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Biomedical subjects

L Abrams

Publications and source records attributed to L Abrams.

At least 19 recordsLinked to original sources
PubMed2004

Prenatal diagnosis of de novo X;autosome translocations.

The identification of a de novo apparently balanced structural chromosome rearrangement at prenatal diagnosis can be problematic and raises unique genetic counseling issues. Two breakpoint rearrangements such as reciprocal translocations or inversions have a 6.7% empiric risk of phenotypic abnormality. Abnormal phenotypes are thought to result from gene disruption, position effect, or deletion at one of the breakpoints. Prenatal diagnosis of de novo X;autosome translocations is rare, and presents additional unique risks due to the effects of X-inactivation and the possibility of disruption of the single active copy of an X-linked gene. We report the identification of a de novo apparently balanced t(X;6)(q26;q23) ascertained after amniocentesis for advanced maternal age. The parents were counseled regarding the risk of a de novo apparently balanced translocation, including the potential risk of an X-linked Mendelian disorder resulting from disruption of a gene at the Xq26 breakpoint. While the normal X chromosome was late replicating in all metaphases, no conclusions from this data could be drawn as the X-inactivation ratio in amniocytes might not be representative of other tissues. The possibility of future premature ovarian failure was also noted due to the position of the breakpoint at Xq26, although no specific risk could be ascribed. The parents elected to continue the pregnancy, and at 17 months of age, the proband was phenotypically and developmentally normal. Long-term follow-up will be required to assess development delay and any fertility issues. Based on review of the few cases reported to date and excluding any risk for later reproductive abnormalities, we estimated the risk of phenotypic abnormality or developmental delay in a prenatally ascertained de novo X;autosome carrier to be as high as 50%. This case illustrates the complexities in counseling for prenatally ascertained de novo X;autosome translocations and the need for additional cases to be reported.

Adult↗
PubMed2003

Politics and governance at the interface between water and development.

Water is not just a technical issue--it always has to be addressed within a complex political context. The water sector professional is generally unskilled in political processes, but political skill and awareness is needed to avoid negative politicization of water.

Conservation of Natural Resources↗
PubMed2001

Autosomal recessive tetralogy of Fallot, unusual facies, communicating hydrocephalus, and delayed language development: a new syndrome?

We report a pattern of malformation affecting five of seven siblings born to unaffected Afghani parents who are first cousins. Their first two children died during infancy of cyanotic congenital heart defects. Two living male siblings have tetralogy of Fallot, developmental delay principally affecting language skills, and short palpebral fissures or midfacial hypoplasia. Another male has communicating hydrocephalus and hypertelorism. The striking number of siblings with tetralogy of Fallot, or another cyanotic congenital heart defect, and the parental consanguinity, suggests autosomal recessive inheritance in this family. While several other families have been identified with apparent recessive inheritance of tetralogy of Fallot, the associated malformations in our family suggest a unique, and previously unreported, malformation pattern.

Adolescent↗
PubMed2000

Tetrasomy 15q25-->qter: cytogenetic and molecular characterization of an analphoid supernumerary marker chromosome.

Tetrasomy for the distal long arm of chromosome 15 is a rare finding. It has been previously described in seven patients, all of whom had a supernumerary marker chromosome (SMC) derived from distal 15q. These SMC contained no apparent centromeres (C-band/alpha-satellite negative), and belong to a novel class of SMC with neocentromeres. We present the oldest surviving patient with tetrasomy for distal 15q. The proposita was a 10-year-old girl with moderate to severe mental retardation, absent speech, hypotonia, minor facial anomalies, unusual digits, and pigmentation anomalies. Mosaicism for a symmetrical SMC was identified in metaphases from lymphocytes and fibroblasts. Parental karyotypes were normal, indicating a de novo origin for the SMC. FISH with a whole chromosome paint for chromosome 15 showed that the SMC was derived entirely from chromosome 15. However, C-banding and FISH with chromosome 15 probes D15Z1, D15S11, SNRPN, and PML were all negative. FISH with the FES probe at 15q26 showed hybridization to both ends of the SMC. The marker was interpreted as an analphoid inverted duplication of 15q25-->qter containing a presumed neocentromere. Previous molecular studies suggested either a mitotic or paternal meiotic origin for these distal 15q SMC. However, molecular analysis with chromosome 15 polymorphic markers showed that the analphoid SMC(15) in the proposita originated from a maternal meiotic error. The origins and mechanisms involved in formation of these distal 15q SMC appear to be more diverse than for the proximal pseudodicentic SMC(15).

Abnormalities, Multiple↗
PubMed2000

Supramolecular steric effects as the means of making reactive carbon radicals persistent. Quantitative characterization of the external surface of MFI zeolites through a persistent radical probe and a langmuir adsorption isotherm

The photochemistry of tetraphenylacetone (1) adsorbed on the external surface of a MFI zeolite (the sodium form of LZ-105) has been investigated in combination with computational chemistry, surface area measurements, EPR analysis, and classical adsorption isotherms. All of the methods are consistent with a supramolecular structural model in which 1 is first adsorbed strongly through intercalation of a single benzene ring into a hole on the LZ-105 external surface (site I) followed by a weaker binding to the external framework between the holes (site II) until a monolayer of 1 is formed. From both computational and surface area measurements, it is estimated that the site I holes on the external surface will be filled at ca. 0.3-0.5 wt %/wt loading of 1/LZ-105, which corresponds to 6.5 x 10(18) (ca. 10(-)(5) mol) of holes or molecules of 1 adsorbed in holes per gram of zeolite. The supramolecular composition of ca. 0.3-0.5% of 1 on LZ-105 characterizes a "break point" for the photochemistry and the EPR measurements, since it represents the value for saturation of the site I holes with 1. These conclusions are supported quantitatively by experimental isotherms of the adsorption of 1 on LZ-105. Photolysis of 1 intercalated in the site I holes causes fragmentation into two isomeric supramolecular diphenylmethyl (DPM) radicals, one (DMP)(in) which is adsorbed into the internal surface and becomes strongly persistent (half-life of many weeks) and the other (DMP)(ex) which diffuses on the external surface and rapidly dimerizes (less than a few minutes) to produce the radical-radical combination product tetraphenylethane (2). Photolysis of 1 adsorbed on the solid external surface produces two supramolecularly equivalent DPM radicals (DMP)(ex) that diffuse on the external surface and rapidly dimerize to produce 2, and do not produce persistent DPM radicals.

Journal Article↗
PubMed2000

Characterization of metalworking fluid exposure indices for a study of acute respiratory effects.

Although metalworking fluids have been widely used throughout industry for decades, occupational exposures to metalworking fluid aerosols and their constituents have not been well characterized. This article describes an exposure assessment for a study of metalworking fluid aerosols and acute respiratory effects. This exposure assessment was unique in its inclusion of multiple exposure measures relevant to a complex environment, and extensive personal sampling for bacteria and endotoxin. The specific objectives were to: (1) obtain indices of personal exposure to metalworking fluid aerosols in an automotive transmission plant, either directly (by sampling) or indirectly (by estimation), and (2) identify and adjust for sources of error in exposure/dose measures, where possible. No prior studies have characterized personal exposures to metalworking fluid aerosols so extensively. Exposure data were obtained during a pilot phase and three principal rounds of data collection over a 15-month period in conjunction with spirometric testing. Subjects worked in one of two machining departments, Case and Valve Body, or in a comparison department, Final Assembly. The primary exposure measures for this study were thoracic fraction particulate, thoracic fraction bacteria (viable plus non-viable), and total endotoxin. Mean personal air concentrations of thoracic particulate across all study rounds were 0.13 mg/m3 in Final Assembly, 0.32 mg/m3 in Valve Body, and 0.56 mg/m3 in Case. Average personal exposures to thoracic fraction bacteria were 0.38 bacteria/cc in Final Assembly, 0.87 bacteria/cc in Valve Body, and 2.66 bacteria/cc in Case. Average personal endotoxin measurements, collected in Round 3 of the study, were 16.4 endotoxin units (EU)/m3 in Assembly, 34.7 EU/m3 in Valve Body, and 234 EU/m3 in Case. Sump fluid contained on the order of 10(8) bacteria/ml, and 10(4)-10(5) EU/ml. Air concentrations of thoracic particulate, thoracic bacteria, and total endotoxin were highly correlated in metalworking operations. Thus, reducing airborne particulate levels should also reduce ambient bacteria and endotoxin, which are suspect agents of respiratory impairment. The elevated endotoxin levels in Final Assembly were unexpected, and suggest an independent source of endotoxin contamination in this department.

Acute Disease↗
PubMed2000

Electromyography during stereotactic pallidotomy for Parkinson's disease.

In stereotactic pallidotomy for Parkinson's disease, care must be taken to avoid internal capsule injury while maximizing improvement of rigidity and tremor. In 21 patients, intraoperative electromyography (EMG) was used to assess stimulation thresholds required for capsular responses and to monitor muscle tone and tremor. Surface EMG electrodes were placed on the face and multiple muscle groups of the extremities. The stimulation and lesion electrode was introduced via MRI-guided stereotaxis toward a point 2-3 mm anterior to the midcommissural point, 5-6 mm inferior to the AC-PC plane, and 21-22 mm lateral to the midline. Exact targets were modified according to MRI-visualized anatomy. With stimulation at 5 and 50 Hz, thresholds for detection of EMG responses were usually seen at 4-5 mA. EMG responses were consistently seen prior to visual observation of muscle activity. Timing of EMG response relative to stimulus aided in differentiating stimulus-related movement from spontaneous tremor. Resting spontaneous EMG activity was seen to decrease as rigidity was improved by incremental lesion production. EMG activity related to tremor was recorded; tremor decrease by lesion production was documented by EMG recording. Patient cooperation with physiologic testing during stimulation and lesion production may become limited. Intraoperative EMG monitoring provides an adjunct to improve reliability of assessment of capsular stimulation and rigidity while providing documentation of lesion impact on rigidity and tremor.

Aged↗
PubMed1999

Aging on the input versus output side: theoretical implications of age-linked asymmetries between detecting versus retrieving orthographic information.

This experiment tested for age-linked asymmetries predicted under Node Structure theory (NST; D. G. MacKay & D. M. Burke, 1990) between detecting versus retrieving orthographic information. Older adults detected that briefly presented words were correctly spelled (e.g., endeavor) or misspelled (e.g., endeavuor) as readily as did young adults. However, they were less able than young adults to retrieve the correctly and incorrectly spelled words that they had seen. These age-linked asymmetries were not due to educational factors, stimulus characteristics, sensory-level factors, task complexity, floor or ceiling effects, general slowing, or cohort-related activities, but they were consistent with NST predictions and with similar asymmetries in a wide range of other studies. By contrast, repetition deficits in detecting and retrieving repeated- versus unrepeated-letter misspellings (e.g., elderdly vs. elderkly) were symmetrical or equivalent in magnitude for young and older adults. Implications for a wide range of theories of cognitive aging and of repetition deficits are discussed.

Adolescent↗
PubMed1998

Age-linked declines in retrieving orthographic knowledge: empirical, practical, and theoretical implications.

This study developed and tested a Transmission Deficit hypothesis of how aging affects retrieval of orthographic knowledge. Young, older, and very old adults heard a tape-recorded series of difficult-to-spell words of high and low frequency, spoken slowly, clearly and repeatedly, and wrote down each word at their own pace. With perceptual errors and vocabulary differences factored out, misspellings increased with aging, especially for high-frequency words. In addition, data from a metamemory questionnaire indicated that the oldest adults were aware of their declining ability to spell. These findings were not due to general slowing, educational factors, hours per week spent reading, writing, or solving crossword puzzles, or age-linked declines in monitoring or detecting self-produced errors. However, the results fit Transmission Deficit predictions, and suggested an age-linked decline in retrieval of orthographic knowledge that resembles age-linked declines in spoken word retrieval observed in many other studies. Practical implications of this age-linked decline for conceptions of normal aging are noted.

Adolescent↗
PubMed1998

"The view" and the canine connection: an atlas of mandibular anterior tooth esthetics.

Restoring splinted mandibular incisors and canines with full crown restorations has always presented a challenge in creating an esthetic illusion of reality of normal individual teeth. This treatise is designed to present the rules for mandibular anterior esthetics that have been distilled from almost 4 decades of clinical practice of restoring dentitions that have been severely compromised by the deformities of disease or accident. The resultant formula systematically creates the desired results with a high degree of predictability.

Crowns↗
PubMed1998

Duplication cyst of the antrum: a case report.

Gastrointestinal duplication is a rare congenital anomaly. Although it usually presents within the first few years of life, it may appear much later as described in this report of a 19-year-old man who had symptoms of gastric outlet obstruction. He was found to have a noncommunicating antral duplication cyst. The cyst was managed by antrectomy with excision of the cyst and several centimetres of duodenum. Microscopically the duplication cyst contained a mucosa, submucosa and muscularis. There was no evidence of ulceration or malignant cells. His recovery was smooth. The etiology, presentation and management of antral duplication cysts causing gastric outlet obstruction are discussed.

Adult↗
PubMed1997

Acute respiratory effects on workers exposed to metalworking fluid aerosols in an automotive transmission plant.

Exposure to metalworking fluids has been linked to modest cross-shift reductions in FEV1 and occupational asthma. To identify responsible agents, we measured personal exposures to thoracic particulate (TP), viable plus nonviable thoracic bacteria (BAC), and vapor phase nicotine (VPN) (as a surrogate for tobacco particulate) among 83 machinists exposed to soluble oils and 46 dry assemblers working in an automotive transmission machining plant using biocides infrequently. The participants completed interviews and performed pre- and postshift spirometry on Monday and Thursday of the same week in each of three rounds of data collection (June 1992, January 1993, June 1993). Generalized estimating equations were used to combine information across rounds in multiple regression models of cross-shift and cross-week changes in forced expiratory volume, I second (FEV1) and forced vital capacity (FVC). Mean seniority was 19 years among machinists. Mean personal TP levels were 0.41 mg/m3 in machinists and 0.13 mg/m3 in assemblers. Six of the 83 machinists and none of the 46 assemblers experienced a greater than 19% cross-shift decrement in FEV1 or FVC at least once (p = .07). In regression models using either TP or BAC, among subjects with lower baseline (Monday preshift) FEV1/FVC ratios, increasing exposure was significantly associated with increasing cross-shift decrements in FEV1 and FVC in linear models, and with increased likelihood of a 10% or greater cross-shift decrement in FEV1 or FVC in logistic models. Adjustment of TP for VPN did not affect models significantly. We conclude that clinically important cross-shift decrements in pulmonary function are associated with exposure to metalworking fluid aerosols within a high-seniority population.

Adult↗
PubMed1996

Acquired defects of glycogen synthase activity in cultured human skeletal muscle cells: influence of high glucose and insulin levels.

To determine whether defects of muscle glycogen synthase (GS) activity can be acquired by exposure to elevated glucose or insulin levels, human skeletal muscle cells obtained by needle biopsy from normal control subjects were grown in culture for 4-6 weeks followed by 4 days of fusion and differentiation in media containing either normal (5.5 mmol/l glucose and 22 pmol/l insulin) or increased concentrations of glucose (20 mmol/l), insulin (30 micromol/l), or both. After fusion in normal media, acute stimulation by 33 nmol/l insulin for 1 h increased GS fractional velocity (FV) approximately twofold (from 9.01 +/- 1.26 to 16.31 +/- 2.40, P < 0.05). Increasing the media glucose concentration alone to 20 mmol/l during fusion had no effect on basal FV but caused a marginal impairment of the insulin-stimulated GS response (from 8.51 +/- 1.33 to 12.99 +/- 1.90, P = 0.08). Increasing the media insulin concentration to 30 micromol/l during fusion at 5.5 mmol/l glucose also did not alter basal GS FV (10.61 +/- 1.69%) but completely abolished the normal insulin-stimulated increase in GS activity (to 11.63 +/- 1.55%, NS). The combination of high insulin (30 micromol/l) and high glucose (20 mmol/l) during fusion had no greater effect on the FV of either basal (11.66 +/- 2.16%, NS) or insulin-stimulated (9.20 +/- 1.80%, NS) GS activity than high insulin alone. Fusion in hyperinsulinemic media altered the kinetic parameters of GS with a near doubling of the basal Km0.1 and Vmax0.1 for uridinediphospho-glucose. Hyperinsulinemia also totally prevented the normal insulin-stimulated threefold increase in the Vmax0.1 and the 65% decrease in the A0.5 for glucose-6-phosphate. GS mRNA and protein expression, determined by RNase protection assay and immunoblotting, respectively, were unaffected by changes in media conditions. We conclude that exposure of human skeletal muscle cells primarily to high insulin induces severe insulin resistance through multiple acquired posttranslational defects, which affect both the kinetic characteristics and absolute activity of the GS enzyme.

Actins↗
PubMed1996

Cross-language facilitation, semantic blindness, and the relation between language and memory: a reply to Altarriba and Soltano.

This comment corrects some inaccuracies, points to some methodological problems, and makes three substantive observations regarding the Altarriba and Soltano (1996) article. First, token individuation theory does not explain what is new and interesting in the Altarriba and Soltano data, namely cross-language semantic facilitation in lists and a list-sentence effect, that is, a large difference in the effect of semantic repetition when identical translation equivalents occurred in sentences versus lists. Second, Altarriba and Soltano's small and nonsignificant semantic blindness effect for translation equivalents in split-language sentences is attributable to the peculiar nature of their materials, procedures, analyses, and experimental design. These problems nullify their conclusion that semantic blindness does not occur, and we discuss several clear cases where semantic blindness has been demonstrated. Finally, we suggest an explanation for Altarriba and Soltano's unexplained effects (cross-language facilitation and the list-sentence effect) and show why these effects are important for the general issue of relations between language and memory.

Humans↗
PubMed1996

GI manifestations of Ehlers-Danlos syndrome.

Ehlers-Danlos syndrome (EDS) is an inherited disorder of connective tissue that is distinguished not only by the triad of skin hyperextensibility, articular hypermobility, and tissue fragility but also by its heterogeneity on clinical, genetic, and biochemical grounds. The phenotypical variance that characterizes this syndrome often makes its recognition difficult, and failure to recognize the disease despite a classic course is not uncommon. Diagnosis is paramount, however, so life-threatening associations can be searched for and unique principles of management can be instituted. Patients are prone to GI catastrophes such as perforation and massive bleeding, which can be compounded by grave surgical and vascular complications. A thorough knowledge of the GI manifestations of EDS and their management is mandatory to prevent unnecessary morbidity and mortality.

Ehlers-Danlos Syndrome↗
PubMed1995

Glucose transport in cultured human skeletal muscle cells. Regulation by insulin and glucose in nondiabetic and non-insulin-dependent diabetes mellitus subjects.

A primary human skeletal muscle culture (HSMC) system, which retains cellular integrity and insulin responsiveness for glucose transport was employed to evaluate glucose transport regulation. As previously reported, cells cultured from non-insulin-dependent diabetic (NIDDM) subjects displayed significant reductions in both basal and acute insulin-stimulated transport compared to nondiabetic controls (NC). Fusion/differentiation of NC and NIDDM HSMC in elevated media insulin (from 22 pM to 30 microM) resulted in increased basal transport activities but reduced insulin-stimulated transport, so that cells were no longer insulin responsive. After fusion under hyperinsulinemic conditions, GLUT1 protein expression was elevated in both groups while GLUT4 protein level was unaltered. Fusion of HSMC under hyperglycemic conditions (10 and 20 mM) decreased glucose transport in NC cells only when combined with hyperinsulinemia. Hyperglycemia alone down-regulated transport in HSMC of NIDDM, while the combination of hyperglycemia and hyperinsulinemia had greater effects. In summary: (a) insulin resistance of glucose transport can be induced in HSMC of both NC and NIDDM by hyperinsulinemia and is accompanied by unaltered GLUT4 but increased GLUT1 levels; and (b) HSMC from NIDDM subjects demonstrate an increased sensitivity to impairment of glucose transport by hyperglycemia. These results indicate that insulin resistance in skeletal muscle can be acquired in NC and NIDDM from hyperinsulinemia alone but that NIDDM is uniquely sensitive to the additional influence of hyperglycemia.

Adult↗