Biomedical subjects
Publications and source records attributed to A Khan.
A case of an isolated mesenteric desmoid (fibroma) is presented with two unusual characteristics. First, it arises from the mesentery of the appendix. Second, it presents as a twisted desmoid. The CT and US characteristics are presented. This patient was without risk factors for mesenteric fibrosis such as Gardner's syndrome or previous surgery.
Primary thymic squamous cell carcinoma is uncommon and has only rarely been linked to a pre-existing thymoma. We are reporting a case of primary thymic squamous cell carcinoma with pituitary metastases, in a patient with a long standing thymoma.
A case of extramedullary plasmacytoma of the larynx is presented. The case is unique for the extramedullary plasmacytoma's marked extension into the mediastinum. The computed tomography (CT) features are described.
The CT findings of a patient with relapsing polychondritis involving the larynx, tracheobronchial tree, and nasal cartilage are described. In the proper clinical setting, a characteristic constellation of findings when noted on CT can aid in differentiating this rare inflammatory disease from other causes of airway compromise. CT is the most useful imaging modality, because cartilage and soft tissue components are well visualized. If diagnosed early, appropriate treatment may prevent life-threatening airway obstruction.
A case of calcified pulmonary metastases from medullary carcinoma of the thyroid is reported. This uncommon cause of multiple calcified pulmonary nodules is demonstrated on a computerized tomography (CT) scan and proven by pathology.
Mucoepidermoid tumor of the lung is a rare endobronchial neoplasm with a wide spectrum of appearance. We present a case report and describe the plain film and computed tomography (CT) findings.
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PURPOSE: To prevent damage to the recurrent laryngeal nerve during thyroid or parathyroid surgery, spontaneous and evoked electromyography (EMG) can be used to locate the recurrent laryngeal nerve or determine when the nerve is being disturbed. Two commercial electrodes have been introduced to receive laryngeal EMG. This study compares the clinical performance of the two electrodes. PATIENTS AND METHODS: The Xomed-Treace endotracheal tube electrode (Xomed-Treace, Jacksonville, FL) and the RLN postcricoid laryngeal electrode (RLN Systems, Jefferson City, MO) were placed concomitantly in 11 patients during 14 surgical procedures. RESULTS: The RLN electrode provided feedback as to placement by providing a heart-beat artifact. The RLN electrode was found to be both more sensitive and more electrically noisy. On stimulation, the Xomed tube electrode produced generally higher EMG amplitudes, perhaps because of the different muscles they monitor. In one case, the Xomed tube failed to provide-EMG responses. Only at low electrical stimulation intensities could left and right vocalis muscles be identified with the Xomed tube. A laryngologist was needed to place the RLN electrode, whereas the attending anesthesiologist was able to place the Xomed tube. CONCLUSION: Both electrodes provided useful EMG information and helped confirm the location of the recurrent laryngeal nerve. Who will place the electrode, tumors extrinsic or intrinsic to the larynx, cost, and size requirements should be considered when choosing an electrode.
A patient without prior history of renal failure or hemodialysis presented with weakness of the extremities. On magnetic resonance imaging (MRI), a peri-odontoid soft-tissue mass hypointense to muscle on both T1- and T2-weighted images was noted without obvious bony destruction. Pathological examination revealed degenerated fibrocartilage which stained for amyloid. Further, peroxidase staining for beta-2 microglobulin was positive. We describe the first case of a beta-2 microglobulin peri-odontoid amyloidoma without preceding history of hemodialysis and a review of literature is performed.
The pharmacokinetics and pharmacodynamics of recombinant human chorionic gonadotrophin (rHCG) were investigated in three studies of healthy volunteers. After single intravenous doses of 25, 250 and 1000 microg, rHCG and urinary HCG (uHCG) showed linear pharmacokinetics described by a bi-exponential model, although the area under the curve (AUC) for uHCG was ~29% lower than for rHCG. After intramuscular or subcutaneous administration (absolute bioavailability, 40-50% for both), rHCG pharmacokinetics could be described by a first-order absorption, one-compartment model. During multiple subcutaneous dosing, the amount of HCG increased by approximately1.7-fold. A comparison of liquid and freeze-dried rHCG and freeze-dried uHCG showed pharmacokinetic bioequivalence. In down-regulated male subjects, single doses of 125 microg rHCG, given intravenously, intramuscularly or subcutaneously, produced comparable increases in serum testosterone, inhibin and 17beta-oestradiol, with little further increase during repeated subcutaneous administration (in female subjects, this produced a sustained comparable increase in serum androstenedione and testosterone concentrations). In conclusion, the pharmacokinetics and pharmacodynamics of rHCG are similar to those of uHCG and are not affected by the use of different formulations. In healthy subjects, rHCG produces pharmacodynamic responses consistent with HCG physiology and is suitable for use in the same clinical indications as uHCG. The secured source and high purity of rHCG may offer important advantages.
According to a previous report, only the smaller anions, like chlorides,that readily fit into the anion binding site of alpha-amylase can cause an increased stability (relative to enzymes in aqueous solution), and the anions that are too large to fit into the binding site should have no effect on the enzyme. Even though the results on large benzoate ions are consistent with the above postulate, much larger citrate ions from sodium and potassium citrate show stabilization at moderate salt concentrations and follow an expected trend of low stability only at large salt concentrations. The citrate ions from ammonium citrate exhibit very little to almost no stabilization. In addition, low to moderate concentrations of NaCl that provide a large stability to the enzyme show almost no stability in the presence of EDTA. We put forward an inactivation model that involves a reversible dissociation of the anion bound to the protein, followed by a reversible inactivation step of calcium ion dissociation and an irreversible denaturation step of apoenzyme.
Dephinium cashmirianum Royle (Ranunculaceae) has yielded the new base cashmiradelphine (12), together with the known alkaloids anthranoyllycoctonine (9), lycaconitine (15), avadharidine (17), lappaconitine (4), and N-deacetyllappaconitine (7). Pyridinium chlorochromate oxidation of lycoctonine furnished the new aldehyde lycoctonal (11). The arrhythmogenic and heart rate effects of several of these diterpenoidal alkaloids have been measured on the isolated guinea atria. Lappaconitine was arrhythmogenic at 10(-4)M concentrations. But in contrast to the reference drug aconitine, lappaconitine did not increase the heart rate. In anesthetized rabbits injected with lappaconitine, N-deacetyllappaconitine, and lappaconine up to 1 mg/kg, cardiac arrhythmia was quickly observed. Even up to 5 mg/kg, the other substances were non-arrhythmogenic.
The authors studied 53 girls (44.5%) and 66 (55.5%) boys in Karachi, Pakistan, to determine their blood lead levels. The association between blood lead levels/water lead levels and the possible risk factors and symptoms associated with lead toxicity was explored. The mean lead level for the entire group was 7.9 microg/dl (standard deviation = 4.5 microg/dl). Thirty (25.2%) of the children had lead levels that exceeded 10 microg/dl; 12 (10.0%) of these had lead levels that exceeded 15 microg/dl. Thirteen (20.9%) of the children under the age of 6 yr (n = 62) had lead levels greater than 10 microg/dl, and 6 (9.6%) had levels in excess of 15 microg/dl. The authors found no association (p > .05) between high lead levels in water and blood lead levels in children. Mean blood lead levels were highest in the group of children exposed to various risk factors for lead absorption (e.g., exposure to paint, remodeling, and renovation; use of lead utensils; pica). There was a significant association between a history of exposure to paint/renovation activities and a history of pica. High blood lead levels in the children in Karachi stress the urgency for actions that control lead pollution. Screening programs should be instituted by the state. Individuals must become aware of lead's toxicity, and they must avoid substances that contain lead.
Fifteen cancer patients have developed catheter-related infections caused by the Mycobacterium fortuitum complex (M. fortuitum and Mycobacterium chelonae) at M. D. Anderson Cancer Center since 1978. Eleven patients had bacteremia and four had catheter site infections. Nine infections were caused by M. fortuitum and six by M. chelonae. All four bacteremic patients whose catheters were initially removed and who were treated with antibiotics recovered, whereas for all of the seven bacteremic patients whose catheters remained in place, the infection relapsed or treatment failed. Six (86%) of the latter group ultimately responded to additional antibiotic therapy when the catheter was removed. Successful treatment of local catheter infections was accomplished by catheter removal alone or in combination with antibiotic therapy. Fourteen additional cases have been reported, and eight (57%) of these patients also had underlying cancer. Patients with septicemia or an infection at the catheter insertion site responded to catheter removal and appropriate antibiotics. Patients with infection in the catheter tunnel (tunnel infection) responded only after surgical excision of the tissue surrounding the infected tunnel. M. fortuitum complex is a cause of catheter-related bacteremia in patients with cancer. Appropriate treatment consists of antibiotic therapy and catheter removal. Tunnel infections usually also require surgical excision.
In Acholeplasma laidlawii membranes the ratio between the dominating lipids, monoglucosyldiglyceride (MGDG) and diglucosyldiglyceride (DGDG), depends on temperature, configuration of incorporated fatty acids, and membrane cholesterol content, which affect the molecular geometry of the lipids. MGDG and DGDG have wedge- and rod-like molecular shapes, respectively, that are modifiable. The packing constraints of lipids in amphiphilic aggregates, i.e., the area of the hydrocarbon-water interface and the volume and length of the hydrocarbon chains, are important in determining the aggregate structure. Pure MGDG forms a reversed hexagonal- (HII) phase structure with different acyl chain contents, while DGDG forms a lamellar phase. Depending on the unsaturated acyl chain content in the lipids, an in vitro mixture of MGDG and DGDG forms lamellar or cubic phases at physiologic temperatures. A high degree of cis-unsaturation, large amounts of MGDG and high temperatures favor formation of the cubic phase. Addition of cholesterol corresponding to the maximal amount incorporable into A. laidlawii induces a transition from a lamellar or a cubic phase to a reversed hexagonal phase. Lipid mixtures containing only unsaturated acyl chains are more sensitive to the bilayer-destabilizing effect of cholesterol than are mixtures with equal amounts of saturated and unsaturated acyl chains. The lamellar phase is the only one compatible with a functional biological membrane. Consequently, the balance between lipids that form lamellar and other mesophase structures must keep within certain limits. The cubic and reversed hexagonal structures were discovered under conditions not existing in the living Acholeplasma cell. Thus, the response of A. laidlawii lipid metabolism to external and internal stimuli can be predicted on the basis of molecular shapes and is necessary to the maintenance of optimal membranes stability. The reduced capacity of Acholeplasma membranes to incorporate cholesterol is a consequence of this regulation.
OBJECTIVE: The purpose of this investigation was to assess the utility of allowing free adjustment of window width and level in comparison with the use of a fixed lung window in the CT evaluation of diffuse lung disease. MATERIALS AND METHODS: Six radiologists each judged 36 cases (28 diffuse lung disease and 8 normal) using a standardized form. In half of the sessions, images were viewed in a fixed lung window (level = -500 HU; width = 2,000 HU). In the other sessions, the observer was able to adjust the window and level freely while viewing the images. Each case was seen twice in separate sessions: once in a fixed lung window and once with window width and level adjusted by the reader. A variety of diagnostic features were evaluated using a 5 point scale. These included visibility of fine lung structures, abnormalities of the lung parenchyma, and overall evaluation of the lung. RESULTS: The visibility of lung structures was not improved with adjustable window settings. Receiver operating characteristic (ROC) analysis showed fixed windows to be superior to adjustable windows for overall evaluation of the cases [fixed A(z) = 0.90, adjustable A(z) = 0.84, p < 0.05, jackknife method]. Time to rate each case was increased by 15% with window width and level adjustment. CONCLUSION: Free adjustment of window width and level produced no improvement in reader performance over that achieved with fixed window width and level.
It has been our practice to perform total myelography in all cases of lumbar disc disease including the various syndromes of spinal stenosis, because experience has indicated that myelographic abnormalities in the cervical and thoracic areas could have clinical importance despite the presence of gross changes in the lumbar region. Failure to establish a definite diagnosis by restricted lumbar myelography makes it mandatory to evaluate all levels of the spinal axis. Recently, 3 patients with thoracic spinal cord tumors presented with primary signs and symptoms of lumbar spine disorders. Evidence of spinal cord disease was minimal and could be readily overlooked. Total myelography disclosed varying degrees of lumbar spinal pathology, but also showed evidence of lesions in the thoracic region. One proved to be an intramedullary astrocytoma of the spinal cord, and two were schwannomas. The symptoms of low-back pain and lumbar radiculopathy improved after excision of the schwannomas and following x-ray therapy and chemotherapy in the patient with the intramedullary neoplasm.
During the 2 years of the study, 402 patients and an equal number of age- and sex-matched controls were investigated for the presence of diarrhoeal pathogens. Pathogenic organisms were recovered from 277 (68.9%) patients and 97 (24.1%) controls. In the patient group, possible bacterial pathogens were found in 210 (52.2%) cases. Enteropathogenic Escherichia coli (EPEC) was the most frequently found potential pathogen, being recovered in 132 cases (32.8%) with serotypes 026, 086, 0111 and 0124 being the most frequently identified. Other bacterial pathogens identified were enterotoxigenic E. coli (ETEC) 57 (14.2%), Shigella 13 (3.2%) and Salmonella eight (2%). Rotavirus was identified in 33 (8.2%) cases. Mixed bacterial and viral infections were also seen in 26 (6.5%) cases. In the control group, enteric pathogens were recovered from 97 (24.1%) specimens. The most common bacterial pathogen found in this group was again EPEC (40, 9.9%), with serogroups 018, 044, 0111 and 0126 being the most frequent. Giardia lamblia and Entamoeba histolytica were found in 31 (7.7%) and 10 (2.5%) controls, respectively. Rotavirus was found in 16 (4%) controls. The results of both centres where the study was performed (Karachi and Rawalpindi) were compared.