Biomedical subjects

O Ogunremi

Publications and source records attributed to O Ogunremi.

9 recordsLinked to original sources

PubMed2000

Purification of first-stage larvae of Elaphostrongylus cervi (Nematoda: Protostrongylidae) from feces.

Parasites are often found in a milieu that requires extensive preparation and labor-intensive cleaning before they are suitable for use in analytical procedures. Application of modern techniques in immunology and molecular biology demands pure yields of parasites. To purify first-stage (L1) larvae of Elaphostrongylus cervi, fecal suspensions from an infected red deer were processed by the Baermann method and embedded in a gel matrix with the objective of selectively trapping fecal debris. About half the number (50.9%) of embedded larvae migrated out of the gel within a 24-hr period and were collected as clean parasite suspensions, virtually free from fecal debris. The numbers of L1 emigrating from gels were inversely proportional to the fecal debris content and the thickness of the gel. Removal of fecal debris from Baermann fluid by sieving prior to gel embedment enhanced the yield of pure L1.

Animals↗

PubMed1999

Evaluation of excretory-secretory products and somatic worm antigens for the serodiagnosis of experimental Parelaphostrongylus tenuis infection in white-tailed deer.

Three different antigen preparations of Parelaphostrongylus tenuis were assessed for their effectiveness in an indirect enzyme-linked immunosorbent assay (ELISA) to diagnose experimental infection of white-tailed deer (WTD). The antigen preparations were the excretory-secretory products of third-stage larvae (ES-L3), somatic antigens of third-stage larvae (sL3), and somatic antigens of the adult stage (sA) of P. tenuis. The relative sensitivities of the antigen preparations in indirect ELISA were ES-L3 > sL3 > sA. Immunoglobulin G (IgG) antibodies to ES-L3 and sL3 could be detected 14 days postinfection and were consistently present in all infected animals from the first month to the end of the experiment at 5 months. In contrast, IgG antibodies to sA could not be detected at any time in 2 infected WTD. ES-L3 and sL3 proved reliable in the early detection of anti-P. tenuis antibodies and in the serological monitoring of experimentally infected animals. Significant cross-reactivity between all P. tenuis antigen preparations and sera from animals infected with parasites other than P. tenuis may preclude their use for field diagnosis. Nevertheless, isolation of unique P. tenuis antigen(s) should lead to the development of a specific serological test for infected white-tailed deer.

Animals↗

PubMed1999

Serological diagnosis of Parelaphostrongylus tenuis infection in white-tailed deer and identification of a potentially unique parasite antigen.

Serological diagnosis of Parelaphostrongylus tenuis infection should offer many advantages over the currently used method of fecal analysis that relies on a patent infection. Toward this end, we investigated the presence of P. tenuis-specific antibodies in experimentally infected white-tailed deer (WTD) and of unique P. tenuis antigens that may be exploited for serodiagnosis. WTD infected with 6, 20 or 100-150 P. tenuis third-stage larvae (L3) had anti-parasite antibodies from as early as 21 days postinoculation (dpi) until the end of the experiment (147 dpi). Peak anti-P. tenuis enzyme-linked immunosorbent assay (ELISA) titers in individual animals ranged from 1:70 to 1:5,700. Serum from infected WTD reacted with 5 distinct P. tenuis L3 antigens (105, 45, 37, 32, and 19 kDa) as detected by the immunoblotting technique. Serum from caribou infected with Parelaphostrongylus andersoni or Elaphostrongylus rangiferi reacted with all antigens except the 37-kDa antigen of L3, indicating that it may be unique to P. tenuis and can serve as a serodiagnostic antigen. The 37-kDa antigen appears to be present in the adult P. tenuis but not adult E. rangiferi or E. cervi. The development of an ELISA utilizing the unique antigen of P. tenuis should lead to a reliable diagnostic assay for P. tenuis infection in WTD.

Animals↗

PubMed1997

Distinct immunological states in murine cutaneous leishmaniasis by immunising with different amounts of antigen: the generation of beneficial, potentially harmful, harmful and potentially extremely harmful states.

Infection of BALB/c mice with a standard and substantial number of Leishmania major parasites results in progressive disease, following the induction of a parasite-specific Th2 response. These mice have been designated as "susceptible" on this basis. We show that distinct types of immune response can be generated in "susceptible" BALB/c mice depending upon the number of parasites employed for infection, and that the pathophysiological consequences of such distinct responses are dramatically different. Infection with very low numbers of parasites results in the exclusive induction of a cell-mediated, Th1 response, and the generation of resistance to the standard and substantial challenge. Spleen cells from such resistant mice can confer resistance upon normal mice when transferred to them, but these spleen cells do not contain T cells expressing DTH or Th1 effector cells that produce IFN gamma on short term culture (48 hrs) with parasite antigen. The immune response in this case appears to result in the virtual elimination of parasites from the lymph node draining the site of infection and, by implication, from the infected mouse. We suggest that such elimination results in the absence of antigen stimulation and hence of effector T cells, and that "memory Th1 cells" are responsible for the capacity of spleen cells to confer resistance on normal mice. We predict such mice will not suffer parasitemia upon immune suppression, i.e. are not susceptible to reactivation disease. This is the "beneficial state". In contrast to this infection with a very low number of parasites infection with a low number usually results in one of two states: (i) The generation of a response with a very small Th2 component, production of a small amount of antibody, chronic parasitemia and hence chronic generation of parasite-specific effector Th1/Th2 cells, or (ii) The generation of a response with a greater Th2 component, the production of more antibody, the formation of a frank lesion, and the long term generation of a stable, mixed Th1/Th2 response. We refer to the latter state as borderline leishmaniasis in analogy with borderline leprosy. Parasites can be recovered from the draining lymph node in both these cases many months after infection. We therefore believe that mice infected with a low number of parasites, that harbour a chronic subclinical infection, will suffer reactivation disease upon immune suppression, and we consequently designate the state generated as potentially harmful. We consider mice with borderline disease to be in a harmful state. Mice immunised with high doses of parasite antigen produce in the long term Th2 responses, whereas those immunised with lower doses produce Th1 responses. Mice immunised to produce a Th2 response were subsequently infected with a very low number of parasites that is normally contained. The generation of a Th2 response results in the generation of a Th2 imprint, such that the response to the low dose infection is modulated from a Th1 to a Th2 mode, resulting in progressive disease. We argue that immunisation/vaccination, resulting in a state that deviates the protective response to a non-protective mode, may result in epidemics. Such a state has the potential for being extremely harmful.

Animals↗

PubMed1996

Towards a strategy of universally efficacious vaccination against pathogens uniquely susceptible to cell-mediated attack.

Infection by some intracellular parasites is contained only by cell-mediated immunity, and yet antibody is produced at the expense of the cell-mediated response upon natural infection, leading to chronic or fatal disease. Effective vaccination must therefore generate an immunological imprint ensuring a strong and stable cell-mediated response upon infection. Such diseases include leprosy, tuberculosis, the leishmaniasis and AIDS (Kaplan and Cohn (1986) Int. Rev. Exp. Pathol. 28, 45-78; Surcel et al. (1994) Immunology 81, 171-176; Pearson et al. (1983) Rev. Infect. Dis. 5, 907-927; Clerici and Shearer (1993) Immunol. Today 14, 107-111). BALB/C mice are susceptible to Leishmania major, a protozoan that causes cutaneous leishmaniasis in man, by the criterion that substantial infection results in antibody production and progressive disease (Locksley and Scott (1991) Immunoparasitology Today, A58-A61; J.N. Menon and P.A. Bretscher, unpublished data). Infection of BALB/C mice with very few parasites results in an exclusive cell-mediated, Th1-like response and resistance to an ordinarily pathogenic, high dose challenge. This resistance is associated with a strong and stable cell-mediated response (Bretscher et al. (1992) Science 257, 539-542; J.N. Menon and P.A. Bretscher, unpublished data). The generation of this Th1 imprint by low dose infection has been achieved with three very different strains of the parasite. There is a similar dependency of susceptibility and resistance on relative parasite dose in 'susceptible' and 'resistant' mice and in mice of 'intermediate susceptibility'. For example, 'resistant' mice are resistant to substantial infection but succumb to infection with very high doses of parasites. We therefore propose that infection of a genetically diverse population with a very low dose of viable parasites, that does not induce antibody in any individual, will either induce cell-mediated immunity and contain the parasite, or the parasite will grow until it reaches the threshold required to induce cell-mediated immunity, thereby generating the required imprint. Low dose infection may thus constitute universally efficacious vaccination. The pertinence of these observations to improving the efficacy of BCG vaccination against tuberculosis is discussed.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Genetics of resistance to Trypanosoma congolense in inbred mice: efficiency of apparent clearance of parasites correlates with long-term survival.

To study the genetic parameters of resistance to Trypanosoma congolense infection, highly susceptible BALB/c and relatively resistant C57BL/6 mice were crossed to produce reciprocal F1 and F2 offspring. Mice were infected with T. congolense and monitored for parasitemia within the first 2 wk and also for their survival periods. BALB/c mice showed unrestrained parasite growth to the time of death (median survival period, msp = 12.0 days), whereas in C57BL/6 mice, parasitemia reached an initial peak on day 6 and was followed by a rapid apparent clearance of the parasites in an average period of 3 days. Their msp was 163.0 days. The F1 mice cleared the parasites, following the first peak of parasitemia, in an average period of 4 days and had an msp of 69.5 days. Thus, the F1 offspring displayed an intermediate phenotype between susceptible and resistant parents in terms of parasite clearance and survival period. Resistance in F2 mice, as measured by survival times, was inherited as a polygenic trait. Among F2 mice, there was an inverse correlation between the time taken to clear the initial wave of parasitemia and the survival period, r = -0.58; P < 0.05. Thus, the pattern of control of the parasites following the first peak of parasitemia appears to be a good predictive factor for the survival period of mice infected with T. congolense.

Animals↗

PubMed1993

A non-hemolytic assay for the activation of the alternative pathway of bovine complement.

An assay for assessing activation of the bovine alternative pathway of complement was developed. The assay focused on events on the surface of yeast. Yeast cells were incubated with EGTA-Mg2+ plasma, washed and the yeast-bound complement proteins eluted by 100 mM methylamine. Detection of eluted proteins was achieved by Western blot and ELISA. An ELISA for the quantification of the Bb fragment of factor B was chosen to measure activation of the alternative pathway of complement. Using this system, it was possible to demonstrate the kinetics of deposition of Bb on yeast incubated with plasma samples from individual cattle and to show differences between cattle. We were able to categorize cattle into 'fast or slow amplifiers' of the alternative pathway of complement. We suggest that this classification has implications for host protection against invading microorganisms.

Animals↗

PubMed1993

Differences in the activity of the alternative pathway of complement in BALB/c and C57Bl/6 mice.

The deposition of C3b on the surface of zymosan was assessed in inbred strains of mice. Mg(2+)-EGTA plasma from C57Bl/6 and BALB/c mice was incubated with zymosan and deposited C3b was eluted by methylamine. Eluted C3b was detected and quantified by Western blot and an enzyme-linked immunosorbent assay. 3- to 4-fold more C3b was deposited on zymosan incubated with C57Bl/6 plasma than on zymosan incubated with BALB/c plasma (p < 0.01). Data on the kinetics of deposition of C3b suggest a faster and greater activity of the alternative pathway of complement (ACP) in C57Bl/6 than in BALB/c. Higher C3b deposition in C57Bl/6 plasma occurs in the presence of higher plasma factor H concentration (1.3-fold of BALB/c concentration; p < 0.01) and is accompanied by higher factor H deposition on zymosan (3- to 10-fold of BALB/c concentration; p < 0.01). Demonstrable differences in the activity of the proteins of the ACP may provide a biological basis for the genetic variation in innate resistance to infectious organisms observed in inbred strains of mice.

Animals↗

PubMed1970

Sleep and hypnotics: further experiments.

Two experiments compatible with that used to investigate the effect of clinical doses (200 mg.) of amylobarbitone were set up to investigate the effects of clinical doses of chloral hydrate (800 mg.), dichloral phenazone (1,300 mg.), and Mandrax (methaqualone 250 mg. and diphenhydramine 25 mg.) over a period of one to two weeks.Four healthy male subjects were used in each experiment and received placebo or drug throughout a period of six to eight weeks when control records, drug records, and drug withdrawal records were obtained.Chloral hydrate was found to depress rapid eye movement (R.E.M.) sleep appreciably though less consistently than amylobarbitone. No withdrawal R.E.M. sleep rebound was found.Neither dichloralphenazone nor Mandrax was found consistently to depress R.E.M. sleep, though occasional nights when R.E.M. sleep was low occurred more often with Mandrax.In the light of other experiments it is postulated that there exists a "threshold" in the dose of a hypnotic, and that when this is exceeded the drug will produce R.E.M. reduction. Thus it may be possible to prescribe a drug which is clinically useful while avoiding withdrawal effects.

Adult↗