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N Levy

Publications and source records attributed to N Levy.

At least 37 records · Page 2Linked to original sources
PubMed2001

Polymorphic short tandem repeats for diagnosis of the Charcot-Marie-Tooth 1A duplication.

BACKGROUND: A 1.5-Mb microduplication containing the gene for peripheral myelin protein 22 (PMP22) on chromosome 17p11.2-12 is responsible for 75% of cases of the demyelinating form of Charcot-Marie-Tooth disease (CMT1A). Methods for molecular diagnosis of CMT1A use Southern blot and/or amplification by PCR of polymorphic poly(AC) repeats (microsatellites) located within the duplicated region, or the detection of junction fragments specific for the duplication. Difficulties with both strategies have led us to develop a new diagnostic strategy with highly polymorphic short tandem repeats (STRs) located inside the CMT1A duplicated region. METHODS: We tested 10 STRs located within the duplication for polymorphic behavior. Three STRs were selected and used to test a set of 130 unrelated CMT1A patients and were compared with nonduplicated controls. The study was then extended to a larger population of patients. Alleles of interest were sequenced. A manual protocol using polyacrylamide electrophoresis and silver staining and an automated capillary electrophoresis protocol to separate fluorescently labeled alleles were validated. RESULTS: We identified three new STRs covering 0.55 Mb in the center of the CMT1A duplication. One marker, 4A, is located inside the PMP22 gene. The two others, 9A and 9B, more telomerically positioned, have the highest observed heterozygosity reported to date for CMT1A markers: 0.80 for 9A, and 0.79 for 9B. Tetra- and pentanucleotide repeats offered clear amplification, accurate sizing, and easy quantification of intensities. CONCLUSIONS: Combined use of the three STRs allows robust diagnosis with almost complete informativeness. In our routine diagnosis for CMT1A, they have replaced the use of other polymorphic markers, either in a manual adaptation or combined with fluorescence labeling and allele sizing on a DNA sequencer.

Charcot-Marie-Tooth Disease↗
PubMed2000

Linkage of X-linked myopathy with excessive autophagy (XMEA) to Xq28.

X-linked myopathy with excessive autophagy (XMEA, MIM 310440) is a rare inherited mild myopathy. We have used 32 polymorphic markers spanning the entire X chromosome to exclude most of the chromosome except the Xq28 region in a large XMEA family. Using three additional families for linkage analysis, we have obtained a significant two-point lod score with marker DXS1183 (Z = 2.69 at theta = 0). Multipoint linkage analysis confirmed the assignment of the disease locus with a maximal lod score of 2.74 obtained at recombination fraction zero. Linkage of XMEA to the Xq28 region is thus firmly established. In addition, we have ruled out the Emery-Dreifuss muscular dystrophy to be allelic with XMEA by direct sequencing of the emerin gene in three of our families.

Biopsy↗
PubMed2000

Administration of prostaglandin f(2 alpha) during the early bovine luteal phase does not alter the expression of ET-1 and of its type A receptor: a possible cause for corpus luteum refractoriness.

Luteal regression is initiated by prostaglandin F(2 alpha) (PGF(2 alpha)). In domestic species and primates, demise of the corpus luteum (CL) enables development of a new preovulatory follicle. However, during early stages of the cycle, which are characterized by massive neovascularization, the CL is refractory to PGF(2 alpha). Our previous studies showed that endothelin-1 (ET-1), which is produced by the endothelial cells lining these blood vessels, plays a crucial role during PGF(2 alpha)-induced luteolysis. Therefore, in this study, we compared the effects of PGF(2 alpha) administered at the early and mid luteal phases on ET-1 and its type A receptors (ETA-R) along with plasma ET-1 and progesterone concentrations, and the mRNA levels of PGF(2 alpha) receptors (PGF(2 alpha)-R) and steroidogenic genes. As expected, ET-1 and ETA-R mRNA levels were markedly induced in midcycle CL exposed to luteolytic dose of PGF(2 alpha) analogue (Cloprostenol). In contrast, neither ET-1 mRNA nor its receptors were elevated when the same dose of PGF(2 alpha) analogue was administered on Day 4 of the cycle. In accordance with ET-1 expression within the CL, plasma ET-1 concentrations were significantly elevated 24 h after PGF(2 alpha) injection only on Day 10 of the cycle. The steroidogenic capacity of the CL (plasma progesterone as well as the mRNA levels of steroidogenic acute regulatory protein and cytochrome P450(scc)) was only affected when PGF(2 alpha) was administered during midcycle. Nevertheless, PGF(2 alpha) elicited certain responses in the early CL: progesterone and oxytocin secretion were elevated, and PGF(2 alpha)-R was transiently affected. Such effects probably result from PGF(2 alpha) acting on luteal steroidogenic cells. These findings may suggest, however, that the cell type mediating the luteolytic actions of PGF(2 alpha), possibly the endothelium, could yet be nonresponsive during the early luteal phase.

Animals↗
PubMed2000

Role of tumor necrosis factor alpha and its type I receptor in luteal regression: induction of programmed cell death in bovine corpus luteum-derived endothelial cells.

The role of tumor necrosis factor alpha (TNF alpha) and its type I receptor (TNFRI) in structural luteolysis was investigated. A semiquatitative reverse-transcription polymerase chain reaction (RT-PCR) was used to characterize the pattern of TNFRI mRNA expression within the corpus luteum (CL) throughout the estrous cycle and its cellular distribution. Increase in TNFRI mRNA levels was recorded both in regressed luteal tissue and in CL of cows injected with prostaglandin F(2 alpha). All three major cell types composing the CL, steroidogenic (large and small) and endothelial cells expressed the TNFRI gene. A densitometric analysis of TNFRI mRNA expression revealed that resident endothelial cells had significantly higher levels of TNFRI mRNA than steroidogenic luteal cells. The physiological effects associated with TNFRI expression were investigated in the various luteal cell types. TNF alpha-induced programmed cell death (PCD) in dose- and time-dependent manners of cultured luteal endothelial cells (LECs) but not of in vitro luteinized steroidogenic cells. Several lines of evidence are provided to show that progesterone regulates luteal cell survival: 1) CL and LECs express progesterone receptor mRNA, 2) physiological levels of the steroid abolished TNF alpha-induced PCD of LECs, and 3) progesterone-producing cells are protected from PCD. In conclusion, this study suggests that TNF alpha-induced PCD during structural luteolysis is mediated by TNFRI, primarily affects endothelial cells, and that the decline in progesterone, preceding structural luteolysis, is a prerequisite for the initiation of apoptosis in endothelial cells.

Animals↗
PubMed2000

Does the addition of fentanyl to bupivacaine in caudal epidural block have an effect on the plasma level of catecholamines in children?

We evaluated the effect of adding fentanyl to bupivacaine, compared with bupivacaine alone, on the stress response. The effect was evaluated by determining blood levels of epinephrine (E) and norepinephrine (NE) in pediatric patients receiving caudal epidural blocks. Sixty children, 1-8 yr of age, scheduled for elective herniorrhaphy, were randomly allocated to two groups of 30 patients each. Group A received inhaled anesthesia and caudal epidural block with bupivacaine 0.25% alone, 1.0 mL/kg. Group B received identical anesthesia; however, fentanyl 1 microg/kg was added to the bupivacaine in the caudal block. Blood samples for E and NE plasma levels were drawn at induction time (H(0)), at the end of surgery (H(1)), and in the postanesthesia care unit (H(2)). In both groups, there was a significant decrease in the E and NE plasma levels, when comparing H(1) and H(2) with H(0) within the same group (P < 0.001). There were no significant differences in the E and NE plasma levels between the two groups at H(0), H(1), and H(2) (P = 0.5, P = 0.12, P = 0.5, respectively). Pain scores (modified Children's Hospital of Eastern Ontario Pain Score) were also similar in both groups (P = 0. 19). This study suggests that adding fentanyl 1 microg/kg to bupivacaine in the caudal epidural block in children does not influence plasma levels of E and NE, nor does it improve the analgesic intensity of the caudal block.

Adjuvants, Anesthesia↗
PubMed2000

[Impact of an anti-hepatitis B virus (HBV) immunization program in patients undergoing dialysis in Havana, Cuba].

The follow-up of HBV markers in selected high infection risk populations, in patients from the hemodialysis and peritoneal dialysis services was used to assess the effectiveness of a special vaccination program. Viral infection markers were studied in prevalence cross sections of the whole population of patients, and also by recording the reports of clinical cases of hepatitis B occurred during that period in those groups of patients. The prevention program consisted of the vaccination of all patients negative to the viral markers and the indication of vaccination for the new cases during the period of the kidney disease, just before the start of the treatment at the hemodialysis unit; besides all the persons susceptible to infection that had already been included in the program, regardless of the stage of the disease. The results show the benefit of the vaccination in these patients, but it is more effective in the period before the treatment with dialysis where there is a lower possibility of being exposed to the virus and the immune system is still competent. Once the program was established, after a follow up o 6 years, there have been no reports of new cases of hepatitis B and the incidence of the disease has been declining.

Adult↗
PubMed1999

Associative memory in a multi-modular network.

Recent imaging studies suggest that object knowledge is stored in the brain as a distributed network of many cortical areas. Motivated by these observations, we study a multimodular associative memory network, whose functional goal is to store patterns with different coding levels--patterns that vary in the number of modules in which they are encoded. We show that in order to accomplish this task, synaptic inputs should be segregated into intramodular projections and intermodular projections, with the latter undergoing additional nonlinear dendritic processing. This segregation makes sense anatomically if the intermodular projections represent distal synaptic connections on apical dendrites. It is then straightforward to show that memories encoded in more modules are more resilient to focal afferent damage. Further hierarchical segregation of intermodular connections on the dendritic tree improves this resilience, allowing memory retrieval from input to just one of the modules in which it is encoded.

Algorithms↗
PubMed1999

Demyelinating X-linked Charcot-Marie-Tooth disease: unusual electrophysiological findings.

X-linked Charcot-Marie-Tooth disease (CMT-X) is caused by mutations of connexin-32 (Cx-32), which encodes a gap-junction protein. Whether the neuropathy is primarily demyelinative or axonal remains to be established. We report findings of prominent demyelination in a 71-year-old woman with late-onset disease. Electrophysiological studies revealed a nonuniform slowing of motor conduction velocities and dispersion of compound action potentials indicative of a demyelinating process which was confirmed by nerve biopsy. Such electrophysiological features are unusual in hereditary neuropathies and are more commonly found with acquired chronic demyelinating neuropathies. A systematic search confirmed the molecular genomic diagnosis of CMT-X, illustrating the value of such tests in sporadic cases. Severity of clinical symptoms and signs may vary with age and sex of the patient. The pathology of CMT-X in other reported cases has been variably interpreted as axonal, demyelinating, or showing both features. Our observations emphasize the demyelinative nature.

Action Potentials↗
PubMed1999

Effect of caudal block on the plasma adrenaline and noradrenaline concentrations in paediatric patients undergoing ilioinguinal herniorrhaphy.

This study compared the effect of two anaesthetic techniques on the catecholamine levels in children undergoing ilioinguinal herniorrhaphy. Forty male paediatric patients ASA class I were allocated randomly to one of two groups: the control group (n = 20) received general anaesthesia including intravenous fentanyl; and the caudal group (n = 20) received caudal anaesthesia with bupivacaine 0.25% 1 mL kg-1 combined with general anaesthesia but without opioids. Plasma adrenaline and noradrenaline concentrations were measured at induction, at the end of surgery and in the post-anaesthesia care unit (PACU). In the caudal group, there were significant decreases in the adrenaline and noradrenaline concentrations at the end of surgery and in the PACU compared with baseline concentrations. In the control group, there was a significant increase in PACU concentrations of adrenaline and noradrenaline compared with baseline concentrations. These findings suggest that the addition of a caudal block to general anaesthesia in children undergoing ilioinguinal herniorrhaphy decreases significantly the neurohormonal responses to surgery.

Anesthesia, Caudal↗
PubMed1999

Characterization and regulation of type A endothelin receptor gene expression in bovine luteal cell types.

Our previous studies demonstrated that endothelin-1 (ET-1), a 21-amino acid vasoconstrictor peptide, has a paracrine regulatory role in bovine corpus luteum (CL). The peptide is produced within the gland where it inhibits progesterone production by acting via the selective type A endothelin (ETA) receptors. The present study was designed to characterize ETA receptor gene expression in different ovarian cell types and its hormonal regulation. ETA receptor messenger RNA (mRNA) levels were high in follicular cells as well as in CL during luteal regression. At this latter stage, high ETA receptor expression concurred with low prostaglandin F2alpha receptor mRNA. The ETA receptor gene was expressed by all three major cell populations of the bovine CL; i.e. small and large luteal cells, as well as in luteal endothelial cells. Among these various cell populations, the highest ETA receptor mRNA levels were found in endothelial cells. cAMP elevating agents, forskolin and LH, suppressed ETA receptor mRNA expression in luteinized theca cells (LTC). This inhibition was dose dependent and was evident already after 24 h of incubation. In luteinized granulosa cells (LGC), 10 and 100 ng/ml of insulin-like growth factor I and insulin (only at a concentration of 2000 ng/ml) markedly decreased ETA receptor mRNA levels. In both LGC and LTC there was an inverse relationship between ETA receptor gene expression and progesterone production; insulin (in LGC) and forskolin (in LTC) enhanced progesterone production while inhibiting ETA receptor mRNA levels. Our findings may therefore suggest that, during early stages of luteinization when peak levels of both LH and insulin-like growth factor I exist, the expression of ETA receptors in the gland are suppressed. This study demonstrates physiologically relevant regulatory mechanisms controlling ETA receptor gene expression and further supports the inhibitory role of ET-1 in CL function.

Animals↗
PubMed1999

The critical region of overlap defining the AZFa male infertility interval of proximal Yq contains three transcribed sequences.

The position of deletion breakpoints in a series of four AZFa male infertility patients has been refined using new markers derived from BAC clone DNA sequence covering the AZFa male infertility interval. The proximal half of the AZFa interval is occupied by pseudogene sequences with homology to Xp22. The distal half contains an anonymous expressed sequence tag (named AZFaT1) found transcribed in brain, testis, and skeletal muscle and the DFFRY and DBY genes. All the patients have AZFaT1 and DFFRY deleted in their entirety and three patients additionally have DBY deleted. The three patients with AZFaT1, DFFRY, and DBY deleted show a severe Sertoli cell only syndrome type I phenotype, whereas the patient that has retained DBY shows a milder oligozoospermic phenotype. The expression of DBY in a cell line from this latter patient is unaltered; this shows that it is the loss of genes lying within the deletion that is responsible for the observed oligozoospermia. RT-PCR analysis of mouse testis RNA from normal and XXSxr(a) mice (devoid of germ cells) has shown that Dby is expressed primarily in somatic cells and that the level of expression is unaltered during germ cell differentiation. This contrasts with Dffry where no transcripts are detectable in XXSxr(a) mouse testis and expression occurs specifically in testis mRNA in a germ cell dependent fashion.

Adult↗
PubMed1999

Intraovarian regulation of luteolysis.

The corpus luteum is a transient gland, which is only functional for 17-18 days in the cyclic cow or for up to 200 days in the pregnant cow. Regression of the corpus luteum is essential for normal cyclicity as it allows the development of a new ovulatory follicle, whereas prevention of luteolysis is necessary for the maintenance of pregnancy. Evidence acquired over the past three decades indicated that PGF2 alpha is the luteolytic hormone in ruminants. Nevertheless, the detailed mechanisms of PGF2 alpha action are just beginning to be clarified. A pivotal role for an endothelial cell product endothelin 1 (ET-1) has been documented in PGF2 alpha-induced luteal regression. ET-1 inhibited progesterone production by luteal cells in a dose-dependent manner via selective ET-1 binding sites (ETA). The inhibitory action of PGF2 alpha on progesterone secretion (in vivo and in vitro) was blocked by a selective ETA receptor antagonist. This implied that ET-1 (through ETA receptors present on steroidogenic cells) may have mediated the inhibitory effect of PGF2 alpha. The involvement of ET-1 in luteal regression was also suggested by the observation that the highest concentrations of ET-1 coincide with uterine PGF2 alpha surges. Furthermore, PGF2 alpha administration upregulated ET-1 expression within the corpus luteum. Later stages of luteal regression, which involve programmed cell death (PCD), are presumably mediated by immune cells. ET-1 may also be involved in this process by promoting leukocyte migration and stimulating macrophages to release tumour necrosis factor alpha (TNF alpha). The TNF alpha receptor type 1 (p55) is present on luteal cells (endothelial and steroidogenic cells) and could initiate PCD and the structural demise of the corpus luteum.

Animals↗