The fermentation of whole wheat flour by Pediococcus pentosaceus / Fermentación de harina de trigo integral con Pediococcus pentosaceus

A whole wheat flour:water brew (1:3) was fermented (at 32 °C) with a Pediococcus pentosaceus culture at inoculation levels ( I) of log10 I = 0 (control), 5, 6, 7 and 8 cfu/g brew. A direct relationship was observed between the inoculation level and the absolute values of the b and c parameters of the fitted fermentation equation: pH = a + bt + ct2. The first derivative of the fermentation equation was used to determine the duration of the lag phase period. When the inoculation level was increased from log 10 I = 0 to log10 I = 8 cfu/g brew the lag phase period ( Lp) and the fermentation time ( t) decreased from 5.2 to 0.8 h and from 18.0 to 4.2 h, respectively. The model lag phase period and the model fermentation time at inoculation levels other than those examined in this study were calculated using the equa tions LpM= 5.2 + 0.0245 I - 0.0714 I2 and tM5.0 = 18 - 1.15 I- 0.075 I2, respectively. The acid production phase comprised 68% of the fermentation period. The fermentation rate ( F) within each of the three periods of the fermentation increased as the inoculation level increased. The acid production rate- inoculation plot showed a discontinuity at an inoculation level of log10 I = 7.0 cfu/g brew.

Walking deficits and centrophobism in an α-synuclein fly model of Parkinson's disease

Parkinson's disease (PD) is a movement neurodegenerative disorder, characterized by bradykinesia, rigidity and tremor, constituting difficulties in walking and abnormal gait. Previous research shows that Drosophila expressing human α-synuclein A30P (A30P) develop deficits in geotaxis climbing; however, geotaxis climbing is a different movement modality from walking. Whether A30P flies would exhibit abnormal walking in a horizontal plane, a measure more relevant to PD, is not known. In this study, we characterized A30P fly walking using a high-speed camera and an automatic behavior tracking system. We found that old but not young A30P flies exhibited walking abnormalities, specifically decreased total moving distance, distance per movement, velocity, angular velocity and others, compared with old control flies. Those features match the definition of bradykinesia. Multivariate analysis further suggested a synergistic effect of aging and A30P, resulting in a distinct pattern of walking deficits, as seen in aged A30P flies. Psychiatric problems are common in PD patients with anxiety affecting 40–69% of patients. Central avoidance is one assessment of anxiety in various animal models. We found old but not young A30P flies exhibited increased centrophobism, suggesting possible elevated anxiety. Here, we report the first quantitative measures of walking qualities in a PD fly model and propose an alternative behavior paradigm for evaluating motor functions apart from climbing assay.

Effects of mutant Drosophila K+ channel subunits on habituation of the olfactory jump response

The olfactory-jump response assay was used to analyze habituation in Drosophila mutants of potassium (K(+)) channel subunits. As with physiological assays of the giant fiber-mediated escape reflex, mutations at loci that encode K(+) channel subunits have distinct effects on habituating the olfactory-jump response. The data for slowpoke and ether à go-go indicate similar effects on habituation of the olfactory-jump response and the giant fiber-mediated escape. Habituation in the olfactory jump assay in Hyperkinetic and Shaker mutants was drastically different from the degree of defect in the giant fiber-mediated escape reflex, indicating differential control mechanisms underlying the two forms of non-associative conditioning.

The Drosophila nitric-oxide synthase gene (dNOS) encodes a family of proteins that can modulate NOS activity by acting as dominant negative regulators

Nitric oxide (NO) is involved in organ development, synaptogenesis, and response to hypoxia in Drosophila. We cloned and analyzed the only gene in the fly genome that encodes Drosophila nitric-oxide synthase (dNOS). It consists of 19 exons and is dispersed over 34 kilobases of genomic DNA. Alternative transcription start sites and alternative splice sites are used to generate a remarkable variety of mRNAs from the dNOS gene. We identified eight new transcripts that are widely expressed throughout Drosophila development and encode a family of DNOS-related proteins. Alternative splicing affects both the 5'-untranslated region and the coding region of the dNOS primary transcript. Most of the splicing alterations in the coding region of the gene lead to premature termination of the open reading frame. As a result, none of the alternative transcripts encode an enzymatically active protein. However, some of these shorter DNOS protein products can effectively inhibit enzymatic activity of the full-length DNOS1 protein when co-expressed in mammalian cells, thus acting as dominant negative regulators of NO synthesis. Using immunoprecipitation, we demonstrate that these short DNOS protein isoforms can form heterodimers with DNOS1, pointing to a physical basis for the dominant negative effect. Our results suggest a novel regulatory function for the family of proteins encoded by the Drosophila NOS gene.

Preparation and achievement of American College of Surgeons level I trauma verification raises hospital performance and improves patient outcome

OBJECTIVE

The purpose of this study was to assess the impact on patient outcome and hospital performance of preparing for and achieving American College of Surgeons (ACS) Level I trauma verification.

METHODS

The center was a previously designated state regional trauma center located adjacent to a major metropolitan area. Preparation for ACS verification began in early 1996 and was completed in early 1998. Final verification took place in April 1999. Data were analyzed before (1994) and after (1998) the process. There was a marked increase in administrative support with trauma named one of the hospital's six centers of excellence. Two full-time board-certified trauma/critical care surgeons were added to the current six trauma surgeons. Their major focus was trauma care. Trauma support staff was also increased with case managers, a trauma nurse practitioner, additional trauma registrars, and administrative support staff. Education and continuous quality improvement were markedly expanded starting in 1996.

RESULTS

There were 1,098 trauma patients admitted in 1994, and 1,658 in 1998. Overall mortality decreased (1994, 7.38%; 1998, 5.37%; p < 0.05). There was a marked decrease in mortality for severely injured (Injury Severity Score > 30) patients (1994, 44% mortality [38 of 86]; 1998, 27% [22 of 80]; p < 0.04). Average length of stay also decreased (1994, 12.22 days; 1998, 9.87 days; p < 0.02). This yielded an estimated cost savings for 1998 of greater than $4,000 per patient (total saving estimate of $7.4 million).

CONCLUSION

Trauma system improvement as related to achieving ACS Level I verification appeared to have a positive impact on survival and patient care. There were cost savings realized that helped alleviate the added expense of this system improvement. The process of achieving ACS Level I verification is worthwhile and can be cost effective.

Disruption of neurotransmission in Drosophila mushroom body blocks retrieval but not acquisition of memory

Surgical, pharmacological and genetic lesion studies have revealed distinct anatomical sites involved with different forms of learning. Studies of patients with localized brain damage and work in rodent model systems, for example, have shown that the hippocampal formation participates in acquisition of declarative tasks but is not the site of their long-term storage. Such lesions are usually irreversible, however, which has limited their use for dissecting the temporal processes of acquisition, storage and retrieval of memories. Studies in bees and flies have similarly revealed a distinct anatomical region of the insect brain, the mushroom body, that is involved specifically in olfactory associative learning. We have used a temperature-sensitive dynamin transgene, which disrupts synaptic transmission reversibly and on the time-scale of minutes, to investigate the temporal requirements for ongoing neural activity during memory formation. Here we show that synaptic transmission from mushroom body neurons is required during memory retrieval but not during acquisition or storage. We propose that the hebbian processes underlying olfactory associative learning reside in mushroom body dendrites or upstream of the mushroom body and that the resulting alterations in synaptic strength modulate mushroom body output during memory retrieval.

Functional anatomy: from molecule to memory

The Drosophila memory gene amnesiac is expressed in neurons that project to mushroom body axons. Blockade of synaptic transmission in the amnesiac-expressing cells disrupts memory, but not learning, suggesting presynaptic and postsynaptic sites for memory formation.

Biocatalytic preparation of a chiral synthon for a vasopeptidase inhibitor: enzymatic conversion of N(2)-

[4S-(4I,7I,10aJ)]1-Octahydro-5-oxo-4-[phenylmethoxy)carbonyl]amino]-7H-pyrido-[2,1-b] [1,3]thiazepine-7-carboxylic acid methyl ester (BMS-199541-01) is a key chiral intermediate for the synthesis of Omapatrilat (BMS-186716), a new vasopeptidease inhibitor under development. By using a selective enrichment culture technique we have isolated a strain of Sphingomonas paucimobilis SC 16113, which contains a novel L-lysine epsilon-aminotransferase. This enzyme catalyzed the oxidation of the epsilon-amino group of lysine in the dipeptide dimer N(2)-[N[phenyl-methoxy)-carbonyl] L-homocysteinyl] L-lysine)1,1-disulphide (BMS-201391-01) to produce BMS-199541-01. The aminotransferase reaction required alpha-ketoglutarate as the amino acceptor. Glutamate formed during this reaction was recycled back to alpha-ketoglutarate by glutamate oxidase from Streptomyces noursei SC 6007. Fermentation processes were developed for growth of S. paucimobilis SC 16113 and S. noursei SC 6007 for the production of L-lysine epsilon-amino transferase and glutamate oxidase, respectively. L-lysine epsilon-aminotransferase was purified to homogeneity and N-terminal and internal peptides sequences of the purified protein were determined. The mol wt of L-lysine epsilon-aminotransferase is 81 000 Da and subunit size is 40 000 Da. L-lysine epsilon-aminotransferase gene (lat gene) from S. paucimobilis SC 16113 was cloned and overexpressed in Escherichia coli. Glutamate oxidase was purified to homogeneity from S. noursei SC 6003. The mol wt of glutamate oxidase is 125 000 Da and subunit size is 60 000 Da. The glutamate oxiadase gene from S. noursei SC 6003 was cloned and expressed in Streptomyces lividans. The biotransformation process was developed for the conversion of BMS-201391-01 to BMS-199541-01 by using L-lysine epsilon-aminotransferase expressed in E. coli. In the biotransformation process, for conversion of BMS-201391-01 (CBZ protecting group) to BMS-199541-01, a reaction yield of 65-70 M% was obtained depending upon reaction conditions used in the process. Phenylacetyl or phenoxyacetyl protected analogues of BMS-201391-01 also served as substrates for L-lysine epsilon-aminotransferase giving reaction yields of 70 M% for the corresponding BMS-199541-01 analogs. Two other dipeptides N-[N[(phenylmethoxy)carbonyl]-L-methionyl]-L-lysine (BMS-203528) and N,2-[S-acetyl-N-[(phenylmethoxy)carbonyl]-L-homocysteinyl]-L-lysine (BMS-204556) were also substrates for L-lysine epsilon-aminotransferase. N-alpha-protected (CBZ or BOC)-L-lysine were also oxidized by L-lysine epsilon-aminotransferase.

nalyot, a mutation of the Drosophila myb-related Adf1 transcription factor, disrupts synapse formation and olfactory memory

nalyot (nal) is a novel olfactory memory mutant of Drosophila, encoding Adf1, a myb-related transcription factor. Following extended training sessions, Adf1 mutants show normal early memory but defective longterm memory. Adf1 shows widespread spatiotemporal expression, yet mutant alleles reveal no discernible disruptions in gross morphology of the nervous system. Studies at the larval neuromuscular junction, however, reveal a role for Adf1 in the modulation of synaptic growth-in contrast to the role established for dCREB2 in the control of synaptic function (Davis et al., 1996). These findings suggest that Adf1 and dCREB2 regulate distinct transcriptional cascades involved in terminal stages of synapse maturation. More generally, Adf1 provides a novel link between molecular mechanisms of developmental and behavioral plasticity.

Nitric oxide interacts with the retinoblastoma pathway to control eye development in Drosophila

Animal organ development requires that tissue patterning and differentiation is tightly coordinated with cell multiplication and cell cycle progression. Several variations of the cell cycle program are used by Drosophila cells at different stages during development [1] [2]. In imaginal discs of developing larvae, cell cycle progression is controlled by a modified version of the well-characterized mammalian retinoblastoma (Rb) pathway [3] [4], which integrates signals from multiple effectors ranging from growth factors and receptors to small signaling molecules. Nitric oxide (NO), a multifunctional second messenger [5], can reversibly suppress DNA synthesis and cell division [6] [7]. In developing flies, the antiproliferative action of NO is essential for regulating the balance between cell proliferation and differentiation and, ultimately, the shape and size of adult structures in the fly [8] [9] [10]. The mechanisms of the antiproliferative activity of NO in developing organisms are not known, however. We used transgenic flies expressing the Drosophila nitric oxide synthase gene (dNOS1) and/or genes encoding components of the cell cycle regulatory pathways (the Rb-like protein RBF and the E2F transcription factor complex components dE2F and dDP) combined with NOS inhibitors to address this issue. We found that manipulations of endogenous or transgenic NOS activity during imaginal disc development can enhance or suppress the effects of RBF and E2F on development of the eye. Our data suggest a role for NO in the developing imaginal eye disc via interaction with the Rb pathway.

Developmental expression of an amn(+) transgene rescues the mutant memory defect of amnesiac adults

The Drosophila memory gene amnesiac (amn) has been proposed to encode a neuropeptide protein, which includes regions homologous to vertebrate pituitary adenylyl cyclase-activating peptide (PACAP; Feany and Quinn, 1995). Definitive experiments to link this gene to memory formation, however, have not yet been accomplished (Kandel and Abel, 1995). The experiments described here demonstrate that the putative amn transcript is involved in adult memory formation. With the use of a UAS-amn(+) transgene, we show complete rescue of memory defects in amn(28A), a mutant allele caused by the insertion of a GAL4 enhancer trap transposon (Moore et al., 1998). Study of the amn(28A) reporter reveals widespread expression in the adult brain but also enriched expression in the embryonic and larval nervous systems. To begin addressing the temporal requirement of amn in memory, we asked whether the memory defects could be rescued by restricting transgenic expression to the adult stage. A heat-shock regimen shown previously to rescue fully the amn ethanol sensitivity defect (Moore et al., 1998) failed to rescue the memory defect. These results, coupled with previous genetic and anatomical studies, suggest that adult memory formation and ethanol sensitivity have different temporal and spatial requirements for amn.

latheo encodes a subunit of the origin recognition complex and disrupts neuronal proliferation and adult olfactory memory when mutant

The Drosophila latheo (lat) gene was identified in a behavioral screen for olfactory memory mutants. The original hypomorphic latP1 mutant (Boynton and Tully, 1992) shows a structural defect in adult brain. Homozygous lethal lat mutants lack imaginal discs, show little cell proliferation in the CNS of third instar larvae, and die as early pupae. latP1 was cloned, and all of the above mentioned defects of hypomorphic or homozygous lethal lat mutants were rescued with a lat+ transgene. lat encodes a novel protein with homology to a subunit of the origin recognition complex (ORC). Human and Drosophila LAT both associate with ORC2 and are related to yeast ORC3, suggesting that LAT functions in DNA replication during cell proliferation.

latheo, a Drosophila gene involved in learning, regulates functional synaptic plasticity

Mutations in the latheo (lat) gene disrupt associative learning in Drosophila , but a role for LAT in regulating neuronal function has not been demonstrated. Here, we report that LAT plays a central role in regulating Ca2(+)- and activity-dependent synaptic plasticity. Immunological localization of the LAT protein indicates it is present at synaptic connections of the larval neuromuscular junction (NMJ) and is enriched in presynaptic boutons. Basal synaptic transmission amplitude at the lat mutant NMJ is elevated 3- to 4-fold, and Ca2+ dependence of transmission is significantly reduced. Multiple forms of synaptic facilitation and posttetanic potentiation (PTP) are strongly depressed or absent at the mutant synapse. Our results suggest that LAT is a novel presynaptic protein with a role in the Ca2(+)-dependent synaptic modulation mechanisms necessary for behavioral plasticity.

Ethanol intoxication in Drosophila: Genetic and pharmacological evidence for regulation by the cAMP signaling pathway

Upon exposure to ethanol, Drosophila display behaviors that are similar to ethanol intoxication in rodents and humans. Using an inebriometer to measure ethanol-induced loss of postural control, we identified cheapdate, a mutant with enhanced sensitivity to ethanol. Genetic and molecular analyses revealed that cheapdate is an allele of the memory mutant amnesiac. amnesiac has been postulated to encode a neuropeptide that activates the cAMP pathway. Consistent with this, we find that enhanced ethanol sensitivity of cheapdate can be reversed by treatment with agents that increase cAMP levels or PKA activity. Conversely, genetic or pharmacological reduction in PKA activity results in increased sensitivity to ethanol. Taken together, our results provide functional evidence for the involvement of the cAMP signal transduction pathway in the behavioral response to intoxicating levels of ethanol.

Integrins: a role for adhesion molecules in olfactory memory

A gene required for short-term memory in Drosophila, Volado, encodes an alpha integrin and is preferentially expressed in the mushroom bodies of the adult brain. Adhesion molecules of this kind may play a role in olfactory memory by altering the strength of synaptic connections in an experience-dependent manner.

Gene discovery in Drosophila: new insights for learning and memory

Genetic approaches have been used to investigate increasingly complex biological systems. Here we review the current state of genetic analysis of learning and memory in the fruitfly, Drosophila melanogaster. Emerging findings support two main themes. First, discovery and manipulation of genes involved with behavioral plasticity in genetically accessible systems such as D. melanogaster enables dissection of the biochemical, cellular, anatomical, and behavioral pathways of learning and memory. Second, because core cellular mechanisms of simple forms of learning are evolutionarily conserved, biological pathways discovered in invertebrates are likely to be conserved in vertebrate systems as well.

Defective learning in mutants of the Drosophila gene for a regulatory subunit of cAMP-dependent protein kinase

Disruptions of a Drosophila gene encoding a regulatory subunit of cAMP-dependent protein kinase homologous to mammalian RIbeta (dPKA-RI) were targeted to the first (noncoding) exon of dPKA-RI via site-selected P element mutagenesis. Flies homozygous for either of two mutant alleles showed specific defects in olfactory learning but not in subsequent memory decay. In contrast, olfactory acuity and shock reactivity, component behaviors required for normal odor avoidance learning, were normal in these mutants. Northern and Western blot analyses of mRNA and protein extracted from adult heads have revealed a complex lesion of the PKA-RI locus, including expression of a novel product and over- or underexpression of wild-type products in mutants. Western blot analysis revealed reductions in RI protein in mutants. PKA activity in the absence of exogenous cAMP also was significantly higher than normal in homogenates from mutant adult heads. These two mutant alleles failed to complement each other for each of these phenotypic defects, eliminating second-site mutations as a possible explanation. These results establish a role for an RI regulatory subunit of PKA in Pavlovian olfactory conditioning.

The Drosophila mutation turnip has pleiotropic behavioral effects and does not specifically affect learning

The Drosophila mutant turnip (tur) was isolated on the basis of its poor performance in an olfactory learning task, and also has a reduction in protein kinase C (PKC) activity. PKC has been found in the nervous systems of a wide range of organisms and appears to have an important role in learning and memory-related processes. Unfortunately, previous reports documenting the learning defect of tur lacked the controls required to assess the origins of the poor performance of the mutant. We have analyzed the effects of the tur mutation on both associative and nonassociative learning as well as on PKC activity. Additionally, the effects of the mutation on the task-relevant sensorimotor abilities of the flies were assessed. Although we were able to replicate previous behavioral and biochemical results obtained with tur, we discovered that the tur mutation also affected response to electric shock and caused a drastic reduction in the locomotor ability of the flies. Because locomotion is an essential component of the learning assays, this result makes it impossible to conclude that tur specifically affects learning and demonstrates the crucial importance of sensorimotor controls in conditioning experiments.

Associative learning disrupted by impaired Gs signaling in Drosophila mushroom bodies

Disruptions in mushroom body (MB) or central complex (CC) brain structures impair Drosophila associative olfactory learning. Perturbations in adenosine 3',5' monophosphate signaling also disrupt learning. To integrate these observations, expression of a constitutively activated stimulatory heterotrimeric guanosine triphosphate-binding protein alpha subunit (Galphas*) was targeted to these brain structures. The ability to associate odors with electroshock was abolished when Galphas* was targeted to MB, but not CC, structures, whereas sensorimotor responses to these stimuli remained normal. Expression of Galphas* did not affect gross MB morphology, and wild-type Galphas expression did not affect learning. Thus, olfactory learning depends on regulated Gs signaling in Drosophila MBs.

Discovery of genes involved with learning and memory: an experimental synthesis of Hirschian and Benzerian perspectives

The biological bases of learning and memory are being revealed today with a wide array of molecular approaches, most of which entail the analysis of dysfunction produced by gene disruptions. This perspective derives both from early "genetic dissections" of learning in mutant Drosophila by Seymour Benzer and colleagues and from earlier behavior-genetic analyses of learning and in Diptera by Jerry Hirsh and coworkers. Three quantitative-genetic insights derived from these latter studies serve as guiding principles for the former. First, interacting polygenes underlie complex traits. Consequently, learning/memory defects associated with single-gene mutants can be quantified accurately only in equilibrated, heterogeneous genetic backgrounds. Second, complex behavioral responses will be composed of genetically distinct functional components. Thus, genetic dissection of complex traits into specific biobehavioral properties is likely. Finally, disruptions of genes involved with learning/memory are likely to have pleiotropic effects. As a result, task-relevant sensorimotor responses required for normal learning must be assessed carefully to interpret performance in learning/memory experiments. In addition, more specific conclusions will be obtained from reverse-genetic experiments, in which gene disruptions are restricted in time and/or space.

CREB and the formation of long-term memory

Cyclic AMP response element binding protein (CREB)-responsive transcription plays a central role in the formation of long-term memory in Drosophila, Aplysia and mice. Agents that disrupt the activity of CREB specifically block the formation of long-term memory, whereas agents that increase the amount or activity of the transcription factor accelerate the process. These results have led to the recent hypothesis that CREB is pivotal in the switch from short-term (protein synthesis independent) to long-term (protein synthesis dependent) memory.

Effects of a conditional Drosophila PKA mutant on olfactory learning and memory

The requirement for cAMP-dependent protein kinase (PKA) in associative learning of Drosophila was assessed in mutant flies hemizygous for a cold-sensitive allele, X4, of the DC0 gene, which encodes the major catalytic subunit of PKA. DC0X4 hemizygotes died as third-instar larvae at 18 degrees C, the restrictive temperature, but were viable when raised at 25 degrees C. Shifting adult DC0X4 hemizygotes from 25 degrees C to 18 degrees C led to a decrease in PKA activity from 24% to 16% of wild-type without impairing viability. At 25 degrees C, DC0X4 hemizygotes exhibited reduced initial learning relative to controls but normal memory decay in a Pavlovian olfactory learning assay. Shifting the temperature from 25 degrees C to 18 degrees C prior to training reduced initial learning to a similar extent in DC0X4 hemizygotes and controls but resulted in a steeper memory decay curve only in DC0X4 hemizygotes. These observations are suggestive of a role for PKA in medium-term memory formation in addition to its previously established role in initial learning.

Molecular cloning of linotte in Drosophila: a novel gene that functions in adults during associative learning

The linotte (lio) gene was identified in a screen for mutations that disrupted 3 hr memory after olfactory associative learning, without affecting the perception of odors or electroshock. The mutagenesis yielded a transposon-tagged gene disruption, which allowed rapid cloning of genomic DNA. The lio transcription unit was identified via rescue of the lio1 learning/memory defect by induced expression of a lio+ transgene in adults. The perception of odors or electroshock remained normal when the lio+ transgene was expressed in these lio1 flies. Learning/memory remained normal when the lio+ transgene was expressed in wild-type (lio+) flies. The lio gene produces only one transcript, the level of expression of which varies throughout development. Sequence analysis indicates that lio encodes a novel protein.

Molecular and biochemical characterization of dNOS: a Drosophila Ca2+/calmodulin-dependent nitric oxide synthase

Nitric oxide (NO) is an intercellular messenger involved with various aspects of mammalian physiology ranging from vasodilation and macrophage cytotoxicity to neuronal transmission. NO is synthesized from L-arginine by NO synthase (NOS). Here, we report the cloning of a Drosophila NOS gene, dNOS, located at cytological position 32B. The dNOS cDNA encodes a protein of 152 kDa, with 43% amino acid sequence identity to rat neuronal NOS. Like mammalian NOSs, DNOS protein contains putative binding sites for calmodulin, FMN, FAD, and NADPH. DNOS activity is Ca2+/calmodulin dependent when expressed in cell culture. An alternative RNA splicing pattern also exists for dNOS, which is identical to that for vertebrate neuronal NOS. These structural and functional observations demonstrate remarkable conservation of NOS between vertebrates and invertebrates.

A Drosophila CREB/CREM homolog encodes multiple isoforms, including a cyclic AMP-dependent protein kinase-responsive transcriptional activator and antagonist

We have characterized a Drosophila gene that is a highly conserved homolog of the mammalian cyclic AMP (cAMP)-responsive transcription factors CREB and CREM. Uniquely among Drosophila genes characterized to date, it codes for a cAMP-responsive transcriptional activator. An alternatively spliced product of the same gene is a specific antagonist of cAMP-inducible transcription. Analysis of the splicing pattern of the gene suggests that the gene may be the predecessor of the mammalian CREB and CREM genes.

Dissection of memory formation: from behavioral pharmacology to molecular genetics

Behavioral pharmacology has suggested an intricate, multiphasic pathway of memory consolidation. An integrated molecular pharmacological approach in Drosophila has lent support to this theory recently by dissecting consolidated memory into two genetically distinct components: a cycloheximide-insensitive, anesthesia-resistant memory and a cycloheximide-sensitive long-term memory. In addition, experiments using inducible dominant-negative transgenes in Drosophila or gene knockouts in mice demonstrate a role for cAMP-responsive transcription factors in formation of long-term memory. These studies support the application of reverse-genetic strategies, including the use of temporally specific agonists and antagonists, to advance the functional dissection of memory formation.

CREB as a memory modulator: induced expression of a dCREB2 activator isoform enhances long-term memory in Drosophila

Genetic studies of memory formation in Drosophila have revealed that the formation of a protein synthesis-dependent long-term memory (LTM) requires multiple training sessions. LTM is blocked specifically by induced expression of a repressor isoform of the cAMP-responsive element-binding protein (CREB). Here, we report an enhancement of LTM formation after induced expression of an activator isoform of dCREB2. Maximum LTM is achieved after one training session, and its formation depends on phosphorylation of the activator transgene. A model of LTM formation based on differential regulation of CREB isoforms is proposed.

Genetic dissection of consolidated memory in Drosophila

Behavioral and pharmacological experiments in many animal species have suggested that memory is consolidated from an initial, disruptable form into a long-lasting, stable form within a few hours after training. We combined these traditional approaches with genetic analyses in Drosophila to show that consolidated memory of conditioned (learned) odor avoidance 1 day after extended training consisted of two genetically distinct, functionally independent memory components: anesthesia-resistant memory (ARM) and long-term memory (LTM). ARM decayed away within 4 days, was resistant to hypothermic disruption, was insensitive to the protein synthesis inhibitor cycloheximide (CXM), and was disrupted by the radish single-gene mutation. LTM showed no appreciable decay over 7 days, was sensitive to CXM, and was not disrupted by the radish mutation.

Induction of a dominant negative CREB transgene specifically blocks long-term memory in Drosophila

Consolidated memory after olfactory learning in Drosophila consists of two components, a cycloheximide-sensitive, long-term memory (LTM) and a cycloheximide-insensitive, anesthesia-resistant memory (ARM). Using an inducible transgene that expresses a dominant negative member of the fly CREB family, LTM was specifically and completely blocked only after induction, while ARM and learning were unaffected. These results suggest that LTM formation requires de novo gene expression probably mediated by CREB family genes.

Memory through metamorphosis in normal and mutant Drosophila

To establish that a stable, long-lasting form of memory exists in Drosophila, we trained third-instar larvae by electroshocking them in the presence of a specific odor using a Pavlovian conditioning procedure. We show that conditioned odor avoidance produced in larvae still was present in adults 8 d later. Such memory through metamorphosis was specific to the temporal pairing of odor and shock; presentations of odors alone or shock alone did not produce a change. Thus, the memory involved associative processes. We also show that similar training of the single-gene memory mutants dunce and amnesiac did not yield any detectable learning in larvae or memory retention in adults, suggesting that these mutations interfere with long-term memory (LTM) formation even if LTM is induced independently of earlier memory retention processes.

Differential effects of dunce mutations on associative learning and memory in Drosophila

Initial learning, 30- and 180-min memory retention after Pavlovian conditioning of an odor avoidance response was quantified in dnc1, dnc2, dncM11 and Canton-S (wild-type) homozygotes and in dnc1/FM7, dnc2/FM7, dncM11/FM7, dncM11/Can-S, Can-S/FM7, dnc1/dncM11 and dnc2/dncM11 heterozygotes. Our results consistently showed that a) the dunce mutations are semi-dominant for initial learning and b) genetic variants carrying the enzymatically hypomorphic dnc2 mutation produce learning scores lower than those of the amorphic dncM11. Analysis of this particular set of retention intervals, using a modified statistical model designed to evaluate decay rates, revealed no discernable effects of the dunce mutations on memory formation 30 to 180 min after training. These results are consistent with a model of memory formation, in which dunce is hypothesized to disrupt acquisition and/or short-term memory.

Identification of linotte, a new gene affecting learning and memory in Drosophila melanogaster

We describe the identification of linotte, a new autosomal gene in Drosophila involved with learning and memory. The linotte mutant was derived from a PlacW transposon mutagenesis and was screened for three-hour memory deficits after classical conditioning of an olfactory avoidance response. Sensory and motor systems (olfactory acuity and shock reactivity) required for the classical conditioning experiments were normal in mutant linotte flies--indicating that the mutation disrupts learning/memory specifically. A chromosomal deficiency of the 37D region, where the linotte P insert was localized in situ, failed to complement linotte's memory defect, and flies from two lines homozygous for independent PlacW excisions show normal memory--indicating that the P insertion is responsible for the mutant phenotype. Additional behavior-genetic data suggest that linotte gene is non-vital.

Human amyloid precursor protein ameliorates behavioral deficit of flies deleted for Appl gene

Drosophila amyloid precursor protein-like (Appl) gene encodes a protein product (APPL) similar to beta-amyloid precursor protein (APP) associated with Alzheimer's disease. To understand the in vivo function of APPL protein, we have generated flies deleted for the Appl gene. These flies are viable, fertile, and morphologically normal, yet they exhibit subtle behavioral deficits. We show that a fast phototaxis defect in Appl- flies is partially rescued by transgenes expressing the wild-type, but not a mutant, APPL protein. We further demonstrate a functional homology between APPL and APP, since transgenes expressing human APP show a similar level of rescue as transgenes expressing fly APPL.

latheo, a new gene involved in associative learning and memory in Drosophila melanogaster, identified from P element mutagenesis

Genetic dissection of learning and memory in Drosophila has been limited by the existence of ethyl methanesulfonate (EMS)-induced mutations in only a small number of X-linked genes. To remedy this shortcoming, we have begun a P element mutagenesis to screen for autosomal mutations that disrupt associative learning and/or memory. The generation of "P-tagged" mutant alleles will expedite molecular cloning of these new genes. Here, we describe a behavior-genetic characterization of latheoP1, a recessive, hypomorphic mutation of an essential gene. latheoP1 flies perform poorly in olfactory avoidance conditioning experiments. This performance deficit could not be attributed to abnormal olfactory acuity or shock reactivity-two task-relevant "peripheral" behaviors which are used during classical conditioning. Thus, the latheoP1 mutation appears to affect learning/memory specifically. Consistent with chromosomal in situ localization of the P element insertion, deficiencies of the 49F region of the second chromosome failed to complement the behavioral effect of the latheoP1 mutation. Further complementation analyses between latheoP1 and lethal alleles, produced by excision of the latheoP1 insert or by EMS or gamma-rays, in the 49F region mapped the latheo mutation to one vital complementation group. Flies heterozygous for latheoP1 and one of two EMS lethal alleles or one lethal excision allele also show the behavioral deficits, thereby demonstrating that the behavioral and lethal phenotypes co-map to the same locus.

Reassessment of the effect of biological rhythm mutations on learning in Drosophila melanogaster

A link between learning deficits and circadian period-lengthening mutations in Drosophila melanogaster previously has been reported. Mutant long-period males performed poorly in two learning assays involving experience-dependent courtship inhibition. In one, normal males that have courted fertilized females subsequently show courtship inhibition with virgin females. In the other, normal males that have courted sexually immature males subsequently fail to court other immature males. Those results have been reassessed in an extended study of genetic variants involving the period gene. 1. Long-period perL1 males demonstrated poor conditioned courtship inhibition when exposed to fertilized females; they showed normal courtship conditioning when exposed to immature males. This could be due to a perL1-associated olfactory deficit with fertilized females, since perL1 males were unable to discriminate behaviorally between fertilized and virgin females. 2. Other long-period males, including perL2 males and transgenic perL1 males bearing a truncated form of the per+ gene, were conditioned normally by fertilized females. Thus, the courtship inhibition defect is specific to the perL1 mutant strain. 3. perL1 (and other per mutant) flies showed normal acquisition and retention of a classically conditioned olfactory avoidance response. 4. Results from a new conditioned courtship inhibition experiment are presented; males exposed to fertilized females during training showed further courtship inhibition during subsequent exposure to fertilized females. From the perspective of learning theory, this can be viewed as a savings experiment.

Regulation of tyrosine hydroxylase-containing amacrine cell number in larval frog retina

To determine whether production of new neurons of a particular type is regulated by the presence of previously differentiated neurons of the same type, we ablated all tyrosine hydroxylase immunoreactive (THIR) cells from larval frog retina with the neurotoxin 6-hydroxydopamine, and examined the retinas in subsequent weeks for newly generated THIR neurons. Three weeks after neurotoxin administration, new THIR cells appeared near the zone of neural proliferation at the ciliary margin at a higher density than that of normal retina, while the densities of other amacrine cell types, serotonin (t-HT) immunoreactive and substance P immunoreactive (SPIR), remained the same as controls. Thus the production of new retinal TRIR cells is selectively up-regulated following ablation of previously differentiated cells of this type.