Protein gene product 9.5-immunoreactive nerve fibres and cells in human skin

Summary Sections of human skin were processed according to the indirect immunofluorescence technique with a rabbit antiserum against human protein gene product 9.5 (PGP 9.5). Immunoreactivity was detected in intraepidermal and dermal nerve fibres and cells. The intraepidermal nerves were varicose or smooth with different diameters, running as single processes or branched, straight or bent, projecting in various directions and terminating in the stratum basale, spinosum or granulosum. The density of the intraepidermal nerves varied between the different skin areas investigated. PGP 9.5-containing axons of the lower dermis were found in large bundles. They separated into smaller axon bundles within the upper dermis, entering this portion of the skin perpendicular to the surface. Then they branched into fibres mainly arranged parallel to the epidermal-dermal junctional zone. However, the fibres en route to the epidermis traversed the upper dermis more or less perpendicularly. Furthermore, immunoreactive dermal nerve fibres were found in the Meissner corpuscles, the arrector pili muscles, hair follicles, around the eccrine and apocrine sweat glands and around certain blood vessels. Such fibres were also observed around most subcutaneous blood vessels, sometimes heavily innervating these structures. Numerous weakly-to-strongly PGP 9.5-immunoreactive cells were found both in the epidermis and in the dermis.     

细胞外钠离子浓度对羊浦肯野纤维膜钠泵活动的影响

采用离子选择电极测量羊浦肯野纤维细胞膜内钠离子活度(~(ai)N_a),细胞间钾离子活度(a~ok)及细胞膜电位(v_m),观察不同浓度低钠,无钙液对其影响,在无钙低钠液中,细胞内Na~+逐出,α~iNa 降低,其变化速率,幅值与[Na]_o 相关,同时也受细胞 a~iNa 初始水平(aiNa(o))的影响。aiNa 下降6min 时的稳态水平与[Na]_o 呈直线正相关,这些结果表明,[Na]_o 降低时,细胞膜钠泵活动加强,细胞内 Na~+逐出增加,其最终结果是使 Na+跨膜梯度维持相对稳定,因而可以认为是 Na~+跨膜梯度而不是单纯的细胞内 Na~+控制膜钠泵活动。在低 Na~+液引起细胞内 Na~+主动逐出增加的同时,细胞膜出现超极化,[Na]_o 愈低,膜超极化程度愈高,从低钠液引起的 a~i_(Na),V_m,α~o_k 变化之间的时程关系看,膜超极化主要由加大的外向泵电流引起,同时发生的细胞间 K~+浓度变化对其也有一定影响。     

Identification of separate vasopressin-neurophysin II and oxytocin-neurophysin I containing nerve fibres in the external region of the bovine median eminence

Summary Immuno-enzyme histochemical investigations showed the presence, in the external region of the bovine median eminence, of accumulations of vasopressin-neurophysin II-and oxytocin-neurophysin I-complexes. These two hormone-neurophysin complexes are located in separate fine varicose nerve fibres. The results strongly plead against an important role of tanycytes in the transport of vasopressin, oxytocin and neurophysins from the cerebrospinal fluid to the hypophysial portal blood-vessels.This work was supported by a grant from the Belgian Nationaal Fonds voor Geneeskundig Wetenschappelijk Onderzoek.     

The transverse tubular system of cat intrafusal muscle fibres

Summary A modified staining technique for transverse tubular and sarcoplasmic reticular systems was used to investigate their occurrence in different types of intrafusal muscle fibres in cat tail spindles. Intrafusal muscle fibres can be divided into three basic regions, namely, the periaxial space (A-region), intracapsular area (B-region) and the extracapsular area (C-region); the components of these systems were seen to vary in structure and distribution. The occurrence of these systems also varied among the different types of intrafusal muscle fibres, namely, the bag₁, bag₂ and chain fibres. In bag₁ fibres components were sparse in the A-region, increased slightly in the B-region, but were most developed in the C-region; triads were consistently located at the border between A- and I-bands. In bag₂ fibres membrane components were noted in the A-region but were more abundant in the B-region where some tubular components showed transverse and longitudinal branches linked together in the form of a network; membrane systems diminished towards the C-region. The majority of triads were located within the A-bands. In chain fibres the membrane systems occurred more commonly in the A-region, while in the B- and C-regions, the transverse tubular system possessed numerous transverse and longitudinal branches forming irregularly distributed tubular networks. Some tubular branches were dilated, while other branches terminated as sacs among arrays of the sarcoplasmic reticular system in I-bands. Some transverse tubules bifurcated into two branches with numbers of dilated sarcoplasmic reticular cisternae lying on either side, or between, the branches. Triads sometimes occurred between A- and I-bands, but, generally, were situated well within A-bands.     

Scanning electron microscopy of isolated peripheral nerve fibres

Summary The surface morphology of normal myelinated nerve fibres prepared in different ways for scanning electron microscopy has been studied and compared with the surface features of similar fibres undergoing retrograde changes. Nodes of Ranvier, paranodal specializations, artefactual fractures of the myelin, and the endoneurial collagen sheaths are described. A regular pattern of elevations, usually with a pitted or depressed surface seen on normal myelinated fibres after certain preparative procedures are thought to be artefacts produced during preparation and to be related to the neurokeratin network.Alterations in the surface structure of fibres central to long-standing nerve transections include irregular protuberances, serial surface corrugations and large swellings, all associated with demyelination. Fibres that have undergone retrograde degeneration consist of endoneurial tubes with focal swellings occupied by macrophages or myelin debris, together with fine unmyelinated and small myelinated regenerating axons. Strict centrifugal progression of myelination of regenerating axons was not observed.We thank Mr. R. A. Willis for his collaboration and for taking the SEM photographs of normal nerve fibres, and the Cambridge Scientific Instrument Co. Ltd. for permission to reproduce the SEM photographs of experimental nerve fibres. We also thank Dr. A. Boyde for access to his SEM and for helpful comments on interpretation of the scanning electron micrographs, Prof. J. Z. Young, Dr. P. K. Thomas, and Dr. R. H. M. King for discussion, and Messrs. P. Reynolds and D. Gunn for photography.A grant from the Muscular Dystrophy Group of Great Britain is gratefully acknowledged.     

鸡的缝匠肌中的慢肌纤维在切断神经后所发生肥大的长期性和内部结构的观察

鸡的缝匠肌是含有Ⅰ型(慢)纤维和Ⅱ型(快)纤维的混合肌,在该肌的神经被切断并阻止其再生后1、4与6个月进行观察。冰冻切片结合肌原纤维三磷酸腺苷酶(m-ATP-ase)的染色法显示慢肌纤维发生成倍的肥大。在去神经6个月后快、慢纤维仍然因酸或碱性预处理而呈现染色的反转。在电镜下观察,去神经后发生肥大的慢纤维仍然呈现微丝的正常排列。清楚的A、Ⅰ带与 H 带。它的 Z 线清楚但在有些纤维中的有些很短的段落变得模糊或分裂,在去神经6个月的肌肉,有些慢纤维仅局部结构模糊但绝大部分地区呈现结构完好,这说明这种鸟类的混合肌的慢纤维在去神经后结构上仍有很大的稳定性。以上观察也说明这种去神经肥大的现象除了在发生原因上值得注意以外,它在肥大的程度与持久性上和其他的实验性肌肉肥大相比也是很显著的。     

Collagen's role in the cortical bone's behaviour: a numerical approach

Literature devoted to experimental measurements of the elastic properties of the human cortical bone gives us a relatively wide spectrum of values. This proves that the result depends on the bone itself and on the area from where the sample has been taken. Ultrasonic measurement, which is a fine technology, points out complex maps. The reason of this very strong heterogeneity is not completely explained. The present study is based on a numerical model of the human cortical bone, the SiNuPrOs model and aims to suggest an explanation. If one admits that mineral apposition occurs around collagen fibres, the spatial orientation of these fibres would have an important consequence on the elastic properties of the medium. On the basis of homogenisation theory allowing to compute all the components of the elasticity tensor, this study quantifies the main influence of this architectural orientation and its effect on the anisotropy of the cortical bone.     

A synchrotron radiation X-ray diffraction study of the crystallinity of tendon fibres

The equatorial diffraction pattern of tendon collagen fibres was measured during short successive exposures at different lengths using a double focusing X-ray synchrotron radiation camera with film and with an area detector. Similarly, patterns from thin fibres from premature rats were recorded. The patterns unambiguously illustrate the relationship between fibre crystallinity and the age of the animal. Further, the results indicate that in the initial part of the linear region of the stiffness-versus-length curve, the collagen fibres are characterized by a quasihexagonal arrangement of collagen molecules, whereas at the end of this region, the molecular arrangement becomes hexagonal.     

Key signalling factors and pathways in the molecular determination of skeletal muscle phenotype

The molecular basis and control of the biochemical and biophysical properties of skeletal muscle, regarded as muscle phenotype, are examined in terms of fibre number, fibre size and fibre types. A host of external factors or stimuli, such as ligand binding and contractile activity, are transduced in muscle into signalling pathways that lead to protein modifications and changes in gene expression which ultimately result in the establishment of the specified phenotype. In skeletal muscle, the key signalling cascades include the Ras-extracellular signal regulated kinase-mitogen activated protein kinase (Erk-MAPK), the phosphatidylinositol 3'-kinase (PI3K)-Akt1, p38 MAPK, and calcineurin pathways. The molecular effects of external factors on these pathways revealed complex interactions and functional overlap. A major challenge in the manipulation of muscle of farm animals lies in the identification of regulatory and target genes that could effect defined and desirable changes in muscle quality and quantity. To this end, recent advances in functional genomics that involve the use of micro-array technology and proteomics are increasingly breaking new ground in furthering our understanding of the molecular determinants of muscle phenotype.