The displacement of calcium from osteocalcin at submicromolar concentrations of free lead

Lead, an environmental toxin, is known to impair some of the functional properties of osteocalcin, a small protein (MW, 5700) active in bone mineralization and resorption. To investigate a possible mechanism of lead toxicity at the molecular level, we have studied the interaction of lead with osteocalcin using 43Ca and 1H NMR. The measured 43Ca NMR linewidth as well as longitudinal relaxation rate (1/T1) of 43CaCl2 progressively increased with increasing amounts of added osteocalcin. A titration measuring 43Ca linewidth as a function of [Ca2+]/[Osteocalcin] ratio could be fitted to a single metal binding site with a dissociation constant of 7 microM. The 43Ca 1/T1 of Ca-osteocalcin decreased in the presence of Pb2+ due to competitive displacement of Ca2+ by Pb2+. The magnitude of decrease in the effect of osteocalcin on 43Ca 1/T1 in the presence of Pb2+ was consistent with the existence of only one tight divalent cation binding site. An analysis of the NMR T1 data in osteocalcin solutions containing both Pb2+ and Ca2+ yielded a Pb-osteocalcin dissociation constant of about 2 nM. The 1H NMR spectra showed Pb-induced changes in the same aliphatic and aromatic resonances of osteocalcin that are also affected by Ca(2+)-binding, supporting interaction of Pb2+ at the Ca2+ site. However, the existence of significant differences between the Pb-osteocalcin and Ca-osteocalcin NMR spectra indicates some differences in the structures of the two complexes. Since Pb2+ inhibits the binding of osteocalcin to hydroxyapatite, the high affinity of Pb2+ for osteocalcin would indicate significant inactivation of osteocalcin even at submicromolar free lead levels. Pb(2+)-induced inactivation of osteocalcin could affect bone mineral dynamics and may be related to the observed inverse correlation between blood Pb(2+)-levels and stature and chest circumference observed in growing children.

Nuclear magnetic resonance measurement of intracellular sodium in the perfused normotensive and spontaneously hypertensive rat heart

We have used 23Na nuclear magnetic resonance spectroscopy to examine the relationship between intracellular sodium and cardiac muscle alterations in genetic hypertension. In the spontaneously hypertensive rat (SHR) compared with the normotensive Wistar-Kyoto rat (WKY) (aged 15 to 19 weeks), mean systolic blood pressures (measured using the tail-cuff method) were significantly (P < .05) different (WKY: 118 +/- 8 mm Hg, n = 5; SHR: 185 +/- 9 mm Hg, n = 5). Heart weights were also increased significantly (P < .05) in SHR (grams dry heart to kilograms body weight ratio was 0.73 +/- 0.04, n = 5, for SHR and 0.55 +/- 0.02, n = 5, for WKY). Intracellular sodium levels, measured using shift-reagent-aided and triple quantum filtered (TQF) nuclear magnetic resonance techniques, were significantly increased (P < .05) in the isolated Langendorff perfused hypertensive rat hearts (17.3 +/- 3.6 mmol/L, n = 5) compared with normotensive rat hearts (8.4 +/- 2.3 mmol/L, n = 5). These data demonstrate increased sodium in cardiac muscle in essential hypertension. We also investigated the effect of pacing on cardiac TQF 23Na nuclear magnetic resonance and found an increase in TQF Na+ content in both WKY and SHR hearts on stepped up pacing. These results support the existence of sodium pump lag in the rat heart perfused at physiologic Ca2+ concentration and suggest that the hypertensive rat heart has adapted to compensate for increased basal intracellular Na+ and maintain a normal response to increased heart rate. Our data appear to suggest an ionic contribution to the cardiac hypertrophy of genetic hypertension in the rat.

Aspiration cytodiagnosis of clear cell hepatocellular carcinoma in an elderly woman. A case report

The cytohistologic features of a clear cell hepatocellular carcinoma are described. The case occurred in an elderly woman. An aspirate was obtained from a solitary mass in the right lobe of the liver. The liver carcinoma was found to be the clear cell type, with infrequent bile and hyaline (Mallory body-like) bodies in the cytoplasm. The fact that clear cell type hepatocellular carcinoma possesses specific cellular characteristics and immunocytochemical features renders this case report useful in establishing a correct cytohistologic diagnosis, especially since this tumor variant shows a striking resemblance to "clear cell" tumors that originate in other organs and that may cause a diagnostic dilemma.

Multinuclear NMR studies of intracellular cations in the prehypertensive rat kidney

We previously reported a significant derangement of intracellular free calcium ion concentration in the isolated perfused kidney of adult spontaneously hypertensive rat (SHR) (J. Biol. Chem. 267, 3637-3643, 1992). In order to investigate whether an abnormality in intracellular free calcium or another ion precedes the development of elevated blood pressure in SHR, we have now compared intracellular free Ca2+, Na+ and pH, using 31P, 19F, and triple quantum-filtered (TQ) 23Na NMR, in perfused kidneys from prehypertensive young SHR and normotensive young Wistar-Kyoto (WKY) rats (5-6 weeks old) which showed no significant difference in blood pressure (B.P. = 120 +/- 5 mmHg and 115 +/- 3 mmHg, for SHR and WKY rats, respectively). Like the adult kidney, no significant differences in intracellular ATP concentration or intracellular pH were found between young prehypertensive SHR and normotensive WKY rat kidneys. The TQ 23Na NMR signal was 47% higher in the SHR kidney, but, due to biological variability and measurement errors, this difference could not be shown to be statistically significant. However, a significant (40%; P < 0.05) increase was found in O2 consumption rate, a measure of the Na+/K(+)-ATPase activity, of the young prehypertensive SHR kidney in comparison to the age-matched WKY rat kidney (7.25 +/- 0.75 for SHR vs. 5.17 +/- 0.18 mumol O2/min g for WKY rat, n = 6). Furthermore, a highly significant (92%; P < 0.02) increase in intracellular free Ca2+ concentration was observed in kidneys from young SHR that had not yet developed high blood pressure in comparison to the kidneys from young normotensive WKY rats (648 +/- 76 nM vs. 339 +/- 39 nM, n = 4), despite the fact that there was no significant difference in blood pressure. Increased intracellular free Ca2+ thus appears to be part of a primary defect, in the prehypertensive young SHR kidney, which may, by way of increased release of arachidonic acid, and subsequent increased production of vasoconstricting arachidonic acid metabolites via the cytochrome P450 pathway, induce elevated blood pressure in the adult SHR.

Needle aspiration cytology in the diagnosis of mucinous cystadenocarcinoma of pancreas. A study of five cases with an emphasis on utility and differential diagnosis

In this study, our experience with five cases of mucinous cystadenocarcinoma of the pancreas is described, which was seen over a 13-yr period. The diagnosis in four of the cases was made from aspirated material that was obtained under computed tomography (CT) guidance and, in one case, following an intraoperative aspirate. In four cases, the tumor was found to be in the head of pancreas, whereas in one case, the neoplasm was located in the tail. All the cases were elderly male patients. As a result of our study, it is believed that aspiration cytodiagnosis of mucinous cystadenocarcinoma (a rare subtype of pancreatic carcinoma) can be made with confidence when performed intraoperatively or with imaging assistance. Also, aspiration cytology is a sensitive, specific, and relatively simple procedure that provides adequate material on which a confident diagnostic interpretation can be made of this uncommon neoplasm.

Suitability of the Vero cell method for titration of diphtheria antitoxin in the United States potency test for diphtheria toxoid

The in vitro Vero cell method for titration of diphtheria antitoxin in immunized guinea pig sera was standardized to obtain comparable results to the in vivo toxin neutralization (TN) test in guinea pigs used to test potency of adsorbed diphtheria toxoid according to the United States Minimum Requirements. In the Vero cell method, the antitoxin titers of the guinea pig sera, obtained 4 weeks after immunization, were markedly dependent on the toxin dose level used in the assay. A toxin dose level termed the Lcd/1 dose (limit of cytopathic dose at 1 IU/ml) for Vero cell method gave comparable estimates of antitoxin activity to the in vivo TN method performed at L+/1 dose of toxin. The Lcd/1 toxin dose level for the Vero cell method is defined as the minimum concentration of diphtheria toxin required to produce a cytopathic effect on Vero cells in 4 days when the solution of diphtheria toxin is mixed with an equal volume of standard diphtheria antitoxin whose concentration is 1 IU/ml. When lower dose levels of toxin were used in the Vero cell assay (Lcd/10 to Lcd/1000), the concentrations of antitoxin in 4 weeks guinea pig sera were 2 to 11.7 times lower than with the Lcd/1 dose level and similarly lower than those measured by the in vivo TN test at L+/1 level. In contrast, the concentration of antitoxin measured in sera from guinea pigs who have been boosted with diphtheria toxoid increased approximately two-fold with the Lcd/1000 dose level.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscular sufficiency, serum protein, enzymes and bioenergetic studies (31-phosphorus magnetic resonance spectroscopy) in chronic malnutrition

Muscle sufficiency was significantly lower in 1336 children with chronic malnutrition of moderate to severe degree. Eighteen children with a chronic moderate degree of malnutrition and 8 well-nourished, age-matched controls were selected for biochemical and 31-phosphorus magnetic resonance spectroscopy (31-P MRS) studies. The results showed that: (a) serum total protein, albumin, iron, calcium and inorganic phosphate were similar in both groups; (b) serum enzyme levels were significantly increased in the malnourished group; (c) 31-P MRS showed significantly higher means for total ATP, beta-ATP, alpha-ATP and inorganic phosphate for the malnourished compared to the control group. In chronic malnutrition, proteins are maintained by degradation in muscle resulting in release of amino acids and enzymes. 31-P MRS studies showing increases in total ATP, beta-ATP and inorganic phosphate and a decrease in phosphocreatine suggest that ATP is maintained at the cost of phosphocreatine.

Comparison of adjuvant activities of aluminium phosphate, calcium phosphate and stearyl tyrosine for tetanus toxoid

The adjuvant activity of three adjuvants, aluminium phosphate (AIPO4), calcium phosphate (CaHPO4) and stearyl tyrosine for tetanus toxoid (TT) were compared to soluble TT in mice at a dose of 0.5 Lf (1/10th of the single human dose) and in guinea-pigs at a dose of 7.5 Lf (1.5 times the single human dose). Three TT preparations varying in purity were used: (1) ammonium sulphate precipitated formalin detoxified tetanus toxin (AS-TT); (2) AS-TT ultrafiltered to remove low molecular weight peptides (UF-TT): and (3) chromatographically purified tetanus toxin subsequently detoxified with formalin (CP-TT). After primary immunization of mice, AIPO4 absorbed TTs induced higher toxin-neutralizing and IgG (by ELISA) antibodies than CaHPO4, stearyl tyrosine adsorbed or soluble TT preparations, but this difference was no longer present after secondary immunization. TT preparations of varying purities showed similar antibody responses after primary and secondary immunizations when adsorbed on each adjuvant. CP-TT preparation showed the highest neutralizing antibody level amongst soluble preparations after the first dose. All the preparations induced mainly IgG1 antibodies. However, stearyl tyrosine adsorbed TT induced relatively higher IgG2a and IgG2b responses than AIPO4, CaHPO4 adsorbed or soluble TTs particularly after booster injection. No preparation induced detectable IgG3 or IgM antibodies. AIPO4 adsorbed preparations induced higher IgE antibodies than CaHPO4 and stearyl tyrosine adsorbed vaccines. Among the soluble preparations, CP-TT induced lower anti-TT IgE antibodies than standard AS-TT. All these preparations were also tested in the US potency test for adsorbed TT in guinea-pigs. While all the preparations passed this test, AIPO4 adsorbed TT preparations induced higher neutralizing and IgG antibodies than CaHPO4 and stearyl tyrosine adsorbed or soluble TT preparations. In these animal models, purified TT was a strong immunogen and traditional AIPO4 adjuvant gave the highest antibody responses.

The role of early flap coverage in the management of open fractures of both bones of the leg

Sixty patients with type III injuries (open fractures) of the tibia were treated in a prospective fashion by combined orthopaedic and plastic surgical schemes based on the principles of early radical cleaning, a second-look operation, and early coverage of soft tissue defects with an appropriate local or distant flap. Stabilization of fractures was achieved by external fixation in most cases and patients were allowed to walk within 4-8 weeks (partial weight bearing). Bony union was achieved in 23.4 weeks. The mean hospital stay was 3.5 weeks. Limb salvage was achieved in all cases and there were no major complications.

Diagnosis of umbilical metastasis (Sister Mary Joseph's nodule) by fine-needle aspiration: an immunocytochemical study

During a ten year period, since we introduced needle aspiration cytology at our institution, we have diagnosed five cases of umbilical metastasis (Sister Mary Joseph's nodule). In none of the cases was any false negative or false positive diagnosis rendered and the primary carcinoma was found below the diaphragm. In all the five cases, cell blocks of the aspirate were subsequently prepared, and highlighted the histologic features of the tumour which corresponded with the cytologic diagnosis. Immunohistochemical staining on the aspirate material in all the cases was considered quite useful in substantiating the cytohistologic diagnosis. Based on our findings, we suggest that fine-needle aspiration cytology as an initial diagnostic procedure in cases suspected of umbilical metastasis should be considered, since it is not only a simple, fast, accurate, and inexpensive diagnostic procedure, but can also save the patient from an invasive surgical procedure, the benefit of which is questionable.

Studies on the inheritance of repellent tolerances in Aedes aegypti

Two laboratory strains and 6 inbred strains of Aedes aegypti were tested against deet, ethyl hexanediol, dimethyl phthalate, and Indalone. Reciprocal crosses and backcrosses of 2 inbred strains were tested against deet only. Results obtained were compatible with a quantitative genetic model in which the effects of the factors involved were multiplicative. Certain inbred strains differed significantly from cognate laboratory and/or inbred strains in tolerance to one or more test materials. Heritability in the broad sense (H2) was estimated at 0.05 for deet, 0.22 for ethyl hexanediol, 0.48 for dimethyl phthalate, and 0.51 for Indalone. Partial dominance was observed in the inheritance of tolerance to deet.

Impact of television on children

Television viewing has a great impact on various aspects of child's life. This study was carried out at Sir Padampat Mother & Child Health Institute, Jaipur (Rajasthan). The aim was to study the effects of television viewing on a child's eating habits, general physical health, physical activities, interest in study and school performance. Only 250 children of 3-10 years age groups were studied for a period of nine months (January 1992 to September 1992). Average duration of television exposure to an individual child was 18.5 hours per week in the study. Significant changes were observed in a childs' eating habits, weight, physical activity, sleep pattern, interest in study and general physical health. Increase in weight was observed in 19.6% children suggesting that the television viewing may predispose to childhood obesity. In 30.4% cases decrease in physical activity was found, 18.4% children showed decreased interest in study, while 10% children showed decrease in school performance, and sleep pattern was disturbed in 24% children. Medical problems were found in 11.6% children. Significantly two children had precipitation of fits on television viewing.

Biodegradable microspheres as controlled-release tetanus toxoid delivery systems

Purified tetanus toxoid, a high-molecular-weight protein, was entrapped within poly(L-lactic acid) (PLA) and poly(D,L-lactic/glycolic acid) (PLGA) microspheres prepared by either a solvent extraction or a solvent evaporation method carried out in a multiple emulsion system (water-in-oil-in-water). The physical integrity and antigenicity of the protein treated under different processing conditions were investigated. A reduction of antigenicity that was related to the percentage of aggregated protein was noticed under some experimental conditions. This partial loss of antigenicity was associated with the lyophilization process and affected by the nature of the organic solvent. All types of microspheres prepared with different molecular weight PLA and PLGA displayed a high protein-loading efficiency (> 80%) but their size was strongly influenced by polymer molecular weight (3000 versus 100,000). Protein release pattern was influenced by both polymer molecular weight and composition (PLA versus PLGA). A constant release pattern after an induction period of 10 days was observed for microspheres composed of high-molecular-weight polymers (PLA and PLGA). The release rate was lower from PLA microspheres than from PLGA microspheres. In contrast, a continuously increasing release rate preceded by a burst was observed for low-molecular-weight (3000) PLGA microspheres. Microencapsulated tetanus toxoid was significantly more immunogenic in mice than fluid toxoid as determined by IgG anti-tetanus antibody levels and neutralizing antibodies. However, the magnitude and duration of the antibody response did not differ significantly from a similar dose of aluminium phosphate-adsorbed toxoid. We conclude that microencapsulated tetanus toxoid shows significant adjuvant activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Tuberculous radiculomyelitis (arachnoiditis): myelographic (and CT myelographic) appearances

Tuberculous radiculomyelitis (arachnoiditis) remains one of the important causes of paraplegia in India. The diagnosis usually rests on clinical history and examination, and on laboratory findings in the cerebro-spinal fluid (CSF). Few descriptive reports are available of the myelographic appearance, with water-soluble contrast media, in tuberculous radioculomyelitis (arachnoiditis). A retrospective review of 21 myelograms and 10 computed tomographic (CT) myelograms, in 14 patients with tuberculous radiculomyelitis, was carried out, with a view to describing, in detail, the radiographic features. An attempt was made to assess the use of the radiologic procedures in diagnosis and follow up in these patients. Conventional myelographic findings included block (8/14), irregular subarachnoid space (9/14), filling defects (8/14), sluggish contrast flow (2/14), root thickening (3/14) and atrophic cord (2/14). Computed tomographic myelography showed reduced contrast density in portions of the opacified CSF ring around the cord in affected region (6/7) and, in addition, demonstrated septa and adhesions. Intravenous contrast CT was not found to be useful (2/2). Follow-up studies showed partial resolution (3/6), deterioration (1/6) and status quo of radiological findings (2/6). Although these changes can be seen in chronic radiculomyelitis (arachnoiditis) from other causes, such as leukaemic infiltration/lymphoma, other chronic central nervous system infections and iatrogenic causes, including repeated intrathecal injections, conventional myelography appeared to be useful for diagnosis and follow up in tuberculous radiculomyelitis (arachnoiditis).

MR imaging and angiography in tuberculous meningitis

MRI was performed on 26 patients with tuberculous meningitis, with particular reference to document the cranial nerve abnormalities. MR angiography (MRA) was performed in 20 of the patients. Meningeal enhancement in the basal cisterns or over the convexity of brain was seen in all patients; two show ependymal enhancement. Tuberculomas, single (3), multiple (12) or miliary (2) were detected in 17 patients. Of the 9 patients with cranial nerve palsies, 7 showed contrast enhancement with or without thickening of the involved nerve. Abnormality signal intensity of the involved nerve was seen on proton density and T2-weighted images in one of these patients. MRA revealed focal arterial narrowing in 10 patients, the vessels commonly affected being the terminal segment of the internal carotid artery and the proximal segments of the middle and anterior cerebral arteries. One patient also had a small aneurysm of the proximal middle cerebral artery. Infarcts, haemorrhagic (8) or bland (6), were detected in 14 patients; most were the basal ganglia and internal capsules, large middle or anterior cerebral arterial territory infarcts being seen in only two cases.

Is the higher incidence of ischemic disease in patients with hypertension and diabetes related to intracellular depletion of high energy metabolites?

To study mechanisms underlying ischemia in hypertension and non-insulin dependent diabetes mellitus (NIDDM), 31P-magnetic resonance spectroscopy was used to evaluate adenosine triphosphate and 2,3 diphosphoglycerate (2,3 DPG) levels in erythrocytes of control (n = 21), hypertensive (n = 22), and NIDDM (n = 10) subjects. Compared to adenosine triphosphate levels in controls (2.22 +/- 0.10 mM), both hypertensive (1.89 +/- 0.10 mM, sig = 0.05 versus normal) and NIDDM subjects (1.57 +/- 0.13 mM, sig = 0.05 versus normal) exhibited lower values. NIDDM subjects also displayed suppressed levels of 2,3 DPG (6.84 +/- 0.48 mM, sig = 0.05 versus normal and EH), compared to hypertensives (8.34 +/- 0.27 mM). These data suggest cellular energy metabolism is disrupted in hypertension and NIDDM. Both conditions may thereby sensitize tissues to ischemic damage, lower adenosine triphosphate levels by decreasing energy reserves, and lower 2,3 DPG levels by inhibiting hemoglobin-oxygen dissociation.

MRI in intraspinal tuberculosis

We studied 20 patients with intraspinal tuberculosis (TB), to characterise the MRI features of tuberculous meningitis and myelitis. MRI leptomeningitis and intramedullary involvement in 11 patients, intramedullary lesions alone in 5, leptomeningitis alone in 2, and isolated extradural disease in 2. TB leptomeningitis was characterised by loculation of the cerebrospinal fluid (CSF), nerve root thickening and clumping (seen only in the lumbar region) or complete obliteration of the subarachnoid space on unenhanced images. Gd-DTPA-enhanced images proved useful in 6 cases, revealing linear enhancement of the surface of the spinal cord and nerve roots or plaque-like enhancement of the dura-arachnoid mater complex. Intramedullary lesions included tuberculomas (8), cord oedema (5) and cavitation (3). In seven cases of intramedullary tuberculoma multiple lesions with skip areas were seen, without significant cord swelling. One patient had an isolated lesion in the conus medullaris. The lesions were iso- or hypointense on T1-weighted images, iso-, hypo- or hyperintense on T2-weighted images and showed rim or nodular enhancement with contrast medium.

Linking radiosilver to monoclonal antibodies reduced by ascorbic acid. Comparison of results with stable silver using gravimetric technique and silver 110-M using radiotracer technique

Radiosilver-111 and Radiogold-199 were proposed by us (1) as suitable isotopes for radioimmunotherapy in areas such as India by reason of their suitable half-lives and B-emissions (Ag-111 T1/2 = 7.45 d and Au-199 T1/2 = 3.15 d). Since silver is monovalent, it is difficult to link to conventional bifunctional chelates. We therefore explored the use of sulfur-based linkers (2). Encouraged by the Thakur and De Fulvio Technique (3) of linking technetium to disulfide groups in antibodies reduced by ascorbic acid that is eminently biocompatible, we have explored the linkage of silver to immunoglobulin reduced by ascorbic acid. The linkage of silver was assessed with stable Ag-108 using dialysis to quantify the free silver after the reaction of silver and reduced immunoglobulins in various molar ratios (1:1, 1:2, 1:5, 1:10). The silver quantity was estimated gravimetrically after precipitation as chloride. It was observed that using these molar ratios there was negligible silver efflux into the dialysate, suggesting stable linkage. We also assessed the linkage using Ag-110M as radiotracer. The comparative results with the two techniques are described.

Proliferation of Reed-Sternberg cells and variants in Hodgkin's disease

The proliferative activity and the origin of multinucleated Reed-Sternberg cells and mononuclear variants in Hodgkin's disease have been studied in the past using several techniques. The presence of both proliferating-cell nuclear antigen and the cell-proliferation-associated antigen Ki-67 have also been reported in Hodgkin's disease. P34cdc2 is the protein product of the cell-cycle-control cdc-2 gene. Using a monoclonal antibody against the protein p34, cases of three different histological subtypes of Hodgkin's disease have been studied along with normal tonsil and follicular lymphoma as controls. In all these cases of Hodgkin's disease, positive p34 staining was seen in the majority of Reed-Sternberg cells and mononuclear variants (> 80%), along with a proportion of small lymphocytes, mainly T cells. Staining was predominantly cytoplasmic and occasionally additional nuclear signals were apparent. In two cases, double immunostaining with the anti-p34 antibody and CM-1 for p53 demonstrated positive signals for both proteins within the same neoplastic cells. Although the presence of p34 in Reed-Sternberg or variant cells reflects mitosis and hence suggests proliferation, the possibility of endomitosis remains and may explain the multinucleated appearance of Reed-Sternberg cells.

Role of repellents in vector control and disease prevention

Repellents are an inexpensive and practical means of protection against nuisance and disease vector arthropods in conjunction with or when other control measures are not feasible. Appropriate selection of skin and/or clothing repellents along with proper wear of clothing can provide adequate protection from biting arthropods, and are available in a wide variety of forms including lotions, creams, foams, soaps, aerosols, sticks, and towellettes. A coordinated effort among different research groups associated with advances in the science of insect repellents such as mode of action information, doses of repellents to generate threshold level responses and controlled release delivery mechanisms, may help in understanding the mechanisms by which repellents work. This in turn may revolutionize the development of repellents for personal protection and their use in vector control.

Removal of endotoxin from antibody preparations for clinical use. Assessment of polymyxin-sepharose CNBr affinity chromatography

Despite attempts to maintain asepsis, good manufacturing practices, and the use of terminal sterilization by millipore filtration, the nuclear practitioner is always worried about the possibility of endotoxin contamination. Methods, such as ion-exchange chromatography, have been tried for removing endotoxins during the preparation of radiolabeled antibodies, and so on. As suggested by Stevenson (1990), we evaluated the Issekutz technique (1) of endotoxin removal by affinity chromatography using a polymyxin cyanogen bromide (CNBr) Sepharose column. The endotoxin content of millipore filtrates of heat killed/sonicated suspensions of Pseudomonas pyocyaneus, E. coli were measured using a Sigma (St. Louis, MO) Endotoxin Assay Kit before and after filtration through such columns and compared with the results obtained using gel exclusion and ion-exchange columns of the same length and diameter. Reduction of endotoxin content to undetectable levels by the polymyxin column was observed. The use of such columns for terminal endotoxin removal analogous to terminal sterilization is advocated especially when developing a radiopharmaceutical such as radiolabeled antibodies for in house use.