Fe(II) formation after interaction of the amyloid <Emphasis Type="Italic">β</Emphasis>-peptide with iron-storage protein ferritin

The interaction of amyloid β-peptide (Aβ) with the iron-storage protein ferritin was studied in vitro. We have shown that Aβ during fibril formation process is able to reduce Fe(III) from the ferritin core (ferrihydrite) to Fe(II). The Aβ-mediated Fe(III) reduction yielded a two-times-higher concentration of free Fe(II) than the spontaneous formation of Fe(II) by the ferritin itself. We suggest that Aβ can also act as a ferritin-specific metallochaperone-like molecule capturing Fe(III) from the ferritin ferrihydrite core. Our observation may partially explain the formation of Fe(II)-containing minerals in human brains suffering by neurodegenerative diseases.     

Direct neural effect of lateral hypothalamic stimulation on insulin secretion by pancreases of normal and obese rats

Perfusion of CNS intact pancreases with 200 mg/dl glucose with concomitant lateral hypothalamic area (LHA) stimulation significantly inhibited insulin secretion both in normal and obese rats. Sprague-Dawley, Zucker lean (FaFa) and Zucker obese (fafa) rats all responded in a similar manner, suggesting a general effect unrelated to metabolic state. Insulin secretion during mins 25-40 of perfusion was inhibited in Sprague Dawley, lean Zucker and obese Zucker rats by 31%, 42% and 33%, even though LHA stimulation took place from mins 20-25. Thus, the duration of inhibition was greater than the period of LHA stimulation, indicating that this pathway can induce prolonged changes in the responsiveness of the pancreas. The data presented in this study demonstrate that LHA stimulation, in the absence of humoral factors, results in a direct CNS-mediated suppression of insulin secretion which is relatively long lasting. This effect may illustrate a basic control mechanism by the CNS to regulate the endocrine pancreas.     

Spent Rooibos (Aspalathus linearis) Tea Biomass as an Adsorbent for Organic Dye Removal

Spent rooibos (Aspalathus linearis) tea biomass can be used as an inexpensive biosorbent for xenobiotic removal. Seventeen dyes have been tested for their affinity to spent rooibos tea biomass. Eight dyes were used to study the adsorption process in detail. The dye adsorption has been described with the Langmuir isotherm. The calculated maximum adsorption capacities reached the value of over 200 mg of dye per gram of dried rooibos biomass for Bismarck brown Y. Spent rooibos tea biomass was also magnetically modified by contact with microwave-synthesized magnetic iron oxide nano- and microparticles. This new type of magnetically responsive biocomposite material can be easily separated by means of strong permanent magnets. Both native and magnetically modified spent rooibos biomass have shown excellent adsorption capacities for various types of organic dyes, so they are highly promising adsorbents in environmental technologies for selected xenobiotic removal.     

Magnetically modified microalgae and their applications

The majority of algal cells can interact with a wide range of nano- and microparticles. Upon interaction the modified cells usually maintain their viability and the presence of foreign material on their surfaces or in protoplasm can provide additional functionalities. Magnetic modification and labeling of microalgal biomass ensures a wide spectrum of biotechnological, bioanalytical and environmental applications. Different aspects of microalgal cell magnetic modification are covered in the review, followed by successful applications of magnetic algae. Modified cells can be employed during their harvesting and removal, applied in toxicity microscreening devices and also as efficient adsorbents of different types of xenobiotics.     

One‐step magnetic modification of yeast cells by microwave‐synthesized iron oxide microparticles

Baker's yeast (Saccharomyces cerevisiae) cells were magnetically modified with magnetic iron oxide particles prepared by microwave irradiation of iron(II) sulfate at high pH. The modification procedure was very simple and fast. Both non‐cross‐linked and glutaraldehyde cross‐linked magnetic cells enabled efficient sucrose conversion into glucose and fructose, due to the presence of active intracellular invertase. The prepared magnetic whole‐cell biocatalyst was stable; almost the same catalytic activity was observed after 1‐month storage at 4°C. Simple magnetic separation and stability of the developed biocatalyst enabled its reusability without significant loss of enzyme activity.

Significance and Impact of the Study

Magnetic whole yeast cell biocatalyst containing intracellular invertase in its natural environment has been prepared. Magnetic properties enable its easy separation from reaction mixture. Magnetically modified Saccharomyces cerevisiae cells have been used for invert sugar production, hydrolysing sucrose into glucose and fructose. The described magnetization procedure employing microwave‐synthesized iron oxide microparticles is a low‐cost and easy‐to‐perform alternative to already existing magnetization techniques.     

Quantitative structure-activity relationship (QSAR) analysis of surfactants influencing attachment of a Mycobacterium sp. to cellulose acetate and aromatic polyamide reverse osmosis membranes.

A series of 23 neutral, anionic, and zwitterionic surfactants were tested at a concentration of 0.1% wt/vol for their influence on attachment of a Mycobacterium sp. to cellulose acetate (CA) and polyamide (PA) reverse osmosis (RO) membranes. Four cell attachment bioassays were used: (1) semiconcurrent addition of surfactant and bacteria to RO coupons (standard assay); (2) surfactant pretreatment of RO membranes (membrane pretreatment assay); (3) surfactant treatment of adsorbed cells (detachment assay); and (4) surfactant pretreatment of mycobacteria (cell pretreatment assay). Seventeen surfactants inhibited attachment to PA membranes, whereas 15 inhibited attachment to CA in standard assays and, in 13 cases, the same surfactant inhibited attachment to both PA and CA. Despite greater cell attachment to PA than CA, surfactants were typically more effective in the former membrane system. More surfactants were effective in impairing cell attachment than in promoting detachment and a number enhanced attachment in membrane pretreatment assays, suggesting surface modification of RO membranes. Cell pretreatment inhibited attachment to CA membranes, suggesting the bacterial surface was also a target for detergent activity. Multivariate regression and cluster analyses indicated that critical micellar concentration (CMC) was positively correlated with Mycobacterium attachment in CA and PA standard assays. Surfactant dipole moment and octanol/water partitioning (LogP) also contributed to detergent activity in the PA system, whereas dipole moment, molecular topology (i.e., connectivity indices), and charge properties influenced activity in the CA system. Influential variables in membrane pretreatment assays included the LogP, topology indices, and charge properties, whereas CMC played a diminished role. Surfactant dipole moment was most influential in CA membrane detachment assays. Increasing system ionic strength by LiBr addition strengthened inhibition of cell attachment to CA membranes by dodecylbenzene sulfonic acid (DBSA) and promoted DBSA adsorption to CA surfaces as indicated by attenuated total reflection Fourier-transform infrared spectrometry. Results indicate that inhibition of bacterial attachment to RO membranes may be maximized by manipulating surfactant molecular structure to optimize surface adsorption behavior.     

Effect of age on the insulin secretory response of perfused rat pancreas to arginine and tolbutamide

In this study we compared the ability of perfused pancreases from 2 1/2 month-old and 12 month-old rats to secrete insulin in response to arginine or tolbutamide. The results indicate that the insulin secretory response to either secretagogue was between 25-85% greater (two-way analysis of variance, P less than .01) by perfused pancreases of older rats. On the other hand, islet cell mass was approximately three-fold greater in the pancreases of the older rats. When this difference in mass of insulin secretory tissue was taken into consideration, it became apparent that insulin secretion per beta cell by perfused pancreases of the older rats was only half that of the younger rats in response to either arginine or tolbutamide (two-way analysis of variance, P less than 0.001). Thus, the decline with age in the ability of the beta cell to secrete insulin, previously noted in response to glucose, involves other insulin secretagogues as well.     

Identification and catabolic activity of well-derived gasoline-degrading bacteria from a contaminated aquifer.

Approximately 300 gasoline-degrading bacteria were isolated from well water and core material from a shallow coastal aquifer contaminated with unleaded gasoline. Identification of 244 isolates revealed four genera: Pseudomonas, Alcaligenes, Nocardia, and Micrococcus, with pseudomonads making up 86.9% of bacteria identified. A total of 297 isolates was sorted into 111 catabolic groups on the basis of aerobic growth responses on 15 gasoline hydrocarbons. Each test hydrocarbon was degraded by at least one isolate. Toluene, p-xylene, ethylbenzene, and 1,2,4-trimethylbenzene were most frequently utilized as growth substrates, whereas cyclic and branched alkanes were least utilized. Most isolates were able to grow on 2 or 3 different hydrocarbons, and nearly 75% utilized toluene as a sole source of carbon and energy. Isolates were remarkably specific for hydrocarbon usage, often catabolizing only one of several closely related compounds. A subset of 220 isolates was sorted into 51 groups by polyacrylamide gel electrophoresis. Pseudomonas aeruginosa was partitioned into 16 protein-banding groups (i.e., subspecies) whose catabolic activities were largely restricted to substituted aromatics. Different members of subspecies groups defined by protein-banding pattern analysis often exhibited different growth responses on the same hydrocarbon, implying marked strain diversity. The catabolic activities of well-derived, gasoline-degrading bacteria associated with this contaminated aquifer are consonant with in situ adaptation at the site.     

Development of magnetic biosorbents for metal uptake

Two types of magnetic biosorbent were prepared by novel protocols from epichlorhydrin-cross-linked Saccharomyces cerevisiae cell walls and their biosorption characteristics were compared to those of non-magnetic cell walls. The magnetic biosorbents I and II were capable of binding Cu maximally to 225 and 50 mmol/g, Cd to 90 and 25 mmol/g and Ag + to 80 and 45 mmol/g respectively. These values compare with 400, 125 and 75 mmol/g, respec-tively, for non-magnetic cell walls.