Isolation and partial characterization of metallothionein in the liver of the red-eared turtle (Trachemys scripta) following intreperitoneal administration of cadmium

Cadmium was distributed predominantly in the liver (42% of the body burden) after intraperitoneal injection with 10 mg Cd/kg/day for 6 days, although the kidney, spleen, heart, gonads and shell also contained substantial amounts of the metal. The major cadmium-containing fraction of the liver cytosol eluted in the position of mammalian metallothionein on a Sephadex G-75 column and was further resolved into two isoforms by reverse-phase HPLC. The two isoforms had high cysteine contents (17–22 residues/molecule) and lacked aromatic amino acids, a composition similar to that of other vertebrate metallothioneins. The turtle metal-binding protein had other properties characteristic of vertebrate metallothioneins including heat stability (85°C for 10 min), a relatively high absorbance at 245 nm, a low absorbance at 280 nm and a high metal content (approximately 6 nmol cadmium/nmol protein).     

Morphology and histochemistry of the ambiens muscle of the red-eared turtle (Pseudemys scripta)

Six fiber types have been described in the ambiens muscle of red-eared turtles. These include one slow oxidative type, two fast oxidative types, two fast oxidative and glycolytic types, and one fast glycolytic type. Fiber types are non-randomly distributed throughout cross sections of the muscle. There is a decreasing gradient of oxidative staining and an increasing gradient of glycolytic staining along an axis from the superficial to deep regions of the muscle. The slow oxidative fibers are predominantly located within one or two fascicles of the superficial surface of the muscle. The fast glycolytic fibers are predominant in deep fascicles. In contrast to previous reports of histochemically monotypic intrafusal fibers in turtle muscle, ambiens muscle spindles have been observed containing one to eleven intrafusal fibers, including two fiber types. Fiber diameter and area are consistently smaller than observed in most extrafusal fibers. Spindles are predominantly located in superficial and cranial fascicles of the ambiens muscle and are located in regions characterized by extrafusal fibers with high oxidative activity.