The biological properties of recombinants of glycoprotein hormones in which the alpha and beta subunits were differentially deglycosylated have been investigated. Specific deglycosylation of the alpha subunit generated a recombinant that had more receptor-binding activity but did not produce hormone response in the target cells. The deglycosylated alpha + beta recombinant was also an antagonist of the action of the native hormone. Thus, the carbohydrates in the alpha subunit play a dominant role in the transduction of the hormone signal into the cell.

Radioimmunological techniques were utilized to probe possible changes in conformation of gonadotropins (human chorionic gonadotropin--hCG; and ovine luteinizing hormone--oLH) following chemical deglycosylation (DG-hCG and DG-LH). All antisera produced in rabbits, rats or mice contained antibodies that were specific to the deglycosylated hormones with the native hormones showing weak and non-parallel cross-reaction (less than 5%), but with rabbit antibodies to native hormones the deglycosylated hormones were fully reactive. Using hCG, asialo-hCG (A-hCG) and DG-hCG, we have shown that removal of sugars internal to sialic acid is required to produce these specific antibodies. These are in complete agreement with the observations that extensive deglycosylation of these hormones is necessary to induce changes in biological activity at the cellular level. Based on these data, we suggest that chemical deglycosylation results in changes in antigenic structure of these hormones by generation of new determinants or exposure of previously buried sites and these changes are of no consequence to receptor recognition.

The biological properties of glycosylated (native) and deglycosylated gonadotropins are different. The immunological characteristics of antibodies prepared against deglycosylated lutropin and human chorionic gonadotropin were investigated. Distinct antibodies of rabbit polyclonal antisera against deglycosylated lutropin and deglycosylated chorionic gonadotropin were separated by affinity chromatography on divinylsulfonyl-Sepharose-immobilized hormone or antagonist columns, respectively, in successive runs. Antibodies that could discriminate between agonist and antagonistic forms of the hormones could thus be obtained. In radioimmunoassays using 125I-labeled antagonists and respective antagonist antibodies, only the deglycosylated hormones or their deglycosylated alpha-subunits showed preferential reaction. Based on recombinations using different deglycosylated subunits, it was concluded that the loss of antennary sugars in the alpha-subunits was mainly responsible for the changes that led to the formation of antagonist-specific antibodies. Only the agonist-specific antibody could neutralize hormone action. Thus, the type and extent of glycosylation appears to influence the antigenic structure of these secreted glycoproteins.

The follicular fluid is an important milieu for the growing and maturing oocyte and granulosa cells. In this study we investigated: (1) the properties of gonadotrophin-binding sites in the supernatant fraction of porcine follicular fluid (pFF) and compared them with those of membrane-bound receptors, and (2) the relative changes that occur in pFF and granulosa cell receptor-binding activity following hormone priming of gilts. 125I-Labelled human chorionic gonadotrophin (hCG) and 125I-labelled ovine FSH (oFSH) binding to particulate and supernatant fractions of pFF were hormone-specific and saturable. The concentration of 125I-labelled hCG-binding sites was roughly 50-fold higher in particulate than in supernatant fractions of pFF. However, 30-40% of the total 125I-labelled hCG-binding activity in pFF was present in the supernatant fraction of commercial batches of pFF. 125I-Labelled oFSH binding to pFF membranes was markedly higher than to supernatant fractions. Binding of 125I-labelled hCG and 125I-labelled oFSH to granulosa cells and supernatants of pFF showed a time-dependent variation in response to hormone priming. The results suggest that gonadotrophin-binding sites in the supernatant fraction of pFF have properties similar to those of their membrane-bound counterparts. 125I-Labelled hCG-binding activity in the supernatant fraction of pFF was shown to be more stable than detergent-solubilized LH/hCG receptors, even in glycerol-preserved preparations. Based on a number of criteria, we have speculated that pFF may have components which may be similar in structure to the extracellular domain of the LH/hCG receptor.

The present study was conducted to determine the changes in serum biochemical parameters and lipid profile by oral administration of ethanolic extract of Polyalthia cerasoides stem bark (PcEE 400 mg/kg b. wt) in streptozotocin (45 mg/kg b. wt) induced diabetic rats. Albino rats of weighing between 200-230 g were induced with single dose of streptozotocin (dissolved in 0.1 M ice cold citrate buffer (pH = 4.5) at a dose 45 mg/kg b. wt). Diabetes was confirmed after 48 h in streptozotocin induced rats showing fasting blood glucose levels ≥ 250 mg/dl. The rats were randomly divided into five groups (n = 6). Group I and II (normal and diabetic controls), Group III (normal rats fed with 400 mg of PcEE), Group IV (diabetic rats fed with 400 mg of PcEE), Group V (diabetic rats fed with 20 mg of Glibinclamide). After 21 days animals were sacrificed and blood samples were collected for biochemical analysis. The results showed that the extract significantly (p < 0.05) reduced serum ALT, AST and ALP levels when compared to the diabetic control. The urea and creatinine levels are also controlled significantly (P <0.05). Similarly TC, LDL, VLDL-cholesterol, TG and total lipids of serum were significantly (P <0.05) decreased in streptozotocin induced diabetic rats but HDL-cholesterol levels remained unchanged when compared to the diabetic control animals. The results clearly suggested that the extract has the ability to retain the altered biochemical parameters as normal in diabetic animals and tt was effective as glibinclamide treated animals. Hence the study reveals the therapeutic use of PcEE on diabetes and its complications