Ion selectivity of the Vibrio alginolyticus flagellar motor.

The marine bacterium, Vibrio alginolyticus, normally requires sodium for motility. We found that lithium will substitute for sodium. In neutral pH buffers, the membrane potential and swimming speed of glycolyzing bacteria reached maximal values as sodium or lithium concentration was increased. While the maximal potentials obtained in the two cations were comparable, the maximal swimming speed was substantially lower in lithium. Over a wide range of sodium concentration, the bacteria maintained an invariant sodium electrochemical potential as determined by membrane potential and intracellular sodium measurements. Over this range the increase of swimming speed took Michaelis-Menten form. Artificial energization of swimming motility required imposition of a voltage difference in concert with a sodium pulse. The cation selectivity and concentration dependence exhibited by the motile apparatus depended on the viscosity of the medium. In high-viscosity media, swimming speeds were relatively independent of either ion type or concentration. These facts parallel and extend observations of the swimming behavior of bacteria propelled by proton-powered flagella. In particular, they show that ion transfers limit unloaded motor speed in this bacterium and imply that the coupling between ion transfers and force generation must be fairly tight.     

Identification of a new carcinoembryonic antigen (CEA) family member in human fetal liver--cloning and sequence determination of pregnancy-specific glycoprotein 7

The carcinoembryonic antigen gene family consists of the CEA- and the Pregnancy-Specific Glycoprotein- (PSG) subfamilies. Human fetal liver express several PSGs. Here we report cloning and sequencing of a new PSG subfamily member, PSG7. It is the fifth type of PSG found in fetal liver. PSG7 has the N-A1-A2-B2-C domain arrangement. Unlike other PSGs the N-terminal of PSG7 is unblocked. PSG7 has a cysteine in the C-terminal domain, which may allow dimerization. Variability analysis according to Wu and Kabat reveals that the region in the N-domain corresponding to complementarity determining region 3 of immunoglobulin is different between PSG subfamily members. Many members, including PSG7, contain the RGD sequence in this region. The CD2 region as well as two other short sequences (in N and A1 domains respectively) also show some variability. The function of PSGs is probably linked to the N-domain and the CDR2- and CD3-like regions are most likely responsible for ligand binding.     

Conformation of methylated sequences in HeLa cell 18-S ribosomal RNA: nuclease S1 as a probe

18-S rRNA from HeLa cells was digested with nuclease S1. Under the conditions employed 15% of the total nucleotides and some 50% of the methylated nucleotides were released as low-molecular-weight products. The material which was precipitable by 70% ethanol after nuclease S1 digestion was subjected to further digestion by combined T1 plus pancreatic ribonucleases or by T1 ribonuclease alone, and fingerprints were prepared. It was found that the four sites which are modified late during ribosome maturation, and which contain base modifications, were all accessible to nuclease S1. By contrast fewer than one-half of the sites which are modified early during ribosome maturation, and which contain 2'-O-methyl groups, were accessible to nuclease S1; the remainder were protected, presumably by secondary or tertiary interactions within 18-S rRNA.     

Heterogeneous staining of rat hepatocyte nuclei by HBFP technique

Synopsis The non-enzymatic histochemical technique Haematoxylin-Basic Fuchsinpicric acid (HBFP) was studied in fresh-frozen and Carnoy-fixed, paraffin-embedded rat liver sections. The hepatocyte nuclei fell into two populations and showed either a crimson red or purple staining in frozen as well as paraffin sections. The heterogeneous staining of the rat heptocyte nuclei was also present when the tissue sections were stained by Methyl Green-Pyronin stain. The differing nuclear staining was present in the isolated nuclei also. The HBFP technique, therefore, appears potentially useful when applied to liver and other tissues as well.     

Preliminary observations on plant-rock type relationships in the Shiraz-Dashte Arjan area,South-West Iran

Summary In the Dashte-Arjan area near Shiraz, rock formations appear to control the distribution of various plant species. The Fars formation (Miocene) and the Asmari-Jahrom formation (Eocene-Oligocen) sediments are characterized by distinet plant species and life forms. Among the characteristic calciphytes of Asmari-Jahrom limestones are Astragalus acutus, Amygdalus lyciodes, Cerasus microcarpa, and Fraxinus rotundifolia. The Fars formation limestones are characterized by Astragulus gossypinus, Acantholimon flexuosum, Noaea mucronata and Phlomis bruguieri, Except for Glycrrhiza glabra, white and red marls seem to have similar species, such as Alhagi maurorum and Carthamus oxyacantha. Gypsum of Fars formation has Berberis integerrima and Rosa beggeriana. Various life forms have been distinguished and were found to be confined to different rock types as well.Nomenclature of species is given in table 1.We are greately indebted to Dr. P.H. Davis and Prof. G. Pontecorvo F.R.S. for critically reading this paper and making some invaluable suggestions. We are grateful to the University Research Grant Commission for providing us a grant for this work. We are also indebted to the Dean, College of Arts & Sciences, Pahlavi University, Shiraz, Iran for providing us with a vehicle during this work.     

Influence of clay minerals on sorption of bacteriolytic enzymes

Myxobacteria presumably produce extracellular bacteriolytic enzymes when they are growing in soil. In order to study their ecological significance, adsorption experiments were performed with lytic enzymes produced byMyxococcus virescens in casitone media. Different soils as well as montmorillonite and kaolinite can rapidly adsorb the bacteriolytic but not the proteolytic enzymes. About 1 gm of montmorillonite per liter of cell-free culture solution is enough for the adsorption of 97% of the bacteriolytic enzymes. The adsorption per unit weight is about 100 times greater on montmorillonite than on kaolinite. About 40% of the adsorbed enzymes can be eluted with solutions of high pH or high ionic strength. The only desorbed bacteriolytic enzyme is the alanyl-∈-N-lysine endopeptidase.     

Staining of Some Specific Regions of Human Chromosomes,particularly the Secondary Constriction of No. 9

SEVERAL procedures have been described recently which produce specific patterns of differential staining in human chromosomes^1–9. Techniques which involve DNA denaturation and reannealing reveal deeply stained areas on centromere and secondary constriction regions which have been equated with constitutive heterochromatin⁹.