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At least 883 records · Page 49Linked to original sources
PubMed1990

Future medical prospects for Sandostatin.

Because of its widespread distribution within the nervous system and gastroenteropancreatic (GEP) system, and its diverse physiological inhibitory actions on various gastrointestinal functions, including endocrine and exocrine secretion, motility, liver and splanchnic blood flow and absorption, native somatostatin has been viewed as a possible therapy for many diseases. However, its short duration of action and consequent limited clinical usefulness have been overcome with the availability of Sandostatin (octreotide, Sandoz Ltd), a long-acting, synthetic octapeptide analog of the naturally occurring hormone. Sandostatin represents a significant advance in the treatment of growth hormone (GH) and thyrotropin (TSH)-secreting pituitary tumors and GEP endocrine tumors (carcinoid tumor, VIPoma, glucagonoma, insulinoma, and gastrinoma). Preclinical in vitro and animal studies have shown the antineoplastic activity of the compound. Moreover, because of a possible direct effect on somatostatin receptor-positive endocrine tumor cells and an indirect effect whereby Sandostatin lowers GH, insulin-like growth factor type 1 (IGF-1), and numerous gastrointestinal peptides, Sandostatin may prove useful as an adjunctive therapy in cancer patients. In vivo labeling of somatostatin receptor-positive tumors with radiolabeled somatostatin analogs now allows localization of such tumors and their metastases. In addition, targeted irradiation of these tumors by beta particle-emitting isotopes attached to such somatostatin analogs may become possible. The use of Sandostatin in acute esophageal variceal bleeding, pancreatic pseudocysts, gastrointestinal, and pancreatic external fistulae, short bowel syndrome, dumping syndrome and acquired immunodeficiency syndrome (AIDS)-related refractory hypersecretory diarrhea has provided encouraging results.(ABSTRACT TRUNCATED AT 250 WORDS)

Forecasting↗
PubMed1990

Dose-response relationship for the induction of structural chromosome aberrations in human spermatozoa after in vitro exposure to tritium beta-rays.

The effects of tritium (HTO) beta-rays on human sperm chromosomes were studied using our interspecific in vitro fertilization system between human spermatozoa and zona-free hamster oocytes. Semen samples were treated with media containing 1.53-24.3 mCi/ml HTO for about 80 min. 1290 spermatozoa from the controls and 1842 spermatozoa from the irradiated groups were karyotyped. The incidence of spermatozoa with structural chromosome aberrations increased linearly with increasing dosage. Breakage-type aberrations occurred far more frequently than exchange-type. Chromosome-type aberrations appeared far more frequently than chromatid-type. All of these types of aberrations showed linear dose-dependent increases. The RBE values of HTO beta-rays relative to X-rays were calculated for the above-mentioned 5 indices, respectively. Their RBE values ranged from 1.89 to 3.00 when the absorbed dose was estimated to be the minimum, whereas the values ranged between 1.04 and 1.65 when the absorbed dose was estimated to be the maximum.

Beta Particles↗
PubMed1994

The influence of large deletions on the mutation frequency induced by tritiated water and X-radiation in male Drosophila melanogaster post-meiotic germ cells.

Tritium beta radiation (3H beta-radiation) in the form of tritiated water was used to induce mutations at the alcohol dehydrogenase (Adh) locus in male Drosophila melanogaster post-meiotic germ cells. All 23 Adh null mutations were large deletions (> 20 kb), determined by genetic complementation and Southern blot analyses. 27 Adh null mutations have been induced by 100-kVp X-rays (Aaron, 1979) and have been genetically and molecularly characterized (Ashburner et al., 1982; Chia et al., 1985; LoMonaco et al., 1987; Mahmoud et al., 1991). In contrast to 3H beta-radiation, 100-kVp X-rays induced a bimodal distribution of Adh null mutations, intragenic mutations, < or = 250 bp, and large deletions, > 100 kb. A statistically significant difference was observed between the frequency of large deletions (23/23 or 1.0) induced by 3H beta-radiation and the frequency of large deletions (19/27 or 0.7) induced by 100-kVp X-rays. However, a statistical difference was not observed between the size distribution of the large deletions induced by 3H beta-radiation and X-rays. The relative deletion frequency (RDF) induced by 3H beta-radiation and 100-kVp X-rays was (1.0/0.7 = 1.4). The relative biological effectiveness (RBE) of these two radiation sources was 1.4, determined from the ratio of the regression coefficients of the respective 3H beta-radiation and X-ray sex-linked recessive lethal (SLRL) dose-response data. The large difference in size between the two classes of X-ray-induced Adh null mutations and the increase in mutation frequency and deletion frequency for 3H beta-radiation with respect to X-rays may indicate that the relative deletion frequency (RDF) is the molecular biological basis for the increase in the RBE for radiation sources with a mean LET value < or = 10 keV/microns.

Alcohol Dehydrogenase↗
PubMed1979

Ultrastructural observations on the granular leucocytes of the tuatara Sphenodon punctatus (Gray).

The granular leucocytes of an active, mature female tuatara, Sphenodon punctatus (Gray) were examined in the electron microscope. Eosinophils contained a lobulated nucleus, homogeneous, dense, irregularly shaped granules, assorted smaller granular inclusions, mitochondria and beta-glycogen. Endoplasmic reticulum, Golgi complexes and ribosomes were scanty. Immature neutrophils (myelocytes) were regular in outline and contained a compact nucleus. In the adjacent centrosomal region were paired centrioles with connected microtubules, and Golgi complexes. Ovoid electron-dense granules, mitochondria, lipid droplets and numerous microfilaments arranged randomly or in bundles, lay in the cytoplasm. Mature neutrophils were often highly irregular in outline, had a segmented nucleus and contained possibly a second type of granular inclusion. The basophils were regular in outline with a compact nucleus. Numerous ovoid homogeneous, electron-dense granules, mitochondria, beta-glycogen particles and some microfilaments were seen in the cytoplasm. The granules in many basophils appeared 'altered' or degenerate and most of these contained microtubules. The cytology of the granulocytes of the tuatara is compared with that in other vertebrates.

Animals↗
PubMed1979

Ultrastructural observations on the erythrocytes and thrombocytes of the tuatara, Sphenodon punctatus (Gray).

The erythrocytes of Sphenodon punctatus (Gray) are nucleated, ellipsoidal and flattened, and contain 55--65 microtubules in their marginal band. The thrombocytes are also flattened, ellipsoidal, nucleated cells and in electron-microscopic preparations occurred in aggregrates. The thrombocytes appeared to be 'activated' and possessed many pseudopodia which were devoid of organelles. The latter were concentrated in the perinuclear region and were encircled by a ring of microtubules. The organelles included ribosomes, mitochondria, membrane--bound dense material and numerous actin-like microfilaments. Cytoplasmic vacuoles contained a moderately dense, filamentous material and/or spheroidal electron-dense inclusions, beta-glycogen particles were scattered in the general cytoplasm and were most concentrated in the pseudopodia. The erythrocytes and thrombocytes of S. punctatus are compared with those in other vertebrates.

Animals↗
PubMed1979

A computer-aided three-dimensional display system for ultrasonic diagnosis of a breast tumour.

This paper describes a three-dimensional (3-d) display method by which the shape of an abnormal tissue, say, a breast tumour is represented as a line picture on a cathode ray tube (crt). The 3-d image consists of a set of overlaid contour lines, each of which shows the boundary of the tissue and is obtained from the corresponding B-scan digitized image by using image processing techniques such as smoothing and Laplacian. The system together with the 3-d algorithm is explained and some of the experimental results and pertaining problems are discussed.

Beta Particles↗
PubMed1992

Genetic consequences of radioactive contamination for populations of Arabidopsis.

Populations of Arabidopsis thaliana (L.) Heynh. growing within a 30 km radius of Chernobyl and characterized by radioactive contamination levels ranging from 0.02 to 240 mR h-1 were analyzed for the frequency of embryonic lethal mutations in 1987 and 1988. Plots that retained high levels of radioactive contamination long after the initial exposure were characterized by a high frequency of mutant plants. Plots with low levels of radioactive contamination, which were significantly reduced soon after exposure, were characterized by a decrease in the initially high proportion of mutant plants. Populations of Arabidopsis exposed to insignificant radioactive contamination showed no increase in the frequency of mutant plants; mutation levels were comparable to those found in control plants.

Accidents↗
PubMed1996

Radioactivity in two tide-washed marsh areas in the eastern Irish Sea: a radiological assessment.

The doses received by man from exposure to artificial radionuclides deposited onto marsh land during tidal inundation on the English side of the Solway Firth and the Dee Estuary have been assessed. The range of total doses received by the different marsh user groups was similar in both study areas, varying from < 1 microSv year-1 to approximately 55 microSv year-1, with total dose dominated by the contribution from external exposure (generally 80% of the total). The maximum doses in both study areas were received by people working on the marshes and are well below the annual dose limit recommended by ICRP for members of the public (1 mSv year-1). The largest dose estimated (56 microSv year-1) is only 6% of the recommended dose limit.

Animals↗
PubMed1983

Overproduction of bacteriophage Q beta maturation (A2) protein leads to cell lysis.

Double-stranded cDNA from the maturation (or A2) protein gene of the RNA bacteriophage Q beta has been cloned such that its expression is regulated by the E. coli lac promoter/operator. Induction of the A2 clone is lethal to the host. The basis of this lethality is cell lysis, which is correlated with synthesis of the A2 protein. No other major proteins appear to be made from the A2 gene when inducer is added. Plasmid-derived A2 protein specifically complements infecting Q beta A2 amber mutants. Lysis activity is abolished in clones that synthesize truncated or internally deleted A2 polypeptides ranging from 10% to 95% of the length of wild-type protein. We conclude that host lysis is promoted by the maturation protein itself, rather than by a separate lysis protein. The A2 protein probably allows for the release of progeny Q beta phage particles following normal infection.

Cell Survival↗
PubMed1996

Tissue response to commercial silicone and polyurethane elastomers after different sterilization procedures.

Two different commercial polymeric materials, a silicone and a polyurethane (PUR), were studied with regard to correlations between the chemical and physical compositions of the polymer surfaces and the biological response on implantation. Test specimens of the materials were manufactured according to standard procedures. The specimens were implanted in rats for 10 and 90 days. Before implantation the polymers were sterilized in three different ways, namely, beta irradiation, ethylene oxide sterilization and steam sterilization. The polymers were characterized before and after the implantation with respect to the chemical composition and the morphology of the surfaces. After implantation the biological response was evaluated by counting numbers of macrophages, giant cells, fibroblasts and other cells present at the surfaces. The thickness of the fibrous capsule surrounding the test specimens was measured at the thickest and thinnest parts. PUR surfaces showed signs of degradation already after sterilization and after 10 to 90 days of implantation, pits and cracks appeared, especially in the ethylene oxide sterilized samples. However, differences in the biological responses were small and independent of the sterilization method. After 10 days of implantation the capsule thickness and the amounts of cell material adhering at the surfaces were different, and it appears that the silicone rubber induces more tissue response than PUR. The differences in the early tissue response evened out after 90 days implantation time and a steady state situation evolved, which was similar for the silicone and the polyurethane.

Animals↗
PubMed1996

Postoperative irradiation treatment and bioresorbable implants in orthopaedic surgery: an experimental in vitro study.

The influence of applied radiation on the degradation of a polyglycolide (PGA) test specimen was studied in vitro. There was no significant difference in the time-dependent degradation behaviour between the irradiated test specimen and controls. Mandatory irradiation of an operation site following surgery therefore does not contradict the employment of bioresorbable implants in orthopaedic surgery.

Absorption↗
PubMed1983

An improved instantaneous frequency meter for use with a multi-trace CRO: re-examination of the principles involved.

The instantaneous frequency display of single unit discharges provides a useful measure of neuronal activities. Such a device must produce voltage outputs proportional to the reciprocal of each inter-spike interval by on-line computation of the hyperbola of V = a/t. Segment approximation of the required hyperbola can be made by a series of exponential functions which increase in time constants by a factor of m. Numerical analysis of a normalized function indicates possible error maxima of 3.4, 2.4 and 1.1% for m of 2, 1.8 and 1.5, respectively. This prediction is fully confirmed by the actual performance where m of 1.5 is adopted. The test circuit combines only readily available ICs and other components, to give a linear F-V conversion over a dynamic range of 4-600 Hz with error maxima of approximately 1%. The outputs are square pulses of approximately 1.5 ms in duration through the use of a flexible sample-hold circuit. Compared with that of earlier models, this display mode gives better photographic records with the base-line in simultaneous multi-trace display. Simple and systematic methods are described for designing a circuit to one's own specifications, and also for compensating for component variations.

Animals↗
PubMed1989

Radio-adaptive response: characterization of a cytogenetic repair induced by low-level ionizing radiation in cultured Chinese hamster cells.

Pretreatment with low doses of beta-rays from incorporated tritiated thymidine ([3H]dThd) or of Co-60 gamma-rays (1 or 5 cGy) rendered actively growing Chinese hamster V79 cells more resistant to the induction of micronuclei or sister-chromatid exchanges (SCEs) by a subsequent high dose of gamma-rays (1 Gy). This adaptive response to ionizing radiation (radio-adaptive response) can be induced by an optimal range of low doses of 3H beta-rays, but not by much lower or higher adapting doses. Full expression of the adaptive response induced by the exposure to low doses of 60Co gamma-rays occurred 4 h after the adapting dose. The cells pre-exposed to low doses of gamma-rays showed cross-resistance to challenge doses of gamma-rays themselves and also of mitomycin C (MMC) and near ultraviolet light (UV-B, 313 nm), but not to those of ethyl methanesulfonate (EMS) or cis-platinum (II) diammine dichloride (cisplatin) for SCE induction. These results suggest that the radio-adaptive response mechanistically couples to the repair network which copes with chromatin lesions induced by MMC and UV-B.

Animals↗
PubMed1994

Genetic effects of testicular incorporation of 137Cs in mice.

A comparative estimation of the frequencies of genetic disorders induced in germ cells of male mice by a single or long-term exposure to incorporated 137Cs or to external gamma-radiation has been carried out. The frequencies of dominant lethal mutations induced by a single exposure were similar with both types of radiation. In stem cell spermatogonia the frequency of reciprocal translocations was significantly lower in the case of single 137Cs administration than upon external gamma-radiation. Upon long-term administration the genetic efficiencies of both types of radiation were similar.

Animals↗
PubMed1994

A role for reactive oxygen species in zymosan and beta-glucan induced protein tyrosine phosphorylation and phospholipase A2 activation in murine macrophages.

Previously we have shown that reactive oxygen species (ROS) formation induced by phorbol ester in association with vanadate is essential for protein tyrosine phosphorylation and phospholipase A2 (PLA2) activation. Here we show that the interaction of beta-glucan particles (glucanp) or zymosan with complement receptor type 3 (CR3) leads, when associated with vanadate, to a cascade of reactions culminating in PLA2 activation. Vanadate + zymosan (or glucanp) markedly enhance protein tyrosine phosphorylation in bone marrow derived macrophages (BMMs), whereas neither of the agents alone has any effect. The enhancement was due to both sustained activation of protein tyrosine kinase (PTK) and inactivation of protein tyrosine phosphatase (PTP) as assessed in lysates of treated cells. Zymosan elevates membranal PKC, an effect that is potentiated by vanadate. Activation of both PTK and PKC leads to the activation of NADPH oxidase and to ROS formation. The formed ROS together with vanadate are potent inactivators of PTP leading to amplification of tyrosine phosphorylation and myelin basic protein kinase (MBP-K) activation. The activation of the cascade of protein kinases eventually leads to activation of PLA2. All the activation steps, i.e., activation of PTK, NADPH oxidase, MBP-K,PLA2 and the inactivation of PTP are sensitive to the NADPH oxidase inhibitor diphenyleneiodonium (DPI), to antioxidants and to PKC inhibitors. Thus, ROS formation (in the presence of vanadate) is critical for protein phosphorylation processes constituting the regulatory pathway of PLA2 activation by ligand-CR3 interaction.

Animals↗
PubMed1995

The preparation of an autologous saliva for use with patients undergoing therapeutic radiation for head and neck cancer.

PURPOSE: At the present time there is no general agreement about how to prevent the symptoms and clinical signs that accompany therapeutic irradiation for head and neck cancer. Because saliva is the principal protector of the oral tissues, it is logical to assume that many of these changes are due to the radiation-induced damage to the salivary glands. We have observed that the flow and composition of saliva is normal in most patients before their irradiation. Theoretically, it should, therefore, be possible to collect their saliva before they commence their course of radiation, store it in a "saliva bank," and give it back to them when they undergo radiation. The key to the use of such an autologous saliva is the fabrication of a technique that disinfects or sterilizes the saliva yet preserves its protective properties. The objective of this study was to prepare an autologous saliva that would be used by patients during their irradiation for head and neck cancer. MATERIALS AND METHODS: Stimulated saliva was obtained from healthy subjects; none of the subjects consumed any medications. The saliva was treated by a variety of techniques. Included among them were heat, radiation, filtration, centrifugation, and an antibacterial agent. The samples were analyzed for total protein, amylase, viscosity, and sterility; individual salivary proteins were assessed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. RESULTS: The results showed that beta radiation (> 2.5 kGy) and lyophilization + chlorhexidine (0.03% to 0.12%) could be used to prepare a sterile autologous saliva that retained most of its protective properties.

Adult↗
PubMed1987

Parity violation and chiral symmetry breaking of a racemic mixture.

The chiral symmetry breaking of a racemic mixture by the parity violating weak interaction is considered. Particular attention is given to a mechanism recently proposed by Mason and Tranter whereby the weak neutral current interaction in chiral molecules leads to the differential absorption of unpolarized light by D vs. L enantiomers. After extending the usual theory of optical activity to include weak neutral currents, it is found that for spin-allowed transitions in typical organic molecules the weak photoabsorption asymmetry is much smaller than the value obtained using the reasoning of Mason and Tranter. Upon making a comparison with other mechanisms, it is concluded that differential radiolysis by beta electrons is likely to produce the largest symmetry breaking effect by the weak interaction.

Beta Particles↗