Dynamic of the GRF-induced GH response in genetically obese Zucker rats: influence of central and peripheral factors

To determine the time onset of the growth hormone (GH) alteration in the genetically obese rat, we studied the in vivo and in vitro rat growth hormone releasing factor (rGRF(1-29)NH2)-induced GH secretion in 6- and 8-week-old lean and obese male Zucker rats. Under sodium pentobarbital anesthesia, rGRF(1-29)NH2 (GRF) was injected intravenously at two doses: 0.8 and 4.0 micrograms/kg b.w. Basal serum GH concentrations were similar in lean and obese age-matched animals. The GH response to both GRF doses tested was unchanged in 6-week-old obese rats as compared to their lean litter mates. In contrast, a significant decrease of the GH secretion in response to 4.0 micrograms/kg b.w. GRF was observed in the 8-week-old obese rats. The effect of GRF (1.56, 6.25 and 12.5 pM) was further studied in vitro, in a perifusion system of freshly dispersed anterior pituitary cells of lean and obese Zucker rats. Basal GH release was similar in the 6-week-old animal group. In contrast, it was significantly decreased in 8-week-old obese rats as compared to their lean litter mates. Stimulated GH response to 1.56 and 6.25 pM GRF was significantly greater in the 6-week-old obese group than in the age-matched control group. In contrast, the GH response to all GRF concentrations tested was significantly decreased in the 8-week-old obese rats as compared to their respective lean siblings. In 8-week-old obese rats, a decrease of GH pituitary content and an increase of hypothalamic somatostatin (SRIF) concentration were observed. Insulin and free fatty acid serum were significantly increased in 8-week-old obese rats. In contrast, lower insulin-like growth factor I serum levels were observed in the obese animals as compared to their lean litter mates. Finally, to further clarify the role of the periphery in the inhibition of GH secretion observed in the 8-week-old fatty rats, we exposed cultured pituitary cells of 8-week-old lean animals to 17% serum of their obese litter mates. A significant decrease of GRF-stimulated GH secretion of lean rat pituitary cells exposed to the obese serum was noted (P less than 0.05). This study demonstrates that, in the obese Zucker rat, an alteration of the GH response to GRF is evident by the 8th week of life. This defective GH secretion could be related to peripheral and central abnormalities.     

Partial characterization of chitinolytic enzymes from Streptomyces albidoflavus

Streptomyces albidoflavus NRRL B-16746 secreted three types of chitinolytic enzymes: N -acetyl-glucosaminidase, chitobiosidase and endochitinase. Optimal activity for all three types of enzymes occurred at pH 4–6; however 55–74% of the chitobiosidase and endochitinase activity was detectable at pH 8–10. Chitobiosidase activity originated from two strongly acidic (pI < 3.0) proteins with molecular mass of 27 kDa and 34 kDa, while endochitinase activity originated from five major acidic proteins (pI 5.1, 5.3, 5.75, 5.8–5.9 and 6.4) with molecular mass of 59, 45, 38.5, 27 and 25.5 kDa. Purified chitobiosidases significantly reduced spore germination and germ tube elongation of Botrytis cinerea and Fusarium oxysporum. Chitinolytic enzymes with significant activity at pH 4–10 may be used, transgenically, to reduce the growth and/or development of a broad spectrum of insects and fungi that are major economic pests.     

The influence of glycyl residues on the flexibility of peptide hormones in solution. A 13C-nuclear-magnetic-resonance study of luteinizing hormone-releasing hormone (luliberin) and its des-glycinamide10 N-ethylamide analog.

13C nuclear magnetic resonance spectroscopy in used to gain information on the flexibility of the backbone in peptide hormones and peptide hormone analogs. 13C spin-lattice relaxation times (T1) were measured on luliberin, the luteinizing-hormone-releasing hormone and des(Gly-NH2)10-luliberin-N-ethylamide in aqueous solution at 25.2 and 67.9 MHz at temperatures of 32 degrees, 40 degrees and 55 degrees C. The 13C spin-lattice relaxation times indicate increased flexibility of the peptide backbone in the immediate environment of glycyl residues in luliberin (less than Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) and the hormone analog des(Gly-NH2)10-luliberin-N-ethylamide (less than Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-NH-CH2CH3) in aqueous solutions. 13 C NMR spectroscopy is shown to be a sensitive technique for monitoring the time-averaged conformational flexibility of peptides in solution. Activation energies (Ea) of about 25 kJ/mol were obtained for rotational reorientation of non-terminal alpha-carbons in the peptide backbone. Rotation of methyl groups was characterized by an Ea of 9.6 kJ/mol whereas reorientation of the N-terminal pyroglutamyl residue showed an Ea value of 14.6 kJ/mol. The Ea values of individual carbons in the side-chains of prolyl, arginyl and leucyl residues in the peptides were similar to those obtained for the alpha-carbon of the same amino acid residue in the peptide backbone of the hormones.     

The effect of high buffer cardioplegia and secondary cardioplegia on cardiac preservation and postischemic functional recovery: a 31P NMR and functional study in Langendorff perfused pig hearts.

High buffer cardioplegia may provide protection against ischemic damage by reducing the extent of intracellular acidosis. Secondary cardioplegia may improve postischemic recovery by restoration of high energy phosphates, ionic gradients, and intracellular pH. To test these hypotheses, pig hearts were arrested with high buffer (150 mM MOPS) cardioplegia or modified St. Thomas' solution II and then kept ischemic at 12 degrees C for 8 h. High energy phosphates and intracellular pH were followed during the period of ischemia, using 31P nuclear magnetic resonance spectroscopy, and functional recovery was followed during reperfusion. The hearts arrested by high buffer cardioplegia showed significantly higher intracellular pH than hearts preserved with St. Thomas' solution, but there were no significant differences in high energy phosphates. There were no significant differences in functional recovery. We found, however, that secondary cardioplegia abolished ventricular fibrillation, and resulted in improved functional recovery after 8 h of ischemic preservation compared with the hearts reperfused with Krebs-Henseleit solution alone. Our results suggest that despite attenuating the decreases in intracellular pH, high buffer cardioplegia does not improve recovery following 8 h of preservation at 12 degrees C. Secondary cardioplegia reduces the incidence of ventricular fibrillation and improves postischemic functional recovery of the myocardium.     

31P NMR studies of metabolism in Acanthamoebacastellanii: Polyphosphate release from encysted cells

${}^{31}\text{P NMR}$ studies of $\text{Acanthamoeba}\text{castellanii}$ have shown that encysting cells release polyphosphate into the encystment medium. Mature cysts contain low levels of polyphosphate, as do vegetative cells. Young cysts (7 days) show detectable levels of nucleotide diphosphates and triphosphate similar to those observed in vegetative cells. Mature cysts (90 days) show only excreted polyphosphate as well as a component which has a chemical shift of a phosphodiester. The inorganic phosphate peak in the cyst shows that the cyst milieu is liquid-like and that the intracellular environment maintains a pH between 6 and 7.5 in the presence of extracellular values from 4 to 9.     

Performance bonuses and the quality of primary health care delivered by family health teams in Brazil: A difference-in-differences analysis

BackgroundPay-for-performance (P4P) programmes to incentivise health providers to improve quality of care have been widely implemented globally. Despite intuitive appeal, evidence on the effectiveness of P4P is mixed, potentially due to differences in how schemes are designed. We exploited municipality variation in the design features of Brazil’s National Programme for Improving Primary Care Access and Quality (PMAQ) to examine whether performance bonuses given to family health team workers were associated with changes in the quality of care and whether the size of bonus mattered.Methods and findingsFor this quasi-experimental study, we used a difference-in-differences approach combined with matching. We compared changes over time in the quality of care delivered by family health teams between (bonus) municipalities that chose to use some or all of the PMAQ money to provide performance-related bonuses to team workers with (nonbonus) municipalities that invested the funds using traditional input-based budgets. The primary outcome was the PMAQ score, a quality of care index on a scale of 0 to 100, based on several hundred indicators (ranging from 598 to 660) of health care delivery. We did one-to-one matching of bonus municipalities to nonbonus municipalities based on baseline demographic and economic characteristics. On the matched sample, we used ordinary least squares regression to estimate the association of any bonus and size of bonus with the prepost change over time (between November 2011 and October 2015) in the PMAQ score. We performed subgroup analyses with respect to the local area income of the family health team. The matched analytical sample comprised 2,346 municipalities (1,173 nonbonus municipalities; 1,173 bonus municipalities), containing 10,275 family health teams that participated in PMAQ from the outset. Bonus municipalities were associated with a 4.6 (95% CI: 2.7 to 6.4; p < 0.001) percentage point increase in the PMAQ score compared with nonbonus municipalities. The association with quality of care increased with the size of bonus: the largest bonus group saw an improvement of 8.2 percentage points (95% CI: 6.2 to 10.2; p < 0.001) compared with the control. The subgroup analysis showed that the observed improvement in performance was most pronounced in the poorest two-fifths of localities. The limitations of the study include the potential for bias from unmeasured time-varying confounding and the fact that the PMAQ score has not been validated as a measure of quality of care.ConclusionsPerformance bonuses to family health team workers compared with traditional input-based budgets were associated with an improvement in the quality of care.

Nasser Fardousi and colleagues investigate the association between performance bonuses and the quality of primary health care delivered by family health teams in Brazil.     

Warming counteracts defoliation‐induced mismatch by increasing herbivore‐plant phenological synchrony

Climate change is altering phenology; however, the magnitude of this change varies among taxa. Compared with phenological mismatch between plants and herbivores, synchronization due to climate has been less explored, despite its potential implications for trophic interactions. The earlier budburst induced by defoliation is a phenological strategy for plants against herbivores. Here, we tested whether warming can counteract defoliation‐induced mismatch by increasing herbivore‐plant phenological synchrony. We compared the larval phenology of spruce budworm and budburst in balsam fir, black spruce, and white spruce saplings subjected to defoliation in a controlled environment at temperatures of 12, 17, and 22°C. Budburst in defoliated saplings occurred 6–24 days earlier than in the controls, thus mismatching needle development from larval feeding. This mismatch decreased to only 3–7 days, however, when temperatures warmed by 5 and 10°C, leading to a resynchronization of the host with spruce budworm larvae. The increasing synchrony under warming counteracts the defoliation‐induced mismatch, disrupting trophic interactions and energy flow between forest ecosystem and insect populations. Our results suggest that the predicted warming may improve food quality and provide better growth conditions for larval development, thus promoting longer or more intense insect outbreaks in the future.