Biomedical subjects

C Jung

Publications and source records attributed to C Jung.

At least 55 records · Page 3Linked to original sources

PubMed2001

Phytoseiid dispersal at plant to regional levels: a review with emphasis on management of Neoseiulus fallacis in diverse agroecosystems.

Dispersal behaviors of phytoseiid and tetranychid mites are key factors in understanding predator-prey dynamics and biological control of pest mites at different spatial levels in agricultural and natural ecosystems. In this review, ambulatory and aerial dispersal of both mite groups are discussed at spatial levels of leaf, plant, crop and region. Emphasis is on dispersal of phytoseiids, and specifically, the specialist-predator, Neoseiulusfallacis (Garman), and two-spotted spider mite prey, Tetranychus urticae (Koch). Dispersal aspects that are discussed are ambulation on a leaf; plant or in a prey patch; aerial dispersal between plants; behavior and aerodynamics of aerial take-off; modeling vs. monitoring of dispersal distance; fates of dispersing mites that land on soil substrates; plants as take-off platforms and landing targets for dispersers; and regional dispersal patterns and integrated mite management.

Agriculture↗

PubMed2001

Inhibition of endothelin-converting enzyme activity in the rabbit basilar artery.

OBJECTIVE: Endothelin (ET)-1 may be involved in the regulation of cerebrovascular resistance under pathological conditions, most notably during the development of vasospasm after subarachnoid hemorrhage. Blocking ET-converting enzyme activity may be a promising approach to the prevention of cerebral vasospasm after subarachnoid hemorrhage. METHODS: In this study, the effects of several putative ET-converting enzyme inhibitors were investigated after intracisternal application in rabbits, to inhibit basilar artery contractions induced by big ET-1 (2 x 10(-6) mol/L). RESULTS: In the group pretreated with [D-Val22]big ET-1[16-38] (2 x 10(-5) mol/L) (n = 8), the angiographically measured diameter of the basilar artery changed from 0.63 +/- 0.12 mm to 0.66 +/- 0.12 mm. In the control group (n = 8), the diameter of the basilar artery decreased from 0.71 +/- 0.13 mm to 0.57 +/- 0.15 mm. These results corresponded to an increase in vessel diameter of 5 +/- 10% in the treatment group and a decrease in vessel diameter of 20 +/- 16% in the control group (P = 0.014). In the group pretreated with captopril (2 x 10(-4) mol/L) (n = 8), the angiographically measured diameter of the basilar artery changed from 0.64 +/- 0.11 mm to 0.71 +/- 0.10 mm. These results corresponded to an increase in vessel diameter of 14 +/- 19% in the treatment group, compared with a decrease in vessel diameter of 20 +/- 16% in the control group (P = 0.014). CONCLUSION: These results demonstrate that [D-Val22]big ET-1[16-38] and captopril act as highly potent ET-converting enzyme inhibitors, affecting big ET-1-induced contraction of the rabbit basilar artery.

Animals↗

PubMed2001

Redistribution of glycolipid raft domain components induces insulin-mimetic signaling in rat adipocytes.

Caveolae and caveolin-containing detergent-insoluble glycolipid-enriched rafts (DIG) have been implicated to function as plasma membrane microcompartments or domains for the preassembly of signaling complexes, keeping them in the basal inactive state. So far, only limited in vivo evidence is available for the regulation of the interaction between caveolae-DIG and signaling components in response to extracellular stimuli. Here, we demonstrate that in isolated rat adipocytes, synthetic intracellular caveolin binding domain (CBD) peptide derived from caveolin-associated pp59(Lyn) (10 to 100 microM) or exogenous phosphoinositolglycan derived from glycosyl-phosphatidylinositol (GPI) membrane protein anchor (PIG; 1 to 10 microM) triggers the concentration-dependent release of caveolar components and the GPI-anchored protein Gce1, as well as the nonreceptor tyrosine kinases pp59(Lyn) and pp125(Fak), from interaction with caveolin (up to 45 to 85%). This dissociation, which parallels redistribution of the components from DIG to non-DIG areas of the adipocyte plasma membrane (up to 30 to 75%), is accompanied by tyrosine phosphorylation and activation of pp59(Lyn) and pp125(Fak) (up to 8- and 11-fold) but not of the insulin receptor. This correlates well to increased tyrosine phosphorylation of caveolin and the insulin receptor substrate protein 1 (up to 6- and 15-fold), as well as elevated phosphatidylinositol-3' kinase activity and glucose transport (to up to 7- and 13-fold). Insulin-mimetic signaling by both CBD peptide and PIG as well as redistribution induced by CBD peptide, but not by PIG, was blocked by synthetic intracellular caveolin scaffolding domain (CSD) peptide. These data suggest that in adipocytes a subset of signaling components is concentrated at caveolae-DIG via the interaction between their CBD and the CSD of caveolin. These inhibitory interactions are relieved by PIG. Thus, caveolae-DIG may operate as signalosomes for insulin-independent positive cross talk to metabolic insulin signaling downstream of the insulin receptor based on redistribution and accompanying activation of nonreceptor tyrosine kinases.

Adipocytes↗

PubMed2001

Augmentation of apoptosis and tumor regression by flavopiridol in the presence of CPT-11 in Hct116 colon cancer monolayers and xenografts.

CPT-11, a DNA topoisomerase I inhibitor, has demonstrated clinical activity in colorectal cancer. Flavopiridol, a cyclin-dependent kinase inhibitor, is rapidly emerging as a chemotherapy modulator. To enhance the therapeutic index of CPT-11 in colon cancer, we studied the combination of these two drugs in relatively resistant human colon cancer cells, Hct116. Exposure of parental Hct116 cells to clinically achievable concentrations of SN-38 (the active metabolite of CPT-11) induces p21 and a G(2) arrest. However, these conditions fail to induce apoptosis. In contrast, Hct116 cells that are p21 deficient (p21-/- Hct116) readily undergo apoptosis after treatment with SN-38. In this study we show that the parental Hct116 cells can be sensitized to undergo apoptosis by the addition of flavopiridol after SN-38 treatment. The induction of apoptosis was greatest with sequential therapy consisting of SN-38 followed by flavopiridol. Clonogenic assays also showed greatest inhibition with this sequence. Sequential treatment with SN-38 followed by flavopiridol was associated with higher activation of caspase-3 and greater cleavage of both p21 and XIAP, an inhibitor of apoptosis, compared with other treatment schedules. CPT-11 induced some tumor regressions but no complete responses in the p21-intact Hct116 xenografts. CPT-11 with flavopiridol more than doubled tumor regression, compared with CPT-11 alone, and produced a 30% complete response rate. Our studies indicate that CPT-11 induces cell cycle arrest rather than cell death and that flavopiridol, by activating the caspase cascade, cleaves the inhibitors of apoptosis and sensitizes the cells to undergo cell death. Thus, flavopiridol combined with CPT-11 may provide a completely new therapeutic approach in the treatment of colon cancer.

Animals↗

PubMed2000

Measuring the quantity and activity of mitochondrial electron transport chain complexes in tissues of central nervous system using blue native polyacrylamide gel electrophoresis.

Mitochondrial dysfunction and degeneration are associated with many neurodegenerative disorders. A dysfunctional mitochondrial electron transport chain (ETC) impairs ATP production and accelerates the generation of free radicals. To evaluate mitochondrial function, reliable methods are needed. Conventional spectrophotometric assays may not eliminate interference from nonspecific enzyme activities and do not measure quantities of specific ETC complexes. Blue native polyacrylamide gel electrophoresis (BN-PAGE) has been used to resolve mitochondrial ETC complexes. Combined with histochemical staining, it has also been applied to measure ETC enzyme activities in muscles. The current study is to determine (1) whether BN-PAGE can be used to detect ETC complexes from different regions of the central nervous system (CNS) and (2) the quantitative range of BN-PAGE in measuring the amounts and activities of different ETC complexes. By systematically varying the protein amount and the time of histochemical reactions, we have found linear ranges comparable to spectrophotometric assays for measuring enzyme activities of several ETC complexes. In addition, we found linear ranges for measuring protein quantities in several ETC complexes. These results demonstrate that BN-PAGE can be used to measure the amount and activity of the ETC enzymes from the nerve tissues and, thus, can be applied to evaluate the functional changes of mitochondria in neurodegenerative disorders.

Animals↗

PubMed2000

Autocatalytic nitration of P450CAM by peroxynitrite.

Peroxynitrite (PN) gains high selectivity as a physiological oxidizing and nitrating agent through catalysis by metal ions. This was established for the heme-thiolate (P450) enzyme prostacyclin synthase which was tyrosine nitrated and inhibited at low PN levels [FEBS Lett. 382 (1996) 101]. Other P450 proteins reacted in a similar manner and a ferryl species (Compound II) has been identified as an intermediate during reactions with PN [Nitric Oxide 3 (1999) 142]. Here we investigated cytochrome P450CAM and found that it catalyzes the decomposition of PN as well as an increased nitration of phenol. The latter at the expense of phenol hydroxylation is characteristic for the proton-assisted PN action. PN also caused self-nitration of P450CAM at several tyrosine residues. Two of them, Y96 and Y305 were largely protected in the presence of the ligand metyrapone. Unlike other heme-thiolate proteins P450CAM did not form distinct spectral intermediates characteristic for Compound II. We conclude that P450CAM serves as a model for the nitration of prostacyclin synthase with respect to its autocatalytic tyrosine nitration and its prevention by blocking the active site.

Binding Sites↗

PubMed2000

FT-Infrared spectroscopic studies of the iron ligand CO stretch mode of iNOS oxygenase domain: effect of arginine and tetrahydrobiopterin.

The iron ligand CO stretch vibration mode of the inducible nitric oxide synthase oxygenase domain (iNOSox) has been studied from 20 to 298 K. iNOSox in the absence of arginine reveals a temperature-dependent equilibrium of two major conformational substates with CO stretch bands centered at about 1945 and 1954 cm(-)(1). This behavior is not qualitatively changed when tetrahydrobiopterin (H(4)B) is bound. Arginine binding changes significantly the spectrum by formation of a sharp CO stretch mode band at about 1905 cm(-)(1) and indicates the formation of a hydrogen bond to the CO ligand. For temperatures lower than 250 K, the stretch vibration frequency decreases almost linearly with decreasing temperature and indicates that the coupling between the CO ligand and the arginine/protein in the active site via the hydrogen bond is very strong. Flashphotolysis of the CO ligand carried out at 25 K revealed the CO stretch mode of the photodissociated CO ligand trapped in the heme pocket. There is a negative linear relation between the stretch vibration frequencies of the photodissociated and the iron-bound CO indicating that the photodissociated ligand stays near the heme.

Animals↗

PubMed2000

Intermediates in the reaction of substrate-free cytochrome P450cam with peroxy acetic acid.

Freeze-quenched intermediates of substrate-free cytochrome 57Fe-P450(cam) in reaction with peroxy acetic acid as oxidizing agent have been characterized by EPR and Mossbauer spectroscopy. After 8 ms of reaction time the reaction mixture consists of approximately 90% of ferric low-spin iron with g-factors and hyperfine parameters of the starting material; the remaining approximately 10% are identified as a free radical (S' = 1/2) by its EPR and as an iron(IV) (S= 1) species by its Mossbauer signature. After 5 min of reaction time the intermediates have disappeared and the Mossbauer and EPR-spectra exhibit 100% of the starting material. We note that the spin-Hamiltonian analysis of the spectra of the 8 ms reactant clearly reveals that the two paramagnetic species, e.g. the ferryl (iron(IV)) species and the radical, are not exchanged coupled. This led to the conclusion that under the conditions used, peroxy acetic acid oxidized a tyrosine residue (probably Tyr-96) into a tyrosine radical (Tyr*-96), and the iron(III) center of substrate-free P450(cam) to iron(IV).

Camphor 5-Monooxygenase↗

PubMed2000

Substrate binding to 15beta-hydroxylase (CYP106A2) probed by FT infrared spectroscopic studies of the iron ligand CO stretch vibration.

CYP106A2 has been expressed in E. coli with a high yield of up to 130 mg per litre of culture, purified to electrophoretic homogenity and found to be active in 15beta-hydroxylation of deoxycorticosterone using the adrenal redox proteins adrenodoxin and adrenodoxin reductase. Inspite of catalytic activity no substrate binding was detectable by UV-Vis spectroscopy. In contrast, an effect of substrate binding has been detected using the CO stretch mode infrared spectrum indicating that deoxycorticosterone binds in the heme pocket near the iron ligand.

Bacillus megaterium↗

PubMed2000

Clay-bridged electron transfer between cytochrome p450(cam) and electrode.

We demonstrate a very fast heterogeneous redox reaction of substrate-free cytochrome P450(cam) on a glassy carbon electrode modified with sodium montmorillonite. The linear relationship of the peak current in the cyclic voltammogram with the scan rate indicates a reversible one-electron transfer surface process. The electron transfer rate is in the range from 5 to 152 s(-1) with scan rates from 0.4 to 12 V/s, respectively. These values are comparable to rates reported for the natural electron transfer from putidaredoxin to P450(cam). The formal potential of adsorbed P450(cam) is -139 mV (vs NHE) and therefore positively shifted by 164 mV compared to the potential of substrate-free P450(cam) in solution. UV-VIS and FTIR spectra do not indicate an influence of the clay colloidal particles on the heme and the secondary structure of P450(cam) in solution. However, P450(cam) adsorbed on the surface of the clay-modified electrode may undergo partial dehydration resulting in the shift of the formal potential.

Bentonite↗

PubMed2000

C-terminal phosphorylation of the high molecular weight neurofilament subunit correlates with decreased neurofilament axonal transport velocity.

We probed the relationship of NF axonal transport of neurofilaments (NFs) to their phosphorylation state by comparing these parameters in two closely-aged groups of young adult mice - 2 and 5 months of age. This particular time interval was selected since prior studies demonstrate that optic axons have already completed axonal caliber expansion and attained adult NF levels by 2 months but, as shown herein, continue to increase NF-H C-terminal phosphorylation. NF axonal transport was monitored by autoradiographic analysis of the distribution of radiolabeled subunits immunoprecipitated from optic axon segments at intervals following intravitreal injection of 35S-methionine. Both the peak and front of radiolabeled NFs translocated faster in 2- vs. 5-month-old mice. This developmental decline in NF transport rate was not due to reduced incorporation of NFs into the cytoskeleton, nor to an overall decline in slow axonal transport. By excluding or minimizing other factors, these findings support previous conclusions that C-terminal NF phosphorylation regulates NF axonal transport.

Aging↗

PubMed2000

Insulin-like signaling in yeast: modulation of protein phosphatase 2A, protein kinase A, cAMP-specific phosphodiesterase, and glycosyl-phosphatidylinositol-specific phospholipase C activities.

Previously, we have described significant effects of human insulin on glucose metabolism in the yeast Saccharomyces cerevisiae under conditions of growth limitation. These regulations apparently rely on a transmembrane receptor capable of binding human insulin and responding by tyrosine/serine phosphorylation of a specific set of polypeptides [Müller, G., Rouveyre, N., Crecelius, A., and Bandlow, W. (1998) Biochemistry 37, 8683-8695; Müller, G., Rouveyre, N., Upshon, C., Gross, E., and Bandlow, W. (1998) Biochemistry 37, 8696-8704; Müller, G., Rouveyre, N., Upshon, C., and Bandlow, W. (1998) Biochemistry 37, 8705-8713]. To characterize the molecular link between the initial steps in insulin-like signaling in yeast and the changes in the activities of glycogen synthase and glycogen phosphorylase, we examined here the effects of human insulin on a set of key regulatory enzymes of glycogen metabolism, protein phosphatase 2A (PP2A), cAMP-specific phosphodiesterase (cAMP-PDE), and protein kinase A (PKA). PP2A was activated about 2-fold by insulin in spheroplasts and in intact cells, whereas the fraction of active PKA was significantly reduced in a cAMP-independent manner as well as through a subsequent up to 3-fold increase in particulate cAMP-PDE activity accompanied by a 50% decrease in cytosolic cAMP levels. In addition, glycosyl-phosphatidylinositol-specific phospholipase C (GPI-PLC), which in isolated rat adipocytes is activated by insulin, was stimulated to up to 5-fold by glucose and 10-fold by glucose plus insulin in both yeast spheroplasts and intact cells leading to a concentration-dependent leftward shift of the glucose-response curve for activation of the GPI-PLC. GPI-PLC was most pronouncedly stimulated by authentic human insulin compared to various insulin analogues and insulin-like growth factor I. In addition to lipolytic cleavage by GPI-PLC, the GPI anchor of the cAMP-binding ectoprotein, Gce1p, was secondarily processed by a rapid proteolytic event. As the GPI-PLC reaction is rate limiting, the efficiency of the two-step anchor cleavage was significantly increased when insulin was present together with glucose as compared to glucose alone. The insulin concentrations effective in modulating PP2A, PKA, cAMP-PDE, and GPI-PLC activities correlate well with those required for half-saturation of the specific binding sites as well as for stimulation of protein phosphorylation and glycogen accumulation. The data suggest that mammalian insulin-sensitive cells and yeast share (part of) the key regulatory mechanism (consisting of PP2A, PKA, cAMP-PDE, and GPI-PLC) involved in the transduction of the insulin signal from the respective receptor systems to glycogen synthase and phosphorylase.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2000

Phospho-dependent association of neurofilament proteins with kinesin in situ.

Recent studies demonstrate co-localization of kinesin with neurofilament (NF) subunits in culture and suggest that kinesin participates in NF subunit distribution. We sought to determine whether kinesin was also associated with NF subunits in situ. Axonal transport of NF subunits in mouse optic nerve was perturbed by the microtubule (MT)-depolymerizing drug vinblastine, indicating that NF transport was dependent upon MT dynamics. Kinesin co-precipitated during immunoprecipitation of NF subunits from optic nerve. The association of NFs and kinesin was regulated by NF phosphorylation, since (1) NF subunits bearing developmentally delayed phospho-epitopes did not co-purify in a microtubule motor preparation from CNS while less phosphorylated forms did; (2) subunits bearing these phospho-epitopes were selectively not co-precipitated with kinesin; and (3) phosphorylation under cell-free conditions diminished the association of NF subunits with kinesin. The nature and extent of this association was further examined by intravitreal injection of (35)S-methionine and monitoring NF subunit transport along optic axons. As previously described by several laboratories, the wave of NF subunits underwent a progressive broadening during continued transport. The front, but not the trail, of this broadening wave of NF subunits was co-precipitated with kinesin, indicating that (1) the fastest-moving NFs were associated with kinesin, and (2) that dissociation from kinesin may foster trailing of NF subunits during continued transport. These data suggest that kinesin participates in NF axonal transport either by directly translocating NFs and/or by linking NFs to transporting MTs. Both Triton-soluble as well as cytoskeleton-associated NF subunits were co-precipitated with kinesin; these data are considered in terms of the form(s) in which NF subunits undergo axonal transport.

Animals↗

PubMed2000

Hypophosphorylated neurofilament subunits undergo axonal transport more rapidly than more extensively phosphorylated subunits in situ.

Axonal transport of neurofilaments (NFs) has long been considered to be regulated by phosphorylation. We present evidence that in optic axons of normal mice, the rate of NF axonal transport is inversely correlated with the NF phosphorylation state. In addition to 200 kDa NF-H and 145 kDa NF-M, axonal cytoskeletons from CNS contained a range of phospho-variants of NF-H migrating between 160-200 kDa, and of NF-M migrating at 97-145 kDa. While 160 kDa phospho-variants of NF-H have been well characterized, we confirmed the identity of the previously-described 97 kDa species as a hypophospho-variant of NF-M since (1) pulse-chase metabolic labeling confirmed the 97 kDa species to be a new synthesis product that was converted by phosphorylation over time into a form migrating at 145 kDa, (2) the 97 kDa protein reacted with multiple NF-M antibodies, including one specific for hypophosphorylated NF-M, and (3) dephosphorylation converted NF-M isoforms to 97 kDa. Autoradiographic analyses following metabolic radiolabeling demonstrated that hypophosphorylated NF-H and NF-M isoforms underwent substantially more rapid transport in situ than did extensively phosphorylated isoforms, while NF-H subunits bearing a developmentally delayed C-terminal phospho-epitope transported at a rate slower than that of total 200 kDa NF-H. Differential transport of phospho-variants also highlights that these variants are not homogeneously distributed among NFs, but are segregated to some extent among distinct, although probably overlapping, NF populations, indicating that axonal NFs are not homogeneous with respect to phosphorylation state.

Animals↗

PubMed2000

Novel germline mutation (300-305delAGTTGA) in the human MSH2 gene in hereditary non-polyposis colorectal cancer (HNPCC).

Hereditary non-polyposis colorectal cancer (HNPCC) is a common hereditary syndrome characterized by the high incidence and early onset of colorectal cancer. The majority of the HNPCC families carry germline mutations in either the MSH2 or the MLH1 mismatch repair gene. A 46 year-old female patient whose family history fulfilled the Amsterdam criteria for HNPCC was diagnosed with undifferentiated adenocarcinoma of the transverse colon. Recognizing the Lynch 2 syndrome (the existance of multiple HNPCC related cancers in a pedigree), we used polymerase chain reaction followed by direct sequencing to screen the coding regions of both the MSH2 and the MLH1 genes for germline mutations in DNA from the patient. We detected a novel germline mutation (300-305delAGTTGA) in exon 2 of human MSH2. We noted microsatellite instability in four microsatellite loci. Immunohistochemistry showed a lack of expression of the MSH2 gene product in the tumor, suggesting that the mutation is a disease-causing mutation.

Base Pair Mismatch↗

PubMed2000

Bone-muscle strength indices for the human lower leg.

This cross-sectional study is based on images from the lower leg as assessed by peripheral quantitative computer tomography (pQCT). Measurements were performed in 39 female and 38 male control subjects and 15 female professional volleyball players, all between 18 and 30 years of age. The images were obtained at shank levels of 4%, 14%, 33%, and 66% from the distal end. Bone and muscle cross-sectional areas, and the bones' density-weighted area moment of resistance and of inertia were assessed. From these, muscle-bone strength indices (MBSIs) were developed for compression (CI = 100. bone area/muscle area) and bending (BI = 100. bone area moment of resistance/muscle area/tibia length). Significant correlations between muscle cross-sectional area and bone were found at all section levels investigated. The strongest correlation for compression was observed in the sections at 14% (correlation coefficient r = 0.74), where 4.10 +/- 0.46 cm(2) bone, on average, was related to 100 cm(2) muscle. The compression index (CI) at the 14% level was independent of the tibia length. Interestingly, the 15 athletes had significantly greater CIs than the control subjects. This is most probably due to the greater tension development in the athletes. The highest correlation for bending was for anteroposterior bending at 33% of tibia length (r = 0.81), where the area moment of resistance, R, was on, average, 4.21 +/- 0.54 cm(3)/100 cm(2) muscle/m tibia length. Analysis of the bones' area moment of inertia showed that buckling is a possible cause of bending at the 33% and 66% levels, but not at the 14% level. No gender differences in MBSI were found. Likewise, age was without significant effect. The data show that bone architecture depends critically on muscle cross section and tension development. Moreover, bone geometry (e.g., the tibia length) influences the geometrical distribution of bone mineral, as it was found that long bones adapted to the same compressive strength are wider than short ones. We conclude that MBSIs offer a powerful diagnostic tool for bone disorders and may contribute to improving the treatment of bone metabolic and other diseases.

Absorptiometry, Photon↗

PubMed2000

Survival and plant-prey finding by Neoseiulus fallacis (Acari: Phytoseiidae) on soil substrates after aerial dispersal.

In a greenhouse and in an open field, aspects of aerial and ambulatory dispersal of the phytoseiid mite. Neoseiulus fallacis (Garman) were studied with a focus on events that would occur after aerially dispersing mites had landed on soil or associated substrates. We measured recovery of predators on lima bean plants (Phaseolus lunatus L.) that were infested with the two-spotted spider mite, Tetranychus urticae Koch. Factors thought to affect movement and colonization were distance to a receiver unit from a release (landing) point, intervening soil surfaces such as clods, gravel, fine soil and grass, and management of soil surfaces such as mulching. watering or both. In the field, the effect of distance (0.11-1.76 m) from a landing point to a receiver unit was significant, with a negative log-linear relationship. Soil surfaces such as clods and management actions such as watering with mulching allowed for more capture of predators on bean plants with prey than did other treatments. Environmental conditions greatly affected survival of N. fallacis. Predators in the field that were present on bare soil suffered high mortality (ca. 90%) at fluctuating daytime conditions of 26.4 +/- 4.8 degrees C and 56 +/- 13.4% RH. Predators only suffered 10% mortality in the greenhouse under the same setting, but under more controlled and favorable environmental conditions. Effects of environmental conditions, mode of dispersal and implications to biological control are discussed.

Animals↗

PubMed2000

Identification of a subtle t(16;19)(p13.3;p13.3) in an infant with multiple congenital abnormalities using a 12-colour multiplex FISH telomere assay, M-TEL.

There is increasing evidence that cytogenetically invisible chromosome rearrangements are an important cause of genetic disease. Clues to the chromosomal location of these rearrangements may be provided by a specific clinical diagnosis, which can then be investigated by targeted FISH or molecular studies. However, the phenotypic features of some microdeletion syndromes are difficult to recognise, particularly in infants. In addition, the presence of other chromosome aneuploidy may mask the typical clinical features. In the present study, the presence of tubers on cranial magnetic resonance imaging (MRI) of a 5-week-old infant prompted an investigation, by FISH, with probes from the tuberous sclerosis gene, TSC2. This and further FISH deletion mapping studies revealed a submicroscopic deletion encompassing the entire TSC2 gene and the adjacent PKD1 gene on one chromosome 16, confirming a del(16)(p13.3). Because of the large number of abnormal phenotypic features in this infant, we performed a 12-colour FISH assay (M-TEL) to screen for subtelomeric rearrangements involving the del(16p). The M-TEL assay revealed a cryptic der(16)t(16;19)(p13.3;p13.3). Further FISH with 19p and 19q subtelomeric probes demonstrated that this was derived from a balanced maternal t(16;19)(p13.3;p13.3). Importantly, 24-colour painting by multiplex FISH (M-FISH) failed to detect the translocation in either the infant or his mother. Based on our FISH mapping studies, we estimate the size of the trisomic region from 19p13.3 to be approximately 2 Mb, and the region of monosomy for 16p13.3 as 2.25 Mb. This case adds to the growing literature which indicates that many apparent chromosomal deletions are unbalanced translocations. The M-TEL assay provides a sensitive alternative to M-FISH for the detection of these subtle telomeric rearrangements.

Abnormalities, Multiple↗