Clinical characteristics of sevoflurane in children. A comparison with halothane

BACKGROUND

For pediatric patients, sevoflurane may be an alternative to halothane, the anesthetic agent used most commonly for inhalational induction. The induction, maintenance, and emergence characteristics were studied in 120 unpremedicated children 1-12 yr of age randomly assigned to receive one of three anesthesia regimens: sevoflurane with oxygen (group S), sevoflurane with nitrous oxide and oxygen (group SN), or halothane with nitrous oxide and oxygen (group HN).

METHODS

Anesthetic was administered (via a Mapleson D, F or Bain circuit) beginning with face mask application in incremental doses to deliver maximum inspired concentrations of 4.5% halothane or 7% sevoflurane. End-tidal concentrations of anesthetic agents and vocal cord position were noted at the time of intubation. Elapsed time intervals from face mask application to loss of the eyelash reflex, intubation, surgical incision, and discontinuation of the anesthetic were measured. Heart rate, systolic, diastolic, and mean blood pressures, and end-tidal anesthetic concentrations were measured at fixed intervals. Anesthetic MAC-hour durations were calculated. The end-tidal concentration of anesthetic was adjusted to 1 MAC (0.9% halothane, 2.5% sevoflurane) for at least the last 10 min of surgery. Intervals from discontinuation of anesthetic to hip flexion or bucking, extubation, administration of first postoperative analgesic, and attaining discharge criteria from recovery room were measured. Venous blood was sampled at anesthetic induction, at the end of anesthesia, and 1, 4, 6, 12, and 18-24 h after discontinuation of the anesthetic for determination of plasma inorganic fluoride content.

RESULTS

Induction of anesthesia was satisfactory in groups SN and HN. Induction in group S was associated with a significantly greater incidence of excitement (35%) than in the other groups (5%), resulting in a longer time to intubation. The end-tidal minimum alveolar concentration multiple of potent inhalational anesthetic at the time of intubation was significantly greater in patients receiving halothane than in patients receiving sevoflurane. Induction time, vocal cord position at intubation, time to incision, duration of anesthesia, and MAC-hour duration were similar in the three groups. During emergence, the time to hip flexion was similar among the three groups, whereas the time to extubation, time to first analgesic, and time to attaining discharge criteria were significantly greater in group HN than in groups S and SN. Mean heart rate and systolic blood pressure decreased during induction in group HN but not in groups S and SN. The maximum serum fluoride concentration among all patients was 28 microM.

CONCLUSIONS

Sevoflurane with nitrous oxide provides satisfactory anesthetic induction and intubating conditions; however, induction using sevoflurane without nitrous oxide is associated with a high incidence of patient excitement and prolonged time to intubation. There were greater decreases in heart rate and systolic blood pressure during induction with halothane than with sevoflurane; however, these differences may be dose-related. The more rapid emergence with sevoflurane when compared with halothane is consistent with the low solubility of sevoflurane in blood and tissues. Children receiving sevoflurane for up to 9.6 MAC-hours did not develop high serum fluoride concentrations.

Self-efficacy and confidence in outcomes as determinants of self-care practices in inner-city, African-American women with non-insulin-dependent diabetes

The purpose of this study was to examine the extent to which perceived self-efficacy and confidence in outcomes, selected demographic variables, and disease characteristics (age, duration of diabetes, presence of documented complications) affect an individual's adherence over time to a diabetes regimen of home glucose testing, medication/insulin administration, diet, and exercise. A convenience sample of 118 inner-city, African-American women with type II, non-insulin-dependent diabetes mellitus receiving outpatient care at a large urban hospital were asked to complete measures of each of the psychosocial variables on two occasions, separated by an interval of 4 to 5 months, and coinciding with their next scheduled clinic visit. Bivariate and multivariate analyses at Times 1 and 2 demonstrated the ability of self-efficacy alone to explain diet, exercise, and home-testing behaviors while suggesting variability within individuals in sense of self-efficacy over time.

Maximum acceptable frequencies for females performing a drilling task in different wrist postures

This paper presents a study on the effect of wrist posture; flexion, extension, ulnar deviation, and radial deviation on maximum acceptable frequencies (MAF) for a drilling task using a psychophysical approach. Twelve females were selected from a college population to serve as subjects and an adjustable workstation was used to simulate a drilling task. The results revealed that flexion, extension, and radial deviation all had a significant effect on MAF but, ulnar deviation did not. The postures have been ranked in order of possible risk of contributing to CTD injury, with neutral having the lowest rank (lowest risk) and flexion having the highest rank (greatest risk).

Endothelium-dependent regulation of coronary tone in the neonatal pig

We examined the effects of endothelium-dependent responses on coronary perfusion pressure (CPP) in isolated, blood-perfused neonatal pig hearts under conditions of controlled coronary flow. Baseline CPP was increased 8%-21% by the cyclooxygenase inhibitor indomethacin (10-100 microM), and 30%-92% by NG-monomethyl-L-arginine (L-NMMA, 10-100 microM), an inhibitor of nitric oxide (NO) synthase, suggesting that both prostaglandin and nitric oxide synthesis contribute to basal coronary tone. Both acetylcholine (ACh) and bradykinin (BK) decreased CPP. These effects were enhanced by preconstriction with endothelin-1. L-NMMA markedly attenuated BK-induced coronary vasodilation and converted the ACh response to constriction, indicating a significant role for NO release in these responses. After 1 h of total, global normothermic ischemia and 45 min of reperfusion, vasoconstrictor responses to endothelin-1 and ACh were enhanced, while BK-induced dilation was significantly reduced. L-Arginine supplementation during reperfusion did not restore vasodilatory responses to ACh or BK. The magnitude of L-NMMA-induced coronary vasoconstriction during reperfusion was similar to that observed without ischemia-reperfusion. Coronary vasodilation in response to sodium nitroprusside, a NO precursor that causes endothelium-independent vasodilation by directly activating smooth muscle guanylate cyclase, was unaffected by ischemia-reperfusion. We conclude that NO production in the neonatal coronary circulation contributes to both basal tone and the response to ACh and BK. After ischemia-reperfusion, basal NO production and smooth muscle relaxation mediated by guanylate cyclase are intact, whereas agonist-stimulated dilation is significantly impaired.

Pharmacokinetics of methylprednisolone in elderly and young healthy males

OBJECTIVE

To characterize and compare the pharmacokinetics of a single intravenous dose of methylprednisolone in elderly and young healthy males.

DESIGN

A randomized, parallel pharmacokinetic trial.

SETTING

A public university-affiliated hospital.

SUBJECTS

Seven healthy, elderly white males (aged 69 to 82 years) and five healthy, young white males (aged 24 to 37 years) who gave informed consent and fulfilled all screening criteria.

MEASUREMENTS

Serial blood samples were obtained over a 24-hour study period after intravenous administration of a 10-mg dose of methylprednisolone. Serum methylprednisolone concentrations were determined by high performance liquid chromatography and utilized to determine the pharmacokinetic parameters.

RESULTS

Methylprednisolone serum concentrations declined in a linear manner in both groups. However, 4 hours after the dose, the mean serum concentration of methylprednisolone was 50.9 +/- 15.1 ng/mL in the elderly group and 37.6 +/- 7.5 (P = 0.07) ng/mL in the young group. The clearance of methylprednisolone was 237 +/- 62 mL/h/kg, with a volume of distribution of 1.10 +/- 0.07 L/kg, for the elderly group, whereas the young males had a mean drug clearance of 359 +/- 90 mL/h/kg (P < 0.05) and a mean volume of distribution of 1.28 +/- 0.34 L/kg. The half-life of methylprednisolone ranged from 1.90 to 5.40 hours in the elderly group; the range was 1.99 to 3.31 hour (P = 0.016) in the young group.

CONCLUSION

A slower methylprednisolone clearance was noted in the elderly group compared with the young counterparts. This pharmacokinetic alteration seen in healthy elderly subjects may contribute to the increased incidence of adverse effects from chronic glucocorticoid therapy that has been observed among elderly patients.

Prolonged neonatal myocardial preservation with a highly buffered low-calcium solution

Optimal methods of myocardial preservation remain controversial in the neonate. This study compared prolonged hypothermic storage of neonatal hearts with modified University of Wisconsin solution (group I) with a solution formulated to promote anaerobic glycolysis by providing proton buffering with histidine (100 mmol/L) and exogenous glucose and insulin (group II). Hearts from piglets aged 3 to 5 days were given a single dose of either solution (n = 6 each), subjected to 20 hours of global ischemia at 4 degrees C, and reperfused with an erythrocyte-enhanced perfusate in an isovolumic Langendorff preparation. After 1 hour of reperfusion, in comparison with hearts preserved with University of Wisconsin solution, those in group II demonstrated (mean +/- standard error of the mean) greater left ventricular developed pressure (101 +/- 7 versus 62 +/- 9 mm Hg, p < 0.01) and the first derivative of left ventricular pressure (816 +/- 23 versus 614 +/- 69 mm Hg.sec-1, p < 0.05). Diastolic indices were reduced to a similar degree in the two groups. Myocardial oxygen consumption was significantly greater (38.8 +/- 2.4 versus 11.8 +/- 2.4 microliters oxygen.min.g-1, p < 0.01) in group II hearts. Group I hearts vasoconstricted (6% increase in coronary vascular resistance) in response to an intracoronary infusion of acetylcholine (20 nmol.min-1); in contrast, acetylcholine produced coronary dilation in group II hearts (5% decrease in coronary resistance, p < 0.02) that was similar to that observed in nonischemic control hearts. These results demonstrate enhanced preservation of myocardial contractility, oxidative metabolism, and vascular function in neonatal hearts provided by a solution designed to buffer protons and promote anaerobic glycolysis during ischemia.

Brain stem integration of vocalization: role of the midbrain periaqueductal gray

1. The contribution of the midbrain periaqueductal gray (PAG) to the central regulation of vocalization was investigated by analyzing the electromyographic (EMG) changes in respiratory, laryngeal, and oral muscles evoked by microinjection of D,L-homocysteic acid (DLH) in the PAG of unanesthetized, precollicular decerebrate cats. Moderate to large (6-40 nmol) doses of DLH evoked natural-sounding vocalization as well as increases in inspiratory depth and respiratory rate. 2. Two basic types of vocalization were evoked, each associated with a distinct and characteristic pattern of respiratory, laryngeal and oral EMG changes. Type A vocalization (voiced sounds such as howl/mew/growl) was characterized by excitation of the cricothyroid (CT) and thyro-arytenoid (TA) muscles, and inhibition of the posterior crico-arytenoid (PCA) muscle, whereas type B vocalization (unvoiced hiss sounds) was characterized by excitation of the PCA and TA muscles and no significant activation of the CT muscle. In addition, stronger expiratory (external oblique, internal oblique, internal intercostal) EMG increases were associated with type A responses, and larger increases in genioglossus and digastric muscle activity were associated with type B responses. 3. Microinjections of small doses of DLH (300 pmol-3 nmol), also evoked patterned changes in muscle activity (usually without audible vocalization) that, although of lower amplitude, were identical to those evoked by injections of moderate to large DLH doses. In no such experiments (175 sites) were individual muscles activated by small dose injections of DLH into the PAG. Further, type A vocalization/muscle patterns were evoked from PAG sites caudal to those at which type B vocalization/muscle patterns were evoked. 4. Considered together these results indicate: that the PAG contains topographically separable groups of neurons that coordinate laryngeal, respiratory, and oral muscle patterns characteristic of two fundamental types of vocalization and that the underlying PAG organization takes the form of a representation of muscle patterns, rather than individual muscles. 5. The patterns of EMG activity evoked by excitation of PAG neurons were strikingly similar to previously reported patterns of EMG activity characteristic of major phonatory categories in higher species, including humans (e.g., vowel phonation, voiceless consonant phonation). These findings raise the possibility that the sound production circuitry of the PAG could well be utilized by cortical and subcortical "language structures" to coordinate basic respiratory and laryngeal motor patterns that are necessary for speech.

Thyroid hormone potentiates the antiviral action of interferon-gamma in cultured human cells

Human interferon-gamma (hIFN gamma) exhibits a number of biological effects, including antiviral activity in homologous cells. The antiviral activity of recombinant (r) hIFN gamma, estimated by inhibition of vesicular stomatitis virus yield, was potentiated up to 120-fold in human fibroblast (BG-9) cells exposed to free L-T4 (0.5 x 10(-10) mol/L). Thyroid hormone alone did not induce the antiviral state in BG-9 cells. L-T3 also potentiated the antiviral action of rhIFN gamma, but D-T4 and D-T3 were ineffective. The antiviral effect of hIFN alpha in BG-9 cells was not influenced by thyroid hormone. Exposure of rhIFN gamma-treated BG-9 cells to L-T4 for only 3 h was sufficient to potentiate hIFN gamma-mediated antiviral activity. Similar potentiation by L-T4 of the antiviral effect of rhIFN gamma in HeLa cell cultures was also observed. Although the mechanism of potentiation of rhIFN gamma action by thyroid hormone is incompletely understood, the absence of antiviral activity of thyroid hormone alone indicates that the iodothyronine effect does not depend upon hormonal action on genes able to be stimulated by IFN gamma.

Variability and consistency in speech breathing during reading: lung volumes, speech intensity, and linguistic factors

Lung volumes during reading and associated factors such as speech intensity and linguistic influences were studied in six healthy young women over 7 to 10 sessions, using respiratory inductive plethysmography. Intrasubject variability of lung volumes over the sessions was almost as great as the intersubject variability. Some of the intrasubject variability was associated with natural variations of speech intensity within a "comfortable loudness" range. The lung volume variability during reading is contrasted with high degrees of both inter- and intrasubject consistency in the location of inspirations, which occurred almost exclusively at grammatically appropriate places in the texts (paragraph, sentence, clause, and phrase boundaries). Within each reading passage, lung volumes were significantly increased for (a) louder utterances, (b) inspirations at sentence and paragraph boundaries compared to inspirations at other locations within sentences, (c) longer utterances compared to shorter utterances, and (d) initial breaths compared to final breaths. The implications of these findings for the neural control of breathing during speech are considered.

Acute respiratory acidosis: large-dose furosemide and cerebrospinal fluid ions

NaCl cotransport carrier is known to be involved in transepithelial fluid absorption and secretion in various tissues. Recent studies indicate that Na-K-2Cl cotransport carrier also exists in the choroid plexus cells and that inhibition of the carrier decreases cerebrospinal fluid (CSF) production. In this study, we used large-dose intravenous furosemide, an inhibitor of Na-K-2Cl carrier, to determine the effects on cisternal CSF ionic composition in acute respiratory acidosis. In pentobarbital-anesthetized mechanically ventilated dogs, renal pedicles were ligated to prevent furosemide-induced diuresis. The experimental group (group II, n = 7) received 400 mg/kg of furosemide intravenously, and group I (control group, n = 7) received the vehicle. In group II, serial serum and CSF furosemide concentrations were approximately 10(-3) and 10(-5) mol/l, respectively. During 5 h of acute respiratory acidosis in both groups, the mean arterial PCO2 increased approximately 25 Torr, with comparable changes in CSF PCO2. In both groups, CSF [HCO3-] and [H+] rose approximately 3 meq/l and 20 neq/l, respectively. Changes in CSF [Na+], [K+], [Cl-], and [Na(+)-Cl-] were also similar and were not significantly different from each other when the two groups were compared. These data show that furosemide at the dose that inhibits NaCl cotransport carrier does not significantly alter ionic composition of cisternal CSF.

Klippel-Feil syndrome associated with malformed larynx. Case report

We report a case of a 45-year-old man with Klippel-Feil syndrome with fusion of the C2-3 and C4-5 cervical vertebrae and severe voice impairment associated with malformation of the laryngeal cartilages. The condition was also complicated by bilateral inflexibility of the arms and legs and external malformation of the ears. This case broadens the spectrum of anomalies, of branchial arch derivation, now identified in association with Klippel-Feil syndrome. We discuss the possibility that perturbation of segmentation, distinct from somitogenesis, may be linked to Klippel-Feil syndrome-associated craniofacial abnormalities.

Recovery characteristics of desflurane versus halothane for maintenance of anesthesia in pediatric ambulatory patients

BACKGROUND

Desflurane is a new potent, inhaled anesthetic agent with low blood-gas solubility that should allow for the rapid induction of and emergence from anesthesia. However, its extreme pungency makes desflurane unacceptable for induction of anesthesia in children. This study was undertaken to determine the airway properties of desflurane administered by mask after anesthetic induction with halothane and nitrous oxide, and to compare the emergence and recovery properties of minimum alveolar concentration (MAC)-equivalent concentrations of desflurane or halothane in nitrous oxide in pediatric patients undergoing ambulatory surgery.

METHODS

Forty-five children undergoing ambulatory surgery for inguinal hernia repair, orchiopexy, and/or circumcision were randomized into two groups. Both groups were premedicated with intranasal midazolam and given halothane and nitrous oxide by mask to induce anesthesia. A caudal block was placed in children in both groups after anesthetic induction. For maintenance of anesthesia, group I patients (n = 22) were switched over to desflurane (1 MAC) and nitrous oxide, and group II patients (n = 23) continued to receive halothane (1 MAC) and nitrous oxide. All patients breathed spontaneously throughout the entire procedure, and all anesthetics were terminated abruptly at the conclusion of surgery. Recovery indicators (time to first response, length of time in the recovery room and length of time in the hospital) and the quality of the anesthetic emergence were assessed by a nurse blinded to each patient's anesthetic. This observer was present with the patient throughout his or her ambulatory hospitalization and continuously assessed the recovery indicators according to preset criteria.

RESULTS

The groups did not differ with respect to age, weight, or dose of midazolam. Although group I (desflurane) had a longer anesthesia time (52 +/- 12 min vs. 42 +/- 10 min), their time to first response (9.5 +/- 6.8 min vs. 20.9 +/- 14.7 min) and their recovery room time (21 +/- 10.7 min vs. 29 +/- 14.6 min) were less than those in group II (halothane). There was a trend for patient emergence from desflurane anesthesia to be associated with a higher incidence of emergence delirium (50% vs. 21%). The two groups were similar with respect to overall duration of postoperative ambulatory hospitalization.

CONCLUSIONS

In children premedicated with intranasal midazolam, desflurane maintenance anesthesia allows for a faster recovery. However, depending on the institution's criteria for ambulatory surgical patient discharge, desflurane may or may not affect the overall hospitalization time.

Retinoic acid inhibition of thyroxine binding to human transthyretin

All-trans retinoic acid is a potent inhibitor of [125I]-thyroxine (T4) binding to human erythrocyte membranes and can block the activation by thyroid hormone of erythrocyte Ca(2+)-ATPase [J. Biol. Chem. (1989) 264, 687-689]. In the present studies, retinoic acid was examined for its ability to displace thyroxine from binding sites on human transthyretin (TTR). Scatchard analysis of [125I]T4 binding to purified TTR, determined by equilibrium dialysis, revealed two classes of binding sites with association constants of 3.2 x 10(9) M-1 and 8.1 x 10(6) M-1. All-trans retinoic acid also displaced [125I]T4; 40% of the specifically bound [125I]T4 was displaced at a retinoic acid concentration of 2 x 10(-5) M. Analysis of the high affinity T4 binding site suggests that the Ka for retinoic acid to that site is approx. 10(7) M-1. 8-Anilinonaphthalene-1-sulfonate (ANS), a strongly fluorescing dye, binds to the thyroxine binding sites on TTR. T4 and 3,5,3'-L-triiodothyronine (T3) shifted the fluorescence emission maximum and intensity of an ANS-TTR solution toward the spectrum obtained from uncomplexed ANS. All-trans retinoic acid caused a similar shift in the emission spectrum of ANS, but was less potent than T4. Retinol failed to quench the emission intensity of the ANS-TTR complex, while 13-cis-retinoic acid was less effective than all-trans retinoic acid.

Assay and purification of Fv fragments in fermenter cultures: design and evaluation of generic binding reagents

Fv fragments whose genes have been cloned using common PCR primers carry identical peptide motifs at their termini. We have raised antibodies against the C-terminal motif of the VH chain GQGTTVTVSS and evaluated their utility as reagents for the assay and purification of Fvs in the fermenter culture. Three different Fvs were included in the investigation. We found that the motif was exposed and available for capture when Fv fragments were blotted onto nitrocellulose paper or adsorbed directly onto microtiter plates. In contrast, the motif was either partially or totally obscured when the Fv was complexed with immobilised antigen or when free in solution. This reactivity profile enabled us to develop a general-purpose assay for Fv protein, but not a general-purpose assay for monitoring active Fv. The apparent inaccessibility of the C-terminus of VH conflicts with currently held views on the three-dimensional structure of these molecules.

Rabbit skeletal muscle sarcoplasmic reticulum Ca(2+)-ATPase activity: stimulation in vitro by thyroid hormone analogues and bipyridines

Sarcoplasmic reticulum-enriched membranes from rabbit skeletal muscle contained Ca(2+)-ATPase activity which was significantly enhanced (26% increase, P < 0.001) in vitro by physiological concentrations (10(-10) M) of L-thyroxine (T4) and 3,3',5-triiodo-L-thyronine (T3). In contrast, the biologically inactive iodothyronine analogues D-T4 and 3,3',5,5'-tetraiodothyroacetic acid (Tetrac) (10(-10) M) were without effect on enzyme activity. 3,5-Dimethyl-3'-isopropyl-L-thyronine (Dimit), a bioactive analogue, was highly effective as a Ca(2+)-ATPase stimulator, increasing enzyme activity by 43% (P < 0.02 vs. T4 effect). A bipyridine cardiac inotropic agent, milrinone, has been reported to be thyromimetic in a myocardial membrane Ca(2+)-ATPase system, and in concentrations from 10(-10) to 10(-5) M enhanced skeletal muscle SR membrane Ca(2+)-ATPase activity in vitro (P < 0.001). Milrinone analogues which have been previously shown to enhance rabbit myocardial membrane Ca(2+)-ATPase activity, and which have a twist relationship of the pyridine rings, were also striated muscle Ca(2+)-ATPase stimulators. We conclude that (1) striated muscle is a mammalian tissue in which physiological levels of biologically relevant thyroid hormone analogues, particularly Dimit, stimulate Ca(2+)-ATPase activity in vitro by a non-genomic mechanism; (2) cardiac bipyridine analogues which are thyromimetic in vitro in rabbit heart, and which have structural homologies with thyroid hormone, are stimulators of rabbit striated muscle sarcoplasmic reticulum Ca(2+)-ATPase activity.

Cardiopulmonary bypass significantly reduces surfactant activity in children

Lung injury remains an important problem after cardiopulmonary bypass. The contribution of altered surfactant concentration or activity to pulmonary dysfunction after cardiopulmonary bypass is unclear. Recent evidence indicates that alveolar surfactant exists in specific aggregate forms that differ with respect to density, phospholipid composition, and function. A transition from surface active, higher density, large aggregates of surfactant to lower density, small aggregates that possess reduced surface activity has been demonstrated after experimental lung injury. The purpose of the present study was to examine surfactant aggregate fractions before and after bypass in children. Twelve acyanotic patients, aged 2 to 12 years, underwent intraoperative pulmonary function testing followed by bronchoalveolar lavage before incision and approximately 1 hour after termination of cardiopulmonary bypass. Saturated phosphatidylcholine pool sizes and total protein content of the small- and large-aggregate fractions of bronchoalveolar lavage fluid were determined. One hour after termination of cardiopulmonary bypass, the ratio of saturated phosphatidylcholine in small-aggregate as compared with that in large-aggregate fractions increased (mean +/- standard error) from 0.19 +/- 0.03 to 0.37 +/- 0.07 (p < 0.02), as did the ratio of saturated phosphatidylcholine to protein in the small-aggregate fraction (from 0.04 +/- 0.01 to 0.08 +/- 0.02, p < 0.05). Reductions in forced vital capacity (-19% +/- 5%), inspiratory capacity (-15% +/- 3%), and small airway flow rates (-32% +/- 6%) were also observed after bypass. These changes were accompanied by a fivefold increase in alveolar polymorphonuclear leukocyte content. The present study suggests that cardiopulmonary bypass of moderate duration in relatively healthy children is associated with surfactant changes that are similar in type and magnitude to those observed in experimental lung injury.

Inositol phosphates modulate binding of thyroid hormone to human red cell membranes in vitro

D-Myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] and D-myo-inositol 4,5-bisphosphate (10(-6) mol/L) displaced specifically bound L-[125I] T4 from human erythrocyte membranes in vitro by up to 80%. D-Myo-inositol 1,3,4,5-tetrakisphosphate, D-myo-inositol 1-monophosphate, and D-myo-inositol 1,4-bisphosphate were ineffective in decreasing thyroid hormone binding to membranes. The effect of Ins(1,4,5)P3 on high affinity binding reflected a change in Kd (5.8 x 10(-11) vs. 1.5 x 10(-11) mol/L) and binding capacity (15 vs. 2 fmol/mg membrane protein) in the absence and presence of Ins(1,4,5)P3, respectively. Ins(1,4,5)P3 also displaced T3 from red cell membranes. Thus, selected inositol phosphates regulate the abundance of sites available for binding of thyroid hormone by human red cell membranes. This stereospecific action of inositol phosphates is among several plasma membrane effects recently described for these members of the signal-transducing phosphoinositide pathway.

Construction, characterisation and kinetics of a single chain antibody recognising the tumour associated antigen placental alkaline phosphatase

The murine monoclonal antibody H17E2 recognises placental alkaline phosphatase (PLAP), an antigen present in the human term placenta and also expressed by many tumours. The antibody is of value in both immunoscintigraphy and radioimmunotherapy in testicular and ovarian cancer. The small size of genetically engineered single chain antibodies (SCAs) should give diagnostic and therapeutic advantages of improved tumour penetration and increased blood clearance compared to IgG. Employing recombinant DNA techniques a SCA based on H17E2 has been expressed in Escherichia coli and has been shown to bind placental alkaline phosphatase specifically. When administered to nude mice bearing human tumour xenografts, the H17E2 SCA effectively localised to tumour whilst a co-administered non-specific SCA did not. H17E2 SCA achieves tumour: blood ratios that are superior to those achieved with whole IgG, probably owing to its rapid blood clearance. We conclude that the H17E2 SCA is suitable for further investigation as an agent for clinical imaging and therapy. Additionally, the SCA can also be used for the construction of antibody based fusion proteins to target other effector functions to tumour cells.

Microbial models of mammalian metabolism: involvement of cytochrome P450 in the N-demethylation of N-methylcarbazole by Cunninghamella echinulata

1. As previously reported (Yang and Davis 1992), N-methylcarbazole (NMC) is converted to N-hydroxymethylcarbazole (NHMC), and 3-hydroxy-N-hydroxymethylcarbazole (3-OH-NHMC), two relatively stable carbinolamine metabolites by the fungus Cunninghamella echinulata (ATCC 9244). Decomposition of these two carbinolamines yields the corresponding dealkylated metabolites, carbazole and 3-hydroxycarbazole. In the present study, the possible involvement of cytochrome P450 in the requisite N-alkyl hydroxylation reaction was examined. 2. Carbon monoxide, a classical P450 inhibitor, markedly inhibited the formation of NHMC, as did potassium cyanide. 1-Benzylimidazole, piperonyl butoxide and SKF-525A inhibited the formation of both NHMC and 3-OH-NHMC, while beta-naphthoflavone (5,6-benzoflavone) induced their formation. 3. The source of the oxygen atom in the metabolite NHMC was examined by GC/MS analysis of NHMC formed during incubation of NMC in H218O-enriched medium which resulted in no incorporation of labelled oxygen into the metabolite. 4. An intermolecular isotope effect was not observed for the formation of NHMC suggesting that C-H bond cleavage is not a rate limiting step in the formation of this metabolite under the conditions examined. 5. It was concluded that P450 enzymes may be involved in the N-demethylation of NMC catalyzed by this fungal model of mammalian metabolism, and provides further support for biochemical and mechanistic parallels between mammalian metabolism and microbial systems catalyzing phase-1 biotransformations.

Effects of aging, diet, and sex on plasma glucose, fructosamine, and lipid concentrations in barrier-raised Fischer 344 rats

We studied the relationships of plasma glucose, fructosamine, triglycerides, and cholesterol as a function of age, gender, and diet in barrier-raised Fischer 344 rats aged 5 to 26 months, fed a diet either ad libitum or restricted to 60% of the ad libitum caloric intake. The complex relationships of these plasma levels to age, gender, and diet led to the development of a model with age, diet, and sex as covariates. Overall, fasting plasma glucose concentrations were reduced by approximately 25% in rats on the restricted diet, compared to ad libitum-fed animals. There was a significant age-dependent decline in glucose levels in male animals, whereas in females there was an increase in plasma glucose with aging. Plasma fructosamine levels in calorie-restricted animals, overall, were reduced by 7% compared to levels in animals fed ad libitum. There was a significant positive correlation between plasma glucose and fructosamine levels. Mean plasma triglyceride content was decreased by 50% in calorie-restricted rats compared to ad libitum-fed animals. A significant decrease in triglyceride levels with increasing age was seen in male animals, and an increase with aging in females. There was a significant positive correlation between plasma glucose and triglyceride levels. Plasma cholesterol levels in calorie-restricted animals were reduced by 7% compared to levels in ad libitum-fed animals. An increase of cholesterol concentration with aging was significant in both males and females. Analysis of the data showed that there were significant differences between male and female Fischer 344 rats in the response of plasma glucose and fructosamine to aging and calorie restriction. Changes of plasma triglyceride and cholesterol with aging and dietary calorie restriction were also different in males and females. Studies of the effect of aging on glycemia and blood lipid content should take into account the contributions of animal sex.

Acute cellular actions of thyroid hormone and myocardial function

The mechanisms of actions of thyroid hormone in various tissues are largely viewed as cell nucleus-mediated. However, several actions of this hormone are definitively extranuclear, and these include effects on the activities of Ca(2+)-adenosine triphosphatases (ATPases) of myocardial sarcolemma and, apparently, sarcoplasmic reticulum in animal models. Both effects would serve to reduce cytoplasmic (sarcoplasmic) [Ca2+]. Sarcoplasmic reticulum uptake of Ca2+ from sarcoplasm is mediated by Ca(2+)-ATPase and is deficient in end-stage heart failure; thyroid hormone can enhance sarcoplasmic reticulum Ca(2+)-ATPase activity acutely via an extranuclear mechanism or indirectly via the myosin-associated Ca(2+)-ATPase gene. Such actions would serve to improve myocardial relaxation, thus improvement in diastolic dysfunction, and may be cardioprotective if excessive levels of sarcoplasmic [Ca2+] develop during reperfusion of previously ischemic tissue. Action of thyroid hormone on sarcolemmal Ca(2+)-ATPase activity will enhance Ca2+ efflux, and a recently described effect of the hormone on myocardial Na+ inactivation current may serve to increase or reduce sarcoplasmic [Ca2+], depending upon the vector of Na+/Ca2+ exchange. This article reviews acute effects of thyroid hormone on the heart that are extranuclear in mechanism.

Congenitally missing permanent mandibular incisors and their association with missing primary teeth in the southern Chinese (Hong Kong)

A radiographic survey of a random sample of 454 girls aged 5.9 +/- 0.5 yr and 521 boys aged 5.8 +/- 0.4 y was undertaken to establish data on the incidence of congenitally missing mandibular incisor teeth amongst the Southern Chinese and to compare these figures with those of a similar previous study of 12-yr-olds so to eliminate factors such a trauma or extractions which may have artificially inflated the 12-yr-old incidence data. The proportion of 5-yr-old girls and boys affected by hypodontia in the permanent mandibular incisor region was 0.086 and 0.046 respectively (a significant difference between sexes, P < 0.02), compared with 0.047 and 0.034 for the 12-yr-olds (a non-significant difference) so other factors must have contributed to the discrepancy between the two groups of children. A very strong correlation (P < 10(-25)) between missing primary and missing permanent mandibular incisors is present in this group, and this has implications for prognosis and treatment planning. A fundamental developmental defect is implied.

Pulmonary and upper airway afferent influences on the motor pattern of vocalization evoked by excitation of the midbrain periaqueductal gray of the cat

It has been established previously that natural-sounding vocalization is evoked by excitation of the midbrain periaqueductal gray (PAG). It is not known, however, whether the motor output for such vocalization is invariant, or whether it is influenced by afferent discharge. We have investigated, in the unanesthetized precollicular decerebrate cat, the patterns of upper airway and respiratory EMG activity evoked by microinjection into the PAG of the excitatory amino acid D,L-homocysteic acid (6 to 40 nmol in 30-200 nl), under conditions of varied pulmonary and upper airway afferent input. The PAG-evoked pattern in the control state consisted of a 1- to 2-min sequence of episodic vocalizations (hiss or howl-like) with expiratory (vocalization) durations of generally less than 2 s, separated by one or more inspirations. During such PAG-evoked vocalization, a significant prolongation of the expiratory duration and an extended discharge in laryngeal, intercostal and abdominal muscles was evoked by the application of warm, humidified static air pressures (5-30 cm H2O) either: (i) to the lungs and tracheo-bronchial tree via a tracheostomy, or (ii) as an airflow through the upper airways in an expiratory direction. In contrast, if the development of the usual vocalization-related air pressures (5-45 cm H2O) in the lungs and airways was prevented by opening a tracheal cannula to the atmosphere, shortened respiratory durations (inspiratory and expiratory) occurred. The effects evoked by static pressure inflations of the lungs could be blocked by bilateral vagotomy or reversibly blocked by unilateral vagotomy combined with vagal cooling sufficient to abolish Hering-Breuer reflexes. These results indicate that the motor pattern for vocalization evoked by excitation of PAG is exquisitely sensitive to pulmonary and upper airway afferent input.