Bcl-2 protein and apoptosis in pediatric acute lymphoblastic leukemia

Many chemotherapeutic agents are thought to exert their genotoxic effects through induction of programmed cell death (PCD) (apoptosis) in tumor cells. The bcl-2 is an anti-apoptotic oncoprotein and can confer a survival advantage to tumor cells by preventing apoptosis. Overexpression of bcl-2 may therefore be implicated in resistance to chemotherapy. We studied the significance of bcl-2 expression and the PCD index in pediatric acute lymphoblastic leukemia. Evaluation of bcl-2 by immunocytochemistry and PCD by an enzymatic end labelling technique using biotin-dUTP was carried out in a total of 55 cases and 40 controls. Bcl-2 was found to be expressed in 47% (26/55) of the acute lymphoblastic leukemia cases. The positive cells varied from 0-49% among individual samples. Pre-treatment (spontaneous) apoptosis was observed in 62% (34/55) cases. The mean pre-treatment PCD index was 8.27 1.3%, while the median PCD index was 5. The PCD value for the leukemic samples analyzed were then classified as either high apoptosis values ( 5) and low apoptosis values (<5). PCD index was high in 53% (29/55) and low in 47% (26/55). However, 23% (13/55) of cases did not show presence of either apoptosis or bcl-2. There was no association between clinical and laboratory parameters with the apoptotic index or bcl-2 protein expression. However, evaluation of apoptotic index and bcl-2 expression on day 7 of induction chemotherapy showed a borderline correlation between these markers and initial WBC count, presence of mediastinal mass and hepatosplenomegaly. Follow-up of these patients is being done to look for any association between treatment response and apoptosis.

Tumor proliferative compartment, multidrug resistance gene product and apoptosis regulatory p53 and bcl-2 proteins in pediatric acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most frequent childhood tumor. Although the cure rate has increased dramatically over the past few years, the molecular and cellular biology of this disease is still not fully understood. Important factors affecting prognosis include age, leucocyte count, cytogenetic abnormalities, immunophenotype and sex. However, the role of cell kinetics, tumor associated genes and drug resistance have rarely been investigated in pediatric ALL. This preliminary study looks at these aspects in this disease. Immunocytochemical analysis of the tumor suppressor protein p53, the anti apoptotic protein bcl-2, the multidrug resistance (MDR) gene product P-glycoprotein and the proliferation marker, Ki-67 were done using appropriate monoclonal antibodies. A total of 88 previously untreated children with confirmed ALL diagnosis and 40 age matched controls were included in the study. Ki-67 was expressed in 81% and P-glycoprotein in 68% of all cases. P53 expression was observed in 68% and Bcl-2 in 50% of cases. Fifty percent of all cases also showed concomitant expression of bcl-2 and p53. Since wild-type p53 is known to negatively regulate the expression of bcl-2, the co-expression of these two proteins having contrasting functions suggests that the p53 may be of a mutant variety. In addition, the expression of p53 also correlates to the presence of the multidrug gene product P-glycoprotein. Control samples were negative for all the four markers. P53, bcl-2 and P-glycoprotein can all influence chemotherapy resistance, the first two by regulating programmed cell death and the third by influencing intracellular drug levels. All patients are now being followed up to assess treatment response and to study the prognostic significance of the analyzed markers.

Unique regulation of crystal protein production in Bacillus thuringiensis subsp. yunnanensis is mediated by the cry protein-encoding 103-megadalton plasmid

In sporulating cultures of Bacillus thuringiensis subsp. yunnanensis HD977, two cell types are observed: cells forming only spores and cells forming only crystals. Curing analysis suggested that the crystal proteins are plasmid encoded. Through plasmid transfer experiments, it was established that a 103-MDa plasmid is involved in the crystal production. Conjugal transfer of this plasmid to Cry- recipient cells of Bacillus thuringiensis subsp. kurstaki HD73-26 conferred the ability to produce crystals exclusively on asporogenous cells of the recipient, indicating that the 103-MDa plasmid mediates the unique regulation of Cry protein production. When the dipteran-specific cryIVB gene was introduced into wild-type (Cry+) and Cry- backgrounds of B. thuringiensis subsp. yunnanensis by phage CP51ts45-mediated transduction, similar to all other B. thuringiensis strains, irregular crystals of CryIVB protein were produced by spore-forming cells in both backgrounds. However, the synthesis of the bipyramidal inclusions of B. thuringiensis subsp. yunnanensis was still limited only to asporogenous cells of the transductant. Thus, it appears that the unique property of exclusive crystal formation in asporogenous cells of B. thuringiensis subsp. yunnanensis is associated with the crystal protein gene(s) per se or its cis acting elements. As the crystals in B. thuringiensis subsp. yunnanensis were formed only in asporogenous cells, attempts were made to find out whether crystal formation had any inhibitory effect on sporulation. It was observed that both Cry+ and Cry- strains of B. thuringiensis subsp. yunnanensis (HD977 and HD977-1, respectively) exhibited comparable sporulation efficiencies. In addition, the Cry- B. thuringiensis subsp. kurstaki host (HD73-26) and its Cry+ transconjugant (HD73-26-16), expressing the B. thuringiensis subsp. yunnanensis crystal protein, were also comparable in their sporulation efficiencies, indicating that production of the crystal proteins of B. thuringiensis subsp. yunnanensis does not affect the process of sporulation.

A three-receptor model for the interaction of the K88 fimbrial adhesin variants of Escherichia coli with porcine intestinal epithelial cells

Four phenotypes of pigs distinguished by the variant(s) of K88 fimbrial adhesin (K88ab, K88ac, K88ad) that bind to their intestinal epithelial cells (I-none of the variants, II-K88ad, III-K88ab and K88ac, and IV-all three variants) have been identified. We hypothesize that the differences between the phenotypes are defined by the presence or absence of K88 adhesin receptors. We propose a three-receptor model to account for the observed phenotypes: 1) Receptor bed which binds all three variants and is found in phenotype IV, 2) Receptor be which binds K88ab and K88ac and is found in phenotype III and IV, and 3) Receptor d which binds K88ad and is found in phenotype II. We have identified the be receptor activity as a pair of mucin-type sialoglycoproteins (210 and 240 kDa). Although neither the bcd nor d receptor has been identified biochemically, their presence has been established using both blocking and receptor localization studies. Blocking studies using phenotype IV brush borders demonstrated that K88ab and K88ac fimbriae block the binding of E. coli expressing any of the K88 variants, but K88ad fimbriae block only K88ad E. coli binding. These results indicate that two receptors (bcd and bc) exist in the phenotype IV animals. Receptor localization studies on intestinal sections from phenotype IV animals showed that K88ab and K88ac adhesin binding is continuous from the crypt to the tip of the villus. The binding of the K88ad adhesin binding is multifocal in phenotype IV pigs, but continuous from crypt to tip of the villus in sections of phenotype II pigs. These studies verify the presence of two receptors (bcd and bc) in phenotype IV animals, and indicate that the K88ad receptor in phenotype IV animals (bcd) is different than in phenotype II animals (d).

Argyrophilic nuclear organizer regions (AgNORs) in pediatric acute lymphoblastic leukemia

Nuclear organizer regions (NORs) code for ribosomal RNA and are associated with non-histone nucleoproteins which can be identified by silver staining (AgNORs). AgNORs have been correlated to proliferative activity of tumors and hence may be prognosis-related. The present study evaluates the possible prognostic importance of the AgNORs in tumor cells of patients with pediatric acute lymphoblastic leukemia (ALL). A significant increase in AgNOR counts was observed in ALL patients as compared to normal controls. Further, a significant positive correlation was observed between AgNOR counts and total WBC count at diagnosis. A negative correlation was also observed between AgNOR counts and age of the patients. Logistic regression analysis revealed further correlation between AgNOR counts and disease with an odds ratio of 1.29 (P = 0.03) as compared to normal controls. These results therefore suggest that AgNOR counts may be significant in the evaluation of pediatric ALL.

Management of Perthes disease of late onset in southern India. The evaluation of a surgical method

We analysed the short-term outcome after varus osteotomy for Perthes' disease in 48 older children from south-west India, comparing them with 30 historical controls. The children were between 7 and 12 years of age at the onset of the disease. All had stage-I or stage-II disease, with half or more of the epiphysis involved. The operated children had an open-wedge subtrochanteric varus osteotomy with derotation or extension and a trochanteric epiphyseodesis. Weight-bearing was avoided until late stage III. The non-operated children had been treated symptomatically by conservative methods. At the time of healing, 62.5% of the operated group had spherical femoral heads compared with 20% of those treated non-operatively (p < 0.001). Of the operated children with Catterall group-IV involvement, 48% had good results as against 24% of the non-operated group (p < 0.05). The percentage increase in the radius of the affected femoral head compared with the normal side was significantly lower in children who had operations (14.68 v 25.65; p < 0.001). We have shown that the short-term results of early surgical containment in children over seven years of age are satisfactory.

MANAGEMENT OF PERTHES DISEASE OF LATE ONSET IN SOUTHERN INDIA

We analysed the short-term outcome after varus osteotomy for Perthes’ disease in 48 older children from south-west India, comparing them with 30 historical controls.

The children were between 7 and 12 years of age at the onset of the disease. All had stage-I or stage-II disease, with half or more of the epiphysis involved. The operated children had an open-wedge subtrochanteric varus osteotomy with derotation or extension and a trochanteric epiphyseodesis. Weight-bearing was avoided until late stage III. The non-operated children had been treated symptomatically by conservative methods.

At the time of healing, 62.5% of the operated group had spherical femoral heads compared with 20% of those treated non-operatively (p < 0.001). Of the operated children with Catterall group-IV involvement, 48% had good results as against 24% of the non-operated group (p < 0.05). The percentage increase in the radius of the affected femoral head compared with the normal side was significantly lower in children who had operations (14.68 v 25.65; p < 0.001).

We have shown that the short-term results of early surgical containment in children over seven years of age are satisfactory.

Study of Biaxial Stress Induced by Cosputtered Thin Molybdenum Silicide Films in Silicon Single-Crystal Substrates

Bending of 25 mm-diameter (100) silicon wafers produced by 100 nm-thick cosputtered molybdenum–silicon films has been investigated just after deposition, after rapid thermal annealing and after etching of the deposits. Values of biaxial stress in the films were determined by the use of a widely used relation. The Mo:Si ratio in the as-deposited films was 89:11. Radii of curvature of substrates were measured by a double-crystal X-ray diffractometer. Blank wafers with three widely different radii of curvature (33, 62 and 250 m) were chosen as specimens and their curvatures were taken into account in the determination of the value of biaxial stress in wafers with deposits. All the wafers were convex when viewed from the polished surface side on which the films were deposited. Values of σ for wafers with as-deposited films were in the range 3 × 108 to 14 × 108 Nm−2 (tensile). Wafers with higher initial bending showed higher values of stress. Deposition led to degradation of perfection, as revealed by broadening of the diffraction curves and the contrast in the topographs. Rapid thermal annealing at 1273 and 1373 K (3–4 min) led to formation of the MoSi2 phase and to a notable relaxation of stress. The values of σ were in the range 1 × 107 to ~6 × 108 N m−2 (tensile). The value of the stress was lowest for the blank wafer with smallest bending. Annealing also improved the degree of crystalline perfection of the silicon. Experiments performed after etching of the annealed specimens showed no significant change in the radii of curvature.

Differential effect of ultraviolet-B radiation on certain metabolic processes in a chromatically adapting Nostoc

The impact of UV-B radiation on growth, pigmentation and certain physiological processes has been studied in a N2-fixing chromatically adapting cyanobacterium, Nostoc spongiaeforme. A brownish form (phycoerythrin rich) was found to be more tolerant to UV-B than the blue-green (phycocyanin rich) form of N. spongiaeforme. Continuous exposure to UV-B (5.5 W m-2) for 90 min caused complete killing of the blue-green strain whereas the brown strain showed complete loss of survival after 180 min. Pigment content was more strongly inhibited in the blue-green strain than in the brown. Nitrogenase activity was completely abolished in both strains within 35 min of UV-B treatment. Restoration of nitrogenase occurred upon transfer to fluorescent or incandescent light after a lag of 5-6 h, suggesting fresh synthesis of nitrogenase. Unlike the above processes, in vivo nitrate reductase activity was stimulated by UV-B treatment, the degree of enhancement being significantly higher in the blue-green strain. Like the effect of UV-B on nitrogenase, 14CO2 uptake was also completely abolished by UV-B treatment in both strains. Our findings suggest that UV-B may produce a deleterious effect on several metabolic activities of cyanobacteria, especially in cells lacking phycoerythrin. Strains containing phycoerythrin appear to be more tolerant to UV-B, probably because of their inherent property of adapting to a variety of light qualities.