摘要:

AbstractMitotic rates of epithelial cells in Sprague‐Dawley rat mammary glands were investigated in the virgin rat, and during pregnancy, lactation and involution. In addition, rates of cell division were determined in mammary gland neoplasms induced by dimethylbenz(a)anthracene (DMBA). The mammary gland epithelium of the virgin rat exhibited a slight but continuous mitotic activity through all phases of the estrous cycle, indicating a low rate of cell renewal. During pregnancy the rate increased markedly, attaining a peak on the twelfth day. The rates of mitosis declined during lactation and involution. The majority of DMBA induced mammary gland neoplasms exhibited mitotic rates lower than the normal mammary gland during pregnanc

ISSN:0003-276X    

DOI:10.1002/ar.1091740102

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

年代:1972

数据来源: WILEY

摘要:

AbstractGuinea pig eggs can be fertilized invitroin a chemically defined medium originally developed by Biggers, Whitten and Whittingham for the cultivation of fertilized mouse eggs. When unfertilized eggs were inseminated in this medium (abbr. BWW) with fresh epididymal spermatozoa, sperm penetration occurred not earlier than two hours after insemination. Quick and efficient sperm penetration occurred when the eggs were inseminated with spermatozoa pre‐incubated in BWW for 11‐18 hours. Spermatozoa started to pass through the zona pellucida as early as 10‐15 minutes following insemination and all the eggs were penetrated by spermatozoa within one hour. The time needed for functional capacitation of guinea pig spermatozoa is estimated to be no less than two hours under the experimental conditions used, the optimal time possibly being 8‐12 hours or even longer. The possibility ofin vitrosperm capacitation and fertilization of eggs in media much simpler than BWW (e.g., Earle's solution with or without albumin) is su

ISSN:0003-276X    

DOI:10.1002/ar.1091740103

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

年代:1972

数据来源: WILEY

摘要:

AbstractHematic barriers were studied in femoral and sciatic nerves and their peripheral branches in male albino rabbits by means of fluorescence microscopy and ultra‐freezing and drying technics. The fluorescent tracer used was a diaminoacridine, acriflavine neutral, which is non‐toxic at the 20 mg/kg dose administered intravenously, has a low molecular weight (259.7), and has a unique quality of chemically bindingin vivowith nuclear DNA and RNA. This latter property of acriflavine neutral permitted the observation of fluorescent nuclei where the substance penetrated and no fluorescence where it did not penetrate. The interface between the two regions was identified as a locus of a hematic barrier.Three hematic barrier loci were observed in spinal nerves and their branches: (1) in the plasma membranes of the cells forming inner lamellae of the “perineurial epithelium,” (2) in the luminal face of the plasma membrane of endothelialcellsforming the wall of endoneurial capillaries, and (3) in the “perineurial epithelial” sheath which surrounds endoneurial precapillaries. These barriers appeared to be dependent on normal living physiologic processes for their proper maintenance. In addition, they were very similar to some of the hematic barriers associated with the central ner

ISSN:0003-276X    

DOI:10.1002/ar.1091740104

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

年代:1972

数据来源: WILEY

摘要:

AbstractSynaptic junctions from the lateral geniculate nucleus of the quokka brain have been examined by electron microscopy after glutaraldehyde fixation and PTA staining. Junctions can be divided into two groups:discontinuous‐continuousandcontinuous‐continuous, depending on the continuity or lack of it of the presynaptic membrane. The postsynaptic membrane always has a continuous appearance.The dense projections have the following characteristics: 1. an irregular outline due to the presence of spikes; 2. in some cases, an external electron‐opaque “skin” and an internal, relatively electron‐translucent core; 3. adjacent projections may have one or more stands of the presynaptic network between them and extending to the internal coat of the presynaptic membrane; 4. the gap between the bases of dense projections varies from 5 to 69 nm, with a mean value of 23 nm. Seventy‐six percent of these measurements fall within the range 5‐25 nm, while many of the larger gaps separating dense projections are subdivided into smaller components by the presence of one or more strands of the presynap‐tic network.Features 2 and 3 have not been previously described in exactly the form seen here. It is not known whether they are confined to marsupial synapses or whether they highlight important general features of syna

ISSN:0003-276X    

DOI:10.1002/ar.1091740105

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

年代:1972

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091740106

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

年代:1972

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091740101

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

年代:1972

数据来源: WILEY