Model for inactivation of alpha-amylase in the presence of salts: theoretical and experimental studies

According to a previous report, only the smaller anions, like chlorides,that readily fit into the anion binding site of alpha-amylase can cause an increased stability (relative to enzymes in aqueous solution), and the anions that are too large to fit into the binding site should have no effect on the enzyme. Even though the results on large benzoate ions are consistent with the above postulate, much larger citrate ions from sodium and potassium citrate show stabilization at moderate salt concentrations and follow an expected trend of low stability only at large salt concentrations. The citrate ions from ammonium citrate exhibit very little to almost no stabilization. In addition, low to moderate concentrations of NaCl that provide a large stability to the enzyme show almost no stability in the presence of EDTA. We put forward an inactivation model that involves a reversible dissociation of the anion bound to the protein, followed by a reversible inactivation step of calcium ion dissociation and an irreversible denaturation step of apoenzyme.     

Electron therapy using wedge filters. I. Experimental studies using wedge filters made from polystyrol

Based on dose measurements at the phantom, the dose distributions obtained during electron therapy by the use of wedge filters made of polystyrol are reported. Energy doses from 15 to 42 MeV were applied; angles of wedges amounted to 10 degrees, 30 degrees, 45 degrees, and 60 degrees. Only by wedge-angles larger than 45 degrees, it was possible to bring about significant changes in the dose distribution. The results obtained are presented diagrammatically. The influence exerted by the wedge-angle and by electron energy upon the inclination of the 50%-isodose to the axis of the useful beam is shown by tables.     

Risks of alcohol consumption in laboratory studies involving human research participants.

Research protocols that include alcohol consumption raise a number of critical issues with regard to potential risks to research participants, researchers, and institutions. This article seeks to highlight some of these issues by presenting some of the potential risks and discussing relevant dimensions and parameters of these risks. Risks to individual research participants are the primary focus of concern, but consideration of risks associated with aspects of the experimental, contextual, and institutional setting are also considered. The authors conclude with recommendations for individuals conducting studies involving alcohol consumption by human research participants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Renal sugar transport in the winter flounder. I. Renal clearance studies

The renal handling of several sugars was examined using clearance techniques in the winter flounder Pseudopleuronectes americanus. The nonmetabolizable sugar alpha-methyl-D-glucoside was extensively reabsorbed, with consequent accumulation in renal tissue to nearly twice plasma concentration. Both glucose and phlorizin abolished reabsorption and reduced tissue-to-plasma ratios (T/P). D-Galactose was reabsorbed. However, the T/P for free galactose was only 0.6 (total sugar was 1.7). Glucose and phlorizin produced only a transient decrease in reabsorption and no change in T/P. 2-Deoxy-D-glucose showed neither net reabsorption nore secretion. Nevertheless, kidney T/P were inexcess of 6 for total sugar and 1.2 for free sugar, indicating entry through the peritubular face of the tubule. Neither glucose nor phlorizin altered 2-deoxy-D-glucose clearance, but both reduced T/P for total sugar (2.4) and free sugar (0.7). Thus, several systems govern the handling of these sugars at the luminal membrane of the renal tubule, just as has been previously demonstrated at the peritubular membrane in this species.     

Explicit and implicit memory in the elderly: Evidence for double dissociation involving medial temporal- and frontal-lobe functions.

Groups of normal old people living in institutions or in the community and young adults were administered tests of implicit (IM) and explicit (EM) memory with word-stem (WSC) and word-fragment (WFC) completion paradigms. Neuropsychological tests sensitive to frontal and medial temporal lobe function were also administered. Age differences were observed on both tests of EM and on all neuropsychological tests. Priming effects on WSC were smaller in the institutionalized group than the other 2 groups. Comparisons of EM and IM test results with neuropsychological test scores revealed several effects, including significant correlations (a) between EM scores on both tests and performance on standard memory tests in both aged groups and (b) between IM scores of both aged groups on WSC and frontal-lobe test performance. The results provide evidence of a double dissociation with respect to involvement of brain regions in EM and IM. They also indicate that repetition priming in WSC and WFC involve different mechanisms and that frontal-lobe dysfunction is a factor in reduced priming on the WSC test. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Radiation-induced alterations in murine lymphocyte homing patterns. I. Radiolabeling studies

A study of heterogeneity among muscarinic receptors was carried out with new rigid molecules, comprising structures in the fused quinuclidine-valerolactone, quinuclidine-cyclohexenone, quinuclidine-cyclohexanone and quinuclidine-cyclohexane derivatives. These are structurally related to the potent muscarinic agent, 3-acetoxyquinuclidine but substantially different from in it conformation. All proved to antagonize acetylcholine-like activity, but to a different extent in different systems. The equipotent molar ratio with respect to atropine (as 1) was: isolated guinea pig ileum, 10,000-1,000; salivary gland (mouse), 1,000-100; superior cervical ganglion (cat), 100-10; CNS (mouse), approximately 10. It is suggested that the rigid structure induces a three-point constrained fit in the receptor (onium group, hydrophobic moiety and carbonyl group), but that not all muscarinic receptors are capable of responding equally. In this case, receptor specificity of the drug is a direct consequence of its graded departure from the preferred conformation of acetycholine and, therefore, is necessarily associated with partial loss of potency.     

Scale Transition in Steel-Concrete Interaction. I: Model

This paper deals with the analysis of reinforced concrete (RC) structures with special emphasis on modeling of the interaction between concrete and reinforcement. A new mode for consideration of the response of the composite material at the member (structural) scale is proposed. It is obtained from extension of the fracture energy concept, originally developed for the simulation of cracking of plain concrete, to reinforced concrete. Hereby, the fracture energy related to the opening of primary cracks is increased in order to account for bond slip between steel and concrete. This increase is determined from the distribution of bond slip by means of a one-dimensional composite model introduced at the bar scale. The model consists of steel bars and the surrounding concrete. Between these two components, a nonlinear bond stress–bond slip relation is considered. The obtained results at the bar scale, such as the average crack spacing between adjacent cracks and the load-displacement response of the composite material, form the basis for determination of the increase of the fracture energy at the member scale. The performance of the proposed transition of the steel-concrete interaction from the bar scale to the member scale is assessed by means of reanalysis of experiments performed on RC bars. The application of the respective material model for reinforced concrete to real-life engineering structures is reported in Part II of this series.     

In vitro studies of chemical mutagens and carcinogens. I. Stability studies in cell culture medium

A quantitative microbial assay was used to study the stability of known mutagenic and carcinogenic compounds in cell culture medium. Ten direct-acting carcinogens, when incubated in culture medium with 15% fetal bovine serum at pH 7.2-7.4 and 37 degrees C, became inactive at varying rates. Biologic half-lives of the test compounds ranged from 8 minutes to 67 hours. In contrast, six procarcinogens showed no significant inactivation after 3 weeks' incubation. The biologic half-lives of each compound were presented, and the significance of these findings as they relate to cell culture carcinogenesis and mutagenesis assays was discussed.     

Preliminary studies on the validity of in vitro measurement of drug toxicity using HeLa cells. I. Comparative in vitro cytotoxicity of 27 drugs

Combined drug toxicity to HeLa cells was studied in vitro with use of the microtitre MIT-24 test system. Whether drug toxicity to HeLa cells is representative of drug toxicity to other cultivated cells was investigated by a comparison of the MIT-24 toxicity of 27 drugs to HeLa cells with their toxicity to various permanent cell lines and more differentiated primary cell cultures as reported in the literature, together with original recordings of the MIT-24 toxicity of 9 of the drugs to human fetal kidney cells. A similarity of drug toxicity to all cell types was found. Thus the MIT-24 recordings may be representative of a basal drug cytotoxicity, probably corresponding to local drug irritation and to causal systemic drug toxicity.     

Fundamental Mathematical Model for AOD Process. Part I: Derivation of the Model

This paper presents a new simulation model for the AOD process that takes the local variations into account but is still computationally efficient. The new idea here was to model AOD reactor as a combination of a plug flow reactor for the plume zone and a continuously stirred tank reactor (CSTR) for the bath and surface slag. This approach adopted has many advantages compared with the previous models. At first, it offers an effective method for considering the locally varying conditions as the gas bubbles rise in the plume. The model can be built computationally very effective compared to CFD due to significantly smaller amount of variables. The validation of the model is also easier as it has features that can be experimentally determined. The model is based on the simultaneous solution of conservation equations of mass, species and energy in all the vertical cells of the plug flow reactor, and a single volume in bath and surface slag. A novel method was developed and used for solving the rates in a mass transfer controlled multi‐component reaction system. In this Part I of this paper, the model is presented and its features discussed by few illustrative examples. In the following Part II, the model is broadly validated with new full scale industrial AOD process measurements for carbon release rate, melt composition, slag composition and bath temperature rise during final stages of carbon removal.     

Transplantation of Peyer''s patches under the kidney capsule in syngeneic mice. I. Morphological studies

The morphology of Peyer's patches transplanted under the kidney capsule in syngeneic mice was studied up to 30 days after transplantation. Changes undergoing in transplants were arbitrarily divided into three stages: the initial stage of necrosis, then from the third day on -- clearing of dead tissues, and finally, from the fifth day -- lymphoid regeneration. Starting from the ninth day on, the lymphoid structure of the transplants was quite distinct. Transplants appeared to be similar to Peyer's patches in situ. Reconstituted transplants contained a huge number of blood vessels located with lymphocytes. The epithelial cysts were found in all the transplants. They were formed by remnants of persisted intestinal epithelium covering Peyer's patches in situ. The possibility of epithelial influence on lymphoid regeneration of the transplants is discussed.     

Histopathological studies on the toxicity of ochratoxin A in rats. I. Acute oral toxicity

Traumatic spinal cord lesions in children are infrequent (2 to 5 per cent of all cases admitted to specialised paraplegic centres depending on whether the upper age limit is set at 10 or 15 years). Traffic accidents are responsible for at least 50 per cent of the lesions; playground accidents and various sports add another 35 per cent. A large proportion of the accidents have been found to be related to the child's normal desire for adventure and exploration. The segment most frequently involved in our own series of 18 cases was the cervical and upper thoracic spine. Histopathological studies have shown that splitting of the cartilaginous end-plate in the growth zone of the vertebrae is a common finding. Radiological signs of spinal trauma are less evident than in adults; they may be totally missing. Precise neurological assessment must rely on repeated examination and close clinical observation, especially in the comatous child with a head injury. Spinal cord involvement must be suspected and the child treated as a paraplegic until definite proof of a normal neurological status is available. Due to a highly labile water electrolyte balance in the early post-traumatic stage and considerable fluctuations in plasma volume and temperature regulation, permanent monitoring of the cardiovascular function, body temperature and diuresis is mandatory. In children below the age of 10, deep vein thrombosis and embolism are exceptional (sepsis creates a high-risk situation requiring anticoagulation). In the initial treatment of spinal injury only conservative measures should be considered; there are no indications for laminectomy, nor for spinal fusion. In the tetraplegic child below the age of 6, skull-traction should be avoided and immobilisation of the cervical segment achieved by bilateral padded head-rests.     

Physically Based Model for Simulating Flow in Furrow Irrigation. I: Model Development

Researchers developed several mathematical models for simulating furrow irrigation using the Saint-Venant equations. Most of these irrigation models use numerical techniques to solve these equations, which in general, require extensive programming and computational skills. Moreover, several of these models consider uniform soil and use empirical equations for modeling infiltration. In this article, a physically based furrow irrigation model was presented for simulating flow in irrigated furrows under both uniform and layered soils. The model consisted of an overland flow and an infiltration module that are modeled using analytical solution of the zero-inertia and the Green and Ampt [one-dimensional and two-dimensional infiltration equations) equations, respectively. Furthermore, the infiltration was also modeled using the Kostiakov-Lewis infiltration equation. The model considered all possible furrow shapes and included graphical user interface. The developed model was evaluated using the field data and the model performance was discussed in the second part of the article.     

Yale studies of patient care. I. The evaluation of the febrile patient

Alkanals as carriers of rancid flavour of fat-containing foods were stored in mixtures with nonlipidic substances. The intensity of odour due to alkanals decreased with increasing time of storage, the changes being more pronounced in case of casein than in that of cellulose. Results of sensory tests did not depend on the molecular mass of aldehyde. The water content affected the sensory evaluation only slightly. The formation of aldolization products or polymers and of gluey flavour compounds modified the character of flavour and confused less experienced judges. Both the binding of alkanals and the aldolization reactions were enhanced by presence of primary amino groups.     

Shaping of isodose curves in intracavitary irradiation using the afterloading method. A feasibility study involving mathematical simulation

The possibility of adjusting the irradiation scheme to shape the isodose curve around an intracavitary source arrangement was studied mathematically. The total number of millicurie hours of irradiation for each source position was derived by a linear programming approach, taking into account the shape of the tumor in three different cases. The practical isodose curves obtainable with the source arrangement chosen were compared with the shape desired.