Influence of dynamic power compensation in an isothermal titration microcalorimeter

A theoretical analysis in Laplace's transformed domain based on a power balance represents a suitable model for an isothermal titration calorimeter with dynamic power compensation, designed and implemented in our laboratory. A rigorous calibration of the injection system and the calorimetric response was also made. Using electrically generated heat pulses, two different time constants have been determined from the calorimetric transfer function and assigned to the physical parts of the calorimeter. The same was done for a protein-ligand interaction. The binding of 2'-CMP to ribonuclease A at low and high ionic strengths was used to check the apparatus and the results were compared with those obtained by other authors (Wiseman, T.; Williston, S.; Brandts, J.F.; Lung-Nan, L. Anal. Biochem. 1989, 179, 131-137). In this case, the analysis showed a different time constant for the heat source. Independently of the nature of the heat source, the calorimetric time constants obtained while working under compensation are always smaller than those corresponding to a noncompensated system. The improvement of the calorimetric response introduced by dynamic power compensation is thus explained in terms of the reduction of the time constants characteristic of the calorimeter. This theoretical model can be used to predict the shape of the thermogram for any given reaction of either known or supposed thermodynamic parameters. Therefore, the calorimetric study is extended to the other nucleotides, 2'-UMP and 5'-dUMP, which have not hitherto been reported in the literature.     

Presence of intestinal, liver and heart/adipocyte fatty-acid-binding protein types in the liver of a chimaera fish

Exact tests of equivalence and efficacy with a non-zero lower bound based on two independent binomial proportions for comparative trials are proposed. These exact tests are desirable for studies with small sample sizes. They generalize classical methods to include testing of null hypotheses of prespecified differences and can be used to demonstrate a new treatment's efficacy or its equivalence to a standard treatment. The proposed exact tests use unconditional distributions of the test statistics. Variances of test statistics are estimated via a constrained maximum likelihood method (Farrington and Manning). Data from oncology and vaccine clinical trials are used to illustrate the exact tests.     

Potentiometric methods for determining boron, hydrogen cyanide and hydrogen chloride compounds and their use in controlling the quality of manufacturing and natural environments

The authors present basic science for, elaborate and set as methodic recommendations some potentiometric methods using ion-selective electrodes. Efficiency of those methods was proved in experiments with such substances as boron compounds, hydrogen cyanide, hydrogen chloride. High sensitivity, selectivity, accuracy and rapidity of the methods with handy technique make the facilities available for analysis of air at workplace, ambient atmosphere, water and biologic materials, detecting wide range of concentrations. Practical application of the methods enabled to specify measures to preserve health of workers and general population, helped in hygienic evaluation of work conditions in composition materials production, high-temperature soldering, optic glass industry.     

The establishment of the I-PSS in the CIS countries taking into account its cultural and linguistic features. International Prostate Symptom Score

I-PSS adaptation to cultural and linguistic features of CIS population has been made in two stages. The 1st stage consisted of adaptation of the questionnaire's text and its check up by the specialists. At the 2nd stage a random sample of 46 males at the age 60 to 80 years were tested and retested. Reliability of the results has been proved in repeated tests and comparison of the adjusted questionnaire with its English-American variant. The authors propose to use adapted questionnaire I-PSS which meets international requirements in the countries members of CIS.     

Flow cytometric analysis of macrophage response to ceramic and polyethylene particles: effects of size, concentration, and composition

The aim of this work was to study the effect of a dose of 150 microCi 131I on the barrier properties of the thyroid epithelium in pregnant female rats. Thirty-five female Wistar rats were divided into a control and four experimental groups (each distinguished by the time of 131I injection: group I--no less then 12 days before mating; groups II, III, and IV--on 5th, 10th, and 16th days of gestation, respectively). The thyroid glands were fixed in Bouin's fluid, embedded in paraffin, and stained immunohistochemically for thyroglobulin and fibronectin. In group IV the appearance of follicles with fibronectin-positive colloid demonstrates the penetration of blood plasma into the follicular lumen. There are more fibronectin positive follicles in group III. Regardless of the nature of the follicles' contents, numerous thyrocytes with an intensive fibronectin positive reaction begin to appear in the follicles. In group II the number of fibronectin positive follicles and thyrocytes is clearly reduced, and in group I only a few remain. In group IV there is a noticeable reduction in the quantity of colloid inside the follicles and often an absence of any thyroglobulin positive reaction. There are thyrocytes in which thyroglobulin positive granules localized in the basal zone. There is thyroglobulin positive staining in the stroma and blood vessels. In group II thyroglobulin is no longer found in the stroma. Small doses of 131I provoke a serious breakdown in the thyroid epithelium's barrier properties, although these changes are of a transient nature. The central zone of the thyroid gland reacts more actively and dynamically to exposure to radioactive iodine than the peripheral zone.     

Reduced production of PGE2 and PGF2 alpha from decidual cell cultures supplemented with N-3 polyunsaturated fatty acids

A diet rich in n-3 polyunsaturated fatty acid (PUFA) may reduce the intrauterine production of prostaglandins and prolong pregnancy. We tested this hypothesis by assessing the influence of various PUFAs on the spontaneous production of PGE2 and PGF2 alpha from decidual cell cultures. In addition, we assessed prostaglandin and cytokine production stimulated by lipopolysaccharides (LPS) in order to mimic parturition where infection is involved. In both settings, we found that after supplementing with n-3 PUFA, PGE2 and PGF2 alpha were significantly reduced. After supplementing with n-6 PUFA, there was a significant increase in both prostaglandins. Both n-3 and n-6 PUFAs reduced the production of interleukin 1 (IL-1), while n-6 PUFAs reduced TNF production. PUFAs did not influence IL-6 production. Our findings support the hypothesis that dietary n-3 PUFA may prolong pregnancy by reducing intrauterine production of prostaglandins.     

cis-Elements in the 5''-region of the Oct-1 gene. Possibilities of autoregulation

The anti-diuretic hormone vasopressin (AVP) regulates water excretion from the kidney by increasing the water permeability of the collecting duct. AVP binds to V2-receptors and induces the translocation of aquaporin-2 water channels (AQP-2) into the apical plasma membrane of principal cells. By this mechanism AVP controls water reabsorption in the kidney. The effects of AVP on the endolymphatic sac (ES) of the inner ear, which is thought to mediate reabsorption of endolymph, were investigated. Both the V2-receptor and the AQP-2 water channel were found to be expressed in the ES epithelium. In the ES AVP binds to receptors most probably of the V2-subtype. Application of AVP to organotypically cultured ES inhibits membrane turnover in ribosomal-rich cells of the ES epithelia, which is thought to mediate translocation of AQP-2 into the surface membrane. This suggests that AVP has contrasting effects in the inner ear and kidney, which may be physiologically useful for maintaining endolymphatic pressure during severe hypovolemia. Animal experiments show that AVP causes endolymphatic hydrops after systemic application to guinea-pigs, which suggests a causal role for the increased AVP levels found in humans suffering from Ménière's disease.     

Doctors who perform operations. A study on in-hospital surgery in four diverse geographic areas (first of two parts)

The generous supply of surgeons in the United States stimulated a study of their operative work based on all operations performed by all physicians in hospitals of four geographic areas. Each operation was assigned a California Relative Value to permit work-load comparisons between specialties and practices. General practitioners constituted more than one quarter of physicians who performed operations but accounted for less than one tenth of total work. Surgical specialists, about half the physicians in the study, performed about 80 per cent of total operative work. Work loads of surgical specialists varied by certification, specialty, age and practice organization status. We conclude that far too many physicians perform surgical operations and that work loads of surgical specialists are modest. Calculations involving reallocation of operative work loads suggest that the total volume of operations in this study could have been handled by a substantially smaller cadre of busier surgical specialists.     

The development of allergy in infants of allergic parents: a prospective study concerning the role of heredity

Ninety-four infants of allergic mothers were studied from birth to age 24 months. If the father was also allergic, the family history was termed bilateral (36 infants); if the father was not allergic, the family history was termed unilateral (58 infants). Data concerning family history, methods of feeding (bottle versus breast) and allergic skin reactivity were obtained. Significantly, more infants developed allergy if they were from a bilateral allergic parentage (P = less than 0.044). When skin test negative, bottle-fed infants with a bilateral family history were compared to breast-fed infants with a unilateral family history, there was significantly less asthma in the latter group (P = less than 0.047). During the first three months of life there was significantly less atopic dermatitis in the breast-fed infants with an unilateral family history than in the breast-fed infants with a bilateral family history (P = less than 0.027). In this study it remained unclear why infants with positive allergy skin tests demonstrated a different incidence of allergic disease from those who were skin-test negative when the variables of family history were the same.