Sensitivity of Mexican water bodies to regional climatic change: three study alternatives applied to remote sensed data of Lake Patzcuaro

Historical aerial photography over closed basins enables the observation of lake surfaces at variable water levels and climatic conditions. Thus, the assessment at the landscape level of subtle variations in inundated areas depends on a suitable framework for processing historical imagery, frequently available at different scales and resolutions.The present paper deals with Lake Patzcuaro as a case study and the application of three analytical procedures to remote sensed data of 1974, including two maps commercially available and nine aerial photographs. Computer-based processing of images and further incorporation into GIS led to three different outputs: topographic map (TM-GIS), photomosaic 1 (P₁) and photomosaic 2 (P₂). Aerial photographs assemblages were georeferenced by means of GCP's, 86 located by means of INEGI vectorial polygons (P₁), and 40 determined directly at the field by GPS (P₂).In conclusion, TM-GIS lack of photointerpretation for the lake as an image derived from a topographic map; while P₂ involved an unacceptable RMS. P₁ thus became the best option for the calculation of areas not only because of the lower RMS associated, but the additional photointerpretation of limnological zones exclusive to aerial photographs. As a background picture, P₁ also facilitates the analysis of historical images on a comparative basis.     

Naphthalene-induced changes in carbohydrate metabolism in Sarotherodon mossambicus Peters (Pisces: Cichlidae)

Sarotherodon mossambicus Peters was exposed to naphthalene concentrations ranging from 7.9 to 0.92 mg/l for periods ranging from 4 days to 10 weeks and changes in glycogen, glucose, pyruvic acid and lactic acid contents of liver and muscle were studied. While glucose levels remained unaffected, major effects could be seen in the other constituents following both lethal and sublethal naphthalene treatment. Whereas glycogen and pyruvic acid levels showed considerable reduction, lactic acid levels increased markedly. These changes are indicative of a metabolic stress leading to a shift to anaerobic metabolism. The effects do not appear to be related to the feeding and growth rates of the naphthalene-intoxicated fish.     

The program of friend cell erythroid differentiation: Early changes in Na+/K+ ATPase function

Treatment of Friend erythroleukemia cells with several different chemical agents causes an early decrease in the ⁸⁶Rb⁺ influx mediated by Na⁺/K⁺ adenosine triphosphatase (ATPase). These agents, which induced Friend cells to differentiate, include dimethylsulfoxide (DMSO), ouabain, hypoxanthine, and actinomycin D. The magnitude of the early decrease in ⁸⁶Rb⁺ influx correlates with the proportion of cells in cultures of inducible Friend cell clones which later go on to synthesize hemoglobin. Compounds which do not incude differentiation in these cells, such as xanthine, exogenous hematin, and erythropoietin, do not cause a change in ⁸⁶Rb⁺ influx. A change in the intracellular K⁺ ion concentration does not occur during induction by DMSO because, although there is a decrease in K⁺ content per cell soon after induction, there is a parallel decrease in cell volume. These results and previous observations from this laboratory are discussed in terms of the posible involvement of the Na⁺/K⁺ ATPase in Friend cell differentiation.     

Regulation of ammonia (NH3-N) metabolism in the marine pulmonate,onchidium verruculatum. I. effects of a neuroendocrine centre on tissue ammonia levels

Effect of ganglionic extirpations and replacement on the ammonia levels in the blood and various tissues of the marine pulmonate, O. verruculatum was studied. Three hrs after extirpation of the pleurovisceral (PV) complex only and not any other ganglia, revealed a significant (P < 0.001) decline in the blood and foot ammonia levels and significant (P < 0.001) increment in the hepatopancreatic ammonia level. However, no change was observed in the mantle and nephridial ammonia levels. Replacement of the PV complex, either via implantation of intact ganglia or boiled and unboiled homogenate administration (1 gn/animal) into the ganglionectomised group, restored ammonia levels in the blood and foot and showed significant (P < 0.005) decrease in hepatopancreatic ammonia levels. The results are discussed in the light of hormonal regulation of the nitrogen metabolism.     

Hypercaloric diet and chronic stress desynchronizes the temporal pattern of rats’ insulin release

This study evaluated the effects of the association between obesity and chronic stress on the temporal pattern of serum levels of biochemical and hormonal markers. Obesity model was achieved by hypercaloric diet exposure. Wistar rats were divided into four groups: standard chow (C), hypercaloric diet (HD), stress + standard chow (S), and stress + hypercaloric diet (SHD) and analysed at three time points: ZT0, ZT12 and ZT18. Chronic stress was performed 1 h/per day, 5 days/per week, during 80 days. The presence of temporal pattern in naïve animals’ insulin release was accomplished. Hypercaloric diet induced obesity, increasing rats’ insulin and glucose levels; while chronic stress reduced insulin levels. There were interactions between chronic stress and obesity in serum insulin and glucose levels; and between time points and obesity in insulin levels. In conclusion, long exposure to hypercaloric diet and chronic stress were able to desynchronize temporal pattern of insulin release, contributing to the pathophysiology of obesity and its complications.     

The Return of the King or Bringing Snails to the Garden? The Human Dimensions of a Proposed Restoration of European Bison (Bison bonasus) in Germany

Human dimensions research can help resource and wildlife managers make informed decisions, target information efforts, and gain a greater understanding of the factors that comprise attitudes toward wildlife management efforts. Despite these often-stated merits, studies addressing the human dimensions of resource and wildlife management efforts are rare in Europe. A proposed restoration of free-ranging European bison ( Bison bonasus ) in North Rhine-Westphalia, Germany, has presented an opportunity to help address this research gap. During May to July 2006, we used a randomly distributed, self-administered questionnaire ( n = 398) to assess local residents' attitudes, beliefs, and levels of support or opposition toward the proposed restoration. These factors were compared across two administrative regions spanned by the proposed restoration area. We found that respondents from the Siegen-Wittgenstein region held significantly more positive attitudes and significantly higher knowledge levels than respondents from the Hochsauerlandkreis region. Principal components analysis revealed that attitudes comprised a general attitude factor pertaining to issues such as the importance of conserving bison for future generations and a lifestyle impact factor, which included items pertaining to bison-caused damages to trees and crops. Logistic regression was used to show the influence of fear of bison on attitudes. We discuss the likely causes and management implications of our findings and provide suggestions to managers wishing to target information efforts and address the concerns of those affected by the proposed restoration.