Requirement for phosphatidylinositol 4,5-bisphosphate in the Ca(2+)-induced phospholipid redistribution in the human erythrocyte membrane

In order to investigate how calcium on the cytosolic side of human erythrocytes induces the transmembrane redistribution of phospholipids, we studied the effect of this cation on the transmembrane movements of spin-labeled phospholipids (phosphatidylserine (PS) and phosphatidylcholine (PC)) incorporated into inside-out vesicles derived from human erythrocytes. We found that the extent of the Ca(2+)-induced lipid scrambling was dependent upon the level of phosphatidylinositol 4,5-bisphosphate (PIP2) contained in the external leaflet of inside-out vesicles. The level of PIP2 in this leaflet, which normally accounts for 80% of the total membrane PIP2, was manipulated either by ATP depletion of the original erythrocytes or by incorporation of exogenous PIP2. Similarly, loading the outer monolayer of the membrane of intact erythrocytes with exogenous PIP2 caused, in a dose-dependent way, the scrambling of spin-labeled phosphatidylethanolamine, sphingomyelin, PC, and PS and in parallel the stomatocytic conversion of the cells. Both scrambling and stomatocytosis were strictly dependent on the presence of divalent cations in the medium. Mg2+ could replace Ca2+ but required a 10 times higher concentration. The effect was specific for PIP2, the other phosphoinositides being unable to induce the lipid redistribution. The shape change, but not the scrambling, required a normal ATP level. These results show that Ca2+ or Mg2+ trigger the lipid redistribution either from the internal or the external side of the membrane, provided that enough PIP2 is present on that side. Thus, no specific protein is required for this process. We infer that the ATP-dependent shape change of erythrocytes after incubation with PIP2 and Ca2+ results from the bilayer imbalance due to the activity of the aminophospholipid translocase which relocates PS and phosphatidylethanolamine to the inner monolayer without simultaneous outward diffusion of PC and sphingomyelin.

The involvement of the Ca-dependent K channel and of the KCl co-transport in sickle cell dehydration during cyclic deoxygenation

We have investigated the mechanisms involved in sickle cell dehydration upon continuous or cyclic deoxygenation: the Ca(2+)-activated K+ channel and the KCl co-transport system. Short-term continuous deoxygenation (1 h) of sickle cells in a Ca(2+)-containing medium promoted a stimulation of the efflux of K+ and cell dehydration. This latter was reduced by the replacement of Ca2+ in the medium by EGTA, but not by addition of [(dihydro-indenyl) oxy] alkanoic acid (DIOA), an inhibitor of the KCl co-transport. During cycles of deoxygenation-reoxygenation, cell dehydration was partly prevented by EGTA and significantly reduced by DIOA only in the presence of Ca2+. The present data support the view that sickle cell dehydration during deoxygenation arises from the stimulation of the Ca(2+)-dependent K+ permeability leading to water loss, whereas during reoxygenation periods, subsequent activation of the KCl co-transport also contributes to cell dehydration.

Importance of ground-glass attenuation in chronic diffuse infiltrative lung disease: pathologic-CT correlation

PURPOSE

To correlate areas of ground-glass attenuation at computed tomography (CT) with findings at open lung biopsy in chronic diffuse lung disease.

MATERIALS AND METHODS

The cases of 26 patients were included on the basis of (a) extensive areas of ground-glass attenuation as the predominant (n = 17) or exclusive (n = 9) abnormality at CT in the absence of honeycombing and (b) histologic evaluation at open lung biopsy. Severity of ground-glass attenuation was scored in the lobe sampled at biopsy, with separate analysis of associated lung changes.

RESULTS

Correlation of CT with histologic findings at the 37 biopsy sites demonstrated that ground-glass attenuation corresponded to inflammation in 24 (65%) cases and to fibrosis in 13 (54%) cases. Eleven of the 13 patients (85%) with fibrosis had traction bronchiectasis or bronchiolectasis. These findings were not present in any of the patients with inflammation.

CONCLUSION

In patients with chronic diffuse infiltrative lung disease, areas of ground-glass attenuation not associated with traction bronchiectasis or bronchiolectasis are a reliable indicator of inflammation.

Cellular distribution of polyphosphoinositides in rat hepatocytes

The distribution of total phospholipids, phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) was studied in isolated rat hepatocytes: (i) by mass assay and isotopic labelling in the fractions of plasma membranes, microsomes, mitochondria and nuclei prepared from isolated hepatocytes and (ii) by immunolocalization of PIP2 with a specific antibody (kt3g) in whole hepatocytes and isolated nuclei. Mass measurement and isotopic labelling showed that PIP was distributed in all four fractions. PIP2 was present in the plasma membrane and the nuclei. In whole cells, PIP2 was also detected in the plasma membrane by immunolocalization with the anti-PIP2 antibody kt3g. In unpolarized single hepatocytes, PIP2 distributed evenly throughout the plasma membrane. However, in polarized cell couplets, PIP2 was the most often undetectable in the lateral domain between the cells, and distributed preferentially in the sinusoidal domain of the plasma membrane. These results suggest that hepatocytes segregate PIP2 in particular domains of their plasma membrane. In purified fractions of nuclei, immunolocalization experiments showed that PIP2 was present uniquely in the nuclear envelope.

Characterization of structural and functional phosphoinositide domains in human erythrocyte membranes

In the erythrocyte membrane, only a fraction (50-60%) of phosphatidylinositol 4,5-bisphosphate (PIP2) and of phosphatidylinositol 4-phosphate (PIP) is rapidly turned over by specific kinases and phosphatases and accessible to hydrolysis by the polyphosphoinositide (PPI)-specific phospholipase C (PLC). To investigate whether the metabolic segregation of PPI resulted from preferential interactions with proteins, we have measured the accessibility of PPI to bee venom phospholipase A2 (PLA2) in native erythrocyte membranes, or after treatments designed to remove peripheral proteins and cytoplasmic domains of integral proteins. In native membranes, PPI, as well as the other major phospholipids, behaved as two distinct fractions (R1 and R2) differing by their sensitivity to PLA2. Such a behavior was not observed in PIP and PIP2 containing artificial vesicles. Evidence was provided that the highly sensitive fraction of PIP and PIP2 (R1) may be identical to the PLC-sensitive and rapidly metabolized pool. Removal of peripheral proteins, followed by proteolysis of the cytoplasmic domain of integral proteins, mainly glycophorins and band 3, led to a reduction of the R1 fraction of PIP and of PIP2. It is proposed that the rapidly metabolized pool of PIP2 and PIP, involved in the regulation of major cellular functions, would be maintained in its functional state through interactions with integral proteins.

Pulmonary nodules: detection with thick-section spiral CT versus conventional CT

Spiral volumetric computed tomography (CT) with single breath-hold technique was compared with conventional sequential CT in 39 patients. The spiral CT protocol consisted of a 10 mm/sec table feed during a 24-second breath hold at 145 mA, with reconstruction of images at 10-mm intervals; one (n = 21) or two (n = 18) sequences were necessary to screen the complete lung. Conventional CT was performed with a 1-second scan time, 145 mA, and contiguous 10-mm-thick sections. In the 39 patients studied with each technique, no lung nodule was detected in three, two had a single nodule, and 29 had multiple nodules. Two patients with normal findings at chest radiography and three with a solitary pulmonary nodule at conventional CT had multiple nodules at spiral CT. Mean number of nodules per patient was significantly higher with spiral versus conventional CT (18 +/- 4.5 vs 12.6 +/- 3.2 [mean +/- standard error of the mean], P = .01) as were the number of nodules less than 5 mm in diameter per patient (12.7 +/- 3.7 vs 8.4 +/- 2.3, P < .05) and 5-10 mm in diameter (2.9 +/- 0.9 vs 2.4 +/- 0.8, P < .05). Respiratory motion artifacts were never observed with spiral CT although they were present on four conventional CT scans.

Characterization of phosphoinositide kinases in normal and sickle anaemia red cells

PtdIns and PtdInsP kinases from normal erythrocyte (AA) membranes and sickle cell anaemia erythrocyte (SS) membranes have been characterized. PtdIns kinase was studied in native membranes under conditions in which PtdInsP kinase and PtdInsP phosphatase do not express any activity. Kinetic analysis of the AA and SS PtdIns kinases indicate similar Km values for PtdIns and ATP but higher Vmax values for SS PtdIns kinase. PtdInsP kinase was partially purified from erythrocyte ghosts by NaCl extraction. The kinetic parameters of PtdInsP kinase determined under these conditions were similar in AA and SS NaCl extracts. These data suggest the presence of some effector of PtdIns kinase in SS cell membranes, resulting in a greater activity of the enzyme. This leads consequently, to increase the PtdIns4P pool and to activate PtdInsP kinase, in agreement with our previous observations of a greater [32P]Pi incorporation in both polyphosphoinositides in SS cells relatively to AA cells.

Computed tomography assessment of ground-glass opacity: semiology and significance

Among the computed tomography (CT) signs of parenchymal lung disease, the ground-glass pattern is the one most difficult to diagnose and most influenced by CT technique. Ground-glass opacity may result from changes in the airspaces or interstitial tissues in acute or chronic infiltrative lung disease. It may also be seen as a consequence of increased capillary blood volume in redistribution of blood flow due to airway disease, emphysema, or pulmonary thromboembolism. Definition of this sign on high-resolution CT (HRCT) images, its various HRCT patterns, and potential pitfalls in its recognition are described with special attention to optimal HRCT technique.

Central pulmonary thromboembolism: diagnosis with spiral volumetric CT with the single-breath-hold technique--comparison with pulmonary angiography

Forty-two patients were prospectively evaluated with spiral volumetric computed tomography (CT) and selective pulmonary angiography of each lung to detect central pulmonary thromboembolism. Spiral volumetric CT images obtained with either 90 mL of 30% contrast material or 120 mL of 12% contrast material were graded as excellent or good in 98% of the examinations (41 patients). Diagnosis of pulmonary embolism with spiral volumetric CT was based on the direct visualization of intraluminal clots: partial filling defects (n = 41; 37%), complete filling defects (n = 51; 46%), "railway track" signs (n = 6; 5%), and mural defects (n = 14; 12%). All 23 patients with normal findings of spiral volumetric CT had normal findings of pulmonary angiography. With spiral volumetric CT, the finding of 112 central emboli (eight main, 28 lobar, and 76 segmental) corresponded exactly to the angiographic findings, but nine intersegmental lymph nodes were erroneously interpreted as filling defects. In one case of normal pulmonary angiographic findings, asymmetry in pulmonary arterial perfusion was misinterpreted as pulmonary embolism with spiral volumetric CT. Spiral volumetric CT can reliably depict thromboemboli in second- to fourth-division pulmonary vessels.

Cerebrofaciothoracic dysplasia: a new family

We describe two brothers, born to consanguineous parents, who had facial dysmorphism, complex anomalies of the vertebrae and ribs, enlarged cerebral ventricles and septum pellucidum, mental retardation, and affable behaviour. The features are similar to those previously described in three unrelated children and may represent new cases of cerebrofaciothoracic dysplasia.

Prenatal diagnosis of Fryns' syndrome

We report on a new case of ultrasonographic prenatal diagnosis of Fryns' syndrome during the second pregnancy of a young woman whose first child died 90 min after birth and was diagnosed as having this autosomal recessive condition. The feasibility of diagnosis in utero and timing in the phenotypic expression of this multimalformation syndrome are discussed.

Asymmetric distribution of phosphoinositides and phosphatidic acid in the human erythrocyte membrane

The distribution of phosphoinositides and phosphatidic acid (PA) between the outer and inner layers of the human erythrocyte membrane was investigated by using two complementary methodologies: hydrolysis by phospholipase A2 (PLA2) and immunofluorescence detection with monoclonal antibodies against polyphosphoinositides. The contents of phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP) and PA were decreased by 15-20% after 60 min incubation with PLA2, while that of phosphatidylinositol (PI) was increased. Studies with 32P-labelled cells revealed that PLA2 treatment led to indirect effects on the metabolism of these phospholipids. Therefore, the asymmetric distribution of phosphoinositides and PA was inferred from the data obtained in ATP-depleted erythrocytes. In these cells with arrested phosphoinositide metabolism, the asymmetric distribution of the major phospholipids was maintained: PLA2 hydrolyzed approx. 20% of PI, PIP2 and PA (but no PIP) indicating their localization in the outer layer of the membrane. This finding was confirmed by immunofluorescence studies with antibodies specific to each phosphoinositide. External addition of anti-PIP2 but not anti-PIP gave a positive reaction both in control and in ATP-depleted erythrocytes. A pretreatment of cells with PLA2 led to a decrease in the intensity of anti-PIP2 staining. These results demonstrate that significant fractions of PIP2, PI and PA are localized on the outer surface of the erythrocyte membrane.

Smith-Magenis syndrome: a new contiguous gene syndrome. Report of three new cases

Interstitial deletion of the short arm of chromosome 17 was detected in three patients. They all had a similar phenotype with mental retardation, behavioural problems, facial dysmorphism, brachycephaly, a broad face with a flat midface, and short and broad hands. All three cases were ascertained over a six month period by two neuropaediatricians aware of this specific anomaly, which suggests that this microdeletion is not particularly rare. Comparison of the clinical and cytogenetic findings in a total of 24 patients allows a new contiguous gene syndrome to be defined that only high resolution analysis can detect. In two cases, molecular analysis confirmed the cytogenetic results. The Charcot-Marie-Tooth type Ia gene has recently been localised to the 17p11.2 sub-band.

[Prenatal diagnosis and psychiatric diseases: "to be normal or not to be"]

Recent developments in molecular biology have broadened the scope of antenatal diagnosis to include multifactorial diseases whose expression is unpredictable, variable and delayed. These diseases include some psychiatric conditions. These new capabilities raise difficult ethical problems which lead the authors to a more general discussion of antenatal diagnosis and its objectives.

Mechanisms involved in platelet activation induced by a monoclonal antibody anti glycoprotein IIb-IIIa: inositol phosphate production is not the primary event

The mechanisms involved in platelet aggregation by a monoclonal antibody (mAb) P256 specific for the GPIIb-IIIa complex was investigated following metabolic 32P labelling of platelets. When compared with thrombin, inositol phosphates (InsP) production during P256-induced activation was delayed and no apparent peak, but a small and sustained production of [32P]-Ins(1,4,5)P3 and [32P]-Ins(1,3,4,5)P4, was observed between 20 and 90 s. [32P]-Ins(1,3,4)P3 was also produced with a maximum after 90 s. Addition of the ADP scavenger creatinine phosphate/creatine phosphokinase (CP/CPK) and of the cyclooxygenase inhibitor aspirin together with P256 almost totally abolished InsP formation, whereas platelet aggregation and protein phosphorylation were partially inhibited. F(ab')2 fragments of P256 also aggregated platelets but to a smaller extent than IgG, and without any measurable InsPs. To characterize further P256-induced activation, the phosphorylation of p43, the main substrate of protein kinase C (PKC) and the phosphorylation of tyrosine protein (P-Tyr) was also studied. PKC activation was smaller with P256-IgG than with thrombin but both thrombin and P265-IgG induced a similar profile of P-Tyr involving seven major bands, whereas P256-F(ab')2 only occasionally activated PKC but always significantly phosphorylated a 64,000 molecular weight P-Tyr. The data indicate that the binding of P256 to GPIIb-IIIa, in contrast with thrombin, does not initially lead directly to the activation of the phosphoinositide phospholipase C to produce InsP's but rather involves the activation of protein kinases and also both fragments F(ab')2 and Fc play a specific role in the platelet responses to the mAb. Only the crosstalk between the two pathways evoked by F(ab')2 and Fc respectively allows the activation of all platelet activation systems.

Ca2+ permeability in deoxygenated sickle cells

Deoxygenation of sickle cells is known to increase cation permeabilities (Na+, K+, and Ca2+). The possible mechanisms involved in the increased uptake of Ca2+ were investigated: activation of Ca2+ channels, involvement of the anion channel, and the formation of endocytic vacuoles. The Ca2+ channel blocker nifedipine reduced the deoxy-stimulated Ca2+ uptake by about 30% to 40%. The anion channel inhibitor DIDS (4,4' diisothiocyanate stilbene 2,2' disulfonate) inhibited the deoxy-stimulated Ca2+ uptake by approximately 50%. Maximal possible endocytic uptake, measured by using an impermeant marker ([3H] inuline), accounted for 6% to 9% of the total Ca2+ uptake. These data indicate that the deoxygenation-induced increase in Ca2+ permeability could result from both the activation of a Ca2+ channel and of a transport system for cations involving interactions between polymerized hemoglobin S, band 3 and other membrane components. Endocytosis appears to play only a minor role in the Ca2+ uptake of deoxygenated sickle cells.

[Neonatal screening for phenylketonuria and hypothyroidism. An optimizing system]

Screening for phenylketonuria and hypothyroidism in neonates is currently performed on blood samples collected on the 5th day of life. The efficacy of blood-sampling is evaluated subsequently. Double-sampled and non-sampled children are not always identified. We present a system which provides complete control of child, and was tested experimentally over one year on the 4,260 births in a maternity hospital. The sampling done by the maternity hospital as very thorough: only 0.47% of the children were not sampled spontaneously (ET = 1.07 10(-3)). The sampling of children transferred to pediatric units before the 5th day was a little less rigorous: 6.06% were not sampled before the telephone reminder (ET = 1.86 10(-2)). After a year our system ensured a 100% sampling after identification and telephone reminder for non sampled children, and allowed us to spot and count cases of double-sampling.

Human epithelial thymic tumours: heterogeneity in immunostaining of epithelial cell markers and thymic hormones

Different hormones (thymulin, thymosin alpha 1, vasopressin), antigenic markers of cortical and subcapsular/medullary thymic areas and tumour associated antigens were studied on paraffin or frozen section and cultures of human epithelial thymic tumours ('thymomas'). Thymulin, thymosin alpha 1 and for the first time vasopressin are found in most tumours. The epithelial cells of five 'thymomas' had markers of both cortical (TE3) and subcapsular/medullary thymic regions (A2B5 and/or TE4 and/or anti-p19). Leu-7, a marker of subcapsular epithelial cells was positive only in two tumours. The histological classification into cortical and medullary tumours does not correspond to our immunofluorescence results. The presence of these markers does not support the theory of different embryologic origin of the cortical and subcapsular/medullary epithelial cells. Transferrin receptors were detected on only some epithelial cells of thymic 'carcinomas'. Adenocarcinoma related antigen and carcino embryonic antigen only stained a few epithelial cells of all the tumours. There is no expected correlation between the presence of epidermal growth factor receptors on cell membranes and the number of proliferative cells stained by the anti-Ki67 antibodies. Immunostainings were heterogeneous according to the epithelial thymic tumours, independent of histological classification and not yet useful for prognosis.

Hepatic hypervitaminosis A: a familial observation

Four siblings with hepatic fibrosis are described. The liver damage in these patients was secondary to chronic ingestion of massive doses of vitamin A for congenital ichthyosis. Although the extrahepatic manifestations were helpful in the diagnosis of hypervitaminosis A, the distinctive features of hepatic histopathology were confirmatory. The plasma concentrations of vitamin A and retinol-binding protein were misleading. The recovery from the liver damage in these patients was slow despite a complete withdrawal of the vitamin A intake. These cases show the importance of hepatic vitamin A assessment in the diagnosis of hepatic fibrosis.

Functional heterogeneity of polyphosphoinositides in human erythrocytes

After labelling of erythrocytes with [32P]P1 for 23 h, the specific radioactivities of the phosphomonoester groups of PtdIns4P and of PtdIns(4,5)P2 approached equilibrium values which were close to that of the gamma-phosphate of ATP (78-85%), showing that almost all of these phosphate groups were metabolically active. Phosphoinositidase C (PIC) activation, using Ca2+ and the ionophore A23187, of 32P-prelabelled erythrocytes was used to investigate a possible functional heterogeneity of the phosphoinositides. Hydrolysis of PtdIns(4,5)P2, measured from its radioactivity, decreased as function of the time of prelabelling up to a constant value equal to that measured from its content. In contrast, hydrolysis of PtdIns4P, determined both from radioactivity and from content, was always the same. These data suggest that newly labelled molecules of PtdIns(4,5)P2, initially accessible to PIC, then moved towards a PIC-resistant pool. This was further confirmed by measuring the fraction of labelled PtdIns(4,5)P2 molecules accessible to PIC after a prelabelling period of 5 min and different times of reincubation. Hydrolysis by PIC was also measured in erythrocytes in which the phosphoinositide content had been modified by activation (Mg2+-enriched cells) or inhibition (ATP-depleted cells) of the phosphoinositide kinases. The sizes of the PIC-resistant pools of polyphosphoinositides were not affected by these treatments, indicating that the kinases (and the phosphatases) act on the PIC-sensitive pools. This was also shown by the decrease in the production of Ins(1,4,5)P3 upon PIC activation in ATP-depleted erythrocytes. A model is presented in which the PIC-sensitive pools of polyphosphoinositides are those which are accessible to the kinases and the phosphatases and are rapidly turned over.

CpG dinucleotides are mutation hot spots in phenylketonuria

The coding region of the phenylalanine hydroxylase (PAH) gene contains 22 CpG dinucleotides, including five doublets in the seventh exon of the gene. We hypothesized that CpG doublets could represent mutation hot spots in PAH deficiencies and we carried out the systematic sequence analysis of exon 7 in 20 unrelated PAH-deficient kindreds of Mediterranean ancestry. This procedure resulted in the detection of two novel missense mutations whose location and nature (CG to CA and CG to TG) were consistent with the accidental deamination of a 5-methylcytosine in a CpG doublet (codon 261arg----gln and codon 252arg----trp). Moreover, the codon 261 mutation was found to be associated with mutant restriction fragment length polymorphism (RFLP) haplotype 1, the most frequent mutant RFLP haplotype at the PAH locus in the studies reported thus far. However, since the mutation was detected in only 36% of haplotype 1 mutant alleles, it appears that this haplotype at the PAH locus is genotypically heterogeneous in Mediterranean countries.

Heterogeneity of ribosomal autoantibodies from human, murine and canine connective tissue diseases

Antiribosomal auto-antibodies (anti-Rib.Ab) have been studied in connective tissue diseases (human, dog and mouse) by immunoblotting after one-dimensional (1D) or two-dimensional (2D) gel electrophoresis of rat ribosomes. Anti-Rib.Ab could be found in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and other connective tissue diseases (progressive systemic sclerosis, PSS; Sjögren syndrome, SjS; mixed connective tissue disease, MCTD; and dermatomyositis, DM with the frequencies 41.7%, 54.6% and 33%, respectively. Immunoblotting after 1D gel electrophoresis showed the great heterogeneity of ribosomal proteins recognized by the anti-Rib.Ab. In the SLE, however, the most frequent antibodies stained bands of the 40S subunit: 30 kDa (34% of positive sera), 19.5 kDa (24.5%) and 43 kDa (17%). In RA, the 25-kDa band of the 60S subunit was the most common (54% of positive sera). In the other human connective tissue diseases, there was no particular predominance. In the MRL/1, anti-Rib.Ab were very frequent (92.6%). The 43-kDa band of the 40S subunit was found in 100% of positive sera. Seventeen out of nineteen dogs with SLE gave positive results on immunoblot, and all of them stained the 43-kDa band of the 40S subunit. 2D gel electrophoresis gave identification of Po, L7, L5, Sb, S19, S13 and L2 proteins in SLE, S3 and SjS, L35a and L37a in RA, and L7, S6 and/or L7a in MRL/1.