Scaling law for excitons in 2D perovskite quantum wells

Ruddlesden–Popper halide perovskites are 2D solution-processed quantum wells with a general formula A₂A’_n-1M_nX_3n+1, where optoelectronic properties can be tuned by varying the perovskite layer thickness (n-value), and have recently emerged as efficient semiconductors with technologically relevant stability. However, fundamental questions concerning the nature of optical resonances (excitons or free carriers) and the exciton reduced mass, and their scaling with quantum well thickness, which are critical for designing efficient optoelectronic devices, remain unresolved. Here, using optical spectroscopy and 60-Tesla magneto-absorption supported by modeling, we unambiguously demonstrate that the optical resonances arise from tightly bound excitons with both exciton reduced masses and binding energies decreasing, respectively, from 0.221 m₀ to 0.186 m₀ and from 470 meV to 125 meV with increasing thickness from n equals 1 to 5. Based on this study we propose a general scaling law to determine the binding energy of excitons in perovskite quantum wells of any layer thickness.

Hybrid 2D layered perovskites are solution-processed quantum wells whose optoelectronic properties are tunable by varying the thickness of the inorganic slab. Here Blancon et al. work out a general behavior for dependence of the excitonic properties in layered 2D perovskites.

Specific sequence homology and three-dimensional structure of an aminoacyl transfer RNA synthetase

Few and limited amino acid sequence homologies have been found among eight bacterial aminoacyl transfer RNA (tRNA) synthetases whose primary structures are known. The entire 939-amino acid primary structure of Escherichia coli isoleucyl-tRNA synthetase is now reported. In a sequence of 11 consecutive amino acids matching a sequence in E. coli methionyl-tRNA synthetase, there are ten identical residues and one conservative change. This is the strongest homology recorded between any two aminoacyl tRNA synthetases. This part of the methionine enzyme's three-dimensional structure has been determined, and it occurs in a mononucleotide binding fold; a close three-dimensional structural homology of this part of the enzyme with Bacillus stearothermophilus tyrosyl-tRNA synthetase has also been reported. The three synthetases probably fold identically in this region.

The epidemiology of neuroendocrine tumors in Taiwan: a nation-wide cancer registry-based study

Background

The epidemiology of neuroendocrine tumors (NETs) is not well illustrated, particularly for Asian countries.

Methods

The age-standardized incidence rates and observed survival rates of NETs diagnosed in Taiwan from January 1, 1996 to December 31, 2008 were calculated using data of the Taiwan Cancer Registry (TCR) and compared to those of the Norwegian Registry of Cancer (NRC) and the US Surveillance, Epidemiology, and End Results (SEER) program.

Results

During the study period, a total of 2,187 NET cases were diagnosed in Taiwan, with 62% males and a mean age of 57.9 years-old. The age-standardized incidence rate of NETs increased from 0.30 per 100,000 in 1996 to 1.51 per 100,000 in 2008. The most common primary sites were rectum (25.4%), lung and bronchus (20%) and stomach (7.4%). The 5-year observed survival was 50.4% for all NETs (43.4% for men and 61.8% for women, P<0.0001). The best 5-year observed survivals for NETs by sites were rectum (80.9%), appendix (75.7%), and breast (64.8%).

Conclusions

Compared to the data of Norway and the US, the age-standardized incidence rate of NETs in Taiwan is lower and the major primary sites are different, whereas the long-term outcome is similar. More studies on the pathogenesis of NETs are warranted to devise preventive strategies and improve treatment outcomes for NETs.

The mouse slalom mutant demonstrates a role for Jagged1 in neuroepithelial patterning in the organ of Corti

The Notch signalling pathway has recently been implicated in the development and patterning of the sensory epithelium in the cochlea, the organ of Corti. As part of an ongoing large-scale mutagenesis programme to identify new deaf or vestibular mouse mutants, we have identified a novel mouse mutant, slalom, which shows abnormalities in the patterning of hair cells in the organ of Corti and missing ampullae, structures that house the sensory epithelia of the semicircular canals. We show that the slalom mutant carries a mutation in the Jagged1 gene, implicating a new ligand in the signalling processes that pattern the inner ear neuro-epithelium.

Human salivary histatins: promising anti-fungal therapeutic agents

Histatins constitute a group of small, cationic multifunctional proteins present in the saliva of human and some non-human primates. The most significant function of histatins may be their anti-fungal activity against Candida albicans and Cryptococcus neoformans. Histatins have been extensively studied at both the protein and gene levels. The structure-function relationship of histatins with respect to their candidacidal activity has also been studied by means of recombinant histatin variants, as well as by chemically synthesized histatin fragments. The mechanism of histatins' action on Candida albicans is not clear, but it appears to be different from that of azole-based anti-fungal drugs which interrupt ergosterol synthesis. During the past 20 years, fungal infections have become more prevalent as a result of the emergence of AIDS, as well as, paradoxically, modern medical advances. The toxicity of current anti-fungal medicine, the emergence of drug-resistant strains, and the availability of only a few types of anti-fungal agents are the major disadvantages of current anti-fungal therapy. Therefore, the importance of the search for new, broad-spectrum anti-fungals with little or no toxicity cannot be overemphasized. The following properties make histatins promising anti-fungal therapeutic agents: (1) They have little or no toxicity; (2) they possess high cidal activities against azole-resistant fungal species and most of the fungal species tested; and (3) their candidacidal activity is similar to that of azole-based antifungals. Current research efforts focus on the development of improved histatins with enhanced cidal activity and stability, and of suitable and effective histatin delivery systems. These and other approaches may help to outpace the growing list of drug-resistant and opportunistic fungi causing life-threatening, disseminating diseases. The histatins with improved protective properties may also be used as components of artificial saliva for patients with salivary dysfunction.

Age-related maculopathy: an expanded genome-wide scan with evidence of susceptibility loci within the 1q31 and 17q25 regions

PURPOSE

We seek to identify genetic loci that contribute to age-related maculopathy susceptibility.

METHODS

Families consisting of at least two siblings affected by age-related maculopathy were ascertained using eye care records and fundus photographs. Additional family members were used to increase the power to detect linkage. Microsatellite genotyping was conducted by the National Heart, Lung and Blood Institute Mammalian Genotyping Service and the National Institutes of Health Center for Inherited Disease Research. Linkage analyses were conducted with parametric (autosomal dominant; heterogeneity lod score) and nonparametric methods (S(all) statistic) using three diagnostic models. False-positive rates were determined from simulations using actual pedigrees and genotyping data.

RESULTS

Under our least stringent diagnostic model, model C, 860 affected individuals from 391 families (452 sib pairs) were genotyped. Sixty-five percent of the affected individuals had evidence of exudative disease. Four regions, 1q31, 9p13, 10q26, and 17q25, showed multipoint heterogeneity lod scores or S(all) scores of 2.0 or greater (under at least one model). Under our most stringent diagnostic model, model A, the 1q31 heterogeneity lod score was 2.46 between D1S1660 and D1S1647. Under model C, the 17q25 heterogeneity lod score at D17S928 was 3.16. Using a threshold of 1.5, additional loci on chromosomes 2 and 12 were identified.

CONCLUSIONS

The locus on chromosome 1q31 independently confirms a report by Klein and associates mapping an age-related maculopathy susceptibility gene to this region. Simulations indicate that the 1q31 and 17q25 loci are unlikely to be false positives. There was no evidence that other known macular or retinal dystrophy candidate gene regions are major contributors to the genetics of age-related maculopathy.

Cloning, sequencing and expression in Escherichia coli of the D-2-hydroxyisocaproate dehydrogenase gene of Lactobacillus casei

D-2-Hydroxyisocaproic acid dehydrogenase (D-HicDH) from Lactobacillus casei was purified and partially sequenced. A 65-mer oligodeoxyribonucleotide probe corresponding to the N-terminal 23 amino acids was synthesized and a physical map was made of the genomic region which hybridized most strongly. A strongly hybridising restriction fragment was highly purified and eventually cloned at low frequency in pBR322. The original clones spontaneously produced D-HicDH at about 0.05% of total protein and showed viability problems in that 10- to 12-h growth-lag periods occurred after diluting stationary cultures into fresh medium. Subcloning into pGEM3 plasmids for sequencing with concomitant ExoIII deletion led to clones which no longer exhibited the growth inhibition characteristics but now made D-HicDH as 3 to 5% of total protein. Subcloning downstream from a double PL PR promoter in plasmid pJLA601 gave a highly inducible clone that builds large inclusion bodies of largely denatured D-HicDH. The gene transcript was mapped for L. casei and Escherichia coli hosts. The promoter, terminator and Shine-Dalgarno sequence are functional in both organisms. The gene encodes a protein subunit of 38 kDa, whereby 67% of the sequence could be checked by correlation with partial peptide sequences from the original enzyme. So far no Lactobacillus gene has been found to utilize the Arg codons AGG and AGA.

Reduced connexin 43 expression in high grade, human prostatic adenocarcinoma cells

Gap junction-mediated communication is required for normal cellular growth and differentiation. As cancer is thought to be a manifestation of the breakdown of cell-cell communication, with the concomitant loss of growth control, it would be expected that alterations in the primary structure, processing, oligomerization or trafficking of connexin (cxn) molecules would have a profound effect on the neoplastic process. Here we a present a preliminary immunohistochemical and molecular analysis of cxn 43 expression in prostatic epithelial cells from resected human tissue. Our data indicate that benign prostatic epithelial cells express cxn 43 protein, but that this expression is diminished in more advanced, anaplastic cancer cells. These data suggest that decreased connexin expression is not involved in the initiation of prostate cancer, but rather occurs during the progression of the disease.

Aspergillus fumigatus alb1 encodes naphthopyrone synthase when expressed in Aspergillus oryzae

Conidial pigment biosynthesis is an important virulence factor in Aspergillus fumigatus, a human fungal pathogen. Involvement of DHN-melanin pathway in the biosynthesis of A. fumigatus conidial pigment implies that the Alb1p polyketide synthase (PKS) is a 1,3,6, 8-tetrahydroxynaphthalene (T4HN) synthase. The Alb1p, however, shows higher sequence similarity to a naphthopyrone synthase than to a T4HN synthase. To clarify the function of Alb1p, the alb1 gene was overexpressed in a heterologous host Aspergillus oryzae. The Alb1p PKS product in this heterologous expression system was identified as heptaketide naphthopyrone instead of pentaketide T4HN. The data suggest that Alb1p is a naphthopyrone synthase.

Molecular structure, dynamic expression, and promoter analysis of zebrafish (Danio rerio) myf-5 gene

We isolated a 1,438 bp cDNA fragment that encoded Myf-5 myogenic factor of zebrafish. The deduced amino acid contained 237 residues, including the basic helix-loop-helix domain that is conserved in all known Myf-5. The zebrafish myf-5 transcripts were first detectable at 7.5 hpf, increased substantially until 16 hpf, and then declined gradually to an undetectable level by 26 hpf. During somitogenesis, zebrafish myf-5 transcripts were distributed mainly in the somites and segmental plates. Prominent signals occurred transiently in adaxial cells in two parallel rows but did not extend beyond the positive-signal somites. Various lengths of upstream region of zebrafish myf-5 fused with EGFP gene were used to carry out transgenic analysis. Results showed that a small, 82 bp (nucleotide positions from -82 to -1), regulatory cassette is sufficient to control the somite- and stage-specific expression of zebrafish myf-5 during early development.

Functional organization of mammalian hexokinases: both N- and C-terminal halves of the rat type II isozyme possess catalytic sites

Previous work has shown that catalytic function is associated exclusively with the C-terminal half of the Type I isozyme of mammalian hexokinase. In contrast, we now demonstrate that both halves of the Type II isozyme possess comparable catalytic activities. Mutation of a catalytically important Ser residue to Ala at analogous positions in either the N- or the C-terminal halves (S155A or S603A, respectively) of the rat Type II isozyme resulted in approximately 60% reduction in specific activity of the enzyme, with more than 90% reduction in the doubly mutated enzyme (S155A/S603A). Catalytic activity was retained in a chimeric hexokinase comprising the N-terminal half of Type II hexokinase and catalytically inactive (by site-directed mutation) C-terminal half of the Type I isozyme. The N- and C-terminal catalytic sites of Type II hexokinase are similar in V(max) and K(m) (approximately equal to 130 microM) for glucose; however, the N-terminal site has a lower (0.45 vs 1.1 mM) K(m) for ATP, is slightly more sensitive to inhibition by the product analog 1,5-anhydroglucitol-6-P, and is much more sensitive to inhibition by P(i). It is suggested that the Type II isozyme most closely resembles the 100-kDa hexokinase which resulted from duplication and fusion of a gene encoding an ancestral 50-kDa hexokinase and which was the precursor for the contemporary Type I, Type II, and Type III mammalian isozymes. Subsequent evolutionary changes could then have led to functional differentiation of the N- and C-terminal halves, as seen with the Type I (and possibly the Type III) isozyme.

The syntheses and biological properties of 1-N-(S-4-amino-2-hydroxybutyryl)-gentamicin B and 1-N-(S-3-amino-2-hydroxypropionyl)-gentamicin B

The syntheses of 1-N-(S-4-amino-2-hydroxybutyryl)-gentamicin B and 1-N-(S-3-amino-2-hydroxypropionyl)-gentamicin B, designated sch 20287 and Sch 21420, respectively, by procedures similar to those developed by KAWAGUCHI and co-workers for the transformation of kanamycin A to amikacin are described. The in vitro microbiological properties of Sch 20287 and Sch 21420 are compared with amikacin, gentamicin and tobramycin.

Studies of the mechanism of human salivary histatin-5 candidacidal activity with histatin-5 variants and azole-sensitive and -resistant Candida species

Histatins are a group of small, cationic, antifungal peptides present in human saliva. A previous molecular modeling analysis suggested structural similarity between the Phe14-His15 and His18-His19 dipeptide sequences in histatin-5 (Hsn-5; a 24-amino-acid polypeptide) and the sequence of miconazole (one of the azole-based antifungal therapeutic agents), implying that the mechanisms of killing of Candida albicans by these two molecules may be similar. To further elaborate on this observation, we have produced two variants of Hsn-5 in which Phe14-His15 or His18-His19 dipeptide sequences were replaced by Ala-Ala (F14A/H15A and H18A/H19A) to eliminate the phenyl and imidazole rings of the side chains and assessed their candidacidal activities against C. albicans. In addition, we tested azole-resistant C. albicans and Candida glabrata strains for their susceptibilities to Hsn-5. Analysis of the purified recombinant proteins for their candidacidal activities indicated that both variants were significantly less effective (the molar concentrations required to kill half of the maximum number of cells [ED50s], approximately 67 and approximately 149 microM for F14A/H15A and H18A/H19A, respectively) than the unaltered Hsn-5 (ED50, approximately 8 microM) at killing C. albicans, suggesting that the two dipeptide sequences are important for the candidacidal activity of Hsn-5. Assessment of the candidacidal activity of Hsn-5 with the well-characterized azole-resistant strains of C. albicans and C. glabrata, however, suggested that the mode of action of histatins against Candida is distinct from that of azole-based antifungal agents because Hsn-5 kills both azole-sensitive and azole-resistant strains equally well.

Conjugal transfer of nisin plasmid genes from Streptococcus lactis 7962 to Leuconostoc dextranicum 181

Acriflavine-generated mutants of Streptococcus lactis 7962 with various combinations of plasmid molecular masses were screened for nisin production. Nisin was produced by both the wild type and mutants that contained a 17.5-megadalton plasmid, which was obscured by chromosomal fragments. No nisin was produced by plasmid-free mutants. Sucrose fermentation and nisin production were simultaneously expressed. A transconjugant obtained from nisin-producing donor S. lactis 7962 and recipient Leuconostoc dextranicum 181 was a "supernisin" producer. The L. dextranicum Nis+ transconjugant was resistant to S. lactis 7962 phage and vancomycin (greater than 1,000 micrograms/ml), and it contained an extra 17.5-megadalton plasmid.

Efficacy of paced breathing for insomnia: enhances vagal activity and improves sleep quality

Fourteen self-reported insomniacs (SRI) and 14 good sleepers (GS) had their cardiac neuronal activity assessed by heart rate variability (HRV) under controlled respiration at a slow frequency rate of 0.1 Hz, and a forced rate of 0.2 Hz during daytime rest. Nighttime sleep was measured by polysomnography. The SRI showed depressed high frequency power of HRV compared to the GS. An increased total power of HRV was observed among the SRI during slow, paced breathing compared with spontaneous breathing and 0.2 Hz. Sleep onset latency, number of awakenings, and awakening time during sleep were decreased and sleep efficiency was increased if SRI practiced slow, paced breathing exercises for 20 min before going to sleep. Our results indicate that there is autonomic dysfunction among insomniacs, especially in relation to vagal activity; however, this decreased vagal activity can be facilitated by practicing slow, paced breathing, thereby improving sleep quality.

Manipulation of avian primordial germ cells and gonadal differentiation

The authors hypothesized that donor primordial germ cells (PGC) are useful as vehicles of gene transfer in birds. The PGC have been identified in the blastula prior to incubation. They have been isolated from the Stage 7 germinal crescents, Stage 17 blood, and Stage 30 gonads. The percentages of PGC in these three embryonic sources were 2, .003 and 1.5%, respectively. The isolated PGC have been used as antigens to produce specific antibodies that have served as major tools in identification, isolation, and forming enriched in vitro cultures of PGC. Sterile hosts for normal donor PGC have been induced by use of ultraviolet irradiation, treatment with the chemical busulfan, and crossing rooster with female quail to form a sterile host termed "quickens." Micromanipulator technology, along with refinement of techniques to avoid trauma, will allow 80% hatchability. Integration of all the above biotechnology has led to successful use of PGC as vehicles of gene transfer and production of autogenic quail.

Altered expression of circadian clock genes in human chronic myeloid leukemia

Circadian clock genes use transcriptional-translational feedback loops to control circadian rhythms. Recent studies have demonstrated that expression of some circadian clock genes displays daily oscillation in peripheral tissues including peripheral blood and bone marrow. Circadian rhythms regulate various functions of human body, and the disruption of circadian rhythm has been associated with cancer development and tumor progression. However, the direct links between aberrant circadian clock gene expression and human disorders remain largely unknown. In this study, comparisons were made between the expression profiles of 9 circadian clock genes from peripheral blood mononuclear cells (PBMCs) and polymorphonuclear cells (PMNs) from 18 healthy volunteers. Peripheral blood (PB) total leukocytes from 54 healthy volunteers and 95 patients with chronic myeloid leukemia (CML) were also investigated. Similar expression profiles of all 9 circadian clock genes were observed in PBMCs and PMNs of healthy individuals. In PB total leukocytes of healthy individuals, the daily pattern of PER1, PER2, PER3, CRY1, CRY2, and CKIε expression level peaked at 0800 h, and BMAL1 peaked at 2000 h. Daily pattern expression of these 7 genes was disrupted in newly diagnosed pre-imatinib mesylate-treated and blast crisis-phase patients with CML. Partial daily pattern gene expression recoveries were observed in patients with CML with complete cytogenetic response and major molecular response. The expression of CLOCK and TIM did not show a time-dependent variation among the healthy and patients with CML. These results indicate a possible association of the disrupted daily patterns of circadian clock gene expression with the pathogenesis of CML.

Candidacidal activity of recombinant human salivary histatin-5 and variants

Human salivary histatins possess fungicidal and bactericidal activities. The current investigation evaluates the structure-function relationship of histatins with regard to their candidacidal activity by using recombinant histatin-5 and its variants produced in Escherichia coli. The purified recombinant histatins were examined for their candidacidal activity and secondary structure. The m21 (with Lys-13 replaced by Thr [Lys-13-->Thr]) and m71 (Lys-13-->Glu) variants are significantly less effective than recombinant histatin-5 in killing Candida albicans, suggesting that Lys-13 is critical for candidacidal activity. The m68 (Lys-13-->Glu and Arg-22-->Gly) variant is significantly less potent than the recombinant histatin-5 as well as m71, indicating that Arg-22 is crucial for the cidal activity. The candidacidal activities of m1 (Arg-12-->Ile), m2 (Arg-12-->Ile and Lys-17-->Asp), m12 (Arg-12-->Lys and His-21-->Leu), and m70 (His-19-->Pro and His-21-->Arg) variants, however, are comparable to that of recombinant histatin-5, indicating that Arg-12, Lys-17, His-19, and His-21 are not functionally important. The conformational preferences of histatin-5 and variants were determined by circular dichroism. The results indicate that all proteins have a strong tendency to adopt alpha-helical conformation in trifluoroethanol. Previously, we have shown that the alpha-helical conformation is one of the important structural requirements for eliciting appreciable candidacidal activity. Collectively, the data suggest that in addition to the helical conformation, specific residues such as Lys-13 and Arg-22 in the sequence of histatin-5 are, indeed, important for candidacidal activity.

Pharmacokinetics and in vivo potency of soluble epoxide hydrolase inhibitors in cynomolgus monkeys

BACKGROUND AND PURPOSE

Soluble epoxide hydrolase inhibitors (sEHIs) possess anti-inflammatory, antiatherosclerotic, antihypertensive and analgesic properties. The pharmacokinetics (PK) and pharmacodynamics in terms of inhibitory potency of sEHIs were assessed in non-human primates (NHPs). Development of a sEHI for use in NHPs will facilitate investigations on the role of sEH in numerous chronic inflammatory conditions.

EXPERIMENTAL APPROACH

PK parameters of 11 sEHIs in cynomolgus monkeys were determined after oral dosing with 0.3 mg·kg(-1). Their physical properties and inhibitory potency in hepatic cytosol of cynomolgus monkeys were examined. Dose-dependent effects of the two inhibitors 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) and the related acetyl piperidine derivative, 1-trifluoromethoxyphenyl-3-(1-acetylpiperidin-4-yl) urea (TPAU), on natural blood eicosanoids, were determined.

KEY RESULTS

Among the inhibitors tested, TPPU and two 4-(cyclohexyloxy) benzoic acid urea sEHIs displayed high plasma concentrations (>10 × IC(50)), when dosed orally at 0.3 mg·kg(-1). Although the 4-(cyclohexyloxy) benzoic acid ureas were more potent against monkey sEH than piperidyl ureas (TPAU and TPPU), the latter compounds showed higher plasma concentrations and more drug-like properties. The C(max) increased with dose from 0.3 to 3 mg·kg(-1) for TPPU and from 0.1 to 3 mg·kg(-1) for TPAU, although it was not linear over this range of doses. As an indication of target engagement, ratios of linoleate epoxides to diols increased with TPPU administration.

CONCLUSION AND IMPLICATIONS

Our data indicate that TPPU is suitable for investigating sEH biology and the role of epoxide-containing lipids in modulating inflammatory diseases in NHPs.

Synthesis and evaluation of polycyclic pyrazolo[3,4-d]pyrimidines as PDE1 and PDE5 cGMP phosphodiesterase inhibitors

Polycyclic pyrazolo[3,4-d]pyrimidines (represented by 3 and 4) were synthesized as analogues of the recently reported polycyclic guanine phosphodiesterase (PDE) inhibitors. From the structure-activity relationship (SAR) development of a series of compounds, it was discovered that C-3 benzyl and N-2 methyl disubstitution on the pyrazole ring gave the best combination of potency and selectivity for PDE1 and PDE5 cGMP PDEs as represented by compound 4c: PDE1, IC50 = 60 nM; PDE3, IC50 = 55,000 nM; PDE5, IC50 = 75 nM. These compounds were also evaluated in vivo and found to be good orally active antihypertensives in laboratory animal models. Finally, comparisons were made of the in vitro and in vivo profiles of the pyrazolo-[3,4-d]pyrimidine compound 4c with those of two representative guanine compounds.

Uniform GFP-expression in transgenic medaka (Oryzias latipes) at the F0 generation

A green fluorescent protein (GFP) cDNA flanked by inverted terminal repeats (ITR) of adeno-associated virus was constructed. The construct sharply improved the efficiency and specificity of the transient expression of genes driven by two general promoters (cytomegalovirus and medaka beta-actin) and one muscle-specific promoter (zebrafish alpha-actin) in transgenic medaka. In addition, treatment with ITR sequence-containing constructs resulted in a dramatic increase in the number of embryos showing uniform GFP-expression at F0. Of the GFP-positive embryos, 34.6% (81/234), 10% (10/60), and 18% (38/212) showed homogenous GFP-expression for the derivative constructs of the cytomegalovirus, alpha-actin, and beta-actin promoters, respectively. As a result of uniform GFP-expression, green fluorescence in founders was (a) extended for an entire lifetime without degradation, and (b) transmitted as a genetic trait to F1 and F2 progeny of some transgenic lines via Mendelian inheritance. A Southern blot analysis revealed a random integration of the transgene into the genome of founders and progeny in both head-to-tail and tail-to-tail concatemerization patterns. Interestingly, some transgenic medaka with uniform and strong fluorescence could be visually noticeable to the unaided eye.

Enhanced expression and stable transmission of transgenes flanked by inverted terminal repeats from adeno-associated virus in zebrafish

Mosaic expression of transgenes in the F0 generation severely hinders the study of transient expression in transgenic fish. To avoid mosaicism, enhanced green fluorescent protein (EGFP) gene cassettes were constructed and introduced into one-celled zebrafish embryos. These EGFP gene cassettes were flanked by inverted terminal repeats (ITRs) from adeno-associated virus (AAV) and driven by zebrafish alpha-actin (palpha-actin-EGFP-ITR) or medaka beta-actin promoters (pbeta-actin-EGFP-ITR). EGFP was expressed specifically and uniformly in the skeletal muscle of 56% +/- 8% of the palpha-actin-EGFP-ITR-injected survivors and in the entire body of 1.3% +/- 0.8% of the pbeta-actin-EGFP-ITR-injected survivors. Uniform transient expression never occurred in zebrafish embryos injected with EGFP genes that were not flanked by AAV-ITRs. In the F0 generation, uniformly distributed EGFP could mimic the stable expression in transgenic lines early in development. We established five transgenic lines derived from palpha-actin-EGFP-ITR-injected embryos crossed with wild-type fish and 11 transgenic lines derived from pbeta-actin-EGFP-ITR-injected embryos crossed with wild-type fish. None of these transgenic lines failed to express the transgene, a result confirmed by polymerase chain reaction analysis. Stable mendelian transmission of the transgenes was achieved in both alpha-actin and beta-actin transgenic lines without changing the patterns of expression and integration. Progeny inheritance test and Southern blot analysis results strongly suggest that transgenes flanked by AAV-ITRs were integrated randomly into the genome at a single locus with a concatamerized multiplier. Thus, incorporating AAV-ITRs into transgenes results in uniform gene expression in the F0 generation and stable transmission of transgenes in zebrafish.

Edge preference of retinal and tectal neurons in common toads (Bufo bufo) in response to worm-like moving stripes: the question of behaviorally relevant 'position indicators'

Previous experiments have shown that during prey-catching behavior (orienting, snapping) in response to a worm-like moving stripe common toads, Bufo bufo (L.) exhibit a contrast- and direction-dependent edge preference. To a black (b) stripe moving against a white (w) background (b/w), they respond (R*) preferably toward the leading (l) rather the trailing (t) edge (Rl* greater than Rt*), thus displaying 'head preference'. If the contrast-direction is reversed (w/b), the stripe's trailing edge is preferred (Rl* less than Rt*), hence showing 'tail preference'. In the present study, neuronal activities of retinal classes R2 and R3 and tectal classes T5(2) and T7 have been extracellularly recorded in response to leading and trailing edges of a 3 degrees X 30 degrees stripe simulating a worm and traversing the centers of their excitatory receptive fields (ERF) horizontally at a constant angular velocity in variable movement direction (temporo-nasal or naso-temporal). The behavioral contrast-direction dependent edge preferences are best resembled by the responses (R) of prey-selective class T5(2) neurons (Rl:Rt = 10:1 for b/w, 0.3:1 for w/b) and T7 neurons (Rl:Rt = 6:1 for b/w, 0.4:1 for w/b); the T7 responses may be dendritic spikes. This property can be traced back to off-responses dominated retinal class R3 neurons (Rl:Rt = 6:1 for b/w, 0.5:1 for w/b), but not to class R2 (Rl:Rt = 1.2:1 for b/w and 0.9:1 for w/b). The respective edge preference phenomena are independent of the direction of movement. When stimuli were moved against a stationary black-white structured background, the 'head preference' to the black stripe and the 'tail preference' to the white stripe were maintained in class R3, T5(2), and T7 neurons. If the stripe traversed the ERF together with the structured background in the same direction at the same velocity, the responses of tectal class T5(2) and T7 neurons were strongly inhibited, particularly in the former. Responses of retinal R2 neurons in comparable situations could be reduced by about 50%, while class R3 neurons responded to both the stimulus and the moving background structure. The results support the concept that the prey feature analyzing system in toads applies principles of (i) 'parallel' and (ii) 'hierarchial' information processing. These are (i) divergence of retinal R3 neuronal output contributes to stimulus edge positioning and (in combination with R2 output) area evaluation in tectal neurons and to stimulus area evaluation and (in combination with R4 output) sensitivity for moving background structures in pretectal neurons.(ABSTRACT TRUNCATED AT 400 WORDS)