Antigenic variation in Porphyromonas gingivalis ribotypes recognized by serum immunoglobulin G of adult periodontitis patients.

We obtained clinical isolates of Porphyromonas gingivalis of known ribotype from patients diagnosed with adult periodontitis and used Western blot methodology to evaluate profiles of antigens recognized by IgG in heterologous and homologous patient sera. Our aims were to identify isolates belonging to different serogroups, to learn if serogroup membership is related to ribotype to assess variation in IgG responses of patients to antigens is homologous and heterologous ribotypes, and to determine the frequency of shared and variable antigens in different biochemical classes recognized across different serogroups and ribotypes. Blots of separation patterns of 28 isolates were developed in sera from patients and bound IgG was quantified by digital image densitometry. The membership of isolates in different serogroups was determined by correlation and hierarchical cluster analysis of isolate whole-cell IgG binding profiles. Two major isolate clusters, each with two subclusters, were found. Isolates within the same ribotype clustered together in some cases but not others. Homologous isolates ranked high in IgG binding levels relative to those from different patients irrespective of ribotype. Patient subgroups with IgG responses dominant for different ribotypes and serogroups were revealed by correlation analysis. The IgG binding profiles observed for individual protein and proteinase-resistant antigens across both homologous and heterologous isolates were very dissimilar. Furthermore, the frequency of antigens both shared across all ribotypes and recognized by IgG in patient sera was unexpectedly low. Only two protein antigens (Mr 44 kDa and 27 kDa) were strongly recognized across all ribotypes by different sera. We conclude that the IgG response of patients infected with a particular P. gingivalis serotype or ribotype is directed mainly against antigens that are not shared by other potentially infective clonal types.

Visual disability resulting from a dislocated intraocular lens.

Complications may arise from the failure to remove a dislocated intraocular lens, even when it appears to rest in a benign position and pose no problems. We examined a patient with a second intraocular lens left in the inferior vitreous cavity. Shifting the loose lens resulted in eventual complications and visual disability; removing the dislocated lens and replacing the functional intraocular lens yielded good results.

Keratotomy model of pseudomonas keratitis: gentamicin chemotherapy.

BACKGROUND: Chemotherapy of bacterial keratitis requires frequent application of antibiotic drops. Collagen shields containing antibiotics could reduce the need for frequent antibiotic application. To determine the effect of gentamicin-containing collagen shields and gentamicin drops on Pseudomonas keratitis, a new keratotomy model of infection was employed. METHODS: Model--contact lenses (58% water content) presoaked in 1% bovine serum albumin and exposed to 10(8) colony forming units per mL of Pseudomonas aeruginosa strain 27853, were found to reproducibly retain 5.9 (log base 10) colony-forming units. Rabbit corneas were scarified centrally with two perpendicular intersecting diamond knife cuts (5 mm x 5 mm x 0.2 mm), and bacteria-impregnated contact lenses were positioned and held in place for 24 hours with partial tarsorrhaphies. Treatment--Fourteen hours after lens removal (38 hours after infection), corneas were treated for 8 hours with collagen shields hydrated in saline (control), or shields impregnated with 800 micrograms gentamicin during manufacture, or one drop every 30 minutes of fortified gentamicin drops (14 mg/mL). The rabbits were killed and corneas collected for bacterial enumeration after 8 hours of treatment (46 hours after infection). RESULTS: Model--Slit-lamp examination and microbiologic confirmation showed uniformity of keratitis in all eyes. Treatment--Corneas treated with saline (controls) contained 6.4 (log base 10) Pseudomonas. Corneas treated with gentamicin-impregnated collagen shields (total drug = 800 micrograms) and fortified gentamicin drops (total drug = 21 mg) showed a reduction in viable bacteria of 2 logs and 6 logs, respectively, relative to the control. CONCLUSIONS: In this new model of Pseudomonas keratitis, the amount of gentamicin introduced into collagen shields during manufacture effectively reduced bacterial growth in infected rabbit corneas. However, larger amounts of drug applied as fortified drops on a frequent dosing schedule were more effective by a factor of three. Treatment of keratitis with antibiotic-impregnated collagen shields may reduce the need for very frequent application of topical drops, but may be more effective with topical drop supplementation to increase the amount of drug available over the course of therapy.

Transforming growth factor alpha and its receptor in neural retina.

Transforming growth factor alpha (TGF-alpha) stimulates mitosis of many ectodermal cells but has not previously been studied for its role in neural tissues such as retina. We examined bovine retina for the presence of TGF-alpha mRNA, TGF-alpha protein and for the presence and location of the TGF-alpha/EGF receptor. Biochemical studies demonstrated a high level (770 fmol/mg protein) of specific, high affinity (Kd = 2 nM) TGF-alpha/EGF receptors in membrane homogenates of neural retina, but undetectable binding to homogenates of retinal pigment epithelium. Light microscopic autoradiograms of sections of neural retinal tissue incubated with 125I-EGF indicated that specific TGF-alpha/EGF receptors were present on one or more cell types of the retina with the exception of the outer segments of the photoreceptor cells. In addition, retinal cells appear to synthesize TGF-alpha since both mRNA for TGF-alpha and TGF-alpha protein (4.2 ng/mg protein) were detected in retinal extracts using cDNA hybridization and TGF-alpha RIA techniques. The role(s) of TGF-alpha and its receptor in retina is unknown, but it is possible that they interact via an autocrine/paracrine mechanism to influence retinal regeneration, proliferative retinopathies or neural transmission.

Patient attitudes toward physician consent in epidemiologic research.

Attitudes of patients toward the necessity of physician consent in epidemiologic studies were assessed. Questionnaires were mailed to women with breast, endometrial and ovarian cancers who had previously participated in a personal interview study (N = 692). Of respondents (N = 514), only 2 per cent would have preferred their physician to have withheld approval, and half considered physician permission necessary. Thirty-five per cent reported that their doctor talked to them about the study prior to the interview. Implications of including physician consent in study protocols are discussed.

KIE: The initiation of contact with a patient for an epidemiologic study is usually contingent upon the prior consent of the attending physician. To assess the attitudes of patients toward the necessity of physician consent, questionnaires were mailed to 692 women with breast, endometrial, or ovarian cancers who had previously participated in a personal interview study. Only 2% of the 514 respondents would have preferred that their physicians withhold approval; half considered physician permission necessary. One-third of the patients--most frequently black women and women of lower educational levels--reported that their doctors had talked to them about the study prior to the interview.

Myxobacters from arid mexican soil.

Myxobacters were found to be common inhabitants of the arid soils from the Monterrey, Nuevo Leon, Mexico, area. Thirteen species of the genera Myxococcus, Archangium, Cystobacter, Stigmatella, Polyangium, and Chondromyces were isolated on a mineral salts agar supplemented with bakers' yeast and filter paper. Greater species diversity per soil sample was found in the region receiving 400 to 800 mm of annual rainfall as compared with soils from an area having only 200 to 400 mm of rainfall.