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Biomedical subjects

K Chawla

Publications and source records attributed to K Chawla.

At least 19 recordsLinked to original sources
PubMed2001

An unusual case of neonatal brain abscess following Klebsiella pneumoniae septicemia.

A case of solitary brain abscess in a term neonate caused by Kiebsiella pneumoniae is described. K. pneumoniae, although a common cause of neonatal septicemia, is rarely implicated as an etiological agent for cerebral abscess in this age-group. The interest of this case lies in the rarity of the causative organism and atypical features. In the absence of predisposing factors in the neonate, we suspect that the infection was transmitted vertically from the mother before or at the time of delivery since there was evidence of asymtomatic urinary tract infection in the antenatal period.

Adult↗
PubMed2001

Castleman's disease and superior vena cava thrombi: a rare presentation and a review of the literature.

Castleman's disease is a clinicopathological entity in which growth of lymphoid tissue is unregulated. It may present as asymptomatic involvement of one lymph node group or as a multicentric disease with systemic symptoms. Unlike localized disease, for which surgical excision is curative regardless of the histological type, multicentric disease often necessitates aggressive systemic therapy and portends a poor outcome. Superior vena caval thrombosis is an uncommon manifestation associated with Castleman's disease.

Castleman Disease↗
PubMed1999

Isolation and characterization of MC3T3-E1 preosteoblast subclones with distinct in vitro and in vivo differentiation/mineralization potential.

A series of subclonal cell lines with high or low differentiation/mineralization potential after growth in the presence of ascorbic acid (AA) were derived from murine MC3T3-E1 cells. Subclones were characterized in terms of their ability to mineralize a collagenous extracellular matrix both in vitro and in vivo and express osteoblast-related genes. When compared with nonmineralizing cells, mineralizing subclones selectively expressed mRNAs for the osteoblast markers, bone sialoprotein (BSP), osteocalcin (OCN), and the parathyroid hormone (PTH)/parathyroid hormone-related protein (PTHrP) receptor. In contrast, alkaline phosphatase mRNA was present in certain nonmineralizing as well as mineralizing subclones, suggesting that its expression may be subject to different controls from other osteoblast markers. Only highly differentiating subclones exhibited strong AA-dependent induction of a transiently transfected OCN promoter-luciferase reporter gene, indicating that there was a good correlation between mRNA levels and transcriptional activity. Consistent with its postulated role in biomineralization, BSP as measured by Western blotting was only present in mineralizing subclones. After implantation into immunodeficient mice, highly differentiating subclones formed bone-like ossicles resembling woven bone, while poorly differentiating cells only produced fibrous tissue. Interestingly, subclones with both high and low differentiation potential produced similar amounts of collagen in culture and expressed comparable basal levels of mRNA encoding Osf2/Cbfa1, an osteoblast-related transcription factor. Although some strongly differentiating cells exhibited a modest AA-dependent up-regulation of Osf2/Cbfa1 mRNA, there was no clear relationship between levels of this message and induction of mRNAs for other differentiation markers. Thus, the mere presence of Osf2/Cbfa1 in a subclone was not sufficient for osteoblast differentiation. These subclones will be very useful for studying critical events in osteoblast differentiation and mineralization.

Animals↗
PubMed1995

Dual-beam imaging for online verification of radiotherapy field placement.

PURPOSE: Due to the poor quality of megavoltage (MV) radiographs, detection and assessment of discrepancies in radiation field placement are difficult. Furthermore, the high imaging dose required to produce the megavoltage radiograph prohibits frequent image acquisition, particularly for those fields that require the use of an "open-field" exposure. For these small, or conformal, radiation fields, an alternate method of verifying field placement is required if the out-of-field dose is to be minimized. An open-field image acquired with a kilovoltage (kV) source would (a) deliver a very low patient dose, (b) increase the visibility of bony landmarks, and (c) simplify intercomparison of portal and prescription images. This article describes the development of a dual-beam imaging system that produces diagnostic quality "double-exposure" portal images for verifying radiation field placement. METHODS AND MATERIALS: The dual-beam system consists of a kV x-ray tube mounted on the gantry of a medical linear accelerator. The kV beam shares the same isocenter (+/- 1 mm) as the treatment beam but is at 45 degrees to the central axis. Both the kilovoltage and megavoltage images are collected with a fluoroscopic imaging system that uses a low-noise CCD camera to accumulate the light emitted from a phosphor screen. Two 45 degrees mirrors are used to remove the CCD camera from the x-ray beam. The light integration on the CCD array is controlled by a mechanical shutter, allowing easy synchronization with the radiation exposures. The camera is shielded by a lead housing to reduce the number of x-rays reaching the CCD array. A conventional thickness phosphor screen is used for both the kV and MV exposures. In the dual-beam imaging procedure, an open-field kV radiograph is acquired with the patient in treatment position. Immediately following, a MV image is acquired with the beam-defining blocks in position. Summation of the two images produces an online double-exposure image. The anatomical information in either the kV or MV image can be emphasized by weighting the images appropriately. This system was used to acquire MV and kV images of both a contrast-detail phantom and a Rando head phantom. Dual-beam images were also acquired for a pituitary treatment, demonstrating the feasibility and usefulness of the dual-beam technique. RESULTS: Analysis of the contrast-detail images produced with the MV and kV beams shows the expected advantage of using the kV x-ray beam. Images of a Rando head phantom confirm these results. A clinical demonstration of the dual-beam system for verifying the delivery of a pituitary field is shown. The quality of the dual-beam image is similar to the prescription (simulation) image, contains a larger anatomical region, and delivers a lower integral dose to the patient. In addition, the kV beam also enhances the visibility of small markers implanted in the prostate. CONCLUSIONS: A dual-beam imaging system has been developed for the radiographic verification of small, conformal fields. This development demonstrates the advantages and feasibility of using a kV x-ray beam in combination with the treatment beam to improve the accuracy of detecting patient setup errors.

Humans↗
PubMed1994

Postpartum ovarian vein thrombosis.

Ovarian vein thrombosis is a rare occurrence in the postpartum period. Two cases of postpartum ovarian vein thrombosis are presented. The differential diagnosis is extensive because many diseases can present with similar symptoms. Early diagnosis is essential for appropriate treatment and prevention of the potential sequelae that can occur. Computerized tomography with contrast is the optimal imaging modality for the diagnosis.

Adolescent↗
PubMed1988

Tests of functional equivalence between pimozide pretreatment, extinction and free feeding.

Both pimozide pretreatment and free feeding caused within-session and between-session decrements in variable interval operant performance; response decrements generated under pimozide were maintained on transfer to free feeding, and vice versa. On subsequently testing under extinction conditions (after food deprivation and drug free) large initial increases in responding were seen in all groups, and subsequent response decrements in extinction were steeper than in either pimozide or free feeding conditions. The effects of pimozide pretreatment do not resemble those of extinction, but may in some circumstances be functionally equivalent to a decrease in drive level.

Animals↗
PubMed1988

Ruptured pyogenic Baker's cyst.

The authors present the case of a patient who developed a ruptured Baker's cyst. Methods of diagnosis and treatment are discussed.

Adult↗
PubMed1988

Portal venous air: a benign occurrence.

Air in the portal venous system after a colonic examination (colonoscopy or barium enema) or umbilical vein catheterization is a benign, selflimiting condition. The underlying intestinal pathology, however, is important in determining the status of the patient. Supportive treatment and antibiotic therapy is all that is needed for these patients.

Adult↗
PubMed1986

Synchronous cancers of the colon and rectum: report of eight cases.

This study reviews eight patients collected over a period of 3 yr with synchronous primary adenocarcinomas with special emphasis on presentation of illness, diagnosis, location of tumors, and their association with benign polyps. All of the synchronous carcinomas in this study were located in different surgical segments and all associated benign polyps were located in the same surgical segments. Workup included colonoscopy followed by completion of colon examination by barium enema. All patients underwent surgical resection of their tumors. It is therefore concluded that the incidence their tumors. It is therefore concluded that the incidence of synchronous tumors of the large colon is high enough to warrant total colon examination either by colonoscopy or barium enema.

Adenocarcinoma↗