Heterotrophic bacteria of the freshwater neuston and their ability to act as plasmid recipients under nutrient deprived conditions

Significantly higher numbers of Gram-negative heterotrophic bacteria were present at the air-water interface (neston) of freshwater lakes than in the bulk water. Neuston bacteria were distinguished as a population distinct from bacteria in the bulk water by a higher incidence of pigmented colony types and significantly greater levels of multiple resistance to antibiotics and heavy metals. The incidence of plasmids in 236 neuston and 229 bulk water strains were similar (14 and 16.2%, respectively). Nine of 168 plasmid-free strains and 2 of 14 plasmid carrying strains, isolated from both bulk water and neuston, acted as recipients of plasmid R68.45 in plate matings with aPseudomonas aeruginosa donor strain PAO4032 at 21°C, but at frequencies below that of matings with a restriction-minus recipient strain ofP. aeruginosa, strain PAO1168. In a model system composed of nutrient-free synthetic lake water, plasmid R68.45 was shown to transfer betweenP. aeruginosa strains at frequencies between 10⁻³ and 10⁻⁵. Transconjugants were detected about 100 times more frequently at the interface than in the bulk water, which in part reflected a greater enrichment of the donor at this site. None of the aquatic isolates were able to act as recipients of plasmid R68.45 in this model system with strain PAO4032 as donor. The results suggest that under nutrient deprived conditions, the spread of plasmid R68.45 and similar plasmids by lateral transfer into this particular aquatic population would be a rare event.     

Tolerance induction by a poorly arthritogenic collagen II can prevent collagen-induced arthritis

Collagen type II (CII)-induced arthritis (CIA) can be induced in 78% of B10.RIII mice (H2r) by intradermal (id) immunization with CII of bovine origin in complete Freund's adjuvant (CFA), whereas immunization with CII of chick origin induces arthritis in less than 5% of these mice. Nevertheless, tolerization of B10.RIII mice with intravenously injected chick CII renders the animals resistant to induction of CIA by immunization with bovine CII. Such tolerization can be achieved either by intravenous injection of 500 micrograms chick CII 1 week prior to immunization with bovine CII in CFA or by such an intravenous injection of chick CII 2 weeks after immunization with bovine CII in CFA. Postimmunization treatment results in a significant decrease in the concentration of antibody to bovine CII. Preimmunization administration of chick CII causes a marked decrease in the antibody reactive with chick CII without a significant effect on the anti-bovine CII antibody concentration. In DBA/1 mice, a strain in which both bovine CII and chick CII can induce a high incidence of the disease, intravenous injection of bovine CII can also prevent arthritis induced by chick CII, even when given 7 or 14 days after immunization. The fact that chick CII as tolerogen is quite effective in preventing arthritis in B10.RIII mice, while as immunogen it is very ineffective in inducing arthritis in this strain, may be interpreted as evidence for interaction between different epitopes on CII in the pathogenesis of CIA.     

Sequential homologies between procarboxypeptidases A and B from porcine pancreas

Automated Edman degradation of monomeric procarboxypeptidases A and B from porcine pancreas shows that their N-terminal regions (from residue 1 to 34-37) present a high degree of sequential homology to each other as well as to other related procarboxypeptidases. Conformational predictions based on these sequences confirm their structural homology and indicate the probable existence of two beta-turns, one beta-chain and a long alpha-helix in them. On the other hand, tryptic peptide maps on a reverse-phase column indicate great sequential similarities (if not identity) between monomeric procarboxypeptidase A and the procarboxypeptidase A subunit isolated from its binary complex with proproteinase E.     

Statistical analysis for the spatial validity of a model to forecast the daily number of forest fires

In earlier papers a qualitative and quantitative model was developed for predicting the number of forest fires occurring per day. This model permits the forecast at 00.00 hours Universal Time Convention (UTC) of any day (d), the number of forest fires per day for a range of several days (d tod+5) over a particular region. Input data are the number of forest fires in the region during two preceding days (d–2 andd–1) and the type of day (real and evaluated from radiosonde ford–2,d–1,d and predicted from meteorological medium-range forecasts, i.e. of European Centre, ford+1,d+2,d+3,d+4 andd+5. As this model requires data obtained by radiosonde, particularly temperatures and geopotentials at 850 and 700 hPa and dew points (or specific humidity) at 850 hPa, this study investigates the spatial validity of the model in relation to the distance from the radiosonde station (RS). The highest quality forecast is obtained for the region immediately surrounding the RS, and diminishes with increasing distance from it, this being due to the data obtained from the RS not being representative of the atmospheric column over the region. Hence, the derivation of the critical distance for a particular quality level of measurement. Conversely, fixed quality level implies a specific separation between RS and the region for the prediction, with a higher predictive quality implying a shorter distance.     

Isolation of Propionibacterium acnes from central nervous system infections

Propionibacterium acnes is a common skin colonizer and its involvement in central nervous system (CNS) infections may be related with previous neurosurgical procedures. P. acnes was isolated in pure or mixed cultures from ten patients with CNS infections during a 5-year period. The clinical presentation, treatment and outcome were retrospectively reviewed. Nine out of 11 patients had CNS infections after a neurosurgical procedure. The clinical presentation was: brain abscess (five patients), subdural or epidural empyema (four patients) and shunt meningitis (one patient). Three patients had also secondary meningitis. All patients received antibiotic therapy and all abscesses and empyemas were drained. The patient with shunt meningitis cured without catheter removal. Only one patient with a brain abscess by P. acnes died, but several months thereafter and as a consequence of a Gram-negative superinfection. P. acnes is a pathogen for the CNS and infections must be surgically managed under adequate antibiotic treatment.     

Electromyography of back muscles during quadrupedal and bipedal walking in primates

Despite the extensive electromyographic research that has addressed limb muscle function during primate quadrupedalism, the role of the back muscles in this locomotor behavior has remained undocumented. We report here the results of an electromyographic (EMG) analysis of three intrinsic back muscles (multifidus, longissimus, and iliocostalis) in the baboon (Papio anubis), chimpanzee (Pan troglodytes), and orangutan (Pongo pygmaeus) during quadrupedal walking. The recruitment patterns of these three back muscles are compared to those reported for the same muscles during nonprimate quadrupedalism. In addition, the function of the back muscles during quadrupedalism and bipedalism in the two hominoids is compared. Results indicate that the back muscles restrict trunk movements during quadrupedalism by contracting with the touchdown of one or both feet, with more consistent activity associated with touchdown of the contralateral foot. Moreover, despite reported differences in their gait preferences and forelimb muscle EMG patterns, primates and nonprimate mammals recruit their back muscles in an essentially similar fashion during quadrupedal walking. These quadrupedal EMG patterns also resemble those reported for chimpanzees, gibbons and humans (but not orangutans) walking bipedally. The fundamental similarity in back muscle function across species and locomotor behaviors is consistent with other data pointing to conservatism in the evolution of the neural control of tetrapod limb movement, but does not preclude the suggestion (based on forelimb muscle EMG and spinal lesion studies) that some aspects of primate neural circuitry are unique. © 1994 Wiley-Liss, Inc.     

TCEN-49, a monoclonal antibody that identifies a central body antigen in the planarian Dugesia (Girardia) tigrina. Implications for pattern formation and positional signalling mechanisms

We have produced monoclonal antibodies (mAbs) against antigens of the freshwater planarian Dugesia (G.) tigrina (Girard) using standard protocols. One of these mAbs, TCEN-49, detects an antigen (TCEN-49Ag) present in most cells of the central area of the body, including the pharynx. Labelled cells seem more related by position than by lineage, suggesting that TCEN-49Ag is involved somehow in the expression of central body positional identity. The spatial and temporal changes in TCEN-49Ag expression during growth/degrowth and regeneration have been monitored and the implications of these results are discussed.     

Analysis of the activation process of porcine procarboxypeptidase B and determination of the sequence of its activation segment

The molecular events which lead to the proteolytic transformation of porcine procarboxypeptidase B (PCPB) in carboxypeptidase B (CPB) have been determined. Among pancreatic and other tested proteinases, trypsin is the only one capable of generating carboxypeptidase B activity from the zymogen, in vitro. In the first step of this process, trypsin produces cleavage at the boundary between the activation region and the CPB region. Subsequently, a definite sequence of cleavages occurs at the C-terminal end of the released activation segment of 95 residues, giving rise to characteristic intermediates and to a proteolytically resistant activation fragment of 81 residues. In this process, the newly formed CPB participates in the quick-trimming of the released activation peptides. Only a single CPB species is formed in the activation process. This fact and the inability of the released activation peptides to inhibit CPB--and, therefore, their inability to slow down the kinetics of appearance of CPB activity--are two important characteristics differentiating between the activation processes of procarboxypeptidases A and B. The sequence of the 95 residues (MW = 12,835) of the activation region of porcine PCPB has also been deduced, largely from the information obtained by Edman degradation of its fragments and in part by considerations of homology with the rat precursor. The porcine PCPB activation region contains a high percentage of acidic residues, lacks cysteines, methionines, and side-chain posttranslational modifications, and presents a low but significant homology (31%) with the corresponding sequence of porcine procarboxypeptidase A.