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Biomedical subjects

H Davis

Publications and source records attributed to H Davis.

At least 271 records · Page 15Linked to original sources
PubMedDate not supplied

Determinants of endothelium-dependent femoral artery vasodilation in youth.

OBJECTIVE: Decreased endothelium-dependent arterial dilation to reactive hyperemia has been shown in adults to be associated with various manifestations of cardiovascular diseases and cardiovascular risk factors. In a sample of children, we examined the relationships between flow-mediated femoral artery dilation and anthropometric, demographic, cardiovascular, and serum lipid variables that have been associated with cardiovascular diseases. METHOD: Thirty-three asymptomatic, healthy 11 to 14 years olds were randomly selected from participants in a longitudinal cardiovascular health study. There were 17 boys and 16 girls; 21 whites and 12 blacks. Sixteen had documented family history of premature myocardial infarction (ie, < or = 55 years of age) in first-degree relatives and 17 did not. Measurements included fasting lipids, anthropometrics, blood pressure and heart rate at rest and during supine exercise, postural change, and forehead cold stimulation. Femoral artery dilation to reactive hyperemia was measured via high resolution ultrasound. RESULTS: Bivariate analyses indicated flow-mediated dilation was negatively correlated with systolic pressure increases to postural change, forehead cold stimulation and dynamic exercise, greater average skinfold thickness, and body fat via dual x-ray absorptiometry and positively correlated with cardiovascular fitness (all ps < .05). Stepwise multiple regression revealed that cardiovascular fitness and systolic pressure reactivity to exercise significantly predicted flow-mediated dilation accounting for 31% of the variance (p < .01). CONCLUSIONS: Decreased flow-mediated dilation is associated with decreased cardiovascular fitness, increased systolic pressure reactivity to various stressors, and increased indices of body fatness in asymptomatic youth. Further research is warranted to better understand early relationships between this noninvasive measure of endothelial function and cardiovascular risk factors in youth.

Adolescent↗
PubMedDate not supplied

Acute effects of transcendental meditation on hemodynamic functioning in middle-aged adults.

OBJECTIVE: Increased peripheral vasoconstriction (ie, total peripheral resistance, or TPR) has been implicated as playing an important role in the early development of essential hypertension. Some studies have demonstrated that Transcendental Meditation (TM) reduces high blood pressure, but the hemodynamic adjustments behind these blood pressure reductions have not been elucidated. The aim of this study was to provide a preliminary investigation of the acute effects of TM on TPR. METHODS: Subjects were 32 healthy adults (16 women and 16 men; 30 white and two African American; mean age, 46.4 +/- 3.9 years). Subjects were divided into a TM group of long-term TM practitioners (eight white women, nine white men, and one African American man; mean years of twice-daily TM practice, 22.4 +/- 6.7) and a control group (eight white women, five white men, and one African American man). Hemodynamic functioning was assessed immediately before and during three conditions: 20 minutes of rest with eyes open (all subjects), 20 minutes of TM (TM group), and 20 minutes of eyes-closed relaxation (control group). RESULTS: During eyes-open rest, the TM group had decreases in systolic blood pressure (SBP) and TPR, compared with increases in the control group (SBP: -2.5 vs. +2.4 mm Hg, p < .01; TPR: -0.7 vs. +0.5 mm Hg/liter per minute, p < .004). During TM, there was a greater decrease in SBP due to a concomitantly greater decrease in TPR compared with the control group during eyes-closed relaxation (SBP: -3.0 vs. +2.1 mm Hg, p < .04; TPR: -1.0 vs. +0.3 mm Hg/liter per minute, p < .03). CONCLUSIONS: TPR decreased significantly during TM. Decreases in vasoconstrictive tone during TM may be the hemodynamic mechanism responsible for reduction of high blood pressure over time. The results of this study provide a preliminary contribution to the understanding of the underlying hemodynamic mechanisms responsible for the beneficial influence of TM on cardiovascular risk factors.

Adult↗
PubMedDate not supplied

The effects of life events on cardiovascular reactivity to behavioral stressors as a function of socioeconomic status, ethnicity, and sex.

OBJECTIVE: The purposes of this study were 1) to examine the effects of stressful life events on cardiovascular reactivity to acute laboratory stressors in youth and 2) to determine whether these effects varied as a function of socioeconomic status, ethnicity, and/or sex. METHODS: Four hundred eighty-three youths (mean age = 16.7 years; 249 Caucasian Americans [126 males, 123 females] and 234 African Americans [109 males, 125 females]) completed the Adolescent Resources Challenge Scale (ARCS), a measure of stressful life events, and underwent two laboratory stressors (a car-driving simulation and the Social Competence Interview) during which blood pressure, heart rate, cardiac output, and total peripheral resistance were assessed. RESULTS: Youths who reported high levels of stressful life events showed smaller increases in blood pressure (both systolic and diastolic) and heart rate to the car-driving simulation but larger increases in cardiac output in response to the Social Competence Interview than did youths who reported low levels of stressful life events. The effect of stressful life events on cardiovascular reactivity was not moderated by sex, ethnicity, or socioeconomic status. Higher family socioeconomic status was associated with greater blood pressure, heart rate, and cardiac output increases in response to the Social Competence Interview. CONCLUSIONS: The attenuating effects of stressful life events on cardiovascular reactivity in response to car-driving simulation in youths are consistent with an inoculation effect, whereas the potentiating impact of stressful life events on reactivity observed during the social stressor interview is compatible with a possible cost of coping effect.

Adaptation, Psychological↗
PubMedDate not supplied

A behavioural programme for the modification of encopresis.

This paper describes a behaviour modification programme for the treatment of encopresis. The programme, which is carried out by the parents over a relatively short period of time in the home setting, aims to make the child aware of internal cues prior to elimination and to rearrange the contingencies for appropriate use of the toilet. To date, seven of eleven children, both continuous and discontinuous encopretics, have been treated successfully and have remained clean for up to 7 months regardless of other problems in the child and his family. From a relatively detailed analysis of those treated it can be concluded that a behavioural approach is effective with chronic encopretic children, many of whom had been previously treated unsuccessfully by both physical and psychotherapeutic procedures. The failures suggest, firstly that careful assessment of each child and the motivation of the parents is required, so that the standard programme can be modified to suit each individual case. Secondly a maintenance programme must follow the intensive treatment procedure to ensure that parents continue to handle the child consistently.

Behavior Therapy↗
PubMedDate not supplied

A comparison of aspects of the maternal speech environment of retarded and non-retarded children.

This study was concerned to explore aspects of the maternal speech environment of mentally retarded children. Eight mothers were observed in interaction with their retarded children and compared with mothers on non-retarded infants who had been matched in terms of various socio-economic indices and language behaviour. The mothers of the retarded children were found to be significantly more stimulating vocally, more responsive and less directive than the controls. The findings are discussed in terms of possible reasons for such differences and the implications for the child.

Adult↗
PubMedDate not supplied

Working with families of children with special needs: the parent adviser scheme.

This paper describes a project in which an attempt is made to provide regular, ongoing support and counselling for families of children with severe developmental delays and intellectual or physical impairments. This service is available to both English speaking and Bangladeshi families, and is concerned with the needs of the whole family, not just the child. Professionals already working in this field are trained in counselling skills and then work in partnership with the families, attempting to develop a respectful, open relationship based upon active listening.

Bangladesh↗
PubMedDate not supplied

Survey of the clinical use of electrocochleography.

A questionnaire on the clinical use of electrocochleography (ECochG) was distributed to clinics throughout the world which use this method. The 26 replies comprised 3696 cases with a median age of 22.5 years. The majority (57.1%) were tested with a transtympanic promontory electrode. The risk of any undesirable effect from this electrode placement was negligible (less than 0.1%), but a greater probability (less than 1.0%) of serious complication from general anesthetics was revealed. On the benefit side, ECochG added significant information to the diagnoses of 87.8% of the children and 34.2% of the adults, and in 48.2% of the children and 2.0% of the adults this information was a primary factor in the hearing evaluation and decision on management. The cases for which ECochG was most helpful were predominantly children and neonates with complex neurological or psychiatric problems which interfered with reliable testing by other methods. Comparisons of ECochG with other methods were reported in 63.2% of the cases. The respondents judged 97.4% of those comparisons to reflect favorably on the validity of ECochG.

Action Potentials↗
PubMedDate not supplied

Brain stem and other responses in electric response audiometry.

For electric response audiometry of young children who require sedation, an indicator is desired that is more reliable than the slow vertex potential. There are four leading candidates: 1) The electrocochleogram (ECochG) is very reliable with a transtympanic electrode on the promontory, but this is a surgical procedure and requires a general anesthetic. 2) The early midbrain responses give similar information with external electrodes, but they are complex and low in voltage. 3) The muscle reflexes (sonomotor responses) are a crude indicator with high and variable thresholds and are not suited to precise audiometry. 4) The "middle" responses, perhaps cortical in origin, are good candidates, but they have not yet been adequately validated in the clinic. For the midbrain responses and particularly for the ECochG, close synchronization of nerve impulses is essential. This requires a compromise with selectivity of frequency. High-tone audiometry by electrocochleography and midbrain responses is satisfactory, but limitations are increasingly severe below 2 kHz, where each sound wave is a separate acoustic stimulus. Low-frequency tones stimulate the basal turn of the cochlea at relatively low sensation levels. This makes assessment of the apical portion of the cochlea very difficult, even with the midbrain "frequency-following response" (FFR).

Acoustic Stimulation↗
PubMedDate not supplied

New insights in the evaluation of cochlear impairment.

A major new insight into cochlear mechanisms is the recognition of an active process, the cochlear amplifier, that contributes energy to the mechanical movement of the basilar membrane at low sound intensities. The extra energy makes possible the great sensitivity of hearing and also the very sharp tuning of individual neural units, ie, the tips of their tuning curves. The inner hair cells are the final receptor cells, but the outer hair cells are essential for the amplifier action. The amplifier is much more sensitive to anoxia, ototoxic drugs, noise, etc, than the inner hair cell system alone. Severe impairment of the amplifier causes a sensorineural hearing loss with recruitment. Only the tails of tuning curves remain. Thus the cochlea is a dual sensory system, a robust but insensitive broadly tuned passive component sided by a vulnerable, sensitive sharply tuned active component.

Acoustic Stimulation↗
PubMedDate not supplied

The scope of practice of diabetes educators in the state of Georgia.

PURPOSE: The purpose of this study was to identify and describe the scope of practice trends of diabetes educators in the state of Georgia. METHODS: The Diabetes Educator Responsibilities Questionnaire (DERQ) was sent to 221 members of the American Association of Diabetes Educators listed in the 1995 membership directory in Georgia. Of the 221 members, 97 returned completed questionnaires. This population of healthcare professionals comprised the sample population. RESULTS: In assessing the primary responsibilities of the sample, more than 50% of the respondents performed six of the nine educator roles. Less than 50% of the respondents indicated that they "Always" or "Frequently" used behavior modification strategies in teaching people with diabetes. CONCLUSIONS: The questionnaire used in this study should be expanded to elicit more detailed information regarding decisions to use or not use behavior modification techniques in diabetes education.

Behavior Therapy↗
PubMedDate not supplied

Effects of Theraband and lightweight dumbbell training on shoulder rotation torque and serve performance in college tennis players.

The purpose of this study was to determine whether a 4-week isotonic resistance training program using Theraband elastic tubing and lightweight dumbbells would significantly increase concentric shoulder rotator strength or velocity of serve or both in a group of elite-level tennis players. Twenty-two male and female varsity college tennis players were randomly assigned to control or 4-week training groups. Subjects were pre- and posttested in concentric internal and external rotation torque using an isokinetic dynamometer. Functional performance was assessed before and after training by recording the peak and average velocities of eight maximal serves. The experimental group exhibited significant gains in internal rotation torque at both slow (120 deg/sec) and fast speeds (300 deg/sec) for total work and in peak torque to body weight ratio and torque acceleration energy at the fast speed. This group also exhibited significant gains in external rotation torque for the same parameters at fast speed. Regarding speed to serve, the experimental group exhibited significantly greater increase in peak speed (+6.0% compared with -1.8%) and average speed (+7.9% compared with -2.3%) compared with the control group. Men exhibited greater internal and external rotation torque on all parameters and in peak and mean speed of serve on both evaluations. Men also exhibited greater imbalance in external to internal rotation torque ratios. In conclusion, resistance training using Theraband tubing and lightweight dumbbells may have beneficial effects on strength and functional performance in college-level tennis players.

Acceleration↗
PubMedDate not supplied

Fluvoxamine-associated sexual dysfunction.

OBJECTIVE: To report two cases of sexual dysfunction induced by fluvoxamine, a selective serotonin reuptake inhibitor (SSRI). SETTING: University teaching hospital. PATIENTS: Two depressed patients who developed ejaculation and orgasmic difficulties after initiation of fluvoxamine therapy. DISCUSSION: The literature concerning sexual dysfunction with serotonergic antidepressants is reviewed, and speculated mechanisms for this untoward effect are discussed. CONCLUSIONS: Sexual dysfunction associated with antidepressant drugs, including SSRIs, may be underreported. This troublesome adverse effect may significantly affect patient comfort and compliance. Careful evaluation of sexual function is warranted, prior to and during drug treatment, especially as more serotonergic antidepressant agents become available.

Adult↗
PubMedDate not supplied

Brain stem electric response audiometry (BSERA).

Brain stem electric responses, recorded with external electrodes on vertex and ear lobes, are excellent for audiometry of young children. The vertex-positive wave with latency of 6 to 9 msec resembles closely the action potential of the auditory nerve, with the same high-intensity short-latency component and low-intensity long-latency component. Thresholds are reliable with filtered clicks at 1 000 Hz and higher. Practical advantages and theoretical limitations are summarized.

Acoustic Stimulation↗
PubMedDate not supplied

The audiometric utility of brain stem responses to low-frequency sounds.

The human scalp-recorded vertex-positive brain stem response to a click or high-frequency tone pip is an excellent audiometric indicator. Its latency of 6-9 ms is practically independent of the polarity of the stimulus but is inversely related to intensity. With a 4,800- or 2,400-Hz tone pip (filtered click) its threshold of detectability is usually at or below 10 dB SL. With a 500-Hz tone pip, with rise and fall of 2-3 ms, the response at 30 dBSL is low in amplitude, rounded in wave form, and has a latency of about 10 ms. When the polarity of the stimulus is reversed, the latency shifts by 1 ms. At and above 40 dB, this late response is obsured by a larger and earlier response. High-pass (1,500 Hz) masking noise does not affect the low-level response but the earlier high-level response is reduced in amplitude and delayed by about 1 ms. The large early response seems to be initiated by stimulation of the basal turn of the cochlea by the low-frequency transient. The frequency-following response (FFR) to a 500-Hz tone burst with a 2-ms rise time has a threshold at about 40 dB SL. Its relatively short latency is appropriate to the basal turn. A later low-amplitude apically generated response can sometimes be detected, either at a lower stimulus level or in the presence of high-pass masking noise. The usual FFR often has complex wave forms and some individuals show only an onset response, even at 70 dB SL. It is almost impossible to edentify with certainty the first individual waves of FFR as they relate to the individual waves of the tone burst and as they change amplitude with intensity. The audiometric usefulness of the high-threshold responses to 500 Hz that are initiated in the basal turn is doubtful. The low-threshold responses initiated in the apical turn are so difficult to identify with certainty that they are not likely to be of clinical value unless high-pass masking noise can be used to clarify them.

Acoustic Stimulation↗