神经退变和再生的构筑变化

将夹伤的大鼠坐骨神经分离成单根纤维,观察98d内轴突和许旺细胞的构筑变化过程发现,损伤既使轴浆转运阻断、积累的细胞器退变,也使髓鞘板层,特别是斯兰氏切迹撕裂、变形或侵入轴突。轴突或髓鞘虽可各呈单一的退变,但以两者并存多见。伤后1d即出现富含微管的再生芽,它被增殖的许旺细胞突起及其基底膜包绕,并逐步发育成熟。根据再生的特征性构筑变化,提出了再生芽、无髓和有髓纤维、斯兰氏切迹、朗氏结与神经小束的初见、发育和成熟高峰期的时间顺序。无髓纤维的发育成熟早于有髓纤维。     

FINE STRUCTURAL LOCALIZATION OF ADENOSINETRIPHOSPHATASE ACTIVITY IN HEART MUSCLE MYOFIBRILS

Activity of myofibrillar adenosinetriphosphatase was demonstrated histochemically at a fine structural level in isolated, unfixed or hydroxyadipaldehyde-fixed cardiac myofibrils in the rat, using a lead precipitation technique and either Ca⁺⁺ or Mg⁺⁺ as activating ion. Activity in relaxed myofibrils was found in the A band, but not the H, I, or Z bands. Deposits of final product frequently exhibited an axial periodicity of near 365 A, and bore a close relationship to filaments within the A band. Several patterns of distribution occurred in contracted myofibrils. In myofibrils which had shortened to the point of disappearance of the I band, final product was distributed throughout the sarcomere, except for the unreactive Z band. A second type of distribution occurred in strongly contracted fibers in which there was intensification of activity in the center of the sarcomere. These findings are discussed in the light of the recent morphological evidence and it is suggested that the distribution of final product is consistent with localization of enzyme activity to the cross-bridges between the thick and thin filaments.     

A FINE STRUCTURE STUDY OF LIPID IN MOUSE LIVER REGENERATING AFTER PARTIAL HEPATECTOMY

The fine structure of liver 3½ to 72 hours after partial hepatectomy has been compared with that of liver from sham-operated animals; all animals were 60- to 90-day old male mice of the C3H strain. Numerous small bodies with diameters ranging from 300 to 1,000 A have been observed distributed randomly throughout the cytoplasm of the hepatic parenchymal cells at early intervals after partial hepatectomy. In material fixed in osmium tetroxide and embedded in methacrylate, they appear as uniformly electron-opaque bodies, but in permanganate-fixed liver, they display only a peripheral rim of electron-opaque material surrounding a clear core. Each of these cytoplasmic bodies appears to be located within a vesicle. A few of the opaque bodies are also present in sinusoids and in the spaces of Disse; these bodies are not located within vesicular structures. Fat droplets of various sizes are easily distinguished in regenerating liver; with the increase in number of these fat droplets at later postoperative intervals, there occurs a concomitant decrease in the number of cytoplasmic bodies. It is suggested that the cytoplasmic bodies contain some lipid component. Possible explanations of the origin, nature, and fate of the cytoplasmic bodies are discussed.     

SOME PROPERTIES OF A MAJOR STRUCTURAL GLYCOPROTEIN OF SCIATIC NERVE

The major protein of rat sciatic nerve is a glycoprotein which consists of a protein moiety attached to galactose, mannose and perhaps other sugars. On controlled tryptic digestion, it splits into a glycopeptide and a smaller fragment similar in molecular size to peripheral nerve basic proteins. Both the basic proteins of peripheral nervous system (PNS) myelin and the glycoprotein are antigenically active when administered to guinea pigs and produce sciatic nerve lesions similar to those described for experimental allergic neuritis. It is suggested from the amino acid analysis and its antigenic properties that the protein moiety of the glycoprotein may contain a sequence which is similar to the basic proteins of PNS myelin.     

THE FINE STRUCTURAL LOCALIZATION OF ENDOGENOUS AND EXOGENOUS PEROXIDASE ACTIVITY IN KUPFFER CELLS OF RAT LIVER

Endogenous peroxidase activity has been demonstrated in sections of rat liver fixed briefly by glutaraldehyde perfusion and incubated in Graham and Karnovsky's medium for cytochemical demonstration of peroxidase activity (29). In 25–40% of sinusoidal cells, an electron-opaque reaction product is localized in segments of the endoplasmic reticulum, including the perinuclear cisternae, a few Golgi vesicles and saccules and in some large membrane-bounded granules. This staining is abolished after prolonged fixation or boiling of tissue sections in glutaraldehyde, and in the absence of H₂O₂ or DAB from the incubation medium. Furthermore, the reaction is inhibited completely by sodium azide and high concentrations of H₂O₂, and partially by KCN and aminotriazole. Among the different cells in hepatic sinusoids, the nonphagocytic "fat-storing" cells (39) are always peroxidase negative, whereas the lining cells in process of erythrophagocytosis are consistently peroxidase positive. The possible biological significance of endogenous peroxidase in Kupffer cells is discussed. In addition, the uptake of exogenous horseradish peroxidase by Kupffer cells has been investigated. The exogenous tracer protein, which in contrast to endogenous peroxidase of Kupffer cells is not inhibited by prolonged aldehyde fixation, is taken up by micropinocytosis and remains confined to the lysosomal system of Kupffer cells. The significance of these observations in respect to some recent studies suggesting localization of exogenous peroxidases in the endoplasmic reticulum of Kupffer cells and peritoneal macrophages (22, 23) is briefly discussed.     

A FINE STRUCTURAL ANALYSIS OF INTERCELLULAR JUNCTIONS IN THE MOUSE LIVER

Zonulae occludentes and gap junctions were examined both in the intact mouse liver and in a junction-rich membrane fraction from homogenized mouse liver. These preparations were visualized with the techniques of uranyl acetate staining en bloc, staining with colloidal lanthanum, negative staining with phosphotungstate, and freeze-cleaving. The zonula occludens is arranged as a meshwork of branching and anastomosing threadlike contacts sealing the lumen of the bile canaliculus from the liver intercellular space. The gap junction is characterized in section by a 20 A gap between the apposed junctional membrane outer leaflets, and permeation of this space with lanthanum or phosphotungstate reveals a polygonal lattice of subunits with a center-to-center spacing of 90–100 A. Freeze-cleaved gap junctions show a similar lattice. Extraction of junction-rich fractions with 60% aqueous acetone results in a disappearance of the 20 A gap in sectioned pellets and an inability to demonstrate the polygonal lattice with either the freeze-cleave or negative staining techniques. Extraction of the membranes with 50% acetone does not produce this effect. Thin-layer chromatography of the acetone extracts reveals a group of phospholipids in the 60% extract that are not detectable in the 50% extract. Acetone does not cause any detectable change in the structure of the zonula occludens, but the occluding junction becomes leaky to lanthanum following acetone treatment. The effects of other reagents on the junctions are reported.     

SCHWANN CELL PROLIFERATION IN DEVELOPING MOUSE SCIATIC NERVE : A Radioautographic Study

Proliferation of Schwann cells in neonatal mouse sciatic nerve was studied radioautographically in 1-µ glycol methacrylate sections. 28 mice were injected with thymidine-³H, 4 µc/g, 48 hr after birth, and were killed serially over the next 4 days. For the cell cycle following injection, the generation time was approximately 24 hr as determined by grain-count halving data; the duration of synthesis phase was 8 hr as determined from a curve constructed from the per cent of mitotic figures containing label; and the labeling index was 9% at 2 hr after injection. With these estimates, the per cent of Schwann cells proliferating was calculated to be 27%. In addition, roughly 25% of dividing cells appeared to cease division during the cell cycle under study. The relationship of these findings to other events during maturation of nerve is discussed.     

THE FINE STRUCTURAL LOCALIZATION OF ACETYLCHOLINESTERASE AT THE MYONEURAL JUNCTION

A study of the cytochemical localization of acetylcholiriesterase activity, combining histochemistry with electron microscopy, showed that the final product of the reaction, which was deposited at or near enzyme sites, occurred at four places in the myoneural junction. These included: plasma membrane of the muscle covering the junctional folds, the primary and secondary synaptic clefts, parts of the plasma membrane covering the axon terminal, and vesicular structures in the terminal axoplasm. No reaction occurred in the presence of 10^-4 eserine or DFP, whereas 10^-5 DFP inhibited the reaction at all sites except in the vesicles of the terminal axon. These findings are discussed with reference to the histochemical method used and to the occurrence of esterolytic activity in the vesicles, as well as to some of the current hypotheses concerning the relationship of the site of acetylcholinesterase and synaptic transmission.     

FINE STRUCTURAL LOCALIZATION OF A BLOOD-BRAIN BARRIER TO EXOGENOUS PEROXIDASE

Horseradish peroxidase was administered to mice by intravenous injection, and its distribution in cerebral cortex studied with a recently available technique for localizing peroxidase with the electron microscope. Brains were fixed by either immersion or vascular perfusion 10–60 min after administration of various doses of peroxidase. Exogenous peroxidase was localized in the lumina of blood vessels and in some micropinocytotic vesicles within endothelial cells; none was found beyond the vascular endothelium. Micropinocytotic vesicles were few in number and did not appear to transport peroxidase while tight junctions between endothelial cells were probably responsible for preventing its intercellular passage. Our findings therefore localize, at a fine structural level, a "barrier" to the passage of peroxidase at the endothelium of vessels in the cerebral cortex. The significance of these findings is discussed, particularly with reference to a recent study in which similar techniques were applied to capillaries in heart and skeletal muscle.     

SUBCELLULAR DISTRIBUTION AND TRANSPORT OF ACETYLCHOLINE IN CAT VENTRAL ROOTS AND SCIATIC NERVE

Abstract— The axonal transport of radioactive ACh, which was labelled by injecting radioactive choline into the ventral horn of the cat, was studied. Radioactivity analysed as ACh was transported in the nerves at a rate of 20–25 cm/24 h from the place of injection. Morphological and biochemical analysis after density gradient centrifugation revealed that endogenous ACh was principally distributed in three fractions-(a) a soluble fraction (provided homogenization was carried out in the presence of eserine), (b) a vesicular fraction (diameter 600–1600 A) in the 0.4M-sucrose layer of the density gradient, and (c) a fraction containing very small structures (size 90–100 A) in the 0.8–1.0 M-sucrose interphase. The radioactive ACh, however, was exclusively found in the soluble fraction (supernatant) after density gradient centrifugation. Analysis of ACh metabolites showed that radioactive ACh may have been formed locally in the nerves after transport of its precursor. Thus the morphologic and metabolic results do not support the hypothesis that ACh is transported in vesicles.     

AXONAL TRANSPORT OF PHENYLETHANOLAMINE-N-METHYLTRANSFERASE IN TOAD SCIATIC NERVE

—The presence of phenylethanolamine-N-methyltransferase (EC 2.1.1.-) and dopamine-β-hydroxylase (EC 1.14.2.1) activities was demonstrated in the sciatic nerve of the toad, Bufo marinus. The rates of accumulation of phenylethanolamine-N-methyltransferase (PNMT) and dopamine-β-hydroxylase (DBH) proximal to a ligation of the sciatic nerve were studied. DBH accumulated proximal to the ligation at a more than 10-fold faster rate than PNMT. By measuring the rate of loss of enzyme activity distal to a ligation, an estimate of per cent clearance of each enzyme was made. Based on the per cent of enzyme activity free to move, the absolute transport rates for each enzyme were estimated to be: PNMT, 3.6 mm/24 h; DBH, 102 mm/24 h. PNMT activity (89 per cent) was recovered in the soluble fraction of sciatic nerve homogenates with no change occurring in the subcellular distribution of the enzyme proximal to ligations. In contrast, 43 per cent of DBH activity was found in the soluble fraction of sciatic nerve homogenates; but a disproportionate increase in paniculate DBH activity was found proximal to sciatic nerve ligations. Reduction of toad body temperature to 4°C resulted in a complete but totally reversible block of the axonal transport of both PNMT and DBH.     

SCP_3在小鼠精母细胞核内的表达及定位

目的探讨SCP,蛋白在雄性小鼠减数分裂各阶段精母细胞核内的表达及定位。方法采用免疫组织化学染色法初步检测SCP,蛋白在曲细精管中的细胞定位,进一步利用免疫荧光FITC／DAPI共染技术显示该蛋白在减数分裂各阶段精母细胞核内的表达。结果免疫组织化学染色结果显示,在完整的曲细精管内只有精母细胞呈阳性染色。免疫荧光分析证实在减数分裂1前期的细线期、偶线期、粗线期及双线期精母细胞核内均有明显的SCP,绿色荧光信号,并且在不同分裂阶段的细胞核内阳性着色条带的数目、状态不同。在处于终变期及中期Ⅰ的精母细胞核内,只有散在的片状或点状荧光信号,直至后期Ⅰ阶段完全消失。结论SCP,蛋白在雄性小鼠减数分裂各阶段精母细胞核内的表达与SC的形成、成熟、解体同步,参与了同源染色体之间的联会和重组。     

大鼠和小鼠睾丸表皮生长因子表达的免疫组织化学定位观察

为了了解大鼠和小鼠睾丸是否产生ＥＧＦ及其细胞定位,本实验用ＥＧＦ单克隆抗体对大鼠和小鼠睾丸进行了免疫细胞化学定位研究,结果显示：（１）出生后,大鼠和小鼠睾丸即开始产生ＥＧＦ,分泌活动主要位于睾丸间质细胞。（２）至性成熟期,少数精原细胞、精母细胞及个别圆形精子细胞和管周肌样细胞也产生ＥＧＦ,使生精小管尤其是血睾屏障管腔小室侧的ＥＧＦ分泌增加。（３）在本实验中,睾丸支持细胞未见明显ＥＧＦ阳性染色。结果表明,大鼠和小鼠睾丸是可以产生ＥＧＦ的,间质细胞是其主要的ＥＧＦ分泌细胞。进入性成熟期后,少数精原细胞、精母细胞及个别圆形精子细胞和管周肌样细胞也产生ＥＧＦ。大鼠和小鼠睾丸在发育过程中ＥＧＦ分泌量呈上升趋势,至性成熟期达分泌高峰     

THE RESPIRATORY RATE OF THE SCIATIC NERVE OF THE FROG IN REST AND ACTIVITY

1. With the indicator method of Haas, the rates of carbon dioxide production have been measured in the case of the sciatic nerve, various parts of the brain, and the sartorius muscle of the frog. The rate of respiration of the sciatic nerve is from 10 to 30 per cent of that of the other tissues, varying somewhat with the individual. 2. Stimulation of the sciatic nerve with induction shocks sufficient to induce tetanus of the muscle does not increase the output of carbon dioxide from the sciatic nerve, even if continued as long as 30 minutes. Sartorius muscle used as a control showed a marked increase in carbon dioxide production upon relaxation after contraction resulting from such stimulation. 3. These facts indicate that the nerve impulse does not depend upon processes leading to the production of carbon dioxide.