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Biomedical subjects

A K Raina

Publications and source records attributed to A K Raina.

At least 19 recordsLinked to original sources
PubMed2004

Impact of blast induced transitory vibration and air-overpressure/noise on human brain--an experimental study.

Human response to blast induced ground vibration and air-overpressure/noise is a major concern of current mining activity. This is because the fact that mines are fast transgressing the habitats and people are getting educated. Consequently the response of humans is changing and expectedly will increase in days to come with no viable and economic alternative to blasting--an essential component of mining. The response of humans can be purely physiological or psychological in nature or combination of both depending upon the situation and conditions of mining. Where physiological response is documented in terms of effects on ears and lungs there is a meager amount or no literature available regarding effects of blasting on the brain. Moreover, the studies on transitory phenomenon like the effects of blasting on humans are rare in comparison to the whole body vibration studies. This study was designed to address the issues as a precursor to a major initiative. The preliminary investigations conducted with the monitoring of EEG responses of humans to vibration and air-overpressure/noise due to blasting revealed that there is no major response of the brain to transitory vibrations and noise.

Adult↗
PubMed2004

Mitotic and gender parallels in Alzheimer disease: therapeutic opportunities.

In this review, we discuss the role of cell cycle dysfunction in the pathogenesis of Alzheimer disease and propose that such mitotic catastrophe, as one of the earliest events in neuronal degeneration, may, in fact, be sufficient to initiate the neurodegenerative cascade. The question as to what molecule initiates cell cycle dysfunction is now beginning to become understood and, in this regard, the gender-predication, age-related penetrance and regional susceptibility of specific neuronal populations led us to consider luteinizing hormone as a key mediator of the abnormal mitotic process. As such, agents targeted toward luteinizing hormone or downstream sequelae may be of great therapeutic value in the treatment of Alzheimer disease.

Alzheimer Disease↗
PubMed2003

X-ray contrast media induce aortic endothelial damage, which can be prevented with prior heparin treatment.

X-ray contrast media induce damage to the endothelial layer of vessels and initiate the formation of thrombosis, which is a complication for clinical diagnostic procedures. The future determination of the mechanisms, which underlie the damaging effect of X-ray contrast medium on vascular wall cells, especially vascular endothelium and possible prevention of this damage by vasoprotector, will result in a larger application in diagnostic procedures. The aim of the present study is to analyze the effect of X-ray contrast media (Verographin, Iodamid and Iodolipol) on the arterial endothelium morphology by using ultrastructural techniques (scanning and transmission electron microscopy, SEM and TEM respectively). Experiments have been carried out on New Zealand white rabbits (6 month old) and Wistar rats (6-8 month old) after a single injection of X-ray contrast media with and without prior heparin treatment. Control groups of animals were exposed to the same procedure but without X-ray contrast media injection and only received isotonic saline solution. The following time points were selected: 1, 6, 24, 72 h and 7 days. At the end of the experiments, animals were anesthetized by pentobarbital and then perfused with a balanced buffer for 1 min and followed by perfusion fixation with Karnovsky's fixative containing buffered solution of 2.5% paraformaldehyde and 2.5% glutaraldehyde (pH 7.36) at least 30 min. The aortic tissue was removed and immediately placed into a fresh portion of the same fixative. Aortic samples were then prepared for scanning and transmission electron microscopy (SEM and TEM respectively). Immediately after the injection of X-ray contrast media, the number of microvilli and blebs on the luminal surface of the endothelial cells (EC) significantly increased. Very often, nuclear portions of the EC sharply protruded into the vessel lumen. Clusters of spindle-shaped EC were seen throughout the endothelial monolayer. These changes persist through the 72-h period after X-ray contrast media injection. Moreover, the desquamation and denudation of the EC from the monolayer is often observed and this is accompanied by the presence of a microthrombus on the vessel surface. Seven days after the post-injection period, endothelial monolayers still show severe damage, which often coexists with the presence of a different sized microthrombus on the vessel surface. However, the degree of lesion formation in most areas is substantially decreased as compared to the early period of post-injection (24 and 72 h). Heparin treated group shows intact morphology similar to the control experimental groups (saline injected group). Infrequently, minimal morphological changes of the endothelium, such as increased number of microblebs and microvilli, were seen with heparin treatment. We conclude that the negative side effects of the X-ray contrast media can be eliminated by a single injection of heparin or other vasoprotector prior to the diagnostic procedure.

Animals↗
PubMed2001

Redox-active iron mediates amyloid-beta toxicity.

While amyloid-beta toxicity is mediated by oxidative stress and can be attenuated by antioxidants, the actual biochemical mechanism underlying neurotoxicity remains to be established. However, since aggregated amyloid-beta can interact with transition metals, such as iron, both in vitro and in vivo, we suspected that bound iron might be the mediator of toxicity such that holo- and apo-amyloid would have differential effects on cellular viability. Here we demonstrate that when amyloid-beta is pretreated with the iron chelator deferoxamine, neuronal toxicity is significantly attenuated while conversely, incubation of holo-amyloid-beta with excess free iron restores toxicity to original levels. These data, taken together with the known sequelae of amyloid-beta, suggest that the toxicity of amyloid-beta is mediated, at least in part, via redox-active iron that precipitates lipid peroxidation and cellular oxidative stress.

Amyloid beta-Peptides↗
PubMed2001

Identification of four additional myoinhibitory peptides (MIPs) from the ventral nerve cord of Manduca sexta.

Four new myoinhibitory peptides were isolated and identified from the ventral nerve cord of adult Manduca sexta. The new peptides are related to two previously identified myoinhibitory peptides also isolated from adult M. sexta, Mas-MIP I and Mas-MIP II. The sequences of the new peptides are APEKWAAFHGSWamide (Mas-MIP III), GWNDMSSAWamide (Mas-MIP IV), GWQDMSSAWamide (Mas-MIP V), and AWSALHGAWamide (Mas-MIP VI). Mas-MIPs III-VI were found to inhibit spontaneous peristalsis of the adult M. sexta anterior hindgut (ileum) in vitro.

Animals↗
PubMed2001

Abortive apoptosis in Alzheimer's disease.

Multiple studies suggest that neuronal death in Alzheimer's disease (AD) is the result of an apoptotic mechanism. However, the stereotypical manifestations that define the terminal phases of apoptosis, such as chromatin condensation, apoptotic bodies, and blebbing, are not seen in AD. In this study, we show that the caspases, such as caspase 6, which cleave amyloid-beta protein precursor (A beta PP) and presenilins, are localized to the pathological lesions associated with AD. However, while upstream caspases such as 8 and 9 are clearly found in association with the intraneuronal pathology in AD, downstream caspases such as 3, 6 and 7 are present only at control levels. Given that execution of apoptosis requires amplification of the caspase-mediated apoptotic signal, our results indicate that in AD there is a lack of effective apoptotic signal propagation to downstream caspase effectors. Therefore, while the presence of caspases, especially caspase 6, in association with extracellular deposits of amyloid-beta, could obviously have important ramifications on the proteolytic processing of A beta PP and, thereby, on disease pathogenesis, it seems that AD represents the first in vivo situation reported in which the initiation of apoptosis does not proceed to caspase-dependent cell death. This novel phenomenon of apoptotic avoidance, which we term abortive apoptosis, or abortosis, may represent an exit from the caspase-induced apoptotic program that leads to neuronal survival in AD.

Adult↗
PubMed2001

Neurons in Alzheimer disease emerge from senescence.

A number of cell cycle markers are associated with the selective neuronal pathology found in Alzheimer disease. However, the significance of such cell cycle markers is clouded by duplicity of function in that many such proteins are also involved in apoptosis and/or DNA repair following oxidative damage. To clarify whether or not neurons in Alzheimer disease do in fact emerge from a quiescent status, with subsequent entry into the G1 phase of the cell cycle, in this study we focused on a family of MORF4-related proteins that are associated with emergence from senescence. Our results show that many neurons in vulnerable regions of Alzheimer disease brain, but not in control brain, have increased MORF4-related proteins indicating re-entry into the cell cycle. Immunoblot analysis showed a specific disease-related increase in a 52 kDa protein that is likely the human homologue of the MORF4-related transcription factor. The novel localization of such a transcriptional activating protein to selectively vulnerable neurons in Alzheimer disease provides compelling evidence for mitotic re-entry as part of the pathogenesis of neuronal dysfunction and death in Alzheimer disease.

Acetyltransferases↗
PubMed2001

Activation and redistribution of c-jun N-terminal kinase/stress activated protein kinase in degenerating neurons in Alzheimer's disease.

Cellular responses to increased oxidative stress appear to be a mechanism that contributes to the varied cytopathology of Alzheimer's disease (AD). In this regard, we suspect that c-Jun N-terminal kinase/Stress activated protein kinase (JNK/SAPK), a major cellular stress response protein induced by oxidative stress, plays an important role in Alzheimer disease in susceptible neurons facing the dilemma of proliferation or death. We found that JNK2/SAPK-alpha and JNK3/SAPK-beta were related to neurofibrillary pathology and JNK1/SAP-Kgamma related to Hirano bodies in cases of AD but were only weakly diffuse in the cytoplasm in all neurons in control cases and in non-involved neurons in diseased brain. In this regard, in hippocampal and cortical regions of individuals with severe AD, the activated phospho-JNK/SAPK was localized exclusively in association with neurofibrillar alterations including neurofibrillary tangles, senile plaque neurites, neuropil threads and granulovacuolar degeneration structures (GVD), completely overlapping with tau-positive neurofibrillary pathology, but was virtually absent in these brain regions in younger and age-matched controls without pathology. However, in control patients with some pathology, as well as in mild AD cases, there was nuclear phospho-JNK/SAPK and translocation of phospho-JNK/SAPK from nuclei to cytoplasm, respectively, indicating that the activation and re-distribution of JNK/SAPK correlates with the progress of the disease. By immunoblot analysis, phospho-JNK/SAPK is significantly increased in AD over control cases. Together, these findings suggest that JNK/SAPK dysregulation, probably resulting from oxidative stress, plays an important role in the increased phosphorylation of cytoskeletal proteins found in AD.

Adolescent↗
PubMed2000

Oxidative stress in Alzheimer's disease.

Oxidative balance is emerging as an important issue in understanding the pathogenesis of Alzheimer's disease. Examination of Alzheimer's disease brain has demonstrated a great deal of oxidative damage, associated with both hallmark pathologies (senile plaques and neurofibrillary tangles) as well as in normal appearing pyramidal neurons. While this suggests that oxidative stress is a proximal event in Alzheimer's disease pathogenesis, the mechanisms by which redox balance is altered in the disease remains elusive. Determining which of the proposed sources of free radicals, which include mitochondrial dysfunction, amyloid-beta-mediated processes, transition metal accumulation and genetic factors like apolipoprotein E and presenilins, is responsible for redox imbalance will lead to a better understanding of Alzheimer's disease pathogenesis and novel therapeutic approaches.

Alzheimer Disease↗
PubMed2000

Cyclin' toward dementia: cell cycle abnormalities and abortive oncogenesis in Alzheimer disease.

Recent evidence has associated the aberrant, proximal re-expression of various cell cycle control elements with neuronal vulnerability in Alzheimer disease, a chronic neurodegeneration. Such ectopic localization of various cyclins, cyclin-dependent kinases, and cyclin inhibitors in neurons can be seen as an attempt to re-enter the cell cycle. Given that primary neurons are terminally differentiated, any attempted re-entry into the cell division cycle in this postmitotic environment will be dysregulated. Since successful dysregulation of the cell cycle is also the hallmark of a neoplasm, early cell-cycle pathophysiology in Alzheimer disease may recruit oncogenic signal transduction mechanisms and, hence, can be viewed as an abortive neoplastic transformation.

Alzheimer Disease↗
PubMed2000

Altered cell-matrix associated ADAM proteins in Alzheimer disease.

Alterations in cell-matrix 'contact' are often related to a disruption of cell cycle regulation and, as such, occur variously in neoplasia. Given the recent findings showing cell cycle alterations in Alzheimer disease, we undertook a study of ADAM-1 and 2 (A Disintegrin And Metalloprotease), developmentally-regulated, integrin-binding, membrane-bound metalloproteases. Our results show that whereas ADAM-1 and 2 are found in susceptible hippocampal neurons in Alzheimer disease, these proteins were not generally increased in similar neuronal populations in younger or age-matched controls except in association with age-related neurofibrillary alterations. This increase in both ADAM-1 and 2 in cases of Alzheimer disease was verified by immunoblot analysis (P < 0.05). An ADAM-induced loss of matrix integration would effectively "reset" the mitotic clock and thereby stimulate re-entry into the cell cycle in neurons in Alzheimer disease. Furthermore, given the importance of integrins in maintaining short-term memory, alterations in ADAM proteins or their proteolytic activity could also play a proximal role in the clinico-pathological manifestations of Alzheimer disease.

ADAM Proteins↗
PubMed2000

Further characterization of the gonad-specific virus of corn earworm, Helicoverpa zea.

The gonad-specific virus (GSV) is a DNA virus infecting the reproductive tracts of adults of both sexes of the corn earworm, Helicoverpa zea, causing severe tissue deformities leading to sterility. Atypical occlusion bodies containing large concentrations of virions embedded in a granular matrix were seen in the lumen of the oviduct and the bursa copulatrix of infected females. The virus, transmitted by both sexes, was successfully propagated in vivo and in tissue culture. The GSV genome is about 225 kb in size, with no apparent similarity to the nucleopolyhedrovirus type species, AcMNPV, genomic DNA, as determined by Southern hybridization. PCR amplification of GSV genomic DNA with primers derived from the highly conserved polyhedra gene of several baculoviruses indicated no similarity. GSV at 10(-2) female equivalents (based on virus obtained from the bursa copulatrix and oviducts of one infected female) injected into a newly emerged female and mated to a normal male resulted in >95% agonadal progeny. However, at lower doses, some of the adult progeny looked normal but apparently carried a low level of the virus that could be responsible for sustenance of infection in a given colony, as well as in nature.

Animals↗
PubMed2000

Abortive oncogeny and cell cycle-mediated events in Alzheimer disease.

Alzheimer disease, the leading cause of senile dementia, is characterised by the degeneration of select neuronal populations. While the mechanism(s) underlying such cell loss are largely unknown, recent findings indicate inappropriate re-entry into the cell cycle resembling an abortive oncogeny. In postmitotic neurons, such mitotic re-entrance is deleterious and one that involves virtually the entire spectrum of the described pathological events in Alzheimer disease including, ultimately, cell death.

Alzheimer Disease↗
PubMed2000

Protein disulfide isomerase in Alzheimer disease.

There is a great deal of evidence that places oxidative stress as a proximal event in the natural history of Alzheimer disease (AD). In addition to increased damage, there are compensatory increases in the levels of free sulfhydryls, glucose-6-phosphate dehydrogenase, and NAD(P)H:quinone oxidoreductase 1. To investigate redox homeostasis further in AD, we analyzed protein disulfide isomerase (PDI), a multifunctional enzyme, which catalyzes the disruption and formation of disulfide bonds. PDI plays a pivotal role in both secreted and cell-surface-associated protein disulfide rearrangement. In this study, we show that PDI specifically localizes to neurons, where there is no substantial increase in AD compared to age-matched controls. These findings indicate that the neurons at risk of death in AD do not show a substantial change in PDI to compensate for the increased sulfhydryls and reductive state found during the disease. This suggests that, despite compensatory reductive changes in AD, the level of PDI is sufficiently high physiologically in neurons to accommodate a more reducing environment.

Adolescent↗
PubMed2000

Oxidative stress, antioxidants, and Alzheimer disease.

Recent evidence in the field of Alzheimer disease research has highlighted the importance of oxidative processes in its pathogenesis. Examination of cellular changes shows that oxidative stress is an event that precedes the appearance of neurofibrillary tangles, one of the hallmark pathologies of the disease. Although it is still unclear what the initial source of the oxidative stress is in Alzheimer disease, it is likely that the process is highly dependent on the presence of redox-active transition metals, such as iron and copper. Because of the proximal role that oxidative stress mechanisms seem to play in the pathogenesis of Alzheimer disease, further investigation in this realm may lead to novel therapeutic strategies.

Alzheimer Disease↗
PubMed2000

Histochemical and immunocytochemical approaches to the study of oxidative stress.

We review an array of newly developed in situ detection methods that can be used for the qualitative and semi-quantitative measurement of various indices related to oxidative stress. The importance of in situ methods over bulk analysis cannot be overstated when considering the structural and cellular complexity of tissue and the effects of diseases thereof. Indeed, in situ detection allows detection of specific cell types affected or specific localization such that a process affecting only a small fraction of the tissue or cells can be readily visualized. Consequently, a positive signal in situ indicates real levels that cannot be masked by unrelated or compensatory responses in adjacent cells, and corrections can be easily made for the modifications to long-lived proteins during physiological aging. In fact, the damage to extracellular matrix proteins of major vessels, provides a cumulative record of long-term oxidative insult. Yet the same properties that make vessels ideal markers for aging limits their sensitivity to detect disease-specific changes unless in situ techniques are used.

Alzheimer Disease↗