Antigen density in ELISA; effect on avidity dependency

Two different densities of an antigen (bovine serum albumin, BSA) were used on paper disks is an enzyme-linked immunosorbent assay (ELISA) for chicken IgG anti-BSA antibodies. Disks of different antigen density but containing the same amount of the antigen showed a difference in immunoreactivity. Samples containing large amounts of low avidity antibodies gave higher absorbance when disks of lower antigen density were used. This phenomenon was not due to a competition between antibodies of various immunoglobulin classes. These findings may indicate that antigen density affects the sensitivity of ELISA to antibodies of various avidities.     

Registry of experimental cancers of the National Cancer Institute

This report describes the organization and functions of the Registry of Experimental Cancers and gives the chronology of events that led to its establishment. Currently 21,500 accessions have been coded; the vast majority are spontaneous and induced cancers, chiefly of rodents, and also a wide variety of nonneoplastic diseases. Accessions are accepted from contributors working in laboratories in this country and abroad. The material is available for study by responsible scientists, and a limited number of study sets is available for loan on request.     

Photostabilizing effect of Ni(II) chelates in polymers. II. Effect of diamagnetic chelates on polypropylene phosphorescence

Examination of the phosphorescence emission form polypropylene shows the lifetime of the emission to be unaffected by a hydroxybenzophenone light stabilizer but significantly shorted by a diamagnetic Ni(II) chelate stabilizer.     

Clinical comparison of the XPERT non-contact tonometer and the conventional Goldmann applanation tonometer

OBJECTIVES: To examine the changing relationship between general and vascular surgical workload on a vascular "firm", over a 6-year period. DESIGN: Retrospective review. SETTING: Leicester Royal Infirmary and Professorial Surgical Unit, U.K. 1987-1992. METHOD: Analysis of audit of all surgical admissions. Relation of vascular surgery to general surgery. RESULTS: There has been a slight decrease (5%) in the number of general surgical elective admissions. Overall, the number of general surgical admissions, both elective and emergency, show a slight increase of about 3%. In contrast the number of vascular admissions increased by 42%. Of the general surgical procedures carried out 75.9% were either minor or intermediate, whereas 92.5% of vascular procedures were coded as major or higher. There has been a three times increase in the number of carotid endarterectomies, a similar increase in the number of the femorodistal bypass grafts and a halving of the number of major amputations. There has also been a five times increase in the number of angioplasties carried out. CONCLUSIONS: Our figures show the progressive, rapid increase in vascular surgical workload, compared to general surgery, and the need for the continued expansion of vascular surgery as a speciality.     

The global burden of trachomatous visual impairment: I. Assessing prevalence

This paper summarizes primary epidemiologic studies of trachomatous blindness to develop age-/sex-/region-specific estimates of the global prevalence of trachomatous blindness and low vision. These studies are first examined for their validity and then employed to derive a 'minimum' prevalence of trachomatous visual impairment. This method yield a global total for 1990 of approximately 640,000 cases of trachomatous blindness, corresponding to a prevalence of 0.12/1,000 (lower and upper bounds, 0.10 to 0.14/1,000). When those with low vision due to trachoma are included, 1.5 million cases of visual impairment are estimated, corresponding to a prevalence of 0.28/1,000 (lower and upper bounds, 0.15 to 0.75/1,000). A second approach, labeled the 'projected' prevalence of trachomatous visual impairment, selects country-wide studies to derive representative regional prevalence values. A global total of 2,899,000 blind ("projected' prevalence of 0.55/1,000 with lower and upper bounds, 0.37 to 0.83/1,000) is estimated for 1990. With trachomatous low vision included, greater than 6.7 million individuals in 1990 have visual impairment from trachoma ("projected' prevalence of 1.28/1,000 with lower and upper bounds, 0.53 to 4.29/1,000). Analysis of the distribution of the global prevalence by age, gender, visual acuity and region provide direction for trachoma research and programme priorities. Attention is drawn to the limited studies and resulting wide variation in the estimates of trachomatous visual impairment prevalence as indicated by the lower and upper bound estimates. It is recommended that this epidemiologic uncertainty be reflected in global and regional estimates of trachomatous visual impairment prevalence in order to draw attention to how little is known and emphasize the need for further surveys. A second paper incorporates these findings in an assessment of the global burden of trachomatous visual impairment.     

Preliminary study of two methods of treatment for laryngeal nodules

To date, a limited number of formal studies have assessed the efficacy of voice therapy for laryngeal nodules. The present study represents a preliminary stage of inquiry in a series of planned studies on this topic. Thirteen women with nodules participated as paid subjects. Some subjects received "confidential voice therapy," some received "resonant voice therapy," and some received no therapy (control condition) over a period of approximately 2 weeks. Pre- and post-therapy measures of phonatory effort, auditory-perceptual status of voice, and laryngeal appearance provided evidence of a benefit from therapy. Baseline measures were then repeated 2 weeks after therapy was terminated. The final results indicated that, for auditory-perceptual and phonatory effort measures, the likelihood of benefiting from therapy directly covaried with compliance scores (reflecting the reported extraclinical utilization of the therapy technique), but not with therapy type (confidential vs. resonant voice therapy). At this level, the results point to the importance of assessing not only therapy type but also compliance in future, larger studies. A series of other positive and negative factors in the present research design were identified based on the results. These should be considered in future studies.     

T helper cell-dependent, microbial superantigen-mediated B cell activation in vivo

The repair of slowly repairing potentially lethal damage (PLD) in radiosensitive cells from the severe combined immunodeficient (scid) mouse was compared with that in Balb/c 3T3 cells with "wild-type" radiosensitivity and that in RD13B2 cells derived from scid cells whose sensitivity is normal because of the presence of fragments of human chromosome 8. Treatment with 0.23 M NaCl was used for fixation of slowly repairing PLD. The scid cells repaired PLD sensitive to 0.23 M NaCl to a great extent whin 3-4 h, similarly to Balb/c 3T3 and RD13B2 cells. This indicates that the scid mutation hardly affects the repair of PLD sensitive to 0.23 M NaCl. On the other hand, as reported previously, the rapidly repairing PLD that is sensitive to 0.5 M NaCl was repaired only slowly (3-4 h) in scid cells, in contrast to the rapid repair (within 1 h) seen with Balb/c 3T3 and RD13B2. This suggests that scid mutation is responsible for this repair at reduced rate. To confirm the independence of repair of 0.23 M NaCl-sensitive PLD from that of 0.5 M NaCl-sensitive PLD, both treatments with 0.23 M NaCl and 0.5 M NaCl were combined in each line. It is found that the repair of either PLD was not affected by the other treatment. The scid mutation impaired only the repair of 0.5 M NaCl-sensitive PLD.