Segmental colonic transit after oral 67Ga-citrate in healthy subjects and those with chronic idiopathic constipation.
Measurement of segmental colonic transit is important in the assessment of patients with severe constipation. 111In-diethylenetriamine pentaacetic acid (DTPA) has been established as the tracer of choice for these studies, but it is expensive and not readily available. 67Ga-citrate is an inexpensive tracer and when given orally is not absorbed from the bowel. It was compared with 111In-DTPA in colonic transit studies in nonconstipated control subjects and then in patients with idiopathic constipation. METHODS: Studies were performed after oral administration of 3 MBq (81 microCi) 67Ga-citrate or 4 MBq (108 microCi) 111In-DTPA in solution. Serial abdominal images were performed up to 96 h postinjection, and computer data were generated from geometric mean images of segmental retention of tracer, mean activity profiles and a colonic tracer half-clearance time. RESULTS: There were no differences in segmental retention of either tracer or in mean activity profiles between control subjects and constipated patients. Results in constipated subjects were significantly different from those in controls. The mean half-clearance times of tracer for control subjects were 28.8 h for 67Ga-citrate and 29.9 h for 111In-DTPA in control subjects and 75.0 h for 67Ga-citrate and 70.8 h for 111In-DTPA in constipated patients. CONCLUSION: Oral 67Ga-citrate can be used as a safe alternative to 111In-DTPA for accurate measurement of segmental colonic transit. (+info)
Mechanism of citrate metabolism in Lactococcus lactis: resistance against lactate toxicity at low pH.
Measurement of the flux through the citrate fermentation pathway in resting cells of Lactococcus lactis CRL264 grown in a pH-controlled fermentor at different pH values showed that the pathway was constitutively expressed, but its activity was significantly enhanced at low pH. The flux through the citrate-degrading pathway correlated with the magnitude of the membrane potential and pH gradient that were generated when citrate was added to the cells. The citrate degradation rate and proton motive force were significantly higher when glucose was metabolized at the same time, a phenomenon that could be mimicked by the addition of lactate, the end product of glucose metabolism. The results clearly demonstrate that citrate metabolism in L. lactis is a secondary proton motive force-generating pathway. Although the proton motive force generated by citrate in cells grown at low pH was of the same magnitude as that generated by glucose fermentation, citrate metabolism did not affect the growth rate of L. lactis in rich media. However, inhibition of growth by lactate was relieved when citrate also was present in the growth medium. Citrate did not relieve the inhibition by other weak acids, suggesting a specific role of the citrate transporter CitP in the relief of inhibition. The mechanism of citrate metabolism presented here provides an explanation for the resistance to lactate toxicity. It is suggested that the citrate metabolic pathway is induced under the acidic conditions of the late exponential growth phase to make the cells (more) resistant to the inhibitory effects of the fermentation product, lactate, that accumulates under these conditions. (+info)
Imaging experimental intraabdominal abscesses with 99mTc-PEG liposomes and 99mTc-HYNIC IgG.
OBJECTIVE: To evaluate the accuracy of technetium-99m-labeled polyethylene glycol-coated liposomes (99mTc-PEG liposomes) and technetium-99m-labeled nonspecific human immunoglobulin G (99mTc-HYNIC IgG) for the scintigraphic detection of experimental intraabdominal abscesses in comparison with that of a standard agent, gallium-67 citrate. BACKGROUND: Scintigraphic imaging techniques can be very useful for the rapid and accurate localization of intraabdominal abscesses. Two newly developed radiolabeled agents, 99mTc-PEG liposomes and 99mTc-HYNIC IgG, have shown to be excellent agents for imaging experimental focal infection, but have not yet been studied in the detection of abdominal abscesses. METHODS: Intraabdominal abscesses were induced in 42 rats using the cecal ligation and puncture technique. Seven days later, randomized groups of rats received 99mTc-PEG liposomes, 99mTc-HYNIC IgG, or 67Ga citrate intravenously. The rats were imaged up to 24 hours after the injection. The biodistribution of the radiolabel was determined by counting dissected tissues ex vivo. Macroscopic intraabdominal abnormalities and focal uptake on the images were independently scored on a semiquantitative scale. RESULTS: 99mTc-PEG liposomes provided the earliest scintigraphic visualization of the abscess (as soon as 2 hours after the injection vs. 4 hours for the other two agents). Liposomes, IgG, and gallium all showed similarly high absolute uptake in the abscess. Focal uptake of liposomes and gallium correlated best with the extent of the macroscopic abnormalities. CONCLUSIONS: 99mTc-PEG liposomes and 99mTc-HYNIC IgG performed at least as well as the standard agent, 67Ga citrate, in the detection of experimental intraabdominal abscesses, with obvious advantages such as lower radiation exposure and more favorable physical properties. Of the two technetium agents, the liposomes seemed to be superior, providing the earliest diagnostic image and the best correlation with the inflammatory abnormalities. In addition, the preferential localization of radiolabeled PEG liposomes holds promise for targeted delivery of liposome-encapsulated drugs. (+info)
Metabolic behaviour and cleavage capacity in the amphibian egg.
During the winter season the full grown Bufo arenarum oocyte shows the metabolic behaviour characteristic of differentiated tissues of the same species. Due to seasonal variations, during the amplexus period, it acquires the metabolic behaviour of the segmenting egg. Short-time-induced ovulations (5-6 h) determine germinal vesicle breakdown immediately before the expulsion of the oocyte, without modifying the ovarian metabolism of the same. The incidence of the operative type of metabolism upon their capacity to cleave after insemination and needle pricking, has been studied in coelomic oocytes, which have attained nuclear maturation and have not experienced oviducal secretion effects. The results obtained indicate that the segmenting capacity of the egg is attained only when, through biochemical modifications, the oocyte acquires the metabolic behaviour characterizing embryonic cells. It is postulated that the metabolic changes observed in the oocyte constitue a fundamental aspect of cytoplasmic maturation. (+info)
Differences in phosphofructokinase regulation in normal and tumor rat thyroid cells.
The kinetic and molecular properties of a phosphofructokinase derived from a transplantable rat thyroid tumor lacking regulatory control on the glycolytic pathway were studied. The properties of the near-purified enzyme (specific activity 140 units/mg) were compared with those of phosphofructokinase from normal rat thyroid (specific activity 134 units/mg). The electrophoretic mobilities and gel elution behavior of these two enzymes were almost similar. The thyroid tumor phosphofructokinase showed, however, a greater degree of size and/or shape heterogeneity in the presence of ATP than the normal thyroid enzyme, as determined by gel filtration and sucrose density gradient centrifugation. Kinetic studies below pH 7.4 showed a sigmoid response curve for both enzymes when the velocity was determined at 1 mM ATP with varying levels of fructose-6-P. The interaction coefficient, however, was 4.2 and 2.6 for normal and tumor thyroid phosphofructokinase, respectively. Ammonium sulfate decreased the cooperative interactions with the substrate fructose-6-P in both enzymes. The thyroid tumor enzyme, however, was less sensitive to the inhibition by ATP and by citrate. The reversal of citrate inhibition by cyclic 3':5'-adenosine monophosphate was also less effective with the thyroid tumor phosphofructokinase, while the protective effect of fructose-6-P was stronger. The difference in citrate inhibition between tumor and normal thyroid enzyme was not strongly affected by varying the MgCl2 concentration up to 10 mM. It is concluded that the complex allosteric regulation typical of the normal thyroid phosphofructokinase is still present in the enzyme isolated from the thyroid tumor tissue. The latter, however, is more loosely controlled by its physiological effectors, such as ATP, citrate, and cyclic AMP. (+info)
Myositis ossificans demonstrated by positive gallium-67 and technetium-99m-HMDP bone imaging but negative technetium-99m-MIBI imaging.
Gallium-67-citrate and 99mTc-diphosphate bone imaging agents are localized in myositis ossificans, a tumor-like benign soft-tissue mass that makes it impossible to differentiate between malignant tumor and the infection/inflammatory process. We present such a myositis ossificans patient whose bone and 67Ga-citrate imagings showed increased uptake in the left thigh and two foci of the right gluteal region leading to inconclusive results. Technetium-99m-MIBI imaging showed the absence of substantial uptake in these regions. ACT scan confirmed myositis ossificans. The lack of 99mTc-MIBI uptake in myositis ossificans means that 99mTc-MIBI imaging may be useful in the differential diagnosis. (+info)
Radiation exposure from gallium-67-citrate patients.
OBJECTIVE: Serial monitoring of patients was performed to determine the radiation exposure contributed by patients injected with 67Ga-citrate to their surroundings. Radiology and nursing staff distance exposure estimates were made for various patient care tasks and imaging tests. METHODS: Fifteen adult patients were surveyed early (mean 4.3 min) and 11 of the 15 were surveyed at 3 d (mean 68.8 h) postinjection. The standard adult lymphoma imaging activity of 333-407 MBq (9-11 mCi) resulted in a range of 3.7-8.1 MBq/kg (0.1-0.22 mCi/kg). Dose rate measurements were made in the anterior, posterior, and left and right lateral projections at the level of the umbilicus, at distances of patient's surface and at 30.5 cm and 100 cm with a calibrated ion chamber. Time of contact-routine task analyses also were obtained for nursing and radiology personnel. Using a radiation survey-derived biexponential pharmacokinetic relationship, radiation exposures were determined for hospital personnel and family members at various times after injection. RESULTS: Based on the study population survey results, the mean instantaneous exposures (microSv/h) for an administered activity of 370 MBq (10 mCi) 67Ga-citrate were determined. The task analyses revealed the maximum patient contact time for any procedure performed at a distance equal to, or less than, 30.5 cm was 30 min. CONCLUSION: The quantitation of radiation exposure scenarios from 67Ga-citrate patients has determined that no special precautions are necessary for medical personnel when performing routine tasks associated with these patients. (+info)
Randomised trial of two pharmacological methods of bowel preparation for day case colonoscopy.
AIMS: To undertake a prospective, single blind, randomised trial comparing the efficacy and tolerance of two outpatient colonoscopy bowel preparation regimens. METHODS: Patients aged between 18 months and 16 years being admitted for day case colonoscopy were allocated randomly to receive either Picolax (an oral, sugar free powder containing sodium picosulphate 10 mg/sachet with magnesium citrate) and clear fluids or bisacodyl tablets with an unrestricted diet and a phosphate enema just before colonoscopy. Patient compliance, bowel frequency, and associated symptoms were recorded, and the adequacy of the bowel preparation was assessed in a blinded manner. RESULTS: 63 of 66 patients completed the trial. Mean age, mean weight, extent of colonoscopy, and distribution of underlying pathology were similar in both groups. Bowel preparation was good or excellent in all of the patients in the Picolax group (n = 32) compared with 22 patients in the bisacodyl/phosphate enema group (n = 31). The latter group experienced more abdominal discomfort during bowel preparation but three of the Picolax group vomited and the lack of solid food distressed some children. CONCLUSIONS: All bowel preparation methods have limitations and unpleasant side effects but the use of Picolax and clear fluids proved superior to bisacodyl tablets and a phosphate enema in children undergoing day case colonoscopy. (+info)