摘要:

AbstractThe purpose of this study is to investigate the possibility that hair growth is triggered by the loss of a specific hair follicle inhibitor.If the loss of an inhibitor is a sufficient cue for the triggering of hair growth, then hair follicles in skin grafts placed on hairless mice should remain in the growth phase of the hair growth cycle, and never enter the resting phase. This would be expected because hairless skin has no hair follicles, and therefore presumably produces no hair follicle inhibitor itself. Thus, no build‐up of a hair follicle inhibitor within the graft should occur.Female hairless mice (HRS/J) approximately 60 days of age received skin grafts from haired female litteremates. These skin grafts took well and remained healthy throughout the period of investigation, which ranged from 240–380 days.The hair follicles of the grafts undergo cycles of growth and rest. They may remain in the resting phase for as long as two to three months. Therefore, hair follicles of grafts placed on the backs of the hairless mice do not remain permanently in the growth phase of the hair cycle.Additional experiments help rule out the possibility that (1) the lack of continuous hair growth of the hair follicles in the grafts is due to the scar preventing the diffusion of inhibitors from the graft into the host skin, and (2) that the hair follicle remnants in the host hairless skin produce a hair follicle inhibitor in sufficient concentration so that the hair follicles of the graft enter the resting ph

ISSN:0003-276X    

DOI:10.1002/ar.1091680401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe secretory end‐pieces of the submandibular gland of rats during the first week of postnatal development are studied with regard to the fine structure of the secretion granules in these end‐pieces. The terminal ends of the secretory ducts during this period consist of two types of cells; one cell is an acinar‐type and the other is a duct‐type found in the gland of adult rats. The secretion granules of the acinar‐type cells are similar in appearance to those of the acinar cells in the gland of adult rats, and the structure of these granules remains the same throughout the week. However, granules widely different in appearance are present in the duct‐type cells, and their structure varies in different cells as well as within a single cell at different stages of development. These granules contain unusual substructures which are not found in the secretion granules of adult rats, suggesting that the granules are transitory. Granules containing short tubular profiles are predominant in the gland of one day‐old rats. A large number of granules in three day‐old rats contain elongated tubules. More granules of widely different substructures are present in the gland of seven day‐old rats than in the gland of younger rats. The matrix of the granules in seven day‐old rats is of higher density than that of the granules in younger rats. In the dense matrix of these granules, less dense tubules form fingerprint‐like or somewhat mo

ISSN:0003-276X    

DOI:10.1002/ar.1091680402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractTo supply some additional data about the intra‐osseous connections of the seventh nerve in a potentially available experimental animal, the baboon, 16 neuromuscular complexes (otic ganglion, nerve which results from the junction between the lesser petrosal nerve and the and the communicating branch, lesser petrosal nerve, communicating branch, initial part of the greater petrosal nerve, all three intra‐osseous parts of the facial nerve, stapedius muscle, auricular branch of the vagus) were macroscopically evaluated with the aid of a microdissecting scope, and removed in toto. Two dissections were achieved only partially. Each neuromuscular complex was fixed in 5% formalin, dehydrated, embedded in paraffin, sectioned serially at 10 to 15 μ, and either stained with Luxol Fast Blue or impregnated by Bodian's silver technique. In all specimens considered, the auricular branch of the vagus, before it joined the descending intra‐osseous part of the facial nerve, gave off an ascending bundle. This bundle sent a few ramifications to the stapedius muscle and finally mixed with axones in the intra‐osseous segment of the seventh nerve close to the second facial genu. The fibers in the ascending bundle were predominately myelinated with a diameter varying from 1.7 μ to 9.9 μ. The communicating branch proper separated from the fibers of the second intra‐osseous part of the facial nerve, and continued anteriorly through the sheath toward the geniculate ganglion. From there, the branch as an isolated bundle extended further anteriorly to reach the otic ganglion, after it joined the lesser petrosal nerve. The number of fibers in the communicating branch ranged from 50 to 580, and the diameter of myelinated fibers varied between 1.7 and 4.4 μ. Numerous ganglion cells, presumably of the autonomic type, found in the communicating branch, in the lesser petrosal nerve, and occasionally in the second intra‐osseous part of the facial nerve resembled by their form and diameter the ganglion cells in th

ISSN:0003-276X    

DOI:10.1002/ar.1091680403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractFirst molar tooth germs were dissected from one‐ and seven‐day‐old mice, fixed in gluteraldehyde and impregnated in bulk using silver nitrate for the demonstration of reticulin. After impregnation the tooth germs were embdded in Epon, and thin sections cut for examination with both the light and electron microscope. Control tooth germs were prepared similarly, but were not impregnated with silver. Light microscopic examination showed the classical picture of von Korff fibres. These were associated with the formation of mantle dentine. von Korff fibres were not found associated with forming circumpulpal dentine. Examination of successive sections with the electron microscope showed silver particles between the widely separated, newly differentiated, odontoblasts. In forming circumpulpal dentine, the odontoblasts were closely aligned and no silver particles were found in the now narrowed extracellular spaces. Examination of control sections revealed that the extracellular compartment between the newly differentiated odontoblasts consisted of ground substance and a few sparse collagen fibrils which were too small to be resolved with the light microscope. It is considered that the “von Korff fibres” seen with the light microscope represent silver impregnation of the extracellular material, which is mainly ground substance, in the continuum between the widely separated odo

ISSN:0003-276X    

DOI:10.1002/ar.1091680404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractForelimbs of adult eastern spotted newts were irradiated with 2000 or 3000 r of x‐rays, and were amputated through the elbow region. Limbs treated in this way or infused by means of a Singer microinfusion apparatus with amphibian Ringer's solution were observed as controls. Experimental limbs were infused at various times with (1) amphibian Ringer's solution containing material extracted from two‐week‐old blastemata from unirradiated limb stumps or (2) one of four concentrations of alkaline phosphatase dissolved in Ringer's solution.Small polyps or blastema‐like conical structures were the only regenerative responses that followed the various infusion procedures. Blastemal extract and Ringer's solution alone seemed to be equally effective in inducting these regenerative growths, but no such growths followed mere irradiation and amputation. Alkaline phosphatase was more effective than either the blastemal extract or Ringer's solution in inducing the growth of conical structures. These initial growths in a number of cases persisted as very short cones composed mostly of amorphous cartilage and connective tissue or as pseudoblastematous aggregations of cells. However, extensive regression of tissues and shortening of the limb was seen rather frequently in limbs treated with alkaline phosphatase.Ringer's solution and blastemal extracts did little to reverse the regeneration‐inhibiting effects of irradiation on amputated limbs. It appears that alkaline phosphatase caused a more frequent, if still limited, reversal of these effects, and it is suggested that a part of these inhibitory effects may result from damage done to the production of alkaline ph

ISSN:0003-276X    

DOI:10.1002/ar.1091680405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractIn 12 cats unilateral transection of the phrenic nerve was followed, after survival periods of 1–30 days, by histological examination of the nerve trunk peripheral to the level of the lesion. In osmium preparations from all of the transected nerves the myelinated fibres showed incomplete degeneration while in three nerve portions impregnated with silver, some persisting axis cylinders were observed. Concurrent studies on the diaphragmatic plexus in six animals showed persistence of some nerve fibres in the crural and posterolateral zone on the side of transection while a comparable number of degenerated fibres were present in the contralateral crural zone. Bilateral phrenectomy in one animal showed persistence of fibres in the crural and posterolateral zones of the left and right sides. Following mobilization of the peripheral third of the phrenic nerve from its interserosal position degeneration was observed in one fasciculus of the diaphragmatic plexus on the side of the lesion.This evidence supports the possibility that accessory fibres join the phrenic nerve in the peripheral third of its cours

ISSN:0003-276X    

DOI:10.1002/ar.1091680406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractIncorporation of tritiated uridine in embryonic and extraembryonic tissues of normal and actinomycin D treated rats was determined by radioautography on days 7 through 11 of gestation. Precursor incorporation was equated with RNA synthesis and correlated with developmental events and with previously determined teratogenic effects of actinomycin D.Uptake of uridine increased progressively in untreated animals from days 7 through 10 in decidua, trophoblastic giant cells, and visceral and parietal yolk sac endoderm, and remained relatively high in all except visceral yolk endoderm which dropped sharply on day 11. Actinomycin D did not significantly alter uptake in decidua and parietal yolk sac endoderm but caused appreciable reduction of uptake in trophoblast and visceral yolk sac epithelium on days 9 and 10.Uridine incorporation in embryonic ectoderm of untreated animals was relatively low but measurable at all times after day 7 and increased steadily through day 11. It was significantly depressed by actinomycin D on days 9 and 10. These observations correlated well with known developmental events and with teratogenic manifestations following actinomycin D treatment.Tritiated actinomycin D was shown by radioautography to be present in the embryo on day 9, 10 and 11 of gestation, and was shown to be bound to DNA, by virtue of its disappearance after application of deoxyribonuclease. It was concluded that the teratogenic action of actinomycin D in rats is probably dependent on direct intraembryonic inhibition of RNA synthesis.

ISSN:0003-276X    

DOI:10.1002/ar.1091680407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractHelical filaments have been found within dilated intracristal spaces of normal rat salivary gland mitochondria. Filament diameter measured 35–45 Å, and the helix diameter and pitch were 140–155 Å. They were found in as many as 25% of the mitochondria of acinar and intercalated duct cells. Helices were not found in mitochondria of the striated duct

ISSN:0003-276X    

DOI:10.1002/ar.1091680408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe solubility of purified cholesterol digitonide in absolute and aqueous ethanols was investigated. The results indicate that preservation of cholesterol (or other 3‐B‐hydroxysterols) in tissues prepared for electron and light microscopy by digitonin‐containing fixatives may not be quantitative when ethanol and, in particular, absolute ethanol, is used for dehydr

ISSN:0003-276X    

DOI:10.1002/ar.1091680409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY