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Biomedical subjects

M J Smith

Publications and source records attributed to M J Smith.

At least 55 records · Page 3Linked to original sources
PubMed2001

Human GLI-2 is a tat activation response element-independent Tat cofactor.

Zinc finger-containing GLI proteins are involved in the development of Caenorhabditis elegans, Xenopus, Drosophila, zebrafish, mice, and humans. In this study, we show that an isoform of human GLI-2 strongly synergizes with the Tat transactivating proteins of human immunodeficiency virus types 1 and 2 (HIV-1 and -2) and markedly stimulates viral replication. GLI-2 also synergizes with the previously described Tat cofactor cyclin T1 to stimulate Tat function. Surprisingly, GLI-2/Tat synergy is not dependent on either a typical GLI DNA binding site or an intact Tat activation response element but does require an intact TATA box. Thus, GLI-2/Tat synergy results from a mechanism of action which is novel both for a GLI protein and for a Tat cofactor. These findings link the GLI family of transcriptional and developmental regulatory proteins to Tat function and HIV replication.

Animals↗
PubMed2001

Neurotensin gene expression increases during proestrus in the rostral medial preoptic nucleus: potential for direct communication with gonadotropin-releasing hormone neurons.

Neurotensin (NT)-containing neurons in the rostral portion of the medial preoptic nucleus (rMPN) of the brain may play a key role in regulating the pattern of secretion of GnRH, thereby influencing the reproductive cycle in females. The major goals of this study were to determine whether NT messenger RNA (mRNA) levels in the rMPN exhibit a unique pattern of expression in temporal association with the preovulatory LH surge and to assess whether NT neurons may communicate directly with GnRH neurons. We analyzed NT gene expression in rats using in situ hybridization over the day of proestrus and compared this with diestrous day 1. We also determined whether the high-affinity NT receptor (NT1) is expressed in GnRH neurons using dual-label in situ hybridization and whether this expression varies over the estrous cycle. We found that NT mRNA levels in the rMPN increase significantly on the day of proestrus, rising before the LH surge. No such change was detected on diestrous day 1, when the LH surge does not occur. Furthermore, we observed that a significant number of GnRH neurons coexpress NT1 mRNA and that the number of GnRH neurons expressing NT1 mRNA peaks on proestrus. Together with previous findings, our results suggest that increased expression of NT in the rMPN may directly stimulate GnRH neurons on proestrus, contributing to the LH surge. In addition, our results suggest that responsiveness of GnRH neurons to NT stimulation is enhanced on proestrus due to increased expression of NT receptors within GnRH neurons.

Animals↗
PubMed2001

Neural signals that regulate GnRH neurones directly during the oestrous cycle.

GnRH, produced by a loose network of neurones in the basal forebrain, is the primary brain signal responsible for the release of LH and FSH from the anterior pituitary gland. The ovarian steroid hormone oestradiol feeds back at both the central nervous system and the anterior pituitary to regulate the patterns of release of GnRH and the gonadotrophins. Although recent evidence indicates that oestradiol may act directly on some GnRH neurones through classical genomic mechanisms, data from published studies have demonstrated that neurotransmission of afferent neuronal systems that are receptive to oestradiol is necessary to drive reproductive cyclicity. Many classical neurotransmitters and neuropeptides alter GnRH neuronal activity, through direct and sometimes indirect actions. This review focuses on the neurotransmitters that regulate GnRH neurones by binding to and activating specific membrane receptors that are expressed in GnRH neurones. These include the catecholamines, gamma-aminobutyric acid, glutamate, neuropeptide Y, neurotensin, beta-endorphin and vasoactive intestinal polypeptide. On the basis of recent molecular and neuroanatomical evidence, it is proposed that oestradiol influences the activity of these neurotransmitter and neuropeptide systems within the GnRH network to drive reproductive cyclicity.

Animals↗
PubMed2001

Distribution of 14C cylindrospermopsin in vivo in the mouse.

Radiolabelled 14C cylindrospermopsin (CYN) has been prepared and used to investigate the distribution and excretion of CYN in vivo in male Quackenbush mice. At a dose of 0.2 mg/kg (i.e., approx. median lethal dose) the following mean (SD) urinary and faecal recoveries (cumulative) were obtained, respectively: (0-6 hours, n = 4) 48.2 (29.3)%, 11.9 (21.4)%; (0-12 hours, n = 12) 66.0 (27.1)%, 5.7 (5.6)%; (0-24 hours, n = 12) 68.4 (26.7)%, 8.5 (8.1)%. Mean (SD) recoveries from livers at 6 hours were 20.6 (6.4)% (n = 4), at 48 hours 13.1 (7.7)% (n = 8), and 5-7 days were 2.1 (2.1)% (n = 8). A substantial amount (up to 23%) can be retained in the liver for up to 48 hours with a lesser amount retained in the kidneys. The excretion patterns show substantial interindividual variability between predominantly faecal or urinary excretion, but these patterns are not related in any simple manner to the outcome in terms of toxicity. There is at least one methanol-extractable metabolite as well as a nonmethanol-extractable metabolite in the liver. The methanol-extractable metabolite was not found in the kidney and is more hydrophilic than CYN itself on reverse phase.

Alkaloids↗
PubMed2000

Relation of systemic sympathetic nervous system activation to echocardiographic left ventricular size and performance and its implications in patients with mitral regurgitation.

We have previously demonstrated that the systemic sympathetic nervous system (SNS) is activated in proportion to an increase in cineventriculographic left ventricular (LV) end-systolic volume and decrease in ejection fraction (EF) in patients with chronic mitral regurgitation (MR). However, the relation between noninvasive echocardiographic measures of LV size and performance and systemic SNS activation and their clinical implications in patients with MR is not known. We studied 17 MR patients with echocardiography, arterial norepinephrine (NE) sampling, and [3H]-NE infusions and arterial blood sampling to determine NE kinetic parameters using a 2-compartment analysis, including extravascular NE release rates (NE2, index of SNS activity) and the metabolic clearance rate from the vascular compartment. The arterial NE values correlated with LV end-systolic dimensions (r = 0.50, p = 0.04), but not with LV end-diastolic dimensions, and EF or fractional shortening measures. The NE2 values correlated with LV end-systolic dimensions (r = 0.53, p = 0.03) and inversely with LVEF (r = -0.45, p = 0.07) and fractional shortening (r = 0.43, p = 0.08) measures, but not with LV end-diastolic dimensions. The metabolic clearance rate values showed an inverse correlation with LV end-diastolic (r = -0.52, p = 0.03) and end-systolic (r = -0.49, p = 0.04) dimensions, but not with LV performance measures. The increase in NE2 values was progressive as the LV endsystolic dimensions increased and more marked at LV end-systolic dimensions > or = 40 mm. Thus, activation of the SNS is related to an increase in echocardiographic LV end-systolic dimensions and a decrease in LV performance measures in chronic MR. Medica, Inc.

Adult↗
PubMed2000

The natural osmolyte trimethylamine N-oxide (TMAO) restores the ability of mutant tau to promote microtubule assembly.

Coding region and intronic mutations in the gene for microtubule-associated protein tau cause frontotemporal dementia and Parkinsonism linked to chromosome 17 (FTDP-17). Most coding region mutations effect a reduced ability of tau protein to interact with microtubules and lead to the formation of a filamentous pathology made of hyperphosphorylated tau. Here we show that trimethylamine N-oxide (TMAO) restores the ability of tau with FTDP-17 mutations to promote microtubule assembly. To mimic phosphorylation, serine and threonine residues in tau were singly or multiply mutated to glutamic acid, resulting in a reduced ability of tau to promote microtubule assembly. With the exception of the most heavily substituted protein (27 glutamic acid residues), TMAO increased the ability of mutant tau to promote microtubule assembly. However, it had no significant effect on heparin-induced assembly of tau into filaments.

Amino Acid Substitution↗
PubMed2000

An alternative approach to antifouling based on analogues of natural processes.

A number of marine organisms are able to resist fouling pressure and remain essentially free of fouling. Some organisms are totally devoid of even the first stages of biofilm formation involving bacteria and microalgae. A key feature in recent research has been the realisation that previous low adherence technology is an insufficient technical solution and that natural models, based on marine and other organisms, incorporate other passive techniques for fouling resistance. These characteristics may be incorporated into physical analogues of the natural processes. This paper describes ways of producing physical analogues of some such characteristics, the application of such techniques to surfaces in the marine environment and the environmental impact. The paper includes some results of recent trials and a cost comparison.

Biofilms↗
PubMed2000

The p44S10 locus, encoding a subunit of the proteasome regulatory particle, is amplified during progression of cutaneous malignant melanoma.

Gene amplification is frequently present in human tumors, although specific target genes relevant to many amplified loci remain unidentified. An expression cloning assay enabled identification of a candidate oncogene derived from human chromosome 3p14.1. The cDNA retrieved from morphologically transformed cells contained the full-length protein coding region and detected an abundant transcript in the same cells. Sequence analysis revealed identity with the wild-type sequence of p44S10, a highly conserved subunit of the 26S proteasome that exhibits similarity to the Arabidopsis fus6/cop11 family of signaling molecules. p44S10 gene copy number and mRNA expression were increased in association with segmental 1.8 - 11-fold chromosomal gains in cutaneous malignant melanoma cell lines (5/13; 40%) and tumors (2/40; 5%), and in breast cancer MCF-7 cells. Likewise, malignant progression of human radial growth phase WM35 melanoma cells was associated with amplification and increased expression of endogenous p44S10, and increased expression of p44S10 was sufficient to induce proliferation of WM35 cells in vivo. The results demonstrate segmental copy number gains within chromosome 3p in cutaneous malignant melanoma and suggest that deregulation of a proteasome regulatory particle subunit may contribute to the malignant phenotype.

Adenosine Triphosphatases↗
PubMed2000

Correct heteroduplex formation for mutation detection analysis.

BACKGROUND: The majority of mutation detection methods for unknown mutations are polymerase chain reaction (PCR)-based methods dependent on the formation of heteroduplexes between wild-type and mutant strands of DNA. METHODS AND RESULTS: This report discusses the difficulties associated with forming heteroduplexes with a large DNA fragment and the implications for subsequent mutation detection by the chemical cleavage of mismatch technique and other methods reliant on heteroduplex formation. It was found that the size and sequence context of the fragment being investigated inhibited correct heteroduplex formation. The problem was overcome by dividing the sequence into two overlapping fragments. CONCLUSIONS: Early identification of this problem in other fragments will help with the rapid optimization of PCR-based mutation detection methods.

Base Pair Mismatch↗
PubMed2000

SOX14 is a candidate gene for limb defects associated with BPES and Möbius syndrome.

Members of the SOX gene family encode proteins with homology to the HMG box DNA-binding domain of SRY, the Y-linked testis-determining gene. SOX genes are expressed during embryogenesis and are involved in the development of a wide range of different tissues. Mutations in SRY, SOX9 and SOX10 have been shown to be responsible for XY sex reversal, campomelic dysplasia and Waardenburg-Hirschsprung disease, respectively. It is likely that mutations in other SOX genes are responsible for a variety of human genetic diseases. SOX14 has been identified from a human genomic library and the mouse and chicken sequences obtained by polymerase chain reaction amplification. The SOX14 amino acid sequence is highly conserved across these species, suggesting an important role for this protein in vertebrate development. SOX14 is expressed in the neural tube and apical ectodermal ridge of the developing chicken limb. This is the only SOX gene known to be expressed in the apical ectodermal ridge, a structure that directs outgrowth of the embryonic limb bud. Human SOX14 is localised to a 1.15-Mb yeast artificial chromosome on chromosome 3q23, close to loci for BPES (blepharophimosis, ptosis, epicanthus inversus syndrome) and Mobius syndrome. Although SOX14 maps outside these loci, its expression pattern and chromosomal localisation suggest that it is a candidate gene for the limb defects frequently associated with these syndromes.

Amino Acid Sequence↗
PubMed2000

Work organization and ergonomics.

This paper examines the impact of sociotechnical and business trends on work organization and ergonomics. This analysis is performed with the use of Balance Theory (Smith and Carayon-Sainfort, Int. J. Ind. Ergon. 1989, 4, 67-79). The impact on work organization and the work system of the following sociotechnical and business trends is discussed: re-structuring and re-organizing of companies, new forms of work organization, workforce diversity, and information and communication technology. An expansion of Balance Theory, from the design of work systems to the design of organizations, is discussed. Finally, the issue of change is examined. Several elements and methods are discussed for the design of change processes.

Commerce↗
PubMed2000

Modulation of immune function by dietary lectins in rheumatoid arthritis.

Despite the almost universal clinical observation that inflammation of the gut is frequently associated with inflammation of the joints and vice versa, the nature of this relationship remains elusive. In the present review, we provide evidence for how the interaction of dietary lectins with enterocytes and lymphocytes may facilitate the translocation of both dietary and gut-derived pathogenic antigens to peripheral tissues, which in turn causes persistent peripheral antigenic stimulation. In genetically susceptible individuals, this antigenic stimulation may ultimately result in the expression of overt rheumatoid arthritis (RA) via molecular mimicry, a process whereby foreign peptides, similar in structure to endogenous peptides, may cause antibodies or T-lymphocytes to cross-react with both foreign and endogenous peptides and thereby break immunological tolerance. By eliminating dietary elements, particularly lectins, which adversely influence both enterocyte and lymphocyte structure and function, it is proposed that the peripheral antigenic stimulus (both pathogenic and dietary) will be reduced and thereby result in a diminution of disease symptoms in certain patients with RA.

Antigens↗
PubMed2000

Reduced binding of protein phosphatase 2A to tau protein with frontotemporal dementia and parkinsonism linked to chromosome 17 mutations.

Coding region and intronic mutations in the tau gene cause frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). We have previously reported that ABalphaC, a major form of protein phosphatase 2A (PP2A) in brain, binds tightly to tau protein in vitro and is a major tau phosphatase in vivo. Using in vitro assays, we show here that the FTDP-17 mutations G272V, DeltaK280, P301L, P301S, S305N, V337M, G389R, and R406W inhibit by approximately 20-95% the binding of recombinant three-repeat and four-repeat tau isoforms to the ABalphaC holoenzyme and the AC core enzyme of PP2A. Reduction in binding was maximal for tau proteins with the G272V, DeltaK280, and V337M mutations. We also show that tau protein can be specifically coimmunoprecipitated with endogenous PP2A from both rat brain and transfected cell extracts. It is significant that, by using similar coimmunoprecipitation assays, we show that all FTDP-17 mutations tested, including the N279K mutation, alter the ability of tau to associate with cellular PP2A. Taken together, these results indicate that FTDP-17 mutations induce a significant decrease in the binding affinity of tau for PP2A in vivo. We propose that altered protein-protein interactions between PP2A and tau may contribute to FTDP-17 pathogenesis.

3T3 Cells↗
PubMed2000

Normal saline wound dressing--is it really normal?

Gauze swabs soaked in normal saline are frequently used as dressing on open wounds. Their exact mechanism of action is not known. This study was designed to assess the hypothesis that normal saline dressings act in part as an osmotic dressing. Ten patients had skin ulcers (n = 10) dressed with normal saline soaked sponges. Acting as controls (n = 10) identical sponges were placed upon intact skin. The sponge fluid osmolarity and electrolyte concentrations were serially assayed to test our hypothesis. In the control group, the osmolarity, sodium and chloride concentrations increased with time as a result of evaporation, altering it from an isotonic to a hypertonic dressing. However, in the ulcer group, the osmolarity, sodium and chloride concentrations in the sponge fluid remained relatively isotonic with time. This result is statistically significant (P< 0.05). We postulate that, as a result of evaporation, the sponge dressing increases its tonicity. This draws fluid from the wound into the dressing so that a dynamic equilibrium occurs and the sponge dressing regains isotonicity. The dressing remains functional provided that the wound fluid is absorbed freely from the wound. This process is terminated when either the dressing completely absorbs the wound fluid or the dressing dries out. The latter often occurs prematurely in a contaminated wound or in a wound where exudate forms a non-permeable barrier which prevents osmosis and allows the remaining water in the dressing to evaporate completely. This correlates with the observation in clinical practice that for maximum efficacy the dressing should be changed regularly.

Chlorides↗
PubMed2000

Tau gene mutation K257T causes a tauopathy similar to Pick's disease.

Exonic and intronic mutations in Tau cause neurodegenerative syndromes characterized by frontotemporal dementia and filamentous tau protein deposits. Here we describe a K257T missense mutation in exon 9 of Tau. The proband, a 47-yr-old male, presented with severe personality changes followed by semantic memory loss. A diagnosis of Pick's disease was made. The symptoms progressed until death at age 51. The proband's brain showed a marked frontotemporal atrophy that was most pronounced in the temporal lobes. Numerous tau-immunoreactive Pick bodies were present in the neocortex and the hippocampal formation, as well as in some subcortical brain regions. Their appearance and staining characteristics were indistinguishable from those of sporadic Pick's disease. Diffuse staining for hyperphosphorylated tau was also observed in some nerve cell bodies. Immunoblot analysis of sarkosyl-insoluble tau showed 2 major bands of 60 and 64 kDa and 2 very minor bands of 68 and 72 kDa. Upon dephosphorylation, these bands resolved into 6 bands consisting of 3-repeat and 4-repeat tau isoforms, with an overall preponderance of 3-repeat tau. Isolated tau filaments were narrow, irregularly twisted ribbons. Biochemically, recombinant tau proteins with the K257T mutation showed a reduced ability to promote microtubule assembly, suggesting that this may be the primary effect of the mutation. In addition, the K257T mutation was found to stimulate heparin-induced assembly of 3-repeat tau into filaments. Taken together, the present findings indicate that the K257T mutation in Tau can cause a dementing condition similar to Pick's disease.

Frontal Lobe↗
PubMed2000

The effect of callosotomy on novel versus familiar bimanual actions: a neural dissociation between controlled and automatic processes?

The corpus collosum is the large band of fibers that connects the two cerebral hemispheres of the brain. Individuals who have had the fibers of these tracts surgically severed by callosotomy are able to draw two different spatial figures simultaneously using the left and right hands, without evidence of interactions in the spatial planning processes. Paradoxically, tasks (e.g., tying shoes) that appear to depend on spatial interactions between the left and right hands, each of which is controlled by a separate cerebral hemisphere, pose little difficulty. How can this be? In the study reported here, we observed that well-learned cooperative actions of the hands remain intact in 2 callosotomy patients, whereas actions novel to these patients are virtually impossible for them to produce without visual guidance. We infer that duplicate memory engrams of well-learned actions can be accessed by both cerebral hemispheres without callosal mediation, whereas callosal interactions are necessary for precise cross-matching of sensory information during spatial planning or perceptual-motor learning.

Adult↗