser pulses delivered. The authors found that a 480-nm, flashlamp-pumped pulsed dye laser can fragment completely all the types of human gallstones that were tested, although there is significant variability in gallstone susceptibility to laser lithotripsy. This susceptibility varies with CT appearance: dense stones require fewer pulses and lower energies for fracture and fragmentation, compared to faint or rimmed stones. The authors anticipate that CT characterization of gallstones may be a clinically useful screening tool before laser lithotripsy.

Theoretical considerations for optimizing intensity differences between primary musculoskeletal tumors and normal tissue with spin-echo magnetic resonance imaging.

In the radiographic assessment of primary musculoskeletal tumors, it is important for therapy planning to accurately define the extent of a tumor. Using a double spin-echo pulse sequence, the T1 and T2 relaxation times and relative hydrogen densities of several neoplastic tissues and of several normal tissues in four patients were measured. Neoplasms measured included one fibrosarcoma, two osteosarcomas, and one giant cell tumor. Normal tissues measured included normal muscle, fat, and bone marrow. Using a mathematical model of the double spin-echo pulse sequence, the intensity difference between each tumor and each normal tissue for multiple values of TR and TE was calculated. These calculated intensity differences were then used to plot isodifference contour curves for each tissue pair. These plots enabled us to pick combinations of TR and TE that optimized the signal difference between tumor and normal tissue. When comparing tumor with predominantly fatty tissue such as marrow or subcutaneous fat, optimal signal difference in our imager occurred at a TR of 600 to 800 msec and a very short TE. When comparing tumor with muscle, optimal signal difference occurred with very long TR times, and TE times ranging from 30 to 90 msec. These preliminary results suggest that an optimal scanning protocol for primary musculoskeletal tumors should contain at least two different pulse sequences with widely separated TR values (500 and 2000 msec in our instrument), and short to intermediate values of TE (28 and 56 msec in our instrument). It is believed that analysis of isodifference contour plots is a useful method for optimizing intensity differences between any two tissue types.

High resolution sonography of the menisci of the knee.

High-resolution real-time ultrasonography (5, 7.5, and 10 MHz) was used to examine the menisci of the knee in ten normal volunteers and in ten patients with knee injuries. The posterior horns of the medial and lateral menisci were easily demonstrated. Normal anatomy and pathologic changes could be imaged in the menisci, capsular ligaments, and articular cartilage. While the menisci were seen in all subjects, the weight-bearing portion of the femoral articular cartilage could not be seen in several of the symptomatic patients who could not flex their knees. Ultrasound promises to be a useful, noninvasive adjunct to conventional techniques in evaluating the injured knee--especially in assessing the posterior horns of the menisci, an area difficult to assess with arthroscopy.

Gastric carcinoid tumor. Its occurrence with ossification and diffuse argyrophil-cell hyperplasia.

A case of two gastric carcinoid tumors accompanied by diffuse argyrophil-cell hyperplasia occurred in a 39-year-old woman. One of the gastric carcinoid tumors demonstrated stromal ossification. Diffuse argyrophil-cell hyperplasia accompanied by gastric carcinoid tumors has been reported previously. The significance of this association is unknown.

Optimizing pulse sequences for magnetic resonance imaging of the musculoskeletal system.

On the surface, pulse sequence optimization seems like a difficult problem because of the many variables involved. In practice, however, the simple strategy of obtaining both T1- and T2-weighted images of the body part in question is adequate in most musculoskeletal imaging. This strategy virtually guarantees the production of images with adequate contrast between normal and abnormal tissue, no matter which of the common background tissues is considered. Although intravenous contrast agents can improve the already excellent contrast between musculoskeletal tissues, it is too early to tell the exact role they will play in the work-up of musculoskeletal disease.

Artifacts, normal variants, and imaging pitfalls of musculoskeletal magnetic resonance imaging.

This article is an early attempt to catalogue some of the many artifacts, normal variants, and imaging pitfalls that the authors have seen in musculoskeletal MRI. The study of such phenomena is potentially very rewarding and may help to prevent some cases of misdiagnosis with MRI.

Ultrasonography of the knee.

Sonography is a useful modality in the diagnosis of a wide variety of knee disorders, including lesions of the articular cartilage, tendons and ligaments, menisci, synovial space, and adjacent vessels and muscles. Sonography is noninvasive, rapidly performed, widely available, readily accepted by patients, uses no ionizing radiation, and is relatively inexpensive compared to other conventional imaging studies of the menisci, making it a potentially attractive screening examination for knee injuries. Although it is difficult to state the exact place of sonography in the diagnostic workup of knee disorders, we feel that sonography is vastly underutilized. With additional refinements in ultrasound technology and scanning techniques, we expect further expansion of its role in the evaluation of the knee.

Magnetic resonance imaging of internal derangement of the temporomandibular joint.

MRI is currently capable of diagnosing anterior derangements of the temporomandibular joint. Although large prospective studies comparing MRI with conventional modalities have not yet been done, early evidence suggests that findings seen on high-resolution surface coil MR images correlate very well with CT, arthrographic, and surgical findings. Much additional work will need to be performed before MRI of the temporomandibular joint becomes a standard diagnostic tool. However, we believe strongly that it will begin to replace arthrography and CT for diagnosing internal derangements within the next few years.

Magnetic resonance imaging of musculoskeletal neoplasms.

MRI has been shown to be very useful in the work-up of musculoskeletal neoplasms. The lack of ionizing radiation, the superb contrast resolution, and the ability to directly scan the sagittal and coronal planes make MRI a very attractive imaging mode for treatment planning. With spin-echo MRI, maximum contrast between tumor and fatty tissues generally occurs with short TR and TE times (T1-weighted images). Likewise, maximum contrast between tumor and muscle, tendon, or ligaments occurs with long values of TR and TE (T2-weighted images). Early experience suggests that the already exceptional contrast resolution seen with MRI can be improved even more with the administration of intravenous contrast agents. Just as with CT, fatty tumors can usually be easily distinguished from other tissue types with MRI by means of their differential intensity behavior at different pulse sequences. Fluid-filled tumors, such as unicameral bone cysts or aneurysmal bone cysts may be suspected in the same manner, especially if a fluid-fluid level is seen within the lesion. Otherwise, MRI has not been useful so far in noninvasively determining the histologic type of tumors. Our experience and that of others suggests that MRI is equal or superior to CT in the work-up of musculoskeletal neoplasms. This is especially striking when it is remembered that one is comparing an immature MRI technology with a mature CT technology. Although CT presently has a central role in the staging of musculoskeletal tumors, MRI will shortly supplant it in many cases.

Repairs of the rotator cuff. Correlation of functional results with integrity of the cuff.

We evaluated the results of 105 operative repairs of tears of the rotator cuff of the shoulder in eighty-nine patients at an average of five years postoperatively. We correlated the functional result with the integrity of the cuff, as determined by ultrasonography. Eighty per cent of the repairs of a tear involving only the supraspinatus tendon were intact at the time of the most recent follow-up, while more than 50 per cent of the repairs of a tear involving more than the supraspinatus tendon had a recurrent defect. Older patients and patients in whom a larger tear had been repaired had a greater prevalence of recurrent defects. At the time of the most recent follow-up, most of the patients were more comfortable and were satisfied with the result of the repair, even when they had sonographic evidence of a recurrent defect. The shoulders in which the repaired cuff was intact at the time of follow-up had better function during activities of daily living and a better range of active flexion (129 +/- 20 degrees compared with 71 +/- 41 degrees) compared with the shoulders that had a large recurrent defect. Similar correlations were noted for the range of active external and internal rotation and for strength of flexion, abduction, and internal rotation. In the shoulders in which the cuff was not intact, the degree of functional loss was related to the size of the recurrent defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Analytical chemistry of cyclamates: a review.

The analytical chemistry of cyclamates is reviewed, the emphasis being on methods of assay, tests for impurities and methods of determination in food and drug products.

The fate of pharmaceutical chemicals in the aquatic environment.

Increased demands for potable water, especially where supplies are drawn from lowland rivers has necessitated a greater degree of water re-use. As water undertakings have a duty to maintain the wholesome quality of potable water supplies, increasing concern is being expressed over the presence of organic micro-contaminants (contaminants found at microgram litre-1 concentrations). This study outlines some of the problems encountered in assessing the risk from pharmaceutical chemicals which might enter the water cycle from domestic and industrial sources. Analytical chemistry was of value for only a few of the 200 compounds studied. However, much useful information was derived from the human metabolic routes of the drugs and is collated in Appendix I. Biodegradation studies and other ecotoxicity/environmental toxicology data may be required to a greater extent in the future. Particular consideration is given to vulnerable sections of the population.

Magnetic resonance imaging of the musculoskeletal system.

MRI is a complementary technique to CT in the examination of the spine, the hip, and musculoskeletal tumors. In some cases, it provides diagnostic information not available with any other modality, including CT. MRI has the potential to be very useful in the assessment of various marrow-based disorders and may someday obviate the need for contrast-aided studies of ligaments, tendons, and cartilage.

Lung-volume reduction surgery for diffuse emphysema: radiologic assessment of changes in thoracic dimensions.

Patients with severe, diffuse emphysema may be candidates for pneumectomy (lung-volume reduction surgery, LVRS) to improve lung and respiratory muscle function. To identify candidates who might benefit from this surgery, it is necessary to understand how lung volumes and respiratory function are effected. In this article, the authors demonstrate a significant difference in lung size on chest radiographs obtained before and after surgery. Thirty-five of 71 consecutive patients undergoing LVRS had both preoperative and postoperative chest radiographs and pulmonary function tests available for retrospective review. Preoperative and postoperative measurements of lung height, transthoracic diameters, mediastinal width, heart size, diaphragmatic arc, and intercostal spaces were compared using paired t-tests. Radiographic measurements where also correlated with changes in lung volumes as measured by pulmonary function tests. Lung heights (right, left, mean lateral) and coronal diameter at the aortic arch were reduced after surgery (all p < 0.05). Forced vital capacity, forced expiratory volume in 1 second (FEV1), and vital capacity increased, and total lung capacity and residual volume decreased after surgery (all p < 0.05). Left lung height showed a significant correlation (p = 0.025) with FEV1; all other correlations between radiographic changes and pulmonary function test changes were not significant. The explanation for improved lung function in patients after LVRS is not completely clear and is probably multifactorial. Radiologic alterations reflect anatomic changes caused by surgery and support the theory that modifications of chest wall configuration occur and are likely responsible, in part, for improved symptomatology and respiratory function.

Parasites and condition of coexisting populations of white-tailed and exotic deer in south-central Texas.

We examined the parasites and physical condition of coexisting white-tailed deer (Odocoileus virginianus), axis deer (Axis axis), fallow deer (Dama dama), and sika deer (Cervus nippon) on the YO Ranch (Kerr County, Texas, USA) during December 1982 to January 1984. White-tailed deer harbored 12 species of parasites. Exotic deer were infected with nine species of parasites. All parasites recovered from exotic deer and white-tailed deer have been reported from white-tailed deer. Exotic deer had higher condition ratings than white-tailed deer.