Well-identifiable human chromosomes Isolated from mitotic fibroblasts by a new method

Summary Metaphase chromosomes isolated from human fibroblasts by lysis of mitotic cells in the presence of the intercalating DNA-specific fluorochrome propidium iodide appear relatively long, even after exposure to vinblastine sulfate overnight. Therefore, they can be easily banded and thereby unequivocally identified. Chromosomes isolated in this way may be employed in flow analysis and sorting without loosing the inducibility of their band patterns.     

Anaerobic Oxidation of Acetylene by Estuarine Sediments and Enrichment Cultures

Acetylene disappeared from the gas phase of anaerobically incubated estuarine sediment slurries, and loss was accompanied by increased levels of carbon dioxide. Acetylene loss was inhibited by chloramphenicol, air, and autoclaving. Addition of ¹⁴C₂H₂ to slurries resulted in the formation of ¹⁴CO₂ and the transient appearance of ¹⁴C-soluble intermediates, of which acetate was a major component. Acetylene oxidation stimulated sulfate reduction; however, sulfate reduction was not required for the loss of C₂H₂ to occur. Enrichment cultures were obtained which grew anaerobically at the expense of C₂H₂.     

Targeted point mutation that creates a unique Eco RI site within the signal codons of the beta-lactamase gene without altering enzyme secretion or processing

A method has been developed for constructing site-specific mutations by using a strongly selectable marker on which to "piggy-back" a desired mutation that may be phenotypically silent. Using this approach, a new unique Eco RI restriction site has been generated at the beginning of the signal codons of the beta-lactamase gene of the plasmid pBR322. The consequential alteration of the second amino acid of the signal from Ser to Arg has no effect on either the transport or the processing of the beta-lactamase.     

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.     

Stereochemical aspects of forcing special substrate hydrazides to behave either as electrophiles or as nucleophiles during catalysis by crude papain

Restriction of hydrazides of N-blocked amino acids mainly to electrophilic action, in acylating crude papain, has been achieved by means of a large amount of aniline, with formation of insoluble anilides of N-acylamino acids. Similarly, nucleophilic behavior, on the part of a hydrazide, has been promoted by introducing a large proportion of an N-acylamino acid to produce an insoluble N¹,N²-diacylhydrazine. Achiral, chiral and racemic hydrazides and their corresponding N-acylamino acids were utilized in the study. Among the more informative combinations of reactants were Z-dl-alanine hydrazide with aniline and then with Z-glycine. A stereospecific response in the former situation produced Z-l-alanine anilide. In the latter case, a stereoselective interaction produced Z-Gly-NHNH-lAla-Z more rapidly than Z-Gly-NHNH-d-Ala-Z. The final incubation period yielded an optically pure D product. Differences in stereochemical control have been delineated in terms of different spatial aspects for interactions at the S and S′ subsites of sulfhydryl proteolytic enzymes. A racemic reactant encountered firm stereospecificity as an electrophile at the S subsite but only modest stereoselectivity as a nucleophile at the S′ subsite. The ready availability of crude papain allows an effective procedure for the synthesis of substantial quantities of diacylhydrazines.     

Evaluation of a new modified pediatric bubble oxygenator

A comparison was made of the S-070 Pediatric Bubble Oxygenator, which was unreliable above flow rates of approximately 1.5 L/min, with a modified S-070A, which proved to be extremely efficient to flow rates of 2.5 L/min.     

A theory of Brownian coagulation in a bounded planar region

A method for calculating time-dependent probabilities and rates of coagulation is given for particles on a bounded two-dimensional region. Equations are derived and solved for the random variations of displacements between two particles which undergo independent Brownian motion and bind irreversibly upon collision. The solution is used to calculate expected times required for collisions of particles. Comparison with earlier models shows that revised boundary values and initial conditions predictably lengthen required collision times by about a factor of four. Applicatons of the methodology are discussed.     

Genetic variability of the tumorous-head maternal effect in Drosophila melanogaster

Summary The tumorous-head maternal effect in Drosophila melanogaster is produced by a recessive gene (tuh-1) in chromosome 1. Polymorphism exists at this locus. This maternal effect, which is part of the normal variation found in this species, is detected with the aid of a mutant gene. In the presence of the maternal effect, a semi-dominant mutant gene (tuh-3) causes homoeotic changes in the eye-antennal imaginal discs. The phenotype in the adult is known as the tumorous-head abnormality. The mutant gene, which is located in the right arm of chromosome 3, is characterized by reduced penetrance. Using the penetrance of the mutant gene as the criterion, the results of these experiments show that the level of the maternal effect activity is influenced remarkably by modifiers present in wild type strains. The assay is to mate females homozygous for tuh-1 with males homozygous for tuh-3 and to determine the percent of the offspring showing the tumorous head abnormality. Using this procedure, it was observed that parental females with various combinations of chromosomes 1 and 3 from Lausanne and Stephenville wild type strains show great variability in the level of maternal effect activity. Modifiers in chromosome 1 and 3 from the Stephenville strain increase the level of the maternal effect activity. The level is reduced if these chromosomes are replaced by those from the Lausanne strain. A major locus in chromosome 3 is in the same region occupied by clusters of functionally related genes with regulating action. These results demonstrate that the penetrance of a mutant gene, which acts during embryogenesis, is influenced by modifiers which act during oogenesis.This investigation was supported by Public Health Service Research Grant GM 18664 to Arizona State University from the National Institute of General Medical Sciences