High juvenile mortality in cheetahs (Acinonyx jubatus) and its consequences for maternal care

Juvenile mortality in cheetahs was found to be extremely high compared to other large mammals, with approximately 72.2% of litters dying before they emerged from the lair at eight weeks of age. An average of 83.3% of cubs alive at emergence died by adolescence at 14 months of age, thus cheetah cubs were estimated to have only a 4.8% chance of reaching independence at birth. The instantaneous rate of mortality was highest immediately after cubs emerged from the lair. Before emergence, lion predation was the major source of this mortality, although some cubs died from starvation after they were abandoned by their mothers, or as a result of grass fires and inclement weather. After emergence, predation again accounted for virtually all cub mortality, with lions and spotted hyaenas taking approximately the same proportion of cubs. Overall predation accounted for 73.2% of cheetah cub deaths in this study, with 78.2% of these being killed by lions. The extent of maternal care, in the form of vigilance and antipredator behaviour, mirrored cub susceptibility to mortality and, in the case of vigilance, possibly also starvation. The probability of a cheetah mother responding aggressively to a predator was found also to depend on the species of predator. This study highlights the importance of the influence of juvenile mortality on patterns of parental care.     

Crystallization and preliminary crystallographic studies of the precursor and mature forms of a neutral lipase from the fungus Rhizopus delemar

A neutral lipase from the filamentous fungus Rhizopus delemar has been crystallized in both its proenzyme and mature forms. Although the latter crystallizes readily and produces a variety of crystal forms, only one was found to be suitable for X-ray studies. It is monoclinic (C2, a = 92.8 Å, b = 128.9 Å, c = 78.3 Å, β = 135.8) with two molecules in the asymmetric unit related by a noncrystallographic diad. The prolipase crystals are orthorhombic (P2₁2₁2₁, with a = 79.8 Å, b = 115.2 Å, c = 73.0 Å) and also contain a pair of molecules in the asymmetric unit. Initial results of molecular replacement calculations using the refined coordinates of the related lipase from Rhizomucor miehei identified the correct orientations and positions of the protein molecules in the unit cells of crystals of both proenzyme and the mature form. © 1994 John Wiley & Sons, Inc.     

1.56 Å structure of mature truncated human fibroblast collagenase

The X-ray crystal structure of a 19 kDa active fragment of human fibroblast collagenase has been determined by the multiple isomorphous replacement method and refined at 1.56 Å resolution to an R-factor of 17.4%. The current structure includes a bound hydroxamate inhibitor, 88 waters and three metal atoms (two zincs and a calcium). The overall topology of the enzyme, comprised of a five stranded β-sheet and three α-helices, is similar to the thermolysin-like metalloproteinases. There are some important differences between the collagenase and thermolysin families of enzymes. The active site zinc ligands are all histidines (His-218, His-222, and His-228). The presence of a second zinc ion in a structural role is a unique feature of the matrix metalloproteinases. The binding properties of the active site cleft are more dependent on the main chain conformation of the enzyme (and substrate) compared with thermolysin. A mechanism of action for peptide cleavage similar to that of thermolysin is proposed for fibroblast collagenase. © 1994 Wiley-Liss, Inc.     

Mapping of Murine Fibroblast Growth Factor Receptors Refines Regions of Homology between Mouse and Human Chromosomes

The genes for the fibroblast growth factor receptors Fgfr2, Fgfr3, and Fgfr4 have been mapped in the mouse using an interspecific backcross mapping panel. The Fgfr loci map to previously defined regions of homology between human and mouse chromosomes and provide additional information regarding human/mouse comparative mapping.     

Nuclear and chloroplast transformation inChlamydomonas reinhardtii: strategies for genetic manipulation and gene expression

Transformation of the nuclear, chloroplast, and mitochondrial genomes can now be accomplished inChlamydomonas reinhardtii. Many biosynthetic pathways are carried out in the chloroplast, and efforts to manipulate these pathways will require that gene products be directed to this compartment. Chloroplast proteins are encoded in either the chloroplast or nuclear genome. In the latter case they are synthesized in the cytoplasm and imported post-translationally into the chloroplast. Thus, strategies for expressing foreign genes or overexpressing endogenous genes whose products reside in the chloroplast could involve either genome. This paper reviews the present status of transformation methodology for the nuclear and chloroplast genomes inChlamydomonas. Considerations for expressing gene products in the chloroplast are discussed. Experimental evidence for homologous recombination during transformation of the nuclear genome is presented.     

Analysis of the frequency of inheritance of transposed Ds elements in Arabidopsis after activation by a CaMV 35S promoter fusion to the Ac transposase gene

The Ac/Ds transposon system of maize shows low activity in Arabidopsis. However, fusion of the CaMV 35S promoter to the transposase gene (35S::TPase) increases the abundance of the single Ac mRNA encoded by Ac and increases the frequency of Ds excision. In the experiments reported here it is examined whether this high excision frequency is associated with efficient re-insertion of the transposon. This was measured by using a Ds that carried a hygromycin resistance gene (HPT) and was inserted within a streptomycin resistance gene (SPT). Excision of Ds therefore gives rise to streptomycin resistance, while hygromycin resistance is associated with the presence of a transposed Ds or with retention of the element at its original location. Self-fertilisation of most individuals heterozygous for Ds and 35S::TPase produced many streptomycin-resistant (strep^r) progeny, but in many of these families a small proportion of strep^r seedlings were also resistant to hygromycin (hyg^r). Nevertheless, 70% of families tested did give rise to at least one strep^r, hyg^r seedling, and over 90% of these individuals carried a transposed Ds. In contrast, the Ac promoter fusion to the transposase gene (Ac::TPase) produced fewer strep^rhyg^r progeny, and only 53% of these carried a transposed Ds. However, a higher proportion of the strep^r seedlings were also hyg^r than after activation by 35S::TPase. We also examined the genotype of strep^r, hyg^r seedlings and demonstrated that after activation by 35S::TPase many of these were homozygous for the transposed Ds, while this did not occur after activation by Ac::TPase. From these and other data we conclude that excisions driven by 35S::TPase usually occur prior to floral development, and that although a low proportion of strep^r progeny plants inherit a transposed Ds, those that do can be efficiently selected with an antibiotic resistance gene contained within the element. Our data have important implications for transposon tagging strategies in transgenic plants and these are discussed.     

Demography and social structure of one group of muriquis (Brachyteles arachnoides)

We monitored one group of muriquis, or woolly spider monkeys (Brachyteles arachnoides), over a 9-year period at Fazenda Montes Claros, Minas Gerais, Brazil. The group grew from 22 to 42 individuals due to the births of 21 surviving infants. Eight immigrations involving immature females were offset by emigrations and disappearances. The home range of the group expanded as the group size increased. The group traveled as a cohesive unit during the first 6 years of the study, but recently it has begun to show greater tendencies to fission temporarily into smaller subgroups. Six adult males from the other muriqui group at this site have simultaneously increased their associations with the main study group. These observations indicate that the group is in a state of transition which may lead, ultimately, either to its division into two smaller units or to a more fluid social structure.     

Site-directed mutagenesis of the yeast PRP20/1SRM1 gene reveals distinct activity domains in the protein product

Prp20/Srm1, a homolog of the mammalian protein RCC1 in Saccharomyces cerevisiae, binds to double-stranded DNA (dsDNA) through a multicomponent complex in vitro. This dsDNA-binding capability of the Prp20 complex has been shown to be cell-cycle dependent; affinity for dsDNA is lost during DNA replication. By analyzing a number of temperature sensitive (ts) prp20 alleles produced in vivo and in vitro, as well as site-directed mutations in highly conserved positions in the imperfect repeats that make up the protein, we have determined a relationship between the residues at these positions, cell viability, and the dsDNA-binding abilities of the Prp20 complex. These data reveal that the essential residues for Prp20 function are located mainly in the second and the third repeats at the amino-terminus and the last two repeats, the seventh and eighth, at the carboxyl-terminus of Prp20. Carboxyl-terminal mutations in Prp20 differ from amino-terminal mutations in showing loss of dsDNA binding: their conditional lethal phenotype and the loss of dsDNA binding affinity are both suppressible by overproduction of Gsp1, a GTP-binding constituent of the Prp20 complex, homologous to the mammalian protein TC4/Ran. Although wild-type Prp20 does not bind to dsDNA on its own, two mutations in conserved residues were found that caused the isolated protein to bind dsDNA. These data imply that, in situ, the other components of the Prp20 complex regulate the conformation of Prp20 and thus its affinity for dsDNA. Gsp1 not only influences the dsDNA-binding ability of Prp20 but it also regulates other essential function(s) of the Prp20 complex. Overproduction of Gsp1 also suppresses the lethality of two conditional mutations in the penultimate carboxyl-terminal repeat of Prp20, even though these mutations do not eliminate the dsDNA binding activity of the Prp20 complex. Other site-directed mutants reveal that internal and carboxyl-terminal regions of Prp20 that lack homology to RCC1 are dispensable for dsDNA binding and growth.