摘要:

AbstractBranchial sodium uptake was measured across secondary lamellae (SL) using the isolated‐perfused head preparation. This study was correlated with histological examination.Freshwater trout,Salmo gairdneri, were exposed to various artificial media: distilled water (DW), fresh water (FW: NaCl<200 μl/1; Ca++= 1.5 mM/1), FW + 5 mM CaCl2and FW + 10 mM CaCl2. These environments altered the number and forms of “chloride cells” (CC) located in SL and were related to changes in maximal transport rate of Na+. An increase in a specific type of CC (round) was associated with an increase in Vmax, and a decrease in round cells was associated with a decrease in Vmax.Relative to FW, exposure to DW increased the density of round cells, FW + 5 mM CaCl2had no effect, and FW + 10 mM CaCl2produced an initial degeneration of CC followed by restoration and increase in protruding round cells.We conclude that secondary lamellar chloride cells play an important role in Na+

ISSN:0022-104X    

DOI:10.1002/jez.1402410202

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe relationship between carbonic anhydrase and calcification in the gorgonianLeptogorgia virgulatawas examined by analysis of the enzyme's activity, its cellular locations and its response to inhibition by Diamox. Enzyme activity was 2.7 nmol μg−1protein s−1at 4°C. Carbonic anhydrase localization at the light level using immunofluorescent techniques and at the ultrastructural level using Hansson's method showed activity in the scleroblasts and axial epithelium. Specifically, at the electron microscopic level this activity was found to be very high on the membranes of the spicule‐forming vacuole and electron‐dense bodies. Membranes of the microvilli and plasma membranes of the desmocytes showed high activity of this enzyme. The activity on the scleroblast plasma membranes was variable. This enzyme is possibly present in the axis. Regenerated branch tips incubated in seawater containing 10−4M and 10−6M Diamox showed an increase in45Ca uptake into the spicules and axes. The tissue o fbranch tips incubated in 10−6M Diamox showed a decrease in45Ca uptake. The observation that carbonic anhydrase is located adjacent to calcifying structures and organelles associated with spicule formation suggests that the enzyme is involved in calcification. The increase in45Ca uptake from enzyme inhibition may suggest that carbonic anhydrase is involved in the reg

ISSN:0022-104X    

DOI:10.1002/jez.1402410203

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

年代:1987

数据来源: WILEY

摘要:

AbstractCatecholamines (dopamine or norepinephrine) injected under the blastoderm of the unincubated chick embryo produced a thickened primitive streak and prevented the migration of axial mesoblast after 24 h. The mesoblastic cells that accumulated in the primitive streak contained many intracytoplasmic yolk granules. After 48 h, neural tube, notochord, and somites were severely affected, and their cells appeared loaded with yolk inclusions. Heart, lateral plates, blood cells, and blood vessels differentiated normally. At the onset of gastrulation, the level of glycogen was fivefold lower in catecholamine‐treated embryos than in control embryos. Injection of glucose plus dopamine, at equimolar concentrations resulted in normal development both at 24 h and at 48 h. Because adrenegic stimulation of glycogenolysis in differentiated cells is usually mediated by cAMP and/or by calcium, we attempted to determine whether these substances could reproduce the effects of catecholamines. Only calcium was able to produce, to a limited extent, the same morphogenetic disturbances as those produced by catecholamines, whereas the chelating agent, ethylenediamine tetraacetic acid, when administered with dopamine, partially inhibited the effects of catecholamines. An increase in the number of yolk granules was the only common finding among embryos treated with cAMP and catecholamines. Blood and a well differentiated, gastrular endoderm always developed, independently of the nature of the substance with which the embryos had been treated. Morphogenetic disturbances caused by exogenous catecholamines could be due to depletion of glucose. Alternatively, a different metabolic commitment might exist within the diverse populations of cells that constitute the mesoblastic laye

ISSN:0022-104X    

DOI:10.1002/jez.1402410204

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe present study was designed to examine the effects of changes in Ca2+concentration in a culture medium on the development of 11‐day mouse embryos (plug day = day 0). The embryos were individually cultured for 24 hours by rotating bottles using a culture medium of 25% rat serum and 75% Waymouth's medium. The Ca2+concentration was changed by adding EGTA or CaCl2to the Waymouth's medium. The Ca2+concentrations examined were 0.5, 1.0, 1.5, 2.0, and 3.0 mM in 95% oxygen and 1.0, 2.0, and 3.0 mM in 60% oxygen. Development of embryos was evaluated on the basis of heartbeat, survival, growth, and differentiation. In 95% oxygen, the best survival was obtained at 1.5 mM Ca2+, while growth and differentiation were little affected by changes in Ca2+concentrations except at 0.5 mM. In 60% oxygen, rhythmical heartbeats were difficult to maintain in many of the embryos at all Ca2+concentrations examined, although reasonable development was obtained at 3.0 mM Ca2+. The optimal conditions were a culture medium containing 1.5 mM Ca2+and an oxygen concentration of 95%. The addition of Waymouth's medium to the rat serum is useful in controlling the Ca2+concentration of the culture mediu

ISSN:0022-104X    

DOI:10.1002/jez.1402410205

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

年代:1987

数据来源: WILEY

摘要:

AbstractMicrofilaments, which are organized into bundles in the apical ends of neuroepithelial cells, are generally thought to play a major role in generating the driving forces for neural tube closure. Because of their proximity to the luminal surface, the contractile activity of these microfilament bundles results in conspicuous changes in the overall shape of neuroepithelial cells, most notably apical costriction and apical surface folding. In the present study, we have used morphometric methods and computer‐assisted image analysis to reveal the distribution of microfilament‐mediated forces in the developing midbrain during initial contact of apposing neural folds in chick embryos at Hamburger and Hamilton stage 8+of development (Hamburger and Hamilton (1951) J. Morphol.,88:49–92). The degree of apical constriction, apical surface folding, and bending of the neuroepithelium was used as a barometer of local microfilament activity. Results indicate that cells forming the floor and midlateral walls of the developing midbrain consistently show a higher degree of apical constriction and surface folding than those at other locations. These same regions of the neuroepithelium also exhibit the greatest degree of bending. We conclude that the principal driving forces for closure of the neural tube, at the level of the midbrain, are concentrated in certain regions of the neuroepithelium (i.e., the floor and midlateral walls of the forming neural tube) rather than uniformly distri

ISSN:0022-104X    

DOI:10.1002/jez.1402410206

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

年代:1987

数据来源: WILEY

摘要:

AbstractA group of 88 newts,Triturus cristatus carnifex(Laurenti), was rendered totally anemic by administering acetylphenylhydrazine (APH) in the breeding water for 48 h at a concentration of 25 mg/liter. The course of erythron restoration was followed for 5 months, sacrificing four specimens per week and analyzing the blood and spleen hemopoietic tissue. The return to the normal values of the red blood cell count occurred through marked increases in concentration at fairly regular intervals, which is best explained by a discontinuous, rhythmic erythropoiesis. This fact is strictly correlated with the intermittent mitotic activity observed in the spleen and with the periodic appearance of large quantities of immature elements in the blood smears. The APH‐induced synchronization of newt erythropoietic activity revealed the approximate length of each erythropoietic cycle to be 4 to 5 weeks and the erythropoietic life span to be 50 to 60 day

ISSN:0022-104X    

DOI:10.1002/jez.1402410207

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe formaldehyde‐glutaraldehyde‐sucrose (FGS) method for in situ localization of catecholamines has been applied to the nervous system of the marine polyclad flatwormNotoplana acticola. This histochemical fluorescence technique revealed the presence of a small population of fluorescent cells within the brain. The number and positions of these neurons were constant in animals of the same size, but varied with the size of the worm. The brains of small animals (8 mm in length) were found to contain 20 fluorescent cells, whereas the largest animals studied (30 mm in length) were found to have 28 such cells. Various intermediate cell numbers were found in animals between these two sizes. The origin of the newly added fluorescent cells is uncertain. Peripheral fluorescence was found in association with the tentacular ocelli (eyespots) and interneurons within the ventral submuscular nerve plexus. The fluorescent spectrum from these cells measured in situ had a λmaxof 526 nm. Treatment with HCl shifts this peak to 530 nm. L‐dopamine fluoresces with a similar peak emission before HCl treatment (525.5 nm) and shifts to the appropriate longer wavelength (530 nm) following acidification. This strongly suggests that the fluorescent substance in the neurons is dopaminergic in

ISSN:0022-104X    

DOI:10.1002/jez.1402410208

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

年代:1987

数据来源: WILEY

摘要:

AbstractFemale green iguanas,Iguana iguana, were caught in Belize, Central America (17°N), in December, at the onset of seasonal gonadal activity. The animals were immediately transferred to San Diego (32°N). Ovarian follicular development continued, with peak plasma hormone levels measured in January and February; 200 pg/ml for progesterone (P) and 800 pg/ml for total estrogens (Et= estradiol [E2] + estrone [E1]). E2was the predominant estrogen throughout the cycle. Follicular atrophy was indicated in April with circulating progesterone and estrogen levels decreasing to baseline (refractory phase) levels (P= 20 pg/ml; Et= 50 pg/ml). Approximately midway through the refractory phase of their annual reproductive cycle (late May), either the D‐Arg6analog of Chicken II or mammalian GnRH was administered via intraperitoneal osmotic pumps for 14 days to nine females. The analog of chicken II induced a fivefold increase in total circulating estrogens within 3–4 days after induced a fivefold increase in total circulating estrogens within 3–4 days after implantation. Both continuous and pulsatile delivery of the chicken II analog produced a similar pattern of steroidogenic response. A radical sham control animal showed no increase in steroidogenesis. Mammalian GnRH produced a pattern of similar duration, although the magnitude of the steroidogenic response was only half that produced by the chicken II analog. Estrogen titers approached baseline levels in all treatment groups two days after treatment ceased. Progesterone levels increased in all treatment groups during the delivery of exogenous GnRH, although the increases were not consistent. Untreated male cagemates housed with treated females exibited increased territoriality, courtship behavior, and mating, which began on day 4 or 5 of the treatment period. The control female was not courted by its male c

ISSN:0022-104X    

DOI:10.1002/jez.1402410209

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe study of myoblast proliferation and fusion to form myotubes in vivo has centered around the role of the innervating motoneurones. Hormonal factors such as prostaglandin E1(PGE1) are important during in vitro myogenesis, but their role in vivo has yet to be elucidated. In vitro, PGE1appears to switch myoblast from a mitotic to a fusion mode. Consistent with this hypothesis, administration of PGE1to chicken embryos decreased the number of myonuclei incorporated into their muscles. The effect of inhibitors of prostaglandin synthesis (aspirin and indomethacin) on in vivo myogenesis was not, however, as expected. Both drugs decreased the number of myonuclei incorporated into the muscles of treated embryos, which is the opposite of what would have been expected if they were enabling myoblasts to undergo additional divisions by delaying their onset from the mitotic cycle. The simplest explanation of this observation is that the effect of aspirin and indomethacin is mediated by a prostaglandin other than E1, or by a systemic factor whose levels are regulated by a prostaglandin. The maximum extent of the reduction caused by PGE1and the inhibitors of prostaglandin synthesis was only 25–30%, suggesting that only a subpopulation of myoblasts is effected by these drugs. The number of myotubes formed in the treated embryos closely paralleled the total number of myonuclei, indicating that the number of myoblasts fusing to form a myotube is constant even when the total number of available myoblasts is diminishe

ISSN:0022-104X    

DOI:10.1002/jez.1402410210

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

年代:1987

数据来源: WILEY

摘要:

AbstractStudies on the endocrine control exerted upon cellular multiplication in mussel mantle tissue (the site of the gonad in this species) are rendered difficult by its extremely heterogeneous nature and require the use of a quantifiable bioassay. Measurement of specific ATCase activity gives a good estimation of pyrimidine biosynthesis; in mussels, the specific activity of this enzyme is highest in the mantle tissue and is closely correlated to the gonadosomatic index. Stimulatory action of cerebral ganglia in organ culture experiments are associated with increases of specific ATCase activity. Antimitotic substances, such as 5 fluorouracile or arabinocytosine on the other hand, induce a decrease of ATCase activity in mantle explants. The utilization of ATCase activity measurements, in the study of gametogenic controls, is proposed in species in which the gonad is not a differentiated organ.

ISSN:0022-104X    

DOI:10.1002/jez.1402410211

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

年代:1987

数据来源: WILEY