Neurological infection and complications of SARS-CoV-2: A review

The primary target of severe acute respiratory syndrome coronavirus 2 is the respiratory system including the nose and lungs, however, it can also damage the kidneys, cardiovascular system and gastrointestinal system. Many recent reports suggested that severe acute respiratory syndrome coronavirus 2 infections can also affect the central nervous system as well as peripheral nervous system that lead to the several neurological complications. The virus can break the blood brain barrier and enters the brain via haematological route or directly by the angiotensin-converting enzyme 2 receptors present on endothelial cells of many cerebral tissues. The neurological complications are manifested by headache, dizziness, encephalopathy, encephalitis, cerebrovascular disease, anosmia, hypogeusia, muscle damage, etc. This review article described the possible routes and mechanism of nervous system infection and the range of neurological complications of COVID-19 that may help the medical practitioners and researchers to improve the clinical treatment and reduce the mortality rate among patients with viral diseases.

Structural characterization of the goat uterine estrogen receptor activation factor using an endogenous calcium activated neutral protease

An expedient method for the purification of a calcium activated neutral protease (CANP) of the goat uterus has been designed. This enzyme, purified to homogeneity, has been used as a tool in the structural characterization of the estrogen receptor activation factor II (E-RAF II) that dimerizes with an alternative form of estrogen receptor (ER), the non-activated estrogen receptor (naER). The enzyme cleaves the E-RAF into two fragments, alpha and beta, of molecular mass 32 and 30 kDa, respectively. The beta retains the DNA binding activity, as well as the capacity to dimerize with the naER. On the other hand, the cholesterol binding activity and the ATPase function are shared by both alpha and beta fragments. The E-RAF domain that binds to the nuclear periphery appears to be localized on the beta fragment. The beta fragment, however, is incapable of entering the nucleus on its own.

Enterocyte viability and mitochondrial function after graded intestinal ischemia and reperfusion in rats

Ischemia/reperfusion of the small intestine can lead to metabolic and structural alterations in the mucosa. Cellular dysfunction occurs when mitochondrial metabolism is compromised, which may ultimately lead to impaired organ function. The aims of this study were to assess the suppression of cellular and mitochondrial oxidative metabolism and involvement of mitochondria in the ischemia/reperfusion injury. The mitochondria were prepared from isolated enterocytes obtained from the small intestine of anesthetized adult rats following different time periods of ischemia and ischemia followed by 5 min reperfusion. Cellular and mitochondrial function were assessed using MTT (3-(4,5-Dimethylthiazol-2-yl) -2,5-diphenyl tetrazolium bromide) reduction assay. Ischemia of increasing time periods caused a progressive decrease in cellular and mitochondrial MTT reduction in enterocytes and reperfusion showed further decrease of MTT formazan formation. Inclusion of 1 mM succinate, as respiratory substrate, showed reversal of suppression of mitochondrial function in 30-60 min ischemia whereas 90 min ischemia or short time period ischemia followed by 5 min reperfusion indicated an irreversible damage to mitochondria. This study indicated that mitochondria are a sensitive target of damage due to oxygen deficiency and possibly due to sudden burst of oxygen free radicals. Mitochondria can withstand short periods of ischemia whereas long duration ischemia or reperfusion results in irreversible damage to mitochondrial function.

Luminal exposure of oxidants alter colonic absorptive function

The colonic lumen is likely to contain oxidants derived from unabsorbed dietary materials including transition metals, rancid fat, drugs and bacterial metabolites. The present study looks at the effect of luminal exposure of different oxidants on colonic mucosal lipid peroxidation and absorptive function. All the oxidants tested induced fluid and electrolyte secretion and indomethacin, a prostaglandin synthesis inhibitor reversed this effect. Oxidants did not induce mucosal lipid peroxidation. This study suggests that oxidants induce functional alterations in colon possibly through stimulation of prostaglandin generation without influencing mucosal lipid peroxidation.

Oxygen free radical-induced damage during colonic ischemia/reperfusion in rats

Reperfusion injury following ischemia is thought to be the consequence of reactive oxygen species. Role of these free radicals on the damaging effects of ischemia in colon has been investigated. A rat experimental model was used in which colon was subjected to ischemia and reperfusion and mucosal damage was assessed by biochemical and histological studies. Activity of myeloperoxidase, a neutrophil marker, was increased after ischemia (I) and ischemia/Reperfusion (I/R). Lipid peroxidation products such as malonaldehyde and conjugated diene did not show any change in the experimental colonic mucosa as compared to control. Mucosal level of low molecular weight thiols were found to be altered after I/R. A decrease in alpha-tocopherol level was noticed after ischemia and the decrease was prominent after reperfusion. Histology indicated morphological changes in colon due to ischemia and reperfusion and the damage was more severe after reperfusion. These results suggest that colonic mucosal damage occurs during I/R and free radicals generated by the infiltrated neutrophils may play a role in this damaging process.

Lipid peroxidation of colonocyte membranes

Effects of various oxidants on the colonic membrane lipid peroxidation have been studied in rats. 2,2-Azobis (2-amidinopropane) dihydrochloride (ABAP), which generates free radicals by thermal decomposition, induced peroxidation as judged by the formation of conjugated diene, malondialdehyde (MDA), and depletion of arachidonic acid. Exposure to other oxidants which require free iron for peroxidation was ineffective. Alpha tocopherol level was not altered on exposure to various oxidants except with ABAP which depleted its level in these membranes. Exposure of the membranes to both ABAP and xanthine-xanthine oxidase (X-XO) decreased total protein thiols, whereas other oxidants had no significant effect. Isolated colonocyte membranes were found to contain considerable amount of nonesterified fatty acids as part of the total lipids and removal of free fatty acids from the membrane using fatty acid-free albumin made the membranes susceptible to iron-induced free radical generation and lipid peroxidation. These studies suggest that colonocytes are possibly protected from lipid peroxidation by the free fatty acids associated with the membrane.

Colonic mucosal antioxidant enzymes and lipid peroxide levels in normal subjects and patients with ulcerative colitis

Oxygen-derived free radicals have been implicated in the pathogenesis of ulcerative colitis. Mammalian tissues contain antioxidant systems that offer protection from the damaging effect of these active species. In the present study, the activity of the antioxidant enzymes catalase, glutathione peroxidase, glutathione transferase and glutathione reductase were measured in rectal biopsies from patients with ulcerative colitis and compared with that obtained from normal subjects. A significant decrease in the activity of glutathione transferase was observed in ulcerative colitis (48.32 +/- 6.73 units/mg protein, mean +/- s.e.) compared to normal (68.20 +/- 6.83; P = 0.015). There was no difference in the activity of other antioxidant enzymes between controls and ulcerative colitis. Myeloperoxidase, a marker for neutrophil infiltration, was considerably increased in ulcerative colitis while malonaldehyde, the end product of lipid peroxidation, was not increased. The reduced activity of glutathione transferase in ulcerative colitis may be an additional factor in the pathogenesis of mucosal damage in this disease.