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Biomedical subjects

J Law

Publications and source records attributed to J Law.

At least 73 records · Page 4Linked to original sources
PubMed1994

Effect of genetically modifying the lactococcal proteolytic system on ripening and flavor development in cheddar cheese.

THREE BATCHES OF SIX CHEDDAR CHEESES WERE MANUFACTURED BY USING THE FOLLOWING LACTOCOCCAL STRAINS: (i) UC317 as a control; (ii) JL3601, a proteinase-negative derivative of UC317 transformed with high-copy-number plasmid pCI3601 containing the cloned proteinase gene complex from UC317; (iii) AM312, a proteinase-negative derivative of UC317 transformed with plasmid pMG36enpr containing the neutral proteinase gene from Bacillus subtilis; (iv) AC322, JL3601 transformed with pMG36enpr; (v) AC311, UC317 transformed with plasmid pNZ1120, which contains the aminopeptidase N (pepN) gene from Lactococcus lactis subsp. lactis MG1363; and (vi) AC321, JL3601 transformed with pNZ1120. Organoleptic and chemical analyses indicated that (i) the control cheeses, which were made with UC317, were of the highest quality; (ii) cheeses made with strains harboring pCI3601 in addition to either pMG36enpr (AC322) or pNZ1120 (AC321) did not ripen in a significantly different manner than cheeses made with AM312 (containing only pMG36enpr) or AC311 (containing only pNZ1120), respectively; (iii) cheeses made with strains that overproduce pepN did not have improved body, texture, and flavor characteristics; and (iv) cheeses made with strains harboring the neutral proteinase from B. subtilis (AM312 and AC322) underwent greatly accelerated proteolysis.

Journal Article↗
PubMed1994

Regions, networks and fluids: Anaemia and social topology.

This is a paper about the topological presuppositions that frame the performance of social similarity and difference. It argues that 'the social' does not exist as a single spatial type, but rather performs itself in a recursive and topologically heterogeneous manner. Using material drawn from a study of the way in which tropical doctors handle anaemia, it explores three different social topologies. First, there are 'regions' in which objects are clustered together, and boundaries are drawn round each cluster. Second, there are 'networks' in which distance is a function of relations between elements, and difference a matter of relational variety. These two forms of spatiality are often mobilized in social theory. However, we argue that there are other kinds of social space, and here consider the possible character of a third, that of 'fluid spatiality'. In this, places are neither delineated by boundaries, nor linked through stable relations: instead, entities may be similar and dissimilar at different locations within fuid space. In addition, they may transform themselves without creating difference.

Anemia↗
PubMed1994

A comparison of mammographic phantoms.

It is important to establish and maintain high standards of image quality in mammography in order to detect breast cancer at an early stage. A commonly used method of assessing image quality in mammography is to use test phantoms. This paper reports a comparison of seven mammographic phantoms. These are the Ackermann (DuPont, Stevenage), Barts (White and Tucker), CIRS XI (Computerized Imaging Reference Systems, USA), Leeds TOR(MAX) and Leeds TOR(MAM) (Faxil, Leeds), Newcastle, and RMI 152 (Gammex RMI, Nottingham). These phantoms were assessed on the detectability of the various details and bar patterns contained in each. Step wedges and simulated anatomical features were not assessed. The effect on phantom images of changes in contrast, caused by changing tube potential from 25 kV to 35 kV, and of changes in resolution, caused by different focal spot sizes and by different magnifications, were investigated. It was deduced from the results of this study that there was no single phantom which was clearly superior to all the others. The three phantoms which had the greatest sensitivity to changes in imaging parameters were the Leeds TOR(MAM), the Newcastle and the Ackermann (DuPont) phantoms.

Breast Neoplasms↗
PubMed1994

Identifying speech and language delay.

Publication of the Hall report has prompted many health authorities to cut back on the range of routine child health screening programmes. In some areas health visitors are playing a less central role in child health surveillance. James Law and Carrie Pollard argue the need for routine screening of all children for speech and language delay, and that health visitors--with more adequate specialist training--should carry out these checks. Problems may persist for many years if not tackled in the pre-school years, they warn.

Child, Preschool↗
PubMed1993

Perceptual and conceptual cueing in implicit and explicit retrieval.

Subjects saw or heard words in a list (e.g. limerick) and then took two successive tests. The first was a yes/no recognition test in which auditory/visual modality of test words was manipulated orthogonally to the study modality. The second test varied with experimental conditions: subjects produced words to either perceptual (fragment) cues (l- -e-ick) or conceptual cues (What name is given to a lighthearted five-line poem?), under either explicit or implicit retrieval instructions. The major findings were: (a) that regardless of the type of retrieval cue (perceptual or conceptual) the degree of dependency between recognition and cued recall was greater than that between recognition and implicit retrieval; and (b) that modality shifts adversely affected perceptually cued explicit and implicit retrieval, whereas they had no effect either on conceptually cued retrieval or on recognition. These results suggest that the memory system subserving, and the processes involved in, conceptual priming differ from those underlying recognition and perceptual priming.

Analysis of Variance↗
PubMed1993

Measurement of focal spot size in mammography X-ray tubes.

Three different measurement techniques for estimating the size of focal spots in X-ray tubes are described. These are the pin-hole, the slit and the star pattern or resolution pattern, and all are well known. Results are reported for a number of modern mammography X-ray tubes employed in a screening programme, using all three techniques. The results are compared with each other and with makers' specifications, IEC tolerances and UK Department of Health guidelines. Agreement between slit and star pattern results is generally within a few per cent, while pin-hole results are usually appreciably smaller. Although the slit technique is the most reliable for estimating focal spot size, both the others have a useful role, especially in revealing focal spot condition. Compliance with makers' specifications is usually demonstrated, but compliance with Department of Health guidelines is only found on the width of broad foci.

Breast Neoplasms↗
PubMed1993

Calibration of ion chambers for use in mammography.

There is at present no UK calibration service for ion chambers for mammography, where X-ray beams are produced from tubes having molybdenum targets and filters. This paper reports calibrations against a radiotherapy secondary standard (calibrated for beams from tungsten targets with aluminium filters) using beams from both types of target and filter. Two examples of the Radcal mammography dosimeter were found to have calibration factors which varied by less than 1% in molybdenum target beams from 30 to 40 kV. Differences between calibrations using the two types of X-ray beam did not exceed about 2%. All calibration factors were within about +/- 2% of 1.0. Errors are thought to be within +/- 3%. The results of an independent calibration of one of these dosimeters against a similar chamber calibrated by CEC are also reported. Calibrations of this kind can only be temporary expedients until adequate calibration facilities for mammography beams become available, but are nevertheless useful.

Calibration↗
PubMed1993

The influence of focal spot size on image resolution and test phantom scores in mammography.

This paper reports an experimental investigation of the extent to which focal spot size influences image resolution in mammography. Films of two different phantoms, both containing high contrast bar patterns, were obtained using three different foci from 0.9 to 0.1 mm, and three degrees of magnification with the smallest of those foci. Some influence of focal spot size was detectable in all films except for the 0.1 mm focus at low magnification, where it was negligible in comparison with film-screen unsharpness, but effects attributed to the film-screen system were more important than focus size except with the 0.9 mm focus or at high magnification. However, a nominal 0.4 mm focus may have an effective size of 0.9 mm close to the chest wall side of the film. These two phantoms, and two others, were used to investigate the changes of perceptibility of "realistic" details, all of which depend on a combination of contrast, resolution and noise, with changes of focal spot size and magnification. As expected, when judged in this way image quality improved as focal spot size decreased. With the fine focus it also improved as magnification increased, unlike changes in high contrast resolution which decreased for high magnification. Thus conventional bar patterns are not always a good guide to detail perceptibility in mammograms, where the effects of noise may be as important as those of focal spot size.

Female↗
PubMed1993

Variations in individual radiation dose in a breast screening programme and consequences for the balance between associated risk and benefit.

In a breast screening programme there is a small but inevitable risk of inducing some breast cancers that may appear many years later. This risk has to be compared with the benefits of detecting existing cancers at an early stage. In the current UK screening programme, for women aged 50-64 years and with a 3-year screening interval, the numbers detected greatly exceed the numbers predicted to be induced. For the individual, only those with very large and thick breasts who also have many views taken during the screening process appear to be at any appreciable risk, and the number for whom the risk of induction exceeds the probability of cancer detection is of the order of less than 1 per million, a risk level normally considered negligible. Results are also presented for younger age groups, and for a range of dose levels. Down to age 35 years, induction exceeds detection in less than about 1% of those screened, if a 3-yearly interval is maintained. The effect of shorter screening intervals is briefly considered. All results are based on repeat screening rounds (incidence rounds) using a single view and not on the initial (prevalence) round, and use UK data for breast cancer incidence. The calculation requires a number of assumptions and is intended as a preliminary one, pending more data on doses and numbers of women requiring specific numbers of films in screening programmes, but sufficient to promote discussion of the appropriate age range for breast screening.

Adult↗
PubMed1993

The contribution of lactococcal starter proteinases to proteolysis in cheddar cheese.

The contribution of the lactococcal proteinase to proteolysis and flavor development in Cheddar cheese was investigated using the starter strains Lactococcus lactis ssp. lactis UC317, its proteinase-negative derivative FH041, and variants of UC317 modified in proteinase production, location, and specificity. Lactococcus lactis ssp. lactis FH041 was transformed by electroporation with plasmids pCI3601, pCI3602, or pNZ521. Plasmids pCI3601 and pCI3602 harbor the cloned proteinase genes of L. lactis ssp. lactis UC317 on a high copy number vector and, as such, encode an increased concentration of cell wall-associated and secreted enzymes, respectively. Plasmid pNZ521 contains the cloned proteinase genes from Lactococcus lactis ssp. cremoris SK11. Assessment of proteolysis and flavor development in Cheddar cheese made with these strains revealed that starter proteinases are required for the accumulation of small peptides and free amino acids in Cheddar cheese. Proteolysis was not enhanced by an approximately threefold increase in concentration of the lactococcal proteinase. The strain in which the proteinase remained attached to the cell wall appeared to contribute more to proteolysis than the strain that secreted the enzyme. Water-soluble peptides unique to Lactococcus lactis ssp. cremoris SK11 and L. lactis ssp. lactis UC317 were detected by PAGE and HPLC, respectively. Sensory evaluation showed that the flavors of all cheeses made with proteinase-positive starters were similar, but cheeses made with proteinase-negative starters lacked flavor.

Amino Acids↗
PubMed1992

In vitro stability of EDTA and DTPA immunoconjugates of monoclonal antibody 2G3 labeled with indium-111.

Monoclonal antibody 2G3 directed against a high molecular weight glycoprotein on breast and ovarian cancer cells was conjugated with bicyclic DTPA (or EDTA) anhydride or benzyl isothiocyanate DTPA (benzyl DTPA) and labeled with 111In. DTPA anhydride was more reactive with the antibody than benzyl DTPA, and kinetics of labeling with 111In were more rapid for DTPA substituted 2G3 than for benzyl DTPA substituted 2G3. On the other hand, 111In-2G3 conjugates prepared using DTPA anhydride were subject to more extensive dimerization and higher losses in immunoreactivity than those prepared using benzyl DTPA. On the basis of measurement of transchelation to transferrin, the stability of 111In-2G3 prepared using DTPA anhydride or benzyl DTPA did not differ during incubation in human plasma for 6 days at 37 degrees C. These results suggest that an important advantage of benzyl DTPA over DTPA anhydride for preparing 111In-labeled antibodies is the prevention of intermolecular (and intramolecular) crosslinking during conjugation which ultimately leads to alterations in conformation and losses in immunoreactivity of the radioimmunoconjugate.

Antibodies, Monoclonal↗