The Journal of Experimental Zoology Part A: Ecological and Integrative Physiology

doi: 10.1002/jez.1402600101pmid: N/A

Reilly, Stephen M.; Lauder, George V.

doi: 10.1002/jez.1402600102pmid: N/A

A quantitative analysis of the muscle activity patterns (motor patterns) used by tiger salamanders (Ambystoma tigrinum) during terrestrial feeding is presented to provide comparative data on motor output during prey transport in amphibians, compare prey transport motor patterns to those used during initial prey capture, and test the generality of previously proposed models of the feeding cycle in tetrapods.

Pynnönen, Kirsi

doi: 10.1002/jez.1402600103pmid: N/A

Previous studies have revealed that freshwater bivalves subjected to acid stress suffer from severe electrolyte imbalance. A typical initial reaction is a transitory increase in concentration of Ca in the hemolymph during the first few days of exposure to such stress. Although this calcium obviously originates from the CaCO3 reserves in the clam, a possible ambient origin has never been ruled out. In the present study the uptake of Ca was studied under both circumneutral and acid conditions: two freshwater unionids, Anodonta anatina and Unio tumidus, were exposed to a bathing medium that contained 45Ca for a period of 24 hrs. In order to study the effect of the ambient Ca concentration on the efficiency of uptake of Ca, two media with different Ca concentrations (35 and 3.5 mg Ca/1; 4 × 106 cpm 45Ca/1 and 4 × 105 cpm 45Ca/1, respectively) were used. The role of the ingested food as a source of Ca was evaluated by feeding the clams with algae labeled with 45Ca. After the clams had been exposed for 24 hrs to 45Ca, the accumulation of 45Ca in the soft parts, including hemolymph, calcium concretions and glochidial larvae, was measured. Low pH (4–4.5) significantly decreased the uptake of 45Ca from the medium, whereas the addition of aluminum (900 μg/1) had only a minor effect on the uptake of 45Ca. The sites of accumulation of 45Ca under acidified conditions did not change: in all cases highest values for 45Ca concentration were measured in the gills, where the calcium concretions sequestered a large part of the 45Ca. A 90% decrease in the ambient Ca concentration caused a similar decrease in the uptake of 45Ca. Clams were able to utilize both dietary and waterborne Ca.

Paajaste, Marita; Nikinmaa, Mikko

doi: 10.1002/jez.1402600104pmid: 1791421

We studied the effect of noradrenaline on the methaemoglobin (metHb) concentration in rainbow trout red cells. The erythrocytes were incubated in physiological medium with or without noradrenaline and the percentage of metHb of total Hb content was measured. Noradrenaline lowered the metHb content significantly as compared to controls. To study if the effect of noradrenaline was caused by adrenergic intracellular alkalinization, cells were treated with noradrenaline + carbonic anhydrase or noradrenaline + acetazolamide. Carbonic anhydrase inhibits the adrenergic increase in intracellular pH, but did not reduce the effect of noradrenaline on the metHb concentration. Acetazolamide accentuates the increase in intracellular pH. However, there was no difference in the methaemoglobin content of noradrenaline‐incubated and noradrenaline + acetazolamide‐incubated cells. These results show that the effect of noradrenaline on the methaemoglobin content is independent from the adrenergic increase in intracellular pH. However, amil‐oride treatment inhibited the effect of noradrenaline on the methaemoglobin content, suggesting that the protein mediating sodium/proton exchange may also be involved in controlling cellular methaemoglobin levels.

Mangum, Charlotte

doi: 10.1002/jez.1402600105pmid: N/A

The Berkner and Marshall hypothesis suggests that the atmosphere was virtually anoxic until the late Precambrian, and that the abrupt and coincidental appearance in the fossil record of the major animal phyla reflects the rise of PO2 to a level that supported animal life. In a more recent version the rise of PO2 is supposed to permit previously soft‐bodied animals, which had arisen during the anoxic period, to form fossilizable hard parts. The animal kingdom is conceived as fundamentally and primitively anaerobic and only secondarily aerobic. These ideas were incorporated into the Thiobiotic Theory, which supposes that a meiofauna endemic to the anoxic sulfide layer in marine sediments is a relict community of the pre‐normoxic Precambrian. This fauna consists of a number of simple metazoan phyla, including free‐living platyhelminths (but not cnidarians) which this theory regards as representatives of the ancestral Eumetazoa.

Hsu, Sheau‐Yu; Goetz, Frederick William

doi: 10.1002/jez.1402600106pmid: N/A

The in vitro effects of sodium orthovanadate (Na3VO4), a G‐protein activator, on ovulation and prostaglandin (PG) synthesis were investigated in the brook trout (Salvelinus fontinalis) ovary. PGE and PGF levels in incubation medium of either extrafollicular (EF) tissue or follicles were measured by specific radioimmunoassays (RIA). PGE levels in follicle incubates were increased by Na3VO4 at both pre‐germinal vesicle breakdown (preGVBD) and preovulatory (preOV) stages. However, an increase of PGF levels in follicle incubates was observed only in preGVBD follicles in the presence of Na3VO4. The preOV follicles spontaneously released more PGF than preGVBD follicles and the level was not affected by Na3VO4 treatment. In contrast, in incubates of EF tissue, Na3VO4 induced dosage‐dependent increases in PGE and PGF at either stage. The Na3VO4‐stimulated increase of PGE in preOV follicle incubates was significantly reduced by the translational inhibitor, cycloheximide (5 μM), but not by the transcriptional inhibitor, actinomycin (5 μM). PGF levels in preOV follicle incubates were also significantly reduced by cycloheximide and actinomycin in controls, but not in the presence of 0.1 mM Na3VO4. The results suggest that protein synthesis was required for Na3VO4 to increase accumulation of PGE, and in maintaining control PGF levels in preOV follicles. In addition, since PGF levels in preOV follicles were not reduced by either inhibitor in the presence of Na3VO4, a Na3VO4‐stimulated increase of PGF levels was unmasked that apparently acts through a non‐translational pathway. In vitro ovulation was also significantly increased by 0.1 mM Na3VO4. However, the Na3VO4‐induced ovulation was not inhibited by either actinomycin or cycloheximide. The data imply that the mechanism(s) by which Na3VO4 induces ovulation are distinct from that for stimulating PG accumulation. When preOV follicles were incubated with 10 μM forskolin, no stimulatory effect on ovulation, or on PGE and PGF levels was observed. The data strongly indicate that the effects of Na3VO4 on ovulation and ovarian PG levels were not mediated by an increase in cAMP.

Morales, Magda H.; Osuna, Roberto; Sánchez, Eric

doi: 10.1002/jez.1402600107pmid: 1791422

Vitellogenin (VTG) synthesis has been described as an ideal system to study the hormonal regulation of gene expression. In Xenopus the molecular aspects of this control have been analyzed; however, in other non‐mammalian species such as reptiles, very few studies approaching this level have been undertaken. We report on the induction by estradiol‐17β of VTG‐like proteins in liver explants from adult males and immature male and female lizards (A. pulchellus). A concentration of 10−7 M was optimum for adult males while a higher concentration (10−6 M) is required for the immature animals. No differences were observed in the hormonal induction in male and female immature animals, suggesting that there are no sexual distinctions in the liver at this stage.

Licht, Paul; Denver, Robert J.; Pavgi, Sushama; Herrera, Brenda

doi: 10.1002/jez.1402600108pmid: N/A

The relation between seasonal changes in plasma thyroxine (T4) and T4 binding activity was studied in three species of turtle previously shown to differ in the nature of their binding proteins; additional direct measurements of a high affinity T4 binding protein (TBP) were made in one species using RIA. In the painted turtle, Chrysemys picta (Family Emydidae), a species with large seasonal changes in plasma T4, the binding protein measured by activity and RIA showed significant seasonality. Binding activity correlated with direct estimates of TBP by RIA. TBP was minimal upon emergence from hibernation and maximal in late summer (July–August), about a month after the peak in plasma T4. In contrast, two other nonemydid species, the green turtle (Chelonia mydas) and Mexican tortoise (Gopherus flavomarginatus) showed relatively low plasma T4 and binding activity with no significant seasonality in either. Electrophoretic studies (PAGE) confirmed that T4 binding in C. picta is almost wholly associated with a high affinity, low capacity TBP; whereas, it is confined to high capacity sites (probably albumin) in the other species. The transport of T4 is clearly handled differently in these three turtles. In the green turtle and tortoise, one would expect relatively constant free T4 (fT4) throughout the year. Marked seasonal fluctuations (an order of magnitude) in the ratios of TBP to total T4 in C. picta due to the temporal lag between the two may cause profound changes in fT4 with peaks in late spring.

Kwon, Hyuk B.; Choi, Han H.; Ahn, Ryun S.; Yoon, Yong D.

doi: 10.1002/jez.1402600109pmid: N/A

Rana ovarian follicles at different developmental stages were obtained from frogs collected at different seasons. Isolated follicles were sorted into five different classes (Class I–V) by size and cytoplasmic pigmentation. They were incubated for 6 hours in amphibian Ringer in the presence or absence of frog pituitary homogenate (FPH, 0.05 pituitary/ml) and changes in steroid production by follicles were assessed by measuring estradiol (E2), testosterone (T), and progesterone (P4) in media and follicles by radioimmunoassay. Small follicles (size range 0.22–0.7 mm) secreted very low or non‐detectable levels of the three steroids in the presence or absence of FPH. Medium‐sized vitellogenic follicles (0.70–1.11 mm) actively secreted all the three types of steroids tested (E2, P4, and T). Larger follicles (1.15–1.58 mm), isolated during September–February, secreted much more T than E2 and P4. In contrast, fully grown follicles (> 1.50 mm) collected late in the hibernation period secreted more P4 and less T than the large follicles and very low levels of E2; however, follicles (Class V) collected in breeding season (May) secreted solely P4 and negligible amounts of T and E2. All types of follicles produced very low levels of the steroids without FPH stimulation. Intrafollicular levels of steroids essentially reflected those which accumulated in the medium. Oocyte responsiveness to exogenous hormone, as evidenced by germinal vesicle breakdown (GVBD), increased as the breeding season approached. The data indicate that only the medium‐sized follicles produced considerable amounts of E2 while larger follicles produced mainly T and full‐grown follicles collected during breeding season produced only P4.

Chan, W. Y.; Lee, K. K. H.; Tam, P. P. L.

doi: 10.1002/jez.1402600110pmid: 1791423

The ability of mouse forelimb buds at stage 1 (Wanek et al., '89a) of development to regenerate after amputation was investigated. The findings were as follows: 1. Outgrowths in the form of hillocks were found at the sites of amputation in 116 (95%) out of 122 embryos examined 24 hours after amputation. Examination of the amputated region after various intervals of time revealed that the outgrowths were established from flank tissues at the anterior and posterior borders of the wound. 2. Ectodermal thickening was found on the distal margin of the outgrowths in 21 (66%) out of 32 specimens examined. These thickenings were histologically similar to the apical ectodermal ridge (AER) present on the control limb buds. 3. Alkaline phosphatase activity was detected on the ectodermal thickening in 11 (79%) out of 14 experimental limb buds examined. The pattern of expression of alkaline phosphatase activity was similar to that observed in control limb buds. 4. There was no correlation between the size of the outgrowths and the presence of the ectodermal thickening or the enzymatic activity. The outgrowths developed despite the absence of ectodermal thickening and enzymatic activity, suggesting that the thickening and the presence of alkaline phosphatase are not crucial for the initiation and formation of the outgrowths. 5. Explants of the outgrowths, when grafted beneath adult kidney capsules, differentiated extensively into various tissues, which included bones, epiphyseal plates, skeletal muscles, and skin derivatives. Control explants also gave rise to the same spectrum of tissues. Hence, the flank tissues surrounding the site of amputation in E10 mouse embryos can regenerate to form a structure that is morphologically and histochemically similar to a limb bud and the mesenchyme within the structure is histogenetically competent to produce the variety of tissues that is normally found in the adult limb.