Caprolactam,a light-promoted growth inhibitor in sunflower seedlings

A neutral growth inhibitor, isolated from methanolic extracts of sunflower seedlings, was characterized by spectral data as caprolactam. Light-grown se     

Strict co-linearity of genetic and protein folding domains in an intragenically duplicated rat lens γ-crystallin gene

Two complementary DNA clones pRLγ-2 and pRLγ-3 of different rat lens γ-crystallin messenger RNAs have been used to identify γ-crystallin gene sequences in rat genomic DNA. Subsequently, the DNA present in the 18,000 to 20,000 bases region of the EcoRI digest, giving rise to a strong doublet hybridization signal, was cloned in λ phage Charon-4A. One of the clones, λRCHγ-3, carrying an insert of 17,500 bases has been characterized in detail. From analysis at the restriction enzyme level with 5′-, “middle” and 3′-specific subprobes of pRLγ-3 it could be deduced that λRCHγ-3 contains only one γ-crystallin gene. The coding sequences of this gene are interrupted by intronic DNA. The primary structure of this gene and its flanking regions have been established by sequencing the relevant regions of a subclone of λRCHγ-3, designated pRCHγ-3.1. The sequence data show that the γ-crystallin gene extends over 2700 bases of rat genomic DNA. The gene is split by two introns, one of 87 base-pairs after the third translation codon and a large one of 1880 base-pairs after codon 84. The mosaic structure of the gene is strictly co-linear with the structure of the γ-crystallin polypeptide in that the large intron is positioned in a region which specifies the so-called “connecting peptide” and which links the two highly symmetrical and homologous protein domains. Although expected from the cDNA and protein sequence no introns were observed between the coding regions in the DNA specifying the two homologous folding motifs present in each protein domain. The relevance of this phenomenon in terms of the evolution of the mature γ-crystallin gene is discussed.     

The phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate and stimulation of 3H-choline incorporation into endoplasmic reticulum membranes and other subcellular fractions of Krebs II ascites cells during in vitro incubation

Summary After transfer of Krebs II ascites cells from the mouse peritoneum to suspension culture addition of the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA) causes an early stimulation of ³H-choline incorporation into phosphatidylcholine (PC). Choline transport into the treated cells, however, was unaffected. Within 30 min of TPA treatment ³H-choline incorporation was almost 300% above the control level. During a 5 hr period of suspension culture the overall patterns of ³H-choline incorporation were similar in TPA-treated and control cultures though the rate was greatly accentuated by the presence of the phorbol ester. Incubation of cells with cycloheximide prior to incubation with TPA did not result in an inhibition of the TPA-directed ³H-choline incorporation. After 3 hr incubation with TPA there were large increases in radioactivity in all subcellular fractions. At 20 hr, however, the values were not far from those of the control. During the first 3 hr of incubation with TPA the incorporation of ³H-choline into light rough (LR) and smooth (S) membranes was stimulated to levels of 400% and 320% respectively above control values. At later times the profiles of radioactivity in membrane subfractions in TPA-treated and control cultures were similar. The results illustrate an early effect of TPA on PC biosynthesis in Krebs II ascites cells while at later times of incubation the stimulatory effect was virtually abolished.     

Effect of the Osmotic Pressure of the Growth Medium on fabB Mutants of Escherichia coli

Temperature-sensitive, unsaturated fatty acid (fabB) auxotrophs of Escherichia coli can grow at the restrictive temperature in the absence of unsaturated fatty acid in a medium with a high osmotic pressure. If a mutant culture was starved for unsaturated fatty acids and harvested just before the lysis started, the fatty acid composition of the cells was the same as that of cells grown until late log phase in a high-osmotic medium. Evidence is presented that the in vivo unsaturated fatty acid biosynthesis is significantly increased in a high osmotic medium. The increase is probably due to a partial activation of the temperature-sensitive fabB product. Besides the stimulation of the temperature-sensitive fabB product, a minimal osmotic pressure of the medium appeared to be necessary to allow growth of cells containing lipids with a changed fatty acid composition. fabA mutants are unable to grow in a high-osmotic medium in the absence of unsaturated fatty acids. No increase in the in vivo unsaturated fatty acid biosynthesis could be detected in the temperature-sensitive fabA mutants.     

Acid-Soluble Breakdown of Homologous Deoxyribonucleic Acid Adsorbed by Haemophilus influenzae: Its Biological Significance

Competent bacteria of Haemophilus influenzae strain Rd were exposed to various kinds of radioactive deoxyribonucleic acid (DNA) for short periods of time and at relatively low temperature. The fate of phage HP1 DNA was studied most extensively. Adsorbed DNA was partially acid solubilized by lysogens and by nonlysogens with very similar kinetics. The biological activity of the DNA decreased extensively in both lysogenic and nonlysogenic recipients. 2,4-Dinitrophenol had no effect on the acid solubilization but largely abolished the biological inactivation. Inactivation kinetics for three different markers and for the triple combination were roughly the same. The presence of 2,4-dinitrophenol in the medium, or the HP1 prophage in the chromosome, did not alter this observation. This suggests that acid solubilization involves the destruction of whole DNA molecules. In view of the absence of DNA homology between phage and host, it is concluded that acid-soluble breakdown of adsorbed transforming DNA is not an integral part of the donor DNA integration process. Behavior of mutant bacteria indicates that neither exonuclease III nor exonuclease V is involved.     

The ultrastructural localization of a cholinesterase in the body muscle of plaice (Pleuronectes platessa)

Summary By means of a histochemical method adapted for electron microscopy a cholinesterase in body muscle cells of plaice (Pleuronectes platessa) has been localized to the sarcolemma. The cholinesterase activity disappeared from the sarcolemma after the muscle tissue had been incubated with a bacterial enzyme, which had earlier been shown, by biochemical methods, to be able to liberate this cholinesterase activity from plaice muscle.The provision of live plaices from Kristineberg Zoological Station, Fiskebäckskil, Sweden, is gratefully acknowledged. We are greatly indebted to Dr. Åke Bovallius, FOA, who provided the starting material for the bacterial enzyme. We would like to express our sincere thanks to Prof. Lennart Nicander for valuable discussions and for placing the resources of the Department of Anatomy and Histology, Royal Veterinary College, to our disposal.     

Teaching of Fertility Regulation in Medical Schools: A Survey in the United States and Canada, 1964

Fertility regulation is taught didactically in 82 of 94 medical school departments of obstetrics and gynecology in the United States and Canada, but students are given clinical experience in only 59 medical schools, according to a survey conducted in 1964 by a committee of the American Public Health Association. Legal prohibitions impeded teaching in 1964 in two States and in all of Canada. Nearly all schools teach that help with fertility regulation should be offered for medical and socioeconomic stress, and most teach that it should be offered routinely in premarital counselling and in the postpartum period, but only two-thirds teach that this help should be given to unmarried adults and only one-third teach that any person requesting help with fertility regulation should receive it.     

Do light/dark cycles of medium frequency enhance phytoplankton productivity?

It has been suggested that turbulence with the resultant light/dark cycle and light gradient through which phytoplankton move, enhances their productivity. The stationary bottle incubation technique for estimating rates of primary productivity has mainly been criticized because of bottle effects, the elimination of natural turbulence and the presence of photo-inhibition. In a series of experiments where productivity was measured over static profiles and compared to the productivity in a mixed system, no definite conclusion could be reached regarding the effect of varying light/dark cycles of medium frequency (seconds to minutes). It appeared as though the ratio of the euphotic depth to mixing depth (Z _eu/Z _m) influenced productivity more than the duration of the light/dark cycle. The static bottle incubation method gave higher integral productivities than the mixed samples at low ratio's ofZ _eu/Z _m. It is suggested that mixing has two separate, but synergistic effects i.e. it not only moves the phytoplankton cells through a light/dark cycle, but also decreases the boundary layer, which increases the rate of exchange through the cell wall of nutrients and metabolites. In doing so more nutrients are available and light could be utilized more efficiently and therefore, productivity is increased.     

Plant-Derived Neurotoxic Amino Acids (β-N-Oxalylamino-l-Alanine and β-N-Methylamino-l-Alanine): Effects on Central Monoamine Neurons

In the present study the subacute effects of beta-N-oxalylamino-L-alanine (BOAA) and beta-N-methylamino-L-alanine (BMAA) on CNS monoamine neurons in rats were investigated following intracisternal injections or local intracerebral administration into substantia nigra. In vitro effects of BOAA and BMAA on high-affinity synaptosomal uptake of dopamine (DA), noradrenaline (NA), and serotonin (5-HT) were also examined. Intracisternal administration of BMAA decreased NA levels in hypothalamus, whereas no effects were seen on DA or 5-HT levels. Following intranigral injections of BOAA, NA levels tended to decrease in several regions, whereas the DA levels and the levels of DA metabolites were unaffected in all regions analyzed. Loss of tyrosine hydroxylase (TH) immunoreactivity in the intranigral injection sites and the presence of TH-immunoreactive pyknotic neurons near the borders of the injection sites were observed following both BOAA and BMAA treatments. Furthermore, substance P-immunoreactive terminals in substantia nigra pars reticulata were also found to have disappeared within the lesioned area following either BOAA or BMAA injections. Incubations with both BOAA and BMAA (10(-5) M) reduced high-affinity [3H]NA uptake in cortical synaptosomes to 69% and 41% of controls, respectively, whereas the striatal high-affinity [3H]DA uptake and the cortical high-affinity [3H]5-HT uptake were unaffected by BOAA or BMAA. The results demonstrate that both BOAA and BMAA can affect central monoamine neurons, although the potency and specificity of these substances on monoamine neurons when administered acutely into cerebral tissue or liquor cerebri seem to be low. However, the in vitro studies indicate selective effects of both compounds on NA neurons in synaptosomal preparations.     

Arginine utilization by Chlorella autotrophica and Chlorella saccharophila

Chlorella saccharophila can utilize the amino acids arginine, glutamate. ornithine and proline as sole sources of nitrogen for growth. By comparison C. autotrophica utilized only arginine and ornithine. Following osmotic shock of Chlorella autotrophica from 50 to 150% artificial seawater rapid synthesis of proline (the main osmoregulatory solute in this alga) occurred in cells grown on arginine or citrulline. However, little proline synthesis occurred in ornithine-grown cells. Distribution of radiolabelled carbon from [¹⁴C]-arginine assimilation following osmotic shock of C. autotrophica agrees with the following pathway of arginine utilization: arginine→citrulline→ornithine→glutamate semialdehyde→pyrroline-5-carboxylate→proline. These 4 steps are catalysed by arginine deiminase (EC 3.5.3.6), citrullinase (EC 3.5.1.20), ornithine transaminase (EC 2.6.1.13) and pyrroline-5-carboxylate reductase (EC 1.5.1.2), respectively. Of these 4 enzymes, only arginine deiminase and pyrroline-5-carboxylate reductase were detected in the crude extract of the 2 Chlorella species. Arginine deiminase did not require specific cations for optimal activity. The deimi-nase showed maximal activity at pH 8.0 and followed Michaelis-Menten kinetics with an apparent K_m for L-arginine of 0.085 m M for the C. autotrophica enzyme and 0.097 m M for that of C. saccharophila. The activity of arginine deiminase was not influen-ced by growing C. saccharophila on arginine. Ornithine competitively inhibited arginine deiminase with an apparent K, of 2.4 m M for the C. autotrophica enzyme, and 3.8 m M for that of C. saccharophila . Arginine utilization by Chlorella is discussed in relation to that of other organisms.