Gregory J. Anderson

Visual attention in infant monkeys: effects of dietary fatty acids and age.

Effects of dietary essential fatty acids on visual attention were explored longitudinally in infant rhesus monkeys with a visual paired-comparison paradigm. Sets of primate faces and of patterns were presented at Weeks 2, 5, 9, and 13 to 9 infants deficient in omega-3 fatty acids and 8 fed a standard nursery diet. Familiarization to 1 member of each pair preceded simultaneous presentation of both stimuli. Infants fed the deficient diet showed longer individual looks in both immediate and 24-hr tests. Duration of looks decreased with age to familiar but not to novel stimuli. The proportion of time looking at the novel stimulus (% novel) increased with age but was not affected by diet. Look duration and % novel were differentially affected and may reflect different underlying processes.

Uptake of fatty acids by the developing rat brain

Polyunsaturated fatty acids are avidly taken up by the developing rat brain. To explore the specificity of this process, [1-14C]labeled 16∶0, 18∶2n−6, 18∶3n−3, and 22∶6n−3 each were co-injected with [3H]18∶1n−9 into the jugular vein of two-wk-old functionally hepatectomized and shamoperated control rats. The radioactivities present in the brain, liver and serum were assessed 30 min after injection. Uptake of labeled fatty acids into brain lipids steadily increased with increasing degree of unsaturation, with more than twice as much uptake of 22∶6n−3 compared to 16∶0. Phosphatidylcholine was the principal radioactive species in the brain except for animals injected with [1-14C]22∶6n−3, in which more of the label was incorporated into phosphatidylethanolamine. Determination of watersoluble oxidation products in the brain and serum revealed that the greater uptake of the more unsatrated fatty acids did not result from differences in rates of degradation.

Effects of dietary n-3 fatty acids on the phospholipid molecular species of monkey brain

Abstract: We examined the changes in the molecular species of brain ethanolamine glycerophospholipids of monkeys fed diets containing widely ranging amounts of n‐3 fatty acids. Two groups of rhesus monkeys were fed pre‐ and postnatally either a control diet (soy oil; containing 8% of fatty acids as 18:3n‐3) or a deficient diet (safflower oil; containing <0.3% 18:3n‐3). The brains of these animals were analyzed at 22 months of age. A third group of monkeys was fed the safflower oil diet to 22 months of age and then switched to a fish oil diet (28% long‐chain n‐3 fatty acids) for 1–2 years before autopsy. The molecular species of the diacyl, alkylacyl, and alkenylacyl ethanolamine glycerophospholipids from frontal cortex were separated by HPLC. A total of 24 molecular species were identified. Fatty acids in the sn‐2 position differed markedly among the diet groups, but the sn‐1 position always contained only 16:0, 18:0, or 18:1. In the diacyl subclass of the control brain, the n‐3 molecular species represented 41% of total and the n‐6 species 45%, whereas in the deficient brain the n‐3 molecular species decreased to 9% and n‐6 molecular species increased to 77%. The fatty acid 22:5n‐6 did not replace 22:6n‐3 in a symmetrical fashion in the molecular species of the deficient brain. In the brains of the fish oil‐fed monkeys, the n‐3 molecular species amounted to 61% and n‐6 molecular species were reduced to 25%. The species 18:1–22:6, 16:0–22:6, and 18:0–22:6 generally changed proportionally in response to diet. However, 18:1–20:4, 16:0–20: 4, and 18:0–20:4 responded differently. The fish oil diet led to an increase in the proportion of 18:1–20:4 in the alkenylacyl subclass, whereas 16:0–20:4 and 18:0–20:4 decreased. Thus, total species containing sn‐1 18:1 increased at the expense of sn‐1 16:0 in the fish oil animals. Regardless of diet, each subclass of ethanolamine glycerophospholipid showed a strikingly different ratio of sn‐1 16:0 to 18:0 to 18:1 for a given sn‐2 fatty acid. In conclusion, the different diets had profound qualitative and quantitative effects on the molecular species of brain phospholipids, and these changes have implications for possible functional changes.

Can prenatal N-3 fatty acid deficiency be completely reversed after birth? Effects on retinal and brain biochemistry and visual function in rhesus monkeys.

Our previous studies of rhesus monkeys showed that combined prenatal and postnatal n-3 fatty acid deficiency resulted in reduced visual acuity, abnormal retinal function, and low retina and brain docosahexaenoic acid content. We now report effects of n-3 fatty acid deficiency during intrauterine development only. Rhesus infants, born to mothers fed an n-3 fatty acid deficient diet throughout pregnancy, were repleted with a diet high in alpha-linolenic acid from birth to 3 y. Fatty acid composition was determined for plasma and erythrocytes at several time points, for prefrontal cerebral cortex biopsies at 15, 30, 45, and 60 wk, and for cerebral cortex and retina at 3 y. Visual acuity was determined behaviorally at 4, 8, and 12 postnatal weeks, and the electroretinogram was recorded at 3–4 mo. Total n-3 fatty acids were reduced by 70–90% in plasma, erythrocytes, and tissues at birth but recovered to control values within 4 wk in plasma, 8 wk in erythrocytes, and 15 wk in cerebral cortex. At 3 y, fatty acid composition was normal in brain phospholipids, but in the retina DHA recovery was incomplete (84% of controls). Visual acuity thresholds did not differ from those of control infants from mothers fed a high linolenic acid diet. However, the repleted group had lower amplitudes of cone and rod ERG a-waves. These data suggest that restriction of n-3 fatty acid intake during the prenatal period may have long-term effects on retinal fatty acid composition and function.

Pedicle screw placement in the thoracic spine: a comparison of image-guided and manual techniques in cadavers.

Study Design. A cadaveric study comparing image guidance technology to fluoroscopic guidance as a means of pedicle screw placement in the thoracic spine, using a unique starting point for screw placement. Objective. To assess accuracy of thoracic pedicle screw placement using image guidance versus fluoroscopic guidance for screw insertion. Summary of Background Data. While use of pedicle screws in the thoracic spine has been increasing, its adoption has been slower than for the lumbar spine, reflecting concern regarding possible vascular or spinal cord injury due to screw malplacement. Given these risks, efforts to improve the accuracy of thoracic pedicle screw placement remain appropriate. Stereotactic guidance has been applied in other aspects of spinal surgery to improve the accuracy of instrumentation placement. Methods. Pedicle screws were placed in the thoracic spines of eight cadavers, using either a stereotactic guidance or a manual, fluoroscopically guided technique. A slightly more superior and lateral starting point from prior descriptions was used. Each cadaver was instrumented with pedicle screws in the upper thoracic (T1–T2), middle thoracic (T4–T7), and lower thoracic (T9–T10) regions. In the upper and middle thoracic regions, screws with a 4.0-mm shank diameter were used while in the lower thoracic region a shank diameter of 4.5 mm was used. Postinstrumentation CT scans, followed by anatomic dissections, were used to evaluate screw exit rates and orientation relative to the pedicle axis. Exit rates for the two techniques and the effect of vertebral level on exit rate were compared using a &khgr;2 analysis. The effect of pedicle diameter was tested using a Pearson correlation coefficient. Results. No significant differences in the overall exit rates or orientation were found between the two techniques. There were significant differences in exit rates between the middle (47%), compared with the upper (9%) and lower (16%) thoracic regions, respectively (P < 0.001). A significant correlation between pedicle diameter and exit rate was also found (P < 0.0001). Conclusion. Our study showed no significant differences in the overall exit rates between the two techniques. Image guidance may increase confidence of surgeons with limited experience in thoracic pedicle screw placement. Successful placement of screws within the pedicle varies with the anatomic diameter of the pedicle itself. Concerns regarding accuracy of screw placement should be greatest in the middle thoracic vertebrae (T4–T7), where pedicle diameters are smallest and proximity of the great vessels is nearest.

The incorporation of n-3 and n-6 essential fatty acids into the chick embryo from egg yolks having vastly different fatty acid compositions.

ABSTRACT: The effect of egg yolk fatty acid composition on essential fatty acid utilization by the developing chick embryo was studied by feeding laying hens a fat-free diet supplemented with oils containing widely divergent contents of the essential n-6 and n-3 fatty acids. A control hen was fed a commercial feed for laying hens. The diets contained 20 to 4370 mg/100 g n-3 fatty acids and 360 to 8020 mg/100 g n-6 fatty acids. Fertile eggs were collected in pairs: one was incubated and the other served as an unincubated control. The fatty acid content of the unincubated egg and the newly hatched chick from each pair was compared. Some 50% of the total fatty acids in the egg yolk were incorporated into the tissues of the newly hatched chick. Regardless of diet, more yolk n-6 fatty acids were incorporated into the chick compared to saturated or monounsaturated fatty acids. The percentage of incorporation especially increased from the eggs containing relatively low amounts of n-6 fatty acids. The percentage of incorporation of n-3 fatty acids was similar to that of saturated and monounsaturated fatty acids when n-3 fatty acids were plentiful in the egg yolk, but increased significantly when n-3 fatty acids were low in the eggs. There was a generally linear relationship between essential fatty acids in the egg and in the chick, although levels of docosabexaenoic acid [DHA; 22:6(n-3)] in the brain did not respond proportionally. The developing chick preferentially removed DHA from the yolk, but did not synthesize more DHA when the amount of the DHA precursor, 18:3(n-3), in the yolk was increased. We concluded that the developing chick embryo requires 0.4–1.1% of egg energy as n-3 fatty acids and 4.8–6.2% as n-6 fatty acids, or a “dietary” ratio of n-6/n-3 of 5 to 14. This requirement may have relevance for humans as well.

Safety of anterior commissure-posterior commissure-based target calculation of the subthalamic nucleus in functional stereotactic procedures

The subthalamic nucleus (STN) is a common target of functional stereotactic surgeries. High-field magnetic resonance imaging and sophisticated computer systems provide precise identification of the nucleus location in stereotactic space. However, it is unclear what additional benefit these techniques provide over traditional anterior commissure-posterior commissure (AC-PC)-based standard atlas coordinate calculation methods based on the AC-PC plane. The accuracy of AC-PC-based standard atlas coordinate targeting of the STN using 1.5-tesla images compared with direct visualization of the nucleus on fused 3-tesla images was examined. A retrospective examination of stereotactic images from 20 patients (40 STN targets) who underwent deep brain stimulation for Parkinson’s disease was undertaken at our institution. Two methods were used to identify the STN stereotactic coordinates: (1) an AC-PC-based standard atlas coordinate calculation obtained by a series of measurements using 1.5-tesla images, and (2) a computer workstation calculation using fused 3-tesla and 1.5-tesla images. Euclidean distances between two sets of coordinates of the same target were calculated in three dimensions. Differences along individual X, Y, and Z axes were analyzed to determine whether there was a greater difference in one direction than in another. Data from the right and left sides were pooled to increase the sample power. The anterior-posterior and lateral frame tilts were compared to X, Y, and Z differences to find a correlation using linear regression. Statistical analyses were performed. The accuracy of the position of the STN calculated with state-of-the-art imaging systems was not significantly better than that obtained using traditional AC-PC-based standard atlas coordinate calculation if the frame was aligned with the AC-PC plane. The mean difference was 0.45 mm, 0.72 mm, and 0.98 mm in the X, Y, and Z axes, respectively. Therefore, it is possible to effectively target the STN for stereotactic treatment of Parkinson’s disease, for instance in a situation where expensive advanced technology is unavailable.

Incorporation of chylomicron fatty acids into the developing rat brain.

The developing brain obtains polyunsaturated fatty acids from the circulation, but the mechanism and route of delivery of these fatty acids are undetermined. 14C-labeled chylomicrons were prepared by duodenal infusion of [1-14C]16:0, [1-14C]18:2(n-6), [1-14C]18:3(n-3), or [1-14C]22:6(n-3) into adult donor rats, and were individually injected into hepatectomized 2-wk-old suckling rats. After minor correction for trapped blood in the brain, the incorporation of chylomicron fatty acids after 30 min was nearly half that of a co-injected free fatty acid reference. [1-14C]22:6(n-3)-labeled chylomicrons showed an average 65% greater incorporation than chylomicrons prepared from the other fatty acids. This apparent selectivity may have been partly due to lower oxidation of 22:6(n-3) in the brain compared to the other fatty acids tested, based on recovered water-soluble oxidation products. The bulk of the radioactivity in the brain was found in phospholipid and triacylglycerol, except that animals injected with [1-14C]22:6(n-3) chylomicrons showed considerable incorporation also into the fatty acid fraction instead of triacylglycerol. These data show that chylomicrons may be an important source of fatty acids for the developing rat brain.

Reversibility of the effects of dietary fish oil on the fatty acid composition of the brain and retina of growing chicks

Dietary fish oil increases levels of (n-3) fatty acids in the brain and retina of younger animals but has less effect in adults. The duration of the effects of fish oil in young animals, as well as the extent of reversibility of the effects, are unknown. Laying hens were fed either a fish oil diet or a soybean oil-based control diet. Resulting chicks were assigned to three diet groups: chicks from fish oil and soybean oil hens were continued on fish oil and soybean oil diets, respectively, for 0, 3, 6, or 9 weeks, and additional chicks from the fish oil hens were fed the fish oil diet for 0, 3, or 6 weeks and then reversed to the soybean oil diet for a period of 3 weeks. The fatty acid composition of the brain, retina, liver, and serum of the reversal chicks was compared with chicks fed the fish oil diet only or the soybean oil diet only. Brain levels of docosahexaenoic acid (22:6(n-3)) decreased substantially when reversal from the fish oil diet to the control diet was begun at hatching, but did not decrease when reversal was begun at later times. Other (n-3) fatty acids in the brain, docosapentaenoic acid (22:5(n-3)) and eicosapentaenoic acid (20:5(n-3)), decreased substantially at all ages, and to a greater extent than 22:6(n-3). Brain arachidonic acid (20:4(n-6)), which was low in fish oil chicks, rose to control after reversal at hatching, but recovered only partially when reversal was begun at later times. A similar patterns was observed in the retina. Serum and liver (n-3) fatty acids fell to control in all reversal chicks, and (n-6) fatty acids increased to control, except in chicks reversed at 6 weeks. This study demonstrates that by 3 weeks of age the chick brain strongly resists diet-induced lowering of high levels of 22:6(n-3).

Comparison of three techniques for calculation of target coordinates in functional stereotactic procedures.

We compared three techniques of target coordinate determination for various functional stereotactic procedures. All procedures were based on preoperative MRI with contiguous 3-mm cuts. The first technique involved determination of anatomical landmarks and fiducial markers of the stereotactic frame on the monitor screen of an MRI scanner and calculation of the target point using a series of formulas; the second technique used a Leksell tabletop localizer, and the third technique is a part of ‘Stealth’ stereotactic navigation software. Final coordinates for the procedure were derived from all three techniques and subsequently adjusted using intraoperative electrical macrostimulation. We found that difference between techniques was on average 0.9 ± 0.4 mm in each of three directions, and 1.8 ± 0.9 mm in absolute distance. There were 7 cases in which one of the techniques had a discrepancy of more than 3 mm (more than 1 MRI slice thickness) compared with the other two, indicating a potential error in coordinate determination. This difference could potentially result in inappropriate placement of the electrode, thus affecting the procedure outcome. In 6 cases, such an error apparently occurred with the first or second technique of calculation. The average number of mapping trajectories decreased from 1.8 to 1.4 since this stereotactic software became a part of operative planning. We conclude that use of computerized planning software increases the precision of target coordinate calculation and improves the accuracy of functional stereotactic procedures.