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Biomedical subjects

A Middleton

Publications and source records attributed to A Middleton.

At least 19 recordsLinked to original sources
PubMed2001

Modulation by cellular cholesterol of gene transcription via the cyclic AMP response element.

The effect of rapid changes in cellular cholesterol content on adenosine 3',5'-cyclic monophosphate (cAMP) response element-mediated gene transcription was investigated. The study was carried out in Chinese hamster ovary (CHO-K1) cells permanently expressing the human beta(2)-adrenoceptor. Gene transcription was quantified using a reporter gene (secreted placental alkaline phosphatase) under the transcriptional control of cAMP response element (CRE) sequences. Cellular cholesterol was reduced by 42% or elevated by 47% by incubating cells for 1 hr with methyl-beta-cyclodextrin alone or methyl-beta-cyclodextrin complexed with cholesterol, respectively. There was a significant negative correlation between the free cholesterol content of the cells and CRE-mediated gene expression in response to 10(-6) M isoprenaline (slope = -4.57 +/- 0.73, P < 0.001), indicating that beta(2)-adrenoceptor-mediated activation of the CRE is inhibited by cholesterol. Cyclic AMP accumulation in response to isoprenaline (10(-12) to 10(-5) M) was also inhibited in cholesterol-enriched cells and enhanced in cholesterol-depleted cells compared to controls (P < 0.05, two-way ANOVA). Cholesterol also inhibited serum-mediated enhancement of CRE-driven gene expression, and we present data suggesting that the pathway activated by serum and inhibited by cholesterol could be independent of adrenoceptor activation and protein kinase A. We conclude that in CHO-K1 cells cholesterol inhibits at least two processes that can stimulate CRE-mediated gene expression. One is isoprenaline activation of cAMP synthesis, the other is activated by serum. These findings demonstrate that activation of gene transcription by extracellular stimuli could be influenced by cellular cholesterol content.

Adrenergic beta-Agonists↗
PubMed2001

Zolmitriptan versus sumatriptan for the acute oral treatment of migraine: a randomized, double-blind, international study.

This randomized, double-blind, parallel-group study compared the efficacy and tolerability of zolmitriptan (2.5 or 5 mg) and sumatriptan (50 mg) in the acute oral treatment of up to six moderate-to-severe migraine attacks. The intention to treat (ITT) population comprised of 1522 patients: 500 treated with zolmitriptan 2.5 mg (2671 attacks), 514 with zolmitriptan 5 mg (2744 attacks) and 508 with sumatriptan 50 mg (2693 attacks). Overall, the 2-h headache response rates in these groups were 62.9, 65.7 and 66.6%, respectively. There were no statistically significant differences between sumatriptan 50 mg and zolmitriptan 2.5 mg (P = 0.12) or 5 mg (P = 0.80). Approximately 40% of patients in each group reported a 2-h headache response in > or = 80% of attacks. There were no statistically significant differences between the groups in the rates of headache response at 1 h (zolmitriptan 2.5 mg 36.9%, zolmitriptan 5 mg 39.5% and sumatriptan 50 mg 38.0%) or 4 h (70.3, 72.9 and 72.2%, respectively) or in the rates of meaningful migraine relief at 1, 2 or 4 h or sustained (24-h) pain relief. All treatments were well tolerated. In conclusion, zolmitriptan (2.5 or 5 mg) proved similarly efficacious compared with sumatriptan (50 mg), both in terms of response rates and consistency across attacks.

Administration, Oral↗
PubMed2001

Foot problems in patients with systemic sclerosis.

OBJECTIVES: To assess the nature of the foot problems experienced in patients with systemic sclerosis (SSc) and patient awareness of such problems. METHODS: Fifty unselected patients (42 females, eight males) with SSc were assessed by means of examination by a senior podiatrist, completion of a questionnaire detailing past and present foot problems, determination of random plasma glucose, plain X-rays of the feet, and measurement of the ankle/brachial index and of digital pulses by Doppler ultrasound. RESULTS: Eighty-six per cent of patients reported colour changes in their feet in response to temperature changes, 82% reported pain usually related to cold, 26% had suffered foot ulceration and 8% had a history of foot surgery. Podiatry assessment confirmed the presence of significant abnormalities, including ulcerations in 10%, pre-ulcerative lesions in 34%, toenail changes in 62%, callus formation in 80% and calcinosis in 18%. Forty per cent of the patients had problems with the fitting of shoes, and 19% had been provided with footwear from the hospital. Plain films of the feet demonstrated the presence of erosions in 6%, soft-tissue calcification in 17%, osteopenia in 26% and degenerative changes in 60% of cases. Ten per cent of the patients had an abnormal ankle brachial index (less than 1.0). Only 21% of the 47 patients in whom digital pulses were examined had normal pulses in all toes, and in 26% all toe pulses were absent. CONCLUSION: Although problems with the hands are well recognized in SSc, foot problems also occur in the majority of patients, and can be a cause of major disability. Care of the feet is therefore an important part of the management of SSC.

Adult↗
PubMed2000

In-hospital delay in the diagnosis of breast cancer.

BACKGROUND: There is evidence that delay in the diagnosis of breast cancer may prejudice survival. The aim of this study was to determine the incidence, time trends and causes of delay in a dedicated breast clinic. METHODS: The interval between first breast clinic visit and a definitive diagnosis was recorded in all patients with invasive breast cancer between 1988 and 1997. In all patients with a delay of 3 months or more, the case notes were reviewed for evidence of a triple assessment (clinical examination, imaging and needle biopsy). The principal cause of delay was identified. RESULTS: Of 1004 patients with invasive breast cancer, there was a delay in diagnosis of 3 months or more in 42 patients between 1988 and 1997, an incidence of 4.2 per cent. The median delay was 6 months and the median age at diagnosis was 53 (range 27-89) years. Triple assessment was undertaken in 30 patients; ten did not have a needle biopsy performed and three patients had no mammography. The principal cause of delay was: false-negative or inadequate fine-needle aspiration cytology (FNAC) in 19 patients, failure of follow-up in eight, clinical signs did not impress in five, FNAC not carried out in four, false-negative mammogram in three, failure of needle localization in two and one patient did not accept clinical advice. The annual incidence of delay in diagnosis did not change significantly over the 10-year interval. CONCLUSION: Triple assessment is not sufficiently sensitive to detect every breast cancer and a small incidence of diagnostic delay is therefore inevitable with current techniques.

Adult↗
PubMed1999

Congenital non-syndromal sensorineural hearing impairment due to connexin 26 gene mutations--molecular and audiological findings.

We screened DNA from 72 sibships and 138 sporadically affected individuals with congenital non-syndromal sensorineural hearing impairment (NSSNHI) for mutations in the 26 (CX26) gene. A total of 20 (27.8%) of the sibships and 11 (7.9%) of the sporadically affected individuals were homozygous or compound heterozygotes for CX26 mutations. A total of 11 (17.2%) of 64 individuals with severe and 30 (30%) of 100 with profound NSSNHI compared to eight (8.7%) of 92 persons with moderate and none (0%) of 19 individuals with mild hearing impairment were homozygous or compound heterozygotes for CX26 mutations (chi2 test, 3 df, P = 0.000). CX26 mutation status bad no effect on the symmetry of the hearing impairment or configuration of the audiogram. In addition, serial audiograms showed no evidence of progression of the hearing impairment or differences in the severity of the hearing impairment in affected siblings in persons whether or not due to CX26 mutations. Sporadically affected individuals with congenital NSSNHI should be routinely tested for mutations in CX26, especially if the hearing impairment is severe or profound in severity, since identification of a mutation in CX26 allows use of Mendelian recurrence risks.

Audiometry, Pure-Tone↗
PubMed1998

Differential roles of extracellular signal-regulated kinase-1/2 and p38(MAPK) in interleukin-1beta- and tumor necrosis factor-alpha-induced low density lipoprotein receptor expression in HepG2 cells.

The inflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF), elevated in inflammatory, malignant, and infectious diseases, induce low density lipoprotein (LDL) receptor transcription in HepG2 cells, and such an induction can account for hypocholesterolemia associated with these states. However, the signaling mechanisms of cytokine-mediated LDL receptor induction are largely unexplored. In the present studies, we examined the potential involvement of different mitogen-activated protein kinase (MAPK) pathways. Northern analysis demonstrated that IL-1beta or TNF significantly increased LDL receptor transcript in HepG2 cells, whereas expression of another tightly regulated sterol-responsive squalene synthase gene was unaffected. IL-1beta treatment resulted in transient activation of three MAPK cascades, namely p46/54(JNK), p38(MAPK), and ERK-1/2, with maximal activation of 20-, 25-, and 3-fold, respectively, occurring 15-30 min after cytokine addition. PD98059, a specific inhibitor of MAPK kinase activity, inhibited IL-1beta-induced LDL receptor expression. In contrast, SB202190, a specific inhibitor of p38(MAPK), enhanced IL-1beta-induced LDL receptor expression, with a concomitant increase in ERK-1/2 activity. Similarly, TNF induced LDL receptor expression also required ERK-1/2 activation. Finally, sterols repressed IL-1beta induced receptor expression, without affecting ERK-1/2 activation. These results show that IL-1beta- or TNF-induced LDL receptor expression requires ERK-1/2 activation, that the p38(MAPK) pathway negatively regulates LDL receptor expression, and that sterols inhibit induction at a point downstream of ERK-1/2 in HepG2 cells.

Animals↗
PubMed1998

Elevation of cyclic AMP by iloprost and prostaglandin E1 increases cholesterol efflux and the binding capacity for high-density lipoproteins in human fibroblasts.

Elevation of cAMP concurrently enhances cholesterol efflux and binding of HDL3 in human skin fibroblasts. These effects were observed regardless of the route by which cAMP levels were increased. Cholesterol efflux and HDL3 binding were stimulated by the cAMP analogue CPT-cAMP, the adenylate cyclase activator forskolin, and by iloprost and prostaglandin E1 (PGE1) (which elevate cAMP via receptor-mediated processes). Dideoxyforskolin and PGF2alpha, which do not elevate cAMP, altered neither cholesterol efflux nor binding of HDL3. Inhibition of protein kinase A with H89 abolished the stimulatory effects of CPT-cAMP and iloprost, suggesting protein kinase A involvement in enhancing cholesterol efflux and HDL3 binding. Enhancement of HDL3 binding by iloprost was due to increased maximal capacity of the cells to bind HDL3, i.e., a greater number of HDL3 binding sites. A positive correlation was demonstrated between changes in HDL3 binding and changes in [3H]cholesterol efflux. The data are compatible with a model in which cholesterol efflux is partially dependent upon HDL binding to the cells. A short exposure to iloprost was sufficient to stimulate cAMP synthesis, triggering a chain of events leading to increased HDL3 binding and [3H]cholesterol efflux 20-24 h later. We conclude that both cholesterol efflux and the maximal capacity for HDL3 binding are enhanced by elevation of cellular cAMP. Cyclic AMP-elevating prostanoids could initiate these responses in vivo.

Alprostadil↗
PubMed1998

Attitudes of deaf adults toward genetic testing for hereditary deafness.

Recent advances within molecular genetics to identify the genes for deafness mean that it is now possible for genetic-counseling services to offer genetic testing for deafness to certain families. The purpose of this study is to document the attitudes of deaf adults toward genetic testing for deafness. A structured, self-completion questionnaire was given to delegates at an international conference on the "Deaf Nation," held at the University of Central Lancashire in 1997. The conference was aimed at well-educated people, with an emphasis on Deaf culture issues. Eighty-seven deaf delegates from the United Kingdom returned completed questionnaires. The questionnaire had been designed to quantitatively assess attitudes toward genetics, interest in prenatal diagnosis (PND) for deafness, and preference for having deaf or hearing children. The results from this study provide evidence of a predominantly negative attitude toward genetics and its impact on deaf people, in a population for whom genetic-counseling services are relevant. Fifty-five percent of the sample thought that genetic testing would do more harm than good, 46% thought that its potential use devalued deaf people, and 49% were concerned about new discoveries in genetics. When asked about testing in pregnancy, 16% of participants said that they would consider having PND, and, of these, 29% said that they would prefer to have deaf children. Geneticists need to appreciate that some deaf persons may prefer to have deaf children and may consider the use of genetic technology to achieve this. Any genetic-counseling service set up for families with deafness can only be effective and appropriate if clinicians and counselors take into consideration the beliefs and values of the deaf community at large.

Congresses as Topic↗
PubMed1997

Prelingual deafness: high prevalence of a 30delG mutation in the connexin 26 gene.

Prelingual non-syndromic (isolated) deafness is the most frequent hereditary sensory defect. In >80% of the cases, the mode of transmission is autosomal recessive. To date, 14 loci have been identified for the recessive forms (DFNB loci). For two of them, DFNB1 and DFNB2, the genes responsible have been characterized; they encode connexin 26 and myosin VIIA, respectively. In order to evaluate the extent to which the connexin 26 gene (Cx26) contributes to prelingual deafness, we searched for mutations in this gene in 65 affected Caucasian families originating from various countries, mainly tunisia, France, New Zealand and the UK. Six of these families are consanguineous, and deafness was shown to be linked to the DFNB1 locus, 10 are small non consanguineous families in which the segregation of the trait has been found to be compatible with the involvement of DFNB1, and in the remaining 49 families no linkage analysis has been performed. A total of 62 mutant alleles in 39 families were identified. Therefore, mutations in Cx26 represent a major cause of recessively inherited prelingual deafness since according to the present results they would underlie approximately half of the cases. In addition, one specific mutation, 30delG, accounts for the majority (approximately 70%) of the Cx26 mutant alleles. It is therefore one of the most frequent disease mutations so far identified. Several lines of evidence indicate that the high prevalence of the 30delG mutation arises from a mutation hot spot rather than from a founder effect. Genetic counseling for prelingual deafness has been so far considerably impaired by the difficulty in distinguishing genetic and non genetic deafness in families presenting with a single deaf child. Based on the results presented here, the development of a simple molecular test could be designed which should be of considerable help.

Australia↗
PubMed1996

Elevation of cyclic AMP in human skin fibroblasts results in increased capacity for HDL binding.

Pre-incubation of cultured human skin fibroblasts, lung fibroblasts and vascular smooth muscle cells, for 24 h with cAMP-elevating agents resulted in a significant increase (40-60%) of the cells' capacity to bind HDL. The increase was due to enhancement of the maximal binding capacity of a high affinity saturable site which binds HDL in preference to LDL. The effect was dependent upon the concentration of the cAMP-elevating agents and required more than 4 h to become evident. Cyclic AMP-mediated elevation of HDL binding occurred in cells with access to an exogenous source of cholesterol, which could be the physiological donor LDL or non-lipoprotein in origin. The observed effects were not subsequent to changes in cellular balance of cholesterol to cholesterol ester and were not due to inhibition of cellular proliferation.

Cells, Cultured↗
PubMed1992

Cyclic AMP stimulates the synthesis and function of the low-density lipoprotein receptor in human vascular smooth-muscle cells and fibroblasts.

1. Cyclic AMP-elevating agents stimulate low-density lipoprotein (LDL) receptor activity in human vascular smooth-muscle cells by increasing the rate of receptor protein synthesis. The stimulation is not secondary to the decrease in the regulatory pool of free cholesterol, since it is unaffected, or even enhanced, by inhibition of cholesterol synthesis and esterification, or inhibition of the conversion of cholesterol into its repressor metabolites. The cyclic AMP-mediated up-regulation of the receptor is maintained at low concentrations of inhibitory sterols, but is eventually over-ridden at high concentrations of these sterols. 2. Cyclic AMP-elevating agents also stimulate the hydrolysis of lysosomal cholesterol esters, thus increasing the cellular cholesterol pool and repressing the expression of the LDL receptor. This cholesterol-mediated repressive effect of cyclic AMP can be prevented by chloroquine, which inhibits lysosomal actions, or by ketoconazole, which inhibits conversion of free cholesterol into its repressor metabolite. Thus the cyclic AMP stimulation of the LDL receptor can be masked by the rapid mobilization of free cholesterol from existing cholesterol esters within cultured cells. 3. We have observed that elevated cyclic AMP concentrations will up-regulate the LDL receptor in cholesterol-depleted human vascular smooth-muscle cells, skin fibroblasts and foetal-lung fibroblasts. We propose that our results are evidence for a cyclic AMP-stimulated, sterol-independent, control of LDL-receptor synthesis which is of widespread occurrence in human cells.

Cells, Cultured↗
PubMed1990

Agents which increase cyclic AMP have diverse effects on low-density-lipoprotein-receptor function in human vascular smooth-muscle cells and skin fibroblasts.

Receptor-mediated binding and metabolism of low-density lipoproteins (LDL) in cultured human vascular smooth-muscle cells and skin fibroblasts are altered by increased cellular cyclic AMP concentrations. However, the LDL receptor does not respond to changes in cyclic AMP concentration in a simple manner. The activation of adenylate cyclase with forskolin, or the addition of membrane-permeant cyclic AMP analogues, initially decreases the expression of the LDL receptor, but is followed by a substantial increase in receptor expression after 24 h. This increase does not occur in the presence of inhibitors of RNA or protein synthesis, and is due to doubling of the Bmax. of the LDL receptor, without alteration of its affinity for LDL. By contrast, elevation of cyclic AMP concentration by inhibition of phosphodiesterases results in decreased receptor expression throughout the 24 h period. These two response patterns are reproducible phenomena, consistently observed in low-passaged cells derived from seven unrelated individuals.

1-Methyl-3-isobutylxanthine↗
PubMed1988

Forensic dental training in Australia.

To facilitate in the identification of victims of a major disaster a trained dental manpower reserve is required. In the state of New South Wales, Australia, an annual three-day training course has been designed to familiarize dentists from both the public and private sectors with identification techniques. The course is aimed to preserve the flexibility of personnel so that they can be utilized in a variety of roles rather than rigidly structuring the make up of a team. It is envisaged though, that in a mass disaster situation teams would be specialized into dental autopsy, antemortem or comparison roles.

Disaster Planning↗