To gain insight into the mechanism of sarcopenia and the protective effect of melatonin, the gastrocnemius muscles of young (3–4 months), early-aged (12 months), and old-aged (24 months) wild-type C57BL/6J female mice were examined by magnetic resonance and microscopy. Locomotor activity, lactate production, and nuclear apoptosis were also assessed. The results support the early onset of sarcopenia at 12 months of age, with reduction of muscle fiber number, muscle weight/body weight ratio, lactate, and locomotor activity. Lipid droplet infiltration and autophagosomes were also detected. These changes driven little effects on the early-aged muscle, but they got worse in old-aged animals by the progressive damage of the muscle. Old-aged muscle showed a reduction of the mitochondrial number, a destruction of the mitochondrial cristae, and swelling. Tubular aggregates and nucleic acid fragmentation were the most striking findings in old-aged muscle, reflecting a broad damage with loss of autophagy efficacy. Oral melatonin administration conserved the normal muscular architecture, weight, muscle fiber number, and activity in the old age; it stimulated lactate production, prevented mitochondrial damage and tubular aggregates, and reduced the percentage of apoptotic nuclei in aged muscles. Altogether, gastrocnemius muscle showed age-mediated signs of sarcopenia that were reduced by melatonin treatment.

Fish liver is considered as a key organ that controls various life functions. The cellular and stromal elements of liver of eighteen specimens of adult grass carp were investigated by light- and electron- microscopy and enzyme histochemistry. The liver was formed of two lobes with a long process extended from the right lobe. Serial paraffin section of the liver identified different kinds of vascular- biliary structures as follows: 1) pancreatic– venous–biliary–arteriolar tracts (P-VBAT); 2) venous-biliary-arteriolar tracts, (VBAT); 3) pancreatic–venous– biliary tracts (P-VBT); 4) venous-biliary tracts (VBT); 5) venous–arteriolar tracts (VAT); 6) isolated veins named as venous tracts (VT); 7) isolated bile ducts, named as biliary tracts (BT); 8) biliary-arteriolar tracts (BAT); 9) pancreatic–biliary tracts (P-BT); 10) pancreatic– venous tracts (P-VT). Macrophages aggregates were associated with VBT and P-BT. The hepatic parenchyma was consisted of many populations of cells. Histochemically, the hepatocytes were strongly reacted with PAS, and Best's carmine. Moreover, strong staining patterns for acid phosphatase, ATPase, and alkaline phosphatase were demonstrated in hepatocytes. The hepatic satellate (Ito) cells were observed in the space of Disse and between hepatocytes. Rodlet cells and eosinophilic granular/ mast cells were encountered in the liver of grass carp. The sinusoids were lined by fenestrated endothelial cells and Kupffer cells. Moreover, dendritic-like cells were demonstrated in the sinusoids and perisinusoidal connective tissue. The biliary duct system was constituted of bile canaliculi, ductules, and bile ducts. Telocytes with their characteristics telopodes were located around bile ducts. The current findings are offering fundamental data on histology of grass carp liver.

Many studies have been carried out to investigate the occurrence and distribution of telocytes (TCs) in many organs. However, their morphological development is still unclear. This study was performed to demonstrate the morphological development of TCs in rabbits' lung from fetal to postnatal life using light-, electron- microscopy, immunohistochemistry, morphometrical and statistical analysis. During the fetal life, these cells formed an extensive network of telopodes (Tps) which were in close contact with developing alveoli, bronchioles, stem cells and many other interstitial components. In addition, the TCs' number was significantly increased around the neocapillaries in fetal lung. In the fetal life, TCs were stellate in shape and characterized by large cell bodies and many short Tps that contained abundant rER, mitochondria, and ribosomes. By gradual increasing of ages, TCs were spindle in shape with two Tps contained a massive amount of secretory structures (exosomes, ectosomes, and multivesicular bodies). Moreover, TCs in postnatal lung showed a significant decrease in number and diameter of their cell bodies and a significant increase in the length of Tps compared with those in fetal life. The TCs contributed with pneumocytes and endothelium in the formation of air-blood barrier. The TCs' immunohistochemical profiles for CD34, vimentin, c-kit, connexin 43, vascular endothelial growth factor (VEGF), and neuron- specific enolase (NSE) differed between ages during the lung development. This study provided an evidence that TCs contributed to angiogenesis, the formation of the air-blood barrier, lung organization, and development.

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