Hx Group Research Articles

Influence of hypophysectomy on renal proteoglycans and their modulation by insulin-like growth factor-I and its receptor.

Hypophysectomy leads to growth retardation of the animals, which is believed to be related to the deficiency of certain growth factors influencing the metabolism and synthesis of glycoproteins. Conceivably, the extracellular matrix proteins (ECM) are also affected, in particular the sulfated proteoglycans (PGs). In this study, we investigated the status of the ECM proteins and sulfated PGs, and the expression and de novo synthesis of insulin-like growth factor-I (IGF-I) receptor (IGF-IR) in hypophysectomized (Hx) rats. The studies were extended to ascertain the effect of IGF-I on the de novo synthesis of glomerular ECM glycoproteins in Hx rats. An organ perfusion system was used in which isolated rat kidneys were radiolabeled with either [35S]sulfate or [35S]methionine, after which IGF-IR and ECM macromolecules were isolated and characterized by biochemical and tissue autoradiographic procedures. Hypophysectomy resulted in a fall in IGF-I levels in serum and isolated renal glomeruli. Reduced synthesis of ECM proteins, i.e. type IV collagen, laminin, and sulfated PGs, and reduced synthesis and mRNA expression of IGF-IR were observed in the glomeruli of the Hx rats. Tissue autoradiographic studies revealed a reduced grain density (concentration of radiation) over various cell types of the glomerulus. After inclusion of IGF-I in the perfusion medium not only was synthesis restored to normal in Hx rats, but it far exceeded the control basal values in the intact animals. Under the influence of IGF-I, the magnitude of increased synthesis of the ECM proteins, in particular the sulfated PGs, was highly accentuated in the kidneys of the Hx group compared to the controls. Also, a remarkably increased [35S]sulfate incorporation was observed in the glomerular mesangial cells. The analysis of IGF-IR by specific binding studies revealed a decreased concentration of the receptors, but an increased IGF-I-binding affinity, the latter of which probably contributed to the IGF-I-induced accentuated synthesis of renal glomerular PGs in the Hx group.

Effects of Hypophysectomy on Coho Salmon Interrenal: Maintenance of Steroidogenic Pathway and Restoration of in Vitro Responsiveness to Adrenocorticotropin after Handling

The role of the pituitary in regulating interrenal activity in coho salmon ( Oncorhynchus kisutch) was examined using short- (1 week) or long- (10 week) term hypophysectomized (Hx) animals. In experiments in which Hx animals were injected with ovine growth hormone (oGH), triiodothyronine, or vehicle, plasma cortisol was significantly lower (close to nondetectable, 1 ng/ml) in vehicle-injected or hormone-treated short- and long-term Hx animals compared to vehicle-treated sham-operated (SO animals). Treatment of long-term Hx animals with oGH led to a significant increase in plasma cortisol, in comparison to other Hx groups. Interrenal responsiveness to ACTH or cAMP was not consistently affected by hypophysectomy or hormone treatment. Pregnenolone-supported cortisol production by tissue from Hx groups was at least as great as that by tissue from SO animals: production by tissue from GH-treated, long-term Hx animals was significantly greater than that by tissue from Hx or SO animals. Similar experiments utilizing handling stress (handling and anesthesia) instead of hormone injection as a variable revealed that the response of tissue from Hx animals to ACTH or cAMP was significantly reduced in the absence of handling in comparison with SO animals. However, utilization of pregnenolone as a substrate by tissue from Hx animals was no different from that by tissue from SO animals and was independent of handling. These results indicate that the maintenance of the steroid-biosynthetic pathway is pituitary independent. The decrease in tissue responsiveness to ACTH or cAMP in undisturbed Hx animals may be partially attributable to: (1) the absence of nonpituitary/ nonpituitary-mediated factors that are stimulated by handling and which probably upregulate ACTH receptors and mediating systems; and/or (2) to the presence of inhibitory factors which are decreased after handling.

An insulin-like growth factor I-resistant state in cartilage of diabetic rats is ameliorated by hypophysectomy. Possible role of metabolism.

This study investigated the effect of IDDM on cartilage anabolic activity in rats. Rats were injected with STZ to induce IDDM, were hypophysectomized, or were injected with STZ and hypophysectomized. After 14 days, control (intact and sham-Hx) and Hx rats were normoglycemic, whereas the rats with IDDM exhibited hyperglycemia and glycosuria. The HxDb rats, however, had normal blood glucose levels and no glycosuria. Both growth, serum levels of IGF-I, and basal cartilage 35SO4 incorporation measured in vitro were decreased in the Hx, IDDM, and HxDb groups. IGF-I added in vitro significantly stimulated 35SO4 incorporation by cartilage explants from control and Hx animals, whereas explants from the animals with IDDM were unresponsive. Explants from the HxDb rats, however, were stimulated by IGF-I in a dose-related manner. Because Hx corrected the glycemic status of the IDDM rats and restored cartilage responsiveness to IGF-I, a second set of experiments was undertaken to further investigate the relationship between cellular metabolism and anabolic activity in cartilage. Cartilage explants from rats fasted for 48 h showed significantly decreased basal 35SO4 incorporation, which was as low as that in explants from rats with severe IDDM. Whereas explants from the IDDM rats were completely unresponsive, those from the fasted rats (and fed rats) were significantly stimulated by the added IGF-I. However, incubation in the presence of 2-D-G, which causes intracellular glucopenia, or in the absence of glucose, completely blocked the anabolic response to IGF-I in otherwise responsive tissues. In conclusion, an important component of diabetic growth inhibition appears to be tissue resistance to the anabolic action of IGF-I, a condition that is correctable by Hx and that may be a result of metabolic impairment at the tissue level.

Different Roles for the Pituitary and Adrenal Cortex in the Control of Enkephalin Peptide Localization and Cortico-Medullary Interaction in the Sheep Adrenal during Development

We have investigated the effect of adrenocorticotrophic hormone (ACTH) replacement after fetal hypophysectomy on the pattern of localization of enkephalin-containing peptides (enkephalins) and phenylethanolamine N-methyltransferase (PNMT) in the fetal sheep adrenal. We have also investigated the relative roles of the fetal pituitary and adrenal cortex in determining the extent of the interdigitation of the peripheral adrenaline (AD)-containing cells of the adrenal medulla with the inner zones of the adrenal cortex in the late gestation fetus. Fetal hypophysectomy (Hx; n = 12) or sham operations (n = 8) were performed at 109-118d. At 138 or 139d, ACTH (1-24) (10.5 micrograms/h) was infused intravenously for 72 h into 4 Hx fetuses (Hx + ACTH group). Saline was infused for 72 h into 4 Hx fetuses (Hx + Sal) and into 4 sham-operated fetal sheep (Intact + Sal). Fetal adrenal glands were collected at autopsy from 141/2d Intact + Sal, Hx + Sal and Hx + ACTH groups, from 4 intact fetal sheep at 145-147d gestation (145/7d Intact group) and 4 Hx fetal sheep at 147-164d gestation (147/64d Hx group). Adrenals were also collected from 4 newborn lambs at 10-12d after birth (10/12d Newborn group). Using the peroxidase-antiperoxidase immunocytochemical staining method, sections of adrenal glands (10-12 microns) from all groups were stained anti-PNMT. Sections of adrenal glands from the 141/2d groups were also stained separately with anti-dopamine-beta-hydroxylase (anti-D beta H) and anti-enkephalin (anti-ENK).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the Baroreceptor Reflex System on Atrial Natriuretic Factor Secretion during Volume Expansion in Dogs

1. The purpose of this study was to determine whether the baroreceptor reflex system affects the secretion of atrial natriuretic factor directly or indirectly during acute volume expansion. 2. Lactated Ringer's solution containing low mol. wt. dextran was infused at 20 ml/kg for 1 h into dogs in which baroreceptors had been denervated surgically (Vx), dogs in which the autonomic system had been blocked with hexamethonium (Hx) and control dogs. 3. The plasma noradrenaline level was significantly higher in the Vx group and lower in the Hx group than in the control group throughout the experiment. The plasma levels of arginine vasopressin in the Vx and Hx groups were significantly higher than in the control group. 4. The plasma atrial natriuretic factor levels in the three groups showed similar increases during and after volume expansion. 5. The plasma atrial natriuretic factor level was significantly correlated with the right atrial pressure during volume expansion. 6. From these results, it seems unlikely that changes in the plasma level of atrial natriuretic factor during volume expansion are regulated by the baroreceptor reflex directly or indirectly by systemic changes in the sympathetic nervous system or arginine vasopressin secretion.

Effect of hypophysectomy on the occupied and unoccupied binding sites for 1,25-dihydroxyvitamin D 3 in rat intestine

It is not known why the intestinal active transport of calcium per unit of mucosal mass is not affected by hypophysectomy (HX) even though serum 1,25-dihydroxyvitamin D 3 [1,25(OH) 2D 3 and intestinal calcium-binding protein are decreased. In order to study the effect of HX on the quantity of intestinal receptor of 1,25(OH) 2D 3 and its binding characteristics, the intestinal total occupied and unoccupied binding sites for 1,25(OH) 2D 3 were measured, by the use of the mercurial reagent mersalyl, in the intestine of HX and age-matched control rats. In addition, the effect of bovine growth hormone (bGH) replacement on the quantity of both binding states was examined in the HX rats. Results of Scatchard analysis and sucrose density gradients showed that the 3.5S receptor of the HX rat intestine was not distinguishable from that seen in the intact rat intestinal cytosol. Under vitamin D-supplemented conditions, HX was shown to reduce the levels of occupied receptors when the data were expressed on the basis of cytosolic protein. The reduced occupied sites could, in fact, have resulted from the reduction in plasma 1,25(OH) 2D 3 levels. No synthesis rates were determined. The unoccupied and total binding sites for 1,25(OH) 2D 3 per length of intestine were lower in the HX group than in the intact group. Administration of bGH resulted in an increase of endogenously occupied binding sites without affecting the total binding activity. Under vitamin D-depleted (-D) conditions, the total binding activity (intestinal) for 1,25(OH) 2D 3 was increased in the intact but not in the -DHX rats. Administration of bGH to the -DHX rat resulted in no effect on the binding levels of 1,25(OH) 2D 3 receptor. The current study demonstrates that HX does not affect the binding affinity and the concentration of intestinal total binding receptor 1,25(OH) 2D 3. The decrease in endogenously occupied binding sites for 1,25(OH) 2D 3 without an affect on the intestinal active transport of calcium could be interpreted to mean that HX affects other factors controlling calcium absorption than 1,25(OH) 2D 3.

Effect of hypophysectomy and 1,25-dihydroxyvitamin D on duodenal calcium absorption.

Intestinal active and passive transport of calcium were studied in hypophysectomized (HX) and intact rats using the in vivo duodenal loop technique. In the vitamin D-supplemented condition, hypophysectomy resulted in a decrease in serum 1,25-dihydroxyvitamin D [1,25-(OH)2D]. Hypophysectomy prevented a gain in body weight and decreased intestinal mucosal weight and total calcium absorption. When the data were expressed per unit mucosal wet weight, duodenal active calcium transport was not different in the HX and intact groups, but passive transport was persistently decreased by hypophysectomy. Administration of bovine GH to the HX rats did not change the mucosal mass, but enhanced both active and passive duodenal transport to calcium. Vitamin D depletion for 6 weeks decreased serum 25-hydroxy-vitamin D and 1,25-(OH)2D levels in both intact and HX rats to about the same level. After bovine GH and 1,25-(OH)2D3 replacement, the calcium absorption studies suggest that 1) 1,25-(OH)2D3 enhances intestinal calcium passive transport as well as active transport in intact and HX rats; 2) GH enhances both active and passive transport of calcium in the presence of sufficient quantities of 1,25-(OH)2D; 3) this latter effect is independent of the metabolism of vitamin D; and 4) a decrease in mucosal mass is one of the factors that results in decreased calcium absorption after hypophysectomy.

Application of vibrational spectroscopy to the estimation of electron-donating properties of organometallic groups : III. Determination of σ-constants of Ph nMX and HX groups (X  O, S, NR)

It has been established that in compounds of the Ph nMXC 6H 6NO 2 type good linear correlations exist between spectral characteristcs and electron-donating properties of XMPh n groups, namely, the integral intensities of v(Ar) and v s (NO 2), for each examined class of compounds. The intensities of v s (NO 2) have been found to be more sensitive to the electronic effect of substituents and solvation effects. The use of these values has made it possible to determine the σ constants which take into account the direct polar conjugation of XH and XMPh n groups with the reactive center (σ + p, σ + R). The factors affecting the solvation sensitivity of these values are discussed.

Effects of hypophysectomy and prolactin on the water-balance response of the newt, Taricha torosa

Prolactin treatment (20 μg/day for 7 days) of intact terrestrial Taricha torosa lowered the rates of both water uptake (from 51.1 ± 2.1 to 32.1 ± 1.4 μl/g/hr) and urine formation (from 52.4 ± 2.7 to 31.1 ± 1.9 μl/g/hr). Compared with shams, hypophysectomized (HX) newts also showed lower rates of water uptake and urine formation (from 59.3 ± 3.4 to 38.9 ± 2.0 μl/g/hr and from 54.9 ± 3.8 to 34.5 ± 2.4 μl/g/hr, respectively). Prolactin treatment of hypophysectomized newts (HX + P) further lowered the rates of water uptake (to 28.6 ± 2.0 μl/g/hr) and urine formation (to 23.2 ± 1.7 μl/g/hr). Subcutaneous injection of 200 mU arginine vasotocin (AVT) elicited a 20.6 ± 1.6% weight gain after 4 hr in sham-operated control newts, compared with 15.1 ± 1.1% in HX and 7.6 ± 1.2% in HX + P animals. Weight gains in sham-HX and HX groups resulted from both an increase in cutaneous osmotic permeability and a reduction in rate of urine formation. However, even after AVT stimulation, cutaneous permeability in HX newts did not equal that found in uninjected control (sham) animals. Weight gain in AVT-injected HX + P animals was due almost entirely to decreased urine production, with cutaneous permeability remaining essentially unchanged. These data add to the growing body of evidence indicating that prolactin acts to decrease integumental permeability in amphibians, rather than to increase it as was previously thought.

Apparent hydrogen bonding by strongly immobilized spin-labels.

The hyperfine separations of nitroxide spin-labels which are tightly bound within hemoglobin exhibit a substantial temperature dependence even when the hemoglobin is immobilized by freezing or precipitation. It is shown that NO.--HX hydrogen bond formation by the spin-label within its binding site is a good explanation for the observed temperature dependence. Comparative studies using different hemoglobin derivatives and two different spin-labels suggest that the HX group may be some element of the protein matrix and that this hydrogen bond may be a factor in the stabilization of the label within its binding site. The hyperfine separation of a fatty acid spin probe incorporated into aqueous bilayer dispersons of dipalmitoylphosphatidylcholine also exhibits a temperature dependence at low temperature which is qualitatively similar to that of the spin-labeled hemoglobin systems. Saturation transfer electron paramagnetic resonance measurements indicate that label motion is not the source of this temperature dependence. A hydrogen-bond equilibrium between water molecules and the nitroxide NO. group appears to be a plausible source of the temperature-dependent hyperfine separation in the lipid bilayer system. Small amplitude torsional oscillation or librational motion by the nitroxide may also produce additional changes in the hyperfine separation which are difficult to distinguish from hydrogen-bonding effects under some circumstances. The apparent hydrogen-bond equilibrium exhibits a strong thermal and environmental dependence which may be of importance in a number of biophysical spin-label measurements.

Effect of testosterone administration on the epiphyseal cartilage of hypophysectomized rats

For the study of the mechanism of action of testosterone histological, carbohydrate-, and enzyme histochemical investigations were carried out on the epiphyseal cartilage of (1) hypophysectomized rats treated with testosterone [(THX group); (2)] hypophysectomized rats without hormonal treatment (HX group), and (3) intact, untreated control rats. The results were compared with the data obtained in a previous experiment in which intact rats were treated with testosterone (T group). The experiments showed that testosterone exerts a peripheral direct effect on the enzyme system of the epiphyseal cartilage cells by changing their metabolism in the direction of early ageing. This effect elicits characteristic changes in enzyme activity of the cartilage cells if normal hypophyseal activity is present. Impairment and ossification of the epiphyseal cartilage ensue also in hypophysectomized animals treated with testosterone (THX), even faster than in animals subjected only to hypophysectomy (HX), but this process has lost its characteristic feature: the initial increase of enzyme activity in the cartilage cells. Thus, the presence or absence of the hypophysis only modifies the effect of testosterone. Presumably, the latter effect - though not asserting itself through the hypophysis - is highly dependent on hypophyseal activity, that is, on the presence of the hormones produced or mediated by the hypophysis. If testosterone does influence the secretion of these hormones and the activity of the hypothalamus, a central effect of testosterone seems also to be involved in the changes of the epiphyseal cartilage disc.