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Biomedical subjects

R E Anderson

Publications and source records attributed to R E Anderson.

At least 109 records · Page 6Linked to original sources
PubMed1996

Biosynthesis of the unsaturated 14-carbon fatty acids found on the N termini of photoreceptor-specific proteins.

In the vertebrate retina, a number of proteins involved in signal transduction are known to be N-terminal acylated with the unusual 14 carbon fatty acids 14:1n-9 and 14:2n-6. We have explored possible pathways for producing these fatty acids in the frog retina by incubation in vitro with candidate precursor fatty acids bearing radiolabels, including [3H]14:0, [3H]18:1n-9, [3H]18:2n-6, and [3H]18:3n-3. Rod outer segments were prepared from the radiolabeled retinas for analysis of protein-linked fatty acids, and total lipids were extracted from the remaining retinal pellet. Following saponification of extracted lipids, fatty acid phenacyl esters were prepared and analyzed by high pressure liquid chromatography (HPLC) with detection by continuous scintillation counting. Transducin, whose alpha-subunit (Gt alpha) is known to bear N-terminal acyl chains, was extracted from the rod outer segments and subjected to SDS-polyacrylamide gel electrophoresis and fluorography to detect radiolabeled proteins. Gt alpha was also subjected to methanolysis, and the resulting fatty acyl methyl esters were analyzed by HPLC. The identities of HPLC peaks coinciding with unsaturated species of both phenacyl esters and methyl esters were confirmed by reanalyzing them after catalytic hydrogenation. The results showed that 14:1n-9 can be derived in the retina from 18:1n-9 and 14:2n-6 from 18:2n-6, most likely by two rounds of beta-oxidation, but that neither is produced in detectable amounts from 14:0. Retroconversion of unsaturated 18 carbon fatty acids to the corresponding 14 carbon species showed specificity, in that 18:3n-3 was not converted to 14 carbon fatty acids in detectable amounts. Myristic acid (14:0), 14:1n-9, and 14:2n-6 were all incorporated into Gt alpha. A much less efficient incorporation of 18:1n-9 into Gt alpha was also observed, but no radiolabeling of Gt alpha was observed in retinas incubated with 18:3n-3. Thus, retroconversion by limited beta-oxidation of longer chain unsaturated fatty acids appears to be the most likely metabolic source of the unusual fatty acids found on the N termini of signal transducing proteins in the retina.

Animals↗
PubMed1996

Biochemical effects of dietary linoleic/alpha-linolenic acid ratio in term infants.

Recent statements concerning linoleic (LA) and alpha-linolenic acid (LNA) intakes for infants include a desirable range of LA/LNA ratios. To evaluate several dietary LA/LNA ratios, the fatty acid patterns of plasma and erythrocyte phospholipid fractions, as well as plasma total lipid fractions, were determined shortly after birth and at 21, 60, and 120 d of age in term infants fed formula with 16% of fat as LA and either 0.4, 0.95, 1.7, or 3.2% as LNA (LA/LNA ratios of approximately 44, 18, 10, and 5). The content of all n-3 fatty acids in both plasma fractions was higher at all times in infants who received the highest LNA intake; however, the docosahexaenoic acid (DHA) content was only half that shortly after birth or reported in breast-fed infants of comparable ages. The LA content of plasma lipids of all groups was higher at all times than shortly after birth but did not differ among groups. The arachidonic acid (AA) content was higher in infants who received the lowest LNA intake, but only half that at birth or reported in breast-fed infants. In contrast, the DHA content of the erythrocyte phospholipid fraction did not differ among groups until 120 d of age when it was higher in those who received the highest LNA intake and the AA content of this fraction did not differ among groups at any time. These data demonstrate that dietary LA/LNA ratios between 5 and 44 do not result in plasma or erythrocyte lipid levels of DHA or plasma lipid levels of AA similar to those at birth or reported by others in breast-fed infants. However, the data indicate that the LA/LNA ratio of the formula is an important determinant of the amounts of DHA and AA required to achieve plasma and erythrocyte levels of these fatty acids similar to those of breast-fed infants.

Dietary Fats↗
PubMed1996

Effect of dietary alpha-linolenic acid intake on incorporation of docosahexaenoic and arachidonic acids into plasma phospholipids of term infants.

The fractional conversion rates of plasma phospholipid alpha-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) to docosahexaenoic acid (22:6n-3) and arachidonic acid (20:4n-6), respectively, and the fractional rates of incorporation of 22:6n-3 and 20:4n-6 into plasma phospholipids were determined in 27 healthy 3-wk-old term infants who had received formulas with approximately 16% of fat as 18:2n-6 and 0.4% (n = 6), 1.0% (n = 11), or 3.2% (n = 10) as 18:3n-3 from birth. The infants were given a single dose of both [U-13C] 18:2n-6 and [U-13C] 18:3n-3 with a feeding, and blood samples were collected 8, 12, and 24 h afterward for determination of the isotopic enrichments of the [M + 18] isotopomers of plasma phospholipid fatty acids by negative chemical ionization gas chromatography/mass spectrometry. A simple precursor/product compartmental model was used to estimate fractional rates of conversion and incorporation. All infants converted 18:3n-3 to 22:6n-3 and 18:2n-6 to 20:4n-6. Although the fractional rate of conversion of 18:3n-3 to 22:6n-3 did not differ among groups, the fractional rate of incorporation of 22:6n-3 into the plasma phospholipid fraction was greater in infants who received 3.2% vs. 0.4% or 1.0% 18:3n-3 (4.1 +/- 2.2 vs. 1.6 +/- 1.5 or 2.0 +/- 1.0% of the plasma phospholipid 22:6n-3 pool daily). The fractional rate of conversion of 18:2n-6 to 20:4n-6 was less in infants who received the 3.2% 18:3n-3 intake (0.4 +/- 0.3% of the plasma phospholipid 18:2n-6 pool daily vs. 1.1 +/- 0.7% and 0.8 +/- 0.5% in those who received 0.4 and 1.0% 18:3n-3, respectively). The fractional rate of incorporation of 20:4n-6 into plasma phospholipid also was less in the 3.2% vs. the 0.4 and 1.0% 18:3n-3 groups (2.7 +/- 1.4% vs. 5.9 +/- 2.6 and 4.4 +/- 1.7%, respectively, of the plasma phospholipid 20:4n-6 pool daily).

Arachidonic Acid↗
PubMed1996

Nitric oxide synthase inhibition by L-NAME prevents brain acidosis during focal cerebral ischemia in rabbits.

This experiment examined the effects of nitric oxide (NO) synthase inhibition on brain intracellular pH, regional cortical blood flow, and NADH fluorescence before and during 3 h of focal cerebral ischemia using in vivo fluorescence imaging. Thirty fasted rabbits under 1% halothane were divided into four treatment groups receiving N omega-nitro-L-arginine methyl ester (L-NAME) intravenously at 20 min prior to ischemia (0.1, 1, and 10 mg/kg and 1 mg/kg + 5 mg/kg L-arginine) and two control groups (nonischemic and ischemic). In ischemic controls, brain pH(i), declined to 6.73 +/- 0.03 at 30 min and remained acidotic through the remainder of the ischemic period. In the 0.1 mg/kg group, brain pH(i) fell after 30 min of ischemia to 6.76 +/- 0.05 (p < 0.05), but then improved progressively despite occlusion. In the 1 mg/kg group, brain pH(i), remained normal despite middle cerebral artery (MCA) occlusion. In the 10 mg/kg group and in the combined L-NAME + L-arginine group, pH(i) fell after 30 min of ischemia to 6.81 +/- 0.03 (p < 0.05) and remained acidotic. During occlusion, regional cortical blood flow dropped in a dose-dependent manner. After 3 h of ischemia, regional cortical blood flow was 33.9 +/- 10.9 and 25.1 +/- 8.9 ml/100 g/min at doses of 0.1 and 10.0 mg/kg, respectively, L-NAME treatment did not significantly alter the increased NADH fluorescence that accompanied occlusion. This study shows that L-NAME can prevent intracellular brain acidosis during focal cerebral ischemia independent from regional cortical blood flow changes. This experiment suggests that NO is involved in pH(i) regulation during focal cerebral ischemia.

Acidosis↗
PubMed1996

Nitric oxide synthase inhibition by L-NAME during repetitive focal cerebral ischemia in rabbits.

The effects of nitric oxide synthase inhibition on brain acidosis, regional cortical blood flow (rCBF), and NADH redox state were examined using in vivo fluorescence imaging during four 15-min periods of moderate focal cerebral ischemia, each separated by three 5-min reperfusion periods followed by a final 3-h reperfusion period. Fasted rabbits under 1.5% halothane were divided into six groups of seven animals each: nonischemic controls, ischemic controls, and the following drug groups receiving NG-nitro-L-arginine methyl ester (L-NAME) intravenously 20 min before repetitive ischemia (as follows: 0.1 mg/kg, 1 mg/kg, 10 mg/kg, and 1 mg/kg + 5 mg/kg L-arginine). L-NAME at 0.1 and 1 mg/kg prevented the development of significant brain acidosis throughout the four ischemic insults. L-NAME at 10 mg/kg reduced preischemic rCBF by 21% (P < 0.05) and did not mitigate brain acidosis after the third and fourth ischemic insults. Brain intracellular pH returned toward baseline after the 3-h final reperfusion in all groups. NADH redox state was significantly (P < 0.05) elevated from baseline controls in all groups during the last three ischemic insults. During the final reperfusion period, NADH redox state returned toward baseline values only in the 0.1 mg/kg L-NAME and ischemic control group. In conclusion, low-dose L-NAME attenuated brain acidosis independent from rCBF changes during intermittent, moderate focal cerebral ischemia.

Animals↗
PubMed1996

Cerebral blood flow xenon-133.

The technique of using the intra-arterial clearance method with the diffusible, inert gas 133Xe to measure rCBF has been well established over the past 30 years. By using this method, equations for calculation of rCBF are not very complicated. Because 133Xe is a low gamma emitter and small doses are used, the risk of radiation exposure to the patient and to medical personnel is quite small. Given this fact, it is less harmful than cerebral angiography which requires higher doses of radiation and much larger volumes of injected contrast media. The primary limitation is the "look-through" phenomenon in which the calculated rCBF might not truly represent areas (lesions) of low flow. The magnitude of change or level of rCBF, however, can have an important neurologic meaning. The assessment of collateral flow either during balloon occlusion study or during carotid surgery is of very important clinical value in the interest of the patient's well-being.

Cerebrovascular Circulation↗
PubMed1995

cDNA sequence and gene locus of the human retinal phosphoinositide-specific phospholipase-C beta 4 (PLCB4).

Defects in the Drosophila norpA (no receptor potential A) gene encoding a phosphoinositide-specific phospholipase C (PLC) block invertebrate phototransduction and lead to retinal degeneration. The mammalian homolog, PLCB4, is expressed in rat brain, bovine cerebellum, and the bovine retina in several splice variants. To determine a possible role of PLCB4 gene defects in human disease, we isolated several overlapping cDNA clones from a human retina library. The composite cDNA sequence predicts a human PLC beta 4 polypeptide of 1022 amino acid residues (MW 117,000). This PLC beta 4 variant lacks a 165-amino-acid N-terminal domain characteristic for the rat brain isoforms, but has a distinct putative exon 1 unique for human and bovine retina isoforms. A PLC beta 4 monospecific antibody detected a major (130 kDa) and a minor (160 kDa) isoform in retina homogenates. Somatic cell hybrids and deletion panels were used to localize the PCLB4 gene to the short arm of chromosome 20. The gene was further sublocalized to 20p12 by fluorescence in situ hybridization.

Amino Acid Sequence↗
PubMed1995

Cerebral blood flow during cardiac operations: comparison of Kety-Schmidt and xenon-133 clearance methods.

This study simultaneously compared the standard Kety-Schmidt and the modified xenon-133 (133Xe) clearance techniques for measuring cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRO2) during cardiac operations. The validity of the CBF method is important because our management of the patient during cardiopulmonary bypass (CPB) is based, in part, on our understanding of the cerebral hemodynamics during CPB. In 20 patients undergoing coronary artery bypass grafting, CBF and CMRO2 were determined by both methods. Measurements were made before onset of CPB and once during CPB. Ten patients underwent CPB with systemic normothermia (37 degrees C) and 10 with systemic hypothermia (27 degrees C). Anesthesia consisted of fentanyl and midazolam. CPB pump flows were kept at 2.2 to 2.4 L.min-1.m-2 and alpha-stat pH management was used. Xenon-133 clearance significantly underestimated CBF and CMRO2 relative to the Kety-Schmidt technique before CPB and at both bypass temperatures. Values obtained by 133Xe clearance were approximately 50% of that measured by the Kety-Schmidt method. The modified 133Xe technique as typically used during cardiac operations does not appear to measure CBF accurately; this leads to corresponding errors in CMRO2 calculations. Determination of CMRO2 and cerebral autoregulatory function during cardiac operations appears to be more appropriate if based on the more direct Kety-Schmidt technique. Accordingly, our management of CPB with respect to cerebral perfusion as it has been determined by the modified 133Xe clearance method may require reassessment.

Blood Gas Analysis↗
PubMed1995

Treatment with basic fibroblastic growth factor following focal cerebral ischemia does not prevent neuronal injury.

This experiment determined if postischemic administration of basic fibroblast growth factor (bFGF) would result in neovascularization to minimize neuronal injury following a focal cerebral ischemia insult. Fifty-eight Sprague-Dawley rats underwent middle cerebral artery (MCA) occlusion and were divided into three groups receiving either vehicle, serum, or 50 ng bFGF biweekly through an indwelling ventricular cannula. At variable time intervals, the animals underwent carbon black perfusion of capillary beds and histological staining for assessment of neuronal injury. Following MCA occlusion, there was a significant decrease in capillary bed density in peri-infarction cortex which normalized by two weeks. The number of alive neurons in the peri-infarction cortex was also significantly decreased compared to contralateral control cortex. The chronic administration of bFGF commencing two days after MCA occlusion did not result in either a significant increase in capillary bed density or the number of alive neurons in the peri-infarction cortex.

Animals↗
PubMed1995

Antiretroviral activity of stavudine (2',3'-didehydro-3'-deoxythymidine, D4T).

Stavudine, 2',3'-didehydro-3'-deoxythymidine (D4T), is a potent inhibitor of HIV-1 reverse transcriptase in vitro. In clinical studies, stavudine has excellent oral bioavailability in excess of 80%. The dose-limiting toxicity is peripheral neuropathy, which occurred in 15% of stavudine versus 6% of zidovudine-treated patients for 80 weeks in a randomized, blinded, phase III trial. Stavudine-treated groups have experienced significant increases in mean CD4 cell counts and decreases in both mean serum p24 antigen levels and infectious HIV titers in peripheral blood mononuclear cells. In subjects with prior zidovudine treatment, the duration of these responses is limited; CD4 counts and serum p24 antigen levels return to baseline after approximately 6 months. The effect of stavudine on clinical outcome and survival has not yet been established in comparative trials. Stavudine offers an additional therapeutic option to those individuals who are refractory to or intolerant of other available antiretrovirals.

Animals↗
PubMed1995

Effect of dietary fat and environmental lighting on the phospholipid molecular species of rat photoreceptor membranes.

We have previously shown that retinas of albino rats adapt to bright cyclic light (500-800 lx) by lowering the levels of docosahexaenoic acid (22:6n-3) in their rod outer segment (ROS) phospholipids. In the present study, we addressed the role of dietary fat in this process. Pregnant rats were kept in 1 lx or 250 lx cyclic illuminance (12L:12D) and fed diets containing 10% (by weight) of either hydrogenated coconut oil (COC, no n-3 or n-6 fatty acids), linseed oil (LIN, n-3 and n-6 fatty acids), or safflower oil (SAF, only n-6 fatty acids), starting 4 days before delivery. Pups were weaned at 3 weeks of age and continued on the same diet and light regime. At 12 weeks of age, 3 or 4 animals in each diet-light group were killed and the remaining animals were stressed continuously with 2000 lx light for 24 hr and then kept in 1 lx cyclic light for 10 days. Fatty acids and phospholipid molecular species (PLMS) of ROS membranes were determined. For prestressed groups, those animals fed the LIN diet had high levels of 22:6n-3 and PLMS containing 22:6n-3, with little 22:5n-6. Compared to the LIN group, the COC and SAF groups had lower levels of 22:6n-3- and 22:6n-3)-containing PLMS and higher levels of 22:5n-6 and molecular species containing 22:5n-6, such as 22:5n-6/22:6n-3, 16:0/22:5n-6 and 18:0/22:5n-6. Within each dietary group, animals raised in 250 lx cyclic illuminance had lower levels of 22:6n-3 and 22:5n-6 compared to those raised at 1 lx. This light effect was greater for 22:6n-3 in the LIN group than for 22:5n-6 in the SAF group. After the acute light stress, those animals raised in 1 lx showed dramatic reduction in PLMS containing 22:6n-3 and 22:5n-6, especially polyenoic species such as 22:6n-3/22:6n-3 in the LIN group and 22:5n-6/22:6n-3 in the COC and SAF groups. In contrast, animals raised in 250 lx showed much smaller changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Albinism, Ocular↗
PubMed1995

Effect of dietary fat on the response of the rat retina to chronic and acute light stress.

We designed an experiment to study the role of light history and polyunsaturated fatty acids (PUFA) on the susceptibility of the albino rat retina to light damage. Albino rats were born to dams that had been kept in either 1 lx or 250 lx cyclic light for 0-4 days prior to delivery and fed one of three diets containing either 10% (by weight) hydrogenated coconut oil (COC, no n-3 nor n-6 fatty acids), safflower oil (SAF, high n-6, < 0.1% n-3 fatty acids), or linseed oil (LIN, high n-3, low n-6 fatty acids). After weaning, the rats were maintained in the same light environment and fed the same diets for 9 weeks, at which time some were killed and their retinas processed for morphometric analysis. Animals raised in bright cyclic light had shorter ROS lengths and thinner outer nuclear layers (ONL) than rats raised in dim cyclic light. The LIN animals had a thinner ONL than animals of the SAF or COC groups. Rats from each diet and light rearing groups were exposed to constant illumination of 2000 lx for 24 hr, after which they and non-exposed controls were placed in 1 lx cyclic light for 10 days and analysed for changes in ONL thickness. In the 250 lx (bright; B) groups, there was no effect of acute light stress on ONL thickness, although both control and stressed LIN animals had a thinner ONL than the corresponding COC and SAF groups. However, in the rats raised in 1 lx cyclic light, acute stress resulted in significant retinal damage (i.e. decrease in ONL thickness) in the three diet groups combined. The superior region was damaged the most and the severity was dependent on diet, as evidenced by the LIN group having a greater reduction in ONL thickness than the SAF group after light stress. From these results we conclude that rats on diets high in n-3 fatty acids are more susceptible to photoreceptor cell loss than animals fed n-6 or no polyunsaturated fatty acids when raised in dim cyclic light. These results show that both diet and light history play a role in the susceptibility of the retina to acute and chronic effects of light and suggest a role for lipid peroxidation in retinal light damage.

Albinism, Ocular↗
PubMed1995

Design and implementation of the stavudine parallel-track program.

In a randomized, double-blind, large, simple trial, the safety and efficacy of two weight-adjusted dose levels of stavudine were evaluated in patients with advanced human immunodeficiency virus (HIV) infection. All patients were refractory to or intolerant of both zidovudine and didanosine. Patients weighing > or = 60 kg received 20 or 40 mg of stavudine twice daily. The dose was reduced to 15 or 30 mg for patients weighing 40-59 kg and to 10 or 20 mg for those weighing < 40 kg. The primary efficacy end points were survival and time to clinical progression of HIV disease. The primary safety end point was time to dose-limiting neuropathy. A total of 8127 patients were enrolled as of 31 July 1993. Although many patients who might have benefitted from stavudine were reached by the parallel-track program, a review of demographic data revealed disproportionate representation by white men from large metropolitan areas on both coasts.

Adult↗