Quantitative tritium autoradiography of mammalian chromosomes

The rates of tritiated thymidine accumulation in each of the chromosome types in Chinese hamster line Don and strain Don-C have been assayed by quantitative tritium autoradiography. The late-replicating nature of the X and Y chromosomes is readily apparent. Many chromosomes exhibit three separate steps of synthesis, with reduced rates of thymidine incorporation between 3 and 4 hours and again between 5 and 6 hours. The same three-step pattern can be seen in scintillation data from FUdR synchronized cells, with 40% of the DNA made in each of the first two steps and 20% in the final step.This research was supported in part by Grant GB-7248 from the National Science Foundation and by Grant E-286 from The American Cancer Society.     

Linkage of the locus for conversion of albumin (Acf-1)in the house mouse,Mus musculus

The linkage of the locus for conversion of albumin (Acf-1) has been established on chromosome 1 with the following gene order and recombination percentages: Id-1 19.3±5.2% Acf-1 4.2±1.7% Dip-1 18.4±4.2% Lp.This work was supported by NIH Postdoctoral Fellowship 1F32 GM0527701, Grant BMS75-03397 from the National Science Foundation, Grant ACS VC-17-R from the American Cancer Society, and Contract NO1-ES42159 from the National Institute of Environmental Health Sciences. The Jackson Laboratory is fully accredited by the American Association for the Accreditation of Laboratory Animal Care.     

Cylindrical structures in the chloroplasts of Sirogonium melanosporum

Summary Cylindrical structures with outside diameters of 390 to 410 Å have been observed in the chloroplasts of mature vegetative cells of the filamentous, green alga Sirogonium melanosporum. These cylindrical structures are either parallel to one another or randomly oriented in the stroma matrix of the chloroplast. Some of the outer cylindrical structures of the complex appear to be continuous with thylakoid membranes, suggesting a relationship between these two structures.This work was supported by an Institutional Grant from the American Cancer Society to the University of Arizona and by grant GB2440 from the National Science Foundation to R. W. Hoshaw. The authors thank Dr. Wayneferris for the use of the electron microscope supported by NSF grant GB3330.     

Genetic mapping of aminoglycoside and fusidic acid resistant mutations in Bacillus subtilis

Summary Mutations governing resistance to neamine, neomycin, kanamycin and fusidic acid have been mapped within the ribosomal region of theBacillus subtilis genome using PBS1-mediated transduction. The probable order of these closely linked markers is: This work was supported by a predoctoral training grant, GM-1290, from the National Institutes of Health, administered by the Department of Microbiology, N.Y.U. School of Medicine, and by a research grant from the National Science Foundation, GB-16782, awarded to I.S.     

Phenocopies induced by thymine inEscherichia coli

Summary A uracilless strain ofE. coli upon starvation for uracil adapts to synthesize this compound. These adaptations are of two sorts, heritable and non-heritable. The latter are induced by the presence of thymine although little or none of the uracil is synthesized by the demethylation of thymine. The non-heritable adaptations arise in a discontinuous fashion at a rate 10 times as high as the genetic reversions. The non-heritable uracil-independent cells are considered to be phenocopies because they mimic the phenotype of the genetic revertants.With 2 Figures in the TextThis research was supported in part, by grants from the American Cancer Society, the U. S. Public Health Service and the National Science Foundation.     

The formation of ring canals by cell furrows in Drosophila

Summary Fifteen ring canals or intercellular bridges connect the oocyte and 15 nurse cells in Drosophila. Recently, Koch and King (1969) proposed that these ring canals formed independently of a cell furrow and that cytokinesis during the 4 cell divisions producing the 16 cells occurred through fusion of vesicles aligned along the division plane. Serial sections of germaria, fixed with glutaraldehyde, have been studied with the electron microscope, and no evidence has been found for fusion of vesicles in the cleavage of cells. The probability that the chromate-OsO₄ fixation used by Koch and King resulted in an artifact is discussed.The author gratefully acknowledges the assistance of Mrs. Joan Chlebowski; and the support of National Science Foundation grants GB-9780, GB-5780 and GB-24956; National Institutes of Health grant RR-05539; and an appropriation from the Commonwealth of Pennsylvania.     

Hypoxylon cohaerens: Cytology of the ascus

The haploid chromosome number ofHypoxylon cohaerens apparently is 5, based on counts made at meiotic prophase and meiotic and mitotic metaphases. Newly formed ascospores are at first uninucleate, becoming binucleate following mitosis in the ascospore. Subsequently, one of the two nuclei disappears. Maturing ascospores are uninucleate.Scientific Paper No. 3732 Washington State University. College of Agriculture, Project 1767. This study was supported in part by National Science Foundation Grant GB-19924.     

1,25-Dihydroxy vitamin D2 induces leukemia cell differentiation

This work supported in part by the NIH (USPHS), Council for Tobacco Research, American Institute for Cancer Research, and the Cornell Consolidated and Cornell Biotechnology Program which is sponsored by the New York State Science and Technology Foundation, a consortium of industries, the US Army Research Office and the National Science Foundation.     

Distribution of constitutive heterochromatin in mammalian chromosomes

Using a special staining technique, a survey of the chromosomes of many mammalian species showed that constitutive heterochromatin is present in all cases and that the heterochromatin pattern appears to be specific and consistent or each chromosome and each taxon. Usually heavy heterochromatin is found in the centromeric areas, but terminal heterochromatin is not uncommon. Occasionally interstitial heterochromatin bands occur. In some species, such as the Syrian hamster and Peromyscus, many chromosome arms are completely heterochromatic.Supported in part by Research Grant GB-13661 from the National Science Foundation.     

In vitro culture of tissue from the tunicateStyela clava

Summary Pharyngeal explants and circulatory hemocytes from the tunicateStyela clava were cultured in a medium containing tunicate plasma, artificial seawater, RPMI 1640, and antibiotics. Pharnngeal tissue remained viable and proliferated for up to 72 d in vitro. Proliferative activity maintained the pool of hemocytes within explants and facilitated the migration of pharyngeal hemocytes from explants into culture supernatants. The diversity of morphologically distinct cell types within the hemocyte pool of pharyngeal cultures indicated that cell division was followed by regulated differentiation. In contrast to pharyngeal cultures, suspensions of circulatory hemocytes did not survive for prolonged periods in vitro. Proliferative activity could not be detected in circulatory hemocyte cultures. These results are discussed in terms of the differentiation state of hemocytes and the efficacy of culture conditions. This study was supported by the National Science Foundation, Washington, DC (grant DCB 85 19848) and by BRSG funds from UCLA Schools of Medicine and Dentistry. Flow cytometric facilities were sponsored in part by a Johnson Cancer Center Core Grant (CA 16042). David A. Raftos is a Fulbright Postdoctoral Fellow and recipient of a Frederik B. Bang Scholarship in Marine Invertebrate Immunology administered by the American Association of Immunologist. Dan L. Stillman was supported by an REU supplement from the National Science Foundation.     

Buoyant densities of DNA of mammals

One characteristic of DNA, CsCl buoyant density peak values, was determined for DNA samples isolated from 93 species belonging to 11 orders of mammals. The CsCl buoyant density values varied over a very narrow range, 1.696–1.701 g/cm³. Satellite DNAs were found in a number of species. The function and origin of these satellite DNAs are not known.This work was supported by grant DRG-269 from the Damon Runyon Memorial Fund for Cancer Research, Inc., and GB-6657 from the National Science Foundation.     

The influence of genetic background on expression of mutations at the diabetes locus in the mouse. I. C57BL/KsJ and C57BL/6J strains

Two new diabetic strains, C57BL/KsJ-db ^2J and C57BL/6J-db ^2J, have been developed. C57BL/KsJ-db ^2J/db^2J mice are indistinguishable from C57BL/KsJ-db/db mice, the original diabetes mutation. Both have severe diabetes characterized by hyperphagia, obesity, marked hyperglycemia, temporarily elevated plasma insulin concentrations, and typical degenerative changes in the islets of Langerhans. In contrast, C57BL/6J-db ^2J/db^2J mice, although also hyperphagic and obese, have mild diabetes characterized by transitory hyperglycemia and markedly elevated plasma insulin concentrations coupled with marked hypertrophy of the islets and increased proliferative capacity of beta cells. The mild diabetes-like syndrome produced by diabetes-2J on the C57BL/6J background is similar to that produced by the obese gene (ob) on the same background. The islet responses, whether atrophy or hypertrophy, appear to be due to the interaction of diabetes-2J (and possibly obese) with modifiers in the genetic background rather than being peculiar to the specific mutant. The markedly different disease patterns that result when the same gene is placed on different inbred backgrounds emphasize the importance of strict genetic control in biochemical and physiological studies with these and other obesity mutants.Supported in part by NIH Research Grants AM 14461 from the National Institute of Arthritis and Metabolic Diseases; CA 05873 from the National Cancer Institute; ACS E-162, a Janice M. Blood Memorial Grant for Cancer Research from the American Cancer Society; GB 27487 from the National Science Foundation; and an allocation from the Southwaite Foundation.     

Hypoxylon rubiginosum: Cytology of the ascus and surface morphology of the ascospore

Summary The haploid chromosome number ofHypoxylon rubiginosum is 5. The ascospore is uninucleate when formed, becoming binucleate following a mitosis. One of the nuclei subsequently disintegrates. Maturing ascospores are uninucleate.The morphology of the ascospore, as revealed by the scanning electron microscope, is described. The outer wall layer — the perisporium — shows heretofore undescribed surface fibrils. The possible significance of the fibrils is discussed.Paper No. 3205. Washington State University College of Agriculture Project 1767. This study was supported in part by National Science Foundation Grants GB-5219 and GB-8004.     

Chromosomes and evolution of the ground squirrel,Spermophilus richardsonii

Summary Chromosomes were analyzed from two geographically isolated populations of Spermophilus richardsonii. The diploid chromosome number was 36 in S. r. richardonii (Montana population) and 34 in S. r. elegans (Wyoming-Colorado population). The richardsonii Karyotype differed from elegans by the presence of two pairs of acrocentric autosomes whereas the elegans Karyotype lacked acrocentric autosomes and had an extra pair of submetacentrics.A chromosomal polymorphism, produced by centric fusion, probably existed in the more primitive richardsonii population. After ancestral stock of the elegans population became geographically isolated, both populations of S. richardsonii evolved independently and developed different karyotypes derived from the original polymorphism. Although the karyotypes have evolved to a stage found in valid species, the populations may not have been separated long enough to attain reproductive isolation.This investigation was supported by a grant from the National Science Foundation (GB-503).     

Linkage groups inAscobolus immersus

Thirty-two genes (31 mutants and themt gene) have been mapped in 9 linkage groups. There are at least 28 loci distributed as follows: two loci each in groups I, IV, V, VII, VIII and IX; 3 in group VI; 8 or more loci in group II; and 5 loci in group III.Supported by Grant GB-3325 from the National Science Foundation.     

Regeneration in the central nervous system of a pulmonate mollusc,Melampus

Summary The left cerebral ganglion was ablated from 72 anesthetized, adult Melampus bidentatus (Mollusca: Pulmonata). Skin incisions were well healed and normal feeding and locomotion observed four days after surgery. Dissections of animals sacrificed weekly showed that most nerves and connectives regrew within 30 days, attaching to the swollen end of the major labial nerve. The enlarged end of this nerve later developed into a distinctive bud; some of these buds contained cell bodies as soon as 42 days after surgery. As the first known report of central nervous tissue regeneration in molluscs, this study points to the need for controls in experiments involving section or ablation of nervous tissue in molluscs.I am grateful to Dr. W.D. Russell-Hunter for his guidance in the course of this work. Support was principally provided by a grant from the National Science Foundation to Dr. Russell-Hunter (Research Grant No. GB-36757 continued as BMS-72-02511-A01)and by two successive grants to the author from the Theodore Roosevelt Memorial Fund of the American Museum of Natural History, New York     

Morphogenic effects of halogenated thymidine analogues on Drosophila. I. Quantitative analysis of lesions induced by 5-bromodeoxyuridine and 5-fluorouracil

When 5-fluorouracil (FU) is offered simultaneously with 5-bromodeoxyuridine (BUdR) to Drosophila larvae, a variety of bristle modifications and hyperplastic growths are found on the wings of the adult flies. Administration of FU alone will not stimulate growth in Drosophila, while high concentrations of BUdR offered alone will induce a lower frequency of growth modifications than induced by BUdR plus FU. Comparison of the morphological response induced by sequential treatment with the two analogues and that by simultaneous treatment with the analogues at the same concentrations indicates that maximum response is achieved by the presence of both analogues at the same time. These observations suggest that BUdR may be the primary agent in upsetting morphogenesis in Drosophila, while FU plays a subsidiary role leading to intensification of the morphogenic effects when it is present during the treatment period. The incorporation of BUdR-H³ and FU-H³ in Drosophila tissues was demonstrated by autoradiography. BUdR-H³ was incorporated in nuclei of both larval and imaginal disc cells, and the isotopic label was removable by deoxyribonuclease. Following dietary administration of FU-H³, tritium was found in RNA, primarily in cytoplasmic regions. Since BUdR is a known mutagen, consideration was given to the hypothesis that the altered growth patterns in Drosophila wings are the result of somatic cell mutational events induced by BUdR. Validity of the argument that recessive mutations on the X chromosomes can be readily expressed in the somatic cells of the male with one X chromosome as opposed to the female with two X chromosomes was tested by comparing the frequency of the induced somatic cell lesions in male and female zygotes. The males showed a higher frequency of induced supernumeraries, while the icidence of bristle effects and total wings affected was the same in both sexes.This research was supported by grants to T. M. R. from the National Science Foundation (GB-11745) and by an Institutional Research Grant (No. IN-40H) to the University of Michigan from the American Cancer Society.     

Plastids in sieve elements and companion cells of Tilia americana

Summary Contrary to an earlier report, the sieve elements and companion cells of Tilia americana contain plastids. In young sieve elements and companion cells the plastids contain a moderately electronopaque matrix and internal membranes; the latter are very numerous in the plastids of the sieve elements. Plastids of mature sieve elements contain an electron-transparent matrix, apparently fewer internal membranes than the plastids of young elements, and a single starch grain each. The plastids of companion cells undergo little or no structural modification during cellular differentiation, and apparently contain no starch.This research has been supported by the National Science Foundation, grants GB-5950 and GB-8330.     

Histochemical activation of rat-liver lysosomes by dimethyl sulfoxide

Summary The Gomori reaction for acid phosphatase was enhanced by inclusion of dimethyl sulfoxide (DMSO) in reaction media for incubation of cryostat sections of unfixed rat-liver tissue. The reaction was also detectably increased by DMSO in formol-calcium fixed tissue. Enhancment of the Gomori reaction for acid phosphatase by DMSO was reversible.Supported by Grant GB-3817 from the National Science Foundation and by the University Research Coucil and the Cancer Institutional Grant Committee of the University of North Carolina     

Hypoxylon deustum: The chromosome number

Summary The haploid chromosome number ofHypoxylon deustum is 4. Ascospores are uninucleate when formed, becoming binucleate shortly thereafter. One of the two nuclei disappears in maturing ascospores. Mature ascospores are apparently uninucleate. The significance of these and other findings to the taxonomy of the fungus is discussed.Scientific Paper No. 3008. College of Agriculture, Washington State University. Project 3767.This study was supported in part by National Science Foundation Grant GB-5219.