Lobar holoprosencephaly with craniofacial defects in a Friesian calf: A case report.

BACKGROUND: Holoprosencephaly is a forebrain deformity that results from varying degrees of separation failure of cerebral hemispheres. The condition is classified based on the degree of non-separation of the hemispheres which, in turn, determines its severity. Holoprosencephaly is usually accompanied by craniofacial defects whose severity tends to reflect the extent of brain deformities. In humans, holoprosencephaly is one of the commonest congenital brain anomalies but in animals, reported cases are scarce. The condition has multifactorial aetiology that involves interactions between several genetic and environmental factors. CASE PRESENTATION: A 4-day-old female Friesian calf with a deformed face was reported to the Faculty of veterinary medicine and surgery, Egerton University. The calf and the dam were sired by the same bull. On clinical and radiographic examination, the calf had a short snout that curved dorsally with bilateral cleft lip, right-sided cleft jaw and a largely absent primary palate. Anatomopathological examination revealed brain deformities which included ventral fusion of frontal lobes of cerebral hemispheres, large merged lateral ventricles without septum pellucidum and fornix, hypoplastic corpus callosum, high degree of non-separation between diencephalic structures, poorly developed hippocampal formation and hypoplastic olfactory lobe, optic chiasma, and nerve. CONCLUSION: The case was confirmed as lobar holoprosencephaly based on characteristic anatomopathological findings. The aetiology of the defects in the present case could not be determined though they are thought to be either a result of recessive inheritance or exposure to teratogenic steroid alkaloids through materials fed to the dam during early pregnancy.

Fasting in the ureotelic Lake Magadi tilapia, Alcolapia grahami, does not reduce its high metabolic demand, increasing its vulnerability to siltation events.

Lake Magadi, Kenya, is one of the most extreme aquatic environments on Earth (pH~10, anoxic to hyperoxic, high temperatures). Recently, increased water demand and siltation have threatened the viable hot springs near the margins of the lake where Alcolapia grahami, the only fish surviving in the lake, live. These Lake Magadi tilapia largely depend on nitrogen-rich cyanobacteria for food and are 100% ureotelic. Their exceptionally high aerobic metabolic rate, together with their emaciated appearance, suggests that they are energy-limited. Therefore, we hypothesized that during food deprivation, Magadi tilapia would economize their energy expenditure and reduce metabolic rate, aerobic performance and urea-N excretion. Surprisingly, during a 5-day fasting period, routine metabolic rates increased and swimming performance (critical swimming speed) was not affected. Urea-N excretion remained stable despite the lack of their N-rich food source. Their nitrogen use switched to endogenous sources as liver and muscle protein levels decreased after a 5-day fast, indicating proteolysis. Additionally, fish relied on carbohydrates with lowered muscle glycogen levels, but there were no signs indicating use of lipid stores. Gene expression of gill and gut urea transporters were transiently reduced as were gill rhesus glycoprotein Rhbg and Rhcg-2. The reduction in gill glutamine synthetase expression concomitant with the reduction in Rh glycoprotein gene expression indicates reduced nitrogen/ammonia metabolism, most likely decreased protein synthesis. Additionally, fish showed reduced plasma total CO2, osmolality and Na+ (but not Cl-) levels, possibly related to reduced drinking rates and metabolic acidosis. Our work shows that Lake Magadi tilapia have the capacity to survive short periods of starvation which could occur when siltation linked to flash floods covers their main food source, but their seemingly hardwired high metabolic rates would compromise long-term survival.

Metabolism and antioxidant defense in the larval chironomid Tanytarsus minutipalpus: adjustments to diel variations in the extreme conditions of Lake Magadi.

Insect larvae are reported to be a major component of the simple but highly productive trophic web found in Lake Magadi (Kenya, Africa), which is considered to be one of the most extreme aquatic environments on Earth. Previous studies show that fish must display biochemical and physiological adjustments to thrive under the extreme conditions of the lake. However, information for invertebrates is lacking. In the present study, the occurrence of the larval chironomid Tanytarsus minutipalpus is reported in Lake Magadi for the first time. Additionally, changes in larval metabolism and antioxidant defense correlated with diel variations in the extremely hostile environmental conditions of the lake are described. Wide variations in water temperature (20.2-29.3°C) and dissolved oxygen content (3.2-18.6 mg O2 l-1) were observed at different times of day, without significant change in water pH (10.0±0.03). Temperature and dissolved oxygen were higher at 13:00 h (29.3±0.4°C and 18.6±1.0 mg O2 l-1) and 19:00 h (29.3±0.8°C and 16.2±1.6 mg O2 l-1) and lower at 01:00 h (21.1±0.1°C and 10.7±0.03 mg O2 l-1) and 07:00 h (20.2±0.4°C and 3.2±0.7 mg O2 l-1). Significant and parallel increases in parameters related to metabolism (cholinesterase, glucose, cholesterol, urea, creatinine and hemoglobin) and the antioxidant system (SOD, GPx, GR, GSH and GSSG) were observed in larvae collected at 13:00 h. In contrast, no significant changes were observed in pro-oxidants (ROS and NO), TOSC and oxidative damage parameters (LPO and DNA damage). Therefore, the observed increases in temperature and dissolved O2 content in Lake Magadi were associated with changes in the antioxidant system of T. minutipalpus larvae. Adjustments performed by the chironomid larvae were efficient in maintaining body homeostasis, as well as protecting biomolecules against oxidative damage, so that oxidative stress did not occur. GSH-GSSG and GPx-GR systems appeared to play an essential role in the adjustments displayed by the chironomid larvae during the diel changes in the extreme conditions of Lake Magadi.