Sergio A. Jimenez

Hydroxyproline content determines the denaturation temperature of chick tendon collagen

Abstract A series of nine procollagen samples in which the hydroxyproline content varied from

Hydroxyproline stabilizes the triple helix of chick tendon collagen

Abstract The thermal stability of unhydroxylated procollagen relative to hydroxylated procollagen was investigated using pepsin digestion at various temperatures in the interval 15° to 35° as an enzymatic probe of conformation. The results demonstrate that the unhydroxylated molecules thermally denature between 20° and 25°, while the hydroxylated molecules are stable at least to 35°. This finding suggests that the presence of hydroxyproline in the molecule contributes significantly to the thermal stability of collagen. The results also suggest that triple strand formation may be required for normal secretion.

Regulation of fibroblast proliferation and collagen synthesis by cytokines

Fibroblasts are ubiquitous mesenchymal cells which synthesize collagen and other matrix macromolecules for the structural support of connective tissues. They are important in wound repair but also contribute connective tissue proteins to areas of chronic inflammation. In pathological processes such as hepatic cirrhosis, this may become deleterious to the host. Certain fibrotic diseases such as scleroderma and some forms of interstitial pneumonitis and interstitial nephritis are characterized by the presence of prominent mononuclear cell infiltrates. Studies in several laboratories have recently established that mononuclear cells produce soluble mediators capable of regulating several fibroblast functions including migration, proliferation and collagen synthesis. However, many of the studies on the immunoregulation of fibroblasts appear to present contradictory or mutually exclusive data. In this review Bruce Freundlich and his colleagues discuss the difficulties in identifying the factors that regulate fibroblast proliferation and collagen synthesis.

Stimulation of normal human fibroblast collagen production and processing by transforming growth factor-β

Transforming growth factor-beta (TGF beta) a growth factor with diverse effects on cellular growth and metabolism, caused dramatic stimulation of total protein and collagen synthesis by confluent normal human dermal fibroblasts in culture in a dose-dependent manner. Gel electrophoresis of the newly synthesized macromolecules from the culture media of TGF beta treated cultures demonstrated accelerated procollagen processing. These results indicate that TGF beta is capable of qualitatively and quantitatively influencing the biosynthesis of matrix molecules by fibroblasts, and raise the possibility that TGF may play a role in the development of normal and pathologic fibrogenesis.

Transcriptional control of human diploid fibroblast collagen synthesis by γ-interferon

Abstract Recombinant γ-interferon (rec γ-IFN) caused potent inhibition of collagen synthesis by cultured confluent human diploid fibroblasts in a dose-dependent manner. Gel electrophoresis of the newly synthesized proteins from the culture media of rec γ-IFN-treated fibroblasts demonstrated a selective depression of procollagen without a significant change in non-collagenous proteins. Dot blot hybridization to a Type I procollagen cDNA probe showed that the inhibition of collagen production was accompanied by a decrease in the levels of collagen mRNA. These results indicate that rec γ-IFN is capable of exerting transcriptional modulation of collagen biosynthesis and suggest that it may play an important role in regulation of normal and pathologic fibrogenesis.

Identification of collagen α1(I) trimer in embryonic chick tendons and calvaria

Abstract Collagen with a molecular composition [ α 1 (I)] 3 has been identified in acetic acid extracts from lathyritic chick embryo tendons and calvaria. These molecules characteristically have greater solubility than Type I collagen at neutral pH and contain increased amounts of hydroxylysine residues. It is suggested that these molecules represent a separate gene product of embryonic cells which may be important in the process of maturation and development.

PGE2 causes a coordinate decrease in the steady state levels of fibronectin and types I and III procollagen mRNAs in normal human dermal fibroblasts

Prostaglandin E2 (PGE2) caused inhibition of collagen and fibronectin synthesis by confluent cultures of human dermal fibroblasts. Dot-blot hybridization to cDNA probes complementary to Types I and III procollagens and fibronectin demonstrated that inhibition of protein production was accompanied by a coordinate decrease in the steady-state levels of the corresponding mRNAs. Blockade of transcription by actinomycin D demonstrated that PGE2 did not alter the stability of these mRNA. These results indicate that PGE2 is capable of exerting modulation of extracellular matrix biosynthesis, and that these effects occur at a transcriptional level.

Progressive systemic sclerosis: Mode of presentation, rapidly progressive disease course, and mortality based on an analysis of 91 patients

The overwhelming majority of patients with PSS present with combinations of Raynauds phenomenon, sclerodactyly, polyarthralgias, or swelling of an extremity. However, the clinical presentation of PSS may be atypical; 14% of patients in the present series initially sought medical attention for symptoms other than Raynauds phenomenon, tight skin, or joint pain. In the present series, only 31% of patients fulfilled the ARA criteria for PSS at the time of initial medical evaluation. Most patients manifested advanced disease by the time the criteria were fulfilled. The ARA criteria for the classification of PSS appear to have limited value with regard to making the diagnosis in an individual patient. Rapidly progressive PSS occurred in 17.6% of patients in this series and represents a particularly fulminant form of the disease whose course may not be predictable on clinical grounds at the time of initial medical evaluation or diagnosis. Patients destined to develop renal or cardiorespiratory failure usually do so in the first 3 years of disease. Close observation of PSS patients during the first 12 to 18 months may serve to identify those individuals who will undergo an accelerated disease course. Prognosis for patients with rapidly progressive PSS is poor and is associated with significantly higher mortality compared with patients with a more protracted disease course. Future therapeutic trials in PSS should be designed with the recognition that a subgroup of patients with this disorder will have a rapidly progressive disease course.

Decreased thermal stability of collagens containing analogs of proline or lysine

Abstract Fibroblasts were incubated with analogs of proline or lysine and the thermal stability of procollagen molecules containing the analogs was investigated using pepsin digestion at different temperatures as an enzymatic probe of conformation. The procollagens containing either 4-cis-hydroxy- l -proline, 3,4-dehydroproline, or 4,5-trans-dehydrolysine were less stable than normal procollagen and these abnormal collagens were largely in a non-triplehelical conformation within the cells at 37 °C. These results support the idea that procollagen molecules which are not in a triple-helical conformation are not secreted at a normal rate. Procollagens containing both 4,5-trans-dehydrolysine and a proline analog were much less stable than molecules containing a single type of analog. This result suggests that simultaneous administration of both types of analogs may have a greater effect on collagen accumulation in whole-animal experiments than administration of a single analog.

Detection of nuclear lamin B epitopes in oocyte nuclei from mice, sea urchins, and clams using a human autoimmune serum.

Somatic nuclei typically contain two or three major proteins, the lamins A, B, and C or their antigenically related equivalents, interspersed between the chromatin and its attachment site, the inner nuclear membrane. The late oocyte nuclear envelopes of the previously investigated Xenopus and Spisula germinal vesicles, however, have no chromatin attached and only one lamin-like protein. Since mouse and sea urchin germinal vesicles have chromatin attached, we tested them for the possible presence of more than one lamin. In both species we found two different lamins incorporated in their nuclear envelope structure. One lamin is recognized by anti-lamin B and the other by anti-lamin AC antibodies. Spisula germinal vesicles were found to contain not only the nuclear envelope-bound lamin (clamin), but also a 65-kDa protein cross-reactive with anti-lamin B antibodies. This protein is present unattached to any structure and is apparently soluble. Our findings provide a possible explanation of the early presence of lamin B in pronuclei of mouse and sea urchin contrary to the late appearance of a lamin B equivalent in amphibian embryos. In Spisula, as in Xenopus, the presence of a lamin B equivalent could not be documented in the nuclear envelopes of early embryos, indicating that a separate lamin B equivalent is not essential for chromatin binding to the envelope in these species during early embryogenesis. The results also indicate that the nuclear complement of structural proteins might vary substantially in the same cell type of different species.