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Biomedical subjects

J Curry

Publications and source records attributed to J Curry.

54 records · Page 3Linked to original sources
PubMed1992

Cloning and expression of an embryo-specific mRNA up-regulated in hydrated dormant seeds.

Dormant seeds do not germinate when imbibed in water even when conditions are favorable for germination. These hydrated seeds remain viable, but growth-arrested for weeks due to unknown restrictions within the embryo. As a model system for the study of the molecular processes occurring in dormant seeds, we have chosen to examine gene expression in Bromus secalinas, a grass species that produces seeds with high levels of embryonic dormancy. Using differential screening for mRNAs present in hydrated dormant embryos, we have identified a cDNA clone, pBS128, that encodes a mRNA transcript found in the embryos of hydrated seeds of B. secalinus as well as in embryos from mature dry seeds. Striking differences in pBS128 transcript levels appear upon hydration of dormant and nondormant seeds. Upon imbibition pBS128 transcript levels increase over four-fold in dormant seeds, but rapidly decline and disappear in nondormant seeds, which subsequently germinate. The pBS128 transcript appears to be embryo-specific since the transcript is not detectable in either non-stressed or dehydrated seedling tissue. Application of 50 microM ABA to nondormant seeds arrests germination and enhances pBS128 transcript levels. The nucleotide sequence of the nearly full-length pBS128 cDNA shows no homology to other reported genes, and the putative protein sequence does not exhibit the hydrophilic characteristics of the ABA-responsive LEA (late embryogenesis abundant) proteins.

Abscisic Acid↗
PubMed1991

Sequence analysis of a cDNA encoding a group 3 LEA mRNA inducible by ABA or dehydration stress in wheat.

A cDNA clone (pMA2005) of a Group 3 LEA (late embryogenesis abundant) protein has been sequenced from wheat. The wheat cDNA clone codes for a protein with ten tandem repeats of an 11 amino acid sequence and has homology to other Group 3 LEAs reported in barley, carrot, cotton and rape (L. Dure et al., Plant Mol Biol 12: 475-486, 1989). The deduced amino acid sequence indicates that the wheat protein has a molecular weight of 23,000 and is a basic, hydrophilic protein. Northern analysis with the cDNA clone shows that dehydration of wheat shoot tissue results in increased transcript levels that correlate with increases in endogenous ABA.

Abscisic Acid↗
PubMed1991

srfA is an operon required for surfactin production, competence development, and efficient sporulation in Bacillus subtilis.

The srfA locus of Bacillus subtilis is defined by a transposon Tn917 insertion and is required for production of the peptide secondary metabolite surfactin. The srfA locus was isolated by cloning the DNA flanking srfA::Tn917 insertions followed by chromosome walking. The cloned region is an operon of over 25 kb which covers the transcription initiation region but not the intact 3' end of srfA. csh-293, which was previously identified as a Tn917lac mutation that impairs competence development and causes a conditional defect in sporulation, was known to be located in the vicinity of the srfA locus within the B. subtilis genome. The csh-293::Tn917lac mutation was discovered to cause a defect in surfactin production and was shown to be located in the srfA operon by its cotransformation with srfA mutations and by Southern hybridization analysis. Insertion mutations in srfA, created by the chromosomal integration of plasmids bearing overlapping srfA DNA fragments, were examined for their effects on surfactin production, competence, and sporulation. All three processes were found to require the intact 5' half of the srfA operon, whereas the 3' half of srfA was found to be required for sporulation and surfactin production but not competence. These experiments show that srfA gene products function in B. subtilis cell specialization and differentiation.

Amino Acid Sequence↗
PubMed1991

Role of fitness in mediating stress: a correlational exploration of stress reactivity.

Researchers have investigated the effect of exercise on reducing subjects' responsiveness to stress. Results from the initial studies were positive, yet these studies often did not use objective measures of fitness. This investigation applied more rigorous methodology than past experiments to assess the relationship between fitness and reactivity to stress. Maximal oxygen consumption was measured to indicate the fitness of recreational cyclists who were then exposed to three stressful situations (mental subtraction, speech preparation, and the cold pressor test). Heart rate, frontalis electromyographic (EMG) levels, and self-report of tension were monitored during the stress-inducing tasks. Physical fitness was significantly related to heart rate taken during the subtraction and cold pressor tasks, with EMG during subtraction, and with self-report during all three stressor tasks. These results further support the hypothesized association of physical fitness and reducing response to stress.

Adaptation, Psychological↗
PubMed1988

Comparison of tactile preferences in children with and without cerebral palsy.

Fifteen normal preschool children and 15 preschool children with cerebral palsy were presented with 10 pairs of objects and asked to identify their preference for one of the objects in each of the pairs. Five objects of different textures were used. The children only handled the objects; they did not view them during testing. The children with cerebral palsy chose hard objects significantly more often than they chose soft objects; the normal children had no significant choice preferences. Eleven of the children with cerebral palsy had choice patterns significantly different from those of the normal children. The apparent preference of the children with cerebral palsy for hard objects and their avoidance of soft objects suggests that they may have decreased tactile awareness and need the greater proprioceptive input that hard objects provide. The findings of this study indicate that preschool children with cerebral palsy may be at high risk for somatosensory disorders, which could markedly affect their hand function.

Cerebral Palsy↗
PubMed1987

Enthalpy-entropy compensations in drug-DNA binding studies.

We present a comparative study of calorimetrically derived thermodynamic profiles for the binding of a series of drugs with selected DNA host duplexes. We use these data to demonstrate that comparisons between complete thermodynamic profiles (delta G zero, delta H zero, delta S zero, delta Cp) are required before drug binding can be used as a probe of DNA conformation, since enthalpy-entropy compensations can cause two drug-DNA binding events to exhibit similar binding free energies (delta G zero) despite being driven by entirely different thermodynamic forces (delta H zero, delta S zero). In this work, we employ a combination of spectroscopic and calorimetric techniques to characterize thermodynamically the DNA binding of netropsin and distamycin (two minor groove-directed ligands), ethidium (an intercalator), and daunomycin (a combined intercalator/groove binder). Our free energy data (delta G zero) show that each drug exhibits similar binding affinities at 25 degrees C for the alternating copolymer duplex poly[d(A-T)].poly[d(A-T)] and for the homopolymer duplex poly(dA).poly(dT). However, our calorimetric measurements reveal that the nature of the thermodynamic forces (delta H zero, delta S zero) that drive drug binding to these two host duplexes at 25 degrees C are entirely different, despite similar binding free energies (delta G zero) and similar salt dependencies (lnK/ln[Na+]). Specifically, the 25 degrees C binding of all four drugs to the alternating copolymer poly[d(A-T)].poly[d(A-T)] is overwhelmingly enthalpy driven, whereas the corresponding binding of each drug to the homopolymer duplex poly(dA).poly(dT) is overwhelmingly entropy driven. Thus, the similar binding free energies (delta G zero) we measure for complexation of each drug with poly[d(A-T)].poly[d(A-T)] and poly(dA).poly(dT) result from compensating changes in the enthalpy and entropy terms. Comparison with the thermodynamic profiles for the complexation of these drug molecules to other DNA host duplexes at 25 degrees C reveals that the binding of each is strongly enthalpy driven, except when the poly(dA).poly(dT) homopolymer serves as the host duplex. This comparison allows us to conclude that poly[d(A-T)].poly[d(A-T)] behaves thermodynamically as the more "normal" host duplex toward drug binding, whereas the entropy-driven binding to the poly(dA).poly(dT) duplex represents "aberrant" behavior. Furthermore, since each of the four drugs exhibits different modes of DNA binding, we conclude that the observed entropy-driven behavior for binding to poly(dA).poly(dT) reflects an intrinsic property of the homopolymer duplex that is perturbed in a common manner upon ligation rather than a common property of all four binding ligands. To rationalize the large positive entropy changes that drive drug complexation with poly(dA).poly(dT) duplex, we propose a model that emphasizes binding-induced perturbations of the more highly hydrated, altered B conformation of the homopolymer. Our results suggest that an aberrant thermodynamic binding profile may reflect an unusual DNA conformation in the host duplex. However, before such a conclusion can be reached, complete thermodynamic binding profiles must be examined, since enthalpy-entropy compensations can cause two binding events to exhibit similar binding constants even when they are driven by very different thermodynamic forces.

Calorimetry↗
PubMed1987

Peritoneal transport of cefonicid.

The pharmacokinetic characteristics of cefonicid, a highly protein-bound expanded-spectrum cephalosporin, were examined in six noninfected, clinically stable patients undergoing continuous ambulatory peritoneal dialysis. After a 1.0-g intravenous dose of cefonicid, the mean concentrations in serum were 105 +/- 25 and 35.6 +/- 14.4 micrograms/ml at 3 and 72 h, respectively. Despite a prolonged half-life in serum of 49.7 +/- 18 h, the penetration into peritoneal fluid was low. The average concentration in dialysate over the 72-h study period was 2.7 micrograms/ml. The serum clearance was 2.6 +/- 1.0 ml/min, and the distribution volume was 0.14 +/- 0.02 liter/kg. Dosage recommendations and clinical considerations for cefonicid use in continuous ambulatory peritoneal dialysis patients are discussed.

Cefamandole↗
PubMed1982

Potentiation of the ganglionic blocking action of norepinephrine by cocaine.

Concentration-response curves for the blocking action of norepinephrine were determined in the isolated stellate ganglion of the hamster. The blocking effect of norepinephrine on the postganglionic compound action potential from preganglionic nerve stimulation at 0.2 Hz was reduced by phentolamine (10(-5) M), but was not altered by propranolol (10(-6) M). Cocaine (10(-6) and 10(-5) M) increased the sensitivity of the ganglion to norepinephrine. These concentrations of cocaine produced less than 25% blockade when applied alone. The local anesthetic, procaine, did not change the sensitivity of the ganglion to norepinephrine. The blockade by norepinephrine in the presence of cocaine was antagonized by phentolamine and unaffected by propranolol. The time course of the blockade by norepinephrine was more rapid in onset and slower in recovery in the presence of cocaine. If it is assumed that cocaine is blocking norepinephrine uptake into cells within the ganglion, these results indicate that the catecholamine uptake mechanism is involved in terminating the blocking action of exogenously applied norepinephrine.

Animals↗
PubMed1977

Culture and microscopy of microorganisms in frozen sections.

A simple method is described in which frozen sections are prepared from tissue cell suspensions with added microorganisms and then cultured. The enhanced growth of the organisms makes their indentification easier. A number of applications is suggested.

Culture Media↗
PubMedDate not supplied

Establishment of a beam line at the Fermi National Accelerator Laboratory for proton radiography.

A proton beam is extracted from the 200-MeV linear accelerator at the Fermi National Accelerator Laboratory to investigate the efficacy of proton radiography in medical diagnosis. Fluence rates from 2 X 10(3) to 2 X 10(5) protons/cm2s over a 28-cm diameter field are obtained with a full width at half-maximum beam-energy spread of less than 3.61 MeV. The system is designed to radiography most parts of the human body, including the head, with high-speed screen-film as the imaging medium. Beam extraction and test results along with the medical implications of the beam quality are reported.

Laboratories↗
PubMedDate not supplied

Stereotactic core-needle biopsy of the breast: a report of the Joint Task Force of the American College of Radiology, American College of Surgeons, and College of American Pathologists.

A national task force consisting of members from the American College of Radiology, the American College of Surgeons, and the College of American Pathologists examined the issues surrounding stereotactic core-needle biopsy for occult breast lesions. Their report includes indications and contraindications, informed consent, specimen handling, and management of indeterminate, atypical, or discordant lesions.

Biopsy, Needle↗