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Biomedical subjects

D A Weber

Publications and source records attributed to D A Weber.

106 records · Page 6Linked to original sources
PubMed1975

[Renal blood flow after selective injection of different dosages of diatrizoate into the renal artery. An experimental study in the dog (author's transl)].

The characteristic biphasic renal haemodynamic response to diatrizoate injected into the renal artery was shown in the dog with the 133-Xenon washout technique. A brief increase in renal blood flow (RBF) during the first ten seconds is followed by a more prolonged period of diminuished RBF. A dose of 4 ml. diatrizoate 60% resulted in the maximum RBF increase of 43% after ten seconds, but even 1 ml. diatrizoate raised the RBF 24%. The initial vasodilator effect of diatrizoate compares well in its extent with the most potent renal vasodilators.

Animals↗
PubMed1975

Time-dependent image quality using 99mTc-pyrophosphate.

Technetium-99m-labeled pyrophosphate has proved to be a useful skeletal-imaging agent. In this study, specific areas of the skeleton were imaged at times ranging from 1/2 to 6 1/2 hr after injection of 99mTc-pyrophosphate. Count ratios between abnormal and normal bone with respect to adjacent soft tissue were obtained for selected regions of interest on computer-stored scintillation camera images. The results show that image quality improves most rapidly from 1/2 to 2 hr, but further modest gain in quality does occur on views recorded between 2 and 6 hr. All lesions detected on the later images were also observed on the early ones and the ratios of uptake between abnormal and normal bone from computer-processed scintillation camera images did not change appreciably with time after the 1/2-hr images. Our results confirm the clinical impression that overall image quality is better on views obtained at least 3 hr after injection. Further delays in imaging beyond 3-4 hr after injection probably will not result in any appreciable gain in diagnostic accuracy.

Bone Neoplasms↗
PubMedDate not supplied

Body-size corrections for in vivo neutron activation analysis.

Differences in body size and shape can cause large variances in the results of in vivo neutron activation analysis. Preliminary body-size correction data were obtained for the delayed-gamma neutron activation facility (DGNA) at Brookhaven National Laboratory (BNL), based on phantom standards of different sizes, used in combination with computer simulations on the effect of different body sizes.

Body Composition↗
PubMedDate not supplied

Ultra-high-resolution imaging of small animals: implications for preclinical and research studies.

Recent developments in the use of pinhole SPECT and dedicated PET for UHR small animal imaging have identified the technology that can be used to provide images with spatial resolution of the order of 1 to 3 mm. In SPECT imaging, rotating camera pinhole SPECT has provided the means to use existing equipment to achieve UHR images. It has the disadvantages of low sensitivity and requires special image software to reconstruct tomographic slices. However, with minimal additional cost to an imaging laboratory, pinhole SPECT can provide a quantitatively accurate imaging technique for small-animal studies. New detector technology offers considerable promise; however, more studies are required before any one system can be singled out as offering major advantages over the pinhole SPECT method for general purpose small-animal SPECT imaging. The search for the means to achieve better sensitivity with UHR continues. In PET imaging, with few exceptions, the general trend has been to design systems dedicated to small-animal imaging to achieve UHR images with satisfactory sensitivity for quantitative UHR imaging. Several of the ring configuration, small-animal PET imaging systems provide good sensitivity and high spatial resolution. The cost of many of these systems, however, is relatively high, and investigators continue to explore different detector materials and imaging geometries to develop an instrument with acceptable levels of sensitivity with UHR imaging capability. We believe that both small-animal SPECT and PET imaging techniques now offer practical UHR imaging methods for quantitative small-animal imaging. As these tools are implemented in the investigation of new radiopharmaceuticals, we expect the utility of in vivo small animal assays will support further research in optimizing this technology.

Animals↗
PubMedDate not supplied

Hepatography and liver lymphography by retrograde biliary ethiodol infusion: an experimental study in the dog.

Ethiodol in dosages of 0.5-3 ml/kg was retrogradely infused with hydrostatic pressure of 50--100 cm water into the biliary system of nine cholecystectomized dogs equipped with a Thomas cannula in the second portion of the duodenum, allowing cannulation of the common bile duct with a Foley catheter under direct vision. A total of 18 examinations were performed. A dense hepatogram and complete visualization of the hepatic lymph nodes were obtained when the infused Ethiodol dosage exceeded the capacity of the biliary system by 10 ml or more. The hepatogram lasted for three to four months and the lymph nodes were opacified for a year and longer. Contrary to angiographic contrast agents, Ethiodol retrogradely infused into the biliary system primarily refluxes from the biliary system to the lymph and not to the blood. Judged by serial chest radiographs and lung scans, pulmonary Ethiodol emboli did not occur. A significant temporary increase in serum bilirubin and liver enzymes followed the procedure but these returned to normal within a week to a month. Periodic needle biopsies of the liver showed Ethiodol droplets initially in the interstitium and lymphatics, and subsequently in hepatocytes, Kupffer's cells and the epithelium of small bile ductules. No hepatic damage was found histologically on long-time follow-up examinations.

Animals↗
PubMedDate not supplied

Comparison of renal cortical perfusion assessed with angiography and xenon washout technique in hydrated and dehydrated dogs: a preliminary observation.

Selective renal angiograms and xenon washout curves were performed under general anesthesia with pentobarbital in hydrated or dehydrated dogs weighing 22-27 kg. Compared to the hydrated animals a significant overall decrease in the angiographic cortical perfusion was found in the dehydrated dogs which was reversible with the infusion of 200 ml isotonic saline. The total renal blood flow, the rapid flow component and the percent of total flow to the first compartment assessed with the xenon washout technique was however not significantly different in hydrated and dehydrated animals. It is suggested that temporary cortical ischemia might occur in dehydration which differs from the well known pathologic condition of cortical ischemia since total renal blood flow appears to be normal in the former and there is a fast recovery with isotonic saline infusion. The observed findings in dehydration could be explained with redistribution of blood away from the outer cortex to the inner cortex and to the medulla.

Angiography↗
PubMedDate not supplied

Effect of pregnancy on development of seizures.

Some women develop seizures or experience increased seizure frequency during pregnancy. Although the reason for this increased susceptibility during pregnancy has not been established, hormonal changes have been hypothesized to be a factor. This study compared the rates of kindling in rats kindled during the first, second, or third trimester and female controls during diestrus. No significant differences in kindling rate were found between the controls and the pregnant rats. Although some differences in kindling rate were seen when the animals were separated into groups depending on stage of pregnancy kindled, these did not reach statistical significance. Using this model, seizure susceptibility was not significantly altered during pregnancy.

Animals↗
PubMedDate not supplied

Effect of seizures during pregnancy on seizure susceptibility in offspring.

The risk of epilepsy is higher in the offspring of epileptic mothers than epileptic fathers. It has been hypothesized that seizures during pregnancy may alter subsequent seizure susceptibility in the offspring. To test this hypothesis, pregnant rats were fully kindled during the first, second, or third trimesters. In addition, another group of pregnant rats were kindled during the first trimester and then stimulated daily to induce generalized tonic-clonic seizures until delivery. The rate of kindling in the offspring of the four groups was then compared with sham-operated controls. No significant difference in rate of kindling was noted between the offspring of sham-operated controls and kindled mothers. This study fails to support the hypothesis that maternal seizures during pregnancy lead to increased seizure susceptibility in the offspring.

Animals↗