Comparing an Imaging-guided Pathway with the Standard Pathway for Staging Muscle-invasive Bladder Cancer: Preliminary Data from the BladderPath Study

Transurethral resection of bladder tumour (TURBT) is central to the diagnosis of muscle-invasive bladder cancer (MIBC). With the oncological safety of TURBT unknown, staging inaccuracies commonplace, and correct treatment of MIBC potentially delayed, multiparametric magnetic resonance imaging (mpMRI) may offer rapid, accurate, and noninvasive diagnosis of MIBC. BladderPath is a randomised trial comparing risk-stratified (5-point Likert scale) image-directed care with TURBT for patients with newly diagnosed BC. To date, we have screened 279 patients and randomised 113. Here we report on the first 100 participants to complete staging: 48 in pathway 1 (TURBT) and 52 in pathway 2 (mpMRI for possible MIBC, Likert 3-5). Fifty of 52 participants designated Likert 1-2 (probable NMIBC) from both pathways were confirmed as having NMIBC (96%). Ten of 11 cases diagnosed as NMIBC by mpMRI have been pathologically confirmed as NMIBC, and 10/15 cases diagnosed as MIBC by mpMRI have been treated as MIBC (5 participants underwent TURBT). The specificity of mpMRI for identification of MIBC remains a limitation. These initial experiences indicate that it is feasible to direct possible MIBC patients to mpMRI for staging instead of TURBT. Furthermore, a 5-point Likert scale accurately identifies patients with low risk of MIBC (Likert 1-2), and flexible cystoscopy biopsies appear sufficient for diagnosing BC. PATIENT SUMMARY: We are conducting a clinical trial to assess whether some bladder tumour surgery can be replaced by magnetic resonance imaging scans to determine the stage of the cancer in patients whose tumours appear to be invasive. Our early data suggest that this approach is feasible. The data also show that using a visual score ('Likert scale') can help to identify bladder tumours that are very unlikely to be invasive, and that taking a biopsy in the outpatient clinic when first inspecting the bladder via a camera (diagnostic flexible cystoscopy) is useful for confirming bladder cancer.

Replacing TURBT with mpMRI for staging MIBC: Pilot data from the BladderPath study

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Background: The diagnostic pathways for bladder cancer are largely unchanged for 30 years. The BladderPath trial objectives are to: improve staging, accelerate treatment, and reduce iatrogenic tumour spread by avoiding TURBT. We hypothesise that substituting TURBT with mpMRI will avoid unnecessary surgery, accelerate correct MIBC treatment and improve outcomes. Methods: A randomised phase 2/3 trial of standard of care (Pathway 1) versus risk-stratified mpMRI-directed care (Pathway 2) in visually-diagnosed incident bladder cancer. Patients with bladder lesions suspicious for malignancy at flexible cystoscopy are stratified by a 5-point Likert scale: strongly agree (1) or agree (2) that the lesion is NMIBC, equivocal (3) NMIBC or MIBC, and agree (4) or strongly agree (5) the lesion is MIBC. All patients are randomised; those with probable NMIBC (Likert 1 & 2) undergo TURBT in both pathways, and those with possible MIBC (Likert 3-5) undergo TURBT (Pathway 1) or mpMRI (Pathway 2). Endpoints: feasibility, time to correct MIBC therapy and clinical progression-free survival. We report preliminary feasibility data. Results: To date, 218 potentially eligible patients have been registered; on cystoscopy, 151 patients had no bladder lesions and 5 were excluded for other reasons. Of 62 patients randomised, we report results from 45 with preliminary data. Of the 21 patients in Pathway 1, 11 patients classified as probable NMIBC underwent TURBT (pathology: 11/11 NMIBC); 9/10 patients classified as possible MIBC underwent TURBT (pathology: 4/9 NMIBC & 5/9 MIBC) and 1 patient incorrectly underwent mpMRI (staging: MIBC). Of the 24 patients in Pathway 2, 11/12 patients classified as probable NMIBC underwent TURBT (pathology: 9/11 NMIBC & 2/11 MIBC) and one patient incorrectly underwent mpMRI (staging: NMIBC); 12 patients classified as possible MIBC underwent mpMRI (staging: 6/12 NMIBC & 6/12 MIBC). Conclusions: A 5-point Likert scale accurately identifies patients with a low risk of MIBC (Likert 1 & 2). It is feasible to randomise possible MIBC patients to TURBT or mpMRI for staging. The study is ongoing to investigate the intermediate outcome of time to correct therapy for MIBC and NMIBC and the final outcome of clinical progression-free survival. Clinical trial information: 35296862.

The level of threonine in tobacco seeds is limited by substrate availability, while the level of methionine is limited also by the activity of cystathionine γ-synthase

Methionine and threonine are two essential amino acids whose low levels limit the nutritional quality of seeds. The current objective was to define factors that regulate and might increase their levels in seeds. Feeding experiments carried out on receptacles of developing tobacco (Nicotiana tabacum) capsules showed that 1 mM of S-methylmethionine increased the level of methionine to contents similar to 2.5 mM of homoserine, an intermediate metabolite of the aspartate family of amino acids. The latter also increased the level of threonine. Based on these findings, we generated tobacco seeds that expressed a combination of bacterial feedback-insensitive aspartate kinase (bAK), which was previously reported to have a high level of threonine/methionine, and feedback-insensitive cystathionine γ-synthase (CGS), the regulatory enzyme of the methionine biosynthesis pathway. Plants expressing this latter gene previously showed having higher levels of methionine. The results of total amino acids analysis showed that the level of threonine was highest in the bAK line, which has moderate levels of methionine and lysine, while the highest level of methionine was found in seeds expressing both heterologous genes. The results suggest that the level of threonine in tobacco seeds is limited by the substrate, while that of methionine is limited also by the activity of CGS.

Sonographic assessment of arterial frequency and distribution within the brachial plexus: a comparison with the cadaveric record

We investigated the number and distribution of arteries within the brachial plexus territory using a portable ultrasound device, and compared these findings with known cadaveric data. We recruited 200 volunteers and carried out 400 brachial plexus examinations in a prospective observational study design. We identified arteries within the brachial plexus in more than 90% of subjects. Most of these were located in the upper and middle zones of the plexus and therefore lie within the possible path of a block needle. These findings correlate well with previous cadaveric studies, suggesting that arteries within the brachial plexus territory can be reliably identified with a portable ultrasound device. The presence of these vessels may impact upon the safety and efficacy of brachial plexus blockade. Routine pre-procedural sonographic assessment may offer improved safety and efficacy. You can respond to this article at http://www.anaesthesiacorrespondence.com.

Effect of different sprint training regimes on the oxygen delivery-extraction in elite sprinters

AIM

The effects of sprint training regimes of varying distance schedules on the oxygen delivery-extraction relationship were investigated in 15 young (22+/-1 years) healthy males national-level sprinters.

METHODS

During one session subjects performed four sprints, in a schedule of increasing distance order (100, 200, 300 and 400 m), and during the other session, in a schedule of decreasing distance order (400, 300, 200, and 100 m). All sprint bouts were performed on a treadmill at a speed of 22 km/h-1, which corresponds to 85% of subjects' maximal speeds. The order of the running sequences during sessions was balanced over subjects.

RESULTS

During both sprint schedules, all variables except for oxygen extraction in the incremented training regime, increased significantly from rest to exercise. Training regimes were not different with regard to cardiac output and absolute oxygen uptake. However, the decreasing compared to the increasing scheme was characterized by significantly (P<0.05) higher mean values of heart rate (194.5+/-4.1 185.2+/-5.7 beats/min-1, respectively), oxygen extraction (54.3+/-3.8 and 47.1+/-3.4 mL/L-1, respectively) and lactate (10.6+/-0.5 and 9.2+/-0.7 mmol/L-1, respectively), while stroke volume was significantly (P<0.05) lower (100.4+/-4.5 and 109.7+/-4.4 mL, respectively).

CONCLUSION

The present study indicates that in sprinters performing a similar distance at the same speed, but under different training regimes interplay exists between oxygen delivery and extraction, suggesting a link between the type of training scheme and physiological cardiovascular and skeletal muscle metabolic adaptations. This may explain the absence of differences between the conditions in absolute oxygen uptake and peak power output.

Red grain botryomycosis due to Staphylococcus aureus--a novel case report

Staphylococcus aureus and some other bacteria are known to cause botryomycosis. These bacteria are known to produce yellowish-white soft grains. Only Actinomadura pelletieri is known to produce red grains. We report here a case of an intensely inflammatory type of botryomycosis. A 35-year-old male labourer presented with swelling, redness and multiple sinuses on his foot, of eight months duration. The purulent discharge contained bright red coloured grains, 0.5 to 1 mm in size, which were round to oval in shape. Gram-positive cocci were demonstrated in crushed granules and tissue sections. Culture yielded pure and heavy growth of Staphylococcus aureus . He responded very well to cefazolin. There is no other report of such red grain botryomycosis due to Staphylococcus aureus , available in literature. This is first case report of its kind in world literature.

Effects of different sprint cycling bouts on left ventricular function in top cyclists

AIM

The study investigated lactic acid and left ventricular function in response to two different sprint cycling schedules varying in their time schedule, in 15 healthy national level cyclists (23+/-1 years).

METHODS

During one testing session subjects performed four strenuous bouts in a schedule of increasing time order: 1, 2, 3 and 4 min. In the other session, they performed a decreasing order: 4, 3, 2 and 1 min. Resting time between bouts in the increasing schedule were 2, 3, and 4 min, respectively. Resting times for the decreasing schedules were 4, 3 and 2 min, respectively. Exercise bouts were performed on an electrical cycle ergometer at 85% of each subject's maximal speed velocity.

RESULTS

In both sprint cycling schemes, mean end-systolic volume and mean end-diastolic volume decreased significantly (P < 0.05) with bout's time. However, there was a significant interaction effect regarding schedule order and lactate accumulation. In the incremented scheme, lactate accumulated gradually during the session, while a high level of lactate was maintained throughout the decremented scheme (from 3.8+/-0.7 to 11.8+/-1.8 and from 9.5+/-1.5 to 10.8+/-1.9 mmol.L-1, respectively). Furthermore, analysis of cardiac function during the two schemes demonstrates different physiological responses. The decreasing scheme was characterized by a higher mean heart rate, a lower mean stroke volume and a lower mean end-diastolic volume (P < 0.05) indicating that during the two schemes, the functional mechanisms underlying cardiac response, are different.

CONCLUSION

Our data suggest that in the face of high levels of lactic acid, during the decreasing scheme, venous return may be impeded, most likely due to reduced left ventricular filling time and inadequate vasodilatation of the arteries during the early phase of cycling bout. In addition, it suggests that the decreasing scheme may yield a better anaerobic and cardiovascular training method.

Transgenic tobacco plants overexpressing the Met25 gene of Saccharomyces cerevisiae exhibit enhanced levels of cysteine and glutathione and increased tolerance to oxidative stress

The cysteine biosynthesis pathway differs between plants and the yeast Saccharomyces cerevisiae. The yeast MET25 gene encoded to O-acetylhomoserine sulfhydrylase (AHS) catalyzed the reaction that form homocysteine, which later can be converted into cystiene. In vitro studies show that this enzyme possesses also the activity of O-acetyl(thiol)lyase (OASTL) that catalyzes synthesis of cysteine in plants. In this study, we generated transgenic tobacco plants expressing the yeast MET25 gene under the control of a constitutive promoter and targeted the yeast protein to the cytosol or to the chloroplasts. Both sets of transgenic plants were taller and greener than wild-type plants. Addition of SO(2), the substrate of the yeast enzyme caused a significant elevation of the glutathione content in representative plants from each of the two sets of transgenic plants expressing the yeast gene. Determination of non-protein thiol content indicated up to four-folds higher cysteine and 2.5-fold glutathione levels in these plants. In addition, the leaf discs of the transgenic plants were more tolerant to toxic levels of sulphite, and to paraquat, an herbicide generating active oxygen species.

In vivo analysis of various substrates utilized by cystathionine gamma-synthase and O-acetylhomoserine sulfhydrylase in methionine biosynthesis

To gain insight into the evolution of the methionine biosynthesis pathway, in vivo complementation tests were performed. The substrate specificity of three enzymes that intrinsically use different homoserine-esterified substrates and have different sulfur assimilation pathways was examined: two cystathionine gamma-synthases (the Escherichia coli enzyme that naturally utilizes O-succinylhomoserine [OSH]) and the Arabidopsis thaliana enzyme that naturally exploits O-phosphohomoserine [OPH]. Both of these act through the transsulfuration pathway. The third enzyme investigated was O-acetylhomoserine (OAH) sulfhydrylase of Leptospira meyeri, representing the enzyme that utilizes OAH and operates through the direct sulfhydrylation pathway. All the three enzymes were able to utilize OSH and OAH as substrates, with different degrees of efficiency, but only the plant enzyme was able to utilize OPH as a substrate. In addition to their inherent activity in the transsulfuration pathway, the two cystathionine gamma-synthases were also capable of acting in the direct sulfhydrylation pathway. Based on the phylogenic tree and the results of the complementation tests, we suggest that the ancestral gene was able to act as OAH or OSH sulfhydrylase. In some bacteria and plants, this ancient enzyme most probably evolved into a cystathionine gamma-synthase, thereby maintaining the ability to utilize various homoserine-esterified substrates, as well as various sulfur sources, and thus keeping the multisubstrate specificity of its ancestor. In some organisms, this ancestral gene probably underwent a duplication event, which resulted in a cystathionine gamma-synthase and a separate OAH or OSH sulfhydrylase. This led to the development of two parallel pathways of methionine biosynthesis, transsulfuration and direct sulfhydrylation, in these organisms. Although both pathways exist in several organisms, most seem to favor a single specific pathway for methionine biosynthesis in vivo.

[The ubiquitin-proteasome system: the relationship between protein degradation and human diseases]

The ubiquitin-proteasome system is the major machinery in the cell for specific intracellular degradation. Degradation of a protein via the ubiquitin-proteasome pathway involves two successive steps: 1. Covalent attachment of multiple ubiquitin molecules to the substrate, and 2. Degradation of the tagged protein by the 26S proteasome complex. Via targeting of many substrates, the system regulates a broad array of basic cellular processes such as cell cycle, differentiation and signal transduction. Therefore, it is not surprising that aberrations in the system underlie the pathogenesis of many human diseases, among them malignancies, neurodegenerative diseases and many disorders of the immune and inflammatory response. In some pathologies the involvement of the system is direct, whereas in others the mechanistic linkage is less clear. It is expected that the ongoing extensive research in this area will shed light on the underlying pathogenetic mechanisms of the ubiquitin system-related diseases, and will lead to the development of mechanism-based therapeutic modalities.

Bilateral choanal atresia associated with nasal dermoid cyst and sinus: a case report and review of the literature

The relationship of choanal atresia to various systemic malformations is well acknowledged by the CHARGE acronym: colobomas, heart defects, atresia choanae, retarded growth and development, genito-urinary defects, and ear defects. In the past, we have reported the finding of an isolated skull base malformation associated with choanal atresia. We report here a unique case of choanal atresia associated with a patent foramen cecum and intracranial extension of a dermoid sinus. The embryogenesis of this condition is accounted for by the mesodermal flow theory of choanal atresia formation, and implies a need for thorough imaging of the anterior skull base in cases of bilateral atresia.

Spinal nerve injury enhances subthreshold membrane potential oscillations in DRG neurons: relation to neuropathic pain

Primary sensory neurons with myelinated axons were examined in vitro in excised whole lumbar dorsal root ganglia (DRGs) taken from adult rats up to 9 days after tight ligation and transection of the L(5) spinal nerve (Chung model of neuropathic pain). Properties of subthreshold membrane potential oscillations, and of repetitive spike discharge, were examined. About 5% of the DRG neurons sampled in control DRGs exhibited high-frequency, subthreshold sinusoidal oscillations in their membrane potential at rest (V(r)), and an additional 4.4% developed such oscillations on depolarization. Virtually all had noninflected action potentials (A(0) neurons). Amplitude and frequency of subthreshold oscillations were voltage sensitive. A(0) neurons with oscillations at V(r) appear to constitute a population distinct from A(0) neurons that oscillate only on depolarization. Axotomy triggered a significant increase in the proportion of neurons exhibiting subthreshold oscillations both at V(r) and on depolarization. This change occurred within a narrow time window 16-24 h postoperative. Axotomy also shifted the membrane potential at which oscillation amplitude was maximal to more negative (hyperpolarized) values, and lowered oscillation frequency at any given membrane potential. Most neurons that had oscillations at V(r), or that developed them on depolarization, began to fire repetitively when further depolarized. Spikes were triggered by the depolarizing phase of oscillatory sinusoids. Neurons that did not develop subthreshold oscillations never discharged repetitively and rarely fired more than a single spike or a short burst, on step depolarization. The most prominent spike waveform parameters distinguishing neurons capable of generating subthreshold oscillations, and hence repetitive firing, was their brief postspike afterhyperpolarization (AHP) and their low single-spike threshold. Neurons that oscillated at V(r) tended to have a more prolonged spike, with slower rise- and fall-time kinetics, and lower spike threshold, than cells that oscillated only on depolarization. The main effects of axotomy were to increase spike duration, slow rise- and fall-time kinetics, and reduce single-spike threshold. Tactile allodynia following spinal nerve injury is thought to result from central amplification ("central sensitization") of afferent signals entering the spinal cord from residual intact afferents. The central sensitization, in turn, is thought to be triggered and maintained in the Chung model by ectopic firing originating in the axotomized afferent neurons. Axotomy by spinal nerve injury enhances subthreshold membrane potential oscillations in DRG neurons, augments ectopic discharge, and hence precipitates neuropathic pain.

Functional cross-excitation between afferent A- and C-neurons in dorsal root ganglia

Electrophysiological recordings were made in vitro from primary afferent neurons with unmyelinated axons (C-neurons) in excised rat dorsal root ganglia. Spike activity triggered in neurons with myelinated axons (A-neurons) by stimulation of the peripheral nerve or the dorsal root produced a transient depolarization in passive neighboring C-neurons that share the same ganglion. About 90% of neurons sampled responded with this "cross-depolarization". Cross-depolarization was associated with functional excitation as indicated by an increase in firing probability in response to previously subthreshold intracellular test pulses. Furthermore, it yielded a net increase of the input resistance of the affected C-neurons. We suggest that functional coupling among DRG neurons could serve a metabolic role, providing a functionally relevant feedback signal useful for controlling the excitability of nociceptive sensory endings. In addition, the results provide a novel mechanism whereby afferent nociceptors could be stimulated by activity in low-threshold mechanoreceptors, particularly in the event of nerve injury. Hence, the coupling between afferent A- and C-neurons in dorsal root ganglia provides a novel candidate mechanism for neuropathic pain.

Candidate gene analysis in Rett syndrome and the identification of 21 SNPs in Xq

Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder that affects females. Exclusion mapping studies using a new family with maternal inheritance of RTT defined Xq28 as the candidate region for the RTT gene. Six candidate genes were selected for mutation analysis based on their established expression patterns and known functions in the CNS. These are: Glutamate receptor subunit 3 (GLUR3), GABA receptor subunit alpha 3 (GABRA3), GABA receptor subunit e1 (GABRE1), Vacuolar ATPase subunit 1 (VATPS1, XAP3), the human homologue of plexin 3-SEX (XAP6) and the Synaptobrevin-like protein (SYBL1). Major rearrangements involving these genes were excluded by Southern analysis. No disease-causing mutations were found, but several single-nucleotide polymorphisms (SNPs) were detected. These SNPs will be useful in future linkage analysis and whole-genome association studies for other diseases. The genomic characterization of GLUR3 and GABRA3 will allow mutational analysis of these genes as candidates for other X-linked neurological disorders mapping to Xq25-Xq26 and Xq28.

Membrane potential oscillations in dorsal root ganglion neurons: role in normal electrogenesis and neuropathic pain

Abnormal afferent discharge originating at ectopic sites in injured primary sensory neurons is thought to be an important generator of paraesthesias, dysaesthesias, and chronic neuropathic pain. We report here that the ability of these neurons to sustain repetitive discharge depends on intrinsic resonant properties of the cell membrane and that the prevalence of this characteristic increases after nerve injury. Recording from primary sensory neurons in excised rat dorsal root ganglia, we found that some cells show subthreshold oscillations in their membrane potential. The amplitude, frequency, and coherence of these oscillations were voltage sensitive. Oscillations gave rise to action potentials when they reached threshold. Indeed, the presence of oscillations proved to be a necessary condition for sustained spiking both at resting membrane potential and on depolarization; neurons without them were incapable of sustained discharge even on deep depolarization. Previous nerve injury increased the proportion of neurons sampled that had subthreshold oscillations, and hence the proportion that generated ectopic spike discharge. Oscillatory behavior and ectopic spiking were eliminated by [Na(+)](o) substitution or bath application of lidocaine or tetrodotoxin (TTX), under conditions that preserved axonal spike propagation. This suggests that a TTX-sensitive Na(+) conductance contributes to the oscillations. Selective pharmacological suppression of subthreshold oscillations may offer a means of controlling neuropathic paraesthesias and pain without blocking afferent nerve conduction.

Chronic rhinitis: a manifestation of chronic lymphocytic leukemia

Chronic rhinitis is a condition that occasionally reflects underlying systemic disease. In such cases, physical examination, nasal endoscopy, and computed tomography may be nonspecific. Diagnosis and treatment of the underlying illness may improve nasal symptoms, which may prove refractory to standard rhinitis therapy. A case of chronic rhinitis secondary to nasal involvement of chronic lymphocytic leukemia (CLL) is presented. Biopsy was important in clarifying the cause of the rhinitis. Treatment of the CLL with chlorambucil was successful in alleviating nasal symptoms, and systemic effectiveness was reflected by a decrease in the patient's white cell count. Chronic rhinitis as a manifestation of CLL can be successfully managed through systemic treatment of the underlying disease. Biopsy can be helpful in confirming the cause of rhinitis and should be considered in refractory cases of rhinitis.

Effect of age and nerve injury on cross-excitation among sensory neurons in rat dorsal root ganglia

Spike activity in dorsal root ganglion (DRG) neurons depolarizes passive neighbors that share the same ganglion. We asked whether age or prior nerve injury affect this 'cross-depolarization' signal. Intracellular recordings made from excised DRGs in vitro revealed that the prevalence and duration of cross-depolarization were no greater in adult than in young rats, and that its amplitude was significantly smaller in adults. The amplitude of cross-depolarization was not affected by nerve injury. The decrease in membrane input resistance (R(in)) observed during cross-depolarization was less than that expected from equivalent depolarization alone. This affirms prior evidence that the neural process underlying cross-depolarization causes a net increase in R(in).

Cross-excitation in dorsal root ganglia does not depend on close cell-to-cell apposition

About 90% of neurons in dorsal root ganglia (DRGs) of rats 2-5 weeks of age are depolarized and excited by impulse activity in neighboring neurons that share the same DRG. Synaptic contacts are extremely rare in DRGs, but instances of close membrane apposition between pairs of neuronal somata are not uncommon, especially in prenatal rats. Close membrane apposition could permit electrotonic interactions among neighboring DRG neurons. We carried out an ultrastructural examination of DRGs taken from rats 2-5 weeks of age and found that by this age < 2% of cells remain in close apposition with neighbors. The remainder are separated by one or two layers of satellite glial cytoplasm. It is, therefore, unlikely that close apposition between adjacent neurons contributes significantly to functional cross-excitation in the DRG.

Spike-evoked suppression and burst patterning in dorsal root ganglion neurons of the rat

1. A low level of spontaneous impulse discharge is generated within dorsal root ganglia (DRGs) in intact animals, and this activity is enhanced following nerve injury. Many physiological stimuli present in vivo are capable of augmenting this ectopic discharge. Whatever their cause, episodes of sharply accelerated DRG firing tend to be followed by 'after-suppression' during which discharge falls below baseline rate. In this study we examined the process of postexcitation suppression of firing rate, and how it shapes spike patterning in primary sensory neurons. 2. We recorded intracellularly from sensory neurons in excised rat DRGs in vitro. Trains of spikes triggered by intracellular current pulses evoked a prolonged hyperpolarizing shift. This shift appeared to be due to activation of a Ca(2+)-dependent K+ conductance (9K(Ca)). Spikes evoked by just-suprathreshold pulses triggered a hyperpolarizing shift and spike cessation. As the shift decayed, spiking was restored. The net result was bursty (on-off) discharge, a previously unexplained peculiarity of ectopic discharge in some DRG neurons in vivo. 3. Conditioning nerve tetani delivered to axons of neurons which share the DRG with the impaled neuron evoked transient depolarization ('cross-depolarization'). However, when stimulus strength was increased so as to include the axon of the impaled neuron, the net result was a hyperpolarizing shift. Nerve stimulation that straddled the threshold of the axon of the impaled neuron drove it intermittently, but it always drove axons of at least some neighbouring neurons. The result was dynamic modulation of the membrane potential of the impaled neuron as cross-depolarization and spike-evoked hyperpolarizing shifts played off against one another. Membrane potential shifted in the hyperpolarizing direction whenever the axon was activated, and shifted in the depolarizing direction whenever it was silent. Dynamic modulation of this sort probably also occurs in vivo when stimuli are drawn over the surface of the skin.

Cloning and expression of an Arabidopsis thaliana cDNA encoding a monofunctional aspartate kinase homologous to the lysine-sensitive enzyme of Escherichia coli

As in many bacterial species, the first enzymatic reaction of the aspartate-family pathway in plants is mediated by several isozymes of aspartate kinase (AK) that are subject to feedback inhibition by the end-product amino acids lysine or threonine. So far, only cDNAs and genes encoding threonine-sensitive AKs have been cloned from plants. These were all shown to encode polypeptides containing two linked activities, namely AK and homoserine dehydrogenase (HSD), similar to the Escherichia coli thrA gene encoding a threonine-sensitive bifunctional AK/HSD isozyme. In the present report, we describe the cloning of a new Arabidopsis thaliana cDNA that is relatively highly homologous to the E. coli lysC gene encoding the lysine-sensitive AK isozyme. Moreover, similar to the bacterial lysine-sensitive AK, the polypeptide encoded by the present cDNA is monofunctional and does not contain and HSD domain. These observations imply that our cloned cDNA encodes a lysine-sensitive AK. Southern blot hybridization detected a single gene highly homologous to the present cDNA, plus an additional much less homologous gene. This was confirmed by the independent cloning of an additional Arabidopsis cDNA encoding a lysine-sensitive AK (see accompanying paper). Northern blot analysis suggested that the gene encoding this monofunctional AK cDNA is abundantly expressed in most if not all tissues of Arabidopsis.

Chemically mediated cross-excitation in rat dorsal root ganglia

Primary afferent neurons in mammalian dorsal root ganglia (DRGs) are anatomically isolated from one another and are not synaptically interconnected. As such, they are classically thought to function as independent sensory communication elements. However, it has recently been shown that most DRG neurons are transiently depolarized when axons of neighboring neurons of the same ganglion are stimulated repetitively. Here we further characterize this functional coupling. In electrophysiological recordings made from excised rat DRGs, we found that DRG "cross-depolarization" is excitatory in that it is accompanied by an increase in the probability of spiking in response to otherwise subthreshold test pulses delivered intracellularly. Cross-depolarization contributes to this mutual cross-excitation. However, at least as important a contribution comes from a net increase in the neurons' input resistance (Rin) triggered by the stimulation of neighboring neurons. This change in Rin occurs even when cross-depolarization is absent or is balanced out. The amplitude of cross-depolaration was found to be voltage-dependent, with a reversal potential at approximately -23mV. Reversibility and the change in Rin both indicated that activity of neighboring neurons causes a membrane conductance change that is chemically mediated. Thus, far from being isolated, most DRG neurons participate in ongoing mutual interactions in which neuronal excitability is continuously modulated by afferent spike activity. This intraganglionic dialog appears to be mediated, at least in part, by an activity-dependent diffusable substance(s) released from neuronal somata and/or adjacent axons, and detected by neighboring cell somata and/or axons.

Three-dimensional modelling of tumor-induced ovarian angiogenesis

It is now well established that unrestricted growth of tumors is dependent upon angiogenesis. However, previous studies on tumor growth have not yet revealed how the transition to an angiogenetic state in ovarian malignancy is reflected in the vascular architecture of the ovary. We report here our preliminary observations based upon three-dimensional imaging of normal and tumor-induced ovarian angiogenesis created with a computer-assisted three-dimensional interactive application. The findings suggest that tumor-induced angiogenesis creates a bizarre vascular architecture, with a possible link to chaotic behavior.

Isolation and biological properties of scorpionvenom proteins: iv-comparative study on four proteinases isolated from the venom of isometrus vittatus

1) Four proteinases were isolated from the venom of a local scorpion species Isonietrus vittatus collected from Sindh region, Pakistan and named PRO,(IA) PRO,(IB) PRO(IVA) and PRO(IVB). 2) Successive chromatography on Sephadex G-50, CM-Cellulose and Sephadex G-100 yield 25.5 mg, 20.5 mg, 24.0 mg and 20.0 mg of PRO,(IA) PRO(IB), PRO,(IVA) and PRO(IVB) respectively. 3) The purified toxins were homogenous by gel filtration chromatography and SDS-polyacrylamide gel electrophoresis (SDS-PAGE) giving single peak and band with an apparent molecular weight of 80.0 kda, 75.5 kda, 19.0 kda and 17.0 kda by gel filtration and 81.0 kda, 74.7 kda, 18.25 kda and 17.2 kda by SDS-PAGE. 4) PRO,(IA) PRO,(IVA) and PRO(IVB) have LD(50s) of 1.27 mg/kg, 1.91 mg/kg, 1.68 and 1.70 mg/kg respectively. The former two also caused marked alteration of serum enzyme and chemical constituent levels at sublethal dose whereas PRO(IVA) and PRO(IVB) were found to be less effective. 5) Enzymatic and biological activities of all four were inhibited by heating at 62 degrees C. Both activities were also inhibited by 1.8 mM EDTA and 1.2mM PMSF. Activities were enhanced by Ca(2+) but retarded and inhibited by Cu(4+) and Mg(2+), respectively.

Ongoing activity in neuroma afferents bearing retrograde sprouts

Electrophysiological recordings were made from axons teased from the sciatic nerve 17-34 mm (mean 26.8 mm) central to a chronic nerve-end neuroma in adult rats. 23 fibers (2% of those sampled) appeared to have had a sprout(s) that grew in the retrograde (central) direction for at least this distance. Nine of the 23 (39%) carried spontaneous ongoing discharge. The parent fiber was myelinated (an A-fiber) in most instances, but unmyelinated (a C-fiber) in some. Thus, following nerve injury, a subset of afferent axons undergo retrograde sprouting, and many of them fire spontaneously. These contribute, along with the afferents whose trapped ends terminate at the injury site, to the ectopic afferent barrage generated in neuromas.

Axonal cross-excitation in nerve-end neuromas: comparison of A- and C-fibers

1. We recorded from single afferent axons ending in chronic sciatic nerve end neuromas in rats with the use of the teased-fiber method. Axons were sought that had ongoing impulse discharge originating in the neuroma. 2. Recording from myelinated (A-) fibers, tetanic stimulation of neighboring axons (50 Hz, 5 or 10 s, intensity adequate to drive A-fibers) caused an increase, and sometimes a decrease, in the rate of ongoing discharge in 68% of the fibers tested. In addition, some initially silent neuroma A-fibers (1.4%) were activated in this way. Both A beta and A delta fibers responded, although the likelihood of response was greater in A beta fibers. We call this form of interfiber cross-excitation "crossed afterdischarge." 3. In contrast to A-fibers, crossed afterdischarge was evoked with these stimulation parameters in < or = 5% of the spontaneously active unmyelinated (C-) fibers sampled. No initially silent C-fibers were activated. 4. C-fibers remained largely insensitive to cross-excitation by neighboring axons even when the strength of stimulus pulses was increased so as to include neighboring A + C-fibers. 5. The difference between A- and C-fibers could not be accounted for on the basis of the maturity of the neuroma, rate and pattern of ongoing discharge, or use of Flaxedil paralysis. 6. The difference between A- and C-fibers is discussed in terms of two alternative mechanisms that may underlie crossed afterdischarge: mediation by a neurotransmitter(s) in a nonsynaptic mode, and mutual K+ depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)

Ventilation-perfusion patterns in lung diseases (with reference to those observed in pulmonary embolism)

The frequency distributions of ventilation-perfusion (V-P) patterns in various lung diseases were compared to those observed in pulmonary embolism in order to determine whether the specific V-P patterns for pulmonary embolism constituted a frequent finding in these disorders. The results showed that a segmental or lobar perfusion defect with normal ventilation, was associated with a high probability of thromboembolic lung disease, and was not present in any of the other lung diseases studied.

Amplitude distribution in the right ventricle

Amplitude distribution in the right ventricle obtained from ECG-gated ventriculography has been reviewed and six amplitude distribution patterns were identified. Homogeneous distribution was rarely observed even in patients without any cardiac or pulmonary diseases. Furthermore, there was no difference in frequency distribution of the amplitude distribution patterns between the control group, patients with coronary diseases, and those with recent inferior myocardial infarction. It was concluded that amplitude distribution could not be used to detect hypokinetic areas in the right ventricle.

Unusual cholescintigraphic findings in polyarteritis nodosa

Bile duct cysts as a consequence of liver infarcts have exceptionally been described in polyarteritis nodosa. A case is reported in which necrotic changes due to arterial occlusion, as well as the resulting hepatic bile duct cysts, were clearly demonstrated by diethyl IDA cholescintigraphy.