Pharmacokinetics of the 13C labeled anticancer agent temozolomide detected in vivo by selective cross-polarization transfer

The anticancer agent temozolomide labeled with ¹³C (8-Carbamoyl-3-13C-methylimidazo-[5,1-d]-1,2,3,5-tetrazin-4-(3H)-one), was noninvasively detected in subcutaneous RIF-1 tumors by a selective cross polarization ¹³C NMR method, at a field strength of 9.4T. Pharmacokinetics of the drug, at a dose of 150 mg/kg, were determined for intravenous and intraperitoneal modes of administration (three animals per mode). The half-life of the drug in the tumors was approximately 60 min. The uptake and clearance of the drug, however, varied significantly between individual hosts, for both modes of administration. These results demonstrate the feasibility of obtaining pharmacokinetics of anticancer agents for individual tumors without the need for a label that might modify drug activity (e.g., fluorine). The variability of the in vivo measurements, even within the same tumor model, demonstrates the necessity of directly monitoring the tumor to evaluate drug pharmacokinetics.     

Treatment planning in residential institutions

In child and youth care in the Netherlands, systematic planning of treatment is more and more considered to be a condition for effective and well founded treatment. Although workers are convinced of the benefits of treatment plans, treatment planning is not yet a natural and integrated part of residential care. There are several pressure points. In this article a model of treatment planning will be presented that contributes to an answer to these pressure points. The theoretical bases and the practical implications of this model will be discussed.     

Characterization and isolation of SOB2, a human sperm protein with a potential role in oocyte membrane binding

G12 monoclonal antibody (mAb), one of a library of constructed mAb directed against human sperm proteins, was found by immunoperoxidase staining to label the post-acrosomal and neck regions of fixed human cauda epididymal and ejaculated spermatozoa. Epithelium and fluid of caput epididymis were strongly labelled while there was no staining on testis and efferent ducts. Western lot analysis revealed that G12 antibody reacted with proteins of 17.5, 18 and 19 kDa in human spermatozoa. This pattern seems to be specific for mature human spermatozoa, as it has not been observed either in other human tissues tested, or in spermatozoa from different animals. SOB2, the corresponding protein, was isolated from NP40-extracted human spermatozoa by using preparative electrophoresis, followed by isoelectrofocusing according to its isoelectric point of 6.4 G12 Fab fragments strongly inhibited binding of human spermatozoa to zona-free hamster oocytes (up to 86% inhibition at 200 micrograms/ml). Impairment of binding was dependent on the concentration of purified G12 immunoglobulin (Ig)G1, and significant even at 10 micrograms/ml. There was no inhibitory effect of G12 antibody on sperm motility parameters or triggering of the acrosome reaction and it did not inhibit binding to human zona pellucida. These results indicate that SOB2 is likely to participate in membrane oocyte binding, and my be potential candidate for the development of a contraceptive vaccine.      

Voltage dependence of the pattern and frequency of discrete Ca2+ release events after brief repriming in frog skeletal muscle

Applying a brief repolarizing pre-pulse to a depolarized frog skeletal muscle fiber restores a small fraction of the transverse tubule membrane voltage sensors from the inactivated state. During a subsequent depolarizing test pulse we detected brief, highly localized elevations of myoplasmic Ca²⁺ concentration (Ca²⁺ “sparks”) initiated by restored voltage sensors in individual triads at all test pulse voltages. The latency histogram of these events gives the gating pattern of the sarcoplasmic reticulum (SR) calcium release channels controlled by the restored voltage sensors. Both event frequency and clustering of events near the start of the test pulse increase with test pulse depolarization. The macroscopic SR calcium release waveform, obtained from the spark latency histogram and the estimated open time of the channel or channels underlying a spark, exhibits an early peak and rapid marked decline during large depolarizations. For smaller depolarizations, the release waveform exhibits a smaller peak and a slower decline. However, the mean use time and mean amplitude of the individual sparks are quite similar at all test depolarizations and at all times during a given depolarization, indicating that the channel open times and conductances underlying sparks are essentially independent of voltage. Thus, the voltage dependence of SR Ca²⁺ release is due to changes in the frequency and pattern of occurrence of individual, voltage-independent, discrete release events.     

Total cortisol,free cortisol,and growth hormone associated with brief social separation experiences in young macaques

Many behavioral, immunological, and physiological consequences of brief maternal separation in bonnet (Macaca radiata) and pigtail monkeys (Macaca nemistrina) have been documented. However, the impact of social separation on plasma cortisol and growth hormone is unknown for these particular species. In the present study, the behavioral and endocrinological consequences of a 2-week maternal separation in socially housed infant bonnet and pigtail monkeys were followed. In seven pairs (separated and matched control) of bonnet and six pairs of pigtail infants, plasma was obtained under baseline, separated, and reunion conditions twice weekly for the duration of the study. Blood samples were obtained from both infants of the pair in approximately 10 min. Plasma total cortisol, free cortisol, and growth hormone were measured in these samples. Focal animal behavioral observations were made on all subjects twice daily throughout the study period. In both species, total cortisol and free cortisol rose immediately following maternal separation in comparison to the matched nonseparated controls and returned to basal levels (e.g., that of matched non-separted controls) following reunion with the mother. In contrast, plasma growth hormone rose only in the pigtail infants over a time course that peaked around the time of reunion. Multiple regression techniques indicated for the first week of separation, in the separated but not control subjects, that mean plasma free and total cortisol was positively related to distress behaviors (vocalization and postural slouch) observed during this week and negatively related to social behaviors (play and proximity to others) noted during the same period. In contrast, plasma growth hormone was related to both species and sex of the subjects but unrelated to behavioral variables. © 1995 John Wiley & Sons, Inc.     

Distribution of glutathione and glutathione-related enzyme systems in mitochondria and cytosol of cultured cerebellar astrocytes and granule cells

The cellular and regional distribution of glutathione (GSH) and GSH-related enzyme systems involved in cellular defense against reactive oxygen species and electrophilic xenobiotics in the nervous system has been extensively studied. However, little is known about the subcellular distribution of GSH systems in brain tissue and cultured neural cells. The present study investigates the distribution of mitochondrial and cytosolic GSH and GSH-related enzymes in cultured cerebellar astrocytes and granule cells, and compares them with levels in the adult rat cerebellum. Cytosolic GSH levels and cytosolic activities of glutathione reductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) in astrocytes were 57, 153, 245, and 92% higher than those found in granule cells, respectively. In contrast, granule cells contained significantly higher mitochondrial GSH levels than astrocytes. Granule cells also demonstrated comparable mitochondria/cytosolic concentrations of GSH and GR, GPX and GST activities to those observed in the cerebellar tissue, whereas ratios in astrocytes were markedly lower. Although in vitro treatments with 100 μM ethacrynic acid depleted both cytosolic and mitochondrial GSH in cultured astrocytes and granule cells in a time-dependent fashion, cellular GSH in granule cells was more resistant to the GSH-depleting agent than astrocytes. These results suggest that although GSH and GSH-related enzymes are abundant in cytosolic compartments of astrocytes, mitochondrial pools are relatively small. Since brain mitochondria are sites of significant hydrogen peroxide generation, the mitochondrial localization of GSH and its associated enzymes in neural cells provide important defenses against toxic oxygen species in the nervous system. Differences in subcellular distribution of GSH systems in individual neural cell types may provide a basis for selective cellular and/or subcellular expression of neurotoxicity.     

Transactional models of early education effectiveness - What is the message for policy?

There is now a substantial body of American research evidence demonstrating that early education programmes can have major long term effects right through into adult life. Cost-benefit analysis has enabled the data to be transformed into a compelling case for public financial investment. But insufficient attention has been paid to explaining how a short term preschool programme could have such enduring effects. The effects are best understood by applying a transactional model which shows how processes in the school and community transformed and amplified short term effects into long term outcomes. Adopting a transactional model modifies the messages for policy. The results of evaluations carried out in one society may not apply in another. In some school systems there may be more effective strategies than early education for improving educational prospects.