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Biomedical subjects

E Schwartz

Publications and source records attributed to E Schwartz.

At least 109 records · Page 6Linked to original sources
PubMed1995

Temperature tolerance of hydrogenase expression in Alcaligenes eutrophus is conferred by a single amino acid exchange in the transcriptional activator HoxA.

Expression of the soluble (SH) and membrane-bound (MBH) hydrogenases in the facultatively lithoautotrophic bacterium Alcaligenes eutrophus is dependent on the transcriptional activator HoxA and the alternative sigma factor sigma 54. Deletion analysis revealed that a region 170 bp upstream of the transcriptional start of the SH operon is necessary for high-level promoter activity. Mobility shift assays with DNA fragments containing the SH upstream region and purified beta-galactosidase-HoxA fusion protein isolated from Escherichia coli or authentic HoxA isolated by immunoaffinity chromatography from A. eutrophus failed to detect specific binding. In contrast, A. eutrophus extracts enriched for HoxA by heparin-Sepharose chromatography and ammonium sulfate fractionation produced a weak but discrete shift in the mobility of the target DNA. This effect was not observed with comparable extracts prepared from hoxA mutants. A similar experiment using antibodies against HoxA confirmed that HoxA was responsible for the observed mobility shift. Extracts prepared from a temperature-tolerant mutant of A. eutrophus gave a stronger retardation than did those from the wild type. Unlike the wild type, the hox(Tr) mutant is able to grow with hydrogen at temperatures above 33 degrees C because of a mutation in the regulatory gene hoxA. In this paper, we show that a single amino acid substitution (Gly-468-->Val) in the C-terminal part of HoxA is responsible for temperature tolerance. The SH upstream region also contains sequence motifs resembling the E. coli integration host factor (IHF) binding site, and purified E. coli IHF protein shifted the corresponding indicator fragment.

Alcaligenes↗
PubMed1995

Haematopoietic cancer mortality among vehicle mechanics.

OBJECTIVE AND METHODS: This historical cohort study investigated causes of death among car and mobile equipment mechanics in the District of Columbia's Department of Public Works. Men who were employed for at least one year between 1977 and 1989 were eligible for inclusion in the cohort; follow up was up to the end of 1991. Three cases of leukaemia (index cases) had been reported among these workers before the inception of this study. This research was undertaken to estimate the relative risk of haematological cancer among mechanics working for the District of Columbia. RESULTS: Among the 335 male fleet maintenance workers, the all cause standardised mortality ratio (SMR) was 0.50 (33 observed deaths, 95% confidence interval (95% CI) 0.35-0.70), and the all cancer SMR was 0.55 (nine deaths, 95% CI 0.25-1.05). Three deaths from lymphatic and haematopoietic cancer were observed; the SMR was 3.63 (95% CI 0.75-10.63). In the subgroup with highest potential for exposure to fuels and solvents, the SMR for leukaemia and aleukaemia was 9.26 (two deaths, 95% CI 1.12-33.43), and the SMR for other lymphatic and haematopoietic neoplasms was 2.57 (one death from malignant lymphoma, 95% CI 0.06-14.27). All three lymphatic and haematopoietic cancer deaths were among car and mobile equipment mechanics (one was an index case). The two additional index cases were a fourth mechanic who died of leukaemia in 1992, after mortality follow up ended, and a fifth mechanic who was diagnosed with leukaemia in 1988 and is still alive. CONCLUSION: Many garage mechanics in this cohort regularly used petrol to clean parts and to wash their hands; some workers would occasionally siphon petrol by mouth. Benzene, a recognised cause of haematological cancer, is a component of petrol. Previous research indicates that garage mechanics may be at risk of leukaemia and other haematological cancers, presumably due to exposure to petrol; this study supports those findings.

Adult↗
PubMed1995

Organellar clusters formed by mitochondrial-rough endoplasmic reticulum associations: an ordered arrangement of mitochondria in hepatocytes.

Our objective was to determine if mitochondrial-rough endoplasmic reticulum (mt-RER) associations provide for an ordered arrangement of mitochondria in the cell. If such an ordered arrangement exists, it might be manifested by grouping of mitochondria according to size and biochemical properties. Liver homogenate was subjected to rate zonal centrifugation for fractionating mitochondrial clusters. These clusters were then examined for morphological and biochemical characteristics. Scanning electron microscopy (SEM) showed that (1) mitochondria were held together in clusters by rough endoplasmic reticulum, (2) clusters consisted of mitochondria of comparable size, and (3) a 45-fold difference in average mitochondrial volume existed between the organelles of the fastest and slowest sedimenting clusters. Transmission electron microscopy (TEM) affirmed that all of the organellar clusters examined were mitochondria associated with rough endoplasmic reticulum. Cytochrome oxidase and mitochondrial DNA were found to be proportional to mitochondrial volume, indicating that these components were synthesized in proportion to increases in volume. Conversely, succinic dehydrogenase and ornithine carbamoyl transferase were increased disproportionately (2.9-fold and six-fold, respectively) with increase in mitochondrial volume. It is evident from this biochemical heterogeneity that clusters composed of larger mitochondria differ functionally from clusters of smaller mitochondria. The size-ordered arrangement suggests that this organization is in some way related to the biogenesis of hepatocyte mitochondria. It is also conjectured that the biochemical heterogeneity is a consequence of addition of selected proteins (e.g., succinic dehydrogenase and carbamoyl transferase) to mitochondria in a developmental process as they mature into larger organelles.

Animals↗
PubMed1995

Lineage-specific alternative splicing of the human Fc gamma RIIA transmembrane exon requires sequences near the 3' splice site.

The human Fc gamma RIIA gene produces multiple transcripts, including those with (Fc gamma RIIa1) and without (Fc gamma RIIa2) the single exon encoding the transmembrane domain (TM). Previously, a fluorescence-based RT-PCR assay showed lineage-specific differences in Fc gamma RIIA transcript ratios (Fc gamma RIIa2/Fc gamma RIIa1). The mechanism of this lineage-specific expression was investigated in this study. Differential transcript stability does not play a major role, because transcript ratios remained constant in cells with both low (K562) and high (Dami) ratios following actinomycin D treatment. Transient expression studies in K562 and Dami cells using a minigene construct containing a 5.0 kb genomic fragment including the TM exon and adjacent intron and exon sequences showed recapitulation of endogenous transcript ratios. The TM exon was efficiently spliced in by the constitutive splicing machinery in HeLa cells, an Fc gamma RIIA-negative cell line. Lineage-specific TM exon skipping was markedly diminished by two independent minigene mutations: a point mutation of the first nucleotide of the TM exon, and a five basepair intronic deletion near a putative branchpoint. These data demonstrate that cis-acting sequences in or near the TM exon 3' splice acceptor site contribute to lineage-specific differences in Fc gamma RIIA transcript ratios.

Alternative Splicing↗
PubMed1995

Megakaryocyte-specific positive regulatory sequence 5' to the human PF4 gene.

Platelet factor 4 (PF4) is only expressed in platelets and is an appropriate marker for studying megakaryocytic differentiation. We previously characterized cDNA and genomic clones for human PF4 (hPF4) and now present transient expression studies defining the promoter of the gene. 12-O-tetradecanoyl-phorbol-13- acetate (TPA) induces megakaryocytic differentiation of human erythroleukemia (HEL) cells, providing an excellent model system for the study of megakaryocyte-specific promoter activity. Luciferase reporter-gene constructs containing sequences from -2074 to +49 were used to map regions that may regulate PF4 gene expression. The sequence in the region -239 to -107 increased basal promoter activity by four- to five-fold in TPA-induced HEL cells. The sequence between -239 and -107 contains 53 consecutive thymidine residues. Functional studies using constructs in this region show that poly(T) and the region -187 to -107 are necessary for the total increase in activity in TPA-induced HEL cells. Mobility-shift assays show that the poly(T) tract binds TPA-inducible proteins. The results suggest a complex promoter for the PF4 gene involving a basal nonspecific promoter element between -107 and +49, a positive promoter element between -239 and -107 binding specific nuclear proteins from megakaryocyte-lineage cells, and a silencer-like region between -2074 and -1653.

Base Sequence↗
PubMed1995

Decision-making in environmental health.

Despite our current knowledge about harmful exposures obtained from environmental epidemiology studies, preventive action is lacking in many fronts. To reverse this trend, results from environmental epidemiological studies must be translated from theory into public health practice more efficiently. This process requires epidemiology to provide the right type of data for decision-making and to communicate the results of environmental epidemiology studies in a form understandable to the community at large and to those empowered to take action. Tools for decision-making based on epidemiological data need to be developed further, and the epidemiologist has a role to play in the process of addressing the solutions to the problems they study. Similarly, while those with decision-making responsibilities are not expected to be directly involved with technical aspects of conducting epidemiological studies, it is necessary that they learn new ways of thinking and of evaluating information on health. They have a responsibility to understand the implications of the uncertainties in the information and the value this information has for decision-making. Decision-making involves choosing among alternative ways of meeting objectives. Often, however, there may be a number of objectives that may be in competition or conflict. Not infrequently, this combination of uncertainty and conflict produces diverse conclusions about the "best alternative" when viewed by different observers. A decision-maker must choose between competing alternatives, and may face uncertainties and difficulties at every step. These difficulties, however, should not serve as excuses for lack of action. While it is true that increasing evidence about a potential environmental health problem would aid the decision-making process, lack of action while waiting for more evidence may also carry significant adverse consequences.

Data Interpretation, Statistical↗
PubMed1994

Partially oxygenated sickled cells: sickle-shaped red cells found in circulating blood of patients with sickle cell disease.

A previously uncharacterized type of sickled cell was found in venous blood of patients with sickle cell disease when blood was collected without exposure to air and fixed immediately with 1% glutaraldehyde solution equilibrated with 5% oxygen. These cells were either elongated, resembling irreversibly sickled cells (ISCs), or nonelongated, with a raisin-like shape. Both types assumed a normal discoidal shape upon full oxygenation. Since these cells exist only under partially oxygenated conditions, they are described as partially oxygenated sickled cells (POSCs). POSCs are morphologically distinct from partially deoxygenated sickled cells formed during deoxygenation by having rounded edges, while the latter have sharp edges. Transmission electron microscopy of POSCs revealed various amounts of misaligned Hb S polymers. Investigations in vitro demonstrated the formation of POSC-like cells by partial oxygenation of deoxygenated cells. Since POSCs contain intracellular fibers and sickle readily upon deoxygenation, they may have clinical and pathological significance.

Anemia, Sickle Cell↗
PubMed1994

Interaction of rare illegitimate recombination event and a poly A addition site mutation resulting in a severe form of alpha thalassemia.

The clinical diversity of thalassemia depends on interaction of diverse genetic defects. We have characterized a severe form of alpha thalassemia caused by coinheritance of a rare alpha-globin gene deletion and a nondeletional defect in a southern Italian family. The proband, a 7-year-old girl, exhibited an abnormal hemoglobin electrophoresis pattern with hemoglobin H and hemoglobin Barts, indicating inheritance of H and hemoglobin Barts, indicating inheritance of a severe form of alpha thalassemia. Southern blot analysis of DNA showed normal as well as aberrant alpha-globin gene fragments indicating heterozygosity for a deletional form of alpha thalassemia in the proband and her mother. The coinheritance of a nondeletional form of alpha thalassemia (alpha alpha T) was suspected because of the severity of the proband's phenotype and the presence of normal alpha-globin gene fragments in the father. Selective polymerase chain reaction of the paternal alpha 1- and alpha 2-globin genes in the proband followed by DNA sequence analysis showed an AATAAA to AATGAA mutation in the polyadenylation signal sequence of the alpha 2-globin gene. Genomic DNA mapping and sequence analysis of a unique polymerase chain reaction product generated across the deletion breakpoint of the maternal allele showed a 5,201-bp deletion extending from 870 nucleotides 5' of the alpha 2-globin gene to nucleotide +519 in the alpha 1-globin gene. This deletion is similar to that previously suggested by blotting studies in a Greek family (Pressley et al, Nucleic Acids Res 8:4889, 1980) and removes the entire alpha 2-globin gene and a portion of the 5' end of the alpha 1-globin gene. Sequence characterization of the resultant aberrant truncated alpha 1-globin gene from the proband showed a 27 nucleotide duplication corresponding to the 3' end of the alpha-globin gene IVS-2 region separated by the insertion of a tetranucleotide (GGTT), suggesting that this deletion is caused by an illegitimate recombination event.

Base Sequence↗
PubMed1994

Erythrocytapheresis therapy to reduce iron overload in chronically transfused patients with sickle cell disease.

Chelation therapy with deferoxamine is effective in preventing the risk of transfusional iron overload, but treatment failure is common because of noncompliance. To reduce the transfusional iron load, we have evaluated longterm erythrocytapheresis in 14 subjects with sickle cell disease and stroke (11) or other complications (3) as an alternative to simple transfusion. Subjects were treated with erythrocytapheresis using the Haemonetics V50 (Haemonetics Corp, Braintree, MA) to maintain the target pretransfusion hemoglobin S (Hb S) level less than 50% for 6 to 71 months. The transfusional iron load and the donor blood usage were analyzed for a 6- to 36-month study period and were compared with similar data from a subset of 7 subjects previously treated with conventional (target Hb S < 30%) and modified (target Hb S < 50%) simple transfusion protocols. The effect of erythrocytapheresis on iron accumulation was determined by assessment of serum ferritin levels in the absence of iron chelation. The mean transfusional iron load and donor blood usage with erythrocytapheresis were 19 +/- 14 mg iron/kg/yr (range, 6 to 50) and 188.4 +/- 55.2 mL packed-red blood cells (RBC)/kg/yr (range, 107 to 281), respectively. Of 6 subjects receiving no iron chelation therapy, 5 maintained normal or nearly normal serum ferritin levels during 11 to 36 months of erythrocytapheresis. In comparison with conventional simple transfusion and modified simple transfusion, erythrocytapheresis reduced iron loading by 87% (P < .01) and 82% (P < .01), respectively, but increased donor blood usage by 23% and 73%, respectively. Subjects with pre-erythrocytapheresis Hb levels > or = 8.0 g/dL had lower iron accumulation (P < .001) and less donor blood usage (P < .005) than subjects with Hb levels < or = 8.0 g/dL. Although donor blood usage is increased in comparison with simple transfusion, long-term erythrocytapheresis markedly reduces or prevents iron accumulation. This form of transfusion therapy allows the cessation of iron chelation in well-chelated subjects and, if used as the initial form of transfusion therapy, may prevent long-term complications of sickle cell disease without risk of iron overload and the need for chelation therapy.

Adolescent↗
PubMed1994

Systematic use of automated fluorescence-based sequence analysis of amplified genomic DNA for rapid detection of point mutations.

Several approaches are now available for screening populations for known mutations in a given gene. However, for detection of multiple mutations in a population that has not been characterized or for detection of new mutations, the value and efficiency of these screening procedures decreases. Although more than 100 different beta-thalassemia mutations have so far been described, the spectrum of mutations in the Eastern Mediterranean and Israel has not been defined in detail. We have used automated fluorescence-based DNA sequence analysis of PCR-amplified genomic DNA employing a cycle-sequencing strategy coupled with advanced analysis software to rapidly detect beta-thalassemia mutations in Israeli patients. This method enabled rapid identification of eight different mutations in 10 patients, including two rare mutations, one of which has never been described in this geographic region. Our results show that automated fluorescence-based DNA sequence analysis of amplified genomic DNA is a rapid and reliable method for detection of point mutations and small deletions or insertions in both heterozygous and homozygous states. This approach is particularly effective for a relatively small gene such as beta-globin, but it can also be used for rapid detection of mutations in large genes by first sequencing clusters of exons and intron/exon borders.

Automation↗
PubMed1994

Prior hepatitis A virus infection enhances acute hepatitis E virus infection.

The epidemiology and clinical manifestations of hepatitis E virus (HEV) and hepatitis A virus (HAV) are similar. However, two distinct diseases develop after exposure to each one of the viruses, which are apparently unrelated clinically. It is interesting to note that all reported epidemics and single cases of acute HEV infection indicate previous exposure to HAV. This fact leads us to hypothesize that acute HEV infection is dependent on past infection by hepatitis A virus, and that the sequential infections could not solely be explained on independent outbreaks. This hypothesis, where past HAV infection serves to support acute HEV infection, may have current practical implications, and could improve our understanding of the virology and pathophysiology of the disease.

Adolescent↗
PubMed1994

Community surveillance of falls among the elderly using computerized EMS transport data.

Because falls are common among the elderly and are associated with high morbidity and mortality, community surveillance has been recommended. The purpose of this study was to characterize the impact of falls among the elderly on emergency medical transport services (EMS) and to explore the potential for community surveillance of falls through the use of computerized EMS data. Computerized EMS data and United States census data for 1990 for persons aged > or = 65 in Forsyth County, NC, were used to produce EMS transport rates for falls and to make comparisons by age, gender, race, and residence (nursing home vs community). A fall was reported as the cause for EMS summons in 15.1% (613 of 4,058) of cases. Transport rates in 1990 for falls were 7.8 per 1,000, 25.4 per 1,000, and 58.5 per 1,000 for the age groups of 65 to 74 years, 75 to 84 years, and 85 years and older. Rates were higher for females than for males (17.1 per 1,000 v 8.1 per 1,000) and higher for whites than for African-Americans (14.3 per 1,000 v 10.3 per 1,000). Rates for nursing home residents were four times that of community residents (70.6 per 1,000 v 16.0 per 1,000). Over 50% of nursing home fallers were transported between midnight and 0400 compared with 25% of community dwellers. EMS summons for older adults reporting a fall accounts for a significant portion (15%) of all transports in this county. Computerized EMS data demonstrated patterns of falls among the elderly that are consistent with known demographic factors. The potential for using computerized EMS data as a practical means of community surveillance should be further explored.

Accidental Falls↗
PubMed1994

Abnormalities of fibrillin in acquired cutis laxa.

BACKGROUND: Degeneration of elastic tissue in acquired cutis laxa has been previously described, but microfibrils have not been adequately studied. OBJECTIVE: We determined whether the microfibrillar component of elastic tissue is affected in skin of a patient with acquired cutis laxa. METHODS: Lesional skin was examined with indirect immunofluorescence and immunoelectron microscopy with antibodies to fibrillin. RESULTS: Indirect immunofluorescence showed a reduction in the distribution of fibrillin in the papillary dermis, where there was loss of the usual pattern of microfibrils perpendicular to the epidermis. Immunoelectron microscopy showed a typical distribution of elastic microfibrils around elastin of normal skin. In skin affected by cutis laxa microfibrils appeared morphologically normal but appeared less frequently in selected sites. CONCLUSION: The microfibrillar component of elastic fibers was reduced in the papillary dermis of this patient with acquired cutis laxa.

Actin Cytoskeleton↗
PubMed1994

[Anesthesia for MRI examination].

Magnetic resonance imaging (MRI) requires the patients to stay for 30-45 min in a magnetic closed noisy space. Therefore most children and agitated adults require general anaesthesia or sedation in order to high quality images. Anaesthesia may be given by several routes (TIVA, inhalational or intrarectal administration) using common drugs. However, the magnetic field limits the selection of patients undergoing MRI and the spectrum of anaesthetic and monitoring equipment. The magnetic field may have deleterious effects on implanted ferromagnetic devices. It may attract objects towards the magnet centre at a dangerous speed. Moreover it may disturb the function of monitors and anaesthesia machines which should be tested for a specific magnetic field strength before introducing their use in a given MRI unit.

Adolescent↗
PubMed1994

A prospective comparative study of the compression hip screw and the gamma nail.

Achieving bony union and early weight bearing in peritrochanteric femur fractures poses a continuous challenge for the orthopedic surgeon. Current standards of surgical fixation for the myriad possible fracture patterns include the compression hip screw (CHS), the 90 degrees/95 degrees blade plate, and locked intramedullary nails. The gamma nail (GN) was designed as a "hybrid" of these devices, combining theoretical biomechanical advantages that should allow earlier postoperative weight bearing with surgical technique advantages that should decrease operative morbidity. Because these theoretical advantages were unproven in a clinical setting, we prospectively randomized 75 consecutive patients with peritrochanteric femur fractures into two groups to examine the fixation of these fractures with the GN as compared to the CHS. We found no significant differences in preoperative or intraoperative parameters. Postoperatively, the subtrochanteric fracture group treated with the GN achieved earlier weightbearing status, although this was not statistically significant. 72 patients were available for follow-up at a minimum of 6 months. All fractures had clinically and radiographically healed, and 94% of the patients continued to be ambulatory. Major complications included missed distal locking screws (one patient), cutting out of the lag screw superiorly in the femoral head (two patients), and a femur fracture at the distal end of the GN (one patient). In our series, the GN produced clinical results commensurate with current standards of fixation for peritrochanteric femur fractures. Although the GN allowed earlier independent weightbearing status in patients with subtrochanteric fractures, the procedure was technically more demanding and had a significant learning curve.

Adult↗