Localization of sentinel nodes in head and neck tumours by combined lymphoscintigraphy and bone scintigraphy

Sentinel node scintigraphy in tumours of the head and neck region was combined with bone scintigraphy to provide anatomical landmarks in order to better locate the lymph node uptake. 99Tc(m)-nanocolloid (40 MBq) was injected in the peritumour region 1 h after the administration of bone-seeking 99Tc(m)-methylene diphosphonate (200 MBq). After 5 min, A-P and lateral projections of the head and neck region were acquired. In all the 26 patients examined, the surrounding anatomy was clearly depicted. In 23 patients, the lymphatic drainage was identified within 30 min. In these patients, all hot spots appearing outside the deposited activity could be located according to the neck region classification system of the Memorial Sloan-Kettering Hospital. No lymphatic drainage was visualized in the remaining three patients. The injection of bone-seeking activity 1 h before deposition of the radiocolloid provided images visualizing soft tissues as well as skeletal structures, thus improving the topical diagnosis. Correlation with the results of surgery was not performed. The administration of a small amount of bone-seeking activity prior to sentinel node scintigraphy of head and neck tumours improves the anatomical localization of the lymph node activity.

A spatially varying compton scatter correction for SPECT utilizing the integral Klein-Nishina cross section

An algorithm correcting for the fraction of scattered events in SPECT and planar imaging is proposed. The algorithm utilizes a pixel-based multi-channel analyser for data acquisition. The method was designed to operate on a local level by three subtraction steps: (a) Subtracting a modified Klein-Nishina single scatter distribution, pixel by pixel, from the events obtained experimentally in the upper half of the photo-peak window. (b) Subtracting a mirrored distribution of the unscattered events hence obtained from that of total events in the lower half of the window, thus giving the scatter distribution in this part of the window. (c) Subtracting the sum of the scatter distributions in both window halves from the corresponding sum of total events in order to obtain the unscattered photons within the photo-peak window. The accuracy of the method was validated experimentally, using a new rCBF phantom allowing for imaging in matter corresponding to soft tissue and approximately in air, respectively. After correction for photon scattering and attenuation, the regional difference in SPECT values in soft tissue equivalent matter and in low-density matter (simulating air) was only 1.5 +/- 7.2% (mean +/- 1 SD), thus indicating a high accuracy of the correction method. Provided that an accurate and stable pixel peak-alignment routine is available, the method can be applied using a minimum of three windows.

Mapping pathological (99m)Tc-d,l-hexamethylpropylene amine oxime uptake in Alzheimer's disease and frontal lobe dementia with SPECT

Seventeen patients with probable Alzheimer's disease (AD), 7 patients with frontal lobe dementia (FLD) and 19 control subjects (NOR) were examined by (99m)Tc-d,l- hexamethylpropylene amine oxime ((99m)Tc-HMPAO) SPECT. Images were standardised in the same 3D space and averaged within each group. After normalisation, the three sets of images were analysed in all cerebral lobes, hippocampus, thalamus and basal ganglia. In AD, the (99m)Tc-HMPAO uptake values were significantly reduced, as compared to NOR, in the parietal, temporal and insular lobes. In patients with FLD, the uptake was altered in all lobes with the exception of the parietal lobe. The uptake in the nucleus caudatus decreased significantly in both AD and FLD as compared to NOR. The uptake in the anterior cingulate cortex was significantly reduced in FLD. Subtraction images highlighted all significantly decreased areas. In conclusion, standardising SPECT in a common space and subtracting data from a control group improves the visual interpretation of images. In this study, the typical temporo-parietal and fronto-parietal (99m)Tc-HMPAO uptake reductions were found in AD and FLD, respectively. The uptake in the nucleus caudatus was found to decrease significantly in AD and FLD and the one in the anterior cingulate cortex was reduced in FLD.

Effects of acute hypobaric hypoxia on regional cerebral blood flow distribution: a single photon emission computed tomography study in humans

Single Photon Emission Computed Tomography (SPECT) and radiopharmaceutical stabilizing agents allowed us to investigate regional cerebral blood flow (CBF) distribution in six resting healthy subjects during acute laboratory hypobaric hypoxic conditions. In the hypobaric experiment stabilized 99mTc-D, L-hexamethyl-propylene amine oxime was injected 40 min after reaching hypoxic conditions corresponding to an altitude of 5500 m above sea level. Arterial blood sample was taken after five additional minutes. Mean arterial oxygen pressure and haemoglobin saturation were 28 mmHg and 56%, respectively. The control experiment was performed similarly, apart from barometric pressure and blood gas analysis. We analysed CBF distribution in 12 regions of functional interest bilaterally in frontal, parietal, temporal, occipital cortex, in the hippocampus, in the basal ganglia and other central structures of brain. No overall effect of hypoxia on normalized regional CBF distribution in the considered regions was found. Motor cortex (Brodmann 4) and basal ganglia were the only regions in which hypobaric hypoxia significantly increased relative distribution of the radiopharmaceutical [F(1,5)=18.30; P < 0.008 and F(1,5)=10.85; P < 0.022, respectively]. Despite severe hypoxia, we did not observe any major regional CBF redistribution. We found a small relative increase in blood flow to the motor cortex and the basal ganglia, at rest after 40 min of hypobaric hypoxia, suggesting a preferential compensatory mechanism of these functional regions of brain.

A novel phantom design for emission tomography enabling scatter- and attenuation-"free" single-photon emission tomography imaging

A newly designed technique for experimental single-photon emission tomography (SPET) and positron emission tomography (PET) data acquisition with minor disturbing effects from scatter and attenuation has been developed. In principle, the method is based on discrete sampling of the radioactivity distribution in 3D objects by means of equidistant 2D planes. The starting point is a set of digitised 2D sections representing the radioactivity distribution of the 3D object. Having a radioactivity-related grey scale, the 2D images are printed on paper sheets using radioactive ink. The radioactive sheets can be shaped to the outline of the object and stacked into a 3D structure with air or some arbitrary dense material in between. For this work, equidistantly spaced transverse images of a uniform cylindrical phantom and of the digitised Hoffman rCBF phantom were selected and printed out on paper sheets. The uniform radioactivity sheets were imaged on the surface of a low-energy ultra-high-resolution collimator (4 mm full-width at half-maximum) of a three-headed SPET camera. The reproducibility was 0.7% and the uniformity was 1.2%. Each rCBF sheet, containing between 8.3 and 80 MBq of 99mTcO4- depending on size, was first imaged on the collimator and then stacked into a 3D structure with constant 12 mm air spacing between the slices. SPET was performed with the sheets perpendicular to the central axis of the camera. The total weight of the stacked rCBF phantom in air was 63 g, giving a scatter contribution comparable to that of a point source in air. The overall attenuation losses were <20%. A second SPET study was performed with 12-mm polystyrene plates in between the radioactive sheets. With polystyrene plates, the total phantom weight was 2300 g, giving a scatter and attenuation magnitude similar to that of a patient study. With the proposed technique, it is possible to obtain "ideal" experimental images (essentially built up by primary photons) for comparison with "real" images degraded by photon scattering and attenuation losses. The method can serve as a tool for experimental validation and intercomparison of attenuation and scatter correction methods. Moreover, the large flexibility of this phantom design will allow investigations of arbitrary activity distributions and autoradiography or other imaging techniques such as PET, x-ray computed tomography or magnetic resonance imaging.

The interleukin-1 system in the testis

The interleukin-1 (IL-1) family consists of two agonist proteins, IL-1 alpha and IL-1 beta, and one antagonist, IL-1 receptor antagonist (IL-1ra), which blocks the action of the agonists by binding and competing at the IL-1 receptor level. IL-1 beta and to a lesser extent IL-1 alpha were originally described as rapidly inducible proinflammatory cytokines released by activated macrophages. However, IL-1 alpha has been found to be constitutively produced by certain tissues, and noninflammatory functions have been proposed for this protein, although they have not yet been well elucidated. Consistent with this suggestion, we previously showed that the intact rat testis constitutively produces large amounts of IL-1 alpha at both the mRNA and protein levels. The expression of IL-1 alpha was found to be confined to Sertoli cells, with evidence of a developmental as well as a stage-dependent production pattern. In more recent studies, we have found indications that the testis can also initiate production of IL-1 beta upon stimulation with inflammatory inducers such as endotoxin. Further, we have detected constitutive testicular expression of IL-1ra, opening up the possibility that IL-1 action in the testis may be specifically regulated by paracrine mechanisms. Recent data have demonstrated that the testis can produce more than one isoform of IL-1 alpha with indications of both post-transcriptional and post-translational modifications, resulting in at least three distinct bio- and immunoreactive IL-1 alpha proteins. We conclude that all three classical IL-1 ligands and novel IL-1 alpha isoforms are present in the testis and may serve as paracrine mediators under physiological or pathophysiological conditions. The function of this testicular IL-1 agonist-antagonist network is a current focus of investigation.

Registration of neuroimaging data: implementation and clinical applications

Image registration brings images into a form in which each voxel corresponds to a predetermined anatomic entity and is necessary for comparisons of data across scans. Intrasubject registration is a matter of translating and rotating one image volume into correspondence with another. Intersubject registration is more difficult because it requires the removal of individual anatomy dependence from the data. This article describes, with the help of clinical examples, automated methods for intrasubject registration of scans within and between modalities, and intersubject registration used for registering a three-dimensional brain atlas with a patient's brain scan.

Reproducibility and repeatability of 99Tcm-HMPAO rCBF SPET in normal subjects at rest using brain atlas matching

The aim of this study was to assess regional cerebral blood flow (rCBF) in normal subjects at rest using 99Tcm-HMPAO single photon emission tomography (SPET). Analysis of reproducibility and repeatability was performed both before and after normalization of flow data. Six healthy volunteers were examined, three times each, according to a routine rCBF protocol. A computerized brain atlas was used to evaluate flow data in eight selected regions. The overall reproducibility of rCBF was evaluated from two scans performed at an average interval of 3 months. Repeatability was evaluated from two scans, 3 h apart and without re-injection of 99Tcm-HMPAO. For the normalized (relative) flow data, the reproducibility was +/- 1.3% and the repeatability +/- 2.2% (i.e. methodological errors dominate). For the non-normalized flow data, the corresponding values were +/- 14.8% and +/- 5.9%. rCBF SPET with 99Tcm-HMPAO is highly reproducible provided that the flow data are normalized. The variation in flow between individuals at one point in time and 3 months later was less than +/- 5% for all brain regions.

A 3-year follow-up study of preformed beta-quartz glass-ceramic insert restorations

OBJECTIVE

The purpose of this study was to evaluate the clinical performance of preformed beta-quartz glass-ceramic insert restorations.

METHODS AND MATERIALS

Nine Class I and 30 Class II beta-quartz glass-ceramic insert restorations were placed in 16 patients who were seen regularly by personnel at Umeå University Dental School. The California Dental Association criteria were used to evaluate the restorations at baseline, 6 months, and 1, 2, and 3 years after luting. The occurrence of postoperative sensitivity, the time taken to manufacture each restoration, and certain periodontal conditions were also evaluated.

RESULTS

Sixty-nine percent of the restorations were rated satisfactory at the 3-year examination. During the follow-up period, 4 became loose and 7 were fractured or had flaking surfaces. Caries was registered in connection with 1 restoration. Excellent ratings were obtained for marginal integrity, anatomic form, surface, and color in 62%, 84%, 32%, and 44% of the restorations, respectively. There was no statistically significant difference in the occurrence of plaque and bleeding on probing in comparison with the controls. The mean overall time for placement was 38 minutes. The estimated survival rate (Kaplan-Meier) was 59% after 3.5 years.

CONCLUSION

The quality of the beta-quartz glass-ceramic restorations in the present study was inferior to that presented in most earlier studies of ceramic or resin composite posterior restorations placed in patients treated at university clinics. Both the technique and the beta-quartz glass-ceramic inserts have to be evaluated in more long-term studies to assess the possibility of their serving as an alternative restorative technique.

Biodistribution of liposomal 131I-VIP in rat using gamma camera

Vasoactive intestinal peptide (VIP), a 28 amino-acid peptide was labeled with 131I and encapsulated into liposomes. 131I-VIP or liposomal 131I-VIP was administered intravenously into the rats. The distribution was studied by a gamma camera and established by counting the radioactivity in the removed organs. The elimination half-life for the liposomal 131I-VIP in both blood and lungs was significantly longer (5.29 and 9.28 min, respectively) than that obtained after the administration of 131I-VIP (0.62 and 3.18 min, respectively). Dynamic scans using a gamma camera after the administration of liposomal 131I-VIP showed a higher uptake of the liposomal form into the lungs compared with 131I-VIP. The lack of VIP in asthmatics has been shown in previous studies. However, the clinical investigations using VIP were disappointing most probably due to the rapid degradation of the peptide in the bronchial tract. This in fact is supported by our previous study, in which we demonstrated that VIP had a half-life of 0.45 min in blood. We conclude that the encapsulation of VIP in liposomes prolongs its elimination half-life in plasma and enhances its uptake in lungs. This observation may increase the clinical use of VIP in both diagnostic and therapy.

The somatostatin analogue octreotide inhibits neuroblastoma growth in vivo

Neuroblastoma, a neural crest-derived childhood tumor of the sympathetic nervous system, may in some cases differentiate to a benign ganglioneuroma or regress due to apoptosis. However, the majority of neuroblastomas are diagnosed as metastatic tumors with a poor prognosis despite intensive multimodal therapy. The neuropeptide somatostatin (SOM) has been shown to inhibit neuroblastoma growth and induce apoptosis in vitro. Therapeutic effects of SOM analogues are dependent on tumor expression of high-affinity receptors. In the present study, human neuroblastoma SH-SY5Y cells were grown as xenografts in nude rats. In vivo SOM receptor expression in the xenografts was identified using scintigraphy with 111In-pentetreotide. Rats were randomized to treatment with the long-acting SOM analogue octreotide (10 microg s.c. every 12 h), 13-cis-retinoic acid (4 mg orally every 24 h), or vasoactive intestinal peptide (40 microg s.c. every 24 h) and compared with controls. Tumor volume was assessed every second day and tumor weight after 10-12 d. Octreotide treatment inhibited neuroblastoma growth significantly with reduced tumor volumes at 10 and 12 d compared with untreated controls (mean 3.56 and 4.24 versus 6.48 and 8.01 mL, respectively; p < 0.01). Also, tumor weights after 10-12 d were reduced in octreotide-treated animals (n = 8, median weight 2.90 g, range 1.67-5.57 g) compared with untreated rats (n = 14, 7.54 g, 1.65-10.82 g, p = 0.005). Serum IGF-I decreased significantly over time both in rats treated with octreotide and in untreated controls. It is concluded that treatment with the SOM analogue octreotide may significantly decrease neuroblastoma tumor growth in vivo. Further studies are warranted to establish the role of SOM analogues in the treatment of children with unfavorable neuroblastoma.

Sympathotropic drugs and the distribution of 99mTc-hydroxymethylene diphosphonate. Experimental studies in the mouse

OBJECTIVE

The uptake of bone-seeking radiopharmaceuticals depends on the blood flow, which is influenced by the sympathetic nervous system. Our aim was to study the effect of sympathomimetic drugs on the distribution of bone-seeking agents.

MATERIAL AND METHODS

Various sympathomimetic and beta-blocking drugs were injected in mice at different times in relation to the administration of 99mTc-HDP. Three hours after this, venous blood and various organs were removed and their activities were related to the administered activity. A kinetic study of the whole-body activity retention after administration of terbutaline was also made.

RESULTS

The biodistribution of 99mTc-HDP was similar after the administration of sympathomimetics and of beta-antagonists. All drugs gave rise to an increased soft tissue activity and a decreased bone activity, corresponding to a lowered quality of the potential bone scan. Terbutaline gave rise to an increased excretion of 99mTc-HDP. The mechanisms behind the findings cannot be entirely explained.

CONCLUSION

Drug interference with the sympathetic nervous system causes undesirable effects on the biodistribution of 99mTc-HDP in the mouse. Studies in humans are necessary to evaluate whether clinical treatment with sympathotropic drugs affects the bone scintigram.

In vivo dynamic distribution of 131I-glucagon-like peptide-1 (7-36) amide in the rat studied by gamma camera

The in vivo distribution of glucagon-like peptide-1 (7-36) amide (GLP-1) was studied in a rat model using radiolabeled GLP-1 (131I-GLP-1) depicted by a gamma-camera. The dynamic scan showed a rapid clearance from the blood circulation after an intravenous (i.v.) injection of 131I-GLP-1. After 10 min, the major part of the radioactivity was accumulated in the kidneys, whereas about 9% (of the blood value) was found in the brain. The pharmacokinetic study using 125I-GLP-1 demonstrated a rapid elimination from plasma, with a half-life of 3.3 +/- 0.6 min, a clearance of 117 +/- 15 mL/min, and a distribution volume of 557 +/- 61 mL. The elimination half-lives for the intact 125I-GLP-1 in lungs and kidneys were determined to 3.7 and 3.9 min, respectively. The metabolite GLP-1 (9-36) amide was followed in blood, lung, and kidney. All other organs assumed to contain low molecular weight fragments of GLP-1. The present study suggest that GLP-1 and/or its labeled metabolites cross the blood-brain barrier. Also the kidney plays an essential role in GLP-1 elimination after an i.v. administration, which can be of clinical interest especially in patients with kidney insufficiency who are treated with GLP-1.

Resting state rCBF mapping with single-photon emission tomography and positron emission tomography: magnitude and origin of differences

Single-photon emission tomography (SPET), using technetium-99m hexamethylpropylene amine oxime, and positron emission tomography (PET), using oxygen-15 butanol were compared in six healthy male volunteers with regard to the mapping of resting state regional cerebral blood flow (rCBF). A computerized brain atlas was utilized for 3D regional analyses and comparison of 64 selected and normalized volumes of interest (VOIs). The normalized mean rCBF values in SPET, as compared to PET, were higher in most of the Brodmann areas in the frontal and parietal lobes (4.8% and 8.7% respectively). The average differences were small in the temporal (2. 3%) and occipital (1.1%) lobes. PET values were clearly higher in small VOIs like the thalamus (12.3%), hippocampus (12.3%) and basal ganglia (9.9%). A resolution phantom study showed that the in-plane SPET/PET system resolution was 11.0/7.5 mm. In conclusion, SPET and PET data demonstrated a fairly good agreement despite the superior spatial resolution of PET. The differences between SPET and PET rCBF are mainly due to physiological and physical factors, the data processing, normalization and co-registration methods. In order to further improve mapping of rCBF with SPET it is imperative not only to improve the spatial resolution but also to apply accurate correction techniques for scatter, attenuation and non-linear extraction.

Somatostatin in neuroblastoma and ganglioneuroma

Neuroblastoma, a childhood tumour of the sympathetic nervous system, may in some cases differentiate to a benign ganglioneuroma or regress due to apoptosis. Somatostatin may inhibit neuroblastoma growth and induce apoptosis in vitro and was therefore investigated. Using a radioimmunoassay, we found that all ganglioneuromas contained high somatostatin concentrations (> 16 pmol/g), significantly higher than neuroblastomas (n = 117, median 2.8 pmol/g), healthy adrenals, Wilms' tumours, phaeochromocytomas and other neuroendocrine tumours (P < 0.001). Neuroblastomas contained more somatostatin than control tumours (P < 0.001-0.05). Neuroblastomas amplified for the MYCN oncogene contained less somatostatin than non-amplified tumours (1.2 pmol/g versus 4.0 pmol/g, respectively; P = 0.026). In a clinically unfavourable neuroblastoma subset (age > 12 months, stage 3 or 4) 16 children with high concentrations of somatostatin in primary tumours had a better prognosis than 23 with low somatostatin (46.7% versus 0% survival at 5 years, P < 0.005). Scintigraphy using 111In-pentetreotide identified tumours expressing high-affinity somatostatin receptors in vivo. However, no significant correlation was found between somatostatin receptor expression and peptide content in 15 tumours. Similarly, human SH-SY5Y neuroblastoma xenografts grown in nude rats showed low somatostatin concentrations, but were positive for somatostatin receptor scintigraphy. Treatment of these rats with the somatostatin analogue octreotide seemed to upregulate in vivo receptor expression of somatostatin and vasoactive intestinal peptide more effectively than 13-cis retinoic acid. In conclusion, somatostatin in neuroblastoma is associated with differentiation to benign ganglioneuromas in vivo and favourable outcome in advanced tumours. Furthermore, somatostatin receptor scintigraphy may identify tumours with high-affinity receptors in children that might benefit from targeted therapy using synthetic somatostatin analogues.

Comparison of technetium-99m-MIBI and technetium-99m-tetrofosmin uptake by musculoskeletal sarcomas

Technetium-99m-MIBI was initially developed for heart studies but it can also be used to depict tumors, predict multidrug resistance and evaluate chemotherapy. Recently, 99mTc-tetrofosmin, which exhibits similar physical properties, has been launched for heart studies. Tumor uptake and prediction of multidrug resistance have also been reported regarding the latter tracer. A comparison of these two tracers regarding the detectability of musculoskeletal sarcoma has been made.

METHODS

Twenty patients with musculoskeletal sarcoma of the extremities or pelvis underwent planar examination after the administration of 99mTc-MIBI and 99mTc-tetrofosmin with an interval of 2-7 days. The tumor activity was compared with one ipsilateral and one contralateral background region.

RESULTS

There was a small, but not significant, difference in favor of 99mTc-MIBI with regard to both background regions.

CONCLUSION

Technetium-99m-MIBI and 99mTc-tetrofosmin can both be used to visualize musculoskeletal sarcomas. The choice may depend on which agent is used routinely for myocardial studies in the laboratory.

Activity in the gastrointestinal tract after administration of bone-seeking radiopharmaceuticals. Experimental studies in mice

PURPOSE

To test the possibility that (radio)activity of non-pertechnetate nature is excreted into the gastrointestinal tract at bone scintigraphy.

MATERIAL AND METHODS

The distribution of a bone-seeking radiopharmaceutical (99mTc-HDP) was studied in an experimental mouse system by dissecting different organs and assessing their activity with a gamma-counter.

RESULTS

A comparison of the activity of the submandibular glands, which are assumed to accumulate only pertechnetate, and the gastrointestinal tract showed that a significant fraction of the activity excreted into the gastrointestinal tract did not consist of pertechnetate. Part of the excretion took place in the stomach. It was not connected to a specific bone-seeking agent or 99Mo/99mTc generator. Nor did it increase with time between make-up and injection. The excretion of the non-pertechnetate activity was reduced by cimetidine and omeprazole. These gastric-secretion blocking drugs did not reduce excretion of pertechnetate or significantly affect the general distribution of the radiopharmaceutical.

CONCLUSION

There is a significant excretion of non-pertechnetate activity in the gastrointestinal tract. Part of this may be caused by excretion of the undegraded radiopharmaceutical by the stomach mucosa.

Accumulation of 99mTc-MIBI in bone marrow

99mTc-MIBI (Sestamibi) was originally developed for myocardial perfusion studies. The agent also may be used for the depiction and characterization of tumors. Performing such examinations has shown uptake in skeletal structures in several patients suggesting bone engagement of the disease which later was excluded. Retrospective evaluation of 44 examinations with 99mTc-MIBI performed in order to localize diseased parathyroid in patients with suspected hyperparathyroidism showed skeletal activity in 21 (48%) patients. Although these patients represent a selected group, the observation indicates a mechanism for skeletal accumulation of this radiopharmaceutical. Evaluation of another 13 normocalcemic patients undergoing whole-body registration for malignancy staging or to assess lower extremity ischemia with 99mTc-MIBI showed skeletal activity in 6 (46%) patients. Complementary mouse experiments confirmed skeletal uptake of 99mTc-MIBI, where most of the activity is taken up by the red bone marrow. It is concluded that homogeneous, diffuse weak skeletal activity at examination with 99mTc-MIBI is a normal finding and does not indicate malignancy.

Sweat glands accumulate Tc-99m MIBI

Tc-99m MIBI, which was originally developed for myocardial perfusion studies, may also be used for depiction and characterization of tumors. Forty-one patients with suspected hyperparathyroidism were examined with Tc-99m MIBI to localize a parathyroid adenoma or hyperplasia. In 19 of these patients (46%), bilateral symmetrical activity corresponding to the large deep apocrine sweat glands of the axillae was present. Sweat gland activity was not correlated with serum calcium levels. Although these patients may represent a selected group, the observation is clinically relevant regardless of its reason or mechanism. It is important also to be aware of this cause for activity in the axilla when assessing lymph node involvement in breast cancer patients using Tc-99m MIBI.

Characterization of beta-lactam-resistant Klebsiella oxytoca isolated in a neonatal intensive care unit

The occurrence of Klebsiella oxytoca resistant to ampicillin, piperacillin, aztreonam and cefuroxime in a neonatal intensive care unit, including two cases of septicemia, was shown to consist of a spread on three consecutive occasions caused by three different biochemical Klebsiella oxytoca phenotypes. All isolates, except six surface isolates from one infant belonging to phenotype 1, were sensitive to cefotaxime (MIC 0.5-4 mg/l) and ceftazidime (MIC 0.25-1 mg/l). Isolates of phenotypes 1 and 2 produced a beta-lactamase with an isoelectric point of 5.5 and isolates of phenotype 3, a beta-lactamase with an isoelectric point of 7.9. The beta-lactamases of all three phenotypes hydrolysed benzylpenicillin and more slowly cephalothin. All phenotype 1 isolates carried a 2.9 Md plasmid and most isolates also a 36 Md plasmid. All phenotype 2 isolates carried a 4.8 Md plasmid and one isolate also a 30 Md plasmid. The phenotype 3 isolates carried only one 85 Md plasmid.

In vitro cytotoxic properties of plasma samples from uremic patients

The effect of uremic plasma on the growth of cultured cells was compared to that of control and of nonuremic plasma. Multiplication of D98 and 3T3 cells was measured by cell counting and by 3H-Thymidine incorporation. Uremic plasma was taken from severely uremic children (plasma creat. greater than 0.45 mM) and from hemodialyzed (HD) patients; plasma samples from HD patients were obtained at the beginning and the end of dialysis sessions. The 3H-Thymidine incorporation in the presence of uremic plasma (3665 +/- 520 cpm, n - 23) was lower than in the presence of control plasma (7700 +/- 1.080 cpm, n = 14) (P less than 0.01). The rate of 3H-Thymidine incorporation decreased regularly in the presence of increasing amounts of uremic plasma. 3H-Thymidine incorporation in post dialysis plasma was greater than in predialysis plasma (3902 +/- 664 cpm vs 9430 +/- 1540 cpm, n = 8) (P less than 0.01). To investigate the properties of the cytotoxic material, studies were performed with plasma ultrafiltrate (UF) and ultrafiltrate fractions obtained by G-15 Sepadex filtration. Uremic UF and fractions displayed no cytotoxic properties when cultured alone. Preincubation of uremic UF and the "middle molecular" fraction with control plasma restored a cytotoxic effect which, for total ultrafiltrate, was similar to that observed with uremic plasma. Thus, uremic plasma displays cytotoxic properties related to ultrafiltrable molecules which are not cytotoxic by themseleves but which are cytotoxic in the presence of plasma macromolecules.