Biomedical subjects

J DeMerritt

Publications and source records attributed to J DeMerritt.

2 recordsLinked to original sources

PubMed1993

Stress-induced hypertension in the borderline hypertensive rat: stimulus duration.

Blood pressure and circulating catecholamines were evaluated in borderline hypertensive rats (BHR) that were exposed to daily sessions of either short (20 min) or long (120 min) duration air-jet stimulation. Indirect measures of systolic blood pressure indicated that within 2 weeks both experimental groups developed stress-induced hypertension in comparison to home cage controls. Animals exposed to 120 min stress sessions had significantly higher systolic blood pressure relative to the 20 min group. However, direct measures of blood pressure taken after 5 weeks of daily stress did not reveal any differences between the stress groups. Daily measurements indicated that acute changes in blood pressure during stress were modest and transient, suggesting little contribution to the chronic elevation in blood pressure observed as a consequence of stress. Circulating catecholamines were significantly increased by the stressor. Epinephrine returned to baseline within 60 min, although norepinephrine remained elevated throughout the 120 min session. The results indicate that increasing the duration of daily air jet stimulation did not impact the development of stress-induced hypertension over the 5-week measurement period.

Animals↗

PubMedDate not supplied

Hemifacial spasm: MR imaging features.

MR imaging was used to evaluate the relationship of the root exit zone of the seventh cranial nerve to surrounding vascular structures in 13 patients with clinically documented hemifacial spasm and in 70 asymptomatic patients. MR imaging clearly demonstrated the course of the seventh nerve from the root exit zone of the brainstem to the internal auditory canal and its relationship to the surrounding vertebrobasilar system. The presence of a vascular structure at the root exit zone of the seventh nerve was identified in all 13 patients with hemifacial spasm. In the 70 asymptomatic patients, examination of 140 seventh nerves revealed that 21% had contact by a vascular structure at the root exit zone of the seventh nerve. Our results indicate that although neurovascular contact may be asymptomatic, MR demonstration of a vascular structure at the root exit zone of the seventh cranial nerve in a patient with hemifacial spasm may implicate neurovascular compression as the cause of symptomatology. This finding may alter therapeutic management. Because of the inherent limitations of CT in the visualization of posterior fossa structures, MR imaging should be considered the initial screening procedure in the assessment of patients with hemifacial spasm.

Adult↗