Cost of exome analysis in patients with intellectual disability: a micro-costing study in a French setting

BACKGROUND

With the development of next generation sequencing technologies in France, exome sequencing (ES) has recently emerged as an opportunity to improve the diagnosis rate of patients presenting an intellectual disability (ID). To help French policy makers determine an adequate tariff for ES, we aimed to assess the unit cost per ES diagnostic test for ID from the preparation of the pre-analytical step until the report writing step and to identify its main cost drivers.

METHODS

A micro-costing bottom-up approach was conducted for the year 2018 in a French setting as part of the DISSEQ study, a cost-effectiveness study funded by the Ministry of Health and performed in collaboration with the GAD (Génétique des Anomalies du Développement), a genetic team from the Dijon University Hospital, and a public sequencing platform, the Centre National de Recherche en Génomique Humaine (CNRGH). The analysis was conducted from the point of view of these two ES stakeholders. All of the resources (labor, equipment, disposables and reagents, reusable material) required to analyze blood samples were identified, collected and valued. Several sensitivity analyses were performed.

RESULTS

The unit nominal cost per ES diagnostic test for ID was estimated to be €2,019.39. Labor represented 50.7% of the total cost. The analytical step (from the preparation of libraries to the analysis of sequences) represented 88% of the total cost. Sensitivity analyses suggested that a simultaneous price decrease of 20% for the capture kit and 50% for the sequencing support kit led to an estimation of €1,769 per ES diagnostic test for ID.

CONCLUSION

This is the first estimation of ES cost to be done in the French setting of ID diagnosis. The estimation is especially influenced by the price of equipment kits, but more generally by the organization of the centers involved in the different steps of the analysis and the time period in which the study was conducted. This information can now be used to define an adequate tariff and assess the efficiency of ES.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT03287206 on September 19, 2017.

Prediction of Breast Cancer Treatment-Induced Fatigue by Machine Learning Using Genome-Wide Association Data

BACKGROUND

We aimed at predicting fatigue after breast cancer treatment using machine learning on clinical covariates and germline genome-wide data.

METHODS

We accessed germline genome-wide data of 2799 early-stage breast cancer patients from the Cancer Toxicity study (NCT01993498). The primary endpoint was defined as scoring zero at diagnosis and higher than quartile 3 at 1 year after primary treatment completion on European Organization for Research and Treatment of Cancer quality-of-life questionnaires for Overall Fatigue and on the multidimensional questionnaire for Physical, Emotional, and Cognitive fatigue. First, we tested univariate associations of each endpoint with clinical variables and genome-wide variants. Then, using preselected clinical (false discovery rate < 0.05) and genomic (P < .001) variables, a multivariable preconditioned random-forest regression model was built and validated on a hold-out subset to predict fatigue. Gene set enrichment analysis identified key biological correlates (MetaCore). All statistical tests were 2-sided.

RESULTS

Statistically significant clinical associations were found only with Emotional and Cognitive Fatigue, including receipt of chemotherapy, anxiety, and pain. Some single nucleotide polymorphisms had some degree of association (P < .001) with the different fatigue endpoints, although there were no genome-wide statistically significant (P < 5.00 × 10^-8) associations. Only for Cognitive Fatigue, the predictive ability of the genomic multivariable model was statistically significantly better than random (area under the curve = 0.59, P = .01) and marginally improved with clinical variables (area under the curve = 0.60, P = .005). Single nucleotide polymorphisms found to be associated (P < .001) with Cognitive Fatigue belonged to genes linked to inflammation (false discovery rate adjusted P = .03), cognitive disorders (P = 1.51 × 10^-12), and synaptic transmission (P = 6.28 × 10^-8).

CONCLUSIONS

Genomic analyses in this large cohort of breast cancer survivors suggest a possible genetic role for severe Cognitive Fatigue that warrants further exploration.

Prediction of Breast Cancer Treatment-Induced Fatigue by Machine Learning Using Genome-Wide Association Data

BACKGROUND

We aimed at predicting fatigue after breast cancer treatment using machine learning on clinical covariates and germline genome-wide data.

METHODS

We accessed germline genome-wide data of 2799 early-stage breast cancer patients from the Cancer Toxicity study (NCT01993498). The primary endpoint was defined as scoring zero at diagnosis and higher than quartile 3 at 1 year after primary treatment completion on European Organization for Research and Treatment of Cancer quality-of-life questionnaires for Overall Fatigue and on the multidimensional questionnaire for Physical, Emotional, and Cognitive fatigue. First, we tested univariate associations of each endpoint with clinical variables and genome-wide variants. Then, using preselected clinical (false discovery rate < 0.05) and genomic (P < .001) variables, a multivariable preconditioned random-forest regression model was built and validated on a hold-out subset to predict fatigue. Gene set enrichment analysis identified key biological correlates (MetaCore). All statistical tests were 2-sided.

RESULTS

Statistically significant clinical associations were found only with Emotional and Cognitive Fatigue, including receipt of chemotherapy, anxiety, and pain. Some single nucleotide polymorphisms had some degree of association (P < .001) with the different fatigue endpoints, although there were no genome-wide statistically significant (P < 5.00 × 10-8) associations. Only for Cognitive Fatigue, the predictive ability of the genomic multivariable model was statistically significantly better than random (area under the curve = 0.59, P = .01) and marginally improved with clinical variables (area under the curve = 0.60, P = .005). Single nucleotide polymorphisms found to be associated (P < .001) with Cognitive Fatigue belonged to genes linked to inflammation (false discovery rate adjusted P = .03), cognitive disorders (P = 1.51 × 10-12), and synaptic transmission (P = 6.28 × 10-8).

CONCLUSIONS

Genomic analyses in this large cohort of breast cancer survivors suggest a possible genetic role for severe Cognitive Fatigue that warrants further exploration.

Prediction of treatment (tx)-induced fatigue in breast cancer (BC) patients (pts) using machine learning on genome-wide association (GWAS) data in the prospective CANTO cohort

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Background: Many BC survivors report fatigue. The relevant genomic correlates of fatigue after BC are not well understood. We applied a previously validated machine learning methodology (Oh 2017) to GWAS data to identify biological correlates of fatigue induced after tx. Methods: We analyzed 3825 BC pts with GWAS data (Illumina InfiniumExome24 v 1.1) from the CANTO study (NCT01993498). The outcome of this study was post-tx fatigue 1 year after the end of primary chemotherapy/radiotherapy/surgery using the EORTC C30 fatigue subscale (overall fatigue) and the EORTC FA 12 fatigue domains (physical/emotional/cognitive). For each domain, we limited the study group to those with zero baseline fatigue and defined severe fatigue change as score increase above the third quartile. We tested univariate correlations between severe fatigue in each domain and 496539 SNPs as well as relevant clinical variables. The machine learning prediction model based on preconditioning random forest regression (PRFR) (Oh et al., 2017), was then built using the SNPs with ancestry adjusted univariate p-value < 0.001 and clinical variables with Bonferroni adjusted p-value < 0.05. The model was validated in a holdout subset of the cohort. Gene set enrichment analysis (GSEA) was performed using MetaCore to identify key biological correlates relevant to tx-induced fatigue. Results: Distinct results were found by fatigue domain (table). GSEA showed that the cognitive fatigue model SNPs included biomarkers for cognitive disorders (p = 1.6 x 10-12) and glutamatergic synaptic transmission (p = 1.6 x 10-8). Conclusions: A SNP based model had differential performance by fatigue domain, with a potential genetic role on risk and biology for tx induced cognitive fatigue. Further research to explore biomarkers of tx induced fatigue are needed. [Table: see text]

Genetic polymorphisms of Th2 interleukins, history of asthma or eczema and childhood acute lymphoid leukaemia: Findings from the ESCALE study (SFCE)

BACKGROUND

Previous studies on the putative role of allergy in the aetiology of childhood leukaemia have reported contradictory results. The present study aimed to analyse the relation between a medical history of asthma or eczema and childhood acute lymphoid leukaemia (ALL) in light of potential candidate gene-environment interactions.

METHODS

Analyses were based on a subset of 434 cases of ALL and 442 controls successfully genotyped and of European ancestry children enrolled in a French population-based case-control study conducted in 2003-2004. Information about medical history was obtained during a standardized interview with the mothers. Candidate polymorphisms in genes of the Th2 cytokines IL4, IL10, IL13 and IL4-receptor, were genotyped or imputed.

RESULTS

None of the variant alleles were directly associated with childhood acute lymphoid leukaemia. A medical history of asthma or eczema was reported more often in the control group (OR = 0.7 [0.5-1.0]). This association was mostly seen in the group of children not carrying the IL13-rs20541 variant allele (Interaction Odds Ratio IOR 1.9, p-interaction = 0.07) and in those carrying the IL10 triple variant haplotype (IOR 0.5, p-interaction = 0.04). No interaction was observed with the candidate polymorphisms in IL4 and IL4R.

CONCLUSION

This study provides a new insight into the relationship between allergic symptoms and childhood acute lymphoid leukaemia, by suggesting this inverse association could be limited to children carrying certain genetic polymorphisms. If confirmed, these results could help better understand the biological mechanisms involved in the development of childhood acute lymphoid leukaemia.

Genetic Variants Related to Longer Telomere Length are Associated with Increased Risk of Renal Cell Carcinoma

BACKGROUND

Relative telomere length in peripheral blood leukocytes has been evaluated as a potential biomarker for renal cell carcinoma (RCC) risk in several studies, with conflicting findings.

OBJECTIVE

We performed an analysis of genetic variants associated with leukocyte telomere length to assess the relationship between telomere length and RCC risk using Mendelian randomization, an approach unaffected by biases from temporal variability and reverse causation that might have affected earlier investigations.

DESIGN, SETTING, AND PARTICIPANTS

Genotypes from nine telomere length-associated variants for 10 784 cases and 20 406 cancer-free controls from six genome-wide association studies (GWAS) of RCC were aggregated into a weighted genetic risk score (GRS) predictive of leukocyte telomere length.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Odds ratios (ORs) relating the GRS and RCC risk were computed in individual GWAS datasets and combined by meta-analysis.

RESULTS AND LIMITATIONS

Longer genetically inferred telomere length was associated with an increased risk of RCC (OR=2.07 per predicted kilobase increase, 95% confidence interval [CI]:=1.70-2.53, p<0.0001). As a sensitivity analysis, we excluded two telomere length variants in linkage disequilibrium (R2>0.5) with GWAS-identified RCC risk variants (rs10936599 and rs9420907) from the telomere length GRS; despite this exclusion, a statistically significant association between the GRS and RCC risk persisted (OR=1.73, 95% CI=1.36-2.21, p<0.0001). Exploratory analyses for individual histologic subtypes suggested comparable associations with the telomere length GRS for clear cell (N=5573, OR=1.93, 95% CI=1.50-2.49, p<0.0001), papillary (N=573, OR=1.96, 95% CI=1.01-3.81, p=0.046), and chromophobe RCC (N=203, OR=2.37, 95% CI=0.78-7.17, p=0.13).

CONCLUSIONS

Our investigation adds to the growing body of evidence indicating some aspect of longer telomere length is important for RCC risk.

PATIENT SUMMARY

Telomeres are segments of DNA at chromosome ends that maintain chromosomal stability. Our study investigated the relationship between genetic variants associated with telomere length and renal cell carcinoma risk. We found evidence suggesting individuals with inherited predisposition to longer telomere length are at increased risk of developing renal cell carcinoma.

Genome-wide association study identifies multiple risk loci for renal cell carcinoma

Previous genome-wide association studies (GWAS) have identified six risk loci for renal cell carcinoma (RCC). We conducted a meta-analysis of two new scans of 5,198 cases and 7,331 controls together with four existing scans, totalling 10,784 cases and 20,406 controls of European ancestry. Twenty-four loci were tested in an additional 3,182 cases and 6,301 controls. We confirm the six known RCC risk loci and identify seven new loci at 1p32.3 (rs4381241, P=3.1 × 10-10), 3p22.1 (rs67311347, P=2.5 × 10-8), 3q26.2 (rs10936602, P=8.8 × 10-9), 8p21.3 (rs2241261, P=5.8 × 10-9), 10q24.33-q25.1 (rs11813268, P=3.9 × 10-8), 11q22.3 (rs74911261, P=2.1 × 10-10) and 14q24.2 (rs4903064, P=2.2 × 10-24). Expression quantitative trait analyses suggest plausible candidate genes at these regions that may contribute to RCC susceptibility.

Copy number variations alter methylation and parallel IGF2 overexpression in adrenal tumors

Overexpression of insulin growth factor 2 (IGF2) is a hallmark of adrenocortical carcinomas and pheochromocytomas. Previous studies investigating the IGF2/H19 locus have mainly focused on a single molecular level such as genomic alterations or altered DNA methylation levels and the causal changes underlying IGF2 overexpression are still not fully established. In the current study, we analyzed 62 tumors of the adrenal gland from patients with Conn's adenoma (CA, n=12), pheochromocytomas (PCC, n=10), adrenocortical benign tumors (ACBT, n=20), and adrenocortical carcinomas (ACC, n=20). Gene expression, somatic copy number variation of chr11p15.5, and DNA methylation status of three differential methylated regions of the IGF2/H19 locus including the H19 imprinting control region were integratively analyzed. IGF2 overexpression was found in 85% of the ACCs and 100% of the PCCs compared to 23% observed in CAs and ACBTs. Copy number aberrations of chr11p15.5 were abundant in both PCCs and ACCs but while PCCs retained a diploid state, ACCs were frequently tetraploid (7/19). Loss of either a single allele or loss of two alleles of the same parental origin in tetraploid samples resulted in a uniparental disomy-like genotype. These copy number changes correlated with hypermethylation of the H19 ICR suggesting that the lost alleles were the unmethylated maternal alleles. Our data provide conclusive evidence that loss of the maternal allele correlates with IGF2 overexpression in adrenal tumors and that hypermethylation of the H19 ICR is a consequence thereof.

A high-resolution allelotype of B-cell chronic lymphocytic leukemia (B-CLL)

The most frequent chromosomal aberrations in B-cell chronic lymphocytic leukemia (B-CLL) are deletions on 13q, 11q, and 17p, and trisomy 12, all of which are of prognostic significance. Conventional cytogenetic analysis and fluorescence in situ hybridization (FISH) are used for their detection, but cytogenetic analysis is hampered by the low mitotic index of B-CLL cells, and FISH depends on accurate information about candidate regions. We used a set of 400 highly informative microsatellite markers covering all chromosomal arms (allelotyping) and automated polymerase chain reaction (PCR) protocols to screen 46 patients with typical B-CLL for chromosomal aberrations. For validation, we compared data with our conventional karyotype results and fine mapping with conventional single-site PCR. All clonal cytogenetic abnormalities potentially detectable by our microsatellite PCR (eg, del13q14 and trisomy 12) were picked up. Allelotyping revealed additional complex aberrations in patients with both normal and abnormal B-CLL karyotypes. Aberrations detectable in the samples with our microsatellite panel were found on almost all chromosomal arms. We detected new aberrant loci in typical B-CLL, such as allelic losses on 1q, 9q, and 22q in up to 25% of our patients, and allelic imbalances mirroring chromosomal duplications, amplifications, or aneuploidies on 2q, 10p, and 22q in up to 27% of our patients. We conclude that allelotyping with our battery of informative microsatellites is suitable for molecular screening of B-CLL. The technique is well suited for analyses in clinical trials, it provides a comprehensive view of genetic alterations, and it may identify new loci with candidate genes relevant in the molecular biology of B-CLL.

Tuberculosis in Siberia: 2. Diagnosis, chemoprophylaxis and treatment

OBJECTIVE

To assess tuberculosis diagnosis, chemoprophylaxis and therapy in Siberia as a paradigm for the Russian Federation.

DESIGN

Data was obtained from official sources and through visits to dispensaries and hospitals in 1994.

RESULTS

Tuberculosis disease and cure is classified according to a Dispensary Group Register based principally on clinical and radiological criteria. Isoniazid is widely used for chemoprophylaxis and post-therapy and may be linked to high levels of isoniazid resistance. Combination drug therapy is individualized, frequently changed, and given orally, parenterally or intra-bronchially. Galvanization, autotransfusion of ultra-violet irradiated blood, antioxidants and steroids are used as adjunct treatment. Ambulatory treatment is uncommon. Surgical treatments including lobectomy and pneumonectomy are used in 5-10% of patients.

CONCLUSION

Tuberculosis is increasing in Siberia. An improved drug supply using short course standardized regimens is required supported by high quality co-ordinated bacteriological services. Surgery retains a useful role, but many adjunct therapies should be abandoned.

Tuberculosis in Siberia: 1. An epidemiological and microbiological assessment

SETTING

Siberia, Russian Federation.

OBJECTIVE

To assess the situation regarding tuberculosis as a paradigm for the Russian Federation.

DESIGN

Data was obtained from official sources and through visits to dispensaries and hospitals in 1994.

RESULTS

The downward trend in notifications of tuberculosis throughout Russia reversed in 1990/91, the rate increasing from 34/100,000 to 42.9/100,000 in 1993. Incidence rates are higher in Siberia, varying from approximately 43 to 108/100,000; prevalence is 250-300/100,000. The tuberculosis service is centralized and based on specialized polyclinics and dispensaries. An extensive surveillance system employs regular fluorography and tuberculin testing: half of the cases diagnosed are detected by fluorography, against 1% through contact tracing. Patients are classified principally on clinical and radiological grounds. Bacille Calmette-Guérin immunisation is performed at birth and at age 7, and again at 13, 21, and 28 years if Mantoux test is negative. Microscopy and culture services are organisationally separate, and direct comparison of smear and culture data is not possible. Drug resistance to isoniazid and streptomycin is probably high and resistance to rifampicin low, but data on susceptibility of isolates from new cases are not available.

CONCLUSION

Tuberculosis is increasing in Siberia. Homelessness, unemployment and alcoholism are important factors, but concurrent human immunodeficiency virus (HIV) infection appears to be uncommon. Prisons probably form a significant reservoir of infectious cases.

Cultured rat skeletal muscle cells treated with cytochalasin exhibit normal dystrophin expression and intracellular free calcium control

Many studies performed to elucidate the molecular and cellular processes involved in muscular dystrophies have led to the working hypothesis of a key role for the cytoskeleton elements linking the extracellular matrix to myofibrils. It was recently suggested that cytochalasin B treatment of mouse soleus muscle promoted cell damage mediated by a cytosolic increase in free calcium concentration. Since intracellular calcium overload may be a primary event resulting from the alteration of cytoskeletal structure, this study was intended to evaluate whether or not the integrity of the F-actin microfilament network is necessary for calcium homeostasis. The developmental establishment of the normal cytoarchitecture was altered by treatment of myoblasts with the actin-disrupting agents cytochalasin B and D, and the effects were compared with those in myoblasts treated with colchicine. These drugs modified the morphogenesis in that they prevented the formation of elongated myotubes by myoblast fusion, but did not prevent the maturation of contractile myogenic cells. The subcellular organisation of actin filaments visualised by confocal fluorescence microscopy was modified by colchicine and cytochalasins, but appearance of contractile apparatus and mechanical activity were not precluded. Sarcolemmal addressing of dystrophin, the subsarcolemmal protein lacking in Duchenne muscular dystrophy, was not prevented by cytochalasin. The evaluation of the basal activity of cytosolic calcium measured with indo-1 suggested that the disruption of actin or microtubules did not prevent developing muscle cells to maintain a low basal calcium activity. We propose that the global integrity of the cytoskeleton network is not crucial for the maintenance of calcium homeostasis in muscle cells developing in vitro. These results are discussed with regard to current theories attempting to understand the functional consequences of an abnormal expression of the dystrophin-glycoprotein complex interacting with the extracellular matrix and the cytoskeleton.

Genetic mapping of a susceptibility locus for insulin-dependent diabetes mellitus on chromosome 11q

Loci in the major histocompatibility complex (MHC) on chromosome 6 and the insulin (INS) region on chromosome 11 have been implicated in susceptibility to insulin-dependent diabetes mellitus (IDDM) through candidate gene investigations, but they may account for less than 50% of genetic risk for the disease. Genome-wide linkage studies have led to localization of more than 10 susceptibility loci for insulin-dependent diabetes in the non-obese diabetic (NOD) mouse and the BB rat. Similar studies are now possible in humans through the development of dense genetic maps of highly informative microsatellite loci obtained using polymerase chain reaction analysis. We have applied microsatellite markers from recent Généthon maps, and other highly informative markers, in a genome-wide linkage study in IDDM. Here we report evidence for the localization of a previously undetected susceptibility locus for IDDM in the region of the FGF3 gene on chromosome 11q. Our results shows the potential of genome-wide linkage studies to detect susceptibility loci in IDDM and other multifactorial disorders.

A study of structure and degradation of nonpolymeric biomaterials implanted in bone using reflected and transmitted light microscopy

Orthopedic biomaterials currently are made of metal alloy coated with one or more thin layers of dense or porous ceramic or metal. Sections of these materials implanted in human bone were made without altering the implant or bone-implant interfaces. Bone containing an implant was fixed and then embedded in polymethylmethacrylate. Thick sections were made using a cooled, low speed diamond saw, then ground and polished. Some were stained by fuchsin-toluidine staining solution, others were acid etched to reveal the structure of the metal contained in the prosthesis. Observation by reflected and transmitted light microscopy revealed microstructure of the implant material as well as features of the surrounding tissues.

Appearance and evolution of calcium currents and contraction during the early post-fusional stages of rat skeletal muscle cells developing in primary culture

Primary cultures from enzymatically dissociated satellite cells of newborn rat skeletal muscles enabled developmental in vitro studies of mechanical and electrical properties during the first steps of myogenesis. The present work focused on the appearance, evolution and roles of two types of calcium currents (ICa,T and ICa,L) and of depolarization-induced contractile activity during the early stages of muscle cell development in primary culture. Prefusional mononucleated cells (myoblasts), young myotubes of 1 day (with less than 10 nuclei) or 2–3 days (more than 9 nuclei) and myoballs from 4–6, 7–9, 10–12 and 13–16 days cultures were patch-clamped (whole-cell configuration), and calcium currents and contraction simultaneously recorded. Sodium but not calcium currents could be recorded at the myoblast stage. In young myotubes (1 day), ICa,L was present with high incidence as compared to ICa,T, which was poorly expressed. Contractile responses appeared at the next stage (2-3 days) while the occurrence of ICa,T progressively increased. This developmental evolution of the calcium currents and contraction expression was accompanied by some changes in their characteristics: the ICa,T/ICa,L amplitudes ratio progressively increased and the time-to-peak of contraction progressively decreased with the age of myoballs. Physiological functions for calcium currents in developing muscle are suggested and discussed: ICa,T, which is transiently expressed, could be involved in the pacemaker-like activity while ICa,L could serve as an early contraction triggering mechanism and/or initially to fill and then to maintain the intracellular calcium stores.

Pineal photoreceptor cells in culture: fine structure, and light/ dark control of cyclic nucleotide levels and melatonin secretion

Trout pineal photoreceptor cells were dissociated by trypsin-DNase digestion and further purified by a Percoll gradient centrifugation. Total cells or purified photoreceptor cells were then embedded in a collagen gel, or layered on culture-treated polycarbonate membranes, or maintained in suspension, with RPMI 1640 medium or BGjb medium. It has been shown that cells maintain a rhythmic production of melatonin for at least seven 24 h light/dark cycles under these conditions. In this complementary study, the morphofunctional state of the photoreceptor cells was examined 1) by electron (transmission, scanning) microscopy, and 2) by pharmacological tests under different lighting conditions. Using polycarbonate membranes together with RPMI 1640 medium appeared the most suitable. The segmented organization of photoreceptor cells was well preserved when using the culture-treated membranes. It tended to disappear in cells embedded in the collagen gel and was lost after passage through the Percoll gradient. However, this one allowed obtention of an homogeneous population of photoreceptors, as recognized by their intracellular components. Intracellular organelles were rather well preserved in the embedded photoreceptors. The study also provides novel information on the nature of second messengers involved in the photoperiodic control of melatonin production in photoreceptor cells. From the effects of an adenylyl cyclase activator and a phosphodiesterase inhibitor it appeared that 1) total cells and Percoll-selected cells behaved similarly, 2) the nocturnal rise in melatonin secretion was associated with an increase in cAMP content, and 3) a fall in cAMP may be a mechanism through which light reduces melatonin secretion by photoreceptor cells. Cyclic GMP, the metabolism of which also appeared to be controlled by light, did not seem involved in the photoperiodic control of melatonin production. The method proposed herein offers interesting perspectives for the study of the photoneuroendocrine properties of isolated photoreceptor cells.

Cytochemical evidence of an organized microtubular cytoskeleton in Xenopus laevis oocytes: involvement in the segregation of mitochondrial populations

An organized microtubular cytoskeleton was discovered in the cytoplasm of Xenopus laevis oocytes. The microtubules were observed in 10- to 30-micron cryostat sections by indirect immunoperoxidase labeling using an antibody to tubulin. A gradual extraction of cells with a nonionic detergent was essential for good penetration of the antibody into the cells. In the cytoplasm of all previtellogenic oocytes, a dense network of criss-crossed long microtubules was associated in a basket-like structure surrounding the mitochondrial mass. At the beginning of vitellogenesis, the network meshes enlarged, while clusters of mitochondria migrated, in close association with microtubule bundles. At the beginning of vitellogenesis, the reorganization of the microtubular network, mostly in the vegetal hemisphere, occurred during the segregation of the mitochondrial populations. Reorganization is characterized by (1) a temporary enlargement of the network and close association of mitochondrial clusters with microtubular bundles, and (2) a progressive organization of a ring-shaped microtubular structure in the crown elaboration area. It is hypothesized that these modifications of the microtubular cytoskeleton contribute to the maintenance of cell shape and the polarized organization of the cell.

Acetylated low density lipoprotein endocytosis by human syncytiotrophoblast in culture

Low density lipoproteins (LDL) were chemically modified (acetyl LDL) and then conjugated to colloïdal gold (gold acetyl LDL), firstly, to visualize the acetyl LDL binding sites, and secondly, to demonstrate a possible internalization by human syncytiotrophoblast in culture. Cells were obtained by a trypsin DNase method followed by a Percoll gradient centrifugation. After 3 days of culture the syncytiotrophoblast characterization was performed by using ultramicroscopy, immunohistochemistry, and by studying the secretion of gestational hormones during culture. Binding experiments showed gold acetyl LDL attached to the membrane with random distribution. After incubation at 37 degrees C, gold acetyl LDL was internalized by the syncytiotrophoblast following the classical receptor mediated endocytosis process and a non-specific internalization process. These results suggest the existence in the placenta of a 'scavenger pathway' concomittant of the classical LDL internalization. This phenomenon may be related to the high amount of cholesterol required by the human placenta for its cellular growth and intensive progesterone synthesis.

An efficient isolation procedure of Ca-tolerant ventricular myocytes from ferret heart for applications in electrophysiological studies

A simple procedure which provides a large yield of isolated ferret ventricular myocytes is described. The enzymatic dissociation was performed by perfusion of the whole heart with the "Langendorff method" at 37 degrees C, without an incubation period. Special attention was given to the period of perfusion with Ca-free or low-calcium containing solutions and to the proportion of both collagenase and elastase used. The viability and calcium tolerance of the isolated cells were tested by ultrastructural and electrophysiological studies. Photo-microscopy showed that 60 to 80% of the isolated cells had an elongated shape (18 microns in diameter, 150 microns in length) and did not beat spontaneously in normal Tyrode solution. The morphological and ultrastructural integrity of these cells was shown in SEM by their smooth surface with regularly spaced T-tubule openings and in TEM by the regular distribution of the transverse tubular system, mitochondrium and sarcomeres. Using the whole-cell patch-clamp technique, they had a resting membrane potential of -72 mV, two types ("Purkinje like" and "ventricular like") of action potentials could be elicited and they were correctly affected by well-known modulators of calcium channels. This technique was successfully applied to the rat heart and could be used for heart dissociation of small mammals. It can simultaneously provide isolated cells of different regions of the heart and can be easily and routinely used by any investigator.

5'-Nucleotidase activity in the pineal organ of the pike. An electron-microscopic study

To date, it is still unknown whether the metabolism of purine nucleotides and nucleosides plays an important role in the pineal organ of lower vertebrates. We have therefore investigated the sites of 5'-nucleotidase activity in the pineal organ of the pike (Esox lucius L.). Various ultracytochemical procedures were used. An intense ecto-5'-nucleotidase activity was characteristic of the entire plasma membrane of the phototransducers (cone-like and modified photoreceptor elements) and the interstitial cells, with exception of the portions facing the basal lamina of the pericapillary spaces. Additionally, intracellular sites of activity were also visualized in the inner segment and the pedicle of the phototransducers. Most of the intracellular deposits were apparently cytosolic and only few seemed to be associated with the membrane of the clear "synaptic" vesicles of the pedicle. Phagocytotic cells in the pineal lumen also showed a strong enzymatic activity on the outer surface of their plasmalemma (in ectoposition). This was apparently not the case for the cell types of the tissues surrounding the pineal vesicle. The present study emphasizes the importance of the occurrence and metabolism of purine nucleotides and nucleosides in a photoreceptive pineal organ.

Ultrastructural visualization of the internalization of low density lipoprotein by human placental cells

Low density lipoproteins (LDL) were conjugated to colloidal gold to visualize the route for internalization of LDL in the cultured cells of human term placenta. Cells were obtained from placental villi (caesarian section) by a standard trypsin-DNase dispersion method followed in some cases by a Percoll gradient centrifugation step. Employing electron microscopy it was observed that after 3 days of culture, cells obtained by trypsin-DNase dispersion were a mixture of macrophages, mononucleated cells and large multinucleated cells. When the cells were incubated for 3 days after the Percoll purification, essentially multinucleated cells identical to the syncytiotrophoblast were present. The number of LDL receptor was increased by preincubation in medium with lipoprotein depleted serum. In binding experiments cells incubated at 4 degrees C for 2 h with medium containing gold LDL conjugates showed gold LDL attached to the plasma membrane without characteristic localization. After incubation with gold LDL at 37 degrees C for various times, the three cellular types showed ligand internalization. Gold LDL endocytosis involved first coated pits but also uncoated plasmalemmal invaginations. Then gold LDL was further observed in coated and non coated vesicles, smooth walled endosomes, multivesicular bodies and tubular vesicles. Lastly free gold particles were observed in lysosome like dense bodies. These results prove the internalization of gold LDL conjugates by human cultured placental cells, particularly by syncytiotrophoblast like multinucleated cells. This accumulation of LDL (the major cholesterol carrying protein in humans) is recognised to be responsible for the exogenous cholesterol supply indispensable to the progesterone biosynthesis and cellular growth of the placenta.

[A functional flagella with a 6 + 0 pattern]

The male gamete of the Gregarine Lecudina tuzetae has been studied with transmission electron microscopy and microcinematography. It is characterized by a flagellar axoneme of 6 + 0 pattern, a reduction of the chondriome, and the abundance of storage polysaccharide or lipid bodies. The movements of the flagella are of the undulating type and they are performed in the three dimensions of space. They are very slow, with a cycle time of about 2s. The structure of the axoneme components are similar to those of flagella with a 9 + 2 pattern. Each doublet has overall dimensions of 350 x 220 A; the space between the adjacent doublets is about 160 A. The A subfiber bears arms like dynein arms. The diameter of the axoneme is about 1,000 A. The basal body consists of a cylinder of dense material 2,500 A long and 1,300-1,400 A in diameter; a microtubule 200 A in diameter is present in the axis. This study shows that a 6 + 0 pattern can generate a flagellar movement. The mechanism of the flagellar movement of the male gamete of L. tuzetae does not require the presence of central microtubules and it would include molecular interactions of the dynein-tubulin type between the adjacent peripheric doublets. The slowness of the movements is discussed in terms of the axoneme's structure and its energy supply. Finally, the phylogenetic significance of this flagella is examined on the basis of the morphopoietic potentialities of the centriolar structures.