Recombination between satellite phage P4 and its helper P2. I. In vivo and in vitro construction of P4: :P2 hybrid satellite phage

P4::P2 hybrid satellite phages which carry a portion (including the P2 head gene Q and the cohesive end) of the left end of the P2 chromosome linked to the essential part of the P4 chromosome have been isolated by in vivo as well as in vitro recombination. These hybrids express gene Q and grow in the presence of a P2 helper even if defective in gene Q.     

Survival and transfer in the human gut of poorly mobilizable (pBR322) and of transferable plasmids from the same carrier E. coli

We examined the survival of a host Escherichia coli K-12 bacterium containing two transferable plasmids (pLM2, pSL222-4) and one poorly mobilizable plasmid (pBR322), and the transfer of these three plasmids to endogenous bacteria in the human intestinal tract. The survival of this plasmid-carrying host organism in four human volunteers was 3.5 to 6 days at recovery rates of 10^?1 to 10^?4. This finding was similar to our previous survival data on the same organism bearing a single plasmid. The K-12 strain appeared to be under a strong selective disadvantage in the human gut, since, even when bearing a tetracycline-resistant plasmid, its titer did not increase despite the administration of tetracycline. Studies of transferability showed that, while the transfer-depressed incFII plasmid pSL222-4 transferred at a frequency of 10^?1 in culture, its transfer in the human gut was much less frequent. The number of new recipients per donor cell ingested was about 10^?5, which included new recipients arising by multiplication. The recovery of pSL222-4 transcipients was enhanced by the administration of tetracycline on day 6. Neither the transfer-repressed, broad host range incP plasmid pLM2, nor the plasmid pBR322, could be detected in any endogenous host bacteria. Using the transfer and mobilization frequencies obtained in culture and the number of new recipients of pSL222-4 in the intestinal tract, we estimated that any in vivo mobilization of pBR322 to a new recipient could not occur at a frequency higher than 10^?12.     

Comparison of the nucleotide sequence of cloned DNA coding for an apolipoprotein (apoVLDL-II) from avian blood and the amino acid sequence of an egg-yolk protein (apovitellenin I): equivalence of the two sequences

We have compared the amino acid sequences of two low-molecular-weight avian apoproteins: apoVLDL-II from very low-density lipoproteins of hen plasma and apovitellenin I from hen egg yolk. The sequence of White Leghorn apoVLDL-II was derived from the nucleotide sequence of cloned apoVLDL-II DNA (Chan et al., 1980). The sequenator was used to determine the amino acid sequence of apovitellinin I from two breeds of hen (White Leghorn and Australorp). The sequences from the two breeds were not only identical, but they also completely matched the predicted sequence derived from the apoVLDL-II DNA sequence. The identity reported here establishes that this protein is transported intact from the blood to the egg yolk.     

An enzymatic method for microdetermination of aphidicolin: a promising anticancer drug

We have developed a method, based on the in vitro inhibition of purified human DNA polymerase alpha, the major enzyme of DNA replication, which allows the rapid and accurate determination of pmol amounts of aphidicolin, a promising anticancer drug. The efficacy of this simple method was verified by the determination of aphidicolin in the liver, spleen, blood and urine of mice treated parenterically with the drug. Given its sensitivity and the avoidance of radioactive tracers, this enzymatic method is suitable for the determination of the drug in body fluids and tissue biopsies from living humans. It allows the detection and quantitation of aphidicolin in the presence of inactive metabolite(s) with very similar chemical structure(s) such as those generated by liver microsomal oxidases. The technique will also be useful to monitor the purification of the drug from cultures of Cephalosporium aphidicola.     

The effect of a liquid elemental diet on cell proliferation in the colon of rats

Summary A liquid elemental diet (Vivonex) was given to rats for 6 days while control animals received a normal diet. At the end of the experiment each animal received one intraperitoneal injection of tritiated thvmidine at 8a.m. Animals from each group were killed hourly during the first 24h after the injection and the proliferative activity was studied by autoradiography of the mucosa of the colon using the labeled mitoses-wave method.The epithelial cell proliferation was significantly decreased in the colon of the Vivonex-fed animals.     

Presence of nucleoside triphosphates and calcium associated with mycobacteriophage I3

The association of nucleoside triphosphate molecules and calcium ions with purified particles of mycobacteriophage I3 has been documented. The content of nucleoside triphosphate has been determined to be 118 molecules per phage particle by equilibrium dialysis against labelled ATP or 148 molecules per phage particle by the direct determination of labelled nucleoside triphosphate. The concentration of bound Ca²⁺ exhibited a high degree of variation between different batches, which may be due to the nonspecific binding of Ca²⁺ by the virus particles. However, the tightly bound Ca²⁺ not removable by dialysis against calciumspecific chelating agent, showed a constant value of 2985 atoms/phage particle.Abbreviations EGTA Ethylene glycol-bis (-aminoethylether)-N,N¹ tetraacetic acid - PFU plaque forming unit - NTP nucleoside triphosphate     

Restriction analysis of the Streptomyces glaucescens genome by agarose gel electrophoresis

A method for the analysis of total DNA of Streptomyces glaucescens is described. The relevant steps are (a) extraction and purification of DNA, (b) restriction of DNA samples with type II restriction enzymes, (c) one dimensional separation of restriction fragments by agarose gel electrophoresis. A typical banding pattern was obtained for each wild type strain, independant of growth conditions or age of the culture. Mutant strains exhibited in most cases the same banding pattern as the parent wild type strain. Only in one specific mutant class a fragment of about 9 megadalton was missing.     

Molecular mechanisms of the origin of chromosome aberrations and the structural organisation of eukaryotic DNA

Summary A new hypothesis on the appearance of exchange chromosomal aberrations has been suggested. According to this hypothesis, temporal duplex polynucleotide structure should arise during G₁ and G₂ phases during the correction of DNA. The size of the duplex, as a rule, should be restricted to the size of complementary nucleotide sequences in the regions of repetitions. Any polynucleotide break in a duplex zone would result in chromosome breakage and if complementary broken ends interact with each other, then exchange chromosome aberrations may be formed. This hypothesis would explain such previously obscure phenomena as extremely high frequencies of exchanges after mutagen treatment, the nature of mitotic crossing-over, negative interference, change of aberration types before replication, the low frequency of damaged structural genes during aberration formation, etc.     

A negative image of the quiescent centre in regenerating root apices of Zea mays

Usually the presence of the quiescent centre in roots is demonstrated by the absence of labelled nuclei following treatment of the root with appropriate radioactive markers. By modification of the pulselabelling technique, a negative image of the quiescent center, showing more intense labelling from [³H]thymidine than the surrounding area, was obtained in regenerating root apices of Zea mays L.