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Biomedical subjects

H R Winn

Publications and source records attributed to H R Winn.

At least 145 records · Page 8Linked to original sources
PubMed1991

A comparison of primary cultures of rat cerebral microvascular endothelial cells to rat aortic endothelial cells.

A method to culture rat cerebral microvascular endothelial cells (RCMECs) was developed and adapted to concurrently obtain cultures of rat aortic endothelial cells (RAECs) without subculturing, cloning, or "weeding." The attachment and growth requirements of endothelial cell clusters from isolated brain microvessels were first evaluated. RCMECs required fetal bovine serum to attach efficiently. Attachment and growth also depended on the matrix provided (fibronectin approximately laminin much greater than gelatin greater than poly-D-lysine approximately Matrigel greater than hyaluronic acid approximately plastic) and the presence of endothelial cell growth supplement and heparin in the growth medium. Non-endothelial cells are removed by allowing these cells to attach to a matrix that RCMECs attach to poorly (e.g., poly-D-lysine) and then transferring isolated endothelial cell clusters to fibronectin-coated dishes. These cell cultures, labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarboxyamine perchlorate (DiI-Ac-LDL) and analyzed using flow cytometry, were 97.7 +/- 2.6% (n = 6) pure. By excluding those portions designed to isolate brain microvessels, the method was adapted to obtain RAEC cultures. RAECs do not isolate as clusters and have different morphology in culture, but respond similarly to matrices and growth medium supplements. RCMECs and RAECs have Factor VIII antigen, accumulate DiI-Ac-LDL, contain Weibel-Palade bodies, and have complex junctional structures. The activities of gamma-glutamyl transferase and alkaline phosphatase were measured as a function of time in culture. RCMECs had higher enzymatic activity than RAECs. In both RCMECs and RAECs enzyme activity decreased with time in culture. The function of endothelial cells is specialized depending on its location. This culture method allows comparison of two endothelial cell cultures obtained using very similar culture conditions, and describes their initial characterization. These cultures may provide a model system to study specialized endothelial cell functions and endothelial cell differentiation.

Animals↗
PubMed1991

Symptomatic cerebral vasospasm following tumor resection: report of two cases.

The authors report two cases of symptomatic cerebral vasospasm following resection of an acoustic neuroma and a left sphenoid wing meningioma. Vascular spasm was documented by transcranial Doppler and angiography studies. Both patients responded to hypervolemic therapy. Possible mechanisms contributing to this rare complication are discussed.

Adult↗
PubMed1991

Two cases of fatal atlantoaxial distraction injury without fracture or rotation.

Atlantoaxial injuries, regardless of mechanism, typically result in bony injury. We present two unusual cases of fatal traumatic C-1-C-2 distraction without associated fracture or rotation. The ligamentous anatomy, common underlying structural/medical predispositions, and the possible mechanism of injury are discussed.

Adult↗
PubMed1991

Results of neutron radiosurgery for inoperable arteriovenous malformations of the brain.

Twenty patients with inoperable arteriovenous malformations (AVMs) of the brain were treated with neutron radiosurgery. A 50 MeV cyclotron was used to deliver 9 Gy in a single fraction through 7 to 14 isocentric portals. The size and shape of the portals were customized to each treatment site. Nineteen patients have been followed for a median duration of 24 months following neutron radiosurgery. A radiographically demonstrable partial response was seen in 8 patients (42%). No complete responses were observed. There has been one post-treatment hemorrhage, no fatalities, and no evidence of radiation toxicity. The low response rate and absence of toxicity suggest that the appropriate dose for neutron radiosurgical treatment of AVMs is higher than the dose of 9 Gy at isocenter used in this initial study.

Adult↗
PubMed1991

Lack of sympathetic and cholinergic influences on cerebral vasodilation caused by sciatic nerve stimulation in the rat.

We studied the influences of sympathetic and cholinergic mechanisms on pial arteriolar responses during cortical activation in the rat. Adult male Sprague-Dawley rats were anesthetized with alpha-chloralose and urethane and mechanically ventilated. Pial arterioles on the somatosensory cortex were visualized on a video monitor through a closed cranial window. Changes in arteriolar diameter induced by sciatic nerve stimulation (0.2 V, 5 Hz, 5 ms, for 20 s) were measured before and after (a) ipsilateral superior cervical ganglionectomy (n = 5), (b) intravenous (0.5 mg/kg) administration and topical (10(-5) M) application of atropine (n = 5), and (c) lesion of the nucleus basalis magnocellularis (the major source of intracerebral acetylcholine neurons, n = 7). Unilateral nucleus basalis magnocellularis lesions were performed stereotactically by injection of ibotenic acid (25 nmol/microliter). Sensory cortex cholinergic denervation was confirmed histologically. These treatments had no significant effect on arteriolar responses to sciatic nerve stimulation. Thus, the present results suggest that neither sympathetic nor cholinergic mechanisms play a significant role in somatosensory evoked cerebral vasodilation.

Animals↗
PubMed1991

Adenosine release and changes in pial arteriolar diameter during transient cerebral ischemia and reperfusion.

We utilized the closed cranial window technique in the anesthetized rat to determine changes in CSF concentrations of adenosine, inosine, and hypoxanthine and pial arteriolar diameter during transient (20 min) forebrain ischemia and reperfusion. After mock CSF under the cranial window was allowed to equilibrate with cerebral interstitial fluid, endogenous adenosine concentration was found to be 0.16 +/- 0.05 microM, while inosine and hypoxanthine were 0.35 +/- 0.17 and 1.23 +/- 0.47 microM, respectively. The concentration of adenosine in CSF increased 4.2-fold during ischemia and 13.8-fold during the first 5 min of reperfusion. Inosine and hypoxanthine concentrations were also significantly increased during ischemia and reperfusion. After 1 h of reperfusion, CSF adenosine and inosine levels had decreased from peak value but remained significantly above preischemic values. In contrast, hypoxanthine remained at peak concentrations even after 60 min of reperfusion. Preischemic arteriolar diameter was 42.6 +/- 11.3 microns and was not significantly changed after 20 min of ischemia. However, during the first 5 min of reperfusion, arteriolar diameter increased significantly (p less than 0.05), coincident with peak adenosine concentrations. By 60 min of reperfusion, arteriolar diameter had returned to baseline. These results indicate that during the postischemic period, adenine nucleosides and hypoxanthine in CSF are elevated and could affect reperfusion.

Adenosine↗
PubMed1991

Effects of topical adenosine analogs and forskolin on rat pial arterioles in vivo.

We utilized the closed window technique to study the in vivo responses of rat pial arterioles to superfused adenosine agonists. Adenosine and its analogs dilated pial arterioles and exhibited the following order of potency: 5'N-ethylcarboxamide adenosine (NECA) greater than 2-chloroadenosine (2-CADO) greater than adenosine = R-N6-phenylisopropyladenosine (R-PIA) = S-PIA greater than N6-cyclohexyladenosine (CHA). This potency profile suggests that cerebral vasodilation is mediated through the A2 receptor. Forskolin (10(-9) M) potentiated the vasodilation caused by 10(-6) M NECA, thus implicating adenylate cyclase activation during NECA-induced vasodilation and providing further support for involvement of the A2 receptor.

2-Chloroadenosine↗
PubMed1991

Posterior cervical arthrodesis with AO reconstruction plates and bone graft.

The efficacy of posterior arthrodesis of the cervical spine with AO reconstruction plates and autogenous bone graft was evaluated in a prospective study. The technique of surgical exposure and the application of the reconstruction plates fixed with screws to the lateral masses is described in detail. Of 30 patients with unstable cervical spines, all had solid fusions based on flexion and extension radiographs at follow-up averaging 17.8 months. No patient's neurologic function deteriorated. All incomplete spinal cord injuries improved at least one Frankel level. There were no neurologic or vascular complications. At follow-up, three patients had fusions extending one level longer than those instrumented. Three other patients had an increase in kyphosis compared with the operative reduction, which was not clinically significant. Although a single screw loosened in three other patients, none had an increased deformity, and all progressed to successful arthrodesis. This technique is particularly advantageous when spinous processes, laminas, and facets are injured or deficient, or when facet-type fusions are indicated.

Adolescent↗
PubMed1991

Influence of hyperglycemia on cerebral adenosine production during ischemia and reperfusion.

We hypothesized that systemic hyperglycemia would alter cerebral adenosine concentrations during ischemia and reperfusion. In the present study, we analyzed brain tissue and cerebrospinal fluid (CSF) from hyperglycemic and normoglycemic rats before ischemia, after 15 min of incomplete forebrain ischemia, and during 60 min of reperfusion. Hyperglycemic rats received 3 g/kg of 17% D-glucose intraperitoneally, which increased blood glucose to 357 +/- 23 mg/100 ml compared with 128 +/- 12 mg/100 ml in normoglycemic rats. Brain tissue was sampled by the freeze-blow technique, and CSF was obtained by collecting cortical perfusate from the closed cranial window. Tissue and CSF were analyzed for adenosine and its metabolites inosine and hypoxanthine, and tissue was also analyzed for adenine nucleotides. Hyperglycemia significantly attenuated the increase in brain tissue and CSF adenosine and its metabolites during ischemia while preserving adenine nucleotide concentrates. This attenuation of ischemic adenosine production persisted after 5 min of reperfusion in tissue and throughout 60 min of reperfusion in CSF. Because adenosine, a cerebral vasodilator, can inhibit the release of neuronal excitotoxins as well as affect neutrophil-endothelial interactions, adenosine has been proposed as an endogenous neuroprotector. Thus the attenuation of adenosine and its metabolites may be a factor in the pathogenesis of increased ischemic brain injury associated with systemic hyperglycemia.

Adenine Nucleotides↗
PubMed1991

Hyperglycemia and neurological outcome in patients with head injury.

To examine the relationship between serum glucose and the outcome of patients suffering from head injury, the authors retrospectively reviewed the clinical course of 169 patients admitted for treatment to Harborview Medical Center (a regional trauma center). All patients underwent craniotomy for evacuation of intracranial hematoma and/or placement of a subarachnoid bolt for intracranial pressure monitoring under general anesthesia. Patients with a Glasgow Coma Scale (GCS) score of 8 or less had significantly higher serum glucose levels than patients with GCS scores of 12 to 15 (mean +/- standard error of the mean 192 +/- 7 mg/dl vs. 130 +/- 8 mg/dl or 10.7 +/- 0.4 mmol/liter vs. 7.2 +/- 0.4 mmol/liter) (p less than 0.0001). Patients who subsequently remained in a vegetative state or died had significantly higher glucose levels both on admission and postoperatively than patients who had good outcome or moderate disability (217 +/- 12 mg/dl vs. 167 +/- 6 mg/dl or 12.1 +/- 0.7 mmol/liter vs. 9.3 +/- 0.3 mmol/liter on admission, and 240 +/- 16 mg/dl vs. 156 +/- 5 mg/dl or 13.3 +/- 0.9 mmol/liter vs. 8.9 +/- 0.3 mmol/liter postoperatively) (p less than 0.0001). Among the more severely injured patients (GCS score less than or equal to 8), a serum glucose level greater than 200 mg/dl (11.1 mmol/liter) postoperatively is associated with a significantly worse outcome (p less than 0.01). The authors conclude that severely head-injured patients frequently develop hyperglycemia and the elevated serum glucose level may aggravate ischemic insults and worsen the neurological outcome in such patients.

Adult↗
PubMed1991

Induction of transformational changes in normal endothelial cells by cultured human astrocytoma cells.

Endothelial cell proliferation is a significant biological feature of malignant astrocytomas. The ability of the cells of these tumors to elaborate mitogenic angiogenesis factors has been well documented. However, less is known about the transformational effects that neoplastic astrocytes may have on the endothelial cells within malignant astrocytomas. In this study, the hypothesis that humoral factors elaborated by cells derived from malignant astrocytomas induce transformational changes in normal endothelial cells in vitro is investigated. Conditioned medium (CM) was prepared from exponentially growing cultures of a human glioblastoma cell line (UW18) and from two rat brain-tumor cell lines: an anaplastic astrocytoma (R175A) and a glioblastoma with sarcomatous elements (9L). Subconfluent target bovine aortic arch endothelial cells (BAEC's) were exposed for 48 hours to varying concentrations of CM prepared from each of these tumors, and then evaluated for transformational changes. Different molecular weight (MW) fractions of UW18 CM were prepared by molecular ultrafiltration, and each fraction was tested for transforming activity. Transformation endpoints included changes in cellular deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) content and distribution (measured by differential flow cytometry) and changes in de novo DNA synthesis determined by 3H-thymidine incorporation. Significant changes in the amount and distribution of DNA and RNA were observed in the BAEC's treated with UW18 CM compared to untreated BAEC's. At 10% concentrations of UW18 CM, changes in the RNA profile of target BAEC's were evident, and at 30% concentrations of UW18 CM, an irregular bimodal distribution was well established. Patterns of DNA were also altered in a concentration-dependent manner, with significant aneuploidy developing at UW18 CM concentrations of 20%. The DNA synthesis in BAEC's increased with increasing CM concentrations, up to a maximum of about 250% of control values at 30% concentrations of UW18 CM. The transformational changes induced after exposure of BAEC's to CM prepared from R175A and 9L were significantly less than those observed with UW18 CM. Molecular ultrafiltration was used to prepare UW18 CM fractions with MW cutoffs of less than 10 kD, 10 to 30 kD, and greater than 30 kD. Transformational activity was significant only in CM's with an MW of 10 to 30 kD. It is concluded that the UW18 human glioblastoma cell line elaborates a soluble factor, or group of factors, with an MW in the 10- to 30-kD range, capable of inducing transformational alterations in target normal endothelial cells, and that such transformation may account for some of the abnormal endothelial cell changes associated with malignant astrocytomas.

Aneuploidy↗
PubMed1991

Management of head injury. Posttraumatic seizures.

Posttraumatic seizures are relatively common among patients with severe head injuries, with major risk factors being penetrating head wound, hematoma, depressed skull fracture, and, for late seizures, early seizures. Management of late posttraumatic seizures, if they do develop, follows the treatment of patients with epilepsy. Their treatment should be determined by the type of seizure (i.e., partial or generalized) and the individual responsiveness of the patient to drug therapy. Prophylactic administration of antiepileptic drugs to prevent posttraumatic epilepsy has been frequently tried. The data supports a short-term but not a long-term effect of the most commonly used drug, phenytoin. A decision of whether to use prophylaxis, with what, and for how long needs to consider the likely benefit (i.e., the chance of seizures if untreated and the likelihood that the proposed treatment will substantially reduce that chance) and risk (i.e., medical or behavioral adverse effects) of this treatment strategy.

Adult↗
PubMed1991

Relative effects of brain and non-brain injuries on neuropsychological and psychosocial outcome.

Based on the 242 consecutive surviving head injury cases and 132 general trauma cases, this study examined the contribution of brain and non-brain injuries to cognitive and psychosocial outcome 1 month postinjury. The study also examined the relationships among various head injury severity indices. The head injury severity indices were all correlated but patients with Glasgow Coma Scale scores in the mild range had broadly ranging scores on the other head injury severity indices (Abbreviated Injury Scale and time to follow commands). Neuropsychological outcome was related to brain injury severity, but was not independently influenced by severity of other systems injuries. Psychosocial outcome related to both brain and non-brain injuries independently. When evaluating trauma outcome, it is important to consider the contributions of both brain and other system injuries.

Abbreviated Injury Scale↗
PubMed1990

A randomized, double-blind study of phenytoin for the prevention of post-traumatic seizures.

BACKGROUND: Antiepileptic drugs are commonly used to prevent seizures that may follow head trauma. However, previous controlled studies of this practice have been inconclusive. METHODS: To study further the effectiveness of phenytoin (Dilantin) in preventing post-traumatic seizures, we randomly assigned 404 eligible patients with serious head trauma to treatment with phenytoin (n = 208) or placebo (n = 196) for one year in a double-blind fashion. An intravenous loading dose was given within 24 hours of injury. Serum levels of phenytoin were maintained in the high therapeutic range (3 to 6 mumol of free phenytoin per liter). Follow-up was continued for two years. The primary data analysis was performed according to the intention to treat. RESULTS: Between drug loading and day 7, 3.6 percent of the patients assigned to phenytoin had seizures, as compared with 14.2 percent of patients assigned to placebo (P less than 0.001; risk ratio, 0.27; 95 percent confidence interval, 0.12 to 0.62). Between day 8 and the end of year 1, 21.5 percent of the phenytoin group and 15.7 percent of the placebo group had seizures; at the end of year 2, the rates were 27.5 percent and 21.1 percent, respectively (P greater than 0.2 for each comparison; risk ratio, 1.20; 95 percent confidence interval, 0.71 to 2.02). This lack of a late effect could not be attributed to differential mortality, low phenytoin levels, or treatment of some early seizures in patients assigned to the placebo group. CONCLUSIONS: Phenytoin exerts a beneficial effect by reducing seizures only during the first week after severe head injury.

Adult↗
PubMed1990

Vancomycin pharmacokinetics in hydrocephalic shunt prophylaxis and relationship to ventricular volume.

Vancomycin pharmacokinetics were determined in 25 patients receiving ventriculoperitoneal shunts for hydrocephalus. Computed tomography scan-derived ventricular-brain ratio as an expression of hydrocephalus varied between 9.3% and 15.4% (12.9% +/- 1.7%). One hour prior to surgery each patient received 1 g of vancomycin infused intravenously over 60 minutes. Samples of cerebrospinal fluid and venous blood were obtained 1 hour later and vancomycin levels assayed by fluorescence polarization immunoassay. There were 11 females and 14 males, with a mean age of 44.5 +/- 10.3 years and a mean weight of 72.0 +/- 11.4 kg. All had normal renal function. Levels of vancomycin in the cerebrospinal fluid at 1 hour ranged from 0.1 to 1.5 micrograms/mL (0.9 +/- 0.3). Weight did not affect these values (p greater than 0.1). Simultaneous blood vancomycin levels varied between 9.1 and 38.7 micrograms/mL (22.3 +/- 8.3). Ventricular volume, expressed as the ventricular-brain ratio, did not correlate with cerebrospinal fluid vancomycin levels (p greater than 0.5). There was no significant increase in concentrations of vancomycin in CSF as cerebrospinal fluid protein concentration increased, nor when blood vancomycin concentration was greater than 20 mg/dL (therapeutic range) (p greater than 0.1). No patient had evidence of infection at 6 months follow up. These results indicate minimal cerebrospinal fluid penetrance of vancomycin when administered systemically 1 hour prior to shunt surgery. In addition concentrations of vancomycin in cerebrospinal fluid bear no relationship to weight, ventricular volume, meningeal inflammation, or blood levels in the therapeutic range. The minimum inhibitory concentration of vancomycin for staphylococci is 1.5 to 3.1, and as bactericidal levels of 5 to 8 minimum inhibitory concentration are needed to kill organisms, a combination of both systemic and intraventricular vancomycin may be needed to ensure adequate cerebrospinal fluid and tissue concentration of antibiotic during shunt prophylaxis.

Adult↗
PubMed1990

Role of adenosine in regulation of regional cerebral blood flow in sensory cortex.

We have previously demonstrated that rat pial arterioles located on the somatosensory cortex dilated in response to contralateral sciatic nerve stimulation (SNS). We hypothesized that the vasodilation was mediated by adenosine, released as a result of somatosensory cortex activation. To test this hypothesis, we examined the effects of SNS (0.15-0.2 V, 5 ms, 5 Hz for 20 s) on pial arterioles under conditions of altered adenosine availability. Cerebrospinal fluid (CSF) adenosine was altered by perfusing mock CSF, under a cranial window in anesthetized rats, containing either an adenosine uptake competitor (dipyridamole or inosine) or an adenosine receptor blocker (theophylline). With CSF only, SNS caused pial arterioles (resting diam, 29 +/- 1 micron) to dilate by 38 +/- 10% (peak magnitude) for 32 +/- 2 s. Dipyridamole (10(-6) M) significantly (P less than 0.02) enhanced both the magnitude (to 62 +/- 12%) and duration (to 68 +/- 10 s) of the response. Similarly, inosine (10(-3) M) significantly (P less than 0.02) potentiated the vasodilative response from resting values of 27 +/- 5% and 34.8 +/- 4.1 s to 37 +/- 6% and 89.6 +/- 14.1 s. In contrast, theophylline (5 x 10(-5) M) significantly (P less than 0.001) attenuated arteriolar vasodilation from resting values of 38 +/- 5% and 29.3 +/- 1.2 s to 18 +/- 3% and 22.0 +/- 0.9 s. Neither dipyridamole nor theophylline had a significant effect on neuronal response (sensory-evoked response) recorded from the somatosensory cortex. These results suggest that adenosine is involved in the regulation of pial vasodilation during cerebral cortical activation.

Adenosine↗
PubMed1990

Postoperative CT contrast enhancement following lobectomy for epilepsy.

Contrast-enhanced computerized tomography (CT) is frequently utilized immediately after surgery to determine the presence of residual tumor, but the response of nontumor brain tissue is unclear. Consequently, the authors investigated the postoperative CT contrast enhancement in six patients undergoing lobectomy for epilepsy. Preoperative CT scans were obtained in all cases and revealed no enhancing lesions. All patients underwent craniotomy with electrocorticography while awake, followed by lobectomy. Computerized tomography scans with and without administration of contrast material were obtained on postoperative Days 3, 7, and 30. Edema, artifact, and enhancement of the resection margins were seen on postoperative Days 3 and 7, but had resolved in all patients by Day 30. It is concluded that postoperative CT scans for assessment of residual tumor are best obtained at 30 days or thereafter, when normal brain does not enhance and edema and artifact have diminished.

Adult↗