Alternative retinoid X receptor (RXR) ligands

Retinoid X receptors (RXRs) control a wide variety of functions by virtue of their dimerization with other nuclear hormone receptors (NRs), contributing thereby to activities of different signaling pathways. We review known RXR ligands as transcriptional modulators of specific RXR-dimers and the associated biological processes. We also discuss the physiological relevance of such ligands, which remains frequently a matter of debate and which at present is best met by member(s) of a novel family of retinoids, postulated as Vitamin A5. Through comparison with other natural, but also with synthetic ligands, we discuss high diversity in the modes of ligand binding to RXRs resulting in agonistic or antagonistic profiles and selectivity towards specific subtypes of permissive heterodimers. Despite such diversity, direct ligand binding to the ligand binding pocket resulting in agonistic activity was preferentially preserved in the course of animal evolution pointing to its functional relevance, and potential for existence of other, species-specific endogenous RXR ligands sharing the same mode of function.

Significance of plasma copper and caeruloplasmin concentrations in rheumatoid arthritis

To understand the role of copper in initiating protein alterations in rheumatoid arthritis (RA) as reported previously, concentrations of copper anc caeruloplasmin were determined in RA patients. The mean copper concentration of the RA population examined was 24.8 mumol/l (157.5 mug/100 ml), and the mean caeruloplasmin concentration in this RA population was 45.52 mg/100 ml. These values are not different from those reported by previous workers. However, when the RA population was divided into three groups according to sex and oestrogen therapy it was found that caeruloplasmin and copper concentrations in the group of female RA patients on oestrogens was significantly different from other groups (P less than 0.001). A highly significant (P less than 0.01) positive correlation was obtained between copper and caeruloplasmin concentrations (r = 0.91). Concentrations of copper and caeruloplasmin failed to explain the low sulphydryl content of plasma which was observed to be independent of these two parameters. Increased alpha2-globulin concentration, which was refractory to chrysotherapy but 'finger-printed' with a pure preparation of caeruloplasmin in electrophoresis, along with the absence of Kayser-Fleischer rings, supports the contention that copper is not present in a free ionic state in RA patients. This study shows that only a concurrent oestrogen therapy raises copper and caeruloplasmin concentration significantly in a female RA population. Past investigators appear to have overlooked this fact, and it could be that a disproportionate sex distribution (more female rheumatoid arthritics) could cause misleading results in RA studies. The role of oestrogens, copper, and caeruloplasmin in causing exacerbation of RA symptoms is discussed.

Anderson-Fabry disease: a histopathological study of three cases with observations on the mechanism of production of pain

A clinical review and histopathological study of three cases of Anderson-Fabry disease is presented and pathological changes in the central and peripheral nervous systems are reported, in some sites for the first time. These are telangiectatic changes in vessels of the sympathetic ganglia in the vertebral trunk; storage of glycolipid in pigmented cells of the substantia nigra and in anterior horn cells; and degeneration of nerve fibres in the dorsal root entry zone and substantia gelatinosa of the spinal cord. The histopathological findings suggest that in this disease pain is due to involvement of dorsal root ganglion cells with associated axonal degeneration of the small fibres in pathways subserving pain.

Late onset GM2-gangliosidosis. Clinical, pathological, and biochemical studies on 8 patients

Eight cases of late onset G_M2-gangliosidosis are described. 4 presented before the age of 2 years and 4 between 3½ and 10 years. Gait disturbance, intellectual deterioration, and fits were prominent features. Optic atrophy was seen at a late stage in 2 patients. An exaggerated startle reaction to sound and an unusual type of cherry red spot at the macula were seen for the first time in this condition. Pathological changes were similar to those described in Tay-Sachs disease. There was an increase in the amount of a ganglioside chromatographically identical with that found in Tay-Sachs disease. A partial deficiency of hexosaminidase A was found in 2 cases and a profound deficiency in 4. There was no correlation between the age of onset of symptoms and the degree of enzyme deficiency. The evidence presented is consistent with an autosomal recessive mode of inheritance.