Cladribine modifies functional properties of microglia.

Cladribine (CdA), an oral prodrug approved for the treatment of relapsing multiple sclerosis, selectively depletes lymphocytes. CdA passes the blood-brain barrier, suggesting a potential effect on central nervous system (CNS) resident cells. We examined if CdA modifies the phenotype and function of naive and activated primary mouse microglia, when applied in the concentrations 0·1-1 µM that putatively overlap human cerebrospinal fluid (CSF) concentrations. Primary microglia cultures without stimulation or in the presence of proinflammatory lipopolysaccharide (LPS) or anti-inflammatory interleukin (IL)-4 were treated with different concentrations of CdA for 24 h. Viability was assessed by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Phagocytotic ability and morphology were examined by flow cytometry and random migration using IncuCyte Zoom and TrackMate. Change in gene expression was examined by quantitative polymerase chain reaction (qPCR) and protein secretion by Meso Scale Discovery. We found that LPS and IL-4 up-regulated deoxycytidine kinase (DCK) expression. Only activated microglia were affected by CdA, and this was unrelated to viability. CdA 0·1-1 µM significantly reduced granularity, phagocytotic ability and random migration of activated microglia. CdA 10 µM increased the IL-4-induced gene expression of arginase 1 (Arg1) and LPS-induced expression of IL-1ß, tumor necrosis factor (TNF), inducible nitric oxide synthase (iNOS) and Arg1, but protein secretion remained unaffected. CdA 10 µM potentiated the increased expression of anti-inflammatory TNF receptor 2 (TNF-R2) but not TNF-R1 induced by LPS. This suggests that microglia acquire a less activated phenotype when treated with 0·1-1 µM CdA that putatively overlaps human CSF concentrations. This may be related to the up-regulated gene expression of DCK upon activation, and suggests a potential alternative mechanism of CdA with direct effect on CNS resident cells.

Long-term effects of methylprednisolone following transection of adult rat spinal cord.

Clinically, high-dose treatment with the glucocorticosteroid, methylprednisolone (MP), within 8 h after spinal cord injury, has been shown to improve neurological recovery. The current standard of care is to administer MP as a bolus of 30 mg/kg followed by a 23-h infusion of 5.4 mg/kg/h to spinal cord injured patients. To better understand the role of MP in neuroprotection, we have studied how MP administration affects macrophage accumulation, tissue loss, and axonal dieback at 1, 2, 4 and 8 weeks after a complete transection of the eighth thoracic spinal cord in the adult rat. A 30 mg/kg dose of MP was administered intravenously at 5 min, and 2 and 4 h after injury. The number of ED1 (antibody against microglia/macrophages) -positive cells was quantified in a 500-micrometer-wide strip of tissue directly adjacent and parallel to the transection. At all time points, MP treatment led to a significant decrease in the number of ED1-positive cells in both rostral and caudal stumps. Over the 2-month post-transection period, the average MP-induced reduction in the number of ED1-positive cells was 82% in the rostral cord stump and 66% in the caudal stump. Using a computerized image analysis system, it was observed that MP treatment resulted in a significant reduction in tissue loss in both cord stumps at 2, 4 and 8 week post-injury. Over the 2-month post-lesion period, the average MP-induced reduction in tissue loss in the caudal cord stump was higher than that in the rostral stump; 48 versus 37%, respectively. Immunostaining for neurofilaments and growth-associated protein-43 (GAP-43) revealed the presence of numerous axons near and in the lesion site. Anterograde neuronal tracing with biotinylated dextran amine showed that, in MP-treated animals, dieback of vestibulospinal fibres, but not of corticospinal fibres, was significantly diminished at all time points studied. In addition, with MP administration, 1 and 2 weeks after injury, an increase in the number of vestibulospinal fibres was found at 1 and 2 mm from the transection, suggesting transient regenerative sprouting of these fibres. The results demonstrate that treatment with MP shortly after spinal cord transection in the adult rat led to a long-term reduction of ED1-positive cells and spinal tissue loss, reduced dieback of vestibulospinal fibres, and a transient sprouting of vestibulospinal fibres near the lesion at 1 and 2 weeks post-lesion. The possible relationships between the inflammatory changes, spinal tissue sparing, and axonal survival and sprouting are complex and need to be further explored.

Thickness of tibial inserts in total knee arthroplasty.

The thickness of the ultrahigh-molecular-weight polyethylene used in the tibial inserts of total knee arthroplasties has become topical in recent years. A discrepancy has been found between the nomenclature of tibial inserts and the actual minimum thickness of polyethylene. Although the recommended minimum thickness is being discussed, it is important to clarify what is actually being used, with an indication to change and unify how these inserts are named.

Brainstem dysfunction is provoked by a less pronounced hypoglycemic stimulus in diabetic BB rats.

Recent studies suggest that moderate hypoglycemia impairs brainstem function in normal humans and rats. To examine whether diabetes alters this response, simultaneous auditory-evoked potentials were recorded directly from the inferior colliculus (IC) and from the brainstem before and after controlled hypoglycemia (clamp) in awake insulin-dependent diabetic BB/Wor rats. Hyperglycemic diabetic animals were studied either during hyperinsulinemic euglycemia (5.6 mmol/l, n = 4) or mild hypoglycemia (3.5 mmol/l, n = 9). Nondiabetic controls were also studied at 3.5 mmol/l (n = 7) and at 2.8 mmol/l (n = 6). Brainstem function was not affected during euglycemia in diabetic rats. However, when plasma glucose was lowered to 3.5 mmol/l, the diabetic rats showed a 10% delay in IC evoked potential (ICEP) latency, whereas nondiabetic animals did not. This occurred despite similar counterregulatory hormones in both groups. The brainstem auditory-evoked potential (BAEP) localized the defect in the diabetic group to an area in or near the IC. When glucose levels were lowered to 2.8 mmol/l, however, brain function was impaired in nondiabetic rats as well. Again the defect was restricted to an area in or near the IC. We conclude that mild hypoglycemia causes a functional impairment in the IC region of the brainstem in both nondiabetic and diabetic rats. However, in the diabetic rats, this alteration occurs after a less pronounced hypoglycemic stimulus. Our findings suggest that chronic hyperglycemia leads to metabolic adaptions that render the diabetic brain more susceptible to mild hypoglycemia.

Moderate hypoglycemia impairs the function of the inferior colliculus in the awake rat.

To assess the effect of acute hypoglycemia on the brain stem auditory pathway, we implanted electrodes into the inferior colliculus (IC) and subsequently recorded auditory-evoked potentials from the IC (ICEP) and brain stem (BAEP) in normal awake rats during euglycemic and hypoglycemic hyperinsulinemia (2 hours). Latencies of the ICEP and peak V of the BAEP were significantly prolonged by hypoglycemia (approximately 2.7 mmol/L). The change in the BAEP was principally between peak III and peak V. suggesting an effect in or near the IC. ICEP and BAEP latencies did not change during euglycemic hyperinsulinemia. We conclude that the function of the IC is very sensitive to episodes of moderate hypoglycemia. These data provide direct evidence that the scope of adverse central nervous system effects resulting from hypoglycemia extends beyond cognitive centers to include the brain stem.

Morphology of embryonic neostriatal cell suspensions transplanted into adult neostriata.

Embryonic neostriatal cell suspensions were transplanted into intact or kainic acid-lesioned neostriata of adult host rats. These transplants survived and were sacrificed at 34-78 days posttransplantation. Nissl and Golgi preparations revealed neurons present within the transplants. Neurons with abundant dendritic spines (Spiny type I) were most frequent, but those with fewer spines (Spiny type II) and smooth dendrites (Aspiny II and III) were also present. These results indicate that neostriatal transplants are populated by the major output and internuncial neurons of the neostriatum.