Systemic carboplatin for retinoblastoma: change in tumour size over time.

BACKGROUND/AIM: Chemotherapy for intraocular retinoblastoma is used to shrink individual retinal tumours to a size amenable to focal treatments. Quantitative data regarding retinal tumour response following treatment with primary systemic carboplatin are reported. METHODS: Changes in area and largest basal diameter of tumours that were exposed to carboplatin, had no concomitant focal treatment, and had digital funduscopic photography performed before and after treatment, were measured. Response was evaluated. RESULTS: 36 tumours were measured following one treatment: 34/36 (94.4%) responded, with a 37.1% mean decrease in area (median = 37.0%; range 4.0%-76.7%). Mean reduction in basal diameter was 21.3% (med = 21.0%; -7.9%-52.5%). 20 tumours were treated with a second cycle: 15/20 (75.0%) responded. Mean decrease in area was 17.8% (med = 15.3%; -7.0%-49.7%). The mean cumulative decrease in area after two treatments was 55.1% (med = 56.2%; 33.0%-74.5%). Mean cumulative reduction in basal diameter was 33.6% (med = 33.6%; 10.9%-53.2%). 12 tumours were treated with a third cycle: 3/12 (25.0%) responded, 8/12 were stable, and one progressed. Mean decrease in area was 5.4% (med = 7.2%; -17.7%-20.6%). Cumulative decrease in area after three treatments was 58.1% (med = 57.3%; 34.8%-77.2%). Mean cumulative reduction in basal diameter was 38.8% (med = 38.2%; 19.1%-54.1%). CONCLUSIONS: Carboplatin caused measurable shrinkage of retinoblastoma tumours. Response was greatest following the initial treatment and decreased with subsequent treatments.

Albers-Schönberg disease (autosomal dominant osteopetrosis, type II) results from mutations in the ClCN7 chloride channel gene.

Albers-Schönberg disease, or autosomal dominant osteopetrosis, type II (ADO II), is the most common form of osteopetrosis, a group of conditions characterized by an increased skeletal mass due to impaired bone and cartilage resorption. Following the assignment of the gene causing ADO II to chromosome 16p13.3, we now report seven different mutations in the gene encoding the ClCN7 chloride channel in all 12 ADO II families analysed. Additionally, a patient with the severe, autosomal recessive, infantile form of osteopetrosis (ARO) was identified as being homozygous for a ClCN7 mutation. From genotype-phenotype correlations, it seems that ADO II reflects a dominant negative effect, whereas loss-of-function mutations in ClCN7 do not cause abnormalities in heterozygous individuals. Because some ARO patients have mutations in both copies of the ClCN7 gene, ADO II is allelic with a subset of ARO cases.

Agonist-stimulated ligand binding by the platelet integrin alpha IIb beta 3 in a lymphocyte expression system.

The ligand binding activity of the platelet integrin alpha IIb beta 3 is initiated by agonist-generated intraplatelet signals. We studied this process in vitro by expressing recombinant alpha IIb beta 3 in Epstein-Barr virus-immortalized B lymphocytes. We found that phorbol ester stimulation induced the adhesion of lymphocytes expressing alpha IIb beta 3 to immobilized fibrinogen. Moreover, replacement of the transmembrane and cytoplasmic domains of the alpha and beta subunits of alpha IIb beta 3 with those of alpha L beta 2 significantly increased adherence, whereas replacement of only the cytoplasmic domains significantly decreased adherence. This suggests that transmembrane segments are involved in the agonist-induced modulation of alpha IIb beta 3 activity. Similar results were seen when the alpha IIb beta 3 activation-dependent monoclonal antibody PAC-1 was substituted for immobilized fibrinogen. We also found that the adherence of lymphocytes expressing beta 3 with either of the two alpha IIb/alpha L chimeras was similar to that of cells expressing alpha IIb beta 3, whereas the adherence of cells expressing alpha IIb with either of the two beta 3/beta 2 chimeras was substantially decreased, suggesting that the identity of the cytoplasmic domain of beta 3, but not of alpha IIb, is critical for alpha IIb beta 3 function. This report indicates that B lymphocytes contain signal transduction pathways involving protein kinase C that can increase the ligand binding activity of alpha IIb beta 3 and demonstrates the utility of these cells as an expression system for the study of agonist-stimulated alpha IIb beta 3 function.

Proliferating cell nuclear antigen in developing and adult rat cardiac muscle cells.

During early development, rat cardiac muscle cells actively proliferate. Shortly after birth, division of cardiac muscle cells ceases, whereas DNA synthesis continues for approximately 2 weeks at a progressively diminishing rate. Little DNA synthesis or cell division occurs in adult cardiocytes. Thus, developing cardiac muscle cells are an ideal system in which to examine the expression of cell cycle-regulated genes during development. We chose to examine proliferating cell nuclear antigen (PCNA), a gene expressed at the G1/S phase boundary of the cell cycle. Northern blots of RNA from cardiac muscle cells from 18-day-old rat fetuses and from day 0, 5, and 14 neonatal as well as adult rat hearts revealed that the PCNA mRNA was found in cardiac muscle cells from all ages. However, because it was possible that this was a result of fibroblast PCNA gene expression, we used reverse transcription followed by polymerase chain reaction to see if it was possible to detect the message for PCNA in cardiac muscle cells from all ages. Because of the great sensitivity of this technique, RNA was recovered from 25 isolated adult cardiac muscle cells. Polymerase chain reaction amplification products for PCNA produced from the RNA isolated from these cells conclusively demonstrated that mRNA for this gene, which normally is associated with proliferating cells, is expressed in adult cardiac muscle cells that no longer divide. Furthermore, Western blot analysis demonstrated that the PCNA protein was found only in embryonic and neonatal cells and not in adult rat cardiac muscle cells. Therefore, it might be inferred from these data that PCNA might be regulated at the posttranscriptional level in adult cardiac muscle cells.