bluuebunny/crossref_metadata_2025 huggingface dataset:
Jelly release in the eggs of the white sturgeon, Acipenser transmontanus: An enzymatically mediated event
Authors: Cherr Gary N. , Clark Wallis H.
Published: June 2005

The thin electron‐dense jelly layer that coats A. transmontanus eggs is released and hydrates when the eggs contact freshwater. This jelly release is dependent on a trypsin‐like protease and divalent cations since specific trypsin inhibitors and Ca++‐Mg++‐free freshwater block release. Chymotrypsin inhibitors have no effect on jelly release. The jelly consists of protein and carbohydrate and is the only layer of the egg envelope that contains sialic acid. The major component of jelly is a glycoprotein with a molecular weight of 110,000 daltons.
Angiotensin‐converting enzyme activity in tissues of the rainbow trout
Authors: Galardy R. , Podhasky P. , Olson K. R.
Published: June 2005

Angiotensin‐converting enzyme activity (ACE) was assayed in homogenized rainbow trout tissues and plasma. The physiological role of ACE was examined by injection of the ACE inhibitor captopril (SQ 14,225) into the dorsal aorta of chronically cannulated trout. Gills and corpuscles of Stannius exhibited greatest ACE activity and contained over 30 times more enzyme than plasma on a per‐wet‐weight basis. ACE was barely detectable in skeletal muscle, liver, and kidney tissues. Captopril lowered dorsal aortic pressure (DAP) within 1 min after injection. Pressure fell 5–7 mm Hg below control over the next 30 min and remained at this level for an additional hour. Because the gills receive the entire cardiac output they are, like the mammalian lungs, ideally situated to regulate plasma hormone levels. Activation of angiotensin II (AII) appears to be only one example of branchial metabolic capability.
Effects of insulin on the fine structure of hepatocytes from winter‐acclimatized carps: Studies on protein synthesis
Authors: Sáez Lino , Amthauer Rodolfo , Rodríguez Esteban , Krauskopf Manuel
Published: June 2005

Male and female winter‐acclimatized carps were injected with insulin. This treatment resulted in a sharp decrease in the liver glycogen content. Although an increase in the ribosomal RNA level was also observed, a cell‐free system obtained from the hormone‐treated fish exhibited less amino acid incorporation activity as compared to the control fish. However, polysomes from insulin‐treated fish exhibited a higher amino acid incorporating activity when a soluble fraction of untreated winter carps was used.

Insulin induced a profound change in the cytoarchitecture of the winter carp hepatocyte. The cytoplasm and nuclei showed all the features of the summer carp liver cell. The nucleolar components were totally intermingled suggesting a high rate of gene expression as in the case of the summer‐acclimatized fish.
Effects of light‐deprivation on development of photopositive behavior in Xenopus laevis tadpoles
Authors: Copp Newton H. , McKenzie Tracey
Published: June 2005

The development of amphibian sensory systems and behavior is generally considered to proceed normally without reference to sensory experience during embryonic or larval stages. Most of the supporting research, however, has concentrated on the retinotectal (visual) systems of anurans and has ignored behaviors directed by other sensory systems. We demonstrate that early exposure to light is necessary for the development of photopositive behavior in Xenopus laevis tadpoles, a behavior probably directed by the pineal complex. Light‐deprivation during the tadpoles' first 10 days of development results in a long‐lasting reduction in the tadpoles' light preference. The development of a strong light preference is not influenced by light‐deprivation before the tadpoles are 2 days old or after the tadpoles are 10 days old, but light‐deprived tadpoles recover a weak light preference after subsequent days of rearing in the light. Lengthening the tadpoles' exposure to light during the first 10 days of development produces increasingly strong light preferences. Considering the important role of the pineal complex in guiding phototactic behaviors in anurans, we suggest that light‐deprivation alters photopositive behavior in Xenopus tadpoles by altering the development of the pineal complex.
The culture of 12‐ and 13‐day rat embryos using continuous and noncontinuous gassing of rotating bottles
Authors: Priscott P. K. , Yeoh G. C. T. , Oliver I. T.
Published: June 2005

A technique for the culture of 12‐ and 13‐day rat embryos is presented. The culture method described utilizes the opening of the extraem‐bryonic membranes together with a simple bottle rotator during incubation to facilitate tissue oxygenation. This method was compared with a more elaborate device that enabled constant gassing during incubation. Best results were obtained with 12‐day embryos cultured for 24 hr in closed bottles. Thereafter, there was a marked falloff in embyronic development in culture. Optimal medium conditions were 25% rat serum in tissue culture medium with a gas phase of 60% O2, 5% CO2, 35% N2. The culture method described allows for larger numbers of embryos to be cultured more simply than previous methods and should be valuable to workers wishing to study embryos in the more advanced stages of organogenesis.
Photoperiodic control of antler cycles in deer. VI. Circannual rhythms on altered day lengths
Authors: Goss Richard J.
Published: June 2005

Groups of sika deer were exposed to light and dark periods of equal lengths but different from 12 hr. Light cycles were 4.94L/4.94D, 6L/6D, 8L/8D, and 21L/21D. In all experiments, deer underwent circannual cycles of antler replacement, testis size, molting, and coat color. The results indicate that the previously reported abolition of circannual cycles on 12L/12D was due to the 12‐hr duration of the light or dark periods, not their equivalence. They also eliminate the possibility that the circannual cycle might be the sum of 365 circadian cycles. Circannual antler cycles appear to be expressed under artificial light cycles to which the deer cannot entrain.
Transepithelial potential measurements in the isolated, perfused head of a marine teleost
Authors: Claiborne J. B. , Evans David H.
Published: June 2005

The transepithelial potential (TEP) across the gills of a seawater teleost, the long‐horned sculpin (Myoxocephalus octodecimspinosus), was measured both in vivo and utilizing an isolated, perfused head preparation (IPHP). The TEP of the IPHP was compared to that of the whole animal while in normal seawater and Na‐ or Cl‐free seawater. The TEP or the IPHP in seawater was similar to that measured in vivo ( + 7.7 versus +7.2 mV, respectively). Na‐free seawater induced a depolarization of both the IPHP and the intact fish, while Cl‐free seawater hyperpolarized the TEP in vivo.

The positive TEP of the sculpin, measured both in vivo and in vitro, is indicative of a transbranchial Na+ to Cl− permeability ratio greater than unity. The IPHP of the sculpin exhibits differential ion permeabilities similar to that of the whole animal. TEP comparisons described here should be applied to other IPHP systems now in use.
Does vitamin A act on pattern formation via the epidermis or the mesoderm?
Authors: Maden M.
Published: June 2005

To determine whether the effect of vitamin A on pattern formation in the regenerating axolotl limb was due to a change in the blastemal mesoderm or the epidermis, tissue grafts were exchanged between normal and retinoic acid‐treated animals. The results were conclusive. The combination of treated epidermis and untreated mesoderm resulted in normal regenerates. The combination of treated mesoderm and untreated epidermis produced regenerates that were serially duplicated in the proximodistal axis just as the controls were. We may, therefore, conclude that vitamin A acts on the mesodermal cells of the blastema in causing proximodistal duplications.
Luminal composition and maturation of spermatozoa in the male genital ducts of the Port Jackson shark, Heterodontus portusjacksoni
Authors: Jones Russell C. , Jones Nigel , Djakiew Daniel
Published: June 2005

The functions of the epididymis of H. portusjacksoni were studied to assess the significance of its structural differentiation and to provide a basis for assessing the evolution of the vertebrate epididymis. It was shown that posttesticular sperm maturation occurs within the epididymis. The maturation process involves the development of the capacity for motility, and the formation of sperm bundles. However, the process does not involve ultrastructural changes. Micropuncture studies of the epididymal luminal fluids showed that in the region where sperm mature the ducts absorb most of the extracellular fluid leaving the testis, and secrete a denser proteinaceous fluid. Determinations of sodium and potassium showed that there is a barrier to the free movement of these ions between blood and the lumen of the genital ducts. The ratio of sodium:potassium was high (36.6:1) in the ductuli efferentes, but reduced to a ratio of 3.4:1 at the distal end of the epididymis. The epididymal fluids contain membrane‐bound, cytoplasmic bodies 3–4 μm in diameter which form a separate layer from spermatozoa during centrifugation. The bodies contain mitochondria, ribosomes, endoplasmic reticulum, lipid droplets, and a lower concentration of sodium than the surrounding fluid. It is concluded that the epididymis in the shark carries out some of the main functions of the mammalian epididymis.
Distribution of a proteinase inhibitor of epididymal origin in the tissues and secretions of the male reproductive tract of mice
Authors: Poirier Gary R. , Nicholson Nanette
Published: June 2005

Monoclonal antibodies to a low molecular weight, acid‐stable acrosin‐trypsin inhibitor isolated from epidiyml homogenates were used to localize the inhibitor in tissues and secretions of the male reproductive tract of mice. The inhibitor, identified by indirect immunofluorescence, is present in the testes and in the apical portion of the epithelial cells from the caput region of the epididymis of both intact and efferentiectomized animals. Sperm isolated from the testes and caput epididymal region show inhibitor‐positive fluorescence on the anterior acrosomal region. The inhibitor could not be localized on ductus or electroejaculated sperm or ductus sperm previously incubated in a purified inhibitor solution. Furthermore, the inhibitor was not visible in the copulatory plug of recently inseminated animals or on sperm recovered from the uterus or from an artificial capacitating medium. The inhibitor could be detected by an enzyme‐linked immunosorbent assay in the supernatants of detergent treated or frozen‐thawed caput sperm but not of ductus sperm. The data suggest that the inhibitor, made in both the testes and caput epididymis where it associates with the sperm, is lost from the sperm or irreversibly masked during the epididymal sojourn.
Partially irreversible cold‐induced lipid phase transitions in mammalian sperm plasma membrane domains: Freeze‐fracture study
Authors: Holt W. V. , North R. D.
Published: June 2005

In an effort to investigate the nature of the cellular injury caused when mammalian spermatozoa are cooled prior to cryopreservation, the occurrence of thermal phase transitions amongst the lipid components of the sperm plasma membrane was investigated by the use of freeze‐fracture electron microscopy. The mechanisms by which glycerol and egg yolk exert protective effects during semen cooling and freezing were also examined.

Ram and blackbuck spermatozoa, maintained at 30°C prior to fixation at this temperature, exhibited randomly distributed intramembranous particles over the acrosomal, postacrosomal, and flagellar regions of the plasma membrane. In contrast, spermatozoa fixed at 5°C after slow cooling to this temperature exhibited particle clustering over the postacrosomal region of the head as well as over the tail. These effects were not influenced by the presence of egg yolk or glycerol during the cooling procedure, although these substances protected the spermatozoa against loss of motility.

Particle clustering over the sperm tail, induced by the slow cooling process, was found to be only partially reversible. The extensive areas of particle‐free lipid, noted to result from the cooling procedure, were absent if the spermatozoa were rewarmed to 30°C; however, the original distribution of particles was not restored and numerous small particle‐free domains persisted. It is proposed that this type of irreversible change within the sperm plasma membrane may contribute to the loss of motility and fertility suffered by spermatozoa after cooling and freezing. Furthermore, it is suggested that protective substances such as egg yolk may exert their effects by countering these deleterious changes, rather than by preventing their occurrence.
Regeneration of whole limbs in toad tadpoles treated with retinol palmitate after the wound‐healing stage
Authors: Niazi I. A. , Ratnasamy C. S.
Published: June 2005

In young Bufo melanosticus tadpoles at the spatula stage of limb development, the left hindlimb was amputated through the shank and the right hindlimb was left intact. One day later, when the amputation surface was covered by wound epidermis, the tadpoles were immersed in 15 IU/ml of retinol palmitate solution for 2 days up to blastema formation and thereafter reared in plain water. Contrary to the situation in untreated controls, all the resultant regenerates of the vitamin‐treated tadpoles were complete limbs containing elements from the pelvic girdle to the phalanges. Retinol palmitate treatment inhibited the development of the foot in the unamputated right limbs. These results show that retinol palmitate has a different effect on dedifferentiating cells of a regenerating limb from that on cells that are differentiating in a normally developing limb.
β‐Alanine transport in the isolated hepatocytes of the elasmobranch Raja erinacea
Authors: Shuttleworth T. J. , Goldstein L.
Published: June 2005

Cells were isolated from the liver of the skate and the uptake of β‐alanine followed using [14C]‐β‐alanine. The isolated hepatocytes showed good viability, were found to accumulate β‐alanine from the incubation medium, and did so in a manner indicating a transport system involving a saturable carrier. The data for the rate of β‐alanine uptake suggest that this may be a rate‐limiting step in the oxidation of the amino acid by the liver. Experiments indicated that the transport system could distinguish β‐alanine from certain structurally similar molecules (L‐alanine and taurine, but not γ‐amino butyrate). Cells isolated from fish adapted to a diluted environment (50% seawater) showed no significant change in the uptake rate. However, evidence indicates that, over the range of β‐alanine concentrations occurring in the fish, the uptake rate would be acutely sensitive to small changes in the concentration in the blood, thus forming a self‐regulating system for the metabolism of β‐alanine.
Fate of stored secretion following ligation of the seminal vesicle–coagulating gland in the rat
Authors: Brown Randall D. , Shepherd Benjamin A. , Martan Jan
Published: June 2005

Unilateral ligation of the seminal vesicle‐coagulating gland complex in castrated and testes intact sexually mature rats resulted in a significant asymmetry in weight after 14 days, with ligated glands heavier in both groups. Differences in weight between glands resulted from ligation, and the primary route by which stored secretion is eliminated from these glands is by spontaneous ejaculation rather than resorption via the glandular epithelia.
Neuromuscular relationships during claw regeneration in Californian snapping shrimp
Authors: Stephens Philip J. , Leferovich John M.
Published: June 2005

We have examined the innervation patterns of the two excitor axons to the closer muscle in the dimorphic (snapper and pincer) claws of Californian snapping shrimp (Alpheus californiensis). In both claws the fastcloser excitor (FCE) axon supplies all of the closer muscle fibers. The slowcloser excitor (SCE) axon, however, makes functional connections only with fibers on the dorsal and ventral margins, which are composed of slow‐type fibers in the large snapper claw and of intermediate‐type fibers in the smaller pincer claw. The central band of fast fibers in the pincer closer muscle is not innervated by the SCE.

During claw regeneration, the closer muscle is initially composed of a population of fast fibers in the pincer and intermediate‐type fibers in the snapper. The innervation patterns of the two excitatory motor axons in regenerating claws at this stage are the same as in fully developed claws. During the first intermolt period some fast‐closer muscle fibers in the pincer claw differentiate into intermediate‐type fibers, but the axon innervation patterns do not change. If the correlation between SCE axon innervation pattern and the regional distribution of different muscle fiber types is indicative of nerve‐muscle interactions, the present data suggest that the trophic influence must proceed from nerve‐to muscle.
Induction of starfish oocyte maturation by maturation‐promoting factor of mouse and surf clam oocytes
Authors: Kishimoto Takeo , Yamazaki Kimie , Kato Yoshihiro , Koide Samuel S. , Kanatani Haruo
Published: June 2005

Maturation‐promoting factor (MPF) has been known to be produced in the cytoplasm of starfish and amphibian oocytes, where it triggers meiotic maturation. Cytoplasm obtained from maturing oocytes of either mouse or surf clam was found to induce maturation when injected into immature starfish oocytes. These facts suggest that MPF is also produced in oocytes of the mouse and surf clam and that MPF acts in a general, nonspecific manner in mammals, echinoderms, and molluscs.
Differences in phosphorylation of the two large subunits of brine shrimp Na, K‐ATPase
Authors: Churchill Lynn
Published: June 2005

Analysis of purified Na,K‐ATPase from brine shrimp nauplii revealed two molecular forms of the α subunit separable by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis [G.L. Peterson, R.D. Ewing, S.R. Hootman, and F.P. Conte (1978) J. Biol. Chem. 253:4762]. The molecular form with lower mobility is designated α1 and the one with higher mobility, α2 in a neutral or alkaline gel system. Differences in Na+‐dependent, K+‐sensitive phosphorylation of these two molecular forms have been investigated by directly measuring the radioactivity present in each phosphoprotein after separation of the two forms by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis. In the presence of Na+, Mg2+, and ATP, when the ATP concentration is above 1 μM, both α subunits are phosphorylated, although the phosphoprotein content of α1 is considerably greater than that of α2. Below 1 μM ATP, the phosphoprotein content of α2 is even further reduced. These striking differences in phosphorylation at low ATP concentrations are not due to a greater instability of the α2 phosphoprotein during the long electrophoresis times or during fixation, staining, and destaining. The proportion of total phosphoprotein content in α2, as well as the relationship between phosphoprotein content and ATP concentration, is unchanged when the radioactive analysis is performed on frozen gels that have been electrophoresed for shorter times, even though the actual amount of phosphorylation is 15 times greater than with fixed gels. Since the concentration of α1 and α2 vary during development [G.L. Peterson, L. Churchill, J.A. Fisher, and L.E. Hokin (1982) J. Exp. Zool. 221:295], the differences in phosphorylation may be relevant to differences in Na,K‐ATPase activity during different development stages.
Absence of branchial edema in perfused heads of rainbow trout (Salmo gairdneri)
Authors: Perry S. F. , Lauren D. J. , Booth C. E.
Published: June 2005

Using scanning electron microscopy, a histological comparison was made between gills from unperfused, blood‐perfused and saline‐perfused trout heads. All gills examined appeared non‐edematous, and no other morphological abnormalities were evident. The results are compared with those from a similar study using isolated eel holobranchs in which saline‐perfusion resulted in severe and irreversible branchial edema.
Catalase, glutathione peroxidase, and superoxide dismutase in the rete mirabile and gas gland epithelium of six species of marine fishes
Authors: Morris Shirley M. , Albright John T.
Published: June 2005

Rete mirabile and gas gland epithelium from the swim bladders of six species of marine fishes were assayed for catalase, glutathione peroxidase, and superoxide dismutase activity. Correlation of the results of these assays with measurements of the concentration of oxygen in the lumen of the normal steady state swim bladders revealed that swim bladders in species containing higher levels of oxygen also exhibited higher levels of superoxide dismutase activity in the rete mirabile/gas gland epithelium region. There appeared to be no correlation between oxygen concentration and the level of catalase or glutathione peroxidase activity. Induction of the inflatory reflex in Opsanus tau by a single deflation of the swim bladder resulted in an increase in the percent of oxygen in the swim bladder lumen 18 to 24 hours later, but this was not accompanied by any significant increases in antioxidant enzyme activity. Swim bladders that were deflated three times at 24‐hour intervals showed further increases in oxygen concentration at the end of the 72‐hour period but no alteration in superoxide dismutase activity.
Identification, synthesis, and characterization of the yolk polypeptides of Plodia interpunctella
Authors: Shirk Paul D. , Bean Daniel , Millemann Audrey M. , Brookes Victor J.
Published: June 2005

The mature eggs of Plodia interpunctella were found to contain four major polypeptides. These yolk polypeptides (YPs) were found to have approximate molecular weights of 153,000 daltons (YP1), 69,000 daltons (YP2), 43,000 daltons (YP3), and 33,000 daltons (YP4) as determined by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). In addition, we found YP1 was resolved by a 5% polyacrylamide gel into two separate polypeptides of 153,000 and 147,000 daltons. All of the YPs could be labeled in vivo or in vitro with [35S]‐methionine. Yolk peptide 1 and YP3 were synthesized by fat body of pharate adult and adult females and secreted into the hemolymph. Yolk peptide 2 and YP4 were synthesized and secreted into incubation medium by ovaries that contained vitellogenic oocytes, but these polypeptides were not found in the hemolymph. Fat bodies of males synthesized and secreted an immunoprecipitable polypeptide similar to YP3 as well as immunoprecipitable polypeptides larger than 200,000 daltons that had no counterparts in the oocytes. Peptide mapping by protease digestion showed each YP to be cleaved into unique fragments, suggesting that no precursor‐product relationship exists between the YPs. Ion exchange chromatography and gel permeation chromatography separated the yolk proteins into two groups with approximate molecular weights of 462,000 and 264,000 daltons. By resolving these peaks on SDS‐PAGE, it was found that YP1 and YP3 formed the 462,000‐dalton yolk protein and YP2 and YP4 formed the 264,000‐dalton yolk protein.
Identification and characterization of glycoproteins secreted by the skin of the day 16 fetal mouse
Authors: Janzen R. G. , Van Blerkom J. , Runner M. N.
Published: June 2005

The secretion of tissue‐specific proteins during mouse skin development, was investigated by incubating day 16 fetal skin explants in the presence of [35S]methionine and analyzing the medium electrophoretically. The medium was found to contain five proteins, which could be classified into two groups according to molecular weight. The kinetics of release of these proteins indicated that they were specifically secreted and not released by cytolysis. Mapping of the proteins by partial proteolytic digestion revealed that although the digestion patterns between the two molecular weight groups were different, within each group similar patterns were seen, suggesting that they were structurally related. Incubation in the presence of tunicamycin resulted in the decrease in molecular weight of the secreted proteins, indicating that the proteins were glycosylated. The results suggest that the two groups of structurally related glycoproteins were secreted by the peridermal layer of the fetal skin.
Cell death in cultured dorsal and ventral chick wing bud epithelia
Authors: Boutin Eugenie L. , Fallon John F.
Published: June 2005

We have examined the fate of cultured stage 20 and 25 dorsal and ventral wing bud epithelia and have found evidence that the requirements of apical ectodermal ridge and nonridge limb ectoderms for in vitro survival are different. As previously reported for the apical ectodermal ridge (Boutin and Fallon, '84), dorsal and ventral ectoderms were extensively necrotic after 12 hours of culture in serum‐containing medium. The survival of dorsal and ventral limb epithelia at 18 hours was not improved by a collagen substratum, 10% Nuserum, epidermal growth factor, nerve growth factor, multiplication‐stimulating activity, insulin, or insulin, transferrin, and selenium. This is in contrast to our observations on the ridge which remains vital for at least 24 hours in insulin or insulin, transferrin, and selenium.
Blastema cell cycle in vitro and attempted restimulation of blastema cell cycling in denervated blastemata of the adult newt, Notophthalmus viridescens
Authors: Tomlinson Bruce L. , Globus Morton , Vethamany‐Globus Swani
Published: June 2005

The durations of the adult newt blastema cell‐cycle phases were determined in vitro. In both ganglionated (G) and nonganglionated (nG) blastemata the total cell‐cycle time was 62 hr; G1 + ½M, S, and G2 + ½M were 18, 37, and 7 hr, respectively. The lack of a significant difference in the durations of cell‐cycle phases between G and nG explants suggests that nerve withdrawal does not influence the rate of progression through the cycle. A novel strategy was employed involving cell‐cycle suppression (denervation in vivo) and continuous labeling followed by restimulation with nerves in vitro, in anticipation that nerve‐dependent restricted cells will resume cycling. The data indicate that following prolonged denervation (48 hr), blastema cells may become refractory to neurotrophic factor.
Regional differences in the distribution of myogenic and chondrogenic cells in axolotl limb blastemas
Authors: Cameron Jo Ann , Hinterberger Timothy J.
Published: June 2005

The distribution of myogenic and chondrogenic cells was determined for axolotl limb blastemas at the medium bud stage, before precartilage condensation occurred. Myogenic potential of midstylopod (upper) and distal‐zeugopod (lower) amputation level blastemas, divided into distal, proximal‐core, and proximal‐peripheral regions, was assayed in vitro. Significantly more myonuclei were observed in upper level proximal‐periphery cultures than in ones from any of the other regions. Since cartilage cells give rise almost exclusively to cartilage in the regenerate (Steen, 1968), a heritable cell marker, triploidy, was used to trace the location of chondrogenic cells in histological sections of upper level early and medium bud blastemas. Although there was mixing of the graft cartilage‐derived cells and host soft‐tissue‐derived cells, the previous cartilage cells were found more frequently within the core region at early and medium bud stages. The results of these studies indicate that more chondrogenic cells are present in the core from a very early stage, and that more myogenic cells are present in the proximal periphery by the medium bud stage.
Reconstruction of a thyroid gland equivalent from cells and matrix materials
Authors: Bell E. , Moore H. , Mitchie C. , Sher S. , Coon H.
Published: June 2005

A living thyroid gland equivalent has been fabricated with a cultivated strain of rat thyroid cells (FRTL), dermal or thyroid fibroblasts, and matrix materials. The mixture becomes tissuelike in vitro by virtue of interactions between fibroblasts and collagen. Initially in vitro the thyroid cells are uniformly distributed as single cells and a small number of clusters containing less than 10 cells. When implanted into thyrodectomized hosts the thyroid cells in the tissue lattice become organized into follicles containing a colloidlike material. The follicles were found in clusters in sizes up to 0.3 mm. The clusters are vascularized. It is thought that they arise within clones rather than by an aggregation process. Using an antithyroglobulin antibody it was shown that both thyroid cells and the colloidlike material within follicles reacted positively. Development of follicles was strictly dependent on whether hosts were thyroidectomized. In nonthyroidectomized hosts no follicles were observed. We conclude that an organotypic structure can develop in vivo from a “gland‐equivalent” fabricated with adult cells and matrix materials combined in vitro, and that cells cultivated for years in vitro retain the capacity to express differentiated functions in a reconstituted organ equivalent in vivo.
Peptidergic pathways in the avian brain
Authors: Blähser Sabine
Published: June 2005

The results obtained by topographical studies on the immunoreactive peptide systems in the embryonic and adult avian brain (domestic fowl, domestic mallard, pigeon, Japanese quail, and zebra finch) can be realized only by means of phylogenetical comparisons. The comparative studies mainly demonstrate a fascinating constancy of the immunological properties and the spatial distribution of the neuropeptides. Independent of the development of the neopallium, and the increasing cerebral complexity, the spatial distribution of the neuropeptides, the location of their main perikaryal accumulations which are interconnected by immunoreactive fiber projections (and thereby forming widespread but continuous peptide systems) remain nearly unchanged during vertebrate evolution. The recognition of the neuropeptides as integral parts of the central nervous system is demonstrated by the fact that neuropeptidergic structures connect sensory inputs with central nervous areas as well as with the peripheral endocrinium.
Immunohistochemistry of the hypothalamic neuropeptides and anterior pituitary cells in the Japanese quail
Authors: Mikami Shin‐Ichi , Yamada Shizuhiro
Published: June 2005

The pars distalis of the avian adenohypophysis consists of well‐defined cephalic and caudal lobes which are distinct in their cellular constituents. Immunocytochemical investigations on the pituitary hormones of the pars distalis of the Japanese quail reveal five types of secretory cells, adenocorticotropin (ACTH) cells, prolactin (PRL) cells, thyroid‐stimulating hormone (TSH) cells, growth hormone GH (STH) cells, and FSH/LH (gonadotropic) cells. The ACTH cells, TSH cells, and PRL cells are restricted to the cephalic lobe, and GH (STH) cells are confined to the caudal lobe, while FSH/LH cells are distributed throughout the cephalic and caudal lobes.

The median eminence of birds has distinct anterior and posterior divisions, each with different neuronal components. The avian hypophysial portal vessels also consists of two groups, anterior and posterior. The peculiar arrangement and distribution of the avian hypophysial portal vessels are possibly related to the distribution of neuropeptides in the two divisions of the median eminence and to the cytological and functional differentiation of two lobes of the pars distalis.

The localization of perikarya and fibers containing luteinizing hormone releasing hormone (LHRH), somatostatin, vasotocin, mesotocin, corticotropin‐releasing factor (CRF), vasoactive intestinal polypeptide (VIP), glucagon, metenkephalin, and substance P in the hypothalamus and median eminence of the Japanese quail has been investigated by means of immunohistochemistry using antisera against the respective neuropeptides. LHRH‐, somatostatin‐, VIP‐, met‐enkephalin‐, and substance P‐immunoreactive fibers are localized in the external layer of the anterior and posterior divisions of the median eminence, while CRF‐ and vasotocin‐reactive fibers are demonstrated only in the external layer of the anterior division of the median eminence. The metenkephalin fibers are thicker in the anterior median eminence but the substance P fibers are more abundant in the posterior division. Mesotocin fibers occur only in the internal layer of the median eminence and neural lobe.
Ontogeny of hypothalamo‐adenohypophyseal‐gonadal (HAG) interrelationships in the chick embryo
Authors: Woods James E. , Thommes Robert C.
Published: June 2005

In the male chick embryo the components of the hypothalamo‐adenohypophyseal‐testicular axis initially function independenty of each other. It is not until days 12.5–13.5 that the adenohypophysis begins to regulate testosterone synthesis and secretion; on day 13.5 plasma testosterone reaches a maximum embrynic level. This feed forward regulation of the pituitary‐testicular unit appears to involve a cause and effect relation between a statistically significant increase in the number of testicular interstitial cell LH receptors on days 12.5 and 13.0 and anincrease in plasma LH levels on day 13.5 (up‐regulation). Subsequently, events occur that are interpreted as indicative of the feedback phase of this endocrine axis. Plasma LH levels decrease after day 13.5. Also on day 13.5 and al subsequent embryonic days, there is a significant decline in the volume density of testicular LH receptor‐positive interstitial cells (IC) associated with an internalization of the LH receptor complexes and a marked decline in plasma testosterone levels (down‐regulation). It is strongly suggested that the decline in the number of LH receptor‐positive ICs and the internalization of the LH receptor complexes in indicative of a “desensitization” of the ICs followed by a decrease in testosterone synthesis and secretion. Comparable events that occur in the female embryo with respect to the development of the hypothalamo‐adenohypophyseal‐ovarian axis are also discussed in this minireview.
Thyroidal influence on body growth
Authors: King David B. , May James D.
Published: June 2005

This review of thyroid influence on body growth in poultry is organized around the following parameters of growth: 1) increase in body weight and skeletal size, 2) muscle growth, and 3) growth of cartilage and bone. The greatest effect of goitrogens on growth of embryos occurs during late embryogenesis at a time when normal thyroid hormone levels are increasing. Posthatching growth is reduced in severely hypothyroid animals, and body weight gain is affected more than bone growth. Thyroid hormone replacement restores body growth of thyroidectomized chickens, but supplemental hormone in normal animals has no beneficial effect on growth. Excessive T3 (fed at 1 ppm) is detrimental to growth and feed efficiency. No clear correlation between thyroid hormone concentration and growth rate of normal chickens has been identified. Growth depression in sex‐linked dwarf birds is at least partially reversed by supplemental T3. Muscle growth is reduced in goitrogen‐treated chickens and the growth reduction is reversed by supplemental thyroxine. Total DNA accumulation is reduced in hypothyroid chickens, but muscle mass relative to DNA content is normal following long‐term treatment; this suggests some regulation of muscle mass relative to DNA content. T3 increases the number of muscle fiber nuclei in hypothyroid chickens and the uptake of 3H‐thymidine into nuclei within the basal lamina. T3 directly stimulates growth and maturation of embryonic chick cartilage and enhances the in vitro action of somatomedins on cartilage growth. There is little information concerning the role of the thyroid in posthatching cartilage and bone growth in poultry.
Aspects of the neuroendocrine control of ovulation and broodiness in the domestic hen
Authors: Sharp Peter J. , Macnamee Michael C. , Talbot Richard T. , Sterling Robert J. , Hall Terence R.
Published: June 2005

The neuroendocrine control of ovulation and broodiness in the domestic hen involves complex interactions between hypothalamic neuropeptides, neurotransmitters, and ovarian steroids which regulate the secretion of luteinizing hormone (LH) and prolactin. Nuclear progesterone receptor is localized in many neurons throughout the hypothalamus but is absent from LHRH neurons. Hence, the positive feedback action of progesterone on LH release is not mediated by a genomic mechanism within the LHRH neuron. Precursors of 5‐hydroxytryptamine (5HT) and dopamine (Da) inhibit the preovulatory release of LH, while the turnover rates of these neurotransmitters in the anterior hypothalamus decrease when preovulatory levels of LH are at their highest. Further, a population of receptors for 5HT which occurs in the anterior hypothalamus in laying birds is absent in nonlaying, incubating hens. Taken together, these observations suggest that the preovulatory surge of LH is mediated by a transitory decrease in the inhibitory action of 5HT and possibly DA, on the secretion of LHRH. Neurons containing 5HT may play a role in the regulation of prolactin release and, more specifically, in the control of broodiness. Drugs which enhance the function of 5HT neurons stimulate prolactin release while increased prolactin secretion in incubating hens is associated with an increase in the turnover of 5HT in the anterior hypothalamus. No receptors for 5HT were demonstrable in the anterior pituitary gland, showing that the prolactin‐releasing activity of 5HT must be mediated by a prolactin‐releasing factor (PRF). A candidate for a physiological PRF is vasoactive intestinal polypeptide (VIP). Cell bodies containing VIP are abundant in the basal hypothalamus and have terminals in the median eminence. Further, VIP stimulates prolactin release in incubating hens both in vivo and in vitro and this response of the pituitary gland to VIP is enhanced after “priming” with estrogen. Dopamine may also play a role in the regulation of prolactin release in incubating hens. When plasma prolactin levels are high, DA exerts an inhibitory effect on prolactin release. It is suggested that the secretion of prolactin in incubating hens is regulated by a short‐loop feedback mechanism which stimulates the turnover of hypothalamic DA.
Steroidogenesis in granulosa cells during follicular maturation: Evidence for desensitization‐resensitization during the ovulation cycle
Authors: Hertelendy F. , Asem E. K.
Published: June 2005

Output of progesterone, the end product of the steroidogenic pathway, was studied in isolated chicken granulosa cells in relation to follicular maturation and during the ovulation cycle with particular reference to the period between the LH peak and ovulation. The evidence gathered from a series of experiments conducted during the past 2–3 years in the authors' laboratory indicate that the steroidogenic capacity of granulosa cells during follicular maturation is regulated not so much by receptors‐coupled adenylatete cyclase activity as has been proposed by other investigators, but by the activity of key steroidogenic enzymes, particularly the cholesterol 20,22 demolase. Furthermore, granulosa cells undergo cyclic sensitization following the endogenous LH surge reaching maximal responsiveness about 1 hr before oviposition. This is followed by a rapid desensitization shortly before ovulation. This desensitization extends to the second and subsequent developing follicles probably in proportion to the evolving LH receptors. It is suggested that granulosa cells remain in such a desensitized state for several hours postovulation, during which time progesterone responses to LH are attenuated and consequently ovulation does not occur prematurely. It is proposed that this intraovarian mechanism is an important component of the physiological events that regulate the ovulation cycle in the domestic fowl.
Regulation of prolactin and its role in gallinaceous bird reproduction
Authors: El Halawani M. E. , Burke W. H. , Millam J. R. , Fehrer S. C. , Hargis B. M.
Published: June 2005

There are major changes in ciruclating luteinizing hormone (LH), prolactin (PRL), estrogens (E), and progesterone (P) in relation to the onset of reproduction, egg laying, incubation, and care of young. LH levels increase in the prelaying period, followed some days later by increased circulating levels of E, P, and PRL. Levels of these hormones tend to stabilize during egg laying with periodic ovulatory cycle changes. Around the onset of incubation PRL levels increase, while LH, E, and P levels fall. During incubation PRL reaches very high levels, falling sharply when incubation is terminated. Stimulatory effects of hypothalamic neurotransmitters, peptides, and ovarian steroids on PRL secretion have been shown. The prelaying increase is dependent on E and P and the high levels of incubation require a functional serotonergic system. The causal relationships and roles of PRL in incubation of gallinaceous birds are, however, still unclear.
Is the avian circadian system a neuroendocrine loop?
Authors: Cassone Vincent M. , Menaker Michael
Published: June 2005

Avian circadian organization is a result of a complex interaction of photoreceptive and oscillatory components. The known components include the pineal gland, the lateral eyes, the suprachiasmatic nuclei (SCN), and extraocular brain photoreceptors. The pathways by which these components integrate circadian rhythmicity suggest a neuroendocrine loop in which the SCN inhibits pineal and ocular oscillators during the course of subjective day via a multisynaptic neuronal pathway which includes the superior cervical ganglia (SCG). During the night, the pineal in turn inhibits SCN activity via its secretion of the hormone melatonin into the blood circulation. This neuroendocrine loop, it is proposed, synchronizes multiple oscillators within each component and maintains the stability and precision of the system.
Adrenal gland: Some evidence for the structural and functional zonation of the steroidogenic tissues
Authors: Holmes W. N. , Cronshaw James
Published: June 2005

There are two regions of steroidogenic tissue in the bird adrenal gland: a subcapsular zone (SCZ) 40–60 cells thick consisting of cells with irregularly shaped nuclei, relatively little smooth endoplasmic reticulum, and mitochondria with shelflike cristae that surrounds an inner zone (IZ) of tissue comprised of smaller cells with rounded nuclei, a more abundant endoplasmic reticulum, and mitochondria with tubular cristae. The cristae in the mitochondria of IZ cells, but not hte SCZ cells, seem to be quite labile and only assume the tubular configuration when subjected to corticotropic stimulation. The properties of the steroidogenic cells in the two zones are quantitatively distinct, the cells of the SCZ producign relatively more aldosterone and relatively less corticosterone than the cells of the IZ. The corticotropic responsiveness of the IZ cells is dependent on the synthesis of protein in the cytoplasm and a normal pattern of microfilament assembly. The dose responsiveness of both the IZ and the SCZ cells in vitro is a complex quadratic function of the corticotropin concentration to which they are exposed; the semilogarithmic linear response to corticotropin is restricted to a narrow midrange of concentrations, and at high concentrations cells from both zones of the gland respond submaximally. Throughout the dose‐response range, however, the steroidogenic cells of the IZ are more sensitive and more responsive to corticotropic stimulation than are the cells of the SCZ.
Stress and adrenal function
Authors: Harvey S. , Phillips J. G. , Rees A. , Hall T. R.
Published: June 2005

The natural environment is composed of various potentially hostile stressors. It is a basic requirement of life that the cells of an organism must be maintained within closely defined physiological limits. The maintenance of a constant interior mileu results from physiological and behavioural homeostatic adaptations. The physiological regulation of homeostatis is achieved by complex endocrine interactions, principally by the hormones secreted from the adrenal glands. In this brief review the responses of the avian adrenal glands to stressful stimuli, the mechanism of adrenal activation, and the function of the adrenal responses will be considered.
Pancreatic hormones, insulin/glucagon molar ratios, and somatostatin as determinants of avian carbohydrate metabolism
Authors: Hazelwood Robert L.
Published: June 2005

The endocrine pancreas of birds contains cell populations similar, if not identical, to those found in mammalian pancreata, although the topographical distributions of these cell types differ to some extent. Insulin‐secreting (b) cells, glucagon‐secreting (a) cells, somatostatin‐secreting (D) cells, and pancreatic polypeptide‐secreting (PP or F) cells are distributed unequally among the four pancreatic lobes, with most of the A cells located in the third and splenic lobes and PP cells residing in both islet tissue and in acinar tissue. Glucagon appears to be a (the?) major pancreatic hormone involved in metabolic glucoregulation in birds. Yet the essentiality of insulin for this regulatory purpose also has been established. As a result, current thought is directed toward the molar ratio of insulin to glucagon (I/G) as a dominant force in homeostasis rather than toward either of the two hormones separately. Molar I/G ratios have been useful in mammals in studying the needs of the organism to produce glucose to meet a metabolic crisis/need and, when compared with that found in normal Aves, a value of 1.8–2.2 has been established. Such a molar ratio is indicative of a catabolic recovery of nutrients in mammals, suggesting that birds normally are in a catabolic mode (like diabetic, starving, or exercising mammals). Somatostatin (SRIF) is known to inhibit the release of all pancreatic hormones but has a greater inhibitory action on glucagon secretion than it does on any of the other peptides. (It has least effect on APP.) Recent studies have provided evidence indicating that SRIF may be very important in Aves in regulating the I/G molar ratio appropriate for the metabolic condition present at any given time. Such “fine tuning” of the endocrine pancreas by SRIF would allow the appropriate hormone mixture to be released against any metabolic background to effect carbohydrate homeostasis.
Gastrointestinal hormones in birds: Morphological, chemical, and developmental aspects
Authors: Rawdon B. B.
Published: June 2005

Historically, the enterochromaffin cell was the first endocrine cell type detected in avian gut; subsequently, a number of types of such cells were distinguished on the basis of the ultrastructural features of the secretory granules. More recently, immunocytochemical procedures have revealed somatostatin‐, pancreatic polypeptide (PP)‐, polypeptide YY‐, glucagon‐, secretin‐, vasoactive intestinal peptide (VIP)‐, gastrin‐, cholecystokinin‐, neurotensin‐, bombesin‐, substance P‐, enkephalin‐, motilin‐, and FMRFamide‐like immunoreactivity in avian gastrointestinal endocrine cells. Most endocrine cells are located in the antrum; there are a number in the proventriculus and small intestine but few in the gizzard, cecum, and recum, Several avian gastroenteropancreatic hormones, including glucagon, VIP, secretin, bombesin, neurotensin, and PP, have been isolated and sequenced. They resemble the equivalent mammalian peptides in terms of molecular size but differ in amino acid composition and sequence; some (e.g., VIP) differ only in minor respects, others (e.g., secretin) more radically. Gastrointestinal endocrine cells appear late in development; available data indicate that few types are recognized by either immunocytochemistry or electron microscopy before 16 days of incubation. Experimental evidence has shown that at least the majority of gut endocrine cells are of endodermal origin and are not derived from the neural crest or neuroectoderm as earlier proposed. In early embryos, the progenitors of gastrointestinal endocrine cells are more widespread than are the differentiated cells in chicks at hatching. This, along with other observations, raises the question of factors that might influence the differentiation of gut endocrine cells.