Search PubMed⌕ Search

Biomedical subjects

A Flynn

Publications and source records attributed to A Flynn.

At least 19 recordsLinked to original sources
PubMed1999

Personal hormone monitoring for contraception.

OBJECTIVE: To determine the effectiveness and acceptability of personal hormone monitoring for contraception. DESIGN: A large prospective study was carried out on personal hormone monitoring for contraception when used with abstinence during the identified fertile days. SETTING: Three country study under the auspices of the departments of Obstetrics and Gynaecology of the Universities of Birmingham, Dublin and Dusseldorf SUBJECTS: Seven hundred and ten women, median age 30, were recruited from the general population. They were required to have regular menstrual cycles (23-35 days) and to be delaying their next pregnancy. INTERVENTIONS: Personal hormone monitoring consists of a hand held monitor and disposable test sticks which measure changes in urinary concentrations of oestrone-3-glucuronide and luteinising hormone. An algorithm estimated the fertile days which were displayed by a red light. OUTCOME MEASURES AND RESULTS: One hundred and sixty two pregnancies occurred in 7209 cycles of use, of which 67 were method related pregnancies. The 13 cycle life-table method pregnancy rate (95 per cent CI) was 12. 1 per cent (9.3-14.8). The system allowed analysis of the effect of changes to the algorithm to modify the defined fertile period. As a result the algorithm was changed to increase the median warning of the luteinising hormone surge to six days. With the revised algorithm, half of the method pregnancies would have been prevented giving a calculated method pregnancy rate of 6.2 per cent (4.2-8.3) and method efficacy of 93.8 per cent. The continuation rate after 13 cycles was 78 per cent. CONCLUSION: Personal hormone monitoring proved simple to use and will be of value to women who do not want to use other methods of contraception.

Adolescent↗
PubMed1998

The phosphorylation of eukaryotic initiation factor eIF4E in response to phorbol esters, cell stresses, and cytokines is mediated by distinct MAP kinase pathways.

Initiation factor eIF4E binds to the 5'-cap of eukaryotic mRNAs and plays a key role in the mechanism and regulation of translation. It may be regulated through its own phosphorylation and through inhibitory binding proteins (4E-BPs), which modulate its availability for initiation complex assembly. eIF4E phosphorylation is enhanced by phorbol esters. We show, using specific inhibitors, that this involves both the p38 mitogen-activated protein (MAP) kinase and Erk signaling pathways. Cell stresses such as arsenite and anisomycin and the cytokines tumor necrosis factor-alpha and interleukin-1beta also cause increased phosphorylation of eIF4E, which is abolished by the specific p38 MAP kinase inhibitor, SB203580. These changes in eIF4E phosphorylation parallel the activity of the eIF4E kinase, Mnk1. However other stresses such as heat shock, sorbitol, and H2O2, which also stimulate p38 MAP kinase and increase Mnk1 activity, do not increase phosphorylation of eIF4E. The latter stresses increase the binding of eIF4E to 4E-BP1, and we show that this blocks the phosphorylation of eIF4E by Mnk1 in vitro, which may explain the absence of an increase in eIF4E phosphorylation under these conditions.

Animals↗
PubMed1998

Inter and intra-individual variations in urinary excretion of pyridinium crosslinks of collagen in healthy young adults.

OBJECTIVES: To investigate the inter- and intra-individual variation in the excretion of pyridinium crosslinks of collagen in first morning void urine samples in healthy young adults. DESIGN: An observational study in which urinary pyridinium crosslinks of collagen were measured in fasting first void urine samples over five consecutive days. SETTING: The study was conducted in the Department of Nutrition, University College, Cork, Ireland. SUBJECTS: A total of 17 healthy young adults (11 females and 6 males) aged 22-26 y were recruited from University College, Cork. The subjects were without any history of bone or articular disease, and with no intake of medicine that could affect bone or cartilage metabolism. RESULTS: There were large intra-individual variations in the excretion of both pyridinoline (Pyr) and deoxypyridinoline (Dpyr) in first morning void urine samples and the ratios of intra- to inter-individual variation were high. In comparison, inter-individual variation in excretion of crosslinks was relatively low. No significant day-to-day variation was observed either in Pyr or Dpyr excretion when either five, four or three consecutive days or four or three non-consecutive days of urine sampling were used. However, there were significant differences between any two consecutive or non-consecutive days in both Pyr and Dpyr excretion. CONCLUSIONS: The relatively large day-to-day variation in urinary excretion of the pyridinium crosslinks emphasises the need to use multiple samples to characterise the crosslink excretion of an individual. The present study demonstrates that urine sampling for these crosslinks necessitates at least a 3 d collection to ensure that day-to-day effects are not a significant source of variation included in the data analysis.

Adult↗
PubMed1998

The effect of dietary sodium intake on biochemical markers of bone metabolism in young women.

To investigate the effect of a low (80 mmol/d) or high (180 mmol/d) Na intake for 14d on biochemical markers of bone turnover in Na-sensitive and Na-non-sensitive healthy young women, twenty-nine subjects were screened for responsiveness of urinary Ca excretion to increasing dietary Na intake (40, 80, 120 and 200 mmol/d for 7 d). In a crossover study, the eight Na-sensitive and eight of the twenty-one Na-non-sensitive subjects were randomly assigned to diets containing either 80 or 180 mmol Na/d for 14d followed by crossover to the alternative diet for a further 14 d. Dietary Ca was restricted to 12.5 mmol/d throughout. During each dietary period, fasting morning first void urine samples (last 3 d) and fasting blood serum samples (morning of twelfth day) were collected. Increasing Na intake from 80 to 180 mmol/d increased urinary Na about twofold in both the Na-sensitive and Na-non-sensitive groups and increased urinary Ca excretion (by 73%) in the Na-sensitive group only. Biochemical markers of bone resorption (urinary pyridinoline and deoxypyridinoline) and bone formation (serum osteocalcin and bone-specific alkaline phosphatase; EC 3.1.3.1) were unaffected by increasing dietary Na in either group. It is concluded that the Na-induced calciuria observed in the Na-sensitive healthy young women did not result in increased bone resorption or turnover and, despite restricted Ca intake, adaptation of dietary Ca absorption may have compensated for the increased urinary Ca loss.

Adult↗
PubMed1998

The effect of short-term calcium supplementation on biochemical markers of bone metabolism in healthy young adults.

The influence of Ca supplementation of the usual diet for 14 d on biochemical markers of bone turnover was investigated in healthy young adults aged 21-26 years. In a crossover study, eighteen subjects (five male and thirteen female) were randomly assigned to their self-selected diet (about 22 mmol Ca/d) or their self-selected diet with a 20 mmol/d Ca supplement (about 40 mmol Ca/d) for 14 d followed by crossover to the alternative diet for a further 14 d. During each dietary period fasting morning first void urine samples (last 3 d) and fasting blood serum samples (morning of twelfth day) were collected. Ca supplementation reduced urinary excretion of pyridinoline (14%) and deoxypyridinoline (16%) (biochemical markers of bone resorption) but had no effect on biochemical markers of bone formation (serum osteocalcin and bone-specific alkaline phosphatase; EC 3.1.3.1). It is concluded that Ca supplementation of the usual diet in young adults suppresses bone resorption over a 2-week period. If sustained, this could result in suppression of the bone remodelling rate and an increase in bone mass over time. The findings of this short-term study with a relatively small number of young adults highlight the need for a longer-term intervention study of the effect of increased Ca intake on bone mass in this age group.

Adult↗
PubMed1997

Heat shock increases the association of binding protein-1 with initiation factor 4E.

The effects of heat shock on the regulation of the cap-binding initiation factor 4E (eIF4E) and its inhibitory binding protein, 4E-BP1, have been examined in Chinese hamster ovary cells and in cardiac myocytes. Heat shock increased the association between eIF4E and 4E-BP1, and this was associated with a dephosphorylation of 4E-BP1. These effects did not appear to be due wholly to decreased activity of the p70 S6 kinase pathway, which is implicated in the control of 4E-BP1, and they were not mediated by the stress-activated p38 microtubule-associated protein kinase pathway. Increased binding of 4E-BP1 to eIF4E correlated with a decrease in the amount of eIF4G which co-purified with the latter. This could account for the previously observed impairment of eIF4F function during heat shock, and, since heat shock protein mRNAs are believed to be relatively cap-independent, could provide a mechanism for the selective up-regulation of the synthesis of heat shock proteins and other stress proteins during heat shock.

Animals↗
PubMed1997

Mitogen-activated protein kinases activate the serine/threonine kinases Mnk1 and Mnk2.

Mitogen-activated protein (MAP) kinases bind tightly to many of their physiologically relevant substrates. We have identified a new subfamily of murine serine/threonine kinases, whose members, MAP kinase-interacting kinase 1 (Mnk1) and Mnk2, bind tightly to the growth factor-regulated MAP kinases, Erk1 and Erk2. MNK1, but not Mnk2, also binds strongly to the stress-activated kinase, p38. MNK1 complexes more strongly with inactive than active Erk, implying that Mnk and Erk may dissociate after mitogen stimulation. Erk and p38 phosphorylate MNK1 and Mnk2, which stimulates their in vitro kinase activity toward a substrate, eukaryotic initiation factor-4E (eIF-4E). Initiation factor eIF-4E is a regulatory phosphoprotein whose phosphorylation is increased by insulin in an Erk-dependent manner. In vitro, MNK1 rapidly phosphorylates eIF-4E at the physiologically relevant site, Ser209. In cells, Mnk1 is post-translationally modified and enzymatically activated in response to treatment with either peptide growth factors, phorbol esters, anisomycin or UV. Mitogen- and stress-mediated MNK1 activation is blocked by inhibitors of MAP kinase kinase 1 (Mkk1) and p38, demonstrating that Mnk1 is downstream of multiple MAP kinases. MNK1 may define a convergence point between the growth factor-activated and one of the stress-activated protein kinase cascades and is a candidate to phosphorylate eIF-4E in cells.

3T3 Cells↗
PubMed1997

Continuous, pulsed or single acute irradiation of a transplanted rodent tumour model.

BACKGROUND: Recent advances in remote afterloading pulsed mode brachytherapy have provided a much needed tool for the radiation oncologist. It has the versatility of optimised physical dose distribution along with improved staff radiation protection and patient nursing. PURPOSE: This preliminary study was designed to explore the radiobiological equivalence between conventional continuous low dose rate tumour irradiation (CLDR) and the new technique of pulsed dose irradiation (PDR). MATERIALS AND METHODS: Subcutaneous isogenic sarcomas transplanted in female John's Strain Wistar rats were irradiated locally with acute, pulsed or continuous interstitial low dose-rate exposures at 9-11 mm mean diameter. RESULTS: As expected, single acute doses (5-40 Gy) were more effective (P < 0.01) in achieving tumour growth delay (1.4 days/Gy) than CLDR exposure (4-51 Gy) over 24-48 h (0.93 days/Gy). However, PDR treatment (8 hourly fractions/day) at high dose-rate (8-48Gy) over 8-72 h was significantly (P = 0.01) more effective (1.66 days/Gy) than CLDR but not acute exposures. CONCLUSIONS: These data suggest that, clinically a significantly improved therapeutic ratio may also be achievable with pulsed high dose rate brachytherapy, and that further radiobiological studies with in-vivo tumour models are needed.

Animals↗
PubMed1996

Insulin-stimulated phosphorylation of initiation factor 4E is mediated by the MAP kinase pathway.

The cap-binding initiation factor 4E (eIF4E) is regulated by phosphorylation and by the inhibitory binding protein 4E-BP1. Here we show that insulin-induced phosphorylation of eIF4E is not significantly affected by rapamycin, but is sensitive to wortmannin, which inhibits phosphatidylinositol 3'-kinase and blocks the activation of MAP kinase. Since PD098059, an inhibitor of MAP kinase activation, also blocks insulin-induced phosphorylation of eIF4E, the MAP kinase pathway seems to mediate this effect. Phosphorylated eIF4E can still bind to 4E-BP1. These data illustrate that (i) distinct signalling pathways mediate the phosphorylation of eIF4E and 4E-BP1 and (ii) phosphorylation of eIF4E, unlike that of 4E-BP1, does not lead directly to the release of 4E-BP1.

Androstadienes↗
PubMed1996

Both rapamycin-sensitive and -insensitive pathways are involved in the phosphorylation of the initiation factor-4E-binding protein (4E-BP1) in response to insulin in rat epididymal fat-cells.

There is mounting evidence that in fat and other insulin-sensitive cells activation of protein synthesis may involve the dissociation of a protein (4E-BP1) from eukaryotic initiation factor (eIF)-4E thus allowing formation of the eIF-4F complex. This study compares the effects of insulin and epidermal growth factor (EGF) on the phosphorylation of 4E-BP1 in fat-cells (followed by gel-shift assays and incorporation of 32P) and on its association with eIF-4E. Several lines of evidence suggest that mitogenactivated protein kinase (MAP kinase) is not involved in these effects of insulin. Insulin causes much more extensive phosphorylation and dissociation of 4E-BP1 from eIF-4E than EGF, although EGF activates MAP kinase to a much greater extent than insulin. Moreover, MAP kinase does not phosphorylate 4E-BP1 when it is complexed with eIF-4E. In contrast, insulin activates the 40S ribosomal protein S6 kinase (p70S6K) 18-fold compared with a 2-fold activation by EGF, and the time course of this activation is similar to the phosphorylation and dissociation of 4E-BP1. Rapamycin, a specific inhibitor of the activation of this latter kinase, inhibits dissociation of 4E-BP1 from eIF-4E in cells incubated with insulin but reveals a phosphorylated from of 4E-BP1 which remains bound to eIF-4E. It is concluded that in rat epididymal fat-cells, the effects of insulin on 4E-BP1 involves multiple phosphorylation events. One phosphorylation event is rapamycin-insensitive, occurs only on bound 4E-BP1 and does not initiate dissociation. The second event does result in dissociation and is blocked by rapamycin, suggesting that the p70S6K signalling pathway is involved: p70S6K itself is probably not involved directly as this kinase does not phosphorylate 4E-BP1 in vitro.

Adipocytes↗
PubMed1996

Insulin and phorbol ester stimulate initiation factor eIF-4E phosphorylation by distinct pathways in Chinese hamster ovary cells overexpressing the insulin receptor.

We have developed a one-dimensional isoelectric focusing technique to measure changes in the steady-state phosphorylation of the cap-binding initiation factor, eIF-4E. We have used a Chinese hamster ovary cell line transfected with the human insulin receptor (CHO.T cells) to study the regulation of eIF-4E phosphorylation by insulin and other stimuli. Exposure of CHO.T cells to insulin, phorbol ester or serum resulted in a rapid increase (up to twofold) in eIF-4E phosphorylation. As a control, we have also performed experiments with the parental cell line, CHO.K1 cells, in which both serum and phorbol ester, but not nanomolar concentrations of insulin, produce similar changes in eIF-4E phosphorylation. We have used two complementary approaches to study the role of protein kinase C (PKC) in these responses: a highly specific inhibitor of PKC and down-regulation of PKC by prior treatment of the cells with phorbol ester. In CHO.T cells, both approaches indicate that PKC is required for the response to phorbol ester but that insulin and serum each increase eIF-4E phosphorylation by a mechanism(s) independent of this protein kinase. Similarly, PKC is necessary for the effects of phorbol ester, but not of serum, on eIF-4E phosphorylation in CHO.K1 cells. These data indicate that multiple signal transduction mechanisms are involved in the modulation of eIF-4E phosphorylation and the implications of these findings are discussed.

Amino Acid Sequence↗
PubMed1996

Glucose stimulates the activity of the guanine nucleotide-exchange factor eIF-2B in isolated rat islets of Langerhans.

Over short time periods glucose controls insulin biosynthesis predominantly through effects on preexisting mRNA. However, the mechanisms underlying the translational control of insulin synthesis are unknown. The present study was carried out to determine the effect of glucose on the activity and/or phosphorylation status of eukaryotic initiation and elongation factors in islets. Glucose was found to increase the activity of the guanine nucleotide-exchange factor eIF-2B over a rapid time course (within 15 min) and over the same range of glucose concentrations as those that stimulate insulin synthesis (3-20 mM). A nonmetabolizable analogue of glucose (mannoheptulose), which does not stimulate insulin synthesis, failed to activate eIF-2B. The best characterized mechanism for modulating eIF-2B activity involves changes in the phosphorylation of the alpha-subunit of its substrate eIF-2. However, in islets, no change in eIF-2 alpha phosphorylation was seen under conditions where eIF-2B activity was increased, implying that glucose regulates eIF-2B via an alternative pathway. Glucose also did not affect the phosphorylation states of three other regulatory translation factors. These are the cap-binding factor eIF-4E, 4E-binding protein-1, and elongation factor eEF-2, which do not therefore seem likely to be involved modulating the translation of the preproinsulin mRNA under these conditions.

Animals↗
PubMed1996

Replacement of hairpin and loop implants by optimised straight line sources.

Remote after loading is desirable for all forms of brachytherapy but is difficult in the oral cavity because the tight curvature at the top of implanted loops impedes passage of the source. For this reason we investigated differential loading of straight catheters to simulate a conventional loop or hairpin. Using a pulsed brachytherapy remote after loader the top four dwell positions of straight catheters were given two to four times the dwell time of other source positions. This raised the reference isodose to cover the surface mucosa without significantly changing either the total volume treated or the volume receiving > 150% of reference dose when compared with conventional loop implants of equivalent source length and separation. This optimised straight line implant should therefore be amenable to remote afterloading and have similar dose/volume characteristics to loops.

Brachytherapy↗
PubMed1996

Effect of dietary calcium intake and meal calcium content on calcium absorption in the rat.

Fifty-four male and forty-five female 7-week-old rats, Wistar strain, average weights 190 g and 140 g respectively, were randomized by weight into three groups of eighteen rats each (males) and three groups of fifteen rats each (females) and fed on a semi-purified diet containing (per kg) 2 (low), 5 (normal) or 20 g (high) Ca as CaCO3 for 2 weeks. Each group was then further randomized into three groups of six rats each (males) and five rats each (females) and given a meal (10 g of the same diet) containing either 2, 5 or 20 g Ca as 47CaCO3. 47Ca was determined in quantitative daily collections of faeces over 7 d and fractional absorption of 47Ca estimated by extrapolating the linear portion (days 3-7) of the plot of log 47Ca retention v. time back to the time of isotope administration. Absorption of meal Ca was higher in males than in females and was affected similarly in males and females by previous dietary Ca intake and meal Ca content. Fractional absorption of meal Ca decreased with increasing previous dietary Ca intake and with increasing meal Ca content, and the combined effect of these two variables caused fractional Ca absorption to vary from 11-89%. Absolute absorption of meal Ca decreased with increasing previous dietary Ca intake and increased with increasing meal Ca content. The influence on Ca absorption of variations in meal Ca content (load effect) was greater than that of variations in previous dietary Ca intake (adaptive effect). These results show that previous dietary Ca intake and meal Ca content are both major determinants of Ca absorption from meals in intact rats fed in the normal way and that the rat responds to these factors in a manner similar to that reported for humans. This study provides further evidence of similarities between rats and humans in dietary Ca absorption.

Animal Feed↗
PubMed1996

Microsurgical correction of bilateral facial contour deformities.

Bilateral facial contour deformities are difficult reconstructive problems to correct. This paper summarizes our experience with five adult patients who were operated on for the correction of bilateral contour deformities. The etiologies of the contour deformities were one case of systemic lupus erythematosus, three cases of hemangioma/lymphangiomas, and one case of systemic lipodystrophy. Patient ages at the time of surgical correction ranged from 19 to 65 years. In two patients, staged microvascular free-tissue transfers were performed. In three patients, a single free flap was used for reconstruction. Seven microvascular free flaps were used to reconstruct facial contour: three superficial inferior epigastric flaps and four inframammary extended circumflex scapular flaps. In three patients, recipient sites were dissected by means of a limited preauricular incision, and the superficial temporal artery and vein were utilized as recipient vessels. The two remaining patients underwent free-tissue transfer to branches of the external carotid system. There were no flap losses in this series. Follow-up ranged from 1 to 4 years. A stable restoration of facial contour was achieved in all five patients. Microsurgical correction of soft-tissue contour problems is possible in bilateral deformities, and superior results are easier to achieve than in unilateral facial contour deformities. Either single or staged reconstructions can restore facial contour depending on the distribution of soft-tissue requirements.

Adult↗