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The Obese strain (OS) of chickens spontaneously develops autoimmune thyroiditis several weeks after hatching, characterized by severe lymphoid infiltration and circulating thyroglobulin antibody. Sundick & Wick (1974) found that the thyroid glands of OS embryos and newly hatched chicks actually incorporated more 131I than normal controls when the parents of both groups were fed a Protamone-supplemented diet. Since this material-an iodinated casein containing thyroactive substances-drastically reduced thyroidal uptake of 131I several experiments were designed to compare OS and normal chicks free from these effects. In the first experiment the dietary supplementation of OS and normal hens were changed from Protanione to pure thyroxine and triiodothyronine. Their eggs were collected daily and incubated. The hatched chicks were tested for 20-hr 131I uptake and it was determined that 11-18 days after the food switch, the inhibition of uptake by Protamone was reversed, and the newly hatched OS chicks still had a significantly increased 20-hr 131I uptake when compared to the normal controls. Comparison of the offspring of a special hock of OS hens that lays without hormonal supplementation, with the parental Cornell C strain from which the OS is derived, similarly revealed a higher 20-hr 131I uptake by the OS (P < 0.005). The increased thyroidal uptake of OS was apparent as early as 4 hr after 131I administration and seemed to be independent of slight variations in the amount of 127I available to the chicks, and also seemed to be independent of maternally derived thyro- globulin antibody vertically transferred into OS chicks. These results suggest that an abnormality of the OS thyroid gland might be a prerequisite for the spontaneously occurring autoimmune thyroiditis in this strain. [ABSTRACT FROM AUTHOR]

On dispersal the seed of Acer platanoides contained a dormant embryo, from which dormancy could be removed by chilling but not by hormone application. Dormany was deep in the embryonic axis, particularly in the radicle, but less so in the cotyledons. Under the storage conditions employed the dormancy pattern was modified so that during the subsequent incubation at 20°C, cotyledon expansion of isolated embryos from stored fruits was more rapid than that of isolated embryos from newly dispersed fruits. In addition, the dormancy of isolated embryos from fruits stored for several weeks could be broken by incubation in kinetin. It was concluded that embryo dormany in this seed can be divided into two phases, an initial phase when the embryo responds to chilling but not to cytokinins, and a later phase when cytokinins also become effective. The relationship between this transition and the apparent gradual reduction in the depth of embryo dormancy during storage is also discussed. The chilling period necessary for dormancy breaking was reduced by kinetin and to a lesser extent by gibberellin, indicating a close relationship between the concentrations of these hormones and the chilling requirement. [ABSTRACT FROM AUTHOR]

The activities of trypsin inhibitors and Aspergillus‐proteinase inhibitors have been assayed in barley embryos germinating in different conditions. The Aspergillus‐proteinase inhibitor activity increased about 20‐fold during 6 days at 20°C both in separated embryos germinating on nutrient agar and in the embryos of undissected grains germinating on agar with or without mineral salts. Significant inhibitor activity was also present in root tips at later stages of vegetative growth. Whether any changes occurred in the molecular weight distribution of the inhibitors present in the seedlings was studied by gel filtration on Sephadex G‐75; only minor changes were observed. The trypsin inhibitor activity per seedling remained roughly constant in all cultures. In gel filtration experiments all the activity appeared to be due to the inhibitor species present in resting embryos. [ABSTRACT FROM AUTHOR]

Hypophysial tissue of mink (Mustela vison) embryos, newborn young and kits aged 1 day to 27 weeks was examined by light and electron microscopy. Among the embryos five different ontogenetic stages were distinguished. It appears that the primordium of the pituitary gland differentiates in early embryonic life. Several types of glandular cells containing variable amounts of granular material were recognizable by the time of birth. The role of the granular cells and the origin of the lumina in the pars distalis are speculated upon (in the Discussion). [ABSTRACT FROM AUTHOR]

A histochemical investigation on the content of ascorbic acid in chick embryonic tissues was undertaken using an improved technique. The concentration of ascorbic acid was found to be higher in the tissues which are involved in active biosynthetic mechanisms. Although the overall localization of ascorbic acid in intestine and proventriculus was less yet their secretory areas were rich in this vitamin. A significant successive increase in intensity of staining for ascorbic acid in the tissues from 15th to 21st day was evident from the data. The maximum ascorbic acid deposition was found in almost all the tissues of 21st day embryo as compared to the other age groups. This increase is correlated with the hatching process. [ABSTRACT FROM AUTHOR]

The phenylalanine-specific tRNAPhe from 13-day-old chick embryo muscle was purified. Its fluorescent and hydrophobic Y+ base was excised by mild acid treatment and characterized chromatographically and by its ultraviolet absorption and fluorescent spectra. The compound obtained after removal of the Y+ base from chick embryo tRNAPhe was characterized. 1. Chick embryo t RNAPhe looses by the removal of the Y+ base its phenylalanine acceptor capacity. 2. In this state it has a reduced sedimentation coefficient of 2.8 S. a low Tm value (22 °C), only rudimentary hyperchromicity, but unchanged electrophoretic properties. 3. The compound obtained after removal of the Y+ base from chick embryo tRNAPhe regains normal melting behaviour and phenylalanine acceptor capacity when exposed to special renaturation conditions. 4. The Km of the renatured form is 0.25 × 10-6 M and V = 220 pmol × min-1 × ml-1 as compared tO Km = 0.11 × 10-6 M and V = 370 pmol x min-1 × ml-1 for the native chick embryo tRNAPhe. [ABSTRACT FROM AUTHOR]

1. Chick embryo fibroblasts, that cease to grow after a finite number of passages in culture, have been cultured in the presence of radioactive D-glucosamine. Incorporation of radioactivity into cellular macromolecules is very similar for cells regardless of their position in the finite life span. 2. The labelled substances removed by trypsin from the surface of non-confluent cells growing in different parts of the life span were analysed. Smooth membrane fractions isolated from trypsinised cells were also compared. 3. The labelled substances were very similar, in particular the extent of sialylation of the total glycoprotein fraction of early phase or late phase cells. Minor differences were found, however. 4. It was found that mucopolysaccharides constitute a larger proportion of the labelled material from the surface of late phase cells than from the surface of early phase cells. Conversely early phase cells were relatively rich in several glycopeptides compared to late phase cells. [ABSTRACT FROM AUTHOR]

1. Heavy rapidly-labeled RNA from chick embryo nuclei separates on electrophoresis in 2.4% polyacrylamide gel into at least four fractions with the mobilities of rRNA precursors, and a fraction of ‘giant’ RNA remaining at the start. 2. The heavy fractions with mobilities of rRNA precursors pass into solution without heating during phenol treatment at pH 8.3 or during phenol-1.6% dodecylsulphate treatment at pH 5. 3. The ‘giant’ can be partially solubilized without heating by phenol-1.6% dodecyl-sulphate treatment at pH 5 but the extraction becomes efficient only on heating to 65 °C or on raising the pH to 8.3. 4. Precautions are discussed to prevent the degradation of heavy RNA at elevated pH and the aggregation of rNA at elevated temperature during phenol extraction. [ABSTRACT FROM AUTHOR]

The factors that control the growth and development of hair follicles are largely unknown. Likewise little is known about why follicles periodically enter resting phases (telogen) and subsequently recenter an active growth phase (anagen). The dermal papilla of hair follicles probably influences follicular growth through the exact nature of this influence is obscure. To help delineate the role of dermal papillae in this regard, a series of hair follicles from 15 human embryos of various ages and from 2 human adults have been examined. The cells which form the dermal papillae were examined from the time they begin to congregate around the early hair peg to the point at which they reside within the follicular bulb. The plasma membranes of adjacent cells are attached by a focal types of intermediate junction. The junctions also connect the mesenchymal cells of the dermal papillae of human adult follicles. Cellular attachments of this type may have a similar function in regrowth or repair of adult tissue as they do in growth and development during embryogenesis. [ABSTRACT FROM AUTHOR]

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Factors influencing adventitious bud and root development, callus induction and embryogenesis were investigated in stem and leaf cultures of Petunia inflata B.. E. Fries and Petunia hybrida cv. Cascade and cv. Rose du ciel grown on a synthetic nutrient medium. Indoleacetic acid caused limited callus development and root formation whereas naphthaleneacetic acid induced abundant roots. 2,4-Dichloropbenoxyacetic acid promoted callus growth and differentiation of embryos which eventually developed into plantlets. Cytokinins such as beuzyladenine, zeatin and kinetin induced bud development. A combination of auxins and cytokinins caused an interaction which was manifested in altered morphogenetic response. Thus 2,4-dichiorophenoxyacetic acid in conjunction with benzyladenine caused suppression of bud development and retarded differentiation of embryos. Likewise, when benzyladenine was used with indoleacetic acid root development was totally inhibited and abundant buds were produced. [ABSTRACT FROM AUTHOR]

The development of serum proteins, immunoglobulins and the immune response was studied in opossum ‘embryos’. Serum proteins gradually increased from birth to 80 days of age when adult values were obtained. γM immunoglobulins were found at all stages of development but γG immunoglobulins were less regularly present. Those ‘embryos’ which were 5 days or older at the time of immunization had an immune response to bacteriophage f2 and ‘embryos’ 15 days or older responded to a hapten determinant, DNP. γM antibodies were most prominent but γG antibodies could also be detected in the immune response of opossum ‘embryos’. [ABSTRACT FROM AUTHOR]

Rat lympllocytes cultured of mouse embryo cell monolayers produced large pyroninophilic cells (LPC) which lysed tile mouse cells. The LPC that developed on monolayers of any particular strain of mouse (originator monolayers) were tested, by transfer, for their ability to lyse monolayers of other mouse strains. The distribution of lysis among the various strains of mouse revealed a definite pattern of specificity. Analysis of the H-2 allelic complement of the morose strains tested suggests that the lymphocytes were sensitized upon exposure to the mouse embryo monolayers against one or more of the antigens determined by the H-2 locus. The presence or absence of one or all of the antigens in other strains determined whether monolayers of these strains were lysed completely, partially, or not at all. It was concluded that the cultures obtained are an in vitro reflection of the graft versus host immune reaction. It was produced in the tissue culture as a primary response by normal lymphocytes. [ABSTRACT FROM AUTHOR]

Eighty lambs were divided into four groups, each comprising twenty animals. Half the lambs in each group were vaccinated with viable eggs and half with the activated embryos of Echinococcus granulosus, Taenia hydatigena, T. ovis or T. pisiformis. These lambs together with ten control animals were subsequently challenged with eggs of E. granulosus. Only a few hydatid cysts were established from the challenge infection in the lambs immunized with the homologous eggs or embrs os. Only one acephalocyst in one animal survived. The metabolism of this cyst was of a low order compared with that of most of those in the controls. Hydatid cysts were established from the challenge infection almost as frequently in the animals vaccinated with eggs or embryos of the sheep metacestodes T. hydatigena and T. ovis, as in the controls. Fluid accumulated in only a few hydatid cysts from the challenge infection in those sheep vaccinated with the activated embryos of these heterologous species. The injection of viable eggs or activated embryos of the rabbit metacestode T. pisiformis induced no resistance to the establishment or to the survival of the challenge infection of E. granulosus. [ABSTRACT FROM AUTHOR]

The formation of antibody to goat erythrocytes has been studied in embryos and young chicks. Opsonizing antibody was measured by accelerated clearance of antigen and the sensitivity of this technique compared with haemagglutination tests. A wide range of immunizing doses of goat erythrocytes was used; all induced immunity. Small amounts of antibody were detected as early as the day of hatching but vigorous antibody production did not occur until 3 days later. An immune response could be induced in 12-day-old embryos and the most vigorous response was obtained by injection of 14-day-old embryos. Antibody production was relatively poor between the fifteenth day of embryonic life and 15 days after hatching. This was due to the presence of maternal antibody. [ABSTRACT FROM AUTHOR]

Rabbits vaccinated by intramuscular injection with the viable eggs or the activated embryos of Taenia pisiformis, T. ovis or T. hydatigena, were subsequently challenged per os with eggs of T. pisiformis. A single intramuscular injection of viable eggs or activated embryos of T. pisiformis induced a relatively solid immune response to the establishment and also to the long-term survival of the challenge infection of T. pisiformis. A single intramuscular injection of the activated embryos of both T. ovis and T. hydatigena also induced some resistance to the establishment and long-term survival of a challenge infection with T. pisiformis but no significant immune response to a similar challenge infection was detected in those rabbits vaccinated with the viable eggs of these two sheep metacestodes. [ABSTRACT FROM AUTHOR]

Erythrocytes labelled with chromium51 were injected into embryos and young chicks and a similar challenge given soon after the majority of the initial dose had been eliminated. While tolerance was the typical response in embryos and chicks up to 3 days of age, immunity could be induced in most chicks from this time onwards. The intensity of the immune response increased rapidly until the 12th day of age. No maternal antibody could be detected. Pretreatment of the embryo with testosterone impaired the immune response of 14-day-old chicks. [ABSTRACT FROM AUTHOR]

In Indotristicha ramosissima (Wight) van Royen there is normal syngamy. However, the polar nucleus is not fertilized so that a primary endosperm nucleus is not formed. Consequently, there is no endosperm in the seed. The post-fertilization dissolution of the nucellar cells below the embryo sac results in the formation of a pseudo-embryo sac into which the growing pro- embryo penetrates. The first division of the zygote is transverse and the development of the embryo conforms to the Solanad type. The embryo possesses a large, coenocytic haustorial cell which disorganizes by the time the embryo is fully differentiated. The integuments and the ovary wall are rich in starch deposits which disappear during maturation. In the mature seed, the outermost layer of the outer integument becomes mucilaginous. The cells of the inner epidermis of the ovary wall become binucleate and occasionally multinucleate. [ABSTRACT FROM AUTHOR]

The sizes and shapes of different parts of pyrenes obtained from two diallel crosses of raspberry were influenced both by maternal effects and by interaction effects involving maternal and genetic factors. The relative importance of these effects depended upon the environment in which the crosses were made. For a diallel made under field conditions interactions with maternal factors were large but considerably reduced by applying auxin to the developing fruits. For a diallel made in a glasshouse maternal effects were more important and maternal interaction effects less so. Application of auxin to the fruits reduced endosperm or embryo size in some crosses and increased it in others. It is postulated that these responses were related to the endogenous content of growth substances, negative responses indicating their presence in supraoptimal concentration, and that variations in the responses provide clues to the physiological factors which govern successful pyrene development. [ABSTRACT FROM AUTHOR]

The drupes or achenes of Potamogeton schweinfurthii A. Benn. and P. richardi Solms. can float for long periods and germination only occurs naturally once the fruits have sunk. The factors controlling their floating, sinking and germination have been investigated. After brief reference to water depths at which these species occur in Uganda, fruit structure is described. The epicarp and mesocarp are initially green in both species and remain green in ripe, floating fruits of P. schweinfurthii. The sheathed embryo lies along the rim of the stony endocarp beneath a lid which can be detached by surgery. Of the factors relating to buoyancy and sinking in P. schweinfurthii, daylight compared with almost total darkness decreased the rate of discoloration of the green floating fruits, the rate at which the pericarp disintegrated and the rate of sinking. Measurements of respiratory oxygen uptake, net photosynthesis rates and density changes, in a series of unripe to just-sunk fruits of P. richardi, suggest that this light-dependence of floating fruits is connected with the maintenance of constant volume and density through gaseous relations within an intact cuticle. During prolonged darkness, fruit density increased at constant mass by shrinkage of the soft parts, caused by degenerative changes and absence of photosynthesis. Neither species germinated in the dark, compared with 100% of light-stored, sunken fruits or with similarly stored fruit from which epicarp and mesocarp had been scraped. In the light, substantial germination also occurred in both freshly shed and older floating fruits after surgical exposure of the embryo. No after-ripening period is required. Presumptive evidence was obtained for the promoting effect of red light on germination in P. schweinfurthii. [ABSTRACT FROM AUTHOR]

The gametes and embryos of many cold water marine organisms are adversely affected by the temperatures maintained in most laboratories and will die or develop abnormally if left on the stage of a microscope for prolonged periods. Temperature control becomes a serious problem in time-lapse cinemicrographic studies of morpho-genetic movements, for example, when the period of filming continues for one or more hours. A stage equipped with a liquid cooling system or a thermostatically controlled cold room can be used to solve this problem but these methods may be awkward, inconvenient, lacking in versatility or prohibitively expensive.

The embryonic osteocranium of the elapid snake, Naja haje (Egyptian cobra) has been studied. The osteocranium of the 166-mm embryo has been graphically reconstructed and described in detail. Those of younger and older embryos as well as the just-hatched young have been also investigated. The membrane-bones make their appearance before any sign of ossification in the cartilaginous cranium. The maxillary, palatine and pterygoid premordia have an earlier appearance than the other bony premordia. The fused premaxillae arise beneath the antero-medial part of the solum nasi of the nasal capsules. They send dorsally the rudiment of the processus nasalis and posteriorly two small processes. The nasal develops as a protecting bony roof for the cartilaginous nasal capsule. It possesses a median descending portion which penetrates deeply between the capsules. The frontal arises at first over the fenestra olfactoria advehens and the planum antorbitale, then extends posterioly. Its median descending portion has not yet ossified. The prefrontal embraces the postero- lateral surface of the nasal capsule. It is perforated by the foramen of the lacrymo-nasal duct, the lacrymal bone is completely absent. The parietal is very long forming the incomplete roof and the side wall of the temporal region. It is quite apart from the frontal. The cranial roof between the two frontals and two parietals is bridged by connective tissue. Both the frontal and parietal bones form well developed lateral down- growths. The postfrontal is present, lying just lateral to the anterior part of the descending process of the parietal, but the postorbital is completely lacking. There is only one temporal bone which is regarded as the supra- temporal. This bone arises just lateral to the auditory capsule, its posterior part is intercalated between the quadrate and the capsule. The squamosal, tabular, jugal and quadratojugal are totally absent. The maxilla arises directly below the anterior half of the eye. It sends inwards a well developed palatal process. The rudiments of the maxillary teeth, including those of the poisonous fangs, have not yet been attached to the bone. The prevomer forms the medial wall and floor of the bony capsule which surrounds Jaccbson's organ. It consists of a medial portion which extends nearly vertically and a ventral one which extends horizontally. The septomaxilla forms the lateral wall and a part of the floor of Jacobson's organ bony capsule. It possesses a very long posterior projection. The palatine arises medial to the maxilla, posteriorly it is about to touch the anterior tip of the pterygoid. The pterygoid is very long, occupying about half the total length of the palate. Both the palatine and pterygoid carry teeth which have riot yet been completely attached to the bones. The ectopterygoid arises lateral to the hind extremity of the palatine and the anterior half of the pterygoid. The parasphenoid is a narrow elongated bone which arises in between the anterior halves of the trabeculae cranii. It is completely separate from the lateral down- growths of the frontals and from the basisphenoid. Other than the cartilage-bone, the articular, each ramus of the lower jaw is composed of the following membrane-bones: dentary, splenial, angular, and the combined supra-angular and prearticular. The fusion between the supra-angular and prearticular takes place in late embryos. As regards the cartilage-bones, the basioccipital ossifies perichondrally in the posterior part of the basal plate, behind the basicranial fenestra. The exoccipital ossifies in the occipital arch, and spreads medially forming a center in the posterior part of the tectum synoticum. The basisphenoid ossifies in the anterior region of the basal plate (including the crista sellaris) and the posterior ends of the trabeculae cranii. The basicranial fenestra is still present in its center. The supraoccipital arises from a pair of perichondral lamellae formed on the dorsal and ventral surfaces of the anterior part of the tectum synoticum. Laterally, on either side, it extends slightly in the roof of the auditory capsule, but this lateral part must not be considered as an epiotic since its independent ossification is not observed. The opisthotic arises from two perichondral lamellae on the outer and inner surfaces of the postero-lateral part of the auditory capsule. It is quite separate from the exoccipital. The prootic ossifies perichondrally in the anterior portion of the auditory capsule, as far backwards as the anterior margin of the fenestra ovalis. The epipterygoid is completely lacking. The quadrate bone is formed by the perichondral ossification of the quadrate cartilage and the intercalare. The stapes and the shaft of the columella auris ossify perichondrally, but the processus dorsalis is still cartilaginous. The laterosphenoid bone is wedged between the auditory capsule and the basisphenoid, it is completely fused with the prootic. It is of double origin; its ventral part arises by the perichondral ossification of the laterosphenoid cartilage while its dorsal part arises without cartilaginous preformation. The articular arises perichondrally round the hind part of Meckel's cartilage, it is distinct from the combined supra-angular and prearticular. No ossification occurs in the hyoid apparatus. [ABSTRACT FROM AUTHOR]

The paper deals with the structure and the degeneration of the pronephros in "Cirrhina mrigala," an Indian carp. The earliest stage that was available for the study was the free swimming larva measuring 6 mm in total length. The embryonic development of the pronephros in teleosts has been described by several workers. It is an established fact that the pronephros in teleosts is a transient larval organ except in a few species in which it persists throughout adult life. The earliest stage that was available for the study was a free-swimming larva measuring 6 mm in length. At this stage, the pronephros is well developed and consists of the pronephric chamber containing the pronephric glomerulus and a pair of pronephric tubules.

The effect of the saline-soluble proteins of the lens on the development of the eye was studied on the chick embryo In Ovo. The lens extract caused retardation of the differentiation and development of the lens, and provoked malformations of the optic cup and diencephalon. This activity is localized to fractions of extract characterized by the presence of a crystalline and of nucleotides. The action on the neural plate can be related to the presence of lens antigens in the neural tissues in the embryo younger than 2 days, and in the optic cup even in the 3-day old embryo. This investigation was supported by a grant-in-aid from the National Research Council of Natural Sciences (Sweden). The work on lens proteins referred to in the discussion was supported by the National Council to combat blindness (U.S.A.). [ABSTRACT FROM AUTHOR]

The article examines the existence of homologous inhibition in chick embryos. A qualitative examination of the embryo was conducted which studied shape of the head, cerebral vesicles and sensory organs, spinal medulla, extremities, blood, and cardiac tissue. Particular abnormalities of the brain were found in nearly fifty percent of cases in which brain extract was injected.

The article presents information on a study of the development of the skull of lemuroids. The author studied the development of the chondrocranium in the following stages of Loris embryos collected. Most of the regions of the chondrocraniurn are noticed as procartilaginous structures. The occipital region shows the cartilaginous arches prominently. In the posterior region of the basal plate, the occipital arches are united with the former, the hypophysial foramina piercing the occipital arches. The basal plate is cartilaginous and on either side, the procartilaginous optic capsules are noticed. In the region of the hypophysis, the basal plate continues into a broad cartilaginous plate below it and posteriorly, there is a procartilaginous crista transversa.

The article focuses on the dermal connective tissue of the head of Petromyzon. The skin of the Petromyzon larva consist of an epidermis and dermal aponeurosis. The same constitution of the skin is found in the adult. In young embryos there is a thin basal membrane separating the epithelium of the skin from the densely collected cells of the underlying ectomesoderm. These cells are evidently fibrocytes, forming new thin layers of collagenous fibres inside the basal membrane. This process can be seen in embryos aged about 500-600 hours.

Eggs of Myxine glutinosa provided with their characteristic anchor filaments have been recorded but a few times since they were described in 1859. The author obtained two eggs of Myxine containing embryos. The state of preservation of the embryos is not very good as probably they were merely placed in alcohol. Nevertheless, the younger of the two is usable for anatomical purposes, whereas the older embryo is not so good, it having shrunk considerably. The head and neck region of the Myxine embryos is sunk down in a deep groove of the yolk of the embryo, so that the upper surface of the embryo lies at the same level as the outline of the yolk surface.

1. A paired nasal septum has been observed in the subcerebral portion of the nasal capsule of a 21 mm. embryo of Sus domestica. 2. In a 36 mm. embryo of Procavia capensis an intertrabecle corresponding to the posterior edge of the interorbital septum was found protruding caudad into the hypophysial canal. 3. A real fenestra basicranialis anterior is formed neither in Procavia, Sus, Elephantulus, nor in Erinaceus. In the latter the anterior end of the parachordal plate shows a well defined boundary suggesting a posterior border of an ancestral fenestra basicranialis anterior. By caudad chondrification the hypophysial plate joins the anterior end of the parachordal plate. The formation of this part of the central stem is compared with that of the chelonian taenia intertrabecularis. [ABSTRACT FROM AUTHOR]

In the first part of the study the ontogenetical development of the head, especially the skull, was followed in some sharks and rays. These investigations resulted in some general statements about the relationship between these groups of fish and the conclusion was drawn that these groups of selachians are but distantly related to each other, so distantly in fact, that it is not possible to derive them from common selachian ancestors. In the second part the experiences obtained in the first part were used for a phylogenetical discussion of the recent shark and ray groups. This discussion was based on the morphology of the skull in adult recent shark and ray genera. To answer some of the questions that arose, an investigation into the dorsal fins was necessary and the results of such an investigation were added. The present third part of the work contains an attempt to widen the phylogenetical discussion to embrace the Acanthodians, the Arthrodires and the Chimaeroids, the Anthirchi and the Agnatha. It will thus contain far-reaching comparisons of sharks and rays, embryonic as well as adult, with these groups and these groups with one another.

In his study on the cranial development of Teleostomian fishes, the author had the opportunity of showing that the dermal bones in Amia calva, related to sensory canals, develop in close connection to the sensory organs in the canals. The author tried in the same paper to compare the rudiments of the canal bones in question with the canal bones in other recent fishes as well as in certain groups of extinct fishes in order to establish possible homologies between these bones. As far as the origin of the canal bones is concerned the author's observations seem to be accepted. Even the morphological value of the rudiments of the canal bones for comparative purposes has been accepted to a certain degree, especially by paleontologists, the objections advanced having chiefly concerned the interpretation of certain homologies. Lately the author had the opportunity of examining a series of embroynic stages of Amia Calva. This series is far more completed than the material on which he based his previous investigation.

Mouse embryo cells incubated m medium with 0.5% serum contain only few cells which synthesize DNA. When the serum concentration was raised, DNA synthesis was induced and the pools of the deoxyribonucleoside triphosphates expanded. In such cultures the pool of dGTP was the smallest of the deoxyribonucleoside triphosphate pools and its size corresponded to only approximately 30 sec of DNA synthesis. The dCTP pool was 10-20 times larger than the dGTP pool. Addition of hydroxyurea resulted in an almost instantaneous loss of the pool of dGTP and also in a decrease in the size of the dATP pool. In contrast the pools of dCTP and dTTP increased. However, the turnover of the dTTP pool was greatly diminished. Removal of hydroxyurea from the medium resulted in a rapid normalization of the triphosphate pools but only in a more gradual restoration of DNA synthesis. During incubation in 1-β-D-arabinofuranosyl-cytosine (arabinosyl-cytosine), the pools of dATP, dGTP and dTTP expanded, while the pool of dCTP showed an initial decrease. The turnover of the dTTP pool was not maxkedly affected in spite of the fact that DNA synthesis was greatly reduced. When arabinosyl-cytosine was removed the pools were normalized and DNA synthesis was slowly restored. Our results thus show that the inhibition of DNA synthesis by hydroxyurea is correlated with diminishing pools of dGTP and dATP and a decreased turnover of dTTP, indicating a generally decreased deoxyribonucleotide formation presumably due to the inhibition of the enzyme ribonucleoside-diphosphate reductase. The inhibition of DNA synthesis by arabinosylcytosine is not correlated with a similar depletion of deoxyribonucleoside triphosphate pools. [ABSTRACT FROM AUTHOR]

Secondary cultures of embryonic rat cells (17-19 day of gestation) require for growth the presence of serum in the culture medium; a growth stimulating fraction has been isolated from fetal calf serum. It will be shown that cells incubated in medium without this active fraction are stopped in the G1 phase of the cell cycle about 3 hours prior to the beginning of DNA synthesis. This has been confirmed by incorporation of methyl-[³H]thymidine, labelling index, mitosis index and cytophotometry. Cells already triggered at this critical point come into mitosis in spite of the fact that, the stimulating factor is omitted from the culture medium. Resting cells, preincubated in inactive medium for 15 to 40 hours can be stimulated by adding the active component to the medium; they resume DNA synthesis after a lag phase of about 20 hours and come into mitosis another 10 hours later. Embryonic rat cells after spontaneous transformation into a permanent cell line do not require the presence of this stimulating factor for at least 3 cell generations. For secondary cultures of embryonic mouse and hamster cells the same active serum fraction is essential for growth. Embryonic mouse cells after spontaneous transformation into a permanent cell line are as independent from this stimulating activity as permanent rat cells; the same holds for KB and HeLa cells. [ABSTRACT FROM AUTHOR]

The interspecific hybrid Arbacia lixula ... × Paracentrotus lividus ... which stops developing at the onset of gastrulation, was previously found to contain much more DNA of maternal origin (P. lividus) than DNA of paternal origin. In spite of this, the RNA synthesized by the blocked gastrula hybridizes better with DNA of paternal type than with DNA of maternal type. An explanation of thru observation was sought in the present paper by means of saturation and competition experiments. The higher affinity of RNA from the hybrid gastrula for paternal DNA could be due to the fact that RNA of paternal type is complementary to a longer portion of the corresponding DNA than RNA of maternal type. This explanation was not satisfactory since the number of genes of paternal type which are active in the hybrid is not very different from the number of genes of maternal type. In normal embryos of A. lixula and P. lividus, RNA from unfertilized eggs and from plutei was found to be less competitive against labeled RNA from gastrulae than gastrula RNA itself. Transcription of the genome is therefore partially stage-specific. This stage-specificity is maintained in the hybrid as far as transcription of the maternal genome is concerned, but is lost as far as transcription of the paternal genome is concerned. The hybrid gastrula was shown to synthesize more RNA molecules of A. lixula type than does the normal gastrula of this species, whereas RNA of P. lividus type is produced in equal amounts m normal and in hybrid embryos. These observations explain the hybridization properties of the RNA synthesized by the blocked gastrula. The results suggest that the genes of paternal type that are very active in the hybrid are those genes which m normal embryos are transcribed at all stages of development and probably also in the adult. This class of genes is much more active in a foreign cytoplasm than in the cytoplasm of its own species. On the other hand, the genes whose activity is restricted to the gastrula stage m normal embryos are not active in the hybrid. This class of genes does not seem to function in a foreign cytoplasm. [ABSTRACT FROM AUTHOR]

The present results, together with physicochemical evidence presented elsewhere, indicate that α-crystallin from calf lens is composed of two acidic and two basic polypeptide chains. The acidic polypeptides could be isolated by chromatography on SE-Sephadex at, pH 5.5 in the presence of 7 M urea. It could be demonstrated that both S-carboxymethylated acidic polypeptides are of equal molecular weight and amino add composition. In both chains N-acetylmethionyl-aspartate was found as the N-terminal and serine as the C-terminal residue. Peptide mapping reveals one unique peptide region for each polypeptide. In embryonic α-crystallin only one acidic polypeptide can be detected. From comparative amino acid analysis, peptide maps as well as physicochemical behaviour it may be deduced that the polypeptide present in the early embryonic stages is identical with the adult acidic polypeptide A-2. [ABSTRACT FROM AUTHOR]

An inducing factor isolated from 9- to 11-days-old chicken embryos causes differentiation of the amphibian gastrula ectoderm into mesodermal (trunk and tail) structures. This inducing activity is prevented by an inhibitory factor. The inhibitor is found after gel filtration on Sephadex G-200 in the void volume. After precipitation with hexadecylpyridinium chloride the inhibitor redissolves at ionic strengths I = 0.4–1.0. In isoelectric focusing experiments the factor bands near pH 3. The inhibitor is tentatively characterized as an acidic glycoprotein. [ABSTRACT FROM AUTHOR]

RNAase from 13-day-old chicken-embryo red cells was purified. Nuclei and cytoplasmic fractions were used as source of the enzyme. The nuclear enzyme was purified 1440-fold and the one from cytoplasm, 1683-fold. Both enzyme preparations showed the same optimum pH and ion specificity, but different ionic strength dependence and temperature stability. Kinetic studies with these RNAase fractions indicated that both of them are endonucleases with specificity for pyrimidine nucleotide bases in the substate, hydrolyzing poly(U) or poly(A, U, G) faster than poly(C) or poly(A, C, G). Both enzyme fractions showed strong dependence on the sedondary structure of RNA, and did not hydrolyze single stranded DNA. The implications of these characteristics on the enzyme role are discussed. [ABSTRACT FROM AUTHOR]