Complex expression of the genes coding for plasminogen activators and their inhibitors in HeLa-smooth muscle cell hybrids.

As cells progress through the multistep process of neoplastic transformation, they eventually acquire the property of invasive behavior. Although both plasminogen activators (PA) and their inhibitors (PAI) contribute to this process, their regulation in normal and transformed cells remains poorly defined. Because somatic cell hybrids provide useful tools for examining the transformation pathway, tumorigenic and invasive HeLa cells were fused with human normal vascular smooth muscle cells and tested for invasion-related parameters, including the expression of PA and PAI genes, and matrix degradation. Both parental cell lines produced large amounts of PAI activities with no detectable PA in either cellular or secreted form. Opposite findings were obtained with the hybrid cell lines, which demonstrated the presence of receptor-bound and secreted PA but absence of enzymatically measurable PAI activities. Both urokinase-type and tissue-type PA were found in cell-associated and secreted form in the hybrid cells. In addition, expression of the urokinase-type PA receptor gene was found in the three hybrid cells and the vascular smooth muscle cells but not in the HeLa cells. Expression of active, receptor-bound and secreted PA provided the nontumorigenic hybrid cells with the enzymatic tools to degrade extracellular proteins in a plasminogen-dependent manner. Thus, the hybrid cells lost tumorigenicity while retaining the tissue-degrading capability of HeLa cells. These hybrid cell lines should prove to be important reagents for investigating the complex regulatory control of PA and PAI gene expression.     

Ganglion cells of chicken retina possess nicotinic rather than muscarinic acetylcholine receptors

Chicken retinas were exposed to intravitreal kainic acid to destroy amacrine and bipolar cells at low concentrations, and horizontal cells at high concentrations in addition. Ganglion cells were destroyed by intravitreal injections of colchicine. Low doses of kainic acid reduced the number of binding sites for both [³H]quinuclidinyl benzilate (muscarinic acetylcholine receptors) and N-[propionyl ³H]-bungarotoxin (nicotinic acetylcholine receptors), with little additional loss at higher doses. In contrast, colchicine reduced the number of binding sites for N-[propionyl-³H]-bungarotoxin, but had little or no effect on the number of binding sites for [³H]quinuclidinyl benzilate. These results are consistent with the idea that, in chicken retina, cholinergic amacrine cells make contact with ganglion cell dendrites at sites which possess mainly nicotinic acetylcholine receptors, while both types of receptor are involved in interactions between amacrine cells and perhaps bipolar cells.     

Parallel episodes of phyletic dwarfism in callitrichid and cheirogaleid primates

The Callitrichidae are the smallest anthropoids, whereas the Cheirogaleidae include the smallest of all primates. Using species‐level analyses, we show that these are derived conditions; both neonatal and adult body mass decreased in a gradual, phyletic manner in parallel across callitrichids, and across cheirogaleids. We identify lineages with particularly rapid decreases and highlight the pygmy marmoset, Callithrix pygmaea, as a phenotypic outlier. The life‐history traits associated with body‐mass reduction in each clade suggest that the convergent evolution of small body size was achieved by changes in different ontogenetic stages. Body‐size reduction in callitrichids appears to be almost exclusively due to alterations in prenatal growth rate, whereas body‐size reduction in cheirogaleids may have been largely due to reduced duration of growth phases. Finally, we use these results to discuss some of the debates surrounding the evolution of Homo floresiensis and suggest potential parallels between the evolution of H. floresiensis and callitrichids.     

Microcephaly genes and the evolution of sexual dimorphism in primate brain size

Microcephaly genes are amongst the most intensively studied genes with candidate roles in brain evolution. Early controversies surrounded the suggestion that they experienced differential selection pressures in different human populations, but several association studies failed to find any link between variation in microcephaly genes and brain size in humans. Recently, however, sex‐dependent associations were found between variation in three microcephaly genes and human brain size, suggesting that these genes could contribute to the evolution of sexually dimorphic traits in the brain. Here, we test the hypothesis that microcephaly genes contribute to the evolution of sexual dimorphism in brain mass across anthropoid primates using a comparative approach. The results suggest a link between selection pressures acting on MCPH1 and CENPJ and different scores of sexual dimorphism.     

Altering Visual Perception Abnormalities: A Marker for Body Image Concern

The body image concern (BIC) continuum ranges from a healthy and positive body image, to clinical diagnoses of abnormal body image, like body dysmorphic disorder (BDD). BDD and non-clinical, yet high-BIC participants have demonstrated a local visual processing bias, characterised by reduced inversion effects. To examine whether this bias is a potential marker of BDD, the visual processing of individuals across the entire BIC continuum was examined. Dysmorphic Concern Questionnaire (DCQ; quantified BIC) scores were expected to correlate with higher discrimination accuracy and faster reaction times of inverted stimuli, indicating reduced inversion effects (occurring due to increased local visual processing). Additionally, an induced global or local processing bias via Navon stimulus presentation was expected to alter these associations. Seventy-four participants completed the DCQ and upright-inverted face and body stimulus discrimination task. Moderate positive associations were revealed between DCQ scores and accuracy rates for inverted face and body stimuli, indicating a graded local bias accompanying increases in BIC. This relationship supports a local processing bias as a marker for BDD, which has significant assessment implications. Furthermore, a moderate negative relationship was found between DCQ score and inverted face accuracy after inducing global processing, indicating the processing bias can temporarily be reversed in high BIC individuals. Navon stimuli were successfully able to alter the visual processing of individuals across the BIC continuum, which has important implications for treating BDD.     

Trans-specific evolution of opsin alleles and the maintenance of trichromatic colour vision in Callitrichine primates

Many New World (NW) primates possess a remarkable polymorphism in an X-linked locus, which encodes for the visual pigments (opsins) used for colour vision. Females that are heterozygous for opsin alleles of different spectral sensitivity at this locus have trichromatic colour vision, whereas homozygous females and males are dichromatic, with poor colour discrimination in the red-green range. Here we describe an extensive survey of allelic variation in both exons and introns at this locus within and among species of the Callitrichines (marmosets and tamarins). All five genera of Callitrichines have the X-linked polymorphism, and only the three functional allelic classes described previously (with maximum wavelength sensitivities at about 543 nm, 556 nm and 563 nm) were found among the 16 species and 233 or more X-chromosomes sampled. In spite of the homogenizing effects of gene conversion, phylogenetic analyses provide direct evidence for trans-specific evolution of alleles over time periods of at least 5-6 million years, and up to 14 million years (estimated from independent phylogenies). These conclusions are supported by the distribution of insertions and deletions in introns. The maintenance of polymorphism over these time periods requires an adaptive explanation, which must involve a heterozygote advantage for trichromats. The lack of detection of alleles that are recombinant for spectral sensitivity suggests that such alleles are suboptimal. The two main hypotheses for the selective advantage of trichromacy in primates are frugivory for ripe fruits and folivory for young leaves. The latter can be discounted in Callitrichines, as they are not folivorous.