Extraction of hypotensive principles from seeds of Cassia tora

Seeds of Cassia tora Linn. (Leguminosae) are known in Chinese medicinal herbal practice as Chueh-ming-tzu. Aqueous and methanol extracts from these seeds elicit hypotensive effects on anesthetized rats. Preliminary phytochemical studies show that the active hypotensive principles are derived from the kernel of the seed and consist of mainly glycosides.

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.

Conformational fluctuations of DNA helix

Treatment of a homogeneous sample of circular DNA molecules that contain at least one single-strand scission per molecule with ligase yields a population of covalently closed circles heterogeneous in the topological winding number alpha. Under proper conditions, the product molecules with different values of alpha can all be resolved by gel electrophoresis. The distributions in alpha for several DNAs, covalently closed at different temperatures, have been determined and the results have been interpreted in terms of thermal fluctuations of the DNA helix.

On the degree of unwinding of the DNA helix by ethidium. II. Studies by electron microscopy

When a negatively twisted covalently closed DNA is annealed with single-stranded fragments of the same DNA, under proper conditions a loop (or loops) may form by the disruption of a segment (or segments) of base pairs between the complementary strands of the covalently closed DNA, and the formation of base pairs between the strands of the covalently closed DNA and the single-stranded fragments. Since such a process involves essentially no net gain or loss of the number of base pairs, it is driven by the free energy favoring the reduction of the number of superhelical turns. If the fragments are sufficiently long or are present at a sufficiently hig concentration during annealing, the most stable product between a covalently closed DNA and the DNA fragments (under conditions favoring the formation of double-stranded DNA) is a looped molecule devoid of superhelical turns. The size of the looped region or regions, which can be measured by electron microscopy, provides a way to determine the degree of superhelicity of the covalently closed DNA in the absence of the fragments. When this is compared with the degree of superhelicity of the covalently closed DNA determined by titration with the intercalative dye ethidium, the unwinding angle of the DNA double helix due to the intercalation of an ethidium can be calculated. Such measurements were done on two samples of phage PM2 DNA with different extents of supercoiling. The results are in agreement with the value 26 degree obtained recently by alkaline titration of covalently closed PM2 DNA samples in CsC1 density gradients (Wange, J.C., (1974) J. Mol. Biol. 89, 783-801).

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.

Thermodynamic properties of superhelical DNAs

Binding isotherms of ethidium to the superhelical DNA from phage PM2, and to PM2 DNA containing -1 single-chain scission per molecule, have been determined at six temperatures from 2.5 to 50 degrees, in 3M CsCl-0.01 M Na3EDTA. Spectrophotometric measurements in both the visible and ultraviolet (uv) regions were used to obtain the binding isotherms. The isotherm at 20 degrees was also obtained by determining the free ethidium concentrations in equilibrium with DNA-ethidium complexes in boundary sedimentation experiments. A simple thermodynamic analysis shows that for a superhelical DNA with v bound ethidium per nucleotide, the change in free energy per unit change in the number of superhelical turns T, dGT/dT, is directly related the ratio of the free ethidium concentrations, cf,v and cf,v, in equilibrium with the ethidium complexes of the superhelical and the nicked DNA, respectively, at the same values of v. The relationship is dGT/dT = (360/E)RTln (cf,v/cf,v), where e is the unwinding angle of the DNA helix per bound ethidium molecule. Experimentally, it was found that ln (cf,v/cf,v) = a1(v - vc), where a1 is a constant at a given temperature and vc is the value of v at which the originally superhelical DNA is completely relaxed, i.e., containing no superhelical turns. The equation relating dGT/dT and v, upon transformation and integration, gives finite difference GT,v=o = -a1NRTvc2/2, where finite difference GT,v=0 is the free energy of superhelix formation of the superhelical DNA in the absence of ethidium and N is the number of nucleotides per DNA molecule. This equation is independent of the unwinding angle e. The values of a1 are 11.2 plus or minus 0.9, 11.2 plus or minus 0.7, 11.2 plus or minus 0.6, 10.7 plus or minus 0.8, 10.0 pl.us or minus 1.0, and 9.8 plus or minus 1.4 at 2.5, 10, 20, 30, 40, and 50 degrees, respectively. Measurements with lambda b2b5c DNA, and monomeric and trimeric lambda dv DNA, indicate that the constant a1 is insensitive to the molecular length of DNA. The present results are compared with the previous results of Bauer and Vinograd (Bauer, W., and Vinograd, M. (1970), J. Mol. Biol. 47, 419), obtained by a statistical mechanical analysis of the ethidium binding isotherms (determined by density gradient centrifugation measurements) to two forms of simian virus 40 DNA at 25 degrees. The effects of superhelical turns on a number of processes, such as the binding of a ligand which unwinds or winds the DNA helix, the denaturation of a DNA segment, and the formation of hair-pinned structures from base sequences with a twofold rotational symmetry, are discussed from the thermodynamic point of view, based on the present results.

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.

Adrenaline-induced acute massive pulmonary oedema in the dog

Pericardiotomy followed by intravenous injection of adrenaline (1 mg/kg body weight) provides a reliable method for the production of acute massive lung oedema in the dog. The lung wet weight: heart wet weight ratio is found to be the best assessment of the degree of lung oedema. A ratio greater than two represents massive lung oedema.

Effect of circularity and superhelicity on transcription from bacteriophagelambda DNA

We studied RNA synthesis in vitro from closed-circular lambda DNA molecules with varying degrees of superhelicity. The four circular templates examined had 0, -50, -110, and -160 superhelical turns under the conditions of the transcription assay. We found that the total amount of RNA synthesis increases as the template acquires more negative superhelical turns. This increased transcription results from more frequent initiation of RNA chains. Transcription of circular DNA with no superhelical turns appears to mimic RNA synthesis in vivo more closely than transcription from either highly superhelical or linear DNA with regard to two criteria: preferential transcription of the region corresponding to early genes and sensitivity to repression by lambda cI protein. We suggest that the physical basis for the increased initiation of RNA chains from superhelical DNA is the fact that unwinding events are energetically favored on a DNA molecule with negative superhelical turns. Possible general mechanisms are: (a) RNA polymerase must unwind the DNA duplex as a prelude to initiation; (b) the DNA itself must assume a new conformation at the promoter site which requires an unwinding of the DNA duplex.

Alignment of two DNA helices: a model for recognition of DNA base sequences by the termini-generating enzymes of phage lambda, 186, and P2

Based on the 3'- and 5'-terminal sequences of DNA of phage lambda, P2, and 186, a model is proposed for recognition of DNA sequences by enzymes responsible for generation of cohesive ends. Two copies of the cohered ends, either on separate molecules or on a concatemer, are aligned with their helical axes parallel but running in opposite directions. The nicking system is dimeric, with each of the two monomers carrying identical sequence-recognition sites. Two pairs of nicks are introduced into the two aligned DNA molecules by the nicking system. The applicability of this model to other biological processes, such as integration of a viral genome into a host genome and the cutting of concatemeric T7 DNA, is discussed.