Effect of preslaughter handling on muscle glycogen level and selected meat quality traits in beef.

The ante-mortem and post-mortem glycogen levels in bull muscle were studied to determine their influence on the ultimate pH, cooking loss and shear force. Forty-three bulls (13 Holstein, 12 crosses Holstein × Belgium blue, 9 Slovak Pied and 9 crosses Slovak Pinzgauer × Piemontese) were tied, housed and divided in control (A, n = 30) and stressed (B, n = 13) groups before slaughter. At the institute abattoir, the group B animals were mixed and kept overnight. In group A, bulls were slaughtered immediately after arrival at the abattoir. The following values of muscle were determined: (1) glycogen ante mortem from m. semitendinosus (ST) (biopsy technique, Biotech Nitra), (2) glycogen post mortem (1 hr, 3 hr, 48 hr) from longissimus dorsi muscle (LD), (3) ultimate pH, cooking loss and shear force 48 h post mortem. The results show that the glycogen concentrations ante mortem (ST) and 1 hr post mortem (LD) from unstressed animals were similar (p > 0.05). The ante-mortem and post-mortem (1 hr, 3 hr) muscle glycogen concentration were depleted (p < 0.01) in all stressed bulls. Differences between stressed and unstressed animals (p < 0.01) were found in ultimate pH, cooking loss and in shear force (p < 0.05). Significant correlations (p < 0.01) between ante-mortem (ST) and postmortem (LD, 1 hr, 3 hr) muscle glycogen and ultimate pH and cooking loss supported the possibility of using an efficient biopsy technique in combination with a simple method of glycogen estimation (iodide method) to predict metabolic exhaustion (glycogen depletion) and/or dark cutting condition of bulls.

The decrease in growth hormone (GH) response after repeated stimulation with GH-releasing hormone is partly caused by an elevation of somatostatin tonus.

Repeated injection of GHRH leads to a decrease in the GH response in normal subjects. Arginine (Arg) stimulates GH secretion by suppression of hypothalamic somatostatin. To confirm these findings, eight normal men were examined in a series of five settings: test 1 (GHRH/GHRH-TRH), 100 micrograms GHRH injected iv, followed by 100 micrograms GHRH, iv, after 120 min and 200 micrograms TRH, iv, after 150 min; test 2 (GHRH/Arg-TRH), like test 1, but instead of the second GHRH injection, a 30 g Arg infusion over 30 min; test 3 (GHRH/GHRH-Arg-TRH), like test 1, but additionally a 30 g Arg infusion after 120 min; test 4 (GHRH-Arg-TRH), iv GHRH and Arg infusion initially, followed by iv TRH after 30 min; and test 5 (TRH), 200 micrograms TRH, iv, at 0 min. For statistical evaluation, the area under the GH curve (AUC) from 0-120 min was compared with the AUC from 120-240 min. The GH response to the second administration of GHRH was significantly lower (P < 0.02) than the first increase [AUC, 0.5 +/- 0.01 min.mg/L (mean +/- SE) vs. 1.2 +/- 0.3]. No significant differences were found between the GH responses to either GHRH or Arg alone (AUC, 0.9 +/- 0.2 min.mg/L vs. 0.9 +/- 0.2). A larger GH increase (P < 0.02) was seen after GHRH-Arg compared to GHRH alone (AUC, 1.9 +/- 0.4 min.mg/L vs. 1.2 +/- 0.3). The GH response (P < 0.02) to GHRH-Arg stimulation was lower after previous GHRH injection than after GHRH-Arg stimulation alone (AUC, 1.9 +/- 0.4 min.mg/L vs. 3.5 +/- 0.9). There was a statistically significant difference between the TRH-stimulated TSH response in test 4 compared to that in test 5. We could show that decreasing GH responses to repeated GHRH can be avoided by a combined stimulation with GHRH/Arg. These findings suggest that the decreased GH response to a second GHRH bolus may be partly due to an elevated hypothalamic somatostatin secretion, which can be suppressed by Arg. The lower GH response to GHRH-Arg stimulation after a previous GHRH bolus suggests, furthermore, that the readily available GH pool in the human pituitary may be limited.

Changes in anterior pituitary response in patients with idiopathic hypothalamic hypogonadism caused by pulsatile GnRH therapy and testosterone replacement.

OBJECTIVE: This study evaluated in male patients with idiopathic hypothalamic hypogonadism the effect of pulsatile GnRH therapy or testosterone replacement on the response of all anterior pituitary hormones to adequate dynamic stimuli. PATIENTS AND DESIGN: In nine patients with idiopathic hypothalamic hypogonadism--mean age 21 +/- 1 (mean +/- SE)--a combined pituitary stimulation (CPS) with 200 micrograms TRH, 100 micrograms GnRH, 100 micrograms CRH and 100 micrograms GRH and an insulin tolerance-test (ITT) with 0.1 U insulin/kg body weight were performed. Both tests were repeated during pulsatile GnRH therapy and thereafter on testosterone replacement. MEASUREMENTS: Hormone levels were measured by immunometric assays. For statistical analysis the area under the curve (AUC) was used as a measure for hormone response. RESULTS: Testosterone levels did not differ significantly during GnRH therapy (16.6 +/- 2.1 nmol/L) and testosterone replacement (18.5 +/- 1.7 nmol/L). No significant differences were observed before and during the two treatment modalities for TSH and ACTH. PRL increase was significantly higher during GnRH therapy (AUC: 73580 +/- 8940) compared to the rise before treatment (AUC: 36161 +/- 5853; p < 0.01) and on testosterone replacement (AUC: 49995 +/- 6158; p < 0.01). The GH response to CPS and ITT was higher under testosterone replacement (AUC: 1826 +/- 353 and 1423 +/- 125) compared with the pretreatment situation (AUC: 727 +/- 115; p < 0.05 and 541 +/- 110; p < 0.01) and also more pronounced than under GnRH therapy (AUC: 1148 +/- 180 and 798 +/- 129; p < 0.05). FSH and LH after CPS rose significantly more during GnRH therapy (AUC: 864 +/- 122 and 2215 +/- 219) than before (AUC: 418 +/- 61 and 1424 +/- 277; p < 0.01) and on testosterone treatment (342 +/- 83 and 1153 +/- 323; p < 0.05). CONCLUSION: These results show that GnRH exerts a stimulatory effect on PRL secretion and may modulate GH secretion independently from sex steroids.

Effect of bromocriptine and SMS 201-995 on growth of human somatotrophic and non-functioning pituitary adenoma cells in vitro.

The effect of the dopamine agonist bromocriptine and the somatostatin analog SMS 201-995 on growth of 12 human somatotrophic and 13 non-functioning adenoma cell cultures was investigated. When adenoma cells were maintained in medium supplemented with 5% fetal calf serum, cell counts of 10 of 12 somatotrophic cultures increased to 145 +/- 6 and 171 +/- 9% (mean +/- SD) and in 12 of 13 non-functioning cell cultures up to 125 +/- 12 and 217 +/- 15% after 3 days of incubation. In most cases bromocriptine and SMS 201-995 dose dependently (1 nmol/l to 10 mumol/l) inhibited adenoma cell growth but there was only (1, 10 mumol/l) a significant inhibitory effect at high doses of both drugs. A 1 mumol/l concentration of bromocriptine decreased cell counts of 5 of 12 somatotrophic cell cultures (range 84 +/- 3 to 76 +/- 6% vs control = 100%) and in 5 of 13 non-functioning cell cultures (range 85 +/- 4 to 71 +/- 7%). A 10 mumol/l concentration of bromocriptine decreased cell counts in all 12 somatotrophic (range 87 +/- 1 to 61 +/- 8%) and in 12 of 13 non-functioning adenoma cultures (range 87 +/- 6 to 57 +/- 3%). Bromocriptine specifically inhibited growth because its effect could be reversed by the dopamine D2-receptor antagonist haloperidol. Both 1 and 10 mumol/l SMS 201-995 significantly decreased cell counts in three of six somatotrophic (87 +/- 3 to 38 +/- 3%) cell cultures. In two of five cases growth of non-functioning adenoma cultures was suppressed by 1 mumol/l SMS 201-995, and in four of five cases by 10 mumol/l (86 +/- 3 to 74 +/- 4%). The growth inhibitory effect of both bromocriptine and SMS 201-995 was not just due to an effect on growth of fibroblasts contaminating the adenoma cell cultures, because it could be observed also when adenoma cells were maintained in a D-valine-supplemented medium that suppresses fibroblast growth. In summary, both bromocriptine and SMS 201-995 at high doses were able to inhibit cell growth of cultured somatotrophic and non-functioning adenomas in vitro. However, the mechanism of this inhibitory effect is not yet well understood.

Secretion of polypeptide growth factors by human nonfunctioning pituitary adenoma cells in culture.

The growth-promoting activities of tumor-conditioned media (TU-CM) obtained from 23 cultured human nonfunctioning pituitary adenomas were studied in vitro. TU-CM obtained from adenoma cell cultures increased both cell counts (range: 108-179%; control = growth in serum-free medium = 100%) and 3H-thymidine incorporation (112-139%) of rat pituitary cell cultures, indicating that TU-CM contains growth-stimulating substances. TU-CM was also able to stimulate the growth of normal fibroblasts (3H-thymidine incorporation: 164-178%; cell counts: 145-157%) and endothelial cells (3H-thymidine incorporation: 131-149%; cell counts: 181-217%), suggesting the presence of - possibly angiogenic-growth factors that act on these cell types. However, the growth of hormone-producing cells was also stimulated, since TU-CM increased 3H-thymidine incorporation into rat pituitary cells in the presence of D-Val-MEM, a medium specifically inhibiting growth of fibroblasts. Addition of neutralizing antibodies against transforming growth factor alpha (TGF-alpha), epidermal growth factor (EGF), insulin-like growth factor I (IGF-I) and basic fibroblast growth factor (bFGF), either alone or in different combinations, reduced the growth-promoting activity of TU-CM on rat pituitary cells (range: 96-71%; control = growth effect of TU-CM without antibodies = 100%), strongly indicating the presence of these growth factors in TU-CM. All 4 antibodies together completely inhibited the growth-stimulatory activity of TU-CM, strongly suggesting that these growth factors play the major role among growth-stimulating substances in TU-CM. This is the first study giving evidence that TGF-alpha, EGF, IGF-I and bFGF are secreted by nonfunctioning adenoma cells indicating that the growth factors could be involved in growth regulation of pituitary adenomas by paracrine or autocrine mechanisms.

Evaluation of halothane sensitivity and prediction of post-mortem muscle metabolism in pigs from a muscle biopsy using (31)P NMR spectroscopy.

Phosphorus nuclear magnetic resonance ((31)P NMR) measurements were made on biopsy samples from pig muscles. Two experiments were performed, one in France and one in Czechoslovakia. In experiment 1, the muscle samples were obtained by surgery from the Biceps femoris muscle of 10 pigs with various genetic types (5 Large White, 1 Large White × Landrace, 4 Pietrains). In experiment 2, the muscle samples were obtained by shot biopsy from the Longissimus dorsi muscle of 11 Belgian Landrace × Duroc pigs, of which 6 were halothane-negative and 5 halothane-positive. The pigs were slaughtered by electrostunning and exsanguination respectively 3 weeks and 1 week after the biopsy, and meat quality traits (pH(1), reflectance and water holding capacity) were determined. The changes in adenosine triphosphate (ATP), creatine phosphate (CP), inorganic phosphate (P(i)) and pH, as deduced from NMR, were faster in Pietrains than in Large Whites, and in halothane-positive than in halothane-negative pigs. The value of the CP/P(i) ratio at 40 min after taking biopsy allowed discrimination between halothane-positive and halothane-negative pigs. The values of pH, creatine phosphate and adenosine triphosphate, as measured at definite times on the biopsies, were correlated with the rate of post-mortem metabolism (r approx 0·8) and with meat quality traits. (31)P NMR measurements combined with a rapid and efficient biopsy technique appear as an alternative tool for assessment of both halothane sensitivity and prediction of meat quality in pigs.

Prediction of meat quality in live pigs using stress-susceptible and stress-resistant animals.

A new in-vivo procedure for predicting the potential meat quality in live pigs was devised using stress-susceptible (halothane positive) and stress-resistant (halothone negative) pigs. The potential meat quality in live pigs was determined using small biopsy samples of M. longissimus dorsi (LD). Meat quality was assessed by the combined measurements of pH and water-holding capacity (WHC) on the 12 000 g supernatant after incubation of 500 mg biopsy LD muscle with an equal volume of 150 mm KCl at 39°C for 45 min. With the LD muscles of halothane positive (n = 37) and halothane negative (n = 55) pigs, high correlations (r = -0·854) were observed between the supernatant (i.e. fluid) pH and WHC of the biopsy samples, between fluid pH of the biopsy samples and 1-h post-mortem (pH(60)) LD muscles (r = 0·951), and between pH(60) and WHC (r = -0·956). The experimental data show that our in-vivo test can differentiate halothane positive from halothane negative pigs and can also predict the potential meat quality in live pigs. The test could be applied to select pigs with differences in WHC to improve meat quality.

Presence of growth hormone-releasing hormone-like immunoreactivity in human tumors: characterization of immunological and biological properties.

The distribution and physical and biological properties of GH-releasing hormone-like immunoreactivity (GHRH-IR) in human tissues and tumors was investigated using a specific GHRH RIA, gel chromatography, immunoaffinity chromatography, and bioassay with cultured rat anterior pituitary cells. Variable concentrations of GHRH-IR, ranging from 1.4-39.0 ng/g wet wt, were found in normal liver, lung, placenta, and pancreas. In the latter tissue, however, a different chromatographic profile and a marked decrease in GHRH-IR after immunoaffinity occurred, suggesting that GHRH-IR in pancreatic extracts is not native GHRH. In all tumors examined (n = 35) GHRH-IR could be detected, and four tumors (three carcinoids and one jejunal carcinoma) contained a very high amount of GHRH-IR (greater than 1000 ng/g wet wt). Affinity chromatography of tumor extracts led to a significant loss (greater than 50%) of GHRH-IR in nine tumors. The four tumors containing large amounts of GHRH-IR were obtained from two patients with active acromegaly and two patients who had no clinical evidence of acromegaly. Using antibodies with different specificities for GHRH-(1-44) and GHRH shortened at the C-terminus, varying concentrations of GHRH-(1-44) in these tumors were found, ranging from 10-87% of the total GHRH-IR. The biological activity of GHRH in the four tumor extracts was similar to that of synthetic GHRH alone or GHRH added to control tissue subjected to extraction. These results demonstrate the presence of GHRH-IR in the majority of normal tissues and tumors, which, though they may produce large amounts of biologically active GHRH, do not always lead to acromegaly.