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Biomedical subjects

J Joseph

Publications and source records attributed to J Joseph.

At least 73 records · Page 4Linked to original sources
PubMed1999

Molecular pathway involved in HIV-1-induced CNS pathology: role of viral regulatory protein, Tat.

The broad range of histological lesions associated with HIV-1 are somewhat subtle relative to the clinical manifestations that occur as a result of HIV infection. Although it is clear that HIV has a causative role in CNS disease, dementia appears to be a consequence of the infiltration of inflammatory cells and cytokine dysregulation rather than the amount of virus in CNS. The HIV transregulatory protein Tat plays an important intracellular as well as extracellular role in the dysregulation of cytokines. The cytokines and possibly chemokines that are induced by Tat modify the action of astrocytes such that the survival of neurons is compromised. Pathogenetic alteration induced by Tat involves a series of interactions between circulating monocyte/macrophages, endothelial cells, and astrocytes. Cytokine dysregulation induced by viral infection and extracellular Tat leads to alterations in expression of adhesion molecules and promotes migration of non-infected inflammatory cells into the CNS compartment. We demonstrate here that recombinant HIV-1 Tat protein introduced by stereotaxic injection into mouse brain can induce pathologically relevant alterations including macrophage invasion as well as astrocytosis. The mechanism of destruction of the CNS by Tat appears to involve autocrine and paracrine pathways that depend not only on Tat, but cytokine and chemokine signaling pathways that are altered by viral infection. In this review, we discuss various pathogenic effects of Tat in brain cells and provide experimental evidence for an increased TNF-alpha level in CSF in mice injected intracerebrally with Tat protein.

Animals↗
PubMed1999

Extra-adrenal mineralocorticoids and cardiovascular tissue.

In experimental models where chronic inappropriate (relative to sodium intake and intravascular volume) elevations in circulating mineralocorticoids (aldosterone or deoxycorticosterone) are created, a reactive fibrosis with vascular remodeling is observed in systemic organs and the heart. Until recently, it was assumed that aldosterone was derived solely from adrenal glands via the circulation; however, there is now convincing evidence that cells of the heart and vasculature express genes responsible for the formation of both aldosterone and corticosterone and are capable of producing these steroids. Vascular endothelial and smooth muscle cells express CYP11B1 and CYP11B2, genes responsible for 11 beta -hydroxylase and aldosterone synthase, respectively. Furthermore, smooth muscle cells elaborate aldosterone. There is evidence that similar regulatory mechanisms operate in vascular cells as in adrenal cortex, since aldosterone synthase and 11 beta -hydroxylase expression are differentially modulated by low sodium/high potassium, angiotensin II and ACTH. It is likely that such localized corticosteroid production also occurs at sites of tissue repair, where populations of collagen-producing myofibroblasts, nourished by a neovasculature, predominate. Using a subcutaneous pouch model of granulation tissue we have obtained compelling data which would support such a notion. The mineralocorticoid receptor antagonist, spironolactone, severely attenuates pouch formation over a 2-week period and significantly reduces pouch wall hydroxyproline concentration. This effect is apparent even following adrenalectomy, when circulating corticosteroids are undetectable; however, with adrenalectomy alone, pouch formation is barely affected. This we took to be a possible indication of an effect of local, non-adrenal steroids in maintaining pouch tissue. Spironolactone inhibits angiogenesis. A recent clinical study demonstrates the efficacy of low-dose spironolactone in enhancing survival in patients with advanced chronic cardiac failure. Although it is not known how spironolactone brings about such an improvement in survival, we would propose that inhibition of fibrous tissue formation and/or angiogenesis might be important contributory factors. Further studies are required to address the relative contributions of circulating vs local aldosterone in promoting normal vs pathologic connective tissue formation.

Adrenal Glands↗
PubMed1999

Molecular characterization and interviral relationships of a flexuous filamentous virus causing mosaic disease of sugarcane (Saccharum officinarum L.) in India.

A virus isolate causing mosaic disease of commercial sugarcane was purified to homogeneity. Electron microscopy revealed flexuous filamentous virus particles of ca 890 x 15 nm. The virus isolate reacted positively with heterologous antiserum to narcissus latent virus form UK, but failed to react with potyvirus group specific antiserum. N-terminal sequencing of the intact coat protein (CP) and the tryptic peptides indicated that the virus was probably a potyvirus but distinct from several reported potyviruses. Comparison of the 3'-terminal 1084 nucleotide sequence of the RNA genome of this virus revealed 93.6% sequence identity in the coat protein coding region with the recently described sugarcane streak mosaic virus (Pakistani isolate). The molecular weight of the coat protein (40 kDa) was higher than that deduced from the amino acid sequence (34 kDa). The apparent increase in size was shown to be due to glycosylation of the coat protein which has not been reported thus far in the family, Potyviridae. This is the first report on the molecular characterization of a virus causing mosaic disease of sugarcane in India and the results demonstrate that the virus is a strain of sugarcane streak mosaic virus, a member of the Tritimovirus genus of the Potyviridae. We have named it sugarcane streak mosaic virus--Andhra Pradesh isolate (SCSMV-AP).

Amino Acid Sequence↗
PubMed1999

Determination of 3'-terminal nucleotide sequence of pepper vein banding virus RNA and expression of its coat protein in Escherichia coli.

Pepper vein banding virus (PVBV) is an important virus infecting chilli pepper in south India. Earlier reports suggested it to be a distinct potyvirus. The nucleotide sequence of PVBV RNA from the 3'-end (3862 nt) was determined. Analysis of the nucleotide and deduced amino acid sequence revealed that it encompasses a partial open reading frame encoding the partial sequence of VPg, NIa-protease, NIb, coat protein (CP) and 3'-untranslated region (UTR). Comparison of the amino acid sequence of CP and the nucleotide sequence of 3'-UTR with those of other potyviruses confirmed an earlier observation that PVBV is a distinct member of the Potyvirus sub-group and it had significant similarity to a recently characterized virus infecting chilli pepper, chilli vein-banding mottle virus (CVbMV), from Thailand. The analysis showed that both PVBV and CVbMV might represent strains of the same virus. Further, the PVBV CP gene was overexpressed in E. coli, which assembled into potyvirus-like particles (PVLPs). The assembled particles were shown to encapsidate the CP mRNA.

3' Untranslated Regions↗
PubMed1999

Effects of aging on cerebellar noradrenergic function and motor learning: nutritional interventions.

Aging is associated with a decline in motor coordination and the ability to learn new motor learning skills. This loss of function is correlated with a decline in cerebellar beta-adrenergic receptor function. We have examined the role of oxidative stress on this system by exposing young rats to normobaric hyperoxia. This exogenous oxidative insult results in a decline in cerebellar beta-adrenergic receptor function that resembles what is observed in normal aged rats. This effect of hyperoxia is blocked by antioxidants. We have also examined the effects of nutritional supplementation of aged rats with diets high in antioxidant capacity. Foods such as blueberries and spinach can prevent and/or reverse age-related declines in cerebellar noradrenergic receptor function.

Action Potentials↗
PubMed1999

Effect of normobaric hyperoxia on two indexes of synaptic function in Fisher 344 rats.

The physiological response of two central nervous system neurotransmitter receptors to oxidative stress was studied using the rat model of hyperoxia. We show that hyperoxia leads to a decline in the ability of isoproterenol (ISO) to augment GABAergic responses in cerebellar Purkinje neurons in vivo. This effect is reversed by the N-tert-butylalpha-phenylnitrone (PBN). We also show that hyperoxia produces a decline in the ability of oxotremorine (OXO) to stimulate dopamine (DA) release in striatal slices. This effect is accompanied by an increase in hydroxyl radical levels in the CNS reflected in an increase in 2,3-DHBA, suggesting that the change is the result of an increased level of oxidative stress. We also show a time dependent effect of hyperoxia on both beta-adrenergic and muscarinic receptor function. We examined the interaction between age and hyperoxia exposure and found that in 12-month-old rats there is a decline in the baseline response prior to oxygen exposure that may interfere with observing a subsequent effect of hyperoxia. Differential effects were observed between the cerebellum and striatum with respect to the interaction of age and time of oxygen exposure. Overall, the data suggest that age and hyperoxia may be acting via a common mechanism because there was no synergistic effect of the two conditions.

Animals↗
PubMed1999

Characterization of the adduct formed from the reaction between homocysteine thiolactone and low-density lipoprotein: antioxidant implications.

Homocysteine thiolactone is a cyclic thioester that is implicated in the development of atherosclerosis. This molecule will readily acylate primary amines, forming a homocystamide adduct, which contains a primary amine and a thiol. Here, we have characterized and evaluated the antioxidant potential of the homocystamide-low-density lipoprotein (LDL) adduct, a product of the reaction between homocysteine thiolactone and LDL. Treatment of LDL with homocysteine thiolactone resulted in a time-dependent increase in LDL-bound thiols that reached approximately 250 nmol thiol/mg LDL protein. The thiol groups of the homocystamide-LDL adduct were labeled with the thiol-reactive nitroxide, methanethiosulfonate spin label. Using paramagnetic relaxing agents and the electron spin resonance spin labeling technique, we determined that the homocystamide adducts were predominately exposed to the aqueous phase. The homocystamide-LDL adduct was resistant to myoglobin- and Cu2(+)-mediated oxidation (with respect to native LDL), as measured by the formation of conjugated dienes and thiobarbituric acid reactive substances, and the depletion of vitamin E. This antioxidant effect was due to increased thiol content, as the effect was abolished with N-ethylmaleamide pre-treatment. We conclude that the reaction between homocysteine thiolactone and LDL generates an LDL molecule that is more resistant to oxidative modification than native LDL. The potential relationship between the homocystamide-LDL adduct and the development of atherosclerosis is discussed.

Antioxidants↗
PubMed1999

Performance of the platelet function analyser PFA-100 in testing abnormalities of primary haemostasis.

The PFA-100 device is a new instrument for the in-vitro testing of platelet function. Primary haemostasis is stimulated by recording the closure time taken for platelets to seal a 150 microm aperture in the centre of a membrane coated with collagen and either epinephrine or ADP. Patients with type 3 von Willebrand's disease (n = 4) all had infinitely prolonged closure times (> 200 s) with both types of cartridge. A patient with afibrinogenemia exhibited only slightly prolonged closure times of 111 and 166 s for the ADP and epinephrine membranes, respectively. Patients with Glanzmann's thrombasthenia (n = 6) and Bernard Soulier syndrome (n = 2) had grossly prolonged closure times (> 200 s) with both types of cartridges. These results confirmed that the PFA-100 system was highly dependent on normal von Willebrand factor, glycoprotein Ib and glycoprotein IIb/IIIa levels but not on plasma fibrinogen. Patients with storage pool disease (n = 6) and Hermansky Pudlak syndrome (n = 7) had prolonged closure times with the epinephrine cartridge. There was no evidence of enhanced platelet function in patients with antiphospholipid syndrome, in sickle-cell disease or thalassemia. However, ingestion of aspirin resulted in a near consistent and significant prolongation of the closure time for the epinephrine cartridge but not for the ADP cartridge in both normal subjects and patients. The test offers a reliable, reproducible, rapid and simple means of assessing high-shear platelet function in vitro.

Blood Platelets↗
PubMed1998

Nitration of gamma-tocopherol and oxidation of alpha-tocopherol by copper-zinc superoxide dismutase/H2O2/NO2-: role of nitrogen dioxide free radical.

Copper-zinc superoxide dismutase (Cu,ZnSOD) is the antioxidant enzyme that catalyzes the dismutation of superoxide (O2*-) to O2 and H2O2. In addition, Cu,ZnSOD also exhibits peroxidase activity in the presence of H2O2, leading to self-inactivation and formation of a potent enzyme-bound oxidant. We report in this study that lipid peroxidation of L-alpha-lecithin liposomes was enhanced greatly during the SOD/H2O2 reaction in the presence of nitrite anion (NO2-) with or without the metal ion chelator, diethylenetriaminepentacetic acid. The presence of NO2- also greatly enhanced alpha-tocopherol (alpha-TH) oxidation by SOD/H2O2 in saturated 1, 2-dilauroyl-sn-glycero-3-phosphatidylcholine liposomes. The major product identified by HPLC and UV-studies was alpha-tocopheryl quinone. When 1,2-diauroyl-sn-glycero-3-phosphatidylcholine liposomes containing gamma-tocopherol (gamma-TH) were incubated with SOD/H2O2/NO2-, the major product identified was 5-NO2-gamma-TH. Nitrone spin traps significantly inhibited the formation of alpha-tocopheryl quinone and 5-NO2-gamma-TH. NO2- inhibited H2O2-dependent inactivation of SOD. A proposed mechanism of this protection involves the oxidation of NO2- by an SOD-bound oxidant to the nitrogen dioxide radical (*NO2). In this study, we have shown a new mechanism of nitration catalyzed by the peroxidase activity of SOD. We conclude that NO2- is a suitable probe for investigating the peroxidase activity of familial Amyotrophic Lateral Sclerosis-linked SOD mutants.

Electron Spin Resonance Spectroscopy↗
PubMed1998

Prevalence of serious eye disease and visual impairment in a north London population: population based, cross sectional study.

OBJECTIVE: To estimate the magnitude of serious eye disorders and of visual impairment in a defined elderly population of a typical metropolitan area in England, and to assess the frequency they were in touch with, or known to, the eye care services. DESIGN: Cross sectional survey using two stage cluster random sampling. SETTING: General practices in north London. SUBJECTS: Random sample of people aged 65 and older, drawn from a defined population of elderly people registered with 17 general practice groups. MAIN OUTCOME MEASURES: Proportions and population prevalence estimates were determined for visual acuity, assessed with the person's own spectacles (if any), classified into four categories: prevalence of cataract, age related macular degeneration, and refractive error causing visual impairment and of definite primary open angle glaucoma; and status of contact with eye services. RESULTS: 1547 of 1840 (84%) eligible people were examined. The population prevalence of bilateral visual impairment (visual acuity <6/12) was 30%, of which 72% was potentially remediable. 92 of these 448 cases (21%) had visual acuity <6/60 ("blindness") in one or both eyes. Prevalence of cataract causing visual impairment was 30%; 88% of these people were not in touch with the eye services. The prevalence of vision impairing, age related macular degeneration was 8% and of glaucoma (definite cases) was 3%. Three quarters of the people with definite glaucoma were not known to the eye services. CONCLUSIONS: Untreated visual impairment and eye disorders affect a substantial proportion of people aged 65 years and older. These findings should contribute to the setting up of future strategies for preservation of sight and eye health services in general.

Age Distribution↗
PubMed1998

Depletion of nitric oxide causes cell cycle alterations, apoptosis, and oxidative stress in pulmonary cells.

Nitric oxide (NO.) is important in the regulation of mitochondrial function, cell signaling, and gene expression. To elucidate how endogenous NO. regulates the function of airway epithelial cells, we used carboxy-PTIO, a hydrophilic, negatively charged NO. trap, to scavenge NO. from rat lung epithelial (RLE) and rat pleural mesothelial (RPM) cells and to determine the elicitation of cell cycle alterations, apoptosis, and oxidative stress. The reaction of NO. with PTIO causes the formation of PTI, which is measured by electron spin resonance (ESR) and is a quantitative measure of NO. formation. ESR spectroscopy revealed the production of NO. in RLE or RPM cells over a period from 1 to 24 h of exposure, indicating scavenging of NO. by PTIO. Cycle analyses in confluent RLE or RPM cells revealed two- to threefold increases in S and G2/M phases after exposure to 100-200 microM PTIO as well as increases in the fraction of cells undergoing apoptosis. Direct addition of PTI to cells failed to elicit cell cycle perturbations or apoptosis. The guanylyl cyclase inhibitor ODQ mimicked the effects of PTIO. 8-Bromo-cGMP but not 8-bromo-cAMP ameliorated the PTIO- or ODQ-mediated cell cycle perturbations and apoptosis, suggesting that cGMP-dependent pathways are involved in these cell cycle perturbations. Treatment of log-phase cells with PTIO resulted in more dramatic cell cycle perturbations compared with cells treated at confluence. Assessment of 5-bromo-2'-deoxyuridine incorporation to measure DNA synthesis demonstrated decreases in PTIO-treated compared with sham cells in addition to a cell cycle arrest in late S or G2/M phase. Last, incubation with dichlorofluorescin diacetate revealed oxidative stress in PTIO- but not in PTI-exposed RLE or RPM cells. We conclude that the depletion of endogenous NO. induces oxidative stress, cell cycle perturbations, and apoptosis. Our findings illustrate the importance of endogenous NO. in the control of cell cycle progression and survival of pulmonary and pleural cells and that a critical balance between NO. and superoxide may be necessary for these physiological events.

Animals↗
PubMed1998

Generation and initial characterization of a novel polyclonal antibody directed against homocysteine thiolactone-modified low density lipoprotein.

Elevated plasma homocysteine (homocysteinemia) are presumed to be responsible for the development of coronary artery disease, however, the precise etiology is unclear. We examined the possibility that the adduct formed from the reaction between homocysteine thiolactone, a metabolic product of homocysteine, and apolipoprotein B-100 lysyl residues of low density lipoprotein (LDL) was immunogenic. New Zealand White rabbits were immunized with this adduct at 6-week intervals. Antisera collected following the 3rd immunization was assayed for antibody titers using solid phase ELISA techniques. Titers (defined as the inverse of the greatest serum dilution in which there was a significant difference (P < 0.05) between the percentage antibody bound from the antiserum and the pre-immune serum) were approximately 10(5). In competition-based ELISAs, homocysteine thiolactone-treated LDL competed for binding with the antiserum, as the 50% inhibitory concentration was approximately 10 microg/ml. Neither homocysteine, homocystine (homocysteine disulfide), nor Cu2-oxidized LDL competed for binding. LDL in which lysyl residues were derivatized by acetylation or methylation were not recognized by the antiserum. Homocysteine thiolactone-treated plasma competed for binding to the antiserum, whereas native plasma did not. All lipoprotein fractions from the homocysteine thiolactone-treated plasma competed for binding to the antiserum. We conclude that homocysteine thiolactone-modified LDL is highly immunogenic and specific for homocysteine thiolactone-modified lysines. The potential for using this antibody as a diagnostic tool for measuring plasma homocysteine concentrations and the implications for understanding diseases induced by homocysteinemia are discussed.

Antibody Specificity↗
PubMed1997

NEAR's flyby of 253 mathilde: images of a C asteroid

On 27 June 1997, the Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 1212 kilometers of asteroid 253 Mathilde. Mathilde is an irregular, heavily cratered body measuring 66 kilometers by 48 kilometers by 46 kilometers. The asteroid's surface is dark (estimated albedo between 0.035 and 0.050) and similar in color to some CM carbonaceous chondrites. No albedo or color variations were detected. The volume derived from the images and the mass from Doppler tracking of the spacecraft yield a mean density of 1.3 +/- 0.2 grams per cubic centimeter, about half that of CM chondrites, indicating a porous interior structure.

Journal Article↗