Sources of performance variability in deep learning-based polyp detection

PURPOSE

Validation metrics are a key prerequisite for the reliable tracking of scientific progress and for deciding on the potential clinical translation of methods. While recent initiatives aim to develop comprehensive theoretical frameworks for understanding metric-related pitfalls in image analysis problems, there is a lack of experimental evidence on the concrete effects of common and rare pitfalls on specific applications. We address this gap in the literature in the context of colon cancer screening.

METHODS

Our contribution is twofold. Firstly, we present the winning solution of the Endoscopy Computer Vision Challenge on colon cancer detection, conducted in conjunction with the IEEE International Symposium on Biomedical Imaging 2022. Secondly, we demonstrate the sensitivity of commonly used metrics to a range of hyperparameters as well as the consequences of poor metric choices.

RESULTS

Based on comprehensive validation studies performed with patient data from six clinical centers, we found all commonly applied object detection metrics to be subject to high inter-center variability. Furthermore, our results clearly demonstrate that the adaptation of standard hyperparameters used in the computer vision community does not generally lead to the clinically most plausible results. Finally, we present localization criteria that correspond well to clinical relevance.

CONCLUSION

We conclude from our study that (1) performance results in polyp detection are highly sensitive to various design choices, (2) common metric configurations do not reflect the clinical need and rely on suboptimal hyperparameters and (3) comparison of performance across datasets can be largely misleading. Our work could be a first step towards reconsidering common validation strategies in deep learning-based colonoscopy and beyond.

Study of the effect of photon self-absorption on the detection efficiency of HPGe detector in measurements of an activated uranium sample

The photon self-absorption effect of uranium on the full-energy peak (FEP) efficiency calibration of high purity germanium (HPGe) detector was studied as a function of energy using an activated uranium sample has a thickness of 1 mm. The absolute efficiencies of the detector were obtained with the use of gamma standard sources and gamma rays of radionuclides created by irradiating the uranium sample with secondary neutrons. The measurements were carried out with the use of a Planar HPGe detector. MCNP simulation code was used to verify the experimental results. The comparison of the empirical results with the simulation results showed a good agreement. To interpret the efficiencies, the reaction rates were calculated using two methods: (1) - the use of the efficiency curve from the standard sources combined with the self-absorption correction of the uranium material and (2) - the use of the efficiency curve obtained from gamma rays in the sample.

Abstract 312: Redirecting T cells to tumor targets with functionally diverse CD3-binding antibodies

Bispecific antibodies that redirect cancer-killing T cells towards tumors are promising next-generation cancer therapies. While there are hundreds of T cell engagers (TCEs) in development, there is only one approved and marketed CD3-binding TCE. The high rate of attrition is largely attributable to dose-limiting toxicities, including cytokine release syndrome, due in part to the small pool of high affinity CD3-binding antibodies that are commonly used. The discovery of safe and effective TCEs is limited because diverse panels of parental CD3 antibodies are hard to produce, the pairing of parentals is hard to perfect, and the sheer complexity and volume of data is hard to action. In this study, we will present a panel of functionally diverse, fully human CD3-binding parental antibodies. We will present data characterizing the diversity of our panel across multiple parameters, including sequence diversity, CD3 affinity, epitope binding, T cell activation, cytokine release, and tumor cell killing. Using OrthoMab࣪, our clinically-validated bispecific engineering platform, allows this panel to be tested with a series of tumor-associated antigens (TAAs) in a matrix format. Results from high-throughput production and characterization of bispecific antibodies will be presented. These multidimensional datasets of TCE composition and function allow for the identification of pairs that are optimal candidates for clinical development. This work will show how the diversity of our CD3-binding panel, combined with a robust bispecific protein engineering technology, can be used to quickly assess large and diverse TAA-binding panels discovered through our technology stack. An integrated workflow that doubles the data with diverse panels of parentals, assembles stable, safe, and manufacturable TCEs, and visualizes multidimensional datasets are critical to successfully identifying lead therapeutic candidates to bring the next generation of cancer therapies to patients sooner.

Citation Format: Lindsay DeVorkin, Tim M. Jacobs, Raffi Tonikian, Karine Hervé, Kate Caldwell, Yuri Hwang, Cristina Faralla, Wei Wei, Katherine J. Lam, Harveer Dhupar, Tran NT Tran, Melissa Cid, Lena M. Bolten, Tova Pinsky, Kush Dalal, Kevin A. Heyries, Bryan C. Barnhart. Redirecting T cells to tumor targets with functionally diverse CD3-binding antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 312.

Influence of type of dwelling on the prevalence of chronic respiratory diseases in Ho Chi Minh City, Viet Nam

SETTING and OBJECTIVE: Exposure to pollutants is related to the type of dwelling inhabited. Besides tobacco smoke, indoor air pollution is a significant risk factor for chronic respiratory disease (CRD). The prevalence of CRD by type of dwelling was studied in Ho Chi Minh City, Viet Nam.DESIGN: A total of 1561 people living in four type of dwellings were enrolled. Information on respiratory health, lung function, dwelling characteristics and sources of indoor pollution was obtained using a symptom and demographics questionnaire and spirometry. The two main respiratory health outcomes were clinical chronic CRD (CCRD) and chronic obstructive respiratory disease (CORD) (forced expiratory volume in 1 sec/forced vital capacity <0.7). We used binary logistic regression adjusted for age, sex, time spent at home, smoking status, certain occupational exposures, previous tuberculosis, presence of pets, rats or cockroaches at home, wall dampness, biofuel use and use of airconditioning.RESULTS: The prevalence of CCRD (24.3%) and CORD (5.3%) in the type of dwellings studied were not similar (χ² P < 0.0001). CCRD and CORD prevalence was similar in tube houses and apartments. Compared to people living in apartments, those living in rental single rooms had a 46% higher risk of developing CCRD. The odds ratio of having CORD in people living in rental single rooms and in rural houses were respectively 4.64 (95%CI 1.97-10.5) and 2.99 (95%CI 1.21-7.37).CONCLUSION: Type of dwelling was associated with CCRD and CORD morbidity.

Effect of the stiffness of bone substitutes on the biomechanical behaviour of femur for core decompression

Core decompression is the most common procedure for treatment of the early stages of osteonecrosis of the femoral head. The purpose of this study was to compare the biomechanical performance of four different bone graft substitutes combined with core decompression. Subject-specific finite element models generated from computed tomography (CT) scan data were used for a comprehensive analysis. Two different contact conditions were simulated representing states of osseointegration at the interface. Our results showed that the use of a low-stiffness bone substitute did not increase the risk of femoral fracture in the early postoperative phase, but resulted in less micromotion and interfacial stresses than high-stiffness bone substitutes.

Alterations of insulin-like growth factor-1 receptor gene copy number and protein expression are common in non-small cell lung cancer

Aims

Insulin-like growth factor-1 receptor (IGF1R) is a tyrosine kinase membrane receptor involved in tumourigenesis that may be a potential therapeutic target. We aimed to investigate the incidence and prognostic significance of alterations in IGF1R copy number, and IGF1R protein expression in resected primary non-small cell lung cancer (NSCLC), and lymph node metastases.

Methods

IGF1R gene copy number status was evaluated by chromogenic silver in situ hybridisation and IGF1R protein expression was evaluated by immunohistochemistry in tissue microarray sections from a retrospective cohort of 309 surgically resected NSCLCs and results were compared with clinicopathological features, including EGFR and KRAS mutational status and patient survival.

Results

IGF1R gene copy number status was positive (high polysomy or amplification) in 29.2% of NSCLC, and 12.1% exhibited IGF1R gene amplification. High IGF1R expression was found in 28.3%. There was a modest correlation between IGF1R gene copy number and protein expression (r=0.2, p<0.05). Alterations of IGF1R gene copy number and protein expression in primary tumours were significantly associated with alterations in lymph node metastases (p<0.01). High IGF1R gene copy number and protein expression was significantly higher in squamous cell carcinomas (SCC) compared with other subtypes of NSCLC (p<0.05). There were no other associations between IGF1R status and other clinicopathological features including patient age, gender, smoking status, tumour size, stage, grade, EGFR or KRAS mutational status or overall survival.

Conclusions

High IGF1R gene copy number and protein overexpression are frequent in NSCLC, particularly in SCCs, but they are not prognostically relevant.

Experimental and computational studies on the femoral fracture risk for advanced core decompression

BACKGROUND

Two questions are often addressed by orthopedists relating to core decompression procedure: 1) Is the core decompression procedure associated with a considerable lack of structural support of the bone? and 2) Is there an optimal region for the surgical entrance point for which the fracture risk would be lowest? As bioresorbable bone substitutes become more and more common and core decompression has been described in combination with them, the current study takes this into account.

METHODS

Finite element model of a femur treated by core decompression with bone substitute was simulated and analyzed. In-vitro compression testing of femora was used to confirm finite element results.

FINDINGS

The results showed that for core decompression with standard drilling in combination with artificial bone substitute refilling, daily activities (normal walking and walking downstairs) are not risky for femoral fracture. The femoral fracture risk increased successively when the entrance point is located further distal. The critical value of the deviation of the entrance point to a more distal part is about 20mm.

INTERPRETATION

The study findings demonstrate that optimal entrance point should locate on the proximal subtrochanteric region in order to reduce the subtrochanteric fracture risk. Furthermore the consistent results of finite element and in-vitro testing imply that the simulations are sufficient.

A population-based binational register for monitoring long-term outcome and possible disease concordance among blood donors and recipients

BACKGROUND AND OBJECTIVES

Even with appropriate donor deferrals and advanced screening tests, the risk of disease transmission through blood transfusion cannot be completely disregarded. Efficient monitoring of possible disease transmission between blood donors and recipients should be an important component of a comprehensive haemovigilance system.

MATERIALS AND METHODS

We assembled the Scandinavian Donations and Transfusions (SCANDAT) database, with data on virtually all blood donors and recipients who have been registered at least once in any of the computerized local blood bank databases in Sweden and Denmark since the start of computerized registration in 1966. The records of these individuals, with their entire computerized donation and/or transfusion histories and all donor-component-recipient connections, were linked to nationwide population and health registers to attain essentially complete follow-up for up to 36 years regarding reproduction, hospital morbidity, cancer, and death.

RESULTS

After data cleaning, the database contained 1,134,290 blood donors who contributed 15,091,280 records of donations and 1,311,079 recipients who received 11,693,844 transfusions. The data quality in the existing data sources was satisfactory. From the data obtained from local blood banks, 4.6%, 1.6%, and 6.4% of the person, donation, and transfusion records, respectively, had to be discarded after review of the legitimacy of recorded values, and comparisons with independent, external databases.

CONCLUSION

It is possible to use existing computerized data, collected in routine health care, in haemovigilance systems for monitoring long-term outcome and disease concordance in blood donors and transfusion recipients.

Phospholipid molecular species, beta-oxidation, desaturation and elongation of fatty acids in Atlantic salmon hepatocytes: effects of temperature and 3-thia fatty acids

We have investigated the effects of a 3-thia fatty acid (TTA) and of temperature on the fatty acid (FA) metabolism of Atlantic salmon (Salmo salar). One experiment investigated the activity of the peroxisomal beta-oxidation enzyme, acyl-CoA oxidase (ACO), and the incorporation of TTA into phospholipid (PL) molecular species. Salmon hepatocytes in culture were incubated either without TTA (control(spades)) or with 0.8 mM TTA (TTA(spades)) in a short term (48 h) temperature study at 5 degrees C and at 12 degrees C. TTA was incorporated into the four PL classes studied: phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidylserine (PS). TTA was preferentially esterified with 18:1, 16:1, 20:4 and 22:6 in the PLs. Hepatocytes incubated with TTA had higher ACO activity at 5 degrees C than at 12 degrees C. In a second experiment salmon were fed a diet based on fish meal-fish oil without any TTA added (control) or a fish meal-fish oil diet supplemented with 0.6% TTA for 8 weeks at 12 degrees C and 20 weeks at 5 degrees C. At the end of the feeding trial, hepatocytes from fish acclimated to high or low temperatures were isolated from both dietary groups and incubated with either [1-(14)C]18:1 n-9 or [1-(14)C]20:4 n-3 at 5 degrees C or 12 degrees C. Radiolabelled 18:1 n-9 was mainly esterified into neutral lipids (NL), whereas [1-(14)C]20:4 n-3 was mainly esterified into PL at both temperatures. The rate of elongation of [1-(14)C]18:1 n-9 to 20:1 n-9 was twice as high in hepatocytes from fish fed the control diet than it was in hepatocytes from fish fed the TTA diet, at both temperatures. The amount of [1-(14)C]20:4 n-3 converted to 22:6 n-3 was approximately the same in hepatocytes from the two dietary groups, but there was a tendency to higher production of 22:6 n-3 at the lower temperature. Oxidation of [1-(14)C]18:1 n-9 to acid soluble products (ASP) and CO(2) was approximately 10-fold greater in hepatocytes kept at 5 degrees C than in those kept at 12 degrees C and the main oxidation products formed were acetate, oxaloacetate and malate.

Beta-oxidation, esterification, and secretion of radiolabeled fatty acids in cultivated Atlantic salmon skeletal muscle cells

The white muscle of Atlantic salmon metabolizes FA with different chain lengths and different saturations at different rates, but few details are available on the processes involved or the products formed. We have investigated how multinucleated muscle cells (myotubes) in culture metabolize [1-(14)C]8:0, [1-(14)C]18:1n-9, and [1-(14)C]20:5n-3. The myotubes were formed by the differentiation of isolated myosatellite cells from the white skeletal muscle of salmon fry. Almost all (98%) of the [1-(14)C]8:0 substrate was oxidized to acid-soluble products (ASP) and (14)CO2 after 48 h of incubation, whereas only approximately 50% of the [1-(14)C]18:1n-9 and [1-(14)C]20:5n-3 substrates were oxidized. However, only one cycle of beta-oxidation was measured by the method used. For all three substrates, the main ASP were acetate and a combined fraction of oxaloacetate and malate. Nearly twice as much radioactivity from the [1-(14)C]20:5n-3 substrate was found in the cellular lipids as radioactivity from [1-(14)C]18:1n-9, indicating that [1-(14)C]20:5n-3 was taken up into muscle cells more rapidly than [1-(14)C]18:1n-9. Approximately 10% of the added [1-(14)C]20:5n-3 substrate and 5% of the added [1-(14)C]18:1n-9 substrate was secreted from the muscle cells into the culture media as esterified lipids. Immunocytochemical staining showed that the cells synthesized apolipoprotein A-I. Differentiated muscle cells also expressed peroxisome proliferator-activated receptor alpha (PPARalpha) and PPARbeta, two transcription factors that are involved in regulating beta-oxidation.

Studies on the transport of acetyl groups from peroxisomes to mitochondria in isolated liver cells oxidizing the polyunsaturated fatty acid 22:4n-6

The oxidation of the fatty acid [1-(14)C]22:4n-6 was studied in isolated hepatocytes. Labeled acetate was the main acid soluble product identified by HPLC after short incubation periods. At low substrate concentrations and longer incubations [(14)C]acetate was gradually replaced by labeled beta-hydroxybutyrate, acetoacetate and oxaloacetate/malate. Preincubation with 2-tetradecylglycidic acid (TDGA), an inhibitor of mitochondrial fatty acid oxidation, did not reduce the oxidation but acetate was the only product recovered. TDGA also strongly inhibited the metabolism of added [1-(14)C]acetate to mitochondrial oxidation products. During the preparation procedure of hepatocytes the cellular L-carnitine concentration was decreased but it was restored after preincubation with L-carnitine. With low [1-(14)C]22:4n-6, concentrating a low level of [(14)C]acetate and high levels of labeled mitochondrial oxidation products were recovered after preincubation with L-carnitine. A small amount of [(14)C]acetylcarnitine was also detected under this incubation condition. The results suggest that a significant part of labeled acetyl groups from the peroxisomal oxidation of [1-(14)C]22:4n-6 is transported to the mitochondria as free acetate. Moreover, the results also suggest that L-carnitine at physiological concentrations may facilitate the transport of part of the acetyl groups from peroxisomes to mitochondria as acetylcarnitine. However, the possibility that an increased cellular L-carnitine concentration may stimulate oxidation of [1-(14)C]22:4n-6 in mitochondria could not be excluded.

Metabolism of very long chain polyunsaturated fatty acids in isolated rat germ cells

Which cell type is responsible for the high levels of very long chain polyunsaturated fatty acids in testis and whether this fatty acid pattern is a result of a local synthesis are not presently known. In this study, fatty acid conversion from 20:4n-6 to 22:5n-6 and from 20:5n-3 to 22:6n-3 was investigated in isolated rat germ cells incubated with [1-14C]-labeled fatty acids. The germ cells elongated the fatty acids from 20- to 22-carbon atoms and from 22- to 24-carbon atoms but had a low delta6 desaturation activity. Thus, little [14C]22:5n-6 and [14C]22:6n-3 were synthesized. When Sertoli cells were incubated with [1-14C]20:5n-3 for 24 h, an active fatty acid elongation and desaturation were observed. In vivo germ cells normally have a higher content of 22:5n-6 or 22:6n-3 than Sertoli cells. An eventual transport of essential fatty acids from Sertoli cells to germ cells was thus studied. Different co-culture systems were used in which germ cells were on one side of a filter and Sertoli cells on the opposite side. When isolated pachytene spermatocytes or round spermatids were added to the opposite side of a semipermeable filter, approximately 1 nmol [14C]22:6n-3 crossed the filter. Little of this was esterified in the germ cells. Similarly, in using [1-14C]20:4n-6 in identical experiments, very little [14C]22:5n-6 was esterified in germ cells on the opposite side of the filter. Although the very active synthesis of 22:5n-6 and 22:6n-3 observed in Sertoli cells suggests a transport of these compounds to germ cells, this was not experimentally determined.

Studies on the metabolism of essential fatty acids in isolated human testicular cells

The essential fatty acid 22:6(n-3) is a minor component of the Western diet, but a major fatty acid in human testis and semen. In mature spermatozoa, the physical and fusogenic properties of the plasma membrane are probably influenced by its particular fatty acid composition. In this study, the synthesis of 22:6(n-3) and 22:5(n-6) was investigated in isolated human testicular cells. [1-(14)C]20:4(n-6), [1-(14)C]20:5(n-3), [1-(14)C]22:4(n-6) and [1-(14)C]22:5(n-3) were incubated in a 'crude' cell suspension (consisting of a mixture of the cells in the seminiferous tubule), and in fractionated pachytene spermatocytes and round spermatids. The esterification of fatty acids in lipid and phospholipid classes and the fatty acid chain elongation and desaturation were measured. The crude cell suspension metabolized the fatty acids more actively than did the fractionated germ cell suspension, indicating that types of cell other than the germ cells are important for fatty acid elongation and desaturation and thus the production of 22:6(n-3). This finding is in agreement with previous results in rats that indicated that the Sertoli cells are the most important type of cell for the metabolism of essential fatty acids in the testis. Some [1-(14)C]20:5(n-3) was elongated to [(14)C]22:5(n-3) in the fractionated germ cells, but very little was elongated further to [(14)C]24:5(n-3),possibly restricting the formation of [(14)C]22:6(n-3). In the fractionated germ cells, the fatty acid substrates were recovered primarily in the phospholipid fraction, indicating an incorporation in the membranes, whereas in the crude cells, more substrates were esterified in the triacylglycerol fraction. In the phospholipids, more radioactivity was recovered in phosphatidylcholine than in phosphatidylethanolamine and more radioactivity was recovered in phosphatidylethanolamine than in phosphatidylinositol or phosphatidylserine.

Differences in the conversion of the polyunsaturated fatty acids [1-(14)C]22:4(n-6) and [1-(14)C]22:5(n-3) to [(14)C]22:5(n-6) and [(14)C]22:6(n-3) in isolated rat hepatocytes

The reasons why most cellular lipids preferentially accumulate 22:6(n-3) rather than 22:5(n-6) are poorly understood. In the present work the metabolisms of the precursor fatty acids, [1-(14)C]20:4(n-6), [1-(14)C]22:4(n-6) versus [1-(14)C]20:5(n-3), [1-(14)C]22:5(n-3) in isolated rat hepatocytes were compared. The addition of lactate and L-decanoylcarnitine increased the formation of [(14)C]24 fatty acid intermediates and the final products, [(14)C]22:5(n-6) and [(14)C]22:6(n-3). In the absence of lactate and L-decanoylcarnitine, no [(14)C]24 fatty acids and [(14)C]22:5(n-6) were detected when [1-(14)C]22:4(n-6) was the substrate, whereas small amounts of the added [1-(14)C]22:5(n-3) was converted to [(14)C]22:6(n-3). Lactate reduced the oxidation of [1-(14)C]22:4(n-6) and [1-(14)C]22:5(n-3) while L-decanoylcarnitine did not. No significant differences between the total oxidation or esterification of the two substrates were observed. By fasting and fructose refeeding the amounts of [(14)C]24:4(n-6) and [(14)C]24:5(n-3) were increased by 2.5- and 4-fold, respectively. However, the levels of [(14)C]22:5(n-6) and [(14)C]22:6(n-3) were similar in hepatocytes from fasted and refed versus fed rats. With hepatocytes from rats fed a fat free diet the levels of [(14)C]24 fatty acid intermediates were low while the further conversion of the n-6 and n-3 substrates was high and more equal, approx. 33% of [1-(14)C]22:4(n-6) was converted to [(14)C]22:5(n-6) and 43% of [1-(14)C]22:5(n-3) was converted to [(14)C]22:6(n-3). The moderate differences found in the conversion of [1-(14)C]22:4(n-6) versus [1-(14)C]22:5(n-3) to [(14)C]22:5(n-6) and [(14)C]22:6(n-3), respectively, and the equal rates of oxidation of the two substrates could thus not explain the abundance of 22:6(n-3) versus the near absence of 22:5(n-6) in cellular membranes.

Identification of genomic imbalances in gastric MALT lymphoma using arbitrarily primed PCR DNA fingerprinting

Arbitrarily primed PCR (AP-PCR) is a unique method to identify the cancer cell specific losses and gains of chromosomal regions by targeting specific genes or chromosomal segments. In the present study, introducing the AP-PCR technique with a single primer, we have ascertained the gains and losses of DNA fingerprints in 15 MALT lymphoma samples. Out of 15 prominent DNA fingerprints, the signal intensity of two fingerprints, labeled bands G and I, were significantly lower in 40 and 50% of tumors as compared to adjacent normal DNA fingerprints, respectively. Similarly, gains of signal intensity of DNA fingerprints (bands A and C) were detected in 13% of tumor samples studied. Variations in signal intensities were also found in other bands within a few samples. Although, the functional importance of these bands is unknown, this study indicates that the AP-PCR generated under or over amplified DNA fingerprints may participate during the progression of MALT lymphoma in human stomach. Moreover, these studies also suggest that the AP-PCR technique, with different primers, can be utilized for the determination of new chromosomal segments in MALT lymphoma samples that can be used for the identification of these diseases.

Noninvasive measurement of microvascular leakage in patients with dengue hemorrhagic fever

Dengue shock syndrome (DSS) is a potentially lethal complication of dengue virus infection associated with hypotension and leakage of plasma water into the extravascular space. To determine whether the underlying pathophysiology of DSS is distinct from that in milder forms of the disease, we assessed microvascular permeability, by use of strain gauge plethysmography, in Vietnamese children with DSS (n=19), or dengue hemorrhagic fever (DHF) without shock (n=16), and in healthy control children (n=15). At admission and after fluid resuscitation, the mean coefficient of microvascular permeability (K(f)) for the patients with dengue was approximately 50% higher than that for the control patients (P=.02). There was no significant difference in K(f) between the 2 groups of patients with dengue; this suggests the same underlying pathophysiology. We hypothesize that in patients with DSS, the fluctuations in K(f) are larger than those in patients with DHF, which leads to short-lived peaks of markedly increased microvascular permeability and consequent hemodynamic shock.

The etiology of bacterial pneumonia and meningitis in Vietnam

BACKGROUND

To date no studies on the incidence of Haemophilus influenzae type b (Hib) disease, Hib carrier rates in infants and children or the proportion of bacterial meningitis cases caused by Hib in Vietnam have been performed. The availability of safe and highly effective Hib vaccines makes such information important.

METHODS

The bacterial etiology of a sample of infants and children with pneumonia and meningitis seen at Pediatric Hospital No. 1 in Ho Chi Minh City was studied by culture and latex agglutination of blood, cerebrospinal fluid, urine and pleural fluid. The carriage rate of pneumococci and Hib was studied in a sample of outpatient children.

RESULTS

Hib caused 53% of 34 culture-proven bacterial meningitis cases and pneumococci caused 18%. Of 31 meningitis cases diagnosed by latex agglutination, 39% were caused by Hib and 55% by pneumococci. Ninety percent of cases of Hib meningitis occurred in children <1 year of age. Fifty percent of meningitis cases were associated with acute respiratory infection. In 213 bacteremic pneumonia cases 92.5% of blood cultures grew Streptococcus pneumoniae and only 1% grew Hib. The carrier rate of Hib in outpatients <5 years of age with upper respiratory tract infection increased from 2% to 7.6% between 1993 and 1996.

CONCLUSION

Hib is the most frequent cause of meningitis in infants and children admitted to hospitals in South Vietnam. Ninety percent of Hib meningitis cases occur in patients < 1 year of age. Bacteremic Hib pneumonia in Vietnam is rare. The results suggest that Hib is the major cause of meningitis in Vietnam but do not permit conclusions regarding its true incidence. The carrier rate of Hib in children <5 years of age in Vietnam has increased to approximately 7% since 1993.

Secretion of ferritin by rat hepatoma cells and its regulation by inflammatory cytokines and iron

The possibility that serum ferritin is a secreted protein and an acute phase reactant regulated by inflammatory hormones and iron was examined in a hepatic cell line that secretes plasma proteins. Differentiated rat hepatoma cells released albumin and ferritin into the medium, as determined by rocket immunoelectrophoresis and isolation of ferritin by standard procedures plus immunoaffinity chromatography, following labeling with radioactive amino acid. Administration of interleukin-1-beta (IL-1) or tumor necrosis factor-alpha (TNF) doubled the amounts of ferritin released into the medium over 24 and 48 hours. Together, the cytokines had more than an additive effect. Albumin secretion was diminished by IL-1, but not TNF. Iron, administered as an iron dextran complex or as a 1:1 chelate with nitrilotriacetate (Fe-NTA), also enhanced ferritin release, but had no effect on albumin. Intracellular ferritin concentrations did not change significantly with cytokine treatment, but increased in response to iron. With or without treatments, release of ferritin and albumin from cells into the medium was inhibited by brefeldin A, an inhibitor of Golgi function. The effect of each of the cytokines and of iron on ferritin and albumin was also blocked by dichlorofuranosylbenzimidazole (DRB), an inhibitor of transcription. The stimulatory effect of Fe-NTA on ferritin secretion was diminished by TNF, and this was partially counteracted by IL-1, indicating additional regulatory complexity. These results show for the first time that hepatic cells secrete ferritin, that this ferritin secretion is regulated by iron and inflammatory cytokines, and that the mechanisms of regulation differ from those for intracellular ferritin. The results would explain why serum ferritin increases in inflammation or when iron flux is enhanced.

Nuclear entry, oligomerization, and DNA binding of the Drosophila heat shock transcription factor are regulated by a unique nuclear localization sequence

In normally growing Drosophila cultured cells the Drosophila heat shock transcription factor (dHSF) is localized in the cytosol and translocates into the nucleus after heat shock. In the cytosol of nonshocked cells, the dHSF is present as a monomer that cannot bind DNA. Upon stress, the dHSF enters the nucleus where it is observed to be a trimer. A novel nuclear localization sequence (NLS) in the dHSF was found to be responsible for stress-dependent nuclear entry. Deletion of the NLS prevents nuclear entry, as expected, yet surprisingly also allows constitutive oligomerization and DNA binding in the cytosol. Further analysis of the NLS by mutagenesis suggests that the two functions of nuclear entry and oligomerization are separable in that distinct residues present in the NLS are responsible for each. Mutations in certain basic residues completely block nuclear entry, as expected for a constitutive NLS. In addition, two residues were found in the NLS that, when altered, allowed constitutive nuclear entry of dHSF independent of stress. These residues may interact with a putative cellular component or possibly other domains of the HSF to prevent nuclear entry in normally growing cells. The NLS can also function autonomously to target a beta-galactosidase fusion protein into the nucleus in a heat shock-dependent fashion.

Comparison of artemisinin suppositories, intramuscular artesunate and intravenous quinine for the treatment of severe childhood malaria

Severe malaria remains a major cause of mortality and morbidity for children living in many tropical regions. With the emergence of strains of Plasmodium falciparum resistant to both chloroquine and quinine, alternative antimalarial agents are required. The artemisinin group of compounds are rapidly effective in severe disease when given by intramuscular or intravenous injection. However, these routes of administration are not always available in rural areas. In an open, randomized comparison 109 Vietnamese children, aged between 3 months and 14 years, with severe P.falciparum malaria, were allocated at random to receive artemisinin suppositories followed by mefloquine (n = 37), intramuscular artesunate followed by mefloquine (n = 37), or intravenous quinine followed by pyrimethamine/sulfadoxine (n = 35). There were 9 deaths: 2 artemisinin, 4 artesunate and 5 quinine-treated children. There was no difference in fever clearance time, coma recovery, or length of hospital stay among the 3 groups. However, parasite clearance times were significantly faster in artemisinin and artesunate-treated patients than in those who received quinine (P < 0.0001). Both artemisinin and artesunate were very well tolerated, but children receiving these drugs had lower peripheral reticulocyte counts by day 5 of treatment than those in the quinine group (P = 0.011). No other adverse effect or toxicity was found. There was no treatment failure in these 2 groups, but 4 patients in the quinine group failed to clear their parasites within 7 d of starting treatment and required alternative antimalarial therapy. Artemisinin suppositories are easy to administer, cheap, and very effective for treating children with severe malaria. In rural areas where medical facilities are lacking these drugs will allow antimalarial therapy to be instituted earlier in the course of the disease and may therefore save lives.

Pharmacokinetics of oral artesunate in children with moderately severe Plasmodium falciparum malaria

The pharmacokinetic properties of oral artesunate (3 mg/kg) were determined in 10 Vietnamese children, aged from 6 to 15 years, with acute falciparum malaria of moderate severity. Plasma concentrations were measured using a bioassay and expressed in terms of antimalarial activity equivalent to dihydroartemisinin, the principal biologically active metabolite. Oral artesunate was absorbed rapidly with a mean time to peak plasma bioactivity of 1.7 h (95% confidence interval [95% CI] 0.8-2.6). There was wide variation in peak plasma concentrations with a mean value equivalent to 664 ng of dihydroartemisinin/mL (95% CI 387-9410, range 179-1395) and a four-fold variation in the area under the plasma concentration-time curves. Elimination from plasma was rapid with a mean (95% CI) half-life of 1.0 h (95% CI 0.8-1.4). Plasma antimalarial levels were below the limit of detection in all cases by 12 h, despite the relatively high dose of artesunate used. Oral artesunate is rapidly absorbed and rapidly eliminated in children with moderately severe malaria but there is considerable variation between individuals.

Serum ferritin: does it differ from tissue ferritin?

Serum ferritin isolated from the horse was structurally compared with horse spleen ferritin and was found to differ markedly in molecular weight, iron content, carbohydrate, subunit size and amino acid sequence. The results are summarized and initial results obtained with candidate clones of pieces of two serum ferritin subunits are described.

Malignant rhabdoid tumor. A study with two established cell lines

BACKGROUND

Malignant rhabdoid tumor (MRT), originally described as a rare renal sarcoma in childhood, has been known to express phenotypic diversity. In this study, unique characteristics of the MRT cells were investigated by using established cell lines.

METHODS

Immunocytochemical, ultrastructural, cytogenetic, and molecular (by polymerase chain reaction, PCR) analyses were done for two MRT cell lines, one of renal and one of extrarenal origin, before and after differentiation-induction with either 12-O-tetradecanoyl phorbol-13-acetate (TPA) or transretinoic acid (RA).

RESULTS

The proliferating cells in the original tumor tissues as well as in the established cell lines demonstrated neural, epithelial, and mesenchymal markers morphologically. Both cell lines had karyotypic abnormalities including chromosome 22q11.2. The cell line from the extrarenal MRT, Tm87-16, demonstrated distinct morphologic changes with neuroblastic differentiation and produced numerous neuritic processes after treatment with either TPA or RA. The cell line from the renal MRT, STM91-01, suggested schwannian differentiation but did not change morphologically after chemical induction. Both cell lines expressed c-myc, but did not express N-myc, MyoD1, tyrosine hydroxylase, or neural cell adhesion molecule (N-CAM). With PCR and immunocytochemical study, a high level of chromogranin expression was detected by the cells of Tm87-16 only after TPA induced differentiation.

CONCLUSIONS

MRT cells demonstrated diverse phenotype of neuro-ecto-mesenchymal differentiation. The results of this study suggest that MRT may be derived from a primitive pluripotential cell, such as neural crest or equivalent. MRT, therefore, might be categorized as one of the subsets of primitive neuroectodermal tumor.

Cytogenetic analysis of 39 pediatric central nervous system tumors

Consistent cytogenetic abnormalities have been described in many pediatric solid tumors, including Ewing's sarcoma, Wilms' tumor, and neuroblastoma. Similar analysis of pediatric central nervous system (CNS) tumors has been hampered by technical problems. We report chromosome results from 39 pediatric CNS tumors. Abnormalities of chromosome 17 were noted in 3 of 11 primitive neuroectodermal tumors (including i(17q) in 2 tumors), confirming data observed by other investigators. Cells from 2 of 11 primitive neuroectodermal tumors (PNET) exhibited loss or structural abnormalities involving chromosome 11. Loss or distal deletion of chromosome 7q was noted in cells from two PNETs. Because other investigators have shown loss of heterozygosity on 17p in about one-third of PNET, we propose that chromosome regions 7q and 11 are areas worthy of further study in pediatric PNET. Numerical abnormalities were noted in 6 of 21 astrocytomas. Hyperdiploidy was demonstrated in 1 of 4 pilocytic astrocytomas and pseudopolyploidy was demonstrated in 4 of 13 anaplastic astrocytomas. Structural chromosome abnormalities (translocations, deletions) were noted in 4 of 13 anaplastic astrocytomas. Complex structural anomalies were observed in one craniopharyngioma. A rhabdoid tumor of the brain exhibited multiple complex structural rearrangements but did not exhibit the monosomy 22 observed in some rhabdoid tumors. Hypodiploidy and loss of chromosome 22 were noted in a clinically aggressive meningioma, corroborating observations by other investigators.

Establishment of a rhabdoid tumor cell line with a specific chromosomal abnormality, 46,XY,t(11;22)(p15.5;q11.23)

The malignant rhabdoid tumor is a rare, poorly understood tumor which occurs primarily in children. The kidney is a frequent primary site of origin, but the tumor has arisen in other mesodermally derived tissues as well. Controversy exists regarding the embryonic origin of the rhabdoid tumor and recent histopathologic studies suggest that it may be of neuroepithelial origin. Our immunohistochemical and electron micrographic studies support this theory. No consistent chromosome abnormalities have been reported in this tumor and no cell lines are available for study. We have established and characterized the first rhabdoid tumor cell line. It possesses a specific chromosomal abnormality, 46,XY,t(11;22)(p15.5;q11.23). The translocation may provide an important clue to the pathogenesis of the tumor as well as an opportunity for further study of the involved chromosome regions.

Isolation, Amino-Acid Sequence, Synthesis and Biological Properties of Urotensin I from Hippoglossoides elassodon

Abstract A 41-residue urotensin I neuropeptide (H-UI) was isolated from urophyses of the marine teleost Hippoglossoides elassodon (the flathead sole). The peptide was recognized by its partial cross-reactivity in a radioimmunoassay developed for Catostomus (sucker) Ul (S-UI), and was purified by reversed-phase high-performance liquid chromatography. The amino-acid sequence was shown to be H-Ser-Glu-Glu-Pro-Pro-Met-Ser-lle-Asp-Leu-Thr-Phe-His-Met-Leu-Arg-Asn-Met-lle-His-Arg-Ala-Lys-Met-Glu-Gly-Glu-Arg-Glu-Gln-Ala-Leu-lle-Asn-Arg-Asn-Leu-Leu-Asp-Glu-Val-NH(2). H-UI is 66% homologous with S-UI and 63% homologous with Cyprinus (carp) Ul (C-UI). Like S- and C-UI, H-UI is about 50% homologous with the frog skin peptide sauvagine and with Catostomus and mammalian corticotropin-releasing factors. H-UI had similar vasodilatory effects in mammals, and similar adrenocorticotropin-releasing effects (in rat and goldfish) to S-UI, C-UI, sauvagine and the corticotropin-releasing factors, but had relatively low potency (e.g. 10% to 30% of the vasodilatory potency of S- and C-UI) in all the bioassay systems studied.

CRF, urotensin I, and sauvagine stimulate the release of POMC-derived peptides from goldfish neurointermediate lobe cells

In teleost fishes, the melanotropes of the neurointermediate lobe of the pituitary gland release numerous peptides--adrenocorticotropin (ACTH), melanotropin (MSH), lipotropin (LPH), corticotropin-like intermediate lobe peptide (CLIP), and endorphin--which are derived from the precursor molecule proopiomelanocortin. Superfused, isolated, dispersed goldfish neurointermediate lobe cell columns were used to investigate the release of immunoreactive (ir) alpha-MSH and ir ACTH from goldfish melanotropes. Stimulation of neurointermediate lobe cell columns with pulses of the structurally homologous peptides, Catostomus urotensin I (UI), ovine corticotropin-releasing factor (oCRF), or sauvagine, produced a significant increase in the concomitant release of ir alpha-MSH and ir ACTH. UI was two to three times as potent as ovine CRF or sauvagine. These studies suggest that CRF- and UI-like peptides stimulate the secretory activity of teleost melanotropes.

TRH stimulates the release of POMC-derived peptides from goldfish melanotropes

The release of immunoreactive (ir) alpha-MSH and ir ACTH from goldfish (Carassius auratus) melanotropes was investigated using superfused isolated dispersed neurointermediate lobe cell columns. Stimulation of neurointermediate lobe cell columns with pulses of TRH evoked dose-dependent increases in the concomitant release of ir alpha-MSH and ir ACTH. Reversed-phase high performance liquid chromatography (RP-HPLC) was used to characterize the alpha-MSH and ACTH immunoreactivities released from a neurointermediate cell column under spontaneous release conditions. Six peaks of ir alpha-MSH were revealed. Three of these peaks were identified as des-acetyl alpha-MSH, mono-acetyl alpha-MSH and di-acetyl alpha-MSH. Seven peaks of ir ACTH were revealed. Four of these peaks were tentatively identified as ACTH variants. These studies suggest that TRH stimulates the release of peptide hormones from teleost melanotropes and that the goldfish neurointermediate lobe in vitro releases numerous peptides derived from POMC.

The thyroid and hypoxic moderation of systemic hypertension in the spontaneously hypertensive rat

Surgically thyroidectomized (TX), sham-operated euthyroid (EU), or thyroidectomized with dietary hormone replacement (RPL), 8-week-old male spontaneously hypertensive rats were subjected to 4 weeks of either of two altitude treatments: normoxia (N; lab altitude = 1520 m) or hypobaric hypoxia (H; simulated altitude = 3658 m). Systolic blood pressure (SBP) was attenuated in all hypoxic and in TX-N rats (p less than 0.05). Thyroidectomy reduced oxygen consumption, rectal temperature, and hormonal indices of thyroid function, as well as attenuating hypoxia-induced polycythemia and right ventricular hypertrophy. Thyroidectomy decreased the sensitivity of aortic rings to KCl and isoproterenol with no differences between EU-N and EU-H or between TX-N and TX-H apparent. Vessel responsiveness in RPL-H was consistent with the hypothyroid status indicated by hormonal measurement, while RPL-N vessel responsiveness was characteristic of euthyroid vessels. Since EU-H rats were euthyroid, with similar vascular responses to EU-N, hypoxia-induced attenuation of SBP does not require hypothyroid-like vascular alterations. Thus, hypoxia and thyroidectomy appear to mitigate systemic hypertension by different mechanisms.

[Significance of chromosomal mosaicism diagnosed by amniocentesis]

Second-trimester amniocentesis, performed in a 39-year-old woman, revealed on two different taps a weak aneuploid cell line 47,XY+C or X (2 clones), with a strong majority of fetal cells being 46,XY normal (15 clones). A chromosome examination carried out on cord blood after the birth of a phenotypically normal infant confirmed the presence of mosaicism, with 12% of the cells being 47,XXY. The authors consider the manner in which mosaicism diagnosed by amniocentesis may be interpreted, pointing out the danger of hasty conclusions in this domain, which has not yet been adequately explored.