EFFECTS OF CONFINEMENT/CROWDING ON UREOGENESIS IN THE GULF TOADFISH OPSANUS BETA

In order to elucidate the cues for, and the biochemical mechanisms of, the transition to ureogenesis in the gulf toadfish Opsanus beta, experiments on the effects of confinement/crowding were carried out. Confinement of toadfish to small volumes of water initiated a switch to nearly complete reliance on ureogenesis for nitrogen excretion within 24­48 h. Further experiments suggested that this switch was probably due to the physical confinement per se, rather than to a measurable build-up of ammonia in the water. However, the possibility of the response being triggered by a very low concentration of a pheromone-like substance was not excluded by our experimental design. The activities of several enzymes of ureogenesis, ornithine­citrulline transcarbamoylase, aspartate amino transferase and glutamine synthetase, increased in the liver of toadfish during confinement. Notably, glutamine synthetase activity increased almost fourfold within 24 h, and this increase preceded increases in urea excretion. A number of plasma and liver amino acid concentrations changed during confinement: there were declines in plasma asparagine, glutamate and glycine levels and an increase in plasma valine, as well as a decline in liver alanine and an increase in liver arginine concentrations. Liver glutamine was not detectable. When the amino acid data are taken together with the enzyme activity changes, it appears that the switch to ureogenesis occurs primarily upstream of the ornithine­urea cycle, at the level of supply of nitrogen to the pathway. The results are discussed in the context of the habitat of toadfish.

Pulsatile urea excretion in the toadfish (Opsanus beta) is due to a pulsatile excretion mechanism, not a pulsatile production mechanism

When subjected to a crowding/confinement protocol in the laboratory, toadfish become facultatively ureotelic, excreting approximately 90 % of their nitrogenous waste as urea-nitrogen (urea-N). The great majority of this excretion occurs via large, irregular pulses from the head region which occur on average once per day, with a duration of 3 h or less. Pulses measured chemically by the appearance of urea-N in the external water were identical to those measured by assaying [14C]urea appearance in the water from the blood plasma. Individual toadfish maintained plasma urea concentrations over widely differing ranges (6600­39 890 µmol-N l-1). However, independent of absolute levels, both [14C]urea and total urea were distributed at ratios close to unity between the blood plasma and the water compartments of liver and white muscle. At times of pulsatile excretion, plasma urea concentration fell sharply. These decreases, distributed throughout the tissues of the whole body, closely matched the sizes of the measured excretion pulses. Between pulses, plasma urea concentration increased steadily at a much slower rate; the rate of rise, when distributed throughout the tissues of the whole body, corresponded to the time-averaged excretion rate over the whole day. Infusion of a typical pulse amount of urea immediately after the end of a natural pulse event raised plasma urea concentration slightly above the pre-pulse level, but did not induce another pulse event. Plasma cortisol levels declined by approximately 60 % over the 4 h period prior to a natural pulse event and then rose quickly again once the pulse had occurred. These results indicate that urea pulses are due to activation of an excretion mechanism that rapidly clears urea from the blood plasma, thereby lowering stores throughout the whole body. Metabolic production of urea is continuous and is not responsible for pulsatile excretion. The pulse event is not triggered by a specific plasma urea threshold, but may involve the hypothalamo­interrenal axis.

Pulsatile urea excretion in the ureagenic toadfish Opsanus beta: an analysis of rates and routes

This study focused on the rates and routes of urea-N and ammonia-N excretion in the ureagenic toadfish and on the possibility that urea-N excretion occurs in pulses. Experimental approaches included the following: confinement in small individual containers with automated hourly sampling of water to follow temporal excretion patterns; divided chambers to separate excretion from the anterior and posterior parts of the fish; collection of urine and rectal fluid via chronic indwelling catheters; and gavage with [14C]-labelled polyethylene glycol 4000 to detect regurgitation of gastrointestinal fluids. When a standardized 'crowding' pre-treatment was employed to induce ureotelic behaviour, the fish exhibited significant elevations in the activity of glutamine synthetase in liver, kidney and gills, elevated plasma and bile urea-N levels, but unchanged ammonia-N and urea-N levels in most other body fluids. Unencumbered ureotelic fish confined in small containers excreted 82 % of their waste-N as urea-N and 18 % as ammonia-N; almost all (94 %) of this urea-N excretion occurred in a single pulse of less than 3 h duration about once every 24 h. This daily pulse did not occur by regurgitation of gut fluids, by excretion through prominent pores behind the pectoral fins or by discharge of rectal fluid or urine. Intestinal and urinary excretion accounted for less than 10 % of whole-body urea-N excretion and a negligible fraction of ammonia-N excretion. Pulsatile urea-N excretion occurred at the head end across the gills and/or body surface. Ammonia-N excretion, which was not pulsatile, also occurred largely through the head end. However, once the toadfish had been placed in divided chambers, urea-N excretion became continuous rather than pulsatile, and ammonia-N excretion increased greatly. A severe stress response was indicated by high levels of plasma cortisol, and the skin, which lacks scales, became a significant route of both ammonia-N and urea-N excretion. We speculate that the normal adaptive significance is that ureotelism facilitates cryptic behaviour, allowing the toadfish to virtually eliminate N-waste excretion during long periods while it remains sheltered in burrows. However, during severe stress, the effects of extremely high cortisol levels overwhelm the ammonia and urea retention mechanisms, and both substances leak across the general body surface.

Essential roles of NF-kappaB and C/EBP in the regulation of intercellular adhesion molecule-1 after respiratory syncytial virus infection of human respiratory epithelial cell cultures

To determine the molecular mechanism(s) of respiratory syncytial virus (RSV)-induced intercellular adhesion molecule-1 (ICAM-1) upregulation in respiratory epithelial cells (REC; A549 cell cultures), we investigated the roles of the transcription factors NF-kappaB and C/EBP. Increases in ICAM-1 message required de novo mRNA synthesis. ICAM-1 promoter constructs (luciferase reporter gene) transfected into A549 monolayers demonstrated promoter activation following RSV infection. Activation was abolished by site-specific mutation of the NF-kappaB (-228) or C/EBP (-239) sites. These data support the critical role of the activation of NF-kappaB and C/EBP in RSV-induced ICAM-1 expression by REC.

The role of angiotensin in the canine renal vascular response to barbiturate anesthesia

The influence of barbiturate anesthesia on renal blood flow was assessed by the xenon washout method in trained dogs with catheters chronically implanted in the renal artery. Anesthesia induced with either thiopental sodium or pentobarbital sodium resulted in a striking reduction in renal blood flow (4.1 +/- 0.1 vs. 2.6 +/- 0.2 ml/g per min; P less than 0.001) without a change in arterial pressure. The reduction in blood flow was prevented by a high salt intake and partially reversed by agents which interrupt the renin-angiotensin system (BPF 9a; 1-Sar,8-Ala-angiotensin II; propranolol) but not by alpha-adrenergic blocking agents (phentolamine and phenoxybenzamine). Anesthesia blunted the renal vascular response to angiotensin II (P less than 0.0005) whereas responsiveness to norepinephrine was increased (P less than 0.05). We conclude that barbiturate anesthesia induces a major, angiotensin-mediated renal vascular response which must be considered in the interpretation of experiments performed under these conditions.

Initial observations on using magnesium metal in peripheral nerve repair

Biodegradable magnesium metal filaments placed inside biodegradable nerve conduits might provide the physical guidance support needed to improve the rate and extent of regeneration of peripheral nerves across injury gaps. In this study, we examined basic issues of magnesium metal resorption and biocompatibility by repairing sub-critical size gap injuries (6 mm) in one sciatic nerve of 24 adult male Lewis rats. Separated nerve stumps were connected with poly(caprolactone) nerve conduits, with and without magnesium filaments (0.25 mm diameter, 10 mm length), with two different conduit filler substances (saline and keratin hydrogel). At 6 weeks after implantation, magnesium degradation was examined by micro-computed tomography and histological analyses. Magnesium degradation was significantly greater when the conduits were filled with an acidic keratin hydrogel than with saline (p < 0.05). But magnesium filaments in some animals remained intact for 6 weeks. Using histological and immunocytochemical analyses, good biocompatibility of the magnesium implants was observed at 6 weeks, as shown by good development of regenerating nerve mini-fascicles and only mild inflammation in tissues even after complete degradation of the magnesium. Nerve regeneration was not interrupted by complete magnesium degradation. An initial functional evaluation, determination of size recovery of the gastrocnemius muscle, showed a slight improvement due to magnesium with the saline but not the keratin filler, compared with respective control conduits without magnesium. These results suggest that magnesium filament implants have the potential to improve repair of injured peripheral nerve defects in this rodent model.

Solid-phase synthesis of trisubsituted guanidines

The solid-phase library synthesis of trisubstituted guanidines was accomplished. Amines were loaded onto the 4-formyl-3,5-dimethoxyphenoxymethyl linker via reductive amination. Subsequent acylation with Fmoc-4-aminomethylbenzoic acid followed by Fmoc deprotection gave solid-supported primary amines. Alternatively, sulfonylation of resin-bound secondary amines with 4-cyanobenzenesulfonyl chloride followed by borane reduction also gave solid-supported primary amines. Both resins were acylated with isocyanates to furnish solid-supported ureas. Dehydration of ureas with p-toluenesulfonyl chloride in pyridine gave solid-supported carbodiimides. Nucleophilic addition of amines to the carbodiimide bond followed by cleavage off the solid support gave trisubstituted guanidines.

Internal or external wall diameter for abdominal aortic aneurysm screening?

INTRODUCTION

The national abdominal aortic aneurysm (AAA) screening programme measures internal wall diameter; however, current UK intervention criteria use external wall diameter. Our aim was to determine the clinical significance of the difference between these two measurements.

PATIENTS AND METHODS

Fifty patients on an aneurysm surveillance programme were ultrasound scanned by two experienced vascular scientists, blinded to the other's results. Maximum anteroposterior internal wall and maximum anteroposterior external wall diameters were measured.

RESULTS

The median difference between internal and external diameter was 6 mm (IQR 6-7) for scientist 1 and 7 mm (IQR 5-8) for scientist 2. This was statistically significant (P < 0.0002). External wall diameter displayed less interobserver variability (3 mm vs 6 mm).

CONCLUSIONS

Screening measurements underestimate aneurysm size by 6 mm and display greater variability in comparison to external wall measurements. These findings should be understood to prevent a delay in the detection and treatment of AAAs.

Isolation of 20 glycosides from the starfish Henricia downeyae, collected in the Gulf of Mexico

Thirteen new (1-13) and seven known (14-20) steroid glycosides were isolated from Henricia downeyae, collected from the offshore waters of the northern Gulf of Mexico. Ethanolic extracts of these starfish caused growth inhibition in bacteria and fungi, potent antifouling activity against barnacle and bryozoan larvae, and feeding deterrent activity against a marine fish. The known compounds are typical glycosides found in several species of the family Echinasteridae, i.e., Echinaster sp. and Henricia laeviuscola. One of the new compounds belongs to this group, whereas the remaining 12 new compounds represent a novel series of steroid glycosides which have aglycons with structural similarities to the "asterosaponins". They possess a delta 9(11) 3 beta, 6 alpha-dihydroxysteroidal aglycon with 23-oxo or 22,23-epoxy functionalities and often a 20-hydroxyl group in the side chain. The sulfate is located at C-6 and the saccharide moiety at C-3, in contrast with the asterosaponins which have the sulfate at C-3 and the oligosaccaride moiety at C-6. All the new compounds contain a glucuronic acid unit, which is uncommon among steroid glycosides from echinoderms. The structures of the new compounds, isolated in amounts ranging from 3.4 to 0.9 mg, were determined by interpretation of their spectral data and by comparison with spectral data of known compounds.

Intranuclear distribution of the inducing metal in primary rhabdomyosarcomata induced in the rat by nickel, cobalt and cadmium

In primary rhabdomyosarcomata, induced in the rat by intramuscular implantation of powdered metallic nickel, cobalt and cadmium, at least 50% of the high content of inducing metal that accumulates in the nuclei of each tumour, is bound by the nucleoli. The remainder is distributed approximately equally between the nuclear sap and chromatin.

Concordant prune belly syndrome in monozygotic twins

We report 2 cases of concordant prune belly syndrome occurring in monozygotic twins. In addition to suggesting a genetic basis for this disease, our 12-year follow-up of these cases illustrates that these patients with an otherwise poor prognosis can have normal growth, development, and renal function with appropriate treatment.

The effect of sodium salicylate on antibiotic susceptibility and synergy in Klebsiella pneumoniae

Sodium salicylate was combined with the antibiotics amikacin, aztreonam, cefazolin, cefonicid, cefoperazone, ceftizoxime, norfloxacin, doxycycline, clindamycin, imipenem, mezlocillin and trimethoprim-sulphamethoxazole. The activity of the combinations was tested against encapsulated strains of Klebsiella pneumoniae, which differed markedly in their antibiotic susceptibility. The addition of salicylate (from 2 to 350 mg/l) to cultures increased the MIC of most antimicrobial agents from two- to four-fold, with the exception of imipenem and amikacin. Inhibition by imipenem was largely unchanged, and that of amikacin was increased in the presence of salicylate. The synergy of the combination of cefazolin and amikacin was abolished by salicylate, while the synergistic activity of imipenem and amikacin was significantly increased by salicylate. Doxycycline activity was most severely affected by salicylate as antimicrobial activity was significantly diminished at salicylate levels as low as 5 mg/l. In contrast, significant loss of inhibitory activity with other antimicrobials required at least 100 mg/l of salicylate. The clinical implications of salicylate on the sensitivity of K. pneumoniae to antimicrobials are discussed.

Solution-phase library synthesis of furanoses

The solution-phase synthesis of amido-, urea-, and aminofuranoses was achieved. Alkylated furanose aldehydes were treated with primary amines in the presence of sodium triacetoxyborohydride to give secondary amines. Subsequent acylation with acid chlorides and isocyanates afforded amidofuranoses and ureafuranoses, respectively. Second, reductive amination of furanose aldehydes with secondary amines yielded tertiary amines. The resulting acetonides were treated with alcohols in the presence of acid to yield mixed acetals. In the library syntheses, functionalized scavenger resins were used in the purification of intermediates and products.

Development of a larval bioassay for susceptibility of cat fleas (Siphonaptera: Pulicidae) to imidacloprid

Strategies for controlling cat fleas, Ctenocephalidesfelisfelis (Bouché), have undergone dramatic changes in the past 5 yr. With the advent of on-animal treatments with residual activity the potential for the development of insecticide resistance increases. A larval bioassay was developed to determine the baseline susceptibility of field-collected strains of cat fleas to imidacloprid. All four laboratory strains tested showed a similar level of susceptibility to imidacloprid. Advantages of this bioassay are that smaller numbers of fleas are required because flea eggs are collected for the test. Insect growth regulators and other novel insecticides can also be evaluated. Using a discriminating dose, the detection of reduced susceptibility in field strains can be determined with as few as 40 eggs.

Solid-phase library synthesis of alkoxyprolines

The library synthesis of alkoxyprolines was achieved using an acid-stable, nucleophile-cleavable solid support. A hydroxythiophenol linker derived from Merrifield resin was esterified with the corresponding ethers of BOC-hydroxyproline. Removal of the BOC protecting group with trifluoroacetic acid followed by acylation gave solid-supported hydroxyproline derivatives. Cleavage from the solid support with excess primary amines or excess secondary amines followed by purification of the crude products from the excess amine by supported liquid-liquid extraction gave the alkoxyproline library in high purity.

Measuring the kidneys-practical applications using a growth and hypertrophy chart

A graphic and practical method for displaying renal growth utilizes a growth-hypertrophy chart. It is best suited for following renal growth on sequential intravenous urograms in patients with urinary tract infection, reflux and problems in which renal growth reflects the efficacy of therapy. The chart uses established standards for normal kidney length, and rates of growth and hypertrophy, and enables one to tell at a glance whether the renal growth is normal. Pitfalls both in the method of measuring the renal lengths and in the interpretation of the measurements are discussed.

Potentiation of aminoglycoside inhibition and reduction of capsular polysaccharide production in Klebsiella pneumoniae by sodium salicylate

This study determined the effects of sodium salicylate combined with several aminoglycoside antibiotics on the growth and capsular polysaccharide (CPS) production of Klebsiella pneumoniae. Salicylate significantly enhanced in inhibitory effect of all aminoglycoside antibiotics against all bacterial strains tested. The production of CPS was decreased by 62-86% when 2.5 mM salicylate was used. Amikacin combined with salicylate reduced CPS only slightly more than salicylate alone. The chelating agents, ethylenediamine tetra-acetic acid and ethylene bis tetraacetic acid, which have similar CPS-reducing properties, did not enhance the inhibitory effect of amikacin. Noncapsular variants of strains of K. pneumoniae were as susceptible to amikacin as the fully encapsulated strains, with or without salicylate present. Therefore, the combination of salicylate and the aminoglycosides acted synergistically to inhibit K. pneumoniae growth, but the increase in antibiotic sensitivity with salicylate was not a result of a reduction in CPS production. The use of salicylate in maximum therapeutic doses may enhance the activity of aminoglycosides sufficiently to allow the dose of aminoglycoside to be reduced when infections due to K. pneumoniae are treated.

Drosophila melanogaster larvae detect low doses of UVC radiation as manifested by a writhing response

Exposure of insects and higher orders of animals to UVC radiation has been shown to result in toxicity with a delayed expression. We have observed an immediate writhing response in slowly wandering third instar larvae of Drosophila melanogaster exposed to UVC radiation at doses that were not lethal. UVB and UVA radiation had no effect. Mutants for the visual and sensory systems appeared to respond normally, but CO(2) anesthesia resulted in reversible inhibition. ebony and silver mutants, which affect different pathways in catecholamine metabolism, showed an absent to reduced response. Using UVC lasers, we were able to demonstrate a response in different regions of the larval body. Furthermore, a 193 nm laser that penetrates only 2-5 micron(s) was able to induce a response but unable to kill the larvae. These results suggest a photochemical reaction occurs in the cuticle which produces free radicals that stimulate the nerves and muscle which are present immediately below the epidermis. Possible targets for the UVC radiation are catecholic compounds secreted and processed into the cuticle of third instar larvae just to pupariation whose primary function is to crosslink the protein and carbohydrate components.

Simian virus 40 encapsidation: characterization of early intermediates

Simian virus 40 chromosomes were separated into various species by a two-step purification consisting of low-ionic-strength glycerol gradient sedimentation followed by low-ionic-strength agarose gel electrophoresis. For each species of simian virus 40 chromosome purified, the comigrating DNA and proteins were identified by agarose or polyacrylamide gel electrophoresis, respectively. Two species of chromosomes were identified which contained form I and form II DNA and large amounts of viral protein; they migrated more slowly than most of the free simian virus 40 chromosomes, which contained very little viral protein. The nuclease susceptibility of these chromosomes suggests to us that they are intermediates in encapsidation, and we describe an encapsidation model.

Using Qualitative Disease Risk Analysis for Herpetofauna Conservation Translocations Transgressing Ecological and Geographical Barriers

Through the exploration of disease risk analysis methods employed for four different UK herpetofauna translocations, we illustrate how disease hazards can be identified, and how the risk of disease can be analysed. Where ecological or geographical barriers between source and destination sites exist, parasite populations are likely to differ in identity or strain between the two sites, elevating the risk from disease and increasing the number and category of hazards requiring analysis. Simplification of the translocation pathway through the avoidance of these barriers reduces the risk from disease. The disease risk analysis tool is intended to aid conservation practitioners in decision making relating to disease hazards prior to implementation of a translocation.

Whole body vibration and dynamic restraint

The purpose of this study was to identify changes due to whole body vibration in peroneus longus (PL) activation following ankle inversion perturbation. Participants were 22 (age 22.1 +/- 1.8 yrs, ht 168.8 +/- 8.2 cm, mass 65.5 +/- 11.2 kg) physically active male and female students with no recent history of lower extremity injury. Measurements of PL electromechanical delay (EMD), reaction time, and muscle activation were collected from two groups (WBV and control) over 3 time intervals (pretreatment, posttreatment, and 30 min posttreatment). Two-way ANOVAs were used to compare groups over time for all dependent variables. No group x time interactions were detected (p < 0.05) for any of the dependent variables. Whole body vibration did not alter PL EMD, reaction time, peak EMG, or average EMG. The use of WBV for enhancing ankle dynamic stability was not supported by this study. However, more data are needed to determine if WBV is an effective intervention in other areas of injury prevention or rehabilitation. These data were not consistent with the hypothesis that WBV enhances muscle spindle sensitivity.