Triterpene constituents of Caltha palustris

The structure of a new triterpene lactone, palustrolide, has been elucidated as 3β,23-dihydroxylupan-13β→28 lactone on the basis of physico-chemical studies. In addition, sitosterol, its glucoside, hederagenin, 16,17-dihydroxykauran-19-oic acid and hederagenic acid have been characterized.     

Polyamine metabolism in ripening tomato fruit : I. Identification of metabolites of putrescine and spermidine

The metabolism of [1,4-¹⁴C]putrescine and [terminal methylene-³H]spermidine was studied in the fruit pericarp (breaker stage) discs of tomato (Lycopersicon esculentum Mill.) cv Rutgers, and the metabolites identified by high performance liquid chromatography and gas chromatography-mass spectrometry. The metabolism of both putrescine and spermidine was relatively slow; in 24 hours about 25% of each amine was metabolized. The ¹⁴C label from putrescine was incorporated into spermidine, γ-aminobutyric acid (GABA), glutamic acid, and a polar fraction eluting with sugars and organic acids. In the presence of gabaculine, a specific inhibitor of GABA:pyruvate transaminase, the label going into glutamic acid, sugars and organic acids decreased by 80% while that in GABA increased about twofold, indicating that the transamination reaction is probably a major fate of GABA produced from putrescine in vivo. [³H]Spermidine was catabolized into putrescine and β-alanine. The conversion of putrescine into GABA, and that of spermidine into putrescine, suggests the presence of polyamine oxidizing enzymes in tomato pericarp tissues. The possible pathways of putrescine and spermidine metabolism are discussed.     

A collaborative study to establish an International Standard Rabies immunoglobulin of human origin

Because the supply of the International Standard for Anti-rabies Serum was very low, the WHO initiated a search for a replacement product. The US Food and Drug Administration agreed to undertake a collaborative study using a human rabies immunoglobulin previously purchased for use as a US standard. The potency of this product was determined, in International Units (IU) per millilitre using the rapid fluorescent focus inhibition test for measuring rabies antibody. The mean potency value was found to be 59 IU per ampoule. In June 1984 this preparation was accepted by WHO as the International Standard for Rabies Immunoglobulin.     

Sulfate transport in human placenta: further evidence for a sodium-independent mechanism

Sulfate transport in isolated placental brush-border membrane vesicles has properties consistent with an anion exchange process. To ascertain the relevance of this finding to sulfate accumulation by the fetus and placenta in vivo, we examined sulfate transport in human placental tissue slices, comparing sulfate uptake with that of a non-metabolizable amino acid marker, alpha-aminoisobutyrate (AIB). In contrast to AIB, which was actively concentrated from physiological media, sulfate uptake by the placenta slice was concentrative only in the absence of sodium and at low pH. Uptake of sulfate reached a steady state after 60 min. It was blocked by DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonate), a specific inhibitor of anion transport, but not by ouabain. We found no evidence for Na(+)-dependent uptake of sulfate in incubated placental tissue. It seems unlikely that Na(+)-dependent sulfate transport by the placenta can be responsible for net sulfate accumulation by the human fetus.     

Effect of seat belts on injuries to front and rear seat passengers.

Data on 2520 occupants of cars involved in accidents were analysed in relation to injury and the severity of the crash to investigate the effect of rear seat passengers on injury to restrained and unrestrained front seat occupants and vice versa. Unrestrained front seat occupants showed a higher incidence of serious injury when there were rear seat passengers. The presence of a rear seat passenger did not affect significantly the overall incidence of injury among restrained front seat occupants within the range of crash severity considered. Unrestrained rear seat passengers behind unrestrained front seat occupants showed a higher incidence of moderate injury and a lower incidence of no injury than those behind restrained front seat occupants. It is concluded that legislation on seat belts has not greatly increased the risk of person to person injury.     

Morphology and cell population kinetics of primary spermatogonia in the frog (Rana esculenta) (Amphibia: Anura)

Two morphologically distinct primary spermatogonial cell types were observed in the frog testis and distinguished on the basis of nuclear characteristics. They have been designated the pale and dark types of primary spermatogonia. On the basis of a kinetic analysis, it is proposed that the pale spermatogonia possess the faculty of self-renewal as well as that of forming dark spermatogonia; they are thus bipotential stem cells comparable to the undifferentiated type of mammalian spermatogonia. The dark spermatogonia, in contrast, are committed to a single pathway, i.e. to form secondary sperrnatogonia, and can be defined as differentiated or committed elements of the primary spermatogonial population. The number of stem cell spermatogonia and differentiated spermatogonia vary according to the period of the year, as does the rate of turnover of stem cells, with nearly 60–90% of cells temporarily out of the cell cycle at any given time. It is indicated that the spermatogonial population represents a 'cell renewal system' in a steady state for appreciably long periods of time, however, changing with season in as far as the magnitude of yield of spermatogonial cells is concerned. This implies that an equality should exist between the rate at which stem cells enter cell-cycling and the rate at which daughter cells change their morphological identity.     

Enhancement of Neurospora VS ribozyme cleavage by tuberactinomycin antibiotics.

Several examples of inhibition of the function of a ribozyme or RNA-protein complex have shown that certain antibiotics can interact specifically with RNA. There are, however, few examples of antibiotics that have a positive, rather than a negative, effect on the function of an RNA. We have found that micromolar concentrations of viomycin, a basic, cyclic peptide antibiotic of the tuberactinomycin group, enhance the cleavage of a ribozyme derived from Neurospora VS RNA. Viomycin decreases by an order of magnitude the concentration of magnesium required for cleavage. It also stimulates an otherwise insignificant transcleavage reaction by enhancing interactions between RNA molecules. The ability of viomycin to enhance some RNA-mediated reactions but inhibit others, including translation and Group I intron splicing, demonstrates the potential for natural selection by small molecules during evolution in the 'RNA world' and may have broader implications with respect to ribozyme expression and activity in contemporary cells.     

Molecular Characterization of Mycobacterium avium Complex Isolates from Caribbean Patients by DT1/DT6-PCR,Nonradioactive Southern Hybridization,and the Accuprobe System

A genetic fingerprinting analysis of Caribbean isolates of M. avium complex (MAC) from AIDS patients by a Southern blotting technique after Pstl digestion with nonradioactive DNA probes coding for single-copy sequences DT1 and DT6 was performed. In parallel, a selective amplification of a 187-bp fragment within the DT6 sequence with AV6/AV7 primers for Mycobacterium avium and of a 666-bp fragment within the DT1 sequence of M. intracellulare with the IN38/IN41 primers was also performed, and the molecular speciation with these two methods was compared with results obtained with DNA probes of the Accuprobe system. 66 strains investigated comprised 31 international reference isolates of MAC belonging to serovars 1–28 and 42–44, and 35 clinical isolates including 24 strains from Caribbean AIDS patients. 91.43% of the clinical isolates tested gave concordant data with the DT1/DT6 Southern hybridization and PCR as compared with 74.28% for PCR and Accuprobe, and 71.43% for Accuprobe and Southern hybridization. Our results corroborated previous findings showing that the DT1 probe was specific for M. intracellulare, whereas the DT6 probe was specific for M. avium (reference serovars 2 and 3 probed positive both with DT1 and DT6 probes). Contrary to DT1 probe, which did not reveal sufficient polymorphism to discriminate between MAC isolates, DT6 probe showed an interesting polymorphism giving four distinct clusters. Three clusters corresponded to profiles previously reported for reference and/or clinical isolates; however, a fourth cluster was discovered in five Caribbean isolates from four AIDS patients that did not correspond to previously published genetic patterns. When probed with the insertion sequence IS1245, this cluster retained its homogeneity. Received: 9 May 1996 / Accepted: 10 June 1996     

Structure of iron saturated C‐lobe of bovine lactoferrin at pH 6.8 indicates a weakening of iron coordination

The bilobal lactoferrin is an approximately 76 kDa glycoprotein. It sequesters two Fe³⁺ ions together with two ions. The C‐terminal half (residues, Tyr342–Arg689, C‐lobe) of bovine lactoferrin (BLF) (residues Ala1–Arg689) was prepared by limited proteolysis using trypsin. Both C‐lobe and intact BLF were saturated to 100%. Both of them retained up to nearly 85% of iron at pH 6.5. At pH 5.0, C‐lobe retained 75% of iron whereas intact protein could retain only slightly more than 60%. At pH 4.0 both contained 25% iron and at pH 2.0 they were left with iron concentration of only 10%. The structure of iron saturated C‐lobe was determined at 2.79 Å resolution and refined to R_cryst and R_free factors of 0.205 and 0.273, respectively. The structure contains two crystallographically independent molecules, A and B. They were found to have identical structures with an r.m.s. shift of 0.5 Å for their C^α atoms. A high solvent content of 66% was observed in the crystals. The average value of an overall B‐factor was 68.0 Ų. The distance of 2.9 Å observed for the coordination bond between Fe³⁺ ion and N^e2 of His595 appeared to be considerably longer than the normally observed values of 1.9–2.2 Å. This indicated that the coordination bond involving His595 may be absent. Other coordination distances were observed in the range of 2.1–2.3 Å. Based on the present structure of iron saturated C‐lobe, it may be stated that His595 is the first residue to dissociate from ferric ion when the pH is lowered. Proteins 2016; 84:591–599. © 2016 Wiley Periodicals, Inc.     

Nano‐assembly of nanodiamonds by conjugation to actin filaments

Fluorescent nanodiamonds (NDs) are remarkable objects. They possess unique mechanical and optical properties combined with high surface areas and controllable surface reactivity. They are non‐toxic and hence suited for use in biological environments. NDs are also readily available and commercially inexpensive. Here, the exceptional capability of controlling and tailoring their surface chemistry is demonstrated. Small, bright diamond nanocrystals (size ?30 nm) are conjugated to protein filaments of actin (length ?3–7 µm). The conjugation to actin filaments is extremely selective and highly target‐specific. These unique features, together with the relative simplicity of the conjugation‐targeting method, make functionalised nanodiamonds a powerful and versatile platform in biomedicine and quantum nanotechnologies. Applications ranging from using NDs as superior biological markers to, potentially, developing novel bottom‐up approaches for the fabrication of hybrid quantum devices that would bridge across the bio/solid‐state interface are presented and discussed.