Yolk Sac Contents Research Articles

Early administration of antibiotics to turkey poults deteriorates maternal immunity and impairs post-vaccination antibody synthesis

Abstract It was assumed that early antibiotic administration can slow down yolk sac resorption and decrease maternal antibody transfer and lysozyme levels in the yolk sac content and serum, meaning that disrupting the development of humoral immunity in turkeys. The experiment was conducted on female turkeys divided into following group: CON (control) – received no coccidiostat or antibiotics, MON – received monensin in the feed for 56 days; ENR and DOX – received enrofloxacin or doxycycline per os for the first 5 days of life. Additionally, half of the birds in each of this group were vaccinated against turkey rhinotracheitis (TRT) the disease caused by avian metapneumoviruses (aMPV) and Newcastle disease caused by Newcastle disease virus (NDV) at the first day of life (IN), and against omitobacteriosis caused by Ornithobacterium rhinotracheale (ORT) at 28 day of life (SC). On days 1, 3 and 5 of the birds' lives, yolk sacs were collected to assess their resorption. Yolk sac resorption was assessed by calculating yolk sac relative weight based on the measurement of the yolk sac mass and body weight of turkeys. On days 1, 3, 5, 7 and 56, blood was collected to assess anti-aMPV, anti-NDV, anti-ORT antibody titers and immunoglobulin and lysozyme levels. Early administration per os of ENR and DOX or feeding diets containing MON did not inhibit yolk sac resorption, but reduced levels of specific maternal anti-aMPV, anti-NDV and anti-ORT antibodies and IgY and IgM in the yolk sac. Enrofloxacin and doxycycline decreased the titers of anti-aMPV and anti-NDV antibodies and the level of maternal IgY and IgM in turkeys, which could be due to the direct effect exerted by antibiotics on maternal antibodies present in the circulatory system of poults and the inhibition of post-vaccination synthesis of specific antibodies. The administration of antibiotics in the early rearing period should only be implemented in situations of clearly confirmed disease states when the expected health benefits outweigh the risk of weakening immunity.

Cellular and humoral immunity of broilers subjected to posthatch fasting and a prestarter diet containing conjugated linoleic acid

This study aimed to evaluate the immunity of chickens up to 35 d subjected to posthatch fasting and supplementation with conjugated linoleic acid (CLA). A total of 320 chicks were housed in a completely randomized design with a 2×2 factorial arrangement (0 or 12 h of fasting×0.000 or 0.025% CLA in a prestarter diet), totaling 4 treatments (No-F-12 h; F-12 h; No-CLA; CLA) with 8 replicates of 10 birds each. The relative weights (% body weight) of the spleen and bursa were determined 12 h posthatch (Post-12 h) and then weekly. Immunoglobulin Y (IgY) titers against Newcastle disease virus (NDV) were measured by ELISA in the yolk sac contents Post-12 h and in the serum weekly. Hypersensitivity to phytohemagglutinin (PHA) inoculation was evaluated by toe-web swelling response on d 13 and 34, 4 times a day (after 3 h, 6 h, 12 h, and 24 h inoculation, respectively, PHA-3 h, PHA-6 h, PHA-12 h, and PHA-24 h). The data were subjected to analysis of variance (P < 0.05). F-12h reduced the Post-12 h relative weight of the spleen, and CLA reduced the relative weight of the bursa at this stage and at 28 d. At 13 d, F-12 h reduced PHA-3 h, whereas PHA-12 h was increased by CLA. At 34 d, CLA reduced PHA-3 h. A greater reaction was observed in the No-F-12 h-CLA chicks, for the PHA-24 h. In the Post-12 h evaluation, F-12h reduced, whereas CLA increased NDV-specific IgY titers in the yolk sac. No-F-12 h-No-CLA chicks had the lowest serum titers. At 21 d, F-12 h-CLA chicks exhibited the highest serum titers. Titers were higher in the F-12 h-No-CLA chicks, when compared to other treatments. At 28 d, fasting reduced the titers. In conclusion, F-12 h and CLA accelerated the transfer of immunoglobulins from the yolk sac to the serum. F-12 h impairs cellular immunity, whereas CLA favors it.

Characteristics of Escherichia coli isolated from broiler chickens with colibacillosis in commercial farms from a common hatchery

To investigate the epidemiologic aspects of colibacillosis in broiler chickens, 83 Escherichia coli isolates obtained from the pericarditis and perihepatitis lesions in broiler chickens from 4 commercial farms, 5 isolates recovered from 5 samples of yolk sac contents that were pooled from 25 emaciated chicks, and 4 fecal isolates obtained from a hatchery that supplied chicks to the 4 commercial farms mentioned above were genetically and bacteriologically characterized. Using pulsed-field gel electrophoresis (PFGE), a total of 92 isolates were classified into 33 pulsotypes. Identical pulsotypes were observed in isolates obtained from hatchery samples and the affected broiler chickens on multiple farms at various sampling times. Seventeen representative isolates with no common origin belonging to 6 pulsotypes and an additional 27 isolates with the other pulsotypes were used for further experiments. Isolates with identical pulsotypes exhibited common traits for virulence-associated genes, lipopolysaccharide core types, and phylogenetic groups. Nine of the isolates were serologically typed as O125 with various types of H antigens and 3 were typed as O25:H4. In the 27 isolates resistant to ceftiofur (CTF), which is a third generation cephalosporin, the blaCTX-M-2, blaCMY-2, blaCTX-M-14, blaCTX-M-65 genes were found in 15, 8, 3, and 1 isolate(s), respectively, and another isolate resistant to CTF had both the blaCTX-M-2 and the blaCMY-2 genes. In the 16 isolates with the blaCTX-M-2 gene, the chromosomal location of the gene was identified in 12 isolates. The plasmid-mediated quinolone resistance genes, oqxAB and aac(6')-Ib-cr, were found in 2 and 3 isolates, respectively. Conjugation experiments revealed that the blaCTX-M-2 (4 isolates), blaCTX-M-14 (3 isolates), blaSHV-12 (1 isolate), and oqxAB (2 isolates) genes were transferred. Our data suggest that E. coli strains with identical pulsotypes had been caused the incidences of colibacillosis and that the antimicrobial resistance genes on conjugative plasmids and those integrated into the chromosome may be spread among avian pathogenic E. coli strains in multiple farms.

Effect of egg weight on composition, embryonic growth, and expression of amino acid transporter genes in yolk sac membranes and small intestines of the domestic pigeon (Columba livia)

The objective of this study was to investigate the effect of egg weight on the composition of the egg, the growth of the embryo, and the expression of amino acid transporter genes in the yolk sac membranes and small intestines of the domestic pigeon (Columba livia). A total of 240 fertilized eggs were collected and divided into two groups based on the weight of the eggs, light (LE) and heavy (HE). The composition of 20 eggs from each group was measured, and the remaining eggs were weighed and placed in an incubator. On embryonic days (E) 9, 11, 13, and 15 and day of hatch (DOH), 15 embryos/hatchlings from each group were measured for embryonic growth, and samples were collected. The HE had heavier yolk and albumen weights than the LE (P < 0.01). Compared with the LE, the HE had heavier yolk-free embryonic body and yolk sac weights from E13 to DOH (P < 0.05). Additionally, the HE had larger yolk sac membrane weights from E13 to E15 (P < 0.05) and had more residual yolk sac content on DOH than those of the LE (P < 0.01). The yolk absorption was greater for the HE than for the LE from E11 to E13 (P < 0.05). Furthermore, the abundance of CAT2 and PepT1 mRNA in the yolk sac membranes was greater in the HE than in the LE on E13 (P < 0.05). Compared with the LE, the gene expression of EAAT2 in the intestine on E13 was greater in the HE, whereas the expression of EAAT3 was lower in the HE (P < 0.05). Taken together, our results suggest that egg weight influenced the composition of the eggs, embryonic development, and expression of amino acid transporter genes in the yolk sac membranes and small intestines of pigeon embryos.

Changes in yolk sac membrane absorptive area and fat digestion during chick embryonic development

The capacity of yolk sac (YS) utilization by the chick embryo may be affected by structural changes in the YS membrane (YSM) and by the mechanisms within its cells for digestion, absorption, and transfer of nutrients. Two experiments were conducted to examine structural and digestive changes in the YS of the broiler chick embryo; weights of embryo, YS, and YSM, as well as the total area of the YSM and the absorptive area of the YSM, were measured between embryonic day (E) 5 and E21. In addition, fat content, lipase activity, and bile acid concentration in the YSM and YS contents (YSC) were measured between E11 and E21. Results showed that YSM weight increased from 0.19 g on E5 to 6.46 g on E15, and decreased by 3.74 g between E17 and E21. The absorptive YSM area increased from 536 mm² on E5 (51% of total YSM area) to 6,370 mm² (86% of total area) on E17, and decreased to 4,439 mm(2) on E21 (85% of total area). The smaller YSM area between E17 and E21 did not decrease the rate of YS fat utilization, which could suggest that YSM mechanisms for fat absorption, digestion, and secretion increased during that period. Total YSM lipase activity relative to fat content (units per g of YSM fat) increased from approximately 1,000 units on E15 to 1,500 units on E21. The detection of lipase in the YSM lends support to the hypothesis that YS lipids are hydrolyzed in the lipolysosomes of the YSM. The current study also confirmed for the first time that bile acids are present in the YS, with levels that ranged from 0.61 to 1.06 µmol/g in the YSM, and may suggest that bile is synthesized in the YSM of the chick embryo. Results of the current study contribute to our understanding of the developmental changes that affect YS functionality and could give insight into the coordination between the embryo's demands and YSM morphological, absorptive, digestive, and secretive changes.

Transfer of Chicken Immunoglobulin Y (IgY) from the Hen to the Chick

Chicks depend on maternal antibodies as the main source of passive natural humoral protection until they become immunocompetent. Immunoglobulin Y (IgY), the avian homologue of mammalian IgG is transferred from the circulation of the hen into the egg yolk and then absorbed by the embryo. In the post-hatching period, protein integrity within the yolk sac is critical for normal absorption of the yolk sac content and for IgY transfer to the circulation of the chick. Factors affecting transfer of IgY to the chick may threaten the chick's immune status and increase disease susceptibility during the early post-hatching period. Here we review basic concepts of IgY with special emphasis on the mechanisms of IgY transfer to egg yolk and yolk sac during embryonic development and first days post-hatching.

Effects of in ovo Administration of L-carnitine on Hatching Events and Juvenile Performance of Layer-type Chick

The effects of in ovo injection of L-carnitine on hatchability and juvenile performance of 360 layer- type chicks were investigated. Fertilized eggs were injected in air chamber with L-carnitine (500 and 1000 µmol) dissolved in 0.9% of Saline (NaCl) at d 18 of incubation. Two control groups (non-injected and injected with 0.9% of Saline were also included. Hatched chicks was recorded after every 4 h, beginning at 490 h of incubation and ending at 514 h, for incubation length and hatching spread determination. At the end of incubation, hatched chicks were recorded according to treatment for determination of hatchability. At 3, 7 and 14 d post-hatch, chick body weight (BW) and morbidity were recorded. Also, at d 3 and 7 post-hatch, 14 birds from each of 2 replicate groups within each treatment were used for intestine and yolk sac weight determination. Results indicate that BW, hatchability, or relative intestine weights were not affected by treatment. However, incubation length was longer while hatching spread was shorter in L-carnitine groups compared to control groups. Yolk sac relative weight was decreased by treatment with L-carnitine (P < 0.05). Also, the percentage of chicks showing morbidity sign was lower in L-carnitine treated groups from d 7 onwards. The results of the present study suggest that in ovo injection of L-carnitine at d 18 of incubation delayed hatching time but resulted in narrower hatching spread, faster utilization of yolk sac content and improved morbidity.

Evidence that maternal conjugated linoleic acid negatively affects lipid uptake in late-stage chick embryos resulting in increased embryonic mortality

An experiment was performed to determine the effect of maternal dietary conjugated linoleic acid (CLA) on growth and composition of surviving chick embryos and residual yolk sacs during the last week of development when lipid utilization becomes prevalent. After 14 d on experimental diets, hatchability of non-cooled eggs obtained from CLA-fed hens (0.5% of the diet) was 10%, where 20% of surviving CLA embryos died after d 13 of incubation. Hatchability was 93% for controls and only 4.36% of mortality occurred after d 13 of incubation. Decline in yolk sac weight in control embryos (0.75 g/d) was significantly greater than that from viable CLA embryos (0.51 g/d). Growth rate (2.6 g/d) of surviving embryos from d 13 to 20 was reduced in CLA embryos in comparison to growth rate of controls (3.0 g/d). Relative proportion of lipid in residual yolk sacs in embryos from control-fed hens decreased from 26.72% (d 13) to 15.94% (d 19) during incubation, whereas little change was evident in residual yolk sac from CLA embryos on d 13 (21.52%) to d 19 (20.39%). Fatty acid analysis of residual yolk sac contents suggested that transport of fatty acids from the contents (liquid yolk) to the yolk sac membrane was not impaired in CLA embryos, as shown by a similar pattern in reduction of total fatty acids in residual yolk sac contents between treatment groups. Apart from 18:1n-9 (d 17), there were no consistent differences in the fatty acid content between embryos from hens fed the control diet or the CLA diet at any time point. Maternal CLA led to increased 18:0 and decreased 18:1n-9 in yolk lipid and embryonic tissues compared with controls across time. These findings could possibly suggest that CLA embryos had less capacity to use yolk lipids from the residual yolk sac during the last week of incubation.

Dynamics of yolk sac content absorption and intestine development in ducklings fed mixtures with increasing dietary methionine level

The experiment was carried out with ducklings fed-control feed mixture (Met level 0.3%) and mixtures supplemented with dl-methionine at the dose of 0.03 (II); 0.07 (III) 0.12 (IV) and 0.18% (V). In 5 h post-hatch (12 birds) and on days 3, 4, 6 always 18 birds were taken out from each treatment and killed, then the yolk sac (YS) and intestine were removed. The weight and chemical composition of YS residues (in them also amino acids) were analysed. Moreover on days 1, 3, 4 and 6, the amino acid pattern of YS residual protein was elaborated as well as length and weight of intestine were recorded. Increased doses of supplemental Met improved body weight gain after 4 days of ducklings life. All determined parameters were not affected by treatment. Development of intestines, yolk sac weight and yolk sac composition (DM, fat, protein, amino acid composition) changed with age; however, without any clear effect from dietary methionine level. No differences between sex and analysed parameters were stated.

The effects of dietary conjugated linoleic acid alone or incombination with linoleic acid and oleic acid on fatty acid composition of egg yolk, embryo mortality and chick yolk sac content retention in chickens

Conjugated linoleic acid (CLA) reduced the level of C18:1( n − 9) and increased the level C18:0 in yolk, which in turn was associated with embryo mortality. C18:1( n − 9) was reported to play an important role in chick embryo development. Therefore, the objective was to determine if the reduction in the level of yolk C18:1( n − 9) was responsible for CLA-related embryo mortality. Eight chickens per treatment were fed diets containing 5 g/kg linoleic acid (LA), 5 g/kg CLA, 5 g/kg CLA plus 30 g/kg linoleic acid (CLA + LA) or 5 g/kg CLA plus 30 g/kg oleic acid (CLA + O) for 13 d. Chickens were artificially inseminated weekly. Eggs were collected daily, held at 15 °C for 24 h and then incubated. Hatched chicks were killed within 24 h and body and residual yolk weights were measured. For fatty acid analysis, three eggs from each treatment were collected on day 8. After the seventh day of feeding, embryo mortality was 100% in the fertile eggs from the CLA group. Overall hatch (%) in the groups LA, CLA + LA, and CLA + O was 98, 94, and 91%, respectively. After the seventh day of feeding, CLA levels in yolks from the groups LA, CLA, CLA + LA, and CLA + O was 0.4, 2.6, 2.1, and 1.7 g/100 g, respectively. The ratio of C18:0/C18:1( n − 9) of yolks from the LA, CLA, CLA + LA, and CLA + O was 0.3, 0.9, 0.9, and 0.3, respectively. Adding O to diet (CLA + O) prevented CLA-induced decrease in yolk C18:1( n − 9) and increase in yolk C16:0 and C18:0. While C18:1( n − 9) was actually decreased 50%, C18:2( n − 6) was increased 42% in the yolk from the group CLA + LA compared to the group CLA + O. Egg yolks from hens fed CLA group had lower level of C20:4( n − 6) than the LA group (1.3 and 2.1 g/100 g, respectively). The O (CLA + O), but not LA (CLA + LA) appeared to prevent CLA-induced retain yolk in hatched chicks. These data, in light of previous reports, suggest that CLA-related embryo mortality is not associated with specific fatty acids (i.e. C18:1, n − 9 and CLA), but is related to changes in the ratio of saturated to unsaturated fatty acids.

Nutrition of the Developing Embryo and Hatchling

Nutrient needs central to satisfactory egg incubation well-being undergo several major changes from fertilization until the reliance of the chick on feed. Glucose is central, with the initiation of incubation until the chorioallantois accesses O2 to use for fatty acid oxidation. Nutrient recovery from albumen and yolk is largely commensurate with body assembly through to completion of the embryo by 14 d. Remaining albumen mixes with the amniotic fluid and is orally consumed until initiation of emergence. A portion of the albumen is absorbed by the small intestine to expand body glycogen reserves. The residual not absorbed contains digestive enzyme contributions and enters the yolk sac through its stalk at the jejunum and ileum. Interaction of the albumen-amnion digestive enzyme mixture with yolk sac contents leads to diverse alterations that influence subsequent use of lipids. Rapid removal of very low-density lipoprotein ensues, until pipping with triglycerides, expanding body fat depots while cholesterol deposits in the liver. A concurrent translocation of Ca from shell mineralizes the skeletal system while also crossing yolk sac villi for deposition on phosvitin-based granules accruing in its lumen. Loss of chorioallantois with pipping and the start of pulmonary respiration predispose a dependence on glycolysis to support emergence. Small intestinal villi progressively reorient their enterocytes from macromolecule transfer to competence at digestion and absorption after hatching. Mobilization of body fat complements contributions from the yolk sac to provide fatty acids for generating energy, heat, and water while also combining with hepatic cholesterol for membrane expansion and continued development. Calcified granules evacuate the yolk sac to further skeletal mineralization in the absence of shell contributions. Egg mass, its interior quality, and turning during early incubation directly influence the ability of the embryo to access nutrients and provide resources to support emergence and the transition of the chick to self-sufficiency.

Influence of environmental and nutritional stressors on yolk sac utilization, development of chicken gastrointestinal system and its immune status

The impact of practically all the everyday stress factors occurring in the first days of the chick life on the rate of the utilisation of the yolk sac content, on the chicken immune status and on the growth of the animal's body and intestinal masses was investigated. The impact of the stress was investigated during the first five days of chick's life. The chicks were divided into five groups, each comprising 44 birds. The first chick group was exposed to moderate cold (2–3°C below the optimal temperature for the chick age). The second group was exposed to moderate heat (2–3 °C above the optimal temperature for the age). The third and fourth group were deprived of feed and drinking water for 12 hours and 24 hour, respectively. The fifth chick group was the control group: the birds in this group had optimal environmental conditions and received feed and drinking water immediately upon entering the trial. Ten chicks were taken every day and weighed. Their blood samples were obtained for the assessment of infectious bursal disease virus antibody titres using ELISA method. After that, the birds were sacrificed, their intestinal masses weighed and the quantity of resorbed yolk measured.The greatest body and intestinal masses were found in the control animals. The body and intestinal masses were the lowest in the group which was denied water and food for 24 hours. The resorption of the yolk sac content was approximately equal in all the chick groups, but the resorption rate varied by days. The highest resorption was observed in the chick groups on the day when feed was denied to them, so that this high resorption could be associated with the bird's body energy requirements.The resorption of the remaining yolk is associated with feed intake: in chicks to which feed is withheld the yolk is resorbed through the yolk sac wall directly into the blood, which increased its usability. When energy requirements are not satisfied, the chick's body probably utilises resorbed antibodies from the yolk remnants, as their glycoprotein composition is suitable for this purpose.

Results of salmonella isolation from poultry products, poultry, poultry environment, and other characteristics.

Five hundred sixty-nine Salmonella were isolated out of 4745 samples from poultry products, poultry, and poultry environment in 1999 and 2000 from the Pacific northwest. These Salmonella were identified to their exact source, and some were serogrouped, serotyped, phage typed, and tested for antibiotic sensitivity. Food product samples tested included rinse water of spent hens and broilers and chicken ground meat. Poultry environment samples were hatchery fluff from the hatcheries where eggs of grandparent broiler breeders or parent broiler breeder eggs were hatched and drag swabs from poultry houses. Diagnostic samples were of liver or yolk sac contents collected at necropsy from the young chicks received in the laboratory. Of these samples tested, 569 were Salmonella positive (11.99%). Ninety-two Salmonella were serogrouped with polyvalent somatic antisera A-I and the polymerase chain reaction. Somatic serogroups B and C comprised 95.25% of all the Salmonella. Out of a total of 569 positive samples, 97 isolates of Salmonella were serotyped. A total of 16 serotypes and an unnamed Salmonella belonging to serogroup C1 were identified. The Salmonella serotypes were heidelberg (25.77%); kentucky (21.64%); montevideo (11.34%); hadar and enteritidis (5.15% each); infantis, typhimurium, ohio, and thompson (4.12% each); mbandaka and cerro (3.09% each); senftenberg (2.06%); berta, istanbul, indiana, and saintpaul (1.03% each); and an unnamed monomorphic Salmonella (2.06%). Ninety-two Salmonella were tested for drug sensitivity with nine different antimicrobials. All of the 92 Salmonella were resistant to erythromycin, lincomycin, and penicillin except one sample (S. berta), which was moderately sensitive to penicillin. All of the tested Salmonella were susceptible to sarafloxacin and ceftiofur. The percentages of Salmonella susceptible to sulfamethoxazole-trimethoprim, gentamicin, triple sulfa, and tetracycline were 97.83%, 92.39%, 86.96%, and 82.61%, respectively.

Changes in ion content and transport during development of embryonic rainbow trout

Wet mass and water content of four lots of whole eggs did not change throughout embryonic development of rainbow trout Oncorhynchus mykiss. Eggs in all four lots accumulated Na+. Eggs in lots 2 and 4 also accumulated Ca2+ and Cl‐, whereas eggs in lot 1 showed no significant change in Ca2+ or Cl‐ and eggs in lot 3 showed no change in Cl‐and a small loss of Ca2+. Although the Na+ content of embryonic tissues increases in the later stages of development, the yolk sac content remained constant, indicating uptake of Na+ from the environment. Na+ uptake by whole eggs was non‐saturable, consistent with diffusion of Na+ across the chorion into the perivitelline fluid. Na+ uptake in dechorionated embryos was saturable, as was Ca2+ uptake by both whole eggs and dechorionated embryos, consistent with active uptake or facilitated diffusion mechanisms at the surface of embryos. Very low Ca2+ uptake rates in dechorionated embryos suggest that the Ca2+ uptake mechanism is not fully developed until after hatching.

Effects of Delayed Placement and Used Litter on Broiler Yields

Male broiler chicks having either immediate or a 24-hr delayed access to feed and water after transportation from the hatchery were placed in floor pens having new or used pine shaving. All birds received common feeds not containing antimicrobials other than coccidiostats to 7 wk. Chicks experiencing delayed access had a 50% reduction in yolk sac contents compared to those placed earlier, reduced weight gain at 3 wk which was never recovered, and additional mortality Employing used litter also led to reductions in weight gain at 3 wk, but birds subsequently compensate. Broilers delayed in placement had reduced carcass weight and a decreased percentage of grade A's, but proportion of parts after cone deboning was unaffected. Although birds reared on used litter had carcass weight similar to those on new litter, bruised drumsticks were more apparent and the proportion of breast fillets increased at the expense of rib cage and frame, particularly with delayed placement. For the most part, the adverse effects of delayed placement were independent of those resulting from used litter.

Uterine specializations in elasmobranchs

The uterus of the elasmobranch demonstrates a variety of structural and physiological specializations associated with the mode of reproduction utilized by a particular species. Reproductive modes include (1) oviparity (Raja erinacea and Raja eglanteria), (2) aplacental viviparity, yolk sac variety (Squalus acanthias), with oophagy and intrauterine cannibalism (Carcharias taurus), and with trophonemata (Urolophus jamaicensis), and (3) placental viviparity (Rhizoprionodon terraenovae and Carcharhinus plumbeus). In oviparous species, the uterus harbors the egg capsule during capsule sclerotization and thereafter until oviposition, which in skates can be several days. The uterus is specialized for synthesis and secretion of materials that may contribute to capsule surface structure or chemistry or that may facilitate biochemical events associated with capsule polymerization, including provision of oxygen and elimination of water generated by the tanning reaction. In aplacental yolk sac species, as well as those species with oophagy and intrauterine cannibalism, the uterus functions as a respiratory membrane and a regulator of the ionic and osmotic environment (Squalus) but provides no supplemental nutrients to augment the yolk sac contents. In stingrays and placental sharks, however, the uterus assumes the additional function of providing nutrients to the developing embryos after the yolk stores have been depleted. Nutrient provision varies from uterine secretions of epithelial origin in the form of histotroph or uterine milk in stingrays to the transfer of material from the maternal vascular system in some placental sharks. Common features shared by all elasmobranchs include (1) increased vascularity of the uterine mucosa, (2) physiological maintenance of specific intrauterine ionic and osmotic environments in some species, (3) provision of secretory products, (4) increase in surface area for respiratory and metabolic exchange, (5) structural specializations of junctional complexes and intercellular spaces for fluid transport in some species, (6) thinning of the uterine epithelium to reduce the diffusion distance for respiratory exchange in stingrays, and (7) provision of nutrients in some viviparous species. J. Exp. Zool. 282:438–459, 1998. © 1998 Wiley-Liss, Inc.

Molecular characterization and phylogenetic relationships of a protein with potential oxygen-binding capabilities in the grasshopper embryo. A hemocyanin in insects?

Arthropodan hemocyanins, prophenoloxidases (PPOs), and insect hexamerins form a superfamily of hemolymph proteins that we propose to call the AHPH superfamily. The evolutionary and functional relationships of these proteins are illuminated by a new embryonic hemolymph protein (EHP) that is expressed during early stages of development in the grasshopper embryo. EHP is a 78-kDa soluble protein present initially in the yolk sac content, and later in the embryonic hemolymph. Protein purification and peptide sequencing were used to identify an embryonic cDNA clone coding for EHP. In situ hybridization identifies hemocytes as EHP-expressing cells. As deduced from the cDNA clone, EHP is a secreted protein with two potential glycosylation sites. Sequence analysis defines EHP as a member of the AHPH superfamily. Phylogenetic analyses with all the currently available AHPH proteins, including EHP, were performed to ascertain the evolutionary history of this protein superfamily. We used both the entire protein sequence and each of the three domains present in the AHPH proteins. The phylogenies inferred for each of the domains suggest a mosaic evolution of these protein modules. Phylogenetic and multivariate analyses consistently group EHP with crustacean hemocyanins and, less closely, with insect hexamerins, relative to cheliceratan hemocyanins and PPOs. The grasshopper protein rigorously preserves the residues involved in oxygen binding, oligomerization, and allosteric regulation of the oxygen transport proteins. Although insects were thought not to have hemocyanins, we propose that EHP functions as an oxygen transport or storage protein during embryonic development.

Utilization of the Sex-Linked Gene for Imperfect Albinism (S*ALS).: 2. Yolk Sac Lipid Utilization

The gene for sex-linked imperfect albinism (S*ALS) has been associated with reduced early growth and slow utilization of the yolk sac contents. Neonatal growth was studied using albino and nonalbino full siblings that were dissected at 2-d intervals from Day 16 of incubation to 7 d after hatch. Fatty acid composition of the yolk, yolk sac membrane, and liver was determined to study neonatal lipid metabolism. At hatch, albinos had similar BW and lower (P < 0.01) liver weights, suggesting reduced lipid transfer from the yolk sac during late incubation. Nonalbinos started gaining weight at 3 d after hatch, 1 d earlier than albino chicks. Albinos had reduced growth (P < 0.01), larger yolk sacs (P < 0.05), and similar (P > 0.05) yolk uptake from hatch to 7 d after hatch. Albino chicks also had lower body temperatures (P < 0.05) at 2, 4, and 6 d after hatch. Albinos had a slower rate of transfer of yolk lipids to the developing embryo in the last 2 d of incubation. The fatty acid composition of the yolk and yolk sac membrane was similar for both genotypes during the last 3 d of incubation, except for the level of stearic acid, which was higher (P < 0.05) for nonalbinos on Day 18 of incubation for both tissues and at 1 d after hatch for the yolk. The fatty acid composition of the livers of albinos and nonalbinos were similar (P > 0.05) during the neonatal period. For both genotypes, the hepatic level of oleic acid increased to Day 20 of incubation, remained constant to 1 d after hatch, and decreased sharply thereafter. The major difference between the genotypes was a slower rate of transfer of yolk lipids to the developing albino embryo in the last 2 d of incubation.

Ultrastructure of uterine trophonemata, accommodation for uterolactation, and gas exchange in the southern stingray, Dasyatis americana

The southern stingray, Dasyatis americana, displays aplacental viviparity, embryos being retained in the maternal uterus throughout gestation and initially nourished by the yolk sac contents. During gestation the uterus develops vascularized appendages, trophonemata, that secrete viscous nutrient histotroph that is subsequently ingested by the embryo as it grows to term. There is a 3750% increase in wet mass from the egg to the term fetus. Trophonemata are 1.5 cm long, narrower at the base, and spatulate at the tip. Surface epithelial cells form a pattern of surface cables, each with a small blood vessel at its core. In females containing fertilized eggs, the epithelium is simple and cuboidal. In contrast, in uteri containing late-term fetuses, the epithelium is squamous. Epithelial cells, with periodic acid – Schiff positive cytoplasmic vesicles, form invaginated crypts. Epithelial cells produce proteinaceous, mucous, and lipid secretions, thus we have coined the term uterolactation to describe this phenomenon.

Intubation of Weight-Selected Chicks with Soybean Oil or Residual Yolk: Effect on Early Growth and Development

Experiments were conducted to study the role of residual yolk on growth and development of chicks during the 1st wk after hatch. Surgical removal of the yolk sac at hatch reduced early body weight gains. Intubating chicks with a mixture of soybean meal and soybean oil or with residual yolk obtained from chicks at hatch increased body weights and enhanced development of the liver and pancreas. Whereas intubation with residual yolk reduced absorption of yolk sac contents, absorption was similar for chicks that consumed mash ad libitum or were intubated with the soybean meal-soybean oil diet. After cessation of yolk intubation, absorption of residual yolk resumed. Removal of the yolk sac decreased amylase and lipase activity in the pancreas. In the intestinal chyme, activity of amylase, trypsin, and chymotrypsin was reduced by yolk sac removal. Intubation with yolk increased enzyme activity (amylase excepted) in the pancreas or intestinal chyme only in chicks that had their yolk sacs removed. There was evidence that contents of the yolk sac did not enter the intestine via the yolk stalk, but were absorbed directly via the blood.