The aortic and skeletal lesions of lathyrism in rats on a diet of sweet pea

Matrix cross-linking lysyl oxidases are induced in response to myocardial infarction and promote cardiac dysfunction

AIMS

After myocardial infarction (MI), extensive remodelling of the extracellular matrix contributes to scar formation. While aiming to preserve tissue integrity, this fibrotic response is also associated with adverse events, including a markedly increased risk of heart failure, ventricular arrhythmias, and sudden cardiac death. Cardiac fibrosis is characterized by extensive deposition of collagen and also by increased stiffness as a consequence of enhanced collagen cross-linking. Members of the lysyl oxidase (LOX) family of enzymes are responsible for the formation of collagen cross-links. This study investigates the contribution of LOX family members to the heart response to MI.

METHODS AND RESULTS

Experimental MI was induced in C57BL/6 mice by permanent ligation of the left anterior descending coronary artery. The expression of LOX isoforms (LOX and LOXL1-4) was strongly increased upon MI, and this response was accompanied by a significant accumulation of mature collagen fibres in the infarcted area. LOX expression was observed in areas of extensive remodelling, partially overlapping with α-smooth muscle actin-expressing myofibroblasts. Tumour growth factor-β as well as hypoxia-activated pathways contributed to the induction of LOX expression in cardiac fibroblasts. Finally, in vivo post-infarction treatment with the broadband LOX inhibitor β-aminopropionitrile or, selectively, with a neutralizing antibody against the canonical LOX isoform attenuated collagen accumulation and maturation and also resulted in reduced ventricular dilatation and improved cardiac function.

CONCLUSION

LOX family members contribute significantly to the detrimental effects of cardiac remodelling, highlighting LOX inhibition as a potential therapeutic strategy for post-infarction recovery.

The effect of chronic beta-aminoproprionitrile intoxication on the periodontium of the rat. A light microscopic and histochemical study with review of the literature

This histologic study of the periodontium of male white rats with chronic lathyrism demonstrates the appearance, progression, and persistence of certain pathologic changes caused by disordered collagen synthesis and maturation. Typical lesions were seen after 6 weeks. These include increased vascularity, especially in the periapical region, hyalinization and calcification of the transseptal fibers, alveolar bone and cementum resorption, interruption of the periodontal fibers with formation of typical hyaline zones surrounded by palisades of atypical fibroblasts, known as "lathyritic bodies," and an increase in mast cells.

Effects of beta-aminoproprionitrile on formation and mineralization of rat bone matrix

Bones of 4-week-old Sprague-Dawley rats fed a diet containing 0.25% beta-aminoproprionitrile (beta-APN) for 21 days and injected with 3H-proline, 3H-tetracycline, and cold tetracycline at 5-, 10-, and 20-day intervals were analyzed for incorporation of 3H-proline and 3H-tetracycline. Tibial cross sections were examined by fluorescent microscopy to determine the linear bone apposition between intervals and the distribution and intensity of tetracycline bands. The incorporation of 3H-proline was similar in beta-APN-treated and control rats. Incorporation of 3H-tetracycline, however, was significantly lower in beta-APN-treated rats. Fluorescent microscopy of tibial cross sections showed a comparable amount of linear matrix apposition in control and treated rats. It is suggested that beta-APN does not inhibit the bone matrix formation but does interfere with its mineralization.

Basal lamina deficiency in Schwann cells induced by beta-aminopropionitrile (BAPN) in rat dorsal root ganglion culture

In cultures of rat dorsal root ganglion (DRG) treated with beta-aminopropionitrile (BAPN), the following abnormalities were observed. Abnormalities in the size and the shape of collagen fibers; longer periodicity of collagen fibers in BAPN (70 +/- 5 nm) than in control (66 +/- 6 nm) (P less than 0.025); lack of basal lamina of both unmyelinated and myelinated Schwann cells; and abundant amorphous materials in the interstitial area between fibroblasts or peripheral cells and Schwann cells associated with neurites. Detachment of the explant from the collagen substratum also occurred and showed dose dependency. In contrast to the alterations of connective tissue, the neurites were well preserved in this experimental regimen.

Aortic aneurysm associated with cardiac defects in theophyline stimulated chick embryos

Theophylline(1 ml 0.02 M in 0.15 M saline) was administered to embryonic chicks (Hamburger-Hamilton developmental stages 24.27). The drug was topically applied to the surface of the chorioallantoic membrane in the vicinity of the embryonic heart. At necropsy, 63% (44/70) of the theophylline-exposed embryos demonstrated an aneurysm in the ascending aorta. Among the cases exhibiting aortic aneurysm, 48% (21/44) of the embryos demonstrated ventricular septal defects. Four cases of truncus arteriosus were also observed. The morphogenesis and mechanism of theophylline-induced cardiac defects with accompanying aortic aneurysm may be related to the development of the conotruncal region of the heart.

The oxytalan fiber system in the mandibular periodontal ligament of the lathyritic mouse

Experimental lathyrism was produced in young albino mice with a diet containing 50% sweet pea seed (Lathyrus odoratus). After 7 days on the lathyritic diet, sections of themandibular molar and incisor periodontal ligaments, when oxidized and treated with aldehyde fuchsin, demonstrated enhanced staining of the oxytalan fibers and numerous vessels. At this time aldehyde fuchsin or orcein also revealed marked pathological changes in the periodntal ligament of all molars. When athyrism was prolonged for 12 weeks, both the molar and incisor oxytalan systems were still readily identifiable although the molar periodontal ligament continued to be serverely affected by lathyrism. The oxytalan fibers retained their characteristic tooth-vascular association in all of the lathyritic mice. Oxytalan fibers of the lathyritic and control animals showed similar reactions to enzyme digestion with beta-glucuronidase, elastase, and pepsin. However, gingival elastic fibers reacted in a different way from oxytalan fibers with beta-glucuronidase and elastase treatment. These findings indicate that in the lathyritic mouse the oxytalan fiber system of functioning teeth possesses a high degree of permanence and is metabolically distinct from collagen and elastic fibers.

The teratogenic effects of beta-aminopropionitrile in hamsters

The teratogenicity of beta-aminopropionitrile (beta APN) was evaluated in golden Syrian hamsters; single doses of 1250, 2500, and 3750 mg/kg given on days 7-13 produced fetal mortality, growth retardation and malformations. All time-dose combinations produced gross external abnormalities with the highest rate (92.5%) occurring following day-12 treatment. High frequencies of skeletal abnormalities including deformities of the ribs, fibula, and scapula occurred after days-10-12 treatment. Deformed ribs occurred in 100% of fetuses exposed on day 11 to any of the dosages. The types of abnormality generally resembled those produced by lathyrogens in other species except for exencephaly and encephalocele, which occurred after treatment on day 7. These results indicate that betaAPN is a typical teratogen, capable of producing abnormalities of the central nervous system early in gestation, and may reflect a broader mechanism for its activity than previously suggested.

A case of spontaneous dissecting aneurysm of the internal carotid artery

Images