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Biomedical subjects

M Maes

Publications and source records attributed to M Maes.

At least 325 records · Page 18Linked to original sources
PubMed1988

Different effects of intermittent and continuous growth hormone (GH) administration on serum somatomedin-C/insulin-like growth factor I and liver GH receptors in hypophysectomized rats.

To determine if the pattern of GH delivery is important for the regulation of serum somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) and liver somatogenic receptors, we have measured serum Sm-C/IGF-I concentrations and free (H2O-treated homogenates) and total (MgCl2-treated homogenates) liver GH-binding sites in hypophysectomized rats treated for 7 days with rat GH (rGH), given either continuously by osmotic minipumps (50 and 250 micrograms/day) or intermittently (four sc injections of 12.5 micrograms/day). At a daily dose of 50 micrograms, intermittent rGH produced greater weight gain [+29.7 +/- 0.8 g (mean +/- SE)] than continuous GH infusion (23.3 +/- 2.0 g; P less than 0.01). Likewise, the serum Sm-C/IGF-I concentration rose more with intermittent (0.33 +/- 0.1 U/ml) than with continuous delivery (0.17 +/- 0.01 U/ml; P less than 0.01). The serum Sm-C/IGF-I level achieved with repeated GH injections was even greater than that after continuous delivery of a 5-fold higher GH dose (250 micrograms/day; 0.27 +/- 0.02 U/ml; P less than 0.05). Continuous infusions of 50 and 250 micrograms rGH/day increased the number of liver total GH receptors by 2.5-fold over that of controls. In contrast, frequent GH injections did not affect GH binding, and the serum Sm-C/IGF-I concentration did not correlate with liver GH-binding sites in the GH-injected rats (r = 0.189; P = NS). Induction of hepatic PRL receptors was 10-fold higher when GH was given continuously than when it was given intermittently. The close correlation observed between GH- and PRL-binding sites in all GH-treated rats (r = 0.955; P less than 0.001) suggests that their regulation may be linked. These data suggest that the regulatory mechanism controlling Sm-C/IGF-I production and growth might be different from those that regulate GH receptor concentrations, with GH pulses being crucial for the maximal stimulation of Sm-C/IGF and growth, but continuous exposure to GH being required for up-regulation of liver GH receptors.

Animals↗
PubMed1988

Decreased serum insulin-like growth factor I response to growth hormone in hypophysectomized rats fed a low protein diet: evidence for a postreceptor defect.

In protein-calorie malnutrition, serum IGF-I concentrations are low despite high GH. This GH resistance might be due to a reduced number of liver GH binding sites as suggested by studies performed in fasted rats that were refed a low protein diet. To determine whether a postreceptor defect in GH action might also contribute to the GH resistance, we measured the number and the affinity constant of the liver GH binding sites and the serum IGF-I responses to injections of recombinant bGH in hypophysectomized female rats, fed a standard (15% protein) diet (N = 25) or a low (5%) protein diet (N = 25) for 8 days. There were no significant differences in the liver GH binding capacities between the 15% and the 5% protein-fed rats, whether expressed as pmol per liver (20.6 +/- 3.5 vs 14.4 +/- 1.3; mean +/- SEM; P less than 0.2; N = 5, respectively), pmol per mg DNA (1.08 +/- 0.16 vs 0.84 +/- 0.07; P less than 0.4) or fmol per mg of protein (28.98 +/- 5.04 vs 30.26 +/- 2.00; P greater than 0.5). Likewise, the affinity constants of the GH binding sites of the 15% and the 5% protein-fed rats were not significantly different (0.78 +/- 0.05 vs 0.78 +/- 0.07 x 10(9) l/mol; P greater than 0.5). Despite these non-significant reductions in liver GH binding sites, the IGF-I responses 24 h after sc injections of increasing doses of bovine GH were blunted in the rats fed the 5% protein diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Early changes in serum concentrations of somatomedin-C induced by dietary protein deprivation in rats: contributions of growth hormone receptor and post-receptor defects.

To define the mechanism(s) for the decrease of somatomedin concentrations in acute protein malnutrition, we have assessed the relationships between serum immunoreactive somatomedin-C/insulin-like growth factor-I (Sm-C/IGF-I), serum immunoreactive GH and total (MgCl2-treated homogenates) as well as free (water-treated homogenates) liver somatogenic (GH) binding sites in growing rats fed a 5% protein diet for 12 or 24 h and given an s.c. injection(s) of rat GH (rGH) or saline. Control rats were fed a 15% protein diet and injected with rGH or saline. After 12 and 24 h of protein restriction, body weight was 6.9 and 8.2% below controls respectively (P less than 0.001), while Sm-C/IGF-I concentrations were reduced by 58 and 66% respectively (P less than 0.001 vs controls). Serum GH concentrations were not affected by the low protein intake. Furthermore, injection(s) of 50-100 micrograms rGH failed to raise serum Sm-C/IGF-I concentrations in the protein-deficient animals. The number of total and free GH-binding sites was modestly (15-20%) decreased at 12 and 24 h in the protein-restricted rats. Serum Sm-C/IGF-I concentrations correlated weakly with free and total binding sites (r = 0.48 and 0.38 respectively). Affinity constants of GH-binding sites were not changed by protein restriction. The profound reduction in Sm-C/IGF-I concentrations within a few hours of beginning protein restriction, and the discordance between this reduction and the small decline in somatogenic binding sites, suggests that, in addition to GH receptor loss, a postreceptor defect may participate in the GH resistance occurring in the early stages of protein deficiency.

Animals↗
PubMed1988

Repeated dexamethasone suppression test in major depression.

A review is made on the repeated dexamethasone suppression test (DST) in patients with a major depression. In those patients treated with conventional antidepressants the gradual normalization of the DST results is significantly correlated with the evolution of the clinical picture as measured with the Hamilton Depression Rating Scale. Normalization of the DST precedes symptomatic improvement and can be used as a predictor of good clinical outcome. Persistent dexamethasone non-suppression after treatment and complete clinical recovery predicts early clinical relapse. Patients with recurrent depression tend to have consistency of their response to dexamethasone over multiple depressive episodes.

Antidepressive Agents↗
PubMed1987

Relationship between the dexamethasone suppression test and the L-tryptophan/competing amino acids ratio in depression.

Levels of L-tryptophan (L-TRP), of the competing amino acids (CAA) valine and leucine, and of postdexamethasone cortisol taken at 8 a.m., 4 p.m., and 11 p.m. were determined in serum samples from 140 depressive patients. The relationships between postdexamethasone cortisol values, the CAA, and the L-TRP/CAA ratio were assessed using Pearson and Spearman correlation coefficients and multiple regression. There was a significant correlation between postdexamethasone cortisol and both L-TRP and the L-TRP/CAA ratio. The highest correlation coefficients were obtained for the 8 a.m. cortisol values. Nonsuppressors, in comparison with suppressors, showed a significantly lower L-TRP value and L-TRP/CAA ratio.

Adult↗
PubMed1987

Cortisol response to dexamethasone and noradrenergic function in depression.

Positive correlations between measures of hypothalamic-pituitary-adrenal (HPA)-axis activity and noradrenergic turnover have been reported in depression. To investigate this relationship the authors measured peak postdexamethasone cortisol levels (8 a.m., 4 p.m. and 11 p.m.) and the 24-hour urinary 3-methoxy-4-hydroxy-phenylglycol (MHPG) flow in 84 depressed patients. The results show that there is no positive association between those measures of HPA-axis and noradrenergic activity. On the contrary, patients with severe non-suppression (greater than or equal to 10 micrograms/dl or 277 nmol/l) tended to have a lower MHPG-excretion.

Adult↗
PubMed1987

The cortisol suppression index and the dexamethasone suppression test in major depression.

The pre- and postdexamethasone cortisol levels are determined at 8 a.m. in 106 depressive patients. The patients are classified according to DSM-III in two categories: minor depression (300.40, 296.82, 309.00) and major depression (296.X2, 296.X3, 296.X4). The cortisol suppression index (CSI) e.g. the ratio of pre- and postdexamethasone cortisol levels is calculated. The clinical relevance of the CSI for major depression is compared to the dexamethasone suppression test (DST). The CSI is significantly (p = 0.018) lowered in patients with major depression as compared to those with minor depression. The CSI depends (r = -0.929) on changes of the postdexamethasone cortisol levels. The DST is more useful as an external validating criterion for major depression than is the CSI. The determination of the CSI is not an asset in the diagnosis of major depression.

Adult↗
PubMed1986

Regulation of somatomedin-C/insulin-like growth factor I by nutrients.

Nutritional intake is an important regulator of plasma somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) concentrations in plasma. Concentrations in humans are reduced to the hypopituitary range by fasting for only a few days, and their normalization after fasting depends on the adequacy of energy and protein in the refeeding diet. The changes correlate with changes in nitrogen balance. In rats we have observed a close relationship between change in plasma Sm-C/IGF-I and hepatic GH binding with fasting and refeeding, suggesting that alterations in GH binding might be responsible partly for changes in Sm-C/IGF-I. When malnourished humans are given nutrient repletion, the increase in Sm-C/IGF-I is far more dramatic than changes in other nutrient-related serum proteins.

Adult↗
PubMed1986

Low serum somatomedin-C in insulin-dependent diabetes: evidence for a postreceptor mechanism.

In insulin-dependent diabetic rats, plasma somatomedin (Sm) levels are low and are not corrected by GH treatment, suggesting GH resistance. To define the mechanism of this GH-resistant state, the number and affinity constant of bovine liver GH-binding sites and the serum Sm-C responses to injections of bovine GH were determined in control (diluent-injected) and diabetic (streptozotocin-injected; 40 mg/kg BW) hypophysectomized rats. The affinity constants (Ka) of the GH-binding sites of control (0.92 +/- 0.07 X 10(9) M-1) and diabetic animals (0.68 +/- 0.04 X 10(9) M-1) were not significantly different (P less than 0.1). Likewise, there were no significant differences in the liver GH-binding capacities between control and diabetic hypophysectomized rats, whether these capacities were expressed as picomoles per liver (26.99 +/- 3.43 vs. 22.27 +/- 2.55, controls vs. diabetics), picomoles per mg DNA (1.26 +/- 0.15 vs. 1.10 +/- 0.12), or femtomoles per mg protein (30.95 +/- 4.08 vs. 29.98 +/- 2.70). Despite the absence of alterations in liver GH-binding sites, the Sm-C responses 24 h after sc injections of graded doses of bovine GH were severely blunted in the diabetic animals. The maximal serum Sm-C response in the controls was 0.81 +/- 0.12 U/ml, but was only 0.09 +/- 0.01 U/ml in the diabetics (P less than 0.01). The dose of GH required to achieve the half-maximal Sm-C response (ED50) was similar in diabetic and nondiabetic rats (700-900 micrograms). The absence of significant alterations in liver GH binding and the decreased maximal serum Sm-C response without changes in the ED50 suggest that the GH-resistant state in insulin-dependent diabetes is due to a postreceptor defect.

Animals↗
PubMed1984

Low serum somatomedin-C in protein deficiency: relationship with changes in liver somatogenic and lactogenic binding sites.

We have investigated whether the low serum levels of somatomedin-C (SM-C) observed in protein malnutrition could be related to changes in liver growth hormone and prolactin binding. Growing female rats were fasted for 3 days and subsequently refed for 14 days with isocaloric diets containing 5% (low) or 25% (normal) protein. Control rats were fed a normal protein diet during the entire study. The numbers and affinity constants of somatogenic (GH) and lactogenic (PRL) binding sites were determined by analysis of saturation curves using liver homogenates incubated with 125I-labelled bovine growth hormone and 125I-labelled ovine prolactin. Serum SM-C and growth hormone concentrations were measured by radioimmunoassay. After fasting for 3 days body weight dropped by 21% (P less than 0.01 vs. controls) and serum SM-C by 53% (P less than 0.01), while GH and PRL binding capacities decreased respectively by 63% (P less than 0.01) and 62% (P less than 0.01). On refeeding with a normal protein diet, body weight, serum SM-C, GH and PRL binding capacities returned to control values. In contrast, with low protein intake, body weight, SM-C, GH and PRL binding capacities remained respectively 16%, 55%, 49% and 81% lower than controls (P less than 0.01). No significant changes in serum growth hormone concentrations occurred with fasting or refeeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Relationship between plasma somatomedin-C and liver somatogenic binding sites in neonatal rats during malnutrition and after short and long term refeeding.

To determine the mechanism(s) for the growth retardation associated with malnutrition early in life, the relationships among plasma somatomedin-C (SM-C), plasma GH, and hepatic bovine GH-binding sites were assessed in rat pups that were milk-deprived from birth until weaning (21 days). After this period of malnutrition, body weight, tail length, plasma SM-C, and liver GH-binding capacity of the malnourished animals were significantly (P less than 0.001) reduced below those of control, well fed rats [SM-C at 21 days, 0.06 +/- 0.01 vs. 0.30 +/- 0.04 U/ml (mean +/- SE); GH binding, 2.96 +/- 0.39 vs. 7.19 +/- 0.80 pmol/liver]. The number of GH-binding sites per mg DNA was also reduced (0.59 +/- 0.06 vs. 1.08 +/- 0.11 pmol/mg DNA; P less than 0.001). After 1 week of ad libitum refeeding (days 21-28), body weight and tail length of malnourished pups increased significantly but showed no signs of catching up with that of control pups. Plasma SM-C and liver GH-binding capacity in the malnourished rats also rose significantly (P less than 0.005) after refeeding, but remained as far below controls as at 21 days [SM-C on day 28, 0.19 +/- 0.02 vs. 0.53 +/- 0.02 U/ml (P less than 0.001); GH binding, 6.59 +/- 0.99 vs. 12.94 +/- 1.60 pmol/liver (P less than 0.005)]. After 7 weeks of refeeding (days 21-70), tail length but not body weight recovered, while plasma SM-C levels were normalized. The mean number of GH binding sites per mg DNA in the malnourished rats was not significantly different from that in controls and reached for the males and the females, respectively, 79% and 86% of control binding. When expressed per liver, GH binding followed a similar pattern; for the males, binding capacity returned to 73% of the control value (20.45 +/- 1.82 vs. 27.93 +/- 3.49 pmol/liver; P = NS), and for the females, it returned to 77% of the control value (36.42 +/- 1.76 vs. 47.42 +/- 4.13 pmol/liver; P less than 0.01). In the young rats up to day 28, liver GH-binding capacities correlated with plasma SM-C concentrations (r = 0.81; P less than 0.01), while in the adult rats no correlation was present. During malnutrition and refeeding, there were no changes in the affinity constants of the hepatic GH-binding sites or in plasma GH concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1984

[Sterility caused by protein deficiency: the role of prolactin].

The first piece of research was made on mice in order to try to determine the importance of the ration of protein in the food in the maintenance of pregnancy and the mechanism by which protein lack leads to sterility. Five groups of 100 couples were given diets which contained 23.5%, 12.48%, 10.50%, 7.01% and 0% of protein respectively over a period of 100 days. The drop in the percentage of protein was obtained by adding detoxicated cassava flour and the diet without any protein was made up of starch, maize oil, mineral salts and vitamins. The number of litterings per 100 couples was only lowered when the diet was down to 7.01% of protein and at the same time it was only with this diet that one found a significant reduction in the number of young per litter. When the diet had no protein in it at all no young were born at all. Pregnant rats were fed diets which contained 23.5%, 7.01% or no protein at all. In this last diet we watched to stop coprophagia. There was very little difference in the number of implantations and young born with a diet of 7.01% of protein but a very significant drop with the diet without protein. With this last diet was very little significant difference in the series whether one had watched to stop coprophagia or not. An injection of 10 I.U. of HCG from the 3rd to the 13th day of pregnancy in rats fed a protein-free died did not alter significantly the number of implantations and did lead to complete resorption of the embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Intergeneric transfer and exchange recombination of restriction fragments cloned in pBR322: a novel strategy for the reversed genetics of the Ti plasmids of Agrobacterium tumefaciens.

Transmission of ColE1/pMB1-derived plasmids, such as pBR322, from Escherichia coli donor strains was shown to be an efficient way to introduce these plasmids into Agrobacterium. This was accomplished by using E. coli carrying the helper plasmids pGJ28 and R64drd11 which provide the ColE1 mob functions and tra functions, respectively. For example, the broad host-range replication plasmid, pGV1150, a co-integrate plasmid between pBR322 and the W-type mini-Sa plasmid, pGV1106, was transmitted from E. coli to A. tumefaciens with a transfer frequency of 4.5 x 10(-3). As pBR322 clones containing pTiC58 fragments were unable to replicate in Agrobacterium, these clones were found in Agrobacterium only if the acceptor carried a Ti plasmid, thus allowing a co-integration of the pBR322 clones with the Ti plasmid by homology recombination. These observations were used to develop an efficient method for site-specific mutagenesis of the Ti plasmids. pTiC58 fragnents, cloned in pBR322, were mutagenized in vitro and transformed into E. coli. The mutant clones were transmitted from an E. coli donor strain containing pGJ28 and R64drd11 to an Agrobacterium containing a target Ti plasmid. Selecting for stable transfer of the mutant clone utilizing its antibiotic resistance marker(s) gave exconjugants that already contained a co-integrate plasmid between the mutant clone and the Ti plasmid. A second recombination can dissociate the co-integrate plasmid into the desired mutant Ti plasmid and a non-replicating plasmid formed by the vector plasmid pBR322 and the target Ti fragment. These second recombinants lose the second plasmid and they are identified by screening for the appropriate marker combination.

Agrobacterium tumefaciens↗
PubMed1983

Ontogeny of liver somatotropic and lactogenic binding sites in male and female rats.

Developmental changes in liver somatotropic (GH) and lactogenic (PRL) binding sites were evaluated in male and female rats from birth to sexual maturity, and compared with growth velocity, plasma GH, PRL, testosterone, and estrogens. The affinity (Ka) and the concentration of these sites were determined from the analysis of equilibrium saturation curves with [125I]bovine GH and [125I]ovine PRL, incubated with liver homogenates. GH receptors rose from 6.4 fmol/mg protein at 8 days of age to 30.3 fmol/mg protein in males and 39.4 fmol/mg protein in females at 28 days. This surge occurred concomitant with the fall of plasma GH observed after birth. It preceded by about 1 week the acceleration of growth velocity and the increase of plasma GH seen at puberty. After the peak of growth velocity (42 days), GH receptors increased steadily until 120 days in females (63.8 fmol/mg protein), whereas in males they reached a concentration of 33.5 fmol/mg protein after a transient decrease to a nadir of 13.3 fmol/mg protein a day 50. From day 8 to day 35, PRL receptors in males remained at a constant level of 10.3 fmol/mg protein, whereas in females they increased progressively from 4.8 to 21.5 fmol/mg protein. Thereafter, in most pubertal males, they became undetectable, whereas plasma testosterone was rising. In contrast, PRL receptors in females increased 3-fold between day 42 (18.9 fmol/protein) and day 50 (50.2 fmol/mg protein). Between days 8 and 120, the Ka of GH and PRL receptors showed no significant changes with age and sex (GH: 0.66 X 10(9) M-1; PRL: 0.97 X 10(9) M-1). In conclusion, the rise of liver GH receptors occurring before puberty in male and female rats may be of importance for the initiation of the pubertal growth spurt. The inverse relationship between plasma testosterone and liver PRL receptors in pubertal male rats suggests that physiological concentrations of testosterone may inhibit PRL receptors. In contrast, in female rats an opposite change of PRL receptors is observed during puberty.

Aging↗
PubMed1983

Low plasma somatomedin-C in streptozotocin-induced diabetes mellitus. Correlation with changes in somatogenic and lactogenic liver binding sites.

To determine the mechanism for the decrease of somatomedin levels in insulin-dependent diabetes, the relationships among plasma immunoreactive somatomedin-C (Sm-C), plasma growth hormone (GH) and prolactin (PRL), and the somatogenic and lactogenic binding sites in liver were assessed in rats with nonketotic diabetes mellitus of different duration (1 wk or 1 mo) and severity (50 or 60 mg streptozotocin/kg BW). One week after administration of 60 mg streptozotocin (STZ)/kg, plasma Sm-C concentrations were significantly decreased (0.23 +/- 0.03 versus 0.43 +/- 0.03 U/ml in controls; mean +/- SEM, P less than 0.01). In contrast, plasma GH concentrations, bovine GH (bGH) binding, and human GH (hGH) binding were not significantly changed. After 1 mo of diabetes, no further decrease in plasma Sm-C content was observed despite a reduction in plasma GH and PRL concentrations and reduced hepatic bGH binding capacity (5 +/- 2 versus 38 +/- 4 fmol/mg protein; P less than 0.01). In the group of rats injected with 50 mg STZ/kg, the Sm-C was reduced at 1 mo but hepatic GH binding was not. In a second study, diabetic rats (75 mg STZ/kg) were treated after 3 wk with insulin (10 U lente per day for 7 days). This treatment normalized Sm-C levels and partially restored the GH binding capacity (treated: 49 +/- 4 fmol/mg protein versus untreated diabetics: 28 +/- 6 fmol/mg protein; P less than 0.01 and versus controls: 68 +/- 4 fmol/mg protein; P less than 0.05).2+ suggest that in an early phase of nonketotic diabetes, the low plasma Sm-C is not due primarily to reduced GH receptor number.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗