The preparation of bile acid amides and oxazolines, II, the synthesis of the amides and oxazolines of ursodeoxycholic acid, deoxycholic acid, hyodeoxycholic acid and cholic acid

Bile acid amides and oxazolines were synthesized by a sequence of steps involving the reaction of the free bile acid with formic acid to yield the formyloxy derivative, preparation of the formyloxy acid chloride, condensation of the acid chloride with 2-amino-2-methyl-1-propanol to give the amide and, finally, cyclization of the amide with thionyl chloride to give the oxazoline. The oxazolines were characterized by physical constants, thin layer and gas-liquid chromatography and identified by elemental analysis and gas-liquid chromatography-mass spectrometry. Some of the bile acid oxazoline derivatives alter the activity of bacterial 7-dehydroxylases $\text{in vitro}$, and inhibit the growth of certain anaerobic bacteria in pure culture.     

Structural variation in the heterochromatin of rye chromosomes in triticales

Summary Although Giemsa C-banding techniques have been used extensively for assaying cereal heterochromatin, a more specific technique for analyzing cereal heterochromatin has been developed recently with the isolation of DNA sequences present in heterochromatin and their employment in in situ hybridization to cereal chromosomes. A number of triticales were examined for the occurrence of modified rye chromosomes using the in situ hybridization technique. With a heterogeneous sequence probe the amount of rye heterochromatin appears to be relatively constant in wheat backgrounds but when a specific sequence probe was employed variation was observed. Whether this variation reflects polymorphism in rye or whether it is a result of adaption of the rye genome to coexistence with the wheat genome in triticales is discussed. — The triticale Rosner was examined in detail and it was established that the rye chromosome 2R had been replaced by the wheat chromosome 2D.     

Measurement of membrane potential inBacillus subtilis: A comparison of lipophilic cations,rubidium ion,and a cyanine dye as probes

Summary Two of the commonly used probes for measuring membrane potential—lipophilic cations and the cyanine dye diS-C₃(5)—indicated nominally opposite results when tetraphenylarsonium ion was added as a drug to suspensions of metabolizingBacillus subtilis cells. [³H]-Triphenylmethylphosphonium uptake was enhanced by the addition, indicating hyperpolarization, yet fluorescence of diS-C₃(5) was also enhanced, indicating depolarization. Evidence is presented that both effects are artifactual, and can occur without any change in membrane potential, as estimated by⁸⁶Rb⁺ uptake in the presence of valinomycin. The fluorescence studies suggest that tetraphenylarsonium ion displaces the cyanine dye from the cell envelope, or other binding site, into the aqueous phase.The uptake characteristics of the radiolabeled lipophilic cations were quite unusual: At low concentrations (e.g., less than 10 m for triphenylmethylphosphonium) there was potential-dependent uptake of the label to a stable level, but subsequent addition of nonradioactive lipophilic cation caused further uptake of label to a new stable level. Labeled triphenylmethylphosphonium ion taken up to the first stable level could be displaced by 10mm magnesium ion, whereas⁸⁶Rb⁺ uptake was unperturbed. Association of the lipophilic cations with the surface of de-energized cells was concentration-dependent, but there was no evidence for cooperative binding. This phenomenon of stimulated uptake inB. subtilis (which was not seen inEscherichia coli cells or vesicles) is consistent with a two-compartment model with access to the second compartment only being possible above a critical cation concentration. We tentatively propose such a model, in which these compartments are the cell surface and the cytoplasm, respectively.Triphenylmethylphosphonium up to 0.5mm exhibited linear binding to de-energized cells; binding of tetraphenylphosphonium and tetraphenylarsonium was nonlinear but was not saturated at the highest concentration tested (1mm). The usual assumption, that association of the cation with cell surfaces is saturated and so can be estimated on de-energized cells, therefore leads to undercorrected estimates of cytoplasmic uptake inB. subtilis, and hence to overestimates of membrane potential. We describe a more realistic procedure, in which the estimate of extent of binding is based on a mean aqueous concentration related both to the external concentration and to the much higher internal concentration that exists in energized cells. Using this procedure we estimate the membrane potential inB. subtilis to be 120 mV, inside-negative. The procedure is of general applicability, and should yield more accurate estimates of membrane potential in any system where there is significant potential-dependent binding.Work performed while on sabbatical leave from Department of Biology, Ben-Gurion University of the Negev, Beer-Sheva, Israel.     

Effect of abscisic acid on CO2 exchange in Lemna gibba

The effects of abscisic acid (ABA) on photosynthesis, dark respiration, and photorespiration were studied in Lemna gibba L. plants. The initial concentration of ABA in the nutrient solution was 10⁻⁷M and in a few experiments, 10⁻⁶M. The cultures were grown in the same solution for time periods ranging from one hour to 12 days. Net photosynthesis, measured as CO₂ uptake by infrared gas analyser technique, was inhibited after four hours of ABA treatment and reached a minimum after four to seven days depending on the time of the year. After 12 days a substantial recovery of photosynthesis was observed. Dark respiration was significantly stimulated after two to seven days of ABA treatment but then returned to the control level. The transient effects of ABA on photosynthesis and dark respiration corresponded to the previously measured time course of [¹⁴C]-ABA uptake by Lemna . Photorespiration measured as oxygen inhibition of photosynthesis was not affected by ABA.     

Joint Segregation of Biochemical Loci in Salmonidae. II. Linkage Associations from a Hybridized Salvelinus Genome (S. NAMAYCUSHxS. FONTINALIS)

The results of more than 300 pairwise examinations of biochemical loci for joint segregation in brook trout (Salvelinus fontinalis) and in the hybridized genome of lake trout (S. namaycush) x brook trout are summarized. Nineteen loci have been assigned to the following eight linkage groupings on the basis of nonrandom assortment, including cases of both classical linkage and pseudolinkage: ODH with PMI with PGI-3, PGI-2 with SDH, ADA-1 with AGP-2, AAT-(1,2) with AGP-1 with MDH-1, MDH-3 with MDH-4, LDH-3 with LDH-4, IDH-3 with ME-2 and GUS with CPK-1. Pseudolinkage (an excess of nonparental progeny types) was observed only for male testcross parents. The results suggest that this phenomenon involves homeologous chromosome arms as evidenced by the de novo association of presumed duplicate loci in each case. Classical linkage has not been found for the five pairs of duplicate loci examined in Salvelinus, suggesting that not all of the eight metacentrics in the haploid complement involve fusions of homeologous chromosomes. Females consistently showed a greater degree of recombination.     

Inhibition of the pancreatic microsome enzyme release phenomenon by inhibitors of signal peptidase activity

The protease-sensitive release of α-amylase from rat pancreatic microsomes, incubated at 37°C, was inhibited by protease inhibitors which have been reported to inhibit signal peptidase activity. Protease inhibitors which did not affect signal peptidase activity also failed to inhibit amylase release from microsomes. Although the observed amylase release was in the opposite direction to enzyme secretion and involved fully-synthesised proteins, rather than nascent peptides, it is proposed that the enzyme release phenomenon reported from this laboratory (Pearce et al. (1978) Biochem. J. 176, 611–614) is related to the protein transporting mechanism involved in secretion.     

Flight performance of the moth, Manduca sexta, at variable gravity

The tethered and free flight of Manduca sexta were studied during period 1,2, and 0 times normal gravity (g) produced in an aeroplane by flying through parabolic trajectories. Moths in tethered flight did not change their aerodynamic output in response to increases or decreases in gravity. Some moths in free flight at 0 g maintained a position in the box by flying against a surface, or into the angle between two surfaces. In the absence of gravity as an orienting stimulus, the positive dorsophotic response to light was dominant. As the period of 0 g continued, moths were increasingly likely to periodically reduce the amplitude of their wingbeat and/or stop flying, for the equivalent of a few wingbeats. Only at 0 g, moths very occasionally spread their wings and floated freely for a few seconds. At 0 g moths retained control of rolling and yawing movements but stability in pitch was greatly reduced or absent.     

Discriminant analysis on cells from developing squamous cancer of the respiratory tract

Cytologic preparations made from the tracheobronchial tree taken by the Schreiber catheter have been scanned by three color microphotometry. The digitized cell images were processed by the analytical cytodiagnostic programs of the TICAS system. Cells were sorted into two control groups and five groups of increasing atypia ranging from normal epithelium to invasive squamous cell carcinoma. Standard statistical tests, including Wilk's Lambda, Rao's V, and the Kruskal-Wallis tests are performed on these subsets of cell image features. This study demonstrates that discriminant analyses permit differentiation between normal cells and those from marked atypia or carcinoma and that the classification achieves a high degree of agreement with visual assignment.     

Stimulation of cellular RNA synthesis in mouse-kidney cell cultures infected with SV40 virus

In confluent primary mouse-kidney cell cultures, abortive infection with SV40 has been demonstrated to cause an increase in the bulk of cellular RNA (mainly rRNA). However, the increase in the rate of rRNA synthesis is not involved in the initiation of the virus-induced cellular DNA replication since after actinomycin D treatment (0.05 μg/ml, from 6 to 9 h p.i.) the onset of cellular DNA replication takes place at a time when the rate of rRNA synthesis is still depressed.