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L Whitmore

Publications and source records attributed to L Whitmore.

9 recordsLinked to original sources
PubMed2003

Analysis of peptaibol sequence composition: implications for in vivo synthesis and channel formation.

The sequence entries in the Peptaibol Database were analysed to provide information on compositional features of this unusual family of peptides. The non-standard amino acid alpha-aminoisobutyric acid represents almost 40% of the residues in all the known sequences. Glutamine is the only significant polar residue in peptaibols, and the position and number of these residues appear to be related to their functional properties as ion channels. Aromatic residues are clustered at the termini, which may contribute to stabilization of the peptide vertically within the bilayer. The peptide chain length is strongly weighted towards the longer members of the family (16-20 residues) and likely to be an important feature in their mode of action as transmembrane permeabilizers. The significant skewing towards even numbers of residues and the bias in pairwise distributions of amino acids have implications for the nature of the in vivo synthesis of these peptides via large non-ribosomal protein complexes.

Amino Acid Sequence↗
PubMed1989

Modification of left-right pairing during the development of individual crest synapses in the rat interpeduncular nucleus.

The synaptic organization of the rat interpeduncular nucleus is highly ordered in the normal adult. By 90 days of age, 90% of crest synapses in its intermediate subnuclei are formed by two cholinergic endings, one from each medial habenula. Stereological calculation of the number of crest synapses per intermediate subnucleus, based on total samples of crest synapses in 3-4 sections through the subnucleus, allows comparisons of afferent pairing among ages without interference by other developmental changes. Between 21 and 90 days of age, the total number of crest synapses per intermediate subnucleus increases tenfold (p less than 10(-8], from 90,000 at 21 days of age, through 130,000 at 28 days, 440,000 at 45 days, to 1,000,000 at 90 days. The volume of the intermediate subnucleus increases fivefold during the same interval. Electron microscopic degeneration was used to estimate the pairing of left and right habenula afferents at crest synapses at the same ages. Through 21 days of age, only one-third of crest synapses are formed with pairing of one left and one right medial habenula afferent, whereas two-third have both afferent endings arising from the same medial habenula. At 28 days of age left-right pairing has increased to 43%, and at 45 days of age 53%, or 240,000, are so paired. The number of same-side paired crest synapses at 45 days, 210,000, is 3.5 times the number so paired at 21 days (p = .003). This indicates continued formation of considerable numbers of crest synapses with this transient mode of airing as late as 45 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1986

Serum cholesterol, triglyceride, and high-density-lipoprotein concentrations in men with different dietary and exercise regimens in Puriscal, Costa Rica.

Mean serum cholesterol and triglyceride concentrations were higher for two groups of sedentary middle-aged and elderly men than for a group of physically-active, middle-aged farmers, all from rural Puriscal, Costa Rica. The mean serum cholesterol, triglyceride, and high-density lipoprotein (HDL)-risk factor levels of the three groups were all higher than the comparable US means. Dietary fat and cholesterol intake were also greater for the Puriscal men than for the comparable US counterpart. No correlations were found between dietary fat or cholesterol and the corresponding serum levels. Age was correlated with serum cholesterol and HDL-risk factor values. Weight was also correlated with these variables as well as with serum triglyceride concentrations. A high prevalence of obesity was found among the middle-aged sedentary men.

Adult↗
PubMed1985

Gestational changes in the germinal matrix of the normal rhesus monkey fetus.

To explain the reported predisposition to germinal matrix hemorrhage in premature infants, pathogenetically important morphological features of the germinal matrix should be present in the 3rd trimester and rapidly change near term. Such features were sought in this study of the germinal matrix and its vasculature in normal rhesus monkey fetuses. The matrix cells, glia, ependyma, and capillaries showed no important structural changes during the 3rd trimester. The terminal vein tributaries were greatly enlarged by 148 days, but cellular and collagen support in their walls was minimal at this time. The latter features developed by the final days of gestation. These findings do not support a structural immaturity or specialization of the germinal matrix predisposing to germinal matrix hemorrhage. Our results, therefore, support the recent emphasis on physiological parameters in the pathogenesis and prevention of germinal matrix hemorrhage.

Animals↗
PubMedDate not supplied

The peptaibol database: a sequence and structure resource.

The peptaibols are a large family of membrane-active peptides with considerable sequence homology, but with different biological properties and three-dimensional structures. They constitute a rich resource of naturally occurring 'mutants' which are potentially valuable for structure/function studies of ion channels. A searchable on-line database of sequences and structures of the peptaibols has been created at http://www.cryst.bbk.ac.uk/peptaibol, as a resource for the biological and structural community. In this paper, the contents and organization of the website are discussed as well as procedures for submission of new entries to the database. At present, more than 300 peptaibol sequences are stored in the database. Each sequence entry contains its full literature reference and information about its biological source. Tools are provided for searching for specific peptaibol sequences or groupings of sequences, and for locating peptaibols containing specified sequence motifs. In addition the website acts as a database for structural information. The coordinates of all currently available peptaibol x-ray and NMR structures are included and complemented, where appropriate. with molecular graphics illustrations. These include figures of model channel structures and comparisons between different peptaibol structures. The peptaibol database thus provides a tool for ready access to information and a means of investigating the sequences and structures of this class of polypeptides.

Amino Acid Sequence↗