The functional anatomy of the lower limb of the howler monkey (Alouatta caraya)

The howler monkey possesses unique anatomical adaptations associated with its arboreal habit. The behavioral elements are described by locomotor pattern, substrate, timing and rhythm of movement. The most significant motor adaptations are correlated clearly and directly with musculoskeletal features of the lower limb. The orientation of the joints within the limb, the shape of the joint surfaces, their bony environments, and the important planes of muscular control are the foundations for the observable locomotor behaviors.     

Altricial and precocial mammals: A model of neural and muscular development

This model of growth offers a quantitative definition for altricial and precocial newborns, makes muscular strength a benchmark for locomotor independence, and discriminates related genera as well as genera across major taxonomic divides. The model contrasts four theoretical conditions of the neonate (I, small brain, weak musculature; II, small brain, strong musculature; III, large brain, weak musculature; IV, large brain, strong musculature) with species from three orders of placental mammal. Each species exhibits a distinct mother-infant strategy from the altricial red panda cub (condition I) and the golden lion tamarin (condition III) to the precocial wildebeest calf (condition IV). The model proposes that early growth rates of brain and muscle correlate with nutrition, maternal effort during gestation and lactation, and parental care, whereas postnatal muscular growth correlates directly with adult body size and locomotor repertoire. An example of condition II (small brain, strong musculature) has not been found. This suggests that muscle does not grow in advance of the brain and that the brain acts as a pacemaker of growth. In order to increase our understanding of exotic species, noninvasive measures (body weight and length) and observations (opening of the eyes and ears, hair density, weaning, and the abilities to ther-moregulate and to move) should be supplemented with analysis of the differential tissue and organ growth. In both theoretical and practical ways analysis of deceased individuals contributes to the understanding of all species.     

Identification of the human papilloma virus-1a E4 gene products.

Antibodies prepared against a human papilloma virus-1 (HPV-1) E4/beta-galactosidase fusion protein identified several polypeptides in HPV-1, but not HPV-2 or 4, induced papillomas. The major E4 protein, that represented up to 30% of total cellular protein, was a 16/17-K doublet which was purified by column chromatography and analysed for amino acid content. A peptide derived by chymotryptic digestion was purified by h.p.l.c. and subjected to amino acid sequencing. The unique sequence obtained, Gly-His-Pro-Asp-Leu-Ser-Leu, identified the 16/17-K doublet as a product of the HPV-1 E4 gene region. Antibodies to both the E4/beta-galactosidase fusion protein and the 16/17-K doublet identified two smaller polypeptides (10/11-K) which may represent spliced products of E4. We propose that the products of the HPV-1 E4 gene region are not classical DNA tumor virus early proteins and suggest that they play a role in virus maturation.     

Purification of a serum factor which reverses dibutyryl cAMP induced differentiation

We have previously shown [Grabham et al. (1988) Expt. Eye Res. 47, 123-133] that the adenovirus 12 transformed human retinoblast cell line (Ad 12 HER 10), like a number of other cell types of neuroepithelial origin, can be induced to differentiate in response to exposure to dibutyryl cAMP, and that this differentiation can be rapidly reversed by foetal calf serum. We present data here to show that a single protein, which we have termed differentiation reversal factor (DRF) and have isolated from serum, is responsible for this activity. Following reversal by DRF the growth rate of these cells was shown to be stimulated in serum-free medium. Using ammonium sulphate fractionation, gel filtration chromatography (Ultrogel AcA44), anion exchange chromatography (DEAE cellulose) and preparative gel electrophoresis, DRF has been purified to homogeneity, as judged by polyacrylamide gel electrophoresis in the presence and absence of SDS. The protein has a mol. wt of 72,000 and appears to exist in vivo as a monomer. The concentration of DRF in serum is in the range 100-500 micrograms/ml and is capable of reversing cAMP-induced differentiation of various primary human neuroepithelial cells at physiological concentrations.     

Adaptive surface antigen variation in Mycoplasma bovis to the host immune response

Abstract The variability of predominant Mycoplasma bovis surface antigens in the presence of specific immune pressure was analyzed in an in vitro assay to determine if M. bovis could escape immune destruction. We have shown that serum antibodies from immunized or experimentally infected calves and monoclonal antibodies which specifically react with previously characterized or as yet undefined major M. bovis membrane surface proteins cause repression of expression or shortening of the target protein, or induce switching to expression of an antigenically distinct variant protein. We have further demonstrated that removal of the inducing antibody results in reversion to the original phenotype. These results suggest that the level of expression and the length of M. bovis surface antigens in the host is modulated by cognate antibodies. According to the surface antigenic variation systems, random selection of preexisting variants resistant to antibody-mediated inhibition or direct regulation of gene expression may be means by which this organism evades host immune defences.     

Mechanisms of species coexistence: a field test of theoretical models using intertidal snails

Competitor coexistence is often facilitated by spatial segregation. Traditionally, spatial segregation is predicted to occur when species differ in the habitat in which they are either superior at competing for resources or less susceptible to predation. However, predictions from a behavioural model demonstrate that spatial segregation and coexistence can also occur in the absence of such interspecific trade‐offs in competitive ability and vulnerability to predation. Unlike other models of competitor coexistence this model predicts that when species rank both habitat productivity and ‘riskinesses’ similarly, but differ slightly in their habitat‐specific vulnerabilities to predators, they will tend to segregate across habitats, with the species experiencing the higher ratio of mortality risk across the habitats occurring primarily in the safer habitat. Here, we investigate the hypothesis that intraspecific trade‐offs between resource availability and mortality risk can lead to spatial segregation of competing species by (1) documenting the spatial (i.e. intertidal) distribution of two marine snails, Littorina sitkana and L. subrotundata and (2) performing field experiments to quantify growth and mortality rates of each species at ‘low’ and ‘high’ intertidal heights. Our results indicate that both species agree on the rankings of habitat riskiness and productivity, experiencing higher predation and higher growth in low‐ than in high‐intertidal habitats. However, L. sitkana and L. subrotundata experienced differences in their habitat‐specific mortality risks and growth rates. Despite both species being similarly at risk of predation in high‐intertidal habitats (where mortality was lower), L. subrotundata was subject to significantly higher mortality than L. sitkana at the low‐intertidal height. In contrast, growth rate differences between habitats were greater for L. sitkana than for L. subrotundata. Whereas both species grew at the same rate at the high‐intertidal level (where growth was lower), L. sitkana individuals grew more rapidly than L. subrotundata snails at the low‐intertidal level. As predicted by the behavioural model, the species that experienced the higher ratio of mortality across habitats (i.e. L. subrotundata) occurred exclusively in the safer, high‐intertidal habitat. Taken together, these results provide support for the hypothesis that spatial segregation, and potentially competitor coexistence, can occur in the absence of interspecific trade‐offs in resource acquisition ability or vulnerability to predation.     

Folded Structures in Protonated Reduced Dipeptides

Reduced dipeptides with the general formula RCO-Xaa- rXbb-N⁺HR′R′′ (rXbb, reduced analogue of residue Xbb: NH-C^α HR¹ -C_r H₂) are shown to adopt a folded conformation in solution and in the solid state. The protonated reduced amide bond is an active proton donor capable of interacting with a peptide carbonyl to give a strong hydrogen bond topologically equivalent to the i+2 or i+3? i interaction. The resulting conformation is similar to the γ- or β-turn structure found in peptides and proteins.     

Direct ex vivo simian immunodeficiency virus (SIV)-specific cytotoxic activity detected from small intestine intraepithelial lymphocytes of SIV-infected macaques at an advanced stage of infection.

Human immunodeficiency virus (HIV) induces a profound disorganization of the lymphoid tissues with marked abnormalities of the immune system at the terminal stage of infection. Since the digestive mucosal immune system is by far the largest lymphoid organ of the body, we attempted to evaluate its functional activity in advanced stages of simian immunodeficiency virus (SIV) infection in the SIV-macaque model of HIV infection. Two chronically intravenously SIV-infected macaques, including one at the AIDS stage, were studied. Intestinal intraepithelial lymphocytes (IEL) were isolated, analyzed, and compared to lymphocytes obtained from blood, spleen, and different lymph nodes: IEL were predominantly CD8+ T lymphocytes expressing the alphaE beta7 integrin and lacking the CD28 coactivatory molecule. A direct ex vivo SIV-specific cytotoxic activity was prominently found in the IEL of both macaques and was weaker or absent in the other sites. To our knowledge, this is the first report of SIV-specific cytotoxic activity from small intestine IEL in SIV-infected macaques. Considering the high similitude of the SIV-macaque model with the HIV infection in humans, these results may be highly important for the pathogenesis of HIV infection and more generally important for the characterization and function of digestive CD8+ IEL population.