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Biomedical subjects

A Malhotra

Publications and source records attributed to A Malhotra.

At least 19 recordsLinked to original sources
PubMed2006

Biodosimetry using chromosome aberrations in human lymphocytes.

In vitro dose-response calibration curves for (60)Co gamma rays have been established for unstable chromosome aberrations in human peripheral blood lymphocytes. The observed dose-response data were fitted to a linear quadratic model. The calibration curve parameters were used to estimate the equivalent whole-body dose and dose to the irradiated region in partial body irradiation of cancer patients. The derived partial body doses and fractions of lymphocytes irradiated were in agreement with those estimated from the radiotherapy regimes.

Adult↗
PubMed2006

Evidence for a Müllerian mimetic radiation in Asian pitvipers.

Müllerian mimicry, in which toxic species gain mutual protection from shared warning signals, is poorly understood in vertebrates, reflecting a paucity of examples. Indirect evidence for mimicry is found if monophyletic species or clades show parallel geographic variation in warning patterns. Here, we evaluate a hypothesis of Müllerian mimicry for the pitvipers in Southeast Asia using a phylogeny derived from DNA sequences from four combined mitochondrial regions. Mantel matrix correlation tests show that conspicuous red colour pattern elements are significantly associated with sympatric and parapatric populations in four genera. To our knowledge, this represents the first evidence of a Müllerian mimetic radiation in vipers. The putative mimetic patterns are rarely found in females. This appears paradoxical in light of the Müllerian prediction of monomorphism, but may be explained by divergent selection pressures on the sexes, which have different behaviours. We suggest that biased predation on active males causes selection for protective warning coloration, whereas crypsis is favoured in relatively sedentary females.

Animals↗
PubMed2006

Effect of increased lung volume on sleep disordered breathing in patients with sleep apnoea.

BACKGROUND: Previous studies have shown that changes in lung volume influence upper airway size and resistance, particularly in patients with obstructive sleep apnoea (OSA), and that continuous positive airway pressure (CPAP) requirements decrease when the lung volume is increased. We sought to determine the effect of a constant lung volume increase on sleep disordered breathing during non-REM sleep. METHODS: Twelve subjects with OSA were studied during non-REM sleep in a rigid head-out shell equipped with a positive/negative pressure attachment for manipulation of extrathoracic pressure. The increase in lung volume due to CPAP (at a therapeutic level) was determined with four magnetometer coils placed on the chest wall and abdomen. CPAP was then stopped and the subjects were studied for 1 hour in three conditions (in random order): (1) no treatment (baseline); (2) at "CPAP lung volume", with the increased lung volume being reproduced by negative extrathoracic pressure alone (lung volume 1, LV1); and (3) 500 ml above the CPAP lung volume(lung volume 2, LV2). RESULTS: The mean (SE) apnoea/hypopnoea index (AHI) for baseline, LV1, and LV2, respectively, was 62.3 (10.2), 37.2 (5.0), and 31.2 (6.7) events per hour (p = 0.009); the 3% oxygen desaturation index was 43.0 (10.1), 16.1 (5.4), and 12.3 (5.3) events per hour (p = 0.002); and the mean oxygen saturation was 95.4 (0.3)%, 96.0 (0.2)%, 96.3 (0.3)%, respectively (p = 0.001). CONCLUSION: An increase in lung volume causes a substantial decrease in sleep disordered breathing in patients with OSA during non-REM sleep.

Adult↗
PubMed2006

Pre-eclampsia is associated with sleep-disordered breathing and endothelial dysfunction.

Pre-eclamptic toxaemia (PET) may be associated with both endothelial dysfunction (ED) and sleep-disordered breathing (SDB). It was hypothesised that females with PET would demonstrate both SDB and ED, and that a correlation between these two would suggest a potential causative association. A total of 17 females with PET and 25 matched females with uncomplicated pregnancy were studied. They underwent a nocturnal ambulatory sleep study (using Watch_PAT100) and noninvasive evaluation of endothelial function utilising the reactive hyperaemia test (using Endo_PAT 2000). A higher ratio of post- to pre-occlusion pulse-wave amplitude (endothelial function index (EFI)) indicated better endothelial function. Females with PET had a significantly higher respiratory disturbance index (RDI) and lower EFI than controls (18.4+/-8.4 versus 8.3+/-1.3.h(-1), and 1.5+/-0.1 versus 1.8+/-0.1, respectively). Blood pressure significantly correlated with RDI and with EFI. EFI tended to correlate with RDI. In conclusion, these results suggest that both sleep-disordered breathing and endothelial dysfunction are more likely to occur in females with pre-eclamptic toxaemia than in females with uncomplicated pregnancies. The current authors speculate that respiratory disturbances contribute to the functional abnormality of the blood vessels seen in females with pre-eclamptic toxaemia, although causality cannot be determined based on this study.

Adult↗
PubMed2006

Technetium Tc-99m ethyl cysteinate dimer brain single-photon emission CT in mild traumatic brain injury: a prospective study.

PURPOSE: To explore the role of single-photon emission CT (SPECT) in initial diagnostic evaluation of patients with mild traumatic brain injury (MTBI) and to identify subgroups in which it may serve as a useful diagnostic tool. MATERIALS AND METHODS: Patients with MTBI seen during a 14-month period were prospectively included in this study. All patients had a CT of head within 12 hours of injury and SPECT by using technetium Tc99m ethyl cysteinate dimer (Tc99m-ECD) within 72 hours of injury. Both SPECT and CT findings were compared with clinical features such as posttraumatic amnesia (PTA), postconcussion syndrome (PCS), and loss of consciousness (LOC). RESULTS: Ninety-two patients with MTBI underwent SPECT in the study period. There were 28 children and 64 adults, with male-to-female ratio of 4.5 to 1. CT findings were abnormal in 31 (34%) and SPECT in 58 (63%). The most common abnormality was hypoperfusion in the frontal lobe(s) in adults and the temporal lobe in children. A significantly higher number of perfusion abnormalities were seen in patients with PTA (P = .03), LOC (P = .02), and PCS (P = .01) than in patients without these symptoms. Compared to CT, SPECT had a much higher sensitivity for detecting an organic basis in these subgroup, of patients (P < .05). CONCLUSION: Tc99m-ECD SPECT can be used as a complementary technique to CT in initial evaluation of patients with MTBI. It is particularly useful in patients having PCS, LOC, or PTA with normal CT scan.

Adolescent↗
PubMed2005

Do healthy potential kidney donors in india have an average glomerular filtration rate of 81.4 ml/min?

BACKGROUND: Until now, a normal reference range for glomerular filtration rate (GFR) in adult Indian potential kidney donors has not been determined and values from a western population are being used as reference. AIM: To determine the reference range of GFR in healthy adult Indian potential kidney donors. BASIC PROCEDURES: GFR was measured in 610 (250 male, 360 female, average age 35.16 years) healthy potential kidney donors using the 99mTc-DTPA (diethylenetriamine pentaacetic acid) two-plasma sample method of Russell. RESULTS: The mean body surface area (BSA)-normalized GFR value of a young healthy Indian adult potential kidney donor was calculated as 81.4 +/- 19.4 ml/min/1.73 m2 BSA--for males it was 82.3 +/- 21.3 ml/min/1.73 m2 BSA and for females 80.8 +/- 18.1 ml/min/1.73 m2 BSA. There was no significant difference between derived mean GFR values in males and females with a p value of 0.37. CONCLUSIONS: The normal GFR value for the healthy Indian adult potential kidney donor appears to be much lower than the accepted value for a western population. The mean GFR value of a young healthy Indian adult potential kidney donor is 81.4 +/- 19.4 ml/min/1.73 m2 BSA, which is significantly different from the normal value of 109-125 ml/min derived from a western population. These findings might be useful in deciding on a suitable kidney donor in an Indian context.

Adult↗
PubMed2005

Use of atropine in patients with recent myocardial infarction during exercise myocardial perfusion study. Use of atropine during exercise myocardial perfusion SPECT.

BACKGROUND: Patients with recent myocardial infarction frequently require a myocardial perfusion study for risk stratification. However a conclusive study cannot be accomplished in many due to non-attainment of target heart rate. AIM OF THE STUDY: To evaluate the effect of pre-stress administration of atropine in exercise performance of patients with recent myocardial infarction. MATERIAL AND METHODS: Study included 43 test and 43 control patients and were matched for their age, sex, status of pretest exercise tolerance, area of infarction and for interval between infarction and stress thallium test. Atropine (0.01 mg/kg) was administered intravenously 3 min prior to treadmill stress in all the 43 test patients and no atropine was administered to control patients. RESULTS: Target heart rate was attained in 95.3% patients receiving atropine compared to in 67.4% of control patients. There was no significant difference between mean ages (p>0.33), basal BP (p>0.47), peak BP (p>0.18) of both groups. There was significant difference between the increment in exercise-induced heart rate (p<0.004), peak heart rate (p<0.001) and double product (p<0.001) attained between both groups. No significant adverse effect was noted in patients who received atropine. CONCLUSION: Pre-stress administration of atropine in patients with recent myocardial infarction is safe and results in a significantly better exercise performance, which might be useful in decreasing the number of equivocal myocardial perfusion studies.

Adult↗
PubMed2005

Embryology of the adrenal glands and its relevance to diagnostic imaging.

An understanding of the embryology of the adrenal glands is necessary to appreciate the location of adrenal ectopic, or rest, tissue which can occur anywhere along the course of gonadal descent. This tissue usually has no clinical significance, but may become hyperplastic in patients with primary or secondary adrenal pathology. In congenital adrenal hyperplasia, hyperplastic rest tissue may present as a soft-tissue mass, particularly in the gonads and retroperitoneum, and may be mistaken for tumour. The adrenal in the neonate is proportionately much larger than in the adult; in renal ectopy or agenesis the ipsilateral adrenal is normally sited and may be mistaken for a kidney because of its size. This review article illustrates the embryology of the adrenal with particular emphasis on the relevance of embryology to pathology.

Adrenal Gland Neoplasms↗
PubMed2005

Thallium-201 versus Tc99m-glucoheptonate SPECT for evaluation of recurrent brain tumours: a within-subject comparison with pathological correlation.

BACKGROUND: Thallium-201 (Tl-201) is the most commonly used tracer for functional imaging of recurrent brain tumours. However, the physical properties of Tl-201 are not particularly suitable for this application, thus, a technetium-99 (Tc99m) labelled alternative with more favourable physical properties has been sought. The aim of this study was to compare the ability of Tl-201 and Tc99m-glucoheptonate single photon emission computed tomography (SPECT) to detect viable recurrent tumour and differentiate post-radiation gliosis. METHOD: Brain SPECT with Tl-201 and Tc99m-glucoheptonate was performed in 20 patients with malignant brain tumour in whom recurrent disease was suspected. Tracer uptake in the mass was defined as high, moderate or low and was correlated with histological verification of the lesion in all cases. RESULTS: Recurrent tumour was demonstrated in 17 patients by both Tl-201 and Tc99m-glucoheptonate SPECT and confirmed by surgical resection in all 17 patients. Three patients had no tracer uptake on either Tl-210 or Tc99m-glucoheptonate SPECT and surgical resection revealed only fibrotic tissue with areas of necrosis. Tc99m-glucoheptonate images were found to correlate more closely with the surgical findings with regard to the location of tumour margin, extent of tumour invasion and intratumoural necrosis. CONCLUSION: Tc99m-glucoheptonate brain SPECT is an accurate agent for SPECT imaging of recurrent brain tumours and may provide more information about the location of the tumour margin and its extent and intratumoural necrosis than Tl-201. Tc99m-glucoheptonate may be a viable replacement for Tl-201.

Adolescent↗
PubMed2005

Evaluation of Tc99m-glucoheptonate for SPECT functional imaging of medulloblastoma.

OBJECTIVES: Functional imaging of medulloblastoma using SPECT has been a difficult problem as this tumour does not concentrate conventional brain tumour imaging radiopharmaceuticals. This study aimed to evaluate Tc99m-glucoheptonate as a "brain tumour-seeking" radiopharmaceutical for functional imaging of medulloblastoma. METHODS: Tc99m-glucoheptonate brain SPECT was performed in 27 patients with medulloblastoma after radiation therapy and with clinical suspicion of tumour recurrence. Histological verification was obtained within 7 days in patients with a SPECT diagnosis of tumour recurrence. Patients with a SPECT diagnosis of post-radiation gliosis were clinically observed for a minimum period of one year after the SPECT study. RESULTS: Fourteen patients had increased radiotracer uptake in the primary tumour bed, suggesting tumour recurrence. Histopathology confirmed viable medulloblastoma in all cases. Thirteen patients had no increased tracer uptake in the primary tumour bed, suggesting post-radiation gliosis. They all had a clinical course consistent with post-radiation gliosis. CONCLUSION: Tc99m-glucoheptonate is an ideal SPECT tracer for functional evaluation of medulloblastoma. SPECT utilising Tc99m-glucoheptonate is a reliable diagnostic modality to differentiate tumour recurrence from post-radiation gliosis in patients with medulloblastoma.

Adolescent↗
PubMed2005

Investigation of the effects of ischemic preconditioning on the HRV response to transient global ischemia using linear and nonlinear methods.

Ischemic preconditioning (IP) has been used as a strategy to prevent cell death in various organs, including the brain and the heart. Investigation of the effects of ischemic preconditioning mostly employed models with reduced complexity, such as cell cultures, tissue slices or perfused organ preparations. Although such models can provide valuable insight into the protective mechanism of preconditioning, the functional (re)organization of the control mechanisms at the level of the living organism cannot be assessed. The purpose of the present animal model study was to evaluate the effect of global ischemic preconditioning on the heart rate variability (HRV) response to the asphyxia insult. The data consisted of 4 h RR interval measurements recorded in five preconditioned and five non-preconditioned Wistar rats. Using linear (time and frequency domain) and nonlinear (approximate entropy and parameters of Poincare plots) measures, we evaluated the dynamic time course of the HRV response to the asphyxia insult and the effect of preconditioning on the autonomic neurocardiac control. Both the linear and nonlinear parameters indicate a faster recovery of the baseline HRV corresponding to the preconditioned groups, though only the spectral analysis identifies a statistically significant difference between the two groups. For the preconditioned group, at about 90 min after the asphyxic insult, the autonomic neural balance (measured by LF/HF ratio) appears fully recovered. The small variation of the rest of the parameters indicates the necessity of further investigation including the design of a larger study with a higher statistical power. Our results show for the first time that global ischemic preconditioning influences the HRV response to the asphyxia injury. The neuroprotective effect of preconditioning translates into a faster recovery of the basal HRV and the autonomic modulation of the heart.

Algorithms↗
PubMed2005

Diagnosis of ectopic gastric mucosa using 99Tcm-pertechnetate: spectrum of scintigraphic findings.

We highlight the spectrum of scintigraphic findings likely to be encountered in patients with ectopic gastric mucosa with illustrative cases for each such finding. 11 children (aged 4 months to 120 months, all males) underwent (99)Tc(m)-pertechnetate scintigraphic evaluation for ectopic gastric mucosa. Functioning ectopic gastric mucosa was detected in Meckel's diverticulae in three patients, in small bowel duplications in four, in a gastric duplication in one, and in intrathoracic foregut duplication cysts in three. Ectopic functioning gastric mucosa in Meckel's diverticulum, and gastric duplication is visualized simultaneously with the stomach while in intestinal duplications tracer activity can be visualized in the dynamic sequence and even before gastric tracer visualization. In the three patients with intrathoracic duplication cysts, the functioning ectopic gastric mucosa was evident only in the delayed (99)Tc(m)-pertechnetate images, much later than the visualization of stomach activity. Therefore, acquisition of delayed images are useful when the initial images are equivocal or negative in children with intrathoracic foregut duplication cysts. In addition, we suggest a hypothesis of a possible mechanism for the uptake of pertechnetate in ectopic gastric mucosa in some patients with intrathoracic forget duplication cysts. In conclusion, a variety of scintigraphic patterns may be found in patients with ectopic gastric mucosa undergoing (99)Tc(m)-pertechnetate scintigraphy depending upon the location and size of the ectopic tissue.

Child↗
PubMed2004

Control of cardiac function and noise from a decaying power spectrum.

Evidence is presented that adds to the debate surrounding the question: To what extent does neural control of cardiac output exploit noise? The transduction capability of cardiac afferent neurons, situated in and adjacent to the heart, is vital to feedback in control of cardiac function. An analysis of in situ cardiac afferent activity shows evidence of independent and exponentially distributed interspike intervals. An anatomical basis for such memoryless interspike intervals ultimately derives from the fact that each afferent neuron is associated with a field of sensory neurites, or bare nerve endings, that transduce local chemical and mechanical stimuli in a many-to-one fashion. As such, cardiac afferent neurons and their sensory neurite inputs are respectively modeled here by the Hodgkin-Huxley equations forced by "red" noise (decaying power spectrum) perturbing an otherwise constant subthreshold input. A variable barrier competition model is derived from these equations in order to address the question: How are noisy inputs being processed by sensory neurons to cause each spike? It is found that ion channels are responsible for significant input "whitening" (increased spectral power at higher frequency) through differentiation of the inputs. Such whitening is a means to distinguish low-frequency control signals from otherwise red noise fluctuations. Furthermore, spiking occurs when backward moving averages of the whitened inputs, over a window of the order of the sodium activation time scale, exceed an approximately constant barrier.

Action Potentials↗
PubMed2004

Prevalence of vesicoureteral reflux in patients with incidentally diagnosed adult hypertension.

OBJECTIVES: To evaluate the prevalence of vesicoureteral reflux (VUR) in hypertensive patients without any other evidence of renal involvement. Reflux nephropathy may be clinically latent and present in early adulthood as hypertension when superimposed confounding factors are added. METHODS: The medical records of 157 adult hypertensive patients with normal renal parameters and low-probability, captopril-enhanced renal dynamic scan findings who underwent direct radionuclide voiding cystoscintigraphy between June 1998 and May 2003 were retrospectively analyzed. RESULTS: VUR was documented in 30 patients (19.1%). In those 30 patients, VUR was mild in 8 (26.6%), moderate in 6 (20%), and severe in 16 (53.3%) patients. Bilateral VUR was seen in 7 patients, graded as severe in all cases. The prevalence by age was 20% in the 18 to 30-year-old group, 16.6% in the 31 to 45-year-old group, and 20% in the older than 45-year-old group. CONCLUSIONS: The results of this study have shown that VUR is present in a significantly large proportion of adult patients with hypertension without any apparent renal parenchymal or renovascular involvement.

Adult↗
PubMed2004

The utility of AFLPs for supporting mitochondrial DNA phylogeographical analyses in the Taiwanese bamboo viper, Trimeresurus stejnegeri.

An amplified fragment length polymorphism (AFLP) assay was performed on individuals representing discrete haplotypes from two genetically distinct mtDNA lineages of the bamboo viper, Trimeresurus stejnegeri (Schmidt), within Taiwan. AFLP (525 polymorphic markers from five primer pairs) and mtDNA genetic distances were highly correlated and an analysis of molecular variance, and a Bayesian approach similarly partitioned estimates of genetic similarity according to the mtDNA phylogeographical pattern. These results are discussed in relation to biogeographical hypotheses, comparative rates of mtDNA molecular evolution, and in the identification of evolutionary significant units of Taiwanese T. stejnegeri. In spite of the high degree of congruence between the genetic datasets, the AFLP phylogenetic analysis did not support the mtDNA tree, suggesting that no contemporary barriers to gene flow exist between individuals from the two mtDNA lineages.

Analysis of Variance↗
PubMed2004

Role of skeletal scintigraphy in advanced retinoblastomas.

PURPOSE: To document the incidence of skeletal metastases exclusively in advanced cases of retinoblastoma and to rationalize the use of preoperative skeletal scintigraphy in such patients. MATERIAL AND METHODS: Preoperative bone scans of 36 consecutive patients with advanced retinoblastoma who underwent skeletal scintigraphy during 1998 to 2003 were analyzed retrospectively. Bone scans were classified as: Grade 1 (high probability scan for skeletal metastases), Grade 2 (equivocal malignant or benign abnormalities), or Grade 3 (normal or certainly benign lesions). RESULTS: Grade 1 scan was found in 3 (8.33%) patients; bone metastases were confirmed by additional investigations. Grade 2 scan was found in 5 (13.88%) patients; bone metastases were excluded in all by additional investigations. Grade 3 scan was found in the remaining 28 (77.77%) patients. Extraorbital extension of disease was demonstrated by fine needle aspiration of lymph nodes in five patients, which included all three patients with Grade 1 scan. In addition to lymph node metastases, two patients had intracranial extension of the disease; demonstrated by contrast-enhanced magnetic resonance imaging of the head. One patient had liver metastases detected on abdominal ultrasound. None of the patients had skeletal metastases only. CONCLUSION: Routine preoperative bone scan is not justified in patients with locally advanced retinoblastoma. Bone scan should only be performed in patients with documented extraocular metastatic disease.

Adolescent↗
PubMed2004

Evaluation of 99mTc-L-methionine brain SPECT for detection of recurrent brain tumor: a pilot study with radiological and pathological correlation.

PURPOSE: To evaluate technetium labeled L-methionine for imaging recurrent brain tumors. MATERIAL AND METHODS: Brain SPECT with 99mTc-L-methionine was performed to evaluate tumor viability in 42 patients with primary brain tumor. Findings of SPECT were correlated with radiological and histopathological findings as reference. RESULTS: 99mTc-L-methionine showed localized increased uptake in 40 patients with tumor recurrence, whereas 2 patients with post-radiation gliosis did not show tracer accumulation. A low differential uptake rate (DUR) 2.43 +/- 0.74 and methionine retention (MR) index 0.93 +/- 0.03 was seen in cases of post-radiation gliosis. A high DUR (36.20 +/- 10.31) and MR index (4.87 +/- 2.37) was seen in cases of recurrent tumor. Mean DUR in high-grade tumors (44.01 +/- 8.46) was significantly higher (P<0.001) than in low-grade tumors (30.42 +/- 7.38), and mean MR index in high-grade tumors (7.03 +/- 2.05) was significantly higher than in low-grade tumors (3.27 +/- 0.82) (P<0.001). CONCLUSION: 99mTc-L-methionine can be used as a SPECT tracer to differentiate tumor recurrence from post-radiation gliosis.

Adult↗