Experimental determination of wall shear rate in canine carotid arteries perfused in vitro

The mathematical model of Hung (Tsai and Hung, 1984) is employed to determine the wall shear rate acting on canine carotid arteries perfused in vitro. Model equations for pulsatile flow in a deformable vessel are coupled with experimental data of dynamic pressure drop, flow rate, vessel radius and radial wall motion. Derived quantities, e.g. velocity profiles and wall shear, are obtained for vessels exposed to 'normotensive' hemodynamics, 'hypertension' simulations and perfusions in which the compliance of the vessel wall is deliberately altered. Our results indicate that wall shear varies markedly as a function of the hemodynamic environment. The effects of vessel radius vs flow rate on the development of wall shear are also demonstrated. It is found that convective processes correlate with the magnitude of wall shear in the 'hypertension' simulations. The present findings and complementary published data may explain, at least in part, the variations in vessel wall transport and endothelial cell biology we observe as a function of the hemodynamic environment. For example we have documented that the exposure of canine carotids to 'hypertensive' (vs 'normotensive') hemodynamics is associated with an increased flux of lipoproteins (LDL) into the intima and luminal media. Alternations in wall compliance, on the other hand, profoundly influence endothelial shape, orientation and cytoskeletal array.     

Influence of gestation on jugular plasma thyroxine levels in Murrah buffalo and Karan Swiss cows

Plasma samples from 106 pregnant Karan Swiss (Brown Swiss x Sahiwal) cows and 108 Murrah buffalo were tested for thyroxine (T(4)) levels to determine the relationship between the hormonal changes and advancing pregnancy in the two species. All samples were collected within 2 months (January and February) to avoid seasonal interference on T(4) levels. In pregnant cows, the concentration of T(4) increased sharply during the first trimester, reaching a peak at the third month of gestation followed by a gradual decline until the last month of pregnancy. In pregnant buffalo, peripheral plasma T(4) levels fluctuated slightly throughout pregnancy without exhibiting a specific trend. Statistical analysis revealed that the magnitude of T(4) levels was significantly lower in buffalo (P < 0.01) than in the cows throughout pregnancy and that the hormonal patterns of the two species were significantly different (P < 0.05) during gestation. It was hypothesized from this study that T(4) requirements for the fetal buffalo calf may be lower than that for the fetal cattle calf since the buffalo gestation period is a month longer and the metabolic rate lower vis-a-vis the cow.     

Magnetically controlled targeted micro-carrier systems

Magnetically controlled targeted drug delivery systems are aimed at concentrating drugs at a defined target site, with the aid of a magnetic field. This technique has been developed specifically for directing drugs away from the reticuloendothelial system (RES). Literature on this topic suggests that these delivery systems are capable of altering the distribution of chemotherapeutic agents in the body. Hence these delivery devices offer the possibility of improving the therapeutic efficacy of the associated drugs. This paper reviews the work done to date towards the development and evaluation of biodegradable and non-biodegradable magnetic targeted drug delivery systems and outlines their future prospects and limitations in cancer chemotherapy.     

Characterization of a protease with alpha- and beta-fibrinogenase activity from the Western diamondback rattlesnake, Crotalus atrox.

A metalloprotease from the rattlesnake Crotalus atrox venom was isolated and purified from multiple-step chromatographies including anion-exchange chromatography, gel permeation and reversed-phase HPLC. The fraction was shown to be homogeneous as judged by SDS-gel electrophoresis. It also showed a high proteolytic activity against alpha- and beta-chains of fibrinogen molecules. Further characterization of the purified fraction with fibrinogenase activity indicated that it is a single-chain protease with a molecular mass of about 24 kDa and an acidic isoelectric point. It is relatively heat stable up to about 65 degrees C, inhibited by EDTA, beta-mercaptoethanol, but not by phenylmethanesulfonyl fluoride, N alpha-p-tosyl-L-phenylalanine chloromethyl ketone and N alpha-p-tosyl-L-lysine chloromethyl ketone, soybean trypsin inhibitor and aprotinin. Amino acid analysis showed that the enzyme possesses an amino acid composition very similar to some metalloproteases characterized before from the closely related rattlesnake venoms. N-Terminal sequence analysis of the enzyme corroborated some similarity between this enzyme and the reported sequences of these enzymes characterized from the Crotalidae snake family. This study indicated the presence of a novel fibrinogenase (termed Catroxase) with N-terminal sequence different from the metalloprotease with hemorrhagic activity isolated from the same Western diamondback rattlesnake.     

Nucleotide sequence of cDNA for Acacia confusa trypsin inhibitor and implication of post-translation processing.

Synthetic oligonucleotides corresponding to all possible sequences of N-terminal and C-terminal region of Acacia confusa trypsin inhibitor were used to generate ACTI-related sequences using the polymerase chain reaction on the cDNAs encoding ACTI of the seeds of legume, A. confusa. The deduced amino acid sequence agreed with that determined by the peptide analysis except an extra amino acid residue, serine, was found at the junction of A and B chain, which was removed by post-translation processing with specific protease(s). The substrate specificity of the protease(s) was found to cleave at the C-terminal sites of asparagine and serine, which was also shown to be the same case for another plant protein, abrin, isolated from legume, Abrus precatorius.     

HH2A,an immortalized bovine mammary epithelial cell line,expresses the gene encoding mammary derived growth inhibitor (MDGI)

Summary We have established and partially characterized a spontaneously immortalized bovine mammary epithelial cell line, designated HH2a. The cells express the gene encoding for mammary derived growth inhibitor (MDGI) when grown on released collagen gels in the presence of lactogenic hormones. This is the first report of a cell line that expresses MDGI. Immunohistochemical studies showed that HH2a cells contain keratin intermediate filaments and desmosomes. When plated on confluent monolayer of live fibroblasts, HH2a cells extensively contacted with fibroblasts. When embedded in the collagen gels, they rearranged themselves to produce three-dimensional duct-like outgrowths extending into the matrix. The HH2a cell line should be useful in investigations of the roles of cell-cell and cell-extracellular interactions in regulation of breast epithelial cell proliferation, and of the hormonal regulation of MDGI gene expression.     

Selective ectodomain phosphorylation and regulated cleavage of beta-amyloid precursor protein.

The beta-amyloid precursor protein (beta APP) is a highly conserved integral membrane protein expressed in most mammalian tissues and found at highest levels in the nervous system. Cerebral deposition of the amyloid beta-peptide (A beta), derived by proteolysis of beta APP, is an early and invariant feature of Alzheimer's disease. Protein phosphorylation by protein kinase C (PKC) has been found to regulate the metabolism of beta APP into nonamyloidogenic and amyloidogenic derivatives, but both the mechanism of these effects and the nature of beta APP phosphorylation are unknown. When labeled in vivo with [32P]orthophosphate, beta APP was phosphorylated only on serine residues in the N-terminal half of the extracellular domain, resulting in the secretion of phosphorylated soluble beta APP. PKC-mediated stimulation of beta APP secretion and concurrent inhibition of A beta release did not involve enhanced phosphorylation of beta APP and proceeded in the absence of cytoplasmic or extracellular phosphorylation of the precursor. The region of beta APP required for this indirect regulation by PKC was largely restricted to a 64 amino acid stretch around the secretory cleavage site. Moreover, in a truncated molecule designed to release soluble beta APP without the need for proteolytic cleavage, secretion was no longer regulated by PKC. Our data indicate that PKC-mediated pathways play a pivotal role in the control of beta APP metabolism and amyloid formation. However, in contrast to current postulates, this regulation is independent of beta APP phosphorylation and instead involves phosphorylation of other substrates that alter beta APP processing, such as beta APP-cleaving proteases.     

Selected factors limiting the microbial degradation of recalcitrant compounds

Summary The focus of this review is to examine some of the reasons biodegradation may not take place in the environment even though its occurrence in the laboratory has been demonstrated. Some approaches for dealing with chemical persistence will be discussed. In addition, the potential of bioremediation as an in situ clean-up technology will be considered.     

Evaluation of microbial surfactants for recovery of hydrophobic pollutants from soil

Summary Several microbially produced biosurfactants were evaluated for their ability to remove hydrophobic compounds from soil. The biosurfactants produced byPseudomonas aeruginosa UG2 andAcinetobacter calcoaceticus RAG-1 displayed the best results, with recovery of [¹⁴C]hexachlorobiphenyl from soil slurries of 48.0 and 41.9%, respectively.P. aeruginosa UG2 produced higher levels of extracellular biosurfactants than four otherP. aeruginosa strains.P. aeruginosa UG2 culture filtrate containing biosurfactants enhanced the recovery of several other individual hydrocarbons and polychlorinated biphenyl compounds, as well as several hydrocarbons in a mixture, from soil. The results, suggest that biosurfactants produced byP. aeruginosa UG2 have the potential for remediation of hydrophobic pollutants in soil environments.