Conservation Biology of the Genus Alouatta

As assessed by the IUCN Mace–Lande system, seven (35%) of the 20 Alouatta species and subspecies with adequate data are classified as threatened, i.e., critically endangered, endangered, or vulnerable (Rylands et al., 1995). This percentage is much lower than the 75 to 100% threatened taxa for the other large-bodied genera: Ateles, Lagothrix, and Brachyteles. Only 5 of the 16 Neotropical genera have lower percentages of threatened taxa than that of Alouatta: Cebuella, Pithecia, Saguinus, Saimiri, and Cebus. The threatened howler taxa occupy small distributions in areas of forest fragmentation. In general, populations are most affected by major habitat disturbance, such as total deforestation and flooding from dam construction, and by human hunters. Facilitated by their ability to exploit folivorous diets in small home ranges, howlers can tolerate considerable habitat fragmentation but not the increased exposure to hunting that may accompany it. Howlers seem particularly vulnerable to yellow fever and bot fly parasitism. Although the former threat may decrease by increasing fragmentation of the habitat, other sorts of parasitism may increase in disturbed habitats. The low genetic variability of the Central American howlers suggests a resistance to inbreeding depression potentially experienced during population bottlenecks. Greater between-population variability may still exist. Although howlers are not readily bred in captivity, they respond well to translocation. Translocation has been successfully achieved for 4 howler species and is a viable option for introducing new genetic variability into population fragments and repopulating areas from which howlers are extinct. Their pattern of bisexual dispersal facilitates colonization of regenerating habitats, and in suitable, protected habitats they have shown the capacity for strong population recovery.     

Effect of insulin on ultrastructure and glycogenesis in primary cultures of adult rat hepatocytes

Insulin in the presence of high concentrations of glucose has a beneficial trophic effect on the development of primary cultures of hepatocytes. Compared to the situation observed in hormone-free control cultures, the flattening of the reaggregated hepatocytes is enhanced, and the reconstituted cell trabeculae are enlarged and tend to form a confluent monolayer after 3 days; the survival time is prolonged from 3 to 5 or 6 days. Ultrastructural modifications are also initiated by insulin; numerous glycogen particles appear after 24 h, in between the cisternae of the proliferated smooth endoplasmic reticulum. After 48 h, large amounts of glycogen are stored, and numerous polysomes are present. A small number of cells showed an increased synthesis of lipid droplets in the lumen of the smooth endoplasmic reticulum and form liposomes at the same time. After 72 h, cytolysomes filled with glycogen develop, simulating glycogenosis type II. Simultaneously, microtubules and microfilaments, closely related to numerous polysomes, appear in cytoplasmic extensions constituting undulating membranes. The biochemical data demonstrate that, in the absence of insulin, a high concentration of glucose stimulates glycogenesis and hinders glycogenolysis. This effect of glucose on polysaccharide synthesis is progressively lost. The addition of insulin to the culture induces after 48 and 72 h, a three- to fivefold increase of the glucose incorporation into glycogen, as compared to the controls. The presence of insulin is required to maintain the hepatocyte's capacity to store glycogen. Glycogen synthetase is converted into its active form under the influence of glucose. Insulin increases the rate of activation.     

A cholesterol-enriched diet enhances egg production and egg viability without altering cholesterol Content of biological membranes in the copepod Acartia hudsonica

Copepods may lack the capacity for de novo synthesis of cholesterol, while at the same time their dietary levels of sterol vary. We tested the hypothesis that copepods maintain the cholesterol contents of their biological membranes despite varying dietary levels of cholesterol. Acartia hudsonica were acclimated for 5 d to phytoplankton alone or phytoplankton supplemented with cholesterol, at a level sufficient to induce a maximal response on egg production rates. Biological membranes were prepared from the copepods and cholesterol contents assayed. Egg production and hatch rates were measured (the former to confirm that supplemented cholesterol was being assimilated). Analyses of marker enzymes indicate that the majority of membrane-associated cholesterol in the copepod resides in the plasma membrane. In membranes fractions, cholesterol normalized to protein or activity of Na+/K+-ATPase is not significantly different for supplemented and unsupplemented groups (29 and 33 mu g cholesterol mg(-1) protein, respectively; 0.24 and 0.25 mg cholesterol U(-1) Na+/K+-ATPase, respectively). At the same time, acclimating animals to a diet enriched with cholesterol enhances egg production by up to 1.8-fold and egg viability by 1.5-fold. We conclude that a cholesterol-enriched diet stimulates both egg production and hatching rates without altering cholesterol contents of plasma membranes in the copepod A. hudsonica.     

Comparison of two hydrodensitometric methods for estimating percent body fat.

This study compared the two following hydrodensitometric methods for estimating percent body fat (%BF): 1) estimation of residual volume (RV) by helium dilution before and after measurement of immersed mass at RV, and 2) determination of immersed mass at a comfortable level of expiration (approximately functional residual capacity) with measurement of the associated gas volume by oxygen dilution. Twelve men [27.9 +/- 7.5 (SD) yr; 79.32 +/- 12.79 kg; 180.5 +/- 9.9 cm] were tested for %BF via both methods on each of two separate visits within 3 days by using a counterbalanced design. The two helium dilution measurements yielded a technical error of measurement of 0.2% BF and an intraclass correlation coefficient of 0.999. Corresponding values for the oxygen dilution method were 0.4% BF and 0.999, respectively. There was no difference (P = 0.80) between the helium dilution (16.9 +/- 9.3% BF) and oxygen dilution (16.9 +/- 9.4% BF) methods, and the individual differences ranged from -0.7 to 0.6% BF. The interclass correlation coefficient between the two methods was 0.999 with a SE of estimate of 0.4% BF. Whereas both methods were precise and reliable and yielded similar results, the oxygen dilution technique was more expedient and was preferred by the subjects because they were not required to exhale to RV.     

Influence of late season fire on early successional vegetation of an Oklahoma prairie

Abstract. The study of vegetation dynamics in tallgrass prairie in response to fire has focused on dormant season fire in late successional prairies. Our objective was to determine if late season fire of varying frequency results in divergent successional patterns in an early successional tallgrass prairie disturbed by grazing and cultivation. Specifically, we evaluated the influence of late‐summer fires of varying frequency on community composition and species richness. We collected vegetation and environmental data on two sites burned in the late growing‐season at varying frequencies. These communities differed in composition depending primarily on edaphic factors, time since the last burn, and year‐to‐year variation. We interpret the time effect as related to changes in species composition accompanying plant succession that followed disturbance either from cropping and heavy grazing on the loamy site or heavy grazing on the shallow site. Other unidentified factors also have a role in vegetation dynamics on this prairie. Community composition and species richness were not consistently responsive to frequency of growing‐season fires.     

Haptoglobin and CCR2 receptor expression in ovarian cancer cells that were exposed to ascitic fluid: Exploring a new role of haptoglobin in the tumoral microenvironment

Haptoglobin (Hp) is an acute-phase protein that is produced by the liver to capture the iron that is present in the blood circulation, thus avoiding its accumulation in the blood. Moreover, Hp has been detected in a wide variety of tissues, in which it performs various functions. In addition, this protein is considered a potential biomarker in many diseases, such as cancer, including ovarian carcinoma; however, its participation in the cancerous processes has not yet been determined. The objective of this work was to demonstrate the expression of Hp and its receptor CCR2 in the ovarian cancer cells and its possible involvement in the process of cell migration through changes in the rearrangement of the actin cytoskeleton using western blot and wound-healing assays and confirming by confocal microscopy. Ovarian cancer cells express both Hp and its receptor CCR2 but only after exposure to ascitic fluid, inducing moderated cell migration. However, when the cells are exposed to exogenous Hp, the expression of CCR2 is induced together with drastic changes in the actin cytoskeleton rearrangement. At the same time, Hp induced cell migration in a much more efficient manner than did ascitic fluid. These effects were blocked when the CCR2 synthetic antagonist RS102895 was used to pretreat the cells. These results suggest that Hp-induced changes in the cell morphology, actin cytoskeleton structure, and migration ability of tumor cells, is possibly “preparing” these cells for the potential induction of the metastatic phenotype.