Hepatic encephalopathy (HE) is a neuropsychiatric hepatic‑induced syndrome in which several factors are involved in promoting brain perturbations, with ammonia being the primary factor. Motor impairment, incoordination, and gut dysbiosis are some of the well‑known symptoms of HE. Nevertheless, the link between the direct effect of hyperammonemia and associated gut dysbiosis in the pathogenesis of HE is not well established. Thus, this work aimed to assess motor function in hyperammonemia and gut dysbiosis in mice. Twenty‑eight Swiss mice were distributed into three groups: two‑week and four‑week hyperammonemia groups were fed with an ammonia‑rich diet (20% w/w), and the control group was pair‑fed with a standard diet. Motor performance in the three groups was measured through a battery of motor tests, namely the rotarod, parallel bars, beam walk, and static bars. Microbial analysis was then carried out on the intestine of the studied mice. The result showed motor impairments in both hyperammonemia groups. Qualitative and quantitative microbiological analysis revealed decreased bacterial load, diversity, and ratios of both aerobic and facultative anaerobic bacteria, following two and four weeks of ammonia supplementation. Moreover, the Shannon diversity index revealed a time‑dependent cutback of gut bacterial diversity in a treatment‑time‑dependent manner, with the presence of only Enterobacteriaceae, Streptococcaceae, and Enterococcaceaeat at four weeks. The data showed that ammonia‑induced motor coordination deficits may develop through direct and indirect pathways acting on the gut‑brain axis.

Prenatal alcohol exposure (PAE) refers to fetal exposure to alcohol during pregnancy through placental barrier transfer from maternal blood. The postnatal outcomes of PAE differ among exposed individuals and range from overt (serious) alcohol-related behavioral and neurophysiological impairments to covert (silenced) symptoms. The aims of the present investigation were to assess the postnatal neurobehavioral disturbances, particularly, motor coordination and sensory-motor function in mice with PAE. Female mice with positive vaginal plugs were divided into three groups: group 1: Et + Pyr: received two i.p injections of ethanol (1 g/kg) followed by pyrazole (100 mg/kg). Group 2: Pyr: received an i.p injection of pyrazole (100 mg/kg). Group 3: C: of saline controls received, in equal volume, saline solution (NaCl 0.9%). After birth, mice pups were weighed and subjected to behavioral tests for motor function screening using the motor ambulation test, cliff aversion, surface righting, and negative geotaxis, while at the adult stage, mice were subjected to the open field, rotarod, parallel bars, and static rods tests. Our data show an obvious decrement of body weight from the first post-natal day (P1) and continues over the adult stage. This was accompanied by an obvious impaired sensory-motor function which was maintained even at the adult stage with alteration of the locomotor and coordination abilities. The current data demonstrate the powerful neurotoxic effect of prenatal ethanol exposure on the sensory-motor and coordination functions, leading to suppose possible structural and/or functional neuronal disturbances, particularly the locomotor network.

Parkinson's disease (PD) affects the nervous system of patients in a gender-discriminative way. In regards to the epidemiological observations, amongst the 10 million people worldwide who are living with PD, recent reports have stated 1.5 times the greater incidence in men than in women. What is more, while growing evidence is showing gender as a considerable biological variable, preclinical research on PD has shown tangible explanations of epidemiological observation. Indeed, it has been shown that the symptoms are delayed in women especially because of a high dopamine level in the striatum, possibly due to the activity of estrogens. Thus, in this chapter, the authors present an overview of sexual dimorphism in PD and the possible mechanisms linking the differences observed between men and women in the incidence of PD.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) preferentially infects cells in the respiratory tract, but several studies have also demonstrated low levels of SARS-CoV-2 copies in the liver. The hypothesis that patients with COVID-19 may develop liver dysfunction is supported by findings showing abnormal liver test results in such patients, but the exact mechanisms by which SARS-CoV-2 induces liver damage remain unclear. Liver injury in COVID-19 patients has probably a multifactorial etiology including the rapid onset of a systemic pro-inflammatory state due to viral infection, the use of potentially hepatotoxic drugs, pneumonia-associated hypoxia, and the eventual direct injury of the liver by SARS-CoV-2. This chapter will discuss the potential pathophysiological mechanisms for SARS-CoV-2 hepatic tropism and an overview about the main biochemical and histopathological findings observed in liver from COVID-19 patients. Finally, the effects that this infection can produce in patients with chronic liver disease will be also discussed.