The effect of the macrolide antibiotic tylosin on microbial diversity in the canine small intestine as demonstrated by massive parallel 16S rRNA gene sequencing

Background  

Recent studies have shown that the fecal microbiota is generally resilient to short-term antibiotic administration, but some bacterial taxa may remain depressed for several months. Limited information is available about the effect of antimicrobials on small intestinal microbiota, an important contributor to gastrointestinal health. The antibiotic tylosin is often successfully used for the treatment of chronic diarrhea in dogs, but its exact mode of action and its effect on the intestinal microbiota remain unknown. The aim of this study was to evaluate the effect of tylosin on canine jejunal microbiota. Tylosin was administered at 20 to 22 mg/kg q 24 hr for 14 days to five healthy dogs, each with a pre-existing jejunal fistula. Jejunal brush samples were collected through the fistula on days 0, 14, and 28 (14 days after withdrawal of tylosin). Bacterial diversity was characterized using massive parallel 16S rRNA gene pyrosequencing.     

Availability of salts is not a limiting factor for the land crab Gecarcinus lateralis (Freminville)

The land crab Gecarcinus lateralis (Freminville) is restricted to within ≈ 250 m of the shore on Bermuda. Previous work demonstrated that availability of water did not account for the exclusion of crabs from inland habitats. The crabs' inability to produce dilute urine led to the hypothesis that availability of salts becomes limiting away from the shore. In the laboratory, osmoregulatory abilities of land crabs were tested under several ecologically realistic conditions. Salts were provided in interstitial water of various salinities in damp-sand “burrows”, in “drinking water” of various salinities, or in natural and artificial foods. Crabs maintained hemolymph concentrations very well even when exposed to salinities < 1% seawater (SW), particularly when given a choice of how much contact to have with test salinities (“drinking-water” regime). Rates of ion loss were apparently extremely low, even when low-ion artificial food (flavored filter paper) was passing through the gut. In the field, potential sources of salts were compared with the crabs' osmoregulatory abilities. All available water (rain, dew) was very dilute, and there was no evident gradient in availability of salts at increasing distances from shore that could account for the limited distribution of crabs. Concentrations of ions in forage plants were also low, and also showed no gradient correlated with the crabs' range limit. Crabs that were ion-depleted and then fed vegetation from inland of the normal range showed significant recovery in hemolymph concentrations. We concluded that availability of salts is adequate beyond the existing range of the land crabs, and is not the range-limiting factor. This is paradoxical, given the limited osmoregulatory abilities of crab antennal glands, and raises the question of how land crabs accomplish such extraordinary conservation of ions; the physiological mechanism (extrarenal modification of urine) will be described elsewhere. Factors that limit how far inland land crabs live remain enigmatic; hypotheses for further work are presented.     

Subfragments of the papain solubilized TL antigen.

TL antigen was solubilized from the tumor ASLI (TL. 1,2,3) by papain digestion. The subfragments of 125I-labeled TL were examined by two methods. The first involved immune precipitation followed by electrophoresis on SDS-acrylamide gels. This treatment yielded three bands of molecular weight 39,000 and 19,000, as well as material which migrated with the tracking dye. In the second procedure the papain digested material was partially purified on Sephadex G-200. The active fraction from G-200 was labeled with 125Iodine, mixed with alloantiserum and rechromatographed on G-200. The isolated immune complexes were boiled in SDS and 2-mercaptoethanol, then separated on a SDS-Sephadex G-150 column. Two radioactive peaks were eluted indicating an absence of the 19,000 m.w. component following the latter method of purification.     

Exposure to ozone reduces influenza disease severity and alters distribution of influenza viral antigens in murine lungs.

Exposure to ambient levels of ozone (0.5 ppm) was shown to alter the pathogenesis of respiratory infection after aerosol infection of mice with influenza A virus. A semiquantitative method for determination of the sites of virus replication by direct immunofluorescence indicated that exposure to ozone reduced the involvement of respiratory epithelium in the infectious process and resulted in a less widespread infection of the alveolar parenchyma. Furthermore, the ozone-mediated alteration in viral antigen distribution was consistent with significantly reduced influenza disease mortality and prolonged survival time, but only when the oxidant was present during the course of infection. Reduced disease severity in ozone-exposed animals appeared to be independent of peak pulmonary virus titers, pulmonary interferon titers, and pulmonary and serum-neutralizing antibody titers. These studies suggested that the distribution of influenza virus in the murine lung was a key factor in disease severity.     

Craniofacial suture stenosis: morphologic effects

Craniofacial anomalies, such as Apert's and Crouzon's syndromes, are presumed to be related to premature growth arrest of cranial base growth sites. However, premature growth arrest at cranial vault sutures in animals appears to play a causative role in the development of cranial deformities characteristic of single-suture, or simple, craniosynostosis in humans. To study the possible causative role of cranial vault and other (interface) suture stenoses on the development of craniofacial deformity, a vault suture and an interface suture between the cranial vault and facial skeleton were simultaneously immobilized. Thirty-one New Zealand White rabbits at 9 days of age underwent implantation of dental amalgam growth markers adjacent to cranial vault and facial sutures. In the experimental group (n = 15), methylcyanoacrylate adhesive was applied over the coronal (vault) and frontonasal (interface suture between vault and facial skeleton) sutures to immobilize them. The remaining 16 animals served as sham-treated controls. All animals underwent serial radiographic cephalometry to document growth effects in the cranial vault, cranial base, and facial skeleton. Application of adhesive resulted in statistically significant (p less than 0.05) reduction in growth at the coronal and frontonasal sutures. This was accompanied by an overall significant reduction in neurocranial vault length during the first 30 days of development.(ABSTRACT TRUNCATED AT 250 WORDS)     

Sublethal damage during cryopreservation of rainbow trout sperm

Although cellular damage during cryopreservation of freshwater fish spermatozoa has been reported in several studies, there is a lack of correlation between this damage and the fertility rates of eggs using postthawed milt. The apparent lack of such correlation may be due to other undetected sublethal cryodamage, which could affect the cell functionality and viability. This may be extremely important for freshwater fish spermatozoa whose ability to fertilize the egg requires dilution in water or hypoosmotic solutions, an hazardous environment for the cells. This study tested the change in cell permeability during cryopreservation, using Hoechst 33258 to assess cell permeability. The permeability of spermatozoa at different times after dilution in several hypoosmotic media were investigated. In the first trial, fresh semen, sperm diluted in freezing media (CPT), and freeze/thawed semen were studied. Three CPT were tested (Me2SO, DMA, and methanol). In the second trial, the addition of egg yolk as a membrane stabilizer was investigated. Samples were frozen at -20 degreesC/min in a programmable cooler and thawed in a 25 degreesC water bath. Dilution in the CPTs slightly increased the susceptibility of cells to damage but freezing/thawing caused a dramatic increase in the fragility of cells, which were killed in a few seconds after their contact with the hypoosmotic solutions. Egg yolk provided a significant protection to the membrane, allowing the cells a greater and more prolonged survival in the fertilization media. Samples frozen with Me2SO displayed the best results. These results are consistent with the achieved fertility rates that demonstrated sublethal cryodamage in the function of the sperm membrane that was not detected by standard procedures. Copyright 1998 Academic Press.     

Slipped-strand mispairing in a plastid gene: rpoC2 in grasses (Poaceae)

An exception to the generally conservative nature of plastid gene evolution is the gene coding for the beta" subunit of RNA polymerase, rpoC2. Previous work by others has shown that maize and rice have an insertion in the coding region of rpoC2, relative to spinach and tobacco. To assess the distribution of this extra coding sequence, we surveyed a broad phylogenetic sample comprising 55 species from 17 angiosperm families by using Southern hybridization. The extra coding sequence is restricted to the grasses (Poaceae). DNA sequence analysis of 11 species from all five subfamilies within the grass family demonstrates that the extra sequence in the coding region of rpoC2 is a repetitive array that exhibits more than a twofold increase in nucleotide substitution, as well as a large number of insertion/deletion events, relative to the adjacent flanking sequences. The structure of the array suggests that slipped-strand mispairing causes the repeated motifs and adds to the mechanisms through which the coding sequence of plastid genes are known to evolve. Phylogenetic analyses based on the sequence data from grass species support several relationships previously suggested by morphological work, but they are ambiguous about broad relationships within the family.      

Inhibition of growth of ASL-1w murine leukemia cells by anti-thymus leukemia antigen (TL) serum in the absence of complement.

Previous studies have shown that the cell surface expression of thymus leukemia antigen (TL) on ASL-1w leukemia cells varies with the progression of the cells through the growth cycle. Expression of TL is maximal in S phase, and its quantitative expression varies directly with DNA synthesis. In the present study, the effect of anti-TL serum on the growth of ASL-1w cells was examined. The antiserum, tested in the absence of complement, affected the growth of these cells in biphasic manner. When the antiserum concentration was 0.1% or greater, there was a rapid decline in the rate of DNA synthesis, and after 5 to 7 hr, cell death. When the antiserum concentration was 0.067% or less, the decline in the rate of synthesis of DNA did not become apparent until 5 to 6 hr after treatment. Under these conditions, there was approximately a 20% increase in cell number after 24 hr of culture. The hypothesis that treatment of ASL-1w cells with the lesser concentration of anti-TL serum blocks the cells in G2 phase of the cell cycle is discussed.     

The Middlemen of MACOS

Prompted by a recent review in American Anthropologist, I interviewed two people who played central roles in the training and dissemination of MACOS, a social studies curriculum unit designed for the fifth grade during the era of intensive curriculum reform beginning in the sixties. The article briefly discusses both how MACOS came to be and what subsequently happened to it.