Sister chromatid exchange frequency in breast cancer cases

Sister chromatid exchange (SCE) were studied in 22 patients with breast cancer (i.e., four stage II; 12 stage III, six stage IV) and 10 normal healthy females as age-matched controls. The data obtained in these cases followed a Poisson distribution. An apparent increase in the average rate of SCE/cell was observed with the advancing stage of breast cancer.

Multi-drug resistance in salmonellae isolated from enteric fever cases at Porur--a semi urban area near Madras City

A total of 249 isolations of Salmonella were made during 1991, of which 67.46 per cent were resistant to chloramphenicol. Resistance to ampicillin, co-trimoxazole and amoxycillin was higher (82.91, 77.69, 81.42 per cent respectively). Salmonella typhi was predominant agent forming 94.78 per cent and Salmonella paratyphi A caused the remaining infections. 44.98 per cent of the isolations were in children. This outbreak has been discussed in the light of other reports from India.

Ligand and proton exchange dynamics in recombinant human myoglobin mutants

Site-specific mutants of human myoglobin have been prepared in which lysine 45 is replaced by arginine (K45R) and aspartate 60 by glutamate (D60E), in order to examine the influence of these residues and their interaction on the dynamics of the protein. These proteins were studied by a variety of methods, including one and two-dimensional proton nuclear magnetic resonance spectroscopy, exchange kinetics for the distal and proximal histidine NH protons as a function of pH in the met cyano forms, flash photolysis of the CO forms, and ligand replacement kinetics. The electronic absorption and proton nuclear magnetic resonance spectra of the CO forms of these proteins are virtually identical, indicating that the structure of the heme pocket is unaltered by these mutations. There are, however, substantial changes in the dynamics of both CO binding and proton exchange for the mutant K45R, whereas the mutant D60E exhibits behavior indistinguishable from the reference human myoglobin. K45R has a faster CO bimolecular recombination rate and slower CO off-rate relative to the reference. The kinetics for CO binding are independent of pH (6.5 to 10) as well as ionic strength (0 to 1 M-NaCl). The exchange rate for the distal histidine NH is substantially lower for K45R than the reference, whereas the proximal histidine NH exchange rate is unaltered. The exchange behavior of the human proteins is similar to that reported for a comparison of the exchange rates for myoglobins having lysine at position 45 with sperm whale myoglobin, which has arginine at this position. This indicates that the differences in exchange rates reflects largely the Lys----Arg substitution. The lack of a simple correlation for the CO kinetics with this substitution means that these are sensitive to other factors as well. Specific kinetic models, whereby substitution of arginine for lysine at position 45 can affect ligand binding dynamics, are outlined. These experiments demonstrate that a relatively conservative change of a surface residue can substantially perturb ligand and proton exchange dynamics in a manner that is not readily predicted from the static structures.

Gunshot wounds in children under 10 years of age. A new epidemic

Before 1980 we had not treated any children with gunshot wounds who were younger than 10 years of age, but the number has increased dramatically each year since then. Thirty-four children younger than 10 years of age were treated for gunshot wounds from 1980 to 1987. Sociologic and epidemiologic data were assessed by a child-abuse team and police. Other studies have concluded that gunshot wounds in young children were usually caused by unintentional injury, child abuse, or neglect. From our present study we add a further, and very disturbing, category, that of attempted or intentional pediatric homicide. The children in this category were shot in retaliation for gang activities of their older siblings. This study demonstrates that the majority of our patients' childhood gunshot wounds were related to gang violence and retaliation, the availability of handguns in the home, and child neglect. The prevalence of childhood gunshot wounds in the inner city is increasing dramatically.