Somites in zebrafish doubly mutant for knypek and trilobite form without internal mesenchymal cells or compaction.

In vertebrates, paraxial mesoderm is partitioned into repeating units called somites. It is thought that the mechanical forces arising from compaction of the presumptive internal cells of prospective somites cause them to detach from the unsegmented presomitic mesoderm [1-3]. To determine how prospective somites physically segregate from each other, we used time-lapse microscopy to analyze the mechanics underlying early somitogenesis in wild-type zebrafish and in the mutants trilobite(m209) (tri), knypek(m119) (kny), and kny;tri, which are defective in convergent extension during gastrulation. Formation of somite boundaries in all of these embryos involved segregation, local alignment, and cell-shape changes of presumptive epitheloid border cells along nascent intersomitic boundaries. Although kny;tri somites formed without convergence of the presomitic mesoderm and were composed of only two cells in their anteroposterior (AP) dimension, they still exhibited AP intrasegmental polarity. Furthermore, morphogenesis of somite boundaries in these embryos proceeded in a manner similar to that in wild-type embryos. Thus, intersomitic boundary formation in zebrafish involves short-range movements of presumptive border cells that do not require mechanical forces generated by internal cells or compaction of the presomitic mesoderm.

Measurement and manipulation of cytosolic pH in polarizing zygotes.

The role of cytosolic pH (pHc) in establishment and expression of developmental polarity was examined in zygotes of the brown alga Pelvetia. pHc was measured and manipulated at specific developmental stages during the first zygotic cell cycle. pHc was measured using pH-sensitive microelectrodes and by confocal ratio imaging of dextran-conjugated SNARF 1 (dc SNARF 1) loaded cells. The two techniques yielded very similar values of pHc in the cellular cortex, but ratio imaging was not effective in measuring endoplasmic pHc values. As zygotes formed a developmental axis, cortical pHc decreased abruptly by approximately 0.1 units, and a small but significant difference in pHc was detected at the thallus and rhizoid poles. The cortical cytosol was relatively acidic at the presumptive rhizoid pole. The magnitude of the pHc difference increased following initiation of rhizoid growth. pHc was manipulated by treating zygotes with membrane-permeant weak acids (propionic and benzoic acid) or bases (methylamine and procaine), which effectively clamp pHc to specific values in a concentration-dependent manner. pHc values in treated zygotes were measured for each concentration of acid or base, and a dose response curve was generated. Zygotes in which pHc had been clamped were examined for their ability to form a developmental axis and to initiate rhizoid outgrowth (germination). Both developmental processes were inhibited by relatively small (0.2-0.3 pH units) perturbations of pHc. The permissive ranges of pHc were slightly different, germination (permissive pHc range-pH 7.0 to 7.7) being more acid tolerant than axis formation (permissive pHc range-7.2 to 7.8).

The effect of adsorption on the acid production of caries and noncaries-producing streptococci.

Eighteen different Streptococcus strains including S mutans, sanguis, mitis, salivarius, bovis, and 2F2, were assayed for their relative adsorption to synthetic hydroxyapatite and for quantities of lactic acid produced while in the adsorbed state. The results indicated that all S mutans and some S sanguis have an enhanced metabolic activity while adsorbed to hydroxapatite as compared to control suspensions without hydroxyapatite.

Cryoablation of benign breast tumors: evolution of technique and technology.

We report on improvements in cryoprobe design and techniques of cryoablation as a minimally invasive alternative to open surgery for the treatment of benign breast tumors. In the study, which was conducted in 12 centers, 124 lesions in 102 patients were monitored for a period of 12 months after cryoablation. Two different treatment techniques were used: Double HI FREEZE and Tailored Freeze. In patients treated with the Tailored Freeze technique significantly better results were recorded 12 months after the procedure: the median reduction in tumor volume was 91%, 73% of all tumors treated were nonpalpable, 84% of lesions less than 2.5 cm in maximum diameter were nonpalpable, and none of the 31 mammograms performed yielded abnormal findings. Patient satisfaction was good to excellent in 92% of the patients. The safety profile of this technique was excellent; all complications were minor. Evolution of cryoablation freezing techniques, coupled with improvements in cryoprobe design, has resulted in significant improvements in both safety and effectiveness.

Sensitivity of Porphyromonas and Prevotella species in liquid media to argon laser.

The phototoxicity of argon laser irradiation was studied in aqueous suspensions of Porphyromonas endodontalis (American Type Culture Collection [ATCC] 35406), Porphyromonas gingivalis (ATCC 33277), Prevotella denticola (ATCC 33184) and two strains of Prevotella intermedia (ATCC 15033 and 49046), all "black-pigmented bacteria," BPB, that accumulate cellular porphyrins. Several of these species have been implicated in the etiology of periodontal disease. Non-black-pigmented bacteria were also studied to test the specificity of irradiation as a potential photodynamic treatment for periodontal infections. Cell suspensions were irradiated with an argon laser at fluences of 20-200 J/cm2. When cultured in hemin-supplemented media, ATCC 15033 was the most sensitive to irradiation. However, a second strain of the same species (ATCC 49046) was resistant. The photosensitivity of other species ranked ATCC 33277 > 35406 = 33184 = 35496. When hemin was replaced in media by hemoglobin, ATCC 33277 became resistant to irradiation. Protoporphyrin IX content in BPB cells was shown not to be a major factor determining photosensitivity. Oxygen was required during irradiation for BPB species to be affected. Non-black-pigmented bacteria were much less sensitive to irradiation than BPB.

Educating residents for managed care: report on a multidisciplinary conference.

A growing number of residency programs are preparing their graduates for the realities of managed care practice. In 1996, The Cleveland Clinic Foundation, a private, nonprofit academic medical center, hosted a two-day conference on managed care education to develop innovative instructional and evaluative approaches that, where appropriate, would build on existing expertise. The conference was attended by invited national experts who had a stake in residents' education: clinical faculty, residents, medical educators, executives of managed care organizations, and representatives of other interested organizations. Participants spent much of their time in four small break out groups, each focusing on one of the following topics that were judged particularly relevant to managed care: preventive and population-based medicine, appropriate utilization of resources, clinician-patient communication, and interdisciplinary team practice. Participants shared existing materials, discussed teaching goals and objectives, and generated ideas for teaching methods, teaching materials, and evaluative methods for their respective topics. The authors summarize the recommendations from the four groups, with an overview of the issues that emerged during the conference concerning curriculum development, integration of managed care topics into existing curricula, staging of the curriculum, experiential teaching methods, negative attitudes and resistance, evaluation of trainees and profiling, program assessment, faculty development, and cooperation between academic medical centers and managed care organizations.

Relationships of serum opsonins and complement in human experimental gingivitis.

This study assessed the phagocytosis of polymorphonuclear neutrophils and the opsonic capacity of serum in experimental human gingivitis. Relationships were sought among these two measurements, clinical indices of gingivitis and complement-related opsonins. Measurements of chemiluminescence provided an index of phagocytosis and of opsonic capacity. Test group Plaque Index scores were higher than the control group on Days 7, 14, and 21, while the Gingival Index of the test group was elevated only on Day 21. Phagocytosis of test subjects' PMNs and opsonic capacity of their sera were no different from that of the controls'. Levels of C3 in both nonactivated and activated sera of the test group were significantly lower than that of the control group only on Day 14. In the test group, differences of per cent C3 conversion occurred between Days 14 and 21, and Plaque Index scores were inversely correlated with the order of per cent C3 data on these same days. Our results also indicate that complement contributes significantly to the serum opsonic capacity. The levels of developing plaque and subsequent gingival inflammation are apparently related to the degree of complement activation.

Comparison of the antimicrobial effectiveness of regular and fresh scent Clorox.

The antimicrobial properties of two different compositions of sodium hypochlorite were compared in a tube dilution study. Absorbent paper points were contaminated with Streptococcus faecalis or Candida albicans and exposed to 5.25% or 2.62% concentrations of "regular" or "fresh scent" sodium hypochlorite (Clorox) for periods ranging from 15 to 120 s. The points were then removed from the sodium hypochlorite solution, placed into a growth medium, incubated, and the presence or absence of growth recorded. Results showed that formulary changes involved in the manufacture of the "fresh scent" sodium hypochlorite had no apparent effect on its antimicrobial properties, as both compositions proved equally effective against the test organisms at each concentration evaluated.

Phototoxicity of argon laser irradiation on biofilms of Porphyromonas and Prevotella species.

Species of Prevotella (Pr.) and Porphyromonas (Po.) and other microorganisms were cultivated as biofilms on agar medium and examined for their susceptibility to argon laser irradiation (continuous mode; wavelengths, 488-514 nm; fluences, 20-200 J cm(-2)). Fluences of 35 to 80 J cm(-2) inhibited biofilm growth in Po. endodontalis, Po. gingivalis, Pr. denticola, Pr. intermedia, Pr. melaninogenica and Pr. nigrescens. A fluence of 70 J cm(-2) did not affect biofilm growth in species of Bacillus, Candida, Enterobacter, Proteus, Pseudomonas, Staphylococcus and Streptococcus. The phototoxic effects of argon laser irradiation against Prevotella and Porphyromonas species were: (1) caused by the radiation alone; (2) modified by biofilm age; (3) dependent on the presence of atmospheric oxygen; (4) influenced by medium supplements of hemin, hemoglobin and blood; (5) greater when compared with other microbial species; (6) demonstrated without augmentation with an exogenous photosensitizer; and (7) apparently unrelated to the protoporphyrin content of the cells. Overall, these in vitro findings suggest that low doses of argon laser radiation may be effective in the treatment and/or prevention of clinical infections caused by biofilm-associated species of Prevotella or Porphyromonas.

Primary lymphoma of the large intestine.

Three cases of primary colonic lymphoma are presented and the literature for this disease is reviewed. Colonic lymphoma occurs in from 0.5 to 2 per cent of all cases of neoplastic disease of the colon, and comprises 15 to 20 per cent of cases of primary gastrointestinal lymphoma. The disease can occur at any age, from 3 years to 89 years; the average age is 50 years. Men are affected twice as often as women. The disease most commonly presents as a painful abdominal mass. The cecum is the area of involvement in 70 per cent of cases. The tumors are usually large, averaging over 7 centimeters. The most common histological types are histiocytic or lymphocytic tumors. Surgery is the principle treatment mode; about half are thought to be potentially curable at the time of surgical exploration. The role of adjuvant therapy has not yet been clearly defined, although data from some studies indicate increased survival in those patients given adjuvant radiation therapy. Survival is decreased in patients with tumors larger than 5 centimeters or with histiocytic cell type. Overall 5-year survival is 39 per cent.

Neutrophil chemotaxis and periodontal health relationships of young adult people in Thailand.

Polymorphonuclear neutrophils (PMN) from 26 young patients with periodontitis exhibited about 10 per cent less chemotaxis compared to healthy-matched control subjects. This modest but significant reduction of PMN chemotaxis occurred when the attractants were derived from either autologous or heterologous sera. The lower chemotaxis function was attributable to the nature of the PMN in periodontitis and not to the capacity of the patients' serum to generate chemo-attractants. Random migration of PMN was the same in both patients and controls. Kinetic studies with endotoxin-activated human sera showed no difference between the PMN of two periodontitis patients and their controls. No significant correlations were found between chemotaxis and the clinical periodontal indices; however, PMN chemotactic values were lower in localized periodontitis than in the generalized form of the disease.

Neutrophil chemi-luminescence and opsonic activities of young people with periodontitis in Thailand.

The polymorphonuclear neutrophils (PMN) produced significantly-higher chemi-luminescence (CL) peak values than neutrophils of healthy-paired controls when each population of cells was challenged with zymosan pre-opsonized with autologous serum. This enhanced CL was not attributable to the metabolic activity of the cells, but was shown, by cross-over experiments and additional testing with a single source of cells, to be directly associated with the opsonizing capacity of the patient's serum. The results suggest that peripheral PMN from young periodontitis patients have oxidative metabolic activities similar to subjects free of this disease, and that the enhanced PMN metabolism of patients may be due to a corresponding increase of serum opsonins.

Microbiology teaching in American dental schools.

A comprehensive questionnaire on current practices relevant to teaching microbiology to dental students was sent to all dental schools in the United States. The survey collected information on resources available, modes of teaching, and evaluation processes. Seventy percent (42/60) of the schools responded. Great variation was found in the teaching of microbiology largely due to the variety of educational resources, perspective of subject matter by the faculty, and the backgrounds of entering students. Data are presented that document the integration of microbiology with other courses, placement of microbiology in the curriculum, class attendance policies, availability of advanced selective and/or elective courses, and National Board reviews. These and other data indicate some prevailing trends in the teaching of microbiology to dental students.