Wiley

Monoamine compounds, such as serotonin (5‐HT), have been previously suggested to regulate the early development of the chick embryo. Possible roles for 5‐HT in chick morphogenesis were investigated further by examining the distribution of sites that concentrate 5‐HT as well as the ability of embryos to synthesize 5‐HT during this period. Following the in vitro incubation of chick embryos with 5‐HT, cells accumulating 5‐HT were localized by the formaldehyde‐induced fluorescence (FIF) technique; these sites of 5‐HT concentration were mapped and studied with respect to changes in their developmental patterns during morphogenesis. Locations of 5‐HT FIF included two regions of the brain within the floor plate of the mesencephalon and caudal myelencephalon, and within scleratome cells of somites advanced in differentiation. Additionally, two separate zones of 5‐HT FIF appeared in the neural tube caudal to the somites in conjunction with a small band of intense FIF in the caudal end of the notochord. Once established, the capabilities for 5‐HT concentration in the brain and somites persisted at the same locations during development, whereas these capabilities in caudal portions of the embryo were transient and appeared to move down the embryo as the embryo lengthened. These changes in the patterns of 5‐HT FIF in caudal segments of the neural tube and notochord correlated spatio‐temporally with the progression of caudal neuropore closure. Additional experiments, involving the use of anti‐5‐HT immunocytochemistry, were undertaken to examine the characteristics of 5‐HT concentration. The mechanism(s) of 5‐HT concentration at all locations appeared to have a high affinity and specificity for 5‐HT; however, in contrast to the transient mechanism situated more caudally in the embryos, the uptake mechanism at rostral locations required energy and was blocked by a 5‐HT uptake inhibitor (fluoxetine). The ability of embryos to synthesize 5‐HT was demonstrated by the generation of 5‐HT (localized by FIF and immunocytochemistry) in embryos treated with the 5‐HT precursors, 5‐hydroxytryptophan or L‐tryptophan. Confirming evidence of 5‐HT synthesis was provided by a marked reduction in immunostaining obtained with either precursor in the presence of 5‐HT synthesis inhibitors (R04–4602 or para‐chlorophenylalanine). Although the sites of synthesis remain uncertain, endogenous 5‐HT was detected (after monoamine oxidase inhibition) at all sites of 5‐HT concentration. These results provide further support for the suggestion that 5‐HT may be involved in various aspects of morphogenesis at specific sites within the chick embryo.

Morphometric studies were performed on 12 mammalian species (degu, dog, guinea pig, hamster, human, monkey, mouse, opossum, rabbit, rat, stallion, and woodchuck) to determine volume density percentage (V_v%), volume (V), and numerical density (N_v) of seminiferous tubule components, especially those related to the Sertoli cell, and to make species comparisons. For most species, measurements were taken both from stages where elongate spermatids were deeply embedded within the Sertoli cell and from stages near sperm release where elongate spermatids were in shallow crypts within the Sertoli cell. Montages, prepared from electron micrographs, were used to determine V_v% of Sertoli cell components in seminiferous tubules. Excluding the tubular lumen, the Sertoli cell occupied from a high of 43.1% (woodchuck) to a low of 14.0% (mouse) of the tubular epithelium. There was a strong negative correlation (r =−0.83; P<0.005) of volume occupancy of Sertoli cells with sperm production. Nuclear volume, as determined by serial reconstruction using serial thick sections, ranged from a high of 848.4 μm³ (opossum) to a low of 273.8 μ³ (degu). There was no correlation (r=0.02) of nuclear volume with volume occupancy (V_v%) in the tubule. Sertoli cell volume was determined by point‐counting morphometry at the electron‐microscope level as the product of the nuclear size and points determined over the entire cell divided by points over the nucleus. Sertoli cell V ranged from 2,035.3 μm³ (degu) to 7,011.6 μm³ (opossum) and was highly correlated (r=0.85; P<0.001) with nuclear size. However, there was no significant correlation between the Sertoli cell size (V) and volume occupancy (V_v%; r = 0.13) or sperm production (r = 0.21). Stereological estimates of the numerical density (N_v) of Sertoli cells ranged from a high of 101.9 × 10⁶ (monkey) to a low of 24.9 × 10⁶ (rabbit) cells per cm³ of testicular tissue. There was no correlation of numerical density of Sertoli cells with sperm production (r=0.002). A negative correlation was, however, observed between the numerical density of the Sertoli cells and the Sertoli cell size (r=−0.79; P<0.002). Data from the present study are compared with those previously published. This is the first study to compare Sertoli cell morphological measurements using unbiased sampling techniques. Morphometric data are provided which will serve as a basis for other morphometric studies.

Các kháng nguyên, lympho bào và tế bào hỗ trợ tương tác trong các cơ quan lympho ngoại biên để sinh ra miễn dịch. Hai loại tế bào đã được nghiên cứu về chức năng hỗ trợ trong nuôi cấy: đại thực bào đơn nhân và tế bào gai Ia phong phú không thực bào. Các kháng thể đơn dòng đã được sử dụng để nghiên cứu các đại thực bào chuột (MØ) và tế bào gai (DC) tách biệt bao gồm α-đại thực bào (F4/80, M1/70), α-tế bào gai (33D1), α-thụ thể Fc (2.4G2) và α-Ia (B21-2). Trong bài báo này, các kháng thể đã được sử dụng để nhuộm các tế bào hỗ trợ trong các lát cắt từ kẹp lạnh của lá lách chuột, hạch lympho và mảng Peyer. Mỗi cơ quan đều được biết đến là có các tiểu vùng phong phú về hoặc đại thực bào, hoặc tế bào B, hoặc tế bào T. Chúng tôi đã phát hiện ra rằng các tế bào hỗ trợ trong mỗi tiểu vùng có kiểu hình khác nhau. (1) Các vùng phong phú đại thực bào: Các đại thực bào xếp hàng tại vị trí cung cấp kháng nguyên (vùng biên giới của lá lách, xung quanh bạch huyết vào hạch, và bên dưới biểu mô của mảng Peyer) đã được nhuộm bằng M1/70 nhưng không có F4/80. F4/80 phong phú trên các đại thực bào ở các vị trí khác: tủy đỏ lá lách, tủy hạch, và xung quanh bạch huyết thoát ra của mảng Peyer. (2) Các nang phong phú B-lymphocyte: Các tế bào gai nang, giữ lại các phức hợp miễn dịch ngoại bào, tập trung ở phía ngoài của trung tâm sinh nang. Khu vực này đã được nhuộm mạnh bằng kháng thể α-thụ thể Fc 2.4G-2, nhưng không bằng M1/70, F4/80, hay 33D1. (3) Các khu vực T: Các tế bào interdigiting của các khu vực T đã được liên kết với các tế bào gai tách biệt. Các tế bào phong phú Ia không đều đã phân bố đồng nhất trong các khu vực T của mỗi cơ quan. Tuy nhiên, nhuộm bằng 33D1 không được phát hiện và bị hạn chế ở các điểm của các tế bào không thực bào tại giao điểm tủy đỏ/trắng của lá lách. F4/80, M1/70 hoặc 2.4G2 cũng không nhuộm khu vực T, ngoại trừ khu vực gần với động mạch trung tâm của lá lách. Do đó, các dấu hiệu bề mặt chính và vị trí của các tế bào ứng cử chính trong các cơ quan lympho chuột là các đại thực bào M1/70⁺ tại vị trí xâm nhập kháng nguyên; đại thực bào F4/80⁺ xung quanh các khu vực thoát bạch huyết; tế bào gai trung tâm sinh nang, có thể phong phú 2.4G2; và các tế bào interdigitating phong phú Ia trong khu vực T.

An ultrastructural study by transmission electron microscopy (TEM) of the vertebrae of embryonic, larval, juvenile and mature medaka shows that each vertebra consists of a core of notochordal cells surrounded by a sheath of bone. The vertebral bone lacks either fully or partially embedded cells in the matrix throughout development. Bone matrix is secreted by a layer of cells that lies over the outer surface of the vertebral bone. During the early stages of osteogenesis, these cells secrete bone matrix all around themselves. However, because of the gradual flow of the newly synthesized bone matrix through intercellular spaces, matrix‐producing cells do not become trapped in their own secretion. In later stages of osteogenesis, these cells secrete matrix only toward the already‐deposited bone. This polarized matrix secretion allows the osteoblasts to stay always on the bone surface and never to become trapped in the matrix as osteocytes.

The cytochemistry and ultrastructure of the lysosomal area of the rat's yolk sac placenta was studied at various stages of development. The lysosomal area, located at the apical end of the yolk sac epithelial cell between the microvillous border and the nucleus, consisted of dense bodies that persisted from day 10 of pregnancy through gestation and multivesicular bodies that are present only through day 12. Acid phosphatase activity was restricted to the dense material and to the membranes of this area. Two types of pinocytotic vesicles were present in all stages of development. One was a tubular structure containing dense material and the other, a saccular, clear structure containing a “fuzz‐lining” and membrane remnants. Possible relationships between the pinocytotic vesicles and the dense and multi‐vesicular bodies were considered.

The injection of Triton WR‐1339 on day 11 of pregnancy resulted in a vacuolation of the dense and multivesicular bodies. This vacuolation began 15 minutes after injection and maximum effect was reached within 12‐‐24 hours. A reorganization of the lysosome area occurred on days 15‐‐16 in those animals in which pregnancy continued to term. This reorganization consisted of an increase in the dense material within the vacuoles and a reduction in vacuole size. The vacuoles remained distended in those animals in which death and resorption of the fetus occurred. The first cellular changes associated with death occurred between 48‐‐60 hours post‐injection. The microvilli became shorter, thicker and reduced in number; the pinocytotic vesicles disappeared from the cell surface; the endoplasmic reticulum became dilated and vesiculated; and vesicles were formed from the cristae of the mitochondria.

With the injection regimen used in this study, 25% of the litters were resorbed while the remainder of the pregnant rats delivered viable fetuses at term.