Probing nearby molecular vibrations with lanthanide-doped nanocrystals.

The photoluminescence (PL) of lanthanide-doped nanocrystals can be quenched by energy transfer to vibrations of molecules located within a few nanometers from the dopants. Such short-range electronic-to-vibrational energy transfer (EVET) is often undesired as it reduces the photoluminescence efficiency. On the other hand, EVET may be exploited to extract information about molecular vibrations in the local environment of the nanocrystals. Here, we investigate the influence of solvent and gas environments on the PL properties of NaYF4:Er3+,Yb3+ upconversion nanocrystals. We relate changes in the PL spectrum and excited-state lifetimes in different solvents and their deuterated analogues to quenching of specific lanthanide levels by EVET to molecular vibrations. Similar but weaker changes are induced when we expose a film of nanocrystals to a gas environment with different amounts of H2O or D2O vapor. Quenching of green- and red-emitting levels of Er3+ can be explained in terms of EVET-mediated quenching that involves molecular vibrations with energies resonant with the gap between the energy levels of the lanthanide. Quenching of the near-infrared-emitting level is more complex and may involve EVET to combination-vibrations or defect-mediated quenching. EVET-mediated quenching holds promise as a mechanism to probe the local chemical environment-both for nanocrystals dispersed in a liquid and for nanocrystals exposed to gaseous molecules that adsorb onto the nanocrystal surface.

The use of a whole body index with bone scintigraphy to monitor the response to therapy in Paget's disease.

Bone scintigraphy has long been used to assess Paget's disease and investigate the response to therapy. Objective visual assessment is, however, difficult. The aim of this study was to derive, from a bone scintigram, an index which objectively measured the extent and severity of Paget's disease in the entire skeleton. This whole body index would provide a single numerical value which could be used to monitor the response to therapy in both monostotic and polyostotic disease. Comparison with other methods of assessing the condition, such as biochemical markers and pain scores, would also be possible. The whole body index was developed and used to retrospectively analyse 80 bone scintigrams on 40 patients. The majority of patients (36) received treatment with a bisphosphonate between the two scintigrams. Whole body index was compared with serum alkaline phosphatase measured at the same time; a significant correlation was found (before treatment P=0.001, after treatment P<0.001). The change in whole body index and alkaline phosphatase following treatment with various bisphosphonates was also investigated and a significant correlation found (P<0.001). Whilst performing the analysis it was also noted that the increase in uptake of the radiopharmaceutical was significantly greater in the cortical long bones than in the trabecular axial skeleton. This study suggests that a whole body index may be a suitable tool for assessing the response to treatment in Paget's disease.

The use of scintigraphy to demonstrate the rapid esophageal transit of the oval film-coated placebo risedronate tablet compared to a round uncoated placebo tablet when administered with minimal volumes of water.

As our population ages, and the consumption of pharmaceutical products rises, the incidence of solid oral dosage forms lodging in the esophagus is likely to increase and may be formulation dependent. The aim of this study was to compare the esophageal transit of the commercial film-coated risedronate tablet and a round uncoated tablet resembling the alendronate 10 mg tablet which is reported to cause esophagitis if ingested with little to no water. Water volumes of 30 ml and 50 ml were selected as these volumes can detect formulations prone to esophageal adhesion and a habits and practice study showed that these volumes are within the range preferred by women (7-385 ml). A total of 28 healthy postmenopausal women completed the four-way crossover scintigraphy study. For both volumes of water, the film-coated placebo risedronate tablet had a statistically significant faster esophageal transit time than the uncoated placebo tablet (P=0.002 for 30 ml water and P<0.001 for 50 ml water). Among those taking the round, flat, uncoated tablet, five subjects had esophageal stasis (transit >20 s) and in three subjects the tablet remained in the esophagus at the end of the 10-min imaging period. No stasis was observed for the oval film-coated placebo risedronate tablet. This study demonstrates that tablet size, shape and coating are pharmaceutical parameters which can be controlled to minimize esophageal contact of a dosage form with esophageal tissue.

Production and characterization of 188Re-C595 antibody for radioimmunotherapy of transitional cell bladder cancer.

UNLABELLED: Bladder cancer was responsible for >12,000 deaths in the United States in 1999. The high-molecular-weight glycoprotein MUC1 mucin is overexpressed on bladder tumors and represents a useful target for radioimmunoscintigraphy and radioimmunotherapy. We report on the production and initial tracer studies of a 188Re-antibody complex directed against this target and intended for intravesical radioimmunotherapy of superficial bladder cancer. METHODS: 188Re perrhenate was eluted from a 188W/188Re generator. C595 antibody was reduced with 2-mercaptoethanol and was labeled in the presence of stannous tartrate. The final reaction mixture contained high-molecular-weight contamination, which was removed from the complex using an affinity separation technique. The specificity and integrity of the antibody complex were tested by radioimmunoassay and size exclusion chromatography. Tumor localization was investigated using an ex vivo model in human cystectomy specimens. Tracer amounts of the complex were also administered intravesically to three patients with bladder cancer, who were then imaged by gamma scintigraphy. RESULTS: The complex was immunoreactive (70% +/- 17%) and specific for MUC1 antigens. A peak corresponding to a protein of 150 kDa was observed on size exclusion chromatography, showing that the complex was homogeneous. Binding to bladder tumors was observed in an ex vivo model in which tumors were successfully imaged in four specimens. The mean tumor-to-normal tissue ratio in ex vivo bladders was 7:1. Tumor uptake after intravesical administration was confirmed in three patients with bladder cancer (mean tumor-to-normal tissue ratio, 4:1). CONCLUSION: The C595 antibody was labeled with 188Re, providing a radioimmunoconjugate with high immunoreactivity and specificity. Its ability to localize in tumors both in an ex vivo model and after intravesical administration to patients has been shown. This approach will now be extended for the therapy of superficial bladder cancer.

Does simple estimation of 131I-metaiodobenzylguanidine uptake in patients with neural crest tumours correlate with clinical outcome?

A retrospective study was undertaken in six patients (three male and three female) with neural crest tumours who received therapeutic doses of 131I-meta-iodobenzylguanidine (131I-MIBG) (6.7-10.5 GBq). The age range of the patients was 13-65 years (mean 36 years). Quantification of tumour uptake was obtained from images acquired with a large-field-of-view gamma camera on a single occasion between 2 and 10 days post-treatment. Tumour uptake was calculated to be 0.1% and 3.2% of the administered dose, corresponding to uptakes of 6.7-142.8 MBq. Tumour volume was assessed from computed tomography (CT) or magnetic resonance (MR) images and estimates of tumour dose made from the Medical Internal Radiation Dosimetry scheme (MIRD) tables. Estimated doses were between 7 and 113 Gy. Most significantly, our findings indicate that high tumour uptake did not always correlate with good clinical response.

Molecular characterization of a hydroxymethylglutaryl-CoA reductase gene from mulberry (Morus alba L.).

The genus Morus consists of trees and shrubs, which are distributed in temperate and subtropical regions. Commonly known as mulberry, a few of the Morus species are valued for their foliage, which constitutes the chief feed for mulberry silkworms. Steroids and isoprenoid compounds present in the foliage not only add nutritive factors to the feed but also contribute greatly to silkworm health and silk production. Mevalonate synthesis, which is the first step in isoprenoid biosynthesis, is catalyzed by the enzyme hydroxymethylglutaryl-CoAreductase (HMGR). A genomic clone, Mahmg1, was isolated from Morus alba and its expression characterized in mulberry and transgenic tobacco. In mulberry, Mahmg1 transcripts were highest in young leaves and flowers. The promoter region of the Mahmg1 gene was fused to the beta-glucuronidase (GUS) reporter gene and the fusion introduced into tobacco. In imbibed embryos, GUS expression was limited to the cotyledons, epicotyl, and root elongation zone. Later, GUS staining was observed in floral tissues, guard cells, and the heads of trichomes on the stem and petioles. Mahmg1::GUS activity increased 3-4-fold by treatment with 100 microM abscisic acid and 15-80-fold in dark-grown versus light-grown seedlings. These results show that expression of the Mahmg1 gene is differentially regulated by developmental and environmental cues, suggesting that its HMGR isozyme a may provide a precursor for synthesis of specific isoprenoids during mulberry growth and development.

Esophageal transit of risedronate cellulose-coated tablet and gelatin capsule formulations.

Risedronate sodium is an orally active antiresorptive agent and a member of the pyridinyl class of bisphosphonates. It has been approved for the treatment of Paget's disease of the bone and is under development as a chronic therapy for the treatment and prevention of osteoporosis. A novel cellulose film-coated tablet formulation was developed to optimize esophageal transit of this bisphosphonate. The aim of the present study was to compare the esophageal transit of the film-coated tablet formulation of risedronate with its original gelatin capsule dose form. A total of 25 elderly, healthy volunteers (mean 66 years), who were dysphagia-free, participated in this randomized cross-over study. On separate occasions, volunteers swallowed radiolabeled placebo formulations with 50 ml water. Dynamic images with participants in a sitting position were recorded for 10 min using a gamma camera. Scintigraphic imaging showed a delay in esophageal transit (greater than 15 s) in 28% of patients in the capsule group but in none of the tablet group (P<0.05). The mean transit times of the capsules and tablets were 23.8 and 3.3 s, respectively. Esophageal transit of film-coated tablets was faster than gelatin capsules, suggesting that film-coated tablets would be the appropriate formulation for all pivotal trials with risedronate and for subsequent commercialization.

Molecular characterization of three differentially expressed members of the Camptotheca acuminata 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) gene family.

Camptotheca acuminata is a Chinese tree that produces the anti-cancer monoterpenoid indole alkaloid camptothecin (CPT). 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) supplies mevalonate for the terpenoid moiety of CPT and its hydroxylated derivative 10-hydroxycamptothecin (10-OH-CPT). We previously described the isolation of a gene encoding HMGR from C. acuminata (hmg1) and analyzed its expression in transgenic tobacco [6]. Here, we report on the isolation of genomic (hmg2) and cDNA (hmg3) clones representing two additional HMGR gene family members and characterize the expression of all three genes in C. acuminata. Transcript levels for two family members were highest in the shoot apex, dry seeds (hmg1), and bark (hmg3) which are the tissues containing the highest levels of CPT and 10-OH-CPT respectively. Levels of hmg3 mRNA also correlated with the accumulation of 10-OH-CPT during germination. In C. acuminata leaf disks, hmg1 mRNA increased in response to wounding, and this induction was suppressed by methyl jasmonate (MeJA), in agreement with results previously obtained in transgenic tobacco [6]. In contrast, wounding and MeJA did not affect hmg2 or hmg3 transcript levels in C. acuminata. These results show that members of the C. acuminata HMGR gene family are differentially expressed in various tissues under different physiological conditions which may contribute to the regulation of monoterpenoid indole alkaloid synthesis in this species.

Sustained harvest of camptothecin from the leaves of Camptotheca acuminata.

Over a 12-week period, new growth was collected at different intervals from Camptotheca acuminata trees to determine whether a leaf harvest strategy would be an efficient means for the production of the alkaloid camptothecin. Because camptothecin accumulates in young leaves and because the harvesting of young tissue stimulates axillary bud outgrowth, this strategy increased the harvestable amount of camptothecin from trees in a nondestructive manner.

Bedside nuclear medicine investigations in the intensive care unit.

The functional nature of nuclear medicine procedures makes them especially valuable in the management of patients undergoing intensive care. However, the severe nature of the patient's condition invariably prevents him or her from attending the nuclear medicine department for diagnostic investigations. We have piloted a bedside nuclear medicine service using a four-probe detector system linked to an IBM computer with curve processing software. Protocols for a range of radionuclide probe investigations, including renal, hepatobiliary, gastric outflow and lung vascular permeability, using 99Tcm and 111In radiopharmaceuticals have been established. The measurement of lung vascular permeability in patients with clinical symptoms of adult respiratory distress syndrome was considered to be a valuable procedure on the intensive care unit. Due to the poor availability of 113Inm, which had previously been used for the measurement of lung permeability, we used a technique based on in vivo labelling of serum transferrin with 111In-chloride together with 99Tcm-red blood cells for the calculation of the plasma protein accumulation index. Other procedures include the measurement of gastric outflow in patients previously on parenteral feeding, and the assessment of hepatobiliary and renal function. The equipment proved to be reliable and convenient for use at the bedside, although ultrasound imaging was essential for the correct positioning of the probe detectors over smaller organs such as the kidneys and the gallbladder. The high sensitivity of the probe detectors required only low administered amounts of activity, minimizing radiation protection measures for patients and staff. The administration of radiopharmaceuticals via indwelling lines and tubes presented particular problems and we recommend that parenteral injections should not be given through manifold giving set, or via Teflon cannulae.

Effect of bran, ispaghula, and inert plastic particles on gastric emptying and small bowel transit in humans: the role of physical factors.

BACKGROUND: Coarse bran is known to accelerate transit through the whole gut and to increase stool weight. This effect is much reduced by grinding the bran, suggesting that particle size influences gut motor patterns. AIMS: To compare the effect of 15 g coarse bran with 15 g inert plastic particles and 7 g of ispaghula on the gastric emptying and small bowel transit of a rice pudding test meal. SUBJECTS: 13 healthy volunteers. METHODS: Transit of 99mTc labelled rice studied by gamma-scintigraphy measuring gastric emptying and colonic arrival over 10 hours. Small bowel transit was estimated from the difference between time to 50% gastric emptying and 50% colonic arrival. RESULTS: Bran delayed gastric emptying by 22 (SEM 8) minutes compared with control values of 88 (SEM 6) minutes p < 0.05. Ispaghula and plastic particles had no significant effect. Small bowel transit was accelerated compared with control values of 322 (SEM 29) minutes, decreasing by 95 (29) minutes and 62 (22) minutes after bran and plastic particles respectively. Ispaghula again showed no significant effect. CONCLUSION: Coarse bran delays gastric emptying and accelerates small bowel transit. The marked acceleration of small bowel transit also seen with inert plastic particles may be due to increased upper gut secretions after stimulation of enteric nerves.

Assessment of completeness of thyroid ablation by estimation of neck uptake of 131I on whole-body scans: comparison of quantification and visual assessment of thyroid bed uptake.

Thyroid cancer is treated by thyroidectomy followed by radioiodine ablation of the residual active tissue in the thyroid bed. Completeness of ablation can be assessed from neck images of whole-body 131I scans by visual estimation or quantitative analysis By visual assessment, ablation can be considered complete if there is no uptake in the neck or the uptake is empirically considered too small. By quantification, ablation is considered complete if neck uptake is < 1%. Further radioiodine therapy is considered necessary only if neck uptake exceeds 1% of the administered dose. Both visual assessment and quantification of thyroid bed uptake were applied to 46 scans after diagnostic or therapeutic doses of 131I had been administered to 25 patients who were being followed up for follicular or papillary carcinoma of the thyroid. The results were compared to assess the effect of either method on determining the need for a further ablative dose of 131I. Visual assessment overestimated thyroid bed uptake in 10 of 46 (22%) of the scans. Bearing in mind the unpleasantness of radioiodine ablation and the potential for bone marrow toxicity, it is recommended that quantification of neck uptake should be routinely performed as a guide to completeness of ablation and to determine the need for a therapeutic dose of the isotope. This should help to avoid unnecessary radioiodine treatment in patients with thyroid cancer.

Planar, SPET and three-dimensional immunoscintigraphy of suspected recurrent colorectal cancer using 111In-B72.3 (Oncoscint CR-OV): effect of administered activity.

The monoclonal antibody conjugate 111In-B72.3 was the first such antibody-based radiopharmaceutical for tumour detection to be granted a propriety product licence in Europe. However, the optimum activity of 111In for planar and SPET imaging is yet to be established. A baseline study of 20 patients with suspected recurrent colorectal cancer has been carried out to assess any effect of administered activity of radionuclide on image quality and tumour detection. Ten patients were administered 80 MBq 111In-Oncoscint and 10 patients a larger amount of activity, 150 MBq (resulting in effective dose equivalents of 25 and 47 mSv, respectively). Planar, orthogonal SPET and 3D volume-rendered SPET images were obtained and the image quality was assessed. The clinical results were compared with computed tomography (CT) and in selected patients magnetic resonance imaging (MRI). No difference in the overall tumour detection was apparent between the two groups and the use of 150 MBq 111In for planar imaging alone cannot be justified. Orthogonal and 3D SPET imaging was helpful in confirming sites of uptake and may justify the use of the higher administered amount of activity; however, false-positive results raise the need for caution in the interpretation of these images. Volume-rendered 3D images offer an attractive method of displaying antibody data and require further evaluation.

Impaired oesophageal transit of capsule versus tablet formulations in the elderly.

Drug induced oesophageal injury is an important and preventable cause of iatrogenic injury. In most cases the injury is considered to be due to mucosal contact from formulations lodged in the oesophagus. A scintigraphic study was performed comparing the oesophageal transit of enteric coated tablets with similar sized and shaped gelatin capsules, using a population of elderly healthy volunteers similar in age (50-79 years) to the population most likely to be receiving regular treatment. Twenty three volunteers injected the radiolabelled tablet or capsule with 50 ml of water while sitting on two separate occasions according to a randomisation schedule. Oesophageal transit was assessed by gamma scintigraphy. Gastric residence was also assessed in 11 of 23 subjects. While the tablet was readily cleared from the oesophagus, mean transit time 4.3 seconds (range 1.0-14.0), the capsule often showed a comparatively prolonged holdup, mean transit time 20.9 seconds (range 1.5-174.5). Ten of 11 tablets emptied from the stomach intact, while all 11 capsules broke up in the stomach. Gelatin capsules showed a clear tendency to remain within the oesophagus of healthy elderly volunteers, while similar sized enteric coated tablets did not. These studies show the importance of assessing oesophageal transit when designing the formulation of drugs with a potential for oesophageal injury.