Subcellular distribution of hydrolase in germinating pea cotyledons

The subcellular distribution of hydrolases in germinating peacotyledons was investigated by differential and sucrose densitygradient centrifugations. Acid phosphatase was present in atleast two kinds of subcellular components. One was slightlyheavier than mitochondria, and the other was so light that itremained on the upper part of the gradient after sucrose densitygradient centrifugation. Protease was localized in the smooth-surfacedmicrosomal fraction which contained antimycin A-insensitiveNADH₂-cytochrome c reductase and no RNA. Aryl esterase existedin a soluble form in the cytoplasm. (Received July 22, 1971; )     

Statistical properties of the ordinary least-squares,generalized least-squares,and minimum-evolution methods of phylogenetic inference

Summary Statistical properties of the ordinary least-squares (OLS), generalized least-squares (GLS), and minimum-evolution (ME) methods of phylogenetic inference were studied by considering the case of four DNA sequences. Analytical study has shown that all three methods are statistically consistent in the sense that as the number of nucleotides examined (m) increases they tend to choose the true tree as long as the evolutionary distances used are unbiased. When evolutionary distances (d_ij's) are large and sequences under study are not very long, however, the OLS criterion is often biased and may choose an incorrect tree more often than expected under random choice. It is also shown that the variance-covariance matrix of d_ij's becomes singular as d_ij's approach zero and thus the GLS may not be applicable when d_ij's are small. The ME method suffers from neither of these problems, and the ME criterion is statistically unbiased. Computer simulation has shown that the ME method is more efficient in obtaining the true tree than the OLS and GLS methods and that the OLS is more efficient than the GLS when d_ij's are small, but otherwise the GLS is more efficient.Offprint requests to: M. Nei     

Control of angiotensinogen production by H4 rat hepatoma cells in serum-free culture

Summary A serum-free, hormone and attachment factor supplemented culture for rat H4 hepatoma cells was established. In the defined medium (Dulbecco's Modified Eagle's +Ham's F12+insulin, transferrin, fibronectin liver cell growth factor, and sodium selenite), H4 cells grew equally well as in 10% fetal bovine serum supplemented medium. H4 cells in either defined or serum-containing culture conditions produce transferrin but not albumin or alpha-fetoprotein. In this paper we have studied the effect of various hormones and pressor peptides on the production of angiotensinogen by H4 cells cultured in defined conditions. Only glucocorticoid hormone had a significant effect on the production of angiotensinogen, whereas other hormones previously reported to exert their effect on angiotensinogen production had little or no effect. This work was supported by grant P01 CA37589 from the National Institutes of Health, Bethesda, MD.     

Amyloid β-Mediated Zn2+ Influx into Dentate Granule Cells Transiently Induces a Short-Term Cognitive Deficit

We examined an idea that short-term cognition is transiently affected by a state of confusion in Zn²⁺ transport system due to a local increase in amyloid-β (Aβ) concentration. A single injection of Aβ (25 pmol) into the dentate gyrus affected dentate gyrus long-term potentiation (LTP) 1 h after the injection, but not 4 h after the injection. Simultaneously, 1-h memory of object recognition was affected when the training was performed 1 h after the injection, but not 4 h after the injection. Aβ-mediated impairments of LTP and memory were rescued in the presence of zinc chelators, suggesting that Zn²⁺ is involved in Aβ action. When Aβ was injected into the dentate gyrus, intracellular Zn²⁺ levels were increased only in the injected area in the dentate gyrus, suggesting that Aβ induces the influx of Zn²⁺ into cells in the injected area. When Aβ was added to hippocampal slices, Aβ did not increase intracellular Zn²⁺ levels in the dentate granule cell layer in ACSF without Zn²⁺, but in ACSF containing Zn²⁺. The increase in intracellular Zn²⁺ levels was inhibited in the presence of CaEDTA, an extracellular zinc chelator, but not in the presence of CNQX, an AMPA receptor antagonist. The present study indicates that Aβ-mediated Zn²⁺ influx into dentate granule cells, which may occur without AMPA receptor activation, transiently induces a short-term cognitive deficit. Extracellular Zn²⁺ may play a key role for transiently Aβ-induced cognition deficits.     

Purification of a fibrolast-inhibitory factor from Actinobacillus actinomycetemcomitans Y4

Abstract A factor showing inhibitory activity against human gingival fibrolasts was extracted from the cytosol fraction of Actinobacillus actinomycetemcomitans Y4. The activity markedly inhibited the proliferation of human gingival fibrolasts, but had no effect on cell viability or gross morphology. No such activity was found in cytosol fractions from either Porphyromonas gingivalis 381 or Escherichia coli HB101. The extract from A. actinomycetemcomitans Y4 was then purified by anion-exchange chromatography, hydroxyapatite chromatography and gel-filtration chromatography to give a single band on SDS-PAGE with an apparent molecular mass of 65 kDa. The purification ratio was 183-fold with a recovery rate of 5% compared with the crude extract (starting material) when the activity was assessed by direct cell counts.     

Biochemical Study on the Critical Period for Treatment of the Mottled Brindled Mouse

Hemizygous mottled brindled mice (Mobr/y mice) were treated by subcutaneous injection of copper and were decapitated on postnatal day 14. Cytochrome c oxidase (COX) activity of the brain mitochondria in the mice given 10 micrograms of copper/g on day 4 or 7 showed significant increases compared with that of untreated Mobr/y animals, and these mice had no neurological symptoms. Mice given 10 micrograms of copper/g on day 12 showed neither increases in COX activity nor clinical improvement. The brain levels of copper, noradrenaline, and dopamine in the mice treated on day 12 were the same as those in animals treated on day 4 or 7. The in vitro activities of dopamine-beta-hydroxylase of the brain were also the same among the treated mice, irrespective of the date of treatment. The results indicate that delays in copper treatment produce irreversible changes in COX activity of the brain and lead to clinical unresponsiveness to treatment.     

Development of skill of children in the performance of the family computer game "Super Mario Brothers".

The development of skill of children in the performance of a family computer game (Super Mario Brothers) was investigated among three groups of different age: kindergarten children (6 years old) and primary school children (9 and 12 years old). The skill to perform the game with either hand was evaluated by the mean scores gained by the children. In the normal (right and dominant) situation, the mean score improved significantly with advancement of age. Similar was true in the reversed (left hand dominant) situation, but more distinctly. The mean scores were significantly higher in the normal than in the reversed situations. The experienced children were superior to the inexperienced children in playing the game. The correlation between the reaction time and the game score was also investigated with the same subjects for the 9- and 12-year-old school children. Almost no correlation could be elucidated.     

The bacterial cell division protein FtsZ forms rings in swarmer cells of Proteus mirabilis

Bacterial FtsZ assembles and constricts after chromosomal segregation in the course of cell division. Here we examined the localization of FtsZ in multinucleated swarmer cells of Proteus mirabilis by immunostaining. FtsZ was found to localize to the point of karyomitosis in swarmer cells of P. mirabilis, which is equivalent to filamentous mutants of Escherichia coli defective in the ftsI or ftsQ genes that are involved in later steps of cell division. Thus our findings suggest that the appearance of swarmer cells results from cellular functions immediately after FtsZ assembly.