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Biomedical subjects

S Balachandran

Publications and source records attributed to S Balachandran.

At least 37 records · Page 2Linked to original sources
PubMed1998

Activation of the dsRNA-dependent protein kinase, PKR, induces apoptosis through FADD-mediated death signaling.

The dsRNA-dependent protein kinase (PKR) is considered to play a key role in interferon-mediated host defense against viral infection and conceivably malignant transformation. To investigate further the mechanisms of PKR-induced growth inhibition, we have developed tetracycline-inducible murine cell lines that express wild-type PKR or a catalytically inactive PKR variant, PKRdelta6. Following induction, the growth of the wild-type PKR-expressing cells was similar to that of cells transfected with vector alone, while cells expressing PKRdelta6 became malignantly transformed. Significantly, treatment with dsRNA caused the wild-type PKR-overexpressing cells to undergo programed cell death while, conversely, cells expressing PKRdelta6 were completely resistant. Our studies demonstrated that activation of PKR induces the expression of members of the tumor necrosis factor receptor (TNFR) family, including Fas (CD95/Apo-1) and pro-apopotic Bax. In contrast, transcripts representing Fas, TNFR-1, FADD (Fas-associated death domain), FLICE, Bad and Bax were ablated in cells expressing PKRdelta6. The involvement of the death receptors in PKR-induced apoptosis was underscored by demonstrating that murine fibroblasts lacking FADD were almost completely resistant to dsRNA-mediated cell death. Thus, PKR, a key cellular target for viral repression, is a receptor/inducer for the induction of pro-apoptotic genes by dsRNA and probably functions in interferon-mediated host defense to trigger cell death in response to virus infection and perhaps tumorigenesis.

3T3 Cells↗
PubMed1997

Phloem sap proteins from Cucurbita maxima and Ricinus communis have the capacity to traffic cell to cell through plasmodesmata.

In angiosperms, the functional enucleate sieve tube system of the phloem appears to be maintained by the surrounding companion cells. In this study, we tested the hypothesis that polypeptides present within the phloem sap traffic cell to cell from the companion cells, where they are synthesized, into the sieve tube via plasmodesmata. Coinjection of fluorescently labeled dextrans along with size-fractionated Cucurbita maxima phloem proteins, ranging in size from 10 to 200 kDa, as well as injection of individual fluorescently labeled phloem proteins, provided unambiguous evidence that these proteins have the capacity to interact with mesophyll plasmodesmata in cucurbit cotyledons to induce an increase in size exclusion limit and traffic cell to cell. Plasmodesmal size exclusion limit increased to greater than 20 kDa, but less than 40 kDa, irrespective of the size of the injected protein, indicating that partial protein unfolding may be a requirement for transport. A threshold concentration in the 20-100 nM range was required for cell-to-cell transport indicating that phloem proteins have a high affinity for the mesophyll plasmodesmal binding site(s). Parallel experiments with glutaredoxin and cystatin, phloem sap proteins from Ricinus communis, established that these proteins can also traffic through cucurbit mesophyll plasmodesmata. These results are discussed in terms of the requirements for regulated protein trafficking between companion cells and the sieve tube system. As the threshold value for plasmodesmal transport of phloem sap proteins falls within the same range as many plant hormones, the possibility is discussed that some of these proteins may act as long-distance signaling molecules.

Journal Article↗
PubMed1997

Relationship of serotype, leukotoxin gene type and lysogeny in Actinobacillus actinomycetemcomitans to periodontal disease status.

Actinobacillus actinomycetemcomitans has been associated with different forms of periodontitis, particularly with localized juvenile periodontitis (LJP). The bacterium possesses several virulence factors which have been shown to interact with the host immune system. Among these factors, leukotoxin, surface antigens (serotype) and bacteriophages have been suggested directly or indirectly to influence the course of infection. However, few studies have been able to show associations between these factors and periodontal disease, alone or in combination. Thus, the purpose of the present study was to investigate possible correlations between periodontal disease status and selected virulence factors (serotype, presence of bacteriophages, and the presence of a 530 bp deletion in the promoter region of the leukotoxin gene). 36 subjects took part in the study. Serotype c was the most frequently found serotype among periodontally affected subjects, although serotypes a and b were also present. 27 out of 36 strains harbored bacteriophages, and there was strong evidence that some of the bacteriophages were different from the previously characterized phi Aa phage. A. actinomycetemcomitans containing the F-fragment phage were more frequently associated with periodontal disease. Five strains, all serotype b, 3 from LJP patients and 2 from healthy subjects, showed a 530-bp deletion in the promoter region of the leukotoxin gene.

Actinobacillus Infections↗
PubMed1993

Direct invasion of the transverse colon by a cecal tumor.

Direct invasion of the transverse colon is known to result from noncontiguous primary tumors spreading along ligamentous attachments or from direct extension of metastatic disease involving the greater omentum. The resultant desmoplastic reaction produces characteristic findings on barium enema. However, to our knowledge, these findings have not been reported to result from extension of a cecal tumor to the transverse colon via the pericolonic fat. We present such a case and discuss the radiographic findings.

Adenocarcinoma↗
PubMed1993

Operative cholangiography performed during laparoscopic cholecystectomy.

Operative cholangiography is an important adjunct to laparoscopic cholecystectomy, a recently developed surgical procedure in which cholecystectomy is performed through four abdominal ports under sustained pneumoperitoneum and the direct vision of a video laparoscope. Operative cholangiogram can effectively identify incidental choledocholithiasis or anatomic variation in the biliary system that may significantly influence the surgical approach or postoperative management of the patient. Unique features portrayed on operative cholangiogram in patients undergoing laparoscopic cholecystectomy include unusual displays of pneumoperitoneum, subcutaneous emphysema, visualization of the unresected gallbladder, and overlying surgical hardware that must remain in the operating field during film exposure.

Cholangiography↗
PubMed1992

CT evaluation of the abdominal wall.

Computed tomography (CT) is a useful method for evaluating the abdominal wall. Pathology includes hernia, hematoma, infection and inflammation, tumor, and post-traumatic, post-operative, and miscellaneous conditions. The CT findings of these various abnormalities are presented.

Abdominal Muscles↗
PubMed1989

Pancreatic carcinoma masquerading as renal cell carcinoma.

Three cases of pancreatic carcinoma that arose in the tail and extended into the adjacent left kidney are presented. Because of misleading symptoms and radiographic features, the tumors were misdiagnosed as primary renal tumor. In most cases, computed tomography (CT) provides the correct diagnosis and prevents unnecessary surgery.

Adenocarcinoma↗
PubMed1988

Pseudocyst following splenectomy: impact of CT and ultrasound on its diagnosis and management.

Three cases of pseudocysts occurring after splenectomy are presented. Sonography and computed tomography were helpful in diagnosing the pseudocysts as well as providing guidance for subsequent drainage. Demonstration of a cystic mass adjacent to the tail of the pancreas following splenectomy suggests the diagnosis of postsplenectomy pseudocyst and has important implications for clinical management.

Adult↗
PubMed1987

Uptake of indium-111-labeled leukocytes by brain metastasis.

Uptake of indium-labeled leukocytes was seen in two cases of histologically proven brain metastasis. In one, this led to misdiagnosis of the lesion as an abscess. On histological evaluation, a large number of white blood cells or macrophages was seen at the neoplastic sites. Reasons for leukocyte accumulation around metastatic brain neoplasms are discussed. In contrast to the current reports that indium-labeled leukocyte scans can differentiate intracranial infection from tumor, these cases demonstrate their lack of specificity in the detection of brain abscess.

Aged↗
PubMed1987

A comparative study of electroencephalography and computed axial tomography in recent cerebral infarction.

In order to re-assess the present role of electroencephalography in the investigation of cerebral infarct, we prospectively studied 50 adults with recent supratentorial cerebral infarction over a ten-month period. All 50 patients had EEG's and CT scans within the first two weeks of the apoplectic event. The time span between the two procedures was one week or less in all patients. We monitored the following EEG parameters: characteristics of alpha rhythm (depressed, unchanged, or enhanced); prevalence, type, rhythmicity, and topography of focal slowing; and presence or absence of FIRDA. We grouped the patients on the basis of CT findings as follows: depth of the infarct (cortical-subcortical, deep white matter, or lacunar); size of the infarct (large, medium, or small); and presence or absence of mass effect. Statistical analysis revealed no differences with regard to the EEG parameters between the groups. However, when patients were categorized according to topography of the infarct, the group with parietal infarct showed a significantly higher incidence of depressed alpha rhythm compared with the groups with frontal or occipital infarct. Of the 50 patients, four patients whose history and clinical presentation suggested infarct had normal CT scans despite the presence of EEG abnormality. On the contrary, in two patients, the EEG was normal, whereas the CT confirmed the infarct. Our data suggested that physiological factors may play a major role in the pathogenesis of EEG abnormalities in cerebral infarct, thus accounting for the discrepancies between the EEG parameters and CT findings observed in our population. It was also suggested that EEG's be included routinely in the investigation of cerebral infarct.

Adult↗
PubMed1986

Cystic islet cell tumor of the pancreas.

Presented is the fifth case of a cystic islet cell tumor of the pancreas. The diagnosis is usually made postoperatively but should be considered in a patient with "recurrent pseudocyst" or a history incompatible with pseudocyst in combination with a cystic area in the pancreas. Computed tomography is preferred for diagnosis, and resection is the preferred therapy.

Adenoma, Islet Cell↗