Structure, composition, and mechanical properties of shark teeth

The teeth of two different shark species (Isurus oxyrinchus and Galeocerdo cuvier) and a geological fluoroapatite single crystal were structurally and chemically characterized. In contrast to dentin, enameloid showed sharp diffraction peaks which indicated a high crystallinity of the enameloid. The lattice parameters of enameloid were close to those of the geological fluoroapatite single crystal. The inorganic part of shark teeth consisted of fluoroapatite with a fluoride content in the enameloid of 3.1 wt.%, i.e., close to the fluoride content of the geological fluoroapatite single crystal (3.64 wt.%). Scanning electron micrographs showed that the crystals in enameloid were highly ordered with a special topological orientation (perpendicular towards the outside surface and parallel towards the center). By thermogravimetry, water, organic matrix, and biomineral in dentin and enameloid of both shark species were determined. Dentin had a higher content of water, organic matrix, and carbonate than enameloid but contained less fluoride. Nanoindentation and Vicker's microhardness tests showed that the enameloid of the shark teeth was approximately six times harder than the dentin. The hardness of shark teeth and human teeth was comparable, both for dentin and enamel/enameloid. In contrast, the geological fluoroapatite single crystal was much harder than both kinds of teeth due to the absence of an organic matrix. In summary, the different biological functions of the shark teeth ("tearing" for Isurus and "cutting" for Galeocerdo) are controlled by the different geometry and not by the chemical or crystallographic composition.     

The LIM protein Ajuba is recruited to cadherin-dependent cell junctions through an association with alpha-catenin

Cell-cell adhesive events affect cell growth and fate decisions and provide spatial clues for cell polarity within tissues. The complete molecular determinants required for adhesive junction formation and their function are not completely understood. LIM domain-containing proteins have been shown to be present at cell-cell contact sites and are known to shuttle into the nucleus where they can affect cell fate and growth; however, their precise localization at cell-cell contacts, how they localize to these sites, and what their functions are at these sites is unknown. Here we show that, in primary keratinocytes, the LIM domain protein Ajuba is recruited to cadherin-dependent cell-cell adhesive complexes in a regulated manner. At cadherin adhesive complexes Ajuba interacts with alpha-catenin, and alpha-catenin is required for efficient recruitment of Ajuba to cell junctions. Ajuba also interacts directly with F-actin. Keratinocytes from Ajuba null mice exhibit abnormal cell-cell junction formation and/or stability and function. These data reveal Ajuba as a new component at cadherin-mediated cell-cell junctions and suggest that Ajuba may contribute to the bridging of the cadherin adhesive complexes to the actin cytoskeleton and as such contribute to the formation or strengthening of cadherin-mediated cell-cell adhesion.     

Copulatory behavior of adult tamarins (Saguinus fuscicollis) castrated as neonates or juveniles: Effect of testosterone treatment

The sexual interactions of Saguinus fuscicollis males castrated as neonates, at 37 days of age, or prepubertally with adult intact females were studied. Prepubertally castrated males were observed while receiving testosterone, and while being treated with saline. Males castrated neonatally or at 37 days of age were observed while receiving testosterone. Neonatal castrates had previously been studied without hormone treatment and therefore no control condition was included for these animals. Prepubertally castrated males showed Mounts, Mounts with Thrusts, and Sexual Tongue Flicking when treated with saline only. In three of the four males, all measures of sexual behavior increased with testosterone treatment. Neonatally castrated males had failed to display any mounting or thrusting without testosterone treatment during a previous study. During the present study, three of the four males did not respond to testosterone treatment with sexual behavior. The fourth male and one male castrated at 37 days of age displayed some sexual behavior. These results suggest that most neonatally castrated males are not able to respond to testosterone with the activation of copulatory behavior. The findings are consistent with the hypothesis that in callitrichids the sensitive period for behavioral differentiation is shifted into neonatal life. However, some neonatally castrated males show a weak response to testosterone. This may reflect an extended and perhaps partially prenatal period of sensitivity.     

Catecholamine release by catecholamines in the eel does not require the presence of brain or anterior spinal cord

The catecholamine-producing chromaffin cells of the American eel are strongly innervated by fibers, which, by ultrastructural criteria, seem to be cholinergic. However, neither removal of the brain nor removal of the brain combined with extirpation of the anterior spinal cord prevents the release of catecholamines into the circulation by catecholamines. It appears that the chromaffin cells are controlled by both nervous and humoral stimuli, and that at least some of the latter do not require the presence of "preganglionic" innervation.     

Effects of exogenous catecholamines on plasma catecholamines and glucose in the sea lamprey,Petromyzon marinus

Summary The effects of exogenous dopamine (DA), norepinephrine (NE) and epinephrine (E) on endogenous catecholamine (CA) titers and glycemia were studied with a highly specific and sensitive radioenzymatic assay (REA) in cardiac-cannulated, prespawning sea lampreys. Neither DA nor NE had a specific effect on the endogenous titers of the other two CAs, or on glycemia. In contrast, E caused a strong increase of both DA and NE at three different doses, one of which must have been in the physiological ranges. This increase may be due to direct stimulation of E on the NE and DA cells. E also caused hyperglycemia 45 min after the injection; however, this effect occurred only with unphysiologically high doses. An estimation of the disappearance rate of exogenous CAs revealed a mammalian-like speed, ranging from 3–5.5 min.Abbreviations CA catecholamines - DA dopamine - E epinephrine - NE norepinephrine - REA radioenzymatic assay     

Effects of prepubertal ovariectomy on the development of scent glands, scent marking, and aggressive behaviors of female tamarin monkeys (Saguinus fuscicollis)

The effects of prepubertal ovariectomy on scent gland development, scent marking behavior, and on social interactions with strange adult conspecifics were studied in adult females cohabiting with intact males. Eight females were ovariectomized and eight underwent control surgery at 6 months of age. All were returned to their families after surgery and allowed to reach sexual maturity. At 18 months of age, each female was permanently paired with an adult, intact male. When the subjects were 21 months old, the social interactions of all pairs with strange adults were tested in a situation analogous to a territorial encounter. The scent marking activities of the subjects and their mates were studied during “territorial encounters,” in trial-free control situations, and in the presence of novel objects. Ovariectomy prior to puberty retarded the development of the scent gland but did not inhibit it completely. Social interactions with strange conspecifics were also affected. Ovariectomized females showed fewer threat displays than did control females, but there was no significant difference in the amount of injurious aggression both female groups directed at the strangers. Under all testing conditions, ovariectomized females tended to scent mark less frequently with the circumgenital-suprapubic gland than did controls. This difference was statistically significant only under some of the testing conditions. Intact females scent marked more frequently than their males but ovariectomized females did so only under trial-free testing conditions. The sternal scent gland was used very infrequently by all subjects and there was no difference in marking activity between males and females or between ovariectomized and control females.     

Lack of effects of castration on scent marking, displays, and aggression in a South American primate (Saguinus fuscicollis).

The social interactions of 12 adult, permanently cohabiting male-female pairs with strange conspecifics were studied before and after the male of each pair was either castrated or underwent control surgery. Prior to surgery, the pairs directed a relatively high amount of injurious aggression and displays toward the stranger. Aggression, display behavior, and scent marking tended to be more frequent in females. Moreover, female strangers received more aggression than male strangers, particularly by female subjects. Castration of the males did not result in a decrease in aggression, display behavior, and scent marking. On the contrary, the agression scores of all subjects tended to be higher after surgery, an increase which was probably caused by extraexperimental variables.     

Influence of microgravity on crystal formation in biomineralization.

Biomineralized tissues are widespread in animals. They are essential elements in skeletons and in statocysts. The function of both can only be understood with respect to gravitational force, which has always been present. Therefore, it is not astonishing to identify microgravity as a factor influencing biomineralization, normally resulting in the reduction of biomineralized materials. All known biominerals are composite materials, in which the organic matrix and the inorganic materials, organized in crystals, interact. If, during remodeling and turnover processes under microgravity, a defective organization of these crystals occurs, a reduction in biomineralized materials could be the result. To understand the influence of microgravity on the formation of biocrystals, we studied the shell-building process of the snail Biomphalaria glabrata as a model system. We show that, under microgravity (space shuttle flights STS-89 and STS-90), shell material is built in a regular way in both adult snails and snail embryos during the beginning of shell development. Microgravity does not influence crystal formation. Because gravity has constantly influenced evolution, the organization of biominerals with densities near 3 must have gained independence from gravitational forces, possibly early in evolution.     

The morphology and histology of the endocrine pancreas of the southern hemisphere lamprey, Geotria australis gray

The location and arrangement of the pancreatic endocrine tissue in larval and adult Geotria australis (Geotriidae) differ markedly from those exhibited by the comparable stages of Northern Hemisphere lampreys (Petromyzontidae). In larval Geotria australis, the main zones of islet proliferation are located laterally between the oesophagus and the inner edge of the two large intestinal diverticula unique to this species rather than dorsal and ventral to the oesophagus. In adult Geotria australis, the islet follicles are closely packed into a single discrete capsule which could be easily removed surgically, rather than into cranial, intermediate, and caudal cords. The differences in the adult can be related to a lack of involvement of the bile duct in islet formation during metamorphosis. While B cells were found in both larval and adult islet follicles, the PI acidophilic cells and argyrophilic cells, which appeared respectively at stages 3 and 4 in metamorphosis, were present in all adult stages.