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Biomedical subjects

D Mills

Publications and source records attributed to D Mills.

At least 55 records · Page 3Linked to original sources
PubMed1997

Three-dimensional structure of NADH-dehydrogenase from Neurospora crassa by electron microscopy and conical tilt reconstruction.

NADH-dehydrogenase (Complex I) is the first complex of the mitochondrial respiratory chain. It is an amphipatic molecule located in the inner mitochondrial membrane and is composed of at least 35 unique subunits encoded by both mitochondrial and nuclear DNA. The whole complex was isolated in detergent from the fungus Neurospora crassa. It is very stable in its isolated form and was analysed as such by electron microscopy. Its mass, determined by dark-field scanning electron microscopy was estimated as 1.12 MDa. The complex was imaged by transmission electron microscopy, by negative staining and by cryo-electron microscopy. A three-dimensional model, with a resolution estimated at 35 A, was calculated from images of negatively stained complexes by the random conical tilt reconstruction technique. This model confirms the general L-shape of the molecule, with arms of equal length and corroborates the hypothesis of a subdivision of the whole complex into three functional domains. Immuno-labelling of the 49 kDA subunit of the peripheral arm allowed its localization within the complex. This is a first step in the subunit mapping of Complex I and the understanding of its activity.

Animals↗
PubMed1997

Fil1, a G-protein alpha-subunit that acts upstream of cAMP and is essential for dimorphic switching in haploid cells of Ustilago hordei.

A constitutive mutation, fil1, that causes filamentous growth in the haplophase of the dimorphic smut fungus Ustilago hordei, was previously shown to be genetically associated with a 50-kb deletion within a 940-kb chromosome. Physiological studies suggested that a gene that functions upstream of adenylyl cyclase was deleted in the mutant. Representational difference analysis of isolated chromosomes was used to obtain deletion-specific DNA probes and corresponding genomic cosmid clones. Complementation analysis identified a cosmid clone and subsequently a 2.1-kb insert that converted transformants of the mutant strain 10.1a(fil1) from the filamentous to the sporidial cell type. A single open reading frame of 354 codons that encodes a putative alpha-subunit of the heterotrimeric G-proteins was identified. Fil1 displayed a high degree of sequence identity to Gpa1 from the basidiomycete Cryptococcus neoformans and CPG-2 from the ascomycete Cryphonectria parasitica. FIL1, when introduced on a self-replicating vector, was found to suppress filamentous growth of starved haploid wild-type strains and restore normal mating response to the fil1 mutant, but did not suppress sexual dimorphism of either strain. Fil1 appears to function analogously to mammalian G alpha proteins, which are coupled to cAMP production via adenylyl cyclase, to regulate dimorphic switching in U. hordei.

Amino Acid Sequence↗
PubMed1997

Speech perception abilities of adult and pediatric Nucleus implant recipients using the Spectral Peak (SPEAK) coding strategy.

A series of 73 postlinguistically deafened adults and 34 prelinguistically deafened children were evaluated with the Spectral Peak (SPEAK) coding strategy of the Nucleus 22-channel cochlear implant. The adults who received consecutive implants demonstrated rapid acquisition of open-set speech recognition skills in the initial postoperative period. Group mean sentence recognition improved to 53.5% (n = 52) after 2 weeks, 62.1% (n = 55) after 1 month, 69.8% (n = 57) after 3 months, and 74.4% (n = 42) after 6 months of use. At the 6-month evaluation interval, 43% of subjects scored greater than 90% on sound-alone sentence recognition in quiet and only one patient (2.4%) scored less than 10%. Mean monosyllabic word recognition was 35.6% after 6 months of use. The 34 prelinguistically deafened children were converted from the Multipeak strategy to Spectral Peak strategy at four large pediatric implant centers. After 6 months of using the new coding strategy, the children demonstrated significant improvements in their speech perception abilities.

Adult↗
PubMed1996

Fatty acids stimulate activity and restore respiratory control in a proton channel mutant of cytochrome c oxidase.

(1) Removal of a carboxyl at residue 132 of subunit I of Rhodobacter sphaeroides cytochrome c oxidase significantly inhibits electron transfer and makes proton pumping undetectable [Fetter et al. (1995) Proc. Natl. Acad. Sci. USA 92, 1604-1608]. When reconstituted into phospholipid vesicles (COV), wild-type oxidase shows respiratory control that is partially released by either valimomycin or nigericin and fully released by the two ionophores combined. Under the same conditions, the D132A mutant COV show anomalous ionophore responses, including inhibition by valinomycin or by CCCP. Nevertheless, oxidase activity results in development of a similar membrane potential in COV containing either wild-type or D132A oxidase, and the ionophore responses of the membrane potential are similar for both enzymes. (2) Long chain fatty acids such as arachidonic acid, but not fatty alcohols, stimulate steady-state electron transfer activity 3-7-fold, with either detergent-solubilized (purified) D132A oxidase or the reconstituted form. The effect is specific for this mutant and is not seen with wild-type or other mutants of similar overall activity. Arachidonate-treated D132A COV show normal ionophore responses to valinomycin and nigericin and full release of respiration in presence of both ionophores or of CCCP. Thus, arachidonate and some other fatty acids abolish the ionophore anomalies seen when the D132A enzyme is reconstituted in their absence. (3) Fatty acid addition does not restore proton pumping, likely because fatty acids also induce proton permeability and some degree of uncoupling. A model of D132A function is presented and possible roles for the fatty acids in 'chemical rescue' of the mutant are discussed.

Alcohols↗
PubMed1996

Construction of recombinant aroA salmonellae stably producing the Shigella dysenteriae serotype 1 O-antigen and structural characterization of the Salmonella/Shigella hybrid LPS.

The TN501 mercury resistant transposon containing the rfp and rfb loci encoding biosynthesis of the O-antigen of Shigella dysenteriae serotype 1 lipopolysaccharide (LPS) was constructed and introduced into aroA mutants of Salmonella typhimurium and Salmonella dublin. In five recombinant strains, both homologous LPS and hybrid LPS, consisting of Salmonella lipid A-core and Shigella O-antigen, were produced. All derivatives but one (SL3235) stably inherited the new trait. Immunofluorescence microscopy, using mixtures of differentially-labelled antibodies specific for either the Salmonella or the Shigella O-antigen, demonstrated that individual bacteria produced both types of LPS. Qualitative and quantitative analysis of polysaccharides obtained by mild hydrolysis of purified LPS was carried out by methylation analysis and NMR spectroscopy, and revealed that the ratio of Salmonella to Shigella O-antigen repeating units in the high molecular weight fraction of isolated polysaccharides varied from 1.3: 1 to 8.4:1 as based on the relative proportions of 1,4,5-tri-O-acetyl-2,3-di-O-methyl-L- rhamnitol (Salmonella repeating unit) and 1,3,5-tri-O-acetyl-2,4-di-O-methyl-L-rhamnitol (Shigella repeating unit). The attachment site of the Shigella O-antigen to the Salmonella core was investigated by construction of a mutant rfp-rfb gene cluster encoding the synthesis of only one repeat unit of the Shigella dysenteriae type 1 O-antigen, and its introduction into a rough Salmonella strain. This hybrid organism produced a polysaccharide with the following structure, [formula: see text] demonstrating that the Shigella dysenteriae type 1 O-antigen is linked at position O-4 of the subterminal D-glucose unit in the Salmonella core.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed1996

Healthcare reform: a survey of college health services.

As federal legislators moved closer to enacting significant healthcare reform during fall 1994, it was apparent to the college health community that campus health programs could be significantly affected. Uncertainty over the impending legislation led college health directors to consider two important questions: What is the federal government going to do? and What could college health directors do to position their organizations more effectively to respond to pending reform? The former question was debated on a daily basis throughout the United States with no resolution in sight. The latter question was the ultimate focus of this survey research involving 56 of 79 schools (71% response rate from institutions in 38 states). Half of the schools had enrollments between 15,001-25,000 students; 86% used prepaid fees as their primary financing mechanism. Survey results identified college health directors' preferences for 27 different organizational strategies in response to possible healthcare reform initiatives.

Health Care Reform↗
PubMed1995

Combination therapy with colestipol and psyllium mucilloid in patients with hyperlipidemia.

OBJECTIVE: To test whether combining psyllium mucilloid with half the usual dose of colestipol reduces the adverse effects associated with colestipol and maintains or increases its efficacy in the treatment of hyperlipidemia. This strategy might make bile acid sequestrants, which are seldom used because they cause adverse effects such as bloating and constipation, more tolerable and less expensive. DESIGN: A randomized, parallel-group, double-blind, controlled trial. SETTING: An outpatient clinic in a tertiary care hospital. PATIENTS: 121 patients who had moderate primary hypercholesterolemia (total cholesterol level > 6 mmol/L and < 8 mmol/L; triglyceride level < 3 mmol/L) after following a low-fat diet for 1 year (National Cholesterol Education Program Step Two diet). INTERVENTION: 5 g of cellulose placebo; 5 g of colestipol; 2.5 g of colestipol plus 2.5 g of psyllium; or 5 g of psyllium three times daily before meals for 10 weeks. MAIN OUTCOME MEASURES: At baseline and at weeks 4 and 10, fasting blood lipid levels and apoprotein concentrations were measured and a quality-of-life instrument was completed. RESULTS: A combination of 2.5 g of psyllium and 2.5 g of colestipol was better tolerated than and as effective as either 5 g of colestipol alone or 5 g of psyllium alone. The combination therapy and colestipol alone did not differ significantly with respect to changes in individual lipid values. The ratio of total cholesterol to high-density lipoprotein cholesterol (HDL) was reduced by 18.2% (95% CI, 12.3% to 24%) with the combination therapy; by 10.6% (CI, 2.0% to 15.4%) with colestipol alone; by 6.1% (CI, 1.5% to 10.6%) with psyllium alone; and by 0.1% (CI, -4.8% to 7%) with placebo (P = 0.0002). Combination therapy reduced the ratio of total cholesterol to HDL significantly more than did colestipol alone or psyllium alone (P < 0.05). CONCLUSIONS: These findings suggest that adding psyllium to half the usual dose of bile acid sequestrant resins maintains the efficacy and improves the tolerability of these resins.

Adult↗
PubMed1995

Consonant perception by users of Nucleus and Clarion multichannel cochlear implants.

A study was carried out to compare the consonant perceptions of five Nucleus multichannel cochlear implant users, five Clarion-CIS users, and four Clarion-CA users. All subjects were administered the Iowa Medical Consonant Recognition Test in the auditory-only condition. The groups averaged approximately 1 year of implant use at the time of testing, and the average age at implantation was 47 years for the Nucleus users, 60 years for the Clarion-CIS users, and 56 years for the Clarion-CA users. The percent-corrected scores for all three devices were variable and ranged from 34% to 84%, with each group averaging about 50% correct consonant recognition. Consonant feature information transmission was calculated for five features: manner of articulation, nasality, place of articulation, duration, and voicing. The highest information transmission in the Nucleus group was for the features of duration (71%), nasality (60%), and voicing (57%), which agrees with previous studies. The Clarion-CIS group had the highest information transmission for duration, place of articulation, manner of articulation, and nasality (50%, 29%, 28%, and 27%). The Clarion-CA group had the highest information transmission for the features voicing, place of articulation, and duration (41%, 40%, and 37%). This study indicates that the Clarion device may carry some acoustic information related to place of articulation, a feature that has not been found to be encoded well by other multichannel cochlear implants.

Adult↗
PubMed1994

Response of clones of Eucalyptus microtheca to NaCl in vitro.

We studied the response of nodal segments of Eucalyptus microtheca F.J. Muell. to salt stress in a tissue culture system. Three clones of Eucalyptus microtheca (37, 42 and 43) were grown in vitro under saline conditions (0-140 mM NaCl) for three months. The survival of all three clones decreased with increasing concentrations of NaCl in the medium, but the presence of up to 70 mM NaCl stimulated rooting in Clones 37 and 42. Shoot elongation of Clone 43 was less affected by salt than that of Clones 37 and 42. Leaf growth, expressed as leaf length, was stimulated 40% in Clone 42 and 33% in Clone 43, but was progressively inhibited up to 27% by 70 mM NaCl in Clone 37. Massive accumulation of Na(+) and Cl(-) occurred, especially in Clones 42 and 43 (4000 and 3000 mmol Na(+) kg(DW) (-1), respectively), as the salinity of the culture solution increased, and this was correlated with inhibition of growth. Because of a reduction in the accumulation of K(+) with increasing salinity, the K(+)/Na(+) ratio decreased from a control value of 4.5 to 0.14 in shoots grown in the presence of 140 mM NaCl. The development of techniques for selecting seedlings by monitoring the physiology of shoots in vitro instead of testing whole plants in vivo will provide a relatively simple method of selection for woody trees.

Journal Article↗
PubMed1993

Planned sexual behaviour of young Australian visitors to Thailand.

OBJECTIVE: To research the knowledge of AIDS and other sexually transmitted diseases among young Australian tourists to Thailand, and their intended sexual behaviour. DESIGN AND SETTING: A cross-sectional survey by anonymous, self-administered questionnaire, of persons seeking pre-travel medical advice in private clinics in five Australian cities. PARTICIPANTS: 213 consecutive patients travelling to Thailand without a spouse or partner. RESULTS: Only 34% of the sample reported a definite intention not to have sex in Thailand. Regarding choice of potential partners: 24.5% more men than women said they would have sex with a Thai national; 13.7% of men said they would have sex with a "bar girl"; and 21.7% more women than men said they would choose a fellow Australian traveller. Eighty-two per cent of the sample reported that they would use condoms 100% of the time, and there was no significant difference between the number of men and women who expressed this intention. CONCLUSIONS: Although not obviously "sex tourists", many young Australian travellers are likely to have sex while visiting Thailand. These data have important implications for education and prevention programs to control the spread of human immunodeficiency virus (HIV) and other sexually transmitted diseases.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Subcompartments of the endoplasmic reticulum.

The endoplasmic reticulum (ER) is the largest continuous endomembrane structure in the cytoplasm. It may be viewed as a series of unique subcompartments. In this review, we examine the rough ER, nuclear envelope and several smooth ER subcompartments. Consideration is given to the characteristic properties and functions of the ER and its domains, and to the formation and maintenance of subcompartments. Associations within the ER membrane bilayer, and with constituents of the cytoplasm and the ER lumen, contribute to the formation of domains and lead to the establishment of subcompartments that reflect specialized functions and vary according to the physiologic state and phenotype of the individual cell. Although the structural complexity of some ER subcompartments (such as the sarcoplasmic reticulum) is highly elaborate, the ER remains a dynamic organelle, subject to assembly and disassembly, capable of extensive remodelling and active in exchange with other organelles through mechanisms of membrane transport.

Animals↗
PubMed1991

Physiological role of epidermal growth factor on adipose tissue development in vivo.

The ability of epidermal growth factor (EGF) to affect adipose tissue development in vivo was investigated. The subcutaneous administration of EGF to newborn NBR rats for 10 days resulted in decreased body weight and fat pad weight that occurred in a dose-dependent fashion. At a dose of 1 micrograms/g of body weight, injected EGF resulted in a 50% decrease of fat pad weight. Although kidney weight was also diminished, the weight of other organs such as liver and intestine remained unchanged or even slightly increased, suggesting that the effect of EGF on fat pad development was not due to a generalized inhibitory action of EGF on the development of the neonate rats. The number of adipocyte precursors in inguinal fat pads of EGF-treated animals was higher than in control animals (1.3-fold for 0.3 micrograms/g of body weight of EGF and 1.8-fold for 1.0 micrograms/g of body weight), whereas the number of mature adipocytes and the amount of triglyceride accumulated per fat pad were concomitantly lower. Adipocyte precursors isolated from EGF-treated animals displayed a reduced differentiation ability in culture and a higher sensitivity to the inhibitory effect of EGF than did cells isolated from control animals. These experiments demonstrate that EGF can retard adipose tissue development in vivo and suggest that EGF plays an important physiological role in the control of adipocyte differentiation.

Adipose Tissue↗
PubMed1991

Decreased transforming growth factor-beta response and binding in insulin-independent teratoma-derived cell lines with increased tumorigenic properties.

The mouse C3H teratoma-derived cell line 1246 is an adipogenic cell line which stringently requires insulin to proliferate and differentiate in defined medium. From this cell line an insulin-independent cell line called 1246-3A was isolated. It was found that, in contrast to 1246 cells, 1246-3A cells had lost the ability to differentiate and became tumorigenic when injected at a density of 10(6) cells/mouse into syngeneic host C3H mice. In addition, they produce in their culture medium transforming growth factor alpha- and beta-like polypeptides which stimulate their proliferation. Highly tumorigenic insulin-independent cell lines able to give rise to tumor when injected at a density of 10(4) cells/mouse were isolated by using an in vitro-in vivo shuttle technique. The highly tumorigenic cell lines have lost the response to TGF-beta 1. The binding of TGF-beta 1 to the nontumorigenic parent cell line or to cells displaying increased tumorigenic properties was investigated. The data presented here indicate that the increased tumorigenicity is accompanied by a progressive decrease of specific binding of TGF-beta 1 to the cells. However, the decreased number of cell surface TGF-beta 1 binding sites in the highly tumorigenic cells did not correlate with an increase in the secretion of TGF-beta protein by the tumorigenic cells, as all of TGF-beta produced by the cells was in a latent form. Affinity cross-linking experiments indicated that the 1246 cell line displayed several TGF-beta cross-linked molecular species (MW 140, 92, and 70 kDa). Increase of tumorigenicity was accompanied by a marked decrease in the intensity of the cross-linked bands, particularly of the 92 and 70 kDa species.

Animals↗
PubMed1991

IS801, an insertion sequence element isolated from Pseudomonas syringae pathovar phaseolicola.

A transposable element, designated IS801, was isolated from strain LR781 of Pseudomonas syringae pathovar phaseolicola in two independent events using the entrapment plasmid, pUCD800. IS801 is 1517 base pairs in length and contains open reading frames that potentially encode proteins of 311 and 172 amino acids, as well as smaller proteins. Unlike most other prokaryotic transposable elements, IS801 lacks terminal repeats. Sequence analysis revealed two target pentamers for IS801 insertion that differ by one base pair. One copy of IS801 generated a perfect duplication of its target, TGAAC. The second copy of IS801 was flanked by the target, TGGAC, at one end, and TGAAC at the other end. A third copy of IS801 was cloned from pMMC7105, an indigenous plasmid of strain LR781, and it was flanked by copies of the pentamer TGAAC.

Amino Acid Sequence↗
PubMed1991

Decrease in transforming growth factor beta 1 binding during differentiation of rat adipocyte precursors in primary culture.

Transforming growth factor beta 1 (TGF-beta 1) binding and action were investigated during differentiation of adipocyte precursors freshly isolated from rat inguinal fat-pad cultivated in defined medium. The data presented in this paper indicate that TGF-beta 1 inhibits differentiation of adipocyte precursors with a 50% effective dose of 9 pM. Time course experiments demonstrate that TGF-beta 1 is active only when it is added to the cells while they are still undifferentiated. If added after the cells have started to differentiate, TGF-beta 1 is less active or becomes inactive. 125I-TGF-beta 1 binding studies on adipocyte precursors before and after differentiation indicate a 10-fold decrease in the number of TGF-beta 1 binding sites after the cells have differentiated. Blocking of the differentiation process by treating the cells with fetal bovine serum or with prostaglandin F2 alpha prevented the decrease in the number of TGF-beta 1 receptors, thereby demonstrating that this change in binding was specifically linked to the differentiation process. Experiments cross-linking 125I-TGF-beta 1 to adipocyte precursors showed that 125I-TGF-beta 1 is specifically cross-linked to two bands with molecular weights of 92,000 and 70,000. After differentiation, a decrease in the intensity of the cross-linked bands was observed. These results demonstrate that loss of cell surface TGF-beta 1 binding sites follows differentiation of adipocyte precursors.

Adipose Tissue↗