豚鼠精母细胞联会复合体的电镜观察

以微铺展法制备豚鼠精母细胞联会复合体标本,经硝酸银染色后作电镜观察,建立了SC组型。与有丝分裂染色体组型比较,发现二者有良好的一致性。在粗线期,X,Y轴的配对区很短,配对区的X轴和Y轴没有明显变细。未发现银染SC具有着丝粒,并对可能的原因做了分析讨论。Synaptonemal complexes (SC) in Guinea pig (Cavia porcellus) spermatocytes prepared with micro-spreading technique and silver staningwere analyzed by electron microscopy.The meiotic SC karyotype was constructed from 7 cells and compared with the mitotic chromosome karyotype. There is a good agreement between them. At pachytene, there is only a very a very short pairing region in which X-and Y-axis are not stinctly thin.The kinetochore thin. The kinetochore was not found on each SC in our experiments and probable reason has been discussed.     

褐家鼠精母细胞中联会复合体的研究 Ⅱ.性染色体配对形态和行为的研究

用表面铺展-AgNO_3和PTA染色技术,对雄性褐家鼠性染色体配对形态和行为进行研究表明:X和Y轴在减数分裂前期Ⅰ的不同阶段固缩速度不同;性染色体在配对之前轴心增粗、配对延迟到早粗线期;性染色体首次配对起始区发生在X和Y短臂端粒区,其次配对起始区发生在X与Y长臂的端粒区或长臂的中间区;在中粗线期几乎整条Y与约1/3 X配对形成X-YSC;配对区的侧生组分分为两股,其中一股发生泡状变形,不配对片段发生多种变形。本文对X和Y配对起始位点,配对的同源性及XY轴心增厚与变形机制作了讨论.     

家鸡联会复合体的亚显微结构分析

本文以表面铺展——硝酸银染色技术,对家鸡的联会复合体(Syneptonemal Complex,SC)作亚显微结构分析。根据对10个精母细胞和10个卵母细胞SC的测量结果,绘制组型图。发现雌雄家鸡的常染色体的SC组型相同。在精母细胞中,性染色体(ZZ)的行为与常染色体相似。在卵母细胞中,性染色体ZW的长度不同,长轴为Z,短轴为W,两者之间只有部分配对,形成SC。从早粗线期到晚粗线期,由同源配对调整为非同源配对。另外,在一只雌鸡中,第一次观察到,有些细胞的常染色体能正常配对,而性染色体完全不配对的现象。     

X-Y染色体片段交换

同源染色体的配对交换是减数分裂的特性之一。那么,减数分裂时X—Y染色体之间是否发生配对交换?经典的染色体遗传学说认为X—Y之间没有同源性,这就从根本上否定了X—Y之间有配对交换的可能。然而,后来大量的研究表明,在哺乳动物中X—Y之间有同源部分,能够进行配对交换,并且发现X—Y的配对交换和常染色体一样是经常发生的。弗格森-史密斯(Ferguson-smith)于1966年发现有××男性,即具有女性的染色体组成而表现型是男性。他观察到一些××男性具有他父亲的Y染色体上的睾丸决定因子基因     

小麂、黑麂、赤麂精母细胞联会复合体的比较研究

本工作以界面铺张——硝酸银染色技术,对小麂(Muntiacus reeuesi)、黑麂(M.crinifrons)和赤麂(M.muntjak)的精母细胞联会复合体(Syna ptonemal complex,SC)进行亚显微结构的比较研究。结果表明: 1.SC的平均相对长度和臂比指数同有丝分裂细胞相应染色体的数值有很好的一致性。根据SC的相对长度和臂比指数绘制了三种麂的SC组型图。雄性黑麂减数分裂前期形成一个复杂的易位多价体,意味着其核型的演化过程涉及两次染色体易位和一次臂间倒位。 2.在减数分裂前期,性染色体的形态和行为同常染色体的有明显差异,如性染色体嗜银性较强,配对延迟等。XY的配对起始于早粗线期,在中粗线期,Y的全长均同X配对;XY-SC开始解体于晚粗线期。 3.在粗线期,X染色体未配对区域出现自身折叠,形成“发夹”状结构。这种“发夹”结构的形成,可能是在性染色体的进化过程中,X染色体通过不对称易位得到的重复片段在减数分裂前期同源配对的一种细胞学表现。     

德国(虫非)蠊精母细胞联会复合体(SC_s)组型及辐射诱发的SC_s畸变

以表面铺展法制备德国(虫非)蠊精母细胞联会复合体(SC_s)标本,经硝酸银染色后作电镜观察。结果表明,减数分裂SC_s组型和有丝分裂染色体组型基本一致;在减数分裂前期,X染色体自身折叠形成典型的“发夹”状结构。电离辐射诱发SC_s出现多种畸变,如倒位、重复、缺失、易位以及SC提前分离等。对X染色体自身折叠形成的可能机制、SC缠绕交叉与染色体交换的关系以及SC畸变分析的潜在应用价值和遗传学意义作了讨论。     

四种猕猴属动物精母细胞联会复合体的比较研究

本工作采用去污剂微铺展——硝酸银染色技术研究熊猴、平顶猴、藏酋猴、恒河猴及其亚种毛耳猴的精母细胞联会复合体（SC）核型、SC的结构及其在减数分裂中的行为。结果表明这几种动物的SC核型以及SC的发育过程基本一致。SC的形成开始于偶线期,成熟于粗线期,解体于双线期。在减数分裂前期,性染色体轴呈强嗜银性,配对明显落后于常染色体。根据减数分裂前期性染色体的形态和行为,性染色体的配对可分为五种类型。此外,本文还对XY染色体的同源性和侧轴加粗等现象进行了讨论。     

中国人精母细胞和卵母细胞联会复合体的电镜观察

以微铺展技术结合硝酸银染色,对中国人精母细胞和流产胎儿卵巢联会复合体的形态和行为作了电镜观察。列出中国人的SC核型和模式图。根据减数分裂前期XY的复杂形态变化,XY的配对可分为5种类型。对XY短臂之间形成的SC和XY长臂顶端的次级联合以及XY配对的性质和机理作了描述和讨论。本文还报道了一个罕见的三倍体精母细胞,对三倍体精母细胞中SC的配对行为以及和人类染色体疾病病因的可能关系作了分析和讨论。     

玉米联会复合体的电镜观察

以改进的去污剂微铺展技术制备玉米联会复合体标本,硝酸银染色,以光镜和电镜作相继观察。结果表明,三倍体玉米配对时除形成三价体和出现同源转换及双联会复合体外,还出现单价体和非同源配对。本文列出了玉米的SC核型,并对联会复合体侧轴加厚的数目、分布形式作了描述。     

小鼠富集着丝粒DNA在小鼠减数分裂粗线期染色体上的原位杂交

本工作用Hoechst 33258及着丝粒特异抗体间接免疫荧光法显示的小鼠粗线期染色体主缢痕区,与以小鼠富集着丝粒(SFA)DNA为探针在粗线期染色体上的原位杂交主缢痕区作了比较。发现SFA DNA探针不仅杂交于全部常染色体联会复合体上的着丝粒区,并且杂交于着丝粒周围的异染色质区;而且,也杂交于X,Y染色体的着丝粒区。由此结论:此富集SFA DNA中含有全套常染色体及X,Y染色体的SFA DNA。     

中华鳖精母细胞联会复合体的研究

本文以微铺展技术制备中华鳖精母细胞联会复合体标本,经硝酸银染色后电镜观察,分析了SC组型。并与有丝分裂染色体组型相比较,发现二者有着良好的一致性,而且微小染色体的SC结构和着丝粒清晰,未发现形态上有分化的性染色体。中华鳖SC的研究为其细胞遗传学及性别决定机制提供了重要的依据。 Abstract　Synaptonemal Complexes (SC) in Trionyx sinensis spermatocytes prepared with micro-spreading technique and silver staining was analyzed by electron microscopy. The meiotic SC karyotype was constructed from 10 cells and compared with mitotic chromosome karyotype. There is a good agreement between them. The structure and kinetochores of micro-chromosomes are very distinctive on each SC. There does not exist differential sex chromosome.     

Spontaneous contractions in elasmobranch vessels in vitro

Isolated vessels from four elasmobranchs, yellow stingray (Urolophus jamaicensis), clearnose skate (Raja eglanteria), ghost shark (Hydrolagus novaezelandiae), and spiny dogfish (Squalus acanthias), were examined for the presence of spontaneous contractions (SC). SC were observed in otherwise unstimulated dorsal aortas (DA) from stingray and ghost shark, but not in skate DA. Unstimulated ventral aortas (VA) did not exhibit SC. After treatment of VA with a contractile agonist, SC appeared in stingray and skate but not ghost shark or dogfish. SC in stingray VA were subsequently inhibited by either epinephrine (10(-5) M) or indomethacin (10(-4) M). Agonist contraction also elicited strong SC in ductus Cuvier from stingray, but not from ghost shark or dogfish. SC in dogfish hepatic portal veins (HPV) produced a rhythmical oscillation in tension. The frequency of HPV SC was highest (approximately 1 min(-1)) in intact veins and lower (approximately 3 min(-1)) in vein segments, indicative of a dominant pacemaker in the intact vessel. SC in HPV were depressed during the first 30 min of hypoxia, but there was substantial recovery over an additional 30 min of hypoxia and complete recovery upon return to normoxia. Addition of 80 mM KCl completely inhibited HPV SC and lowered resting tone. These results show that SC are a common feature of elasmobranch vessels and there appears to be a correlation between swimming behavior and the propensity for SC. KCl inhibition of SC and tonus in HPV is highly unusual for vascular smooth muscle.     

Discontinuities and unsynapsed regions in meiotic chromosomes have a trans effect on meiotic recombination of some chromosomes in human males

During meiosis, homologous chromosome pairing and synapsis are essential for subsequent meiotic recombination (crossing-over). Discontinuous regions (gaps) and unsynapsed regions (splits) were most frequently observed in the heterochromatic regions of bivalent synaptonemal complex (SC) 9, and we have previously demonstrated that gaps and splits significantly altered the distribution of MLH1 recombination foci on SC 9. Here, immunofluorescence techniques (using antibodies against SC proteins and the crossover-associated MLH1 protein) were combined with a centromere-specific fluorescence in situ hybridization technique that allows identification of every individual chromosome. The effect of gaps/splits on meiotic recombination patterns in autosomes other than chromosome 9 during the pachytene stage of meiotic prophase was then examined in 6,026 bivalents from 262 pachytene cells from three human males. In 64 analyzed cells with a gapped SC 9, the frequency of MLH1 foci in SCs 5 and 10 and in SC arms 10q, 11p and 16q was decreased compared to 168 analyzed cells with a normally-synapsed SC 9 (controls). In 24 analyzed cells with splits in SC 9, there was a significant reduction in MLH1 focus frequency for SC 5q and the whole SC5 bivalent. The positioning of MLH1 foci on other SCs in cells with gapped/split SC 9 was not altered. These studies suggest that gaps and splits not only have a cis effect, but may also have a trans effect on meiotic recombination in humans.     

Synaptonemal complex damage in relation to meiotic chromosome aberrations after exposure of male mice to cyclophosphamide

The genetic implications of induced synaptonemal complex (SC) damage are not known. However, on theoretical grounds, such aberrations could be involved in mechanisms leading to potentially heritable defects. Cyclophosphamide (CP), a chemical reported to cause structural and numerical chromosomal aberrations in the mouse, was used to determine if SC damage observed in meiotic prophase is related to subsequent metaphase chromosomal aberrations. Male mice were injected i.p. with CP. In some instances, mice were also injected simultaneously with tritiated thymidine to label DNA so that cells could be tracked autoradiographically through spermatogenesis. Prophase, primary metaphase (M1), and secondary metaphase (M2) samples were sequentially harvested at appropriate times from the same individual, and nuclei were examined for aberrations. Correlation coefficients between SC and metaphase chromosome aberrations were calculated. The inclusion of tritium labeling increased the number and significance of positive correlations. Positive correlations were found between (1) dose-dependent total SC damage and damage to M1, and to a lesser extent, M2 chromosomes; (2) SC breaks/fragments and M1 chains/rings as well as isochromatid breaks/fragments; (3) SC asynapsis and M1 chromatid breaks/fragments; (4) SC multi-axial configurations and M1 chains/rings as well as isochromatid and chromatid breaks/fragments; and (5) SC multi-axial configurations and M2 hyperploidy. These correlations do not define mechanistic or causal relationships between SC and chromosomal damage. However, taken together with the observation that induced SC damage is many times greater than ensuing metaphase chromosome damage, they substantiate SC analysis as a highly sensitive indicator of potentially heritable effects of this (and presumably other) genotoxic agents.     

Evaluation of four mathematical functions to describe scrotal circumference maturation in Nellore bulls

Four functions to characterize scrotal circumference (SC) growth in Nellore bulls were compared to identify which was the most suitable for biological interpretation. Nellore bulls (n = 532), born between September and December of 1992 to 1994 were used in the study. Measurements were made on fixed dates in January, April, July and October of each year. At the time of SC measurements, the ages of the bulls ranged from 200 to 1300 d. The functions used to describe the data were: Brody, SC = A (1 - B exp -kt); Logistic, SC = A/(1 + B exp -kt); Gompertz, SC = A exp(-B exp -kt) and Richards SC = A (1 + B exp -kt)m, where SC is the scrotal circumference at t days of age, A is the estimated SC at maturity, B is the integration constant established by the initial values of SC and t, k is the maturity constant, which equals the ratio between the maximum rate of growth and SC at maturity; m is the inflection point parameter for Richards function, which did not converge. The Brody, Gompertz and Logistic functions fitted the data in a similar fashion, with similar values for the statistics EMS and R2, and they reached convergence with similar computational costs. The Logistic function presented the best pattern of average prediction error, and therefore, it was selected for biological interpretation. For the Logistic function, estimated SC at maturity (A) was 37.95 cm at 72 mo of age. The maturity index (k) was .11 cm, and the inflection point (time of maximum growth) was reached at 13.09 mo of age at an average SC of 18.97 cm.     

Enantiomeric degradation of 2-(4-Sulfophenyl)Butyrate via 4-sulfocatechol in Delftia acidovorans SPB1

Enrichment cultures with enantiomeric 2-(4-sulfophenyl)butyrate (SPB) as the sole added source(s) of carbon and energy for growth yielded a pure culture of a degradative bacterium, which was identified as Delftia acidovorans SPB1. The organism utilized the enantiomers sequentially. R-SPB was utilized first (specific growth rate [mu] = 0.28 h(-1)), with transient excretion of an unknown intermediate, which was identified as 4-sulfocatechol (4SC). Utilization of S-SPB was slower (mu = 0.016 h(-1)) and was initiated only after the first enantiomer was exhausted. Suspensions of cells grown in S-SPB excreted 4SC, so metabolism of the two enantiomers converged at 4SC. The latter was degraded by ortho cleavage via 3-sulfo-cis,cis-muconate. Strain SPB1 grew with 4SC and with 1-(4-sulfophenyl)octane (referred to herein as model LAS) but not with commercial linear alkylbenzenesulfonate (LAS) surfactant, which is subterminally substituted but nontoxic. It would appear that metabolism of the model LAS does not represent metabolism of commercial LAS.     

Extracellular matrix protein SC1/hevin in the hippocampus following pilocarpine-induced status epilepticus

Pilocarpine-induced status epilepticus (SE) mimics many features of temporal lobe epilepsy and is a useful model to study neural changes that result from prolonged seizure activity. In this study, distribution of the anti-adhesive extracellular matrix protein SC1 was examined in the rat hippocampus following SE. Western blotting showed decreased levels of SC1 protein in the week following SE. Immunohistochemistry demonstrated that the decrease in overall SC1 protein levels was reflected by a reduction of SC1 signal in granule cells of the dentate gyrus. Interestingly, levels of SC1 protein in neurons of the seizure-resistant CA2 sector of the hippocampus did not change throughout the seizure time course. However, at 1 day post-SE, a subset of neurons of the hippocampal CA1, CA3, and hilar regions, which are noted for extensive neuronal degeneration after SE, exhibited a transient increase in SC1 signal. Neurons exhibiting enhanced SC1 signal were not detected at 7 days post-SE. The cellular stress response was also examined. A prominent induction of heat-shock protein (Hsp70) and Hsp27 was detected following SE, while levels of constitutively expressed Hsp40, Hsp90, Hsp110, and Hsc70 showed little change at the time points examined. The subset of neurons that demonstrated a transient increase in SC1 colocalized with the cellular stress marker Hsp70, the degeneration marker Fluoro-Jade B, and the neuron activity marker activity-regulated cytoskeleton-associated protein (Arc). Taken together, these findings suggest that SC1 may be a component of the 'matrix response' involved in remodeling events associated with neuronal degeneration following neural injury.     

Analysis of various types of competition in Tn5-mutants of alfalfa rhizobium bacteria (Sinorhizobium meliloti)]

Nodulation, rhizospheral, and saprophytic types of competitiveness (NC, RC, and SC, respectively) were studied in the highly active strains CXM1-105 and CXM1-188 of the alfalfa rhizobium Sinorhizobium meliloti. The competitiveness was estimated with the use of markers of antibiotic resistance. It was found that the mutant strain T37, which was characterized by a drastically decreased NC, had higher SC and RC than the parental strain. The mutant T107 (with a moderately decreased NC) did not differ from the parental strain with respect to RC but had a higher SC. The mutant T27 (with the lowest NC) did not differ from the parental strain with respect to SC or RC. In the mutant Tb1, the NC and RC were decreased and the SC was the same as in the parental strain. In Tb7, the SC was decreased and RC was increased. In the mutant T795, all of the three types of competitiveness were decreased. The difference between the mutants studied and the parental strain with respect to NC and RC was confirmed using an indirect method (the ability to form effective symbiosis after mixed inoculation together with the an ineffective tester strain CXM1-48) and the X-Gluc staining method (using the S. meliloti RmM4gus tester strain carrying the gene of beta-glucuronidase). However, the decreased SC that the mutants exhibited when they were cultivated together with parental strains in a plant-growth substrate (vermiculite) was not observed in the case of their cocultivation in liquid media. The independent variation of different types of competitiveness indicate that rhizobia have several separate gene systems determining their survival in in planta and ex planta ecological niches.