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Biomedical subjects

C K Reddy

Publications and source records attributed to C K Reddy.

7 recordsLinked to original sources
PubMed2003

Multimodal map and complex basin of attraction of a simple hopper.

In this paper, we study the global dynamics of a simple passive mechanical model for hopping. The hopper is a two-mass, single-spring system constrained to move in the vertical direction (under gravity) above a rigid ground. The hopper model and its basic dynamics including the existence of incessant hopping motions have been reported elsewhere. Here, we extend the study to investigate the global dynamics of the hopper. The global map of the hopper is multimodal. We construct an approximate analytic map near the fixed points of the map and show that the fixed points exhibit one-way stability. We also show that the map is invariant under the inversion of the mass ratio of the hopper. Next, we construct the global basin of attraction of these fixed points and show that their structure is highly complex and retains form at finer scales. This structure of the basin of attraction contains regions where the fate of an arbitrary initial condition becomes unpredictable.

Journal Article↗
PubMed2001

Do water molecules mediate protein-DNA recognition?

A comprehensive analysis of interfacial water molecules in the structures of 109 unique protein-DNA complexes is presented together with a new view on their role in protein-DNA recognition. Location of interfacial water molecules as reported in the crystal structures and as emerging from a series of molecular dynamics studies on protein-DNA complexes with explicit solvent and counterions, was analyzed based on their acceptor, donor hydrogen bond relationships with the atoms and residues of the macromolecules, electrostatic field calculations and packing density considerations. Water molecules for the purpose of this study have been categorized into four classes: viz. (I) those that contact both the protein and the DNA simultaneously and thus mediate recognition directly; (II) those that contact either the protein or the DNA exclusively via hydrogen bonds solvating each solute separately; (III) those that contact the hydrophobic groups in either the protein or the DNA; and, lastly (IV) those that contact another water molecule. Of the 17,963 crystallographic water molecules under examination, about 6% belong to class I and 76% belong to class II. About three-fourths of class I and class II water molecules are exclusively associated with hydrogen bond acceptor atoms of both protein and DNA. Noting that DNA is polyanionic, it is significant that a majority of the crystallographically observed water molecules as well as those from molecular dynamics simulations should be involved in facilitating binding by screening unfavorable electrostatics. Less than 2% of the reported water molecules occur between hydrogen bond donor atoms of protein and acceptor atoms of DNA. These represent cases where protein atoms cannot reach out to DNA to make favorable hydrogen bond interactions due to packing/structural restrictions and interfacial water molecules provide an extension to side-chains to accomplish hydrogen bonding.

Base Sequence↗
PubMed1995

Cusum as an aid to early assessment of the surgical trainee.

Tests of knowledge, aptitude and psychomotor skills have been used to assess and select surgical trainees but none of these is reliable in the long term. The industrial quality-control method of the cusum was used to assess performance progress in 17 surgical trainees. Trainees were assessed on their ability to perform, independently, selected surgical operations using the criterion of procedure duration. Cusum profiles were compared with scores from at least four independent assessors using a modified Royal Australasian College of Surgeons' mentor form. The cusum identified all trainees who were considered either satisfactory or less able by their mentors. This objective evaluation was reliable after 25 procedures, whether for appendicectomy or combined with herniorrhaphy and cholecystectomy. Evaluation of surgical performance using the cusum may prove to be a more objective tool for assessing surgical trainees than early impressions or less clinically oriented tests.

Clinical Competence↗
PubMed1992

Renal papillary necrosis in Kuwait.

In 2,158 consecutive routine urograms, 85 patients (51 males and 34 females) were found to have typical changes of renal papillary necrosis, an incidence of 3.9% (2.8% in males, 9.4% in females). The changes were bilateral in 60 patients (71.6%) and unilateral in 25 (29.4%). 3 patients were diabetics, 4 had sickle cell anaemia and 7 had obstructive uropathy. 19 patients admitted to analgesic abuse. The remaining 52 patients were idiopathic but a combination of analgesic abuse and dehydration may have been the cause in this group. The possible reasons for the high incidence of RPN especially in females in this hot desert environment are discussed. The literature on the subject is briefly reviewed.

Adult↗
PubMed1991

Life-threatening post-nephrolithotomy hemorrhage resulting in cessation of kidney function, treated by transcatheter arterial embolization with subsequent restoration of excretory function.

A massive post-nephrolithotomy renal hemorrhage was successfully controlled by selective arterial embolization using Gelfoam particles. Prior to embolization, the kidney showed no excretory function due to complete obstruction of its collecting system by blood clots. Long-term observation revealed restoration of excretory function of the treated kidney and only minimal loss of its parenchyma.

Adult↗