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Biomedical subjects

J McDowell

Publications and source records attributed to J McDowell.

At least 19 recordsLinked to original sources
PubMed1991

Repair of cartilage lesions using biological implants. A comparative histological and biomechanical study in goats.

We report the experimental use of three different biological implants to restore articular surface defects: glutaraldehyde-fixed bovine meniscal xenograft, glutaraldehyde-fixed bovine costal cartilage xenograft, and viable osteochondral allografts. The grafts were implanted in the knees of 19 goats who were allowed free-field activity and were studied for up to one year. The natural articular surfaces of meniscal fibrocartilage provided excellent articular surfaces at all times. Equally good articular surfaces were restored by host tissue growth covering costal cartilage grafts at six months, but by 12 months this surface had degenerated. The majority of the allografts survived and integrated with the host at six months, but many showed signs of failure at 12 months. Only three out of seven ungrafted defects healed completely at six months and the healed surfaces were degenerating at 12 months.

Animals↗
PubMed1990

The prevalence of Chlamydia trachomatis infection among mothers of children with trachoma.

The authors studied the epidemiology of Chlamydia trachomatis infection in a trachoma-endemic area of central Kenya. Children with abnormal ocular discharge were evaluated for clinical evidence of trachoma and were cultured for C. trachomatis. Isolated strains of C. trachomatis were immunotyped with monoclonal antibodies. Overall, 221 children from 207 families were evaluated. Clinically, 91 children (41%) had trachomatous follicular inflammation, and 130 (59%) had papillary hypertrophy without visible follicle and were labeled as having mucopurulent conjunctivitis. C. trachomatis was isolated from 31 of 91 children with trachoma (34%) and 17 of 130 children with conjunctivitis (13%) (p less than 0.001). Twenty-two C. trachomatis strains were immunotyped: 17 were from children with trachoma (nine type A, one A/L2, five B, one Ba, and one E) and five were from children with conjunctivitis (two A, one Ba, one D, and one F). A total of 168 mothers were evaluated for cervical C. trachomatis infection, and seven (4%) were culture-positive. Two strains were immunotyped as serovar E. The authors conclude that C. trachomatis ocular infections are due to heterogeneous serovars in this area, that most cases of trachoma are due to C. trachomatis infection with the classic trachoma serovars (A, B, or Ba), and that cervical C. trachomatis infection is uncommon among mothers of children with trachoma.

Adolescent↗
PubMed1990

Phenotypic modulation in sub-populations of human articular chondrocytes in vitro.

Human articular cartilage has been separated into surface (approx. 15% of tissue depth) and deep zones (remaining tissue) and the constituent chondrocytes released by enzymic digestion. Subsequent culture either as a low density monolayer or as a suspension over agarose revealed distinct morphological and synthetic behaviour in the two populations. Whilst in monolayer these morphological differences disappeared with time in culture, over agarose they remained. Surface zone cells formed two types of cell cluster; one that was highly cellular with little extracellular matrix, and the other less frequent, which formed copious amounts of fibrillar matrix. Both types of cluster were surrounded by a layer of flattened chondrocytes. In contrast, deep cells formed a single cluster type that lacked a surrounding cell layer, but formed large amounts of sparse cartilage-like matrix and comprised morphologically typical chondrocytes. In monolayer, both populations gradually ceased to synthesise cartilage matrix components with the exception of link protein. In suspension, whilst the chondrogenic phenotype per se was preserved, there was, nevertheless, a loss in qualitative synthetic heterogeneity, which exists between surface and deep cells, that was not accompanied by changes in the differential rate of 35S incorporation into proteoglycan. Under these conditions, surface cells that normally do not synthesise keratan sulphate initiated de novo synthesis of this glycosaminoglycan. Consequently, it appears that the observed modulation in synthetic ability of the cell sub-populations is independent of the cluster morphology, which, once established, remains constant throughout the culture period.

Cartilage, Articular↗
PubMed1989

Measurement of megakaryocyte frequency and ploidy distribution in unfractionated murine bone marrow.

Measurement of megakaryocyte frequency, ploidy distribution, and maturation stage have been complicated by the low frequency of megakaryocytes in either bone marrow or spleen. Due to harsh labeling conditions, previous studies utilizing flow cytometry have not quantified cell recovery or megakaryocyte frequency. We have modified our two-color fluorescence-activated cytometric technique in order to identify megakaryocytes in unfractionated murine bone marrow with a fluoresceinated cell surface immunologic probe (heterologous polyclonal platelet antiserum) and to selectively measure megakaryocyte DNA content with propidium iodide using isosmolar conditions. Under these conditions, total nucleated cell recovery from unfractionated normal murine bone marrow, after all preparative procedures, averaged 68.0% +/- 5.0% (SD) with 93.5% +/- 2.0% DNA staining efficiency. Mean megakaryocyte frequency (n = 30) was 0.14% +/- 0.04%. Using both our previously described gating technique with single parameter analysis and our modified dual parameter technique, the modal megakaryocyte ploidy class was 16N. Low ploidy megakaryocytes, 2N and 4N, constituted 9.8% and 10.8%, respectively, of the total megakaryocyte population. Analysis of the megakaryocyte population with respect to cell surface fluorescence intensity demonstrated that the dimly fluorescent population contained an increased proportion of lower ploidy class cells (2N + 4N + 8N) compared with brightly fluorescent cells, which contained an increased proportion of higher ploidy cells (16N + 32N). Our modifications of the two-color technique yielded improved recovery of total nucleated bone marrow cells from unfractionated bone marrow and provided more precise measurements of megakaryocyte frequency and ploidy than previously available.

Animals↗
PubMed1988

Screening for Chlamydia trachomatis infection in a pregnancy counseling clinic.

Five hundred twenty asymptomatic women attending a pregnancy counseling clinic were interviewed and screened for cervical Chlamydia trachomatis infection before therapeutic abortion. Overall, 56 (10.8%) women were culture positive for C. trachomatis. Restricting testing to women with risk factors for infection or who had cervical leukocytosis on Gram staining of cervical mucus, or who were seropositive for C. trachomatis antibodies proved impractical because of insensitivity or nonspecificity. We evaluated three chlamydia diagnostic tests to determine which test had the best performance characteristics. In comparison with culture, the direct fluorescent antigen test had a sensitivity of 89% and a positive predictive value of 78%, whereas the enzyme immunoassay had 96% and 69%, respectively. When analysis was redone with any two positive laboratory tests to define true infection status, the performance parameters of enzyme immunoassay were sensitivity 98%, specificity 98%, and positive predictive value 87%. We conclude that all women undergoing therapeutic abortion require testing for C. trachomatis infection and that enzyme immunoassay is the most effective and practical test in this group of women.

Abortion Applicants↗
PubMed1988

Etiology and outcome of acute pelvic inflammatory disease.

We studied 71 women with the clinical diagnosis of acute pelvic inflammatory disease (PID) by laparoscopy and comprehensive microbiology in order to define the major etiologic determinants of poor fertility prognosis after tubal infection. Fifty women were found to have acute PID. Of the 50 women, 23 were pregnancy seeking and had a subsequent evaluation to determine fertility outcome. Seven of 13 women with non-gonococcal infection had an adverse reproductive outcome, compared with none of 10 women with gonococcal infection (P = .007). Two groups of causes for adverse reproductive outcome were found. Of the seven infertile women, four had initial tubal abscess, and three had evidence of Chlamydia trachomatis infection. This study directly documents the poor fertility prognosis for women with tubal abscess and suggests that women with culture and/or serological evidence of chlamydial infection also have a poor fertility prognosis.

Abscess↗
PubMed1988

Perinatal lead exposure alters the development of delta- but not mu-opioid receptors in rat brain.

1. Low level lead exposure has been shown to impair the development of opioid peptide levels in the brain, and to impair antinociceptive responses to opioid drugs. We have now studied the effects of lead exposure on the development of opioid receptors using ligand binding studies. 2. The ontogenesis of mu- and delta-opioid binding sites was studied using rat whole brain membranes and [3H]-[D-Ala2MePhe4-Gly-ol]enkephalin and [3H]-[D-Pen2,D-Pen5]enkephalin as binding ligands. Rats were exposed to lead during development by addition of lead acetate (at 100-1000 p.p.m.) to the maternal drinking water from conception to postnatal day 14. 3. Perinatal lead exposure had no significant effects on the binding affinity (KD) or binding capacity (Bmax) for the mu-opioid receptor measured at postnatal days 10, 21 and 30. Lead exposure (at 1000 p.p.m.) increased the KD for the delta-opioid receptor at postnatal days 15, 21, 35 and 50 but had no effect on the binding capacity. No indications of overt toxicity were observed and blood lead levels were in the ranges considered to represent subclinical lead toxicity in man. 4. The lack of effect of lead on mu-receptor binding contrasts with previously described impairment of antinociceptive effects of mu-agonists suggesting that the toxicity is not manifested at the mu-binding site. However, the delta-opioid receptor appears to be more sensitive to lead exposure and the persistent changes in delta-site affinity after cessation of lead exposure suggest irreversible damage in the production of the receptor protein.

Animals↗
PubMed1988

Use of allophycocyanin allows quantitative description by flow cytometry of alveolar macrophage surface antigens present in low numbers of cells.

Autofluorescence has limited quantitative description by flow cytometry of certain alveolar macrophage surface antigens. Autofluorescence is most significant when macrophages are excited by blue light and emission is monitored in the green-yellow light range. Because of recent advances in flow cytometry and in the development of fluorescent labeling compounds, such as allophycocyanin, autofluorescence can be minimized by the use of red excitation and emission wavelengths. We have developed a three-step labeling technique that discretely identifies the minor subpopulation of normal rat alveolar macrophages that express Class II major histocompatibility (Ia) antigens. Using this technique, we observed that alveolar macrophage Ia antigen expression increases at least fourfold after intravenous administration of bacillus Calmette-Guerin to previously primed rats. Additionally, we observed that in vitro treatment of alveolar macrophages by exposure to gamma interferon results in an increase in Ia antigen expression. This new method is significant because flow cytometry is a powerful tool with which to analyze quickly, accurately, and reproducibly alveolar macrophage surface antigens.

Animals↗
PubMed1987

Enhanced susceptibility of trypsinized HeLa cells to Chlamydia trachomatis infection.

An improved cell culture method for the recovery of Chlamydia trachomatis from clinical samples was evaluated. Freshly trypsinized HeLa 229 cells were infected in suspension culture and compared to a standard monolayer culture method. Among 1085 specimens evaluated, 84 were positive by both methods, 978 were negative by both methods, 2 were positive by the monolayer method only, and 21 were positive by the suspension method only. Inclusion counts were two-fold higher in the suspension culture method than in the monolayer method (p less than .001). It is concluded that freshly trypsinized HeLa 229 cells infected in suspension culture are more susceptible to infection with Chlamydia trachomatis than standard monolayer cells.

Bacteriological Techniques↗
PubMed1987

Anti-clonotypic autoantibodies in pregnancy.

Idiotypic T-cell receptors for antigen have been identified in previous studies by use of anti-clonotypic monoclonal antibodies. To determine whether anti-receptor autoantibodies play a role in immune regulation, we have used normal pregnancy as a model. T-cell clones were generated from the peripheral blood of a primiparous woman by priming her lymphocytes to stimulating cells from her husband. As a control, T cells primed to lymphocytes from HLA different controls were used. Purified IgG was prepared from this woman's serum and tested for its reactivity with cell surface antigens expressed by autologous T-cell clones. We have identified one anti-HLA-DR reactive clone specific for the immunizing HLA haplotype of the child that reacted with autologous F(ab')2 in immunofluorescence studies. When tested in functional studies, the F(ab')2 blocked the capacity of the clone to lyse specific target cells, while triggering clonal proliferation in the absence of stimulating cells. The determinant(s) recognized by autoantibodies in the F(ab')2 preparation comodulate with the T3 antigen present on the surface of the cells. These data suggest that sera obtained during pregnancy contain autoantibodies which behave similarly to heterologous anti-clonotypic antibodies. Such anti-T-cell receptor antibodies may play a role in maternal tolerance to the fetus.

Autoantibodies↗
PubMed1987

Postabortal Chlamydia trachomatis salpingitis: correlating risk with antigen-specific serological responses and with neutralization.

Serum antibodies to Chlamydia trachomatis were studied by microimmunofluorescence (micro-IF) testing and by immunoblotting among 52 women with C. trachomatis cervical infection. All women underwent therapeutic abortion, and 10 (19.2%) subsequently developed laparoscopically confirmed salpingitis. Women who developed salpingitis had lower geometric mean titers of micro-IF antibody before abortion (14.9 x/divided by 2.3) than did women who did not develop salpingitis (41.6 x/divided by 4.9, P less than .01). Women who developed salpingitis significantly less often had serum IgA antibodies to a 60-kilodalton (kDa) chlamydial antigen (P = .02) and IgG antibodies to antigens of 75-kDa (P = .008), 60-kDa (P = .03), and 57-kDa (P = .0003). Serum antibodies to 100-kDa, 32-kDa, and 29-kDa antigens occurred only in women who did not develop salpingitis. Differences in antibody prevalence to specific chlamydial antigens were not due to differences in serum antibody titers between the two groups. No correlation between neutralizing sera and the risk of postabortal salpingitis was detected.

Abortion, Therapeutic↗
PubMed1987

High-frequency switching in Candida strains isolated from vaginitis patients.

High-frequency switching and strain variability at the site of infection was assessed in 11 patients with acute Candida albicans vaginitis. By cloning cells directly from the site of infection, it was demonstrated that 4 of the 11 isolates contained multiple-switch phenotypes at the site of infection and that 9 of the 11 isolates were in a high-frequency mode of switching (10(-2) to 10(-3)). Isolates could be separated into four general categories of switching repertoires. To demonstrate that multiple phenotypes at the site of a single infection represented the same strain, EcoRI digests of total cell DNA were separated on agarose gels, and Southern hybridization patterns with two cloned midrepeat sequences were compared.

Candida albicans↗
PubMed1986

Ontogenesis of delta-opioid receptors in rat brain using [3H][D-Pen2,D-Pen5]enkephalin as a binding ligand.

The ontogenesis of delta-opioid receptors has been studied in the postnatal period up to day 50 using the highly selective delta-site ligand [3H][D-Pen2,D-Pen5]enkephalin ([3H]DPDPE) in binding studies. Analyses of saturation curves revealed marked increases in binding capacities between the second and fourth postnatal week with little change in affinity. In contrast to findings with [3H][D-Ala2,D-Leu5]enkephalin binding could not be detected before postnatal day 10 which may be associated with the low affinity and specific activity of DPDPE. A low specific binding for [3H]DPDPE poses methodological problems in the use of this ligand for ontogenic studies.

Animals↗
PubMed1986

Perturbation of the immune network in herpes gestationis.

We have studied the development of anti-idiotypic antibodies to HLA and of autoantibodies reacting with alloactivated T lymphoblasts in a woman with herpes gestationis (HG). This primigravida developed an elevated titer of anti-HLA antibodies, (Ab1), in association with a low titer and late appearance of anti-anti-HLA antibodies (Ab2). At delivery she developed only minimal levels of antibodies reacting with autologous T lymphoblasts (T1), sensitized against the immunizing HLA antigens of the child. Her serum reacted, however, with T lymphoblasts, primed in AMLC against autologous T blasts alloactivated in vitro against her husband (T2). Because healthy gravidae do not show such antibodies, it appears that they are peculiar to and may represent a perturbation of the idiotypic network in regard to the immune

Autoantibodies↗