Blood pressure variability and the type a behavior pattern in adolescence

The present investigation assessed the relationship between Type A behavior and blood pressure variability in a sample of 211 adolescents. Consistent with the adult literature, analyses revealed an association between Type A behavior and both systolic blood pressure variability and peak systolic pressure. The measures of diastolic blood pressure, however, were unrelated to Pattern A. The association with systolic variability remained when controlling for initial blood pressure level, sex, weight, and age. Subsidiary analyses of the components of Pattern A showed that high systolic variability teenagers are characterized by Type A speech characteristics (quick response latencies) and high levels of hostility. These findings support the validity of the Type A construct in adolescence.     

Effects of passive enhancement on graft and host. Graft adaptation by alloantibody as the mechanism of prolonged skin allograft survival

The cellular response to passively enhanced allogeneic skin grafts in mice was investigated using alloantiserum raised in hyperimmunized (C57BL/6 X A/J)F1 (B6AF1) against B10.D2oSn (B10.D2) mice. B6AF1 mice given B10.D2 skin grafts and passively enhanced with B6AF1 anti-B10.D2 alloantiserum (anti-31) showed delayed development of the ability to generate high levels of specific cytotoxicity in vitro. This delayed responsiveness was not transferable in vivo to freshly skin grafted mice, nor could cell-mediated suppression of development of in vitro responses be demonstrated in mixing experiments. These results suggested that alloantiserum acted on the graft. When skin grafts from passively enhanced animals were transferred to naive recipients prolonged graft survival was seen. Our results suggest that the mechanism of prolonged graft survival of the passively enhanced murine skin graft was through alteration of inherent graft immunogenicity, rather than a direct effect on the host.     

The effect of repeated administration of hexarelin, a growth hormone releasing peptide, and growth hormone releasing hormone on growth hormone responsivity

OBJECTIVE Hexarelin is a synthetic six-amino-acid compound capable of releasing GH in animals and in man. Its mechanism of action is not understood and little is known about the GH response after repeated administration. The aim of this study was to determine the GH response to the administration of two intravenous boluses of hexarelin, growth hormone releasing hormone (GHRH) or hexarelin with GHRH. DESIGN Single boluses of hexarelin (1 μg/kg), GHRH-(1–29)-NH₂ (1 μg/kg) or hexarelin with GHRH-(1–29)-NH₂ were administered intravenously. Each study was performed on two further occasions, with a second bolus being administered 60 or 120 minutes after the first. A control study was performed giving saline intravenously. Studies were performed in a random order. SUBJECTS Six healthy adult males (25.4–34.1 years) were studied. MEASUREMENTS Serum GH was measured by radioimmunoassay. GH secretion rates were derived from the measured serum GH concentrations using the technique of deconvolution analysis. RESULTS The peak GH secretion rate following the first intravenous bolus of hexarelin was greater than that following the first bolus of GHRH-(1–29)-NH₂ (P < 0.001), and was greatest following the administration of hexarelin with GHRH-(1–29)-NH₂ (P < 0.001). The coadministration of the two secretagogues resulted in peak GH secretion rates significantly greater than the arithmetic sum of those following their isolated administration (P = 0.001), demonstrating synergism. Compared to saline, the administration of a second bolus of hexarelin, GHRH-(1–29)-NH₂ or both resulted in significant further GH secretion (P = 0.02, P = 0.002, P = 0.03, respectively). The administration of a second bolus of hexarelin or hexarelin with GHRH-(1–29)-NH₂ 120 minutes after the first bolus resulted in lower peak GH secretion rates (P = 0.03). The reductions in peak GH secretion rates following the 60-minute boluses were not statistically significant. The peak GH secretion rates following the first GHRH-(1–29)-NH₂ boluses were similar to those following the 60 and 120-minute GHRH-(1–29)-NH₂ boluses (P = NS). Irrespective of the interval between the boluses of hexarelin with GHRH-(1–29)-NH₂, the peak GH secretion rates following the second boluses were not significantly different from the arithmetic sum of those following the administration of the second boluses of hexarelin or GHRH-(1–29)-NH₂, indicating loss of synergism on repeated administration. CONCLUSIONS This study shows that hexarelin is a potent GH secretagogue active after two successive doses; the magnitude of the GH response to the second dose was influenced by the dosing interval. Hexarelin and GHRH-(1–29)-NH₂ are synergistic, a property which is lost after repeated administration. These findings may help our understanding of GHRPs and may have implications for the potential use of hexarelin and other GHRPs as therapeutic agents.     

Tumour-necrosis factor from the rabbit. II. Production by monocytes.

Mononuclear cells from normal rabbit blood were cytotoxic to a number of cell lines in vitro. The cytotoxic cells were contained in the monocyte-enriched fraction adherent to plastic. Supernatants of the monocyte-enriched fraction had the same cytotoxic specificity as the parent cells. The cytotoxic factor precipitated in 50% saturated ammonium sulphate solution and on gel filtration was heterogeneous with a mol.-wt. range of 30--50,000 u. On the basis of specificity and molecular characteristics, this cytotoxic factor closely resembles rabbit tumour-necrosis factor (TNF) suggesting that TNF or a closely related factor is a normal product of mononuclear phagocytes.