Interline differences in morphology of the precentromeric region of polytene X-chromosome in Drosophila melanogaster salivary glands]

Morphology of the Drosophila melanogaster polytene X chromosome section 20 in normal flies, in strains carrying inversions that break pericentric heterochromatin at different points, and at the background of the Su(UR)ES mutation has been examined. In all of the strains carrying the Su(UR)ES mutation section 20 displayed a distinct banding pattern till to the section 20F, while in the wild-type strains this region was represented by beta-heterochromatin. The strains carrying different inversions substantially differed in the number and morphology of bands forming section 20. In the Su(UR)ES mutants the most proximal X chromosome euchromatin gene, su(f), is mapped to the boundary between sections 20E and F, while rDNA forming the middle part of the X chromosome mitotic heterochromatin is located in the proximal part of section 20F. All large bands observed in section 20 of the w; Su(UR)ES strain were also present in In(1)sc4; Su(UR)ES, which breaks heterochromatin in the distal part. Hence, the bands of polytene chromosome section 20 are virtually devoid of mitotic heterochromatin.     

Experience in isolating Campylobacter jejuni from patients with acute intestinal diseases

Erythrite agar, a commercial culture medium produced by the Research Institute for Culture Media (Makhachkala, USSR), is suitable for the cultivation of C. jejuni after the addition of hemolized sheep blood. The addition of antibiotics to the medium permits its use for the isolation of C. jejuni from feces. By means of this medium C. jejuni has been isolated from the feces of 10% of patients hospitalized on account of acute infectious intestinal diseases.     

The allosteric nature of substrate inhibition of rabbit skeletal muscle fructose-1,6-diphosphatase

The mechanism of substrate inhibition of rabbit skeletal muscle fructose-1.6-bisphosphatase was examined. Analysis of substrate saturation curves obtained at different concentrations of Mg2+ revealed that the inhibiting effect of the substrate is manifested only within the complex with Mg2+, whereas the free form of the substrate causes no inhibition. Evidence for the allosteric nature of substrate inhibition was obtained by partial desensitization of the enzyme in the presence of salicylates. It was shown that fructose-1.6-bisphosphatase inhibition by the substrate obeys positively cooperative kinetics and is noncompetitive with respect to the substrate involved in the catalytic process. Studies on enzyme modification in the presence of DTNB and pyridoxal-5'-phosphate demonstrated that the inhibiting concentrations of the substrate are bound to the center which differs from the allosteric site for AMP. It is suggested that the antagonism of simultaneous action of AMP and high substrate concentrations may be due to the competition of the phosphate groups of these ligands for binding to the common lysine residue located in the overlapping region of two allosteric sites.     

Isolation of FAB and Fc fragments from murine immunoglobulin G1]

Two methods of isolating Fab- and Fc-fragments from mouse immunoglobulin G1 are presented. The first method involves fractionation of papain protein hydrolysate on a column with DEAE- (or DE-32)-cellulose adjusted with 0.005 M K-phosphate buffer, pH 8. The Fab-fragment was eluted from the column with the starting buffer. The Fc-fragment was eluted, with the buffer ionic strength being increased to 0.4 M. Another method involves protein fractionation on an ion exchanger adjusted with 0.004 M Tris-H3PO4 buffer, pH 8.5. All the protein was column bound. The Fab-fragment was eluted with 0.04 M Tris-buffer containing a 0.004 M mixture of K-phosphates, pH 8.6. The Fc-fragment was eluted, with ionic strength being raised to 0.4 M with phosphates. As none of the methods assures isolation of absolutely pure Fab- or Fc-fragments, it is requird that cross absorption of antisera with respective immunosorbents may be carried on in order to obtain monospecific antisera to these fragments.     

Autoregulation of coronary vessels following the acute blood loss and its combination with preexisting immobilization stress]

A 6-hour immobilization stress and a 2-hour posthaemorrhagic hypotension caused elevation of the coronary flow, deterioration of coronary autoregulation, decreasing of the coronary dilation reserve, and diminishing of the left ventricular pressure. In the "stress + haemorrhage" group, the changes of the coronary vessels autoregulation ability were less obvious. Concentration of NO3-/NO2- in the blood serum was elevated after stress. Inhibition of the NO-synthase decreased the coronary flow. Thereupon, a pre-existing immobilization stress alters the coronary vessels tone.