Psychological Research with Pediatric Conditions: If We Specialize, Can We Generalize?

Considered threats to validity and generalizability of psychologicalresearch with pediatric populations and proposed ways to betterunderstand and manage these problems. Variation due to characteristicsof acute and chronic conditions (e.g., duration, severity, illnesscourse), settings and referral patterns, family environmentalcharacteristics, as well as investigators' decisions concerningcriteria and recruitment limit inferences concerning the impactof pediatric conditions on psychological development and generalizabilityof findings. These problems call for an expanded use of replication,cross-center, population-based, and theory-driven research.Scientific progress will be made by increasing dialogues andcollaboration among researchers concerning generalizabilityproblems and improving research training in epidemiologicalmethods, analysis of large-scale data sets, and meta-analysis.     

Determination of combretastatin A-4 and its phosphate ester pro-drug in plasma by high-performance liquid chromatography

High-performance liquid chromatography with both absorbance and fluorescence detection has been applied to the determination of the potential anti-tumour agent combretastatin A-4 and its phosphate ester in murine and human plasma. The presence of different interfering peaks in the two species makes absorbance detection at 295 nm the method of choice for the mouse, and fluorescence detection (295 nm/390 nm) for human plasma. The calibration was linear over the range studied (0.01-50 microM for combretastatin A-4, 0.02-200 microM for combretastatin A-4 phosphate), with quantitation limits of 0.05 microM for both drugs in the mouse, and 0.05 microM and 0.0125 microM for the phosphate ester and free drug, respectively, in human plasma. The method should be useful for pharmacokinetic studies in the forthcoming Phase I clinical trial of combretastatin A-4 phosphate.     

DNA Sequence analysis of the PorB protein of nonserotypeable serogroup C ET-15 meningococci suggests a potential mutational hot spot on their serotype antigens

The nucleotide sequences of the PorB proteins from 28 nonserotypeable serogroup C ET-15 meningococci recovered from invasive meningococcal disease cases were determined. PCR amplification of the porB genes responsible for encoding the serotype antigen was used for DNA sequence determination and identification of the nature of the serotype antigen. DNA sequencing revealed that three strains were of serotype 2a, and of the remaining 25 strains, 20 were found to have an identical single point mutation in the region of the VR3 gene, which encodes surface-exposed loop VI, where the serotype 2a epitope resides. This nonsynonymous mutation was confirmed by synthetic peptide immunochemical analysis to confer new serospecificity to these serotype 2a mutants. This finding of a potential novel mutational hot spot on the PorB proteins of meningococci may have implications for pathogenesis and vaccine development.     

Comparison of viable cell yield from excised versus aspirated adipose tissue

The correction of soft-tissue defects by adipose tissue transplantation often produces poor and unpredictable results. The implantation of isolated and cultured preadipocytes offers a solution to this problem since these cells differentiate into adipocytes when implanted in vivo. A field of major interest is to maximize the yield of preadipocytes isolated from adipose tissue showing only low contamination with other cell types. Aspiration and excision are two concurrent clinical ways of harvesting adipose tissue for the isolation of preadipocytes. This tissue is usually discarded after surgery. In this study, the yield of preadipocytes obtained from liposuction material was compared to that of excised adipose tissue. Furthermore, we determined the loss of precursor cells if isolation of preadipocytes was delayed for 24 h. Preadipocytes were isolated from the stromal cell fraction of human subcutaneous adipose tissue samples. Harvesting of adipose tissue by suction was performed according to the Coleman procedure (manually applied negative pressure using a 10-ml syringe with a blunt tip cannula). Isolation was either carried out within 60 min after extraction or after storage for 24 h in culture medium at 4 degrees C. Isolated preadipocytes were cultured for 24 h, trypsinized and counted in a Neubauer chamber. Our results show clearly that the yield of preadipocytes isolated from liposuction material (within 60 min after extraction and after 24 h of storage) is higher than the cell yield from excised adipose tissue. Overnight storage for 24 h leads to a significant loss of preadipocytes in excised tissue but not in liposuction material. The high yield of cells isolated from liposuction material proves that extraction by suction does not damage the stromal cell fraction in the adipose tissue. If cell isolation is not performed immediately after the operation, liposuction material is clearly the better alternative for storage.     

Development and Evaluation of an Interactive CD-ROM Refusal Skills Program to Prevent Youth Substance Use: “Refuse to Use”

An interactive CD-ROM program designed to reduce adolescent substance use was developed and evaluated. The program uses video vignettes to teach refusal skills and socially acceptable responses to substance use situations, specifically offers of marijuana. In a randomized pretest-to-posttest experiment with 74 public school students from six classes in three high schools, significant changes were observed at posttest on (1) the adolescent's personal efficacy to refuse the offer of marijuana, (2) the adolescent's intention to refuse marijuana if offered, and (3) the adolescent's perceptions of the social norms associated with substance use and the importance of respecting another's decision to refuse a drug offer. In addition, adolescents in the treatment condition were able to recall approximately 50% of the portrayed refusal strategies. Findings are discussed with regard to the potential benefits of an interactive multimedia approach for conducting substance use interventions.     

Changes in Lower Leg Anterior Compartment Pressure Before,During, and After Creatine Supplementation

OBJECTIVE: To determine if 35 days of creatine supplementation (Cr) followed by 28 days of no supplementation altered lower leg anterior compartment pressure (ACP) at rest and after exercise. DESIGN AND SETTING: Subjects were divided into 2 treatment groups: (1) high dose (0.3 g Cr.kg body mass(-1).d(-1) for 7 days followed by 0.03 g Cr.kg body mass(-1).d(-1) for 28 days), or (2) low dose (0.03 g Cr.kg body mass(-1).d(-1) for 35 days). After 35 days, supplementation was terminated, and no Cr was ingested for 28 days. SUBJECTS: Sixteen physically active, healthy, college-aged males (O(2)max = 47.6 +/- 5.1 mL.kg(-1).min(-1)). MEASUREMENTS: At baseline, 7 days and 35 days of supplementation, and 28 days postsupplementation, ACP was measured preexercise and immediately, 1, 5, 10, and 15 minutes postexercise after a treadmill run at 80% O(2)max. RESULTS: For ACP, there was no significant group-by-time interaction, but there was a significant time effect for group when the data were combined. ACP was significantly increased at preexercise, immediately postexercise, and 1, 5, and 10 minutes from baseline to 7 days. ACP remained significantly elevated from baseline at 35 days immediately postexercise and 1 minute postexercise. After 28 days of no supplementation, ACP began to return to presupplementation levels, with only the 1-minute postexercise measurement significantly elevated from baseline. CONCLUSIONS: Creatine supplementation increased ACP at rest and after exercise, and ACP began to return to normal after 28 days of no supplementation.     

Effect of High Doses of Radiation on Human Neutrophil Chemotaxis, Phagocytosis and Morphology

Human neutrophils were exposed to varying amounts of ionizing radiation up to 1,000,000 rad and evaluated as to their ability to respond to chemotactic stimuli and phagocytize and kill bacteria. Striking morphologic and functional resistance to radiation was apparent. At doses up to 5,000 rad there was little or no impairment of chemotaxis. As the dosage increased to 50,000 rad, chemotaxis decreased to approximately 50% of nonirradiated control values. At very high doses of radiation (250,000 to 1,000,000 rad) neutrophils failed to respond significantly to chemotactic stimuli. Effects of radiation as measured by phagocytosis and the degree of ultrastructural change paralleled the chemotaxis results.     

Mucosal immunization with PLGA-microencapsulated DNA primes a SIV-specific CTL response revealed by boosting with cognate recombinant modified vaccinia virus Ankara

Systemically administered DNA encoding a recombinant human immunodeficiency virus (HIV) derived immunogen effectively primes a cytotoxic T lymphocyte (CTL) response in macaques. In this further pilot study we have evaluated mucosal delivery of DNA as an alternative priming strategy. Plasmid DNA, pTH.HW, encoding a multi-CTL epitope gene, was incorporated into poly(D,L-lactic-co-glycolic acid) microparticles of less than 10 microm in diameter. Five intrarectal immunizations failed to stimulate a circulating vaccine-specific CTL response in 2 Mamu-A*01(+) rhesus macaques. However, 1 week after intradermal immunization with a cognate modified vaccinia virus Ankara vaccine MVA.HW, CTL responses were detected in both animals that persisted until analysis postmortem, 12 weeks after the final boost. In contrast, a weaker and less durable response was seen in an animal vaccinated with the MVA construct alone. Analysis of lymphoid tissues revealed a disseminated CTL response in peripheral and regional lymph nodes but not the spleen of both mucosally primed animals.     

Characteristics of transmitter release at regenerating frog neuromuscular junctions

1. A study was made of the onset of transmission and the characteristics of transmitter release from regenerating nerve terminals in frog muscle fibres.

2. Soon after transmission had been restored, some junctions were found which responded to nerve stimulation with only subthreshold end-plate potentials.

3. The evoked transmitter release had a non-linear dependence on the external calcium concentration, like that seen at normal junctions.

4. The synaptic delay was only slightly longer than normal, and the amplitudes of single quantum potentials evoked by nerve stimulation seemed to have a normal distribution.

5. The mean amplitude of the spontaneous miniature end-plate potentials was often substantially smaller than the mean amplitude of the evoked quantal potentials at a given end-plate. Some of these small spontaneous potentials were due to transmitter release from the axon terminal. Possible explanations for this discrepancy in size of spontaneous and evoked potentials are discussed. Two to three weeks after reinnervation began, the amplitude of the spontaneous miniature end-plate potentials returned to normal.