Biochemical events associated with activation of smooth muscle contraction

Biochemical events associated with activation of smooth muscle contraction were studied in neurally stimulated bovine tracheal smooth muscle. A latency period of 500 ms preceded increases in isometric force and myosin light chain phosphorylation. However, stimulation resulted in the rapid hydrolysis of inositol phospholipids as demonstrated by increases in inositol phosphates by 500 ms. Inositol trisphosphate increased 2-fold with no significant change in inositol tetrakisphosphate. The apparent activation state of myosin light chain kinase was assessed indirectly through measurements of the fractional activation of a second calmodulin-dependent enzyme, cyclic nucleotide phosphodiesterase. The fractional activation of cyclic nucleotide phosphodiesterase increased after neural stimulation to a maximal extent by 500 ms and remained at this level for at least 4 s. The monophosphorylation of myosin light chain increased after 500 ms and reached a maximum value by 2 s. Diphosphorylation also occurred but to a much lesser extent. Fractional activation of cyclic nucleotide phosphodiesterase and myosin light chain phosphorylation both decreased after 10 min continuous stimulation, although the force response remained at a maximal level. These observations demonstrate that inositol trisphosphate formation and activation of cyclic nucleotide phosphodiesterase (and hence most likely myosin light chain kinase) by calmodulin precede myosin light chain phosphorylation and that these events are sufficiently rapid to mediate the contractile response of neurally stimulated tracheal smooth muscle.

Intramolecular Long-Distance Electron Transfer in Organic Molecules

Intramolecular long-distance electron transfer (EI) has been actively studied in recent years in order to test existing theories in a quantitative way and to provide the necessary constants for predicting ET rates from simple structural parameters. Theoretical predictions of an "inverted region," where increasing the driving force of the reaction will decrease its rate, have begun to be experimentally confirmed. A predicted nonlinear dependence of ET rates on the polarity of the solvent has also been confirmed. This work has implications for the design of efficient photochemical charge-separation devices. Other studies have been directed toward determining the distance dependence of ET reactions. Model studies on different series of compounds give similar distance dependences. When different stereochemical structures are compared, it becomes apparent that geometrical factors must be taken into account. Finally, the mechanism of coupling between donor and acceptor in weakly interacting systems has become of major importance. The theoretical and experimental evidence favors a model in which coupling is provided by the interaction with the orbitals of the intervening molecular fragments, although more experimental evidence is needed.

Ventilator use in progressive neuromuscular disease: impact on patients and their families

The question of extending the lives of patients with progressive neuromuscular disease by means of ventilator support is controversial. It has been documented that ventilators can prolong the lives of patients with Duchenne muscular dystrophy by between two and 25 years, but few studies have assessed the effects of their use on individual or family functioning, or the quality of survival. A sample of patients with progressive disease and families living in the community was surveyed to assess these effects. Most of the sample were satisfied with their decision to extend life with the ventilator, but they found the experience significantly stressful in the home. Both patients and families believed their health-care team could have met their needs more comprehensively. Recommendations are made for health-care professionals working with patients with late-stage neuromuscular disease who need to use ventilators.

Isolation and expression of a new mouse homeobox gene

A homeobox-containing clone has been isolated from an adult mouse kidney cDNA library and shown by DNA sequence analysis to be a new isolate, Hox-6.1. A genomic clone containing Hox-6.1 has been isolated and found to contain another putative homeobox sequence (Hox-6.2), within 7 kb of Hox-6.1. In situ hybridization of mouse metaphase chromosomes shows this Hox-6 locus to be located on chromosome 14 (14E2). Hox-6.1 has been studied in detail and the predicted protein sequence of the homeobox is 100% homologous to the Xenopus Xeb1 (formally AC1) homeobox and the human c8 homeobox (Carrasco et al. 1984; Boncinelli et al. 1985; Simeone et al. 1987). Southern blotting shows that the DNA sequence encoding Hox-6.1 is single copy. Expression of Hox-6.1 has been studied in adult tissues and embryos by RNase protection assays, Northern blotting analysis and in situ hybridization. RNase protection assays show that Hox-6.1 transcripts are present in embryos between days 9 1/2 and 13 1/2 of gestation and in extraembryonic tissues at day 9 1/2. Adult expression is detectable in kidney and testis but not in liver, spleen and brain. One major transcript is detectable on Northern blots of kidney and day-13 1/2 embryo RNA. In kidney, this transcript is 2.7 kb whereas in embryos the major transcript is smaller at 1.9 kb, a much fainter band being visible at 2.7 kb. Localized expression of Hox-6.1 is observed in the spinal cord and prevertebral column of day-12 1/2 embryos, and in the posterior mesoderm and ectoderm of day-8 1/4 embryos. An anterior boundary of expression is located just behind the hindbrain whereas the boundary in the mesoderm is located at the level of the 7th prevertebra.

Secretion and processing of staphylococcal nuclease by Bacillus subtilis

We have studied the secretion and processing of Staphylococcus aureus nuclease in Bacillus subtilis. We show that the initial species of nuclease found in the cell supernatants during short-term radioactive labeling (pulse-chase) had a molecular weight of approximately 18,800 and comigrated in a sodium dodecyl sulfate-polyacrylamide gel with staphylococcal nuclease B. This nuclease B form was processed to the mature nuclease A extracellularly by a phenylmethylsulfonyl fluoride-sensitive protease. The nuclease B-processing site is a consensus signal peptidase site, and the processing of nuclease B was coupled to secretion as judged by pulse-chase experiments. The nuclease A was shown by microsequencing of the N terminus to be 2 amino acid residues shorter than the nuclease A described for S. aureus Foggi. The nuclease B form was still the first species found in the culture supernatant after removal of the N-terminal 26 amino acids of the native 60-amino-acid signal peptide. However, removal of the N-terminal 72 amino acids abolishes secretion of any nuclease form and leads to the intracellular accumulation of nuclease.

Effects of isoproterenol on active force and Ca2+ X calmodulin-sensitive phosphodiesterase activity in porcine coronary artery

Relaxation of vascular smooth muscle following beta-adrenergic stimulation may result from reduction of the cytoplasmic Ca2+ concentration, reduction in the sensitivity of the contractile apparatus to Ca2+, or both. To help resolve these possibilities, we measured the extent of activation of Ca2+ X calmodulin-sensitive phosphodiesterase in intact porcine coronary artery strips as a functional indicator of the cytoplasmic Ca2+ concentration. Both calmodulin-stimulated phosphodiesterase activity and active force increased during K+ stimulation of coronary artery strips. Relaxation of K+-contracted artery strips following stimulus withdrawal was accompanied by rapid inactivation of Ca2+ X calmodulin-sensitive phosphodiesterase. The temporal relationship between isoproterenol-induced relaxation and inactivation of Ca2+ X calmodulin-sensitive phosphodiesterase was studied in both histamine- and K+-contracted tissues. Stimulation of strips with 10 microM histamine or with 44 mM K+ led to comparable increases both in active force and in calmodulin-stimulated phosphodiesterase activity. Thereafter, sustained contraction elicited by histamine was accompanied by a decrease in calmodulin-stimulated phosphodiesterase activity. Isoproterenol rapidly relaxed histamine-contracted strips and accelerated the decrease in phosphodiesterase activity. In contrast, sustained contraction in response to K+ was accompanied by a sustained elevation of calmodulin-stimulated phosphodiesterase activity. Isoproterenol treatment of K+-contracted tissues led to relaxation that was slow and incomplete, and it had very little effect on calmodulin-stimulated phosphodiesterase activity. We conclude that reduction of the cytoplasmic Ca2+ concentration is important for rapid relaxation of the coronary artery following beta-adrenergic stimulation. We cannot disallow the possibility that a decrease in the sensitivity of the contractile apparatus to Ca2+ is involved to some degree.

Homoeobox gene expression in mouse embryos varies with position by the primitive streak stage

Pattern formation in animal development requires that genes be expressed differentially according to position in the sheets of cells that make up the early embryo. The homoeobox-containing genes of Drosophila are control genes active both in the establishment of a segmentation pattern and in the specification of segment identity. In situ hybridization experiments confirm that these genes are expressed in a segmentally-restricted manner and that their expression presages morphological differentiation of segmental structures. Homoeobox genes have recently been isolated from the mouse and have been shown to be expressed during mouse development. Using in situ hybridization, we show here that expression of the mouse homoeobox gene Mo-10 (ref. 7) is spatially restricted in the developing embryo and that localization of expression is already evident within the germ layers before their morphological differentiation. These findings support the suggestion that the homoeobox genes of mammals, like those of Drosophila, may be important in pattern formation.

Phorbol diesters alter the contractile responses of porcine coronary artery

We have studied the effects of activators of the Ca++- and phospholipid-dependent enzyme protein kinase C on isometric tension development by both intact and skinned coronary artery strips. The intact strips contracted upon incubation with 12-O-tetradecanoylphorbol-13-acetate. 12-O-tetradecanoylphorbol-13-acetate produced a leftward shift in the concentration-response relationship for contraction of the tissues by K+, histamine and norepinephrine. Phorbol-12,13-dibutyrate elicited contraction of detergent-skinned artery strips when the free Ca++ concentration in the bathing media was 0.1 microM or greater. This effect was diminished greatly in the presence of polymyxin B, a putative inhibitor of protein kinase C. Phorbol-12,13-dibutyrate shifted the Ca++ concentration-tension response relationship for the skinned tissue to the left. These results are consistent with a role for protein kinase C in regulating the contractile responses of coronary arterial smooth muscle to a variety of stimuli, at least in part by increasing the sensitivity of the contractile apparatus to Ca++.

Direct measurements of intramolecular electron transfer rates between cytochrome c and cytochrome c peroxidase: effects of exothermicity and primary sequence on rate

Rapid mixing of ferrocytochrome c peroxidase [cyt c peroxidase(II)] and ferricytochrome c [cyt c(III)] results in the reduction of cyt c(III) by cyt c peroxidase(II). In 10 mM phosphate, pH 7.0, the rate of decay of cyt c peroxidase(II) and the rate of accumulation of cyt c(II) give equal first-order rate constants: k = 0.23 +/- 0.02 s-1. Equivalent results are obtained by pulse radiolysis using isopropanol radical as the reducing agent. This rate is independent of the initial cyt c(III):cyt c peroxidase(II) ratios. These results are consistent with unimolecular electron transfer occurring within a cyt c(III)-cyt c peroxidase(II) complex. When cyt c is replaced by porphyrin cyt c (iron-free cyt c), a complex still forms with cyt c peroxidase. On radiolysis, using e-aq as the reducing agent, intracomplex electron transfer occurs from the porphyrin cyt c anion radical to cyt c peroxidase(III) with k = 150 s-1. This large rate increase with increasing delta G degrees suggests that the barrier for intracomplex electron transfer is large. Finally, we have briefly investigated how the cyt c peroxidase(II)----cyt c(III) rate depends on the primary structure of cyt c(III). We find the reactivity order to be as follows: yeast (k = 3.4 s-1) greater than horse (k = 0.3 s-1) greater than tuna (k = 0.2 s-1). These results mirror a report [Ho, P. S., Sutoris, C., Liang, N., Margoliash, E. & Hoffman, B. M. (1985) J. Am. Chem. Soc. 107, 1070-1071] on excited state reactions of the cyt c/cyt c peroxidase couple.

Genetic analysis of spontaneous and induced palatal slit in C57BL/6 mice

The results of experiments designed to elucidate the nature of the genetic factors underlying the palatal slit defect in C57BL/6 mice indicate that probably two loci in females and four in males determine the difference in susceptibility to the spontaneous defect between the C57BL/6 and SWV/BcTa strains of mice. Moreover, it appears that these are not the same genes determining the difference between these same strains in palatal slit response to maternal treatment with triamcinolone. Additional evidence is presented to support the view that in the C57BL/6 strain the triamcinolone-induced palatal slit and cleft palate responses are not correlated.

A new complication of AIDS: thoracic myelitis caused by herpes simplex virus

Progressive thoracic myelopathy occurred in a patient with AIDS. Concurrent opportunistic infections included disseminated systemic cytomegalovirus, aspergillosis, and cutaneous herpes simplex virus (HSV). At autopsy, immune stains indicated that the myelopathy was caused by HSV type 2 infection of the spinal cord.

Secretion of staphylococcal nuclease by Bacillus subtilis

The staphylococcal nuclease (nuc) gene from Staphylococcus aureus has been cloned and expressed in Bacillus subtilis. The nuclease protein was expressed either from its own promoter and translation start signals, or from a combination of a B. subtilis promoter, ribosome binding site, and a signal peptide sequence. Greater than 80% of the active gene product was secreted into the medium, whereas, when a signal peptide sequence was absent, as little as 4% of the nuclease activity was found in the culture medium. Intracellular (or cell-bound) nuclease, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting, was shown to have the molecular weight of the predicted precursor protein with the signal peptide. Levels of nuclease reached 50 mg per liter in the culture medium, depending on the growth medium and the strain used. These findings indicate the prospective use of nuclease as a model system for studying secretion of heterologous proteins in B. subtilis.

Neurologic complications in acquired immunodeficiency syndrome (AIDS)

Neurologic syndromes in AIDS are of four types: infections, para-infections, neoplastic, and paraneoplastic. All levels of the neuraxis can be affected. Neurologic complications may be the initial symptom or the cause of death. Aggressive evaluation, including biopsy of cerebral lesions, is indicated because effective treatment can be given.

Neuropathy and anti-MAG antibodies without detectable serum M-protein

Anti-MAG IgM antibodies were detected by ELISA in a patient with slowly progressive peripheral neuropathy. Serum IgM content was normal, and no M-protein was detected by serum protein electrophoresis, immunoelectrophoresis, or immunostaining. By immunoblot analysis, the anti-MAG antibodies were IgMk; they reacted with human and bovine MAG but not with mouse MAG. The data suggest that there was an anti-MAG IgM M-protein in concentration too low to be detected by conventional techniques. Tests for anti-MAG antibodies should be done in patients with slowly progressive neuropathy of unknown etiology, even in the absence of detectable serum M-protein.

Host specificity of filamentous, segmented microorganisms adherent to the small bowel epithelium in mice and rats

Germfree rats and mice were given by gavage samples of ileal homogenates prepared from conventional rats and mice. Filamentous, segmented procaryotes adhered to the small bowel epithelium in the ex-germfree mice only when the homogenate was made from mouse bowel and in the ex-germfree rats only when the inoculum came from rats. Thus, the filamentous microorganisms are host animal specific.

The role of myosin light chain kinase phosphorylation in beta-adrenergic relaxation of tracheal smooth muscle

Myosin light chain kinase from smooth muscle has been shown to be phosphorylated by cyclic AMP-dependent protein kinase, which leads to a decrease in the affinity of the kinase for Ca2+ . calmodulin and, hence, a decrease in enzymatic activity. This event has been proposed as a mechanism for the relaxation of smooth muscle in response to increased intracellular concentrations of cyclic AMP. The ratio of myosin light chain kinase activities measured in the presence of 4 microM or 100 microM Ca2+, at 1 microM calmodulin, permits evaluation of such a change in the calmodulin activation properties of myosin light chain kinase. This activity ratio was decreased by phosphorylation of either purified bovine tracheal smooth muscle myosin light chain kinase, or the endogenous myosin light chain kinase in a homogenate of tracheal smooth muscle, with the addition of the catalytic subunit of cyclic AMP-dependent protein kinase. The ratio was unchanged, however, by activation of the endogenous cyclic AMP-dependent protein kinase in homogenates of tracheal smooth muscle by the addition of cyclic AMP. Incubation of tracheal smooth muscle with isoproterenol, at a concentration sufficient to relax the muscle and to increase phosphorylase a formation, had no effect upon the activity ratio. Incubation of tracheal smooth muscle for 2 hr in the presence of carbachol resulted in a transient increase and then a decrease in myosin light chain phosphate content to control values with no decrease in isometric force. The addition of isoproterenol at 2 hr still resulted in relaxation. These findings are inconsistent with a role of myosin light chain kinase phosphorylation in mediating relaxation of tracheal smooth muscle by beta-adrenergic agonists. Cyclic AMP-dependent effects on cytoplasmic calcium concentrations may be more important in mediating relaxation.

The lidgap defect in mice: update and hypotheses

The open eye defect in the mouse can result from the action of mutant genes or of teratogens. Among the genetic forms, the lidgap series poses a particular challenge. The lidgap defect appears to be a complex genetic trait and may serve as a model for the genetic analysis of other genetically complex morphological defects in mammals. Extensive breeding data, together with data on the response of the trait to in utero treatment with cortisone, have been analyzed. The results lead us to propose a model involving a single major locus with a series of alleles of graded strength, hypomorphs. The ranking is lg greater than lgstn = lgSt greater than lgM1. The lg/lg genotype alone can be sufficient to produce the lidgap trait, but the "weaker" alleles require a second or even third locus acting in the same pathway. In addition, there is evidence that a recessive suppressor locus is present in the system. These hypotheses are testable and some experiments to develop them further are discussed.

The safety of egg-containing vaccines for egg-allergic patients

Forty-two patients with a history of egg sensitivity were evaluated for receiving avian-grown vaccines. After giving a history and undergoing physical examination, each patient was skin-tested with egg antigens and six egg-propagated vaccines, given an oral egg challenge, and finally, when possible, given a vaccine challenge. Thirty-seven of the 42 patients (88%) were ultimately given one or more of the vaccines with no reactions or only minimal ones to both egg protein and vaccine; they had mild reactions consisting of pruritus, headache, and apprehension. Immunization was withheld from three patients who had a history of severe reactions after egg ingestion and strongly positive skin reactivity to both egg and vaccine. A history of egg intolerance should not, by itself, disqualify a patient from receiving one of these vaccines. However, a history of exquisite sensitivity to egg protein indicates that a severe vaccine reaction is likely. An intradermal skin test utilizing 0.02 ml of a 1:100 dilution of the vaccine and resulting in a wheal of greater than 5 mm was found to be the test that most reliably predicted those patients who should not receive the vaccine.

Effect of hemorrhage and anoxia on hepatic gluconeogenesis and potassium balance in the rat

Previous investigations have demonstrated impairment of hepatic gluconeogenic activity during both hypovolemia and sepsis, but the mechanisms responsible remain unclear. The present study was designed to determine the influence of lack of oxygen on gluconeogenesis independent of humoral factors, products of ischemic peripheral tissues or pH changes. Livers obtained from Sprague-Dawley rats fasted 24 hours were perfused with Krebs-Henseleit buffer containing 5 mM lactate for 30 minutes. In the control group (n = 8) perfusion was continued; in others, anoxia was induced by perfusing with buffer equilibrated with 95% N2 and 5% CO2 for periods of 15, 30, or 60 minutes (n = 4, 5, and 5, respectively). The initial conditions were then reinstituted for an additional 45 minutes. Anoxia caused hepatic release of K+, indicative of disordered hepatic cellular ionic gradients and an abrupt cessation of gluconeogenesis. Reoxygenation partially reversed these alterations but some impairment of gluconeogenesis persisted and the degree of uptake of K+ from the perfusion media was decreased as the duration of anoxia increased. The degree of restoration of gluconeogenesis after a period of anoxia was closely associated with restoration of cellular uptake of K+. By comparison, livers taken from hypovolemic animals maintained at a mean arterial blood pressure of 40 mm Hg until the beginning of the decompensatory stage of shock exhibited a gluconeogenic capacity of only 41% of control animals and was comparable to the compromise induced by between 30 and 60 minutes of anoxia. These results suggest that the abilities to restore hepatic electrolyte balance and gluconeogenesis after oxygen deprivation are affected in parallel and may reflect a common dependence on the restoration of ATP stores after the insult.

Transcription of the 'non-transcribed' spacer of Drosophila melanogaster rDNA

We have detected a set of transcripts in Drosophila melanogaster cells which are homologous to repeating elements within the 'non-transcribed' spacer region of rDNA. The RNA molecules range from 240 to 1680 nucleotides, differing in length by an integral value of 240 nucleotides. We have sequenced several AluI fragments which characterise the main 240 nucleotide repeating element. We find that each of these fragments contain a segment of approximately 50 nucleotides, which is homologous to the transcription initiation site for pre-rRNA.

Occurrence of oligoclonal bands in multiple sclerosis and other CNS diseases

The results of cerebrospinal fluid agarose gel electrophoresis in 300 consecutive patients were correlated with neurological examinations and diagnoses, other cerebrospinal fluid studies, and the results of evoked potential examinations. The presence of oligoclonal bands was the most sensitive test for multiple sclerosis (MS); bands were present in from 100% (11/11) of patients with definite MS to 82% (27/33) of those with possible MS (classified by McAlpine criteria). The visual evoked response was the next most sensitive study. Thirty-eight patients without MS or related disorders had bands in the IgG region. Three patients had plasma cell dyscrasias. Seven patients had thick single bands. Single bands did not correlate with chronic polyneuropathy but appeared to be an artifact of storage. Twenty-eight patients had active neurological disease, including cerebral infarction (in 5), viral infection (in 4), remote effect of carcinoma (in 4), and acute and chronic polyneuropathies (in 6). In acute illnesses (i.e., vascular insults), repeat electrophoresis showed disappearance of bands. In continually active disease, bands persisted. These results indicate that the presence of oligoclonal bands provides sensitive supporting evidence for the diagnosis of MS but that bands may be present in other disorders, including those not directly related to infection or abnormal immune response. The data suggest that oligoclonal bands may represent an immune response to neurological injury that is prominent in disorders with a particularly intense or continuous antigenic stimulus.

Phosphorylation of myosin light chain in skeletal and smooth muscles

Significant differences in the properties of myosin light chain phosphorylation in skeletal and smooth muscles may be important in considering the role of myosin phosphorylation in contraction. Repetitive, low-frequency stimulation of fast-twitch skeletal muscle resulted in phosphorylation of myosin light chain. Some of the factors leading to phosphorylation under these conditions include 1) partial activation of myosin light chain kinase with each stimulus, 2) a slow rate (t1/2 = 1 s) of inactivation of the kinase activity, and 3) a very slow rate of dephosphorylation by myosin light chain phosphatase. Myosin light chain phosphorylation was correlated with potentiation of isometric twitch tension in posttetanic potentiation and staircase responses. Stimulation of contraction in bovine tracheal smooth muscle by the cholinergic agonist carbachol was correlated with phosphorylation of the myosin light chain. The initial rate and maximum extent of phosphorylation during the first minute of stimulation was dependent on the concentration of carbachol. Phosphate incorporation into light chain declined after 1 min whereas isometric tension was maintained. beta-Adrenergic inhibition of tension development was accompanied by a decrease in the rate and extent of phosphorylatable myosin light chain phosphorylation but was not associated with reduced affinity of myosin light chain kinase for calcium-calmodulin.

Combined effects of sodium nitroprusside and propranolol on hypoxic pulmonary vasoconstriction

Recent clinical experience and previous experimental work indicate that propranolol may reverse sodium-nitroprusside-induced inhibition of hypoxic pulmonary vasoconstriction (HPV). Accordingly, the authors decided to test this possibility in an experimental model that allows direct examination of pharmacologic influence on HPV. Six mongrel dogs were anesthetized with pentobarbital and intubated. Following a left thoracotomy, the left lower lobe (LLL) was ventilated independently but synchronously with the rest of the lung. Selective hypoxia of the LLL (95% nitrogen and 5% CO2) caused a 59 +/- 6% (mean +/- SE) decrease in the electromagnetically measured fraction of the cardiac output perfusing the LLL and a 287 +/- 65% increase in the pulmonary vascular resistance of the LLL from their respective prehypoxic values. Propranolol, 1 mg/kg intravenously, caused a 76 +/- 5% beta-blockade, as determined by an isoproterenol infusion test, but did not cause a significant change in the LLL HPV response. Sodium nitroprusside (SNP) infusion, caused a 38 +/- 4% decrease in systemic arterial pressure, and nearly abolished LLL HPV. Most important, the addition of propranolol to sodium nitroprusside did not significantly change the SNP induced inhibition of LLL HPV. The authors conclude that in acute lung disease, propranolol does not alter lobar HPV and does not reverse sodium nitroprusside inhibition of lobar HPV.

Detoxification Enzyme Differences Between a Herbivorous and Predatory Mite

The detoxification capabilities of the predatory mite Amblyseius fallacis and its herbivorous prey Tetranychus urticae are fundamentally different. The activities of mixed-function oxidase and trans-epoxide hydrolase are higher in the prey than in the predator; those of cis-epoxide hydrolase and glutathione transferase are lower; and esterase activity is similar. Dissimilarities may be related both to differing adaptations to plant allelochemicals and to the higher respiration rate of the predator. Hydrolytic and conjugating reactions appear more important than oxidative pathways in imparting organophosphate resistance to these acarines. These resistances provide insecticide selectivity favorable to the predator and improved integrated pest control.

Constrained linear inversion of optical scattering data for particle size spectra: an approach to angular optimization

A methodology for investigating the variation of particle size distributions retrieved from constrained linear inversion of optical scattering data is presented. By plotting the expected inversion error vs angular scanning parameters (for typical size distribution vectors) one can determine sets of optimum angles based on a minimum error criteria at each particle size. An expression for the expected inversion error at each radius knot is derived. In addition a formulation for the Fredholm quadrature matrix in terms of Legendre coefficients and polynomials is introduced. This method of computation is advantageous when a large number of angles are to be investigated. The derived results are applied to the special case of a Junge Continental Aerosol.

Closing the gap in quality assurance: A tool for evaluating group leaders

A commitment to quality assurance means offering a cycle of feedback to those being evaluated. How to meet that commitment was the question asked by the Health Education Department of a large Health Maintenance Organization whose more than 70 facilitators annually provide instruction for over 3,000 enrollees. As part of the multi-faceted endeavor to develop a systematic quality assurance program for the department's offerings, a reliable participant-scored standardized tool had to be constructed. The staff of the department first identified two concepts as critical for quality instruction: interpersonal skills and technical competence. Based on these criteria a 49-item questionnaire was developed and tested during "pre-pilot" and pilot stages. By computer analysis, 27 items with an alpha-reliability coefficient of .94 remained to form the tool the department uses. The development of the evaluation tool and its use are described.

Respiratory and cardiovascular responses to PEEP in artificially ventilated patients after cardiopulmonary bypass surgery

The respiratory and haemodynamic effects of incremental levels of positive and expiratory pressure (PEEP) to 9 cm H2O were studied in ten adult patients 3--6 hours after uneventful cardiopulmonary bypass surgery. Functional residual capacity was increased and deadspace-tidal volume ratio tended to fall, the latter approaching significance at +6 and +9 cm PEEP. Thus lung volume was increased and there was a tendency to improved gas distribution to the alveoli. However there was no significant change in PaO2, alveolar-arterial oxygen tension difference or venous admixture. Cardiac index, and left ventricular strokework index were marginally depressed at 6 cm PEEP and further at 9 cm, while right atrial pressure and pulmonary artery occlusion pressure were raised at 9 cm PEEP. It would appear that low levels (3--6 cm) of PEEP do not improve gas exchange in the lungs to any worthwhile degree, and levels (6--9 cm) may impair cardiac performance.

A transcriptionally active pseudogene in xenopus laevis oocyte 5S DNA

DNA that encodes the Xenopus laevis 5S pseudogene is transcribed following microinjection into oocyte nuclei. Transcription in injected oocytes is accurate, is mediated by RNA polymerase III and is initiated at the first nucleotide of the pseudogene. The level of pseudogene transcription can be as high as 85% of that of the normal 5S gene. The results suggest that the observed absence of pseudogene transcripts of defined length in vivo probably is due to inefficient termination of transcription.

Prolonged intracerebral infection with poliovirus in asymptomatic mice

A heretofore unrecognized prolonged asymptomatic infection has been identified in mice intracerebrally inoculated with Lansing strain type II poliovirus. Virus was detected by infectivity assay and nucleic acid hybridization and was found in brains as long as 77 days after injection. Viral RNA replication occurred, indicating that persisting virus was not an inactive residuum of the infecting dose. Virus was sometimes found by infectivity even when viral RNA could not be demonstrated by hybridization, but detection by nucleic acid hybridization alone never occurred. Among 56 animals--including mice that died of infection, mice with prolonged infection, and survivors from which virus was not recovered--no animal had a serum neutralization titer above 1:2 in a plaque reduction assay Moreover, brain homogenates of 30 survivors without virus did not have neutralization titers above 1:4 in the plaque reduction assay. These findings were the same as in mock-infected mice.

R-factor responsible for an outbreak of multiply antibiotic-resistant Klebsiella pneumoniae

Seven serotypes of Klebsiella pneumoniae isolated from different patients demonstrated resistance to the same eight antibiotics. A plasmid carrying resistance determinants to these antibiotics and mercury salts could be transferred in toto to a plasmidless strain of Escherichia coli. All E. coli transconjugants showed the same antibiotic resistance pattern. Digestion with restriction endonucleases yielded patterns that were identical for each of the R-factor transferred from the multiply resistant serotypes. Moreover, deoxyribonucleic acid-deoxyribonucleic acid hybridization demonstrated identity between the probe, pMAC20 (an R-factor from one serotype), and all R-factors isolated from the multiply resistant strains of K. pneumoniae and the E. coli transconjugants tested.

First arch malformation: a new craniofacial mutant in the mouse

The first arch malformation arising in a BALB/c strain of mice, has been shown to be inherited as a single autosomal recessive gene and is given the provisional gene symbol far. Affected newborns have extensive bony defects of the face and skull, including a cleft secondary palate, and die within 24 hours of birth. Most of the abnormalities occur in bones derived from the first branchial arch and most of the bony derivatives of the first arch are abnormal in the mutant.

Amyotrophic lateral sclerosis: search for poliovirus by nucleic acid hybridization

Radioactive-labeled complementary DNA (cDNA) probes specific for either poliovirus type I or type II were hybridized with cellular RNA from the brains of patients dying of amyotrophic lateral sclerosis. In 11 brains examined, the percentage of hybridization for either polio type was the same as the percentage in normal brains. Although hybridization is a sensitive method for detection of viral genome material in infected cells, inability to detect viral nucleic acid by current techniques does not preclude the presence of viral genetic material in the tissue examined.