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Biomedical subjects

F G Diaz

Publications and source records attributed to F G Diaz.

At least 37 records · Page 2Linked to original sources
PubMed2000

Topical insulin and accumulation of excitotoxic and other amino acids in ischemic rat cerebral cortex.

Insulin plays a neuroprotectant role in the brain and spinal cord during ischemia. However, studies have shown insulin to increase the sensitivity of cultured cortical cells to glutamate toxicity. The present study looked at the relationship between topically administered insulin (1 mIU insulin/ml and 100 mIU insulin/ml) during a four-vessel model of global ischemia and the accumulation of amino acids, especially glutamate, from the ischemic rat cerebral cortex. The lower dose of insulin was found to attenuate the release of excitotoxic and other amino acids from the cortex in ischemia/reperfusion. This may occur because insulin increases glucose availability to glial cells resulting in maintenance of glycolysis and ionic pumps that can reduce glutamate release and maintain uptake during ischemia/reperfusion. The higher dose of insulin, which significantly increased the amount of aspartate, glutamate, taurine, and GABA during reperfusion, may act to stimulate the amount of glycogen stored in astrocytes, reducing the availability of glucose for metabolic purposes.

Administration, Topical↗
PubMed2000

Topical glucose and accumulation of excitotoxic and other amino acids in ischemic cerebral cortex.

Pre-ischemic hyperglycemia aggravates brain damage due to transient global ischemia as demonstrated by exacerbation of brain lesions. Lactacidosis and elevated glutamate levels have been implicated as mechanisms of the increased damage. Our objective was to determine the effects of different levels of glucose (0, 66.5, 450 mg/dL) in cortical superfusates on the ischemia/reperfusion-evoked release of amino acids from the rat cerebral cortex. Physiologic levels of glucose significantly reduced the amount of aspartate, glutamate and gamma-aminobutyric acid and the supra-physiologic levels of glucose reduced the amount of aspartate and phosphoethanolamine released from the cortex during ischemia/reperfusion in comparison with no glucose. The decrease in glutamate release may be due to increased availability of glucose for glycolysis with the subsequent formation of ATP and lactate, which has been shown to act as an energy source for neurons. The decreased levels may also reflect the continued energy-dependent uptake of glutamate by glial cells.

Animals↗
PubMed2000

An unusual subdural empyema: case report.

Subdural empyema in a 38-year-old patient with congenital hemangioma, suppurative parotitisis, soft tissue phlegmonia and osteomyelitis is reported. The clinical, radiological and surgical features are outlined. A review of the literature reveals the uniqueness of this case.

Adult↗
PubMed2000

A brief review of the effects of chronic hydrocephalus on the gonadotropin releasing hormone system: implications for amenorrhea and precocious puberty.

Precocious puberty and amenorrhea have been associated with hydrocephalus, but the pathogenesis has not been determined. Approximately 22 cases of amenorrhea, and a few cases of precocious puberty, have been reported in hydrocephalic patients. Shunt treatment leads to initiation and maintenance of normal reproductive cycles in most cases. An underlying mechanism responsible for reproductive dysfunction may involve the role of gonadotrophin releasing hormone (GnRH). The exact pathway by which hydrocephalus disrupts the hypothalamic GnRH system is unknown. However, compressive forces, ischemia, and impairment of neurotransmitter feedback loops are likely candidates.

Amenorrhea↗
PubMed2000

The relationship of blunt head trauma, subarachnoid hemorrhage, and rupture of pre-existing intracranial saccular aneurysms.

Patients with a history of closed head trauma and subarachnoid hemorrhage are uncommonly diagnosed with an intracranial saccular aneurysm. This study presents a group of patients in whom a pre-existing aneurysm was discovered during work-up for traumatic subarachnoid hemorrhage. Without an accurate pre-trauma clinical history, it is difficult to define the relationship between trauma and the rupture of a pre-existing intracranial saccular aneurysm. We retrospectively reviewed 130 patients who presented to Detroit Receiving Hospital between 1993 and 1997 with a diagnosis of subarachnoid hemorrhage (SAH). Of these 130 patients, 70 were spontaneous, and 60 had a history of trauma. Mechanisms of trauma include motor vehicle accident, assault, or fall from a height. Of the 60 patients with subarachnoid hemorrhage and a history of trauma, 51 (86%) did not undergo conventional four-vessel angiography, and had no further neurological sequelae. Nine patients (14%) had a suspicious quantity of blood within the basal cisterns or Sylvian fissure and had a four-vessel angiogram. Five patients (8%) were diagnosed with a saccular intracranial aneurysm, and all underwent surgical clipping of the aneurysm. We conclude that the majority of patients (92%), with post-traumatic SAH do not harbor intracranial aneurysms. However, during initial evaluation, a high level of suspicion must be entertained when post-traumatic subarachnoid hemorrhage is encountered in the basal cisterns or Sylvian fissure, as 8% of our population were diagnosed with aneurysms.

Adult↗
PubMed2000

Cellular transplantation and spinal cord injury.

Spinal cord injury is often characterized by immediate and irreversible loss of sensory and motor functions below the level of injury. Cellular transplantation in various experimental models of spinal cord injury has been used as a strategy for reducing deficits and improving functional recovery. The general strategy has been aimed at promoting regeneration of intrinsic injured axons with the development of alternative pathways that facilitate a partial functional connection. Other objectives of cellular transplantation studies have included replacement of lost cellular elements, alleviation of chronic pain, and modulation of the inflammatory response after injury. This review focuses on the cell types that have been used in spinal cord transplantation studies in the context of evolving biological perspectives, technological advances, and new therapeutic strategies and serves as a point of reference for future studies.

Animals↗
PubMed2000

Impact simulation on pre-formed prosthesis for large cranial defect.

Cranioplasty greater than 10 cm2 in size is challenging task for neurosurgeon. There are many successful trials to fill the small defect with various materials. Proper cranioplasty can provide subsequently restoration of cerebral protection, cosmetic aspect and neuronal function. However, larger defect may not provide adequate protection from the auto, industrial or sport accident even with cranioplasty. In this study, patch design using two popular materials was evaluated and compared with bone material. Then impact-releasing holes were implemented to the patch. The movement of the large patch and its effect on the underlying brain tissue upon simulated impact was evaluated by using finite element analysis.

Biomechanical Phenomena↗
PubMed1999

Patterns of immediate early gene mRNA expression following rodent and human traumatic brain injury.

Cell stimulation which leads to degeneration triggers a prolonged wave of immediate early gene (IEG) transcription that correlates with neuronal demise. In order to determine the relevance of the prolonged IEG response to human traumatic brain injury, we analyzed IEG mRNA levels in brain tissue isolated following a controlled penetrating injury and an injection of the excitotoxin Quinolinic acid (QA), as well as from tissue recovered during routine neurosurgery for trauma. Total RNA was extracted from tissue and subjected to Northern analysis of IEG mRNAs (c-fos and zif/268). Both models produced rapid and prolonged waves of IEG transcription that appeared to correlate with the severity of injury. Increases in zif/268 mRNA were observed within 1 h with levels reaching their peak at 6 h following excitotoxic injury and 3 h following a controlled penetration. In general, human traumatic brain injury resulted in variable increases in IEG mRNA levels following traumatic injury with the largest IEG mRNA increases observed in tissue collected 0-10 h after injury. This post-injury time corresponds to the peak of the prolonged IEG response observed in rodents following excitotoxic injury. Comparisons were made in IEG response between rodent frontal cortex and human cortex, because the majority of the human tissue originated from the cerebral cortex. These results further support the hypothesis that prolonged IEG transcription serves as a marker of traumatic brain injury and may play a role in neurodegeneration and/or glial activation. Moreover, observations of similar IEG patterns of expression reinforces the importance of rodent models of brain injury providing useful information directly applicable to human brain injury.

Animals↗
PubMed1999

Spinal aspergillus osteomyelitis.

Aspergillus species are uncommon etiologic agents of vertebral osteomyelitis. We describe two patients with lumbar vertebral aspergillosis precipitated by the use of corticosteroids and review 39 cases in the literature. The mean age of the population was 40.04 years. There was male predominance (78% of cases), mainly lumbar involvement (53.7%), and monomicrobial nature of infection; 65.8% of the patients had predisposing factors, while 34.1% had none. Back pain (53.6% of cases) was the predominant symptom, while neurological deficits were present in 29.2% of the patients. White blood cell counts were elevated in 12.2% of the patients, and erythrocyte sedimentation rates were >40 mm/h in 39%. The overall recovery rate was 68.3%, and the mortality rate was 26.8%. Although aspergillus osteomyelitis is primarily treated medically, certain cases may require surgical intervention.

Adult↗
PubMed1998

Real-time measurement of ischemia-evoked glutamate release in the cerebral cortex of four and eleven vessel rat occlusion models.

Interstitial levels of the neurotransmitter glutamate and cerebral blood flow changes were compared in two models of rat forebrain ischemia using the dialysis electrode technique and laser doppler flowmetry with brain temperature controlled. Ten-minute periods of cerebral ischemia were elicited by the four and an eleven vessel occlusion and compared to carotid artery transection. Elapsed time from the onset of ischemia to the ischemic plateau was 76.8+/-57.9 s in 4VO vs. 14.8+/-1.3 s in 11VO animals. Percent residual cerebral blood flow (CBF) was 13.5+/-8.8% during 4VO as opposed to 4.5+/-2.9% during 11VO. Concomitantly, cerebral glutamate levels rose to 255. 7+/-72.8 micromol l-1 in the 4VO animals in comparison with levels of 138.5+/-78.7 and 135.7+/-40.2 micromol l-1 in the 11VO and carotid transection animals. During the first 89.6+/-47.4 s of reperfusion, glutamate levels rose to a second higher peak of 315. 1+/-179.2 micromol l-1 in 7 of 12 animals. Following reperfusion, glutamate levels in the 4VO and 11VO animals returned towards basal levels. This study demonstrates that 11VO causes a rapid drop in CBF to near zero levels, better mimicking complete forebrain ischemia than the traditional 4VO technique. Moreover, the 'low flow' state of cerebral ischemia, produced by traditional 4VO, results in a higher interstitial level of glutamate than a 'no flow' state, as exhibited by the 11VO technique. The dialysis electrode, used simultaneously with laser doppler flowmetry, real-time data acquisition, and continuous brain temperature control, in this new rat model, provides real-time evidence that glutamate levels in the interstitial space are enhanced during a low flow state of cerebral ischemia. Furthermore, not before demonstrated, glutamate transients are seen to occur during the first 90 s of reperfusion, and, to the best of our knowledge, the glutamate levels recorded by this technique are the highest in the literature.

Animals↗
PubMed1998

Management of elevated intracranial pressure in patients with Cryptococcal meningitis.

BACKGROUND: The most important predictor of early mortality in patients with HIV-associated cryptococcal meningitis is mental status at presentation; patients who present with altered mental status have up to 25% mortality. Historically, cerebrospinal fluid (CSF) diversion in HIV-negative patients with cryptococcal meningitis and signs of elevated intracranial pressure (ICP) has improved survival. In an effort to affect survival and morbidity rates in patients with HIV-associated cryptococcal meningitis, we have initiated aggressive management of elevated ICP in patients with focal neurologic deficits, mental obtundation, or both. METHODS: We identified 10 patients with HIV-associated cryptococcal meningitis who presented with symptoms consistent with elevated ICP, including headache, mental obtundation, papilledema, and cranial nerve palsies. Elevated opening pressure was defined as > 20 cm CSF during lumbar puncture. In patients with elevated opening pressures who had focal neurologic deficits or mental status changes refractory to serial lumbar puncture, management consisted of immediate placement of lumbar drains for continuous drainage of CSF to maintain normal ICP (10 cm CSF). Patients with persistent elevations of spinal neuraxis pressure following lumbar drainage underwent placement of lumbar peritoneal shunts. RESULTS: All patients returned to their baseline level of consciousness following normalization of ICP. Two patients were weaned from lumbar drainage. Eight patients eventually required placement of lumbar peritoneal shunts for persistently elevated ICP despite successful antifungal therapy. Follow-up ranged from 1 to 15 months. One shunt infection occurred, one lumbar peritoneal shunt was converted to a ventriculoperitoneal shunt, and one shunt was removed. CONCLUSIONS: Elevated ICP in patients with HIV-associated cryptococcal meningitis is a significant source of morbidity and mortality. The use of lumbar drainage and selective placement of lumbar peritoneal shunts in the management of elevated ICP in patients with HIV-associated cryptococcal meningitis can ameliorate the sequelae of elevated ICP.

Adult↗
PubMed1998

Cerebral monitoring devices: analysis of complications.

The use of indwelling cerebral monitoring devices (ICMDs) is common in the intensive care of neurosurgical patients. ICMDs are used to measure and treat intracranial pressure (ICP), temperature, blood flow and the microchemical environment. Intracranial hemorrhage (ICH) and infection are risks of ICMD use [4]. This study presents ICMD use at Detroit Receiving Hospital (DRH) from July 1993- March 1997. Analysis of complications associated with ICMD placement will test the hypothesis that complication rate depends upon type of ICMD used. A log of all patients having ICMDs at DRH has been kept since 1993. This log was used to identify complications of ICMD placement. Each case was reviewed and the following data obtained: diagnosis, patient age, initial Glasgow Coma Score, Glasgow Outcome Score, type of ICMD, number of ICMDs per patient, duration of implant and complication. Descriptive and non-parametric statistics were used to compare samples of interest. The following number of ICMDs were placed: 274 ventriculostomies, 229 Camino intra parenchymal ICP monitors, and 33 other ICMDs. Complications in these 536 cases include 21 infections, 15 ICHs, 1 granuloma and 1 persistent cerebrospinal fluid leak. Complication was analyzed as a function of ICMD type using Chi-Square test for independence. The rate of infection and ICH was significantly higher in the ventriculostomy group (p = 0.0001). These results support the hypothesis that complications of ICMD use are due to the type of device implanted. The determinants of ICMD complication is undoubtedly multifactorial. The clinician must consider the complication rate related to a particular ICMD among other factors when choosing to place an ICMD.

Brain Injuries↗
PubMed1998

Microanatomical considerations for the fenestration of the septum pellucidum.

The anatomical foundations for the endoscopic fenestration of the septum pellucidum have not been presented previously in an isolated fashion. Using a surgical microscope, the microsurgical anatomy of the septum pellucidum, lateral ventricles, and surrounding structures was examined in ten adult brains injected with silicone rubber. The mean anteroposterior length of the septum pellucidum was 41 mm (range 40-42). Its mean height was 13.11 mm (range 12-15) at the level of the foramen of Monro; 10 mm (range 9-11) at the frontal horns, and 8 mm (range 7-10) at the ventricular atrium. One to three septal veins delimited 2 or 3 avascular areas in the septum pellucidum. We found an anterior area which was consistently avascular and large enough to be fenestrated safety. More posterior areas, while avascular, were inconsistent in their size and shape.

Adult↗
PubMed1998

Use of interactive-intraoperative guidance during vertebrectomy and anterior spinal fusion with instrumental fixation: technical note.

Anterior decompressive procedures for the treatment of vertebral tumors have become increasingly popular in an attempt to improve the quality of life, relieve pain, and preserve or restore neurologic function. However, these procedures carry a significant rate of complications including hardware failure, due in part to technical factors. A computer-assisted system allowing for precise preoperative planning and real-time intraoperative interactive image localization has been implemented for spine instrumentation to optimize anterior instrumental fixation. We discuss our initial clinical experience and application to anterior vertebrectomy, and vertebral reconstruction with anterior instrumental fixation. We believe that computer-assisted spine surgery using infrared-based technology offers the necessary elements to make its use fast, reliable, and intuitive, providing an accurate and safe approach for optimization of spine surgery.

Adult↗
PubMed1998

Microsurgical anatomy of the suboccipital segment of the vertebral artery.

The craniocervical regions of seven cadavers (14 sides) injected with silicone rubber were dissected under a Zeiss OPMI surgical microscope. The present study provides a detailed description of the suboccipital segment of the vertebral artery, with particular attention to its loops, branches, supporting osteofibrous structures, adjacent nerves, and surrounding venous structures. Several ligaments fixating the vertebral artery to surrounding structures, which have not been described in previous anatomical studies, were found. The authors propose an anatomically based subdivision of the suboccipital segment of the vertebral artery into five subsegments: infraforaminal, foraminal, supraforaminal, horizontal, and intramembranous. Measurements of surgically and clinically important features were obtained. Surgical approaches to this region are suggested based on a more informed understanding of the local anatomy.

Cadaver↗
PubMed1998

Patterns of heat-shock protein 70 biosynthesis following human traumatic brain injury.

Heat-shock protein 70 (hsp70) is activated upon cellular stress/injury and participates in the folding and intracellular transport of damaged proteins. The expression of hsp70 following CNS trauma has been speculated to be part of a cellular response which is involved in the repair of damaged proteins. In this study, we measured hsp70 mRNA and protein levels within human cerebral cortex subjected to traumatic brain injury. Specimens were obtained during routine neurosurgery for trauma and processed for Northern mRNA and Western protein analysis. The largest increase in hsp70 mRNA levels was detected in trauma tissue obtained 4-6 h following injury. By 24 h, hsp70 mRNA levels were similar to nontrauma comparison tissues. hsp70 protein expression exhibited its greatest increases at 12-20 h post-injury. Immunocytological techniques revealed hsp70 protein expression in cells with neuronal-like morphology at 12 h after injury. These results suggest a role for hsp70 in human cortex following TBI. Moreover, since the temporal induction pattern of hsp70 biosynthesis is similar to that reported in the rodent, our observations validate the importance of rodent brain injury models in providing useful information directly applicable to human brain injury.

Blotting, Northern↗
PubMed1998

Heat-shock protein 72 expression in excitotoxic versus penetrating injuries of the rodent cerebral cortex.

The induction of heat shock protein 72 (hsp72) has been described in various experimental models of brain injury. The present study examined hsp72 expression patterns within the rodent cerebral cortex in experimental paradigms designed to mimic two mechanisms of damage produced by penetration of the cerebral cortex: (1) tissue tearing from the missile track and (2) diffuse excitotoxicity during temporary cavitation and shock wave formation. Adult male Spaque-Dawley rats received controlled penetration (stab) or injection of the NMDA receptor excitotoxin, quinolinic acid (QA), into the frontal cortex and were killed 1-24 h later. Tissue from the lesioned, sham-operated, or contralateral uninjected cortex was processed for Western and immunocytochemical analyses of hsp72 protein expression. By 12 h, both controlled penetration and excitotoxic brain injuries produced significant increases in hsp72 immunoreactivity, which decreased toward control levels at 24 h. However, the severity and regional distribution of hsp72 expression varied between the two models. Specifically, the controlled penetration injury produced many hsp72-expressing cells near the needle track, while immunoreactive cells within the QA-injected cortex were found in the periphery of the lesion site. Morphological assessment of brain sections subjected to dual-labeling procedures demonstrated that cells expressing hsp72 were primarily neuronal in both models of injury. These results suggest that although controlled penetration and diffuse excitotoxicity may induce similar temporal and cellular patterns of hsp72 expression, the spatial location of hsp72-immunoreactive cells may differ between the two models.

Animals↗