Developmental regulation of preproenkephalin (PENK) gene expression in the adrenal gland of the ovine fetus and newborn lamb: effects of hypoxemia and exogenous cortisol infusion

1997 ◽  
Vol 155 (1) ◽  
pp. 143-149 ◽  
Author(s):  
M Fraser ◽  
SG Matthews ◽  
G Braems ◽  
T Jeffray ◽  
Keyword(s):  
Gene Expression ◽  
Adrenal Gland ◽  
Plasma Cortisol ◽  
Late Gestation ◽  
Mrna Levels ◽  
Fetal Sheep ◽  
Adult Sheep ◽  
Organ Systems ◽  
Response To Stress ◽  
In Pregnancy

Development of the fetal adrenal gland is crucial not only for maturation of several fetal organ systems and the initiation of parturition, but also for the development of the fetal response to stress. The enkephalin-related peptides are present in the chromaffin cells of the fetal adrenal medulla and are secreted in response to stress and with sympathetic stimulation. However, changes in expression of preproenkephalin (PENK) with gestation and in response to stress have not been studied in detail. Therefore we examined the developmental pattern of PENK gene expression in the adrenal gland of fetal and newborn lambs, and of adult sheep. We also determined whether levels of PENK mRNA in the fetal adrenal gland changed in response to exogenous glucocorticoids in late gestation, or in response to hypoxemia. Adrenal glands were removed from fetal sheep, lambs and adult sheep at different stages of development for measurement of PENK mRNA. Cortisol was infused (5 micrograms/min) for 12, 24 or 96 h beginning on day 124-129 of gestation. Moderate hypoxemia was induced for 48 h beginning on day 126-130, or at day 134-136 of gestation, by lowering the maternal fractional inspired oxygen. At the end of the treatment periods, the ewes and fetuses were euthanized. Adrenal PENK mRNA were measured by Northern blot analysis. PENK mRNA levels in fetal adrenals were significantly higher (P < 0.05) on days 140-141 of gestation than earlier in pregnancy, and then decreased significantly with the onset of parturition (days 142-146). After cortisol infusion to the fetus for 96 h there was a significant reduction in adrenal PENK mRNA levels. Hypoxemia resulted in a significant increase in PENK mRNA levels in fetuses at day 126-130 of gestation, but not at the later time in pregnancy when endogenous plasma cortisol concentrations were higher. We conclude that there is a decrease in levels of PENK mRNA in the fetal adrenal gland before parturition at the time of the endogenous prepartum rise in plasma cortisol. Hypoxemia led to an elevation of PENK mRNA levels in fetuses at less than 130 days, but after that time, when the basal and stimulated cortisol responses had risen, there was no significant effect of hypoxemia on PENK mRNA. Cortisol infusion to the fetus at this stage of pregnancy resulted in a decrease in adrenal PENK mRNA levels. We suggest that cortisol may play an important role in the regulation of fetal adrenal PENK mRNA levels and enkephalin synthesis by the adrenal gland of the fetal sheep.

Divergent changes in plasma ACTH and pituitary POMC mRNA after cortisol administration to late-gestation ovine fetus

1998 ◽  
Vol 274 (3) ◽  
pp. E417-E425 ◽  
Author(s):  
T. M. Jeffray ◽  
S. G. Matthews ◽  
G. L. Hammond ◽  
J. R. G. Challis
Keyword(s):  
Plasma Cortisol ◽  
Late Gestation ◽  
Pars Intermedia ◽  
Mrna Levels ◽  
Plasma Acth ◽  
Negative Feedback Regulation ◽  
Fetal Sheep ◽  
Pomc Mrna ◽  
Free Cortisol ◽  
Ovine Fetus

Plasma concentrations of cortisol and adrenocorticotropic hormone (ACTH) rise in the late-gestation sheep fetus at approximately the same time as there is an increase in the plasma levels of corticosteroid- binding globulin (CBG). We hypothesized that intrafetal cortisol infusion during late pregnancy would stimulate an increase in fetal plasma CBG, which in turn would bind cortisol and diminish glucocorticoid negative-feedback regulation of the fetal pituitary, leading to an increase in plasma ACTH concentrations. Cortisol was infused into chronically catheterized fetal sheep beginning at 126.1 ± 0.5 days of gestation and continued for 96 h. Control fetuses were infused with saline. In cortisol-infused fetuses, the plasma cortisol concentrations rose significantly from control levels (4.4 ± 0.6 ng/ml) to 19.3 ± 3.1 ng/ml within 24 h and remained significantly elevated throughout the infusion period. Plasma immunoreactive (ir) ACTH concentrations were significantly elevated in cortisol-infused fetuses within 24–48 h and remained significantly higher than in controls throughout the 96-h experimental period. Plasma free cortisol concentrations increased 10-fold and remained significantly elevated in cortisol-infused animals, despite a rise in plasma corticosteroid-binding capacity. Levels of pituitary proopiomelanocortin (POMC) mRNA in the fetal pars distalis and pars intermedia were 96 and 38% lower, respectively, after 96 h of cortisol infusion. Therefore physiological elevations of plasma cortisol, in the late-gestation ovine fetus, lead to increases in mean plasma irACTH concentrations, but this is not associated with increases in fetal pituitary POMC mRNA levels.

Hypothalamic-pituitary disconnection in fetal sheep blocks the peripartum increases in adrenal responsiveness and adrenal ACTH receptor expression

2005 ◽  
Vol 289 (2) ◽  
pp. R410-R417 ◽  
Author(s):  
Nancy K. Valego ◽  
Yixin Su ◽  
Luke C. Carey ◽  
Sharla F. Young ◽  
Stephen B. Tatter ◽  
...  
Keyword(s):  
Plasma Cortisol ◽  
Receptor Expression ◽  
Late Gestation ◽  
Mrna Levels ◽  
Acth Stimulation ◽  
Fetal Sheep ◽  
Protein Levels ◽  
Overnight Incubation ◽  
Acth Receptor ◽  
Underlying Mechanisms

Although it has been recognized for over a decade that hypothalamic-pituitary disconnection (HPD) in fetal sheep prevents the late gestation rise in plasma cortisol concentrations, the underlying mechanisms remain unclear. We hypothesized that reductions in adrenal responsiveness and ACTH receptor (ACTH-R) expression may be mediating factors. HPD or sham surgery was performed at 120 days of gestation, and catheters were placed for blood sampling. At ∼138 days of gestation, fetuses were killed, and adrenals were removed for cell culture and analyses of ACTH-R mRNA and protein. After 48 h, adrenocortical cells were stimulated with ACTH for 2 h, and the medium was collected for cortisol measurement. The same cells were incubated overnight with medium or medium containing ACTH or forskolin (FSK), followed by ACTH stimulation (as above) and cortisol and cellular ACTH-R mRNA analyses. HPD prevented the late gestation increase in plasma cortisol and bioactive ACTH and reduced adrenal ACTH-R mRNA and protein levels by over 35%. HPD cells secreted significantly less cortisol than sham cells (3.2 ± 1.2 vs. 47.3 ± 11.1 ng·ml−1·2 h−1) after the initial ACTH stimulation. Overnight incubation of HPD cells with ACTH or FSK restored cortisol responses to acute stimulation to levels seen in sham cells initially. ACTH-R mRNA levels in cells isolated from HPD fetuses were decreased by over 60%, whereas overnight incubation with ACTH or FSK increased levels by approximately twofold. Our findings indicate that the absence of the cortisol surge in HPD fetuses is a consequence, at least in part, of decreased ACTH-R expression and adrenal responsiveness.

Thyroid hormones and the mRNA of the GH receptor and IGFs in skeletal muscle of fetal sheep

2002 ◽  
Vol 282 (1) ◽  
pp. E80-E86 ◽  
Author(s):  
A. J. Forhead ◽  
J. Li ◽  
R. S. Gilmour ◽  
M. J. Dauncey ◽  
A. L. Fowden
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Thyroid Hormones ◽  
Gestational Age ◽  
Plasma Cortisol ◽  
Mrna Abundance ◽  
Late Gestation ◽  
Fetal Sheep ◽  
Igf I ◽  
I Gene

Thyroid hormones are required for the normal development of skeletal muscle in utero, although their mechanism of action is poorly understood. The present study examined the effects of the thyroid hormones on the gene expression of the growth hormone receptor (GHR) and the insulin-like growth factors (IGFs) IGF-I and IGF-II, in skeletal muscle of fetal sheep during late gestation (term 145 ± 2 days) and after manipulation of plasma thyroid hormone concentration. Thyroidectomy at 105–110 days of gestation suppressed muscle GHR and IGF-I gene expression in fetuses studied at 127–130 and 142–145 days. Muscle GHR mRNA abundance remained unchanged with increasing gestational age in intact and thyroidectomized fetuses. In the intact fetuses, a decrease in muscle IGF-I gene expression was observed between 127–130 and 142–145 days, which coincided with the normal prepartum surges in plasma cortisol and triiodothyronine (T3). At 127–130 days, downregulation of muscle IGF-I mRNA abundance was induced prematurely in intact fetuses by an infusion of cortisol for 5 days (2–3 mg · kg−1 · day−1 iv), which increased plasma cortisol and T3 concentrations to values seen near term. However, increasing plasma T3 alone by an infusion of T3 for 5 days (8–12 μg · kg−1 · day−1 iv) in intact fetuses at this age had no effect on GHR or IGF-I gene expression in skeletal muscle. In the thyroidectomized fetuses, no additional change in the low level of muscle IGF-I mRNA abundance was seen with increasing gestational age, but at 127–130 days, IGF-I gene expression was reduced further when plasma cortisol and T3 concentrations were increased by exogenous cortisol infusion. Muscle IGF-II mRNA abundance was not affected by thyroidectomy, gestational age, or exogenous hormone infusion. These findings show, in the sheep fetus, that thyroid hormones may influence the growth and development of skeletal muscle via changes in the local activity of the somatotrophic axis.

scholarly journals Developmental regulation of corticotrophin receptor gene expression in the adrenal gland of the ovine fetus and newborn lamb: effects of hypoxia during late pregnancy

2001 ◽  
Vol 169 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M Fraser ◽  
GA Braems ◽  
Keyword(s):  
Adrenal Gland ◽  
Receptor Gene ◽  
In Situ Hybridisation ◽  
Adult Life ◽  
Late Pregnancy ◽  
Mrna Levels ◽  
Fetal Sheep ◽  
Altered Expression ◽  
Adult Sheep ◽  
Adrenal Tissue

Responsiveness of the fetal sheep adrenal gland to adrenocorticotrophin (ACTH) increases in late pregnancy, resulting in increased glucocorticoid production. Development of this responsiveness is an important determinant of fetal hypothalamic-pituitary-adrenal function and depends, in part, on the potential for ACTH binding to adrenal tissue. In the present study, we have examined the developmental pattern of ACTH receptor (ACTH-R) expression during the latter half of pregnancy and in neonatal and adult life. As hypoxaemia induces increases in cortisol and ACTH secretion, in addition to increasing fetal adrenal responsiveness, a further aim of this study was to investigate whether hypoxaemia was associated with altered expression of the ACTH-R gene. Whole adrenal glands were removed from fetal sheep, lambs and adult sheep at different stages of development for measurement of ACTH-R mRNA. Moderate hypoxaemia was induced for 48 h beginning on days 124-128, or on days 132-134 of gestation, by decreasing the maternal fractional inspired oxygen. ACTH-R mRNA was detected by northern blotting using a cDNA cloned in our laboratory and by in situ hybridisation. ACTH-R mRNA (3.6 kb major transcript) was detected in adrenal tissue at day 63 of gestation. Its relative abundance increased significantly (P<0.05) between days 126-128 and 140-141 of pregnancy, increased further with the onset of spontaneous labour, and remained increased in newborn lambs at 7 h-7 days after birth. ACTH-R mRNA levels then decreased in adrenal tissue from lambs and adult sheep (P<0.05). Hypoxaemia for 48 h significantly increased ACTH-R mRNA expression in adrenals of the older fetuses (days 134-136) compared with that in controls (P<0.05), but was without effect in younger fetuses. We conclude that levels of ACTH-R mRNA in the fetal adrenal gland increase as term approaches, coincident with the endogenous prepartum surge in plasma ACTH and cortisol. Sustained hypoxaemia resulted in an upregulation of mRNA encoding for ACTH-R, but only in older fetuses and in association with a sustained increase in plasma cortisol. These results are consistent with cortisol, ACTH, or both, contributing to increased fetal adrenal responsiveness, by increasing expression of fetal adrenal receptors for ACTH.

Control of hepatic insulin-like growth factor II gene expression by thyroid hormones in fetal sheep near term

1998 ◽  
Vol 275 (1) ◽  
pp. E149-E156 ◽  
Author(s):  
Alison J. Forhead ◽  
Juan Li ◽  
R. Stewart Gilmour ◽  
Abigail L. Fowden
Keyword(s):  
Gene Expression ◽  
Growth Factor ◽  
Thyroid Hormones ◽  
Plasma Cortisol ◽  
Plasma Concentrations ◽  
Mrna Abundance ◽  
Mrna Levels ◽  
Insulin Like Growth Factor ◽  
Fetal Sheep ◽  
Fetal Plasma

The effects of thyroid hormones on hepatic insulin-like growth factor (IGF) II gene expression and their interaction with cortisol in the ontogenic control of this gene were investigated in fetal sheep during late gestation (term 145 ± 2 days) and after experimental manipulation of fetal plasma hormone concentrations. In intact fetuses, a significant decrease in hepatic IGF-II mRNA abundance was observed between 127–130 and 142–145 days of gestation, which coincided with the normal prepartum rise in plasma cortisol and triiodothyronine (T3) concentrations. This ontogenic decline in hepatic IGF-II gene expression was abolished in fetuses in which the prepartum rise in plasma T3, but not cortisol, was prevented by fetal thyroidectomy. At 127–130 days, downregulation of hepatic IGF-II mRNA abundance was induced prematurely in intact fetuses by an infusion of cortisol for 5 days (2–3 mg ⋅ kg−1 ⋅ day−1iv). Plasma concentrations of cortisol and T3 in the cortisol-infused intact fetuses were increased to values seen close to term. Similar findings were observed in thyroidectomized fetuses, in which, despite thyroidectomy, cortisol infusion significantly increased plasma T3 concentrations and caused a premature decrease in hepatic IGF-II mRNA levels. However, in intact fetuses at 127–130 days, the increasing of T3 concentrations alone by exogenous T3 infusion (8–12 μg ⋅ kg−1 ⋅ day−1iv for 5 days) had no effect on hepatic IGF-II mRNA levels. Overall, a decrease in hepatic IGF-II mRNA abundance was only observed in fetuses in which there were concurrent increases in plasma cortisol and T3 concentrations. When observations from all fetuses were considered, irrespective of gestational age or treatment, hepatic IGF-II mRNA levels were negatively correlated with plasma cortisol and T3 but not thyroxine concentrations. Partial correlation analysis of hepatic IGF-II, cortisol, and T3 values showed that the plasma concentration of cortisol in the fetus had the predominant effect on hepatic IGF-II mRNA abundance. These findings show that T3 may mediate, in part, the maturational effects of cortisol on hepatic IGF-II gene expression but that it is ineffective without a concomitant rise in fetal plasma cortisol. Hence, increased concentrations of both cortisol and T3 appear necessary to induce downregulation of hepatic IGF-II mRNA abundance in fetal sheep close to term.

Opposite effects of glucocorticoid on hepatic 11 β-hydroxysteroid dehydrogenase mRNA and activity in fetal and adult sheep

1994 ◽  
Vol 143 (1) ◽  
pp. 121-126 ◽  
Author(s):  
K Yang ◽  
E T M Berdusco ◽  
J R G Challis
Keyword(s):  
Gene Expression ◽  
Fetal Liver ◽  
Reductase Activity ◽  
Mrna Level ◽  
Hydroxysteroid Dehydrogenase ◽  
Fetal Life ◽  
Mrna Levels ◽  
Fetal Sheep ◽  
Adult Sheep ◽  
Hepatic Level

Abstract The level of 11 β-hydroxysteroid dehydrogenase (11β-HSD) mRNA in the fetal sheep liver increases dramatically between day 130 and term (term=day 145), but the causal factors remain unknown. The present study was designed to determine the effects of exogenous glucocorticoid on the fetal hepatic 11 β-HSD gene expression. Dexamethasone (dex; 2 μg/min over 15 min every 2 h) or saline was infused into chronically-catheterized fetal sheep at day 130 of gestation for 4 days. At the end of infusion, the lower right lobe of the liver was collected, total cellular RNA extracted and subjected to Northern blot analysis. It was found that the level of the hepatic 11 β-HSD mRNA in dex-treated fetuses was about four times higher than that in the saline-treated controls. To examine whether changes occur in the response of hepatic 11 β-HSD gene expression to glucocorticoids in adulthood, we also treated non-pregnant ewes with dex (10 mg/day) for 4 days. By contrast, this treatment regime in adult sheep produced a small but significant decrease in hepatic 11 β-HSD mRNA levels. We also determined whether age-specific changes in the hepatic level of 11 β-HSD mRNA following dex treatment were reflected in the level of 11 β-HSD enzyme activity. Hepatic 11 β-HSD activity was determined by a standard in vitro conversion assay using cortisol and cortisone as physiological substrates. In both fetal and adult livers, 11-oxoreductase activity (cortisone→cortisol) was predominant. Following dex treatment, there was a significant increase in the fetal hepatic level of both 11β-dehydrogenase (cortisol→cortisone) and 11-oxoreductase activities. Furthermore, the C-11 activation index, an indicator of glucocorticoid net gain, was also increased in the fetal liver by dex. In marked contrast, dex treatment in the adult did not alter the C-11 activation index though it produced a significant decrease in the hepatic level of both 11 β-dehydrogenase and reductase activities. In summary, these results indicate that (1) exogenous glucocorticoid exerts opposite effects on hepatic 11 β-HSD gene expression in fetal and adult sheep; (2) dex-induced age-specific changes in the level of 11β-HSD mRNA are carried though to the level of 11β-HSD protein; and (3) since 11 β-HSD reductase activity is predominant in both fetal and adult sheep livers, the liver may be a potential extra-adrenal source of cortisol. Furthermore, we speculate that (1) the dramatic increase in the fetal hepatic 11 β-HSD mRNA level at term may be due to the elevated fetal plasma concentration of glucocorticoid; and (2) glucocorticoid-induced increases in the fetal hepatic 11β-HSD gene expression and the resultant increase in the C-11 activation index during the last days of fetal life may play a crucial role in fetal organ maturation and in the endocrine mechanisms leading to parturition. Journal of Endocrinology (1994) 143, 121–126

scholarly journals Plasma Leptin Concentration in Fetal Sheep during Late Gestation: Ontogeny and Effect of Glucocorticoids

Endocrinology ◽  
2002 ◽  
Vol 143 (4) ◽  
pp. 1166-1173 ◽  
Author(s):  
A. J. Forhead ◽  
L. Thomas ◽  
J. Crabtree ◽  
N. Hoggard ◽  
D. S. Gardner ◽  
...  
Keyword(s):  
Adrenal Gland ◽  
Gestational Age ◽  
Plasma Cortisol ◽  
In Utero ◽  
Late Gestation ◽  
Fetal Sheep ◽  
Developmental Control ◽  
Near Term ◽  
Plasma Leptin ◽  
Sheep Fetus

Abstract The ontogeny and developmental control of plasma leptin concentration in the fetus are poorly understood. The present study investigated plasma leptin concentration in chronically catheterized sheep fetuses near term, and in neonatal and adult sheep. The effect of glucocorticoids on plasma leptin in utero was examined by fetal adrenalectomy and exogenous cortisol or dexamethasone infusion. In intact, untreated fetuses studied between 130 and 140 d (term, 145 ± 2 d), plasma leptin concentration increased in association with the prepartum cortisol surge. Positive relationships were observed between plasma leptin in utero and both gestational age and plasma cortisol. Plasma leptin was also inversely correlated with fetal paO2. The ontogenic rise in plasma leptin was abolished by fetal adrenalectomy. In intact fetuses at 123–127 d, plasma leptin was increased by infusions of cortisol (3–5 mg kg−1d−1, +127 ± 21%) for 5 d and dexamethasone (45–60 μg kg−1d−1, +268 ± 61%) for 2 d. However, the cortisol-induced rise in plasma leptin was transient; by the fifth day of infusion, plasma leptin was restored to within the baseline range. These findings show that, in the sheep fetus, an intact adrenal gland is required for the normal ontogenic rise in plasma leptin near term. Furthermore, fetal treatment with exogenous and endogenous glucocorticoids increases circulating leptin concentration in utero.

scholarly journals Endocannabinoid System in Pregnancy Maintenance and Labor: A Mini-Review

2021 ◽  
Vol 12 ◽  
Author(s):  
Melissa L. Kozakiewicz ◽  
Chad A. Grotegut ◽  
Allyn C. Howlett
Keyword(s):  
Early Pregnancy ◽  
Endocannabinoid System ◽  
Current Theory ◽  
Multiple Organ ◽  
Late Gestation ◽  
Signaling System ◽  
Organ Systems ◽  
A Cell ◽  
Term Labor ◽  
In Pregnancy

The endocannabinoid system (ECS) is a cell-signaling system present in multiple organ systems and is an integral part of sustaining the microenvironment necessary for early pregnancy success and maintenance. It plays a significant role in embryo development, transport and implantation as well as placentation. The current theory behind the initiation of term labor is that it is a complex, multifactorial process involving sex steroid hormones, prostaglandin production and interplay at the maternal-fetal interface resulting in increased expression of receptors and gap junctions that promote uterine activation. There is increasing evidence that, in addition to early pregnancy events, the ECS plays a regulatory role in pregnancy maintenance and the timing of labor. This review presents an overview of the ECS in pregnancy that focuses on late gestation and parturition.

Circulating insulin-like growth factors (IGFs), IGF-binding proteins (IGFBPs) and tissue mRNA levels of IGFBP-2 and IGFBP-4 in the ovine fetus

1995 ◽  
Vol 145 (3) ◽  
pp. 545-557 ◽  
Author(s):  
J M Carr ◽  
J A Owens ◽  
P A Grant ◽  
P E Walton ◽  
P C Owens ◽  
...  
Keyword(s):  
Binding Proteins ◽  
Mrna Level ◽  
Common Factor ◽  
Late Gestation ◽  
Mrna Levels ◽  
Igf Binding Proteins ◽  
Fetal Sheep ◽  
Igf I ◽  
Igf Binding ◽  
Igfbp 3

Abstract The IGF-binding proteins (IGFBPs) are a family of at least six structurally related proteins, which bind the IGFs and modulate their actions, including the regulation of preand postnatal growth. In this study we have examined the relationship between circulating and tissue mRNA levels of IGFBPs and related this to circulating IGFs in the fetal sheep over the gestational period when rapid growth and development occurs. Circulating IGFBP-2, as measured by Western ligand blot (WLB), increases between early and mid gestation, remains high, then declines throughout late gestation (P=0·0002). Circulating IGFBP-3 increases throughout gestation, as measured by WLB or RIA (P=0·04 and P=0·0001 respectively), as does circulating IGFBP-4 (P=0·004). These ontogenic changes in circulating IGFBPs-2 and -4 are paralleled by changes in liver mRNA for these proteins and, for IGFBP-2, by those in kidney IGFBP-2 mRNA also. This suggests that liver and kidney may be the primary contributors to circulating IGFBP-2 and the liver to circulating IGFBP-4. IGFBP-2 mRNA is present in the heart and lung in early gestation but barely detectable in these tissues after approximately 60 days gestation. IGFBP-4 mRNA is also present in the heart in early but not late gestation, but is abundant in the lung throughout gestation. These results demonstrate tissue specific and developmental regulation of IGFBPs-2 and -4 at the mRNA level. To assess any role the circulating IGFs may play in mediating these changes in IGFBPs, or vice versa, both plasma IGF-I and IGF-II were measured by RIA. Circulating IGF-I increases as gestation progresses (P=0·0001), while circulating IGF-II increases between early and mid gestation, remains high (P=0·01), then declines. Circulating IGF-I is positively correlated with fetal weight (r=0·66, P=0·03), circulating IGFBP-3 (r=0·54, P=0·01) and IGFBP-4 (r=0·52, P=0·01). Circulating IGF-II positively correlates with circulating IGFBP-2 (r=0·48, P=0·02) throughout gestation and at 1 day postnatally. These relationships are consistent with circulating IGF-I influencing IGFBPs-3 and -4, and similarly, IGF-II determining IGFBP-2, or vice versa. Alternatively, these correlations may reflect coordinate regulation of IGF and IGFBP by a common factor. Journal of Endocrinology (1995) 145, 545–557

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