Parkinson's disease: genetics and beyond

Parkinson's disease (PD) is characterized clinically by resting tremor, rigidity, bradykinesia and postural instability due to progressive and selective loss of dopamine neurons in the ventral substantia nigra, with the presence of ubiquitinated protein deposits called Lewy bodies in the neurons. The pathoetiology of cell death in PD is incompletely understood and evidence implicates impaired mitochondrial complex I function, altered intracellular redox state, activation of proapoptotic factors and dysfunction of ubiquitinproteasome pathway. Now it is believed that genetic aberration, an environmental toxin or combination of both leads to a cascade of events culminating in the destruction of myelinated brainstem catecholaminergic neurons. Also the role of production of significant levels of abnormal proteins, which may misfold, aggregate and interfere with intracellular processes causing cytotoxicity has recently been hypothesized. In this article, the diverse pieces of evidence that have linked the various factors responsible for the pathophysiology of PD are reviewed with special emphasis to various candidate genes and proteins. Furthermore, the present therapeutic strategies and futuristic approaches for the pharmacotherapy of PD are critically discussed.

Conservative debridement of postoperative Meleney's gangrene following a caesarean section

Meleney's gangrene is almost exclusively postoperative and is caused by multiple bacteria. This case review describes the conservative management of Meleney's gangrene in a young patient following a Caesarean section.

Rhodobacter capsulatus nifA1 promoter: high-GC -10 regions in high-GC bacteria and the basis for their transcription

It was previously shown that the Rhodobacter capsulatus NtrC enhancer-binding protein activates the R. capsulatus housekeeping RNA polymerase but not the Escherichia coli RNA polymerase at the nifA1 promoter. We have tested the hypothesis that this activity is due to the high G+C content of the -10 sequence. A comparative analysis of R. capsulatus and other alpha-proteobacterial promoters with known transcription start sites suggests that the G+C content of the -10 region is higher than that for E. coli. Both in vivo and in vitro results obtained with nifA1 promoters with -10 and/or -35 variations are reported here. A major conclusion of this study is that alpha-proteobacteria have evolved a promiscuous sigma factor and core RNA polymerase that can transcribe promoters with high-GC -10 regions in addition to the classic E. coli Pribnow box. To facilitate studies of R. capsulatus transcription, we cloned and overexpressed all of the RNA polymerase subunits in E. coli, and these were reconstituted in vitro to form an active, recombinant R. capsulatus RNA polymerase with properties mimicking those of the natural polymerase. Thus, no additional factors from R. capsulatus are necessary for the recognition of high-GC promoters or for activation by R. capsulatus NtrC. The addition of R. capsulatus sigma(70) to the E. coli core RNA polymerase or the use of -10 promoter mutants did not facilitate R. capsulatus NtrC activation of the nifA1 promoter by the E. coli RNA polymerase. Thus, an additional barrier to activation by R. capsulatus NtrC exists, probably a lack of the proper R. capsulatus NtrC-E. coli RNA polymerase (protein-protein) interaction(s).

RNA polymerase subunit requirements for activation by the enhancer-binding protein Rhodobacter capsulatus NtrC

Rhodobacter capsulatus NtrC is an enhancer-binding protein that activates transcription of the R. capsulatus sigma 70 RNA polymerase, but does not activate the Escherichia coli sigma 70-RNA polymerase at the nifA1 promoter. We utilized R. capsulatus:E. coli hybrid RNA polymerases assembled in vitro to investigate the subunits required for protein-protein interaction with RcNtrC at the nifA1mut1 promoter. Assembly of core Rc alpha beta beta' or hybrid RNA polymerases containing the Rc beta beta' subunits absolutely require the inclusion of an omega subunit, with the Ec omega subunit only partially promoting RNA polymerase assembly. The Rc alpha Ec beta beta' RNA polymerase is not activated by RcNtrC. Moreover, a mutant form of the Rc alpha lacking the alpha C-terminal domain, when assembled with the Rc beta beta'omega and sigma 70 subunits, is activated by RcNtrC. These results suggest that the R. capsulatus alpha subunit is not important for RcNtrC interaction. All hybrid RNA polymerases that contained the Rc beta' were activated by RcNtrC, suggesting that the Rc beta' subunit plays an important role. It is proposed that RcNtrC recruits R. capsulatus sigma 70-RNA polymerase to the promoter through interaction with Rc beta'. RcNtrC interacts with RNA polymerase from a unique position, with dimers centered at -118 bp from the start site. Placing the RcNtrC tandem binding sites on the opposite face of the helix (-113 bp) completely abolished transcription activation. Moving the RcNtrC tandem binding sites 20 bp closer to or further from the promoter significantly reduced activation, again suggesting unique spatial constraints on how RcNtrC interacts with the R. capsulatus RNA polymerase.

Comparative efficiency of national health systems: cross national econometric analysis

OBJECTIVE

To improve the evidence base for health policy by devising a method to measure and monitor the performance of health systems.

DESIGN

Estimation of the relation between levels of population health and the inputs used to produce health.

SETTING

191 countries.

MAIN OUTCOME MEASURE

Health system efficiency (performance).

RESULTS

Estimated efficiency varied from nearly fully efficient to nearly fully inefficient. Countries with a history of civil conflict or high prevalence of HIV and AIDS were less efficient. Performance increased with health expenditure per capita.

CONCLUSIONS

Increasing the resources for health systems is critical to improving health in poor countries, but important gains can be made in most countries by using existing resources more efficiently.

Nicastrin binds to membrane-tethered Notch

The presenilins and nicastrin, a type 1 transmembrane glycoprotein, form high molecular weight complexes that are involved in cleaving the beta-amyloid precursor protein (betaAPP) and Notch in their transmembrane domains. The former process (termed gamma-secretase cleavage) generates amyloid beta-peptide (Abeta), which is involved in the pathogenesis of Alzheimer's disease. The latter process (termed S3-site cleavage) generates Notch intracellular domain (NICD), which is involved in intercellular signalling. Nicastrin binds both full-length betaAPP and the substrates of gamma-secretase (C99- and C83-betaAPP fragments), and modulates the activity of gamma-secretase. Although absence of the Caenorhabditis elegans nicastrin homologue (aph-2) is known to cause an embryonic-lethal glp-1 phenotype, the role of nicastrin in this process has not been explored. Here we report that nicastrin binds to membrane-tethered forms of Notch (substrates for S3-site cleavage of Notch), and that, although mutations in the conserved 312-369 domain of nicastrin strongly modulate gamma-secretase, they only weakly modulate the S3-site cleavage of Notch. Thus, nicastrin has a similar role in processing Notch and betaAPP, but the 312-369 domain may have differential effects on these activities. In addition, we report that the Notch and betaAPP pathways do not significantly compete with each other.

Mutation of conserved aspartates affect maturation of presenilin 1 and presenilin 2 complexes

Presenilin (PS1 and PS2) holoproteins are transiently incorporated into low molecular weight (MW) complexes. During subsequent incorporation into a higher MW complex, they undergo endoproteolysis to generate stable N- and C-terminal fragments (NTF/CTF). Mutation of either of two conserved aspartate residues in transmembrane domains inhibits both presenilin-endoproteolysis and the proteolytic processing of APP and Notch. We show that aspartate-mutant holoprotein presenilins are not incorporated into the high molecular weight, NTF/CTF-containing complexes. Aspartate-mutant presenilin holoproteins also preclude entry of endogenous wild-type PS1/PS2 into the high molecular weight complexes, but do not affect the incorporation of wild-type holoproteins into lower molecular weight holoprotein complexes. These data suggest that the loss-of-function aspartate-mutants cause altered PS complex maturation, and argue that the functional presenilin moieties are contained in the high molecular weight presenilin NTF/CTF-containing complexes.

Treatment of subacute hepatitis with Lamivudine and intravenous Glycyrrhizin: a pilot study

Subacute hepatitis is a common and distinct clinicopathological entity due to Hepatitis B and E viruses in India. Lamivudine has been established as a safe and effective antiviral agent for the treatment of chronic HBV hepatitis. This drug was administered orally along with intravenous (I/V) Glycyrrhizin, an immunomodulator drug, in an open pilot trial to assess its efficacy in the treatment of subacute hepatitis. The results establish the safety and efficacy of Lamivudine in combination with I.V. Glycyrrhizin in subacute Hepatitis.

Bacillus circulans endophthalmitis

An 80-year-old woman presented with right endophthalmitis, characterized by chalky white deposits covering her posterior capsule. This occurred 17 months after uncomplicated right cataract surgery. A three-port pars plana vitrectomy and partial posterior capsulectomy isolated Bacillus circulans, and the patient made a rapid and full recovery on topical cephalothin and prednisolone acetate 1%. The case demonstrates that, unlike endophthalmitis due to other Bacillus spp., B. circulans endophthalmitis does not necessarily follow a fulminant course. It is the first report describing a subacute presentation, and response to posterior capsulectomy and simple antibiotic therapy It is also the first description of B. circulans causing white plaques in the posterior capsule, a finding characteristic of chronic endophthalmitis and previously considered pathognomonic of Proprionibacterium acnes endophthalmitis.

Carboxyl-terminal fragments of Alzheimer beta-amyloid precursor protein accumulate in restricted and unpredicted intracellular compartments in presenilin 1-deficient cells

Absence of functional presenilin 1 (PS1) protein leads to loss of gamma-secretase cleavage of the amyloid precursor protein (betaAPP), resulting in a dramatic reduction in amyloid beta peptide (Abeta) production and accumulation of alpha- or beta-secretase-cleaved COOH-terminal fragments of betaAPP (alpha- or beta-CTFs). The major COOH-terminal fragment (CTF) in brain was identified as betaAPP-CTF-(11-98), which is consistent with the observation that cultured neurons generate primarily Abeta-(11-40). In PS1(-/-) murine neurons and fibroblasts expressing the loss-of-function PS1(D385A) mutant, CTFs accumulated in the endoplasmic reticulum, Golgi, and lysosomes, but not late endosomes. There were some subtle differences in the subcellular distribution of CTFs in PS1(-/-) neurons as compared with PS1(D385A) mutant fibroblasts. However, there was no obvious redistribution of full-length betaAPP or of markers of other organelles in either mutant. Blockade of endoplasmic reticulum-to-Golgi trafficking indicated that in PS1(-/-) neurons (as in normal cells) trafficking of betaAPP to the Golgi compartment is necessary before alpha- and beta-secretase cleavages occur. Thus, although we cannot exclude a specific role for PS1 in trafficking of CTFs, these data argue against a major role in general protein trafficking. These results are more compatible with a role for PS1 either as the actual gamma-secretase catalytic activity or in other functions indirectly related to gamma-secretase catalysis (e.g. an activator of gamma-secretase, a substrate adaptor for gamma-secretase, or delivery of gamma-secretase to betaAPP-containing compartments).

Intellectual psycho-educational and functional status of low birth weight survivors beyond 5 years of age

To determine the intellectual, psycho-educational and functional status of low birth weight (LBW) survivors (birth weight < or = 2000 gms) beyond 5 years of age and to compare their status with normal birth weight counterparts. This was cross-sectional study. On hospital based cohort on longitudinal follow-up at the High Risk and Well Baby Clinics of a teaching hospital. The demographic data of these children was recorded. A detailed physical examination was performed. The tests of cognition included the Stanford Binet and the Raven's Progressive Matrices. Academic achievement was evaluated by the Wide range achievement test-Revised (WRAT-R). Assessment of visuo motor integration was done by the Bender Gestalt Test. The proportion of children having soft neurological signs was determined. Vineland Social Maturity Scale was performed on all children. Fifty-nine LBW children and fifty-seven matched control children participated in the study. 27 of LBW children were examined at a mean age of 7.0 +/- 1.1 years (group I) and 32 were examined at a mean age of 10.6 +/- 1.2 years (group II). The LBW children as a group performed in the normal range on the tests of cognition and academic achievement, but were significantly disadvantaged (p < 0.005) as compared to controls. A higher percentage of LBW children had low scores on the Bender Gestalt. Test as compared to controls but the difference was not significant. A significantly higher proportion of LBW children of both the groups showed the presence of soft neurological signs as compared to controls. The social quotient as assessed by the vineland Social Maturity Scale was significantly lower in the LBW children as compared to controls. Thus, though the LBW children were performing in the normal range on various measures, comparison with the control group showed that they were clearly disadvantaged on nearly every measure tested, emphasizing the need for early detection and referral for special education.

Mutation of the conserved N-terminal cysteine (Cys92) of human presenilin 1 causes increased A beta42 secretion in mammalian cells but impaired Notch/lin-12 signalling in C. elegans

The presenilin proteins are involved in the proteolytic processing of transmembrane proteins such as Notch/lin-12 and the beta-amyloid precursor protein (betaAPP). Mutation of a conserved cysteine (Cys60Ser) in the C. elegans presenilin sel-12 has a loss-of-function effect on Notch/lin-12 processing similar to that of null mutations in sel-12. In contrast, in mammalian cells, most missense mutations increase gamma-secretase cleavage of betaAPP. We report here that mutation of this conserved cysteine (Cys92Ser) in human presenilin 1 confers a loss-of-function effect in C. elegans, but causes increased A beta42 secretion in mammalian cells. These data suggest that the role of presenilins in Notch/lin-12 signalling and betaAPP processing are either separately regulated activities or independent activities of the presenilins.

Nicastrin modulates presenilin-mediated notch/glp-1 signal transduction and betaAPP processing

Nicastrin, a transmembrane glycoprotein, forms high molecular weight complexes with presenilin 1 and presenilin 2. Suppression of nicastrin expression in Caenorhabditis elegans embryos induces a subset of notch/glp-1 phenotypes similar to those induced by simultaneous null mutations in both presenilin homologues of C. elegans (sel-12 and hop-1). Nicastrin also binds carboxy-terminal derivatives of beta-amyloid precursor protein (betaAPP), and modulates the production of the amyloid beta-peptide (A beta) from these derivatives. Missense mutations in a conserved hydrophilic domain of nicastrin increase A beta42 and A beta40 peptide secretion. Deletions in this domain inhibit A beta production. Nicastrin and presenilins are therefore likely to be functional components of a multimeric complex necessary for the intramembranous proteolysis of proteins such as Notch/GLP-1 and betaAPP.

Mutation of conserved aspartates affects maturation of both aspartate mutant and endogenous presenilin 1 and presenilin 2 complexes

Presenilin (PS1 and PS2) holoproteins are transiently incorporated into low molecular weight (MW) complexes. During subsequent incorporation into a higher MW complex, they undergo endoproteolysis to generate stable N- and C-terminal fragments. Mutation of either of two conserved aspartate residues in transmembrane domains inhibits both presenilin-endoproteolysis and the proteolytic processing of beta-amyloid precursor protein and Notch. We show that although PS1/PS2 endoproteolysis is not required for inclusion into the higher MW N- and C-terminal fragment-containing complex, aspartate mutant holoprotein presenilins are not incorporated into the high MW complexes. Aspartate mutant presenilin holoproteins also preclude entry of endogenous wild type PS1/PS2 into the high MW complexes but do not affect the incorporation of wild type holoproteins into lower MW holoprotein complexes. These data suggest that the loss of function effects of the aspartate mutants result in altered PS complex maturation and argue that the functional presenilin moieties are contained in the high molecular weight complexes.

Molecular genetics of Alzheimer's disease: the role of beta-amyloid and the presenilins

Alzheimer's disease is the most common neurodegenerative disorder of aging, accounting for an estimated two-thirds of all cases of senile dementia. Epidemiologic studies have failed to resolve any single cause of Alzheimer's disease and suggest a complex etiology, with environmental and genetic factors influencing the pathogenesis. Although the majority of cases are sporadic, a small number display familial clustering. Genetic analyses of these pedigrees have identified four genes that are involved in the development of Alzheimer's disease.

Serum TNF-alpha and free radical scavengers in neonatal septicemia

Tumor necrosis factor-alpha (TNF-alpha) and free radicals have been implicated in the pathogenesis of neonatal septicemia and its complications. This case control study was conducted between November 1996 to July 1997 to determine the levels of TNF-alpha and free radical scavengers viz. superoxide dismutase (SOD) and glutathione peroxidase (GPX) in the serum of 30 septic neonates and 20 healthy controls. Patients with neonatal sepsis registered significantly higher levels of TNF-alpha, SOD and GPX in comparison to controls (p < 0.05). The neonates with septic shock had five fold increase in TNF-alpha levels (2262 +/- 605.8 pg/ml) as compared to those without shock (738.8 +/- 728.8 pg/ml). There was no statistically significant difference in levels of antioxidant enzymes between neonates with shock and without shock. The levels of TNF-alpha and antioxidant enzymes were not affected by the type of organism isolated in blood culture.

Status of lipid peroxidation and antioxidant enzymes in hypoxic ischemic encephalopathy

OBJECTIVE

To compare the activities of key antioxidant enzymes [superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase] and the level of malonyl dialdehyde (MDA) in neonates with hypoxic ischemic encephalopathy (HIE) and controls.

DESIGN

Prospective cross sectional study.

SETTING

Tertiary care level II neonatal unit of teaching hospital.

METHODS

Fifteen term new borns with HIE were registered for the study whereas normal term appropriate for gestational age babies were enrolled as controls. Clinical features were recorded. Activities of SOD, GPx, catalase and the content of MDA were estimated at 24 hours of age. The results obtained were statistically analyzed.

RESULTS

Activities of SOD and Catalase and the level of MDA were significantly higher in cases as compared to the controls. There was however no significant alternation in the activity of GPx levels in both the groups.

CONCLUSION

The increased activities of antioxidant enzymes are unable to counteract the excessively generated oxidants in vivo, as is evident from the increased MDA levels. Hence, oxygen free radicals may play a significant role in the pathogenesis of HIE.

Effect of lithium on hepatic and serum elemental status under different dietary protein regimens

Lithium carbonate at the dose level of 1.1 g/kg was administered in diet to normal (18% protein), low-protein- (LP; 8%) and high-protein (HP; 30% diet)-fed rats for a period of 1 mo. The LP diet resulted in a significant decrease in the hepatic levels of zinc, iron, copper, manganese, calcium, and serum levels of calcium and sodium. The HP diet caused a marked decrease in copper and calcium levels in liver, but an increase in potassium levels in serum was observed. Lithium treatment to normal rats led to a significant reduction in the hepatic contents of zinc, copper, potassium, calcium, and serum contents of potassium and sodium, whereas an elevation in serum contents of calcium was noticed. Administration of lithium to protein-deficient rats increased the hepatic concentration of manganese and serum concentration of calcium and the levels almost reached the normal limits. On the other hand, there was a marked depression in potassium contents in the serum of LP- as well as HP-fed rats following lithium treatment when compared to LP and HP groups, respectively.