Antarctic surface temperature and elevation during the Last Glacial Maximum

Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations.

Fertility and Pregnancy in Primary Adrenal Insufficiency in Germany

Autoimmune adrenalitis (AA) and congenital adrenal hyperplasia (CAH) are the most common reasons for acquired and monogenetic primary adrenal insufficiency. Both concern women in their fertile years. The aim of the work was to examine fertility rates, pregnancy outcome, and children's characteristics in AA and CAH patients in 2 German endocrine centers. One hundred and fifty-eight women were contacted. Thirty-nine patients with CAH due to 21-hydroxlase deficiency and 54 AA patients agreed and were included. Information about course and outcome of pregnancies was obtained by questionnaire and telephone interview. Fertility rates were calculated and compared to expected values from the German general population. Twelve CAH patients (30.8%) had 25 pregnancies, which resulted in 16 children. In AA patients, 93 pregnancies in 42 women (75%) were reported resulting in 73 childbirths. Fertility rates were normal in nonclassic CAH and in AA-only patients, but significantly reduced in classic CAH and autoimmune polyendocrine syndrome type 2 (APS-2). Rates of miscarriages were high in all CAH (36%) and APS-2 (22%) patients. The majority of children in both groups were born at term, but rates of cesarean section were elevated in classic CAH and in AA patients<5 years before or after diagnosis. Children born to CAH patients weighed significantly less than expected and 33.3% of them were born small for gestational age. Fertility seems not to be reduced in general, but specific in classic CAH and APS 2 patients. Nevertheless all CAH and AA patients seem to be at risk of miscarriages and cesarean section.

Synchronous change of atmospheric CO2 and Antarctic temperature during the last deglacial warming

Understanding the role of atmospheric CO2 during past climate changes requires clear knowledge of how it varies in time relative to temperature. Antarctic ice cores preserve highly resolved records of atmospheric CO2 and Antarctic temperature for the past 800,000 years. Here we propose a revised relative age scale for the concentration of atmospheric CO2 and Antarctic temperature for the last deglacial warming, using data from five Antarctic ice cores. We infer the phasing between CO2 concentration and Antarctic temperature at four times when their trends change abruptly. We find no significant asynchrony between them, indicating that Antarctic temperature did not begin to rise hundreds of years before the concentration of atmospheric CO2, as has been suggested by earlier studies.

Orbital and millennial Antarctic climate variability over the past 800,000 years

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, approximately 800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.

Orbital and millennial Antarctic climate variability over the past 800,000 years

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, approximately 800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.

Orbital and Millennial Antarctic Climate Variability over the Past 800,000 Years

A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, approximately 800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records.

Atmospheric trends and radiative forcings of CF4 and C2F6 inferred from firn air

The atmospheric histories of two potent greenhouse gases, tetrafluoromethane (CF4) and hexafluoroethane (C2F6), have been reconstructed for the 20th century based on firn air measurements from both hemispheres. The reconstructed atmospheric trends show that the mixing ratios of both CF4 and C2F6 have increased during the 20th century by factors of approximately 2 and approximately 10, respectively. Initially, the increasing mixing ratios coincided with the rise in primary aluminum production. However, a slower atmospheric growth rate for CF4 appears to be evident during the 1990s, which supports recent aluminum industry reports of reduced CF4 emissions. This work illustrates the changing relationship between CF4 and C2F6 that is likely to be largely the result of both reduced emissions from the aluminum industry and faster growing emissions of C2F6 from the semiconductor industry. Measurements of C2F6 in the older firn air indicate a natural background mixing ratio of <0.3 parts per trillion (ppt), demonstrating that natural sources of this gas are negligible. However, CF4 was deduced to have a preindustrial mixing ratio of 34 -1 ppt (-50% of contemporary levels). This is in good agreement with the previous work of Harnisch et al. (18) and provides independent confirmation of their results. As a result of the large global warming potentials of CF4 and C2F6, these results have important implications for radiative forcing calculations. The radiative forcings of CF4 and C2F6 are shown to have increased over the past 50 years to values in 2001 of 4.1 x 10(-3) Wm(-2) and 7.5 x 10(-4) Wm(-2), respectively, relative to preindustrial concentrations. These forcings are small compared to present day forcings due to the major greenhouse gases but, if the current trends continue, they will continue to increase since both gases have essentially infinite lifetimes. There is, therefore, a large incentive to reduce perfluorocarbon emissions such that through the implementation of the Kyoto Protocol, the atmospheric growth rates may decline in the future.

Atmospheric methane and nitrous oxide of the Late Pleistocene from Antarctic ice cores

The European Project for Ice Coring in Antarctica Dome C ice core enables us to extend existing records of atmospheric methane (CH4) and nitrous oxide (N2O) back to 650,000 years before the present. A combined record of CH4 measured along the Dome C and the Vostok ice cores demonstrates, within the resolution of our measurements, that preindustrial concentrations over Antarctica have not exceeded 773 +/- 15 ppbv (parts per billion by volume) during the past 650,000 years. Before 420,000 years ago, when interglacials were cooler, maximum CH4 concentrations were only about 600 ppbv, similar to lower Holocene values. In contrast, the N2O record shows maximum concentrations of 278 +/- 7 ppbv, slightly higher than early Holocene values.

Stable Carbon Cycle-Climate Relationship During the Late Pleistocene

A record of atmospheric carbon dioxide (CO2) concentrations measured on the EPICA (European Project for Ice Coring in Antarctica) Dome Concordia ice core extends the Vostok CO2 record back to 650,000 years before the present (yr B.P.). Before 430,000 yr B.P., partial pressure of atmospheric CO2 lies within the range of 260 and 180 parts per million by volume. This range is almost 30% smaller than that of the last four glacial cycles; however, the apparent sensitivity between deuterium and CO2 remains stable throughout the six glacial cycles, suggesting that the relationship between CO2 and Antarctic climate remained rather constant over this interval.

High-resolution record of Northern Hemisphere climate extending into the last interglacial period

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 degrees C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.

Eight glacial cycles from an Antarctic ice core

The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long--28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.

CO(2) concentration measurements on air samples by mass spectrometry

A new technique for measuring CO(2) concentration in air samples, based on mass spectrometry, is described as an alternative to the common gas chromatographic method. Using a dual inlet isotope ratio mass spectrometer (IRMS), the ratio of the abundances of the m/z peaks 44 and 28 is determined. The precision of measurements (standard deviation <3 ppmv) is generally as good as the analysis with gas chromatography for small air samples (<1 ml STP of air). A major advantage of this new method is the possibility of parallel elemental and isotopic measurements of many air components. The technique is further improved by new wide mass range mass spectrometers allowing simultaneous intensity measurements of several m/z values between 28 and 44, resulting in an uncertainty of <0.5 ppm. The precision is somewhat limited by the production of N(2)O and NO(2) from N(2) and O(2) in the ion source, which accounts for about half of the signal strength at m/z 44. Copyright 2000 John Wiley & Sons, Ltd.

16 degrees C rapid temperature variation in central greenland 70,000 years Ago

Variations in the (29)N(2)/(28)N(2) ratio of air bubbles trapped in polar ice cores and their relation to variations of the (18)O/(16)O of the ice allow past surface temperature variations and ice age-gas age differences to be determined. High-resolution measurements of (29)N(2)/(28)N(2) in Dansgaard-Oeschger event 19 (around 70,000 years before the present) in ice from Central Greenland show that at the beginning of the event, the ice age-gas age difference was 1090 +/- 100 years. With the use of a combined firn densification, temperature, and gas diffusion model, the delta(18)O(ice)-temperature coefficient alpha was determined to be 0. 42 +/- 0.05 per mil per kelvin. This coefficient implies a mean surface temperature change of 16.0 kelvin (between 14.3 and 18.1 kelvin), which differs substantially from values derived from borehole temperatures and modern spatial delta(18)O(ice)-surface temperature correlations.

Identification and characterization of the putative retinoblastoma control element of the rat insulin-like growth factor binding protein-2 gene

The authors previously identified a silencer of the rat IGFBP-2 gene. Sequence examination of the silencer has revealed that it contains the target sequence for the pRb (retinoblastoma) tumour suppressor gene, referred to as the retinoblastoma control element (RCE) which is frequently found in the regulatory element of cellular oncogenes and growth factors. The presence of RCE suggests that the IGFBP-2 gene may be regulated by the pRb tumour suppressor gene. An in vitro gel retardation assay has shown that the putative RCEs from the IGFBP-2 gene are complexed with multiple nuclear factors from the rat liver BRL-3A cells. These DNA-protein complexes were not detected with the nuclear extracts from the cells that were growth arrested at the G1/S border of the cell cycle by high cell density. Using specific antibodies, Sp1 was shown to be one of the components for the multiple DNA-protein complex while pRb does not appear to be directly involved in the formation of the complex.

Cell-density (cycle) dependent silencer of the rat insulin-like growth factor binding protein-2 (IGFBP-2) gene

An element which has a negative effect on transcription has been identified in the 5'-flanking region of the rat insulin-like growth factor binding protein-2 (IGFBP-2) gene. This element was confirmed to be a silencer by truncation or by linking it to a heterologous promoter. The silencer activity disappeared in the growth-arrested BRL-3A cells at the G1/S border by high cell density where the IGFBP-2 production is highly elevated. This observation may represent a novel mechanism through which gene expression is controlled by modulation of a silencer. Taken together, these results suggest a regulatory link between cell growth and IGFBP-2 expression regulated by its silencer.

Insulin-like growth factors (IGFs) and IGF binding proteins-1, -2, and -3 in newborn serum: relationships to fetoplacental growth at term

Cord sera were obtained from term, Chilean newborns exhibiting various patterns of intrauterine growth and assayed for IGF-1, IGF-2, IGFBP-1, IGFBP-2, and IGFBP-3 by specific radioimmunoassays (RIA). Serum levels of each peptide were correlated with birth weight (BW), ponderal index (PI), and placental weight (PW). Total IGF-1 levels correlated with BW (r = 0.665, P = 0.0001). PI (r = 0.527, P = 0.004), and PW (r = 0.596, P = 0.0017). In contrast, IGF-2 failed to correlate with any growth parameter. Of the three binding proteins, IGFBP-3 exhibited the strongest relationship to each growth parameter. IGFBP-3 correlated significantly with BW (r = 0.71, P < 0.0001), PI (r = 0.782, P < 0.0001), and PW (r = 0.57, P = 0.0029). In addition IGFBP-3 levels positively correlated to IGF-1 levels (r = 0.614, P = 0.0005). By contrast, circulating IGFBP-1 and IGFBP-2 were inversely related to IGF-1 levels. All five peptides were subjected to multiple regression analysis and related to BW. Significant relationships between the predicted BW and the actual BW were observed in these infants (r = 0.802, P = 0.0006). The BWs of a cohort of unrelated North American infants were also predicted using the Chilean-derived equation and found to be significantly related to their actual BWs (r = 0.453, P = 0.0033). These relationships were strengthened by the inclusion of estimated gestational age (EGA) as an independent variable. These data point to particularly important roles for IGF-1 and IGFBP-3 in regulating fetal growth at term, and suggest that they are regulated in a coordinated manner during the latter stage of gestation. Furthermore, they suggest that IGFBPs play multiple, and potentially opposing, regulatory roles in modulating IGF action. Lastly, an integrated expression of IGF activity derived from one population significantly correlated with newborn BW in a geographically and culturally distinct population.

Influence of insulin-like growth factor-binding protein-2 on plasma clearance and transfer of insulin-like growth factors-I and -II from plasma into mammary-derived lymph and milk of goats

Plasma clearance of insulin-like growth factors-I and -II (IGF-I and -II) and insulin-like growth factor-binding protein-2 (IGFBP-2) from lactating goats (n = 4) was determined following a single intravenous injection of the corresponding 125I-labelled human protein. Transfer of these proteins out of the vascular space was monitored by their subsequent appearance in mammary-derived lymph and milk. Clearance of 125I-IGFBP-2 from circulation was 0.37 +/- 0.06 ml/min/kg, which is markedly greater than that of 125I-IGF-I or -II (0.11 +/- 0.01 and 0.12 +/- 0.01 ml/min/kg respectively). This was also reflected in longer elimination half-lives for IGF-I (353 +/- 6 min) and -II (254 +/- 8 min) compared with IGFBP-2 (110 +/- 9 min). Three hours after injection of the 125I-labelled protein, the plasma:lymph ratio of trichloroacetic acid-precipitable radioactivity was 1.54 +/- 0.04, 3.3 +/- 0.6 and 4.1 +/- 0.4 for IGFBP-2, IGF-I and -II respectively. The form of 125I-IGFBP-2 in lymph was not different from that of plasma. Elevation of plasma concentrations of IGFBP-2 by its intravenous infusion significantly decreased plasma half-life of both IGF-I and -II (251 +/- 8 and 198 +/- 7 min respectively). Although the amount and rate of transfer of IGF into mammary-derived lymph was decreased slightly by IGFBP-2, concentrations eventually obtained were not different from control. However, secretion of IGFs into milk was significantly reduced by IGFBP-2, particularly in the case of IGF-I. These results are consistent with the ability of all three compounds to cross the vascular endothelium intact and of IGFBP-2 to decrease the uptake of IGF by mammary epithelium and subsequent secretion into milk. IGFBP-2 may well have acted to target plasma IGF towards non-mammary tissues, thus explaining the more rapid plasma clearance of IGFs in the presence of elevated IGFBP-2.

Cell-density-dependent modulation of the rat insulin-like-growth-factor-binding protein 2 and its gene

The steady-state level of the rat insulin-like-growth-factor-binding protein 2 (IGFBP-2) and insulin-like-growth-factor-II (IGF-II) mRNA increased approximately 20-fold when BRL-3A cells were cultured at increasingly higher cell densities. This increase could not be accounted for by paracrine or autocrine factors, or by the addition of insulin, IGF-I, transforming growth factor beta (TGF-beta), cAMP or IGFBP-2 to the culture medium. A reporter gene assay carrying the promoter domain of the IGFBP-2 gene indicated that the promoter-dependent IGFBP-2 transcription is tenfold higher in high-density cells. The increase in the IGFBP-2 message was accompanied by an increase in the level of protein in the medium. When confluent BRL-3A cells were reseeded at low cell density, the IGFBP-2 mRNA disappeared at a rate significantly faster than in normal conditions. A protein synthesis inhibitor, cycloheximide, was able to prevent the decay of the message observed after the switch from high to low densities. In summary, these findings suggest a regulatory link between cell density and IGFBP-2.

Ontogeny of insulin-like growth factor-binding protein-1, -2, and -3: quantitative measurements by radioimmunoassay in human fetal serum

There is evidence for a role for IGF-I in the endocrine control of human fetal growth despite the low serum IGF-I concentrations. The formation in serum of binary complexes between IGF-I or -II and either of six IGF binding proteins (IGFBP-1 to -6) and, in particular, of long-lived ternary complexes between IGF-I or -II, IGFBP-3, and acid-labile subunit is thought to regulate IGF-I bioavailability by increasing its serum half-life. The present study assesses the bioavailability of circulating IGF-I in 19- to 35-wk gestation human fetuses in utero 1) by quantitative RIA measurements of IGF and IGFBP in serum and 2) by examining whether serum proteolysis of IGFBP-3 may further increase IGF-I bioavailability. Fetal serum concentrations of IGFBP-3, IGF-I, and IGF-II were low with marked or only modest increases with gestational age (p < 0.001, p < 0.005, and p < 0.05, respectively). The mean molar ratio between IGF-I plus -II and IGFBP-3 demonstrated a molar excess of IGF (50%) similar to that in adolescents but in contrast to the 1:1 molar ratio in adults. The median IGFBP-2 concentration was 3-fold elevated to a molar concentration similar to that of IGFBP-3 (adult serum displays 10-fold higher IGFBP-3 concentrations). The median serum IGFBP-1 concentration was not elevated as previously reported in newborns. IGFBP-3 protease activity was not increased in fetal serum, in contrast to pregnancy serum and amniotic fluid.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth hormone and parathyroid hormone stimulate IGFBP-3 in rat osteoblasts

Osteoblast-like cells prepared from calvaria of newborn rats produce insulin-like growth factor (IGF) I and several insulin-like growth factor binding proteins (IGFBPs) in vitro. Among the IGFBPs found in conditioned cell culture medium, IGFBP-3 is the most abundant. Intact IGFBP-3, as assessed by 125I-labeled IGF-II ligand blot analysis, is more abundant in culture media of cells exposed to growth hormone (GH) or to parathyroid hormone (PTH), both at 5 x 10(-9) mol/l, for 24 h. At the same time, concentrations of IGF-I are increased in media of cells exposed to PTH but not to GH, compared with hormone-free control cultures. IGFBP-3 mRNA is increased in osteoblasts exposed to PTH or to GH but not in response to 5 x 10(-9) mol/l IGF-I. PTH exerts a rapid (within 2 h) stimulatory effect on IGF-I and IGFBP-3 production, both at the message and peptide levels, whereas GH increases only IGFBP-3, both at the message and peptide levels (after 24 h). We conclude that IGF-I does not mediate increased IGFBP-3 production by rat osteoblasts in response to GH and PTH.

[Neurocysticercosis]

A 49-year-old woman from Croatia, resident in Switzerland for 22 years, had a history of headaches and arterial hypertension for 8 years. While in hospital for assessment and treatment she developed focal seizures. She had an eosinophilia (10%) and computed tomography of the skull demonstrated cysts and multiple calcified foci in the left cerebral hemisphere. Antibodies against Taenia solium antigen were found in both serum and cerebrospinal fluid. Anthelminthic treatment with albendazole (15 mg/kg daily for 25 days) and anticonvulsive treatment with phenytoin (serum levels between 10 and 20 mg/l) markedly improved the symptoms and the cysts regressed. Neurocysticercosis, caused by the larvae of the pork tapeworm, is occurring even more frequently because of the migration of people from countries where the disease is endemic.

Insulin-like growth factors and their binding proteins in plasma and milk after growth hormone-stimulated galactopoiesis in normally lactating women

We performed a double-blind randomized placebo-controlled trial of recombinant human growth hormone (hGH) in normally lactating women (N = 8 per group) to investigate the endocrine mode of action of the galactopoietic effect of this hormone. Insulin-like growth factors I (IGF-I) and II (IGF-II) and their binding proteins (IGFBP-1, IGFBP-2 and IGFBP-3) were measured by radioimmunoassay in plasma and milk samples collected throughout the study. All assays were validated for human plasma and milk. Human GH treatment (0.1 IU.kg-1 body wt.day-1 for 7 days) increased plasma concentrations of IGF-I from 22.1 +/- 1.3 nmol/l (mean +/- SEM) to 59.7 +/- 2.5 nmol/l (p < 0.01). At the end of the study the increase in plasma IGF-I correlated significantly with the increase in milk volume (r = 0.67, p < 0.005, N = 16). The IGF-I levels were considerably lower in milk, with 0.14 +/- 0.03 nmol/l before and 0.31 +/- 0.04 nmol/l after hGH treatment. The increase in milk IGF-I levels (134.0 +/- 14.5%) with hGH treatment was significant (p < 0.01) and plasma and milk IGF-I concentrations correlated significantly when considering all samples of the study (r = 0.45, p < 0.001, N = 56). The concentrations of IGF-II were not changed significantly with hGH treatment in plasma (52.5 +/- 2.5 nmol/l before and 42.6 +/- 3.9 nmol/l after treatment) or milk (2.1 +/- 0.29 nmol/l before and 2.3 +/- 0.49 nmol/l after hGH treatment).(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating levels of IGFs and IGF binding proteins in human cord serum: relationships to intrauterine growth

Cord sera were obtained from 44 term, human infants exhibiting various patterns of intrauterine growth and were assayed for IGF-1, IGF-2, and IGFBP-1, 2, and 3 by specific RIAs. Serum levels were correlated with birth weight (BW), ponderal index (PI), and placental weight (PW). Total IGF-1 levels correlated significantly with BW (r = 0.392), PW (r = 0.351), and PI (r = 0.481). By contrast, the correlation of IGF-2 with birth weight was not statistically significant (r = 0.264, P = 0.091). The association of IGF-2 with PI, however, was significant (r = 3.348, P = 0.024). IGFBP-3 exhibited significant correlations with BW, PI, and PW, similar to those seen with IGF-1. IGFBP-1 and IGFBP-2, however, were not significantly related to growth parameters. IGF-1 levels correlated strongly with IGFBP-3 levels (r = 0.646, P = 0.001). By contrast, IGF-1 correlated with the reciprocal of both IGFBP-1 and IGFBP-2. Based upon in vitro affinity constants, theoretical concentrations for each [IGF/IGFBP] complex, free IGFs, and free IGFBPs were calculated for each infant. Multiple regression analysis was performed including all 11 calculated variables and correlated with each growth parameter. This analysis revealed that an integrated expression of IGF activity exhibited stronger correlations with growth than each individual peptide species (BW, r = 0.681; PI, r = 0.660; PW, r = 0.658). These data further support roles for IGF related peptides (IGFRPs) in human fetal and placental growth and suggest regulatory/counterregulatory roles for the IGFBPs. It also supports the hypothesis that individual IGFRPs interact in a complex manner to define 'net IGF activity' in relation to fetal growth and/or metabolic status.

Role for membrane and secreted insulin-like growth factor-binding protein-2 in the regulation of insulin-like growth factor action in lung tumors

The insulin-like growth factors (IGFs) have been implicated in the autocrine and/or paracrine growth of a number of tumor types, including lung tumors. Importantly, insulin-like growth factor-binding proteins (IGFBPs), which both enhance and inhibit the physiological and biological actions of the IGFs, have been shown to be secreted in vitro by a wide range of tumors. In particular, IGFBP-2 is frequently produced by human tumor cells, suggesting that this protein may be an important determinant of IGF action in tumors. In the present study, we investigated IGFBP-2 effects in lung tumor cells by examining the influence of IGFBP-2 on IGF-receptor interaction and the biological actions of IGF-I and IGF-II. Affinity cross-linking studies demonstrated expression of type-I and type-II IGF receptors on small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) cells and the presence of abundant membrane-associated IGFBP in SCLC cells but not in NSCLC cells. An antiserum specific for IGFBP-2 was used in immunoprecipitation and immunoblotting studies which demonstrated that the membrane-associated IGFBP identified by affinity cross-linking in SCLC cells is IGFBP-2. In NSCLC cells, both IGF-I and IGF-II bound predominantly to IGF-I receptors, whereas in SCLC cells binding was principally to surface-associated IGFBP-2. SCLC cells failed to respond to IGF-I and -II stimulation in a DNA synthesis assay. For NSCLC cells, IGF-II was a more potent stimulator of DNA synthesis than IGF-I. Soluble IGFBP-2 inhibited the binding of radiolabeled IGF-I and -II to both SCLC and NSCLC cells in a concentration-dependent manner and inhibited IGF-stimulated DNA synthesis in NSCLC cells. These observations indicate that both soluble and membrane-associated IGFBP-2 compete with IGF receptors for ligand binding and, thus, are likely to be important determinants of IGF responsiveness. The findings of the present study also indicate that the type-I receptor on NSCLC cells contains a high-affinity binding site for IGF-II which presumably mediates the biological effects of IGF-II in these cells, thereby implicating IGF-II in the autocrine/paracrine growth of NSCLC.

Genomic structure and regulation of the promoter of the rat insulin-like growth factor binding protein-2 gene

We describe the complete genomic organization of the rat insulin-like growth factor binding protein-2 (rIGFBP-2) gene. This single-copy gene spans over 36 kilobases (kb) and is split into four exons of 475, 224, 141, and 472 nucleotides (nt), and three introns of 32 kb, 686, and 1793 nt, respectively. A single transcription start site (-90) was mapped by S1 protection assay and primer extension. The putative promoter of the rIGFBP-2 gene does not possess TATA or CAAT elements; however, it contains three GC-rich regions located 37, 57, and 81 nt 5' of the cap site. Deletion analysis of the 0.6-kb region of the upstream sequences and transfection of these constructs into BRL-3A and Chinese hamster ovary cells were used to localize possible cis-acting elements. The three GC boxes enhanced chloramphenicol acetyltransferase and luciferase transcription almost to the same level as the XbaI-NsphI (-579 to +1) fragment and displayed synergism and orientation dependence. In addition a similar positive effect on luciferase transcription has been obtained by cotransfecting these fragments with varying amounts of Sp1 expression vector into Drosophila cells that lack endogenous Sp1. In vitro gel mobility shift assays demonstrated that box 1 (GGGCGG), box 2 (GGGAGG), and box 3 (GGGAAGG) bind to SpI with variable affinities and display cooperativity. A protein that gave a similar DNA binding pattern was present in nuclear extracts of BRL-3A cells. To analysis using consensus or aberrant Sp1 elements and a polyclonal Sp1 antiserum to inhibit DNA binding were performed. These in vivo and in vitro data demonstrated that Sp1 plays an important role in the regulation of the expression of rIGFBP-2.

Sp1 interacts with the consensus sequence for Egr-1 gene product with a cellular factor(s) and activates the transcription through this element

We report that Sp1 from nuclear extracts of BRL-3A cells interacts with the consensus DNA sequence for the Egr-1 gene product in an overlapping manner. Purified Sp1 failed to bind to this sequence and with the addition of sub-saturating level of nuclear extracts, the binding activity appeared. In Drosophila cells (SL2), exogenously expressed Sp1 activated the transcription through the Egr-1 site. These findings suggest that Sp1 can be targeted to a non-Sp1 (Egr-1) site with a cellular factor(s) and can activate the transcription through this element.

Insulin-like growth factor (IGF) I and II and IGF binding protein (IGFBP) 1, 2 and 3 in serum from patients with Cushing's syndrome

In the present study of twenty-two patients with Cushing's syndrome, serum insulin-like growth factor (IGF)-I concentrations were normal to high with an increased mean IGF-I concentration, 40% above that of healthy subjects of the same age (p < 0.001). Serum IGF-II concentrations were normal. The morning serum IGF binding protein (IGFBP)-1 concentrations were within the range of healthy controls. IGFBP-1 was inversely correlated to the IGF-I concentration (p < 0.001) and to the 24 h urinary cortisol excretion (p < 0.005) with a combined R squared value of 0.58. In contrast to IGFBP-1, serum IGFBP-2 and IGFBP-3 concentrations were elevated by 1.89 +/- 1.78 SD and 0.92 +/- 0.78 SD (mean +/- 2 SD), respectively. Although increased, the serum IGFBP-2 concentration was inversely correlated to the IGF-I concentration (r = -0.67, p < 0.001). Immunoreactive IGFBP-3 was increased in proportion to IGF-I and the molar ratio [IGFBP-3]:[IGF-I] + [IGF-II] was close to unity (1.04 +/- 0.14), as that of healthy subjects. In serum from patients with Cushing's syndrome, with increased immunoreactive IGFBP-3, there was a corresponding increase in intact glycosylated 40-43 kDa IGFBP-3 as determined by Western ligand blotting. Neutral size chromatography of serum from patients with Cushing's syndrome showed that IGF-I and IGFBP-3 immunoreactivity were predominantly found at the elution volume of the ternary 150 kDa IGF-I/IGFBP-3/acid labile subunit complex and a similar pattern was displayed by normal serum.(ABSTRACT TRUNCATED AT 250 WORDS)

The RIA for IGFBP-2 in man--a meagre catch?

In man IGFBP-2 is by concentration the second most important IGF binding protein in serum, the most abundant carrier protein in milk and CSF. In serum its levels are age dependent. There is no good evidence, to date, for a regulation of its production or degradation by insulin. IGF-I treatment increases serum IGFBP-2 concentration. IGFBP-2 is at least partially metabolized by the kidney, since it accumulates in serum of patients with renal failure and normalizes after renal transplantation. Individuals with neoplastic diseases very often present with elevated serum levels.

Cloning and characterization of the gene encoding murine insulin-like growth factor-binding protein-2, mIGFBP-2

We present a characterization of the single-copy gene, mIGFBP-2, encoding the murine insulin-like growth factor-binding protein-2 (mIGFBP-2). It consists of four exons with sizes of 470 +/- 2, 227, 141 and > 475 nucleotides (nt). The first intron spans 23 kb of genomic sequence, and the complete gene extends to more than 28 kb. Two kb of the 5'-flanking region were sequenced. This region has no TATA or CAAT boxes but is G+G-rich and contains several potential regulatory sequence motifs. A total of five GC boxes, which may serve as potential binding sites for a transcription factor, Sp1, are present immediately upstream of the transcription start point (tsp). By primer extension, we identified a single tsp at nt position -85 +/- 2. The murine IGFBP-2 locus was mapped to the proximal region of mouse chromosome 1, to a region of conserved synteny with human chromosome 2q. A comparison of the deduced amino acid sequences of mouse, rat and human IGFBP-2 reveals a high degree of homology between all three species.

Insulin-like growth factor (IGF)-I, -II and IGF binding protein-2 (IGFBP-2) in the plasma of children with Wilms' tumour

Insulin-like growth factors (IGF)-I, -II and IGF binding protein-2 (IGFBP-2) have been measured in plasma of children with Wilms' tumour. The mean levels for total serum IGF-I and -II were not significantly altered in Wilms' tumour as compared with normal control plasma. However, the chromatographic profiles for IGF-I and -II in these groups were different with regard to the presence of IGF binding proteins and high molecular weight forms of IGFs; the high molecular weight form (9-15 kD) of IGF-II was significantly reduced in Wilms' tumour. Levels of IGFBP-2 were substantially elevated in serum from Wilms' tumour patients (1025 +/- 112 ng/ml compared with 416 +/- 44 ng/ml in controls), and inversely correlated with the levels of high molecular weight forms of IGF-II. We suggest that IGFBP-2 measurements might be of value as a marker for monitoring this type of tumour, either as an adjunct to diagnosis or surveillance of tumour growth during therapy.

Insulin-like growth-factor-binding protein gene expression and protein production by human tumour cell lines

The secretion of insulin-like growth-factor-binding proteins (IGFBPs) and expression of the genes encoding IGFBP-1, IGFBP-2 and IGFBP-3 have been studied in a panel of cell lines derived from breast carcinomas, Wilms' tumour, neuroblastoma, retinoblastoma, colon carcinoma, liver adenocarcinoma, Burkitt's lymphoma and a non-small-cell lung carcinoma. All cell lines, with the exception of the Burkitt's lymphoma cell line, secreted IGFBPs, as detected by affinity labelling. A 34-kDa BP was present in the conditioned media of all IGFBP-secreting cell lines, whereas BPs ranging from 18 kDa to 53 kDa were variably secreted. All IGFBP-secreting cell lines expressed the IGFBP-2 gene as determined by Northern blot analysis. The Wilms' tumour, the neuroblastoma and the retinoblastoma cell line expressed the IGFBP-2 gene only. All other cell lines, with the exception of the Burkitt's lymphoma, expressed the IGFBP-2 gene and, in addition, either the IGFBP-1 gene and/or the IGFBP-3 gene. IGFBP-1 gene expression could be detected by reverse transcriptase polymerase chain reaction only. IGFBP-3 gene expression was detected by Northern blot analysis, but transcripts were less abundant than IGFBP-2 mRNAs. These findings indicate that the expression of multiple BP genes and the secretion of BPs may be a common property of tumour cells.

Differential regulation of insulin-like growth factor binding protein (IGFBP)-2 mRNA in liver and bone cells by insulin and retinoic acid in vitro

Isolated cells produce insulin-like growth factors (IGFs) and their binding proteins (IGFBPs). Two distinct cell types were studied with regard to IGFBP-2 expression: (i) rat hepatocytes, which produce IGF I at a high rate and thus regulate its plasma concentration; and (ii) rat osteoblasts, which are targets of IGF I action. IGFBP-2 expression is low in hepatocytes prepared from normal adult rats and high in calvaria cells from newborn rats. Retinoic acid stimulates IGFBP-2 production by liver cells. Insulin suppresses both basal and retinoic acid-induced IGFBP-2 mRNA expression in hepatocytes and has no such effect on osteoblasts. Retinoic acid and insulin regulate IGFBP-2 expression in a tissue-specific manner.

Structure of the human insulin-like growth factor binding protein-2 gene

Insulin-like growth factors (IGFs) are polypeptide hormones with structural homology to proinsulin. IGFs circulate in blood bound to specific IGF binding proteins (IGFBPs). cDNA sequences of six members of a family of human and rat IGFBPs have been published. Here we present a partial characterization of the human IGFBP-2 gene. This single copy gene is located on chromosome 2 and spans a total of more than 32 kilobases (kb) of genomic sequence. It is organized in four exons with sizes of more than 568, 220, 141, and 496 nucleotides. The intron between exon one and exon two contributes 27 kb to the size of the IGFBP-2 gene. The second and the third introns comprise 1.1 kb and 1.95 kb, respectively. When the structure of the IGFBP-2 gene is compared to that of the IGFBP-1 and IGFBP-3 genes, the exon boundaries are found to be conserved in these three genes. A single transcriptional start site was localized to 113 +/- 2 nucleotides 5' of the ATG start codon of IGFBP-2 translation. Furthermore, the region between nucleotides -635 and -2 upstream of the ATG was demonstrated to exhibit promoter activity in human Jurkat K16 cells. This region is devoid of TATA or CAAT consensus sequence motifs and has a high content of dC and dG nucleotides. In this respect the putative IGFBP-2 promoter region resembles the promoters which are often associated with housekeeping genes.

Quality of emergency room triage of medical inpatients to an acute care clinic or chronic health care facilities

OBJECTIVE

To evaluate the accuracy of emergency room triage by general internists assigning medical patients to four different health care settings.

DESIGN

Prospective trial.

SETTING

Medical emergency room of a university hospital providing primary and referral care.

PATIENTS

974 consecutive patients admitted for acute medical care, excluding patients admitted to intensive care units.

INTERVENTION AND MEASUREMENTS

After primary evaluation patients were assigned to one of four groups: A) acutely ill requiring acute care in a general medical ward (n = 598); B) acutely ill requiring acute care limited to two to three days (n = 201); C) chronically ill with realistic chances for rehabilitation (n = 77); and D) chronically ill requiring definite referral to skilled nursing home care (n = 98). Nine months later, outcome and placement after index hospitalization were evaluated in surviving patients.

MAIN RESULTS

159 (16%) patients died; three (1%) were lost to follow-up. Evolution confirmed the appropriateness of the initial triage of 90% of the remaining 812 patients (83%). Allocations were correct in 96%, 95%, and 91% of cases in groups A, B, and C, respectively. In group D, only 44% were definitely transferred to nursing homes; 56% were rehabilitated and returned to their previous social settings or entered homes for the aged.

CONCLUSIONS

Clinical judgment of general internists in an emergency room adequately identifies patients requiring acute care of regular or short duration and chronically ill patients with realistic prospects for rehabilitation. But the need for nursing home placement is overestimated. To avoid patient misplacement the authors propose direct access to a specialized geriatric assessment facility.

Triiodothyronine (T3) stimulates insulin-like growth factor (IGF)-1 and IGF binding protein (IGFBP)-2 production by rat osteoblasts in vitro

Osteoblast-like cells prepared from neonatal rat calvariae and grown under serum-free conditions produce IGF-1 and IGFBPs. In contrast to growth hormone, T3 and PTH increased both IGF-1 mRNA expression and net IGF-1 release in calvaria cells. In addition, they stimulated net production of IGFBP-3 and of an IGFBP with an apparent molecular weight of 32 kDa which was recognized by an antiserum against rat IGFBP-2. Bone cells expressed remarkably high levels of mRNA for IGFBP-2, the predominant IGFBP in serum of newborn rats. T3 at low physiological concentrations but not growth hormone stimulated IGFBP-2 mRNA expression and IGFBP-2 production in bone cells in vitro. Thus, IGFBPs are differentially regulated by these hormones and may play an autocrine/paracrine regulatory role in bone.

Expression of Insulinlike Growth Factor (IGF) and IGF-Binding Protein Genes in Human Lung Tumor Cell Lines

BACKGROUND

The presence of multiple, low-molecular-weight, insulinlike growth factor (IGF)-binding proteins in lung tumor cell-conditioned medium and lung cancer patient serum has been recently reported.

PURPOSE

To begin to elucidate the genetic basis for these observations, the present study examines the expression by lung tumor cell lines of three IGF-binding protein genes, namely, IGFBP-1, IGFBP-2, and IGFBP-3. Since IGF-binding proteins are thought to modulate the biologic action of the IGFs, the relationship between the expression of IGF-binding protein genes and the genes encoding IGF-I and IGF-II also has been investigated.

METHODS

Gene expression was studied in four small-cell lung cancer (SCLC) and three non-small-cell lung cancer (NSCLC) cell lines using Northern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR) for IGFBP-1.

RESULTS

IGFBP-1 gene expression was detected by Northern blot analysis in one NSCLC cell line only. However, RT-PCR revealed that the IGFBP-1 gene was expressed in all four SCLC cell lines and in two of the three NSCLC lines. Northern blot analysis of IGFBP-2 gene expression demonstrated that all lung tumor cell lines expressed this gene. A low level of IGFBP-3 gene expression was detected in one SCLC cell line and in all three NSCLC cell lines. All lung tumor cell lines expressed the IGF-II gene as determined by Northern blot analysis. In marked contrast, none of the lines showed evidence of IGF-I gene expression using this method. However, RT-PCR revealed a low level of IGF-I gene expression in one SCLC and one NSCLC cell line only.

CONCLUSIONS

These observations indicate 1) that IGF-binding proteins secreted by lung tumors are encoded by at least three different genes; 2) that there may be a close association between IGF-II and IGFBP-2 gene expression, such that, where there is production of IGF-II, IGFBP-2 is the principal BP; and 3) that the IGF-II gene is more widely expressed than the IGF-I gene in human lung tumor cell lines.

The ovarian expression of the antigonadotropic insulin-like growth factor binding protein-2 is theca-interstitial cell-selective: evidence for hormonal regulation

To begin the process of identification and charactization of rat ovarian insulin-like growth factor binding proteins, we have undertaken to explore the ovarian expression, cellular localization, and hormonal regulation of the insulin-like growth factor binding protein-2 (IGFBP-2) gene for which an antigonadotropic potential has recently been demonstrated. To this end, a solution hybridization/RNase protection assay was employed wherein total ovarian RNA (20 micrograms) from immature (21-23 days old) female rats was hybridized with a [32P]-labeled IGFBP-2 riboprobe. As in liver, a single protected fragment (550 bases long) corresponding to IGFBP-2 transcripts was identified in whole ovarian material. Cellular localization studies revealed the IGFBP-2 gene to be exclusively expressed in the theca-interstitial rather than the granulosa cell compartment. To confirm the cellular distribution of the IGFBP-2 protein, media conditioned by cultured granulosa or theca-interstitial cells were subjected to immunoprecipitation using two IGFBP-2-directed polyclonal antisera. Expectedly, both antibodies (but not non-immune rabbit serum) readily immunoprecipitated the 28 kDa rat IGFBP-2 species generated by hepatic BRL-3A cells. Similarly, both antibodies effectively immunoprecipitated an IGFBP the size of rat IGFBP-2 elaborated by theca-interstitial cells. In contrast, neither antibody immunoprecipitated the 28-29 kDa IGFBP species elaborated by granulosa cells otherwise readily apparent in conventional Western ligand blots. Hypophysectomy resulted in a 3-fold decrease (P less than 0.05) in the relative (densitometrically-quantified) abundance of ovarian IGFBP-2 transcripts, a diametrically opposed effect (P less than 0.05) being noted at the level of the liver. In contrast, treatment of immature hypophysectomized rats with a diethylstilbestrol-containing subcutaneous silastic implant for a total of 5 days resulted in a concordant 3-fold increase (P less than 0.05) in the relative abundance of IGFBP-2 transcripts in both ovary and liver when compared with untreated hypophysectomized controls. Taken together, these findings document rat ovarian IGFPB-2 gene expression to be theca-interstitial (rather than granulosa) cell-selective, and subject to upregulatory control by pituitary principle(s) and/or by estrogens. Although equally estrogen-dependent, hepatic IGFBP-2 gene expression proved constitutive in nature and subject to (diametrically opposed) inhibitory control by (potentially distinct) pituitary principle(s).