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Biomedical subjects

J R Murphy

Publications and source records attributed to J R Murphy.

At least 253 records · Page 14Linked to original sources
PubMed1979

Host defenses in murine malaria: evaluation of the mechanisms of immunity to Plasmodium yoelii infection.

The immune response of random-bred mice to infection with a relatively avirulent strain of Plasmodium yoelii was measured in terms of parasitemia, splenomegaly, immediate and delayed hypersensitivity to a P. yoelii antigen preparation, resistance to challenge with a virulent variant of P. yoelii, and nonspecific resistance to L. monocytogenes. Avirulent P. yoelii produced a self limiting infection which resolved in 21 days. Peak parasitemia and splenomegaly were observed at 14 days, and infected mice were resistant to challenge with virulent P. yoelii from 7 days through at least 126 days. Mice infected with avirulent P. yoelii developed humoral immunity as judged by immediate hypersensitivity reactions and the capacity of their serum to passively protect normal mice against virulent P. yoelii. At no time did mice infected with the avirulent P. yoelii display evidence of cell-mediated immunity, as expressed by delayed-type hypersensitivity and increased resistance to L. monocytogenes. In fact, at the height of avirulent P. yoelii infection there was decreased resistance to L. monocytogenes in both liver and spleen, and the macrophages of the undisturbed peritoneal cavity were similarly defective. It was concluded that the defense mechanism of mice against P. yoelii is mediated by humoral factors in the absence of demonstrable cell-mediated immunity.

Animals↗
PubMed1979

Mechanisms of immunity in typhus infection: adoptive transfer of immunity to Rickettsia mooseri.

When nonimmune guinea pigs are inoculated intradermally (i.d.) with Rickettsia mooseri (R. typhi), the rickettsiae replicate at the site of inoculation, leading to the development of a grossly observable lesion. In contrast, guinea pigs which have recovered from R. mooseri infection are resistant to challenge and prevent both rickettsial growth and the formation of lesions. To study the mechanisms of this immunity, sera or splenic cells collected from nonimmune or immune guinea pigs were inoculated separetely into nonimmune recipients. Splenic cells collected from immune donors protected R. mooseri-naive recipients from i.d. challenge as measured by control of rickettsial growth and by prevention of development of lesions at i.d. sites of inoculation. In contrast, serum from immune and nonimmune doners failed to protect nonimmune recipients by either criterion.

Animals↗
PubMed1979

Host defenses in murine malaria: analysis of the mechanisms of immunity to Plasmodium berghei generated in response to immunization with formalin-killed blood-stage parasites.

Syngeneic B6D2F1 (C57Bl/6 x DBA/2) mice were immunized with a nonliving antigen prepared from mixed blood forms of Plasmodium berghei strain NYU-2. Consistently greater than 80% of the vaccinated mice survived virulent challenge, and protective immunity was demonstrable from 1 week through at least 4 months after immunization. However, vaccination did not prevent the development of patient infection after challenge. Instead, infections in vaccinated mice progressed to about 10% parasitemia and were then subsequently cleared. In contrast, infections initiated in nonvaccinated mice progressed beyond 10% parasitemia and were uniformly fatal within 4 weeks. Sera collected from normal mice, nonvaccinated mice infected with P. berghei, or vaccinated mice before challenge failed to passively protect recipients against virulent infection. On the other hand, sera collected from vaccinated mice after recovery from a challenge infection conferred upon passively immunized recipients protection from homologous virulent challenge, which was manifest as a delay in the onset of overt infection. It was concluded, therefore, that vaccination altered the immunological potential of the host in such a way as to allow the production of a protective humoral factor, probably specific antibody, in response to infection with the virulent parasites.

Animals↗
PubMed1979

Host defenses in murine malaria: successful vaccination of mice against Plasmodium berghei by using formolized blood parasites.

Infections of normal ICR mice with the NYU-2 strain of Plasmodium berghei (Pb) are uniformly fatal. However, a proportion of mice that have been vaccinated with a formalin-killed antigen prepared from the blood stages of Pb survive an otherwise lethal challenge. Such immunity is not induced by immunization with normal mouse erythrocytes. The level of acquired anti-malarial immunity is related to the size and number of doses of antigen, and intravenous injection is superior to the subcutaneous route of vaccination. The addition of the adjuvants BCG and Corynebacterium parvum to the immunizing regimen improved the level of protection to a variable extent, depending on the batch of plasmodial antigen with which they were used. The adjuvants were most efficacious when used with batches of antigen which were poorly protective when used alone. These adjuvants were found never to protect ICR mice against Pb unless used in combination with specific antigen.

Adjuvants, Immunologic↗
PubMed1978

Isolation of nontoxinogenic mutants of Vibrio cholerae in a colorimetric assay for cholera toxin using the S49 mouse lymphosarcoma cell line.

A mouse lymphosarcoma (S49) cell line that is growth-inhibited by agents that elevate intracellular concentrations of adenosine 3':5'-cyclic phosphate was used in a sensitive and convenient colorimetric assay for cholera toxin. S49 cells suspended in Dulbecco's modified Eagle's minimal essential medium containing 10(-5)--10(-6) M RO 20-1724, an analogue of 4-(3,4-demethoxybenzyl)-2-imidazolidinone and a phosphodiesterase inhibitor, were growth-inhibited by subnanogram concentrations of cholera toxin. Effects of toxin were detected by the absence of a yellow pH change (phenol red indicator) which normally accompanies the production of acid metabolites by lymphoma cells. An assay using S49 cells grown in microtiter plates, which is capable of detecting 10 pg of cholera toxin or 0.01 units of cholera antitoxin, was used in screening for nontoxinogenic mutants of Vibrio cholerae strain 569B. The properties of two mutants of the Tox--phenotype, which lacked biologically and immunologically detectable toxin products, are described.

Animals↗
PubMed1978

Mechanisms of immunity in typhus infection: some characteristics of Rickettsia mooseri infection of guinea pigs.

Rickettsia mooseri infection has been studied in syngeneic guinea pigs inoculated intradermally with the objective of developing a model for the study of immune mechanisms. Characterization of infection included the following: a study of replication, dissemination, and clearance of rickettsiae; measurement of the antibody response with different rickettsial antigens and tests; and attempts to measure the cell-mediated immune response using the correlate of delayed-type hypersensitivity skin reactions. Following intradermal inoculation, rickettsiae replicate locally and then spread to the draining lymph nodes and subsequently cause systemic infection. Spread to draining lymph nodes occurred before the appearance of circulating antibody, whereas systemic infection occurred afterwards. Two distinct patterns of acquired resistance developed. The first was marked by a cessation of rickettsial growth within a given organ and the second by a clearance of rickettsiae. The duration of each of these phases differed markedly from one organ to another. Delayed-type hypersensitivity was not demonstrated by skin testing.

Animals↗
PubMed1978

Host defenses in murine malaria: induction of a protracted state of immunity with a formalin-killed Plasmodium berghei blood parasite vaccine.

Random-bred mice were immunized with a nonliving antigen prepared from mixed-blood forms of Plasmodium berghei, strain NYU-2, in combination with Corynebacterium parvum and/or living BCG. A high proportion of intravenously immunized mice survived virulent challenge, but subcutaneous vaccination was less effective. Vaccinated mice developed a patent infection after challenge similar to that observed in normal controls. However, between days 12 to 20 postchallenge, infections in some vaccinated mice became subpatent, whereas infections in all normal controls progressed until death. The incidence of recrudescent infection was low and, eventually, a state of sterile immunity was established. The capacity of vaccinated mice to withstand P. berghei challenge was sustained at a fairly stable level for the 6-month period of observation. Mice that had survived a primary infection with P. berghei almost completely suppressed a second and larger challenge with the same organism.

Animals↗
PubMed1978

Mechanisms of immunity in typhus infection: some characteristics of intradermal Rickettsia mooseri infection in normal and immune guinea pigs.

Rickettsia mooseri infection in skin at sites of intradermal inoculation was studied in nonimmune and immune guinea pigs with respect to dynamics of infection, localization of rickettsiae within tissues, and gross and microscopic pathology. Intradermal inoculation of R. mooseri into nonimmune guinea pigs resulted in gross lesions which, in magnitude, were directly related to the number of rickettsiae inoculated. The lesions progressively enlarged through 3 or 4 days and remained enlarged through at least 7 days. Histological examination revealed an early acute inflammation which progressed to a predominantly monocyte-macrophage inflammation and subsequently condensed into lymphocyte-containing granulomatous foci. Rickettsiae in the skin at sites of inoculation increased in numbers from 6 h through 3 days, in parallel with the increasing diffuse monocyte-macrophage inflammatory response, and then declined markedly on days 4 or 5 as ganulomatous foci appeared. Some rickettsiae, however, persisted through at least day 7. Fluorescent-antibody studies suggested that R. mooseri infected only a subset of cells available, i.e., cells associated with the microvascular system. Dissemination of infection was demonstrated by the presence of rickettsiae in the skin at sites distant from the point of inoculation. Immune guinea pigs, made immune by intradermal infection with R. mooseri 12 days before intradermal challenge, displayed an accelerated response. The lesions were maximal by 24 to 48 h and subsequently regressed. The inflammatory response of immune guinea pigs was a greater magnitude than the response of similarly challenged nonimmune guinea pigs, and the respose from acute inflammation through the formation of granulomatous lesions was accelerated. The number of rickettsiae in the skin of immune guinea pigs declined steadily from the time of inoculation, until no rickettsiae were recovered on or after day 3. Furthermore, dissemination of rickettsiae to sites in skin distant from the site of inoculation was not demonstrable. The results are discussed in terms of pathogenesis and of immunity to typhus.

Animals↗
PubMed1978

Bacteriophage conversion of heat-labile enterotoxin in Escherichia coli.

A temperate phage designated obeta1 (omicron beta) was mitomycin C induced and isolated from heat-labile enterotoxin (LT)-producing Escherichia coli E2631-C2. Phage obeta1 infected the nonlysogenic, nontoxigenic, mitomycin C-sensitive strain of E. coli K-12 (CSH38) and converted it to lysogeny and enterotoxigenicity. After the establishment of lysogeny, E. coli CSH38(obeta1) produced produced LT and phage particles at maximal levels following mitomycin C induction. The LT Tox+ character is carried by the temperate phage obeta1.

Coliphages↗
PubMed1978

Evidence that the regulation of diphtheria toxin production is directed at the level of transcription.

It has been known for several decades that iron inhibits the production of diphtheria toxin by Corynebacterium diphtheriae by preventing expression at maximal levels. We examined the inhibition kinetics of toxin production after the addition of either iron or rifampin to iron-limited cultures of C7 (betatox+). Iron-mediated inhibition of toxin production was found to be linear within the range of 16 nM to 16 micron. The inhibition kinetics following the addition of iron or rifampin was almost identical. [3H]RNA extracted from iron-limited toxigenic C. diphtheriae was found to hybridize to a greater extent to corynephage beta DNA than either [3H]RNA extracted from toxigenic C. diphtheriae before the onset of toxin production or [3H]RNA extracted from nonlysogenic, nontoxigenic C. diphtheriae.

Corynebacterium diphtheriae↗
PubMed1978

Isolation and characterization of extragenic suppressor strains of Corynebacterium diphtheriae.

The isolation and characterization of two different nonsense suppressor strains of Corynebacterium diphtheriae C7 sup+(-)tox- are described. Appropriate lysogens of these strains with corynephage beta, carrying known class II tox premature polypeptide chain termination mutations [C7sup-1(betatox-30) and C7sup-2(betatox-45)], each produce a 62,000-dalton polypeptide with nicotinamide adenine dinucleotide: elongation factor-2 adenosine diphosphate ribosyltransferase activity in addition to a chain-terminated polypeptide of 30,000 or 45,000 daltons, respectively. In addition, purified protein of 62,000 daltons, resulting from the suppression of the nonsense mutations tox-30 and tox-45, will react with antisera purified against the terminal 17,000 daltons of the toxin molecule and are immunologically identical to toxin by radial immunodiffusion. The suppression pattern of lysogenic derivatives of C7sup-1(-)tox- and C7sup-2(-)tox- with other class II and III mutants of corynephage beta was determined.

Bacteriophages↗
PubMed1978

Determination of Corynebacterium diphtheriae toxigenicity by a colorimetric tissue culture assay.

Chinese hamster ovary (CHO) cell cultures in microtiter wells are sensitive to growth inhibition and killing by picogram quantities of diphtheria toxin. In the absence of biologically active toxin, the CHO cell culture produces sufficient acidic metabolites to change the phenol red pH indicator from pink to yellow within 56 h. In the presence of 10 pg of toxin per well, growth inhibition can be observed microscopically within 24 h. Diphtheria toxin can be qualitatively assayed from culture supernatants of Corynebacterium diphtheriae or from beta-phage agar plaque plugs. The colorimetric CHO cell assay method for determining toxigenicity allows for the large-scale screening of either diphtheria toxigenicity or antitoxin titration of sera.

Animals↗
PubMed1978

Myxoma of the equine respiratory tract.

Bronchial myxoma occurred in an aged Arab mare with longstanding respiratory disease wrongly attributed to chronic obstructive pulmonary disease. Blood gas and maximum intrathoracic pressure change measurements were not consistent with this latter diagnosis, and this was supported by aerosol antigen provocation tests. Radiography demonstrated a hilar mass in the thorax, and this proved to be a myxoma at necropsy.

Animals↗
PubMed1977

Toxicologic and teratologic studies of oxibendazole in ruminants and laboratory animals.

Acute toxicity of oxibendazole was assessed with single oral doses given to mice (4 to 32 g/kg of body weight), sheep (230 to 600 mg/kg), and cattle (600 mg/kg); there were no ill effects. Subacute toxicity did not occur with multiple doses given 5 days to cattle (30 to 75 mg/kg/day) and to sheep (10 to 50 mg/kg/day). Chronic effects did not occur with daily doses of 3 to 30 mg/kg given 98 days to rats and dogs. Teratogenicity of the compound was studied in mice, rats, and sheep medicated at a dose level of 30 mg of oxibendazole/kg and in cattle given 75 mg/kg on selected dates during pregnancy. Microscopically, rodent fetuses seemed normal, and on gross physical examination, lambs and calves were free of malformations and ossification variations.

Abnormalities, Drug-Induced↗
PubMed1976

Isolation and partial characterization of a corynebacteriophage beta, tox operator constitutive-like mutant lysogen of Corynebacterium diphtheriae.

We have isolated and partially characterized a beta-phage mutant lysogen of Corynebacterium diphtheriae, C7(betatoxct1+), which is partially insensitive to iron inhibition of diphtheria toxin production. tox expression by C7(betatoxct1+) was found to be partially constitutive. In the presence of concentrations of iron that almost completely inhibit the expression of diphtheria toxin by the wild type, C7(beta), the level of toxin production by C7(betatoxct1+) was found to be at least 25 times that of the parent. The purified tox gene product of C7(betatoxct1+) was immunologically and electrophoretically identical to, and equally as toxic as, diphtheria toxin purified from C7(beta). In addition, the partial N-terminal amino acid sequence was found to be identical to diphtheria toxin. This data strongly suggests that the mutation allowing for the constitutive expression of tox in C7(betatoxct1+) is outside of the structural gene. Furthermore, the constitutive expression of diphtheria toxin was found to be cis dominant in the double lysogen C7(betacrm45+/betatoxct1+). The data presented is consistent with the existence of a tox operator locus.

Bacteriophages↗