Complement component 3 levels in the cerebrospinal fluid of cognitively intact elderly individuals with major depressive disorder

Late-life major depression (LLMD) is a risk factor for the development of mild cognitive impairment and dementia, including Alzheimer's disease (AD) and vascular dementia. Immune dysregulation and changes in innate immune responses in particular, have been implicated in the pathophysiology of both LLMD and AD. Complement system, a key component of the innate immune mechanism, is known to play an important role in synaptic plasticity and cognitive functions. However, its role in LLMD remains unknown. In the present study, we examined the levels of complement component 3 (C3, the convergence point of all complement activation pathways) in the cerebrospinal fluid (CSF) of elderly depressed subjects compared to healthy controls; as well as the relationship of CSF C3 levels with amyloid-beta (Aβ42 and Aβ40), total tau (T-tau) and phosphorylated tau (P-tau) proteins and cognition scores. CSF was obtained from 50 cognitively intact volunteers (major depression group, N = 30; comparison group, N = 20) and analyzed for levels of C3 by ELISA. C3 levels were marginally lower in the major depression group relative to the comparison group. We did not find any significant association of C3 with the AD biomarkers Aβ42 reflecting plaque pathology, P-tau related to tau pathology or the neurodegeneration biomarker T-tau. In contrast, C3 was positively correlated with CSF Aβ40, which may reflect Aβ deposition in cerebral vessel walls. We observed a negative correlation between C3 levels and Total Recall on the Buschke Selective Reminding Test (BSRT) for memory performance in the depressed subjects when controlling for education. This initial evidence on C3 status in LLMD subjects may have implications for our understanding of the pathophysiology of major depression especially in late life.

Increased levels of ascorbic acid in the cerebrospinal fluid of cognitively intact elderly patients with major depression: a preliminary study

Major depressive disorder (MDD) in the elderly is a risk factor for dementia, but the precise biological basis remains unknown, hampering the search for novel biomarkers and treatments. In this study, we performed metabolomics analysis of cerebrospinal fluid (CSF) from cognitively intact elderly patients (N = 28) with MDD and age- and gender-matched healthy controls (N = 18). The CSF levels of 177 substances were measured, while 288 substances were below the detection limit. Only ascorbic acid was significantly different, with higher levels in the MDD group at baseline. There were no correlations between CSF ascorbic acid levels and clinical variables in MDD patients at baseline. At the 3-year follow-up, there was no difference of CSF ascorbic acid levels between the two groups. There was a negative correlation between CSF ascorbic acid and CSF amyloid-β₄₂ levels in all subjects. However, there were no correlations between ascorbic acid and other biomarkers (e.g., amyloid-β₄₀, total and phosphorylated tau protein). This preliminary study suggests that abnormalities in the transport and/or release of ascorbic acid might play a role in the pathogenesis of late-life depression.

The recency ratio is associated with reduced CSF glutamate in late-life depression

Glutamate is the principal excitatory neurotransmitter in the central nervous system, and is thought to be involved in the process of memory encoding and storage. Glutamate disturbances have also been reported in psychiatric disorders, such as schizophrenia and major depressive disorder (MDD), and in Alzheimer's disease. In this paper, we set out to study the relationship between cerebrospinal fluid (CSF) glutamate levels and memory performance, which we believe has not been reported previously. In particular, we focused on recall performance broken down by serial position. Our prediction was that the recency ratio (Rr), a novel cognitive marker of intellectual impairment, would be linked with CSF glutamate levels. We studied data from a group of cognitively intact elderly individuals, 28 of whom had MDD, while 19 were controls. Study results indicated that Rr levels, but no other memory score, were inversely correlated with CSF glutamate levels, although this was found only in individuals with late-life MDD. For comparison, glutamine or GABA were not correlated with any memory performance measure.

Output order and variability in free recall are linked to cognitive ability and hippocampal volume in elderly individuals

Adapted from the work of Kahana and colleagues (e.g., Kahana, 1996), we present two measures of order of recall in neuropsychological free recall tests. These are the position on the study list of the first recalled item, and the degree of variability in the order in which items are reported at test (i.e., the temporal distance across the first four recalled items). We tested two hypotheses in separate experiments: (1) whether these measures predicted generalized cognitive ability, and (2) whether they predicted gray matter hippocampal volume. To test hypothesis 1, we conducted ordinal regression analyses on data from a group of 452 participants, aged 60 or above. Memory performance was measured with Rey's AVLT and generalized cognitive ability was measured with the MMSE test. To test hypothesis 2, we conducted a linear regression analysis on data from a sample of 79 cognitively intact individuals aged 60 or over. Memory was measured with the BSRT and hippocampal volume was extracted from MRI images. Results of Experiment 1 showed that the position of the first item recalled and the degree of output order variability correlated with MMSE scores only in the delayed test, but not in the immediate test. In Experiment 2, the degree of variability in the recall sequence of the delayed trial correlated (negatively) with hippocampal size. These findings confirm the importance of delayed primacy as a marker of cognitive ability, and are consistent with the idea that the hippocampus is involved in coding the temporal context of learned episodes.

Hippocampus and basal forebrain volumes modulate effects of anticholinergic treatment on delayed recall in healthy older adults

Introduction

Volumes of hippocampus and cholinergic basal forebrain are associated with delayed recall performance and may modulate the effect of a muscarinic receptor antagonist on delayed recall in healthy volunteers.

Methods

We studied 15 older adults before and after the oral administration of a single dose of 1 or 2 mg of the preferential M1 muscarinic receptor antagonist trihexyphenidyl (Artane™) or placebo in a double-blind randomized cross-over design. Hippocampus and basal forebrain volumes were measured using magnetic resonance imaging.

Results

We found a significant interaction between treatment and hippocampus volume and a trend level effect between treatment and anterior basal forebrain volume on task performance, with an attenuation of the association between volume size and performance with trihexyphenidyl.

Discussion

These findings suggest a reduction of delayed recall performance with increasing doses of the muscarinic antagonist that is related to an uncoupling of the association of task performance with cholinergic basal forebrain and hippocampus volumes.

A study on the specificity of the association between hippocampal volume and delayed primacy performance in cognitively intact elderly individuals

Delayed recall at the primacy position (first few items on a list) has been shown to predict cognitive decline in cognitively intact elderly participants, with poorer delayed primacy performance associated with more pronounced generalized cognitive decline during follow-up. We have previously suggested that this association is due to delayed primacy performance indexing memory consolidation, which in turn is thought to depend upon hippocampal function. Here, we test the hypothesis that hippocampal size is associated with delayed primacy performance in cognitively intact elderly individuals. Data were analyzed from a group (N=81) of cognitively intact participants, aged 60 or above. Serial position performance was measured with the Buschke selective reminding test (BSRT). Hippocampal size was automatically measured via MRI, and unbiased voxel-based analyses were also conducted to explore further regional specificity of memory performance. We conducted regression analyses of hippocampus volumes on serial position performance; other predictors included age, family history of Alzheimer's disease (AD), APOE ε4 status, education, and total intracranial volume. Our results collectively suggest that there is a preferential association between hippocampal volume and delayed primacy performance. These findings are consistent with the hypothesis that delayed primacy consolidation is associated with hippocampal size, and shed light on the relationship between delayed primacy performance and generalized cognitive decline in cognitively intact individuals, suggesting that delayed primacy consolidation may serve as a sensitive marker of hippocampal health in these individuals.

Plasma BDNF levels vary in relation to body weight in females

Brain derived neurotrophic factor (BDNF) has been implicated in the pathophysiology of depression as well as neuropsychiatric and neurodegenerative disorders. Recent studies show a role of BDNF in energy metabolism and body weight regulation. We examined BDNF levels in plasma and cerebrospinal fluid (CSF) samples from age matched elderly depressed and control subjects. Also, the association of BDNF levels with age, gender, body weight, body mass index (BMI), and cognitive performance was evaluated. We did not find any significant differences in plasma and CSF BDNF levels between depressed and control subjects. Plasma BDNF levels were negatively correlated with age (but not with BMI and body weight), when analyses were performed including both depressed and control subjects. A significant reduction in plasma BDNF levels was observed in females as compared to male subjects, and the change in BDNF levels were significantly and positively related to body weight in females. Furthermore, significant increases in Total Recall and Delayed Recall values were found in females as compared to males. In conclusion, the lower BDNF levels observed in females suggest that changes in peripheral BDNF levels are likely secondary to an altered energy balance. However, further studies using larger sample size are warranted.

Lower CSF amyloid beta peptides and higher F2-isoprostanes in cognitively intact elderly individuals with major depressive disorder

OBJECTIVE

Major depressive disorder is common in the elderly, and symptoms are often not responsive to conventional antidepressant treatment, especially in the long term. Soluble oligomeric and aggregated forms of amyloid beta peptides, especially amyloid beta 42, impair neuronal and synaptic function. Amyloid beta 42 is the main component of plaques and is implicated in Alzheimer's disease. Amyloid beta peptides also induce a depressive state in rodents and disrupt major neurotransmitter systems linked to depression. The authors assessed whether major depression was associated with CSF levels of amyloid beta, tau protein, and F2-isoprostanes in elderly individuals with major depressive disorder and age-matched nondepressed comparison subjects.

METHOD

CSF was obtained from 47 cognitively intact volunteers (major depression group, N=28; comparison group, N=19) and analyzed for levels of soluble amyloid beta, total and phosphorylated tau proteins, and isoprostanes.

RESULTS

Amyloid beta 42 levels were significantly lower in the major depression group relative to the comparison group, and amyloid beta 40 levels were lower but only approaching statistical significance. In contrast, isoprostane levels were higher in the major depression group. No differences were observed in total and phosphorylated tau proteins across conditions. Antidepressant use was not associated with differences in amyloid beta 42 levels.

CONCLUSIONS

Reduction in CSF levels of amyloid beta 42 may be related to increased brain amyloid beta plaques or decreased soluble amyloid beta production in elderly individuals with major depression relative to nondepressed comparison subjects. These results may have implications for our understanding of the pathophysiology of major depression and for the development of treatment strategies.

The neurobiology of cognitive control in successful cocaine abstinence

INTRODUCTION

Extensive evidence demonstrates that current cocaine abusers show hypoactivity in anterior cingulate and dorsolateral prefrontal cortex and respond poorly relative to drug-naïve controls on tests of executive function. Relatively little is known about the cognitive sequelae of long-term abstinence in cocaine addicts.

METHODS

Here, we use a GO-NOGO task in which successful performance necessitated withholding a prepotent response to assay cognitive control in short- and long-term abstinent cocaine users (1-5 weeks and 40-102 weeks, respectively).

RESULTS

We report significantly greater activity in prefrontal, cingulate, cerebellar and inferior frontal gyrii in abstinent cocaine users for both successful response inhibitions and errors of commission. Moreover, this relative hyperactivity was present in both abstinent groups, which, in the presence of comparable behavioral performance, suggests a functional compensation.

CONCLUSIONS

Differences between the short- and long-abstinence groups in the patterns of functional recruitment suggest different cognitive control demands at different stages in abstinence. Short-term abstinence showed increased inhibition-related dorsolateral and inferior frontal activity indicative of the need for increased inhibitory control while long-term abstinence showed increased error-related ACC activity indicative of heightened behavioral monitoring. The results suggest that the integrity of prefrontal systems that underlie cognitive control functions may be an important characteristic of successful long-term abstinence.

Levels of cerebrospinal fluid neurofilament light protein in healthy elderly vary as a function of TOMM40 variants

Neurofilament light (NFL) proteins in cerebrospinal fluid (CSF) are a marker of neuronal damage, especially subcortical axonal injury and white matter disease. Subjects with Alzheimer's disease (AD) have shown elevated levels of CSF NFL as compared to controls. However, the presence of the APOE ε4 allele, an established risk factor for AD, was not found to associate with higher CSF NFL concentrations. We examined whether TOMM40 variants, which have been reported to influence age of onset of AD and are in linkage disequilibrium with APOE, have an effect on CSF NFL levels, in 47 healthy, cognitively intact individuals with or without APOE ε4. Our results show that the presence of APOE ε4 alone does not affect CSF NFL levels significantly; however APOE and TOMM40 appear to interact. Subjects with APOE ε4 have higher CSF NFL levels than non-ε4 carriers, only when they do not carry a short poly-T variant of TOMM40, which is associated with later age of onset of AD, and may act as protective against the dose effect of ε4.

A DTI study of white matter microstructure in individuals at high genetic risk for schizophrenia

Structural brain developmental anomalies, particularly those in frontotemporal white matter pathways, may have a genetic component and place people at increased risk for schizophrenia. The current study employed Diffusion Tensor Imaging (DTI) to measure fractional anisotropy (FA) as a quantitative indicator of white matter integrity. We examined twenty-two participants at high genetic risk for schizophrenia (HR), 23 people with schizophrenia (most of whom were family members of those at HR) and 37 non-psychiatric controls for comparison. In those at HR, reduced FA was observed in the cingulate and angular gyri bilaterally. In a few regions, FA was higher in HR participants than in comparison participants. These regional variations in FA might reflect differences in white matter development from comparison participants. Our data provide some evidence that abnormal white matter integrity may be detectable before the onset of a psychotic illness, although longitudinal studies are necessary to determine whether these individuals at genetic risk with abnormal FA will develop illness and whether these changes are associated with the genetic risk for the disorder.

The neural substrates of impaired prosodic detection in schizophrenia and its sensorial antecedents

OBJECTIVE

Individuals with schizophrenia show severe deficits in their ability to decode emotions based upon vocal inflection (affective prosody). This study examined neural substrates of prosodic dysfunction in schizophrenia with voxelwise analysis of diffusion tensor magnetic resonance imaging (MRI).

METHOD

Affective prosodic performance was assessed in 19 patients with schizophrenia and 19 comparison subjects with the Voice Emotion Identification Task (VOICEID), along with measures of basic pitch perception and executive processing (Wisconsin Card Sorting Test). Diffusion tensor MRI fractional anisotropy valves were used for voxelwise correlation analyses. In a follow-up experiment, performance on a nonaffective prosodic perception task was assessed in an additional cohort of 24 patients and 17 comparison subjects.

RESULTS

Patients showed significant deficits in VOICEID and Distorted Tunes Task performance. Impaired VOICEID performance correlated significantly with lower fractional anisotropy values within primary and secondary auditory pathways, orbitofrontal cortex, corpus callosum, and peri-amygdala white matter. Impaired Distorted Tunes Task performance also correlated with lower fractional anisotropy in auditory and amygdalar pathways but not prefrontal cortex. Wisconsin Card Sorting Test performance in schizophrenia correlated primarily with prefrontal fractional anisotropy. In the follow-up study, significant deficits were observed as well in nonaffective prosodic performance, along with significant intercorrelations among sensory, affective prosodic, and nonaffective measures.

CONCLUSIONS

Schizophrenia is associated with both structural and functional disturbances at the level of primary auditory cortex. Such deficits contribute significantly to patients' inability to decode both emotional and semantic aspects of speech, highlighting the importance of sensorial abnormalities in social communicatory dysfunction in schizophrenia.

Visual white matter integrity in schizophrenia

OBJECTIVE

Patients with schizophrenia have visual-processing deficits. This study examines visual white matter integrity as a potential mechanism for these deficits.

METHOD

Diffusion tensor imaging was used to examine white matter integrity at four levels of the visual system in 17 patients with schizophrenia and 21 comparison subjects. The levels examined were the optic radiations, the striate cortex, the inferior parietal lobule, and the fusiform gyrus.

RESULTS

Schizophrenia patients showed a significant decrease in fractional anisotropy in the optic radiations but not in any other region.

CONCLUSIONS

This finding indicates that white matter integrity is more impaired at initial input, rather than at higher levels of the visual system, and supports the hypothesis that visual-processing deficits occur at the early stages of processing.

Voxelwise correlational analyses of white matter integrity in multiple cognitive domains in schizophrenia

Patients with schizophrenia show deficits in several neurocognitive domains. However, the relationship between white matter integrity and performance in these domains is poorly understood. The authors conducted neurocognitive testing and diffusion tensor imaging in 25 patients with schizophrenia. Performance was examined for tests of verbal declarative memory, attention, and executive function. Relationships between fractional anisotropy and cognitive performance were examined by using voxelwise correlational analyses. In each case, better performance on these tasks was associated with higher levels of fractional anisotropy in task-relevant regions.

Brain morphometry using diffusion-weighted magnetic resonance imaging: application to schizophrenia

Loss of cortical gray matter is accompanied by a commensurate increase in the sulcal and intraventricular cerebrospinal fluid volume. On diffusion-weighted magnetic resonance imaging, this would be reflected as a higher apparent diffusion coefficient in affected brain regions. On the basis of the above premise, we suggest that the apparent diffusion coefficient may be used as a surrogate marker for the assessment of regional brain volume deficits. We demonstrate this approach by voxelwise analysis of registered apparent diffusion coefficient images from a group of 15 patients with schizophrenia and 15 age-matched healthy controls. We found widespread regional apparent diffusion coefficient increases in patients. Affected areas included the bilateral insular cortex, hippocampus, temporal lobe, and occipital areas. These results largely concur with previous findings of cortical volume deficits in schizophrenia.

Abnormal white matter integrity in healthy apolipoprotein E epsilon4 carriers

Apolipoprotein E epsilon4 is a major genetic risk factor for Alzheimer's disease, but the neurobiological basis for this risk is unknown. We used diffusion tensor imaging to measure diffusion anisotropy in the parahippocampal gyrus white matter in healthy elderly apolipoprotein E epsilon4 carriers and noncarriers. We also measured volumes of the lateral ventricles and temporal horns as proxies of cerebral atrophy. The epsilon4 carriers (n=14) showed significantly lower fractional anisotropy and higher radial diffusivity in the parahippocampal white matter 15 mm below the anterior commissure-posterior commissure plane than noncarriers (n=15). No group differences in ventricular volumes were found, nor were diffusion tensor imaging measures modulated by ventricular volumes. Diffusion tensor imaging may be sufficiently sensitive to detect preclinical brain changes related to Alzheimer's disease.

Reduced left angular gyrus volume in first-episode schizophrenia

OBJECTIVE

Research suggests that the normal left-greater-than-right angular gyrus volume asymmetry is reversed in chronic schizophrenia. The authors examined whether angular gyrus volume and asymmetry were abnormal in patients with first-episode schizophrenia.

METHOD

Magnetic resonance imaging scans were obtained from 14 inpatients at their first hospitalization for psychosis and 14 normal comparison subjects. Manual editing was undertaken to delineate postcentral, supramarginal, and angular gyri gray matter volumes.

RESULTS

Group comparisons revealed that the left angular gyrus gray matter volume in patients was 14.8% less than that of the normal subjects. None of the other regions measured showed significant group volume or asymmetry differences.

CONCLUSIONS

Patients with new-onset schizophrenia showed smaller left angular gyrus volumes than normal subjects, consistent with other studies showing parietal lobe volume abnormalities in schizophrenia. Angular gyrus pathology in first-episode patients suggests that the angular gyrus may be a neuroanatomical substrate for the expression of schizophrenia.

Klinefelter's syndrome (XXY) as a genetic model for psychotic disorders

Males with an extra-X chromosome (Klinefelter's syndrome) frequently, although not always, have an increased prevalence of psychiatric disturbances that range from attention deficit disorder in childhood to schizophrenia or severe affective disorders during adulthood. In addition, they frequently have characteristic verbal deficits. Thus, examining brain magnetic resonance imaging (MRI) scans of these individuals may yield clues to the influence of X chromosome genes on brain structural variation corresponding to psychiatric and cognitive disorders. Eleven adult XXY and 11 age matched XY male controls were examined with a structured psychiatric interview, battery of cognitive tests, and an MRI scan. Ten of eleven of the XXY men had some form of psychiatric disturbance, four of whom had auditory hallucinations compared with none of the XY controls. Significantly smaller frontal lobe, temporal lobe, and superior temporal gyrus (STG) cortical volumes were observed bilaterally in the XXY men. In addition, diffusion tensor imaging (DTI) of white matter integrity resulted in four regions of reduced fractional anisotropy (FA) in XXY men compared with controls, three in the left hemisphere, and one on the right. These correspond to the left posterior limb of the internal capsule, bilateral anterior cingulate, and left arcuate bundle. Specific cognitive deficits in executive functioning attributable to frontal lobe integrity and verbal comprehension were noted. Thus, excess expression of one or more X chromosome genes influences both gray and white matter development in frontal and temporal lobes, as well as white matter tracts leading to them, and may in this way contribute to the executive and language deficits observed in these adults. Future prospective studies are needed to determine which gene or genes are involved and whether their expression could be modified with appropriate treatments early in life. Brain expressed genes that are known to escape inactivation on extra-X chromosomes would be prime candidates.

Quantitative comparison of algorithms for inter-subject registration of 3D volumetric brain MRI scans

The objective of inter-subject registration of three-dimensional volumetric brain scans is to reduce the anatomical variability between the images scanned from different individuals. This is a necessary step in many different applications such as voxelwise group analysis of imaging data obtained from different individuals. In this paper, the ability of three different image registration algorithms in reducing inter-subject anatomical variability is quantitatively compared using a set of common high-resolution volumetric magnetic resonance imaging scans from 17 subjects. The algorithms are from the automatic image registration (AIR; version 5), the statistical parametric mapping (SPM99), and the automatic registration toolbox (ART) packages. The latter includes the implementation of a non-linear image registration algorithm, details of which are presented in this paper. The accuracy of registration is quantified in terms of two independent measures: (1) post-registration spatial dispersion of sets of homologous landmarks manually identified on images before or after registration; and (2) voxelwise image standard deviation maps computed within the set of images registered by each algorithm. Both measures showed that the ART algorithm is clearly superior to both AIR and SPM99 in reducing inter-subject anatomical variability. The spatial dispersion measure was found to be more sensitive when the landmarks were placed after image registration. The standard deviation measure was found sensitive to intensity normalization or the method of image interpolation.

DTI and impulsivity in schizophrenia: a first voxelwise correlational analysis

Compromised white matter (WM) integrity in inferior frontal WM has been related to impulsivity in men with schizophrenia. However, these relationships may be more widespread. Fractional anisotropy (FA) derived from diffusion tensor imaging of 25 men with schizophrenia was transformed into Talairach space. Correlations between FA and impulsiveness were examined on a voxelwise basis. We found negative correlations between FA and impulsivity in inferior frontal WM, anterior cingulate, caudate, insula, and inferior parietal lobule. Positive correlations were obtained in the left postcentral gyrus, right superior/middle temporal gyrus, and bilateral fusiform gyrus. These areas may comprise a fronto-temporo-limbic circuit that modulates impulsivity. The voxelwise correlation method can serve as a hypothesis-generation method for relating target behaviors to their underlying neural networks.

MRI study of white matter diffusion anisotropy in schizophrenia

Diffusion tensor imaging (DTI) can provide information about brain white matter integrity. The results of DTI studies in schizophrenia are somewhat variable and could benefit from standardized image processing methods. Fourteen patients with schizophrenia or schizoaffective disorder and 14 healthy volunteers underwent DTI. Scans were analyzed using a rigorous voxelwise approach. The key dependent variable, fractional anisotropy, was lower for patients in the corpus callosum, left superior temporal gyrus, parahippocampal gyri, middle temporal gyri, inferior parietal gyri, medial occipital lobe, and the deep frontal perigenual region. Regions showing reduced white matter fractional anisotropy are known to be abnormal in schizophrenia. The voxelwise method used in the current study can provide the basis for hypothesis-driven research.

A role for the bilateral involvement of perirhinal cortex in generalized kindled seizure expression

The perirhinal cortex (PRh) has been suggested as a substrate for the expression of generalized clonic seizures in the late stages of kindling development (stages 4-5). Using the induction of Fos as a marker of neuronal activation, the PRh region was investigated after kindling or nonkindling electrical stimulation. Nonkindling electrical stimulation of the PRh elicited stimulus-locked behaviors, without afterdischarge. These behaviors were characterized by rearing and bilateral forelimb clonus which were terminated upon electrical stimulus offset in half of the rats displaying this behavior (with the other half expressing self-sustained seizures). In these animals, Fos immunoreactivity was found throughout neocortical and subcortical structures in the hemisphere ipsilateral to the stimulating electrode. By contrast, Fos-immunoreactivity in the contralateral hemisphere was localized primarily in the PRh and frontal motor cortex. Likewise, similar patterns of Fos immunoreactivity were observed in both hemispheres of rats following kindling to one generalized clonic seizure from several limbic and paleocortical structures. These results suggest that the bilateral involvement of the PRh is critical in producing the bilateral behaviors associated with generalized clonic seizure expression. In support of this interpretation, infusion of 3 M KCl directly into the contralateral PRh of rats kindled to a single stage 4-5 (generalized clonic) seizure from the ipsilateral amygdala reduced seizure manifestations from a generalized clonic seizure (stage 4-5) to a unilateral clonic seizure (stage 3) without affecting measures of focal excitability. Taken together, these data indicate a role for the bilateral involvement of the PRh in generalized clonic seizure expression whether evoked from the naive or kindled state. These results further indicate that bilateral behaviors require the bilateral involvement of the structures necessary for the expression of these behaviors.

Corticotropin-releasing hormone: potentiation of cocaine-kindled seizures and lethality

Carbamazepine (CBZ) blocks the development of local anesthetic seizures kindled by cocaine and lidocaine. Cocaine and lidocaine release corticotropin-releasing hormone (CRH) in hypothalamic cell cultures, and this effect is also blocked by CBZ. Because CRH administered intracerebroventricularly (i.c.v.) can produce seizures, its potential role in the development of cocaine seizures and in the anticonvulsant effects of CBZ was studied. CRH (at doses of 5, 10, and 100 micrograms) potentiated cocaine-kindled seizure development and lethality in a dose-related fashion. CRH also reversed the effects of CBZ on cocaine kindling and lethality, but only at the highest doses, which also affected cocaine kindling. Thus, a selective role for CRH in the anticonvulsant effects of CBZ was not demonstrated. The findings suggest a potentially important role for CRH in exacerbating cocaine-seizure evolution and its associated lethality and confirm the inhibition of cocaine kindling and lethality by CBZ.

Drug discrimination in rats successively trained to discriminate diazepam and pentobarbital

In Phase 1, rats were trained to discriminate either diazepam or pentobarbital from the no-drug condition. Diazepam, pentobarbital, triazolam, meprobamate, and zopiclone occasioned 100% drug-lever responding in tests under both training conditions; but the generalization gradients determined under the pentobarbital training condition were shifted to the right of those determined under the diazepam training condition. In Phase 2, the training drugs were reversed for the two groups, as well as which lever was paired with drug or no drug, in an effort to produce greater specificity of the Phase 2 discrimination. In Phase 2 tests, the Phase 1 training drug occasioned responding on the Phase 2 drug lever in all rats, suggesting that retraining overrode the Phase 1 discrimination. There were indications, however, that Phase 1 training influenced Phase 2 responding: 1) Rats ceased responding partway through no-drug training sessions using the former drug lever, and criterion performance was somewhat more difficult to maintain in Phase 2. 2) In Phase 2, dose-effect curves determined under pentobarbital training were shifted even further to the right of those determined under diazepam training than in Phase 1.

Chronic carbamazepine inhibits the development of local anesthetic seizures kindled by cocaine and lidocaine

The effects of carbamazepine (CBZ) treatment on local anesthetic-kindled seizures and lethality were evaluated in different stages of the kindling process and under different methods of CBZ administration. Chronic oral CBZ inhibited the development of both lidocaine- and cocaine-induced seizures, but had little effect on the fully developed local anesthetic seizures. Chronic CBZ also decreased the incidence of seizure-related mortality in the cocaine-injected rats. Acute CBZ over a range of doses (15-50 mg/kg) had no effect on completed lidocaine-kindled or acute cocaine-induced seizures. Repeated i.p. injection of CBZ (15 mg/kg) also was without effect on the development of lidocaine- or cocaine-kindled seizures. The differential effects of CBZ depending upon stage of seizure development suggest that distinct mechanisms underlie the development versus maintenance of local anesthetic-kindled seizures. The effectiveness of chronic but not repeated, intermittent injections of CBZ suggests that different biochemical consequences result from the different treatment regimens. The possible utility of chronic CBZ in preventing the development of toxic side effects in human cocaine users is suggested by these data, but remains to be directly evaluated.

Fingerstick glycosylated hemoglobin, plasma protein, and albumin

We have developed techniques that permit the affinity-chromatographic determination of glycosylated hemoglobin, plasma protein, and albumin on fingerstick samples of whole blood. The fingerstick glycohemoglobin technique takes advantage of the high sensitivity of measurement of hemoglobin by absorbance at 414 nm. The glycosylated plasma protein is assayed by a highly sensitive method based on binding of Coomassie blue. An enzyme-linked immunosorbent assay is used to measure albumin in the bound and nonbound fractions of an aminophenylboronic acid chromatographic separation. The fingerstick method for assay of glycosylated plasma albumin gives results that are approximately 40% higher than comparable values obtained on the same patient with a 1-ml plasma sample determined with the bromcresol green technique. There is good correlation of fingerstick glycoalbumins with fingerstick glycohemoglobins and glycosylated plasma protein values. These procedures should be useful for children and for large-scale ambulatory screening for diabetes mellitus.

Comparison and contrast of affinity chromatographic determinations of plasma glycated albumin and total glycated plasma protein

Techniques for affinity measurement of glycated albumin and for glycated total plasma protein have been developed. The two techniques were contrasted. Both techniques are linear over a 100-fold range of sample concentrations. There appears to be a non-specific early glucose binding phase to non-albumin plasma proteins. Although this phase is detected by radioactive incorporation and thiobarbituric acid, it does not interfere with the affinity determination, which does not appear to detect the early binding species. The correlation of glycated albumin levels with glycated hemoglobin levels is much stronger than that of glycated globulin levels with glycated hemoglobin levels. Due to the large contribution of glycated albumin levels to total glycated serum protein levels, the correlation of the latter with glycated hemoglobin levels is sufficiently strong to allow the use of either technique as an adequate index of glycation.

Clinical use and time relationship of changes in affinity measurement of glycosylated albumin and glycosylated hemoglobin

Simple techniques for measurement of glycosylated hemoglobin and glycosylated albumin by affinity chromatography on m-aminophenylboronic acid agarose columns have recently been developed. This study explored the time course of changes in glycoalbumin versus those of glycohemoglobin in response to rapid changes in ambient glucose concentration. One would predict that glycoalbumin levels would change more rapidly than glycohemoglobin levels due to the shorter half-life of albumin than hemoglobin. This was found to be the case in a group of rabbits rendered diabetic with alloxan. Glycoalbumin levels plateaued 4 weeks after alloxan administration, while glycohemoglobin levels were still rising. In a group of diabetic patients in whom glucose levels were initially poorly controlled, strict diet or intensive insulin management were used to rapidly bring glucose levels under control. In this group of patients, the glycoalbumin values entered the normal range and plateaued, while glycosylated hemoglobin levels were still falling. Glycoalbumin determination by affinity chromatography is a valuable adjunct to glycosylated hemoglobin determination in evaluating near term control of blood sugar values.

Aminophenylboronic acid affinity chromatography and thiobarbituric acid colorimetry compared for measuring glycated albumin

Two techniques originally developed for measurement of glycated ("glycosylated") hemoglobin but also applicable to determination of glycated albumin are the thiobarbituric acid colorimetric technique (I) and the aminophenylboronic acid affinity chromatographic procedure (II). The latter reliably distinguishes diabetics from nondiabetics, and concentrations of glycated hemoglobin and glycated albumin are linearly correlated. I is nonspecific; it neither correlates with diabetic status nor with values derived via the affinity technique. Most of the chromogenic material is present in the fraction of albumin that does not bind to aminophenylboronic acid. Glucose interferes significantly with I but only slightly with II. Prolonged incubation of plasma with glucose dramatically increases the II-determined glycated albumin. Reactivity with thiobarbituric acid increases much less, and mainly in the II-bound fraction. This fraction contains a high proportion of nonspecifically reactive material. The percentage of glycated albumin determined in crude plasma samples by II differs only slightly from the value determined by purifying the albumin from the plasma. This technique appears more promising than I for eventual clinical applications.

Aminophenylboronic acid affinity chromatography and thiobarbituric acid colorimetry compared for measuring glycated albumin

Two techniques originally developed for measurement of glycated ("glycosylated") hemoglobin but also applicable to determination of glycated albumin are the thiobarbituric acid colorimetric technique (I) and the aminophenylboronic acid affinity chromatographic procedure (II). The latter reliably distinguishes diabetics from nondiabetics, and concentrations of glycated hemoglobin and glycated albumin are linearly correlated. I is nonspecific; it neither correlates with diabetic status nor with values derived via the affinity technique. Most of the chromogenic material is present in the fraction of albumin that does not bind to aminophenylboronic acid. Glucose interferes significantly with I but only slightly with II. Prolonged incubation of plasma with glucose dramatically increases the II-determined glycated albumin. Reactivity with thiobarbituric acid increases much less, and mainly in the II-bound fraction. This fraction contains a high proportion of nonspecifically reactive material. The percentage of glycated albumin determined in crude plasma samples by II differs only slightly from the value determined by purifying the albumin from the plasma. This technique appears more promising than I for eventual clinical applications.

Use of aminophenylboronic acid affinity chromatography to measure glycosylated albumin levels

A simple technique for the measurement of glycosylated albumin by affinity chromatography on m-aminophenylboronic acid agarose columns is presented. The technique relies on bromcresol green determination of albumin in the nonbound and bound fractions. There is a linear correlation between albumin concentration of the bound fraction and glycohemoglobin values in individuals. A control nondiabetic plasma pool with a glycohemoglobin value of 7.10% +/- 0.05% (mean +/- SEM) had a glycoalbumin value of 1.64% +/- 0.06%, while a diabetic control plasma pool with a glycohemoglobin value of 13.63% +/- 0.07% had a glycoalbumin value of 4.02% +/- 0.12%. Compared with results from the affinity technique, the preponderance of colorimetric reaction determined with the thiobarbituric acid procedure is nonspecific, in that it does not correlate with diabetic status or with values derived by the affinity procedure. The bulk of thiobarbituric acid-reactive material is present in the fraction of albumin that does not bind to aminophenylboronic acid. This nonbound fraction contains plasma glucose, which significantly interferes with thiobarbituric acid determinations but only very slightly interferes with the affinity procedure. Prolonged incubation of plasma with 500 mg/dl glucose dramatically increases affinity-determined glycosylated albumin. Thiobarbituric acid reactivity increases much less, the increase being mainly in the fraction bound to aminophenylboronic acid. The percentage glycosylated albumin determined by the affinity technique in crude plasma samples differs very slightly, if at all, from that determined by purification of the albumin from plasma. The affinity technique appears very promising for eventual clinical applications in the management of diabetes.