Dietary Flaxseed Oil Supplementation Mitigates the Effect of Lead on the Enzymes of Carbohydrate Metabolism, Brush Border Membrane, and Oxidative Stress in Rat Kidney Tissues

Lead is a heavy metal widely distributed in the environment. Lead is a ubiquitous environmental toxin that is capable of causing numerous acute and chronic illnesses. Human and animal exposure demonstrates that lead is nephrotoxic. However, attempts to reduce lead-induced nephrotoxicity were not found suitable for clinical use. Recently, flaxseed oil (FXO), a rich source of ω-3 fatty acids and lignans, has been shown to prevent/reduce the progression of certain types of cardiovascular and renal disorders. In view of this, the present study investigates the protective effect of FXO on lead acetate (PbAc)-induced renal damage. Rats were pre-fed normal diet and the diet rich in FXO for 14 days, and then, four doses of lead acetate (25 mg/kg body weight) were administered intraperitoneally while still on diet. Various serum parameters, enzymes of carbohydrate metabolism, brush border membrane (BBM), and oxidative stress were analyzed in rat kidney. PbAc nephrotoxicity was characterized by increased serum creatinine and blood urea nitrogen. PbAc increased the activities of lactate dehydrogenase and NADP-malic enzyme, whereas it decreased malate and glucose-6-phosphate dehydrogenase, glucose-6-phosphatase, fructose-1, 6-bisphosphatase, and BBM enzyme activities. PbAc caused oxidant/antioxidant imbalances as reflected by increased lipid peroxidation and decreased activities of superoxide dismutase, glutathione peroxidase, and catalase. In contrast, FXO alone enhanced the enzyme activities of carbohydrate metabolism, BBM, and antioxidant defense system. FXO feeding to PbAc-treated rats markedly enhanced resistance to PbAc-elicited deleterious effects. In conclusion, dietary FXO supplementation ameliorated PbAc-induced specific metabolic alterations and oxidative damage by empowering antioxidant defense mechanism and improving BBM integrity and energy metabolism.     

A new species of Bradyidius (Copepoda, Calanoida) from the Gulf of Carpentaria, Australia

A new species of copepod belonging to the family Aetideidae,Bradyidius slyliformis sp. nov. is described and figured. Therelationship of this species to the other 12 members of thegenus is discussed. ¹Present address: 121 Jalan Athinahapan Dua, Taman Tun Dr Ismail,60000 Kuala Lumpur, Malaysia     

"In vitro" study on release of cyclic AMP and thyroid hormone in autonomously functioning thyroid nodules

The TSH effect on slice and the incubation medium cyclic AMP levels and T3 and T4 released from 8 autonomously functioning thyroid nodules (AFTN) and their respective perinodular (PN) tissues were examined. The thyroid slices were incubated in Eagle's Medium containing TSH (5 to 100 mU/ml) for 60 min and 300 min for tissue cyclic AMP generation and for cyclic AMP, T3 and T4 release, respectively. Basal cyclic AMP levels were not different either in AFTN and in PN slices or into the incubation medium. In both tissues TSH produced a similar cyclic AMP generation. In contrast, cyclic AMP released into the incubation medium was significantly higher in AFTN than in PN tissues, after TSH stimulation. Basal T3 values and TSH-stimulated T3 release in AFTN were not different from PN tissue. However, basal T4 levels were significantly higher in AFTN than in PN tissue as well as T4 released in response to TSH. In addition, T3/T4 ratio was lower in AFTN than in PN tissues. The cyclic AMP released into the incubation medium correlated with both T3 and T4 release in PN tissue but in the AFTN tissue no correlations were found. These findings suggest that the adenylate cyclase-cyclic AMP system is more sensitive to TSH-stimulation in AFTN when compared with PN tissue and that AFTN tissue has a preferential T4 secretion.     

Glucocorticoid inhibition of immunoreactive beta-endorphin release from the anterior lobe of the rat pituitary: in vitro and in vivo studies

Glucocorticoid control of pituitary beta-endorphin (beta-END) release was investigated in vitro and in vivo. Cultured cells of both rat anterior (AL) and neurointermediate (NIL) lobe released beta-END-like immunoreactivity (beta-END-LI) in response to epinephrine (10(-7) M); however, only the response of AL cells was prevented by corticosterone (10(-8)-10(-6) M) or dexamethasone (10(-9)-10(-7) M). Gel chromatographic analysis (Sephadex G-50) revealed that the major forms of beta-END-LI released by AL cells corresponded to beta-END and beta-lipotropin (beta-LPH) in molecular size, whereas virtually all of the immunoreactivity released by NIL cells resembled beta-END. In vivo administration of dexamethasone attenuated the stress-induced release of beta-END-LI in a dose- and time-related fashion, having a more pronounced effect on plasma levels of beta-END-LI corresponding to beta-LPH in molecular size. Metyrapone (100 mg/kg), an inhibitor of glucocorticoid synthesis, evoked a rapid (20-40 min) four- to sixfold increase in total plasma beta-END-LI and 75% of this rise was due to immunoreactivity resembling beta-LPH in size. This response was diminished by coadministration of either dexamethasone (0.05-1.25 mg/kg) or corticosterone (0.05-1.25 mg/kg) and completely prevented by 4-hr pretreatment with dexamethasone (50 micrograms/kg). The briskness of the plasma beta-END-LI response to acute changes in glucocorticoid status suggests that a "rapid" feedback mechanism operates in the physiologic control of pituitary beta-END-LI secretion. Moreover, the ability of glucocorticoids to selectively inhibit AL release of beta-END-LI in vitro and their pronounced effect on plasma levels of beta-END-LI resembling beta-LPH, a marker of AL secretion, together indicate that glucocorticoids exert a selective influence over the secretion of AL corticotrophs in vivo. This demonstration of differential regulation of the AL versus IL secretion of beta-END-LI in vivo most likely reflects a phenomena having biologic importance related to the different physiologic actions of the several molecular forms of beta-END-LI secreted by the two tissues.     

Activation of Ca2+ influx by metabolic substrates in Saccharomyces cerevisiae: role of membrane potential and cellular ATP levels

Influx of Ca2+ into cells of Saccharomyces cerevisiae was measured under non-steady-state conditions, which enable measurements of the initial rate of transport across plasma membranes without interference by the vacuolar Ca2+ transport system. Removal of glucose from the incubation medium led to inactivation of Ca2+ influx within 5 min. Readdition of glucose led to a transient increase in the rate of Ca2+ transport, reaching a peak after 3-5 min. A second increase was observed 60-80 min later. To examine whether the first transient activation of Ca2+ influx by glucose was mediated by membrane hyperpolarization, influx of 45Ca2+ was measured in the presence and absence of metabolic substrates (glucose, glycerol, and glucose plus antimycin A) in cells hyperpolarized to different values of membrane potential (delta psi). Logarithms of the rate of Ca2+ influx were plotted against values of delta psi. Two different slopes were obtained, depending upon whether the metabolic substrate was present or absent. Ca2+ influx in the presence of the metabolic substrates was always higher than expected by their effect on delta psi. Glycerol plus antimycin A did not affect Ca2+ influx. It was concluded that metabolized substrates activate Ca2+ influx not only by effects on delta psi but also by additional mechanism(s). Since no simple correlation between Ca2+ influx and intracellular ATP levels was observed, it was concluded that ATP levels do not affect the initial rates of Ca2+ transport across the plasma membrane of S. cerevisiae.     

Transient increase in Ca2+ influx in Saccharomyces cerevisiae in response to glucose: effects of intracellular acidification and cAMP levels

Influx of 45Ca2+ into Saccharomyces cerevisiae was measured under experimental conditions which enabled measurements of initial rate of transport across the plasma membrane, without interference by the vacuolar Ca2+ transport system. Addition of glucose or glycerol to the cells, after pre-incubation in glucose-free medium for 5 min, caused a rapid, transient increase in 45Ca2+ influx, reaching a peak at 3-5 min after addition of substrate. Ethanol, or glycerol added with antimycin A, had no effect on 45Ca2+ influx. We have shown previously that this increase is not mediated by an effect of the substrates on intracellular ATP levels. Changes in membrane potential accounted for only a part of the glucose-stimulated 45Ca2+ influx. The roles of intracellular acidification and changes in cellular cAMP in mediating the effects of glucose on 45Ca2+ influx were examined. After a short preincubation in glucose-free medium addition of glucose caused a decrease in the intracellular pH, [pH]i, which reached a minimum value after 3 min. A transient increase in the cellular cAMP level was also observed. Addition of glycerol also caused intracellular acidification, but ethanol or glycerol added with antimycin A had no effect on [pH]i. Artificial intracellular acidification induced by exposure to isobutyric acid or to CCCP caused a transient rise in Ca2+ influx but the extent of the increase was smaller than that caused by glucose, and the time-course was different. We conclude that intracellular acidification may be responsible for part of the glucose stimulation of Ca2+ influx.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation and characterization of Y chromosome DNA probes.

A sorted, cloned Y chromosome phage library was screened for unique Y chromosome sequences. Of the thousands of plaques screened, 13 did not hybridize to radiolabeled 46,XX total chromosomal DNA. Three plaques were characterized further. Clone Y1 hybridized to multiple restriction enzyme fragments in both male and female DNA with more intense bands in male DNA. Clone Y2, also found in female and male DNA, is probably located in the pseudosutosomal region because extra copies of either the X or Y chromosomes increased Y2 restriction enzyme fragment intensity in total cellular DNA. Clone Y5 was male specific in three of four restriction enzyme digests although in the fourth a light hybridizing band was observed in both male and female DNA. Clone Y5 was sublocalized to band Yq 11.22 by hybridization to a panel of cellular DNA from patients with Y chromosome rearrangements. Clone Y5 can be used to test for retention of the proximally long arm Y suggested to cause gonadal cancer in carrier females. The long series of GA repeats in Y5, anticipated to be polymorphic, may provide a sensitive means to follow Y chromosome variation in human populations.     

Successful synthesis of a glial-specific blood–brain barrier shuttle peptide following a fragment condensation approach on a solid-phase resin

Successful manual synthesis of the TD2.2 peptide acting as a blood–brain barrier shuttle was achieved. TD2.2 was successfully synthesised by sequential condensation of four protected peptide fragments on solid-phase settings, after several unsuccessful attempts using the stepwise approach. These fragments were chosen to minimise the number of demanding amino acids (in terms of coupling, Fmoc removal) in each fragment that are expected to hamper the overall synthetic process. Thus, the hydrophobic amino acids as well as Arg(Pbf) were strategically spread over multiple fragments rather than having them congested in one fragment. This study shows how a peptide that shows big challenges in the synthesis using the common stepwise elongation methodology can be synthesised with an acceptable purity. It also emphasises that choosing the right fragment with certain amino acid constituents is key for a successful synthesis. It is worth highlighting that lower amounts of reagents were required to synthesise the final peptide with an identical purity to that obtained by the automatic synthesiser.