Processive action of T4 endonuclease V on ultraviolet-irradiated DNA.

The action of the dimer-specific endonuclease V of bacteriophage T4 was studied on UV-irradiated, covalently-closed circular DNa. Form I ColE1 DNA preparations containing average dimer frequencies ranging from 2.5 to 35 pyrimidine dimers per molecule were treated with T4 endonuclease V and analysed by agarose gel electrophoresis. At all dimer frequencies examined, the production of form III DNA was linear with time and the double-strand scissions were made randomly on the ColE1 DNA genome. Since the observed fraction of form III DNA increased with increasing dimer frequency but the initial rate of loss of form I decreased with increasing dimer frequency, it was postulated that multiple single-strand scissions could be produced in a subset of the DNA population while some DNA molecules contained no scissions. When DNA containing an average of 25 dimers per circle was incubated with limiting enzyme concentrations, scissions appeared at most if not all dimmer sites in some molecules before additional strand scissions were produced in other DNA molecules. The results support a processive model for the interaction of T4 endonuclease V with UV-irradiated DNA.     

V.A.T.E.R. association and its limits

Comparative investigation of 92 cases of V.A.T.E.R. syndrome (4 personal cases) and 62 cases of caudal regression (Duhamel syndrome) (2 personal cases) are performed. There is much analogy between these two entities. Initial impairment would be an early dysfunction of mesoderm setting up located on esophagus in V.A.T.E.R. syndrome and on kidneys in Duhamel syndrome. Etiopathogenic factors remain unknown. Genetic counseling is good. Detection of only one mesodermal malformation leads to inquire other unnoticed anomalies (kidneys, heart, spine, alimentary duct).     

Further purification and characterization of T4 endonuclease V.

T4 endonuclease V, which is involved in repair of ultraviolet-damaged DNA, has been purified 3600 fold from T4D-infected Escherichia coli. The enzyme shows optimal activity at pH 7.2 and does not require added divalent ions. Endonuclease V attacks both native and heat-denatured DNA provided that the DNA has been irradiated, and the enzyme activity is dependent on the dose of ultraviolet irradiation. The rate and the extent of the reaction are greater with irradiated native DNA although the Km values for the two types of DNA are the same (2.25 - 10(-5) M). The enzyme is readily inactivated by heat and is sensitive to p-chloromercuribenzoate. Endonuclease V-treated irradiated DNA is degraded by spleen phosphodiesterase only when the DNA has been treated with alkaline phosphatase, suggesting that the enzyme produces 5'-phosphoryl termini.     

Kinematics of normal locomotion—A statistical study based on T.V. data

A T.V.-computer system for the measurement and analysis of the kinematics of normal and abnormal locomotion has been developed which has the following characteristics: minimum encumberment to the subject or patient, determination of absolute coordinates of anatomical landmarks, analysis of 3 or 4 strides, and automation of data conversion and analysis. Analysis techniques have been developed which take advantage of the accuracy of the marker coordinates, and with suitable application of noise reduction filtering, permit direct calculation of velocities and accelerations (both linear and angular). Examples of some of these derived parameters vs time are presented. The results of a statistical study on a group of normal subjects walking at slow, comfortable and fast cadences yield the ranges of many velocities and accelerations not previously available.     

Immunosuppressive ATS. V. Analysis of the effect of anti-thymocyte serum on T lymphocyte subsets

The effect of anti-thymocyte serum (ATS) on functional T cell subsets within the immunoregulatory network was examined. We found that low doses of ATS depleted the IL 2-producing subset of T helper cells and higher doses of antiserum also eliminated cytotoxic precursors. It was estimated that a standard low dose of ATS, which reduced T helper cells 80-fold, depleted cytotoxic precursors only about four-fold. The data indicate that ATS acts on different T cell subsets in a dose-dependent fashion and suggest that monoclonal antibodies might be used to preferentially deplete specific T cell subpopulations. Two monoclonal rat anti-mouse Lyt sera, however, proved ineffective in inducing functional changes in vivo, although an alloantiserum to Lyt1.1 was able to reduce cell-mediated cytotoxicity in a dose-dependent fashion. The results support the feasibility of specific depletion of T cell subsets with anti-lymphoid antibodies.