Comparative study of physical properties of three suture materials: silk, e-PTFE (Gore-Tex), and PLA/PGA (Vicryl)

The aim of this in-vitro study was to compare the physical properties of three suture materials used in periodontal surgery: silk, expanded polytetrafluoroethylene (e-PTFE), and polylactic acid/polyglycolic and (PLA/PGA). Five physical tests were carried out on each of the three suture materials: strain to failure, tensile strength, knot tensile strength, knot slippage, and capillarity. For each test, 30 samples of each suture material were used. In all cases, the statistical results showed that the e-PTFE and the PLA/PGA threads were superior.     

Intravenous immunoglobulin (i.v. IgG) for previously treated acute or for chronic idiopathic thrombocytopenic purpura (ITP) in childhood: a prospective multicenter study

In a prospective multicenter study 42 thrombocytopenic (less than 30 X 10(9) platelets/l) children with chronic idiopathic thrombocytopenic purpura (ITP) or with acute ITP, dependent on or refractory to corticosteroids, were given 0.4 g i.v. IgG/kg body weight/day on 5 consecutive days and thereafter once a week if the platelet count fell to less than 20 X 10(9)/l or if the patient bled. After the initial 5 days of i.v. IgG the platelets rose within a mean of 7-8 days to greater than 30 X 10(9)/l in all and to greater than 150 X 10(9)/l in 33 of 42 patients (79%). After a mean observation time of 26.6 months 26 of 42 patients (62%) showed a satisfactory long-term effect, i.e. no need for treatment for at least 6 months without bleeding and with no platelet counts below 20 X 10(9)/l. No difference in response rate was found between children with chronic and those with previously treated acute ITP. These results indicate that i.v. IgG could be used to control emergency situations, e.g. to stop bleeding or to prepare a patient for surgery. I.v. IgG also represents a good alternative to treatment modalities, such as splenectomy and/or the administration of cytostatic immunosuppressants with potentially serious side effects. In addition to the expected transient rise in serum IgG levels, i.v. IgG induced a more prolonged elevation of serum IgM. Platelet associated IgG, elevated before therapy, was correlated with the clinical long-term outcome.     

Effects of hypothermia on rat brain pHi and phosphate metabolite regulation by 31P-NMR

The effects of arterial alphastat regulation on brain intracellular pH (pHi) and several phosphate metabolites were assessed in anesthetized rats during hypothermia (28.6 +/- 0.2 degrees C) and normothermia (36.2 +/- 0.2 degrees C) by using 31P high-field (8.5 T) nuclear magnetic resonance (NMR). There were significant differences in pHi and metabolite ratios at the two temperatures under conditions of equal minute ventilation. During hypothermia, the brain pHi was 0.09 U higher, the phosphocreatine-to-inorganic phosphate (PCR/Pi) ratio 49% larger, and Pi-to-ATP 20% lower than at normothermia. These changes were fully reversible on warming the animal. The change in brain pHi/temperature was -0.011U/degrees C (95% confidence interval -0.007 to -0.016). The brain's ability to regulate its pHi and phosphate metabolism during hypercapnic acid-base stress was studied by using 10% CO2 ventilation. Hypothermic rats showed a larger fall in brain pHi (0.145 +/- 0.01 U, 7.15-7.01) with 10% CO2 than normothermic rats (0.10 +/- 0.02 U, 7.06-6.96). Similarly ventilated rats had a larger fall in arterial pH with 10% CO2 at hypothermia (0.36 +/- 0.04 U) than normothermia (0.24 +/- 0.01 U), so the delta brain pH/delta arterial pH was the same at both temperatures. The brain PCr-to-Pi ratio decreased approximately 20% during 10% CO2 breathing in both hypothermic and normothermic animals. Brain pHi and metabolite ratios returned to base line 30-50 min after CO2 washout in both groups. In summary, lowering body temperature while maintaining constant ventilation leads to changes in brain pHi and metabolites.(ABSTRACT TRUNCATED AT 250 WORDS)     

Brain amino acid concentrations during diving and acid-base stress in turtles

To assess the role of brain amino acid neurotransmitters in the breath hold of diving animals, concentrations of free amino acids present in the brains of turtles immediately after 2 h of apneic diving (at 20 degrees C) were measured. Additionally, the same measurements were performed on four other groups of animals subjected to 2 h of hypercapnia (8% CO2 in air), anoxia (N2 breathing), anoxia plus hypercapnia (8% CO2-92% N2), or air breathing (control). Significant changes in the concentrations of the inhibitory amino acid neurotransmitters known to affect respiration [gamma-aminobutyric acid (GABA) and taurine] were seen. GABA increased significantly in those animals subjected to anoxia, whereas taurine decreased significantly in the diving animals and increased significantly in those subjected to anoxia plus hypercapnia. These results suggest that the attenuated central ventilatory drive during diving in these animals may be related to alterations in brain concentrations of GABA and taurine.     

Effects of hypercapnia on brain pHi and phosphate metabolite regulation by 31P-NMR

The ability of brain cells to regulate intracellular pH (pHi) and several phosphate metabolites was evaluated during 1 h of hypercapnia (inspiratory CO2 fraction of 0.10 and 0.05) in anesthetized rats by 31P high-field (145.6 MHz) nuclear magnetic resonance spectroscopy. Body temperature was maintained at 37 +/- 0.5 degrees C. Fully relaxed spectra were obtained for controls and 30-50 min after CO2 loading and CO2 withdrawal. Spectra were taken serially every 2.5 min after gas mixtures were changed. Brain pHi decreased 0.10 +/- 0.02 units [7.06 +/- 0.01 (SE)] to 6.96 +/- 0.01 (P less than 0.001) after 30-50 min of 10% CO2 breathing, and arterial pH decreased 0.24 +/- 0.01 units. Brain pHi decreased by 0.045 +/- 0.01 units (7.05 +/- 0.01 to 7.01 +/- 0.01, P less than 0.05) during 5% CO2 breathing. Brain pHi returned to control values after 30-50 min of CO2 washout in both groups. In three of six animals breathing 10% CO2, there was an undershoot in brain pHi by 0.07-0.09 units between 2.5 and 20 min of hypercapnia. Three animals exhibited an overshoot in pHi by 0.06-0.11 units between 7.5 and 17.5 min during CO2 washout. Phosphocreatine-to-Pi and Pi-to-beta-ATP ratios changed during hypercapnia and returned to base line after withdrawal of CO2. The findings of a smaller brain pHi change than arterial pH change and undershoots and overshoots in pHi support the view that pHi regulation involves active processes such as transmembrane ion transport.     

Unknown phosphate compounds in tail muscle of intact conscious newts by 31P NMR

Unknown phosphate resonances at 0 and -21.6 ppm have been identified in 31P NMR spectra of tail muscle of unanesthetized newts which do not correspond to known phosphate-bearing compounds in skeletal muscle cells. The concentrations of both unknowns decrease markedly during muscular activity and severe hypoxia (conditions associated with decreased intracellular pH and increased cellular levels of inorganic phosphate). The unknown at 0 ppm increases in concentration with imposition of moderate hypoxia. Our data suggest that these unknowns may be liable storage compounds for a high energy phosphate bond, and are involved in newt skeletal muscle phosphogen metabolism.     

Chronic granulomatous disease,a heterogeneous syndrome

Chronic granulomatous disease (CGD) is a clinical syndrome, the unifying characteristics of which are a severe predisposition to bacterial and fungal infections, an impaired ability of phagocytic leukocytes to kill certain microorganisms and the failure of these cells to produce microbicidal oxygen metabolites. In CGD the causal biochemical defect and the mechanism of genetic transmission vary from family to family. At least six different molecular defects have been found to underly the X-linked and at least three other the autosomal recessive form of CGD. Diagnosis of carriers is possible in most instances, and prenatal diagnosis by fetoscopic placental vessel puncture has become feasible.