Monochromatic computed tomography with a compact laser-driven X-ray source.

A laser-driven electron-storage ring can produce nearly monochromatic, tunable X-rays in the keV energy regime by inverse Compton scattering. The small footprint, relative low cost and excellent beam quality provide the prospect for valuable preclinical use in radiography and tomography. The monochromaticity of the beam prevents beam hardening effects that are a serious problem in quantitative determination of absorption coefficients. These values are important e.g. for osteoporosis risk assessment. Here, we report quantitative computed tomography (CT) measurements using a laser-driven compact electron-storage ring X-ray source. The experimental results obtained for quantitative CT measurements on mass absorption coefficients in a phantom sample are compared to results from a rotating anode X-ray tube generator at various peak voltages. The findings confirm that a laser-driven electron-storage ring X-ray source can indeed yield much higher CT image quality, particularly if quantitative aspects of computed tomographic imaging are considered.

Advanced electronics for the CTF MEG system.

Development of the CTF MEG system has been advanced with the introduction of a computer processing cluster between the data acquisition electronics and the host computer. The advent of fast processors, memory, and network interfaces has made this innovation feasible for large data streams at high sampling rates. We have implemented tasks including anti-alias filter, sample rate decimation, higher gradient balancing, crosstalk correction, and optional filters with a cluster consisting of 4 dual Intel Xeon processors operating on up to 275 channel MEG systems at 12 kHz sample rate. The architecture is expandable with additional processors to implement advanced processing tasks which may include e.g., continuous head localization/motion correction, optional display filters, coherence calculations, or real time synthetic channels (via beamformer). We also describe an electronics configuration upgrade to provide operator console access to the peripheral interface features such as analog signal and trigger I/O. This allows remote location of the acoustically noisy electronics cabinet and fitting of the cabinet with doors for improved EMI shielding. Finally, we present the latest performance results available for the CTF 275 channel MEG system including an unshielded SEF (median nerve electrical stimulation) measurement enhanced by application of an adaptive beamformer technique (SAM) which allows recognition of the nominal 20-ms response in the unaveraged signal.

The Food Situations Questionnaire: a measure of children's willingness to try novel foods in stimulating and non-stimulating situations.

This paper reports the development and validation of a self-report measure of food neophobia for children. Items described hypothetical situations in which novel foods might be encountered and asked children to report how they would feel about tasting or eating them. Ten items, representing two correlated subscales, were selected from among a larger number, using standard item selection measures with a total of 335 children, aged 7-12 years. The two subscales represent willingness to try novel foods in highly stimulating circumstances and willingness to try novel foods in non-stimulating circumstances. The test was shown to significantly predict actual willingness to taste novel foods in a laboratory situation. In addition, it was shown to predict such willingness better than parents' reports of the children's neophobia. Finally, the test was shown to have satisfactory internal and test-retest reliabilities.

Gingival hyperplasia complicating acute myelomonocytic leukemia.

Many systemic illnesses manifest clinical signs in the oral cavity. A remarkable case of gingival hyperplasia heralding the presence of acute myelomonocytic leukemia (AML FAB-M4) is described. The oral manifestations of acute leukemia are reviewed.

Effects of prior exposure to palatable and unpalatable novel foods on children's willingness to taste other novel foods.

In two studies, 7- to 9-year-old and 10- to 12-year-old children received taste exposure to four good-tasting familiar, four good-tasting novel or four bad-tasting novel foods. Following this exposure phase, they saw a series of different foods, familiar and novel, and rated their willingness to taste them. For older children, exposure to the novel-good foods increased willingness to taste novel foods in comparison to the familiar-good control, while exposure to the novel-bad foods had no effect. For younger children, exposure to both novel-good and novel-bad foods decreased willingness to taste novel foods. The studies were originally framed in terms of children's schemas about novel foods and how exposure to good- and bad-tasting novel foods constituted provision of schema-inconsistent (novel-good) or schema-consistent (novel-bad) information. While such a framework accounted well for the results for the older children, it did not account for those for the younger children. The behaviour of the younger children was tentatively explained in terms of their attempt to regulate arousal produced by the initial exposure to the novel foods.

Cytotoxic therapy-induced D-xylose malabsorption and invasive infection during remission-induction therapy for acute myeloid leukemia in adults.

PURPOSE: To study the sequential changes in the intestinal absorption of an oral pentose probe, D-xylose, in patients receiving therapy for untreated acute myeloid leukemia (AML), and to correlate these changes to infectious morbidity. PATIENTS AND METHODS: Serial D-xylose absorption studies were conducted in 110 consecutive adult patients admitted to a university-affiliated tertiary care hospital for remission-induction therapy for untreated newly diagnosed AML. Serial serum D-xylose levels were obtained 1 hour after a 5-g oral dose of D-xylose at baseline and weekly for 4 weeks until marrow recovery. These results were correlated with invasive infection using multivariate techniques. RESULTS: The mean (+/- SEM) serum D-xylose levels were 0.88 +/- 0.03, 0.69 +/- 0.03, 0.58 +/- 0.02, 0.53 +/- 0.02, and 0.73 +/- 0.02 mmol/L at baseline and weeks 1 to 4, respectively (P < .0001, analysis of variance [AN-OVA]). Time to malabsorption varied with induction regimen (P = .007, log-rank test). Bloodstream infections during week 2 correlated with malabsorption (P = .007). Neutropenic enterocolitis correlated independently with induction regimen (P = .009), malabsorption at week 2 (P = .02), and the development of candidemia (P = .005). Hepatosplenic fungal infection correlated with induction regimen (P = .03), malabsorption at week 2 (P = .02), and fever at diagnosis (P = .003). Malabsorption was unrelated to the duration of severe neutropenia and the administration of parenteral nutrition. CONCLUSION: Serial D-xylose absorption studies in subjects with AML produced a characteristic profile of cytotoxic therapy-related damage to the functional integrity of the intestinal epithelium that was regimen dependent, myelosuppression independent, and predictive for invasive infectious complications. Further study to validate these observations appears warranted.

Invasive fungal disease in adults undergoing remission-induction therapy for acute myeloid leukemia: the pathogenetic role of the antileukemic regimen.

Using multivariate techniques, we studied the relationships of cytotoxic regimen, intestinal mucosal damage, and fungal colonization in the pathogenesis of invasive fungal disease in 138 patients undergoing induction therapy for untreated acute myeloid leukemia (AML) according to three institutional protocols: AML-84 (cytarabine/daunorubicin), AML-87 (high-dose cytarabine/etoposide/daunorubicin), and AML-88 (mitoxantrone/etoposide). Invasive fungal disease occurred in 36%, 6%, and 2.6% of patients participating in protocols AML-87, AML-84, and AML-88, respectively (chi 2 = 23.465; P < .0001). Protocol AML-87 was the strongest independent predictor in the multivariate model (RR = 26.7; P < .0001). Cytotoxic therapy-related epithelial damage in the gut, as measured by D-xylose malabsorption, correlated with invasive fungal disease and protocol AML-87. Fungal colonization, a predictor of invasive fungal disease, correlated with frequent modifications of antibiotic regimens. These results demonstrate the role of cytotoxic regimen-related gut epithelial damage, antibiotic-prescribing behavior, and fungal colonization in the pathogenesis of invasive fungal disease in patients with leukemia.

Reduced requirement for antibiotic therapy targeting gram-negative organisms in febrile, neutropenic patients with cancer who are receiving antibacterial chemoprophylaxis with oral quinolones.

An open, nonrandomized, phase 2 study of 53 adult patients who had 60 neutropenic episodes was conducted to determine if quinolone antibacterial prophylaxis could reduce the need during febrile episodes for parenteral therapy directed at gram-negative organisms. Suspected infections among recipients of quinolones were treated empirically with vancomycin and ceftazidime; therapy with the latter was discontinued after 24-48 hours in the absence of infection due to gram-negative organisms. In five neutropenic episodes, patients had no fever or infection. An aerobic gram-negative bacillus was isolated during only 1 (1.8%) of 55 febrile episodes. Febrile episodes occurred at a median of day 15 of cytotoxic therapy. Vancomycin monotherapy was successful in 22 (50%) of 44 evaluable cases. Modification of the vancomycin regimen by the addition of metronidazole or rifampin increased the response rate to 40 (91%) of 44. Response occurred after a median of 4.5 days. Parenteral empirical therapy with amphotericin B was required in only 3 (7%) of 44 cases. The study strategy safely permitted a reduction in the amount and duration of antibiotic therapy directed against gram-negative organisms in febrile neutropenic patients.

Pathology and clinical features of gastro-intestinal lymphoma in Saudi Arabia.

The histopathology and clinical presentation of 19 cases of primary gastrointestinal lymphoma is described. Our patients are similar to others in the Middle East but have a lower incidence of diarrhoea and malabsorption. All revealed a widespread chronic inflammatory background. Four patients with primary gastric lymphoma had endoscopic biopsies from the duodenum; these biopsies were completely free from tumour but showed a moderate to severe diffuse lymphoplasmacytic infiltrate. Electron microscopy shows that tumour cells penetrate basement membranes and invade the epithelium which becomes thin and attenuated. Substances which inhibit lymphocyte tropism might be useful in preventing intestinal ulceration. The MALT concept has been found useful in classification of the tumours. Two patients with unusual mesenteric node histology are described and it is thought that the appearances may indicate a substantial capacity for differentiation in the group of tumours.

Crystalloid structures in retroperitoneal paragangliomas: a light and electron microscopic study.

Samples from three clinically functional retroperitoneal paragangliomas were studied by light and electron microscopy. The tumors exhibited a Zellballen pattern histologically, and ultrastructurally all three neoplasms consisted of cells containing catecholamine granules. Prominent cytoplasmic crystalloids were present in all cases. The crystalloids were identified in routine histologic sections, demonstrated eosinophilia, and stained with periodic acid-Schiff, Giemsa, phloxine-tartrazine, and azan stains. Ultrastructurally the crystalloids were osmiophilic, often appeared as slender needles, were membrane bound, and demonstrated a periodicity of 9 nm. The crystalloids, unlike the catecholamine granules, were negative for catecholamine fluorescence. X-ray microanalysis, however, revealed the selective presence of chromium in both catecholamine granules and crystalloids.

A rural hospital's impact on a community's economic health.

This research illustrates the importance of a hospital to the economic health of a community. A simulation model of a rural community in Oklahoma is used to demonstrate how the implementation of the DRG reimbursement policy has impacted a rural community, and to project how the closing of the hospital would impact the economy of the community. The results indicate that rural hospitals play a vital role in the economics of their communities. The closing of a rural hospital has a devastating impact on the community, while the DRG reimbursement policy has had a significant impact on the community.

Sex differences in small-magnitude heart-rate responses to sexual and infant-related stimuli: a psychophysiological approach.

Small-magnitude (2-3 beats per minute) heart-rate responses can show sex differences if assessed with a psychophysiological approach in which temporally fine-grained methods are used to determine topographical differences. Such differences emerged when 15 males and 37 females were shown videosegments depicting emotional scenes. Specifically, males accelerated to erotic segments (couples making love), while females accelerated to segments showing babies crying. In addition, the peak development of baby-cry-elicited accelerations occurred about 1 second before that of erotic segment-elicited accelerations. The results are consistent with a preparatory-response interpretation, but more research is needed both to investigate the generality of these sex differences in heart-rate responses, and to determine the role of experiential and psychosocial factors.

Mixed bacteriophage infection of Escherichia coli: exclusion of superinfecting T4 by T7.

Escherichia coli was infected with T7, then with T4. When the time between the addition of the tow phages was 5 or more minutes, T4 was excluded and most of the infective centres yielded T7 progeny. The DNA of excluded T4 was injected, but it did not replicate nor was it degraded extensively. Transcription of this T4 DNA was largely inhibited, and the transcripts produced were not translated. A variety of T7 amber mutants was examined for the capacity to exclude T4. Amongst the early T7 genes, only the product of gene 1, the T7 RNA polymerase, was essential for T4 exclusion. None of the late genes examined was essential for exclusion.

Renal morphology of freshwater trout.

The nephron of the euryhaline freshwater salmonids is composed of the renal corpuscle and the renal tubules. Throughout much of the renal corpuscle, only the lamina densa separates the fenestrated processes of the endothelial cells from the foot processes of the visceral epithelium. The renal tubule consists of five distinct segments. The neck segment is short and intermittently ciliated; it lacks the mucous cells which appear in the neck segment of some teleosts. The proximal segment bears a dense bruch border and is both structurally and functionally divisible into a first and a second segment. The first portion is typified by the presence of short apical tubules, variously sized apical vacuoles, and numerous lysosomes. The second proximal segment is distinguished by the abundance and distribution of mitochondria throughout the cytoplasm. Infoldings of the basilar plasmalemma are especially prominent in this region. A cilated intermidate segment intervenes briefly between the proximal and distal portions of the tubule. The distal segment consists of cuboidal cells which bear scattered, short microvilli, small vesicles and multivesicular bodies. Renal tissue from several species of trout was examined in order to establish the basis for a common pattern of histological and ultrastructural characteristics within the family Salmonidae. In all species examined, renal structure was very similar and could readily be compared with that previously described in other freshwater and marine species.