Abstract Brain uptake of iron‐59 and iodine‐125‐labelled transferrin from blood in the adult rat has been investigated using graphical analysis to determine the blood‐brain barrier permeability to these tracers in experiments that lasted between 5 min and 8 days. The blood‐brain barrier permeability ( K in ) to 59 Fe was 89 ± 10 −5 ml/min/g compared to the value of 7 ± 10 −5 ml/min/g for 125 I‐transferrin, which is similar to that of albumin, a plasma marker. The autoradiographic distribution of these tracers in brain was also studied to determine any regional variation in brain uptake after the tracers had been administered either system‐ically or applied in vitro. No regional uptake was seen for 125 I‐transferrin even after 24 h of circulation. In contrast, 59 Fe showed selective regional uptake by the choroid plexus and extra‐blood‐brain barrier structures 4 h after administration. After 24 h of circulation, 59 Fe distribution in brain was similar to the transferrin receptor distribution, as determined in vitro, but was unlike the distribution of non‐haem iron determined histochemically. The data suggest that brain iron uptake does not involve any significant transcytotic pathway of transferrin‐bound iron into brain. It is proposed that the uptake of iron into brain involves the entry of iron‐loaded transferrin to the cerebral capillaries, deposition of iron within the endothelial cells, followed by recycling of apotransferrin to the circulation. The deposited iron is then delivered to brain‐derived transferrin for extracellular transport within the brain, and subsequently taken up via transferrin receptors on neurones and glia for usage or storage.
Isolated myelin basic protein (MBP) was less effective than an equivalent amount of spinal cord in inducing protection against experimental allergic encephalomyelitis produced by a challenge of either cord, purified myelin or MBP. Complete protection was only obtained when an MBP challenge was preceded by spinal cord treatment. There was a 100% incidence of disease in the guinea pigs pretreated with MBP before challenge with spinal cord or myelin, but the onset was delayed by 3–4 weeks and the disease was less severe than in the controls. Recurrent disease was seen in some control and pretreated animals challenged with spinal cord but not in animals challenged with MBP.
This study evaluated using an estrus detection patch as a simple, cost-effective reproductive management tool to identify animals that have been or are in standing heat at split-timed AI (STAI) and the necessity of the second gonadotropin-releasing hormone (GnRH) injection at STAI synchronized with a 7-Day CO-Synch + controlled intravaginal drug release (CIDR) protocol for beef cattle. Multiparous lactating crossbred beef cows (n = 216) were stratified by age, BW, BCS, and post-partum interval (PPI) to 2 treatment groups: CTRL = timed-AI (TAI) at 72 h post CIDR removal (n = 67), or TRT = STAI at 72 or 84 h post CIDR removal (n = 149). All females received GnRH plus a CIDR insert on d 0, prostaglandin F2α, CIDR removal, and an Estrotect heat-detector patch on d 7. Beginning at 72h post-CIDR removal, a patch score (PS) was given (1 = < 50% removed; 2 = ≥ 50% removed) to cows from both treatment groups and all cows in the CTRL group received a second GnRH injection, regardless of PS, at TAI. Cows in the TRT group with a PS of 2 only received no GnRH at TAI. At 84 h TAI, the remaining TRT cows not inseminated at 72 h were given a second PS and cows with a PS 1 received a second GnRH injection and cows with a PS of 2 did not. Blood samples for Progesterone (P4) concentration were collected from all cows on d-11 and 0 to determine percent of cows cycling. Data were analyzed using Proc Genmod with treatment and AI technician (2 technicians) as fixed effects, sire (2 sires) as a random effect, and BW, BCS, age, and PPI as covariates. There was no treatment × AI technician interaction (P = 0.97); therefore, all data were pooled for main effects. Timed-AI pregnancy rates were similar (P = 0.83) between the CTRL (45%) and TRT (45%) groups. The percentage of cows cycling in each treatment group was similar (P = 0.10) and averaged 77%. Pregnancy rates were greater (P < 0.01) for cows with a PS of 2 (50%) compared with a PS of 1 (21%), regardless of treatment. However, by extending TAI to 84 h in unresponsive cows, 82% of the TRT cows did not receive a second injection of GnRH at TAI. Using a heat-detector can reduce the percentage of cows that require GnRH at TAI without compromising pregnancy rates.
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