Effect of age, diet and tissue type on PCr response to creatine supplementation

Creatine/phosphorylcreatine (PCr) responses to creatine supplementation may be modulated by age, diet, and tissue, but studies assessing this possibility are lacking. Therefore we aimed to determine whether PCr responses vary as a function of age, diet, and tissue. Fifteen children, 17 omnivorous and 14 vegetarian adults, and 18 elderly individuals (“elderly”) participated in this study. Participants were given placebo and subsequently creatine (0.3 g·kg−1·day−1) for 7 days in a single-blind fashion. PCr was measured through phosphorus magnetic resonance spectroscopy (31P-MRS) in muscle and brain. Creatine supplementation increased muscle PCr in children (P < 0.0003) and elderly (P < 0.001), whereas the increase in omnivores did not reach statistically significant difference (P = 0.3348). Elderly had greater PCr increases than children and omnivores (P < 0.0001 for both), whereas children experienced greater PCr increases than omnivores (P = 0.0022). In relation to diet, vegetarians (P < 0.0001), but not omnivores, had significant increases in muscle PCr content. Brain PCr content was not affected by creatine supplementation in any group, and delta changes in brain PCr (−0.7 to +3.9%) were inferior to those in muscle PCr content (+10.3 to +27.6%; P < 0.0001 for all comparisons). PCr responses to a standardized creatine protocol (0.3 g·kg−1·day−1 for 7 days) may be affected by age, diet, and tissue. Whereas creatine supplementation was able to increase muscle PCr in all groups, although to different extents, brain PCr was shown to be unresponsive overall. These findings demonstrate the need to tailor creatine protocols to optimize creatine/PCr accumulation both in muscle and in brain, enabling a better appreciation of the pleiotropic properties of creatine

Effect of heat stress and oil formulation on conidial germination of Metarhizium anisopliae s. s. on tick cuticle and artificial medium

The effect of heat stress (45 °C) versus non-heat stress (27 °C) on germination of Metarhizium anisopliae sensu stricto (s.s.) isolate IP 119 was examined with conidia formulated (suspended) in pure mineral oil or in water (Tween 80, 0.01%), and then applied onto the cuticle of Rhipicephalus sanguineus sensu lato (s.l.) engorged females or onto culture medium (PDAY). In addition, bioassays were performed to investigate the effect of conidia heated while formulated in oil, then applied to blood-engorged adult R. sanguineus females. Conidia suspended in water then exposed to 45 °C, in comparison to conidia formulated in mineral oil and exposed to the same temperature, germinated less and more slowly when incubated on either PDAY medium or tick cuticle. Also, conidial germination on tick cuticle was delayed in comparison to germination on artificial culture medium; for example, germination was 13% on tick cuticle 72 h after inoculation, in contrast to 61.5% on PDAY medium. Unheated (27 °C) conidia suspended in either water or oil and applied to tick cuticle developed appressoria 36 h after treatment; whereas only heat-stressed conidia formulated in oil developed appressoria on tick cuticle. In comparison to conidia heated in mineral oil, there was a strong negative effect of heat on germination of conidia heated in water before being applied to arthropod cuticle. Nevertheless, bioassays [based primarily on egg production (quantity) and egg hatchability] exhibited high percentages of tick control regardless of the type of conidial suspension; i.e., water- or oil-formulated conidia, and whether or not conidia were previously exposed to heat. In comparison to aqueous conidial preparations, however, conidia formulated in oil reduced egg hatchability irrespective of heat or no-heat exposure. In conclusion, mineral-oil formulation protected conidia against heat-induced delay of both germination and appressorium production when applied to the cuticle of R. sanguineus