Developmental studies on expression of monoclonal antibody-defined cytokeratins by thymic epithelial cells from normal and autoimmune mice

A major component of the thymic microenvironment is a network of thymic epithelial cells (TEC) which are able to express class II major histocompatibility complex products and to secrete thymic hormones. In the present investigation, we used a panel of anti-cytokeratin (CK) antibodies to establish distinct cytokeratin-defined TEC subsets. Four subpopulations were identified. One, in the cortex, is defined by anti-CK8 and anti-CK18 monoclonal antibodies (MAb). The other three subsets are medullary, two minor ones respectively reactive with anti-CK19 and KL1 monoclonal antibodies (the latter being specific for CK3 and 10), and a major one characterized by negative reaction with the above-mentioned MAb but strongly positive after labeling with a polyclonal (and polyspecific) anti-keratin immunoserum. Ontogenetic studies revealed that the CK8+/18+ TEC subset is the first to be detected in fetal life. Moreover, the numbers of CK3/10+ cells and CK19+ cells decrease in aging normal mice, a phenomenon that seems to occur early in autoimmune mice. We also observed that these two medullary TEC subsets are sensitive to high-dose in vivo treatment with hydrocortisone, which stimulates a dramatic increase in CK3/10+ cells and a certain decrease in CK19+ cells. Our results indicate that a number of mouse TEC subsets can be distinguished by cytokeratin expression. Such a strategy can be applied to analyze TEC sensitivity to drugs and might also be useful to further understanding of differential TEC function regarding intrathymic T-cell differentiation.     

维生素A缺乏大鼠致敏后免疫功能低下对肺炎的影响机制

目的探讨维生素A（VA）缺乏对致敏后免疫细胞发育、功能的影响机制。方法：低VA饲料喂养大鼠8周时用卵蛋白致敏并分组。VAS组隔天口服vA100u,治疗3次;VAD组与正常组口服大豆油。用免疫组织化学法观察细胞角蛋白19（CK19）、病理学检查肺与脾病理变化、ELISA法检查血清Th因子水平等。结果VAD组胸腺萎缩,胸腺上皮细胞（TEC）肥大、聚集、CK19少。血IL—10、IL-4、胸腺索a-1升高。肺感染病灶多,肺泡隔浸润细胞较少与红细胞渗出多。VAS组胸腺细胞增生,TEC内CK193上调,血IFN—γ水平较低、IL-4、IL-10明显下调。小气道单层纤毛柱状上皮正常,管壁淋巴细胞浸润较重,肺泡区巨噬细胞多、渗出红细胞少。结论VA缺乏并致敏后胸腺TEC、胸腺细胞等发育和功能异常。补充VA改善胸腺TEC结构、促进淋巴细胞增生与非特异免疫功能,保护呼吸道黏膜与肺泡上皮。     

The stroma of the thymus of the rat: morphology and antigen diffusion, a reconsideration

This work reconsiders aspects of the morphology of the capsule, of the blood vasculature, of the distribution of reticular fibers, and of the diffusion of intramediastinally injected antigens in the stroma of the thymus of the rat. This was done by an analysis of standard sections of normal thymuses, of sections of thymuses perfused with colloidal carbon, of silver-impregnated sections, and of sections of thymuses of rats injected intramediastinally with a fluorescent antigen or intravenously with Trypan blue, and by electron microscopy of the thymic capsule. The capsule consisted of two layers: an outer layer covering the entire periphery of a thymic lobe, and an inner layer which outlined the entire convoluted peripheral cortex of a lobe. Cortical vessels entered the capsule and septa in which they formed a capillary network. These capsular capillaries were fenestrated and leukocytes were often present near them. Adipocytes were also seen near these vessels in some areas of the capsule, and often at the bases of septa and trabeculae. Furthermore, much of the medulla had a dense network of coarse reticular fibers, whereas the remainder of the medulla and the cortex contained a loose network of fine fibers stretching out from the capsule, septa, and trabeculae. Intramediastinally injected fluorescent antigens were observed to spread in the capsule and septa and to diffuse in the fiber networks stretched across the cortex and the medulla. Fluorescence also highlighted cortical reticular cells but not the thymocytes. Intravenously injected Trypan blue stained the capsule, the septa, the cortical reticular cells, and the autofluorescent cells outlining the corticomedullary junction of each lobule. The unusual penetration of capillaries from the thymic parenchyma into the thymic capsule suggested that the capsular capillaries participate in peculiar thymic events, such as the recruitment of blood stem-cells. It is concluded that small amounts of blood antigens normally exude from capsular capillaries and diffuse into the fibers extending from the capsule across the cortex. The phenomenon would be increased under conditions causing thymic involution. An explanation is proposed to account for the development of involution which involves the exudation of antigens from the capsular capillaries. A comparable mechanism could also account for the development of a particular experimental immune tolerance.     

Stages of the rat thymic medulla development in foetal period

Development of thymic medulla was examined on consecutive gestational days (GD) in Wistar rats. Medullary thymic epithelial cells (TEC) were identified by immunocytochemical localisation of neuron-specific enolase (NSE). Organisation of thymic medullary architecture was determined by interaction of thymocytes with NSE-positive TEC, that led to formation of lymphoepithelial complexes (GD 19), in which the cells exhibited proliferative activity or traits of apoptosis. The studies indicated that differentiation events and organisation of thymic medulla require stage-specific interactions between TEC and thymocytes.     

Histogenesis of the rat thymic medulla during first stages of development

We investigated first stages of thymic medulla organisation in foetuses of Wistar strain rats. between 13th and 17th days of foetal life (GD). Medullary cells were identified by immunocytochemical localisation of neuron-specific enolase (NSE) as well as by traits of ultrastructure. The first thymic medullary precursor cells which were reactive for NSE were at first spread all over the thymic primordium. In the period of thymus colonisation by lymphoid cells, the following stages were distinguished in medulla organisation: (1) migration of NSE+ cells to the central portion of the thymus (GD 14-15), (2) small medullary epithelial patches, distributed within the thymus (GD 16), and (3) expansion of medullary patches into medullary compartment (GD 17). At the second and third stages of the medulla organisation, an increase in the number of NSE+ cells, followed by differentiation of their ultrastructure and increase in their biological activity were observed. We conclude that formation of medullary architectural pattern is controlled by interactions between maturing epithelial cells and developing lymphoid cells and by angiogenesis in the region.     

Kinetics of thymic stroma development in the foetal period

The kinetics of thymic epithelial cell development was examined in Wistar strain rats between 13th and 21st days of foetal life. The studies were based on immunocytochemical localisation of cytokeratin 16 (CK 16), Ki67 and on ultrastructural observations of thymus development. Expression of CK16 in individual groups was evaluated using the Micro Image v.4.0 software. In order to monitor changes in CK16 expression in individual days of foetal life, their results were subjected to statistical analysis, demonstrating: (1) correlation between CK16 expression and duration of foetal life, (2) most pronounced CK16 expression on the 16th day of foetal life, (3) typical localisation of CK16-positive cells in individual days of foetal life. The morphological observations suggest that individual subpopulations of epithelial cells differ in their kinetics of proliferative activity.     

Effect of chronic ethanol consumption on postnatal development of renal (Na + K)-ATPase in the rat.

Renal (Na + K)-ATPase was studied to ascertain whether it follows the pattern of adaptation of membrane-bound enzymes that are inhibited by acute ethanol exposure and develop greater activity after chronic ethanol treatment. A colony of rats was given 20 per cent (v/v) ethanol as sole drinking solution throughout gestation, lactation and following weaning. (Na + K)-ATPase and ouabain-insensitive Ca(2+)-ATPase activities were determined; regional distribution of these enzymes was assessed in renal cortex and outer medulla. Control rats drank tap water. (Na + K)-ATPase in whole homogenate of kidney increased with age in controls and ethanol-fed rats, but the latter showed higher values at every age studied. Between 15 and 60 days of age, the control group showed 2-fold increases in cortex and 5-fold in outer medulla, whereas ethanol-fed rats reached a 3-fold increase in the enzyme activity in both renal regions. Ca(2+)-ATPase showed the same time course in developing kidney of both groups. Chronic ethanol treatment of adult rats resulted in an increase of (Na + K)-ATPase activity in cortex and outer medulla, but no change in other ATPases. Since an earlier maturational development of renal (Na + K)-ATPase was displayed by ethanol-fed rats, underlying mechanisms that may account for these results are discussed.     

Thymic epithelial requirement for γδ T cell development revealed in the cell ablation transgenic system with TSCOT promoter

In order to investigate the role of thymic epithelial cell (TEC) subsets during T-cell development, we established a new transgenic system, enabling inducible cell-specific ablation as well as marking the TEC subsets using bicistronic bacterial nitroreductase and EGFP genes. Two different lengths of the TSCOT promoter in transgenic mice, named 3.1T-NE and 9.1T-NE, drive EGFP expression into TECs. In adult life, EGFP expression was located in the medulla with a smaller 3.1 kb TSCOT promoter, while it was maintained in the cortex with a 9.1 kb promoter, suggesting putative TEC specific as well as compartment specific cis elements within two promoters. Nitroreductase induced cell death was specific without bystander killing upon the treatment of prodrugs such as nitrofurantoin and metronidazol. The degree of cell death was dependent on the dose of the prodrug in the cell and the fetal thymic organ cultures (FTOCs). Fetal thymic stromal populations were analyzed based on the expression levels of EpCAM, MHCII, CDR1 and/or UEA-1. EGFP expression patterns varied among subsets indicating the differential TSCOT promoter activity in each TEC subset. Prodrug treatment in FTOCs reduced the numbers of total and subsets of thymocytes. A CD4⁺CD8⁺ double positive cell population was highly susceptible in both transgenic lines. Surprisingly, there was a distinct reduction in γδ T cell population only in the 9.1T-NE thymus, indicating that they require a NTREGFP expressing TEC population. Therefore, these results support a division of labor within TEC subsets for the αβ and γδ lineage specification.     

Na+--K+-adenosine triphosphatase and some oxidoreductases in the kidney of rats with spontaneous hypertension]

The activities of the Na+--K+-ATPase, succinic dehydrogenase (SDH/, lactic dehydrogenase (LDH/ and glucose-6-phosphat dehydrogenase (G-6-PDH/ were studied in the cortex outer and inner medulla of the kidneys of rats with spontaneous hypertension (SHR) and were compared with those of control normotensive Wistar rats. The SHR aged 6--8 weeks had durint the prehypertensive and the early hypertensive stage the same enzymatic activities as control rats. Rats with a steady SH aged 16-22 weeks had low specific activity of the, Na+--K+-ATPase, SDH and LDH in the outer medulla. The latter can be associated with decreased intensity of the energy metabolism and a reduction of the active sodium transport in the ascending limb of the loop of Henle in the SHR rats and cold cause the phenomenon of exaggerated natriuresis characteristic of hypertension.     

Ovipositor ultrastructure of the striped bitterling Acheilognathus yamatsutae (Teleostei: Acheilognathinae) during spawning season

The ovipositor of striped bitterling Acheilognathus yamatsutae was subjected to ultrastructure and histochemical analysis during spawning season using light and electron microscopy. Although the ovipositor of A. yamatsutae is a long cylindrical tube with smooth external surface, it was possible to confirm the presence of well-developed fingerprint structure using scanning electron microscopy. Internal aspect analysis of ovipositor revealed formation of 5–8 longitudinal folds. Cross section analysis revealed that the ovipositor is composed of an outer epithelial layer, a mid connective tissue layer, and an inner epithelial layer. The outer epithelial layer contains 7–9 cell layers composed mainly of epithelial and mucous cells. Result of AB–PAS (pH 2.5) and AF–AB reaction showed that mucous cells contained mainly acidic carboxylated mucosubstances. The connective tissue layer was loose and made mainly of collagen fibers and some muscle fibers, along with blood vessels and a small number of chromatophores. The inner epithelial layer, which is a single layer, is composed of columnar epithelia. Observation under transmission electron microscope enabled distinction of the outer epithelial layer into superficial, intermediate and basal layers. Although the types of cells in the superficial tissue layer were diverse, they all shared the development of glycocalyx covered microridges. The majority of epithelial cells in the intermediate layer were cuboidal shaped, while those in the basal layer were columnar. Two types (A and B) of secretory cells were observed in the outer epithelial layer. The connective tissue layer had two types of chromatophores including xantophore and melanophore, in addition to a well-developed nerve fiber bundles. Columnar epithelial cells, mitochondria-rich cells and rodlet cells were observed in the inner epithelial layer. Microvilli were well developed on the free surface of columnar epithelial cells.     

斜带石斑鱼胸腺的显微和超微结构

本文通过解剖及组织切片技术、光学显微镜、透射和扫描电子显微镜技术,对斜带石斑鱼(Epinephelus coioides)胸腺器官组织进行了观察研究。结果表明:斜带石斑鱼胸腺实质主要由胸腺细胞(淋巴细胞)和网状上皮细胞构成。鱼体从Ⅰ龄之后,其胸腺发生明显的变化,与幼鱼有所不同,主要是胸腺可明显区分为三个区域:胸腺外皮质区、内皮质区和髓质区。外皮质区主要由网状上皮细胞、黏液细胞、成纤维细胞和少量淋巴细胞构成,细胞排列疏松;内皮质区主要由密集的淋巴细胞和网状上皮细胞组成,以含有大量的淋巴细胞为特征;髓质区主要由淋巴细胞和较多的网状上皮细胞构成,总体特征是淋巴细胞数量比内皮质区的少,且细胞排列较疏松。外皮质区、内皮质区相当于高等脊椎动物的皮质;髓质区相当于高等脊椎动物的髓质。髓质区之下有结缔组织,在Ⅱ龄以上的成体出现胸腺小体(Hassall's corpuscles)或类似胸腺小体的结构,而且随着年龄的增加,胸腺外皮质区增厚,结缔组织增加,还表现在内皮质区和髓质区组织逐渐萎缩变薄,胸腺的细胞组成类型和淋巴细胞数量上有所变化等等。这些现象在Ⅱ龄鱼开始出现,即胸腺呈现退化迹象,在Ⅲ龄以上鱼体呈现明显的退化和萎缩。胸腺表面扫描电镜结果表明:其上皮细胞表面具有微嵴以及由微嵴组成的指纹状结构,有一些微孔分布。透射和断面扫描电镜的结果进一步表明:胸腺组织内的细胞成分复杂,除了淋巴细胞和网状上皮细胞外,还具有巨噬细胞、肥大细胞、肌样细胞、浆细胞、指状镶嵌细胞和纤维细胞等。     

Ultrastructural localization of Na+,K+-ATPase in rat and rabbit kidney medulla

Na+,K+-ATPase was localized at the ultrastructural level in rat and rabbit kidney medulla. The cytochemical method for the K+-dependent phosphatase component of the enzyme, using p-nitrophenylphosphate (NPP) as substrate, was employed to demonstrate the distribution of Na+, K+- ATPase in tissue-chopped sections from kidneys perfusion-fixed with 1% paraformaldehyde-0.25% glutaraldehyde. In other outer medulla of rat kidney, ascending thick limbs (MATL) were sites of intense K+-dependent NPPase (K+-NPPase) activity, whereas descending thick limbs and collecting tubules were barely reactive. Although descending thin limbs (DTL) of short loop nephrons were unstained, DTL from long loop nephrons in outer medulla were sites of moderate K+-NPPase activity. In rat inner medulla, DTL and ascending thin limbs (ATL) were unreactive for K+-NPPase. In rabbit medulla, only MATL were sites of significant K+-NPPase activity. The specificity of the cytochemical localization of Na+,K+-ATPase at reactive sites in rat and rabbit kidney medulla was demonstrated by K+-dependence of reaction product deposition, localization of reaction product (precipitated phosphate hydrolyzed from NPP) to the cytoplasmic side of basolateral plasma membranes, insensitivity of the reaction to inhibitors of nonspecific alkaline phosphatase, and, in the glycoside-sensitive rabbit kidney, substantial inhibition of staining by ouabain. The observed pattern of distribution of the sodium transport enzyme in kidney medulla is particularly relevant to current models for urine concentration. The presence of substantial Na+,K+-ATPase in MATL is consistent with the putative role of this segment as the driving force for the countercurrent multiplication system in the outer medulla. The absence of significant activity in inner medullary ATL and DTL, however, implies that interstitial solute accumulation in this region probably occurs by passive processes. The localization of significant Na+,K+-ATPase in outer medullary DTL of long loop nephrons in the rat suggests that solute addition in this segment may occur in part by an active salt secretory mechanism that could ultimately contribute to the generation of inner medullary interstitial hypertonicity and urine concentration.     

ELECTRON MICROSCOPY OF PHIALIDES AND CONIDIOGENESIS IN TRICHODERMA SATURNISPORUM

Each phialide had a thick-walled neck region located immediately below a light microscopically inconspicuous collarette. The thickened wall of the phialide neck was multilaminate, with layers of different electron transmission properties. A developmental stage in the formation of the first conidial initial was observed. Conidial initials blew out through the thickened neck region, increased in size, and were eventually delimited by centripetally developing septa. Mature, winged conidia had an electron-opaque outer wall layer and an electron-transparent inner wall layer. The wing was formed by separation of these outer and inner wall layers and buckling or wrinkling of the outer layer. As early as they could be discerned, conidial initials had developed the electron-opaque wall layer which characterized mature conidia. Each conidium-delimiting septum became bilayered; the upper layer formed part of the conidial base, and the lower layer became a portion of the wall of the next conidial initial. Phialides lacked an electron-opaque wall layer, and they possessed areas of abundant rough endoplasmic reticulum, as well as free ribosomes. Lipid globules were also abundant, especially in conidia. The distinction between phialides and annellides was questioned.     

Identification of Novel Thymic Epithelial Cell Subsets Whose Differentiation Is Regulated by RANKL and Traf6

Thymic epithelial cells (TECs) are critical for the normal development and function of the thymus. Here, we examined the developmental stages of TECs using quantitative assessment of the cortical and medullary markers Keratin 5 and Keratin 8 (K5 and K8) respectively, in normal and gain/loss of function mutant animals. Gain of function mice overexpressed RANKL in T cells, whereas loss of function animals lacked expression of Traf6 in TECs (Traf6ΔTEC). Assessment of K5 and K8 expression in conjunction with other TEC markers in wild type mice identified novel cortical and medullary TEC populations, expressing different combinations of these markers. RANKL overexpression led to expansion of all medullary TECs (mTECs) and enlargement of the thymic medulla. This in turn associated with a block in thymocyte development and loss of CD4⁺CD8⁺, CD4⁺ and CD8⁺ thymocytes. In contrast, Traf6 deletion inhibited the production of most TEC populations including cortical TECs (cTECs), defined by absence of UEA-1 binding and LY51 expression, but had no apparent effect on thymocyte development. These results reveal a large degree of heterogeneity within the TEC compartment and the existence of several populations exhibiting concomitant expression of cortical, medullary and epithelial markers and whose production is regulated by RANKL and Traf6.     

ELECTRON MICROSCOPY OF PHIALOCONIDIOGENESIS IN METARRHIZIUM ANISOPLIAE

Fine-structure observations with two different fixation procedures showed that phialide necks possessed a thickened electron-transparent wall layer. Phialoconidia developed from a wall layer which originated 1–1.5 μm within phialide necks. After conidium initials blew out of phialide tips and organelles entered, conidia were delimited by transverse septa which did not appear to be plugged by Woronin body-like plugs. Instead, septa appeared to become functionally complete by continued centripetal growth. Conidium-delimiting septa moved distally out of phialide necks as subsequent conidium initials formed. During this distal movement, septa increased in thickness and lamellae appeared on the conidium side; mature conidia had bipolarly lamellate cell walls. Conidial walls had a thin, ridged electron-dense outer wall layer and a thicker electron-transparent inner wall layer which increased in thickness centripetally after septum delimitation. Conidia were usually uninucleate and possessed conspicuous storage vacuoles with lipid and protein contents. Conidia also possessed numerous presumably lipid droplets. Multivesicular bodies were observed near conidium-delimiting septa and conidium walls which were increasing in thickness.     

Distribution and colocalization of nitric oxide synthase and NADPH-diaphorase in adrenal gland of developing,adult and aging Sprague-Dawley rats

The distribution and colocalization of nitric oxide synthase and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-diaphorase) was investigated in the adrenal gland of developing, adult and aging rats with the use of immunohistochemical and histochemical techniques. Nitric oxide synthase-immunoreactive neurons within the adrenal gland were found from the 20th day of gestation onwards. During early development the neurons were found as small clusters of smaller-size cells compared to those observed in the adult gland. Their number reached that of adult level by the 4th day after birth, and in the glands from aging rats a 28.6% increase was observed. Whilst no immunofluorescence was seen in chromaffin cells during early development, some cells from glands of aging rats showed nitric oxide synthase-immunoreactivity with varying intensity. The immunoreactive neurons from postnatal rat adrenals were also positive for NADPH-diaphorase, whilst those in prenatal rats were negative or lightly stained. Nitric oxide synthase-immunoreactive nerve fibres were present in all adrenal glands examined from the 16th day of gestation onwards. A considerable degree of variation in the distribution of immunoreactive fibres both in medulla and outer region of cortex at the different age groups was observed and described. Most, but not all, nitric oxide synthase-immunoreactive nerve fibres also showed NADPH-diaphorase staining.     

Renal medullary nitric oxide deficit of Dahl S rats enhances hypertensive actions of angiotensin II

Studies were designed to examine the hypothesis that the renal medulla of Dahl salt-sensitive (Dahl S) rats has a reduced capacity to generate nitric oxide (NO), which diminishes the ability to buffer against the chronic hypertensive effects of small elevations of circulating ANG II. NO synthase (NOS) activity in the outer medulla of Dahl S rats (arginine-citrulline conversion assay) was significantly reduced. This decrease in NOS activity was associated with the downregulation of protein expression of NOS I, NOS II, and NOS III isoforms in this region as determined by Western blot analysis. In anesthetized Dahl S rats, we observed that a low subpressor intravenous infusion of ANG II (5 ng. kg(-1). min(-1)) did not increase the concentration of NO in the renal medulla as measured by a microdialysis with oxyhemoglobin trapping technique. In contrast, ANG II produced a 38% increase in the concentration of NO (87 +/- 8 to 117 +/- 8 nmol/l) in the outer medulla of Brown-Norway (BN) rats. The same intravenous dose of ANG II reduced renal medullary blood flow as determined by laser-Doppler flowmetry in Dahl S, but not in BN rats. A 7-day intravenous ANG II infusion at a dose of 3 ng. kg(-1). min(-1) did not change mean arterial pressure (MAP) in the BN rats but increased MAP in Dahl S rats from 120 +/- 2 to 138 +/- 2 mmHg (P < 0.05). ANG II failed to increase MAP after NO substrate was provided by infusion of L-arginine (300 microg. kg(-1). min(-1)) into the renal medulla of Dahl S rats. Intravenous infusion of L-arginine at the same dose had no effect on the ANG II-induced hypertension. These results indicate that an impaired NO counterregulatory system in the outer medulla of Dahl S rats makes them more susceptible to the hypertensive actions of small elevations of ANG II.     

Histochemical characterization of silver-induced metallothionein in rat kidney

Histochemical characterizations of Ag-induced metallothionein (MT) in the kidney of the rat have been reported. Ag, Cu and Zn contents increased in kidney and liver after Ag injection. In particular, the Cu content in kidneys increased dramatically after three injections of Ag. Sephadex G-75 elution profiles of the renal cytosol of rats injected with Ag revealed that the accumulated Cu in the kidney was bound to MT as were Ag and Zn. In addition, localization of Cu- and Ag-MT in the kidney was studied using autofluorescent signals, which are dependent on Cu- or Ag-thiol clusters, and immunohistochemistry. Although the MT induced by Ag was predominantly observed in the cortex of the kidney, some MT signals were also detected in the outer stripe of the outer medulla, as well as in the kidneys of LEC rats, an animal model of Wilson disease (a hereditary disorder of Cu metabolism). In these LEC rats, the Cu-MT also accumulated in the outer stripe of the outer medulla of the kidney. From these results, one possibility could explain that the Cu-MT detected in the outer stripe of the outer medulla in the kidney of Ag-injected rat was associated with the Cu transporter affected by Ag.     

A contribution to knowledge of the compartments and the fascial and septal formations of the popliteal fossa in the human fetus and the adult.

A contribution to knowledge of the compartments and the fascial and septal formations of the popliteal fossa in the human fetus and the adult. A study was made in human fetuses from the 3rd month onwards, newborn and the adult of the fascial and septal formations and the compartments of the popliteal fossa. Observations of serial sections of the knee of human fetuses, of macroscopic preparations of the knee of newborns and of ultrasound images of the popliteal fossa in adults showed that: the fascial formation covering the popliteal fossa consists of the popliteal fascia and the superficial fascia. The bud of the popliteal fascia is observable in the 3-month fetus as a layer of thin fibrillar connective tissue which is thicker in the tracts between the muscle buds. At birth the popliteal fascia is clearly a separate anatomical entity of continuous laminar structure which is thicker in the tracts between the muscles and thinner where it covers them. The superficial fascia becomes evident in fetuses at a later stage (6th month) in the form of a thin lamina in the frontal plane which at birth is well defined and observable as a thin continuous line deep below the subcutaneous layer. The septal formation consists of four septa: two in the sagittal plane (lateral and medial) and two in the frontal plane (lateral and medial). The bud of these septa appears in 4-month fetuses after the appearance of the popliteal fascia. They branch off from the thicker connective areas between the muscles buds as connective prolongations which later assume a laminar aspect and eventually become compact and form septa. In at-term fetuses and newborns these septal formations are clearly recognizable as antomical entities, which branch off from the deep surface of the thicker tracts of the popliteal fascia and are inserted into the femur. The relationships and connections with the muscular groups are also clearly visible. The organization and demarcation of the compartments, which is already delineated in the 6-month fetus, seems to be completed at birth, considering the presence of the superficial fascia, the popliteal fascia and the septa. It is possible to distinguish a superficial compartment between the popliteal and the superficial fascia an a deep compartment between the frontal septa, the skeletal plane and the popliteal fascia. This deep compartment is clearly subdivided by the two sagittal septa into three sectors (medial, intermediate and lateral). The medial and lateral sectors contain muscles, while the intermediate compartment contains the vasculonervous bundle and the popliteal adipose body.     

Intrinsic organization of the medial cerebral cortex of the lizard Lacerta pityusensis: A golgi study

The morphology of cells and the organization of axons were studied in Golgi-Colonnier and toluidine blue stained preparations from the medial cerebral cortex of the lizard Lacerta pityusensis. In the medial cortex, six strata were distinguished between the superficial glial membrane and the ependyma. Strata I and II formed the outer plexiform layer, stratum III formed the cellular layer, and strata IV go VI the inner plexiform layer. The outer plexiform layer contained smooth bipolar neurons; their dendrites were oriented anteroposteriorly and their axons were directed towards the posterior zone of the brain. Five neuronal types were observed in the cellular layer. The spinous pyramidal neurons had well-developed apical dendrites and poorly developed basal ones. Their axons entered the inner plexiform layer and gave off collaterals oriented anteroposteriorly. The small, sparsely spinous pyramidal neurons had poorly developed dendrites and their axons entered the inner plexiform layer. The spinous bitufted neurons had well-developed apical and basal dendritic tufts. Their axons gave off collaterals that reached the outer and inner plexiform layers of both the dorsomedial and dorsal cortices. The sparsely spinous horizontal neurons had dendrites restricted to the outer plexiform layer. Their axons entered the inner plexiform layer. The sparsely spinous, multipolar neurons had their soma close to stratum IV and their axons entered the outer plexiform layer. In stratum V of the inner plexiform layer were large, spiny polymorphic neurons; they had dendrites with long spines, and their axons reached the cellular layer. On the basis of these results, we have subdivided the medial cortex into two subregions: the superficial region, which contains the neurons of the cellular layer and their dendritic domains, and the deep region, strata V and VI, which contains the large, spiny polymorphic neurons. The neurons in the medial cortex of these lizards resembles those in the area dentata of mammals. On this basis, the superficial region may be compared to the dentate gyrus and the deep region to the hilar region of the hippocampus of mammals.