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Biomedical subjects

A Havron

Publications and source records attributed to A Havron.

13 recordsLinked to original sources
PubMed1994

Family physician management of HIV and AIDS: a Vermont study.

BACKGROUND: The purpose of this study was to survey family physicians regarding the barriers to providing primary care for persons with human immunodeficiency virus (HIV) infections and acquired immunodeficiency syndrome (AIDS) in a small, rural state with a low incidence of infection. The study focused on issues facing family physicians, such as lack of training and experience, skill in managing the complications of HIV and AIDS, fears about transmission, patients' fears about seeing a physician who treats patients with HIV or AIDS, and lack of community consultative and ancillary services. METHODS: All 132 members of the Vermont Academy of Family Physicians were mailed a 33-item survey questionnaire; 106 (80%) responded. RESULTS: Fifty-seven percent of family physicians currently provide medical care for HIV-positive asymptomatic patients, and 45% provide care for symptomatic patients. Seventy-three percent of family physicians either currently manage or are willing to be trained to manage HIV complications. CONCLUSIONS: The results of this study indicate that a majority of physicians are willing to provide a wide spectrum of medical treatment and services to patients with HIV or AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Pupal parasitoids (Hymenoptera: Pteromalidae) of muscoid filth flies in Israel.

Pupal parasitoids of muscoid flies were collected monthly on three farms in southern Israel in preparation for an IPM programme for the control of filth-breeding flies. 50% and 25.5% of viable puparia collected during 1985 and 1986/87, respectively, were parasitized. Three species of Spalangia Latreille and two species of Muscidifurax Girault & Saunders (Hymenoptera: Pteromalidae) accounted for 82.0% and 94.2% of parasitoids recovered in the two seasons. Variation in the seasonal abundance and distribution of the leading parasite species are discussed in connection with their conservation and possible use for augmentative releases within IPM projects.

Animals↗
PubMed1981

Hepatic contrast agents for computed tomography: high atomic number particulate material.

We used a stepwise approach to identify, design, synthesize, and test new high atomic number particulate contrast agents that would be especially well suited for use with computed tomography (CT). Our goal was to produce extremely radiopaque compounds with highly selective biodistribution to the normal liver. In this way, dose requirements could be lessened and toxicity minimized. Suspensions of cerium, gadolinium, and dysprosium oxide particles and silver iodide colloid were tested and compared with standard agents. All four experimental agents were selectively concentrated in the reticuloendothelial systems of rats and rabbits. These compounds produced greater and longer opacification of normal livers and larger liver-to-tumor differences in rabbits with hepatic tumors than did equivalent amounts of standard, iodinated agents. Lesions as small as 5 mm were visible with CT. These experimental materials have favorable characteristics as hepatic contrast agents, but their toxicity and long term retention may limit clinical use.

Animals↗
PubMed1981

Radiopaque liposomes: a promising new contrast material for computed tomography of the spleen.

Radiopaque, positively charged liposomes were made from lecithin, cholesterol, and stearylamine and carried diatrizoic acid salts (Renografin). Following intravenous administration of radiopaque liposomes in rats and rabbits, the spleen had the highest iodine concentration and was opacified on CT images. Contrast concentrations peaked at 30 minutes and gradually declined over a period of 24 hours. At 30 minutes, spleen CT values in rats had increased by 2.9 HU for each milligram of injected iodine (4 mg I/kg); maximum values were more than 6 times those obtained with an equivalent amount of Renografin alone. Peak spleen CT numbers of over 100 HU were consistently achieved following injections of 133 mg I/kg of opaque liposomes in rats. No acute toxicity was observed. These new contrast agents seem promising for CT of the spleen.

Animals↗
PubMed1980

Heavy metal particulate contrast materials for computed tomography of the liver.

Silver iodide colloid was used as a model of a particulate hepatic contrast agent for computed tomography (CT). Following intravenous administration to rabbits, approximately 90% of the injected dose was phagocytized by the liver's reticuloendothelial system, resulting in a four- to five-fold increase in the liver CT number. Suspensions of CeO2, Dy2O3, and Gd2O3 were prepared using stabilizers to prevent clumping. Particles of appropriate size for reticuloendothelial cell uptake were selected by centrifugation. Intravenous injections of the three suspensions increased the CT number of rabbit liver by approximately 30 Hounsfield units (HU: 1,000 scale) for each experimental contrast agent resulted in a minimum addition of 250 HU to the liver CT number. A linear relationship was found between the CT number and its contrast material concentration. This relationship was also tested in vitro by ashing samples of livers containing various amounts of contrast material. Standard curves of CT number versus contrast material concentration in the liver were plotted, which predicted the amount of liver enhancement obtained after contrast material injection. There may be a use for heavy metal-containing particulate materials as hepatic contrast agents, since they opacify the liver more selectively, to a higher degree, and for longer periods than the conventional biliary and urographic iodinated contrast materials.

Animals↗
PubMed1976

Photochemical cross-linking of neighboring residues in protein-nucleic acid complexes: rnase and pyrimidine nucleotide inhibitors.

Iradiation of the stable complexes formed between RNase and its competitive inhibitors cytidine 2'(3'),5'-diphosphate (pCp), and uridine 2'(3'),5'-diphosphate (pUp), resulted in covalent bond formation between the pyrimidine nucleotides and the enzyme. The photochemical reactions were initiated by ultraviolet light of lambda greater than 300 mn, employing acetone as a photosensitizer. This method was found to yield less undesired by-products, particularly photolyzed amino acids and aggregates resulting from protein-to-protein cross-linking, than the direct method of irradiation with light of lambda 260 nm. Tryptic digrestion of the modified protein, and chromatographic analysis of the peptides thus obtained, revealed a single and specific peptide which bacame covalently linked to both nucleotide inhibitors. The amino acid composition of this peptide is consistent with the sequence Asn-67-Arg-85 of RNase. Part of this peptide (residues 78 through 83) is close to the enzyme's binding site for the pyrimidine moiety of the nucleotides. Denatured RNase failed to cross-link to the inhibitors, and the extent of pUp cross-linking could be reduced by the addition of another competitive inhibitor (3'-UMP). Finally, the presence of excess inhibitor in the irradiation mixture did not lead to nonspecific cross-linking. This indicates that specificity is also achieved due to the fact that unbound excited inhibitor molecules do not react with the protein but prefer to follow different and faster reaction paths.

Amino Acids↗
PubMed1976

Reactivity and selectivity in light-induced free radical reactions of 2-propanol with purine and pyrimidine mononucleotides and dinucleoside monophosphates.

Photoalkylation reactions with 2-propanol, initiated with di-tert-butyl peroxide, of a variety of purine and pyrimidine mononucleotides and dinucleoside monophosphates lead to the substitution of an alpha-hydroxyisopropyl group for the H-8 atom of adenosine and the addition of the alcohol across the 5,6-double bond of the pyrimidines. Adenosine moieties blocked at their 3'-hydroxyl group are alkylated faster than those blocked at their 5'-hydroxyl. The reactivity of the uridine moieties of 3'-UMP, 5'-UMP, and uridylyl-(3',5')-uridine is not affected by the location of the phosphate group. However, the uridine moiety of uridylyl-(3',5')-adenosine is modified faster than that of adenylyl-(3',5')-uridine. It is suggested that steric hindrance imposed by the phosphate group determines the reactivity of adenosine moieties, while base stacking involving adenosine determines the reactivity of uridine moieties. These two effects play a major role in controlling the nature and degree of the selectivity of these photoalkylation reactions for either adenosine or uridine. Cytidine has been found to be inert in these reactions.

1-Propanol↗
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↗