Search PubMed⌕ Search

Biomedical subjects

D Major

Publications and source records attributed to D Major.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

Influenza A (H1N1) vaccine efficacy in animal models is influenced by two amino acid substitutions in the hemagglutinin molecule.

The immunogenicity and protective efficacy of formalin-inactivated vaccines prepared from influenza A (H1N1) viruses grown in MDCK cells and in eggs was compared in animal models. The A/Chr/157/83 virus grown in MDCK cells (157M) differed by two amino acid substitutions in the HA molecule from the corresponding virus grown in eggs (157E) and the two viruses could be distinguished antigenically by monoclonal and polyclonal antibodies. Following two intramuscular injections of vaccine in ferrets, guinea pigs, and hamsters, both vaccines were equally immunogenic when antibody was analyzed by hemagglutination inhibition using homologous virus. However, single radial hemolysis analysis following antibody cross-adsorption showed that antibody stimulated by 157E vaccine was exclusively strain specific whereas that produced by the 157M vaccine was more broadly reactive. When immunized hamsters were challenged with virus cultivated on mammalian (MDCK) cells, the homologous vaccine induced a higher degree of protection than the corresponding egg-grown vaccine.

Amino Acid Sequence↗
PubMed1989

[Congenital diaphragmatic hernia. Therapeutic re-evaluation].

Twenty-eight patients with "High-Risk" diaphragmatic hernia were treated without postoperative ipsilateral chest drains. Overall survival was 71%. This study suggests that, in cases of complete absence of the diaphragm, the use of a mesh pervious to air is as noxious postoperatively as an underwater chest drain. This idea is supported by experiments in cats with a left pneumonectomy, in which part of the diaphragm was replaced either by a macroporous mesh or by a microporous prosthesis impervious to air at normal pressures. Moreover, barotrauma may occur preoperatively and when assisted ventilation is required, inspiratory pressure must be strictly limited.

Animals↗
PubMed1987

Pulmonary barotrauma in congenital diaphragmatic hernia: experimental study in lambs.

A left diaphragmatic hernia was created surgically in 20 fetal lambs between 93 and 110 days of gestation. Ten animals were alive with defects at cesarean section near term (135 to 140 days). These animals and two controls were submitted to various transpulmonary pressure gradients (inspiratory pressure minus pleural pressure). Hemodynamic and ventilatory studies were performed after the correction of the hernia. Morphometric analysis of the lung was carried out in all cases. The results showed a highly significant linear correlation between the transpulmonary pressure gradient employed and the pulmonary interstitial emphysema found at morphometry. Our data suggest that using low ventilatory pressures and not draining the pleural cavity results in less trauma to both lungs and may prevent one of the components of the pulmonary hypertension so often seen in newborns with congenital diaphragmatic hernia.

Animals↗
PubMed1987

Serological studies with influenza A(H1N1) viruses cultivated in eggs or in a canine kidney cell line (MDCK).

Pairs of influenza A(H1N1) viruses cultivated from the same clinical specimen in canine kidney (MDCK) cells or in embryonated hens' eggs can frequently be distinguished by their reactions with monoclonal antibodies to haemagglutinin and with antibodies in ferret or human sera. Egg-adapted virus, further passaged in MDCK cultures remained "egg-like" in serological characteristics indicating that the differences in their serological reactions were not a direct result of host cell-dependent glycosylation of the haemagglutinin. Haemagglutination-inhibiting (HI) or virus neutralizing antibodies in human sera can be detected more frequently, and to higher titre, in tests employing virus grown exclusively in MDCK cells than in tests with virus adapted to growth in embryonated eggs. Striking differences were detected in the serological reactions in HI tests when sera from ferrets infected with egg-grown virus were tested against a series of strains of influenza A(H1N1) virus isolated in 1983 and adapted to growth in eggs. In contrast, sera from ferrets infected with MDCK-derived virus failed to distinguish serologically between the same viruses that had been passaged exclusively in MDCK cells and also revealed relatively small differences between their egg-adapted counterparts.It was concluded that the cell substrate used for virus isolation and cultivation is a factor that should be considered when interpreting the results of strain characterization of influenza A(H1N1) isolates and in sero-surveys using these viruses.

Influenza A Virus, H1N1 Subtype↗
PubMed1986

Biochemical and antigenic analysis using monoclonal antibodies of a series of of influenza A (H3N2) and (H1N1) virus reassortants.

Reassortant influenza A viruses with high growth capacity in eggs and suitable as candidate vaccine strains or as standard reagents for influenza HA quantification were prepared using the high yielding A/PR/8/34 (H1N1) as one parent and a number of 'wild' strains of influenza A (H1N1) or (H3N2) viruses as the other parent. The genetic and antigenic composition of the reassortants was determined. The parental derivation of genes in the reassortants was established by electrophoretic analysis of virus RNA and virus induced polypeptides. The haemagglutinin (HA) antigens of the three H1N1 viruses (NIB-6, NIB-7 NIB-12) were found to resemble those of the parental viruses when tested against a panel of monoclonal antibodies and using the HI test. A similar correspondence between the antigenic characteristics of the HA of the influenza A (H3N2) reassortants (NIB-1, NIB-4, NIB-5, NIB-8 and NIB-11) and parental viruses was noted. Therefore laboratory manipulations to produce the reassortants did not result in the selection of significant antigenic variants.

Animals↗
PubMed1984

The effect of nitrous oxide on the oxyhaemoglobin dissociation curve.

The influence of nitrous oxide on the oxyhaemoglobin dissociation curve (ODC) was studied using blood from twenty healthy patients. When the blood samples were exposed to 50 per cent N2O during the determination of the ODC, a left shift was observed and the P50 was decreased by 1.06 kPa (8 mmHg). This shift cannot be explained by temperature, pH, PCO2, or 2,3-DPG effects. Following exposure of the blood to N2O-free gases, the shift disappeared rapidly, and a normal P50 (3.46 kPa) (26 mmHg) was reobtained. In keeping with this reversibility, blood samples taken before and during 45 minutes of N2O-curare anaesthesia showed identical dissociation curves to those which had been obtained during the in vitro N2O exposure experiment.

2,3-Diphosphoglycerate↗