Biomedical subjects
Publications and source records attributed to G Mitra.
Diafiltration of salt and ethanol from human serum albumin was shown to be a competitive alternative to freeze drying. At least 99% of the original alcohol content could be removed in approximately five volume changes. Data on changes in ionic strength, bacteriological buildup, permeate flux, and dimer contents are presented.
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The first convenient chemical synthesis of 7alpha-hydroxyandrost-4-ene-3,17-dione is reported. Androsta-4,6-diene3, 17-dione was converted into its 6alpha, 7alpha-epoxy-derivative; reduction of the epoxide with aluminum amalgam gave 7alpha-hydroxyandrost-4-ene-3,17-dione. This reducing agent is more efficient than chromous acetate for the purpose.
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Safety concerns for immunoglobulin preparations have led us to study partition/inactivation of two prototype retroviruses, mouse xenotropic type C and lymphadenopathy-associated virus (LAV) of the acquired immunodeficiency syndrome (AIDS), during manufacture and storage of immunoglobulins. Reduction of infectious retrovirus titers were 10(5) to 10(8)-fold through Cohn-Oncley cold ethanol fractionation from plasma to fraction II, 10(3) to 10(5)-fold through incubation at pH 4.0 and another 10(4)-fold through incubation of the purified liquid immunoglobulin preparations at 27 degrees C or 45 degrees C. The results support the clinical and epidemiological evidence that therapeutic immunoglobulin preparations do not transmit AIDS virus.
In a comparative study, seven commercially available immunoglobulin preparations and one experimental preparation, processed by various manufacturers in the United States and Europe, were investigated for non-IgG proteins and impurities. The basic fractionation methodology affects the purity of subsequently processed intravenous preparations. Five of the seven products manufactured in Europe contained varying amounts of plasma proteins other than IgG. A residual heterologous protein was detected and quantitated in one product whose processing includes porcine pepsin treatment. Only one of the eight products was low in aggregates (as judged by both anticomplement activity and nephelometric turbidity), while three products contained anticomplement activity at levels high enough to be a potential cause of reactions in patients. In general, the level of prekallikrein activator activity was proportional to that of amidolytic activity; four products had only trace levels of amidolytic activity as well as prekallikrein activator. Only one product contained significant isoagglutinin levels, while six products had detectable IgA levels.
The Pharmacological utility of various exogenous proteins is considerably impeded, since upon infusion, they are liable to rapid systemic clearance, proteolysis, in addition to eliciting severe immunological reactions. Upon conjugation with hydrophilic polymers like polyethylene glycol and dextran, the altered topology of proteins, often hinders interaction with their corresponding complementary surfaces. This is manifest in their increased circulatory-lives, as a fall out of decreased binding to proteases, pre-existing antibodies and other opsonins that mediate clearance by the reticuloendothelial-system as well as receptors mediating specific organ uptake. Further, an increase in conjugate size beyond the threshold limit of 70 kDa, permits small proteins to escape clearance via renal filtration. Upon covalent modification, proteins are generally endowed with an intrinsic inertness which is reflected in their enhanced stability in extremes of pH and temperature, presence of proteases and other denaturing conditions. The enhanced intracellular stability of conjugates which may also be responsible for their altered immunological properties is likely to be a consequence of the changed physiochemical properties of the conjugates. The therapeutic efficacy of these conjugates in clinical trials indicate their tremendous utility in pharmacological procedures.