摘要:

Direct development is a common reproductive mode in living amphibians characterized by absence of the free-living, aquatic larval stage. In Eleutherodactylus, a species-rich genus of New World frogs, evolution of direct development from the ancestral biphasic ontogeny is correlated with a comprehensive modification in embryonic cranial patterning, including the loss of many larval-specific components and the precocious formation of many adult (postmetamorphic) structures. We use scanning electron microscopy (SEM) to examine the emergence and early migration of cranial neural crest cells in Eleutherodactylus coqui to begin to assess the possible role of the neural crest in mediating these evolutionary changes. As in metamorphosing frogs, cranial crest cells emerge prior to neural fold closure and assemble into three streams: rostral, rostral otic, and caudal otic. These streams contribute to the face and first visceral (mandibular) arch, to the second (hyoid) arch, and to posterior (branchial) arches, respectively. Rostrocaudal position, morphology, and/or migration patterns distinguish subpopulations of cells within the rostral stream and caudal otic stream. With the possible exception of the small size of the rostral otic and caudal otic streams, evolution of direct development in E. coqui has not altered basic patterns of neural crest emergence or early migration as assessed by SEM. If observed evolutionary changes in embryonic cranial patterning are mediated by the neural crest, then they likely involve later aspects of crest migration or more subtle features related to pattern formation such as cell behavior and commitment, or gene expression.

ISSN:1422-6405    

DOI:10.1159/000147725

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Vertebrate skeletal muscles contain a family of myosin heavy chain (MyHC) proteins whose expression varies with clonal origin, developmental age, hormonal state, and innervation patterns. The number of MyHC genes and their regulation have been intensely studied in mammals and birds. However, comparatively little is known about MyHC expression in other vertebrates. To understand better MyHC regulation in amphibians, I have examined the fiber type expression of two tadpole stage-specific MyHC transcripts in Xenopus laevis. cDNAs for these transcripts, called MyHC E3 and MyHC E19, were used to synthesize digoxigenin labeled antisense RNA probes. In situ hybridization of these probes revealed that MyHC E3 was expressed throughout the myotome but was most abundant in the core fibers of the axial muscles, which are larval type II. In contrast, El9 was expressed most abundantly in the small diameter peripheral fibers of the axial muscles, which are larval type I. Transcripts of both genes were detected exclusively in skeletal muscle; neither heavy chain was expressed in cardiac muscle, smooth muscle, or lymph heart muscle. E3 expression was first detected at late gastrula in both segmented and unsegmented dorsal mesoderm. It remained abundant throughout premetamorphosis in myotomal muscle, and was also found in the levator hyoideus and mandibularis muscle of the head, and in abdominal wall muscles. In contrast, E19 was first detected at tailbud in the tail tip and its expression spread anteriorly among larval type I and type II fibers of the myotome and head muscles during the next few hours of development. The patterns of expression suggest that MyHC E3 is expressed predominately in larval type II fibers, and MyHC E19 is initially expressed predominately in larval type I fibers but as development proceeds is expressed in both type I and type II.

ISSN:1422-6405    

DOI:10.1159/000147726

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The distribution of F-actin, vimentin and α-tubulin was studied immunohistochemically in bovine seminiferous and straight testicular tubules, rete testis and intertubular tissue during postnatal development. Sites of antigenicity were detected by ABC immunoperoxidase technique and visualized by metal-enhanced deposition of diaminobenzidine. Within the seminiferous epithelium, F-actin appears at 20 weeks and is found in adult Sertoli cells as part of specialized cell contacts. In peritubular cells, F-actin increases gradually from 4 to 30 weeks when the adult concentration is achieved. After 20 weeks, subepithelial fibro-blasts of the mediastinum testis start to express F-actin and at 52 weeks, a thick layer of positive myofibroblasts is seen beneath the epithelia of rete testis and straight testicular tubules. Testicular macrophages and light intercalated cells (LIC) are also characteristically decorated following F-actin immunoreaction. Vimentin is localized in perinuclear position in pre-Sertoli cells of 4-20 weeks and in adult Sertoli cells. During the period of transformation from pre-Sertoli to Sertoli cells, the perinuclear vimentin coat is absent. The epithelia of rete testis and straight tubules exhibit a strong vimentin immunoreaction in their basal parts. This specific pattern does not change from 4 weeks to adulthood. α-Tubulin is absent in 4-week-old seminiferous tubules. At 8 weeks, the perinuclear area of pre-Sertoli cells reacts positive. The α-tubulin content increases in these cells continuously, and from 30 weeks on nearly the entire supranuclear cytoplasm of Sertoli cells is heavily decorated. The epithelial of rete and straight tubules display a growing number of α-tubulin-positive cells from 4 to 40 weeks. From then on, nearly all epithelial cells contain α-tubulin, particularly in a narrow zone beneath their lateral cell bor

ISSN:1422-6405    

DOI:10.1159/000147727

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Secretory particles, designated as ‘vesiculosomes’, were isolated and purified from bovine seminal vesicle fluid. The protein pattern was characterized using one- and two-dimensional gel electrophoresis. Native vesiculosome fractions were used for immunization of female New Zealand rabbits. The resulting vesiculosome antiserum was used for immunohistochemical studies, designed to obtain data on the intracellular formation, the localization and the potential release from secretory cells of the respective proteins present in these particles. The specificity and sensitivity of the antiserum was tested by Western blot analysis and by an ELISA system. Western blot analysis of isolated vesiculosomes separated on SDS-PAGE showed several heterogeneous immunoreactive bands in the range of 16 kD and above 66 kD, indicating a polyvalent mixture of immunoglobulins. Immunohistochemical staining of different bovine tissues, nevertheless, revealed a strong reaction exclusively at the apical portion of secretory cells of the seminal vesicle and the ampulla of the vas deferens and of intraluminal secretion. The antiserum recognizes both secretory granules and plasma membrane proteins of seminal vesicle epithelium, supporting the concept of vesiculosomes to represent cytoplasmic particles formed from plasma membranes surrounding apical ‘blebs’ of the cells that are released physiologically during se

ISSN:1422-6405    

DOI:10.1159/000147728

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The morphometric effects of postnatal exposure to alcohol on the neurons of the paraventricular hypothalamic nucleus (PVN) have been studied in four different topographic subdivisions of the nucleus: rostral, intermediate medial, intermediate lateral and caudal. Male mice were exposed to alcohol during lactation and after weaning by addition of 20% of ethanol to the drinking water that was first ingested by the mother and thereafter by the experimental animals themselves. Animals were sacrificed at the 25th, 35th, 45th, 55th and 100th postnatal day. Nuclear sizes of the PVN neurons (perimeter, area and maximum diameter) were determined in both control and experimental alcohol-treated groups. The shape of these neuronal nuclei was also determined and compared. PVN responds globally to alcohol exposure, showing a decrease in the neuronal nuclear sizes in the four studied PVN subdivisions of the alcohol-treated mice at the 35th to 45th and 100th day. We suggest that these decreases could be related to changes in gonadal hormone levels induced by alcohol exposure and/or disturbances of brain neurotransmitter and neuropeptide metabolism caused by ethanol.

ISSN:1422-6405    

DOI:10.1159/000147729

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

Plastic corrosion casts of the rat retinal vasculature were studied by scanning electron microscopy. This technique demonstrated the entire retinal vasculature of the rat. The retinal blood vessels supplying the rat’s retina have a definite and fairly constant pattern. At the disk there are usually six main artery and vein branches that run symmetrically towards the periphery. Veins are wider and more tortuous. The characteristic arrangement of endothelial cell nuclear indentations clearly differentiates arteries from veins. Retinal arteries have side-arm and dichotomous branchings. The number of vessel branches is greater on the nasal side than on the temporal side of the retina. The vein-over-artery crossing phenomenon is more frequent than the artery-over-vein. Retinal capillaries appear tortuous and are arranged cylindrically in two layers. The superficial network of capillaries comes essentially from arterioles, while deep layer capillary networks are more regularly and densely arranged and are mainly connected with venules. The inner and the outer capillary networks have interconnections, vertical runs and short vascular bridges. Within the retina there are regional variations in capillary pattern and distribution. More regular, dense and rich capillary networks are observed in the peripheral area than at the posterior pole area. No arteriovenous shunts were seen. The study of such plastic casts makes possible a more accurate assessment of some aspects of vascular abnormalities. These findings will be helpful in further investigations of retinal vascular abnormalitie

ISSN:1422-6405    

DOI:10.1159/000147730

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

In an attempt to elucidate the effects of denervation on development and maintenance of the structure of the fungiform papilla, unilateral neurectomy of the chorda tympani-lingual nerve of rats was performed at day 1 and at weeks 1, 2, 3, 4, 7, and 10 after birth. Specimens were obtained at days 3, 7 and 10, weeks 2, 3, 4, 6, and 8, and months 3 and 4 after neurectomy for examination by light and scanning electron microscopy. At first, the fungiform papillae were atrophic, then progressed to forms resembling filiform papillae. When an immature fungiform papilla was denervated, it eventually changed to a papilla identical to normal filiform papillae. The elicited changes differed according to the time of neurectomy; it was found that early neurectomy resulted in a more rapid and marked morphological change of the fungiform papillae. The filiform-like papillae derived from the fungiform ones showed various shapes, sizes, and orientations and were rarely present on the unoperated control side of the lingual dorsum. Sections of the filiform-like papillae revealed that they had no taste buds. These findings suggest: (1) Morphogenesis and structural maintenance of the fungiform papillae require the presence of the chorda tympani and/or lingual nerve. (2) Completion of differentiation and maturation differ in time among fungiform papillae. (3) Fungiform papillae may be transformed filiform papillae induced and maintained by a neurotrophic factor or factors coming from the chorda tympani and/or lingual nerve. (4) Fungiform papillae are rarely innervated contralaterally.

ISSN:1422-6405    

DOI:10.1159/000147739

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

In mammals, transduction of sodium stimuli occurs via amiloride-sensitive sodium channels. In rat, gustatory physiological sensitivity to sodium stimuli develops gradually during the early postnatal period. In addition, if pregnant rats are subjected to dietary sodium restriction during gestation, their offspring fail to develop normal gustatory physiological responses to sodium and sensitivity to amiloride. In the present study, we used polyclonal antibodies raised against amiloride-sensitive sodium channels to ascertain whether gustatory function is correlated with the immunological presence of the transduction apparatus for sodium stimuli in the taste buds of neonatal rats and adult offspring of sodium-restricted dams. The results indicate that antiamiloride-sensitive sodium channel antisera bind cells within taste buds of neonatal and adult rats, regardless of maternal dietary condition. Therefore, despite the functional absence of taste system amiloride-sensitive sodium channels, the antigenic determinants of these channels are expressed. These data suggest that the onset of normal gustatory sodium sensitivity in neonatal normal rats results from the progressive activation of existing, quiescent channels. Furthermore, they rule out the possibility that the failure to synthesize channel protein underlies the lack of gustatory sodium and amiloride sensitivity in the offspring of sodium-restricted rats.

ISSN:1422-6405    

DOI:10.1159/000147740

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

The extant diapsids (amniotes with two temporal fenestrae) consist of archosaurs (birds and crocodiles) and of lepidosaurs (sphenodon and squamates). The dichotomy of these two lineages occurred in the upper Permian. Originally, the intraarticular knee ligaments were three cruciates. The intermediate cruciate (a posterior one with guiding function) is present in all diapsids, whilst the medial one (an anterior with guiding function) is absent in birds. The lateral cruciate ligament is subdivided into a lateral anterior and a medial posterior shank. The posterior shank disappeared in birds and crocodiles. The anterior shank disposes of a guiding function in archosaurs, and is in the course of reduction in lepidosaurs. The reduction process has progressed least in sphenodons, whereas the lateral cruciate of chameleons is totally absent. The anterior cruciates of birds (the lateral one) and of chameleons (the medial one) are hence not homologous. The morphology and function of the cruciate ligaments can be related with gait evolution.

ISSN:1422-6405    

DOI:10.1159/000147741

出版商:S. Karger AG    

年代:1995

数据来源: Karger

摘要:

In this study, a total of 125 female and 175 male adult human skulls from Central Anatolia were examined. The incidence and localization of the rare occipital foramen found on the squama of occipital bone were investigated. This foramen has significant importance during suboccipital craniotomies since it transmits the occipital emissary vein. In the present study, the occipital foramen was found in 8 (2.6%) skulls. Its location was closer to the foramen magnum but not to the external occipital protuberance.

ISSN:1422-6405    

DOI:10.1159/000147742

出版商:S. Karger AG    

年代:1995

数据来源: Karger