Reduced growth cone motility in cultured neurons from Drosophila memory mutants with a defective cAMP cascade

Drosophila memory mutants dunce (dnc) and rutabaga (rut) are known to have altered intracellular cAMP levels, nerve terminal growth, and plasticity of synaptic transmission. Because the growth cone is responsible for neurite outgrowth and synaptogenesis, video microscopy was used to examine growth cone morphology and behavior of mutant neurons in larval CNS cultures. We found that growth cone exploratory movement was nearly arrested by both mutations, even though they change cAMP levels in opposite directions. The dnc phenotype could be mimicked by normal neurons when perfused with dibutyryl cAMP (db-cAMP) or forskolin. In contrast, rut growth cones became active when perfused with db-cAMP. Furthermore, motility was also restored by counterbalancing the effects of the two genes in double mutants, indicating that dynamic control of growth cone motility in developing Drosophila neurons requires optimal cAMP levels within an operational range. These findings represent the first demonstration of altered growth cone properties in learning and memory mutants and establish in a natural setting the role of cAMP in growth cone motility and neuronal plasticity.

Heteromultimeric interactions among K+ channel subunits from Shaker and eag families in Xenopus oocytes

Heteromultimeric interactions of K+ channel subunits across different families have been thought to contribute to the functional diversity of ionic currents, as suggested by previous genetic evidence. We present here direct demonstration in Xenopus oocytes that subunits from distinct eag and Shaker families functionally interact, most likely as heteromultimeric channels. Coexpression with eag accelerates the inactivation and slows the recovery from inactivation of the transient Shaker current. Site-directed mutagenesis indicates that the eag carboxyl terminus is crucial for this interaction, exerting effects preferentially on N-type inactivation. Many members of the eag and Shaker families have now been identified and their human homologs implicated in cardiac and neurological disorders. Studies on channel subunit interactions may prove important in understanding the disease pattern and the complex functions of the brain.

Altered habituation of an identified escape circuit in Drosophila memory mutants

Genetic approaches in Drosophila have advanced our understanding of the molecular mechanisms of different forms of learning, including habituation, but relevant neural components have not been explored. We show that a well defined neural circuit that underlies an escape response can be habituated, providing for the first time excellent opportunities for studying physiological parameters of learning in a functional circuit in the fly. Compared with other forms of conditioning, relatively little is known of the physiological mechanisms of habituation. The giant fiber pathway mediates a jump-and-flight escape response to visual stimuli. The jump may also be triggered electrically at multiple sites in the tethered fly. This response shows parameters of habituation, including frequency-dependent decline in responsiveness, spontaneous recovery, and dishabituation by a novel stimulus, attributable to plasticity in the brain. Mutations of rutabaga that diminish cAMP synthesis reduced the rate of habituation, whereas dunce mutations that increase cAMP levels led to a detectable but moderate increase in habituation rates. Surprisingly, habituation was extremely rapid in dunce rutabaga double mutants. This corresponds to the extreme defects seen in double mutants in other learning tasks, and demonstrates that defects of the rutabaga and dunce products interact synergistically in ways that could not have been predicted on the basis of simple counterbalancing biochemical effects. Although habituation is localized to afferents to the giant fiber, cAMP mutations also affected performance of thoracic portions of the pathway on a millisecond time scale that did not account for behavioral plasticity. More significantly, spontaneous recovery and dishabituation were not as clearly affected as habituation in mutants, indicating that these processes may not overlap entirely in terms of cAMP-regulating mechanisms. The analysis of habituation of the giant fiber response in available learning and memory mutants could be a crucial step toward realizing the promise of memory mutations to elucidate mechanisms in neural circuits that underlie behavioral plasticity.

Two isoforms of Drosophila dynamin in wild-type and shibire(ts) neural tissue: different subcellular localization and association mechanisms

The temperature-sensitive mutations of the shibire (shi) gene in Drosophila cause endocytic arrest, resulting in neurotransmission block and paralysis at high temperatures. However, underlying mechanism for the defects is not yet known. We examined the subcellular distribution of dynamin, a product of the shi gene, by immunoblotting and immunocytochemical assays. Two isoforms of dynamin with apparent M(r) of 92 kD and 94 kD have been detected in wild-type and shi(n) adult neural tissue. The two isoforms were reproducibly associated with different subcellular fractions of head homogenates. The 94kD isoform is fractionated in the low speed (2.000 x g) pellet containing plasma membrane fragments, and the 92kD isoform in the high speed (130,000 x g) pellet. In this procedure, very little dynamin remained in the high speed supernatant fraction. The 94 kD isoform represents the majority (65-75%) of total dynamin and appears to be a peripheral membrane protein. It can be extracted from the low speed membrane pellet by high salt, Na2CO3 (pH 11) or Triton X-100 treatments. Extracted 94kD dynamin from both wild-type and mutant homogenates is able to reassociate with artificial phospholipid vesicles at both permissive and restrictive temperatures. Binding of the 94 kD dynamin to liposomes appears to be pH-dependent, varying most significantly within the physiological pH range, which may be functionally important. The 92 kD isoform cannot be released by high salt or Na2CO3 treatments and only a small fraction is released by Triton X-100, suggesting a different mechanism of association with cell structures. The distribution of the two isoforms is not altered by the presence of stabilized microtubules in homogenates. No apparent degradation or subcellular redistribution of mutant dynamin was detected in two shi(n) alleles after heat shock or block of the dynamin GTPase activity, suggesting that intracellular redistribution or degradation of mutant dynamin are not involved in the endocytosis arrest in these mutants. These observations resemble the effect of endocytosis arrest by GTP-gamma-S in rat brain synaptosomes (Takei et al., 1995), in which dynamin is trapped at the neck of invaginated pits but is absent in the clathrin-coated distal end undergoing internalization. Our finding that endocytosis arrest by shi(n) mutations and GTP-gamma-S do not lead to cumulation of dynamin in the low speed pellet fraction further suggests that the 94 kD isoform remains associated with the plasma membrane during coated vesicle pinch-off and that the two isoforms do not appear to correspond to different functional states of dynamin but are likely to be involved in separate cellular compartments within the membrane cycling pathway (e.g., the plasma membrane, endosomes, and endoplasmic reticulum).

K252a-potentiation of EGF-induced neurite outgrowth from PC12 cells is not mimicked or blocked by other protein kinase activators or inhibitors

Epidermal growth factor (EGF) has recently been shown to cause certain strains of PC12 cells to extend short neurites. This EGF-induced differentiation of PC12 was found to be potentiated by the protein kinase inhibitor, K252a, in that PC12 cells treated with both EGF and K252a extended long branched neurites similar to those induced by nerve growth factor (NGF). As reported here no other protein kinase inhibitor or activator mimicked or blocked the effect of K252a on EGF-induced PC12 differentiation. Cyclic adenosine 3',5'-monophosphate (cAMP) also potentiated EGF-induced neurite outgrowth from PC12 cells, but the mechanism of this potentiation was different from that of K252a. Cells that had been exposed to EGF and then stripped of their neurons extended neurites again when retreated with EGF in the absence of RNA synthesis or when treated with NGF in the absence of RNA synthesis. Thus EGF can prime PC12 cells for either EGF or for NGF, a finding that further suggests that EGF and NGF use similar signaling pathways to induced neuronal differentiation of PC12.

Functional expression of Shaker K+ channels in cultured Drosophila "giant" neurons derived from Sh cDNA transformants: distinct properties, distribution, and turnover

Expression of transgenic Shaker (Sh) channels has not previously been examined in Drosophila neurons. We studied K+ current by whole-cell recording in cultured "giant" neurons derived from germline transformants. Independent lines were generated by using a P-element vector, in which transcription of the 29-4 cDNA, one of the Sh splicing variants (Iverson and Rudy, 1990), was under the control of a heat shock (HS)-inducible promoter. Transformants in wild-type and two different Sh mutant backgrounds all exhibited an HS-inducible, A-type K+ current that was characterized by a much slower recovery from inactivation and a higher sensitivity to 4-aminopyridine than native K+ currents of Sh 29-4 currents expressed in Xenopus oocytes. Despite similarities in the kinetic and pharmacological properties of the HS-induced current in all backgrounds examined, host-dependent differences in the peak current amplitude have been consistently observed between multiple lines of 29-4 ShM and 29-4 Sh120 that might reflect differential channel subunit assembly in different hosts. Isolation of the novel 29-4 currents allowed determination of the channel turnover rate in cultured neurons. These currents persisted for up to 3 d or more, comparable with the durations previously reported for Na+ and Ca2+ channels. Surprisingly, the percentage of cells expressing inactivating K+ currents remained approximately the same with or without HS induction, suggesting that some mechanisms exist to restrict functional expression of inactivating K+ channels, including transgenic Sh channels and those not encoded by the Sh locus, to certain types of neurons.

Differential physiology and morphology of motor axons to ventral longitudinal muscles in larval Drosophila

Morphological and physiological characteristics of the two major motor axons supplying the commonly studied ventral longitudinal muscle fibers (6 and 7) of third-instar Drosophila melanogaster larvae were investigated. The innervating terminals of the two motor axons differ in the size of their synapse-bearing varicosities. The terminal with the larger varicosities also fluoresces more brightly when stained with the vital fluorescent dye 4-(4-diethylaminostyryl)-N-methylpyridinium iodide (4-Di-2-Asp) and occupies a larger total contact area on the muscle fiber. Through selective simultaneous recording of synaptic currents from identified boutons in living preparations during elicitation of synaptic potentials, it was shown that the axon with the smaller varicosities generates a large excitatory junction potential (EJP) in muscle 6 and that the axon with the larger varicosities generates a smaller EJP. Short-term facilitation is more pronounced for the smaller EJP. In preparations treated with 4-Di-2-Asp, the fluorescence of smaller varicosities increases with stimulation that elicits the large EJPs, indicating an activity-dependent entry of calcium that enhances mitochondrial fluorescence. The differences in morphology and physiology of the two axons are similar to, though less pronounced than, those observed in "phasic" and "tonic" motor axons of crustaceans.

Concomitant alterations of physiological and developmental plasticity in Drosophila CaM kinase II-inhibited synapses

Ca2+/calmodulin-dependent protein kinase II (CaM kinase) has been implicated in neural plasticity that underlies learning and memory processes. Transformed strains of Drosophila, ala1 and ala2, expressing a specific inhibitor of CaM kinase are known to be impaired in an associative conditioning behavioral paradigm. We found that these transformants had altered short-term plasticity in synaptic transmission along with abnormal nerve terminal sprouting and directionality of outgrowth. These results represent an interesting parallel with the activity-dependent regulation of synaptic physiology and morphology by the cAMP cascade in Aplysia and Drosophila. In contrast to the learning mutants dunce and rutabaga, which are defective in the cAMP cascade, inhibition of CaM kinase in ala transformants caused increased sprouting at larval neuromuscular junctions near the nerve entry point, rather than altering the higher order branch segments. In addition, synaptic facilitation and potentiation were altered in a manner different from that observed in the cAMP mutants. Furthermore, synaptic currents in ala transformants were characterized by greater variability, suggesting an important role of CaM kinase in the stability of transmission.

Calcium/calmodulin-dependent protein kinase II and potassium channel subunit eag similarly affect plasticity in Drosophila

Similar defects in both synaptic transmission and associative learning are produced in Drosophila melanogaster by inhibition of calcium/calmodulin-dependent protein kinase II and mutations in the potassium channel subunit gene eag. These behavioral and synaptic defects are not simply additive in animals carrying both an eag mutation and a transgene for a protein kinase inhibitor, raising the possibility that the phenotypes share a common pathway. At the molecular level, a portion of the putative cytoplasmic domain of Eag is a substrate of calcium/calmodulin-dependent protein kinase II. These similarities in behavior and synaptic physiology, the genetic interaction, and the in vitro biochemical interaction of the two molecules suggest that an important component of neural and behavioral plasticity may be mediated by modulation of Eag function by calcium/calmodulin-dependent protein kinase II.

Altered mechanoreceptor response in Drosophila bang-sensitive mutants

Bang-sensitive mutants of Drosophila melanogaster (bas1, bssMW1, eas2, tko25t) display seizure followed by paralysis when subjected to mechanical shock. However, no physiological or biochemical defect has been found to be common to all of these mutants. In order to observe the effects of bang-sensitive mutations upon an identified neuron, and to study the nature of mechanically induced paralysis, we examined the response of a mechanosensory neuron in these mutants. In each single mutant and the double mutant bas1 bssMW1, the frequency of action potentials in response to a bristle displacement was reduced. This is the first demonstration of a physiological defect common to several of the bang-sensitive mutations. Adaptation of spike frequency, cumulative adaptation to repeated stimulation (fatigue) and the time course of recovery from adaptation were also examined. Recovery from adaptation to a conditioning stimulus was examined in two mutants (bas1 and bssMW1), and initial recovery from adaptation was greater in both mutants. Quantification of receptor potentials was complicated by variability inherent in extracellular recording conditions, but examination of the waveform and range of amplitudes did not indicate clear mutant defects. Therefore the differences observed in the spike response may be due to an alteration of the transfer from receptor potentials to action potential production. DNA sequence analysis of tko and eas has indicated that they encode apparently unrelated biochemical products. Our results suggest that these biochemical lesions lead to a common physiological defect in mechanoreceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Improved stability of Drosophila larval neuromuscular preparations in haemolymph-like physiological solutions

Neuromuscular preparations from third instar larvae of Drosophila are not well-maintained in commonly used physiological solutions: vacuoles form in the muscle fibers, and membrane potential declines. These problems may result from the Na:K ratio and total divalent cation content of these physiological solutions being quite different from those of haemolymph. Accordingly haemolymph-like solutions, based upon ion measurements of major cations, were developed and tested. Haemolymph-like solutions maintained the membrane potential at a relatively constant level, and prolonged the physiological life of the preparations. Synaptic transmission was well-maintained in haemolymph-like solutions, but the excitatory synaptic potentials had a slower time course and summated more effectively with repetitive stimulation, than in standard Drosophila solutions. Voltage-clamp experiments suggest that these effects are linked to more pronounced activation of muscle fiber membrane conductances in standard solutions, rather than to differences in passive muscle membrane properties or changes in postsynaptic receptor channel kinetics. Calcium dependence of transmitter release was steep in both standard and haemolymph-like solutions, but higher external calcium concentrations were required for a given level of release in haemolymph-like solutions. Thus, haemolymph-like solutions allow for prolonged, stable recording of synaptic transmission.

K252a potentiates epidermal growth factor-induced differentiation of PC12 cells

Epidermal growth factor (EGF) induced short neurites in two different strains of PC12 cells. The length of the EGF-induced neurites was markedly increased in the presence of the protein kinase inhibitor K252a, which is known to inhibit differentiation induced by nerve growth factor (NGF). EGF-induced differentiation of PC12 required RNA synthesis and activity of the ras proto-oncogene product. EGF increased the levels of three neurofilament proteins and the mRNA level of two late response genes (SCG10 and 63) known to be induced by NGF. Together, EGF and K252a caused a greater increase in these mRNAs than did either agent alone. K252a did not alter the extent of EGF-induced autophosphorylation of the EGF receptor, but it did decrease the extent of receptor phosphorylation in the absence of added EGF. Thus, the ability of the EGF receptor to trigger neuronal differentiation may depend on the state of its phosphorylation at serine and/or threonine residues. Two other strains of PC12 did not extend neurites when exposed to EGF, even when K252a was also present. Thus, the differentiating effect of EGF on PC12 is PC12 strain-specific.

Modulation of different K+ currents in Drosophila: a hypothetical role for the Eag subunit in multimeric K+ channels

We examined the role of the ether a go-go (eag) gene in modulation of K+ currents and the possibility of its protein product Eag as a subunit in the heteromultimeric assembly of K+ channels by voltage-clamp analysis of larval muscle membrane currents. Previous DNA sequence studies indicate that the eag gene codes for a polypeptide homologous to, but distinct from, the Shaker (Sh) K+ channel subunits (Warmke et al., 1991), and electrophysiological recordings revealed allele-specific effects of eag on four identified K+ currents in Drosophila larval muscles (Zhong and Wu, 1991). Further studies of eag alleles indicated that none of the eag mutations, including alleles producing truncated mRNA messages, eliminate any of the four K+ currents, and that the mutational effects exhibit strong temperature dependence. We found that both W7, an antagonist of Ca2+/calmodulin, and cGMP analogs modulated K+ currents and that their actions were altered or even abolished by eag mutations. These results suggest a role of eag in modulation of K+ currents that may subserve integration of signals at a converging site of the two independent modulatory pathways. The Sh locus is known to encode certain subunits of the IA channel in larval muscle. The existence of multiple eag and Sh alleles enabled an independent test of the idea of Eag as a K+ channel subunit by studying IA in different double-mutant combinations. An array of allele-specific interaction between eag and Sh was observed, which reflects a close association between the Sh and eag subunits within the IA channel. Taken together, our data strengthen the possibility that the eag locus provides a subunit common to different K+ channels. The role of the eag subunit for modulating channels, as opposed to that of Sh subunits required for gating, selectivity, and conductance of the channel, suggest a combinatorial genetic framework for generating diversified K+ channels.

Differential ultrastructure of synaptic terminals on ventral longitudinal abdominal muscles in Drosophila larvae

The innervation of ventral longitudinal abdominal muscles (muscles 6, 7, 12, and 13) of third-instar Drosophila larvae was investigated with Nomarski, confocal, and electron microscopy to define the ultrastructural features of synapse-bearing terminals. As shown by previous workers, muscles 6 and 7 receive in most abdominal segments "Type I" endings, which are restricted in distribution and possess relatively prominent periodic terminal enlargements ("boutons"); whereas muscles 12 and 13 have in addition "Type II" terminals, which are more widely distributed and have smaller "boutons". Serial sectioning of the Type I innervation of muscles 6 and 7 showed that two axons with distinctive endings contribute to it. One axon (termed Axon 1) has somewhat larger boutons, containing numerous synapses and presynaptic dense bodies (putative active zones for transmitter release). This axon also has more numerous intraterminal mitochondria, and a profuse subsynaptic reticulum around or under the synaptic boutons. The second axon (Axon 2) provides somewhat smaller boutons, with fewer synapses and dense bodies per bouton, fewer intraterminal mitochondria, and less-developed subsynaptic reticulum. Both axons contain clear synaptic vesicles, with occasional large dense vesicles. Approximately 800 synapses are provided by Axon 1 to muscles 6 and 7, and approximately 250 synapses are provided by Axon 2. In muscles 12 and 13, endings with predominantly clear synaptic vesicles, generally similar to the Type I endings of muscles 6 and 7, were found, along with another type of ending containing predominantly dense-cored vesicles, with small clusters of clear synaptic vesicles. This second type of ending was found most frequently in muscle 12, and probably corresponds to a subset of the "Type II" endings seen in the light microscope. Type I endings are thought to generate the 'fast' and 'slow' junctional potentials seen in electrophysiological recordings, whereas the physiological actions of Type II endings are presently not known.

Differential modulation of potassium currents by cAMP and its long-term and short-term effects: dunce and rutabaga mutants of Drosophila

The cAMP concentration in Drosophila is increased by mutations of the dunce (dnc) gene and decreased by mutations of the rutabaga (rut) gene. Such mutants provide a unique means for exploring the role of cAMP in functional and developmental regulation of membrane currents. Four distinct K+ currents have been identified in Drosophila larval muscle fibers, i.e. the voltage-activated transient IA and delayed IK and the Ca(2+)-activated fast ICF and slow ICS. Results from our voltage-clamp studies indicated that both IA and IK were increased in dnc alleles. Normal muscle fibers treated with dibutyryl-cAMP showed a similar increase of IA, but no significant effect on IK. In contrast to the dnc alleles, the rut mutations appeared to enhance ICS greatly while leaving the amplitude of other currents largely unchanged. In addition, the dibutyryl-cAMP-induced increase in IA was not observed in rut fibers. Caffeine and W7, which are known to interfere with several second messenger pathways, also modulated K+ currents in larval muscle fibers. The currents in dnc and rut fibers showed strikingly altered responses to caffeine and W7. The results demonstrate that the various K+ currents in Drosophila muscles are affected by altered cAMP cascades in the mutants. The fact that not all dnc and rut mutant defects can be mimicked or reversed by acute application of cAMP suggests that long-term modulation of K+ currents by cAMP may involve mechanisms distinct from the short-term effect of cAMP.

Development and maintenance of a simple reflex circuit in small-patch mosaics of Drosophila: effects of altered neuronal function and developmental arrest

A combined genetic, anatomical, and behavioral approach has been undertaken to study the developmental and functional plasticity of identified bristle mechanosensory neurons in Drosophila. A stereotyped grooming reflex in decapitated flies enabled simple but reliable assessments of the functional output of individual bristle sensory cells to correlate with their axonal projections and terminal arbors revealed by the cobalt backfill technique. Construction of small-patch mosaics that contain only a single mutant bristle allowed functional perturbation of individual neurons within an otherwise normal environment. Mutations that affect nerve excitability and membrane recycling have been used to examine their effects on neuronal pathfinding, arborization, and the initiation and maintenance of functional connections. Previous studies (Burg and Wu, 1986, J. Neurosci. 6:2968-2976; 1989, Dev. Biol. 131:505-514) have demonstrated that para(ts)nap(ts) double-mutant sensory neurons, in which action potentials are unconditionally blocked by defects in sodium currents, and eag Sh double-mutant sensory cells, in which membrane excitability is increased by alterations in potassium currents, can establish and maintain central projections that are indistinguishable from their functionally normal counterparts. Mutations of the shi(ts) gene cause a temperature-sensitive, reversible block of the membrane recycling process, resulting in arrest of neuronal growth in culture (Kim and Wu, 1987, J. Neurosci. 7:3245-3255) and depletion of synaptic vesicles that leads to transmission blockade at established synapses (Ikeda, Ozawa, and Hagiwara, 1976, Nature 259:489-491; Koenig and Ikeda, 1983, J. Neurobiol. 14:411-419; 1989, J. Neurosci. 9:3844-3860). Prolonged heat treatments (up to 16% of total development time) of small-patch shi(ts) mosaics at different pupal stages did not prevent the establishment of central projections characteristic of the various sensory cell types. However, none of the shi(ts) sensory neurons heat-pulsed during the initial or the final 16% of pupal development were able to initiate the reflex behavior, although a proportion of those treated in other periods apparently established functional contacts with appropriate targets to support the characteristic cleaning reflex. The possibility exists that the membrane recycling process blocked in shi(ts) cells provides a crucial mechanism for cell-cell interactions taking place during initial differentiation and final synaptic stabilization, and possibly competition, in the developing sensory neuron. Heat treatments of adult shi(ts) mosaics blocked the reflex initiated by the mutant (but not the surrounding normal) bristles, as expected from the effect of synaptic block.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiovascular autonomic dysfunction in non-insulin-dependent diabetes mellitus and its relation to renal dysfunction

To investigate the relationship between cardiovascular autonomic neuropathy and nephropathy in patients with non-insulin-dependent diabetes mellitus (NIDDM), 45 patients underwent noninvasive cardiovascular reflex tests, including the Valsalva ratio, the 30:15 ratio and postural changes in systolic blood pressure (delta SBP), along with measurement of creatinine clearance (CCr) and daily protein excretion (DPE). Clinical symptoms in 30 patients were also noted and correlated with the results of the autonomic function tests. Thirty-four normal subjects underwent the same cardiovascular reflex tests and served as controls. The results showed that NIDDM patients had a significantly lower 30:15 ratio than normal subjects. However, no significant difference in either the Valsalva ratio or delta SBP was found between diabetic patients and controls. A positive correlation between the 30:15 ratio and CCr, but not DPE, was noted in diabetics. Although abnormal cardiovascular reflex tests appeared in patients who had no autonomic symptoms, abnormal test results were not parallel with the severity of symptoms. These results show that NIDDM patients have poorer cardiovascular autonomic function which may precede the appearance of autonomic symptoms. The 30:15 ratio was weakly correlated with CCr and this suggests that the incidence of cardiovascular dysfunction increases as the renal functional reserve decreases.

Removal of nitrogen and phosphorus from swine wastewater by intermittent aeration processes

Nitrogen and phosphorus removal in a methane fermentation plus activated sludge method type pig farm (M-III) with an intermittent aeration process (IAP) was evaluated in comparison with a continuous aeration process (CAP) based on the full-scale and bench-scale experiments. Operation conditions for the treatment system were the same except for the aeration program (in the CAP), a consecutive 24-hr aeration was used, whereas in the IAP, the aeration and non-aeration periods were alternated at intervals of 3:1 hr. BOD and TOC removal efficiencies with the intermittent aeration were as high as those with the continuous operation (92-98%). In the removal of nitrogen and phosphorus, large differences between IAP and CAP were observed. At an influent T-N/TOC ratio of 0.1, removal efficiencies for T-N in the bench-scale IAP was 70%, and for T-P was 22%, respectively. At an even higher influent T-N/TOC ratios of 0.3-1.0, the removal efficiencies for T-N were decreased to about 59-61%, whereas that for T-P were -0.3-13%. In a full-scale plant, removal efficiencies for T-N with IAP and CAP were 42% and -0.09%, respectively. The results of this study show the successful performance of a simple IAP for piggery wastewater: simultaneous, one-sludge denitrification with nitrification in single-activated sludge reactor in a pig farm.

Ionic channels in cultured Drosophila neurons

Cultured "giant" Drosophila neurons derived from cytokinesis-arrested embryonic neuroblasts express various membrane channels and excitability patterns. Both current- and voltage-clamp recordings could be performed on the same neuron owing to the large cell size, thus making it possible to elucidate the functional role of individual types of channels. This culture system has been used to analyze the mutational perturbations in ion channels and the resultant alterations in membrane excitability.

Interactions of membrane excitability mutations affecting potassium and sodium currents in the flight and giant fiber escape systems of Drosophila

We have studied the influence of the K(+)-current mutations eag and Sh and the Na(+)-current mutation napts upon two well-defined neural circuits that underlie flight and an escape response in Drosophila, recording from dorsal longitudinal and tergotrochanteral muscles. Mutations of Sh and eag affected refractory period and following frequency, but not latency, of the jump-and-flight escape response. The napts mutation altered these 3 physiological parameters of the "jump" (TTM), but not the "flight" (DLM), branch, suggesting differences in the vulnerability of different circuit components to the mutation. In contrast to their interaction in some other systems, napts did not counteract the effects of eag and Sh upon these physiological parameters in eag Sh; nap triple mutants. In eag Sh double mutants, in which multiple K+ currents may be diminished, flight muscles showed abnormal rhythmic activity not associated with flight, and some flies also had an abnormal wings-down posture. The low-frequency spikes probably originated in the flight muscle motoneurons, but the coordination between muscle fibers during this "non-flight activity" was distinct from flight. Nevertheless, in spite of the presence of this non-flight activity in resting eag Sh flies, those animals with normal wing posture were also able to fly, with a normal pattern of muscle activity. This suggests that in these mutants, the DLM motoneuron circuit is able to switch between two patterns of output, non-flight activity and flight.(ABSTRACT TRUNCATED AT 250 WORDS)

Synaptic plasticity in Drosophila memory and hyperexcitable mutants: role of cAMP cascade

Activity-dependent synaptic plasticity has been implicated in the refinement and modification of neural circuits during development and learning. Previous studies show that activity-induced facilitation and potentiation are disrupted at larval neuromuscular junctions in the memory mutants dunce (dnc) and rutabaga (rut) of Drosophila. The diminished learning-memory capacity and synaptic transmission plasticity have been associated with altered cAMP levels since dnc affects the cAMP-specific phosphodiesterase and rut affects adenylate cyclase. In this study, the morphology of larval motor axon terminals was examined by anti-HRP immunohistochemistry. It was found that the numbers of terminal varicosities and branches were increased in dnc mutants, which have elevated cAMP concentrations. Such increase was suppressed in dnc rut double mutants by rut mutations, which reduce cAMP synthesis. More profuse projections of larval motor axons have also been reported in double-mutant combinations of ether à go-go (eag) and Shaker (Sh) alleles, which display greatly enhanced nerve activity as a result of reduction in different K+ currents. Therefore, we examined combinations of dnc and rut with eag and Sh mutations to explore the possible relation between activity- and cAMP-induced morphological changes. We found that the expanded projections in dnc were further enhanced in double mutants of dnc with either eag or Sh, an effect that could again be suppressed by rut. The results provide evidence for altered plasticity of synaptic morphology in memory mutants dnc and rut and suggest a role of cAMP cascade in mediating activity-dependent synaptic plasticity.

Clinical features and comprehensive treatment of late stage radiation skin injuries

105 patients with late stage radiation skin injury were treated from 1970 to 1986, using drugs combined with surgical intervention according to the clinical features of the injury. Drug therapy consisted of topical application of urea, antibiotics, trypsin and elastase, and systematic use of alpha 2-Macroglobulin. Of 62 patients receiving medication, 55 (88.7%) were completely or basically treated and 7 failed. Of 51 lesions of 43 patients receiving surgical treatment, 47 healed by first intention. In 4 patients, necrosis of partial and/or peripheral skin flaps healed after renewed repair.