Regulation of idiotope expression. IV. Genetic linkage of two D region-dependent T15 idiotopes to the IgH allotype

The idiotopic (Id) repertoire of antibody response to phosphocholine was studied in mouse strains with different IgH allotypes. The T15 idiotype-bearing (T15+) serum antibody and antibody plaque-forming cells (PFC) were characterized with four monoclonal anti-Id that recognize distinct Id determinants on T15+ antibody encoded by VH-1 (of the S107 gene family), DH FL16.1, JH-1 and Vk22 germ-line genes. We have previously shown that expression of the Id designated AB1-2 and B36-82 depends on the third hypervariable loop (D region), whereas the other Id, MaId5-4 and B24-44, are influenced by VH structures outside of the D region. All four Id were expressed in the PC-response of all mouse strains tested, except the Ighj strains (C3H/HeJ, CBA/H-T6, PL/j), where the D region-dependent Id, AB1-2 and B36-82, were absent. The other Id, however, were normally expressed on individual PFC as well as the serum antibody of the Ighj strains. Expression of AB1-2 and B36-82 on 50% of PFC occurred in (BALB/c-Igha x C3H/HeJ-Ighj)F1 mice. The absence of Id correlated with a unique RFLP of the S107 gene family in Ighj strains. Finally, Id expression segregated with the appropriate RFLP pattern in individual (BALB/c x C3H/HeJ)F2 mice. These data demonstrate a selective genetic linkage of discrete T15 Id determinants, AB1-2 and B36-82 with the Igh allotype. By comparing these results with the available Ig sequences, we suggest that the Ighj allotype may be associated with an allelic form of the DH-FL16.1 segment which with VH-1, JH-1, and the Vk 22 code for the phosphocholine-specific antibody in the mouse.     

Insect capture and growth of the insectivorous Drosera rotundifolia L.

Summary Rates of insect capture increased with leaf area in the insectivorous plant Drosera rotundifolia, and growth of new leaves was related to insect capture. However, increased leaf growth was counterbalanced by leaf abscission which was in turn related to insect capture and leaf growth. Leaf loss equaled leaf growth in plants having natural rate of insect capture. A large proportion of the nitrogen gain from prey was stored in the hypocotyl; it was estimated from feeding experiments that about 24% to 30% of the nitrogen stored in the hypocotyl after winter originated from insect capture in the previous season. The effect of insect capture is discussed in relation to the life cycle of Drosera.     

Diversity,metabolic types and δ13C carbon isotope ratios in the grass flora of Namibia in relation to growth form,precipitation and habitat conditions

The grass flora of Namibia (374 species in 110 genera) shows surprisingly little variation in ¹³C values along a rainfall gradient (50–600 mm) and in different habitat conditions. However, there are significant differences in the ¹³C values between the metabolic types of the C4 photosynthetic pathway. NADP-ME-type C4 species exhibit the highest ¹³C values (–11.7 ) and occur mainly in regions with high rainfall. NAD-ME-type C4 species have significantly lower ¹³C values (–13.4 ) and dominate in the most arid part of the precipitation regime. PCK-type C4 species play an intermediate role (–12.5 ) and reach a maximum abundance in areas of intermediate precipitation. This pattern is also evident in genera containing species of different metabolic types. Within the same genus NAD species reach more negative ¹³C values than PCK species and ¹³C values decreased with rainfall. Also in Aristida, with NADP-ME-type photosynthesis, ¹³C values decreased from –11 in the inland region (600 mm precipitation) to –15 near the coast (150 mm precipitation), which is a change in discrimination which is otherwise associated by a change in metabolism. The exceptional C3 species Eragrostis walteri and Panicum heterostachyum are coastal species experiencing 50 mm precipitation only. Many of the rare species and monotypic genera grow in moist habitats rather than in the desert, and they are not different in their carbon isotope ratios from the more common flora. The role of species diversity with respect to habitat occupation and carbon metabolism is discussed.     

Localization of α1-adrenoceptors in rat and human hearts by immunocytochemistry

The localization of the ai adrenoceptors (₁-AR) in the heart tissues from rat and human and in the cultured heart cells from neonatal rats was studied by indirect immunofluorescence and postembedding electronmicroscopical immuno-gold technique. With antipeptide antibodies directed against the second extracellular loop of the human ₁-AR (AS sequence 192–218), this receptor was found to be localized along the sarcolemma in both human and rat hearts. Similar localization sites were detected in cultivated rat neonatal cardiomyocytes. Beside the localization in cardiomyocytes, ₁-AR were identified in endothelial cells of capillaries and smooth muscle cells of coronary vessels, in neuronal endings, in mast cells of cultivated heart cells but not, or in less amount in fibroblasts. Interestingly, in the right atrium of rat heart the localization of ₁-AR was found to be near or on atrial natriuretic factor (ANF) granules, providing the basis for the -adrenergic influence on ANF release. The immunocytochemical studies further confirm and complete the findings known by using autoradiographic binding studies with specific ligands.     

Drosophila Syntaxin Is Required for Cell Viability and May Function in Membrane Formation and Stabilization

The role of the Drosophila homologue of syntaxin-1A (syx) in neurotransmission has been extensively studied. However, developmental Northern analyses and in situ hybridization experiments show that SYX mRNA is expressed during all stages and in many tissues. We have isolated new mutations in syx that reveal roles for syx outside the nervous system. In the ovary, SYX is present in the germarium, but it is predominantly localized to nurse cell membranes. Mitotic recombination experiments in the germ-line show SYX is essential for oogenesis and may participate in membrane biogenesis in the nurse cells. In the early embryo, a large contribution of maternally deposited RNA is present, and the protein is localized at cell membranes during cellularization. After the maternal contribution is depleted, zygotically produced SYX assists secretion events occurring late in embryogenesis, such as cuticle deposition and neurotransmitter release. However, SYX is also required in larval imaginal discs, as certain hypomorphic mutant combinations exhibit rough eyes and wing notch defects indicative of cell death. Furthermore, recombinant clones that lack syx cause cell lethality in the developing eye. We propose that, similar to its roles in cuticle secretion and neurotransmitter release, SYX may mediate membrane assembly events throughout Drosophila development.     

Double blind randomised controlled trial of effect of metoprolol on myocardial ischaemia during endoscopic cholangiopancreatography.

OBJECTIVE--To evaluate the effect of metoprolol, a beta adrenergic blocking drug, on the occurrence of myocardial ischaemia during endoscopic cholangiopancreatography. DESIGN--Double blind, randomised, controlled trial. SETTING--University Hospital. SUBJECTS--38 (two groups of 19) patients scheduled for endoscopic cholangiopancreatography. INTERVENTIONS--Metoprolol 100 mg or placebo as premedication two hours before endoscopy. MAIN OUTCOME MEASURES--Heart rate, arterial oxygen saturation by continuous pulse oximetry, ST segment changes during endoscopic cholangiopancreatography (an ST segment deviation > 1 mV was defined as myocardial ischaemia), electrocardiogram monitored continuously with a Holter tape recorder. RESULTS--All patients had increased heart rate during endoscopy compared with rate before endoscopy, but heart rate during endoscopy was significantly lower in the metoprolol group compared with the placebo group (P = 0.0002). Twenty one patients (16 placebo, 5 metoprolol; P = 0.0008) developed tachycardia (heart rate > 100/min) during the procedure, and 11 patients (10 placebo, 1 metoprolol; P = 0.003) developed myocardial ischaemia. One patient in the placebo group had an acute inferolateral myocardial infarction. In the 10 other patients with signs of myocardial ischaemia during endoscopy the ST deviation disappeared when the endoscope was retracted. In all patients myocardial ischaemia was related to increases in heart rate, and 10 of the 11 patients had tachycardia coherent with myocardial ischaemia. CONCLUSIONS--Metoprolol prevented myocardial ischaemia during endoscopic cholangiopancreatography, probably through lowering the heart rate. Thus, tachycardia seems to be a key pathogenic factor in the development of myocardial ischaemia during endoscopy.     

Evaluation of a remotely operated vehicle (ROV) as a tool for studying the distribution and abundance of zooplankton

Conventional methods for measuring zooplankton distributionsare too laborious and time consuming to permit sufficient temporaland spatial resolution in many instances. An ability to makemore efficient and precise measurements would be useful. Weevaluated the potential for using the video system of a commerciallyavailable remotely operated vehicle (ROV) to measure the distributionand abundance of zooplankton by calibrating ROV counts withcounts based on a conventional sampling procedure (a Schindlertrap), and by using an ROV to measure the density of zooplanktonin a small lake. As configured here, this particular ROV wassuitable for measuring the density of the cladocerans Daphniaand Holopedium. It was also suitable for assessing the distribution,but not absolute densities, of Chaoborus and Leptodora. Imagequality was inadequate for quantitative estimates of copepod(Diaptomus minutus) abundance, and prevented us from studyingbehavioral responses of copepods to the vehicle. We concludethat the ROV has at least three useful features: it can be usedto locate patches of those species that are imaged effectively;a large number of samples (videotapes) can be collected almostsynoptically with high spatial resolution; the ROV enables insitu observation of zooplankton. The ROV also has three importantlimitations: the small image volume makes it difficult to studyrare organisms; inadequate image resolution precludes studiesof relatively small organisms (e.g. the calanoid copepod D.minutus);zooplankton respond to the presence of the ROV.     

Sequential activation of cyclin E and cyclin A gene expression by human papillomavirus type 16 E7 through sequences necessary for transformation.

To investigate E7-dependent biochemical changes which are involved in cellular transformation, we analyzed the influence of human papillomavirus type 16 (HPV-16) E7 on the expression of cell cycle regulatory proteins. Expression of E7 in established rodent fibroblasts (NIH 3T3), which was shown to be sufficient for transformation of these cells, leads to constitutive expression of the cyclin E and cyclin A genes in the absence of external growth factors. Surprisingly, expression of the cyclin D1 gene, which encodes a major regulator of G1 progression, is unaltered in E7-transformed cells. In transient transfection experiments, the cyclin A gene promoter is activated by E7 via an E2F binding site. In 14/2 cells, which were used as a model system to analyze the role of HPV-16 E7 in the transformation of primary cells, we observed rapid E7-dependent activation of cyclin E gene expression, which can be uncoupled from activation of the cyclin A gene, since the latter requires additional protein synthesis. E7-driven induction of cyclin E and cyclin A gene expression was accompanied by an increase in the associated kinase activities. Two domains of the E7 oncoprotein, which are designated cd1 and cd2, are essential for transformation of rodent fibroblasts. It is shown here that growth factor-independent expression of the cyclin E gene requires cd2 but not cd1, while activation of cyclin A gene expression requires cd1 function in addition to that of cd2. These data suggest that cyclin A gene expression is controlled by two distinct negative signals, one of which also restricts expression of the cyclin E gene. The ability of E7 to separately override each of these inhibitory signals, via cd1 and cd2, cosegregates with its ability to fully transform rodent fibroblasts. Unlike serum growth factors, E7 induces S-phase entry without activating cyclin D1 gene expression, in keeping with the finding that cyclin D1 function is not required in cells transformed by DNA tumor viruses.     

15N-ammonium and 15N-nitrate uptake of a 15-year-old Picea abies plantation

Throughfall nitrogen of a 15-year-old Picea abies (L.) Karst. (Norway spruce) stand in the Fichtelgebirge, Germany, was labeled with either ¹⁵N-ammonium or ¹⁵N-nitrate and uptake of these two tracers was followed during two successive growing seasons (1991 and 1992). ¹⁵N-labeling (62 mg ¹⁵N m^-2 under conditions of 1.5 g N m^-2 atmospheric nitrogen deposition) did not increase N concentrations in plant tissues. The ¹⁵N recovery within the entire stand (including soils) was 94%±6% of the applied ¹⁵N-ammonium tracer and 100%±6% of the applied ¹⁵N-nitrate tracer during the 1st year of investigation. This decreased to 80%±24% and 83%±20%, respectively, during the 2nd year. After 11 days, the ¹⁵N tracer was detectable in 1-year-old spruce needles and leaves of understory species. After 1 month, tracer was detectable in needle litter fall. At the end of the first growing season, more than 50% of the ¹⁵N taken up by spruce was assimilated in needles, and more than 20% in twigs. The relative distribution of recovered tracer of both ¹⁵N-ammonium and ¹⁵N-nitrate was similar within the different foliage age classes (recent to 11-year-old) and other compartments of the trees. ¹⁵N enrichment generally decreased with increasing tissue age. Roots accounted for up to 20% of the recovered ¹⁵N in spruce; no enrichment could be detected in stem wood. Although ¹⁵N-ammonium and ¹⁵N-nitrate were applied in the same molar quantities (¹⁵NH ₄ ⁺ : ¹⁵NO ₃ ^- =1:1), the tracers were diluted differently in the inorganic soil N pools (¹⁵NH ₄ ⁺ /NH ₄ ⁺ : ¹⁵NO ₃ ^- /NO ₃ ^- =1:9). Therefore the measured ¹⁵N amounts retained by the vegetation do not represent the actual fluxes of ammonium and nitrate in the soil solution. Use of the molar ammonium-to-nitrate ratio of 9:1 in the soil water extract to estimate ¹⁵N uptake from inorganic N pools resulted in a 2–4 times higher ammonium than nitrate uptake by P. abies.