Macro and Micro Anatomical Observation on the Testes of Local Dog (Canis lupusfamiliaris) of Assam

Background: The study on testes of local dog of Assam is of great value in regard to germplasm conservation. The aim of the study was to evaluate the gross and histomorphological examination of testes of male reproductive system. Methods: The testes were collected at the time of castration from Department of Surgery and Radiology, College of Veterinary Science, Assam Agricultural University, Khanapra, Guwahati, Assam, India. The research was carried out for a period of one year in Department of Anatomy and Histology, College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati, Assam. Then gross anatomical studies were made on it and the tissue samples were fixed in 10% neutral buffered formalin solution and were processed as per the standard technique of procedure (Luna, 1968). The paraffin blocks were sectioned in Shandon Finesse microtome at 5 µm thickness and the sections were stained with Mayer’s Haematoxylin and Eosin staining technique for Cellular details as per the method of Luna (1968). Result: Grossly, the testes of local dog consisted of two surface viz., lateral and medial and two ends i.e. upper end and lower end. The upper end of the testes was occupied by the head of the epididymis and the lower end of the testes was occupied by the tail of the epididymis. Mediastinum testis was observed in the centre of testes of local dog. Histologically, the testes were covered by serous layer (Tunica vaginalis), connective tissue layer (Tunica albugenia) and vascular layer (Tunica vasculosa) from outside to inwards. Spermatogenic cells like spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa, and sertoli cells were observed in seminiferous tubules. The sertoli cells were attached to the basement membrane of seminiferous tubules. Cluster of Leyding cells were found between the semineniferous tubules and it contained large spherical nuclei. The epididymides were lined by pseudo stratified ciliated columnar epithelium.

Molecular Organization of the Early Stages of Nucleosome Phase Separation Visualized by Cryo-Electron Tomography

It has been proposed that the intrinsic property of nucleosome arrays to undergo liquid-liquid phase separation (LLPS) in vitro is responsible for chromatin domain organization in vivo. However, understanding nucleosomal LLPS has been hindered by the challenge to characterize the structure of resulting heterogeneous condensates. We used cryo-electron tomography and deep learning-based 3D reconstruction/segmentation to determine the molecular organization of condensates at various stages of LLPS. We show that nucleosomal LLPS involves a two-step process: a spinodal decomposition process yielding irregular condensates, followed by their unfavorable conversion into more compact, spherical nuclei that grow into larger spherical aggregates through accretion of spinodal material or by fusion with other spherical condensates. Histone H1 catalyzes more than 10-fold the spinodal-to-spherical conversion. We propose that this transition involves exposure of nucleosome hydrophobic surfaces resulting in modified inter-nucleosome interactions. These results suggest a physical mechanism by which chromatin may transition from interphase to metaphase structures.

Chromosomes distribute randomly to, but not within, human neutrophil nuclear lobes

The proximity pattern and radial distribution of chromosome territories within spherical nuclei are well understood to be random and non-random, respectively. Whether this distribution pattern is conserved in the partitioned or lobed nuclei of polymorphonuclear cells is unclear. Here we use chromosome paint technology and a novel high-throughput imaging analysis pipeline to examine the chromosome territories of all 46 chromosomes in hundreds of single human neutrophils – an abundant and famously polymorphonuclear immune cell.By comparing the distribution of chromosomes to randomly shuffled controls, and validating with orthogonal chromosome conformation capture technology, we show for the first time that all human chromosomes randomly distribute to neutrophil nuclear lobes, while maintaining a non-random radial distribution within these lobes. Furthermore, by leveraging the power of this vast dataset, we are able to reveal characteristics of chromosome territories not detected previously. For example, we demonstrate that chromosome length correlates with three-dimensional volume not only in neutrophils but other human immune cells.This work demonstrates that chromosomes are largely passive passengers during the neutrophil lobing process, but are able to maintain their macro-level organisation within lobes. Furthermore, the random distribution of chromosomes to the naturally partitioned nuclear lobes suggests that specific transchromosomal interactions are unimportant in mature neutrophils.