Linkage of the DNA-segment D7S13 (pB79a) with the cystic fibrosis locus

Summary A map distance of 2.9 cM between D7S13 (pB79a) and the cystic fibrosis (CF) locus was obtained from the analysis of 13 informative families with a history of CF. This result is based solely on the HindIII restriction fragment length polymorphism (HindIII-RFLP) at D7S13, since the interpretation of the Msp1-RFLP at this locus was found to be unreliable.     

The nucleotide sequences of barley cytoplasmic glutamate transfer RNAs and structural features essential for formation of δ-aminolevulinic acid

In chloroplasts and a number of prokaryotes, -aminolevulinic acid (ALA), the universal precursor of porphyrins, is synthesized by a multistep enzymatic pathway with glutamyl-tRNA^Glu as an intermediate. The ALA synthesizing system from barley chloroplasts is highly specific in its tRNA requirement for chloroplast tRNA^Glu; a number of other Glu-tRNAs are inactive in ALA formation although they can be glutamylated by chloroplast aminoacyl-tRNA synthetases. In order to obtain more information about the structural features defining the ability of a tRNA to be recognized by the ALA synthesizing enzymes, we purified and sequenced two cytoplasmic tRNA^Glu species from barley embryos which are inactive in ALA synthesis. By using glutamylated tRNAs as a substrate for the overall reaction, we showed that Glu-tRNA reductase is the enzyme responsible for tRNA discrimination.     

New form of lignolytically active mycelium generated by immobilization of protoplasts isolated from the white rot fungi Heterobasidion annosum and Polyporus pinsitus

Summary Immobilized mycelia regenerated from immobilized protoplasts isolated from lignin-degrading Basiodiomycetes have been shown to be able to decompose specifically ¹⁴C-labelled dehydropolymers of coniferylalcohol (DHP-lignin) and monomeric lignin-related compounds more intensively than native mycelium, by decarboxylation, demethylation, ring and side chain cleavage. Protoplasts of two white rot fungi were immobilized by entrapment in Na- alginate gel and remained intact after the immobilization procedure. Within the first 3 days of incubation in culture medium, regeneration of hyphal cells occurred. Since hyphal cells regenerated from protoplasts within gel beads were hindered from stretching by the matrix, the microbial immobilized cells differed from native mycelium in terms of their morphology. The time course and extent of lignin degradation by native mycelium and regenerated mycelium of the examined white rot fungi also differed, a sign that there may also be differences between them in terms of the physiology of lignin degradation.     

Lipase production of Staphylococcus carnosus in a dialysis fermentor

Summary In a newly constructed one-vessel dialysis fermentor, a strain of Staphylococcus carnosus TM300 carrying the lipase secretion plasmid pLipPS1 was used to investigate exoenzyme and biomass production. The bacterial culture grows in an inner compartment of 21 volume, separated from a 101 nutrient broth compartment by a conventional dialysis membrane. In order to avoid substrate depletion and to prolong the growth phase, a highly concentrated nutrient broth was used. The biomass production reached 60 g cell dry weight/l. The increase in extracellular lipase concentration was directly coupled with the increase of cell mass and reached a value of 230 mg/l culture supernatant. Harvesting the cells in the late growth phase, the lipase content was about 30% of the total exoproteins in the supernatant.     

Ion Homeostasis in Chloroplasts under Salinity and Mineral Deficiency: II. Solute Distribution between Chloroplasts and Extrachloroplastic Space under Excess or Deficiency of Sulfate, Phosphate, or Magnesium

Spinach (Spinacia oleracea var “Yates”) plants grown hydroponically were exposed to an excess or deficiency of various mineral ions. Solutes were measured in leaf extracts and in isolated intact chloroplasts. Under phosphate (120 millimoles per liter NaH₂ PO₄), sulfate (200 millimolar per liter (Na₂ SO₄), or magnesium excess (150 millimolar per liter MgCl₂), concentrations of these ions in leaf extracts increased, but in chloroplasts, concentrations of all ions remained constant. Concentrations of quarternary ammonium compounds in chloroplasts increased. Under mild phosphate or magnesium deficiency, concentrations of these ions decreased in chloroplasts less than in whole leaf extracts. Under severe sulfate deficiency causing chlorosis in younger leaves, sulfate concentrations in chloroplasts remained even unchanged, despite a drastic decrease of sulfate concentrations both in green and in chlorotic leaves. Together with results from a companion study (G Schröppel-Meier, WM Kaiser 1988 Plant Physiol 87: 822-827) our data demonstrate that leaf cells are able to keep the concentrations of several mineral ions rather constant in metabolically active compartments even at extremely large variations of ion concentrations in the culture solution and in the leaves.     

Studies on the link between HMG-CoA reductase and cholesterol 7 alpha-hydroxylase in rat liver

Under most experimental conditions, there is a covariation between the rate-limiting enzyme in cholesterol biosynthesis, HMG-CoA reductase, and the rate-limiting enzyme in bile acid biosynthesis, cholesterol 7 alpha-hydroxylase. The most simple explanation for the coupling between the two enzymes is that newly synthesized cholesterol is a substrate for an unsaturated cholesterol 7 alpha-hydroxylase and that substrate availability is of major regulatory importance for this enzyme. The following results seem, however, to rule out that such a simple regulatory mechanism is of major importance and that HMG-CoA reductase activity per se is of importance in the regulation of cholesterol 7 alpha-hydroxylase. 1) The apparent degree of saturation of cholesterol 7 alpha-hydroxylase, as measured in vitro in rat liver microsomes, was found to be relatively high (70-90%) under most experimental conditions, including starvation, cholestyramine treatment, and cholesterol treatment. A significant decrease in the degree of saturation was obtained first after a drastic reduction of total concentration of cholesterol in the microsomes by treatment with high doses of triparanol, an inhibitor of cholesterol biosynthesis. 2) The stimulatory effect of cholesterol feeding on cholesterol 7 alpha-hydroxylase activity in rats seems to be an effect on the enzyme activity (enzyme induction?) rather than an effect on substrate availability. Thus, the stimulatory effect of cholesterol feeding was retained also after almost complete removal of the endogenous cholesterol by extraction with acetone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiovascular and Pulmonary Effects of a New Sedative/Analgesic (Medetomidine) as a Preanaesthetic Drug in the Dog

Cardiovascular and pulmonary effects of a new sedative/analgesic (medetomidine) as a preanaesthetic drug in the dog. A study was carried out to investigate the possible usefulness of medetomidine (Farmos Group, Turku, Finland) for premedication prior to general anaesthesia with thiopental sodium and halothane. The main emphasis was laid on the circulatory and respiratory effects of medetomidine. Dogs treated with xylazine (2 mg/kg) or placebo (physiological saline solution) served as controls. Medetomidine caused a decrease in blood pressure, heart rate and respiratory rate at all dose levels tested. These decreases were essentially dose -dependent, but there were great individual variations. It is concluded that the drug can be useful for premedication at the lowest dose level tested (10 μ/kg). The sedative effect, however, is so strong that an even lower dose might be sufficient for the present purpose.