Search PubMed⌕ Search

Biomedical subjects

S Schwartz

Publications and source records attributed to S Schwartz.

At least 199 records · Page 11Linked to original sources

Supply pricing update.

Explore the source record for details and available documents.

Catalogs, Commercial as Topic↗

Feeding impairments in children: diagnosis and effective intervention.

The four main requirements for oral-motor development are stability and mobility of the ingestive system, rhythmicity, sensation, oral-motor efficiency and economy. Ingestion can be divided into oral, pharyngeal and esophageal stages. The main categories of pathology encountered in our swallowing and dysphagia clinic are encephalopathies (including cerebral palsy), genetic disorders (including chromosomal aberrations), syndromes associated with swallowing difficulty (e.g. Rett, Dandy-Walker, DiGeorge), head injuries, brain tumors, developmental delay and the oral deprivation syndrome (e.g. due to prolonged tube feeding on a preterm infant). The behavioral expression of the many different pathologies falls into three categories: (1) resistance to accepting food orally; (2) lack of energy and endurance to do the 'work' of eating; and (3) oral-motor disabilities resulting in an inability to produce the necessary motor skills for ingestion. Expect expression and exacerbation of feeding problems during periods of most active growth, i.e. from birth to 2 years and during the adolescent growth spurt. Identify the source of the feeding problem. Establish its pathology and note the clinical manifestations. Determine if the problem has a strictly physiologic origin or whether it may be exacerbated by the feeding interaction between child and feeder. Determine what diagnostic tests are needed and refer child for testing Formulate the treatment approach based on clinical observations and results of diagnostic tests. Teach and monitor treatment which can be given by caregivers. Set time limits for treatment and clearly state expected results. Evaluate progress by comparing outcome to stated treatment objectives. Refer children with more severe problems to a multidisciplinary treatment team.

Adolescent↗

Comparative sequence analysis of a gene-rich cluster at human chromosome 12p13 and its syntenic region in mouse chromosome 6.

The Human Genome Project has created a formidable challenge: the extraction of biological information from extensive amounts of raw sequence. With the increasing availability of genomic sequence from other species, one approach to extracting coding and regulatory element information is through cross-species sequence comparison. To assess the strengths and weaknesses of this methodology for large-scale sequence analysis, 227 kb of mouse sequence syntenic to a gene-rich cluster on human chromosome 12p13 was obtained. Primarily through percent identity plots (PIPs) of SIM comparative sequence alignments, the sequence of coding regions, putative alternative exons, conserved noncoding regions, and correlation in repetitive element insertions were easily determined. The analysis demonstrated that the number, order, and orientation of all 17 genes are conserved between the two species, whereas two human pseudogenes are absent in mouse. In addition, apart from MIRs, no direct correlation of distribution or position of the majority of repetitive elements between the two species is seen. Finally, in examining the synonymous and nonsynonymous substitution rates in the conserved genes, a large variation in nonsynonymous rates is observed indicating that the genes in this region are diverging at different rates. This study indicates the utility and strength of large-scale cross-species sequence comparisons in the extraction of biological information from raw sequence, especially when combined with other computational tools such as GRAIL and BLAST.

Amino Acid Sequence↗

Effect of starvation on organ blood flow in the senescent rat.

To investigate the amino acid requirements of the senescent rat, as part of a study directed toward nutritional support in the aged, it was necessary to determine amino acid levels in plasma and tissue, but also regional blood flow of the animals subjected to fast. Only this latter allows the determination of the amounts of each amino acid present in the tissue before starvation by extrapolation of values measured during starvation. As plasma and tissue amino acid had been previously determined, the aim of this study had been to measure regional blood flow in the liver, kidney, testis, spleen, stomach, small intestine and large intestine in senescent rats submitted to 1, 5, 9 and 15 days of starvation. Twenty-four-month-old male Wistar rats (n = 16) were divided into four groups (n = 4), and submitted to starvation for 1, 5, 9 and 15 days. Blood flow in the liver, kidney, testis, spleen, stomach, and small and large intestine was measured by injecting 0.5 ml of a microsphere solution (15 microns diameter) labelled with 57Co, 0.25 microCi/ml. Over the 15-day period studied, the response to starvation showed two distinct phases: an early effect (from day 1 to day 9) in which there were decreases in the weight of the organs and in organ blood flow, and a second phase (from day 9 to day 15) in which blood flow and organ weight were maintained. However, organ blood flow related to mass was not substantially affected by starvation. This implies that measurement of substrate plasma concentration alone can reliably reflect organ substrate flow.

Aging↗

Trust me: technical and institutional determinants of health maintenance organizations shifting risk to physicians.

This paper examines the factors that influence a Health Maintenance Organization (HMO) to shift risk to doctors through an incentive arrangement called capitation, where physicians are paid a fixed amount per patient for a period of time for any and all medical services required by the patient. Multispecialty-medical-group (Group) HMOs are more likely to shift risk than Independent Physician Associations (IPA) HMOs. Within IPA HMOs, larger enrollment per physician is positively associated with more risk shifting. We find that institutional factors signaling legitimacy play an important role in determining risk shifting. For-profit HMOs are less likely to shift risk, which we interpret as reflecting consumer distrust of for-profit HMOs. However, for-profit HMOs that are federally qualified, which we interpret as a signal of legitimacy, are more likely to shift risk.

Capitation Fee↗

Evaluation of mental retardation: recommendations of a Consensus Conference: American College of Medical Genetics.

A Consensus Conference utilizing available literature and expert opinion sponsored by the American College of Medical Genetics in October 1995 evaluated the rational approach to the individual with mental retardation. Although no uniform protocol replaces individual clinician judgement, the consensus recommendations were as follows: 1. The individual with mental retardation, the family, and medical care providers benefit from a focused clinical and laboratory evaluation aimed at establishing causation and in providing counseling, prognosis, recurrence risks, and guidelines for management. 2. Essential elements of the evaluation include a three-generation pedigree: pre-, peri-, and post-natal history, complete physical examination focused on the presence of minor anomalies, neurologic examination, and assessment of the behavioral phenotype. 3. Selective laboratory testing should, in most patients, include a banded karyotype. Fragile X testing should be strongly considered in both males and females with unexplained mental retardation, especially in the presence of a positive family history, a consistent physical and behavioral phenotype and absence of major structural abnormalities. Metabolic testing should be initialed in the presence of suggestive clinical and physical findings. Neuroimaging should be considered in patients without a known diagnosis especially in the presence of neurologic symptoms, cranial contour abnormalities, microcephaly, or macrocephaly. In most situations MRI is the testing modality of choice. 4. Sequential evaluation of the patient, occasionally over several years, is often necessary for diagnosis, allowing for delineation of the physical and behavioral phenotype, a logical approach to ancillary testing and appropriate prognostic and reproductive counseling.

Diagnosis, Differential↗

AU-rich mRNA instability elements on human papillomavirus type 1 late mRNAs and c-fos mRNAs interact with the same cellular factors.

Expression levels of human papillomavirus type 1 late genes are determined in part by an AU-rich inhibitory sequence in the 3' untranslated region on the late mRNAs. Fine mapping of the AU rich inhibitory sequence revealed that it mapped to a 57 nucleotide sequence, consisting of an AU-rich region containing two AUUUA motifs and a U-rich region containing three UUUUU motifs. An internal deletion showed that the U-rich region was required for inhibition. Point mutations in the AUUUA- and UUUUU-motifs inactivated the inhibitory sequence. Analysis of the stability of mRNAs containing the AU-rich sequence in sense or anti-sense orientation showed that mRNAs containing the AU-rich sequence in sense orientation had reduced half life. Analysis of RNA-protein interactions revealed that binding to the inhibitory sequence of three poly(U) binding proteins (38, 44 and 46 kDa) correlated with inhibition and that the same proteins bind to the AU-rich mRNA instability element in the 3' untranslated region on the human c-fos mRNA. We speculate that the human papillomavirus late mRNAs, produced from several hundred copies of the virus genome present in infected cells, compete with the c-fos mRNAs for destabilizing cellular factors and that this may lead to elevated Fos protein levels in human papillomavirus infected cells.

Adenine↗

An apparently acentric marker chromosome originating from 9p with a functional centromere without detectable alpha and beta satellite sequences.

Recently, we studied a patient with minor abnormalities and an apparently acentric marker chromosome who carried a deleted chromosome 9 and a marker chromosome in addition to a normal chromosome 9. The marker was stable in mitosis but lacked a primary constriction. The origin of the marker was established by fluorescent in situ hybridization (FISH) using a chromosome 9 painting probe. Hybridization of unique sequence 9p probes localized the breakpoint proximal to 9p13. Additional FISH studies with all-human centromere alpha satellite, chromosome 9 classical satellite, and beta satellite probes showed no visible evidence of these sequences on the marker [Curtis et al.: Am J Hum Genet 57:A111, 1995]. Studies using centromere proteins (CENP-B, CENP-C, and CENP-E) were performed and demonstrated the presence of centromere proteins. These studies and the patient's clinical findings are reported here.

Abnormalities, Multiple↗

Mosaic trisomy 22: a case presentation and literature review of trisomy 22 phenotypes.

In a case of mosaic trisomy 22 the trisomic cells were detected primarily in fibroblasts. Results of initial lymphocyte chromosome analysis were normal. However, mosaicism was suspected because the patient had hypomelanosis of Ito, hemiatrophy, failure to thrive, and mental retardation. Mosaicism was confirmed in cultured fibroblasts. Repeat cytogenetic analysis of peripheral blood demonstrated a low level of trisomic metaphase cells, which was confirmed by interphase fluorescent in situ hybridization (FISH) analysis. Molecular studies supported maternal disomy in the child's disomic cells. The phenotype of this condition overlaps that of non-mosaic trisomy 22 chromosome mosaicism in general and to some extent the Ullrich-Turner syndrome phenotype. Improved cytogenetic and molecular techniques now allow better delineation of aneuploidy syndromes. Molecular and FISH studies added information about this case (mosaicism and uniparental disomy) not appreciated by routine cytogenetic analysis of lymphocytes. The detection of low-level mosaicism and/or uniparental disomy in such cases may change the clinical classification and our understanding of pathogenesis and recurrence risk of these disorders.

Adult↗

Duplication 14(q24.3q31) in a father and daughter: delineation of a possible imprinted region.

A number of clinical reports have described children with a variety of congenital anomalies in association with uniparental disomy (upd) of chromosome 14, suggesting that at least some genes on chromosome 14 are subject to parent of origin, or imprinting, effects. However, little else is known about this putative imprinting of chromosome 14. Both maternal and paternal upd have been observed, but a consistent phenotype has only been suggested for the former. Here we report on a child with developmental delay, microcephaly, distinct facial findings, and who has a duplication of 14q24.3q31. The same cytogenetic abnormality was found in her phenotypically normal father. We hypothesize that this segment of chromosome 14 contains maternally silenced genes, and that this duplicated segment defines an imprinted region on chromosome 14. Alternatively, this cytogenetic duplication may be unrelated to the girl's phenotypic anomalies, and this duplication may contain genes that are not subject to dosage effect.

Abnormalities, Multiple↗

Sex chromosome markers: characterization using fluorescence in situ hybridization and review of the literature.

Fluorescence in situ hybridization (FISH) using biotin labeled X- and Y-chromosome DNA probes was utilized in the analysis of 23 sex chromosome-derived markers. Specimens were obtained through prenatal diagnosis, because of a presumptive diagnosis of Ullrich-Turner syndrome, mental retardation, and minor anomalies or ambiguous genitalia; three were spontaneous abortuses. Twelve markers were derived from the X chromosome and eleven from the Y chromosome; this demonstrates successfully the value and necessity of FISH utilizing DNA probes in the identification of sex chromosome markers. Both fresh and older slides, some of which had been previously G-banded, were used in these determinations. We have also reviewed the literature on sex chromosome markers identified using FISH.

Adolescent↗

Delayed diagnosis in patients with Prader-Willi syndrome due to maternal uniparental disomy 15.

Prader-Willi syndrome (PWS) results from absence of the normally active paternally inherited genes on proximal 15q, due to del(15)(q11q13) or by maternal uniparental disomy (UPD) 15 in most cases. In addition to a higher frequency of hypopigmentation among deletion patients, minor phenotypic differences between deletion and UPD patients have recently been reported, including lower birth weight in the deletion group, shorter birth length in males with UPD, and shorter course of gavage feeding and later onset of hyperphagia in females with UPD. We previously reported that those with UPD had a less "typical" facial appearance, and they less often had skin picking, skill with puzzles, and high pain threshold. There were no children younger than 3.5 years of age in the UPD group, in contrast to several of them in the deletion group, suggesting a possible diagnostic delay in the UPD group. To assess this possibility and seek reasons for it, we reviewed the charts of 60 PWS patients with complete molecular testing. Mean age at diagnosis of patients with UPD was significantly higher than in the deletion group. Mean percentiles of birth weights and lengths of patients with UPD were significantly lower than in those with deletion. Mean duration of gestation, mean duration of gavage feeding, and mean age at onset of hyperphagia did not differ significantly between groups. Delay in the diagnosis of patients with UPD, which may influence the management and impact of the disorder, might be explained by a lower frequency of typical facial anomalies in this group.

Child↗

Unexpected familial recurrence in Angelman syndrome.

We report on two instances of familial recurrence of Angelman syndrome which, from pedigree analysis, appear incompatible with currently known mechanisms of inheritance of this disorder. In these two families, deletion-positive Angelman syndrome has recurred in cousins. Several established mechanisms for deletion-positive familial recurrence have been ruled out. In each family, molecular cytogenetic studies show typical chromosome 15 deletions, and DNA methylation analysis verifies the maternal origin of the deleted chromosomes in all four individuals. Since the mothers of the affected individuals in each family are not known to be related, these recurrences appear to be secondary to coincidental, de novo events. This conclusion is consistent with direct and indirect estimates of the population frequency of Angelman syndrome.

Angelman Syndrome↗

Pervasive occult gastrointestinal bleeding in an Alaska native population with prevalent iron deficiency. Role of Helicobacter pylori gastritis.

OBJECTIVE: To confirm prevalent iron deficiency among Yupik Eskimos living in Alaska and to explore the frequency of and potential lesions accounting for occult gastrointestinal bleeding. DESIGN: Descriptive survey. SETTING: Rural Arctic community. SUBJECTS: A total of 140 adult volunteers from 3 villages in the Yukon-Kuskokwim Delta region of western Alaska. MAIN OUTCOME MEASURES: Daily iron intake, hematologic and biochemical indexes of iron status, fecal hemoglobin levels, stool parasites, and endoscopic findings. RESULTS: While dietary iron intake by Yupiks was similar to that of a reference population, iron deficiency prevalence was increased 13-fold in Yupik men and 4-fold in Yupik women. Fecal hemoglobin levels were elevated in 90% of subjects contrasted with only 4% of a reference group; median levels were 5.9 and 0.5 mg of hemoglobin per gram of stool, respectively. Among 70 Yupik subjects with elevated fecal hemoglobin levels who had endoscopy performed, 68 (97%) had an abnormal gastric appearance consisting of erythema, mucosal thickening, diffuse mucosal hemorrhages, erosions, or ulcerations. Gastric biopsies revealed chronic active gastritis with associated Helicobacter pylori in 68 (99%) of 69. No other hemorrhagic gastrointestinal disease was detected. CONCLUSIONS: Based on this study sample, occult gastrointestinal bleeding appears to be pervasive in the Yupik population and likely underlies the prevalent iron deficiency. An atypical hemorrhagic gastritis associated with H pylori infection is present almost universally and may represent the bleeding source.

Adult↗

Detection by monoclonal antibodies of the Wilms' tumor (WT1) nuclear protein in patients with acute leukemia.

The WT1 gene encodes a transcriptional regulator which during embryogenesis is involved in growth control and differentiation of diverse tissues. It is also expressed in few human malignancies, including acute leukemia. We tested 3 different monoclonal antibodies (MAbs H2, H7, HCl7) and the polyvalent serum WTC-19 for WT1 protein detection in mononuclear cell (MNC) preparations of 104 newly diagnosed acute leukemia patients. Using RT-PCR, these MNC preparations were also analyzed for WT1 gene expression. MAbs H2, H7 and HCl7 and the polyclonal WTC-19 exhibited nuclear immunoreactivity in 63 of 99, 28 of 56, 38 of 60 and 22 of 43 WT1 gene-expressing leukemia samples, respectively. With these antibodies, no WT1 immunoreactivity was found in MNCs from blood of healthy volunteers, from CD34+ progenitor cell-enriched leukapheresis products of patients conditioned for peripheral stem cell harvest or from reactive bone marrow. Contrary to WTC-19, all MAbs reacted highly specifically with the WT1 protein (0.71 vs. 1.0). The WT1 protein was heterogeneously detected in leukemia blast preparations by all antibodies, irrespective of cell morphology. Very few HL60 cells and blasts from newly diagnosed leukemia patients interspersed among normal blood MNCs (50 blasts among 5 x 10(5) MNCs) were easy to identify by indirect immunofluorescence using MAbs H2 and HCl7. Taken together, MAbs H2 and HCl7 were superior to MAb H7 and the polyvalent WTC-19 in detecting the WT1 nuclear protein.

Antibodies, Monoclonal↗

Construction and screening of a cosmid library generated from a somatic cell hybrid bearing human chromosome 15.

A cosmid library has been constructed with DNA isolated from a mouse/human hybrid cell line designated A15, which was previously characterized and shown to retain chromosome 15 as the only human material. The library was generated and stored as 34 independent pools of primary colonies at 8-10,000 colonies per pool. Screening colonies representing pools of this library by hybridization with a human-specific repetitive probe has facilitated the identification of random clones bearing human inserts. To data, 43 unique clones have been isolated and the inserts mapped by fluorescence in situ hybridization (FISH) to chromosome 15. An STS was generated for each of these clones by end sequencing of the inserts. Two of these clones, c36 and MR23, were mapped by FISH to 15q26.1, and end-sequence data revealed homology to different regions of the FES protooncogene. Sequence generated from the other end of the c36 insert was found to match the previously identified and unmapped coding sequence EST00075. In addition to the identification of such random clones, establishment of the library as pools was expected to facilitate the PCR-based identification of unique clones representing specific regions of chromosome 15. Screening of the library pools with primers specific to the FES region led to the recovery of five independent clones facilitating the development of a cosmid contig encompassing the FES gene. One of the cosmids isolated by PCR-based analysis was derived from the same pool as M23 and was subsequently shown to be identical to M23. The data offer the first report of a chromosome 15 cosmid library and demonstrate the value of utilizing pools to evaluate libraries generated from complex sources like somatic cell hybrids.

Animals↗