Temporomandibular joint and Giant Panda's (Ailuropoda melanoleuca) adaptation to bamboo diet.

Here, we present new evidence that evolutionary adaptation of the Ailuripodinae lineage to bamboo diet has taken place by morphological adaptations in the masticatory system. The giant panda in the wild and in captivity removes without an exception the outer skin of all bamboo shoots, rich in abrasive and toxic compounds, by the highly adapted premolars P3 and P4. The temporomandibular joint (TMJ) allows sidewise movement of the jaw and the premolars can, in a cusp-to-cusp position, remove the poorly digestible outer skin of the bamboo before crushing the bamboo with molars. Based on the evidence presented here, we suggest that adaptation of TMJ to lateral movement for enabling cusp-to-cusp contact of premolars is the crucial evolutionary factor as which we consider the key to understand the Ailuropodinae lineage adaptive pathway to utilize the bamboo resource.

On the hydrolytic behavior of tinidazole, metronidazole, and ornidazole.

Using two UV-spectrophotometric methods, the hydrolysis of tinidazole was studied at pH 1.00-8.45 at 80 degrees C. The reaction followed apparent first-order kinetics throughout the studied range. No kinetic salt effect was detected, indicating that at least one of the reacting partners forming the transition state has a charge of 0. The reaction rate macro constants M(1)-M(4) were calculated to be 3.35 x 10(-2) M(-1) h(-1), 1.45 x 10(-2) h(-1), 3.76 x 10(-6) M h(-1), and 2.85 x 10(-11) M(2) h(-1), respectively. At pH >or= 7, the uncharged tinidazole was decomposed by the hydroxide ion; the reaction was found out to involve a proton transfer from the ethylsulfonylethyl side chain. At around pH 4.5, the degradation of the uncharged tinidazole was due to the solvent. In more acidic conditions, the reaction mechanism could not be fully resolved. The alkaline hydrolysis of metronidazole was studied on the basis of literature data. A general reaction mechanism was proposed, but an unequivocal explanation for the inflection point in the pH rate profile at pH 6 could not be found. The implications of the proposed reaction mechanism for the hydrolytic behavior of ornidazole were discussed.

Two stability-indicating UV spectrophotometric methods for the analysis of hydrolyzed tinidazole.

Two UV spectrophotometric methods have been validated for the analysis of hydrolyzed tinidazole solutions. The pH of the samples must be 5.00-7.00 for both methods. The multiwavelength method may be used for samples degraded at pH 6-12 if the amount of conserved 5-nitroimidazole species is at least 93 mol.% of the original; the amounts of tinidazole and its two known impurities may be determined simultaneously. The accuracy was within 100+/-8% and the repeatability of measurement was

Lago amazonas: fact or fancy?

It has been suggested that a huge lake, Lago Amazonas, covered a large part of the Amazon basin until as recently as two thousand years ago. According to this hypothesis, the topmost sediments in western Amazonia are almost universally young deposite of lacustrine and deltaic origin. The hypothesis has gained some attention among biologists because of its implications for biological phenomena in Amazonia, especially biogeography and biodiversity. According to the available geological data, however, Amazonia is geologically far more complex than assumed by the lake hypothesis. In the following discussion we will point out the weaknesses of the Lago Amazonas hypothesis, and indicate alternative explanations of the surface geology that are based on tectonically controlled fluvial deposition.

Foi proposta a idéia que uma parte importante da bacia do Amazonas foi coberta por um vasto lago, Lago Amazonas, até há época tão recente como dois mil anos atrás. Segundo esta hipótese os sedimentos de topo na região ocidental da Amazônia são quase universalmente depósitos recentes de origem lacustre e estuário. A hipótese tem chamado atenção dos biólogos pelas suas implicações com fenômenos biológicos na Amazônia, particularmente com a biogeografìa e a biodiversidade.A Amazônia, apresenta, contudo, uma unidade geologicamente muito mais complexa do que pressupõe esta hipótese de lago, hipótese que nem tem apoio dos dados disponíveis sobre o tectonismo, a geomorfologia, a estratigrafia e os solos. Vastas áreas nas regiões do Peru e da Bolivia da bacia do Amazonas se caracterizam atualmente pela deposição fluvial, dominada pelos processos tectônicais. São processos que foram ativos durante dezenas de milhões de anos explicando assim a acumulação dos sedimentos Quaternários não-consolidados, característicos da região ocidental da Amazônia. Há uma variação extensa dos sedimentos de topo tanto pela sua composição como pela sua idade devido às influências locais de fatores diferentes. A hipótese que pressupõe o ambiente de depósitos ter no recente passado diferido basicamente do ambiente atual, precisava, para ser aceita, provas mais convincentes do que foi presentado pelos proponentes da hipótese de Lago Amazonas.Devido à instalidade e heterogeneidade do meio ambiente da Amazônia, é preciso prudência quando se generaliza baseando-se nas observações duma área limitada. Sistemas de depósitos diferentes são capazes de produzir sedimentos estratigrafica mente semelhantes, independentemente um do outro. Sem ter provas evidentes tanto da continuidade como da deposição simultanea, estabelecer uma correlação entre formações de locais remotos parece muito arriscado.