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Biomedical subjects

S Kahn

Publications and source records attributed to S Kahn.

At least 19 recordsLinked to original sources

Accuracy of radiography in grading and tissue-specific diagnosis--a study of 200 consecutive bone tumors of the hand.

OBJECTIVE: To determine the usefulness of radiography and magnetic resonance imaging in differentiating benign from malignant bony tumors of the hand and in making a tissue-specific diagnosis. DESIGN: Two hundred consecutive bony tumors of the hand, the details of which originated from a national databank, were studied in a prospective way by radiography (100%) and by MRI (25%). All tumors were graded on a five-point scale, from certainly benign to certainly malignant, using location and morphology as diagnostic parameters. For all tumors a tissue-specific diagnosis was made, by the proposal of three possibilities in decreasing order of probability. Histological diagnosis was made by peer review, according to the WHO classification. RESULTS: By the combining of "certainly" and "probably" benign (grades I and II) and "certainly" and "probably" malignant (grades IV and V), a correct grading was obtained in 165 (82.5%) of the cases (154 of the 173 benign and 11 of the 27 malignant tumors). A correct tissue-specific diagnosis was included in the three proposed differentials in 87.5%. MRI confirmed a correct diagnosis made on radiography in 72% and improved the grading capability by correctly upgrading malignant tumors and downgrading benign tumors in, respectively, 8% and 12%. The capability to obtain a tissue-specific diagnosis improved with change of an incorrect diagnosis on radiography to a correct one on MRI in 12 cases (24%). CONCLUSION: Subjective (semiquantitative) grading on radiography by an expert group proved to be excellent when compared with the results of a quantitative analysis of individual grading parameters. Multiple logistic regression analysis of these parameters resulted in a grading formula containing only six variables. The additional value of MRI in grading was amply demonstrated. Already high accuracy of radiography, in making a tissue-specific diagnosis, improved substantially after the performance of MRI.

Adult↗

Origin and evolution of highly pathogenic H5N1 avian influenza in Asia.

Outbreaks of highly pathogenic avian influenza caused by H5N1 viruses were reported almost simultaneously in eight neighbouring Asian countries between December 2003 and January 2004, with a ninth reporting in August 2004, suggesting that the viruses had spread recently and rapidly. However, they had been detected widely in the region in domestic waterfowl and terrestrial poultry for several years before this, and the absence of widespread disease in the region before 2003, apart from localised outbreaks in the Hong Kong Special Autonomous Region (SAR), is perplexing. Possible explanations include limited virus excretion by domestic waterfowl infected with H5N1, the confusion of avian influenza with other serious endemic diseases, the unsanctioned use of vaccines, and the under-reporting of disease as a result of limited surveillance. There is some evidence that the excretion of the viruses by domestic ducks had increased by early 2004, and there is circumstantial evidence that they can be transmitted by wild birds. The migratory birds from which viruses have been isolated were usually sick or dead, suggesting that they would have had limited potential for carrying the viruses over long distances unless subclinical infections were prevalent. However, there is strong circumstantial evidence that wild birds can become infected from domestic poultry and potentially can exchange viruses when they share the same environment. Nevertheless, there is little reason to believe that wild birds have played a more significant role in spreading disease than trade through live bird markets and movement of domestic waterfowl. Asian H5N1 viruses were first detected in domestic geese in southern China in 1996. By 2000, their host range had extended to domestic ducks, which played a key role in the genesis of the 2003/04 outbreaks. The epidemic was not due to the introduction and spread of a single virus but was caused by multiple viruses which were genotypically linked to the Goose/GD/96 lineage via the haemagglutinin gene. The H5N1 viruses isolated from China, including the Hong Kong SAR, between 1999 and 2004 had a range of genotypes and considerable variability within genotypes. The rising incidence and widespread reporting of disease in 2003/04 can probably be attributed to the increasing spread of the viruses from existing reservoirs of infection in domestic waterfowl and live bird markets leading to greater environmental contamination. When countries in the region started to report disease in December 2003, others were alerted to the risk and disease surveillance and reporting improved. The H5N1 viruses have reportedly been eliminated from three of the nine countries that reported disease in 2003/04, but they could be extremely difficult to eradicate from the remaining countries, owing to the existence of populations and, possibly, production and marketing sectors, in which apparently normal birds harbour the viruses.

Animals↗

Topical testosterone treatment for chronic allograft failure in liver transplant recipients with recurrent hepatitis C virus.

INTRODUCTION: Liver transplant recipients with allograft failure due to recurrent hepatitis C virus (HCV) infection often develop marked muscle wasting and ascites prior to death and are denied repeat liver transplantation. We sought to determine whether topical testosterone therapy is associated with improved muscle mass and survival in patients with chronic allograft failure post-liver transplant. METHODS: We performed a retrospective review of liver transplant recipients with chronic allograft failure. Group 1 patients were treated for >6 months with testosterone gel 1%; group 2 patients were untreated. RESULTS: Fourteen patients were identified with stage 3 or 4 fibrosis, muscle wasting, and allograft failure due to recurrent HCV. Group 1 (n=9) patients had statistically significant improvement in albumin, testosterone, muscle strength, well-being, and MELD/CTP scores, while there was no improvement seen for any of these parameters in group 2 (n=5). There were no deaths in group 1, while four of five patients in group 2 died on average 84 days posttransplant. Adverse effects of testosterone treatment included lower extremity edema (which resolved upon dose adjustment), hypertension, and pruritus. CONCLUSIONS: Topical testosterone gel appears to increase muscle strength, stimulate albumin synthesis, and improve survival in patients with allograft failure post-liver transplant.

Administration, Topical↗

Biomarker profiling of plasma from acute coronary syndrome patients. Application of ProteinChip Array analysis.

AIM: Acute coronary syndrome (ACS) is one of the leading causes of death in the world and remains a complex pathophysiologic process involving inflammatory, hemostatic and vascular processes. The purpose of this study was to identify unique proteomic biomarkers present in patients with ACS using a newly developed proteomic profiling technique, surface enhanced laser desorption/ionization (SELDI). METHODS: Citrated plasma samples obtained from clinically confirmed cases of ACS (n=100) and age matched controls (n=25) were profiled using SELDI-time of flight (TOF)-mass spectrometry (Ciphergen Biosystems, Freemont, CA, USA). A strong anion exchange (SAX) ProteinChip Array was used to profile these samples. In addition to spectra profiles, protein density plots were be obtained from the generated molecular profile. RESULTS: The SELDI profile in the molecular weight (MW) range of 0-150 kDa revealed a prominent 66.3 kDa albumin peak along with several distinct components at 28 kDa, 13.7 kDa and 6.5 kDa. Additional minor molecular components were also noted in the lower MW range (<6 kDa). There was a cluster of peaks between 10 and 12 kDa that were unique to the patients with ACS; about 1/3 of the ACS patients exhibited these peaks as evident in the ProteinChip Array spectrum. None of the age-matched controls exhibited the peaks in this MW range, nor did the normal human plasma pool that was used as an additional control. The relative intensity of these novel molecular components in the range of 10-12 kDa represent unique proteins/peptides which are generated in specific pathologic states associated with ACS. CONCLUSIONS: These observations suggest that patients with ACS have a unique cluster of molecular components that are present in their SELDI profile. It might be possible to use these patterns to identify high-risk patients who may be more susceptible to the development of unstable plaque, which may eventually lead to myocardial infarction. Identification and characterization of these molecular components will also help in the understanding of the pathogenesis of ACS. These unique peaks may represent pathologic proteins, novel inflammatory mediators or protease cleavage products. Further studies need to be done to better characterize and identify these molecular components and their pathologic role in ACS.

Acute Disease↗

Treatment of refractory acute leukemia with timed sequential chemotherapy using topotecan followed by etoposide + mitoxantrone (T-EM) and correlation with topoisomerase II levels.

A phase I/II clinical study evaluated 17 patients with refractory/recurrent acute leukemia treated with 1.5 mg/m2/day topotecan on days 1-3 followed by etoposide (100 mg/m2/day)+mitoxantrone (10 mg/m2/day) on days 4, 5 and 9, 10. Timed sequential chemotherapy using the topoisomerase I-inhibitor topotecan before the topoisomerase II-inhibitors, etoposide+mitoxantrone (T-EM) treatment is proposed to induce topoisomerase II protein levels and potentiate the cytotoxic activity of the topoisomerase II-directed drugs. Fourteen patients had refractory and three had recurrent acute leukemia. The majority of patients were heavily pre-treated with greater than three re-induction chemotherapy regimens. Ten patients responded to T-EM treatment (59%). Four of seventeen (24%) had a complete remission and one had a partial remission. Four additional patients (24%) who scored complete leukemia clearance had no evidence of disease with complete white and red blood cell recovery but with platelet counts less than 100,000. The lack of platelet recovery in one patient having a partial response was scored as a partial leukemia clearance. The toxicity profile included major non-hematological toxicity including grade 3 mucositis (29%) and neutropenic fever (65%). Paired measurements of intracellular levels of topoisomerase II isoforms alpha and beta in leukemia blast cells (bone marrow) collected before (day 0) and after topotecan treatment (day 4) showed that a relative increase of topoisomerase IIalpha (Topo IIalpha) > or = 40% strongly correlated with response after T-EM treatment. Increased Topo IIalpha levels also corresponded to increased DNA fragmentation. Two patients who had an increase of Topo IIalpha of 20-25% had either a PR or PLC while patients with a < 10% increase showed no response to T-EM treatment. We conclude that timed sequential chemotherapy using topotecan followed by etoposide+mitoxantrone is an effective regimen for patients with refractory acute leukemia, and demonstrate Topo IIalpha protein level increases after topotecan treatment.

Acute Disease↗

(99m)Tc antigranulocyte monoclonal antibody imaging for the detection and assessment of inflammatory bowel disease newly diagnosed by colonoscopy in children.

OBJECTIVE: This prospective study evaluated a (99m)Tc antigranulocyte monoclonal antibody Fab' imaging agent (Sulesomab) in children with inflammatory bowel disease (IBD) newly diagnosed by colonoscopy. MATERIALS AND METHODS: Ten children (4 boys, 6 girls; mean age 14 years) with newly diagnosed Crohn's disease (n = 6) or ulcerative colitis (n = 4) were studied. Colonoscopy was performed in all of these patients. Within 24 h after colonoscopy, they underwent scintigraphy with (99m)Tc-Sulesomab. Abdominal/pelvic images were acquired at 30 min (planar) and 2-4 h (planar and SPECT) after injection of Sulesomab. Eighty bowel segments were evaluated semi-quantitatively by the investigators, using these three sets of images. The Pediatric Disease Activity (PDA) was correlated with the erythrocyte sedimentation rate (ESR), white blood cell (WBC) count, albumin, Kirschner's score, the Sulesomab bowel segment with maximum uptake, and the sum of Sulesomab score in each segment. RESULTS: The median PDA score was 26 (range 12.5-40). Three children had normal ESR and six normal WBC counts. All patients had at least one positive mucosal biopsy for IBD. While using the Kirschner's scale, the maximal severity of colonoscopy findings was graded as none (n = 2), mild (n = 4), moderate (n = 3), or severe (n = 1). Of the 59 segments evaluated with endoscopy, 35 were found to be endoscopically abnormal. The planar images identified 17 of these abnormal segments and the SPECT images 20. Nine of these ten children had abnormal bowel uptake by scintigraphy. Thus, the sensitivity of Sulesomab per patient was 90 % and per bowel segment 57 %. The correlation coefficient between the scintigraphic score for the segment with the Sulesomab maximum activity and the PDA was 0.3 (P = 0.41). CONCLUSION: In pediatric IBD assessment, planar imaging with Sulesomab did not prove very sensitive in detecting inflammation in each bowel segment. However, SPECT detected the presence of inflammation in the majority of patients. A trial comparing (99m)Tc-HmPAO-WBC with Sulesomab in a large number of patients is required.

Antibodies, Monoclonal↗

Linear lesion radiofrequency ablation in canine vagal atrial fibrillation: effects of special catheters designed for efficiency, and the critical role of lesions from the crista terminalis to the superior vena cava.

OBJECTIVE: To determine whether specially devised catheters could be used to place radiofrequency (RF) linear lesions quickly and efficiently for termination and/or prevention of atrial fibrillation (AF). METHODS: Two versions of 2 different types of ablating catheters were used in 12 canines with AF induced by rapid pacing during vagal stimulation. 1) Modified basket catheters in two versions, one designed to produce caudo-cranial linear lesions through extended bare electrode-splines in contact with the atrial wall; and the other designed to produce horizontal linear lesions by revolving within the atrium. Together these would form "longitude and latitude" grids in the atrium. 2) The second catheter type was 2 versions of coil electrodes with thermocouples centered under each of the large-area coil electrodes. One version of these deflectable coil electrodes was intended to produce lesions in the tricuspid valve annulus-inferior vena cava (IVC) isthmus; and along the crista terminalis from the superior vena cava (SVC) to the IVC. A different type of deflection angulation on the second version was intended to produce more horizontal lesions from the crista to the tricuspid annulus. Guidance was fluoroscopic, and by electrograms and transesophageal echo. Gross pathologic examinations followed each experiment. Prior to use in canines, all electrode configurations were tested in vitro on fresh bovine preparations suspended in saline at 37 degrees C. RESULTS: The bare spline and coil electrode catheter configurations produced discrete non-perforating non-charring lesions in the in vitro preparations. One dog died of exsanginating hemorrhage. Post mortem examination revealed the lesions to be extremely variable, ranging from no evidence of effective RF delivery to deep lesions with perforation. Seven clinical successes were achieved (6 complete), with the coil electrode catheters accounting for 5 of the 7, although the procedure times were shorter with the baskets. Critical lesions were those from the crista to the SVC. Planned trans-isthmus lesions were not done, but may be needed to prevent atrial flutter not seen prior to effective AF ablation. CONCLUSIONS: Special basket and coil-electrode catheters may be useful but require refinement. The finding that lesions between the crista terminalis and the SVC were critical to success may be applicable to some cases of AF in humans.

Animals↗

Socio-economic disparities in preterm birth: causal pathways and mechanisms.

Preterm birth is the leading cause of infant mortality in industrialised societies. Its incidence is greatly increased among the socially disadvantaged, but the reasons for this excess are unclear and have been relatively unexplored. We hypothesise two distinct sets of causal pathways and mechanisms that may explain social disparities in preterm birth. The first set involves chronic and acute psychosocial stressors, psychological distress caused by those stressors, increased secretion of placental corticotropin releasing hormone (CRH), changes in sexual behaviours or enhanced susceptibility to bacterial vaginosis and chorioamnionitis, cigarette smoking or cocaine use, and decidual vasculopathy. The second hypothesised pathway is a gene-environment interaction based on a highly prevalent mutation in the gene for methylenetetrahydrofolate reductase (MTHFR), combined with low folate intake from the diet and from prenatal vitamin supplements, consequent hyperhomocysteinemia, and decidual vasculopathy. We propose to test these hypothesised pathways and mechanisms in a nested case-control study within a prospectively recruited and followed cohort of pregnant women with singleton pregnancies who deliver at one of four Montreal hospitals that serve an ethnically and socio-economically diverse population. Following recruitment during the late first or early second trimester, participating women are seen at 24-26 weeks, when a research nurse obtains a detailed medical and obstetric history; administers several scales to assess chronic and acute stressors and psychological function; obtains blood samples for CRH, red blood cell and plasma folate, homocysteine, and DNA for the MTHFR mutation; and performs a digital and speculum examination to measure cervical length and vaginal pH and to obtain swabs for bacterial vaginosis and fetal fibronectin. After delivery, each case (delivery at < 37 completed weeks following spontaneous onset of labour or prelabour rupture of membranes) and two controls are selected for placental pathological examination, hair analysis of cotinine, cocaine, and benzoylecgonine, and analysis of stored blood and vaginal specimens. Statistical analysis will be based on multiple logistic regression and structural equation modelling, with sequential construction of models of potential aetiological determinants and covariates to test the hypothesised causal pathways and mechanisms. The research we propose should improve understanding of the factors and processes that mediate social disparities in preterm birth. This improved understanding should help not only in developing strategies to reduce the disparities but also in suggesting preventive interventions applicable across the entire socio-economic spectrum.

Adult↗

Being "the other therapist": the varieties of adjunctive experience with hypnosis.

Clinicians who utilize hypnosis in their practices are frequently approached with requests to participate in the care of patients who are currently in treatment with a primary therapist. Surprisingly, a review of the literature indicated that no research has been done on this common practice. This article provides a discussion of some of the important issues as well as the variables to consider in deciding whether to enter into this arrangement. It will serve as a starting point in generating further research on this crucial topic.

Adult↗

A furin-like convertase mediates propeptide cleavage of BACE, the Alzheimer's beta -secretase.

The novel transmembrane aspartic protease BACE (for Beta-site APP Cleaving Enzyme) is the beta-secretase that cleaves amyloid precursor protein to initiate beta-amyloid formation. As such, BACE is a prime therapeutic target for the treatment of Alzheimer's disease. BACE, like other aspartic proteases, has a propeptide domain that is removed to form the mature enzyme. BACE propeptide cleavage occurs at the sequence RLPR downward arrowE, a potential furin recognition motif. Here, we explore the role of furin in BACE propeptide domain processing. BACE propeptide cleavage in cells does not appear to be autocatalytic, since an inactive D93A mutant of BACE is still cleaved appropriately. BACE and furin co-localize within the Golgi apparatus, and propeptide cleavage is inhibited by brefeldin A and monensin, drugs that disrupt trafficking through the Golgi. Treatment of cells with the calcium ionophore, leading to inhibition of calcium-dependent proteases including furin, or transfection with the alpha(1)-antitrypsin variant alpha(1)-PDX, a potent furin inhibitor, dramatically reduces cleavage of the BACE propeptide. Moreover, the BACE propeptide is not processed in the furin-deficient LoVo cell line; however, processing is restored upon furin transfection. Finally, in vitro digestion of recombinant soluble BACE with recombinant furin results in complete cleavage only at the established E46 site. Taken together, our results strongly suggest that furin, or a furin-like proprotein convertase, is responsible for cleaving the BACE propeptide domain to form the mature enzyme.

Alzheimer Disease↗

Characterization of Alzheimer's beta -secretase protein BACE. A pepsin family member with unusual properties.

The cerebral deposition of amyloid beta-peptide is an early and critical feature of Alzheimer's disease. Amyloid beta-peptide is released from the amyloid precursor protein by the sequential action of two proteases, beta-secretase and gamma-secretase, and these proteases are prime targets for therapeutic intervention. We have recently cloned a novel aspartic protease, BACE, with all the known properties of beta-secretase. Here we demonstrate that BACE is an N-glycosylated integral membrane protein that undergoes constitutive N-terminal processing in the Golgi apparatus. We have used a secreted Fc fusion-form of BACE (BACE-IgG) that contains the entire ectodomain for a detailed analysis of posttranslational modifications. This molecule starts at Glu(46) and contains four N-glycosylation sites (Asn(153), Asn(172), Asn(223), and Asn(354)). The six Cys residues in the ectodomain form three intramolecular disulfide linkages (Cys(216)-Cys(420), Cys(278)-Cys(443), and Cys(330)-Cys(380)). Despite the conservation of the active site residues and the 30-37% amino acid homology with known aspartic proteases, the disulfide motif is fundamentally different from that of other aspartic proteases. This difference may affect the substrate specificity of the enzyme. Taken together, both the presence of a transmembrane domain and the unusual disulfide bond structure lead us to conclude that BACE is an atypical pepsin family member.

Amino Acid Sequence↗

Epinephrine fails to enhance performance of food-deprived rats on a delayed spontaneous alternation task.

Increases in blood glucose levels after epinephrine injection appear to contribute to the hormone's effects on learning and memory. The present experiment evaluated whether epinephrine-induced enhancement of spontaneous alternation performance would be attenuated in fasted rats that had blunted increases in circulating glucose levels after injections of epinephrine. Rats deprived of food for 24 h prior to injection of epinephrine exhibited significant attenuation of the increase in blood glucose levels seen in fed rats. When the rats were tested on a delayed spontaneous alternation task, epinephrine enhanced performance in fed rats but not in rats deprived of food for 24 h. These findings are consistent with the view that hyperglycemia subsequent to epinephrine injections contributes to the memory-enhancing effects of epinephrine.

Animals↗

Myocardial injury in children with respiratory syncytial virus infection.

OBJECTIVE: Respiratory syncytial virus (RSV) infection is associated with a number of extrapulmonary manifestations, including a sepsis-like syndrome characterized by any combination of hypothermia, fever, apnea, hypovolemia, and myocardial dysfunction. We hypothesized that RSV can have a direct injurious effect on the myocardium of infants and children that can be detected by the presence of cardiac troponin I (cTnI), a highly sensitive and specific marker of myocardial injury, in the blood of patients infected with the virus. DESIGN: Serial cTnI measurements were obtained from patients admitted with documented RSV infection to the pediatric intensive care unit (PICU). PARTICIPANTS: Data were collected and analyzed from 22 RSV infected patients and 11 control patients. RESULTS: Elevated levels of cTnI were detected in 54.5% (12/22) of the study population during their PICU admission. The average cTnI level was significantly higher in the RSV infected group than in controls. There was a significant association between the presence of a positive troponin assay and the occurrence of a cardiovascular event, the need for inotropic support, and the requirement of mechanical ventilation. Patients who required inotropic support had a significantly higher cTnI level than the rest of the study population. CONCLUSION: A large percentage of children admitted to the PICU with RSV infection have myocardial damage as detected by the use of commercially available troponin assays. Additionally, in a portion of these patients, this damage is clinically significant, leading to cardiovascular instability and the need for inotropic support.

Journal Article↗

A negative search for a paramyxoviral etiology of Paget's disease of bone: molecular, immunological, and ultrastructural studies in UK patients.

Paget's disease of bone is a common bone disease characterized by increased and disorganized bone remodeling at focal sites throughout the skeleton. The etiology of the disease is unresolved. A persistent viral infection has long been suggested to cause the disease. Antigen and/or nucleic acid sequences of paramyxoviruses (in particular measles virus [MV], canine distemper virus [CDV], and respiratory syncytial virus [RSV]) have been reported in pagetic bone by a number of groups; however, others have been unable to confirm this and so far no virus has been isolated from patients. Here, we reexamined the question of viral involvement in Paget's disease in a study involving 53 patients with established disease recruited from seven centers throughout the United Kingdom. Thirty-seven patients showed clear signs of active disease by bone scan and/or histological assessment of the bone biopsy specimens and 12 of these had not received any therapy before samples were taken. Presence of paramyxovirus nucleic acid sequences was sought in bone biopsy specimens, bone marrow, or peripheral blood mononuclear cells using reverse-transcription polymerase chain reaction (RT-PCR) with a total of 18 primer sets (7 of which were nested), including 10 primer sets (including 3 nested sets) specifically for MV or CDV. For each patient at least one sample was tested with all primer sets by RT-PCR and no evidence for the presence of paramyxovirus RNA was found in any patient. In 6 patients, bone biopsy specimens with clear histological evidence of active disease tested negative for presence of measles and CDV using immunocytochemistry (ICC) and in situ hybridization (ISH). Intranuclear inclusion bodies, similar to those described by others previously, were seen in pagetic osteoclasts. The pagetic inclusions were straight, smooth tubular structures packed tightly in parallel bundles and differed from nuclear inclusions, known to represent MV nucleocapsids, in a patient with subacute sclerosing panencephalitis (SSPE) in which undulating, diffuse structures were found, arranged loosely in a nonparallel fashion. In the absence of amplification of viral sequences from tissues that contain frequent nuclear inclusions and given that identical inclusions are found in other bone diseases with a proven genetic, rather than environmental, etiology, it is doubtful whether the inclusions in pagetic osteoclasts indeed represent viral nucleocapsids. Our findings in this large group of patients recruited from throughout the United Kingdom do not support a role for paramyxovirus in the etiology of Paget's disease.

Aged↗

Disclosing the truth: informed participation in the Antemortem Database Project for Survivors of Srebrenica.

This article describes a human rights investigation designed to identify bodies exhumed from mass graves in Srebrenica, Bosnia-Herzegovina and the psychological impact of participation on family members, most of whom believed the disappeared could still be alive. A community education intervention, conducted in both group and individual settings, was effective in helping families make an informed decision about participation. For informed participants, the psychological benefits outweighed any deleterious effects. The article concludes that fully disclosing the truth to potential participants, providing culturally and temporally sensitive psychosocial preparation, and securing informed consent are basic ethical and human rights principles that must be upheld at all times. Further studies are necessary to measure the impact of human rights activities of this nature on the survivor participants and implementers alike.

Bosnia and Herzegovina↗