The nature of the residual alpha-mannosidase in plasma in bovine mannosidosis.

Acidic alpha-mannosidase (EC 3.2.1.24), optimum pH 4.25, is absent from the plasma of Angus calves with mannosidosis, and the residual alpha-mannosidase activity has an optimum pH of 5.5, intermediate between that of the acidic and neutral alpha-mannosidases. This 'intermediate' alpha-mannosidase differs from the acidic form in its kinetic properties, its lack of marked inhibition by EDTA and its thermolability at 55 degrees C and physiological pH. Isoelectric focusing and ion-exchange chromatography show that it exists in at least two forms. The presence of a secondary peak at pH 5.5 in the pH/activity profile of normal plasma and the effect of heating at 55 degrees C indicate that such a form is present in normal plasma. The residual activity in the plasma of a calf with mannosidosis is therefore probably not the product of the defective gene. A differential assay, based on their different stabilities at 55 degrees C, has been developed for measuring the acidic and intermediate alpha-mannosidases in plasma. There was no correlation between the concentrations of the two enzymes in the plasma of Angus cows heterozygous for mannosidosis or in the plasma of normal animals. This precludes the use of the intermediate form as a reference enzyme for the acidic activity in a test for heterozygosity for mannosidosis based on the gene-dosage phenomenon. The concentrations of the intermediate activity were comparable in normal animals and animals homozygous or heterozygous for mannosidosis.     

The hydrophobic nature of the pig intrinsic factor receptor in the intestine

The pig intestinal intrinsic factor receptor has been isolated and dissociated into its α and β subunits. The β subunit was found to be more hydrophobic than the α subunit. In a detergent solution only the α subunit was accessible to digestion with papain. The whole isolated receptor was introduced into artificial single bilayer liposomes where is apparently was randomly oriented. Liposomes containing the receptor were digested with papain and the polypeptide segments that stayed in the lipid fraction were extracted and analyzed using sodium dodecyl sulfate polyacrylamide gel electrophoresis. Four species were found with $\text{M}{}_{\mathrm{<mtext>r</mtext>}}$ values of 23 000, 45 000, 70 000 and 86 000.     

The chemical nature of the factor responsible for embryonic induction

The discovery by Hans Spemann of the “organizer” tissue and its ability to induce the formation of the amphibian embryo’s neural tube inspired leading embryologists to attempt to elucidate embryonic induction’s underlying mechanisms. Since then several studies have described several developmental model system to better understand the role of specific signaling molecules, the interplay of different signals and tissue interactions in regulating tissue induction and patterning events. Different groups of workers set out to subject embryonic amphibian tissues and inductive adult organs to various extraction methods in the hope that the active agents could be isolated and chemically identified. In addition, a large number of well characterized chemical compounds were tested.     

Molecular nature of human epidermal growth factor (hEGF)-like immunoreactivity in human plasma

To investigate the molecular features of hEGF in the circulatory system, we analyzed hEGF-like immunoreactivity (hEGF-LI) in human serum and plasma by our two-site enzyme immunoassay (EIA), using an aliquot of each fraction obtained by gel filtration of human serum or plasma on Sephadex G-100. The results demonstrated that the majority of the hEGF-LI in the plasma (HMW X hEGF-LI) emerged in the void volume, while a small amount of hEGF-LI (LMW X hEGF-LI) eluted at a position similar with that of standard hEGF. After reduction of HMW X hEGF-LI with 2-mercaptoethanol, hEGF-LI emerged at the same elution position as that of standard hEGF, suggesting that the predominant form of hEGF may circulate as a complex with some macromolecule(s) in human blood. The biochemical properties of the plasma component(s) with high molecular weight which form the complex with hEGF and the physiological significance of this circulating complex still remain to be clarified.     

The multicomponent nature of teratoma cell adhesion factor

The multicomponent nature of teratoma cell adhesion factor has been demonstrated. Fractionation of crude ascites fluid on a DEAE cellulose ion exchange column shows that two or more components are involved in teratoma adhesion factor (TAF) activity. Glycoproteins (or proteoglycans) in fractionated ascites fluid were localized in polyacrylamide gels. The possible role of these sugar-containing molecules in teratoma cell adhesion and current hypotheses on the mechanism of carbohydrate involvement in intercellular adhesion are discussed.     

The nature of big plasma somatostatin: implications for the measurement of somatostatin-like immunoreactivity in human plasma

Big plasma somatostatin (BPS) represents an artifact of measurement. High-molecular-weight globulins (α, β, and γ) in human plasma inhibit, in a concentration-dependent manner, the binding of radiolabeled somatostatin analogs to antibody directed against somatostatin. The magnitude of inhibition varies with antibody and plasma sample and is greatest for the α-globulin fraction. The mechanism of inhibition involves binding of plasma globulins to antibody, thereby blocking tracer-binding sites, and does not involve inhibition by somatostatin bound noncovalently to plasma proteins or tracer degradation. Thus BPS arises from a property of plasma rather than of somatostatin and so it is suggested that this mechanism may account for the presence of other “big” forms of hormones in plasma.     

The nature of serum factor precipitating autologous alpha-globulins in rabbits

The nature of serum factor, resulted from the immune response to human albumin being a precipitant of auto-alpha-globulins in rabbits, have been studied. The use of ion exchange, immunoaffinity chromatography and immunoelectrophoresis has shown, that antibodies to human albumin, carrying the binding site to alpha-globulin in antigen-binding fragment are the factor responsible for alpha-globulin precipitation. The synthesis of antibodies cross-reacting to alpha-globulin gives the evidence of the selective derangement of tolerance to one of organism self antigens during the immune response to heterologous antigen.     

On the mechanism of the nonspecific cell response to the action of damaging agents and the nature of hormesis

A conception of the molecular mechanism of the universal nonspecific cell response (NCR) to the action of all damaging factors of physical and chemical nature is described. The mechanism is shown to be closely related to the general principles of the structural-functional organization of cells and to the properties of biological macromolecules. Among them are the phenomenon of nonspecific regulation of the enzyme activity by low-molecular substances and the compartmentation of the latter within the cell, which is provided by the system of intracellular membranes. Special attention is paid to the role of disturbance of the barrier function, of membranes in the development of the nonspecific cell response, and the activation of repair of cell injuries. Based on the theory of nonspecific cell response, the stimulating effect of weak action of agents that damage the cells at high doses (the phenomenon named as hormesis) is explained.     

Smoke treatment triggers the release of a novel DNA damaging factor by lymphocytes

Abstact Organic fuel smoke is a hazardous agent, which pushes the cells towards“prooxidant state', leading to 4,46,400 strand breaks/cell/day as against 47,000 strand breaks/cell/day produced by constitutive oxygen radicals. This prooxidants scenario switches on a plethora of intercellular events. Here we report a novel DNA damaging factor released by lymphocytes, upon treatment with smoke condensate. Human lymphocytes, when exposed to cow dung cake smoke condensate, were found to release a low molecular weight factor into the media at 20 min of exposure. The conditioned media, displayed a propensity of inducing DNA damage in fresh, normal lymphocytes, which were not exposed to any damaging agent. The above DNA damaging effect of the conditioned media was not due to any residual presence of Polycyclic Aromatic Hydrocarbons, which were present in the smoke. The release of this factor was in correlation with the DNA damaging event, taking place in the cells. This secondary DNA damaging factor had a molecular weight less than 5 kd. The factor had the cell death inducing propensity when allowed to act on lymphocytes