Synthetic peptide homologous to beta protein from Alzheimer disease forms amyloid-like fibrils in vitro

Progressive amyloid deposition in senile plaques and cortical blood vessels may play a central role in the pathogenesis of Alzheimer disease. We have used x-ray diffraction and electron microscopy to study the molecular organization and morphology of macromolecular assemblies formed by three synthetic peptides homologous to beta protein of brain amyloid: beta-(1-28), residues 1-28 of the beta protein; [Ala16]beta-(1-28), beta-(1-28) with alanine substituted for lysine at position 16; and beta-(18-28), residues 18-28 of the beta protein. beta-(1-28) readily formed fibrils in vitro that were similar in ultrastructure to the in vivo amyloid and aggregated into large bundles resembling those of senile plaque cores. X-ray patterns from partially dried, oriented pellets showed a cross-beta-conformation. A series of small-angle, equatorial maxima were consistent with a tubular fibril having a mean diameter of 86 A and a wall composed of pairs of cross-beta-pleated sheets. The data may also be consistent with pairs of cross-beta-sheets that are centered 71-A apart. [Ala16]beta-(1-28) formed beta-pleated sheet assemblies that were dissimilar to in vivo fibrils. The width of the 10-A spacing indicated stacks of about six sheets. Thus, substitution of the uncharged alanine for the positively charged lysine in the beta-strand region enhances the packing of the sheets and dramatically alters the type of macromolecular aggregate formed. beta-(18-28) formed assemblies that had even a greater number of stacked sheets, approximately equal to 24 per diffracting domain as indicated by the sharp intersheet reflection. Our findings on these homologous synthetic assemblies help to define the specific sequence that is required to form Alzheimer-type amyloid fibrils, thus providing an in vitro model of age-related cerebral amyloidogenesis.

Arachidonic acid to eicosapentaenoic acid ratio in blood correlates positively with clinical symptoms of depression

In this study of 20 moderately to severely depressed patients, diagnosed using current research diagnostic criteria and excluding known bipolar affective disorder and reactive depression, we investigated relationships between severity of depression and levels and ratios of n-3 and n-6 long-chain polyunsaturated fatty acids (PUFA) in plasma and erythrocyte phospholipids (PL). Severity of depression was measured using the 21-item Hamilton depression rating scale (HRS) and a second linear rating scale (LRS) of severity of depressive symptoms that omitted anxiety symptoms. There was a significant correlation between the ratio of erythrocyte PL arachidonic acid (AA) to eicosapentaenoic acid (EPA) and severity of depression as rated by the HRS (P < 0.05) and the LRS for depression (P < 0.01). There was also a significant negative correlation between erythrocyte EPA and the LRS (P < 0.05). The AA/EPA ratio in plasma PL and the ratio of erythrocyte long-chain (C20 and C22 carbon) n-6 to long-chain n-3 PUFA were also significantly correlated with the LRS (P < 0.05). These findings do not appear to be simply explained by differences in dietary intake of EPA. We cannot determine whether the high ratios of AA/EPA in both plasma and erythrocyte PL are the result of depression or whether tissue PUFA change predate the depressive symptoms. We suggest, however, that our findings provide a basis for studying the effect of the nutritional supplementation of depressed subjects, aimed at reducing the AA/EPA ratio in tissues and severity of depression.

A thyroid-specific nuclear protein essential for tissue-specific expression of the thyroglobulin promoter

A rat thyroglobulin promoter fragment, capable of directing thyroid-specific transcription, binds at least three different factors, TTF-1, TTF-2 and UFA, which are all present in nuclear extracts of the differentiated rat thyroid cell line FRTL-5. TTF-1 and TTF-2 are FRTL-5 specific, as demonstrated by their absence in nuclear extracts prepared from cell lines that do not express any thyroid-differentiated function, while UFA is present in all cell lines tested. TTF-1 has been extensively purified. It binds to the rat thyroglobulin promoter at three different sites which share sequence homology. Mutations in two of the three sites decrease both binding of TTF-1 in vitro and promoter function in vivo. This suggests that the tissue-specific expression of the thyroglobulin genes is mediated, at least in part, by the presence of a transcription factor exclusively in thyroid cells.

Cognitive dysfunction in older subjects with diabetes mellitus: impact on diabetes self-management and use of care services. All Wales Research into Elderly (AWARE) Study

OBJECTIVE

To determine whether cognitive impairment is associated with changes in self-care behaviour and use of health and social services in older subjects with diabetes mellitus.

RESEARCH DESIGN AND METHODS

This was a community based, case-control study of subjects registered with general practices participating in the All Wales Research into Elderly (AWARE) Diabetes Study. The 396 patients aged 65 years or older with known diabetes mellitus were compared with 393 age- and sex-matched, non-diabetic controls. Adjusted odds ratio estimates of normal performance on Mini-Mental State Examination (MMSE) and Clock Drawing Test (numbers and hands) were determined. Information on self-care behaviours and use of services was obtained.

RESULTS

A total of 283 (71%) diabetic subjects scored 24 or more on MMSE, compared with 323 (88%) of controls (OR 0.54, P<0.0005). The mean (S.D.) scores were 24.5 (5.1) and 25.7 (4.3), respectively (difference between means 1.22; 95% CI 0.56, 1.88; P<0. 001). Clock testing demonstrated that 257 (65%) and 286 (72%) diabetic subjects correctly placed the numbers and hands, respectively, compared with 299 (76%) and 329 (84%) of controls (OR 0.59, P<0.001 and P<0.52, P<0.0005, respectively). Both test scores declined with increasing age, earlier school leaving age and deteriorating visual acuity. Of other variables examined, only need for oral hypoglycaemic drugs or insulin, history of stroke, dementia or Parkinson's disease and symptoms of autonomic neuropathy significantly impaired one or more cognitive test scores. The odds ratios (95% CI) for normal cognitive test results in subjects with diabetes after adjusting for all significant variables was 0.74 (0. 56, 0.97), P=0.029 for MMSE scores and 0.63 (0.44, 0.93), P=0.019, and 0.58 (0.38, 0.89), P=0.013, for the numbers and hands parts of the clock test, respectively. In comparison with diabetic subjects with no evidence of cognitive impairment, diabetic subjects with an MMSE score <23 were significantly less likely to be involved in diabetes self-care (P<0.001) and diabetes monitoring (P<0.001). A low MMSE score was also significantly associated with higher hospitalisation in the previous year (P=0.001), reduced ADL (activities of daily living) ability (P<0.001) and increased need for assistance in personal care (P=0.001).

CONCLUSIONS

Elderly subjects with predominantly Type 2 diabetes mellitus display significant excess of cognitive dysfunction, associated with poorer ability in diabetes self-care and greater dependency. Routine screening of cognition in older subjects with diabetes is recommended.

EBNA-2 and EBNA-LP cooperate to cause G0 to G1 transition during immortalization of resting human B lymphocytes by Epstein-Barr virus

Epstein-Barr virus (EBV) is unusual among DNA tumour viruses in that the virus particle is able to infect and immortalize resting cells with very high efficiency. Mutation of the viral genome has indicated that at least six viral genes (LMP-1 and EBNAs 1, 2, 3A, 3C and LP) are essential for immortalization. We demonstrate that the activation of a G1 cyclin, cyclin D2, is an early event following infection with EBV and that cyclin D2 activation is dependent on the expression of viral genes. The different levels of cyclin D2 transcripts in Burkitt's lymphoma cell lines expressing different subsets of EBV immortalizing genes suggest an involvement of EBNA-2 or EBNA-LP in cyclin D2 regulation. By exposing resting primary B cells to a purified preparation of the EBV surface glycoprotein gp340, we have been able to achieve efficient expression of plasmid DNAs introduced by electroporation. Vectors encoding two viral genes, EBNA-2 and EBNA-LP, are sufficient to activate the expression of cyclin D2 in this system. Thus, the progression of resting B lymphocytes into the G1 phase of the cell cycle can be reconstituted in the absence of virus by the cooperation of two of the six viral genes required for immortalization.

Incorporation of radioactive polyunsaturated fatty acids into liver and brain of developing rat

The incorporation of radioactivity from orally administered linoleic acid-1-14C, linolenic acid-1-14C, arachidonic acid-3H8, and docosahexaenoic acid-14C into the liver and brain lipids of suckling rats was studied. In both tissues, 22 hr after dosing, 2 distinct levels of incorporation were observed: a low uptake (from 18:2-1-14C and 18:3-1-14C) and a high uptake (from 20:4-3H8 and 22:6-14C). In adult rats, the incorporation of radioactivity into brain lipids from 18:2-1-14C and 20:4-3H was considerably lower than the incorporation into the brains of the young rats. In the livers of the suckling rats, the activity from the 18 carbon acids was associated mostly with the triglyceride fraction, whereas the activity from the 20:4-3H8 and 22:6-14C was concentrated in the phospholipid fraction. In the brain lipids, the activity from the different fatty apid fatty acids, some of the activity in the 18:2-1-14C and 18:3-1-14C experiments was associated with 20 and 22 carbon polyunsaturated fatty acids; however, radioactivity from orally administered 20:4-3H8 and 22:6-14C was incorporated intact into the tissue phospholipid to a much greater extent compared with the incorporation of radioactivity into 20:4 and 22:6 in the experiments where 18:2-1-14C and 18:3-1-14C, respectively, were administered. Possible reasons for these differences are discussed. Rat milk contains a wide spectrum of polyunsaturated fatty acids, including linoleate, linolenate, arachidonate, and docosahexaenoate. During the suckling period in the rat, there is a rapid deposition of 20:4 and 22:6 in the brain. The results of the present experiments suggested that dietary 20:4 and 22:6 were important sources of brain 20:4 and 22:6 in the developing rat.

Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men

BACKGROUND

Vegetarians have lower platelet and plasma concentrations of n-3 polyunsaturated fatty acids (PUFAs) than do omnivores. We recently showed that male vegetarians have higher platelet aggregability than do omnivores.

OBJECTIVE

We investigated whether male vegetarians (n = 17) who consumed an increased amount of dietary alpha-linolenic acid (ALA) showed any changes in their tissue profile of PUFAs, plasma thromboxane concentrations, platelet aggregability, or hemostatic factors.

DESIGN

During the study, all subjects maintained their habitual vegetarian diets except that a proportion of dietary fat was replaced with vegetable oils and margarines that were provided. Initially, all subjects consumed a low-ALA diet (containing safflower oil and safflower oil-based margarine) for 14 d; they then consumed either a moderate-ALA diet (containing canola oil and canola oil-based margarine) or a high-ALA diet (containing linseed oil and linseed oil-based margarine) for 28 d. Blood samples were collected at day 0 (baseline), day 14, and day 42.

RESULTS

Eicosapentaenoic acid, docosapentaenoic acid, total n-3 PUFAs, and the ratio of n-3 to n-6 PUFAs were significantly increased (P < 0.05), whereas the ratio of arachidonic acid to eicosapentaenoic acid was decreased (P < 0.05), in platelet phospholipids, plasma phospholipids, and triacylglycerols after either the moderate-ALA or high-ALA diet compared with the low-ALA diet. No significant differences were observed in thrombotic risk factors.

CONCLUSION

ALA from vegetable oils (canola and linseed) has a beneficial effect on n-3 PUFA concentrations of platelet phospholipids and plasma lipids in vegetarian males.

Determinants of restenosis and lack of effect of dietary supplementation with eicosapentaenoic acid on the incidence of coronary artery restenosis after angioplasty

The effect of an eicosapentaenoic acid-rich encapsulated preparation of fish oil on the incidence of early restenosis after coronary angioplasty was assessed by a randomized double-blind placebo-controlled study. A total of 108 patients received either 10 capsules of fish oil (1.8 g eicosapentaenoic acid, 1.2 g docosahexaenoic acid) or 10 control capsules (50% olive oil, 50% corn oil), commencing the day before angioplasty and continuing for 4 months after angioplasty, in addition to treatment with aspirin and verapamil. In 101 (94%) of the 108 patients, follow-up angiographic or postmortem result was evaluated at a mean (+/- SD) of 100 (+/- 22) days. Angiographic restenosis was observed in 34% of patients (29% of lesions) in the fish oil-treated group and 33% of patients (31% of lesions) in the control group (no significant difference). The overall incidence of angiographic restenosis was significantly higher in patients with 1) recurrent angina pectoris, 2) a positive exercise test at follow-up after angioplasty, 3) residual stenosis greater than 30% immediately after angioplasty, and 4) dilation of the left anterior descending or right coronary artery. Biochemical investigations showed a greater decrease in the serum triglyceride levels in the fish oil-treated group versus the control group (p less than 0.05) but no differences between the two groups in cholesterol levels or platelet counts over the 4 month period. In conclusion, in this study, the administration of fish oil at a dose of 10 capsules/day did not reduce the incidence of early restenosis after coronary angioplasty.

Prehospital advanced life support: benefits in trauma

The Boston Emergency Medical Service system was studied to determine the effects of Advanced Life Support (ALS) prehospital trauma care compared to Basic Life Support (BLS) treatment. The severity of injury and clinical status of patients was defined and monitored using the Trauma Score (TS) described by Champion. The TS on arrival at the hospital increased significantly more for patients receiving field ALS care than for patients transported by BLS ambulances (p = 0.01). ALS resuscitation had most influence on patients with TS 4-13 and did not delay transport time. Furthermore, a positive change in prehospital TS was significantly related to an increased chance of long-term survival for any given severity of injury (p = 0.0002). From these data we conclude that the TS is useful for prehospital triage and that appropriate field ALS resuscitation results in more favorable outcomes following major trauma.

Plasma lipids in human linoleic acid deficiency

A clinical case of linoleic acid deficiency has been investigated because of the unknown effect in an adult man. The patient had had all but 60 cm of his small intestine removed and was maintained solely by intravenous therapy for 100 days, without fat. At this stage there was no clinical evidence of malnutrition, but his serum phospholipids were found to contain 10% 5,8,11 eicosatrienoic acid and he developed a skin rash. A soybean fat emulsion containing 86 g/l of linoleic acid was given intravenously for 12 days, discontinued for 43 days and then resumed. During each period of fat administration (linoleic acid intake 22.8 g/day) the serum phospholipid content of eicosatrienoic acid fell and arachidonic acid rose. Simultaneously the serum triglycerides fell to normal, the proportions of the triglycerides carried by the lipoproteins (d < 1.006) rose to normal and the rash disappeared. A second case of linoleic acid deficiency, in this instance associated with severe malnutrition, was investigated and here also a high level of plasma triglycerides was mostly associated with lipoproteins with d < 1.006. In an attempt to estimate his minimal daily requirements, feeding 7.5 g/day of linoleic acid in this form did not eliminate the eicosatrienoic acid, but instead allowed a small increase. It is concluded that adult man requires at least 7.5 g/day of linoleic acid and that the proportion of the triglycerides carried by the very low density lipoproteins is lowered in the absence of linoleic acid.

Prevalence of diabetes in care home residents

OBJECTIVE

To determine the prevalence of known and undetected diabetes diagnosed either by an elevated fasting baseline sample or by a 2-h post-glucose load sample in a group of residents of care homes in an urban-district setting.

RESEARCH DESIGN AND METHODS

We completed individual interviews with patients and caregivers in 30 care homes (both residential and nursing homes) in two metropolitan districts of Birmingham, West Midlands, U.K. All care homes were under the supervision of primary care physicians (general practitioners). We carried out 75-g oral glucose tolerance tests (OGTTs) in consenting residents without previous known diabetes. Criteria for diagnosis of diabetes were obtained from the World Health Organization (1998) and the American Diabetes Association (1997).

RESULTS

Of 636 residents available for study, 76 residents (12.0%) were known to have diabetes; of the 560 remaining residents, 286 either refused to participate or were deemed too ill or unavailable to undergo testing. Complete data on 274 OGTTs were obtained (median age 83 years, range 45-101). A total of 46 subjects were diagnosed as having diabetes and 94 as having impaired glucose tolerance. Allowing for subjects who refused or were unable to participate, the calculated total prevalence (which includes known and newly detected diabetes) was 26.7% (95% CI 21.9-32.0). The calculated overall prevalence of impaired glucose tolerance was 30.2% (25.2-35.6).

CONCLUSIONS

In a group of care home residents not known to have diabetes and able to undergo testing, a substantial proportion have undetected diabetes based on a 2-h postglucose load. These residents warrant further study as they may be at higher cardiovascular risk and require an intervention.

Outbreak of carbapenem-resistant Pseudomonas aeruginosa producing VIM-8, a novel metallo-beta-lactamase, in a tertiary care center in Cali, Colombia

The prevalence of imipenem resistance among Pseudomonas aeruginosa isolates at a 195-bed tertiary care medical center in Cali, Colombia, rose from 2% in 1996 to 28% in 1997 and to over 40% in 2003. Many isolates showed high-level multiresistance, and phenotypic characterization suggested the spread of a predominant strain with minor variants. Sixty-six resistant isolates collected between February 1999 and July 2003 from hospitalized patients (n = 54) and environmental samples (n = 12) were subjected to a fuller analysis. Genetic fingerprints were compared by pulsed-field gel electrophoresis (PFGE) of SpeI-digested genomic DNA, and bla(IMP) and bla(VIM) genes were sought by PCR. PFGE and serotyping indicated that 52 of the 66 isolates belonged to a single strain, with 82% similarity; the PFGE pattern for this organism was designated pattern A. Two further pairs of isolates represented single strains; the remaining nine isolates were unique, and in the case of one isolate, no satisfactory PFGE profile could be obtained. The pattern A isolates were mostly of serotype O12 and were highly resistant to imipenem (MICs, 32 to >256 microg/ml), with this resistance decreased eightfold or more in the presence of EDTA. They yielded amplicons with bla(VIM)-specific primers, and sequencing of DNA from a representative isolate revealed bla(VIM-8), a novel allele with three polymorphisms compared with the sequence of bla(VIM-2). Two of these nucleotide changes were silent, but the third determined a Thr139Ala substitution. Only 4 of 13 resistant isolates (2 clinical isolates and 2 environmental isolates) assigned to other PFGE types carried bla(VIM) alleles, whereas the others were less multiresistant and mostly had lower levels of imipenem resistance (MICs, < or =32 microg/ml) which was not significantly reduced by EDTA. No bla(IMP) alleles were detected. During 2003, when the environmental study was undertaken, serotype O12 isolates with bla(VIM) were recovered from sinks and stethoscopes in the most-affected units, although not from the hands of staff; the problem declined once these reservoirs were disinfected and hygienic precautions were reinforced.

Pathways of activation of the Epstein-Barr virus productive cycle

The promoter for the 2.8-kb RNA of Epstein-Barr virus encoding BZLF1 and BRLF1 was identified and shown to be activated by both BZLF1 and BRLF1 but not by 12-O-tetradecanoylphorbol-13-acetate. Site-directed mutagenesis suggests that two binding sites for BZLF1 within the promoter contribute to the transactivation by BZLF1. The early kinetics of induction of the 2.8- and 1.0-kb RNAs encoding BZLF1 and BRLF1 in Akata cells treated with anti-immunoglobulin indicate that both RNAs appear within 60 min. The results indicate some likely pathways of activation of Epstein-Barr virus productive cycle gene expression.

Impact of an interdisciplinary low vision service on the quality of life of low vision patients

AIM

To investigate the impact of an interdisciplinary low vision service on the vision related quality of life of service users.

METHODS

71 patients were interviewed 2 weeks before their appointment with the service and again 6 months later to assess any changes in their vision related quality of life. The majority of these patients had age related macular degeneration.

RESULTS

After contact with the service the majority of patients indicated a reduction in concern about most quality of life issues. They were significantly less anxious about deterioration of their vision, safety within the home, and coping with everyday life.

CONCLUSION

Improvements in many areas of their vision related quality of life indicate that this interdisciplinary low vision service has a positive impact on the lives of service users. However many patients were still unable to carry out their preferred everyday activities, and feelings of loneliness and isolation were unchanged. The identification of issues unrelieved by input from the service will be important in planning future service delivery.

Stability of XGCGCp, GCGCYp, and XGCGCYp helixes: an empirical estimate of the energetics of hydrogen bonds in nucleic acids

The stabilizing effects of dangling ends and terminal base pairs on the core helix GCGC are reported. Enthalpy and entropy changes of helix formation were measured spectrophotometrically for AGCGCU, UGCGCA, GGCGCCp, CGCGCGp, and the corresponding pentamers XGCGCp and GCGCYp containing the GCGC core plus a dangling end. Each 5' dangling end increases helix stability at 37 degrees C roughly 0.2 kcal/mol and each 3' end from 0.8 to 1.7 kcal/mol. The free energy increments for dangling ends on GCGC are similar to the corresponding increments reported for the GGCC core [Freier, S. M., Alkema, D., Sinclair, A., Neilson, T., & Turner, D. H. (1985) Biochemistry 24, 4533-4539], indicating a nearest-neighbor model is adequate for prediction of stabilization due to dangling ends. Nearest-neighbor parameters for prediction of the free energy effects of adding dangling ends and terminal base pairs next to G.C pairs are presented. Comparison of these free energy changes is used to partition the free energy of base pair formation into contributions of "stacking" and "pairing". If pairing contributions are due to hydrogen bonding, the results suggest stacking and hydrogen bonding make roughly comparable favorable contributions to the stability of a terminal base pair. The free energy increment associated with forming a hydrogen bond is estimated to be -1 kcal/mol of hydrogen bond.

Contributions of dangling end stacking and terminal base-pair formation to the stabilities of XGGCCp, XCCGGp, XGGCCYp, and XCCGGYp helixes

The role of stacking in terminal base-pair formation was studied by comparison of the stability increments for dangling ends to those for fully formed base pairs. Thermodynamic parameters were measured spectrophotometrically for helix formation of the hexanucleotides AGGCCUp, UGGCCAp, CGGCCGp, GCCGGCp, and UCCGGAp and for the corresponding pentanucleotides containing a 5'-dangling end on the GGCCp or CCGGp core helix. In 1 M NaCl at 1 X 10(-4) M strands, a 5'-dangling nucleotide in this series increases the duplex melting temperature (Tm) only 0-4 degrees C, about the same as adding a 5'-phosphate. In contrast, a 3'-dangling nucleotide increases the Tm at 1 X 10(-4) M strands 7-23 degrees C, depending on the sequence [Freier, S. M., Burger, B. J., Alkema, D., Neilson, T., & Turner, D. H. (1983) Biochemistry 22, 6198-6206]. These results are consistent with stacking patterns observed in A-form RNA. The stability increments from terminal A.U, C.G, or U.A base pairs on GGCC or a terminal U.A pair on CCGG are nearly equal to the sums of the stability increments from the corresponding dangling ends. This suggests stacking plays a large role in nucleic acid stability. The stability increment from the terminal base pairs in GCCGGCp, however, is about 5 times the sum of the corresponding dangling ends, suggesting hydrogen bonding can also make important contributions.

The effects of dietary alpha-linolenic acid compared with docosahexaenoic acid on brain, retina, liver, and heart in the guinea pig

The aim of this study was to compare two different strategies to elevate brain, retina, liver, and heart docosahexaenoic acid (DHA) levels in guinea pigs. First, we used an increasing dose of alpha-linolenic acid (ALA) relative to a constant linoleic acid (LA) intake, and second, we used two levels of dietary DHA provided in conjunction with dietary arachidonic acid (AA). The percentage DHA and AA of total phospholipids in retina, liver, and heart, and in the brain phosphatidylethanolamine and phosphatidylcholine was studied in female pigmented guinea pigs (3 wk old) fed one of five semisynthetic diets containing 10% (w/w) lipid for 12 wk. The LA content in the diets was constant (17% of total fatty acids), with the ALA content varying from 0.05% (diet SFO), to 1% (diet Mix), and to 7% (diet CNO). Two other diets (LCP1 and LCP3) had a constant LA/ALA ratio (17.5:1) but varied in the levels of dietary AA and DHA supplementation. Diet LCP1 was structured to closely replicate the principal long chain polyunsaturated fatty acids (PUFA) found in human breast milk and contained 0.9% AA and 0.6% DHA (% of total fatty acids) whereas diet LCP3 contained 2.7% AA and 1.8% DHA. At the end of the study, animals were sacrificed and tissues taken for fatty acid analyses. We found no significant effects of diets on the growth of guinea pigs. Diets containing ALA had profoundly different effects on tissue fatty acid compositions compared with diets which contained the long chain PUFA (DHA and AA). In the retina and brain phospholipids, high-ALA diets or dietary DHA supplementation produced moderate relative increases in DHA levels. There was no change in retinal or brain AA proportions following dietary AA supplementation, even at the highest level. This was in contrast to liver and heart where tissue DHA proportions were low and AA predominated. In these latter tissues, dietary ALA had little effect on tissue DHA proportions although the proportion of AA was slightly depressed at the highest dietary ALA intake, but dietary DHA and AA supplements led to large increases (up to 10-fold) in the proportions of these PUFA. Tissue uptake of dietary AA and DHA appeared maximal for the LCP1 diet (replicate of breast milk) in the heart. There were no significant changes in the plasma levels of 11-dehydrothromboxane B2 (a thromboxane A2 metabolite) for any diet. The data confirm that dietary ALA is less effective than dietary DHA supplementation (on a gram/gram basis) in increasing tissue DHA levels and that tissues vary greatly in their response to exogenous AA and DHA, with the levels of these long chain metabolites being most resistant to change in the retina and brain compared with liver and heart. Dietary DHA markedly increased tissue DHA proportions in both liver and heart, whereas the major effect of dietary AA was in the liver. Future studies of the effects of dietary DHA and AA supplementation should examine a variety of tissues rather than focusing only on neural tissue.

Disturbed handling of ascorbic acid in diabetic patients with and without microangiopathy during high dose ascorbate supplementation

Abnormalities of ascorbic acid metabolism have been reported in experimentally-induced diabetes and in diabetic patients. Ascorbate is a powerful antioxidant, a cofactor in collagen biosynthesis, and affects platelet activation, prostaglandin synthesis and the polyol pathway. This suggests a possible close interrelationship between ascorbic acid metabolism and pathways known to be influenced by diabetes. We determined serum ascorbic acid and its metabolite, dehydroascorbic acid, as indices of antioxidant status, and the ratio, dehydroascorbate/ascorbate, as an index of oxidative stress, in 20 matched diabetic patients with and 20 without microangiopathy and in 22 age-matched control subjects. Each study subject then took ascorbic acid, 1 g daily orally, for six weeks with repeat measurements taken at three and six weeks. At baseline, patients with microangiopathy had lower ascorbic acid concentrations than those without microangiopathy and control subjects (42.1 +/- 19.3 vs 55.6 +/- 20.0, p less than 0.01, vs 82.9 +/- 30.9 mumol/l, p less than 0.001) and elevated dehydroascorbate/ascorbate ratios (0.87 +/- 0.46 vs 0.61 +/- 0.26, p less than 0.01, vs 0.38 +/- 0.14, p less than 0.001). At three weeks, ascorbate concentrations rose in all groups (p less than 0.0001) and was maintained in control subjects (151.5 +/- 56.3 mumol/l), but fell in both diabetic groups by six weeks (p less than 0.01). Dehydroascorbate/ascorbate ratios fell in all groups at three weeks (p less than 0.0001) but rose again in the diabetic groups by six weeks (p less than 0.001) and was unchanged in the control subjects. Dehydroascorbate concentrations rose significantly from baseline in all groups by six weeks of ascorbic acid supplementation (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)