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Biomedical subjects

S Parameswaran

Publications and source records attributed to S Parameswaran.

At least 19 recordsLinked to original sources
PubMed2004

Antipsychotic polypharmacy.

The administration of more than one drug for a single medical condition is considered to be polypharmacy. There are many possible reasons for polypharmacy: (1) psychosis is a chronic disease that cannot be cured; (2) expectations to improve patients' quality of life beyond what drugs can actually do is high; (3) the lack of side effects and interactions can cause physicians to be more daring in terms of potential complications; (4) information from the Internet may cause patients and their families to demand medications; (5) the diluted mental health system allows legal guardians and other mental health professionals to force physicians to provide multiple drugs; (6) many new drugs are available; and (7) physicians are forced to shorten hospitalization days. The 1997 American Psychiatric Association Practice Research Network found that 17% of 146 patients with schizophrenia were treated concurrently with more than one antipsychotic medication. Polypharmacy may increase the risk of adverse effects, drug interactions, noncompliance, and medication errors. It is not wise to use polypharmacy only to prevent side effects and drug and interactions. Our attempts to reduce polypharmacy may fail, as academicians also propagate polypharmacy, and all of the algorithms indicate polypharmacy as an option, putting physicians in a legal and ethical bind. Techniques such as experimental ward, peer review, computer information feedback, and comparing different techniques may temporarily reduce polypharmacy but long-term outcome is not affected. Scientific data on the efficacy of polypharmacy is needed in order to sort out good and bad polypharmacy.

Antipsychotic Agents↗
PubMed2004

Drug therapy in schizophrenia.

Over 40 different antipsychotic medications have been introduced around the world, 21 of which are available in the United States. The conventional antipsychotic drugs introduced in late 50s have two major groups of disadvantages, efficacy and safety. All of the atypical antipsychotic agents have higher 5-HT(2) blocking than D(2) blocking. Atypical antipsychotic agents differ in their receptor action and side effect profile. Among them, clozapine has superior efficacy, and both clozapine and olanzapine have a higher propensity to cause weight gain and possibly diabetes. Quetiapine is difficult to use in acute psychotic states as a result of titration. Ziprasidone and aripiprazole are less sedating, and diabetes as well as weight gain have not been reported with their use. In an acute setting, antipsychotic monotherapy in therapeutic doses is the most useful. AAP drugs are preferred because of the lack of acute EPS symptoms. Intramuscular preparations of haloperidol and ziprasidone are sometimes required to treat acute patients. The goal in acute treatment is to prevent harm to self or others by decreasing excitatory symptoms. Continuing the antipsychotic medication treatment after the acute symptoms are controlled reduces the likelihood of a relapse. The neuroleptic medication should be continued indefinitely. The minimum amount antipsychotic drugs necessary to prevent a relapse should be used, based on clinical decision.

Animals↗
PubMed2004

Side effects of atypical antipsychotic drugs.

Recently there has been increased concern over the side effects of the atypical antipsychotic drugs, including diabetes, hyperlipidemia and obesity. The relationship between diabetes and antipsychotic drugs requires a careful analysis. Patients with schizophrenia are known to suffer from diabetes more often than the general population. In addition, a number of case reports indicate that the conventional antipsychotic as well as atypical antipsychotic drugs produce diabetes. Clozapine and olanzapine, in particular, have been implicated producing diabetes as well as diabetic ketoacidosis. Epidemiological surveys have supplemented the case reports, finding increased incidence of diabetes in patients treated with atypical antipsychotic agents, but these surveys have not yielded consistent results regarding the differential effects of the various atypical antipsychotic drugs. The mechanism by which antipsychotic agents produce diabetes is not elucidated. Weight gain and consequent alteration in triglycerides and cholesterol have been known to occur frequently with olanzapine and clozapine. The ensuing metabolic syndrome itself may cause insulin resistance and diabetes. In the absence of definitive scientific data on the differential effects of antipsychotic drugs in inducing diabetes, clinical prudence and careful monitoring of all patients on atypical antipsychotic drugs is necessary. Aripiprazole and ziprasidone have not been shown to increase weight or produce diabetes, but more information on the diabetogenic effects of ziprasidone and aripiprazole is needed. In order to assess the differential effects of atypical antipsychotic drugs in producing diabetes and the mechanisms by which they produce this reaction, further research is necessary.

Animals↗
PubMed2004

The use of antiparkinsonian agents in the management of drug-induced extrapyramidal symptoms.

Antipsychotic drugs induce extrapyramidal symptoms such as dystonia, akathisia and parkinsonian symptoms early in treatment, and tardive dyskinesia later in treatment. With the advent of atypical antipsychotic drugs, the incidence of extrapyramidal symptoms has decreased, but the danger still exists. There are many reasons that extrapyramidal symptoms are still a problem. Most often, psychiatrists use doses higher than the recommended dose of atypical antipsychotic agents. For example, the use of 8 to 10 mg of risperidone, 30 to 40 mg of olanzapine, or 1200 to 1500 mg of quetiapine daily is not uncommon. In addition, combinations of both conventional and atypical antipsychotic drugs are used together in many instances. Extrapyramidal symptoms produce unnecessary suffering and add to the health burden; therefore, prompt recognition of these symptoms is necessary. If EPS occur, it is of paramount importance to start an antiparkinsonian agent immediately to provide relief to the patient. In high-risk patients, prophylactic antiparkinsonian therapy is indicated but routine prophylaxis with antiparkinsonian agents is harmful. As only a segment of patients may develop EPS, many patients receive prophylactic medication unnecessarily, and the side effects of antiparkinsonian drugs prescribed without clinical indication may add to the health burden of the patient. If prophylactic antiparkinsonian treatment is initiated, it should be discontinued at least two weeks after its initiation. The long term use of antiparkinsonian treatment is not therapeutically beneficial to the patient, and studies indicate that the gradual withdrawal of antiparkinsonian medication will not produce recurrence of EPS.

Animals↗
PubMed2004

Rehabilitation of schizophrenic patients.

Schizophrenia is a maldevelopmental disorder of the brain that manifests in positive, negative, cognitive and affective symptoms. Currently, the mainstay of treatment involves pharmacotherapy. The limitations of antipsychotic treatment are that they can only control symptoms and cannot cure the illness, and 20% of patients do not respond, thus leading to the requirement of maintenance treatment. Patients that do respond continue to have disabling residual symptoms such as amotivation and isolation, maladaptive behavior, and impaired social functioning. These symptoms prevent patients from attaining educational, occupational, and social roles. Psychosocial interventions and models of quality of life in schizophrenia are based on the notion that increases in psychosocial functioning will be related to improvement in subjective experiences, such as self-esteem and satisfaction with life. The comparative effect of specific treatment methods and the additional benefits of multiple treatments need to be explored. Diversified techniques have also been employed, such as shaping, cognitive process therapy, mastery-oriented skill training, motivation and enhancement. Issues in designing psychosocial interventions and the role of various professionals in providing such interventions need to be carefully considered. Predictor variables and the indications for particular therapies in an individual need to be explored. Generalizability of the gains made by rehabilitation/recovery is also an important consideration. Patients in jail, chronic mental hospitals, private facilities, and the Veterans Administration system are all different in their ability to benefit, their motivations, and the severity of their psychopathology. Therefore, it is very difficult to generalize findings from one setting to another.

Humans↗
PubMed2003

Intracranial aneurysmal bone cyst manifesting as a cerebellar mass.

A 17-year-old boy presented with symptoms of raised intracranial pressure for a month. Investigations revealed a large extra-cerebellar mass. The lesion was radically resected. It arose from the petrous bone. Histology revealed that the lesion was an aneurysmal bone cyst [ABC].

Adolescent↗
PubMed1999

Hydraulic conductivity, albumin reflection and diffusion coefficients of pig mediastinal pleura.

Hydraulic conductivity (L), albumin reflection coefficient (sigma), and albumin diffusion coefficient (D) were measured across pig mediastinal pleura. The tissue (7 mm diameter) was bonded between two chambers. Flow (Q) of lactated Ringer solution between the chambers was measured in turn at driving pressures (DeltaP) of 2, 4, and 6 cm H(2)O. Value of L was proportional to the slope of the Q-DeltaP curve. Then Q was measured in turn at three albumin osmotic pressure differences (Deltapi equivalent to -1, -2, and -3 g/dl albumin concentration difference, DeltaC) with DeltaP constant at either 2, 3, 4, or 6 cm H(2)O. From Starling's equation, magnitude of sigma was the slope of the Q-Deltapi curve divided by the slope of the Q-DeltaP curve. We measured the diffusion of 0, 2, 5, and 10 g/dl albumin with tracer (125)I-albumin. Tracer mass (M) that diffused across the pleura was measured for 10 h using a well-type NaI(T1) detector. D was calculated from the slope of the M-time curve. Values of L averaged 2.0 x 10(-8) cm(3). s(-1). dyne(-1) (n = 23). Values of sigma were small (0.02-0.05) and sigma increased as flow increased 20-fold. D (n = 24) increased 3-fold from 2.7 x 10(-8) cm(2)/s as DeltaC increased from 0 to 10 g/dl. The small values of sigma indicated that mediastinal pleura provided little restriction to the passage of protein.

Albumins↗
PubMed1999

Effect of hyaluronidase on albumin diffusion in lung interstitium.

Albumin diffusion measured in an isolated segment of rabbit lung interstitium with a radioactive tracer ((125)I-albumin) technique was independent of albumin concentration and similar to the free diffusion of albumin in water (Qiu et al, 1998. J Appl Physiol 85: 575-583). We studied the effect of hyaluronidase on the diffusion of albumin. Isolated rabbit lungs were inflated with silicon rubber by way of airways and blood vessels, and two chambers were bonded to the sides of a approximately 0.5-cm thick slab enclosing a vessel with an interstitial cuff. One chamber was filled with 2 g/dl albumin solution containing (125)I-albumin and 0.02 g/dl hyaluronidase. Unbound (125)I was removed from the tracer by dialysis before use. The other chamber filled with Ringer's solution was placed within a NaI(Tl) scintillation detector. Diffusion of tracer was measured continuously for 120 h. Albumin diffusion coefficient (D) and interstitial area (A) were obtained by fitting the tracer-time curve with the theoretical solution of the equation describing one-dimension diffusion of a solute across a membrane. D averaged 5.2 x 10(-7) cm(2)/s for albumin diffusion with hyaluronidase, 20% less than that measured previously without hyaluronidase. Hyaluronidase had no effect on A. Results indicated an interaction between albumin and interstitial hyaluronan that was the opposite of the steric effect on albumin excluded volume measured in solution.

Animals↗
PubMed1999

Laparoscopic colectomy yields similar morbidity and disability regardless of patient age.

This study compared the outcome factors of morbidity and the length of disability in older and younger patients following laparoscopic colorectal surgery. All patients undergoing laparoscopic segmental resection during the study period were included. Morbidity was determined by reviewing the medical records, and disability by a patient-administered questionnaire. The series was divided into two age cohorts (</=64 and >/=65 years), which did not differ significantly in gender or type of procedure. Between these two groups we found no significant differences in mean duration of ileus (3.3 days in both groups), the mean length of hospitalization (5.7 vs. 6.3 days, respectively), morbidity rate (18% vs. 21%), or time until returning to partial activity (1.6 vs. 1.6 weeks) or to full activity (3 vs. 2 weeks). Our findings demonstrate that neither the morbidity rate nor the disability period after laparoscopic techniques differ between elderly and younger patients. We therefore endorse the use of laparoscopy regardless of patient age.

Activities of Daily Living↗
PubMed1999

Effect of concentration and hyaluronidase on albumin diffusion across rabbit mesentery.

OBJECTIVE: To measure the diffusion coefficient of albumin through rabbit mesentery using the steady-state flux of radioactive tracer 125I-albumin. The effect of albumin concentration and testicular hyaluronidase were also studied. METHODS: Mesenteric tissue was bonded between two plates, exposing a 7 mm diameter surface, with two chambers on either side. One chamber was filled with a test solution of albumin containing the radioactive tracer and the other with lactated Ringer solution. The solutions in both chambers were stirred with small magnetic cylinders. The chamber filled with lactated Ringer solution was placed in a well-type NaI(Tl) detector, and the radiation emitted from the tracer that diffused across the mesentery was monitored continuously for 9 hours. The diffusion coefficient (D) was calculated using Fick's law of diffusion. The diffusion coefficient was measured at albumin concentration differences (delta C) between approximately 0 and 10 g/dL. The diffusion coefficient was also measured with testicular hyaluronidase at three different albumin-concentration differences. RESULTS: The diffusion coefficient increased significantly (P < 0.0001) approximately three-fold from a mean value of 2.2 x 10(-8) +/- 1.2 x 10(-8) (SD) cm2/s at 0-0.5 g/dL delta C to 5.9 x 10(-8) +/- 1.1 x 10(-8) (SD) cm2/s at 10 g/dL delta C. The values are much less than the free diffusion coefficient of albumin (6 x 10(-7) cm2/s). Testicular hyaluronidase added to the albumin solution decreased D by approximately 60%, but did not eliminate the increase in D with delta C. CONCLUSIONS: The increase in D with delta C and the reduced D with hyaluronidase were attributed to a reduced albumin-excluded volume caused by an interaction between albumin and hyaluronan. Further studies are required to define this interaction.

Albumins↗
PubMed1998

Effect of concentration on albumin diffusion in lung interstitium.

The transport of macromolecules through the lung interstitium depends on both bulk transport of fluid and diffusion. In the present study, we studied the diffusion of albumin. Isolated rabbit lungs were inflated with silicon rubber via airways and blood vessels, and two chambers were bonded to the sides of a 0.5-cm-thick slab that enclosed a vessel with an intersititial cuff. One chamber was filled with either albumin solution (2 or 5 g/dl) containing tracer 125I-albumin or with tracer 125I-albumin alone; the other was filled with Ringer solution. Unbound 125I was removed from the tracer by dialysis before use. The chamber with Ringer solution was placed in the well of a NaI(Tl) scintillation detector. Diffusion of tracer through the interstitium was measured continuously for 60 h. Tracer mass (M) showed a time (t) delay followed by an increase to a steady-state flow (dM/dt constant). Albumin diffusion coefficient (D) was given by L2/(6T), where T was the time intercept of the steady-state M-t line at zero M, and L was interstitial length. Interstitial cuff thickness-to-vessel radius ratio (Th0/R) was estimated by using Fick's law for steady-state diffusion. Both D and Th0/R were independent of albumin concentration. D averaged 6.6 x 10(-7) cm2/s, similar to the free D for albumin. Values of Th0/R averaged 0.047 +/- 0.024 (SD), near the values measured histologically. Thus pulmonary interstitial constituents offered no restriction to the diffusion of albumin.

Albumins↗
PubMed1998

Reconstruction of lower leg defects using a medial island fasciocutaneous flap.

It is usually a major task providing soft tissue cover to significant defects of the lower leg. A wide variety of flaps and techniques are available, each with its advantages and limitations. Previously described anatomic study of the septocutaneous vessels of the leg have indicated a consistent lower most perforator at 9-12 cm from the tip of the medial malleolus. An island fasciocutaneous flap based on this perforator vessels can be raised subfascially. After the vessels have been dissected clean down to the posterior tibial artery, it can be rotated up to 180 degrees degrees. Successful soft tissue reconstruction was achieved in 18 patients. Most of the tissue loss was due to trauma and were around the ankle and the heel. There were 7 minor complications which resolved completely after 2 months. Its simplicity of design and elevation plus its extensive arc of rotation makes it a reliable and versatile flap in the reconstruction of lower leg defects.

Adolescent↗
PubMed1998

Effect of flow on hydraulic conductivity and reflection coefficient of rabbit mesentery.

OBJECTIVE: To measure the hydraulic conductivity and reflection coefficient for albumin, as defined by the Starling equation, in rabbit mesentery. METHODS: A section of rabbit mesentery was fixed between two chambers filled with lactated Ringer solution. Flow (Q) of Ringer solution was measured across the mesentery at driving pressures (delta P) between 1 and 6 cm H2O. Hydraulic conductivity was proportional to the slope of the Q-delta P curve. At constant delta P (approximately -2, -4, or -6 cm H2O), flow was measured at three different albumin concentration differences (0.5, 1, and 1.5 g/dl). Unstirred layer effects were minimized by magnetic stirrers. Reflection coefficient was the negative of the slope of the Q-delta pi curve divided by the slope of the Q-delta P curve, where delta pi was the albumin osmotic pressure difference. Hydraulic conductivity was measured before and after testicular hyaluronidase was added to the Ringer solution. RESULTS: There was no significant difference in conductivity per unit area (Lp) for the three different driving pressures. Hyaluronidase increased hydraulic conductivity significantly (p < 0.01) by 72 +/- 56%, indicating that hyaluronan and other glycosaminoglycans contributed to tissue fluid resistance. Reflection coefficient (sigma) increased from 0.02 to 0.14 as flow increased eightfold. CONCLUSIONS: The results suggest that the mesentery tissue provides little restriction to the passage of albumin. The increase in conductivity in the presence of hyaluronidase indicates that tissue hyaluronan and other glycosaminoglycans provide fluid resistance to bulk flow.

Albumins↗
PubMed1996

Case report: malignant teratoma in the thyroid gland.

Malignant teratomas of the thyroid gland are rare. These are highly malignant tumours with a high frequency of local recurrence and metastases following surgery. We report a case of malignant teratoma of the thyroid gland in a 35-year-old female, who developed local recurrence immediately following total thyroidectomy. Despite achieving local control following chemotherapy and local radiotherapy, the patient developed distant relapse illustrating the aggressive nature of the disease.

Adult↗
PubMed1995

Age-related changes in albumin-excluded volume fraction.

The space available to large macromolecules, such as albumin and globulin, is less than the total interstitial fluid volume due to the dense matrix formed by the interstitial ground substance. Changes in excluded volume are likely to indicate changes in the composition of the matrix. Sprague-Dawley rats were anesthetized with sodium pentobarbital. Serum, mesenteric tissue, and peritoneal fluid samples were obtained. Albumin contents were determined by microrod electrophoresis. Serum and mesenteric tissue chloride concentrations were measured by the coulometric-amperometric method. Serum and mesenteric tissue sample chloride concentrations were not significantly different, suggesting that this loose connective tissue is composed almost entirely of extracellular matrix. Matrix hydration decreased with a regression slope of -0.014 (microgram tissue water/microgram tissue dry wt)/10 days. Serum and tissue albumin concentrations decreased between 210 and 630 days of age. Mesenteric loose connective tissue albumin-excluded volume fraction increased by 80% over this age range. The increase could not be accounted for by dehydration alone, suggesting that the increase in excluded volume fraction for albumin is also due to changes in tissue glycosaminoglycans or collagen.

Aging↗
PubMed1995

Age-related changes in rat interstitial matrix hydration and serum proteins.

Measurements of effects of age-related changes on loose connective tissue protein concentrations and water are lacking. Tissue hydration is an important determinant of tissue protein diffusion coefficients and hydraulic conductivity. Sprague-Dawley rats (ages 11, 30, 57, and 89 wk) were anesthetized. Blood and mesenteric tissue samples were taken. Tissue water content was determined by microgravimetric technique. Protein content was determined by electrophoresis. Tissue hydration decreased 18% between 11 and 89 wk with one-half the fall occurring between 57 and 89 wk. Tissue albumin concentration decreased 37% between 11 and 89 wk. Serum albumin increased 22% between 11 and 30 wk and then decreased by 37% to 1.4 g/dl in 89-wk rats. Serum total protein concentration increased by 13% between 11 and 89 wk, whereas tissue total protein concentration decreased 30% with age to 1.9 g/dl at 89 wk. The results suggest that age-related tissue dehydration is due, in part, to a shift in the colloid osmotic pressure components of Starling equilibrium favoring fluid reabsorption.

Aging↗
PubMed1995

Age-related changes in perimicrovascular protein distribution.

The diffusion hypothesis for physiological aging proposes that an increase in interstitial matrix fiber-to-gel ratio causes a decrease in nutrient diffusion to the cells. This hypothesis predicts a decrease in interstitial matrix protein with age. The objective was to test this hypothesis by determining age-related changes in plasma protein distribution in perimicrovascular and distal regions of rat mesentery interstitial matrix. Rats that were 77, 140, 210, 315, 455, and 630 days old were anesthetized with pentobarbital sodium, and a mesenteric loop was exteriorized. Intravital video microspectrophotometry was performed using wavelengths of 280, 320, and 700 nm. Perimicrovascular protein concentrations from the protein absorbance images were used to obtain the histogram, mean, and skewness of the proximal and distal protein concentration distributions. An exponential gradient model was also used to obtain the proximal and distal protein concentrations and gradient decay constants. Proximal protein concentration increased from 77- to 140-day-old rat and then decreased gradually through 210-, 315-, 455-, and 630-day-old rats. Distal concentration decreased gradually from 140- to 630-day-old rats. There was an increase in positive skewness of the proximal protein distributions from 140- through 630-day-old rats. We found an age-related decrease in perimicrovascular protein and propose that this is due to a decrease in protein permeability with age. The results support the diffusion theory of aging.

Aging↗