Risk of feather damage explains fault bar occurrence in a migrant hawk,the Swainson's hawk Buteo swainsoni

Fault bars are common stress‐induced feather abnormalities that could produce feather damage thus reducing flight performance. For that reason, it has been hypothesized that birds may have evolved adaptive strategies that reduce the costs of fault bars (the ‘fault bar allocation hypothesis’). An untested prediction of this hypothesis is that fault bars in important feathers for flight (wing and tail) should be less abundant where they produce more feather damage. We tested such a prediction using moulted wing and tail feathers of the long‐distance migrant Swainson's hawk Buteo swainsoni in its Argentinean wintering quarters. We recorded the occurrence of fault bars of different strengths (light, medium and strong) and the damage (lost of a portion of the vane) produced by them. The occurrence of fault bars was very variable, with strong ones being rare throughout and light and medium fault bars being more frequent in the tail than in the wing. Risk of feather damage was similarly high and low across feather groups for strong and light fault bars, respectively, and higher in the wing than in the tail for medium strength. The occurrence of fault bars of different strengths on different feather groups was negatively correlated with their propensity to produce feather damage. At low damage risk (<5%), the occurrence of fault bars was highly variable depending on the feather group, but above 5% of feather damage the occurrence of fault bars was highly reduced throughout. Our results supports the ‘fault bar allocation hypothesis’ of natural selection reducing fault bar occurrence where fault bars are more risky, but further suggest that selection pressure could be relaxed in other instances, leaving the way free for other mechanisms to shape fault bar occurrence.     

Inheritance of a mutant histocompatibility gene and a new mammary tumor virus genome in the B6.KH-84 mouse strain

The potential association between integration or deletion of mouse mammary tumor virus (MMTV) retroviral sequences and the appearance of non-H-2 histocompatibility (H) antigen mutations was investigated. Genomic blots from inbred strains carrying 22 loss, gain-loss, and gain mutations on the BALB/c and C57BL/6 backgrounds were hybridized with probes homologous to the long terminal repeat (LTR) and envelope (env) regions of MMTV. Twenty-one mutants were identical in restriction patterns to the respective background strains with all tested restriction enzymes and both probes. However, genomic blots of one gain mutant, B6.C-KH-84, exhibited restriction fragments which were not exhibited by either of the parental strains, C57BL/6 or BALB/c. An additional 5.5 kb Eco RI fragment was observed with the env probe and additional 9.2 kb and 5.5 kb fragments were observed with the LTR probe. These observations were substantiated by hybridization of these two probes with genomic blots generated with additional restriction enzymes. Assuming that the new provirus contains a single, internal Eco RI site as has been observed for other MMTV proviral sequences, it is presumed that the new provirus includes both 5 and 3 LTRs in addition to the env region. Based on the unique sizes of the observed restriction fragments relative to other identified MMTV proviral sequences, this provirus has been designated Mtv-22. The potential role of Mtv-22 in the genesis of the gained histocompatibility antigen in B6.C-KH-84 is discussed.On leave of absence from Istituto Nazionale per to Studio e la Cura dei Tumori, Milano, Italy     

Summer dynamics of the deep chlorophyll maximum in Lake Tahoe

Vertical profiles of chlorophyll and phytoplankton biomass weremeasured in Lake Tahoe from July 1976 through April 1977. Adeep chlorophyll maximum (DCM) persisted during summer and earlyautumn (July—October) near 100 m, well below the mixedlayer and at the upper surface of the nitracline. The DCM coincidedwith the phytoplankton biomass maximum as determined from cellcounts. In addition, the composition of the phytoplankton assemblagewas highly differentiated with respect to depth. Cyclotellastelligera was the predominant species in the mixed layer whilethe major species in the DCM layer included C. ocellata andseveral green ultraplanktonic species. In situ cell growth playsa substantial role in maintaining the DCM, but sinking of cellsfrom shallower depths and zooplankton grazing above the DCMmay contribute to the maintenance of the DCM. Calculations supportthe interpretation that the summer DCM persists at the boundarybetween an upper, nutrient-limited phytoplankton assemblageand a deeper, light-limited assemblage.     

Doxorubicin and epirubicin iron-induced generation of free radicalsIn vitro. A comparative study

To ascertain any differences in myocardial injury exerted by the anthracyclines doxorubicin and epirubicin, their ability to generate oxygen free radicals when mixed with Fe(II) was examined in vitro using an oxygen electrode. 5–250 g/ml doxorubicin or epirubicin consumed oxygen when mixed with 50 or 100 mol/1 Fe(II). Addition of 75 mol/1 cytochrome C showed that of the consumed oxygen, approximately 80% entered the monovalent pathway of oxygen reduction. The strong inhibitory effect of 250 mg/1 catalase indicates that most of the superoxide radicals generated are further reduced to hydrogen peroxide by both anthracyclines. Addition of metal chelators DTPA (100/mol/1), or DDTC (50 mol/1) did not affect oxygen consumption, whereas EDTA (100/mol/1) or desferrioxamine (100 mol/1) with anthracyclines and Fe(II) rather stimulated oxygen consumption. It is concluded that there are no significant differences in the amount or proportion of generated oxygen free radicals between doxorubicin and epirubicin when mixed with Fe(II) in a cell-free system in vitro. Thus, the ability of the anthracyclines, in conjunction with iron alone, to generate radicals does not explain the differences of the drugs in causing myocardial injury.     

Expression of the β-subunit of β-conglycinin in seeds of transgenic plants

Soybean (Glycine max (L.) Merr.) seeds contain the storage protein -conglycinin, encoded by a multigene family. -Conglycinin consists of three subunits; , , and . A genomic clone for a -subunit of -conglycinin has been characterized by restriction-enzyme mapping and hybrid selected in-vitro translation followed by immunoprecipitation. In order to determine the developmental regulation of this -subunit gene, its expression was studied in seeds of transgenic petunia (Petunia hybrida) and tobacco (Nicotiana tabacum L.) plants. The -subunit expressed in seeds of petunia and tobacco was recognized by anti--conglycinin serum at a relative molecular mass of 53 000, equivalent to that of the native protein. Separation of the petunia-seed proteins by isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis showed that multiple isoelectric forms of the -subunit were produced. There was approximately a twofold variation in the accumulation of the -subunit protein in the mature seeds of transgenic petunia plants, each containing a single -subunit gene. However, the level of protein accumulation in mature seeds and the amount of -subunit mRNA in developing seeds was not correlated. Accumulation of the -subunit protein in transgenic seeds was less than the -subunit protein that accumulated in transgenic petunia seeds containing a single -subunit gene and less than the amount of the -subunit in mature soybean seeds which contain 8–13 -subunit genes. In transgenic tobacco plants, the accumulation of the -subunit protein in seeds was generally well correlated with the number of genes that were incorporated in the different transformants.Abbreviations kb kilobase - kDa kilodalton - M_r relative molecular mass - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis     

Innervation of the superficial pineal of the rat using retrograde tracing methods

Fast blue (FB), rhodamine microspheres (RH), horseradish peroxidase (HRP), and wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) were used as retrograde tracers to study the innervation of the rat superficial pineal gland (SP). One of the tracers was injected into the gland of each animal. All four retrograde tracers injected into the gland always labeled neurons in the superior cervical ganglia (SCG). No retrograde labeling was ever seen in the suprachiasmatic nuclei, paraventricular hypothalamic nuclei, lateral hypothalamus, habenular nuclei, amygdalar nuclei, or superior salivatory nuclei. Retrograde labeling was seen in the anterior hypothalamic nuclei, anterior thalamic nuclei, lateral geniculate bodies, and midbrain tectal structures when a tracer spread from the injection site to the overlying cortex, tectum, or commissures. Control studies included injection of tracer into the subarachnoid space around the SP or into structures adjacent to the SP. Only the injection of FB or WGA-HRP into the subarachnoid space labeled neurons in the SCG. This labeling was probably due to the spread of tracer to the choroid plexus. These results agree with recent work confirming the existence of a direct projection of the SCG into the interstitium around pinealocytes. The evidence does not substantiate an innervation originating in the habenular nuclei; the superior salivatory nuclei; or any other diencephalic, midbrain, pontine, or medullary structure.     

Factors Involved in Hydrolysis of Microcrystalline Cellulose by Acetivibrio cellulolyticus

Acetivibrio cellulolyticus cellulase obtained by the water elution of residual cellulose from the growth medium was compared with the cellulase activity present in culture supernatants. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis indicated that water elution released most of the protein bands which adhered to undigested cellulose from the culture medium. The enzyme in the culture supernatant and that eluted from residual cellulose had specific activities for Avicel hydrolysis that were 20- to 40-fold greater than that of Trichoderma reesei cellulase. However, Ca²⁺ and a reducing agent such as dithiothreitol were required for maximum Avicel hydrolysis rates by these A. cellulolyticus enzyme preparations. The effect of these agents on p-nitrophenyl lactopyranoside hydrolysis suggested that they were required by an exoglucanase component. Supernatant enzyme preparations contained large amounts of carbohydrate which was separated from most of the cellulase protein by phenyl-Sepharose chromatography. Removal of this carbohydrate, which interfered with protein fractionations, allowed for an activity stain analysis of the supernatant enzyme.