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Biomedical subjects

D H Davis

Publications and source records attributed to D H Davis.

At least 55 records · Page 3Linked to original sources
PubMed1990

Stereotactic resection of occult vascular malformations.

Angiographically occult vascular malformations can be identified on computerized tomography and magnetic resonance imaging. Surgical excision, when possible, is the treatment of choice in symptomatic lesions. Because these malformations are usually small and can be located in surgically treacherous areas of the brain, stereotactic resection should be considered. Stereotactic resection of a pathologically verified occult vascular malformation was performed in 26 patients in this series (13 females and 13 males, mean age 30 years). Seventeen patients presented with a seizure disorder, four with an intracerebral hemorrhage, and four with a progressive neurological deficit; one patient was asymptomatic. Sixteen patients had normal neurological examinations, nine had neurological signs referable to their lesion, and one had a visual field deficit related to a previous temporal lobectomy. In six patients evidence of acute hemorrhage was found on imaging studies or at surgery, and 11 patients had evidence of previous hemorrhage on imaging studies, determined at surgery or by histological examination. Three patients had evidence of both acute and previous hemorrhage and six patients had no evidence of hemorrhage. Lesions were located in cortical or subcortical areas in 21 patients, in the thalamus or basal ganglia in three, and in the posterior fossa in two. Following stereotactic resection, 24 patients were improved, one patient was unchanged, and one patient was worse. Without stereotaxis or intraoperative ultrasound studies, localization of these lesions at conventional craniotomy can be difficult. A stereotactic craniotomy is ideally suited to the treatment of these benign circumscribed, but potentially devastating lesions.

Adolescent↗
PubMed1990

Effects of capsaicin (C) and dihydrocapsaicin (DC) on serum ethanol (ET) concentration of ET treated CF-1 mice.

In this study adult male CF-1 mice were treated on a daily basis as follows: Group A - controls, Group B - ethanol (ET) treated (1.25 g ET/kg body weight (b.wt.], Group C - ET plus 4 mg Capsaicin (C)/kg b.wt., and Group D - ET plus 4 mg dihydrocapsaicin (DC)/kg b.wt. At the end of the sixth week experimental period the animals were anesthetized, exsanguinated and hepatectomized. Our study suggests that ET administered at the rate of 1.25 g ET/kg b.wt. reaches a mean serum value of 43 + 14 mg/dL within 15 minutes. In addition, chronic ET ingestion significantly decreases mean hepatic glycogen content and mean serum triglyceride concentration of the animals. Conjoint administration of ET plus C decreases significantly mean body weight and mean ET and the triglyceride concentration of the serum. Prolonged ET ingestion plus DC administration decreases mean wet liver weight and lowers significantly the mean serum ET, cholesterol and triglyceride concentrations of CF-1 mice.

Alcoholism↗
PubMed1989

Artful design: writing the proposal for research in the naturalist paradigm.

The preparation of the research proposal for a study that involves an emergent research design compels the investigator to negotiate the paradox of planning what should not be planned in advance. This paper is a guide to writing the proposal for research in the naturalist paradigm, and includes illustrative sections of a proposal recently funded by the National Center for Nursing Research.

Data Collection↗
PubMed1989

Stereotactic resection of pediatric vascular malformations.

The technique of computer-assisted stereotactic resection of intra-axial neoplasms can also be used in the treatment of vascular malformations. We report a series of 12 pediatric patients with supratentorial lesions who underwent stereotactic resections between 1985 and 1988. There were 5 boys and 7 girls, with mean age 8 years (range 3-16). Epilepsy was the presenting symptoms in 8 children, hemorrhage in 3, and in 1 the lesion was incidentally diagnosed. Seven lesions were angiographically occult. All lesions were resected without mortality or morbidity. Seizures resolved in 7 of 8 cases, with the remaining patient experiencing a reduction in seizure frequency. Illustrative cases are presented.

Adolescent↗
PubMed1989

Treatment of colloid cysts of the third ventricle by stereotaxic microsurgical laser craniotomy.

The therapeutic strategies employed in the management of anterior third-ventricular mass lesions remain controversial. Resection by conventional craniotomy, whether via a transcallosal or transcortical approach, carries well-known risks and limitations. Alternatively, in this region traditional stereotaxy has been relegated to use with biopsy only or cyst aspiration procedures. Combining aspects of both conventional and stereotaxic techniques has allowed total removal of 12 colloid cysts in six women and six men ranging in age from 25 to 71 years. No mortality and minimal morbidity have been associated with the procedures. There has been no evidence of recurrence in an average follow-up period of 19 months. By coupling the benefits of stereotaxic precision and localization to the microsurgical management of colloid cysts, several rewards have been realized: 1) only a limited cortical dissection is needed; 2) the hazards of callosal or forniceal injury can be avoided; 3) the lesion is easily localized regardless of ventricular size; 4) hemostasis can be readily achieved with bipolar cautery or defocused laser power; and 5) most importantly, a total resection is possible with little risk to the patient. Stereotaxic microsurgical laser craniotomy provides a new option for the management of colloid cysts and other anterior third-ventricular lesions.

Adult↗
PubMed1989

Dihydrocapsaicin (DC) protects against serum hyperlipidemia in guinea pigs fed a cholesterol-enriched diet.

Juvenile guinea pigs were maintained either on a standard diet (cholesterol-free) or a 0.5% cholesterol-enriched vitamin C deficient diet for six weeks. Half of the animals of each dietary group were treated with dihydrocapsaicin (DC) at the rate of 8 mg per animal per day. DC administration significantly altered food consumption, body weight, and dry weight of feces of animals maintained on the standard diet. In addition, the mean serum triglyceride concentration of these animals was significantly decreased with DC treatment. Food consumption, body weight and (wet) fecal weight of animals maintained on the 0.5% cholesterol-enriched diet were significantly lower than the corresponding values in control animals even though the liver was much larger in proportion to the total body weight. The mean serum cholesterol concentration of the animals fed a cholesterol-enriched diet was significantly elevated. However, in animals also receiving DC, the cholesterol and triglyceride levels were comparable to controls fed a regular diet. The gross and microscopic fatty infiltration of the liver observed in the cholesterol-fed animal were minimized in those animals fed cholesterol and DC.

Animals↗
PubMed1988

Infants at risk for sudden infant death syndrome (SIDS): differential prediction for three siblings of SIDS infants.

The outcome for three siblings of SIDS (SSIDS) infants was predicted, using as a risk model the sleep and respiratory characteristics of a SIDS victim studied extensively during the neonatal period. The SIDS infant had shown unstable state organization and deviant respiration patterns, including a deficit of brief apneic pauses. Like the SIDS infant, the SSIDS infants and a group of 16 normal infants were observed in the home for 7-hr periods when they were 2, 3, 4, and 5 weeks old. Two of the infants showed normal sleep and respiratory characteristics, and they were predicted to develop without respiratory dysfunction. In contrast, the third infant showed a pattern of deviancies similar to the SIDS infant; and at 4 months, she had prolonged apneic episodes, requiring resuscitation on two occasions. The findings are consistent with the notion of subtle central nervous system (CNS) dysfunction in SIDS risk infants from the time of birth.

Arousal↗
PubMed1988

Computer-assisted stereotactic biopsy of intracranial lesions in pediatric patients.

A computer-assisted stereotactic biopsy technique has been used in 30 patient (ages 5 months to 16 years) with intracranial lesions (supratentorial in 23 and infratentorial in 7). The computer program integrates stereotactically gathered imaging data and permits preoperative planning of a biopsy trajectory. Diagnostic tissue was obtained in 27 cases. In 2 cases, therapeutic interventions--third ventriculostomy and cyst aspiration--were accomplished at the time of the biopsy. There were no major complications related to the procedure; however, 2 patients had transient neurologic deficits. Computer-assisted stereotactic biopsy is a valuable diagnostic procedure in the pediatric patient with an intracranial lesion.

Adolescent↗
PubMed1987

Behavioral states of premature infants: implications for neural and behavioral development.

Nine premature and 28 full-term infants were observed in their homes for 7 hr when they were 2, 3, 4, and 5 weeks post-term, and the sleeping and waking states displayed by these infants were compared. For these comparisons, the observation day was divided into two mutually exclusive contexts: times when the baby was alone and times when the baby was with the mother. The premature infants spent more time alone (mean of 5.4 hr a day) than the full-terms (4.6 hr). Over the total 7-hr day, the premature infants spent more time in alert, nonalert waking activity, and sleep-wake transition than the full-terms, and they spent less time in drowse and total sleep. These results clearly indicate that, at the same post-term ages, the sleep-wake states of premature infants differ markedly from those of full-terms. Four states showed significant Group X Context interactions indicating that state differences between premature and full-term infants were also a function of the context in which the infants were observed. For example, the prematures exhibited more fuss or cry and more drowse when alone; whereas the full-terms exhibited more of these states when with their mothers. This finding of context-related differences between prematures and full-terms has implications for the conflicting reports in the literature, as heretofore the states of prematures and full-terms have been compared from observations made in a single situation. The results indicate that prematures exhibit significant commonality in their neurobehavioral development through the early post-term period despite heterogeneity among them in their exposure to prenatal, perinatal, and early postnatal stresses.

Arousal↗
PubMed1987

The sleeping and waking states of infants: correlations across time and person.

Study of the sleeping and waking states of infants was extended to the time domain by analyzing their temporal covariation over a 4-week interval using the intra-person correlation coefficient. As a methodological question, inter-person and intra-person correlation matrices were compared. Twenty-eight fullterm, normal infants were observed in the home weekly from 2 to 5 weeks of age. Over each 7-hour observation, the following states were recorded every 10 seconds: Alert, Non-Alert Waking Activity, Fussing, Crying, Daze, Drowse, Sleep-Wake Transition, Active Sleep, Quiet Sleep, and Unclassified Sleep (sleep during periods of the day when a mother was holding her baby). Data were obtained in two social contexts: when the baby was with the mother and when alone. Significant individual differences were found for each of the states in both social contexts. When the baby was alone, there were a greater number of intra-person correlations than inter-person correlations. All correlations between the waking states and Active Sleep or Quiet Sleep were negative, suggesting the hypothesis that the underlying neurobiological mechanisms may allow a degree of substitution among coupled sleep and wake states. This is an extension of the original hypothesis by Roffwarg, Muzio, and Dement. There were fewer systematic relationships among the states when the babies were with their mother in comparison with periods when they were alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Child Behavior↗
PubMed1987

Computer-assisted stereotactic biopsy of intracranial lesions.

The use of a computer program that allows the integration of stereotactically gathered CT, MRI and digital angiographic data in the planning of a biopsy trajectory is described. This system has been used to perform 447 stereotactic biopsies in 439 patients. Intracranial hemorrhages occurred in three patients; combined morbidity and mortality was less than 1%. Incorporation of angiographic data and visualization of the surgical trajectory enhances the safety and accuracy of stereotactic biopsy of intracranial lesions.

Biopsy↗
PubMed1985

Theophylline affects sleep-wake state development in premature infants.

This study investigated the prolonged effects on state behavior of theophylline administered to infants for apnea of prematurity. There were three groups: Four premature infants who had received theophylline in the preterm period, five premature infants who had not received theophylline, and twenty-eight normal fullterm infants. The Theophylline infants had been off the drug for at least one month prior to the beginning of the study. Sleep-wake states were observed in the home for seven-hour periods when all infants were the same corrected ages: two, three, four and five weeks post-term. Data from the portion of the day that the infants were alone were analysed for this study. The state organization of the Theophylline group differed significantly from those of the other groups. They exhibited more non-alert waking activity, more alert, more drowse or transition, and less active sleep than did the Non-Theophylline and Fullterm infants. The state distributions of the latter two groups did not differ. On the basis of similarities between the results of this study and of a previous animal study, it was concluded that theophylline altered the normal development of state organization in premature infants. These effects persisted long after the drug had cleared the body.

Female↗
PubMed1985

Pseudoclaudication. A review of etiology, diagnosis, and treatment.

The authors have presented an historical and clinical review of the pseudoclaudication syndrome. This disorder has become increasingly recognized during the past years, and it is important to keep in mind that pseudoclaudication can coexist with vascular insufficiency. Appropriate diagnosis and treatment can be rendered only when the correct diagnosis or diagnoses are made. As always, a thorough history and physical examination together with supplementary radiologic and neurophysiologic studies will lead the clinician to the correct cause of the symptoms presented and an appropriate course of treatment.

Cauda Equina↗
PubMed1983

A 32-year experience with the surgical treatment of selected brachial plexus lesions with emphasis on its reconstruction.

Twenty-five patients with brachial plexus injury were treated by anastomosis, neurolysis, and calvicular decompression. The patients treated by anastomosis are described in detail because evidence of regrowth of axons across the anastomosis can be documented, whereas the effects of neurolysis are difficult to judge. The techniques of brachial plexus reconstruction are illustrated. Clinical improvement occurred in 93% of patients treated with anastomosis, 89% of those treated with neurolysis, and 100% of those treated with decompression. Electromyographic studies provided valuable information in assessment before and after surgery. The benefits of surgical therapy of brachial plexus injuries outweigh the risks in carefully selected patients.

Adolescent↗