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Biomedical subjects

M B Jackson

Publications and source records attributed to M B Jackson.

At least 127 records · Page 7Linked to original sources
PubMed1981

Single channel currents induced by complement in antibody-coated cell membranes.

An extracellular patch electrode was used to record ionic currents from individual complement-induced channels in the membranes of antibody-coated skeletal muscle. The amplitude of the single-channel currents leads to an estimate of 90 pS for the unit conductance. The kinetics of channel opening and closing show marked variability and complexity. Channels flicker open and closed repeatedly, indicating that once these lesions form, they undergo rapid structural transitions between discrete conducting and nonconducting states.

Animals↗
PubMed1980

Nucleation and the kinetics of microtubule assembly.

A kinetic model was developed for the purpose of interpreting scanning calorimetric data of microtubule assembly. The model consists of two steps. The first step is a highly exothermic nucleation with a strong dependence upon temperature and concentration. The second step is the elongation of the nuclei or microtubules by the addition of tubulin dimer to growing ends. Computer fits to the data provided the values of the parameters of the model. The model successfully simulated various experiments.

Calorimetry↗
PubMed1980

Preliminary experience of the use of meptazinol as an obstetric analgesic.

Following an open pilot trial, meptazinol [m(3-ethyl-1-methyl-hexahydro-1-H-azepin-3-yl) phenol hydrochloride] was compared to pethidine in a single-blind study in women requiring analgesia during labour. Meptazinol provided significantly better analgesia than pethidine with similar but possibly less distressing maternal side effects. There were no obvious adverse effects in the newborn.

Apgar Score↗
PubMed1979

Properties and biosynthesis of cyclopropane fatty acids in Escherichia coli.

The lipid phase transition of Escherichia coli phospholipids containing cyclopropane fatty acids was compared with the otherwise homologous phospholipids lacking cyclopropane fatty acids. The phase transitions (determined by scanning calorimetry) of the two preparations were essentially identical. Infection of E. coli with phage T3 inhibited cyclopropane fatty acid formation over 98%, whereas infection with mutants which lack the phage coded S-adenosylmethionine cleavage enzyme had no effect on cyclopropane fatty acid synthesis. These data indicate that S-adenosylmethionine is the methylene in cyclopropane fatty acid synthesis.

Coliphages↗
PubMed1978

Phase behavior of lipids from Halobacterium halobium.

Mixtures of dipalmitoylphosphatidylcholine with purple membrane lipids, red membrane lipids, or total lipids of Halobacterium halobium have been studied with differential scanning calorimetry. A comparison of red and purple membrane lipids reveals no difference in their phase behavior, indicating that lipid phase behavior plays no role in the in vivo separation of red and purple membranes. The effects of variation of the salt content of the suspending solution have also been examined. Studies of the melting behavior of these mixtures as H. halobium lipid content is varied suggest that the gel to liquid-crystal transition does not occur in the lipids of H. halobium.

Bacteriorhodopsins↗
PubMed1978

An estimate of the minimum amount of fluid lipid required for the growth of Escherichia coli.

The lipid phase transition of Escherichia coli was studied by high sensitivity differential scanning calorimetry. A temperature sensitive unsaturated fatty acid auxotroph was used to obtain lipids with subnormal unsaturated fatty acid contents. From these studies it was concluded that E. coli can grow nromally with as much as 20% of its membrane lipids in the ordered state but that if more than 55% of the lipids are ordered, growth ceases. Studies with wild-type cells show that the phase transition ends more than 10 degrees C below the growth temperature when the growth temperature is either 25 degrees C or 37 degrees C.

Calorimetry, Differential Scanning↗
PubMed1978

Phase transitions of the purple membranes of Halobacterium halobium.

Purple membranes of Halobacterium halobium were studied by differential scanning calorimetry. No transition was detected at temperatures below 70 degrees C. A small endothermic transition was seen at about 80 degrees C and a larger one at 100 degrees C. The larger transition is the irreversible denaturation of bacteriorhodopsin. The smaller transition is accompanied by a change in the visible absorption spectrum and is believed to be reversible, involving a cooperative change in crystalline structure of the membrane.

Bacteriorhodopsins↗
PubMed1978

Gaucher's disease and pregnancy.

Two patients with Gaucher's disease during pregnancy are reported. In one there were severe puerperal hemorrhagic complications attributable to thrombocytopenia secondary to infiltration of the reticuloendothelial system by Gaucher cells. The conclusion as reported in previous literature, which is reviewed, regarding the absence of hemorrhagic complications is disputed since on of the cases reported here showed that these may be severe and occur late in the puerperium.

Adult↗
PubMed1977

Studies of the lipid phase transitions of Escherichia coli by high sensitivity differential scanning calorimetry.

High sensitivity adiabatic differential scanning calorimetry was performed on lipids, membrane vesicles, and whole cells of Escherichia coli enriched in particular unsaturated fatty acids by genetic means. Information concerning the shape of the transition is discussed. Transitions with an asymmetric shape reminiscient of a second order transition were observed. Comparison between the lipid transition observed in whole cells, membrane vesicles, and extracted lipids enriched in elaidate reveal some basic similarities. Studies of synthetic lipids were undertaken in an attempt to interpret the shapes of these transitions as a function of the lipid components of the membrane.

Calorimetry↗
PubMed1976

Oligopeptide transport in proline peptidase mutants of Salmonella typhimurium.

Investigations of peptide transport in Salmonella typhimurium are presented. A strain designated proB25, a proline auxotroph, grew on a variety of di, tri-, and tetrapeptides containing proline. In contrast (Pro)6, peptides acylated on the NH2 terminus and Ala-Pro-D-Ala did not satisfy the nutritional requirement of proB25 for proline because they were not transported. A derivative of proB25, strain TN87, deficient in a proline aminopeptidase and an X-Pro dipeptidase, was able to utilize only four of 25 proline-containing peptides investigated. The inability of TN87 to grow on most of these peptides was due to the lack of the requisite peptidase activity. Evidence for a functional dipeptide transport system in this strain is indicated by growth on Pro-Leu and Pro-Ala, and by growth inhibition by certain X-Pro dipeptides. Leu-Pro, Val-Pro, Met-Pro, and Arg-Pro cause temporary growth inhibition of strain TN87 whereas Gly-Pro, Ala-Pro, and Pro-Pro have no effect on growth. Evidence for a functional oligopeptide transport system is indicated by growth on Pro-Val-Gly and Pro-Gly-Gly and by uptake of label from L-methionyl-L-methionyl-L-[14C]methionine and L-alanyl-L-prolyl-[14C]glycine. The presence of multiple oligopeptide transport systems for certain proline-containing peptides was demonstrated using triornithine-resistant mutants (oligopeptide permease deficient) and competition experiments. Finally L-Ala-L-Pro-[14C]Gly is shown to be transported intact into strain TN87.

Acyltransferases↗
PubMed1976

A beta-coupled gauche kink description of the lipid bilayer phase transition.

A statistical-mechanical model for a lipid bilayer was built around the assumption that beta-coupled gauche kinks are the only nonstraight hydrocarbon chain configurations allowed. Packing of these chains was considered and expressions for the energy and entropy are developed based on those considerations. A solution was obtained which was not exact but was still accurate enough to be useful. In addition, an intermolecular potential was formulated which includes the attractive and repulsive forces between the hydrocarbon chains, the polar group repulsions, and hydrophobic forces. Combining the solution to the kinking model and the intermolecular potential, we obtain the total free energy of the lipid bilayer, which exhibits a first-order phase transition at a characteristic temperature. The theoretical heat of transition indicates that kinks alone can provide enough disorder for the transition to occur. Other physical quantities can be calculated, including order parameters. The order parameters calculated here give a picture of chains which are rigid near the polar group and more fluid near the methyl group.

Binding Sites↗
PubMed1975

The terminal sequences of Bombyx mori 18S ribosomal RNA.

The 5' and 3' terminal T1 oligonucleotides of 32p-labelled B. mori 18S ribosomal RNA were isolated by a two dimensional electrophoretic (diagonal) technique. Nucleotide sequence analysis showed that the 3' terminal fragment, (G)AUCAUUAOH, is identical to that previously obtained from the 18S rRNA of several other eukaryotic species. The sequence of the B. mori 5' terminal fragment is pUCCUCG.

Animals↗