Temperature control of initiation of protein synthesis in Escherichia coli

When an exponentially growing culture of Escherichia coli is cooled to below 8 °C, initiation of protein synthesis appears to be blocked, while the elongation of initiated proteins continues until they are completed. This is demonstrated here by showing that nascent polypeptide chains increase in size during a 5 °C incubation and that f2 viral coat protein is completed, but not initiated. Upon rewarming, the cells initiate protein synthesis synchronously. This is demonstrated by a transient rise in the incorporation of methionine which is used to initiate protein synthesis.     

Quantum theory of nerve excitation

Based on quantum transitions of membrane dipoles, the four fundamental properties of nerve impulse are derived in this paper: the all-or-none response, the strength-duration relation, refractoriness and refractory period and frequency modulation. Furthermore, the theory offers a physical mechanism for nerve excitation similar to a two-level ammonia maser. It also implies non-threshold excitation at elevated temperatures. The role of trimethylamine ions near the surface of a phospholipid membrane is briefly discussed to indicate a possible connection between theory and reality.     

Genetic Recombination in Coprinus. IV. a Kinetic Study of the Temperature Effect on Recombination Frequency

At the restrictive conditions (35 degrees under continuous light) Coprinus lagopus is unable to initiate premeiotic S phase which takes place normally within 8-10 h of karyogamy. A shift-up to the restrictive conditions causes an arrest of the basidiocarps at this critical stage. A prolonged arrest causes a reversal to mitosis (Lu 1974b). Incubation of basidiocarps at the restrictive conditions before this critical stage causes no increase in recombination frequency (R.F.) in the loci studied. An arrest of 4 h at the critical stage still causes no R.F. increase, but 12-13 h and 18-19 h arrests cause increases of 50% and 90% over the controls, respectively. Thus R.F. can be increased even before the cells are fully committed to meiosis.-A 3-h heat treatment at the beginning of S phase (or 8 h before karyogamy) also causes some (30%) increase in R.F. while the same treatment at late S phase (or 3 h before karyogamy) causes a substantial (164%) increase in R.F. over the controls. A 3-h heat treatment before S phase causes no increase in R.F.-Pachytene is also responsive to temperature treatments (Lu 1969). The maximum R.f. increase is 100% by heat and 220% by cold treatment. The shortest time that can cause the maximum increase in recombination by high temperature is 3 h and that by cold treatment is 7 h. These durations are correlated with the length of the pachytene stage under the treatment conditions. The kinetic data show that the increase in R.F. caused by high and low temperatures follows two-hit kinetics and their rate of increase is almost identical. The higher increase in R.F. by low temperature can be attributed to the increased duration of pachytene and therefore R.F. is a function of time. The longer the homologous chromosomes are held together, the higher the recombination frequency.     

Alternation of respiratory pathways during the development of wheat leaf

P?i vývoji listu p?enice se zmen?uje stupeň inhibice dýchání fluoridem, monojodacetátem a malonátem a poměr mezi radioaktivitami¹⁴CO₂ uvolněného z glukosy-6-¹⁴C a glukosy-l-¹⁴C (C₆/C₁), co? svěd?í o zvět?ování podílu pentosovího cyklu v celkové respiraci. Tato změna v?ak neni zp?sobena absolutním zvět?ením aktivity pentosového eyklu u star?ích list?, nýbr? p?edev?ím poklesem aktivity glykolytického systému. Naproti tomu u list? oddělených od obilky se pri sní?ení vlhkosti atmosféry méní poměr mezi dýchacími cestami v d?sledku aktivace pentosového cyklu. Na základě disproporce mezi procentem glykolytického podílu respirace vypo?tenym ze sní?ení poměru C₆/C₁ p?i inhibici dýchání fluoridem a procentem inhibice dý chání fluoridem bylo diskutováno o mo?ných p?íoinách vysokých poměr? C₆/C₁ u mladých list?, u nich? byly v některých p?ípadech zji?těny hodnoty těchto poměr? dokonce vy??í ne? jedna.