Transforming growth factor-β inhibition of interleukin-1 activity involves down-regulation of interleukin-1 receptors on chondrocytes

Interleukin-1 (IL-1) plays an important role in cartilage destruction associated with inflammatory and degenerative arthritis because of its ability to induce matrix degrading enzymes. Previously, we have shown that the IL-1-induced chondrocyte protease activity was inhibited by transforming growth factor-β (TGF-β). In this paper, we show that TGF-β inhibits the IL-1-induced synthesis of collagenase and stromelysin by reducing the steady-state mRNA levels in rabbit articular chondrocytes. We further demonstrate that TGF-β-treated chondrocytes show reduced ¹²⁵I-IL-1 binding that returns to a normal level when TGF-β is removed from the culture medium. The inhibitory effect of TGF-β is observed for both naturally occurring as well as fibroblast growth factor (FGF)-inducible binding sites (receptors). Scatchard analysis of receptor—ligand interactions demonstrate that the reduced binding is due to a reduction in the number of receptors for IL-1 and is not due to changes in affinity. Affinity cross-linking studies suggest that control chondrocytes contain two major cross-linked bands of M_r =116 and 80 kDa and a minor band of M_r =100 kDa. FGF-treated cells show enhanced levels of all the bands, plus an additional 200-kDa band. TGF-β treatment of chondrocytes results in the reduction of all of these bands in both control as well as FGF-induced cells. These observations suggest that the ability of TGF-β to down-regulate the IL-1 receptor may be a mechanism by which it exerts its effects in antagonizing the IL-1 activity on chondrocytes.     

Increased degradation of dermal collagen in diabetic rats.

The effect of alloxan induced diabetes on the dermal collagen content of albino rats was studied in relation to few lysosomal enzymes. Diabetes decreased the dermal collagen content. The specific activities of the lysosomal enzymes studied in the diabetic rat skin were elevated. It has been established that lysosomal enzymes degrade the connective tissue components. Thus, it may be suggested that the increase in the lysosomal enzymes studied should have facilitated the decrease in dermal collagen content of diabetic rats by increasing the degradation of dermal collagen.     

Camouflage by edge enhancement in animal coloration patterns and its implications for visual mechanisms.

Animal camouflage patterns may exploit, and thus give an insight into, visual processing mechanisms. In one common type of camouflage the borders of the coloured patterns are enhanced by high contrast lines. This type of camouflage is seen on many frogs and we use it as the basis for speculating about vision in a small, frog-eating snake. It is argued that a simple categorization of intensity profiles, such as that invoked by a mechanism that detects phase-congruence, occurs at an early stage of snake vision. We show that edge-detectors using a phase-congruence strategy will be unable to distinguish between 'natural' step-edges and the enhanced border profiles commonly seen on cryptic animals, and that the camouflage will be effective over a wide range of spatial scales.     

Effects of prolactin and androgens on enzymes of carbohydrate metabolism in prostate of castrated bonnet monkeys Macaca radiata (Geoffroy).

Effects of prolactin (PRL), bromocriptine (Br), testosterone propionate (TP), dihydrotestosterone (DHT) and the combinations of these androgens with PRL/Br on the specific activities of caudal and cranial prostatic cellular enzymes involved in carbohydrate metabolism in castrated mature bonnet monkeys have been studied. Castration decreased all the enzymes studied such as hexokinase (HK), 6-phosphofructokinase (6-PFK), glyceraldehyde-3-phosphate dehydrogenase (G-3-PD), pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G-6-PD) and 6-phosphogluconate dehydrogenase (6-PGD) in the cranial and caudal prostates. PRL elevated the activities of all the enzymes above normal except G-3-PD of cranial lobe. In the caudal lobe, PRL brought back the activities of HK, PFK, PK, G-6-PD to normal and 6-PGD above normal except G-3-PD. TP/DHT treatment increased all the enzymes in both the lobes. PRL given along with TP/DHT further enhanced the androgen action with regard to HK, PK, G-6-PD and 6-PGD of cranial and PFK, G-3-PD, PK, G-6-PD and 6-PGD of caudal lobe. Br treatment did not produce any alteration of these enzymes in both the lobes. In the cranial lobe, during Br+TP/DHT treatment, the stimulating effects of androgen were unaffected on all the enzymes except PK. On the other hand in the caudal, the stimulatory effects of androgens were affected and the activities of HK, PFK, PK and 6-PGD were significantly decreased. The present results suggest that PRL has a direct as well as a synergistic action with androgens on enzymes of EMP and HMP shunt in the prostates of monkeys.     

Orthogonal beta beta motifs in proteins.

A super-secondary structural motif comprising two orthogonally oriented beta-strands connected by short linking segments of less than or equal to 5 residues has been identified from a data set of 65 independent protein crystal structures. Of the 42 examples from 14 proteins, a vast majority have only a single residue as the linking element. Analysis of the conformational angles at the junction reveals that the recently described type VIII beta-turn occurs frequently at the connecting hinge, while the type II beta-turn is also fairly common.     

Structural basis of C3b binding by glycoprotein C of herpes simplex virus.

Glycoproteins C (gC) from herpes simplex virus type 1 (HSV-1) and HSV-2, gC-1 and gC-2, bind the human complement fragment C3b, although the two glycoproteins differ in their abilities to act as C3b receptors on infected cells and in their effects on the alternative complement pathway. Previously, we identified three regions of gC-2 (I, II, and III) which are important for C3b binding. In this study, our goal was to identify C3b-binding sites on gC-1 and to continue our analysis of gC-2. We constructed a large panel of mutants by using the cloned gC-1 and gC-2 genes. Most of the mutant proteins were transported to the surface of transiently transfected L cells and reacted with one or more monoclonal antibodies to discontinuous epitopes. By using 31 linker insertion mutants spread across the coding region of gC-1, we identified four regions in the ectodomain of gC-1 which are important for C3b binding, three of which are similar in position to C3b-binding regions I, II, and III of gC-2. Region III shares some similarities with the short consensus repeat found in CR1, the human complement receptor. These were, in part, the targets for construction of 20 single amino acid changes in region III of gC-1 and gC-2. These mutants identified similarities and differences in the C3b-binding properties of gC-1 and gC-2 and suggest that the amino half of region III is more important for C3b binding. However, our results do not support the concept of a structural relationship between the short consensus repeat of CR1 and gC, since mutations of some of the conserved residues, including three of four cysteines in region III, had no effect on C3b binding. Finally, we constructed four deletion mutants of gC-1, including one which lacked residues 33 to 123, as well as residues 367 to 449. This severely truncated molecule, lacking four cysteines and five potential N-linked glycosylation sites, was transported to the cell surface and retained its ability to bind monoclonal antibodies as well as C3b. Thus, the four distinct C3b-binding regions of gC-1 and several epitopes within two different antigenic sites are localized within residues 124 to 366.     

Substrate-Induced Stability of Glyceraldehyde 3-Phosphate Dehydrogenase from Mung Beans (Vigna radiata L.)

Time-dependent thermal inactivation of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) present in the extract of mung beans at different periods of germination showed biphasic kinetics in the 12-h germinated seeds but single exponential decay at 24 h of germination. The glyceraldehyde 3-phosphate (G-3-P) concentration in the deproteinated extracts was found to increase with period of germination up to 36 h, parallel to that of GAPDH activity. G-3-P was found to offer protection of the enzyme against thermal inactivation and trypsin digestion. It is suggested that accumulation of G-3-P in germinating mung beans may be of physiological significance and it might offer protection to the enzyme in vivo against thermal inactivation and proteolysis.     

Studies on the mechanism of uptake of low density lipoprotein-proteoglycan complex in macrophages

Earlier, we (Vijayagopal, P. et al. (1988) Biochim. Biophys. Acta 960, 210) showed that mouse peritoneal macrophages metabolize low density lipoprotein (LDL)-proteoglycan complex by a receptor pathway distinct from the acetyl-LDL receptor. Further studies were conducted to probe further into the mechanism of LDL-proteoglycan complex uptake by macrophages. Both 125I-methyl-LDL-proteoglycan complex and 125I-LDL-proteoglycan complex were taken up and degraded by the cells to the same extent. Similarly, the ability of these ligands to stimulate cholesteryl ester synthesis was also indistinguishable. These results rule out the possibility of apoB,E receptor involvement in the uptake of LDL-proteoglycan complex in macrophages. Sodium fluoride, cytochalasin D and aggregated LDL inhibited degradation of the complex by 24%, 26% and 28%, respectively, indicating that phagocytosis is only a minor pathway for the uptake. Both binding and degradation of the complex were not inhibited by excess hyaluronic acid suggesting that ligand recognition was not through hyaluronic acid binding sites. As compared to acetyl-LDL, the cellular degradation of LDL-proteoglycan complex was retarded. Macrophages exhibited a rapid stimulation of [3H]inositol trisphosphate (IP3) release and diacylglycerol production when incubated with LDL-proteoglycan complex. Furthermore, pertussis toxin produced a 62% inhibition of LDL-proteoglycan complex mediated IP3 release, suggesting that LDL-proteoglycan complex metabolism in macrophages is dependent upon the G-protein coupled signal transduction mechanism. These results show that receptor mediated endocytosis plays a major role in the metabolism of LDL-proteoglycan complex in macrophages.     

Plant regeneration via somatic embryogenesis in creeping bentgrass (Agrostis palustris Huds.)

We have established a high-frequency plant regeneration system via somatic embryogenesis from mature seeds of creeping bentgrass (Agrostis palustris Huds). The effects of 2,4-dichlorophenoxyacetic acid (2,4-D), 3.6-dichloroo-anisic acid (dicamba) and 6-benzyladenine (BA) on callus formation and embryogenesis were evaluated. Callus produced on the Murashige and Skoog (MS) (1962) medium containing 2,4-D had low embryogenic potency. In the presence of 30 M dicamba, addition of 2.25 to 9 M BA significantly enhanced embryogenic callus formation over dicamba alone. Optimum frequency of somatic embryogenesis was achieved on MS basal medium containing 30 M dicamba and 2.25 M BA. Over 80% of somatic embryos germinated and formed plantlets on half-strength MS basal medium. These plantlets grew normally in the greenhouse.Abbreviations MS Murashige and Skoog medium - 2,4-D 2,4-dichlorophenoxyacetic acid - BA 6-benzyladenine - dicamba 3, 6-dichloro-o-anisic acid