bluuebunny/crossref_metadata_2025 huggingface dataset:
Cortical integration in tetrahymena: An exercise in cytogeometry
Authors: Nanney D. L.
Published: June 2005

The numbers and positions of contractile vacuole pores (CVP) have been examined in strains representing ten genetically isolated groups of Tetrahymena pyriformis. In all strains the position of the CVP's moves, relative to the individual ciliary rows, as a function of the total number of ciliary rows in the cortex (Corticotype). Similarly, the number of CVP's varies in a systematic way through the corticotypic array in each strain. The development of contractile vacuole pores is shown to be regulated by gross geometrical properties of the cortex and can be described with the aid of a simple geometrical model. At least three classes of strains can be distinguished by the patterns of correlation between CVP position and corticotype. Further discriminations are possible within each class through the relationships between CVP number and corticotype. These observations aid in understanding ciliate morphogenesis and Tetrahymena taxonomy.
The response of X‐irradiated limbs of adult urodeles to autografts of normal cartilage
Authors: Eggert Ronald C.
Published: June 2005

The left forelimbs of 100 adult newts (Triturus viridescens) were exposed to 1,560 or 2,000 r of localized x‐irradiation; right and left forelimbs were amputated through the distal humerus. Eighty of the left irradiated forelimbs were then implanted autoplastically with cartilage taken from the dorsal cartilaginous plate of the unirradiated contralateral scapula and rendered virtually free of all cell types other than chondrocytes by subjection to manual stripping of soft tissues and perichondrium (60 cases) and manual stripping combined with brief alcohol immersion (20 cases).

The results showed that the unirradiated right forelimbs regenerated normally in all cases. They also showed that the irradiated left control limbs (no implants) failed to regenerate in all cases (20). In contrast, those irradiated limbs implanted with unirradiated cartilage developed blastemata which differentiated into irregular masses of cartilage. No blastema developed following dedifferentiation of irradiated stump tissues. The blastema developed concomitantly with the breakdown of the implanted cartilage. Since these two events were separated by a time interval of two weeks, it is concluded that the blastema was formed by a direct, massive contribution of cells from the normal autograft. Further, the histologic evidence presented indicates that the majority, if not all, of the blastema cells derived from chondrocytes of scapular origin in adult newts and implanted autoplastically into irradiated limb tissue has differentiated into chondrocytes.
The influence of neural retina and lens on the development of embryonic lens vesicles in Amblystoma punctatum and Triturus viridescens
Authors: Reyer Randall W.
Published: June 2005

Embryonic lens vesicles from both species of salamander self‐differentiated into a small lens with fibers when implanted into either the dorsal fin or anterior chamber of the larval eye. Growth of these lenses was very slow in Amblystoma and somewhat faster in Triturus. When implanted into the pupil in place of the extirpated host lens, the embryonic lens vesicles differentiated normally and had a normal rate of growth. Lens regeneration from the host iris in Triturus was frequently inhibited by the implanted lens. A statistical analysis by the method of covariance showed that, in both species, lenses from the implants were largest in the lentectomized eyes, smaller in the vitreous chamber of eyes with intact host lens and smallest in the anterior chamber, host lens present. In Amblystoma, the growth rates, as indicated by the coefficients for linear regression, were significantly different between lenses developing in the absence of the host lens and those growing from implants into either the anterior or vitreous chambers of eyes containing the host lens. In Triturus, a significant difference was observed only between growth rates of lenses in the lentectomized eyes and in the anterior chambers, host lens present or in the dorsal fin. These results show that the neural retina stimulates growth and differentiation of embryonic lens vesicles and that the host lens retards their growth.
Analysis of some of the variables associated with the proliferative response of human lymphoid cells in culture
Authors: Wilson Darcy B.
Published: June 2005

Human blood leucocytes from certain individuals cultured alone — as “controls” for experiments designed to demonstrate the mutual reactivity of mixed cultures of leucocytes from different donors — revealed an intense proliferative response by the fifth day as measured by the incorporation of radioactive thymidine. Furthermore, thymidine incorporation into control leucocyte cultures from most donors was markedly elevated by the seventh day of culture. Because these high background levels tended to obscure the mutual reactivity of mixed leucocyte cultures, experiments were designed to elucidate the nature of and to circumvent these difficulties. By supplementing the growth media with human plasma, rather than calf serum, the background activity of the control cultures could be maintained at low levels without compromising the mutual reactivity of lymphocytes in the nixed cultures. One other source of variability which proved simple to control was the relative number of “contaminating” non‐lymphoid cells in the cultures. This factor was important since, in the preparation of the leucocyte suspensions with erythrocyte sedimentation procedures, the number of contaminating granulocyte cell types can be expected to vary over a wide range.

Phytohemagglutinin (PHA) was used as a mitogen in experiments designed to define further some of the parameters of the lymphocyte response in vitro. When a standard number of lymphocytes — either as a “purified” suspension or as one containing significant numbers of contaminating granulocytes — was cultured with various concentrations of PHA, a dose‐dependent response was observed. Partially purified lymphocyte suspensions were only one‐half to one‐third as active as non‐purified leucocyte suspensions containing the same number of lymphocytes. This could not be attributed to a deleterious effect of PHA on purified cultures with a lower cell density since (1) the peak response of both cultures occurred with the same concentration of PHA, and (2) the maximal reactivity to PHA could be restored by increasing the granulocyte content.
The ontogeny of the multiple molecular forms of hemoglobin in the developing chick under normal and experimental conditions
Authors: Simons Jarid Allan
Published: June 2005

A total of five molecular forms of hemoglobin appear during the development of the chick embryo. In the seven day embryo, the earliest stage studied, four of these forms are present. Hb I, preponderant in the early embryo, decreases to become a minor component at hatching; Hb II, a minor component in the early embryo, increases to become the major component at hatching; Hb III is present throughout as a minor component. Hb IV is first detectable in the nine day embryo and remains a minor component. Hb E is present as a minor component in the seven day embryo and is last found in the eleven day embryo. After hatching there is no further change in the hemoglobin pattern.

In ovo oxygen deficiency and chromate retard the progressive shift from Hb I to Hb II. In vitro oxygen deficiency and chromate accelerate heme synthesis and preferentially the synthesis of Hb I.

Cobalt in vivo results in a decrease in Hb I and a corresponding increase in Hb III and Hb IV. The in vivo incorporation of Fe59 indicates that the effect of cobalt is to enhance the rate of degradation of Hb I.

The progressive shift from Hb I to Hb II which occurs in normal embryogenesis is discussed in terms of the control of hemoglobin synthesis at the translational level.
The effects of thiourea, photoperiod and the pineal gland on the thyroid, adrenal and reproductive organs of female hamsters
Authors: Reiter Russel J. , Hoffman Roger A. , Hester Ralph J.
Published: June 2005

Two experiments were conducted to test the influence of ambient light and the pineal gland on the pituitary‐thyroidal and pituitary‐gonadal axes of female golden hamsters. The results show that the thyroid glands of dark‐exposed [light:dark (LD) 1:23 in hours], goitrogen‐treated (1% aqueous thiourea as drinking fluid) animals hypertrophy less than those of similarly treated animals maintained in long daily periods of illumination (LD 16:18). Goitrogen‐induced thyroidal hypertrophy is accompanied by hypothyroidism. The hypertrophic response of the thyroid glands in either light cycle was not affected by removal of the pineal gland. Microscopically the thyroid glands of goitrogen‐treated animals kept in either long or short daily photoperiod exhibited changes normally associated with hypertrophy and concomitant hypofunction of the gland.

The exposure of intact female hamsters to LD cycles of 1:23 caused a significant reduction in the weight of the uteri and adrenal glands within 35 days. Likewise, removal of the eyes led to atrophy of the same organs. Although darkness caused a variable change in ovarian weight, histological studies of ovaries from dark‐exposed and blinded animals suggested minimal hormonal output. The atrophic responses of the ovaries, uteri and adrenal glands were prevented by pinealectomy. These data suggest that darkness activates the pineal gland to secrete a substance(s) which modified pituitary‐target organ relationships.

Hypothyroidism induced by the administration of thiourea to intact female hamsters in both long (LD 16:8) and short (LD 1:23) daily light cycles caused a reduction in weight of the ovaries, uteri and adrenal glands. With one exception, these responses were not altered by pineal removal. The uterine weights of the dark‐exposed hypothyroid animals that were pinealectomized were comparable to those of animals given fresh drinking water and maintained in LD cycles of 16:8 (normal controls). The relationship of the secretion of thyroid stimulating hormone to adrenocorticotrophic and gonadotrophic hormone release by the pituitary is discussed.
Regeneration of the caudal neurosecretory system in the cichlid teleost Tilapia mossambica
Authors: Fridberg Gunnar , Nishioka Richard S. , Bern Howard A. , Fleming Warren R.
Published: June 2005

After total extirpation of the caudal neurosecretory system in the teleost Tilapia mossambica by ligature and removal of the caudal peduncle, a new system regenerates rapidly. The new neurosecretory cells differentiate from ependyma. A series of transitional stages between slightly modified ependymal cells and fully developed caudal neurosecretory neurons can be readily constructed. Immediately after the operation, the distal part of the remaining spinal cord undergoes degeneration, during which no traces of the caudal system can be found. Eleven days after the operation the first signs of the new system appear, and after three weeks a potentially functional, although much reduced, system has developed, the elements of which are detectable with the electron microscope. After 5–6 months, an extensive system has regenerated; however, the neurohemal area equivalent to the normal urophysis is contained within the spinal cord. There is strong cytologic evidence for a considerable release of elementary neurosecretory granules into the cerebrospinal fluid in the regenerating and regenerated system, possibly by several different mechanisms. Prominent tubular reticula occur in the distal (preterminal) parts of the neurosecretory axons, and the possibility of local axonal production of vesicles and granules is strongly supported. Signs of secretion into the central canal and of distal production of neurosecretory material are also present in normal Tilapia, but both phenomena are much more strikingly demonstrated in regenerating systems.
On the role of metal cations in cellular adhesion: Effect on cell surface charge
Authors: Armstrong Peter B.
Published: June 2005

An examination has been made of the hypothesis that the role of divalent cations in promoting reaggregation of dissociated cells is principally to reduce the negative electrostatic charge at the cell surface. This hypothesis would suggest that cells in the presence of different divalent cations would reaggregate at identical rates if the concentrations of the different cations were so adjusted that in all cases the cells possess the same charge. This expectation has not been fulfilled. Magnesium ion was most effective in promoting reaggregation, calcium somewhat less so, and strontium and barium had little or no effect.
Induction of altered patterns of cortical morphogenesis and inheritance in Paramecium aurelia
Authors: Wille John J.
Published: June 2005

The effect of phenethyl alcohol (PEA) on cortical morphogenesis in Paramecium aurelia in relation to the fission cycle was investigated by the method of sister cell analysis. PEA interferes with cortical morphogenesis by suppressing the formation of cortical units, presumably by the inhibition of kinetosome production. The action of PEA at different timed stages during the fission cycle shows that there are series of “transition points” beyond which PEA no longer has any effect on cell division, but still blocks cortical unit formation, while at a later time, both cell division and cortical morphogenesis are unaffected. Incompletely divided cells, “chains,” lacking oral membranelles are produced after prolonged PEA treatment. The specific inhibition of oral membranelle formation is shown by the effect of PEA on oral morphogenesis during fertilization and reorganization in the absence of cell division. The gullet condition following PEA‐treatment during conjugation is restored to normal through successive cell generations, except for those cells lacking oral membranelles. The results indicate that chemical modification of the cortex can result in persistent changes in the pattern of cortical organization.
Origin and development of retinal melanin in Amblystoma punctatum devoid of ovarian pigment
Authors: Piatt Jean
Published: June 2005

This report is concerned with the origin and elaboration of melanin in the retinal epithelium of Amblystoma punctatum. The animals used in this study developed from a single clutch of unpigmented eggs. The tapetum of such animals is devoid of ovarian pigment and, consequently, the initial formation of melanin can be readily followed. Specifically examined is the possibility of active involvement of melanocytes in the formation of tapetal pigment.

Eyes were transplanted from embryos at stage 32+ into the gill region and ventral flank of embryos at stage 28. Data were obtained concerning the initial appearance of melanin and its subsequent elaboration in the tapetum of the grafts correlated with the presence or absence of melanocytes in the immediate vicinity.

Melanin first appears in the flank grafts two to three days before melanocytes reach the area. Sequence of melanin elaboration in both types of graft follows more closely that of the donor animals than that of the less advanced hosts. Melanin always appears first in the anterior portion of both grafts and intact eyes, despite the fact that melanocytes are just as closely associated with the posterior pole of the eyes. It is concluded that melanin production is an intrinsic property of the retinal epithelium in Amblystoma.
Insect neurometamorphosis. III. Nerve cord shortening in a moth, galleria mellonella (L.), may be accomplished by humoral potentiation of neuroglial motility
Authors: Pipa Rudolph L.
Published: June 2005

Nerve cord segments were removed from last stage larvae and pharate pupae and transplanted into recipients of known developmental age. When transplanted into larvae the connectives shortened maximally in near‐synchrony with their host's counterpart; in both, potentiation began during early pupal development, and was completed 1.5–2.5 days after ecdysis. Histological comparisons revealed metamorphic changes in transplants, changes which paralleled those normally occurring in situ. Shortening of transplanted segments is not adventitious, and it would seem that shortening of the transplant and the host's counterpart are manifestations of the same phenomenon.

Larval connectives transplanted into pupae younger than two days shorten completely; those transplanted into pupae aged two days or older, or into adults, do not. Actively shortening connectives shorten completely when transplanted into pupae two days old, or into younger pupae, but not when transplanted into larvae, or into pupae three or more days old. This affirms a critical period in the early pupa when activation is maximal. The nature and source of the potentiating factors are unknown, but most likely they are blood‐borne.

Connectives with cauterized ganglia will shorten even though axon degeneration is pronounced. This shortening, too, is potentiated during the critical period. The hypothesis is advanced that humoral factors may be potentiating shortening by activating neuroglial motility.

Connectives which shorten slightly in situ will shorten entirely if transplanted into hosts in the critical period. The inhibition removed by the operation may be mechanical, since connectives which shorten in situ are located in body segments which also shorten.
On the similar orientation of fibrillar structures and rows of esterolytic invaginations in plasmodia of the slime mold, Physarum confertum Macbr.
Authors: Bauer L. G.
Published: June 2005

The localization of thiolacetic acid esterase activity in plasmodia of the slime mold, Physarum confertum Macbr., permitted the visualization of a system of esterolytic invaginations of the plasma membrane which appeared closely related to the arrangement of fibrillar structures. Fibrils running perpendicularly to the long axis of tubes and channels of the conducting system were found to be attached to relatively large lateral infoldings, while rows of smaller invaginations seemed to follow the course taken by the fibrils. In living and fixed specimens, constrictions in the diameter of tubes and channels were observed at the level of fibrils and linearly arranged rows of infoldings. These findings suggest that esterase‐positive infoldings may result from the contraction of fibrillar structures which are attached to the plasma membrane at multiple points along their length.
Studies on the physiology and genetics of the rotifer, Asplanchna. III. Results of outcrossing, selfing, and selection
Authors: Birky C. W.
Published: June 2005

Sympatric populations of Asplanchna brightwelli and A. girodi do not hybridize, so that these two morphological species represent distinct biological species or syngens. Populations of A. brightwelli from Tennessee and Indiana may be crossed to give viable F1, F2, and backcross generations. These two widely separated populations may thus be assigned to a single biological species. A program of repeated selfing with selection for high clonal viability has been carried out with A. brightwelli. Clonal viability declined with the first selfing, then rose with succeeding generations of selfing and selection, to or above the viability of clones obtained by inbreeding within the parental mixed stock. Selfing also led to an increase in the homogeneity of the growth rates of groups of sibling clones obtained by selfing, suggesting increased homozygosity in the selfed, selected lines. The results of the selfing and selection experiments suggest that wild stocks of Asplanchna are heterozygous for a number of recessive detrimental and lethal genes affecting the growth rate and viability of clones. The heterozygosity of the natural populations, together with the failure of geographically isolated populations of a morphological species to become reproductively isolated, suggests that these rotifers are not extreme inbreeders. It is suggested that the maintenance of recessive detrimentals in these rotifers, in which the males are haploid, may indicate that the phenotype of a male is determined to a large extent by the genotype of its mother. Such maternal effects would protect detrimentals from selection in the male offspring of heterozygous females.
Studies on the mechanism of implant‐induced supernumerary limb formation in urodeles. I. The histology of supernumerary limb formation in the adult newt, triturus viridescens
Authors: Carlson Bruce M.
Published: June 2005

Supernumerary structures were formed in adult Triturus forelimbs following subcutaneous implantation of pieces of frog kidney. The gross and microscopic events in supernumerary limb formation were described in this paper. The first few days after implantation comprise a stage of wound healing and phagocytosis, the latter by both the epidermis and inflammatory cells of the host. Following this the tubular portions of the implant degenerate. During the height of this degeneration, the first dedifferentiated cells of the host are seen. These cells increase in number and gather around a central focus to form a blastema. From the blastema, first cartilage and then muscle differentiate, and elongation proceeds concomitantly with this differentiation. The final result of the kidney implant may be no growth at all, periosteal chondrification not preceded by a blastema or a true supernumerary structure ranging in complexity from a cartilaginous nodule to a fully developed supernumerary limb. The results of this experiment indicate that aside from the initial stimulus and the ultimate degree of morphogenetic complexity attained, the development of a supernumerary structure is very similar to the regeneration of an amputated limb.
Studies on the mechanism of implant‐induced supernumerary limb formation in urodeles. II. The effect of heat‐treatment, lyophilization and homogenization on the inductive capacity of frog kidney
Authors: Carlson Bruce M. , Morgan Charles F.
Published: June 2005

In experiments designed to test the effect of physical manipulations upon the ability of frog kidney implants to induce supernumerary limbs in Triturus viridescens, kidney tissue from adult Rana pipiens was treated by boiling, lyophilization and homogenization. Normal kidney induces supernumerary growth in over 90% of cases. Boiling at 100°C for ten minutes destroyed the ability of the kidney implant to stimulate supernumerary growth. Lyophilization did not affect the inductive capacity of the implant. Normal percentages of accessory growth were observed after multiple injections of frog kidney homogenates. It was concluded that some chemical agent(s) present in frog kidney is responsible for the inductive effect.
Genetic and experimental studies on a lethal trait (“Short Toes”) in the Mexican axolotl (Ambystoma mexicanum)
Authors: Humphrey R. R.
Published: June 2005

A recessive lethal factor (s) discovered in the Mexican axolotl induces (1) reduction in length of limbs and number of phalanges, (2) failure of complete development of Mullerian ducts, and (3) renal pathology and dysfunction leading to death.

Larvae homozygous for s, in parabiosis with normal animals, show no improvement in length of limbs or number of phalanges. Transplants of the forelimb area between normal and s/s embryos produce limbs of donor type. The character of the limbs in the s/s thus appears independent of nutritional or hormonal influences.

The Mullerian ducts of s/s reared as parabionts with normal animals remain incomplete. The duct derived from a pronephric transplant from an s/s into a normal embryo attains full length, however, as does the duct from the reciprocal type of transplant. Probably intrinsic factors in duct epithelium and related stroma combine in s/s larvae to limit duct growth.

Death of affected animals usually occurs before they are one year of age. Although some attain sexual maturity, none has reproduced.

Gene s was probably carried by some of the white axolotls imported from Cracow by the Wistar Institute in the early 1930's. No linkage with other genes has been demonstrated.
Observations on nuclear differentiation in Ascaris
Authors: Swartz Frank J. , Henry Mary , Floyd Alton
Published: June 2005

A microdensitometric survey of the DNA content of adult Ascaris nuclei was undertaken to determine the relationship between these values and those expected as a consequence of somatic chromatin diminution. The species diploid value was derived from measurements of Feulgen stained sperm nuclei and unreduced primary oocytes. The somatic DNA values, expected to be hypodiploid if unaltered following diminution, fall into three groups. The first, the intestinal nuclei, are closest of all positively staining nuclei to the anticipated values but are nevertheless in the tetraploid range. A second group of somatic cells, constituting the uterine epithelium, pharyngeal glands and excretory cell present nuclei with quantities of DNA suggestive of high degrees of polyploidy. A “polyploid” gradient exists within the nuclei of the uterine epithelium. Values equivalent to 150‐ploid are found in the posterior half of the uterus, becoming progressively lower toward both ends. The gradient corresponds closely to the known protein synthetic activity of the epithelium. Nuclei of the pharyngeal glands and excretory cell, among the largest nuclei reported, stain distinctly with the Feulgen reaction but their degree of “polyloidy” has not been estimated. On occasion, the excretory nucleus has been noted to be Feulgen negative.

The third group of nuclei include those of the somatic muscle and ganglia. By all of the cytological tests for DNA applied (Feulgen staining with standard and fluorescent Schiff reagent, acridine orange and methyl green staining) the muscle nuclei are negative; however, they contain considerable amounts of RNA. Some of the neuron nuclei are negative while others show a faint membrane‐associated staining. The Feulgen‐negative nuclei of the adult most likely represent those which remain in the originally diminished condition.
Detection of qualitative differences between the RNA of livers and kidneys of adult chickens and a temporal and regional study of liver RNA in chick embryos
Authors: Miyagi M. , Kohl D. , Flickinger R. A.
Published: June 2005

RNA preparations from livers and kidneys of adult chickens were qualitatively distinguished by DNA‐RNA hybridizations involving double saturation experiments. This technique was used to study the temporal and regional synthesis of liver‐like RNA in the developing chicken embryo. It was found that the amount of liver‐like RNA in the embryo increases from two and one half days to three and one half days of development. Furthermore, this liver‐like RNA was found in greater amounts in the areas of three and one half day embryos containing the differentiating liver rudiment.
Differentiation of chromatophorotropins from the prawn, Palaemonetes vulgaris, and the fiddler crab, Uca pugilator
Authors: Fingerman Milton , Couch Ernest F.
Published: June 2005

The fiddler crab, Uca pugilator, and the prawn, Palaemonetes vulgaris, produce chromatophorotropins that disperse the red pigment in both species, concentrate the red pigment in both species, and disperse the melanin of the fiddler crab. The prawn does not have melanophores. However, the hormone obtained from organs of either the prawn or the crab that concentrates the pigment in the erythrophores of the prawn is different from the hormone present in the same extract which has the same physiological effect on the erythrophores of the crab. The identical conclusion was arrived at when the hormonal control of red pigment dispersion was considered. Furthermore, it was evident that dispersion of the red pigment and melanin dispersion in the fiddler crab were caused by different substances, when extracts of organs from Palaemonetes vulgaris as well as from Uca pugilator were tested.
Age‐dependent intraclonal conjugation in Euplotes crassus
Authors: Heckmann Klaus
Published: June 2005

In Euplotes crassus each of the five different mating‐types is determined by a different allele at the mating‐type locus. There is complete dominance among these alleles so that in diploid cells only one of them is phenotypically expressed. It was observed that in heterozygous clones expressing only one mating‐type, cells arose after about 500 consecutive fissions which expressed another mating‐type. This observation led to the finding that in E. crassus, late in the life history of a clone, a stage is reached in which the dominance relationship among the mating‐type alleles is abolished. A cell heterozygous at the mating‐type locus is at that stage no longer stable with respect to mating‐type transmission, its mitotic progeny expresses either one of their two mating‐type alleles and are therefore able to conjugate with each other, as soon as different mating‐types are expressed. It is further shown that intraclonal conjugation inaugurates new life cycles so that mating‐type instability seems to serve the same function as autogamy in other ciliates, i.e., it starts new life cycles for cells which have failed to find interclonal mates.

A few heterozygous clones have been found which were not able to enter the stage of mating‐type instability. It is shown that they are genetically related and that they can be interpreted as carrying a dominant mutation which does not allow them to enter the life cycle stage of mating‐type instability.
The development of the electromyogram in chick embryos
Authors: Boëuthius Jöurgen
Published: June 2005

Electromyograms (EMG's) of developing chick embryos were recorded with an electrolytically sharpened tungsten electrode and with a concentric unipolar electrode.

Earlier observations of the occurrence of movements on the sixth day were confirmed. Before the twelfth day, only small irregular potentials could be obtained from the muscles (amplitude less than 50 μV). After the twelfth day, the amplitude of the action potentials (potentials) increased rapidly. Up to the fifteenth day, the potentials were mainly monophasic (amplitude 150 μV). On the seventeenth day, the amplitude reached about 500 μV and the potential configuration was similar to that of the adult. The duration of the potentials did not change significantly during this period.

The EMG activity occurred in bursts. The duration of the bursts from the wing muscles tended to be less than one second whereas in the leg muscles it was generally 2‐5 seconds. This difference in burst duration was systematically studied on six embryos aged 14‐17 days and its functional significance was discussed.

To obtain a rough estimate of the maximal firing frequency of the motor units, the “overall frequency” of the potentials was measured. A steep increase in frequency was found between the twelfth and fifteenth day and an interference pattern of the adult type was obtained on the seventeenth day. The temporal correlation between these changes in the EMG pattern and other properties of the developing muscles was discussed.
Actinomycin D: Effect on induced metamorphosis in the Mexican axolotl
Authors: Prahlad K. V. , Delanney L. E.
Published: June 2005

Actinomycin D was used to inhibit the action of T3 in the induction of metamorphic changes in the Mexican axolotl. Am D was administered before and after (in hours) T3 injection as follows: (1) ‐48; (2) ‐24; (3) ‐8; (4) 0; (5) +24; (6) +48; (7) +72; (8) +120; (9) +168. Five μg Am D administered alone was not lethal. However the majority of the animals injected with T3 and Am D died within 30 to 33 days. All experiments were at 20°. Suppression of metamorphic change was greater in group 2 than 1 and greater in groups 4 and 5 than 6. Group 3 showed maximum inhibitory effects of Am D. Very little inhibition was seen in groups 7 through 9. Gill filament resorption and sloughing of skin could not be inhibited completely in any of the groups. Exophthalmia was seen in all except group 3. Least changes occurred in the main gill rachis and the fins. When Am D was administered to hypophysectomized axolotls eight hours prior to T3 there was complete gill filament resorption before any change was observed in controls. Also skin sloughing and exophthalmia were precocious in Am D and T3 injected hypophysectomized axolotls. The observations above indicate variable responses in the metamorphosing tissues of the axolotl to Am D. Hence utmost caution is necessary in the interpretation of any of the inhibitory effects of Am D at the cellular level.
Histopathology of intersexuality in mosquitoes
Authors: Anderson John F.
Published: June 2005

Masculine expressivity in several species of mosquitoes is dependent upon low larval rearing temperatures. At elevated temperatures femininity prevails in both sexual genotypes. This paper is concerned with the histological development of organs of genotypic males of Aedes stimulans (A. stimulans) and ix Aedes aegypti (A. aegypti) before, during and after their determination to a specific sexual form. Intersexuality of homologous and nonhomologous organs was shown to arise in a manner that has not been previously reported in insects. Homologous organs develop similarly in the two sexes up to a critical stage, after which divergent morphogenesis commences. This critical period occurs at an earlier stage of ontogeny in males than it does in females. At elevated temperatures and during their period of plasticity, organs of genotypic males developed in a feminine manner. Determination began approximately at the time of divergent development. If the temperature remained high at this time, organs continued their feminine development, but if the temperature was lowered before feminine specialization, masculinity quickly ensued. Nonhomologous organs that are found only in males were present during ontogeny of larvae which were reared at elevated temperatures. These organs reached a high degree of juvenile masculine specialization during the larval period, but then histolyzed during pupal development. Nonhomologous organs that are present only in females were also studied. Primordia of the median oviduct, spermathecae and related feminine parts were the ones selected. In genotypic males which were reared at high temperatures, the primordia appeared at the same time and developed in the same manner as did those of a normal female. When larvae were reared at elevated temperatures just long enough to activate these primordia and were then exposed to low temperatures, the discs developed into masculine genital appendages of abdominal segment eight.
Tissue specific esterase isozymes of the mouse (Mus musculus)
Authors: Ruddle Frank H. , Harrington Linda
Published: June 2005

For this report, the tissue‐specific esterase isozymes of 35 organs of the mouse, Mus musculus, were studied by means of starch gel electrophoresis. Zymogram patterns of organs from males and females of the inbred strains SJL/J, C57BL/6J, and RF/J were compared. The ensemble of esterase isozymes expressed by each organ is in most instances distinctly unique. Sexual dimorphisms are reported for the submaxillary gland and the kidney. These are believed to be under hormonal control. It is postulated that enzyme differences between the male and female with regard to the submaxillary gland and kidney may be significant in the biosynthesis and/or secretion of pheromones.
Developmental studies of the dipteran salivary gland. IV. Changes in DNA content
Authors: Laufer H. , Rao B. , Nakase Y.
Published: June 2005

The DNA content of the salivary gland was measured by the method of Burton in larvae of Chironomus thummi at four stages of development during the onset of the larval‐pupal metamorphosis. The amount of DNA at first increased in the gland, from 0.28 μg/gland at the mid‐fourth instar to 0.45 μg/gland in the early prepupa. This increase was immediately followed by a significant decrease in the amount of DNA to 0.37 μg/gland in the late prepupa.

The loss of DNA is considered to be of major interest since it occurred at a time when chromosomal puffing is observed in some regions of the chromosomes. Puffing reflects gene activity. Furthermore, the loss of DNA was preceded in the early prepupa by an increase in the gland's DNase content. The change in this enzyme represents the first detectable chemical change signaling the onset of glandular metamorphosis and suggests that portions of the polytenic chromosomes are the substrate for this hydrolase. This suggestion is substantiated by the constancy of the cell number within the salivary gland and the loss of nuclear volume in individual gland cells. The destruction of the gland appears to be a self‐regulated programmed event occurring in the course of normal development and seems to be mediated by the control of the enzyme DNase.
Cortical slippage in Tetrahymena
Authors: Nanney D. L.
Published: June 2005

Two strains of Tetrahymena pyriformis manifest similar deviations from the usual pattern of stomatogenesis. Some of the cells develop oral anlagen in the normal manner on the right postoral meridian (meridian 1), but others have oral primordia displaced to the left or (less frequently) to the right by one or more ciliary rows. The other caudal organelles, the cytoprocts and contractile vacuole pores, are displaced in a similar manner. In the course of successive fissions and repeated stomatogenic shifts, the stomatogenic site, and indeed all cortical structures, are expected to completely circumnavigate the cell. These observations support the interpretation that the various kineties are not permanently differentiated with respect to their morphogenetic capacities.
Fine structure of gametes of Nereis limbata (Annelida) before and after interaction
Authors: Fallon John F. , Austin C. R.
Published: June 2005

The acrosome of the Nereis limbata spermatozoon is a vesicular body which is shaped in the form of a double‐walled hollow cone. As such it encloses an axial chamber housin the anterior part of a rod‐like structure which, posteriorly, fits into a deep invagination in the nucleus. When the acrosome undergoes reaction preparatory to and during penetration of the egg envelope, it opens anteriorly, discharging its contents, and the axial chamber, together with its contained rod, is expanded and portruded as the acrosome filament.

The chorion of the egg is about 0.7 μ thick, and is traversed completely by microvilli which project at intervals. Numerous broad canals extend about three‐quarters through the chorion. It is by one of these canals that the acrosome filament passes in the initial stages of sperm penetration.

The cortex of the egg has a wide zone of densely packed alveoli which contain moderately electron‐dense material, the jelly precursor. Cortical reaction to sperm entry involves fusion between adjacent alveoli and opening up of alveoli onto the cytoplasmic surface of the egg. Released jelly precursor, evidently becoming hydrated, flows into the perivitelline space and thence through the pores in the chorion that accommodate the microvilli (flowing around the microvilli which persist), so as to form a thick layer about the egg.
Pentose phosphate pathway activity of the chick embryo in ovo
Authors: Wenger Eleanor , Wenger Byron S. , Kitos Paul A.
Published: June 2005

Using a novel radio‐respirometer, the relative activity of the pentose phosphate pathway has been determined at various stages of development of the chick embryo, by comparing the recovery of C14O2 from glucose labeled in position one (G‐1) to that from glucose labeled in position six (G‐6). Resiprometry was performed on the intact embryo in ovo using concentrations of glucose within the range found in normal embryonic body fluids. Significantly greater recovery of C14O2 from G‐1 relative to that from G‐6 was obtained at 68–72 hours and again at 6–8 days. These periods correspond in temporal position with previously reported maxima in glucose‐6‐phosphate deydrogenase activity in the brain of the developing chick embryo and are considered to support the interpretation that patterns of the enzyme activity, determined on homogenates in vitro, reflect patterns of activity of the pentose phosphate pathway in ovo.
Diurnal variations of the fattening response to prolactin in the golden topminnow, Fundulus chrysotus
Authors: Lee Richard W. , Meier Albert H.
Published: June 2005

Fattening was induced in sexually mature golden topminnows, Fundulus chrysotus, by daily injections of prolactin or luteinizing hormone. However, the time of treatment was of fundamental importance. Whereas injectins given during the middle of a 16‐hour photoperiod stimulated an increase in body weight and fat stores, injections given early in the light period caused a loss in body weight and lipid reserves. These results suggest that the phasing of diurnal rhythms of prolactin and/or luteinizing hormone release from the pituitary may be important in regulating the annual cycle of fat stores.

Prolactin, alone, did not induce substantial fattening, if any at all, in hypophysectomized topminnows. Accordingly, the necessity for other pituitary factors at the midphotoperiod interval is apparent. In addition, the deoreases in the lipid and dry nonlipid components of hypophysectomized F. chrysotus by prolactin injections, early in the photoperiod or at midday, suggest there is at least one extra‐hypophyseal factor which exhibits a diurnal periodicity affecting the responses to prolactin.
Regeneration of a sensory system: The formation of central connections by normal and transplanted cerci of the house cricket Acheta domesticus
Authors: Edwards John S. , Sahota T. S.
Published: June 2005

The abdominal cerci of the house cricket, Acheta domesticus, regenerate after amputation. Regenerating sensory fibers establish normal functional connection with the giant fiber system in the terminal ganglion.

When cercal regenerates were transplanted to the stumps of the mesothoracic legs, a cercus developed instead of the usual leg regenerate. The regenerate cercus sent fibers to the mesothoracic ganglion. Histological and electrophysiological evidence is presented which demonstrates the formation of synaptic contact with elements of the giant fiber system in the ganglion of the segment receiving the graft.

It is inferred that regenerating sensory fibers can recognize the central fibers on which they normally terminate, in this case the giant fibers, at some distance from the normal region of synaptic contact. They recognise the cell as a whole rather than a specific synaptic area.
Temporal skin factors influencing the development of melanoblasts in piebald mice
Authors: Mayer Thomas C.
Published: June 2005

The mechanism involved in the development of the pigmentary pattern in piebald (s/s) mouse embryos was investigated through the use of a combination grafting method. Skin from a potentially white spotted area of piebald embryos ranging in age from 11 days to birth was combined with 9‐day neural tubes. Following grafting of the tissues to chick host embryos, melanoblasts migrated from the nerual tube into the developing skin, and the appearance of pigment in the hair follicles and interfollicular epidermis of the grafted skin was determined. Eleven‐day s/s skin produced pigmented hair in only 16% of the cases, and no melanocytes were found in the interfollicular epidermis. By 13 days 79% of the grafts formed pigmented hair while the epidermis remained pigment‐free. Combination grafts recovered from implanting embryonic skin 16 days and older produced pigment regularly both in the hair follicles and the interfollicular epidermis. Contrl grafts of skin only were devoid of pigment in all ages tested.

These results indicate that an inhibitor of melanoblast differentiation or survival is present in piebald skin at 11 days of embryonic age. Conditions favorable for melanoblast differentiation appear in s/s skin by 13 days and, by 16 days, melanoblasts undergo differentiation in both the hair follicle and the epidermis. A mechanism of action of piebald during development is proposed.
Lysosomes in the spleen of the chick embryo. I. Description in the normal spleen
Authors: Kimmel Charles B.
Published: June 2005

The spleen of the 19‐day chick embryo is shown to contain large amounts of hydrolytic enzymes active at acid pH (acid phosphatase, acid deoxyribonuclease, acid ribonuclease, cathepsin, aryl‐sulfatase and β‐glucuronidase), which are associated with subcellular particles that have the properties of lysosomes. (1) The enzymes can be sedimented with subcellular fractions which contain particles approximately the size of mitochondria. (2) The enzymes are associated with a band of particles of greater density than mitochondria in sucrose gradients. (3) The activities of the structure‐linked enzymes are latent. (4) The cytochemically demonstrable activity of acid phosphatase is found in discrete regions of the cytoplasm of the spleen cells.

The amount of activity increases with developmental age of the embryonic spleen. This finding is correlated with the increase in detectable acid phosphatase‐containing particles. The most marked period of lysosome production is from the twelfth to the sixteenth day of development.

Previous investigations have shown that both major types of phagocytic cells, granulocytes and macrophages, differentiate in the embryo spleen. It is known that in the mammal these cells are rich in lysosome. The production of lysosomes in the spleen is correlated with the differentiation of granulocytes, and with the functional development of the spleen as a reticuloendothelial organ.
Developmental disappearance of a fowl red blood cell antigen
Authors: Sanders Bob G.
Published: June 2005

Rabbit antisera against red blood cells from three‐day‐old chickens, absorbed with adult chicken red blood cells, identify an antigen on the red blood cells of young chickens that is not detectable in adults. The antigen is present on all red blood cells at hatching. Approximately 50 days after hatching, cells with the antigen start to disappear and are completely undetectable by 120 days. Studies aimed at elucidating the mechanism of the developmental antigenic change suggested that the antigen or a component of the antigen is lost during development rather than being coated by a serum component or embedded in the red blood cell membrane. Various experiments were performed in an attempt to alter the proportion of cells carrying the antigen.
Analysis of prefission morphogenesis in Paramecium aurelia
Authors: Gill Kulbir S. , Hanson Earl D.
Published: June 2005

Paramecium aurelia has been exposed to varying concentrations of actinomycin D for extended periods and to a high concentration starting at various specific times in the cell cycle. Extended exposures at 5 μg of actinomycin per 1.0 ml of culture medium are lethal as are 24 hour exposures at 20 μ/1.0 ml. Exposures initiated at selected times in the interfission period reveal transition and stabilization points, similar to those found in Tetrahymena, that is, exposure prior to the transition point almost invariably blocks a given developmental event. Exposure after the transition point may or may not result in blockage but exposure after the stabilization point typically never shows blockage. Also the normal sequence of developmental events can be upset by exposure to actinomycin. These results are interpreted as being consistent with sequential action of the genes in the cell cycle and as indicating independence of final genetic control of different developmental processes, though all processes are dependent on common prior events. The macronucleus of exposed cells shows aggregation of dark material that is neither DNA nor RNA, and is probably a protein, but whose normal function is not known.