Experimental Feeding of Hydrilla verticillata Colonized by Stigonematales Cyanobacteria Induces Vacuolar Myelinopathy in Painted Turtles (Chrysemys picta)

Vacuolar myelinopathy (VM) is a neurologic disease primarily found in birds that occurs when wildlife ingest submerged aquatic vegetation colonized by an uncharacterized toxin-producing cyanobacterium (hereafter “UCB” for “uncharacterized cyanobacterium”). Turtles are among the closest extant relatives of birds and many species directly and/or indirectly consume aquatic vegetation. However, it is unknown whether turtles can develop VM. We conducted a feeding trial to determine whether painted turtles (Chrysemys picta) would develop VM after feeding on Hydrilla (Hydrilla verticillata), colonized by the UCB (Hydrilla is the most common “host” of UCB). We hypothesized turtles fed Hydrilla colonized by the UCB would exhibit neurologic impairment and vacuolation of nervous tissues, whereas turtles fed Hydrilla free of the UCB would not. The ability of Hydrilla colonized by the UCB to cause VM (hereafter, “toxicity”) was verified by feeding it to domestic chickens (Gallus gallus domesticus) or necropsy of field collected American coots (Fulica americana) captured at the site of Hydrilla collections. We randomly assigned ten wild-caught turtles into toxic or non-toxic Hydrilla feeding groups and delivered the diets for up to 97 days. Between days 82 and 89, all turtles fed toxic Hydrilla displayed physical and/or neurologic impairment. Histologic examination of the brain and spinal cord revealed vacuolations in all treatment turtles. None of the control turtles exhibited neurologic impairment or had detectable brain or spinal cord vacuolations. This is the first evidence that freshwater turtles can become neurologically impaired and develop vacuolations after consuming toxic Hydrilla colonized with the UCB. The southeastern United States, where outbreaks of VM occur regularly and where vegetation colonized by the UCB is common, is also a global hotspot of freshwater turtle diversity. Our results suggest that further investigations into the effect of the putative UCB toxin on wild turtles in situ are warranted.     

On the substrate specificity of cathepsins B1 and B2 including a new fluorogenic substrate for cathepsin B1.

Cathepsin B1 from bovine spleen exhibited its greatest rates of hydrolysis on peptide β-naphthylamide (βNA) derivatives containing paired basic residues, i.e., Cbz-Arg-Arg-βNA, t-Boc-Lys-Lys-βNA, and t-Boc-Lys-Arg-βNA. Internal peptide bonds were not attacked. At its pH 6.5 optimum, cathepsin B1 hydrolyzed Cbz-Arg-Arg-βNA (K_m 0.18 mM) 64 times faster than Bz-DL-Arg-βNA (K_m 3.3 mM or 1.6 mM for the L isomer) and was therefore chosen to replace the latter as a more soluble and sensitive substrate for the assay of cathepsin B1. Although cathepsin B2 had no action on the β-naphthylamide substrates, it did manifest carboxypeptidase activity by attacking COOH-terminal residues exposed by the action of cathepsin B1. At its pH 5.0 optimum, cathepsin B2 behaved as a SH-dependent, non-specific carboxypeptidase by releasing COOH-terminal amino acids from a variety of Cbz-Gly-X substrates and polypeptides such as glucagon, Val-Leu-Ser-Glu-Gly, and penta-lysine.     

Contractility of rat testicular seminiferous tubules in vitro: Prostaglandin F1α and indomethacin

The frequency of spontaneous $\text{in vitro}$ contractions of seminiferous tubules of the rat appeared to be increased in a dose-dependent manner by prostaglandin F_1α. PGF_1α treatment increased the tonus of the smooth muscle cells in the wall of the tubules as indicated by a reduction in the diameter of the tubules. When the tubules were rinsed successively with fresh Tyrode's solution, the contractile frequency was diminished. Returning the original bathing medium to the tubules restored their contractile frequency, as did treatment of the rinsed tubules with PGF_1α (10^-7 M). Pre-injecting the rats with indomethacin tended to reduce the contractile frequency of the extirpated tubules. Treating the tubules with a solution of indomethacin for 90 min. $\text{in vitro}$ was more effective than pretreatment $\text{in vivo}$ in reducing contractile frequency, but a combination of these two procedures produced the greatest inhibition. PGF_1α restored the contractile frequency of the indomethacin-treated tubules. Our results indicate that PGs modulate the $\text{in vitro}$ contractility of the tubules.     

Formation of micronuclei in erythrocytes of the fathead minnow (Pimephales promelas) after acute treatment with mitomycin C or cyclophosphamide

Despite the widespread use of the fathead minnow in ecotoxicology, there have been relatively few studies on genotoxicity biomarkers in this small, warm-water fish species. Consequently, we investigated the effect of two known genotoxins, mitomycin C and cyclophosphamide, on micronucleus induction in spleen and peripheral blood erythrocytes of this species. Initially, 96-h experiments after intra-peritoneal (i.p.) injections of mitomycin C and cyclophosphamide were undertaken to determine the maximum tolerated dose (MTD). From these studies, MTDs of 10 and 400 mg/kg, respectively, were obtained: doses that were higher than those reported for other fish species. Next, an assessment of micronucleus induction at 1, 2, 4, 8 and 14 days after injection was undertaken for each compound at the MTD. Mitomycin C at 10 mg/kg significantly induced micronuclei in erythrocytes from the spleen, but not from the peripheral blood, at 8 and 14 days. In addition, the overall levels of micronuclei observed were lower than most previously published data from other fish species. In contrast to mitomycin C, treatment with 400 mg/kg cyclophosphamide failed to significantly induce micronuclei in erythrocytes from any of the tissues employed, in contrast to previous reports of significant induction in other species. The reasons for the apparent relative insensitivity of the fathead minnow to these clastogens, with respect to both MTDs and micronucleus induction, are not clear. The fathead minnow, however, has previously been described as relatively insensitive compared to other fish species with respect to selected carcinogens and cytochrome P450 inducers; the latter suggesting that the lack of a significant induction following cyclophosphamide exposure may be due to low metabolic activation in vivo. Consequently, further clarifying work is required to delineate the response shown, considering the extensive use of this species in ecotoxicology research and regulatory testing.     

Restoring leptin signaling reduces hyperlipidemia and improves vascular stiffness induced by chronic intermittent hypoxia

Chronic intermittent hypoxia (IH) during sleep can result from obstructive sleep apnea (OSA), a disorder that is particularly prevalent in obesity. OSA is associated with high levels of circulating leptin, cardiovascular dysfunction, and dyslipidemia. Relationships between leptin and cardiovascular function in OSA and chronic IH are poorly understood. We exposed lean wild-type (WT) and obese leptin-deficient ob/ob mice to IH for 4 wk, with and without leptin infusion, and measured cardiovascular indices including aortic vascular stiffness, endothelial function, cardiac myocyte morphology, and contractile properties. At baseline, ob/ob mice had decreased vascular compliance and endothelial function vs. WT mice. We found that 4 wk of IH decreased vascular compliance and endothelial relaxation responses to acetylcholine in both WT and leptin-deficient ob/ob animals. Recombinant leptin infusion in both strains restored IH-induced vascular abnormalities toward normoxic WT levels. Cardiac myocyte morphology and function were unaltered by IH. Serum cholesterol and triglyceride levels were significantly decreased by leptin treatment in IH mice, as was hepatic stearoyl-Coenzyme A desaturase 1 expression. Taken together, these data suggest that restoring normal leptin signaling can reduce vascular stiffness, increase endothelial relaxation, and correct dyslipidemia associated with IH.     

Overcoming seed dormancy in ex situ plant germplasm conservation programmes; an example in the endemic Argyranthemum (Asteraceae: Anthemideae) species from the Canary Islands

Germplasm of 21 diverse Argyranthemum taxa was collected from contrasting ecological zones in the Canary Islands. Seed dormancy was considerable in the majority of taxa. Extensive investigations, based on a germination test procedure algorithm for Asteraceae, with achenes from ray and disc florets of five contrasting taxa identified a procedure to promote full (85%) germination of the seeds from both ray and disc florets of all five taxa; viz, excision of the seeds from the achenes, followed by testing at 15°C with 2.6×10^-3 m GA₃ co-applied. Subsequent tests showed that this regime was effective in promoting full germination in seeds from both ray and disc florets of the remaining 16 taxa. The results are discussed in the context of ex situ plant germplasm conservation.     

Quantitative assessment of pair formation behavior in captive whooping cranes (Grus americana)

Instantaneous scan sampling for mean distance and synchronous action patterns and all-occurrence sampling for unison call, dance, strut, and hoover-up behaviors were conducted for five potential whooping crane pairs at Patuxent Environmental Science Center, Laurel, Maryland. Dance, strut, and hoover-up differed among pairs, as did total frequency of social behaviors. It was unclear whether or not total frequency of social behaviors during pair formation can be used as an index for potential breeding success. The relative importance of different action patterns should be used as indices of pair compatibility in captive whooping cranes. © 1995 Wiley-Liss, Inc.     

Some generalized stochastic compartment models for digesta flow

Digesta flow models have been based on linear compartment theory that assumes exponential retention times, and on a generalized theory that incorporates nonexponential (Erlang) retention times (Matis, 1987, Journal of Theoretical Biology 124, 371-376). This paper develops a new family of passage models for heterogeneous digesta by mixing the previous models with assumed parametric, usually gamma, mixing distributions. The utility of the resulting models is demonstrated with experimental data on two treatments, namely a chopped and a ground straw, given to each of four cows. Treatment differences are apparent in the preferred model form and in the means of the estimated mean residence times. The models are relatively easy to fit to data using standard estimation procedures, and they should have broad application to other compartment modeling problems with "heterogeneous particles."