Inhibiting the stringent response blocks Mycobacterium tuberculosis entry into quiescence and reduces persistence

The stringent response enables Mycobacterium tuberculosis (Mtb) to shut down its replication and metabolism under various stresses. Here we show that Mtb lacking the stringent response enzyme Rel_Mtb was unable to slow its replication rate during nutrient starvation. Metabolomics analysis revealed that the nutrient-starved rel_Mtb -deficient strain had increased metabolism similar to that of exponentially growing wild-type bacteria in nutrient-rich broth, consistent with an inability to enter quiescence. Deficiency of rel_Mtb increased the susceptibility of mutant bacteria to killing by isoniazid during nutrient starvation and in the lungs of chronically infected mice. We screened a pharmaceutical library of over 2 million compounds for inhibitors of Rel_Mtb and showed that the lead compound X9 was able to directly kill nutrient-starved M. tuberculosis and enhanced the killing activity of isoniazid. Inhibition of Rel_Mtb is a promising approach to target M. tuberculosis persisters, with the potential to shorten the duration of TB treatment.

Novel inhibitors of Mycobacterium tuberculosis GuaB2 identified by a target based high-throughput phenotypic screen

High-throughput phenotypic screens have re-emerged as screening tools in antibiotic discovery. The advent of such technologies has rapidly accelerated the identification of 'hit' compounds. A pre-requisite to medicinal chemistry optimisation programmes required to improve the drug-like properties of a 'hit' molecule is identification of its mode of action. Herein, we have combined phenotypic screening with a biased target-specific screen. The inosine monophosphate dehydrogenase (IMPDH) protein GuaB2 has been identified as a drugable target in Mycobacterium tuberculosis, however previously identified compounds lack the desired characteristics necessary for further development into lead-like molecules. This study has identified 7 new chemical series from a high-throughput resistance-based phenotypic screen using Mycobacterium bovis BCG over-expressing GuaB2. Hit compounds were identified in a single shot high-throughput screen, validated by dose response and subjected to further biochemical analysis. The compounds were also assessed using molecular docking experiments, providing a platform for their further optimisation using medicinal chemistry. This work demonstrates the versatility and potential of GuaB2 as an anti-tubercular drug target.

Medical causes of temporary or definitive leaves from a French counterterrorist unit pre-internship

INTRODUCTION

Each year, the French Special Weapons And Tactics team, Groupe d'Intervention de la Gendarmerie Nationale, recruits new members through a physically demanding 8-week selection process. The goal of this study is to estimate the incidence and the causes for temporary or final interruptions during this process for medical reasons.

SUBJECTS, MATERIAL AND METHODS

All of the candidates for the November 2015 selection process were included in this prospective study. The number and reasons for temporary or final interruptions were documented by military general practitioners.

RESULTS

The applicants were 48 law enforcement professionals (2 women, mean age 29.4 years, range 22-35). In 14 cases, a temporary interruption was required and in five cases the selection process prematurely ended. Fifty-two per cent of the temporary interruptions were due to sprains, tendinopathies, fractures or muscle tears, 11% were due to burns, wounds or subcutaneous bruises, 16% were due to cranial trauma and 21% were due to medical causes.

DISCUSSION

The high prevalence of minor traumatology that we observed is similar to the ones observed in other cohorts describing initial training for military personnel in the conventional forces. However, the presence of other pathologies in our study, such as cranial trauma or medical causes, is due to the specificity of this internship selection granting access to an elite unit.

A Modular, Fully Integrated Ultra-High-Throughput Screening System Based on Confocal Fluorescence Analysis Techniques

The rapid increase in size of compound libraries, as well as new targets emerging from the Human Genome Project, require progress in ultra-high-throughput screening (uHTS) systems. In a joint effort with scientists and engineers from the biotech and the pharmaceutical industry, a modular, fully integrated system for miniaturized uHTS was developed. The goal was to achieve high data quality in small assay volumes (1-4 μL) combined with reliable and unattended operation. Two new confocal fluorescence readers have been designed. One of the instruments is a 4-channel confocal fluorescence reader, measuring with 4 objectives in parallel. The fluorescence readout is based on single-molecule detection methods, allowing high sensitivity at low tracer concentrationsand delivering an information-rich output. The other instrument isa confocal fluorescence im aging reader, where the imagesare analyzed in terms of generic patternsand quantified in units of intensity per pixel. Both readers are spanning the application range from assays with isolated targets in homogenous solution or membrane vesiclebased assays (4-channel reader) to cell-based assays (imaging reader). Results from a comprehensive test on these assay types demonstrate the high quality and robustness of this screening system.

Development of a high-throughput cell-based assay for superoxide production in HL-60 cells

Superoxide affects many normal and pathogenic cellular processes, and the detection of superoxide produced by cells is therefore of interest for potential therapeutic applications. To develop a high-throughput cell-based assay for the detection of extracellular superoxide production that could be run in a 384-well or 1536-well format, 2 luminescent reagents, Lucigenin and Diogenes, and one fluorescent reagent, Oxyburst Green BSA, were tested. HL-60 cells, which had been differentiated to a neutrophil-like phenotype with DMSO and frozen in large batches, were used in assays. All 3 superoxide detection reagents performed well statistically in terms of IC(50) reproducibility and met a desired Z' value requirement of >0.4. When tested against a 1408-compound test set at 5 or 10 microM compound concentration, a higher hit rate was obtained with the 2 luminescent reagents compared with that obtained with the fluorescent Oxyburst Green BSA reagent. The Oxyburst Green BSA assay was ultimately chosen for compound profiling and high-throughput screening activities. This 1536 superoxide detection assay using cryopreserved differentiated HL-60 cells represents a shifting paradigm toward the utilization of more therapeutically relevant cells in early drug development activities.

A standard operating procedure for assessing liquid handler performance in high-throughput screening

The thrust of early drug discovery in recent years has been toward the configuration of homogeneous miniaturized assays. This has allowed organizations to contain costs in the face of exponential increases in the number of screening assays that need to be run to remain competitive. Miniaturization brings with it an increasing dependence on instrumentation, which over the past several years has seen the development of nanodispensing capability and sophisticated detection strategies. To maintain confidence in the data generated from miniaturized assays, it is critical to ensure that both compounds and reagents have been delivered as expected to the target wells. The authors have developed a standard operating procedure for liquid-handling quality control that has enabled them to evaluate performance on 2 levels. The first level provides for routine daily testing on existing instrumentation, and the second allows for more rigorous testing of new dispensing technologies. The procedure has shown itself to be useful in identifying both method programming and instrumentation performance shortcomings and has provided a means to harmonizing instrumentation usage by assay development and screening groups. The goal is that this type of procedure be used for facilitating the exchange of liquid handler performance data across the industry.

The chemokine interleukin-8 acutely reduces Ca(2+) currents in identified cholinergic septal neurons expressing CXCR1 and CXCR2 receptor mRNAs

The chemokine IL-8 is known to be synthesized by glial cells in the brain. It has traditionally been shown to have an important role in neuroinflammation but recent evidence indicates that it may also be involved in rapid signaling in neurons. We investigated how IL-8 participates in rapid neuronal signaling by using a combination of whole-cell recording and single-cell RT-PCR on dissociated rat septal neurons. We show that IL-8 can acutely reduce Ca(2+) currents in septal neurons, an effect that was concentration-dependent, involved the closure of L- and N-type Ca(2+) channels, and the activation of G(ialpha1) and/or G(ialpha2) subtype(s) of G-proteins. Analysis of the mRNAs from the recorded neurons revealed that the latter were all cholinergic in nature. Moreover, we found that all cholinergic neurons that responded to IL-8, expressed mRNAs for either one or both IL-8 receptors CXCR1 and CXCR2. This is the first report of a chemokine that modulates ion channels in neurons via G-proteins, and the first demonstration that mRNAs for CXCR1 are expressed in the brain. Our results suggest that IL-8 release by glial cells in vivo may activate CXCR1 and CXCR2 receptors on cholinergic septal neurons and acutely modulate their excitability by closing calcium channels.

Loratadine versus cetirizine: assessment of somnolence and motivation during the workday

OBJECTIVE

This parallel-group, double-blind study compared the somnolence and motivation profiles of 2 second-generation antihistamines, loratadine and cetirizine, in patients with allergic rhinitis.

BACKGROUND

Second-generation antihistamines were developed to provide symptomatic relief from allergic disorders without the unwanted side effects of first-generation antihistamines, including somnolence. Recent research has indicated that not all second-generation antihistamines are comparable with respect to somnolence and other cognitive processes.

METHODS

Patients aged > or = 12 years and actively exhibiting symptoms of allergic rhinitis were randomized to 2 treatment groups to receive 10 mg loratadine or 10 mg cetirizine daily at 8:00 AM for 1 week. After patients took the medication, their somnolence and degree of motivation to perform activities were recorded in an electronic diary using a visual analog scale 4 times during the workday (8:00 AM, 10:00 AM, noon, and 3:00 PM).

RESULTS

Sixty patients (31 men, 29 women) were randomized to treatment. Somnolence scores were similar for both groups at baseline and at the time of dosing (8:00 AM). However, there was a statistically significant difference in somnolence scores between the loratadine and cetirizine groups at 10:00 AM (P = 0.008), noon (P = 0.001), and 3:00 PM (P < 0.001), with the cetirizine group showing a greater degree of somnolence. The scores on motivation to perform activities were similar for both groups at the baseline and 8:00-AM measurements. In parallel with the somnolence scores, there were statistically significant differences in motivation scores between the loratadine and cetirizine groups at 10:00 AM (P = 0.014), noon (P = 0.001), and 3:00 PM (P < 0.001), indicating that patients taking loratadine were relatively more motivated during the workday.

CONCLUSION

The results of this study demonstrate that in patients aged > or = 12 years who had allergic rhinitis, cetirizine use promoted somnolence and decreased motivation to perform activities during the workday compared with loratadine.

Cervical myelopathy due to rheumatoid arthritis. Case report and review of the literature

We present the case report of a 62 year-old female suffering from destructive rheumatoid arthritis (RA) for more than 20 years. She had complaints of progressive gait impairment and numbness in hands and feet. Neurological examination showed an unstable gait and pyramidal tract signs. Anterior atlantoaxial subluxation with pannus formation and cervical myelopathy were demonstrated using conventional X-ray studies and MRI. She was conservatively treated with a soft collar. Treatment with methotrexate and an intensive gait revalidation program were started. RA commonly involves the cervical spine, usually in advanced systemic disease after a mean delay of 16 years. Subluxations of the cervical spine are found in 43 to 86%, 50% of these patients are asymptomatic. The reported rate of neurological impairment due to cervical instability ranges from 7 to 58%. The three most common lesions resulting from cervical RA are atlantoaxial subluxation (50 to 70%), subaxial subluxation (15 to 25%) and cranial settling (20%). It is important to differentiate between cranial settling and atlantoaxial instability, as the latter may have a more benign history with less than 20% showing progressive instability. Cranial settling progresses in 35 to 50% of patients. The commonest presenting features of rheumatoid cervical myelopathy are isolated sensory symptoms. Most patients were found to have multiple neurological deficits once the myelopathy was diagnosed. A mean delay of 31 weeks between the first symptom and the diagnosis of the myelopathy is reported. The sensory symptoms are often misinterpreted as being due to entrapment neuropathy or rheumatoid peripheral neuropathy. Radiographic analysis indicates that the posterior atlantoodontoid interval (< or = 14 mm) is an important parameter that shows excellent correlation with the severity of paralysis.

Magnetic resonance imaging of cartilaginous tumors: is it useful or necessary?

OBJECTIVE

A retrospective study was undertaken to compare the diagnostic accuracy of plain radiography and magnetic resonance (MR) imaging in the diagnosis of cartilaginous tumors.

PATIENTS

The study population consisted of 68 patients with a histologically proven cartilaginous tumor.

DESIGN

For each lesion, a comparative analysis of "plain radiography" versus "plain radiography together with MR study" was performed by two radiologists together. Recently reported literature data were used as criteria by which to define accuracy rating.

RESULTS AND CONCLUSIONS

MR imaging improves accuracy in diagnosing low-grade chondrosarcomas. Since osteochondromas have a characteristic appearance on plain films, MR imaging contributes only in the diagnostic workup of cases in which malignant transformation is suspected.

Magnetic resonance imaging of pelvic bone tumors

The aim of our study was to determine the value of magnetic resonance (MR) imaging in the diagnostic workup of pelvic bone tumors. We retrospectively evaluated the MR findings in 60 pelvic bone tumors. Owing to its high contrast resolution and multiplanar imaging capabilities, MR offers a clear depiction of cortical, medullar or soft tissue involvement, intratumoral necrosis, and relationship to neurovascular structures, and may be considered as the modality of choice for the staging of pelvic bone tumors. Since grading of bone tumors reaches a high accuracy on conventional radiography (CR), the value of MR imaging is rather complementary. Although the role of MR imaging in tissue characterization is mostly limited to recognition of tumoral components, accurate tissue characterization if often possible (e.g. in low-grade chondrosarcoma, eosinophilic granuloma, aneurysmal bone cyst, giant cell tumor, and chordoma). MR imaging in osteochondromas, metastases, and fibrous dysplasia remains of limited value since most of these lesions are well recognized on CR and/or CT. CR remains the first choice examination in diagnosis and grading of bone tumors, but MR imaging has significantly improved staging and tissue characterization in bone tumor imaging. The aim of our study is to determine the value of magnetic resonance (MR) imaging in the diagnostic workup of pelvic bone tumors, i.e. in staging, in differentiating benign from malignant tumors (grading), and in further characterization of tumors or tumoral components.

Magnetic resonance imaging of cartilaginous tumors: a retrospective study of 79 patients

OBJECTIVE

Hyaline cartilaginous tumors are characterized by extremely high signal intensity on T2-weighted images. Recently, some distinctive MR features of cartilaginous bone tumors were reported in small series. Low signal intensity septa surrounding high signal intensity cartilage lobules were seen on T2-weighted images in low-grade chondrosarcomas. On spin-echo T1-weighted images after Gd contrast injection, marked 'septal' or 'ring-and-arc' enhancement was observed in low-grade chondrosarcomas and enchondromas. The purpose of this study was to determine sensitivity and specificity of these MR findings in diagnosis of cartilaginous tumors, and to assess the value of MR in diagnostic workup of these lesions.

MATERIALS AND METHODS

Retrospective evaluation of MR findings in 79 cartilaginous tumors and in 79 non-cartilaginous tumors. All lesions were biopsy proven. Each MR examination was independently reviewed by two experienced radiologists without knowledge of clinical data, radiographic and/or CT findings, or histological diagnosis. All lesions were evaluated for morphology (lobular or non-lobular), presence of a high signal intensity mass on T2-weighted images, presence of low signal intensity septa separating high signal intensity lobules on T2-weighted images, and evidence of septal ('ring-and-arc') enhancement.

RESULTS

None of the reviewed parameters is useful in diagnosing osteochondromas. Since osteochondromas have a characteristic appearance on plain radiography, the value of MR imaging in the workup of these lesions remains limited. MR findings in enchondromas have a low specificity and a low sensitivity. Low-grade chondrosarcomas, often hard to diagnose on plain radiography and difficult to differentiate from enchondromas, are characterized by the MR tandem of 'low signal intensity septa on T2-weighted images' together with 'septal or ring-and-arc enhancement' (sensitivity 92.3%, specificity 76.5%). High-grade chondrosarcomas are easily recognized on plain radiography.

CONCLUSIONS

In differentiating cartilaginous from non-cartilaginous tumors, MR features are highly specific but lack sensitivity. Grading potentials of MR parameters are promising due to the high accuracy in diagnosing low-grade chondrosarcomas.

Determination of lactate, pyruvate, beta-hydroxybutyrate and acetoacetate with a centrifugal analyser

Lactate, pyruvate, beta-hydroxybutyrate, and acetoacetate are intermediary metabolites normally occurring in blood. Their relative concentrations are an expression of nutritional balance in energy metabolism. The simultaneous determination of these four analytes is of special interest in the understanding of energy homeostasis. Rapid, precise routine measurement of these four analytes is basic for the first orientation of the diagnosis of inborn errors of intermediary metabolism, especially those affecting fuel homeostasis. We describe an adaptation of the Cobas Fara II centrifugal analyser of some previously reported methods using the supernatant of a unique deproteinized blood sample for the determination of the four analytes. Reference values are calculated for a pediatric population. The difficulties involved in the diagnosis and follow-up of mitochondrial diseases in children require the standardization of analytical procedures for the correct interpretation of the results.

Magnetic resonance arthrography of the scapulohumeral joint in dogs, using gadopentetate dimeglumine

Six scapulohumeral joints (3 normal joints and 3 joints with radiographic evidence of osteochondrosis) underwent conventional magnetic resonance (MR) imaging and MR scapulohumeral arthrography to evaluate delineation of the articular cartilage. The MR arthrography was performed, using 5 ml of 500 microM gadopentetate dimeglumine (Gd-DTPA) as a contrast medium. Delineation of normal articular cartilage and cartilage defects was less accurate after intra-articular administration of Gd-DTPA. Therefore, it was concluded that MR arthrography with Gd-DTPA is unrewarding for evaluation of osteochondrosis lesions.

Intramolecular Homolytic Displacement. XXIII. Selectivity in the Induced Decomposition of Ethyl t-Butylperoxymethylpropenoate by Radicals Formed From Methyl Propanoate and Derivatives

Thermal decomposition of t-butyl peracetate in a solution of ethyl t- butylperoxymethylpropenoate in methyl propanoate led to the products of substitution of the three different hydrogens in the molecule of the methyl ester by the 2,3-epoxy-2-ethoxycarbonylpropyl group. An SHi reaction on the peroxide function, following the addition to the double bond, is responsible for the formation of these epoxides . Such a result is due to the low regioselectivity of the hydrogen abstraction from methyl propanoate by t- butoxyl radicals, and no improvement could be obtained by changing the relative ratios of the reactants, in converse to previous results described for similar reactions. Thus, selective creation of alkyl radicals was developed through the generation of tributylstannyl radicals as mediator radicals, by reaction of t- butoxyl radicals on tributyltin hydride or hexabutylditin ; the mediator radicals abstract an iodine atom from the alkyl iodide. Application of this methodology to the three iodo derivatives of methyl propanoate permitted us to obtain selectively each of the three epoxides.

MR imaging of eosinophilic granuloma: report of 11 cases

The findings in 11 patients with histologically proven eosinophilic granuloma (EG) examined by magnetic resonance imaging (MRI) are described. In contrast with the variable appearance of EG on conventional radiography and computed tomography (CT), relatively constant features--intermediate to high signal intensity on T1-weighting, high signal intensity on T2-weighting, marked enhancement--were found on MRI. MRI was superior to other imaging methods in demonstrating bone marrow involvement and any accompanying soft tissue mass or inflammation. Intermediate to high signal intensity on T1-weighting and marked contrast enhancement could not be "explained" by histological findings. Prediction of the evolutionary phase of EG by MRI remains questionable because of the phase I (proliferative) histology of all 11 lesions.

Pathologic correlations with magnetic resonance images of osteochondrosis lesions in canine shoulders

Twelve shoulders in 6 dogs with clinical and radiographic evidence of osteochondrosis were examined by magnetic resonance imaging performed on a 0.5-T superconductive system. Scans were obtained with 5-mm-thick slices and 0.75-mm pixel size. Unenhanced T1-weighted spin-echo and unenhanced T2*-weighted gradient-echo images were obtained, using a high-resolution surface coil. The T1-weighted sequences were repeated after IV injection of 0.1 mmol of gadopentetate dimeglumine/kg of body weight (0.2 ml/kg). In 6 joints, histologic examination of synovia and articular cartilage was carried out. The magnetic resonance images were correlated with arthrographic, arthroscopic, and histologic findings. Magnetic resonance imaging was useful in evaluating the extent of subchondral lesions and the severity of inflammatory changes within the subchondral bone. Areas of low signal (visible subchondrally on T1-weighted images that were enhanced by administration of contrast medium) indicated active inflammatory changes within the subchondral bone. Although articular cartilage discontinuity could be detected, loose cartilage flaps could not always be reliably demonstrated. Signal inhomogeneity within the articular cartilage was presumed to correspond with zones of cartilage degeneration.

Controlled diet in phenylketonuria may cause serum carnitine deficiency

Serum carnitine levels may be reduced in patients with phenylketonuria (PKU) owing to low carnitine intake, deficient carnitine synthesis and acylcarnitine production from phenylalanine metabolites. In order to investigate the possible carnitine deficiency we determined serum carnitine in its different forms and the precursors and cofactors involved in its synthesis in a group of patients with PKU or hyperphenylalaninaemia. Free, total and acylcarnitine values were significatively reduced only in PKU patients with Phe-restricted diet which had not been supplemented with carnitine. Acylcarnitine/free carnitine ratio and all the other parameters studied were normal in all patients. We conclude that the low serum carnitine levels in PKU patients with a strict diet are a consequence of the low carnitine intake.

Diagnostic imaging of muscular tumors

Eight patients with muscular tumors--all malignant--were reviewed. Seven patients were examined by magnetic resonance imaging. Some of them also underwent conventional radiology and computed tomography. One patient was examined by computed tomography only. An overview and short description of the muscular tumors are given. The findings with the different imaging techniques are presented, followed by a discussion of the role of the imaging techniques. The final conclusion is that MRI is the modality of choice for detection, staging, and follow-up of muscular tumors, although the signal intensity features are not always specific.

Nerve sheath tumors: evaluation with CT and MR imaging

Tumors of nerves are classified into benign (schwannoma and neurofibroma) and malignant nerve sheath tumors. Schwannomas almost always occur as solitary lesions, whereas neurofibromas may occur alone or in a greater number, especially in patients with the peripheral form of von Recklinghausen's disease. Benign nerve sheath tumors often present as asymptomatic, slowly growing soft tissue masses. Although malignant nerve sheath tumors are relatively rare, a sudden increase in the size of a lesion, in particular in a patient with neurofibromatosis, should raise the suspicion of malignant change. On computed tomography (CT) and magnetic resonance imaging (MR) a benign nerve sheath tumor usually appears as a well-defined, oval, spherical or fusiform mass with smooth borders and distinct outlines, located in the subcutaneous tissue or centered at the expected anatomic location of a nerve, with displacement of adjacent soft tissues. Generally nerve sheath tumors have a low density on unenhanced CT scans. On MR they are isointense to muscle on T1-weighted images, whereas on T2-weighted images the signal intensity is high. Both on CT and MR the degree of contrast enhancement is moderate to marked and may be homogeneous or inhomogeneous. MR has become the method of choice for evaluating the anatomic location, contour, and relation of a nerve sheath tumor to adjacent neural, vascular, and muscular structures. The imaging criteria for malignant nerve sheath tumors are not specific enough to distinguish them from other malignant soft tissue tumors, so that neither CT nor MR can establish a definite diagnosis.

Adipose tumors of soft tissues

Thirteen patients with lipoma were examined at least with MRI, which revealed homogeneous and high signal lesions in both T1 and T2 WI sequences. On CT, these lesions were characterized by very negative density values. Sonography was useful to differentiate a lipoma from an old hematoma that share the same signal on MRI. Eighteen cases of biopsy proven liposarcomas were evaluated with at least two techniques. Tumor heterogeneity was the most important clue to malignancy. With CT, contrast injection was necessary because two cases out of eight appeared homogeneous on native examinations. Lobular pattern and large size are constant signs associated with liposarcoma. The correlation of imaging and histology classification was only successful with differentiated tumors. Angiography unspecifically reveals the malignancy of liposarcoma. MRI is better than CT to evaluate tumor expansion and to differentiate the mass from the surrounding tissue.

CT of soft tissue tumors

We review the documented strengths and weaknesses of CT in the evaluation of soft tissue tumors and we describe what we believe to be an optimal CT technique. We also briefly outline the relation of CT to the other techniques in the diagnosis of soft tissue tumors and relate some particular CT findings to the major tumor types.

Vascular soft tissue tumors: medical imaging

Histologically, tumors of the vascular system are divided into three categories. Benign types can be localized (hemangioma) or involve large segments of the body (angiomatosis). Vascular tumors of intermediate malignancy are known as hemangioendotheliomas. Angiosarcoma is one of the rarest malignant soft tissue neoplasms. The authors present the morphological and SI features of 17 histologically proven vascular tumors (16 benign, 1 malignant) examined by MRI. The results are compared with the findings on other imaging techniques. On T1-WI, the tumors are slightly hyperintense to muscle with interspersed areas of low SI corresponding to fibrous septa, calcifications, or fastly flowing blood, and areas of SI equal to fat. On T2-WI, the lesions are more homogeneous and markedly hyperintense to fat. MRI is superior to all other imaging techniques for evaluation of extent and characterization of vascular soft tissue tumors. Angiography remains helpful in demonstrating feeding or draining vessels.

How many channels should there be in a gap junction?

The junctional resistance of the gap junctions between the lateral giant axons of the crayfish has been measured in coupled and uncoupled conditions and the number of gap junction particles has been counted under the same conditions. From these two sets of data it can be concluded that the plaque-forming particles observed in freeze fracture replicas of the synaptic area are all gap junctional particles and that their channels are open. Based on this and published results from other isolated pairs of coupled cells, an inverse relationship has been found between the input resistance of the cells and the calculated number of open gap junctional channels between them. The relationship applies to both excitable and nonexcitable cells.

[Medical rehabilitation of patients after amputation of the leg in sarcoma]

An analysis of data of 348 patients with malignant tumors of soft tissues has shown that 128 of them had been subjected to the amputation of extremities at different levels. The use of microsurgical techniques favours the improvement of the method of amputation of lower extremities, in particular the transplantation of a calcaneoplantar flap onto the stump end. In order to make the treatment of phantom limb pains more effective acupuncture should be included into the complex of therapeutic measures in addition to traditional methods. Close contacts with prostheses-makers can facilitate earlier prosthesis which can give positive effects on the following rehabilitation of such patients.

Variation of gap junction sensitivity to H ions with time of day

Conductance of gap junctions between segments of the lateral axons of the crayfish nerve cord is reduced by cytoplasmic acidification. Simultaneous measurements of axoplasmic pH and junctional conductance at 09.00 and 12.00 h revealed a shift of about 0.25 pH units in the apparent pK of the crayfish electrotonic synapse. These findings indicate that gating mechanisms of gap junctions are not fixed properties, but may rather be modulated by other, possibly humoral, factors.

Effects of protein reagents on electrotonic coupling in crayfish septate axon

The lateral giant axons of the crayfish nerve cord are composed of segments contributed by each ganglion, which are electrotonically coupled by way of gap junctions. We have investigated the involvement of protein residues in regulating the resistance of crayfish junctional channels by determining effects of group-specific protein reagents. When applied to well-coupled axons, the sulfhydryl group reagents N-ethylmaleimide (NEM) and diamide uncoupled the segments; junctional resistance (Rj) was increased without changing membrane resistance or axoplasmic pH (pHi). The uncoupling produced by NEM could be reversed by alkalinization of the cytoplasm (addition of ammonium chloride to the external medium). Another sulfhydryl reagent (p-chloromercuribenzoic acid) increased Rj to a lesser extent. A disulfide reagent and three amino and three carboxyl group reagents had no effect on the Rj of these axons. The effect of group-specific reagents on partially uncoupled axons was tested by applying the drugs to axons previously exposed to weak acids. N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline recoupled partially uncoupled axons by decreasing Rj and prevented subsequent uncoupling of the junction by low pHi. Another carboxyl group reagent, as well as sulfhydryl and amino group reagents, either had no effect or uncoupled the axons further by increasing Rj. These experimental results suggest that amino acid residues, possibly containing carboxyl and sulfhydryl groups, control the opening and closing of junctional channels and may thus be associated with the channels' active sites.

Effects of the dipolar form of phloretin on potassium conductance in squid giant axons

The effects of phloretin on membrane ionic conductances have been studied in the giant axon of the squid, Loligo pealei. Phloretin reversibly suppresses the potassium and sodium conductances and modifies their dependence on membrane potential (Em). Its effects on the potassium conductance (GK) are much greater than on the sodium conductance; no effects on sodium inactivation are observed. Internal perfusion of phloretin produces both greater shifts in GK(Em) and greater reductions maximum GK than does external perfusion; the effect of simultaneous internal and external perfusion is little greater than that of internal perfusion alone. Lowering the internal pH, which favors the presence of the neutral species of weakly acidic phloretin (pKa 7.4), potentiates the actions of internally perfused phloretin. Other organic cations with dipole moments similar to phloretin's have little effect on either potassium or sodium conductances in squid axons. These results can be explained by either of two mechanisms; on postulates a phloretin "receptor" near the voltage sensor component of the potassium channel which is accessible to drug molecules applied at either the outer or inner membrane surface and is much more sensitive to the neutral than the negatively charged form of the drug. The other mechanism proposes that neutral phloretin molecules are dispersed in an ordered array in the membrane interior, producing a diffuse dipole field which modifies potassium channel gating. Different experimental results support these two mechanisms, and neither hypothesis can be disproven.

Studies on calcium and sodium in uterine smooth muscle excitation under current-clamp and voltage-clamp conditions

The objective of these studies was to define the roles of calcium and sodium in uterine smooth muscle excitation. The double sucrose-gap technique was used for current-clamp and voltage-clamp experiments. It was shown that neither sodium nor calcium alone is capable of supporting excitation in estrogen-dominated uterine smooth muscle. Calcium dependence was explained in part by increased membrane "leakage" current in calcium-free solution and calcium control of the voltage dependence of the early transient conductance. High concentrations of TTX did not affect the magnitude of the peak transient current while La(+++), Mn(++), and Co(++) greatly reduced or abolished it and decreased the steady-state current. From these and other data it was concluded that the regenerative mechanism in uterine smooth muscle has the functional characteristics of a single transient conductance channel whose activation requires the presence of both sodium and calcium. Insensitivity to TTX indicates that the molecular structure of the channel is unlike that in certain sodium-dependent systems, while the effects of La(+++), Mn(++), Co(++), and Ca(++) reveal a similar dependence of conductances on extracellular polyvalent cations.