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Biomedical subjects

S M Davis

Publications and source records attributed to S M Davis.

At least 127 records · Page 7Linked to original sources
PubMed1991

Ethnic and gender differences in Southwestern students' sources of information about health.

Students from several rural, Southwestern schools rated family, television, teachers and doctors as the most important of 11 sources of information about various health topics. However, doctors were only the fifth-ranked source of information about sex and reproduction and the seventh-ranked source of information about drugs, with friends being the fourth- and third-ranked sources of information about these two more personal and sensitive topics. American Indians reported even stronger reliance on doctors than did Hispanic and Anglo students, and rated clinic nurses as much more important sources of health information than did the other two ethnic groups. Females showed greater reliance on social sources and less on electronic media than did male students, and high school students relied more on print media and less on television, nurses and family than did younger children. Students felt more knowledgeable about smoking, alcohol and exercise than about diet, the heart-blood system and cancer; however, American Indians felt less informed about smoking and alcohol than did Anglos or Hispanics. These findings (especially when compared to previous results) suggest that effective health education programs must be tailored to particular populations and based on specific knowledge of their attitudes, behavior and environment.

Adolescent↗
PubMed1991

Asthma in the elderly. A comparison between patients with recently acquired and long-standing disease.

To characterize asthma in the elderly, 25 consecutive nonsmoking pulmonary clinic patients over the age of 70 who met the American Thoracic Society criteria for asthma were identified. Of these, 12 patients (48%) had developed asthma at an advanced age (greater than 65 yr). This group with late-onset asthma had a mean duration of disease of 5.1 +/- 2.5 yr. The remaining group with early-onset asthma had a mean duration of illness of 31.4 +/- 14.6 yr. On the day of evaluation each patient underwent pulmonary function testing off all medication for at least 12 h. These two groups were indistinguishable by symptoms and medication requirements. Immediate hypersensitivity skin testing to 43 aeroallergens was uniformly negative in all 25 patients but the histamine control was always positive. IgE levels in both groups were not different from those in elderly control subjects. Those with early-onset asthma had a greater likelihood of previous allergic disease (p less than 0.001) and a significantly greater degree of airflow obstruction in pre- and postbronchodilator pulmonary function testing (p less than 0.05). This study suggests that long-standing asthma may lead to chronic persistent airflow obstruction and thereby mimic chronic bronchitis and emphysema (COPD).

Adult↗
PubMed1991

Effects of 4 percent and 6 percent carboxyhemoglobin on arrhythmia production in patients with coronary artery disease.

In this study, we assessed the effects of exposure to 4 percent and 6 percent carboxyhemoglobin on ventricular arrhythmias in 41 subjects (nonsmokers) with documented coronary artery disease. We used a randomized, double-blind, crossover design. On day 1, a training session with no exposure, the baseline carboxyhemoglobin level was measured, and a supine bicycle exercise test was done. On days 2 through 4, subjects were exposed to room air, 100 parts per million (ppm)2 carbon monoxide (target, 4 percent blood carboxyhemoglobin), or 200 ppm carbon monoxide (target, 6 percent blood carboxyhemoglobin), and they then did a supine bicycle exercise test. Radionuclide ventriculography was performed at rest and during exercise. Ambulatory electrocardiogram recordings were made during the four consecutive days to determine the frequency of premature ventricular contractions at various intervals. The frequency of single premature ventricular contractions per hour during exercise was significantly greater on the 6 percent carboxyhemoglobin day than on the room air day (167.72 +/- 37.99 for 6 percent carboxyhemoglobin compared with 127.32 +/- 28.22 for room air, p = 0.03). The frequency of multiple premature ventricular contractions per hour was also significantly greater during exercise on the 6 percent carboxyhemoglobin day compared with the room air day (9.59 +/- 3.70 for the 6 percent carboxyhemoglobin day compared with 3.18 +/- 1.67 for the room air day, p = 0.02). Patients who developed increased arrhythmias during exercise on the 6 percent carboxyhemoglobin day were significantly older than those who had no increased arrhythmia, and, in addition, exercised longer and had a higher peak workload during exercise. No effect of carbon monoxide exposure was seen on the 4 percent carboxyhemoglobin day.

Aged↗
PubMed1990

Epileptic seizures in acute stroke.

We evaluated prospectively the incidence of early seizures in 1000 consecutive patients with stroke and transient ischemic attacks to determine whether seizure occurrence correlates with stroke type, pathogenesis, or outcome. Seizures occurred in 44 patients (4.4%; SE, 0.7%), including 10 (15.4%) of 65 (SE, 4.5%) with lobar or extensive hemorrhage, 6 (8.5%) of 71 (SE, 3.3%) with subarachnoid hemorrhage, 24 (6.5%) of 370 (SE, 1.3%) with cortical infarction, and 4 (3.7%) of 109 (SE, 1.8%) with hemispheric transient ischemic attacks. Lacunar infarcts and deep hemorrhages were not associated with seizures. Arteriovenous malformation was a common cause of lobar hemorrhage with early seizures, but in cortical infarcts there was no association between seizure occurrence and pathogenesis. Seizures generally occurred within 48 hours of stroke onset, were usually single, partial, and readily controlled. Seizures were not associated with a higher mortality or worse functional outcome.

Acute Disease↗
PubMed1990

Genetic evidence that Neisseria gonorrhoeae produces specific receptors for transferrin and lactoferrin.

Transferrin (TF) and lactoferrin (LF) are probably the major sources of iron (Fe) for Neisseria gonorrhoeae in vivo. We isolated mutants of N. gonorrhoeae FA19 that were unable to grow with Fe bound to either TF (TF-) or LF (LF-) or to both TF and LF ([TF LF]-). The amount of Fe internalized by each of the mutants was reduced to background levels from the relevant iron source(s). The wild-type parent strain exhibited saturable specific binding of TF and LF; receptor activity was induced by Fe starvation. The TF(-)-specific or LF(-)-specific mutants were almost completely lacking in receptor activity for TF or LF, respectively, whereas the [TF LF]- mutants bound both TF and LF as well as the wild-type strain. All mutants utilized citrate and heme normally as Fe sources. These results demonstrate that ability to bind TF or LF is essential for gonococci to scavenge appreciable amounts of Fe from these sources in vitro. In addition, the TF and LF Fe acquisition pathways are linked by the mutual use of a nonreceptor gene product that is essential to Fe scavenging from both of these sources; this gene product is not required for Fe acquisition from other sources.

Binding, Competitive↗
PubMed1989

Carotid endarterectomy: why question it now?

Carotid endarterectomy has been accepted widely as an important stroke-prevention tool since the 1950s, in spite of the lack of any proof of its efficacy in randomized, controlled clinical trials in either symptomatic or asymptomatic patients. While surgery for asymptomatic carotid disease always has been controversial, the indications and benefits of carotid endarterectomy in symptomatic patients now are being questioned also, although the available evidence suggests that the operation, when performed in expert hands, reduces the incidence of subsequent strokes in patients with minor, carotid-territorial ischaemic events and significant ipsilateral carotid disease. (A morbidity and mortality rate of more than 3% is unacceptable, and hence the procedure should be undertaken only by those who are skilled in its performance). For each patient, a decision has to be made as to whether the potential reduction of the risk of stroke outweighs the immediate surgical risk of stroke or death. Some large, expensive and important randomized clinical trials are either proposed or under way in North America and Europe to evaluate the precise role of carotid endarterectomy in the prevention of strokes. The basis for the current questioning of carotid endarterectomy and the rationale for these trials are addressed in this review.

Carotid Arteries↗
PubMed1989

Magnetic resonance imaging in posterior circulation infarction: impact on diagnosis and management.

To compare the diagnostic yield of magnetic resonance imaging (MRI) with computed tomography (CT) in posterior circulation infarction, we used proton MRI with a 0.3 Tesla magnet and a 3rd generation CT scanner in 25 patients. Age-matched controls were compared in a blinded fashion. Seventeen patients (68%) showed relevant pathology on MRI not seen on CT, 11 with normal CT and six with more extensive lesions, chiefly in the brain stem. Evidence of abnormal vertebrobasilar blood flow was seen in 8/25 (32%) of patients, suggested by vascular high intensity signals on MRI. Two tissue and one flow abnormality were seen in the control group. MRI provides additional information concerning infarct site, extent and pathogenesis in posterior circulation infarction.

Adult↗
PubMed1989

Phenytoin-carbamazepine cross-sensitivity.

A case of phenytoin-carbamazepine cross-sensitivity is presented. Similar signs and symptoms occurred during administration of both drugs. A common metabolic intermediate is offered as a possible explanation of the mechanism. Clinicians should be careful when choosing alternatives in patients with hypersensitivity reactions to anticonvulsants. Valproic acid may be the safest choice in this setting.

Adult↗
PubMed1988

The checkerboard cardiovascular curriculum: a culturally oriented program.

A cardiovascular health education curriculum was designed and pilot-tested with 218 fifth grade students from rural New Mexico. The program incorporated materials, examples, and exercises relevant to the Navajo and Pueblo American Indian and Hispanic cultures of the students. Significant increases in knowledge about the cardiovascular system, exercise, nutrition and obesity, tobacco use, and habit change were found, suggesting a culturally oriented program may help promote a healthy lifestyle in minority group children.

Cardiovascular Diseases↗
PubMed1987

Dynamic CT brain scanning in the haemodynamic evaluation of cerebral arterial occlusive disease.

Dynamic cerebral CT scanning (DCT) was used to quantitatively analyse the haemodynamic effects of extracranial and intracranial arterial occlusive lesions in 17 patients with TIA's or minor cerebral infarcts. Using DCT and gamma variate curve fitting, mean transit times were determined for the terminal internal carotid arteries, middle cerebral arteries and middle cerebral-supplied Sylvian cortex at the level of the Circle of Willis. Six patients were studied sequentially, four before and after transcranial bypass surgery. No arterial or tissue delays were found in patients without haemodynamic arterial lesions or cortical infarcts. Seven of nine patients with haemodynamic, extracranial carotid lesions showed ipsilateral delays in arterial or tissue transit times. Tissue delays usually correlated with CT or clinical evidence of infarction. Improved haemodynamics in patients re-studied correlated with the effects of surgery or clinical recovery. DCT has several important limitations but has the potential to provide additional haemodynamic information about the cerebral circulation in selected patients with cerebral arterial occlusive disease.

Adult↗
PubMed1987

Analysis of dynamic computed tomography scan brain images.

Dynamic computed tomography (DCT) of the brain can be used to study the transit time of first passage of a bolus injection of intravenous contrast medium. Comparison of cerebral perfusion with corresponding sites in the left and right cerebral hemispheres is of diagnostic interest because a real difference may be indicative of differential damage. A method for estimating the mean transit time and approximating its standard error, by assuming a gamma function for the response curve and an appropriate error structure, is presented. Expressed as log-linear regression, estimation is achieved by maximum likelihood using a statistical package such as GLIM or SPSSX. Statistical comparison of the mean transit time to or between corresponding sites can be made; issues of model fit and biologic interpretation need to be considered as an integral part of statistical inference. These methods enable users of CT equipment (without specific software for estimation of mean transit time) to use any log-linear routine for diagnostic purposes. An example of the fit procedure and interpretation in the light of clinical evidence is given.

Brain↗
PubMed1986

Antishock trousers: a collective review.

Antishock trousers have become an integral part of emergency medical care for many traumatic and life-threatening emergencies. This article represents a summary of the current state of knowledge concerning the use of this device. A brief history of the development of antishock garments is discussed. This is followed by a discussion of human clinical studies and results of clinical research on hemodynamics, respiration, use in head injury, and effects on vascular hemostasis. Indications, contraindications, complications, and recommended procedure for use are discussed. Based on randomized prospective studies, antishock garments have not, as yet, been shown to improve patient morbidity or mortality. Proper use of antishock garments requires an understanding of both their function and their limitations.

Acidosis↗
PubMed1986

Wheezing in the elderly. Asthma and other causes.

The evaluation and treatment of patients who complain of wheezing take on special significance in the elderly. Although asthma may begin late in life, it is distinctly uncommon. When it does, it is clinically undistinguishable from asthma present at an earlier age. If severe, the disease may require treatment with corticosteroids as well as bronchodilators. Any side effects are particularly troublesome in the elderly, and careful patient monitoring is essential. Wheezing in the elderly may also signal the onset of other diseases such as chronic obstructive pulmonary disease, congestive heart failure, pulmonary aspiration, pulmonary embolism, and bronchogenic carcinoma. Consideration of these causes of wheezing will lead to appropriate diagnostic studies and specific therapy.

Aged↗
PubMed1985

Intravenous digital subtraction angiography in patients with carotid territory ischemia: a prospective trial.

To evaluate the place of intravenous digital subtraction angiography (IV-DSA) in the investigation of patients with carotid territory ischemia, we have compared the IV-DSA and conventional angiographic (CA) findings in 40 patients in a prospective study. Arterial disease was assessed by grading stenosis from zero (normal artery) to six (complete occlusion) and recording any luminal ulceration. In 59 of 66 bifurcations imaged by both techniques, the IV-DSA evaluation of any internal carotid artery origin disease was within one grade of the CA assessment, with three false negatives and four false positives. Luminal ulceration was less reliably predicted, and two clinically important middle cerebral artery lesions were missed by IV-DSA. In 11 patients who had carotid endarterectomy, there was a good correlation between surgical, CA, and IV-DSA findings, although some ulcerations were not detected by either angiographic technique. These results suggest that IV-DSA is a sensitive technique for detection of carotid bifurcation stenosis when the study is of good quality, but that intracranial lesions may be missed.

Carotid Artery, External↗