ObjectiveTo analyze the combined effects of the silk protein sericin and swimming exercise on histomorphometry of the plantar muscle in Wistar rats.MethodsForty adult rats were randomly allocated into 5 groups comprising 8 animals each, as follows: Control, Injury, Sericin, Swim, and Swim plus Sericin. Three days after crushing of the sciatic nerve the rats in the Swim and Swim plus Sericin Groups were submitted to swimming exercise for 21 days. Rats were then euthanized and the plantar muscle harvested and processed.ResultsCross-sectional area, peripheral nuclei and muscle fiber counts, nucleus/fiber ratio and smallest muscle fiber width did not differ significantly between groups. Morphological analysis revealed hypertrophic fibers in the Swim Group and evident muscle damage in the Swim plus Sericin and Injury Groups. The percentage of intramuscular collagen was apparently maintained in the Swim Group compared to remaining groups.ConclusionCombined treatment with sericin and swimming exercise did not improve muscle properties. However, physical exercise alone was effective in maintaining intramuscular connective tissue and preventing progression of deleterious effects of peripheral nerve injury.

Physical exercise may help maintain muscle properties and functional improvement after peripheral nerve lesion, which may be enhanced by using biocompatible substances, such as sericin. The aim of this study was analyse the effect of sericin associated with swimming exercise on the phenotype, innervation, and functionality of the plantar muscle of Wistar rats. Forty randomly divided adult rats were used in five groups of eight animals: control, injury, sericin, exercise, exercise and sericin. The application of sericin was done on the spot, 100 μL, shortly after nerve compression. Three days after sciatic nerve compression, the swimming and swimming and sericin groups were submitted to physical swimming exercise for 21 days. Afterwards, the animals were euthanised and the plantar muscle was dissected and submitted to histochemical and histoenzymological techniques. The grip strength test did not show alterations in muscular functionality, and the control presented greater muscle mass in relation to the other groups, the same did not occur for muscle length. Polymorphic neuromuscular junctions were detected in the groups, although without significant morphometric alterations of the area, major and minor diameters. The percentage of type I fibres was lower in the lesion group and there was no difference in fibres IIa and IIb between groups. The area of fibres I, IIa and IIb remained constant between groups. Sericin biopolymer combined with swimming exercise did not affect plantar muscle function, submitted to experimental axonotmosis, whose contractile properties were altered by nerve injury.

Summary Knowledge of skeletal muscle adaptations is important to understand the functional deficits in cerebral palsy (CP). This study aimed to investigate the morphofunctional characteristics of skeletal muscle in a CP animal model. Initially, pregnant Wistar rats were injected intraperitoneally with saline or lipopolysaccharide over the last five days of pregnancy. The control group (n = 8) consisted of male pups born to females injected with saline. The CP group (n = 8) consisted of male pups born to females injected with lipopolysaccharide, which were submitted to perinatal anoxia [day of birth, postnatal day 0 (P0)] and sensorimotor restriction (P1‐P30). The open‐field test was undertaken on P29 and P45. On P48, the animals were weighed, and the plantaris muscle was collected and its weight and length were measured. Transverse sections were stained with haematoxylin‐eosin, NADH‐TR, Masson's trichrome and non‐specific esterase reaction for analysis. and transmission electron microscopy was performed. In the CP group, reductions were observed in mobility time, number of crossings and rearing frequency, body weight, muscle weight and length, and nucleus‐to‐fibre and capillary‐to‐fibre ratios. There was a statistically significant increase in the percentage area of the muscle section occupied by collagen; reduction in the area and increase in the number of type I muscle fibres; increase in myofibrillar disorganization and Z‐line disorganization and dissolution; and reduction in the area and largest and smallest diameters of neuromuscular junctions. Thus this animal model of CP produced morphofunctional alterations in skeletal muscle, that were associated with evidence of motor deficits as demonstrated by the open‐field test.

Cerebral Palsy (CP) refers to chronic childhood encephalopathy. The objective of this study was to verify effects of CP model that combines prenatal exposure to LPS, perinatal anoxia and sensorimotor restriction on EDL muscle. Male Wistar rat pups were separated: a) Control-pups of mothers injected with saline during pregnancy and b) Cerebral Palsy-pups of mothers injected with LPS during pregnancy, and submitted to perinatal anoxia and sensorimotor restriction. The CP group presented hypertrophy in the type IIB fibers and increase of nuclei/fiber and capillary/fiber ratios. The intrafusal fibers of CP group presented 26 % atrophy in the crosssectional area and intramuscular collagen volume increase 34 %. CP group showed myofibrillar disruption and Z-line disorganization and the NMJs presented increases of 22 % in area.This animal model of CP produces motor deficits and macro and microscopic alterations and in the ultrastructure of the EDL muscle.

Abstract. The aim of the study was to evaluate the reliability of urinary excretion rate of C-peptide as a marker of B-cell function during fasting. Ten obese subjects of both sexes fasted for 5 days. Diurnal serum C-peptide was collected before and on the 5th day; morning serum samples (for glucose, insulin and C-peptide) and 12-h urine samples (7.00 to 19.00 h) were collected daily. Body weight decreased from 138.7 ± 15.9 to 132.9 ± 15.6 kg. Morning glucose, insulin (–40%) and C-peptide (–50%) fell significantly throughout the study. Mean diurnal C-peptide values were 2.19 ±0.69 nmol/l before and 0.60 ±0.19 nmol/l after fasting (P < 0.0001) and its secretion rate was 909.4 ± 297.9 and 244.4 ± 83.9 nmol/12 h (P < 0.005), respectively. Excretion rate of C-peptide fell progressively from basal (11.2 ± 4.2 nmol/12 h) to a nadir value of 1.3 ± 0.8 nmol/12 h (P < 0.0005); similarly, the C-peptide to creatinine clearance ratio fell from 0.062 ± 0.035 to 0.028 ± 0.015 (P < 0.05). These results indicate that fasting modifies renal metabolism of C-peptide thus creating several complications in the quantitative interpretation of urinary levels as an index of its secretion rate from the B-cell.