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Biomedical subjects

R L Johnson

Publications and source records attributed to R L Johnson.

At least 217 records · Page 12Linked to original sources
PubMed1990

The biophysical profile. A literature review and reassessments of its usefulness in the evaluation of fetal well-being.

Antenatal monitoring studies to assess fetal well-being and to identify the compromised fetus are in widespread use. This literature review analyzes the theoretical basis for fetal monitoring and the clinical research that has defined its utility, and it discusses the variations in protocols and scoring systems for the biophysical profile. While recognizing that there, is as yet, no consensus on the optimal monitoring protocol, the authors espouse one approach in which the cardiac nonstress test and the amniotic fluid volume are the initial tests, with full biophysical profile reserved for abnormal test outcomes. This approach to monitoring should be expeditious without diminishing its predictive value.

Embryonic and Fetal Development↗
PubMed1990

An outbreak of illness among aerospace workers.

A multispecialty panel of physicians evaluated a case series of 53 composite-materials workers in a large aircraft manufacturing facility who filed workers' compensation claims for illness labeled by the media as the "aerospace syndrome." Possible skin and respiratory tract exposures included formaldehyde, phenol, particulates, epoxy resins, and trace organic solvents, but measured concentrations were well below all regulatory and consensus standards. Most workers had histories of transient skin or respiratory tract irritation consistent with the known potential toxicity of these materials. None of the workers tested had immunoglobulin IgG or IgE antibodies to human serum albumin complexed with formaldehyde. A majority (74%) met DSM-III-R [Diagnostic and Statistical Manual of Mental Disorders, 3rd edition, revised] criteria for major depression, panic disorder, or both. Most of these psychiatric disorders were of a recent onset, correlating in time with the use of phenol- and formaldehyde-impregnated composite material. Psychosocial factors were thought to have played a major role in the high prevalence of illness in this group and should be evaluated directly in well-controlled epidemiologic studies of similar crisis-building situations in the future.

Air Pollutants, Occupational↗
PubMed1989

Structure of (3S)-3-tert-butyloxycarbonylamino-2-piperidone.

C10H18N2O3, Mr = 214.27, monoclinic, P2(1), a = 15.515 (2), b = 6.730 (1), c = 12.541 (2) A, beta = 113.6 (2) degrees, V = 1200.0 A3, Z = 4, Dx = 1.186 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 0.54 cm-1, F(000) = 464, T = 295 K. The final R value for 1611 observed (3139 unique) reflections is 0.055. In both the independent molecules A and B of the asymmetric unit of the title compound, the conformation of the urethane moiety is trans. The lactam group of molecule A is non-planar, the C(9)-N(2)-C(10)-C(6) torsion angle being 12.4 (14) degrees. One main difference between molecules A and B is in the value of the phi[C(5)-N(1)-C(6)-C(10)] torsion angle [52.3 (11) degrees for molecule A while -86.5 (10) degrees for molecule B] as a consequence of a rotation of the ring relative to the tert-butyloxycarbonylamino substituent. A second major difference is the delta-lactam ring conformation which is approximate half-chair for molecule A while boat for molecule B.

Chemical Phenomena↗
PubMed1989

Crystal-state structural analysis of two gamma-lactam-restricted analogs of Pro-Leu-Gly-NH2.

The crystal structures of two analogs of Pro-Leu-Gly-NH2 (1), containing a gamma-lactam conformational constraint in place of the -Leu-Gly- sequences, are described. The highly biologically active (S,R)-diastereomer 2a is semi-extended at the C-terminus, with the N-terminal Pro residue in the unusual "C5" conformation [psi 1 = -0.8(15) degrees] stabilized by a (peptide)N-H...N(amino) intramolecular H-bond [the N(3)...N(4) separation is 2.687(11)A]. Conversely, the N,N'-isopropylidene aminal trihydrate of the (S,S)-diastereomer 2b, compound 3, adopts a beta-bend conformation at the C-terminus, as already reported for 1. However, the backbone torsion angles [phi 2 = 57.4(4), psi 2 = -129.9(3) degrees; psi 3 = -92.3(4), phi 3 = 6.4(5) degrees] lie close to the values expected for the corner residues of an ideal type-II' beta-bend. A weak intramolecular 4----1 H-bond is seen between the Gly carboxyamide anti-NH and Pro C = O groups. In the newly formed 2,2,3,4-tetraalkyl-5-oxo-imidazolidin-1-yl moiety the psi 1 torsion angle is 12.9(4) degrees and the intramolecular N(3)...N(4) separation is 2.321(4)A.

Lactams↗
PubMed1989

Analogs of oxytocin containing a pseudopeptide Leu-Gly bond of cis and trans configuration.

Analogs of deamino-oxytocin wherein the Leu-Gly peptide bond has been replaced by a tetrazole moiety or by a double bond of trans configuration were synthesized and their biological activities evaluated. Trans double bond was found to be the most appropriate substitution for the amide bond (uterotonic activity 24% of the deamino-oxytocin). In the case of all three analogs low but prolonged galactogogic activity was found and the ratio of uterotonic in vitro and in vivo activity was surprisingly high (ranging from 4.5 to 20).

Animals↗
PubMed1989

Diffusion of the Interspecies Electron Carriers H(2) and Formate in Methanogenic Ecosystems and Its Implications in the Measurement of K(m) for H(2) or Formate Uptake.

We calculated the potential H(2) and formate diffusion between microbes and found that at H(2) concentrations commonly found in nature, H(2) could not diffuse rapidly enough to dispersed methanogenic cells to account for the rate of methane synthesis but formate could. Our calculations were based on individual organisms dispersed in the medium, as supported by microscopic observations of butyrate-degrading cocultures. We isolated an axenic culture of Syntrophomonas wolfei and cultivated it on butyrate in syntrophic coculture with Methanobacterium formicicum; during growth the H(2) concentration was 63 nM (10.6 Pa). S. wolfei contained formate dehydrogenase activity (as does M. formicicum), which would allow interspecies formate transfer in that coculture. Thus, interspecies formate transfer may be the predominant mechanism of syntrophy. Our diffusion calculations also indicated that H(2) concentration at the cell surface of H(2)-consuming organisms was low but increased to approximately the bulk-fluid concentration at a distance of about 10 mum from the surface. Thus, routine estimation of kinetic parameters would greatly overestimate the K(m) for H(2) or formate.

Journal Article↗
PubMed1989

Sustained maximal ventilation after endurance exercise in athletes.

Although impaired respiratory muscle performance that persists up to 5 min after exercise is stopped has been demonstrated during exhaustive exercise in normal young men, it is not known whether impaired respiratory muscle function follows endurance exercise to exhaustion in highly trained athletes. To study the effects of exercise on sustained maximal voluntary ventilation immediately after exercise, eight elite cross-country skiers performed a 4-min maximal sustained ventilation (MSV) test before and immediately after exhaustive exercise. Subjects were encouraged to maintain maximal ventilation (VE) throughout the MSV test. To encourage greater effort, rapid visual feedback of VE was provided on a computer terminal along with a target VE based on their 12-s maximum voluntary ventilation (MVV). The subjects (7 males, 1 female) were 18.5 +/- 0.9 yr old (mean +/- SD) and exercised for 62.5 +/- 16.7 min at 77 +/- 5% of their maximum oxygen consumption during which average VE was 106.7 +/- 24.2 l/min BTPS. The mean MVV was 196.0 +/- 29.9 l/min or 107% of their age- and height-predicted MVV. Before exercise the MSV was 86% of the MVV or 176.7 +/- 30.5 l/min, whereas after exercise the MSV was 90% of the MVV or 180.3 +/- 28.9 l/min (P = NS). The total volume of gas expired during the 4-min MSV was 706.7 +/- 121.9 liters before and 721.2 +/- 115.5 liters after exercise (P = NS). In this group of athletes, exhaustive exercise produced no deleterious effects on the ability to perform a 4-min MSV test immediately after exercise.

Adolescent↗
PubMed1989

G-protein-linked signal transduction systems control development in Dictyostelium.

G-protein-linked cAMP receptors play an essential role in Dictyostelium development. The cAMP receptors are proposed to have seven transmembrane domains and a cytoplasmic C-terminal region. Overexpression of the receptor in cells, when the endogenous receptor is not present, results in a 10- to 50-fold increase in cAMP-binding sites. Antisense cell lines, which lack cAMP receptors, do not enter the developmental program. Ligand-induced phosphorylation is proposed to occur on serine and threonine residues in the receptor C-terminus. The kinetics of receptor phosphorylation and dephosphorylation correlate closely with the shift of receptor mobility and the adaptation of several cAMP-induced responses. Two alpha-subunits, G-alpha-1 and G-alpha-2, have been cloned and specific antisera developed against each. Both subunits are expressed as multiple RNAs with different developmental time courses. The mutant Frigid A has a functional defect in G-alpha-2 which prevents it from entering development. We propose that G-protein-linked receptor systems will be a major component in the development of many organisms.

Amino Acid Sequence↗
PubMed1989

Back-country water treatment to prevent giardiasis.

This study was conducted to provide current information on the effectiveness of water treatment chemicals and filters for control of Giardia cysts in areas where treated water is not available. Four filters and seven chemical treatments were evaluated for both clear and turbid water at 10 degrees C. Three contact disinfection devices were also tested for cyst inactivation. Filters were tested with 1-liter volumes of water seeded with 3 x 10(4) cysts of G. lamblia produced in gerbils inoculated with in vitro cultured trophozoites; the entire volume of filtrate was examined for cyst passage. Chemical treatments were evaluated at concentrations specified by the manufacturer and for contact times that might be expected of hikers (30 minutes) and campers (eight hours, i.e., overnight). Two of the four filter devices tested were 100 percent effective for Giardia cyst removal. Of the other two filters, one was 90 percent effective and the other considerably less effective. Among the seven disinfection treatments, the iodine-based chemicals were all significantly more effective than the chlorine-based chemicals. None of the chemical treatments achieved 99.9 percent cyst inactivation with only 30-minute contact. After an eight-hour contact each of the iodine but none of the chlorine preparations achieved at least 99.9 percent cyst inactivation. None of the contact disinfection devices provided appreciable cyst inactivation. Heating water to at least 70 degrees C for 10 minutes was an acceptable alternative treatment.

Animals↗
PubMed1989

Economic benefits of hospital system automation.

The healthcare community is the only industry whereby systems have not been largely purchased for the cost savings, return on investment, productivity improvement or competitive advantage. Yet all four reasons are believed to apply to healthcare. The savings documented in this article are not all inclusive, but instead are representative of savings which have been realized, and are presented in summary form so the healthcare community will begin to realize there are advantages to installing hospitalwide patient care and clinical systems.

Cost-Benefit Analysis↗
PubMed1989

Fetal goitrous hypothyroidism. A new diagnostic and therapeutic approach.

We present a first case in whom fetal hypothyroidism with goiter was both successfully diagnosed and treated in utero. An obstetrical sonogram at 33 weeks revealed a bilobed fetal neck mass, compatible with enlarged thyroid gland, associated with neck hyperextension, reduced gastric fluid, and polyhydramnios. Umbilical blood sampling after volume reduction amniocentesis confirmed fetal hypothyroidism with a euthyroid mother. Fetal T4 measured 1.3 micrograms/dl, free T4 0.3 ng/dl, and thyroid-stimulating hormone 186 microU. Intraamniotic levothyroxine, 500 micrograms, was given twice with a 14-day interval. The head flexed, gastric fluid increased, and amniotic fluid levels returned to normal. Prenatal (36 weeks) and neonatal blood sampling demonstrated return to euthyroid indices. Ultrasonic estimates of thyroid volume decreased by over 50%. Vaginal delivery at 39 weeks was uncomplicated. The newborn appeared normal and is being maintained on thyroid replacement therapy.

Adult↗
PubMed1988

A chemoattractant receptor controls development in Dictyostelium discoideum.

During the early stages of its developmental program, Dictyostelium discoideum expresses cell surface cyclic adenosine monophosphate (cyclic AMP) receptors. It has been suggested that these receptors coordinate the aggregation of individual cells into a multicellular organism and regulate the expression of a large number of developmentally regulated genes. The complementary DNA (cDNA) for the cyclic AMP receptor has now been cloned from lambda gt-11 libraries by screening with specific antiserum. The 2-kilobase messenger RNA (mRNA) that encodes the receptor is undetectable in growing cells, rises to a maximum at 3 to 4 hours of development, and then declines. In vitro transcribed complementary RNA, when hybridized to cellular mRNA, specifically arrests in vitro translation of the receptor polypeptide. When the cDNA is expressed in Dictyostelium cells, the undifferentiated cells specifically bind cyclic AMP. Cell lines transformed with a vector that expresses complementary mRNA (antisense) do not express the cyclic AMP receptor protein. These cells fail to enter the aggregation stage of development during starvation, whereas control and wild-type cells aggregate and complete the developmental program within 24 hours. The phenotype of the antisense transformants suggests that the cyclic AMP receptor is essential for development. The deduced amino acid sequence of the receptor reveals a high percentage of hydrophobic residues grouped in seven domains, similar to the rhodopsins and other receptors believed to interact with G proteins. It shares amino acid sequence identity and is immunologically cross-reactive with bovine rhodopsin. A model is proposed in which the cyclic AMP receptor crosses the bilayer seven times with a serine-rich cytoplasmic carboxyl terminus, the proposed site of ligand-induced receptor phosphorylation.

Amino Acid Sequence↗
PubMed1988

Silicone rubber catheter venography using standard angiographic techniques.

Single- and double-lumen silicone rubber central venous catheters were subjected to in vitro destructive testing. Using this data we devised a clinical technique for the detection of central venous thrombosis incorporating mechanical injection of the catheters, serial filming, and magnification radiography. In 20 patients studied, thrombosis was detected in 12 and extravasation in 3. Two partially occluded catheters burst during forceful injection. Our technique demonstrated the presence and extent of thrombosis at the catheter tip more clearly than did other venographic methods and has been especially useful in assessing the results of thrombolytic therapy.

Catheterization, Central Venous↗