Anti-obesity effects of olivetol in adult zebrafish model induced by short-term high-fat diet

Obesity is a complex disease caused by various factors, and synthetic drugs used to treat it can have side effects. Natural compounds, such as olivetol, could be a promising alternative. Olivetol is a substance found in certain lichen species and has anti-inflammatory and anti-cancer properties. In this study, researchers conducted in-silico molecular docking studies and found that olivetol had significant binding affinity with receptors involved in obesity. They also investigated the effects of olivetol on a diet-induced obese zebrafish model and found that high doses of olivetol reduced excessive fat accumulation and triglyceride and lipid accumulation. The low dose of olivetol showed a significant reduction in liver enzymes' levels. However, the high dose of olivetol resulted in a significant increase in HMG-CoA levels. These results suggest that olivetol may be a promising anti-obesity agent for the treatment of hyperlipidemia-related disorders, but further research is necessary to understand its full effects on the body.

Nanogels as novel drug nanocarriers for CNS drug delivery

Nanogels are highly recognized as adaptable drug delivery systems that significantly contribute to improving various therapies and diagnostic examinations for different human diseases. These three-dimensional, hydrophilic cross-linked polymers have the ability to absorb large amounts of water or biological fluids. Due to the growing demand for enhancing current therapies, nanogels have emerged as the next-generation drug delivery system. They effectively address the limitations of conventional drug therapy, such as poor stability, large particle size, and low drug loading efficiency. Nanogels find extensive use in the controlled delivery of therapeutic agents, reducing adverse drug effects and enabling lower therapeutic doses while maintaining enhanced efficacy and patient compliance. They are considered an innovative drug delivery system that highlights the shortcomings of traditional methods. This article covers several topics, including the involvement of nanogels in the nanomedicine sector, their advantages and limitations, ideal properties like biocompatibility, biodegradability, drug loading capacity, particle size, permeability, non-immunological response, and colloidal stability. Additionally, it provides information on nanogel classification, synthesis, drug release mechanisms, and various biological applications. The article also discusses barriers associated with brain targeting and the progress of nanogels as nanocarriers for delivering therapeutic agents to the central nervous system.

Exploring the contribution of pro-inflammatory cytokines to impaired wound healing in diabetes

Background

Impaired wound healing is the most common and significant complication of Diabetes. While most other complications of Diabetes have better treatment options, diabetic wounds remain a burden as they can cause pain and suffering in patients. Wound closure and repair are orchestrated by a sequence of events aided by the release of pro-inflammatory cytokines, which are dysregulated in cases of Diabetes, making the wound environment unfavorable for healing and delaying the wound healing processes. This concise review provides an overview of the dysregulation of pro-inflammatory cytokines and offers insights into better therapeutic outcomes.

Purpose of review

Although many therapeutic approaches have been lined up nowadays to treat Diabetes, there are no proper treatment modalities proposed yet in treating diabetic wounds due to the lack of understanding about the role of inflammatory mediators, especially Pro-inflammatory mediators- Cytokines, in the process of Wound healing which we mainly focus on this review.

Recent findings

Although complications of Diabetes mellitus are most reported after years of diagnosis, the most severe critical complication is impaired Wound Healing among Diabetes patients. Even though Trauma, Peripheral Artery Disease, and Peripheral Neuropathy are the leading triggering factors for the development of ulcerations, the most significant issue contributing to the development of complicated cutaneous wounds is wound healing impairment. It may even end up with amputation. Newer therapeutic approaches such as incorporating the additives in the present dressing materials, which include antimicrobial molecules and immunomodulatory cytokines is of better therapeutic value.

Summary

The adoption of these technologies and the establishment of novel therapeutic interventions is difficult since there is a gap in terms of a complete understanding of the pathophysiological mechanisms at the cellular and molecular level and the lack of data in terms of the assessment of safety and bioavailability differences in the individuals' patients. The target-specific pro-inflammatory cytokines-based therapies, either by upregulation or downregulation of them, will be helpful in the wound healing process and thereby enhances the Quality of life in patients, which is the goal of drug therapy.

Role and mechanistic actions of protein kinase inhibitors as an effective drug target for cancer and COVID

Kinases can be grouped into 20 families which play a vital role as a regulator of neoplasia, metastasis, and cytokine suppression. Human genome sequencing has discovered more than 500 kinases. Mutations of the kinase itself or the pathway regulated by kinases leads to the progression of diseases such as Alzheimer's, viral infections, and cancers. Cancer chemotherapy has made significant leaps in recent years. The utilization of chemotherapeutic agents for treating cancers has become difficult due to their unpredictable nature and their toxicity toward the host cells. Therefore, targeted therapy as a therapeutic option against cancer-specific cells and toward the signaling pathways is a valuable avenue of research. SARS-CoV-2 is a member of the Betacoronavirus genus that is responsible for causing the COVID pandemic. Kinase family provides a valuable source of biological targets against cancers and for recent COVID infections. Kinases such as tyrosine kinases, Rho kinase, Bruton tyrosine kinase, ABL kinases, and NAK kinases play an important role in the modulation of signaling pathways involved in both cancers and viral infections such as COVID. These kinase inhibitors consist of multiple protein targets such as the viral replication machinery and specific molecules targeting signaling pathways for cancer. Thus, kinase inhibitors can be used for their anti-inflammatory, anti-fibrotic activity along with cytokine suppression in cases of COVID. The main goal of this review is to focus on the pharmacology of kinase inhibitors for cancer and COVID, as well as ideas for future development.

A pan-cancer analysis of HAVCR1 with a focus on diagnostic, prognostic and immunological roles in human cancers

OBJECTIVES

Cancer is one of the most prominent causes of death world wide. Identification of novel cancer biomarkers woud help with cancer diagnosis and possible treatment.

METHODS

In this study, we comprehensively studied the diagnostic, prognostic, and therapeutic values of the hepatitis A virus cellular receptor 1 (HAVCR1) gene across multiple cancers from a pan-cancer point of view via a detailed in silico approach.

RESULTS

HAVCR1 expression was up-regulated in a variety of malignancies. The up-regulated HAVCR1 was closely related to the poor prognosis in patients with esophageal carcinoma (ESCA), lung adenocarcinoma (LUAD), and stomach adenocarcinoma (STAD). Moreover, DAVID analysis showed that HAVCR1, along with different other associated genes, was involved in numerous cancer-associated signaling pathways across ESCA, STAD, and LUAD. Furthermore, in these cancers, HAVCR1 was also found closely associated with some other parameters such as promoter methylation, tumor purity, level of CD8+ T immune cells, genomic alterations, and chemotherapeutic drugs.

CONCLUSION

HAVCR1 was overexpressed in multiple tumors. However, the up-regulated HAVCR1 is a valuable diagnostic and prognostic biomarker as well as a therapeutic target in only ESCA, STAD, and LUAD patients.

Delay in the diagnosis of dementia in urban India: Role of dementia subtype and age at onset

BACKGROUND

Early diagnosis of dementia is crucial for timely intervention. However, frequently, there is a substantial delay in diagnosis. Therefore, it is essential to recognise and address the barriers to early diagnosis. These have not been systematically studied in India. We at a specialist memory clinic in India investigated the time from symptom onset to diagnosis of dementia and factors contributing to the delay.

METHODS

In this cross-sectional study, consecutive patients with dementia (n = 855) seen at a private hospital underwent a standard clinical assessment and investigations. The primary outcome variable was time from symptom onset to diagnosis (TTD). The association of age, education, gender, dementia subtype, and age of onset on TTD were examined using a univariate analysis of covariance.

RESULTS

The median TTD was 24 months; 43% were diagnosed after 24 months. There was a significant association between TTD and age at onset (young onset-median 36 months vs. late onset-24 months) and dementia subtype. Patients with vascular dementia were diagnosed significantly earlier as compared to patients with Alzheimer's disease (AD) and frontotemporal dementia (FTD) [median 18, 24, and 30 months, respectively]. There was no effect of gender or education on the TTD.

CONCLUSION

About 40% of patients with dementia were diagnosed more than 2 years after symptom onset, particularly young onset dementias and FTD. Our study findings highlight the gaps in diagnosing patients with dementia in urban India and have significant implications for developing and implementing multifaceted interventions to improve the early diagnosis of dementia.

Evaluation of Vascular Cognitive Impairment Using the ICMR-Neuro Cognitive Tool Box (ICMR-NCTB) in a Stroke Cohort from India

Background and Purpose

Vascular cognitive impairment (VCI) presents with a spectrum of cognitive impairment due to stroke and poses a huge socioeconomic burden especially in low middle-income countries. There is a critical need for early recognition and identification of VCI patients. Therefore, we developed and validated culturally appropriate neuropsychological instruments, the ICMR-Neuro Cognitive Tool-Box (ICMR-NCTB) and Montreal Cognitive Assessment (MoCA) to diagnose vascular MCI and dementia in the Indian context.

Methods

A total of 181 participants: 59 normal cognition, 25 stroke with normal cognition, 46 vascular MCI (VaMCI) and 51 vascular dementia (VaD) were recruited for the study. The ICMR-NCTB and MoCA were administered to patients with VCI and major cognitive domains were evaluated.

Results

The ICMR-NCTB was found to have good internal reliability in VaMCI and VaD. The sensitivity of the ICMR-NCTB to detect VaMCI and VaD ranged from 70.8% to 72.9% and 75.9% to 79.7%, respectively, and the specificity for VaMCI and VaD ranged from 84.8% to 86.1% and 82.5% to 85.2%, respectively. The MoCA had excellent sensitivity and specificity to detect VaMCI and VaD at ideal cut-off scores.

Conclusion

The ICMR-NCTB is a valid neuropsychological toolbox that can be used for comprehensive cognitive assessment and diagnosis of VCI in India. In addition, the Indian version of MoCA is more adept as a screening instrument to detect VCI due to its high sensitivity. The ICMR-NCTB will aid in early detection and management of many patients, thereby reducing the burden of vascular MCI and dementia in India.

MoCA in five Indian languages: A brief screening tool to diagnose dementia and MCI in a linguistically diverse setting

INTRODUCTION AND OBJECTIVES

Early dementia diagnosis in low and middle-income countries (LMIC) is challenging due to limited availability of brief, culturally appropriate, and psychometrically validated tests. Montreal Cognitive Assessment (MoCA) is one of the most widely used cognitive screening tests in primary and secondary care globally. In the current study, we adapted and validated MoCA in five Indian languages (Hindi, Bengali, Telugu, Kannada, and Malayalam) and determined the optimal cut-off points that correspond to screening for clinical diagnosis of dementia and MCI.

METHODS

A systematic process of adaptation and modifications of MoCA was fulfilled. A total of 446 participants: 214 controls, 102 dementia, and 130 MCI were recruited across six centers.

RESULTS

Across five languages, the area under the curve for diagnosis of dementia varied from 0.89 to 0.98 and MCI varied from 0.73 to 0.96. The sensitivity, specificity and optimum cut-off scores were established separately for five Indian languages.

CONCLUSIONS

The Indian adapted MoCA is standardized and validated in five Indian languages for early diagnosis of dementia and MCI in a linguistically and culturally diverse population.

Picture-naming test for a linguistically diverse population with cognitive impairment and dementia

BACKGROUND

Picture-naming tests (PNTs) evaluate linguistic impairment in dementia due to semantic memory impairment, impaired lexical retrieval or perceptual deficits. They also assess the decline in naming impairment at various stages of dementia and mild cognitive impairment (MCI) that occurs due to progressive cognitive impairment. With the increasing numbers of people with dementia globally, it is necessary to have validated naming tests and norms that are culturally and linguistically appropriate.

AIMS

In this cross-sectional study we harmonized a set of 30 images applicable to the Indian context across five languages and investigated the picture-naming performance in patients with MCI and dementia.

METHODS & PROCEDURES

A multidisciplinary expert group formed by the Indian Council of Medical Research (ICMR) collaborated towards developing and adapting a picture naming test (PNT) known as the ICMR-PNT in five Indian languages: Hindi, Bengali, Telugu, Kannada and Malayalam. Based on cross-cultural adaptation guidelines and item-wise factor analysis and correlations established separately across five languages, the final version of the ICMR-PNT test was developed. A total of 368 controls, 123 dementia and 128 MCI patients were recruited for the study. Psychometric properties of the adapted version of the ICMR-PNT were examined, and sensitivity and specificity were examined.

OUTCOMES & RESULTS

The ICMR-PNT scores in all languages combined were higher in controls compared with patients with dementia and MCI (F_{2, 615} = 139.85; p < 0.001). Furthermore, PNT scores for MCI was higher in comparison with patients with dementia in all languages combined (p < 0.001). The area under the curve across the five languages ranged from 0.81 to 1.00 for detecting dementia. There was a negative correlation between Clinical Dementia Rating (CDR) and ICMR-PNT scores and a positive correlation between Addenbrooke's Cognitive Examination-III (ACE-III) and ICMR-PNT scores in control and patient groups.

CONCLUSIONS & IMPLICATIONS

The ICMR-PNT was developed by following cross-cultural adaptation guidelines and establishing correlations using item-wise factor analysis across five languages. This adapted PNT was found to be a reliable tool when assessing naming abilities effectively in mild to moderate dementia in a linguistically diverse context.

WHAT THIS PAPER ADDS

What is already known on this subject Picture-naming evaluates language impairment linked to naming difficulties due to semantic memory, lexical retrieval or perceptual disturbances. As a result, picture naming tests (PNTs) play an important role in the diagnosis of dementia. In a heterogeneous population such as India, there is a need for a common PNT that can be used across the wide range of languages. What this study adds to existing knowledge PNTs such as the Boston Naming Test (BNT) were developed for the educated, mostly English-speaking, Western populations and are not appropriate for use in an Indian context. To overcome this challenge, a PNT was harmonized in five Indian languages (Hindi, Bengali, Telugu, Kannada and Malayalam) and we report the patterns of naming difficulty in patients with MCI and dementia. The ICMR-PNT demonstrated good diagnostic accuracy when distinguishing patients with mild to moderate dementia from cognitively normal individuals. What are the potential or actual clinical implications of this work? With the growing number of persons suffering from Alzheimer's disease and other forms of dementia around the world, its critical to have culturally and linguistically relevant naming tests and diagnosis. This validated ICMR-PNT can be used widely as a clinical tool to diagnose dementia and harmonize research efforts across diverse populations.

Bilingualism and Its Implications for Neuropsychological Evaluation

OBJECTIVE

In the background of a large population of bilinguals globally, the study aimed to develop standards of neuropsychological testing in the context of bilingualism. Because bilingualism is known to affect cognitive processes, bilinguals and monolinguals were compared on their performance on cognitive tests, to investigate the possibility of the need for separate normative data for the two groups.

METHOD

A comprehensive neuropsychological test battery, standardized across five Indian languages: the Indian Council of Medical Research-Neuro Cognitive Tool Box (ICMR-NCTB) was administered to 530 participants (267 monolingual and 263 bilinguals matched for age and education). A systematic method of testing cognition in bilinguals was developed; to identify the appropriate language for testing, ensure language proficiency of examiner, and to interpret the bilingual responses. Additionally, the performance of bilinguals on the ICMR-NCTB was compared with monolinguals.

RESULTS

Cognitive testing in the bilingual context was performed in the most proficient language of the participants, by examiners well versed with the language. Results from the language-based tests suggested that the frequent occurrence of borrowed- and language-mixed words required consideration while scoring. The reported bilingual effect on cognitive processes did not reflect as differences in the performance between bilinguals and monolinguals.

CONCLUSIONS

Observations from the study provide robust recommendations for neuropsychological testing in the context of bilingualism. Results indicate that separate normative data may not be required for bilinguals and monolinguals. The study will be relevant and provide a reference framework to address similar issues in the large population of bilinguals in other societies.

Validation of ICMR Neurocognitive Toolbox for Dementia in the Linguistically Diverse Context of India

Objectives: The growing prevalence of dementia, especially in low- and middle-income countries (LMICs), has raised the need for a unified cognitive screening tool that can aid its early detection. The linguistically and educationally diverse population in India contributes to challenges in diagnosis. The present study aimed to assess the validity and diagnostic accuracy of the Indian Council of Medical Research-Neurocognitive Toolbox (ICMR-NCTB), a comprehensive neuropsychological test battery adapted in five languages, for the diagnosis of dementia.

Methods: A multidisciplinary group of experts developed the ICMR-NCTB based on reviewing the existing tools and incorporation of culturally appropriate modifications. The finalized tests of the major cognitive domains of attention, executive functions, memory, language, and visuospatial skills were then adapted and translated into five Indian languages: Hindi, Bengali, Telugu, Kannada, and Malayalam. Three hundred fifty-four participants were recruited, including 222 controls and 132 dementia patients. The sensitivity and specificity of the adapted tests were established for the diagnosis of dementia.

Results: A significant difference in the mean (median) performance scores between healthy controls and patients with dementia was observed on all tests of ICMR-NCTB. The area under the curve for majority of the tests included in the ICMR-NCTB ranged from 0.73 to 1.00, and the sensitivity and specificity of the ICMR-NCTB tests ranged from 70 to 100% and 70.7 to 100%, respectively, to identify dementia across all five languages.

Conclusions: The ICMR-NCTB is a valid instrument to diagnose dementia across five Indian languages, with good diagnostic accuracy. The toolbox was effective in overcoming the challenge of linguistic diversity. The study has wide implications to address the problem of a high disease burden and low diagnostic rate of dementia in LMICs like India.

Validation of Indian Council of Medical Research Neurocognitive Tool Box in Diagnosis of Mild Cognitive Impairment in India: Lessons from a Harmonization Process in a Linguistically Diverse Society

BACKGROUND/AIMS

In a linguistically diverse country such as India, challenges remain with regard to diagnosis of early cognitive decline among the elderly, with no prior attempts made to simultaneously validate a comprehensive battery of tests across domains in multiple languages. This study aimed to determine the utility of the Indian Council of Medical Research-Neurocognitive Tool Box (ICMR-NCTB) in the diagnosis of mild cognitive impairment (MCI) and its vascular subtype (VaMCI) in 5 Indian languages.

METHODS

Literate subjects from 5 centers across the country were recruited using a uniform process, and all subjects were classified based on clinical evaluations and a gold standard test protocol into normal cognition, MCI, and VaMCI. Following adaptation and harmonization of the ICMR-NCTB across 5 different Indian languages into a composite Z score, its test performance against standards, including sensitivity and specificity of the instrument as well as of its subcomponents in diagnosis of MCI, was evaluated in age and education unmatched and matched groups.

RESULTS

Variability in sensitivity-specificity estimates was noted between languages when a total of 991 controls and 205 patients with MCI (157 MCI and 48 VaMCI) were compared due to a significant impact of age, education, and language. Data from a total of 506 controls, 144 patients with MCI, and 46 patients with VaMCI who were age- and education-matched were compared. Post hoc analysis after correction for multiple comparisons revealed better performance in controls relative to all-cause MCI. An optimum composite Z-score of -0.541 achieved a sensitivity of 81.1% and a specificity of 88.8% for diagnosis of all-cause MCI, with a high specificity for diagnosis of VaMCI. Using combinations of multiple-domain 2 test subcomponents retained a sensitivity and specificity of >80% for diagnosis of MCI.

CONCLUSIONS

The ICMR-NCTB is a "first of its kind" approach at harmonizing neuropsychological tests across 5 Indian languages for the diagnosis of MCI due to vascular and other etiologies. Utilizing multiple-domain subcomponents also retains the validity of this instrument, making it a valuable tool in MCI research in multilingual settings.

Nanoemulsions: A Better Approach for Antidiabetic Drug Delivery

Conventional delivery of antidiabetic drugs faces many problems like poor absorption, low bioavailability, and drug degradation. Nanoemulsion is a unique drug technology, which is very suitable for the delivery of antidiabetic drugs. In recent years, the flaws of delivering anti-hypoglycaemic drugs have been overcome by choosing nanoemulsion drug technology. They are thermodynamically stable and also provide the therapeutic agent for a longer duration. Generally, nanoemulsions are made up of either oil-in-water or water-in-oil and the size of the droplets is from fifty to thousand nanometer. Surfactants are critical substances that are added in the manufacturing of nanoemulsions. Only the surfactants which are approved for human use can be utilized in the manufacturing of nanoemulsions. Generally, the preparation of emulsions includes mixing of the aqueous phase and organic phase and using surfactant with proper agitation. Nanoemulsions are used for antimicrobial drugs, and they are also used in the prophylaxis of cancer. Reduction in the droplet size may cause variation in the elastic and optical behaviour of nanoemulsions.

A Screening Tool to Detect Stroke Aphasia: Adaptation of Frenchay Aphasia Screening Test (FAST) to the Indian Context

Background:

Aphasia is a common consequence of stroke. To optimize recovery, it becomes critical as there are early identification and treatment of language deficits. The rising burden of stroke aphasia and lack of screening tools in the Indian context necessitates the need for a screening tool.

Objective:

We aimed to adapt and validate the Frenchay Aphasia Screening Test (FAST) to the Indian context in two widely spoken Indian languages, Telugu and Kannada, for the literate and illiterate population.

Methods:

A systematic process of adaptation and culturally appropriate modifications of the original FAST were done in 116 healthy controls and 115 patients. The validity of the adapted test was established.

Results:

The optimum cut-off values for detecting aphasia in our sample ranged from 25 to 25.5 (literate) and 13.5 to 15.5 (illiterate) with high sensitivity and specificity. There was also a significant correlation between aphasia scores for adapted FAST and the Western Aphasia Battery (WAB), establishing good convergent validity.

Discussion:

Results of the adaptation and validation of two Indian versions of FAST, suggest that it is an easy-to-use screening measure for detecting stroke-related language disabilities. The psychometric properties of the Indian version of FAST met the standardised requirements for adaptation and validation.

Conclusions:

The Indian version of FAST was found to be a reliable and valid bedside screening tool for aphasia in stroke patients. We aim that this study will facilitate the use of the test across other Indian languages and a large clinical population in the future.

Dementia Diagnosis in Seven Languages: The Addenbrooke’s Cognitive Examination-III in India

Objective

With the rising burden of dementia globally, there is a need to harmonize dementia research across diverse populations. The Addenbrooke’s Cognitive Examination-III (ACE-III) is a well-established cognitive screening tool to diagnose dementia. But there have been few efforts to standardize the use of ACE-III across cohorts speaking different languages. The present study aimed to standardize and validate ACE-III across seven Indian languages and to assess the diagnostic accuracy of the test to detect dementia and mild cognitive impairment (MCI) in the context of language heterogeneity.

Methods

The original ACE-III was adapted to Indian languages: Hindi, Telugu, Kannada, Malayalam, Urdu, Tamil, and Indian English by a multidisciplinary expert group. The ACE-III was standardized for use across all seven languages. In total, 757 controls, 242 dementia, and 204 MCI patients were recruited across five cities in India for the validation study. Psychometric properties of adapted versions were examined and their sensitivity and specificity were established.

Results

The sensitivity and specificity of ACE-III in identifying dementia ranged from 0.90 to 1, sensitivity for MCI ranged from 0.86 to 1, and specificity from 0.83 to 0.93. Education but not language was found to have an independent effect on ACE-III scores. Optimum cut-off scores were established separately for low education (≤10 years of education) and high education (&gt;10 years of education) groups.

Conclusions

The adapted versions of ACE-III have been standardized and validated for use across seven Indian languages, with high diagnostic accuracy in identifying dementia and MCI in a linguistically diverse context.

Green chemistry synthesis of nano-cuprous oxide

Green chemistry and a central composite design, to evaluate the effect of reducing agent, temperature and pH of the reaction, were employed to produce controlled cuprous oxide (Cu2O) nanoparticles. Response surface method of the ultraviolet-visible spectroscopy is allowed to determine the most relevant factors for the size distribution of the nanoCu2O. X-ray diffraction reflections correspond to a cubic structure, with sizes from 31.9 to 104.3 nm. High-resolution transmission electron microscopy reveals that the different shapes depend strongly on the conditions of the green synthesis.

Total output and switching in category fluency successfully discriminates Alzheimer's disease from Mild Cognitive Impairment, but not from frontotemporal dementia

Verbal fluency tasks require generation of words beginning with a letter (phonemic fluency; PF) or from a category (category fluency; CF) within a limited time period. Generally, total output on CF has been used to discriminate Mild Cognitive Impairment (MCI) from Alzheimer's disease (AD), while poor PF has been used as a marker for behavioral-variant frontotemporal dementia (bvFTD). However, in the absence of this disparate performance, further characterization of the task becomes necessary.

Objective

We examined whether fluency, as well as its components, clustering (successively generated words belonging to a category) and switching (shifting between categories) carried diagnostic utility in discriminating AD from MCI and bvFTD.

Methods

PF (letter 'P') and CF ('animals') tasks were administered in English to patients with MCI (n=25), AD (n=37), and bvFTD (n=17). Clustering and switching scores were calculated using established criteria.

Results

Our findings suggested that up to 85% of AD and MCI could be successfully discriminated based on total number of responses and switching in CF alone. PF-CF disparity was not noted in AD or bvFTD. Performance on clustering or switching also proved insufficient to discriminate AD from bvFTD.

Conclusion

Switching was found to be useful when differentiating AD from MCI. In AD and bvFTD, the course of progression of the disease may lead to attenuation of total number of responses produced on both tasks to an extent where clustering and switching may not be useful measures to discriminate these dementias from each other.

Total output and switching in category fluency successfully discriminates Alzheimer's disease from Mild Cognitive Impairment, but not from frontotemporal dementia

Verbal fluency tasks require generation of words beginning with a letter (phonemic fluency; PF) or from a category (category fluency; CF) within a limited time period. Generally, total output on CF has been used to discriminate Mild Cognitive Impairment (MCI) from Alzheimer's disease (AD), while poor PF has been used as a marker for behavioral-variant frontotemporal dementia (bvFTD). However, in the absence of this disparate performance, further characterization of the task becomes necessary.

Transduction of physical force by the vascular wall Role of phospholipase C and cytochrome P450 metabolites of arachidonic acid

The blood vessel wall responds actively to an elevation in transmural pressure. This pressure-induced myogenic response is thought to set the basal level of vascular tone upon which metabolic and neural influences operate in concert to regulate organ blood flow. The cellular mechanisms that mediate the vascular muscle response to mechanical deformation via a changing transmural pressure include membrane depolarization, activation of phospholipase C, and a rise in intracellular [Ca(2+)](i), which appear to be nonadapting-remaining active as long as the pressure stimulus is applied. This brief review addresses some of the cellular events mediating transduction of transmural pressure by the vessel wall. Two possible mechanisms that are responsible for the nonadapting nature of pressure-induced myogenic tone are also explored, namely, formation of a P450 metabolite of arachidonic acid, which acts to buffer activation of K(+) channels as intracellular Ca(2+) rises, and direct activation of Ca(2+) channels by diacylglycerol. Evidence is provided suggesting that activation of phospholipase C is responsible for both the release of the arachidonic acid substrate for P450 enzymes and for the formation of diacylglycerol via its action on membrane-bound phospholipids.

Acute effects of prostaglandin E1 and E2 on vascular reactivity and blood flow in situ in the chick chorioallantoic membrane

The chick chorioallantoic membrane (CAM) subserves gas exchange in the developing embryo and shell-less culture affords a unique opportunity for direct observations over time of individual blood vessels to pharmacologic interventions. We tested a number of lipids including prostaglandins PGE(1&2) for vascular effects and signaling in the CAM. Application of PGE(1&2) induced a decrease in the diameter of large blood vessels and a concentration-dependent, localized, reversible loss of blood flow through small vessels. The loss of flow was also mimicked by misoprostol, an agonist for 3 of 4 known PGE receptors, EP(2-4), and by U46619, a thromboxane mimetic. Selective receptor antagonists for EP(3) and thromboxane each partially blocked the response. This is a first report of the effects of prostaglandins on vasoreactivity in the CAM. Our model allows the unique ability to examine simultaneous responses of large and small vessels in real time and in vivo.

Differential effect of amyloid β on the cytochrome P450 epoxygenase activity in rat brain

One of the prominent features of Alzheimer's disease is the excessive accumulation of the protein amyloid beta (Aβ) in certain areas of the brain leading to neurodegeneration. Aβ is cytotoxic and disrupts several cytoprotective pathways. Recent literature has demonstrated that certain cytochrome P450 (CYP) products are neuroprotective, including epoxide metabolites of arachidonic acid (AA), epoxyeicosatrienoic acids (EETs). The action of Aβ with respect to regionally produced EETs in the brain has yet to be defined. Epoxygenases metabolize AA into four regioisomers of EETs (14,15-, 11,12-, 8,9- and 5,6-EET). EETs are rapidly degraded into dihydroxyeicosatrienoic acids (DiHETEs) by soluble epoxide hydrolase (sEH). To determine the effect of Aβ on the epoxygenase activity in different regions of the brain, microsomes were prepared from the cerebrum and cerebellum of adult Sprague-Dawley rats and incubated with 1 and 10 μM Aβ for 30 min after which epoxygenase activity assay was performed. Mass spectrometry indicated that incubation with Aβ reduced 14,15-EET production by 30% as compared to vehicle in the cerebrum, but not in the cerebellum. When we separated the cerebrum into cortex and hippocampus, significant decrease in the production of total EETs and DiHETEs were seen in presence of Aβ (81% and 74%) in the cortex. Moreover, 11,12-EET production was decreased to ∼70% of vehicle in both cortex and hippocampus. Epoxygenase activity in the cultured astrocytes and neurons also showed reduction in total EET and DiHETE production (to 80% and ∼70% of vehicle respectively) in presence of Aβ. Altogether, our data suggest that Aβ reduces epoxygenase activity differentially in a region-specific and cell-specific manner. The reduction of cytoprotective EETs by Aβ in the cerebrum may make it more prone to degeneration than the cerebellum. Further understanding of these interactions will improve our ability to protect against the pathology of Alzheimer's disease.

Limits on intrinsic magnetism in graphene

We have studied magnetization of graphene nanocrystals obtained by sonic exfoliation of graphite. No ferromagnetism is detected at any temperature down to 2 K. Neither do we find strong paramagnetism expected due to the massive amount of edge defects. Rather, graphene is strongly diamagnetic, similar to graphite. Our nanocrystals exhibit only a weak paramagnetic contribution noticeable below 50 K. The measurements yield a single species of defects responsible for the paramagnetism, with approximately one magnetic moment per typical graphene crystallite.

Contribution of epoxyeicosatrienoic acids to the hypoxia-induced activation of Ca2+-activated K+ channel current in cultured rat hippocampal astrocytes

Brief hypoxia differentially regulates the activities of Ca(2+)-activated K(+) channels (K(Ca)) in a variety of cell types. We investigated the effects of hypoxia (<2% O(2)) on K(Ca) channel currents and on the activities of cytochrome P450 2C11 epoxygenase (CYP epoxygenase) in cultured rat hippocampal astrocytes. Exposure of astrocytes to hypoxia enhanced macroscopic outward K(Ca) current, increased the open state probability (NPo) of 71 pS and 161 pS single-channel K(Ca) currents in cell-attached patches, but failed to increase the NPo of both the 71 pS and 161 pS K(Ca) channel currents recorded from excised inside-out patches. The hypoxia-induced enhancement of macroscopic K(Ca) current was attenuated by pretreatment with tetraethylammonium (TEA, 1 mM) or during recording using low-Ca(2+) external bath solution. Exposure of astrocytes to hypoxia was associated with generation of superoxide as detected by staining of cells with the intracellular superoxide detection probe hydroethidine (HE), attenuation of the hypoxia-induced activation of unitary K(Ca) channel currents by superoxide dismutation with tempol, and as quantitated by high-pressure liquid chromatography/fluorescence assay using HE as a probe. In cultured astrocytes in which endogenous CYP epoxygenase activity has been inhibited with either miconazole or N-methylsulfonyl-6-(2-propargyloxyphenyl) hexanamide (MSPPOH) hypoxia failed to increase the NPo of both the 71 pS and 161 pS K(Ca) currents and generation of superoxide. Hypoxia increased the level of P450 epoxygenase protein and production of epoxyeicosatrienoic acids (EETs) from cultured astrocytes, as determined by immunohistochemical staining and LC/MS analysis, respectively. Exogenous 11,12-EET increased the NPo of both the 71 pS and 161 pS K(Ca) single-channel currents only in cell-attached but not in excised inside-out patches of cultured astrocytes. These findings indicate that hypoxia enhances the activities of two types of unitary K(Ca) currents in astrocytes by a mechanism that appears to involve CYP epoxygenase-dependent generation of superoxide and increased production or release of EETs.

Identifying endothelium-derived hyperpolarizing factor: recent approaches to assay the role of epoxyeicosatrienoic acids

Investigation of endothelial regulation of vascular reactivity and tone has led to the discovery of chemical mediators such as nitric oxide (NO) and prostacyclin (PGI2). Evidence has emerged indicating another as yet unidentified hyperpolarizing agent (endothelium-derived hyperpolarizing factor or EDHF) that is different from NO and PGI2 and exerts it effects through calcium-activated potassium channels (KCa). Previous studies to identify EDHF have been carried out using inhibitors that block NOS and COX before application of KCa channel and/or muscarinic receptor antagonists. Such pharmacological manipulation has complicated interpretation of results, clearly pointing to the need for altered approaches to verify previous studies. Evidence has emerged that potential EDHF candidates vary with vessel size, species and tissue beds, indicating that there may be more than one EDHF. To date, the most commonly described and best characterized of them all are a set of arachidonic acid metabolites, epoxyeicosatrienoic acids (EETs). These compounds are synthesized both intra- and extravascularly. Until recently, methodology to detect EETs in the microvasculature has been tedious and expensive, limiting the experimentation that is necessary to confirm EETs as an EDHF. This review describes state-of-the-art methods for assaying EETs in biological samples, after summarizing evidence for EETs as an EDHF and introducing emerging concepts of the role of extravascular EETs in linking neuronal activity to localized blood flow during functional hyperemia.

Hybrid fuzzy logic committee neural networks for recognition of swallow acceleration signals

Biological signals are complex and often require intelligent systems for recognition of characteristic signals. In order to improve the reliability of the recognition or automated diagnostic systems, hybrid fuzzy logic committee neural networks were developed and the system was used for recognition of swallow acceleration signals from artifacts. Two sets of fuzzy logic-committee networks (FCN) each consisting of seven member networks were developed, trained and evaluated. The FCN-I was used to recognize dysphagic swallow from artifacts, and the second committee FCN-II was used to recognize normal swallow from artifacts. Several networks were trained and the best seven were recruited into each committee. Acceleration signals from the throat were bandpass filtered, and several parameters were extracted and fed to the fuzzy logic block of either FCN-I or FCN-II. The fuzzified membership values were fed to the committee of neural networks which provided the signal classification. A majority opinion of the member networks was used to arrive at the final decision. Evaluation results revealed that FCN correctly identified 16 out of 16 artifacts and 31 out of 33 dysphagic swallows. In two cases, the decision was ambiguous due to the lack of a majority opinion. FCN-II correctly identified 24 out of 24 normal swallows, and 28 out of 29 artifacts. In one case, the decision was ambiguous due to the lack of a majority opinion. The present hybrid intelligent system consisting of fuzzy logic and committee networks provides a reliable tool for recognition and classification of acceleration signals due to swallowing.

Dual regulation of the cerebral microvasculature by epoxyeicosatrienoic acids

Epoxyeicosatrienoic acids (EETs) are lipid metabolites that are synthesized in vascular endothelial cells. They are released by stimulation of their muscarinic receptors, and induce vaso-relaxation of cerebral blood vessels. In addition, cytochrome P450 epoxygenase enzymes, which catalyze the formation of epoxyeicosatrienoic acids, especially after stimulation by the excitatory neurotransmitter glutamate, are present in astrocytes, an abundant cell type in the brain that extends foot processes onto the cerebral microvessels. Using a modification of an efficient, recently developed, fluorescent assay, we have detected the presence of EETs in endothelial cells cultured from the cortex of rat brains as well as in neonatal astrocytes. We propose that both these cell types provide a dual supply of EETs to increase cerebral blood flow in order to meet systemic as well as localized nutrient demands of cells in the brain.

Fluorescent HPLC assay for 20-HETE and other P-450 metabolites of arachidonic acid

This study describes a fluorescent HPLC assay for measuring 20-hydroxyeicosatetraenoic acid (20-HETE) and other cytochrome P-450 metabolites of arachidonic acid in urine, tissue, and interstitial fluid. An internal standard, 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid, was added to samples, and the lipids were extracted and labeled with 2-(2,3-naphthalimino)ethyl trifluoromethanesulfonate. P-450 metabolites were separated on a C18 reverse-phase HPLC column. Coelution and gas chromatography-mass spectrometry studies confirmed the identity of the 20-HETE peak. The 20-HETE peak can be separated from those for dihydroxyeicosatrienoic acids, other HETEs, and epoxyeicosatrienoic acids. Known amounts of 20-HETE were used to generate a standard curve (range 1-10 ng, r(2) = 0.98). Recovery of 20-HETE from urine averaged 95%, and the intra-assay variation was <5%. Levels of 20-HETE were measured in 100 microliter of urine and renal interstitial fluid or 0.1 mg of renal tissue. The assay was evaluated by studying the effects of 1-aminobenzotriazole (ABT) on the excretion of 20-HETE in rats. ABT reduced excretion of 20-HETE by >65% and inhibited the formation of 20-HETE by renal microsomes. The availability of this assay should facilitate work in this field.

Production of 20-HETE and its role in autoregulation of cerebral blood flow

In the brain, pressure-induced myogenic constriction of cerebral arteriolar muscle contributes to autoregulation of cerebral blood flow (CBF). This study examined the role of 20-HETE in autoregulation of CBF in anesthetized rats. The expression of P-450 4A protein and mRNA was localized in isolated cerebral arteriolar muscle of rat by immunocytochemistry and in situ hybridization. The results of reverse transcriptase-polymerase chain reaction studies revealed that rat cerebral microvessels express cytochrome P-450 4A1, 4A2, 4A3, and 4A8 isoforms, some of which catalyze the formation of 20-HETE from arachidonic acid. Cerebral arterial microsomes incubated with [(14)C]arachidonic acid produced 20-HETE. An elevation in transmural pressure from 20 to 140 mm Hg increased 20-HETE concentration by 6-fold in cerebral arteries as measured by gas chromatography/mass spectrometry. In vivo, inhibition of vascular 20-HETE formation with N-methylsulfonyl-12, 12-dibromododec-11-enamide (DDMS), or its vasoconstrictor actions using 15-HETE or 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (20-HEDE), attenuated autoregulation of CBF to elevations of arterial pressure. In vitro application of DDMS, 15-HETE, or 20-HEDE eliminated pressure-induced constriction of rat middle cerebral arteries, and 20-HEDE and 15-HETE blocked the vasoconstriction action of 20-HETE. Taken together, these data suggest an important role for 20-HETE in the autoregulation of CBF.

Measurements of acceleration during videofluorographic evaluation of dysphagic patients

Accelerometry represents a noninvasive technique for the assessment of the swallowing mechanism. However, the underlying physiological events that give rise to the acceleration signal are poorly understood. In the present study, the acceleration signal was measured simultaneously during videofluorography examination. Preliminary results revealed that the signal occurred during laryngeal elevation and the magnitude of acceleration correlated well with the laryngeal displacement. Acceleration measurements present a potentially useful noninvasive tool.

Salt-induced liquid-liquid phase separation of protein-surfactant complexes

We report the cloud-point curve determination of lysozyme-sodium-doderyl-sulfate (SDS) complexes in solution. By varying the pH, salt concentration, and relative ratio of lysozyme to SDS, the phenomenon of clouding and liquid-liquid phase separation is investigated under different solution conditions. For the temperature, concentration, and pH ranges used in this study, the clouding phenomenon appears to be controlled by the electrostatic interaction between the lysozyme-SDS complexes. Any change in the solution condition that leads to a decrease in the charge on the lysozyme-SDS complexes results in an increase in cloud-point temperature. A generalized Flory-Huggins theory for polydisperse polymers is used to describe the cloud-point curve.

Cat cerebral arterial smooth muscle cells express cytochrome P450 4A2 enzyme and produce the vasoconstrictor 20-HETE which enhances L-type Ca2+ current

1. Cerebral arteries express cytochrome P450 4A enzymes (P450 4A) and produce 20- hydroxyeicosatetraenoic acid (20-HETE), a potent constrictor of pial arterioles. It is not known which cell type in the vessel wall is responsible for the formation of 20-HETE. We examined whether freshly isolated cerebral arterial muscle cells (VSMCs) express P450 4A and produce 20-HETE. We also studied the effect of 20-HETE on pressurized cerebral arteries and on whole-cell L-type Ca2+current (ICa) recorded in cat cerebral VSMCs. 2. Cat cerebral VSMCs incubated with [14C]arachidonic acid ([14C]AA) produced 20-HETE (3.9 +/- 1.1 pmol min-1 (mg protein)-1). 3. Reverse transcription-polymerase chain reaction studies revealed that cat cerebral VSMCs express mRNA for P450 4A which metabolizes AA to 20-HETE. Cloning and sequencing of the cDNA amplified from mRNA isolated from VSMCs showed > 96 % amino acid homology to the rat and human P450 4A2 and 4A3. 4. 20-HETE (1-300 nM) induced a concentration-dependent constriction of cat cerebral arteries, which was inhibited by nifedipine. 5. Addition of 10 and 100 nM 20-HETE to the bath increased peak ICa by 50 +/- 3 and 100 +/- 10 %, respectively. This effect was not influenced by altering the frequency of depolarization. 20-HETE (100 nM) failed to increase ICa in the presence of nifedipine. 6. These results demonstrate that cat cerebral VSMCs express P450 4A enzyme, and produce 20-HETE which activates L-type Ca2+ channel current to promote cerebral vasoconstriction.

20-Hydroxyeicosatetraenoic acid-induced vasoconstriction and inhibition of potassium current in cerebral vascular smooth muscle is dependent on activation of protein kinase C

20-Hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450 metabolite of arachidonic acid, is a potent vasoconstrictor, and has been implicated in the myogenic activation of renal and cerebral arteries. We examined the role of protein kinase C (PKC) in the signal transduction pathway by which 20-HETE induces vasoconstriction and inhibition of whole-cell K+ current in cat cerebral vascular smooth muscle. 20-HETE induced a concentration-dependent constriction in isolated pressurized cat middle cerebral arteries (-29 +/- 8% at 1 microM). However, in the presence of an N-myristoylated PKC pseudosubstrate inhibitor peptide (MyrPsiPKC-I(19-27)), 20-HETE induced a concentration-dependent vasodilation (26 +/- 4% at 1 microM). In whole-cell voltage clamp studies, application of 20-HETE inhibited whole-cell K+ current recorded in cat cerebral vascular smooth muscle cells, an effect that was attenuated by MyrPsiPKC-I(19-27). Further evidence for the role of PKC activation in response to 20-HETE is the finding that 20-HETE increased the phosphorylation of myristoylated, alanine-rich PKC substrate in cultured cat cerebral vascular smooth muscle cells in a concentration- and PKC-dependent manner. These data provide evidence that PKC is an integral part of the signal transduction pathway by which 20-HETE elicits vasoconstriction of cerebral arteries and inhibition of whole-cell K+ current in cat cerebral vascular smooth muscle.

Role of P-450 arachidonic acid epoxygenase in the response of cerebral blood flow to glutamate in rats

BACKGROUND AND PURPOSE

Glutamate, a major excitatory neurotransmitter in the brain, has been implicated in the hyperemic response to increases in the activity of neurons, but the mechanism of glutamate-induced dilation of cerebral blood vessels is unknown. Glutamate has been shown to enhance the release of arachidonic acid (AA) in brain tissue and cultured astrocytes. We have previously shown that astrocytes metabolize AA to vasodilator products, epoxyeicostrienoic acids (EETs), and express a P-450 AA epoxygenase, P-450 2C11. We tested the hypothesis that glutamate-induced dilation of cerebral arterioles is mediated in part by changes in the formation and release of EETs by perivascular astrocytes.

METHODS

Primary astrocyte cultures were prepared from 3-day-old rat pups. The cells were labeled with [14C]AA, and the effect of glutamate on the formation of EETs from [14C]AA by cultured astrocytes was studied. The expression of P-450 2C11 protein in the microsomal fractions of cultured astrocytes was assessed by Western blot. In vivo cerebral blood flow measurements were made in adult rats by laser-Doppler flowmetry after administration of glutamate into the subdural space of the rat before and after treatment with miconazole.

RESULTS

Glutamate treatment (100 mumol/L for 30 minutes) induced a threefold increase in the formation of EETs from [14C]AA by cultured astrocytes, and the increase was inhibited by miconazole (20 mumol/L), an inhibitor of P-450 AA epoxygenase. Treatment with glutamate (100 mumol/L) for 12 hours increased the expression of P-450 2C11 protein in the microsomal fraction of cultured astrocytes. The response of laser-Doppler cerebral blood flow to administration of glutamate (500 mumol/L) into the subdural space of the rat was significantly attenuated after treatment with miconazole (20 mumol/L for 30 minutes).

CONCLUSIONS

These findings suggest a role for a P-450 AA epoxygenase in astrocytes in the coupling between the metabolic activity of neurons and regional blood flow in the brain.

Identification of a putative microvascular oxygen sensor

The vascular response to changes in oxygen levels in the blood and tissue is a highly adaptive physiological response that functions to match tissue oxygen supply to metabolic demand. Defining the cellular mechanisms that can sense physiologically relevant changes in PO2 and adjust vascular diameter are vital to our understanding of this process. A cytochrome P450 (P450) enzyme of the 4A family of omega-hydroxylases was localized in renal microvessels, renal cortex, and a striated muscle microvascular bed (cremaster) of the rat. In the presence of molecular oxygen, this P450 enzyme catalyzes formation of 20-HETE from arachidonic acid (AA). Prior studies have shown that 20-HETE potently contracts renal and cerebral arteries and arterioles. The present study demonstrates that 20-HETE constricts striated muscle arterioles as well. In both intact renal microvessels and enriched renal cortical microsomal enzyme preparations, the formation of 20-HETE was linearly dependent on PO2 between 20 and 140 mm Hg. Homogenates of cremaster tissue produced 20-oxygen HETE when incubated with AA. They also expressed message for P450 4A enzyme, as determined by Southern and Western blots. Administration of 17-octadecynoic acid (17-ODYA), which is a P450 4A inhibitor, attenuated the constriction of third-order cremasteric arterioles in response to elevation of superfusion solution PO2 from approximately equal to 3 to 5 mm Hg to approximately equal to 35 mm Hg. 17-ODYA had no effect on basal vascular tone or response of cremaster arterioles to vasoactive compounds. These results demonstrate the existence of P450 omega-hydroxylase activity and 20-HETE formation in the vasculature and parenchyma of at least two microvascular beds. Our data suggest that a P450 enzyme of the 4A family has the potential to function as an oxygen sensor in mammalian microcirculatory beds and to regulate arteriolar caliber by generating 20-HETE in an oxygen-dependent manner.

Molecular characterization of an arachidonic acid epoxygenase in rat brain astrocytes

BACKGROUND AND PURPOSE

Brain parenchymal tissue metabolizes arachidonic acid (AA) via the cytochrome P450 (P450) epoxygenase to epoxyeicosatrienoic acids (EETs). EETs dilate cerebral arterioles and enhance K+ current in vascular smooth muscle cells from large cerebral arteries. Because of the close association between astrocytes and the cerebral microcirculation, we hypothesized that brain epoxygenase activity originates from astrocytes. This study was designed to identify and localize an AA epoxygenase in rat brain astrocytes. We also tested the effect of EETs on whole-cell K+ current in rat cerebral microvascular smooth muscle cells.

METHODS

A functional assay was used to demonstrate endogenous epoxygenase activity of intact astrocytes in culture. Oligonucleotide primers derived from the sequence of a known hepatic epoxygenase, P450 2C11, were used in reverse transcription/polymerase chain reaction of RNA isolated from cultured rat astrocytes. The appropriate size reverse transcription/polymerase chain reaction product was cloned into a plasmid vector and sequenced. A polyclonal peptide antibody was raised against P450 2C11 and used in Western blotting and immunocytochemical staining of cultured astrocytes. A voltage-clamp technique was used to test the effect of EETs on whole-cell K+ current recorded from rat cerebral microvascular muscle cells.

RESULTS

Based on elution time of known standards and inhibition by miconazole, an inhibitor of P450 AA epoxygenase, cultured astrocytes produce 11,12- and 14,15-EETs when incubated with AA. The sequence of a cDNA derived from RNA isolated from cultured rat astrocytes was 100% identical to P450 2C11. Immunoreactivity to glial fibrillary acidic protein, a marker for astrocytes, colocalized with 2C11 immunoreactivity in double immunochemical staining of cultured astrocytes. EETs enhanced outward K+ current in muscle cells from rat brain microvessels.

CONCLUSIONS

Our results demonstrate that a P450 2C11 mRNA is expressed in astrocytes and may be responsible for astrocyte epoxygenase activity. Given the vasodilatory effect of EETs, our findings suggest a role for astrocytes in the control of cerebral microcirculation mediated by P450 2C11-catalyzed conversion of AA to EETs. The mechanism of EET-induced dilation of rat cerebral microvessels may involve activation of K+ channels.

Formation and action of a P-450 4A metabolite of arachidonic acid in cat cerebral microvessels

The purpose of this study was to determine whether arachidonic acid can be converted to 20-hydroxyeicosatetraenoic acid (HETE) by P-450 enzymes in cat cerebral microvasculature, to identify the P-450 isoforms responsible for the formation of this metabolite, and to characterize the vasoactive effects of 20-HETE on these vessels. Cerebral microvessels were isolated by filling them with a suspension of magnetized iron oxide (particle size = 10 microns) and separated from minced cerebral cortical tissue using a magnet. Cat cerebral microvessels were homogenized and incubated with [14C]arachidonic acid (AA), and cytochrome P-450-dependent metabolites of AA were separated by reverse-phase high-pressure liquid chromatography. A major metabolite that coeluted with synthetic 20-HETE was identified. The formation of this metabolite was dependent on NADPH and was inhibited by 17-octadecynoic acid (ODYA), a specific suicide-substrate inhibitor of the omega-hydroxylation of AA by P-450 enzymes. Western blot analysis confirmed the presence of a P-450 enzyme of the 4A gene family in cat cerebral microvessels. Gas chromatography/mass spectrometry analysis revealed that this metabolite has an identical mass-to-charge ratio (391 m/z) as that of standard 20-HETE. Exogenous 20-HETE constricted pressurized cat pial arteries in a concentration-dependent manner with a threshold concentration of < 1.0 nM. 20-HETE (1 nM) inhibited the activity of a 217-pS K+ channel recorded in cell-attached patches of isolated cat cerebral microvascular muscle cells. Blockade of endogenous P-450 activity with 17-ODYA markedly increased the activity of the 217 pS K+ channel in these cells, an action that was completely reversed by a nanomolar concentration of 20-HETE, suggesting that 20-HETE might be an endogenous modulator of the 217 pS K+ channel in cerebral arterial muscle cells. These results demonstrate the presence of P-450 4A enzyme activity in the cerebral microvasculature of the cat that converts AA to 20-HETE. The potent vasoconstrictor effects of 20-HETE on cerebral vessels suggests that metabolites of P-450 enzymes of the 4A gene family could play an important role in regulating cerebral microvascular tone.

Pressurization of isolated renal arteries increases inositol trisphosphate and diacylglycerol

Inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol (DAG) concentrations were measured in isolated, cannulated dog renal arteries under control conditions (0 mmHg) and in response to step elevations in transmural pressure. There was a pressure-dependent increase in IP3 at 60 and 120 mmHg, reaching significance at 120 mmHg (P < 0.05) and a significant increase in DAG at both 60 and 120 mmHg measured after maintaining pressure for 15 min. Similarly, IP3 measurements made 90 s after a step increase in transmural pressure also exhibited a pressure-dependent profile, again reaching significance at 120 mmHg. Calculation of active tension demonstrated these renal arteries developed pressure-dependent myogenic tone. To assess the role of the endothelium in this regard, IP3 was measured before and after endothelial removal at 0 and 60 mmHg. Pressure-dependent myogenic tone was still present upon endothelial removal. In the absence of the endothelium, we observed a significant increase in total IP3 at 60 compared with 0 mmHg; furthermore, the increase in IP3 in the absence of the endothelium was significantly greater than that observed when the endothelium was intact. Given that the primary source of IP3 is via the actions of phospholipase C (PLC) on phosphatidylinositol 4,5-bisphosphate, these biochemical data directly demonstrate that elevation of transmural pressure in dog renal arteries activates PLC.

Assay of heat-labile enterotoxins by their ADP-ribosyltransferase activities

Simple enzymatic assays to detect heat-labile enterotoxins whose modes of action are similar to that of cholera toxin were evaluated. The assays are performed by using an artificial substrate, diethylamino benzylidine-aminoguanidine, which is an ADP-ribose acceptor. The product, formed in the presence of NAD+, can be quantitated by spectrofluorometric, spectrophotometric, or high-performance liquid chromatographic (HPLC) methods. As little as 25 ng (spectrofluorometry) or 125 ng (spectrophotometry or HPLC) of cholera toxin can be detected in an assay volume of 250 microliters. The detection limit for heat-labile enterotoxin by either the spectrophotometric or HPLC methods was 125 ng/250 microliters. Because the results are quantitative, the enzymatic methods can be used for medium development, determination of factors that influence toxin production, and other applications that heretofore could be accomplished only with difficulty. The enzymatic methods add a new dimension to the assay of toxins that ribosylate arginine residues of proteins. Sensitivities of the assays might be improved by developing better synthetic substrates, and applications could be broadened by the development of artificial substrates containing other functional groups.

Use of substituted (benzylidineamino)guanidines in the study of guanidino group specific ADP-ribosyltransferase

A number of substituted (benzylidineamino)guanidines with different substitutents in the benzene nucleus are synthesized by coupling substituted benzaldehydes with aminoguanidine, and these compounds are tested as substrates for cholera toxin catalyzed ADP-ribosylation. A spectrophotometric assay method for the measurement of ADP-ribosyltransferase activity is developed, making use of the absorption characteristics of some of these compounds and the difference in the ionic character of the free compounds and the ADP-ribosylated products. The kinetic parameters for the ADP-ribosylation of these compounds are evaluated. A correlation between log kcat or log (kcat/Km) and the Hammett substituent constant sigma is observed. This correlation suggests the importance of substrate electronic effects on the enzymatic reaction. The reactivity of these compounds as acceptors of ADP-ribosyl groups in the reaction catalyzed by cholera toxin increases with increasing electron-donating power of the substituents in the benzene function. The effect is primarily on the catalytic rate constant, kcat, not on the binding constant, Km. The results are consistent with an SN2 reaction mechanism in which the deprotonated guanidino group makes a nucleophilic attack on the C-1 carbon of the ribose moiety.