[Beyond the trenches, two German pioneers of plastic surgery]. / Au-delà des tranchées, deux pionniers allemands de la chirurgie plastique.

Cosmetic and reconstructive surgery has existed in many forms since antiquity, but it was the impulse given by the Great War that gave birth to plastic and cosmetic surgery as we know it today. After the Great War, the names of the most famous pioneers of the allies' side are Sir Harold Gillies, Mac Indoe and also Hippolyte Morestin; however, the surgeons of the enemy axis, beyond the trenches, faced the same constraints with their own war casualties. We present the destinies of two great pioneers of plastic surgery within the beautiful German Bismarckian period: Professor Erich Lexer, and "non-professor" Jakob Joseph.

Acute Lower Extremity Fracture Management in Chronic Spinal Cord Injury: 2022 Delphi Consensus Recommendations.

Our objective was to develop a clinical practice guideline (CPG) for the treatment of acute lower extremity fractures in persons with a chronic spinal cord injury (SCI). Methods: Information from a previous systematic review that addressed lower extremity fracture care in persons with an SCI as well as information from interviews of physical and occupational therapists, searches of the literature, and expert opinion were used to develop this CPG. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system was used to determine the quality of evidence and the strength of the recommendations. An overall GRADE quality rating was applied to the evidence. Conclusions: Individuals with a chronic SCI who sustain an acute lower extremity fracture should be provided with education regarding the risks and benefits of operative and nonoperative management, and shared decision-making for acute fracture management should be used. Nonoperative management historically has been the default preference; however, with the advent of greater patient independence, improved surgical techniques, and advanced therapeutics and rehabilitation, increased use of surgical management should be considered. Physical therapists, kinesiotherapists, and/or occupational therapists should assess equipment needs, skills training, and caregiver assistance due to changes in mobility resulting from a lower extremity fracture. Therapists should be involved in fracture management as soon as possible following fracture identification. Pressure injuries, compartment syndrome, heterotopic ossification, nonunion, malunion, thromboembolism, pain, and autonomic dysreflexia are fracture-related complications that clinicians caring for patients who have an SCI and a lower extremity fracture may encounter. Strategies for their treatment are discussed. The underlying goal is to return the patient as closely as possible to their pre-fracture functional level with operative or nonoperative management.

Understanding the Functional Impact of VOC-Ozone Mixtures on the Chemistry of RNA in Epithelial Lung Cells.

Introduction: Ambient air pollution is associated with premature death caused by heart disease, stroke, chronic obstructive pulmonary disease (COPD), and lung cancer. Recent studies have suggested that ribonucleic acid (RNA) oxidation is a sensitive environment-related biomarker that is implicated in pathogenesis. Aims and Methods: We used a novel approach that integrated RNA-Seq analysis with detection by immunoprecipitation techniques of the prominent RNA oxidative modification 8-oxo-7,8-dihydroguanine (8-oxoG). Our goal was to uncover specific messenger RNA (mRNA) oxidation induced by mixtures of volatile organic compounds (VOCs) and ozone in healthy human epithelial lung cells. To this end, we exposed the BEAS-2B human epithelial lung cell line to the gas- and particle-phase products formed from reactions of 790 ppb acrolein (ACR) and 670 ppb methacrolein (MACR) with 4 ppm ozone. Results: Using this approach, we identified 222 potential direct targets of oxidation belonging to previously described pathways, as well as uncharacterized pathways, after air pollution exposures. We demonstrated the effect of our VOC-ozone mixtures on the morphology and actin cytoskeleton of lung cells, suggesting the influence of selective mRNA oxidation in members of pathways regulating physical components of the cells. In addition, we observed the influence of the VOC-ozone mixtures on metabolic cholesterol synthesis, likely implicated as a result of the incidence of mRNA oxidation and the deregulation of protein levels of squalene synthase (farnesyl-diphosphate farnesyltransferase 1 [FDFT1]), a key enzyme in endogenous cholesterol biosynthesis. Conclusions: Overall, our findings indicate that air pollution influences the accumulation of 8-oxoG in transcripts of epithelial lung cells that largely belong to stress-induced signaling and metabolic and structural pathways. A strength of the study was that it combined traditional transcriptome analysis with transcriptome-wide 8-oxoG mapping to facilitate the discovery of underlying processes not characterized by earlier approaches. Investigation of the processes mediated by air pollution oxidation of RNA molecules in primary cells and animal models needs to be explored in future studies. Our research has thus opened new avenues to further inform the relationship between atmospheric agents on the one hand and cellular responses on the other that are implicated in diseases.

[Dujarrier scandal: Yesterday and today]. / Le procès Dujarier-Geoffre.

From the municipal archives of the "dujarrier-geoffre" procès in 1929, we analyse an evolution in jurisprudence. Nowadays, the judgment would have to be more merciful to the surgeon (finally condemned) or to the victim who lost her left leg and her "maison de couture"? We review the birth of "medical responsibility" at the "belle époque" in France. Finally with the help of the "sou medical" archives, we show the evolution of plastic surgeons' sinistrality since 1993 (no data before).

Anatomical Variants in Renal Transplantation, Surgical Management, and Impact on Graft Functionality.

INTRODUCTION: Chronic kidney disease (CKD) is a priority problem due to its high prevalence. According to the modalities of renal replacement therapy, kidney transplantation (TR) offers to be the best alternative. TR presents multiple factors of dependence of success; among them is the management of the anatomical variants of the graft and the surgical decision on the basis of these. Therefore, the objective of this study is to determine the frequency of variants in the graft, its surgical management, and the impact on the functionality of the transplanted kidney. MATERIAL AND METHODS: This was an observational, retrospective study of patients in the renal transplant unit of the Siglo XXI National Medical Center from 2002-2016. The analysis begins in the description of the population doing bivariate analysis to establish relative risks. For variables with a central tendency, the parametric tests analysis of variance, Student t paired, and unpaired will be used. In the case of nominal variables, the proportion's difference will be estimated using the chi-square test, establishing significance when P is ≤ .05. SPSS 21 software was used. RESULTS: There were a total of 773 patients, with 576 transplants from living donors and 197 from deceased donors. In the case of the artery, a greater number of variants is observed-27.8% being alive versus 17.3% of the variants found in deceased donors. For the renal vein, 12.7% of the kidneys were taken from living donor vs 6.1% from deceased donors. This required one more day of hospitalization (6 vs 7 days of single vs multiple vessels); likewise, increases in immediate post-transplant infections were 5% for single vessels vs 8% in the case of multiple variants. CONCLUSIONS: The importance of knowing the anatomical variants prior to the TR allows them to plan the potential surgical maneuvers, decreasing the times aimed at improving the immediate functionality of the renal graft, while also considering the increase in hospital expenses due to the greater number of days of hospitalization.

Specific Antigens by Federal Entity in Patients at the Transplant Unit of Specialities Hospital, National Medical Center Twenty-First Century, Mexico.

BACKGROUND: The study of the kidney transplant involves understanding the immunologic basis, such as histocompatibility and the genetic basis of a population. In Mexico, the study of the genetic basis has led to a genetic map by federal entities. METHODS: We performed an HLA study with 1,276 kidney transplant patients (recipients and donors) in the Hospital of the National Medical Center Twenty-First Century, determining HLA class I (A, B, and Cw) and class II (DRß1 and DQß1) antigens with the use of SSOP-PCR. A descriptive analysis was conducted with measures of central tendency (mean, SD). RESULTS: Of 1,276 HLA patients studied, we obtained 2,552 results for each class by the composition of the 2 haplotypes, and for HLA-Cw we processed 796 patients, for a total of 1,592 antigens for this class. We found antigens specific to each federal entity, and it was found that the Federal District had the highest number of specific antigens (10) followed by Morelos (7), Querétaro and Mexico State (3 each), and Tamaulipas, Aguascalientes, Michoacán, Guerrero, Puebla, and Oaxaca (1 each). CONCLUSIONS: The genetic map allows us to know proportions of antigens in every state in the center and south of Mexico owing to the diversity and area of influence of the National Medical Center XXIst Century, as well as the wide number of patients. Furthermore, there are still preserved proportionally distinct genetic roots in every entity.

The Most Common HLA Antigens Found in Patients With Renal Transplants at the Specialties Hospital of "La Raza" Medical Center, Mexico.

BACKGROUND: The knowledge to understand transplant acceptance or rejection derives directly from knowing its genetic material and the major histocompatibility complex involved in immune response, so it is essential to identify the most common alleles in the Mexican population. METHODS: In the northern areas of the Federal District (DF), Hidalgo, and Mexico State, we performed an analysis of HLA class I (A and B) and HLA class II (DRß1 and DQß1) with the use of the PCR-SSP process (Invitrogen). We performed measures of central tendency and percentages of common alleles in the study population. RESULTS: We analyzed 718 results of patients before renal transplantation: 313 pairs of recipients and living donors and 92 patients receiving cadaveric donation. HLA allele A 02 536 (37.32%) was the most common allele found. In HLA B, the most common allele corresponded to 35, in 321 (22.35%), which was the most polymorphic. In HLA DRß1 the most common was 04, in 447 (31.12%), which was the least polymorphic; the most common was 03, in 777 (54.10%). CONCLUSIONS: We corroborated the frequency of alleles found in the considered population, which corresponds to the northern part of Mexico City as well as the states of Mexico and Hidalgo. It was determined that there is no risk allele for developing chronic kidney disease.

Disability following combat-sustained nerve injury of the upper limb.

Injuries to the limb are the most frequent cause of permanent disability following combat wounds. We reviewed the medical records of 450 soldiers to determine the type of upper limb nerve injuries sustained, the rate of remaining motor and sensory deficits at final follow-up, and the type of Army disability ratings granted. Of 189 soldiers with an injury of the upper limb, 70 had nerve-related trauma. There were 62 men and eight women with a mean age of 25 years (18 to 49). Disabilities due to nerve injuries were associated with loss of function, neuropathic pain or both. The mean nerve-related disability was 26% (0% to 70%), accounting for over one-half of this cohort's cumulative disability. Patients injured in an explosion had higher disability ratings than those injured by gunshot. The ulnar nerve was most commonly injured, but most disability was associated with radial nerve trauma. In terms of the final outcome, at military discharge 59 subjects (84%) experienced persistent weakness, 48 (69%) had a persistent sensory deficit and 17 (24%) experienced chronic pain from scar-related or neuropathic pain. Nerve injury was the cause of frequent and substantial disability in our cohort of wounded soldiers.

The measurement of photoneutron dose in the vicinity of clinical linear accelerators.

In Brazil, the replacement of rather old cobalt and cesium teletherapy machines with high-energy (E > 10 MV) medical linear accelerators (linacs) started in the year 2000, as part of an effort by the Ministry of Health to update radiotherapy installations. Since then, the contamination of undesirable neutrons in the therapeutic beam generated by these high-energy photons has become an issue of concern when considering patient and occupational doses. The walls of the treatment room are shielded to attenuate the primary and secondary X-ray fluence, and this shielding is generally considered adequate also to attenuate neutrons. However, these neutrons are scattered through the treatment room maze and might result in a radiological problem at the door entrance, an area of high occupancy by the workers of a radiotherapy facility. This paper presents and discusses the results of ambient dose equivalent measurements of neutron using bubble detectors. The measurements were made at different points inside the treatment rooms, including the isocentre and the maze. Several radiation oncology centres, which are users of Varian Clinac or Siemens machines, have agreed to allow measurements to be taken at their facilities. The measured values were compared with the results obtained through the semi-empirical Kersey method of neutron dose equivalent calculation at maze entrances, with reported values provided by the manufacturers as well as values published in the literature. It was found that the measured values were below the dose limits adopted by the Brazilian Regulatory Agency (CNEN), requiring no additional shielding in any of the points measured.

Neutron scattering in concrete and wood: Part II--Oblique incidence.

The knowledge of neutron reflection coefficients is of practical interest when projecting the shielding of radiotherapy rooms, since it is known that about 75% of the neutrons at the maze entrance of these rooms are scattered neutrons. In a previous paper, the energy spectra of photoneutrons were calculated, when reflected by ordinary, high-density concrete and wood barriers, using the MCNP5 code, considering normal incidence and neutron incident energies varying between 0.1 and 10 MeV. It was found that the mean energy of the reflected neutrons does not depend on the reflection angle and that these mean energies are lower in wood and barytes concrete, compared with ordinary concrete. In the present work, the simulation of neutron reflection coefficients were completed, considering the case when these particles do not collide frontally with the barriers, which constitute the radiotherapy room walls. Some simulations were also made to evaluate how neutron equivalent doses at the position of the room door is affected when the maze walls are lined with neutron absorbing materials, such as wood itself or borated polyethylene. Finally, capture gamma rays dose at the entrance of rooms with different maze lengths were also simulated. The results were discussed in the light of the albedo concepts presented in the literature and some of these results were confronted with others, finding good agreement between them.

Malignant melanoma of soft parts. A "non plastic surgeon's land"?

Malignant melanoma of soft parts (MMSP) (or "clear cell sarcoma") is a very rare tumour that shows up without primitive skin involvement (except in subcutaneous prolongations of deep tumours), mostly predominant in the extremities of young adults. Eight files of MMSP were studied retrospectively. The mean patient is a male of 35 years old affected in an extremity (four upper, three lower and one gluteal), according to classical descriptions. The importance of radical surgery in these cases has been extensively established. Confronted with these cases, the plastic surgeon must be aware of the specifics of this rare entity to ensure its proper inclusion in his clinical suspicion. Just in case.

A comparison of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa.

BACKGROUND: The purpose of this study was to compare anesthetic efficacy and postoperative analgesia of 0.5% ropivacaine and 1% mepivacaine for sciatic nerve block in the popliteal fossa (popliteal block). METHODS: A prospective, double-blind study was carried out in 58 adult patients scheduled for outpatient foot or ankle surgery. They were randomized to receive popliteal block with 40 ml of either 0.5% ropivacaine (group R) or 1% mepivacaine (group M). An atraumatic, Teflon-coated needle connected to a neurostimulator was used to make a single puncture using a posterior approach. The times to onset of sensory and motor block, and the need for intraoperative sedation were recorded. Before discharge, patients were asked to document the time to first analgesic use, time to return of full sensation in the foot, and their evaluation of the technique. RESULTS: Onset time (mean+/-standard deviation, 95% confidence interval) of both sensory block (6.5+/-5.1 min, 4.47-8.49, in group R and 6.2+/-3.7 min, 4.83-7.69, in group M) and motor block (6.6+/-4.4 min, 4.81-8.23, in group R and 7.9+/-4.1 min, 6.29-9.53, in group M) was similar in both groups. Postoperative analgesia lasted longer in group R (15.2+/-5.1 h, 13.25-17.21) than in group M (5.7+/-1.8 h, 5.01-6.41; P<0.001). Duration of sensory block was longer in group R (20.7+/-6.2 h, 18.51-23.01) than in group M (6.5+/-1.7 h, 5.86-7.16; P<0.001). Acceptance of the anesthetic procedure was similar in both groups. CONCLUSION: In this study we demonstrated that both 0.5% ropivacaine and 1% mepivacaine for popliteal block produced rapid, effective and safe anesthesia but postoperative analgesia was more long-lasting with ropivacaine.

Expression of prolactin gene and secretion of prolactin by rat retinal capillary endothelial cells.

PURPOSE: Prolactin fragments inhibit blood vessel formation, whereas anti-prolactin antibodies induce angiogenesis in the cornea. Endothelial cells from brain capillaries and the umbilical vein produce prolactin, and this study was undertaken to determine whether retinal capillary endothelial cells could be a source for prolactin in the eye. METHODS: Primary cultures of rat retinal endothelial cells were investigated for the expression of prolactin mRNA by reverse transcription-polymerase chain reaction (RT-PCR) and Southern blot analysis and by in situ hybridization. The prolactin protein was analyzed by immunocytochemistry, enzyme-linked immunoabsorbent assay, Western blot analysis, and the Nb2-cell bioassay. The effect of prolactin and the 16-kDa prolactin fragment on retinal endothelial cell proliferation was investigated, and the expression of the cloned prolactin receptor was analyzed by RT-PCR and Southern blot analysis. RESULTS: Retinal endothelial cells expressed prolactin mRNA and full-length 23-kDa prolactin. Prolactin was observed in the cytoplasm of cells and in their conditioned medium at levels 300 times those described in endothelial cells from other vessels and species. Exogenous 16-kDa prolactin inhibited rat retinal endothelial cell proliferation, whereas 23-kDa prolactin was inactive. No evidence was obtained for the expression of the cloned prolactin receptor in these cells, but the prolactin receptor was amplified in whole rat retina. CONCLUSIONS: Endothelial cells from the microcirculation of rat retina produce and release prolactin. That the cloned prolactin receptor was not expressed in these cells argues against direct autocrine effects of prolactin. Possible paracrine effects are suggested by the expression of the prolactin receptor in retinal tissue.

Anabolic steroids induce region- and subunit-specific rapid modulation of GABA(A) receptor-mediated currents in the rat forebrain.

Anabolic-androgenic steroids (AAS) have become significant drugs of abuse in recent years with the highest increase reported in adolescent girls. In spite of the increased use of AAS, the CNS effects of these steroids are poorly understood. We report that in prepubertal female rats, three commonly abused AAS, 17alpha-methyltestosterone, stanozolol, and nandrolone, induced rapid and reversible modulation of GABAergic currents in neurons of two brain regions known to be critical for the expression of reproductive behaviors: the ventromedial nucleus of the hypothalamus (VMN) and the medial preoptic area (mPOA). All three AAS significantly enhanced peak synaptic current amplitudes and prolonged synaptic current decays in neurons of the VMN. Conversely all three AAS significantly diminished peak current amplitudes of synaptic currents from neurons of the mPOA. The endogenous neuroactive steroids, 3alpha-hydroxy-5alpha-pregnan-20-one and 5alpha-androstane-3alpha,17beta-diol, potentiated currents in the VMN as did the AAS. In contrast to the negative modulation induced by AAS in the mPOA, the endogenous steroids potentiated responses in this region. To determine the concentration response relationships, modulation by the AAS, 17alpha-methyltestosterone (17alpha-meT), was assessed for currents evoked by ultrafast perfusion of brief pulses of GABA to acutely isolated neurons. Half-maximal effects on currents elicited by 1 mM GABA were elicited by submicromolar concentrations of AAS for neurons from both brain regions. In addition, the efficacy of 10(-5) to 10(-2) M GABA was significantly increased by 1 microM 17alpha-meT. Previous studies have demonstrated a striking dichotomy in receptor composition between the VMN and the mPOA with regard to gamma subunit expression. To determine if the preferential expression of gamma(2) subunit-containing receptors in the VMN and of gamma(1) subunit-containing receptors in the mPOA could account for the region-specific effects of AAS in the two regions, responses elicited by ultrafast perfusion of GABA to human embryonic kidney 293 cells transfected with alpha(2), beta(3), and gamma(2) or alpha(2), beta(3), and gamma(1) subunit cDNAs were analyzed. As with native VMN neurons, positive modulation of GABA responses was elicited for alpha(2)beta(3)gamma(2) recombinant receptors, while negative modulation was induced at alpha(2)beta(3)gamma(1) receptors as in the mPOA. Our data demonstrate that AAS in doses believed to occur in steroid abusers can induce significant modulation of GABAergic transmission in brain regions essential for neuroendocrine function. In addition, the effects of these steroids can vary significantly between brain regions in a manner that appears to depend on the subunit composition of GABA(A) receptors expressed.

Properties and sex-specific differences of GABAA receptors in neurons expressing gamma1 subunit mRNA in the preoptic area of the rat.

Gamma-aminobutyric acid type A (GABAA) receptors expressed within the medial preoptic area (mPOA) are known to play a critical role in regulating sexual and neuroendocrine functions. In the rat brain, high levels of expression of the gamma1 subunit mRNA of the GABAA receptor are restricted to a limited number of regions that mediate sexual behaviors, including the mPOA. The biophysical and pharmacological profiles of native gamma1-containing receptors in neurons are unknown. Here, we have characterized the properties of GABAA receptor-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) and currents elicited by fast perfusion of GABA to isolated mPOA neurons of juvenile male and female rats. No significant sex-specific differences were evident in the mean peak amplitude, distribution of event amplitudes, kinetics of current decay, or the frequency of sIPSCs. The profile of modulation of sIPSCs by diazepam, beta-CCM and zolpidem, allosteric modulators that act at the benzodiazepine (BZ) site of the GABAA receptor, support the assertion that mPOA neurons of both sexes express functional gamma1-containing receptors. The ability of zolpidem to modulate both sIPSC amplitude and currents elicited by rapid perfusion of GABA to mPOA neurons differed significantly between the sexes. Zolpidem reversibly induced negative modulation of currents in mPOA neurons isolated from male rats, but had no effect in mPOA neurons from female rats. Concentration-response analysis of responses in neurons acutely isolated from male rats indicated an IC50 of 58 nM with maximal decreases of approximately 50% of control peak current amplitude. In situ hybridization analysis demonstrated that levels of the gamma1 subunit mRNA are significantly higher in mPOA neurons from male than female rats. No significant sex-specific differences were detected in the levels of alpha1, alpha2, or alpha5 mRNAs. These results suggest that native gamma1-containing receptors are expressed in primary neurons of the mPOA and that sex-specific differences in the expression of this subunit may contribute to sexual dimorphism in GABAA receptor modulation by compounds acting at the BZ site.

Temporal dynamics of convergent modulation at a crustacean neuromuscular junction.

At least 10 different substances modulate the amplitude of nerve-evoked contractions of the gastric mill 4 (gm4) muscle of the crab, Cancer borealis. Serotonin, dopamine, octopamine, proctolin, red pigment concentrating hormone, crustacean cardioactive peptide, TNRNFLRFamide, and SDRNFLRFamide increased and -allatostatin-3 and histamine decreased the amplitude of nerve-evoked contractions. Modulator efficacy was frequency dependent; TNRNFLRFamide, proctolin, and allatostatin-3 were more effective when the motor neuron was stimulated at 10 Hz than at 40 Hz, whereas the reverse was true for dopamine and serotonin. The modulators that were most effective at high stimulus frequencies produced a significant decrease in muscle relaxation time; those that were most effective at low stimulus frequencies produced modest increases in relaxation time. Thus modulator actions that appear redundant when examined only at one stimulus frequency are differentiated when a range of stimulus dynamics is studied. The effects of TNRNFLRFamide, serotonin, proctolin, dopamine, and -allatostatin-3 on the amplitude and facilitation of nerve-evoked excitatory junctional potentials (EJPs) in the gm4 and gastric mill 6 (gm6) muscles were compared. The EJPs in gm4 have a large initial amplitude and show relatively little facilitation, whereas the EJPs in gm6 have a small initial amplitude and show considerable facilitation. Modulators that enhanced contractions also enhanced EJP amplitude; -allatostatin-3 reduced EJP amplitude. The effects of these modulators on EJP amplitude were modest and showed no significant frequency dependence. This suggests that the frequency dependence of modulator action on contraction results from effects on excitation-contraction coupling. The modulators affected facilitation at these junctions in a manner consistent with a change in release probability. They produced a change in facilitation that is inversely related to their action on EJP amplitude.

Modulation of oscillator interactions in the crab stomatogastric ganglion by crustacean cardioactive peptide.

The modulation of the pyloric rhythm of the stomatogastric ganglion of the crab, Cancer borealis, by crustacean cardioactive peptide (CCAP) is described. CCAP activated pyloric rhythms in most silent preparations, and altered the phase relationships of pyloric motor neuron firing in all preparations. In CCAP, the pyloric rhythms were characterized by long lateral pyloric (LP) neuron bursts of action potentials. The threshold for CCAP action was approximately 10(-10) M, with increasing effects at higher CCAP concentrations. The changes in motor pattern evoked by CCAP produced significant changes in LP-innervated muscle movement. These movements were additionally potentiated by CCAP applications to isolated nerve-muscle preparations. Thus, enhanced motor neuron firing and increase of the gain of the neuromuscular junctions are likely to operate coordinately in response to hormonally released CCAP. High CCAP concentrations sometimes resulted in modification of the normal 1:1 alternation between the pyloric dilator (PD) and LP neurons to patterns of 2:1, 3:1, or 4:1 alternation. CCAP seems to activate slow intrinsic oscillations in the LP neuron, as well as enhance faster oscillations in the pacemaker group of PD/anterior burster (AB) neurons. Simulations of fast and slow oscillators with reciprocal inhibitory coupling suggest mechanisms that could account for the mode switch from 1:1 alternation to multiple PD bursts alternating with one LP neuron burst.

TNRNFLRFamide and SDRNFLRFamide modulate muscles of the stomatogastric system of the crab Cancer borealis.

The effects of the extended FLRFamide-like peptides, TNRNFLRFamide and SDRNFLRFamide, were studied on the stomach musculature of the crab Cancer borealis. Peptide-induced modulation of nerve-evoked contractions was used to screen muscles. All but 2 of the 17 muscles tested were modulated by the peptides. In several muscles of the pyloric region, peptides induced long-lasting myogenic activity. In other muscles, the peptides increased the amplitude of nerve-evoked contractions, excitatory junctional potentials, and excitatory junctional currents, but produced no apparent change in the input resistance of the muscle fibers. The threshold concentration was 10(-10) M for TNRNFLRFamide and between 10(-9) M to 10(-8) M for SDRNFLRFamide. The absence of direct peptide-containing innervation to these muscles and the wide-spread sensitivity of these muscles to the peptides suggest that TNRNFLRFamide and SDRNFLRFamide may be released from neurosecretory structures to modulate stomatogastric musculature hormonally. We speculate that hormonally released peptide will be crucial for maintaining appreciable muscle contraction in response to low-frequency and low-intensity motor discharge.

Decoding synapses.

The strength of many synapses is modified by various use and time-dependent processes, including facilitation and depression. A general description of synaptic transfer characteristics must account for the history-dependence of synaptic efficacy and should be able to predict the postsynaptic response to any temporal pattern of presynaptic activity. To generate such a description, we use an approach similar to the decoding method used to reconstruct a sensory input from a neuronal firing pattern. Specifically, a mathematical fit of the postsynaptic response to an isolated action potential is multiplied by an amplitude factor that depends on a time-dependent function summed over all previous presynaptic spikes. The amplitude factor is, in general, a nonlinear function of this sum. Approximate forms of the time-dependent function and the nonlinearity are extracted from the data, and then both functions are constructed more precisely by a learning algorithm. This approach, which should be applicable to a wide variety of synapses, is applied here to several crustacean neuromuscular junctions. After training on data from random spike sequences, the method predicts the postsynaptic response to an arbitrary train of presynaptic action potentials. Using a model synapse, we relate the functions used in the fit to underlying biophysical processes. Fitting different neuromuscular junctions allows us to compare their responses to sequences of action potentials and to contrast the time course and degree of facilitation or depression that they exhibit.