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Biomedical subjects

R L Davis

Publications and source records attributed to R L Davis.

At least 325 records · Page 18Linked to original sources
PubMed1983

Evaluation of neurotoxicity after subarachnoid injection of large volumes of local anesthetic solutions.

Recent case reports describing prolonged neurologic deficit after accidental spinal anesthesia with large volumes of 2-chloroprocaine have led to the suggestion that chloroprocaine may be more likely to cause such complications than other local anesthetics. We evaluated the neurologic effects of lumbar puncture alone and of large-volume subarachnoid administration of 2-chloroprocaine (3%), bupivacaine (0.75%), lidocaine (2%), Elliott's solution B (which is similar to CSF), or the carrier solution of 2-chloroprocaine (Nesacaine) in 48 sheep and 8 monkeys. Cerebrospinal fluid of sheep was collected on days 1 and 7 for biochemical and biological analyses, and CSF pressures of monkeys were recorded before and after injection. Animals were observed for neurologic deficits for seven days. Twelve sheep were unable to stand. Monkeys, on the other hand, had no apparent neurologic deficits. Autopsies revealed that 5 of the 12 sheep had lumbar subpial demyelination with macrophage infiltration: two of the five had received lidocaine; two received 2-chloroprocaine; and one had only a lumbar puncture. Two other sheep also had subpial demyelination: one had received lidocaine and one received 2-chloroprocaine. Three of the eight monkeys had lumbar subpial demyelination with macrophage invasion; two had received bupivacaine, and one received 2-chloroprocaine. No solution produced significant abnormalities in sheep CSF composition. We conclude that no local anesthetic or solution was more neurotoxic than another when injected in large volumes into the subarachnoid space of sheep or monkeys.

Anesthesia, Epidural↗
PubMed1982

Age-related chemosensitivity of stem cells from human malignant brain tumours.

After radiation therapy and chemotherapy for malignant glioma, patients aged 50 or under survive longer than patients over 50. Data from Brain Tumor Study Group trials show that, without treatment, these age groups have similar survival; therefore unperturbed tumour growth does not account for the difference. Sixteen consecutive patients with malignant glioma were studied, half of whom were less than or equal to 50 years of age; none had been treated before initial surgery, and all were subsequently treated with radiation and chemotherapeutic agents (in all but two patients, with nitrosoureas). Median survival of those aged greater than 50 was less than or equal to 50 years was 54 + weeks whereas that of those aged greater than 50 was 37 weeks. The longer survival for younger patients could not be attributed to tumour type, size, or location, pretreatment Karnofsky status, or mode of treatment. In-vitro sensitivity testing of clonogenic cells obtained from biopsy specimens showed that tumour cells from seven of eight patients aged less than or equal to 50 years were sensitive to 1,3-bis (2-chloroethyl)-1-nitrosourea (greater than 40% cell kill at clinically achievable concentrations) compared with only one patient with sensitive cells out of eight older patients. Patient age was inversely correlated with in-vitro cell kill, and patients with sensitive cells were significantly younger than those with resistant cells. Therefore influence of age on survival after treatment of malignant gliomas is probably due to inherent differences in the sensitivity of clonogenic cells to radiation and/or chemotherapeutic agents.

Age Factors↗
PubMed1982

Granulocytic sarcoma of the brain after renal transplantation.

A case of granulocytic sarcoma of the brain in a renal transplant recipient treated with immunosuppressive agents is presented. While the increased risk of malignant lymphoma, particularly large-cell lymphoma (reticulum cell sarcoma, histiocytic lymphoma, immunoblastic sarcoma) in these patients is well known, this appears to be the first report of a granulocytic sarcoma. Granulocytic sarcoma, a rare tumor composed of immature granulocytic elements, almost never involves the parenchyma of the brain. Histochemical examination may be necessary to distinguish this lesion from other poorly-differentiated neoplasms.

Adult↗
PubMed1982

Radiation effects in the canine brain evaluated by quantitative computed tomography.

Quantitative computed tomography (QCT) and histopathology were used to assess the effects of large single doses of x irradiation on the normal canine brain. Measurable changes demonstrated by QCT included increased contrast enhancement and enlargement of the lateral ventricles, which were observed prior to any clinical signs. The results suggest that QCT methods are effective in the noninvasive evaluation of radiation-induced brain injury.

Animals↗
PubMed1982

Comparison of the brain tissue response in rats to injury by argon and carbon dioxide lasers.

This study compares the acute and chronic response of brain tissue to injury by equal power density, focused argon (Ar) and carbon dioxide (CO2) laser beams. A cortical incision from 0.2-second laser pulses of 12.5 X 10(3) W/cm2 power density was made in the exposed cortex of 32 rats using either the CO2 or the Ar laser. The brains were examined at intervals from 1/2 hour to 1 month after injury. Histologically, all brain incisions were sharply demarcated hemispheroidal defects with a vaporized center bordered by a zone of coagulation necrosis surrounded by edema. The laser incisions were found to be of equal depth (less than 1 mm). The average cortical surface diameter of the CO2 laser incision was 0.86 mm for a focused beam spot size 0.45 mm in diameter, compared with 0.65 mm with the Ar laser, which had a focused beam spot size 0.15 mm in diameter. In both incisions, some delayed depth effect was observed. A progression of the tissue necrosis by approximately 17% was observed during the first 24 hours after injury. During the first 4 hours after injury, the Evans blue blood-brain barrier defect (EBBD) surrounding the cortical incisions averaged 5.80 mm2 for the CO2 incision and 0.888 mm2 for the Ar incision. In both types of brain incision, the EBBD appeared to resolve by 24 hours after injury. At 1 month after injury, a core of coagulation necrosis surrounded by mild fibrillary gliosis was observed. At the power density and focused beam spot sizes used, there was no significant difference in the overall brain tissue response to Ar and CO2 laser lesions.

Animals↗
PubMed1982

Malignant optic glioma presenting radiologically as a "cystic" suprasellar mass: case report and review of the literature.

The diagnosis of malignant glioma of the optic nerves and chiasm may be difficult because these rare lesions may mimic other suprasellar lesions. We report a case of glioblastoma multiforme of the optic chiasm in which the appearance of the lesion on computed tomographic (CT) scan was consistent with that of craniopharyngioma or cystic pituitary adenoma. We suggest that malignant optic glioma should be considered in the differential diagnosis of an adult with progressive visual loss of rapid onset, even when ophthalmological examination strongly suggests extrinsic compression of the anterior optic pathways and when the CT scan apparently indicates a cystic mass lesion.

Adult↗
PubMed1982

Persistence and late malignant transformation of childhood cerebellar astrocytoma. Case report.

A 5-year-old girl with juvenile pilocytic astrocytoma subsequently had multiple episodes of symptomatic recurrence over the course of 21 years of follow-up review. This lesion underwent histological transformation to an anaplastic small-cell neoplasm 21 years after the initial resection and diagnosis. Late transformation of benign childhood cerebellar astrocytomas to malignant astrocytic tumors is very rare; transformation to an anaplastic small-cell neoplasm has not been reported previously. This case and other reported cases in which juvenile pilocytic astrocytoma recurred after a long interval indicate the requirement of long-term follow-up review of these patients before assuming either a cure or arrest of the tumor's growth.

Astrocytoma↗
PubMed1982

Pharmaceutical services in long-term care facilities: a certificate approach to teaching skills.

The University of Tennessee College of Pharmacy has developed a certificate program for Pharmaceutical Services in Long-Term Care Facilities. Pharmacists who are required to provide such services generally have had minimal experience in doing so. The certificate is composed of six home-study courses, a researched paper, and an on-site clerkship experience. Each pharmacist is evaluated for his or her mastery of the material at regular intervals. The program is designed to be completed in 6 months.

Certification↗
PubMed1981

Defect in cyclic AMP phosphodiesterase due to the dunce mutation of learning in Drosophila melanogaster.

Cyclic AMP is an intracellular mediator ('second messenger') in the nervous and endocrine control of cellular function, regulating different processes in different cell types. Although evidence is incomplete, it seems that cyclic AMP enhances the calcium-mediated release of neurotransmitter in some neurones. A simple form of memory in the mollusc Aplysia is probably encoded as a cyclic AMP-induced enhancement of neurotransmission at certain synapses of the central nervous system. The possibility that cyclic AMP participates in learning mechanisms may be explored using genetic mutants. For this purpose the fruitfly Drosophila is suitable as it is genetically well characterized and can learn through olfaction, vision or taste. We show here that independent searches for mutations of olfactory learning and of cyclic AMP metabolism, and for mutations causing female infertility have each led to the same gene--the dunce gene. Our evidence indicates that the normal dunce gene may specify a cyclic AMP phosphodiesterase.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1981

Dunce mutants of Drosophila melanogaster: mutants defective in the cyclic AMP phosphodiesterase enzyme system.

The cyclic AMP and cyclic GMP phosphodiesterase activities present in flies of six mutant strains of the dunce gene and in the parent wild-type strains are characterized. All of the mutants exhibit aberrant cyclic AMP metabolism. The mutant strains dunceM14, dunceM11, and dunceML appear to be amorphic, because they completely lack the cAMP-specific phosphodiesterase normally present in adult flies. These strains exhibit extremely high levels of cAMP. The mutant strains dunce1, dunce2, and dunceCK are hypomorphic and exhibit reduced levels of the cAMP-specific phosphodiesterase. These strains exhibit less marked increases in cAMP content compared with the three amorphic strains. The dunce2 strain possesses a residual enzyme activity that exhibits anomalous kinetics compared with those of the normal enzyme. The possibility that the dunce locus is the structural gene for the cAMP-specific phosphodiesterase is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1981

Cortical damage from Zenker's solution applied to the dura mater.

An experimental and clinical study was undertaken to determine whether Zenker's solution without glacial acetic acid (modified Zenker's solution) applied to the external surface of the dura mater can penetrate to injure the underlying cortex. Adult cats and dogs, the dura of which had an average thickness of 0.2 and 0.25 mm, respectively, were given intravenous Evans blue dye as an indicator of blood-brain barrier breakdown. This was followed by the application of modified Zenker's solution to the dura in a manner identical to the clinical practice. When the animals were killed 1 or 2 hours later, the cortex beneath the dura painted with modified Zenker's solution was stained massively. The thickness of human dura was measured; it varied from 0.22 to 0.28 mm in infants of 3 months or less, 0.27 to 0.42mm in infants 4 months to 12 months of age, and 0.32 to 0.45 mm in children to 1 to 18 years of age. Modified Zenker's solution applied to fresh dura for 3 minutes at autopsy gave visual evidence 1 hour later of penetration to the cortex beneath. In operative procedures for craniosynostosis, 69 patients were treated with modified Zenker's solution; of these, 7 developed seizures in the immediate postoperative period. No seizures occurred among the 39 patients on whom modified Zenker's solution was not used. It is concluded that modified Zenker's solution applied to the dura can damage the cortex beneath.

Acetates↗
PubMed1981

Extraneural metastatic medulloblastoma during childhood.

From 1960 to 1977, 59 patients with histologically confirmed medulloblastoma were initially treated at Childrens Hospital of Los Angeles. Of this group, 49 have died and, of these, 34 were autopsied. Among the autopsied cases, 2 infants had neck masses that proved to be medulloblastoma that had spread from the cerebellar vermis before any surgical intervention. Four additional patients who had undergone a posterior fossa craniectomy without either the pre- or postoperative placement of a cerebrospinal fluid-diverting shunt were found to have extraneural metastatic medulloblastoma at autopsy. The extraneural metastatic medulloblastoma rate in the autopsied cases was 17.6% (6 of 34). Our series shows that the incidence of the extraneural spread of medulloblastoma is associated with being young, being male, and having diffuse tumor involvement of the subarachnoid space.

Age Factors↗
PubMed1980

Medulloblastoma presenting as neck tumors in 2 infants.

Extension of neuroepithelial neoplasms outside the neuraxis, though uncommon, is well known and usually follows surgical intervention. More unusual is the brain tumor that appears beyond the bounds of the central nervous system prior to operative manipulation. Two infants presented with soft tissue masses in the neck that proved to be medulloblastomas. Autopsy examination in both infants showed primary medulloblastoma of the cerebellar vermis with extensive spread through the subarachnoid spaces. The neck masses may have been direct extensions from the central nervous system tumors, though this was not proved in either case.

Cerebellar Neoplasms↗