花粉管中的微丝和微管

对花粉管中的微丝和微管研究的几个问题的进展进行了综述, 包括微丝和微管在花粉管中的分布;微丝和微管在花粉管胞质流动、细胞器运动以及花粉管生长中的作用等几个方面。并对今后这些方面研究的重要问题进行了论述。     

FREEZE-FRACTURE OF MICROTUBULES AND BRIDGES IN MOTILE AXOSTYLES

A freeze-fracture study of the motile axostyles of the flagellate protozoa Saccinobaculus and Pyrsonympha has been undertaken in order to obtain a view of the relationships of microtubules and their cross bridges not dependent on conventional preparative procedures. Reactivation studies using isolated axostyles prepared for freeze-fracture and then thawed demonstrate that we are observing the structure of a potentially functional axostyle. Cross fractures through the axostyle demonstrate more extensive interrow bridging than expected on the basis of observations of thin-sectioned material. Each microtubule has approximately sixfold bridge-binding sites with connections to as many as four interrow bridges. Measurements of microtubule diameter and spacing are significantly larger than those made from sectioned material and may indicate that conventional processing for electron microscopy results in the loss of structurally important water within the microtubule in addition to loss of intertubule material. Longitudinal fractures through the axostyle at various orientations demonstrate a minimum longitudinal periodicity of 160 Å for both the spacing of the globular subunits within the microtubule wall and the spacing of the intrarow bridges. While intrarow bridges are strictly periodic and always oriented in parallel, interrow bridges are not strictly periodic and can be oriented at varying angles to the microtubule axis.     

MICROFILAMENTS AND CELL LOCOMOTION

The role of microfilaments in generating cell locomotion has been investigated in glial cells migrating in vitro. Such cells are found to contain two types of microfilament systems: First, a sheath of 50–70-A in diameter filaments is present in the cytoplasm at the base of the cells, just inside the plasma membrane, and in cell processes. Second, a network of 50-A in diameter filaments is found just beneath the plasma membrane at the leading edge (undulating membrane locomotory organelle) and along the sides of the cell. The drug, cytochalasin B, causes a rapid cessation of migration and a disruption of the microfilament network. Other organelles, including the microfilament sheath and microtubules, are unaltered by the drug, and protein synthesis is not inhibited. Removal of cytochalasin results in complete recovery of migratory capabilities, even in the absence of virtually all protein synthesis. Colchicine, at levels sufficient to disrupt all microtubules, has no effect on undulating membrane activity, on net cell movement, or on microfilament integrity. The microfilament network is, therefore, indispensable for locomotion.     

MICROTUBULES IN BIOLOGICAL CELLS AS CIRCULAR WAVEGUIDES AND RESONATORS

The microtubules in the cellular cytoskeleton have a fundamental role in the living processes of biological cells. They are hollow cylinders which resemble circular waveguides or cylindrical resonators. The cutoff and resonant frequencies of the transverse magnetic and transverse electric modes of the microtubule cavities are in the band of soft x-rays. This suggests the possibility of interaction of electromagnetic cavity modes with inner electrons in atoms (e.g., in carbon, nitrogen, and oxygen). Biological cells (e.g., the yeast cells of spherical shape) may also represent cavity resonators. In this case, the resonant frequencies may be in the infrared region.     

FERRITIN PARTICLES IN MACROPHAGES AND IN ASSOCIATED MAST CELLS

In a variety of tissues (lymph node and glandular stroma), mast cells have been found in close and often intimate association with macrophages containing numerous ferritin-like particles in their cytoplasm and within cytoplasmic vacuoles (siderosomes). Phagocytic vacuoles in a given macrophage differed markedly. Some contained abundant Prussian blue-reactive material and others contained periodic acid-Schiff reactive substance at the light microscope level, and ultrastructurally some were filled with ferritin particles and others were not. Ferritin-like particles have also been observed occasionally in the mast cells associated with macrophages and even within the matrix of some of the granules in these mast cells.     

CENTROSOMES AND MICROTUBULES DURING MEIOSIS IN THE MUSHROOM BOLETUS RUBINELLUS

The double centrosome in the basidium of Boletus rubinellus has been observed in three planes with the electron microscope at interphase preceding nuclear fusion, at prophase I, and at interphase I. It is composed of two components connected by a band-shaped middle part. At anaphase I a single, enlarged centrosome is found at the spindle pole, which is attached to the cell membrane. Microtubules mainly oriented parallel to the longitudinal axis of the basidium are present at prefusion, prophase I and interphase I. Cytoplasmic microtubules are absent when the spindle is present. The relationship of the centrosome in B. rubinellus to that in other organisms and the role of the cytoplasmic microtubules are discussed.     

METABOLIC PATTERNS IN THREE TYPES OF PHAGOCYTIZING CELLS

Some chemical and metabolic characteristics of polymorphonuclear leukocytes and monocytes from peritoneal exudates of the guinea pig, and of alveolar macrophages from the same animal, have been compared. Changes in the metabolic patterns of these three types of cell have been followed during the act of phagocytosis. The effect of conventional inhibitors of metabolism, and of anaerobiosis on the phagocytic ability of each of the three cell types mentioned has also been determined. From these studies it was found that alveolar macrophages depend to a considerable degree upon oxidative phosphorylation to provide energy for phagocytosis. The other two types of cell depend only on glycolysis as the source of metabolic energy for that function. In some experiments aimed at obtaining information on the possible role of complex lipids in the function of the cell membrane, it was noted that phagocytosis stimulated the incorporation of inorganic phosphate-P³² into the phosphatides of both types of cell from peritoneal exudates—whether these were free-swimming or adherent to a surface. This phenomenon has not yet been detected in the case of alveolar macrophages.     

实验性肾炎鼠肾小球巨噬细胞的分离与鉴定

采用大鼠加速型抗基底膜肾炎模型。在注射抗GBM血清后72小时,肾炎鼠出现大量蛋白尿,取肾,使肾组织通过不同孔径的筛网收集肾小球,接种于塑料培养瓶温育20小时后,单个核细胞游离并贴壁。台盼蓝拒染试验检测其活性>98％,抗CD68单抗细胞免疫化学法及非特异性脂酶染色鉴定MΦ纯度>95％。     

ON THE ROLE OF MICROTUBULES IN MOVEMENT AND ALIGNMENT OF NUCLEI IN VIRUS-INDUCED SYNCYTIA

Infection of baby hamster kidney (BHK21-F) cells with the parainfluenza virus SV5 causes rapid and extensive cell fusion. Time-lapse cinematography shows that when cells fuse, their nuclei migrate straight to the center of the syncytium at rates of 1–2 µ/min. Nuclei are often arranged in long, tightly packed, parallel rows in syncytia derived from the fibroblastic BHK21-F cells. Polarization microscopy shows birefringent material between and parallel to these rows of nuclei, and electron microscopy shows bundles of cytoplasmic microtubules, ~250 A in diameter, and filaments, ~80 A in diameter, parallel to and between the rows of nuclei. Colchicine treatment causes disappearance of microtubules from BHK21-F cells and an apparent increase in the number of 80-A filaments. Although colchicine-treated, SV5-infected cells fuse, their nuclei do not migrate or form rows but remain randomly scattered through the syncytial cytoplasm. Incubation at 4°C does not disrupt microtubules in BHK21-F cells. Rows of nuclei have been isolated from SV5-induced syncytia, and the nuclei in them have been found to be intimately associated with microtubules but not with other cytoplasmic structures. These results suggest that microtubules demarcate cytoplasmic channels through which nuclei migrate and that they may also be involved in the mechanism of nuclear movement.     

CYTOPLASMIC MICROTUBULES IN DIFFERENT ANIMAL CELLS

In avian, murine, and human cells fixed with glutaraldehyde, cytoplasmic microtubules 180 to 250 A in diameter and of undetermined length were found. These cytoplasmic microtubules are similar to those described by Ledbetter and Porter in plant cells after the same glutaraldehyde fixation. The cytoplasmic microtubules in animal cells are connected with the satellites of the centrioles and are similar to the mitotic spindle fibers. Their protein nature and their possible role in maintaining the shape of the cells are discussed. Their presence in all examined animal cells as well as in plant cells favors the hypothesis that they are a permanent component of the cytoplasm.     

微管与肿瘤细胞运动——免疫细胞化学研究

运用免疫细胞化学方法对三种不等恶性程度人结肠腺癌细胞株HT-29分化较好,呈上皮样,细胞排列紧密,呈聚集性生长;免疫细胞化学显示;微管不甚明显。SW480及SW620细胞呈梭形。细胞间松散,常呈单个生长,免疫细胞化学显示微管十分丰富,该种形态特征与原发肿瘤恶性程度一致,前为高分化结肠腺癌,后为高恶性度结肠腺癌,具较强转移潜能,加入TGFβ1后,三株细胞均呈生长加速,多见分裂相,但微管未见明显改变,说明细胞快速分裂并非肿瘤浸润的唯一原因,加入道诺红菌素作用后,SW480及SW620微管结构出现明显改变,表现为断裂,卷曲或呈颗粒状。提示道诺红菌素能破坏细胞微管成分,微管的破坏可能抑制肿瘤细胞的转移。     

镉离子对微管、管蛋白巯基和在体轴浆转运的作用

大鼠腹角注入~3H亮氨酸,3h后坐骨神经内注射 Cd~(2 )30μl,50mM Cd~(2 )轻度减小标记蛋白的轴浆转运距离,75或 100mM 阻断转运在注射点。巯基抑制剂马来酰胺与 50mM Cd~(2 )伍用的效应相加,使转运也阻断在注射点。巯基供应剂二巯基丁二钠则完全抵消100mMCd~(2 )对转运的阻断作用。Cd~(2 )还使坐骨神经匀浆上清液的巯基含量减少,马来酰胺与Cd~(2 )伍用则巯基进一步降低。自兔脑提取了微管的亚基管蛋白,Cd~(2 )降低管蛋白巯基的程度与其浓度呈线性关系。电镜的验证证明,Cd~(2 )使在体神经的微管解聚、微管减少或基本消失。由于巯基、微管和转运的变化程度均与Cd~(2 )的浓度大小有关,并且同一浓度的Cd~(2 )使微管和转运的受累程度相互对应,因此Cd~(2 )可能借络合管蛋白的巯基使微管解聚而阻断转运。实验进一步证明以前的论断,微管解聚可能是Cd~(2 )等药物阻断转运的一个中间环节,微管可能参与在体轴浆转运的机制。