Examination of Genetic Relatedness of Marine Synechococcus spp. by Using Restriction Fragment Length Polymorphisms

The relatedness of several marine Synechococcus spp. was estimated by DNA hybridization. Strains isolated from various geographical locations and representing a diversity of DNA base compositions and phycobiliprotein profiles were compared by restriction fragment length polymorphisms for a number of genes. DNAs from two marine red algae and a cryptomonad alga (which exhibit a phycobiliprotein composition similar to that of the marine Synechococcus spp.) and Synechococcus strain PCC6301 (Anacystis nidulans) were also included in the comparison. Strains WH8008, WH8018, and WH7805 were shown to be very similar to one another, as were strains WH7802 and WH7803. Strains WH8110 and WH5701 were clearly unrelated to any of the other strains, and no marine Synechococcus isolate showed any similarity to the freshwater Synechococcus strain PCC6301 or the eucaryotic algae. The method is relatively straightforward and sensitive and uses a variety of basic molecular biology techniques. Its utility in ascertaining the genetic relatedness and diversity of marine Synechococcus spp. and possible extension to field studies are discussed.     

The genetics and expression of an esterase locus inAnopheles gambiae

The main polymorphic system of esterase isoenzymes in adults of the G3 laboratory strain ofAnopheles gambiae consists of two to five major bands of activity per individual. The bands are designated 5S, 5F, 13, 14, and 15. In genetic crosses, the genes which coded for the bands assorted as three codominant alleles, Est A, Est B, and Est C, at a single autosomal locus. Homozygotes for the Est C allele were significantly underrepresented among backcross progeny. The developmental pattern of esterase expression was examined. Esterase gene expression in embryos was first detectable between 2 and 12 hr after oviposition. The initiation or termination of expression of some of the bands corresponded to boundaries between developmental stages. Most of the esterase fractions were not specifically localized within the tissues tested, with the exception of a series of bands which were restricted largely to adult male testes.     

Cementum annulation and age determination in Homo sapiens. II. Estimates and accuracy

The cementum annulation aging technique was evaluated in a sample of 80 clinically extracted premolars (age range 11–70 years). Demineralized thin sections (7μm) stained with hematoxylin were used. The correlation (r) between age and adjusted count (number of annulations added to age of tooth eruption) was 0.78 for the entire sample (N = 73) and 0.86 for a subsample in which teeth with periodontal disease were excluded (N = 55). Standard error of the estimates ranged from 4.7 to 9.7 years depending on sex and health status of the tooth. The technique provided significantly better estimates for females than for males. The overall inaccuracy (mean absolute error) of the technique was 6.0 years, with a bias (mean error) of 0.26 years. Reduced major axis regression of adjusted count on age produced a slope of 0.797 for the entire sample and 0.889 for the nonperiodontal disease subsample. These slopes are consistent with a hypothesis of annual deposition of cementum rings given a decrease in cementogenesis with increasing age.     

The cylindrical or tubiliform glands of Nephila clavipes

The cylindrical or tubiliform glands of the spider Nephila clavipes have been studied and compared to the large ampullates on which we have previously reported. The three pairs of cylindrical or tubiliform glands secrete the fibroin for the organism's egg case. Their solubilized luminar contents migrate as a homogeneous band in Sodium dodecyl sulfate polyacrylamide gel electrophoresis and turn out to be a larger protein than that produced by the large ampullates. The excised cylindrical glands remain metabolically active for several hours in a simple culture medium, where fibroin synthesis can be monitored through the incorporation of 14C alanine. The glands' response to a fibroin production stimulus does not reach the magnitude displayed by the large ampullates, but this is to be expected since their products supply different functions in this organism. This fibroin also seems to be elongated discontinuously. Translational pauses have been detected in the secretory epithelium of cylindrical and large ampullate glands of Nephila as well as in the silk glands of Bombyx mori. Since these glands produce the fibroin for the females egg case, they should prove to be an interesting model system.     

Mannitol metabolism in cultured plant cells

Non-structural storage carbohydrates were measured in 9-day-old barley ( Hordeum vulgare L. cv. Brant) primary leaves. Accumulation rates of starch, sucrose and total non-structural carbohydrates (TNC) were approximately linear when measured between 2- and 12-h of light. Progressively higher TNC accumulation rates were observed at higher irradiance levels (i.e., comparing 250, 550 and 1050 ·mol m⁻² s⁻¹). Synthesis of a low-molecular-weight fructan also was enhanced by high irradiances. Low irradiance treatments decreased leaf sucrose levels and there was a corresponding increase in the lag period preceding starch synthesis in the light. Increased starch accumulation rates were usually observed when sucrose concentrations were high. These and other results suggested that cytosolic sucrose concentrations affected starch metabolism in the chloroplast. However, sucrose accumulation rates increased and starch storage decreased when barley seedlings were transferred from 20 to 10°C during the light period. Lowering the night temperature from 20 to 10°C for a single dark period 8-days after planting increased the TNC content of barley primary leaves at the beginning of day nine. In this experiment, TNC accumulation rates of treated and untreated leaves were similar. Changes in the accumulation rate of TNC were usually observed within 2- to 4-h after barley seedlings were exposed to altered environmental conditions. Monitoring rapid changes in leaf carbohydrate levels is a sensitive method for assessing the effects of environmental treatments on photosynthetic metabolism.     

The amino terminus of the yeast F1-ATPase beta-subunit precursor functions as a mitochondrial import signal

The ATP2 gene of Saccharomyces cerevisiae codes for the cytoplasmically synthesized beta-subunit protein of the mitochondrial F1-ATPase. To define the amino acid sequence determinants necessary for the in vivo targeting and import of this protein into mitochondria, we have constructed gene fusions between the ATP2 gene and either the Escherichia coli lacZ gene or the S. cerevisiae SUC2 gene (which codes for invertase). The ATP2-lacZ and ATP2-SUC2 gene fusions code for hybrid proteins that are efficiently targeted to yeast mitochondria in vivo. The mitochondrially associated hybrid proteins fractionate with the inner mitochondrial membrane and are resistant to proteinase digestion in the isolated organelle. Results obtained with the gene fusions and with targeting-defective ATP2 deletion mutants provide evidence that the amino-terminal 27 amino acids of the beta-subunit protein precursor are sufficient to direct both specific sorting of this protein to yeast mitochondria and its import into the organelle. Also, we have observed that certain of the mitochondrially associated Atp2-LacZ and Atp2-Suc2 hybrid proteins confer a novel respiration-defective phenotype to yeast cells.     

G-11 staining in Turner's syndrome with mos 45,X/46,X,r(?)

Mos 45,X/46,X,r(?) in 4 patients with Turner's syndrome and no signs of virilization, and in one pair of monozygotic twins, one of them with clitoral hypertrophy, was studied using combined cytogenetic techniques and specially G-11 staining for the characterization of the X or Y origin of the rings. In all 6 patients the ring was G-11 positive, attesting its Y origin. Both twins were operated and bilateral streak gonads with a bilateral nodule of testicular tissue were found. Similar small rings were also studied in one patient with mos 46,XX/46,X,r(X) and in one nonvirilized Turner's syndrome patient with a larger ring; in these two cases the ring was G-11 negative. It seems that the small rings occasionally found in Turner's syndrome are more frequently from Y origin and therefore prophylactic gonadectomy should be considered.     

Uptake of transferrin and iron by cultured rat placental cells

This paper describes a method for the culture of rat placental cells. The method involved separation of the basal layer from the labyrinth and sequential digestion of the cells. The cells were demonstrated not to be fibroblasts and are described in terms of their appearance under the light and electron microscopes. Transferrin and iron uptake by the cells was examined and compared with results achieved using other methods of study. The results showed that transferrin bound to receptors on the cell surface and that the transferrin, once bound, was taken into the cell. Only this internalized transferrin was capable of donating iron to the cells. The iron was accumulated within the cells and did not appear to be released to the incubation medium. The apparent dissociation constant (Ka) for transferrin was found to be 6.96 X 10(6) M-1, a value similar to that described by earlier workers. The placental cells had 3.4 X 10(11) binding sites/microgram DNA, equivalent to approximately 1 X 10(6) sites/cell. From these data, and from the rate of accumulation of iron by the cells, the receptor turnover time was estimated as being between 5 and 10 min.     

Translocation of photoassimilate from leaves of two popyploid genotypes of tall fescue differing in photosynthetic rates

The photosynthetic rate of a decaploid genotype (1-16-2) of tall fescue ( Festuca arundinacea Schreb.) is about twice that of a common hexaploid genotype (V6-802) (Plant Physiol. 72: 16–21, 1983). Translocation of photosynthate out of the leaves is a possible means of regulating carbon assimilation. To evaluate this possibility, we have examined a) translocation velocity, b) time course of translocation from leaves, c) photoassimilate partitioning pattern into whole plants in pulse and chase experiments, and d) interveinal distances between two ploidy genotypes. Most of the ¹⁴C accumulated in sucrose, and the labelled carbon moved down the leaf blades at similar velocities (6 to 10 cm h⁻¹) in both genotypes. Recent ¹⁴C assimilate was rapidly translocated from the fed area of the leaf blade. For example, the decaploid and the common hexaploid had translocated 40 and 26% of the ¹⁴C, respectively, at 6 h, and 79 and 49% of the ¹⁴C, respectively, at 24 h. Partitioning of ¹⁴C among plant organs was considerably different between the genotypes after a 24 h chase. For example, out of the total ¹⁴C recovered from the whole plant, the decaploid had retained 40% in the labelled leaf with 10, 33 and 29% in other leaves, stem bases and roots, respectively; whereas the hexaploid had retained 91% in the labelled leaf with 4, 3 and 2% in other leaves, stem bases and roots, respectively. However, the higher rate of translocation was correlated with greater interveinal distances in the decaploid genotype. These results suggested that the higher translocation percentage in the decaploid than the hexaploid genotype was due to greater sink activity.