Growth and development of biofeedback: A bibliographic update

Computerized literature searching techniques were used to examine publication patterns in the worldwide biofeedback literature. Searches were completed in the United States and in Japan for the years 1985 through 1987. The results were used to update the results of an earlier study (Hatch & Riley, 1985) that covered the years from 1964 through 1984. Publication growth curves were generated for several media, including scientific journal articles, books, doctoral dissertations, and popular magazine articles. Although publication of information about biofeedback remains active worldwide, there has been a declining trend in effect for the past several years. The American database grossly underestimated the number of Japanese biofeedback articles, and it is likely that the literatures of other countries outside of North America were similarly underestimated. Possible explanations for the various trends noted are discussed.These results were presented in part at the Twentieth Annual Meeting of the Association for Applied Psychophysiology and Biofeedback. We gratefully acknowledge the assistance of Margaret Cyr-Provost in preparing the data for analysis.     

Density-induced down regulation of epidermal growth factor receptors

Summary Previous studies have shown that cell density can regulate the binding of several growth factors. To determine whether cell density exerts a uniform effect on the expression of epidermal growth factor (EGF) receptors, seven cell lines were examined in detail. For each cell line, EGF binding was found to decrease as cell density increases. Scatchard analysis of the binding data reveals that decreases in EGF binding are due to reductions in the number of cell surface EGF receptors. The only apparent exception is the effect of cell density on the binding of EGF to A-431 cells. For these cells, increases in cell density lead to two effects: decreases in the number of high affinity EGF receptors and increases in the total number of EGF receptors. In addition to the effects of cell density on EGF receptors, it was determined that increases in cell density can coordinately down-regulate receptors for as many as four different growth factors. Overall, the findings described in this report for EGF and those previously described for transforming growth factor type-β (TGF-β) and fibroblast growth factor (FGF) demonstrate the existence of a common mechanism for down-regulating growth factor receptors. This work was supported by grants from the Nebraska Department of Health (89-51), the National Cancer Institute (Laboratory Research Center Support Grant, CA36727), and the American Cancer Society (Core Grant ACS SIG-16). EDITOR'S STATEMENT The paper by Rizzino et al. demonstrates that receptor number decreases as a function of cell density. This may represent a mechanism by which cell proliferation is reduced as cell density increases.     

Psychophysiological responsivity on a laboratory stress task: Methodological implications for a stress-muscle hyperactivity pain model

A stress-muscle hyperactivity-pain (SMP) model has been proposed to explain the etiology of certain musculoskeletal pain disorders. According to this model, subjects should show physiological arousal during periods of stress relative to periods of rest. In a test of this prediction, 31 subjects performed a reaction time task that has been used in previous laboratory studies. Multiple psychophysiological variables were monitored during initial and final 10-minute baselines, during performance on nine 2-minute reaction time tasks, and during 36-second rest intervals following each of the 2-minute tasks. Results showed small but statistically significant differences generally supporting the SMP model when masseter EMG was averaged over time periods of 12 seconds to 2 minutes, but not when masseter EMG was averaged over 10- to 18-minute blocks. These results demonstrated the importance of carefully selecting time intervals for analysis. Additional analyses that compared TMD with symptom-free subjects revealed small differences in EMG that supported the SMP model. Analyses of EMG over shorter time intervals also showed, however, that masseter EMG increased during the 36-second rest interval following performance on a 2-minute stress task; this result suggested that a modification of the SMP model may be necessary.This research was supported in part by Grant 2 S06RR08038-17 funded by the National Institutes of Health.     

Bleomycin-Iron Damage To Dna With Formation Of 8-Hydroxydeoxyguanosine and Base Propenals. Indications That Xanthine Oxidase Generates Superoxide From Dna Degradation Products

Bleomycin, in the presence of ferric salts, oxygen and a suitable reductant, degrades DNA with the release of base propenals, detected as thiobarbituric acid (TBA) reactivity, and the formation of 8-hydroxydeo-xyguanosine (80HdG) detected by HPLC. When xanthine oxidase is added to the incubated mixture of DNA degradation products, TBA-reactivity is destroyed but 80HdG formation is increased. EPR Spin trapping experiments show that hydroxyl radicals (OH) are formed in the reaction mixture and can be inhibited by the inclusion of either superoxide dismutase or catalase. These findings suggest that the base propenals and possibly malondialdehyde, formed from them, are aldehydic substrates for xanthine oxidase and, the product of this reaction is superoxide (O₂^-) and hydrogen peroxide (H₂O₂). Thus, TBA reactivity is destroyed in the formation of O₂^- and H₂O₂ which stimulate further oxidative damage to DNA resulting in increased 8OHdG formation.     

A new method for study of normal lens developmentin vitro using pulsatile delivery of PDGF or EGF in HL-1 serum-free medium

Summary A new culture method was used to study increases in wet and dry weight and soluble protein during normal development of the transparent lens. Seven different media with more than ten different additives were tested for their effects on cultured lens transparency.In vivo, rat lenses increased 53% in soluble protein content between 3 and 5.5 days of age. Only HL-1 serum-free medium containing 15 μg/ml insulin plus 1–2 ng/ml BB platelet-derived growth factor (PDGF), or 5–7 ng/ml epidermal growth factor (EGF) allowed similar growthin vitro, during the same time period. Normal lens grwoth occurred in culture when fresh medium was delivered to lenses as a pulse every 4–6 hours. Lenses decreased in dry weight and soluble protein content, and became opaque when the same medium was delivered continuously. Lenses increased only 26% and 32% in soluble protein content when delivered pulses of HL-1 medium containing BB PDGF or EGF in the absence of insulin. We suggest that pulsatile delivery of medium containing insulin and PDGF or EGF stimulates lens growth during developmentin vitro. This pulsatile organ culture system is presented as a new approach for studying the effects of growth factors on cell proliferation, differentiation, and receptor regulation in a developing tissue. This work was supported by grants from EY-07031 and EY-04542 from the National Eye Institute and a grant from the Oculon Corporation. Editor's statement This report documents an in vitro system that may mimic lens development and response to growth regulators and hormones. The system may be useful for application to other organs and provide a foundation for cell and molecular level analysis.     

Neuromuscular development following tetrodotoxin-induced inactivity in mouse embryos

Developmental aspects of the neuromuscular system in mouse embryos chronically paralyzed in utero with tetrodotoxin (TTX) between embryonic days 14 and 18 were studied using biochemical and histological methods. The number of lumbar spinal motoneurons (MNs) was higher in inactive embryos than in controls suggesting a decreased motoneuron cell death. In association with the increase in MN number, choline acetyltransferase activity was significantly increased in both spinal cord and peripheral synaptic sites. Paralyzed muscles exhibited a decreased number of mature myofibers and the nuclei were centrally located. Creatine kinase activity was greatly decreased and total acetylcholine receptor and receptor cluster numbers per myofiber were significantly increased in paralyzed muscles. A similar pattern of changes occurs in the neuromuscular system of the mutant mouse muscular dysgenesis (mdg). However, in contrast to the mdg mutant, tetrodotoxin-treated muscles were similar to controls in their innervation pattern, in the ultrastructural aspects of the excitation–contraction coupling system (i.e., dyads and triads) and in the extent of dihydropyridine binding. Thus, neuromuscular inactivity is not sufficient to impair the pattern of muscle innervation or the appearance of either the triadic junctions or dihydropyridine receptors. These results indicate that alterations of dihydropyridine binding sites and triads in muscular dysgenesis cannot be accounted for by inactivity but rather must reflect a more primary defect involving the structural gene(s) regulating the development of one or more aspects of muscle differentiation.     

Neurogenesis, control, and functional significance of gasping

Gasps are frequently the first and last breaths of life. Gasping, which is generated by intrinsic medullary mechanisms, differs fundamentally from other automatic ventilatory patterns. A region of the lateral tegmental field of the medulla is critical for the neurogenesis of the gasp but has no role in eupnea. Neuronal mechanisms in separate brain stem regions may be responsible for the neurogenesis of different ventilatory patterns. This hypothesis is supported by the recording of independent respiratory rhythms simultaneously from isolated brain stem segments. Data from fetal and neonatal animals also support gasping and eupnea being generated by separate mechanisms. Gasping may represent the output of a simple but rugged pattern generator that functions as a backup system until the control system for eupnea is developed. Pacemaker elements are hypothesized as underlying the onset of inspiratory activity in gasping. Similar elements, in a different brain stem region, may be responsible for the onset of the eupneic inspiration with neural circuits involving the pons, the medulla, and the spinal cord serving to shape efferent respiratory-modulated neural discharges.     

Modification of enzyme activity in reversed micelles through clathrate hydrate formation.

The physical phenomenon of clathrate hydrate formation in protein-containing reversed micelles is described. Hydrate formation in reversed micelles is a method of adjusting the water to surfactant molar ratio, wo, which influences micellar size. Lipase and alpha-chymotrypsin encapsulated in large reversed micelles of high wo show significant enhancements in activity when the micelle size is reduced through hydrate formation. Alternate methods of micelle size adjustments also show enhancements in activity. The implications for improving the activity of such encapsulated enzymes recovered from fermentation media through phase transfer into reversed micelles are discussed.