Temperature modulates the Ca current of HIT-T15 and mouse pancreatic β-cells

The effects of raising temperature on the Ca²⁺, currents of insulin-secreting HIT and mouse pancreatic β-cells were studied. Currents were measured in 3 mM Ca²⁺ containing solutions using standard whole-cell techniques. Increasing temperature from 22°C to 35°C increased peak Ca²⁺, current amplitude, percent (fast) inactivation and decreased the time-to-peak of the current. Ca²⁺ currents in HIT and mouse β-cells responded in the same manner to an imposed physiological burstwave with test-pulses: (i) application of the burstwave inactivated the test-pulse Ca²⁺ current at both high and low temperatures; (ii) Ca²⁺, current inactivation leveled off during the plateau phase at 20–22°C whereas there was an apparent continual decay at 33–35°C; and (iii) recovery from inactivation occurred during the interburst period at both temperatures. Application of a physiological burstwave without test-pulses to mouse β-cells before and after addition of 0.2 mM Cd²⁺ resulted in a Ca²⁺ difference current. This current activated during the hyperpolarized interburst phase, activated, inactivated and deactivated rapidly and continually during the plateau phase, and recovered from inactivation during the interburst. Although raising temperature strongly modified HIT and mouse β-cell Ca²⁺ current, our work suggests that other channels, in addition to Ca²⁺ channels, are likely to be involved in the control of islet bursts, particularly at different temperatures. In addition, the effect of temperature on islet cell Ca²⁺, current may be partly responsible for the well-known temperature dependence of glucose-dependent secretion.     

Analysis of Cyp26b1/Rarg compound-null mice reveals two genetically separable effects of retinoic acid on limb outgrowth

The role of retinoic acid (RA) in limb development is unclear, although it has been suggested to be a proximalizing factor which plays a morphogenetic role in pattern formation. Exogenous RA produces a teratogenic effect on limb morphology; similarly, changes in the endogenous distribution of RA following genetic ablation of the RA-metabolizing enzyme, CYP26B1, result in phocomelia accompanied by changes in expression of proximo-distal (P-D) patterning genes, increased cell death, and delayed chondrocyte maturation. Here we show that disruption of RA receptor (RAR) gamma in a Cyp26b1^−/− background is able to partially rescue limb skeletal morphology without restoring normal expression of proximo-distal patterning genes. We further show that embryos deficient in CYP26B1 exhibit early localized domains of mesenchymal cell death, which are reduced in compound-null animals. This model reveals two genetically separable effects of RA in the limb: an apoptotic effect mediated by RARγ in the presence of ectopic RA, and a P-D patterning defect which is uncovered following the loss of both CYP26B1 and RARγ. These data provide genetic evidence to clarify the roles of both RA and CYP26B1 in limb outgrowth and proximo-distal patterning.     

Development of consistently crossable wheat genotypes for alien wheat gene transfer through fine-mapping of the <Emphasis Type="Italic">Kr1</Emphasis> locus

Breeders can force sexual hybridisation between wheat and related grass species to produce interspecific hybrids containing a dihaploid set of wheat and related chromosomes. This facilitates the introgression of desirable genes into wheat from the secondary gene pool. However, most elite European wheat varieties carry genes that suppress crossability, making the transfer of novel traits from exotic germplasm into elite wheat varieties difficult or impossible. Previous studies have identified at least five crossability loci in wheat. Here, the crossability locus with the largest effect, Kr1 on chromosome arm 5BL, was fine-mapped by developing a series of recombinant substitution lines in which the genome of the normally non-crossable wheat variety ‘Hobbit sib’ carries a recombinant 5BL chromosome arm containing segments from the crossable variety ‘Chinese Spring’. These recombinant lines were scored for their ability to cross with rye over four seasons. Analysis revealed at least two regions on 5BL affecting crossability, including the Kr1 locus. However, the ability to set seed is highly dependent on prevailing environmental conditions. Typically, even crossable wheat lines exhibit little or no seed set when crossed with rye in winter, but show up to 90% seed set from similar crosses made in summer. By recombining different combinations of the two regions affecting crossability, wheat lines that consistently exhibit up to 50% seed set, whether crossed in the UK winter or summer conditions, were generated, thus creating a very important tool for increasing the efficiency of alien wheat transfer programmes.     

Comparison of kinetic variables and muscle activity during a squat vs. a box squat

The purpose of this investigation was to determine if there was a difference in kinetic variables and muscle activity when comparing a squat to a box squat. A box squat removes the stretch-shortening cycle component from the squat, and thus, the possible influence of the box squat on concentric phase performance is of interest. Eight resistance trained men (Height: 179.61 ± 13.43 cm; Body Mass: 107.65 ± 29.79 kg; Age: 24.77 ± 3.22 years; 1 repetition maximum [1RM]: 200.11 ± 58.91 kg) performed 1 repetition of squats and box squats using 60, 70, and 80% of their 1RM in a randomized fashion. Subjects completed the movement while standing on a force plate and with 2 linear position transducers attached to the bar. Force and velocity were used to calculate power. Peak force and peak power were determined from the force-time and power-time curves during the concentric phase of the lift. Muscle activity (electromyography) was recorded from the vastus lateralis, vastus medialis, biceps femoris, and longissimus. Results indicate that peak force and peak power are similar between the squat and box squat. However, during the 70% of 1RM trials, the squat resulted in a significantly lower peak force in comparison to the box squat (squat = 3,269 ± 573 N, box squat = 3,364 ± 575 N). In addition, during the 80% of 1RM trials, the squat resulted in significantly lower peak power in comparison to the box squat (squat = 2,050 ± 486 W, box squat = 2,197 ± 544 W). Muscle activity was generally higher during the squat in comparison to the box squat. In conclusion, minimal differences were observed in kinetic variables and muscle activity between the squat and box squat. Removing the stretch-shortening cycle during the squat (using a box) appears to have limited negative consequences on performance.     

Atherogenic lipids and lipoproteins trigger CD36-TLR2-dependent apoptosis in macrophages undergoing endoplasmic reticulum stress

Macrophage apoptosis in advanced atheromata, a key process in plaque necrosis, involves the combination of ER stress with other proapoptotic stimuli. We show here that oxidized phospholipids, oxidized LDL, saturated fatty acids (SFAs), and lipoprotein(a) trigger apoptosis in ER-stressed macrophages through a mechanism requiring both CD36 and Toll-like receptor 2 (TLR2). In vivo, macrophage apoptosis was induced in SFA-fed, ER-stressed wild-type but not Cd36?(/)? or Tlr2?(/)? mice. For atherosclerosis, we combined TLR2 deficiency with that of TLR4, which can also promote apoptosis in ER-stressed macrophages. Advanced lesions of fat-fed Ldlr?(/)? mice transplanted with Tlr4?(/)?Tlr2?(/)? bone marrow were markedly protected from macrophage apoptosis and plaque necrosis compared with WT →Ldlr?(/)? lesions. These findings provide insight into how atherogenic lipoproteins trigger macrophage apoptosis in the setting of ER stress and how TLR activation might promote macrophage apoptosis and plaque necrosis in advanced atherosclerosis.     

Ethnic group differences in cardiometabolic disease risk factors independent of body mass index among American youth

Objective: The purpose of this analysis was to identify any ethnic group differences in the prevalence of cardiometabolic disease risk factors independent of BMI in United States youth. Design and Methods: Data on 3,510 boys and girls aged 8‐11 years from the 1999‐2008 National Health and Nutrition Examination Surveys were analyzed to determine the prevalence of 1 or ≥3 cardiometabolic disease risk factors: abnormal waist circumference and systolic (SBP) and diastolic blood pressure (DBP), increased concentrations of fasting triglyceride, and decreased concentrations of high‐density lipoprotein (HDL) cholesterol before and after adjusting for BMI. Results: Abnormal waist circumference and HDL‐cholesterol significantly differed by ethnic group before and after adjusting for BMI (P < 0.01). Non‐Hispanic blacks were significantly less likely to have abnormal HDL‐cholesterol concentrations than were Hispanics and non‐Hispanic whites, but non‐Hispanic whites were significantly more likely to have elevated triglycerides and three or more abnormal cardiometabolic risk factors than non‐Hispanic blacks. Conclusion: These findings point to ethnic group disparities not related to BMI alone, even in children as young as 8‐11 years. Programs to prevent and treat eventual cardiometabolic disease in children could be tailored for specific ethnic backgrounds as a result.