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M J Hubbard

Publications and source records attributed to M J Hubbard.

At least 55 records · Page 3Linked to original sources
PubMed1986

The isolation of plasma membrane and characterisation of the plasma membrane ATPase from the yeast Candida albicans.

Plasma membrane ghosts were isolated from Candida albicans ATCC 10261 yeast cells following stabilisation of spheroplasts with concanavalin A, osmotic lysis and Percoll density gradient centrifugation. Removal of extrinsic proteins with NaCl and methyl alpha-mannoside gave increased ATPase and chitin synthase specific activities in the resultant plasma membrane fraction. Sonication of this fraction yielded unilamellar plasma membrane vesicles which exhibited ATPase and chitin synthase specific activities of 4.5-fold and 3.0-fold, respectively, over those of the plasma membrane ghosts. ATPase activity in the membrane ghosts was optimal at pH 6.4, showed high substrate specificity (for Mg X ATP) and was inhibited 80% by sodium vanadate but less than 4% by oligomycin and azide. The effects of a range of other inhibitors were also characterised. Temperature effects of ATPase activity were marked, with a maximum at 35 degrees C. Breaks in the Arrhenius plot, at 12.2 degrees C and 28.9 degrees C, coincided with endothermic heat flow peaks detected by differential scanning calorimetry. ATPase was solubilised from the plasma membranes with Zwittergent in the presence of glycerol and phenylmethylsulphonyl fluoride and partially purified by glycerol density gradient centrifugation. The solubilised enzyme hydrolysed Mg X ATP at Vmax = 20 mumol X min-1 X mg-1 in the presence of phospholipids, with optimal activity at pH 6.0--6.5.

Adenosine Triphosphatases↗
PubMed1986

Isolation and morphological characterization of a mycelial mutant of Candida albicans.

In this paper we describe the isolation of a novel strain of Candida albicans which is a mycelium at ambient temperatures. Mutagenesis of C. albicans ATCC 10261 with N-methyl-N-nitro-N-nitrosoguanidine followed by plating on solid media at 28 degrees C yielded colony morphology variants which were characterized by a raised, rough-surfaced colony of irregular outline in marked contrast to the flat, shiny circular colonies of the parental 10261 strain. One mutant colony, hOG301, was studied in detail. Strain hOG301 was stable and exhibited mycelial morphology over a wide temperature range (5 to 40 degrees C) in several media. The hyphae comprising hOG301 mycelium were examined by light microscopy, scanning electron microscopy, and transmission electron microscopy and showed morphological features described in the literature as being typical of both true hyphae and pseudohyphae. In contrast to 10261, hOG301 was not pathogenic after intraperitoneal injection in mice. This is the first report of a mycelial C. albicans that is stable at ambient temperatures.

Animals↗
PubMed1985

The kinetics and divalent cation inhibition of plasma membrane ATPase in the yeast Candida albicans.

The kinetics of ATP hydrolysis and cation effects on ATPase activity in plasma membrane from Candida albicans ATCC 10261 yeast cells were investigated. The ATPase showed classical Michaelis-Menten kinetics for the hydrolysis of Mg X ATP, with Km = 4.8 mM Mg X ATP. Na+ and K+ stimulated the ATPase slightly (9% at 20 mM). Divalent cations in combination with ATP gave lower ATPase activity than Mg X ATP (Mg greater than Mn greater than Co greater than Zn greater than Ni greater than Ca). Divalent cations inhibited the Mg X ATPase (Zn greater than Ni greater than Co greater than Ca greater than Mn). Free Mg2+ inhibited Mg X ATPase weakly (20% inhibition at 10 mM). Computed analyses of substrate concentrations showed that free Zn2+ inhibited Zn X ATPase, mixed (Zn2+ + Mg2+) X ATPase, and Mg X ATPase activities. Zn X ATP showed high affinity for ATPase (Km = 1.0 mM Zn X ATP) but lower turnover (52%) relative to Mg X ATP. Inhibition of Mg X ATPase by (free) Zn2+ was noncompetitive, Ki = 90 microM Zn2+. The existence of a divalent cation inhibitory site on the plasma membrane Mg X ATPase is proposed.

Adenosine Triphosphatases↗
PubMed1985

Characterization of a tetraploid derivative of Candida albicans ATCC 10261.

A morphometric analysis of Candida albicans yeast cells utilizing scanning electron microscopy showed that the cell volume and the DNA content of a tetraploid strain (derived by cell fusion) were 2.4 to 3.0 and 2.0 times, respectively, those of the progenitor diploid strain, ATCC 10261. The pathogenicities of both strains were similar.

Candida albicans↗
PubMed1985

Morphological studies of N-acetylglucosamine induced germ tube formation by Candida albicans.

In N-acetylglucosamine induced germ tube formation by Candida albicans, multiple (up to five) protuberances appeared within 90 min at 37 degrees C on each yeast cell. The protuberances were extensions of the cytosol and contained vesiclelike structures. Usually only one protuberance subsequently developed into a germ tube. The germ tubes emanated from all aspects of the cell surface but seldom from the budding (long axis) poles. Pseudohyphae, which originated from the budding pole, exhibited a marked constriction at the site of emergence and were 0.6-2.5 microns in diameter compared with a diameter of 0.6-0.8 micron for germ tubes. The presence of septa confirmed that germ tubes are precursors of septate mycelia. Ultrathin-section transmission electron microscopy of aldehyde plus osmium fixed cells revealed electron-lucent walls with a thin electron-dense outer layer. A fibrillar border was also routinely associated with germ tubes. Poststaining with potassium permanganate revealed, in addition, a previously invisible fuzzy layer on the outer region of the cell wall which extended over bud scars and germ tubes and which coalesced at sites of contact between cells.

Acetylglucosamine↗
PubMed1984

Wrist joint arthroplasty in rheumatoid arthritis: a comparison between the Meuli and Swanson prostheses.

A personal series of twelve wrist arthroplasties performed on ten patients with rheumatoid arthritis of the radio-carpal joint were reviewed in retrospect. Six arthroplasties were of the Meuli metal/plastic/metal design and six were of the Swanson silastic type with an additional silastic ulnar head prosthesis. Both prostheses were successful in giving a pain free stable joint with some degree of useful movement. The Meuli appeared to give a greater range of movement than the more constrained Swanson prosthesis. Although complications were encountered it is concluded that wrist arthroplasty does have a place in the management of patients with rheumatoid arthritis of the radio-carpal joint. Our present policy is to continue with the use of the Swanson design because of the advantages of a cement free prosthesis.

Arthritis, Rheumatoid↗
PubMed1981

Calmodulin-like activity in a mineralising tissue: the rat molar tooth germ.

Calmodulin, a calcium binding protein, has been implicated in the regulation of many calcium-dependent biological processes. Since calcium has an important role in hard tissue genesis, both at intra- and extracellular levels, we anticipate that calcium binding proteins may modulate this process. The present study investigated a mineralising tissue, the rat molar tooth germ, to determine the presence of calmodulin-like activity. A heat-treated cell-free extract of tooth germs provided enhancement of Ca2+-dependent Mg2+-ATPase and 3':5'-nucleotide phosphodiesterase activity. No enhancement occurred in the absence of calcium or in the presence of trifluoperazine. SDS-polyacrylamide gel electrophoresis of this extract revealed a protein band of approximately 18,000 mol. wt. These findings indicate the presence of calmodulin-like activity in rat molar tooth germs and support the proposal that calcium and calcium binding proteins, in particular calmodulin, have a major regulatory role in the biology of mineralising tissues.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1981

Parasexual genetic analysis of Candida albicans by spheroplast fusion.

Doubly auxotrophic strains of Candida albicans were selected from mutagenized cultures. Spheroplasts prepared from the auxotrophic strains were fused with polyethylene glycol. Prototrophic derivatives formed by this fusion protocol from auxotrophic strains were selected by complementation on minimal medium. These prototrophs had a cell volume twice that of the original strain and were shown to be heterozygous at four loci. Prototrophs obtained by this procedure infrequently gave rise to auxotrophic recombinants whose cell volume remained twice that of the original strain. It is suggested that these auxotrophic recombinants arise from mitotic crossing-over. This paper is the first report of a parasexual cycle in C. albicans.

Candida albicans↗
PubMed1981

Rapid dissection of rodent molar-tooth germs.

A rapid rate of isolation of molar-tooth germs from rodents aged from 19 embryonic days to 7 days postnatal can be achieved. The procedure is of direct application to biochemical studies of odontogenesis where relatively large amounts of tissue are often required. The quality of dissection, assessed by morphological and organ culture criteria, extends the application of this procedure to general use in the isolation of molar-tooth germs from rodents.

Animals↗
PubMed1980

The effect of acrylic cement on the union of internally fixed experimental fractures of the femoral shaft in the rabbit.

Ninety rabbits had an osteotomy of the femoral shaft followed by medullary nail fixation. They were divided into three groups: group 1 acted as controls; in group 2 intramedullary acrylic cement was added; and in group 3 an external collar of acrylic cement was added at the osteotomy site. Bone healing was assessed by histological examination which included fluorochrome vital staining, vascular perfusion techniques and microradiology. All the osteotomies in groups 1 and 2 united. There was, however, a 100 per cent failure rate in group 3.

Animals↗
PubMed1980

A prospective controlled trial of valgus osteotomy in the fixation of unstable pertrochanteric fractures of the femur.

A total of 62 patients with unstable pertrochanteric fractures of the neck of the femur was subjected to either nail plating with 130 degrees neck-shaft angle or valgus osteotomy using a neck-shaft angle of at least 140 degrees. The patients were assessed in terms of ability to walk and stability of fracture fixation. A clear superiority of valgus osteotomy over the controls was demonstrated in terms of fracture fixation, but the difference in terms of ability to walk was less remarkable.

Adult↗