Colon Specific Delivery of Indomethacin: Effect of Incorporating pH Sensitive Polymers in Xanthan Gum Matrix Bases

In the present study, an attempt has been made to design controlled release colon-specific formulations of indomethacin by employing pH responsive polymers Eudragit (L100 or S100) in matrix bases comprised of xanthan gum. The prepared tablets were found to be of acceptable quality with low-weight variation and uniform drug content. In vitro release studies indicated rapid swelling and release of significant percentage of drug in the initial period from matrix tablets composed of xanthan gum alone. Addition of pH responsive polymers Eudragit (L100 or S100) to xanthan gum matrix resulted in negligible to very low drug release in the initial period in acidic to weakly acidic medium. Furthermore, with increase in pH of the dissolution medium due to dissolution of Eudragit L100/Eudragit S100 that resulted in the formation of a porous matrix, faster but controlled drug release pattern was observed. Thus, a sigmoidal release pattern was observed from the designed formulations suitable for colonic delivery. Drug release mechanism in all cases was found to be of super case II type, indicating erosion to be the primary cause of drug release. Since the drug release from almost all the matrix bases in the initial phase was negligibly low and followed with controlled release for about 14–16 h, it was concluded that a matrix design of this composition could have potential applications as a colon-specific drug delivery device with additional advantage of easy scale-up and avoidance of all-or-none phenomenon associated with coated colon-specific systems.     

Effect of cortisol on human fetal lung in organ culture

Human fetal lung tissue obtained during the second trimester was cultured as organ culture with or without cortisol. The effect of cortisol on the phospholipid metabolism, as related to the appearance of osmiophilic lamellar bodies and the localisation of newly incorporated choline, was studied. In cortisol-treated explants, the concentration of saturated lecithins and the incorporation of (Me-3H)-choline into saturated lecithins increases significantly concomitantly with an increased number of osmiophilic lamellar bodies. The labelled choline is predominantly associated with these bodies. The obtained results indicate that cortisol accelerates the synthesis of pulmonary surfactant in the human fetal lung as early as in the second trimester.     

Conversion of 1′-deoxy-2H-ABA to2H-ABA in cell-free extracts fromCercospora rosicola

Abscisic acid (ABA) biosynthesis in the fungusCercospora rosicola has been studied previously by feeding potential intermediates to growing cultures and examining the products. The present work describes the isolation and partial characterization of an enzyme system which catalyzes the last step in this pathway, the conversion of 1′-deoxy-²H-ABA to²H-ABA. Enzyme extracts were prepared from cold-pressed mycelia of actively growingC. rosicola in tricine buffer containing sucrose and β-mercaptoethanol. Low-speed supernatants and resuspended microsomal preparations were active in converting 1′-deoxy-²H-ABA to²H-ABA. Optimum conditions for the reactions were established at 10 μM substrate, 300 μl enzyme extract in a total volume of 1 ml. Reaction products were chromatographed by reverse-phase high-performance liquid chromatography (HPLC). The presumptive ABA fractions were collected and the²H-ABA was measured by combined gas chromatography-mass spectrometry (GC-MS) with an²H-ABA standard. Most of the enzyme activity was found in the microsomal fraction. Typical reaction rates were on the order of 1.5 pmol²H-ABA formed/min/mg protein. The reaction required NADPH and was enhanced by FAD. Triarimol, a substituted pyrimidine, which inhibits ABA synthesis inC. rosicola, had no effect on the conversion of 1′-deoxy-²H-ABA to²H-ABA.     

Inhibition of anion transport in the red blood cell membrane by anionic and non-anionic arginine-specific reagents

Arginine specific reagents are found to be powerful inhibitors of anion exchange in the red blood cell membrane. Some of these inhibitors such as cyclohexandione, phenylglyoxal and 2, 3-butandione are found to produce their inhibition by interacting covalently with band 3. In contrast to the action of these compounds, the inhibition caused by the phenylglyoxal derivative 4-hydroxy-3-nitrophenyl-glyoxal has been found to be completly reversible. In extending the studies on the mode of action of these compounds on sulfate exchange and to get some more information about their binding site, the degree of inhibition caused by different phenylglyoxal derivatives which have a similar core but differ in their substituent groups have been compared. The interaction between the binding sites of these compounds and other anion transport inhibitors have also been studied.     

Inhibition of abscisic acid biosynthesis inCercospora rosicola by triarimol

The fungicide triarimol was tested for its effect on abscisic acid (ABA) accumulation in growing culturesof Cercospora rosicola. ABA accumulation was reduced by approximately 50% with 10^?8 M triarimol. Growth ofC. rosicola, as measured by dry weight accumulation, was inhibited by triarimol concentrations at or greater than 10^?7 M. These results are compared with those obtained with clomazone, ancymidol, and paclobutrazol, which inhibit ABA accumulation by 50% at concentrations of 5 × 10^?5, 5 × 10^?6, and 5 × 10^?7 M, respectively. Triarimol, therefore, is among the most potent inhibitors of ABA biosynthesis reported to date. Feeding studies with [¹⁴C]mevalonic acid confirmed the inhibition of ABA biosynthesis by 5 × 10^?8 M triarimol. These results support previous suggestions that one or more of the steps in the ABA biosynthetic pathway from mevalonic acid is catalyzed by cytochrome P-450. Feeding studies with 1′-deoxy-[²H]-ABA in resuspended cultures ofC. rosicola show that the conversion of this substrate is not inhibited by triarimol.     

Glucose-6-phosphate dehydrogenase deficiency and sulfadimidin acetylation phenotypes in Egyptian oases

Screening of 1315 males from two Egyptian oases for glucose-6-phosphate dehydrogenase deficiency (G-6PD) found an incidence of 5.9%. The rate of acetylation of sulfadimidin was also studied, and a bimodal distribution was found with 73% rapid acetylators. There is a correlation between high frequency of G-6PD deficiency and high frequency of slow acetylation rate. This work was supported by a grant from the International Center of Agricultural Research in the Dry Areas (ICARDA), Nile Valley project of faba beans.     

Seasonal variations in thalli and carrageenan composition of Gigartina pistillata (Gmelin) Stackhouse (Rhodophyta, Gigartinales) harvested along the Atlantic coast of Morocco

The biology and biochemistry of Gigartina pistillata (Gmelin) Stackhouse collected monthly at Nation Beach (Morocco), was studied during one year. The biological study showed one period of active growth from April to July. The thallus composition was quite stable during the major part of the year. The dry matter was maximum in May and August and minimum in January. The maximum carrageenan content occurred in June and September (about 37%) and the minimum carrageenan content occurred in February (19.0%). The total nitrogen content varied significantly, with a maximum in January (1.98%) and a minimum in August (0.7%). The ash content was significant (23–32%) with a maximum in August and a minimum in May. The carrageenan extracted from natural populations of Gigartina pistillata was a mixture of lambda‐type and kappa‐type carrageenans. The 3,6‐anhydrogalactose varied between 4.5 mol% in June to 25 mol% in February. For industrial applications the extract could be considered as a lambda‐type. The best period for harvest of G. pistillata in Morocco is between July and August when biomass and viscosity are at their maximum. A relationship between the physical characteristics of G. pistillata carrageenans and its seasonal cycle was deduced.     

Succession of Indigenous Pseudomonas spp. and Actinomycetes on Barley Roots Affected by the Antagonistic Strain Pseudomonas fluorescens DR54 and the Fungicide Imazalil

In recent years, the interest in the use of bacteria for biological control of plant-pathogenic fungi has increased. We studied the possible side effects of coating barley seeds with the antagonistic strain Pseudomonas fluorescens DR54 or a commercial fungicide, imazalil. This was done by monitoring the number of indigenous Pseudomonas organisms and actinomycetes on barley roots during growth in soil, harvest after 50 days, and subsequent decomposition. Bacteria were enumerated by traditional plate spreading on Gould's S1 agar (Pseudomonas) and as filamentous colonies on Winogradsky agar (actinomycetes) and by two quantitative competitive PCR assays. For this we developed an assay targeting Streptomyces and closely related genera. DR54 constituted more than 75% of the Pseudomonas population at the root base during the first 21 days but decreased to less than 10% at day 50. DR54 was not successful in colonizing root tips. Initially, DR54 affected the number of indigenous Pseudomonas organisms negatively, whereas imazalil affected Pseudomonas numbers positively, but the effects were transient. Although plate counts were considerably lower than the number of DNA copies, the two methods correlated well for Pseudomonas during plant growth, but after plant harvest Pseudomonas-specific DNA copy numbers decreased while plate counts were in the same magnitude as before. Hence, Pseudomonas was 10-fold more culturable in a decomposition environment than in the rhizosphere. The abundance of actinomycetes was unaffected by DR54 or imazalil amendments, and CFU and quantitative PCR results correlated throughout the experiment. The abundance of actinomycetes increased gradually, mostly in numbers of DNA copies, confirming their role in colonizing old roots.     

Protein and carbohydrate composition of larval food affects tolerance to thermal stress and desiccation in adult Drosophila melanogaster

Larval nutrition may affect a range of different life history traits as well as responses to environmental stress in adult insects. Here we test whether raising larvae of fruit flies, Drosophila melanogaster, on two different nutritional regimes affects resistance to cold, heat and desiccation as well as egg production and egg-to-adult viability. We raised larvae on a carbohydrate-enriched and a protein-enriched growth medium. We found that flies developed on the high protein medium had increased heat and desiccation tolerance compared to flies developed on the carbohydrate-enriched medium. In contrast, flies developed on the carbohydrate-enriched growth medium recovered faster from chill coma stress compared to flies developed on a protein-enriched medium. We also found gender differences in stress tolerance, with female flies being more tolerant to chill coma, heat knockdown and desiccation stress compared to males. Egg production was highest in females that had developed on the protein-enriched medium. However, there was a sex-specific effect of nutrition on egg-to-adult viability, with higher viability for males developing on the sucrose-enriched medium, while female survival was highest when developing on the protein-enriched medium. Our study indicates that larval nutrition has a strong impact on the ability to cope with stress, and that the optimal nutrient composition varies with the type of stress.