Effects of statistical noise and digital filtering on the parameters calculated from the impulse response function

Radiotracers are widely used for the investigation of organ perfusion and function. One of the quantitative approaches to analyze radiotracer data is the calculation of the impulse response function, which is obtained by deconvolution analysis of the time-activity curves measured over the organ. Since exactness of the calculated impulse response function depends both on the counting statistics and on the deconvolution algorithm applied, computer simulated time-activity curves were used to test the least squares deconvolution program based on the matrix regularization algorithm. Criteria of clinical importance (error in the calculated organ function parameters) and criteria of mathematical importance (deconvolution and reconvolution error) were investigated. For three typical impulse response functions f(t), it was found that: 1. In cases of noncompartmental vascular-capillary f(t)'s, a high degree of smoothing is preferable during deconvolution, in this way the error becomes systematic but controllable. 2. Noncompartmental vascular-tubular f(t)'s are noise sensitive, but fortunately, noise in the data can be held to a minimum. 3. Compartmenta f(t)'s need only a minimal degree of smoothing; their components can be identified in a second step using a multiexponential least squares fit.     

Buchbesprechungen

Ohne Zusammenfassung     

抗人生长激素免疫血清的制备和鉴定

Using small dosage of human growth hormone to immunize rabbit or guinea pig, it is able to induce anti-hGH antibody formation with high titre and high affinity that could be applied to hGH RIA. In the present study five rabbits and three guinea pigs were immunized with 125-200 micrograms and 250-285 micrograms per animal of hGH respectively, followed by boosters of 10-20 or 160-250 micrograms of hGH at 2-4 week intervals for 6 or 3 months. Blood was drown 1-2 weeks before each booster for determination of antibody formation. Antibody titre and affinity were successively observed and specificity of antibody was determined for the final bleeding. It was shown that titres of immune sera from guinea pigs were much higher than those of rabbit immune sera, but vice versa for antibody affinity. This might be due to larger immunogen dose used for guinea pigs than for rabbits. Fourteen different peptide hormones were tested in reference to cross-immunoreactivity to anti-hGH antibody. It could be demonstrated that the major cross-reactive hormones are hFSH and hLH, and hTSH also reacts to rabbit anti-hGH immune sera at a lesser degree. These cross reactivities are obviously owing to the molecular homogeneities between hGH and these hormones especially of their alpha-subunits.     

Virus-like particles in Dermacentor reticulatus ticks

Virus-like particles were found in the brain and salivary glands of Dermacentor reticulatus ticks double infected with Coxiella burnetii and Rickettsiella phytoseiuli. The particles were spherical (diameter of about 70 nm) and consisted of an electron-dense inner core and a dense external coat.     

Mechanisms and role of collagen biodegradation in pathology

Three stages in collagen biodegradation are considered: intracellular post-translational degradation of normal procollagen prior to its extracellular secretion; specific enzymatic cleavage of collagen fibrils in the extracellular space; and unspecific proteolysis of the cleaved despiralized molecular fragments. Enzymes involved in collagen breakdown are described. The importance of collagen biodegradation to morphogenesis and morphostasis is discussed, as are its disturbances in a number of pathological conditions.     

Inhibitory effects of Santolina chamaecyparissus extracts against spasmogen agonists

Several extracts of Santolina chamaecyparissus ssp. squarrosa antagonized in a concentration-dependent way the contractions of rat duodenum, guinea-pig ileum, rat vas deferens and rat uterus as induced by acetylcholine, histamine, noradrenaline, oxytocin and serotonin. Polar extracts were less active than apolar extracts, and it was necessary to assay the former at higher concentrations. Only the lyophilized aqueous extract produced a slight hypotensive effect when given intravenously at 150 mg/kg to urethananesthetized rats.