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Biomedical subjects

C Heller

Publications and source records attributed to C Heller.

At least 55 records · Page 3Linked to original sources
PubMed1992

Field inversion gel electrophoresis in denaturing polyacrylamide gels.

The velocities of single stranded DNA molecules in denaturing polyacrylamide gels during symmetric and asymmetric field inversion were measured at different pulse times and gel concentrations. Under the conditions chosen in our study, pulse times as short as a few milliseconds lead to a retardation of DNA molecules larger than 400 bases. We found that a field inversion with an electric field in the forward direction of about double the strength of that applied in the backward direction is a good compromise between the degree of retardation, the temperature control requirements and the run time of the gel.

DNA, Single-Stranded↗
PubMed1992

A short-term psychiatric inpatient program for adolescents.

Third-party payers have become increasingly unwilling to fund long-term hospitalizations for adolescents. Inpatient adolescent programs have had to develop strategies to treat this difficult patient population much more rapidly. In late 1989 a short-term adolescent treatment program, known as the STAT program, was developed and implemented at a private psychiatric hospital in Massachusetts. The program aimed for a two- to three-week length of stay, a reduction of 30 to 50 percent. To accomplish this goal, the program shifted from a treatment-based approach to a focus on crisis management, patient evaluation and stabilization, and transition to outpatient services. Many staff concerns were allayed during the program's implementation. Short-term treatment for adolescents can be viable if appropriate exclusion criteria are developed for admissions and an adequate range of outpatient treatment services are available.

Adolescent↗
PubMed1991

Model and computer simulations of the motion of DNA molecules during pulse field gel electrophoresis.

A model is presented for the motion of individual molecules of DNA undergoing pulse field gel electrophoresis (PFGE). The molecule is represented by a chain of charged beads connected by entropic springs, and the gel is represented by a segmented tube surrounding the beads. This model differs from earlier reptation/tube models in that the tube is allowed to leak in certain places and the chain can double over and flow out of the side of the tube in kinks. It is found that these kinks often lead to the formation of U shapes, which are a major source of retardation in PFGE. The results of computer simulations using this model are compared with real DNA experimental results for the following cases: steady field motion as seen in fluorescence microscopy, mobility in steady fields, mobility in transverse field alternation gel electrophoresis (TFAGE), mobility in field inversion gel electrophoresis (FIGE), and linear dichroism (LD) of DNA in agarose gels during PFGE. Good agreement between the simulations and the experimental results is obtained.

Chemical Phenomena↗
PubMed1991

Biotinylation of transducin and G0 from bovine brain.

A method is described for modifying G proteins with biotin. With transducin, better results were obtained with the amino group-specific derivative BXNHS (biotinyl-epsilon-aminocaproic acid N-hydroxysuccinimide ester) as compared to the -SH-group specific reagent MBB (maleimidobutyrylbiocytin). Modification occurred under conditions preserving functional activity: Interaction of the biotinylated transducin with rod outer segment membranes was shown by its light-dependent association and by a GTP gamma S-binding assay. G0 from bovine brain was also biotinylated under conditions preserving its activity. Biotinyl-alpha 0 was shown to bind to a streptavidin Sepharose matrix. Biotinyl-G proteins, therefore, are proposed as tools for extracting proteins (receptors and effector systems), which interact under specific conditions with G proteins.

Animals↗
PubMed1990

Field inversion gel electrophoresis with different pulse time ramps.

The influence of different pulse time ramps on the separation of yeast chromosomes with field inversion gel electrophoresis (FIGE) was investigated by the means of two dimensional gel electrophoresis. The problem of band inversion, which makes it difficult to distinguish DNA molecules of different size, has been solved by using double randomized pulse times. A major disadvantage of the field inversion technique is thereby overcome, making this system comparable to other pulsed field techniques.

Chromosomes, Fungal↗
PubMed1989

A systematic study of field inversion gel electrophoresis.

The mobilities of oligomers of phage lambda DNA and of yeast chromosomes in agarose gels during field inversion gel electrophoresis (FIGE) were measured at different pulse times and electric fields. Also the ratios between forward and backward pulse times and/or field gradients were varied. The problem of 'band inversion' during FIGE, leading to an ambiguity in the mobility of large DNA fragments, was solved by using two dimensional gel electrophoresis with different parameters in the first and second dimension. The results are compared with those obtained with other pulsed electrophoresis systems and with a theoretical model.

Bacteriophage lambda↗
PubMed1989

Fatal accidental enflurane intoxication.

Among reported cases of abuse of volatile anesthetics there is only one of enflurane intoxication. We report another fatal enflurane intoxication. A 21-year-old man found dead seemed to have experimented with enflurane. Three and one-half days after death high amounts of enflurane were detected in blood, brain, and subcutaneous fat. Gas chromatographic quantification revealed the following high enflurane concentrations: blood: 130 mg/l-1, brain: 350 mg/l-1, and subcutaneous fat: 100 mg/l-1. Histologic signs of drug-induced damage were lacking. No suicide intentions became known. It was concluded that the young man died of an accidental intoxication while abusing enflurane.

Adult↗
PubMed1989

DNA sequencing with direct blotting electrophoresis and colorimetric detection.

We describe optimized procedures for colorimetrically-detected DNA sequencing with direct blotting electrophoresis. One-step protocols for Sequenase and Klenow enzyme are given. The clapping technique has been adapted to allow convenient casting of very thin gels with an optimal lower gel (transfer) surface. This gives very sharp band patterns, enabling more than 350 bases from a single loading to be read with confidence. The crucial points for direct blotting electrophoresis are discussed. Background problems resulting from unspecific binding of streptavidin to the nylon membranes have been eliminated by the use of high concentrations of SDS in the incubation buffer; and using a single large glass tube for all incubation and washing steps is a very convenient and effective development protocol. Automation of the colorimetric development process is described.

Base Sequence↗
PubMed1986

[Etryptamine, a new designer drug with a fatal effect].

Capsules with etryptamine have been commonly available on the market since the middle of 1985. Up to 1962 this CNS-stimulating, monoamine-oxidase-inhibiting drug was sold as an antidepressant (Monase). A case of fatal intoxication is reported. The exact amount of etryptamine taken several hours before death are not known, but it could have been in the range of 700 mg. This drug was detected in tissue by means of common analytical techniques (GLC, GC-MS, HPLC, TLC). Etryptamine cross-reacts with the Emit-st amphetamine assay and can also be detected in urine using these techniques. The level in postmortem blood was 1.1 mg/l. The effects the young man showed were like those known from intoxication with amphetamines, MAO inhibitors, and thymoleptics. Malignant hyperthermia is discussed as a possible cause of death. It is suggested that trade in etryptamine should be controlled.

Adult↗
PubMed1984

Influence of phosphatase inhibitors and nucleotides on [3H]dexamethasone binding in cytosol of human placenta.

The purpose of this investigation was to establish the properties of [3H]dexamethasone binding sites in cytosol of human placenta at term. Cytosol containing 20 mM sodium molybdate (MoO4Na2) was incubated for 120 min at 20 degrees C with 40 nM [3H]dexamethasone. The following properties were observed: (a) a single population of binding sites of high affinity and low capacity was measured by Scatchard analysis; (b) potent glucocorticoids such as dexamethasone and cortisol displaced the tritiated ligand, progesterone showed an intermediate activity, whereas cortisone, testosterone and 17 beta-estradiol were ineffective competitors; (c) ultracentrifugation on 16-41% glycerol gradients containing 20 mM MoO4Na2 yielded sedimentation values of 10.25 +/- 0.35 S (n = 4 placentas); (d) the binding sites could be differentiated from the enzyme 11 beta-hydroxysteroid dehydrogenase, as the activity of the former, but not that of the latter, was greatly dependent on the presence of MoO4Na2 in the incubation medium. Inactivation of binding sites labelled with [3H]dexamethasone by incubation at 20 degrees C was prevented by phosphatase inhibitors such as 20 mM MoO4Na2 (P less than 0.01), 20 mM sodium tungstate (WO4Na2) (P less than 0.01) and to a lower extent by 5 mM ATP and cAMP (P less than 0.05). 50 mM NaF, 5 mM GTP or cGMP had no effect. The protection afforded by MoO4Na2 and WO4Na2 was correlated with a significant inhibition of the activity of acid phosphatase, but not alkaline phosphatase. Neither ATP nor cAMP modified phosphatase activity. It is suggested that binding sites for [3H]dexamethasone in cytosol of human placenta showed properties similar to those described for glucocorticoid receptors in target cells, and that these binding sites are regulated by phosphorylation and dephosphorylation mechanisms.

Acid Phosphatase↗
PubMed1983

Inhibition of progesterone synthesis in placenta by administration of dexamethasone to pregnant rats.

Glucocorticoid receptors have been detected in placenta from several species, including the rat, although the biological function of corticoids is unknown in placenta from the latter species. The present experiments examined the effect of glucocorticoid treatment on placental progesterone biosynthesis from endogenous precursors by incubated basal zone trophoblast and labyrinthine zone of placentas from adrenalectomized-ovariectomized rats at the end of pregnancy. It was found that a higher proportion of synthesized progesterone was retained in the tissue than that released into the incubation medium. Treatment of rats on the 17th-18th day of pregnancy with 10 micrograms/ml of dexamethasone in the drinking saline for 3 days, produced a significant inhibition of progesterone detected in tissue and medium of incubated placental zones. In vitro addition of dexamethasone (10(-4) M) was also effective in reducing progesterone in the placental zone studied (LZ). Serum progesterone of intact rats was in the range of rats near parturition (approx 25 ng/ml) and dropped to almost undetectable levels in rats with adrenalectomy and ovariectomy, with or without dexamethasone treatment, suggesting that in late pregnancy the rat placenta does not contribute significantly to circulating levels of progesterone. This glucocorticoid effect could not be extended to estrogens, as we, in accord with the work of other groups, failed to detect estrogen synthesis in rat placenta. It is suggested that a function for glucocorticoid receptors in rat placenta may be the inhibition of local progesterone production.

Adrenalectomy↗
PubMed1983

The placenta as a glucocorticoid target tissue: exchange assay of (3H)-dexamethasone binding and effect of steroids on receptor content.

Binding of (3H)-dexamethasone was studied in high speed supernatant (HSS) of basal zone trophoblast and labyrinthine zone of rat placenta using an exchange assay. The system showed the following characteristics: (1) maximum binding was attained after 120 min of incubation; (2) molybdate was required in the medium to measure binding sites at 20 degrees C and equilibrium conditions; (3) exchange was near 90-100% between ligand and corticosterone added during a preincubation; (4) low capacity (190-250 fmoles/mg protein), high affinity (Kd 10(-8) M) binders were determined by saturation analysis; (5) competition with other steroids in vitro revealed that in basal zone trophoblast, only dexamethasone displaced the ligand, whereas in labyrinthine zone corticosterone, progesterone and testosterone competed to a smaller degree than dexamethasone. We have also studied the effect of in vivo treatment of pregnant rats for four days with dexamethasone, corticosterone, estradiol, progesterone or testosterone, on (3H)-dexamethasone binding. Of all tested compounds, only dexamethasone treatment (which was suspended 24 h before the experiment to prevent receptor occupancy by exogenous hormone) significantly decreased binding of the tritiated hormone in HSS of labyrinthine zone and basal zone trophoblast. These results suggest that dexamethasone regulates its own receptor in placenta. The physiological aspect of this phenomenon requires elucidation of the role of glucocorticoids on placental function in the rat.

Animals↗
PubMed1978

Specific cell-induced transformation of Paramecium surface antigens.

Paramecia may induce in other paramecia specific changes in the expression of genes determining surface protein synthesis, probably via cell-to-cell contact. Transformation from one antigenic type to a newly induced one is stimulated by the pretreatment of a cell with 5-fluorouracil. These observations are considered in terms of the regulation of the activity of genes in stable cells and in unstable cells which tend to transform spontaneously.

Animals↗
PubMed1976

Rhmod, a second kindred (Craig).

Three Rhmod siblings were found to have identical Rh: w1, w2, -3, -4, w5 (see article) phenotypes. All had stomatocytic hemolytic anemia. On quantitative hemagglutination studies, as well as on hand tests, all Rh antigens were not equally depressed. Rh17 (Hr0, 'not D') and Rh29 (RH, 'total Rh') were both normal. Rh5 (hr", e) was only slightly depressed. Rh25 (LW) had 50% of the expression expected in normal Rh:-1 cells. Rh1 (Rh0, D), Rh13 (RhA), Rh14 (RhB), Rh15 (RhC), and Rh16 (RhD), were severely depressed. Rh2 (rh', C) was depressed, while Rh7 (rhi, Ce) was absent. Both Rh19 (hrS) and Rh31 (hrB) were depressed. Rh12 (rhG, G) was distinctly depressed, scoring considerably less than rGrG red cells. The unrelated parents, the child of the proposita, and some siblings of each parent showed lessened depression of Rh antigens without displaying the consistent pattern that might be expected from a presumed single suppressor gene. Absence of a consistent pattern may have resulted from differing Rh genotypes, but a frequently observed depression involved Rh14, Rh15, and Rh16 (RhB, RhC, and RhD) without an effect on either Rh1 (RH3 or D) or Rh13 (RhA).

Female↗