Robert S. Bienkowski

Control of Collagen Deposition in Mammalian Lung

Abstract This review considers the mechanisms controlling collagen deposition in mammalian lung in five different states: normal development, fibrosis, erosion, pneumonectomy, and the steady state. Deposition is the net result of positive and negative processes. The major positive processes are control of cell number and type, regulation of transcription and translation, post-translational modifications, fibril formation, and covalent cross-linking. The negative mechanisms are intracellular degradation, collagenase-mediated degradation, and phagocytosis, and they are integral to the life cycle of collagen. Cytokines and growth factors have many and complex effects on all the processes that constitute collagen metabolism. Interleukin-1 and tumor necrosis factor-α can either stimulate or inhibit collagen accumulation, presumably depending on the immediate environment. Interleukin-6 inhibits collagen degradation, and γ-interferon inhibits collagen production. Platelet derived growth factor and fibroblast growth factor have powerful mitogenic effects on connective tissue cells in lung, and can also affect collagen production directly. Transforming growth factor-β activates a battery of processes that uniformly contribute to accumulation of collagen. Transforming growth factor-β may be the “master switch” for a fibrotic program in lung. Therapeutic approaches to controlling lung fibrosis by manipulating cytokine levels are promising. Prostaglandin E has uniformly negative effects on net collagen accumulation and may play a central role in an erosion program.

An audit of adverse events in children sedated with chloral hydrate or propofol during imaging studies

We examined records of sedations provided by the paediatric anaesthesiology staff for 455 children (ages 1 mo‐17 yr) undergoing MRI or CT scans at our institution over a twelve‐month period with regard to the monitoring of adverse events: excessive sedation, agitation, vomiting, hypoxaemia, and major airway compromise. One hundred‐and‐thirty‐one patients (29%) received chloral hydrate; 324 patients (71%) received propofol. All patients were monitored with continuous noninvasive pulse oximetry and received supplemental oxygen via nasal cannulae. Of the patients who received chloral hydrate, 64 (49%) were over one year of age; of the patients who received propofol, 318 (98%) were one year of age or older. In the chloral hydrate group, 23 patients (19%) were deemed excessively sedated and four patients (3%) were agitated; no patients in the propofol group experienced any of the adverse outcomes reviewed. Furthermore, no patients in either group had significant airway compromise and none was admitted to the hospital as a result of the sedation.

Measurement of intracellular collagen degradation

Abstract Intracellular degradation of newly synthesized collagen is quantitated by incubating fibroblasts with [14C]proline and determining the percentage of total [14C]hydroxyproline that is present in a low molecular weight fraction. Several problems make this difficult. (1) Commercial [14C]proline is often contaminated with [14C]hydroxyproline and must be purified before use. (2) Salt and [14C]proline interfere with the determination of [14C]hydroxyproline in the low molecular weight fraction and must be removed by preparative ion-exchange chromatography. (3) Epimerization of trans- to cis-hydroxyproline during acid hydrolysis is variable and must be taken into account. (4) Loss of [14C]hydroxyproline during processing varies; [3H]hydroxyproline can be used as an internal measure of recovery, even though tritium may be lost during hydrolysis. An analytic cation-exchange resin is used for the final quantitation of [14C]hydroxyproline in the low and high molecular weight fractions. With these methods, degradation of newly synthesized collagen can be determined with a precision of ± 3%.

Ondansetron with propofol reduces the incidence of emesis in children following tonsillectomy

PurposeThis study tested the hypothesis that the antiemetic effects of a combination of ondansetron and propofol were superior to propofol alone in children undergoing tonsillectomy surgery.MethodsA prospective, randomized, double-blind, placebo-controlled study design was employed. Young children underwent mask induction with halothane, nitrous oxide and oxygen and then hadiv access established: older children hadiv induction with propofol. All patients received 0.3 mg·kg−1 mivacurium and 2–4 μg·kg−1 fentanyliv and 30 mg·kg−1 acetaminophenpr to a maximum dose of 650 mg. Following induction, patients received either 100 μg·kg−1 ondansetron or placebo. Anaesthesia was maintained with 120 – 140 μg·kg−1·min−1 propofol, nitrous oxide and oxygen to maintain vital signs within 20% of baseline. After surgery, in all patients the tracheas were extubated in the operating room without use of neuromuscular reversing agents. Episodes of emesis were recorded by PACU nurses for four to six hours. A telephone interview on the following day was also used for data recovery. Groups were compared in relation to age using the Mann-Whitney test, and with respect to sex and number of episodes of vomiting using the Fisher Exact Test.ResultsThree of the 45 patients who received ondansetron vomited (6.7%), whereas 10 of the 45 patients who received placebo vomited (22.2%). (P = 0.035)ConclusionOndansetron in a dose of 100 μg·kg−1, when combined with propofol for children undergoing ton-sillectomy reduced the incidence of postoperative vomiting to very low levels.RésuméObjectifVérifier l’hypothèse voulant que les effets antiémétiques d’une combinaison d’ondansétron et de propofol soit supérieure à ceux du propofol seul chez des enfants qui subissent une amygdalectomie.MéthodeOn a utilisé une étude prospective, randomisée et en double aveugle contre placebo. Chez les jeunes enfants, l’induction au masque s’est faite avec de l’halothane et un mélange de protoxyde d’azote et d’oxygène, et on a établi ensuite l’accèsiv; chez les enfants plus âgés, c’était une inductioniv avec du propofol. Tous les patients ont reçu 0,3 mg·kg−1 de mivacurium et 2 — 4 μg·kg−1 de fentanyliv et 30 mg·kg−1 d’acétaminophènepr jusqu’à une dose maximale de 650 mg. Après l’induction, les patients ont reçu soit 100 μg·kg−1 d’ondansétron ou un placebo. L’anesthésie a été maintenue avec 120 – l40 μg·kg−1·min−1 de propofol et d’un mélange de protoxyde d’azote et d’oxygène pour conserver les signes vitaux à ± 20% des mesures de base. Après la chirurgie, on a extubé tous les patients dans la salle d’opération sans utiliser de décurarisant. Les épisodes de vomissements ont été notés pour une période de 4 – 6 h par les infirmières de la salle de réveil. Le jour suivant, une interview téléphonique a aussi fourni des données sur la récupération. On a comparé les groupes selon l’âge par le test de Mann-Whitney et selon le sexe et le nombre d’épisodes de vomissements par le test exact de Fisher.RésultatsTrois patients sur 45 qui ont reçu de l’ondansétron ont eu des vomissements (6,7%), mais 10 patients sur 45 qui avaient reçu le placebo (22,2%). (P = 0,035)ConclusionUne dose de 100 μg·kg−1 d’ondansétron combinée à du propofol et administrée à des enfants lors d’une amygdalectomie a réduit l’incidence postopératoire de vomissements à de très bas niveaux.

Propofol reduces the incidence of vomiting after tonsillectomy in children

We compared the effect of a propofol‐based anaesthetic to an isoflurane‐based anaesthetic on the incidence of postoperative vomiting in children following tonsillectomy. Thirty‐nine children were enrolled in the study and randomized to receive one of the proposed anaesthetics. All patients underwent a mask induction with halothane, nitrous oxide, and oxygen. Intravenous access was established and all children received fentanyl (2–4 μg·kg‐1) i.v., mivacurium (0.3 mg·kg‐1) i.v. and acetaminophen (10–15 mg·kg‐1) p.r. Following tracheal intubation, patients received either isoflurane (0.8–1.6%) or propofol (120–180 μg·kg‐1 min‐1) i.v. with nitrous oxide 70%/oxygen 30% for maintenance of anaesthesia. Vital signs were maintained within 20% of baseline. All patients were extubated in the operating room. PACU nursing staff recorded episodes of vomiting for 4–6 h prior to discharge. A telephone interview the following day was also used for data recovery. Age, sex, and duration of the procedure were not significantly different between the two study groups. Of 19 patients who received propofol, four vomited (21%); in contrast, of the 20 patients who received isoflurane, 11 vomited (55%). This difference is significant (P= 0.048 two‐tailed Fishers Exact Test). These data suggest that using propofol for anaesthesia can diminish the incidence of vomiting following tonsillectomy.

A comparison of propofol and chloral hydrate for sedation of young children during magnetic resonance imaging scans

The purpose of this study was to compare the effects of two methods of providing sedation for young children undergoing magnetic resonance imaging (MRI) studies on efficiency of scanner utilization. Thirty‐nine patients were randomized to receive either propofol or chloral hydrate. Age and gender distributions were not significantly different between the groups. Induction time was significantly less for propofol than for chloral hydrate (6 ± 3 min vs 41 ± 9 min; P < 0.0001); and recovery time for propofol was significantly shorter than for chloral hydrate (18 ± 7 min vs 47 ± 28 min; P < 0.0001). Procedure times were not significantly different. Three of 19 patients who received chloral hydrate moved and their scans were interrupted; two of these received propofol. None of the patients in the propofol group moved. Utilization efficiency of the MRI scanner, defined as 100 ± (Procedure Time)/(Induction Time + Procedure Time), was 87 ± 6% for propofol and 45 ± 13% for chloral hydrate. These data demonstrate that propofol sedation allows the MRI scanner to be utilized more efficiently than chloral hydrate sedation.

A criterion to determine whether cis-4-hydroxyproline is produced in animal tissues

Hydrolyzates of tissues that had been labeled with [14C]proline often contain significant amounts of cis-4-hydroxy[14C]proline. Since animal cells do not contain an enzyme which can effect formation of cis-4-hydroxyproline, there are only two possible explanations for its presence. Either it is formed during acid hydrolysis of trans-4-hydroxyproline (which is synthesized by cells and is a common constituent of connective tissues), or it is produced by a nonenzymatic mechanism such as attack by oxygen radicals. It is important to resolve this issue because if a nonenzymatic mechanism is active in connective tissues, then it will be necessary to reevaluate currently accepted ideas about production of hydroxyproline. This communication describes a method for distinguishing between the two alternate explanations. Tissues or cells are labeled with [14C]proline, and then a known amount of trans-4-hydroxy[3H]proline is added to each sample before hydrolysis; the relative amounts of [14C]- and [3H]-cis-4-hydroxyproline are compared after hydrolysis. It is known from a separate series of measurements with mixtures of [14C]- and [3H]-trans-4-hydroxyproline standards that there is a very high correlation (r = 0.998) between acid-induced formation of the [14C]- and [3H]-cis epimers. One can thus compare the amount of cis-4-hydroxy[14C]proline in a hydrolyzate from a biological system with the amount that would be expected if it were all formed during acid hydrolysis. This method was used to show that fibroblasts cultured under conditions commonly used to study collagen metabolism do not produce cis-4-hydroxyproline. This result strongly suggests that nonenzymatic hydroxylation does not normally occur in cell culture systems.

Limitation on sensitivity of measuring collagen degradation: Studies with cultured liver cells

Intracellular degradation of newly synthesized collagen is studied by incubating cells with (14C)proline and measuring the hydroxy(14C)proline in a low molecular weight fraction relative to total hydroxy-(14C)proline synthesized. This communication describes a fundamental limitation on the precision with which the measurement can be made; the limitation derives from an irreducible uncertainty in estimating the background radioactivity contributed by the isotope used for metabolic labeling. The problem is illustrated by experiments with cultured liver cells. In rat hepatocytes, the hydroxy-(14C)proline in the low molecular weight fraction was barely detectable above background; the degradation was 29%, however the uncertainty was +/- 28%. In contrast, significant amounts of hydroxy(14C)proline were detected in fractions from human and rat hepatoma cells; and while the levels of degradation were approximately the same as in rat hepatocytes, the measurements could be made with substantially greater precision.