Impact of deep learning on radiologists and radiology residents in detecting breast cancer on CT: a cross-vendor test study

AIM

To investigate the effect of deep learning on the diagnostic performance of radiologists and radiology residents in detecting breast cancers on computed tomography (CT).

MATERIALS AND METHODS

In this retrospective study, patients undergoing contrast-enhanced chest CT between January 2010 and December 2020 using equipment from two vendors were included. Patients with confirmed breast cancer were categorised as the training (n=201) and validation (n=26) group and the testing group (n=30) using processed CT images from either vendor. The trained deep-learning model was applied to test group patients with (30 females; mean age = 59.2 ± 15.8 years) and without (19 males, 21 females; mean age = 64 ± 15.9 years) breast cancer. Image-based diagnostic performance of the deep-learning model was evaluated with the area under the receiver operating characteristic curve (AUC). Two radiologists and three radiology residents were asked to detect malignant lesions by recording a four-point diagnostic confidence score before and after referring to the result from the deep-learning model, and their diagnostic performance was evaluated using jackknife alternative free-response receiver operating characteristic analysis by calculating the figure of merit (FOM).

RESULTS

The AUCs of the trained deep-learning model on the validation and test data were 0.976 and 0.967, respectively. After referencing with the result of the deep learning model, the FOMs of readers significantly improved (reader 1/2/3/4/5: from 0.933/0.962/0.883/0.944/0.867 to 0.958/0.968/0.917/0.947/0.900; p=0.038).

CONCLUSION

Deep learning can help radiologists and radiology residents detect breast cancer on CT.

Enrichment in procoagulant microparticles in calcified human aortic valve – role in valvular endothelium alterations and enhanced thrombogenicity

Background

Aortic stenosis (AS) is characterized by endothelial dysfunction (ED), inflammatory cell infiltration, myofibroblastic and osteoblastic differentiation. Subclinical leaflet thrombosis was recently linked to higher rates of stroke and transient ischemic attack after transcatheter aortic valve implantation (TAVI). Procoagulant microparticles (MPs) are associated with ED, inflammation and clot formation. There is limited evidence regarding intra-valvular MPs content and their potential biological effects. This question is particularly relevant in TAVI in which the residing native valve could constitute a source of thrombotic activity enhancing leaflet thrombosis and valve dysfunction.

Purpose

Therefore, we hypothesized that MPs trapped within the native aortic valve contribute to valvular dysfunction including enhanced thrombogenicity.

Methods

Human valves were collected from patients undergoing surgical valve replacement for AS or aortic insufficiency (AI). Pro-thrombotic, pro-inflammatory, and ED markers were identified in the calcified vs non-calcified part of the valves by Western-blot. Calcium content was measured through colorimetric method. MPs were extracted from human pathological valves, and quantified through their prothrombinase activity. Primary cultures of porcine valvular endothelial cells (VEC) were treated with the MPs (10 nmol/L) or thrombin (1U/ml) for 24hrs. Phenotypic change was appreciated through gene expression pattern assessed by RT-qPCR. IL-8 secretion was measured by ELISA.

Results

The phenotype of the AS valve was characterized through increased expression of thrombogenic (tissue factor, thrombomodulin, PAI-1), adhesive (VCAM-1, ICAM-1) and inflammatory (COX-1, COX-2) molecules in the calcified part of the valve. Moreover, MPs content was increased in the calcified vs non-calcified part of the valve or AI valves. MPs levels was correlated with valvular calcium content (R=0.3862: p<0.001). Tissue factor was increased in MPs extracted from AS vs AI. The biological effect of MPs was tested on VEC in-vitro. Results showed dramatic increase in expression of inflammatory cytokines (CXCL10, CCL11, CXCL8, MCP1) adhesion molecules (VCAM-1, ICAM-1, SELP, SELE) and proangiogenic factors (VEGFR2, ANGPTL4) in VEC exposed to MPs (24h) from AS vs AI. Enhanced secretory phenotype was evidenced through IL-8 determination in the supernatant of VEC stimulated with MPs from AS valve.

Conclusion

Calcified aortic valve is a potent reservoir of MPs, acting as a pro-thrombogenic source per se and promoting a switch of VEC phenotype toward prothrombotic, proinflammatory and proangiogenic pattern. These data suggest that MPs released from the native valve constitute an important source of mediators involved in enhanced thrombogenicity and valvular remodeling.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): GERCA-Groupe Etudes Reali Commercia Avignon

Optimisation of Radiation Therapy in Bladder Preservation Therapy for Patients With Clinical Stage T2N0M0 Bladder Cancer

AIMS

A novel bladder preservation therapy, the OMC (Osaka Medical College) regimen, which combines radiation therapy with balloon-occluded arterial infusion of anticancer agents, is a treatment option for patients with muscle-invasive bladder cancer (MIBC). We retrospectively analysed the effects of changes in radiation dose and irradiation field on treatment efficacy and adverse events.The purpose of this study is to use the results of this study to help determine a course of radiation therapy for bladder preservation therapy of cT2N0M0 MIBC.

MATERIALS AND METHODS

We examined 352 patients with clinical stage T2N0M0 (cT2N0M0) MIBC classified into the following groups based on the irradiation method: group A, the whole pelvis (50 Gy/25 fractions) + local bladder (10 Gy/5 fractions); group B, the small pelvis (50 Gy/25 fractions) + local bladder (10 Gy/5 fractions); group C, the whole pelvis (40 Gy/20 fractions) + local bladder (10 Gy/5 fractions).

RESULTS

The complete response rate, 3-year overall survival and progression-free survival rates in group A were 92.9%, 94.9% and 82.1%, respectively; in group B were 87.2%, 86.7% and 76.7%, respectively; and in group C were 95.2%, 92.6% and 71.1%, respectively. No significant differences between the groups were noted. The incidence of ≥grade 3 urinary tract and gastrointestinal toxicities were not significantly different among the groups (group A: 7.8%, 1.7%; B, 11.1%, 0%; C, 7.1%, 1.8%, respectively). The 3-year progression-free rates of the common iliac lymph node (CILN) region in patients who received whole-pelvis and small-pelvis irradiation were 99.0 and 89.0% (P < 0.01), respectively, with the latter group having significantly high lymph node recurrence in the CILN region.

CONCLUSIONS

Our findings showed that the optimal radiation therapy for patients with cT2N0M0 MIBC undergoing the OMC regimen is whole-pelvis irradiation including the CILN region, with a total dose of 50 Gy/25 fractions.

Primary hemostatic disorders drive early and late major bleedings of patients with atrial fibrillation after transcatheter aortic valve replacement

Introduction

Patients with atrial fibrillation (AF) are likely to have multiple co-morbidities and receive anticoagulants after TAVR, which lead to a poor prognosis including bleeding events. Closure time adenosine diphosphate (CT-ADP) is a primary hemostasis point-of-care test used as a surrogate marker of high molecular weight (HMW) multimers defect of Von Willebrand factor (VWF). Our prior studies suggest that prolongation of CT-ADP (&gt;180 seconds) after TAVR is a major determinant of early and late major/life-threatening bleeding complications (MLBCs).

Purpose

To evaluate the impact of post-procedural CT-ADP &gt;180sec on bleeding events in AF patients.

Methods

We included 878 patients from our prospective TAVR registry between 2010 and 2019. Bleeding complications were assessed according to the VARC-2 (Valve Academic Research Consortium-2) criteria. Major adverse cardiac and cerebrovascular events (MACCE) was defined as a composite of all-cause death, myocardial infarction, stroke, and heart failure hospitalization within 1-year after TAVR. Ongoing primary haemostasis disorder was defined by post-procedure CT-ADP &gt;180sec. Primary endpoint was the occurrence of MLBCs during the first year and the second endpoint was 1-year MACCE.

Results

Patients with AF had a higher incidence of all-cause mortality (15% vs. 8%, p=0.002), MACCE (29% vs. 20%, p=0.002), and MLBCs (20% vs. 12%, p=0.001) within 1-year compared to non-AF patients. When the cohort was split into 4 subgroups according to AF and CT-ADP &gt;180sec, patients with AF and CT-ADP &gt;180sec had the highest risk of MLBCs (log-rank test; p&lt;0.001) (Figure). Multivariate Cox regression analysis confirmed that the patients with AF and CT-ADP &gt;180sec had 4.6-fold higher risk of MLBCs within 1 year compared to non-AF patients with CT-ADP ≤180sec (hazard ratio: 4.60; 95% confidence interval: 2.18 - 9.68; p&lt;0.001).

Conclusion

Among TAVR patients, AF with post-procedural CT-ADP &gt;180 sec was identified as a strong independent predictor of MLBCs at 1-year follow-up. Our study suggest that persistent primary haemostasis disorders contribute to a higher risk of bleeding events particularly in AF patients and may be considered for a tailored and risk-adjusted antithrombotic therapy after TAVR.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Dr Matsushita received a grant from Edwards Lifesciences.

Protective effects of dapagliflozin on vascular remodeling in the carotid artery following balloon injury – potential role of angiotensin and purinergic signaling

Introduction

Sodium-glucose co-transporter 2 (SGLT2) inhibitors have been shown to reduce the risk of cardiovascular events independently of glycemic control. The possibility that SGLT2 inhibitors improve endothelial regeneration and vascular restenosis is unknown.

Purpose

To examine whether dapagliflozin, a selective SGLT2 inhibitor, could prevent neointima thickening induced by balloon injury and, if so, to determine the underlying mechanisms. The effect of dapagliflozin was compared to that of losartan, an angiotensin type 1 receptor (AT1R) antagonist.

Methods

Saline, dapagliflozin (1.5 mg/kg/day), or losartan (30 mg/kg/day) were administered orally for 5 weeks to male Wistar rats. Balloon injury of the left carotid artery was performed 1 week after starting the treatment and sacrificed 4 weeks later. Vascular reactivity was assessed on left (injured) and right (healthy) carotid artery rings. The extent of neointima was assessed by histomorphometric analysis, changes of target factors by immunofluorescence, RT-qPCR and histochemistry.

Results

Dapagliflozin and losartan treatments reduced neointima thickening by 32% and 27%, respectively. Blunted contractile responses to phenylephrine and relaxations to acetylcholine and down-regulation of eNOS were observed in the injured artery. These effects were not modified by the dapagliflozin or the losartan treatments. RT-qPCR investigations indicated an increased in gene expression of inflammatory (IL-1beta, ITGAM, VCAM-1), oxidative (p47phox, p22phox) and fibrotic (TGF-beta1) markers and a decreased of eNOS in the injured carotid. However, these changes were not affected by the pharmacological treatments. By contrast, significant increased levels of AT1R angiotensin receptor and NTPDase1 (CD39) ectonucleotidase were observed in the restenotic carotid artery of the dapagliflozin group. Histochemical analysis evidenced important NTPDase1 activity in the neointima.

Conclusions

Dapagliflozin effectively reduced neointimal thickening. As the contribution of AT1R and P2Y2 ATP receptor in smooth muscle cell proliferation and neointima formation has been reported in the literature, the present data suggest that dapagliflozin prevents restenosis through interfering with angiotensin and/or extracellular nucleotides signaling. SGLT2 transporter represent potential new target for limiting vascular restenosis.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): This work was supported by AstraZeneca

Venous thromboembolism in non-critically ill patients with COVID-19 infection

Background

Systemic coagulation activation and thrombotic complications are frequent among critically ill patients with COVID-19. Limited data are available in non-intensive care unit (ICU) patients.

Purpose

To determine the incidence, risk factors and prognosis of venous thromboembolism (VTE) in non-ICU COVID-19 patients.

Methods

We studied consecutive COVID-19 patients admitted to general ward at Strasbourg Hospital, France (25.02.2020–19.04.2020). The primary outcome was any VTE complication. The secondary outcome was the composite of death or transfer to ICU.

Results

Among the 289 patients included (62.2 ± 17.0 years, 59.2% male), VTE occurred in 49 (17.0%). Padua prediction score for VTE was similar between VTE and non-VTE patients. VTE imaging tests were performed in 100 (34.6%) patients and VTE diagnosed in median 7 (3–11) days after admission. On-admission, time from symptom onset to admission (OR 1.07, CI 95% [1.00–1.16], P = 0.045), Improve score (OR 1.37, [1.02–1.83], P = 0.032), leukocyte count (OR 1.16, [1.06–1.27], P = 0.001) and lack of thromboprophylaxis (OR 27.85, CI 95% [9.35–82.95], P < 0.001) were independent predictors of VTE. The incidence of the composite of death or ICU transfer was 31.0% and more frequent among patients with VTE (47.9% vs. 27.9%, P = 0.01). Fever (OR 5.37, CI 95% [1.44–19.97], P = 0.012), VTE (OR 3.44, CI 95% [1.63–7.25], P = 0.001), lymphopenia (OR 0.32, 95% CI [0.15–0.71]; P = 0.005) and extent of COVID-19 evaluated by chest CT severity (OR 1.56, 95% CI [1.12–2.16]; P = 0.007) were independently associated with in-hospital death or transfer to ICU (Table 1, Fig. 1).

Conclusions

The 17.0% incidence of VTE in non-ICU patients with COVID-19 was associated with worse outcomes. Given the high incidence of VTE in ward patients, there is an urgent need to investigate the optimal anticoagulation regimen.

P2Y12 inhibition by clopidogrel increases adverse clinical outcomes in patients undergoing transcatheter aortic valve replacement

Introduction

Current recommendations support short-term dual antiplatelet therapy (DAPT) for patients undergoing transcatheter aortic valve replacement (TAVR) despite no relevant study exploring the extent of platelet inhibition by clopidogrel.

Purpose

To assess whether P2Y12 inhibition by clopidogrel as evaluated by vasodilator-stimulated phosphoprotein flow cytometry test (VASP-FCT) impacts 1-year clinical outcomes in patients undergoing TAVR.

Methods

Patients were included in a prospective registry between February 2010 and May 2019. VASP-FCT was assessed 24h after the procedure. Responder to clopidogrel was defined by a platelet reactivity index ≤50%.

Results

Of 640 patients who underwent TAVR with preprocedural clopidogrel therapy, we enrolled 491 patients for whom VASP data were available. Responders were identified in 22% (n=110) of patients and low responders were 78% (n=381) of patients. Low body mass index, active cancer, and clopidogrel on admission were found to be independent predictors of responder. Mean transaortic pressure gradient was lower in the responder group at 1-month post-TAVR (9.9±4.4 mmHg vs. 11.2±5.8 mmHg, p=0.03) but was similar at 1-year (11.5±6.2 mmHg vs. 11.9±7.4 mmHg, p=0.74). By multivariate Cox regression analysis, patients responding to clopidogrel (hazard ratio [HR]: 2.19; 95% confidence interval [CI]: 1.04 to 3.64; p=0.04), prior PCI (HR: 2.12; 95% CI: 1.07 to 4.37; p=0.03), and mean transaortic pressure gradient at baseline (HR: 0.07; 95% CI: 0.01 to 0.70; p=0.02) were identified as independent predictors of 1-year adverse clinical outcomes, including all-cause death, myocardial infarction, stroke, and heart failure hospitalization.

Conclusions

Appropriate P2Y12 inhibition by clopidogrel is a major determinant of adverse clinical events after TAVR. In sum, the present data challenges the need of DAPT as a standard therapy during TAVR.

Figure 1

Funding Acknowledgement

Type of funding source: None

Residual inflammation is a major determinant of myocardial recovery and cardiovascular outcome in takotsubo patients

Background

Recent insights have emphasized the importance of myocardial and systemic inflammation in Takotsubo Syndrome (TTS).

Objective

In a large registry of unselected patients, we sought to evaluate whether residual high inflammatory response (RHIR) could impact cardiovascular outcome after TTS.

Methods

Patients with TTS were retrospectively included between 2008 and 2018 in three general hospitals. 385 patients with TTS were split into three subgroups, according to tertiles of C-reactive protein (CRP) levels at discharge (CRP&lt;5.2 mg/l, CRP range 5.2 to 19 mg/l, and CRP&gt;19 mg/L). The primary endpoint was the impact of RHIR, defined as CRP&gt;19 mg/L at discharge, on cardiac death or hospitalization for heart failure.

Results

Follow-up was obtained in 382 patients (99%) after a median of 747 days. RHIR patients were more likely to have a history of cancer or a physical trigger. Left ventricular ejection fraction (LVEF) at admission and at discharge were comparable between groups. By contrast, RHIR was associated with lower LVEF at follow-up (61.7 vs. 60.7 vs. 57.9%; p=0.004) and increased cardiac late mortality (0% vs. 0% vs. 10%; p=0.001). By multivariate Cox regression analysis, RHIR was an independent predictor of cardiac death or hospitalization for heart failure (hazard ratio: 1.97; 95% confidence interval: 1.11 to 3.49; p=0.02).

Conclusions

RHIR was associated with impaired LVEF recovery and was evidenced as an independent factor of cardiovascular events. All together these findings underline RHIR patients as a high-risk subgroup, to target in future clinical trials with specific therapies to attenuate RHIR.

Main results

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): GERCA (Groupe pour l'Enseignement, la prévention et la Recherche Cardiovasculaire en Alsace)

Predictive impact of PVL assessments on clinical outcomes in patients undergoing TAVR

Introduction

Paravalvular leakage (PVL) following transcatheter aortic valve replacement (TAVR) is associated with greater mortality. In clinical practice, determining PVL severity after TAVR remains challenging and often requires multiparametric assessment.

Purpose

This study sought to evaluate the respective value of various modalities of PVL assessments, including transthoracic echocardiography (TTE), cine-angiography, aortic regurgitation index (ARI), and closure time with adenosine diphosphate (CT-ADP), in the prediction of adverse clinical outcomes.

Methods

We included 1044 patients from our prospective TAVR registry between February 2010 and May 2019. Major adverse cardiac and cerebrovascular events (MACCE) was defined as a composite of all-cause death, myocardial infarction, stroke, and heart failure hospitalization within 1-year. Established cutoff values of ARI (&lt;25) and CT-ADP (&gt;180 sec) were used to assess the presence of PVL after TAVR.

Results

Moderate to severe PVL occurred in 14.2% and 5.2% of patients as measured by TTE and angiography. The rate of patients with ARI &lt;25 and CT-ADP &gt;180 sec were 36.5% and 24.9%, respectively. Among the four modalities, PVL evaluated by angiography predicted poorer clinical outcomes (Log rank test; p=0.001), whereas TTE, ARI &lt;25, and CT-ADP &gt;180 sec were not associated with 1-year MACCE. By multivariate Cox regression analysis, moderate to severe PVL by angiography was an independent predictor of 1-year MACCE (hazard ratio: 1.96; 95% confidence interval: 1.22–3.00; p=0.007).

Conclusions

Paravalvular leakage measured by angiography was evidenced as the most meaningful modality in the prediction of adverse clinical outcomes. Future multicenter studies are warranted to ensure these findings in the current TAVR era.

Figure 1

Funding Acknowledgement

Type of funding source: None

Incomplete recovery of takotsubo cardiomyopathy is a major determinant of cardiovascular mortality

Introduction

Although there is an apparent rapid and spontaneous recovery of left ventricular ejection fraction (LVEF) in patients with takotsubo cardiomyopathy, recent studies have demonstrated the long-lasting functional impairment in those patients.

Purpose

We sought to evaluate the predictors of incomplete recovery in chronic phase and its impact on cardiovascular mortality after takotsubo cardiomyopathy.

Methods

Patients with takotsubo cardiomyopathy between 2008 and 2018 were retrospectively enrolled in three different institutions. Takotsubo cardiomyopathy was diagnosed according to the European Society of Cardiology Heart Failure Association criteria. After exclusion of in-hospital deaths, 407 patients were split into 2 subgroups according whether their LVEF were &gt;50% (recovery group; n=333), or ≤50% (incomplete recovery group; n=74) at follow-up. The primary endpoint was the impact of incomplete recovery on cardiovascular mortality.

Results

Patients with incomplete recovery were more likely to be male, to have dementia, pacemaker, and supraventricular arrhythmia. C-reactive protein (CRP) levels on admission, at peak, and at discharge were significantly higher in patients with incomplete recovery. By multivariate logistic regression analysis, lower EF at discharge (odds ratio [OR]: 0.91; 95% confidence interval [CI]: 0.88 to 0.95; p&lt;0.001) and higher CRP levels (OR: 5.56; 95% CI: 1.86 to 16.61; p&lt;0.001) were independent predictors of incomplete recovery at follow-up. The cumulative event-free survival rate according to cardiovascular death was significantly lower in the incomplete recovery group (p&lt;0.001; log-rank test).

Conclusions

We demonstrate that incomplete recovery after takotsubo cardiomyopathy is characterized by a residual systemic inflammation and an increased cardiac mortality at follow-up. Altogether, our findings underline patients with persistent inflammation as a high-risk subgroup, to target in future clinical trials with specific therapies to attenuate inflammation.

Funding Acknowledgement

Type of funding source: None

A laser-induced pulsed water jet for layer-selective submucosal dissection of the esophagus

Background and aims: Conventional water jet devices have been used for injecting fluid to lift up lesions during endoscopic submucosal dissection or endoscopic mucosal resection procedures. However, these devices cannot dissect the submucosal layer effectively. Here we aim to elucidate the dissection capability of a laser-induced pulsed water jet and to clarify the mechanism of dissection with layer selectivity. Materials (Subjects) and methods: Pulsed water jets were ejected from a stainless nozzle by accelerating saline using the energy of a pulsed holmium: yttrium-aluminum-garnet laser. The impact force (strength) of the jet was evaluated using a force meter. Injection of the pulsed jet into the submucosal layer was documented by high-speed imaging. The physical properties of the swine esophagus were evaluated by measuring the breaking strength. Submucosal dissection of the swine esophagus was performed and the resection bed was evaluated histologically. Results: Submucosal dissection of the esophagus was accomplished at an impact force of 1.11-1.47 N/pulse (laser energy: 1.1-1.5 J/pulse; standoff distance: 60 mm). Histological specimens showed clear dissection at the submucosal layer without thermal injury. The mean static breaking strength of the submucosa (0.11 ± 0.04 MPa) was significantly lower than that of the mucosa (1.32 ± 0.18 MPa), and propria muscle (1.45 ± 0.16 MPa). Conclusions: The pulsed water jet device showed potential for achieving selective submucosal dissection. It could achieve mucosal, submucosal, and muscle layer selectivity owing to the varied breaking strengths.

Re-evaluation of the formalin-ether sedimentation method for the improvement of parasite egg recovery efficiency

The formalin-ether sedimentation (FES) method is considered as reliable method of fecal examination for the detection of parasites. In this study, we re-evaluated several aspects of FES such as (i) pretreatment of feces; (ii) filtration of fecal suspensions; (iii) test-tube material and (iv) substitution of ether by other organic solvents as to see an improvement in parasite egg recovery. The egg count was represented by the number of ova detected per 100 μg of sediment. Pre-treatment of feces with formalin (pH 7) increased egg detection rate remarkably compared with original FES method. Use of three layers of gauze dramatically reduced the sediment in the final product, and led to an increase in the number of ova detected. Use of polypropylene test tubes instead of glass test tubes also increased the number of egg detection. None of the organic solvents used to replace the ether produced better results. Based on these findings, we proposed a modified FES procedure. Further, we also compared the parasite positive rate and the number of ova recovered by using original FES and the modified FES procedures by examining 112 fecal samples collected from school children of parasite endemic area in Nepal. Feces collected from Nepal had many parasite ova, and these fecal samples barely displayed false-negative results even by method with low sensitivity. When the mean number of Hemenolepis nana, hookworm, T. trichiura, and A. lumbricoides ova recovered by original FES and the modified FES methods was compared, the values obtained by modified FES were superior (higher). This result suggested that the modified FES is effective and better for the recovery of parasite ova in areas of low-intensity parasitic infection.

Neonatal hypothyroidism and early undernutrition affect myelin and myelin precursor membranes in a different way

The lipid and protein composition as well as the activity of 2'3' cyclic nucleotide 3' phosphohydrolase (CNPH) and the distribution of individual proteins separated by SDS-PAGE were studied in myelin and in a fraction closely related to myelin or assumed to be a precursor membrane of mature myelin (fraction SN4) isolated from 20-day-old rats made hypothyroid at birth or submitted to early malnutrition. In both experimental conditions lipid and protein components were found to be reduced in myelin when data were expressed as mg/g fresh tissue, but the results were close to those obtained in normal controls when data were expressed as mg/mg total protein of each fraction. CNPH activity was normal in myelin but markedly reduced in fraction SN4. Although the results appear to suggest that both experimental conditions produce a reduction in the amount of myelin but no qualitative changes, the data obtained with SDS-PAGE show that the distribution of the various types of proteins present in this fraction and fraction SN4 was abnormal. Myelin and fraction SN4 isolated from malnourished animals displayed a protein profile which was quite similar to that found in fraction SN4 isolated from normal rats, indicating a delay in the process of myelin maturation. The changes in protein composition of myelin and fraction SN4 produced by neonatal hypothyroidism on the other hand differed clearly from those produced by early malnutrition; the ratio small basic protein: large basic protein (SBP:LBP) was found to be reduced in both membrane fractions in the former condition and the protein patterns of myelin and that of fraction SN4 were different, at variance with what was found in the case of malnourished animals. Our findings appear to suggest that the effects of early malnutrition and neonatal hypothyroidism upon myelin and myelin-related membranes are different, and that myelination is more affected in the latter condition.