bluuebunny/crossref_metadata_2025_split huggingface dataset:
Replication of macronuclear DNA in the cytoplasm of Tetrahymena pyriformis
Authors: Andersen H. A. 
Published: April 2021

ABSTRACT
Previous experiments showed that a synchronous population of Tetrahymena could divide even though DNA replication was blocked during the latter half of the preceding S-period by addition of methotrexate plus uridine (M + U). Furthermore, it was found that the DNA fraction which was in replication at the time of inhibition became localized in the cytoplasm following elimination from the nucleus at the time of division. When the inhibitory treatment (M + U) was removed prior to or at the time of the cell division the cells were found to engage in new DNA replication and continue growth. Two questions arose from these studies. First, is the DNA replication normal following release from M + U? Second, what is the fate of the cytoplasmic DNA? In the present paper DNA replication has been studied using incorporation of 5-bromodeoxyuridine and centrifugation of the labelled DNA in CsCl gradients. It is concluded that the DNA which finished replication prior to the effect of the M + U treatment replicates again during the S-period of the next cell generation. On the other hand, the DNA fraction which was stalled in replication and subsequently eliminated from the nucleus also replicates in the cytoplasm in the next generation but during G2 period, out of phase with the undamaged nuclear DNA. The cytoplasmic DNA replication appeared to be a continuation of the replication initiated in the nucleus in the previous generation.
Differences in density of concanavalin a-binding sites due to differences in surface morphology of suspended normal and transformed 3t3 fibroblasts
Authors: Collard J. G. , Temmink J. H. M. 
Published: April 2021

ABSTRACT
Calculations of the density of Concanavalin A (Con A)-binding sites on normal and transformed fibroblasts have, as yet, been based on the unproven assumption that suspended cells are smooth spheres. We studied the surface morphology of suspended normal and transformed fibroblasts with scanning and transmission electron microscopes, and found a large difference in surface morphology between suspended normal and transformed 3T3 cells. When this difference in surface morphology was taken into account, the estimated cell surface area of normal 3T3 cells was approximately seven times larger than that of transformed 3T3 cells. Since equal numbers of 3H-Con A molecules are bound on normal and transformed cells, the density of Con A-binding sites is approximately seven times greater on transformed than on normal 3T3 cells.
The difference in density of Con A-binding sites between normal and transformed fibroblasts might be sufficient to explain the difference in agglutination response, as originally suggested by Burger, and may also be the cause of the different degrees of clustering of Con A-binding sites on the plasma membrane of these cells.
Membrane specialization in the rat epididymis. I. Rod-shaped intramembrane particles in the apical (mitochondria-rich) cell
Authors: Brown Dennis , Montesano Roberto 
Published: April 2021

ABSTRACT
Following freeze-fracture of the rat epididymis, a population of cells whose apical, but not baso-lateral, plasma membrane contains elongated intramembrane particles was found in the initial segment. From their size, shape and distribution, these cells are assumed to be the socalled apical cells of this segment. Apical cells also contain the enzyme, carbonic anhydrase which, together with the presence of rod-shaped particles on their membranes, permits their classification as ‘mitochondria-rich’ cells, a specialized cell type found in some transporting epithelia. On the basis of these observations, we suggest that the apical cells may play a role in fluid and/or electrolyte transport in the initial segment of the epididymis.
Anomalous preferences of cultured macrophages for hydrophobic and roughened substrata
Authors: Rich Abby , Harris Albert K. 
Published: April 2021

ABSTRACT
Peritoneal macrophages were plated out on a series of artificial haptotactic substrata consisting of grid patterns of vacuum-evaporated palladium metal alternating with hydrophobic untreated polystyrene and with hydrophilic sulphonated polystyrene. By their active locomotion the macrophages accumulated preferentially onto the less hydrophilic of either pair of these alternative substrata. This order of substratum preference is precisely the opposite to that shown by fibroblastic cells. Macrophages were also found to accumulate preferentially onto roughened culture surfaces as opposed to smooth ones, which is again opposite to the behaviour of fibroblasts. These opposite substratum preferences shown by macrophages may reflect physical as well as functional differences in their surfaces, and could serve as assay criteria for macrophages and cell types putatively equivalent to macrophages.
Conformational changes induced by salt in complexes of histones and superhelical nuclear dna
Authors: Levin Jeremy M. , Cook Peter R. 
Published: April 2021

ABSTRACT
When HeLa cells are lysed in solutions containing a non-ionic detergent and 0·75 M-NaCl, structures are released that retain many of the morphological features of nuclei. These nucleoids contain all the nuclear DNA, RNA and the ‘core’ histones, but few other proteins characteristic of chromatin. Their DNA is intact. The core histones dissociate on raising the salt concentration. We have probed the structure of nucleoid-histone complexes using the intercalating dye, ethidium, or the RNA polymerase of Escherichia coli. Both have a higher affinity for superhelical DNA than they do for relaxed DNA. The binding of ethidium is measured fluorometrically, and using this probe we find that the DNA of nucleoids containing all the core histones behaves as if it were supercoiled slightly positively. As the salt concentration is increased, free energy characteristic of negative supercoiling appears between 0·92 M and 0·95 M-NaCl. This transition, which is reversible in the presence of the arginine-rich histones, occurs without dissociation of these histones from the DNA and so must reflect a conformational change in the complex. In contrast to the results with ethidium, we find that RNA polymerase can detect the presence of some negative free energy of supercoiling in nucleoids containing the core histones. The transformations of the free energy that can assist the binding of ethidium and RNA polymerase are discussed.
Studies on heteromorphic selfincompatibility systems: The cytochemistry and ultrastructure of the tapetum of Primula obconica
Authors: Stevens Valda A. M. , Murray B. G. 
Published: April 2021

ABSTRACT
This paper describes the cytochemistry and ultrastructure of the developing tapetum in Primula obconica, a plant with a heteromorphic, sporophytic self-incompatibility system. The tapetum is of the secretory type and cytochemical tests have shown that when it breaks down proteinaceous (esterase) and lipidie components are deposited on the developing pollen grains. Acid phosphatase, a marker of gametophytic enzyme activity, is confined to the cytoplasm and intine of the developing pollen. Ultrastructural studies show that prior to its dissolution the tapetum undergoes a number of changes. In the early stages of development the tapetum is rich in ribosomes and rough endoplasmic reticulum, but following the breakdown of the tapetal cell wall the main components of the cytoplasm are densely staining spherical bodies surrounded by ribosomes and orbicular bodies, which appear to be confined to the cell periphery. As the cells break down, rod-like fibrils can be seen amongst the degenerate organelles and within the bacular cavities of the pollen. On dehiscence the pollen has a lipidie coating in addition to the fibrillar material in the pollen wall and the remnants of the tapetum can be seen adhering to the fibrous layer of the anther wall. Thus the mature, binucleate pollen of P. obconica is demonstrated to carry wall materials of sporophytic origin.
DNA repair in mouse embryo fibroblasts: I. Decline in ultraviolet-induced incision rate accompanies cell transformation
Authors: Elliott G. C. , Johnson R. T. 
Published: April 2021

ABSTRACT
In this paper we examine DNA repair in the mouse. Using stringently applied inhibitors of DNA synthesis (hydroxyurea and l-β-D-arabinofuranosylcytosine) after ultraviolet irradiation we have quantitated an early step in the repair process -the frequency of single-strand DNA breaks, products of enzymic incision -in fibroblasts and epithelial cells grown in vitro from adults and embryos of different ages.
We find that initial rates of incision are very similar in the earliest-passage fibroblasts, regardless of donor age, resembling the rates measured in other rodents while being considerably less than in diploid human fibroblasts. Consistently higher rates of incision are found in adult kidney epithelial cells. With increasing passage number the embryo cultures change with respect to growth rate and chromosome constitution, undergoing spontaneous transformation to established heteroploid cultures. This sequence is accompanied by characteristic changes in initial rates of inhibitor-sensitive incision. An early increase in incision rate, at a time when the cultures are enriched with tetraploid cells, is succeeded by progressive reduction in rate as the cultures become overtly transformed into permanent lines and heteroploidy is established. The lowest rate of incision occurs in a transformed line cloned from a late-passage culture. The decline in incision rate associated with transformation is accompanied by reduced unscheduled DNA synthesis (UDS). The sensitivity to inhibitors of UDS levels in the mouse cultures has been found to vary considerably; inhibitors are most effective in slowly proliferating cultures and apparently not at all when cultures are growing rapidly despite their ability to accumulate DNA breaks in these cells. Caution is needed, therefore, in the interpretation of repair data obtained in the presence of these commonly used inhibitors of DNA synthesis.
Receptor-mediated binding and internalization of colony-stimulating factor (csf-1) by mouse peritoneal exudate macrophages
Authors: Chen Ben D.-M. , Kuhn Charles , Lin Hsiu-San 
Published: April 2021

ABSTRACT
Colony-stimulating factor (CSF-1) purified from L-cell-conditioned medium is a haemopoietic growth factor that specifically stimulates the proliferation and differentiation of mononuclear phagocytes. Using radioactively labelled CSF-1 ([125I]CSF-1), the presence of specific CSF-1 receptor has been identified in the cells of the mononuclear phagocytic series and their precursors only. To determine the fate of [125I]CSF-l bound to peritoneal exudate macrophages (PEM) at 37 °C, we have examined the distribution of radioactivity as a function of time by quantitative electron microscopic autoradiography. At 0°C, we have localized the initial step in the binding of [l25I]CSF-l to the plasma membrane and its invaginations of the mouse PEM. Approximately 16% of the macrophages were not labelled at this time point. When the temperature was raised to 37 °C, the labelled CSF-1 was internalized progressively by the cells in a time-dependent fashion. The proportion of grains associated with the phagolysosome compartment increased progressively, reaching a plateau by 40 min after warming up, while the relative areas of the surface membrane and its invaginations decreased in invaginated membrane. At 37 °C, incubation with unlabelled CSF-1 resulted in a ‘down-regulation’ of the subsequent [125I] CSF-1-binding activity by PEM in a time- and dose-dependent fashion. The restoration of CSF-l-binding activity after CSF-1 induced downregulation was inhibited by cycloheximide, a potent protein synthesis inhibitor. These data provide direct evidence that at 37 °C, saturable binding of CSF-1 to PEM is followed by internalization and cellular degradation of the ligand and possibly its receptor by phagolysosomes.
On the Structure of the Retina
Authors: Nunneley Thomas 
Published: April 2021

ABSTRACT
The retina is the sentient part of the eye, for which all the other textures are formed, and to which they may be said to be subservient. It is coextensive with the choroid proper ; it covers the whole of the convex portion of the vitreous humour, and is covered by the choroid. It terminates in a serrated line, ora serrata, which is readily seen with an inch lens, just where the ciliary processes are continuous with the choroid. There is, according to some anatomists, a circular blood-vessel running near to this edge, if so, it is probably a vein, but it rather appears as a series of capillary loops of the central artery. Some of the older anatomists and opticians described the retina as being continuous over the anterior surface of the crystalline lens, an opinion which has been adopted to a great extent by Arnold, who describes and figures the retina as being continuous with the ciliary body and processes to the edge of the lens *,—pars ciliaris retinœ and processus ciliaris retinœ. This, however, is, without doubt, an error ; though the retina does not terminate wholly and absolutely at the ora serrata, as is commonly described. The nervous structure here ends, but there is, continuous with the suspensory ligament of the lens, a cellular layer, as far as the edge of the lens : this is best seen after the eye has been kept for some time in spirit or Goadby’s solution, by which the layer is rendered opaque and white. Its continuity with the retina may then be readily traced, and, indeed, in some eyes it looks so like a continuation of the whole retina as to render the microscope essential to prove that the nerve-structure is not so prolonged. † The retina has, until very recently, been described as the terminal expansion of the fibres of the optic nerve into a membrane. It is, however, much more than this ; it is one of the most complex, perhaps the most complex, structure to be found in the body, and instead of being thought of as simply a terminal nervous expansion, it should be regarded as in itself a nervous centre ; having the fibres of the nerve expanded it is true in it, and by which it is connected with the brain, but possessed itself of structures and properties peculiar to it, and altogether different from those of the optic fibres, which are expanded in and make part of it. These fibres are for the purpose of conveying to the sensorium the impressions excited in the retina, but are not for receiving the impression, while the other complex structures of the retina receive and appreciate the impressions of external objects.
Clinical Lectures on the Principles and Practice of Medicine
Authors: Bennett John Hughes 
Published: April 2021

ABSTRACT
Although this is a second edition of a work well known, and its main purpose beyond the sphere of our criticism, we think it right to bring it before the notice of our readers, because it contains a large amount of matter bearing directly on microscopic research. Dr. Bennett is one of those teachers of medicine, who has, from an early period of his career, recognised the importance of conducting pathological researches by the aid of the microscope, and in this work abundant evidence is afforded of the value and necessity of this instrument to the practitioner of medicine. In an early number of this Journal (volume I, page 223), we reviewed Dr. Bennett’s ‘Introduction to Clinical Medicine’, and recommended it to the notice of our medical readers, as conveying a just estimate of the value of the microscope in pathological research. In the present work the practical application of this instrument to the various forms of disease in which it may be employed is fully brought out. In fact, with regard to a large number of the forms of disease no true theory of their nature can be formed independent of an investigation by the aid of the microscope. It is in the section devoted to the principles of medicine that Dr. Bennett handles the facts supplied by microscopic research in the most masterly manner. This section should be studied by all those who are anxious to understand the intimate causes engaged in the production of disease, and what are the changes which are necessary to the establishment of health. We should not pretend, even had we space here, to criticise Dr. Bennett’s theoretical or practical conclusions from the observations he records, but we draw attention to them, as showing the comparative valuelessness of any observations or deductions on the intimate nature of organic disease without microscopic investigation.
Methods of preparing the Cochlea for Microscopical Investigation
Authors: Pritchard Urban 
Published: April 2021

ABSTRACT
When I undertook the investigation of the cochlea, at the suggestion of Professor Rutherford, I was totally unacquainted with the method of preserving, softening, and cutting its structures, and were I to enumerate the experiments I made, the valuable cochleæ I spoilt, and the failures I experienced before obtaining any results, I should fill many pages, and only succeed in wearying the reader by the monotomy of my disappointments. I shall therefore confine myself to describing the methods which at last proved successful, merely alluding to the chief points of the fruitless attempts. ‘
On the Head Kidney of Bdellostoma, with a Suggestion as to the Origin of the Suprarenal Bodies
Authors: Weldon W. F. R. 
Published: April 2021

ABSTRACT
The structure of the greater part of the kidney of Bdellostoma and the Myxinoids generally has been known since the time of Johannes Müller. It consists of a simple segmental duct on each side, which represents both the Wolffian and Müllerian ducts of the higher Vertebrates, giving off in its course a series of short tubules, each of which ends in a large glomerulus. These tubules are segmentally arranged, a single pair being present in every segment of the body in the anterior three fourths of the region lying between the anus and the hinder border of the pericardium. The relations of this system of simple segmental tubules, opening into a segmental duct, were described with perfect accuracy by Johannes Müller;1 and no important additions have since been made to the account which he gave.
Fair Utilitarianism
Authors: Fleurbaey Marc , Zuber Stéphane 
Published: April 2021

Utilitarianism plays a central role in economics, but there is a gap between theory, where utilitarianism is dominant, and applications, where monetary criteria are often used. For applications, a key difficulty is to define how utilities should be measured and compared. Drawing on Harsanyi’s (1955) approach, we introduce a new normalization of utilities ensuring that: (i) a transfer from a rich population to a poor population is welfare enhancing, and (ii) populations with more risk-averse people have lower welfare. We study some implications of this “fair utilitarianism” for risk sharing, collective risk aversion, and the design of health policy. (JEL D63, D81)
Portfolio Choices with Many Big Models
Authors: Anderson Evan , Cheng Ai-ru (Meg) 
Published: April 2021

This paper proposes a Bayesian-averaging heterogeneous vector autoregressive portfolio choice strategy with many big models that outperforms existing methods out-of-sample on numerous daily, weekly, and monthly datasets. The strategy assumes that excess returns are approximately determined by a time-varying regression with a large number of explanatory variables that are the sample means of past returns. Investors consider the possibility that every period there is a regime change by keeping track of many models, but doubt that any specification is able to perfectly predict the distribution of future returns, and compute portfolio choices that are robust to model misspecification.This paper was accepted by Tyler Shumway, finance.
Comparison of rehabilitation interventions in nonoperatively treated distal radius fractures: a randomized controlled trial of effectiveness
Authors: Coughlin Tim , Norrish Alan R. , Scammell Brigitte E. , Matthews Paul A. , Nightingale Jessica , Ollivere Ben J. 
Published: April 2021

Aims Following cast removal for nonoperatively treated distal radius fractures, rehabilitation facilitated by advice leaflet and advice video were compared to a course of face-to-face therapy. Methods Adults with an isolated, nonoperatively treated distal radius fracture were included at six weeks post-cast removal. Participants were randomized to delivery of rehabilitation interventions in one of three ways: an advice leaflet; an advice video; or face-to-face therapy session(s). The primary outcome measure was the Disabilities of the Arm, Shoulder and Hand (DASH) score at six weeks post intervention and secondary outcome measures included DASH at one year, DASH work subscale, grip strength, and range of motion at six weeks and one year. Results A total of 116 (97%) of 120 enrolled participants commenced treatment. Of those, 21 were lost to follow-up, resulting in 30 participants in the advice leaflet, 32 in the advice video, and 33 face-to-face therapy arms, respectively at six weeks of follow-up. There was no significant difference between the treatment groups in the DASH at six weeks (advice leaflet vs face-to-face therapy, p = 0.69; advice video vs face-to-face therapy, p = 0.56; advice leaflet vs advice video, p = 0.37; advice leaflet vs advice video vs face-to-face therapy, p = 0.63). At six weeks, there were no differences in any secondary outcome measures except for the DASH work subscale, where face-to-face therapy conferred benefit over advice leaflet (p = 0.01). Conclusion Following cast removal for nonoperatively treated distal radius fractures, offering an advice leaflet or advice video for rehabilitation gives equivalent patient-reported outcomes to a course of face-to-face therapy. Cite this article: Bone Joint J 2021;103-B(6):1033–1039.