The potency of tissue-type plasminogen activator (TPA) determined with chromogen and clot-lysis assays

An assessment was made of two methods for determining the potency of tissue-type plasminogen activator (TPA). A chromogenic microtitre plate assay was established which contained TPA, plasminogen, a synthetic plasmin substrate (H-D-valyl-L-leucyl-L-lysyl-p-nitroaniline dihydrochloride, S2251) and any one of the following stimulators: native fibrinogen, enzymatic and chemical digests of fibrinogen, poly-D-lysine (PDL) and chemical derivatives of the latter. The chromogen assay was compared with an automated clot-lysis (turbidimetric) assay for sensitivity, reproducibility and validity for potency determination. Reference preparations of TPA were titrated in both assays: in the chromogen assay the dose-response curves were non-parallel, whereas parallelism was observed in the clot-lysis assay. Thus, the chromogen assay was restricted in its applicability and disqualified from any routine regulatory use. The potency of individual lots of recombinant (r)TPA could only be estimated in International Units (IU) of TPA activity with the automated clot-lysis assay and the potency values obtained (IU/vial) were in remarkably close agreement with the manufacturers' values.     

The SGLT2 inhibitor dapagliflozin promotes systemic FFA mobilization,enhances hepatic β-oxidation,and induces ketosis

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have been shown to increase ketone bodies in patients with type 2 diabetes; however, the underlying mechanisms have not been fully elucidated. Here we examined the effect of the SGLT2 inhibitor dapagliflozin (1 mg/kg/day, formulated in a water, PEG400, ethanol, propylene glycol solution, 4 weeks) on lipid metabolism in obese Zucker rats. Fasting FFA metabolism was assessed in the anesthetized state using a [9,10-³H(N)]-palmitic acid tracer by estimating rates of plasma FFA appearance (R_a), whole-body FFA oxidation (R_ox), and nonoxidative disposal (R_st). In the liver, clearance (K_β-ox) and flux (R_β-ox) of FFA into β-oxidation were estimated using [9,10-³H]-(R)-bromopalmitate/[U-¹⁴C]palmitate tracers. As expected, dapagliflozin induced glycosuria and a robust antidiabetic effect; treatment reduced fasting plasma glucose and insulin, lowered glycated hemoglobin, and increased pancreatic insulin content compared with vehicle controls. Dapagliflozin also increased plasma FFA, R_a, R_ox, and R_st with enhanced channeling toward oxidation versus storage. In the liver, there was also enhanced channeling of FFA to β-oxidation, with increased K_β-ox, R_β-ox and tissue acetyl-CoA, compared with controls. Finally, dapagliflozin increased hepatic HMG-CoA and plasma β-hydroxybutyrate, consistent with a specific enhancement of ketogenesis. Since ketogenesis has not been directly measured, we cannot exclude an additional contribution of impaired ketone body clearance to the ketosis. In conclusion, this study provides evidence that the dapagliflozin-induced increase in plasma ketone bodies is driven by the combined action of FFA mobilization from adipose tissue and diversion of hepatic FFA toward β-oxidation.     

Refuting phylogenetic relationships

Background  

Phylogenetic methods are philosophically grounded, and so can be philosophically biased in ways that limit explanatory power. This constitutes an important methodologic dimension not often taken into account. Here we address this dimension in the context of concatenation approaches to phylogeny.     

Effets sur le spermatozoïde humain du Diuron (3-(3,4-dichlorophényl)-1,1-diméthyl-urée) et de l’un de ses produits de transformation, la 3,4-dichloroaniline (3,4-DCA) (Etude préliminaire)

Diuron belongs to the family of halogenophenylureas, one of the main groups of herbicides used for more than 40 years. These herbicides absorb sunlight and can be photochemically transformed in the environment (herbicides are transformed on the soil surface exposed to sunlight) or biotransformed by microorganisms present in soil or in water. The metabolites (chlorohydroxyphenylurea, chlorophenylaniline, respectively) are more toxic than the parent compound, as demonstrated by a bioluminescence inhibition assay performed with a marine bacterium (Vibrio fischeri toxicity test). The lipophilicity of these pesticides makes the cell membrane a target for their action, especially the spermatozoa cell membrane. The aim of this study is to use human spermatozoa to evaluate the effect of this urea pesticide and its biotransformed product on the spermatozoa membrane. We investigated the structural and functional effects of these environmental pollutants on spermatozoa. Three million spermatozoa purified on a 95/47.5% Percoll gradient were suspended in 250 μl of modified Earle’s medium (without phenol red) supplemented with 7.5% of human decomplemented serum. Pesticides (Diuron or 3,4-dichloroaniline (3,4-DCA)) were added at a final concentration of 0.1; 1 and 5 mM. Samples were incubated at room temperature for 24 hours. We show that both Diuron and 3,4-DCA decrease motility and vitality of spermatozoa incubated with the highest concentration of pesticides. Our preliminary results show that the effects are more rapid and more intense with the biotransformed product (3,4-DCA) than with Diuron. Addition of herbicide to human spermatozoa increases membrane fluidity, assessed by measuring the fluorescence polarisation anisotropy with a fluorescent probe: 1,6-diphenyl-1,3,5-hexatriene (DPH). Changes in membrane fluidity may be a primary toxic effect of these herbicides. These results suggest that human spermatozoa may constitute a valuable indicator of the toxic effects of pesticides.