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PubMed1991

Studies on ticks of veterinary importance in Nigeria: intrinsic factors influencing oviposition and egg-hatch of Amblyomma variegatum under natural conditions.

During the peak of rains of 1983, 1984 and 1985 in the forest zone of Nigeria, female Amblyomma variegatum engorged to various weights were subjected to different experiments for the purpose of observing the intrinsic factors which influence oviposition and egg-hatch under natural conditions. Two types of oviposition patterns were observed. New terms were introduced to quantify the relationships between the daily weight loss and daily number of eggs oviposited by a tick. These terms are "actual mass", "convertible blood mass", "oviposition efficiency" and "mass conversion rate". A major advantage of adopting the "oviposition efficiency" and "mass conversion rate" is that they relate directly to the measure of the metabolic activity utilized by the tick for the process of oviposition. The entity "convertable blood mass" also enables recognition of individual capability in the utilization of blood mass for oviposition. Investigation on the relationship of weight of eggs with sequence of oviposition showed that eggs were heavier when few eggs were laid than when numerous eggs were oviposited. The heaviest eggs were laid towards the end of oviposition. Two types of relationship were found to exit between the sequence of oviposition and the eclosion period of eggs. Adult A. variegatum engorged to more than 2.49 x were affected by immersion in water for longer than 7 days. Such ticks died without ovipositing and the water in which they were submerged became dark-red. Eggs immersed in water for periods ranging from 1-7 days hatched in about the same number of days as control eggs and their viability in terms of percent-hatch was not affected.

Animals↗
PubMedDate not supplied

Intrinsic factors affecting the management of chronic wounds.

Chronic wounds are a common feature in the elderly or in people with multisystem failure. In order to promote uncomplicated healing, nurses must have the necessary clinical knowledge about the patient's condition and the wound-healing process. This article discusses the intrinsic factors associated with chronic or indolent wounds. The next article in the series will examine the extrinsic factors.

Aged↗
PubMed2002

Reactive Oxygen and Nitrogen Oxide Species-induced Stress, a Major Intrinsic Factor Involved in Carcinogenic Processes and a Possible Target for Cancer Prevention.

Reactive oxygen and nitrogen oxide species and their inducing stress are involved in a variety of physiological and pathological phenomena in aerobes, including humans. For multistage carcinogenic processes, reactive oxygen and nitrogen oxide species-induced stress (RONOSS) serves as a major intrinsic factor and is involved in every step. This means that free radicals, RONOSS and their inducing downstream events may be targets for cancer prevention. It is therefore of importance to elucidate the mechanisms underlying the participation of RONOSS in carcinogenesis and to apply the obtained results for establishment of strategies to control cancer development. Despite the large body of accumulated knowledge due to worldwide efforts dealing with this research field, there still remain numerous uncertainties. In this mini-review, we introduce two examples of such efforts, one concerning a renal carcinogen KBrO(3) and the other dealing with hepatocarcinogenesis caused by a choline-deficient, L-amino acid-defined diet, in order to give some idea about the current understanding of the roles of RONOSS in carcinogenesis.

Journal Article↗
PubMed2003

The functional cobalamin (vitamin B12)-intrinsic factor receptor is a novel complex of cubilin and amnionless.

Imerslund-Gräsbeck syndrome (I-GS, megaloblastic anemia 1) is an autosomal recessive disorder characterized by intestinal cobalamin (vitamin B(12)) malabsorption and proteinuria. I-GS-causing mutations are found in either of 2 genes encoding the epithelial proteins: cubilin and amnionless (AMN). Cubilin recognizes intrinsic factor (IF)-cobalamin and various other proteins to be endocytosed in the intestine and kidney, respectively, whereas the function of AMN is unknown. Here we show that cubilin and AMN colocalize in the endocytic apparatus of polarized epithelial cells and copurify as a tight complex during IF-cobalamin affinity and nondenaturing gel filtration chromatography. In transfected cells expressing either AMN or a truncated IF-cobalamin-binding cubilin construct, neither protein alone conferred ligand endocytosis. In cubilin transfectants, cubilin accumulated in early biosynthetic compartments. However, in cells cotransfected with AMN and the cubilin construct, cubilin trafficked to the cell surface and endosomes, and the cells exhibited IF-cobalamin endocytosis and lysosomal degradation of IF. These data indicate that cubilin and AMN are subunits of a novel cubilin/AMN (cubam) complex, where AMN binds to the amino-terminal third of cubilin and directs subcellular localization and endocytosis of cubilin with its ligand. Therefore, mutations affecting either of the 2 proteins may abrogate function of the cubam complex and cause IG-S.

Amino Acid Sequence↗
PubMed1995

Synergistic inhibition of the intrinsic factor X activation by protein S and C4b-binding protein.

The complement protein C4b-binding protein plays an important role in the regulation of the protein C anticoagulant pathway. C4b-binding protein can bind to protein S, thereby inhibiting the cofactor activity of protein S for activated protein C. In this report, we describe a new role for C4b-binding protein in coagulation. We observed inhibition of the intrinsic factor X activating reaction by the complex of C4b-binding protein and protein S. At the plasma concentration of protein S, the factor X activation was inhibited for 50% and addition of C4b-binding protein led to a potentiation of the inhibition to almost 90%. Because C4b-binding protein alone had no effect on the activation of factor X, we hypothesized that binding of C4b-binding protein to protein S was a prerequisite for optimal inhibition of factor X activation. C4b-binding protein lacking the beta-chain, which is unable to bind to protein S, did not potentiate the inhibitory effect of protein S. In an earlier study, we observed that C4b-binding protein increased the binding affinity of protein S for factor VIII. Therefore, a possible interaction of C4b-binding protein with factor VIII was investigated. C4b-binding protein bound to factor VIII and to thrombin activated factor VIII in a saturable and specific way. Also, factor VIII in complex with von Willebrand factor was able to bind C4b-binding protein. The beta-chain of C4b-binding protein was not required for the interaction with factor VIII because C4b-binding protein lacking the beta-chain also bound to factor VIII. Monoclonal antibodies directed against the alpha-chain of C4b-binding protein inhibited the binding to factor VIII, whereas monoclonal antibodies directed against the beta-chain had no effect on the binding to factor VIII. This finding indicates that the binding site for factor VIII on C4b-binding protein is localized on the alpha-chains of C4b-binding protein. The potentiation by C4b-binding protein of the inhibition of the factor X activation by protein S was blocked by a monoclonal antibody directed against the alpha-chain of C4b-binding protein. This finding indicates that the potentiation of the inhibitory effect of protein S was mediated via an interaction of C4b-binding protein with factor VIII. C4b-binding protein did not bind to factor V and was not able to potentiate the inhibitory effect of protein S on prothrombinase activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗
PubMed1977

Pancreatic extract and the intestinal uptake of vitamin B12. III. Stimulatory effect in the presence of a non-intrinsic factor vitamin B12 binder.

To determine the mechanism by which pancreatic extract (PE) corrects the malabsorption of vitamin B12 in chronic pancreatic insufficiency (CPI), the following hypotheses were investigated: Firstly, PE might stimulate the absorption of vitamin B12 by changing the intestinal pH, secondly PE might stimulate the intestinal uptake of unbound vitamin B12, thirdly PE might abolish the inhibitory effect of vitamin B12 binders on the intestinal uptake of vitamin B12 bound to intrinsic factor (IF). PE had no effect on the pH in the small intestine and did not stimulate the uptake of unbound 57CoB12 by perfused rat intestinal segments. Preincubation of 57CoB12-IF with a non-IF B12-binder from human saliva (R-binder) reduced the uptake of 57CoB12 from 18.5 pg per cm intestine +/- 3.4 S.E.M. to 7.8 +/- 1.6 (p less than 0.02). PE abolished this inhibitory effect (p less than 0.05). The results indicate that PE corrects the malabsorption of vitamin B12 in CPI by an effect on non-IF B12- binders.

Animals↗
PubMed1986

Intrinsic factors that influence measurement of erythrocyte deformability.

The efficiency of rheological tests for measuring erythrocyte deformability is a function of test specificity and test sensitivity. Recent improvements in both specificity and sensitivity have revealed that rheological measurements of erythrocyte deformability are affected by the volume, haemoglobin concentration, and shape of the test erythrocytes. This applies both to filtration methods, using pores of 3-5 micron diameter, and to the measurement of erythrocyte elongation by laser diffractometry. Erythrocyte indices and morphology should therefore be measured routinely in both patients and controls so that the values for these intrinsic factors can be correlated with the results of rheological measurements in all published studies.

Blood Viscosity↗