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D Kahn

Publications and source records attributed to D Kahn.

At least 127 records · Page 7Linked to original sources
PubMed1997

Mutational characterization of promoter regions recognized by the Salmonella dublin virulence plasmid regulatory protein SpvR.

The virulence plasmid-encoded spv regulon is essential for virulence of Salmonella dublin in mice. The spvR gene product belongs to the LysR family of transcriptional regulator proteins. SpvR induces the expression of the spvABCD operon and positively regulates its own expression. DNase I protection analysis with purified SpvR fusion proteins identified SpvR binding sites within the spvA and spvR promoters (P. Grob and D. G. Guiney, J. Bacteriol. 178:1813-1820, 1996). We have used PCR mutagenesis, combined with functional selection for reduced SpvR affinity, to define the DNA elements essential for SpvR binding. For the spvR promoter fragment, a screen for reduced expression was also applied. Sequence analysis of the resulting mutant fragments reveals that the base pair changes are clustered in distinct regions. Determination of the apparent dissociation constants of SpvR for the mutant promoters showed that the spvA LysR-type motif and the upstream palindromic sequences of both promoters play an important role in SpvR recognition.

Animals↗
PubMed1997

Sequential mixed lymphocyte culture after kidney transplantation: induction of tolerance or sensitization.

Serial mixed lymphocyte culture (MLC) was used to monitor the evolution of donor-specific responsiveness over the first 2 years after cadaveric renal transplantation. Lymphocytes obtained from 37 patients at 0, 1, 3, 6, 12, 18 and 24 months following transplantation were assayed in a one-way MLC using donor lymphocytes as stimulator cells. Donor-specific hyporesponsiveness developed in 66% of the patients with functioning grafts. Donor-specific sensitization was noted in 2 patients with functioning grafts and the MLC reactivity remained unchanged compared to the pretransplant value in 8 patients. The patients with donor-specific hyporeactivity tended to remain either free of rejection episodes or experienced early rejection episodes only. Thus, using serial MLC we were able to identify patients who developed hyporeactivity or tolerance to donor antigens. These patients may require less immunosuppression.

Adult↗
PubMed1997

Interaction between panel reactive antibodies, auto- and cold reactive antibodies, and a positive B cell cross-match in renal and cardiac allograft survival.

We analyzed the influence on allograft survival of pretransplant panel reactive antibodies (PRA) < 10%, PRA > 10%, autoantibodies, cold antibodies and a positive B cell crossmatch in 807 renal and 237 cardiac transplant recipients. Donors and recipients were predominantly of mixed ancestry (Khoi, San, Xhosa and Caucasoid). Log rank analysis showed that PRA < 10%, cold antibodies, and a positive B cell cross-match did not influence allograft survival. Autoantibodies were present only in renal recipients; they appeared to have a beneficial effect on allograft survival (P = 0.06). PRA > 10% appeared to have a detrimental effect on allograft survival in both renal (P = 0.07) and cardiac (P = 0.06) recipients. Since autoantibodies and PRA > 10% had opposing effects, the results of renal recipients were reanalyzed after omission of the recipients with autoantibodies and coexisting PRA > 10%. This resulted in augmentation of the protective effect for autoantibodies (P = 0.027) and of the detrimental effect for PRA > 10% (P = 0.020). Two-year survival curves showed that when autoantibodies coexisted with PRA > 10%, the long term, but not the short-term, detrimental effect of PRA > 10% was attenuated. Patients with a positive B cell cross-match clustered in the PRA > 10% group in both renal (PRA negative vs. PRA < 10%; P = 0.0251; PRA < 10% vs. PRA > 10%: P = 0.0011) and cardiac (PRA negative vs. PRA > 10%: P = 0.0085) recipients. We conclude that PRA > 10% is the best indicator to identify recipients at high risk for rejection, and that the influence of antibodies on graft survival can not reliably be established without taking coexisting antibodies into account.

Antilymphocyte Serum↗
PubMed1997

The management of biliary complications following orthotopic liver transplantation.

OBJECTIVE: Review of the biliary complications following orthotopic liver transplantation (OLT) at our institution, and their management and outcome. DESIGN: Retrospective study of medical records of 63 patients who underwent 68 transplant operations. SETTING: The Liver Transplant Unit, Groote Schuur Hospital and Red Cross War Memorial Children's Hospital, Cape Town PATIENTS: Six patients treated for 9 biliary complications. INTERVENTIONS: Reoperation with biliary reconstruction, or non-operative measures by either endoscopic retrograde pancreatography (ERCP) or percutaneous transhepatic cholangiography (PTC). OUTCOME MEASURES: Clinical outcome and survival following treatment for biliary complications. RESULTS: Biliary complications occurred in 8.8% of patients who underwent transplantation at our institution. These consisted of strictures in 4 patients (with leak in 2), bile leak in 1 patient, and unsuspected primary sclerosing cholangitis (PSC) of the recipient duct in 1 patient. The mean time interval of biliary complications following OLT was 8 weeks (range 3-16). Biliary reconstruction was required in 4 patients while 2 patients were treated by endoscopic stenting. After a mean follow-up period of 30 months (range 1-64), 4 patients remained stable, 1 patient developed progressive stricturing of the intrahepatic ducts requiring repeated PTC dilatations, and 1 patient experienced stent blockages requiring endoscopic stent changes (died of unrelated causes). CONCLUSIONS: The rate of biliary complications following OLT at our institution compares favourably with literature reports. While biliary reconstruction is usually needed, endoscopic stenting appears effective in selected cases of biliary stricture and leak. PSC should be excluded prior to transplantation in young patients with cryptogenic cirrhosis.

Adolescent↗
PubMed1996

Symbiotic nitrogen fixation does not require adenylylation of glutamine synthetase I in Rhizobium meliloti.

Symbiotic nitrogen fixation is accompanied by a shift of Rhizobium nitrogen metabolism from ammonium assimilation to ammonium export, which probably involves genetic or metabolic regulation of glutamine synthetase activity. In free-living Rhizobium meliloti glutamine synthetase I (GSI) is regulated post-translationally by reversible adenylylation in response to ammonium addition. Moreover, full expression of the GSI gene glnA requires the transcriptional activator, NtrC. A glnA1 mutant synthesizing a non-adenylylatable GSI produces normal nitrogen-fixing nodules on alfalfa: GSI adenylylation is dispensable for symbiotic nitrogen fixation. This is rationalized by the observation that less GS protein is present in R. meliloti bacteroids than in free-living bacterial cells.

Adenosine Phosphosulfate↗
PubMed1996

Venous thrombectomy in patients presenting with iliofemoral vein thrombosis after renal transplantation.

In this study 14 patients presented with 15 episodes of iliofemoral vein thrombosis after renal transplantation. Seven patients (group 1) had viable renal grafts and were treated with conventional anticoagulation. Eight patients (group 2) had non-viable renal grafts and were subjected to graft nephrectomy and simultaneous venous thrombectomy without anticoagulation. The patients in group 2 had rapid resolution of the signs and symptoms of the iliofemoral vein thrombosis, and noninvasive vascular investigation at follow-up revealed competent and patent deep veins in all patients. In contrast, only 50% of the patients in group 1 had normal venous studies at follow-up. We recommend that renal transplant recipients who develop iliofemoral vein thrombosis and nonviable allograft postoperatively should be subjected to venous thrombectomy at the time of graft nephrectomy.

Adolescent↗
PubMed1996

An alternative PII protein in the regulation of glutamine synthetase in Escherichia coli.

The PII protein has been considered pivotal to the dual cascade regulating ammonia assimilation through glutamine synthetase activity. Here we show that PII, encoded by the glnB gene, is not always essential; for instance upon ammonia deprivation of a glnB deletion strain, glutamine synthetase can be deadenylylated as effectively as in the wild-type strain. We describe a new operon, glnK amtB, which encodes a homologue of PII and a putative ammonia transporter. We cloned and overexpressed glnK and found that the expressed protein had almost the same molecular weight as PII, reacted with polyclonal PII antibody, and was 67% identical in terms of amino acid sequence with Escherichia coli PII. Like PII, purified GlnK can activate the adenylylation of glutamine synthetase in vitro, and, in vivo, the GlnK protein is uridylylated in a glnD-dependent fashion. Unlike PII, however, the expression of glnK depends on the presence of UTase, nitrogen regulator I (NRI), and absence of ammonia. Because of a NRI and a sigma N (sigma 54) RNA polymerase-binding consensus sequence upstream from the glnK gene, this suggests that glnK is regulated through the NRI/NRII two-component regulatory system. Indeed, in cells grown in the presence of ammonia, glutamine synthetase deadenylylation upon ammonia depletion depended on PII. Possible regulatory implications of this conditional redundancy of PII are discussed.

Amino Acid Sequence↗
PubMed1996

Diagnostic imaging of patients with acute scrotal pain.

Common causes of acute scrotal pain include testicular torsion, epididymo-orchitis and trauma. Epididymitis in adult men is typically associated with a history of urinary tract infection or prostatitis. Testicular torsion typically presents in young adults with a sudden onset of severe scrotal pain and, frequently, a history of recurrent episodes that have spontaneously resolved. With scrotal trauma, ultrasound may demonstrate testicular fracture, hematoceles and areas of hemorrhage or testicular infarction. Since both epididymitis and testicular torsion present with scrotal pain and swelling, and may be accompanied by fever and pyuria, Doppler ultrasound or radionuclide imaging may be necessary to make the diagnosis. In acute testicular torsion, color Doppler ultrasound shows absent flow to the epididymis and testis, while nuclear imaging shows central photon-deficient areas in the ischemic hemiscrotum. In epididymo-orchitis, color Doppler ultrasound shows increased flow to the epididymis and testis, while nuclear imaging shows increased perfusion of the affected testis and hemiscrotum.

Acute Disease↗
PubMed1996

An approach to diagnostic imaging of suspected pulmonary embolism.

Risk factors for pulmonary embolism include immobilization, trauma and surgery, particularly for hip fracture. Patients may present with acute respiratory symptoms, including tachypnea, tachycardia and rales. Chest radiographs and clinical and laboratory findings alone cannot provide a firm diagnosis. A completely normal chest radiograph may be seen in up to 40 percent of patients with pulmonary embolism, and as many as 30 percent of persons with pulmonary embolism and no prior cardiopulmonary disease will have a PaO2 greater than 80 mm Hg. The ventilation/perfusion (V/Q) lung scan is central to guiding clinical decisions. V/Q scans interpreted as either normal, near normal or high probability are reasonably diagnostic. A low probability V/Q scan can exclude the diagnosis of pulmonary embolism only if the patient has a clinically low probability of pulmonary embolism. Intermediate V/Q scans are not diagnostic and call for further evaluation. Compression ultrasonography is sensitive in detecting symptomatic deep venous thrombosis in the thigh. When clinical suspicion remains high and noninvasive imaging studies are uncertain, pulmonary angiography is likely to be diagnostic.

Algorithms↗
PubMed1996

Radiation absorbed dose from indium-111-CYT-356.

UNLABELLED: Indium-CYT-356 is an agent developed by CYTOGEN Inc. (CYT) (Princeton, NJ) for the use in staging patients with prostate cancer. This investigation was performed to provide the human dosimetry needed for Food and Drug Administration approval for routine use in patients. METHODS: Biodistribution data collected from three sites were obtained from prostate cancer patients who received diagnostic doses of 111In-CYT-356. Data included blood and urine collections, and the organ uptake value was measured from sequential conjugate whole-body and planar images over a 7-10 day period. Dose contributions from radioactivity in transit through the GI tract were estimated using a compartmental model. The calculations used the MIRD methodology and MIRDOSE 3. RESULTS: The total-body dose observed was 0.14 mGy/MBq, and the effective dose was found to be 0.25-0.29 mSv/MBq. The largest organ doses were found for the liver (1.0 mGy/MBq), kidneys (0.67 mGy/MBq) and spleen (0.88 mGy/MBq). CONCLUSION: The radiation dose to the patient from a typical 185 MBq administration of 111In-CYT-356 is comparable to the dose from other 111In-labeled whole antibodies used in the diagnosis and management of cancer patients. The inclusion of the GI tract as a source organ increases the effective dose by 18%.

Antibodies, Monoclonal↗
PubMed1995

An additional PII in Escherichia coli: a new regulatory protein in the glutamine synthetase cascade.

The PII protein in the glutamine synthetase cascade transduces the nitrogen signal, as sensed by uridylyltransferase, both to the NRII/NRI two-component system and to adenylyltransferase, to regulate the activity of glutamine synthetase. Here we describe the amplification of a chromosomal DNA fragment from Escherichia coli which contains the sequence of a PII homologue. The derived amino acid sequence of this DNA fragment is 67% identical to E. coli PII. It contains the conserved tyrosine residue which is known to be the site of uridylylation in PII. E. coli is the first organism in which two different PII proteins have been detected.

Amino Acid Sequence↗
PubMed1995

Utility of SPECT imaging for determination of vertebral metastases in patients with known primary tumors.

Determining the etiology of a focal lesion seen on bone scan in patients with primary tumors usually requires the use of other imaging procedures or biopsy. Single positron emission computed tomography (SPECT) with high resolution multidetector systems can localize the specific site of a vertebral lesion and in this way potentially differentiate between benign and metastatic disease. SPECT images of the lower thoracic and lumbar spine were reviewed for lesion location and intensity by two experienced interpreters. Follow-up data were adequate to ascertain the cause of 71 lesions seen on SPECT in 29 patients. Twenty-six of these lesions were not seen on planar images. Of the 71 lesions, 44 were benign and 27 metastatic. Of the 15 lesions where the pedicle was involved, 11 were found to metastatic. There were a total of 14 facet lesions, 9 of which were present in vertebra with no lesions at sites other than the facets. All 9 of these isolated facet lesions turned out to be benign. Lesion intensity did not distinguish benign from malignant disease. We conclude that SPECT imaging is useful in determining the etiology of focal lesions seen on bone scan in patients with a known primary tumor referred for evaluation of metastatic disease.

Colonic Neoplasms↗