Fine genetic mapping of the proximal part of mouse Chromosome 2 excludes Pax-8 as a candidate gene for Danforth's short tail (Sd)

Danforth's short tail (Sd) is a semidominant mutation of the mouse with effects on the skeleton and the urogenital system. In view of its phenotype and its position in the proximal part of Chromosome (Chr) 2, three genes qualified as possible candidates: Pax-8, a paired box-containing gene; Midkine (Mdk), a retinoic acid-responsive gene; and a new locus (Etl-4) identified by enhancer trapping with a lacZ reporter gene which showed expression in the notochord, the mesonephric mesenchyme, and the apical ectodermal ridge. Three different backcrosses involving all three genes in different combinations were set up and analyzed. From our results we conclude that Sd, Etl-4, Pax-8, and Mdk are independent loci, with Etl-4 being the closest genetic marker (1.1±1.4 cM) to the Danforth's short tail (Sd) gene.     

Structural features of archaebacterial and eukaryotic proteasomes

The 26S proteasome is the central protease of the ubiquitin-dependent pathway of protein degradation. The molecule has a molecular mass of approximately 2000 kD and has a highly conserved structure in eukaryotes. The 26S proteasome is formed by a barrel-shaped 20S core complex and two polar 19S complexes. The 20S complex has C2 symmetry and is formed by four seven-membered rings of which the outer rings (-type subunits) are rotated by 25.7° relative to the inner rings while the inner rings (-type subunits) are in register. From a comparison of the activity and regulation of the 26S and 20S particles it can be deduced that the 20S particle contains the protease activity while the 19S complex contains isopeptidase, ATPase and protein unfolding activities. In this article we describe the structures of various proteasome complexes as determined by electron microscopy and discuss structural implications of their subunit sequences.     

Changes in serum LH concentrations during normal and abnormal sexual development in the pig.

Serum levels of luteinizing hormone (LH) were determined in fetal and prepubertal pigs from Day 49 postcoitum to 25 weeks of age, and also in unilaterally cryptorchid, freemartin and castrated pigs of similar ages. Serum LH was undetectable in the second trimester of pregnancy, but then gradually increased up to 2 weeks after birth in both sexes. 2-week-old pigs showed irregular LH peaks exceeding 2 ng/ml. Serum LH concentrations decreased during the 3rd and 4th weeks of life. Mean LH concentrations were approximately 2 ng/ml in castrated pigs and 1.3 + or -.7 ng/ml in freemartins. The differentiation and functional activity of the testis appeared to be well correlated with the changes in serum LH concentrations. Changes in serum LH could not be correlated with normal and abnormal gubernacular development.     

Prolactin levels and the LH-response to synthetic LH-RH in the lactating sow

To determine the role of prolactin in the suppression of ovarian activity during lactation in the sow experiments were performed to investigate a possible inhibitory action of prolactin at the pituitary level. Therefore the LH-response to an intravenous injection of 25 μg synthetic LH-RH was measured in the 1st, 2nd and 3rd week of lactation. The compound was injected under high and low concentrations of prolactin in the peripheral blood, the latter achieved by removal of the piglets 6 h before administration of LH-RH. The results showed no difference in the effect of LH-RH injected at high or low prolactin levels. However, although the mean prolactin concentrations in the 1st, 2nd and 3rd week of lactation were similar, the results clearly demonstrated an increase in LH-response as lactation proceeds.The low responsiveness of the pituitary shortly post partum was also observed when the preparturient rise of prolactin was suppressed by treatment with bromoergocryptine. Injections of LH-RH in the last week of gestation given before and after the physiological increase of PRL, which occurred about 48 h before delivery, all showed low LH-response.It is obvious from the presented data that the LH-response to an intravenous injection of 25 μg LH-RH is in no way correlated with the prolactin levels at the time of treatment.     

Metabolism of phenylalanine and tyrosine in tobacco cell lines resistant and sensitive to p-fluorophenylalanine

Chromatography of soluble polyphenols of p-fluorophenylalanine-sensitive and -resistant tobacco cells revealed that the 10-fold increased level found in the resistant line was largely due to the accumulation of two unidentified polyphenols. The uptake of Phe-[U-¹⁴C] and Tyr-[U-¹⁴C] by the resistant line was ca 10 % that by the sensitive line. About 90 % of the phenylalanine-[¹⁴C] which was taken up by both cell lines could be accounted for as free phenylalanine in protein, soluble polyphenols or CO₂. The fate of Tyr-[¹⁴C] was similar to that of phenylalanine except that the incorporation was into insoluble polymeric forms of polyphenols rather than into soluble polyphenols. The resistant line incorporated 9-times more phenylalanine-[¹⁴C] into soluble polyphenols than did the sensitive line. The different ¹⁴C-aromatic amino acid accumulation and incorporation patterns noted with the two cell lines indicates that there are different active pools. Differential uptake rates by the two cell lines might affect the distribution of the absorbed amino acid among the different pools.     

Structural changes in bovine oocytes during final maturation in vivo

On the basis of structural observations bovine oocytes were grouped into four successive classed: 0, those before the luteinizing hormone (LH) surge; 1, those up to 8 h following the LH peak level; 2, those between 8 and 19 h after the LH peak level; and 3, those between 19 h after the LH peak level and ovulation. Oocytes in class 0 had mitochondria located in a generally peripheral position. Interior to the mitochondria were elements of rough endoplasmic reticulum (RER) and numerous membrane-bound vesicles which bore ribosome-like particles on their outer surface. The first visible changesater the LH peak level as seen in class 1 were the formation of the periviteline space with loss of contact between the cumulus cells and the oocyte, and ruffing of the nuclear envelope. These changes were followed b the resumption of meiosis as defined by germinal-vesicle breakdown (GVBD), the disappearance of RER, and the formation fo clusters of mitochondria in association with lipid droplets and elementrs of smooth endolasmic reticulum (SER). The period between 8 and 19 h following LH peak level (class 2) was characterized by intensive clustering of mitochoncria in association with lipid droplets and elements of SER, conversion of lipid, fusion of vesicles, and the appearance of ribosomes in the cytoplasm. During the final stage (class 3), the polar body was extruded, the mitochondria dispersed, and the majority of the organelles became located toward the center of the cell. The relatively organelle-free cortical region contained cortical granules immediately adjacent to the plasma membrane together with aggregates of tubular SER. The structural changes are discussed in the context of follicular steroidogenesis and oocyte developmental competence.     

Pnoepyga immaculata n. sp., eine neue bodenbewohnende Timalie aus dem Nepal-Himalaya

Zusammenfassung Pnoepyga immaculata n. sp. lebt im Areal der beiden anderenPnoepyga-Artenalbiventer (Hodgson 1837) undpusilla Hodgson 1845 und wurde durch ihren markant abweichenden Territorialgesang entdeckt. Sie besitzt eine kurze silberhelle Strophe aus kurzen, in gleichmäßigen Abständen gereihten Pfiff-Elementen, die in der Frequenz leicht abfällt. Neben der Stimme liegen die wesentlichen diagnostischen Merkmale nach jetzigem Kenntnisstand gegenüber sympatrischenalbiventer in wenig größerem Schnabel, der Fleckenlosigkeit von Oberseite, Kopf und Flügeldecken, gegenüberpusilla in den größeren Körperabmessungen, gegenüber sympatrischenalbiventer undpusilla im schwachen grünlichen Schimmer der Oberseite und in der länglichen Schuppung der Unterseite. Es bestehen keine Proportionsunterschiede zwischenimmaculata undalbiventer/pusilla einerseits wie auch nicht zwischen diesen beiden andererseits. Bis jetzt wurden 4 Belegstücke (SammlungenKoelz, Diesselhorst, Martens) und eine durch Bandaufnahme gesicherte Beobachtung zwischen Dhaulagiri in Mittelwest-Nepal bis nahe der Ost-Grenze Nepals bekannt.P. immaculata lebt zur Brutzeit in enger Nachbarschaft mitP. albiventer undP. pusilla, ist jedoch vonalbiventer vertikal getrennt bei nachgewiesenem Kontakt, vonpusilla durch Bevorzugung trockeneren Waldunterwuchses abseits von Bächen. Schon jetzt mußimmaculata als gefährdete Art eingestuft werden, da Waldvegetation in der zur Brutzeit bevorzugten Höhenstufe zwischen 2100 und 3100 m in Nepal weitgehend vernichtet worden ist.

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Pnoepyga immaculata n. sp., a new ground living wren-babbler from the Nepal Himalayas (Timaliidae)

Summary P. immaculata n. sp. was discovered by its voice which strongly differs from the two other sympatric species,albiventer (Hodgson 1837) andpusilla Hodgson 1845. As a territorial song, it displays a silvery strophe arranged of short, more or less regularly spaced whistling notes (fig. 7a–d), slightly descending in pitch. The strophe is about 2 s long. Besides the distinct voice, the essential diagnostic characters in comparison toP. albiventer are the slightly larger bill, plain head, upper side and wing coverts (fig. 1a–d, 2, 4a–d), in comparison topusilla the larger body size (fig. 1i–m), in comparison to sympatricalbiventer andpusilla the slightly olive tinge of the upper side (against warm dark brown in both others, fig. 1e–m), and the more longish scaly feathers of the lower side (against stout scaly appearance in both others, fig. 1 a–d). These characters hold true at least in Central and Eastern Himalayan populations of the respective species. There do not exist proportional differences in the relations of any part of the body betweenimmaculata andpusilla and not between the latter ones as well. Heretofore, 4 museum specimens are known (Koelz Coll.,Diesselhorst Coll.,Martens Coll.) from West-central (Thakkhola, type locality) and East Nepal (Ting Sang La), 3 of them from the presumed breeding grounds (2100–3100 m), one from the winter quarters in the Terai lowlands. A field observation close to the Darjeeling border in far East Nepal is verified by a tape-recording.P. immaculata embarasses the biologist and systematist because it lives in close neighbourhood of the similar speciesalbiventer andpusilla. It must have been overlooked by its apparent scarcity and overall similarity to both other species of the genus. Slight ecological differences rather correspond to the vertical distribution ofalbiventer, which populates a higher forest belt. But both have already been found on territory at close range.P. pusilla inhabits different microbiotopes, especially the close proximity of running water in the same altitudinal belt asimmaculata. When discovered,P. immaculata is to be classified already as an endangered species. Forest vegetation of its preferred altitude is already greatly reduced in the Central and Eastern Nepal Himalayas. To get a more detailed information on its general distribution and biology in order to quickly arrange protected areas and thus to guarantee the survival ofP. immaculata, should be the urgent next step.

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Results of the Himalaya Expeditions ofJ. Martens, No. 163. — For No. 162 see: Stuttgarter Beitr. Naturkde. (A) 453: 1–46, 1990.     

Effect of cholesterol and dipalmitoyl phosphatidylcholine enrichment on the kinetics of Na−Li exchange of human erythrocytes

Summary The effects of cholesterol loading and depletion and of a 10% replacement of native phosphatidylcholine by dipalmitoyl phosphatidylcholine (di 16:0-PC) on kinetic properties of human red cell Na–Li exchange have been studied.Compared to control erythrocytes (cholesterol/phospholipid ratio (C/P=0.8–0.9)),V _max of phloretin-sensitive Li uptake and of Li efflux stimulated by extracellular Na (Na _o ) were reduced by 15–30% in cholesterol-loaded red cells (C/P=1.05–1.33). The apparentK _m values for external Li (Li _o ) and for internal Li (Li _i ) were decreased by about one-third in these cells. Cholesterol depletion (C/P=0.7) exerted opposite effects on the kinetics of Na _o -dependent Li efflux. On augmentingC/P from 0.66 to 1.0,V _max of Na _o -dependent Li efflux was reduced by about 30%; increasingC/P above 1.0 caused no further lowering ofV _max. Li leakage rates monotonically decreased over the whole range ofC/P ratios examined (0.66–1.3). This indicates that Na–Li exchange and Li leak are differentially affected by cholesterol.Incorporation of di 16:0-PC (replacement of 3% of total red cell phospholipids) caused similar kinetic alterations of Na–Li exchange as a rise in membrane cholesterol by 20–50%. Notably, selective incorporation of di 16:0-PC into the outer monolayer increased both intra- and extracellular Li binding affinities of Na–Li exchange and lowered its maximum velocity. Thus, both di 16:0-PC enrichment and cholesterol loading exerted an uncompetitive type of transport inhibition. The results are in agreement with the hypothesis that the kinetic alterations of red cell Na–Li exchange seen in a subgroup of essential hypertensive patients could be due to subtle changes in the molecular species composition of individual phospholipids.     

Uptake and Storage of Choline by Rat Brain: Influence of Dietary Choline Supplementation

In order to elucidate the regulation of the levels of free choline in the brain, we investigated the influence of chronic and acute choline administration on choline levels in blood, CSF, and brain of the rat and on net movements of choline into and out of the brain as calculated from the arteriovenous differences of choline across the brain. Dietary choline supplementation led to an increase in plasma choline levels of 50% and to an increase in the net release of choline from the brain as compared to a matched group of animals which were kept on a standard diet and exhibited identical arterial plasma levels. Moreover, the choline concentration in the CSF and brain tissue was doubled. In the same rats, the injection of 60 mg/kg choline chloride did not lead to an additional increase of the brain choline levels, whereas in control animals choline injection caused a significant increase; however, this increase in no case surpassed the levels caused by chronic choline supplementation. The net uptake of choline after acute choline administration was strongly reduced in the high-choline group (from 418 to 158 nmol/g). Both diet groups metabolized the bulk (greater than 96%) of newly taken up choline rapidly. The results indicate that choline supplementation markedly attenuates the rise of free choline in the brain that is observed after acute choline administration. The rapid metabolic choline clearance was not reduced by dietary choline load. We conclude that the brain is protected from excess choline by rapid metabolism, as well as by adaptive, diet-induced changes of the net uptake and release of choline.