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Biomedical subjects

C Davies

Publications and source records attributed to C Davies.

At least 145 records · Page 8Linked to original sources
PubMed1991

Geotrichum candidum produces several lipases with markedly different substrate specificities.

We have purified and examined the substrate specificity of four lipases from two strains of the mould Geotrichum candidum, ATCC 34614 and CMICC 335426. We have designated the lipases I and II (ATCC 34614), and A and B (CMICC 335426). The enzymes are monomeric and have similar molecular masses and pI. Thus, lipases I and II have native molecular masses of 50.1 kDa and 55.5 kDa, and pI of 4.61 and 4.47, respectively. Lipases A and B are very similar to lipases I and II with native molecular masses of 53.7 kDa and 48.9 kDa, and pI of 4.71 and 4.50, respectively. Treatment with endo-beta-N-acetylglucosaminidase caused a reduction in molecular mass of approximately 4.5 kDa for all four lipases, indicating that these enzymes are glycosylated. Western blotting shows that the lipases are related. However, lipase B from CMICC 335426 shows a remarkable specificity for unsaturated substrates with a double bond at position 9 (cis configuration), and this specificity is not exhibited by the other three lipases. No lipase of this unique specificity has previously been purified to homogeneity. Structural studies using these four lipases should allow insight into the molecular basis of this remarkable specificity.

Blotting, Western↗
PubMed1991

Alternative hammerhead structures in the self-cleavage of avocado sunblotch viroid RNAs.

The plus and minus RNAs of the 247 nt avocado sunblotch viroid (ASBV) undergo site specific RNA self-cleavage reactions in vitro. As with several other self-cleaving RNAs, we proposed hammerhead secondary structures for the sequence around the site of self-cleavage of both RNAs. We have shown previously that, during transcription of a dimeric plus ASBV RNA, a double-hammerhead structure formed and was necessary for self-cleavage. Here, we show that the purified full-length dimeric plus RNA, when incubated under our standard self-cleavage conditions, also self-cleaved by a double-hammerhead structure. In contrast, a dimeric minus ASBV RNA self-cleaved by a double-hammerhead structure during transcription, but by a single-hammerhead structure after purification. This illustrates the importance of the pathway of folding of the RNA in determining which active self-cleaving structure is formed.

Base Sequence↗
PubMed1991

Production and related variables in bovine leukaemia virus-infected cows.

A newly developed milk dot blot test was used to detect anti-bovine leukaemia virus (BLV) antibody in milk samples from 2079 lactating adult cows from among 61 herds. The milk dot blot test was highly repeatable; the concordance rate, compared with the agar gel immunodiffusion test performed on serum, was 83.5%. All herds contained BLV-positive cows; the prevalence rate was 36%. BLV-positive cows tended to come from larger herds and were older and more often later in lactation. Fourteen production and related variables (herd size, age, days open, days in milk, milk somatic cell count, milk, fat, and protein produced in the current lactation, projected production of milk, fat, and protein, and breed class average deviations for milk, fat, and protein) were compared between BLV-positive and BLV-negative cows. Although somatic cell count, milk produced, and projected production of milk and protein were related significantly to BLV status using simple tests of association, once the variables herd size, age and days in milk were controlled, these differences were removed. Further analyses using logistic (outcome: individual cow BLV status) and least-squares regression (outcome: herd proportion of BLV-positive cows) failed to show an association between any of the measured production or related variables and BLV-positivity. We concluded that the effect of BLV on production and related variables in dairy cows was below the sensitivity of our analytical techniques or was non-existent.

Animals↗
PubMed1991

A water-maze discrimination learning deficit in the rat following lesion of the habenula.

Although the habenula occupies a potentially important link between forebrain and midbrain, lesion of the complex produces little effect in most standard behavioral paradigms. More recently, it has been shown that such lesions may impair the ability to initiate or switch responses appropriate to environmental contingencies but only under demanding conditions. Although such deficits have been described as response failures, they could equally well be attributed to restricted attentional mechanisms. The present study was designed to further substantiate a role for the habenula in acquisition of adaptive behavior under demanding conditions and to examine the possible contribution of attentional failure. The initial response preference to 'escape' onto platforms situated in two chambers at the distal end of a water tank was established for groups of lesioned and sham-operated rats. Rats were subsequently trained in discrete trials to escape by choosing the side of the nonpreferred chamber. During training the choice of escape chamber was cued by distracting black or white visual stimuli displayed on the tank sides and above the entrances to the chamber. These were moved over trials so as to be nonpredictive of the appropriate escape position. Lesioned animals were significantly impaired in the acquisition of this positional discrimination. Analysis of response times suggested that both lesion and control animals were attending to the irrelevant visual cue. The results confirm a behavioral inflexibility following lesion of the habenula and suggest that this deficit cannot be explained simply in terms of a failure to attend to environmental cues. The lesion deficit also could not be attributed to a response perseveration.

Animals↗
PubMed1991

Happy to be home? A discharge planning package for elderly people.

Research shows elderly people do not receive the support they need following hospital discharge. If they are to be enabled to return home successfully, patients need careful assessment of their needs well in advance, so that arrangements for adequate aftercare support can be made.

Aftercare↗
PubMed1991

The management of change on a nursing development unit.

This article presents a descriptive account of the management of the change process and the nature of nursing developments which have been implemented on a Nursing Development Unit in Manchester Royal Infirmary. The fundamental aim underlying all innovations is to improve the quality of care delivered to patients. Consequently, the evaluation of the change process and whether it has actually served to improve standards is an issue of concern within this article. It is acknowledged that this case study cannot be upheld as an ideal model for innovation in nursing practice. It may however, serve as an example of how idealistic principles might be combined with realism derived directly from clinical practice, and may thus serve to inspire others along similar paths.

Hospital Units↗
PubMed1991

Dietary modification reduces splitting of glomerular basement membranes and delays death due to renal failure in canine X-linked hereditary nephritis.

Affected male (AM) Samoyed dogs with X-linked hereditary nephritis (HN) demonstrate splitting of all of their glomerular basement membranes (GBM) and rapidly develop renal failure within the first year of life, features reminiscent of those seen in male patients with X-linked HN. In contrast, carrier female (CF) dogs with X-linked HN show only isolated foci of splitting of GBM, and renal failure is never seen at such an early age. In the present study, we assessed whether a diet designed for dogs in renal failure could modify the changes seen in GBM of AM and CF dogs and improve the clinical outcome in the AM dogs. Beginning at 35 days of age, one group of dogs (unaffected, AM, and CF) was fed a regular diet, while a second group was fed a modified diet (i.e., restricted in protein, lipid, calcium, and phosphorus). AM dogs fed the modified diet showed less of a reduction in glomerular filtration rate than AM dogs fed the regular diet, indicative of a delay in the onset and a decrease in the severity of renal damage. Nevertheless, all of the AM dogs eventually died of renal failure regardless of diet. However, the onset and progression of renal failure were delayed and the severity of splitting of GBM was reduced in the AM dogs fed the modified diet; these dogs lived 53% longer than AM dogs fed the regular diet. CF dogs fed the modified diet also showed a reduced severity of splitting of GBM. In addition, when two CF dogs on the modified diet were switched to the regular diet, splitting of their GBM increased, indicating that continual administration of the modified diet was required to maintain the reduced rate of splitting. These studies indicate that dietary modification is beneficial in canine X-linked HN, and suggest that similar benefits (i.e., reduction in severity of splitting of GBM and delay in development of renal failure) might be observed in patients with HN who are treated with an appropriately modified diet.

Animals↗
PubMed1990

Structure, self-cleavage, and replication of two viroid-like satellite RNAs (virusoids) of subterranean clover mottle virus.

Both the genomic and viroid-like satellite RNAs (virusoids) from four subterranean clover mottle virus isolates described by Francki et al. were analyzed in detail. Restriction endonuclease mapping of cDNAs prepared from the genomic RNAs from all isolates showed that these RNAs are closely related if not identical. The two virusoids, which can occur together in the same isolate or individually, were sequenced and shown to be able to form highly base-paired viroid-like secondary structures. The left-hand portions of these structures are almost entirely homologous but the right-hand portions show little similarity. The plus, but not the minus, virusoid RNAs contain sequences that can form the hammerhead self-cleavage structure of certain other self-cleaving viroid, virusoid, and satellite RNAs. Plus, but not minus, RNA transcripts from cDNA clones self-cleaved essentially to completion at the predicted site during transcription in vitro. Northern blot analysis of infected leaf tissue extracts revealed the presence of an oligomeric series of plus RNAs (of monomer size and greater) but minus RNAs were present only as high molecular weight species of heterogeneous size. These findings are in agreement with the lack of minus RNA self-cleavage in vitro. Hence, these virusoid RNAs appear to replicate by a rolling-circle mechanism in which only the plus RNAs self-cleave to form monomeric RNAs.

Base Sequence↗
PubMed1990

Mapping and interpreting complex interactions between psychoactive drugs by simple computer-generated models.

Drug combinations often yield results not readily predictable from those of their separate constituents. Computer programs have been developed to generate models of dual drug effects to analyse the results of experiments involving drug combinations. Single and combined dose-response results of rat locomotor activity are expressed as three-dimensional models. A manually plotted isobol diagram, showing eqi-active dose combinations of amylobarbitone and dexamphetamine, is compared with isobols constructed by the computer. A simple dose model theory is proposed which assumes that the two drugs have merely additive effects; differences between expectations from this theoretical model and the experimental results actually obtained were found by the computer. This computer approach allows detailed analysis of results. Three-dimensional dose response surfaces can provide a simple visual guide to dose combinations whose effects deviate significantly from those expected if the constituents were simply additive. Areas of special interest can thus be highlighted.

Animals↗
PubMed1990

What information should the multiple birth family receive before, during and after the birth?

Advances in the management of the multiple pregnancy and delivery must be accompanied by corresponding improvements in service access outside key centres and especially in the information families receive about what may happen during or after the pregnancy. A major review of birthing services in Victoria has focussed attention on four areas where the quality of information is often inadequate. 1) Prepregnancy and the standard of counselling about the incidence of multiples as a result of fertility drugs and in vitro fertilization procedures and about problems which may accompany a multiple birth. 2) Antenatal: At what stage of the pregnancy should parents be told of the multiple pregnancy and how should monitoring of the mother and procedures such as bedrest take into account what are often conflicting demands within the family? 3) Perinatal: Families are frequently illprepared for a cesarean delivery and for the procedures for premature multiples. The problem is often compounded by separation of the mother from one or both twins. While bereavement services are improving, much still needs to be learned about handling congenital abnormalities in one or more multiples. 4) Postnatal: Irrespective of the level of prenatal advice, families greatly underestimate the workload with multiples. The resulting stress contributes to the incidence of postnatal depression, child abuse and divorce now being reported from multiple birth families. Some suggestions are made from social psychology and genetic counselling about how families can best handle risk information to achieve the goal of neither under- nor overestimating the risks at these different stages of the multiple pregnancy.

Adaptation, Psychological↗
PubMed1990

Increased immobility in an automated forced swimming test following lesion of the habenula in rats: absence of evidence for a contribution from motor impairment.

The effects of lesions of the habenula on responses during a forced swimming test (FST) were examined. Active behavior, documented by turns on a drum immersed in a water tank, were reduced in lesioned rats. Lesioned rats also demonstrated an inability to escape from the water by climbing onto the drum when it was locked in position at the end of the test. There was a tendency for lesioned rats to show more activity in open-field tests either after the FST or independent of such prior testing. Lesioned rats showed no motor or postural abnormalities and were able to maintain position for longer than controls during a rotating rod test. Collectively, the results are compatible with the suggestion that lesions of the habenula impair the ability to change motor strategies under stress but indicate such failures may not be ascribed to gross motor impairment.

Animals↗