Sheets of mucosal epithelial cells were released from guinea pig small intestine after incubation with ethylenediaminetetraacetate . Cells in sheets retained their columnar shape for 24 hr at room temperature, and exclusion of nigrosine suggested they had intact plasma membranes . When sheets were disaggregated individual cells had normal morphology for at least 4 hr. During isolation 16% of the total protein and 24% of the total lactic dehydrogenase were lost from the cells, but subsequent enzyme leakage was low . Leakage increased with shaking, incubation at 37°C, or increasing the oxygen tension of the suspending medium, but was minimal when the Na+ : K+ ratio in the medium was 8 :1 and the osmolarity was high . Losses of particulate enzyme activities were negligible . Respiration was constant for up to 4 hr and was insensitive to calcium, bicarbonate, oxygen tension, and pH . It was inhibited by cyanide and iodoacetate and varied with the Na+ : K+ ratio of the extracellular fluid and the structural integrity of the cells . All preparations concentrated potassium and excluded sodium, but lost this ability if ouabain was added or cells were broken . Potassium-42 uptake was also sensitive to temperature, ouabain, and structural integrity. The preparations are being used to study cell metabolism in the intestinal epithelium.

While neural changes are thought to be responsible for early increases in strength following resistance training (RT), the exact changes in motor unit (MU) firing properties remain unclear. This review aims to synthesize the available evidence on the effect of RT on MU firing properties. MEDLINE (OVID interface), EMBASE (OVID interface), Web of Science (all databases), Cochrane Library, EBSCO CINAHL Plus, PubMed, and EBSCO SportDiscus were searched from inception until June 2021. Randomized controlled trials and non-randomized studies of interventions that compared RT to no intervention (control) were included. Two reviewers independently extracted data from each trial, assessed the risk of bias and rated the cumulative quality of evidence. Motor unit discharge rate (MUDR), motor unit recruitment threshold (MURT), motor unit discharge rate variability (MUDRV), MU discharge rate at recruitment vs. recruitment threshold relationship, and MU discharge rate vs. recruitment threshold relationship were assessed. Seven trials including 167 participants met the inclusion criteria. Meta-analysis (four studies) revealed that MUDR did not change significantly (P = 0.43), but with considerable heterogeneity likely to be present (I2 = 91). Low to moderate evidence supports changes in MUDRV, MUDR at recruitment vs. recruitment threshold relationship, and the MUDR vs. recruitment threshold relationship. Overall, this systematic review revealed that there is a lack of high-quality evidence for the effect of RT on MU firing properties. Heterogeneity across studies undermines the quality of the evidence for multiple outcomes and affects the conclusions that can be drawn.

SUMMARY We have used suspensions of isolated cells to study the metabolism of the mucosal epitheliurn and to compare its activity with that of other tissues in the intestinal wall of guinea pig.Only 4 % of the total glycolytic activity of the intestinal wall could be attributed to the mucosal epithelium. In contrast, about 76% of the activity was located in the intestinal muscle and the remaining 20 % in the intervening tissue.Clearly the view that the major proportion of the glycolytic activity of the small intestine resides in the mucosal epithelium does not apply to the guinea pig. In the light of our resuJts, it would be prudent to re-examine any conclusions about the distribution of metabolic activity throughout the gut wall if the supporting evidence has been drawn from experiments with mucosal homogenates.

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