The sarcoplasmic reticulum of the bat cricothroid muscle

The bat cricothyroid muscle is believed to participate in the production of the short bursts of frequency modulated ultrasound which these animals use as an echolocation device. The evidence seems to indicate that this muscle must be extremely fast acting. It possesses a very well developed sarcoplasmic reticulum, consisting of intercommunicating longitudinal and transverse tubular elements. The transverse elements, situated at the level of the junction between the A and the I bands, are tripartite complexes of tubules called triads, and these are sometimes replaced by more complex structures, the pentads. The intermediate element of the triad appears as a slender continuous tubule, which can be shown to come into close contact with the sarcolemma and also to share with it certain common staining properties. The longitudinal components of the reticulum consist of very numerous tubules which link successive triads to each other and anastomose to form multiple layers of close-meshed reticula in the interfibrillar sarcoplasm. Both the longitudinal and the transverse elements of the sarcoplasmic reticulum form a continuous network across the muscle fiber. It is suggested that the extraordinary development of the sarcoplasmic reticulum in the bat cricothyroid is related to the unusual physiological properties of this muscle.

HISTOPLASMA CAPSULATUM FROM THE LIVER OF A BAT IN COLOMBIA

Of 135 bats (eight species), one of the species Glossophaga sorcina sorcina, a nectar-feeding bat from Girardot, Colombia, harbored Histoplasma capsulatum. The microorganism was cultured from the liver. This is the second report of recovery of this fungus from bat tissue.

TEMPERATURE REGULATION AND METABOLISM IN MEXICAN FREETAIL BATS

Body temperatures of Tadarida mexicana in their natural cave environment were usually maintained at high levels, even when ambient temperatures were low. Oxygen consumption rates were correspondingly higher in low environmental temperatures. However, in laboratory tests, body temperatures and metabolic rates are fairly dependent on ambient temperature.

EFFECT OF ENVIRONMENTAL TEMPERATURES ON INFECTION WITH MYCOBACTERIUM MARINUM (BALNEI) OF MICE AND A NUMBER OF POIKILOTHERMIC SPECIES

Clark, H Fred (Communicable Disease Center, Atlanta, Ga.), and Charles C. Shepard. Effect of environmental temperatures on infection with Mycobacterium marinum (Balnei) of mice and a number of poikilothermic species. J. Bacteriol. 86:1057-1069. 1963.-An exploration was made of the effect of environmental temperature on infections with Mycobacterium marinum of mice, young opossums, and bats, and of 50 species of poikilothermic animals. In artificial medium (7H9 broth) M. marinum grew most rapidly from 25 to 35 C, with generation times of 4 to 6 hr. At 37 C, the generation time was 14 hr; at 20 C, 20 hr; and, at 15 C and lower, little growth was observed. In mice, deep body temperatures were found to be 36.5 to 37.3 C at environmental temperatures of 4 to 30 C. At an environmental temperature of 34 C, they averaged 39.1 C; at 37 C they averaged 40.2 C. Foot-pad temperatures were within a few degrees of ambient temperatures from 10 to 34 C. In mouse foot-pad infections, the optimal environmental temperature for infection was 20 C, and the generation time of the infecting bacilli at this environmental temperature was about 15 hr. Intravenously inoculated mice developed peripheral infections of nose, feet, and tail at environmental temperatures of 4 to 30 C. At these temperatures, they had severe pneumonic involvement, and the mice at lower temperatures tended to succumb most rapidly to systemic infection. At 34 C, the intravenously infected mice did not develop peripheral infections and there was no pulmonary involvement. Young opossums, whose deep body temperatures are only 34 to 36 C, were inoculated in the foot-pad and intravenously. Foot-pad infection developed without systemic involvement. Bats, which assume environmental temperature when at rest, were inoculated in the foot-pad. Foot-pad infections were observed but no systemic disease. The bats could be maintained for only short periods, however. Poikilothermic animals were studied. Deep body temperatures were found to be nearly identical with ambient temperature. A total of 50 species of reptiles, amphibians, and fish were infected intraperitoneally in a number of experiments, as animals were available. Susceptibility to M. marinum was found throughout these species. There was no tendency to peripheral involvement. In experiments to determine the optimal environmental temperature for infection, cricket frogs (Acris), American chameleons (Anolis), young garter snakes (Thamnophis), and the young of three species of turtles were inoculated intraperitoneally. The optimal temperature for infection was found to be 30 C in each case, and infections at 20 C were definitely slower. The generation time of M. marinum in American chameleons at 30 C was about 19 hr; at 20 C, it was about 46 hr; and, at 10 C, the bacilli did not apparently multiply. Transmission studies revealed instances where infected animals shed M. marinum into the waters in which they were kept, and where animals became infected from water containing M. marinum.

SPECIFIC GRANULES IN ATRIAL MUSCLE CELLS

Large populations (up to 600/cell) of spherical, electron-opaque granules ∼0.3 to 0.4 µ in diameter are characteristically found in muscle fibers of mammalian atria. They are absent in muscle fibers of the ventricles. The granules are concentrated in the sarcoplasmic core and occur in lesser numbers in the sarcoplasmic layers between myofibrils and under the plasma membrane. Their intimate association with a central voluminous Golgi complex and the frequent occurrence of material reminiscent of the granular content within the cisternae of the Golgi complex suggest that the latter is involved in the formation of the atrial granules. Atrial granules are larger and more numerous in smaller species (rat, mouse), and generally smaller and less numerous in larger mammals (dog, cat, human); they are absent from the atrial fibers of very young fetuses (rat) but are present in those of newborn animals. A small population of bodies containing glycogen particles and remnants of the endoplasmic reticulum and mitochondria occurs in the sarcoplasmic cores of atrial as well as ventricular muscle fibers in the rat; they contain acid phosphatase and thus appear to be residual bodies of autolytic foci. Their frequency increases with the age of the animal. Typical lipofuscin pigment granules, which are known to contain acid phosphatase and are found in the sarcoplasmic cores in old animals (cat, dog and human), are presumed to arise by progressive aggregation and fusion of small residual bodies.

CYTOCHEMICAL DIFFERENCES IN KIDNEYS FROM WINTER HIBERNATING AND AROUSED BATS (MYOTIS LUCIFUGUS), WITH PARTICULAR REFERENCE TO THE GOLGI ZONE

Kidneys from winter bats (Myotis lucifugus) were removed and fixed in cold formalin-calcium while the animals were in the following states: (a) natural hibernation; (b) arousal from hibernation for 24 hours; (c) laboratory maintained hibernation; and (d) no hibernation since the previous winter. With fixed frozen sections, the lead salt method of Wachstein and Meisel with adenosine triphosphate as substrate (pH 7.2) showed enzymic activity localized in large vacuoles and smaller vesicles or droplets in the Golgi region of distal and proximal tubular epithelial cells of kidneys from hibernating bats. No ATPase activity was detected in the basal lamellae of tubular epithelium from hibernating bats. ATPase activity in the Golgi region was not seen in cells from kidney tubules of bats aroused from hibernation 24 hours previously or of animals that had not hibernated, whereas activity for ATPase was present in the basal infoldings of tubular epithelium from these animals. Inosine di- and triphosphatase and calcium activated ATPase activities were also detected in the Golgi region of hibernating bats but were not present in the basal infoldings of tubular epithelium from active animals. There was little or no activity toward the mono- and diphosphates of adenine, thiamine pyrophosphate, and the di- or triphosphates of guanidine, cytidine, or deoxyadenosine. The loss of enzymic activity from the Golgi region of the tubular epithelium from hibernating bats and its increase in the region of the basal infoldings of tubular epithelium in aroused bats suggests that the Golgi region plays a role in the synthesis of enzymic protein usually identified with the external cell membrane.