bluuebunny/crossref_metadata_2025 huggingface dataset:
Regeneration of larval urodele limbs containing homoplastic transplants
Authors: Foret John E.
Published: June 2005

Forelimbs of larval Ambystoma were amputated through the elbow. In many cases the humerus was partially or totally extripated. Homoplastic transplants, previously labeled with tritiated thymidine, were then inserted into the limb stump, which was re‐amputated through the graft.

Experiments involving the addition of appendicular or visceral skeletal parts revealed fusion of the implant with the humerus and suggested interactions between skeletal components. The morphology of such regenerates was usually normal. The various skeletal elements exhibited a differential susceptibility to regression, Meckel's cartilage being particularly resistant. As a consequence, the distal blastema was often spatially removed from the proximal shoulder region. Nevertheless, reconstitution of the head of the humerus was always observed. The cellular origin of this portion of the regenerate was probably local connective tissue.

Unlike Meckel's cartilage, the humerus released many cells to the accumulation blastema. These labeled cells may have divided at a higher rate than other blastemal cells, suggesting the possibility of tissue‐specific regeneration of cartilage.

Transplanted muscle and connective tissue originating from either the jaw region or the limb behaved similarly to each other. Labeled connective tissue cells proximal to the amputation plane began dividing before the blastema was established, therefore the time of onset of cell division may vary according to the tissue involved and its location with respect to the blastema. A distinction between inductive phenomena and cell contributions was also made.
Cell sorting out according to species in aggregates containing mouse and chick embryonic limb mesoblast cells
Authors: Burdick Morton L.
Published: June 2005

Aggregates were prepared containing mouse and chick embryonic limb mesoblast cells. After 21 to 33 hours in culture, these aggregates showed prominent sorting out of the mouse cells from the chick cells. This sorting out was even more extensive after 46 to 54 hours. This sorting out is contrary to previous reports for mouse‐chick limb aggregates.

After three to four days of culture, chondrification became quite prominent within the aggregates. Accompanying this event, the segregation of mouse and chick cells became less extensive within the chondrified zones. This rescrambling seems to be due at least in part to the interpenetration of neighboring chondrifying regions. Such interpenetration would be expected, due to the expansion which occurs within chondrifying areas. This reshuffling is the probable reason why sorting out was not observed in earlier experiments with mouse‐chick limb aggregates. In these earlier studies, the reports were limited to aggregates which had extensive matrix secretion.

The finding that mouse and chick limb mesoblast cells sort out from each other, together with recent reports that similar sorting out occurs in mouse‐chick heart ventricle aggregates and in mouse‐chick mesonephric aggregates, invalidates the generalization that cell sorting properties for any one tissue are constant from species to species among warm‐blooded vertebrate embryos.
The role of changes in cell contact behavior in amphibian gastrulation
Authors: Johnson Kurt E.
Published: June 2005

Five different methods were used to examine cell contact behavior in normal and interspecific hybrid embryos in an attempt to elucidate the role of cell surface adhesiveness in gastrulation. In normal embryos and viable hybrid embryos, all cells show an increasing tendency to attach to glass in vitro with advancing developmental age. Presumptive mesodermal cells from early gastrulae show a high ability to attach to glass and to reaggregate. The rate of disaggregation of whole embryos shows marked decreases with advancing age from the blastula to late gastrula period. Binary combinations of explanted embryonic germ layer fragments from early gastrulae undergo movements that are reminiscent of portions of gastrulation. At the level of fine structure, cell contacts become increasingly intimate from the blastula to late gastrula period. In hybrid embryos which undergo developmental arrest at the onset of gastrulation, there is a lack of gastrular morphogenetic behavior in some or all portions of the embryo. In those portions of arrested hybrids where some morphogenesis is evident, there is “quasi‐normal” cell contact behavior. Most often, however, there is no recognizable gastrulation and a striking departure from the normal pattern of cell contact behavior. These results show that extent of changes in cell contact behavior and extent of normal gastrulation correlate positively. This suggests that changes in cell surface properties, resulting in the formation of stronger intercellular adhesions, are necessary for the morphogenetic movements of gastrulation.
Melanogenesis in amphibians. III. The buoyant density of oocyte and larval Xenopus laevis melanosomes and the isolation of oocyte melanosomes from the eyes of PTU‐treated larvae
Authors: Eppig John J.
Published: June 2005

The buoyant density of melanosomes isolated from oocytes of Xenopus laevis is about 1.88 g/cm3 while most of the melanosomes synthesized in the larvae have a density of about 1.92 g/cm3. The melanosomes isolated from phenylthiourea‐treated larvae or from their eyes have a density of about 1.88 g/cm3. The oocyte melanin of Xenopus was labelled in vivo by injecting the vitellogenic female with 14C‐DOPA. After these injections, only the melanosomes which band at a density of 1.88 g/cm3, whether from the ovary, normal or PTU‐treated progeny or from the eyes alone of PTU‐treated progeny, were radioactive. It is concluded that the melanosomes found in the eyes of PTU‐treated tadpoles originate in the oocyte.
Development and chromosomal constitution of nuclear‐transplants derived from male germ cells
Authors: Di Berardino Marie A. , Hoffner Nancy
Published: June 2005

Nuclei of spermatogonial cells derived from juvenile and adult (Rana pipiens) were transplanted singly into enucleated eggs to determine whether germ cell nuclei are developmentally totipotent. Control nuclear transfers from undetermined somatic cells promoted genuine cleavage in 77% of the injected eggs and 54% of the complete blastulae derived from this series developed into normal larvae. In contrast to the control study, eggs transplanted with germ cell nuclei formed genuine blastulae in 13% of the cases, and most of the complete blastulae arrested before completing gastrulation. However, three embryos derived from adult germ cell nuclei did attain advanced stages of organogenesis and one of these developed into an abnormal feeding larva. These individuals are the most advanced nuclear‐transplants obtained so far from nuclei of normal adult cells in vivo. Chromosome analyses performed on a sample of nuclear‐transplants derived from germ cells revealed gross chromosomal abnormalities in all individuals except the larva. It is concluded, that even though germ cell nuclei are genetically totipotent, they, like somatic nuclei, undergo developmental restrictions during their process of cell differentiation, and after transplantation to host eggs, give rise to abnormal nuclear‐transplants accompanied in most cases by karyotypic alterations. The significance of the developmental restrictions observed in germ cell nuclei is interpreted as an expression of chromosomal differentiation.
Regulative development in a spiralian embryo as shown by cell deletion experiments on the acoel, Childia
Authors: Boyer Barbara Conta
Published: June 2005

Spiral cleavage and mosaicism are closely associated in the Annelida, Mollusca, and probably the polyclad Turbellaria, but the evolutionary history of these phenomena remains uncertain. The Acoela, the most primitive order of turbellarians, exhibit spiral cleavage but with the formation of duets of micromeres rather than the more typical quartets. The regulative versus mosaic capacities of the acoel, Childia groenlandica, were investigated by deleting various combinations of blastomeres from the two‐cell stage through the third duet. The acoel embryo showed extensive regulative ability since all experiments yielded normal animals except those in which both macromeres were deleted. These abnormal animals were ciliated spheres with a central cavity and indicated that the macromeres are necessary for form and organ differentiation. An inductive interaction between the micromeres and macromeres is suggested. Since mosaicism is probably specialized and a derivative of the indeterminate type of development, the regulative capacity of the acoel embryo suggests that this order lies near the ancestral line of the spiralia and represents an evolutionary stage where the very defined pattern of spiral cleavage is not yet associated with early programming of the cell's fate.
Studies on the uptake of 125 I‐triiodo‐L‐thyronine and 14C‐L‐thyroxine by Mexican axolotl tissues
Authors: Prahlad K. V. , Hollinger T. G.
Published: June 2005

Various Mexican axolotl tissues were collected at different times after a single injection of either 125I‐triiodothyronine (T3) or 14C‐thyroxine (T4) to: (a) 5 day old embryos, (b) 150–170 day old larvae, (c) 1400–1440 day old neotenic adults.

Pattern of total radioactivity was similar in gill, tail and body of embryos injected with T3 or T4. In both the body continued to accumulate the label whereas gill and tail tissues showed a minor peak by three to five hours, a drop by 16 hours and an increase by 96 hours and a reduction by 240 hours. However, a hours and an increase by 96 hours and a reduction by 240 hours. However, a TLC fractionation of butanol extracts of tissues mentioned above indicated that T3 concentration reached a maximum at three hours and later continued to drop. A large amount of radioactivity was associated with the solvent front fraction. TLC fractionation of tissues from T4 injected embryos showed that very little of the radioactivity was associated with T4 up to 48 hours after which time there was an increase in T4 fraction. Thus, it is seen that the uptake of labeled T3 and T4 by embryonic tissues showed variations even though the total radioactivity appeared to be similar. Larval and adult axolotls injected with T3 showed that radioactivity reached a peak by 16 hours in the larval gill, skin and tail and continued to decline later. The liver showed a peak at 24 hours and decreased after that time. All of the above mentioned tissues from adult axolotls showed a peak radioactivity at 16 hours and later continued to drop.

Thus, it is seen that the pattern of labeled thyroid hormone uptake is different in embryonic and post embryonic axolotl tissues. The implications of these results are discussed.
Studies on limb morphogenesis. V. The expression of eudiplopodia and its experimental modification
Authors: Fraser Robert A. , Abbott Ursula K.
Published: June 2005

Embryos homozygous for the autosomal recessive gene (eu) develop supernumerary distal limb parts on the dorsal surface of wings and legs. These from from ectopic ectodermal thickenings which appear a day or more after the primary ectodermal ridge (AER). In addition, a large proportion of the mutant embryos exhibit twinning or more extensive duplications of primary flight feathers in one or more follicles. The expression of eudiplopodia is variable with the postaxial digits being duplicated most frequently. Morphological abnormalities are confined to the limbs and these result from changes in the mutant ectoderm.

The apical ridge regenerates when it is removed from eudiplopod leg buds as late as stage 20 while in normal limbs it fails to regenerate after stage 18. Accessory ridge still froms on eudiplopod limbs at stage 22–23 if ectoderm is removed from the dorsal surface of the limb prior to this time. The results suggest that the development of the accessory ridge is independent of that of the apical ridge. Eudiplopod limb ectoderm can from ridge for several stages after normal ectoderm loses this capacity. This characteristic may be partly suppressed by exposing developing mutant embryos to low incubation temperature in the interval between normal ridge formation and the appearance of accessory ridge.
Studies on limb morphogenesis. VI. Experiments with early stages of the polydactylous mutant eudiplopodia
Authors: Fraser Robert A. , Abbott Ursula K.
Published: June 2005

Prospective limb mesoderm was transplanted to the flank of twoday host embryos in efforts to study tissue specific effects of the avian polydactylous mutant, eudiplopodia. Initially, normal limb mesoderm was placed in the flank of two‐day scaleless hosts and a scaleless limb resulted, ensuring that the regenerating host ectoderm provided the epithelial covering for the graft limb. Eudiplopod limbs developed from grafts of normal mesoderm to two‐day eudiplopod hosts while the reciprocal combination produced normal limbs. Similar transplants showed that eudiplopod ectoderm may respond to leg mesoderm from both quail and talpid2 embryos and does so typically by forming two ridges. Grafts of normal limb mesoderm to three‐and‐one‐half‐day eudiplopod hosts produced supernumerary limbs in the majority of cases whereas most grafts to normal hosts of similar age produced only a skin covered nodule.

It is concluded that the mutant gene extends the time of ectodermal competence for ridge formation and that as a consequence of this specificity the mutant effects are seen only in eudiplopod limb ectoderm.
Conservation of web proteins in the spider, Araneus diadematus
Authors: Peakall David B.
Published: June 2005

Experiments placing “cold” spiders on radiocative webs and measuring the specific activity of successive webs shows that silk protein is highly conserved during the web building cycle. This conservation of web protein is not affected by feeding the spider flies or cold amino acids. It is considered that the timing of web eating to web construction is critical to this efficient re‐cycling.
Sorting out in pseudoplasmodia of Dictyostelium discoideum
Authors: Francis David , O'Day Danton H.
Published: June 2005

During its period of migration the pseudoplasmodium of D. discoideum changes from a homogeneous mass of cells to one in which the cells of the front part stain more darkly with neutral red than those of the rear part. It has been asked whether this color change represents differentiation in situ of two cell type or sorting out of previously differentiated cell types.

Experiments are described which (1) show that the transition of the pseudo‐plasmodia from one type to another is long continued process, and (2) show by means of labeling parts of pseudoplasmodia with vital dyes or C14 thymidine, that exchange of cells across the color boundary separating tip and rear parts is continuous during the life of a pseudoplasmodium. From the results it appears that sorting out of cell types is probably a major cause of the color change.

When combined with previous work, our results suggest that sorting out and redifferentiation are active together both in maintaining and restoring the normal proportions of cell types in a slug. It may prove useful to compare these processes with the components of regeneration in metazoan organisms.
Aspects of cuticle formation in Drosophila melanogaster
Authors: Mitchell Herschel K. , Weber‐Tracy Ursula M. , Schaar Gertraud
Published: June 2005

The molting process and some aspects of puparium formation in Drosophila melanogaster have been examined by electron microscopy and autoradiography. Results indicate clearly alternate phases of production of enzymes involved in cuticle synthesis and enzymes involved in cuticle degradation, in epithelial cells. The synthesis phase begins about four hours before each molt and appears to continue about three hours after puparium formation. Protein which is involved in cuticle structure appears to remain where deposited. On the other hand, metabolic products of tyrosine that are involved in sclerotization and tanning diffuse outward through the cuticle from their origin in the epithelial cells. Channels or canals for transport of materials from cells toward epicuticle have not been observed in larval or prepupal material.
The metabolism of dietary carnitine in Drosophila melanogaster
Authors: Geer B. W. , Dolph W. W. , Maguire J. A. , Dates R. J.
Published: June 2005

Drosophila melanogaster larvae require choline for growth but when fed dl‐carnitine in place of choline, carnitine is decarboxylated to β‐methylcholine and phosphatidyl‐β‐methylcholine is synthesized to replace phosphatidylcholine. Feeding (−)‐carnitine in place of choline results in a moderate deficiency of lecithin‐type phospholipid and a corresponding reduction in growth. The capacity of larvae to employ (+)‐carnitine for phosphatidyl‐β‐methylcholine synthesis and subsequently for growth is very limited. Only 41% as much phosphatidyl‐β‐methylcholine is synthesized by larvae fed 5.7 X 10−4 M (+)‐carnitine as is formed when the same concentration of (−)‐carnitine is fed. This suggests that (−)‐carnitine is the preferred substrate for carnitine decarboxylase, the enzyme that degrades carnitine to form β‐methylcholine. Utilization of carnitine for phospholipid synthesis is clearly dependent upon a choline‐deficient state. The presence of small quantities of choline, either in body tissues or in the diet, inhibits the incorporation of carnitine derivatives into phospholipid. Intact carnitine is needed for maximum larval growth and adult activity, indicating that D. melanogaster larvae synthesize a suboptimal quantity of carnitine. Thus, dietary carnitine supplements in vivo carnitine synthesis for physiological purposes.
The distribution of melanosomes in larvae reared from normal and from pigmentless eggs of Xenopus laevis
Authors: Eppig John J. , Dumont James N.
Published: June 2005

The distribution of pigment granules or melanosomes in tadpoles of Xenopus laevis reared from phenylthiourea (PTU)‐induced pigmentless eggs is compared with the distribution of melanosomes in tadpoles from normal eggs. Some animals from each group were raised in a solution of PTU. It is concluded that melanosomes observed in the central nervous system, liver, epidermis, oral sucker, gut, notochord, and early eye of normal larvae originate in the oocyte. Those in the brain ventricles become engulfed by macrophages. Melanosomes do not appear in these tissues of early tadpoles reared from pigmentless eggs; however, pigment is later synthesized in dermal, meningeal, and peritoneal melanocytes as in the normal larvae. Since the synthesis of new melanin is blocked in embryos reared in PTU, tadpoles derived from pigmentless eggs and reared in PTU are completely devoid of melanosomes.
A biochemical and cytological investigation of differentiation in the interspecific hybrid amphibian embryo Rana pipiens ♀ × Rana sylvatica ♂
Authors: Johnson Kurt E.
Published: June 2005

Starch gel electrophoresis, light microscopy, and electron microscopy were used to investigate biochemical and cytological differentiation in the interspecific hybrid amphibian embryo Rana pipiens ♀ × R. sylvatica ♂. Paternal sylvatica lactate dehydrogenase‐B genes (and possibly LDH‐A genes) begin to function in hybrid embryos at the same time as in normal embryos (when normals are Stage 19, heart beat). Paternal sylvatica genes for phosphoglucomutase, NAD‐malate dehydrogenase, and 6‐phosphogluconate dehydrogenase do not begin to function in hybrid embryos before embryonic death, which occurs approximately six days after fertilization. Cytological results show that hybrid embryos form nucleoli and apparently are equipped for protein synthesis. Hybrid cells are capable of differentiating basement membranes, cilia, myofibrils, and other structures which suggest that these lethal hybrids are capable of substantial protein synthesis after “developmental arrest” at the early gastrula stage. These results are discussed in terms of the cessation of normal development at the early gastrula stage in this and other interspecific hybrid amphibian embryos.
Allograft reactivity in chick embryos
Authors: Seto Frank
Published: June 2005

Kinetic studies with the splenomegaly assay and the in vivo antibody assay of marker allogeneic immunocompetent cells were made to ascertain when in embryonic development the capacity to actively reject foreign cells is manifested by the chick embryo. It was found that (1) the splenomegaly response elicited with equivalent amounts of immunologically competent cells was high in 14‐day embryo hosts but much less in embryo hosts 16‐, and 18‐day of age. Whereas the GVH reaction was effectively reduced in cyclophosphamide‐pretreated 14‐day hosts, no such effect was observed in older hosts; (2) the antibody production by allogeneic immunocytes, as measured with the in vivo assay, was high in 14‐ and 16‐day embryo hosts, but significantly reduced in 18‐day embryo and day‐old chick hosts. In contrast the antibody output remained high in all cyclophosphamide‐pretreated hosts; and (3) the marker immunocytes, cultured in embryo hosts for several days, maintained their antigen‐responsive capacity unimpaired up to the seventeenth day of incubation but showed some loss by the eighteenth day. The experimental findings indicate that the host response during splenomegaly in young embryo hosts is not associated with graft rejection. However, coinciding with the reduction in splenomegaly in older hosts is rejection of donor cells. Alloimmune responsiveness exists as early as the seventeenth‐eighteenth day of chick development.
Effect of the T locus on fertilization in the house mouse
Authors: Olds P. J.
Published: June 2005

Male mice carrying certain combinations of alleles at the T locus are known to be completely sterile, due to the inability of the spermatozoa to reach the site of fertilization. In this study, such spermatozoa were injected into the ovarian bursa of ovulating females, thereby allowing the spermatozoa to reach the eggs. However, the eggs were not fertilized, and perhaps not even penetrated. Spermatozoa from fertile males carrying only one t allele, or from males having no t alleles, when injected into the ovarian bursae of ovulating females, did produce pronuclear and two‐cell zygotes. Penetration of spermatozoa after bursal injection of T/t spermatozoa occurred later, and the eggs' pronuclear stage length was shorter, than after bursal injection of spermatozoa from males having no t alleles or after mating to T/t males, suggesting that the spermatozoan can influence the egg at the pronuclear stage, and that the physiological environment of the spermatozoa can influence the behavior of the spermatozoa during and after penetration of the egg.
The regulation of ovulation in the tsetse‐fly, Glossina pallidipes Austen
Authors: Odhiambo Thomas R.
Published: June 2005

The tsetse‐fly female matures a single oocyte at a time. It ovulates this into the uterus, where it hatches, develops into a fully‐grown larva, and is later larviposited by the mother. It is only then that the next mature oocyte is ovulated, and the whole sequence is repeated. Thus, in this insect, it is possible to differentiate clearly four processes of egg production: (1) oogenesis, (2) oocyte growth and vitellogenesis, (3) ovulation, and (4) oviposition (in this case, larviposition). Mating is necessary to initiate the process of ovulation, but it is not necessary for the earlier processes. In virgin females, oogenesis, oocyte growth and vitellogenesis takes place normally; but the sequentially matured oocytes are lysed within the egg chambers without being ovulated.
The role of protein synthesis in prefission morphogenesis of Paramecium aurelia
Authors: Suhama Mikio , Hanson Earl D.
Published: June 2005

The effect of cycloheximide on formation of contractile vesicles, development of buccal anlage, and fission in Paramecium aurelia was examined. Paramecium exhibits remarkably strong resistance to this inhibitor of protein synthesis. With continuous exposure to lower concentrations (0.14 to 0.94 mg/ml), the daily fission rate is reduced in proportion to the concentration of cycloheximide and is maintained at a constant level. Exposure to higher concentrations (1.83 mg/ml) starting at various specific times in the interfission cycle reveals transition and stabilization points for each morphogenetic event; exposure prior to the transition point completely blocks development of a given event, but after the stabilization point exposure does not affect morphogenesis, and between these points blockage may or may not take place. The formation of the contractile vesicles is a morphogenetic process distinct from other events related to cell division. It occurs earlier than oral morphogenesis and fission and occurs in a step‐wise fashion with the anterior vesicle appearing first and then the posterior one. For fission and buccal development the transition and stabilization points are very similar to those found previously for actinomycin D treatments, suggesting that translation follows immediately on transcription. Resorption of new vesicles was observed; buccal anlage were never resorbed.
Results of selection for susceptibility and resistance to trypan blue teratogenesis in a four‐way outcross mouse population
Authors: Beck Sidney L.
Published: June 2005

A four‐way cross mouse population was established and four successive generations of animals were treated with trypan blue, selection being applied for susceptibility and resistance to the teratogen. The selection was successful, 26.8 ± 1.7% of all animals in the susceptible line (CBHA‐S) being abnormal and only 8.6 ± 1.7% of resistant (CBHA‐R) individuals being affected by the treatment. An unselected control line (CBHA‐C) produced an intermediate frequency of abnormality when treated. The vast majority of the abnormalities produced were of the tail and involved kinking, shortening, vertebral fusions and the occurrence of a completely novel malformation—an accessory tail. Both the proportion of litters affected by the treatment and the proportion of abnormal individuals within affected litters differed in the selected lines.
Calcitonin and ultimobranchial glands in fishes
Authors: Pang Peter K. T.
Published: June 2005

Ultimobranchial bodies in fishes contain follicles or cords of cells which show features of endocrine secretion. Hypocalcemic activities are present in the ultimobranchial bodies of sharks, bony fish and lungfish. Amino acid sequence of salmon calcitonin has been revealed and this hormone has been synthesized in vitro. Administration of mammalian and fish calcitonins has no effect on serum calcium levels of sharks, channel catfish, killifish and coho salmon. Mammalian and fish calcitonins elicit hypocalcemia and hyperphosphatemia in fresh water eels but not in sea water eels. Glandular hyperactivity can be related to calcium metabolism only in some cases. An osmoregulatory function of the gland has been suggested. The activity of this gland seems to be under pituitary control.
The ultimobranchial body of reptiles
Authors: Clark Nancy B.
Published: June 2005

Reptilian ultimobranchial bodies, located anterior to the heart in the region of the thyroid and parathyroid glands, are composed of cell cords and follicles. The cells show secretory activity and are similar histologically and ultrastructurally to ultimobranchial tissue from other vertebrate classes. Turtle ultimobranchial glands are unusual in containing numerous cytoplasmic granules or bodies which appear to be associated with the material seen within the ultimobranchial follicles.

Ultimobranchial extracts from lizards or turtles can induce hypocalcemia in rats. However, calcitonin preparations or ultimobranchial extracts have not induced any significant change in blood calcium or phosphate values in reptiles. Further studies are required in order to clarify the role of the ultimobranchial bodies in this diverse vertebrate group.
The ultimobranchial gland of birds and the effects of nutritional variations
Authors: Bélanger Leonard F.
Published: June 2005

Histological studies have revealed that the ultimobranchial gland of birds consists of duct‐like follicles which are of pharyngeal origin and parenchymal cords apparently derived from the neural crest. Aberrant parathyroid tissue, lymphoid cells and pseudo‐eosinophils are frequently found. The arterial supply of the ultimobranchial body is regulated by the presence of a sprial type of spincter. The parenchymal cells respond by hypertrophy and hyperplasia to hypercalcemia and by a decrease in secretory activity during prolonged hypocalcemia.

At the electron microscopic level, these cells resemble the C cells of the mammalian thyroid. In the chick, they are presumed to be the only source of calcitonin. In other birds, such as the pigeon and the turtle‐dove, the ultimobranchial gland shares this function with the thyroid.

The calcium‐lowering factor, calcitonin, acts on bone at least partly by inhibiting the bone resorptive activity of the osteocytes (osteocytic osteolysis) which is governed by the parathyroid hormone.
The constancy of cortical units in tetrahymena with varying numbers of ciliary rows
Authors: Nanney D. L.
Published: June 2005

The number of cortical units per ciliary row, estimated by counts of argentophilic elements in Chatton‐Lwoff preparations, declines as the number of ciliary rows rises. The total number of cortical units in the entire cell is not demonstrably correlated with the number of ciliary rows. These observations imply that the mechanisms governing the total supply of cortical units are independent of the mechanisms governing their spatial deployment.
Timed reciprocal dermal‐epidermal interactions between comb, mid‐dorsal, and tarsometatarsal skin components
Authors: Lawrence Irvin E.
Published: June 2005

The epithelio‐mesenchymal interactions in development of chicken comb were studied in 106 skin chimeras grown on the chorioallantois. Explants were formed by enzymatic separation and recombinations of epidermis and dermis from the comb area, the mid‐dorsum, and the tarsometatarsus, at stages before and during primordia formation. Under the experimental conditions, reciprocal developmental roles for comb dermis and epidermis were revealed. Comb dermis determines regional character and induces comb type epidermis. The strength of the inductive stimulus is too weak to erase feathers and scales induced (determined) in older mid‐dorsal and tarsometatarsal epidermis. Comb area epidermis of younger developmental stages can respond to feather and scale induction, but older comb epidermis may continue along its initial course of induction. Indeed, when comb epidermis of eight days and older is placed in contact with other dermis it appears to have an inductive role for comb. The onset of keratinization by 13 days limits comb tissue interaction. The respective roles for dermis and epidermis and critical periods in comb development are discussed.
Normal and induced synthesis of δ‐aminolevulinic acid synthetase in developing chick liver
Authors: Simons J. A. , Boell E. J.
Published: June 2005

δ‐Aminolevulinic acid synthetase activity in embryonic chick liver is not detectable until just before hatching when it surges to more than four times the adult level (12 moles ALA/g liver/h) which is reached in the first week after hatching. An injection of 3, 5‐dicarbethoxy‐1, 4‐dihydrocollidine into the egg results in a massive increase in the activity of the enzyme—up to 40 times the adult level. In addition, the enzyme can also be induced in embryonic chick liver by hypoxia.
A method for the production of pigmentless eggs in Xenopus laevis
Authors: Dumont James N. , Eppig John J.
Published: June 2005

Pigmentless oocytes may be obtained from adult Xenopus laevis females by a combination of repeated induced ovulations with human chorionic gonadotrophin (HCG) and the continuous administration of the antimelanogenic compound phenylthiourea (PTU). Pigmentless eggs obtained in this manner are apparently normal since they may be fertilized and subsequently develop into normal, but pigmentless, embryos and tadpoles. Cessation of the PTU and HCG treatments results in normal pigmentation of immature oocytes; however, those oocytes which are more nearly mature become pigmented to a lesser degree. Those oocytes which are mature at the time treatment is stopped remain pigmentless.
On neurogenetic relations in Drosophila melanogaster
Authors: Chiarodo Andrew , Reing C. Michael , Saranchak Harry
Published: June 2005

The thoracico‐abdominal nerve centers of several winged but flightless Drosophila mutants were examined. Cell number estimates were made for the ganglia of bithorax, vestigial, cut, taxi, and Curly mutants, as well as of wild type flies. No numerical hypoplasia was observed in any of the mutants examined, thus confirming the original conclusion of Power ('50) that inability to fly is not correlated with a hypoplasia of the thoracico‐abdominal nerve center.

A numerical hyperplasia was observed in the bithorax and vestigial mutants. The hyperplasia in the bithorax mutant is discussed in relation to the increased peripheral field in the thorax, caused by the action of the bithorax gene. The cause of the hyperplasia in the vestigial mutant remains unknown.
Expression of embryonic and adult erythrocyte antigens in hematopoietic repopulated x‐irradiated chickens
Authors: Sanders Bob G. , Wiley K. L.
Published: June 2005

An antigen is present on the red blood cells of embryonic and young chickens which is lost during development and is undetectable on the red blood cells of adult chickens. In this study, two experiments were performed to determine the presence or absence of the embryonic antigen. First, spleen, liver and bone marrow cells obtained from three day old chicks were transplanted into x‐irradiated adult chickens in order to determine if the embryonic antigen would be expressed on red blood cells in an adult environment but arising from transplanted “young” cells. Red blood cells from the adult x‐irradiated chickens were assayed at various intervals after transplantation for the presence of the embryonic antigen. Additional red blood cell antigenic markers other than the embryonic antigen demonstrated repopulation in the x‐irradiated chickens, but the embryonic antigen was not detectable. Second, three day old, non‐irradiated chickens were transplanted with adult chicken bone marrow cells and their red blood cells assayed at varying intervals up to 40 days in order to determine the effect of a “young” environment upon adult cells. These chickens continued to express the embryonic antigen on all their red blood cells; i.e., no adult‐like cells were found up to 40 days. The x‐irradiation‐transplantation studies indicate that the erythropoietic stem cells containing gene(s) coding for the embryonic antigen are repressed in the adult chicken and that in the young chicken repopulated with adult hemopoietic cells the gene(s) are derepressed.
Effects of injury and stimulation of the hypoglossal nerve and superior cervical ganglion on the mitotic activity of the glossal epithelium
Authors: Hall R. G.
Published: June 2005

Nerves affect the mitotic activity of the tissue that they innervate. The type of effects depend upon the nerve fiber types and conductive activity of the nerve. This was demonstrated by transection or stimulation of the hypoglossal nerve and removal or stimulation of the superior cervical ganglion. Transection of the right hypoglossal nerve produced an average increase of 18.5% in the mitotic activity of the right glossal epithelium. Stimulation of this nerve decreased the mitotic activity by 17.5%. Removal of the right superior cervical ganglion caused an average decrease of 18.4% while stimulation of this ganglion increased the mitotic activity by 17%.
Motility in chick embryos with substitution of lumbosacral by brachial by lumbosacral spinal cord segments
Authors: Narayanan C. H. , Hamburger Viktor
Published: June 2005

In two and one‐half‐day chick embryos, brachial segments were substituted for lumbosacral segments (Bl series) and vice versa (Lb series). Recordings were made of spontaneous (type I) motility in 9‐ to 17‐day embryos at daily intervals. Total embryonic motility (per cent time spent in activity in 10‐minute periods) and total wing and leg motility did not differ significantly from normal in both series. Furthermore, frequency of movements (per minute) was recorded for wings and legs separately and for combined wing/leg movements. In both experimental series, combined wing/leg movements were significantly more frequent and isolated wing or leg movements less frequent than in normal embryos. This means that two brachial or two lumbosacral segments in the experimental embryos are more tightly coupled than the brachial and lumbosacral segments in a normal embryo. Regional differences between brachial and lumbosacral segments are thus demostrable as early as nine days. The increased frequency of combined wing/leg movements persists after hatching. In hatched chicks of the Bl series, legs are incapable of making alternating stepping movements; they are always abducted and adducted simultaneously as in wing flapping. This is another expression of regional specificity of the brachial cord. We assume that regional specifications of spinal cord segments are built into the cord at the stage of operation.
In vitro maturation and ovulation of oocytes of the catfish, Heteropneustes fossilis (Bloch): Effects of mammalian hypophyseal hormones, catfish pituitary homogenate, steroid precursors and metabolites, and gonadal and adrenocortical steroids
Authors: Goswami Shashi V. , Sundararaj Bangalore I.
Published: June 2005

Wolf and Quimby medium and its modified chemically‐defined version were found to be most suitable among the eight media tested for shortterm culture of oocytes of the catfish, Heteropneustes fossilis. The modified Wolf and Quimby was employed to evaluate the relative effectiveness of several hypophyseal and steroid hormones, as well as steroid precursors and metabolites in inducing in vitro maturation and ovulation in the catfish oocytes. With the exception of ovine luteinizing hormone (LH) which gave only a marginal response even at high dose levels, other mammalian hypophvseal hormones (FSH, TSH, LtH, STH and ACTH) and catfish pituitary homogenate were incapable of inducing oocyte maturation. Of the steroid precursors tested, pregnenolone, progesterone and their 17 α‐hydroxy derivatives were slightly effective in inducing oocyte maturation at high concentrations. Steroid metabolites (pregnanediol‐20 β) were ineffective. The sex steroids (testosterone, estrone, estriol and estradiol) did not induce oocyte maturation, while dehydroepiandrosterone and androstenedione gave only a nominal response even at high doses. Corticosteroids, principally hydrocortisone (F) and desoxycorticosterone (DOC) as also their acetates, were the most potent maturation‐inducing agents even at low concentrations. These results strongly suggest that inasmuch as LH and catfish pituitary homogenate per se do not induce oocyte maturation in vitro, the terminal hormones which act directly on the oocytes to induce maturation and ovulation are the corticosteroids principally, DOC and F. The significance of these findings in the hormonal control of ovulation in the catfish is discussed.
Effects of experimental degradation of microtubules on the growth of cultured nerve fibers
Authors: Handel Mary Ann
Published: June 2005

Nerve fiber outgrowth and elongation were studied in spinal ganglia explants cultured with NGF. The effects of cold and colchicine treatments on the degradation of microtubules and on the outgrowth and elongation of nerve fibers were determined. Colchicine inhibited nerve fiber outgrowth and elongation, and degraded the microtubules of the nerve cells, producing an abundance of 100 Å filaments. Cold treatment inhibited fiber outgrowth and elongation, but did not induce degradation of the microtubules of the nerve fibers. The effect of cold treatment on the growth of nerve fibers was reversible. The microtubules of these nerve fibers therefore exhibited differential stability in reaction to microtubule degradative agents, in that they were degraded by colchicine and were resistant to cold treatment. The results indicate also that microtubules may be involved in the outgrowth and elongation of nerve fibers. However, since nerve fibers exposed to colchicine did not retract, it is suggested that microtubules may not be solely responsible for the maintenance of the fiber processes of these cells, but that contacts with other cells and with a supporting matrix could be important in the maintenance of the asymmetric nerve cell processes.
The occurrence of stage specific antigens during early sea urchin development
Authors: Westin Monica
Published: June 2005

Rabbit antisera to homogenates of unfertilized sea urchin eggs were absorbed with pluteus extract. In the same way, antisera to gastrulae or plutei were also made “stage specific” by absorption with extracts of eggs. When tested by means of immunoelectrophoresis the absorbed sera formed precipitates with antigens in extracts from homologous developmental stages. Precipitates of such stage specific antigens were removed from the agar plates and reinjected into rabbits. In this way, monospecific antisera to four stage specific antigens were obtained. Upon closer analysis, the egg specific antigen was found to be heterogeneous, consisting of two components. Both components decreased in concentration and had disappeared by the time of gastrulation. The two pluteus specific antigens seemed to be absent from eggs and earlier stages. By means of isotope incorporation experiments and autoradiography of immunodiffusion plates, it was found that one of these antigens became detectable at the mesenchyme blastula stage while the other was first detected at the prism stage. The fourth antigen, which was clearly detectable from gastrulation onwards, was found to be already present in the unfertilized eggs but at much lower concentrations than in late developmental stages.
The extent of cell contact and the relative frequency of small and large gaps between presumptive mesodermal cells in normal gastrulae of Rana pipiens and the arrested gastrulae of the Rana pipiens ♀ × Rana catesbeiana ♂ hybrid
Authors: Johnson Kurt E.
Published: June 2005

A comparison was made of the area of cell contact and the relative frequency of small and large intercellular gaps in contacts between presumptive mesodermal cells in 21 hour normal Rana pipiens early gastrulae and hybrid R. pipiens ♀ × R. catesbeiana ♂ arrested gastrulae. Normal cells contact neighbors over a large percentage of the cell surface and are usually polygonal. Hybrid cells contact neighbors over a small percentage of the surface and are usually rounded. An objective method was utilized for choosing contacts and for measuring gap dimensions at regular intervals along the contacts. These measurements show that small gaps are more frequent and extensive in normal presumptive mesodermal cells. These results are discussed in terms of the fine structural bases for differences in cell contact behavior.
Postnatal changes in microtubular protein content in several regions of the mouse brain
Authors: Twomey Stanley L. , Wyttenbach Charles R.
Published: June 2005

Quantitative postnatal changes in colchicine‐binding protein are reported in four regions (cerebrum, thalamus‐hypothalamus, brain stem and cerebellum) of the mouse brain. Relative to unit protein and unit wet weight, changes of −27% (cerebrum) to −53% (cerebellum) occur from day 1 to young adult, with the declines taking place prior to day 7 only in the cerebellum. On the basis of total activity per brain region, however, all areas show a several‐fold increase in colchicine‐binding protein. Thus a true loss of this protein does not occur; rather, its synthesis just fails to keep pace with that of non‐tubulin protein and with the increase in tissue mass.

Assay of the brain from 21 day “reeler” mutants reveals no deviations from normal controls even in the extensively retarded cerebellum.

The several factors which quantitatively affect microtubular protein are discussed. It is concluded that the maturational decline per unit protein is most likely due to the growth and myelination of axons, while the increase in total tubulin is due mainly to extensive dendrite formation. More specific relationships cannot presently be made owing to the lack of more quantitative histological information as to changing cell structure in each region and to the cellular heterogeneity of the regions analyzed. From this study it is clear, however, that real spatial and temporal differences in microtubular protein content exist within the brain.
Organ and species specificity of mouse uterine alkaline phosphatase
Authors: Dufour D. , Tremblay A. , Taskar S. , Estrada R.
Published: June 2005

An alkaline phosphatase was isolated from saline extract of mouse uterus by the method of isoelectric focussing. The organ and species specificity of this protein was demonstrated by immunodiffusion studies. This phosphatase was localized immunohistochemically in the endometrical epithelium of mouse uterus.
Gene action on proliferation and migration in the developing neural crest of black and white axolotls, Ambystoma mexicanum, Shaw
Authors: Borack Leonard I.
Published: June 2005

The mitotic index \documentclass{article}\pagestyle{empty}\begin{document}$ \left({\frac{{{\rm number\,of\,dividing\,cells}}}{{{\rm total\,number\,of\,cells}}}} \right) $\end{document} of the neural crest and its derivatives in situ was determined in serially‐sectioned embryos of the black (DD or Dd) and white (dd) strains of the Mexican axolotl, Ambystoma mexicanum, Shaw, to see whether the differences between the strains in the number and distribution of their initial complement of melanophores could be causally related to differences in the pattern of development of their respective neural crests.

Prior to and during the initial appearance of melanophores, the mitotic index of the neural crest in situ in the black axolotl is significantly greater than in the white. Concommitantly, there are more crest cells in the black than in the white prior to crest cell migration. However, during the periods of maximum crest cell migration and initial appearance of melanophores, there are significantly more crest cells in situ in the white than in the black. These crest cells in situ in the white are clumped together mid‐dorsal to the neural tube, while in the black they show the dispersion typical of migrating crest cells.

Following the initial appearance of melanophores, there are no differences between the strains in the number of melanophores dorsal to the neural tube and somites, but there are significantly more crest‐derived cells in this area in the black than in the white. The latter difference between the strains may be causally related to the significantly greater number of cells in the early spinal ganglia of the black axolotl than in the white.
Capacitation of hamster spermatozoa treated with rabbit tubal fluid or rabbit and bovine tubal cystic fluids
Authors: Iwamatsu T. , Chang M. C.
Published: June 2005

The induction of capacitationin vitroof hamster sperm was examined in the presence of rabbit tubal fluid or tubal cystic fluids of cow and rabbit. When mixed with recently‐ovulated eggs in Tyrode's solution containing rabbit tubal fluid, epididymal spermatozoa became capacitated and sperm penetration as well as the formation of pronuclei was observed in most eggs within three hours. Incubation of epididymal spermatozoa in the presence of tubal cystic fluid of rabbit or cow could induce the capacitation of hamster sperm, and sperm penetration was observed by insemination of the incubated sperm. By treatment with these fluids, especially those from rabbits and in the presence of sperm, the zona pellucida was elevated or dissolved. The factor(s) responsible for sperm capacitation and acting on the zona pellucida was relatively heat‐stable. The high incidence of polyspermy was probably due to the abnormal condition of the zona pellucida and the presence of numerous capacitated spermatozoa under the present experimental conditions.