Wiley

Phân bố siêu cấu trúc của hai protein không collagen, osteopontin (OPN) và osteocalcin (OC), ban đầu được chiết xuất từ ma trận xương và được các nhà nghiên cứu đề xuất đóng vai trò quan trọng trong quá trình hình thành xương, đã được nghiên cứu trong các ma trận xương và sụn từ các tấm tăng trưởng của xương chày gà phôi và sau sinh thông qua kỹ thuật miễn dịch hóa học tế bào độ phân giải cao sử dụng kỹ thuật vàng keo. Trong xương, các mẫu phân nhãn miễn dịch sử dụng kháng thể đa dòng chống lại OPN và OC của gà nhìn chung khá tương tự nhau ở chỗ cả hai đều cho thấy sự phân nhãn mạnh mẽ, nhưng thay đổi theo vùng, ở ma trận xương đã khoáng hóa và các vị trí khoáng hóa nhỏ rải rác khắp osteoid và chứa vật liệu hữu cơ cô đặc nổi bật. Osteoid không khoáng hóa thể hiện sự phân nhãn yếu đến trung bình. Trong ma trận xương đã khoáng hóa thực sự, phân nhãn chủ yếu liên quan đến các mảng hữu cơ vô định hình, có mật độ điện tử cao giữa các fibril collagen. Trong sụn tấm tăng trưởng, cả hai protein lần đầu tiên xuất hiện liên quan đến sụn đã được calc hóa trong vùng phì đại, mặc dù các mẫu phân nhãn có phần khác nhau. Đối với OPN, các hạt vàng chủ yếu liên quan đến một mật độ giống như lamina limitans hữu cơ chứa ma trận hữu cơ dạng sợi cô đặc ở ngoại vi các nốt nhỏ và khối lượng lớn của sụn đã calc hóa, với phân nhãn trung bình bổ sung ở bên trong của sụn đã calc hóa. Đối với OC, phân nhãn được quan sát trên các cấu trúc sợi khắp ma trận sụn đã calc hóa, với một số, nhưng ít hơn, phân nhãn ở ngoại vi. Trong các vùng thấp nhất của tấm tăng trưởng, phản ứng chính khi sử dụng cả hai kháng thể được tìm thấy trên một lớp vật liệu hữu cơ vô định hình dày ở ngoại vi của sụn đã calc hóa tại giao diện xương/sụn đã calc hóa trong tương lai, một mẫu phân nhãn vẫn tồn tại sau khi xương được lắng đọng tại các vị trí này. OPN và ở mức độ ít hơn OC cũng tập trung trong các đường xi măng (nghỉ ngơi, đảo ngược). Suốt xương và sụn của xương chày, các tế bào của cả hai dòng osteoblastic và osteoclastic đã được tìm thấy áp sát trực tiếp vào các bề mặt được phân nhãn và lamina limitans của ma trận hữu cơ chứa OPN và OC. Tóm lại, từ các dữ liệu miễn dịch hóa tế bào được trình bày ở đây, kết luận rằng việc liên kết OPN và OC với các vùng khoáng hóa của ma trận ngoại bào của xương và sụn và sự tích tụ của các protein này tại các bề mặt và giao diện mô là phù hợp với những giả thuyết cho rằng chúng đóng vai trò trong quá trình khoáng hóa ngoại bào per se và/hoặc có thể trung gian cho sự bám dính tế bào và động lực học.© Willey‐Liss, Inc.

The development of the eye has been studied in mouse embryos from the ninth day through the nineteenth day of gestation. The tissue was fixed in aldehydes, post‐osmicated and embedded in Epon. The entire eye was sectioned and studied under the light microscope. The development of the eye in the prenatal period is described as having seven stages. In the first stage, the close contact of the optic vesicle with the surface ectoderm is observed. The retinal disc and lens placode begins to form. The second stage shows the invagination of the optic vesicle and the contraction of the margin of the lens pit. In the third stage, the optic cup differentiates into an outer pigment epithelium and an inner retinal layer. The cells of the posterior lens wall start to elongate. During the fourth stage, the cavity of the lens vesicle is completely obliterated by primary lens fibers and the inner neuroblastic layer of the retina is formed with nerve fibers being traced from its cells to the optic stalk. The fifth stage is dominated by the appearance of lids, cornea and optic nerve, the formation of the anterior chamber and the consolidation of the intraocular portion of the embryonic vascular system. In the sixth stage, the eyelids fuse and the anterior margin of the optic cup begins to grow actively. In the last prenatal stage, the third neuron layer of the retina begins to differentiate. The iris and the folds of the ciliary body can be detected.

A stereological method for obtaining estimates of the total number of neurons in five major subdivisions of the rat hippocampus is described. The new method, the optical fractionator, combines two recent developments in stereology: a three‐dimensional probe for counting neuronal nuclei, the optical disector, and a systematic uniform sampling scheme, the fractionator. The optical disector results in unbiased estimates of neuron number, i.e., estimates that are free of assumptions about neuron size and shape, are unaffected by lost caps and over‐projection, and approach the true number of neurons in an unlimited manner as the number of samples is increased. The fractionator involves sampling a known fraction of a structural component. In the case of neuron number, a zero dimensional quantity, it provides estimates that are unaffected by shrinkage before, during, and after processing of the tissue. Because the fractionator involves systematic sampling, it also results in highly efficient estimates. Typically only 100–200 neurons must be counted in an animal to obtain a precision that is compatible with experimental studies. The methodology is compared with those used in earlier works involving estimates of neuron number in the rat hippocampus and a number of new stereological methods that have particular relevance to the quantitative study of the structure of the nervous system are briefly described in an appendix.

The cells of the theca externa of large, antral ovarian follicles in the rat were studied by electron microscopy. Many resembled fibroblasts, while others possessed cytoplasmic filaments and dense bodies characteristic of smooth muscle cells. Filament‐containing cells of intermediate structure appeared to represent transitional forms between the two previous types.

Small numbers of smooth muscle‐like cells were found also around small antral follicles, and many corpora lutea possessed locally well‐defined coats of smooth muscle.

These observations indicate that cells with a probable contractile function are present in the theca externa of ovarian follicles in the rat. These cells may play a role in the process of ovulation.

Nerves exhibiting substance P‐like immunoreactivity were demonstrated in the human periosteum. A network of nerves showing substance P‐like immunoreactivity was seen in the periosteum, while finer strands of immunoreactive nerve fibers were present immediately beneath the surface of the periosteum. Enkephalin‐like immunoreactivity was also studied but could not be demonstrated.

Substance P has previously been suggested to be involved in the mediation of the sensation of pain. The clinically observable marked pain sensitivity of periosteal tissue might be explained by the peptidergic nerves described in this paper.

The extracellular matrix (ECM) of first‐trimester human decidua was examined with indirect immunofluorescence using affinity‐purified antibodies to human collagen types I, III, IV, V, laminin, and fibronectin. In addition, the validity of the classification “mesenchymal‐epithelioid” for differentiated decidual cells was addressed using antibodies to the intermediate filament proteins, vimentin, a mesenchymal marker, and keratin, an epithelial marker. Biosynthesis of extracellular matrix components was examined by radiolabeling of decidual explants in culture with ³H‐proline, followed by immunoprecipitations of synthesized proteins with collagen type‐specific antibodies. Immunofluorescence showed decidual cells are embedded in an extensive network of collagen types I and III, and intracytoplasmic staining suggested synthesis of these collagens by the decidual cells. Collagen type IV and laminin localized in the external lamina which surrounds the differentiated decidual cell, and some fluorescence was evident in the peripheral cytoplasm. Immunoreactive collagen type V was observed in close association with the external lamina and in the peridecidual matrix. Fibronectin localized throughout the decidual ECM and in fibrillar and punctuate patterns in the decidual cell cytoplasm. Differentiated decidual cells retained a “mesenchymal” intermediate filament cytoskeleton containing an abundance of vimentin filaments, but very few, if any, keratin filaments. Collagen types I, III, V, and to a lesser extent, IV, were immunoprecipitated from the medium of decidual explants after 24 hours of culture, demonstrating in vitro synthesis and secretion of these collagens by first trimester human decidua.

The distributions of desmin and vimentin were examined in frozen sections of cardiac muscle from embryonic, newborn, and adult Syrian hamster by using immunofluorescent methods. Frozen sections of newborn and adult skeletal muscle were used for comparison. Cardiac myocytes from day 9 in utero embryos already show a clear association of desmin with the sarcomeric myofibrils. In newborn hearts, desmin is localized in the myofibrillar Z‐line areas as well as in the peripheral cytoplasm of the cell. Three days after birth, desmin is associated with the intercalated discs. Thus, in adult cardiac muscle, desmin is present in both Z‐bands and intercalated discs. Skeletal muscle of newborn and adult hamster also contains desmin associated with the Z‐lines of myofibrils. Vimentin is associated with the myofibrils of day 9 in utero cardiac muscle cells. The protein remains associated with the myofibrillar Z‐lines in the newborns and adults. No detectable staining for vimentin was observed in newborn or adult hamster skeletal muscle. The existence of vimentin as well as desmin in differentiated cardiac muscle may be a consequence of the somewhat more epithelial‐like nature of cardiac cells as compared to skeletal muscle syncitia.

The origin of the epicardium and the formation of the early blood vessels of the heart prior to the opening of the coronary arteries from the aorta have been studied in the 9–13.5 day post coitum (dpc) mouse embryo heart. The epicardium begins to appear by 9 dpc. The majority of the epicardial cells derive from the somatopleural investment of the septum transversum, from where they migrate, associated to form vesicles, to the dorsal aspect of the ventricles and atria. The epicardial cells then migrate over the lateral surfaces and the AV sulcus to the ventral aspect of the heart. In the subepicardial space around the sulcuses, the proliferating epithelial tissue is found, also in vesicular form, for a time. The ventrally migrating primordial epicardial tissue ensheaths lastly the truncus arteriosus, while the sinus venosus is coated with epicardium ab initio, where (and also in the SA sulcus) the epicardial cells derive in part from the cuboidal cells of the pleuroperitoneal canal and in part from the somatopleural cells. The early blood vessel formation follows in space and time the development of the epicardium. The first blood vessels appear by 10 dpc by the invagination of the endocardium into the early sinus muscle, and at the same time in the ventricular chamber by the encasing of the endocardium, as the trabeculae become consolidated into the myocardial walls. By this process sinusoids are formed, some of which penetrate through the myocardium and which, by rapid proliferation, form an interconnected subepicardial plexus. These capillaries proliferate ventrally in the wide subepicardial space, reaching the septating truncus, in which the aorta and pulmonary artery are developing. The definitive coronary artery openings appear by 13 dpc, allowing the high pressure blood from the aorta to flow into a preexisting vascular bed.

Neural crest cells from the cranial region of the neural fold populate the outflow tract of the developing chick heart. Removal of this region of premigratory neural crest has been shown previously to result in a high percentage of conotruncal malformations. The present study was undertaken to define more precisely the regions of premigratory neural crest which are needed for normal conotruncal development. Various regions and lengths of premigratory cranial neural crest were ablated using microcautery. Three defects in conotruncal development were significantly correlated with the neural crest ablation. These were high venticular septal defect, single outflow vessel originating from the right ventricle, and single outflow vessel overriding the ventricular septum.