Effects of temperature and turbulence on the predator-prey interactions between a heterotrophic flagellate and a marine bacterium.

Biotic and abiotic factors can influence interactions between microbial grazers and their prey, thus impacting both the cycling of biogenic carbon within the surface layer of the ocean and the export of carbon to the deep ocean and higher trophic levels. In this study, microcosm experiments were used to evaluate the combined effect of temperature and turbulence on the growth rate of a marine bacterium (Vibrio splendidus), a protistan predator (Paraphysomonas sp.), and the community grazing impact of Paraphysomonas sp. on V. splendidus. It was found that the artificial turbulence generated (1.35 x 10-1 cm2 s-3) significantly increased the rates of growth of Paraphysomonas sp. at high (>10 degrees C), but not low (<5 degrees C) temperatures, and that turbulence had no effect on the growth of V. splendidus. Both flagellate and bacterial growth were temperature dependent and decreased 4- to 6-fold as temperatures decreased from 15 to 0 degrees C. Bacterial grazing mortality by Paraphysomonas sp. was 1.3- to 2.5-fold greater in the turbulent than static treatments among all four temperatures, and the rates of cell-specific ingestion of bacteria by Paraphysomonas sp. was 2-fold greater at 15 and 10 degrees C in the turbulent than in the static treatment. Hence, this study shows that turbulence can influence nanoflagellate grazing at temperatures >5 degrees C and suggests that at low temperatures, increased viscosity may limit the size of organisms that can be affected by small-scale turbulence.

Constitutive and acquired resistance to calcineurin inhibitors in renal transplantation: role of P-glycoprotein-170.

The present study examines whether resistance to Cyclosporin A (CyA) and Tacrolimus (FK506) develops in T cells from individual patients and the role of P-glycoprotein 170 (P-gp) in mediating drug resistance. IC50s were established for CyA and FK506 in cell cultures from 46 renal allograft recipients. P-gp expression and functional activity were determined by flow cytometry. Mean ID50 for CyA was 29 microg/li (range 2.5-100) and for FK506 1.2 microg/li (range 0.085-5.5). The sensitivities to the two drugs were correlated (P = 0.0001). There was variation in the ratio of the ID50s depending on the drug used for treatment (P = 0.02). There was no difference in P-gp expression and functional activity in patients with sensitive or resistant cells. The data indicate an association between the sensitivities to CyA and FK506 and evidence of selective resistance to whichever drug was used. P-gp drug transport does not explain this variation.

Cyclosporin A in refractory idiopathic nephrotic syndrome: 5 years clinical experience.

The use of cyclosporin A (Cy A) in idiopathic nephrotic syndrome, particularly lesions of focal segmental glomerular sclerosis, is controversial. A retrospective study of 10 adult patients with nephrotic syndrome treated with Cy A was performed. Histological diagnosis was established in all patients: focal segmental glomerular sclerosis (n = 6), focal global sclerosis (n = 1), mesangial proliferative glomerulonephritis (n = 1), focal proliferative glomerulonephritis (n = 1) and minimal change disease (n = 1). All patients had previously received immunosuppressive therapy (duration of steroids 1-76 months; 35.0 +/- 12.1, mean +/- SEM). Cy A in a dose of 3-5 mg/kg/day, reduced proteinuria from 16.85 +/- 6.67 to 3.37 +/- 1.48 g/24 hours (P = 0.008), with an associated increase in serum albumin from 15.2 +/- 2.6 to 34.3 +/- 2.5 g/l (P < 0.001). In six patients steroid therapy was discontinued. Cy A was well tolerated for up to 5 years. There was no significant nephrotoxicity. In conclusion, Cy A was effective treatment of refractory idiopathic nephrotic syndrome, including those cases with focal segmental glomerular sclerosis.