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J Dijkstra

Publications and source records attributed to J Dijkstra.

At least 55 records · Page 3Linked to original sources
PubMed1996

Activation of murine lymphocytes by lipopolysaccharide incorporated in fusogenic, reconstituted influenza virus envelopes (virosomes).

We have studied the in vitro activation of murine lymphocytes with LPS incorporated in the membranes of both phospholipid vesicles (liposomes) and vesicles composed of fusogenic, reconstituted influenza virus envelopes (virosomes). The incorporation of Salmonella minnesota rough-LPS in liposomes reduced the potency of LPS to stimulate splenocyte proliferation and cell surface kappa-light chain expression on 70 Z/3 pre-B cells by over 100-fold. Salmonella minnesota rough-LPS inserted into virosomes was at least 10-fold more potent than free LPS, both when prebound virosomes were allowed to be taken up by the cells at neutral pH and when the virosomes were fused into the plasma membrane by low pH treatment. Inactivation of the virosomes by low pH pretreatment reduced the potency of the virosomal LPS to the level of liposome-incorporated LPS. The association of the various LPS forms with the cells was quantitated using radio-iodinated LPS. Correcting for uptake, virosomal LPS remained 2- to 10-fold more potent than free LPS in stimulating B lymphocytes and at least 100-fold more active than liposomal LPS or fusion-inactivated virosomes. After low pH-induced fusion with the plasma membrane, the majority (80%) of the prebound virosomes had fused with the cells, compared with about 8% after neutral uptake. From these results we conclude that LPS inserted into the plasma or endosomal membranes efficiently activates murine lymphocytes. The fusion data suggest that the incorporation into endosomal membranes might be a more effective stimulus.

Animals↗
PubMed1996

A simple but flexible growth function.

The functional form W(t) = Wf - (Wf - Wo) exp[-k infinite (t - T) + 2c(root of t - root of T)] where Wf, Wo, k infinite, c and T are constants, is derived as a growth equation and evaluated using commonly applied growth functions such as the Gompertz, logistic, monomolecular and Richards. Further evaluation is made with reference to sets of observations on growth in a number of animal species ranging from mice to horses. The new function provides a flexible growth equation capable of describing sigmoidal and diminishing returns behaviour. It appears adept at describing sigmoidal patterns exhibiting faster early growth and a fairly low but variable point of inflexion, and can therefore be perceived as a generalised Gompertz equation. The function also has the ability to describe a wide range of hyperbolic shapes when there is no point of inflexion. The analysis described suggests that this simple equation is a worthwhile addition to the corpus of growth functions.

Animals↗
PubMed1995

Analysis of anticholesterol antibodies using hydrophobic membranes.

An analytical immunoblotting procedure and a serological enzyme-linked immunosorbent assay (ELISA) for the characterization of antibodies to cholesterol are described. Hydrophobic membranes consisting of polyvinylidene fluoride (PVDF) are used to immobilize cholesterol for immunodetection by anti-sterol antibodies. To determine whether antibodies to cholesterol were induced after immunization with liposomal cholesterol, we separated total lipid extracts of very-low density lipoproteins by thin layer chromatography (TLC) on silica gel plates and transferred the separated lipid classes to PVDF membranes using isopropanol to facilitate passive diffusion. Lipid transfer was confirmed by exposure of membranes to iodine vapors or by staining of cholesterol with filipin complex. Serum from immunized mice reacted with cholesterol, whereas pre-immune serum or serum from mice injected with control liposomes did not bind. To determine the amount of anti-cholesterol activity in serum, we coated microtiter plates consisting of PVDF membrane wells with cholesterol. The PVDF membrane-based ELISA was found to be more reproducible and four-fold more sensitive than the conventional ELISA on polystyrene plates. These techniques may be useful in the analysis of anti-sterol antibodies and antibodies to other hydrophobic antigens.

Antibodies↗
PubMed1995

Liposomal vaccines.

Liposomes have been used therapeutically to deliver drugs to certain anatomical sites. The use of liposomes to deliver antigens, although not a new concept, has received less attention. At least two vaccines of nearly identical liposome base composition to our vaccines have been tested in humans. A malaria vaccine study showed that the liposomal preparation is quite safe: reaction profiles of volunteers receiving the vaccine demonstrated little reactivity and virtually no pyrogenicity (14). The concentration of MPLA in the vaccine was substantially higher (nearly 50,000 times) than the pyrogenic dose of free lipid A. The same vaccine, but different antigen (gp120, an HIV protein), was tested in volunteers and had the same lack of toxicity (27). In both studies, antibodies and cytotoxic cells specific for the respective antigens were produced. We have several subunit vaccines under development for infectious diseases (gram negative sepsis, fungal infections, protozoan infections), metabolic disorders (hypercholesterolemia, diabetic retinopathy, macular degeneration), and neoplastic diseases (multi-drug resistant cancer, primary and metastatic tumors, and angiogenic hyperproliferative disorders). In each case, one or more antigens were identified that might be useful in immunologic control of biologic proliferation (i.e., pathogen or tumor growth, rise in serum cholesterol, growth of blood vessels). We anticipate that at least one of these vaccines will be ready for testing in humans in the next calendar year.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Simulation of the effects of diet on the contribution of rumen protozoa to degradation of fibre in the rumen.

A previously described mathematical model, that stimulates the metabolic activities of rumen bacteria and protozoa, was used to examine the contribution of protozoa to neutral-detergent fibre (NDF) degradation in the rumen of cattle. Comparisons between predicted and experimentally observed NDF degradation showed general agreement. Further simulations were performed with diets containing variable proportions of concentrate (between 0 and 1 kg/kg diet DM) and at intake levels ranging between 5.3 and 21.0 kg DM/d. The simulated protozoal contribution to NDF degradation was 17-21% at the lowest intake level. Except for the all-concentrate diets, raising the feed intake level reduced this contribution to 5-13% at the highest intake level. The changes in contribution of protozoa to NDF degradation were related to variations in the fibrolytic bacteria: protozoa value and the NDF-degrading activities of protozoa predicted by the model. In simulations where dietary NDF levels were reduced and starch and sugar levels were increased independently, protozoal contribution to NDF degradation generally increased. These differences were reflected also in the generally increased protozoal contribution to NDF degradation predicted in response to a decreased roughage:concentrate value. The contribution of protozoa also generally declined in response to added N. These changes in predicted protozoal contribution to NDF degradation resulting from dietary variations provided possible explanations for the differences in rumen NDF degradation observed when animals are defaunated.

Animal Feed↗
PubMed1995

Idiopathic inflammatory bowel disease: endoscopic-radiologic correlation.

PURPOSE: To assess the comparative and adjunctive diagnostic value of double-contrast barium enema examination (DCBE) and colonoscopy in cases of idiopathic inflammatory bowel disease. MATERIALS AND METHODS: Radiographic and endoscopic findings were correlated, with use of a standardized evaluation sheet, in a prospective, blinded study in 99 patients with previously well-established Crohn disease of the colon (CD [ n = 51]) or ulcerative colitis (UC [n = 48]). RESULTS: Overall, substantial to almost perfect agreement was found in more than 80% of scores with respect to the items of the standardized evaluation sheet in the colon segments depicted with both imaging modalities. Almost perfect agreement (kappa > 60%) was found for two essential diagnostic and differential diagnostic features: aphthoid erosions and fine granularity. CONCLUSION: DCBE and colonoscopy are complementary imaging modalities for optimal detection of all mucosal and structural colon lesions, except inflammatory lesions without distortion of the mucosal relief and small numbers of inflamed superficial erosions and ulcers.

Adolescent↗
PubMed1994

Distribution and localization of bean common mosaic virus and bean black root virus in stems of doubly infected bean plants.

Plants of bean (Phaseolus vulgaris) inoculated first on one primary leaf with strain NY15 of bean common mosaic virus, as inducer, and after three days, on the opposite leaf, with the strain NL3 of bean black root virus, as challenger, did not show systemic necrosis characteristic of the latter strain. This interference phenomenon was studied by determining the amount, distribution and localization of both strains in the part of stem between primary leaves and first trifoliolate leaf in both challenge-inoculated and singly inoculated (control) plants. In dot-blot immunoassay, NL3 was detected seven days after its inoculation as challenger, whereas in control plants its presence was established on day four. Immunostained thick sections revealed a large accumulation of NL3 antigen on day eight in both phloem and cambium, but not yet in the xylem and cortex, contrasted with the controls. In immunogold-silver stained semi-thin sections, most of the NL3 label was present in the companion cells and other phloem parenchyma cells, while in the control plants this virus was also present in xylem vessels and xylem parenchyma cells. Inducer strain NY15 was abundantly present in practically all the cells, including xylem vessels, from day two after challenge inoculation onwards. It is concluded that inducer strain NY15 hampers transport of NL3 to, and its spread in, the stem and prevents the latter strain from exerting its deleterious influence on the water conducting elements.

Fabaceae↗
PubMed1994

Cowpea aphid borne mosaic virus-Morocco and South African Passiflora virus are strains of the same potyvirus.

High performance liquid chromatography (HPLC) profiles of tryptic peptides and partial amino acid sequence analysis have been employed to establish the taxonomic status of the Moroccan isolate of cowpea aphid-borne mosaic virus (CABMV). Some previous reports have suggested CABMV to be very closely related to blackeye cowpea mosaic virus (B1CMV) while other reports have concluded that this relationship is distant. In this report a tryptic digest of the coat protein of CABMV-Morocco was compared with those of the coat proteins of B1CMV-Type, B1CMV-W, the mild mottle strain of peanut stripe virus (PStV-MM) and the NY15 strain of bean common mosaic virus (BCMV-NY15), all of which are now recognised as strains of BCMV. The comparisons also included the NL-3 strain of bean necrosis mosaic virus (BNMV-NL3), which had previously been classified as a strain of BCMV. The HPLC peptide profiles indicated that CABMV-Morocco was distinct from BCMV and BNMV. Amino acid sequence analysis of peptides accounting for more than half of the coat protein confirmed that CABMV-Morocco was not a strain of BNMV or BCMV but was a distinct member of the BCMV subset of viruses that previously has been shown to include BCMV, BNMV, soybean mosaic virus, zucchini yellow mosaic virus, passionfruit woodiness virus and South African Passiflora virus (SAPV). Comparison of the partial sequence data with these and other published sequences revealed that the coat protein of CABMV-Morocco is very similar to that of SAPV suggesting that they are strains of the same virus. Since CABMV was described over 25 years earlier than SAPV, the name CABMV should take precedence and SAPV should be renamed CABMV-SAP, the South African Passiflora strain of CABMV.

Amino Acid Sequence↗
PubMed1994

Simulation of the dynamics of protozoa in the rumen.

A modified mathematical model is described that simulates the dynamics of rumen micro-organisms, with specific emphasis on the rumen protozoa. The model is driven by continuous inputs of nutrients and consists of nineteen state variables, which represent the N, carbohydrate, fatty acid and microbial pools in the rumen. Several protozoal characteristics were represented in the model, including preference for utilization of starch and sugars compared with fibre, and of insoluble compared with soluble protein; engulfment and storage of starch; no utilization of NH3 to synthesize amino acids; engulfment and digestion of bacteria and protozoa; selective retention within the rumen; death and lysis related to nutrient availability. Comparisons between model predictions and experimental observations showed reasonable agreement for protozoal biomass in the rumen, but protozoal turnover time was not predicted well. Sensitivity analyses highlighted the need for more reliable estimates of bacterial engulfment rate, protozoal maintenance requirement, and death rate. Simulated protozoal biomass was increased rapidly in response to increases in dietary starch content, but further increases in starch content of a high-concentrate diet caused protozoal mass to decline. Increasing the sugar content of a concentrate diet, decreased protozoa, while moderate elevations of the sugar content on a roughage diet increased protozoal biomass. Simulated protozoal biomass did not change in response to variations in dietary neutral-detergent fibre (NDF) content. Reductions in dietary N resulted in an increased protozoal biomass. Depending on the basal intake level and dietary composition, protozoal concentration in the rumen was either increased or decreased by changes in feed intake level. Such changes in relative amounts of protozoal and bacterial biomass markedly affected the supply of nutrients available for absorption. The integration of protozoal, bacterial and dietary characteristics through mathematical representation provided an improved understanding of mechanisms of protozoal responses to changes in dietary inputs.

Animals↗
PubMed1993

Absorption of volatile fatty acids from the rumen of lactating dairy cows as influenced by volatile fatty acid concentration, pH and rumen liquid volume.

The effect of rumen liquid volume, pH and concentration of volatile fatty acids (VFA) on the rates of absorption of acetic, propionic and butyric acids from the rumen was examined in lactating dairy cows. Experimental solutions introduced into the emptied, washed rumen comprised two different volumes (10 or 30 l), four levels of pH (4.5, 5.4, 6.3, 7.2) and three levels of individual VFA concentrations (20, 50 or 100 mM-acetic, propionic or butyric acid). All solutions contained a total of 170 mM-VFA and an osmotic value of 400 mOsmol/l. Absorption rates were calculated from the disappearance of VFA from the rumen corrected for passage with liquid phase to the omasum. An increase in initial fluid pH caused a reduction in fractional absorption rates of propionic and butyric acids. Increasing the initial pH from 4.5 to 7.2 reduced fractional absorption rates of acetic, propionic and butyric acids from 0.35, 0.67 and 0.85 to 0.21, 0.35 and 0.28/h respectively. The fractional absorption rates of all VFA were reduced (P < 0.05) by an increase in initial rumen volume. The fractional absorption rate of acetic acid was lower (P < 0.05) at an initial concentration of 20 mM than of 50 mM. The fractional absorption rate of propionic acid tended (P < 0.10) to decrease as the level of concentration increased while fractional absorption rate of butyric acid was not affected by butyric acid concentration. These results indicate that relative concentrations of VFA in rumen fluid might not represent relative production rates and that attempts to estimate individual VFA production from substrate digestion must take account of pH and VFA concentration.

Acetates↗
PubMed1993

Sequence data to settle the taxonomic position of bean common mosaic virus and blackeye cowpea mosaic virus isolates.

The nucleotide sequences of the coat protein genes and 3' non-translated regions (3'-NTRs) of three isolates of bean common mosaic virus (NL1, NL3 and NY15) and one isolate of blackeye cowpea mosaic virus (W) were determined. Comparison of these sequences revealed that the coat proteins of NL1, NY15 and W were identical in size (287 amino acids) and exhibited an overall sequence similarity (94 to 97%), and 84 to 98% in their N-terminal regions. Furthermore, their 3'-NTRs were very similar in length [253 to 256 nucleotides (nt)] and sequence (93 to 96% similarity). In contrast, the coat protein of NL3 had only 261 amino acids and showed 87 to 89% similarity with NL1, NY15 and W whereas its N-terminal region revealed only 46 to 61% similarity. The 3'-NTR of NL3 also displayed appreciable differences, both in length (240 nt) and sequence (56 to 63% similarity). These results, in combination with earlier serological findings, justify the conclusion that NL1, NY15 and W should be considered strains of the same virus, i.e. bean common mosaic virus, and that NL3 is a strain of a different potyvirus for which the name 'bean black root virus' is proposed.

Amino Acid Sequence↗
PubMed1993

Liposome-incorporated ciprofloxacin in treatment of murine salmonellosis.

We used a dehydration-rehydration procedure in order to efficiently incorporate ciprofloxacin into phospholipid vesicles (liposomes), which we then used to treat BALB/c mice that had been infected per os with Salmonella dublin. A single injection of liposome-incorporated ciprofloxacin (LIC) was 10 times more effective than a single injection of free drug at preventing mortality. When free ciprofloxacin was administered twice daily for 5 days, it was more effective than when it was administered as a single dose. Treatment with LIC produced dose-dependent decreases in bacterial counts in spleen, stool, and Peyer's patches, indicating that the drug had distributed to all areas of inflammation, not just to the major reticuloendothelial system organs. Although LIC was cleared rapidly from the blood, drug persisted in the liver and spleen for at least 48 h after administration of a dose of LIC. We attribute the enhanced activity of LIC to the concentration and persistence of active drug in the infected organs. Our results confirm the fact that ciprofloxacin is effective therapy for systemic salmonella infection and show that LIC is even more effective than aqueous ciprofloxacin in our model.

Animals↗
PubMed1992

A proposal for a bean common mosaic subgroup of potyviruses.

In order to elucidate the taxonomic positions of bean common mosaic virus (BCMV) and blackeye cowpea mosaic virus (B1CMV), several strains of these viruses were compared on the basis of host ranges, antigenic properties established with antisera to virions and to N-terminal peptide domains of their coat proteins, and high performance liquid chromatographic peptide profiles. The comparison includes three strains of BCMV, viz. NL1, NL3 and NY15, four strains of B1CMV, viz. Fla, Ind, NR, and W, and the Moroccan isolate (Mor) of cowpea aphid-borne mosaic virus (CABMV), formerly designated as B1CMV-Mor. Based on these parameters, Fla, NR, and W are strains of one virus, whereas NL3, Ind and CABMV-Mor (and possibly NL1 and NY15) are separate viruses. In view of these characteristics which allow similar viruses to be separated, we propose that these viruses be included in a bean common mosaic subgroup of the genus Potyvirus.

Capsid↗
PubMed1992

Relapsing polychondritis: a case diagnosed by direct immunofluorescence and coexisting with pseudocyst of the auricle.

A case of relapsing polychondritis with perichondrial IgG and C3, dermoepidermal IgG, and a coexisting pseudocyst of the auricle is reported. The use of direct immunofluorescence testing in establishing a diagnosis of relapsing polychondritis and the expected findings are reviewed. In some cases direct immunofluorescence may allow a diagnosis of relapsing polychondritis before clinical criteria or a routine histologic evaluation suggests a definite diagnosis.

Aged↗