Late Toxicity and Patient Satisfaction in Hypofractionated Post-Mastectomy Radiotherapy after Immediate-Autologous Reconstruction

PURPOSE/OBJECTIVE(S)

Immediate autologous reconstruction (IAR) is increasingly being used in the context of breast cancer patients (BCP) treated with mastectomy with the need for subsequent radiotherapy treatment. Currently in clinical practice, despite the fact that conventional fractionated RT (CFRT) has been the standard schedule, hypofractionation schemes are becoming increasingly common. Although no results have been reported on tolerance, late toxicity and satisfaction with treatment in this setting. Our aim was to evaluate late side-effects and patient´s satisfaction receiving PMRT after IAR, comparing CFRT vs HFRT.

MATERIALS/METHODS

Between June 2015 and February 2020, 47 patients received either CF or HF PMRT after IAR in a tertiary hospital. IAR was performed with latissimus dorsi (LD) or deep inferior epigastric perforator (DIEP) flaps at the time of mastectomy. The prescribed dose was 50 Gy over 25 fractions in the CF schedule and 40.05 Gy over 15 fractions in the HF schedule. The target volume to be treated was the reconstructed chest-wall and the axillary-supraclavicular nodes if indicated, using intensity-modulated radiotherapy treatment technique. Late toxicity was evaluated using CTCAE v.5.0 criteria, and patient´s global satisfaction was assessed using a self-evaluation questionnaire, in which patients answered a series of selected questions related to radiation therapy from the BREAST-Q questionnaire, from 1-5 points.

RESULTS

Median age was 48 years (28-77) and median follow-up was 51 months (27-99). 25 patients received HFRT and 22 CFRT. Late side effects after PMRT and tolerance until 3 years with both schedules are shown in Table 1. No relationship was found between incidence of late side effects and RT fractionation. Mean patient´s satisfaction was 3.8 in the CFRT schedule and 4 in the HFRT schedule.

CONCLUSION

According to our findings, HFRT after IAR in post-mastectomy setting seems to be safe and well tolerated, with no high rates of severe late toxicity and with a good level of satisfaction of the treated patients. Table 1. Three years side effects of CRFT and HFRT radiotherapy after mastectomy and immediate autologous reconstruction in 47 patients.

Synchronous bilateral breast cancer treated with a 3-week hypofractionated radiotherapy schedule: clinical and dosimetric outcomes

Background and purpose

Synchronous bilateral breast cancer (SBBC) accounts for 1–3.5% of breast cancer patients. The aim of this study was to evaluate dosimetric issues, clinical outcomes, and acute toxicities for SBBC patients receiving synchronous bilateral hypofractionated radiotherapy (SBHRT) and to compare them with patients treated with synchronous bilateral normofractionated RT schedule (SBNRT).

Materials and methods

From April 2016 to March 2020, 39 SBBC patients were referred to our institution. Patients were divided according to their prescription dose: Group A: 50 Gy/25fx (fractions), B: 60–64 Gy/25fx, C: 40.05 Gy/15fx; D: 48 Gy/15fx. Toxicity was evaluated using Common Terminology Criteria for Adverse Events (CTCAE)v.5.0.

Results

34 patients were finally evaluated. Median follow-up was 24 months for NF schedule and 9 months for HF schedule. In the HF schedule, no acute side-effects > G2 were observed and no dermatitis was reported in 6^th month´s assessments. 95% of patients have no evidence of disease and only 1 patient presented local relapse in the first mammography after RT. No distant failures or deaths were observed. Regarding dosimetric issues, the inter-patient average D_mean for the heart was: Group A: 5.0 Gy (4.6–5.5), Group B: 4.4 Gy (4.1–5.4), Group C: 4.8 Gy (4.5–5.1) and Group D: 5.3 Gy (4.4–5.6). For the lungs, the inter-patient average D_mean was: Group A: 10.8 Gy (9.8–12.2), Group B: 11.5 Gy (11.3–12), Group C: 9.8 Gy (9.3–10.5) and Group D: 10.5 Gy (10–11.3).

Conclusions

This is the first study reporting the safety, feasibility, and tolerability of 40.05 Gy/15fx over 3 weeks for the treatment of SBBC patients. Further study with larger accrual is mandatory.

The impact of pipeline changes and temperature increase in a hospital historically colonised with Legionella

Healthcare-related Legionnaires’ disease has a devastating impact on high risk patients, with a case fatality rate of 30–50%. Legionella prevention and control in hospitals is therefore crucial. To control Legionella water colonisation in a hospital setting we evaluated the effect of pipeline improvements and temperature increase, analysing 237 samples over a 2-year period (first year: 129, second year: 108). In the first year, 25.58% of samples were positive for Legionella and 16.67% for amoeba. Assessing the distance of the points analysed from the hot water tank, the most distal points presented higher proportion of Legionella colonisation and lower temperatures (nearest points: 6.4% colonised, and temperature 61.4 °C; most distal points: 50% and temperature 59.1 °C). After the first year, the hot water system was repaired and the temperature stabilised. This led to a dramatic reduction in Legionella colonisation, which was negative in all the samples analysed; however, amoeba colonisation remained stable. This study shows the importance of keeping the temperature stable throughout the circuit, at around 60 °C. Special attention should be paid to the most distal points of the circuit; a fall in temperature at these weak points would favour the colonisation and spread of Legionella, because amoeba (the main Legionella reservoir) are not affected by temperature.

P1188Oral antibiotic treatment for local cardiac implantable electronic device infections: our 6-year experience

INTRODUCTION

Cardiac implantable electronic device (CIED) infection is a severe disease with an increasing incidence due to the rise in the number of CIEDs implanted world-wide. Complete hardware removal is the treatment of choice, but there is little clinical data about the best antimicrobial strategy, such as the best choice of antibiotics, treatment duration and when to switch to oral administration in cases of local CIED infections.

PURPOSE

  In 2013, we designed a new protocol for CIED infection management, by which local infections were treated with complete hardware removal followed by empiric parenteral antibiotic during the first 72h, which was replaced to an oral agent (in case of negative blood cultures) and continued for 10 days. The oral antibiotic was selected according to the local cultures when positive, or to Clindamicin, Levofloxacin or Cotrimoxazole when no germ was identified. Our purpose is to describe our experience and results after the implementation of this strategy.

METHODS

We retrospectively reviewed all consecutive local CIED infection cases from the implementation of the protocol until September 2019, and evaluated the population characteristics, type of infection, rate of positive cultures and outcomes.

RESULTS

We identified 74 cases of CIED infection, of which 46 (62%) were local. The average age of this population was 75.3 ± 13.2 yo and 65% (30) were male. The predominant comorbidities were diabetes (41%), congestive heart failure (30%), and malignancies (22%). Eighteen patients (39%) had previous local infection treated medically without hardware removal. Mean number of previous procedures was 2.65 ± 1.8, and 34 (74%) of the devices were pacemakers (single and dual chamber), 5 (11%) ICDs, 6 (13%)CRT-P and 1 (2%) CRT-D. Blood cultures were negative in all cases, whereas local cultures (exudate or intraoperative tissue) were positive in 32 (70%). The most frequent microorganisms were Staphylococcus epidermidis in 18 (56%) and Staphylococcus aureus in 8 (25%), including 1 case of meticillin-resistance.  Intravenous Vancomycin was administered in all cases during 72 h, followed by oral antibiotics for a mean duration of 8.8 ± 3.3 days. Hardware removal was intended in all cases, with complete or clinical success in 42 and 3 cases respectively (global success rate 97.8%), and in one case (2.2%) an epicardial lead was not removed. During a mean follow-up of 30 months, 1 infection-related death occurred (2%) due to a side effect of intravenous antibiotic therapy, and there was 1 infection relapse (2%) in the only patient without complete hardware removal, related to the remnant epicardial lead.

CONCLUSIONS

Oral antimicrobial treatment with good bioavailability agents, associated with complete hardware removal is an effective strategy for the management of local CIED infections, with a low recurrence rate, and avoiding long hospitalizations and potential side effects of intravenous antibiotic therapy.

P347 Profile of coagulase negative staphylococci native valve infective endocarditis in a referral hospital

METHODS

Prospective observational study with retrospective analysis of 468 episodes of infectious

endocarditis (IE) admitted to our hospital from 2003-2018. Of these, 54 (11%) corresponded to IE by

CNS, and 22 were in native valve. We describe the characteristics of these 22 patients and compare

them with the group of IE by CNS in prosthesis and devices.

RESULTS

Average age was 67 years, with 77% male sex. There were no differences in predisposing

factors. Acquisition was predominant in-hospital (54%), but only previous manipulation was

detected in 31%. The presence of clinical and echocardiographic complications was similar, with

higher incidence of heart failure in the native group (81 vs. 34%, p = 0.001). Surgery was indicated in

86%, but only 50% underwent surgery. Mortality was very high (68% ) even greater than the

prosthetic/device group, although without significant differences.

CONCLUSION

IE due to CNS in native valve present clinical complications, frequently require surgery

and has a high mortality rate.

Functional outcomes after prostatic cryosurgery

OBJECTIVE

To assess the functional effects of prostatic cryosurgery on micturition.

MATERIAL AND METHODS

Prospective study of men who underwent cryosurgery (CS) for prostate cancer between 2013 - 2015. Low urinary tract symptoms (LUTS) and quality of life (QoL) were assessed 1 month before surgery using IPSS questionnaire, a three-day voiding diary (3DVD) and uroflowmetry with ultrasound-measured postvoid residual volume. Need of medical treatment for LUTS was also recorded. The same assessment was performed at 3, 6 and 12 months after CS. Outcomes after surgery were compared to those prior to surgery.

RESULTS

Forty-five patients underwent a CS during the study period, of whom 25 patients could be recruited in the study. Mean age was 73.5 years (range 66-84). Nineteen CS (76%) were performed as a primary procedure, while 6 CS (24%) as a salvage procedure. No statistical differences were found comparing results of IPSS, QoL, D3vd or uroflowmetry and PVR at 3, 6 or 12 months after CS compared to before surgery. Before CS, 8 (32%) patients were on medical treatment for LUTS, while at 6 and 12 months after surgery, 3 (13.6%) and 2 (9.5%) patients required some medication, respectively.

CONCLUSION

According to the punctuation of IPSS, QoL questionnaire, and a 3-day voiding diary, LUTS does not worsen after CS. Prostatic cryosurgery does not seem to impact uroflowmetry results.

A higher Charlson comorbidity index is related to more aggressive characteristics in de novo vesical tumours

OBJECTIVE

To analyze the relationship between the age--adjusted Charlson Comorbidity Index (aCCI) and pathological outcomes of transurethral resection of de novo bladder tumours (BT).

MATERIAL AND METHODS

Data from 208 patients who underwent a transurethral resection (TUR) of a de novo BT between 2007 and 2008 were collected. We recorded the following variables: age, sex, tobacco consumption, comorbidities assessed according to the ICCa (score and mortality rate), disease stage, tumour grade and risk of recurrence and progression. The relationship between the preoperative variables and the final pathological characteristics was analyzed. The multivariate study was conducted with the significant variables (P<.05) from the univariate analysis.

RESULTS

The mean age of the patients was 69.5 ± 12 years, and 77% were men. The mean ICCa was 6.4 ± 2.5. The final pathology results showed a Tx, T0, Ta, T1 and T ≥ 2 in 5.3, 6.7, 31.7, 26.9, and 28.8% of the cases, respectively. 33.3% of the tumours were low-grade and 66.7% were high-grade. 14.3% of the tumours were associated with carcinoma in situ. Among those non musculo-invasive bladder tumour (non-MIBT), 34.7% had a low risk of recurrence and progression, 18.1% had an intermediate risk and 47.2% had a high risk. The patients with a ICCa ≥ 5 had an increased number of MIBT (RR: 2.29; 1.1-4.8; P=.032), high-grade tumours (RR: 3.1; CI: 1.6-6; P=.001) and tumours with a high risk of recurrence and progression (RR: 2.9; CI: 1.4-5.9; P<.001).

CONCLUSION

The ICCa is related to the pathological characteristics of de novo BT. Patients with greater comorbidity can present more aggressive tumours. The ICCa could therefore be useful in clinical practice for identifying patients with worse prognosis.

Predictors, pathological characteristics and outcomes of bladder recurrences following nephroureterectomy

OBJECTIVES

To analyze the predictors for bladder recurrence (BR) after nephroureterectomy (NU) for upper urinary tract tumors (UUTT), as well as its pathological characteristics, outcomes and impact on survival.

MATERIAL AND METHODS

Retrospective study of 117 patients who underwent laparoscopic nephroureterectomy by UUTT between 2007-2012 at our center. The potential predictors for BR were analyzed using Cox regression; Kaplan-Meier curves were employed to study survival.

RESULTS

The sample was composed of 85 men (73%) and 32 women (27%), with a mean age of 70 years. After a mean follow-up of 26 months, 23 patients presented BR (19.6%). In the multivariate analysis, sex (p=.003; HR [female], 3.8) and the location of the UUTT in the distal ureter (p=.002; HR, 4.8) were independent predictors for BR. The median time to BR was 8 months. Fifteen patients presented a nonmuscle-invasive BR (65.2%), and 8 presented a muscle-invasive BR (34.8%). All BRs, except for 2, appeared during the first 2 years. Five cases with nonmuscle-invasive BR presented a new BR. Six patients with muscle-invasive BR died before it could be determined whether cause of death was the BR or an UUTT relapse. The onset of BR showed no repercussion on the survival of patients with UUTT.

CONCLUSIONS

Sex (female) and the location of the UUTT (distal ureter) are predictors for BR after NU. Patients with these characteristics might benefit from adjuvant intravesical treatment and closer monitoring. The onset for RV has no impact on the survival of patients with UUTT.

[Hemodynamic monitoring in the critically patient. Recomendations of the Cardiological Intensive Care and CPR Working Group of the Spanish Society of Intensive Care and Coronary Units]

Hemodynamic monitoring offers valuable information on cardiovascular performance in the critically ill, and has become a fundamental tool in the diagnostic approach and in the therapy guidance of those patients presenting with tissue hypoperfusion. From introduction of the pulmonary artery catheter to the latest less invasive technologies, hemodynamic monitoring has been surrounded by many questions regarding its usefulness and its ultimate impact on patient prognosis. The Cardiological Intensive Care and CPR Working Group (GTCIC-RCP) of the Spanish Society of Intensive Care and Coronary Units (SEMICYUC) has recently impulsed the development of an updating series in hemodynamic monitoring. Now, a final series of recommendations are presented in order to analyze essential issues in hemodynamics, with the purpose of becoming a useful tool for residents and critical care practitioners involved in the daily management of critically ill patients.

A reversible abnormal form of myelin: an X-ray scattering study of human sural and rat sciatic nerves

A sural nerve dissected from a recently dead patient displayed an unusual X-ray diffraction pattern, suggesting that in situ and at the time of the patient's death the myelin sheaths were in a swollen state. Diffraction patterns of the swollen type were also recorded from: (1) a sural nerve from the corpse of a neurologically healthy person after soaking the nerve with Ringer solution at pH 5.5; (2) sciatic nerves dissected from rat cadavers at increasing time after death. In all the cases the swollen patterns reversed to the native type upon superfusion with Ringer solution at pH 7.3. The postmortem effect is to decrease the pH of the fluids surrounding the nerves in the cadavers. Our experiments show that the early postmortem processes have the effect of acidifying PNS nerves and that as a consequence of acidification the myelin sheaths swell.

Malnutrition and myelin structure: an X-ray scattering study of rat sciatic and optic nerves

Taking advantage of the fast and accurate X-ray scattering techniques recently developed in our laboratory, we tackled the study of the structural alterations induced in myelin by malnutrition. Our work was performed on sciatic and optic nerves dissected from rats fed with either a normal or a low-protein caloric diet, as a function of age (from birth to 60 days). By way of electrophysiological controls we also measured (on the sciatic nerves) the height and velocity of the compound action potential. Malnutrition was found to decrease the amount of myelin and to impair the packing order of the membranes in the sheaths.

Study of thermal hydrolysis as a pretreatment to mesophilic anaerobic digestion of pig slurry

Feasibility of anaerobic digestion of pig slurry is dependent, among other factors, on the biogas production rate, which is low compared with other organic wastes, and on the profitable uses of surplus thermal energy produced, a limiting factor in warm geographical areas. The objectives of this work are determining whether low temperature thermal pretreatment (< 90 degrees C) improves pig slurry anaerobic digestion, and determining whether organic matter degradation during the thermal pretreatment is due to thermal phenomena (80 degrees C) or to enzymatic ones (60 degrees C). The thermal degradation tests showed that hydrolysis occurring during the thermal pretreatment is due to thermal phenomena. The increase in soluble substances were significantly larger at 80 degrees C than at 60 degrees C (both during 3 h). Two types of slurry were used in the batch anaerobic digestion tests. The effect of thermal pretreatment differed with the type of slurry: it was positive with almost non-degraded slurries containing low NH4(+)-N concentration, and negative (inhibition of the anaerobic digestion process) when using degraded slurries with high NH4(+)-N content.

Physical structure of the excitable membrane of unmyelinated axons: X-ray scattering study and electrophysiological properties of pike olfactory nerve

The aim of this work was to elicit correlations between physical structure and physiological functions in excitable membranes. Freshly dissected pike olfactory nerves were studied by synchrotron radiation X-ray scattering experiments and their physiological properties were tested by electrophysiological techniques. The scattering spectra contained a sharply oriented equatorial component (i.e. normal to the nerve axis), and an isotropic background. After background subtraction, the equatorial component displayed a weak and fairly sharp spectrum of oriented microtubules, and a strong and diffuse band of almost the same shape and position as the band computed for an isolated myelin membrane. We ascribed this spectrum to the axonal membranes. Under the action of temperature and of two local anesthetics, the spectrum underwent a contraction (or expansion) in the s-direction, equivalent to the structure undergoing an expansion (or contraction) in the direction perpendicular to the plane of the membrane. The main observations were: (i) with increasing temperature, membrane thickness decreased with a thermal expansion coefficient equal to -0.97(+/-0.19) 10(-3) degrees C(-1). The polarity and amplitude of this coefficient are typical of lipid-containing systems with the hydrocarbon chains in a disordered conformation. The amplitude and propagation velocity of the compound action potentials were drastically and reversibly reduced by lowering the temperature from 20 degrees C to 5 degrees C. (ii) Exposing the nerve to two local anesthetics (tetracaine and dibucaine) had the effect of decreasing membrane thickness. Action potentials were fully inhibited by these anesthetics. (iii) Upon depolarization, induced by replacing NaCl with KCl in the outer medium, approximately 25 % of the membranes were found to associate by apposing their outer faces. Electrophysiological activity was reversibly impaired by the KCl treatment. (iv) No detectable structural effect was observed upon exposing the nerves to tetrodotoxin or veratridine. Electrophysiological activity was fully impaired by tetrodotoxin and partially impaired by veratridine. The main conclusions of this work are that axonal membranes yield highly informative X-ray scattering spectra, and that these spectra are sensitive to the functional state of the nerve. These results pave the way to further studies of more direct physiological significance.

Structural and electrophysiological effects of local anesthetics and of low temperature on myelinated nerves: implication of the lipid chains in nerve excitability

X-ray scattering and electrophysiological experiments performed on toad sciatic nerves as a function of the exposure to either low temperature or tetracaine yielded the following results: (i) the main structural effect is to thicken the individual membranes, thus to stiffen the acyl chains and increase the repeat distance of the one-dimensional lattice, phenomena that are typical of lipid-containing systems with disordered chains; (ii) the electrophysiological effect is to decrease the amplitude and velocity of the compound action potential; (iii) the structural and physiological effects of the two agents are practically identical. Since the structural and the electrophysiological parameters have different origins in the nerves (the structure regards the myelin sheath, the electrical signals originate at the nodes of Ranvier) it is inferred that tetracaine and low temperature exert similar effects on the membranes of both the myelin sheath and the nodes of Ranvier. Also, since local anesthetics act by inhibiting the Na+ channels, these observations suggest that the acyl chain conformation modulates the channel function and thus the generation of action potential.

The action of local anesthetics on myelin structure and nerve conduction in toad sciatic nerve

X-ray scattering and electrophysiological experiments were performed on toad sciatic nerves in the presence of local anesthetics. In vitro experiments were performed on dissected nerves superfused with Ringer's solutions containing procaine, lidocaine, tetracaine, or dibucaine. In vivo experiments were performed on nerves dissected from animals anesthesized by targeted injections of tetracaine-containing solutions. In all cases the anesthetics were found to have the same effects on the x-ray scattering spectra: the intensity ratio of the even-order to the odd-order reflections increases and the lattice parameter increases. These changes are reversible upon removal of the anesthetic. The magnitude of the structural changes varies with the duration of the superfusion and with the nature and concentration of the anesthetic molecule. A striking quantitative correlation was observed between the structural effects and the potency of the anesthetic. Electron density profiles, which hardly showed any structural alteration of the unit membrane, clearly indicated that the anesthetics have the effect of moving the pairs of membranes apart by increasing the thickness of the cytoplasmic space. Electrophysiological measurements performed on the very samples used in the x-ray scattering experiments showed that the amplitude of the compound action potential is affected earlier than the structure of myelin (as revealed by the x-ray scattering experiments), whereas conduction velocity closely follows the structural alterations.

Order-disorder phenomena in myelinated nerve sheaths. VI. The effects of quaking, jimpy and shiverer mutations: an X-ray scattering study of mouse sciatic and optic nerves

We report the X-ray scattering study of sciatic and optic nerve myelin from shiverer, jimpy and quaking mice mutants and from the corresponding controls. These three mutations are known to affect dramatically central nervous system (CNS) myelin and to induce comparatively minor alterations in peripheral nervous system (PNS) myelin. Scattering experiments and data reduction were carried out using the techniques and algorithms developed in our laboratory and previously applied to several problems involving the structure of myelin. In sciatic nerve the fraction of myelin elementary pairs of membranes (total myelin) decreases in shiverer and quaking nerves (by approximately 30%) but not in jimpy nerves; in all three mutants the fraction of myelin membrane pairs that are not regularly stacked in the sheaths (loose myelin), the average number of membranes per sheath and the packing disorder are the same as in the control nerves; the repeat distance D and the membrane distance Dcyt across the cytoplasmic space increase in shiverer and decrease in jimpy; in quaking, D also decreases and the decrease is smaller than in jimpy and is not specific for Dcyt; small changes are also observed in the electron density profiles. As for the optic nerve the myelin content decreases dramatically in the three mutants; the very weak signal attests to a tiny amount of pairs of membranes structurally similar to normal CNS myelin. It is surprising that the structure of CNS myelin should be almost normal in the absence of the major structural components, namely myelin basic protein (MBP) for shiverer of proteolipid protein (PLP) for jimpy. The question arises whether the composition of the residual pairs of membranes, operationally identified as myelin in the X-ray scattering experiments, mirrors the composition determined by chemical means on the fraction of nerve tissue histologically identified as myelin, or whether in all circumstances it remains approximately the same.

Order-disorder phenomena in myelinated nerve sheaths: V. Effects of temperature on rat sciatic and optic nerves, and structural differences between the two types of nerve

We describe in this work X-ray scattering and electron microscope studies of rat sciatic and optic nerves as a function of temperature. The scattering experiments were analyzed as described in the previous papers of this series: a variety of parameters were determined, some of which characterize the lattice disorder, others the structure of the motif. The main results are the following. All the parameters determined by the X-ray scattering study vary with temperature and the temperature-dependence is specific for the type of nerve (sciatic or optic). Most of the disorder-related parameters display a minimum or a maximum in the vicinity of physiological temperature (38 degrees C in rat); this observation, strongly supported by the electron microscope study, shows that the degree of organization of myelin is highest near physiological temperature. The structure of the motif, as revealed by the electron density profile, is fairly different in the two types of nerves (in contrast with the assumption made by previous workers); the structure also varies with temperature and the temperature-induced alterations are nerve-type specific. In the two types of nerve the thickness of the lipid bilayer varies with temperature as expected for a lipid-containing system with hydrocarbon chains in the disordered conformation. In sciatic nerve the thickness of the (thinner) cytoplasmic polar layer, which is also the layer most affected by lattice disorder in this type of nerve, decreases dramatically with increasing temperature. In optic nerve, in which lattice disorder predominantly affects the extracellular layer, the thickness of both the cytoplasmic and the extracellular layer is barely affected by temperature.

Order-disorder phenomena in myelinated nerve sheaths. IV. The disordering effects of high levels of local anaesthetics on rat sciatic and optic nerves

Sequences of 15 minute X-ray scattering spectra were recorded with rat sciatic and optic nerves, superfused with tetracaine-containing Ringer solutions. The spectra were analysed using the algorithm advocated in this series of papers. The main results, as a function of the time of exposure to tetracaine, were: the mean value of the repeat distance increases; its variance decreases; the average number of membrane pairs per coherent domain decreases; the fraction of isolated membrane pairs increases. Eventually, the spectra were observed to give way to the continuous intensity curve of a single, isolated membrane pair. At all stages of the experiment the continuous intensity curves were found to differ from one type of nerve to the other, and to be invariant, for each type of nerve, with respect to the tetracaine treatment. The X-ray scattering study clearly identified the nature of the structural differences between the two types of myelin sheaths: in that of native sciatic nerves, packing disorder preferentially affects the cytoplasmic space of the membrane pair, and tetracaine disrupts the packing in that space; in the myelin of optic nerves it is the external space that is preferentially affected by packing disorder and disrupted by tetracaine. The time-course of the structure parameters showed that, at any stage of the experiment, tetracaine acts preferentially on the more highly disordered regions of the structure and totally disrupts them. These results corroborate earlier conclusions reported in the previous papers of this series. An electron microscope study was also performed on tetracaine-treated nerves: the results, in close agreement with those of the X-ray scattering study, neatly confirm the conclusions given above. In a more general way, the remarkable agreement between the results of the analysis of the X-ray scattering spectra and the electron microscope observations strongly supports the validity of the physical model used in this series of papers and the correctness of the mathematical treatment that we advocate. Finally, the relations between this work and the work of others are discussed. It must be stressed that the present work bears on the toxic rather than on the anaesthetic effects of tetracaine.

Order-disorder phenomena in myelinated nerve sheaths. III. The structure of myelin in rat optic nerves over the course of myelinogenesis

An X-ray scattering study was performed on optic nerves dissected from rats aged from ten days to one year. The spectra were analysed using the procedure described in the previous papers of this series. Each experiment yields the values of a variety of parameters: the average D and the variance sigma D of the repeat distance, the average number mean value of N of motifs per crystallite, the fraction alpha loose of myelin that does not belong to the compact sheaths, the sets [idiff(h/D)] and [imotif(k/2D)] that suffice to define, respectively, the spurious scattering and the continuous intensity curve of the elementary membrane pair. A surprising result is that, in the native optic, as previously found in the swollen sciatic nerves, the stacking disorder affects the external space, whereas in native sciatic nerves the disorder affects the cytoplasmic space. An analysis of the evolution of the structure parameters as a function of the age of the animal and a comparison with the results previously obtained with rat sciatic nerves led to the following conclusions: the structure of the elementary membrane pair is constant throughout myelinogenesis; mean value of N is much smaller in optic than in sciatic nerves; mean value of N and the degree of myelination increase with age in the two types of nerve; D is smaller in optic than in sciatic nerves; in optic nerves, D decreases slightly with age, but in sciatic nerves it increases; sigma D is strongly age-dependent in optic nerves, but almost age-independent in sciatic nerves. In contrast to sciatic, the structure of optic nerve myelin was found to be almost insensitive to hypertonic solutions. Finally, a pair of electron density profiles was selected, quite similar to those selected previously in sciatic nerves, one corresponding to Caspar & Kirschner's the other to Worthington & McIntosh's proposals, neither of which can be ruled out according to the criteria used in this work.

Order-disorder phenomena in myelinated nerve sheaths. I. A physical model and its parametrization: exact and approximate determination of the parameters

An algorithm is developed for the analysis of the X-ray scattering spectra of lamellar systems, by reference to a precise physical model. The model consists of identical planar lamellae (the motif), all parallel and stacked in a one-dimensional crystal with four types of defect: stacking disorder, finite size of the crystallites, and presence of diffuse and blank scattering. In addition, the spectra are distorted by collimation aberrations. In order to evaluate the effects of these distortions, the following assumptions are made: (1) beyond some point Slimit the intensity curve can be expressed as a function of a (small) number of parameters; (2) the blank scattering, restricted to very small angles, can be identified and eliminated; and (3) the diffuse scattering is entirely defined by the values of idiff(h/D) at the lattice Sh = h/D (h is a positive integer less than or equal to DSlimit). These assumptions lead to an expression of the whole of the intensity curve as a function of a finite number of parameters: the average D and the variance sigma 2D of the repeat distance, the average number [N] of lamellae per crystallite, the set [idiff(h/D)] and the set [imotif(k/2D)] (where k is a positive integer), which defines the structure of the motif. An algorithm is proposed to determine the value of the various parameters. The derivation of the algorithm involves several operations: construction in real space of periodic functions whose motifs are step-sections of the autocorrelation function; expression in reciprocal space, and in terms of the experimental scattering curves, of the Fourier transform of those periodic functions; analysis of the properties of the two functions. The algorithm is tested using a variety of simulated scattering curves whose parameters [imotif(k/2D)], [idiff(2/D)], D, sigma D, [N] (and collimation distortions) are within the range commonly encountered in experimental conditions. The results show that the values of the parameters retrieved by the algorithms are very close to those used in the simulation. The calculations are fast and easy to implement on a computer. The main virtues of the algorithm are (1) to determine the values of all the parameters at once, eliminating most of the intermediate (and questionable) manipulations (separation of signal from noise, discrimination of overlapping reflections, integration of the intensities) and (2) to yield the continuous intensity curve of a single motif.

Order-disorder phenomena in myelinated nerve sheaths. II. The structure of myelin in native and swollen rat sciatic nerves and in the course of myelinogenesis

The algorithm described in the accompanying paper was applied to X-ray scattering experiments performed with rat sciatic nerves, either as a function of the age of the animal (4 to 30 days), or with adult nerves swollen in non-isotonic media. The results were all consistent with the model of disorder used in the theoretical treatment. The algorithm leads, in one step, from the data to the numerical values of the parameters, avoiding all intermediate manipulation. For each experiment a variety of parameters was determined: the average D and the variance sigma 2D of the repeat distance, the average number [N] of motifs per crystallite, the set [idiff(h/D)], which defines the diffuse scattering, the fraction alphaloose of myelin that does not belong to the compact sheaths, and the set [imotif (k/2D)], which suffices to define the continuous intensity curve of the motif imotif(s). Note the remarkable wealth of information, especially by contrast with conventional analyses which, as a rule, only yield the values of D and of the set [imotif(h/D)] (insufficient to determine the function imotif(s]. The function imotif(s) and the parameters D and sigma D (and thus the local structure of the myelin sheaths) were shown to be almost invariant in the course of myelinogenesis; what varies is mainly the total amount of myelin in the nerve and the number of membranes per sheath. Swelling agents have a dramatic influence on the X-ray scattering spectra, but in spite of the conspicuous variation of D, sigma D and [N] the structure of the motif is invariant. The structure of the motif was shown to be quite different in the native and in the swollen samples; the stacking disorder appears to involve mainly the cytoplasmic space in native myelin, the external space in swollen nerves. The very notion of electron density profile, when disorder is present, is discussed. Two criteria were proposed to select the "best" signs of the reflections: two sets came out at almost the same rank, one corresponding to Caspar & Kirschner's the other to Worthington & McIntosh's proposals, neither of which can be ruled out according to the criteria used in this work.

An X-ray diffraction study of changes in myelin structure during experimental allergic neuritis

In order to determine whether the structure of the myelin membranes is modified during experimental allergic neuritis (EAN), we have performed X-ray diffraction studies of in vivo and of isolated sciatic nerves from Lewis rats exposed to different EAN-producing treatments. We have observed a decrease of the intensities in the X-ray reflections without changes in spatial resolution. The level of decrease correlated with the severity of the demyelinating lesions. In comparison to nerves from normal healthy rats the electron density profile of sciatic nerve myelin from animals in acute stages of EAN showed small differences at both cytoplasmic and extracellular spaces of the myelin membrane. Dynamic X-ray diffraction patterns recorded kinetically in vivo from a nerve injected intraneurally with a neuritogenic antiserum do not show additional reflections characteristic of a distinct lattice of increased periodicity, suggesting that the early stages of demyelination do not involve an intermediate ordered state.

Reversible changes in myelin structure and electrical activity during anesthesia in vivo

X-ray diffraction patterns have been recorded from sciatic nerve myelin by means of dynamic X-ray diffraction either from frogs, during the early stages of anesthesia in vivo induced by n-pentane inhalation, and from frog and rat sciatic nerves isolated immediately after the animal was anesthetized. This approach has enabled to resolve minor changes in myelin structure that occur during anesthesia which were found to be similar in frogs and mammals. The X-ray patterns show a reversible slight decrease in intensity of the even reflections during anesthesia. The electron density profiles from myelin of anesthetized and recovered nerves revealed that the unit membrane structure is practically identical in both circumstances. However, during anesthesia myelin membrane pairs move toward the cytoplasmic side becoming more closely packed by 1.6 A. Physiological activity was estimated during the recovery process: compound action potential recovered its maximal amplitude before myelin recovered its native structure. On the contrary, the conduction velocity seemed to be closely related to the structural recovery. This work provides evidence that early stages of anesthesia by n-pentane in vivo does not change membrane bilayer structure but perturbs the surface interactions between adjacent membrane pairs.

The structural stability of low-density lipoprotein. A kinetic X-ray scattering study of its interaction with arterial proteoglycans

The structural stability of human plasma low-density lipoproteins (LDL) has been studied kinetically by means of dynamic X-ray scattering techniques. At 37 degrees C, rapid deterioration of the lipoproteins present in the insoluble complex which is formed on mixing solutions of LDL and human arterial proteoglycans is observed. This is evidenced by the progressive blurring of the X-ray scattering spectra. At 4 degrees C the X-ray patterns from the insoluble complex show a single reflection centered at 34 A-1, which is characteristic of pure cholesteryl esters organized in a smectic phase. This behaviour contrasted with the high stability exhibited by free LDL at 37 degrees C. Our results show that, in the form of insoluble complex, the lipoprotein molecules are rapidly disrupted and that the neutral lipids segregated with formation of a lipid phase. This suggests that LDL particles become destabilized by their interaction with arterial proteoglycans.

Loosening of paranodal myelin by repetitive propagation of action potentials

We have previously shown by X-ray diffraction techniques that the stability of the myelin lattice is decreased by repetitive stimulation of the nerve. We now show that in rat myelinated fibres this structural change is accompanied by the appearance of voltage-sensitive potassium channels which do not normally participate in the generation of the action potential. Since it has previously been shown that structures associated with potassium channels are found in the internodal and paranodal axolemma membrane but are normally concealed under the myelin sheath, we suggest that the acceleration of myelin swelling after repetitive propagation of the action potential may be due to the opening of paranodal axoglial junctions. To our knowledge this is the first demonstration that nerve activity may regulate the structural properties of the paranode.

Repetitive propagation of action potentials destabilizes the structure of the myelin sheath. A dynamic x-ray diffraction study

Time courses of myelin lattice swelling in toad sciatic nerves preexposed to different treatments were determined by x-ray diffraction using a one-dimensional position-sensitive detector. In the nerves supramaximally stimulated for 1 h at 200 Hz, the subsequent process of myelin swelling occurred 45.0 +/- 7.3 min (n = 24) sooner than in resting controls. Sciatic nerves incubated for 1 h in a Ringer's solution deprived of divalent cations (Ca++ and Mg++) exhibited a kinetics of swelling similar to that shown by the stimulated nerves, that is, 52.5 +/- 14.2 min (n = 6) sooner than controls preincubated for the same time in normal Ringer's solution (with divalent cations). The fact that both pretreatments supramaximal stimulation and removal of divalent cations from the perfusion solution produced a similar effect; namely, a decrease of the myelin lattice stability against swelling in distilled water, suggests that the repetitive propagation of action potentials could modify the ionic composition at either the intraperiod channel or the paranodal axoglial junction complexes.

In vivo structure of frog sciatic nerve myelin membranes: an x-ray diffraction study at 13A resolution

The x-ray diffraction pattern of myelin membranes from a frog sciatic nerve was recorded in vivo at 13 A resolution using a new experimental technique recently developed in our laboratory. The electron density profile was determined for the myelin membranes first in vivo and then, after elimination of the intraneural blood microcirculation, by transection of the nerve. The small structural differences observed between these conditions were statistically nonsignificant (at 95% confidence level). In addition, our results show that the stacking disorder that is present in the myelin membranes of freshly dissected frog sciatics is also characteristic of the myelin sheath in vivo.

A dynamic X-ray diffraction study of anaesthesia action. Changes in myelin structure and electrical activity recorded simultaneously from frog sciatic nerves treated with n-alkanes

Changes induced in the structure and electrical activity of myelin were recorded simultaneously from frog sciatic nerves treated with n-alkanes. The results suggest that the effect of n-alkanes seems to be two-fold: (a) there is an initial reversible phase, in which a significant modification of the X-ray diffraction patterns, concomitant with the continuous fall of the action potential, is observed; (b) there is a final phase which is irreversible. This occurs some time after the complete abolition of the electrical activity. At this stage, further changes of the X-ray diffraction patterns are detected, the most significant of them being in the n-pentane-treated myelin, and consist of an increase in the membrane bilayer thickness.

The effect of the repetitive propagation of action potentials on the structure of toad sciatic nerve myelin membranes: an x-ray diffraction study at 11 A resolution

Equatorial sections of the x-ray diffraction patterns of myelin from toad sciatic nerves recorded at 11 A resolution during long supramaximal repetitive stimulation (240 Hz for two hours) were used to calculate the relative electron density profile of the myelin membranes in this physiological state. The profile was compared to the one determined for the same nerve at rest. The difference between the stimulated profile and the control profile was found to be statistically non-significant. Therefore, when the sciatic nerve fibers are excited the structure of the internodal myelin membranes does not significantly change at 11 A resolution.

X-ray diffraction study of the kinetics of myelin lattice swelling. Effect of divalent cations

The time-course of myelin lattice swelling and its reversal in dissected peripheral nerves was determined by small-angle x-ray diffraction using a position-sensitive proportional detector. The process of swelling can take place either in several hours or in less than 1 h depending on pretreatment of the nerves. The reversal of swelling was always completed within 1 h. The rapid structural transitions involved the disordering of membrane pairs as indicated by the transient appearance of a continuous intensity distribution similar to the membrane pair transform for myelin. The slow transitions involved the gradual replacement of the discrete reflections from the native structure by the reflections from the swollen lattice. Myelin membrane arrays reformed in normal Ringer's solution were much more stable to subsequent swelling than arrays reformed in Ca+2 and Mg+2-free Ringer's. These results suggest that these ions participate in stabilizing the interactions between the external surfaces of adjacent membrane pairs.

A dynamic x-ray diffraction study of anesthesia action. Thickening of the myelin membrane by n-pentane

The structural changes induced in the myelin sheath by n-pentane nerve impulse blockage were studied by small-angle X-ray diffraction using a linear position-sensitive detector. The results show that the thickness of the myelin period lattice increases from 170 to 180 A during n-pentane treatment.

Small-angle X-ray scattering and differential scanning calorimetry studies on reversibly modified human-serum low density lipoproteins

Small-angle x-ray scattering diagrams of human serum low density lipoprotein (LDL) were recorded at several temperatures in solutions of different freezing points. It was found that modifications of the x-ray patterns observed on cooling the lipoprotein samples below 0 degrees C are due to reversible alterations of the LDL surface structure induced by the freezing process (independent of temperature). With both intact and partially dehydrated LDL, differential scanning calorimetry (DSC) carried out in the body temperature range revealed a heat absorption characteristic of the transition from a liquid crystal to an isotropic liquid phase of cholesteryl esters within the lipoproteins (Deckelbaum, R. J., Shipley, R. J., Small, P. M., Lees, R. S., & George, P. K. (1975) Science 190, 392). However, small-angle x-ray scattering diagrams recorded with the same LDL sample before and after the partial removal of water were found to be very different: the scattering curve for intact LDL showed a strong band centered at (36 A)-1 which disappeared upon drying and reappeared upon restoring the water. Our results suggest that the presence of this signal strongly depends on the molecular structure of the lipoprotein surface.

The influence of protein-lipid interactions on the order-disorder conformational transitions of the hydrocarbon chain

The phases of simple systems involving one type of protein (lysozyme or cytochrome c) and one type of lipid (phosphatidic acid) have been characterized by X-ray crystallography, chemical analysis and spin-labeling technique as a function of temperature. They are of the lamellar type with alternative protein monolayers and lipid bilayers. According to the pH, two types of lamellar phases are obtained, one where the lipid-protein interactions are mainly hydrophobic, the other where they are electrostatic. In both cases, a phase transition occurs as temperature is lowered, between a high temperature phase, where all the lipids are in the liquid-like state, and another phase where some lipid chains are rigid. In the case of the phases with electrostatic interaction, it is shown that the onset of the order-disorder transition is shifted towards low temperature as compared with the homologous lipid-water phase and that the protein content of the phase decreases as the ratio of the liquid to rigid hydrocarbon chains decreases. This leads us to suggest that in the systems studied in this work the proteins interact only with lipid in the liquid-like state. In the case of the phases with hydrophobic interaction, it is shown that the extent of hydrophobic interaction between protein and lipid increases as the unsaturation of the hydrocarbon chains increases. The onset of the order-disorder transition shows a greater shift towards low temperature than the one observed in the case of the phase with electrostatic interaction.

Small-angle x-ray scattering study of human serum low-density lipoproteins with differential reactivity for an arterial proteoglycan

The structure and thermal behavior of human serum low-density lipoproteins showing either a high or a low reactivity against a proteoglycan isolated from human arteries have been found to be different from each other. It is suggested that modifications in the lipoprotein surface structure induced by the physical state of the neutral lipids could modulate the affinity of the macromolecule for the arterial component.

Effect of different bathing media on the short-circuit current across the intestine of the rat and guinea-pig

The changes in short-circuit current occurring when one or both solutions bathing the intestine of rat or guinea-pig mounted in flux chambers were recorded. The results with the guinea-pig can be explained in terms of diffusion potentials arising from the ionic replacements, and an electrogenic sodium pump, sensitive to ouabain, in the contraluminal membrane of the cell. In the rat, the situation is more complicated, and the enterocyte probably possesses an electrogenic sodium pump in the brush-border membrane.

Neutron scattering study of human serum low density lipoprotein

Regions of different proton density in the low density lipoprotein (LDL) particle from human serum have been determined by neutron scattering. From measurements in various H2O/D2O mixtures, the LDL particle appears to be quasi-spherical, with the centers of gravity of the hydrocarbon and polar regions coinciding. The average volume occupied by a particle was found to be 3.2 X 10-6 A-3, with the volume fraction occupied by the hydrocarbons being 60%. The ratius of gyration of the hydrocarbon region was 64 A, while that of the polar region was 100 A. consequently, the core of LDL is predominantly occupied by the hydrocarbon chains, while the outer shell is sparsely occupied by protein emerging from the lipid core.