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Biomedical subjects

D F Adams

Publications and source records attributed to D F Adams.

187 records · Page 11Linked to original sources
PubMedDate not supplied

Balloon-occlusion superior mesenteric arteriography for improved visualization of the mesenteric and portal venous anatomy of dogs.

The superior mesenteric arteries of twelve dogs were occluded with an inflated balloon on the tip of an endhole catheter while diatrizoate meglumine and diatrizoate sodium (Renografin 76) was injected distal to the occlusion. The balloon was immediately deflated at the end of contrast injection. Films taken over a 33-second period showed consistently excellent visualization of the mesenteric arteries and veins as well as the portal veins. Comparison with studies performed by the conventional, nonocclusion technique confirmed the superiority of the films obtained with the balloon occlusion method. Histologic examination of the mesenteric artery at the site of balloon inflation and of the small and large bowel revealed no abnormalities.

Angiography↗
PubMedDate not supplied

Liposomes carrying diatrizoate. Characterization of biophysical properties and imaging applications.

We have prepared and characterized a suspension of liposomes carrying diatrizoate. Vesicles were made with egg lecithin, cholesterol, and stearylamine in a 4:1:1 molar ratio, and contained meglumine sodium diatrizoate in their aqueous phase. They ranged up to 2.0 microns in size and had a multilamellar structure. These vesicles were then injected into normal and tumor-bearing rats, as well as normal dogs and a baboon. The iodine component proved to have a prolonged blood pool residence time, was cleared through reticuloendothelial and urinary tissues, and was completely excreted within seven days. The LD50 in mice was 2.3 g I/kg (38.5 g of liposome suspension/kg). Imaging studies with diatrizoate-carrying liposomes demonstrated marked and prolonged contrast enhancement of blood pool, liver, spleen, kidneys, urine, and tumor rims. Furthermore, the blood, liver, and spleen opacification was greater and longer sustained than when an equivalent amount of iodine in free diatrizoate was used. These diatrizoate-carrying liposomes are particularly well suited for computed tomographic imaging of blood pool and reticuloendothelial structures.

Animals↗
PubMedDate not supplied

In vivo 19F NMR imaging of liver, tumor, and abscess in rats. Preliminary results.

In vivo magnetic resonance imaging (MRI) has employed almost exclusively the proton because of its high gyromagnetic ratio and natural abundance relative to other nuclei. Recent research has focused on imaging using nuclei other than 1H, but has been limited by the decreased sensitivity and/or low biologic concentrations of the nuclei. Fluorine (19F), with a gyromagnetic ratio second only to that of hydrogen, is a theoretically attractive nucleus for MRI, but fluorine is present in only minute amounts in most tissues. Perfluorochemical emulsions (PFC), developed as blood replacement agents, appear to be safe vehicles for fluorine administration. We report our initial results of in vivo 19F magnetic resonance imaging of liver, tumor, and abscess in rats given exogenous fluorine.

Abscess↗
PubMedDate not supplied

Imaging of complex NMR spectra.

The Point Spread Function (PSF) in NMR imaging is the result of both the line broadening due to magnet field inhomogeneity and the intrinsic spectrum of the nucleus at resonance. In the case of proton imaging, the line broadening dominates the small chemical shifts and the spectral lines are not resolved. This is not generally the case with other nuclei having strong chemical shifts and the PSF then has a complex structure. During imaging, the complex PSF is convolved with the spatial distribution of the nucleus at resonance and this leads to halo artifacts which are dependent on the imaging technique employed. The images due to the ensemble of spectral lines can be separated in principle by deconvolution of the data with the PSF before reconstruction. In the special case where the complex PSF is spatially independent, it can be obtained from the Free Induction Decay (FID) data produced in the absence of a spatially encoding gradient field. This technique has been successfully applied to in-vivo imaging of exogenous perfluorocarbon material.

Animals↗
PubMedDate not supplied

Essential hypertension: abnormal renal vascular and endocrine responses to a mild psychological stimulus.

We have assessed the influence of a mild emotional stimulus on arterial blood pressure, heart rate, renal blood flow, plasma renin activity (PRA), and plasma aldosterone concentration in 24 normal subjects, eight of who had a parent with hypertension, and in 15 patients with essential hypertension. A nonverbal IQ test, Raven's Progressive Matrices, was employed as the stimulus. In 11 of the 15 hypertensives, arterial blood pressure rose transiently by 7 mm Hg or more, but in only three of 16 normal subjects (x2 = 7.23, p less than 0.01). Transient moderate increases in heart rate were also more common in the hypertensives (p less than 0.01). Renal blood flow rose in 11 of 16 normal subjects and fell in each of the 15 patients with essential hypertension (x2 = 15.1; p less than 0.005). As opposed to the transient changes in arterial pressure and heart rate, the fall in renal perfusion was sustained. The PRA fell in 10 of the 16 normal subjects with a negative family history and rose in 14 of 15 patients with essential hypertension (p less than 0.005). Changes in plasma angiotensin II concentration and in plasma aldosterone were in accord with the changes in PRA, but plasma cortisol did not change. Both the renal vascular response and the change in PRA were intermediate in normal subjects in whom family history was positive for hypertension. For the entire group of 39 subjects there was statistically significant agreement between the direction of the renal vascular response and the directional change in PRA: renal blood flow rose when PRA fell and fell when PRA rose (p less than 0.005). We conclude that there is an abnormality in the control of both the renal circulation and of renin release in patients with essential hypertension in response to psychological provocation, and that a similar process is present in some normotensive subjects whose parents have hypertension.

Adult↗
PubMedDate not supplied

Lyophilized liposomes: a new method for long-term vesicular storage.

To facilitate acceptance and use of radiopaque liposomes as novel CT contrast agents, we developed a technique that permits their long-term storage at room temperature. This study compares standard storage procedures with the new method. Multilamellar vesicles were prepared with egg lecithin, cholesterol and stearylamine (4:1:1 molar ratio) as well as diatrizoate. After synthesis, the vesicles were separated into batches: one portion was kept frozen (FRO), another was lyophilized and stored at room temperature (LYO-RT), and a third was thawed and stored at room temperature (RT). Size, structure and biodistribution of vesicles in all three groups were assessed over a 6-month period. Freeze-drying the vesicles caused no apparent damage to their membranes The RT group showed marked aggregation after 1 month, while the LYO-RT and FRO vesicles showed only a slight shift to larger particles after 6 months. At this time, there was no significant change in the biodistribution of the LYO-RT vesicles compared to FRO. Uptakes in the reticuloendothelial tissues were 15 per cent and 19 per cent respectively. The LYO-RT materials showed additional advantages in that they were always easy to resuspend. This technique appears to be the most successful and convenient procedure for the long-term storage of liposomes.

Animals↗