Reaction of 1,3-bis(2-chloroethyl)-1-nitrosourea with synthetic polynucleotides

The antitumor agent BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea) was incubated with poly(C) and poly(G) in aqueous solution at 37 degrees and pH 7 to produce approximately 0.33 and 0.07% substitution, respectively. Under the same conditions, there was relatively little reaction with poly(A) and poly(U). Poylnucleotides reacted with [14C]BCNU were digested by chemical and enzymatic methods, and the derivative nucleotides were isolated by column chromatography. There were identified by a combination of ultraviolet and mass spectroscopy as 3-(beta-hydroxyethyl)CMP, 3,N4-ethano-CMP, and 7-(beta-hydroxy-ethyl)GMP. This would indicate that BCNU generates active two carbon fragments, probably chloroethyl carbonium ions, which are free to react with nucleotides. The production of these substituted bases may be important to the mechanism of action of the therapeutic nitrosoureas since they would probably alter the function of any nucleic acid which contained them.

Prevention of knee instability. Experimental model for prosthetic anterior cruciate ligament

Loss of the anterior cruciate ligament (ACL) in the dog results in a predictable type of arthritis. This condition can be prevented by successful prosthetic substitution of the anterior cruciate ligament (ACL). The condition is a practical model, and a sensitive index of success and failure for evaluation of prototype prostheses. Changes in the joint can be differentiated on the basis of cruciate insufficiency and reaction to the synthetic implant. The model was defined by replacing the ACL with a mesh or tape Dacron prosthesis in 16 Beagle dogs. Gait and anterior drawer sign are unreliable parameters of ACL insufficiency in dogs. At sacrifice up to 3 years postoperatively, 8 joints out of 32 joints were without arthritic changes. Arthritis developed in all joints in which the prosthesis elongated or broke. Failure always occurred intra-articularly at the mouth of a bone tunnel. Successes were inconsistent even with a single material and animal breed. The drillhole techniques used in ACL reconstructions are difficult to standardize. Variability in placement of the prosthesis is compounded by cutting action of bone edges. Porous mesh did not provide a lattice for true ligament regeneration through the joint. Fixation was not a problem in this series.

Improvement in the results of treatment of osteogenic sarcoma

Experience with 70 patients having osteogenic sarcomas treated between 1968 and 1973 demonstrated the importance of persistence in the management of the disease of these patients. Resection for pulmonary metastases in one or both lungs, often on more than one occasion, will salvage a number of these patients, thus improving the cure rate. Adriamycin has proved an effective palliative agent and a useful adjuvant to surgical therapy. Although the cure rate of tumors arising distal to the knee is much higher than that of more proximally situated tumors, resection of osteogenic sarcomas of the distal part of the femur does not require removal of the entire femur when care is taken to resect well above the site of the apparent tumor. Some osteogenic sarcomas are sensitive to adequate dosages of radiation therapy, but the exact role of this method is yet to be determined. No definite beneficial result could be attributed to any of a variety of modalities of immune stimulation therapy.

Minimizing radiation exposure in dental radiology

Rectangular field collimation gives high quality roentgenograms and reduces unnecessary exposure of radiation to the patient by 73-96 per cent.

'Antigenic' disparity between leukaemic lymphoblasts and normal lymphocytes in identical twins

Circulating lymphocytes of a normal boy were unequivocally stimulated by irradiated leukaemic lymphoblasts from his identical twin with acute lymphoblastic leukaemia. This reaction indicates that there is an `antigenic' disparity between these two types of cells. It is possible that leukaemic cells may acquire new surface antigens or that existing surface antigens of lymphoid cells may be modified during the process of leukaemogenesis.

Isoelectric fractionation and some properties of a protease from soyabean seeds

A protease, capable of hydrolysing benzoyl DL‐arginine p‐nitroanilide(BAPA), and L‐amino acid β‐naphthylamide derivatives, was purified, by isoelectric focusing in the region pH 3–6, from dormant and 6‐day germinated soyabean seeds. The enzyme was focused at pH 4·80. The Km value using BAPA as substrate was found to be 5·03 × 10−4M. Maximum activity of the enzyme towards BAPA was obtained in the pH 8·2–8–5 region. Slight activation was observed in the presence of 0·05 M concentration of Ca2+ and Mg2+ ions. The protease lacked caseinolytic activity, and was not inhibited by Kunitz soyabean trypsin inhibitor.

Spectroscopic studies on the conformation of native and denatured glycinin

Optical rotatory dispersion (ORD) studies and infrared spectra in deuterium oxide indicate that native glycinin exhibits mainly a β‐conformation structure. Ultraviolet difference spectra showed that urea ami guanidine hydrochloride at increasing concentrations cause progressive exposure of tyrosine and tryptophan residues. Ultraviolet difference spectroscopy was also used in following the course of acid‐induced denaturation of glycinin. It was observed that acid denaturation starts approximately at pH 3.50 reaching a maximum at pH 2.0. Data obtained by solvent perturbation of native glycinin using perturbants exhibiting mean diameters of 2.0, 4.4, and 7.2 A indicate that approximately 34 to 37 residues (45%of the total) are accessible to these perturbants whereas the accessibility of tryptophan residues is decreased with increasing mean diameters of the perturbant.