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Biomedical subjects

S Parikh

Publications and source records attributed to S Parikh.

At least 19 recordsLinked to original sources
PubMed2006

Re-activation of a dormant tumor suppressor gene maspin by designed transcription factors.

The controlled and specific re-activation of endogenous tumor suppressors in cancer cells represents an important therapeutic strategy to block tumor growth and subsequent progression. Other than ectopic delivery of tumor suppressor-encoded cDNA, there are no therapeutic tools able to specifically re-activate tumor suppressor genes that are silenced in tumor cells. Herein, we describe a novel approach to specifically regulate dormant tumor suppressors in aggressive cancer cells. We have targeted the Mammary Serine Protease Inhibitor (maspin) (SERPINB5) tumor suppressor, which is silenced by transcriptional and aberrant promoter methylation in aggressive epithelial tumors. Maspin is a multifaceted protein, regulating tumor cell homeostasis through inhibition of cell growth, motility and invasion. We have constructed artificial transcription factors (ATFs) made of six zinc-finger (ZF) domains targeted against 18-base pair (bp) unique sequences in the maspin promoter. The ZFs were linked to the activator domain VP64 and delivered in breast tumor cells. We found that the designed ATFs specifically interact with their cognate targets in vitro with high affinity and selectivity. One ATF was able to re-activate maspin in cell lines that comprise a maspin promoter silenced by epigenetic mechanisms. Consistently, we found that this ATF was a powerful inducer of apoptosis and was able to knock down tumor cell invasion in vitro. Moreover, this ATF was able to suppress MDA-MB-231 growth in a xenograft breast cancer model in nude mice. Our work suggests that ATFs could be used in cancer therapeutics as novel molecular switches to re-activate dormant tumor suppressors.

Amino Acid Sequence↗
PubMed2005

Rabies post-exposure prophylaxis in malnourished children exposed to suspect rabid animals.

Over half of the world's malnourished children live in Asia where more than 90% of reported human rabies deaths occur. In order to determine the effect of malnutrition on the immune response to rabies post-exposure prophylaxis (PEP), 45 children with moderate to severe protein energy malnutrition (PEM) who were exposed to potentially rabid animals were enrolled in a clinical trial. Patients received purified chick embryo cell rabies vaccine (PCECV) on days 0, 3, 7, 14 and 30. Blood was drawn on days 0, 14 and 30 and evaluated for the presence of rabies virus neutralizing antibody. All children that met the protocol criteria developed rabies virus neutralizing antibody titers above the acceptable level of 0.5 IU/mL by day 14 and no serious adverse events were reported. We conclude that children in this study that received four or five doses of rabies vaccine intramuscularly developed an acceptable immune response despite their severe degree of protein energy malnutrition.

Adolescent↗
PubMed2004

Effects of nicotine and a cannabinoid receptor agonist on negative contrast: distinction between anxiety and disappointment?

RATIONALE: Animals trained to lick for a sucrose solution of a given incentive value that subsequently encounter an incentive downshift (i.e. 32-4% sucrose) display an exaggerated decrease in the amount consumed, relative to unshifted controls. This change has been classified as a successive negative contrast (SNC) effect. The emotional component to this robust behavioural change is dynamic and changes from post-shift day (PSD) 1 to 2. Anxiolytics block SNC, but the possible link between anxiety and SNC needs further exploration. Both nicotine and a cannabinoid receptor agonist have been reported to change anxiety and both have actions on the reward process, but their effects on SNC have not been investigated. OBJECTIVES: To determine: (1) whether exposure to SNC evokes an anxiogenic response; (2) whether an anxiolytic dose of nicotine has the same effects on SNC as those of chlordiazepoxide; (3) the effects of a low (anxiolytic) and a high (anxiogenic) dose of the cannabinoid receptor agonist CP 55,940 on SNC. METHODS: Two groups of animals were given access to high (32%) or low (4%) sucrose solutions for 5 min per day for 10 days. On PSD 1 and 2, the shifted group had access to a devalued incentive (from 32 to 4% sucrose) and the unshifted group remained at 4% sucrose. The volumes (ml) of sucrose solution consumed were measured pre-shift and on PSD 1 and 2. In experiment 1, immediately after SNC testing on PSD 1 and 2, the rats were tested in the social interaction and elevated plus-maze tests of anxiety. In experiment 2, the effects of chlordiazepoxide (5 and 7.5 mg/kg) and nicotine (0.1 mg/kg) were examined on PSD 1 and 2. In experiment 3, the effects of CP 55,940 (5 and 40 microg/kg) were examined on PSD 1 and 2. RESULTS: There were no anxiogenic effects of shift in either test of anxiety on either test day. However, on PSD 1, the shifted group had significantly higher locomotor activity and spent a higher percentage of time on the open arms, perhaps reflecting search strategies. Nicotine was without significant effect on SNC on either test day. On PSD 1, chlordiazepoxide (5 mg/kg) and CP 55,940 (5 and 40 microg/kg, IP) blocked SNC. On PSD 2, both doses of chlordiazepoxide and the low, anxiolytic dose of CP 55,940 (5 microg/kg) blocked SNC, the high dose of CP 55,940 was without effect. CONCLUSIONS: The pattern of results allows for the separation between effects on anxiety and SNC. The block of contrast on PSD 1 was independent of changes in anxiety, since both anxiolytic and anxiogenic drug doses were effective. It is suggested that this may provide an animal model of disappointment in which the cannabinoid system plays an important role. An anxiolytic action would seem to be a necessary, but not a sufficient, action to block SNC on PSD 2.

Animals↗
PubMed2004

Low-frequency depression of tension in the cat gastrocnemius muscle after eccentric exercise.

Subjecting a muscle to a series of eccentric contractions in which the contracting muscle is lengthened results in a number of changes in its mechanical properties. These include a fall in isometric tension that is particularly pronounced during low-frequency stimulation, a phenomenon known as low-frequency depression (LFD). Reports of LFD have not taken into account the shift in optimum length for active tension generation to longer muscle lengths that takes place after eccentric contractions. Given the length dependence of the stimulation frequency-tension curve, we tested the hypothesis that the change in this relationship after eccentric exercise is due to the shift in optimum length. We measured LFD by recording tension in response to a linearly increasing rate of stimulation of the nerve to medial gastrocnemius of anesthetized cats, over the range 0-100 pulses per second. Tension responses were measured before and after 50 eccentric contractions consisting of 6-mm stretches starting at 3 mm below optimum length and finishing at 3 mm above it. An index of LFD was derived from the tension responses to ramp stimulation. It was found that LFD after the eccentric contractions was partly, but not entirely, due to changes in the muscle's optimum length. An additional factor was the effect of fatigue. These observations led to the conclusion that the muscle length dependence of LFD was reduced by eccentric contractions. All of this means that after eccentric exercise the tension deficit at low rates of muscle activation is likely to be less severe than first thought.

Adaptation, Physiological↗
PubMed2003

Treatment of hemorrhagic radiation proctitis with 4 percent formalin.

PURPOSE: The purpose of this study was to review our results in patients undergoing treatment with 4 percent formalin for radiation-induced injury to the rectum. METHODS: A retrospective review of office charts was performed, identifying all patients undergoing formalin treatment. Patient gender, initial malignancy, prior treatments, response to treatment with formalin, complications, and length of follow-up were reviewed. All patients had flexible endoscopy to assess for proximal sources of bleeding. The indication for treatment was a symptomatic patient with endoscopic evidence of radiation injury. A cotton pledget was used for direct application of 4 percent formalin to the affected area via a rigid proctoscope or anoscope. The treatment was repeated if blanching did not occur or if bleeding continued. Patients were followed up at three-week to four-week intervals and treatment was repeated based on the above indications. Treatments were continued until cessation of bleeding occurred or, when treatment failed, operative treatment was required. RESULTS: Thirty-six patients were identified. Three were lost to follow-up. Symptoms included bleeding in all but one patient, who presented with an ulcer. There were 33 (26 male) patients. Seventeen (51.5 percent) patients had prior treatment. The number of formalin treatments ranged from 1 to 13, with a mean of 3.4. The follow-up ranged from 1 to 60 months, with a mean of 18 months. Twenty-nine (88 percent) patients had improvement or cessation of symptoms. Four (12 percent) patients failed treatment. Two patients were noted to have full-thickness ulcers and both failed formalin treatment. No complications were noted related to formalin treatment. CONCLUSION: We conclude that formalin therapy is a safe and effective form of treatment that can be performed in the office with minimal discomfort and no complications. It can be performed multiple times until results are achieved. Formalin therapy may be useful as a first-line treatment for chronic radiation proctitis, however, a prospective controlled trial comparing modalities is required to prove this to be true.

Colonoscopy↗
PubMed2002

Risk-adjusted comparative audit. Is Possum applicable to head and neck surgery?

Possum (the physiological and operative severity score for the enumeration of mortality) is used in many surgical specialities for comparative audit. We investigated its validity in relation to head and neck surgery by retrospectively scoring 301 operative interventions. We also applied the P-Possum (Portsmouth Possum) equation for mortality. We compared our observed with the predicted outcomes. We introduced two new variables, radiotherapy and previous surgery to the operative site, to test their association with outcome. We found that Possum is valid for morbidity but predicts more accurately for high-risk than for low-risk groups. Neither Possum or P-Possum accurately predicts mortality. Radiotherapy and previous surgery were both significant for the development of postoperative complications (P = 0.002, P = 0.007 respectively) and are worthy of inclusion in a Possum score for head and neck surgery.

Head and Neck Neoplasms↗
PubMed2002

Resistance to thyroid hormone in a patient without thyroid hormone receptor mutations.

Resistance to thyroid hormone (RTH) is a clinical syndrome characterized by elevated serum thyroid hormone (TH) levels, unsuppressed thyrotropin (TSH) levels, and tissue hyposensitivity to TH. In almost all cases, the genetic basis of RTH lies in mutation of one of the two TH receptor beta (TRbeta) alleles. Recently, patients from several families with phenotypic manifestations of RTH in the absence of TR mutations have been described. We report a case of a 31-year-old woman who presented with goiter, tachycardia, elevated TH levels, unsuppressed TSH, and "inappropriately normal" levels of peripheral TH action markers. In two separate clinical evaluations, the patient exhibited typical clinical and biochemical evidence for peripheral and pituitary RTH. Surprisingly, reverse transcriptase-polymerase chain reaction (RT-PCR) of full-length TRalpha and TRbeta mRNAs, and genomic PCR using primers flanking exons encoding the carboxy-terminal region of TRbeta failed to demonstrate mutations in the TRalpha or TRbeta genes. It is likely that defects in the regulation of TR genes or mutations in transcriptional cofactors involved in TR signaling account for this patient's phenotype.

Adult↗
PubMed2001

Formation and implications of a ternary complex of profilin, thymosin beta 4, and actin.

Data from affinity chromatography, analytical ultracentrifugation, covalent cross-linking, and fluorescence anisotropy show that profilin, thymosin beta(4), and actin form a ternary complex. In contrast, steady-state assays measuring F-actin concentration are insensitive to the formation of such a complex. Experiments using a peptide that corresponds to the N terminus of thymosin beta(4) (residues 6-22) confirm the presence of an extensive binding surface between actin and thymosin beta(4), and explain why thymosin beta(4) and profilin can bind simultaneously to actin. Surprisingly, despite much lower affinity, the N-terminal thymosin beta(4) peptide has a very slow dissociation rate constant relative to the intact protein, consistent with a catalytic effect of the C terminus on conformational change occurring at the N terminus of thymosin beta(4). Intracellular concentrations of thymosin beta(4) and profilin may greatly exceed the equilibrium dissociation constant of the ternary complex, inconsistent with models showing sequential formation of complexes of profilin-actin or thymosin beta(4)-actin during dynamic remodeling of the actin cytoskeleton. The formation of a ternary complex results in a very large amplification mechanism by which profilin and thymosin beta(4) can sequester much more actin than is possible for either protein acting alone, providing an explanation for significant sequestration even if molecular crowding results in a very low critical concentration of actin in vivo.

Actins↗
PubMed2001

Lithium revisited.

OBJECTIVE: To review lithium's utility in the treatment of mood disorders. METHOD: We reviewed the safety, tolerability, teratogenicity, optimal dosing regimens, and mortality-lowering effects of lithium. Clinical relevance and scientific rigour determined which articles we selected for review. RESULTS: Lithium is the paradigmatic treatment for bipolar disorder (BD). In treating BD, optimal maintenance plasma levels may be approximately 0.75 to 0.85 mEq/L. Although nephrogenic diabetes insipidus is not uncommon, irreversible renal failure due to lithium appears to be a rare, idiosyncratic event. Lithium-induced cardiovascular teratology appears to be less common than previously thought. Optimal lithium dosing may be once daily, this agent appears to bestow a robust suicide-lowering effect, and emerging data hint at neurotrophic and neuroprotective effects. CONCLUSION: Lithium remains an effective and integral agent in the treatment of BD. Its ability to lower suicide rates in persons with BD warrants clinical attention.

Adverse Drug Reaction Reporting Systems↗
PubMed2001

Magnetic resonance imaging of the paranasal sinuses: incidental abnormalities and their relationship to patient symptoms.

OBJECTIVES: Magnetic resonance imaging (MRI) is able to demonstrate a wide range of abnormalities in the paranasal sinuses, which are often reported as incidental findings on scans performed for indications other than the evaluation of paranasal sinus pathology. However, the clinical significance of these findings remains undefined. We present a prospective study that determines the prevalence of abnormalities in the paranasal sinuses in a population undergoing MRI scans for suspected intracranial disease. These findings are correlated with clinical data pertaining to nasal and sinus symptoms. STUDY DESIGN: Prospective, cross-sectional study. METHODS: Patients undergoing MRI scans for suspected intracranial pathology were asked to complete a questionnaire pertaining to symptoms of nasal/sinus pathology. The T2-weighted scans of 86 patients (mean age = 51 years) were then reviewed for evidence of paranasal sinus pathology using a standardized method for evaluation and reporting of results. These results were then correlated with those obtained from the patient questionnaire. RESULTS: Radiologic abnormalities were found in the paranasal sinuses of 33 (38%) patients. Abnormalities were most commonly seen in the ethmoid sinuses (44.8%) followed by the maxillary (38%), sphenoid (14%), and frontal (3%) sinuses. Analysis of the clinical data revealed no significant relationship between the presence of clinical symptoms of nasal and sinus pathology and abnormalities on MRI scan. CONCLUSION: The assessment of inflammatory sinus pathology remains controversial. Based on the results of this study, incidental abnormalities of the paranasal sinuses detected on MRI scan do not appear to be related to clinical symptoms.

Adult↗
PubMed2000

The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for carcinoma of the endometrium.

PURPOSE: To develop recommendations for use of high-dose-rate (HDR) brachytherapy in patients with endometrial cancer. METHODS: A panel of members of the American Brachytherapy Society (ABS) performed a literature review, supplemented their clinical experience, and formulated recommendations for endometrial HDR brachytherapy. RESULTS: The ABS endorses the National Comprehensive Cancer Network (NCCN) guidelines for indications for radiation therapy for patients with endometrial cancer and the guidelines on HDR quality assurance of the American Association on Physicists in Medicine (AAPM). The ABS made specific recommendations for HDR applicator selection, insertion techniques, target volume definition, dose fractionation, and specifications for postoperative adjuvant vaginal cuff therapy, for vaginal recurrences, and for medically inoperable primary endometrial cancer patients. The ABS recommends that applicator selection should be based on patient and target volume geometry. The dose prescription point should be clearly specified. The treatment plan should be optimized to conform to the target volume whenever possible while recognizing the limitations of computer optimization. Suggested doses were tabulated for treatment with HDR alone, and in combination with external beam radiation therapy (EBRT), when applicable. For intravaginal brachytherapy, the largest diameter applicator should be selected to ensure close mucosal apposition. Doses should be reported both at the vaginal surface and at 0.5-cm depth irrespective of the dose prescription point. For vaginal recurrences, intracavitary brachytherapy should be restricted to patients with nonbulky (< 0.5-cm thick) disease. Patients with bulky (> 0.5-cm thick) recurrences should be treated with interstitial techniques. For medically inoperable patients, an appropriate applicator that will allow adequate irradiation of the entire uterus should be selected. CONCLUSION: Recommendations are made for HDR brachytherapy for endometrial cancer. Practitioners and cooperative groups are encouraged to use these recommendations to formulate their treatment and dose reporting policies. This will lead to meaningful comparisons of reports from different institutions and lead to advances and appropriate use of HDR.

Brachytherapy↗