Chromosome structure XIII

Summary The history of chromonemata was studied in Dissosteira Carolina L. It was found that each chromosome consists of 2 chromatids at all stages which themselves are again split into half-chromatids or chromonemata proper.Multiplication of threads is believed to occur at metaphase, the cycle being strictly analogous to that of plants with large chromosomes such as Trillium, Tradescantia, Hordeum and Secale, especially the two latter. Four threads per chromosome were observed during the last premeiotic telophase, during diaphase and diakinesis. During leptotene only 2 threads can be seen because the chromosome attenuates so much that half-chromatids can no longer be resolved. The dyad chromosome contains 8 threads which were observed in first telophase and interkinesis. The chromosome of the second anaphase contains four threads again, as the threads do not multiply during the second metaphase.The chromosome threads in Dissosteira Carolina L. are not so easily fixed as those of large plant chromosomes. The resulting images are more diffuse and less obvious, nevertheless the evidence obtainable appears cogent.Approved by the Director of the New York State Agricultural Experiment Station as Journal Paper 160, August 20, 1936.     

On the cytotaxonomy of phasmids (Phasmatodea)

Summary A wide diversity in chromosome complement is found in two species of phasmids of the primitive group Prisopini—Prisopus ariadne Hebard and Prisopus berosus Westwood. P. ariadne has a diploid male complement of 28, comprising 13 pairs of relatively large mediokinetic autosomes and Neo XY sex chromosomes. P. berosus, 2n =49, has relatively small autosomes most of which are mediokinetic, and retains the XO—XX sex mechanism. Chromosomal polymorphism in this species is suggested by the presence of an unequal pair of autosomes and a structural differentiation in the X in one of two males studied.The relative amount of DNA per nucleus in male germ cells (Peulgen cytophotometry) shows a significant difference in total chromosomal content between the complements of the two species.These data are discussed with reference to the cytotaxonomy of phasmids.Supported in part by research grant G-4370 from the National Institutes of Health, Public Health Service.     

A phasic-tonic proprioceptor in the telson of the crayfish Procambarus clarki (Girard)

Summary A proprioceptor in the telson of the crayfish Procambarus clarki was found, which is made up of about five units. These show range fractionation, i.e. different threshold distributions and their response to bending of the telson has a transient and a stationary component. The peak frequencies reached during the period of the transient component were shown to increase with increasing bending velocity and had — with the exception of one case — the highest values when extension (contrary to flexion) was imposed. The position characteristic discharge frequencies of the stationary component and their variation with different telson positions were considerably smaller. The receptor signals movement and position to the central nervous system and is therefore called a phasictonic one.I am grateful to Prof. Dr. T. H. Bullock for his hospitality and interest in this work and also want to thank Mr. John W. Thorson for many constructive discussions. This work was aided by grants from the U.S. Public Health Service, National Science Foundation and Office of Naval Research to Prof. Dr. T. H. Bullock.     

Replication of autosomal heterochromatin in man

Summary In interphase nuclei of leukocytes and oral mucosa cells of normal human males and f males, two types of heterochromatin can he distinguished according to their location in the nucleus. Firstly, nucleolus-associated heterochromatin which consists of one large mass of autosomal segments surrounding the nucleolus, or several large masses if there appears to be more than one nucleolus in the same nucleus. Secondly, scattered heterochromatin composed of a large number of positively heteropycnotic bodies scattered throughout the nucleus and not directly associated with the nucleolus. The correspondence of this type of heterochromatin with chromosome segments is obtained at late prophase where several positively heteropycnotic regions belonging to the autosomes are found scattered throughout the nucleus.In human females sex-chromatin is present in addition to these two types. In leukocytes the sex-chromatin cannot be easily identified due to the large size and number of the scattered heterochromatic bodies, but in oral mucosa cells such a distinction is more easily achieved due to the smaller amount of autosomal heterochromatin.Nucleolus-associated and scattered heterochromatin from leukocytes of both sexes synthesized their DNA at a different period of time from the euchromatin. The asynchrony of replication observed in the heterochromatin at interphase is in agreement with the asynchrony between autosomes and within autosomes described by many authors at metaphase. This does not mean, however, that every segment or chromosome found replicating asynchronously at metaphase contains necessarily heterochromatin.Dedicated to Professor H. Bauer on the occasion of his 60th birthday. — This investigation was supported by a research grant to A. Lima-de-Faria from the Swedish Natural Science Research Council.     

Mitochondrion-desmosome complexes in human hepatocytes

Summary Mitochondrion-desmosome complexes similar to those seen in other epithelia were observed in hepatocytes from normal and diseased human livers of children and adults. Their occurrence could not be explained by random distribution of mitochondria in the cells. The close associations of mitochondria with desmosomes supported the hypothesis that the latter might be special areas of intercellular ionic diffusion between hepatocytes.This work was supported in part by United States Public Health Service Grants AI-1059 and TI AM-5384 from the National Institute of Arthritis and Metabolic Diseases, 5 MOl FR 000-50 from the General Clinical Research Center, HD 00674 from the National Institute of Child Health and Development and by a grant from the Life Insurance Medical Research Fund G-65-50.The author is very grateful to Dr. Alex B. Novikoff for the use of the facilities of his laboratory (supported by United States Public Health Service Grant CA-06576), to Mr. Nelson Quintana and Mrs. Julie Windsor for their superb technical assistance and to Miss Marianne Van Hooren for preparation of the photographs.     

The assay of antimitotics

Summary This paper is concerned with the techniques of testing for antimitotic activity of externally applied stimuli, chemical or physical. Some standard reactions such as c-mitosis, prophase poisoning, mitotic inhibition and chromosome damage are illustrated and the problems of interpretation and misinterpretation are discussed. The general conclusion has been reached that antimitotic action is generally the result of 1. interference with structural change through altering energy flow or resonance and 2. by interference with metabolic processes through blockage of specific enzymes.This paper is dedicated to Dr. Hans Bauer on the occasion of his 60th birthday in recognition of his fundamental and pioneer contributions to both Cytology and Cytogenetics.The work of this laboratory to which reference has been made has been supported by a number of agencies: The Office of Naval Research, National Institutes of Health, National Science Foundation, American Cancer Society and the Michigan State Agricultural Experiment Station.I wish to express my gratitude to the considerable number of senior associates, students and technicians who over the years have contributed extensively to the work summarized in this paper.     

Diploid-tetraploid relationship among old-world members of the fish family Cyprinidae

Evidence suggesting that the goldfish and the carp of the family Cyprinidae are tetraploid species in relation to other members of the same family were presented. The two barb species, Barbus tetrazona and Barbus jasciatus, were chosen as representatives of diploid members of the family Cyprinidae. These barbs had the diploid chromosome number of 50 and 52 and the DNA value 20–22% that of placental mammals, while the goldfish (Carassius auratus) and the carp (Cyprinus carpio) had the diploid chromosome number of about 104 and the DNA value 50–52% that of placental mammals.Supported in part by a grant (CA-05138) from the National Cancer Institute, U.S.Public Health Service, and in part by a research fund established in honor of General James H. Doolittle at Duarte, and by the British Empire Cancer Campaign for Research at Northwood. Contribution No. 11-67, Department of Biology, City of Hope Medical Center. Dr. Junichi Muramoto is a fellow of the Institute for Advanced Learning of the City of Hope Medical Center.     

Chromosome number in the lizard genus Uta (family Iguanidae)

A chromosome number of 34 (12 macro- and 22 microchromosomes) was found to be characteristic of the bone marrow in 47 animals including males from the species Uta antiquus, and both males and females from the following species and subspecies: Uta stansburiana stansburiana, Uta stansburiana stejnegeri, Uta stansburiana elegans, Uta stansburiana klauberi, Uta stansburiana mannophorus, Uta nolascensis, Uta palmeri, and Uta squamata. — Diploid chromosome numbers of 34 and haploid numbers of 17 were found in the nine testis smears examined. — The presence of a large number of hypodiploid figures in the bone marrow smears is attributed to cell fragmentation and the problem of distinguishing the small microchromosomes. — Series of polyploid figures whose chromosome numbers increased in arithmetic rather than geometric progressions were observed in the testis dry smears. Possible alternatives for the origin of these figures are presented. — Problems encountered in the use of chromosome number as a taxonomic character are discussed.Supported in part by Research Grants GB-366 and GB-5416 from the National Science Foundation, and GM-15361 from the United States Public Health Service.     

Specificity of compaction in meiotic chromosomes of the female Chinese hamster

This study describes the sequential alternation of compaction and decompaction in the chromosomes of the Chinese hamster oocyte from diakinesis to metaphase II. A series of micrographs show that the compact metaphase I chromosomes become greatly extended as they enter and pass through anaphase I. Once polarized, the presumptive oocyte chromosomes become exceedingly compact and form a tightly packed mass, each chromosome assuming contours to accomodate dovetailing with its neighbors, while the chromosomes consigned to the polar body remain extended and show signs of the incipient deterioration. Prior to ovulation, the chromosomes of the mass separate and begin to decompact, in part at least, by the previously postulated mechanism of uncoiling. Following ovulation, the chromosomes are greatly extended and, as the metaphase II complement, remain in that state until the advent of fertilization. — Evidence that the compaction patterns are ordered and chromosome specific is presented by observation of the two smallest chromosomes of the complement. At telophase I those chromosomes are markedly different in size and arm ratio; at metaphase II the differences are less pronounced and at mitotic metaphase the two smallest chromosome pairs are so similar in morphology as to be indistinguishable. It is proposed, therefore, that those two chromosomes differ in their fundamental morphology as revealed at the exceedingly compact state of telophase I oocyte chromosomes. Their subsequently established resemblance at mitotic metaphase may be due to allocycly on the part of one or both, resulting in two chromosomes of apparantly similar length and arm ratio.Supported by grants from the Institute of Child Health and Development of the National Institutes of Health, 5 RO1 HDO4846 and the Damon Runyan Foundation, DRG-907.Supported in part by CA-08748 from the Cancer Institute of the National Institutes of Health.     

Hermaphroditism in icerya zeteki cockerell,and the mechanism of gonial reduction in iceryine coccids (coccoidea: Margarodidae morrison)

In the Panamanian iceryine coccid Icerya zeteki Cockerell (Family Margarodidae Morrison) all females become hermaphroditic early in the first instar; occasional males arise from unfertilized eggs, but self-fertilization is assured by the protandry of the hermaphrodite. In the development of the ovotestis, initiation of the male phase is brought about by haploidization of those germ cells destined for spermatogenesis. In both Icerya zeteki and Icerya purchasi this gonial reduction results from the degeneration and elimination of one genome during prophase. Except for minor variations in the coiling cycle of spermatocytes, the chromosomes (n=2) of I. zeteki correspond closely to those of all other haplo-diploid iceryines known. The present status of the species Icerya zeteki Cockerell is reviewed, and on both taxonomicand cytological grounds is judged to be uncertain.Supported in part by National Science Foundation Grant GB — 1922.     

Peculiarities of ovine cells in culture

Summary The chromosome complement of two ovine (Ovis aries L.) kidney cell lines are described. Nuclei of MDOK, the older cell line, are generally larger than those of OK cells, they are hypo-tetraploid and show considerable chromosomal irregularities both in structure and behavior. The OK line observed since its initiation, is now hyper-diploid and exhibits a gradual accumulation of chromosomes. Both cell lines have in common the fact that they now maintain a larger proportion of chromosomes with interstitial centromeres than telocentric chromosomes. This observation parallels similar ones made earlier in bovine cells. However, the processes whereby this condition arose in the respective cultures are believed to be different and are discussed.Dedicated to Professor Dr. H. Bauer on the occasion of his 60th birthday.Supported in part by Contract No. PH 43-63-13 from the National Cancer Institute, National Institutes of Health, Public Health Service.     

Spontaneous fragility of an abnormally wide secondary constriction region in a human chromosome No. 9

Summary In an infant with clinically and cytologically typical Down's syndrome a chromosome No. 9 was found exhibiting an exceptionally large paracentric constriction which proved to be spontaneously fragile. In cells in which this chromosome was broken the centric portion was present whereas the acentric fragment was absent. A No. 9 chromosome with identical morphology was found in the karyotype of the father but no fragility was evident. Autoradiography revealed pronounced late replication in the constriction region, suggesting a duplication or insertion of heterochromatic material. Clinically there was no evidence for any phenotypic expression of this cytological anomaly.Supported in part by the Swiss National Foundation     

A radiation analysis of a comstockiella chromosome system: destruction of heterochromatic chromosomes during spermatogenesis in Parlatoria oleae (Coccoidea: Diaspididae)

In the males of the olive scale insect, Parlatoria oleae (2n=8), the paternal set of chromosomes becomes heterochromatic during late cleavage or early blastula and remains so until spermatogenesis. Immediately before the onset of meiosis in the males one or more heterochromatic chromosomes disappear from each primary spermatocyte. At prophase four euchromatic and from one to three heterochromatic chromosomes are present in each cell. The disappearance of the heterochromatic chromosomes before meiosis could be due either to the dehetero-chromatization of the heterochromatic chromosomes and their subsequent pairing with their euchromatic homologues, or to the destruction of the heterochromatic chromosomes. — The alternative interpretations of spermatogenesis in P. oleae were tested by using chromosome aberrations, which had been induced in the heterochromatic set by paternal X-irradiation, as genetic markers in breeding tests of about 400 X₁ males. Meiosis was examined in X₁ males which showed conspicuous chromosomal rearrangements in their somatic cells. The absence of either heteromorphic chromosome pairs or multivalents at spermatogenesis and the failure of the X₁ males to transmit any form of chromosome aberration induced by paternal irradiation is strong evidence that the heterochromatic chromosomes are destroyed in P. oleae. — The evolutionary relationships of the chromosome systems in the coccids are considered. Models are outlined for the derivation of a Comstockiella system involving chromosome destruction either from a lecanoid sequence or from a hypothetical Comstockiella sequence involving chromosome pairing. Problems concerning the control of chromosome destruction are discussed.From a dissertation submitted in partial fulfillment of the requirements of Doctor of Philosophy in Genetics.This work was supported by grant GB 8196 from the National Science Foundation to Dr. Spencer W. Brown, and by a National Institutes of Health Fellowship 1 F02 CA 44173-01 to the author from the National Cancer Institute.Dedicated to Dr. Sally Hughes-Schrader on the occasion of her seventy-fifth birthday.     

The fine structure of the kinetochore of a mammalian cell in vitro

The chromosomes of Chinese hamster cells were examined with the electron microscope and the following observations were made concerning the structure and organization of the kinetochore. — The kinetochore consists of a dense core 200–300 Å in diameter surrounded hy a less dense zone 200–600 Å wide. The dense core consists of a pair of axial fibrils 50–80 Å in diameter which may be coiled together in a cohelical manner. The less dense zone about the axial elements is composed of numerous microfibrils which loop out at right angles to the axial fibrils. Together the structures comprise a lampbrush-like filament which extends along the surface of each chromatid. Some sections suggested that two such filaments may be present on each chromatid. The fine structure of kinetochores associated with spindle filaments was essentially the same as those free of filaments. The structure and organization of the kinetochore of these mammalian cells was compared to that of lampbrush chromosomes of certain amphibian oöcytes, dipteran polytene chromosome puffs, and the synaptinemal complex seen during meiotic prophase.The authors also wish to thank Dr. Arthur Cole of the Department of Physics for the use of his electron microscope facilities and for his helpful criticism.     

Replication pattern of the X and Y chromosomes in partially synchronized human lymphocyte cultures

The replication pattern of the X and Y chromosomes at the beginning of the synthetic phase was studied in human lymphocyte cultures partially synchronized by the addition of 5-fluoro-2-deoxyuridine (FUdR). The data were evaluated statistically by an analysis of the distribution of silver grain counts over the X and Y chromosomes. —In cells from normal females, one of the X chromosomes began replication later than any other chromosomes of the complement. The short arm of the late replicating X chromosome started replication earlier than the long arm. The telomeric region of the short arm was a preferential site of DNA synthesis at the beginning of replication. —In partially synchronized lymphocyte cultures from a patient with the XXY syndrome, the Y chromosome started replication together with the late replicating X chromosome. The Y chromosome most frequently replicated synchronously with the short arm of the X. The centromeric region of the Y chromosome initiated synthesis before the telomeric region and appeared to replicate synchronously with the telomeric region of the short arm of the X. These findings are discussed with reference to the pairing of the X and Y chromosomes at meiosis.Supported in part by the National Institute of Health Research Grant HD-01979 and National Foundation Birth Defects Research Grant CRCS-40. Dr. Knight was a predoctoral fellow under National Institute of Health Training Program HD-00049-09.     

A reinvestigation of the nucleolus-organizing regions in the salivary gland nuclei of Drosophila melanogaster

Comparisons were made of the morphology of the proximal region of the salivary gland X-chromosome of D. melanogaster following a number of different staining procedures. Azur B was found to be the most satisfactory staining method for identification of the nucleolus. The states of eu- and heterochromatization (sensu Prokofyeva-Belgovskaya) of the bands in the proximal region—particulary striking in the mirror-image duplication of the R(1)2, ring-X, chromosome—contribute to the variability in the banding-pattern, and consequently the refractoriness of this region to cytological investigation. No nucleolus was ever found to be associated with the group of bands presumed to be the Y-chromosome.This investigation was supported in part by a U.S. Public Health Service Research Grant, GM 15009, from the Institute of General Medical Sciences of the National Institutes of Health, and in part by a grant from the Finnish National Research Council for Sciences.     

Gueriniella and the cytotaxonomy of iceryine coccids (Coccoidea:Margarodidae)

The chromosome complement of Gueriniella serratulae (F.) Fernald, Tribe Iceryini, Subfamily Monophlebinae of the primitive coccid Family Margarodidae, is 2 n =6; males are unknown. Reproduction is by thelytokous parthenogenesis. Meiosis is normal; polar bodies do not contribute to the formation of a zygote-substitute nucleus; and development is initiated by a haploid cleavage of the female pronucleus. Diploidy is restored by the fusion of the 2 nuclei resulting from this division. With the exception of Gueriniella, all cytologically known Iceryini are haplo-diploids, with a chromosome complement of n=2. The hypothesis is proposed that Gueriniella is a persistent primitive stemming from the ancestral iceryine stock prior to the loss of the sex chromosomes and the evolution of haplo-diploidy within the tribe. A review of the available evidence from cytology, taxonomy, endosymbiosis, behavior and distribution shows good agreement with this interpretation.Dedicated to Professor Jakob Seiler on the occasion of his 80th birthday.Supported in part by National Science Foundation Grant GB-1922 to S. Hughes-Schrader; we also gratefully acknowledge the support of Professor G. Russo, Director of the Entomological Laboratory, Portici.     

The diffuse diplotene stage of meiotic prophase in Neurospora

The prophase stages of meiosis in Neurospora crassa are re-examined following McClintock (1945) and Singleton (1953). A diffuse chromosome stage occurring between pachynema and diakinesis is described. It is proposed that the diffuse stage does not necessarily represent a condition of intense gene activity in the sense of directing the metabolic activity of the ascus.Supported by U. S. Public Health Service grants AI-01462 and GM-14263.     

The development of the hypophysial portal system in the White-crowned Sparrow,Zonotrichia leucophrys gambelii

Summary The development of the hypophysial portal system has been studied in 35 embryos and 45 nestlings of the White-crowned Sparrow. The primordium of the hypophysis is vascularized by the infundibular (primary) capillary plexus, supplied by the right and left infundibular arteries, which, in the embryo, are constant branches of the right and left internal carotid arteries.The cellular proliferation and differentiation of the pars distalis into rostral and caudal lobes is accompanied by a penetration of portal vessels from the infundibular (primary) capillary plexus into these lobes beginning on the fifth day of incubation. The cellular proliferation of the rostral lobe of the pars distalis and development of the rostral group of the portal vessels precedes that of the caudal lobe of the pars distalis and the development of the caudal group of the portal vessels.The periglandular vessels, which originate in younger embryos from the infundibular (primary) capillary plexus, apparently become a part of the portal vessels.The portal vessels are the sole blood supply to the developing pars distalis of the White-crowned Sparrow; there is no evidence of a direct arterial supply at anytime during embryonic development. The neural-lobe artery appears at the end of incubation as a secondary branch of the right and left infundibular arteries. The rostral and caudal groups of the portal vessels are well-developed at the end of incubation (17–29 mm CRL) when aldehyde-fuchsin positive neurosecretory material first appears in the supraoptic and paraventricular nuclei, in the median eminence and in the neural lobe.The differentiation of the median eminence into rostral and caudal divisions begins at the end of the nestling period although its adult form is not achieved until later. The formation of the portal zone begins at the end of incubation (17–29 mm CRL) and is completed by the time of fledging.Dedicated to Professor Dr. W. Bargmann in honor of his 60th birthday.The investigations reported herein were supported by a research grant (HE 07240 NEUA) from the National Institutes of Health to Professor Vitums, by funds for biological and medical research made available by State of Washington Initiative Measure No 171 to Professor Vitums, by a research grant from the Deutsche Forschungsgemeinschaft to Professor Oksche, by aresearch grant (NB 01353) from the National Institutes of Health to Professor Farner, and by a Research Career Development Award from the National Institute of Arthritis and Metabolic Diseases (5 K 3 AM-18,370) to Professor King. We are grateful to Professor Bargmann for his generosity in making available the facilities of the Anatomisches Institut Kiel for this investigation. We wish to thank Frau Karin Graap and Mrs. Dianne Reno for technical assistance and Miss Janice Austin for the preparation of the drawings.     

The DNA-content (Feulgen) of nuclei during mitosis in a root tip of onion

Summary The microphotometric two-wavelength method is demonstrated to permit, even with only an improvised optical set-up, DNA-measurements which would not be possible, at any rate not with a comparable accuracy, with the conventional method.The data, in agreement with earlier results, show that the largest interphase nuclei in the root meristem have already completed their DNA-synthesis.The mean DNA-contents per set of chromatids at late interphase, prophase, and telophase, appeared to be virtually identical. A natural variation in DNA-content, if any, between individual nuclei at these stage would have a coefficient of variation of significantly less, and most likely much less, than 7.3%. The data from metaphase to middle anaphase are, for technical reasons, not yet conclusive. An indicated, moderate, excess of Feulgen-dye in these as compared with earlier and later stages may not be real.The results are fully compatible with a working hypothesis of strict constancy of the DNA-content per chromatid and of its precise doubling during DNA-synthesis (for necessary qualifications see the discussion). It is pointed out that apparently contradictory results by certain other authors do not, for methodological reasons, yet establish disproof of this hypothesis.Contribution from the Program in Cytology, Department of Botany, University of Wisconsin, Madison, supported in part by grants to Dr.C. Leonard Huskins from the Rockefeller Foundation, the American Cancer Society, and the Research Committee of the Graduate School with funds supplied by the Wisconsin Alumni Research Foundation.supported in part by the U. S. Public Health Service and the Wallace C. and Clara A. Abbott Memorial Fund.