Observation of a cooperative radiation force in the presence of disorder.

Cooperative scattering of light by an extended object such as an atomic ensemble or a dielectric sphere is fundamentally different from scattering from many pointlike scatterers such as single atoms. Homogeneous distributions tend to scatter cooperatively, whereas fluctuations of the density distribution increase the disorder and suppress cooperativity. In an atomic cloud, the amount of disorder can be tuned via the optical thickness, and its role can be studied via the radiation force exerted by the light on the atomic cloud. Monitoring cold (87)Rb atoms released from a magneto-optical trap, we present the first experimental signatures of radiation force reduction due to cooperative scattering. The results are in agreement with an analytical expression interpolating between the disorder and the cooperativity-dominated regimes.

Superradiant rayleigh scattering and collective atomic recoil lasing in a ring cavity.

Collective interaction of light with an atomic gas can give rise to superradiant instabilities. We experimentally study the sudden buildup of a reverse light field in a laser-driven high-finesse ring cavity filled with ultracold thermal or Bose-Einstein condensed atoms. While superradiant Rayleigh scattering from atomic clouds is normally observed only at very low temperatures (i.e., well below 1 microK), the presence of the ring cavity enhances cooperativity and allows for superradiance with thermal clouds as hot as several 10 microK. A characterization of the superradiance at various temperatures and cooperativity parameters allows us to link it to the collective atomic recoil laser.

Evaluation of live renal donors with three-dimensional contrast-enhanced magnetic resonance angiography in comparison to catheter angiography.

BACKGROUND: Catheter angiography is traditionally used to determine renal arterial anatomy in live renal donors. Three-dimensional (3D) contrast-enhanced magnetic resonance imaging (MRA) has been suggested as a noninvasive replacement. We assessed the possibility of using MRA in live renal donors in Malaysia. METHODS: Twenty-six consecutive live renal donors were recruited from 2000 to 2002. All potential donors underwent evaluation of the renal arteries using both techniques. Angiographic findings from both modalities were subsequently compared with surgical findings at the time of donor nephrectomy. The total number and diameter of the arteries and the presence of early branching and renal abnormalities were noted. RESULTS: Both angiographic modalities were able to detect multiple renal arteries with catheter angiography having a sensitivity of 100% and MRA a sensitivity of 97%. MRA missed one 1-mm artery due to a low index of suspicion. Renal artery caliber measurements were not significantly different between the two methods. However, both techniques tended to overestimate the caliber of the renal arteries when compared with measurements taken at surgery. Early branching was found in two arteries at the time of surgery, but only one was detected by both techniques. Renal cysts seen on MR were not detected by catheter angiography. CONCLUSIONS: Our findings suggest that noninvasive MRA is a promising substitute for catheter angiography to evaluate the renal arteries of live donors.

A randomized prospective trial of intrarectal lidocaine for pain control during transrectal prostate biopsy: the Emory University experience.

PURPOSE: We prospectively evaluated the safety and efficacy of intrarectal lidocaine gel as anesthesia during transrectal prostate biopsy. MATERIALS AND METHODS: Of 63 consecutive men undergoing transrectal prostate biopsy 50 who qualified were enrolled in this study. Indications for the procedure were an abnormal prostate on digital rectal examination and/or elevated serum prostate specific antigen. Patients were randomized into group 1-25 who received 10 cc of 2% intrarectal lidocaine 10 minutes before the procedure and group 2-25 controls. No narcotics, sedation or analgesia was given. Pain during biopsy was assessed using a 10-point linear visual analog pain scale. RESULTS: In groups 1 and 2 median patient age was 63 and 66 years (p = 0.139), and median prostate specific antigen was 6.04 (range 1.07 to 263) and 7.24 (range 1.34 to 51.82) ng./ml. (p = 0.337). Digital rectal examination was normal and abnormal in 17 and 15 group 1, and in 8 and 10 group 2 patients, respectively. Ultrasound showed a median prostate volume of 43.6 cc (range 15.3 to 124) in group 1 and 40.3 (range 19.8 to 132) in group 2 (p = 0.710). Final histological results revealed prostate cancer in 7 men (28%) in each group. The median pain score during transrectal prostate biopsy was 2 (range 1 to 5) and 5 (range 1 to 7) in groups 1 and 2, respectively (p = 0.00001). No adverse events were noted. CONCLUSIONS: Intrarectal lidocaine gel is a simple, safe and efficacious method of providing satisfactory anesthesia in men undergoing transrectal prostate biopsy. We recommend its routine administration in all patients during this procedure.

Does Helicobacter pylori infection affect gastric emptying in patients with functional dyspepsia?

The objectives of the study were first, to determine if gastric emptying was altered in patients with functional dyspepsia with and without Helicobacter pylori infection compared with normal healthy volunteers; and second, to determine if there were further alterations in gastric emptying when the infection was eradicated. Gastric emptying was measured using a 99mtechnetium radiolabelled solid meal and gastric emptying time was measured as t1/2, viz. time taken for half the radiolabelled meal to be emptied from the stomach. The mean gastric emptying time for H. pylori-positive patients (n=20) was 56.4+/-24.8 min; H. pylori-negative patients (n=19) 67.8+/-31.8 min; and normal controls (n=20) 58.8+/-18.8min. No significant difference was obtained between the groups (ANOVA; P=0.348). Thirteen of 18 H. pylori-positive patients successfully eradicated the infection following treatment with omeprazole 40 mg o.m. and amoxycillin 500 mg t.d.s. for 2 weeks. The mean difference in the gastric emptying time before and after H. pylori eradication was 23.9+/-13.2 min (P= 0.556). There was no significant difference in the frequency of specific dyspeptic symptoms as well as the overall mean symptom score between the H. pylori-positive and -negative patients. Gastric emptying was not different between patients with functional dyspepsia and normal controls. Helicobacter pylori infection does not appear to affect gastric emptying in patients with functional dyspepsia.

Safety considerations in magnetic resonance imaging (MRI).

MRI is now an important diagnostic tool in medical management. There are numerous safety issues to be considered by the clinicians prior to requesting an MRI examination for their patients. These include those related to the magnetic field, gradient magnetic fields, the patient and contrast medium. This paper discusses the dangers and necessary precautions essential to reduce the risk of untoward complications from MRI.

Perspective graphics as a means of portraying the distribution of radiolabelled ligands in the spinal cord--a pilot study using intrathecally administered 3H morphine.

Tritium-labelled morphine sulphate was injected into the lumbar (L4-5) subarachnoid space of an adult male baboon. Three hours after injection, the animal was sacrificed. Using quantitative light microscopic autoradiographic mapping techniques, contour and perspective diagrams were prepared that described the position of radiolabel and by inference the distribution of morphine binding sites within the spinal cord. High concentrations of 3H was found in the medial regions of laminae I, II (substantia gelatinosa) and III of the dorsal horns. Smaller, but significant levels were seen bilaterally in the spinal anterolateral quadrant. Minimal 3H activity was seen in the remainder of the spinal cord with the lowest level being recorded in the spinal canal. Perspective graphics proved a precise and attractive method for locating the position and quantifying the concentration of radiolabel in baboon spinal cord.

Morphine concentration in brain and spinal cord after subarachnoid morphine injection in baboons.

Tritium-labeled morphine was injected into the lumbar (L4-5) subarachnoid space of three baboons. The animals were sacrificed 3, 6, and 24 hr thereafter. Morphine concentrations were measured at five predetermined positions within the spinal cord, medulla oblongata, and frontal lobes of the brain by scintillation-count assay. The results revealed that morphine ascends in the subarachnoid space and is absorbed into the spinal cord and medulla oblongata in a time-dependent fashion. Ventilation was most depressed and maximal concentrations of morphine were detected in the medulla six hours after injection. Delayed respiratory depression, occasionally reported after intraspinal morphine injection, may therefore be caused as a result of the affinity of morphine for binding sites, possibly opiate receptors, situated within the vital respiratory and cardiovascular neuronal complexes of the medulla.

Ultrastructural features of carcinomas induced in nude mice by the inoculation of human oesophageal carcinoma cell lines.

Thirty tumours induced in athymic mice by the inoculation of cells of human oesophageal carcinoma lines were examined by light and transmission electron microscopy, as were 24 cell strains derived from the mouse tumours. All tumours were carcinomas and displayed varying numbers of desmosomes and tonofilaments. Cytoplasmic organelles resembled those in human oesophageal carcinomas in vivo and marker structures such as intranuclear particles persisted in cells grown in nude mice and in vitro. As the nude mouse carcinomas displayed similarities both to one another and to human carcinomas in situ, the nude mouse xenograft system may become a useful model for further studies on tumour biology.