Surface modification using interfacial assembly of the Streptomyces chaplin proteins

The chaplin proteins are instrumental in the formation of reproductive aerial structures by the filamentous bacterium Streptomyces coelicolor. They lower the water surface tension thereby enabling aerial growth. In addition, chaplins provide surface hydrophobicity to the aerial hyphae by assembling on the cell surface into an amphipathic layer of amyloid fibrils. We here show that mixtures of cell wall-extracted chaplins can be used to modify a variety of hydrophilic and hydrophobic surfaces in vitro thereby changing their nature. Assembly on glass leads to a protein coating that makes the surface hydrophobic. Conversely, the assembly of chaplins on hydrophobic surfaces renders them hydrophilic. Furthermore, we show that chaplins can stabilize emulsions of oil into water and have an unprecedented surface activity at high pH. Interestingly, this high surface activity coincides with the interfacial assembly of chaplins into a semi-liquid membrane, as opposed to the rigid membrane formed at neutral pH. This semi-liquid membrane possibly represents a trapped intermediate in the assembly process towards the more rigid amyloidal conformation. Taken together, our data shows that chaplins are suitable candidate proteins for a wide range of biotechnological applications.     

Plasma renin activity and urinary kallikrein excretion in lead-exposed workers as related to hypertension and nephropathy

Urinary kallikrein activity and plasma renin activity (PRA) in supine and erect positions were determined in 22 men occupationally exposed to lead. In eight of them, suffering from hypertension and/or nephropathy, urinary kallikrein activity was low or absent, while PRA was normal or reduced. The other fourteen non-symptomatic workers showed normal or reduced urinary kallikrein activity and variable PRA. Urinary kallikrein activity of lead-exposed workers was significantly correlated with upright PRA.The relation between lead-exposure and essential hypertension is discussed.     

Increased platelet aggregability is associated with increased prostacyclin production by vessel walls in hypercholesterolemic rabbits

The influences of experimental hypercholesterolemia in the rabbit on platelet-vessel wall interactions have been studied by evaluating the aggregatory response of platelet rich plasma (PRP) to arachidonic acid (AA) stimulation and levels of 6-keto-PGF1 alpha in PRP from normal (N) and hypercholesterolemic (HC) animals prior and after perfusion through the corresponding aortas. In addition, the responses of N PRP to aggregation after perfusion through HC aortas and those of HC PRP perfused through N aortas, and the platelet response to the inhibitory effect of exogenous prostacyclin have been evaluated. The data indicate that in HC rabbits, on one side platelets are hyperreactive to AA and less sensitive to the inhibitory activity of prostacyclin and, on the other, the antiaggregatory activity and prostacyclin production of vessel walls is higher, suggesting compensatory mechanisms in the haemostatic balance.     

Influence of cinnamaldehyde on UV-induced gene conversion and point mutation in yeast: effect on protein synthesis.

The activity of cinnamaldehyde (CIN), a bioantimutagen in bacterial systems, was tested in the D7 strain of yeast Saccharomyces cerevisiae. Yeast cells were UV-irradiated and post-incubated in liquid growth medium for 2 and 4 h with different concentrations of cinnamaldehyde. During the post-incubation period, DNA-damage-specific functions may be induced. This in turn may affect the genotoxicity and in fact a weak decrease in UV-induced convertant and revertant frequencies was observed after 4 h of post-incubation. The presence of CIN in the growth medium increased the UV-induced gene conversion and reversion. The addition of cycloheximide abolished this effect. To evaluate the CIN effect on protein synthesis, extracts of cells UV-treated and post-incubated for 2 h in the presence of 35S-methionine were performed. SDS-gel electrophoresis demonstrated the inhibitory effect of CIN on a UV-specific protein. This work suggests that CIN might interfere with DNA-damage-inducible systems although it did not exert an antimutagenic activity in our experimental conditions.     

ACCUMULATION OF TRIENOIC FATTY ACIDS IN RAT BRAIN AFTER DEPLETION OF LIVER (n-6) POLYUNSATURATED FATTY ACIDS

Abstract— The relative rates of accumulation (mg/g fresh weight) of (n-6)tetraenoic and (n-9)trienoic fatty acids in brain and liver of developing rats during essential fatty acid deficiency, show that accumulation of (n-6) acids in brain occurs concomitantly with depletion of the liver stores of polyunsaturated acids, and indicate that considerable accumulation of trienes occurs in the brain, reaching levels (mg/g) even higher than those present in the liver, only after depletion of tetraenes in the liver. The brain thus incorporates very actively long chain polyunsaturated fatty acids both of the (n-6), and of the (n-9) series, when (n-6) compounds are not available any longer.     

Gender‐specific Effect of Obesity on Balance

Obesity modifies the body geometry by adding mass to different regions and it influences the biomechanics of activities of daily living. Weight influences postural stability, but there is no consensus as to whether the different fat distribution in males and females produces gender‐related effects on balance. The aim of this study was to investigate the effect of body weight increases on postural performance in males and females. A total of 22 obese females (BMI: 41.1 ± 4.1 kg/m²) and 22 obese males (BMI: 40.2 ± 5 kg/m²) were analyzed during a static posture trial on a force platform in standardized conditions. Twenty healthy subjects (10 females, 10 males) constituted the control group. We computed the following parameters related to the center of pressure (CoP): velocity and displacements along the antero‐posterior (AP) and medio‐lateral axis (ML). We found several statistically significant differences between healthy and obese men, in particular regarding the AP and ML CoP parameters, which were correlated to body weight (r = 0.36–0.58). The comparison between healthy and obese females pointed out statistically significant differences in AP parameters and no significant differences in ML displacements. Body weight was found to correlate with AP parameters (r = 0.36–0.74), but not with ML displacements. The increased body mass seems to produce AP instability in both genders and ML destabilization only in males. Rehabilitation programs should take these findings into account by adopting specific interventions to improve ML control in obese males, and through weight loss and strengthening of ankle flexors/extensors in both genders.