A comparative light microscopic evaluation of oxytalan fiber staining with a variety of dye substances.

Staining of oxytalan fibers in marsupial, eutherian and human periodontal ligaments was surveyed with 65 different dyes. Using the criteria of response to preoxidation, distribution, and morphologic appearance, 27 dye preparations in addition to the Gomori aldehyde-fuchsin, Taenzer-Unna orcein, and Weigert resorcin-fuchsin techniques displayed oxytalan fibers. With two exceptions all dyes were cationic and reacted with varying degrees of excellence with different animals. Most dyes produced their best staining results as concentrated solutions in 3% acetic acid, suggesting involvement of oxidatively engendered polyanions predominantly associated with an acid mucopolysaccharide component of the oxytalan fiber. The significance of carboxyl and sulfur-containing groups should not be overlooked in further studies aiming to elucidate oxytalan fiber chemistry and microstructure. This study supported the view that oxytalan fibers belong to the family of elastic tissues and represent a biologically important system within the periodontal ligament.     

Subversion of Host Recognition and Defense Systems by Francisella spp.

Summary: Francisella tularensis is a Gram-negative intracellular pathogen and the causative agent of the disease tularemia. Inhalation of as few as 10 bacteria is sufficient to cause severe disease, making F. tularensis one of the most highly virulent bacterial pathogens. The initial stage of infection is characterized by the “silent” replication of bacteria in the absence of a significant inflammatory response. Francisella achieves this difficult task using several strategies: (i) strong integrity of the bacterial surface to resist host killing mechanisms and the release of inflammatory bacterial components (pathogen-associated molecular patterns [PAMPs]), (ii) modification of PAMPs to prevent activation of inflammatory pathways, and (iii) active modulation of the host response by escaping the phagosome and directly suppressing inflammatory pathways. We review the specific mechanisms by which Francisella achieves these goals to subvert host defenses and promote pathogenesis, highlighting as-yet-unanswered questions and important areas for future study.     

Rabbit Anti-HIV-1 Monoclonal Antibodies Raised by Immunization Can Mimic the Antigen-Binding Modes of Antibodies Derived from HIV-1-Infected Humans

The rabbit is a commonly used animal model in studying antibody responses in HIV/AIDS vaccine development. However, no rabbit monoclonal antibodies (MAbs) have been developed previously to study the epitope-specific antibody responses against HIV-1 envelope (Env) glycoproteins, and little is known about how the rabbit immune system can mimic the human immune system in eliciting such antibodies. Here we present structural analyses of two rabbit MAbs, R56 and R20, against the third variable region (V3) of HIV-1 gp120. R56 recognizes the well-studied immunogenic region in the V3 crown, while R20 targets a less-studied region at the C terminus of V3. By comparison of the Fab/epitope complex structures of these two antibodies raised by immunization with that of the corresponding human antibodies derived from patients chronically infected with HIV-1, we found that rabbit antibodies can recognize immunogenic regions of gp120 and mimic the binding modes of human antibodies. This result can provide new insight into the use of the rabbit as an animal model in AIDS vaccine development.     

ATLAS OF ROENTGENOGRAPHIC POSITIONS

Mere diagnosis of a valvular heart lesion without circulatory incapacity is inconsequential in considering the prognosis for a pregnant woman.There are grave dangers of heart failure during pregnancy, labor or the postpartum period in women who have had congestive failure prior to pregnancy or during a previous pregnancy and delivery.Decisions as to whether or not to recommend avoidance of pregnancy or therapeutic abortion should depend not alone upon the prospect of death during gestation or at the time of delivery, but also upon the possibility of increased impairment of heart function and physical incapacity of the mother in the postpartum period.Because of the extensive surgical procedure there are few indications for interrupting pregnancy after the third lunar month; and because the major circulatory loads do not increase after the eighth month, rarely should labor be prematurely induced after that time.The exertion of labor, although generally inconsequential, in some cases may produce sustained oxygen debt. In cases in which labor in a previous pregnancy has been accompanied by heart failure, cesarean section should be considered as a means of lessening the possibility of serious failure or death, although this is not a frequent consideration.In the resemblance of circulatory changes that occur, during delivery and immediately postpartum, to those changes produced by the closure of an arteriovenous shunt or patent ductus arteriosus, lies a suggestion as to some of the causative factors in heart failure during or soon after delivery. Probably of great importance is the decrease in blood volume and hemoconcentration at delivery followed by the return of water to the circulatory system, with consequent transient increase in blood volume, in the postpartum period. Additionally, the rise of venous pressure after use of oxytocic drugs suggests that rapid infusion of blood from an engorged uterus may cause an abrupt and perhaps poorly tolerated hypervolemia.Death by heart failure in pregnancy and the puerperium has become extremely rare in recent years due to the frequent observations, meticulous diagnosis of impending failure and improved care of cardiac patients jointly by the obstetrician and the internist. In addition to digitalis therapy and sodium restriction, patients exhibiting evidence of impending heart failure may require bed rest through the entire third trimester of pregnancy. Oxygen should be administered during labor in such patients and anoxia guarded against during anesthesia.