Biomedical subjects
Publications and source records attributed to B H Johnson.
In the last fifty years while there have been dramatic changes in the science and technology of pediatrics, there have also been major changes in the participation of families in child health care. Since its founding, ACCH has helped to shape these changes and will continue this leadership in addressing the challenges of the 1990's.
The inhalation anesthetic, desflurance (I-653), is a methyl ethyl ether halogenated entirely with fluorine and differing from isoflurance only in the substitution of fluorine for chlorine on the alpha-ethyl carbon. Relative to presently used potent inhalation anesthetics, desflurane has low blood/gas (0.42) and oil/gas (18.7) partition coefficients. These indicate that it will undergo rapid washin and washout (and hence rapid induction of and recovery from anesthesia) and have a MAC value of about 5%. In the present study we demonstrate that desflurane possesses these characteristics in healthy young volunteers. After a 10-min exposure to desflurane the ratio of alveolar (FA) (determined by end-tidal sampling) to inspired (FI) concentration (FA/FI) was 0.82. Washout was similarly rapid; 10 min after discontinuing administration of desflurane, the alveolar concentration relative to the last concentration during administration of anesthetic (FAO) was 0.11 (FA/FAO). These values are similar to those for nitrous oxide. Volunteers responded to commands an average of 2.7 min after discontinuing anesthetic administration. The values for MAC-awake and MAC (the latter determined by tetanic stimulation of the ulnar nerve using surface electrodes) were 2.42% and 4.58% and the ratio of the former to the latter was 0.53.
Evaluation of a new inhaled anesthetic requires determination of the anesthetic's potential to predispose to ventricular (and other) arrhythmias in an animal model. This need poses logistic and economic burdens if the effects of large numbers of new anesthetics are to be surveyed. We have devised a technique for determining the potential of a new anesthetic to produce arrhythmias using a smaller animal (the rat) than previous methods. Our technique requires preliminary selection of male rats sensitive to the arrhythmias produced by the intravenous injection of epinephrine. Rats are tested after demonstrating the desired sensitivity. Using this model, rats given 1.4% halothane developed premature ventricular extrasystoles at a dose of 2.4 +/- 1.0 micrograms/kg epinephrine, and those receiving 1.6%-2.2% isoflurane at a dose of 28 +/- 24 micrograms/kg. This difference in dose requirements is about two to three times that in humans.
To determine the cardiovascular actions of drugs commonly combined with inhalation anesthetics, we administered one drug from each of several classes of adjuvants to seven swine already anesthetized with equipotent concentrations (1.2 MAC) of desflurane, formerly I-653, a new inhaled anesthetic, or isoflurane. Succinylcholine (1 and 2 mg/kg), atracurium (0.6 mg/kg), and atropine (5 micrograms/kg) plus edrophonium (5 mg/kg) had no cardiovascular effects. Fentanyl was given in amounts that decreased MAC for the inhaled anesthetics by 25%-35%. A dose of 50 micrograms/kg IV had no cardiovascular effects during either anesthetic, whereas 100 micrograms/kg IV modestly increased systemic vascular resistance without changing other variables. Naloxone (100 micrograms/kg IV) during infusion of fentanyl decreased systemic vascular resistance and increased cardiac output during both desflurane and isoflurane anesthesia, increased heart rate during only isoflurane anesthesia, and did not affect mean arterial blood pressure during either anesthetic. Thiopental (2.5 and 5.0 mg/kg IV) decreased mean aortic blood pressure, cardiac output, stroke volume, and systemic vascular resistance during both anesthetics without altering heart rate or left- or right-sided cardiac filling pressures. The addition of 60% nitrous oxide caused no cardiovascular changes during desflurane anesthesia, but increased systemic vascular resistance and decreased cardiac output and stroke volume during isoflurane without altering heart rate or cardiac preload. We conclude that the usual clinical doses of adjuvants commonly administered during anesthesia have no untoward cardiovascular actions during 1.2 MAC desflurane or isoflurane anesthesia in swine.
Desflurane, formerly known as I-653 (CF2H-O-CFH-CF3), is a new inhalation anesthetic derived by fluorine substitution for the alpha-ethyl chlorine of isoflurane (CF2H-O-CClH-CF3). The lower solubility and increased stability of desflurane provided by the C-F bond lessen biotransformation to potentially hepatotoxic metabolites. Repeated administration of desflurane to rats, with or without induced hepatic enzymes, does not result in evidence of hepatic injury. In the recent study we extended the tests for liver cell injury to another species, the pig. Our test included prolonged exposure to desflurane or isoflurane, both in the absence and presence of commonly used adjuvants. We measured plasma alanine aminotransferase activity in eight young female swine anesthetized in random order with desflurane (0.8-1.6 MAC) and isoflurane (0.7-1.4 MAC), for a total dose of about 5.5 MAC-hours of each anesthetic, 3-8 days apart. Plasma alanine aminotransferase activities remained in the normal range, and were not significantly greater over baseline values in samples drawn immediately after, 4 h after, or 3-8 days after (mean +/- SD, 6.1 +/- 2.1) the administration of either anesthetic was discontinued after the first study with either desflurane or isoflurane. Five additional pigs were given a mean total dose of 9.7 MAC-hours of desflurane or isoflurane in conjunction with succinylcholine, N2O, fentanyl, naloxone, atracurium, thiopental, edrophonium, and atropine. No changes in plasma alanine aminotransferase activity were detected in blood samples drawn at termination of the anesthesia, 24 h later, and 4-7 days later (mean +/- SD, 5.8 +/- 1.3).(ABSTRACT TRUNCATED AT 250 WORDS)
We tested the prediction that the alveolar washin and washout, tissue time constants, and pulmonary recovery (volume of agent recovered during washout relative to the volume taken up during washin) of desflurane, sevoflurane, isoflurane, and halothane would be defined primarily by their respective solubilities in blood, by their solubilities in tissues, and by their metabolism. We concurrently administered approximately one-third the MAC of each of these anesthetics to five young female swine and determined (separately) their solubilities in pig blood and tissues. The blood/gas partition coefficient of desflurane (0.35 +/- 0.02) was significantly smaller (P less than 0.01) than that of sevoflurane (0.45 +/- 0.02), isoflurane (0.94 +/- 0.05), and halothane (2.54 +/- 0.21). Tissue/blood partition coefficients of desflurane and halothane were smaller than those for the other two anesthetics (P less than 0.05) for all tissue groups. As predicted from their blood solubilities, the order of washin and washout was desflurane, sevoflurane, isoflurane, and halothane (most to least rapid). As predicted from tissue solubilities, the tissue time constants for desflurane were smaller than those for sevoflurane, isoflurane, and halothane. Recovery (normalized to that of isoflurane) of the volume of anesthetic taken up was significantly greater (P less than 0.05) for desflurane (93% +/- 7% [mean +/- SD]) than for halothane (77% +/- 6%), was not different from that of isoflurane (100%), but was less than that for sevoflurane (111% +/- 17%). The lower value for halothane is consistent with its known metabolism, but the lower (than sevoflurane) value for desflurane is at variance with other presently available data for their respective biodegradations.
Pig embryos at the 1- or 2-cell stage (before the 'block' to development in vitro) were cultured in 8 different media derived from Krebs'-Ringer-bicarbonate medium. A 2 x 2 x 2 factorial arrangement was used for the treatments, with glucose, glutamine and phosphate being the major effects tested. Embryos were obtained from sows approximately 44-48 h after the observation of oestrus, with the majority being at the 1-cell stage. Embryos from each female were randomly assigned to each treatment. After in-vitro culture, all embryos were scored for the stage of development attained and stained to determine final cell number. Significant effects were evident due to female, glucose, glutamine, a phosphate x glucose interaction and a glutamine x glucose interaction. None of the media components tested was inhibitory to embryo development. The greatest development (45-60% morula or blastocyst) was achieved with glucose and glutamine (both alone and in combination) in the media, demonstrating that an amino acid can serve as the sole energy source for complete preimplantation embryonic development in vitro.
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The interactions of glucocorticoids with their receptors somehow determine the cellular responses seen. The high potency glucocorticoid cortivazol differs from the usual glucocorticoids in two ways, structurally and in binding to receptors. Cortivazol contains a phenylpyrazol fused at carbon atoms 2 and 3 to the A ring of the cyclophenathrene, replacing the supposedly essential 3-keto,4,5-double bond pattern of glucocorticoids. Cortivazol binds to the glucocorticoid receptor in the cytosol from CEM C7 cells (a human acute lymphoblastic leukemia line) in a fashion consistent with interaction with at least two sites. Standard glucocorticoids show only one-site binding. In mutant leukemia cells derived from CEM C7, resistant to kill by 10(-6) M dexamethasone and deficient in standard glucocorticoid binding sites, cortivazol still finds a binding site and kills the cells. In wild-type leukemia cells, the binding sites of cortivazol, those with both higher (Kd approximately 5 x 10(-10) M) and lower (Kd approximately 1 x 10(-8] affinity appear to be on forms of the glucocorticoid receptor itself, and not on two different classes of molecules.
From a human placental lambda gt11 cDNA library, we have isolated a cDNA clone that encodes the entire 215-residue amino acid sequence of HMG-1. Analysis of an internal sequence similarity suggests that the DNA-binding domains of HMG-1 are separated by a rather long and flexible linker segment. Southern blotting of DNA digested with BamHI indicated a highly variable number of genes (or pseudogenes) for HMG-1 in different species. Characterization of HMG-1 mRNA expression by Northern blotting showed that three mRNA species of approximately 1.0, 1.4 and 2.4 kb were expressed in all mammalian organs and cell lines examined. These included several rat organs at different stages of development. Northern analysis also suggested the occurrence of HMG-1 mRNA in an invertebrate and a plant species.
Successful development of porcine embryos from the one-cell stage to the blastocyst stage has been accomplished using mouse oviducts in organ culture. One-cell embryos were transferred to mouse oviducts maintained in organ culture and were cultured for 6 days. Control embryos from each donor pig were cultured in a modified Krebs-Ringer bicarbonate medium. Thus control and experimental embryos obtained from the same individual pig could be directly compared. At the end of the culture period, all embryos were scored for the stage of development attained and stained to allow the cell number of each embryo to be counted. In medium alone, only 35.7% of the one-cell embryos reached the morula or blastocyst stage, whereas 78.1% of the one-cell embryos transferred to mouse oviducts reached the morula or blastocyst stage. Of those embryos reaching the morula or blastocyst stage, cell numbers were similar for the two treatments (medium alone vs. oviduct culture). The procedure described for mouse oviduct organ culture provides a simple method for culturing early-stage pig embryos to the morula or blastocyst stage prior to embryo transfer.
Literature dealing with the biological activities of cholesterol autoxidation products and related oxysterols in vivo and in vitro published since the previous 1981 monograph is reviewed. Although several oxysterols are important cholesterol metabolites implicated in bile acids and steroid hormones biosynthesis, effects on cellular membranes and on specific enzyme systems as well as cytotoxic, atherogenic, mutagenic, and carcinogenic activities characterize oxysterols as a class. Circumstantial evidence implicates oxysterols of the human diet and those formed in vivo with human health disorders, but recent work also supports an hypothesis that some oxysterols be endogenous intracellular regulators of de novo sterol biosynthesis. The true physiological relevance, if any, of these matters has not been adduced.
Oviductal fluid (OVF) was harvested chronically from 5 sows beginning on Day 1 of the estrous cycle (Day 0 of estrous cycle = day of detected estrus) and used for embryo culture (Day 3 OVF only). Two experiments were conducted to investigate in vitro development of 1-cell and 2-cell porcine embryos in a modified Kreb's Ringer bicarbonate medium (culture medium, CM), early luteal phase OVF or CM supplemented with OVF (CM-OVF, 25% OVF v/v in CM) with or without transfer to fresh CM. In Experiment 1, 1-cell and 2-cell embryos were harvested from sows (n = 7) approximately 44 h after detected estrus. In Experiment 2, 1-cell embryos were collected from 5 sows treated with altrenogest and gonadotropins, approximately 50 h after injection of human chorionic gonadotropin. The volume of OVF (ml) declined progressively throughout the 4 days of collection (24 h, 8.44 +/- 0.28; 48 h, 6.88 +/- 1.78; 72 h, 4.96 +/- 0.35; 96 h, 4.64 +/- 0.25 after onset of estrus; p less than .01). In both experiments, development to blastocyst stage was lowest among embryos cultured in OVF and highest among those cultured in CM-OVF (Experiment 1: CM, 27.3; OVF, 10; CM-OVF, 63.6; Experiment 2: CM, 26.7; OVF, 0; CM-OVF, 82.4; % blastocyst formation).(ABSTRACT TRUNCATED AT 250 WORDS)
The ratio of lethal-to-anesthetic concentration can be used to define the margin of safety of an inhaled anesthetic. In mechanically ventilated swine the fatal concentration of I-653, a new inhaled anesthetic, was 23.9 +/- 0.06% (mean +/- SE), and of isoflurane, 6.22 +/- 0.23%. The ratio of fatal anesthetic concentration-to-MAC for I-653 (2.45 +/- 0.11) was less than that determined for isoflurane (3.02 +/- 0.13; P less than 0.01) but relatively greater than that reported previously for other inhaled anesthetics. As with other inhaled anesthetics, the concentration of I-653 causing cardiovascular collapse exceeds that producing apnea, making cardiovascular collapse during spontaneous ventilation unlikely. Mean aortic blood pressure and cardiac output decreased as linear functions of anesthetic concentration. Values for these variables for isoflurane were greater than those for I-653 at concentrations exceeding 1.5 MAC. Heart rate, blood lactate concentration, and base-deficit did not change with anesthetic depth. Mixed venous PO2, mixed venous oxyhemoglobin saturation, and the ratio of oxygen transport to oxygen consumption remained at or above values in conscious swine but decreased similarly with both anesthetics when anesthetic concentration increased to within 0.5 MAC of the fatal concentration. Thus, the latter three variables, reflecting the fraction of delivered oxygen that is consumed, and "mean" tissue PO2 appear to be useful indices of anesthetic concentrations approaching those producing cardiovascular collapse.(ABSTRACT TRUNCATED AT 250 WORDS)
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We evaluated the effects of [D-Ala2,Me,Phe4,Met(0)ol]-enkephalin (FK 33-824) and morphine, opioid receptor agonists, on concentrations of LH, cortisol and GH during the follicular phase in heifers. During three trials, oestrous cycles of Angus heifers were synchronized by two injections of prostaglandin F2 alpha (PGF2 alpha) resulting in 17 induced follicular phases over an 80-day period. Treatments were administered 24 h after the second injection of PGF2 alpha. Blood samples were collected at 15-min intervals from 3 h before until 5 h after i.v. administration of 2 ml physiological saline (trials 1, 2 and 3), 0.5 mg morphine/kg (trials 1 and 2) or 1.8 micrograms FK 33-824/kg (trials 1 and 2) or 6.7 micrograms FK 33-824/kg (trial 3). Administration of both doses of FK 33-824 and morphine inhibited episodic release of LH for approximately 60 min. The concentration of cortisol was increased (P less than 0.05) after both doses of FK 33-824, but was unaffected (P greater than 0.5) by morphine or saline. The serum concentration of GH was increased (P less than 0.01) after both doses of FK 33-824 or morphine, but saline was without effect. These results provide evidence of an inhibitory effect of opioid receptor agonists on LH (FK 33-824 and morphine) and a stimulatory effect on cortisol (FK 33-824) and GH (FK 33-824 and morphine) during the follicular phase in heifers. Divergent effects of morphine and FK 33-824 on cortisol observed in this study provide evidence that opioid-induced changes in LH, GH and cortisol result from activation of different opioid receptors.
Embryonic disks were microsurgically isolated from adjacent trophoblast tissue and cultured for varying periods in vitro. During the first 24 h of culture, vesicles (1 to 4/disk) composed of mesoderm and endoderm formed from the ventral surface. In the subsequent culture period, the vesicles continued to increase in size and by 96 h in vitro, most originally multivesiculated explants possessed a single vesicle formed by delamination and coalescence of smaller vesicles. Scanning electron microscopy revealed the formation of grooves and ridges in abnormal attempts at differentiation by the embryonic ectoderm. Endoderm comprising the outer tissue layer of the vesicle underwent a gradual alteration in surface morphology during in vitro culture. Initially flat, with a paucity of microvilli, these cells became dome-shaped with an abundance of microvilli. In addition, they became highly secretory as revealed by the presence of numerous secretory droplets at their surface. After culture for periods of up to 10 d, several explants displayed areas containing pulsating tissue, with contractions occurring at a rate of 20 to 30/minute, indicative of mesoderm differentiation. Culture of porcine isolated embryonic disk in vitro should enhance investigations into the regulation of germ layer formation and differentiation and assist in determining the tissue source of conceptus secretory products.
Three peptide derivatives of primaquine were synthesized. The compounds were tested for radical curative antimalarial activity against Plasmodium cynomolgi in rhesus monkeys and blood schizonticidal antimalarial activity against Plasmodium berghei in mice. All three peptide derivatives showed activity against P. cynomolgi greater than that expected for the primaquine content of each prodrug. The toxicity of one of the peptide derivatives was less than that of primaquine in mice.