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PubMed2004

Variation of total mercury concentrations in pig frogs (Rana grylio) across the Florida Everglades, USA.

The Pig Frog (Rana grylio) is an aquatic frog that is an abundant component of the Everglades ecosystem. South Floridians recreationally and commercially hunt pig frogs in marshes throughout Water Conservation Areas (WCA) and Big Cypress National Preserve (BCNP) in South Florida. Most of these areas are under fish consumption advisories because of high levels of methylmercury present in game fish tissues. It is important to understand how mercury is distributed throughout Pig Frog populations because their consumption from certain areas may present a risk to human health. We sampled 88 pig frogs along a north-south transect through the Florida Everglades. There were substantial differences in total mercury (THg) concentrations from leg muscle tissue among sites. Total mercury in frog leg tissue was highest from areas protected from harvest in Everglades National Park (ENP), with a maximum concentration of 2051 ng/g wet mass. The THg levels in R. grylio leg tissue from most harvested areas are below Federal advisory limits. However, many pig frogs collected near Frog City, and one from WCA 3B and 3AN, harvested sites, had THg levels above the USEPA 0.3 mg/kg Fish Tissue Residue Criterion. Spatial patterns in the mercury found among pig frogs were similar to those of other wildlife species from the Everglades. We found frogs to have high THg levels in areas where alligators and mosquito fish also have high THg. THg in ENP frogs had an exponential relationship to SVL, we found no other relationship in frogs from other sites. Our data suggests that pig frogs should not be harvested or consumed from sites that exceed federal limits.

Animals↗
PubMed1998

Changes in ovarian follicular kinetics in intact blinded and parietal shielded frogs exposed to different spectra of light.

Ovarian follicular kinetics and gravimetric changes in the ovary and oviduct were studied in intact, blinded (BL), and parietal shielded (PS) skipper frog Rana cyanophlyctis exposed to different light spectra. The gonadosomatic index (GSI) increased (P < 0.01) in intact and PS frogs, held in green, yellow, and red light. The maximum increase was in red light followed by yellow and green. The GSI of BL frogs also increased (P < 0.001) in white, green, yellow, and red light. However, the GSI of blinded and parietal shielded (BLPS) frogs increased (P < 0.001) in white and all the colored lights compared with controls. The percentage changes of oviductal weights were similar to the ovarian weights. Data on follicular kinetics revealed a decrease in previtellogenic oocytes in intact and PS frogs placed in blue, green, yellow, and red lights. The previtellogenic oocytes of BL and BLPS frogs decreased in white light, while their number did not vary significantly in other spectra. The vitellogenic oocytes of intact and PS frogs increased in all the spectra, with a maximum increase in red. The vitellogenic oocyte count increased in both BL and BLPS frogs held in white light. The green, yellow, and red spectra stimulated vitellogenic oocyte count of BL frogs. The response of BPLS frogs was similar except for a slightly decreased oocyte count in red light. The pattern of vitellogenic oocyte counts in general exhibited a negative correlation with previtellogenic oocyte counts in all the frogs. The atretic follicular numbers did vary significantly in all of the groups. Red light stimulated ovarian activity maximally, followed by yellow and green. As the ovary exhibited varied response to the different spectra of light even in BL frogs, it may be concluded that extraretinal perception of colored light occurs in this species.

Animals↗
PubMed2001

Aerodynamic stability and maneuverability of the gliding frog Polypedates dennysi.

Gliding has evolved independently in two families of tree frog. Tree frogs glide to descend rapidly to mating sites over temporary pools on the forest floor or to escape predators. The physical mechanisms used by frogs to glide and maneuver were investigated using a combination of observations of live frogs (Polypedates dennysi) gliding in a tilted wind-tunnel and aerodynamic forces and torques measured from physical models of tree frogs in a wind-tunnel. Tree frogs maneuvered in the tilted wind-tunnel using two different turning mechanisms: a banked turn (the frog rolls into the turn) and a crabbed turn (the frog yaws into the turn). Polypedates dennysi possessed overall weak aerodynamic stability: slightly stable about the pitch and roll axis, slightly unstable about the yaw axis. The maneuverability of gliding tree frogs was quantified using a maneuverability index. The maneuverability of tree frogs was roughly equivalent for tree frogs performing a banked turn and performing a crabbed turn. The maneuverability of tree frogs was approximately one-third of the maneuverability of a falcon (Falcon jugger).

Animals↗
PubMed1990

Immune responses of intact and embryonically enucleated frogs to self-lens antigens.

Embryonically enucleated frogs (Xenopus) will tolerate an isogeneic eye implanted during adult life although their immune system has never been previously exposed to eye-specific Ag. We hypothesized that such self-implants survive because they induce tolerance to the eye-specific Ag. We have developed evidence to support this hypothesis by studying the responses of embryonically enucleated or intact frogs, with or without eye implants, to self-lens proteins. After immunization with a low concentration of bovine lens proteins, spleen cells from all intact and all embryonically enucleated frogs displayed significant in vitro proliferation against the Ag. All animals in both groups of frogs also produced high titered xenoantibodies. After immunization with a comparable preparation and concentration of self-lens Ag, splenocytes from only some of the embryonically enucleated and intact frogs showed significant proliferation, and fewer of these frogs produced antibody. When the immunization protocol and Ag concentration were modified to evoke consistent anti-self-lens proliferative and antibody responses from enucleated frogs, intact frogs responded equally well. Because there were no significant differences in the magnitude of the responses, and the percent of enucleated and intact frogs responding did not differ, we conclude that there is little or no immunologic tolerance to self-lens Ag in intact frogs. When either embryonically enucleated or intact frogs were heterotopically implanted with isogeneic eyes and then immunized with self-lens Ag or foreign lens Ag using the optimal immunization protocol, the Ag-specific proliferative responses of their lymphocytes were significantly reduced after immunization with self-, but not foreign Ag. This argues that embryonically enucleated frogs can become tolerant of the organ-specific Ag of the lens, even in adult life.

Animals↗
PubMed1994

Characterization of gamma-glutamyltranspeptidase in the liver of the frog: 2. Response to season, temperature and thyroid hormone in Rana pipiens.

The impact of season and temperature on frog liver gamma-glutamyltranspeptidase was assessed by measuring the activity of this enzyme in plasma membranes isolated from the livers of Rana pipiens obtained as summer and winter frogs; subjected to short-term (3 weeks) temperature acclimation; and subjected to multiple-temperature shifts. Plasma levels of T3 were determined. gamma-Glutamyltranspeptidase was found to be 2.2-fold higher in the summer frog relative to the winter frog; decreased by 44 percent in the summer frog by cold acclimation and increased by 1.7-fold in the winter frog by warm acclimation; and increased by 1.9-fold in the summer frog and 2.8-fold in the winter frog subjected to multiple-temperature shifts. Plasma T3 levels were found to be 42-fold higher in the summer frog relative to the winter frog; decreased by 42 percent by cold acclimation and increased by 2.9-fold by warm acclimation; and decreased by 39 percent and 38 percent in the summer and winter frogs subjected to multiple temperature shifts. T3 replacement during the last phase of the multiple-temperature shift protocol, restored the plasma T3 levels to 75 percent of the control levels and prevented the increase evoked by the multiple-temperature shifts in gamma-glutamyltranspeptidase activity. Indeed, enzyme activity in the T3 replaced state was 19 percent lower than in the control state. The involvement of thyroid hormone as a negative regulator of enzyme activity is discussed.

Animals↗
PubMed2000

Molecular phylogenetic relationships of pond frogs distributed in the Palearctic region inferred from DNA sequences of mitochondrial 12S ribosomal RNA and cytochrome b genes.

The evolutionary relationships of pond frogs distributed in the Far East and Europe were investigated by analyses of nucleotide sequences of mitochondrial 12S ribosomal RNA (12S rRNA) and cytochrome b (cyt b) genes. The nucleotide sequences of a 412-bp segment of the 12S rRNA gene and a 534-bp segment of the cyt b gene were determined by the PCR-direct sequencing method using 19 frogs belonging to six species and one subspecies distributed in the Palearctic region. Phylogenetic trees were constructed by the neighbor-joining and maximum-likelihood methods using Rana catesbeiana or Xenopus laevis as an outgroup. The 412-bp segment of the 12S rRNA gene contained 65 variable sites including gap sites, and the 534-bp segment of the cyt b gene contained 160 variable sites. The nucleotide sequence divergences of the 12S rRNA gene were 0.25-4.83% within the Far Eastern frogs, 0.25-6.22% within the European frogs, and 8.74-11.24% between the Far Eastern and the European frogs, whereas those of the cyt b gene were 3.64-14.73% within the Far Eastern frogs, 0.38-14.42% within the European frogs, and 16.53-23.58% between the Far Eastern and the European frogs. Although most nucleotide substitutions were at the third codon position of the cyt b gene and were silent mutations, 4 amino acid replacements occurred within the Far Eastern frogs, 4 within the European frogs, and 11 between the Far Eastern and the European frogs. The phylogenetic trees constructed from the nucleotide sequence divergences showed slightly different topologies for the 12S rRNA and cyt b genes. R. esculenta from Ukraine was closely related to R. lessonae from Luxembourg in both the 12S rRNA and the cyt b gene sequences.

Animals↗
PubMed2001

Determination of age, longevity and age at reproduction of the frog Microhyla ornata by skeletochronology.

Skeletochronological estimation of age, longevity, age at sexual maturity and breeding of Microhyla ornata was done. Frogs (n=62) were collected locally in August (rainy season) 1997 and brought to the laboratory. Body mass and snout-vent-length (SVL) of each frog was recorded; the 4th toe of both the hind limbs was clipped under anaesthesia, fixed in 10% formalin, demineralized in 5% nitric acid and processed for histology. Limb bones (femur, humerus, tibiofibula and radioulna) of 6 large sized frogs were also processed for skeletochronology in order to study the rate of resorption. Gonads of 25 frogs (belonging to different body size ranges) were processed for histology in order to ascertain the gametogenic status of individual frogs. One to four growth rings consisting of growth zones and lines of arrested growth (LAGs) were noticed in frogs of different body sizes; the number of LAGs remained identical in all the limb bones and phalanges in 5 out of 6 frogs. Back calculation indicated that the resorption rate is very low in this frog. Male frogs possessed sperm bundles in seminiferous tubules in the 1st year, while females showed yolky follicles in the ovary in the 2nd year. Frogs found in amplexus were 3 5 years old. The results suggest that this frog may live for a maximum of 5 years in the natural population.

Age Determination by Skeleton↗
PubMed2004

IgE antibodies of fish allergic patients cross-react with frog parvalbumin.

BACKGROUND: The major allergens in fish are parvalbumins. Important immunoglobulin (Ig)E cross-recognition of parvalbumins from different fish species has been shown. Recently frog parvalbumin alpha has been found to be responsible for a case of IgE-mediated anaphylaxis triggered by the ingestion of frog meat. The aim of this study was to investigate whether IgE antibodies of fish allergic persons cross-react with frog parvalbumin and to appreciate its clinical relevance. METHODS: The sera of 15 fish allergic patients and one fish and frog allergic patient were tested by IgE-immunoblotting against frog muscle extract. Sera were tested against recombinant parvalbumin alpha and beta from Rana esculenta. Skin prick tests were performed in selected patients with recombinant frog parvalbumin. Ca(2+) depletion experiments and inhibition studies with purified cod and frog recombinant parvalbumin were done to characterize the cross-reactive pattern. RESULTS: Fourteen of the sera tested had IgE antibodies recognizing low molecular weight components in frog muscle extract. Calcium depletion experiments or inhibition of patient sera with purified cod parvalbumin led to a significant or complete decrease in IgE binding. When tested against recombinant parvalbumins, three of 13 sera reacted with alpha parvalbumin and 11 of 12 reacted with beta parvalbumin from R. esculenta. Skin prick tests performed with recombinant frog parvalbumin were positive in fish allergic patients. Inhibition studies showed that a fish and frog allergic patient was primarily sensitized to fish parvalbumin. CONCLUSION: Cod parvalbumin, a major cross-reactive allergen among different fish species, shares IgE binding epitopes with frog parvalbumin. This in vitro cross-reactivity seems to be also clinically relevant. Parvalbumins probably represent a new family of cross-reactive allergens.

Animals↗
PubMed1991

Effect of cooling rate on the survival of frozen wood frogs, Rana sylvatica.

Wood frogs (Rana sylvatica) were frozen to -2.5 degrees C under five distinct cooling regimes to investigate the effect of cooling rate on survival. Frogs survived freezing when cooled at -0.16 degrees C.h-1 or -0.18 degrees C.h-1, but mortality resulted at higher rates (-0.30 degrees C.h-1, -1.03 degrees C.h-1, and -1.17 degrees C.h-1). Surviving frogs in the latter groups required longer periods to recover, and transient injury to the neuromuscular system was evident. Some of the frogs that died had patches of discolored, apparently necrotic skin; vascular damage, as indicated by hematoma, also occurred. It is concluded that slow cooling may be critical to the freeze tolerance of wood frogs. Additional studies examined the effect of cooling rate on physiological responses promoting freeze tolerance. Mean glucose concentrations measured in plasma (15-16 mumol.ml-1) and liver (42-45 mumol.g-1) following a 2-h thaw did not differ between slowly- and rapidly-cooled frogs but in both groups were elevated relative to unfrozen controls. Thus, freezing injury to rapidly-cooled frogs apparently was not mitigated by the presence of elevated glucose. Water contents of liver tissue, measured 2 h post-thawing, did not differ between slowly-cooled (mean = 77.6%) and rapidly-cooled (mean = 78.5%) frogs. However, the mean hematocrit of slowly-cooled frogs (48%) was significantly higher than that (37%) of frogs cooled rapidly, possibly owing to differences in the dynamics of tissue water during freezing.

Animals↗
PubMed1993

6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from frog skeletal muscle: purification, kinetics and immunological properties.

Fructose 2,6-bisphosphate is the most potent activator of 6-phosphofructo-1-kinase, a key regulatory enzyme of glycolysis in animal tissues. This study was prompted by the finding that the content of fructose 2,6-bisphosphate in frog skeletal muscle was dramatically increased at the initiation of exercise and was closely correlated with the glycolytic flux during exercise. 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase, the enzyme system catalyzing the synthesis and degradation of fructose 2,6-bisphosphate, was purified from frog (Rana esculenta) skeletal muscle and its properties were compared with those of the rat muscle type enzyme expressed in Escherichia coli using recombinant DNA techniques. 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from frog muscle was purified 5600-fold. 6-Phosphofructo-2-kinase and fructose-2,6-bisphosphatase activities could not be separated, indicating that the frog muscle enzyme is bifunctional. The enzyme preparation from frog muscle showed two bands on sodium dodecylsulphate polyacrylamide gel electrophoresis. The minor band had a relative molecular mass of 55,800 and was identified as a liver (L-type) isoenzyme. It was recognized by an antiserum raised against a specific amino-terminal amino acid sequence of the L-type isoenzyme and was phosphorylated by the cyclic AMP-dependent protein kinase. The major band in the preparations from frog muscle (relative molecular mass = 53,900) was slightly larger than the recombinant rat muscle (M-type) isoenzyme (relative molecular mass = 53,300). The pH profiles of the frog muscle enzyme were similar to those of the rat M-type isoenzyme, 6-phosphofructo-2-kinase activity was optimal at pH 9.3, whereas fructose-2,6-bisphosphatase activity was optimal at pH 5.5. However, the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase from frog muscle differed from other M-type isoenzymes in that, at physiological pH, the maximum activity of 6-phosphofructo-2-kinase exceeded that of fructose-2,6-bisphosphatase, the activity ratio being 1.7 (at pH 7.2) compared to 0.2 in the rat M-type isoenzyme. 6-Phosphofructo-2-kinase activity from the frog and rat muscle enzymes was strongly inhibited by citrate and by phosphoenolpyruvate whereas glycerol 3-phosphate had no effect. Fructose-2,6-bisphosphatase activity from frog muscle was very sensitive to the non-competitive inhibitor fructose 6-phosphate (inhibitor concentration causing 50% decrease in activity = 2 mumol.l-1).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2006

Persistent sex-reversal and oviducal agenesis in adult Xenopus (Silurana) tropicalis frogs following larval exposure to the environmental pollutant ethynylestradiol.

It is known that estrogen-like environmental pollutants can feminise gonadal differentiation in frogs resulting in female-biased sex-ratios at metamorphosis. The long-term effects on reproductive function in frogs following larval exposure to pollutants are less known. Amphibian test systems which allow life-cycle studies are therefore needed. The aim of the present study was to characterise long-term estrogenic effects on the reproductive system of the emerging model species Xenopus (Silurana) tropicalis following larval exposure to ethynylestradiol (EE(2)). EE(2) is a synthetic estrogen that has been detected in sewage effluents and in surface waters. Newly hatched tadpoles (Niewkoop Faber (NF) stage 48) were exposed to the nominal EE(2) concentrations 0 (control), 1, 10, and 100 nM (with analytical chemistry support) until complete metamorphosis (NF stage 66). Effects on the reproductive organs were determined in juveniles (1 month after metamorphosis) and in 9-month-old frogs. Larval exposure to EE(2) caused female-biased phenotypic sex-ratios in both juvenile and adult frogs, which is in agreement with previous work on other frog species. Nearly all (97%) of the 63 EE(2)-exposed 9-month-old frogs had ovaries. Histological evaluation of the gonads of the 9-month-old frogs showed that they were sexually mature. Among the adult frogs with ovaries there was a dose-dependent increase in the frequency of individuals lacking oviducts. Adult frogs exposed to 100 nM EE(2) that had ovaries but no oviducts had lower levels of estrogen receptor alpha (ERalpha) mRNA in the brain than control animals and those exposed to 100 nM EE(2) that had ovaries as well as oviducts. EE(2) exposure did not cause any significant changes in ERalpha mRNA levels in the ovaries of the adult frogs. The reduced level of ERalpha mRNA in the brain of individuals with ovaries lacking oviducts suggests an organizing effect of EE(2) on the central nervous system. The results show that transient early life-stage exposure to an environmental pollutant can induce effects on the reproductive organs and the central nervous system that persist into adulthood. Overall, our data suggest that X. tropicalis, which has a shorter generation time than the well-established model species Xenopus laevis, is a suitable model organism for research on developmental reproductive toxicity in anuran species.

Animals↗
PubMed2001

Organochlorine insecticides, polychlorinated biphenyls, and metals in water, sediment, and green frogs from southwestern Michigan.

In an attempt to explain the etiology of frog deformities and population declines, many possible causative factors have been examined, including the input of synthetic chemicals into aquatic systems, where frogs spend much of their lives, including their entire developmental stages. Deformities in populations of green frogs in wetlands of southwestern Michigan that are influenced by agricultural, urban, or industrial inputs were assessed in this study. Of the 1445 green frogs (Rana clamitans) examined, only four (0.3%) exhibited morphological deformities. This deformity rate is less than the recognized background level of deformities for this species, which is approximately 1%. Concentrations of organochlorine insecticides, polychlorinated biphenyls (PCBs), and metals were determined in water, sediment, frog eggs, tadpoles, and adult green frog tissues. Concentrations of all individual organochlorine insecticides in tissue were less than 6 ng/g, wet wt. Concentrations of sigmaPCBs in tissue did not exceed 100 ng/g, wet wt. Concentrations of toxic metals were less than the limits of detection. Because no significant numbers of green frog deformities were observed in this region, it can be assumed that at these low concentrations, physical malformations in green frogs should not be observed. Significance of study. This study provides information on the incidence of deformities in green frog populations in southwestern Michigan and offers background data on chemical residues in green frogs and their environment.

Animals↗
PubMed1982

Large intestine bacterial flora of nonhibernating and hibernating leopard frogs (Rana pipiens).

The bacteria in the large intestines of 10 northern leopard frogs (Rana pipiens) were enumerated and partially characterized. Four nonhibernating frogs were collected in the summer, four hibernating frogs were collected in the winter, and two frogs just emerged from hibernation were collected in the spring. All frogs had about 10(10) bacteria per g (wet weight) of intestinal contents and about 10(9) bacteria per g (wet weight) of mucosal scraping, although the counts from the winter frogs were slightly less than those from the other two groups of frogs. Another group of 14 summer frogs, after treatment to induce hibernation, showed a drop in bacterial counts accompanied by a change in the composition of the flora. In most frogs, Bacteroides was the dominant organism. Other bacteria repeatedly isolated at high dilutions were strict anaerobes, including butyrigenic and acetogenic helically coiled bacteria; fusobacteria; and acetogenic, small, gram-positive bacilli. These data indicate that the intestinal flora of frogs is similar to that of mammals and birds and that this flora can be maintained at temperatures close to freezing.

Anaerobiosis↗
PubMed2005

Body wiping behaviors associated with cutaneous lipids in hylid tree frogs of Florida.

Body wiping behavior, integumentary secretions and rates of evaporative water loss (EWL) were examined in six species of Florida tree frogs (Anura: Hylidae). Additionally, morphology of the integument and dermal glands were compared among these and one other Florida tree frog (Hyla andersonii), an arid-adapted tree frog (Phyllomedusa hypochondrialis), and a highly aquatic frog (Rana utricularia). An extra-epidermal layer of lipid and mucus, presumably secreted from dermal granular glands, was detected on the skin of all Florida hylid frogs examined. Distinct body wiping behaviors were observed in the hylid frogs, but these were less complex than those described previously in phyllomedusine frogs, which occupy arid habitats, secrete lipids onto their skin, and are regarded as relatively 'waterproof'. Florida hylids occupy seasonally arid habitats and appear to have reduced rates of EWL. The suite of traits we observed in these frogs have been previously documented in a rhacophorid tree frog from seasonally arid regions of India and likely represent an evolutionary convergent response to periodic dehydration stress. The presence of lipids that are spread by simple wiping behaviors to form an extra-epidermal water barrier may represent an early stage of the more advanced adaptations described in more waterproof arboreal frogs.

Animals↗
PubMed2004

Observations on myiasis by the calliphorids, Bufolucilia silvarum and Bufolucilia elongata, in wood frogs, Rana sylvatica, from southeastern Wisconsin.

Larvae of certain species of blowflies (Calliphoridae) can cause myiasis in frogs and toads, but there are few reports from North American amphibians. Of these, most are from toads (bufonids). In this study, we observe primary myiasis in a population of juvenile wood frogs, Rana sylvatica, collected on 22-23 August 2003, from southeastern Wisconsin and compare our observations with previous studies on myiasis from toads. Two (5%) of 39 frogs were infected by the blow fly Bufolucilia silvarum, with an intensity of 28 and 31, whereas 1 (2.5%) of 39 frogs was infected by the blow fly Bufolucilia elongata with an intensity of 14. We found that (1) B. silvarum lay eggs on healthy wood frogs, (2) eggs hatch, with first-instar maggots penetrating under the skin, (3) maggots develop to mature third instars within 13-16 hr of egg hatching, (4) maggots kill the host within 7-47 hr of egg hatching, and (5) maggots consume the entire frog carcass reducing it to bones within 42-59 hr of egg hatching. Our observations on the time of death and how quickly carcasses of wood frogs were consumed by these maggots compared with previous studies on toads suggest that finding infected juvenile wood frogs may be uncommon. Therefore, myiasis by these flies on wood frogs and other small terrestrial anurans may be a phenomenon that is much more common than is currently observed. This is the first report of B. silvarum and B. elongata causing myiasis in wood frogs.

Animals↗
PubMed1999

The role of habitat in structuring Halipegus occidualis metapopulations in the green frog.

The transmission dynamics of the trematode Halipegus occidualis in its definitive host, Rana clamitans, have been examined over a 5-yr period in a North Carolina pond. The breeding season of green frogs coincides with the period of worm recruitment, during which time male frogs are territorial and females show strong site fidelity. This site fidelity allows inferences to be made regarding the suitability of a particular habitat for worm transmission based on frog infection intensities within that habitat. Four foci of infection were identified in the pond by plotting worm infrapopulation size against site of host capture. Sites within infection foci are characterized by shallow water and emergent vegetation, factors favorable for overlapping distributions of the 4 hosts in the life cycle of H. occidualis. Consistent year-to-year worm prevalences and intensities, despite fluctuations in frog population size, are thought to be the result of a relatively constant proportion of the frog population being present in infection foci each year. Removal of worms from heavily infected frogs in the fifth year resulted in further heavy worm recruitment by treated frogs suggesting that site selection can predispose a frog to heavy infection. Further, the sum of removed parasites and those recruited after parasite removal by treated frog hosts was higher than worm infrapopulations observed in previous years, indicating that worm density regulates parasite infrapopulation size in heavily infected frogs.

Animals↗
PubMed2002

Congener-specific analysis of polychlorinated dibenzo-p-dioxins, dibenzofurans, and coplanar polychlorinated biphenyls in frogs and their habitats, Kitakyushu, Japan.

The occurrence and fates of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (coplanar PCBs) were investigated in two species of frog, mountain brown frog (Rana ornativentris) and Japanese brown frog (Rana japonica), and in soil samples. This study was carried out as part of an investigation aimed at determining the cause of extra forelimbs in the mountain brown frog. Frogs, not including malformed ones, and soil samples were collected at three sites in Kitakyushu, Japan, including the site where the malformed frogs were found and two reference sites. All samples were analyzed for PCDDs/PCDFs and coplanar PCBs. Relatively high concentrations of PCDDs/PCDFs and coplanar PCBs were detected in the soils and frogs collected from all three sites. Comparisons of concentrations in frogs and soils indicated that bioaccumulation of PCDDs/PCDFs was much lower than that of coplanar PCBs and that 2,3,7,8-substituted PCDDs/PCDFs were more highly accumulated than non-2,3,7,8-substituted isomers. From comparison of concentrations between the sexes, it was found that concentrations of dioxins, except for PCDDs, were significantly higher in males than in females. In the present study, relatively high concentrations of dioxins in frogs were found and maternal transfer to the eggs was strongly suspected. However, no difference in dioxin concentrations in frogs between the study site and the reference sites was found, so the cause of the malformations was not dioxins and remains unknown.

Animals↗
PubMed1996

Strong expression of the calreticulin gene in the liver of Rana rugosa tadpoles, but not adult frogs.

In the present paper we report the purification of calreticulin (CLT) from livers of the frog, Rana rugosa, the cloning and sequencing of its cDNA, and the CLT gene expression. CLT with M(r) = 52 kDa, estimated by SDS-PAGE, was purified from frog livers. Using rat CLT cDNA as a probe, a 2.4-kilobase frog cDNA clone was isolated from a frog liver cDNA library. The cDNA encoded 419 amino acids including an 18-residue NH2-terminal signal sequence that was 76% homologous to the rat CLT sequence and was 84% homologous to the partial sequence of Xenopus laevis CLT (Treves et al. [1992] Biochem. J. 287:579-581). Phylogenetic relationships estimated from the amino acid sequence of CLTs showed no pronounced variation between the two frog species, R. rugosa and X. laevis. Northern blot analysis indicated that the CLT mRNA level was very high in the liver of tadpoles, but extremely low in adult frogs. Expression levels were also very high in the premature ovary, while moderate expression was observed in the testis and brain of adult frogs. However, there was little histological change in the liver of tadpoles during development. Furthermore, CLT was recognized by Western blot analysis of total proteins in the liver of adult frogs. Immunostaining showed that CLT was distributed in the cytoplasm of liver cells. These results suggest that the expression of the CLT gene is tissue-dependent in the frog, R. rugosa, and that CLT probably functions biochemically in liver cells even when its gene expression is low.

Animals↗