Clinical Validation of Artificial Intelligence-Augmented Pathology Diagnosis Demonstrates Significant Gains in Diagnostic Accuracy in Prostate Cancer Detection

CONTEXT.—

Prostate cancer diagnosis rests on accurate assessment of tissue by a pathologist. The application of artificial intelligence (AI) to digitized whole slide images (WSIs) can aid pathologists in cancer diagnosis, but robust, diverse evidence in a simulated clinical setting is lacking.

OBJECTIVE.—

To compare the diagnostic accuracy of pathologists reading WSIs of prostatic biopsy specimens with and without AI assistance.

DESIGN.—

Eighteen pathologists, 2 of whom were genitourinary subspecialists, evaluated 610 prostate needle core biopsy WSIs prepared at 218 institutions, with the option for deferral. Two evaluations were performed sequentially for each WSI: initially without assistance, and immediately thereafter aided by Paige Prostate (PaPr), a deep learning-based system that provides a WSI-level binary classification of suspicious for cancer or benign and pinpoints the location that has the greatest probability of harboring cancer on suspicious WSIs. Pathologists' changes in sensitivity and specificity between the assisted and unassisted modalities were assessed, together with the impact of PaPr output on the assisted reads.

RESULTS.—

Using PaPr, pathologists improved their sensitivity and specificity across all histologic grades and tumor sizes. Accuracy gains on both benign and cancerous WSIs could be attributed to PaPr, which correctly classified 100% of the WSIs showing corrected diagnoses in the PaPr-assisted phase.

CONCLUSIONS.—

This study demonstrates the effectiveness and safety of an AI tool for pathologists in simulated diagnostic practice, bridging the gap between computational pathology research and its clinical application, and resulted in the first US Food and Drug Administration authorization of an AI system in pathology.

Abstract PD11-02: Subtyping invasive carcinomas and high-risk lesions for machine learning based breast pathology

Background. The female mammary gland can develop a myriad of epithelial proliferative lesions including, high risk lesions, in-situ and invasive carcinomas. Identification of these pre-neoplastic and neoplastic conditions in biopsy specimens is crucial for proper patient management and may sometimes pose diagnostic challenges for pathologists. Recent research has shown that machine learning algorithms applied to whole slide images (WSI) can accurately detect and grade various cancers; herein, we devise and test a system that classifies the most common preneoplastic and neoplastic conditions of the female breast from WSIs. Design. De-identified slides were scanned on Leica AT2 whole slide scanners (20x; 0.5 µm/pixel) from MSK database were retrieved. Clinical diagnostic metadata were extracted from the pathology reports. Using a multi-label multiple-instance learning (ML-MIL) approach, a SE-ResNet50 Convolutional Neural Network (CNN) was trained to classify atypical lobular hyperplasia (ALH), atypical ductal hyperplasia (ADH), lobular carcinoma in situ (LCIS), ductal carcinoma in situ (DCIS), invasive lobular carcinoma (ILC), invasive ductal carcinoma (IDC). In additional morphological subtypes including apocrine, mucinous, solid papillary, micropapillary, and tubular carcinoma were trained. The system uses the WSI as an input and outputs a slide level class and heatmap for the presence of the trained classes. A validation dataset separate from the training set was used to assess performance of the trained model. Results. The CNN was trained on 9,751 surgical specimens (biopsy, 6,289; excision, 3,462) comprising 40,637 slides. The system was validated on 3,183 breast specimens (biopsy, 1,934; excision, 1,249) comprising 11,447 digital slides that were not included in the training of the CNN model. Validation performance in terms of Area Under Receiver Operating Characteristic Curve (AUROC) for each class is shown in Table 1. Conclusion. The trained CNN had a high performance in identifying the presence of ADH, ALH, DCIS, IDC, ILC, LCIS, and, apocrine, micropapillary, mucinous, solid papillary, and tubular carcinomas. Further studies expanding classes to include all clinically relevant lesions and morphologies are underway. In addition, the same approach can be used to detect microinvasions and calcifications in breast tissue.

Table 1.Area Under Receiver Operating Characteristic Curve for Breast Lesion ClassesClassNum. Positive (specimens)Num. Negative (specimens)AUROCADH24718640.903ALH20918860.950LCIS17520080.958DCIS81920920.956IDC52126620.956ILC7131120.934Apocrine2431590.931Micropapillary17230110.927Mucinous1231710.994Solid Papillary1531680.908Tubular carcinoma831750.990

Citation Format: Matthew G Hanna, Patricia Raciti, Alican Bozkurt, Ran Godrich, Julian Viret, Donghun Lee, Philippe Mathieu, Matthew Lee, Eugene Vorontsov, Tomer Sabo, Felipe C Geyer, Jorge S Reis-Filho, Leo Grady, Thomas Fuchs, Christopher Kanan. Subtyping invasive carcinomas and high-risk lesions for machine learning based breast pathology [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD11-02.

Independent real-world application of a clinical-grade automated prostate cancer detection system

Artificial intelligence (AI)‐based systems applied to histopathology whole‐slide images have the potential to improve patient care through mitigation of challenges posed by diagnostic variability, histopathology caseload, and shortage of pathologists. We sought to define the performance of an AI‐based automated prostate cancer detection system, Paige Prostate, when applied to independent real‐world data. The algorithm was employed to classify slides into two categories: benign (no further review needed) or suspicious (additional histologic and/or immunohistochemical analysis required). We assessed the sensitivity, specificity, positive predictive values (PPVs), and negative predictive values (NPVs) of a local pathologist, two central pathologists, and Paige Prostate in the diagnosis of 600 transrectal ultrasound‐guided prostate needle core biopsy regions (‘part‐specimens’) from 100 consecutive patients, and to ascertain the impact of Paige Prostate on diagnostic accuracy and efficiency. Paige Prostate displayed high sensitivity (0.99; CI 0.96–1.0), NPV (1.0; CI 0.98–1.0), and specificity (0.93; CI 0.90–0.96) at the part‐specimen level. At the patient level, Paige Prostate displayed optimal sensitivity (1.0; CI 0.93–1.0) and NPV (1.0; CI 0.91–1.0) at a specificity of 0.78 (CI 0.64–0.89). The 27 part‐specimens considered by Paige Prostate as suspicious, whose final diagnosis was benign, were found to comprise atrophy (n = 14), atrophy and apical prostate tissue (n = 1), apical/benign prostate tissue (n = 9), adenosis (n = 2), and post‐atrophic hyperplasia (n = 1). Paige Prostate resulted in the identification of four additional patients whose diagnoses were upgraded from benign/suspicious to malignant. Additionally, this AI‐based test provided an estimated 65.5% reduction of the diagnostic time for the material analyzed. Given its optimal sensitivity and NPV, Paige Prostate has the potential to be employed for the automated identification of patients whose histologic slides could forgo full histopathologic review. In addition to providing incremental improvements in diagnostic accuracy and efficiency, this AI‐based system identified patients whose prostate cancers were not initially diagnosed by three experienced histopathologists. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Abstract PD6-03: Clinical-grade detection of breast cancer in biopsies and excisions using machine learning

Background: Pathologists reviewing breast tissue slides must identify the presence of many salient features within each slide, including invasive and in situ breast cancer as well as various forms of atypia. In breast pathology particularly, the large volume of slides poses significant challenges for workload management and pathologist productivity (Johnson et al. 2019). The shift to a digital workflow in pathology, augmented by machine learning algorithms, has the potential to increase the efficiency, and productivity of pathologists by identifying cancer and pre-cancerous lesions in digitized slides. While there has been extensive work using machine learning algorithms to detect breast cancer metastasis in lymph nodes (Liu et al. 2018; Steiner et al. 2018), almost no research has been done on using such systems to detect breast cancer in biopsies and excisions.

Methods: We created and assessed Paige Breast Alpha, a machine learning system for the detection of breast cancer in hematoxylin and eosin (H&E) stained whole slide images (WSIs) of glass slides. The system is a binary classifier, intended to draw a pathologist’s attention to concerning features. Concerning features (the positive category) consisted of invasive breast cancer, in situ breast cancer, and various forms of atypia (atypical ductal hyperplasia, atypical lobular hyperplasia, etc. ). The deep learning system is based on the method proposed in Campanella et al. (2019). It learns directly from diagnosis using multiple instance learning, without the need for pixel-wise annotations. Paige Breast Alpha was trained on 17354 images from 3378 patients, and was assessed on 7921 images from 2443 patients. All slides were scanned on a Leica Aperio AT2.

Results: For detecting invasive or in situ cancer at the part level, the system achieved an overall sensitivity of 97.3% and a specificity of 98.0% in biopsies and 96.1% sensitivity and 91.5% specificity in excisions. Each part had between 1—10 slides.

Conclusions: We hypothesized that a machine learning system trained to detect predefined types of breast cancer and pre-cancerous lesions could be applied to a range of breast biopsy and resection WSIs to detect for the presence of these lesions. Herein we showed that the presence of these predefined features can be detected with high accuracy. Future studies are being initiated to assess the potential benefits of such a system when used by a pathologist. Additional systems are under development that would have the capability of subtyping the lesion present, in addition to acting as an overall binary classifier.

Citation Format: Matthew G Hanna, Patricia Raciti, Ran Godrich, Adam Casson, Julian Viret, Donghun Lee, Matthew Lee, Alican Bozkurt, Jillian Sue, Belma Dogdas, Brandon Rothrock, Leo Grady, Christopher Kanan, Thomas Fuchs. Clinical-grade detection of breast cancer in biopsies and excisions using machine learning [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD6-03.

Hydrodynamic model of heat stroke

This work presents an hydrodynamical model of heat stroke, which is a physiopathological state of stress, due to an exposure of animals to an ambient temperature of approximatively 40 degrees C during two hours. The evolution of body temperature during this stress process is characterised by three phases. A first phase of increase is followed by a plateau which occurs before a second phase of increase which can be lethal. The model is based on the analogy of a boat progressively caught in a whirlpool. The evolution of the degree of freedom lost by the boat is mathematically analysed and this study leads to the same three phases. The theoretical curves calculated during this study are well in agreement with the experimental curves obtained with animals. This analogy is compared to a previous one which has been made during another experiment with animals constrained by chemical intoxications. It seems that stress can be considered as a vital vorticity and that hydrodynamic models are powerful tools in understanding this physiopathological state.

Hydrodynamic modelling of stress

This work is a qualitative study of an organism's physiological adaptative response to stress. The experimental data were selected from a previous study leading to the conclusion that stress may be considered as a topological retraction within a vital space that must be more precisely defined. The experimental methodology uses rat poisoning by neurotoxins. The control parameter is the intensity of the toxic doses. Measured parameters are the animals' survival rate and the kinetics of cerebral acetylcholinesterase activity. The results, when expressed as a function of the inverted doses, show a characteristic evolution. The pattern of the curve closely resembles a vortex profile. This analogy is studied more extensively in both the physical and biological domains. These findings help to clarify the concept of biological stress which presents the same vectorial properties as hydrodynamic vorticity. In particular, the dissipation of stress and the dissipation of vorticity seem to obey the same laws. This observation is valid for both diffusion and convection processes. The decompensation phase of stress could be compared with the instability and turbulence in flows. Our approach in this paper is mainly to establish a general and phenomenological description of the stress response fitting experimental observations.

Comparative study of the fluidity of plasma and disc membranes of bovine rod outer segments by electron-spin resonance

The fluidity of isolated plasma and disc membranes from bovine rod outer segments has been compared by electron-spin resonance spectroscopy using the stearic acid spin labels 5-SASL and 16-SASL. This comparison is of interest, given the fact that the disc membranes arise by invagination from the plasma membrane. Analysis of the order parameter in the hydrophilic part of the membrane, and of rotational correlation time in the hydrophobic part, showed a difference of fluidity between these two types of membranes, with a higher fluidity in the disc membranes in both their hydrophilic and hydrophobic regions. For example, at a temperature of 37 degrees C, plasma and disc membranes exhibited values of 0.64 and 0.61 for the order parameter (S), and 9.1 and 14.5 s-1 for the rotational correlation frequency (v), respectively. These findings are discussed in relation to previously described differences in the biochemical compositions of the membranes.

Modifications of erythrocyte membrane fluidity from patients with anorexia nervosa before and after refeeding

Erythrocyte membrane characteristics were compared in 15 normal women and 15 women with anorexia nervosa; the patients were studied at hospital admission and again after 1 month of refeeding. At admission, physical properties of erythrocyte membranes, studied with electron spin resonance spectrometry, significantly differed between the anorexic patients and the normal volunteers. Fluidity from the hydrophobic part of the erythrocyte membrane, estimated by the correlation frequency, was decreased in the patients. After 1 month of refeeding, fluidity increased. One of the possible mechanisms of the variation of membrane fluidity could be the effect of cholesterol on membrane structure. Increased cholesterol levels in anorexic subjects could reduce fluidity. These alterations in membrane fluidity could explain some of the neurobiological abnormalities observed in anorexia nervosa.

Selective modifications of the phospholipid fatty acid composition in human platelet membranes using nonspecific and specific lipid transfer proteins

In order to specifically modify the fatty acid composition of cell membrane phospholipids, we have developed an original method based on the transfer of pure phospholipid molecular species to membranes. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) subclasses containing 18:2n-6 and 22:6n-3 at the sn-2 position were incorporated into human platelet membranes using the endogenous phosphatidylinositol/PC transfer protein (PI/PC-TP) and the phospholipid transfer protein from maize (L-TP), respectively. PI/PC-TP was shown to catalyze a strict exchange of phospholipids between platelet membranes and unilamellar vesicles containing 1,2-diacylglycerophosphocholine (diacyl-GPC; 16:0/18:2-GPC, or 16:0/22:6-GPC). The proportions of 18:2n-6 and 22:6n-3 in diacyl-GPC of platelet membranes were gradually increased from 10.7 to 16.9% and from 0.8 to 10.1%, respectively, whereas the PE and PI fatty acid compositions were not changed. The diacyl-GPC enrichment in 22:6n-3 and 18:2n-6 did not induce changes in membrane fluidity parameters measured by electron-spin resonance of 5- and 16-nitroxy stearic acids. Similarly, 18:2n-6 and 22:6n-3 esterified in 1,2-diacylglycerophosphoethanolamine (diacyl-GPE) have been incorporated in platelet membranes by an apparent exchange process under conditions where donor vesicles had a phospholipid composition equivalent to that of platelet membranes. The proportions of 18:2n-6 and 22:6n-3 were selectively and progressively increased from 6.0 to 21.2% and from 2.2 to 17.2%, respectively, in diacyl-GPE of platelet membranes. Thus, the L-TP- and PI/PC-TP-catalyzed enrichment can be used for studying the modulation of membrane biological activities by defined changes of fatty acid composition of specific phospholipid classes or subclasses.

Effect of specific phospholipid molecular species incorporated in human platelet membranes on thromboxane A2/prostaglandin H2 receptors

The incorporation of albumin-bound docosahexaenoic acid (22:6n-3), but not linoleic acid (18:2n-6), into cellular phospholipids inhibits platelet aggregation induced by the thromboxane analogue U46619. [3H]U46619 specific binding to thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptors, as well as specific binding of the antagonist [3H]SQ29548 to these sites were also decreased in these modified cells (P. G., Swann et al. 1990. J. Biol. Chem. 265: 21692-21697). More than 80% of the 22:6n-3 incorporated in these cells was esterified in the various endogenous phospholipid classes and the remaining was found in neutral lipids and in the unesterified fatty acid pool. In this study, we determined whether the effects observed could be attributed to the esterification of 22:6n-3 in phospholipids and whether the 22:6n-3 biological activity might depend on its esterification in specific phospholipid classes. Therefore, pure phosphatidylcholine (PC) and phosphatidylethanolamine (PE) molecular species were transferred to platelet membranes, using lipid transfer proteins. PC and PE containing palmitate (16:0) and 22:6n-3 or 16:0 and 18:2n-6 at position sn-1 and sn-2, respectively, were incorporated into membranes only at the expense of the corresponding endogenous phospholipid class, by an apparent exchange process. When such modified membranes were tested for specific binding of U46619 and SQ29548, a significant decrease of the receptor site affinity was only observed in membranes highly enriched with 1-palmitoyl-2-docosahexaenoyl-glycerophosphocholine (16:0/22:6-GPC). Fluidity parameters measured by electron spin resonance of 5- and 16-nitroxy-stearic acids were not significantly different in membranes enriched with 16:0/22:6-GPC relative to those enriched with 16:0/18:2n-6-GPC, arguing against a generalized perturbation of the membrane due to 22:6n-3 incorporation. We conclude that molecular species of PC with 22:6n-3 at the sn-2 position can affect TXA2/PGH2 receptors. The selectivity of the inhibitory effect of PC containing 22:6n-3 is discussed.

Reaction of the organism to stress: the survival attractor concept

This paper outlines a phenomenological approach for describing physiological reactions occurring immediately after vital threats. This exemplified by data taken from previous studies relative to chemical intoxications of rats by a neurotoxical drug. The survival rate of the animals and the variations of their cerebral acetylcholinesterase activity are both reported as a function of the drug concentration, and with respect to their age. The collecting of the results may be described as the cusp, a bifurcation set of Thom's Catastrophe Theory. The young animals react by a vital burst which modifies the shape of the cusp. A new fold or pocket takes place, changing it to the butterfly bifurcation set. This pocket supports the survival attractor concept, which appears reactional, transitory and variable in its intensity. In the last part of the paper, an extension of this concept is proposed to the visual domain. Some of patients who have suddenly and partially lost their visual acuity can recover some visual capacity by developing a new ability to see in weak contrasts. This reaction may be described as a visual survival attractor.

Fluidity of chicken ventricular plasma membranes during development in-ovo and after birth: spin labelling and fluorescence studies

The fluidity of isolated chicken ventricular plasma membranes was investigated by ESR spectroscopy, using three doxylstearic spin labels (5-SASL, 10-SASL and 16-SASL), and by fluorescence anisotropy measurements, using DPH probe. The analysis of 2T1 splitting constant and rotational correlation frequency have shown differences, during in-ovo development, characterized by a rigidification phase with a maximum at 19 days of development, just before hatching, followed by a fluidification phase after birth. These phenomena were also improved by DPH fluorescence and dynamical analysis of the hydrophobic 16-SASL probe.

Stimulated release of acetylcholinesterase in rat striatum revealed by in vivo microspectrophotometry

The microspectrophotometric technique allows a direct in vivo measurement of brain extracellular acetylcholinesterase. An optical probe associated with electrodes for stimulation was implanted in striatum of anaesthetized rats to determine the effects of neuronal excitation on the acetylcholinesterase activity. Electrical stimulations induced a reversible increase in acetylcholinesterase activity of about 30 to 50%, with a recovery to baseline occurring after 1 or 2 h. Furthermore, iterative electrical stimulation induced a progressive fading of this phenomenon. An enhancement of acetylcholinesterase activity was also observed by stimulations with potassium injections through a canal of the probe. These results suggest mainly an intracellular origin of the released enzyme and estimate its contribution at about 40% of the whole extracellular enzyme activity.

Simultaneous changes in lipid composition, fluidity and enzyme activity in piglet intestinal brush border membrane as affected by dietary polyunsaturated fatty acid deficiency

The effects of dietary polyunsaturated fatty acid (PUFA) deficiency on intestinal brush border membrane (BBM) fluidity, lipid composition and 5'-nucleotidase activity were examined in piglets. Cholesterol/phospholipid and sphingomyelin (SM)/phosphatidylcholine (PC) ratios were unaffected. However, fluidity was decreased in the external regions and also tended to decrease in the core of the PUFA-deficient pig membrane lipid bilayer. Therefore, the change in the membrane physical properties seemed to be due to the large diet-induced alteration in the phospholipid (PL) fatty acid composition and to the concomitant decrease in PC and increase in phosphatidylserine levels. In the membrane total PL, the arachidonic acid level was slightly lowered, while linoleic, eicosapentaenoic and docosahexaenoic acid levels markedly decreased. PC was mainly concerned by the altered distribution of unsaturated fatty acids, but not SM. However, a significant decrease in (n-6)/(n-3) ratio occurred in the latter. These structural changes were associated with a higher 5'-nucleotidase activity in the intestinal BBM of PUFA-deficient as compared to control piglets.

A spin label study of the membrane effect of various psychoactive drugs in human erythrocytes

The effect of psychoactive agents with different clinical actions: three sedative neuroleptics (trifluoperazine, alimemazine tartrate, chlorpromazine), an anticholinergic agent (trihexyphenidyl hydrochloride), two tricyclic antidepressants (imipramine, desipramine) and lithium carbonate on the rotational correlation frequency (V+) of the spin label 16NS has been comparatively investigated in whole human erythrocytes. V+ was about 40% increased by the three neuroleptics, the anticholinergic agent and the antidepressant molecules at 0.2 mM. By contrast, lithium did not induce any significant change in V+ at the same concentrations. It can be suggested that the increase in "membrane fluidity", observed with a wide variety of drugs, is a non specific effect, unrelated to the psychotropic action, that can be ascribed to the amphiphilic properties of the tested drugs.

[The Catastrophe theory and membrane physiological functions]

This communication is based on a preliminary work which emphasized a topological model of biomembranes from Thom's Catastrophe Theory. In this model called swallowtail bifurcation set, the structural state of a biomembrane was within the control of two structural attractors. Then, the physiological act of this biomembrane resulted in a sudden transfer of weight from the hydrophilic attractor to the hydrophobic attractor. In this consecutive work, the physiological act appears to be one of the four stages which permit to describe the larger notion of cyclic membrane function. Two of these stages unfold in the structural axis of the swallowtail model. They prepare the two others (physiological act and refractory stages) which expand in the functional direction. This conceiving of cyclic membrane function is applied to physiological examples such as the action potential and the endocytosis. Then, changes in this function are discussed on the basis of pathological data.

Rapid postmortem decrease in the ectocellular acetylcholinesterase activity in rat striatum as assessed by in vivo microspectrophotometry

The acetylcholinesterase (AChE) activity in striatum rat was determined before and shortly after death using the in vivo microspectrophotometric method. This technique allowed us to monitor the Ellman colorimetric reaction directly inside the brain using an optical probe implanted in a live animal and to determine locally the AChE activity. Whatever the cause of the animals death, we observed a drastic postmortem decrease of the AChE activity of about 35-50%, 10 min after death. We have verified that the postmortem decrease of brain temperature or pH and postmortem optical properties changes could only explain a fraction of the AChE activity fall (16%). This phenomenon seems to be related to events strictly localized at the cellular level, since local injection of cyanide at the measuring site promotes a decrease of the enzymatic activity (40%) close to the levels observed after death. The origin of this rapid postmortem fall of the AChE activity is discussed. The technical properties of the microspectrophotometric method exclude a decrease of the ectocellular pool of enzyme after death. Our results allow us to envisage the existence of an in vivo endogenous regulation of the AChE activity which disappears shortly after death.

Membrane properties of the sarcolemma and sarcoplasmic reticulum of pigs susceptible to malignant hyperthermia. Action of halothane

The role of sarcolemma and sarcoplasmic reticulum in malignant hyperthermia was studied by the esr technique using the trapezius muscle membrane of both normal and genetically susceptible pigs. Normal and malignant hyperthermia membranes from sarcolemma as well as from sarcoplasmic reticulum did not show significant differences near the polar heads of the phospholipidic bilayer. In contrast, the fluidity and activation energy of normal membranes differed from those in malignant hyperthermia; in both sarcolemma and sarcoplasmic reticulum the mobility of the label was greater than the controls. The presence of halothane was examined, by inducing this disease anesthetically. The drug effect confirmed the above results, i.e. the disease affects mainly the hydrophobic core of the lipid bilayer of both sarcolemma and sarcoplasmic reticulum membranes.

Abnormal fluidity state in membranes of malignant hyperthermia pig skeletal muscle

The fluidity state was analyzed on sarcoplasmic reticulum membranes and phospholipid vesicles prepared from normal and malignant hyperthermia susceptible pig muscle. Electron spin resonance studies were performed to determine the fluidity state at the region near the polar headgroups and in the central core of the bilayer using 5-nitroxide (5-NS) and 16-nitroxide stearic acid (16-NS), respectively. With the 5-NS label, no differences were found between normal and malignant hyperthermia sarcoplasmic reticulum (MH SR) membranes whereas with the 16-NS label, a significant increase of the activation energy was shown with MH membranes. Lower values of fluorescence anisotropy observed with DPH-labeled MH membranes as compared with normal ones, confirmed the higher abnormal fluidity state of these membranes. The fluidizing effect of halothane, a triggering agent of malignant hyperthermia syndrome, was also studied in these membranes. We show that a relatively low concentration of the drug destabilized not only the diseased sarcoplasmic reticulum membranes but also the vesicles made of total phospholipids extracted from MH skeletal muscle. Together, these findings strongly suggest that an overall increase in membrane fluidity may be implied in the MH disease, improving the general membrane defect hypothesis for this syndrome.

Evidence for a structurally specific role of essential polyunsaturated fatty acids depending on their peculiar double-bond distribution in biomembranes

ESR spectrometry with 5-, 7-, 10-, and 12-doxylstearate probes and a combined index considering separately the double-bond numbers of essential and nonessential fatty acids were used to investigate the structural role of the double bonds of polyunsaturated fatty esters in membrane phosphoglycerides. Purified brush border membrane vesicles were prepared from the jejunum of piglets receiving either high (HLA) or low (LLA) dietary levels of linoleic acid (18:2 n-6). In the LLA as compared to the HLA group, there were no significant modifications of (a) the relative contents of cholesterol, phospholipid, and protein and of (b) the phosphoglyceride class distribution, contrasting with very large changes in the fatty acid compositions of each phosphoglyceride. These changes were characterized by an increase in nonessential monoene and triene (18:1 n-9 and 20:3 n-9) and a decrease in essential diene (18:2 n-6) in LLA- as compared to HLA-fed piglets. The essential tetraene 20:4 n-6 remained rather constant despite an overall nonsignificant increase in the LLA group. The total double-bond number (TDBn) was not significantly affected, contrasting with the variations in the double-bond numbers of essential and nonessential fatty acids (DBn(EFA) and DBn(nonEFA), respectively). The combined DBn(EFA)/DBn(nonEFA) index was 1.7-3.3 times lower in LLA than in HLA membrane phospholipids. It was concluded that the diet was able to affect the double-bond distribution in the upper and inner half-parts of the membrane leaflet without changing the total number of double bonds.(ABSTRACT TRUNCATED AT 250 WORDS)

Halothane-induced functional and structural modifications in sarcoplasmic reticulum membranes from pig skeletal muscle

We investigated the effect of halothane on lipid and protein components of sarcoplasmic reticulum membranes isolated from pig trapezius muscle. We studied the relationships between the (Ca2(+)-Mg2+)-ATPase activity and the interaction of the anesthetic with lipid and protein moieties by means of EPR and fluorescence spectroscopic techniques. Our results clearly show that below 5 mumol per mg protein, halothane interacts mainly with the lipid components of the membrane. This interaction is shown to be localized in the central core of the phospholipid bilayer and to induce an increase of the membrane calcium permeability. The interaction with protein components only occurs at higher halothane concentrations and affects its conformational and functional states. These results are discussed with respect to new insights into diethylether-SR membrane interaction and to malignant hyperthermia syndrome in the pig.

In vivo spectrophotometric determination of striatal acetylcholinesterase activity: the modulation induced by the antidepressant amitriptyline

A new technology called in vivo spectrophotometry was applied to the quantitative determination of the variations in local acetylcholinesterase (AChE) activities. Repeated measurements of the enzyme activities in the same live animal allowed the study of the in vivo inhibition of AChE by amitriptyline. Interactions between AChE and this tricyclic antidepressant were investigated at the striatal level in anesthetized rats. In this anesthetized model, AChE assays were shown to be stable for approximately 8 h. The dose-effect relationship was explored in the 2.5- to 50-mg/kg amitriptyline range. A reversible inhibition was observed after acute amitriptyline administration. The maximum of inhibition appeared between 90 and 210 min after the intoxication and reached up to 22% for the 50-mg/kg dose. The threshold dose was established as 8 mg/kg. Evidence for an indirect interaction between tricyclic antidepressant and AChE was demonstrated when the total integrity of the biological system was preserved.

Interaction of antiaggregant molecule ajoene with membranes. An ESR and 1H, 2H, 31P-NMR study

The structure of ajoene, a molecule extracted from garlic, has been studied by 1H-NMR and its interaction with model membranes by 1H-, 2H-, 31-P-NMR and ESR experiments. This study clearly shows that the ajoene molecule is located deep in the layer and is close to the interlayer medium. Moreover while NMR experiments show that the membrane structure is only slightly affected by the presence of ajoene, ESR experiments reveal significant modifications in phospholipid dynamics. This interaction, observed before with the phenothiazine derivative, promazine, results in an increase of the membrane fluidity in its hydrophobic part and could be related to clinical properties of ajoene.

Biophysical interpretation of membrane fluidity by catastrophe theory

We have regrouped the data of two examples where membrane fluidity was progressively modified by pharmacological and physiological agents. In our approach, each initial condition is determined by control parameters (depth of the membrane bilayer explored, concentration of agents). The fluidity is expressed as a state parameters followed on the control space. Then, according to Catastrophe Theory, the results are depicted as tridimensional patterns which can be recognized as bifurcation sets. Consequently, the fluidity is considered as resulting in a compromise phenomenon (normal factor) between two structurally attracting configurations (of hydrophilic and hydrophobic nature). The concepts of membrane activity and membrane function are then discussed on the basis of physiological functionality of biomembranes. The main application of this research interests the pharmacological domain. Indeed, a new classification of drugs could be proposed. According to the loss of membrane functionality, some drugs could imply a too high differentiation of attractors (splitting factor) and others could imply the destruction of the compromise. The first type is characterized by the physical destruction of the membrane. In the second type, the entity of the bilayer is preserved but the membrane is destructurated.

Demonstration of functional acetylcholinesterase on the soma of individual neurones of Aplysia by in vivo microspectrophotometry

The presence of functional acetylcholinesterase is demonstrated in vivo on somatic membranes of single ganglionic neurones of Aplysia using concurrently microspectrophotometry and electrophysiology. The similarity of the effects of an irreversible blocker of acetylcholinesterase and of phospholipase C from Bacillus cereus suggests that acetylcholinesterase is anchored in the membrane via phosphatidylinositol.

Modification of fluidity and lipid-protein relationships in pig intestinal brush-border membrane by dietary essential fatty acid deficiency

The effect of dietary essential fatty acid (EFA) deficiency on the dynamic molecular organization of pig intestinal brush-border membrane (BBM) was studied using purified BBM vesicles. A 6 week dietary treatment of weaning piglets induced a typical EFA-deficient pattern in the lipid composition of both plasma and epithelial membranes. In pigs fed on the EFA-deficient diet, the plasma 20:3(n - 9)/20:4(n - 6) ratio progressively increased and reached a stable value after 3 weeks of experiment, whereas it remained low (less than 0.2) in controls. In the intestinal BBM, the cholesterol/protein, phospholipid/protein and consequently the cholesterol/phospholipid ratios, as well as the phospholipid class distribution, were unchanged. In particular, the sphingomyelin/phosphatidylcholine (SM/PC) molar ratio was not affected. However, the fatty acid composition of phospholipid main classes was markedly modified, leading to decreased lipid fluidity and to a large change in membrane protein behaviour with EFA deficiency. These findings could be interpreted in terms of reduced lipid-protein interactions. Moreover, the increasing gradient of fluidity which took place within the lipidic matrix from its surface was modified by the dietary treatment, as fluidity was lowered by EFA deficiency at different depths of the layer.

Nutrition and biomembranes: additional information concerning the incidence of dietary polyunsaturated fatty acids on membrane organization and biological activity

One of the important questions in biomembranes now is: Do the essential fatty acids (polyunsaturated fatty acids of the n-6 and n-3 series) play an original structural role in the arrangement of the lipid matrix capable, in particular, of triggering modifications of intrinsic protein activities? Preliminary results from our laboratories are presented in rat and piglet fed standard or essential fatty acid-deficient diets. The relative amounts of 18:2 (n-6) and 20:4 (n-6) in total fatty acids of hepatic microsome or enterocyte brush border membrane phospholipids are closely dependent on the type of diet (a globally decreasing effect with deficiency), whereas no differences were observed with relative amounts of cholesterol, phospholipids, and proteins. This effect of deficiency on membrane fatty acids has to be compared to the decreasing specific activities of microsome NADPH-cytochrome c reductase or aniline hydroxylase (studied in rat), to the increasing order of the structure of both membrane microsome and brush border lipid matrix (studied in both rat and piglet), and to the increasing mobility (or accessibility) of the membrane-protein surface-bonded spin-label (studied in the piglet brush border membrane), suggesting a probably defective protein-lipid fit in the case of deficiency. These results could favor conformational change in the whole membrane structure (i.e. proteins and lipids). The specificity of these effects remains to be assessed.

Physical state abnormality of erythrocyte membrane in myotonic dystrophy: a spin label study

Biophysical abnormalities of the erythrocyte membrane in muscular dystrophies have been described by numerous authors. This work presents the results we have obtained on 23 subjects suffering from myotonic muscular dystrophy (MyD, Steinert disease) by the spin label method. Two types of fatty acid spin labels were used: 5-nitroxide stearic acid (5NS) and 16-nitroxide stearic acid (16NS) which probe the membranes respectively near their polar heads and in their hydrophobic core. We measured the classical order parameter, the saturation behaviour of the electron paramagnetic resonance signal, and the label apparent rotation correlation time as a function of the temperature, on fresh and in vitro stored red blood cells. With the 5NS label, no differences were found between controls and patients. With the 16NS label, a highly significant variation in the thermic behaviour of the membrane is observed in its hydrophobic and fluid core. This last result may suggest some similarities between the red blood cell membranes of adult MyD's and healthy children.

Signal transduction in normal and pathological thrombin-stimulated human platelets

Human blood platelets stimulated by thrombin undergo very rapid morphological changes, the most characteristic of which are pseudopod formation and granule centralization. These early changes in shape are accompanied by a transient decrease (30%) in phosphatidyl inositol 4,5-bisphosphate (PIP2) which occurs in the first 10 s after thrombin addition. Transient decreases in phosphatidyl inositol 4-phosphate (PIP) and phosphatidyl inositol (PI) occur later (20-30 s). These events lead to the formation of inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DG) and hence phosphatidate (PA). Two polypeptides are phosphorylated during the same time span: the myosin light chain (P20) and a 43 kDa protein (P43). Concomitant with these molecular changes, platelet 'release reaction' occurs, i.e., liberation of the different granule constituents into the external medium: the earliest concerns dense bodies which liberate adenine nucleotides, calcium and serotonin; alpha-granules then liberate adhesive and specific proteins and are followed by lysosomes which liberate hydrolases. Pathological platelets from patients with inherited disorders, presenting well-characterized and specific defects of either the platelet membrane (GT) or storage granules (GPS and HPS), have also been studied. The results obtained lead to the following conclusions: (1) the transducing system is normal in platelets unable to aggregate; (2) phosphorylation of P20 and P43 proteins can be complete with impaired release; and (3) when platelets lack alpha-granules the transducing system as well as the release of other granule populations are impaired. These results evidence the relationship between the absence of intraplatelet components and metabolic events.

Biochemical and physicochemical determinations in a premyelin fraction obtained by zonal centrifugation in normal mouse and in dysmyelinating mutants (quaking, shiverer, and myelin-deficient)

Myelin and premyelin material denser than myelin were obtained from quaking (Qk), shiverer (Shi), and myelin-deficient (mld) mutant and control mice, using zonal centrifugation on zonal rotor. On these fractions, we performed biochemical analysis (lipids and fatty acid), and, in parallel, we determined the physical structure of membranes by the spin-label method. The hyperfine splitting constant (2 Tll) was used to determine the order of membranes and their rigidity, and frequency of rotation (Vc) was used to measure fluidity. In control mice, the premyelin material contained a lesser amount of sphingolipids than pure myelin, but the relative proportions between hydroxy- and nonhydroxy-cerebroside and sulfatides were similar in the premyelin material and in pure myelin. The premyelin material contained half the alkanes found in the pure myelin and much less very-long-chain fatty acids. The (2 Tll) was lower in the premyelin material, but the (Vc) was similar in myelin and premyelin material. In mutants, the amount of material recovered in the premyelin fraction was reduced in qk, and increased in both shi and mld. The relative amount of sphingolipids were normal in mld, but not in shi mutants, especially in cerebrosides formed with alpha-hydroxylated fatty acids and sulfatides formed with unsubstituted fatty acids. The absolute amounts of sphingolipids were nearly normal in both shi and mld. In the premyelin fraction from qk mutants, both relative and absolute amounts of sphingolipids were drastically altered. In percentage, cerebrosides and sulfatides formed with nonhydroxyfatty acids were dramatically reduced, and, conversely, cerebrosides and sulfatides formed with hydroxyfatty acids were increased. In terms of absolute amount, only cerebrosides and sulfatides formed with nonhydroxyfatty acids were dramatically reduced. In the premyelin fraction, polyunsaturated fatty acids were increased in shi and mld, but decreased in qk. In this mutant, lignoceric (24:0) and nervonic (24:1) acids were drastically reduced. The amount of alkanes in the premylin material from qk and mld was reduced by 50%. The shi fraction was nearly free of alkanes. The maximal apparent coupling constant (hyperfine splitting constant, 2 Tll) was not affected in the mld and qk mutant, but was reduced in the shi mutant premyelin fraction. The Vc was dramatically increased in the qk, slightly decreased in the shi, and close to control in the mld. This work provides additional data on premyelin material prepared in various neurological mutants using continuous gradients in zonal rotor.(ABSTRACT TRUNCATED AT 400 WORDS)

Platelet membrane molecular organization: relationship with membrane bound calcium

The fatty acid spin label 5 nitroxide stearate has been used to determine the membrane organization changes induced by platelet aggregation. A decrease in order is observed with thrombin, even in the presence of EDTA, when aggregation is inhibited. Conversely, after aggregation by the calcium ionophore A23187 the rigidity of the phospholipids is not modified. These effects are discussed in relation to the release of membrane bound calcium induced by thrombin.

Applications of electron spin resonance spectroscopy to microrheology studies of membranes and cells

One of the most powerful tools for the study of the molecular dynamics and molecular organization of biological membranes is the spin label method which uses stable free radicals (nitroxides) studied by electron spin resonance spectroscopy. The spectra are very dependent on the mobility and orientation of these probes in a magnetic field. They give information on the tumbling rate of molecules in liquids, the membrane microviscosity, the order parameter of the phospholipid fatty acid chains, the activation energy of their rotation and their flexibility. The method has interesting applications in the rheological domain; for example it enables measurement of the internal viscosity of erythrocytes and red blood cell orientation in a Poiseulle flow.

A spin label study of the erythrocyte membrane in mothers and sisters of patients suffering from Duchenne Muscular Dystrophy

The erythrocyte membranes of mothers and sisters of boys suffering from Duchenne Muscular Dystrophy (DMD) have been studied by spin labelling. Two oxazolidine nitroxide derivatives of stearic acid were used. With the first of them (16 NS) which probes the hydrophobic part of the phospholipids, we measured the fluidity of the membrane as a function of temperature. The second nitroxide derivative (5 NS) probes the membrane near the phospholipid polar heads. The amplitude of the electron spin resonance signal was studied as a function of the spectrometer microwave power in order to determine the paramagnetic label saturation behaviour. No significant difference was observed between the control adult women and the carrier mothers. On the contrary, almost all the normal young premenarchial girls showed simultaneously a break in the fluidity vs. temperature plot of the 16 NS probe and a saturation phenomenon of the 5 NS label signal. In about 50% of the DMD boys' sisters, no break in the temperature plot nor saturation behaviour was observed. This corresponds to the theoretical repartition between normal and carrier girls if one admits that about 30% of the latter do not have any detectable membrane abnormality, as in the case of the creatine kinase (CK) test which shows about 30% of normal levels in carrier women. The study of the erythrocyte membrane in young girls can then be an useful complementary tool to detect DMD carriers.

Rat brain acetylcholinesterase turnover in vivo: use of a radioactive methylphosphonothiate irreversible inhibitor

A new organophosphorus compound was used in its non radioactive and tritiated forms in order to study rat brain acetylcholinesterase. We measured the activity recovery of the total enzyme and of its two main molecular forms (4 S and 10 S) as a function of time following the inhibition. The radioactive compound allowed us to study the disappearance of the inhibitor irreversibly bound to the enzyme in the main cholinergic areas. Both approaches gave similar results: acetylcholinesterase turn-over proceeds in two steps, a rapid one of about 30 mn and a slow one of about 2 days. Our results suggest an in vivo reactivation process concerning a fraction of the bound inhibitor.

Modulation of adenylate cyclase activity by the physical state of pigeon erythrocyte membrane. 1. Parallel drug-induced changes in the bilayer fluidity and adenylate cyclase activity

The fluorescence anisotropy probe perylene and the spin-labels 5-doxylsterate and 16-doxylstearate were used to estimate the order and internal microviscosity of the pigeon erythrocyte membrane upon perturbation by cationic or neutral amphipathic drugs (chlorpromazine, methochlorpromazine, tetracaine, and octanol) and an anionic drug, octanoic acid. Both methods gave identical results. The fluidity changes were found to strictly correlate with those of adenylate cyclase activity in the presence of GTP when perturbed by the drugs [Salesse, R., & Garnier, J. (1979) Biochim. Biophys. Acta 554, 102-113]. The cationic or neutral drugs, in an intermediate range of concentration, decreased the degree of organization and the internal microviscosity of the lipids together with the activity of the adenylate cyclase. At a higher concentration they reincreased them up to or higher than their initial level before the final destruction of the membrane structure and functions. This concentration effect was time dependent with tetracaine. The quaternary amine methochlorpromazine acted as chlorpromazine only on open ghosts. On intact cells, it inhibited catecholamine receptors at higher concentration and monotonously decreased the order and microviscosity, as the anionic amphipath octanoic acid did. This is taken as evidence that the inner leaflet of the bilayer is the seat for the observed multiphasic changes of viscosity and the control of adenylate cyclase and catecholamine receptors. This could stem from either a preferential intercalation or a surface effect of the amphipaths in the inner leaflet of the membrane. Since the basal activity of adenylate cyclase was not affected in the presence of drugs, it may be inferred that the enzyme holds its activity but that its stimulation is modulated by the membrane physical state.

[Electrophoresis of the membrane proteins of erythrocytes of spontaneously hypertensive rats]

The red blood cell membrane proteins of normal and spontaneous hypertensive Rats were studied by gradient polyacrylamide gel electrophoresis. The electrophoretic patterns of membrane proteins of hypertensive rats show three new bands of 58,000, 24,000 and 22,000 dalton. The existence of these new bands is not correlated with the age and the blood pressure values of the animals.

A spin-label study of sciatic nerves from quaking, jimpy and trembler mice

The spin labels, 5-nitroxide stearic acid and 16-nitroxide stearic acid were incorporated into whole sciatic nerves dissected from normal, quaking, jimpy and trembler mice. With 5-nitroxide stearic acid, we have studied the thermal variation of the maximal apparent coupling constant (T) between 0 degrees C and 50 degrees C. Within this range of temperatures, we obtained identical values of 2 T for nerves from normal and jimpy mice, whereas 2 T was smaller for nerves from quaking and trembler mice. With 16-nitroxide stearic acid, composite spectra were recorded, particularly in the high-field range. A line characteristic of myelin was clearly observed in the spectra of nerves from normal and jimpy mice; its intensity was somewhat less in nerves from quaking mice and much less in spectra from trembler mice. A shoulder in the principal highfield line of the spectrum is modified only with nerves from jimpy mice. The results agree well with those obtained by electron microscopy, which reveal normal myelination in nerves from jimpy mice, a slight modification of the myelin from those of quaking mice and a practically complete demyelination in peripheral nerves from trembler mice. However, the structure of the nerves of jimpy mice also seems to be modified at an, as yet, undetermined level.

A spin label study of rat brain membranes. Effects of temperature and divalent cations

Rat brain myelin, synaptosomal plasma membranes and synaptic vesicles were spin labelled with stearic acid nitroxide derivatives. Their electron spin resonance spectra were studied as a function of temperature and devalent ions (Ca2+ and Mg2+) concentrations. (1) Synaptosomal plasma membranes and synaptic vesicles show identical temperature variations of their order parameter (S = 0.58 at 35 degrees C and S = 0.72 AT 22 DEGREES C). Myelin appears more rigid (S = 0.66 at 35 degrees C and S = 0.76 at 22 degrees C). A discontinuity of the order parameter variation as a function of temperature, is observed between 14.5 degrees C and l9.5 degrees C with the three types of membranes. (2) The hydrophobic core of these membranes is very fluid. No transition temperature is observed. The measured values of the spin label rotation correlation times and rotational activation energies are 2.1 and 2.8 ns at 35 degrees C and 3.1 and 3.6 kcal/mol respectively for synaptosomal plasma membranes and myelin. (3) Ca2+ enhances the membrane rigidity (12+/-0.7% increase of the order parameter at 35 degrees C in the presence of 10(-3) M Ca2+) and increases the transition temperature. At a lower extend, similar effects are observed with Mg2+.