Experimental autoimmune encephalomyelitis (EAE) in CCR2(-/-) mice: susceptibility in multiple strains

Chemokines are low molecular weight cytokines which act as chemoattractants for infiltrating cells bearing appropriate receptors (CCR) to sites of inflammation. It has been proposed that CCR2 on monocytes is responsible for their recruitment into the central nervous system (CNS) in experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis, and two previous reports have described resistance of CCR2(-/-) mice to EAE. The present study examined three different mouse strains with CCR2 deletions for susceptibility to EAE. Animals were studied up to 4 months post-sensitization and were examined by neuropathology, RNase protection assay, in situ hybridization, and in vitro assays. All three strains were found to be susceptible to EAE: C57BL/6 x J129 and Balb c strains, 100%; and C57BL/6, 67%. Unusual in CNS lesions of CCR2(-/-) mice was an overabundance of neutrophils versus monocytes in wild-type animals. An attempt of the immune system to develop compensatory mechanisms for the lack of CCR2 was evidenced by a corresponding increase in mRNA for other chemokines and CCR. Inasmuch as neutrophils replaced monocytes and led to demyelination, our findings support the concept that promiscuity of chemokines and CCR was able to surmount the deletion of CCR2, still resulting in full expression of this autoimmune disease.     

Staphylococcus aureus isolates carrying Panton-Valentine leucocidin genes in England and Wales: frequency, characterization, and association with clinical disease

Staphylococcus aureus isolates carrying the genes that encode for Panton-Valentine leucocidin (PVL), a highly potent toxin, have been responsible for recent outbreaks of severe invasive disease in previously healthy children and adults in the United States of America and Europe. To determine the frequency of PVL-positive isolates sent to the Staphylococcus Reference Unit (United Kingdom) for epidemiological purposes, we tested 515 isolates of S. aureus, and 8 (1.6%) were positive for the PVL locus. A further 470 isolates were selected to explore the association of PVL-positive S. aureus with clinical disease. Of these, 23 (4.9%) were PVL positive and most were associated with skin and soft tissue infections (especially abscesses). The PVL genes were also detected in isolates responsible for community-acquired pneumonia, burn infections, bacteremia, and scalded skin syndrome. Genotyping by pulsed-field gel electrophoresis and multilocus sequence typing revealed that the PVL-positive isolates were from diverse genetic backgrounds, although one prevalent clone of 12 geographically dispersed methicillin-resistant S. aureus (MRSA) isolates was identified (ST80). All 12 isolates were stapylococcal cassette chromosome mec type IVc, had an agr3 allele, and shared a common toxin gene profile (sea-see, seg-sej, eta, etb, and tst negative but etd positive). ST80 strains with similar genetic characteristics have been responsible for community-acquired infections in France and Switzerland. The remaining PVL-positive isolates were mostly methicillin-sensitive S. aureus and belonged to 12 different sequence types, including ST22 and ST30, which are closely related to the most prevalent MRSA clones in United Kingdom hospitals, EMRSA-15 and EMRSA-16, respectively.     

Secretion of vascular endothelial growth factor/vascular permeability factor from human luteinized granulosa cells is human chorionic gonadotrophin dependent

Vascularization is a prominent event during corpus luteum formation, providing low density lipoproteins for steroid biosynthesis and enabling transport of secreted steroids. The process of vascularization is controlled by specific regulators. Vascular endothelial growth factor (VEGF), otherwise named vascular permeability factor (VPF), induces endothelial cell proliferation as well as angiogenesis in vivo and increases capillary permeability. Here we report the expression of VEGF/VPF mRNA by cultured human luteinized granulosa cells (GC) for at least 10 days. Without HCG VEGF/VPF expression declined after day 4 and by day 10 was reduced to approximately 30% of the value at day 4. However, after culture in the presence of 1 U/ml human chorionic gonadotrophin (HCG), expression of VEGF/VPF mRNA by GC was four times greater than control experiments by day 10, and increased 100% from day 4 to day 10. Simultaneously, HCG supplementation increased VEGF/VPF secretion by GC. Medium VEGF/VPF on day 3 was 13 pM without and 11 pM with HCG. Medium VEGF/VPF on day 10 was 6 pM without HCG and 29 pM with HCG. These results suggest that vascularization of the corpus luteum is induced by HCG-mediated effects of VEGF/VPF.      

Ultrafine Electrospun Polyamide‐6 Fibers: Effect of Solution Conditions on Morphology and Average Fiber Diameter

Summary: In the present contribution, the electrostatic spinning or electrospinning technique was used to produce ultra‐fine polyamide‐6 (PA‐6) fibers. The effects of solution conditions on the morphological appearance and the average diameter of as‐spun fibers were investigated by optical scanning (OS) and scanning electron microscopy (SEM) techniques. It was shown that the solution properties (i.e. viscosity, surface tension and conductivity) were important factors characterizing the morphology of the fibers obtained. Among these three properties, solution viscosity was found to have the greatest effect. Solutions with high enough viscosities (viz. solutions at high concentrations) were necessary to produce fibers without beads. At a given concentration, fibers obtained from PA‐6 of higher molecular weights appeared to be larger in diameter, but it was observed that the average diameters of the fibers from PA‐6 of different molecular weights had a common relationship with the solution viscosities which could be approximated by an exponential growth equation. Raising the temperature of the solution during spinning resulted in the reduction of the fiber diameters with higher deposition rate, while mixing m‐cresol with formic acid to serve as a mixed solvent for PA‐6 caused the solutions to have higher viscosities which resulted in larger fiber diameters. Lastly, the addition of some inorganic salts resulted in an increase in the solution conductivity, which caused the fiber diameters to increase due to the large increase in the mass flow.

Average diameter of as‐spun fibers plotted as a function of the viscosity of the solutions.     

Effects of dexamethasone and transient malnutrition on rabbits infected with aerosolized Mycobacterium tuberculosis CDC1551

Malnutrition is common in the developing world, where tuberculosis is often endemic. Rabbits infected with aerosolized Mycobacterium tuberculosis that subsequently became inadvertently and transiently malnourished had compromised cell-mediated immunity comparable to that of the rabbits immunosuppressed with dexamethasone. They had significant leukopenia and reduced delayed-type hypersensitivity responses. Malnutrition dampened cell-mediated immunity and would interfere with diagnostic tests that rely on intact CD4 T-cell responses.     

Cytokines and lipopolysaccharide induce nitric oxide synthase in cultured rat pulmonary artery smooth muscle.

In the current study, we describe cytokine and Escherichia coli lipopolysaccharide (LPS) induction of nitric oxide (NO) synthase mRNA levels in cultured smooth muscle from rat pulmonary artery (RPASM). Exposure of RPASM to interleukin-1 beta, interferon-gamma, or LPS alone did not significantly affect NO synthesis, as determined by nitrite concentrations in media. Exposure to tumor necrosis factor-alpha caused a modest (2x) increase in nitrite production. In contrast, exposure to a combination of the above three cytokines and LPS caused a large increase in NO synthesis. Exposure of RPASM to this combination caused an increase in mRNA levels of NO synthase (as described by Northern blot analysis with 32P-cDNA probe to an inducible form of NO synthase present in murine macrophages) that was apparent as early as 4 h. Expression of the induced gene product after exposure to the cytokine and LPS mixture was evident by significant increases in nitrite production at 12 h. Production of nitrite was completely abolished in the presence of NG-monomethyl-L-arginine (NMA), and this inhibition was reversible by the addition of excess L-arginine. NO synthase mRNA levels were not affected by NMA. The nitrite production induced by the combination of cytokines and LPS was abolished by pretreating cells with cycloheximide. These data indicate that a combination of cytokines and LPS affect expression of the gene for the inducible form of NO synthase in cultured RPASM.     

Diversity of aminoglycoside resistance inEnterobacter cloacae in Greece

NinetyEnterobacter cloacae strains isolated from 12 Greek hospitals were examined in terms of epidemiological types and resistance mechanisms. Using O serotyping 69 % of the strains were assigned to a specific serotype and overall 16 different serotypes were identified. The combination of serotyping, phagetyping and biotyping efficiently discriminated most of the strains, indicating that single epidemic strains were not prevalent, although serotypes 3, 7, and group II predominated. Eight representative strains, all resistant to gentamicin, tobramycin, amikacin and netilmicin, were further examined for transferability and mechanisms of resistance. Aminoglycoside resistance was found to be transferable in most strains, and 13 R plasmids of 40–120 MDa molecular weight were detected. The enzymes detected consisted of three enzymes active against gentamicin [ANT(2), AAC(3)-I and AAC(3)-V]; three active against tobramycin [ANT(2), AAC(3)-V and AAC(6)-I]; two active against netilmicin [AAC(3)-V and AAC(6)-I]; and one active against amikacin [AAC(6)-I]. APH(3) and ANT (3), which modify neomycin and streptomycin plus spectinomycin respectively, were also found. Overall up to five aminoglycoside modifying enzymes were detected on the same R plasmid, AAC(6)-I plus ANT(2) being the most prevalent. The high incidence of multiresistance inEnterobacter cloacae and the fact that resistance is due to enzymatic inactivation of the antibiotics, indicate that in Greece this species might act as a gene pool for the spread of resistance to other bacteria of clinical relevance.     

Albumin adsorption on alkyl chain derivatized polyurethanes: I. The effect of C-18 alkylation

The initial adsorption rate of delipidized Human Serum Albumin (HSA) is increased by addition of C-18 alkyl chains to a polyurethane. The presence of alkyl chains does not appear to influence the total amount of HSA adsorbed after one hour exposure to a 5.0 mg/mL HSA solution. Neither does the desorption following one hour of adsorption appear to be influenced by the presence of alkyl chains. A study of the effects of solution concentration and temperature showed that the initial adsorption rates on both polymers are proportional to the protein concentration raised to the 0.36 power, and that alkylation of the polymer increases the activation energy of the initial adsorption rate above the 14 kJ/mol observed for the underivatized polyurethane. A new technique is presented to quantify the mass of adsorbed protein using Fourier transform infrared spectroscopy and attenuated total reflection optics. This technique uses the absorbance of bulk protein as an internal calibration reference, and appears to be as accurate and perhaps more precise than radiolabeling techniques.     

Persistent efficacy of topical eprinomectin against nematode parasites in cattle

Six studies were conducted to evaluate the persistent efficacy of eprinomectin pour-on against experimental challenges with infective nematode larvae in calves. In each study, calves were randomly assigned to one untreated group and up to four test groups, which were treated with eprinomectin at 500 μg/kg body weight at weekly intervals before single bolus challenge. The calves were necropsied approximately 4 weeks after challenge infection for nematode recovery. Eprinomectin pour-on provided ≥90% efficacy against challenge with Haemonchus placei, Trichostrongylus axei and T. colubriformis at 21 days after treatment and against Cooperia oncophora, C. punctata, C. surnabada, Dictyocaulus viviparus, Nematodirus helvetianus, Oesophagostomum radiatum and Ostertagia ostertagi at 28 days after treatment. Received: 14 April 2000 / Accepted: 18 May 2000