摘要:

AbstractThe transition from aerobic to anoxic conditions induced stable modifications of the kinetic and regulatory properties of 6‐phosphofructo‐1‐kinase (PFK) from the posterior adductor muscle and hepatopancreas of the marine bivalve molluscMytilus edulisL. Anoxia resulted in a reduction in the maximal activity of PFK, a decrease in affinity for fructose‐6‐P (S0.5increased by 60% in muscle and twofold in hepatopancreas), reduced effects of activators (AMP, fructose‐2,6‐P2), and reduced inhibition by ATP (I50increased 2–2.4 fold). Organ‐specific differences in PFK properties were greatest for enzyme activators, with the hepatopancreas enzyme showing much lower Kavalues for AMP and fructose‐2,6‐P2as well as activation by inorganic phosphate (Ka0.07 mM aerobic, 0.11 mM anoxic). By contrast, the muscle enzyme was not affected by Piand neither enzyme was inhibited by citrate. To determine if the anoxia‐induced modifications of PFK were due to covalent modification of the enzyme protein, PFK preparations were incubated with ATP + Mg2++ protein kinase second messengers (cAMP, cGMP, or Ca2+plus phorbol 12‐myristate 13‐acetate) or with Mg2++ alkaline phosphatase. Protein kinase action on posterior adductor muscle PFK increased enzyme Vmax, and affinity for fructose‐6‐P. cAMP‐ or cGMP‐stimulated protein kinase had the same action on hepatopancreas PFK; but incubation with stimulators of protein kinase C had the opposite effect on the enzyme. Alkaline phosphatase treatment reversed the effects of in vitro phosphorylation. The data suggest that the glycolytic rate depression (reverse Pasteur effect) that occurs with the transition to anoxia in these facultative anaerobes is facilitated by reversible phosphorylati

ISSN:0022-104X    

DOI:10.1002/jez.1402570102

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe binding and accessibility of an insect selective neurotoxic polypeptide derived from scorpion venom (AaIT, Mr = 8 kDa) to the cockroach nervous system was studied by the aid of binding assays and light microscopy autoradiography resulting in the following information:1The toxin possesses high paralytic potency to the cockroach (ED50= 4 ng per 100 mg of body weight) and high binding capacity (13.8 ± 1.8 pmol per mg protein) to its nervous system.2When incubated with dissected and anatomically desheathed central nervous tissue the radioiodinated toxin ([125I]AaIT) revealed an obvious high affinity binding specificity. In contrast, the skeletal muscles of the cockroach were completely devoid of specific binding sites of the [125I]AaIT. The latter observation provides additional support for the sodium channel selectivity of the AaIT toxin.3Autoradiography of [125I]AaIT injected into the body cavity in doses inducing a fast paralysis revealed that the central and most parts of the peripheral nervous system are impermeable to the toxin.4In the above injection assays the toxin was shown to bind to the terminal branches of motor nerves at their close proximity to the skeletal muscles. Computerized image analysis of the autoradiographical data followed by electron microscopy of the neuromuscular junctions suggest an accessibility of the terminal axonal membranes to the toxin.The above data, supported by previous electrophysiological studies, led to the conclusion that the peripheral terminal outbranchings of the motor nerves serve as the main sites of accessibility to paralytic polypeptide neurotoxins

ISSN:0022-104X    

DOI:10.1002/jez.1402570103

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe metabolic rates of differentLdh‐Bgenotypes of developingFundulus heteroclitusembryos were examined. Within 24 hours after fertilization, eggs homozygous for the southern (Ldh‐Ba) allele began to exhibit significantly higher oxygen consumption than eggs homozygous for the northern (Ldh‐Bb) allele. No significant differences existed between genotypes with respect to total LDH‐B4activity or ontogeny throughout development. Lactate concentrations were significantly different in the oocytes between genotypes (Ldh‐Ba= 48 mM;Ldh‐Bb= 40 mM). Furthermore, lactate was utilized at a high rate during early development. Lactate utilization was approximately 100 times higher than apparent glucose utilization, and both rates were significantly different between genotypes. Within 24 hours after fertilization, half of the lactate present in the oocyte was utilized in both genotypes. Oxygen consumption and heat dissipation measurements demonstrated that theLdh‐Bahomozygotes increased their metabolic rate dramatically between 10 and 15 hours after fertilization and that theLdh‐Bbhomozygotes did not. It is suggested that lactate is a source of intermediates important for early development and that LDH‐B4may mediate the accumulation of that lactate in the oocyte and the utilization of lactate in the early development of the embryo. This metabolic role may lead to environmentally induced selection

ISSN:0022-104X    

DOI:10.1002/jez.1402570104

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe anatomical structures used during mammalian feeding are morphologically linked by their connecting musculature, suggesting a predictable timing relationship among their movements. Cine‐x‐ray (100 frames per second) was used to record feeding behavior in four adult hyraxes (Procavia syriacus), herbivores. Movement of jaws, tongue, and hyoid bone was cyclic, and prior to the first swallow cycle, cycle duration was constant through time for all structures. Minimum gape, beginning of forward movement of the tongue and hyoid, and beginning of intrinsic tongue expansion occurred simultaneously over a large number of cycles. However, maximum gape, maximum protrusion of hyoid, and maximum forward position of the tongue happened at statistically different points in time. After the first swallow, cycle duration increased. Most of the variation in cycle duration can be explained by variation in the opening or forward phase of movement; the closing and return phases are constant in duration. These results are a quantitative description of the coordination that exists during different feeding behaviors (ingestion, intraoral transport, mastication, and swallowing) in normal, freely functioning hyraxes. The patterns of phase duration differ from some results obtained by using anesthetized anim

ISSN:0022-104X    

DOI:10.1002/jez.1402570105

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

年代:1991

数据来源: WILEY

摘要:

AbstractActin extracted from the electric organ and epaxial muscle of the electric eelElectrophorus electricuswas characterized by several biochemical techniques. Isoelectric focusing gels revealed two isoforms of actin in the electric organ, in contrast to the unique form of actin present in the epaxial muscle of this eel and the rabbit leg muscle, which were used as controls. Proteolytic digestion and immunoblotting analysis confirmed that these isoforms were composed of actin. When actin from the electric organ was mixed with actin from the epaxial muscle or from rabbit muscle and subjected to isoelectric focusing gel, it was possible to identify an alpha‐actin isoform in the electric organ as well as a more basic actin that migrated in the same manner as cytoplasmic actin or gamma actin from smooth muscle. The data are interpreted in terms of the differentiation of the electric organ ofE. electricu

ISSN:0022-104X    

DOI:10.1002/jez.1402570106

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe relative developmental abilities of hamster 2‐ and 8‐cell embryos in culture were compared using two versions of hamster embryo culture medium (HECM). These media differed primarily in the number of amino acids present, i.e., 20 amino acids in HECM‐1 and four amino acids in HECM‐2. When 2‐cell embryos were cultured for 24 h, the percentages of ⩾4‐cell embryos obtained in both HECM‐1 and HECM‐2 were comparable (≃93%); at the end of 48 h, the proportion of ⩾8‐cell embryos obtained in HECM‐1 (82.5%) was significantly (P⩽ 0.001) more than that obtained in HECM‐2 (67.9%). Interchange of media, after 24 h culture, did not enhance the ability of cultured 2‐cell embryos to become blastocysts. When 8‐cell embryos were cultured for 18 h in HECM‐1 and ‐2, there was no appreciable difference in the proportion of total blastocysts formed (89‐91%). However, there were significantly (P⩽ 0.001) more late blastocysts in HECM‐2 than in HECM‐1 (68.2% vs. 38.4%). Embryo development from 2‐ and 8‐cell stages was compared in media that differed by the presence and absence of phenol red and penicillin‐G. There was no difference in embryo development when these compounds were present or absent. Similarly, the difference in pyruvate concentration between HECM‐1 and ‐2 (0.5 and 0.2 mM, respectively) did not affect embryo development. These results show that a) the presence of four amino acids (Phe, Ile, Met, and Gln as in HECM‐2) was not sufficient for 2‐cell embryo development in culture and additional amino acids (as in HECM‐1) were required; and b) the four amino acids were better than 20 amino acids for obtaining late blastocysts starting from the 8‐cell stage. The low percentage of late blastocysts obtained in HECM‐1 was attributed to the presence of inhibitory amino acids in this formulation. Hence, it is concluded that the optimum medium for

ISSN:0022-104X    

DOI:10.1002/jez.1402570107

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

年代:1991

数据来源: WILEY

摘要:

AbstractDechorionated neurulae and early tail‐bud embryos ofCiona intestinalis(Linnaeus) develop into tadpole larvae without fully formed dorsal, ventral, or caudal fins, although other aspects of organ and tissue development appear normal. Groups of dechorionated neurulae treated with the reducing agent glutathione exhibit a 5‐8% enhancement in caudal fin length compared with dechorionated controls. Other reducing substances tested, namely, gallic acid, chlorogenic acid, cysteine, and dithiothreitol, had no effect on fin formation, possibly due either to their rapid oxidation in aerated seawater (chlorogenic and gallic acids) or to kinetic inertness (dithiothreitol and cysteine). These results imply that larval fin morphogenesis requires secretion of a specific reducing substa

ISSN:0022-104X    

DOI:10.1002/jez.1402570108

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

年代:1991

数据来源: WILEY

摘要:

AbstractRegeneration of autotomized limbs by third crab stageRhithropanoepus harrisiifollowed the all‐or‐none rule and was completed without significant alteration of the normal molt cycle. Loss of three to six primary limb buds during late intermolt or early premolt (D0, day 3) resulted in a delay of ecdysis while secondary limb buds were formed. The number of animals delaying ecdysis and producing secondary buds was stimulus dependent. While the number of animals initiating secondary regeneration increased with the number of primary buds lost, fewer animals in these groups were capable of regenerating all of the missing primary buds. Animals not initiating secondary regeneration or regenerating only some of the primary limb buds completed regeneration during the following molt cycle. The duration of the subsequent molt cycle was significantly shorter for all regenerating animals, including the regeneration control group. Partial regeneration and acceleration of subsequent molts appears to be the best allocation of available energy reser

ISSN:0022-104X    

DOI:10.1002/jez.1402570109

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe endocrine regulation of molting was investigated in the crabGecarcinus lateralisby treating tissues from anecdysial (intermolt) animals with the arthropod molting hormone 20‐hydroxyecdysone (20HE) in vitro and observing changes in the incorporation of [35S]‐methionine into proteins. Although total protein synthesis was not affected by levels of 20HE ranging from 10−9to 10−5M, synthesis of five out of 30 protein bands was significantly stimulated at hormone concentrations of 10−9−10−7M, the latter characteristic of proecdysis. Increases were as large as eightfold. Synthesis was not significantly inhibited for any of the integumentary proteins. Treatment of integumentary tissues with 10−5M 20HE (approx. 100 times greater than the highest endogenous concentration) had less effect than physiological concentrations. The dose response varied substantially among integumentary proteins. In some instances, the effects were similar to changes in synthesis that occur in vivo during specific stages of proecdysis (Stringfellow and Skinner, Dev. Biol.,128: 97–110, '88). Midgut gland (hepatopancreas) was also treated with 20HE in vitro. Treatment with 20HE significantly inhibited total protein synthesis in tissue from males, but not in that from females. This treatment inhibited the synthesis of a number of the 32 protein bands examined in both sexes. Synthesis of six protein bands was significantly inhibited in males, while synthesis of three different bands was significantly inhibited in females. This inhibitory action of 20HE is consistent with the atrophy of the midgut gland that occurs during proecdysis (Gibson and Barker, Oceanogr. Mar. Biol. Annu. Rev.

ISSN:0022-104X    

DOI:10.1002/jez.1402570110

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

年代:1991

数据来源: WILEY

摘要:

AbstractInvertebrate fusion and rejection responses are typically assumed to be mutually exclusive and temporally stable states. We here describe a segregant class appearing in an F1cross of the colonial hydroid,Hydractinia symbiolongicarpus, that displays an ontogenetic change in fusibility. Reproductively immature offspring fuse to parental strains and have been observed to remain continuously fused for up to 76 days. By contrast, reproductively mature offspring initially fused with parental strains, only to separate into distinct colonies after a period of 3–21 days postfusion. Experimental manipulations demonstrate that (1) ontogenetic changes in fusibility cannot be removed by resetting a colony to a reproductively immature state, and (2) secondary contact does not result in an accelerated respons

ISSN:0022-104X    

DOI:10.1002/jez.1402570111

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

年代:1991

数据来源: WILEY