Mutations for the autosomal recessive and autosomal dominant forms of polycystic kidney disease are not allelic

Summary The autosomal dominant form of polycystic kidney disease (ADPKD) has been linked to the -globin gene locus on 16p. Linkage studies between the autosomal recessive type (ARPKD) and the 3 HVR of the -globin gene cluster showed that the ARPKD and ADPKD are not allelic.     

Seasonal variation in cell volume of epilimnetic bacteria

The relationship between bacterial cell volume and temperature was examined for field data collected over a 4-year period and through controlled chemostat incubations of aPseudomonas sp. Volumes of planktonic bacteria were found to decrease as water temperature increased. Changes in temperature accounted for 38% of the variation in average cell volume (P<0.001). Average planktobacterial cell volume fell 42% from 0.217m³ in mid-winter to 0.127m³ in mid-summer. Similar results were found for the size distribution of epibacterial cells. Controlled chemostat incubations of aPseudomonas sp. indicated that cell volume was significantly affected by temperature, growth rate, and the interaction of temperature and growth rate. The data suggest that a change in cell volume as a result of a change in temperature is an intrinsic property of planktonic bacteria.     

Dynamics of autotrophic picoplankton in Lake Constance

The vertical distribution, biomass concentrations and growthrates of autotrophic picoplankton (APP) were investigated duringthe growing season (March-October) in Lake Constance in differentdepths. Cell numbers determined by epifluorescence microscopyvaried between 1.0 x 10³ and 1.6 times; 10⁵ cells ml^–1depending on season and water depth. Highest concentrationswere recorded above the thermodine in late summer. Numerically,APP consisted almost exclusively of chroococcoid cyanobactena.During lake stratification several peaks of biomass concentrationsoccurred in epilimsietic waters at intervals of 6–8 weeks.In-situ experiments using a dilution technique and dialysisbags revealed that during summer APP population dynamics wereprimarily driven by combined changes of their growth and grazingrates, whereas temperature was less important. Gross growthrates varied between 0.006 and 0.051 h^–1, grazing ratesbetween 0.002 and 0.053 h^–1. On average APP productionwas completely removed by grazing within the microbial community.Ciliates, heterotrophic nanoflagellates and rotifers have beenidentified as the major consumers of APP cells. APP biomassis small compared to larger phytoplankton, ranging from ito5% of total phytoplankton biovolume. Due to its high gross growthrates, which are on the same level as those of free-living pelagicbacteria, APP contributes slightly more to overall primary productionwith maximum percentages of {small tilde}15% in late summer.     

Oxidation of γ-Hydroxybutyrate to Succinic Semialdehyde by a Mitochondrial Pyridine Nucleotide-Independent Enzyme

An antibody that inhibits over 95% of the cytosolic NADP+-dependent gamma-hydroxybutyrate (GHB) dehydrogenase activity of either rat brain or kidney was found to inhibit only approximately 50% of the conversion of [1-14C]GHB to 14CO2 by rat kidney homogenate. A similar result was obtained with sodium valproate, a potent inhibitor of GHB dehydrogenase. The mitochondrial fraction from rat brain and kidney was found to catalyze the conversion of [1-14C]GHB to 14CO2. The dialyzed mitochondrial fraction also catalyzed the oxidation of GHB to succinic semialdehyde (SSA) in a reaction that did not require added NAD+ or NADP+ and which was not inhibited by sodium valproate. The enzyme from the mitochondrial fraction which converts GHB to SSA appears to be distinct from the NADP+-dependent cytosolic oxidoreductase which catalyzes this reaction.     

Inverse relationships between steroid concentration and volume in preovulatory follicles of the golden hamster

In order to investigate variations in the microenvironment of oocytes within a cohort of maturing follicles the follicular volumes as well as the intrafollicular concentrations of oestradiol (E2) and progesterone (P) were measured in the golden hamster. At 10 h before ovulation the follicular volumes varied from 0.009 to 0.037 mm3 (mean +/- SD: 0.0187 +/- 0.0071 mm3; n = 36). Large follicles (greater than 0.025 mm3; n = 8) contained statistically significantly lower E2 and P levels (30.1 +/- 10.4 and 517 +/- 113 mumol/l, respectively) than the medium sized group (less than 0.025 and greater than 0.015 mm3; n =20): 46.9 +/- 16.0 (P less than 0.02) and 919 +/- 264 (P less than 0.0001) mumol/l, respectively. Small follicles (less than 0.015 mm3) showed the highest steroid levels: 97.0 +/- 33.3 and 1590 +/- 517 mumol/l for E2 and P (P less than 0.001 versus the medium sized group values). Correlation coefficients for the steroid concentrations and the follicular volumes appeared to be -0.674 for E2 and -0.612 for P (P less than 0.001). At the time studied a positive correlation between E2 and P concentrations in the follicles was found: r = 0.655 (P less than 0.001). The mean ratios of intrafollicular over serum steroid concentrations appeared to be approx 36 x 10(3) in the case of E2 and about 17 x 10(3) in the case of P. These results clearly show that there is an inverse relationship between follicular volume and intrafollicular steroid concentrations. The presence of a fine regulatory mechanism for a collective maturation of follicles is hypothesized.     

Human placental 3 beta-hydroxy-5-ene-steroid dehydrogenase and steroid 5----4-ene-isomerase: purification from microsomes, substrate kinetics, and inhibition by product steroids

In human pregnancy, placental 3 beta-hydroxy-5-ene-steroid dehydrogenase and steroid 5----4-ene-isomerase produce progesterone from pregnenolone and metabolize fetal dehydroepiandrosterone sulfate to androstenedione, an estrogen precursor. The enzyme complex was solubilized from human placental microsomes using the anionic detergent, sodium cholate. Purification (500-fold, 3.9% yield) was achieved by ion exchange chromatography (Fractogel-TSK DEAE 650-S) followed by hydroxylapatite chromatography (Bio-Gel HT). The purified enzyme was detected as a single protein band in sodium dodecylsulfate-polyacrylamide gel electrophoresis (monomeric Mr = 19,000). Fractionation by gel filtration chromatography at constant specific enzyme activity supported enzyme homogeneity and determined the molecular mass (Mr = 76,000). The dehydrogenase and isomerase activities copurified. Kinetic constants were determined at pH 7.4, 37 degrees C for the oxidation of pregnenolone (Km = 1.9 microM, Vmax = 32.6 nmol/min/mg) and dehydroepiandrosterone (Km = 2.8 microM, Vmax = 32.0 nmol/min/mg) and for the isomerization of 5-pregnene-3,20-dione (Km = 9.7 microM, Vmax = 618.3 nmol/min/mg) and 5-androstene-3,17-dione (Km = 23.7 microM, Vmax = 625.7 nmol/min/mg). Mixed substrate analyses showed that the dehydrogenase and isomerase reactions use the appropriate pregnene and androstene steroids as alternative, competitive substrates. Dixon analyses demonstrated competitive inhibition of the oxidation of pregnenolone and dehydroepiandrosterone by both product steroids, progesterone and androstenedione. The enzyme has a 3-fold higher affinity for androstenedione than for progesterone as an inhibitor of dehydrogenase activity. Based on these competitive patterns of substrate utilization and product inhibition, the pregnene and androstene activities of 3 beta-hydroxy-5-ene-steroid dehydrogenase and steroid 5----4-ene-isomerase may be expressed at a single catalytic site on one protein in human placenta.     

Do holly leaf spines really deter herbivory?

Summary Although spinose teeth of holly leaves have been widely cited as an example of a physical defense against herbivores, this assumption is based largely on circumstantial evidence and on general misinterpretation of a single, earlier experiment. We studied the response of third and fifth instar larvae of the fall webworm, Hyphantria cunea Drury, a generalist, edge-feeding caterpillar, to intact American holly leaves and to leaves that had been modified by blunting the spines, by removing sections of leaf margin between the spines, or by removing the entire leaf margin. The results suggest that the thick glabrous cuticle and tough leaf margin of Ilex opaca are more important than the spinose teeth in deterring edge-feeding caterpillars. Microscopic examination of mature leaves revealed that the epidermis is thickened at the leaf margin, and that the leaf is cirucumscribed by a pair of fibrous veins. In simple choice tests neither domesticated rabbits nor captive whitetailed deer discriminated between spinescent holly foliage and foliage from which spines were removed. Nevertheless, we found little evidence of herbivory by mammals in the field, either on small experimental trees or in the forest understory. While it is possible that spinose teeth contribute to defense by reducing acceptibility of holly relative to other palatable plant species, we suggest that the high concentrations of saponins and poor nutritional quality of holly foliage may be more important than spines in deterring vertebrate herbivores. The degree of leaf spinescence and herbivory was compared at different heights with the tree canopy to test the prediction that lower leaves should be more spinescent as a deterrent to browsers. Leaves on lower branches of mature forest trees were slightly more spinescent than were upper leaves, and juvenile trees were slightly more spinescent than were mature trees. However, there was no relationship between degree of spinescence and feeding damage. The greater spinescence of holly leaves low in the canopy is probably an ontogenetic phenomenon rather than a facultative defense against browsers.The investigation reported in this paper (No. 87-7-8-77) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Dirctor