Niche overlap of two sympatric-nesting hawks Accipiter spp. in the New Jersey-New York Highlands

The food and habitat niches of two nesting species of hawks Accipiter spp were studied in an extensively forested area of the Eastern Deciduous Forest Biome Nesting habitat was quantitated at 19 Cooper s hawk A cooperu nests and 16 northern goshawk A gentilis nests There was no significant trend for Cooper's hawks to nest in less mature forests than northern goshawks as reported previously for western North America Forest habitats did not differ markedly except that shrub cover was greater at Cooper's hawk nest sites, which were also on flatter terrain and closer to roads, forest openings, and human habitation However, these few differences resulted m reducing habitat-niche overlap considerably (0 538), as was calculated using principal components analysis Mean prey weight was significantly larger for the northern goshawk which follows its 2 2-fold body weight advantage over Cooper's hawk Although bird prey was of primary importance to both Accipiter, goshawks took twice the proportion of mammals compared to their smaller congener Food-niche overlap was lowest by prey species overlap (0 470), followed by prey size class overlap (0 529), and highest by vertical foraging zone overlap (0 816) The Cooper's hawk showed the greatest niche breadth for both food and habitat niches indicating it as more of a generalist Overall, niche complementarity of food and habitat dimensions resulted in niche overdispersion along food and habitat dimensions with a total niche overlap (0 504) that was below the competition threshold These results suggested that competition (past and current) was responsible for segregating niches     

A segregation and linkage study of classical and nonclassical 21-hydroxylase deficiency.

The segregation of classical and nonclassical 21-hydroxylase deficiency (21-OHD) and its linkage to HLA-B was investigated in 220 families. First, the surprisingly high frequency of the nonclassical 21-OHD gene estimated elsewhere was confirmed using a different methodology which avoided particular assumptions concerning the classification of an individual''s genotype. In the present study the gene frequency was found to be .103 +/- .020 in an ethnically pooled sample and was as high as .223 +/- .062 among Ashkenazi Jews. Second, the segregation analysis of families ascertained through a nonclassical 21-OHD proband and those ascertained through a classical 21-OHD proband showed essentially identical results. A partial recessive model with no recombination between 21-OHD and HLA-B fitted the data better than did a complete recessive model with approximately 0.5% recombination between 21-OHD and HLA-B. The support for the partial over the complete recessive model depended on the assumed ascertainment probability, an unknown parameter in these data. Four families provided most of the evidence against the complete recessive model. All these included an unaffected sib who shared both HLA-B specificities in common with the affected proband. Possible explanations for the condition in these families include recombination, gene conversion, mutation in one of the parental gametes, or technical errors.     

Phase behaviour of a diglyceride prodrug: spontaneous formation of unilamellar vesicles

A prodrug (Fig. 1(IV)) is synthesized consisting of the beta-blocker bupranolol which is covalently linked to 1, 3-dipalmitoyl-2-succinyl-glycerol. The resulting lipid-like prodrug is amphipathic and surface active. It disperses readily in H2O above 30 degrees C forming a smectic lamellar phase. This prodrug bears one positive charge at neutral pH and hence the swelling behaviour of dispersions in H2O is similar to that of charged phospholipids: the dispersions show continuous swelling with increasing water content and consequently in the excess H2O region of the phase diagram the thermodynamically most stable structure is the unilamellar vesicle. This includes oligomeric vesicles which may be defined as unilamellar vesicles containing smaller, also unilamellar vesicles entrapped in their internal aqueous compartment. The prodrug dispersions in H2O are polydisperse with vesicle sizes ranging from 0.1 micron to several micron. Sonication of these dispersions produce small unilamellar vesicles of an average size and size distribution similar to sonicated egg phosphatidylcholine dispersions. Unsonicated dispersions of the prodrug in H2O undergo reversibly sharp order-disorder transitions at 32 degrees C with an enthalpy change of delta H = 10 kcal/mol. In sonicated aqueous dispersions this phase transition is asymmetric and significantly broadened indicating that the cooperativity is markedly reduced. The peak temperature and enthalpy change of this broad transition are reduced compared to the transition observed with unsonicated dispersions. The temperature dependence of the electron spin resonance (ESR) hyperfine splitting and order parameter also reflects the order-disorder transition. From ESR spin labeling it is concluded that in sonicated dispersions the prodrug molecule is more mobile and its anisotropy of motion is reduced compared to unsonicated dispersions. This result indicates that the molecular packing in the highly curved bilayers of small unilamellar prodrug vesicles is significantly perturbed compared to bilayers of unsonicated dispersions.     

The zygosity in the human HL-A transplantation system

Summary If by serological methods of tissue typing one antigen only is detected in one or both of the loci LA and 4 of the histocompatibility system HL-A, the question arises whether it is homozygous or heterozygous. The probability thereof is calculated. It depends on the frequency of the known and unknown genes in the HL-A-system. If e.g. the HL-A type of an examinee is 1,3,8 this subject could be homozygous 1,3,8,8 or heterozygous (with an unknown antigen X) 1,3,8,X. The frequencies of homozygous and heterozygous individuals are calculated in all possible combinations of the LA and 4 loci. The results justify always for both the LA-and 4 locus the assumption of heterozygosity, with the one exception that the gene HL-A 2 is under consideration. There the calculations result in a value of 49% for homozygosity (2,2) and 51% for heterozygosity (2,X). Neither alternative is in this case essentially more probable.For transplantations generally heterozygosity can be assumed — with the exception of HL-A 2 — and therefore the minor grade of histocompatibility.National Blood Group Reference Laboratory — WHO (Director: Prof. Dr. P. Speiser)     

Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves

A puzzling population-genetic phenomenon widely reported in allozyme surveys of marine bivalves is the occurrence of heterozygote deficits relative to Hardy-Weinberg expectations. Possible explanations for this pattern are categorized with respect to whether the effects should be confined to protein-level assays or are genomically pervasive and expected to be registered in both protein- and DNA-level assays. Anonymous nuclear DNA markers from the American oyster were employed to reexamine the phenomenon. In assays based on the polymerase chain reaction (PCR), two DNA-level processes were encountered that can lead to artifactual genotypic scorings: (a) differential amplification of alleles at a target locus and (b) amplification from multiple paralogous loci. We describe symptoms of these complications and prescribe methods that should generally help to ameliorate them. When artifactual scorings at two anonymous DNA loci in the American oyster were corrected, Hardy-Weinberg deviations registered in preliminary population assays decreased to nonsignificant values. Implications of these findings for the heterozygote-deficit phenomenon in marine bivalves, and for the general development and use of PCR-based assays, are discussed.      

Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland

The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia.     

The early life history of two sympatric New Zealand octopuses: eggs and paralarvae of Octopus huttoni and Pinnoctopus cordiformis

This study combined morphological and morphometric information on egg clutches, egg capsules and paralarvae of two sympatric coastal octopuses from New Zealand waters, Octopus huttoni and Pinnoctopus cordiformis, to provide species-specific traits to identify their early life stages obtained from field surveys. Eggs of O. huttoni (2.5 mm length; 1 mm width) were entwined with one another forming strings that ranged from 11 to 25.8 mm in length. Eggs of P. cordiformis (6.4 mm length; 1.5 mm width) were significantly bigger than those of O. huttoni and were grouped in small clusters of about seven eggs. Paralarvae O. huttoni and P. cordiformis differed in hatching size (1.4 mm versus 3.1 mm mantle length), number of suckers per arm (four versus eight), number of lamellae per outer demibranch (five versus ten) and arrangements of chromatophores in the body surface (29 to 59 versus 91 to 179), respectively. The morphological traits described in hatchlings from the laboratory allowed comparisons with field-collected paralarvae, suggesting that such characters were reliable species-specific patterns to enable a consistent differentiation between the early life stages of these two sympatric species, even in the absence of the brooding female.