Spontaneous mutations affecting glycerol-3-phosphate dehydrogenase enzyme activity in Drosophila melanogaster.

Significant genetic variance in glycerol-3-phosphate dehydrogenase (GPDH) activity was observed between chromosome lines of Drosophila melanogaster that had each accumulated spontaneous mutations for approximately 300 generations. No restriction map variation was found in a 26-kb region surrounding the entire Gpdh gene. The restriction analysis used is capable of detecting insertions/deletions larger than 0.05 kb. The survey would also detect chromosomal recombinations that include the entire Gpdh coding region. Therefore, if the spontaneous mutations that affected the enzyme activity are located inside the Gpdh gene region, then they are base pair substitutions or structural changes that are smaller than the limit in resolution described above.     

Effect of temperature on the expression of bobbed mutations in Drosophila melanogaster

The expression of two bobbed mutations on the X chromosome was studied at two temperatures 25 degrees C and 18 degrees C (larval developmental time, viability, phenotype of adult...). Results showed that the wm4bb mutation is thermosensitive. Some hypothesis are expressed to explain this phenomenon.     

Effect of sodium hydroxybutyrate on carboxypeptidase H activity and on angiotensin-converting enzyme in different regions of the rat brain

It is revealed, that analogue of the gamma-aminobutyric acid--sodium hydroxybutyrate causes decrease of activities carboxypeptidase H and angiotensin converting enzyme in pituitary gland, hypothalamus and striatum. The most expressed changes of enzyme activities were observed in pituitary gland and hypothalamus. The activity of carboxypeptidase H changes more essentially, than one of angiotensin converting enzyme. The assumption one of mechanisms of influence the hydroxybutyric acid and, possible, the gamma-aminobutyric acid, on neuropeptides level is changes of activity of enzyme of biologically active peptides exchange is expressed.     

The molecular basis of odor coding in the Drosophila antenna

We have undertaken a functional analysis of the odorant receptor repertoire in the Drosophila antenna. Each receptor was expressed in a mutant olfactory receptor neuron (ORN) used as a "decoder," and the odor response spectrum conferred by the receptor was determined in vivo by electrophysiological recordings. The spectra of these receptors were then matched to those of defined ORNs to establish a receptor-to-neuron map. In addition to the odor response spectrum, the receptors dictate the signaling mode, i.e., excitation or inhibition, and the response dynamics of the neuron. An individual receptor can mediate both excitatory and inhibitory responses to different odorants in the same cell, suggesting a model of odorant receptor transduction. Receptors vary widely in their breadth of tuning, and odorants vary widely in the number of receptors they activate. Together, these properties provide a molecular basis for odor coding by the receptor repertoire of an olfactory organ.     

The molecular basis of odor coding in the Drosophila larva

We have analyzed the molecular basis of odor coding in the Drosophila larva. A subset of Or genes is found to be expressed in larval olfactory receptor neurons (ORNs). Using an in vivo expression system and electrophysiology, we demonstrate that these genes encode functional odor receptors and determine their response spectra with 27 odors. The receptors vary in their breadth of tuning, exhibit both excitation and inhibition, and show different onset and termination kinetics. An individual receptor appears to transmit signals via a single ORN to a single glomerulus in the larval antennal lobe. We provide a spatial map of odor information in the larval brain and find that ORNs with related functional specificity map to related spatial positions. The results show how one family of receptors underlies odor coding in two markedly different olfactory systems; they also provide a molecular mechanism to explain longstanding observations of larval odor discrimination.     

Effect of sulfonates on the esterase activity of carboxypeptidase A

The effects of sulfonates on the carboxypeptidase A catalyzed hydrolysis of the ester substrate benzoylglycyl-L-phenyllactate were determined. The modifiers examined were benzenesulfonate, p-toluenesulfonate, 2-phenylethane-sulfonate, methanesulfonate, ethanesulfonate, propanesulfonate, butanesulfonate, pentanesulfonate, hexanesulfonate, heptanesulfonate, and 2,2-dimethyl-2-silapentane-5-sulfonate. Sulfonate activators of peptide hydrolysis were inhibitors of esterase activity. Of the sulfonates studied, 2,2-dimethyl-2-silapentane-5-sulfonate was the most effective inhibitor. 2-Phenylethanesulfonate, hexanesulfonate, heptanesulfonate, and 2,2-dimethyl-2-silapentane-5-sulfonate exhibited uncompetitive inhibition. The remaining sulfonates either did not inhibit or the inhibition was too weak to properly characterize.     

Genetic and molecular analyses of mutations involved in Drosophila raf signal transduction.

We have identified dominant mutations that suppress the lethality associated with an R217-->L mutation in the GTP.Ras binding region (CR1) of the Drosophila raf (D-raf) serine/threonine kinase. Four intragenic and seven extragenic suppressors were recovered. Each of the four intragenic mutations contains one compensatory amino acid change located in either the CR1 or the kinase domain of D-raf. The seven extragenic suppressors represent at least four genetic loci whose effects strongly suggest that they participate in both the sevenless and Drosophila EGF receptor (DER) signaling pathways. One of these mutations, Su(D-raf)34B, is an allele of D-mek which encodes the known signaling molecule MAPK kinase (MEK). A D83V mutation in D-MEK is identified and shown to be sufficient to confer the dominant activity of Su(D-raf)34B.     

The molecular and cellular basis of bitter taste in Drosophila

The extent of diversity among bitter-sensing neurons is a fundamental issue in the field of taste. Data are limited and conflicting as to whether bitter neurons are broadly tuned and uniform, resulting in indiscriminate avoidance of bitter stimuli, or diverse, allowing a more discerning evaluation of food sources. We provide a systematic analysis of how bitter taste is encoded by the major taste organ of the Drosophila head, the labellum. Each of 16 bitter compounds is tested physiologically against all 31 taste hairs, revealing responses that are diverse in magnitude and dynamics. Four functional classes of bitter neurons are defined. Four corresponding classes are defined through expression analysis of all 68 gustatory taste receptors. A receptor-to-neuron-to-tastant map is constructed. Misexpression of one receptor confers bitter responses as predicted by the map. These results reveal a degree of complexity that greatly expands the capacity of the system to encode bitter taste.     

The molecular basis for metameric pattern in the Drosophila embryo

The metameric organization of the Drosophila embryo is generated in the first 5 h after fertilization. An initially rather simple pattern provides the foundation for subsequent development and diversification of the segmented part of the body. Many of the genes that control the formation of this pattern have been identified and at least twenty have been cloned. By combining the techniques of genetics, molecular biology and experimental embryology, it is becoming possible to unravel the role played by each of these genes. The repeating segment pattern is defined by the persistent expression of engrailed and of other genes of the 'segment polarity' class. The establishment of this pattern is directed by a transient molecular prepattern that is generated in the blastoderm by the activity of the 'pair-rule' genes. Maternal determinants at the poles of the egg coordinate this prepattern and define the anteroposterior sequence of pattern elements. The primary effect of these determinants is not known, but genes required for their production have been identified and the product of one of these, bicoid is known to be localized at the anterior of the egg. One early consequence of their activity is to define domains along the A-P axis within which a series of 'cardinal' genes are transcribed. The activity of the cardinal genes is required both to coordinate the process of segmentation and to define the early domains of homeotic gene expression. Further interactions between the homeotic genes and other classes of segmentation genes refine the initial establishment of segment identities.     

Effect of testosterone on carboxypeptidase H activity in the murine hypothalamus and hypophysis

Effects of single intraperitoneal administration of testosterone propionate (3 or 30 mg/kg body weight) on activity of carboxypeptidase H in pituitary body and hypothalamus of female white mouse were studied. It was found that testosterone propionate treatment (3 and 30 mg/kg body weight) increased the carboxypeptidase H activity in pituitary through 0.5 hour and it decreased one in 24 hours after treatment. The carboxypeptidase H activity in hypothalamus was lower as compared with control animals in 24 hours after testosterone propionate treatment in the dose 3 mg/kg body weight. However, the carboxypeptidase H activity in hypothalamus was lower in 0.5 and 24 hours and it was higher in 4 h after testosterone propionate treatment in the dose 30 mg/kg body weight as compared with the control. These data suggest that testosterone affects the carboxypeptidase H activity by changing the level of enzyme gene expression.     

Integrating the molecular and cellular basis of odor coding in the Drosophila antenna

We investigate how the molecular and cellular maps of the Drosophila olfactory system are integrated. A correspondence is established between individual odor receptors, neurons, and odors. We describe the expression of the Or22a and Or22b receptor genes, show localization to dendritic membranes, and find sexual dimorphism. Or22a maps to the ab3A neuron, which responds to ethyl butyrate. Analysis of a deletion mutant lacking Or22a, along with transgenic rescue experiments, confirms the mapping and demonstrates that an Or gene is required for olfactory function in vivo. Ectopic expression of Or47a in a mutant cell identifies the neuron from which it derives and its odor ligands. Ectopic expression in a wild-type cell shows that two receptors can function in a single cell. The ab3A neuron does not depend on normal odor receptor gene expression to navigate to its target in the CNS.     

Characterization and developmental expression of a Drosophila ras oncogene.

We cloned a Drosophila melanogaster ras gene (Dmras64B) on the basis of its homology to the ras oncogen from Harvey murine sarcoma virus. This gene mapped at chromosomal position 64B on the left arm of the third chromosome. Sequencing of Dmras64B revealed extensive amino acid homology with the proteins encoded by the human and Saccharomyces cerevisiae ras genes. The coding region of the Drosophila gene is interrupted by two introns located in different positions with respect to its human counterpart. Dmras64B encodes three different RNAs (1.6, 2.1, and 2.6 kilobases long) that are constantly expressed throughout the development of the fly.     

Characterization of a depurinated-DNA purine-base-insertion activity from Drosophila.

An activity that binds preferentially to depurinated DNA and inserts purines into those sites was partially purified from Drosophila melanogaster embryos. The protein has a sedimentation coefficient of 4.9 S and is devoid of AP (apurinic/apyrimidinic) endonuclease activity. Upon incorporation of purines into apurinic DNA, the number of alkali-labile sites decreases, thus establishing the conversion of depurinated sites into normal nucleotides. The activity requires K+, and is totally inhibited by caffeine or EDTA. Guanine is specifically incorporated into partially depurinated poly(dG-dC) and adenine is specifically incorporated into poly(dA-dT), thus demonstrating the apparent template specificity of the enzyme.     

Effect of the bioflavonoid silymarin on the in vitro activity and expression of superoxide dismutase (SOD) enzyme.

Superoxide dismutase activity and expression of the erythrocytes and lymphocytes of patients suffering from chronic alcoholic liver disease and those of healthy controls were investigated after in vitro incubation with silymarin. It was concluded that silymarin treatment in a concentration achievable by in vivo treatment (10 micrograms/ml) significantly increased the SOD activity of both the erythrocytes and lymphocytes of patients with liver disease, whereas the SOD expression of the lymphocytes enhanced to a considerable extent. These results indirectly indicate that the scavenger silymarin is able to increase the antioxidant protection of the cells by ameliorating the deleterious effects of free radical reactions.     

Characterization of the molecular basis of the alpha 1-antitrypsin F allele.

alpha 1-Antitrypsin (alpha 1AT), the major serum inhibitor of neutrophil elastase, is a highly polymorphic serum protein associated with characteristic isoelectric-focusing (IEF) patterns for most variants. To characterize the molecular basis of the anodal F variant, the DNA sequence of the coding exons of an FZ individual was determined. The F allele differed from the normal M1(Val213) alpha 1AT allele by a single nucleotide transversion of cytosine to thymidine, which results in the amino acid substitution Arg223 CGT----Cys TGT. Inheritance of the F mutation was confirmed by family analysis using allele-specific amplification. In the context that the normal alpha 1AT molecule has only one cysteine residue, a mutation resulting in the addition of a second cysteine may influence the three-dimensional form of the protein and/or permit interaction with other plasma proteins with free-SH groups and may be responsible for the observation that the major F alpha 1AT bands often migrate as doublets in IEF gels.