Biomedical subjects
Publications and source records attributed to R Nijhawan.
Most jaw swellings in infancy are benign odontogenic cysts or tumours. The encounter with an unusual melanotic neuroectodermal tumour of the jaw in a young infant is described in this report. There has been no recurrence, after complete surgical excision, in a follow-up period of six months.
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This study was carried out with the objective of studying the cytomorphology of the wide variety of chest-wall lesions. Two hundred twenty-seven chest-wall lesions were studied over a period of 4 yr. Routine May-Grünwald-Giemsa (MGG) and hematoxylin-eosin (H&E) slides were studied along with special stains, whenever required. The malignant lesions comprised 36.13% of all cases (81/227). Of the 126 benign lesions, the majority were inflammatory in nature (68/126), the next commonest lesion being lipoma (38/126). Rare cases of tuberculosis involving the sternum, epithelioid leiomyosarcoma, and neuroendocrine tumors involving ribs, malignant nerve sheath tumors involving the chest wall, metastatic carcinoma of the stomach and prostate, and papillary carcinoma thyroid are reported in this series. Histopathology was available in 24 cases, and hematological correlation in one case. A 100% cytohistological and cytohematological correlation was found, with no false positives or false negatives. In conclusion, fine-needle aspiration cytology is a rapid, diagnostic tool, eliciting many interesting lesions in the chest wall. It is useful not only in detecting primary and metastatic lesions, but also in follow-up of tumor recurrence.
An object flashed briefly in a given location, the moment another moving object arrives in the same location, is perceived by observers as lagging behind the moving object (flash-lag effect). Does the flash-lag effect occur if the retinal image of the moving object is rendered stationary by smooth pursuit of the moving object? Does the flash-lag effect occur if the retinal image of a stationary object is caused to move by smooth-pursuit eye movements? A disk was briefly flashed in the center of a moving ring such that the ring center was completely 'filled' by the disk. In this display, observers perceived the flashed disk to lag such that it appeared only to partially 'fill' the ring center. The 'unfilled' portion (perceived void) of the moving ring was seen in the color of the background. With smooth pursuit of the ring, the flash-lag effect was eliminated, and observers saw the flashed disk centered on the moving ring. A strong flash-lag effect was observed when observers smoothly pursued a moving point target past a continuously visible stationary ring. Once again, the flashed disk appeared to only partially fill the center of the continuously visible stationary ring, yielding a vivid 'perceived void'. These results are discussed in terms of neural delays and their compensation.
Placental site trophoblastic tumor (PSTT) is very rare. It is an unusual variant of gestational trophoblastic neoplasia usually confined to the uterus, although 10% of patients have metastases. The clinical behaviour of PSTT varies and despite knowledge of its histology, diagnosis of this rare form of trophoblastic disease and prediction of its biological behaviour remains difficult due to only a few cases reported in literature.
The objective of the study was to assess the value of DNA flow cytometry (FCM) and image cytometry (ICM) as an adjunct to routine diagnostic cytology. In this prospective study, 100 consecutive effusion fluids were studied for routine cytology, DNA FCM, and in selected cases, ICM. One half of the centrifuged fluid sample was used for routine cytology and the remaining portion was used for DNA FCM. Nuclear area, nuclear diameter, nuclear perimeter, nuclear convex perimeter, nuclear roundess, and nuclear convex area were measured on at least 100 cells by ICM in cytologically malignant or DNA aneuploid cases along with control cases. Clinical follow-up was done in all cases. There were 22 cytologically malignant cases and 78 cytologically benign cases. Among the 22 cytologically malignant cases, there were 11 aneuploid and diploid cases each by DNA FCM. Out of 78 cytologically benign cases, six (7.7%) were aneuploid by DNA FCM. Smears of these cases showed predominantly reactive mesothelial cells, but the DNA histograms showed hypodiploid (one), hyperdiploid (three), tetraploid (one), and hypertetraploid (one) aneuploidy. Follow-up of these cases showed clinical or histologic features of malignancy except in one case of tetraploid aneuploidy, which did not show any features of malignancy and responded well to antitubercular therapy. Therefore, out of 27 malignant effusions, DNA FCM picked up 16 cases and routine cytology detected 22 cases. Sensitivity and specificity of DNA FCM were thus 59.25% and 98.63%, respectively. There was a statistically significant difference (Student's unpaired t-test, P < 0.05) between cytologically malignant cases and control benign cases in all the nuclear morphometric parameters except for nuclear roundness. There was, however, no statistically significant difference of nuclear morphometric parameters between cytologically benign vs. DNA aneuploid cases and control benign cases. DNA FCM is a useful adjunct for routine diagnostic cytology. Visual diagnostic cytology and morphometric digital microscopy miss some cases of malignancy which can be detected by DNA flow cytometry. Diagn. Cytopathol. 2000;22:81-85.
A case of desmoplastic ameloblastoma of the maxilla in a 25-yr-old woman is presented. Smears prepared from fine-needle aspiration cytology showed two populations of cellular elements: cohesive epithelial clusters with basaloid morphology present, mostly in bidimensional, irregularly outlined clusters with ill-formed palisading of nuclei at the periphery in some, and a mesenchymal component represented by 1) a sparse chunk of moderate-sized tissue fragments made up of spindle- or ovoid-shaped nuclei entrapped in mesenchymal matrix, and 2) many dissociated naked oval-to-spindle-shaped nuclei. The presence of epithelial and mesenchymal components and their benign nature lead us to consider the possibility of benign odontogenic tumors 1) of epithelial origin, such as ameloblastma with a stromal component, e.g., desmoplastic ameloblastoma; 2) of mesenchymal origin, such as odontogenic fibroma; and 3) of mixed epithelial and mesenchymal origin, such as ameloblastic fibroma. Excision and histopathological examination of this lesion confirmed the diagnosis of desmoplastic ameloblastoma. In the given clinical setting and radiological examination, the above cytological features suggest a benign odontogenic tumor, rather than precisely diagnosing any of the entities mentioned above. However, it is important to distinguish between these, since the treatment varies accordingly. The differential diagnosis is discussed.
Continuous, predictable events and spontaneous events may coincide in the visual environment. For a continuously moving object, the brain compensates for delays in transmission between a retinal event and neural responses in higher visual areas. Here we show that it similarly compensated for other smoothly changing features. A disk was flashed briefly during the presentation of another disk of continuously changing color, and observers compared the colors of the disks at the moment of flash. We also tested luminance, spatial frequency and pattern entropy; for all features, the continuously changing item led the flashed item in feature space. Thus the visual system's ability to compensate for delays in information about a continuously changing stimulus may extend to all features. We propose a model based on backward masking and priming to explain the phenomenon.
Objects flashed in alignment with moving objects appear to lag behind [Nijhawan, 1994 Nature (London) 370 256-257]. Could this 'flash-lag' effect be due to attentional delays in bringing flashed items to perceptual awareness [Titchener, 1908/1973 Lectures on the Elementary Psychology of Feeling and Attention first published 1908 (New York: Macmillan); reprinted 1973 (New York: Arno Press)]? We overtly manipulated attentional allocation in three experiments to address the following questions: Is the flash-lag effect affected when attention is (a) focused on a single event in the presence of multiple events, (b) distributed over multiple events, and (c) diverted from the flashed object? To address the first two questions, five rings, moving along a circular path, were presented while observers attentively tracked one or multiple rings under four conditions: the ring in which the disk was flashed was (i) known or (ii) unknown (randomly selected from the set of five); location of the flashed disk was (i) known or (ii) unknown (randomly selected from ten locations). The third question was investigated by using two moving objects in a cost-benefit cueing paradigm. An arrow cued, with 70% or 80% validity, the position of the flashed object. Observers performed two tasks: (a) reacted as quickly as possible to flash onset; (b) reported the flash-lag effect. We obtained a significant and unaltered flash-lag effect under all the attentional conditions we employed. Furthermore, though reaction times were significantly shorter for validly cued flashes, the flash-lag effect remained uninfluenced by cue validity, indicating that quicker responses to validly cued locations may be due to the shortening of post-perceptual delays in motor responses rather than the perceptual facilitation. We conclude that the computations that give rise to the flash-lag effect are independent of attentional deployment.
OBJECTIVE: To investigate the relevance of image analysis for grading breast carcinoma. STUDY DESIGN: Twenty-five ductal breast carcinoma cases were chosen randomly from routine fine needle aspiration clinics. The results of cytomorphologic grading and image morphometry were correlated with those of histologic grading. The five image morphometric parameters studied were nuclear diameter, nuclear area, nuclear roundness, nuclear perimeter and grey level to compare with chromatin texture. RESULTS: Cytologic grading alone had a high correlation with histologic grading. The lowest correlation was found in grade 2 tumors. When cytologic grading was supplemented with image morphometric parameters, the correlation was higher than that of cytologic grading alone. CONCLUSION: Cytologic grading has a high correlation with histologic grading. The correlation improves further on supplementation with image morphometric parameters.
BACKGROUND: To determine the association of chorioamnionitis with placental abruption. SUBJECT AND METHOD: Fifty pregnant women admitted with abruptio placentae were compared to an equally large control group in spontaneous labor with no history of antepartum hemorrhage. Swabs from the cervix and placental membranes were cultured for aerobic and anaerobic organisms. Placental membranes were studied histologically in 40 women of study group and 35 of control group for any evidence of chorioamnionitis. RESULTS: Specific organisms were isolated in 22 (44%) women in the study group and 19 (38%) women in the control group. The cervical swab microbiological flora was similar in both groups but isolation of specific organisms from placental membrane culture was higher in the study group (40%) compared to the controls (18% p<0.05). Evidence of histologic chorioamnionitis was higher in the study group 12/40 (30%), than in the control group 8/35 (22.85%), but the difference was not significant. CONCLUSION: The incidence of silent chorioamnionitis (placental membrane culture positivity) is higher in the abruptio placentae.
The perception of yellow has played a central role in distinguishing two main theories of colour vision. Hering proposed that yellow results from the activation of a distinct retinal-neural mechanism, whereas according to the Young-Helmholtz-Maxwell view, yellow results from the combined activation of red and green cone mechanisms. When red and green images are presented separately to corresponding retinal locations in the two eyes, the resulting sensation is yellow. As the pathways from the two eyes do not converge until the cortex, this suggests that yellow can indeed arise from the central combining of separate red and green channels. I now show that the reverse process can also occur; the visual system can decompose a 'yellow' stimulus into its constituent red and green components. A 'yellow' stimulus was created by optically superimposing a flashed red line onto a moving green bar. If the bar is visible only briefly, the flashed line appears yellow. If the trajectory of the green bar is exposed for sufficient time, however, the line is incorrectly perceived to trail the bar, and appears red. Motion processing occurs in the cortex rather than the retina in primates, and so the ability of motion cues to affect the perception of colour is consistent with the Young-Helmholtz-Maxwell notion of a 'central synthesis' of yellow.
BACKGROUND: There is a need to develop alternative regimen(s) for treating Helicobacter pylori infection because of problems of drug compliance, side-effects and resistance with the conventional regimen consisting of bismuth, metronidazole and an antibiotic. AIMS: To compare prospectively the efficacy of conventional triple therapy (bismuth subcitrate 120 mg QID, amoxycillin 500 mg QID and metronidazole 400 mg TID for 2 weeks with one containing omeprazole (20 mg OD), bismuth subcitrate and amoxycillin (regimen B). METHODS: Sixty two consecutive patients with H pylori infection associated with antral gastritis and/or duodenal ulcer were randomized to two treatment groups and re- evaluated after completion of 2 weeks of therapy and then after a further 4 weeks for eradication of H pylori, ulcer healing and drug side-effects. RESULTS: Regimen B resulted in higher H pylori eradication rate as compared to regimen A (76.7% vs 63.3%, better ulcer healing rate (90.9%, vs 70.6%), lesser side-effects (10.0% vs 36.7%) and better drug compliance (100% vs 93.3%). The difference between the two regimens was significant (p < 0.05) only in respect to side-effects. CONCLUSION: For H pylori eradication, omeprazole, bismuth and amoxycillin combination for 2 weeks is as effective as the conventional therapy and is better tolerated.
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The purpose of this study was to determine whether the Müller-Lyer illusion is produced by a mechanism which uses information defined in the retinal coordinates, or by a mechanism taking into account the three-dimensional (3-D) shape of the illusion figure. The classical Müller-Lyer figure could not be used to address this question since it is two-dimensional. Three-dimensional Müller-Lyer figures were created to see if the illusion they produce is correlated with the shape of the projected retinal image, or with the shape of these figures defined in a 3-D coordinate frame. In the experiments retinal image shape was juxtaposed against the 3-D shape of the illusion displays. For some displays the direction in which the fins pointed, relative to the shafts, in the 3-D frame was the "opposite" of the direction in which they pointed in the retinal images. For such displays, the illusion predicted on the basis of the 3-D structure was the opposite of that predicted on the basis of retinal image shapes. For another 3-D display the fins were oriented such that each projected a single straight line in the retinal image, thus the typical retinal image (< >, > <) was replaced by straight lines (symbol: see text). For all the displays the observed illusion was consistent with how the fins were oriented relative to the shaft in the 3-D coordinate frame, ie with the 3-D shape of the illusion displays. The retinal image shape appeared to play little, if any, role. One conclusion that emerges is that the specific retinal image shape projected by the classical line-drawn pattern is neither necessary nor sufficient for producing the illusion. The present findings are inconsistent with two well known theories of the Müller-Lyer illusion: inappropriate constancy scaling and selective filtering.
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A case of primary amyloidosis, initially detected by fine-needle aspiration of the liver, is reported here. Amorphous acellular metachromatic material was seen extracellularly in between the hepatocytic cords compressing them. This material showed typical apple-green birefringence under crossed bipolars after alkaline Congo-red staining proved its amyloid nature. It was resistant to potassium permanganate pretreatment, indicating it to be of the AL type.
We report a case of poorly differentiated carcinoma of the prostate with lymph node metastasis in a 19-year-old male. He was managed with bilateral orchiectomy, flutamide and recombinant interferon alfa-2b therapy. He showed subjective improvement for 2 months. However, during the 3rd month of treatment there was global deterioration which progressed further till his demise during the 4th month. The beneficial role, if any, of combined hormonal and immunotherapy in advanced prostatic carcinoma is discussed as also the natural history and prognosis of prostatic carcinoma in men under 20 years of age.