Distribution of Fusarium in some British soils

Soil fusaria from various areas in and around Surrey were estimated on medium selective forFusarium. 4 species ofFusarium, F. episphaeria. F. oxysporum, F. roseum andF. solani were detected.F. roseum was the most widely distributed species and present in highest numbers. Among 3 cultivars of this species obtained, non-pathogenic clones of “Culmorum” was always present. The other 3 species ofFusarium were less widely distributed and occurred in lower numbers, withF. solani being the most restricted in distribution and present in very small populations. NoFusarium was recorded for soils from natural field vegetation (except grass areas) and forests.     

Hypermagnesaemia in Presence of Magnesium Depletion in Acute-on-chronic Renal Failure

A patient with renal failure developed hypermagnesaemia, with confusion, drowsiness, and dysarthria. Nevertheless, the dietary magnesium content was low, and investigation showed actual intracellular depletion of magnesium. The cause of this state is not known, though it is presumably connected with a failure to maintain the normal concentration gradient of magnesium across the cell wall. The clinical state and the serum magnesium level returned to normal after treatment with calcium gluconate.     

Multiple T and B cell epitopes in the S1 subunit ("A"-monomer) of the pertussis toxin molecule

The immunogenicity and reactogenicity of Bordetella pertussis vaccine are mediated in part by the S1 subunit of pertussis toxin (PT). To identify the immune epitopes in the S1 subunit of PT, synthetic peptides were prepared and tested for their capacity to induce antibodies in mice with different MHC genotypes. In BALB/c mice, peptides corresponding to sequences 1-17, 70-82 and 189-199 generate T cell proliferative responses, induce the production of antibodies capable of neutralization of the toxin in the Chinese hamster ovary-cell assay, and protect mice from a shock-like syndrome caused by alternate injections of BSA and PT. Protection and neutralization correlated with the ability of these peptides to elicit high anti-PT titers. Different B cell epitopes were detected in other inbred mouse strains. The antibody reactivity against synthetic peptides from two infants vaccinated with pertussis vaccine was tested. These infants had antibodies reactive to a variety of epitopes in the S1 subunit, including peptides 1-17, 70-82, 99-112, 135-145, and 189-199. Thus, it appears that there are multiple T and B cell epitopes in the S1 subunit of PT.     

Determination of plasma bile acids by capillary gas-liquid chromatography-electron capture negative chemical ionization mass fragmentography

Combined capillary gas-liquid chromatography-electron capture negative chemical ionization mass spectrometry of pentafluorobenzyl ester-TMSi ether derivatives of bile acids and isotope dilution using deuterated internal standards are introduced as a sensitive and selective analysis technique for plasma bile acids. As a result of the high ionization efficiency of pentafluorobenzyl derivatives under electron capturing conditions and minimal fragmentation, the detection limit of this technique is low: 1 pg for each bile acid. The high sensitivity enabled the detection and quantitation of atypical bile acids in 200-microliters aliquots of plasma from fasting healthy adults as exemplified by trihydroxycoprostanic acid (0.002 +/- 0.001 mumol/l) and dihydroxycoprostanic acid (0.013 +/- 0.002 mumol/l).     

Influence of ammonium and extracellular pH on the amino and organic acid contents of suspension culture cells of Acer pseudoplatanus

The effects of supplied ammonium and nitrate on the amino and organic acid contents and enzyme activities of cell suspension cultures of Acer pseudoplatanus L. were examined. Regardless of nitrogen source the pH of the culture medium strongly affected the malate and citrate contents of the cells; these organic acid pools declined at pH 5, but increased at pH 7 and 8. Over a period of two days, ammonium had little effect on the responses of the organic acid pool sizes to the pH of the medium. In contrast, ammonium had a strong influence on amino acid pool sizes, and this effect was dependent on the pH of the medium. At pH 5 there was no increase in cell ammonium or amino acid contents, but at higher pH values cellular ammonium content rose, accompanied by accumulation of glutamine, glutamate and asparagine. Over several days, supplied ammonium led to an increase in activity of glutamate dehydrogenase irrespective of any changes in internal ammonium and amino acid contents. If the pH of the medium was allowed to fall below pH 4 in the presence of ammonium, phosphoenolpyruvate (PEP) carboxylase activity declined to a very low value over several days; at higher pH, the activity of this enzyme, and that of NAD malic enzyme and NAD malate dehydrogenase, remained substantial irrespective of whether the nitrogen source was NH⁺₄ or NO-₃.     

Mechanism of Agonist-Induced Down-Regulation and Subsequent Recovery of Muscarinic Acetylcholine Receptors in a Clonal Neuroblastoma X Glioma Hybrid Cell Line

The mechanisms of carbachol-induced muscarinic acetylcholine receptor (mAChR) down-regulation, and recovery following carbachol withdrawal, were studied in the neuroblastoma x glioma hybrid NG108-15 cell line by specific ligand binding assays. N-[3H]Methylscopolamine ([3H]NMS) and [3H]quinuclidinyl benzilate ([3H]QNB) were used as the ligands for the cell surface and total cellular mAChRs, respectively. Exposure of cells to 1 mM carbachol for 16 h decreased the specific binding of [3H]NMS and [3H]QNB by approximately 80%. Bacitracin (1-4 mg/ml) and methylamine (1-15 mM), inhibitors of transglutaminase and of endocytosis, prevented agonist-induced loss of surface mAChRs. Pretreatment of cells with the antimicrotubular agents nocodazole (0.1-10 microM) and colchicine (1-10 microM) prevented carbachol-induced loss of [3H]QNB binding, but not that of [3H]NMS binding. These results indicate that agonist-induced mAChR down-regulation occurs by endocytosis, followed by microtubular transport of receptors to their intracellular degradation sites. When carbachol was withdrawn from the culture medium following treatment of cells for 16 h, receptors recovered and were incorporated to the surface membrane. This recovery process was antagonized by monovalent ionophores monensin (0.1 microM) and nigericin (40 nM), which interfere with Golgi complex function. Receptor recovery was also prevented by the antimicrotubular agent nocodazole. Thus, recovery of receptors appears to be mediated via Golgi complex and microtubular transport to the surface membrane.     

Neurofibromatosis type 2 appears to be a genetically homogeneous disease

Neurofibromatosis type 2 (NF2) is an autosomal dominant syndrome characterized by the development of vestibular schwannomas and other tumors of the nervous system, including cranial and spinal meningiomas, schwannomas, and ependymomas. The presence of bilateral vestibular schwannomas is sufficient for the diagnosis. Skin manifestations are less common than in neurofibromatosis type 1 (NF1; von Recklinghausen disease). The apparent clinical distinction between NF1 and NF2 has been confirmed at the level of the gene locus by linkage studies; the gene for NF1 maps to chromosome 17, whereas the gene for NF2 has been assigned (in a single family) to chromosome 22. To increase the precision of the genetic mapping of NF2 and to determine whether additional susceptibility loci exist, we have performed linkage analysis on 12 families with NF2 by using four polymorphic markers from chromosome 22 and a marker at the NF1 locus on chromosome 17. Our results confirm the assignment of the gene for NF2 to chromosome 22 and do not support the hypothesis of genetic heterogeneity. We believe that chromosome 22 markers can now be used for presymptomatic diagnosis in selected families. The NF2 gene is tightly linked to the D22S32 locus (maximum lod score 4.12; recombination fraction 0). A CA-repeat polymorphism at the CRYB2 locus was the most informative marker in our families (lod score 5.99), but because the observed recombination fraction between NF2 and CRYB2 was 10 cM, predictions using this marker will need to be interpreted with caution.     

Molecular analyses of the lactococcin A gene cluster from Lactococcus lactis subsp. lactis biovar diacetylactis WM4.

The genes responsible for bacteriocin production and immunity in Lactococcus lactis subsp. lactis biovar diacetylactis WM4 were localized and characterized by DNA restriction fragment deletion, subcloning, and nucleotide sequence analysis. The nucleotide sequence of a 5.6-kb AvaII restriction fragment revealed a cluster with five complete open reading frames (ORFs) in the same orientation. DNA and protein homology analyses, combined with deletion and Tn5 insertion mutagenesis, implicated four of the ORFs in the production of and immunity to lactococcin A. The last two ORFs in the cluster were the lactococcin A structural and immunity genes, lcnA and lciA. The two ORFs immediately upstream of lcnA and lciA were designated lcnC and lcnD, and the proteins that they encoded showed similarities to proteins of signal sequence-independent secretion systems. lcnC encodes a protein of 716 amino acids that could belong to the HlyB family of ATP-dependent membrane translocators. LcnC contains an ATP binding domain in a conserved C-terminal stretch of approximately 200 amino acids and three putative hydrophobic segments in the N terminus. The lcnD product, LcnD, of 474 amino acids, is essential for lactococcin A expression and shows structural similarities to HlyD and its homologs. On the basis of these results, a secretion apparatus that is essential for the full expression of active lactococcin A is postulated.     

Structural and energetic consequences of disruptive mutations in a protein core.

We have characterized the properties of a set of variants of the N-terminal domain of lambda repressor bearing disruptive mutations in the hydrophobic core. These mutations include some that dramatically alter the total core residue volume (by up to six methylene groups) and some that place a single polar residue into the otherwise hydrophobic core. The structural properties of the purified proteins have been studied by CD spectroscopy, biological activity, recognition by conformation-specific monoclonal antibodies, and 1H NMR spectroscopy. The stabilities of the proteins have been measured by thermal and guanidine hydrochloride denaturation. Proteins with disruptive core mutations are found to display a continuum of increasingly nonnative properties. Large internal volume changes cause both significant conformational rearrangements and destabilization by up to 5 kcal/mol. Variants with polar substitutions at core positions no longer behave like well-folded proteins but rather display characteristics of molten globules. However, even proteins bearing some of the most disruptive mutations retain many of the crude secondary and tertiary structural features of the wild-type protein. These results indicate that primitive elements of native structure can form in the absence of normal core packing.