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Background The neural projections from the infralimbic region of the prefrontal cortex (IL) to the amygdala are important for the maintenance of conditioned fear extinction. Neurons in this pathway exhibit a unique pattern of structural plasticity that is sex-dependent, but the relationship between the morphological characteristics of these neurons and successful extinction in males and females is unknown. Methods Using classic cued fear conditioning and extinction paradigm in large cohorts of male and female rats, we identified subpopulations of both sexes that exhibited high (HF) or low (LF) levels of freezing on an extinction retrieval test, representing failed or successful extinction maintenance, respectively. We then combined retrograde tracing with fluorescent intracellular microinjections to perform 3D reconstructions of IL neurons that project to the basolateral amygdala (BLA) in these groups. Results HF/LF males exhibited neuroanatomical distinctions that were not observed in HF vs. LF females. A retrospective analysis of behavior during fear conditioning and extinction revealed that despite no overall sex differences in freezing behavior, HF/LF phenotypes emerged in males during extinction, but in females during fear conditioning, which does not involve IL-BLA neurons. Conclusion Our results suggest that the neural processes underlying successful or failed extinction maintenance may be sex-specific. These findings are not only relevant to future basic research on sex differences in fear conditioning and extinction, but also to exposure-based clinical therapies, which are similar in premise to fear extinction, and which are primarily used to treat disorders that are more common in women than in men.

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The purpose of this investigation was to study potential virulence factors associated with Escherichia coli urinary pathogens isolated from patients with urinary tract infection. These factors were compared with characteristics of normal-flora E. coli isolated from stool specimens of healthy individuals without a history of urinary tract infection. The potential virulence factor focused on in this study was hemagglutination (HA) of human type 0 erythrocytes by E. coli urinary pathogens. A total of 265 strains of E. coli isolated from patients with urinary tract infections were tested for their ability to hemagglutinate human type 0 erythrocytes; of these, 148 (56%) were HA positive. Only 6 of 36 fecal E. coli strains (17%) isolated from healthy controls were HA positive. This significant association of the presence of hemagglutinin on E. coli that causes urinary tract infections indicates the likelihood that HA is a marker of virulence. Only 12% (5 of 43) of Proteus mirabilis and 3% (3 of 104) of Klebsiella pneumoniae urinary isolates were HA positive. There was a trend for HA-positive E. coli to be isolated from patients with kidney infections and positive tests for antibody-coated bacteria rather than bladder infections and negative tests for antibody-coated bacteria, although the difference was not statistically significant. There was a significant correlation (P < 0.025) between hemolysin production and HA; 67% (69 of 103) of the isolates that produced hemolysin also hemagglutinated human type 0 erythrocytes. There was no significant correlation between HA and motility, although there was a trend for flagellated organisms to be non-hemagglutinators. There was a marked correlation between the presence of hemagglutinin and the serogroup of the E. coli isolate; serogroups 04, 07, and 050 were almost always HA positive (57 of 63; 90%). In contrast, serogroups 08 and 025 were rarely HA positive (2 of 30; 7%).

Hundred-fold purification of intact microtubules from homogenates of rat brain is reported. The success of purification depends on stabilizing the microtubule structure by the combined effects of hexylene glycol, acidic Ph, and low temperature. A practical, negative stain, electron microscopic assay is used to study purity and stability of microtubule fractions. The purified fractions show a major band which migrates like purified tubulin in the SDS gel electrophoresis system.

An enzyme-linked lectinsorbent assay (ELLA) was developed for quantification of in situ biofilm produced by Staphylococcus epidermidis in polystyrene 96-well tissue culture plates with phosphatase-labeled wheat germ agglutinin (WGA) as a specific probe for the GlcNAcbeta-1,4n component of exocellular matrix material (EMM) that is responsible for intercellular adhesion and accumulation. The ELLA and the modified Christensen dye assay were used to test 13 laboratory strains of coagulase-negative staphylococci and 10 clinical isolates of S. epidermidis. Four biofilm-positive laboratory strains of S. epidermidis were positive by both tests, and six biofilm-negative strains were negative by both. One strain of S. hemolyticus was positive by the ELLA only. Two of the 10 clinical isolates of S. epidermidis were positive by both assays, two were negative by both, and the remaining were positive by the ELLA only. The ELLA was objective, reproducible, specific, sensitive, and useful for screening strains for their capacity to adhere to plastic, produce EMM, and form biofilm.

The association of Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus saprophyticus with tissues of the upper respiratory tract were compared by using an in vivo ferret model. Ferrets were challenged intranasally with a 1-ml volume of radiolabeled staphylococci (3 mg [dry weight]), were allowed to clear the bacteria in vivo for 90 min, and were sacrificed. Tissues from the right nasal fossa were harvested and processed for radioassay or histology. Of the recoverable staphylococci, .96% was associated with mucus gel overlaying mucosa of the turbinates. A quantitative radioassay was developed to study the binding of labeled staphylococci to immobilized crude ferret nasal mucin (FM) and bovine submaxillary gland mucin (BM). Binding showed saturation kinetics and was blocked specifically by BM but not by human Tamm-Horsfall glycoprotein nor orosomucoid. Binding to both FM and BM was significantly inhibited (P c 0.01) when cocci were pretreated with trypsin but not when treated with I8-galactosidase or sodium metaperiodate (except for binding of S. saprophyticus to FM). These results suggest that mucin-binding receptors of the cocci may have protein components. The staphylococcus-binding receptors of both FM and BM appear to contain protein components, based on sensitivity to pretreatment with trypsin.