Effects of Exercise-Diet Therapy on Cognitive Function in Healthy Elderly People Evaluated by Deep Learning Based on Basic Blood Test Data

BACKGROUND

Recent studies reported that vascular cognitive impairment in the elderly caused by arteriosclerosis plays an important role in cognitive disorders in both vascular dementia and Alzheimer's disease. In addition, systemic metabolic disorders such as oxygen metabolism dysfunction could be risk of dementia. Based on these findings, we have developed a deep neural network-based screening test (DNN-based test) of cognitive function using basic blood test data, which allowed prediction of cognitive function expressed by Mini Mental State Examination (MMSE) scores.

AIM

Here, we investigated whether the DNN-based test could be applicable to assessment of the effects of exercise-diet on cognitive function.

METHODS

We studied the following two groups: (1) seven subjects of the local fitness gym (68.6 ± 3.2 years old). We evaluated cognitive function by the DNN-based test using blood data before and after the intervention (for 3 months). These results were compared with the measured MMSE score. (2) we studied a total of 230 subjects (67.9 ± 7.4 years old) who were members of the Tsuminory health class (Apple classroom). We assessed cognitive function by the DNN-based test before and after the intervention (for 2 months). We compared the predicted MMSE scores by the DNN-based test before and after the 2-month intervention.

RESULTS

In the first group, the MMSE score predicted by the DNN-based test increased from 27.1 ± 0.8 to 27.6 ± 0.7 after the intervention period (p = 0.024). The measured MMSE score also increased after exercise, but not significant (P = 0.28). In the second group, the exercise-diet therapy increased the predicted MMSE scores in 189 cases (p < 0.001). In contrast, the therapy significantly reduced the mean MMSE score (p < 0.001).

DISCUSSION

The MMSE score predicted by the DNN-based test were increased by exercise-diet therapy in most subjects. The DNN-based test may be useful to monitor the effect of exercise-diet therapy on cognitive function aged people.

Relationship Between Cognitive Dysfunction and Systemic Metabolic Disorders in Elderly: Dementia Might be a Systematic Disease

Vascular cognitive impairment (VCI) plays an important role in dementia in elderly people, and refers to the contribution of vascular pathology to the entire spectrum of cognitive disorders, ranging from mild cognitive impairment to severe dementia, as well as the pathological spectrum, from 'pure' Alzheimer disease through degrees of vascular comorbidity to 'pure' vascular dementia. In the present study, we investigated the relationship between cognitive dysfunction and systemic metabolic disorders, by employing deep learning (DL). We studied 202 patients (73.4 ± 13.0 years), 94.6% of whom were undergoing treatment for lifestyle diseases, and 68.8% of whom had a history of cerebrovascular disorder. We evaluated cognitive dysfunction by performing a Mini Mental State Examination (MMSE). We performed general blood examination, including Complete Blood Count and Basic Metabolic Panel, and measured cerebral blood oxygenation in the prefrontal cortex (PFC) using time-resolved near infrared spectroscopy (TNIRS). We then used deep neural networks to assess the MMSE scores of the subjects based on the TNIRS parameters and the blood examination data, independently. Next, we compared predicted MMSE scores based on the TNIRS and the blood examination. There was a significant positive correlation between the TNIRS parameters and the blood examination data (r = 0.6, p < 0.01). These observations suggest that cognitive dysfunction in patients with VCI may be caused by combinations of systemic metabolic disorders such as energy and oxygen metabolisms and cerebral circulatory disturbance due to arteriosclerosis resulting from lifestyle-related diseases.

Reliability of Wearable Two Channel CW-NIRS in Measurements of Brain Function

Multi-channel NIRS, so-called optical topography (OT), allows functional mapping of the cortex; however, it takes a long time to set optodes on the head and is relatively expensive. Thus, OT is not suitable as a screening test of brain disorders evaluating many subjects. Recently, a wearable two-channel continuous wave NIRS (CW-NIRS) device has been developed. Such a simple NIRS device may be applicable as a screening test of brain disorders; however, its reliability in measurements of brain function is not yet clear. Here, we tested a two-channel CW-NIRS, which employs single LED (800 nm) for measurement of total hemoglobin (t-Hb) changes. We measured t-Hb changes in the bilateral prefrontal cortex (PFC) during mental arithmetic tasks, employing the CW-NIRS and time-resolve NIRS (TNIRS). The left-right asymmetry of the PFC activity was evaluated by calculating the laterality index (LI; (R-L)/(R + L) of t-Hb), which reflects mental stress. The interval between CW-NIRS and TNIRS measurements was 1-13 days. A significant positive correlation was observed between LI measured by CW-NIRS and TNIRS. These results suggest the reliability of the simple CW-NIRS, and it may be applicable to prevent stress-induced various diseases. Finally, it should be emphasized that the left-right asymmetry of PFC activity is relatively stable.

Effects of Motor Imagery on Cognitive Function and Prefrontal Cortex Activity in Normal Adults Evaluated by NIRS

Recent near-infrared spectroscopy (NIRS) studies demonstrated that physical exercise enhances working memory (WM) performance and prefrontal cortex (PFC) activity during WM tasks in normal adults. Interestingly, the effects of rehabilitation (i.e. physiotherapy) on post-stroke patients could be enhanced by motor imagery (MI), an active process during which the specified action is reproduced within WM without any actual physical movement. However, it is not known whether MI can enhance cognitive function and associated brain activity. To clarify these issues, we evaluated the effect of MI on WM performance and PFC activity during WM tasks in normal adults, employing NIRS. We studied 10 healthy adults. The present study was a crossover comparison test; the MI training and control condition (rest) were applied to the subjects at random. The Time Up and Go method was used for MI training: the subject sat on a chair and conducted MI for 3 min, three times. Neuronal activity (oxyhemoglobin concentration) in the bilateral PFC was measured using 2-CH NIRS during WM tasks. We found that MI improved the behavioral performance of WM compared with the control (p < 0.01). NIRS revealed that MI enhanced PFC activity induced by the WM task compared with the control task (p < 0.01). These results suggest that MI can improve cognitive function and increase associated PFC activity in normal adults.

Effects of Physical Exercise on Working Memory and Prefrontal Cortex Function in Post-Stroke Patients

Physical exercise enhances prefrontal cortex activity and improves working memory performance in healthy older adults, but it is not clear whether this remains the case in post-stroke patients. Therefore, the aim of this study was to examine the acute effect of physical exercise on prefrontal cortex activity in post-stroke patients using near-infrared spectroscopy (NIRS). We studied 11 post-stroke patients. The patients performed Sternberg-type working memory tasks before and after moderate intensity aerobic exercise (40 % of maximal oxygen uptake) with a cycling ergometer for 15 min. We measured the NIRS response at the prefrontal cortex during the working memory task. We evaluated behavioral performance (response time and accuracy) of the working memory task. It was found that physical exercise improved behavioral performance of the working memory task compared with the control condition (p < 0.01). In addition, NIRS analysis indicated that physical exercise enhanced prefrontal cortex activation, particularly in the right prefrontal cortex (p < 0.05), during the working memory task compared with the control condition. These findings suggest that the moderate-intensity aerobic exercise enhances prefrontal cortex activity and improves working memory performance in post-stroke patients.

Cerebral blood oxygenation changes induced by bypass blood flow in moyamoya disease and non-moyamoya cerebral ischaemic disease

BACKGROUND

Superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis has been used to prevent stroke in patients with moyamoya disease (MD) and non-moyamoya ischaemic disease (non-MD). However, little is yet known regarding the difference between these groups of patients in the extent to which the bypass contributes to maintaining adequate cerebral blood oxygenation (CBO), or the temporal changes after surgery. In the present study, we evaluated the CBO changes induced by bypass blood flow in patients with MD and non-MD during the peri-operative periods employing optical spectroscopy.

METHODS

We investigated 13 patients who underwent STA-MCA anastomosis, including 5 MD and 8 non-MD patients. We evaluated the effects of STA blood flow on the CBO in the MCA territory on the anastomosis side, employing visual light spectroscopy during surgery and near infrared spectroscopy (NIRS) at one week after surgery.

FINDINGS

In 4 MD patients and one non-MD patient, the STA blood flow increased the oxyhaemoglobin and cortical oxygen saturation (CoSO2), indicating that the bypass supplied blood flow to the ischaemic brain; the CBO changes were observed more frequently in MD than in non-MD patients (p<0.02). The pre-anastomosis CoSO2 (65.4+/-5.4%) in MD was significantly lower than that (72.8+/-7.6%) in non-MD (p<0.05). Postoperative NIRS demonstrated that the bypass began to supply blood flow to the brain in 5 non-MD patients whose bypass did not supply blood flow during surgery.

CONCLUSIONS

Although MD has vessels of small diameter as compared to non-MD, the bypass begins to supply blood flow to the ischaemic brain earlier in MD than in non-MD after anastomosis. The fact that the CoSO2 in MD was lower than that in non-MD suggested that the perfusion pressure in MD was lower than that in non-MD, and this might account for the difference in the bypass blood supply after anastomosis between MD and non-MD. Our data suggest that, even if the bypass does not supply blood to the brain during surgery in non-MD, the bypass blood flow gradually increases after surgery.

BOLD functional MRI may overlook activation areas in the damaged brain

Clinical applications of blood-oxygenation-level-dependent contrast functional MRI (BOLD-fMRI) have been rapidly moving toward routine non-invasive cortical mapping in the patients with brain disorders. However, it is not yet clear whether the damaged brain shows same cerebral blood oxygenation (CBO) changes during neuronal activation as those in the normal adult. We compared the activation mapping obtained by BOLD-fMRI and the evoked-CBO changes measured by near infrared spectroscopy (NIRS) in normal adults (6 cases) and patients with damaged brain (6 cases of cerebral ischemia and 10 cases of brain tumors in or adjacent to the motor cortex). BOLD-fMRI demonstrated robust activation areas in the primary sensorimotor cortex (PSMC) during contralateral hand grasping tasks in all of the normal adults; however, in the cerebral ischemia (6 cases) and the brain tumors (2 cases), BOLD-fMRI demonstrated only limited activation areas in the PSMC on the lesion side during the task. NIRS demonstrated an increase of focal concentration of oxyhemoglobin and total hemoglobin at the PSMC during the task in all of the normal adults and the patients, indicating the presence of rCBF increase in response to neuronal activation. A focal concentration of deoxyhemoglobin decreased during the task in the normal adults, however, in the patients that showed limited activation areas by BOLD-fMRI, deoxyhemoglobin concentrations increased during the entire course of the task. In summary, the evoked-CBO changes occurring in the damaged brain differed from those in the normal brain. This indicates that BOLD-fMRI may overlook activation areas in the damaged brain.

Increase in focal concentration of deoxyhaemoglobin during neuronal activity in cerebral ischaemic patients

BACKGROUND AND PURPOSE

Blood oxygenation level dependent contrast functional magnetic resonance imaging (BOLD-fMRI) has been applied to functional mapping in brain disorders, based on the assumption that normal adults and patients with brain disorders exhibit similar evoked cerebral blood oxygenation (CBO) changes. This study compared evoked CBO changes measured by near infrared spectroscopy (NIRS) with the activation mapping obtained by BOLD-fMRI in patients with cerebral ischaemia.

METHODS

The study involved six normal adults and six patients with cerebral ischaemia. Hand grasping was performed as a motor task. All patients could perform the task similarly to the controls at the time of examination, but single photon emission computed tomography demonstrated low baseline cerebral blood flow and a decreased haemodynamic reserve in the primary sensorimotor cortex on the lesion side. Using NIRS, concentration changes of deoxyhaemoglobin (Deoxy-Hb), oxyhaemoglobin (Oxy-Hb), and total haemoglobin (Total-Hb) were measured in the primary sensorimotor cortex contralateral to the task. BOLD-fMRI signals were measured by 1.5 T magnetic resonance imaging using an echo-planar technique. Activation maps were calculated by statistical parametric mapping.

RESULTS

In the controls, Deoxy-Hb decreased in association with increases of Oxy-Hb and Total-Hb in the primary sensorimotor cortex during the task. However, in the patients, Deoxy-Hb increased significantly from baseline, while Oxy-Hb and Total-Hb also increased, indicating the presence of rCBF increases in response to neuronal activation. BOLD-fMRI demonstrated only limited activation areas in the primary sensorimotor cortex on the lesion side.

CONCLUSION

The CBO changes in patients with cerebral ischaemia differed from those of normal adults; Deoxy-Hb was increased in activation areas of the patients. This implies that BOLD-fMRI may overlook activation areas in the patients unless both increases and decreases of signal are taken into consideration.

Development of surgical confocal scanning microscope for intra-operative imaging of brain tumors using near infrared fluorescence: technical note

We developed a confocal laser scanning microscope for intra-operative imaging of brain tumors using near infrared fluorescence. The quality of near infrared images of Indocyanine Green (ICG) was compared with the surgical confocal scanning (SCS) microscope and a conventional charge-coupled device (CCD) camera; we compared images of a tube filled with ICG, which was located in the mouse brain. Compared to the CCD camera, the SCS microscope could obtain a more precise image of ICG fluorescence through the brain tissue. In addition, the SCS microscope could image ICG fluorescence clearly in a relatively light room because of elimination of stray light, while the CCD camera required high darkness to obtain ICG images. The present SCS microscope can give useful intra-operative imaging of brain tumors, particularly detection of residual tumor tissues that extend into normal brain tissues.

Changes in cerebral blood oxygenation induced by deep brain stimulation: study by near-infrared spectroscopy (NIRS)

Previous studies have demonstrated that neural activation causes changes in cerebral blood oxygenation (CBO), i.e. increases in tissue levels of oxy-Hb and total-Hb with a decrease in deoxy-Hb concentration. It is unclear, however, whether neural activation always induces the same pattern of CBO changes or not. In the present study, employing a near-infrared spectroscopy (NIRS), we investigated the CBO changes in the frontal lobe induced by direct stimulation of the thalamus (Vim) or globus pallidus (GPi) in patients with Parkinson's disease or essential tremor. The results indicated that under conditions of neural activation in the frontal lobe, oxy-Hb and total-Hb increased in all 6 cases. Deoxy-Hb decreased in 2 cases during GPi stimulation, and increased in 4 cases during low frequency stimulation of the Vim. The above findings suggest that neural activation induces various patterns of CBO change, especially in deoxy-Hb. This implies that functional MRI based on the BOLD contrast may not consistently detect the area of neural activation.

Changes in cerebral blood oxygenation of the frontal lobe induced by direct electrical stimulation of thalamus and globus pallidus: a near infrared spectroscopy study

OBJECTIVE

Blood oxygenation level dependent (BOLD) contrast functional MRI images show activated cortical areas by detecting a reduced concentration of deoxyhaemoglobin (deoxy-Hb) during neuronal activity; however, near infrared spectroscopy (NIRS) has shown various patterns of cerebral blood oxygenation (CBO) changes in the frontal lobe during cognitive tasks. To determine if various patterns of CBO changes occur in the frontal lobe when the brain is directly stimulated, changes in CBO in the frontal lobe induced by deep brain stimulation in patients with implanted electrodes were evaluated.

METHODS

Six patients were studied, including five with Parkinson's disease and one with essential tremor. To reduce tremor or rigidity, the electrodes were implanted at the thalamic nucleus ventralis intermedius (VIM: three Parkinson's disease and one essential tremor) or the globus pallidus internus (GPi: two Parkinson's disease). Using NIRS, changes of deoxy-Hb, oxyhaemoglobin (oxy-Hb) and total haemoglobin (total Hb) were measured in the bilateral frontal lobes during various stimulus conditions.

RESULTS

High frequency (120 Hz) GPi stimulation consistently increased oxy-Hb and total Hb with a decrease of deoxy-Hb in an intensity and time dependent manner. Oxy-Hb and total Hb increased immediately after the onset of stimulation and then gradually decreased when stimulation was continued. By contrast, high frequency (120 Hz) VIM stimulation decreased oxy-Hb, deoxy Hb and total Hb in an intensity dependent manner. In the severe tremor patient with VIM stimulation, frequency response was examined by decreasing stimulus frequencies; deoxy-Hb increased at high frequencies (70-40 Hz), and then decreased below the control level at low frequencies (30-0 Hz), whereas oxy-Hb and total Hb increased consistently at high and low frequencies.

CONCLUSION

The electrical stimulation of GPi and VIM caused various CBO changes in the frontal lobe, which were similar to those found during cognitive tasks. Such a multiplicity of CBO changes in the frontal lobe may be caused by complex neuronal circuits in the frontal lobe which has many neuronal connections to other cortical areas or the basal ganglia.

Effects of aging on language-activated cerebral blood oxygenation changes of the left prefrontal cortex: Near infrared spectroscopy study

The use of positron-emission tomography (PET) has shown a variety of age-related alterations in neuronal activity in elderly patients. Near infrared spectroscopy (NIRS) has shown a multiplicity of evoked cerebral blood oxygenation (CBO) changes during cognitive performance. To evaluate the effects of aging on the CBO changes, we compared the CBO changes induced by cognitive tasks between young adults and older adults by using NIRS. Twenty-six participants performed 6 cognitive tasks to evaluate differences among young adults (mean age+/-SD, 28.8+/-4.4 years) and older adults (50.7+/-8.0 years). We monitored CBO changes in the left prefrontal cortex. We classified several common patterns of the NIRS parameter change and compared the frequency of each pattern in both groups. In both groups, the most common NIRS parameter change was an increase in oxyhemoglobin (Oxy-Hb) and total-hemoglobin (Total-Hb), with a decrease in deoxyhemoglobin (Deoxy-Hb). The frequency of this pattern in the older group, however, was considerably lower than in the young group (P<.01). In addition, decreases of Oxy-Hb and Total-Hb during the tasks were more common in the older groups, (P<.0001), suggesting a decrease of regional cerebral blood flow during the tasks. Age effects varied for specific tasks, with results being significant for verbal fluency and reading, (P<.05). During all tasks, older subjects were less likely than younger subjects to have the typical pattern of increases in Oxy-Hb and Total-Hb. In addition, compared with younger subjects, older subjects had a greater frequency of decreases in Oxy-Hb and Total-Hb. The overall results, as well as results for specific tasks, suggest that functional reorganization or alteration of CBO responses may occur during aging.

Cerebral blood oxygenation changes induced by auditory stimulation in newborn infants measured by near infrared spectroscopy

Recent neuronal activation studies on newborns using functional MRI or near infrared spectroscopy (NIRS) have suggested that the increase in O2 consumption accompanying neuronal activation exceeds the increase in O2 delivery in the visual cortex during photic stimulation. In the present study, we evaluated the cerebral blood oxygenation (CBO) changes induced by auditory stimulation in the frontal lobe of newborns using NIRS. We studied 28 newborns; the postnatal age at CBO measurements was 3.1+/-0.3 days (mean+/-S.E.M.). We measured concentration changes of deoxyhemoglobin (Deoxy-Hb), oxyhemoglobin (Oxy-Hb), and total hemoglobin (Total-Hb) induced by auditory (music) stimulation in the bilateral frontal lobes of the newborns. Twenty-six (92.9%) out of 28 subjects showed increases of Oxy-Hb and Total-Hb during the stimulation. In these subjects, 17 (60.7%) subjects showed an increase of Deoxy-Hb associated with increases of Oxy-Hb and Total-Hb, while nine (32.1%) subjects showed a decrease of Deoxy-Hb. Although the direction of the Deoxy-Hb differed, these two groups did not differ for Oxy-Hb and Total-Hb (P > 0.05). Two (7.1%) subjects showed other changes. The frontal lobe of newborns shows CBO responses similar to those observed in the visual cortex, specifically neuronal activation causes an increase of Deoxy-Hb associated with increases of Oxy-Hb and Total-Hb. These results support the hypothesis that increments in O2 consumption exceed increments in O2 delivery during neuronal activity in newborns.

Continuous suction surgical cottonoid for microneurosurgery

A new suction device for microneurosurgery is presented. A surgical cottonoid is covered with a polyethylene film so that vacuum power is maintained throughout the length of the cottonoid. One end is connected to a vacuum pump via a plastic tube. Five to 10 mm of the surgical cottonoid are exposed for suctioning at the other end of the cottonoid. The suction surgical cottonoid is flexible and safe, avoiding tissue damage. In addition, the surgeon can manipulate the exposed cottonoid at the tip as any other surgical cottonoid.

Language-activated cerebral blood oxygenation and hemodynamic changes of the left prefrontal cortex in poststroke aphasic patients: a near-infrared spectroscopy study

BACKGROUND AND PURPOSE

In normal subjects, regional cerebral blood flow (rCBF) is greatly increased by neuronal activity, whereas the cerebral metabolic rate for O2 is increased only slightly. However, it is not clear what kinds of cerebral blood oxygenation and hemodynamic changes can be induced by language activities in language-relevant areas of poststroke aphasics. In the present study, we investigated the difference in the changes of cerebral blood oxygenation and hemodynamics in the left prefrontal cortex induced by language activities between normal subjects, poststroke nonaphasic patients, and nonfluent aphasic patients using near-infrared spectroscopy (NIRS).

METHODS

Twenty-nine participants performed speech tasks, such as confrontational naming, to evaluate changes among poststroke nonfluent (Broca's) aphasia patients (10 cases; mean+/-SEM, 56.9+/-2.2 years), age-matched normal subjects (13 cases; 50.7+/-2.2 years) and poststroke nonaphasic patients (6 cases; 52.5+/-3.9 years). The optodes of NIRS were placed over the left prefrontal cortex. We analyzed the NIRS parameter (oxyhemoglobin [oxy-Hb], deoxyhemoglobin [deoxy-Hb], and total hemoglobin [total-Hb]) changes by qualitative pattern analysis of the parameter changes and quantitative analysis of the parameter values among the groups.

RESULTS

The most common NIRS parameter change was an increase in oxy-Hb and total-Hb, with a slight decrease or no change in deoxy-Hb in the normal subjects (5 of 13 cases, 38.5%) and the nonaphasic cerebrovascular disease (CVD) patients (3 of 6 cases, 50.0%). In contrast, the most common pattern in the aphasic patients was an increase of deoxy-Hb, with an increase of oxy-Hb and total-Hb (5 of 10 cases, 50%). However, this pattern was observed in only 3 of 13 cases (23.1%) in the normal subjects and 1 of 6 cases (16.7%) in the nonaphasic CVD patients. The mean (+/-SEM) changes of deoxy-Hb of the aphasic patients, the normal subjects, and the nonaphasic CVD patients were 0.78+/-0.29, 0.06+/-0.16, and -0.18 +/- 0.22, respectively. The statistical analysis demonstrated a significant effect for deoxy-Hb (P<0.05), with the aphasic patients differing significantly from the normal subjects and the nonaphasic CVD patients, while the 2 nonaphasic groups did not differ from each other.

CONCLUSIONS

The present results demonstrate a multiplicity of language-activated cerebral blood oxygenation and hemodynamic changes in the left prefrontal cortex in the nonaphasic and aphasic groups. The increase of deoxy-Hb with increases of oxy-Hb and total-Hb in the aphasics during language tasks suggests that the left prefrontal cortex of the aphasics utilizes more oxygen than the nonaphasics during language tasks. Finally, functional MRI, which images the activation area in the brain by detecting the reduced concentration of deoxy-Hb during neuronal activation, should be performed on the patients with cerebral dysfunction, giving special consideration to the possible multiplicity of the rCBF and cerebral oxygen metabolism responses to functional tasks.

Intracranial facial nerve neurinoma: surgical strategy of tumor removal and functional reconstruction

BACKGROUND

Three cases with intracranial facial neurinoma underwent tumor removal and facial nerve reconstruction with or without tympanoplasty. Surgical strategy for each case was tailored to: (1) the site of main tumor mass, (2) its extension along the facial nerve, and (3) involvement of the auditory organs.

METHODS

Surgeries adopted in the three cases were: transpetrosal approach with intracranial-intratemporal facial nerve anastomosis, middle fossa and transmastoid approach with intratemporal facial nerve anstomosis and tympanoplasty, and middle fossa and transmastoid approach with intracranial-intratemporal facial nerve anastomosis and tympanoplasty. The greater auricular nerve was used as the nerve graft for all three cases.

RESULTS

In the follow-up period of 8-13 months there was no tumor recurrence; facial function was scored 20/90 in modified May's scoring system in each case, but two are still in the process of functional recovery. One of the two cases who underwent tympanoplasty showed complete recovery of hearing within 1 month, and the other showed worsened hearing, which was not serviceable at 3 months postoperatively.

CONCLUSION

Systematic surgical approach for tumor removal, facial nerve reconstruction, and auditory reconstruction should be considered in cases with intracranial facial neurinoma due to its varied clinical features.

Noninvasive optical imaging of the subarachnoid space and cerebrospinal fluid pathways based on near-infrared fluorescence

The authors have developed a noninvasive optical method to image the subarachnoid space and cerebrospinal fluid pathways in vivo based on the near-infrared fluorescence of indocyanine green (ICG). The ICG was bound to purified lipoproteins (ICG-lipoprotein) and injected into the subarachnoid space of neonatal and adult rats. The ICG fluorescence was detected by a cooled charge-coupled device camera. After injection of ICG-lipoprotein into the cerebral subarachnoid space of the neonatal rat, ICG fluorescence was clearly detected at the injection site through the skull and skin. The ICG fluorescence was observed in the cerebellum and the lumbar spinal cord 1 and 8 hours postinjection, respectively. After injection of ICG-lipoprotein into the lumbar spinal subarachnoid space of an adult rat, ICG fluorescence was observed from the injection site to the thoracic levels along the spinal subarachnoid space. In addition, with the rat's head tilted downward, ICG fluorescence had extended to the cerebral subarachnoid space by 1 hour postinjection. The ICG fluorescence imaging of the cerebral subarachnoid space demonstrated an increase in fluorescence intensity around the lambdoid suture and the forebrain. On dissection of the rat brain the former location was identified as the supracerebellar cistern and the latter as the olfactory cistern. The results of this study are the first to demonstrate that an optical technique is applicable to imaging of the subarachnoid space and cerebrospinal fluid pathways in vivo. In addition, ICG-lipoprotein provides a sensitive optical tracer for imaging extravascular biological structures. Finally, ICG fluorescence imaging does not require an intricate imaging system because ICG is localized near the surface of the body.

Isotonic mannitol and the prevention of local heat generation and tissue adherence to bipolar diathermy forceps tips during electrical coagulation. Technical note

The authors observed temperature levels of saline and mannitol on the tips of bipolar diathermy forceps during application of power to the forceps and compared the effects of irrigation with saline and isotonic mannitol on electrical coagulation of vessels during neurosurgical operations. There was a marked rise in the temperature of saline corresponding to increased output power of the coagulator; there was no rise in the temperature of the mannitol. Irrigation with isotonic mannitol during surgery resulted in a considerable reduction of adherence of burned tissue and blood clots to forceps tips during coagulation of both arteries and veins compared with that which occurred during irrigation with saline. These results demonstrate that irrigation with an isotonic mannitol surpasses that with conventional ionic fluids, such as a saline, for prevention of both tissue adherence to bipolar diathermy forceps and removal of heat generated during electrical coagulation.

Effects of GABA on axonal conduction and extracellular potassium activity in the neonatal rat optic nerve

GABA depolarizes rat optic nerve axons and modulates axonal conduction through the activation of GABA-A receptors. To address whether an increase of [K+]e plays a major role in GABA actions on the rat optic nerve, we studied the effects of GABA on axonal conduction and [K+]e in the neonatal rat optic nerve in vitro. Double-barrelled K(+)-sensitive microelectrodes were used to record [K+]e. GABA (10(-4)-10(-3) M) increased [K+]e in the neonatal optic nerve. During prolonged application, the [K+]e slowly recovered. The increase in [K+]e induced by GABA was markedly reduced by the GABA-A receptor blocker bicuculline (10(-4) M). Isoguvacine (10(-4) M), a GABA-A agonist, mimicked the effect of GABA but produced larger responses at the same concentration. In contrast, baclofen (10(-4) M), a GABA-B agonist, had no effect on [K+]e. The changes in the compound action potential induced by GABA correlated only partially with the [K+]e changes. Furthermore, the changes in the compound action potential induced by elevation of K+ were far less than those induced by GABA. These results demonstrate that the GABA-evoked accumulation of [K+]e plays a secondary role in GABA actions on the neonatal rat optic nerve.

[A case report of interstitial pneumonia caused by granulocyte colony-stimulating factor]

Several clinical trials have demonstrated that granulocyte colony-stimulating factor (G-CSF) accelerates the recovery of neutropenia in chemotherapy-induced bone marrow suppression. In this report, we describe a 46-year-old female with glioblastoma multiforme who developed interstitial pneumonia due to administration of G-CSF during the phase of immunochemoradiotherapy-induced neutropenia. Thirty-three days after starting immunochemoradiotherapy (ACNU, VCR, IFN -beta, radiation), she developed neutropenia (1,000/microliters). Administration of G-CSF at doses of 125-250 micrograms/day led to an increase of peripheral neutrophil counts. Eleven days later, the patient developed sudden severe respiratory failure and cyanosis with worsening of lung shadows. Blood gas levels on room air were PaO2 49.3mmHg, PaCO2 28.0mmHg, and pH 7.46. At this time, her neutrophil count had risen to 26,080/microliters. LDH and alpha - HBD had also increased to 1,439 IU/l and 1,117IU/l respectively. Chest radiograph and CT scan demonstrated interstitial pneumonia. After treatment with methyl prednisolone, her respiratory symptoms were gradually resolved. A number of side-effects have been reported with granulocyte-macrophage colony-stimulating factor (GM-CSF). These include fluid retention with pericardial and pleural effusion, fever, bone pain, fatigue, and rash. This report also suggests that G-CSF might be a cause of interstitial pneumonia during the phase of immunochemoradiotherapy-induced neutropenia.

Elevation and clearance of extracellular K+ following graded contusion of the rat spinal cord

The elevation and clearance of extracellular potassium concentration ([K+]e) were studied following graded contusion injury of the rat thoracic spinal cord. Animals were anesthetized, paralyzed, laminectomized at T9-T10, and then artificially ventilated. A 10-g rod was dropped 1.25, 2.5, or 5 cm onto the dorsal thoracic cord with the dura intact. After impact, and incision of the dura-arachnoid and pial membranes, double-barreled, potassium-selective microelectrodes were inserted midway between the midline and lateral edge of the cord. For all three injury levels, the elevation of [K+]e was greatest within the first 1000 microns from the dorsal surface. In 50 g-cm injuries, increasing [K+]e was sometimes observed between 250 and 1000 microns; however such gradients were not typically observed in 25 and 12.5 g-cm injuries. Measured at 3-7 min after injury, the mean peak elevations of [K+]e were significantly different, measuring 13 +/- 2.4, 27 +/- 5.5, and 44 +/- 4.2 mM following 12.5, 25, and 50 g-cm contusions, respectively. The exponential half-times of [K+]e clearance averaged 5.8 +/- 1.0, 9.2 +/- 1.8, and 17 +/- 5.7 min for the same respective injury levels. These results indicate that elevation of [K+]e following traumatic injury to the spinal cord is a graded phenomenon, dependent on the energy of impact. This finding is consistent with a mechanism in which simple mechanical injury of cell membranes is the proximate cause of potassium release.

Transient presence of GABA in astrocytes of the developing optic nerve

Immunostaining and high-pressure liquid chromatography (HPLC) were used to study the developmental time course of astrocytic gamma-aminobutyric acid (GABA) expression in rat optic nerve. GABA immunostaining was carried out on cultured astrocytes, and on whole optic nerve. Confocal scanning laser microscopy was used to obtain optical sections in excised whole tissue in order to localize the cellular origins of GABA within the relatively intact optic nerve. GABA immunoreactivity was localized in astrocytes identified by GFAP staining; GABA staining was most intense in early neonatal optic nerve and attenuated over 3 weeks of postnatal development. The staining was pronounced in the astrocyte cell bodies and processes but not in the nucleus. There was a paucity of GABA immunoreactivity by postnatal day 20, both in culture and in whole optic nerve. A biochemical assay for optic nerve GABA using HPLC indicated a relatively high concentration of GABA in the neonate, which rapidly attenuated over the first 3 postnatal weeks. Immunoreactivity for the GABA synthesis enzyme glutamic acid decarboxylase (GAD) was pronounced in neonates but also attenuated with development. These results indicate that GABA and the GABA synthesis enzyme GAD are localized in astrocytes of optic nerve, and that their expression is transient during postnatal development.

Non-synaptic modulation of dorsal column conduction by endogenous GABA in neonatal rat spinal cord

GABAA receptor activation can modulate axonal conduction in the isolated dorsal column of the neonatal rat spinal cord in vitro. However, it is not known whether axonal conduction in the dorsal column can be modulated by endogenous GABA in the developing spinal cord. We consequently compared the effects of GABA, a GABAA agonist, and a GABA uptake inhibitor on axonal conduction in the dorsal column of hemisected neonatal (0- to 9-day-old) rat spinal cords in vitro. Extracellular compound action potentials evoked by supramaximal stimuli were recorded at two points with glass microelectrodes. GABA (10(-4) to 10(-3) M) reversibly decreased the compound action potential amplitude and the population conduction velocity. At 10(-4) M, compound action potential amplitudes fell by 45.0 +/- 6.5% of control while the conduction velocity slowed by 11.8 +/- 4.3% (n = 5). The GABAA receptor agonist, isoguvacine, mimicked the effects of GABA on the dorsal column compound action potential. In contrast, while GABA at 10(-5) M decreased the amplitude by 7.7 +/- 3.1%, it increased conduction velocity by 9.7 +/- 1.3% (n = 5). The GABA uptake inhibitor, nipecotic acid (10(-3) M), consistently decreased the compound action potential amplitude by 17.7 +/- 6.5% (n = 6) but the conduction velocity slowed in four out of six preparations. In two instances, nipecotic acid decreased the amplitude and increased the conduction velocity. The effects of nipecotic acid on the dorsal column compound action potential were blocked in the presence of the GABAA antagonist bicuculline.(ABSTRACT TRUNCATED AT 250 WORDS)

GABA and potassium effects on corticospinal and primary afferent tracts of neonatal rat spinal dorsal columns

The neurotransmitter GABA markedly depresses action potential conduction in neonatal rat spinal dorsal columns. However, GABA sensitivity of the dorsal columns declines with maturation and myelination. At seven to 14 days after birth, the corticospinal tract component of the dorsal columns is immature and unmyelinated compared to the cuneate-gracilis fasciculi. GABA and isoguvacine (a GABAA receptor agonist) were applied to isolated neonatal (seven to 14 days old) dorsal columns during recordings of conducted cuneate-gracilis fasciculi and corticospinal tract action potentials. GABA (10(-4) to 10(-3) M) significantly reduced amplitudes (-28.9% to -69.7%) and increased latencies (+4.8% to +23.9%) of cuneate-gracilis fasciculi responses but had less effect on corticospinal tract response amplitudes (-1.1% to -14.7%) and latencies (+0.9% to +6.2%). Likewise, isoguvacine (10(-5) to 10(-4) M) reduced amplitudes (-26.7% to -37.5%) and increased latencies (+11.2% and +24.0%) of cuneate-gracilis fasciculi responses but had little or no effect on corticospinal tract response amplitudes (-6.2% to -3.8%) or latencies (-0.8% to +1.5%). At 10(-4) and 10(-3) M, GABA rapidly increased extracellular K+([K+]e) from baseline levels of 3.0 mM to 3.7 +/- 0.4 and 6.6 +/- 1.4 mM in cuneate-gracilis fasciculi and increased corticospinal tract [K+]e to 3.9 +/- 0.4 and 4.4 +/- 0.4 mM (mean +/- S.D.). [K+]e declined during drug application and fell below baseline after drug washout. Cuneate-gracilis fasciculi responses, however, did not recover until several minutes after [K+]e returned to baseline. In separate experiments, increasing bath [K+]e concentrations to 3.7 and 6.6 mM reduced cuneate-gracilis fasciculi response amplitudes by only -7.6% and -29.6%. Latencies increased by +1.3% and +3.6% respectively. The results indicate that the cuneate-gracilis fasciculi are more sensitive to GABA than the corticospinal tract and that the GABA effect is not entirely due to [K+]e changes.

The attenuation of GABA sensitivity in the maturing myelin-deficient rat optic nerve

GABA (gamma-aminobutyric acid) can modulate axonal excitability by activating GABAA receptors on some central nervous system axons. The effects of GABA on optic nerve axons decrease significantly during the course of myelination, suggesting that myelination may influence changes in GABA sensitivity. To test this hypothesis, we compared the depolarizing effect of GABA and the GABAA-receptor agonist, muscimol, on optic nerves of myelin-deficient (MD) rats and their unaffected siblings using a modified sucrose-gap technique. Optic nerves from both control and MD rats displayed relatively large GABA-induced depolarizations when studied at an early postnatal period. In both the control and MD rats, the GABA uptake inhibitor nipecotic acid led to a distinct depolarization suggesting endogenous release of GABA. Although the GABA-induced depolarization in the MD rat was significantly greater than that in the control rat at the third postnatal week, the response in the MD rat attenuated with maturation. These results demonstrate that the attenuation of the depolarization induced by GABA and nipecotic acid seen in the normal optic nerve also occurs in the MD rat optic nerve. This suggests that the attenuation of optic nerve sensitivity to GABA is not the result of myelination or interaction with myelin-associated proteins.

A role of GABAA receptors in hypoxia-induced conduction failure of neonatal rat spinal dorsal column axons

GABA (gamma-aminobutyric acid) depresses axonal conduction in neonatal dorsal columns. GABA released by injured spinal neurons may diffuse to white matter and contribute to secondary axonal damage. We studied the effects of hypoxia and GABAA receptor blockade on dorsal column conduction in vitro. The experiments compared the effects of hypoxia on longitudinally hemisected spinal cords and isolated neonatal dorsal columns. Before hypoxia, electrical stimulation elicited robust conducted compound action potentials in both isolated dorsal columns and hemicords. The tissues were superfused for 120 min with a hypoxic Ringer's solution saturated with 95% N2 and 5% CO2, followed by oxygenated Ringer's solution for 90 min. Isolated dorsal columns were remarkably insensitive to hypoxia. Response amplitudes fell by only 11 +/- 7% (n = 5) during hypoxia. In hemicords, however, hypoxia reduced response amplitudes by 56 +/- 16% (n = 5, mean +/- S.E.M.) and re-oxygenation did not restore response amplitude. We applied bicucullin (10(-5) M) to block GABAA receptors in the hemicords during hypoxia. Response amplitudes in bicucullin-treated hemicords fell by only 3 +/- 9% (n = 5) during hypoxia but declined 31 +/- 5% during re-oxygenation. These results suggest that endogenous GABA released from gray matter contributes to hypoxia-induced dorsal-column conduction failure.

Interaction of hypoxia and hypothermia on dorsal column conduction in adult rat spinal cord in vitro

Trauma reduces both action potential amplitudes and conduction velocities, as well as the ability of axons to follow high-frequency stimulation, in spinal cord dorsal columns. Since white matter blood flow falls after spinal cord injury, hypoxia may play a role in post-traumatic axonal dysfunction. We examined the effects of hypoxia on action potential conduction in isolated adult rat dorsal columns under normothermic (37 degrees C) and hypothermic (25 degrees C) conditions. After stabilization in oxygenated Ringer's solution (95% O2 and 5% CO2), the isolated dorsal columns were superfused with hypoxic Ringer's solution (95% N2 and 5% CO2) for 120 min, followed by 90 min of reoxygenation. At 37 degrees C, hypoxia markedly depressed response amplitudes to 25 +/- 9% (mean +/- SEM, n = 7) of prehypoxic levels but paradoxically increased population conduction velocity to 133 +/- 6%. Reoxygenation restored response amplitudes to 57 +/- 11% and population conduction velocities returned to prehypoxic levels. At 25 degrees C, the dorsal columns were significantly less sensitive to hypoxia. Response amplitudes fell to 50 +/- 6% (n = 7) after hypoxia and recovered to 77 +/- 6% after reoxygenation. Normothermic dorsal columns responded to 500-Hz stimuli with minimal amplitude changes before (-9 +/- 3%, n = 7) and after hypoxia (-13 +/- 2%). In hypothermic preparations, 500-Hz stimulation depressed response amplitudes before (-40 +/- 8%, n = 7) and after hypoxia (-56 +/- 8%); they were not significantly different from each other.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient presence and functional interaction of endogenous GABA and GABAA receptors in developing rat optic nerve

GABA (gamma-aminobutyric acid) is a major inhibitory synaptic neurotransmitter with widespread distribution in the central nervous system (CNS). GABA can also modulate axonal excitability by activation of GABAA receptors in CNS white matter regions where synapses and neuronal cell bodies are not present. Studies on cultured glia cells have revealed the synthesis of GABA in rat optic nerve O-2A progenitor cells that give rise to oligodendrocytes and type 2 astrocytes in vitro. We report here that: (i) GABA is detected by immuno-electron microscopy in intact rat optic nerve and is localized to glia and pre-myelinated axons during the first few weeks of postnatal development, but is markedly reduced or absent in the adult; and (ii) neonatal optic nerve is depolarized by GABAA receptor agonists or by the inhibition of GABA uptake. These results demonstrate the presence of functional GABAA receptors, and GABA uptake and release mechanisms in developing rat optic nerve, and suggest that excitability of developing axons can be modulated by endogenous neurotransmitter at non-synaptic sites.

Age-dependent extrasynaptic modulation of axonal conduction by exogenous and endogenous GABA in the rat optic nerve

To ascertain whether endogenous gamma-aminobutyric acid (GABA) exists and exerts physiological effects in the optic nerve, we compared the effects of GABA and related drugs on the neonatal (1 to 22 days of age) and adult (greater than 6 months) rat optic nerve in vitro. GABA (10(-4)-10(-3) M) reversibly depressed the amplitude and increased the latency of compound action potentials in the neonatal optic nerve. In the adult optic nerve, GABA (10(-4)-10(-3) M) had no significant effect on the compound action potential. The GABA-A receptor agonist, isoguvacine (10(-4)-10(-3) M), mimicked these GABA effects on the neonate and adult optic nerve. Lower concentrations (10(-5) M) of GABA increased excitability of the neonatal optic nerve but produced no discernible effects on the adult optic nerve. The GABA-uptake inhibitor, nipecotic acid (10(-3) M), mimicked the effects of GABA (10(-5) M) on the neonatal optic nerve. The GABA-A receptor blockers, picrotoxin and bicuculline (10(-6)-10(-3) M), decreased the latency of compound action potentials in the neonatal optic nerve. Membrane potential recordings indicate that while GABA (10(-5)-10(-3) M) depolarized the neonatal optic nerve dose-dependently, picrotoxin hyperpolarized the axons. In the adult optic nerve, neither GABA-uptake inhibitors nor GABA-A receptor blockers had significant effects on the compound action potential. These results suggest that functional GABA-A receptors and GABA are present in the neonatal rat optic nerve and depolarize axons under physiological conditions. However, this does not appear to be the case in the adult optic nerve.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevation and clearance of extracellular K+ following contusion of the rat spinal cord

The elevation and clearance of extracellular potassium following a standard contusion injury was studied in the thoracic spinal cord of rats. Animals were anesthetized, paralyzed, laminectomized at T9-T11, then artificially ventilated. A 10-g rod was released 5.0 cm above the cord with the dura intact. After impact, the dura-arachnoid and pial membranes were incised to allow penetration of K(+)-selective microelectrodes. Electrodes utilized a valinomycin ionophore and were double-barreled, with tip diameters of 3-5 microns. Extracellular potassium activity ([K+]o) increased with the depth of penetration. The maximum values of [K+]o occurred at depths greater than 500 microns, and remained so with time after injury. These data indicate that a dorsal-ventral gradient of [K+]o develops in spinal cords contused from the dorsal surface, with the greatest elevation of [K+]o in the gray matter. In 8 preparations, the maximum [K+]o was 65 +/- 8 mM (mean +/- S.E.M.) at 5 +/- 1 min after injury. The [K+]o peak values decayed with a half-time of 11.0 +/- 3.4 min. Compared with data available for the injured cat spinal cord, the peak [K+]o recovered relatively rapidly. Although a simple diffusion model could account for the rapid clearance of [K+]o, the persistence of dorsal-ventral [K+]o gradients could not be explained by such a model. It is postulated that secondary injury processes contributed to the persistent [K+]o gradients.

GABA-sensitivity of dorsal column axons: an in vitro comparison between adult and neonatal rat spinal cords

In neonatal rat spinal cord, conduction in the dorsal column is reversibly depressed by GABA. We compared the GABA-sensitivity of dorsal columns in neonate versus adult rats, using in vitro isolated dorsal column preparations. The extracellular compound action potential evoked by submaximal stimuli was recorded with a glass micropipette. GABA (10(-4)-10(-3) M) reversibly depressed the compound action potential of both neonatal and adult rat dorsal columns. The GABA-induced reduction of dorsal column compound action potential amplitudes was blocked by the GABAA antagonist picrotoxin (10(-3) M) and mimicked by the GABAA agonist isoguvacine (10(-4-10(-3) M). The compound action potential reduction by GABA was far less pronounced on adult dorsal columns. The reduction of compound action potential amplitudes by isoguvacine (10(-4)-10(-3) M) was also significantly less in adult dorsal columns. These data suggest that GABAA receptors may play a role in extrasynaptic modulation of spinal long tract conduction in an age-dependent manner.

Randomized double pulse stimulation for assessing stimulus frequency-dependent conduction in injured spinal and peripheral axons

Injury compromises the ability of axons to conduct action potentials at high frequencies. To study stimulus frequency-dependent conduction in injured spinal and peripheral axons, we developed a new stimulation paradigm which applies trains of double pulses at 5 Hz and randomly varied interpulse intervals of 3, 4, 5, 8, 10, 30, 50, and 80 msec. In each double pulse, the first pulse was used to condition the response activated by the second test pulse. Responses elicited by double pulses with 80 msec intervals served as controls. The L5 dorsal root was stimulated to activate dorsal column and dorsal root compound action potentials in pentobarbital anesthetized rats. To injure the spinal cord, we compressed the cord stepwise (0.25 mm every 5 min) until action potential conduction across the compression site was abolished and then decompressed the spinal cord 10 min later. Before injury, conditioning pulses applied 3-80 msec before the test pulses did not alter dorsal column responses except for a slight amplitude augmentation at 20 msec interpulse intervals (mean +/- S. E., + 4.2 +/- 0.8%, P less than 0.02) compared to controls. Injury had 3 effects on the responses. First, it significantly reduced response amplitudes and increased response latencies at 3-5 msec interpulse intervals, i.e., responses activated with 3 msec intervals were 26.0 +/- 7.4% (P less than 0.002, paired t test, n = 6) smaller and had 108 +/- 45 microseconds (P less than 0.04) longer latency than control responses. Second, response amplitude increases at 20 msec interpulse intervals (9.0 +/- 0.7%, P less than 0.0001) significantly exceeded those observed before injury (P less than 0.02, paired t test). Third, injury accentuated response amplitude declines during the stimulus train, most prominently at 80 msec intervals. Spinal cord injury did not affect the dorsal root responses. L5 root compression injury depressed dorsal root action potentials at 3-5 msec interpulse intervals (36.9 +/- 8.4%, n = 4, P less than 0.0001) but had no other effect on the responses. Our data indicate that randomized double pulse evoked potentials are sensitive detectors of acute axonal dysfunction and can be used to quantify stimulus frequency-dependent conduction deficits in injured central and peripheral axons.

GABAA receptors modulate axonal conduction in dorsal columns of neonatal rat spinal cord

gamma-Aminobutyric acid (GABA) can influence conduction in a number of axonal preparations from the peripheral and central nervous system. In the spinal cord, the excitability of primary afferent terminals has long been known to be affected by GABA. Whether conduction in the long fiber tracts of the spinal cord can be similarly modulated is unknown. Since GABA causes a pronounced depression of excitability in preparations of unmyelinated axons, and myelination is incomplete in the neonatal rat, we tested whether GABA can modulate conduction in the dorsal columns of 10-17-day-old rats. Experiments were performed in vitro, on isolated dorsal column segments (n = 18). The extracellular compound action potential evoked by submaximal stimuli was recorded with a glass micropipette positioned 0.5-2.0 mm from a stimulating electrode. At concentrations of 10(-4) - 10(-3) M, GABA decreased excitability, reversibly depressing the compound action potential amplitude, and increasing the latency by 47 +/- 11% and 22 +/- 9% (mean +/- S.E.M., n = 5, 10(-3) M), respectively. These effects were blocked by picrotoxin and mimicked by isoguvacine (10(-4) M), which decreased the compound action potential amplitude by 44 +/- 10% and increased the latency by 9 +/- 4% (n = 5). Lower concentrations of these agents caused a modest increase in excitability. At 10(-5) M, GABA increased the compound action potential amplitude by 14 +/- 2% and decreased the latency by 3 +/- 2% (n = 5). Our results demonstrate that functional GABAA receptors are present in neonatal dorsal columns.(ABSTRACT TRUNCATED AT 250 WORDS)

Neural damage in the rat thalamus after cortical infarcts

Histopathologic changes in the thalamus of 23 rats after somatosensory cortical infarction produced by middle cerebral artery occlusion were examined using the Fink-Heimer silver staining method, immunohistochemistry with antibodies against glial fibrillary acidic protein and laminin, and conventional stains. Middle cerebral artery occlusion produced cortical infarcts in the lateral parietal region, with variable involvement of the frontoparietal parasagittal sensorimotor cortex. Within 3 days after occlusion, massive terminal degeneration but no neuronal changes were apparent in the ipsilateral thalamus. By 1 week after occlusion, abnormal neurons with darkly stained, shrunken nuclei and atrophic perikarya were present in the ipsilateral thalamic nuclei. These neurons were densely argyrophilic in Fink-Heimer sections. Rats with small lateral parietal cortical lesions had degenerating neurons limited to the medial ventroposteromedial nucleus. Large lesions involving the parasagittal sensorimotor cortex resulted in widespread neuronal damage in the ventroposteromedial, ventroposterolateral, intralaminar, and posterior nuclear regions but nowhere else. Immunoreactivity to laminin antibody decreased, and astrocytic proliferation was abundant in affected thalamic areas. These findings are consistent with retrograde neuronal degeneration due to thalamocortical fiber damage in ischemic cortical regions. Such lesions remote from the infarct may influence functional recovery in patients with stroke.

Somatosensory evoked potentials in rat cerebral cortex before and after middle cerebral artery occlusion

We recorded somatosensory evoked potentials in pentobarbital-anesthetized rats before and after middle cerebral artery occlusion. Trigeminal (vibrissae), median (forelimb), and sciatic (hind limb) nerve stimuli produced consistent, robust, and sharply localized responses in the trigeminal, forelimb, and hind limb regions of the somatosensory cortex of 18 rats. These regions are situated at sequentially greater distances from the center of infarcts produced by middle cerebral artery occlusion. In eight rats, occlusion 1-2 mm below the rhinal fissure abolished somatosensory evoked potentials in all three cortical region within minutes. Positive wavelets preceding the primary cortical response were also diminished by the occlusion, suggesting that ischemia affected the thalamocortical white matter. Four of these eight rats did not show histologically apparent ischemic involvement of the hind limb cortical region at 3 hours after occlusion; sciatic nerve evoked potentials recovered substantially in all four rats, and the amplitudes exceeded baseline (129 +/- 30% at 1 hour, 173 +/- 33% at 3 hours) in three of the four rats. Three of the eight rats did not have gross ischemic involvement of the forelimb cortical region; median nerve evoked potentials recovered fully in all eight rats, but the amplitudes did not exceed baseline. All eight rats had evidence of ischemic damage in the trigeminal cortex; no rat showed full recovery in this region, and all but one had trigeminal evoked potentials that were less than 20% of baseline amplitudes by 3 hours after occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective cortical neuronal damage after middle cerebral artery occlusion in rats

We studied histopathologic changes in cerebral cortex of 20 rats after middle cerebral artery occlusion by using the Fink-Heimer suppressive silver impregnation method and conventional stains. At 6 hours after occlusion, Fink-Heimer-stained sections revealed abundant coarsely granular, intensely argyrophilic neurons in the ischemic cortex. These distinctive argyrophilic neurons could be clearly differentiated from neurons that suffered postmortem changes; argyrophilic neurons were present in all layers of the lateral parietal cortex but in only the superficial cortical layers II and III in the parasagittal area of the frontoparietal cortex and the temporo-occipital area. At 24 hours after occlusion as the ischemic region progressed to pannecrosis, argyrophilic neurons were still evident in peri-infarct regions, with more prominent neuritic silver deposits but no changes in number or spatial distribution. Over 2-7 days, the argyrophilic neurons gradually disappeared while many fine silver-impregnated degenerating terminals appeared in the peri-infarct regions. At 3-6 weeks after occlusion, no more argyrophilic neurons were seen in the cortex although degenerating axons were still present in the deep white matter. Our results indicate selective neuronal damage in the superficial cortical layers and massive axonal degeneration in the cerebrum surrounding infarcts. The neuronal damage does not appear to progress beyond 6 hours after middle cerebral artery occlusion. The Fink-Heimer method has many advantages over existing conventional stains for documenting selective neuronal damage in focal cerebral ischemia.

Corticofugal axonal degeneration in rats after middle cerebral artery occlusion

We used the Fink-Heimer method to study degenerating corticofugal axons after unilateral middle cerebral artery occlusion in 14 adult male Long-Evans hooded rats. Axonal degeneration in the pyramidal tracts was prominent at 1-3 weeks, manifesting in well-defined silver-impregnated axonal bundles coursing from the internal capsule to the pyramids and crossing completely to the contralateral spinal cord. In half of eight rats examined at 1-3 weeks, the cortical infarct included the forelimb region of the sensorimotor cortex, and degenerating corticospinal axons could be traced to the lower cervical segments; in rats with involvement of the hindlimb cortical area as well, axonal degeneration extended to the lumbosacral segments. Terminal degeneration products were present in the forebrain, midbrain, and brainstem within 2 days after arterial occlusion; the number of degenerating terminals peaked at 7 days and decreased gradually thereafter up to 6 weeks. Dense terminal degeneration was observed in the trigeminal nuclear complex of all seven rats studied at 2 and 7 days. In these seven rats, five had small cortical infarcts, and silver-impregnated terminals were observed in the lateral reticular formation; in two rats with large cortical lesions, terminal degeneration was prominent in the medial reticular formation as well. We conclude that infarcts produced by middle cerebral artery occlusion cause axonal degeneration in the brainstem and spinal cord. The Fink-Heimer method may be useful for evaluating the rat middle cerebral artery occlusion model.

Extracellular potassium activity and axonal conduction in spinal cord of the myelin-deficient mutant rat

We recorded somatosensory evoked potentials SEPs), extracellular K+ ionic activity ([K+]e), and K+ clearance rates in the spinal cords of 14 myelin-deficient mutant rats and 16 normal male littermates at 16-41 days after birth. Tested under pentobarbital anesthesia (25 mg/kg ip) and hypothermic conditions (32-34 degrees C), myelin-deficient rats had longer cortical SEP latencies (67 +/- 20 ms) compared to those in normal siblings (48 +/- 15 ms; P less than 0.05). Mean baseline [K+]e levels were 2.6 +/- 0.5 mM in myelin-deficient rats and 2.6 +/- 0.8 mM in normal siblings. Clearance times of KCl solutions injected into the spinal cord were biphasic and exponential. The mean initial and secondary exponential half-times were 1.0 +/- 0.5 and 2.7 +/- 1.7 min for myelin-deficient rats and 0.8 +/- 0.4 and 3.8 +/- 3.2 min for normal siblings. Repetitive sciatic nerve stimulation (2-20 Hz, 2- to 6-s trains) produced 1-3 mM transient [K+]e rises in thoracic and lumbar cords of myelin-deficient rats. The [K+]e rises were largest in the dorsal spinal cord at 200-500 microns depth. The normal siblings had smaller or no stimulus-induced [K+]e rises. In myelin-deficient rats, injection of 1 mM 4-aminopyridine (4-AP) solution into the thoracic spinal cord completely suppressed the stimulus-induced [K+]e and markedly increased spinal and cortical SEP amplitudes for several hours. In the normal siblings, the 4-AP injections transiently blocked spinal conduction for 20-30 min but thereafter enhanced cortical SEP amplitudes for 2-3 h. We conclude that sciatic nerve stimulation produces spinal cord [K+]e rises in myelin-deficient rat larger than those in the normal siblings, that the [K+]e transients represent increased K+ release rather than impaired K+ clearance, and that the K+ ions come from 4-AP blockable sources.

Effects of spinal cord compression on repetitive impulse conduction of the ascending fibers of the dorsal column

The effects of spinal cord compression on conduction of compound action potentials (CAPs) in the dorsal column fibers at various stimulus frequencies were analysed in pentobarbital anesthetised cats. The L 6 posterior root was given 1 to 500 Hz stimuli, and the CAPs were recorded from the L 2 posterior column. The 100th CAP was recorded at 100, 200 and 500 Hz. The L 4 cord segment was compressed by stepped increments (0.5 mm/5 min.) with a plastic plate (4 x 10 mm) until the responses at 1 Hz disappeared, then the compression was released. Before compression, each CAP at all frequencies showed almost uniform amplitudes and latencies. During compression, the CAPs were not altered significantly at any frequency until the spinal cord was compressed 2.5-4.0 mm. Further compression produced a progressive decrease in amplitude and increase in latency of the CAPs. At 500 Hz, however, the conduction block (amplitude loss, latency increase) was much severer than that produced at lower frequencies. After release of compression, the CAPs at all frequencies recovered progressively, and became almost stable after about 1 hour. The recovery rate of amplitude was only about 30% compared to the amplitude before compression at 500 Hz, and about 50% at 1 and 200 Hz. However, the recovery rate of amplitude at 100 Hz (65%) exceeded those at 1 and 200 Hz. To observe the difference in recovery rates among them, all the trains of CAPs were analyzed. Before compression, the amplitudes were almost uniform at stimulus frequencies as high as 500 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic myelogenous leukemia and Klinefelter's syndrome

A case of chronic myelogenous leukemia with Klinefelter's syndrome mosaicism in a 27-yr-old male is reported. Cytogenetic analysis provided evidence that the Philadelphia chromosome occurred monoclonally in the XXY cells but not in the XY cells.

Conductivity of dorsal column fibers during experimental spinal cord compression and after decompression at various stimulus frequencies

The effects of spinal cord compression on conduction of dorsal column fibers at various stimulus frequencies were analyzed in pentobarbital anesthetized cats. The responses to L6 dorsal root stimulation at 1 to 500 Hz were recorded from the L2 cord dorsum. The L4 cord segment was compressed gradually until the compound action potential (CAP) at 1 Hz was flat. There was no significant change of CAP at any frequency during the first part of compression, but there was progressive conduction failure, which was more severe with increased stimulus frequency, at a later stage. After decompression, the CAPs at all frequencies recovered progressively for 1 hour but slowly thereafter. However, marked differences were observed in recovery rate at different stimulus frequencies. The recovery rate at 500 Hz was much slower than that at 1 Hz, whereas the recovery rate at 100 Hz exceeded those at 1 Hz. Serial analysis of a train of high frequency impulses revealed the following different response patterns with stimulus frequencies after decompression. At 333-500 Hz the amplitude of CAPs decreased progressively, whereas at 33-125 Hz it increased up to 110-134% of the first CAP and then reached an almost steady level. At 200-250 Hz the amplitude increased transiently and then decreased progressively. The latency increased with decreased amplitude, and decreased with increased amplitude. Conduction failure at a high stimulus frequency (500 Hz) was observed at the compression site. In contrast, augmentation of CAPs at moderately high stimulus frequency (100 Hz) was observed rostral to the compressing site. The conduction failure at high stimulus frequency indicates incomplete impairment of spike generation in axons injured by mechanical compression and that these axons can transmit impulses at a low stimulus frequency. High frequency stimulation may be useful for monitoring of the function of the CNS axons. The mechanism underlying the augmentation of CAPs at moderately high stimulus frequency is briefly discussed.

Immunohistochemical reaction of myocardial fibers with actin antiserum in autopsy cases of myocardial infarction

The purpose of this study was to determine the immunoreactivity of myocardial actin filaments with actin antiserum and to examine the significance of its application to diseased human cardiac muscle. The actin was extracted and purified from chicken gizzards. Anti-actin rabbit serum was prepared and purified by affinity chromatography and defined by an immunoblotting test. Using the avidin-biotin-peroxidase complex (ABC) method, the actin antiserum was applied to paraffin sections prepared from hearts taken from routine autopsies of patients who had died of myocardial infarction. Reactivity was shown to be completely lost, not only in necrotized fibers, but also in non-specific degenerative fibers which could be identified by their eosinophilic cytoplasm with pyknotic nuclei, and clearly remaining and/or diminished cross-striations stained with hematoxylin-eosin. In contrast, hypertrophic myocardial fibers adjacent to granulation or scar tissue and those adjacent to infarcted foci exhibited a more intense reaction. These results indicated that the immunohistochemical reaction of actin filaments can be used for the easy detection of very mild degrees of degeneration of cardial muscle fibers, and for hypertrophic fibers adjacent to diseased foci. Studies of the immunoreactivity of actin protein suggestive of alteration at the molecular level might yield morphological clues regarding the nature of functional activity in the contraction of cardiac fibers.