Using immunocytochemical methods we have studied the distribution of vinculin in the anterior and posterior latissimus dorsi skeletal (ALD and PLD, respectively) muscles of the adult chicken. The ALD muscle is made up of both tonic (85%) and twitch (15%) myofibers, and the PLD muscle is made up entirely of twitch myofibers. In indirect immunofluorescence, antivinculin antibodies stained specific regions adjacent to the sarcolemma of the ALD and PLD muscles. In the central and myotendinous regions of the ALD, staining of the tonic fibers was intense all around the fiber periphery. Staining of the twitch fibers of both ALD and PLD muscles was intense only at neuromuscular junctions and myotendinous regions. Electron microscopy revealed subsarcolemmal, electron-dense plaques associated with the membrane only in those regions where vinculin was localized by immunofluorescence. Using antivinculin antibody and protein A conjugated to colloidal gold, we found that the electron-dense subsarcolemmal densities in the tonic fibers of the ALD contain vinculin; no other structures were labeled. The basal lamina overlying the densities appeared to be connected to the sarcolemma by fine, filamentous structures, more enriched at these sites than elsewhere along the muscle fiber. Increased amounts of endomysial connective tissue were often found just outside the basal lamina near the densities. In tonic ALD muscle fibers, the subsarcolemmal densities were present preferentially over the I-bands. In partially contracted ALD muscle, subsarcolemmal densities adjacent to the Z-disk appeared to be connected to that structure by short filaments. We propose that in the ALD muscle, through their association with the extracellular matrix, the densities stabilize the muscle membrane and perhaps assist in force transmission.The latissimus dorsi muscle of the chick is composed of anterior and posterior slips. The anterior latissimus dorsi (ALD) ~ muscle of the adult is made up largely of tonic muscle fibers, and the posterior latissimus dorsi (PLD) muscle is made up entirely of twitch muscle fibers (19,44). The intracellular and surface membranes of tonic and twitch muscle fibers have distinctive properties. In the twitch myofibers the sarcoplasmic reticulum is far more extensive and uniformly distributed than in the tonic myofibers (42). Also, the Ca 2+ uptake system of twitch muscle fibers is better developed and more efficient than in the tonic myofibers. The transverse 'Abbreviations used in this paper: ALD and PLD, anterior and posterior Jatissimus dorsi, respectively. 240 tubular system (T-system) of the twitch muscle fibers is likewise more extensive and more uniformly distributed than in the tonic myofibers (42). In the twitch muscle fiber, elements of the T-system encircle each sarcomere of the myofibril at the A-I band junction whereas in the tonic muscle fiber the T-system is more randomly distributed, and is often present only at the Z-disk (17,23,24,42,50). Mitochondrial content and oxidative enzyme activity are consid...

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Albino rats were exposed to fluorescent illumination for four to six months at an intensity which would not cause photocoagulation of the retina. Electron and light microscopic studies indicated that the retinas of these animals were irreversibly damaged and that the degeneration was specifically localized to the photoreceptor cells. Photoreceptors were not found in any of these retinas. Prolonged exposure to low intensity, visible light had no apparent effect on the bipolar neurons and ganglion cells or on their interconnections in the inner plexiform layer. Pigment epithelial cells survived the exposure and were unchanged except for extreme compaction of the apical villous processes in the retinal zone where the photoreceptors were located prior to their destruction. In some degenerated retinas the bipolar neurons were displaced along blood vessels extending from the inner ganglion cell layer to the outer retinal layers. Some of these blood vessels apparently formed anastomoses between the central retinal circulation and the choriocapillaries. The outer Miiller cell processes, which contained numerous lamellated and tubular structures, expanded to cover the area adjacent to the pigment epithelium and to form an outer limiting membrane, which was displaced in position in comparison with a normal retina.

Glutamine synthesis and utilization were studied in the plantaris muscle after removal of its functional synergists, the soleus and gastrocnemius muscles. Rat plantaris muscle was compared with unoperated controls at 7, 14, and 30 days after synergist ablation and induction of hypertrophy. Glutamine synthetase activity increased from 6.17 +/- 1.77 to 33.92 +/- 2.23 nmol.h-1.mg protein-1, and glutaminase activities increased from 98.63 +/- 23.05 to 478.70 +/- 64.17 nmol.h-1.mg protein-1 7 days after surgery and remained elevated at 14 and 30 days. Sham-operated controls examined 7 days after surgery did not exhibit significantly increased glutamine synthetase activity. Histological examination revealed a large proliferation of connective tissue cells, as well as cells involved in tissue repair and inflammation; this influx was maximal 1 wk after surgery. The activity of the oxidative enzymes of the pentose phosphate pathway increased from 3.08 +/- 4.31 to 20.86 +/- 1.13 nmol.min-1.mg protein-1 1 wk after surgery. The time course of changes in pentose phosphate pathway enzymes was similar to that of the increases in glutamine synthetase, glutaminase, and cellular infiltration. Increases in muscle wet weight followed a different time course than changes in glutamine synthetase, glutaminase, and pentose phosphate pathway activities. It is concluded that the initial increases in plantaris muscle weight are probably due to edema, connective tissue proliferation, and cells involved in tissue repair and inflammation. The increase in glutamine synthetase activity appears to occur in skeletal muscle, whereas the changes in glutaminase and pentose phosphate pathway activities appear to represent infiltrating inflammatory cells. Furthermore, the increase in glutamine synthetase activity may serve to support the infiltrating cells, which appear to lack substantial capacity for glutamine production. These results represent a functional relationship between skeletal muscle glutamine synthesis and utilization by cells mediating inflammation and connective tissue repair and synthesis.