Utilization of Transferrin-Bound Iron by Medically Important Staphylococcal Species

Staphylococcus aureus is able to utilize efficiently transferrin-bound iron as an iron source, whereas other staphylococci are not. The reason for this difference remains unclear. We compared the activity of siderophore-mediated iron-uptake systems among S. aureus, S. epidermidis, and S. saprophyticus. S. aureus was more susceptible to streptonigrin than the other two staphylococci. S. aureus was able to utilize efficiently transferrin-bound iron in proportion to the level of iron-saturation and produced siderophores in an inverse relation to iron-saturation. In contrast to S. aureus, S. epidermidis and S. saprophyticus were able to utilize only holotransferrin (HT; about 80% iron- saturated) and produced siderophores only in media containing HT. Moreover, they utilized HT less efficiently than S. aureus, though they produced greater amount of siderophores than S. aureus in media containing HT. The ability of the equivalent siderophores per se to capture iron from HT was not significantly different among the three species. Nevertheless, the siderophores from S. aureus stimulated the growth of the staphylococci to a greater degree than did the siderophores from S. epidermidis and S. saprophyticus. The siderophores from S. epidermidis and S. saprophyticus also stimulated the growth of S. aureus to a greater degree than those of the original bacteria which produced them. This indicates that S. aureus possesses a greater ability to produce more-efficient siderophores responding to very low iron-availability, as well as a greater ability to utilize iron-siderophore complexes, than the other two staphylococci. This explains in part the higher virulence of S. aureus compared to other staphylococci.

Tocolytic Effect of Morphine via Increased Metabolic Clearance of Oxytocin in the Baboon

Morphine is known to inhibit nocturnal uterine contractions in several animal models, and oxytocin is known to be a primary causative factor of uterine contractions. The purpose of the present study was to determine the tocolytic effect of morphine in relation to the pharmacokinetics of oxytocin, after a bolus injection of oxytocin. The metabolism of oxytocin was investigated during the third trimester in baboons. Four animals were placed on a tether system with venous and arterial access, including continuous uterine monitoring. Plasma oxytocin levels were determined by radioimmunoassay after extraction with petroleum ether/acetone. Morphine consistently increased the metabolic clearance rate of oxytocin in all four animals (p < 0.05) and this was in accordance with suppressed uterine contractions. We conclude that morphine could be used as an inhibitor of nocturnal uterine contractions, and that this is caused by the morphine induced increased metabolic clearance rate of oxytocin.

Immunoelectronmicroscopical Study on the Axonal Coexistence of Serotonin and Substance-P of Fetal Nerve Tissue Transplantation into the Transected Spinal Cord of Rats / 체질인류학회지

The purpose of this study was taken after transplantation of fetal serotonin and substance-P containing raphe nuclei into the transected thoracic spinal cord (T9-10) of adult rats, a suspension of cells derived from the mesencephalic and medullary raphe nuclei of 13~15 days embryonic rats were injected upper and lower the transected spinal cord. After survival periods of 15 days to 1 year, the animals were sacrificed and the spinal cord, processed for the localization of serotonin and substance-P immunoreactive neurons in the transplanted spinal cord, was studied using ABC immunocytochemistry. Immunocytochemical analysis revealed the presence of many serotonin and substance-P immunoreactive neurons in the transplants. In the mesencephlic implants, however, the serotonin and substance-P immunoreactive neurons were not co-localized with the same neurons. The serotonin and substance-P nerve fibers were densely distributed in lamina I and II of the dorsal horn and in lamina VIII and IX of the ventral horn of all segments of the spinal cord. The nontransplanted control, spinal cord of the rats showed a total absence of serotonin and substance-P immunoreactive fibers below the section. Immunoelctronmicroscopic anlysis demonstrated the presence of numerous synaptic contacts formed by serotonin and substance-P containing boutons which are most likely emanated from the grafted serotonin and substance-P.