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Biomedical subjects

V Allen

Publications and source records attributed to V Allen.

At least 37 records · Page 2Linked to original sources
PubMed1984

Analysis of CAD gene amplification using a combined approach of molecular genetics and cytogenetics.

CAD is a multifunctional protein which catalyzes the first three steps of de novo uridine biosynthesis. Rodent cells resistant to PALA, a specific inhibitor of the ATCase activity of CAD, overproduce the CAD protein and CAD mRNA as a direct result of the amplification of the CAD gene. In order to study the mechanism of CAD gene amplification, a functional Syrian hamster CAD gene was inserted into a cosmid vector using molecular cloning techniques. The cloned genes were assayed for biological function by fusing CAD-deficient Chinese hamster ovary (CHO) cell mutants with protoplasts of E. coli containing the CAD cosmids. Two clones with functional CAD genes were isolated and shown to contain inserts 40 and 45 kb long. The cloned genes could also be introduced into wild type CHO cells by selecting for cells which became resistant to high PALA concentrations in a single step. Transformations of mutant and wild type CHO cells contained multiple active copies of the donated Syrian hamster CAD genes in addition to their endogenous CHO CAD genes. The cloned genes in all transformants analyzed are integrated into host cell chromosomes at single locations defined by in situ hybridization. Independently isolated transformants contain the donated genes in different chromosomes. Co-transformation of CHO cells with two different genes by protoplast fusion is also shown to be possible.

Animals↗
PubMed1984

Further observations on the excretion of salmonella in the faeces of calves fed milk substitute.

Swabs of rectal faeces were obtained daily for 28 days from 90 calves reared in five batches during the summer of 1983. The calves were purchased unweaned in markets and fed a milk-substitute diet. Salmonella typhimurium phage type DT204c was isolated from calves in four batches and Salmonella newport from one. When the data from the 90 calves were considered together the incidence of salmonellas, excretion rose to peak between 5 and 7 days after purchase before declining to low levels during the fourth week. Salmonella was isolated from 55 (61%) calves; 30 were positive on up to four occasions while 21 and 4 animals respectively were positive between 5 and 11 and 15 and 20 times. In the majority of animals infection was probably subclinical since treatment with antibacterial drugs and excretion of S. typhimurium coincided in four calves only.

Animal Feed↗
PubMed1984

The persistence of drug resistant Escherichia coli strains in the majority faecal flora of calves.

Two groups of calves, one of three and the other of two animals, were purchased in markets and reared initially on a commercial veal unit for 1 month and 4 months respectively. They were then moved to the Veterinary School, Langford, and kept for a further 6 and 4 months respectively. The animals were sampled weekly and a continual turnover in the strains forming the majority Escherichia coli faecal flora was demonstrated for all calves. Antibacterial-drug resistance, as measured by an Antibiotic Resistance Index (ARI), increased after arrival on the veal unit and persisted at high levels during the whole of their stay. After moving to Langford the ARI fell. Initially there was a reduction in the average number of resistance determinants per resistant strain and then, after a delay of up to 8 weeks, by an increase in the proportion of isolates that were fully sensitive. The source of the sensitive strains was not ascertained, although their appearance was not associated specifically with either weaning or turning out to pasture.

Animals↗
PubMed1983

The excretion of Salmonella typhimurium in the faeces of calves fed milk substitute.

A total of 495 calves in 16 batches were examined (117 calves in 4 batches in 1979 and 378 in 12 batches in 1982). They were purchased in markets, transported by road to a farm in Somerset and reared on a milk substitute diet for a period of up to five weeks. Salmonella typhimurium phage type DT 193 was endemic in 1979 and phage type DT 204c in 1982. The mortality rates in the two years were 9.4% and 1.9% respectively. The causes of death were not investigated although the majority were probably due to salmonellosis. The rate of isolation of S. typhimurium from the rectal faeces of calves in all groups was either zero or relatively low on arrival. It rose to a peak (which was higher in 1979) in the second or third weeks before declining to low levels by the end of the fourth week of residence on the farm. Data from 162 calves, examined twice weekly for four weeks in 1982, indicated that the distribution of infected calves, based on the number of times that S. typhimurium was isolated from each, was not random. The calves could be assigned to two main categories; those from which the organism was never isolated and those from which it was isolated at least twice. This suggested that salmonella infected calves actively excreted the organism. The association between salmonella excretion and medication of sick animals with antibacterial drugs was strongest during the second week. Over the four-week period nearly 40% of the calves found to be excreting S. typhimurium were not treated, indicating a high incidence of subclinical infection. Salmonella excretion by the calves followed a regular pattern and infection was self-limiting within five weeks. The peak in the salmonella excretion rate and the mortality rate were higher in 1979 when phage type DT 193 was the endemic strain. However, in 1982 the calves received 100 p.p.m. furazolidone in their milk ration during the first week of their stay on the farm, and this may have contributed to the differences noted between the two years.

Animal Feed↗
PubMed1982

Auditory brainstem evoked responses in autistic children.

Auditory brainstem evoked responses (ABRs) were studied in 16 autistic children. Three children had severe delays in wave I latency, indicating defective functioning of the peripheral auditory pathway. The remaining subjects also had delayed wave I latency but only for right ear stimulation at the lowest stimulus intensity. Eight autistic children (and no control subjects) had ABR transmission time values 3 SDs beyond the normal mean, suggesting auditory processing defects peripheral to or within the brainstem auditory pathway. These findings (1) may have no causal relationship to the child's autistic handicaps, (2) may represent distortions in auditory input that impair the learning of language, and (3) may reflect an earlier state in which abnormal input directly caused maldevelopment of forebrain systems necessary for language and cognitive function.

Adolescent↗
PubMed1982

The biotyping of Escherichia coli isolated from healthy farm animals.

A total of 2973 Escherichia coli, isolated from six different groups of animals, were examined for their ability to ferment adonitol, dulcitol, raffinose, rhamnose and sorbose in solid media. Twenty-nine fermentation patterns were recorded although 2443 (82%) of the E. coli belonged to seven of the 32 possible biotypes. Ninety-six O-serotypes were identified within the 2973 E. coli. The number of O-serotypes represented in the 15 most common biotypes ranged from three to 15. Serotypes O8 and O9 were found most commonly in the different groups of animals and several biotypes amongst these two O-serotypes were identified in two or more groups of the animals. The ability of the E. coli to metabolize aesculin, ornithine, salicin and sucrose was also assessed. These test proved less reproducible and were not included in the primary biotyping scheme although their use allowed the enumeration of additional biotypes. The application of biotyping to the study of the ecology of drug-resistant strains of E. coli in five situations is briefly presented.

Amino Acids↗
PubMed1982

The persistence of drug resistant Escherichia coli in the intestinal flora of healthy broiler chicks.

Antibacterial drugs (oxytetracycline, streptomycin and sulphonamides) were included in the drinking water of healthy broiler chicks from the sixth to the twentieth day of life to select a resistant gut flora. On the twenty-first day the birds were divided into three groups and reared in separate rooms until 100 days of age. One group was housed in cages with wire floors while the others were reared on litter. Faeces from adult hens were added regularly to the litter of one of these groups to determine its effect on the gut flora of the chicks. The ecology of Escherichia coli was studied using O-serotyping, biotyping and antibacterial drug resistogram typing. The proportion of E. coli in the dominant faecal flora resistant to two to four antibacterial drugs increased with time to reach a peak several days after the drugs were withdrawn. Thereafter, the level of drug resistance in the E. coli declined equally in all three groups. The majority of organisms with multiple resistance were derived from biotypes of O-serotypes initially resistant to only one drug and were identified before the drugs were administered. The decline in the level of resistance in the dominant faecal flora after the fourth week was due to the appearance of either new O-serotypes or new biotypes of O-serotypes previously shown to be multiply resistant, and which were either sensitive or resistant to only one drug. It is probably that these new strains were derived from the food since several O-serotypes appeared simultaneously in all three groups of birds.

Animals↗
PubMedDate not supplied

A plant for Sam.

Explore the source record for details and available documents.

Aged↗
PubMedDate not supplied

Measurements of interface pressure between body sites and the surfaces of four specialised air mattresses.

Four specialised air mattresses had interface pressure measured under six body sites prone to pressure sores in 10 subjects, supine and sitting. The mattresses were the Clinirest (SSI) and FirstStep (KCI) continuous airflow mattress overlays, and Airwave (Pegasus) and Nimbus (Huntleigh) alternating pressure air mattresses. On the mattress overlays, average supine interface pressures were 2.33 kPa (scapula), 4.15 kPa (elbow), 1.94 kPa (sacrum) and 2.79 kPa (buttock), although they were higher at the occiput (7.97 kPa) and heel (11.7 kPa). The alternating pressure air mattresses had an average minimum interface pressure close to zero for three sites, rising to 4.28 kPa under the heel. Average maximum interface pressures were 8.61 kPa (occiput), 5.21 kPa (scapula), 4.90 (elbow), 4.85 kPa (sacrum), 4.61 kPa (buttock) and 13.2 kPa (heel). No accepted scientific method exists for comparing the two types of mattress. Our data suggest a clinical benefit at the occiput and heel (supine) in using an alternating pressure air mattress and a benefit in using a continuous airflow mattress overlay at other sites.

Air Pressure↗