Development of a Lightweight Crop Disease Image Identification Model Based on Attentional Feature Fusion

Crop diseases are one of the important factors affecting crop yield and quality and are also an important research target in the field of agriculture. In order to quickly and accurately identify crop diseases, help farmers to control crop diseases in time, and reduce crop losses. Inspired by the application of convolutional neural networks in image identification, we propose a lightweight crop disease image identification model based on attentional feature fusion named DSGIResNet_AFF, which introduces self-built lightweight residual blocks, inverted residuals blocks, and attentional feature fusion modules on the basis of ResNet18. We apply the model to the identification of rice and corn diseases, and the results show the effectiveness of the model on the real dataset. Additionally, the model is compared with other convolutional neural networks (AlexNet, VGG16, ShuffleNetV2, MobileNetV2, MobileNetV3-Small and MobileNetV3-Large), and the experimental results show that the accuracy, sensitivity, F1-score, AUC of the proposed model DSGIResNet_AFF are 98.30%, 98.23%, 98.24%, 99.97%, respectively, which are better than other network models, while the complexity of the model is significantly reduced (compared with the basic model ResNet18, the number of parameters is reduced by 94.10%, and the floating point of operations(FLOPs) is reduced by 86.13%). The network model DSGIResNet_AFF can be applied to mobile devices and become a useful tool for identifying crop diseases.

Amidoxime functionalized chitosan for uranium sequestration in vivo

Amidoxime functionalized chitosan (AC) was recommended as a chelator for uranium sequestration in vivo in this study, and the structure-activity relationship was also explored. Compared with ZnNa₃-DTPA, which was a commercial uranium mobilization drug, AC exhibited excellent biocompatibility and uranium removal efficiency, whether by injection or orally, which could reduce the amounts of uranium deposited in kidneys and femurs by up to 43.6% and 32.3%. In particular, ACs still possessed the ability to mobilize uranium in vivo even if administration was delayed for 72 h.

Low-Temperature Vapor-Phase Anion-Exchange Strategy for Wide-Bandgap Double-Perovskite Cs2AgBiCl6 Films toward Weak Ultraviolet Light Imaging

Low-temperature synthesis of high-quality, high-stability, wide-bandgap perovskite films by solution methods is still challenging. Herein, large-scale wide-bandgap Cs₂AgBiCl₆ (CABC) double perovskite films are synthesized by a vapor-phase anion-exchange strategy. By dedicatedly designing an ultrathin TiO₂ modification layer between the substrate and double perovskites, high-quality heterojunctions with matched energy band alignment are formed, contributing to a remarkably enhanced ON/OFF ratio of 2.4 × 10⁴ (86 times) and a responsivity of 16 mA W^-1 (12 times). Additionally, the ultraviolet photodetectors (UV PDs) exhibit an excellent UV detection limit of 1.18 μW cm^-2 (20 nW), a broad linear dynamic range of 146 dB, and a high specific detectivity of 2.06 × 10¹¹ Jones, as well as long-term stability. Finally, we further demonstrate a weak UV imaging system using CABC UV PDs as imaging sensors. The system is capable of imaging weak UV signals as low as 2.94 μW cm^-2 (50 nW). Our results provide a feasible approach for low-temperature fabrication of wide-bandgap perovskite UV PDs and explore the promising application for weak UV detection and imaging.

Metabolomics study of the effect of Danggui Buxue Tang on rats with chronic fatigue syndrome

Danggui Buxue Tang (DBT), a traditional Chinese medicine formula for "invigorating qi and enriching blood", has been reported to produce a good effect on chronic fatigue syndrome (CFS). However, the related mechanism remains largely unresolved. In this study, a metabolomics approach with gas chromatography coupled to mass spectrometry combined with pattern recognition was devised to estimate the extent to which DBT alleviated CFS induced by food restriction and force swimming in rats. After four weeks of treatment, the endurance capability of rats was significantly better and the motionless time was significantly shorter in the DBT group than in CFS model group. Moreover, the activities of SOD and GSH-Px were increased, while the levels of MDA, IL-6 and TNF-α were decreased in the DBT treatment group. Fifteen significantly changed metabolites were observed in the serum of rats with CFS, which was reversed markedly by DBT treatment. Metabolic pathway analysis showed that DBT could possibly alleviate CFS in rats by regulating phenylalanine, tyrosine and tryptophan biosynthesis, glycine, serine and the metabolism of threonine, glycerolipid, glyoxylate, dicarboxylate and tyrosine. It was observed that the metabolism of glycine, serine and threonine was most closely related to the improvement of CFS by DBT treatment. This study showed that DBT could improve CFS effectively and metabolomics was a powerful means to gain insights into the traditional Chinese medicine formulas against CFS.

Improving probiotic spore yield using rice straw hydrolysate

Spore-forming Bacillus sp. has been extensively studied for their probiotic properties. In this study, an acid-treated rice straw hydrolysate was used as carbon source to produce the spores of Bacillus coagulans. The results showed that this hydrolysate significantly improved the spore yield compared with other carbon sources such as glucose. Three significant medium components including rice straw hydrolysate, MnSO₄ and yeast extract were screened by Plackett-Burman design. These significant variables were further optimized by response surface methodology (RSM). The optimal values of the medium components were rice straw hydolysate of 27% (v/v), MnSO₄ of 0·78 g l^-1 and yeast extract of 1·2 g l^-1 . The optimized medium and RSM model for spore production were validated in a 5 l bioreactor. Overall, this sporulation medium containing acid-treated rice straw hydrolysate has a potential to be used in the production of B. coagulans spores.

Metabolomics analysis of serum reveals the effect of Danggui Buxue Tang on fatigued mice induced by exhausting physical exercise

Danggui Buxue Tang (DBT), believed to invigorate 'Qi' (vital energy) and nourish 'Blood' (body circulation), is a traditional Chinese medicine formula. In this study, a metabolomics approach with gas chromatography coupled to mass spectrometry combined with pattern recognition was adopted to investigate the underlying mechanism of the antifatigue effect of DBT on fatigue of mice induced by weight-loaded forced swimming. Fourteen endogenous metabolites, up-regulated or down-regulated, were identified in the model mice by analysis tools of partial least-squares discriminant analysis (PLS-DA) and XCMS online software. Furthermore, the metabolites were reversed by DBT treatment, offering evidence for the antifatigue effect. In addition, intervention of DBT changed the levels of biochemical parameters. DBT showed obvious efficacy on the fatigued mice possibly by regulating the pathways of phenylalanine, tyrosine and tryptophan metabolism, glycine, serine, and threonine metabolism, glyoxylate and dicarboxylate metabolism, pyruvate metabolism, and TCA cycle. This study demonstrated that DBT has a good antifatigue effect and that metabolomics is a powerful means to gain insights into the therapeutic effect of traditional Chinese medicine formulas.

Extracellular pH modulates GABAergic neurotransmission in rat hypothalamus

Changes in extracellular pH have a modulatory effect on GABAA receptor function. It has been reported that pH sensitivity of the GABA receptor is dependent on subunit composition and GABA concentration. Most of previous investigations focused on GABA-evoked currents, which only reflect the postsynaptic receptors. The physiological relevance of pH modulation of GABAergic neurotransmission is not fully elucidated. In the present studies, we examined the influence of extracellular pH on the GABAA receptor-mediated inhibitory neurotransmission in rat hypothalamic neurons. The inhibitory postsynaptic currents (IPSCs), tonic currents, and the GABA-evoked currents were recorded with whole-cell patch techniques on the hypothalamic slices from Sprague-Dawley rats at 15-26 postnatal days. The amplitude and frequency of spontaneous GABA IPSCs were significantly increased while the external pH was changed from 7.3 to 8.4. In the acidic pH (6.4), the spontaneous GABA IPSCs were reduced in amplitude and frequency. The pH induced changes in miniature GABA IPSCs (mIPSCs) similar to that in spontaneous IPSCs. The pH effect on the postsynaptic GABA receptors was assessed with exogenously applied varying concentrations of GABA. The tonic currents and the currents evoked by sub-saturating concentration of GABA ([GABA]) (10 μM) were inhibited by acidic pH and potentiated by alkaline pH. In contrast, the currents evoked by saturating [GABA] (1mM) were not affected by pH changes. We also investigated the influence of pH buffers and buffering capacity on pH sensitivity of GABAA receptors on human recombinant α1β2γ2 GABAA receptors stably expressed in HEK 293 cells. The pH influence on GABAA receptors was similar in HEPES- and MES-buffered media, and not dependent on protonated buffers, suggesting that the observed pH effect on GABA response is a specific consequence of changes in extracellular protons. Our data suggest that the hydrogen ions suppress the GABAergic neurotransmission, which is mediated by both presynaptic and postsynaptic mechanisms.

[A new triterpenoid fom Radix Pittospori]

To investigate chemical constituents from Radix Pittospori, chloroform extract of the roots was subjected to column chromatography with various chromatographic techniques. The structures were elucidated on the basis of physico-chemical property and spectral analysis. Two triterpenoids were identified as 22-acetyl-21-(2-acetoxy-2-methylbutanoyl)-R1-barrigenol(1) and 3alpha-hydroxyl-20-demethylisoaleuritolic-14(15)-ene-28, 30-dioic acid (2). Compound 1 is a new triterpene and compound 2 is isolated from this plant for the first time.

Inhibition of type A GABA receptors by L-type calcium channel blockers

Modulation of type A GABA receptors (GABAA) by L-type Ca++ channel blockers was investigated. The dihydropyridines nifedipine and nitrendipine, and the phenylalkylamine verapamil inhibited recombinant rat alpha1beta2gamma2 receptors recorded from human embryonic kidney (HEK) 293 cells; nifedipine at low concentrations also elicited modest stimulatory effects on GABA-gated current. The IC50 for GABA current inhibition was lowest for nitrendipine (17.3 +/- 1.3 microM), so subsequent studies were focused on further exploring its mechanism and possible site of action. When co-applied with GABA, nitrendipine had minimal effects on initial current amplitude, but significantly enhanced current decay rate. Nitrendipine-mediated inhibition was subunit-selective, as its IC50 was 10-fold lower in alpha1beta2 receptors. Nitrendipine's effect in recombinant human alpha1beta2gamma2 receptors was similar (IC50=23.0 +/- 1.3 microM) to that observed in rat receptors of the same configuration, indicating the site of action is conserved in the two species. The inhibitory effects were dependent on channel gating, were independent of transmembrane voltage, and were also observed in GABAA receptors recorded from hypothalamic brain slices. The pharmacologic mechanism of inhibition by nitrendipine was non-competitive, indicating it does not act at the GABA binding site. Nitrendipine block was retained in the presence of the benzodiazepine antagonist flumazenil, indicating it does not interact at the benzodiazepine site. The actions of nitrendipine were not affected by a mutation (beta2T246F) that confers resistance to the channel blocker picrotoxin, and they were not altered in the presence of the picrotoxin site antagonist alpha-isopropyl-alpha-methyl-gamma-butyrolactone, demonstrating nitrendipine does not act at the picrotoxin site of the GABAA receptor. Possible interaction of nitrendipine with the Zn++ site was also eliminated, as mutation of beta2 H267 to A, which confers resistance to Zn++, had no effect on nitrendipine-mediated inhibition. Our data suggest some of the central effects of dihydropyridines may be due to actions at GABAA receptors. Moreover, the effects may be mediated through interaction with a novel modulatory site on the GABAA receptor.

[Experimental studies on anticoagulant activity of different extract of leech in vitro]

OBJECTIVE

To study the anticoagulant activity of different extracts of Leech.

METHODS

Prothrombin time (PT), thrombin time (TT) and activated partial thromboplastin time (APTT) were determined by coagulometer for blood samples collected from abdominal vein of Wistar rat.

RESULTS

PT, TT, APTT were prolonged remarkably by ethyl acetate part of Leech. PT was prolonged remarkably by hexane part and aqueous solution part of Leech. APTT was prolonged remarkably by n-Butylalcohol part of Leech.

CONCLUSION

The different extracts of Leech have obvious anticoagulant effects. There are new anticoagulant components different from hirudin in Leech.

Functional analysis of GABA(A) receptors in nucleus tractus solitarius neurons from neonatal rats

To gain insight into specific GABA(A) receptor configurations functionally expressed in the nucleus tractus solitarius (NTS), we conducted several physiological and pharmacological assessments. NTS neurons were characterized in thin brain slices from 1-14 day old rats using whole-cell patch clamp recordings. GABA(A-) receptor-mediated currents were detected in all neurons tested, with an average EC(50) of 22.2 microM. GABA currents were consistently stimulated by diazepam (EC(50)=63 nM), zolpidem (EC(50)=85 nM), loreclezole (EC(50)=10.1 microM) and the neurosteroid 5alpha-pregnan-3alpha-hydroxy-20-one (3alpha-OH-DHP). In contrast, GABA-gated currents of the NTS were inhibited by the divalent cation Zn(2+) (IC(50)=33.6 microM) picrotoxin (IC(50)=2.4 microM) and blockade of endogenous protein tyrosine kinase. GABA-activated currents were insensitive to furosemide (10-1000 microM) in all NTS neurons tested. Collectively, the data suggest that in neonatal rats, the predominant alpha subunit isoform present in GABA(A) receptors of the NTS appears to be the alpha1 and/or alpha2 subunit. beta2 and/or beta3 subunits are the major beta isoform, while the predominant gamma subunit is likely gamma2. Our data suggest the contribution to NTS GABA currents by alpha3-alpha6, beta1, gamma1 and delta subunits, if present, is minor by comparison.

Alkaloids from Cynanchum komarovii with inhibitory activity against the tobacco mosaic virus

A pyrroloisoquinoline alkaloid, 2,3-dimethoxy-6-(3-oxo-butyl)-7,9,10,11,11a,12-hexahydrobenzo[f]pyrrolo[1,2-b]isoquinoline (1), whose structure was determined by spectroscopic methods, was isolated from the aerial parts of Cynanchum komarovii, together with two known alkaloids, 7-demethoxytylophorine (2) and 7-demethoxytylophorine N-oxide (3). Alkaloids 2 and 3 had antiviral activities against tobacco mosaic virus.

Application of SSNTDs in radiobiological investigations aboard recoverable satellites

In recent years some Biostack experiments including a wide spectrum of biological objects have been devoted to study of the radiobiological effects on dry seeds aboard recoverable satellites. Some impressive phenomena have been observed. Clearly, the large amount of energy deposited by the highly ionizing heavy nuclei of cosmic rays is the principal reason for the induced aberrations of the chromosomes of wheat root tip cells. A methodical description of the experimental arrangement and procedure of handling and evaluation of given. The preliminary physical and biological results from the experimental "wheat seeds" are presented.

Pentylenetetrazole-induced inhibition of recombinant gamma-aminobutyric acid type A (GABA(A)) receptors: mechanism and site of action

Pentylenetetrazole (PTZ) is a central nervous system convulsant that is thought, based on binding studies, to act at the picrotoxin (PTX) site of the gamma-aminobutyric acid type A (GABA(A)) receptor. In the present study, we have investigated the mechanism and site of action of PTZ in recombinant GABA(A) receptors. In rat alpha 1 beta 2 gamma 2 receptors, PTZ inhibited GABA-activated Cl(-) current in a concentration-dependent, voltage-independent manner, with an IC(50) of 0.62 +/- 0.13 mM. The mechanism of inhibition appeared competitive with respect to GABA in both rat and human alpha 1 beta 2 gamma 2 receptors. Varying subunit configuration (change or lack of alpha subunit isoform or lack of gamma 2 subunit) had modest effects on PTZ-induced inhibition, as evidenced by comparable IC(50) values (0.6-2.2 mM) in all receptor configurations tested. This contrasts with PTX and other PTX-site ligands, which have greater affinity in receptors lacking an alpha subunit. Using a one-site model for PTZ interaction with alpha 1 beta 2 gamma 2 receptors, the association rate (k(+1)) was found to be 1.14 x 10(3) M(-1) s(-1) and the dissociation rate (k(-1)) was 0.476 s(-1), producing a functional k(d) of 0.418 mM. PTZ could only gain access to its binding site extracellularly. Single-channel recordings demonstrated that PTZ decreased open probability by increasing the duration of closed states but had no effect on single-channel conductance or open state duration. alpha-Isopropyl-alpha-methyl-gamma-butyrolactone, a compound known to antagonize effects of PTX, also diminished the effects of PTZ. Taken together, our results indicate that pentylenetetrazole and picrotoxin interact with overlapping but distinct domains of the GABA(A) receptor.

Direct inhibition of glycine receptors by genistein, a tyrosine kinase inhibitor

Genistein, a tyrosine kinase inhibitor, has been widely used to examine potential effects of protein tyrosine kinase (PTK)-mediated regulation of receptor/channel function. Alteration of ion channel function in the presence of genistein has typically led to the conclusion that PTK regulates the activity of the channel under investigation. In the present report, we have assessed the possibility that genistein directly inhibits the glycine receptor, independent of effects on protein tyrosine kinase. Coapplication of genistein with glycine reversibly inhibited the strychnine-sensitive, glycine-activated current recorded from hypothalamic neurons. The time course of genistein action was rapid (within ms). Equilibration of genistein in the intracellular solution did not affect the ability of extracellularly applied genistein to inhibit the glycine response. Glycine concentration-response profiles generated in the absence and presence of genistein indicated the block was due to non-competitive antagonism. The genistein effect also displayed voltage-dependence. Daidzein, an analog of genistein that does not block protein kinases, also inhibited glycine-activated current. Coapplication of lavendustin A, a specific inhibitor of PTK, had no effect on the glycine response. Our results demonstrate that the tyrosine kinase inhibitor genistein has a direct inhibitory effect on glycine receptors that is not mediated via inhibition of PTK.

Influence of subunit configuration on the interaction of picrotoxin-site ligands with recombinant GABA(A) receptors

We have assessed the interaction of picrotoxin and a putative picrotoxin-site ligand [4-dimethyl-3-t-butylcarboxyl-4,5-dihydro (1, 5-a) quinoxaline] (U-93631) with varying configurations of recombinant GABA(A) receptors, using the whole-cell patch clamp technique. In alpha2beta2gamma2 GABA(A) receptors, coapplication of picrotoxin with GABA had minimal effects on initial GABA-activated Cl(-) current amplitude, and subsequently enhanced decay of GABA-activated Cl(-) currents. The half-maximal inhibitory concentration (IC(50)) for picrotoxin in alpha2beta2gamma2 receptors was 10.3+/-1.6 microM. The alpha subunit isoform did not affect picrotoxin-induced inhibition, as IC(50) values for alpha3beta2gamma2 (5.1+/-0.7 microM) and alpha6beta2gamma2 receptors (7.2+/-0.4 microM) were comparable to those obtained in alpha2beta2gamma2 receptors. Interestingly, in receptors lacking an alpha subunit (beta2gamma2 configuration), picrotoxin had a markedly lower IC(50) (0.5+/-0.05 microM) compared to alpha-containing receptors. The inhibitory profile was generally similar for the presumed picrotoxin-site ligand U-93631, i.e., IC(50) values were comparable in all alphabetagamma-containing receptors, but the IC(50) in beta2gamma2 receptors was greater than 10-fold lower. In addition, a modest but significant initial stimulation of GABA-activated current by U-93631 was observed in alpha2beta2gamma2 and beta2gamma2 receptors. A mutation in the second transmembrane domain, shown previously to abolish picrotoxin sensitivity, also greatly attenuated sensitivity to U-93631. Moreover, incubation of receptors with excess U-93631 hindered picrotoxin's ability to gain access to its binding site; both results indicate that U-93631 interacts at the picrotoxin site of the receptor. Our results indicate the presence of an alpha subunit hinders the ability of picrotoxin to block the GABA(A) receptor, and thus provides additional insight into the site of action of picrotoxin. In addition, we have shown that domains important for the actions of picrotoxin also affect U-93631. Thus, this compound should prove to be a useful ligand for analysis of the convulsant site of this receptor.

Effect of extracellular pH on GABA-activated current in rat recombinant receptors and thin hypothalamic slices

We studied the effects of extracellular pH (pHo) on gamma-aminobutyric acid (GABA)-mediated Cl- current in rat hypothalamic neurons and recombinant type-A GABA (GABA(A)) receptors stably expressed in human embryonic kidney cells (HEK 293), using whole cell and outside-out patch-clamp recordings. In alpha3beta2gamma2s receptors, acidic pH decreased, whereas alkaline pH increased the response to GABA in a reversible and concentration-dependent manner. Acidification shifted the GABA concentration-response curve to the right, significantly increasing the EC50 for GABA without appreciably changing the slope or maximal current induced by GABA. We obtained similar effects of pH in alpha1beta2gamma2 receptors and in GABA-activated currents recorded from thin hypothalamic brain slices. In outside-out patches recorded from alpha3beta2gamma2 recombinant receptors, membrane patches were exposed to 5 microM GABA at control (7.3), acidic (6.4), or alkaline (8.4) pH. GABA activated main and subconductance states of 24 and 16 pS, respectively, in alpha3beta2gamma2 receptors. Alkaline pH(o) increased channel opening frequency and decreased the duration of the long closed state, resulting in an increase in open probability (from 0.0801 +/- 0.015 in pH 7.3 to 0.138 +/- 0.02 in pH 8.4). Exposure of the channels to acidic pH(o) had the opposite effects on open probability (decreased to 0.006 +/- 0.0001). Taken together, our results indicate that the function of GABA(A) receptors is modulated by extracellular pH. The proton effect is similar in recombinant and native receptors and is dependent on GABA concentration. In addition, the effect appears to be independent of the alpha-subunit isoform, and is due to the ability of H+ to alter the frequency of channel opening. Our findings indicate that GABAergic signaling in the CNS may be significantly altered during conditions that increase or decrease pH.

The tyrosine kinase inhibitor genistein directly inhibits GABAA receptors

The protein tyrosine kinase (PTK) inhibitor genistein has been widely used to examine potential effects of tyrosine phosphorylation on neurotransmitter function. We report here that genistein inhibits GABAA receptors through a direct effect. Extracellular application of genistein and GABA reversibly inhibited GABA-activated currents recorded from HEK293 cells expressing rat alpha1beta2gamma2S or alpha1beta2 receptors, even when genistein was preequilibrated in the intracellular solution. Daidzein, an analog of genistein that does not block PTK, also inhibited GABA-activated current. Coapplication of lavendustin A, a specific inhibitor of PTK, had no effect on the GABA response. Our results demonstrate that genistein has a direct inhibitory effect on GABAA receptors that is not mediated via inhibition of tyrosine kinase.

Maintenance of recombinant type A gamma-aminobutyric acid receptor function: role of protein tyrosine phosphorylation and calcineurin

In the present study, rundown of gamma-aminobutyric acid (GABA)-activated Cl- channels was studied in recombinant GABAA receptors stably expressed in human embryonic kidney cells (HEK 293), with conventional whole-cell and amphotericin B-perforated patch recording. When [ATP]i was lowered to 1 mM and resting [Ca++]i was buffered to a relatively high level, the response of alpha 3 beta 2 gamma 2 GABAA receptors to relatively low [GABA] (up to 50 microM) did not show rundown in the whole-cell configuration. However, high [GABA] (greater than 200 microM) induced significant rundown, which was observed by decreases in both the maximum GABA-induced current and GABA EC50. Rundown was prevented completely with a solution containing 4 mM Mg(++)-ATP and low resting [Ca++]i, or during perforated patch recording. The magnitude of rundown was comparable in alpha 1 beta 2 gamma 2 and beta 2 gamma 2 receptors. Neither stimulation nor inhibition of protein kinase A or protein kinase C had a significant effect on rundown. However, sodium metavanadate, an inhibitor of protein tyrosine phosphatase, significantly reduced rundown. In addition, inhibition of protein tyrosine kinase activity by either genistein or lavendustin A induced rundown of the GABA response. Inhibition of the Ca++/calmodulin-dependent phosphatase calcineurin with fenvalerate also prevented rundown of the response to GABA. Our results demonstrate that rundown of GABAA receptor function is concentration-dependent, due to depletion of ATP and/or unbuffered [Ca++]i, and does not depend on the presence or subtype of the alpha subunit. We propose that protein phosphorylation at a tyrosine kinase-dependent site, and a distinct unidentified site, which is dephosphorylated by calcineurin, maintains the function of GABAA receptors.

Cell-cell coupling between CO2-excited neurons in the dorsal medulla oblongata

Anatomically coupled neurons (17 of 137) and non-coupled neurons (120 of 137), in and near the nucleus tractus solitarius and dorsal motor nucleus (i.e. solitary complex), were studied by rapid perforated patch recording in slices (rat, 150-350 microm thick, postnatal day 0-21) before, during and after exposure to hypercapnic acidosis. Anatomical coupling refers to the intercellular transfer of Lucifer Yellow and Biocytin into adjoining neurons, presumably via gap junctions [see Dean et al. (1997) Neuroscience 80, 21-40]. Eighty-six per cent of the anatomically coupled neurons (12 of 14) were depolarized by hypercapnic acidosis, a response referred to as CO2 excitation or CO2 chemosensitivity. In all, 28% (12 of 43) of the CO2-excited neurons were anatomically coupled to at least one other neuron. None (0 of 39) of the CO2-inhibited neurons were anatomically coupled, and only 4% (two of 46) of the CO2-insensitive neurons were anatomically coupled. Increasing the fractional concentration of CO2 from five to 10 and 15% in constant bicarbonate (26 mM) decreased intracellular pH (control 7.3 7.4, 22-25 degrees C) by approximately 1.0 and 1.5 pH units, respectively, as measured using the pH-sensitive fluorescent dye, 2',7'-bis (2-carboxyethyl)-5,6-carboxyfluorescein. Nine of the anatomically coupled neurons (six CO2-excited, one CO2-insensitive and two unidentified) exhibited spontaneous electrotonic postsynaptic potential-like activity, suggesting that they were also electrotonically coupled. During hypercapnic acidosis, the amplitudes of electrotonic postsynaptic potentials were unchanged, concomitant with small changes in input resistance. The frequency of electrotonic postsynaptic potentials increased during hypercapnic acidosis in many anatomically coupled neurons (eight of nine), indicating that both neurons of the coupled pair were stimulated. Cell-cell coupling occurred preferentially in and between CO2-excited neurons of the solitary complex. Further, CO2-excited neurons were not electrotonically uncoupled during intracellular acidosis, in contrast to the effect that decreased intracellular pH has on many other types of coupled cells. It was not determined whether anatomical coupling was affected by hypercapnic acidosis since dye mixture was always administered under normocapnic conditions. The high correlation between anatomical coupling, electrotonic coupling activity and CO2-induced depolarization suggests that cell-cell coupling is an important electroanatomical feature in CO2-excited neurons of the solitary complex. CO2-excited neurons have been hypothesized to function in central chemoreception for the cardiorespiratory control systems, suggesting that cell cell coupling may contribute in part to central chemoreception of CO2 and H+.

Cell-cell coupling occurs in dorsal medullary neurons after minimizing anatomical-coupling artifacts

Dye (Lucifer Yellow) and tracer (Biocytin) coupling, referred to collectively as anatomical coupling, were identified in 20% of the solitary complex neurons tested in medullary tissue slices (120-350 microm) prepared from rat, postnatal day 1-18, using a modified amphotericin B-perforated patch recording technique. Ten per cent of the neurons sampled in nuclei outside the solitary complex were anatomically coupled. Fifty-eight per cent of anatomically coupled neurons exhibited electrotonic postsynaptic potential-like activity, which had peak-to-peak amplitudes of < or = 7 mV, with the same polarity as action potentials; increased and decreased in frequency during depolarizing and hyperpolarizing current injection; was maintained during high Mg2+-low Ca2+ chemical synaptic blockade; and was measured only in anatomically coupled neurons. The high correlation between anatomical coupling and electrotonic postsynaptic potential-like activity suggests that Lucifer Yellow, Biocytin and ionic current used the same pathways of intercellular communication, which were presumed to be gap junctions. Anatomical coupling was attributed solely to the junctional transfer of Lucifer Yellow and Biocytin since potential sources of non-junctional staining were minimized. Specifically, combining 0.26 mM amphotericin B and 0.15-0.5% Lucifer Yellow produced a hydrophobic, viscous solution that did not leak from the pressurized pipette tip < or = 3 microm outer diameter) submerged in artificial cerebral spinal fluid. Moreover, unintentional contact of the pipette tip with adjacent neurons that resulted in accidental staining, another source of non-junctional staining, wits averted by continuously visualizing the tip prior to tight seal formation with infrared video microscopy, used here for the first time with Hoffman modulation contrast optics. During perforated patch recording which typically lasted for 1-3 h. Lucifer Yellow was confined to the pipette, indicating that the amphotericin B patch was intact. However, once the patch was intentionally ruptured at the end of recording, the viscous, lipophilic solution entered the neuron resulting in double labeling. Placing a mixture of amphotericin B, Biocytin and Lucifer Yellow directly into the pipette tip did not compromise tight seal formation with an exposed, cleaned soma, and resulted in immediate (<1 min) steady-state perforation at 22-25 degrees C. This adaptation of conventional perforated patch recording was termed "rapid perforated patch recording". The possible functional implication of cell-cell coupling in the dorsal medulla oblongata in central CO2/H+ chemoreception for the cardiorespiratory control systems is discussed in the second paper of this set [Huang et al. (1997) Neuroscience 80, 41-57].

Induced rearrangement of kappa genes in the BLIN-1 human pre-B cell line correlates with germline J-C kappa and V kappa transcription

The human pre-B acute lymphoblastic leukemia cell line, BLIN-1, has been previously shown to undergo kappa light chain rearrangement in vitro, making it a valuable resource for analyzing pre-B to B cell differentiation. We have examined the recombination potential of BLIN-1 by characterizing several independently derived kappa-expressing subclones for DNA rearrangement and V kappa gene usage. Analysis of five kappa-expressing subclones (all having the same heavy chain rearrangement) demonstrated independent kappa light chain rearrangement events by DNA hybridization analysis. Northern blot analysis using probes recognizing the four different V kappa families revealed that two subclones used the most proximal V kappa (V kappa IV), one subclone used a V kappa I, and one subclone used a V kappa II. By polymerase chain reaction analyses, we detected transcripts from rearranged V-J-C kappa genes as well as transcripts from germline J-C kappa and V kappa in BLIN-1 cells induced to rearrange the kappa locus. kappa germline transcripts were also detected in normal developing B cell populations in fetal liver and bone marrow. Our collective results indicate that: (a) BLIN-1 can be induced to rearrange the kappa locus, and this correlates with the expression of germline kappa locus transcripts that may play a role in activating or targeting gene rearrangement; and (b) active rearrangement and usage of V genes representing different kappa families suggest that, like in the mouse, repertoire diversification in humans occurs in the presence of a fixed heavy chain rearrangement.

Invariants of sets of linear varieties

A minimal set of generators of the ring of invariants for four linear subspaces of dimension n in a vector space of dimension 2n is computed, using the symbolic method introduced by Grosshans et al. [Grosshans, F., Rota, G.-C. & Stein, J. A. (1987) Invariant Theory and Superalgebras (Am. Math. Soc., Providence, RI)].