The transformation of the synaptonemal complex into the “elimination chromatin” in Bombyx mori oocytes

In Bombyx mori oocytes the synaptonemal complexes are retained in modified form from pachytene to metaphase I. At the end of pachytene the length and width of the lateral components of the complex increase, whereafter the complexes become compacted during later stages of the meiotic prophase. Ultimately, at metaphase I the modified synaptonemal complexes of individual bivalents fuse to form a more or less continuous sheet between the homologous chromosomes. This sheet corresponds to the structure historically known as the elimination chromatin. It is concluded that in the absence of crossing over and chiasma formation in Bombyx mori females the retainment and subsequent modification of the synaptonemal complex has evolved as a substitute mechanism to ensure regular disjunction of the bivalents.     

The possible contribution of electron microscopy to the understanding of the mechanism of non-disjunction in man.

Sprout inhibition of onion bulbs can be effectively accomplished by low doses of radiation [2,3]. However, wholesomeness data on irradiated onions, particularly with respect to their mutagenic activity, are still insufficient for evaluation [6]. Therefore we examined the mutagenic activity of irradiated onions in bacterial systems. Because onion bulbs contain a considerable amount of free amino acids, we used indicator strains carrying the marker for mutagenicity other than the amino acid requirement.In this paper we describe the results on irradiated onions. We used tests with solid and liquid media, assaying for the streptomycin (SM) dependence in a strain having a tetracycline (TC)-resistance factor, as well as DNA repair tests using two sets of indicator strains.     

Tissue analyses guidelines for diagnosing sulfur deficiency in white wheat

Summary Visual identification of S deficiency in white wheat is difficult since deficiency symptoms are nearly identical with those of N deficiency. In this study, S deficiency was best identified by determining the total N/S ratio rather than S concentration in vegetative tissue. Vegetative growth generally decreased from tillering to boot when the whole plant N/S ratio exceeded 17. The N/S ratio in S-sufficient plants declined gradually with age, implying that the critical N/S ratio may decline with advancing growth. Changes in stem: leaf ratio could have been responsible for the decline since the N/S ratio in stem tissue at heading was less than that of green leaf tissue.Sulphur concentration less reliably indicated S-deficiency, because differences in S levels between S-deficient and S-sufficient wheat, were often less than year-to-year variation of S concentration of plants sampled at the same growth stage. In addition, S concentration in whole plants declined sharply between tillering and heading. These factors make it difficult to designate a critical S level. Sulfur distribution among various plant organs suggests that critical S levels might best be obtained by utilizing green leaf tissue.Nitrogen concentration in S-sufficient wheat plants also decreased quite rapidly with growth, which indicates a similar difficulty for determining critical N percentages. Consequently, the most reliable distinction between N and S deficiency in wheat was accomplished by evaluation of the total N/S ratio in whole plant tissue.Contribution from the Agricultural Research Service, USDA, in cooperation with the Agricultural Experiment Station, Oregon State University. Technical Paper No.3953 of the latter.     

Production and partial characterization of monoclonal antibodies specific for the gamonts of Eimeria tenella.

Thirteen hybridomas secreting monoclonal antibodies (Mabs) specific for the sexual stages (gamonts) of Eimeria tenella were produced by fusing spleen cells of gamont-immunized RBF/Dn mice with FOX-NY myeloma cells. A Mab subisotype profile revealed 1 IgG2a and 12 IgG1. All Mabs demonstrated a similar binding pattern when incubated with parasitic gamonts as determined by the indirect fluorescent antibody test. Ascitic fluid containing Mab (GD9 (IgG1) was produced and used to immunize chicks passively per os. There was a 34% decrease (P less than 0.05) in oocyst output from immunized chicks when compared to control chicks. Passively immunized chicks also had reduced cecal lesion scores when compared to control chicks. These results suggest that Mab GD9 partially inhibited the fertilization process of E. tenella.     

Coordinate Regulation of the Cyclic AMP System with Firing Rate and Expression of Tyrosine Hydroxylase in the Rat Locus Coeruleus: Effects of Chronic Stress and Drug Treatments

Recent studies have demonstrated that chronic stress increases the firing rate and expression of tyrosine hydroxylase (TH) in neurons of the locus coeruleus (LC), the major noradrenergic nucleus in brain. The present study was undertaken to examine the influence of chronic stress and other treatments known to influence the activity of LC neurons on the cyclic AMP (cAMP) second messenger system in these neurons. Chronic (5 days) cold exposure significantly increased levels of TH immunoreactivity in the LC, as previously reported, but not in substantia nigra (SN) or ventral tegmentum (VT), two dopaminergic nuclei studied for comparison. Chronic cold exposure increased levels of cAMP-dependent protein kinase activity in soluble, but not particulate, fractions of the LC, and increased basal and GTP- and forskolin-stimulated adenylate cyclase activity in this brain region. In contrast, levels of the protein kinase and adenylate cyclase in VT, SN, and frontal cortex were not significantly influenced by cold exposure. To study further the relationship between regulation of LC firing rate, TH expression, and the cAMP system in the LC, other treatments known to influence TH were examined. Reserpine treatment, shown previously to increase levels of TH, was found to increase both LC firing rate and levels of soluble cAMP-dependent protein kinase activity in the LC. 6-Hydroxydopamine, shown previously to increase levels of TH and firing rate of LC neurons, also increased soluble levels of protein kinase activity. Other treatments known to either increase (adrenalectomy) or decrease (chronic imipramine) levels of TH in the LC were also found to increase or decrease, respectively, levels of cAMP-dependent protein kinase activity in this brain region.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gene flow inferred from seed dispersal and pollinator behaviour compared to DNA analysis of restriction site variation in a patchy population of Lotus corniculatus L.

Summary Gene flow was investigated in a natural population of Lotus corniculatus L. (Fabaceae) using a combination of pollen and seed dispersal studies and a recombinant DNA technique. The population is spatially heterogeneous and grows with Empetrum nigrum. L. corniculatus is pollinated by the pollen-collecting bumblebee Bombus lapidarius L. Most pollinator flights occurred within patches, as bees usually visit nearest-neighbour plants, show no marked directionality, and forage mostly within patches. Gene flow by seeds is also limited, reinforcing the pattern of gene flow within patches. However, 2.6% of pollinator flights are between patches and considerable pollen carryover also occurs. Thus, gene flow between patches is potentially sufficient to retard or prevent genetic differentiation in spite of the patchy sub-structuring of the population. A sub-set of the population was analysed for restriction fragment length polymorphisms (RFLPs) to document the actual gene flow pattern of the population. The DNA analysis revealed significant levels of genetic differentiation between the patches. The level of gene flow that can be inferred from the distribution of genetic variation is surprisingly restricted, as compared to gene flow inferred from pollinator behaviour, and emphasizes that stochastic processes like genetic drift and founder effects may have a strong impact on the prevailing genetic structure.     

Studies of the Ca2+ transport mechanism of human erythrocyte inside-out plasma membrane vesicles. I. Regulation of the Ca2+ pump by calmodulin

Calcium accumulation by human erythrocyte inside-out vesicles was linear for at least 30 min in the presence of ATP. In untreated inside-out vesicles, 3.76 +/- 1.44 nmol of calcium/min/unit of acetylcholinesterase were transported, compared with 10.57 +/- 2.05 (+/- S.D.; n = 11) in those treated with calmodulin. The amount of calmodulin necessary for 50% activation of Ca2+ accumulation was 60 +/- 22 ng/ml (+/- S.D.; n = 4). The Km (Ca2+) for calmodulin-stimulated accumulation was 0.8 +/- 0.05 microM (+/- S.D.; n = 5) using Ca2+ /ethylene glycol bis(beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA) buffers, or 25 microM with direct addition of unbuffered calcium. In the absence of calmodulin, these values were 0.4 and 60 microM, respectively, Km (ATP) values of 90 and 60 microM in the presence and absence of calmodulin, respectively, were measured at constant magnesium concentration (3 mM). In the presence of calmodulin, a broad pH profile is exhibited from pH 6.6 to 8.2. Maximal calcium accumulation occurs at pH 7.8. In the absence of calmodulin, the pH profile exhibits a linear upward increase from pH 7.0 to 8.2. The (Ca2+-Mg2+)-ATPase activity, measured under identical conditions, was 2.40 +/- 0.72 nmol of Pi/min/unit of acetylcholinesterase in the untreated vesicles and 11.29 +/- 2.87 nmol of Pi/min/unit of acetylcholinesterase (+/- S.D.; n = 4) in calmodulin-treated vesicles. A stoichiometry of 1.6 Ca2+/ATP hydrolyzed was determined in the absence of calmodulin; in the presence of calmodulin, this ratio was decreased to 0.94 Ca2+/ATP hydrolyzed.     

Hyperbaric oxygen toxicity and ribosome destruction in Escherichia coli K12

The viability of resting suspensions of Escherichia coli K12 Ymel exposed to air plus 300 psi (1 psi = 6.895 kPa) oxygen (hyperbaric oxygen) decreased as an apparent first-order process after an initial period of constant viability. Control suspensions exposed to air plus 300 psi nitrogen (hyperbaric nitrogen) did not lose viability over the 96 h of the experiment. It was observed that a decrease in the refractive index of the cells preceded the loss of viability in hyperbaric oxygen. This finding together with electron micrographs, which showed extensive loss of ribosomal particles in bacteria incubated in hyperbaric oxygen, led us to suspect that ribosome injury or disassociation might be important in hyperbaric oxygen toxicity. In support of this we found that cellular RNA, labeled with [5-3H]uridine, was much more rapidly and more completely degraded in hyperbaric oxygen than in hyperbaric nitrogen. Furthermore, a far greater proportion of RNA was degraded than was DNA or protein. A direct assay for ribosome particles by sucrose gradient centrifugation showed that only 34% of the 70S ribosome particles was lost during the first 24 h in hyperbaric nitrogen whereas in hyperbaric oxygen 99.6% of the 70S particles was degraded during the same period. In hyperbaric oxygen the rate of viability loss between 24 and 72 h was equal to the rate of 70S ribosome degradation during the first 24 h. If 70S ribosome disassociation in hyperbaric oxygen continues at the same rate after first 24 h, then cumulative 70S ribosome disassociation or injury may lead to and provide an explanation for irreversible bacterial cell injury and the loss of viability.     

Deletion - translocation del (12) (p11) leads to (t10;12) (p13;pII).

Renewed examinatinon with improved banding techniques of a boy previously reported to have the karyotype 46, XY,del(12)(p11) revealed a translocation 46, XY,t(10;12)(p13;p11), and reexamination of a boy previously reported to have the karyotype 46,XY/46,XY,del(5)(p13) showed the same mosaicism, but with a significantly lower frequency of cells with del(5)(p13), 8% compared with 23% at the time of birth. The decrease of the frequency of cells with chromosome abnormality in mixoploids during the first years of life as found in the present case as well as in prevously reported cases is discussed.     

Effects of inhibitors of protein and RNA synthesis on aldosterone-stimulated changes in phospholipid fatty acid metabolism in the toad urinary bladder.

The effects of an inhibitor of RNA synthesis, cordycepin, and an inhibitor of protein synthesis, cycloheximide, on aldosterone-induced changes in lipid metabolism and phospholipid fatty acid composition have been studied in the toad urinary bladder. At the concentrations employed, the inhibitors abolish the hormone-induced increases in total lipid synthesis, phospholipid fatty acid specific activities, and weight percentage of phospholipid long-chain polyunsaturated fatty acids as well as blocking the aldosterone-mediated increase in sodium transport.