CYTODYNAMICS IN THE THYMUS OF YOUNG ADULT MICE:

Cell proliferation and cell loss in the thymic blast cell population were studied in young adult mice by (1) stathmokinetic methods combined with an analysis of the PLMe-curve after a pulse ³H-TdR, and (2) nigrosin-dye exclusion combined with ³H-TdR-autoradiography. It was calculated that about 17% of the blast cells do not progress into mitosis within the period of an average cell cycle. The dye exclusion studies indicated a rate of blast cell death of about 2–5 %/hr. The two methods of assessing blast cell loss (death) support each other very well. In spite of these findings scintillation countings on thymuses removed from 1 to 17 hr after ³H-TdR injection showed fairly constant levels of thymic radioactivity. This suggests a very extensive reutilization of ³H-labelled break-down products from dying blast cells. The very sparse labelling of pyknotic thymocytes strongly suggests that thymic blast cells do not become pyknotic. The rate of small thymocyte production and disappearance was studied by pulse and repeated ³H-TdR labelling techniques combined with dye exclusion studies and pyknotic counts. The data from the repeated labelling experiment were analysed by use of a model based on the assumption of first order kinetics of small viable, dead, and pyknotic thymocytes. The rate of cell production was estimated to 1–6 %/hr whereas the rates of cell loss due to disintegration, i.e. supravital stainability and nuclear pyknosis, were calculated to 0–02 %/hr and 0–0006 %/hr respectively. Cell loss due to disintegration was less than 2 % of the total loss of small thymocytes. It was concluded that pyknotic counts are a useless method of assessing the cell death in the population of thymic blast cells and small thymocytes. On the basis of a model for thymocyte proliferation, production and loss it is suggested that about 45 % of the small viable thymocytes re-enter the generative cell pool, whereas about 55% disappear by emigration.     

抗体应答期间大鼠脑和胸腺中儿茶酚胺含量的变化

目的：探讨在抗体应答期间,脑和淋巴器官中儿茶酚胺（ＣＡｓ）含量的动态变化,籍以了解免疫状态对中枢和外周ＣＡｓ神经活动的影响。方法：用绵羊红细胞（ＳＲＢＣ）免疫大鼠,在免疫后第２￣７ｄ应用高效液相色谱－电化学检测法（ＨＰＬＣ－ＥＣＤ）测定大鼠下丘脑、海马、脑干和胸腺中云甲肾上腺素（ＮＡ）、肾上腺素（Ａ）、多巴胺（ＤＡ）和高香草酸（ＨＶＡ）的含量。结果：①下且脑和海马内ＮＡ在抗体应答期间升高,而胸腺中     

小鼠生精细胞增殖与凋亡的年龄变化

为研究雄性小鼠睾丸在发生,发育过程生精细胞增殖与凋亡的年龄变化,本研究采用了免疫细胞化学,凋亡细胞原位检测,电镜及体视学图象分析等方法,对胚胎15天到生后10月后发育阶段生精细胞的超微结构,PCNA表达,凋亡情况进行了较深入地研究,结果：（1）精原细胞PCNA反应在胚胎15天为阳性,从胚胎18天到生后5天,降为弱阳性,而阳性的精原细胞在生后7天重新出现,一直到生后6月,仍可见部分精原细胞呈阳性反应;（2）生后3天,可见凋亡的精原细胞染色质浓缩,核膜出现明显的核周隙,核碎裂,凋亡细胞数从生后1天到生后第3周有增加的趋势,于生后第3周出现峰值,之后降低,之后降低,结论：（1）PCNA阳性细胞而密度到生后第2周出现峰值,而凋亡细胞数于生后3周出现峰值,生精细胞凋亡的高峰要滞后其增殖峰1周左右,而且与其所处生精周期的特定阶段有关;（2）精原细胞在胚胎发育过程中向曲细精管周边迁移,其排列由无序到有序;（3）在生后各发育 ,精原细胞始终保持DNA复制的能力。     

METABOLIC CHANGES IN THE BRAINS OF MICE FROZEN IN LIQUID NITROGEN

Abstract— Autolytic changes in the mouse brain, occurring during immersion of the animal in liquid nitrogen, were evaluated by measuring the tissue concentrations of glucose, lactate, pyruvate, α-oxoglutarate, phosphocreatine, creatine, ATP, ADP and AMP. The values thus obtained were compared with those obtained in paralysed mice under nitrous oxide anaesthesia, the brains of which were frozen in such a way that arterial blood pressure and oxygénation were upheld during the freezing. Immersion of unanaesthetized mice in liquid nitrogen gave rise to significant alterations in phosphocreatine, creatine, lactate, lactate/pyruvate ratio, ADP and AMP. A comparison with values obtained in paralysed and anaesthetized mice that were frozen by immersion in liquid nitrogen showed that the metabolic changes observed in the unanaesthetized animals could not be caused by an anaesthetic effect on the metabolic pattern. It is concluded that autolysis in the mouse brain occurs during immersion of the animal in a coolant, mainly because arterial hypoxia develops before the tissue is frozen. A comparison with previous results on rat cerebral cortex indicates that mice offer no advantage for studies of cerebral metabolites in unanaesthetized animals. In both species, accurate analyses of labile cerebral metabolites require that the brain is frozen in a way that prevents arterial hypoxia during the fixation of the tissue.     

MITOCHONDRIAL CHANGES IN THE LIVER OF ESSENTIAL FATTY ACID-DEFICIENT MICE

Livers of mice on diets deficient in essential fatty acids (EFA) have been studied by light and electron microscopy. The most conspicuous changes occur in the mitochondria. In light microscopy the mitochondria appear very much enlarged in the periportal region of the lobule. In electron micrographs they have additional cristae, sometimes very abundant. ranged in stacks in the central cavity. The matrix may be more electron-opaque than normal. This is in contrast with the enlarged mitochondria appearing under other experimental conditions, where the cristae are reduced in number and the matrix is less electron-opaque. It is known that there is an uncoupling of oxidative phosphorylation in EFA-deficient mitochondria. As a hypothesis it is proposed that the uncoupling may be due to a molecular defect caused by the absence of EFA in the structure that determines the spatial relationship between the electron transport chain and oxidative phosphorylation. It is further tentatively suggested that the changes in mitochondria may be attributed to lack of ATP. The possibility is discussed that the mitochondrial changes are ineffective attempts at compensation for this lack.     

CHANGES IN INTESTINAL CELL KINETICS IN THE SMALL INTESTINE OF LACTATING MICE

The enlargement of the small intestine of mice during lactation is due, at least in part, to hyperplasia in the mucosal crypts and villi. The number of cells per crypt increases by 130% and the cell production rate by 63% after 15 days of lactation. These parameters were measured from crypt squashes and sections using both double-label and PLM techniques. Neither the numbers of crypts and villi in the small intestine nor the turnover time of post-mitotic cells on the villi changed. A number of factors appear to act in concert during lactation to trigger this increase in epithelial cell number in the small intestine. The experiments reported suggest a role for the increased quantity of food consumed by the lactating animal, for changing hormonal levels, and for the increased demands placed on the body by milk production.     

CELL POPULATION KINETIC PROFILE OF THE MOUSE THYMUS, AND THE CHANGES INDUCED BY PREDNISOLONE

The cell population kinetic parameters of the thymus in BALB/c mice have been estimated using stathmokinetic and [³H]TdR techniques in both control animals and animals treated with prednisolone. FLM data were analysed by computer using the Gilbert program. The study showed that prednisolone had an inhibitory effect mainly in the DNA synthesis phase and in G₁. Stathmokinetic data also showed a decrease in the cell birth rate and an increase in the apparent cell cycle time (or potential doubling time) after treatment. The labelling index, the mitotic index and the growth fraction were also decreased. The study also shows a good agreement between the data obtained by stathmokinetic and [³H]TdR techniques.     

STUDIES ON THE REGULATION OF LYMPHOCYTE PRODUCTION IN THE MURINE THYMUS AND SOME EFFECTS OF A CRUDE THYMUS EXTRACT

Cell proliferation in the murine thymus was studied in vivo under normal conditions and from 0 to 24 hr after a single injection of a water-soluble extract from mouse thymus, mouse spleen, and mouse skin. The thymus extract reduced during the first 24 hr the mitotic activity 40%; the spleen extract had a weaker inhibitory effect. The skin extract had no such effect. The thymus extract and spleen extract inhibited the flux of cells into the S phase 0–8 hr after the injection of the extract. Initial labelling index was also reduced in this period. Eight hours after injection of the thymus or spleen extracts the inhibited cells initiated DNA synthesis. The rate of progression of blast cells through the cell cycle was normal 24 hr after the injection of the extracts. It was deduced from the analysis that the thymus extract inhibits processes triggering Go/Gi cells into DNA synthesis, the inhibition of G₂ efflux being of minor importance. Finally a model for the regulation of proliferating thymic blast cells and the emigration of small lymphocytes from the thymus is proposed.     

L.sp.HXQ001菌对小鼠胸腺生长及耐受性的影响

目的 研究Ｌ．ｓｐ．ＨＸＱ００１菌株对实验动物的有益作用。方法 实验动物自然口服菌液后,测量其胸腺重和胸腺体重比,对热和疲劳的耐受性。结果 Ｌ．ｓｐ．ＨＸＱ００１菌株可增加小鼠胸腺体重比,增加小鼠对热和疲劳的耐受性。结论 Ｌ．ｓｐ．ＨＸＱ００１菌株可增加小鼠胸腺体重比,增加小鼠对热和疲劳的耐受性。结论 Ｌ．ｓｐ．ＨＸＱ００１菌株有望成为微生态调节剂。     

ULTRASTRUCTURAL CHANGES IN THE MITOCHONDRIA OF CEREBELLAR PURKINJE CELLS OF NERVOUS MUTANT MICE

The maturation of cerebellar Purkinje cells of normal and nervous (nr/nr) mutant mice has been studied by light and electron microscopy. In the mutant, 90% of Purkinje cells selectively degenerate between postnatal days 23 and 50. Losses are greater in lateral than medial regions. Other cerebellar neurons appear normal. The first morphological abnormality recognized is the presence of rounded mitochondria in perikarya of some Purkinje cells of the mutant at 9 days after birth. By 15 days, all nr/nr Purkinje cells contain spherical mitochondria and begin to deviate from the normal maturational sequence. Elaboration of the extensive dendritic tree halts midway and newly formed axon collateral fibers degenerate. In the perikaryon, the basal polysomal accumulation and climbing fiber-somatic spine synapses are sometimes abnormally retained. Cisternae of the Golgi apparatus and rough endoplasmic reticulum cease to form aligned stacks, and decrease in number, while polysomes dissociate into free ribosomes. These changes are progressive, culminating in cell death. Although every nr/nr Purkinje cell demonstrates spherical mitochondria, some cells survive the critical period, retain a near-normal complement of organelles, and reacquire normal-appearing mitochondria. The disorder appears intrinsic to Purkinje cells since all major classes of synapses were identified before cell death.     

A STUDY OF GLUCO-CORTICOSTEROID-INDUCED PYKNOSIS IN THE THYMUS AND LYMPH NODE OF THE ADRENALECTOMIZED RAT

Pyknotic nuclei, observed in the thymus of steroid-treated rats, are dense, homogeneous, intensely basophilic and Feulgen positive. Under the electron microscope, the image is that of a complete segregation of the chromatin from the nuclear sap producing a margin or crescent of condensed chromatin. Approximately 30% of all small thymocytes appeared to undergo this type of degeneration within 3–4 hr after administration of the synthetic corticosteroid, dexamethasone. At this time, pyknotic thymocytes were observed in clusters, probably as a result of the activity of dense reticular cells and macrophages. Topographical and experimental data suggest the existence of a select population of steroid-sensitive thymic cells. Furthermore, on the basis of thymidine-³H incorporation studies, it appears that the steroid-sensitive population of thymocytes does not correspond to "aged" cells. In addition, many plasma cells became pyknotic after the same steroid treatment, indicating an unexpected similarity between their nuclei and those of lymphocytes. Finally, steroid failed to induce pyknosis of thymocytes in a variety of in vitro experiments, suggesting that the in vivo effect of steroid is of an indirect nature. The results are discussed in terms of (a) the nature of the nuclear changes characterizing pyknosis, (b) the hypothetical mechanism whereby steroids trigger such changes, and (c) the population of cells susceptible to steroid-induced pyknosis.     

中华鳖胸腺显微和亚显微结构及其在进化上的意义

应用透射电子显微镜观察了中华鳖胸腺的显微和亚显微结构。发现中华鳖胸腺从结构上可分为皮质和髓质,皮质富含淋巴细胞,髓质富含上皮性网状细胞。在各发育期中华鳖胸腺皮质、髓质交界处和髓质区有明显的囊状胸腺小体和交错突细胞。在２００ｇ以上的成年鳖胸腺内发现有同心圆状胸腺小体。电镜下,胸腺内淋巴细胞分为大、中、小３型。上皮性网状细胞从亚显微结构上分为支持型和分泌型。胸腺囊包括细胞内囊和细胞间囊,以细胞内囊居多     

CYTOKINETIC STUDIES OF THE REGENERATIVE PHASE IN THE JB-1 ASCITES TUMOUR

The cell kinetics of recurrent growth of the murine JB-1 ascites tumour have been investigated 0 hr and 24 hr after aspiration of the main part of the tumour in the plateau phase of growth. The experimental data: growth curve, percentage of labelled mitoses curve and continuous labelling curves combined with cytophotometric determination of single-cell DNA content were analysed using two alternative mathematical models for the cell kinetics. Investigations 24 hr after aspiration showed that the doubling time had decreased to 70 hr as compared with 240 hr in the plateau tumour. This was due to a release of non-proliferating cells into the cell cycle, resulting in an increase in the growth fraction from 44% to 72%. The decrease in the doubling time was also due to a shortening of the mean cell cycle time from 41 to 20.5 hr. The analysis rendered it likely that the aspiration caused a shift in the mode of cell loss from an age-specific elimination of old non-cycling cells with post-mitotic DNA content in the plateau tumour to an elimination of younger cells immediately after mitosis. Investigations from 0 to 10 hr after aspiration verified the release of non-proliferating cells with both G₁ and G₂ DNA content into the cell cycle. The release was initiated from 3 to 6 hr after aspiration. 24 hr after aspiration the experimental data did not indicate any further transition.     

THE GEOTROPIC REACTION OF RODLESS MICE IN LIGHT AND IN DARKNESS

"Black—short ears—kinky tail—rodless" mice, controlled by "pink eyed—dilute—brown" mice, were tested on an inclined plane in order to determine if they are photically sensitive, and, if so, to get a quantitative expression for their visual receptivity. Rodless and control animals were tested in the dark to obtain an expression for normal geotropic orientation. Light was then introduced to modify these reactions if possible. Under light, the controls failed to orient, whereas the rodless gave reactions almost identical with those in the dark. This test has failed in this experiment to suggest sight in the rodless mouse.     

BALB/C小鼠肝细胞结构的年龄变化——光镜与电镜的计量形态学研究

作者研究了1月、6月和12月三个不同年龄组的BALB/c小鼠的肝细胞结构。利用计量形态学方法在光镜与电镜两个水平上对肝细胞整体及重要细胞器的年龄变化进行定量分圻,发现在所观察的结构参数中大部分随年龄而发生动力学变化。文中讨论了某些变化的可能意义。     

VARIATION IN THE DURATION OF MITOSIS IN THE CRYPTS OF LIEBERKUHN OF THE RAT; A CYTOKINETIC STUDY USING VINCRISTINE

The variation in the duration of mitosis ( t _m) with cell position in the small intestinal crypts of the adult rat has been measured by a stathmokinetic technique using vincristine. The value for the whole crypt column was 0.43 hr, or 26 min. At the bottom of the crypt t _m was in excess of 1 hr, but rapidly decreased and throughout the greater part of the proliferative compartment was between 0.40 and 0.50 hr. At the top of the proliferative compartment an increase in t _m was demonstrated.
If the value of 0.43 hr for the whole crypt column is correct, then one argument for postulating the formation of metabolic DNA during differentiation in the small bowel epithelium of the rat becomes invalid. Variations in t _m within the crypt have been shown to increase the values of cell velocity obtained from cumulative birth rate diagrams. Finally further evidence has been presented for the existence of a slowly dividing subpopulation of cells at the base of the crypt. These cells may be important in crypt repopulation after damage with phase specific anti-tumour drugs.     

ANALYSIS OF TIME DEPENDENT CHANGES OF LYMPHOPOIETIC ACTIVITY IN ORGAN CULTURES OF EMBRYONIC CHICKEN THYMUS

The time dependent development of lymphocytes in organ cultures of the thymus obtained from 10-day-old chick embryos was characterized by an initial phase of exponential increase of the number of lymphocytes per thymus followed by a plateau phase with no further increase in cell number. The proportion of cells in DNA synthesis dropped rapidly during the first 10 days of culture. Simultaneously the lymphocytes turned progressively smaller, as evidenced by both cell diameter and dry mass and constituted a homogeneous population of small cells at the end of the culture period. Thymic anlagen partially depleted of lymphoid precursor cells by a short hot pulse with ³H-TdR showed a prolonged exponential phase and reached normal plateau cell numbers 2–4 days later than usual. Furthermore, at least in the first part of the plateau phase, a reduction in the number of lymphoid cells per thymus resulted in a recovery in terms of the cell number which was associated with increased DNA synthesis. These results are compatible with the regulation of thymic lymphopoiesis in organ culture through a mechanism operating via cell density.     

PLASMALOGENASE ACTIVITIES IN THE BRAINS OF JIMPY AND QUAKING MICE

The activity of plasmalogenase, which hydrolyzes the vinyl ether linkage of the plasmalogen molecule, increased markedly in control mouse brains during the period of most active myelin deposition. Only a slight increase in plasmalogenase activity was found in brains from jimpy mice. At all ages studied, the jimpy mouse brains had less plasmalogenase activity than the littermate control brains and this disparity increased with increasing age. By 25 days of age the jimpy brains contained only 43% of the activity observed in control brains. Adult quaking mouse brains also had significantly less plasmalogenase activity when compared to littermate controls. Thus, the plasmalogenase activities correlate well with the degree of myelination.