Influence of colchicine on the synthesis and secretion of proteoglycans and collagen by fetal guinea pig chondrocytes

Effects of the mycotoxin nivalenol on bovine articular chondrocyte metabolism in vitro

Objective

Kashin-Beck Disease (KBD) is an endemic, age-related degenerative osteoarthropathy and its cause is hypothesised to involve Fusarium mycotoxins. This study investigated the Fusarium mycotoxin Nivalenol (NIV) on the metabolism of bovine articular chondrocytes in vitro.

Design

The effect 0.0–0.5 µg/ml NIV on transcript levels of types I and II collagen, aggrecan, matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with thrombospondin motif (ADAMTS) and the tissue inhibitors of MMPs (TIMPs) was investigated using quantitative PCR. Amounts of sulphated glycosaminoglycans, MMPs and TIMPs were assessed using the Dimethylmethylene Blue assay, gelatin zymography and reverse gelatin zymography respectively. Cytoskeletal organisation was analysed using confocal microscopy and cytoskeletal gene and protein levels were measured by quantitative PCR and Western blot analysis, respectively.

Results

NIV caused a dose-dependent increase in aggrecan transcription with a concomitant retention of sGAG in the cell lysate. Furthermore, NIV significantly increased MMPs-2, -3 & -9, ADAMTS-4 and -5, and TIMP-2 and -3 transcript levels but inhibited type I collagen, MMP 1 and TIMP 1 mRNA levels. NIV promoted extensive cytoskeletal network remodelling, particularly with vimentin where a dose-dependent peri-nuclear aggregation occurred.

Conclusion

NIV exposure to chondrocytes decreased matrix deposition, whilst enhancing selective catabolic enzyme production, suggesting its potential for induction of cellular catabolism. This NIV-induced extracellular matrix remodelling may be due to extensive remodelling/disassembly of the cytoskeletal elements. Collectively, these findings support the hypothesis that trichothecene mycotoxins, and in particular NIV, have the potential to induce matrix catabolism and propagate the pathogenesis of KBD.

Transforming growth factor β-induced superficial zone protein accumulation in the surface zone of articular cartilage is dependent on the cytoskeleton

The phenotype of articular chondrocytes is dependent on the cytoskeleton, specifically the actin microfilament architecture. Articular chondrocytes in monolayer culture undergo dedifferentiation and assume a fibroblastic phenotype. This process can be reversed by altering the actin cytoskeleton by treatment with cytochalasin. Whereas dedifferentiation has been studied on chondrocytes isolated from the whole cartilage, the effects of cytoskeletal alteration on specific zones of cells such as superficial zone chondrocytes are not known. Chondrocytes from the superficial zone secrete superficial zone protein (SZP), a lubricating proteoglycan that reduces the coefficient of friction of articular cartilage. A better understanding of this phenomenon may be useful in elucidating chondrocyte dedifferentiation in monolayer and accumulation of the cartilage lubricant SZP, with an eye toward tissue engineering functional articular cartilage. In this investigation, the effects of cytoskeletal modulation on the ability of superficial zone chondrocytes to secrete SZP were examined. Primary superficial zone chondrocytes were cultured in monolayer and treated with a combination of cytoskeleton modifying reagents and transforming growth factor β (TGFβ) 1, a critical regulator of SZP production. Whereas cytochalasin D maintains the articular chondrocyte phenotype, the hallmark of the superficial zone chondrocyte, SZP, was inhibited in the presence of TGFβ1. A decrease in TGFβ1-induced SZP accumulation was also observed when the microtubule cytoskeleton was modified using paclitaxel. These effects of actin and microtubule alteration were confirmed through the application of jasplakinolide and colchicine, respectively. As Rho GTPases regulate actin organization and microtubule polymerization, we hypothesized that the cytoskeleton is critical for TGFβ-induced SZP accumulation. TGFβ-mediated SZP accumulation was inhibited by small molecule inhibitors ML141 (Cdc42), NSC23766 (Rac1), and Y27632 (Rho effector Rho Kinase). On the other hand, lysophosphatidic acid, an upstream activator of Rho, increased SZP synthesis in response to TGFβ1. These results suggest that SZP production is dependent on the functional cytoskeleton, and Rho GTPases contribute to SZP accumulation by modulating the actions of TGFβ.

Involvement of the cytoskeletal elements in articular cartilage homeostasis and pathology

The cytoskeleton of all cells is a three-dimensional network comprising actin microfilaments, tubulin microtubules and intermediate filaments. Studies in many cell types have indicated roles for these cytoskeletal proteins in many diverse cellular processes including alteration of cell shape, movement of organelles, migration, endocytosis, secretion, cell division and extracellular matrix assembly. The cytoskeletal networks are highly organized in structure enabling them to fulfil their biological functions. This review will primarily focus on the organization and function of the three major cytoskeletal networks in articular cartilage chondrocytes. Articular cartilage is a major load-bearing tissue of the synovial joint; it is well known that the cytoskeleton acts as a physical interface between the chondrocytes and the extracellular matrix in 'sensing' mechanical stimuli. The effect of mechanical load on cytoskeletal element expression and organization will also be reviewed. Abnormal mechanical load is widely believed to be a risk factor for the development of osteoarthritis. Several studies have intimated that the major cytoskeletal networks are disorganized or often absent in osteoarthritic cartilage chondrocytes. The implications and possible reasoning for this are more widely discussed and placed into context with their potential relevance to disease and therapeutic strategies.

The role of microtubules in the regulation of proteoglycan synthesis in chondrocytes under hydrostatic pressure

Chondrocytes of the articular cartilage sense mechanical factors associated with joint loading, such as hydrostatic pressure, and maintain the homeostasis of the extracellular matrix by regulating the metabolism of proteoglycans (PGs) and collagens. Intermittent hydrostatic pressure stimulates, while continuous high hydrostatic pressure inhibits, the biosynthesis of PGs. High continuous hydrostatic pressure also changes the structure of cytoskeleton and Golgi complex in cultured chondrocytes. Using microtubule (MT)-affecting drugs nocodazole and taxol as tools we examined whether MTs are involved in the regulation of PG synthesis in pressurized primary chondrocyte monolayer cultures. Disruption of the microtubular array by nocodazole inhibited [(35)S]sulfate incorporation by 39-48%, while MT stabilization by taxol caused maximally a 17% inhibition. Continuous hydrostatic pressure further decreased the synthesis by 34-42% in nocodazole-treated cultures. This suggests that high pressure exerts its inhibitory effect through mechanisms independent of MTs. On the other hand, nocodazole and taxol both prevented the stimulation of PG synthesis by cyclic 0. 5 Hz, 5 MPa hydrostatic pressure. The drugs did not affect the structural and functional properties of the PGs, and none of the treatments significantly affected cell viability, as indicated by the high level of PG synthesis 24-48 h after the release of drugs and/or high hydrostatic pressure. Our data on two-dimensional chondrocyte cultures indicate that inhibition of PG synthesis by continuous high hydrostatic pressure does not interfere with the MT-dependent vesicle traffic, while the stimulation of synthesis by cyclic pressure does not occur if the dynamic nature of MTs is disturbed by nocodazole. Similar phenomena may operate in cartilage matrix embedded chondrocytes.

Similar effects of recombinant human insulin-like growth factor-I and II on cellular activities in flexor tendons of young rabbits: experimental studies in vitro

To improve the understanding of factors with the potential of affecting the healing of flexor tendons, this study compared the cellular effects of recombinant human insulin-like growth factor-II with those of recombinant human insulin-like growth factor-I in matched pairs of deep flexor tendons of young rabbits. Dose-response effects on the synthesis of DNA and matrix proteins of either factor alone or in combination were investigated in short-term culture, and effects on synthesis and turnover of matrix components were compared in long-term culture. Both factors stimulated proteoglycan, collagen, noncollagen protein, and DNA synthesis in a dose-dependent manner in the range of 10-500 ng/ml. Insulin-like growth factor-I increased proteoglycan synthesis to as much as six times that of controls but was less potent than insulin-like growth factor-II. Both factors stimulated increased cell proliferation by as much as five times compared with control values, but insulin-like growth factor-I was more potent than insulin-like growth factor-II. The two factors in combination did not enhance the synthesis of matrix proteins and DNA as compared with either factor alone. Insulin-like growth factor-I counteracted the decrease in collagen synthesis and stimulated protein synthesis to a higher degree than insulin-like growth factor-II in long-term culture. Both factors had similar effects on matrix turnover, with estimated half times (t1/2) for elimination of newly labeled proteoglycans and proteins of 11 and 8 days, respectively. Insulin-like growth factor-II is capable of stimulating cell proliferation and matrix metabolism in tendon explants of young rabbits at levels similar to those of insulin-like growth factor-I; in combination, the two growth factors are unable to augment the stimulatory effects of either of the factors alone.

Division of flexor tendons causes progressive degradation of tendon matrix in rabbits

Deep flexor tendons of 30 rabbits were divided at the ankle level. The effects of unloading on the synthesis and content of matrix components, the synthesis of DNA, and dry weight were investigated. The ability of the tendons to synthesize collagen during short-term culture and the contents of matrix components decreased inversely to the time of unloading. 12 weeks following division, the fibrocartilagnious segments had lost 2/5 of their dry weight, 2/3 of proteoglycan and 1/3 of collagen and non-collagen protein content. Less pronounced losses were observed in the non-fibrocartilaginous segments. A transient increase in cell proliferation in both types of segments was found. These findings indicate that divided flexor tendons undergo a progressive degradation, degradation, which may have implications for delayed suture of deep flexor tendon injuries.

Exposure to air during surgery inhibits cellular activity in flexor tendons

In order to investigate the cellular effects of exposure to air during surgery and to compare the effects of simultaneous irrigation with physiological saline, the deep flexor tendons of both forepaws of 12 rabbits were surgically exposed. In one experiment, the extent of surgical exposure and, in a second experiment, the time of exposure was evaluated. Treated segments of the flexor tendons were collected and labelled in vitro for determination of the ability to synthesize DNA, proteoglycan, collagen and non-collagen protein. With increasing surgical exposure in vivo, an increasing rate of cellular proliferation was observed in segments of the exposed deep flexor tendons examined in vitro. Synthesis of matrix components and the rate of cellular proliferation were reduced by 50% after 40 to 100 minutes of exposure to air and by nearly 100% after 120 minutes of exposure. In contrast, irrigated tendons retained their cellular capacity to proliferate.

Differential effects of insulin-like growth factor-I on matrix and DNA synthesis in various regions and types of rabbit tendons

Tendon healing and integration of tendon grafts may be site or donor specific. To determine if differences exist in sensitivity to growth factors that have the potential to influence tendon repair, we compared the effects of recombinant human insulin-like growth factor-I on various types of tendon segments. The dose response effects on proteoglycan, collagen, noncollagen protein, and DNA synthesis were investigated in short-term explant cultures of intrasynovial intermediate and proximal segments of deep flexor tendons extrasynovial segments of deep flexor tendons, and Achilles tendons of rabbits. The four different types of tendon segments cultured in media without recombinant human insulin-like growth factor-I synthesized similar amounts of each of the matrix components. Intrasynovial proximal segments synthesized 15 times less DNA than other tendon segments. Recombinant human insulin-like growth factor-I stimulated matrix and DNA synthesis of all tendon segments in a dose-dependent manner in intervals from 10 to 1,000 ng/ml. The potency (LogED50) of the stimulation did not differ between the segments. The estimated maximal stimulation (E(max)) of proteoglycan synthesis by recombinant human insulin-like growth factor-I was higher, and of collagen and noncollagen protein synthesis was lower, in intrasynovial proximal segments as compared with that of the other types of segments. In contrast, the estimated maximal stimulation of DNA synthesis by recombinant human insulin-like growth factor-I was 6-fold higher than controls in all types of tendons. These findings demonstrate differences in mitotic capacity between anatomical regions of tendons during culture without recombinant human insulin-like growth factor-I and in matrix synthesis after stimulation with it.

Expression of reduced amounts of structurally altered aggrecan in articular cartilage chondrocytes exposed to high hydrostatic pressure

The effect of hydrostatic pressure on proteoglycan (PG) metabolism of chondrocyte cultures was examined using a specially designed test chamber. Primary cultures of bovine articular chondrocytes at confluence were exposed for 20 h to 5 and 30 MPa continuous hydrostatic pressures and 5 MPa hydrostatic pulses (0.017, 0.25 and 0.5 Hz) in the presence of [35S]sulphate. Northern blot analyses showed that chondrocyte cultures used in this study expressed abundant mRNA transcripts of aggrecan, typical of chondrocytes, but not versican. The cultures also expressed biglycan and decorin. Enzymic digestions with keratanase and chondroitinases AC, ABC and B and subsequent SDS/agarose gel electrophoresis confirmed the synthesis of aggrecans and small dermatan sulphate PGs. The continuous 30 MPa pressure reduced total PG synthesis by 37% as measured by [35S]sulphate incorporation, in contrast to the 5 MPa continuous pressure which had no effect. The high static pressure also reduced total [3H]glucosamine incorporation by 63% and total [14C]leucine incorporation by 57%. The cyclic pressures showed a frequency-dependent stimulation (0.5 Hz, 11%) or inhibition (0.017 Hz, -17%) of [35S]sulphate incorporation. Aggrecans secreted under continuous 30 MPa pressure showed a retarded migration in 0.75% SDS/agarose gel electrophoresis and they also eluted earlier on Sephacryl S-1000 gel filtration, indicative of a larger molecular size. The increased size was consistent with an increase of average glycosaminoglycan chain length as determined by Sephacryl S-300 gel filtration. No change in aggrecan size was observed with the lower (5 MPa) static or cyclic pressures. Continuous 30 MPa hydrostatic pressure slightly reduced the steady-state mRNA level of aggrecan, in parallel with the decline in PG synthesis measured by [35S]sulphate incorporation. The results demonstrated that high hydrostatic pressure could influence the synthesis of PGs, especially of aggrecans, in chondrocytes both at the transcriptional and translational/post-translational levels.

A double-blind randomized controlled trial of colchicine in patients with hepatitis B virus-related postnecrotic cirrhosis

The preliminary results of a prospective double-blind controlled trial of colchicine in 100 patients with hepatitis B virus-related cirrhosis are reported. The patients, 94 males and 6 females, aged 32-80, were assigned to receive either 1 mg of colchicine or an identical placebo orally on a daily basis. The duration of the follow up ranged from 15 to 51 months (median 26 months). Seventy percent had histological proof of cirrhosis. On entry, 80 patients were in Child-Pugh class A, 19 were in class B, and one was in class C. Compared to the placebo group, there was no improvement in the colchicine group after a 24-month follow up in any of the biochemistry data, for example, serum albumin, alkaline phosphatase, alanine and aspartate aminotransferase, bilirubin, and prothrombin time. The difference in the cumulative survival rates at 51 months did not reach statistical significance (p = 0.8) in either group. There was no histological improvement in 30 patients who were willing to undergo repeated liver biopsies. No trend toward improvement of the hepatic pressure gradient was observed in these patients. The serum levels of aminopropeptide of type III procollagen increased significantly in patients in both groups after 24 months of therapy (1.07 +/- 0.06 vs. 1.36 +/- 0.06 U/ml in the colchicine group, 0.93 +/- 0.09 vs. 1.25 +/- 0.07 U/ml in the placebo group; p < 0.05). In addition, neither the clinical deterioration of cirrhosis nor death was prevented in patients receiving colchicine therapy. This report indicates that colchicine has no effect in the treatment of HBV-related postnecrotic cirrhosis.

Cytoskeleton of cartilage cells

The cytoskeleton of chondrocytes consists of microfilaments made of actin, microtubules made of tubulin, and intermediate filaments made of a variety of subunits. Actin filaments are not prominent in vivo but may form in vitro. In culture, changes in filament polymerisation are important in determining cell shape, initiating chondrogenesis, and maintaining the chondrogenic phenotype. Microtubules, besides their role in cell division, organise the distribution of organelles and are involved in secretory transport mechanisms in collagen and proteoglycan synthesis. A variety of intermediate filaments may be present, frequently forming large whorled aggregates. The filaments include vimentin, cytokeratins, and glial fibrillary acidic protein. These may occur at different depths in articular cartilage. Vimentin accumulates during development of some fibrocartilages with increased mechanical loading. Together with other elements of the cytoskeleton, intermediate filaments could form part of a mechanotransduction system by which cells respond to external forces and sense changes in their external environment.

Variations in cellular proliferation and matrix synthesis in intrasynovial and extrasynovial tendons: an in vitro study in dogs

Intrasynovial and extrasynovial flexor tendon grafts recently have been shown to have dissimilar patterns of cellular survival and host integration within the digital sheath. In an effort to determine if fundamental differences exist between these two types of tendons, we investigated the biochemical composition and cellular activity of intrasynovial and extrasynovial tendon segments of 12 adult mongrel dogs in short-term explant culture in MCDB 105 and in DMEM media. Proteoglycan, collagen and noncollagen protein synthesis and content and DNA synthesis were determined following culture in both media. Intrasynovial tendon segments cultured in MCDB 105 medium synthesized significantly less collagen, noncollagen protein, and DNA and had similar amounts of proteoglycans compared to extrasynovial tendons. Comparison of intrasynovial and extrasynovial tendon segment responses in DMEM medium showed that intrasynovial tendons synthesized more proteoglycan, protein, and DNA than they did in MCDB 105. Extrasynovial tendons had similar rates of matrix component and DNA synthesis in both media. Findings that the synthesis of matrix components and DNA between intrasynovial flexor and extrasynovial peroneal tendon segments differ significantly indicate that intrasynovial flexor tendons may be specially adapted to the nutritional milieu provided by an intrasynovial environment. These data are supported by the selective successful stimulation of fibrocartilaginous segments within intrasynovial flexor tendons in media favored for the culture of cartilaginous tissue.

Altered Golgi apparatus in hydrostatically loaded articular cartilage chondrocytes

OBJECTIVES

Articular cartilage proteoglycan content is controlled by joint loading. This study aimed to elucidate the role of hydrostatic pressure in this regulation.

METHODS

Primary cultures of chondrocytes from bovine articular cartilage, grown on coverslips, were subjected to 5, 15, or 30 MPa hydrostatic pressure, applied continuously or cyclically at 0.125 or 0.05 Hz. The Golgi apparatus was visualised either by a fluorochrome coupled wheat germ agglutinin or by transmission electron microscopy. Proteoglycan synthesis was studied by the incorporation of sulphur-35 labelled sulphate.

RESULTS

After 30 MPa continuous hydrostatic pressure, the Golgi apparatus was observed in a compact form with a concomitant decrease in proteoglycan synthesis. The normal stacked appearance of the Golgi apparatus was no more visible in the electron microscopy preparation of the pressurised chondrocytes. This effect was reversible and was also noticed after 15 MPa continuous load, though to a minor extent. Cyclic pressures (5-30 MPa) caused no apparent change in the Golgi apparatus. The shape of some cells changed to a more retracted form after 30 MPa continuous pressure. Nocodazole, which causes disassembly of the microtubules, blocked the compacting influence of pressurisation on the Golgi apparatus, and reduced proteoglycan synthesis to about half of the control level.

CONCLUSIONS

The packing of the Golgi apparatus is dependent on microtubules and may contribute to the inhibition of proteoglycan synthesis observed in articular cartilage subjected to high hydrostatic pressure.

Long-term explant culture of rabbit flexor tendon: effects of recombinant human insulin-like growth factor-I and serum on matrix metabolism

The effects of human recombinant insulin-like growth factor-I (rhIGF-I, 50 ng/ml) on matrix metabolism in the deep flexor tendon from the tendon sheath region of the rabbit were studied in explants cultured for 3 weeks. Tendon segments cultured in medium supplemented with fetal calf serum (FCS) exhibited proliferation of the superficial cell layers. Synthesis of proteoglycan and non-collagen protein (NCP) increased threefold during the first week and remained elevated during the next 2 weeks of culture in medium supplemented with rhIGF-I or FCS, but not in medium without supplements (bovine serum albumin, BSA). The estimated halflife (t1/2) for elimination of newly labeled proteoglycans from the tendon explants ranged from 5.1 to 8.5 days and from 4.9 to 6.8 days for NCP in supplemented medium. Presence of rhIGF-I or FCS did not affect degradation of matrix as compared with BSA. The total hexosamine content per tendon segment was stable during the culture period, but the non-collagen protein content decreased by 25%. Collagen synthesis decreased to 10% of the initial level after 3 weeks in supplemented medium, but to 3% in unsupplemented medium. There was no measurable turnover of collagen in explants cultured in either medium, and the collagen content remained unchanged. Our results suggest that rhIGF-I, as well as FCS, stimulates matrix synthesis but does not influence matrix turnover in rabbit flexor tendon explants in long-term culture as compared with medium without supplements. We conclude that rhIGF-I may be used as a defined growth-promoting factor in serum-free media and may be of importance in tendon healing.

Recombinant human insulin-like growth factor-I stimulates in vitro matrix synthesis and cell proliferation in rabbit flexor tendon

Flexor tendons have an intrinsic ability for repair, with a capacity to metabolize matrix components and to proliferate. To identify factors with the potential of affecting those abilities, the effects of recombinant human insulin-like growth factor (rhIGF-I), insulin and fetal calf serum (FCS) on the synthesis of proteoglycan, collagen, and non-collagen protein and cell proliferation were investigated in short-term explant cultures of the deep flexor tendon of the rabbit. Matrix synthesis and cell proliferation were stimulated dose dependently by rhIGF-I at doses between 10 and 250 and at 10-100 ng/ml, respectively, by insulin at 250-5,000 ng/ml, and by FCS at 2-15%. Estimated maximal stimulation (Emax) of up to three times the control value was observed with rhIGF-I at 250 ng/ml. Maximal stimulation was observed at 5,000 ng/ml with insulin, and FCS at 15%. rhIGF-I was more potent than insulin in stimulating protein synthesis and cell proliferation. The Emax of stimulation of proteoglycan and collagen synthesis by rhIGF-I were two times that of FCS, and the Emax of cell proliferation by FCS was twice that of rhIGF-I. Growth factors thus have the ability to stimulate matrix synthesis and cell proliferation in rabbit flexor tendon. This provides a rationale for further studies on the role of growth factors in flexor tendon healing in humans.

Dehydration inhibits matrix synthesis and cell proliferation. An in vitro study of rabbit flexor tendons

Segments of the deep flexor tendon of the rabbit were exposed to air; the effects of dehydration on in vitro synthesis of proteoglycan, collagen, noncollagenous protein, and cell proliferation were compared with tendon segments that were kept moist with physiologic saline. After 20 min of exposure to air, the tendons lost half and after 40 min all of their ability to synthesize matrix components and to proliferate, whereas irrigated tendons remained viable during the entire experiment.

The degradation of collagen in pig synovium in vitro and the effect of colchicine

Colchicine induced a rapid destruction of the collagenous matrix of pig synovial explants in culture in the presence of serum. The most efficacious doses were 0.01-0.1 micrograms/ml (2.5 x 10(-8) M - 2.5 x 10(-7) M). The histological progression of the tissue breakdown induced by colchicine was very similar, although faster, to that described for other agents (Fell et al., 1986), with cells having basophilic nuclei accumulating in areas of fibril degradation. The loss of collagen correlated with an increase in collagenase production and at the peak of resorption (6 to 8 days) active collagenase was present in the culture media. Immunocytochemical methods demonstrated active collagenase bound to collagen fibrils after only 4 days in culture, before significant collagen degradation could be observed histologically. Collagen breakdown was completely inhibited by cortisol, and partially inhibited by indomethacin: only the inhibition by indomethacin could be reversed by exogenous prostaglandin E2. Vinblastine at a higher dose was as effective as colchicine but the lumicolchicines, which do not disrupt microtubules, were ineffective. Although the precise mechanism of action of colchicine is unknown, this culture system provides a useful in vitro model for increasing our understanding of the cellular mechanisms of tissue breakdown and for elucidating the roles of active collagenase and related metalloproteinases.

Secretion of lamellar bodies in type II pneumocytes in organoid culture: effects of colchicine and cytochalasin B

Lamellar bodies are the morphological correlate to the alveolar surface-active agent. Diminished synthesis of this surfactant in newborns results in the respiratory distress syndrome. Secretion of lamellar bodies and its dependence on the cytoskeleton are not yet well understood and are still controversially discussed in the literature. We therefore used an organoid culture system of fetal mouse lung cells to investigate electron microscopically secretion of lamellar bodies and influence of both colchicine and cytochalasin B on the secretion process. Secretion of lamellar bodies is to be considered as an eccrine secretion, because no other cytoplasmic components were extruded. It includes a very fast component in opening of the secretory vacuole. Synthesis, but not secretion, was inhibited by colchicine; secretion, but not synthesis, was inhibited by cytochalasin B. Furthermore, formation of the histotypic structures in vitro and deposition of the basal lamina were disturbed by cytochalasin B, but not altered by colchicine. After short-term treatment, these effects turned out to be reversible. The results indicate that synthesis of lamellar bodies depends on an intact microtubular system, whereas secretion requires actin filaments in a functional state.

Segmental variation in microstructure, matrix synthesis and cell proliferation in rabbit flexor tendon

An experimental culture system was designed with the purpose of studying matrix synthesis and cell proliferation in the deep flexor tendon of the rabbit forepaw. Special attention was paid to differences between three consecutive defined segments of the tendon from the region of the tendon sheath. There were two fibrocartilaginous areas in the tendon, one in the dorsal part of the proximal segment and one in the volar part of the distal segment. The intermediate segment consisted of regular tendinous tissue. The dorsal aspect of the distal segment was further characterized by a cell rich area related to the entrance of the vinculum longum. Proteoglycan synthesis in vitro was higher in the proximal and distal segments than in the intermediate, while collagen synthesis was highest in the intermediate tendinous segment. Variations in collagen content were reflected in variations in collagen synthesis. The rate of cell proliferation was highest in the intermediate segment. Segmental biochemical characteristics correlated well with morphological variations of the deep flexor tendon. These variations may reflect an adaptation to different mechanical forces acting on the tendon. The segmental variations may also be relevant for the healing capacity of the flexor tendon.

Tendon healing in vivo. An experimental model

Flexor tendon segments were incubated in a diffusion chamber in the subcutis of rabbits. Tendons incubated up to 6 weeks in the diffusion chamber showed proliferating and migrating cells from the epitenon cell layer as well as viable endotenon cells. Explants frozen in liquid nitrogen prior to incubation showed no signs of extrinsic cell contamination and remained non-viable indicating that no cell penetration occurred through the Millipore filter and that cell division seen in non-frozen and incubated tendons was an expression of intrinsic cellular proliferative capacity of the tendon. In tendon segments incubated in chambers for three weeks, collagen synthesis was reduced by 50% and the rate of cell proliferation measured as 3H-thymidine incorporation, was 15 times that of native tendons. Frozen and incubated tendons showed only traces of remaining matrix synthesis or cell proliferation. With this experimental model we have histologically and biochemically shown that tendons may survive and heal while the nutrition exclusively could be based on diffusion and the tendons have an intrinsic capacity of healing. The described model enables further studies on tendon healing and its regulation.

Effect of colchicine on collagen synthesis by liver fibroblasts in murine schistosomiasis

Colchicine, an antimicrotubular agent, was shown to block the transcellular movement of certain structural macromolecules such as collagen. In the present study, the effect of colchicine on collagen synthesis and secretion by monolayer cultures of fibroblasts from livers of mice infected with Schistosoma mansoni was investigated. The effect of colchicine on proliferation of these fibroblasts was studied as well. Collagen and non-collagen protein synthesis was measured by incubating cultures with [14C]proline and measuring the incorporation of radioactivity into these protein fractions in both culture media and cell layers. Proliferation was measured by [3H]thymidine uptake. The isolated fibroblasts actively formed collagen and secreted most of it into the culture medium; 10-20% of the collagenase-sensitive radioactive protein remained in the cell layer. The addition of colchicine to culture medium led to selective inhibition of collagen formation with negligible effects on non-collagen protein synthesis. Fibroblast proliferation was also reduced by colchicine treatment. Both inhibition of collagen synthesis and inhibition of fibroblast proliferation were dose-dependent. Comparison of medium and cell layer collagen radioactivity confirmed inhibition of synthesis rather than only inhibition of secretion. These data suggest that colchicine has a specific effect on synthesis of collagen and proliferative activity by fibroblasts from S. mansoni-infected liver and may, therefore, be useful in modulating schistosomal hepatic fibrosis.

Evaluation of colchicine therapy in primary biliary cirrhosis

We have conducted a double-blind controlled trial of colchicine in patients with primary biliary cirrhosis. Fifty-seven patients with biopsy-proven primary biliary cirrhosis were randomized to receive either 0.6 mg of colchicine twice daily or an identically appearing placebo. Patients underwent clinical and laboratory evaluation every 3 mo and liver biopsy annually. Differences in mean alkaline phosphatase and alanine aminotransferase values between the colchicine and placebo recipients were statistically significant at 4 yr. Differences in mean bilirubin and immunoglobulin M values, although lower in the colchicine group, did not reach statistical significance. In colchicine-treated patients, mean alkaline phosphatase values fell significantly compared with controls, from 281 to 112 IU/L (p less than 0.01). Similarly, mean alanine aminotransferase values fell significantly compared with controls, from 129 to 86 IU/L (p less than 0.05). Bilirubin values remained stable in drug-treated patients, even in those patients with initially elevated bilirubin values, whereas they nearly doubled in subjects receiving placebo. Although biochemical parameters of disease activity improved or stabilized in colchicine-treated subjects, no difference in histologic progression was detected between the two treatment groups. We conclude that colchicine is of clinical benefit to patients with primary biliary cirrhosis as judged by improvement in alkaline phosphatase and alanine aminotransferase activities as well as a tendency for stabilization of bilirubin values.

Cytochemical study of the Golgi apparatus and related organelles of the secretory ameloblasts of rat molar tooth germs cultured with and without colchicine

The Golgi apparatus and Golgi-associated endoplasmic reticulum lysosome (GERL) were examined in the ameloblasts with a cytochemical marker, osmium impregnation, and two enzyme markers, thiamine pyrophosphatase (TPPase) and acid phosphatase (ACPase). In control cultured germs, osmium deposit appeared in one to two immature side cisternae of Golgi stacks; TPPase activity was restricted in a few mature side cisternae and condensing vacuoles. ACPase activity existed in the GERL and, sometimes, in the mature side-cisternae and condensing vacuoles. These findings show that Golgi stacks of ameloblasts consist of several distinct compartments. In colchicine-treated tooth germs, there were morphological and cytochemical changes in both Golgi stacks and GERL. The Golgi apparatus was fragmented and its stacks were scattered throughout the supranuclear region. In some stacks, the number of osmium-positive cisternae was greater than normal; in others they were absent. TPPase and ACPase activity was absent or diminished. These findings suggest the importance of microtubules in the organization of Golgi complex and GERL in the secretory ameloblast.

Drug test chamber: a titanium implant for administration of biochemical agents to a standardized bone callus in situ

A titanium implant in which a conduit is gradually filled with ingrowing bone (the Bone Harvest Chamber) has been modified to allow continuous local treatment of the conduit tissue with biochemical agents. Implants were inserted bilaterally in rabbit tibiae. The tissue content of the bone ingrowth conduits was studied with histology, 99mTc-MDP scintimetry and measurements of total calcium content. Bone was formed in the conduit by endochondral formation starting at both ends and continuing until fusion in the middle. After 2 weeks the bone had not yet met in the middle where fibrous tissue was seen. In eight animals 3H-proline was applied via one of the chambers, with the contralateral chamber as a saline-treated control. The collagen of the harvested tissue from the 3H-proline treated side had a 3H-hydroxyproline content 1000 times greater than had the control side. The 'drug test chamber' makes possible the study of local effects of drugs on healing of mature bone in vivo.

Effects of colchicine on sulfated glycosaminoglycan production and cell detachment in pre-capillary pulmonary endothelial cells

The effects of colchicine on the morphology, substrate adhesiveness, and production of glycosaminoglycan (GAG) macromolecules by cultured pre-capillary pulmonary endothelial cell were studied. Colchicine-treated cells demonstrated altered morphology and decreased substrate adhesiveness compared to untreated cells. In addition, [35S]sulfate incorporation into glycosaminoglycans was decreased 33% after treatment with colchicine. Spectrophotometric measurement of total cellular GAG revealed a similar GAG reduction in colchicine-treated cells. The composition of [35S]sulfate radiolabelled GAG was similar in cultures with and without colchicine, consisting of approximately 56% chondroitin sulfate and the remainder heparin/heparan sulfate. The results indicate that colchicine influences the biological behavior of pre-capillary endothelial cells, in part by altering the amount of glycosaminoglycan molecules produced.

Phenotype modulation in primary cultures of smooth-muscle cells from rat aorta. Synthesis of collagen and elastin

Early in primary culture, arterial smooth-muscle cells undergo a transition from a contractile to a synthetic phenotype. This process includes the loss of myofilaments and of contractility. At the same time, an extensive rough endoplasmic reticulum and a large Golgi complex are formed, and active synthesis of DNA, RNA and proteins commences. In the present study, chemical and immunocytochemical methods were used to investigate the production of extracellular-matrix proteins in relation to this change in phenotypic properties. The results showed that the phase of rapid cellular proliferation that follows the structural modulation of smooth-muscle cells is associated with high rates of collagen and elastin synthesis, as measured by the incorporation of 3H-proline into 3H-hydroxyproline and 3H-valylproline, respectively. SDS-polyacrylamide gel electrophoresis and fluorography indicated that type-I collagen is the main collagen species synthesized by these cells. Smaller amounts of type-V collagen and (although not definitively identified) type-III collagen were also detected. Indirect immunofluorescence and immunoelectron microscopy demonstrated that smooth-muscle cells surround themselves with an incomplete basement membrane, containing laminin and type-IV collagen, and thin fibrils of type-I collagen. Adjacent to these fibrils, aggregates of amorphous, elastin-like material were also found. Our observations confirm and extend earlier notions of a close similarity between the behaviour of arterial smooth-muscle cells during in vitro cultivation and during the early stages of the formation of atherosclerotic lesions.

Effects of colchicine on the gallbladder of the mouse

The effects of colchicine on the mouse gallbladder followed a course depending on the dosage given (0.4-4 mg/100 g body weight). Following 0.5 mg/100 g, by 16 h there was a marked cholestasis with dilatation of the gallbladder and steatosis. There were progressive alterations in the Golgi apparatus and accumulation of vesicles. The apical mucous droplets decreased in number and became pleomorphic and dispersed throughout the cytoplasm. Lipid droplets appeared in numbers on the epithelial cytoplasm. By 48 h the tissues had reverted to normal appearances. When cholecystokinin, pilocarpine or ceruletide were given to animals which had received colchicine 18 h previously, the excess bile from the dilated gallbladder was discharged into the duodenum, remaining apical mucous droplets secreted and electron dense material accumulated in the lateral intercellular space. This formed a quasi-regular array between the epithelial bases and the basement membrane. Biochemically there was a significant decrease in alkaline phosphatase activity and a significant increase in acid phosphatase activity.

Microtubules and the organization of the Golgi complex

Electron microscopic and cytochemical studies indicate that microtubules play an important role in the organization of the Golgi complex in mammalian cells. During interphase microtubules form a radiating pattern in the cytoplasm, originating from the pericentriolar region (microtubule-organizing centre). The stacks of Golgi cisternae and the associated secretory vesicles and lysosomes are arranged in a circumscribed juxtanuclear area, usually centered around the centrioles, and show a defined orientation in relation to the rough endoplasmic reticulum. Exposure of cells to drugs such as colchicine, vinblastine and nocodazole leads to disassembly of microtubules and disorganization of the Golgi complex, most typically a dispersion of its stacks of cisternae throughout the cytoplasm. These alterations are accompanied by disturbances in the intracellular transport, processing and release of secretory products as well as inhibition of endocytosis. The observations suggest that microtubules are partly responsible for the maintenance and functioning of the Golgi complex, possibly by arranging its stacks of cisternae three-dimensionally within the cell and in relation to other organelles and ensuring a normal flow of material into and away from them. During mitosis, microtubules disassemble (prophase) and a mitotic spindle is built up (metaphase) to take care of the subsequent separation of the chromosomes (anaphase). The breaking up of the microtubular cytoskeleton is followed by vesiculation of the rough endoplasmic reticulum and partial atrophy, as well as dispersion of the stacks of Golgi cisternae. After completion of the nuclear division (telophase), the radiating microtubule pattern is re-established and the rough endoplasmic reticulum and the Golgi complex resume their normal interphase structure. This sequence of events is believed to fulfil the double function to provide tubulin units and space for construction of the mitotic spindle and to guarantee an approximately equal distribution of the rough endoplasmic reticulum and the Golgi complex on the two daughter cells.

Articular cartilage cultured with catabolin (pig interleukin 1) synthesizes a decreased number of normal proteoglycan molecules

A homogeneous preparation of catabolin from pig leucocytes caused a reversible dose-dependent (0.01-1 nM) decrease in the synthesis of proteoglycan in slices of pig articular cartilage cultured in serum-free medium. The monomers that were synthesized and secreted in the presence of catabolin had the same average hydrodynamic size and ability to aggregate as the controls, and the core protein was substituted with the same number of glycosaminoglycan chains. The chains were the same average length and charge as normal and were sulphated to the same extent as the controls. Newly synthesized extracellular proteoglycan was not preferentially degraded. A 2-3-fold increase in glycosaminoglycan synthesis occurred in control and catabolin-treated cartilage in the presence of beta-D-xyloside (1 mM), more than 80% being secreted into the medium as free chains. Decreased incorporation of sulphate was not reversed in the presence of lysosomal-enzyme inhibitors, and there was no evidence in pulse-chase experiments of increased intracellular degradation of glycosaminoglycan chains before secretion. It is concluded that catabolin-treated cartilage synthesizes a smaller number of normal proteoglycan molecules.

Synthesis and secretion of proteoglycans by cultured chondrocytes. Effects of monensin, colchicine and beta-D-xyloside

Chondrocytes, isolated from elastic ear cartilage of young rabbits, were grown in monolayer cultures in Ham's F-12 medium. Synthesis and secretion of macromolecules were monitored by labelling with radioactive precursors and the effect of monensin and other experimental agents was investigated. Monensin caused an inhibition of the incorporation of precursors into macromolecular material and a moderate intracellular accumulation when used in higher concentrations. The effect was more pronounced for 35SO4 than for 3H-labelled glucose or proline. p-Nitrophenyl-beta-D-xyloside alleviated this inhibition to some extent, but there was a concomitant increase in the amount of intracellular labelled material. Colchicine and monensin together caused a severe inhibition of the incorporation of 35SO4 and a marked shift of the label to the intracellular compartment. Colchicine also increased the sensitivity of the cells to monensin, lowering the minimal effective concentration about one order of magnitude. The latter results are consistent with the idea that cytoplasmic microtubules have a stabilizing function on the secretory pathways and, that their removal by colchicine, causing a 'randomizing' of the Golgi complex, makes these pathways more vulnerable to monensin.

Proteoglycan aggregate formation by articular chondrocytes. Decrease in link-protein synthesis during culture

The synthesis of link-stabilized proteoglycan aggregates by rabbit articular chondrocytes was investigated by [35S]sulphate labelling of primary monolayer cultures maintained for up to 21 days. (1) At all culture times the cells secreted a high-molecular-weight cartilage-type proteoglycan monomer of which 75%-80% formed aggregates with hyaluronic acid. (2) At 2 days of culture all of the aggregates were in link-stabilized form, but by 21 days only 5% were link-stabilized, as shown by displacement of monomers from the aggregate by hyaluronic acid oligosaccharides. (3) The addition of purified link protein to 21-day culture medium increased the proportion of link-stable aggregate from 5% to 70%. (4) Analysis of [3H]serine-labelled proteoglycan aggregates in the medium showed a marked decrease with culture time in the ratio of 3H-labelled link protein to 3H-labelled core protein present. The results suggest that the secretion of proteoglycan monomers and link protein by articular chondrocytes changes independently during prolonged monolayer culture.

Reduction of peritoneal adhesion formation by colchicine: a comparative study in the rat

Colchicine inhibits processes known to be involved in the pathogenesis of peritoneal adhesions. Daily administration of 50 micrograms of colchicine to 22 rats significantly diminished adhesion formation, as compared with dexamethasone-treated and untreated rats. Rats that developed at least three adhesions of grade 3 (scale 0 to 4) were strikingly less prevalent among the colchicine-treated animals than the untreated group (9.1% versus 40.9%, P less than 0.001). The double product of the number and grading of adhesions was significantly lower (P less than 0.05) in the colchicine group. Colchicine is more effective than dexamethasone in inhibiting adhesion formation in the rat.

Effect of colchicine on the Golgi complex of rat pancreatic acinar cells

Colchicine administered to adult rats at a dosage of 0.5 mg/100 g of body weight effected a disorganization of the Golgi apparatus in pancreatic acinar cells. The results obtained after various periods of treatment (10 min to 6 h) showed (a) changes in all components of the Golgi complex, and (b) occurrence of large vacuoles that predominated in cytoplasmic areas outside the Golgi region. The alterations in Golgi stacks concerned elements of the proximal and distal side: (a) accumulation of transport vesicles, (b) formation of small, polymorphic secretion granules, and (c) alterations in the cytochemical localization of enzymes and reaction product after osmification. Transport vesicles accumulated and accompanied short, dilated cisternae, which lack mostly the reaction products of thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase, and osmium deposits after prolonged osmification. After 4 to 6 h of treatment, accumulated transport vesicles occupied extensive cellular areas; stacked cisternae were not demonstrable in these regions. The changes on the distal Golgi side included GERL elements: condensing vacuoles were diminished; they were substituted by small, polymorphic zymogen granules, which appeared to be formed by distal Golgi cisternae and by rigid lamellae. Unusually extended coated regions covered condensing vacuoles, rigid lamellae, and polymorphic secretion granules. A cytochemical distinction between Golgi components and GERL was possible neither in controls nor after colchicine treatment. The cytochemical alterations in Golgi components were demonstrable 20-30 min following administration of colchicine; at 45 min, initial morphological changes--augmentation of transport vesicles and formation of polymorphic zymogen granules--became apparent. 20 min after administration of colchicine, conspicuous groups of large vacuoles occurred. They were located mostly in distinct fields between cisternae of the endoplasmic reticulum, and were accompanied by small osmium--reactive vesicles. Stacked cisternae were not demonstrable in these fields. Vacuoles and vesicles were devoid of reaction products of thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase. The results provide evidence that formation of stacked Golgi cisternae is impaired after colchicine treatment. The colchicine--induced disintegration of the Golgi complex suggests a regulatory function of microtubules in the organization of the Golgi apparatus.

Studies on the contents of glycosaminoglycans from lungs of silicotic rats and tetrandrine-treated silicotic rats

In this report the differences in the total content of glycosaminoglycans (GAG) and in the relative contents of individual GAG among normal rat lung, silicotic rat lung, and tetrandrine (TT)-treated silicotic rat lung were studied. The differences were also observed with the histochemical method. In normal rat lung the content of GAG was 6.35 mg/g dry tissue. The percentage of heparin sulfate (HeS) was higher than the others. The content of GAG in silicotic rat lung was raised much more than that of the normal rat. Percentages of hyaluronic acid (HyA) and dermatan sulfate (DeS) were higher. Percentage of HeS was lower than that of the normal rat. In silicotic lung GAG existed around the collagen fibers and were netlike in shape. After treatment with TT, most of the GAG were seen to be present within the cells. It was proved that TT could inhibit the increase in the content of GAG in silicotic rat lung and could also obstruct the change in the relative contents of individual GAG.

Synthesis of proteoglycans, collagen, and elastin by cultures of rabbit auricular chondrocytes--relation to age of the donor

Chondrocytes were isolated from the auricular cartilage of rabbits, aged 1 week to 30 months, and grown in short-term cell culture. The cells from the 1-week animals were small, polygonal, and mononucleated, while the chondrocytes from the older animals were larger, rounded, and frequently binucleated. The synthesis of proteoglycans, collagen, and elastin was determined by isotope incubation. Chemical characterization of the proteoglycans was also performed. The production of the matrix macromolecules showed a clear age dependence with peak synthesis occurring at different ages. Proteoglycans were actively synthesized by chondrocytes from all age groups with a broad maximum between 2 weeks and 5 months followed by a sharp decline to about 50% of the 1-week level at 12-30 months. Collagen synthesis peaked at 2 weeks, declining progressively thereafter to about 60% of the 1-week level at 30 months. Elastin synthesis was highest in the 1-week cultures and thereafter fell quickly to very low levels. In all age groups the chondrocytes synthesized predominantly cartilage-typic proteoglycans, i.e., large aggregate forming molecules containing chondroitin sulfate. Monomers and aggregates showed a size maximum at 2-8 weeks. The degree of sulfation of the chondroitin sulfate and the proportion of 6-sulfate increased with age. These findings support the concept of "age programs" for the biosynthesis and turnover of different matrix macromolecules.

Colchicine-induced modulation of collagenase in human skin fibroblast cultures. I. Stimulation of enzyme synthesis in normal cells

Microtubule-active agents affect the secretion of a variety of proteins, including collagenase. To gain insight into the mechanisms involved in this process, we examined the effects of colchicine on the synthesis, secretion, and activity of human skin collagenase. When added to monolayer cultures of human skin fibroblasts, 10(-6) M colchicine produced a mean 3-fold increase in trypsin-activatable collagenase in the culture medium. Stimulation was not observed with lumicolchicine. The enhanced accumulation of collagenase was dose-dependent with 10(-9), 10(-8), 10(-7), and 10(-6) M colchicine giving collagenase activities/mg protein that were 100 +/- 6%, 165 +/- 20%, 186 +/- 34%, and 297 +/- 62% of control, respectively. Although the effect on collagenase was seen under conditions independent of cellular growth (i.e., in serum-free medium), maximum stimulation occurred in subconfluent cultures. The colchicine-induced increase in activity was paralleled by an increase in immunoreactive enzyme protein, suggesting stimulation of enzyme synthesis. The catalytic efficiency of the enzyme (activity per unit immunoreactive protein) was unchanged, however, indicating that a structurally normal enzyme was being synthesized. To examine the process in more detail, the biosynthesis of 3H-labeled collagenase was quantitated in these cultures by specific immunoprecipitation. Although 10(-6) M colchicine produced no increase in total protein synthesis, an increased rate of collagenase synthesis was seen after only 1.5 hr. These data suggest that colchicine has a specific effect on the synthesis of collagenase and may be a useful probe for studying its regulation.

Microtubules and protein secretion in rat lacrimal glands: localization of short-term effects of colchicine on the secretory process

The pathway and kinetics of the secretory protein transport in rat lacrimal exorbital gland have been established by an in vitro time-course radioautographic study of pulse-labeled protein secretion. The colchicine-sensitive steps have been localized by using the drug at various times with respect to the pulse labeling of proteins. Colchicine (10 microM) does not block any step of the secretory protein transport, but when introduced before the pulse it decreases the transfer of labeled proteins from the rough endoplasmic reticulum to the Golgi area, suppressing their temporary accumulation in the Golgi area before any alteration of this organelle is detectable. Moreover, colchicine inhibits protein release only from the secretory granules formed in its presence because the peroxidase discharge is diminished 1 h after colchicine addition, and the secretion of newly synthesized proteins is strongly inhibited only when colchicine is introduced before secretory granule formation. Morphometric studies show that there is a great increase of secondary lysosomes, related to crinophagy, as early as 40-50 min after colchicine is added. However, changes in lysosomal enzymatic activities remained biochemically undetectable. We conclude that: (a) the labile microtubular system does not seem indispensable for protein transport in the rough endoplasmic reticulum-Golgi area but may facilitate this step, perhaps by maintaining the spatial organization of this area; and (b) in the lacrimal gland, colchicine inhibits protein release not by acting on the steps of secretion following the secretory granule formation, but by acting chiefly on the steps preceding secretory granule formation, perhaps by making the secretory granules formed in its presence incapable of discharging their content.

The effect of intraperitoneal colchicine on the formation of peritoneal adhesions in the rat

A double blind study was carried out to determine the effect of colchicine on the formation of intraperitoneal adhesions in the rat. Adhesions were produced by a standard method in 92 rats. The animals were than divided at random into two groups. One group (47 rats) was treated with intraperitoneal colchicine, whilst the other, the control group (45 rats) was treated with intraperitoneal normal saline in the same volume, frequency and duration. Four weeks later the animals were killed for assessment and measurement of adhesions. Two kinds of adhesions were found. 1. "Surface adhesion" - consisting of two serosal surfaces attached together; their area was significantly smaller (p less than 0.00003), and their number was lower (p less than 0.03) in the colchicine group than in the control group. 2. "Filamentous adhesions" - thin, elastic cords connecting omentum or pelvic fat bodies to other viscera; there was no significant difference in their number between the colchicine and the control group. We concluded that post-operative treatment with colchicine reduces the formation of intraperitoneal adhesions in the rat.

Fractionation and characterization of proteoglycans isolated from chondrocyte cell cultures

Chondrocyte cultures were established from foetal bovine tracheal cartilage and maintained in Ham's F12 medium with or without 10% (v/v) foetal calf serum. The proteoglycans were isolated and characterized. (1) The proteoglycans from cultures both with and without serum distributed in associative or dissociative CsCl gradients like proteoglycans from cartilage tissue. (2) The amino acid composition, protein contents and glucosamine/galactosamine ratios were grossly identical with those of the tissue derived proteoglycans. (3) Sedimentation coefficients (s(0)) for the monomers were 21.0S and 22.7S from cultures without and with serum respectively. The s(0) values obtained for aggregates were 72.3S and 93.2S respectively. The limiting viscosity numbers [eta] were 248ml/g and 298ml/g respectively. These data corresponded well to those obtained for the tissue-derived proteoglycans. (4) The sizes of the core proteins and chondroitin sulphate chains respectively were the same for both types of cell-culture proteoglycans and similar to those of the tissue proteoglycans. Both the keratan sulphate-rich region and the hyaluronic acid-binding region were identified. The latter, however, was not resistant to limit digestion with trypsin, in contrast with the fragment derived from the bovine nasal cartilage. (5) About 70% of the cell-culture proteoglycans chromatographed in the void volume on a Sepharose 2B column, whereas reduced and alkylated samples (monomers) chromatographed completely included in the column. The two link proteins present in A1 preparations of cartilage proteoglycans were also present in A1 preparations of cell-culture proteoglycans. (6) A minor portion (10%) of the (35)S-labelled proteoglycans in the cultures was associated with the cells. Reduced and alkylated samples were larger compared with the monomers in the medium, and chromatographed partly (25%) excluded on the Sepharose 2B column. A larger proportion (50%) of the non-reduced samples chromatographed in the void volume of the column.

Monensin and FCCP inhibit the intracellular transport of alphavirus membrane glycoproteins

Temperature-sensitive mutants of semliki forest virus (SFV) and sindbis virus (SIN) were used to study the intracellular transport of virus membrane glycoproteins in infected chicken embryo fibroblasts. When antisera against purified glycoproteins and (125)I- labeled protein A from staphylococcus aureus were used only small amounts of virus glycoproteins were detected at the surface of SFV ts-1 and SIN Ts-10 infected cells incubated at the restrictive temperature (39 degrees C). When the mutant-infected cells were shifted to the permissive temperature (28 degrees C), in the presence of cycloheximide, increasing amounts of virus glycoproteins appeared at the cell surface from 20 to 80 min after the shift. Both monensin (10muM) and carbonylcyanide-p- trifluoromethoxyphenylhydrazone (FCCP; 10-20 muM) inhibited the appearance of virus membrane glycoproteins at the cell surface. Vinblastine sulfate (10 mug/ml) inhibited the transport by approximately 50 percent, whereas cytochalasin B (1 mug/ml) had only a marginal effect. Intracellular distribution of virus glycoproteins in the mutant-infected cells was visualized in double-fluorescence studies using lectins as markers for endoplasmic reticulum and Golgi apparatus. At 39 degrees C, the virus membrane glycoproteins were located at the endoplasmic reticulum, whereas after shift to 28 degrees C, a bright juxtanuclear reticular fluorescence was seen in the location of the Golgi apparatus. In the presence of monensin, the virus glycoproteins could migrate to the Golgi apparatus, although transport to the cell surface did not take place. When the shift was carried out in the presence of FCCP, negligible fluorescence was seen in the Golgi apparatus and the glycoproteins apparently remained in the rough endoplasmic reticulum. A rapid inhibition in the accumulation of virus glycoproteins at the cell surface was obtained when FCCP was added during the active transport period, whereas with monensin there was a delay of approximately 10 min. These results suggest a similar intracellular pathway in the maturation of both plasma membrane and secretory glycoproteins.

Sanfilippo disease type D: deficiency of N-acetylglucosamine-6-sulfate sulfatase required for heparan sulfate degradation

Skin fibroblasts from two patients who had symptoms of the Sanfilippo syndrome (mucopolysaccharidosis III) accumulated excessive amounts of heparan sulfate and were unable to release sulfate from N-acetylglucosamine-6-sulfate linkages in heparan sulfate-derived oligosaccharides. Keratan sulfate-derived oligosaccharides bearing the same residue at the nonreducing end and p-nitrophenyl-6-sulfo-2-acetamido-2-deoxy-beta-D-glucopyranoside were degraded normally. Kinetic differences between th sulfatase activities of normal fibroblasts were found. These observations suggest that N-acetylglucosamine-6-sulfate sulfatase activities degrading heparan sulfate and keratan sulfate, respectively, can be distinguished. It is the activity directed toward heparan sulfate that is deficient in these patients; we propose that this deficiency causes Sanfilippo disease type D.

Morphological and cytochemical alterations of the Golgi apparatus and GERL in rat parotid acinar cells during ethionine intoxication and recovery

The present electron microscopic cytochemical investigation was undertaken to characterize the alterations in the golgi apparatus and GERL of rat parotid acinar cells during ethionine intoxication and recovery. Although the Golgi apparatus and GERL were reduced in size, and some broadening of the Golgi saccules occurred as the result of ethionine treatment, the relative localization of thiamine pyrophosphatase (TPPase) activity in the Golgi saccules, and acid phosphatase activity (AcPase) in GERL, remained unchanged. Shortly after ethionine treatment was stopped, a dramatic redistribution of enzyme activities was noted. Within the first 24 hours of recovery, the Golgi apparatus began to enlarge, and the content of secretory granules increased. By day 3 of recovery, cisternae morphologically identifiable as GERL and forming secretory granules possessed TPPase activity, while AcPase activity was virtually undetectable. After seven days of recovery, the Golgi apparatus and GERL appeared both morphologically and cytochemically normal. The enzyme modulation observed during recovery may be correlated with increased secretory granule production. Furthermore, the presence of TPPase activity in GERL and forming secretory granules lends support to the suggestion that GERL may be derived from the trans Golgi saccule.