bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing heartworm diagnosis in dogs using multiple test combinations
Authors: Lane Jennifer N. , Litster Annette , Little Susan E. , Rodriguez Jessica Y. , Mwacalimba Kennedy K. , Sundstrom Kellee D. , Amirian E. Susan , Guerios Simone D. , Serrano Maria A. , Hays Kellie M. , Levy Julie K.
Published: April 2021

Background

Various heartworm (HW) diagnostic testing modalities detect products of, or reactions to, different life cycle stages of Dirofilaria immitis. Microfilariae (Mf) can be directly visualized in blood, antigen (Ag) from immature and adult heartworms may be detected on commercial assays, and antibody (Ab) tests detect the host immune response to larval stages. Ag and Mf tests are commonly used in dogs, which frequently carry adult HW infections, but Ab tests have only been validated for use in cats. In some HW-infected dogs, Ag is blocked by immune complexing leading to false-negative results. Heat-treatment (HT) to disrupt these complexes can increase the sensitivity of HW Ag tests. The aim of this study was to compare different methods for diagnosing HW infection in dogs at high risk using individual and paired diagnostic tests, including an exploration of using Ab tests designed for cats to test canine samples.

Methods

One hundred stray adult (≥ 2-year-old) dogs in Florida shelters were tested using Mf, HW Ag, and HW Ab tests (feline HW Ab tests currently not commercially validated/approved for use in dogs); two versions of each test platform were used.

Results

Fourteen dogs tested positive using point-of-care (POC) Ag tests; an additional 2 dogs tested positive with microtiter well assay, and an additional 12 dogs tested positive using HT Ag testing. For individual tests, Ag test sensitivity/specificity compared to HT Ag was 50–57%/100%, and Ab tests were 46–64%/82–94%. Sensitivity estimates for individual tests were higher when comparing to non-HT Ag. Pairing POC Ag tests with Mf tests improved sensitivity without loss of specificity, while pairing POC Ag and Ab tests modestly increased sensitivity at the expense of specificity.

Conclusions

Screening dogs for HW infection using both POC Ag and Mf detection, which is recommended by the American Heartworm Society, improved diagnostic performance in this study compared to single Ag test use, but may have missed more than one in four infected dogs. The need to improve access to highly accurate, rapid, and inexpensive large-scale HW testing for dogs in animal shelters remains largely unmet by current testing availability. The development of practical and validated protocols that incorporate heat or chemical treatment to disrupt Ag-Ab complexes in POC testing or decreasing the cost and time required for such testing in reference laboratories might provide solutions to this unmet need. Similar studies performed in countries where the prevalence of parasites such as D. repens or A. vasorum is different to the USA could potentially yield very different positive predictive values for both HT and non-HT Ag tests.

Graphical abstract
Drug-related problems and associated factors in Ethiopia: a systematic review and meta-analysis
Authors: Adem Fuad , Abdela Jemal , Edessa Dumessa , Hagos Bisrat , Nigussie Abraham , Mohammed Mohammed A.
Published: April 2021

Background

Drug-related problems (DRPs) can occur at any stages of medication use processes, and a single drug could be associated with multiple DRPs. Once happened, it adversely affects health outcomes. In Ethiopia, evaluation of the magnitude and factors associated with DRPs had not been attempted at the national level.

Method

The literature search was conducted in the following databases; PubMed, Embase, Medline, and Google Scholar. The quality of the included studies was checked using Joanna Brigg’s Institute (JBI’s) checklist, and data were analyzed using Stata software (version 14.0). The pooled estimate of DRPs was computed by a Random effect model (DerSimonian–Laird method). Cochran’s Q test (I2) statistic)), and Begg’s correlation and Egger’s regression test were assessed for heterogeneity and publication bias, respectively.

Result

Overall, 32 studies with a total sample size of 7,129 were included in the review. The estimated pooled prevalence of DRPs was 70% [0.70 (95% CI 0.64—0.76;I2 = 97.6%p = 0.000)]. Polypharmacy (taking ≥ 5 drugs) [RR = 1.3], medical comorbidity [RR = 1.3], poor medication adherence [RR = 1.7], uncontrolled blood pressure [RR = 1.4], substance use [RR = 1.2], type 2 diabetes [RR = 1.8], significant drug interaction [RR = 1.33], and a negative medication belief [RR = 3.72] significantly influenced the occurrence of DRPs.

Conclusion

The estimated national prevalence of DRPs in Ethiopia was high.Presence of medical comorbidity, using multiple drugs, significant drug interaction, poor medication adherence, uncontrolled blood pressure, type 2 diabetes, substance use and a negative belief about medication significantly influenced the occurrence of DRPs. Initiating and/or strengthening pharmaceutical care services at the health care facilities could lower the occurrence of DRPs. PROSPERO registration number CRD42020162329.
Genetic variability among three Egyptian isolates of Heterorhabditis indica using a new marker technique (SCoT)
Authors: Abd El Azim Amany M. , Khashaba Etr H. K.
Published: April 2021

Background

Entomopathogenic nematodes (EPNs) are a group of nematode families, have the ability to search for their hosts, and are considered as promising biological control candidates for insect pests, providing protection to non-target organisms and the environment.

Results

This study was conducted to isolate indigenous EPN isolates from Egyptian agricultural soils for further use in biological control programs and study their genetic polymorphism among the previously isolated isolates under accession no. MH553167 and MK300683 and the new isolate (MH496627), using the start codon targeted (SCoT) marker. One out of 15 soil samples obtained from a banana cultivated field was positive for the presence of EPNs, using the Galleria baiting method. Morphological analysis and sequencing of the internal transcribed spacer (ITS) region suggested that the isolate obtained belongs to Heterorhabditis indica. The sequence of the ITS was submitted to the National Center for Biotechnology Information (NCBI) and registered under accession no. MH496627. Ten SCoT primers were used in the study; the polymorphic bands were 68 out of 76 with 89% as polymorphism percentage. The highest numbers of bands were 10 bands generated by SCoT 1 and SCoT 18 while SCoT 48 and SCoT 60 recorded the lowest band number (5 bands).

Conclusions

The present study is considered as a preliminary study to demonstrate the effectiveness of the SCoT marker for the first time in assessing genetic relationships in EPNs.
Ovarian Hyperandrogenism and Response to Gonadotropin-releasing Hormone Analogues in Primary Severe Insulin Resistance
Authors: Huang-Doran Isabel , Kinzer Alexandra B , Jimenez-Linan Mercedes , Thackray Kerrie , Harris Julie , Adams Claire L , de Kerdanet Marc , Stears Anna , O’Rahilly Stephen , Savage David B , Gorden Phillip , Brown Rebecca J , Semple Robert K
Published: April 2021

Context

Insulin resistance (IR) is associated with polycystic ovaries and hyperandrogenism, but underpinning mechanisms are poorly understood and therapeutic options are limited.

Objective

To characterize hyperandrogenemia and ovarian pathology in primary severe IR (SIR), using IR of defined molecular etiology to interrogate disease mechanism. To extend evaluation of gonadotropin-releasing hormone (GnRH) analogue therapy in SIR.

Methods

Retrospective case note review in 2 SIR national referral centers. Female patients with SIR with documented serum total testosterone (TT) concentration.

Results

Among 185 patients with lipodystrophy, 65 with primary insulin signaling disorders, and 29 with idiopathic SIR, serum TT ranged from undetectable to 1562 ng/dL (54.2 nmol/L; median 40.3 ng/dL [1.40 nmol/L]; n = 279) and free testosterone (FT) from undetectable to 18.0 ng/dL (0.625 nmol/L; median 0.705 ng/dL [0.0244 nmol/L]; n = 233). Higher TT but not FT in the insulin signaling subgroup was attributable to higher serum sex hormone–binding globulin (SHBG) concentration. Insulin correlated positively with SHBG in the insulin signaling subgroup, but negatively in lipodystrophy. In 8/9 patients with available ovarian tissue, histology was consistent with polycystic ovary syndrome (PCOS). In 6/6 patients treated with GnRH analogue therapy, gonadotropin suppression improved hyperandrogenic symptoms and reduced serum TT irrespective of SIR etiology.

Conclusion

SIR causes severe hyperandrogenemia and PCOS-like ovarian changes whether due to proximal insulin signaling or adipose development defects. A distinct relationship between IR and FT between the groups is mediated by SHBG. GnRH analogues are beneficial in a range of SIR subphenotypes.
Genetically Determined Higher TSH Is Associated With a Lower Risk of Diabetes Mellitus in Individuals With Low BMI
Authors: Bos Maxime M , van Vliet Nicolien A , Mooijaart Simon P , Noordam Raymond , van Heemst Diana
Published: April 2021

Context

Thyroid status is hypothesized to be causally related with the risk of diabetes mellitus (DM), but previous results were conflicting possibly because of a complex interaction between thyrotropin (TSH), body mass index (BMI) and DM.

Objective

This work aims to investigate the causal association between thyroid status with DM and glucose homeostasis and to what extent this association is dependent on BMI.

Methods

A mendelian randomization study was conducted of European-ancestry participants from the UK Biobank population. The present study involved 408 895 individuals (mean age 57.4 years [SD 8.0], 45.9% men), of whom 19 773 had DM. Genetic variants for circulatory TSH, free thyroxine (fT4) concentrations and BMI to calculate weighted genetic risk scores. The main outcome measures included self-reported DM-stratified analyses by BMI. Analyses were repeated for nonfasting glucose and glycated hemoglobin A1c (HbA1c) among individuals without DM.

Results

Genetically determined TSH and fT4 levels were not associated with risk of DM in the total UK Biobank population. However, in analyses stratified on genetically determined BMI, genetically determined higher TSH, and not fT4, was associated with a lower risk for DM only in the low BMI group (odds ratio 0.91; 95% CI, 0.85-0.98 in low BMI; P value for interaction = .06). Similar results were observed for glucose and HbA1c among individuals without DM.

Conclusion

TSH, but not fT4, is a potential causal risk factor for DM in individuals with genetically determined low BMI highlighting potential protective effects of TSH only in low-risk populations.
The Relationship Between Bone and Reproductive Hormones Beyond Estrogens and Androgens
Authors: Mills Edouard G , Yang Lisa , Nielsen Morten F , Kassem Moustapha , Dhillo Waljit S , Comninos Alexander N
Published: April 2021

Reproductive hormones play a crucial role in the growth and maintenance of the mammalian skeleton. Indeed, the biological significance for this hormonal regulation of skeletal homeostasis is best illustrated by common clinical reproductive disorders, such as primary ovarian insufficiency, hypothalamic amenorrhea, congenital hypogonadotropic hypogonadism, and early menopause, which contribute to the clinical burden of low bone mineral density and increased risk for fragility fracture. Emerging evidence relating to traditional reproductive hormones and the recent discovery of newer reproductive neuropeptides and hormones has deepened our understanding of the interaction between bone and the reproductive system. In this review, we provide a contemporary summary of the literature examining the relationship between bone biology and reproductive signals that extend beyond estrogens and androgens, and include kisspeptin, gonadotropin-releasing hormone, follicle-stimulating hormone, luteinizing hormone, prolactin, progesterone, inhibin, activin, and relaxin. A comprehensive and up-to-date review of the recent basic and clinical research advances is essential given the prevalence of clinical reproductive disorders, the emerging roles of upstream reproductive hormones in bone physiology, as well as the urgent need to develop novel safe and effective therapies for bone fragility in a rapidly aging population.
Reflex and Behaviour Patterns Elicited from Implanted Supernumerary Limbs in the Chick
Authors: Székely George , Szentágothai John
Published: April 2021

Limb primordia, both leg and wing, have been transplanted heterotopically in chick embryos on the 3rd day of incubation. Of 11 chicks hatched, 1 had a limb graft situated in the neck, 9 in the thoracic, and 1 in the lumbar region. These supernumerary limbs were supplied with nerves from the respective segments. Muscle tissues underwent degeneration and the joints were ankylotic. The covering skin and feathers were normal and sensitive to mechanical stimuli. Responses of the hosts to stimulation of the supernumerary limbs have been studied. The most common reflex response to light mechanical stimulation of the graft was a flexion reflex of the host’s ipsilateral leg. If the graft was situated in close vicinity of the wing, elevation of the host’s own wing could be elicited. These Timb-specific’ reflexes could be exclusively evoked from the grafts, but never from their neighbourhood. Four cases yielded more complex behaviour reactions always referred to one of the host’s own limbs, i.e. lame walking after stronger stimulation of the graft and cleaning of the host’s foot with the beak when a permanent, painful, stimulus was applied to the supernumerary limb. There was no correlation whatever between the type of the graft and the evoked ‘limb-specific’ responses which appeared only some days after hatching. Pain sensitivity and specific reflexogenic capacity were not strictly associated, since Timb-specific’ responses could be elicited from painless parts of the grafts and the reverse. According to anatomical investigation most of the grafts were supplied exclusively by intercostal nerves which never under normal circumstances convey limb signals and stimulation of which normally never evokes Timb-specific’ responses. Grafts producing only simple reflexes were generally supplied by a single segmental nerve, whereas complex behaviour reactions could be exclusively evoked from grafts with multisegmental inervation and some plexus formation among the supplying nerves. It is difficult to explain the observations made on supernumerary limbs of chicks on the basis of the Weiss-Sperry concept of ‘specific modulation’. As alternative hypothesis the capacity of ‘analysis’ and ‘recognition’ of specific afferent impulse patterns by the c.n.s. is suggested.
Les effets du chloramphénicol sur le développement de l’œuf d’Oursin
Authors: Lallier par R.
Published: April 2021

Le développement normal de l’œuf d’oursin dépend de l’équilibre entre deux tendances opposées qui favorisent respectivement la différenciation de l’ectoderme et de l’entomésoderme (Runnstrôm, 1928a). Cet équilibre peut être rompu expérimentalement par des méthodes opératoires ou sous l’influence d’agents chimiques déterminés. On provoque ainsi l’extension des structures ectodermiques (animalisation) ou entomésodermiques (végétalisation). Un troisième type de modification du développement, la radialisation, est caractérisé par la formation de larves à symétrie radiale. La radialisation s’obtient en traitant les œufs par des agents animalisants en faibles concentrations.
The Development of the Notochord in Chick Embryos
Authors: Jurand A.
Published: April 2021

The literature on the notochord, a structure characteristic of all vertebrates, is very extensive, due to the phylogenetic importance of this organ, its role in early embryonic development, and its central position in the developing vertebral column. As early as 1834 the notochord tissue was described by Müller as being similar in appearance to the parenchyma of plants. Surprisingly, however, in the chick embryo, which is so widely used by embryologists, its development has not very often been the subject of descriptive or experimental investigations. From the early days most work on this fundamental organ was done on fish and amphibians, probably because the notochord in lower vertebrates is more suitable for investigations, as it persists longer, carrying out its function as an embryonic and larval skeleton.
The morphogenesis of the chick primary corneal stroma: I. New observations on collagen organization in vivo help explain stromal deposition and growth
Authors: Bard Jonathan B. L. , Bansal Mohinder K.
Published: April 2021

The primary stroma of the avian cornea contains collagen fibrils in orthogonal array. While investigating the processes underlying its morphogenesis, we have found that stromal organization is not as expected in three important respects. First, the fibrils are not uniform: those near the epithelium (newly laid down) have a maximum diameter of about 20 nm (mean: 17·7 nm), while those near the endothelium (laid down for approx. 40 h) have diameters up to 40 nm (mean: 22·8 nm). Fibrils thus grow rapidly to 20 nm and then continue to enlarge slowly, presumably by diffusion of collagen molecules from the epithelium. Second, the collagen, although orthogonally organized, does not contain layers of parallel fibrils. Instead, SEM observation shows that only a few fibrils lie in a parallel array before this shortrange order is broken by orthogonal fibrils in the same plane. Furthermore, fibrils in corneas that had been freeze dried but not critical-point dried for SEM were widely spaced and the intervening gaps were filled by an extensive matrix that was probably composed of the proteoglycans known to be in the stroma. Third, we have shown experimentally that the stromal undulations seen in sections are not present in vivo but are shrinkage artifacts: the less corneas were shrunk for SEM preparation, the less pronounced were the stromal undulations. We also noted that, even after the distortions required for the stroma to undulate, the constituent fibrils remained orthogonally organized.

These results give insight into the mechanisms underlying stromal morphogenesis and growth. The observations on the growth of collagen fibrils and on collagen organization show that stromal deposition is a more stochastic process than previously thought and, hence, provides support for the view that a complex self-assembly mechanism underlies both fibrillogenesis and the generation of orthogonal organization. The experiments on, and the analysis of, stromal folding show that fibrils slide over one another as undulations form, with the extensive matrix of hydrated proteoglycans being the likely lubricant. This fluidity of the stromal components probably explains how growth can occur without the structure being distorted.
Spontaneous generation of bilateral symmetry in the paired claws and closer muscles of adult snapping shrimps
Authors: Pearce Joanne , Govind C. K.
Published: April 2021

Adult snapping shrimps Alpheus heterochelis (Say) have paired asymmetric claws consisting of a major or snapper claw and a minor or pincer claw. An unusual condition of bilateral symmetry consisting of paired snapper claws arose spontaneously in several snapping shrimps by transformation of the pincer to a snapper in the presence of an existing contralateral snapper claw. Transformation in the external morphology and fibre composition of the closer muscle was completed within two intermoult periods in the majority of cases where true symmetry was achieved and once established became permanent. Thus snapping shrimps, which are by nature solitary, when continually exposed to each other in the laboratory may transform their pincer to a snapper without any trauma to the existing snapper claw.
Identity of cells containing apolipoprotein B messenger RNA, in 6- to 12-week postfertilization human embryos
Authors: Hopkins B. , Brice A. L. , Schofield P. N. , Baralle F. E. , Graham C. F.
Published: April 2021

Apolipoprotein B (Apo B) mRNA has been localized by in situ hybridization to various cell types in the liver, gut and yolk sack of the 6- to 12-week postfertilization human conceptus.

In the fetal liver it is probable that the immature hepatocytes contain Apo B mRNA. In the yolk sack, the Apo B cDNA probe hybridizes mainly to the large endodermal cells and in the fetal gut the epithelium seems responsible for the majority of Apo B mRNA production. The fetal brain did not show any detectable hybridization to the Apo B probe.

Unlike the situation seen in the adult, immunoprecipitation experiments demonstrated that only the B100 form of the protein was synthesized and secreted by the liver, gut and yolk sack at this early stage of human development.
Structure and development of the egg of the glossiphoniid leech Theromyzon rude: characterization of developmental stages and structure of the early uncleaved egg
Authors: Fernández Juan , Olea Nancy , Matte Cecilia
Published: April 2021

Some aspects of the reproductive biology of the glossiphoniid leech, Theromyzon rude, under laboratory conditions, and the staging and structure of its uncleaved egg were studied. Sexually mature animals form breeding communities and fertilization occurs in the ovisacs, presumably around the time of egg laying. Opposition may be postponed for hours or days, but the eggs in the ovisacs remain blocked at first meiotic metaphase. Development of the uncleaved egg, from the time of oviposition to completion of the first cleavage division, has been sub-divided into six stages. At 20°C, the six developmental stages take 5–6 h. Characterization of the stages is based on observations of both live and fixed/cleared eggs. Discharge of the first pole cell, by the end of stage la, is associated with the movement of a ring of contraction between the equator and the animal pole. Discharge of the second pole cell, by the end of stage 1b, is accompanied by contraction of the animal hemisphere which becomes a cone-shaped structure. Polar rings and meridional bands of contraction make their appearance by stages 1c and 1d, respectively. Constriction of the polar rings and shortening of the meridional bands, during stage le, lead to accumulation of ooplasm at both egg poles. In this manner, the teloplasm or pole plasm forms. Completion of the first cleavage furrow, by the end of stage If, is preceded by dorsoventral flattening of the egg and rearrangement of its teloplasm and perinuclear plasm. Structure of the early uncleaved egg has been studied with transmission and scanning electron mi-croscopy of intact or permeabilized preparations. The plasmalemma forms numerous long and some short microvilli evenly distributed across the egg surface. The ectoplasm includes many vesicles, mitochondria, granules and an elaborate network of filament bundles. Staining of this network with rhodamine-labelled phalloidin indicates that it contains F-actin. A less complex network of similar filaments is also present throughout the yolky endoplasm. The meiotic spindle lies close to the egg surface and not far from the presumptive animal pole ectoplasm. It comprises highly developed poles whose structure and relationships are described.
The initiation of new gene transcription duringXenopusgastrulation requires immediately preceding protein synthesis
Authors: Cascio S. , Gurdon J. B.
Published: April 2021

The incubation of Xenopus embryo fragments in cycloheximide at 5 or 10μgml−1 rapidly inhibits protein synthesis to 10 % or less of control levels. In most batches of embryos, treatment with cycloheximide for up to 1 h causes no obvious cellular damage and protein synthesis is fully restored to normal levels 5h later. Transcript analysis with RNA probes shows that the inhibition of protein synthesis at late blastula or early gastrula stages completely suppresses the normal initiation of actin gene transcription at the mid-late gastrula stage. This applies to muscle-specific actin genes, whose transcription is initiated by induction, as well as to cytoskeletal actin genes not activated by induction. Two-dimensional gel protein analysis shows that cycloheximide irreversibly inhibits only 10 % of all genes normally expressed at a postneurula stage and that all of these are genes whose expression is normally initiated during or soon after gastrulation. Cycloheximide treatment causes a limited reduction of DNA synthesis, and no reduction of overall RNA synthesis. We conclude that the initiation of new gene transcription during gastrulation in Xenopus is dependent on the immediately preceding synthesis of certain proteins.
The pattern of innervation in serially duplicated axolotl limbs: further evidence for the existence of local pathway cues
Authors: Stephens Nigel , Holder Nigel
Published: April 2021

The innervation of the biceps muscle was examined in regenerated and vitamin A-induced serially duplicated axolotl forelimbs using retrograde transport of horseradish peroxidase. The regenerated biceps muscle becomes innervated by motor neurones in the same position in the spinal cord as the normal biceps motor pool. In previous experiments in which the innervation of a second copy of a proximal limb muscle was examined in serially duplicated limbs (Stephens, Holder & Maden, 1985), the duplicate muscle was found to become innervated by motor neurones that would normally have innervated distal muscles. In the present study, the innervation of the second copy of biceps was examined under conditions designed to encourage nerve sprouting from ‘correct’ biceps axons. Following either partial limb denervation or denervation coupled with removal of the proximal biceps, the second copy of the muscle was still innervated by inappropriate motor neurones, which again would normally innervate distal limb muscles. These results are interpreted as evidence for the necessity for an appropriate local environment for axonal growth to allow reformation of a correct pattern of motor innervation in the regenerated limb.
Mode of action of ammonia and amine on rRNA synthesis in Xenopus laevis embryonic cells
Authors: Shiokawa Koichiro , Fu Yuchang , Kawazoe Yuichi , Yamana K.
Published: April 2021

Recently, we found that rRNA synthesis in dissociated embryonic cells of Xenopus laevis is selectively inhibited by ammonium salts added to their surrounding medium. Similar effects were also observed in cells treated with amines. In this report, we analysed in more detail the effects of an ammonium salt and trimethylamine on rRNA synthesis in Xenopus embryonic cells cultured under several different conditions.

Results obtained showed that ammonia and trimethylamine inhibit formation of 40S pre-rRNA, without inducing breakdown (wastage) or aberrant processing of the 40S pre-rRNA. Such inibitory effects were also shown not to be due to interference with cellular ATP level. Furthermore, we found that the effects of both ammonium salt and trimethylamine were completely abolished when Na+ in the culture medium of the testing cells was replaced by choline ions. These results favour the view that the inhibition of rRNA synthesis by ammonia and amine is realized at the transcriptional level or at the step before the formation of 40S pre-rRNA, most probably via a slight increase of intracellular pH, but not via an inhibition in energy-generating systems.
Differentiation and innervation of the atrioventricular bundle and ventricular Purkinje system in sheep heart
Authors: Canale E. , Smolich J. J. , Campbell G. R.
Published: April 2021

The development of the atrioventricular bundle (AVB) and ventricular Purkinje system and their innervation have been studied in fetal sheep from 27 to 140 days gestation (term is 147 days). The AVB initially consisted of a primordium, which lacked innervation and was composed of small, relatively undifferentiated myocytes. Differentiation of Purkinje-like cells within the AVB began near its distal end and extended towards the atrioventricular node (AVN). Differentiation of the ventricular Purkinje system extended distally from the region of bifurcation of the AVB from cells that were indistinguishable from the working myocardium and continuous with the AVB primordium. Differentiation of Purkinje-like AVB cells was complete by 46 days gestation but Purkinje fibres were still differentiating within the ventricular wall at 60 days gestation. The main morphological changes included a large increase in cell size and organization into strands, development of characteristic glycogen-filled regions containing many intermediate filaments and early development of myofibrillar M lines compared to the working myocardium.

The differentiation of AVB cells and the ventricular Purkinje system preceded their innervation. The AVB became innervated earlier than ventricular Purkinje fibres, intimate contacts between proximal AVB cells and nerve axons being present at 60 days gestation. Nerve fibres were present in the septomarginal band at this time, however, en passant associations with ventricular Purkinje fibres were rarely observed until 140 days gestation and intimate contacts were not present at any stage.

Although the AVB and ventricular Purkinje system of adult sheep are composed of morphologically similar cells, the present study demonstrates that they differ in origin and their mode of differentiation as well as timing and intimacy of innervation. Innervation is not part of the developmental mechanism leading to the differentiation of Purkinje fibres. No primordium of the ventricular Purkinje system could be identified, suggesting that the mechanism of differentiation of ventricular Purkinje fibres involves recruitment from early working myocardium.
Retinal axons with and without their somata, growing to and arborizing in the tectum of Xenopus embryos: a time-lapse video study of single fibres in vivo
Authors: Harris William A. , Holt Christine E. , Bonhoeffer Friedrich
Published: April 2021

Time-lapse video recordings were made of individual retinal ganglion cell fibres growing to and terminating in the optic tectum of Xenopus embryos. The fibres were stained by inserting a crystal of the lipophilic fluorescent dye, Dil, into the developing retina. Growth cones were observed in the optic tract and tectum using 20 ms flashes of light to induce fluorescence approximately once every minute. Fluorescent images were captured with a SIT camera, processed and saved on a time-lapse video recorder. The main conclusions from observing normal growing fibres are as follows. (1) Axons in the optic tract grow at a steady rate directly toward their targets without retracting or branching. (2) As axons approach the tectum they slow down and their growth cones become more complex. (3) Most terminal branches in the tectum are formed by back branching rather than by bifurcation of leading growth cones.

In a second experiment, labelled growing axons were separated from their cell bodies by removing the retina. Such isolated axons continued to grow for up to 3h in vivo and were capable of recognizing the tectum and arborizing there. This result shows that growth cones must contain the machinery needed to sense and respond to their specific pathways and targets.
Factors controlling induction of commitment of murine erythroleukemia (TSA8) cells to CFU-E (colony forming unit-erythroid)
Authors: Noguchi Tsuyoshi , Fukumoto Hiroaki , Mishina Yuji , Obinata Masuo
Published: April 2021

On addition of DMSO, the MEL cell line TSA8 becomes committed into erythroid progenitor cells (CFU-E) which can form differentiated colonies in the presence of erythropoietin. To understand the mechanism of cellular commitment, the number and the affinity of the receptors for erythropoietin were estimated. The affinity of the receptors did not change before or after induction. The number of receptors changed depending on the growth phase, but was not dependent on the addition of the inducer. Thus, the presence of the receptors for erythropoietin may be required, but are not essential for responsiveness to erythropoietin.

Further examination of the optimum conditions for commitment suggests that the concomitant actions of induced factor(s) with the receptors may control commitment of TSA8 cells to CFU-E.
Inhibitory and stimulatory influences on mesodermal erythropoiesis in the early chick blastoderm
Authors: Kessel Joan , Fabian Barry
Published: April 2021

We use a standing-drop culturing method to investigate the effect on mesodermal erythropoiesis of ectoderm and endoderm from the .area opaca vasculosa (AOV) and area pellucida (AP) of stage-4 chick blastoderms. We find that ectoderm from the AOV and ectoderm and endoderm from the AP exert an inhibitory influence on mesodermal erythropoiesis. This inhibitory influence is coupled with the tendency of the explants to spread out and become flattened in culture. In contrast, endoderm from the AOV is found to be stimulatory, in agreement with previous studies. We correlate these in vitro inhibitory and stimulatory influences with the morphogenetic patterns that occur during normal development.
Evidence against electrophoresis as the principal mode of protein transport in vitellogenic ovarian follicles of Drosophila
Authors: Bohrmann Johannes , Gutzeit* Herwig
Published: April 2021

Charged cell constituents in polytrophic insect follicles are thought to be transported in the nurse celloocyte syncytium by way of electrophoresis. This concept, proposed by Woodruff & Telfer (1980) was based on electrophysiological data and microinjection of heterologous proteins using Hyalophora follicles. By microinjecting fluorescently labelled acidic and basic proteins into the nurse cells or oocyte of vitellogenic Drosophila follicles, we failed to obtain evidence for charge-dependent migration of these molecules. We have also analysed the proteins of nurse cells and oocyte on isoelectric focusing gels, by means of twodimensional gel electrophoresis, and by ion exchange chromatography to see if basic or acidic proteins accumulate in vivo in nurse cells and oocyte, respectively. For the bulk of the follicular proteins we found no accumulation. Further evidence against an electrophoretic transport system in Drosophila was obtained by estimating the intracellular pH from the colour of indicator dyes microinjected into the follicles; the results indicate that the pH in the nurse cell cytoplasm is lower than that in the ooplasm. According to the model developed for Hyalophora, electrophoretic transport would be favoured by high pH in the nurse cell cytoplasm.
Characterization of sea urchin primary mesenchyme cells and spicules during biomineralization in vitro
Authors: Decker Glenn L. , Morrill John B. , Lennarz William J.
Published: April 2021

An in vitro culture system for primary mesenchyme cells of the sea urchin embryo has been used to study the cellular characteristics of skeletal spicule formation. As judged initially by light microscopy, these cells attached to plastic substrata, migrated and fused to form syncytia in which mineral deposits accumulated in the cell bodies and in specialized iilopodial templates. Subsequent examination by scanning electron microscopy revealed that the cell bodies and the filopodia and lamellipodia formed spatial associations similar to those seen in the embryo and indicated that the spicule was surrounded by a membrane-limited sheath derived by fusion of the filopodia. The spicules were dissolved from living or fixed cells by a chelator of divalent cations or by lowering the pH of the medium. However, granular deposits found in the cell bodies appeared relatively refractory to such treatments, indicating that they were inaccessible to agents that dissolved the spicules. Use of rapid freezing and an anhydrous fixative to preserve the syncytia for transmission electron microscopy and X-ray microprobe analysis, indicated that electron-dense deposits in the cell bodies contain elements (Ca, Mg and S) common to the spicule. Examination of the spicule cavity after dissolution of the spicule mineral revealed openings in the filopodia-derived sheath, coated pits within the limiting membrane and a residual matrix that stained with ruthenium red. Concanavalin A-gold applied exogenously entered the spicule cavity and bound to matrix glycoproteins. Based on these observations, we conclude that components of the spicule initially are sequestered intracellularly and that spicule elongation occurs in an extracellular cavity. Ca2+ and associated glycoconjugates may be routed to this cavity via a secretory pathway.
An ultrastructural and morphometric analysis of an in vivo contact guidance system
Authors: Wood Andrew , Thorogood Peter
Published: April 2021

The pectoral fin bud of the developing teleost embryo contains a highly ordered extracellular matrix of collagenous fibrils, called ‘actinotrichia’. During invasion of the fin fold, mesenchymal cells, migrating distally from the base of the fin, become contact aligned by the actinotrichial fibrils. Behavioural aspects of this response have previously been studied using Nomarski differential interference contrast microscopy and time-lapse video recording (Wood & Thorogood, 1984). Here we present an ultrastructural description of these cells and their matrix associations and a computer-based morphometric analysis of selected parameters within the migration substratum, relevant to this in vivo ‘contact guidance’ phenomenon. The study shows that a differentiated and aligned matrix of actinotrichial fibrils can be detected before invasion of the fin fold, at levels up to 40/zm distal to the advancing mesenchymal cell margin. Subsequently, during invasion of the fin fold, aligned mesenchymal cells and processes are almost exclusively associated with actinotrichia and not the intervening surface of the epithelial basal lamina. However, aligned cell processes appear to avoid the smaller actinotrichia and at late stages of development 87·0 % of actinotrichia without cell process contacts are distributed at the lower end of the size range. Study of cell ultrastructure revealed a complete absence of cytoskeletal organization within this mesenchymal cell population, although cytoskeletal components are clearly visible in adjacent epithelia. The computer-based morphometric survey of the migration substratum has shown a gradual but progressive increase in the mean diameter of actinotrichia at a level at which distal cell processes are first detectable in sections of fins. However, at similar levels over the same period the mean value for interactinotrichial spacings remained virtually constant. These results suggest that the spacing between actinotrichia is not significant in contributing to progressive changes in mesenchymal cell phenotype, but that the actinotrichia themselves are strongly implicated in providing the guidance cues to direct cell migration within the developing fin and the initiation of cell migration. These findings are discussed in the general context of cell movement and contact guidance both in vivo and in vitro.
Mechanical aspects of the mesenchymal influence on epithelial branching morphogenesis of mouse salivary gland
Authors: Nogawa Hiroyuki , Nakanishi Yasuo
Published: April 2021

Three activities of mesenchymes from mouse embryonic submandibular gland, lung, stomach, mandible and skin were comparatively studied. The first ability was the induction of branching of submandibular epithelial lobes. Epithelial lobes branched well in recombination with submandibular or lung mesenchyme, less well with stomach mesenchyme, but never with mandibular or dermal mesenchyme. The second behavioural aspect studied was the contraction of collagen gels. When respective mesenchymal cells were dispersed at 2 0×105 cells ml−1 in collagen gels (1×5 mg ml−1) and incubated, dermal mesenchymal cells had the highest gel-contracting activity. The gelcontracting activity of submandibular or lung mesenchymal cells was two thirds as high as that of dermal cells and that of stomach or mandibular mesenchymal cells was much lower. The last activity was to separate three plastic beads that were recombined with mesenchymes in place of epithelial lobes. Salivary or lung mesenchyme effected a large separation of the beads, whereas dermal mesenchyme left beads contacting one another. There was a positive correlation between the branch-inducing activity and the beads-separating activity within the five kinds of mesenchymes. In timelapse cinematography of recombinates, cells of submandibular and lung mesenchyme were observed moving (or flowing) around, and their property was different from that of dermal mesenchyme. In the presence of cytochalasins, both the contraction of collagen gels and separation of plastic beads by submandibular mesenchymal cells were completely inhibited. These results suggest the importance of mechanical influences of the mesenchyme in salivary branching morphogenesis.
Corneal morphogenesis in the Mov13 mutant mouse is characterized by normal cellular organization but disordered and thin collagen
Authors: Bard Jonathan B. L. , Kratochwil Klaus
Published: April 2021

This paper compares corneal development in the normal and in the Movl3 mutant mouse homozygote which does not synthesize type I collagen. During the period 12-14 days of development, there is no obvious difference between cellular organization in the normal and the mutant corneas or, indeed, elsewhere in the eye. In particular, there is normal colonization of the mutant cornea by the mesenchymal cells which will form the endothelium and the fibroblasts. In the early stages of stromal deposition (<14 days), when relatively little collagen is normally laid down, mutant and wild-type corneas differ only in that mutant collagen fibrils are less uniform than normal ones. Later development in the Movl3 mutant cannot usually be studied because almost all mutant embryos are dead by 14 days, but we now have two homozygous embryos from a single, 16-day litter. Their stromas obviously differed from those of their normal littermates: there was markedly less collagen in the mutant cornea and the collagen that was deposited lacked orthogonal organization. Fibril morphology also differed: the diameters of fibrils in the normal corneas peaked sharply at about 20 nm, whereas the diameters of mutant fibrils were spread over the range 5-15 nm, with only a small percentage overlapping the normal distribution.

These results suggest that type I collagen is of negligible importance in controlling the cellular organization of the cornea, but has a dominant role in the formation of normal 20 nm fibrils and of normal stromal organization. They also show that, as collagen production is markedly lower in the mutant than in the wild-type cornea, the production of other collagens cannot compensate in any way for the lack of type I collagen. As the mutant cornea is likely to contain interstitial collagens II, III and V, the almost complete absence of normal fibrils in the mutant stroma is surprising because other workers have shown that each of these collagens forms normal fibrils in vitro.
Cell-cell interactions modulate the responsiveness of PC12 cells to nerve growth factor
Authors: Doherty Patrick , Mann Derek A. , Walsh Frank S.
Published: April 2021

The growth of PC 12 cells on a collagen substratum or on monolayers of several non-neuronal cell types was studied by measuring nerve growth factor (NGF)- dependent increases in the expression of a 150 × 103(Mr) neurofilament protein subunit and the membrane glycoprotein Thy-1. Both responses were found to be greatly suppressed in cultures of fibroblasts as compared to the C2 and G8-1 muscle cell lines and the C6 glioma cell line. This suppression was associated with an inhibition of NGF-dependent neuritic outgrowth from PC12 cells grown on fibroblast monolayers. There was no evidence that fibroblasts secrete soluble molecules that directly inhibit these responses or neutralize NGF. In addition, there was no difference in the neurofilament protein response from PC 12 cells that had been treated with NGF prior to coculture, and the now primed PC12 cells readily extended axons over fibroblast monolayers. These data demonstrate that cell–cell and/or cell–matrix interactions can modulate biochemical responses to NGF and suggest that responsiveness of neuronal cells to environmental cues is not immutable. Control of the latter may be at the level of expression of receptor molecules for cell-surface- or matrix-associated macromolecules and a similar mechanism operating during development could play a role in growth cone guidance.
Vimentin expression in oocytes, eggs and early embryos ofXenopus laevis
Authors: Tang P. , Sharpe C. R. , Mohun T. J. , Wylie C. C.
Published: April 2021

Immunocytochemical studies using a monoclonal antiporcine vimentin antibody reveal a well-organized pattern of staining in Xenopus laevis oocytes, eggs and early embryos. The positions of Xenopus vimentin and desmin in two-dimensional (2D) polyacrylamide gels were first established by immunoblotting of muscle Triton extracts with anti-intermediate filament antibodies (anti-EFA), which cross-react with all intermediate filament proteins (IFPs). The anti-porcine vimentin reacts with vimentin and desmin in muscle 2D immunoblots, but only reacts with one polypeptide in oocyte blots in the position predicted for vimentin (Mr55×103, pl 5·6).

Using an anti-sense probe derived from a Xenopus vimentin genomic clone in RNase protection assays, we show that expression of vimentin begins in previtel-logenic oocytes. The level of expression remains constant throughout oogenesis and in unfertilized eggs. These data suggest that vimentin is expressed in oocytes and eggs. Most interestingly, the immunocytochemical results also show that vimentin is present in the germ plasm of oocytes, eggs and early embryos. It is therefore possible that vimentin has an important role in the formation or behaviour of early germ line cells.
The role of secondary mesenchyme cells during sea urchin gastrulation studied by laser ablation
Authors: Hardin Jeff
Published: April 2021

It has long been thought that traction exerted by filopodia of secondary mesenchyme cells (SMCs) is a sufficient mechanism to account for elongation of the archenteron during sea urchin gastrulation. The filopodial traction hypothesis has been directly tested here by laser ablation of SMCs in gastrulae of the sea urchin, Lytechinus pictus. When SMCs are ablated at the onset of secondary invagination, the archenteron doubles in length at the normal rate of elongation, but advance of the tip of the archenteron stops at the gastrula stage. In contrast, when all SMCs are ablated at or following the gastrula stage, further elongation does not occur. However, if a few SMCs are allowed to remain in gastrulae, elongation continues, although more slowly than in controls. The final length of archenterons in embryos ablated at the gastrula stage is virtually identical to the final length of everted archenterons in LiCl-induced exogastrulae; since filopodial traction is not exerted in either case, an alternate, common mechanism of elongation probably operates in both cases. These results suggest that archenteron elongation involves two processes: (1) active, filopodia-independent elongation, which depends on active cell rearrangement and (2) filo-podia-dependent elongation, which depends on mechanical tension exerted by the filopodia.
Adenosine induces dormancy in starfish blastulae
Authors: Tsuchimori Noboru , Miyashiro Shigeyoshi , Shibai Hiroshiro , Ikegami Susumu
Published: April 2021

External application of 50 μg ml-1 adenosine inhibits development of the starfish Asterina pectinifera at the 256-cell stage when all the embryonic cells differentiate to epithelial cells. Intracellular concentration of adenosine in the adenosine-treated embryo is 2·7 times higher than those of the normal embryo whereas the contents of ATP, ADP, AMP and adenosine 3′,5′-monophosphate are the same for both embryos. Adenosine causes more than 95 % reduction in the rate of protein, DNA and RNA syntheses. By returning the embryo to normal sea water, macromolecular synthesis restarts and the embryo develops to the bipin-naria stage.