Biomedical subjects

D Major

Publications and source records attributed to D Major.

At least 19 recordsLinked to original sources

PubMed1997

Morphometrics of normal and hypoplastic lungs in preterm lambs with gas and partial liquid ventilation

To test the hypothesis that perfluorochemical (PFC) instillation may reduce the pulmonary trauma commonly associated with conventional gas ventilation, we studied 12 lambs with normal lungs and 10 with pulmonary hypoplasia secondary to congenital diaphragmatic hernia (CDH). We used mechanical ventilation for up to 3.5 h, with and without tracheal instillation of LiquiVent PFC liquid. At the end of experimentation lungs were fixed for morphometrical analysis of their components and pulmonary trauma was evaluated by measurement of the perivascular compression index (PCI = % perivascular emphysema/% vessels). In normal lungs good gas exchange and respiratory mechanics were obtained with all modes of ventilation, with no statistical difference in the index of pulmonary trauma with or without instillation of LiquiVent (P >0.05). In the hypoplastic lungs, tracheal instillation of PFC liquid after 30 min of conventional gas ventilation significantly improved PaCO2 (from 107+/-8 to 55+/-6 mmHg, P <0.05), pH (from 7.00+/-0.03 to 7.29+/-0.04, P <0.05), compliance (from 0.08+/-0.01 to 0.25+/-0.03 ml/cmH2O . kg, P <0.05), and ventilatory index (from 1,445+/-148 to 794+/-139, P <0.05). Survival was 6/6 animals with PFC ventilation compared to 1/4 with conventional gas ventilation with no more pulmonary trauma (mean PCI 12.6+/-1.8 vs. 11.4+/-4.0%, P >0.05) for a longer mean ventilatory period in the PFC group. We conclude that the PFC liquid technique of ventilation can improve respiratory physiology when conventional gas ventilation alone is proving inefficient. There was no significant difference in pulmonary trauma at morphometrics between gas and partial liquid ventilation.

Journal Article↗

PubMed1997

Morphometrics of normal and hypoplastic lungs in preterm lambs with gas and partial liquid ventilation.

To test the hypothesis that perfluorochemical (PFC) instillation may reduce the pulmonary trauma commonly associated with conventional gas ventilation, we studied 12 lambs with normal lungs and 10 with pulmonary hypoplasia secondary to congenital diaphragmatic hernia (CDH). We used mechanical ventilation for up to 3.5 h, with and without tracheal instillation of LiquiVent PFC liquid. At the end of experimentation lungs were fixed for morphometrical analysis of their components and pulmonary trauma was evaluated by measurement of the perivascular compression index (PCI = % perivascular emphysema/% vessels). In normal lungs good gas exchange and respiratory mechanics were obtained with all modes of ventilation, with no statistical difference in the index of pulmonary trauma with or without instillation of LiquiVent (P >0.05). In the hypoplastic lungs, tracheal instillation of PFC liquid after 30 min of conventional gas ventilation significantly improved PaCO2 (from 107+/-8 to 55+/-6 mmHg, P <0.05), pH (from 7.00+/-0.03 to 7.29+/-0. 04, P <0.05), compliance (from 0.08+/-0.01 to 0.25+/-0.03 ml/cmH2O . kg, P <0.05), and ventilatory index (from 1,445+/-148 to 794+/-139, P <0.05). Survival was 6/6 animals with PFC ventilation compared to 1/4 with conventional gas ventilation with no more pulmonary trauma (mean PCI 12.6+/-1.8 vs. 11.4+/-4.0%, P >0.05) for a longer mean ventilatory period in the PFC group. We conclude that the PFC liquid technique of ventilation can improve respiratory physiology when conventional gas ventilation alone is proving inefficient. There was no significant difference in pulmonary trauma at morphometrics between gas and partial liquid ventilation.

Animals↗

PubMed1996

Comparison between open and arthroscopic acromioplasties: evaluation of absenteeism.

OBJECTIVE: To evaluate the rate of absenteeism from work in patients who had undergone open or arthroscopic acromioplasty. DESIGN: A retrospective case series. SETTING: A university hospital. PATIENTS: Eighteen patients with excellent results after open acromioplasty performed by one orthopedic surgeon and 20 patients with excellent results after arthroscopic acromioplasty performed by another orthopedic surgeon. MAIN OUTCOME MEASURE: The time between operation and return to work. RESULTS: There were no statistical differences between the two techniques with respect to the return to work, age, sex and type of work. The overall time off work averaged 203 days (range from 42 to 840 days) for the arthroscopic group compared with 144 days (range from 60 to 540 days) for the open group. CONCLUSIONS: Open acromioplasty, a safe and reliable procedure for the general orthopedic surgeon, is associated with a shorter, thought not significant, delay in return to work than the arthroscopic technique.

Absenteeism↗

PubMed1995

Combined gas ventilation and perfluorochemical tracheal instillation as an alternative treatment for lethal congenital diaphragmatic hernia in lambs.

Tracheal instillation of perfluorochemical liquid (PFC) lowers surface tension in the lung and thus might reduce barotrauma commonly associated with conventional gas ventilation (GV) in highly immature and hypoplastic lungs. It could be a promising alternative treatment for congenital diaphragmatic hernia (CDH) when GV alone is proving inefficient. The authors compared data for eight newborn lambs with surgically induced CDH. The animals had GV and were studied (in 2 groups) for up to 3.5 hours. Group 1 (GV, n = 4) had gas ventilation only. In group 2 (PFC, n = 4), after 30 minutes of GV, 10 to 12 mL/kg of warmed, oxygenated PFC liquid (LiquiVent) was instilled into the lung via the trachea under pressure-volume curve monitoring. Arterial pressure, blood chemistry, and pulmonary mechanics were evaluated serially; histological analysis was performed. One preassigned animal in group 1 died after 15 minutes. After 30 minutes of life, the cardiopulmonary profile of survivors was indicative of severe respiratory distress (Pao2 < 72 mm Hg with FIO2 at 1.0, PaCO2 > 90 mm Hg, compliance < 0.10 mL/cm H2O/kg) and not different between groups; the severity of pulmonary hypoplasia was further confirmed postmortem; the ratio of lung weight to body weight was 41% of that observed in control lambs, in both gas-only and combined gas/PFC-ventilated animals, compared with their respective controls. After instillation of PFC, there were dramatic improvements in acid-base status and pulmonary compliance in group 2. Survival at 3.5 hours also was markedly different (4 of 4 PFC animals and 1 of 3 GV animals).(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗

PubMed1995

Cross-reaction but no avidity change of the serum antibody response after influenza vaccination.

Pre- and post-vaccination sera from 19 volunteers were analysed by the haemagglutination inhibition (HI) test, virus neutralization (VN) assay and avidity enzyme-linked immunosorbent assay (ELISA). The sera were tested against the three strains in a commercial inactivated influenza vaccine; A/Beijing/353/89(H3N2); A/Taiwan/1/86 (H1N1) and B/Yamagata/16/88. Additionally, a range of earlier strains and one newer isolate were assayed for HI- and VN-antibodies. Large variations in the pre-vaccination HI titres were observed for the viruses tested. However, 8-9 days after vaccination HI titres increased to above the assumed protective level (HI > or = 40) in most subjects. Although a limited number of patients were analysed at each sampling point, the time-profile we observed in this study is consistent with data we have obtained in earlier trials (Cox, R.J. et al., Vaccine 1994, 12,993-999). The VN titres, on the other hand, were low against all influenza strains before and up to 6 days, but increased rapidly 8-9 days after vaccination. A recent H3N2 isolate, A/Beijing/32/92 (H3N2), which had drifted further away from the vaccine strain, reacted to low titres or were negative in both the HI and VN assays. No change in the serum avidity to the influenza surface antigens was detected after vaccination, whereas sera from subjects naturally infected with influenza showed an increase in avidity to the infecting virus strain. The increase in serum avidity observed in the infected subjects is probably due to the increased and prolonged antigenic stimulus provided by the replicating virus.

Adolescent↗

PubMed1994

Role of charge and hydration in effects of polysialic acid on molecular interactions on and between cell membranes.

Previous studies have shown that the polysialic acid (PSA) moiety associated with the neural cell adhesion molecule (NCAM) has strong antiadhesive properties that can influence a variety of cell-cell interactions. Based on the size and structure of this long linear homopolymer, we have proposed that the activity of PSA results from its physical properties. In the present study, the premise that the charge and hydration properties of PSA underlie its effects on membrane vesicle aggregation is investigated through the manipulation of ionic strength. The results establish that the antiadhesive properties of PSA are accentuated at low ionic strength, where charge and hydration cause expansion of the polymer size, and are absent at high ionic strengths, where the polymer size collapses. These large effects of PSA on aggregation were shown not to result from changes in the osmolarity of the solvent or from the relatively small effect of ionic strength on the intrinsic functional properties of the adhesion receptors. In addition to this influence on overall membrane-membrane interaction, PSA was found to have a highly localized and ionic strength-sensitive effect on the binding of monoclonal antibodies to NCAM. Together these results suggest that the charge and hydration properties of PSA can impede both molecular interactions between apposing membranes and more direct contact of NCAM with other proteins at the cell surface.

Animals↗

PubMed1994

Codominant mixtures of viruses in reference strains of influenza virus due to host cell variation.

Influenza viruses grown in chicken eggs may comprise mixtures of variants, creating problems in establishing international reference strains and in preparing high growth reassortants. We therefore analyzed representative reference strains of H3N2 viruses from 1987 to 1989 by direct sequencing of HA1. Three of seven reference strains had different nucleotides at the same position in nucleotide gels, indicating the presence of codominant mixtures. These nucleotide duplications occurred at residues previously shown to code for amino acids associated with egg adaptation (156, 186, and 193 of HA1). Cloning of these viruses in chicken eggs permitted separation of the mixtures, and the majority of these cloned viruses could be distinguished with monoclonal antibodies. The remaining four reference strains were homogeneous and contained one of the two amino acids usually found at these residues in HA1 (e.g., 145 Glu or Lys, 186 Ser or Ile). Analysis of epidemic H3N2 isolates, for which mammalian cell and egg isolates are available for sequence analysis from the same patient, confirmed that multiple nucleotide changes can occur at residues associated with egg adaptation. When reference or epidemic strains containing codominant mixtures were passaged in eggs one to five times, one of the codominant strains usually became dominant. Similar results were obtained with Madin Darby Canine kidney (MDCK) cells, although the dominant virus usually differed from that in eggs. Attempts to reselect an influenza virus possessing sequence changes in HA1 characteristic of mammalian cells or the original human isolate (i.e., 156 Glu, 158 Glu, 186 Ser) by multiple passages in MDCK cells were not successful, but evidence was obtained that MDCK cells can provide a selective growth advantage. Thus, variants that are dominant in eggs are not necessarily dominant in MDCK cells. To preserve the original genotype of viruses used as reference strains, we recommend the following procedure: (i) cloning in chicken eggs of the candidate virus at a very early passage, (ii) selection and analysis of multiple clones with the same ferret polyclonal and/or monoclonal antibodies used in the initial screening, and (iii) selection of the isolate whose hemagglutinin molecule most closely resembles the clinical isolate.

Animals↗

PubMed1993

Influence of host cell-mediated variation on the international surveillance of influenza A (H3N2) viruses.

Growth of clinical specimens of influenza viruses in eggs can result in the selection of antigenic variants distinct from corresponding viruses grown in mammalian tissue culture. To evaluate the contribution of host cell selection on the antigenic diversity of human influenza isolates, as seen in annual surveillance studies, viruses grown in embryonated eggs were compared by antigenic and genetic analyses with their mammalian tissue culture-grown counterparts. Clinical specimens were gathered from around the world from late 1987 to 1990 and the antigenicity of isolated viruses was assessed by hemagglutination-inhibition assays using immune ferret sera as is currently performed for routine surveillance and the selection of vaccine strains. In addition, viruses were assessed using a panel of anti-H3 HA monoclonal antibodies. The extent of antigenic variation exhibited by the egg-grown strains was far greater than the relative antigenic homogeneity of the tissue culture-grown viruses. Nucleotide sequence analysis of HA1 gene PCR products of 28 MDCK cell and egg derived pairs allowed identification of amino acid substitutions responsible for the antigenic differences observed and the adaptation to growth in eggs. Among these substitutions was a change at amino acid position 186 of HA1 (Ser in tissue culture viruses and lle in egg-grown viruses) which was observed at relatively high frequency. Egg- and MDCK-grown pairs with this single amino acid difference were classified into distinct antigenic groups by ferret sera raised to WHO reference viruses. Given the additional antigenic diversity observed among egg-grown strains, considerable care should be taken in the selection of reference and vaccine strains grown in eggs. Rapid sequence comparisons of MDCK- and egg-grown viruses allow identification of variants arising through egg selection and will prove to be a useful adjunct to antigenic surveillance for the selection of reference and vaccine strains.

Africa↗

PubMed1993

Estimation of lungs' hypoplasia on postoperative chest x-rays in congenital diaphragmatic hernia.

Since we stopped inserting ipsilateral underwater chest drains after surgical reduction of the herniated contents in congenital diaphragmatic hernia, both lungs are allowed to expand at their own pace, making it possible to estimate their degree of hypoplasia on postoperative chest x-rays. Thirty-nine consecutive series of postoperative chest x-rays were examined by an independent reviewer in a blind manner and classified into three groups: none to mild pulmonary hypoplasia (group I, 10 cases); moderate to severe (group II, 20 cases); and very severe hypoplasia (group III, 9 cases). Correlations were done among groups and available anatomical and clinical data. Eight patients out of 9 survived in spite of very severe hypoplasia on postoperative chest x-rays, suggesting that indexes of severity may be misleading when they mistake pulmonary hypoplasia for the cause of death.

Chest Tubes↗

PubMed1993

A new method of treatment for pulmonary hypertension in congenital diaphragmatic hernia: experimental study in cats.

This research proposes a new treatment for pulmonary hypertension secondary to perivascular emphysema, the so-called air-block syndrome. Vibrations applied on the thorax can fraction air bubbles around the vessels into smaller ones, facilitating their redistribution and reabsorption, thus reducing the extrinsic compression on pulmonary vasculature. In cats, pulmonary lesions were obtained by continuous insufflation of air at 40 cm H2O for 2 minutes in a lower lobe of the lung. Vibrations applied on the thorax were produced with the same apparatus as used by physiotherapists to eliminate pulmonary secretions. Thirty-three cats were divided into three groups: lesions without treatment, lesions treated by vibrations, and controls. A catheter was inserted in the pulmonary artery for pulmonary artery pressure (PAP) measurements. One carotid was cannulated for arterial pressure and blood gases monitoring. Morphometric analysis of the lung had also to be carried out in all cases. Results showed a very significant decrease on pulmonary hypertension in the treated group after only 20 minutes of treatment by vibrations (P < .004). Results also confirmed the very strong relationship between PAP variations and perivascular emphysema found on postmortem examination (r2 = .64, P < .01). Extrinsic compression decreased from 29% in the untreated group to 21% in the treated one (n = 10 pairs, P < .08). These data suggest that vibrations may be a new simple treatment for pulmonary hypertension, when perivascular emphysema is involved, and could be useful in congenital diaphragmatic hernia as well in other neonatal pathologies.

Animals↗

PubMed1993

The role of amniotic passage in the egg-adaptation of human influenza virus is revealed by haemagglutinin sequence analyses.

Obtaining an isolate of a human influenza virus in the allantoic cavity of the embryonated hen's egg is more efficient if the clinical sample is initially passaged in the amniotic cavity. To investigate the extent to which the variants present after allantoic propagation are also selected by amniotic passage, clinical virus passaged once in the amnion has been subjected to extensive genetic and antigenic analyses. The data indicate that the natural virus can replicate unrestrictedly within the amnion. However, exposure of amniotic virus to the allantois during the incubation period, which will occur through the hole between the amniotic and allantoic cavities caused by the inoculating needle, allows for the possibility of an egg-adapted variant establishing replication within the allantois and returning to the amnion. These observations illustrate why prior passage in the amnion increases the probability of a variant successfully establishing itself during a subsequent allantoic passage.

Amnion↗

PubMed1992

Index of pulmonary expansion: a new method to estimate lung hypoplasia in congenital diaphragmatic hernia.

In order to find a simple method for assessing the degree of lung hypoplasia in congenital diaphragmatic hernia (CDH), we measured an index of pulmonary expansion (V/P: expiratory tidal volume over inspiratory pressure) in 23 pulmonary normal and 16 CDH neonates. We also measured V/P in 9 newborn lambs, 6 with experimentally induced CDH and 3 controls, and compared V/P values with fractional lung masses (FLM: lung weight over body weight). In animals, the correlation between V/P and FLM was significant (P less than .05), whereas there was a very significant inverse correlation between pulmonary interstitial emphysema found at postmortem and FLM (P less than .01). These findings suggest that V/P could be an indicator of lung hypoplasia and, therefore, of sensitivity to barotrauma. In neonates with CDH, this index could be useful to make comparisons between series and to separate infants who cannot be ventilated at usual pressures without significant barotrauma.

Animals↗

PubMed1992

High growth reassortant influenza vaccine viruses: new approaches to their control.

When a new strain of an influenza virus is required to be incorporated into influenza vaccine, attempts are made to recombine such strains with laboratory adapted viruses, which will grow to high titre in order to improve the yield of the vaccine strain. It is important that such high growth reassortant vaccine strains are not contaminated with genes coding for the antigenic determinants of the high growth laboratory strain. We describe the characterization of two recent high growth reassortants and the application of the polymerase chain reaction to ensure their genetic identity and purity.

Antigens, Viral↗

PubMed1991

Prolonged pumpless arteriovenous perfusion for carbon dioxide extraction.

A method of extracorporeal carbon dioxide extraction from the blood using an efficient microporous membrane oxygenator or membrane gas exchanger was evaluated during pumpless arteriovenous perfusions with a view to its application for partial respiratory support. The first study carried out in dogs revealed some increase in cardiac output, cardiac index, and cardiac work, although this increase was less than that normally expected from the added extracorporeal blood flow. In sheep during 3 to 7 days of continuous bypass, there was practically no hemolysis and relatively stable hemoglobin and hematocrit levels, and the platelet counts remained within safe levels. The maximum extracorporeal blood flow tended to decrease from a mean of 1.55 L/min on day 1 to 1.34 L/min on day 3 to 1.28 L/min on day 7. Carbon dioxide extraction remained efficient throughout the perfusion, but there was a minimal decrease from the first day (10.92 mmol/L) to the third day (8.46 mmol/L) at the higher blood carbon dioxide concentrations; it remained stable thereafter at 9.0 mmol/L.

Animals↗

PubMed1991

Direct isolation in eggs of influenza A (H1N1) and B viruses with haemagglutinins of different antigenic and amino acid composition.

Influenza A (H1N1) and influenza B viruses from clinical samples were isolated in the amniotic cavity of embryonated hens' eggs by classical techniques and propagated in the allantoic cavity. Virus progeny from different eggs which had been inoculated with virus material from the same clinical sample possessed antigenically distinguishable haemagglutinins (HAs). Virus progeny of some eggs possessed HAs which were serologically identical to those of virus isolated in parallel in mammalian (MDCK) cells. These egg-grown viruses possessing HAs with the antigenic phenotype of mammalian cell-grown viruses appeared to be antigenically related to epidemic influenza virus because post-infection human sera reacted to high titre with the virus HA. Specific nucleotide changes were detected in the HAs of the viruses isolated directly in eggs at positions 163 and 189 for influenza A (H1N1) viruses or positions 141 and 196 to 198 for influenza B viruses. Egg-isolated viruses which possessed the antigenic phenotype of mammalian cell-grown viruses retained glycosylation sites at positions 163 and 196. The viruses isolated directly in embryonated hens' eggs which possessed the HA antigenic phenotype and glycosylation sites of MDCK cell-grown virus can, unlike the latter viruses themselves, be used as candidate influenza vaccine viruses.

Amino Acid Sequence↗

PubMed1991

Sequence analysis of the haemagglutinin (HA) of influenza A (H1N1) viruses present in clinical material and comparison with the HA of laboratory-derived virus.

We used the polymerase chain reaction to amplify the HA1 coding region of influenza A (H1N1) viruses present in clinical material from recent cases of influenza in the U.K. Previously, we have demonstrated that isolation of human influenza viruses in embryonated hens' eggs selects variants which have amino acid substitutions in their haemagglutinin (HA) clustering around the receptor-binding site. Such egg-selected variants are often antigenically distinct from each other and from corresponding viruses isolated on mammalian cells. Since in general the virus used for vaccine production is an egg-adapted virus, it is important to determine the extent to which these variants are present in the natural virus which causes disease in man. To achieve this, amplified products from clinical material were cloned and many individual clones sequenced. Our results indicate that the HA of the naturally occurring virus is relatively homogeneous and represented by virus isolated in the laboratory on MDCK cells, whereas the variants isolated in eggs are present only at low levels in clinical material.

Amino Acid Sequence↗

PubMed1990

A host-cell-selected variant of influenza B virus with a single nucleotide substitution in HA affecting a potential glycosylation site was attenuated in virulence for volunteers.

An influenza B virus was passaged in man (virus A) and then in human embryo trachea (C) and into embryonated eggs (D) or directly into eggs (B). Virus A, B, and C had the same (cell-like) haemagglutinin phenotype on reaction with selected monoclonal antibodies while D had an "egg-like" phenotype. The viruses were administered at a dose of 1,000 TCD50 (for MDCK cells) by intranasal inoculation to groups of 27 or 28 volunteers. Viruses A, B, and C all produced disease in six to eight volunteers, whereas D produced no illness and only four volunteers were infected. The viruses shed by the volunteers were indistinguishable from those with which they were inoculated. The haemagglutinin genes of the viruses were sequenced and changes were detected indicating amino acid substitutions at position 196-198 in the attenuated egg-grown virus D whereby a potential glycosylation site present in the other viruses was lost.

Amino Acid Sequence↗

PubMed1990

The hemagglutinin of influenza B virus present in clinical material is a single species identical to that of mammalian cell-grown virus.

When clinical specimens of influenza virus are adapted to grow in embryonated hens' eggs, variants are selected which have specific amino acid substitutions in the hemagglutinin (HA). In contrast, a single virus, distinct from any egg-adapted variant, is selected when virus is isolated on MDCK mammalian cell culture. We have utilized the polymerase chain reaction to determine the nature of the hemagglutinin of influenza B viruses present in clinical material prior to cultivation in the laboratory. Sequence analysis of individual clones of amplified DNA reveals that the HA of clinical virus is essentially homogeneous and identical to the virus derived on MDCK cells. The HA of egg-adapted virus was heterogeneous and nonidentical to that of the clinical material and of the MDCK-derived virus.

Amino Acid Sequence↗