ULTRASTRUCTURAL STUDIES ON THE PERMEABILITY OF THE MESOTHELIUM TO HORSERADISH PEROXIDASE

Peritoneal mesothelium was exposed for 2–60 min to solutions of horseradish peroxidase by incubation in vitro, or after intraperitoneal injection in vivo. Peroxidase was localized, with the electron microscope in the intercellular clefts of the mesothelium, often along their entire lengths, in vesicles adjoining or contiguous with the clefts, and along the peritoneal and basal surfaces of the cell, and also in intracytoplasmic vacuoles. The intercellular junctions of peroxidase-treated mesothelium did not differ from those of controls: open and closed junctions were present in both groups. Intercellular localization was also obtained when the mesothelium was exposed to peroxidase during or after fixation. Although intracellular absorption of peroxidase and its incorporation into larger vacuoles were observed, there was no clearcut evidence of vesicular transport across the mesothelium in these experiments. These findings are consistent with physiologic data which postulate that mesothelial transport can be accounted for, at least in part, by passive diffusion through a system of pores, and they suggest that these pores are located in the intercellular clefts.     

THE PERMEABILITY OF ISOLATED AND IN SITU MOUSE HEPATIC GAP JUNCTIONS STUDIED WITH ENZYMATIC TRACERS

We have studied the effects of phospholipase C from Clostridium welchii on gap junctions in the intact mouse liver and in a junction-rich fraction prepared from mouse liver. Treatment of the isolated junctions results in the disappearance of both the 20 A gap and of the polygonal lattice visible with lanthanum. The junctions are morphologically unaltered, however, when whole livers are perfused with phospholipase via the portal vein. These results suggest that extracellular phospholipase cannot diffuse into the junctional area, but that the enzyme may affect structures within the gap from its cytoplasmic surfaces which become exposed in the isolated preparations. Horseradish peroxidase, which has physical dimensions similar to those of Clostridium phospholipase is also denied access to the 20 A gap in whole liver, while peroxidase reaction product can be seen in the gap in isolated preparations. Beef liver catalase, however, a tracer molecule much larger than peroxidase, cannot penetrate even in isolated fractions. If the cytoplasmic approaches to the gap junction used by peroxidase and phospholipase are available in vivo, and have not been created during the process of mechanical isolation, they may play a role in cell-to-cell passage of molecules larger than ions.     

THE INFLUENCE OF DIETARY PROTEIN DEFICIENCY ON HAEMOPOIETIC CELLS IN THE MOUSE

These experiments examined the effect of a diet limited only in protein (4% by weight) on haemopoietic stem cells in mice. This diet places severe restrictions on growth and cell proliferation and this was reflected in lower numbers of colony forming units (CFUs) and in vitro colony forming cells (CFCs). Differences were apparent in the response of different organs to this stress; for instance, the incidence of spleen CFUs fell sharply from around 40/mg spleen tissue to 1 -4/mg spleen tissue after 3 weeks on a low protein diet. This selective loss did not occur in bone marrow where total CFUs remained proportional to cellular content. Yet a third pattern was shown by thymus CFUs–although the numbers were low these increased from 16/thymus in normal mice to 132/thymus in deprived mice. This was the only organ examined which showed an increase. The effects of a return to a high protein (18 %) diet showed that the spleen was the most responsive organ. By day 5 after the return to 18% protein the spleen contained as many CFUs per million cells as the bone marrow. During this time the content of CFU in the spleen had increased some 50-fold whereas bone marrow CFUs only doubled. The spleen assumes the major reconstitutive role during the refeeding process.     

L-NAME、G-CSF对急性胆道感染大鼠生存率和肺脏影响

目的 :了解大鼠在急性胆道感染时应用 L- NAME、G- csf后 ,其肺脏和生存率的影响。方法 :72只 SD大鼠随机分为 4组 ,即 :假手术组、急性胆道感染组、L- NAME处理组、G- csf处理组。采用胆总管注入大肠埃希菌 0 .2 m l(菌型 :2 5 92 2 ,浓度 4× 10 9CFU/ ml) ,双重结扎制成胆总管的急性胆道感染模型 ,观察肺组织光镜下的一般结构。 72只 SD大鼠随机分为 4组 ,分组方法如上 ,观察每组大鼠在 2 4、48、72 h的存活率。结果 :G- csf处理组与急性胆道感染组比较 ,肺脏病理损害减轻 (P<0 .0 5 ) ,存活率则显著增高 ((P<0 .0 1或 P<0 .0 5 )。L- NAME处理组肺脏病理改变有加重趋势。结论 :外源性细胞因子 L- NAME及 G- csf可影响感染中某些炎性介质的分泌和释放 ,L - NAME加重脏器损害 ,G- csf可减轻脏器损害 ,提高存活率。     

FACTORS AFFECTING THE DURATION OF INTESTINAL PERMEABILITY TO MACROMOLECULES IN NEWBORN ANIMALS

1. In several species, partial, or even complete passive immunization of the offspring is achieved through maternal antibodies which are concentrated in the colostrum. Failure to obtain sufficient colostrum renders newborn farm animals highly susceptible to systemic and enteric infection with E. coli. 2. A significant number of colostrum-fed calves nevertheless develop colisepticaemia and many of these animals are hypo- or even agammaglobulinaemic. A premature termination of intestinal ability to absorb colostral antibodies (closure) may be responsible for some of these cases. 3. Pharmacological doses of certain exogenous corticosteroids are capable of inducing premature closure in rats. It is not certain though whether exogenous corticosterone can induce precocious closure in rat pups or whether exogenous corticosteroids can induce closure in members of other mammalian orders. Corticosteroid levels, however, may influence the efficiency of immunoglobulin absorption. Attempts to delay closure with adrenal suppression in animals with short immunoabsorptive periods have not been effective. 4. In piglets, but not in puppies or calves, starvation can postpone closure for several hours and consumption of food may be necessary before closure can occur. 5. Closure in the rat and pig apparently takes place by different methods.     

ON THE INFLUENCE OF AGGREGATES ON THE MEMBRANE POTENTIALS AND THE OSMOTIC PRESSURE OF PROTEIN SOLUTIONS

1. It is shown that when part of the gelatin in a solution of gelatin chloride is replaced by particles of powdered gelatin (without change of pH) the membrane potential of the solution is influenced comparatively little. 2. A measurement of the hydrogen ion concentration of the gelatin chloride solution and the outside aqueous solution with which the gelatin solution is in osmotic equilibrium, shows that the membrane potential can be calculated from this difference of hydrogen ion concentration with an accuracy of half a millivolt. This proves that the membrane potential is due to the establishment of a membrane equilibrium and that the powdered particles participate in this membrane equilibrium. 3. It is shown that a Donnan equilibrium is established between powdered particles of gelatin chloride and not too strong a solution of gelatin chloride. This is due to the fact that the powdered gelatin particles may be considered as a solid solution of gelatin with a higher concentration than that of the weak gelatin solution in which they are suspended. It follows from the theory of membrane equilibria that this difference in concentration of protein ions must give rise to potential differences between the solid particles and the weaker gelatin solution. 4. The writer had shown previously that when the gelatin in a solution of gelatin chloride is replaced by powdered gelatin (without a change in pH), the osmotic pressure of the solution is lowered the more the more dissolved gelatin is replaced by powdered gelatin. It is therefore obvious that the powdered particles of gelatin do not participate in the osmotic pressure of the solution in spite of the fact that they participate in the establishment of the Donnan equilibrium and in the membrane potentials. 5. This paradoxical phenomenon finds its explanation in the fact that as a consequence of the participation of each particle in the Donnan equilibrium, a special osmotic pressure is set up in each individual particle of powdered gelatin which leads to a swelling of that particle, and this osmotic pressure is measured by the increase in the cohesion pressure of the powdered particles required to balance the osmotic pressure inside each particle. 6. In a mixture of protein in solution and powdered protein (or protein micellæ) we have therefore two kinds of osmotic pressure, the hydrostatic pressure of the protein which is in true solution, and the cohesion pressure of the aggregates. Since only the former is noticeable in the hydrostatic pressure which serves as a measure of the osmotic pressure of a solution, it is clear why the osmotic pressure of a protein solution must be diminished when part of the protein in true solution is replaced by aggregates.     

IN VlTRO BINDING OF PHENYLALANYL-tRNA TO NEONATAL AND ADULT MOUSE BRAIN RIBOSOMES

The ability of brain ribosomes, isolated from mice of various ages, to bind phenylalanyl-tRNA was measured under various reaction conditions. In the presence of template RNA (polyuridylic acid) the binding could be measured by both enzymic and non-enzymic assays. In general, the binding requirements for the brain system were similar to those previously described for microbial and eukaryotic systems. Although previous studies have shown that ribosomes obtained from increasingly older mow brain tissue were less active in polyphenylalanine synthesis, no significant differences in phenylalanyl-tRNA binding to polysome complexes could be detected. The binding of phenylalanyl-tRNA by ribosomes isolated from both neonatal and mature mouse brain tissue was similar with regard to GTP and polyuridylic acid dependence, magnesium ion concentration and reaction kinetics. Similar binding of phenylalanyl-tRNA by young and mature brain ribosomes was also measured with ribonucleoprotein particles previously stripped with puromycin. The results are discussed in light of the rapid alteration of macromolecular synthesis during postnatal brain development and the possible role of the interaction between ribosomes and tRNA.     

提前接受光照对小鼠视网膜TH和bFGF表达的影响

目的在通过手术使小鼠提前睁眼接受光照,并成功诱发近视的基础上,进一步研究TH和bFGF在视网膜中的表达变化,以探讨早产近视的发病机理.方法实验用新生第4d的C57BL/6J小鼠,通过手术分离单侧上、下眼睑,使之提前睁眼并接受正常光照,在第14d检查两眼屈光力,应用RT-PCR和免疫组化方法,检测视网膜中bFGF和TH的表达.结果提前接受光照能诱导形成-9.77±0.09D的相对近视.RT-PCR结果显示提前光照小鼠视网膜TH和bFGFmRNA含量明显减少(t值分别为4.316和12.189,P<0.01).免疫组织化学显示TH免疫阳性反应主要分布在节细胞层、内网层和内核层,bFGF免疫阳性反应主要分布在内网层及其两侧的部分节细胞和内核层细胞,另在内网层和视锥视杆层也有微弱表达.免疫组织化学染色显示提前光照小鼠视网膜中TH和bFGF的表达量明显下降.结论研究表明新生小鼠提前光照后,其视网膜TH和bFGF的表达都明显下降,提示TH和bFGF与早产近视的形成有密切关系.     

黄瓜对霜霉病抗性的显微和超微结构的研究

利用显微及透射和扫描电镜方法,研究了黄瓜对霜霉菌[Pseudoperonosporacubensis(Berk.et Curt.)Rostow.]的抗性机理,结果如下:抗病与感病品种叶表面的气孔密度和大小无明显区别,而病菌分生孢子在叶表面萌发情况有差异。抗病品种被病菌侵染后,细胞迅速颗粒化,与病菌一起死亡,两个侵染点之间的叶肉细胞大量繁殖,细胞中叶绿体减少,膜系统受到破坏,壁增厚,叶表面出现少量很小的病斑;中抗品种表现为少量菌丝蔓延,并产生分生孢子囊梗和孢子,受侵细胞的线粒体和叶绿体膜系统被破坏,随后内细胞和菌丝死亡,但比抗病品种慢,在叶表面形成很多病斑;感病品种表现为叶肉细胞内有大量菌丝蔓延,并产生分生孢子囊梗和孢子,受侵细胞被破坏、解体成碎片,最后与菌丝一起死亡,在叶表面联成大量的病斑。     

幼年和成年小白鼠LDH与SOD动态变化的电泳分析

采用聚丙烯酰胺凝胶圆盘电泳分析方法,研究了幼年鼠和成年鼠睾丸乳酸脱氢酶（ＬＤＨ）同工酶与超氧化物歧化酶（ＳＯＤ）的酶带变化。观察结果表明,成年鼠睾丸的凝胶电泳胶条,多数显现六种ＬＤＨ同功酶带,其中ＬＤＨ５和ＬＤＨ４占优势,ＬＤＨ１、ＬＤＨ２、ＬＤＨ３显带较弱,在正极端ＬＤＨ的下面是第６条酶带,相当于Ｃ亚单位（ＬＤＨｃ）的Ｃ４。幼年鼠睾丸的凝胶电泳胶条,只显现ＬＤＨ１和ＬＤＨ２两条同功酶带,以ＬＤＨ     

INFLUENCE OF CELL VOLUME ON THE GROWTH AND SIZE REDUCTION OF MARINE AND ESTUARINE DIATOMS1

The maximal growth rate (μ_max) of 19 marine and estuarine diatoms decreased with increasing cell volume (V). The relationship between log μ_max (Y) and log V (X) was calculated. Statistical analyses showed that the slope of the equation was not significantly different from those obtained by other researchers and that the 95% confidence intervals of mean μ_max at cell volumes of 10³–10⁵μm³ were not significantly different from those cited in most studies. A new regression line for diatoms was calculated as follows: log μ_max= 0.47–0.14 log V; r =–0.69. The rate of size reduction per generation of the 19 diatom species ranged from 0.03 to 0.87 μm per generation. The rate increased with increasing cell length and cell volume and with decreasing maximum division rate. Statistical analyses showed that the rate was closely related to the cell volume and to the reciprocal of the growth rate. The relationships between maximal growth rate and cell volume and between rate of size reduction and cell volume showed that a diatom with a large volume had a smaller maximal growth rate and a larger rate of size reduction than a diatom with a small volume. The estimates using the equation for the regression line between the rate of size reduction and the reciprocal of maximum division rate indicated that a diatom with a high maximum division rate would need more generation equivalents for a certain size reduction than a diatom with a low maximum division rate, but the periods required for reduction would be approximately equal irrespective of maximum division rate.     

THE EFFECT OF pH ON THE PERMEABILITY OF COLLODION MEMBRANES COATED WITH PROTEIN

The permeability of gelatin-coated collodion membranes, as measured by the flow of water or of dilute solutions through the membranes, has been found to vary with the pH of the solutions. The permeability is greatest near the isoelectric point of the protein; with increasing concentration of either acid or alkali it decreases, passes through a minimum, and then increases. These variations with pH are qualitatively in accord with the assumption that they are due to swelling of the gelatin in the pores of the membrane, the effects of pH being similar to those observed by Loeb on the swelling of gelatin granules. Indications have been found of a similar variable permeability in the case of membranes coated with egg albumin, edestin, serum euglobulin, and serum albumin.     

幼年和成年小白鼠LDH与SOD动态变化的电泳分析

采用聚丙烯酰胺凝胶圆盘电泳分析方法,研究了幼年鼠和成年鼠睾丸乳酸脱氢酶(LDH)同工酶与超氧化物歧化酶(SOD)的酶带变化.观察结果表明,成年鼠睾丸的凝胶电泳胶条,多数显现六种LDH同功酶带,其中LDH\-5和LDH\-4占优势,LDH\-1\,LDH\-2\,LDH\-3显带较弱,在正极端LDH的下面是第6条酶带,相当于C亚单位(LDH\-c)的C\-4.幼年鼠睾丸的凝胶电泳胶条,只显现LDH\-1和LDH\-2两条同功酶带,以LDH\-1占优势.酶谱的变化说明,幼年鼠睾丸的LDH同功酶是以B基因表达为主,成年鼠睾丸的LDH同功酶则转变成以A基因表达为主.LDH\-c酶带的出现,表明成年鼠睾丸还有C基因的表达.睾丸SOD活性带变化提示,成年鼠睾丸的SOD带活性强于幼年鼠的活性,这与成年鼠睾丸的SOD不断地清除超氧化物自由基对精子发生过程的损伤有关.     

THE EFFECT OF CERTAIN ELECTROLYTES AND NON-ELECTROLYTES ON PERMEABILITY OF LIVING CELLS TO WATER

1. Permeability to water in unfertilized eggs of the sea urchin, Arbacia punctulata, is found to be greater in hypotonic solutions of dextrose, saccharose and glycocoll than in sea water of the same osmotic pressure. 2. The addition to dextrose solution of small amounts of CaCl₂ or MgCl₂ restores the permeability approximately to the value obtained in sea water. 3. This effect of CaCl₂ and MgCl₂ is antagonized by the further addition of NaCl or KCl. 4. It is concluded that the NaCl and KCl tend to increase the permeability of the cell to water, CaCl₂ and MgCl₂ to decrease it. 5. The method here employed can be used for quantitative study of salt antagonism.     

THE EFFECT OF ELECTROCONVULSIVE SHOCK ON PROTEIN SYNTHESIS IN MOUSE BRAIN

The effect of a single electroconvulsive shock on protein synthesis in mouse brain cortex was studied by observing the incorporation into protein of intraperitoneally injected [³H]- or [¹⁴C]leucine. When the precursor was injected immediately after the electroshock there was a 50 per cent inhibition of the incorporation which was not seen with injections at times later than 10 min. To investigate a possible specificity, the cerebral cortices of experimental and sham control animals which had been injected with different isotopes were homogenized together and fractionated by differential centrifugation. Cell fractions were then separately extracted with phosphate buffer and with Triton X-100. The ratio of ³H to ¹⁴C in each fraction was compared with that of the total homogenate to reveal any specific effects due to the electroconvulsive shock. The treatment produced a slight inhibition of the incorporation of the isotope into the heavier particulate fractions (i.e. nuclei, mitochondria, synaptosomes) relative to that in the microsome and cell sap fractions. A possible explanation of these results is given with a discussion of the limitations of the technique.     

SOME OBSERVATIONS ON THE PERMEABILITY OF MITOCHONDRIA TO SUCROSE

In experiments carried out with sucrose-isolated rat liver mitochondria, C¹⁴-sucrose seems to penetrate most of the mitochondrial space rapidly, whereas it seems to penetrate the remainder relatively slowly. However, taking into account the wide size distribution found in isolated preparations, these rates have been found consistent with the kinetics expected from the assumption of a single compartment per mitochondrion. These data cannot be readily interpreted on the basis of two mitochondrial spaces, one highly permeable, and another relatively impermeable to sucrose.     

INFLUENCE OF AGE AND ANTIGENIC STIMULATION ON GRANULOCYTE AND MACROPHAGE PROGENITOR CELLS IN THE MOUSE SPLEEN

The frequency and proliferative activity of granulocytic and macrophage progenitor cells were determined in the spleens of C₅₇BL, BALD/c, NZB and CBA mice. These cells were detected by their capacity to form granulocytic and/or macrophage colonies ( in vitro colony-forming cells, CFC) in agar culture. In vitro CFCs were low in frequency in the adult spleen (4–28/10⁵ cells) compared with the bone marrow (180–280/10⁵ cells). However, the neonatal spleen, both in germfree and conventional mice, contained high levels of in vitro CFCs. From the low suiciding index with tritiated thymidine and the small numbers of cluster-forming cells in relation to colony numbers, many in vitro CFCs in the adult C₅₇BL spleen appear to be in a non-cycling state. The level and activity of in vitro CFCs were extremely low in the spleen of adult germfree CBA mice but were greatly increased in conventional mice following the injection of a bacterial antigen.