Chloroplast DNA restriction analysis and the infrageneric grouping ofAllium (Alliaceae)

The utility of chloroplast DNA variation for checking a recently proposed infrageneric classification of the genusAllium was tested. cpDNA restriction patterns of 49 species representing the main subgenera, sections, and subsections of the existing classification were compared. 363 different fragments generated by 4 restriction enzymes were identified and analysed by UPGMA clustering. The resulting phenogram largely confirms the subgeneric classification based on an integration of morphological and other methods.     

Phospholipase C activation in rat pituitary adenoma (GH) cells

The presence of the pertussis toxin (PTX) insensitive GTP-binding proteins (G-proteins) G_q and/or G₁₁ has been demonstrated in three different prolactin (PRL) and growth hormone (GH) producing pituitary adenoma cell lines. Immunoblocking of their coupling to hormone receptors indicates that G_q and/or G₁₁ confer throliberin (TRH) responsive phospholipase C (PL-C) activity in these cells. The contention was substantiated by immunoprecipitation analyses snowing that anti G_q/11-sera coprecipitated PL-C activity. In essence, only G_q/11 (but neither G_i2, G_i3 nor G_o) seems to mediate the TRH-sensitive PL-C activity, while G_o may be coupled to a basal or constitutive PL-C activity. Immunoblocking studies imply that the B-complex also, to some extent, may stimulate GH₃ pituitary cell line PL-C activity. Finally, the steady state levels of G_q/11 mRNA and protein were downregulated upon long term exposure of the GH3 cells to TRH (but not to vasoactive intestinal peptide = VIP).     

RFLP of RT-PCR products: Application to the expression ofCHS multigene family in poplar

A novel method for studying differential expression of multigene family members based on the high sensitivity of RT-PCR completed by restriction site polymorphism of DNA is described. This method allows the identification of specific patterns of expression of fourchalcone synthase genes in a Hunnegem poplar clone (Populus trichocarpa ×Populus deltoides).     

Fine mapping of the Autosomal Dominant Split Hand/Split Foot Locus on Chromosome 7, Band q21.3-q22.1

Split hand/split foot (SHFD) is a human developmental defect characterized by missing digits, fusion of remaining digits, and a deep median cleft in the hands and feet. Cytogenetic studies of deletions and translocations associated with this disorder have indicated that an autosomal dominant split hand/split foot locus (gene SHFD1) maps to 7q21-q22. To characterize the SHFD1 locus, somatic cell hybrid lines were constructed from cytogenetically abnormal individuals with SHFD. Molecular analysis resulted in the localization of 93 DNA markers to one of 10 intervals surrounding the SHFD1 locus. The translocation breakpoints in four SHFD patients were encompassed by the smallest region of overlap among the SHFD-associated deletions. The order of DNA markers in the SHFD1 critical region has been defined as PON–D7S812–SHFD1–D7S811–ASNS. One DNA marker, D7S811, detected altered restriction enzyme fragments in three patients with translocations when examined by pulsed-field gel electro-phoresis (PFGE). These data map SHFD1, a gene that is crucial for human limb differentiation, to a small interval in the q21.3-q22.1 region of human chromosome 7.     

Prey preference and egg production of the carabid beetleAgonum dorsale

In order to elucidate whether the aphidRhopalosiphum padi is low quality food for the carabid beetleAgonum dorsale, as it has previously been found to be for cereal spiders, we performed a series of experiments using fruit fliesDrosophila melanogaster as a standard alternative prey (‘control prey’): 1) Prey preference, 2) Aphid consumption for satiated and starved beetles, 3) Egg production on different diets and 4) Preference experiments with fruit flies coated with a taste of different prey types. Other alternative prey types used were earthworms and sciarid midges, all potential prey in the field.A. dorsale has a low preference for aphids compared to fruit flies. Apparently there is an upper limit to the consumption of aphids independent of hunger and much below the beetles' total food demand. Egg production on a pure diet of aphids is lower than on a pure diet of fruit flies; it is extremely low on a pure diet of earthworms; the highest fecundity is found on a mixed diet. As fruit flies coated with a taste of aphids or sciarid midges are less prefered than flies covered with a taste of fruit flies there may be a chemical factor, acting through taste, involved in determining prey preference.     

Morphology and ontogeny of single-walled multiporous sensilla of hemimetabolous insects

Comparative morphological investigations were made to determine the common organization plan of single-walled multiporous sensilla. The development of multiporous chemoreceptive sensilla of Gryllus, Oncopeltus and Lepisma follows the same path. Each chemoreceptive sensillum is associated with four types of enveloping cell. During ontogeny, enveloping cell 1 secretes the dendritic sheath. Enveloping cell 4 builds the connection of the hair base with the antennal cuticle. In Gryllus and Oncopehus, enveloping cells 2 and 3 build the hair shaft, the wall pores and pore tubules in nearly equal parts. Enveloping cells 2 and 3 lie side by side in the hair process, in which enveloping cell 2 produces the inner part, enveloping cell 3 the outer part of the hair shaft. In Lepisma the predominant part of the hair shaft with the wall pores is formed by the doubled enveloping cells 3. Interpreting our findings and the literature data, a new proposal is given for the homology of the enveloping cells. In singlewalled chemoreceptors, enveloping cell 1 is considered as thecogen and enveloping cell 4 as tormogen cell. Enveloping cell 2 is interpreted as inner trichogcn cell and enveloping cell 3 as outer trichogen cell.     

Principles and practices of medicine

The medical textbooks in our university library present ‘principles’ as the basis which underlies medical ‘practice’. In this article it is argued that this helps different medical logics to co-exist. The example analyzed is that of anemia in the Netherlands. Currently this is defined pathophysiologically, statistically and clinically. These three definitions are intertwined with different strategies for the creation of normal hemoglobin levels and the detection of patients with anemia. The discrepancies between them, however, do not lead to the controversies that might be expected by those who believe in consistency. Instead, the rhetoric of principles-and-practice helps to bring about peaceful co-existence.     

Human cytomegalovirus maturational proteinase: expression in Escherichia coli, purification, and enzymatic characterization by using peptide substrate mimics of natural cleavage sites.

The proteolytic processing of the human cytomegalovirus (HCMV) assembly protein, resulting in truncation of its C terminus, is an essential step in virion maturation. The proteinase responsible for this cleavage is the amino-terminal half of the protein encoded by the UL80a open reading fame. We have obtained high expression levels of this 256-amino-acid HCMV proteinase, assemblin, in Escherichia coli. In addition to the 28-kDa proteinase, a 15-kDa protein comprising the first 143 amino acids and a 13-kDa protein comprising the last 113 amino acids of the 28-kDa HCMV proteinase were present. Both the 28-kDa proteinase and the 15-kDa protein were purified by a two-step chromatographic procedure utilizing anion exchange in urea and dithiothreitol and size exclusion in NaSCN and dithiothreitol. Activation of the purified 28-kDa proteinase required denaturation in urea as well as complete reduction of all five cysteine residues in the molecule. Removal of the urea by dialysis with retention of the reducing agent yielded an active proteinase. Addition of glycerol to 50% enhanced the activity. The HCMV proteinase cleaved the peptides RGVVNASSRLAK and SYVKASVSPE, which are mimics of the maturational (M)- and release (R)-site sequences, respectively, in the UL80a-encoded protein. The cleavage site in the peptides was at the same Ala-Ser scissile bond as observed in the UL80a protein. The Km value for the cleavage of RGVVNASSRLAK (M-site mimic) by the proteinase was similar to that for SYVKASVSPE (R-site mimic), but the turnover (kcat) of the M-site peptide mimic substrate by the proteinase was six to eight times faster. The peptide homologs of the herpes simplex virus type 1 M- and R-site sequences in the UL26-encoded protein were also cleaved by the HCMV proteinase, although at rates slower than those for the HCMV substrates. The HCMV proteinase was inhibited by Zn2+ and by alkylating agents, but only at very high inhibitor concentrations. The purified 15-kDa protein, subjected to the same activation conditions as the 28-kDa proteinase, had no enzymatic activity against the HCMV M- and R-site peptide substrates.