Temporal Organization in Avian Reproduction

Recent studies have demonstrated that biological rhythms haveimportant roles in avian reproduction. In the photoperiodicstimulation of the reproductive complex, there are two systemsinvolved in the interpretation of day length. One system isentrained by the photoperiod, probably by dawn. This entrainedsystem in turn entrains two light-sensitive phases which occurlater in the day. If the photoperi od is long enough, it ispresent during the sensitive phases when it can induce the productionof luteinzing hormone and follicle stimulating hormone. Theinterrenal gland appears to be a part of the entraining systeminasmuch as injections of corticosterone can set a sensitivephase when light can induce gonadal development. The annual cycle of photosensitivity and photorefractorinessappeals to be controlled by the temporal relations between thedaily rhythms of corticosterone and prolactin which change seasonally.When the hormonal relations of photosensitive and photorefractorybirds are simulated by injections of the hormones, the appropriateconditions (photosensitivity or photorefractonness) can be produced.Seasonal changes in the hormonal relations are not direct reflectionsof changes in the photoperiod; they depend on more complex physiologicalexperiences. The systems involved in egg laying and parental behavior mayalso have a temporal basis of biological rhythms. For example,the intensity of the pigeon cropsac response depends on thetime of daily injections of prolactin relative to those of corticosterone.It is apparent that the daily rhythm constitutes the basic structuialunit in the temporal organizationtion of avian reproduction.     

Histogenesis of human extraparenchymal Leydig cells

From 64 consecutive autopsies of patients with neither testicular nor hormonal pathology, 26 showed extraparenchymal Leydig cells, located mainly in the epididymis and in the spermatic cord. The ultrastructural study of these specimens plus those obtained from 2 patients affected with functional testicular tumors leads to the following conclusions: (1) The origin of ectopic Leydig cells is not interstitial Leydig cells having infiltrated the testicular nerves and migrated along them towards ectopic locations. (2) The ectopic Leydig cells are considered to develop from undifferentiated precursor cells, located extraparenchymally, mainly inside and beside the testicular nerves. These precursor cells are similar to those observed in the testicular interstitium and have an ovoid shape and some cytoplasmic projections. The cytoplasm contains vesicles of smooth endoplasmic reticulum, lysosomes, lipid droplets and abundant microfilament bundles. The transformation from these cells into mature Leydig cells implies a progressive differentiation of the cytoplasmic components involved in steroid biosynthesis.     

Histogenesis of chicken aorta endothelium]

The formation of tissue properties of the aorta endothelium of two-week chicken embryos, and one day chickens has been followed. The morphological characteristics of the aorta endothelial lining in adult chickens are given. The endothelium was studied in tangential sections and flat film preparations. Histological certain histochemical and biometrical methods were used. At the end of the second week the signs of a heteromorphous state of the endothelium were already seen most distinctly, which appeared as early as the end of the first week of embryogenesis. Later these signs accumulated and became stronger. The aorta endothelial lining of adult chickens is polymorphous. Certain regularities in the regional distribution of cells of a definite shape and area were observed in it. Throughout embryogenesis the endothelium behaved like a tissue having its oun cambium. The mitotic index drops in the course of embryogenesis. No mitoses have been found in the endothelial lining of adult chickens.     

扬子鳄附肢的组织发生

本文在２２例扬子鳄胚胎中观察了附肢的组织发生过程。孵化第６天,前、后肢芽形成处的组织开始向外隆起。第８天,前、后肢芽突出呈乳状。第１４天,前、后肢芽基部的中胚层浓缩,开始形成肱骨、股骨软骨原基。第１６天,前肢的桡骨、尺骨及后肢的胫骨、腓骨软骨原基出现,软骨原基周围的骨骼肌亦开始分化。第１８天,肱骨、股骨、桡骨、胫骨、腓骨均发生明显的软骨化,前肢尺骨尚未发生软骨化,后肢跖软骨原基形成。第２０天,前肢掌骨原基及后肢的第１、２、３趾骨原基出现。第２４天,前肢第１、２、３、４指骨原基清晰,后肢第１、２、３、４趾骨基节软骨化明显,趾肌开始分化。第３０天,前、后肢的指（趾）骨均发生明显的软骨化,前肢掌骨以上诸骨和后肢跖骨以上诸骨的软骨化趋于成熟,其周围的骨骼肌已较发达。本文着重讨论了扬子鳄附肢组织发生的规律和特点。     

Histogenesis of human esophageal striated muscle tissue

Development of the esophageal striated muscle tissue has been studied in 60 human embryos and fetuses at the age of 6-40 weeks. Stages in differentiation of the muscle fiber have been demonstrated, process of myofibrillogenesis has been studied. In the process of differentiation of the esophageal striated muscle fiber under the basal membrane myosatellitocytes are laid. A conclusion is made about myotomic origin of the human esophageal striated muscle tissue. The developmental peculiarity of the human esophageal striated muscle is formation between muscle fibers of specialized connections. This is explained by conditions of the esophageal functioning, that realizes peristaltic movements.     

Morphology and Cytology of Pea Embryos During Histogenesis

Cytological examination showed that day 3 pea embryo cells wereundifferentiated in terms of morphological or gross cytologicalappearance. Histogenesis had commenced by day 4 and was accompaniedby cytological differentiation with a gradient in vacuolationapparent along the root/shoot axis. Day 3 embryonic cells werecytologically different from meristematic (day 4 and 5) cellsof the shoot apex. Cells of the embryo base appeared to havean intimate association with the middle suspensor cells. Pisum sativum L. cv. ‘Alaska’, pea, morphology, cytology, histogenesis, development     

Bulb Histogenesis in Hordeum bulbosum L.

The histological and associated histochemical phenomena occurringin the developing bud of Hordeum bulbosum were investigated.Naturally the bulb is formed by swelling of the lowest internodeof the spike-bearing stern. Bulb initiation began by a rapidcell division followed by cell elongation. The bulb form wasachieved by forming cell files directed diagonally outward inthe upper part and by a periphery meristern contributing cellsto the middle and the lower parts of the bulb internode. Starchaccumulated in the cells before bulb initiation and was utilizedcompletely only in the elongating cells when bulb elongationoccurred. High content of nucleic acids and total protein, demonstratedby specific stainings, was observed in the cytoplasm of cellsof the intercalary meristem at each internode. In the bulb,these stainings became progressively less as the bulb elongated.