Accommodating unmodeled heterogeneity in double-observer distance sampling surveys.

Mark-recapture models applied to double-observer distance sampling data neglect the information on relative detectability of objects contained in the distribution of observed distances. A difference between the observed distribution and that predicted by the mark-recapture model is symptomatic of a failure of the assumption of zero correlation between detection probabilities implicit in the mark-recapture model. We develop a mark-recapture-based model that uses the observed distribution to relax this assumption to zero correlation at only one distance. We demonstrate its usefulness in coping with unmodeled heterogeneity using data from an aerial survey of crabeater seals in the Antarctic.

Antibodies elicited by influenza virus hemagglutinin fail to bind to synthetic peptides representing putative antigenic sites.

A number of peptides of the hemagglutinin (HA) of X-31 influenza virus have been synthesised. The amino acid sequences of some of these peptides represent regions of HA which have been postulated [Wiley et al., Nature, Lond. 289, 373-378 (1981)] to form the antigenic sites of this molecule. Animals were immunized with free peptide or peptide conjugated to a carrier and the resulting antisera examined for their capacities to bind to homologous peptide, whole HA, reduced and alkylated HA, and intact virus. Not all peptides examined in this way were immunogenic. Only antibodies raised against the C-terminus of HA1 peptide displayed binding to virus. This antiserum bound to the intact HA but not to the reduced and alkylated form of the molecule. These results raise questions as to the feasibility of using synthetic peptides of the influenza HA in short linear sequences to elicit neutralising antibody.

Purification of synthetic oligodeoxyribonucleotides by ion-exchange high-performance liquid chromatography.

Synthetic oligodeoxyribonucleotides ranging from 11 to 37 nucleotides in length and with varying base compositions, prepared by both the phosphotriester and phosphite procedures, have been purified by ion-exchange high-performance liquid chromatography on Whatman Partisil 10/SAX columns using phosphate buffer gradients. The effects of different buffer systems on elution times and resolution have been evaluated. Oligomer composition and length had a marked effect on the resolution achieved. In general the use of formamide buffers gave the best results, particularly in the case of 2'-deoxyguanosine-rich sequences. These methods have also been successfully applied to the purification of mixtures of synthetic oligodeoxynucleotides.

Synthetic ovine corticotropin-releasing factor stimulates adrenocorticotropin release in the ovine fetus over the last fifth of gestation.

Synthetic ovine corticotropin-releasing factor (0.1-1.0 micrograms) was injected intravenously to 6 chronically cannulated ovine fetuses between 104 and 149 days of gestation (term 142-152 days). Arterial plasma immunoreactive adrenocorticotropin was first elevated by this procedure if the fetuses were between 118 and 130 days of gestation, and an increased response occurred later in gestation. This suggests that a progressive reset of the hypothalamic-pituitary-adrenal feedback relationship occurs over the last 2-3 weeks of gestation in the ovine fetus.