Estrogen and Bcl-2: gene induction and effect of transgene in experimental stroke.

Female rodents producing endogenous estrogens are protected from stroke damage in comparison with male counterparts. This natural protection is lost after ovariectomy or reproductive senescence. The aim of this study is to determine whether estrogen reduces early neuronal injury and cell loss after ischemia by increasing the expression of Bcl-2. Male, intact female, ovariectomized, and estrogen-repleted ovariectomized rats were subjected to middle cerebral artery occlusion, and 22 hr later the level and localization of Bcl-2 mRNA and protein were determined. The levels of post-ischemic bcl-2 mRNA and protein were increased exclusively in neurons within the peri-infarct region. Intact females and estrogen-treated castrates demonstrated increased bcl-2 mRNA and protein expression compared with males and estrogen-deficient females, accompanied by a decrease in infarct size. To test the hypothesis that the neuroprotective mechanism of estrogen functions via Bcl-2, we compared ischemic outcome in male, female, and ovariectomized wild-type mice and mice overexpressing Bcl-2 exclusively in neurons. Wild-type female mice sustained smaller infarcts compared with males. Bcl-2 overexpression reduced infarct size in males, but provided no added protection in the female. Moreover, ovariectomy exacerbated infarction in wild-type females, but had no effect in Bcl-2 overexpressors. These data indicate that overexpression of Bcl-2 simulates the protection against ischemic injury conferred by endogenous female sex steroids. We concluded that estrogen rescues neurons after focal cerebral ischemia by increasing the level of Bcl-2 in peri-infarct regions and that estrogen-induced bcl-2 gene expression is an important downstream component of neuronal protection in female stroke.

Microglia are not exclusively associated with plaque-rich regions of the dentate gyrus in Alzheimer's disease.

The functional significance of microglia found in neuritic plaques in Alzheimer's disease (AD) remains a source of controversy. In the present study, we explored the anatomic relationships between microglia and neuritic plaques in order to determine the potential role of microglia in plaque formation. We chose to study the molecular layer of the hippocampal dentate gyrus, a brain region where plaques have a strong tendency to line up parallel to the adjacent granule cell layer. We found that ferritin-labeled microglia were indeed most numerous in the same distinct band as plaques, but that microglia were relatively more common in the outer molecular layer. The distribution of microglia was more variable than that of plaques. Overall, microglial cell distribution was a relatively poor predictor of plaque distribution, particularly when cases were considered individually. Thus, there must be multiple triggers for microglial cell activation and accumulation in the AD brain, triggers which do not all necessarily lead to neuritic plaque formation.

Interlaboratory comparison of neuropathology assessments in Alzheimer's disease: a study of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD)

Concerns about intercenter variation in methods and interpretation prompted CERAD investigators to examine standardization of the neuropathological assessment of Alzheimer's disease (AD). Contiguous frontal lobe sections derived from autopsy brains of eight patients clinically diagnosed as having probable AD and two cognitively normal individuals were distributed to 24 neuropathologists from 18 medical centers in the United States and Canada. Using their routine staining method(s), neuropathologists determined the rank order of severity of AD neuropathology in these cases, as well as semiquantitative and quantitative senile plaque and neurofibrillary tangle frequencies. Ranking of the ten cases revealed 75% inter-rater reliability among the 24 raters. Semiquantitative analyses showed reasonable inter-rater agreement, whereas quantitative measures yielded significant differences between raters for plaque and tangle counts (p < 0.0001). These differences reflected variation in stain sensitivity, staining technique (even when the same stain was used), and interpretation of the histological findings. Ratings on the cases with the highest proportions of diffuse plaques showed the greatest dependence upon stain sensitivity and variability in interpretation. This study indicates that greater attention to quality improvement is needed for the neuropathological evaluation of AD, particularly when pooling data in multicenter studies such as CERAD.

Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1 S169L mutation in a case of familial AD with myoclonus and seizures.

We report clinical, neuropathologic and molecular genetic data from an individual affected by a familial Alzheimer disease (AD) variant. The proband had an onset of dementia at age 29 followed by generalized seizures a year later. He died at age 40. Neuropathologically, he had severe brain atrophy and characteristic histopathologic lesions of AD. Three additional neuropathologic features need to be emphasized: 1) severe deposition of Abeta in the form of diffuse deposits in the cerebral and cerebellar cortices, 2) numerous Abeta deposits in the subcortical white matter and in the centrum semiovale, and 3) numerous ectopic neurons, often containing tau-immunopositive neurofibrillary tangles, in the white maner of the frontal and temporal lobes. A molecular genetic analysis of DNA extracted from brain tissue of the proband revealed a S169L mutation in the Presenilin 1 (PSEN1) gene. The importance of this case lies in the presence of ectopic neurons in the white matter, early-onset seizures, and a PSEN1 mutation. We hypothesize that the PSEN1 mutation may have a causal relationship with an abnormality in neuronal development.

Regionally selective effects of NMDA receptor antagonists against ischemic brain damage in the gerbil.

This study compared the ability of three N-methyl-D-aspartate (NMDA) receptor antagonists to prevent neuronal degeneration in an animal model of global cerebral ischemia. The model employed is characterized by damage to the striatum, hippocampus, and neocortex. Antagonists were administered to gerbils either before or after a 5-min bilateral carotid occlusion. The intraischemic rectal temperature was either maintained at 36-37 degrees C or allowed to fall passively to 28-32 degrees C. Antagonists and doses tested were 1 and 10 mg/kg of MK-801 (pre- or postischemia), 30 mg/kg of CGS 19755 preischemia, four 25 mg/kg doses of CGS 19755 administered between 0.5 and 6.5 h postischemia, and 40 mg/kg of MDL 27,266 (pre- or postischemia). All three NMDA receptor antagonists exhibited some degree of neuroprotective activity when the carotid occlusion was performed under normothermic conditions. Most of the treatments with antagonist markedly reduced striatal damage. CA1 hippocampal and neocortical pyramidal cells were spared by only three of the treatments, however, and the extent of neuroprotection varied widely from case to case. Toxic doses of antagonist were required to protect CA1 pyramidal cells from ischemic damage. Ischemic damage to hippocampal areas CA2-CA3a and CA4 appeared to be resistant to all of these treatments. Most CA1 pyramidal cells that were protected from degeneration by an NMDA receptor antagonist were histologically abnormal. The neuroprotective effects of MK-801 and intraischemic hypothermia appeared to be additive. MK-801 (10 mg/kg) consistently reduced the postischemic brain temperature, but only the magnitude of hypothermia produced soon after reperfusion correlated with its neuroprotective action. These results suggest that NMDA receptor antagonists are relatively poor neuroprotective agents against a moderately severe ischemic insult.

Estrogen receptor antagonist ICI182,780 exacerbates ischemic injury in female mouse.

Recent findings in animals emphasize that experimental ischemic brain damage can be strikingly reduced by estrogen: however, the neuroprotective mechanisms are not well understood. It was hypothesized that estrogen signaling via cognate estrogen receptors (ERs) within the vasculature is an important aspect of cerebral ischemic protection in the female brain, in part by amplifying intraischemic cerebral blood flow (CBF). In the present study, the hypothesis that chronic treatment with the pure ER antagonist ICI182,780 (ICI) would increase ischemic brain damage by a blood flow-mediated mechanism was investigated. Adult C57B1/6J mice were pretreated with either subcutaneous ICI (100 microg/day) or oil/ethanol vehicle for 1 week before 2 hours of middle cerebral artery occlusion (MCAO) and 22 hours of reperfusion. End-ischemic regional CBF was evaluated in additional cohorts using [14C]iodoantipyrine autoradiography. Infarction volume as measured by cresyl violet histology was greater in the striatum of ICI-treated females (70 +/- 3% of contralateral striatum vs. 40 +/- 12% in vehicle-treated females). Cortical injury was not enhanced relative to control animals (39 +/- 6% of contralateral cortex in ICI group vs. 27 +/- 8% in vehicle-treated group). Physiologic variables and ischemic reduction of the ipsilateral cortical laser-Doppler flow signal were similar between groups. Further, ICI treatment did not alter end-ischemic cortical or striatal CBF. The deleterious effect of ICI was limited to females, as there were no differences in stroke damage or CBF between male treatment groups. These data suggest that estrogen inhibits ischemic brain injury in striatum of the female by receptor-mediated mechanisms that are not linked to preservation of intraischemic CBF.

The normal organization of the lateral posterior nucleus of the golden hamster.

As a first step in analyzing the influence of various afferent projections on the development of the hamster lateral posterior nucleus, its normal organization was studied using both light and electron microscopic techniques. Rostrolateral, rostromedial, and caudal subdivisions were identified. The rostrolateral subdivision receives dense projections from the ipsilateral superior colliculus and posterior neocortex, as well as sparser, more restricted projections from the contralateral colliculus and retina. The ipsilateral colliculus is by far the major source of medium-sized (M)terminals with round vesicles. These terminals synapse around the shafts of large central dendrites to form distinctive synaptic clusters. The contralateral colliculus and retina contribute a few M-terminals to the clusters. In contrast, axons from the posterior neocortex form very large (RL-)terminals with round vesicles from the posterior neocortex form very large (RL)terminals with round vesicles which synapse onto numerous appendages of single proximal dendrite, are surrounded by glial lamellae, and rarely participate in the clusters. Axons from all four sources also form small (RS)terminals with round vesicles which synapse on the shafts of small dendrites. Finally, F-terminals with flat or pleomorphic vesicles form symmetric synaptic contacts both within and outside the clusters. The only identified projection to the rostromedial subdivision is from the ipsilateral posterior neocortex, which contributes RL- and RS-terminals. F-terminals are also found, but neither M-terminals nor synaptic clusters are present. The caudal subdivision also receives RL- and RS-terminals from the ipsilateral posterior neocortex. Small inputs from the ipsilateral and contralateral colliculi are present, but their axons form only RS-terminals. No M-terminals or synaptic clusters are found. These results indicate that a large neonatal superior colliculus lesion would eliminate the vast majority of the M-terminals in the synaptic clusters of the ipsilateral lateral posterior nucleus. In subsequent studies (Crain and Hall, '80 a,b,c), we will examine how the remaining inputs from the retina, contralateral superior colliculus, and posterior neocortex contribute to the synaptic organization when it develops after such a lesion.

The organization of the lateral posterior nucleus in neonatal golden hamsters.

The present series of experiments was designeneonatal golden hamsters.

The organization of afferents to the lateral posterior nucleus in the golden hamster after different combinations of neonatal lesions.

After a neonatal lesion of the ipsilateral superior colliculus, the projections to the lateral posterior nucleus from the contralateral superior colliculus and retina expand their terminal fields until they share a common border. In the first experiment described in this paper, we removed both superior colliculi at birth and used the Fink-Heimer method to show that the optic tract projection could expand even further and enter the region which would have been occupied by the terminals of the crossed colliculus projection. Similarly, in the second experiment, we showed that the crossed collicular projection could be increased even more if the contralateral eye as well as the ipsilateral colliculus was removed at birth. Another result of a neonatal superior colliculus lesion is that the projection from the optic tract shares a border with the posterior neocortical projection. In the third experiment, we removed both the ipsilateral superior colliculus and the posterior neocortex at birth and demonstrated that the optic tract projection expanded more than after an ipsilateral colliculus lesion alone. Our results support the hypotheses that the projections from the ipsilateral and contralateral superior colliculi and the retina compete for synaptic space in the lateral posterior nucleus, and that a similar competition between the retinal and cortical projections may also occur.

The organization of the lateral posterior nucleus of the golden hamster after neonatal superior colliculus lesions.

The reorganization of the adult hamster's lateral posterior nucleus after neonatal superior colliculus lesions was studied using primarily light and electron microscopic degeneration techniques. Two types of experiments were conducted. First, the distributions of the remaining afferents from the contralateral superior colliculus, the cotralateral retina, and the ipsilateral posterior neocortex were determined using the Fink-Heimer ('67) technique. Normally the projections from the contralateral superior colliculus and retina are sparse and restricted to small areas in the rostrolateral subdivision. After neonatal lesions of the ipsilateral colliculus, however, these two minor projections greatly increase in density and expand to share a common border. In contrast, the normal projection from the posterior neocortex is dense throughout the rostrolateral subdivision. After a neonatal colliculus lesion, however, this projection is greatly decreased in the region occupied by the optic tract terminals. Second, the ultrastructural organizatin of the rostrolateral subdivision was studied in adult animals whhich had received neonatal colliculus lesions. Normally, this region is characterized by synaptic clusters in which numerous medium-sized terminals (M-terminals), almost all from the ipsilateral colliculus, synapse around the shaft of a large central dendrite. The contralateral colliculus and retina normally contribute only a few M-terminals. After a neonatal colliculus lesion, typical clusters still form, but now the expanded projections from the contralateral colliculus and retina contribute numerous M-terminals. The cortex does not contribute M-terminals in either normal or experimental animals. These results suggest that the afferents to the rostrolateral subdivision normally compete for synaptic space. The various factors that might be involved in determining the outcome of such competition are discussed.

Quantitative autoradiographic analysis of mu and delta opioid binding sites in the rat hippocampal formation.

The distributions of mu and delta opioid binding sites were studied in rat hippocampal formation by using quantitative in vitro autoradiography. Mu binding sites, labeled with 125I-FK-33824, showed a highly organized laminar distribution. Binding was greatest at the foot of the obliterated hippocampal fissure in stratum lacunosum-moleculare of CA3. Stratum pyramidale and stratum lacunosum-moleculare of CA2 and stratum pyramidale of CA3 were next highest in mu binding, followed by stratum oriens and stratum radiatum of CA2, stratum oriens of CA3, and stratum pyramidale of CA1. The distribution of delta binding sites, labeled with 125I-D-ala2-D-leu5-enkephalin in the presence of the unlabeled mu receptor ligand PL-032, was similar to the distribution of mu binding in that binding within each region was greatest in a band centered over stratum pyramidale and in stratum lacunosum-moleculare. Over all, delta binding was greatest in CA2 followed by CA3 and then CA1. Compared to mu binding, delta binding was relatively enriched in stratum moleculare of the dentate gyrus. These laminar distributions correlate reasonably well with the distribution of enkephalin immuno-reactivity in hippocampal formation, although binding was surprisingly low in stratum lucidum, an area rich in dynorphin and enkephalin immunoreactivity.

Evaluation of cerebral biopsies for the diagnosis of dementia.

To identify those patients most likely to benefit from a cerebral biopsy to diagnose dementia, we reviewed a series of 14 unselected biopsies performed during a 9-year period (1980 through 1989) at Duke University Medical Center, Durham, NC. Pathognomonic features allowed a definitive diagnosis in seven specimens. Nondiagnostic abnormalities but not diagnostic neuropathologic changes were seen in five additional specimens, and two specimens were normal. Creutzfeldt-Jakob disease was the most frequent diagnosis. One patient each was diagnosed as having Alzheimer's disease, diffuse Lewy body disease, adult-onset Niemann-Pick disease, and anaplastic astrocytoma. We conclude that a substantial proportion of patients presenting clinically with atypical dementia are likely to receive a definitive diagnosis from a cerebral biopsy. However, in those with coexisting hemiparesis, chorea, athetosis, or lower motor neuron signs, cerebral biopsies are less likely to be diagnostic.

In vitro MR microscopy of the hippocampus in Alzheimer's disease.

We used MR microscopy at 7 tesla to identify the anatomy of the degenerating hippocampus in Alzheimer's disease (AD), which we then correlated with the histopathologic findings in the same specimens. The specimens studied were resected postmortem from 13 patients with confirmed AD and from nine age-matched controls. We imaged the specimens in the coronal plane using either three-dimensional Fourier encoding or single-slice Carr, Purcell, Meiboom, Gill (CPMG) spin echo sequences. On all specimens imaged with the CPMG pulse sequence, we calculated the T2 relaxation times for subfields within the hippocampus. Histologic sections were taken from each specimen and compared with the corresponding MR image. Using histologic boundaries, we quantified the number of neuritic plaques and neurofibrillary tangles in each hippocampal subfield. We measured the area, morphometric characteristics, and width of identifiable signal variant regions on each image and compared these measurements with the histopathologic findings. The mean cross-sectional area of the hippocampus in AD was decreased by 31% compared with the control group. This atrophy was highly correlated with tangle counts within the hippocampus, but not with plaque counts. The width of the gray matter in hippocampal area CA1, as identified by MR, correlated with the total area of the hippocampus. An age-related decrease in the size of a low-signal region that corresponds histologically to input projections comprising part of the perforant pathway was identified. Measurements of the T2 relaxation times of hippocampal subfields showed little regional variability and were not accurate indicators of disease presence or severity (p > 0.05).

Temporal lobe hypometabolism on PET: predictor of seizure control after temporal lobectomy.

To investigate the relationship of temporal lobe hypometabolism demonstrated on PET to surgical outcome and underlying pathology, we reviewed 30 consecutive epilepsy patients who underwent interictal PET studies with 18F fluorodeoxyglucose before temporal lobectomy. Two interpreters blindly reviewed the PET studies and graded them for degree, extent, and location of temporal lobe hypometabolism. Pathologic analysis of en bloc resected tissue showed mesial temporal sclerosis (n = 22), astrocytoma (n = 2), and no pathologic diagnosis (n = 6). Outcome (24 to 40 months' follow-up) was rated as seizure-free (21 patients), significantly improved (five patients), and not significantly improved (four patients). Both the degree and extent of the temporal lobe hypometabolism demonstrated on PET were strongly associated with subsequent seizure control. Pathologic findings, however, did not correlate with degree of PET hypometabolism or subsequent outcome. These data demonstrate that in patients judged to have temporal lobe epilepsy, the presence of temporal lobe hypometabolism is associated with a positive outcome after ipsilateral temporal lobectomy.

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD). Part II. Standardization of the neuropathologic assessment of Alzheimer's disease.

The Neuropathology Task Force of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) has developed a practical and standardized neuropathology protocol for the postmortem assessment of dementia and control subjects. The protocol provides neuropathologic definitions of such terms as "definite Alzheimer's disease" (AD), "probable AD," "possible AD," and "normal brain" to indicate levels of diagnostic certainty, reduce subjective interpretation, and assure common language. To pretest the protocol, neuropathologists from 15 participating centers entered information on autopsy brains from 142 demented patients clinically diagnosed as probable AD and on eight nondemented patients. Eighty-four percent of the dementia cases fulfilled CERAD neuropathologic criteria for definite AD. As increasingly large numbers of prospectively studied dementia and control subjects are autopsied, the CERAD neuropathology protocol will help to refine diagnostic criteria, assess overlapping pathology, and lead to a better understanding of early subclinical changes of AD and normal aging.

Selective neocortical and thalamic cell death in the gerbil after transient ischemia.

In animal models of transients ischemia, selective vulnerability and delayed neuronal death in the hippocampus have been extensively described. However, little is known about selective damage in the neocortex and the thalamus, even though deficits in sensorimotor function are common in humans surviving hypoxic/ischemic episodes. This study investigated the neurodegenerative effects of transient ischemia in the gerbil neocortex and thalamus with use of Cresyl Violet and silver impregnation staining methods. In addition, immunohistochemistry of an astrocyte-associated protein, glial fibrillary acidic protein, was used to assess the astrocytic response to ischemia. Pyramidal cells in layers 3 and 6 of somatosensory and auditory cortex were exceptionally sensitive to ischemia, whereas the neurons in layers 2, 4 and 5 were more resistant to ischemia. More pyramidal cells were killed in layer 3 than in layer 6. This bilaminar pattern of neuronal death developed after periods of ischemia ranging from 3 to 10 min and was identifiable at post-ischemic survival times of 6 h to one month. Somatodendritic argyrophilia in the neocortex was identified as early as 6-12 h after 5 min of ischemia. The greatest number of degenerating cortical neurons were stained two to four days after ischemia. With 10 min of ischemia, argyrophilic neurites and neurons were also found as early as 8 h after the occlusion. The most extensive damage was noted in the ventroposterior nucleus, the medial geniculate nucleus, and the intralaminar nuclei two to four days after ischemia. Thus, selective vulnerability and delayed neuronal death are evident in both the neocortex and the thalamus after transient ischemia. These regions need to be examined when considering the efficacy of potential neuroprotective drugs.

Selective neuronal death after transient forebrain ischemia in the Mongolian gerbil: a silver impregnation study.

An important feature of ischemic brain damage is the exceptional vulnerability of specific neuronal populations and the relative resistance of others. Silver impregnation was used to delineate the extent and time-course of neuronal degeneration produced by 5 min of complete forebrain ischemia in the Mongolian gerbil. Lesions were confined to four brain regions: (1) hippocampal areas CA1, CA2-CA3a and CA4; (2) the dorsomedial portion of the lateral septal nucleus; (3) the dorsolateral portion of the striatum; and (4) the somatosensory neocortex. The ischemic lesion evolved with time in all four regions, but at different rates. Somatic argyrophilia developed rapidly in the striatum and hippocampal area CA4 (maximal in 24 h or less), at intermediate rates in the somatosensory neocortex, hippocampal areas CA1a and CA2-CA3a and the lateral septal nucleus (maximal in 2 days), and slowly in hippocampal area CA1b (maximal in 3 days). These results emphasize that the extent and rate of neuronal degeneration can vary even within a presumably homogeneous neuronal population, as evidenced by the different results in areas CA1a and CA1b. Similar results were obtained from analysis of brain sections stained with Cresyl Violet, hematoxylin-eosin or hematoxylin-eosin/Luxol Fast Blue. Terminal-like silver granules were observed in the projection fields of degenerated neurons. They also appeared, however, in the perforant path terminal zone of the hippocampal dentate molecular layer 1-2 days after transient ischemia and in stratum oriens and stratum radiatum of area CA1b prior to somatic degeneration. These granular deposits could not be clearly related to the degeneration of neuronal somata. Novel findings of this study include the degeneration of some dentate basket cells and lateral septal neurons and the appearance of terminal-like argyrophilia in the hippocampal formation without any obvious relation to somatic degeneration. Some of our results lend support to the hypothesis that ischemic neuronal cell death constitutes an excitotoxic process. Other results, however, suggest that the selective vulnerability of neurons to transient ischemia must involve factors beyond excitotoxicity.

Benzodiazepines protect hippocampal neurons from degeneration after transient cerebral ischemia: an ultrastructural study.

The ability of full and partial benzodiazepine receptor agonists to prevent DNA fragmentation and neuronal death after transient cerebral ischemia was investigated in the Mongolian gerbil. Diazepam (10mg/kg, i.p.) or the partial agonist imidazenil (3mg/kg, i.p.) was administered 30 and 90min after transient forebrain ischemia produced by occlusion of the carotid arteries for 5min. Treatment with diazepam completely protected CA1b hippocampal pyramidal neurons in 94% of the animals and partially protected pyramidal neurons in 6% of the animals, as assessed with a standard Nissl stain three and four days after ischemia. DNA fragmentation was examined by the terminal dUTP nick-end labeling (TUNEL) reaction. Prior to cell death, there were no TUNEL-positive neurons in area CA1b. By three days after ischemia, when neuronal degeneration was nearly complete, 14 out of 16 gerbils exhibited a positive TUNEL reaction throughout area CA1b stratum pyramidale. In 13 out of 14 gerbils treated with diazepam, no TUNEL-positive neurons were observed in this region. Imidazenil was less effective than diazepam with respect to both neuroprotection and prevention of DNA fragmentation. Three days after ischemia, six out of eight gerbils treated with imidazenil showed partial to complete neuroprotection. Imidazenil completely prevented DNA fragmentation in only one of the animals; varying degrees of TUNEL reaction persisted in the remainder. To determine whether the neurons protected by diazepam had a normal ultrastructure, gerbils were killed two to 30 days after ischemia and the hippocampal neurons in area CA1b were examined by electron microscopy. Within the first 48h after ischemia, early cytoplasmic changes of varying degrees (e.g., vacuolation, rough endoplasmic reticulum stacking, swollen mitochondria) and electron-dense dendrites were observed in gerbils not treated with diazepam. Degeneration was nearly complete by three days after ischemia. In contrast, pyramidal neuron ultrastructure appeared normal in gerbils that exhibited complete area CA1b neuroprotection (defined at the light microscope level) by diazepam when studied two, seven or 30 days after ischemia. In gerbils with partial protection of area CA1b, most of the remaining neurons exhibited varying degrees of necrosis when studied 30 days after ischemia. No apoptotic bodies were observed. We conclude that: (i) diazepam can fully protect CA1 pyramidal cells from the toxic effects of transient cerebral ischemia; (ii) when diazepam affords only partial neuroprotection, the residual CA1 pyramidal cells exhibit ultrastructural abnormalities consistent with necrotic damage; and (iii) diazepam is a more efficacious neuroprotectant than the partial benzodiazepine receptor agonist, imidazenil.

Cunninghamella: a newly recognized cause of rhinocerebral mucormycosis.

Cunninghamella, a zygomycete in the order Mucorales, is an extremely rare cause of human infection. Of the five reported cases of human disease caused by this fungus, none involved rhinocerebral infection. Here, the authors document what appears to be the first case of rhinocerebral mucormycosis caused by Cunninghamella bertholletiae in an elderly man who had diabetes with sideroblastic anemia and hemochromatosis. The disease was rapidly fatal. The mycology and classification of this organism are presented, and the previous case reports in the literature are reviewed.

A simple, inexpensive method of monitoring brain temperature in conscious rodents.

A method was developed to monitor brain temperature in conscious, unrestrained rodents. A commercially available thermocouple microprobe was modified so that it could be screwed firmly into a guide cannula that had been stereotactically implanted in the brain. Because the microprobe remains firmly in place, it is possible to record continuously for several hours from a single animal. Because the microprobe is easily removed, one can also record intermittently from several animals at once. The necessary equipment is relatively inexpensive and the modified microprobe can be sterilized and reused indefinitely. This method has proved especially useful for monitoring brain temperature during and after transient cerebral ischemia, an insult that destroys CNS neurons in a temperature-sensitive fashion.