p53 is required for radiation-induced apoptosis in mouse thymocytes

The p53 tumour suppressor gene is the most widely mutated gene in human tumorigenesis. p53 encodes a transcriptional activator whose targets may include genes that regulate genomic stability, the cellular response to DNA damage, and cell-cycle progression. Introduction of wild-type p53 into cell lines that have lost endogenous p53 function can cause growth arrest or induce a process of cell death known as apoptosis. During normal development, self-reactive thymocytes undergo negative selection by apoptosis, which can also be induced in immature thymocytes by other stimuli, including exposure to glucocorticoids and ionizing radiation. Although normal negative selection involves signalling through the T-cell receptor, the induction of apoptosis by other stimuli is poorly understood. We have investigated the requirement for p53 during apoptosis in mouse thymocytes. We report here that immature thymocytes lacking p53 die normally when exposed to compounds that may mimic T-cell receptor engagement and to glucocorticoids but are resistant to the lethal effects of ionizing radiation. These results demonstrate that p53 is required for radiation-induced cell death in the thymus but is not necessary for all forms of apoptosis.

Do all programmed cell deaths occur via apoptosis?

During development, large numbers of cells die by a nonpathological process referred to as programmed cell death. In many tissues, dying cells display similar changes in morphology and chromosomal DNA organization, which has been termed apoptosis. Apoptosis is such a widely documented phenomenon that many authors have assumed all programmed cell deaths occur by this process. Two well-characterized model systems for programmed cell death are (i) the death of T cells during negative selection in the mouse thymus and (ii) the loss of intersegmental muscles of the moth Manduca sexta at the end of metamorphosis. In this report we compare the patterns of cell death displayed by T cells and the intersegmental muscles and find that they differ in terms of cell-surface morphology, nuclear ultrastructure, DNA fragmentation, and polyubiquitin gene expression. Unlike the T cells, which are known to die via apoptosis, we find that the intersegmental muscles display few of the features that characterize apoptosis. These data suggest that more than one cell death mechanism is used during development.

Pharmacological profile of the 5-hydroxytryptamine receptor of Fasciola hepatica body wall muscle

5-HT is a candidate for the excitatory transmitter at the neuromuscular junction in trematodes including Fasciola hepatica. This study has determined the response of a muscle strip preparation from Fasciola hepatica to 5-HT and a range of agonists that distinguish between the vertebrate receptor 5-HT subtypes. 5-HT increased the resting tone and the rhythmic activity of the muscle strip. Of the 19 compounds tested, only 10 had an effect similar to 5-HT and all but 2 of these were tryptamine compounds. 5-HT was more potent than tryptamine whilst 4-OH-tryptamine had no effect, suggesting that the response is mediated by a 5-HT rather than a tryptamine receptor. 5-Fluorotryptamine and 5-carboxyamidotryptamine were the most potent agonists. 8-OH-DPAT also mimicked the effect of 5-HT, though less potently. Assuming that these agents elicit their response through a common receptor, this suggests the presence of a 5-HT receptor with similar properties in terms of agonist recognition as the vertebrate 5-HT1 class of receptor involved in controlling Fasciola muscle motility.

Two-dimensional array transducers using thick film connection technology

A connection technique for two-dimensional array ultrasound transducers developed by combining a conductive lambda/4 mismatching layer with a multi-layer ceramic (MLC) connector using thick-film microelectronic technology is described. The connector consists of 20 thick films of alumina and screen printed metallization with customized interconnections between the layers called vias. Ten ground layers are interleaved between ten signal layers to reduce elecrical crosstalk. A lambda/4 mismatching layer of conductive epoxy is bonded between each PZT element and the silver metal pad of the MLC connector to provide an effective low impedance backing. In the current configuration, a 16x16 transducer array, 0.6 mm element spacing, is expanded to a 16x16 grid of connector pins at a standard spacing of 2.5 mm. Vector impedance, sensitivity, bandwidth, interelement uniformity, and crosstalk are all in good agreement with arrays of conventional fabrication. However, an array with MLC connector can be fabricated more quickly independent of the number of elements.

Two dimensional ultrasonic beam distortion in the breast: in vivo measurements and effects

Two dimensional arrival time data was obtained for the propagation of ultrasound across the breasts of 7 female volunteers. These profiles were extracted through the use of cross-correlation measurements and a simulated annealing process that maintained phase closure while aligning the data. The phase aberration measured in two dimensions had a larger magnitude than previously reported phase aberration measured in one dimension in the breast. A point spread function generation computer program was used to demonstrate the system response degrading effects of the measured phase aberration and the usefulness of current one dimensional phase aberration correction techniques. The results indicate that two dimensional correction algorithms are necessary to restore the system performance losses due to phase aberration.

Complications encountered in the treatment of pilon fractures

A total of 52 tibial plafond (pilon) fractures in 51 patients were retrospectively reviewed from the years 1985-1990 to define the rate of complications encountered during their management. All fractures were managed under faculty supervision at a level I trauma center and its two affiliated institutions. The follow-up period was scrutinized to determine whether or not a complicating event occurred. Major local complications, termed events, were defined as those requiring unplanned surgery due to infection, wound breakdown with subsequent flap coverage, and failure of fixation or fracture healing. Reduction accuracy and final clinical results were not specifically examined. There were 14 (27%) type I, 17 (33%) type II, and 21 (40%) type III Ruedi-Allgower fracture types. The majority (79%) of the fractures were closed and 89% were treated by open reduction and internal fixation. The overall local complication rate was 54%. A total of 21 (40%) pilon fractures (six type I, six type II, and nine type III) had major local complicating events requiring 77 additional operations. Patient follow-up time ranged from 1 week (the occurrence of a major local complication) to 200 weeks (no complication), with a mean of 67 weeks. Kaplan-Meier survivorship (K-M) analysis was utilized to statistically estimate the complication rate in this patient population accounting for the occurrence of censored events. The K-M-determined event rate was 42 +/- 7%. Ten (of 21) pilon fractures had events by 3 weeks, while only two occurred beyond 40 weeks.

Phylogenetic relationships of chemoautotrophic bacterial symbionts of Solemya velum say (Mollusca: Bivalvia) determined by 16S rRNA gene sequence analysis

The protobranch bivalve Solemya velum Say (Mollusca: Bivalvia) houses chemoautotrophic symbionts intracellularly within its gills. These symbionts were characterized through sequencing of polymerase chain reaction-amplified 16S rRNA coding regions and hybridization of an Escherichia coli gene probe to S. velum genomic DNA restriction fragments. The symbionts appeared to have only one copy of the 16S rRNA gene. The lack of variability in the 16S sequence and hybridization patterns within and between individual S. velum organisms suggested that one species of symbiont is dominant within and specific for this host species. Phylogenetic analysis of the 16S sequences of the symbionts indicates that they lie within the chemoautotrophic cluster of the gamma subdivision of the eubacterial group Proteobacteria.

Internal carotid artery occlusion: diagnostic inaccuracy of the ocular pneumoplethysmography

The diagnosis of internal carotid artery (ICA) occlusion has serious management and prognostic consequences. The accuracy of noninvasive techniques in this setting remains questionable, with the result that contrast arteriography remains the diagnostic method of choice in patients in whom ICA occlusion is suspected. Ocular pneumoplethysmography-Gee (OPG-Gee) is one of the noninvasive methods that is still utilized extensively in the evaluation of carotid artery disease. In order to determine the real utility of OPG-Gee, the authors conducted a retrospective comparison of the results of OPG-Gee and arteriography in 26 patients (52 internal carotid arteries) who had undergone both examinations. [table: see text] With the angiography results as the standard of comparison, 4 incorrect diagnoses were obtained by OPG-Gee, thus yielding an overall accuracy of 92 for this method. However, duplex ultrasonography, also performed in the same 26 patients, correctly identified the 2 ICA occlusions defined by angiography and further demonstrated patency in the 48 arteries so shown by angiography. The authors conclude from this experience that OPG-Gee is less reliable than duplex ultrasonography in the diagnosis of ICA occlusion. Furthermore, despite the 92% overall accuracy of their results with OPG-Gee, the occurrence of both false-positive and false-negative results renders this examination modality suspect in the diagnosis of ICA occlusion.

Whole-bowel irrigation as a treatment for acute lithium overdose

STUDY OBJECTIVE

To determine if gastrointestinal decontamination using whole-bowel irrigation (WBI) was an effective treatment for acute ingestion of sustained-release lithium.

METHODS

In a two-phase, crossover protocol, ten normal volunteers ingested in each phase 0.80 mEq/kg sustained-release lithium carbonate. In the second phase, WBI was begun one hour after lithium ingestion, and 10 L of polyethylene glycol solution were administered over five hours. Serum samples were collected every half hour for six hours, every hour for an additional six hours, and then every 24 hours for as long as 72 hours after ingestion. These samples were analyzed for lithium concentration. The area under the lithium serum concentration-versus-time curve was calculated for each phase.

RESULTS

The average area under the lithium serum concentration-versus-time curve in the WBI phase was 67% +/- 11% less than that in the control phase (P less than .0005 using a two-tailed Student's t test). The mean serum lithium concentration was significantly decreased (P = .03) within one hour of beginning WBI.

CONCLUSION

WBI is an effective treatment for acute ingestion of sustained-release lithium. We recommend it as the decontaminant procedure of choice in this situation.

High-speed ultrasound volumetric imaging system. I. Transducer design and beam steering

Transducer design and phased array beam steering are developed for a volumetric ultrasound scanner that enables the 3-D visualization of dynamic structures in real time. The authors describe the design considerations and preliminary evaluation of a high-speed, online volumetric ultrasound imaging system that uses the principles of pulse-echo, phased array scanning with a 2-D array transducer. Several 2-D array designs are analyzed for resolution and main lobe-side lobe ratio by simulation using 2-D fast Fourier transform methods. Fabrication techniques are described for 2-D array transducer. Experimental measurements of pulse-echo point spread responses for 2-D arrays agree with the simulations. Measurements of pulse-echo sensitivity, bandwidth, and crosstalk are included.

High-speed ultrasound volumetric imaging system. II. Parallel processing and image display

For pt.I see ibid., vol.38, no.2, p.100-8 (1991). The authors describe the design, application, and evaluation of parallel processing to the high-speed volumetric ultrasound imaging system. The scanner produces images analogous to an optical camera or the human eye and supplies more information than conventional sonograms. Potential medical applications include improved anatomic visualization, tumor localization, and better assessment of cardiac function. The system uses pulse-echo phased array principles to steer a 2-D array transducer of 289 elements in a pyramidal scan format. Parallel processing in the receive mode produces 4992 scan lines at a rate of approximately 8 frames/s. Echo data for the scanned volume is presented online as projection images with depth perspective, stereoscopic pairs, or multiple tomographic images. The authors also describe the techniques developed for the online display of volumetric images on a conventional CRT oscilloscope and show preliminary volumetric images for each display mode.

Real-time, three-dimensional echocardiography: feasibility and initial use

The purpose of this article is to review new approaches to three-dimensional acquisition and presentation of echocardiographic data. New three-dimensional phased-array devices hold great promise for the development and application of new descriptors for left ventricular performance, myocardial perfusion, and other important indices of cardiac function.

Real time volumetric ultrasound imaging system

A real time volumetric ultrasound imaging system has been developed for medical diagnosis. The scanner produces images analogous to an optical camera and supplies more information than conventional sonograms. Potential medical applications include improved anatomic visualization, tumor localization, and better assessment of cardiac function. The system uses pulse-echo phased array principles to steer a two-dimensional array transducer of 289 elements in a pyramidal scan format. Parallel processing in the receive mode produces 4992 scan lines at a rate of approximately 8 frames/second. Echo data for the scanned volume is presented as projection images with depth perspective, stereoscopic pairs, multiple tomographic images, or C-mode scans.

Specificities compared for a radioreceptor assay and a radioimmunoassay of atrial natriuretic peptide

The main active form of atrial natriuretic peptide (ANP) in the circulation is alpha ANP(1-28) [gamma-ANP(99-126)], although some active and inactive metabolites are also though to be present. Some immunoassays for alpha ANP reportedly detect inactive metabolites, as determined by their comparison with results by receptor assay, which would lead to misleading results for alpha ANP(1-28) measurements. Here we compare a radioreceptor assay (RRA) and a radioimmunoassay (RIA) for alpha ANP and show that their results correlate very well with regard to specificity and that the RIA appears to detect only the active circulating form of alpha ANP(1-28).

Specificities compared for a radioreceptor assay and a radioimmunoassay of atrial natriuretic peptide

The main active form of atrial natriuretic peptide (ANP) in the circulation is alpha ANP(1-28) [gamma-ANP(99-126)], although some active and inactive metabolites are also though to be present. Some immunoassays for alpha ANP reportedly detect inactive metabolites, as determined by their comparison with results by receptor assay, which would lead to misleading results for alpha ANP(1-28) measurements. Here we compare a radioreceptor assay (RRA) and a radioimmunoassay (RIA) for alpha ANP and show that their results correlate very well with regard to specificity and that the RIA appears to detect only the active circulating form of alpha ANP(1-28).

B cell differentiation and lymphocyte surface phenotype in late onset hypogammaglobulinaemia

Lymphocyte function and cell surface phenotype were examined in fifteen patients with late onset hypogammaglobulinaemia. The percentage of surface immunoglobulin-positive B cells in fourteen of the fifteen patients was in the normal range. Patients' B cells expressed MHC class II antigens at normal levels. For one patient, there was relatively high sIgD and low sIgM expression on B cells; the rest of the patients did not differ from controls in surface immunoglobulin density. The proportion of B cells positive for CD5 in patients was comparable to normal controls, and considerably less than in cord blood. However, the pattern of immunoglobulin isotype secretion in vitro by patients' B cells closely paralleled responses of cord blood B cells. Spontaneous secretion of IgM and IgG by patients' B cells was very low. Following polyclonal activation in the presence of autologous T cells, cells from thirteen patients secreted IgM within the normal range in response to at least one activator. The response of patients' purified B cells to IL-2 and gamma-IFN was variable. For four of six tested, B cells cultured with IL-2 and gamma-IFN together with polyclonal activators secreted normal levels of IgM. B cells from the other two patients secreted little or no IgM in response to these cytokines. For fourteen patients, IgG secretion following polyclonal activation remained low both when B cells were cultured with T cells or with a combination of IL-2 and gamma-IFN. IgG subclass imbalance was seen in one patient, whose cells secreted an unusually high proportion of IgG3, and undetectable IgG2 and IgG4; this pattern was consistent whether T cell help was provided by autologous or allogeneic T cells. Similarly purified B cells from this patient showed deficient IgG2 and IgG4 production in response to IL-2 and gamma-IFN.

Experimental results with a real-time adaptive ultrasonic imaging system for viewing through distorting media

An online adaptive phased-array ultrasonic imaging system capable of markedly improving the detectability of targets viewed through inhomogeneous media is described. An online adaptive phase correction technique implemented on a research phased-array scanner is described. The theoretical basis for this technique is presented by describing the relationship between the magnitude of phase aberrations and the regional brightness of speckle and pointlike targets. The system currently generates a corrected image in approximately 0.1 s and utilizes no prior knowledge of the aberrating media or the target. The adaptive imaging algorithm uses regional target brightness as a quality factor. The results of in vitro tests with this system using electronic and physical aberrators for both diffuse and pointlike targets are presented.

Anthropomorphic cardiac ultrasound phantom

A new phantom is described which simulates the human cardiac anatomy for applications in ultrasound imaging, ultrasound Doppler, and color-flow Doppler imaging. The phantom consists of a polymer left ventricle which includes a prosthetic mitral and aortic valve and is connected to a mock circulatory loop. Aerated tap water serves as a blood simulating fluid and ultrasound contrast medium within the circulatory loop. The left ventricle is housed in a Lexan ultrasound visualization chamber which includes ultrasound viewing ports and acoustic absorbers. A piston pump connected to the visualization chamber by a single port pumps degassed water within the chamber which in turn pumps the left ventricle. Real-time ultrasound images and Doppler studies measure flow patterns through the valves and within the left ventricle.

Phase aberration correction in medical ultrasound using speckle brightness as a quality factor

Medical ultrasonic images are degraded by tissues with inhomogeneous acoustic velocities. The resulting phase aberration raises the off-peak response of the imaging system's point spread function (PSF), decreasing dynamic range. In extreme cases, multiple images of a single target are displayed. Phase aberration may become a limiting factor to image quality as ultrasonic frequency and aperture size are increased in order to improve spatial resolution. A method is proposed to correct for unknown phase aberration, which uses speckle brightness as a quality factor. The phase delays of a phased array transducer are modified, element by element, to maximize mean speckle brightness in a region of interest. The technique proposed is analogous to the correction technique used by Muller and Buffington [J. Opt. Soc. Am. 64 (9), 1200-1209 (1974)] to adaptively focus incoherent optical telescopes. The method is demonstrated using a computer model with several different simulated aberration profiles. With this model, mean speckle brightness is calculated using the two-dimensional PSF. Experiments have also been conducted in which speckle brightness is shown to increase as the phase delays of an ultrasonic scanner are modified in order to compensate for a rippled aberrating layer made of silicone rubber. The characteristics of the proposed method, and the possibility of employing it clinically to correct for unknown inhomogeneities in acoustic velocity, are discussed.

Simulation studies of dual-energy x-ray absorptiometry

Computer simulations were performed to predict the performance characteristics of dual-energy x-ray absorptiometry. K-edge filter techniques were analyzed in detail and compared to 153Gd sources in terms of output intensity, precision, patient dose, image contrast, beam hardening, and marrow fat effects. Similar analyses were performed for two dual-kV techniques that have been reported in the literature. The simulations indicate that K-edge filter techniques, or a dual-kV technique combined with K-edge filtering, can provide performance capabilities that equal or exceed those achievable with 153Gd systems. A (70/140) dual-kV technique with conventional (Al or Cu) filtration also has advantages in terms of source output intensity, but is 2-3 X inferior to the K-edge techniques and 153Gd in terms of patient dose and beam-hardening effects.

Marketing strategies of nurse practitioners in New York State

As competition within the health care field increases, marketing strategies are becoming more important for all members of the health care team, including nurse practitioners. The purpose of this research was to identify marketing strategies being used by nurse practitioners in New York state. A total of 285 practitioners responded to a survey containing questions related to marketing techniques traditionally used in the business world: service differentiation, market segmentation and practice promotion. A majority of respondents did not report using many of the marketing strategies contained in the survey, although most nurse practitioners did report identifying themselves as primary care providers in one-on-one interactions with clients. Significantly higher marketing scores were found for nurse practitioners who attended a workshop or seminar on marketing strategies, had three or more years of experience, or who practiced in private outpatient settings.

Multiple, annular, erythematous lesions of the oral mucosa

Benign migratory stomatitis is a relatively rare entity, but because of its benign nature and clinical characteristics, it should be easily recognized by the general practitioner. Biopsy is usually not indicated and treatment consists of reassuring the patient that the lesions are benign even though they may disappear, reappear, and change location; the patient should report back for periodic follow-up.

Properties of acoustical speckle in the presence of phase aberration. Part II: Correlation lengths

In recent years, analysis of the second order statistics of ultrasound speckle has led to accurate prediction and measurements of the average speckle size in the transducer focal zone. In this paper, that work has been extended to the average speckle size as determined by the normalized autocovariance in the presence of transducer phase aberrations. In general, a phase aberration causes a narrowing of the main lobe of the normalized autocovariance in the lateral direction. However, the lateral speckle autocovariance also showed significant side lobes in the presence of phase aberrations, indicating that individual speckles in a region of interest are not independent but are correlated so that less information is present for the task of signal detection when a transducer phase aberration exists. The same evidence of correlated speckle was found in the near field of a transducer in the region of fine speckle texture. This explanation satisfies the quandary of poor detectability in the near field region where the speckle is fine but the lateral resolution is quite degraded. The axial speckle in the presence of phase aberrations showed a small increase in main lobe widths and no evidence of side lobes. Beginning in 1978, the analysis of the second order statistics of speckle images for the purpose of spatial compounding led to accurate measurement and prediction of the cross-correlation curve as a function of transducer aperture translation for purposes of spatial compounding. In this paper, that work has been extended to the presence of transducer phase aberrations. The existence of transducer phase aberrations causes significant increases in the rate of decorrelation of speckle interference patterns as a transducer is translated. This indicates that spatial compounding will result in quite significant improvements in area-wise SNR and low contrast lesion detection for the case of severe random aberrators or focal point errors.

Fundamental correlation lengths of coherent speckle in medical ultrasonic images

Refinements to previous analyses of the natural correlation lengths within simple images and between images to be compounded are presented. Comparison of theoretical and experimental results show very good agreement for the case of Rayleigh scattering media: the correlation length within a simple image is comparable to the resolution cell size; the correlation length between images to be spatially compounded is comparable to, but smaller than, the transducer on array aperture; and the correlation length between images to be frequency-compounded becomes a frequency comparable to their bandwidth. Complications arising from the presence of specular scattering or due to the presence of just a few scatterers are considered. It is shown that straightforward solutions exist for either of these problems taken by itself. When they occur in combination, calibration techniques may lead to unambiguous identification of the contributions to the scattering from diffuse or incoherent scattering and from specular or coherent scattering, and to estimation of the density of diffuse scatterers.

Prophylactic and therapeutic effects of ciclosporin A in murine Schistosomiasis mansoni: studies on bisexual and unisexual infections and the hepatic inflammatory response

Ciclosporin A (CsA), administered subcutaneously as 5 daily injections of 50 mg.kg-1, reduced the numbers of Schistosoma mansoni perfused from MF1 mice at 7 weeks post-infection. The timing of drug administration revealed that the antischistosomal effects were greater when CsA treatment coincided with or was within a few days of infection with the parasite. CsA exerted a clear prophylactic effect, which decreased with time and was virtually abolished by 4 months pre-infection. Adult worms treated in vivo were partially susceptible to CsA. In addition to its antiparasite action, CsA reduced hepatosplenomegaly due to schistosomiasis and diminished the granulomatous inflammatory response of mice to parasite eggs in the liver. The mode of action of CsA is not understood but evidence is presented that supports the proposition that the antiparasite effects are perhaps host-mediated.

Properties of acoustical speckle in the presence of phase aberration. Part I: First order statistics

The first order statistical properties of acoustical speckle patterns are studied as a function of several types of random and structured phase error. Such errors may arise from tissue velocity inhomogeneities or limitations in the acoustical imaging system. In this paper, we review the theory describing the statistical properties of speckle, describe a computer model which predicts the mean speckle brightness in the presence of phase aberrations, and report experiments in which we measure the effect of these aberrations on speckle brightness and variance. We find that the average speckle brightness is significantly reduced by even mild phase aberrations. The phase aberrations studied include focal point errors, random phase errors, and structured errors. Good agreement is found between experiment and computer simulation. We then discuss the implications of these results for imaging through aberrating media, tissue characterization and phase compensation methods.

The CD5+ B cell: a B cell lineage with a central role in autoimmune disease?

It is apparent that B cells are heterogeneous with respect to, for example, the antigens they express on their surface, and the stimuli to which they can respond. It is still unclear to what extent these differences relate to the stage of differentiation (eg. virgin B cells differing from activated B cells or memory cells), or whether distinct developmental lineages might exist. It has been proposed by some authors that, in the mouse, B cells expressing the ly-1 antigen constitute a separate lineage. In man also, a minor population of B cells expresses detectable levels of the CD5 antigen, but far less information is available about these cells. Interest in the CD5+ and ly-1+ B cell subpopulations has been further stimulated by the suggestion that these cells might play a special role in autoimmune disease. Although, in mouse, ly-1+ B cells differ in several respects from ly-1- B cells, the main evidence that they form a separate lineage derives from experiments in which ly-1+ B cells could not be reconstituted with adult bone marrow. It should be borne in mind that the situation is quite different in humans where, following bone marrow transplantation, CD5+ B cells are rapidly restored. Moreover, in the irradiated mice, at least in some of the experiments ly-1+ B cells were in fact reconstituted by adult bone marrow. Furthermore, at least in humans, expression of CD5 can sometimes be induced. There is, as yet, no good evidence that human CD5+ B cells form a distinct lineage, and it is possible that CD5 expression depends upon microenvironmental influences acting on the B cell during its differentiation. Several interesting properties have been attributed to ly-1+ B cells, including the ability to provide help to other B cells, and the secretion of autocrine factors. However there is also evidence that these features are not exclusive to B cells expressing ly-1. It has also been suggested that ly-1+ B cells might be long-lived. It is not yet known whether some of the properties of ly-1+ B cells might be a direct result of their expressing this antigen; this may become more clear when the function of CD5 is elucidated. The suggestion that the repertoire of ly-1+ B cells might be biased towards the expression of certain V genes is very interesting. Many of the hybridomas from neonatal mice produce antibodies which are multi-specific, and therefore well suited to form a first line of defence against potential pathogens.(ABSTRACT TRUNCATED AT 400 WORDS)

Reconstruction of blood vessels from x-ray subtraction projections: limited angle geometry

Several algorithms have been investigated for reconstructing blood vessels from a limited number of x-ray subtraction projections, distributed over a limited range of angles. Both computer simulations and an in vivo animal study were carried out. The best reconstruction performance was achieved using an algorithm that folded in two pieces of a priori knowledge of the vascular density distributions: (1) the object is dilute, consisting mainly of a void; and (2) the density distribution in the reconstructions is most likely to be non-negative. Both the signal-to-noise ratio (SNR) and the signal to out-of-focus blur were quantitated. Compared to tomosynthetic reconstruction (backprojection), the amount of residual blur from out-of-focus planes was significantly reduced with only a small penalty in diminished SNR. The combined effect resulted in significant qualitative image improvement for real arterial distributions as demonstrated in a canine arterial imaging example.

Dosage, timing, and route of administration of cyclosporin A and nonimmunosuppressive derivatives of dihydrocyclosporin A and cyclosporin C against Schistosoma mansoni in vivo and in vitro

The prophylactic and therapeutic effects of cyclosporin A (CsA) against percutaneous Schistosoma mansoni infection in MF1 mice were dose related and dependent on the temporal relationship between drug administration and infection. Antischistosomal activity, assessed by worm recovery from the host 6 weeks after infection, was most effective (complete worm elimination) when CsA was administered at the time of infection. Oral administration of CsA was less effective than subcutaneous injection, and no prophylactic activity was demonstrated by the former route. Derivatives of dihydrocyclosporin A and cyclosporin C, which have been reported to exert only poor immunosuppressive activity, exhibited efficacy against S. mansoni similar to that of CsA and were also less effective when given orally. Subcutaneous, but not oral CsA reduced cercarial skin penetration and transformation success; the derivative of dihydrocyclosporin A, however, was without effect. Moreover, CsA, but not the derivative of dihydrocyclosporin A, reduced the number of worms established after intraperitoneal injection of cercariae. These data provide further insight into the antischistosomal activity of cyclosporins, which appears to be distinct from their immunomodulatory properties, since parasite killing was retained both in immunologically disparate mice and with poorly immunosuppressive cyclosporin derivatives.

In vitro ultrasonic imaging of flow through prosthetic heart valves

A rapid, inexpensive, portable technique has been developed for the qualitative and semiquantitative evaluation of in vitro flow characteristics through prosthetic heart valves. The technique combines a cardiac pulse duplicator and any diagnostic, linear sequential array, ultrasonic imaging system. The pulse duplicator has been modified to include an acoustically transparent aortic section which contains the prosthetic valve to be evaluated. The acoustically transparent section is fabricated from Rho-c rubber and enables direct flow-imaging for several centimeters on both sides of the prosthesis. Aerated tap water is used as a contrast medium. Forward and reverse flow, laminar flow complex eddy patterns, regurgitation, and jets are easily observed in real time over a wide field of view. Time-exposure photography of sequential images and subsequent off-line calculations enable point-by-point determinations of flow velocities. This work allowed preliminary evaluations of four cardiac valves: Bjork-Shiley, St. Jude, caged disk, and Starr-Edwards.

Fast circular tomography device for cardiac imaging: image deflection mechanism and evaluation

A circular tomography system for cardiac imaging is described and measurements of the detector system are presented. Fast tomographic motion is obtained with a custom-made rotating focal spot X-ray tube combined with servo-operated scanning mirrors that deflect the optical image between a large field of view image intensifier and television camera. The motion of the deflection mirrors is locked in frequency and phase to the position of the focal spot with precision analog electronics. Initial measurements on the system components indicate that circular tomograms of the beating heart can be obtained in 1/60 s at rates as high as 30/s. Image degradation due to focal spot tracking error is minimal; however, the optical temporal lag of a P-20 type image intensifier output phosphor results in a factor of three contrast loss for millimeter-sized objects. A linear system analysis in conjunction with the measured temporal step response of the phosphor is in good agreement with the magnitude of this contrast loss.

A signal processing model of diagnostic x-ray scatter

A model of scatter is developed from a signal processing approach. The scattering process is viewed as a nonlinear filter (NLF), which transforms a two-dimensional signal representing phantom thickness into a two-dimensional signal of scattered radiation. The NLF point spread function (PSF) is derived from a single scattering model, using the principles of Compton scattering and x-ray attenuation. The PSF is characterized by three approximations: a constant geometric shape, a volume that depends on the phantom thickness, and a width that depends on the phantom-to-detector distance. This leads to a closed form expression for the scatter-to-primary ratio as a function of phantom thickness, field size, photon energy, source-to-phantom distance, and phantom-to-detector distance. The NLF model is compared with previously reported measurements using constant thickness phantoms, and discrepancies are discussed. The good agreement found between the NLF model and measured data shows that the functional dependence of scatter on the above parameters, previously only explained in terms of empirical models or Monte Carlo simulations, can be incorporated into a signal processing model.

Role of calcium and calmodulin in release of kallikrein and tonin from rat submandibular gland

We investigated the role of calcium and calmodulin as intracellular mediators of kallikrein and tonin release induced by norepinephrine (NE). We studied the secretion rate of kallikrein and tonin from submandibular gland of rat in response to NE in the presence or absence of calcium, two calcium blockers, and four different calmodulin antagonists. Submandibular gland slices were incubated in vitro, and glandular kallikrein and tonin secreted into the incubation medium were determined by direct radioimmunoassays and expressed as nanograms per minute per milligram tissue. NE (10(-5) and 10(-4) M) increased the kallikrein secretion from the control value of 8.2 +/- 2.6 to 134.9 +/- 41.4 (P less than 0.05) and to 191.2 +/- 62.7 (P less than 0.05), and the release of tonin from a basal rate of 3.5 +/- 0.6 to 51.5 +/- 9.1 (P less than 0.05) and to 64.4 +/- 13.7 (P less than 0.05). The deletion of calcium and addition of EGTA into the incubation medium significantly attenuated the secretion of kallikrein and tonin induced by NE. Nifedipine, at concentrations which inhibit voltage-dependent calcium channels, did not affect the release of kallikrein and tonin, and only a high concentration (10(-4) M) reduced the release. TMB-8, a blocker of intracellular calcium, had no effect either. Phenothiazines, triflupromazine (10(-6) M) and trifluoperazine (10(-4) M), decreased significantly the kallikrein release elicited by 10(-5) M NE.(ABSTRACT TRUNCATED AT 250 WORDS)

Intractable periocular hemangioma of infancy

A case of intractable giant periocular hemangioma in an infant is described. This histologically benign but locally invasive tumour is reviewed from the point of view of complications and available treatment modalities. The indications for therapy with a relatively new antifibrinolytic agent, tranexamic acid, are cited.

Explososcan: a parallel processing technique for high speed ultrasound imaging with linear phased arrays

The data acquisition rate in medical ultrasonic imaging devices is limited by the acoustic propagation velocity in the tissues. Typically in such machines the image lines are produced sequentially one line per transmitted pulse. A parallel processing scheme has been implemented which enables the data acquisition rate to increase by a factor of four through the simultaneous acquisition of four B-mode image lines from each individual broadened transmit pulse. The higher data rate can be used to increase the image frame rate to produce independent images that can be averaged in the image frame to reduce noise, or to produce a conventional image at standard video frame rates while reducing patient exposure. Alternatively, the field of view can be increased over that of a normal scan without sacrificing frame rate. These advantages are achieved with little reduction in the measured resolution. The design and performance of this device are described. A sample in vivo image is included.

Ultrasound speckle size and lesion signal to noise ratio: verification of theory

We compare predictions from our published theory of speckle cell size with recently published experimental results and a three dimensional computer simulation for the case of Gaussian pulses from spherically focused transducers in random media. The agreement is very good. We also compare our published theoretical predictions of the signal-to-noise ratio for a circular lesion in a speckle background with published "contrast to speckle ratio" data for anechoic cylindrical lesions in tissue mimicking material. Again, agreement is very good. The verification of these theoretical predictions has important implications for the evaluation of B-scan image quality and the study of tissue characterization.

Adult age differences in the use of story structure in delayed free recall

Thirty-six young adults (M age = 24.3 years) and 36 old adults (M age = 71.8 years) listened to four double-episode stories having either standard, interleaved, or scrambled structure. Two days later they were asked to recall the stories. Analysis of the mean number of nodes recalled revealed no age differences in the recall of standard and scrambled stories with both groups recalling the standard stories equally well and the scrambled stories equally poorly. However, for interleaved stories, young adults followed their pattern of recall for standard stories while old adults followed their pattern for scrambled stories. Also, the age groups differed in their pattern of additions and distortions, with old adults giving more for standard stories and young adults giving more for scrambled stories. Results appear to support models of age-related differences in memory processes and/or strategies when material must be reorganized or hierarchized. Possible metacognitive differences were also discussed; i.e., old adults may aim to tell the story interestingly, while young adults aim to tell it accurately.

A new congenital defect of platelet secretion: impaired responsiveness of the platelets to cytoplasmic free calcium

A 16-year-old boy with a bleeding disorder since infancy has a long bleeding time, normal platelet count and morphology and normal plasma factor-VIII activities. His platelets undergo normal shape change and primary aggregation in response to ADP but show defective 5-hydroxytryptamine (5-HT) secretion and aggregation in response to adrenaline, sodium arachidonate, U44069, PAF-acether, A23187 and low concentrations of collagen. Thrombin and higher concentrations of collagen produce a normal response. Secretion of beta-thromboglobulin and platelet factor 4 parallels that of 5-HT. Thromboxane B2 is produced normally in response to exogenous arachidonate and to stimulation by thrombin, collagen and A23187 in all concentrations tested. The patient's endoperoxides and thromboxane A2 aggregate aspirin-treated platelets, though his platelets are themselves unresponsive. Cyclic AMP is present at normal concentration in the patient's unstimulated platelet-rich plasma, and PGI2 inhibits platelet aggregation by ADP and thrombin in a normal dose-related plasma, and PGI2 inhibits platelet aggregation by ADP and thrombin in a normal dose-related manner. Platelet ultrastructure, 5-HT uptake and content of adenine nucleotides, platelet factor 4 and beta-thromboglobulin are all within normal limits. When the patient's platelets were loaded with the fluorescent dye quin 2, which serves as an indicator of cytoplasmic free calcium ions, their responses to thrombin, whether in the presence or virtual absence of extracellular Ca2+, were entirely normal in respect of free calcium ions, secretion, shape-change and aggregation. In response to ionomycin, however, a normal increase in free calcium ions was accompanied by normal shape-change but virtually no aggregation or 5-HT secretion. The platelet calmodulin content was normal. These findings show that the defect in this patient's platelets is of utilization of cytoplasmic Ca2+ for secretion and aggregation, rather than of Ca2+ uptake or mobilization of Ca2+ from intracellular storage sites. It is suggested that the most likely site of the defect is the phosphorylation of one of the proteins concerned in the secretory mechanism.

Cytoplasmic free Ca2+ in human platelets: Ca2+ thresholds and Ca-independent activation for shape-change and secretion

Cytoplasmic free [Ca2+], [Ca2+]i, was measured in human platelets using the intracellularly-trapped, fluorescent indicator quin2. Basal [Ca2+]i with the Ca2+ -ionophore ionomycin revealed apparent thresholds for shape-change, 5-HT release and aggregation of approx. 0.5 microM, 0.8 microM and 2 microM. Thrombin raised [Ca2+]i to 3 microM fast enough for the Ca2+ to have triggered the cell activation. However, thrombin released more 5-HT than ionomycin could, and in Ca2+ -free medium thrombin evoked shape-change and secretion even when [Ca2+]i remained near basal levels throughout, suggesting the existence of alternative triggers for shape-change and secretory exocytosis.

Angular response of miniature ultrasonic hydrophones

The voltage response of ceramic and polyvinylidene fluoride (PVDF) hydrophones was measured in the receive mode for angles of incidence ranging from 0 degrees to 90 degrees. The measurements were performed at 2.5, 3.5, 5.0, and 8.0 MHz; these frequencies are typical of those used in medical diagnosis. The results are compared to three theoretical models based on diffraction theory; correlation between the measured response and theoretical models is evident for some PVDF hydrophones but not for others, and not for any ceramic hydrophone. The effective radius, as defined in the AIUM-NEMA standard for diagnosis ultrasound, is calculated and compared to the test criteria established in that standard. All of the ceramic hydrophones and two of the five PVDF hydrophones failed to meet the criteria.

A contrast-detail analysis of diagnostic ultrasound imaging

For diagnostic ultrasound imaging, as in computed tomography, a feature of prime importance is the detection of focal lesions of varying size and contrast (echo amplitude) from surrounding tissue. This study describes a new tissue-stimulating phantom which has been used to measure the threshold detection of varying contrast, simulated lesions. The phantom consists of a block of tissue-mimicking gelatin which contains a row of conical targets at a depth of 7 cm. Each cone contains a different tissue-mimicking material so that the echo amplitude of the cones relative to the background material covers a dynamic range of 20 dB. Cross-sectional B-scans, perpendicular to the lengths of the cones, result in images of disks of constant diameter but varying contrast. Parallel cross-sectional scans yield "lesions" varying in diameter from 20 to 1 mm. Relative contrast of the cones vs background tissue is obtained by varying scattering particle sizes from 90 to 300 microns. Ultrasound B-scans of the phantom were examined by medical physicist observers to determine threshold detection of lesions as a function of size and contrast. The results indicate that detection of high contrast targets is limited by the imaging system's spatial resolution. Detection of low contrast targets is limited by the image speckle, i.e., coherent noise.