Biomedical subjects
Publications and source records attributed to V Narayanan.
We report that liquids perform self-propelled motion when they are placed in contact with hot surfaces with asymmetric (ratchetlike) topology. The pumping effect is observed when the liquid is in the Leidenfrost regime (the film-boiling regime), for many liquids and over a wide temperature range. We propose that liquid motion is driven by a viscous force exerted by vapor flow between the solid and the liquid.
The perceived benefits of bandaging for 10 days following pinnaplasty have been questioned by previous studies. The problems arising from these dressings are many [Powell BWEM. The value of head dressings in the postoperative management of the prominent ear. Br J Plast Surg 1989;42:692-4. Bartley J. How long should ears be bandaged after otoplasty? J Laryngol Otol 1998;112:531-2. Wong MC, Sylaidis P. Head dressings for pinnaplasty: a tradition not supported by evidence. Br J Plast Surg 2001;54:81-2], including their slippage [Powell BWEM. The value of head dressings in the postoperative management of the prominent ear. Br J Plast Surg 1989;42:692-4. Bradbury ET, Hewison J, Timmons MJ. Psychological and social outcome of prominent ear correction in children. Br J Plast Surg 1992;45:97-100. Jeffery SLA. Complications following correction of prominent ears: an audit review of 122 cases. Br J Plast Surg 1999;52:588-90]. Eighty children were recruited into a prospective randomised controlled trial comparing the use of a head bandage for only 24 h with a standard practise of a 10-day head bandage. A preoperative measurement of the lateral ear projection (LEP) was made. The outcome measures recorded during the two planned postoperative visits at 10 days (visit 1) and 2 months (visit 2) were: patient satisfaction score, LEP, complications and any unscheduled hospital visits associated with the surgery. There was no significant difference in LEP and patient satisfaction between the two groups at both the scheduled postoperative visits. Differences between the groups in the number of unscheduled visits (p=0.21) did not reach statistical significance. The findings indicate that it is safe and effective to use head bandage for only 24 h following surgical correction of prominent ears. This study shows no benefit from the application of a formal head bandage for any longer than 1 day.
AIM: The vanadium complexes so far tested for their insulin mimetic effects are either mono- or binuclear and contain only acyclic ligands. The leaching or hydrolysis of vanadyl ions from these complexes is much easier, and hence they elicit side effects. In the present study, a new binuclear macrocyclic oxovanadium complex was synthesized, and its efficacy was studied on streptozotocin (STZ)-induced diabetic rats over a period of 30 days. METHODS: The insulin mimetic effect of the complex was tested on the blood sugar level in the STZ-diabetic rats and on the activities of the carbohydrate-metabolizing enzymes present in the liver. RESULTS: Administration of vanadium complex to STZ-induced diabetic rats decreased blood glucose levels from hyperglycaemic to normoglycaemic when compared to diabetic rats. The activity of carbohydrate-metabolizing enzymes such as hexokinase, glucose-6-phosphate dehydrogenase, glycogen synthase and glycogen content were increased to near normal in vanadium complex-administered diabetic rats. The biochemical studies such as assay of blood urea and glutamate oxaloacetate transaminases revealed that the complex is not toxic to the system. CONCLUSION: The nontoxic nature of this complex may be due to the presence of the vanadyl ions in an intact macrocyclic form. Further, the vanadyl ions present in the macrocyclic binuclear oxovanadium complex are very close to each other, and this may enhance the insulin mimetic activity by synergic effect.
Although its function is unknown, alpha-synuclein is widely distributed in neural tissue and is the major component in the pathological aggregates found in patients with Parkinson's disease, Alzheimer's disease, Down's syndrome, and multiple system atrophy. In this report, we have quantified the binding alpha-synucleins to lipid membranes. In contrast to previous studies, we find, using real time equilibrium fluorescence methods, that alpha-synuclein binds strongly to large, unilamellar vesicles with either anionic or zwitterionic headgroups. Membrane binding is also strong for beta-synuclein, phosphorylated alpha-synuclein, and a synuclein mutant that is associated with familial Parkinson's disease. In solution at less than 400 nM, synuclein has a tendency to undergo concentration-dependent oligomerization as determined by changes in intrinsic fluorescence and fluorescence resonance energy transfer. Above this concentration, the protein begins to aggregate into structures visible by light scattering. Although membrane binding does not affect the secondary structure of alpha-synuclein, it greatly inhibits the ability of this protein to self-associate. Taken together, our results indicate that pathological conditions may be associated with a disruption in synuclein-membrane interactions.
BACKGROUND: Rett syndrome (RTT) is a neurodevelopmental disorder caused by mutations in the X-linked methyl CpG binding protein 2 (MeCP2) gene. METHODS: One hundred sixteen patients with classical and atypical RTT were studied for mutations of the MeCP2 gene by using DHPLC and direct sequencing. RESULTS: Causative mutations in the MeCP2 gene were identified in 63% of patients, representing a total of 30 different mutations. Mutations were identified in 72% of patients with classical RTT and one third of atypical cases studied (8 of 25). The authors found 17 novel mutations, including a complex gene rearrangement found in one individual involving two deletions and a duplication. The duplication was identical to a region within the 3' untranslated region (UTR), and represents the first report of involvement of the 3' UTR in RTT. The authors also report the identification of MeCP2 mutations in two males; a Klinefelter's male with classic RTT (T158M) and a hemizygous male infant with a Xq27-28 inversion and a novel 32 bp frameshift deletion [1154(del32)]. Studies examining the relationship between mutation type, X-inactivation status, and severity of clinical presentation found significant differences in clinical presentation between different types of mutations. Mutations in the amino-terminus were significantly correlated with a more severe clinical presentation compared with mutations closer to the carboxyl-terminus of MeCP2. Skewed X-inactivation patterns were found in two asymptomatic carriers of MeCP2 mutations and six girls diagnosed with either atypical or classical RTT. CONCLUSION: This patient series confirms the high frequency of MeCP2gene mutations causative of RTT in females and provides data concerning the molecular basis for clinical variability (mutation type and position and X-inactivation patterns).
The identification of mutations in the transcriptional repressor methyl-CpG-binding protein 2 (MECP2) gene in Rett Syndrome (RTT) suggests that an inappropriate release of transcriptional silencing may give rise to RTT neuropathology. Despite this progress, the molecular basis of RTT neuropathogenesis remains unclear. Using multiple cDNA microarray technologies, subtractive hybridization, and conventional biochemistry, we generated comprehensive gene expression profiles of postmortem brain tissue from RTT patients and matched controls. Many glial transcripts involved in known neuropathological mechanisms were found to have increased expression in RTT brain, while decreases were observed in the expression of multiple neuron-specific mRNAs. Dramatic and consistent decreases in transcripts encoding presynaptic markers indicated a specific deficit in presynaptic development. Employing multiple clustering algorithms, it was possible to accurately segregate RTT from control brain tissue samples based solely on gene expression profile. Although previously achieved in cancers, our results constitute the first report of human disease classification using gene expression profiling in a complex tissue source such as brain.
AIM: To test the efficacy of two dosing regimens of antimicrobial prophylaxis during the removal of impacted lower third molars. DESIGN: Double blind, prospective, placebo-controlled trial. SETTING: Teaching hospital, India. SUBJECTS: 151 patients aged 19-36 having impacted lower third molars removed. METHODS: Random allocation into three groups: placebo (n= 34), metronidazole 1g orally, 1 hour preoperatively (n= 44), or metronidazole 400mg orally eight hourly for 5 days postoperatively (n= 47). Patients were recalled on the sixth postoperative day for assessment of pain scores on the second and sixth days, swelling, differences in mouth opening between preoperative and the sixth postoperative day, and the state of the wound. RESULTS: There were no significant differences in the outcome between the three groups (P= 0.09). CONCLUSION: Antimicrobial prophylaxis does not seem to reduce morbidity after removal of lower third molars.
OBJECTIVES: To find out whether hypotensive anaesthesia minimized blood loss during orthognathic surgery. DESIGN: A prospective randomized clinical study. SUBJECTS AND METHODS: 53 consecutive patients, 15-33 years old, who were to have orthognathic operations were admitted to the study. They were randomly allocated to either normotensive or hypotensive anaesthesia. RESULTS: Median (range) blood loss/operation (ml) under hypotensive anaesthesia was 200 (90-400)ml and under normotensive anaesthesia was 350 (130-1575)ml (P= 0.01), and those for maxillary segmental osteotomy under hypotensive anaesthesia were 85 (40-240)ml and, under normotensive anaesthesia, 175 (100-190)ml (P= 0.05). CONCLUSION: There was pronounced reduction in blood loss during orthognathic operations done under hypotensive anaesthesia compared with those done under normotensive anaesthesia.
P84 and integrin associated protein (IAP) are heterophilic binding partners that are expressed in the central nervous system in addition to a variety of other tissues. Both molecules are known to be involved in cell signaling in nonneural tissues. In the retina, both molecules are expressed prominently in plexiform layers, suggesting a possible association with synapses. Here, we examined the cellular expression and ultrastructural localization of the two molecules in the developing mouse retina. Both appeared to be expressed at one or both sides of synaptic sites, although the expression of IAP in the retina precedes that of P84. Examination of transgenic IAP-null retinae revealed a failure of P84 to become associated with synaptic sites, suggesting the interaction of P84 with IAP was necessary for P84's synaptic localization. These findings suggest that the signaling activities of P84 and IAP are localized to sites of synaptic contact in the retina. Thus this pair of synapse-associated molecules represents a bidirectional signaling system that could function to modify synaptic activity or possibly trophic interactions between central neurons.
Burns due to lime, although well reported as a result of occupational exposure, are uncommon in the sports arena. A case of such a chemical burn, which required surgery in a football goalkeeper is presented. There are safe alternatives to line marking on football pitches the use of which will prevent such injuries and avoid litigation.
PURPOSE: To determine the epidemiology of burns in patients with epilepsy and to identify changes in epidemiology compared with previous studies; to identify further strategies that can be used in the primary and secondary prevention of such injuries in this group of patients. METHODS: A retrospective case note review of 111 patient episodes to a regional burns unit where the admission criterion was a burn secondary to an epileptic seizure. RESULTS: The majority (60 of 111) of burns were due to scald injury and were sustained in a domestic setting. This group of patients (mean age, 42.7 years) accounted for 1.6% of admissions during the study period. The data demonstrate a change in the epidemiology when compared with previous studies. Most burns were small (mean area burnt, 2.2%) but deep, and 72 of 111 patient episodes required surgery, and 12% of patients had reburn injuries requiring readmission. CONCLUSIONS: Scald injuries are now the major cause of burns in those with epilepsy, and the proportion of such patients admitted to a regional burns unit has reduced. Patients and health professionals need to be aware of such injuries and of appropriate prevention strategies.
Cleft lip and palate is one of the most common malformations in man. Although the subject of a great deal of investigation, etiologic factors contributing to these congenital deformities remain largely unknown. Various factors like race, sex, parental age at the time of conception etc. have been listed as the exogenous factors. This article strives to project any significant relationship of these factors to cleft lip and cleft palate.
P84 (also known as SHPS-1, BIT, and SIRP) is a heterophilic adhesive membrane protein involved in receptor tyrosine kinase signaling that is found at synapses in the mammalian central nervous system and in non-neural tissues. We have identified a binding partner for P84 using an expression cloning strategy. Here we report that integrin-associated protein (IAP/CD47) is a predominant binding partner of P84. Immunohistochemistry reveals a virtually identical distribution of P84 and IAP in a variety of adult brain regions. Because IAP has been implicated in cell signaling in cells of the immune system, P84 and IAP represent a heterophilic binding pair that is likely to be involved in bi-directional signaling at the synapse and in other tissues.
Human Xp22.2 has been proposed as a candidate region for the Rett syndrome (RTT) gene. M6b, a member of the proteolipid protein gene family, was mapped to Xp22.2 within one of the RTT candidate regions. In this article we describe the structure of the M6b gene, refine the physical mapping of M6b between markers DXS69E and DXS414, and present the results of mutation analysis of the M6b gene in patients with RTT. The data from mutation analysis on 55 RTT patients make it very unlikely that M6b is involved in RTT.
The distribution of the cell surface molecules M6 and L1 was studied using the immunohistochemistry and in situ hybridization in the developing and adult mouse retina and optic nerve. L1 is a cell adhesion molecule while M6 is a cell surface molecule homologous to the myelin protein proteolipid protein (PLP/DM20). Although both molecules were expressed in retina and optic nerves of embryonic and neonatal mice, our studies show that their patterns of postnatal expression are quite different. While L1 continues to be expressed in optic axons throughout adulthood, expression of M6 on optic axons declines after birth and instead becomes strongly expressed on Müller glial endfeet and in the inner plexiform layer. The modulation of these molecules after birth could provide clues to changing cell-cell interactions occurring in the proximal portion of the optic pathway.
P84 is a neuronal membrane glycoprotein that promotes the attachment and neurite outgrowth of cultured murine cerebellar cells. The heterophilic adhesive properties of P84 and its localization at sites of synaptogenesis suggest that it may be involved in regulation of synapse formation or maintenance. P84 is expressed in subsets of neurons throughout the CNS. By cloning the cDNA encoding murine P84, we have discovered that this molecule is a member of a family of phosphatase-binding proteins and is identical to the murine SHPS-1 cDNA. Here we report the cloning of two alternatively spliced forms of P84 and describe its localization within the CNS by in situ hybridization.
P84 is a novel neural adhesion molecule that may play an important role in synaptogenesis. We have recently cloned a murine cDNA encoding the P84 adhesion molecule. The human homologue of P84 has previously been isolated (by others) as a brain specific cDNA containing CCA repeats. We have mapped the human P84 gene to the subtelomeric region of chromosome 20p (20p13) by FISH. In addition, we have been able to place P84 onto the high resolution physical map of the human genome by utilizing the Unigene database. P84 maps to several YAC clones, between STS markers IB255 and WI-9632, and very close to the polymorphic marker D20S199, in an interval of less than 1 Mb on 20p13. P84 is a strong candidate gene for neurological disorders which map into this region.
In recent years, apoptosis, the process by which cells orchestrate their own demise, has been the subject of increasingly intense investigation, both from the stand-point of basic mechanisms of signal transduction and with regard to its role in normal and pathological processes in the nervous system. For the neurologist, an understanding of the mechanisms by which apoptosis determines at a cellular level the normal form of the nervous system, an appreciation of how both unchecked apoptosis and failure of enactment of the apoptotic pathway contribute to nervous system pathology and a sense of how both induction and inhibition of apoptosis can be exploited therapeutically are critical to applying the basic knowledge in this field to human disease. Early studies made it clear that substances produced by the target tissue influenced the survival of developing neurons. More recent investigations have demonstrated that they do so by influencing the production of a series of endogenous mediators and modulators of neuronal survival. Furthermore, it is evident that apoptosis is important for the development of both neuronal and non-neuronal cells in the peripheral and central nervous systems.