Carbohydrate Mouth-Rinsing Improves Overtime Physical Performance in Male Ice Hockey Players During On-Ice Scrimmages.

PURPOSE: This randomized, double-blind, crossover study examined the effects of mouth-rinsing (MR) with a carbohydrate (CHO) vs. a placebo (PLA) solution on external and internal loads in hydrated ice hockey players during regulation and overtime (OT) periods of an on-ice scrimmage. METHODS: Twelve skilled male hockey players (22.6 [3.4] years, 178.9 [4.7] cm, 84.0 [6.5] kg) played three 20-min regulation periods and one 12-min OT period of small-sided 3-on-3 scrimmage. Skaters repeated 2 min shift and rest intervals. Participants mouth rinsed with 25 mL of CHO or PLA solution approximately every 10 min for a total of 7 rinses. A local positioning system (LPS) tracked external load variables including speed, distance, acceleration, and deceleration. Internal load was monitored with heart rate (HR) sensors and a rating of perceived exertion (RPE). RESULTS: During regulation play, both the conditions developed similar fatigue, with significantly decreased high-intensity distance, average speed and decelerations, and increased RPE, from period 1 to 2 and 3. In OT, CHO MR increased the distance skated at high-intensity (224 [77], 185 [66] m, p = 0.042), peak speed (24.6 [1.6], 23.7 [1.3] km·h-1, p = 0.016), number of sprints (1.9 [1.2], 1.2 [0.9], p = 0.011), and decreased distance skated at slow speed (300 [33], 336 [47], p = 0.034) vs. PLA MR. OT RPE was similar between the two conditions in spite of more work done in CHO MR. CONCLUSIONS: CHO MR may be a valuable practice to protect against decrements in external load with increased playing time in ice hockey, and possibly allows athletes to perform more work relative to perceived levels of exertion.

Dietary Macronutrient and Micronutrient Intake over a 7-Day Period in Female Varsity Ice Hockey Players.

This study examined the energy, macronutrient, and micronutrient intakes of female ice hockey players over a 7-d period including game, practice, and rest days. Twenty-three female varsity players (19.0 ± 1.1 yr, 167.1 ± 6.5 cm, 67.0 ± 8.0 kg) volunteered for the study. Average total daily energy expenditure (TDEE) was estimated over the 7-day period. Average 7-day energy intake (EI) and TDEE were 2354 ± 353 and 2304 ± 204 kcal. The majority (n = 19) of athletes had an EI ≥ 90% of their estimated TDEE. Macronutrient intake was 52% carbohydrate (CHO), 32% fat, and 16% protein of total EI, although CHO intake was slightly below recommendations (5 g/kg BM/d) on game and practice (4.8 ± 1.4 and 4.5 g/kg BM/d) days. Game day EI was greater than practice and rest days. Recommended micronutrient intakes were not met by most athletes for iron, calcium, vitamin D, and potassium, and intakes were similar between game, practice, and rest days. In summary, the average EI for female varsity ice hockey players appeared adequate to meet their energy needs over a weekly cycle of game, practice, and rest days. However, these female athletes would benefit from increasing CHO intake on game and practice days and selecting foods that are rich in vitamins and minerals.

Linker histone epitopes are hidden by in situ higher-order chromatin structure.

BACKGROUND: Histone H1 is the most mobile histone in the cell nucleus. Defining the positions of H1 on chromatin in situ, therefore, represents a challenge. Immunoprecipitation of formaldehyde-fixed and sonicated chromatin, followed by DNA sequencing (xChIP-seq), is traditionally the method for mapping histones onto DNA elements. But since sonication fragmentation precedes ChIP, there is a consequent loss of information about chromatin higher-order structure. Here, we present a new method, xxChIP-seq, employing antibody binding to fixed intact in situ chromatin, followed by extensive washing, a second fixation, sonication and immunoprecipitation. The second fixation is intended to prevent the loss of specifically bound antibody during washing and subsequent sonication and to prevent antibody shifting to epitopes revealed by the sonication process. In many respects, xxChIP-seq is comparable to immunostaining microscopy, which also involves interaction of the primary antibody with fixed and permeabilized intact cells. The only epitopes displayed after immunostaining are the "exposed" epitopes, not "hidden" by the fixation of chromatin higher-order structure. Comparison of immunoprecipitated fragments between xChIP-seq versus xxChIP-seq should indicate which epitopes become inaccessible with fixation and identify their associated DNA elements. RESULTS: We determined the genomic distribution of histone variants H1.2 and H1.5 in human myeloid leukemia cells HL-60/S4 and compared their epitope exposure by both xChIP-seq and xxChIP-seq, as well as high-resolution microscopy, illustrating the influences of preserved chromatin higher-order structure in situ. We found that xChIP and xxChIP H1 signals are in general negatively correlated, with differences being more pronounced near active regulatory regions. Among the intriguing observations, we find that transcription-related regions and histone PTMs (i.e., enhancers, promoters, CpG islands, H3K4me1, H3K4me3, H3K9ac, H3K27ac and H3K36me3) exhibit significant deficiencies (depletions) in H1.2 and H1.5 xxChIP-seq reads, compared to xChIP-seq. These observations suggest the existence of in situ transcription-related chromatin higher-order structures stabilized by formaldehyde. CONCLUSION: Comparison of H1 xxChIP-seq to H1 xChIP-seq allows the development of hypotheses on the chromosomal localization of (stabilized) higher-order structure, indicated by the generation of "hidden" H1 epitopes following formaldehyde crosslinking. Changes in H1 epitope exposure surrounding averaged chromosomal binding sites or epigenetic modifications can also indicate whether these sites have chromatin higher-order structure. For example, comparison between averaged active or inactive promoter regions suggests that both regions can acquire stabilized higher-order structure with hidden H1 epitopes. However, the H1 xChIP-seq comparison cannot define their differences. Application of the xxChIP-seq versus H1 xChIP-seq method is particularly relevant to chromatin-associated proteins, such as linker histones, that play dynamic roles in establishing chromatin higher-order structure.

Hyperosmotic stress: in situ chromatin phase separation.

Dehydration of cells by acute hyperosmotic stress has profound effects upon cell structure and function. Interphase chromatin and mitotic chromosomes collapse ("congelation"). HL-60/S4 cells remain ~100% viable for, at least, 1 hour, exhibiting shrinkage to ~2/3 their original volume, when placed in 300mM sucrose in tissue culture medium. Fixed cells were imaged by immunostaining confocal and STED microscopy. At a "global" structural level (µm), mitotic chromosomes congeal into a residual gel with apparent (phase) separations of Ki67, CTCF, SMC2, RAD21, H1 histones and HMG proteins. At an "intermediate" level (sub-µm), radial distribution analysis of STED images revealed a most probable peak DNA density separation of ~0.16 µm, essentially unchanged by hyperosmotic stress. At a "local" structural level (~1-2 nm), in vivo crosslinking revealed essentially unchanged crosslinked products between H1, HMG and inner histones. Hyperosmotic cellular stress is discussed in terms of concepts of mitotic chromosome structure and liquid-liquid phase separation.