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Biomedical subjects

B Byrne

Publications and source records attributed to B Byrne.

At least 37 records · Page 2Linked to original sources
PubMed1999

Optimisation of a technique for isolating lymphocyte subsets from human endometrium.

Human endometrium is a rich source of lymphocytes which may have unique immunoregulatory functions. The aim of this study was to compare current procedures for endometrial tissue disaggregation, and optimise a method for isolation of endometrial lymphocytes. Tissue was obtained from 41 women undergoing elective hysterectomy or dilation and curettage (D&C) for reasons of benign non-endometrial pathology. Specimens were exposed to reduction/chelation, mechanical or enzymatic disruption. Optimal single cell suspensions of high yields (mean 8.8 x 10(6) range 3.5-18 x 10(6)lymphs) and good viability (60%) were obtained, using a combination of collagenase IV (200 U/ml) and DNase I (35 U/ml). Suspensions were further purified by density gradient centrifugation. Multi-colour flow cytometry was used for analysis of endometrial lymphocyte subsets. Cell suspensions were stained with mAbs specific for CD3, CD4, CD8, CD56, CD45 and CD14, and it was clearly shown that the developed method had no effect on surface glycoprotein expression. Phenotypic analysis revealed consistent populations of endometrial large granular lymphocytes (CD56+CD3-) 54.16%, and T-cells (CD3+) 37.73%. This technique was applicable to the characterisation of T-cell populations, including CD8+ (56.6%), CD4+ (44.0%), and particularly smaller populations of CD4+CD8+(3.56%), CD4-CD8-(3.34%) and CD56+(6.3%) due to it's sensitivity. In conclusion, optimised enzymatic digestion, in combination with flow cytometry provides an effective method for phenotypic examination of small endometrial lymphocyte subpopulations.

Adult↗
PubMed1998

Functional analysis of GnRH receptor ligand binding using biotinylated GnRH derivatives.

The objective of this study was to determine whether the gonadotrophin-releasing hormone (GnRH) ligand binds to the GnRH receptor (GnRH-R) with either the N- and C-termini or the beta-II turn pointing towards the cell. The functionality of GnRH and two biotinylated GnRH derivatives, biotin [D-Lys6]GnRH and biotin [Gln1]GnRH biotinylated at positions 6 and 1, respectively was assessed. Streptavidin was also used in combination with these peptides to investigate the effects of the steric hindrance caused by this molecule on ligand binding when bound to the biotin molecules at the two positions. GnRH bound to the receptor with high affinity, which was not affected by the addition of streptavidin. Both the biotinylated derivatives bound to the receptor though with lower affinities than GnRH. The biotin [D-Lys6]GnRH-streptavidin complex bound to the receptor albeit with lower affinity compared to biotin [D-Lys6]GnRH only, although it maintained its ability to cause receptor internalisation. The ability of the biotin [Gln1]GnRH to bind to the receptor was abolished in the presence of excess streptavidin. Both GnRH and biotin [D-Lys6]GnRH stimulated total inositol phosphate production whereas biotin [Gln1]GnRH exhibited GnRH antagonist activity. It appears that the small biotin molecule can be accommodated within the binding pore when attached to position 1 of the ligand but not when complexed to streptavidin. The fact that biotin [D-Lys6]GnRH maintains functionality when complexed to streptavidin while biotin [Gln1]GnRH does not, suggests that the N- and possibly the C-termini are required for receptor binding. Thus the most likely binding orientation for the ligand is with the N- and C-termini pointing inwards with the residue at position 6 pointing away from the binding site.

Animals↗
PubMed1998

Targeted disruption of the acid alpha-glucosidase gene in mice causes an illness with critical features of both infantile and adult human glycogen storage disease type II.

We have used gene targeting to create a mouse model of glycogen storage disease type II, a disease in which distinct clinical phenotypes present at different ages. As in the severe human infantile disease (Pompe Syndrome), mice homozygous for disruption of the acid alpha-glucosidase gene (6(neo)/6(neo)) lack enzyme activity and begin to accumulate glycogen in cardiac and skeletal muscle lysosomes by 3 weeks of age, with a progressive increase thereafter. By 3.5 weeks of age, these mice have markedly reduced mobility and strength. They grow normally, however, reach adulthood, remain fertile, and, as in the human adult disease, older mice accumulate glycogen in the diaphragm. By 8-9 months of age animals develop obvious muscle wasting and a weak, waddling gait. This model, therefore, recapitulates critical features of both the infantile and the adult forms of the disease at a pace suitable for the evaluation of enzyme or gene replacement. In contrast, in a second model, mutant mice with deletion of exon 6 (Delta6/Delta6), like the recently published acid alpha-glucosidase knockout with disruption of exon 13 (Bijvoet, A. G., van de Kamp, E. H., Kroos, M., Ding, J. H., Yang, B. Z., Visser, P., Bakker, C. E., Verbeet, M. P., Oostra, B. A., Reuser, A. J. J., and van der Ploeg, A. T. (1998) Hum. Mol. Genet. 7, 53-62), have unimpaired strength and mobility (up to 6.5 months of age) despite indistinguishable biochemical and pathological changes. The genetic background of the mouse strains appears to contribute to the differences among the three models.

Alleles↗
PubMed1998

Expression of Legionella pneumophila virulence traits in response to growth conditions.

In nature, Legionella pneumophila replicates exclusively as an intracellular parasite of amoebae, but it also persists in the environment as a free-living microbe. Studies of how this opportunistic pathogen recognizes and responds to distinct extracellular and intracellular environments identified a link between the growth phase and expression of traits previously correlated with virulence. When cultured in broth, only post-exponential-phase L. pneumophila was sodium sensitive, cytotoxic, osmotically resistant, competent to evade macrophage lysosomes, infectious, and motile. Likewise, the L. pneumophila phenotype changed during growth in macrophages. During the intracellular replication period, this bacterium was sodium resistant and lacked flagella; concomitant with macrophage lysis, L. pneumophila became sodium sensitive and flagellated. Expression of the virulent phenotype was a response to starvation, since exponential-phase L. pneumophila became cytotoxic, sodium sensitive, and motile after incubation in broth from stationary-phase cultures, except when it was supplemented with amino acids. Together, these data indicate that while nutrients are plentiful, intracellular L. pneumophila organisms are dedicated to replication; when amino acids become limiting, the progeny express virulence factors to escape the spent host, to disperse and survive in the aquatic environment, and to reestablish a protected intracellular niche favorable for growth.

Animals↗
PubMed1997

Human small intestinal epithelial cells secrete interleukin-7 and differentially express two different interleukin-7 mRNA Transcripts: implications for extrathymic T-cell differentiation.

The small intestinal epithelium, composed of epithelial cells (EC) and intraepithelial T lymphocytes, is exposed to numerous ingested antigens. Small intestinal EC may act as accessory and/or antigen presenting cells for intestinal T cells, some of which may mature extrathymically and regulate local immunity and tolerance. Since interleukin-7 (IL-7) plays an essential role in T cell maturation and activation, we examined its expression by human small intestinal EC. IL-7 was detected by ELISA in supernatants from 4 of 4 epithelial layer (EpL) cultures. Using RT-PCR, IL-7 mRNA was detected in 4 EpL studied, and two distinct IL-7 transcripts were identified in 3 of the 4. The ratios of the intensities of the larger to the smaller bands varied amongst individuals. Furthermore, the intensity ratios were higher in whole-thickness intestine and lamina propria preparations than in their corresponding EpL. This is the first report of the expression of two IL-7 transcripts in human intestine and of IL-7 secretion by human small intestinal EpL cells. This supports the hypothesis that small intestinal EC may influence differentiation and/or activation of neighboring T cells. The differential expression of the two transcripts may have important implications for immune regulation in the intestinal epithelium.

Biopsy↗
PubMed1996

Role of progesterone and nonsteroidal ovarian factors in regulating gonadotropin-releasing hormone self-priming in vitro.

We investigated the effects of gonadotropin surge-attenuating factor (GnSAF), inhibin, and follistatin on GnRH self-priming and its augmentation by progesterone. Two GnRH challenges, 60 min apart, were administered to rat pituitary monolayers after 90-min exposure to medium alone (control), progesterone, GnSAF, inhibin, or follistatin. Inhibin-stripped follicular fluid from superovulated women was used as a source of GnSAF bioactivity. Under control conditions, the greater response to the second GnRH challenge (peak 2, 9.2 +/- 2.1; peak 1, 4.4 +/- 0.9 ng LH/mL; P < 0.01) demonstrated GnRH self-priming. None of the treatments significantly altered the first LH peak. Progesterone markedly increased GnRH self-priming (peak 2, 12.6 +/- 2.5 ng LH/mL; P < 0.01). However, GnSAF and RU486 significantly reduced GnRH self-priming (peak 2, 4.6 +/- 0.9 and 5.6 +/- 1.6 ng LH/mL, respectively; P < 0.01). The augmentation of self-priming induced by progesterone was completely abolished by coincubation with either GnSAF or RU486 (peak 2, 7.5 +/- 1.6 and 4.3 +/- 0.9 ng LH/mL, respectively; P < 0.01). Neither inhibin nor follistatin had any effect on GnRH self-priming or its augmentation by progesterone. The actions of RU486 in the presence and absence of progesterone demonstrate a nonprogestagenic effect of RU486 on the gonadotropes. In conclusion, the suppression of GnRH self-priming, with or without progesterone augmentation, supports the hypothesis that GnSAF acts by maintaining the pituitary in an unprimed state of reduced responsiveness to GnRH.

Animals↗
PubMed1996

The effects of steroidal and non-steroidal ovarian hormones on pituitary responsiveness to gonadotrophin surge-attenuating factor.

Primary pituitary cultures from adult female rats were used to investigate the effects of steroidal (oestradiol and progesterone) and non-steroidal (inhibin, follistatin) ovarian hormones on the suppressive actions of the ovarian factor gonadotrophin surge-attenuating factor (GnSAF) in the control of gonadotrophin secretion. The source of GnSAF was a chromatographic preparation from follicular fluid containing four distinct protein bands as resolved on SDS-PAGE. Oestradiol and progesterone added alone had no effect on gonadotrophin secretion but had a wide range of effects on the suppression of both LH and FSH secretion caused by the non-steroidal factors. Oestradiol, progesterone and oestradiol+progesterone enhanced the suppressive actions of GnSAF on GnRH-induced LH secretion (causing 19.3 +/- 5.2% (P < 0.05), 41.9 +/- 3.4% (P < 0.001) and 32.2 +/- 5.3% (P < 0.001) greater suppression than GnSAF alone). Progesterone and oestradiol+progesterone completely abolished the suppression of basal FSH secretion caused by inhibin (causing 157.1 +/- 22.2%, P < 0.001, and 160.9 +/- 11.3%, P < 0.001, stimulation compared with inhibin alone). Separately the steroids had no effect on the suppression of gonadotrophin secretion caused by follistatin. However, in combination, oestradiol+progesterone potentiated the suppressive actions of follistatin on GnRH-induced LH secretion causing 29.9 +/- 5.3% (P < 0.05) greater suppression than follistatin alone. In combination, high-dose follistatin and GnSAF caused 31.1 +/- 6.5% (P < 0.01) greater suppression than GnSAF alone. Thus in combination high-dose follistatin and GnSAF have additive effects on the suppression of GnRH-induced LH secretion. Recombinant human inhibin and GnSAF added in combination had little further effect compared with either alone suggesting that they may have a similar mechanism of action at the pituitary level. These results demonstrate that while FSH secretion in vitro is mainly controlled by inhibin and follistatin, LH secretion is affected by the presence of a whole range of factors. We have demonstrated that oestradiol and progesterone potentiate the suppressive actions of GnSAF in vitro. These data are compatible with the suggestion that in the late follicular phase it is falling levels of GnSAF that allow positive feedback of the steroids on the pituitary to elicit the LH surge, rather than increases in the stimulatory effects of the ovarian steroids overcoming GnSAF. The actions of GnSAF on the pituitary may be modulated by follistatin but it is unlikely that inhibin has any modulatory effects on the GnSAF-induced suppression of LH secretion.

Animals↗
PubMed1996

Breast milk for preterm infants.

The breast-feeding intentions and achievements of mothers of babies born prematurely were investigated in a prospective enquiry, a postal survey and by interview. The prospective inquiry was conducted from April 19 1993 to March 19 1994 on all 686 infants admitted to the two neonatal units in Nottingham. The aim was to see how many infants were offered mother's breast milk by any route. Feeding records were available for 593 infants of whom 64% were offered mother's breast milk. Gestation did not affect the mother's ability to produce milk. Infants of 24-28 weeks' gestation received breast milk for 4 to 5 weeks on average. The postal questionnaire was sent to 114 mothers whose infants were in the units for over seven days between April and October 1994. The aim was to learn how they felt about producing milk and feeding their preterm infant. 64 [59%] responded. 54% of responders and 49% of non-responders had intended to breast feed. Of the responders 65% produced some milk and 46% were home fully breast feeding. The home interviews were conducted 2-6 weeks after discharge with 16 mothers who fulfilled the criteria for the postal enquiry. The aim was to learn from mothers how the service might be improved and what motivated their choice of feeding. They requested clear guidance, agreed by all the professionals involved; a warm, comfortable and private environment; and a ready supply of breast pumps. Their choice of feeding was motivated primarily by previous experience and family pressure, not by advice from health-care professionals. CONCLUSIONS. Many mothers succeed in supplying milk for their preterm infants and many more might do so if the benefits of human milk to preterm infants were more actively advocated and the support service in the neonatal units developed.

Breast Feeding↗
PubMed1995

Gonadotropin surge-attenuating factor bioactivity in serum from superovulated women is not blocked by inhibin antibody.

Primary pituitary cultures from adult female rats were used to investigate gonadotropin surge attenuating factor (GnSAF) bioactivity. Serum from superovulated women was charcoal-treated and incubated with either an inhibin antibody (MC4), normal sheep serum (NSS), or serum-free defined medium (SFDM) before addition to cell culture. The reduction in GnRH-induced LH secretion (GnSAF bioactivity) produced by the serum (30.1 +/- 6.5%, p < 0.001, of control) was not altered by prior incubation with either MC4 or NSS (24.9 +/- 3.6 and 23.2 +/- 2.7%, p < 0.001, of control, respectively). This indicates that GnSAF bioactivity present in serum from superovulated women is not entirely attributable to inhibin. Recombinant human inhibin reduced basal FSH secretion to 24.6 +/- 4.7% (p < 0.001) of the control value. However, this was totally abolished by prior incubation with MC4, but not NSS. We have also shown that ovarian steroids are not responsible for GnSAF bioactivity in vitro. In conclusion, in contrast to findings in superovulated rats, inhibin antibody did not block GnSAF bioactivity in serum from superovulated women.

Animals↗
PubMed1994

Higher gonadotrophin surge-attenuating factor bioactivity is found in small follicles from superovulated women.

Ovine and rat pituitary bioassays for gonadotrophin surge-attenuating factor (GnSAF) were utilized to determine whether the level of GnSAF bioactivity in pooled human follicular fluid (hFF) from superovulated women varied according to follicle diameter (< or = 11 mm, 12-15 mm and 16-21 mm follicles examined using the ovine bioassay, or < or = 10 mm, 11-13 mm, 14-17 mm, 18-20 mm, 21-24 mm and > or = 25 mm follicles examined using the rat bioassay). When tested using dispersed ovine pituitary cells, GnSAF bioactivity, expressed in terms of the reduction in gonadotrophin-releasing hormone (GnRH)-induced LH secretion, was inversely related to follicle diameter (P < 0.01). In response to 5 microliters hFF/well from follicles of < or = 11, 12-15 and 16-21 mm diameter, GnRH-induced LH secretion was reduced to 40.5 +/- 6.9%, 65.2 +/- 6.6% and 83.7 +/- 7.9% of control respectively. A similar inverse relationship was observed when a second batch of hFF samples from different sized follicles was tested using rat pituitary cell monolayers. Expressing GnSAF bioactivity in terms of the dose required to suppress GnRH-induced LH secretion by rat pituitary cells to 50% of the maximal suppression observed (ED50), the three smallest follicle size pools contained the most GnSAF (ED50 values of 0.13, 2.79 and 5.36 microliters hFF/well from follicles of < or = 10, 11-13 and 14-17 mm respectively). The ED50 values for follicles of 18-20, 21-24 and > or = 25 mm were 8.81, 27.1 and 60.0 microliters hFF/well respectively. Thus hFF from follicles < or = 11 mm was over 450 times more potent than hFF from follicles > or = 25 mm in suppressing GnRH-induced LH release. The ED50 values for inhibin bioactivity (measured as the suppression of basal FSH secretion from rat pituitary monolayers) were much less variable than those for GnSAF bioactivity (between 0.85 and 0.13 microliters hFF/well). Inhibin immunoreactivity, measured by a two-site immunoradiometric assay, followed the same pattern as inhibin bioactivity with lowest concentrations in the smallest follicles (41.96 ng/ml) and highest concentrations in the three largest follicle size groups (56.48-64.48 ng/ml). The specific effects of inhibin on GnRH-induced LH and basal FSH release in these pituitary bioassays were determined by incubating culture dishes with pure recombinant human inhibin at doses of 0.025-25 ng/well. In both the sheep and rat pituitary monolayers, basal FSH was suppressed (ED50 = 0.02 and 0.16 ng/well respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Circulating gonadotrophin surge-attenuating factor from superovulated women suppresses in vitro gonadotrophin-releasing hormone self-priming.

A perifusion system based on ovine pituitary tissue explants was used to investigate the effects of follicular fluid (hFF) and serum from superovulated women on pituitary responsiveness to gonadotrophin-releasing hormone (GnRH). The specific aims of the study were to determine both if gonadotrophin surge-attenuating factor (GnSAF) bioactivity is present in the peripheral circulation as well as in the follicles of superovulated women and if GnSAF suppresses GnRH self-priming in vitro. Two pulses of GnRH, 1 h apart, produced marked peaks in LH secreted from control chambers, with GnRH self-priming evident in the significant difference between the first (134.4 +/- 1.7 - 232.1 +/- 24.0% of basal secretion) and second (183.9 +/- 15.8 - 313.9 +/- 14.0% of basal secretion) LH peaks. Both follicular fluid and serum pooled from two different groups of women produced marked suppression of the first (unprimed) and second (primed) LH peaks. The hFF reduced the first LH peak to 69.6 +/- 7.8 and 60.2 +/- 9.7% and the second LH peak to 57.4 +/- 6.7 and 42.6 +/- 6.5% of control LH secretion. Overall, the serum reduced the first and second LH peaks to 76.8 +/- 4.2 and 62.9 +/- 3.6% of control respectively. These results demonstrated that GnSAF bioactivity suppresses GnRH self-priming, and is present in both the peripheral circulation and hFF. The same material administered to dispersed ovine pituitary monolayers produced similar marked suppression of GnRH-induced LH secretion, with approximately 50-fold less GnSAF bioactivity in serum compared with hFF. Combined doses of oestradiol and progesterone, or hFF from large follicles containing little GnSAF, produced stimulation of GnRH-induced LH secretion and GnRH self-priming (second peaks 78.1 +/- 38.9 and 27.4 +/- 15.7% respectively higher than first peaks). Thus, in conclusion, GnSAF in hFF and serum markedly attenuated both unprimed and primed pituitary response to GnRH, virtually abolishing the GnRH self-priming effect.

Animals↗
PubMed1991

Effects of green or white light for treatment of seasonal depression.

Twelve subjects with winter depression were treated with equal quanta of green or white light in a randomized crossover study. Each treatment condition consisted of 2 hours of exposure each morning for 1 week, with at least 1 interventing week without treatment. Ratings made without knowledge of treatment condition were done before and after each condition. Both treatments significantly reduced depression ratings. White light was significantly more effective than green light in reducing endogenous symptoms, but not the "atypical" symptoms that are common features of winter depression. Furthermore, sequence of treatment conditions influenced antidepressant responses. Broad-band white light may be optimal for maximizing therapeutic response.

Adult↗
PubMed1991

Sex steroids, adiposity and smoking in the pathogenesis of idiopathic hirsutism and polycystic ovary syndrome.

Hyperestronemia may be central to the development of polycystic ovary syndrome. The present study was designed to examine whether increased availability of androstenedione or increased aromatase closely associated with adiposity, plays the dominant role in the development of hyperestronemia. We measured plasma androstenedione, estrone and the estrone/androstenedione ratio (an indirect index of peripheral aromatase activity), in 141 patients with idiopathic hirsutism and in 88 patients with polycystic ovary syndrome. Estrone levels were higher in polycystic ovary syndrome, 250.4 +/- 129 (mean +/- standard deviation) than in idiopathic hirsutism, 210.6 +/- 119 pmol/l, p less than 0.05. Plasma androstenedione levels were higher in polycystic ovary syndrome, 8.24 +/- 3.5, than in idiopathic hirsutism, 7.1 +/- 1.7 nmol/l, p less than 0.0025. However, the estrone/androstenedione ratio was similar in the two groups. In all patients who smoked, androstenedione was higher, 8.14 +/- 3.22 than in nonsmokers, 6.99 +/- 2.96 nmol/l, p less than 0.005. Smokers had a lower body mass index, 23.9 +/- 2.3, than non-smokers 25.6 +/- 4.8 kg/m2, p less than 0.025. However, estrone levels were similar in smokers and in non-smokers. These data indicate that elevated estrone is more closely related to increased availability of androstenedione than to increased aromatase activity. While cigarette smoking appears to increase androstenedione levels, it may inhibit aromatase activity either directly or indirectly because of an associated reduction in adiposity. However, since the relative frequency of polycystic ovary syndrome and idiopathic hirsutism was similar in smokers and non-smokers, smoking did not appear to reduce estrone bioactivity as had been claimed.

Adrenal Glands↗
PubMed1990

Light-induced plasma melatonin suppression in seasonal affective disorder.

1. Subjects with seasonal affective disorder were exposed to 0, 500 and 1000 lux of white light for one hour beginning at 0300 hours. 2. Plasma samples were taken periodically and analysed for melatonin. 3. Plasma melatonin levels were suppressed by exposure to both 500 and 1000 lux light levels, suggesting that SAD patients show no neuroendocrine insensitivity to light but may show supersensitive responses to light.

Female↗
PubMed1990

Treatment of winter depression with a portable, head-mounted phototherapy device.

1. A portable, head-mounted device was developed for administration of light therapy. A randomized crossover protocol was used to test the therapeutic efficacy of this device, compared to a standard light box, for treatment of winter depression. 2. Depressive symptoms were significantly reduced by both the head-mounted device and the light box. 3. Therapeutic efficacy of the two devices was not significantly different. 4. The head-mounted device was rated by patients as significantly more convenient than the conventional light box; this may be important in improving patient compliance.

Adult↗