Search PubMed⌕ Search

Biomedical subjects

M Larsen

Publications and source records attributed to M Larsen.

At least 127 records · Page 7Linked to original sources
PubMed1994

An attempt to implement the nematode-trapping fungus Duddingtonia flagrans in biological control of trichostrongyle infections of first year grazing calves.

An attempt was made to control Ostertagia ostertagi by feeding the nematode-trapping fungus Duddingtonia flagrans (DSM 6703) to grazing calves. One group of calves (group E) was fed the fungal material in the first two months of the grazing season while another group was a non-treated control group (group C). Group E showed significantly lower faecal egg count in August and September. On four occasions in July and September, the herbage larval counts were significantly lower on the plot with the fungal-treated group than those recorded on the control plot. The average abomasal larval and adult worm counts were significantly reduced in August in group E and the average total worm count in the abomasum of group E was reduced by 87% in August compared to the non-treated group C. In October, the difference in average abomasal worm counts between group E and C was insignificant. Due to weight loss at the end of the grazing season, the control group showed a significantly lower average weight increase.

Abomasum↗
PubMed1994

Fluorescein transport across the human blood-retina barrier in the direction vitreous to blood. Quantitative assessment in vivo.

Inward and outward movement of flourescein across the human blood-retina barrier was studied in five healthy volunteers, using a differential spectrofluorometry method that eliminates the contribution of fluorescein glucuronide to the total fluorescence in the vitreous and in plasma. The inward permeability across the blood-retina barrier, which is presumed to be passive, and the diffusion coefficient in the vitreous for fluorescein was calculated from data obtained 1 h after intravenous injection of fluorescein. The rate of elimination of fluorescein from the vitreous across the blood-retina barrier was estimated from data obtained 7 to 12 h after injection of fluorescein. The calculations were based upon the free plasma fluorescein decay curve and the preretinal fluorescein gradient in the vitreous. The mean inward permeability of fluorescein was 1.39 x 10(-7) cm/sec (range: 0.70-2.06 x 10(-7) cm/sec), whereas the mean outward permeability was 1.51 x 10(-5) cm/sec (range: 1.14-1.73 x 10(-5) cm/sec). We have thus found that the movement of fluorescein across the blood-retina barrier is highly asymmetric, the outward transport being more than 100 times faster than the passive inward leakage. This could indicate the presence of an active pumping mechanism in the blood-retina barrier, responsible for fluorescein transport in the direction from the vitreous to the blood.

Biological Transport, Active↗
PubMed1994

Probenecid inhibition of the outward transport of fluorescein across the human blood-retina barrier.

The effect of probenecid on the outward transport of fluorescein from vitreous to blood was studied in 13 insulin-dependent diabetic patients with background retinopathy in a randomised double-masked placebo controlled cross-over study. Fluorescein and fluorescein glucuronide was separated in the vitreous and in plasma by differential spectrofluorometry. The data for fluorescein were analysed using a simplified mathematical model of the eye. The inward permeability was estimated from data obtained 1 h after injection and the outward transport from data obtained 7 h after injection. During placebo treatment the mean inward permeability was 3.75 x 10(-7) cm/sec and the mean outward permeability was 2.25 x 10(-5) cm/sec. During probenecid treatment the mean inward permeability was 3.34 x 10(-7) cm/sec and the mean outward permeability was 1.44 x 10(-5) cm/sec. Thus, we found no significant change in inward permeability (p = 0.5879), whereas a significant decrease of 36% was found in the outward permeability of fluorescein (p = 0.0171). The demonstration that the outward permeability, which is more than 100-fold higher than the inward permeability in the healthy eye, is significantly decreased by probenecid, demonstrates that active transport is involved in movement of fluorescein across the blood-retina barrier from the vitreous to the plasma.

Adult↗
PubMed1994

Absence of foveal avascular zone demonstrated by laser scanning fluorescein angiography.

We present laser scanning fluorescein angiograms of abnormal foveal capillary patterns in a healthy subject and an insulin-dependent diabetic patient with mild diabetic retinopathy. In both subjects capillaries were seen to cross the central foveal area where capillaries are usually absent. The flow pattern of the foveal capillaries, which were visualised with the use of a laser scanning ophthalmoscope, was indistinguishable from that of the more peripheral capillaries, indicating that foveal vessels are functionally normal retinal capillaries. The two cases demonstrate that identification of abnormal capillary patterns induced by retinal disease such as diabetic retinopathy is made difficult by the marked interindividual variation in capillary anatomy. In prospective studies, however, the method may be capable of detecting subtle changes in early diabetic retinopathy with a high degree of sensitivity.

Adult↗
PubMed1994

Early changes in diabetic retinopathy: capillary loss and blood-retina barrier permeability in relation to metabolic control.

In diabetic retinopathy capillary loss and blood-retina barrier leakage are prominent factors. We present a study with quantitative measurements of both capillary loss and leakage and their relation to cumulative metabolic control. Seventeen insulin-dependent diabetic patients with no retinopathy or only mild background retinopathy and 10 years' duration of the disease were included in the study. Status of metabolic regulation had been followed for at least 6 years. Seven healthy subjects were included as controls. In diabetic patients the perifoveal intervascular areas were found to increase significantly with the cumulative HbA1c index (p = 0.02) and in relation to the presence of moderate background retinopathy (p < 0.02). The blood-retina barrier leakage and the area of the foveal avascular zone were not significantly different from healthy subjects and no correlation was found between the HbA1c index and blood-retina barrier permeability. We conclude that perifoveal capillary loss occurs early in the course of diabetic retinopathy and that this loss is related to prior glycemic control and to the ophthalmoscopic retinopathy level.

Adult↗
PubMed1994

Evaluation of canines for accelerant detection at fire scenes.

In recent years, canines have been successfully used in fire investigations to detect accelerant residues. We set out to determine the lower limits at which canines could reliably detect potential accelerants. Measured amounts ranging from 10 to as little as 0.01 microL of gasoline, kerosene, and isopars were applied to preselected spots along a continuous sample path (25 to 40 feet long) made out of burned and unburned wood or nylon carpeting strips at the testing site. Two canines were led past this sample path at least three times and positive alerts and negative responses were recorded. Both dogs were generally able to alert on spots containing 0.01 microL or more of all three accelerants, at or beyond the purge and trap recovery and gas chromatographic detection method employed. The canines did alert occasionally on background, especially that containing traces of styrene residues, either purposely added in specific amounts or formed upon partial pyrolysis of carpeting material. The dogs alerted on sites containing 0.1 to 1.0 microL of freshly applied gasoline or kerosene placed at actual heavily damaged fire scenes, but were less successful on samples containing smaller amounts.

Animals↗
PubMed1993

The role of nematophagous fungi in the biological control of nematode parasites of livestock.

The control of nematode parasites of livestock is presently based entirely on anthelmintic treatment and grazing management. On their own, these methods are not sustainable because parasites invariably develop resistance to anthelmintics and because of increasing public concern about chemical residues in livestock products and the environment. Although alternative, non-chemotherapeutic control strategies, such as vaccines and genetic selection for resistance are the focus of considerable research activity worldwide, biological control of nematode parasites has been virtually ignored. The little work that has been done is restricted largely to western Europe and involves virtually just one fungal species, namely Arthrobotrys oligospora. More recent studies indicate other known nematophagous fungal species are more efficient predators of infective larvae in sheep faeces than A. oligospora, and others have a greater capacity to survive passage through the gastrointestinal tract of ruminants. These findings plus the relatively sparse numbers of microbial competitors in the fresh faecal environment, compared with the plant rhizosphere where biological control of plant parasites is proving a particularly intractable problem, engenders optimism that the biological control of animal parasitic nematodes may become a practical reality. Such control will never be a substitute for chemotherapy, where the primary purpose is worm removal from the host, but should be incorporated together with other options into integrated pest management systems to provide sustainable nematode control of livestock into the twenty-first century.

Animals↗
PubMed1993

Biological control of nematode parasites in cattle with nematode-trapping fungi: a survey of Danish studies.

In Denmark two series of experiments have been performed to study the interactions between larvae of bovine gastrointestinal nematode parasites and nematode-trapping fungi. For practical reasons we were interested in the possibility of depositing nematode-trapping fungi in cattle faeces after passage through the gastrointestinal tract. In the first series, laboratory tests with the fungus Arthrobotrys oligospora showed that motile free-living larvae of a wide range of animal-parasitic nematodes and some soil-living nematodes effectively induce the formation of traps. Larvae of all parasitic nematodes are rapidly captured in these traps. The induction of nets was influenced by temperature, number of larvae, atmosphere, light, and media composition. Captured first- and second-stage larvae were quickly penetrated and killed while third stage larvae were killed slowly, perhaps because they are partially protected by an outer dead sheath. Laboratory and field studies showed that when A. oligospora material was directly mixed into dung a significant reduction in the number of infective parasite larvae in the dung and surrounding herbage occurs. This reduction was also reflected in the acquired worm burden of calves grazing on fungal treated pasture. However, the A. oligospora strain studied in the above mentioned experiments did not survive passage through the alimentary tract of cattle. This prompted us to start a second series of experiments to isolate fungi that could survive gut passage of cattle. Different soil and compost samples were screened by an in vitro stress selection technique. This simulated certain important stress factors which occur during passage through the alimentary tract of ruminants. Rumen exposure was found to be a major limiting factor, but some Arthrobotrys and Duddingtonia strains survived submersion in rumen fluid. In a subsequent in vivo experiment, some of these survivors were fed to calves, and it was hereby demonstrated that isolates of both genera, i.e. Arthrobotrys and Duddingtonia, were able to survive passage through calves and significantly reduce the number of developing preparasitic larvae in dung of fungal treated calves. In a controlled field experiment, isolates of Duddingtonia reduced the level of infective third-stage larvae in herbage by 74-85%.

Animals↗
PubMed1993

Biological control of Ostertagia ostertagi by feeding selected nematode-trapping fungi to calves.

Three nematode-trapping fungi, one Arthrobotrys oligospora and two Duddingtonia flagrans isolates, were fed to Ostertagia ostertagi-infected calves to test their ability to destroy larvae of this parasite in faeces and consequently to reduce the transmission of infective larvae to herbage. The fungi had previously been selected for their capability to pass the alimentary tract of cattle without losing growth and nematode-trapping potentials. Dung was collected from three calves each fed one of the three fungi and placed as 1-kg cow pats on a parasite-free grass plot together with control cow pats from a calf that was not given fungi. The cow pats contained comparable concentrations of parasite eggs. The two D. flagrans isolates were highly effective in that they reduced herbage larval infectivity by 74-85%. In contrast, A. oligospora did not show any effect in the present experiment. Field experiments will demonstrate if D. flagrans represents a potential organism for biological control of bovine gastrointestinal nematodes under practical agricultural management conditions.

Animals↗
PubMed1993

Interferon alpha-2a treatment of patients with subfoveal neovascular macular degeneration. A pilot investigation.

It has recently been suggested that interferon alpha-2a has a beneficial effect on exudative age-related macular degeneration (AMD). So far, results are controversial, and masked, placebo controlled, randomized studies with well-defined inclusion criteria are required to assess the effect of interferon alpha-2a. In preparation for such a study we performed a pilot investigation that included 5 patients with subfoveal neovascularizations. All patients received interferon alpha-2a (Roferon-A, Hoffmann La-Roche) 1.5 mio, IU subcutaneously every second day for 8 weeks. Improved visual acuity was subjectively observed by 4 patients and objectively by 3 patients. Two patients showed decreased central visual field defect. Fluorescein angiography and fundus photography showed ambiguous changes. Amsler chart and contrast sensitivity also showed heterogenous results. Even though the treatment with interferon alpha-2a may show some positive effect, our results are not unequivocal and serve to underline the need for controlled studies before the effect of interferon alpha-2a on neovascular AMD can be reliably assessed.

Adult↗
PubMed1993

Asian affinities and continental radiation of the four founding Native American mtDNAs.

The mtDNA variation of 321 individuals from 17 Native American populations was examined by high-resolution restriction endonuclease analysis. All mtDNAs were amplified from a variety of sources by using PCR. The mtDNA of a subset of 38 of these individuals was also analyzed by D-loop sequencing. The resulting data were combined with previous mtDNA data from five other Native American tribes, as well as with data from a variety of Asian populations, and were used to deduce the phylogenetic relationships between mtDNAs and to estimate sequence divergences. This analysis revealed the presence of four haplotype groups (haplogroups A, B, C, and D) in the Amerind, but only one haplogroup (A) in the Na-Dene, and confirmed the independent origins of the Amerinds and the Na-Dene. Further, each haplogroup appeared to have been founded by a single mtDNA haplotype, a result which is consistent with a hypothesized founder effect. Most of the variation within haplogroups was tribal specific, that is, it occurred as tribal private polymorphisms. These observations suggest that the process of tribalization began early in the history of the Amerinds, with relatively little intertribal genetic exchange occurring subsequently. The sequencing of 341 nucleotides in the mtDNA D-loop revealed that the D-loop sequence variation correlated strongly with the four haplogroups defined by restriction analysis, and it indicated that the D-loop variation, like the haplotype variation, arose predominantly after the migration of the ancestral Amerinds across the Bering land bridge.

Americas↗
PubMed1993

Ocular fluorometry methodological improvements and clinical studies--with special reference to the blood-retina barrier permeability to fluorescein and fluorescein glucuronide.

The measurement of fluorescence in the human eye can be made using relatively simple instruments. Fluorescence is evoked when illumination is absorbed by intrinsic fluorophores in the eye or by artificially introduced extrinsic fluorophores. Intrinsic fluorescence is evidence of important molecular characteristics of the ocular tissues, whereas the extrinsic fluorophores are used primarily in the study of the barriers between the anatomical and physiological compartments of the eye. Blood-retina barrier leakage of fluorescein can be examined after the intravenous injection of fluorescein by quantitative determination of fluorescence in plasma and in the vitreous. From these measurements of the distribution of fluorescein, the permeability of a hypothetical spherical interface between the blood and the retina can be estimated using a mathematical model of the barrier. The use of fluorescein as a tracer is problematic because of its rapid metabolic conversion to fluorescein glucuronide. This metabolite disturbs ocular fluorescence measurements because it fluoresces over the same part of the spectrum as the parent compound. Additionally, the glucuronide occurs in markedly different concentrations depending upon the patient's renal function. With the previously used fluorometry techniques it has been impossible to determine the contribution of fluorescein glucuronide to the vitreous fluorescence. The primary objective of the studies described in this thesis was to develop a method for the determination of fluorescein and fluorescein glucuronide in the human eye and in plasma, and to calculate the blood-retina barrier permeabilities of the two substances. The necessary methodological improvements included a detailed description of the geometrical optics of the eye and the optical filter properties of the lens. A new method was developed for the determination of the spatial locations of ocular fluorescence measurements and the intrinsic lens fluorescence was used to estimate lens transmittance. The new techniques were applied to clinical studies in patients with diabetic retinopathy. It was shown that in insulin-dependent diabetes mellitus, the apparent rate whereby fluorophores are accumulated in the lens is increased in inverse proportion to the quality of metabolic control, i.e. patients who have had consistently poor control have higher fluorescence than patients who have been in good control. An increase in lens fluorescence was also found in the presence of diabetic nephropathy. The results support the assumption that lens fluorometry can provide a rough estimate of cumulative glycaemia and that glucose is involved in certain age-related changes in the lens.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1992

[Physical causes of accidental falls among the elderly in their own homes].

Accidental falls in elderly persons involve considerable illness and great hospital costs. During the period 1971-1986, the incidence has risen from 14 to 19 per 1000 annually. Four hundred and seventy-three individuals aged 60 years or more who had fallen in their own homes and who sought help in Odense Hospital after the accident were interviewed consecutively. The replies to these interviews described the circumstances involved in the fall together with the health and social conditions. Women constituted 78% of the material with preponderance of people living alone as compared with the background population. Just under half of the patients had had a previous fall. Fractures were sustained in 40% of the cases. In 51% of the cases, a definite or probable external circumstance was the cause of the fall. In 150 out of 237 accidental falls, caused by external circumstances, the accident was considered to have been preventable by means of eg more accessible lighting, non-slip carpeting, removal of doorsteps, more suitable arrangement of furniture and better supportive measures beside stairs. The risk of falling is found to increase markedly in persons aged 75 years or more. Prophylactic measures are recommended before patients reach this age by means of information to elderly persons and to persons involved in home care about situations involving risks.

Accidental Falls↗
PubMed1992

HIV infection at outcome of pregnancy in the Paris area, France.

The prevalence of HIV infection in women at end of pregnancy, irrespective of outcome, was determined in a comprehensive survey of both women and medical centres during successive 4-week periods in four areas of the Paris region, France. Blood samples were tested anonymously for antibodies to human immunodeficiency virus (HIV)-1 and HIV-2. Of the 11,593 blood samples 0.40% (95% confidence interval [CI] 0.28-0.51) were positive for HIV-1 and 0.02% (95% binomial interval [BI] 0.002-0.065) for HIV-2. Seroprevalence was higher among women with ectopic pregnancy (2%) (95% BI 0.24-7.04); the rate in women having an elective or therapeutic abortion was more than twice that in those delivering babies (0.70% vs 0.28%, p less than 0.05, relative risk 2.54, 95% CI 1.36-4.75). Studies with neonatal HIV seroprevalence as a surrogate for HIV prevalence in pregnant women would underestimate prevalence in these women.

Abortion, Therapeutic↗
PubMed1992

Lens fluorescence in relation to nephropathy in insulin-dependent diabetes mellitus.

The relationship between diabetic nephropathy and blue-green lens fluorescence, lens transmittance, and other lens fluorometry parameters was studied in patients with long-term insulin-dependent diabetes mellitus. The findings in 10 patients who presented with diabetic nephropathy were compared with those of 11 patients of comparable age and duration of diabetes but without nephropathy. Diabetic nephropathy was associated with increased lens fluorescence (P = 0.04) and decreased lens transmittance (P = 0.045). We propose that lens changes may be responsible for various psychophysical abnormalities in diabetic patients and that our results explain the correlation of these abnormalities with the degree of microangiopathy.

Adult↗
PubMed1992

In vivo passage through calves of nematophagous fungi selected for biocontrol of parasitic nematodes.

The experiment was designed to test the survival and performance of stress selected nematophagous fungi after passage through the gastro-intestinal tract of cattle. Ruminating calves were fed daily with a fixed amount of fungal material grown on barley grains. The excreted dung was collected on days four and five after the start of the feeding experiment. Barley grains were washed out of the excreted dung and incoculated on water-agar plates. After incubation for one week, nine of ten fungal isolates were re-isolated from these plates. The predatory capacity of the fungi in the excreted faeces was tested in a dung pat bioassay and a faecal culture system. In the dung pat bioassay, two fungi of the genus Arthrobotrys and six of the genus Duddingtonia reduced the development of Ostertagia ostertagi third stage larvae by 85% (61%-93%), compared to the number of larvae developed from fungus-free control pats. In seven out of these eight isolates, the reduction of larvae in the faecal cultures was 92% (76%-99%).

Animals↗