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F K Dar

Publications and source records attributed to F K Dar.

At least 19 recordsLinked to original sources
PubMed1995

Characterization of a synthetic peptide mimicking trypsin-cleavage site of rotavirus VP4.

A synthetic peptide corresponding to the trypsin cleavage site on the 84 k protein of bovine rotavirus was synthesized (VP4-peptide). This synthetic peptide could be cleaved by trypsin and therefore possessed the enzyme binding site present on the authentic protein. Further proof that this peptide mimicks the authentic trypsin cleavage site was the specific reaction of anti-peptide serum with the 84 k protein. The reaction of anti-peptide serum with infectious virus neutralized infectivity thereby supporting the biological importance of this site. Another interesting characteristic of this peptide was its ability to bind to the nucleocapsid protein resulting in a laddering effect on the nucleocapsid monomer (45 k), dimer (90 k) and trimer (135 k) [Gorzilia et al., J. Gen. Virol. 66, 1889-1900 (1985); Sabara et al., J. Virol. 53, 58-66 (1985); Sabara et al., J. Gen. Virol. 67, 201-212 (1986)]. Definitive proof of binding was provided by the fact that the increments in the ladder corresponded to the molecular weight of the synthetic peptide and that anti-peptide serum specifically reacted with the ladder formations. The laddering of the nucleocapsid could be eliminated by incubation with trypsin thus further supporting the formation of a synthetic peptide-nucleocapsid complex. Due to the ability of the peptide to bind to trypsin and to the nucleocapsid protein its biological activity was investigated. It appeared that increasing concentrations of the peptide reduced the rate of virus plaque formation, thereby suggesting that virus replication was inhibited. These results illustrate two features of this synthetic peptide which warrant further investigation; (1) its capacity to mimic an enzyme cleavage site and, (2) its ability to complex tightly to another protein. In protection-challenge experiments performed using a murine model, animals immunized with VP4-peptide provided protection passively, to neonates suckling on the immune dams, against a virulent rotavirus. The potential applications of this peptide in rotavirus diagnosis, therapy and synthetic peptides based vaccine is discussed.

Amino Acid Sequence↗
PubMed1995

Suppression of transplant immunity in experimental trichinellosis.

Skin allograft rejection in Balb/c and C57BL/6J mice following experimental infection with 300 larvae of Trichinella spiralis or Trichinella pseudospiralis was studied. Skin grafts from normal C57BL/6J mice were transplanted to infected Balb/c mice and vice versa at days 3, 10, 20 and 30 post-infection. The clinical criteria for graft rejection, scarring and graft falling, were followed. The results indicated that T. spiralis and T. pseudospiralis infections induced a significant delay in graft rejection when compared to the control groups. A maximum rejection time of 24 days was observed in T. spiralis infected C57BL/6J mice which received skin grafts from Balb/c mice on day 3 post-infection. The rejection in the uninfected control group was on day 7 post transplant. The mean rejection times for transplants on various days post-infection, with both species were very similar. Also, the rejection profiles in Balb/c mice were comparable to that observed in C57BL/6J mice, with a maximum delay of 26 days to rejection again obtained in mice transplanted on day 3 post-infection, for both species. When the skin grafts were performed 5 or 10 days prior to infection, the rejection occurred on day 7, as in the control group. The effect of T. spiralis and T. pseudospiralis soluble larval extracts (TSE or TPE) on graft rejection was also examined. Four intraperitoneal injections of 50 micrograms each of TSE or TPE every 48 h for 7 days did not induce any significant delay in graft rejection. In contrast, secretory antigens prepared from cultured larvae in vitro induced significant delays in graft rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Priming and induction of anti-rotavirus antibody response by synthetic peptides derived from VP7 and VP4.

Synthetic peptides derived from bovine rotavirus C-486 (BRV) outer capsid (VP7 and VP4) and inner capsid (VP6) proteins were tested to evaluate their ability to prime and induce an anti-rotavirus antibody response. Peptides corresponding to the amino acid residues 232-255 of VP4 (VP4-peptide), 275-295 of VP7 (VP7-peptide) and 40-60 of VP6 (VP6-peptide) of BRV were chemically synthesized. These peptides were coupled to carrier proteins (either keyhole limpet haemocyanin (KLH) or recombinant rotavirus inner capsid protein-VP6 assembled into virus-like particles (VP6-carrier) were used as carrier to link the synthetic peptides under study), and the resulting conjugates were used to immunize rotavirus seronegative mice. An enzyme-linked immunosorbent assay (ELISA) was used to determine anti-peptide and anti-rotavirus antibody titres in serum samples collected after immunization. All peptides were immunogenic in mice and induced the production of anti-peptide antibodies, but with the exception of VP6-peptide they were not able to induce anti-rotavirus antibodies as measured by ELISA. Western blot analysis indicated that antibodies against each peptide were able to react with the respective authentic viral proteins of various rotavirus serotypes. To determine if a peptide-primed animal would respond to native viral proteins, animals were subsequently injected with purified BRV. A rapid and high anti-rotavirus antibody titre, in addition to a rise in anti-peptide antibody titre, was observed in peptide-primed mice. Furthermore, the sera obtained from these mice neutralized the virus under in vitro conditions. The significance of these results in relation to a potential rotavirus synthetic peptide-based vaccine is discussed.

Amino Acid Sequence↗
PubMed1994

Studies on the survival of aerosolized bovine rotavirus (UK) and a murine rotavirus.

The effect of relative humidity (RH) and temperature on the survival of airborne bovine rotavirus UK isolate (BRV-UK) and a murine rotavirus (MRV) was studied. In any one experiment, the virus under test was suspended in tryptose phosphate broth (TPB) supplemented with uranine (physical tracer) and an antifoam, was aerosolized using a Collison nebulizer into the rotating drum with the RH at either low (30 +/- 5%), medium (50 + 5%) or high (80 +/- 5%) level at 20 +/- 1 degrees C. Following a 15-min period of viral aerosol stabilization, sequential samples of drum air were collected using an All-Glass Impinger (AGI) for 24 h post-aerosolization. Both of the rotavirus isolates were found to survive best at medium RH level and high RH was found least favorable for the survival of these aerosolized rotaviruses. The survival pattern of aerosolized MRV was found to be the best when compared with survival pattern of all animal and human rotavirus isolates studies performed under aerosolized conditions in our laboratory. The findings of these experiments confirm and extend our previous reports on the survival of other animal and human aerosolized rotaviruses and emphasize the fact that air may be one of the vehicles for their dissemination and could explain why it is difficult to control nosocomial outbreaks of rotavirus gastroenteritis and to keep animal colonies rotavirus-free.

Air Microbiology↗
PubMed1994

Molecular determinants of rotavirus virulence: localization of a potential virulence site in a murine rotavirus VP4.

The molecular basis of pathogenesis in vivo for a virulent mouse rotavirus (MRV) and a less virulent bovine rotavirus (BRV) were compared under in vitro and in vivo conditions. Obvious differences in the mobility of several genomic RNA segments were observed in one-dimensional gels. Under in vitro conditions, partial proteolytic peptide mapping identified differences between the two outer capsid proteins of these virus and no difference in inner capsid protein was observed. Since it has been observed by us and others that the gene coding for VP4 protein plays a significant role in determining virulence, the variability observed in the present study between the 84 k proteins (VP4) provided a basis for further investigations in order to locate a potential virulence determinant. A comparison of the carboxypeptidase digests of the MRV- and BRV-VP4 revealed an area of variability between amino acids 307 and 407, which may represent a site of virulence determinant. Under in vivo conditions the virulence of both parenteral BRV and MRV isolates and their corresponding reassortants (with replaced gene 4) were studied in murine and bovine hosts. Like their parents, BRV and MRV isolates, reassortants obtained by replacement of gene 4 in BRV with MRV gene 4 indicated that the dose of the virus isolate used and the clinical outcome in vivo was determined by gene segment 4. The implications of these findings to elucidate the molecular basis of pathogenesis of rotaviruses are discussed.

Animals↗
PubMed1994

Studies on the rate of selective uptake of amino acids by Trichinella larvae in vivo.

Groups of C57BL/6J mice, orally infected with 300 larvae each of Trichinella spiralis or T. pseudospiralis were injected with [3H]-alanine, tyrosine, tryptophan or glycine. The incorporation of isotope labelled amino acids into larval proteins was measured at 2, 6, and 12 months post-infection. It was shown that there is a significant increase in the in vivo uptake of isotope labelled amino acids with time by the larvae of T. spiralis and T. pseudospiralis. The level of uptake was highest for tyrosine followed by tryptophan, alanine and then glycine, for both species. The in vivo uptake of amino acids by T. pseudospiralis larvae was always higher than T. spiralis or the host at 6 and 12 months post-infection. At 2 months post-infection, T. spiralis uptake of these amino acids was higher, except for tyrosine. This may be related to the special needs of these larvae during the process of encystation. The higher metabolic requirements of T. pseudospiralis may be related to the higher energy needs of these non encapsulated, highly motile and mobile muscle larvae.

Alanine↗
PubMed1994

Echinococcus multilocularis: effect of size of inoculum and route of infection on metastasis, amyloidogenesis and alveolar hydatid cysts mass in mice.

Alveolar hydatid disease (AHD) in mice, caused by Echinococcus multilocularis, is characterized by restrictive and metastasizing progressive growth phases. In experimentally induced infections, neither inoculum size (5, 50 or 250 viable cysts) nor the route (intraperitoneal/subcutaneous) of infection altered the course of disease as measured by the size of the larval cyst mass (LCM) produced. Spleen weight and amyloid deposition were also shown to be independent of the route or size of inoculum. Inoculation of a soluble parasite protein extract (AHC-EXT) induced amyloid deposition, with a dose-dependent threshold. These results support our postulate that soluble component(s) of the LCM are the major factor in the pathogenesis of AHD.

Amyloid↗
PubMed1994

Contractile characteristics of the flexor muscle of mice infected with Trichinella spiralis, T. nativa or T. pseudospiralis.

A comparative analysis of skeletal muscle isometric contractile characteristics was performed in vivo on the flexor muscle of mice infected 6 mo earlier with 400 larvae of Trichinella pseudospiralis, Trichinella spiralis, or Trichinella nativa. The control group consisted of age- and sex-matched uninfected mice. The mice were injected with 0.1 ml of 50% urethane in saline, and the skin of the left hind limb was cut open longitudinally. The exposed flexor muscle was freed from the adjacent tissue and left attached freely to the knee joint while the tendon was hooked to a transducer. The signals were amplified with an amplifier connected to a chart recorder. The sciatic nerve was exposed and attached to an electrode. Impulses were generated and muscle contraction recorded. The exposed muscle and nerve were bathed in normal Krebs solution at all times and the animals were kept alive during the experiment. The normal muscle twitch tension of uninfected mice reached an average of 2.26 +/- 0.24 (SD) g. Tetany was achieved at 15 Hz. Low-Ca2+ Krebs depressed the twitch tension to 2.0 +/- 0.08 g while tetany remained at 15 Hz. Muscle twitch tension in mice infected with T. pseudospiralis reached 2.47 +/- 0.17 g and tetany at 15 Hz. Low Ca2+ depressed twitch tension to 1.14 +/- 0.12 g. Tetany was achieved at 20 Hz. In contrast, the muscle twitch of mice infected with T. nativa was significantly reduced to 1.4 +/- 0.09 g and tetany at 15 Hz. Low Ca2+ depressed twitch tension to 0.9 +/- 0.16 g and tetany at 15 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Characterization of two rotaviruses differing in their in vitro and in vivo virulence.

The proteins, genomic RNA and disassembly conditions and pathogenesis in vivo for a virulent mouse rotavirus (MRV) and a less virulent bovine rotavirus (BRV) were compared. An obvious difference in the mobility of several genomic RNA segments were observed in one-dimensional gels. Reassortants obtained by replacement of gene 4 in BRV with MRV gene 4 indicated that the dose of the virus used and the clinical outcome in vivo was determined by gene segment 4. Under in vitro conditions, a comparison of the inner capsid proteins by partial proteolytic peptide mapping did not reveal any difference between corresponding proteins. However, this technique did identify differences between the two corresponding outer capsid proteins of these viruses. These differences, in turn, may account for the increased stability of MRV, as compared to BRV, when subjected to calcium-chelating and chaotropic agents and may be one of the mechanisms involved in conferring virulence on the virus. The observed variability between the 84K proteins (VP4) provided a basis for further investigations in order to locate a potential virulence determinant, since it has been observed by us and others that the gene coding for this protein plays a role in determining virulence. A comparison of the carboxypeptidase digests of the MRV and BRV VP4 revealed an area of variability between amino acids 307 and 407, which may represent the site of a virulence determinant.

Animals↗
PubMed1980

Ophthalmomyiasis caused by the sheep nasal bot, Oestrus ovis (Oestridae) larvae, in the Benghazi area of Eastern Libya.

In a two-year study, from January 1977 to December 1978, 80 human cases of ophthalmomyiasis were recorded at the Benghazi Central Eye Clinic. Infections were due to larvae of the sheep nasal bot, Ostrus ovis. The annual incidence was estimated to be 10 per 100,000 population, with most of the cases occurring amongst males during the months of May, June and July. A typical case history is described to illustrate the clinical features and the treatment used.

Adolescent↗
PubMed1979

Effect of levamisol on tissues of Ascaris lumbricoides.

Levamisol which is highly effective against Ascaris infections, was shown to produce degenerative changes in the intestine and the reproductive system of the worm. Worms that were not expelled by treatment produced only nonviable eggs which could not develop in vitro. Levamisol is thus shown to be not only a highly curative drug, but a compound of significant epidemiological importance.

Animals↗
PubMed1978

Serological and clinical investigations of human hydatid case in Libya.

Fifty surgically confirmed cases of hydatid disease in Eastern Libya were investigated. Of these, 30 had cysts of the liver, five had extra-hepatic abdominal cysts and 15 had cysts in the chest, including the lungs. Ten cases of malignancy of the liver and five cases of malignancy of the lung were used as controls. Differential diagnosis of cancer was made by measuring the ESR and glycoprotein levels (elevated x 4 and x 3 respectively, in cancer cases). Serum bilirubin, SGOT, SGPT and serum alkaline phosphatase levels were also significantly raised in malignancy, while the total protein levels and eosinophilia were the same in both diseases. The intradermal test was positive in 88%, the haemagglutination test in 86% and the complement fixation test in 70% of cases. In the post-operative follow-up, complement-fixing antibodies disappeared somewhat faster than did the haemagglutinins. The positive skin test cases, however, remained positive throughout the 12-month follow-up period.

Blood Sedimentation↗