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Biomedical subjects

M Feingold

Publications and source records attributed to M Feingold.

At least 19 recordsLinked to original sources
PubMed2005

Relaxation dynamics of a single DNA molecule.

The relaxation of a single DNA molecule is studied. The experimental system consists of optical tweezers and a micron-sized bead that is tethered to the bottom of the sample by a single double-stranded DNA molecule. The bead slows down the DNA relaxation from a strongly stretched configuration such that it is passing through stretched equilibrium states. This allows for a theoretical description of the relaxation trajectory, which is in good agreement with experiment.

Computer Simulation↗
PubMed2004

Relaxation dynamics of semiflexible polymers.

We study the relaxation dynamics of a semiflexible chain by introducing a time-dependent tension. The chain has one of its ends attached to a large bead, and the other end is fixed. We focus on the initial relaxation of the chain that is initially strongly stretched. Using a tension that is self-consistently determined, we obtain the evolution of the end-to-end distance with no free parameters. Our results are in good agreement with single molecule experiments on double stranded DNA.

DNA↗
PubMed2000

Novel HOXA13 mutations and the phenotypic spectrum of hand-foot-genital syndrome.

Hand-foot-genital syndrome (HFGS) is a rare, dominantly inherited condition affecting the distal limbs and genitourinary tract. A nonsense mutation in the homeobox of HOXA13 has been identified in one affected family, making HFGS the second human syndrome shown to be caused by a HOX gene mutation. We have therefore examined HOXA13 in two new and four previously reported families with features of HFGS. In families 1, 2, and 3, nonsense mutations truncating the encoded protein N-terminal to or within the homeodomain produce typical limb and genitourinary abnormalities; in family 4, an expansion of an N-terminal polyalanine tract produces a similar phenotype; in family 5, a missense mutation, which alters an invariant domain, produces an exceptionally severe limb phenotype; and in family 6, in which limb abnormalities were atypical, no HOXA13 mutation could be detected. Mutations in HOXA13 can therefore cause more-severe limb abnormalities than previously suspected and may act by more than one mechanism.

Abnormalities, Multiple↗
PubMed2000

Stochastic resonance in the speed of memory retrieval.

The stochastic resonance (SR) phenomenon in human cognition (memory retrieval speed for arithmetical multiplication rules) is addressed in a behavioral and neurocomputational study. The results of an experiment in which performance was monitored for various magnitudes of acoustic noise are presented. The average response time was found to be minimal for some optimal noise level. Moreover, it was shown that the optimal noise level and the magnitude of the SR effect depend on the difficulty of the task. A computational framework based on leaky accumulators that integrate noisy information and provide the output upon reaching a threshold criterion is used to illustrate the observed phenomena.

Acoustic Stimulation↗
PubMed1999

RecA polymerization on double-stranded DNA by using single-molecule manipulation: the role of ATP hydrolysis.

The polymerization of RecA on individual double-stranded DNA molecules is studied. A linear DNA (lambda DNA, 48.5 Kb), anchored at one end to a cover glass and at the other end to an optically trapped 3-micrometers diameter polystyrene bead, serves as a template. The elongation caused by RecA assembly is measured in the presence of ATP and ATP[gammaS]. By using force extension and hydrodynamic recoil, a value of the persistence length of the RecA-DNA complex is obtained. In the presence of ATP, the polymer length is unstable, first growing to saturation and then decreasing. This suggests a transient dynamics of association and dissociation for RecA on a double-stranded DNA, the process being controlled by ATP hydrolysis. Part of this dynamics is suppressed in the presence of ATP[gammaS], leading to a stabilized RecA-DNA complex. A one-dimensional nucleation and growth model is presented that may account for the protein assembly.

Adenosine Triphosphate↗
PubMed1998

Isolated hemihyperplasia (hemihypertrophy): report of a prospective multicenter study of the incidence of neoplasia and review.

Hemihyperplasia is characterized by asymmetric growth of cranium, face, trunk, limbs, and/or digits, with or without visceral involvement. It may be an isolated finding in an otherwise normal individual, or it may occur in several syndromes. Although isolated hemihyperplasia (IHH) is of unknown cause, it may represent one end of the clinical spectrum of the Wiedemann-Beckwith syndrome (WBS). Uniparental paternal disomy of 11p15.5 or altered expression of insulin-like growth factor 2 (IGF2) from the normally silent maternal allele have been implicated as causes of some cases of WBS. IHH and other mild manifestations of WBS may represent patchy overexpression of the IGF2 gene following defective imprinting in a mosaic fashion. The natural history of IHH varies markedly. An association among many overgrowth syndromes and a predisposition to neoplasia is well recognized. Heretofore the risk for tumor development in children with IHH was unknown. We report on the results of a prospective multicenter clinical study of the incidence and nature of neoplasia in children evaluated because of IHH. One hundred sixty-eight patients were ascertained. A total of 10 tumors developed in nine patients, for an overall incidence of 5.9%. Tumors were of embryonal origin (similar to those noted in other overgrowth disorders), including Wilms tumor, hepatoblastoma, adrenal cell carcinoma, and leiomyosarcoma of the small bowel in one case. These data support a tumor surveillance protocol for children with IHH similar to that performed in other syndromes associated with overgrowth.

Humans↗
PubMed1998

Genetic heterogeneity of Saethre-Chotzen syndrome, due to TWIST and FGFR mutations.

Thirty-two unrelated patients with features of Saethre-Chotzen syndrome, a common autosomal dominant condition of craniosynostosis and limb anomalies, were screened for mutations in TWIST, FGFR2, and FGFR3. Nine novel and three recurrent TWIST mutations were found in 12 families. Seven families were found to have the FGFR3 P250R mutation, and one individual was found to have an FGFR2 VV269-270 deletion. To date, our detection rate for TWIST or FGFR mutations is 68% in our Saethre-Chotzen syndrome patients, including our five patients elsewhere reported with TWIST mutations. More than 35 different TWIST mutations are now known in the literature. The most common phenotypic features, present in more than a third of our patients with TWIST mutations, are coronal synostosis, brachycephaly, low frontal hairline, facial asymmetry, ptosis, hypertelorism, broad great toes, and clinodactyly. Significant intra- and interfamilial phenotypic variability is present for either TWIST mutations or FGFR mutations. The overlap in clinical features and the presence, in the same genes, of mutations for more than one craniosynostotic condition-such as Saethre-Chotzen, Crouzon, and Pfeiffer syndromes-support the hypothesis that TWIST and FGFRs are components of the same molecular pathway involved in the modulation of craniofacial and limb development in humans.

Acrocephalosyndactylia↗
PubMed1998

Expression of Wilms' tumor suppressor gene (WT1) in term human trophoblast: regulation by cyclic adenosine 3',5'-monophosphate.

The Wilms' tumor suppressor gene (WT1), which is deleted in some Wilms' tumors, encodes a zinc finger transcription factor. We studied WT1 messenger ribonucleic acid (mRNA) in human term placenta and cytotrophoblasts differentiating into syncytiotrophoblasts in vitro by RT-PCR. The results suggest that WT1 mRNA is expressed in the trophoblasts in a cell-specific fashion. WT1 mRNA expression has been observed to decline remarkably in trophoblast cells after 72 h, when these cells are morphologically differentiated into multinucleated syncytiotrophoblasts. As it is well known that cAMP as a second messenger plays a significant role in cellular proliferation and differentiation of placental cells, we examined the effect of 8-bromo-cAMP on WT1 mRNA expression in undifferentiated cytotrophoblasts and differentiated syncytiotrophoblasts. We observed that cAMP enhanced WT1 mRNA expression in cytotrophoblasts, but remained ineffective in altering WT1 mRNA in syncytiotrophoblasts. In summary, the results of this investigation demonstrate that the WT1 gene is developmentally regulated during trophoblast differentiation. An involvement of the cAMP-mediated system in regulating the WT1 gene in the trophoblast is suggested.

Cell Differentiation↗
PubMed1998

Ultrasound prenatal diagnosis of the Nail-Patella syndrome.

The Nail-Patella syndrome (NPS) is an autosomal dominant connective-tissue disorder characterized by the absence or hypoplasia of the nails and patella, posterior illiac horns, elbow deformities, congenital nephropathy cervical ribs and eye problems. The presence of the posterior iliac horns is pathognomonic and have been observed in more than 80 per cent of cases. In this report, we present the first case of prenatal diagnosis of NPS by ultrasound. The possible kidney involvement, combined with other, milder, complications make the prenatal diagnosis of this syndrome worthwhile.

Adult↗
PubMed1997

Syndrome of microcephaly, facial and hand abnormalities, tracheoesophageal fistula, duodenal atresia, and developmental delay.

We report on six new families (12 new patients) with the syndrome of microcephaly, facial and hand abnormalities, tracheoesophageal fistula, duodenal atresia, and developmental delay. The most common findings were hand abnormalities, microcephaly, short and/or narrow palpebral fissures, broad nasal bridge, anteverted nostrils, ear abnormalities, and micrognathia. Inheritance is autosomal dominant. There is a significant amount of intrafamilial variability especially as it relates to the gastrointestinal findings. Although the first patients reported, who were very young, did not exhibit any developmental delay, they subsequently did develop learning problems, and 87% of our 12 patients had mental retardation or learning difficulties.

Abnormalities, Multiple↗