Biomedical subjects

T T Dao

Publications and source records attributed to T T Dao.

12 recordsLinked to original sources

PubMed2000

Renal kallikrein excretion: role of ethnicity, gender, environment, and genetic risk of hypertension.

BACKGROUND AND OBJECTIVE: Alterations in renal kallikrein excretion are well-described in hypertension, and kallikrein excretion may predict risk of developing hypertension, but kallikrein excretion has not been directly compared across several ethnic strata, nor have the effects of ethnicity, gender, environment, and genetic risk of hypertension been simultaneously considered as determinants of kallikrein. METHODS: We investigated determinants of kallikrein excretion in a cross-section of n = 204 normotensive subjects stratified by ethnicity (119 Caucasian, 33 African-American, 52 Asian), gender (109 men, 95 women), environment (spontaneous electrolyte intake/excretion), and heredity (genetic risk (family history) of hypertension). Results were interpreted by analysis of variance (with Bonferroni post hoc comparison corrections), analysis of covariance, multiple linear regression, and maximum likelihood. RESULTS: Urinary kallikrein activity varied substantially (F = 5.30, P = 0.006) across the three ethnic groups, with African-American values approximately 50% lower than Caucasian (P = 0.005) or Asian (P = 0.02). Ethnicity and gender (T = 3.24, P = 0.001) had independent effects on kallikrein, with women excreting approximately 50% more kallikrein than men, regardless of ethnicity. Subjects at genetic risk of hypertension were over-represented (P = 0.048) in the lower stratum of a bimodal distribution of kallikrein excretion (chi-square = 29.6, P < 0.001). Potassium excretion was diminished in African-Americans (P < 0.001 to P = 0.002), and in a multivariate analysis, potassium excretion was the strongest correlate of kallikrein excretion (T = 4.10, P = 0.0001). In a subset of Caucasian and African-American individuals, African-Americans exhibited diminished excretion of not only kallikrein and potassium, but also aldosterone (P = 0.003), suggesting a mechanistic link between potassium and kallikrein excretion in their ethnic variations. CONCLUSIONS: Kallikrein excretion is influenced by several independent determinants, both hereditary (gender, ethnicity, and genetic risk of hypertension) and environmental (potassium intake and excretion). Ethnicity and environment may interact uniquely to influence kallikrein, as demonstrated by the case of African-Americans with diminutions of both kallikrein and potassium excretion. These results suggest a mechanism whereby kallikrein excretion is diminished in African-Americans, as well as therapeutic strategies to correct this deficiency. Finally, the identified determinants of kallikrein excretion will require analytic adjustment during genetic studies of this 'intermediate phenotype' in hypertension. Journal of Human Hypertension (2000) 14, 461-468

Adult↗

PubMed2000

Gender differences in pain.

A review of the literature on gender and clinical pain reveals a disproportionate representation of women receiving treatment for many pain conditions and suggests that women report more severe pain, more frequent pain, and pain of longer duration than do men. Gender differences in pain perception have also been extensively studied in the laboratory, and ratings of experimentally induced pain also show some sex disparity, with females generally reporting lower pain thresholds and tolerance than males. However, there is little consensus on whether these apparent differences reflect the way men and women respond to pain, differing social rules for the expression of pain, or biologic differences in the way noxious stimuli are processed. In this paper, our working hypothesis is that the higher prevalence of chronic orofacial pain in women is a result of sex differences in generic pain mechanisms and of as-yet unidentified factors unique to the craniofacial system. We will review the evidence concerning gender differences in the prevalence of pain conditions, with a focus on orofacial pain conditions. Evidence and hypotheses concerning biologic and psychosocial factors that could influence prevalence rates will also be discussed.

Chronic Disease↗

PubMed1998

Modulation of myofascial pain by the reproductive hormones: a preliminary report.

STATEMENT OF PROBLEM: The predominance of myofascial pain in women in childbearing years suggests that the reproductive hormones may play a role in this pain disorder. PURPOSE: The potential influence of these hormones on myofascial pain was evaluated. METHODS: Pain patterns were compared across three consecutive menstrual cycles in oral contraceptives users (OC group) and nonusers (Non-OC group). RESULTS: Preliminary results showed that within menstrual cycle variability of daily pain was higher than the nonusers group. In addition to their low variation, pain levels of oral contraceptives users remained positive across the hormonal cycle, whereas in nonusers, peaks of pain alternated frequently with pain-free periods. These data suggest that pain levels in oral contraceptives users may be more constant than those of nonusers. CONCLUSIONS: This potential hormonal influence on myofascial pain levels among oral contraceptives users may represent one of the various adverse effects induced by oral contraceptives at the trigeminal area in sensitive subjects. Evidence supporting the link between estrogen, nitric oxide, and inflammatory processes is presented.

Adolescent↗

PubMed1998

Expression of altered alpha2-adrenergic phenotypic traits in normotensive humans at genetic risk of hereditary (essential) hypertension.

BACKGROUND: Essential (hereditary) hypertension is a common, though complex, trait with substantial heritability, but a still-obscure mode of inheritance. In this disorder with relatively late onset, knowledge of phenotypes with earlier penetrance would aid genetic analyses, as well as assessment of risk. OBJECTIVE: Because alpha2-adrenergic receptor alterations are among the most heritable in experimental genetic hypertension, we hypothesized enhanced expression of alpha2-adrenergic phenotypic traits in still-normotensive humans at genetic risk of hypertension. METHODS: We evaluated hemodynamic (blood pressure, cardiac output, systemic vascular resistance, stroke volume, and cardiac contractility) and biochemical (plasma drug, catecholamine, renin, and chromogranin A levels) responses to alpha2-adrenergic blockade with intravenous yohimbine in 84 normotensive subjects stratified by genetic risk of essential hypertension (67 with positive family histories and 17 with negative family histories of hypertension), as well as 18 subjects with established essential hypertension. Results were evaluated by analysis of variance, normal likelihood ratio test, and by maximum likelihood analysis for bimodality (i.e. mixtures) of response distributions. RESULTS: Blood pressure rose (P<0.001) during alpha2-adrenergic blockade, with greater response (P<0.001) in members of the hypertensive than in members of the normotensive group. Hemodynamically, the rise in blood pressure resulted from an increase in cardiac output (P<0.001), with associated increases in stroke volume (P=0.002) and cardiac contractility (P=0.006), without an overall change in systemic vascular resistance. Biochemically, plasma norepinephrine (P<0.001), epinephrine (P=0.001), and chromogranin A (P=0.02) rose, suggesting augmentation of efferent exocytotic sympathoadrenal activity. Cardiac output and stroke volume responses were correlated to increments in plasma catecholamines (especially epinephrine) for the positive group, but not for the negative group. Baseline plasma catecholamines predicted increments of stroke volume after administration of yohimbine (P=0.003-0.007) for the positive but not for the negative group. Simultaneous comparison of means and variances of cardiac output and stroke volume alpha2-adrenergic responses, by using a normal likelihood ratio test, revealed highly significant (P=0.025 to P<0.0001) differences between the groups of subjects with and without family histories of hypertension. Frequency histogram suggested that there was a bimodal distribution of responses of stroke volume to alpha2-adrenergic blockade for the normotensive group with positive family histories of hypertension; maximum likelihood analysis strongly rejected the hypothesis of a unimodal distribution, whereas the hypothesis of bimodality could not be rejected (chi2=18.4, P=0.0004). The second (exaggerated) mode of response of stroke volume to alpha2-adrenergic blockade, defined by maximum likelihood analysis, was found for 9.5% of subjects in the normotensive group with positive family histories of hypertension, and was characterized by significantly different responses of cardiac output (P=0.001), stroke volume (P<0.001), contractility (P<0.001), heart rate (P=0.03), systemic vascular resistance (P<0.001), and epinephrine (P<0.001). Even prior to alpha2-adrenergic blockade, baseline stroke volume (P=0.01), heart rate (P=0.04), systemic vascular resistance (P=0.005), and catecholamine (P=0.001-0.005) values for this subgroup were different than control values. CONCLUSIONS: We conclude that heterogeneous, bimodally distributed hemodynamic responses to alpha2-adrenergic blockade in subjects with positive family histories of hypertension suggest a discrete subgroup with early expression of perhaps Mendelian traits associated with risk of later development of hypertension. Such phenotypic traits ('intermediate phenotypes'), with earlier penetrance than hypertension itself, can be

Adolescent↗

PubMed1998

Oral splints: the crutches for temporomandibular disorders and bruxism?

Despite the extensive use of oral splints in the treatment of temporomandibular disorders (TMD) and bruxism, their mechanisms of action remain controversial Various hypotheses have been proposed to explain their apparent efficacy (i.e., true therapeutic value), including the repositioning of condyle and/or the articular disc, reduction in the electromyographic activity of the masticatory muscles, modification of the patient's "harmful" oral behavior, and changes in the patient's occlusion. Following a comprehensive review of the literature, it is concluded that any of these theories is either poor or inconsistent, while the issue of true efficacy for oral splints remains unsettled. However, the results of a controlled clinical trial lend support to the effectiveness (i.e., the patient's appreciation of the positive changes which are perceived to have occurred during the trial) of the stabilizing splint in the control of myofascial pain. In light of the data supporting their effectiveness but not their efficacy, oral splints should be used as an adjunct for pain management rather than a definitive treatment. For sleep bruxism, it is prudent to limit their use as a habit management aid and to prevent/limit dental damage potentially induced by the disorder. Future research should study the natural history and etiologies of TMD and bruxism, so that specific treatments for these disorders can be developed.

Behavior Therapy↗

PubMed1997

Comorbidity between myofascial pain of the masticatory muscles and fibromyalgia.

This study compared myofascial pain of the masticatory muscles to fibromyalgia. Study data show that, in both myofascial pain and fibromyalgia patients, facial pain intensity and its daily pattern and effect on quality of life are very similar. This indicates that fibromyalgia should be included in the differential diagnosis for myofascial pain of the masticatory muscles. However, with the higher prevalence of neurologic and gastrointestinal symptoms, and the stronger words used to describe the affective dimension of pain, it is apparent that fibromyalgia may be a more debilitating condition than myofascial pain of the masticatory muscles. Since the intensity of facial pain was strongly and significantly correlated to the body-pain index in fibromyalgia but not in myofascial pain patients, it can be concluded that facial pain may be part of the clinical manifestations of fibromyalgia, but it is unlikely to be related to body pain in myofascial pain patients. On the other hand, while body pain is episodic in most myofascial pain patients, it is constant and more severe in the majority of fibromyalgia patients. This difference in the pain patterns suggests that body pain in fibromyalgia and myofascial pain could have different etiologies. The lack of correlation between the intensity of pain and the length of time since onset also supports the concept that myofascial pain of the masticatory muscles and fibromyalgia are unlikely to be progressive disorders.

Adult↗

PubMed1994

Pain responses to experimental chewing in myofascial pain patients.

Although patients with myofascial pain of the masticatory muscles often report that chewing exacerbates their pain, this has never been verified experimentally. In this study, pain was assessed before and after chewing in 20 asymptomatic subjects and in 61 patients with muscle pain. First, self-reports of pain were obtained with a checklist and on five-point category scales (CAT) at the screening visit. None of the asymptomatic subjects reported that mastication or other jaw movements caused pain. On the other hand, the majority of patients reported that movements were painful (67.2%, checklist; 78.7%, CAT). Afterward, pain intensity at rest and after chewing on wax for 3 min was reported on 100-mm Visual Analogue Scales (VAS). No asymptomatic subjects had pain before or after the chewing test, while about 50% of the patients reported an increase of pain after chewing. In this subgroup, mean pain intensity increased by 102.6%. However, mean pain intensity after chewing decreased by 56.6% in about 30% of the patient sample. These patients had significantly higher resting pain than the first subgroup. These data show that a short chewing test can exacerbate pain in most myofascial pain patients but has no effect in asymptomatic subjects. Surprisingly, the exercise decreased pain in an important subgroup of patients. These results suggest that two subgroups of myofascial pain patients may exist with opposite reactions to exercise. It remains to be seen if these reactions are due to two different pathologies or to the fact that the pre-exercise pain levels were significantly different in the two groups.

Adolescent↗

PubMed1994

Comparison of pain and quality of life in bruxers and patients with myofascial pain of the masticatory muscles.

Although it has been suggested that bruxism is a cause or a risk factor in myofascial pain of the masticatory muscles, the prevalence of pain in bruxers and its characteristics have not been assessed or compared to those of myofascial pain patients in general. In this study, self-reports of pain and quality of life were recorded on 100-mm visual analogue and five-point category scales from two research populations: (1) 19 nocturnal bruxers who participated in a polysomnographic study and (2) 61 patients with myofascial pain of the masticatory muscles with no evidence of bruxism who participated in a controlled clinical trial on the efficacy of oral splints. The data show that pain was more intense in those bruxers who reported pain than among the myofascial pain patients, even though pain was not the chief complaint of bruxers. Both conditions reduced the patient's quality of life, although pain patients (either bruxism or myofascial pain) appeared to be much more affected than bruxers who were pain-free. The fact that pain from bruxism was worst in the morning suggests that it is possibly a form of postexercise muscle soreness. Myofascial pain, which was worst late in the day, is likely to have a different etiology.

Adolescent↗

PubMed1993

Is osteoporosis a risk factor for osseointegration of dental implants?

The success of osseointegration depends in part on the state of the host bed. Concerns have therefore been raised about osteoporosis, a condition believed to be associated with a decrease in bone quality and quantity. However, the orthopedic literature indicates that osteoporotic fractures heal readily and that the level of bone mass and estimates of the parameters associated with bone remodeling present considerable overlap between patients with osteoporosis and control subjects. It also appears that osteoporosis, as diagnosed at one particular site of the skeleton, is not necessarily seen at another distant site. Although the prevalence of osteoporosis increases among the elderly and after menopause, the results of this study indicate that implant failure rate is not correlated with age and sex. A review of the literature and of results of a series of patients treated does not provide a compelling theoretical or practical basis to expect osteoporosis to be a risk factor for osseointegrated dental implants.

Adult↗

PubMed1991

Power and sample size calculations for clinical trials of myofascial pain of jaw muscles.

When a clinical trial is planned, the approximate number of subjects needed for significant differences between/among groups to be detected must be estimated. Sample-size calculations provide the investigator with this information. This paper discusses the choice of outcome measures and describes the steps used to estimate the numbers of subjects necessary for a study that compares treatments for patients with chronic myofascial pain of jaw muscles. Within- and between-subject variances were estimated for the chosen variables, the subjects' pain ratings on visual analogue scales. Sample sizes were then calculated for theoretical differences between groups by pre-treatment means and overall standard deviations (Cohen, 1977). The results of this analysis can be used by other researchers when planning studies involving these types of patients.

Adolescent↗

PubMed1988

Can electrical stimulation be used to establish a physiologic occlusal position?

An electromyographic study was undertaken to discover the mechanism by which the Myo-monitor instrument causes muscle contraction. Our data, which strongly suggest that the distal axons of the motoneurons are directly stimulated, lend support to previous studies showing that the stimulus does not cause reflex activation of the jaw closing muscles. Inasmuch as the stimulus acts only in the periphery without the participation of the central nervous system, the ability of the instrument to produce a reflexly controlled occlusal position is highly questionable. Furthermore, we believe that there is no evidence that reflex jaw closure could ever be used to establish a physiologic occlusal position.

Adult↗

PubMedDate not supplied

Sensory disturbances associated with implant surgery.

PURPOSE: This paper presents a critical review of the literature on neurosensory disturbances associated with implant surgery. MATERIALS AND METHODS: The reviewed literature includes mainly retrospective implant studies and patients' surveys, as well as a few prospective psychophysical studies on sensory disorders following maxillofacial surgeries. RESULTS: The available data suggest that injury to the peripheral branches of the trigeminal nerve and subsequent sensory disturbances are potential complications following implant surgery. Cross-sectional studies suggest that gross tactile sensation was regained in the vast majority of patients. However, data on the spatial and temporal patterns of recovery of this and other somatic sensation such as fine touch, nociception, and temperature sense after implant surgery is still lacking. The prevalence of sensory disturbances depends on several factors: the site of implant placement, the type of surgical procedures adopted, the design of the studies, the sensitivity of the testing methods, the choice of the outcome measures, and the terminology used to describe sensory disturbances. Extreme variation in the reported prevalence of neurosensory disturbances (0% to 100%) suggest that these problems have not been adequately evaluated. CONCLUSION: Although sensory disturbances are transient in the majority of implant patients, their profound impact on the quality of life of the subjects affected and the possibility that they may persist clearly indicate that they should be identified and evaluated through prospective studies, using validated testing protocols and outcome measures.

Dental Implantation, Endosseous↗