Fractional reduction of somatostatin concentration interacted with rat growth hormone releasing hormone to titrate the magnitude of pulsatile growth hormone and prolactin release in perifusion

Growth hormone (GH) pulses in vivo are associated with increased hypothalamic portal growth hormone releasing hormone (GH-RH) concentration and can be prevented by GH-RH antisera. GH pulses are also associated with prior reduction of portal somatostatin (SRIF) concentrations, although SRIF antisera do not abolish GH pulses. In vitro, pulses of GH-RH as well as SRIF withdrawal are followed by pulses of GH release; the presence of GH-RH enhances post-SRIF GH release. We asked four questions: (1) During combined GHRH-SRIF exposure in vitro, must SRIF withdrawal be complete to produce a pulse of GH release, or is there a threshold diminution of SRIF which permits it? (2) When pulsatile GH release does occur, is it an all-or-none phenomenon, or is it titratable by fractional reduction of SRIF? (3) Does varying the GH-RH concentration while administering SRIF systematically alter GH release in response to fractional SRIF reduction? (4) Given a small but distinct effect of GH-RH on release of stored prolactin (PRL) in this system, does fractional SRIF reduction alter PRL release in parallel? Rat pituitary tissue whose hormone stores had been prelabeled with tritium was perifused for 120 min in combined 25 nM SRIF and 3 or 10 nM rat GH-RH (rGH-RH). Then, while maintaining rGH-RH concentrations, the SRIF concentration was left unchanged (control) or was reduced to 20, 15, 10, 5, or 0 nM for 60 min. Release of stored rGH and rPRL was assessed by immunoprecipitation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anaerobic pathogenesis: collagenase production by Peptostreptococcus magnus and its relationship to site of infection.

Fifty isolates of Peptostreptococcus magnus from intraabdominal sepsis, nonpuerperal breast abscess, and diabetic foot infections were examined for collagenase activity using bovine type I collagen. Collagenase production was detected in a higher percentage of strains from nonpuerperal breast and diabetic foot specimens (P less than .001). This enzyme may be responsible for P. magnus playing a more central role in the pathogenesis of nonpuerperal breast abscess and diabetic foot disease than in intraabdominal sepsis.     

Magnesium carbonate is an effective phosphate binder for chronic hemodialysis patients: a pilot study.

OBJECTIVE: This study was designed to evaluate the efficacy of magnesium carbonate as a phosphate binder in hemodialysis patients. DESIGN: This study was a prospective, randomized, open-label trial comparing magnesium carbonate/calcium carbonate versus calcium acetate as a sole phosphate binder. SETTING: This study involved outpatient hemodialysis. PARTICIPANTS: We recruited 30 stable hemodialysis patients without a history of frequent diarrhea. INTERVENTION: After receiving informed consent, we randomized patients 2:1 to magnesium carbonate versus calcium acetate. The dose of each binder was titrated to achieve the Kidney Disease Outcomes Quality Initiative (K/DOQI) phosphate target of <5.5 mg/dL. MAIN OUTCOME MEASURE: The efficacy-phase serum phosphorus concentration and the percentage of patients meeting K-DOQI targets for phosphorus, along with the daily elemental calcium intake, were the primary outcome measures. RESULTS: Magnesium carbonate provided equal control of serum phosphorus (70.6% of the magnebind group and 62.5% of the calcium acetate group had their average serum phosphorus within the K-DOQI target during the efficacy phase), while significantly reducing daily elemental calcium ingestion from phosphate binders (908 +/- 24 vs. 1743 +/- 37 mg/day, P < .0001). CONCLUSION: Magnesium carbonate was generally well-tolerated in this selected patient population, and was effective in controlling serum phosphorus while reducing elemental calcium ingestion.     

The reduction of methemoglobin levels by antioxidants

Preventing the oxidation of hemoglobin in solution is one of the major requirements for the successful production and long-term storage of hemoglobin-based blood substitutes. To this end we have studied the effects of antioxidants on the rate of methemoglobin formation and disappearance in solutions of human and bovine hemoglobin at 4 degrees C and 37 degrees C. Ascorbate and desferal (5 mM) were observed to act as prooxidants, increasing the rate of methemoglobin formation at 37 degrees C. Trehalose, mannitol, glucose, and EDTA (5 mM) had no significant effect. Glutathione and NADH (10 mM) were the most effective antioxidants tested, causing a significant decrease in the rate of methemoglobin formation at 37 degrees C for periods of up to 50 hours. The combination of these antioxidants in bovine hemoglobin at 4 degrees C resulted in the reduction of methemoglobin levels to nearly undetectable levels in approximately 150 hours. In addition, NADH and glutathione were found to reduce methemoglobin levels to 10% over a period of 100 hours in a sample of human hemoglobin that had been stored at 4 degrees C for one year and had 60% methemoglobin. These results suggest that the prevention and reversal of methemoglobin formation during the long-term storage of hemoglobin solutions and hemoglobin-based blood substitutes may now be possible.