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Species' distributions will respond to climate change based on the relationship between local demographic processes and climate and how this relationship varies based on range position. A rarely tested demographic prediction is that populations at the extremes of a species' climate envelope (e.g., populations in areas with the highest mean annual temperature) will be most sensitive to local shifts in climate (i.e., warming). We tested this prediction using a dynamic species distribution model linking demographic rates to variation in temperature and precipitation for wood frogs (Lithobates sylvaticus) in North America. Using long-term monitoring data from 746 populations in 27 study areas, we determined how climatic variation affected population growth rates and how these relationships varied with respect to long-term climate. Some models supported the predicted pattern, with negative effects of extreme summer temperatures in hotter areas and positive effects on recruitment for summer water availability in drier areas. We also found evidence of interacting temperature and precipitation influencing population size, such as extreme heat having less of a negative effect in wetter areas. Other results were contrary to predictions, such as positive effects of summer water availability in wetter parts of the range and positive responses to winter warming especially in milder areas. In general, we found wood frogs were more sensitive to changes in temperature or temperature interacting with precipitation than to changes in precipitation alone. Our results suggest that sensitivity to changes in climate cannot be predicted simply by knowing locations within the species' climate envelope. Many climate processes did not affect population growth rates in the predicted direction based on range position. Processes such as species-interactions, local adaptation, and interactions with the physical landscape likely affect the responses we observed. Our work highlights the need to measure demographic responses to changing climate.

The appropriate management of streamside forests and use of riparian strips is poorly resolved for many systems because of a lack of understanding of the extent to which riparian forests function as environmental buffers for aquatic species versus core (essential) habitat for semi-aquatic and terrestrial species. We studied streamside forests in western North Carolina and eastern Tennessee, USA, to help delineate their functional value for plethodontid salamanders. We established 30 m × 40 m plots at 17 sites (823–1716 m in elevation) in unmanaged forests with closed canopies. Plots contained a portion of a seep or first-order stream along one edge and typically extended 36–38 m into the adjoining forest. We examined use of stream and streamside habitats based on captures during area-constrained searches of cover objects. We observed 6423 plethodontid salamanders belonging to 7 terrestrial-breeding and 12 aquatic-breeding species. Terrestrial-breeders (primarily Plethodon spp.) comprised 37% of terrestrial specimens and were more abundant at higher elevations. Aquatic-breeders (primarily Desmognathus spp.) increased their proportionate use of terrestrial habitat, but declined in overall abundance with elevation. Catches of aquatic-breeders were greatest within 8 m of aquatic habitats (49% of total terrestrial catch of aquatic-breeders), particularly at low elevation sites. The terrestrial zone provided core habitat for one terrestrial-breeder ( D. wrighti ) and six semi-aquatic species ( Desmognathus spp., Gyrinophilus porphyriticus and Eurycea wilderae ) that were broadly distributed throughout plots, and acted as an aquatic buffer for four highly aquatic species ( Desmognathus spp.). The remaining species were terrestrial-breeders ( Plethodon spp.) that were evenly distributed across plots, suggesting that riparian strips would function as important source populations for recolonization following timbering on adjoining land. Because of the vulnerability of plethodontid salamanders to edge effects, effective management of southern Appalachian streamside habitats may require the addition of a terrestrial buffer to protect terrestrial core habitat that immediately adjoins streams and seeps.

A series of in vitro and in vivo bioassays were conducted to assess the ectoparasiticide activity of isopropyl-4-nitro-2,6-bis(trifluoromethyl)-1-benzimidazole-carbamate, an experimental benzimidazole-carbamate class compound. This compound was less potent than permethrin against ectoparasiticide-susceptible larvae of the lone star tick, Amblyomma americanum (L.) (Acari: Ixodidae); larvae of the southern cattle tick, Boophilus microplus (Canestrini); and adult stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae) in vitro, but it was significantly more potent than permethrin against the Santa Luiza strain of B. microplus known to possess high-level resistance to amitraz and pyrethroids. In contrast, the benzimidazole-carbamate was substantially more efficacious than permethrin when applied topically onto rats that were infested with A. americanum nymphs. These results suggest that this experimental compound may be a viable candidate ectoparasiticide that retains significant activity against resistant B. microplus and also suggests that the benzimidazole-carbamate chemistry may be useful for addressing the growing problem of resistance in ectoparasites.

A new series of analogues of 4-(4-fluorophenyl)-2-methylthio-thiophene-3-carbonitrile (1) were synthesized and evaluated for their in vitro and in vivo anthelmintic activity against Haemonchus contortus.

Amphibians are declining globally, and efforts are underway to establish long-term programs to monitor population trends. Because researchers are constrained to sampling a small subset of populations that occur across a landscape, monitoring units should be selected that maximize the statistical independence of population responses to environmental stressors. Breeding sites of pond-breeding amphibians are often clustered locally, and habitat switching between neighboring ponds could significantly compromise both demographic and statistical independence. This raises a fundamental issue of whether the basic monitoring unit for trend analysis should be an individual pond or a cluster of local ponds. To help resolve the degree of demographic independence within a cluster of local ponds, we conducted a spatial-scale analysis of breeding-population synchrony of the wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) in four national parks in Kentucky, North Carolina, and Tennessee, USA. We u...

We have identified and mapped a gene in Toxoplasma gondii that encodes a homologue of SRCAP (Snf2-related CBP activator protein), a member of the SNF/SWI family of chromatin remodeling factors. The genomic locus (TgSRCAP) is present as a single copy and contains 16 introns. The predicted cDNA contains an open reading frame of 8,775 bp and encodes a protein of 2,924 amino acids. We have identified additional SRCAP-like sequences in Apicomplexa for comparison by screening genomic databases. An analysis of SRCAP homologues between species reveals signature features that may be indicative of SRCAP members. Expression of mRNA encoding TgSRCAP is upregulated when tachyzoite (invasive form) parasites are induced to differentiate into bradyzoites (encysted form) in vitro. Recombinant TgSRCAP protein is functionally equivalent to the human homologue, being capable of increasing transcription mediated by CREB.

Fescue toxicosis in cattle occurs as a result of consumption of ergot alkaloids in endophyte-infected (E+, Neotyphodium coenophialum) tall fescue (Festuca arundinacea). The condition is characterized by pyrexia, decreased weight gains, rough hair coats, and decreased calving rates. The objective of this experiment was to investigate whether steers grazing E+ fescue have altered host response to lipopolysaccharide (endotoxin, LPS) challenge compared with steers grazing endophyte-free (E-) fescue. Angus steers (n=8) had continuously grazed either E+ (n=4) or E- (n=4) tall fescue grass for 8 months prior to the experiment. The E+ steers had lower body weight, depressed average daily gain, and decreased basal serum prolactin compared with the E- steers prior to LPS administration. Each steer received a single bolus i.v. injection of LPS (0.2 microgram/kg body weight; Escherichia coli; 026:B6) dissolved in sterile saline, and blood was serially collected every 30 min for 4 h and at 24 h post LPS administration. LPS increased serum tumor necrosis factor-alpha (TNF-alpha), cortisol, and haptoglobin but decreased plasma glucose and IGF-I. Importantly, however, TNF-alpha, cortisol, and IGF-I responses to LPS were greater in E+ compared with E- steers. These results indicated that animals grazing E+ fescue had altered integrated metabolic host response compared with animals grazing E- fescue. Potentially, combined exposure to E+ fescue and a bacterial LPS could have greater deleterious effects on the animal compared with exposure to only one of the two and would likely lead to increased catabolism.

We examined how stream degradation can affect adjoining stream-side communities by comparing the density, age structure, and microhabitats of salamanders in forests adjoining contaminated and noncontaminated section of Beech Flats Creek in the Great Smoky Mountains National Park. A section of Beech Flats Creek was contaminated due to exposure of Anakeesta rock formations in 1963. Chronic changes that have occurred since then include a reduction in pH, and increase in metal concentrations, and a nearly complete elimination of all macroinvertebrates, salamander larvae, and fish. Comparisons of control and impact plots indicate that two stream-breeding species (Desmognathus quadramaculatus; Eurycea wilderae) have been nearly eliminated form impacted stream sections, while two other species (D. ochrophaeus; D. imitator) that breed in both streams and seepages have been reduced by about half. In contrast, terrestrial-breeding species (Plethodan jordani; D. wrighti) appear to have increased markedly following the reduction in stream-breeders. Juvenile P. jordani comprised a significantly greater percentage of the population on impacted plots compared with controls. Microhabitat use on control and impacted plots did not differ significantly for any species. Changes in the densities and age structure of terrestrial breeders on impacted plots may have been due to the elimination of D. quadramaculatus,more » which is a major predator on other salamanders, or to release form competition with adults of stream-breeding species. Overall, our data indicate that stream contamination from Anakeesta exposure can alter the structure of streamside salamander communities both by directly eliminating species with biphasic life cycles, and by indirectly altering ecological interactions among community members. 39 refs., 4 figs., 1 tab.« less

We examined the effects of timber harvesting on southern Appalachian salamander communities in a managed watershed in Pisgah National Forest, western North Carolina, USA. Salamander abundance and species richness were lowest in very young stands and highest in stands more than 120 years old. Comparisons of recent clearcuts less than 5 years old with mature stands more than 80 years old suggest that terrestrial salamanders are completely eliminated or reduced to very low numbers when mature forests are clear cut. Comparisons of stand age categories further suggest that salamander abundance in local communities slowly increases for a century or more after stands are intensively harvested. We roughly estimate that logging during the last century by both the private and public sector has resulted in 1 70% decline in salamander numbers within the study area as a whole. Implementation of an ecosystem-management strategy which reverses the current trend of having landscapes dominated by early and mid-successional forests would help restore depleted populations to levels where salamanders better fulfill their ecological roles as forest-floor insectivores. Other management techniques that would benefit salamanders include leaving buffers along headwater streams, and using harvesting techniques which assure that the basic structure and function of forests remain intact following timbering operations.

I examined the effects of body size on competition among larvae of the salamander Ambystoma opacum. Two opposing hypotheses were tested: (1) size differences among competing individuals reduce the negative effects of competition on larval growth, and (2) size differences reflect a hierarchy in competitive ability in which larger larvae are superior competitors. When larvae preyed on macrozooplankton in their laboratory, a twofold difference in larval size had no effect on prey capture rate. In two other laboratory experiments I reared larvae of three size classes in pairs, and showed that the growth of small larvae was independent of the size of co—occuring individuals when the larvae competed exploitatively for macrozooplankton. Larger individuals negatively affected the growth of smaller individuals only if the larvae physically interacted. The physical interactions included attempts at cannibalism. I also manipulated larval density and the sizes of co—occurring larvae in two field experiments. Although in both experiments I found adverse effects of high density on larval growth, larval growth was independent of the size of co—occuring conspecific larvae. These results suggest: (1) variation in body size does not lead to a reduction in the negative effects of competition; (2) under purely exploitative competition for small prey, larger larvae are not superior competitors; (3) larger larvae do not have a size advantage in physical interactions, but physical interactions may be minimized under field conditions even when density adversely affects larval growth.

Monoclonal antibodies (Mab) were produced against Eimeria tenella merozoites. A single Mab, LPMC-61, was selected because of its ability to bind to merozoites by indirect immunofluorescence assay (IFA) and to inhibit in vitro sporozoite development. Mab LPMC-61 reacts with an approx. 10-12-kDa merozoite polypeptide in reduced SDS-PAGE, but with an approx. 80-kDa protein in non-reduced SDS-PAGE. The monoclonal recognizes similarly sized polypeptides in E. tenella sporozoites, oocysts and schizonts. A partial cDNA (LPMC-61f) encoding the LPMC-61 antigen was identified from an E. tenella sporozoite cDNA library in bacteriophage lambda gt11. In addition to Mab LPMC-61, the recombinant beta-galactosidase/LPMC-61f fusion protein is recognized by hyperimmune rabbit anti-E. tenella sporozoite serum, rabbit anti-E. tenella merozoite serum, and E. tenella-infected and immune chicken sera. DNA sequencing of LPMC-61f cDNA showed that the putative protein has an unusual tandem, non-perfect repeated sequence, with glutamine comprising about 48% of the predicted amino acids. A hydropathicity plot of the predicted amino acid sequence shows a central hydrophilic region, consisting of the repeated sequences, surrounded by hydrophobic regions on both sides. Since the merozoite stage of avian Eimeria has been implicated in the induction of a protective immune response in chickens, LPMC-61 may be an important immunogen for use as a vaccine against E. tenella.

We have optimized a larval immersion microassay (LIM) that offers superior sensitivity, flexibility to accommodate multiple formulations, and a robust capability for rapidly screening many compounds with a minimal requirement of test article for evaluation. Dose-response studies were conducted for representative members from the organophosphate, pyrethroid, pyrazole, carbamate, macrocyclic lactone, and formamidine chemistries against Amblyomma americanum (L.). Time-response experiments revealed that permethrin was the most rapid acting, whereas fipronil had the slowest speed-of-kill against A. americanum. Comparison of drug susceptibility profiles between multiple ixodid ticks suggests that A. americanum is an effective model for predicting compound potency against Boophilus spp. in this bioassay. The LIM is suitable for the identification and characterization of active molecules from small- and medium-sized compound or natural product libraries, and it can be a useful tool to prioritize molecules for further in vivo testing in animal models.

During the course of a collaborative screening program, a set of 1-phenyl-4-pyridyl-butadienes was found to exhibit in vitro activity against Eimeria tenella in a cell-based assay. Activity was dependent on the chain length and degree of unsaturation of the linker between the two aryl groups as well as substitution of the pyridine moiety. Structure-activity relationship studies were subsequently conducted over a larger range of 1,4-diarylbutadienes in order to determine the scope of active compounds, to identify structural patterns governing activity and to enhance in vitro potency against E. tenella. In addition, the efficacy of many compounds for treating coccidiosis in chickens was measured by testing the ability of the compound to prevent or reduce intestinal and cecal lesions when administered by oral gavage. A few compounds in the series were identified that exhibited a moderate degree of in vitro and in vivo activity.

The objective of this experiment was to investigate whether the ergot alkaloid, ergotamine (ET), an alkaloid used to model fescue toxicosis in cattle, modifies the response of cattle to endotoxin (LPS) challenge. Steers (n = 16) were divided into the following treatment groups: control (C), ergotamine (ET), endotoxin (LPS), and ET + LPS. ET and ET + LPS groups received a single bolus intravenous injection of ET (40 microg. kg. body wt(-1)), whereas C and LPS steers received a single bolus injection of sterile vehicle. Thirty minutes after ET/vehicle administration, a single bolus intravenous injection of LPS (0.2 microg. kg. body wt(-1)) was given. Blood was collected at various time points for 48 hr post. Endotoxin increased rectal temperature (RT) and the circulating levels of tumor necrosis factor-alpha (TNF-alpha), cortisol, haptoglobin (Hp), thromboxane B(2) (TXB(2)). The circulating Hp, TNF-alpha, and TXB(2) increases were blunted by pretreatment with ET compared with ET + LPS. Ergotamine by itself increased circulating cortisol and RT, whereas it decreased serum prolactin (PRL). Therefore, whereas administration of LPS at 0.2 microg/kg to steers resulted in an expected response, the combination of ET + LPS attenuated major effects of LPS alone. Thus, acute administration of ET appeared to be anti-inflammatory as it decreased the inflammatory response to LPS, an effect likely driven at least in part by the ET-caused cortisol increase.

In an effort to identify gene products involved in transcriptional regulation in apicomplexan parasites, the Toxoplasma gondii expressed sequence tag (EST) database was examined for sequences containing similarity to known transcriptional components. One EST (dbEST ID #466792) exhibited strong similarity to yeast GCN5 and other histone acetyltransferases (HATs). Primers were designed based on the EST sequence and used to amplify an 850 bp fragment (containing an intron) from T. gondii genomic DNA which was used to identify four cDNA clones from a tachyzoite cDNA library. The complete open reading frame (ORF) of 3.5 kb was elucidated using 5' RACE and genomic sequence. The deduced amino acid sequence of the coding region shows that the C-terminal domain possesses unequivocal similarity to GCN5 family members. However, unlike other lower eukaryotes, T. gondii GCN5 has an extended N-terminal domain similar in length, but not in composition, to metazoan HAT proteins. These features distinguish T. gondii GCN5 as a novel member of the GCN5 family. A portion of the cDNA sequence was used as a probe to isolate three overlapping clones from a T. gondii genomic library, generating a approximately 7.5 kb map of the GCN5 locus which contains seven exons separated by six introns. Southern analysis verifies the predicted map and suggests that a similar locus may be present elsewhere in the genome.

Three sequential experiments were conducted with rabbits to 1) determine the effect of endophyte-infected (E+) tall fescue seed on rabbit performance and examine the effect of anti-ergot alkaloid immunization on rabbit performance and protectiveness against fescue toxicosis, 2) compare immunogens designed to elicit systemic anti-ergot alkaloid antibodies, and 3) select a superior adjuvant. In Exp. 1, rabbits (n = 6/treatment) fed E+ fescue seed diets (20%, 340 ppb total ergot alkaloids) had reduced (P

Beta-adrenergic receptors (betaAR) are abundant in fetal, neonatal, and adult skeletal muscles of cattle; however, only minimal levels of functional betaAR were detected in multinucleated muscle cell cultures prepared from 90- to 150-d fetal bovine skeletal muscle. Two other lines of evidence were consistent with low levels of betaAR expression in bovine muscle cultures. First, treating the cells with 10(-6)M isoproterenol for up to 20 min did not increase intracellular cAMP concentration. Second, neither the quantity of myosin heavy chain (MHC) nor its apparent synthesis rate were changed by treating the cells for 4 d with 10(-7) or 10(-6) M isoproterenol. Despite these results, the mRNA for the beta2AR could be detected in muscle cultures by PCR and on slot blots. Thus, the beta2AR mRNA was expressed, but significant levels of functional receptors could not be detected. Glucocorticoids are known to activate expression of OAR genes in several tissues, and the effect of dexamethasone on OAR gene expression in bovine multinucleated muscle cell cultures was evaluated. The intracellular concentration of cAMP following treatment with isoproterenol was elevated 10-fold by dexamethasone, and the population of functional receptors was elevated by approximately 50%. The effect of dexamethasone on muscle protein synthesis and accumulation was analyzed after pretreating the cells with dexamethasone for 24 h, followed by treatment with dexamethasone and 10(-6)M isoproterenol for an additional 48 h. The quantity of MHC synthesized and the apparent synthesis rate of MHC were stimulated by 10 to 35%. These effects seem to be due to posttranscriptional events, because the quantity of beta2AR receptor mRNA on slot blots was not increased by treatment with dexamethasone. Results of this study emphasize the importance of verifying that muscle cells contain functional betaAR when they are used to study the effects of betaAR agonists on muscle protein metabolism.

Incubation of a rabbit endometrial cell line (HRE-H9 cells) with KCl (5–60 mM) for 30 min enhanced IR-GnRH secretion, with 30 and 60 mM producing the greatest stimulatory effect ( 280±19% and 298±49% of control group, respectively). By adding 30 mM KCl into HRE-H9 culture and increasing the incubation time to 90 min, there was a stepwise increase in IR-GnRH secretion. In the third experiment, treatment of HRE-H9 cells with estradiol (E2, 10−9–10−8M) for 48 h stimulated IR-GnRH secretion ( 215±17% , 168±19% , respectively), whereas P4 treatment did not produce any significant change. Treatment with E 2 + P 4 at all doses tested (10−10–10−6M) augmented the secretion of IR-GnRH ( 140 ± 16% , 153 ± 14% , 276 ± 23% , 259 ± 26% , 198 ± 16% , respectively). Increased IR-GnRH secretion by E2 (10−9M) and E 2 + P 4 (10−8–10−7M) resulted in a reduction in cell content of IR-GnRH ( p ). In conclusion, secretion of IR-GnRH by HRE-H9 cells can be induced by KCl depolarization. Treatment of HRE-H9 cells with E2 and E 2 + P 4 enhanced their secretion of IR-GnRH. Under such conditions, secreted IR-GnRH appears to be derived primarily from intracellular IR-GnRH pools.

We have shown by receptor-binding analyses that the beta-2 adrenergic receptor is present on rat ROS 17/2.8 osteoblast-like cells. This was confirmed by PCR amplification of cDNA copied from the mRNA. The beta-1 adrenoreceptor subtype was absent and its mRNA was not detectable, even at the level of sensitivity afforded by PCR analysis. The beta-adrenergic receptors present on ROS 17/2.8 cells were functional as measured by ligand-induced enhancement of cAMP production. We investigated whether adrenergic agonists could mimic the action of PTH to stimulate bone resorption in neonatal mouse calvariae in organ culture. PTH induced a large increase in cAMP while norepinephrine and isoproterenol induced a small but significant increase. In the presence of a phosphodiesterase inhibitor and an antioxidant, norepinephrine consistently stimulated bone resorption. In order to determine whether functional beta-adrenergic receptors were unique to ROS 17/2.8 cells, human SaOS-2 osteoblast-like cells were also examined for enhancement of cAMP production by norepinephrine, and essentially the same results were obtained. Thus, adrenergic agonists efficiently activate beta-receptors on two osteoblast-like cells and can stimulate bone resorption in intact mouse calvariae.

Two zones of intergradation between populations of Plethodon have been studied for 18 and 20 years, respectively. The data consist of systematic scores of colors, made at least twice annually. Near Heintooga Overlook in the Balsam Mountains (Great Smoky Mountains National Park), the salamanders' cheeks are gray. Proceeding north toward the Smokies, there is increasing frequency and intensity of red color at two, four, and six miles. There has been no change in the scores at any location. The width of the zone and our failure to detect any change can be explained by assuming neutrality of the character and random diffusion during the probable time since contact between the two intergrading forms, which most likely took place after the Hypsithermal Interval, 8,000-5,000 BP. At Coweeta Hydrologic Laboratory in the Nantahala Mountains, Plethodon jordani and P. glutinosus hybridize at intermediate elevations. The lateral white spots of glutinosus decrease and the red on the legs of jordani increases with elevation from 685 m to 1,052 m. At the higher elevation, the proportion of animals scored as "pure" jordani declined significantly from 1974 to 1990, an indication that the hybrid zone is spreading upward. The rate of spread is too great to be explained by random diffusion, so selection for glutinosus characters is the best explanation. The rate of spread of the hybrid zone indicates that hybridization began 60-65 years ago, at the end of the time of intense timbering. Such human disturbances have caused hybridization in other organisms.

Serum progesterone (P4) concentrations were quantitated in 18 Holstein heifers from days 5 to 16 after estrus in an effort to ascertain the effects of pregnancy on circulating levels of this hormone. The P4 concentration rose faster between days 5 and 10 in the pregnant heifers compared to P4 levels in both the non-pregnant heifers and the killed sperm inseminated group. It was found that serum P4 levels were significantly (P The administration of 250μg gonadotropin releasing hormone (GnRH) to 10 Holstein heifers on day 7 after estrus resulted in a significant (P

Extracellular sporozoites of Eimeria tenella were incubated at either 25 or 40 C in the presence of 14 C-lasalocid or 14 C-narasin, both anticoccidial ionophores. Liquid scintillation analysis shows that both ionophores are accumulated by the sporozoites outside their host cell. The relative degree of retention was significantly different for the two incubation temperatures and the concentration of lasalocid retained was consistently greater than that of narasin.

We examined how prey size-distributions influence size-specific foraing rate and food gain, i.e., food intake scaled to metabolic demands, in Jefferson's and small-mouth salamander larvae. Ambystoma jeffersonianum larvae sampled on 17 dates from a farm pond whose fauna was dominated by macrozooplankton and chironomid larvae were rarely gape-limited, and total volume of food in the stomach (VS) showed only a slight tendency to increase with larval size. Although 15 of 17 correlation coefficients of VS with larval size were positive, only 1 of 17 correlations were statistically significant, and body size explained only 8% of the overall variation in VS. Correlation coefficients of food gain and body size were positive in 9 cases and negative in 8, but only 3 were statistically significant.In contrast, Ambystoma texanum larvae in 42 samples taken from five sites dominated by macrozooplankton as well as relatively large isopods and amphipods were almost always gape-limited, and VS tended to increase markedly with larval size. 40 of 42 correlation coefficients of VS and larval size were positive, and 19 correlations were statistically significant. Body size in turn explained about 35% of the overall variation in VS. Correlation coefficients of food gain and larval size were positive in 32 of 42 samples, and 9 of 10 significant correlations were positive.When food is limiting and prey selection is not limited by gape, smaller larvae may grow as fast or in some cases faster than larger larvae because they are nearly as effective foragers, but have lower metabolic demands. Larger larvae may in turn grow faster than smaller larvae in environments which support a broad size spectrum of prey, particularly when gape limitations are highly disproportionate among size classes. The growth rate of larvae in one size class relative to another depends primarily on the extent to which increased foraging rate compensates for higher energy demands as body size increases. Size-specific foraging rate may in turn be strongly influenced by the prey size-distribution within a habitat. These relationships suggest that relative size is not always a good a priori predictor of exploitative competitive ability.

23 identical twin pairs, one with a hematologic malignancy, the other a bone marrow donor, completed the MMPI while in the hospital. The validity, clinical, and Repression-Sensitization scales were scored. Paired t tests for the entire group (aged 16 to 67 yr., M = 44 yr.) showed significant differences on Hs, D, and Hy. Males ( n = 12 pairs) had no significant differences, while females ( n = 11 pairs) had significant differences on Hs, D, Hy, Pa, and R-S. Female patients scored higher on Hs, D, Hy, lower on Pa and were repressors. These findings are congruent with previous research that has yielded psychological differences in people who develop malignancies and those who do not.

Eimeria tenella sporozoites were incubated in the presence of 3 different [14C]-labeled sugars; D-glucose, 2-deoxy-D-glucose and 3-O-methyl-D-glucose. The initial velocity, Vi, of uptake of D-glucose and 2-deoxy-D-glucose was similar, 41 micrograms/10(10) sporozoites/min and 46 micrograms/10(10) sporozoites/min, respectively; whereas that for 3-O-methyl-D-glucose was significantly lower, 17 micrograms/10(10) sporozoites/min. Initial velocity studies also revealed that glucose uptake was a saturable event, with an apparent KT of 20 mM and an apparent Vmax of 312 micrograms/10(10) sporozoites/min. Uptake was unaffected by exogenous sodium levels or the presence of ouabain. However, 0.1 mM phloretin significantly inhibited glucose uptake. Thus, it would appear that E. tenella sporozoites possess a Na-independent, phloretin-sensitive, carrier-mediated monosaccharide-transport system.

Extracellular Eimeria tenella sporozoites exposed to 1.0 ,ug/ml monensin at 40 C had an accelerated rate of sodium influx as well as an increased rubidium uptake that was inhibited by the cardiac glycoside, ouabain. These results suggested the presence of a functional (Na+-K+)-ATPase and its stimulation by monensin. Under the same conditions, sporozoite ATP concentrations declined, lactate production increased and the rate of amylopectin utilization was enhanced. Exposure to monensin also appeared to stimulate the rate of sporozoite glycolysis. The results of this study demonstrated that the cidal effect of monensin on extracellular sporozoites was caused by the capability of the ionophore to act as a transmembrane sodium carrier. The polyether, ionophorous antibiotic, mo- nensin, is an effective anticoccidial agent and has been used extensively for the control of coccid- iosis for more than a decade. Despite its wide use the precise anticoccidial mode of action of this drug is not understood. Smith and Strout (1979) provided evidence that the polyether ionophores are accumulated by free (extracellular) Eimeria tenella sporo- zoites. Later, Smith et al. (1981) demonstrated that this uptake may reduce the number of spo- rozoites capable of invading host cells and may deny the initiation of first generation schizogony for those that do penetrate. In this same study it was shown that monensin may also express a lethal activity against the extracellular sporo- zoite. More recently Long and Jeffers (1982) pre- sented evidence that the merozoites are subject to a similar fate. Thus it appears that the free, invasive stages of the coccidia are susceptible to an anticoccidial activity of monensin. These findings show the utility of a readily available model system, the free sporozoite, for the study of the specific anticoccidial mode of action of the ionophorous antibiotics. In the present study we examined the influence of monensin on sodium and rubidium (as a po