bluuebunny/crossref_metadata_2025 huggingface dataset:
A radioautographic study of the migration and fate of cranial neural crest cells in the chick embryo
Authors: Johnston Malcolm C.
Published: February 2005

The migration and fate of cranial neural fold cells of the chick embryo (White Leghorn strain) were followed radioautographically after replacing crestcontaining fold segments with comparable segments from donor embryos labeled with tritiated thymidine. The behavior of the neural crest cells was found to be remarkably similar to that of their amphibian counterparts. The movements of labeled crest cells into the upper facial region of the chick embryo, in conjunction with their proliferative activity, apparently gave rise to the embryonic facial (medial and lateral nasal, and maxillary) processes. As the cells moved into the visceral arches, they surrounded the core‐ like mescdermal muscle plates.

In the upper face and visceral arch regions, labeled crest cells participated in the formation of cartilage. Judging from the distribution of these cells in the remaining mesenchyme, it appears that the still undifferentiated skeletal and connective tisues of these regions are also of neural crest origin. Labeled crest cells were also found in the root ganglia of the VIIth and of the IXth and Xth nerves and the trigeminal and ciliary ganglia. While labeled neural crest contributed extensively to the formation of sheath cells, it made rather limited contributions to the meninges of the brain.
Transposition of the great vessels and other cardiovascular abnormalities in rat fetuses induced by trypan blue
Authors: Monie I. W. , Takacs Eva , Warkany J.
Published: February 2005

Complete and partial transposition of the great vessels, dextrocardia, and absence or stenosis of the tricuspid or mitral valves were encountered singly or in combination in rat fetuses from mothers injected with trypan blue solution subcutaneously on the 8th or 9th day of gestation. Hearts with transposition of the great vessels were usually characterized by shortness of the aorta and pulmonary trunk, cranial location of the aortic valve, displacement of the coronary arteries, and a channel or “track” extending from the cranial portion (infundibulum) of the right ventricle to the commencement of the transposed pulmonary trunk. Inadequate expansion of the atrioventricular ring about the 12th or 13th day of gestation possibly leads to deformity of the atrioventricular cushions and to absence or stenosis of the tricuspid or mitral valves. Sinuosity of the truncus arteriosus seen in many 13th day and older embryos of the trypan blue series is considered a significant factor in the development of transposition of the great vessels.
The cell web in epithelial cells of the rat kidney
Authors: Clermont Y. , Pereira G.
Published: February 2005

The “cell web,” a supporting fibrillar component of the cytoplasm was investigated in sections of adult rat kidney stained with the tannic acid‐phosphomolybdic acid‐amido black (TPA) technique. At the apex of all tubular epithelial cells and immediately below the brush border of microvilli, the cell web formed a thin layer of tightly knit fibrils which inserted on terminal bars, the latter following a straight or sinuous course in circumscribing the cell apices. On the lateral surfaces of all tubular cells, with the exception of those lining the first segment of the proximal convoluted tubule and the whole distal convoluted tubule, some TPA stained fibrils were seen running from the terminal bars toward the base of the cells. Lastly, at the base of all tubular cells, excepting those of the macula densa and the cortical and papillary collecting ducts, some coarse fibrils, oriented circularly around the tubule, were seen close to the basement membrane.

Thus, in most tubular epithelial cells, cell web fibrils were found below the apical, lateral and basal cell surfaces, making up a framework for the support of the cytoplasm. Cell Web fibrils were also observed in the parietal and visceral epithelial cells of Bowman's capsule.
A rare variation of the inferior mesenteric artery in man
Authors: Gwyn David G. , Skilton J. S.
Published: February 2005

A case in which the inferior mesenteric artery arose from the superior mesenteric artery is recorded in the cadaver of a 76‐year‐old Caucasian male who had died of carcinoma of the lung.

A review of the literature since 1736 indicates that this is an extremely rare abnormality.
Fine structure of fiber types in normal human muscle
Authors: Shafiq S. A. , Gorycki M. , Goldstone L. , Milhorat A. T.
Published: February 2005

The fine structure of fiber types in the human vastus lateralis muscle is described. In contrast to the types in other mammals, the two types (red and white) in this muscle seem to differ only in the number and size of mitochondria and not in the amount of sarcoplasmic reticulum or in the structure of myofibrils. The continuity of fiber plasma membrane with the T tubules in the fiber is described. Occasional degenerate foci, which have been found in the normal muscle, are also described.
The formation and mineralization of dentin
Authors: Bevelander Gerrit , Nakahara Hiroshi
Published: February 2005

Observations were conducted at the light and electron microscope level of the formation and mineralization of dentin. At the light level it was shown that predentin is made up of the odontoblast process, collagen fibers and a ground substance. As mineralization occurs, the fibers tend to condense and thicken in areas adjacent to the odontoblast process. Fibers continue to invade the developing matrix and, as in early dentinogenesis, they appear at all times to be derived from the pulp.

At the E.M. level the significant observations made in reference to dentin formation consist of the identification of granular masses appearing in the interfibrillar spaces initially in the region of the dentino enamel junction. Histochemical tests at the E.M. level demonstrated that the odontoblasts elaborate an acid mucopolysaccharide which concentrates in granules at the base of the odontoblast process. Subsequently these granules are extruded into the matrix where the polysaccharide becomes concentrated in the interfibrillar spaces and to come extent on the collagen fibers. The onset of mineralization occurs in the patches of mucopolysaccharide, later also on the fibers. It appears that the presence of an acid mucopolysaccharide is a prerequisit for mineralization in the dental matrix.
A variation in the plasma membrane of intestinal epithelial cells
Authors: Hampton J. C. , Rosario B.
Published: February 2005

A modification of the plasma membrane of intestinal epithelial cells consisting of an apparent thickening of the inner lamella of the unit membrane is described. The evidence indicates that the thickening can be attributed to a piling‐up of stainable, granular material along the inner surface of the plasmalemma. Similar granules could be found in the cytoplasm, mostly in the region of the terminal web, and in mitochondria. Cells showing these changes were usually devoid of ribosomes and contained many smooth surfaced cytoplasmic vesicles.
The heart weight and ventricular weights of normal adult albino rats
Authors: Krames Barbara B. , Van Liere Edward J.
Published: February 2005

The heart weight as well as the heart weight‐body weight ratios of 264 adult albino rats, 155 males and 109 females were analyzed. The large rats have significantly heavier hearts than small rats, but small adults have on the average significantly higher heart weight‐body weight ratios than large adults.

The heart was partitioned and the ventricle weight‐body weight ratio was also determined. As would be expected boty the right and the left ventricles are heavier in large rats than in small rats. However, the small rats have on the average a significantly higher ventricle weight‐body weight ratio than large animals.

Since there are highly significant differences between the weight of the heart of large and small animals, if heart weights are used in experimental work, rather than heart weight‐body weight ratios, the animals should have a narrow body weight range.

It is thought that these data may be helpful to those who work on the heart of the rat.
Penile spines of the domestic cat: Their endocrine‐behavior relations
Authors: Aronson Lester R. , Cooper Madeline L.
Published: February 2005

The post‐natal development of penile spines, their appearance in adult males, and the changes that occur in them after castration, after treatment of castrated males with testosterone propionate, and after cessation of hormone treatment were studied using both pre and postpuberal castrates. Most of the observations were made on live animals and the conditions of the spines were correlated with levels of sexual activity using data from mating tests with estrous females. In all the conditions of testing, the spines increased in size as the androgen level increased, and decreased in size as the androgen level fell. These changes correlated positively with the rise and depression of mating activity as the androgen levels increased or decreased. The relationship, however, was not always consistent in that sexual behavior declined rapidly in some castrated males before the spines started to decrease in size, and in other castrated males, sexual behavior persisted long after the spines had disappeared. While our data are not inconsistent with the hypothesis that loss of spines leads to reduced stimulation of the penis during intromission and hence to a decline in sexual arousal, it emphasizes that the great variability in sexual behavior after castration must be due to other causes.
Specificity of testosterone and estradiol in the differentiating neonatal rat
Authors: Feder Harvey H.
Published: February 2005

Those components of sexual behavior characteristic of the adult intact male such as intromission and ejaculation, were inhibited in males receiving estradiol dipropionate within the first week of life. Neonatal treatment with testosterone propionate at corresponding ages did not disrupt the capacity for homotypic behavior when the males became adult. The expression of female behavior during adulthood was suppressed in female rats treated during a critical period of early postnatal life with testosterone propionate or estradiol dipropionate.

Spermatogenesis was suppressed in males receiving the estrogen but not the androgen in early postnatal life, whereas ovulation was suppressed in females receiving the estrogen or androgen at corresponding periods.

It was concluded that testosterone is compatible with the normal development of male sexual characteristics but that estradiol is not compatible with development of female sexual characteristics when administered during a critical period of differentiation. The specificity for androgen in adult males is postulated to be partly due to the presence of androgens during the critical period. The specificity for estrogen shown by females in adulthood is thought to be dependent upon the absence of estrogen and androgen during a corresponding developmental stage.
A double replication of a “small‐sample” study of the sexual behavior of DBA/2J male mice
Authors: McGill Thomas E.
Published: February 2005

The sexual behavior scores of three different groups of DBA/2J male mice, run at different times of the year, in two different places, and by different observers, were compared. Of 46 comparisons, two revealed statistically significant differences. It was hypothesized that one measure (% Move) was subject to much environmentally determined variation, while for the other measure (III), the significant difference may have been due to sampling error.

Furthermore, substitution of the data resulting from either replication for the data of the DBA/2J males of the original study did not result in any changes as regards significant differences in sexual behavior among DBA/2J, C57BL, and BALB/c male mice. The results, in general, supported the hypothesis that intensive study of a small sample from an inbred strain would yield replicable results.
Sexual behavior patterns in the prepubertally castrate rat
Authors: Lisk R. D. , Suydam A. J.
Published: February 2005

Prepubertally castrate female rats are capable of showing the lordosis response when given replacement therapy with female sex steroids, regardeless of age at which the ovaries are removed post birth, or when replacement therapy is commenced after adulthood. Estrogen alone is reraly a sufficient stimulus for behavioral estrus. Therefore the natural physiological trigger for estrous behavior in the rat is likely estrogen plus progesterone. Prepubertally castrate male or female rats never showed any male or female behavior following androgen implant in the brain. All rats castrated on day three or ealier, and given implants of estrogen plus progesterone in the preoptic hypothalamic area displayed the lordosis response. Thus the female sex response pattern is present in both sexes in the absence of gonadal hormones from birth. Brain development in the male castrate at birth does not appear to be identical to brain development in the female castrate at birth because a number of males showed the complete male sexual response pattern plus the female response pattern following neural implant of estrogen plus progesteron. The genotypic male thus appears to possess the information necessary to produce the neural connections for male and female sexual response patterns. Androgen acting at birth disrupts the development of the feminine response pattern so that the adult male ordinarily displays only the copulatory pattern.
Relationships of leydig cell characteristics and intratesticular testosterone levels to sexual activity in the African elephant
Authors: Buss Irven O. , Johnson Oscar W.
Published: February 2005

Histological characteristics of testis tissues from 25 African elephants (Loxodonta africana) collected in Uganda, showed no consistent relationships among the following variables: Leydig cell size, cytoplasmic characteristics, and abundance; testicular testosterone content; and age. From these findings, plus field observations of sexual behavior, emerges the hypothesis that individual cyclicity in Leydig cell function was inherent in the elephant population studied. Testosterone content of testes from 32 elephants (including the 25 studied histologically) suggested that lone bulls were not of a senile nature since they contained relatively large quantities of testosterone and were relatively young (from about 12 to 25 years of age). Also, lone bulls were observed searching out estrous females. Among bulls collected from family units and herds, testosterone levels and behavior differed conspicuously. Behavior appeared to be directly related to testosterone content in several instances. Nonaggressive behavior among members of bull herds, plus the high proportion of such aggressive behavior among members of bull herds, plus the high proportion of such individuals with low testosterone content, suggest that some of these animals were in a depressed phase of sexual activity whereas others were undergoing pubertal development.
Variability in body and organ weights in the newborn dog and cat compared with that in the adult
Authors: Latimer Homer B.
Published: February 2005

Body and organ weights of 24 newborn dogs and 35 newborn cats were studied. All of the measurements, except weights of hypophysis, spinal cord and testes are larger in the dogs. As percentages of body weight, the organs are more equally divided, with seven organs relatively heavier in the dogs and eight in the cats. All except two of the measurements of the newborn dogs are more variable than in the newborn cats.

All of the organs are significantly correlated with body weight in the dogs and all except one, in the cats. All 15 of the organs are significantly correlated with body length in the dogs and 13, in the cats. The intercorrelations of the organ weights are somewhat higher in the dogs.

The coefficients of variation of the newborn are compared with similar coefficients in adult dogs and cats. Body weight, body length and the kidneys are more variable in the adult dogs and the other organs, so far as data are available, are more variable in the newborn dogs of both sexes. Seven organs are more variable in adult male cats and three in females. The newborn dog is more variable in body and organ weights than the newborn cat, but weights of body and organs are better correlated in the newborn dog than in the newborn cat.
Perilymphatic fibrocytes in the vestibule of the inner ear
Authors: Hamilton David W.
Published: February 2005

A description is given of the fine structure of perilymphatic fibrocytes and their associated fibers in the vestibule of the inner ear in rats. The identification of the extracellular fibers as keratin is discussed in relationship to their fine structure and to biochemical and biophysical data of other workers. The numerous junctional complexes between fibrocytes are described and it is shown that these do not form zonula occludens as has been reported by other workers.
Daily rhythmic variations in blood coagulation times in rats
Authors: Scheving Lawrence E. , Pauly John E.
Published: February 2005

With all other environmental factors rigidly standardized, normal Sprague‐Dawley rats were maintained under the following schedules: (1) 12 hours of artificial light 0600 to 1800 alternating with 12 hours of darkness‐LD; (2) reversal of the first‐DL; (3) constant darkness‐DD, and (4) constant illumination‐LL.

After the animals had been under a specific lighting regimen for at least three weeks, blood coagulation times were determined on separate groups of 8 to 16 animals at bi‐hourly intervals during a 24‐hour period. Significant daily fluctuations or rhythms in coagulation times under all lighting conditions were found by plotting each of the bi‐hourly mean values as a function of time. The temporal phasing of all rhythms in LD, DL, LL and DD were similar. The major changes found in the different lighting schedules involved overall magnitude, e.g., the overall 24‐hour mean coagulation time for rats maintained in LL was 21% greater than for rats maintained in DD. Although total adrenalectomy or adrenal medullectomy did not abolish the characteristic LD rhythm, there was about a 100% decrease in the mean 24‐hour coagulation time of LD adrenalectomized animals when compared to normal LD animals. No significant decrease was seen in adrenal demedullectomized animals when similarly compared with normal LD animals.
Induction of partial limb regeneration in Rana pipiens by galvanic stimulation
Authors: Smith Stephen D.
Published: February 2005

Forelimbs of small adult frogs (Rana pipiens) were amputated and the stumps implanted with silver‐platinum bimetallic rods insulated except at the tips. The silver end was at the wound surface in some cases. In others, the platinum end was distally placed. Other animals received separate implants of short pieces of bare silver and platinum wire, with the silver piece placed near the wound surface. Controls consisted of animals with either no implant or implants of partially insulated silver or platinum wire.

Only one of the control animals (one with a silver implant) initiated regeneration. Regeneration was minimal with the separate implants (25%), more frequent with the platinum end of a bimetallic couple at the wound surface (70%), and most frequent (83.4%) with the silver end of a bimetallic couple at the wound surface. In three cases in the last named series, lobulated cartilages reminiscent of wrist and hand elements differentiated. The results are ascribed to direct stimulation of the cells, electrophoretic transfer of information‐bearing molecules, or stimulation of nerves.
Some new cytological observations of the normal rat ependymal cell
Authors: Hirano A. , Zimmerman H. M.
Published: February 2005

The ependyma of the lateral ventricle of normal adult rats fixed by intravascular perfusion with either glutaraldehyde or formaldehyde was examined with the electron microscope. Three main observations of the normal ependymal cells were made which, to our knowledge, have not yet been reported.

Ependymal cells were occasionally found directly abutting on blood vessels in the immediate vicinity. In this respect, they were very much like the well‐known perivascular astrocytes and tanycytes. This similarity was strengthened by the morphological details of the junctional areas.

Bundles of the fine fibrils (app. 60 Å) were seen in the nuclei. They were devoid of any membranous boundary and were apparently identical to the fibrils often seen in the perinuclear cytoplasm.

Microtubules, occasionally containing approximately 50 Å central densities, were consistently seen in the apical cytoplasm. They were apparently identical to the familiar microtubules constituting the cillary fine structure which also contained occasional central densities.
Pituitary basophils of the Syrian Hamster: An electron microscopic investigation
Authors: Dekker Andrew
Published: February 2005

Histochemical studies have not clearly defined the types or distribution of bascphils in the hamster's adenohypophysis. Electron microscopy is used in these experiments as a more accurate method for identifying types of basophils. Electron microscopic fields from regional areas of the gland were systematically photographed, and cell types counted. Hypertrophy of the appropriate basophils was observed in response to gonadectomy and thyroidectomy. FSH cells are oval, are adjacent to vascular spaces, have vesiculated endoplasmic reticulum and contain secretory granules measuring 200 mμ maximally. ICSH cells have filigreed cytoplasm, irregular cell borders, and secretory granules measuring 200 mμ maximally. TSH cells are polyhedral, have sparse endoplasmic reticulum, and secretory granules measuring 100 mμ maximally. The three basophilic cell types are randomly distributed throughout the gland.
The tensile properties of single osteons
Authors: Ascenzi Antonio , Bonucci Ermanno
Published: February 2005

The ultimate tensile strength and modulus of elasticity of individual osteons from human and ox compact bone were determined with a specially designed microwave extensimeter. The results were related to the degree of calcification and the orientation of collagen fiber‐bundles in successive lamellae of the osteons. The following conclusions were made: (1) When osteon specimens are dried, their tensile strength and modulus of elasticity increase, while their percent elongation under tension falls. (2) In the osteon samples tested wet, the degree of calcification induces an increase in the modulus of elasticity with additional amounts of calcium salts. (3) The modulus of elasticity in tension of the organic matrix corresponds to that of collagen. (4) In the osteons having a marked longitudinal arrangement of bundles of fibers in successive lamellae, the ultimate tensile strength and modulus of elasticity seem greater and the percentage elongation under tension seems lower than in osteons whose bundles in successive lamellae change through an angle of about 90°. (5) The tensile properties of osteons seem independent of the age of the subject. (6) Human and ox osteons reveal the same tensile behavior. (7) The tensile stress‐strain curves show that, even at the level of single osteons, bone behaves like a complex material, which, according to Sedlin, can be represented by a Hooke body linked in series to a Kelvin body.
The ontogeny and growth of the human tentorium cerebelli
Authors: Klintworth Gordon K.
Published: February 2005

The ontogenetic pattern of the human tentorium cerebelli was reconstructed by analyzing the series of stages through which the tentorium passes in the attainment of maturity. The absolute and relative growth rates were calculated for the maximum cranial breadth, maximum cranial length, and various tentorial dimensions. The relationship between the growth of different parameters was established and expressed mathematically according to Huxley's formula (y = bxk). The growth ratios (k) and constants (b) for different combinations of tentorial and cranial parameters were elicited from logarithmic graphs.
An autoradiographic study of chondrocyte transformation into chondroclasts and osteocytes during bone formation In vitro
Authors: Crelin E. S. , Koch W. E.
Published: February 2005

Excised mouse pubic bone rudiments were exposed to H3‐thymidine. Rudiments preserved immediately after exposure consisted of mesenchyme with a large number of cells showing intense radioactivity. Rudiments incubated on a filter membrane after exposure went through the developmental stages of complete chondrification of the pubic rami followed by periosteal and then endochondral bone formation. Only chondrocytes showed radioactivity in rami consisting of cartilage and periosteal bone that were preserved prior to endochondral ossification. Cell types showing radioactivity in rami preserved during endochondral ossification were chondrocytes, chondroclasts, and osteoblasts and osteocytes of endochondral bone. The results of the study demonstrated that hypertrophic chondrocytes of the calcified cartilage of a developing mammalian long bone not only survive dissolution of their matrix, but transform into chondroclasts and osteoprogenitor cells that give rise to osteoblasts and osteocytes which form endochondral bone in the absence of blood vessels.
Studies of the luteotropic and mammotropic factor found in trophoblast and maternal peripheral blood of the rat at mid‐pregnancy
Authors: Matthies Donald L.
Published: February 2005

Bioassay data demonstrate that trophoblastic elements of the midpregnancy rat placenta contain a substance or substances possessing luteotropic and mammotropic properties. This material is also present in high potency in maternal serum but only at midpregnancy. The standard bioassay animal preparation utilized in demonstrating these properties was the immature, PMSG‐stimulated, hypophysectomized female Long‐Evans rat. The end point for detection of luteotropic activity was the deciduoma reaction and that for detection of mammogenic activity was proliferation of locally treated mammary parenchyma. The local injection of one day 12 placental equivalent daily for seven days consistently induced deciduoma formation and mammary parenchymal proliferation. Similar responses were observed in animals injected with 0.1 ml serum from peripheral blood of the day 12 pregnant rat.

These biological extracts also possessed lactogenic activity, which was demonstrated by mammary secretory response to trophoblastic extracts and midpregnancy serum containing prednisolone acetate in suspension. Assay animals used in detecting this activity had been hypophysectomized, ovariectomized, and adrenalectomized.

The pigeon crop sac responded weakly and tibial epiphyseal cartilage failed to respond to large doses of the biological extracts. No target organs other than the corpus luteum and mammary gland were found. It is proposed that an appropriate designation for this hormone would be Rat Chorionic Mammotropin (RCM).
The vascular architecture of the small intestinal mucosa of the monkey (Macaca mulatta)
Authors: Reynolds David G. , Brim Jack , Sheehy Thomas W.
Published: February 2005

Silicone rubber microvascular injection compounds have been used to describe the mucosal vascular architecture of the monkey's small intestine. The mucosal vascular patterns of this animal differ from the classical description. Instead of the villus blood supply being delivered via a central villus arteriole, the arterioles ramify to the undersurface of the mucosa where they terminate in the capillary plexus surrounding the crypts of Lieberkuhn. The villus capillary net is derived directly from the cryptic capillary plexus and is drained by a single, central villus vein. There is a secondary venous return system that directly drains the cryptic plexus. These secondary venous channels might represent a mechanism that regulates the proportional distribution of blood in the cryptic and villus capillary beds.

This report is intended to describe the vascular patterns only as they occur in the monkey. Observations of rat and rabbit mucosa prepared by the same technique reveal arterial and venous channels extending the length of the villi. These animals, therefore, more closely resemble the classical description.
A comparison of the in vivo incorporation of S35 methionine by two‐celled mouse eggs and blastocysts
Authors: Weitlauf Harry M. , Greenwald Gilbert S.
Published: February 2005

Five‐day‐old mouse blastocysts were transferred into the oviducts of recipients on the second day of pregnancy. S35 methionine was then injected into the recipients and the blastocysts and native 2‐celled eggs were recovered six hours later. Radioautographs reveal that the blastocysts incorporate S35 methionine while exposed to the tubal environment to the same degree that they would in the uterus. However, the 2‐celled eggs in the same oviducal environment incorporate little or no methionine. It is therefore concluded that the difference in the incorporation of S35 methionine is due to maturational changes in the blastocyst rather than to a deficiency of the labelled amino acid in the tubal lumen.
The microscopy of “brown degeneration” in the adrenal gland of the mouse
Authors: Schardein J. L. , Patton G. R. , Lucas J. A.
Published: February 2005

“Brown degeneration,” a pigmentary process of the adrenal gland of the mouse, was consistently induced by administration of ethinyl estradiol. Mice similarly treated with diethylstilbestrol or peanut oil (control) developed only small amounts of pigment. Histochemically, the pigment was ceroid and had its origin in the inner cells of the cortex in both females and males, with the fully developed pigmentation distributed in the cortex in animals of both sexes, and also in the medulla in males. Ultrastructurally, ceroid formation progressed from small pigment granules morphologically similar to lysosomes, to large composite, pleomorphic pigment bodies composed of unique granular configurations and membranous components. The ceroid deposits were interpreted to represent lipid products resulting from altered fat metabolism.
An electron microscopic study of the innervation of papillary muscles in the rat
Authors: Novi Anna M.
Published: February 2005

The left ventricular papillary muscles of rats were studied under the electron microscope. The tissue was fixed in glutaraldehyde 6.25%, postfixed in osmium tetroxide 2% and embedded in Epon 812. Sections were stained with lead according to Karnovsky.

The terminal distribution of nerve fibers and their relationship with target cells represented by cardiac and vascular smooth muscles were investigated. Nerve bundles followed the course of vessels to the perivascular spaces around the smallest arterioles. At this level the bundles became progressively thinner and individual axons were observed leaving the bundles and penetrating between myocardial cells. In the micrographs, the unmedullated axons contained in the bundles were of three different types. Axons of type 1, chiefly containing neurofilaments, were considered the most proximal portion of the nerve fibers involved in the conduction of impulses. Axons of type 2 were characterized by the appearance of agranular and granular vesicles. Axons of type 3, or nerve endings, represented the anatomical endpoint of individual axons. True myoneural junctions (nerve‐muscle close contact) have been detected. More frequently, axons of type 3 end in the intercellular space (loose contact). Only a loose contact relationship was observed between the axons and vessels walls.
Dissociability of developmental processes in the morphogenesis of the ear in Ambystoma, as revealed by X‐ray damage
Authors: Piatt Jean
Published: February 2005

Eggs of Ambystoma maculatum from the same clutch were separated at Harrison's stage eight into three groups and maintained at 8°, 14° and 20°C, respectively, until stage 28. At these three temperatures the respective number of hours between stages eight and 28 were 291, 171, 99. Half of each group was then x‐irradiated with 600 r and the right ear vesicle substituted for that of the non‐irradiated complement. Subsequent development of the irradiated grafts, all reared at 20°C, was compared among the groups.

Within the range of temperatures employed, hypothermia alone has no effect upon final ear development; every left ear in all groups developed normally. Development of irradiated grafts in the 8° group is decidedly more abnormal than in either 14° or 20° groups. With the exception of the VIIIth ganglion, development of the grafts in 14° and 20° groups is approximately the same. On the basis of 8° = 1, average developmental ratings for the three groups are approximately as follows: size — 1:2:2. differentiation — 1:2:2. ganglion — 1:2:5.

The data demonstrate that the chronologically older ear is more radiosensitive than the younger, despite morphological parity among groups at time of irradiation. This suggests that prolonged hypothermia may dissociate in time the invisible or biochemical processes of development from the purely morphological; the pace of the former is less retarded than the latter.
The Tylotrich (Hair) follicle of the american opossum
Authors: Mann Stanley J.
Published: February 2005

Tylotrich follicles are present in the skin of the marsupial, the American opossum (Didelphis virginiana). Their morphology, ancillary structures, time of development, size and distribution of epidermal pads, are similar to tylotrich follicles found in eutherian mammals. The presence of tylotrich follicles in the marsupial suggests that they arose early in the evolution of mammalian skin.
Anatomical changes with age in the heart and ductus arteriosus in the dog after birth
Authors: House Edwin W. , Ederstrom H. E.
Published: February 2005

The heart‐weight to body‐weight ratios were calculated for 242 dogs in 11 groups ranging from one day to adult. The base‐apex diameters, internal transverse diameters, external transverse diameters, and the anterior, posterior, lateral, and interventricular septal wall thicknesses were measured in left ventricles of hearts taken from 45 animals of nine different age groups. The ductus arteriosus was examined for patency in all puppies.

The heart‐weight to body‐weight ratios were found to be highly variable and failed to show significant changes with age. The average ratios increased during postnatal development from 7.17 gm/kg in the newborn to 8.87 in adults.

The left ventricular diameters and wall thicknesses increased progressively with age and were four times larger in adults than in the newborn. Diameter to wall‐thickness ratios were calculated and did not change with age. Since the heart weight increased 10–16 times faster than the wall thickness, wall‐thickness to heart‐weight ratios were found to decrease with age indicating a faster lengthening than thickening of the myocardial fibers. The ductus arteriosus was functionally open in all puppies less than four days of age and did not close anatomically until 7–8 days of age.
Observations on the development of the electrocardiogram
Authors: Paff George Hugo , Boucek Robert Joseph , Harrell Timothy Charles
Published: February 2005

This experiment was designed to reveal the developing pattern of the ECG occurring in chick embryos during the period between 11 and 22 somites and to relate these findings to the appearance of blood circulation and the ability of the heart to exhibit atrioventricular block under the influence of digitalis. Using a unipolar electrode placed directly upon hearts of a graded series, the first recorded ECG was a simple V wave at 11 somites (sometimes 10) which increased in amplitude and rate through the 16 somite stage. In 16 or 17 somite embryos two deflections appeared on the descending limb of the V wave. In the light of subsequent changes these were recognized as the first indications of the P wave and QRS complex. Within an hour of development (17 to 18 somites) three events coincided, i.e., appearance of the primitive P wave and QRS complex; the beginning of blood circulation as evidenced by flow through extraembryonic capillaries; and the ability of the hearts to show a block at the AV junction. This last occurs despite the fact that an obvious PR interval is not present at 18 somites. However, from the 18 to the 21 to 22 somite stage rapid changes in the pattern of the ECG were recorded. The PR interval emerges; the P wave and QRS complex become incisive and are followed by an obvious T wave.

The developmental pattern is the exact duplicate of the changes which can be recorded in reverse, by treating a single 60 hour embryonic heart with eserine (Paff, Boucek and Glander, '66) or apparently any acetylcholinesterase inhibitor (work in progress).
The comparative anatomy and phylogeny of the tentorium cerebelli
Authors: Klintworth Gordon K.
Published: February 2005

The morphology of the tentorium cerebelli was investigated in representatives of the chordata. A tentorium cerebelli characterized birds and mammals but was regularly absent in fishes, amphibians, and reptiles. The data suggest that the tentorium cerebelli emerged relatively late in phylogeny as bilateral folds of dura mater on either side of the brainstem in the cerebro‐cerebellar fissure. Subsequent evolution was characterized by the union of these septa behind the brainstem and by a progressive lengthening of the straight sinus. Tentorial ossification distinguished a further evolutionary step in some mammalian lines. The inferred evolutionary pattern of the tentorium cerebelli resembles the successive stages which the human tentorium undergoes during ontogeny.
Fine structure and staining of mucosubstances on “intercalated cells” from the rat distal convoluted tubule and collecting duct
Authors: Griffith Lyle D. , Bulger Ruth Ellen , Trump Benjamin F.
Published: February 2005

A second and previously unrecognized cell type which is identical to the intercalated cells of the collecting duct exists in the rat distal convoluted tubule. These cells are distinctly different from the principal cells which have long been recognized with light and electron microscopy.

The intercalated cells have numerous irregular apical microvilli, a high concentration of nearly round mitochondria located in the apical cytoplasm, and a basal nucleus.

A variety of coated and uncoated vesicles in the apical cytoplasm were identified by electron microscopy. The cytoplasmic surface of the apical plasmalemma also was studded with club‐shaped densities.

Light and electron microscopic histochemical techniques for acid mucosubstances were carried out on tissue prepared by rapid freezing techniques or intravascular perfusion fixation. The luminal surfaces of the cells from both the distal convoluted tubule and collecting duct stained for acid mucosubstances. In some cases, the intercalated cells stained more intensely with this technique than the adjacent principal cells. The apical cytoplasm of the intercalated cells was also more PAS positive than that of the principal cells.
Electron microscopy of the mouse retina prepared by freeze‐substitution
Authors: Van Harreveld A. , Khattab F. I.
Published: February 2005

The isolated retina of albino mice was fixed by freeze substitution. This method allows the electron microscopic examination of the surface layer of the tissue only. On the scleral side of the retina a considerable space was found between the outer and inner rod segments. In the spaces between the latter, microvilli of the Mueller cells seemed to float freely in the inter‐rod material. On the vitreal side extracellular space was observed in bundles of nonmyelinated fibers which are destined to form the optic nerve, and often in the inner plexiform layer. Treating the retina with 5 mM glutamate caused ballooning of elements in the plexiform layer (probably dendrites) and sometimes of the inner and outer rod segments. No obvious swelling was observed of the Mueller cells, the ganglion cells and of the nonmyelinated nerve fibers.
Migration of embryos in the anastomosed uterine horns of the pig
Authors: Miller O. C. , Dziuk P. J.
Published: February 2005

One ovary was removed from 28 gilts and the uterus was transected, closed and anastomosed in one of four patterns. In three of the patterns the uterine horns were jointed near the uterotubal junction and in the fourth pattern the uterus formed one continuous tube from one oviduct to the cervix. Gilts were mated, then killed at 15 to 60 days of gestation when fetuses were located. The proportion of gilts pregnant was lower (P < 0.05) in the two groups requiring passage of sperm through an anastomosis than in the two groups where fertilization did not require that sperm traverse an anastomosis. Ten gilts were pregnant when killed and embryos were distributed in both horns in each gilt. Embryos can pass through an anastomosis and migrate and are spaced quite evenly even after disturbance of the normal anatomical relationships between uterine horns.
Localization of phosphate in bone cells of fresh calvaria by means of a dilute silver acetate solution
Authors: Kashiwa Herbert K.
Published: February 2005

The silver‐substitution procedure originally recommended by von Kossa was modified to localize soluble phosphate in bone cells. Calvaria from newborn to five‐day‐old Wistar rats were stained fresh in 0.03% Ag acetate prepared in 5% mannitol solution. The substituted silver was reduced to its metallic state with 1% pyrogallol. The tissues were then dehydrated, cleared, and mounted whole. The cytoplasm of osteoblasts, osteocytes and osteoclasts contained black granules which were thought to be sites of phosphates or carbonates. The intracellular black granules were shown not to be due to either chloride precipitation or to silver reduction by ascorbic acid. Both of these compounds were localized outside the cells. Tests to determine the state of the localized phosphate or carbonate in the cells showed that the anions were not in the ionic or diffusible state nor organically bound, but complexed to calcium. This was shown by elution of phosphates from the cells when calcium was chelated by Na2 EDTA in 5% mannitol solution at pH 7. The intracellular black granules were thought not to be sites of insoluble calcium phosphate or carbonate but sites of readily stainable, calcium phosphate which is rendered nondiffusible by being bound to protein or mucoprotein.
Antler growth and osteoporosis I. Morphological and morphometric changes in the costal compacta during the antler growth cycle
Authors: Banks William J. , Epling Glenwood P. , Kainer Robert A. , Davis Robert W.
Published: February 2005

Three three‐year‐old Rocky Mountain mule deer were studied for a year to determine the role of skeletal mineral in antler growth. Costal biopsy material, which was obtained at four‐week intervals, was analyzed histologically and histometrically. There was a cyclic mobilization of costal cortical bone during antler growth despite the dietary access to high quantities of elements essential for bone development. Following antler growth the ribs returned to a stable configuration with few resorption spaces. Corresponding to the period of possible weakening from the internal remodeling, there also appeared to be a thickening of the cortical bone by circumferential lamellar addition. A cyclic physiological osteoporosis was produced.
Investigations on the innervation of the diaphragm in cats and rodents
Authors: Wilson Andrew S.
Published: February 2005

In cats, rats and mice the diaphragm possesses an intrinsic plexus of nerve fibres which are concentrated in a narrow band situated approximately halfway between the edge of the central tendon and the peripheral attachment of the musculature. Contributions to the plexus originate in both phrenic and lower six intercostal nerves and both possess three categories of fibres. The first is composed of unmyelinated fibres which ramify on the walls of companion vessels. The second comprises myelinated fibres ranging from 6–10 μ in diameter and these have been classified as afferent components. The third category, forming the major part of the phrenic outflow but only a minor part of intercostal contributions, comprises inyelinated fibres which range from 10–16 μ in diameter and possess preterminal expansions. Phrenic fibres of the third category have been identified as efferent components because they terminate in motor end plates but the function of corresponding intercostal components cannot be defined conclusively.

Quantitative studies at three distinct levels within each of ten phrenic nerves in cats, show an increase in the number of myelinated fibres of diameter 12–20 μ in the peripheral third of the nerve. This suggests that the phrenic nerve receives an accession of fibres in its peripheral third.
Studies on the fine structure of muscle fibers and associated satellite cells in hypertrophic human deltoid muscle
Authors: Reger James F. , Craig Ann S.
Published: February 2005

Electron microscopy of hypertrophic left deltoid muscle of a nineyear‐old female diagnosed with neuro‐ectodermal dysplasia and concomitant muscle hypertrophy was made. Satellite cells, similar in morphology to myoblasts, are found situated apposed to and beneath the basement lamina of muscle fibers. Satellite cells contain mitochondria, granular ER free ribosomes, polysomes and 50–100 Å thick, randomly oriented filaments. Plasmalemmae of apposed satellite and muscle cells show varying numbers of caveolae and degrees of interdigitation similar to plasmalemmae between fusing myoblasts of embryonic muscle. Discontinuities in the muscle fiber plasmalemma and confluence, or overlie, of satellite cell and muscle fiber plasmalemmae are sometimes seen.

One possible interpretation of the above evidence suggests that, in this example of muscle hypertrophy, satellite cells may assume myoblast‐like properties and serve as focal points for muscle fiber enlargement during muscle hypertrophy.
Determination of the red blood cell count and haemoglobin content of urodele blood
Authors: Friedmann G. B. , Algard F. T. , McCurdy H. M.
Published: February 2005

Red blood cell count and haemoglobin content for blood of normal adult salamanders, Taricha granulosa, are presented. The RBC count is some 4 × 104/mm3 blood and the haemoglobin level some 4.5 gm/100 ml blood. Some evidence suggesting transient changes in these levels for a brief period immediately following hibernation is discussed.
Normal development of the lateral motor column in the brachial cord in Rana pipiens
Authors: Pollack Emanuel D.
Published: February 2005

Counts of differentiating motor cells over the length of the brachial lateral motor column (LMC) indicate that a large decrease in cell number takes place during the larval period. During the same period an increase in nuclear size of the motor cells occurs with a maximum size attained just following forelimb emergence. Comparison between development of the LMC at the brachial and lumbo‐sacral levels indicates a slight lag in brachial LMC development. Cell number remains greater in the brachial LMC than in the lumbo‐sacral LMC, but nuclear size is consistently less in the brachial column. Probably no significant change in cell number occurs after metamorphosis, though there is an increase in cell size.
Effects of X‐irradiation of immature hamsters on growth and development of gonads
Authors: Turbyfill C. L. , Chang M. C.
Published: February 2005

Hamsters were x‐irradiated at 300 R on 1, 7, 14, 21 or 30 days after birth and sacrificed at the age of 33 days.

The body weight, testicular weight and the development of seminiferous tubules were severely affected by irradiation on day 1. The ovarian weight and the number of oocytes were more affected by irradiation on day 7 or 14. Effects of irradiation of immature hamsters on their growth and development of gonads appears to be permanent as irradiation of males on day 1 destroyed all their germ cells by day 33 and irradiation of females on day 7 caused their permanent sterility up to four months of age.