Elimination of the transient ipsilateral retinotectal projection is not solely achieved by cell death in the developing chick.

During development of the projection from the retina to the brain in the chick, a transient ipsilateral retinotectal projection forms and disappears. This disappearance is coincident with a wave of ganglion cell death in the retina. The contribution of cell death to the disappearance of this projection, as opposed to another mechanism such as axon retraction, was examined. Retinal ganglion cells with a projection to the ipsilateral tectum were retrogradely labeled by injection of long-lasting fluorescent dyes into the tectum prior to the onset of ganglion cell death. Large injections of fast blue labeled approximately 1800 ganglion cells in the ipsilateral retina before the period of cell death began. If the injected embryos were allowed to survive past the peak period of ganglion cell death, the average number of labeled ganglion cells in the ipsilateral retina was reduced by somewhat more than half. It is possible that the remaining labeled ganglion cells projected only to nontectal visual nuclei and were labeled by fast blue that had diffused out of the tectum. This was tested by repeating the study using very localized injections of 1,1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate or fluorescent microspheres into the tectum. These small injections confirmed that cells with transient projections to the ipsilateral tectum survived past the elimination of this projection. Thus, ipsilaterally projecting ganglion cells have, at most, a slightly greater propensity for death than the average ganglion cell, and elimination of the transient ipsilateral retinotectal projection in chick can be explained only, in part, by the mechanism of cell death.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of murex single-use diagnostic system with traditional enzyme immunoassay for detection of exposure to human immunodeficiency virus.

Because a retrospective study detected 13 negative Western blots out of 38 single-use diagnostic system (SUDS)-positive cases over a 1-year period, we performed a prospective study to compare the performance of the SUDS test with that of enzyme immunoassay (EIA). Of 888 SUDS-tested sera, 875 (98.4%) were both SUDS and EIA negative and 5 (0.6%) were SUDS, EIA, and Western blot positive. The rate of SUDS-positive samples decreased from 3.16/month in the retrospective study to 1.33/month in the prospective study. The immunoassays had sensitivities and specificities of 100 and 99.7 (SUDS) and 100 and 99.4% (traditional EIA), respectively. In laboratories with experienced personnel, the SUDS test performs as well as the EIA as a screen for infection with the human immunodeficiency virus.     

A physiological approach to surgery for acute rupture of the papillary muscle

There is controversy regarding the optimal management of patients in whom acute papillary muscle rupture develops. This study evaluates the effect of division of the anterolateral papillary muscle on left ventricular (LV) function and compares two methods of treatment--mitral valve replacement (MVR) and mitral valve repair. Thirteen pigs were placed on cardiopulmonary bypass, and interventions were performed in an isolated beating heart preparation. LV function was assessed with a compliant intraventricular balloon at baseline, after division of the anterolateral papillary muscle (Divided), after repair of the divided papillary muscle (Repair), and finally after MVR. Division of the anterolateral papillary muscle caused a significant deterioration in LV function. Function was maintained at this level after mitral valve repair but deteriorated with MVR. Developed pressure measured at baseline was 179 +/- 13 mm Hg; Divided, 148 +/- 11 mm Hg (p less than 0.05 versus baseline); Repair, 149 +/- 15 mm Hg; and MVR, 95 +/- 8 mm Hg (p less than 0.05 versus Divided) at a balloon volume of 20 ml. These results suggest that LV function is impaired by papillary muscle rupture. Repair of the ruptured papillary muscle is associated with better LV function than is MVR.     

1-Methylnicotinamide stimulates cell growth and inhibits hemoglobin synthesis in differentiating murine erythroleukemia cells

Exposure of murine erythroleukemia cells (MELCs) to nicotinamide (NA) or its synthetic analog N′-methylnicotinamide (N′-MN) reduces cell growth and induces terminal differentiation, marked by increased heme and globin accumulation. On the contrary, 1-methylnicotinamide (1-MN), the primary metabolite of excess NA, was found to stimulate cell growth and reduce spontaneous differentiation of cultured MELCs. Log phase MELCs exhibited up to 50% higher cell density above untreated cells when cultured for up to 96 h with 2.5 mM 1-MN. When combined with NA or several chemically-unrelated inducers of hemoglobin synthesis in cultured MELCs, 1-MN reduced the globin mRNA levels and heme accumulation by 40–80%. 1-MN was able to inhibit heme production if present during only the first 24–48 h after NA exposure. Pre-treatment with 1-MN could not confer resistance of cells to effects of NA, suggesting the inhibition is reversible. Commitment to differentiate in semisolid medium by the most potent inducer, 5 mM N′-MN, was inhibited up to 95% by 2.5 mM concentrations of 1-MN. It appears that 1-MN has opposing effects on growth and induction of differentiation than those seen in MELC cultures exposed to NA or N′-MN.     

Fabricating fixed partial dentures using existing restorations

A technique has been described for utilizing an existing fixed splint in the fabrication of a fixed partial denture to replace splinted teeth that are extracted.     

Comparison of positive allergy skin tests among asthmatic children from rural and urban areas living within small geographic area.

BACKGROUND: Evidence of increased asthma and allergic response among urban versus rural residents has been reported. OBJECTIVE: To evaluate the prevalence of allergic response among asthmatic children from urban and rural areas living within close proximity. METHODS: In all, 448 asthmatic children from urban (363) and rural (85) areas were studied. The study group consisted of 234 9-year-olds and 214 12-year-olds. A health questionnaire was completed on each child who subsequently underwent allergic skin prick tests (SPTs). RESULTS: There was significantly more positive SPT response to house-dust mite, mold, cat, and cypress among asthmatic children from urban areas compared with children living in rural areas: 58.3% versus 37.6%, 46.1% versus 31.8%, 17.45 versus 5.9%, and 26.2% versus 15.3%, respectively. Positive SPT for indoor allergens were significantly greater among asthmatic urban residents than asthmatic rural residents: 63.3% versus 45.5%, respectively (P < 0.02). Positive SPT response to all the allergens checked was higher among the 12-year-old age group when compared with the 9-year-olds, 34.6% versus 22.7%, respectively (P = 0.05). CONCLUSIONS: Allergic response measured by SPT is significantly more common among asthmatic children from urban areas as opposed to rural, even though both areas are within small distance of one another. Further, asthmatic children living in urban areas demonstrated more allergic response to both indoor and outdoor allergens. The allergic response tends to increase with increased age in both urban and rural asthmatic children.     

A comparison of three methods of repairing the hard palate.

OBJECTIVE: To compare growth, speech, and nasal symmetry outcomes of three methods of hard palate repair. PATIENTS: Consecutive available records of children born with unilateral bony complete cleft lip and palate over the period 1972 to 1992. INTERVENTIONS: Identical management of lip, nose, alveolus, and soft palate. Hard palate repair by Cuthbert Veau (CV) from 1972 to 1981, von Langenbeck (vL) from 1982 to 1989, or medial Langenbeck (ML) from 1989 to 1991. OUTCOME MEASURES: For growth: GOSLON yardstick or 5-year model index. For speech: articulation test. Nasal anemometry. For nasal symmetry: Coghlan computer-based assessment. All these measures were developed during the period of data collection but not for this project. RESULTS: There was a strong trend toward more favorable anteroposterior maxillary growth with the change from CV to vL to ML techniques. This fell short of statistical significance because of the small sample size. There was a significant reduction in cleft-related articulation faults (p =.01) considered to be related to improved arch form. In the absence of improved rates of velopharyngeal insufficiency or nasal symmetry, increased surgical experience was discounted as a significant contribution to improved growth and articulation outcomes. CONCLUSIONS: Reduced periosteal undermining and residual exposed palatal shelf from CV to vL to ML improved incisor relationships and articulation.