Collaborative assessment: exploring parental injury prevention strategies through bicycle helmet use.

While multiple studies have investigated bicycle helmet use, qualitative studies investigating parental strategies to promote their children's safety are rare. Thirty-four parents were interviewed to explore their injury prevention strategies. Findings suggest that the developmental stage of the child, the child's gender, and rural versus urban residence are all related to strategies parents use and their success in promoting bicycle safety. Peer pressure was the major deterrent, and negative "parent pressure" was also identified as problematic. Themes emerged that may support future injury prevention efforts with children, parents, and their communities and provide agencies information not previously captured quantitatively.

Sustained expression of the pim-1 kinase is specifically induced in myeloid cells by cytokines whose receptors are structurally related.

We have examined the effects of myeloid growth factors on expression of the pim-1 kinase protein in human and murine myeloid cells. pim-1 protein was identified in K562 cells by immunoblotting as a 33 kDa protein. In the human factor-dependent myeloid leukemia cell line M07E, pim-1 protein was induced by interleukin 3 (IL-3) or granulocyte-macrophage colony-stimulating factor (GM-CSF), with maximum expression by 4 h. Expression continued for the duration of growth factor exposure, but declined rapidly when cytokines were removed. GM-CSF induced pim-1 protein in a dose-dependent manner, with expression being proportional to the proliferative effect of the cytokine. To examine the specificity of pim-1 protein induction, we compared pim-1 protein levels in myeloid cells which demonstrated different GM-CSF response phenotypes. We also examined the effects on pim-1 protein expression of different growth factors which induced similar response phenotypes. GM-CSF induced pim-1 protein in several myeloid cell lines, most of which demonstrated a proliferative response, but did not induce pim-1 protein expression in neutrophils or monocytic cells. In contrast, the murine cell line Mac-11 expressed pim-1 message in response to IL-3 and GM-CSF, but not in response to bryostatin or M-CSF, which were equivalent mitogens. In human U937 myeloid cells sustained expression of pim-1 protein was induced by GM-CSF, G-CSF and IL-6, but not by bryostatin. Expression of the pim-1 kinase protein in response to myeloid cytokines depends on both the nature of the growth factor and the response phenotype. The pim-1 kinase may be an important intermediate in transmembrane signaling or response phenotype induced by IL-3, GM-CSF and other cytokines whose receptors are structurally similar. Its constitutive expression in some myeloid leukemia cell lines suggests activation of signal cascades utilized by myeloid growth factors.

Cloning and sequencing of the human c-abl 3' untranslated region.

The human c-abl oncogene gives rise to different mRNA transcripts which vary primarily in that they possess alternative first exons. In the present study, we present the sequence for the human c-abl 3' untranslated region (3'utr) and show that while human and murine c-abl cDNA sequences are generally homologous, human c-abl transcripts unlike the murine c-abl transcripts do not differ significantly in their 3' utrs.

Intracranial pressure changes and family presence.

This study investigated the association between family visits and fluctuations in intracranial pressure (ICP) in a population of 24 patients with ventriculostomies and Richmond bolts. Variables known to influence ICP, such as medications, cerebrospinal fluid (CSF) drainage, suctioning, and other interventions, were taken into account. Recording of ICP by registered nurses at 15-minute intervals during family absence and 5-minute intervals during family presence provided over 10,000 data points. A time series quasi-experimental design was used to analyze the data. A decrease in ICP was indicated during family presence in all but six cases, and in these six, none of the increases in ICP was statistically significant.

Delayed processing of dihydrofolate reductase heterogeneous nuclear RNA in amino acid-starved mouse fibroblasts.

We have studied the metabolism of dihydrofolate reductase (DHFR) RNA in cells synchronized in the G1 phase of the cell cycle by starvation for isoleucine and glutamine. The relative content and stability of DHFR mRNA and the relative rate of transcription of the DHFR gene are similar in starved and exponentially growing cells. However, the relative rate of labeling of DHFR mRNA is about three times lower in starved cells than in exponentially growing cells. When the starved cells are stimulated to reenter the cell cycle by feeding them with complete medium, the relative rate of labeling of DHFR mRNA increases about fourfold within 6 h. However, the relative rate of transcription of the DHFR gene changes very little during this period. Continuous labeling experiments show that starved cells convert DHFR heterogeneous nuclear RNA into cytoplasmic DHFR mRNA much more slowly than serum-limited or exponentially growing cells. Pulse-chase experiments show that DHFR mRNA sequences contained in DHFR heterogeneous nuclear RNA appear to be conserved in starved cells. In addition, the content of DHFR RNA sequences in the nuclei of starved cells is about three times greater than that in exponentially growing cells. Delayed processing of DHFR heterogeneous nuclear RNA is also observed when exponentially growing cells are treated with inhibitors of protein synthesis. Our results suggest that, although delayed processing leads to a decrease in the initial labeling rate of DHFR mRNA, it does not result in a decrease in the actual rate of production of the message.

Platelet-derived growth factor-modulated translatable mRNAs.

The treatment of density-arrested BALB/c 3T3 cells with electrophoretically homogeneous or highly purified preparations of the platelet-derived growth factor (PDGF) stimulated the rapid and selective accumulation of several species of abundant mRNA identified by cell-free translation. These translatable mRNAs appeared long before entry into the S phase. Less PDGF was required for selective mRNA accumulation than for PDGF-modulated DNA synthesis. The translatable mRNAs also accumulated after addition of the epidermal growth factor but not after addition of insulin or platelet-poor plasma. Their selective accumulation was blocked by addition of actinomycin D. Three classes of PDGF-modulated mRNAs were defined. An early (primary) RNA appeared within 30 to 60 min of PDGF addition; its accumulation was not blocked by cycloheximide. Another early mRNA also appeared within 60 min, but treatment with both PDGF and cycloheximide was required for optimal accumulation. A third class, secondary RNAs, began to accumulate later at 90 to 120 min; the appearance of this class was inhibited by cycloheximide. One- and two-dimensional gel electrophoresis of translation products demonstrated that a spontaneously transformed BALB/c 3T3 (ST2-3T3) cell line, which does not require PDGF or epidermal growth factor for growth, constitutively accumulated the secondary growth factor-regulated mRNAs. The accumulation of these translatable mRNAs may be required for PDGF-modulated DNA synthesis.

Cell cycle regulation of dihydrofolate reductase mRNA metabolism in mouse fibroblasts.

We have used the technique of DNA-excess filter hybridization to measure directly the content and metabolism of the mRNA for dihydrofolate reductase (DHFR; 5,6,7,8-tetrahydrofolate:NADP+ oxidoreductase, EC 1.5.1.3). The studies were conducted with a methotrexate-resistant derivative of mouse 3T6 fibroblasts (M50L3) that overproduces the enzyme and its mRNA by a factor of 300 but regulates the level of the enzyme during the cell cycle in the same manner as normal 3T6 cells. We found that, when resting (G0) M50L3 cells were serum-stimulated to reenter the cell cycle, the 10-fold increase in the rate of synthesis of DHFR that occurs at the beginning of S phase was the result of a corresponding increase in DHFR mRNA content. In pulse-labeling experiments, we found that there was a similar increase in the rate of production of the mRNA just prior to S phase. However, the half-life of the mRNA was the same (7.5 hr) in resting and exponentially growing cells. Therefore, the increase in DHFR mRNA content was due to an increase in the rate of production rather than an increase in the stability of the message. The delay between addition of [3H]-uridine to the culture medium and the emergence of DHFR mRNA from the nucleus was 15-20 min for both resting and growing M50L3 cells. A similar delay was observed for total mRNA. Therefore, the time required for the processing of newly synthesized DHFR heterogeneous nuclear RNA into DHFR mRNA is about the same as that for the average mRNA.