Primitive neuroectodermal tumor following successful treatment of Hodgkin's disease.
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Adolescent↗
Biomedical subjects
M Davis
Publications and source records attributed to M Davis.
Preparative separation of nucleosome core particles containing defined-sequence DNA in multiple translational phases.
The nucleosome core particle is composed of an octamer of core histone proteins and about 146 bp of DNA. When reconstituted from purified histone octamer and defined-sequence, nucleosome positioning DNA fragments, the DNA will bind to the histone core in a number of translational phases with respect to the dyad symmetry axis of the histone octamer. Only one of these phases contains symmetrically bound DNA, and it is this species which is required for crystallization and X-ray diffraction studies. We have developed a technique for separating nucleosome core particles, containing defined-sequence 146 bp DNA, which differ only in translational phasing of the DNA with respect to the histone octamer core.
Crystallography, X-Ray↗
Prepulse inhibition of the acoustic startle reflex using visual and auditory prepulses: disruption by apomorphine.
The amplitude of the acoustic startle reflex can be reduced reliably when preceded at short intervals by a weak stimulus (prepulse) which itself does not elicit startle. The magnitude of this prepulse inhibition effect is attenuated by several dopamine agonists, such as apomorphine, especially when there is a relatively small difference between the intensity of the prepulse and the intensity of the background noise over which the prepulse is superimposed. One goal of the present experiment was to test the generality of this disruptive effect of apomorphine on prepulse inhibition by using either an auditory prepulse that included both a change in intensity and a change in frequency relative to the background noise or a visual prepulse stimulus. Apomorphine reduced auditory prepulse inhibition when induced by a small change in stimulus intensity, but not when induced by a change in both intensity and frequency. Apomorphine consistently reduced visual prepulse inhibition with a complete blockade at 100-ms test interval. However, it did not fully block the usual reduction in startle onset latency or even attenuate the increase in startle amplitude when a visual prepulse was presented 5, 10 or 15 ms before the startle stimulus. Consistent with conclusions from other laboratories using auditory prepulse inhibition, these data suggest that apomorphine did not prevent the animal from detecting prepulse presentation under conditions where the drug completely blocked prepulse inhibition. Moreover, they indicate that the blockade of prepulse inhibition by apomorphine was independent of prepulse modality, adding generality to the original finding. Visual prepulse inhibition may be a useful alternative procedure for evaluating the effects of drugs on this attentional process.
Acoustic Stimulation↗
Yohimbine facilitated acoustic startle in combat veterans with post-traumatic stress disorder.
Preclinical and clinical studies have suggested that the acoustic startle reflex (ASR) is a useful model to investigate the neurochemical basis of anxiety and fear states. This work has revealed that the anxiogenic alpha-2 receptor antagonist, yohimbine, increases the amplitude of the ASR in laboratory animals and in healthy human controls. Because of the growing body of data that support the hypothesis that severe stress results in substantial alterations in noradrenergic neuronal reactivity, the present investigation evaluated the effects of yohimbine on the ASR of 18 patients with PTSD and 11 healthy combat controls. Subjects received IV yohimbine (0.4 mg/kg) or saline placebo on 2 separate days in a randomized double blind placebo control design. A trial of two tone frequencies with varied intensity (90, 96, 102, 108, 114 dB) white noise and instantaneous rise time, was delivered binaurally through headphones. Tones were delivered every 25-60 s, for a 40-ms duration. Startle testing was performed 80 min post-infusion and lasted 15-20 min. Yohimbine significantly increased the amplitude, magnitude and probability of the ASR in combat veterans with PTSD, but did not do so in combat controls. Overall startle was significantly larger in the PTSD subjects; however, this did not account for the differential effect of yohimbine, since yohimbine had no significant effect in the control group. This study demonstrates an excitatory effect of yohimbine on the amplitude, magnitude and probability of the ASR in PTSD patients that is not seen in combat controls.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Unclaimed Children revisited: the status of state children's mental health service systems.
In 1982, Jane Knitzer's Unclaimed Children described continued nationwide failure to provide services for children and adolescents with serious emotional disturbances. Since 1982, there has been considerable change in the philosophy, administration, and operation of services for this population. The current study compared state child and adolescent (C/A) mental health systems to those described in Unclaimed Children. Present findings are based on surveys of State Mental Health Representatives for Children and Youth in 1988/89 and 1993. Results indicated a marked increase in the number of state administrative offices and staff for C/A mental health. Much pertinent legislation had been passed. States developed a target population definition and largely officially embraced the Child and Adolescent Services System Program (CASSP) principles of an ideal system of care. Out-of-state placements were high, and placements on adult wards still existed. Counts of these placements were often unavailable to mental health officials.
Adolescent↗
Esophago-airway fistula in AIDS.
Fistula formation between the esophagus and airway in acquired immunodeficiency syndrome is extremely unusual. We report 2 cases, the first in a patient who did not undergo definitive surgical management and died shortly after diagnosis. The second patient was managed successfully for 5 months by insertion of a Celestin endoesophageal prosthesis. This procedure can be performed with low morbidity and mortality, and may become the treatment of choice for this complex problem.
Acquired Immunodeficiency Syndrome↗
Lesions of the central nucleus of the amygdala block conditioned excitation, but not conditioned inhibition of fear as measured with the fear-potentiated startle effect.
Lesions of the amygdala block the expression of fear-potentiated startle following either moderate or extensive light + shock training. The present experiment assessed whether lesions of the amygdala would also block the expression of conditioned inhibition of fear. Rats were given conditioned inhibition training in which a light was paired with shock and a noise and light compound was presented in the absence of shock. Then half of the rats were given bilateral electrolytic lesions of the amygdala and the remaining rats were sham operated. Lesions of the amygdala blocked the expression of fear-potentiated startle to the light. To assess whether conditioned inhibition was disrupted, rats were retrained with light + shock pairings with no further conditioned inhibition training. Amygdala lesioned rats reacquired fear-potentiated startle to the light (Kim & Davis, 1993). Importantly, the noise conditioned inhibitor retained its ability to inhibit fear-potentiated startle to the retrained light. These results indicate that areas of the amygdala critical for initial performance of fear-potentiated startle are not critical for the expression of conditioned inhibition.
Amygdala↗
Habituation of prepulse inhibition of the startle reflex using an auditory prepulse close to background noise.
This study examined whether prepulse inhibition habituates with repeated presentation of the prepulse alone. Prepulse inhibition was determined by measuring the decrement in the startle response when the acoustic startle-eliciting stimulus was preceded by an auditory prepulse. Rats received repetitive exposures of the same auditory prepulse alone (experimental condition) and of a visual prepulse alone (control condition). To reduce habituation of startle itself and the possible dishabituating influence the startle stimulus might have on habituation of prepulse inhibition, startle stimulus presentations were infrequently interspersed among a much larger number of prepulse-alone presentations. Stimulus-specific habituation of prepulse inhibition occurred using an auditory prepulse 2.5 dB, but not 13 dB, above background noise. Implications are discussed for the role of prepulse inhibition in sensory gating.
Animals↗
Relative changes in blood flow with functional electrical stimulation during exercise of the paralyzed lower limbs.
Eight spinal cord injured (SCI) patients performed three sets of exercise with two conditions, 60% and 80% of VO2peak, with an arm crank ergometer. Functional neuromuscular stimulation was used to induce static leg contractions in two of the above sets of exercise. The three exercise sets were performed with no functional neuromuscular stimulation (NOS); with functional neuromuscular stimulation at 40 milliamperes; and with functional neuromuscular stimulation at 80 milliamperes (HIS). The lower limb blood flow was estimated by a photoelectric plethysmograph. Results showed that the lower limb blood flow was consistently reduced across both functional neuromuscular stimulation levels (17.4% from NOS to LOS; 13.8% from LOS to HIS; and 28.8% from NOS to HIS), and work loads (15.3% from rest to 60% VO2peak; 38.0% from 60% VO2peak to 80% VO2peak; and 47.5% from rest to 80% VO2peak). Rate-pressure product was decreased by 8.3% between NOS and HIS at 60% VO2peak (15.7 +/- 3.4 to 14.4 +/- 3.8), by 6.8% between NOS and HIS at 80% VO2peak (18.9 +/- 53 to 17.6 +/- 4.8), and by 12.4% between LOS and HIS at 80% VO2peak (20.1 +/- 6.7 to 17.6 +/- 4.8). These data indicate that in SCI (a) functional neuromuscular stimulation-induced contractions of the lower limb muscles can increase blood flow and thus reduce venous blood pooling in the paralyzed muscles, and (b) such improvements are associated with a reduced rate pressure product.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Sex differences in neonatal stress reactivity.
The question of whether a sexually dimorphic stress reaction exists prior to extensive socialization was addressed by examining sex differences in physiological and behavioral stress reactivity, in healthy, term neonates, after a mildly stressful behavioral assessment procedure. The Neonatal Behavior Assessment Scale (NBAS; Brazelton, 1973) was administered to 18 male and 18 female neonates. Heart rate (HR), salivary cortisol, and behavioral states were assessed before and after the exam. Sex differences included higher cortisol response in males and a greater change in HR and higher NBAS motor performance cluster score in females. Salivary cortisol, HR change, NBAS cluster scores, and behavioral states after NBAS provided 100% discrimination between male and female infants. These findings suggest that there are neonatal sex differences in behavioral and physiological stress reactivity prior to socialization.
Arousal↗
Acoustic startle and anticipatory anxiety in humans: effects of monaural right and left ear stimulation.
The startle reflex elicited by binaural acoustic startle stimuli is potentiated by the threat of electric shock. The present study explored the lateralization of this fear-potentiated startle reflex effect using acoustic startle stimuli delivered binaurally or monaurally to the left or right ear and recorded from the left and right orbicularis oculi muscles. Consistent with previous results, the acoustic startle to binaural stimulation was potentiated during the anticipation of shock. This effect was also present for monaural stimulation but was greater when startle stimuli were delivered to the right than to the left ear. The results are discussed in terms of hemispheric lateralization during shock anticipation.
Acoustic Stimulation↗
Experimental stroke and neuroprotection in the aging rat brain.
BACKGROUND AND PURPOSE: Experimental stroke research has for the most part incorporated the use of young animals despite the importance of aging in cerebrovascular disease in humans. We hypothesized that age-related reductions in the density and function of cortical N-methyl-D-aspartate (NMDA) receptors might limit neuroprotective potential in the elderly. In this study, a model of occlusive stroke in the aging rat brain has been developed and used to establish the effects of age on cerebral infarction and to evaluate the scope for protecting the aging brain during ischemia. METHODS: Focal cerebral ischemia was produced by thermocoagulation of the left middle cerebral artery in adult (11 to 17 months) and aged (28 to 36 months) male Wistar rats. Infarcts were assessed histologically with volumetric analysis of infarct size, hemodynamically by serial cerebral blood flow measurement using the hydrogen clearance technique, and by analysis of specific gravity as an index of brain edema. Neuroprotective potential was assessed using the competitive NMDA receptor antagonist 3-(2-carboxy piperazin-4-yl)propyl-1-phosphonate (D-CPPene). RESULTS: Aging was associated with a significant increase in infarct size, with a mean infarct volume of 40.5 +/- 2.6% of the hemisphere volume in aged rats compared with 30.9 +/- 0.7% in adult rats (P < .01). D-CPPene reduced the mean infarct volume to 33 +/- 1.8% and 20.7 +/- 3.2% in aged and adult rats, respectively (P < .05). Cerebral blood flow fell markedly after infarction, but thereafter D-CPPene-pretreated rats maintained higher cerebral blood flow than untreated animals throughout the duration of the experiment (22.8 +/- 3.2 and 30.1 +/- 5.5 mL.100 g-1.min-1 in treated aged and adult rats, respectively, compared with 11.3 +/- 2.7 and 16.5 +/- 3.2 mL.100 g-1.min-1 in untreated aged and adult groups, 90 minutes after infarction [P < .05]). Pretreatment also reduced cortical edema; mean cortical specific gravity 4 hours after infarction was 1.0381 +/- 0.0013 in untreated aged rats and 1.0391 +/- 0.0014 in untreated adults compared with 1.0458 +/- 0.0031 in treated aged rats and 1.0442 +/- 0.0014 in treated adult rats (P < .05). CONCLUSIONS: Under similar experimental conditions, there was an age-related increase in cerebral infarct size. However, NMDA receptor antagonism was neuroprotective in the aging brain and resulted in a significant reduction in cerebral ischemic damage, less cortical edema, and preservation of cerebral blood flow.
Aging↗
Mechanisms subserving temporal modulation sensitivity in silent-cone substitution.
Temporal contrast sensitivity data were collected with sine-wave-modulated lights for achromatic, chromatic, and silent-cone-substitution stimuli. Achromatic (556- and 642-nm lights in phase) and chromatic (556- and 642-nm lights in counterphase) modulation sensitivities were measured at a constant time-average retinal illuminance of 1256 trolands (Td) and chromaticity of 595 nm. These data were considered to represent isolated temporal responses of luminance and red-green chromatic channels, respectively. Silent cone substitution was achieved with counterphase modulation of the 556- and the 642-nm lights and by suitable adjustment of the modulations or the radiances of the two lights. (1) The peak modulation depth of the 642-nm light was reduced to silence the long-wavelength-sensitive (LWS) cone, and the peak modulation depth of the 556-nm light was reduced to silence the middle-wavelength-sensitive (MWS) cone. These protocols maintained the time-average retinal illuminance and chromaticity as for the control conditions. (2) The luminance of the 642-nm light was decreased to silence the LWS cone and was increased to silence the MWS cone. In this procedure the time-average retinal illuminance and chromaticity differ for the silenced-LWS-cone (1047 Td and 589.5 nm) and the silenced-MWS-cone (4358 Td and 622 nm) conditions. The response modulation of the achromatic and the chromatic channels was calculated for the silent-substitution conditions. The chromatic channel is more sensitive at low frequencies, with a transition to greater achromatic channel sensitivity near 13 Hz for the silenced-LWS-cone condition and near 6 Hz for the silenced-MWS-cone condition.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Assessing patient willingness to reveal health history information.
A survey was designed to determine how willingly patients reveal personal health information on dental health history forms. After giving informed consent, 107 patients at a university dental hygiene program completed a 10-item survey privately and anonymously. The results suggest that a significant number of patients provide inaccurate or incomplete information to questions routinely asked on the dental health history form.
Adult↗
Complications from enteroclysis tube insertion.
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Aged↗
Future roles of management.
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Chief Executive Officers, Hospital↗
Myositis and fasciitis associated with group A beta hemolytic streptococcal infections: development of a rabbit model.
Group A streptococci produce a variety of clinical symptoms ranging from minor pharyngeal infections to life-threatening soft-tissue disease. A rabbit model is described for induction of myonecrosis and fasciitis with group A beta-hemolytic streptococci. Group A streptococcal infections have shown remarkable virulence in recent years, resulting in severe local tissue destruction and life-threatening toxicity. After subcutaneous injection into the thigh of 20 ml broth containing 10(5) to 10(9) cfu/ml, initial soft tissue infection rapidly progressed to rhabdomyolysis. The response of the rabbits to the infection was consistent with the human response.
Adult↗
Electromyograph analysis of the popliteus muscle in level and downhill walking.
It has been proposed that the popliteus muscle is a source of lateral knee pain, typically after downhill activities. Electromyography of the popliteus muscle was recorded in 9 normal subjects during level walking, downhill walking, and walking downhill wearing a 40-lb backpack (to simulate hiking). Popliteal muscle intensity during the midstance phase of walking downhill with weights increased significantly over that of level walking (30% versus 13%, respectively) (p < 0.05). There was a nonsignificant trend (p = 0.07) for a similar increase at terminal swing (51% versus 36%). Significantly greater knee flexion was recorded at loading response, midstance, and terminal stance (p < 0.01) during both downhill trials as compared with level walking. Initial contact position showed no differences. Velocities for downhill walking (72.9 m/min) and downhill walking with weights (71.1 m/min) were significantly less than those of level walking (83.9 m/min) (p < 0.01). Stride analysis showed no significant difference in stance phase duration or in initial double-limb support times between level walking and either downhill condition. These data suggest that increased popliteal muscle activity during midstance in downhill walking with weights is in response to weight bearing with an increased load on a flexed knee. Increased Electromyographic activity may be associated with overuse of the popliteus muscle.
Adult↗