S-adenosyl-methionine-induced apoptosis in PC12 cells

Our previous studies showed that S-adenosyl-methionine (SAM) induced Parkinson's disease-like changes in rat. It caused death to dopamine neurons in the substantia nigra, which appeared shrunken and fragmented, indicative of apoptosis-like changes (Charlton and Crowell [1995] Mol. Chem. Neuropathol. 26:269-284; Charlton [1997] Life Sci. 61:495-502). In this study, we investigated whether SAM causes apoptosis in both undifferentiated PC12 (PC12) cells and nerve growth factor (NGF)-differentiated PC12 (D-PC12) cells. S-adenosyl-homocysteine (SAH), the nonmethyl analog of SAM, was also tested. SAM and SAH (1.0 nM to 10.0 microM) caused lactate dehydrogenase (LDH) release from the PC12 cells and D-PC12 cells; cells with morphological changes and fluorescent DNA fragmentation staining were detected among both PC12 cell and D-PC12 cell. Compared with the PC12 cell, the D-PC12 cell, a postmitotic cell, was more sensitive to the toxic effects of SAM or SAH and presented much greater LDH release, suggesting a lethal effect; surprisingly, the amounts of apoptotic cells did not differ significantly between the two kinds of cells. In medium deprived of exogenous methionine, a decline in LDH release was observed in PC12 and D-PC12 cells. Also, lower levels of intracellular SAM and SAH were observed in the methionine-deleted media, which were reversed by the addition of either SAM or SAH. An antivitamin B(12) monoclonal antibody was added to methionine-depleted medium, resulting in deficiency of both endogenous and exogenous methionine, which caused further decreases in LDH release and reduction in the levels of intracellular SAM and SAH. The preliminary data showed different sensitivities to SAM or SAH between PC12 cell and D-PC12 cells, which suggests that PC12 cell may be more stable as a metabolic model. Apoptosis of PC12 cells was also assessed by PARP cleavage detection, Western blot analysis of Bax and Bcl-2 proteins, and DNA laddering on agarose gel electrophoresis. The proapoptoic protein Bax was dominantly expressed, whereas Bcl-2 was slightly down-regulated by SAM. SAH weakly induced the expression of Bax and slightly decreased Bcl-2 levels. The effects of SAM and its analog, SAH, were demonstrated conclusively to induce apoptosis in PC12 cells.     

Randomized comparison of low-dose involved-field radiotherapy and no radiotherapy for children with Hodgkin's disease who achieve a complete response to chemotherapy.

PURPOSE: Current standard therapy for children and adolescents with Hodgkin's disease includes combination chemotherapy and low-dose involved-field radiation (LD-IFRT). Because radiation may be associated with adverse late effects, the Children's Cancer Group (CCG) investigated whether radiation could be omitted in patients achieving a complete response to initial chemotherapy without jeopardizing the excellent outcome obtained with combined-modality therapy. PATIENTS AND METHODS: Between January 1995 and December 1998, 829 eligible patients were enrolled onto CCG 5942. A total of 501 patients who achieved an initial complete response after risk-adapted combination chemotherapy were randomized to receive LD-IFRT or no further treatment. Event-free survival (EFS) and overall survival were assessed from the date of study entry or the date of randomization, as appropriate. RESULTS: The projected 3-year EFS from study entry for the entire cohort was 87% +/- 1.2%. Among patients who achieved a complete response to initial chemotherapy, 92% +/- 1.9% of those randomized to receive LD-IFRT were alive and disease free 3 years after randomization, versus 87% +/- 2.2% for patients randomized to receive no further therapy (stratified log-rank test; P =.057). With an "as-treated" analysis, 3-year EFS after randomization for the radiation cohort was 93% +/- 1.7% versus 85% +/- 2.3% for patients receiving no further therapy (stratified log-rank test; P =.0024). Three-year survival estimates for patients treated with and without LD-IFRT were 98% +/- 1.1% for patients who received radiation and 99% +/- 0.5% for patients who did not receive radiation. CONCLUSION: LD-IFRT after an initial complete response to risk-adapted chemotherapy improved EFS. At this time, there is no survival advantage for LD-IFRT, but follow-up remains short.     

Use of implantable cardioverter defibrillator and anti-arrhythmic agents in a parturient

We describe a case of a 36-yr-old patient who presented at 14weeks gestation with multifocal dysrrhythmic episodes. Despitetreatment with anti-arrythmic agents and an implantable cardioverterdefibrillator (ICD) in situ, she continued to experience persistentdysrrhythmic episodes. She was delivered by Caesarean sectionat 34 weeks under general anaesthesia. We discuss some of theanaesthetic challenges of parturients with ICD devices. Br J Anaesth 2002; 89: 652–5     

Insulin's effect on synthesis rates of liver proteins. A swine model comparing various precursors of protein synthesis

Insulin's effect on the synthesis of liver proteins remains to be fully defined. Previous studies using various surrogate measures of amino acyl-tRNA have reported variable results of insulin's effect on liver protein synthesis. We determined the effect of insulin with or without amino acid supplementation on the synthesis rates of liver proteins (tissue, albumin, and fibrinogen) using L-[1-13C]Leu as a tracer in 24 male miniature swine. In addition, we compared the isotopic enrichment of different precursors of liver proteins with that of amino acyl-tRNA using L-[1-13C]Leu and L-[15N]Phe as tracers. Although liver tissue fluid enrichment of [13C]Leu and [15N]Phe and that of plasma [13C]ketoisocaproatic acid (KIC) were very similar to that of tRNA, plasma isotopic enrichment of both Leu and Phe were substantially higher (P < 0.01) and VLDL apolipoprotein-B100 enrichment was lower (P < 0.01) than the respective amino acyl-tRNA enrichment. Plasma KIC enrichment most accurately predicted leucyl-tRNA enrichment, whereas plasma Leu enrichment was best correlated with that of tRNA. Neither insulin alone nor insulin plus amino acid infusion had an effect on liver tissue protein synthesis. In contrast, insulin alone decreased the albumin synthesis rate, and insulin with amino acids maintained the albumin synthesis rate. Insulin with or without amino acids inhibited the fibrinogen synthesis rate. These results, based on synthetic rates using amino acyl-tRNA, were consistent with those obtained using KIC or tissue fluid Leu or Phe as precursor pools. These studies demonstrated that plasma KIC enrichment is a convenient and reliable surrogate measure of leucyl-tRNA in liver. We also concluded that insulin has differential effects on the synthesis rates of liver proteins. Whereas insulin with or without amino acid supplement has no acute effect on the synthesis of liver tissue protein, insulin has a substantial inhibitory effect on fibrinogen synthesis. In contrast, insulin administration along with amino supplement is necessary to maintain albumin synthesis rate.     

Nutritional rickets in African American breast-fed infants

OBJECTIVE: To analyze the characteristics of infants and children diagnosed with nutritional rickets at two medical centers in North Carolina in the 1990s. STUDY DESIGN: The physical and radiographic findings, calcium, phosphorus, alkaline phosphatase, and 25-hydroxyvitamin D levels of infants and children diagnosed with nutritional rickets at two medical centers were reviewed. Breast-feeding data were obtained from the North Carolina Women, Infants and Children Program (WIC). RESULTS: Thirty patients with nutritional rickets were first seen between 1990 and June of 1999. Over half of the cases occurred in 1998 and the first half of 1999. All patients were African American children who were breast fed without receiving supplemental vitamin D. The average duration of breast-feeding was 12.5 months. The age at diagnosis was 5 to 25 months, with a median age of 15.5 months. Growth failure was common: length was <5th percentile in 65% of cases, and weight was <5th percentile in 43%. CONCLUSION: Factors that may have contributed to the increase in referrals of children with nutritional rickets include more African American women breast-feeding, fewer infants receiving vitamin D supplements, and mothers and children exposed to less sunlight. We recommend that all dark-skinned breast-fed infants and children receive vitamin D supplementation.     

Radioactive waste minimization implications of clinically-indicated exsanguination procedures

Exsanguination is a method of animal euthanasia approved for use in specific circumstances. Animals undergoing exsanguination are fully anesthetized, and the blood is removed resulting in hypovolemia. In situations where radioactive materials are used as part of a research protocol that remain predominantly suspended in the blood, the exsanguination procedure can result in a significant lowering of residual radioactivity content. This reduction can greatly affect the types of waste management and minimization options that can be subsequently applied. In this study, data were collected from 20 rabbits injected with approximately 29.6 MBq (0.8 mCi) of tritiated thymidine as part of a percutaneous transluminal carotid artery angioplasty study. Residual concentrations of radioactivity were consistently reduced by an average of 88%. The reduction was very significant in this instance, since the residual activities were below the established exemption limit of 1.85 kBq g(-1) (0.05 microCi g(-1)) for disposal of these wastes as non-radioactive. Although the exsanguination procedure can result in significant waste minimization opportunities in certain circumstances, this should not be the rationale for its use. Rather, the method of euthanasia should be based exclusively on sound animal care and use principles, and waste management strategies should then be made following that decision. Health Phys. 79(3):291-293; 2000 Key words: waste, low-level; waste management; radiation protection; blood     

Carboxyl-terminated poly(vinyl alcohol). Chain transfer of methyl propionate to vinyl acetate

Poly(vinyl acetate) was prepared at 60°C with benzoyl peroxide by using methyl[carbonyl-¹⁴C] propionate as chain transfer agent and solvent. The resulting polymer was hydrolysed to poly(vinyl alcohol) (PVAL) having carboxyl end groups and the average number of carboxyl groups per chain was unambiguously determined by comparing the activity of the polymer to that of the methyl propionate. An average density of 1,5 carboxyl groups per chain was found for poly(vinyl alcohol) prepared from poly(vinyl acetate) of DP 80 – 90. Other methods of end group analysis for carboxyl groups in PVAL are discussed.