Infant Mortality Risk and Paternity Certainty Are Associated with Postnatal Maternal Behavior toward Adult Male Mountain Gorillas (Gorilla beringei beringei)

Sexually selected infanticide is an important source of infant mortality in many mammalian species. In species with long-term male-female associations, females may benefit from male protection against infanticidal outsiders. We tested whether mountain gorilla (Gorilla beringei beringei) mothers in single and multi-male groups monitored by the Dian Fossey Gorilla Fund’s Karisoke Research Center actively facilitated interactions between their infants and a potentially protective male. We also evaluated the criteria mothers in multi-male groups used to choose a preferred male social partner. In single male groups, where infanticide risk and paternity certainty are high, females with infants <1 year old spent more time near and affiliated more with males than females without young infants. In multi-male groups, where infanticide rates and paternity certainty are lower, mothers with new infants exhibited few behavioral changes toward males. The sole notable change was that females with young infants proportionally increased their time near males they previously spent little time near when compared to males they had previously preferred, perhaps to encourage paternity uncertainty and deter aggression. Rank was a much better predictor of females’ social partner choice than paternity. Older infants (2–3 years) in multi-male groups mirrored their mothers’ preferences for individual male social partners; 89% spent the most time in close proximity to the male their mother had spent the most time near when they were <1 year old. Observed discrepancies between female behavior in single and multi-male groups likely reflect different levels of postpartum intersexual conflict; in groups where paternity certainty and infanticide risk are both high, male-female interests align and females behave accordingly. This highlights the importance of considering individual and group-level variation when evaluating intersexual conflict across the reproductive cycle.     

Mitochondrial porin of Neurospora crassa: cDNA cloning, in vitro expression and import into mitochondria.

cDNA encoding porin of Neurospora crassa, the major protein component of the outer mitochondrial membrane, was isolated and the nucleotide sequence was determined. The deduced protein sequence consists of 283 amino acids (29,979 daltons) and shows sequence homology of around 43% to yeast porin; however, no significant homology to bacterial porins was apparent. According to secondary structure predictions, mitochondrial porin consists mainly of membrane-spanning sided beta-sheets. Porin was efficiently synthesized in vitro from the cDNA; this allowed us to study in detail its import into mitochondria. Thereby, three characteristics of import were defined: (i) import depended on the presence of nucleoside triphosphates; (ii) involvement of a proteinaceous receptor-like component on the surface of the mitochondria was demonstrated; (iii) insertion into the outer membrane was resolved into at least two distinct steps: specific binding to high-affinity sites and subsequent assembly to the mature form.     

High-affinity binding sites involved in the import of porin into mitochondria.

The specific recognition by mitochondria of the precursor of porin and the insertion into the outer membrane were studied with a radiolabeled water-soluble form of porin derived from the mature protein. High-affinity binding sites had a number of 5-10 pmol/mg mitochondrial protein and a ka of 1-5 X 10(8) M-1. Binding was abolished after trypsin pretreatment of mitochondria indicating that binding sites were of protein-aceous nature. Specifically bound porin could be extracted at alkaline pH but not by high salt and was protected against low concentrations of proteinase K. It could be chased to a highly protease resistant form corresponding to mature porin. High-affinity binding sites could be extracted from mitochondria with detergent and reconstituted in asolectin-ergosterol liposomes. Water-soluble porin competed for the specific binding and import of the precursor of the ADP/ATP carrier, an inner membrane protein. We suggest that (i) binding of precursors to proteinaceous receptors serves as an initial step for recognition, (ii) the receptor for porin may also be involved in the import of precursors of inner membrane proteins, and (iii) interaction with the receptor triggers partial insertion of the precursor into the outer membrane.     

Novel Pathway of Toluene Catabolism in the Trichloroethylene-Degrading Bacterium G4

o-Cresol and 3-methylcatechol were identified as successive transitory intermediates of toluene catabolism by the trichloroethylene-degrading bacterium G4. The absence of a toluene dihydrodiol intermediate or toluene dioxygenase and toluene dihydrodiol dehydrogenase activities suggested that G4 catabolizes toluene by a unique pathway. Formation of a hybrid species of ¹⁸O- and ¹⁶O-labeled 3-methylcatechol from toluene in an atmosphere of ¹⁸O₂ and ¹⁶O₂ established that G4 catabolizes toluene by successive monooxygenations at the ortho and meta positions. Detection of trace amounts of 4-methylcatechol from toluene catabolism suggested that the initial hydroxylation of toluene was not exclusively at the ortho position. Further catabolism of 3-methylcatechol was found to proceed via catechol-2,3-dioxygenase and hydroxymuconic semialdehyde hydrolase activities.     

Dopamine- and octopamine-sensitive adenylate cyclase in the brain of adultCulex pipiens mosquitoes

The effects of dopamine and octopamine on adenylate cyclase activity were studied on the head homogenate of adult Culex pipiens mosquitoes in vitro. Both dopamine and octopamine were shown to increase the cyclic AMP content in the homogenate. The antagonist haloperidol blocked the production of cyclic AMP induced from dopamine but had no effect on the production of cyclic AMP induced by octopamine at the concentrations tested. The opiate agonist etorphine was ineffective at reducing cyclic AMP levels induced by either dopamine or octopamine at the concentrations tested.     

Morphology of the differentiation and maturation of LLC-PK1 epithelia

In the present study, a stereologic approach was utilized to quantitatively assess morphological changes during the differentiation of LLC-PK1 cells into an epithelial membrane. This renal epithelial cell line has been described to undergo morphological changes during differentiation and maturation from subconfluent culture to a confluent epithelial layer. An increase in the number of apical microvilli, interpreted as an areal increase in this membrane domain was reported. This morphological differentiation was found to be accompanied by an increase in the expression of apical Na(+)-dependent hexose transport and the activities of certain brush border enzymes. Since no data are available that quantify the morphologic changes during LLC-PK1 differentiation, a quantitative morphologic-stereologic-investigation was performed for an early (6 days) and a late (12 days) state of confluence of LLC-PK1 monolayer cultures. The following morphological parameters were determined by light and electron microscopic morphometry: volume fractions (Vv) of nuclei, mitochondria, and lysosomes, and surface densities (Sv) of the apical and basolateral cell membrane domains. For the apical membrane surface, the microvillous fraction has been measured separately. Since the stereologic approach used in the present study allows the determination of absolute cell volumes, the absolute measures of organelle volumes (V) and membrane surfaces (S) per average cell can be calculated from volume and surface densities. Although no changes in cell density were found for 6 and 12 day old LLC-PK1 monolayers, indicating ceased cell proliferation due to contact inhibition, remarkable changes were found concerning the absolute cell volume and apical membrane surface. The observed increase in the apical cell surface was exclusively due to the enlarged microvillous surface fraction. This finding is in good agreement with the increased number of Na(+)-dependent hexose transporters as well as with the increased expression of apical membrane marker enzymes observed during the differentiation of LLC-PK1 monolayers.