Biomedical subjects

M Larsen

Publications and source records attributed to M Larsen.

At least 37 records · Page 2Linked to original sources

PubMed2003

Efficiency of feeding Duddingtonia flagrans chlamydospores to grazing ewes on reducing availability of parasitic nematode larvae on pasture.

Gastrointestinal nematodes are of concern in sheep production because of production and economic losses. Control of these nematodes is primarily based on the use of anthelmintic treatment and pasture management. The almost exclusive use of anthelmintic treatment has resulted in development of anthelmintic resistance which has led to the need for other parasite control options to be explored. The blood sucking abomasal parasitic nematode Haemonchus contortus causes severe losses in small ruminant production in the warm, humid sub-tropic and tropics. This study evaluated the effectiveness of a nematode trapping fungus, Duddingtonia flagrans, in reducing availability of parasitic nematode larvae, specifically H. contortus, on pasture. Chlamydospores of D. flagrans were mixed with a supplement feed which was fed daily to a group of crossbred ewes for the duration of the summer grazing season. A control group was fed the same supplement feed without chlamydospores. A reduction in infective larval numbers was observed in fecal cultures of the fungus-fed group. Herbage samples from the pasture grazed by the fungus-fed group also showed a reduction in infective larvae. There were no significant (P > 0.05) differences in overall fecal egg count, packed cell volume or animal weight between fungus-fed and control groups. Tracer animals were placed on the study pastures at the end of the study to assess pasture infectivity. Although tracer animals were only two per group, those that grazed with the fungus-fed group had substantially reduced (96.8%) nematode burdens as compared to those from the control group pasture. Results demonstrated that the fungus did have activity against nematode larvae in the feces which reduced pasture infectivity and subsequently nematode burdens in tracer animals. This study showed that D. flagrans, fed daily to grazing ewes, was an effective biological control agent in reducing a predominantly H. contortus larval population on pasture.

Animal Feed↗

PubMed2003

Biological control of nematode parasites of small ruminants in Malaysia using the nematophagous fungus Duddingtonia flagrans.

Control of nematode parasites of small ruminants in a wet, tropical environment using the nematophagous fungus, Duddingtonia flagrans, was assessed in this study. Two methods of fungal delivery were tested, namely as a daily feed supplement, or incorporated into feed blocks. Initially, pen trials were conducted with individually penned groups of sheep and goats at dose rates of 125,000 spores and 250,000 spores/kg live weight per day. At the lower dose rate this reduction was between 80 and 90% compared with the pre-treatment levels. At the higher dose rate, there was virtually complete suppression (>99% reduction) of larval recovery. Trials using the fungal feed blocks, showed that when animals were individually penned, they consumed only small amounts of the block (particularly goats), hence little effect on larval recovery in faecal cultures was observed. Grouping animals according to species and dose rate induced satisfactory block consumption and subsequent high levels of larval reduction in faecal cultures. These larval reductions were mirrored by the presence of fungus in faecal cultures. This work was followed by a small paddock trial, whereby three groups of sheep were fed either a feed supplement without fungal spores, supplement with spores, or offered fungal blocks. The dose rate of spores in the latter two groups was 500,000 spores/kg live weight per day. Egg counts were significantly reduced in the two fungal groups, compared with the control group and the latter required two salvage anthelmintic treatments to prevent mortality due to haemonchosis. Pasture larval numbers on the two fungal group plots were also much lower than on the control plot.

Animal Feed↗

PubMed2003

An autometallographic technique for myelin staining in formaldehyde-fixed tissue.

A new autometallographic (AMG) technique for staining myelin in formaldehyde- or paraformaldehyde- (PFA) fixed tissue is presented. The tissue sections were exposed to AMG development without prior treatment with silver salts. The method was examined on PFA-fixed tissue from mouse, rat, pig, and formaldehyde-fixed human autopsy material. Samples from brain, spinal cord, cranial, and spinal nerves were either cut on a vibratome, frozen and cryostat sectioned, or embedded and microtome sectioned, before AMG development and counterstaining. The AMG-myelin technique results in a specific black/dark-brown staining of myelin in all parts of the CNS and PNS. It works on all species examined, independent of the histological preparation techniques applied. The AMG staining is stable, stays unchanged through decades, allows counterstaining, and has previously been used with immunohistochemical techniques. On perfusion-fixed tissue the technique works without further fixation, but the intensity of the AMG-myelin staining is increased by increased postfixation time. Additionally, immersion fixation has to last for days depending on the size of the tissue block in order to obtain proper myelin staining. The most feasible explanation of the chemical events underlying the AMG-myelin technique is that nano-sized clusters of metallic silver are formed in the myelin as a result of chemical bounds with reducing capacity, exposed or created by the formaldehyde molecule. The AMG method is simple to perform and as specific as the conventional osmium and luxol fast blue stainings. The present technique is thus an effective, simple, inexpensive, and quick myelin staining method of formaldehyde- or PFA-fixed tissue.

Animals↗

PubMed2002

Lens ageing as an indicator of tissue damage associated with smoking and non-enzymatic glycation--a twin study.

AIMS/HYPOTHESIS: With ageing the long-lived proteins of the human lens undergo denaturation by non-enzymatic glycation. The denaturated proteins are fluorescent, a property that can be assessed in vivo by fluorometry. Our aim was to examine the relative contribution of hereditary and environmental effects on the accumulation of fluorescent compounds in the lens. METHODS: We examined 59 monozygotic and 55 dizygotic healthy twin pairs recruited from a population-based register of twins. Lens autofluorescence was measured on the undilated eye. All subjects underwent an OGTT and information on smoking habits was obtained. The genetic and environmental effects were estimated by structural equation modelling. RESULTS: Lens autofluorescence was related to age (R(2)=53%), current glucose homeostasis (R(2)=10%) and smoking habits (R(2)=10%). After adjusting for these factors, interindividual variation in lens autofluorescence was statistically attributable to hereditary factors by approximately 28% as well as shared environment by 58% and non-shared environment by 14%. The hereditary factor seems not to be linked to a genetic predisposition to diabetes. CONCLUSION/INTERPRETATION: The correlation in lens fluorescence was greater in monozygotic twins than dizygotic twins indicating a genetically predetermined susceptibility for the accumulation of fluorophores in the lens, the relative importance of which was found to increase with age. Since fluorophore formation in the lens is attributable to non-enzymatic glycation our results support that genetic characteristics to some degree determine the susceptibility to glycation related diabetes complications and ageing processes.

Adult↗

PubMed2002

Evaluation of Duddingtonia flagrans in reducing infective larvae of Haemonchus contortus in feces of sheep.

Consequences of nematode infections due to Haemonchus contortus are a serious constraint for the sheep industry worldwide. Development of anthelmintic resistance and increasing concern about the impact of anthelmintic use dictate the need of alternative control. Such an alternative is using the nematode trapping fungus Duddingtonia flagrans to reduce infective larvae levels on pasture. Two trials were conducted to determine the effect of D. flagrans in reducing infective larvae (predominantly H. contortus) in feces. The first trial determined the dose effect of D. flagrans in reducing infective larvae in feces. Eighteen ewes were dewormed to remove existing infections and randomly assigned to six treatment groups: 5 x 10(4), 1 x 10(5), 2.5 x 10(5), 5 x 10(5), 1 x 10(6) or no (control) spores of D. flagrans per kg of body weight mixed in their feed for 7 days. Fecal samples were collected daily from these and from infected donor ewes. Feces from individual-treated ewes were mixed with equal amounts of donor ewe feces, theoretically approximating oral dose spore concentrations of 2.5 x 10(4), 5 x 10(4), 1.25 x 10(5), 2.5 x 10(5), 5 x 10(5) and no spores, and were cultured. Across dosages and during the 7 days of fungus feeding, percent reduction of infective larvae ranged from 76.6 to 100.0%. The second trial determined the effect of D. flagrans at the dose of 10(5) spores per kg body weight on reducing infective larvae in feces from naturally infected lambs. Twenty lambs were randomly assigned to either treatment or control groups based on fecal egg count. Treatment lambs were fed spores mixed in feed for 7 days. Feces were collected daily and cultured. During the 7 days of fungus feeding, the percent reduction of infective larvae ranged from 82.8 to 99.7%. Results of these trials demonstrated that the nematode trapping fungus D. flagrans was highly effective in reducing infective larvae in sheep feces and should be considered as a biological control agent for integrated nematode control programs.

Administration, Oral↗

PubMed2002

Predacious activity of Duddingtonia flagrans within the cattle faecal pat.

Two studies were conducted to investigate the growth and activity of the fungus, Duddingtonia flagrans, within cattle faecal pats. Artificial faecal pats were constructed with the centre separated from the outer layer by a nylon mesh. Eight treatments were tested, by varying the presence/absence of Cooperia oncophora eggs and fungal spores within each layer. With parasite eggs in the centre layer, a statistically lower recovery of larvae was observed compared to both pats with parasite eggs in the periphery and pats with parasite eggs throughout both layers. Regardless of location within the pat, if co-located with the parasite egg, D. flagrans was found to be effective in trapping developing larvae. The reduction in recovery of larvae from pats with parasite eggs and fungal spores in the centre was found to be significantly higher than when parasite eggs were in the centre and fungal spores in the periphery. In the second study, pats were made up in two treatments: pats containing fungal spores and C. oncophora eggs (fungus) and pats containing C. oncophora eggs (control). The pats were incubated at low or high humidity. Ten pats were used in a cross over where five pats incubated at low humidity for 7 weeks were removed, water added and then incubated at a high humidity for 1 week. Another five pats were incubated at a high humidity for 7 weeks, aerated and incubated at a low humidity for 1 week. There was no apparent growth of fungus in faecal pats incubated at a high humidity and less than 20% of larvae were recovered. The growth of D. flagrans was observed in faecal pats incubated at a low humidity, but a corresponding reduction in the percentage recovery of larvae did not occur, except in week 4. No statistical difference between fungal and control pats was seen in the change over pats. Nematophagous activity was assessed throughout the study and observed in the first 4 weeks within the pats containing fungus.

Animals↗

PubMed2002

Diabetic macular oedema: the effect of photocoagulation on fluorescein transport across the blood-retinal barrier.

BACKGROUND/AIM: The visual loss secondary to diabetic macular oedema can be controlled to some extent by photocoagulation, though the mechanism of action is largely unknown. The purpose of the present study was to quantitate the effect of photocoagulation on the blood-retinal barrier using fluorescein as a tracer of passive and active transport. METHODS: A prospective study of 46 eyes in 34 patients with clinically significant macular oedema (CSMO) examined by vitreous fluorometry before and 6 months after macular photocoagulation treatment. RESULTS: In 23 eyes CSMO was not present at follow up (responding eyes), in another 23 other eyes CSMO was still present (non-responding eyes). With reference to the presence or absence of CSMO at follow up, the passive transport (permeability) for responding eyes decreased after photocoagulation in contrast with an increase in non-responding eyes; the difference between the groups at follow up was significant (p=0.03). The active transport for responding eyes decreased slightly at follow up, while it increased for non-responding eyes; the difference between the groups at follow up was not significant (p=0.09). CONCLUSION: Following photocoagulation a reduction of diabetic macular oedema, defined as disappearance of CSMO, is paralleled by a decrease of the passive permeability while the hypothesis of an increase in the active transport from the retina to the blood could not be supported by this study.

Adult↗

PubMed2002

Diabetic macular oedema: a comparison of vitreous fluorometry, angiography, and retinopathy.

AIM: To evaluate the relation between the quantitative measurement of vitreous fluorescein with fluorescein angiography and retinopathy in diabetic patients with and without clinically significant macular oedema (CSMO). METHODS: In a prospective cross sectional study, passive permeability and active, outward transport of fluorescein across the blood-retinal barrier were quantitated with vitreous fluorometry in 61 eyes from 48 patients with CSMO and 22 fellow eyes without CSMO, after exclusion of eyes with previous macular laser treatment and vitreous liquification. All patients were recruited from the university hospital's outpatient clinic. Retinopathy and fluorescein angiograms were evaluated on 60 degree photographs. RESULTS: The passive permeability in CSMO was significantly correlated with the severity of leakage on fluorescein angiograms (r=0.73), the level of retinopathy (r=0.61), and visual acuity (r=0.45). Significant differences between eyes with CSMO and eyes without CSMO were found for passive permeability (p<0.001), fluorescein leakage (p<0.001), visual acuity (p=0.02), and retinopathy (p=0.002). CONCLUSION: Passive permeability of fluorescein quantitated with vitreous fluorometry was correlated both with semiquantitative fluorescein angiography and retinopathy, and a significant increase in passive permeability was found when comparing eyes with CSMO to eyes without CSMO. No such pattern was found for the active transport indicating that passive and not the outward, active transport is the factor of most importance in the development of CSMO.

Adult↗

PubMed2002

Mannitol in cardioplegia as an oxygen free radical scavenger measured by malondialdehyde.

Oxygen free radicals (OFRs) are associated with ischaemia-reperfusion injury involving many organs, including the heart, which can lead to depressed cardiac function and abnormalities in the cardiac ultrastructure. This is seen upon the release of the aortic crossclamp when the ischaemic myocardium is reperfused in patients undergoing cardiopulmonary bypass (CPB). Various studies have shown that by adding OFR scavenging agents or antioxidants to the CPB prime or cardioplegia, cardiac performance improves. Mannitol is an osmotic diuretic with free radical scavenging properties, which has been shown to reduce the extent of ischaemic injury and improve the function of the myocardium. This study evaluated how effective mannitol is as an OFR scavenger by administering different concentrations of cardioplegia antegrade into the aortic root, thus maximising its effects directly upon the myocardium rather than being diluted in the CPB prime. Thirty-three patients undergoing primary coronary artery bypass grafting (CABG) were, by double blind random selection, allocated into one of three groups: group 1, a control group (consisting of 11 patients) receiving no mannitol; group 2 (11 patients), receiving a concentration of 4 g/l; and group 3 (11 patients), receiving 8 g/l. Three blood samples were taken directly from the coronary sinus during bypass: the first sample at the start of bypass, just prior to the crossclamp being applied; the second sample just after removal of the crossclamp; and the third sample just prior to termination of bypass. All samples were then centrifuged and the plasma analysed for malondialdehyde (MDA) using high-performance liquid chromatography (HPLC). MDA, an endproduct of lipid peroxidation, causes cellular damage and disruption of cell membranes when tissue antioxidants are exhausted. The more MDA produced, the greater the depletion of tissue antioxidants secondary to OR formation during reperfusion when the aortic crossclamp is removed. HPLC is a useful biochemical study; however, it is not a direct indicator of depressed myocardial function, such as an invasive test would be, and this should be borne in mind. Statistically, the results do not show a significant difference among the three groups or among the three samples. However, a trend can be seen, which shows lower levels of MDA in the two groups receiving mannitol and there is an indication of a rise in MDA levels upon the start of reperfusion in the two groups receiving mannitol, but not the control group. It is concluded that further samples would be needed to find a significant difference in MDA concentrations.

Adult↗

PubMed2001

[Age related macular degeneration. A widespread disease].

Age-related macular degeneration, AMD, is the commonest cause of legal blindness in the industrialised world. Epidemiological data suggest that in Denmark more than 80,000 persons suffer impaired vision in at least one eye, because of AMD. More than 4000 are legally blind owing to this disease. AMD has two major phenotypes: wet and dry. Most severe visual losses are caused by wet AMD, where new blood vessels form under the macula. A new treatment of this condition is now available. Photodynamic therapy with verteporfin has been investigated in a double-blind, randomised clinical trial with more than 600 patients. This study has been scrutinised by a Cochrane review, which has recommended criteria for the treatment. For eyes meeting these inclusion criteria, photodynamic therapy can reduce the occurrence of moderate and severe visual loss over a two-year period by more than 60%. It is estimated that around 1000 eyes in Denmark will meet the inclusion criteria for photodynamic therapy.

Age Factors↗

PubMed2001

Effectiveness of grazing management in controlling gastrointestinal nematodes in weaner lambs on pasture in Denmark.

A dose and move to clean pasture strategy for nematode control in weaner sheep was compared to a move only strategy. Sixteen ewes with twin lambs (2-3 weeks old) were turned out on infected pasture on 4 May 1999. On 1 July, the lambs were allocated to four groups of eight and weaned on to clean pasture. Two groups (DM1+2) were treated with anthelmintics, while the other two (M1+2) were not treated. Each group was allocated to a separate paddock and set stocked until 27 September when all the animals were slaughtered to perform worm counts. Moving the weaned lambs to clean pasture reduced the faecal egg counts to less than one third within 4 weeks while the treatment reduced it to zero for 4 weeks. Faecal egg counts of the dose and move groups remained significantly lower for 6 weeks (P<0.0001) after moving to the clean pasture. After this period the differences were not significant as the dose and move groups started shedding eggs in faeces. The pasture infectivity was lower in the paddocks grazed by groups (DM1+2). The weight gains and the serum albumin levels were comparable in all four groups. O. circumcinta and Trichostrongylus vitrinus were the major species recovered. The total worm counts were significantly lower in (DM1+2) compared to M1+2, particularly the mean counts in the small intestines (T. vitrinus) (P<0.01). It was concluded that weaning lambs at the beginning of July and moving them before the expected mid-summer rise in herbage infection to a clean pasture will prevent parasitic gastroenteritis and achieve good production whether the move is accompanied by anthelmintic treatment or not. The effects will be subject to prevailing nematode species, local climatic conditions and length of the grazing season.

Animal Feed↗

PubMed2001

Kluyveromyces lactis cytoplasmic plasmid pGKL2: heterologous expression of Orf3p and proof of guanylyltransferase and mRNA-triphosphatase activities.

The predicted ORF3 polypeptide (Orf3p) of the linear genetic element pGKL2 from Kluyveromyces lactis was expressed in Bacillus megaterium as a fusion protein with a His(6X)-tag at the C-terminus for isolation by Ni-affinity chromatography. This is the first time that a yeast cytoplasmic gene product has been expressed heterologously as a functional protein in a bacterial system. The purified protein was found to display both RNA 5'-triphosphatase and guanylyltransferase activities. When the lysine residue present at position 177 of the protein within the sequence motif (KXDG), highly conserved in capping enzymes and other nucleotidyl transferases, was substituted by alanine, the guanylyltransferase activity was lost, thereby proving an important role for the transfer of GMP from GTP to the 5'-diphosphate end of the mRNA. Our in vitro data provides the first direct evidence that the polypeptide encoded by ORF3 of the cytoplasmic yeast plasmid pGKL2 functions as a plasmid-specific capping enzyme. Since genes equivalent to ORF3 of pGKL2 have been identified in all autonomous cytoplasmic yeast DNA elements investigated so far, our findings are of general significance for these widely distributed yeast extranuclear genetic elements.

Acid Anhydride Hydrolases↗

PubMed2001

Anthelmintic resistance on goat farms in Georgia: efficacy of anthelmintics against gastrointestinal nematodes in two selected goat herds.

Gastrointestinal nematode (GIN) parasitism is a major constraint to production of goats in the southeastern United States. The conventional method of control used by producers in this region is frequent use of anthelmintics during the warm season. Overuse of anthelmintics has led to an increase in the incidence of anthelmintic resistance in many parts of the world, but data on prevalence of anthelmintic resistance in GIN of goats in the southeastern United States are very limited. To address this issue, anthelmintic efficacy was determined in goat herds at the Fort Valley State University, Agricultural Research Station (FVSU-ARS) and the University of Georgia, College of Veterinary Medicine (UGA-CVM) using fecal egg count reduction (FECR) tests and DrenchRite((R)) larval development assays (LDA). At FVSU-ARS, 2-year-old Spanish goat does were randomly allocated to one of nine different treatment groups (n = 10): albendazole (ABZ; 20mg/kg body weight (BW)), fenbendazole (FBZ; 20mg/kg BW), ivermectin (IVM; 0.4 mg/kg BW), doramectin (DRM; 0.4 mg/kg BW), moxidectin (MOX; 0.4 mg/kg BW), levamisole (LEV; 12 mg/kg BW), morantel tartrate (MOR; 10mg/kg BW), a combination of IVM (0.4 mg/kg BW) and ABZ (20 mg/kg BW), and untreated controls. At UGA-CVM, goats were randomly allocated to one of five different treatment groups (n = 8): ABZ (20 mg/kg BW), IVM (0.4 mg/kg BW), MOX (0.4 mg/kg BW), LEV (12 mg/kg BW), and untreated controls. All drugs in both experiments were administered orally. Anthelmintic efficacy was calculated by comparing 14-day post-treatment FEC of treated and control animals, and percent reductions were interpreted using the World Association for the Advancement of Veterinary Parasitology guidelines for resistance. For the LDA, nematode eggs were isolated from pooled fecal samples of untreated control goats in each herd and used to perform DrenchRite((R)) assays. In the FVSU-ARS herd, MOX, LEV, the combination of IVM and ABZ, IVM, DRM, ABZ, MOR, and FBZ reduced FEC by 100, 91, 88, 78, 76, 62, 48, and 10%, respectively. In the UGA-CVM herd, MOX, LEV, ABZ and IVM, reduced FEC by 100, 94, 87, and 0%, respectively. In both herds moxidectin was the only drug tested that was fully effective. Results of the LDA were in agreement with results of the FECR tests for both herds. These data demonstrate the presence of GINs resistant to all three major anthelmintic classes in both goat herds.

Animals↗

PubMed2001

Genome organization of the linear cytoplasmic element pPE1B from Pichia etchellsii.

The linear cytoplasmic element pPE1B from Pichia etchellsii CBS2011 (synonym Debaryomyces etchellsii) was totally sequenced. It consists of 12835 bp and has a remarkable high A+T content of 77.3%. The termini of pPE1B were found to consist of inversely orientated identical nucleotide repetitions 161 base pairs long, to which proteins are probably covalently linked at the 5' ends. Ten putative genes (open reading frames, ORFs) were identified, covering 96.5% of the total sequence. The predicted polypeptides correspond to proteins encoded by ORFs 2-11 of the linear plasmids pGKL2 of Kluyveromyces lactis and pSKL of Saccharomyces kluyveri. ORF1, existing on both latter elements, is lacking on pPE1B. An upstream conserved sequence motif (UCS) is located at the expected distance from the start codon of each of the 10 ORFs. As the arbitrarily chosen UCS6 was able to drive expression of a reporter gene in the heterologous pGKL-encoded killer system of K. lactis, extranuclear promoter function is probable. The almost congruent genome organization of pPE1B and other autonomous linear yeast plasmids sequenced so far, i.e. pGKL2 and pSKL, suggests a common, presumably viral, ancestor.

Base Sequence↗

PubMed2001

Small intestinal digestibility of microbial and endogenous amino acids in dairy cows.

The small intestinal digestibility of microbial amino acids and the apparent re-absorption of endogenous amino acids were estimated in three ruminal, duodenal and ileal fistulated lactating dairy cows. The cows were assigned to a 3 x 3 Latin square and fed diets low in amino acids, composed of straw, starch, molasses and urea. The treatments were three straw to concentrate ratios. The digestibilities and re-absorptions were estimated from duodenal and ileal flows of amino acids from feed, microbial and endogenous sources. The duodenal distribution of amino acids between different origins was determined by the difference method and by the amino acid profile method. The ileal distribution was estimated by a simple method where the feed fraction was estimated by the mobile bag method, the endogenous fraction as the water soluble fraction and the microbial fraction as the rest. In ileal samples, 8.0 +/- 1.1, 52.2 +/- 2.9 and 39.8 +/- 2.6% of total amino acid nitrogen (AAN) were of feed, microbial and endogenous origin, respectively, compared with 5.1 +/- 0.9, 61.6 +/- 6.6 and 32.7 +/- 6.9% in duodenal samples. The small intestinal digestibility of microbial AAN was estimated to be 75.1 +/- 1.8% and the apparent re-absorption of endogenous AAN to be 62.3 +/- 11.1%.

Amino Acids↗

PubMed2001

Effects of pseudophakic lens capsule opacification on optical coherence tomography of the macula.

PURPOSE: To report observations on the influence of posterior lens capsule opacification on optical coherence tomographic imaging quality and measurements of macular thickness. METHODS: The retrospective study included 13 eyes in 12 patients of which 2 eyes had a healthy macula and 11 eyes had maculopathy. In all eyes posterior lens capsule fibrosis was present. A clinical examination including biomicroscopy of the macula and an in-vivo macular optical coherence tomography (OCT) before and after YAG-laser membranotomy had been performed. RESULTS: Foveal retinal thickness before and after membranotomy were highly correlated (R = 0.98), and no systematic difference was found between values obtained before vs. after membranotomy (mean thickness 318.7 +/- 92.7 microm vs. 322.2 +/- 97.4 microm; p = 0.221). The signal-to-noise ratio increased in 11 out of 13 eyes after membranotomy (mean signal-to-noise ratio before 47.1 +/- 6.6 dB vs. 52.6 +/- 4.0 dB after; p = 0.004, the change ranging from -1.5 dB to 17 dB). CONCLUSIONS: The qualitative effect of the posterior lens capsule opacification on the OCT-scan consists primarily of a loss of signal and consequently of intraretinal detail, whereas total foveal retinal thickness seems to be reliably assessed even when posterior lens capsule opacification interfering with the biomicroscopic evaluation of retinal edema are present. YAG-laser membranotomy results in a measurable improvement in the OCT signal-to-noise ratio, but OCT seems to yield reliable measurements of foveal retinal thickness before treatment. Consequently the OCT seems to reliably diagnose a macular thickening although not the type of this until after removal of the posterior lens capsule opacification.

Adult↗

PubMed2001

Passive permeability and outward active transport of fluorescein across the blood-retinal barrier in early ARM.

AIM: To study the passive and active transport of fluorescein across the blood-retina barrier in early age related maculopathy (ARM) (soft drusen > 63 microm, hyperpigmentation and/or hypopigmentation in patients above 50 years of age). METHODS: 15 patients and 10 healthy subjects were included. Morphological changes were graded from 30 degrees fundus photographs using a simplified version of the epidemiological ARM study group classification system. Differential vitreous spectrofluorophotometry was used to assess the transport properties of the blood-retina barrier (that is, passive permeability and unidirectional permeability caused by outward active transport from the vitreous to the blood). RESULTS: The passive permeability of the patient group was not significantly different from that of the control group. Four patients with passive permeability more than 3 SD above the mean of the control group (mean 1.8 (SD 0.7) nm/s, range 1.0-3.0 nm/s, data normally distributed) all had centrally located drusen > 500 microm and superjacent pigment clumps of 63-500 microm in diameter. There was no significant difference between the unidirectional permeabilities for the patient group and for the control group (mean 47.4 (29.3) nm/s, range 12.7-91.1 nm/s). CONCLUSION: There was no significant difference in the passive permeability and in the unidirectional permeability of fluorescein. However, the study may indicate that the combination of very large drusen and superjacent pigment clumps in ARM may be associated with a deterioration of the blood-retina barrier.

Aged↗

PubMed2001

Protein standardization IV: Value transfer procedure for the assignment of serum protein values from a reference preparation to a target material.

A new approach for the assignment of values to serum proteins in a target material using a reference preparation has been developed. The procedure describes the general as well as the practical principles involved in the value assignment (with examples). Two models have been developed: 1) The direct value transfer between serum matrices and 2) the indirect value transfer from a pure protein preparation to a serum protein material. The necessary mathematical equations are developed and explained. The data reduction and statistical evaluation are discussed. The practical procedure (the transfer protocol) is based on six dilutions of the reference preparation assayed together with six dilutions of the target material. In this way imprecision is reduced and the proportionality of the two materials (i.e. the presence or absence of matrix effects) can be assessed directly by evaluating a single regression plot. If no matrix effects are found, the regression line will pass through zero with a slope equal to the ratio of the concentrations of the two materials. The transfer protocol is based on a multiple point value assignment obtained by several measurements a day repeated on several days, an important prerequisite being that all reconstitutions and dilutions are controlled by weighing.

Blood Proteins↗