A proton and carbon 13 nuclear magnetic resonance study of neomycin B and its interactions with phosphatidylinositol 4,5-bisphosphate

The entire proton NMR spectrum of the aminoglycoside antibiotic neomycin B has been assigned at physiological pH by a combination of two-dimensional J-resolved and J-correlated and nuclear Overhauser enhancement difference spectroscopy. Unambiguous assignment of all four ring systems is possible without recourse to model or derivative compounds by observing nuclear Overhauser enhancements between as well as within rings. The subsequent assignment of the carbon 13 spectrum is simply achieved using two-dimensional heteronuclear J-correlated techniques. The proton NMR spectrum of a sonicated aqueous dispersion of the intracellular second messenger precursor phosphatidylinositol 4,5-bisphosphate is reported for the first time. The spectrum is consistent with a high degree of side chain unsaturation and a conformation for the myo-inositol head group, which appears highly mobile, in which all bulky substituents are equatorial (except the 2-hydroxyl). Addition of aliquots of phosphatidylinositol 4,5-bisphosphate to an aqueous buffered solution of neomycin B induces complex changes in the whole spectrum of the latter, including downfield shifts of differential magnitude for several well-resolved signals, viz. the anomerics, and the pair of methylene protons of the substituted cyclohexane. The complexation kinetics are fast on the NMR time scale at 25 degrees C. The binding results are discussed in terms of a tentative complexation geometry.     

Small-angle neutron-scattering and electron microscope studies of the chicken liver fatty acid synthase

A structural model for the chicken liver fatty acid synthase is proposed based on electron microscope and small-angle neutron-scattering studies of the enzyme. The model has the overall appearance of two side by side cylinders with dimensions of 160 X 146 X 73 A, with each subunit 160 A in length and 73 A in diameter. The model was constructed by dividing each cylinder into three domains having lengths of 32, 82, and 46 A, with the domain structures in the two subunits being related to each other by a dyad axis. The model is consistent with chemical cross-linking studies which indicated that the subunits are arranged in a head to tail fashion. The cross-linking studies further showed that the beta-ketoacyl synthase active site contains a cysteine and a pantetheine residue from adjacent subunits. It is proposed that the domains which catalyze the addition of C2 units from malonate to the growing fatty acid chain lie in the crevice between the two subunits and that the two independent sets of fatty acid-synthesizing centers lie on the major axis of the model on opposite ends of the molecular dyad.     

Phytic acid. A natural antioxidant

The catalysis by iron of radical formation and subsequent oxidative damage has been well documented. Although many iron-chelating agents potentiate reactive oxygen formation and lipid peroxidation, phytic acid (abundant in edible legumes, cereals, and seeds) forms an iron chelate which greatly accelerates Fe2+-mediated oxygen reduction yet blocks iron-driven hydroxyl radical generation and suppresses lipid peroxidation. Furthermore, high concentrations of phytic acid prevent browning and putrefaction of various fruits and vegetables by inhibiting polyphenol oxidase. These observations indicate an important antioxidant function for phytate in seeds during dormancy and suggest that phytate may be a substitute for presently employed preservatives, many of which pose potential health hazards.     

The use of biochemical markers, serotype and fimbriation in the detection of Escherichia coli clones

Biochemical reactions, O and K serotypes and presence of P-fimbriae were analysed in 116 Escherichia coli strains isolated in blood cultures from patients with bacteraemia and in 99 faecal strains isolated from healthy individuals. By using biochemical typing, the strains could be grouped into six main clusters with similarity index less than 0.8 (Gower, 1971) and altogether 16 subclusters with similarity index 0.82-0.89. The most discriminating tests between the clusters were fermentation of D-tagatose, saccharose, salicin and sorbose. No single biochemical property could differentiate bacteraemic isolates from faecal strains, although strains isolated from blood were significantly more often found in certain subclusters, whereas other subclusters contained mainly control strains. Bacteraemic strains possessed P-fimbriae more often, especially strains isolated from patients with E. coli in the urine concomitantly with bacteraemia. Equally, no single reaction could separate P-fimbriated from non-P-fimbriated strains. D-Tagatose was fermented more often by the P-fimbriated strains; on the other hand, melibiose and lactose fermentation tests were less often positive. Certain O serotypes (O1, O4, O6, O7, O18 and O25) were more common among bacteraemic isolates than controls. K serotypes such as K1, K5 and K52 were also more frequent among blood isolates. We conclude that a combination of biochemical tests, fimbriation and serotyping might be used to identify potentially pathogenic clusters of E. coli.     

Long-term changes in the prevalence of two helminth parasites (Cestoda: Trypanorhyncha) infecting marine fish

Changes in prevalence of the plerocerci of Grillotia angeli Dollfus, 1969 in mackerel, Scomber scombrus L., and of Lacistorhynchus sp. in herring, Clupea harengus L., were recorded over periods of eight years (1978–1985) and 11 years (1974–1984), respectively. Data were collected from 21 year classes of mackerel in an area to the south-west of Britain and Ireland and from seven year classes of herring in the eastern North Sea. Both sets of data showed sharp decreases in parasite prevalence from periods at relatively high levels to others at much lower levels. The changes in prevalence occurred at the same time in both host-parasite systems and coincided with the end of the hydrographic phenomenon known as the mid-70s salinity anomaly. Possible explanations for the changes which are discussed include changes in abundance of first intermediate and definitive hosts, variations in host year class strength, changes in hydrographic conditions and changes in host diet.     

Antibody-dependent cellular cytotoxicity-inducing antibodies against human immunodeficiency virus. Presence at different clinical stages

The presence of antibodies mediating antibody-dependent cellular cytotoxicity (ADCC) against human immunodeficiency virus (HIV)-infected target cells was investigated with 170 sera from patients with varying severity of HIV infection. Approximately 40% of sera from individuals representing all stages of infection were ADCC-positive when tested against HTLV-IIIB infected 0937 clone 2 target cells. The positive sera had higher HIV antibody titers as measured by enzyme-linked immunosorbent assay compared with ADCC-negative sera. ADCC titers were lower in patients with acquired immune deficiency syndrome than in asymptomatic carriers. This decline in ADCC titer was not correlated with a general decrease of HIV antibodies. No correlation between the CD4:CD8 lymphocyte ratio and ADCC activity was found. The possible beneficial effect of ADCC-inducing antibodies early in infection is discussed in relation to the effect of ADCC-inducing antibodies in other retrovirus systems and to the nature of lentivirus infections.     

Expression of tumor necrosis factor receptors on human monocytes and internalization of receptor bound ligand

Tumor necrosis factor (TNF) is a polypeptide produced by monocytes and macrophages. Although TNF receptors have been identified on a variety of cell types, previous studies have not determined whether these receptors also exist on monocytes. In the present work, highly purified recombinant TNF was labeled with 125I. The 125I-labeled TNF bound specifically to receptors on human monocytes and monocyte membrane preparations. A curvilinear Scatchard plot indicated the presence of TNF-binding sites with two different affinities. The results also indicate that receptor-bound TNF is rapidly internalized by monocytes and then degraded intracellularly. These findings are in concert with recent studies demonstrating that TNF immunomodulates monocyte function by an autocrine mechanism.     

Effect of Quinolinic Acid in the Nucleus Basalis Magnocellularis on Cortical High-Affinity Choline Uptake

A transient 45% increase in cortical high-affinity choline uptake (HACU) was observed after an injection of quinolinic acid (QUIN) into the nucleus basalis magnocellularis (nbM) of the rat. This was followed by a steady decline in choline uptake, which resulted in a 46% decrease by day 7. Specific [3H]hemicholinium-3 binding to coronal brain sections showed a similar pattern following injections of QUIN into the nbM. The increase in cortical HACU elicited by QUIN appeared to be dose dependent.     

Polypeptides of the Golgi Apparatus of Neurons from Rat Brain

An antiserum was raised against fractions of the Golgi apparatus of neurons from rat brain. Immunoblots of these fractions with the antiserum showed two principal bands of 185 and 150 kilodaltons (kd) in apparent molecular mass. The antiserum reacted with five or six bands of 200, 150, 130, 100-110, 64, and 40 kd in apparent molecular mass in immunoblots of several crude brain membrane fractions. Affinity-purified antibodies from the different gel bands transferred to nitrocellulose paper were used in immunoblot and immunocytochemical studies. Antibodies eluted from the 200-, 150-, 100-110-, and 64-kd bands reacted not only with the corresponding band but also with the other three bands. Antibodies eluted from the 40-kd band stained only the corresponding band. On light and/or electron microscopic immunocytochemistry, the antiserum stained the Golgi apparatus of rat neurons, glia, liver, and kidney tubule cells. Weaker, segmented, and less consistent staining was observed in nuclear envelopes, rough endoplasmic reticulum, and plasma membranes of neurons. Antibodies eluted from the bands at 200, 150, 100-110, and 64 kd stained intermediate cisterns of the Golgi apparatus of neurons. These findings suggest that a group of related polypeptides of brain membranes is preferentially expressed or enriched in the Golgi apparatus of neurons. Polypeptides with apparent molecular masses of 185 and 150 kd probably represent moieties endogenous to membranes of the neuronal Golgi apparatus.     

Patterns of approximal wear in cheek teeth of a Romano-British population

The approximal surfaces of premolars and molars of 376 adult British-Romano skulls were examined for wear facets. The type of wear was designated as convex, concave, sigmoid, or flat, and the degree was categorised on a three-point scale. Concave wear facets were more frequently seen in the older age groups, but the type of wear was similar on right and left sides. Taking all teeth together or as individual tooth types, concave wear was significantly more likely on mesial rather than distal surfaces. The degree of wear was age related and similar on right and left sides in both males and females. It is suggested that the distribution of concave facets may be related to movements between adjacent teeth.