TGF-beta mediates natural suppressor activity of IL-2-activated lymphocytes

In addition to generating cells with non-MHC-restricted cytotoxic activity that is characteristic of lymphokine-activated killer (LAK) cells, in vitro cultures of lymphocytes with relatively high concentrations of IL-2 generate cells that simultaneously exhibit two distinct types of suppressor activities: veto, the ability of cells to specifically suppress generation of allo-CTL against their own histocompatibility Ags; and natural suppression, the ability of these same cells to nonspecifically suppress the generation of allo-CTL against both their own and unrelated cell surface Ags. In contrast to veto, which is known to require cell-cell contact between veto-active cells and precursors of CTL, natural suppression is known to be mediated by soluble factors. To identify and characterize suppressor factors that might mediate the natural suppressor activity of IL-2-activated lymphocytes, murine spleen cells were cultured with 1000 U/ml IL-2, and, after varying periods of incubation, their LAK cytolytic activity and natural suppressor activity was determined and cell supernatants were collected and tested for their effects on mixed lymphocyte culture-induced generation of allo-CTL. Like the IL-2-activated lymphocytes themselves, supernatants of these cells nonspecifically inhibited mixed lymphocyte culture-induced generation of allo-CTL. Rabbit anti-TGF-beta specifically neutralized the suppressive effects of both LAK cell supernatants and the IL-2-activated lymphocytes themselves. These findings indicate that TGF-beta is the primary mediator of the natural suppressor activity of IL-2-activated lymphocytes.

TGF-beta mediates natural suppressor activity of IL-2-activated lymphocytes

In addition to generating cells with non-MHC-restricted cytotoxic activity that is characteristic of lymphokine-activated killer (LAK) cells, in vitro cultures of lymphocytes with relatively high concentrations of IL-2 generate cells that simultaneously exhibit two distinct types of suppressor activities: veto, the ability of cells to specifically suppress generation of allo-CTL against their own histocompatibility Ags; and natural suppression, the ability of these same cells to nonspecifically suppress the generation of allo-CTL against both their own and unrelated cell surface Ags. In contrast to veto, which is known to require cell-cell contact between veto-active cells and precursors of CTL, natural suppression is known to be mediated by soluble factors. To identify and characterize suppressor factors that might mediate the natural suppressor activity of IL-2-activated lymphocytes, murine spleen cells were cultured with 1000 U/ml IL-2, and, after varying periods of incubation, their LAK cytolytic activity and natural suppressor activity was determined and cell supernatants were collected and tested for their effects on mixed lymphocyte culture-induced generation of allo-CTL. Like the IL-2-activated lymphocytes themselves, supernatants of these cells nonspecifically inhibited mixed lymphocyte culture-induced generation of allo-CTL. Rabbit anti-TGF-beta specifically neutralized the suppressive effects of both LAK cell supernatants and the IL-2-activated lymphocytes themselves. These findings indicate that TGF-beta is the primary mediator of the natural suppressor activity of IL-2-activated lymphocytes.

Stargardt's disease is not allelic to the genes for neuronal ceroid lipofuscinoses

Stargardt's disease is an autosomal recessive condition characterised by a rapid and bilateral loss of central vision at around 7 to 12 years, with typical changes in the macular and perimacular region. It is one of the most frequent causes of macular degeneration in childhood and accounts for 7% of all retinal dystrophies. Considering that inclusions of lipofuscin-like substances are observed in retinal pigmentary cells of patients with Stargardt's disease on the one hand, and that the early symptoms of neuronal ceroid lipofuscinosis (CLN3) are suggestive of Stargardt's disease on the other hand (age of loss of visual acuity, appearance of the fundus), we decided to test allelism of Stargardt's disease with the infantile (CLN1) and juvenile forms of neuronal ceroid lipofuscinosis (CLN3), which map to chromosomes 1p32 and 16p12-p11 respectively. Using highly informative microsatellite DNA markers in eight multiplex families, we were able to exclude Stargardt's disease from the vicinity of the CLN1 and CLN3 loci. These results strongly reject the hypothesis of allelism of Stargardt's disease with the neuronal forms of ceroid lipofuscinosis.

Obstructive sleep apnea manifesting as suspected angina: report of three cases

OBJECTIVE

To describe three cases of obstructive sleep apnea that resembled coronary artery disease and to suggest features that might distinguish these two syndromes.

DESIGN

We present three detailed case reports of patients with severe obstructive sleep apnea and discuss similar cases from the literature.

MATERIAL AND METHODS

Two obese women and one obese man with previously undiagnosed obstructive sleep apnea had chest discomfort, episodic dyspnea, and palpitations, most prominent at night. All three patients had multiple cardiac risk factors and had previously undergone cardiac evaluations, including at least two prior cardiac catheterizations each. Repeated cardiac catheterization revealed less coronary occlusive disease than expected on the basis of the symptoms in all three patients and a small atrial septal defect in one patient. When reassessed, the medical histories suggested obstructive sleep apnea.

RESULTS

Overnight polysomnography documented the presence of severe sleep apnea; the three patients had mean values of 56 disordered breathing events per hour and 44% minimal oxygen saturation. Although bi-level or continuous positive airway pressure yielded initial improvement, all patients had difficulty with routine use of this therapy after 1 1/2 years of follow-up.

CONCLUSION

The initial manifestations of severe obstructive sleep apnea may simulate angina, suggest arrhythmia, or mimic heart failure. Failure to inquire about snoring and daytime somnolence in patients with chest pain may prevent the identification of clinically significant disordered breathing during sleep.

The FET3 gene of S. cerevisiae encodes a multicopper oxidase required for ferrous iron uptake

S. cerevisiae accumulate iron by a process requiring a ferrireductase and a ferrous transporter. We have isolated a mutant, fet3, defective for high affinity Fe(II) uptake. The wild-type FET3 gene was isolated by complementation of the mutant defect. Sequence analysis of the gene revealed the presence of an open reading frame coding for a protein with strong similarity to the family of blue multicopper oxidoreductases. Consistent with the role of copper in iron transport, growth of wild-type cells in copper-deficient media resulted in decreased ferrous iron transport. Addition of copper, but not other transition metals (manganese or zinc), to the assay media resulted in the recovery of Fe(II) transporter activity. We suggest that the catalytic activity of the Fet3 protein is required for cellular iron accumulation.

Molecular characterization of a copper transport protein in S. cerevisiae: an unexpected role for copper in iron transport

We report the identification and characterization of CTR1, a gene in the yeast S. cerevisiae that encodes a multispanning plasma membrane protein specifically required for high affinity copper transport into the cell. The predicted protein contains a methionine- and serine-rich domain that includes 11 examples of the sequence Met-X2-Met, a motif noted in proteins involved in bacterial copper metabolism. CTR1 mutants and deletion strains have profound deficiency in ferrous iron uptake, thus revealing a requirement for copper in mediating ferrous transport into the cell. Genetic evidence suggests that the target for this requirement is the FET3 gene (detailed in a companion study), predicted to encode a copper-containing protein that acts as a cytosolic ferro-oxidase. These findings provide an unexpected mechanistic link between the uptake of copper and iron.

The GEF1 gene of Saccharomyces cerevisiae encodes an integral membrane protein; mutations in which have effects on respiration and iron-limited growth

We have isolated a new class of respiration-defective, i.e petite, mutants of the yeast Saccharomyces cerevisiae. Mutations in the GEF1 gene cause cells to grow slowly on rich media containing carbon sources utilized by respiration. This phenotype is suppressed by adding high concentrations of iron to the growth medium. Gef1- mutants also fail to grow on a fermentable carbon source, glucose, when iron is reduced to low concentrations in the medium, suggesting that the GEF1 gene is required for efficient metabolism of iron during growth on fermentable as well as respired carbon sources. However, activity of the iron uptake system appears to be unaffected in gef1- mutants. Fe(II) transporter activity and regulation is normal in gef1- mutants. Fe(III) reductase induction during iron-limited growth is disrupted, but this appears to be a secondary effect of growth rate alterations. The wild-type GEF1 gene was cloned and sequenced; it encodes a protein of 779 amino acids, 13 possible transmembrane domains, and significant similarity to chloride channel proteins from fish and mammals, suggesting that GEF1 encodes an integral membrane protein. A gef1- deletion mutation generated in vitro and introduced into wild-type haploid strains by gene transplacement was not lethal. Oxygen consumption by intact gef1- cells and by mitochondrial fractions isolated from gef1- mutants was reduced 25-50% relative to wild type, indicating that mitochondrial function is defective in these mutants. We suggest that GEF1 encodes a transport protein that is involved in intracellular iron metabolism.

Regulation of epidermal growth factor receptor expression and growth by protein kinase C and retinoic acid in LLC-PK1 cells

The importance of receptor expression and protein kinase C to epidermal growth factor (EGF)-induced cell proliferation was studied in LLC-PK1 kidney cells. These cells have both high- and low-affinity binding sites for EGF. Neither transforming growth factor-beta nor tumor necrosis factor altered EGF receptor expression. On the other hand, retinoic acid induced a concentration-dependent increase in EGF binding that was maximal at 1 mumol/L. One micromolar of retinoic acid increased EGF binding from 0.38 +/- 0.01 fmol/10(6) cells in controls to 1.10 +/- 0.03 fmol/10(6) in treated cells at 18 hours (n = 8, P < 0.001). The increase in binding was the result of an increase in the Bmax of the high-affinity receptor. The upregulation of the EGF receptor induced by retinoic acid was associated with enhanced EGF-induced growth promotion. A 45-minute incubation of cells with phorbol 12-myristate 13-acetate caused a concentration-dependent decrease in EGF binding that was prevented by a 40-hour, 2 mumol/L pre-exposure to phorbol 12-myristate 13-acetate; 10(-8) mol/L EGF also caused a downregulation of the EGF receptor that was not prevented by phorbol 12-myristate 13-acetate or retinoic acid. Downregulation of protein kinase C did not interfere in the capacity of EGF to induce growth in these cells. These studies demonstrate that EGF receptor upregulation plays an important role in the control of EGF-induced cell growth. Protein kinase C regulates EGF binding in these cells; however, it is not necessary for EGF-induced growth promotion or receptor downregulation.

A gene for Stargardt's disease (fundus flavimaculatus) maps to the short arm of chromosome 1

Stargardt's disease (fundus flavimaculatus) is one of the most frequent causes of macular degeneration in childhood and accounts for 7% of all retinal dystrophies. It is an autosomal recessive condition characterized by a bilateral loss of central vision occurring at age 7-12 years. Genetic linkage analysis of eight families has assigned the disease locus to chromosome 1p21-p13. Multipoint linkage analysis and haplotype analysis has allowed us to establish the best estimate for location of the gene over the locus D1S435 (maximum lod score of 12.66). Our results are consistent with the genetic homogeneity of this condition.

Complementation analysis of Chediak-Higashi syndrome: the same gene may be responsible for the defect in all patients and species

Chediak-Higashi Syndrome is an autosomal recessive disorder, characterized by the presence of large intracellular granules, particularly lysosomes and melanosomes. While the Chediak-Higashi Syndrome is a rare disorder in humans, phenotypically similar syndromes are found in other species. Fusion of normal fibroblasts to Chediak fibroblasts complements the Chediak disorder, restoring normal lysosome size and distribution. Fusion of wild-type with Chediak fibroblasts from human, mouse, or mink demonstrates that wild-type fibroblasts can complement any of the Chediak fibroblasts. Complementation was not observed in interspecific hybrids between Chediak fibroblasts from these species, suggesting that the same gene product is defective in humans, mice, and mink.

Chediak-Higashi syndrome is not due to a defect in microtubule-based lysosomal mobility

Chediak-Higashi Syndrome is an autosomal recessive disorder that affects intracellular vesicle formation. The diagnostic feature of Chediak-Higashi Syndrome is the presence of ‘giant’ lysosomes clustered near the nucleus. Lysosome morphology in macrophages is maintained by microtubules and microtubule-based motors, such as kinesin. Dramatic changes in lysosome morphology can be induced by lowering cytoplasmic pH or by adding phorbol esters. When macrophages from beige mice (a murine homolog of Chediak-Higashi Syndrome) were subjected to these protocols they were able to alter their lysosomal distribution and morphology to the same degree as macrophages from control mice. These results indicate that lysosomes in Chediak cells are capable of interacting with the microtubule-based motor system, suggesting that the defective gene product is not an altered microtubular element involved in lysosomal movement.

Transcriptional repressor ZF5 identifies a new conserved domain in zinc finger proteins

We have cloned a cDNA encoding a new murine C2H2 zinc finger protein, ZF5. The 51.3 kD protein contains five GL1-Kruppel type zinc fingers at the C-terminus. At its N-terminus, ZF5 has a 41 amino acid region which was found to be homologous to the N-termini of several other zinc finger proteins. This region defines a new motif within zinc finger proteins which we have named the Zinc finger N-terminal (ZiN) domain. ZF5 binds to two sites in the c-myc promoter and to the -50 bp site of the herpes simplex thymidine kinase promoter. ZF5 is a transcriptional repressor and its repression domain is located N-terminal to the zinc finger domains. A single 4 kb ZF5 mRNA is expressed widely.

The GABAergic nervous system of Caenorhabditis elegans

gamma-Aminobutyric acid (GABA) is the most abundant inhibitory neurotransmitter in vertebrates and invertebrates. GABA receptors are the target of anxiolytic, antiepileptic and antispasmodic drugs, as well as of commonly used insecticides. How does a specific neurotransmitter such as GABA control animal behaviour? To answer this question, we identified all neurons that react with antisera raised against the neurotransmitter GABA in the nervous system of the nematode Caenorhabditis elegans. We determined the in vivo functions of 25 of the 26 GABAergic neurons by killing these cells with a laser microbeam in living animals and by characterizing a mutant defective in GABA expression. On the basis of the ultrastructurally defined connectivity of the C. elegans nervous system, we deduced how these GABAergic neurons act to control the body and enteric muscles necessary for different behaviours. Our findings provide evidence that GABA functions as an excitatory as well as an inhibitory neurotransmitter.

Zinc deficiency in elderly patients

Zinc is needed for growth and development, DNA synthesis, neurosensory functions, and cell-mediated immunity. Although zinc intake is reduced in elderly people, its deficiency and effects on cell-mediated immunity of the elderly have not been established. Subjects enrolled in "A Model Health Promotion and Intervention Program for Urban Middle Aged and Elderly Americans" were assessed for nutrition and zinc status. One hundred eighty healthy subjects were randomly selected for the study. Their mean dietary zinc intake was 9.06 mg/day, whereas the recommended dietary allowance is 15 mg/day. Plasma zinc was normal, but zinc in granulocytes and lymphocytes were decreased compared with younger control subjects. Of 118 elderly subjects in whom zinc levels in both granulocytes and lymphocytes were available, 36 had deficient levels. Plasma copper was increased, and interleukin 1 (IL-1) production was significantly decreased. Reduced response to the skin-test antigen panel and decreased taste acuity were observed. Thirteen elderly zinc-deficient subjects were supplemented with zinc, and various variables were assessed before and after zinc supplementation. Zinc supplementation corrected zinc deficiency and normalized plasma copper levels. Serum thymulin activity, IL-1 production, and lymphocyte ecto-5'-nucleotidase increased significantly after supplementation. Improvement in response to skin-test antigens and taste acuity was observed after zinc supplementation. A mild zinc deficiency appears to be a significant clinical problem in free-living elderly people.

Heterogeneity versus variability in megalocornea-mental retardation (MMR) syndromes: report of new cases and delineation of 4 probable types

Megalocornea (corneal diameter > or = 13 mm) is associated with mental and neurological impairment, and minor anomalies in Neuhäuser syndrome (megalocornea-mental retardation syndrome). Here we report 4 new cases of megalocornea and mental retardation. Those unrelated patients have a consistent pattern of anomalies with possible recessive inheritance which clearly differs from that of the original patients of Neuhäuser et al. [1975]. We discuss the heterogeneity of the syndromes with megalocornea and mental retardation. Based on these cases and on a review of the literature, we suggest a provisional clinically oriented classification in 5 subtypes: (1) a recessive form type Neuhäuser (with iris hypoplasia and minor anomalies), (2) a recessive form type Frank-Temtamy (with camptodactyly, scoliosis and growth retardation), (3) a recessive type 3, including our 4 personal cases (with normal irides, severe hypotonia, relative or absolute macrocephaly and minor anomalies), (4) a possible Frydman type (with normal irides, megalencephaly and obesity), and (5) provisionally unclassifiable cases.

Characterisation of a highly polymorphic microsatellite at the DXS207 locus: confirmation of very close linkage to the retinoschisis disease gene

Juvenile retinoschisis (RS) is an X linked recessive vitreoretinal disorder for which the basic molecular defect is unknown. The gene for RS has been previously localised by linkage analysis to Xp22.1-p22.2 and the locus order Xpter-DXS16-(DXS43, DXS207)-RS-DXS274-DXS41-Xcen established. To improve the resolution of the genetic map in the RS region, we have isolated a highly polymorphic microsatellite at DXS207, which displays at least nine alleles with a heterozygosity of 0.83. Using this microsatellite and four other Xp22.1-p22.2 marker loci, DXS16, DXS43, DXS274, and DXS41, we performed pairwise and multilocus linkage analysis in 14 kindreds with RS. The microsatellite was also typed in the CEPH (Centre d'Etude du Polymorphisme Humain) reference families. Tight linkage was found between RS and DXS207 (Z(theta) = 14.32 at theta = 0.0), RS and DXS43 (Z(theta) = 8.10 at theta = 0.0), and DXS207 and DXS43 (Z(theta) = 40.31 at theta = 0.0). Our linkage results combined with data previously reported suggest that the DXS207-DXS43 cluster is located less than 2 cM telomeric to the RS locus. The microsatellite reported here will be a very useful marker for further linkage studies with retinoschisis as well as with other diseases in this region of the X chromosome.

Usher syndrome type I associated with bronchiectasis and immotile nasal cilia in two brothers

Usher syndrome type I is an autosomal recessive disease characterised by congenital sensorineural deafness, involvement of the vestibular system, and progressive visual loss owing to retinitis pigmentosa. Here we report the association of this disease with bronchiectasis, chronic sinusitis, and reduced nasal mucociliary clearance in two sibs and we suggest Usher syndrome type I could be a primary ciliary disorder.