THE ACTIVATION OF STARFISH EGGS BY ACIDS : II. THE ACTION OF SUBSTITUTED BENZOIC ACIDS AND OF BENZOIC AND SALICYLIC ACIDS AS INFLUENCED BY THEIR SALTS.

1. Comparison of the rates of activation of unfertilized starfish eggs in pure solutions of a variety of parthenogenetically effective organic acids (fatty acids, carbonic acid, benzoic and salicylic acids, chloro- and nitrobenzoic acids) shows that solutions which activate the eggs at the same rate, although widely different in molecular concentration, tend to be closely similar in C_H. The dissociation constants of these acids range from 3.2 x 10^–7 to 1.32 x 10^–3. 2. In the case of each of the fourteen acids showing parthenogenetic action the rate of activation (within the favorable range of concentration) proved nearly proportional to the concentration of acid. The estimated C_H of solutions exhibiting an optimum action with exposures of 10 minutes (at 20°) lay typically between 1.1 x 10^–4 M and 2.1 x 10^–4 M (pH = 3.7–3.96), and in most cases between 1.6 x 10^–4 M and 2.1 x 10^–4 M (pH = 3.7–3.8). Formic acid (C_H = 4.2 x 10^–4 M) and o-chlorobenzoic acid (C_H = 3.5 x 10^–4 M) are exceptions; o-nitrobenzoic acid is ineffective, apparently because of slow penetration. 3. Activation is not dependent on the penetration of H ions into the egg from without, as is shown by the effects following the addition of its Na salt to the solution of the activating acid (acetic, benzoic, salicylic). The rate of activation is increased by such addition, to a degree indicating that the parthenogenetically effective component of the external solution is the undissociated free acid. Apparently the undissociated molecules alone penetrate the egg freely. It is assumed that, having penetrated, they dissociate in the interior of the egg, furnishing there the H ions which effect activation. 4. Attention is drawn to certain parallels between the physiological conditions controlling activation in the starfish egg and in the vertebrate respiratory center.     

几种游蛇的Cyt b基因片段序列分析及其演化关系

分别从蛇类药材和冷冻保存的新鲜蛇类肌肉标本中提取DNA,经PCR扩增出12种蛇共25个样品的Cyt b基因片段,并用银染测序的方法对DNA序列进行了分析.在此基础上用MEGA软件重建的系统发生树表明,研究的11种游蛇科蛇类可以分为3组:第一组为赤链蛇和水赤链游蛇,第二组为乌梢蛇和灰鼠蛇,第三组为锦蛇属的蛇,它们与第二组较近.锦蛇属是一高度分化的属,该组至少可分为两类,一类包括百花锦蛇和黑眉锦蛇;另一类包括玉斑锦蛇、棕黑锦蛇、红点锦蛇、王锦蛇和双斑锦蛇.后一类还可进一步分为3个亚组,玉斑锦蛇和棕黑锦蛇为第一亚组,红点锦蛇单独为第二亚组,王锦蛇和双斑锦蛇为第三亚组.本研究结果还表明,多年保存的陈旧药材标本可以用DNA序列分析的方法对其进行分子系统演化关系的研究.     

STAGES IN THE ORIGIN OF VERTEBRATES: ANALYSIS BY MEANS OF SCENARIOS

Vertebrates lack an epidermal nerve plexus. This feature is common to many invertebrates from which vertebrates differ by an extensive set of shared-derived characters (synapomorphies) derived from the neural crest and epidermal neurogenic placodes. Hence, the hypothesis that the developmental precursor of the epidermal nerve plexus may be homologous to the neural crest and epidermal neurogenic placodes. This account attempts to generate a nested set of scenarios for the prevertebrate-vertebrate transition, associating a presumed sequence of behavioural and environmental changes with the observed phenotypic ones. Toward this end, it integrates morphological, developmental, functional (physiological/behavioural) and some ecological data, as many phenotypic shifts apparently involved associated transitions in several aspects of the animals. The scenarios deal with the origin of embryonic and adult tissues and such major organs as the notochord, the CNS, grills and kidneys and propose a sequence of associated changes. Alternative scenarios are stated as the evidence often remains insufficient for decision. The analysis points to gaps in comprehension of the biology of the animals and therefore suggests further research.     

MODES OF FORMATION OF PHOSPHATE COMPOUNDS AND THEIR TURNOVER IN CHLORELLA CELLS DURING THE PROCESS OF LIFE CYCLE AS STUDIED BY THE TECHNIQUE OF SYNCHRONOUS CULTURE

1. Starting with uniformly ³²P-labeled Chlorella cells, a synchronousculture was run in a medium containing non-labeled phosphate.During the synchronous growth and division of the algal cells,the changes in amount of total and labeled P in various phosphatecompounds were followed.
2. Characteristic changes were observedwith (acid-soluble) polyphosphate"A", nucleotidic labile phosphates,(acid-insoluble) polyphosphate"C", DNA-P and protein-P. Thelabeled phosphorus of polyphosphate"C" showed a decrease duringthe earlier phase of experiment,although a considerable uptakeof non-labeled P from the culturemedium into this compoundwas observed throughout the experiment.In parallel with theloss of labeled phosphorus in this compound,the increase oflabeled phosphorus occurred in polyphosphate"A", in the nucleotidiclabile-P compounds, and in DNA, suggestingthat these substancesreceived P from polyphosphate "C". Thelabeled P in polyphosphate"A" and in the nucleotidic labile-Pcompounds increased graduallywith the progress of culture,attained their maximum levelsat the stage of ripening, anddecreased markedly during theprocess of "post-ripening" anddivision of cells, indicatingthat these compounds were in activeturnover and playing someimportant roles in the process ofcell maturation and division.
3. The total amounts of inorganic P, RNA-P and lipid-P increasedcontinuously throughout the experiment and showed no significantchange in the content of labeled P.

(Received June 5, 1961; )