Assessing waste collectors' exposure to bioaerosols

Published studies on household wastecollectors' exposure to airborne biologicalagents (bioaerosols) do not indicate highexposures to these agents. However, thesestudies did not consider several factors. Theobjective of this study was to characterize theexposure of waste collectors to bioaerosols andto propose solutions to control exposures tothese agents.Personal exposures of waste collectors tobioaerosols (total bacteria, endotoxins andmolds) were measured for seven types ofcollection during the summer, which representsthe worst conditions. The effect of truckcleaning was also evaluated. Meanconcentrations of bacteria were all in theorder of 10³–10⁴ CFU/m³ of air. Theintervention threshold was exceeded forendotoxins during the collection of compostonce every two weeks in the country. Meanconcentrations varied from 8.5 to 100 endotoxinunits per cubic meter of air (EU/m³). Measuredmean concentrations of molds were between 8,300and 98,170 CFU/m³ of air. Also, the cleaningof an empty garbage truck does not improve thequality of the air. On the other hand, a dirtytruck is not a major source of bioaerosols.The sources of these bioaerosols are leachate,particularly if the waste in the truck is oforganic origin, as well as the garbage pailsthat contain this waste. Unnecessary exposuresto these sources should therefore be avoided. For bioaerosols, stringent personal hygienemeasures remain one of the best means ofprevention.     

Inhibition of the retrograde axonal transport of acetylcholinesterase by the anti-calmodulin agents amitriptyline and desipramine

The possible involvement of calmodulin in mediating the calcium requirement for retrograde axonal transport of acetylcholinesterase was studied in vitro in bullfrog spinal nerves, with the use of the calmodulin inhibitors amitriptyline and desipramine. When nerves were preincubated with 0.2 mM amitriptyline or desipramine for 5 h, and were then ligated and incubated for an additional 17-18 h in drug-containing medium, the accumulation of acetylcholinesterase distal to the ligature was significantly reduced as compared to contralateral control nerves maintained in drug-free medium. The identical degree of transport inhibition observed for both drugs is consistent with their similar anti-calmodulin activity.     

Effects of a Bacterial Hay Preservative (Pediococcus pentosaceus) on Hay under Experimental Storage Conditions

The abundant growth of molds and thermophilic actinomycetes in stored hay decreases its quality and can be hazardous for the producer who inhales these contaminants when the moldy hay is fed in closed barns. These microbes are responsible for a respiratory disease called farmer's lung. Products, including bacterial cultures that can be inoculated in hay, are available to prevent hay deterioration by molds and bacteria. The aim of this study was to verify the effectiveness of Pediococcus pentosaceus (a bacterial inoculant) in preventing hay deterioration at different humidity levels in a laboratory experiment. Mixtures of grasses (mostly alfalfa, timothy, and clover) placed in plastic bags were treated with the commercially available product (live culture of P. pentosaceus) at 500,000 and 5,000,000 CFU/g of hay and humidified at different levels (20, 25, 30, and 35%). Control batches of hay (untreated) were prepared at the same humidity levels. The growth of inoculated bacteria in hay, pH level, and hay deterioration were evaluated. Under these experimental conditions, the growth of P. pentosaceus was abundant only when it was inoculated in very moist hay (35% moisture), resulting in bacterium levels of 6.3 x 10(sup8) CFU/g after 30 days. This abundant growth did not prevent the pH from increasing (final pH of about 9.0), nor did it prevent molding. At lower humidity levels (20, 25, and 30%), the bacterial inoculant used did not grow and did not prevent hay deterioration.     

Characterization of a new four-chain coiled-coil: influence of chain length on stability.

Limited information is available on inherent stabilities of four-chain-coils. We have developed a model system to study this folding motif using synthetic peptides derived from sequences contained in the tetramerization domain of Lac repressor. These peptides are tetrameric as judged by both gel filtration and sedimentation equilibrium and the tetramers are fully helical as determined by CD. The four-chain coiled-coils are well folded as judged by the cooperativity of thermal unfolding and by the extent of dispersion in aliphatic chemical shifts seen in NMR spectra. In addition, we measured the chain length dependence of this four-chain coiled-coil. To this end, we developed a general procedure for nonlinear curve fitting of denaturation data in oligomeric systems. The dissociation constants for bundles that contain alpha-helical chains 21, 28, and 35 amino acids in length are 3.1 x 10(-12), 6.7 x 10(-23), and 1.0 x 10(-38) M3, respectively. This corresponds to tetramer stabilities (in terms of the peptide monomer concentration) of 180 microM, 51 nM, and 280 fM, respectively. Finally, we discuss the rules governing coiled-coil formation in light of the work presented here.     

Production of mutacin-like substances by Streptococcus mutans

Production of inhibitory substances by strains of the Streptococcus mutans group is well documented, but the nature of the substances implied is often unknown. Of nine laboratory strains known to produce inhibitory substances, the optimal conditions for producing inhibition zones on solid media were found to vary between strains but good production was generally obtained on all-purpose media with Tween 80 at 37 degrees C after 2-4 days of aerobic incubation. Streptococcus sanguis Ny101 was found to be more sensitive than Streptococcus rattus LG-1 to all inhibitory substances produced by the S. mutans strains tested. While all strains showed some inhibition, only six showed inhibition after neutralization; arginine incorporated in agar at 0.75% completely eliminated all inhibition zones. However 1% arginine in the overlays did not affect the production of inhibition zones by strains of S. mutans C67-1, Ny257, Ny266, and T8. These strains were shown to elaborate (in a reproducible fashion) inhibitory substances which were not organic acids. Inhibitory activity was never obtained in liquid preparations, except for strains Ny257 and T8 where it was found to be very unstable.     

Changes in lectin binding of lumbar dorsal root ganglia neurons and peripheral axons after sciatic and spinal nerve injury in the rat

Summary The effects of chronic lesions of rat lumbar spinal or sciatic nerves on the binding of Glycine max (soybean) agglutinin to galacto-conjugates, in small-and medium-size primary sensory neurons of the L₄ and L₅ dorsal root ganglia, were examined over a 580-day period. Spinal nerve section resulted in a marked decrease in the population of stained neurons within 7 days. However, despite some retrograde morphological changes triggered by axonal injury, the proportion of stained nerve cells was normalized 180 days postoperatively. This temporary decrease in perikaryal lectin reactivity was initially associated with a marked accumulation of stained material in the nerve, proximal and distal to the site of section, with similar accumulations also being noticeable at each level of injury in sciatic nerves subjected to double ligature. This may reflect the presence of glycocompounds linked to the autolysis of nerve fibers during the phase of retrograde dying-back and Wallerian degeneration. At later stages, stained deposits could be seen scattered along central and peripheral axonal processes of the dorsal root ganglion neurons in the vicinity of the cell body. They may indicate a disturbance in the peripheral turnover of glycoproteins in chronically-transected nerves, with piling up of neuronal products. Sciatic nerve injury caused similar but less severe effects which, except for the L₄ ganglion cells, were rapidly reversible.     

Combined Hepatic Vein, Umbilicoportal Vein, and Superior Mesenteric Artery Catheterization in Portal Hypertension: Estimation of the Portal Fraction of Total Hepatic Blood Flow in Cirrhotic Patients

Hemodynamic data were obtained in 13 cirrhotic patients with severe portal hypertension, undergoing combined hepatic vein, umbilicoportal vein, and superior mesenteric artery catheterization. The relative clearance of indocyanine green, the portohepatic gradient (difference between the free portal venous pressure and the free hepatic venous pressure), and the estimated hepatic blood flow were measured. The portal fraction (PF) of total hepatic blood flow was calculated in all patients using indicator dilution curves obtained from the portal bifurcation, a right hepatic vein, and when possible a left hepatic vein (six cases) after injection of ⁵¹Cr-labeled red blood cells (⁵¹Cr RBC) into the superior mesenteric artery. Flows were overestimated because of loss of indicator through spontaneous portosystemic shunts; however, the ratio between hepatic and portal indicator dilution curves can be used to calculate the portal fraction of total hepatic blood flow since no extrahepatic shunts existed after the bifurcation of the portal vein (as shown on portography). In 10 patients, 15 series of curves were calculable and the PF varied between 30.1 and 100% (mean ± SE: 71.1 ± 6.2%). In the three other patients, only delayed activity from recirculation was detected from portal and hepatic vein samples and PF was 0%; in these three cases, portography and arteriography revealed spontaneous portacaval shunting with reverse and/or stagnant circulation in the portal vein. In the 13 patients, no correlation existed between PF and the relative clearance of indocyanine green or the portohepatic gradient, parameters generally used as indices of severity in cirrhosis. In 10 patients, no correlation was found between PF and the estimated hepatic blood flow.     

A three-dimensional model of an anti-lysozyme antibody

The primary amino acid structure of the lysozyme-binding antibody, HyHEL-10, as determined by amino acid and nucleotide sequencing was utilized to construct a scale model of the Fv (variable region domain of immunoglobulin) using energy-minimized torsional angles of the McPC603 Fv as a prototype template. This model was in turn used as a template for generating a computer-built set of co-ordinates, which were subjected to a total of 600 steps of Adopted Basis Newton-Raphson energy minimizations using the program CHARMM. Only minimal shifts of the backbone (root-mean-square 0.76 A) were required to give an energetically stable structure with a favorable van der Waals' energy. Several notable features were evident from both the scale model and the energy-minimized computer model: (1) the shape of the antibody combining region is that of a very shallow concavity approximately 20 A X 25 A; (2) the concavity is acidic and non-hydrophobic and is bordered by hydrophobic segments; (3) the lower portion of the combining site is dominated by a cluster of tyrosine residues over the L3 and H2 areas; (4) a somatic mutation encoded by the J region of the heavy chain (JH) may contribute significantly to the complementarity of heavy chain H3 to the epitope on hen egg white lysozyme. In addition, the space-filling energy-minimized model revealed that residue 49L, a framework residue, was prominently exposed and accessible in the center of the combining-site concavity. The model suggests that variation in length of complementarity-determining regions may function not only to change directly the shape of the antibody combining site, but may also influence indirectly the nature of the antibody surface by changing the accessibility of residues not usually involved in antigen binding.     

Bacteriology of the oral cavity of BALB/c mice

To be used as a model in dental research, an animal must fulfil experimental needs and information on the composition and variation of its oral flora must be available. Only limited data are available on the indigenous oral bacterial flora of BALB/c mice. In this work, a total of 671 isolates from different sites (saliva, tongue, teeth, and mucosa) of the oral cavity of BALB/c mice were identified. Only 18 different species were isolated, which indicates the relative simplicity of the flora. The predominant species of the total cultivable flora were "Lactobacillus murinus" (38%), Staphylococcus aureus (37%), Streptococcus faecalis (8%), Staphylococcus sciuri (4%), and Escherichia coli (3%). The other species each represent less than 2% of the flora. "Lactobacillus murinus" is found in greater proportion on mucosa than in the other sites, Staph. aureus predominates in saliva, and Strep. faecalis was found in greater proportion in tooth samples. Statistical analyses, using the minimum percentage of similarity, indicate that there is some variation among the microflora of different mice but that this difference is smaller for mice from the same lot. These results set the basis for the study of the variations of the indigenous oral microflora of BALB/c mice under different conditions.