Coronaviruses are extremely susceptible to genetic changes due to the characteristic features of the genome structure, life cycle and environmental pressure. Their remarkable variability means that they can infect many different species of animals and cause different disease symptoms. Moreover, in some situations, coronaviruses might be transmitted across species. Although they are commonly found in farm, companion and wild animals, causing clinical and sometimes serious signs resulting in significant economic losses, not all of them have been classified by the World Organization for Animal Health (OIE) as hazardous and included on the list of notifiable diseases. Currently, only three diseases caused by coronaviruses are on the OIE list of notifiable terrestrial and aquatic animal diseases. However, none of these three entails any administrative measures. The emergence of the SARS-CoV-2 infections that have caused the COVID-19 pandemic in humans has proved that the occurrence and variability of coronaviruses is highly underestimated in the animal reservoir and reminded us of the critical importance of the One Health approach. Therefore, domestic and wild animals should be intensively monitored, both to broaden our knowledge of the viruses circulating among them and to understand the mechanisms of the emergence of viruses of relevance to animal and human health.

This study determined the presence of nitric oxide synthesis isoforms (nNOS, iNOS, and eNOS) in thoracic spinal cord segments and nodose ganglia of rats with gamma-irradiated livers. Male rats (n = 32) were divided into equal groups A, B, C, and D. In group A, the controls, no radiation was applied, while groups B, C, and D received 10 Gy of ionising gamma radiation. The rats of group B were euthanized at the end of the first day (d1), those of group C on the second day (d2), and those of group D on the third day (d3). The liver, spinal cord segments, and nodose ganglion tissues were dissected and fixed, and the liver sections were examined histopathologically. The other tissues were observed through a light microscope. Regeneration occurred at the end of d3 in hepatocytes which were radiation-damaged at the end of d1 and d2. On d1, some nNOS-positive staining was found in the neuronal cells of laminae I–III of the spinal cord and in neurons of the nodose ganglion, and on d3, some staining was observed in lamina X of the spinal cord, while none of note was in the nodose ganglion. Dense iNOS-positive staining was seen on d1 in the ependymal cells of the spinal cord and in the glial cells of the nodose ganglion, and on d3, there was still considerable iNOS staining in both tissues. There was clear eNOS-positive staining in the capillary endothelial cells of the spinal cord and light diffuse cytoplasmic staining in the neurons of the nodose ganglion on d1, and on d3, intense eNOS-positive staining was visible in several endothelial cells of the spinal cord, while light nuclear staining was recognised in the neurons of the nodose ganglion. The nNOS, iNOS, and eNOS isoforms are activated in the spinal cord and nodose ganglion of rats after ionising radiation insult to the liver.

The present study was conducting aiming to throw the light on the retinal structure on the level of both light and electron microscope. Eyeballs of 35 adult clinically healthy goats of both sexes were collected from Beni- Suef abattoir. The eyeballs were clinically examined before they were dissected and fixed in 10% buffed neutral formalin and in Bouin’s solution for 24 hours. The specimens were then processed for light and transmission electron microscope. The retina (pars optica retinae) of the goats extends rostrally to cover the ciliary body as pars ciliaris retinae and the iris as the pars iridis retinae. Pars optica retinae and pars iridis retinae form the light non sensitive parts of the retina, while the sensitive part except at the transition zone; the ora serrata and the optic disc, appeared to be formed of ten layers, named from outward to inward as, retinal pigmented epithelium, rods and cones layer (photoreceptor cell layer), external limiting membrane, outer nuclear layer (cell bodies and nuclei of the photoreceptor cells), outer plexiform layer, inner nuclear layer (contained the horizontal, bipolar, Muller and amacrine cells), inner plexiform layer, ganglionic cell layer, nerve fiber cell layer (unmyelinated nerve fibers) and internal limiting membrane.

The present study deals with a monogenean parasite infecting, some marine fish through light and scan electron microscopy. It revealed that the percentage of infection was 48% (14 out of 50 fish), 28% (14 out of 50 fish), 22% (11 out of 50 fish) and 16% (8 out of 50 fish) in Diplodus noct, Gerres oyena, Lethrinus elongates and Siganus revulatus, respectively. The present work recorded Paranaella diplodae (Polyopisthocotylea; Microcotylidae; Monogenea) as a new species collected from the investigated fish gills. They are lanculate flukes, the haptor is not distinguished from the body proper approximately 1/3 of the whole body length. The surface topography of the parasite bears small pits and conspicuous transverse folds and richly supplied with papillae-like unicellate sensory ending. The opisthohaptor is typical of Microcotylidae. The clamp structure and the haptoral tegument are similar to the rest of the body

The present study aimed to clarify the light and electron microscopic structure of the prostate gland of mature (one-humped camels) during different seasons of the year. Glands of seventy-two mature healthy animals (5-7 years old) were collected from the Cairo slaughter house during one year, (6 samples each month) and prepared to be studied microscopically by the light and electron microscope. The prostate gland was found to be consisted of an external dorsal part dorsal to the neck of the bladder and an internal part situated in the submucosa of the prostatic urethra. During active season (winter and spring), the corpus prostate was enveloped by a thick fibromuscular capsule which sent septa, to divide the gland into lobules. The parenchyma formed of compound tubuloalveolar adenomeres. The alveoli and tubules were lined by high columnar cells and few basal ones. The acini appeared at different stages of secretory activity (synthesis, storage, secretion and exhaustion). Ultrastructurally, the acinar cells contained well developed rough endoplasmic reticulum (rER), numerous mitochondria and a variable number of secretory granules. The duct system began as central collecting sinuses lined by simple columnar secretory epithelium. The pars interna occurred in the submucosa of the prostatic urethra enveloped by a thick fibro-muscular band. The branched tubuloalveolar parenchyma contained adenomeres lined with simple cuboidal epithelium. During the inactive season (summer and autumn), the stroma showed a marked proliferation of the fibromuscular tissue on the expense of the parenchymatous tissue. The adenomeres became very small or even rudimentary with narrow lumina devoid of secretory materials. Marked reduction in the cytoplasmic organelles with a total absence of the secretory granules was also pronounced.