Substrate recognition domain of the Gal2 galactose transporter in yeast Saccharomyces cerevisiae as revealed by chimeric galactose-glucose transporters

The Gal2 galactose transporter takes up galactose in yeast. A homologous glucose transporter from the same organism, Hxt2, was selected, and various chimeras between these two transporters were constructed by making use of homologous recombination in Escherichia coli. Comparison of the galactose transport activities of three series of chimeras enabled us to positively identify a crucial substrate recognition region of 101 amino acids that lies close to the carboxyl terminus of the Gal2 transporter.

Amino acid residues responsible for galactose recognition in yeast Gal2 transporter

A novel, systematic approach was used to identify amino acid residues responsible for substrate recognition in the transmembrane 10 region of the Gal2 galactose transporter of Saccharomyces cerevisiae. A mixture of approximately 25,000 distinct plasmids that encode all the combinations of 12 amino acids in transmembrane 10 that are different in Gal2 and the homologous glucose transporter Hxt2 was synthesized. Selection of galactose transport-positive clones on galactose limited agar plates yielded 19 clones, all of which contained the Tyr446 residue found in Gal2. 14 of the 19 clones contained Trp455 found in Gal2, whereas the other 5 contained Cys455, a residue not found in either Gal2 or Hxt2. When Tyr446 of Gal2 was replaced with any of the other 19 amino acids, no galactose transport activity was observed in the resulting transporters, indicating that Tyr446 plays an essential role in the transport of this sugar. Replacement of 2 amino acids of Hxt2 with the corresponding Tyr446 and Trp455 of Gal2 allowed the modified Hxt2 to transport galactose. The Km of galactose transport for the modified transporter was 8-fold higher than that of Gal2. These results and other evidence unequivocally show that Tyr446 is essential and Trp455 is important for the discrimination of galactose versus glucose.

Transmembrane segment 10 is important for substrate recognition in Ga12 and Hxt2 sugar transporters in the yeast Saccharomyces cerevisiae

A systematic series of chimeras between Ga12 galactose transporter and Hxt2 glucose transporter in yeast was produced to delineate the essential domain for substrate recognition. A domain of 101 amino acids close to the COOH-terminus that has been previously identified as the critical substrate recognition region was further divided into four subdomains, by introducing five restriction enzyme sites at exactly corresponding locations of both genes without changing coding amino acids. When each of all possible 16 modified genes was expressed, all the galactose transport-active chimeras were found to possess Ga12-derived transmembrane segment (TM) 10. Of the 35 amino acids in the TM1O region, only 12 differ between Ga12 and Hxt2, indicating that these 12 amino acids include the critical residue(s) responsible for the differential recognition of galactose and glucose in these transporters.

Determinação da razão ótima de espermatozóides por ovócitos de piabanha Brycon insignis (pisces - characidae)

Determinou-se a razão ótima de espermatozóides por ovócitos da piabanha Brycon insignis, utilizando-se dois machos e duas fêmeas da espécie, submetidos ao procedimento de desova induzida. Os gametas foram extrusados manualmente 200 horas-grau após a aplicação do extrato bruto de hipófise. Os ovócitos foram misturados e deste pool retiraram-se amostras com 2g de ovócitos (701 ovócitos/g). O sêmen do pool foi diluído em solução de NaCL 1,2% de tal forma que, após a adição de 1ml do sêmen diluído aos ovócitos, fossem obtidas as seguintes razões espermatozóides por ovócitos em cada tratamento: T1=86.662, T2=173.324, T3=259.986, T4=346.648 e T5=433.310. A taxa de fertilização do sêmen não diluído usado como controle foi de 65,3%. Após ativação espermática com NaHCO3 1% e fecundação, os ovos foram transferidos para as incubadoras e nelas foram observadas as seguintes percentagens de fertilização em relação à do grupo-controle: T1=35,7%, T2=53,1%, T3=79,1%, T4=93,4% e T5=87,8%. A percentagem de fertilização (em relação ao controle) aumentou de forma linear, segundo a equação de regressão: Y=15,55+0,0002297X (P<0,01; R²=0,98), até a proporção de 314.481 espermatozóides por ovócitos, após o que a taxa de fertilização se estabilizou no limite de 88%.

Zootechnical indices and digestibility in juveniles of tambaqui Colossoma macropomum fed a diet containing particulate maize

Three experiments were done with different particle sizes of corn feed on its zootechnical performance, passing rate and apparent digestibility of juvenile tambaqui (Colossoma macropomum). In the first, 200 juveniles were used and distributed in 20 tanks (220 L), 10 fish per unit (four replicates). The experimental system used to record passage time was composed of five incubators with 200 L. In the second, 75 juveniles were used per 55 days (three replications). In the third, 75 juveniles were used and distributed in five incubators of 200 L. All experiments were performed randomly. Different linear behavior treatments were observed for apparent digestibility of crude protein; and the smaller particle size (150 μm) had better results digestibility. smaller particle size of the corn had better results, affected the growth performance of tambaqui and the apparent digestibility of crude protein and ether extract. Thus, is recommended that a particle size of 150 μm of corn be used for tambaqui.

Nanosecond fluorescence studies of noncovalent interaction of monomeric and dimeric intercalators with DNA

The noncovalent interaction of 2-aminodipyrido[1,2-a:3',2'-d]imidazole (Glu-P-2) and its derivatives, which are potent mutagens isolated from L-glutamic acid pyrolysate, with calf thymus DNA was studied by steady-state and nanosecond fluorescence spectroscopies. The fluorescence of these compounds exhibits static quenching by noncovalent interaction with DNA. Fluorescence lifetimes of the free and intercalated states of these compounds were determined to be 9-10 and 0.5-1 ns, respectively. The bisintercalative effect of the dimeric analogue of Glu-P-2, bis(Glu-P-2)spermine (2GP-SP), to DNA was also investigated. This 2GP-SP, which has two Glu-P-2 moieties at each end of spermine, indicates a strong intramolecular interaction exhibiting remarkable quenching of fluorescence spectrum and lifetime (tau = 3.5 ns) in the absence of DNA. In the presence of DNA, however, the 3.5-ns lifetime component of fluorescence disappeared, and a two-exponential decay of fluorescence (t = approximately 10 and 1.5 ns) was observed at a DNA concentration of more than approximately 0.001 mM P, while the solution containing a very dilute DNA concentration (less than or equal to 0.001 mM P) exhibits a three-component decay of fluorescence (1.5, 3.5, and approximately 10 ns). The potent bis intercalation of two moieties in 2GP-SP with an identical DNA molecule was suggested by the DNA-concentration dependence of these fluorescence lifetimes and their intensity.

Histopathological findings in lungs of hawksbill turtles collected on the coasts of the states of Espírito Santo and Rio de Janeiro, Brazil

ABSTRACT The present work aimed to report the histopathological findings verified in lungs of hawksbill turtles (Eretmochelys imbricata) retrieved from the coasts of the states of Espírito Santo and Rio de Janeiro, Brazil. Between the years 2010 and 2014, 29 E. imbricata individuals were found stranded on the coasts, already dead or dying during treatment. Lung samples of all specimens were collected during necropsies, fixed in 10% neutral buffered formalin, subjected to routine histological processing and classified histomorphologically. The findings revealed that 37.93% of the specimens presented lung lesions. Of these, 90.91% were rescued alive and 9.09% were found dead; 63.63% were females and 36.37% were males. The mean weight was 5.44 Kg and the mean length 39 cm, characterizing young individuals. The animals originated from São Francisco de Itabapoana - RJ, Aracruz - ES, São Mateus - ES, Guarapari - ES, Linhares - ES, Itapemirim - ES, and Anchieta - ES. Macroscopic analysis revealed presence of foam, hyperemia, nodules in the parenchyma, cyst and caseous material. Microscopic examination evidenced heterophilic bronchopneumonia, parasitic granulomatous pneumonia caused by spirorchiids, bacterial granulomatous pneumonia, fungal granulomatous pneumonia, and congestion. It was concluded that juvenile specimens of Eretmochelys imbricata, females and males, originated from the states of Espírito Santo and Rio de Janeiro and found stranded both alive or dead, have significant lung lesions, mainly inflammatory ones, associated or not with infectious agents.

Evolution and Functional Diversification of Serine Racemase Homologs in Bacteria

Amino acid racemases catalyze the interconversion of L- and D-amino acids, maintaining intracellular levels of both D- and L-amino acids. While alanine and glutamate racemases are widespread in bacteria, serine racemase (SerR) is predominantly found in animals. Recently, homologs of animal SerR were reported in some bacterial genomes, but their evolutionary distribution and functional roles remain poorly understood. In this study, we cloned and expressed 20 SerR homologous genes from 13 bacterial species spanning five phyla and characterized their enzymatic activity. Six homologs exhibited serine dehydratase activity, while the remaining showed racemase activity with serine, aspartate, asparagine, or arginine. Notably, the SerR homologs from Parafannyhessea umbonata (Actinomycetota), Clostridium aceticum, Anaerovirgula multivorans, Alkaliphilus oremlandii (Bacillota), Acetomicrobium mobile, and Thermovirga lienii (Synergistota) demonstrated strong arginine racemase activity, with Km values ranging from 0.167 to 0.885 mM and kcat values ranging from 5.86 to 61.5 s-1 for L-arginine. Phylogenetic analysis revealed that bacterial and eukaryotic SerR homologs share a common ancestral gene, and substrate specificity has independently changed multiple times during evolution. Amino acid sequence alignment and analysis of site-directed mutants revealed that residues at positions 146 to 148 and surrounding regions, located near the substrate-binding site, play a crucial role in substrate specificity and/or catalytic activity. These results highlight the evolutionary processes that drive functional diversification in serine racemase homologs.

Composição corporal de tambaqui alimentado com rações contendo farinha de folha de leucena

O objetivo deste trabalho foi avaliar os efeitos da inclusão de farinha de folha de leucena em dietas sobre a composição corporal de juvenis de tambaqui. Um total de 240 juvenis foram distribuídos em 12 caixas plásticas (350 L), em um delineamento experimental inteiramente casualizado com quatro tratamentos (0, 8, 16 e 24 % de inclusão de farinha de folha de leucena) e três repetições. Não houve diferença significativa (p>0,05) entre os tratamentos, indicando que é possível incluir até 24 % de farinha de folha de leucena em rações para juvenis de tambaqui, sem que haja alteração da composição corporal.

Helminth Fauna of Juvenile Green Sea Turtles (Chelonia mydas) from Rio de Janeiro State, Brazil

The helminth fauna of juvenile green sea turtles (Chelonia mydas Linnaeus, 1758) is still poorly known. Herein, we study the gastrointestinal helminths of 28 juvenile green sea turtles found stranded on the north coast of Rio de Janeiro state, Brazil. All turtles were infected showing a rich helminth fauna. In total, 14802 trematodes belonging to 30 species and 5 families including Micros-caphidiidae, Plagiorchiidae, Pronocephalidae, Hapalotrematidae, and Telorchiidae were recovered. An unidentified nematode specimens was also found. The mean intensity was 536 (95% CI = 362 - 853) (range: 1 - 2831), and the species richness was 7.86 (95% CI = 6.46 - 9.21) (range: 1 - 17). The coast of Rio de Janeiro state represents new locality records for Angiodictyum posterovitellatum, Microscaphidium aberrans, M. warui, Octangium hyphalum, O. sagitta, Enodiotrema reductum and Pleurogonius laterouterus. This study confirms that the green sea turtle harbors the richest helminth fauna among sea turtle species and provides useful information on the gastrointestinal helminths of a poorly known stage in the life cycle of this endangered chelonian.

Análise histomorfométrica do útero na espécie canina do nascimento aos seis meses de idade

Objetivou-se caracterizar para a espécie canina o desenvolvimento histológico uterino do nascimento aos seis meses de idade. Foram analisados úteros (n=32) de animais com idades entre um e 180 dias pós-nascimento (DPN), distribuídos em oito grupos: G1-1 DPN (1 Yorkshire Terrier, 1 Poodle, 2 Sem Raça Definida (SRD)/peso médio (Pm)=190g), G2-15 DPN (2 Yorkshire Terrier e 2 SRD/Pm=354g), G3-30 DPN (1 Rottweiler, 1 Poodle, 2 SRD/Pm=985g), G4-45 DPN (1 Poodle, 3 SRD/Pm=1,1kg), G5-60 DPN (1 Yorkshire Terrier, 1 Poodle e 2 SRD/Pm=1,4kg), G6-90 DPN (4 SRD/Pm=2,8kg), G7-120 DPN (1 Poodle e 3 SRD/Pm=6,6kg) e G8-180 DPN (1 Rottweiler, 1 Poodle e 2 SRD/Pm=11kg). A análise histológica constituiu de mensurações das espessuras (µm) da parede uterina, miométrio, endométrio, assim como diâmetro (µm) e número de glândulas endometriais. A análise estatística demonstrou estabilidade e homogeneidade nas estruturas avaliadas com coeficientes de variação baixos (<10%). Observou-se: útero com um DPN: epitélio com células cúbicas simples, miométrio rudimentar, presença de perimétrio e ausência de glândulas endometriais; aos 15 DPN: desenvolvimento de estrutura primordial de formação das glândulas endometriais; dos 30 aos 45 DPN: endométrio e glândulas endometriais simples; aos 60 DPN: glândulas endometriais em lâmina própria com ramificações e discreto pregueamento endometrial; de 90 a 180 DPN: todas as estruturas uterinas apresentaram histoarquitetura de um animal maduro. Todas as variáveis analisadas apresentaram correlação positiva com a idade pós-nascimento (R2≥72,2%). Conclui-se que o útero da cadela desenvolve-se continuamente do nascimento à 180 dias de vida e que apresenta-se desprovido de glândulas endometriais ao nascimento. As primeiras glândulas endometriais são observadas aos 15 dias de vida e apresenta conformação histológica de um animal adulto após 60 dias do nascimento.