Calcineurin A alpha (PPP3CA), calcineurin A beta (PPP3CB) and calcineurin B (PPP3R1) are located on human chromosomes 4, 10q21-->q22 and 2p16-->p15 respectively

Calcineurin (also called protein phosphatase-2B) is a calmodulin-regulated protein phosphatase which plays an important role in signal transduction. The enzyme is a heterodimer of a 58-59 kDa calmodulin-binding catalytic subunit (calcineurin A) and a small (i.e. 19 kDa) Ca(2+)-binding regulatory subunit (calcineurin B). The highly conserved calcineurin B is encoded by a single gene in all tissues except testes, whereas there are three isoforms of calcineurin A (alpha, beta and gamma) encoded by genes on three different chromosomes. This enzyme can play a critical role in transcriptional regulation and growth control in T lymphocytes by a mechanism believed to involve dephosphorylation of the nuclear factor NF-AT which is essential for transcription of the interleukin-2 gene. To better evaluate the potential role of the calcineurin genes in human genetic disorders, we have studied their chromosome locations. Calcineurin B (PPP3R1) is located on human chromosome 2p16-->p15 and calcineurin A beta (PPP3CB, previous gene symbol CALNB) is present on 10q21-->q22. We confirm the localization of calcineurin A alpha (PPP3CA, previous gene symbol CALNA) to chromosome 4 without regional localization.

Enhancement of nitric oxide production from activated macrophages by glycyrrhizin

We studied the actions of glycyrrhizin on nitric oxide production from macrophages and a macrophage cell line RAW264-7. Although glycyrrhizin did not induce nitric oxide from resting macrophages, it enhanced the production of nitric oxide from IFN-gamma activated-macrophages or RAW cells. Glycyrrhizin also enhanced the production of nitric oxide from macrophages stimulated with the supernatant of con A-activated spleen cells. Further, glycyrrhizin enhanced tumor cell killing by macrophages activated with IFN-gamma. This tumor cell killing was mainly by nitric oxide.

Molecular basis for the management of secondary hyperparathyroidism in chronic renal failure

Recent clinical and experimental data suggest that the resistance of parathyroid cells to the physiological concentration of calcitriol plays an important role in the pathogenesis and the progression of secondary hyperparathyroidism in chronic renal failure. This resistance is due to the decreased density of the calcitriol receptor in parathyroid cells, which may result from impaired upregulation of calcitriol receptor. Since patients with larger parathyroid glands were more resistance to calcitriol pulse therapy than those with smaller glands and calcitriol receptor density inversely correlated with gland weight, the size of the parathyroid gland may serve as a marker for the degree of resistance to calcitriol. Furthermore, the possible role of phosphorus in the control of parathyroid function has been suggested recently. Thus, it is most important to prevent the progression of parathyroid hyperplasia in chronic renal failure by the early use of active vitamin D, calcitriol pulse therapy, and dietary phosphorus restriction.

Identification and localization of huntingtin in brain and human lymphoblastoid cell lines with anti-fusion protein antibodies

The Huntington disease (HD) phenotype is associated with expansion of a trinucleotide repeat in the IT15 gene, which is predicted to encode a 348-kDa protein named huntington. We used polyclonal and monoclonal anti-fusion protein antibodies to identify native huntingtin in rat, monkey, and human. Western blots revealed a protein with the expected molecular weight which is present in the soluble fraction of rat and monkey brain tissues and lymphoblastoid cells from control cases. In lymphoblastoid cell lines from juvenile-onset heterozygote HD cases, both normal and mutant huntingtin are expressed, and increasing repeat expansion leads to lower levels of the mutant protein. Immunocytochemistry indicates that huntingtin is located in neurons throughout the brain, with the highest levels evident in larger neurons. In the human striatum, huntingtin is enriched in a patch-like distribution, potentially corresponding to the first areas affected in HD. Subcellular localization of huntingtin is consistent with a cytosolic protein primarily found in somatodendritic regions. Huntingtin appears to particularly associate with microtubules, although some is also associated with synaptic vesicles. On the basis of the localization of huntingtin in association with microtubules, we speculate that the mutation impairs the cytoskeletal anchoring or transport of mitochondria, vesicles, or other organelles or molecules.

Multiphasic modulation of signal transduction into T lymphocytes by monoiodoacetic acid as a sulfhydryl reagent

Actions of monoiodoacetic acid (MIA) as a sulfhydryl reagent on the different stages of the T cell receptor (TCR)-mediated signal transduction were examined. MIA (1 mM) prevented anti-TCR (CD3) monoclonal antibody (mAb)-induced energy-dependent receptor capping but at the same time promoted the anti-CD3 mAb/mitogen-induced tyrosine phosphorylation of the T cell activation-linked cellular proteins of 120, 80, 70, 56, and 40 kDa. Relatively low concentration (0.01 mM) of MIA further promoted anti-CD3 mAb-induced transcription of c-fos, production of IL-2, and cell surface expression of IL-2 receptors. The MIA-promoted TCR-mediated IL-2 production actually required signal transduction that could be inhibited by cyclosporin A, genistein, or H-7. In contrast, the same concentration of MIA as promoted the signal transduction for cell activation severely inhibited the anti-CD3 mAb-triggered signal delivery for cell proliferation, selectively at its early stage. We conclude from these results that MIA differentially affects various steps of signaling into T lymphocytes, suggesting that there exist multiple sites of MIA-sensitive or redox-linked control in the signal cascade.

Electron microscopic analysis of D1 and D2 dopamine receptor proteins in the dorsal striatum and their synaptic relationships with motor corticostriatal afferents

The precise localization of D1 and D2 dopamine receptors within striatal neurons and circuits is crucial information for further understanding dopamine pharmacology. We have used subtype specific polyclonal and monoclonal antibodies against D1 and D2 dopamine receptors to determine their cellular and subcellular distributions, their colocalization, and their differential connectivity with motor cortical afferents labeled either by lesion-induced degeneration or by anterograde transport of biotinylated dextrans. D1 and D2 are primarily expressed in medium-sized neurons and spiny dendrites. Axon terminals containing D1 were rare whereas D2-immunoreactive axon terminals forming symmetrical synapses with dendrites and spines were common. In 2 microns sections, D1 was localized to 53% of neurons, and D2 to 48% of neurons, while mixing D1 and D2 antibodies labeled 78%. By electron microscopy, D1 was localized to 43% of dendrites and 38% of spines while D2 was localized to 38% of dendrites and 48% of spines. Combining D1 and D2 antibodies resulted in the labeling of 88.5% of dendrites and 92.6% of spines. Using different chromogens for D1 and D2, colocalization was not observed. Ipsilateral motor corticostriatal afferents were primarily axospinous and significantly more synapsed with D1 than D2-positive spines (65% vs 47%). Contralateral motor corticostriatal afferents were frequently axodendritic and no difference in their frequency of synapses with D1 and D2 dendrites and spines was observed. These findings demonstrate differential patterns of expression of D1 and D2 receptors in striatal neurons and axon terminals and their differential involvement in motor corticostriatal circuits.

Genomic organization and chromosomal localization of the DUSP2 gene, encoding a MAP kinase phosphatase, to human 2p11.2-q11

The mitogen-induced gene, DUSP2, encodes a nuclear protein, PAC1, that acts as a dual-specific protein phosphatase with stringent substrate specificity for MAP kinase. MAP kinase phosphorylation and consequent enzymatic activation is a central and often obligatory component in signal transduction initiated by growth factor stimulation or resulting from various types of oncogenic transformation. DUSP2 downregulates intracellular signal transduction through the dephosphorylation/inactivation of MAP kinases. To facilitate assessment of the possible role of DUSP2 in growth processes, the genomic structure and chromosomal location of the gene have been determined. DUSP2 has been localized to the pericentromeric region of human chromosome 2 (2p11.2-q11) by analysis of somatic cell hybrids, in situ chromosome hybridization, and genetic linkage analysis using a single-strand conformational polymorphism (SSCP) that has been identified in the 3' UTR of the gene. No consistent translocations or deletions at this chromosomal site have been reported in hematopoietic neoplasias or other tumors.

[The regulation of estradiol and progesterone in tumor necrosis factor production in vitro]

The production of tumor necrosis factor (TNF) induced by lipopolysaccharide (LPS) in peripheral blood mononuclear cells (PBMC) from normal woman were determined. The study investigated the role of regulation of estradiol (E2) and progesterone (P) in the production of TNF in-vitro. The results showed that PBMC would produce TNF when stimulated by E2 or P in culture in-vitro. The appropriate dosages were 125 pmol/L in E2 and 10-20 nmol/L in P. The findings suggested that some sex hormones could play a regulating role in the production of TNF by PBMC. E2 and P may be endogenous substances capable of inducing TNF production. The results revealed a beneficial aspect of sex hormones in anti-cancer treatment.

Bilateral herpes simplex virus type 2 keratitis: a clinicopathologic report with immunohistochemical and ultrastructural observations

This report describes the clinical, histopathologic, ultrastructural, and immunohistochemical findings in two corneal buttons from a 13-year-old girl who developed bilateral progressive corneal stromal opacification during childhood. As determined by light microscopy, both corneal buttons were edematous with a chronic inflammatory infiltrate confined to the deep layers of the stroma. We detected intranuclear eosinophilic inclusions in some epithelial cells. We detected herpesvirus particles in stromal keratocytes and endothelial cells by transmission electron microscopy. Immunohistochemistry studies identified concurrent expression of specific herpes simplex virus type 2 antigen in corneal epithelial cells, in keratocytes in the deep layers of the stroma, and in endothelial cells. The cause of progressive bilateral stromal corneal opacification in this child was herpes simplex virus type 2 keratitis. This condition should be considered in the differential diagnosis of progressive, bilateral corneal opacification in children.

Nucleus reticularis thalami input to the anterior thalamic nuclei in the monkey: a light and electron microscopic study

Three anterograde tracers (PHA-L, WGA-HRP, BDA) placed in the most dorsomedial segment of the anterior part of the nucleus reticularis thalami (NRT) in the Rhesus monkey combined with postembedding immunoctochemistry with anti-GABA antibody resulted in double labeling of a distinct population of synaptic boutons in the thalamic nuclei of the anterior group as well as laterodorsal and mediodorsal nuclei. EM analysis of the labeled terminals in the anteroventral and anteromedial parts of the anterior nuclear complex showed that the NRT input is distributed diffusely and in equal proportion to the dendrites of projection and local circuit neurons.

Promotion of cytotoxic T-cell generation in mixed leukocyte culture by phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis

Phosphatidylinositol-specific phospholipase C (PIPLC) from Bacillus thuringiensis, which cleaves phosphatidylinositol or glycosylphosphatidylinositol on the external cell surface to generate a second messenger for intracellular signal transduction (S. Rahman et al., FEBS Lett. 303:193-196, 1992), was found to preferentially promote the generation of alloantigen-specific cytotoxic T lymphocytes in mixed leukocyte culture. PIPLC affected an early stage of cytotoxic T-lymphocyte activation in culture, and there was no evidence of any soluble cellular mediators of this PIPLC action. PIPLC neither enhanced overall cell proliferation nor noticeably promoted interleukin-2 and -4 production in mixed leukocyte culture. The relative population size of Ly-2+ T cells was increased, however, in a late mixed leukocyte culture with PIPLC. In addition, PIPLC enhanced an anti-CD3 monoclonal antibody-induced early increase in [Ca2+]i. These results suggest a new parasite (bacterium)-oriented mechanism for enhancing antigen-driven host cytotoxic T-lymphocyte immunity which does not include promotion of interleukin-2 production.

Nucleus reticularis thalami connections with the mediodorsal thalamic nucleus: a light and electron microscopic study in the monkey

Wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) and biotinylated dextran amine (BDA) were used as tracers to study nucleus reticularis (NRT) connections with the mediodorsal nucleus (MD). Injections of WGA-HRP in the MD resulted in retrograde labeling of cells in the anteromedial segment of the NRT, the so-called rostral NRT pole. Injections of WGA-HRP and BDA in this NRT region resulted in dense anterograde labeling in the MD. Labeled NRT fibers gave off several collaterals to different MD regions ending with terminal plexuses of thin varicose fibers. In the neuropil, the varicosities were distributed at random, and no tendency to form pericellular baskets was noted. Postembedding immunocytochemistry for GABA was performed on the tissue containing anterograde WGA-HRP label for identification of NRT boutons under electron microscope. The double-labeled boutons were of small to medium size, contained a large number of pleomorphic vesicles, few mitochondria, and formed multiple symmetric synaptic contacts. The number of contacts established by one bouton ranged from 1 to 4 with an average of 1.8 per bouton. About 60% of these boutons made synapses on distal dendrites of GABAergic local circuit neurons; 33% of synaptic contacts were on distal dendrites of thalamocortical neurons, and the rest on their proximal dendrites and soma. NRT boutons were also found in serial synapses and triads. The results demonstrate that the NRT input to the MD is organized so that a single fiber innervates; different MD regions and its terminals form numerous synaptic contacts mostly on the distal dendrites of a large number of local circuit neurons and projection neurons.

Prevention of enhanced parathyroid hormone secretion, synthesis and hyperplasia by mild dietary phosphorus restriction in early chronic renal failure in rats: possible direct role of phosphorus

In order to evaluate the effect of dietary phosphorus (P) restriction on the pathogenesis of secondary hyperparathyroidism (2 degrees HPT) in chronic renal failure (CRF), we studied parathyroid function and parathyroid cell proliferation in 5/6 nephrectomized rats (CRF rats) fed with three different dietary P contents (0.6, 0.3 and 0.1%). Four weeks after 5/6 nephrectomy, serum immunoreactive parathyroid hormone (PTH) concentration, PTH mRNA level in parathyroid glands and the size of parathyroid glands were increased in CRF rats compared to those of sham-operated rats when both groups of rats were fed with normal P (0.6%) diet. These changes were not accompanied by any detectable changes of serum concentrations of calcium (Ca), inorganic phosphate (Pi) or calcitriol. In contrast, such evidence of 2 degrees HPT was obliterated in CRF rats fed with 0.3 or 0.1% P diet. In rats fed with 0.3% P diet, serum concentrations of Ca, Pi, and calcitriol were not different from those of sham-operated rats or from CRF rats fed with normal P diet. In contrast, serum Ca and calcitriol concentrations increased and serum Pi decreased in CRF rats fed with 0.1% P diet. These data suggest that 2 degrees HPT can be completely prevented at the levels of PTH secretion, synthesis and parathyroid cell proliferation by mild dietary P restriction (0.3%) alone, and that such effects may not depend upon the changes in serum concentrations of Ca, Pi or calcitriol, but may depend on reduced dietary P content per se. Thus, mild dietary P restriction from the early stage of CRF may be clinically effective for the prevention of 2 degrees HPT.

"Fenestrin" and conjugation in Tetrahymena thermophila

Certain monoclonal antibodies interact with proteins of Tetrahymena thermophila found in the conjugation junction as well as around the gametic nuclei (pronuclei) of conjugating cells; they also react with the oral primordium and fission zone of vegetative cells and with the cytoproct and contractile vacuole pores of all cells. One of these (FXIX-3A7) was investigated in detail. Immunogold labelling suggests that the material labelled by the 3A7 monoclonal antibody, which we call "fenestrin," is located beneath the epiplasm (membrane skeleton). Immunoblots reveal that the major and perhaps sole antigen is a 64 kDa polypeptide, found in two isoelectric variants. Developmental studies implicate fenestrin in two processes involved in conjugation. The first is "tip transformation." During preliminary starvation ("initiation"), labelling of fenestrin first appeared as a spot at the anterior end of starved mature cells, then after mixing of different mating types ("costimulation") it extended posteriorly along the anterior suture. After pairing, this region spread to form a widened plate. The second process is pronuclear transfer. Fenestrations representing channels between the conjugating cells began to appear 0.5 to 1 h after the conjugants united, and eventually merged to form a small number of temporary large holes during exchange of the transfer pronuclei. A fenestrin envelope also enclosed both the transfer and resident pronuclei; a strand of fenestrin connected the two. Shortly after pronuclear transfer, both transfer and resident pronuclei were released from fenestrin caps and fused to produce a zygotic nucleus (synkaryon) not associated with fenestrin Fenestrin thus appears to be intimately involved in the process of pronuclear exchange.

A processed J chain pseudogene on human chromosome 8 that is shared by several primate species

Human DNA contains two sequences that hybridize to a human J chain gene probe: the J chain gene itself and a second previously uncharacterized sequence. By cloning and sequence analysis we now show this related sequence to be a processed pseudogene, which we have localized using somatic hybrids to chromosome 8 (distinct from the functional gene on chromosome 4) and mapped by linkage analysis to 8q13-q21. The pseudogene provides evidence of an additional DNA insertion event as it contains an AluI element embedded in sequence corresponding to the 3' untranslated region of the gene. The extent of sequence divergence between the pseudogene and the functional J chain gene suggests that the pseudogene was created roughly 40-50 million years ago; consistent with this estimate, Southern blots suggest that the pseudogene is shared by great apes as well as Old World monkeys.

Microcirculation architecture of melanocytic nevi and malignant melanomas of the ciliary body and choroid. A comparative histopathologic and ultrastructural study

PURPOSE

This study was designed to (1) describe the vascular patterns of ciliary body and choroidal nevi by light microscopy, (2) compare the vascular ultrastructure of nevi with vessels of the normal uvea and uveal melanomas, and (3) compare the behavior of ciliochoroidal melanomas with and without a nevus-like vascular architecture.

METHODS

After delineating the vascular patterns of 23 choroidal and ciliary body nevi by light microscopy, the authors identified 49 melanomas that had the same vascular patterns as nevi from a previously published series of 234 uveal melanomas. The survival of these 49 patients who had melanomas with a nevus-like vascular architecture was compared with the 185 patients who had melanomas that lacked this vascular profile.

RESULTS

By light microscopy, the only vascular patterns identified in nevi are "normal" vessels, zones of avascularity ("silent" pattern), straight, and parallel vessels; closed vascular loops and networks were not detected in nevi. By transmission electron microscopy, the vascular basement membrane of malignant melanomas was multilaminar, fragmented, and significantly thicker than in normal eyes or nevi. None of the patients with nevi died of metastatic disease. Fourteen percent of patients whose melanomas had the same vascular profile as nevi died of metastatic disease, whereas 32% of patients whose melanomas had vascular patterns other than those seen in nevi died of metastatic melanoma (P = 0.012).

CONCLUSIONS

The microcirculation architecture marks tumor progression in uveal melanocytic lesions by light and electron microscopy. In the spectrum of these lesions, nevi are benign, melanomas that have the same vascular profile as nevi have an intermediate biologic behavior, and melanomas with vascular networks are strongly associated with death due to metastatic disease.

Evidence for a GABAergic interface between cortical afferents and brainstem projection neurons in the rat central extended amygdala

The synaptic circuitry of the intrinsic GABAergic system of the central extended amygdala (CEA) in relation to efferent neurons and cortical afferents was examined in the present study. Neurons in the CEA projecting to the dorsal vagal complex and the parabrachial complex were identified by the retrograde transport of wheat germ agglutinin-horseradish peroxidase (WGA-HRP). Postembedding GABA-immunocytochemistry revealed that GABA-immunoreactive (GABA-IR) terminals formed largely symmetrical synaptic contacts with the perikarya and proximal dendritic processes of almost all WGA-HRP-labeled neurons in the CEA. To determine the relationship between cortical afferents and CEA GABAergic neurons, WGA-HRP was used to anterogradely label afferents from the insular cortex in combination with postembedding immunogold detection of GABA. Cortical afferents formed asymmetrical synaptic contacts predominantly on small dendrites and dendritic spines. Many of the dendrites postsynaptic to cortical terminals in the central nucleus were immunoreactive for GABA although only relatively few spines were GABA-IR. Combining pre-embedding GAD-immunocytochemistry with cortical lesions resulted in approximately 40% of degenerating terminals of insular cortical origin in the central nucleus in contact with small, GAD-IR dendrites and spines. The present results demonstrate that the neurons providing the major CEA outputs to the brainstem receive an extensive GABAergic innervation, strongly supporting our proposal that CEA efferent neurons are under strong tonic inhibition by intrinsic GABAergic neurons. Further, our finding that the major cortical input to the central nucleus preferentially innervates intrinsic GABAergic neurons suggests that these neurons in the CEA may serve as an interface between the principal inputs and outputs of this forebrain region.

Serial evaluation of parathyroid size by ultrasonography is another useful marker for the long-term prognosis of calcitriol pulse therapy in chronic dialysis patients

To clarify whether the changes of parathyroid size have any correlations with the long-term prognosis of calcitriol pulse therapy, we examined the time course of serum levels of parathyroid hormone (PTH) and size of parathyroid glands in 14 chronic dialysis patients during and after the oral calcitriol pulse therapy. In 5 patients without any detectable glands, secondary hyperparathyroidism was easily controlled by calcitriol pulse therapy and then by conventional oral active vitamin D therapy. In 2 patients with detectable gland(s) in whom size of all parathyroid glands as well as PTH hypersecretion regressed to normal by calcitriol pulse therapy, secondary hyperparathyroidism could then remain controlled at least for 12 months after switching to conventional oral active vitamin D therapy. In contrast, in 7 patients in whom size of all parathyroid glands did not regress to normal by calcitriol pulse therapy, secondary hyperparathyroidism relapsed after switching to the conventional therapy, even if PTH hypersecretion could be controlled temporarily. Our findings suggest that the time course of parathyroid hyperplasia detected by ultrasonography is an important determinant of the efficacy and the prognosis of calcitriol pulse therapy. Thus, the change of parathyroid gland size as well as PTH hypersecretion should be taken into account for the management of secondary hyperparathyroidism.

Localization of the MAGE1 gene encoding a human melanoma antigen to chromosome Xq28

MAGE1 encodes a tumor specific antigen MZ2-E that elicited a cytotoxic T lymphocytic response (CTL) in the patient from whom it was derived. In this study, cDNA and genomic probes have been used to localize this gene by Southern analysis of a human-rodent somatic cell hybrid panel. The probes detect a small multigene family, and both MAGE1 and several other members of this family are located on the long arm of the human X chromosome. A cosmid with a 12-kb insert including the entire MAGE1 gene was biotinylated and used to further localize the gene to Xq28 by in situ hybridization of metaphase spreads. The function of this antigen in normal cells and tumor cells currently remains unclear.

Localization of two genes encoding plasma membrane Ca2+ ATPases isoforms 2 (ATP2B2) and 3 (ATP2B3) to human chromosomes 3p26-->p25 and Xq28, respectively

The plasma membrane Ca2+ ATPases (PMCA) represent a highly conserved, widely dispersed, multigene family in eukaryotes consisting of at least four functional genes. The genes for PMCA isoforms 1 and 4 (ATP2B1 and ATP2B4) have been previously localized to human chromosomes 12q21-->q23 and 1q25-->q32, respectively. Based upon results of fluorescence in situ hybridization (FISH), analysis of somatic cell hybrids, and genetic linkage analyses, we now report localization of ATP2B3 (PMCA isoform 3) to human chromosome Xq28, and confirm the recent localization of ATP2B2 (PMCA isoform 2) to chromosome 3p26-->p25. In contrast to ATP2B1 and ATP2B4, recent studies have suggested tissue specific regulation of expression of both ATP2B2 and ATP2B3 particularly in the nervous system. The genes for several neurological and neuromuscular diseases have been assigned to the distal portion of Xq, and ATP2B3 is a candidate gene for these diseases.

Ocular pathology of MELAS syndrome with mitochondrial DNA nucleotide 3243 point mutation

PURPOSE

The authors describe the clinical, histopathologic, and ultrastructural findings in two eyes obtained at autopsy from a 21-year-old woman with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS syndrome).

METHODS

The eyes were obtained immediately after death. The right eye was fixed in 10% neutral-buffered formalin and processed for standard histologic examination. The left eye was fixed in a neutral-buffered 2.5% glutaraldehyde solution and processed for transmission electron microscopic examination. The authors compared the histologic and ultrastructural findings with the clinical features recorded photographically.

RESULTS

The main clinical ophthalmologic features were bilateral ptosis, chronic external ophthalmoplegia, diffuse choroidal atrophy, atypical pigmentary retinopathy with macular involvement, and patchy atrophy of the iris stroma. Molecular genetic analysis detected a tRNA Leu (UUR) point mutation at position 3243 of mitochondrial DNA (MELAS genotype). Results of histologic and ultrastructural examination showed ragged-red fibers in the rectus muscles, degeneration of photoreceptor outer segments in the macula, hyperpigmentation and atrophy of the retinal pigment epithelium of the macula, atrophy of the iris stroma, early posterior subcapsular cataract, and optic atrophy. The retinal pigment epithelium, inner segments of the photoreceptors, smooth muscle cells of the choroidal and retinal vessels, the dilator and sphincter muscle of the iris, cornea, lens epithelium, and ciliary epithelium all contained many, often enlarged, structurally abnormal mitochondria with occasional paracrystalline inclusions and circular cristae.

CONCLUSIONS

The MELAS-associated mitochondrial DNA nucleotide 3243 point mutation can cause a spectrum of ocular signs and symptoms that may be dependent on the patient's age and the amount of mutant mitochondrial DNA in the tissue. MELAS syndrome should be considered in the differential diagnosis of bilateral ptosis, external ophthalmoplegia, and atypical pigmentary retinopathy with macular involvement.

Brain potentials in a phonological matching task using Chinese characters

In readers of English, involved in a rhyme judgement task, mismatch trials are associated with an enhanced N450 component of the Event Related Potentials (ERPs). It has been suggested that N450 is related to orthographic or phonological priming. In this paper ERPs were recorded during a phonological matching task, using pairs of logographically dissimilar Chinese characters. A pair was considered to match if they sounded alike with identical phoneme sequences. The subjects (native Chinese speakers) were instructed to ignore vowel-inflections, which in Chinese have lexical status. Since sublexical assembly of phonology is not used in reading Chinese characters, and the members of each pair were logographically dissimilar, match and mismatch trials did not suffer in the amount of orthographic or sublexical phonological priming. An enhanced negative component (latency near 400 msec), was observed in ERPs elicited by the second character in non-matching pairs. The negativity could be similar to N450. If this were so, then N450 could not be associated with orthographic priming, nor with sublexical phonology, but would probably be associated with postlexical processing. Also, in both readers of Chinese and English, the negativity enhanced in non-match trials is larger over the right side of the scalp, suggesting a similar brain lateralization of the underlying processes.

Interleukin-2 receptor gamma chain mutation results in X-linked severe combined immunodeficiency in humans

The interleukin-2 (IL-2) receptor gamma chain (IL-2R gamma) is a component of high and intermediate affinity IL-2 receptors that is required to achieve full ligand binding affinity and internalization. We have localized the IL-2R gamma gene to human chromosome Xq13. Genetic linkage analysis indicates that the IL-2R gamma gene and the locus for X-linked severe combined immunodeficiency (XSCID) appear to be at the same position. Moreover, we demonstrate that each of three unrelated patients with XSCID has a different mutation in his IL-2R gamma gene resulting in a different premature stop codon and predicted C-terminal truncation. These data establish that XSCID is associated with mutations of the IL-2R gamma gene product. Since XSCID is characterized by absent or markedly reduced numbers of T cells, our findings imply that IL-2R gamma plays a vital role in thymic maturation of T cells. These results also have important implications for prenatal and postnatal diagnosis, carrier female detection, and gene therapy for XSCID.

Skeletal 210Pb levels and lung cancer among radon-exposed tin miners in southern China

A preliminary case-control study of 19 lung cancer cases older than 55 y and 141 age-matched controls was carried out among a group of underground miners in Southern China who were exposed to 222Rn and its decay products. 210Pb activity levels were measured in the skull to estimate radon exposure. Radon exposure was also estimated in working level months, based on work histories and available industrial hygiene data. There was a smooth gradient of lung cancer risk with categories of skeletal 210Pb level at time of last radon exposure; relative risks of 1.0, 2.9, 3.2, and 4.7 for categories < 51.8, 51.8-77.7, 77.8-107.3, and > or = 107.4 Bq (< 1,400, 1,400-2,099, 2,100-2,899, and > or = 2,900 pCi), respectively. Relative risks were unaffected by adjustment for exposure to arsenic in the mine or by adjustment for working level months. Risks also increased with cumulative working level month exposure, but the gradient of risk lessened after adjustment for exposure to arsenic. 210Pb, at the time of last radon exposure (p = 0.13) and at the current 210Pb level (p = 0.01), was not highly correlated with the working level month estimate. Data were sparse but smoking had minimal effect on risk gradient with level of skeletal 210Pb activity. This study suggests measured 210Pb level may be a more precise predictor of lung cancer risk than working level month.