Stimulation of glucose utilization and lactate production in cultured human fibroblasts by thyroid hormone

Human dermal fibroblasts were obtained by harvesting outgrowing cells from the dermal tissue explants and cultured in Dulbecco's modified Eagle medium containing 10% fetal calf serum. After the cells reached confluency, culture was continued in the medium containing calf serum which was deprived of thyroid hormone by the treatment with activated charcoal. These fibroblasts were responsive to exogeneously added thyroid hormone (triiodothyronine) at physiological concentrations, resulting in enhanced utilization of glucose and production of lactate. This stimulation by thyroid hormone was dependent upon the length of exposure to the hormone and its concentration.The hormone did not show any effects on cellular DNA and protein content. The experimental system described above seems to be easy to reconstitute and should be useful for the elucidation of the mechanism of thyroid hormone action.     

Interaction between the canine diaphragm and intercostal muscles in lung expansion.

Changes in intrathoracic pressure produced by the various inspiratory intercostals are essentially additive, but the interaction between these muscles and the diaphragm remains uncertain. In the present study, this interaction was assessed by measuring the changes in airway opening (DeltaPao) or transpulmonary pressure (DeltaPtp) in vagotomized, phrenicotomized dogs during spontaneous inspiration (isolated intercostal contraction), during isolated rectangular or ramp stimulation of the peripheral ends of the transected C(5) phrenic nerve roots (isolated diaphragm contraction), and during spontaneous inspiration with superimposed phrenic nerve stimulation (combined diaphragm-intercostal contraction). With the endotracheal tube occluded at functional residual capacity, DeltaPao during combined diaphragm-intercostal contraction was nearly equal to the sum of the DeltaPao produced by the two muscle groups contracting individually. However, when the endotracheal tube was kept open, DeltaPtp during combined contraction was 123% of the sum of the individual DeltaPtp (P < 0.001). The increase in lung volume during combined contraction was also 109% of the sum of the individual volume increases (P < 0.02). Abdominal pressure during combined contraction was invariably lower than during isolated diaphragm contraction. It is concluded, therefore, that the canine diaphragm and intercostal muscles act synergistically during lung expansion and that this synergism is primarily due to the fact that the intercostal muscles reduce shortening of the diaphragm. When the lung is maintained at functional residual capacity, however, the synergism is obscured because the greater stiffness of the rib cage during diaphragm contraction enhances the DeltaPao produced by the isolated diaphragm and reduces the DeltaPao produced by the intercostal muscles.     

Does the VP1 gene of foot-and-mouth disease virus behave as a molecular clock?

Summary We have carried out a phylogenetic study of the evolution of the VP1 gene sequence from different serological types and subtypes of foot-and-mouth disease virus (FMDV). The maximum-likelihood method developed by Hasegawa and co-workers (Hasegawa et al. 1985) for the estimation of evolutionary parameters and branching dates has been used to decide between alternative models of evolution: constant versus variable rates. The results obtained indicate that a constant rate model, i.e., a molecular clock, seems to be the most plausible one. However, additional information suggests the possibility that the appearance of serotype CS has been accompanied by an episode of rapid evolution (Villaverde et al. 1991). We discuss the possibility that this evolution of RNA viruses was due to episodic positive Darwinian selection, which would have helped the new variant to escape the immunogenic pressure from the hosts. Offprint requests to: A. Moya     

On the biosynthesis of biotin in Achromobacter IVSW a reinvestigation

[3-¹⁴C, ³⁵S]-L-cysteine was tested as precursor of biotin in Achromobacter IVSW. No significant incorporation was observed, in contradiction with the data previously reported. On the other hand, Achromobacter IVSW converts [³H, ¹⁴C]-dethiobiotin into biotin. This suggests that biotin is biosynthesized in Achromobacter according to the classical dethiobiotin pathway.     

Four new species of Cayaponia (Cucurbitaceae) from Brazil and Bolivia

Four new species ofCayaponia are described and illustrated: three from Brazil (C. cogniauxiana, C. nitida andC. rugosa) and one from Brazil and Bolivia (C. ferruginea).     

Distribution and Numbers of Pygmies in Central African Forests

Pygmy populations occupy a vast territory extending west-to-east along the central African belt from the Congo Basin to Lake Victoria. However, their numbers and actual distribution is not known precisely. Here, we undertake this task by using locational data and population sizes for an unprecedented number of known Pygmy camps and settlements (n = 654) in five of the nine countries where currently distributed. With these data we develop spatial distribution models based on the favourability function, which distinguish areas with favourable environmental conditions from those less suitable for Pygmy presence. Highly favourable areas were significantly explained by presence of tropical forests, and by lower human pressure variables. For documented Pygmy settlements, we use the relationship between observed population sizes and predicted favourability values to estimate the total Pygmy population throughout Central Africa. We estimate that around 920,000 Pygmies (over 60% in DRC) is possible within favourable forest areas in Central Africa. We argue that fragmentation of the existing Pygmy populations, alongside pressure from extractive industries and sometimes conflict with conservation areas, endanger their future. There is an urgent need to inform policies that can mitigate against future external threats to these indigenous peoples’ culture and lifestyles.     

PHENOTYPIC PLASTICITY INDUCED IN TRANSPLANT EXPERIMENTS IN A MUTUALISTIC ASSOCIATION BETWEEN THE RED ALGA JANIA ADHAERENS (RHODOPHYTA,CORALLINALES) AND THE SPONGE HALICLONA CAERULEA (PORIFERA: HAPLOSCLERIDA): MORPHOLOGICAL RESPONSES OF THE ALGA1

The association between the red macroalga Jania adhaerens J. V. Lamour. and the sponge Haliclona caerulea is the most successful life‐form between 2 and 4 m depth in Mazatlán Bay (Mexican Pacific). J. adhaerens colonizes the rocky intertidal area and penetrates into deeper areas only when it lives in association with H. caerulea. The aposymbiotic form of the sponge has not been reported in the bay. To understand the ecological success of this association, we examined the capacity of J. adhaerens to acclimate in Mazatlán Bay using transplant experiments. The transplanted aposymbiotic J. adhaerens did not survive the first 2 weeks; however, J. adhaerens when living in association with H. caerulea, acclimated easily to depth, showing no sign of mortality during the 103 d of the experiment. We conclude that the ability of J. adhaerens to colonize in deeper areas in this hydrodynamic environment may in part rely on the protection provided by the sponge to the algal canopy. Both species contribute to the shape of the associated form. Nevertheless, the morphological variation in the association appears to be dominated by the variation in J. adhaerens canopy to regulate pigment self‐shading under light‐limited conditions and/or tissue resistance under high hydrodynamics. Consequently, our results are consistent with light as the abiotic controlling factor, which regulates the lower depth distribution of the association in Mazatlán Bay, through limiting the growth rate of J. adhaerens. Hydrodynamics may determine the upper limit of the association by imposing high mass losses.