Biomedical subjects

J K Davis

Publications and source records attributed to J K Davis.

At least 19 recordsLinked to original sources

PubMed2000

Sequence analysis and initial characterization of two isozymes of hydroxylaminobenzene mutase from Pseudomonas pseudoalcaligenes JS45.

Pseudomonas pseudoalcaligenes JS45 grows on nitrobenzene by a partially reductive pathway in which the intermediate hydroxylaminobenzene is enzymatically rearranged to 2-aminophenol by hydroxylaminobenzene mutase (HAB mutase). The properties of the enzyme, the reaction mechanism, and the evolutionary origin of the gene(s) encoding the enzyme are unknown. In this study, two open reading frames (habA and habB), each encoding an HAB mutase enzyme, were cloned from a P. pseudoalcaligenes JS45 genomic library and sequenced. The open reading frames encoding HabA and HabB are separated by 2.5 kb and are divergently transcribed. The deduced amino acid sequences of HabA and HabB are 44% identical. The HAB mutase specific activities in crude extracts of Escherichia coli clones synthesizing either HabA or HabB were similar to the specific activities of extracts of strain JS45 grown on nitrobenzene. HAB mutase activity in E. coli extracts containing HabB withstood heating at 85 degrees C for 10 min, but extracts containing HabA were inactivated when they were heated at temperatures above 60 degrees C. HAB mutase activity in extracts of P. pseudoalcaligenes JS45 grown on nitrobenzene exhibited intermediate temperature stability. Although both the habA gene and the habB gene conferred HAB mutase activity when they were separately cloned and expressed in E. coli, reverse transcriptase PCR analysis indicated that only habA is transcribed in P. pseudoalcaligenes JS45. A mutant strain derived from strain JS45 in which the habA gene was disrupted was unable to grow on nitrobenzene, which provided physiological evidence that HabA is involved in the degradation of nitrobenzene. A strain in which habB was disrupted grew on nitrobenzene. Gene Rv3078 of Mycobacterium tuberculosis H37Rv encodes a protein whose deduced amino acid sequence is 52% identical to the HabB amino acid sequence. E. coli containing M. tuberculosis gene Rv3078 cloned into pUC18 exhibited low levels of HAB mutase activity. Sequences that exhibit similarity to transposable element sequences are present between habA and habB, as well as downstream of habB, which suggests that horizontal gene transfer resulted in acquisition of one or both of the hab genes.

Amino Acid Sequence↗

PubMed1999

Environmental enrichment of brown capuchins (Cebus apella): behavioral and plasma and fecal cortisol measures of effectiveness.

No consensus exists about the quantity and variety of environmental enrichment needed to achieve an acceptable level of psychological well-being among singly housed primates. Behavioral and plasma and fecal cortisol measures were used to evaluate the effectiveness of four levels of toy and foraging enrichment provided to eight wild-caught, singly housed adult male brown capuchins (Cebus apella). The 16-week-long study comprised six conditions and began with a 4-week-long preexperimental and ended with a 4-week-long postexperimental period during which the subjects were maintained at baseline enrichment levels. During the intervening 8 weeks, the subjects were randomly assigned to a sequence of four 2-week-long experimental conditions: control (baseline conditions), toy (the addition of two plastic toys to each cage), box (access to a foraging box with food treats hidden within crushed alfalfa), and box & toy (the addition of two plastic toys and access to a foraging box). Behavioral responses to changes in enrichment were rapid and extensive. Within-subject repeated-measure ANOVAs with planned post hoc contrasts identified highly significant reductions in abnormal and undesirable behaviors (and increases in normal behaviors) as the level of enrichment increased from control to toy to box to box & toy. No significant behavioral differences were found between the control and pre- and postexperimental conditions. Plasma and fecal cortisol measures revealed a different response to changing enrichment levels. Repeated-measure ANOVA models found significant changes in both these measures across the six conditions. The planned post hoc analyses, however, while finding dramatic increases in cortisol titers in both the pre- and postexperimental conditions relative to the control condition, did not distinguish cortisol responses among the four enrichment levels. Linear regressions among weekly group means in behavioral and cortisol measures (n=16) found that plasma cortisol was significantly predicted by the proportions of both normal and abnormal behaviors; as the proportion of normal behaviors increased, the plasma cortisol measures decreased. Plasma cortisol weekly group means were also significantly and positively predicted by fecal cortisol weekly group means, but no behavioral measure significantly predicted fecal cortisol weekly group means. In sum, these findings argue strongly that access to a variety of toy and foraging enrichment positively affects behavioral and physiological responses to stress and enhances psychological well-being in singly housed brown capuchins.

Animal Welfare↗

PubMed1999

Genetic and biochemical comparison of 2-aminophenol 1,6-dioxygenase of Pseudomonas pseudoalcaligenes JS45 to meta-cleavage dioxygenases: divergent evolution of 2-aminophenol meta-cleavage pathway.

Nitrobenzene is degraded to pyruvate and acetaldehyde by Pseudomonas pseudoalcaligenes JS45 via a reductive pathway, and by Comamonas sp. JS765 via an oxidative pathway. Although the initial reactions in the degradation of nitrobenzene by the two bacteria are totally different, the lower pathways are similar and converge at the level of 4-oxalocrotonate. In order to further investigate the biochemical properties and reveal the evolutionary relationships between the two lower pathways, the genes encoding the 2-aminophenol 1,6-dioxygenase were cloned and sequenced. 2-Aminophenol 1,6-dioxygenase from P. pseudoalcaligenes JS45 and catechol 2,3-dioxygenase from Comamonas sp. JS765 were able to act on both catechol and 2-aminophenol, but catechol was a suicide substrate of 2-aminophenol 1,6-dioxygenase. The activity of 2-aminophenol 1,6-dioxygenase was restored after removal of catechol and incubation with ascorbate and FeCl(2). Both the alpha-subunit (AmnA) and the beta-subunit (AmnB) of the dioxygenase from P. pseudoalcaligenes JS45 show a high degree of identity to the corresponding subunits of the ring-fission dioxygenase from Pseudomonas sp. AP-3: 67% for the alpha-subunit, and 84% for the beta-subunit. Sequence similarity studies suggest that the beta-subunits of both 2-aminophenol 1,6-dioxygenases are distantly related to homoprotocatechuate 2,3-dioxygenase from Escherichia coli strains W and C and then to catechol 2, 3-dioxygenase from Alcaligenes eutrophus. Four active-site-relevant histidines are conserved in AmnB, but not in AmnA. The lack of conserved histidines indicates the absence of an Fe(2+) binding site in AmnA, which explains the previous observations of only approximately one Fe(2+) per two subunits in the 2-aminophenol 1, 6-dioxygenases from P. pseudoalcaligenes JS45. The 2-aminophenol 1, 6-dioxygenase genes are located upstream of the 2-aminomuconic semialdehyde dehydrogenase gene, and a putative member of the YjgF protein family is upstream of the dioxygenase genes. Transcriptional analysis indicates that the YjgF-like protein, 2-aminophenol 1, 6-dioxygenase, and 2-aminomuconic semialdehyde dehydrogenase are coordinately transcribed. A putative ORF similar to part of the RNA helicase genes is downstream of the dehydrogenase gene. Both the novel organization of the genes and the phylogeny of the dioxygenases and dehydrogenase indicate that the 2-aminophenol pathway in P. pseudoalcaligenes JS45 represents an example of a distant divergent evolution of meta-cleavage pathways.

Amino Acid Sequence↗

PubMed1999

Effects of Mycoplasma fermentans incognitus on differentiation of THP-1 cells.

Mycoplasma fermentans incognitus has been isolated from human tissue in patients both with and without AIDS who died of systemic infection. M. fermentans incognitus and other strains of M. fermentans have been associated with rheumatoid arthritis. While cell extracts of M. fermentans incognitus can induce changes in murine and human cells of the monocytic lineage, little is known about interactions of viable organisms with such cells. Because of the central role of macrophages in chronic inflammation, we examined the effects of M. fermentans incognitus on surface markers and functions of THP-1 cells, a well-characterized human monocytic cell line. This cell line has been used extensively in studies of macrophage differentiation, especially following exposure to phorbol esters. Changes in cell morphology, phagocytosis, rate of cell division, and selected surface markers were evaluated in cultures of THP-1 cells exposed to phorbol myristate acetate (PMA), M. fermentans incognitus, or both. As reported by other investigators, PMA induced THP-1 cells to differentiate into cells resembling tissue macrophages. M. fermentans incognitus only minimally affected changes induced by PMA, slightly increasing the percentage of cells positive for FCgammaRI and major histocompatibility complex (MHC) class II antigens. M. fermentans incognitus alone induced an incomplete arrest in the cell cycle at G0 phase, increased phagocytic ability, and enhanced expression of FCgammaRI, CR3, CR4, and MHC class II antigens.

Carcinogens↗

PubMed1999

Antibody responses after Sendai virus infection and their role in upper and lower respiratory tract disease in rats.

BACKGROUND AND PURPOSE: Sendai virus infection in rats is an excellent model for studying development and role of host defenses throughout the respiratory tract after this infection. Therefore, development of serum antibody responses and disease were studied. METHODS: Forty-two anesthetized pathogen-free 3- to 4- week-old LEW/NCr rats were inoculated intranasally with Sendai virus. At postinoculation days 0, 2, 3, 5, 8, 10, and 14, rats were euthanized by administration of a pentobarbital sodium overdose followed by exsanguination. Serum was obtained from all animals, and nasal wash and bronchoalveolar lavage specimens were collected during selected experiments. An ELISPOT assay was used to measure numbers of Sendai virus-specific antibody-forming cells in respiratory tract lymphoid tissue. RESULTS: Recovery from disease and clearance of virus from respiratory tract tissues coincided with development of serum antibody responses. Upper respiratory tract lymph nodes were the initial and major sites of appearance of antibody-forming cells. Immunoglobulin G was the predominant subtype of these cells during recovery from the infection and in rats resistant to infection. Passive transfer of antisera or specific IgG protected the lower but not the upper respiratory tract. CONCLUSIONS: Circulating components of immunity have a major role in resistance and recovery from disease in the lower respiratory tract, whereas local responses are likely involved in protection of the upper respiratory tract. Local lymphoid tissues are the major production sites of IgG, which contributes to resistance to and recovery from respiratory tract diseases.

Animals↗

PubMed1998

Purification, characterization, and sequence analysis of 2-aminomuconic 6-semialdehyde dehydrogenase from Pseudomonas pseudoalcaligenes JS45.

2-Aminonumconic 6-semialdehyde is an unstable intermediate in the biodegradation of nitrobenzene and 2-aminophenol by Pseudomonas pseudoalcaligenes JS45. Previous work has shown that enzymes in cell extracts convert 2-aminophenol to 2-aminomuconate in the presence of NAD+. In the present work, 2-aminomuconic semialdehyde dehydrogenase was purified and characterized. The purified enzyme migrates as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular mass of 57 kDa. The molecular mass of the native enzyme was estimated to be 160 kDa by gel filtration chromatography. The optimal pH for the enzyme activity was 7.3. The enzyme is able to oxidize several aldehyde analogs, including 2-hydroxymuconic semialdehyde, hexaldehyde, and benzaldehyde. The gene encoding 2-aminomuconic semialdehyde dehydrogenase was identified by matching the deduced N-terminal amino acid sequence of the gene with the first 21 amino acids of the purified protein. Multiple sequence alignment of various semialdehyde dehydrogenase protein sequences indicates that 2-aminomuconic 6-semialdehyde dehydrogenase has a high degree of identity with 2-hydroxymuconic 6-semialdehyde dehydrogenases.

Aldehyde Oxidoreductases↗

PubMed1997

Detection of Mycoplasma pulmonis in cilia-associated respiratory bacillus isolates and in respiratory tracts of rats by nested PCR.

To improve the detection of Mycoplasma pulmonis contamination of isolates of cilia-associated respiratory (CAR) bacillus, we developed a nested PCR method using primers for 16S rRNA gene sequences. Of 140 samples of 16 different CAR bacillus isolates, 73 (52%) were inhibitory in the first PCR, as indicated by the absence of amplicons of the internal control, but only 11 of 140 (7.9%) were inhibitory in the second PCR. Of 27 samples known to contain M. pulmonis, only 12 (44%) were positive in the first PCR, but 25 of 27 (93%) were positive in the second PCR. Nested PCR also detected M. pulmonis in 21 of 61 (34%) CAR bacillus samples from which M. pulmonis could not be cultured and identified 2 additional M. pulmonis-contaminated CAR bacillus isolates. Of 359 respiratory and reproductive tract lavage samples from rats and mice, 35 (9.8%) were inhibitory in the first PCR, but only 15 (4.2%) were inhibitory in the second PCR. Of 72 lavage specimens from rats inoculated with an avirulent, poorly infective M. pulmonis strain, 14 (19%) were positive by nested PCR, but only 2 of 72 (2.8%) were positive by culture. Nested PCR also detected M. pulmonis in 14 of 20 (70%) paraffin sections of lung and trachea from rats and mice inoculated with CAR bacillus isolates known to contain M. pulmonis, whereas single PCR gave no positive results. We conclude that nested PCR is superior to single PCR or culture for detecting M. pulmonis, and that M. pulmonis is present in all but four CAR bacillus isolates in our collection that were from naturally infected rats; the four isolates that were exceptions were obtained from rats from a single colony.

Animals↗

PubMed1997

Bioethical aspects of HIV infection in children.

The care of HIV-infected children is fraught with many bioethical conflicts and dilemmas that require careful attention if care is to be provided appropriately. Understanding of the interplay of such general principles as autonomy, nonmaleficence, confidentiality, and veracity helps to clarify the nature of specific conflicts. This article addresses both general principles and their specific applications to pediatric patients with HIV infection. It addresses these matters from the points of view both of patients and parents. It shows why conflict is practically inevitable, and it points the way toward prevention and resolution of conflict. Practical guidelines are provided in relation to the critical problem of disclosure of diagnosis to the patient.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Pathogenicity of cilia-associated respiratory (CAR) bacillus isolates for F344, LEW, and SD rats.

We conducted experiments to test whether rats of F344, LEW, and SD strains differ in susceptibility to mycoplasma-free isolates of cilia-associated respiratory (CAR) bacillus, whether Mycoplasma pulmonis can affect expression of CAR bacillus disease, and whether isolates of CAR bacillus differ in virulence for rats. In the first experiment, 24 rats of each strain were inoculated intranasally with 10(7) bacilli of CAR bacillus X1428D/AS, and 24 rats of each strain were inoculated with sterile medium (controls). Eight weeks later, eight inoculated rats and eight control rats of each strain were euthanatized, eight inoculated and eight control rats were given 10(6.5) colony-forming units of M. pulmonis X1428D, and eight inoculated rats and eight control rats were sham inoculated. Four rats of each group were euthanatized 4 or 8 weeks after the second inoculation. Severity of lesions in nasal passages, middle ear, trachea, and lungs was assessed by scoring. Rats of all three strains given CAR bacillus had typical lesions of similar severity; M. pulmonis X1428D was avirulent and did not exacerbate CAR bacillus disease. In the second experiment, groups of eight rats of F344 and SD strains were given 10(5) or 10(7) CAR bacillus X1328E, X1428D/AS, or X2450D and euthanatized 8 or 16 weeks later. Isolates X1428D/AS and X2450D caused similar lesions in rats of both strains and at both doses, but CAR bacillus X1328E was avirulent. Rats of the tested strains are similarly susceptible to CAR bacillus disease, but CAR bacillus isolates differ in virulence.

Animals↗

PubMed1997

Detection of urogenital mycoplasmal infections in primates by use of polymerase chain reaction.

Urogenital mycoplasmal infections could affect use of primates as models for reproductive system studies and could affect reproduction in captive primates, but could be useful as animal models of similar human infections. We conducted a pilot study to assess detection of urogenital mycoplasmal infections in primates by use of polymerase chain reaction (PCR). Healthy animals were anesthetized, and vaginal, cervical, or endometrial and urethral swab specimens were collected from females and males, respectively. Specimens were tested by PCR supplemented with dot blotting and nonradiolabeled oligonucleotide probing for 16S rRNA sequences conserved among mollicutes. Specimens with positive results were tested by species-specific PCRs with primers for 16S rRNA sequences of Ureaplasma urealyticum and Mycoplasma hominis and for adhesin gene sequences of Mycoplasma genitalium. Spiked duplicate reactions were included as internal controls for each reaction. Results for 232 specimens from 166 animals indicate that naturally acquired urogenital infections are readily detected and suggest that urogenital mycoplasmal infections are common in laboratory primates (48/166 [29%] overall). M. hominis and U. urealyticum appeared to be common among the studied primates overall and especially in chimpanzees. Mycoplasmas other than M. genitalium, M. hominis, and U. urealyticum appeared to be at least as common as these three, with specimens from 18 of 48 animals (38%) having positive "generic" PCR results, but no positive results in species-specific PCRs.

Animals↗

PubMed1995

Gene expression and production of tumor necrosis factor alpha, interleukin 1, interleukin 6, and gamma interferon in C3H/HeN and C57BL/6N mice in acute Mycoplasma pulmonis disease.

Studies were conducted to determine whether the production of various cytokines is associated with Mycoplasma pulmonis disease expression. Susceptible C3H/HeN and resistant C57BL/6N mice were inoculated intranasally with 10(7) CFU of virulent M. pulmonis UAB CT or avirulent M. pulmonis UAB T. Expression of genes for tumor necrosis factor alpha (TNF-alpha), interleukin 1 alpha (IL-1 alpha), IL-1 beta, IL-6, and gamma interferon (IFN-gamma) in whole lung tissue and TNF-alpha gene expression in bronchoalveolar lavage (BAL) cells was determined by reverse transcription-PCR using specific cytokine primers at various times postinoculation. In addition, concentrations of TNF-alpha, IL-1, IL-6, and IFN-gamma were determined in BAL fluid and serum samples at various times postinoculation. Our results showed that there was a sequential appearance of cytokines in the lungs of infected mice: TNF-alpha, produced primarily by BAL cells, appeared first, followed by IL-1 and IL-6, which were followed by IFN-gamma. Susceptible C3H/HeN mice had higher and more persistent concentrations of TNF-alpha and IL-6 in BAL fluid than did resistant C57BL/6N mice, indicating that TNF-alpha and possibly IL-6 are important factors in pathogenesis of acute M. pulmonis disease in mice. Serum concentrations of IL-6 were elevated in C3H/HeN mice, but not C57BL/6N mice, following infection with M. pulmonis, suggesting that IL-6 has both local and systemic effects in M. pulmonis disease.

Acute Disease↗

PubMed1995

Chronic respiratory mycoplasmosis in C3H/HeN and C57BL/6N mice: lesion severity and antibody response.

Mycoplasma pneumoniae is a leading, worldwide cause of death and disability due to pneumonia. Mycoplasma pulmonis infection in mice is an invaluable model for the study of host defenses against respiratory mycoplasmas in vivo. C3H/HeN mice are much more susceptible to acute inflammatory lung disease due to M. pulmonis than C57BL/6N mice, but little is known about the chronic disease in these mouse strains. We infected C3H/HeN and C57BL/6N mice with 10(4) CFU of M. pulmonis UAB CT and evaluated them at weekly intervals by quantitative mycoplasma culture of nasal passages, trachea, and lungs, assessment of lesion severity in nasal passages, trachea, and lungs, and determination of serum immunoglobulin classes and subclasses by enzyme-linked immunosorbent assay. We found that C3H/HeN mice had 2 to 5 logs more organisms in their lungs and far more severe lung disease than C57BL/6N mice through 63 days postinfection. Although both strains of mice developed the same classes of antibody, C3H/HeN mice had much greater anti-M. pulmonis immunoglobulin G (IgG) responses in the IgG1 and IgG2a subclasses than C57BL/6N mice. These results suggest that adaptive immunity does not effect resolution of chronic mycoplasma infection and disease in the lungs.

Animals↗

PubMed1995

Comparative severity of respiratory lesions of sialodacryoadenitis virus and Sendai virus infections in LEW and F344 rats.

In several chronic diseases, lesions are more severe in LEW rats than in F344 rats. To determine whether or not acute viral diseases also are more severe in LEW rats than in F344 rats, we inoculated 6-7-week-old LEW and F344 rats with 10(7.2) cell culture infective units of sialodacryoadenitis virus or 10(4.7) infective units of Sendai virus. Twenty-four rats of each strain were given each virus. Lesions in nasal passages, tracheas, intrapulmonary airways, and pulmonary alveoli in 6 or 12 rats inoculated with each virus were assessed by scoring 5, 10, and 14 days after inoculation. Both viruses caused typical patchy necrotizing rhinitis, tracheitis, bronchitis, and bronchiolitis, with multifocal pneumonitis, in rats of both strains. Mean lesion indices for LEW rats given sialodacryoadenitis virus were significantly different from those for F344 rats for nasal passages on days 10 (0.999 vs. 0.680) and 14 (0.736 vs. 0.278), bronchi on day 5 (0.479 vs. 0.361), and alveoli on day 5 (0.677 vs. 0.275). Lesion indices for LEW rats given Sendai virus were significantly different from those for F344 rats for nasal passages on days 10 (1.000 vs. 0.611) and 14 (0.778 vs. 0.583); trachea on day 10 (0.625 vs. 0.028); bronchi on days 5 (0.476 vs. 0.331), 10 (0.123 vs. 0.013), and 14 (0.038 vs. 0); and alveoli on days 5 (0.413 vs. 0.114) and 10 (0.185 vs. 0.020). Thus, at the tested doses, both viruses caused more severe respiratory tract lesions in LEW rats than in F344 rats.

Analysis of Variance↗

PubMed1995

In vitro effects of Mycoplasma pulmonis on murine natural killer cell activity.

We evaluated the effect of coculture of virulent and avirulent strains of Mycoplasma pulmonis with mononuclear cells from resistant and susceptible strains of mice on natural killer (NK) cell activity against YAC-1 cells in a standard 4-h 51Cr-release assay. Endogenous NK activity was minimal in the specific-pathogen-free-mice without an external stimulus. There was no correlation between in vivo virulence of the mycoplasmas or host resistance and the in vitro stimulation of NK cell activity. Only two of the avirulent strains of M. pulmonis tested induced significant increases in NK cell activity, and virulent M. pulmonis increased activity only in cells from susceptible C3H/HeN mice.

Animals↗

PubMed1995

Acute Mycoplasma pulmonis infection associated with coagulopathy in C3H/HeN mice.

Experimentally induced infection with high doses of Mycoplasma pulmonis results in acute pneumonia characterized by severe pulmonary hemorrhage, edema, and, often, death in C3H/HeN mice. To determine whether specific disease manifestations were associated with coagulopathy, we measured serum fibrin, fibrinogen degradation products, and plasma fibrinogen concentrations in C3H/HeN mice infected with high doses of a virulent strain of M. pulmonis. We also examined the lungs and other tissues from infected mice for the presence of intravascular fibrin clots and other lesions. Increased concentrations of fibrinogen degradation products indicated that coagulopathy occurs in acute M. pulmonis infection; however, intravascular fibrin clots were not present. Rather than decreasing, as might be expected during a consumptive coagulopathy, fibrinogen concentrations increased. The hyperfibrinogenemia probably is associated with an acute phase response to M. pulmonis infection.

Animals↗

PubMed1994

Role of neutrophils in breakdown of the blood-retinal barrier following intravitreal injection of platelet-activating factor.

Breakdown of the blood-retinal barrier occurs in inflammatory conditions and in ischemic retinal diseases such as diabetic retinopathy. Platelet-activating factor (PAF) is a potent inflammatory mediator which increases vascular permeability. The purpose of this study was to determine if intravitreally-injected PAF would cause breakdown of the blood-retinal barrier and, if so, by what mechanism. Fluorescein angiography was performed before and at 0.5, 1, 2, 3 and 4 hr after PAF injection into the vitreous cavity of rabbit eyes and the eyes were enucleated immediately for light and electron microscopy. Slow flowing thrombi were observed in all PAF-injected eyes. Complete vascular occlusion was observed in 10 of 16 eyes after 3 and 4 hr. There was no fluorescein leakage in any of eyes before or at 0.5 or 1 hr after PAF injection. Fourteen of 20 eyes had fluorescein leakage at 2, 3 and 4 hr after PAF injection. The extent of fluorescein leakage correlated with the degree of polymorphonuclear leukocyte (PMN) margination, disruption of the endothelial cell layer, infiltration into vascular walls and migration into the vitreous cavity. PMNs appeared to migrate by both intercellular and transcellular routes across the endothelium. Pretreatment of rabbits with a PAF inhibitor, BN52021, prevented most of the abnormal findings.

Animals↗

PubMed1993

Interactions of mycoplasmas with B cells: antibody production and nonspecific effects.

Interactions between mycoplasmas and B cells consist primarily of the development of specific antibody and of nonspecific interactions with B lymphocytes or antibody. Antibody responses are important in the resistance to mycoplasmal disease in both humans and animals. However, the ability of mycoplasmas to survive in their host despite vigorous responses suggests that these play a limited role in the host's recovery from infection. Antibody also may prevent dissemination of mycoplasmal infections from mucosal sites and may account for the appearance of systemic mycoplasmal infections in immunocompromised patients. In some cases, antibody responses may contribute to disease pathogenesis through the development of hypersensitivity responses or the deposition of immune complexes. In addition, nonspecific interactions between mycoplasmas and B lymphocytes have been implicated in disease pathogenesis, possibly leading to autoimmune reactions, modulation of immunity, and/or promotion of lesion development. For example, several mycoplasmas, including Mycoplasma pneumoniae and Mycoplasma pulmonis, are able to activate B cells polyclonally in vitro and in vivo, but the mechanisms and consequences of these responses have yet to be defined. In addition to activating B lymphocytes, mycoplasmas are capable of producing chemotactic factors, Fc receptors, and immunoglobulin proteases that may also be involved in lesion development and/or survival of the organisms. Thus, both specific and nonspecific interactions of mycoplasmas with B cells can have important effects on disease progression, especially since many mycoplasmal infections are chronic and the cumulative effect of these interactions may be substantial.

Animals↗

PubMed1993

Cultivation of cilia-associated respiratory bacillus in artificial medium and determination of the 16S rRNA gene sequence.

Cilia-associated respiratory (CAR) bacillus, an unclassified gliding bacterium associated with respiratory disease in rats, mice, and rabbits, has previously been cultivated only in embryonated chicken eggs, cell culture, or cell culture medium supplemented with conditioned medium from cultured tracheas. A reference strain of CAR bacillus, originally isolated in eggs, grew in cell culture flasks as adherent individual bacilli and ropy, whorled fascicles in cell culture media supplemented only with fetal calf serum. Using Dulbecco's minimal essential medium, we isolated CAR bacillus from naturally infected rats and a naturally infected rabbit and from experimentally inoculated mice and rats. Isolates were maintained for up to 20 passages. Isolates from rats were similar in morphology to the reference strain, but most were more actively motile and formed pincushion-like aggregates. The rabbit bacilli were smaller and formed fewer aggregates. DNAs of rat isolates differed only slightly in restriction fragment patterns from that of the reference strain, whereas that of the rabbit isolate was distinctly different. Cultures of CAR bacilli of all strains from rats contained Mycoplasma fermentans, Mycoplasma pulmonis, or both, and cultures of the CAR bacillus from the rabbit contained an unidentified arginine-utilizing mycoplasma. The sequence of the 16S rRNA gene of the reference strain was determined by amplification by polymerase chain reaction, cloning of the product, and sequencing by the dideoxynucleotide chain termination method. Comparison of the sequence with sequences in the GenBank data base indicated that CAR bacillus is a unique organism most closely related to Flavobacterium ferrugineum and Flexibacter sancti.

3T3 Cells↗