Structure/activity relationships in the arginine taste pathway of the channel catfish

To characterize the molecular/structural requirements for activationor antagonism of the arginine taste pathways in catfish, Ictaluruspunctatus, structure/activity studies were performed using integratedmultiunit responses and cross-adaptation. Of all the guanidinium-containingcompounds tested, only L-arginine, L--amino-ß-guanidinopropionic acid (L-AGPA) and L-arginine methyl and ethyl esterswere strong stimuli. Results of functional group substitutionsand modification of the L-arginine parent molecule indicatedthat: (i) stereospecificity was observed with D-arginine beinga much less effective stimulus than L-arginine; (ii) an L-aminogroup must be present and unblocked (-chloro-guanidino-N-valericacid and N-acetyl L-arginine were weak or inactive stimuli);(iii) a free carboxylic acid group was not necessary for activity;(iv) the distance between the anomeric carbon and the guanidiniumgroup was not critical (L-AGPA, having two methylene groupsless than L-arginine was a moderately strong stimulus as wasL-canavanine) and (v) modification or substitution of the guanidinumgroup by other basic groups including amine, methyl or dimethylamineor by an isosterc (ureido) resulted in loss of stimulatory ability.In general, those stimuli and analogs that were good cross-adaptersof L-arginine stimulation were also good competitors for L-[³H]argininebinding to a partial membrane fraction (P2) from catfish tasteepithelium. On the other hand, compounds that were poor cross-adaptingstimuli were also poor binding competitors. While D-argininewas a poor stimulus, it did cross-adapt L-arginine and competedwell with L-[³H]arginine for binding to fraction P2.     

Nonreceptor-mediated responses of adenylate cyclase in membranes from liver, muscle, and white and brown adipose tissue of obese (fa/fa) and lean (Fa/) Zucker rats

Adenylate cyclase activity was determined in membranes of liver, muscle, white adipose tissue, and brown adipose tissue (BAT) of lean (Fa/) and obese (fa/fa) Zucker rats. Responses were monitored following beta-adrenergic receptor stimulation and addition of GTP, GTP gamma S, or forskolin. beta-Adrenergic responses in liver, white adipose tissue, and BAT were lower in obese than in lean animals. No such difference was observed in muscle membranes. Production of cAMP after addition of guanine nucleotides was lower in liver and white adipose tissue membranes from obese rats compared with their lean littermates. Synthesis of cAMP in muscle membranes of obese animals after addition of GTP was either not different, or slightly higher, than that observed in muscle membranes from lean animals. Furthermore, production of cAMP after forskolin addition to muscle membranes of obese rats was significantly higher than that observed from lean rats under the same conditions. Interestingly, BAT membranes of obese rats were significantly more sensitive to guanine nucleotide activation than those of lean animals. The results confirm recent findings indicating inferior function of G proteins in liver plasma membranes of obese Zucker rats, and extend this observation to adipose tissue. The present results further suggest that the "nonreceptor" components (e.g., G proteins) responsible for the activation of adenylate cyclase in BAT membranes of obese rats are more responsive to stimulation than those of lean animals. Such sensitivity may be related to and perhaps compensate for the reduced thermogenic activity in the obese Zucker rat during the development of obesity.     

The differentiation of Staphylococcus aureus from other Micrococcaceae isolated from bovine mammary glands

Haemolysin production, the slide coagulase test and the tube coagulase test were assessed for their capability to differentiate Staphylococcus aureus among other Micrococcaceae in 199 isolates from udders of cows in herds with a low bulk milk somatic cell count. The API-Staph test was used as a reference.
Haemolysin production was less effective in identifying Staph. aureus among Micrococcaceae than a combination of other tests. Differences were found in the predictive values of results from diagnostic protocols in which the slide coagulase test was performed on all Micrococcaceae, or on β-haemolysin-negative Micrococcaceae only. Diagnostic protocols in which haemolysin production was combined with the results of the other tests resulted in excellent diagnostic performance and a reduction in diagnostic procedures. Recommendations for routine Staph. aureus identification in bovine mastitis bacteriology are given.     

Agar and ammonium nitrate influence hyperhydricity,tissue nitrate and total nitrogen content of serviceberry (Amelanchier arborea) shoots in vitro

Shoot tip cultures of Amelanchier arborea Michx.f. were grown on Murashige & Skoog or Woody Plant (WP) medium containing 4.4 M benzyladenine and various concentrations of agar. Increases in agar concentration affected various culture growth variables, decreased culture hyperhydricity and increased tissue nitrate concentration. Additions of ammonium nitrate to cultures grown on WP medium containing 0.4% agar increased all growth variables measured except percent dry weight. Hyperhydricity and tissue nitrate concentration also increase in response to increasing ammonium nitrate in the medium. Since hyperhydricity was shown to be both positively and negatively correlated with increases in tissue nitrate content, it is unlikely that tissue nitrate level alone directly affects hyperhydricity.Abbreviations BA benzyladenine - MS Murashige & Skoog - WP Woody Plant     

Biology and myriapod egg predation by the Neotropical myrmicine antStegomyrmex vizottoi (Hymenoptera: Formicidae)

Summary For the first time for a Neotropical ant and for Myrmicinae, the searching behavior and specialized predation of spirobolid millipede eggs byStegomyrmex vizottoi Diniz will be described. The relationship between morphology and habits is studied, as are nest architecture and distribution of the ant population in the nest chambers. We also report on some observations of behavior in the field and laboratory.We dedicate this paper to William L. Brown Junior, on the occasion of his 70^th birthday.     

Human olfactory neurons respond to odor stimuli with an increase in cytoplasmic Ca2+.

The sense of smell allows terrestrial animals to collect information about the chemical nature of their environment through the detection of airborne molecules. In humans smell is believed to play an important role in protecting the organism from environmental hazards such as fire, gas leaks and spoiled food, in determining the flavor of foods, and perhaps in infant-parent bonding. In addition, the study of human olfaction is relevant to a number of medical problems that result in olfactory dysfunction, which can affect nutritional state, and to the study of the etiology of neurodegenerative diseases which manifest themselves in the olfactory epithelium. Although much is known about behavioral aspects of human olfaction, little is understood about the underlying cellular mechanisms in humans. Here we report that viable human olfactory neurons (HON) can be isolated from olfactory tissue biopsies, and we find that HON respond to odorants with an increase in intracellular calcium concentration ([Cai]).     

Particle size influences decay rates of environmental DNA in aquatic systems

Environmental DNA (eDNA) analysis is a powerful tool for remote detection of target organisms. However, obtaining quantitative and longitudinal information from eDNA data is challenging, requiring a deep understanding of eDNA ecology. Notably, if the various size components of eDNA decay at different rates, and we can separate them within a sample, their changing proportions could be used to obtain longitudinal dynamics information on targets. To test this possibility, we conducted an aquatic mesocosm experiment in which we separated fish-derived eDNA components using sequential filtration to evaluate the decay rate and changing proportion of various eDNA particle sizes over time. We then fit four alternative mathematical decay models to the data, building towards a predictive framework to interpret eDNA data from various particle sizes. We found that medium-sized particles (1–10 μm) decayed more slowly than other size classes (i.e., <1 and > 10 μm), and thus made up an increasing proportion of eDNA particles over time. We also observed distinct eDNA particle size distribution (PSD) between our Common carp and Rainbow trout samples, suggesting that target-specific assays are required to determine starting eDNA PSDs. Additionally, we found evidence that different sizes of eDNA particles do not decay independently, with particle size conversion replenishing smaller particles over time. Nonetheless, a parsimonious mathematical model where particle sizes decay independently best explained the data. Given these results, we suggest a framework to discern target distance and abundance with eDNA data by applying sequential filtration, which theoretically has both metabarcoding and single-target applications.