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Biomedical subjects

H Bennett

Publications and source records attributed to H Bennett.

At least 37 records · Page 2Linked to original sources
PubMed1991

Silver tolerance and accumulation in yeasts.

Debaryomyces hansenii (NCYC 459 and strain 75-21), Candida albicans (3153A), Saccharomyces cerevisiae (X2180-1B), Rhodotorula rubra (NCYC 797) and Aureobasidium pullulans (IMI 45533 and ATCC 42371) were grown on solid medium supplemented with varying concentrations of AgNO3. Although Ag+ is highly toxic towards yeasts, growth on solid media was still possible at Ag concentrations of 1-2 mM. Further subculture on higher Ag concentrations (up to 5 mM) resulted in elevated tolerance. The extent of Ag tolerance depended on whether Ag-containing plates were exposed to light prior to inoculation since light-mediated reduction of Ag+ to Ag0 resulted in the production of a less toxic silver species. Experimental organisms exhibited blackening of colonies and the surrounding agar during growth on AgNO3-containing medium especially at the highest Ag concentrations tested. All organisms accumulated Ag from the medium; electron microscopy revealed that silver was deposited as electron-dense granules in and around cell walls and in the external medium. X-ray microprobe analysis indicated that these granules were metallic Ag0 although AgCl was also present in some organisms. Volatile and non-volatile reducing compounds were produced by several test organisms which presumably effected Ag+ reduction to Ag0.

Candida albicans↗
PubMed1991

Who needs architects?

It is essential to put the NHS estate high on the list of priorities, according to architect, Haydn Bennett. In this article he explains why and provides a few pointers for obtaining the best value for money from the estate.

Architecture↗
PubMed1990

Granulins, a novel class of peptide from leukocytes.

We report the isolation and characterization of a novel class of leukocyte peptides with possible cytokine-like activities which we call granulins. They are cystine-rich with molecular weights of approximately 6 Kda, except for granulin D, which appears to be a dimer. We present the sequence of one member of this family, a 56 residue peptide, granulin A, and amino-terminal sequences for three other granulins from human peripheral leukocytes. A fifth related peptide was isolated and partially sequenced from rat bone marrow, suggesting that at least some of the granulin in peripheral leukocytes is preformed in the marrow. Rat granulin, and human granulin A, are closely related, showing that the granulin structures are highly conserved between species.

Amino Acid Sequence↗
PubMed1988

Actin polymerization and pseudopod extension during amoeboid chemotaxis.

Amoebae of the cellular slime mold Dictyostelium discoideum are an excellent model system for the study of amoeboid chemotaxis. These cells can be studied as a homogeneous population whose response to chemotactic stimulation is sufficiently synchronous to permit the correlation of the changes in cell shape and biochemical events during chemotaxis. Having demonstrated this synchrony of response, we show that actin polymerization occurs in two stages during stimulation with chemoattractants. The assembly of F-actin that peaks between 40 and 60 sec after the onset of stimulation is temporally correlated with the growth of new pseudopods. F-actin, which is assembled by 60 sec after stimulation begins, is localized in the new pseudopods that are extended at this time. Both stages of actin polymerization during chemotactic stimulation involve polymerization at the barbed ends of actin filaments based on the cytochalasin sensitivity of this response. We present a hypothesis in which actin polymerization is one of the major driving forces for pseudopod extension during chemotaxis. The predictions of this model, that localized regulation of actin nucleation activity and actin filament cross-linking must occur, are discussed in the context of current models for signal transduction and of recent information regarding the types of actin-binding proteins that are present in the cell cortex.

Actins↗
PubMed1988

Isolation of an immunoreactive analogue of brain fodrin that is associated with the cell cortex of Dictyostelium amoebae.

We have used a polyclonal affinity-purified antibody made against chicken brain fodrin (both 240 and 235 Kd subunits) as a probe to determine if a fodrinlike protein exists in amoebae of Dictyostelium discoideum. In Western blots of whole cells and the isolated cell cortex, polypeptides measuring 220 and 70 Kd are recognized by the fodrin antibodies. In situ localization by indirect immunofluorescence with antifodrin indicates that the immunoreactive polypeptides are cortical. The immunoreactive analogues copatch and cocap with concanavalin A. At the level of resolution of the electron microscope, immunocytochemistry with antifodrin and colloidal gold confirms that the immunoreactive analogues are cortical proteins associated with microfilaments on the cytoplasmic side of the plasma membrane. We have isolated and characterized the 220 Kd protein to determine if it is similar to fodrin and to investigate its relationship to the 70 Kd polypeptide. The 220 Kd protein can be extracted from the cortex in the absence of detergent and isolated by gel filtration and sucrose density gradient sedimentation. The 220 Kd is a rod-shaped protein 118 +/- 17.8 nm (N = 37) in length. It has a sedimentation coefficient of 9.3 S and Stokes' radius of 13 nm and exists as a dimer of approximately 500,000 daltons (Mr). Isolated 220 Kd binds to actin filaments in vitro when assayed by rotary shadowing. Morphological criteria distinguish 220 Kd from Dictyostelium myosin II heavy chain (215 Kd) and the filaminlike protein at 240 Kd. The 70 Kd polypeptide appears to be a cleavage fragment of the 220 Kd, since it is found after prolonged storage when formerly only the 220 Kd was present. Furthermore, the 220 and 70 Kd polypeptides exhibit similar one-dimensional peptide maps when treated with TPCK trypsin. On the basis of its physical and immunoreactive characteristics, and location in the cell, the 220 Kd may be a fodrinlike protein.

Actin Cytoskeleton↗
PubMed1987

Comparison of halothane and isoflurane for rapid anesthetic induction.

To study the hypothesis that isoflurane will induce anesthesia faster than halothane when given by a single vital capacity breath technique, we studied 20 ASA I and II adults who breathed approximately 4.5 MAC equivalents of either vapor. The patients, randomly assigned to receive either agent, were fully preoxygenated and monitored for cardiovascular, respiratory, and EEG parameters. All subjects were premedicated with 5 micrograms/kg fentanyl IV 5 min before induction. Time to loss of consciousness was significantly longer with halothane than with isoflurane (86 +/- 4 vs 38 +/- 2 sec, respectively) although there were no clinically remarkable differences in cardiovascular or respiratory variables. Patients given halothane had a greater excitatory phase on EEG, whereas those given isoflurane had low frequency predominance. Overall rapid inhalation induction was well-received by all patients and was significantly faster with isoflurane.

Adult↗
PubMed1986

A gradient in the density of intramembrane particles is formed during capping induced by concanavalin A.

During capping of concanavalin A (ConA) by amoebae of Dictyostelium discoideum, each cell becomes polarized, with the ConA at one end and newly extended pseudopodia at the opposite end of the cell. This new polarity is stable until the cap is shed or internalized. Intramembrane particles (IMPs) are widely believed to represent large integral membrane proteins, many of which are ion pumps and channels. Since asymmetric ion currents have been implicated in the development of cell polarity, we have used morphological landmarks associated with the capped cells in freeze-fracture to make a morphometric analysis of the IMP distribution relative to the axis of polarization of the capped cell. Untreated cells in suspension extend pseudopodia randomly from their surfaces. In these cells the numerical density of IMPs is random. However, capped cells demonstrate a density gradient of IMPs with the lowest density usually in the pseudopodia and the highest in the cap. The difference in density between the cap and other regions of the cell is two- to threefold for all IMPs, but can be as much as sevenfold for greater than 12 nm IMPs. This study is the first to document that the numerical density of IMPs is altered in response to ligand-induced capping and demonstrates that the distribution of IMPs in a capped cell is related to the axis of polarization of the cell. These results suggest that the development of cell polarity during capping in Dictyostelium amoebae may be due to the asymmetric distribution of IMPs, which may cause asymmetric ion currents across the cell.

Cell Membrane↗
PubMed1984

Decoration with myosin subfragment-1 disrupts contacts between microfilaments and the cell membrane in isolated Dictyostelium cortices.

We used isolated cortices from ameboid cells of Dictyostelium discoideum to examine the structural nature of attachments between microfilaments and the cell membrane and to determine the effect of myosin subfragment-1 (S-1) on such contacts. By varying several parameters in our previously described isolation procedure (Condeelis, J., 1979. J. Cell Biol., 80:751-758), we have improved this procedure and have been able to isolate stable cortices. In this paper we identify two types of contact sites between microfilaments and the cell membrane similar to those seen in the brush border of intestinal epithelial cells: (a) an end-on attachment between the barbed end of actin filaments and the cell membrane; and (b) a lateral attachment mediated by rod-shaped bridges measuring approximately 6 X 15 nm. The spacing between bridges averages 36 nm, which suggests that the helical twist of the actin filament influences bridge location. Together these contacts account for an average of approximately 25,000 attachments per cell. Incubation of cortices with concentrations of S-1 sufficient to saturate binding sites on the microfilaments caused disruption of the contacts. This observation was confirmed by quantitative morphometry to show a threefold loss in the number of contact sites following S-1 decoration. These results indicate that S-1 decoration should be used with caution when information about the precise location of microfilaments and their attachment to the membrane is required.

Cell Membrane↗
PubMed1983

Intracranial tuberculomas in a child: computed tomographic scan diagnosis and nonsurgical management.

Despite great strides in screening and detection of tuberculosis, urban areas still harbor many children with this disease. The case of a child with probable intracranial tuberculomas who was medically treated with antituberculous therapy and followed with frequent computed tomographic (CT) scans is reported. Despite older textbooks that espouse surgery as the treatment for intracranial tuberculomas, it is suggested that in the era of CT scanning, they should be treated the same as other focal CNS infections. Surgery should be reserved for medical failure or deteriorating conditions.

Antibiotics, Antitubercular↗