Attempts to Displace the Indigenous Antibiotic Resistant Gut Flora of Chicken by Feeding Sensitive Strains of Escherichia coli Prior to Slaughter

Attempts to limit the use of antibiotics have not, in general, resulted in the gut flora in farm animals becoming predominantly sensitive. Partial success has been demonstrated, however, by feeding chickens with antibiotic sensitive Escherichia coli known to be good colonizers of the chicken gut. Where feeding was done prior to slaughter a corresponding reduction in carcass contamination by resistant E. coli was observed.     

EFFICIENCY OF A CYCLIC DESIGN AND A MULTIDIMENSIONAL SCALING SENSORY ANALYSIS TECHNIQUE IN THE STUDY OF SALT TASTE

Multidimensional scaling (MDS) procedures produce maps of stimulus points, the dimensions of which may be sensory and/or physicochemical attributes. Our objective was to test the efficiencies of a cyclic design and a MDS method in the study of saltiness perception. Two levels of NaCl (0.1% and 0.2%, w/v) were added to two nonionic and two ionic gum solutions prepared to two concentrations. Subjects scaled dissimilarities between pairs of solutions and rated each sample for flavor attributes. Solution pairs were selected using cyclic designs. Repeated measures ANOVA determined that added NaCl was the only significant factor affecting saltiness perception. In contrast, from KYST-2A MDS maps, we concluded that saltiness perception was influenced by gum property, gum concentration, presence of calcium and potassium, and related to binding of the sodium ion (Na⁺) as determined by ²³Na nuclear magnetic resonance (NMR) spectroscopy. The MDS cyclic design successfully reduced the number of samples and subjects when using experienced subjects.     

The Effect of Temperature on the Fatty Acid Composition of Tetrahymena pyriformis WH-14

SYNOPSIS. A reduction in the growth temperature of Tetrahymena pyriformis strain WH-14 from 35 C to 15 C resulted in distinct alterations in the fatty acid composition of the glycerophospholipids. The proportion of normal saturated acids declined from 26 to 19%; palmitoleic acid increased by 6%, and the composition of the polyunsaturated fatty acids increased in 18:2 Δ^6,11(n) and decreased in 18:2 Δ^9,12(n) and 18:3 Δ^6,9,12(n). The unsaturation index (the average number of double bonds/100 molecules) did not change with a shift in temperature.
Two biosynthetic pathways exist in Tetrahymena for the formation of unsaturated fatty acids. The observed changes in fatty acid composition that accompany a lowering of the environmental temperature can be accounted for by a reduction in the accumulation of products of the fatty acid pathway leading to the formation of γ-linolenic acid [16:0(n) → 18:0(n) → 18:1 Δ⁹(n) → 18:2 Δ^9,12(n) → 18:3 Δ^6,9,12(n)] and an increase in the components of the pathway leading to the formation of 18:2 Δ^6,11(n) [16:0(n) → 16:1 Δ⁹(n) → 18:1 Δ¹¹(n) → 18:2 Δ^6,11(n)]. The data suggest that the regulatory mechanism in Tetrahymena differs from that found in some bacteria where a simple substitution of unsaturated fatty acids for saturated fatty acids occurs at low culture temperatures.     

The Bonobo–Dialium Positive Interactions: Seed Dispersal Mutualism

A positive interaction is any interaction between individuals of the same or different species (mutualism) that provides a benefit to both partners such as increased fitness. Here we focus on seed dispersal mutualism between an animal (bonobo, Pan paniscus) and a plant (velvet tamarind trees, Dialium spp.). In the LuiKotale rainforest southwest of Salonga National Park, Democratic Republic of Congo, seven species of the genus Dialium account for 29.3% of all trees. Dialium is thus the dominant genus in this forest. Dialium fruits make up a large proportion of the diet of a habituated bonobo community in this forest. During the 6 months of the fruiting season, more than half of the bonobos’ feeding time is devoted to Dialium fruits. Furthermore, Dialium fruits contribute a considerable proportion of sugar and protein to bonobos’ dietary intake, being among the richest fruits for these nutrients. Bonobos in turn ingest fruits with seeds that are disseminated in their feces (endozoochory) at considerable distances (average: 1.25 km after 24 hr of average transit time). Endozoochory through the gut causes loss of the cuticle protection and tegumentary dormancy, as well as an increase in size by water uptake. Thus, after gut passage, seeds are better able to germinate. We consider other primate species as a potential seed disperser and conclude that Dialium germination is dependent on passage through bonobo guts. This plant–animal interaction highlights positive effects between two major organisms of the Congo basin rainforest, and establishes the role of the bonobo as an efficient disperser of Dialium seeds. Am. J. Primatol. 75:394‐403, 2013. © 2013 Wiley Periodicals, Inc.     

Ammonium and phosphate regenerationby the zooplankton of an Amazon floodplain lake

SUMMARY. 1. Regeneration of ammonium and phosphate by macro-zooplankton (Cladocera. adult copepods. and copepodites) was measured in Lake Calado. an Amazon floodplain lake, Macrozooplanktonabundances ranged between 1×10⁴ and 3×10⁵ individuals m⁻².
2. Phosphate regeneration ranged from 0.2 to 1.3 μ mol PO₄ m⁻² b⁻¹at station 1. located 2 km from the Solimoes River, and from 1.6 to8.3 μ mol PO₄ m⁻² h ⁻¹ at station 3, located 7 km from the SolimoesRiver. Ammonium regeneration at stations 1 and 3 ranged from 1.7 to11.9 and from 13.4 to 77.2 μ mol NH₄ m⁻² h⁻¹. respectively.
3. Zooplankton regenerated ammonium and phosphate at similarrates during rising and falling waier. Regeneration by macrozooplankton was low compared to other tropical lakes and compared to microbesand microzooplankton in Lake Calado.     

Record Chromosome Number in a Mammal?

CROSS has reported^{1, 2} chromosome complements in rodents ranging up to 2n=84 (in the North American geomyid Geomys breviceps) and 2n=86 (in the heteromyid Dipodomys merriami). Matthey has contested³ this claim; he maintained that in Geomys bursarius 2n =70 or 72 and he doubted whether a higher number had been confirmed. Numbers in the 2n=70 to 80 range have since been reported⁴ in several genera of Canidae and Ursidae. In general, rodent chromosomes fall into the lower group numbers but, among murines, Lophuromys aquillus is reported to have a chromosome complement of 70 (ref. 5) and Cricetomys gambianus one of 78 (ref, 6). In the gerbilline, Meriones shawii, the number can vary up to 78 (ref. 7).     

In Vitro Excystation of Spironucleus muris

ABSTRACT. In vitro excystation of Spironucleus muris cysts, purified by sequential sucrose and Percoll gradients from mouse feces, was studied. Three in vitro excystation procedures, used for Giardia , were assessed to determine the most useful method. Excystation was monitored by light microscopy and subsequently characterized by transmission and scanning electron microscopy. Spironucleus muris excysted routinely at a level greater than 90% when induced in Hanks' balanced salt solution containing sodium bicarbonate at pH 2.0 and transferred to Tyrodes' salt solution as an excystation medium. Similarly, high rates of excystation were recorded after induction of S. muris cysts in 0.1 M potassium phosphate buffer (pH 7.0) with sodium bicarbonate and excystation in trypticase-yeast extract-iron medium (TYI medium) or phosphate-buffered saline. A lower rate and percentage of excystation were observed after induction of S. muris cysts in an aqueous hydrochloric acid solution (pH 2.0) followed by excystation in TYI medium. All excystation methods produced extremely active S. muris trophozoites with normal morphology. Nonexcysting S. muris cysts have a wall composed of an outer fibrous and an inner membranous portion. Following induction, numerous vesicles appeared in the peritrophic space. Excystation began by the cyst wall opening at one pole, and the anterior part of the trophozoite protruding from the cyst wall. The trophozoite emerged progressively from the cyst wall and the empty cyst wall appeared to collapse. Excysted trophozoites exhibited normal morphological features of S. muris trophozoites isolated from the mouse intestine.     

Fluctuations in Escherichia coli O-serotypes in Pigs Throughout Life in the Presence and Absence of Antibiotic Treatment

A detailed study, throughout life, of the coliform and Escherichia coli gut flora of two pigs, is presented. One pig was given oral tetracycline for 3 d on two separate occasions; the other pig was not treated and housed separately. The fluctuations in numbers of coliforms, O-serotypes of E. coli , the occurrence and persistence of antibiotic resistance, and their interrelations, are analysed for both animals. Oral tetracycline profoundly affected the proportion of antibiotic sensitive and resistant E. coli , and, by selecting for R-factor bearing O-serotypes, limited the number of O-serotypes isolated from individual faceal specimens. Specific O-serotypes exhibited marked differences in their ability to persist in the gut of the control pig. The R-factor bearing O-serotypes, selected by tetracycline treatment, also showed differences in ability to persist after treatment indicating that properties other than the possession of R-factors, decide colonizing ability. The size of the colony sample for serotype analysis is discussed.     

The structure of the ostracode carapace

The carapace ultrastructure of three Recent [Heterocypris incongruens (Ramdohr), Cypridopsis uidua (Müller), and Conchoecia belgica Müller] and one Cretaceous ostracode species [Cypridea propunctata Sylvester-Bradley] has been studied by means of standard electron microscope techniques. The carapace is shown to be an organic structure divisible into an outer epicuticle, a median exocuticle and an inner endocuticle in the three cypridacean ostracodes examined. In Conchoecia belgica only an outer epicuticle and an inner endocuticle were observed, but this may be due to preservation. The chitin structure of the carapace of calcareous ostracodes is shown to be essentially an interlocking lattice, more coarsely developed in the exocuticle; layered (lamellar) chitin is only present in the selvage and in the connective tissue joining the valves at the hinge. The non-calcareous Conchoecia belgica possesses the layered chitin structure common to other crustaceans and to insects. The relationship of the carapace structure to that present in the decapod and insect exoskeleton is discussed. The technical problems met with during this study are considered in order to outline the difficulties associated with the study of organisms of this size.