Franz Schrader

A cytochemical analysis of the functional interrelations of various cell structures in Arvelius albopunctatus (de geer)

Abstract 1. 1. The functional interrelations of nucleus, nucleolus and cytoplasm have been studied cytochemically in material which is peculiarly favorable for such an analysis. The different lobes of the testis of Arvelius albopunctatus — a hemipteran insect — carry spermatocyte and spermatid cells which differ regularly in size but are otherwise normal in their meiotic processes. Thus two of the lobes are characterized by very large cells, three by normal-sized cells, and one by small cells. In these the protein, DNA and RNA content (in arbitrary units) of the nucleus, nucleolus and cytoplasm were correlated with the volume of these cell structures with the following results: 2. 2. The Nucleus: The nuclear volumes of the three sizes of spermatocytes were 200, 400 and 1,600 cubic microns, constituting members of a geometrical series. The increase of total proteins in these various nuclei corresponds to the increase in their volumes, while the DNA was approximately the same in all of them. The nuclear volumes of the spermatids (immediately after nuclear membrane formation) is exactly one-fourth and one-sixteenth of spermatocyte nuclei in the confused stage, depending on whether they derived from a normal or large spermatocyte. Similarly, spermatid nuclei of the normal cell lobe carry one-fourth of the proteins and DNA that are present in spermatocyte nuclei prior to the two meiotic divisions in that lobe. 3. 3. The Nucleolus: The volume of the nucleolus in the large spermatocytes is about four times that of the nucleolus in a normal spermatocyte. The total protein and RNA of such a large nucleolus is proportionally increased whereas the amount of DNA of the nucleus remains unaltered. 4. 4. The Cytoplasm: The ratios of the volumes of the cytoplasm in the three different sizes of spermatocytes have approximately the same order of magnitude as the ratios of nuclear volumes. The increase in the amount of cytoplasm in the normal and large cells over the small cells is accompanied by a rise of proteins and RNA in the cytoplasm. 5. 5. These cytochemical data as well as the cytological analysis lead to the conclusion that in Arvelius the increase in the volumes of the nucleus, nucleolus and cytoplasm, as seen in the normal and large cells as compared with the small cells, represents a true growth. In contrast to these changes in the amounts of proteins and RNA is the quantity of DNA which remains unaltered in the different sizes of nuclei and cells. The findings imply that protein and DNA synthesis can proceed independently of each other, whereas the synthesis of RNA and proteins are closely linked.

The kinetochore of the hemiptera

Summary(1)Breakage of chromosomes was induced by X-rays in adult and nymphal males of Euschistus servus, E. tristigmus and Solubea pugnax (Pentatomidae; Hemiptera-Heteroptera).(2)The diffuse nature of the kinetochore is demonstrated by the ability of chromosome fragments to perpetuate themselves mitotically through many cell generations of spermatogonia.(3)Free fragments, when not immobilized by the effects of radiation, are also capable of meiotic mitosis. A holokinetic, rather than a telomeric, nature is thus demonstrated for the meiotic restriction of kinetochore activity to chromosome ends, normal for Heteroptera and certain other Hemiptera.(4)Simple fragmentation as a factor in the evolution of compound sex chromosomes is supported by the observation that fragments of the X chromosome co-orient with the Y in a typical “touch and go” pairing.(5)The results are discussed with relation to problems of kinetochore structure and mitosis.

THE CHROMOSOMES OF PSEUDOCOCCUS NIPÆ

1. The diploid number of chromosomes in Pseudococcus nipae is ten in both sexes.2. In the maturation of the egg, five tetrads are formed and reduction is probably normal.3. In the spermatogenesis, five chromosomes are developed before the others, and these tend to remain grouped together.4. No tetrads are formed, and in reduction five chromosomes go to one pole (supposedly those evolved first) and five to the other.5. Explanation of this seemingly anomalous behavior is to be sought in the fact that five of the chromosomes carry sex chromatin.6. The case is not so much to be regarded as an illustration of Weismanns ideal type of reduction, as an exceptional example of reduction due to unusual sex chromatin distribution.

The origin of certain nutritive substances in the eggs of hemiptera

Abstract 1. 1) The end chambers of the ovarial lobes in coreid Hemiptera contribute to the nutritive materials which are stored in the growing egg. 2. 2) Such nutritive materials are derived from nuclear DNA as well as cytoplasm. 3. 3) The processes involved include a breakdown of cell walls as well as an irregular fusion of nuclei and an extrusion of DNA in the form of droplets through the nuclear membrane. 4. 4) Before the flow of such materials reaches the egg, the contents of the droplets undergo considerable alteration and become Feulgen-negative. The changes involve the formation of polysaccharides and some depolymerization of DNA, but still further alterations probably take place.

The structure of the kinetochore at meiosis

1. It is suggested that the kinetochores of Amphibia and those of several plants are basically alike in structure and that the superficially striking dissimilarity between them arises from differences in their meiotic properties. 2. The spindle spherule of the kinetochore is fully divided already in the late prophase of the first meiotic division. 3. It is reiterated that the kinetochore is a compound body and that the element directly involved in mitosis is the spindle spherule which lies in a commissural mass or cup. 4. It is suggested that there is some reorganization of the kinetochore at every mitotic cycle and that functional fragments, such as reported by McClintock, originate at a time when the final form shown in metaphase has not yet been assumed. It is suggested that the kinetochores of Amphibia and those of several plants are basically alike in structure and that the superficially striking dissimilarity between them arises from differences in their meiotic properties. The spindle spherule of the kinetochore is fully divided already in the late prophase of the first meiotic division. It is reiterated that the kinetochore is a compound body and that the element directly involved in mitosis is the spindle spherule which lies in a commissural mass or cup. It is suggested that there is some reorganization of the kinetochore at every mitotic cycle and that functional fragments, such as reported by McClintock, originate at a time when the final form shown in metaphase has not yet been assumed.

Polyploidy and fragmentation in the chromosomal evolution of various species of Thyanta (Hemiptera)

Summary1.The tropical species of the genus Thyanta conform, in their chromosome formula (2n♂=12+XY, 2n♀=12+2X), to that which is typical for the Family of Pentatomidae (Hemiptera), while the more northern species examined by us have either added a pair of chromosomes (T. custator and T. pallidovirens) or have doubled the basic number (T. calceata).2.Hybrids between T. custator and T. pallidovirens show only minor disturbances in their meiosis, and the hybrid spermatids carry the same number of chromosomes and amount of DNA as are present in the spermatids of either parent species.3.The meiosis of the hybrid between T. calceata and T. pallidovirens is quite abnormal and there is no chromosome pairing. Nevertheless, chromosome segregation is not completely at random and some functional sperms are formed.4.The nuclei of the six species of Thyanta tested show little difference in their DNA contents. On the other hand, the nuclei of another pentatomid, Arvelius, contain at least twice as much DNA.5.In considering the evolutionary origin of such a high chromosome number as that of T. calceata, the evidence adduced in the present investigation more or less precludes the involvement of polyploidy. Instead, some type of fragmentation was probably responsible for the doubled number.6.It is difficult to conceive of such fragmentation as occurring transversely through the chromosomes. We propose a consideration of “longitudinal fragmentation” or better, a separation of the chromatids of each chromosome and the establishment of “echromatid autonomy”.7.Except where polyploidy is involved, great differences in the nuclear contents of DNA, as observed between some Classes and Orders, must in certain cases be due to different degrees of polyteny and not to the addition of new or different genes. Our evidence demonstrates that relatively large differences of DNA may also exist in systematic groups of a lower category, such as the Genera of the same Tribe, or perhaps even the Species of the same Genus. On this basis, the degree of polyteny may differ even in closely related forms.

THE KINETOCHORE OR SPINDLE FIBRE LOCUS IN AMPHIUMA TRIDACTYLUM

1. The kinetochore is a compound body composed of a commissural region and a spindle spherule, so far as univalent chromosomes are concerned.2. The half spindle component connects with the chromosome through the spindle spherule.3. Already during the diakinetic phases of meiosis, each tetrad has two kinetochores which are distinct and separate from each other. Each of these is provided with two spindle spherules, so that each tetrad carries a total of four spindle spherules.4. In the first spermatocyte division, the kinetochores lead the way to the poles. The dyads resulting from this division each show two spindle spherules until the resting stage is reached.5. At metaphase of the second spermatocyte, each dyad is already sharply differentiated into two chromatids or univalent chromosomes. Each of these carries a kinetochore provided with a spindle spherule.6. Aside from its structure, various staining reactions mark the kinetochore as an organ quite distinct from the ordinary chromomere.7. The possible ...

Haploidy in Metazoa

HE origin of haploidy in T Metazoa, its bearing on the problem of sex determination, and indeed the very existence of haploid individuals have long been the subject of much cogitation. As one or all of these questions have presented themselves in various fields of biology, different investigators have endeavored to explain the moot aspects, each from his own point of view. As a result there is available a conglomeration of hypotheses. To admit that few of these are worth consideration, and none is entirely satisfactory is in itself an appreciation of the difficulties involved. The subject as a whole has repeatedly presented itself in our work on the cytology of the coccids, and the present review has been written not only with the intention of critically evaluating the more important of the various hypotheses but also of discussing the possible bearing that certain features of coccid cytology may have on the question. The central point of interest lies in the fact that so far as is known, all haploid animals are males. The present brief survey of the various attempts to throw light on this peculiarity and the related facts which it involves does not endeavor to go back beyond the period when the role played by the nucleus in the mechanism of heredity first became fully realized.

Polyteny as a factor in the chromosomal evolution of the pentatomini (Hemiptera)

Summary1.ThePentatomini, which constitute a single Tribe within one of the Subfamilies of the hemipteran FamilyPentatomidae, include an unusually large number of species. Though these species vary considerably in their size and color, they are very uniform in their essential external and internal morphology.2.Uniformity also characterizes such features in the Tribe as the chromosome number and meiotic behavior. But in the eleven species here investigated, this uniformity does not extend to the DNA content of the male meiotic cells, as determined by Feulgen cytophotometry.3.The lowest DNA content is found inThyanta which, in this respect, is well separated from an intermediate group whose DNA values vary around a mean that is roughly double the lowest amount. Some evidence is available that a still higher multiple of DNA may be represented in theAcrosternum-Nezara complex of species.4.In view of these cytochemical data, the multiplicity of species coupled with a striking uniformity of morphological and cytological features is provisionally explained on the basis of varying polyteny.

RELATIONSHIP BETWEEN NUCLEAR VOLUMES, AMOUNT OF INTRANUCLEAR PROTEINS AND DESOXYRIBOSENUCLEIC ACID (DNA) IN VARIOUS RAT CELLS

Cytochemical photometric microscopic determinations of proteins and desoxyribosenucleic acid in cells of rat tissues gave the following results :1. A direct correlation exists between different sizes of nuclei and amounts of intranuclear proteins in rat liver cells, while the amount of DNA was found to be independent of nuclear size.2. In the gastric mucosa, where cells with different synthetic activities (parietal and chief cells) occur, there is no parallelism between nuclear size and proteins. The chief cells have a larger amount of protein than parietal cells, while the amount of DNA is the same in both.