摘要:

AbstractThe temporal sequence of activity patterns and intensities (voltage per wingbeat) of electromyograms (EMGs) from 17 muscles in the shoulder and forelimb of the pigeon (Columba livia) were measured during five modes of flight (level flapping, takeoff, landing, vertical ascending, and near vertical descending flight). EMG signals were referenced to wing position using high‐speed movie film. Most muscles exhibited EMG activity during phases within a wingbeat cycle not expected a priori. All muscles exhibited some level of activity within each wingbeat cycle and during all modes of flight. Intensity of EMG activity varied significantly between different modes of flight. Most shifts in temporal patterns were minor with the exception of the humerotriceps. © 1992 Wiley‐Liss,

ISSN:0022-104X    

DOI:10.1002/jez.1402620402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractIn the tobacco hornworm,Manduca sexta, heat shock normally elicits synthesis of the classic heat‐shock proteins. A 1‐hr heat shock of 42°C and above can also increase the relative synthesis of certain 12–18 kD proteins in the epidermis. These 12–18 kD proteins were identified as cuticular proteins for several reasons. Like cuticular proteins, they appear only in the epidermis. They can be precipitated from epidermal homogenates with an antiserum to larval cuticle. The same conditions that increased labeled 12–18 kD proteins in the epidermis also increased labeled 12–18 kD proteins in the cuticle. Some of the epidermal increase may result from a partial inhibition of secretion to the cuticle during 46°C heat shock, causing abnormal accumulation in the epidermis. However, slight increases also occur at lower temperatures, which do not inhibit secretion detectably. Preliminary results also indicate that total quantities of at least one cuticular protein mRNA may increase during heat shock, either because of increased transcription or increased mRNA stability. © 1992 W

ISSN:0022-104X    

DOI:10.1002/jez.1402620403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe V̇o2(standard metabolic rate; cc · h−1) of pregnantSceloporus jarroviincreases to a maximum near term. Immediately following parturition, V̇o2decreases sharply. Approximately 93.6% of the V̇o2of late pregnantS. jarroviis due to litter and non‐reproductive female V̇o2. The difference between measures of the V̇o2of late pregnant lizards and late pregnant V̇o2estimated by summing litter and nonreproductive V̇o2(6.4%) represents the physiological cost of maintaining a litter. This estimate of the physiological cost of pregnancy inS. jarroviis similar to that reported for mammals; however, it is lower than other estimates of the cost of pregnancy in reptiles. Estimates of litter metabolism were obtained by measuring maximum embryo metabolism, using an in vitro technique and multiplying embryo V̇o2by litter size. These results suggest that others have overestimated the physiological cost of pregnancy in reptiles because maximum litter V̇o2has been underestimated. Others have suggested that viviparity is an expensive mode of reproduction because the physiological cost of supporting a litter is an important component of an individual's reproductive effort. Data presented here support the alternative hypotheses that the cost of supporting a litter is not high and constitutes a small fraction of the energy apportioned into reproduction. © 1992 W

ISSN:0022-104X    

DOI:10.1002/jez.1402620404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractGuanyl nucleotide binding‐proteins, or G‐proteins, are ubiquitous molecules that are involved in cellular signal transduction mechanisms. Because a role has been established for cAMP in meiosis and G‐proteins participate in cAMP‐generating systems by stimulating or inhibiting adenylate cyclase, the present study was conducted to examine the possible involvement of G‐proteins in the resumption of meiotic maturation. Cumulus cell‐free mouse oocytes (denuded oocytes) were maintained in meiotic arrest in a transient and dose‐dependent manner when microinjected with the nonhydrolyzable GTP analog, GTPγS. This effect was specific for GTPγS, because GppNHp, GTP, and ATPγS were without effect. Three compounds, known to interact with G‐proteins, were tested for their ability to modulate meiotic maturation: pertussis toxin, cholera toxin, and aluminum fluoride (AlF4−). Pertussis toxin had little effect on maturation in either cumulus cell‐enclosed oocytes or denuded oocytes when meiotic arrest was maintained with dibutyryl cAMP (dbcAMP) or hypoxanthine. Cholera toxin stimulated germinal vesicle breakdown (GVB) in cumulus cell‐enclosed oocytes during long‐term culture, but its action was inhibitory in denuded oocytes. AlF4−stimulated GVB in both cumulus cell‐enclosed oocytes and denuded oocytes when meiotic arrest was maintained with hypoxanthine but was much less effective in dbcAMP‐arrested oocytes. In addition, AlF4−abrogated the inhibitory action of cholera toxin in denuded oocytes and also that of follicle‐stimulating hormone (FSH) in cumulus cell‐enclosed oocytes. Cholera toxin or FSH alone each stimulated the synthesis of cAMP in oocyte‐cumulus cell complexes, whereas pertussis toxin or AlF4−alone were without effect. Both cholera toxin and AlF4−augmented the stimulatory action of FSH on cAMP. These data suggest the involvement of guanyl nucleotides and G‐proteins in the regulation of GVB, although different G‐proteins and mediators may be involved at the oocyte and cumulus cell levels. Cholera toxin most likely acts by ADP ribosylation of the α subunit of Gsand increased generation of cAMP, whereas AlF4−a

ISSN:0022-104X    

DOI:10.1002/jez.1402620405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractDevelopmental changes in the prostaglandin synthesising potential in vitro of follicles of the viviparous guppy during oocyte growth and gestation were investigated. Basal production of PGE and PGF was low in follicles during oocyte growth, maturation, and early gestation, increased in mid and late gestation, and declined at postparturition. A similar pattern was also observed in the production of these prostaglandins by follicles at different developmental stages in the presence of exogenous arachidonic acid. Extrafollicular (EF) ovarian tissue of the guppy synthesised large amounts of PGE and PGF spontaneously as well as from exogenous arachidonic acid. Late gestation follicles and EF tissue incorporated14C‐arachidonic acid into PGE2α, PGF2α, 6‐keto‐PGF1α, and monohydroxyeicosatetraenoic acids. The ability of mid and late gestation stage follicles to synthesise large amounts of prostaglandins suggests that it may be related to ovulation and parturition. Extrafollicular tissue may also play a role in the induction of ovulation and parturition. Dibutyryl cAMP inhibited prostaglandin production by late gestation follicles and EF tissue in a dose‐dependent manner. Although the physiological significance of the effect of cAMP is not known, it is possible that high levels of cAMP during oocyte maturation may inhibit ovulation of mature oocytes by inhibiting prostaglandin synthesis. Cortisol (25 and 250 ng/ml) inhibited PGE and PGF production by late gestation follicles. Both the doses of cortisol tested also inhibited PGE production by EF tissue. However, only the higher dose was effective in inhibiting PGF production by EF tissue. Ovarian steroids such as estradiol‐17β, testosterone, 17α,20β‐P, and progesterone (5 and 50 ng/ml) had no effect on PGE and PGF production by late gestation follicles and EF tissue. Our earlier studies on serum steroid profile in the guppy have shown that cortisol levels decline at periparturition. It is possible that this decline may remove the block on prostaglandin synthesis, leading to increased synthesis of prostaglandins, which are presumably involved in the induction of ovulation and parturition. © 19

ISSN:0022-104X    

DOI:10.1002/jez.1402620406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTo determine the effects of 17β‐estradiol (E2) on the properties of the plasma proteins that bind L‐thyroxine (T4), immature rainbow trout,Oncorhynchus mykiss, were injected intraperitoneally on days 0 and 3 with 0.5 mg E2‐3‐benzoate/100 g body weight, and plasma was sampled on days 4, 7, or 12. Control trout received peanut oil alone. E2caused a small but significant decrease in the free T4index. Saturation analysis on miniature G‐25 Sephadex columns revealed at least two major T4‐binding sites. Filtration on agarose Bio‐gel A 1.5 also indicated two major T4‐binding protein fractions with molecular weights of 150 and 55 kDa with a small proportion of T4binding to a 1,500‐kDa site presumed to be lipoprotein. Addition of unlabeled T4displaced [125I]T4from the 55‐kDa site and unmasked an adjacent site of higher molecular weight. E2increased the proportion of T4 bound to the low‐affinity (150 kDa) site relative to that bound to the high‐affinity (55 KDa site, increased the level of protein associated with the 1,500‐kDa site and its T4binding, and also initiated the production of presumed vitellogenin (VTG), which bound a small amount of T4. It is concluded that the E2‐induced depression in FT4is caused by a shift in T4binding between high‐affinity and low‐affinity sites, and also by binding of small amounts of T4to presumed lipoprotein

ISSN:0022-104X    

DOI:10.1002/jez.1402620407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTo examine the changes in secretion of growth hormone (GH) and prolactin (PRL) with reference to their osmoregulatory roles, changes in pituitary mRNA levels and plasma concentrations of these hormones were examined during seawater adaptation in silvery juveniles (smolts) and precociously mature males (dark parr) of amago salmon (Oncorhynchus rhodurus). Transfer to seawater increased plasma sodium levels in both smolts and dark parr. Smolts adjusted their plasma sodium to the level associated with seawater‐adaptation (165 mEq/liter) within 3 days, whereas no adjustment was seen in dark parr; the latter failed to survive in seawater for more than 3 days. In smolts, plasma GH levels increased significantly 1 day after transfer, whereas there was no significant change in dark parr. An increase in GH mRNA levels was observed in smolts in association with increased plasma GH, whereas there was no change in dark parr. In contrast, a reduction in plasma PRL levels was consistently observed in both smolts and dark parr after transfer to seawater. However, there was no significant change in PRL mRNA levels in either smolts or dark parr. These results suggest that both gene expression and release of GH are activated by seawater transfer only in smolts with adequate seawater adaptability, whereas PRL gene expression is decreased after sea‐water adaptability. © 1992 Wiley‐Lis

ISSN:0022-104X    

DOI:10.1002/jez.1402620408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe objective of this study was to identify, characterize, and examine oviductal secretory proteins (OSP) synthesized de novo by whole oviduct (WO), ampulla (A), and isthmic (I) tissue from ovariectomized (OVX), corn oil (CO)‐, estrogen (E)‐, progesterone (P)‐, and E + P‐treated gilts. Oviducts were collected from OVX gilts after CO, E, P, or E + P treatment for 11 consecutive days and tissue was incubated with3H‐leucine (3H‐leu). Rates of3H‐leu incorporation into nondialyzable macromolecules by WO explants were greater (P<0.01) with E‐ compared to CO‐, P‐, or E + P‐treated gilts and greater (P<0.05) by A explants with E‐ compared to CO‐, P‐, or E + P‐treated gilts. An effect of location was noted, with A having a greater (P<0.01) rate of incorporation than WO or I. Conditioned culture medium was analyzed by one (1D)‐ and two‐dimensional (2D) sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and fluorography. Analyses by 1D‐SDS‐PAGE revealed three major E‐dependent bands (335,000, 100,000, and 80,000 Mr) in WO and A, and one (335,000 Mr) in the I. A 20,000 Mrband found in A was inhibited by E, while a 60,000 Mrband found in the A was induced by P. Analyses by 2D‐SDS‐PAGE resolved major E‐dependent bands 2 (100,000 Mr) and 3 (80,000 Mr) into basic and acidic 100,000 Mrproteins and a 75,000–85,000 Mrprotein (pI2 × 106) that was induced by E and was 6.8‐fold greater in medium from A than from I. This study clearly demonstrates that 1) WO and A tissue from E‐treated gilts de novo synthesize and secrete three major proteins (basic 100,000, acidic 100,000, and 75,000–85,000 Mr); 2) these E‐dependent proteins are not found in I or with other treatment; 3) several protein complexes synthesized by A are inhibited by E treatment; and 4) a high Mrfraction, produced primarily in the

ISSN:0022-104X    

DOI:10.1002/jez.1402620409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effects of the nonsteroidal ecdysone mimic RH 5849 on larvae of a crab (Rhithropanopeus harrisii) and the cypris larva of a barnacle (Balanus amphitrite) have been investigated. Larvae were exposed to exogenous RH 5849 in the concentration range of 0.1–10.0 mg/L. The two lowest concentrations tested (0.1 and 1.0 mg/L) accelerated molting of crab zoeae. RH 5849 did not induce premature apolysis. A concentration of 10 mg/L RH 5849 was toxic to zoeae: these larvae underwent apolysis but not ecdysis and subsequently died. Attachment and metamorphosis of barnacle cyprids was enhanced by 10.0 mg/L RH 5849. Increased attachment may be a result of physiological aging of larvae by the ecdysone mimic. Increased metamorphosis is consistent with the stimulatory effect of 20‐hydroxyecdysone on this process. RH 5849 was first demonstrated as an ecdysone mimic in insects (Wing, Science,241:467–469, '88). The present study provides preliminary evidence for a similar action in crustaceans. © 1992 Wiley‐L

ISSN:0022-104X    

DOI:10.1002/jez.1402620410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe segmentum accelerans in geese is a constriction in the caudal end of the primary bronchus. Experimental evidence suggests that this part of the airway functions as an inspiratory aerodynamic valve, accelerating the incoming airstream past the ventrobronchial openings. The luminal diameter of the segmentum accelerans dilates in the presence of elevated CO2levels, probably through relaxation of smooth muscle. Physiological control of the segmentum acelerans may permit inspiratory aerodynamic valving to be maintained throughout a wide range of ventilatory flows. © 1992 Wiley‐Liss, I

ISSN:0022-104X    

DOI:10.1002/jez.1402620411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY