Electronically excited states of formic acid investigated by theoretical and experimental methods

Absolute cross-section values are reported from high-resolution vacuum ultraviolet (VUV) photoabsorption measurements of gas-phase formic acid (HCOOH) in the photon energy range 4.7-10.8 eV (265-115 nm), together with quantum chemical calculations to provide vertical energies and oscillator strengths. The combination of experimental and theoretical methods has allowed a comprehensive assignment of the electronic transitions. The VUV spectrum reveals various vibronic features not previously reported in the literature, notably associated with (3pa'←10a'), (3p'a'←10a'), (3sa'←2a″) and (3pa'←2a″) Rydberg transitions. The assignment of vibrational features in the absorption bands reveal that the C=O stretching, v₃^'a', the H'-O-C' deformation, v₅^'a^', the C-O stretching, v₆^'a^', and the O=C-O' deformation, v₇^'a^' modes are mainly active. The measured absolute photoabsorption cross sections have also been used to estimate the photolysis lifetime of HCOOH in the upper stratosphere (30-50 km), showing that solar photolysis is an important sink at altitudes above 30 km but not in the troposphere. Potential energy curves for the lowest-lying electronic excited states, as a function of the C=O coordinate, are obtained employing time dependent density functional theory (TD-DFT). These calculations have shown the relevance of internal conversion from Rydberg to valence character governing the nuclear dynamics, yielding clear evidence of the rather complex multidimensional nature of the potential energy surfaces involved.

Thermal desorption effects on fragment ion production from multi-photon ionized uridine and selected analogues

Experiments on neutral gas-phase nucleosides are often complicated by thermal lability. Previous mass spectrometry studies of nucleosides have identified enhanced relative production of nucleobase ions (e.g. uracil⁺ from uridine) as a function of desorption temperature to be the critical indicator of thermal decomposition. On this basis, the present multi-photon ionization (MPI) experiments demonstrate that laser-based thermal desorption is effective for producing uridine, 5-methyluridine, and 2′-deoxyuridine targets without thermal decomposition. Our experiments also revealed one notable thermal dependence: the relative production of the sugar ion C₅H₉O₄⁺ from intact uridine increased substantially with the desorption laser power and this only occurred at MPI wavelengths below 250 nm (full range studied 222–265 nm). We argue that this effect can only be rationalized plausibly in terms of changing populations of different isomers, tautomers, or conformers in the target as a function of the thermal desorption conditions. Furthermore, the wavelength threshold behavior of this thermally-sensitive MPI channel indicates a critical dependence on neutral excited state dynamics between the absorption of the first and second photons. The experimental results are complemented by density functional theory (DFT) optimizations of the lowest-energy structure of uridine and two further conformers distinguished by different orientations of the hydroxymethyl group on the sugar part of the molecule. The energies of the transitions states between these three conformers are low compared with the energy required for decomposition.

This work reveals the first experimental evidence supporting isomer-dependence in the radiation response of a nucleoside.

Communication: Site-selective bond excision of adenine upon electron transfer

This work demonstrates that selective excision of hydrogen atoms at a particular site of the DNA base adenine can be achieved in collisions with electronegative atoms by controlling the impact energy. The result is based on analysing the time-of-flight mass spectra yields of potassium collisions with a series of labeled adenine derivatives. The production of dehydrogenated parent anions is consistent with neutral H loss either from selective breaking of C-H or N-H bonds. These unprecedented results open up a new methodology in charge transfer collisions that can initiate selective reactivity as a key process in chemical reactions that are dominant in different areas of science and technology.

Electron transfer driven decomposition of adenine and selected analogs as probed by experimental and theoretical methods

We report on a combined experimental and theoretical study of electron-transfer-induced decomposition of adenine (Ad) and a selection of analog molecules in collisions with potassium (K) atoms. Time-of-flight negative ion mass spectra have been obtained in a wide collision energy range (6-68 eV in the centre-of-mass frame), providing a comprehensive investigation of the fragmentation patterns of purine (Pu), adenine (Ad), 9-methyl adenine (9-mAd), 6-dimethyl adenine (6-dimAd), and 2-D adenine (2-DAd). Following our recent communication about selective hydrogen loss from the transient negative ions (TNIs) produced in these collisions [T. Cunha et al., J. Chem. Phys. 148, 021101 (2018)], this work focuses on the production of smaller fragment anions. In the low-energy part of the present range, several dissociation channels that are accessible in free electron attachment experiments are absent from the present mass spectra, notably NH₂ loss from adenine and 9-methyl adenine. This can be understood in terms of a relatively long transit time of the K⁺ cation in the vicinity of the TNI tending to enhance the likelihood of intramolecular electron transfer. In this case, the excess energy can be redistributed through the available degrees of freedom inhibiting fragmentation pathways. Ab initio theoretical calculations were performed for 9-methyl adenine (9-mAd) and adenine (Ad) in the presence of a potassium atom and provided a strong basis for the assignment of the lowest unoccupied molecular orbitals accessed in the collision process.

Electronic State Spectroscopy of Halothane As Studied by ab Initio Calculations, Vacuum Ultraviolet Synchrotron Radiation, and Electron Scattering Methods

We present the first set of ab initio calculations (vertical energies and oscillator strengths) of the valence and Rydberg transitions of the anaesthetic compound halothane (CF3CHBrCl). These results are complemented by high-resolution vacuum ultraviolet photoabsorption measurements over the wavelength range 115-310 nm (10.8-4.0 eV). The spectrum reveals several new features that were not previously reported in the literature. Spin-orbit effects have been considered in the calculations for the lowest-lying states, allowing us to explain the broad nature of the 6.1 and 7.5 eV absorption bands assigned to σ*(C-Br) ← nBr and σ*(C-Cl) ← n(Cl) transitions. Novel absolute photoabsorption cross sections from electron scattering data were derived in the 4.0-40.0 eV range. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of halothane in the upper stratosphere (20-50 km).

A new experimental setup designed for the investigation of irradiation of nanosystems in the gas phase: a high intensity mass-and-energy selected cluster beam

DIAM (Dispositif d'Irradiation d'Agrégats Moléculaires) is a new experimental setup devoted to investigate processes induced by irradiation at the nanoscale. The DIAM apparatus is based on a combination of techniques including a particle beam from high-energy physics, a cluster source from molecular and cluster physics, and mass spectrometry form analytical sciences. In this paper, we will describe the first part of the DIAM apparatus that consists of an ExB double spectrometer connected to a cluster ion source based on a continuous supersonic expansion in the presence of ionizing electrons. This setup produces high intensities of energy-and-mass selected molecular cluster ion beams (1000 s of counts s(-1)). The performance of the instrument will be shown through measurements of 6-8 keV beams of protonated water clusters, (H(2)O)(n)H(+) (n = 0-21) and mixed protonated (or deprotonated) water-pyridine cluster ions: PyrH(+)(H(2)O)(n) (n = 0-15), Pyr(2)H(+) (H(2)O)(n) (n = 0-9), and (Pyr-H)(+) (H(2)O).

Electron transfer-induced fragmentation of thymine and uracil in atom-molecule collisions

Ion-pair formation has been studied in hyperthermal (30-100 eV) neutral potassium collisions with gas phase thymine (C(5)H(6)N(2)O(2)) and uracil (C(4)H(4)N(2)O(2)). Negative ions formed by electron transfer from the alkali atom to the target molecule were analysed by time-of-flight (TOF) mass spectrometry. The most abundant product anions are assigned to CNO(-) and (U-H)(-)/(T-H)(-) and the associated electron transfer mechanisms are discussed. Special emphasis is given to the enhancement of ring breaking pathways in the present experiments, notably CNO(-) formation, compared with free electron attachment measurements.

Valence shell electronic spectroscopy of isoprene studied by theoretical calculations and by electron scattering, photoelectron, and absolute photoabsorption measurements

The first ab initio calculations (vertical energies and oscillator strengths) are reported for the neutral electronic transitions of isoprene (2-methyl-1,3-butadiene), CH(2)CHC(CH(3))CH(2). The VUV photoabsorption spectroscopy of the molecule is presented in the energy range 4.6 to 10.8 eV (270-125 nm) with the highest resolution yet reported above 6.05 eV, revealing new spectral features. Valence and Rydberg transitions have been assigned in accordance with the theoretical results and the associated vibronic series have been analysed. The absolute photoabsorption cross sections at energies below 6.89 eV have been used to calculate the photolysis lifetime of isoprene in the upper stratosphere (20-50 km). Electron energy loss spectroscopy (EELS) measurements have enabled further photoabsorption cross sections to be derived in the range 9-28 eV. The first ab initio calculations have been carried out to determine excitation energies to the lowest energy ionic states of isoprene. The calculations are compared with the He(i) photoelectron spectrum (8 to 17 eV) and new vibrational structure is observed in the first photoelectron band.

Virtual reality as a tool for improving spatial rotation among deaf and hard-of-hearing children

The aim of this study was to investigate whether the practice of rotating Virtual Reality (VR) three-dimensional (3D) objects will enhance the spatial rotation thinking of deaf and hard-of-hearing children compared to the practice of rotating two-dimensional (2D) objects. Two groups were involved in this study: an experimental group, which included 21 deaf and hardof-hearing children, who played a VR 3D game, and a control group of 23 deaf and hard-of-hearing children, who played a similar 2D (not VR) game. The results clearly indicate that practicing with VR 3D spatial rotations significantly improved the children's performance of spatial rotation, which enhanced their ability to perform better in other intellectual skills as well as in their sign language skills.

Improving flexible thinking in deaf and hard of hearing children with virtual reality technology

The study investigated whether rotating three-dimensional (3-D) objects using virtual reality (VR) will affect flexible thinking in deaf and hard of hearing children. Deaf and hard of hearing subjects were distributed into experimental and control groups. The experimental group played virtual 3-D Tetris (a game using VR technology) individually, 15 minutes once weekly over 3 months. The control group played conventional two-dimensional (2-D) Tetris over the same period. Children with normal hearing participated as a second control group in order to establish whether deaf and hard of hearing children really are disadvantaged in flexible thinking. Before-and-after testing showed significantly improved flexible thinking in the experimental group; the deaf and hard of hearing control group showed no significant improvement. Also, before the experiment, the deaf and hard of hearing children scored lower in flexible thinking than the children with normal hearing. After the experiment, the difference between the experimental group and the control group of children with normal hearing was smaller.

Enhancing the Induction Skill of Deaf and Hard-of-Hearing Children with Virtual Reality Technology

Many researchers have found that for reasoning and reaching a reasoned conclusion, particularly when the process of induction is required, deaf and hard-of-hearing children have unusual difficulty. The purpose of this study was to investigate whether the practice of rotating virtual reality (VR) three-dimensional (3D) objects will have a positive effect on the ability of deaf and hard-of-hearing children to use inductive processes when dealing with shapes. Three groups were involved in the study: (1) experimental group, which included 21 deaf and hard-of-hearing children, who played a VR 3D game; (2) control group I, which included 23 deaf and hard-of-hearing children, who played a similar two-dimensional (2D) game (not VR game); and (3) control group II of 16 hearing children for whom no intervention was introduced. The results clearly indicate that practicing with VR 3D spatial rotations significantly improved inductive thinking used by the experimental group for shapes as compared with the first control group, who did not significantly improve their performance. Also, prior to the VR 3D experience, the deaf and hard-of-hearing children attained lower scores in inductive abilities than the children with normal hearing, (control group II). The results for the experimental group, after the VR 3D experience, improved to the extent that there was no noticeable difference between them and the children with normal hearing.

DNA methylation represses transcription in vivo

DNA in somatic tissue is characterized by a bimodal pattern of methylation, which is established in the animal through a series of developmental events. In the mouse blastula, most DNA is unmethylated, but after implantation a wave of de novo methylation modifies most of the genome, excluding the majority of CpG islands, which are mainly associated with housekeeping genes. This genomic methylation pattern is broadly maintained during the life of the organism by maintenance methylation, and generally correlates with gene expression. Experiments both in vitro and in vivo indicate that methylation inhibits transcription. It has not yet been possible, however, to determine the role of DNA methylation on specific sequences during normal development. Cis-acting regulatory elements and trans-acting factors appear to be involved in both stage- and tissue-specific demethylation processes. Sp1-like elements have a key role in protecting the CpG island of Aprt (encoding adenine phosphoribosyltransferase) from de novo methylation, and when these elements are specifically mutated, the Aprt CpG island becomes methylated in transgenic mice. We have now characterized an embryo-specific element from the CpG island sequence upstream of Aprt that can protect itself from de novo methylation in transgenic mice as well as reduce methylation of flanking sequences. We placed this element on a removable cassette adjacent to a human HBB (encoding beta-globin) reporter and generated a transgene whose methylation pattern can be switched in vivo. Analysis of globin transcription in this system showed that methylation in cis inhibits gene expression in a variety of tissues, indicating that DNA modification may serve as a global genomic repressor.

Role of DNA methylation in the regulation of transcription

DNA methylation plays an important role in the regulation of gene expression during development. Methyl moieties at CpG residues suppress transcription by affecting DNA-protein interactions, thus altering the accessibility of genes to trans-acting factors in the cell. Because it works in cis, this mechanism is important in the control of X inactivation and genomic imprinting.

Effects of rhGH and rhIGF-1 on renal growth and morphology

It is known that in rodents recombinant human growth hormone (rhGH) and recombinant human insulin-like growth factor (rhIGF-1) increase renal mass. It is uncertain, however, whether renal mass increases in proportion to body growth, or whether renal growth is stimulated selectively. In 120 to 150 g female Sprague-Dawley rats, we measured the effects of rhGH and rhIGF-1 and their combination by the following parameters: kidney weight/body weight ratio, DNA/protein ratio, mRNA of GH receptor and of IGF-1, mitosis index and PCNA (by immunohistology), zonal architecture and glomerular diameter by micromorphometry. Both rhGH and rhIGF-1 dose-dependently increased renal weight and body weight over vehicle treated controls. With rhGH, liver dry weight/body weight ratio increased, but kidney dry weight/body weight ratio remained unchanged (0.99 +/- 0.06 x 10(-3) vs. 1.02 +/- 0.07 in vehicle controls). In contrast, a significant increase of kidney dry weight/body weight ratio was seen in rats treated with rhIGF-1 (1.3 +/- 0.21 x 10(-3). Addition of high doses of rhGH to high doses of rhIGF-1 caused no further increase of the ratio despite a significant further increase of body weight. rhGH increased the abundance of renal GH receptor mRNA (0.46 +/- 0.32 amol/microgram DNA vs. 0.08 +/- 0.07 in controls) and of IGF-1 mRNA (1.35 +/- 0.5 pg/micrograms DNA vs. 0.35 +/- 0.17), whereas no change was seen with IGF-1 treatment. rhGH and rhIGF-1 increased kidney DNA/protein ratio, mitoses and PCNA expression in various renal structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Oral contraception affects osteocalcin serum profiles in young women

The serum concentrations of osteocalcin (bone Gla protein) were followed by continuous blood sampling for 24 h in 9 healthy young women before and during treatment with oestrogen/progestogen combinations for oral contraception. There were marked fluctuations during the 24 h sampling period, values ranging from 0.5 to 10.0 ng/ml. Values displayed an apparent circadian rhythm. Daytime values were on average lower than nocturnal concentrations. During treatment with oral contraceptives there was a significant decrease in osteocalcin levels but fluctuations during the 24 h sampling period were still observed. Almost all individual values obtained at 30 min intervals were lower during treatment. For the whole group the mean osteocalcin concentration decreased by 1.4 ng/ml (p less than 0.01) during treatment. In postmenopausal women high serum levels of osteocalcin are supposed to reflect increased bone turnover secondary to enhanced bone resorption. Oestrogens are known to reduce osteocalcin levels and may reduce bone resorption. In healthy young women alternative mechanisms should be considered but the reduced osteocalcin serum levels in this short-term study indicate that oral contraceptive use may influence bone metabolism.

Neurological disorders in 166 patients with basal ganglia calcification: a statistical evaluation

Patients investigated at our institute during the last decade included 166 (1.2%) who showed uni- or bilateral basal ganglia calcification on computed tomography. We tested the significance of this neuroradiological observation by statistical comparison of these patients' clinical disorders with the findings in a random sample of 622 patients without basal ganglia calcification. The odds for the most common neurological disturbances were similar in patients with and without basal ganglia calcification. After adjustment for differences in age and brain atrophy there was no evidence of a significantly increased risk of dementia (odds ratio 1.1), cerebral infarction (1.4), epilepsy (0.9), vertigo (1.6), headache (1.8), or alcoholism (0.9), which represented the most common diagnoses. We conclude that basal ganglia calcification cannot be considered as a clinically relevant neuroradiological finding in the majority of cases and that it should not be used as an explanation for frequently observed neurological disturbances.

What is the psychiatric significance of bilateral basal ganglia mineralization?

One percent (143) of patients who underwent cranial computed tomography at the Central Institute of Mental Health during the last 10 years had bilateral basal ganglia mineralization (BGM). The relationship of this finding to the psychiatric disorders in the group was evaluated by statistical comparison with a group of patients without BGM (control group). The odds ratios for affective disorders and for organic brain syndromes with affective or paranoid symptoms showed a mild, but statistically significant, increase in patients with BGM. There was no evidence of an increased proportion of dementia, schizophrenia, or alcoholism in those with BGM. Those with BGM had a higher mean age and significantly more cortical atrophy and ventricular enlargement than did patients without. These confounding variables contributed to clinical differences between the BGM and the control groups.

Secretory pattern of growth hormone regulates steroid sulfatase activity in rat liver

Steroid sulfatase activity was quantified in liver microsomes from hypophysectomized adult female rats treated with estradiol and continuous or intermittent human growth hormone (hGH). Hypophysectomy clearly enhanced sulfatase activity as compared to intact female rats. Normal female values were completely restored by continuous infusion of hGH (1.4 i.u./kg/day). Neither the same dose of hGH given as two daily injections nor estrogen replacement therapy had any effect. It is concluded that liver microsome sulfatase activity in the non-pregnant rat is regulated by the sexually dimorphic secretory pattern of GH.

The value of the hydrogen (H2) breath test for the diagnosis of bacterial overgrowth in gastric achlorhydria

Sixteen healthy volunteers, 23 patients with peptic disease, and 38 patients with achlorhydria were investigated with bacterial cultures from gastric juice and a hydrogen (H2) breath test after a standard meal. In acid-secreting subjects upper respiratory tract bacteria were found in 6/39. In every single achlorhydric patient gastric bacterial concentrations were above log 10 5.7/ml. Fecal flora was found in 22/38. The patient with fecal organisms were significantly older than those without (p less than 0.05). The H2 breath test revealed low postprandial carbohydrate fermentation in acid secretors and in achlorhydrics with no fecal flora. The lowest H2 production was found 90 and 120 min after the meal. In achlorhydrics with fecal organisms the mean H2 concentration at these times of measurement was elevated (p less than 0.05). Assuming that a mean H2 concentration at 90 and 120 min above 19 ppm (mean in healthy volunteers at 90 and 120 min + 2 SD) is pathological, the association of fecal bacteria in gastric juice and a "positive" H2 breath test is highly significant (P less than 0.001). Fecal bacteria in the gastric juice would indicate small-intestinal fermentation with a probability of 81%. A gastric culture negative for fecal organisms would predict a "negative" H2 breath test with a probability of 91%.

Assessment of orocoecal transit time by means of a hydrogen (H2) breath test as compared with a radiologic control method

The definition of the orocoecal transit time by means of the hydrogen (H2) breath test is not unequivocal. In this study the orocoecal transit time as measured with an H2 breath test was compared with that obtained with a radiologic method. Two definitions of orocoecal transit time by the H2 breath test were evaluated: the time from eating to the first of three consecutively rising H2 values, and the interval to H2 values 50% above 'small-bowel level'. Transit times measured in accordance with both definitions were closely correlated to that obtained with the radiologic method (A, r = 0.84; B, r = 0.90; for both, p less than 0.001), but transit time measured by definition A gave shorter values than the radiologic method (p less than 0.05). The mean transit time in patients with constipation was significantly longer than that in normal subjects and patients with functional diarrhoea (p less than 0.05). There was a significant correlation between the difference in transit time measured with the H2 breath test and the radiologic method and the transit time measured by the control method. This may indicate that rapid transit is associated with a delayed 'colonic' rise in H2 levels and slow transit with an early H2 rise.

Acute growth hormone deficiency rapidly alters glucose metabolism in rat adipocytes. Relation to insulin responses and binding

To investigate cellular aspects of the antagonism between endogenous GH and insulin in adipose tissue, we examined glucose metabolism, insulin responses, and insulin binding in adipocytes isolated from rats made GH deficient by treatment with antibodies to rat GH (ArGH), which neutralize the biological actions of GH. Adipocytes were incubated in the presence or absence of insulin, and their ability to convert [14C] glucose to CO2 and lipid was measured. Basal glucose utilization was significantly elevated in adipocytes from ArGH-treated rats after 6, 3, or even 1 h of serum treatment compared to that in controls treated with nonimmune serum. This suggests that endogenous GH suppresses glucose metabolism in adipocytes from normal rats. In the presence of insulin, the absolute values of glucose utilization were also higher in cells from ArGH-treated rats than in controls. However, because basal glucose oxidation was higher with GH deficiency, the percent stimulation by insulin was not different in adipocytes from ArGH-treated rats and controls. In keeping with this, the binding of [125I]iodoinsulin was not altered by GH deficiency. These findings indicate that endogenous GH suppresses basal glucose metabolism in adipocytes, and that this effect is rapidly reversed by treatment of normal rats with ArGH. Furthermore, this effect of GH on adipocyte metabolism is independent of changes in insulin binding and appears to account for the enhanced responses to insulin observed with GH deficiency.

A hybrid noncovalent complex of fragments of porcine and human growth hormones with diabetogenic activity

Although porcine GH (pGH) and human GH (hGH) are structurally related, their structures differ to the extent that, unlike hGH, pGH is not active in primates and does not exhibit lactogenic activity. Therefore, it was of interest to determine whether hybrid noncovalent complexes could be formed by complementation of large fragments of pGH with fragments of hGH and to study the immunological and biological properties of such hybrids. For this purpose, pGH was digested with bovine thrombin conjugated to Sepharose. After reduction and S-carbamidomethylation of the digested hormone, two large fragments consisting of residues 1-133 (p1-133T) and 134-191 (p134-191T) were isolated by gel filtration. The human GH fragments used in this work were S-carbamidomethylated peptides 1-134 (h1-134T) and 135-191 (h135-191T) isolated from thrombin-digested hGH. Noncovalent complementation of the peptide fragments was attempted by dissolving equimolar amounts of the materials in 0.5% (wt/vol) ammonium bicarbonate solution containing 6 M guanidine-HCl and then gradually removing the guanidine-HCl by dialysis. Using this method, a hybrid noncovalent complex of peptides p1-133T and h135-191T was produced in 50% yield by weight of starting material. Attempts to produce the reciprocal complex between h1-134T and p134-191T, as well as attempts to recombine the contiguous pGH fragments, p1-133T, and p134-191T, were unsuccessful. The hybrid complex (p1-133T + h135-191T) had 40% the cross-reactivity of native pGH in a rat GH RIA, but it was inert in an hGH RIA. It had very low growth-promoting activity in the 9-day weight gain test in hypophysectomized rats and no detectable in vitro ability to stimulate [14C]phenylalanine incorporation into the protein of the diaphragm of the hypophysectomized rat. When tested for insulin-like activity (stimulation of glucose oxidation in vitro in adipose tissue of hypophysectomized rats), the hybrid complex had less than 1% the activity of native pGH. In contrast, the hybrid complex had approximately 10-20% the diabetogenic activity of native pGH in the ob/ob mouse. The fact that the hybrid complex has substantial diabetogenic activity, although lacking significant anabolic or insulin-like activities, suggests that the structural requirements differ for the expression of these various activities of GH.

Effects of in vivo administration of antiserum to rat growth hormone on body growth and insulin responsiveness in adipose tissue

To explore the short term effects of endogenous GH on body growth, glucose metabolism, and insulin responsiveness in adipose tissue, 35- to 40-day-old male rats were treated with a potent goat antiserum against rat GH (ArGHS). The administration of ArGHS, but not normal goat serum, caused a dose-dependent decrease in body weight gain and longitudinal bone growth, as measured by the tetracycline method. Glucose metabolism was measured by determining the production of CO2 from [14C]glucose in epididymal fat pad. Treatment with ArGHS (0.05-0.5 ml, ip, twice daily for 6 days) resulted in increased insulin sensitivity, as determined by the ED50 values for the effect of insulin. An increased response to a submaximal concentration of insulin was observed 3 h after the administration of 0.5 ml ArGHS. Basal levels were not consistently affected by ArGHS treatment. The maximal response to insulin was significantly increased after treatment with low doses of ArGHS (0.1-0.2 ml/day) and was decreased after treatment with high doses of ArGHS (0.8-1 ml/day) for 6 days. The magnitude of the response, as determined by the percent increase in response to 10 mU/ml insulin, was, however, not different compared to that observed in adipose tissue of normal goat serum-treated rats. These results demonstrate that elimination of endogenous GH results in retarded growth in the rat within 24 h. Moreover, the results suggest that GH is important in insulin sensitivity.

Specific binding of growth hormone to isolated chondrocytes from rabbit ear and epiphyseal plate

Chondrocytes were isolated from rabbit ear, epiphyseal and rib cartilage, and their ability to bind 125I-labeled human growth hormone (hGH) was investigated. The total binding of hormone to ear chondrocytes increased with time until 4-6 h, whereas non-specific binding did not increase. Total binding was 1-3% of total counts added, and non-specific binding was 10-20% of total binding. Unlabeled hGH, bGH and oPRL competed with the binding of labeled hGH in a dose-dependent manner with half-maximal binding at concentrations of 10-20 ng/ml (hGH) and 100 ng/ml (bGH and oPRL). The two latter hormones displaced almost all specific binding of hGH at higher concentrations. Ear chondrocytes from newborn to 4 week old rabbits all showed specific binding of hGH with no clear age dependence. Rib chondrocytes, on the other hand, showed very little specific binding. Epiphyseal chondrocytes from newborn animals yielded intermediate binding values. The finding of specific hGH binding by cultured chondrocytes supports the concept of a direct effect of GH on chondrocytes.

Evidence for a growth hormone releasing factor mediating alpha-adrenergic influence on growth hormone secretion in the rat

The effects of adrenergic receptor agonists on GH secretion were studied in adult, male rats pretreated with reserpine and somatostatin antiserum. Frequent blood samples were obtained from intra-aortic cannulae. Plasma GH was determined by radioimmunoassay. Reserpine (10 mg/kg i.p.) caused a complete suppression of the normal, pulsatile secretion of GH in all animals. Administration of somatostatin antiserum resulted in rapid elevations of plasma GH in reserpine-pretreated rats with peak levels at 30 min. GH levels then fell but remained slightly elevated for the duration of the sampling period (8 h). Apomorphine (0.5 mg/kg i.p.) had no effect on plasma GH levels, whereas clonidine (0.5 mg/kg i.p.) induced release of GH in both antiserum treated and control rats. The results indicate that the alpha-adrenergic influence on the secretion of GH is mediated not by inhibition of somatostatin release but rather by effects on the release of a GHRF.

Effect of LH on the release of cyclic AMP by the rabbit ovary perfused in vivo and in vitro

After perfusion of 10 rabbit ovaries in vitro with a modified Krebs bicarbonate buffer containing dextran and glucose, the concentration of cAMP in the perfusion medium was significantly increased 2-5 min after stimulation with 10 mug LH/ml medium and was higher at 15 and 30 min. Intravenous injection of 100 mug LH/rabbit caused a significant increase of cAMP concentrations in the ovarian venous blood from 8 ovaries 10 min after the injection and the cAMP concentrations were higher after 15 and 30 min. The ovarian blood flow was not changed after the LH injection. It is concluded that perfusion techniques can be useful in analysis of the mechanisms and physiological significance of release of cAMP from the ovary after hormonal stimulation.