Modeling the effects of El Niño, density-dependence, and disturbance on harbor seal (Phoca vitulina) counts in Drakes Estero, California: 1997–2007

Harbor seal ( Phoca vitulina ) haul-out site use may be affected by natural or anthropogenic factors. Here, we use an 11-yr (1997–2007) study of a seal colony located near a mariculture operation in Drakes Estero, California, to test for natural (El Niño-Southern Oscillation (ENSO), density-dependence, long-term trends) and anthropogenic (disturbance or displacement related to oyster production activities) factors that may influence the use of haul-out subsites. Annual mariculture related seal disturbance rates increased significantly with increases in oyster harvest ( r _s= 0.55). Using generalized linear models (GLMs) ranked by best fit and Akaike's Information Criteria, ENSO and oyster production (as a proxy for disturbance/displacement) best explained the patterns of seal use at all three subsites near the mariculture operations, with effects being stronger at the two subsites closest to operations. Conversely, density-dependence and linear trend effects poorly explained the counts at these subsites. We conclude that a combination of ENSO and mariculture activities best explain the patterns of seal haul-out use during the breeding/pupping season at the seal haul-out sites closest to oyster activities.     

Gas exchange characteristics of the sorghum-striga host-parasite association

Gas exchange characteristics are reported for both members of the sorghum-Striga host-parasite association. Both Striga hermonthica (Del.) Benth and Striga asiatica (L.) Kuntze had transpiration rates considerably in excess of those of sorghum (Sorghum bicolor (L.) Moench, cv CSH1). Stomatal conductance in both Striga spp. showed little response to periods of darkness and moderate water stress. Low rates of net CO₂ fixation and high rates of dark respiration led to no net daily (24 hours) C gain, and Striga would appear to be reliant on its host for photosynthate. Infection of sorghum plants with either S. hermonthica or S. asiatica reduced host photosynthetic capacity. Infected sorghum plants were also more prone to water stress, but reduced rates of CO₂ fixation could not be accounted for in terms of lower stomatal conductance. Lower stomatal conductances were associated with an increase in water use efficiency (WUE) in uninfected sorghum; however, Striga-infected sorghum plants had lower WUE than those of uninfected plants. We suggest that Striga exerts a specific effect on processes affecting C acquisition in sorghum leaves. The water relations of S. hermonthica and S. asiatica are not characteristic of plants growing in semiarid environments and are more likely to reflect the nature of the parasitic life-style. Despite transfer of water and solutes from host to parasite, the reduction in C fixation observed in infected sorghum plants appears to be the major determinant of growth reductions observed in sorghum supporting Striga.     

Autotrophy and heterotrophy in root herniparasites

More than 3000 species of flowering plants are at least partially parasitic, acquiring water and solutes from the host via haustoria. More than one third of all parasitic angiosperms - the root hemiparasites - possess green leaves and root systems. In these species there are potentially two opportunities for the capture of water and solutes: an autotrophic or abiotic supply from the external environment, and a heterotrophic or host-derived supply via the haustoria. Most root hemiparasites occur in the Scrophulariaceae, a family also containing autotrophic and holoparasitic plants. Between these two extremes, the root hemiparasites provide an ideal opportunity to investigate the balance between the autotrophic and heterotrophic modes of nutrition in parasitic plants. The tropical hemiparasites within this family are important weeds of cereals and legumes, causing considerable crop losses, and thus fuelling research into the nutritional dependency of these plants on their hosts. These studies have led to some exciting new ideas, particularly with respect to the carbon relations of these plants.     

Affinity labelling of the binding site of rabbit antibody. Evidence for the involvement of the hypervariable regions of the heavy chain

The binding sites of rabbit antibodies with affinity for the haptenic group 4-azido-2-nitrophenyl-lysine have been specifically labelled by photolysis of the hapten-antibody complex. The extent of covalent labelling was 0.5-0.9mol of hapten bound/mol of antibody and, by using an immunoadsorbent, antibody with 1.3mol of hapten/mol was obtained. The antibody was specifically labelled in the binding site and the ratio of labelling of heavy and light chains was in the range 3.3-5.0. The labelled heavy chains were cleaved by CNBr treatment and after reduction and alkylation of the intrachain bonds, were digested with trypsin. Evidence is presented that two regions of the heavy chain, positions 29-34 and 95-114, together contain about 80% of the label on the heavy chain; these two regions respectively include two of the hypervariable regions of rabbit heavy chain.     

Novel thieno[2,3-b]- and [3,4-b]pyrans as potassium channel openers. Thiophene systems—XVII

The syntheses and antihypertensive activity of the thieno[3,4-b]pyran and thieno[2,3-b]pyran isosteres of the potassium channel opener (PCO) RWJ 26629 (± 2a) are reported. While the unsubstituted thiophene derivatives were active at 20 mg/kg, introduction of a strong electron withdrawing group in the 2-position of the thieno[3,2-b] series increased potency. Similar substitution on the thieno[3,4-b] series significantly lowered potency. Compounds 26 and 30 are approximately 5-fold more potent than the prototypic PCO cromakalim (± 1).     

Expression of murine Ia antigens during embryonic development.

An immunochemical analysis of the kinetics of appearance of Ia antigens during embryonic development was performed. Ia antigens first appear on the surface of embryonic cells 11 days postconception and their expression between days 11 and 16 of gestation is confined to the fetal liver. Ia antigen synthesis by fetal liver cells is detectable at day 14. Ia seems to precede Ig as a surface marker of embryonic liver cells, since Ig cannot be detected until day 16 of gestation. H-2 antigens may be immunoprecipitated from day 10 whole embryo cells. F9 primitive teratocarcinoma cells are Ia negative and H-2 negative.     

Transformation of chicken myelomonocytic cells by a retrovirus expressing the v-myb oncogene from the long terminal repeats of avian myeloblastosis virus but not Rous sarcoma virus.

To test the effect of long terminal repeat (LTR) regulatory sequences on the transforming capability of the v-myb oncogene from avian myeloblastosis virus (AMV), we have constructed replication-competent avian retroviral vectors with nearly identical structural genes that express v-myb from either AMV or Rous sarcoma virus (RSV) LTRs. After transfection into chicken embryo fibroblasts, virus-containing cell supernatants were used to infect chicken myelomonocytic target cells from preparations of 16-day-old embryonic spleen cells. Both wild-type AMV and the virus expressing v-myb from AMV LTRs (RCAMV-v-myb) were able to transform the splenocyte cultures into a population of immature myelomonocytic cells. The transformed cells expressed the p48v-Myb oncoprotein and formed compact foci when grown in soft agar. In contrast, the virus expressing v-myb from RSV LTRs (RCAS-v-myb) was repeatedly unable to transform the same splenocyte cells, despite being able to infect fibroblasts with high efficiency. This difference in the transforming activities of v-myb-expressing viruses with different LTRs most likely results from the presence of a factor (or factors) within the appropriate myelomonocytic target cell that promotes specific expression from the AMV but not from the RSV LTR.     

Effect of portacaval anastomosis on the activities of hepatic enzymes related to cholesterol and bile acid metabolism in rats.

1. The effect of a portacaval anastomosis on the activities of hepatic enzymes related to cholesterol metabolism was investigated in rats. 2. Portacaval anastomosis led to a fall in body weight and liver weight/body weight ratio, and to a rise in the activities of hydroxymethylglutaryl-CoA reductase and cholesterol 7alpha-hydroxylase per g of liver. The net effect was to maintain a normal activity of both enzymes per 100 g of rat. Diurnal rhythm in the activities of both enzymes was maintained after portacaval anastomosis. 3. The rate of excretion of total bile acids, per 100 g of rat, in bile fistula rats was not significantly decreased by portacaval anastomosis.