Bacterial growth and killing in chronic ambulatory peritoneal dialysis fluids.

We determined the ability of Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli to survive and grow in peritoneal dialysis fluids from patients undergoing chronic ambulatory peritoneal dialysis. Staphylococci did not survive in commercially available dialysis solutions but grew readily in peritoneal effluents obtained from patients after the dialysis dwell time. The number of CFU doubled 6 and 13 times in 24 h for S. epidermidis and S. aureus, respectively. E. coli grew well in both the pre- and postdialysis peritoneal fluid. Peritoneal macrophages as well as peripheral blood leukocytes inhibited bacterial growth in peritoneal dialysis fluid. However, 10(6) phagocytes per ml were minimally required to obtain a bacteriostatic effect. The addition of serum to peritoneal dialysis fluid increased the antibacterial activity of macrophages and blood leukocytes. The capacity of the aminoglycoside antibiotic tobramycin to reduce bacterial CFU in peritoneal dialysis fluid was only 10% of its bactericidal capacity in standard Mueller-Hinton brush. Peritoneal dialysis fluid had no effect on the antibacterial activity of imipenem.     

Evidence for the involvement of blood flow-related mechanisms in the ovulatory process of the rat

To elucidate whether any relationship exists between ovarian blood flow and ovulation rate, the effects on these parameters were examined in equine chorionic gonadotrophin/human chorionic gonadotrophin (eCG/HCG) (15I U/15I U) primed rats after bilateral ligation and severance of either the ovarian branch of the uterine artery and vein (UL), the ovarian artery and vein (OL) or both sites (UL+OL) in comparison to sham operations. Laser Doppler flowmetry demonstrated the presence of microcirculatory vasomotion and a reduction of blood flow after UL, OL and UL+OL performed during the intervals 0-3 h (78, 66 and 19% of pretreatment values respectively) and 6-9 h (68, 57 and 20%) after HCG. Experiments utilizing radioactive microspheres also indicated decreased ovarian blood flow by UL and OL. Ovulation rate was assessed 20 h after HCG in animals where ligations had been performed at 0, 3, 6 and 9 h after HCG. No ovulations were seen after UL+OL and significantly decreased ovulation rates ( approximately 50% of sham operated animals) were seen after UL at 0 and 3 h and after OL at 0, 6 and 9 h. Progesterone concentrations in blood 20 h after HCG were reduced by OL but not UL and ovarian weights were unaffected by ligation. It is concluded that acute blood flow reduction during the ovulatory interval reduces ovulation rate in the rat.     

Dynamic properties of vestibular reflexes in the decerebrate cat

Summary Vestibulocollic (VCR) and vestibulo-ocular (VOR) reflexes were studied during angular rotation in the horizontal plane in precollicular decerebrate cats. Angular position was modulated by sinusoids or sums of sinusoids with frequencies ranging from 0.05 to 5 Hz.Reflex motor output was measured by recording electromyographic (EMG) activity of the lateral rectus and dorsal neck muscles and discharge of abducens motoneurons. Measured with respect to input angular acceleration VCR motor output displayed a second order lag at low frequencies, bringing mean EMG phase (–136 °) and gain slope (–35 dB/ decade) close to those of an angular position signal at 0.2 Hz. At higher frequencies the lag was counteracted by a second order lead bringing mean phase (–52 °) and gain slope (–5.6 dB/decade) back close to those of an angular acceleration signal at 3 Hz. By contrast, mean phase (–113 ° to –105 °) and gain slope (–21 to –28 dB/decade) of the VOR motor output remained close to those of an angular velocity signal across the entire frequency range.The data suggest that neural pathways producing the VCR receive selective input from irregular type horizontal semicircular canal afferents which provide one lag and one lead in the overall transfer function while the other lag and lead are produced by central pathways.Transaction of the medial longitudinal fasciculus (MLF), which eliminates all of the most direct (three neuron) arcs of the horizontal VCR, did not cause any detectable change in the horizontal VCR at either low or high frequencies. Reductions in overall gain occurred in some cases but these could be attributed to damage to axons outside the MLF. Less direct pathways, probably including vestibulo-reticulospinal pathways, are thus able to produce both the low-frequency, phase-lagging and high-frequency, phase-leading components of the horizontal VCR.Supported in part by NIH grants EY 02249, EY 00100, and NS 02619Recipient of NIH Fellowship NS 06030     

Comparison of Southern transfer hybridization and dot filter hybridization for detection of cervical human papillomavirus infection with types 6, 11, 16, 18, 31, 33, and 35

A commercial dot filter hybridization kit (Virapap Kit) was compared with Southern transfer hybridization for the detection of seven types of human papillomavirus (HPV) in cervical specimens from 450 consecutive females attending a sexually transmitted diseases clinic. In comparison with Southern transfer hybridization, performed with the same probes used in the dot filter kit, the sensitivity, specificity, and positive and negative predictive values of dot filter hybridization were 90%, 94%, 74%, and 98%, respectively. Among patients with cervical cytologic dysplasia, HPV DNA was detected in 44% by dot filter hybridization and in 35% by Southern transfer hybridization. Although 26% of specimens positive by dot filter hybridization were not confirmed by Southern transfer hybridization, cervical dysplasia was detected in 5 (25%) of 20 with HPV DNA detected by dot filter hybridization alone, compared with 25 (8%) of those with no definitive evidence of HPV by either method (P = 0.009) and with 16 (30%) of 53 with HPV DNA detected by both methods (P = 0.7). The kappa statistic for interobserver and intraobserver reproducibility for interpretation of blots was similar for the two methods. The dot filter hybridization method evaluated appears to be a satisfactory alternative to Southern transfer hybridization for detection of HPV DNA.     

Role of interferon in streptococcal infection in the mouse

In previous studies, we have shown the rapid in vitro induction of IFN gamma from human T cells by highly purified peptic extracts of M proteins from Streptococcus pyogenes. The present report extends these in vitro studies and shows that a mixture of both alpha/beta and gamma IFN were present in spleen cell homogenates after in vivo treatment with M protein wild-type (M+) or mutant (M-) S. pyogenes strains. The levels of bacterial-induced IFN were found to be greater in M+ treated animals. Additional studies in vivo showed that pretreatment of mice with heat-killed M+ S. pyogenes organisms significantly protected mice to pneumococcal infection compared to similarly treated M- or control animals (P less than 0.001). Further, antibodies to mouse IFN alpha/beta and antibodies specific to a synthetic N-terminal peptide of mouse IFN gamma enhanced the death of animals due to pneumococcal infection and blocked the protection observed in animals previously treated with heat-killed M+ organisms. Most importantly, treatment of mice with either type of IFN alone enhanced the survival of mice to levels similar to that observed by treatment with M+ organisms (P less than 0.05). The results strongly suggest that IFN can play a crucial role, directly or indirectly, in controlling infection by Streptococcus pneumoniae and perhaps other streptococci.     

Opsonization of four Bacteroides species: role of the classical complement pathway and immunoglobulin

Previous investigators have suggested that opsonization of two Bacteroides species is mediated exclusively by the alternative complement pathway and requires immunoglobulins. In this study, the nature of the opsonic factors in nonimmune human serum for four species of Bacteroides was investigated by measuring uptake of [(3)H]thymidine-labeled bacteria by human polymorphonuclear leukocytes. Normal human serum, C2-deficient serum, immunoglobulin-deficient serum, and serum chelated with ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid (EGTA), MgEGTA, and ethylenediaminetetraacetic acid (EDTA) were used as opsonic sources. Heat inactivation of each of these sera significantly reduced its opsonic activity for all four Bacteroides species, suggesting that serum complement was essential for effective opsonization. All strains were opsonized in the absence of the classical complement pathway; however, kinetics studies revealed that opsonization proceeded at a significantly faster rate when the classical complement pathway was intact. Although two strains were opsonized in immunoglobulin-deficient sera, opsonization was less efficient and appeared to occur via the alternative complement pathway. Unexpectedly, all strains were well opsonized by the classical complement pathway in 10% serum which had been effectively chelated with EGTA or EDTA. The explanation for this finding is unknown; however, it is possible that cell wall cations of Bacteroides species may participate in the activation of complement in chelated serum, resulting in effective opsonization. It was also found that Bacteroides, when incubated with an Escherichia coli strain in normal serum, could compete for opsonins and thereby reduce phagocytosis of E. coli. It is possible that competition for opsonins among bacterial species contributes to the synergistic role these organisms share in mixed floral infections.