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Biomedical subjects

W F Whimster

Publications and source records attributed to W F Whimster.

At least 19 recordsLinked to original sources
PubMed1992

Cardiodynamic effects of dopamine and dobutamine.

On 11 patients undergoing coronary surgery, at the end of the surgical intervention, the inotropic responses to 0.4 and 0.8 microgram x kg-1 x min-1 dopamine and dobutamine given via the aorto-coronary bypass directly into the coronary artery were compared. These dosages correspond to ones 10 times greater applied intravenously. The measurements were made using needle force probes which were implanted into the myocardial offstream area in the left ventricular wall. Bypass flow was measured simultaneously by an electromagnetic flow probe. There is a significant increase in coronary bypass flow induced by both rates of 0.4 and 0.8 microgram x kg-1 x min-1 dobutamine, but there was no significant effect on bypass flow induced by dopamine. Developed myocardial force is raised more by dobutamine medication than by dopamine. However, the rate of contraction increases significantly and relaxation is significantly accelerated by dopamine at both dosages. A significant increase in rate of contraction and relaxation was only induced by the higher dosage of 0.8 microgram x kg-1 x min-1 dobutamine.

Aged↗
PubMed1991

Kinetic aspects of Ki-67 antigen expression in a normal cell line.

Using a normal cell line derived from a human fetus, the disappearance and reappearance of the Ki-67-reactive antigen following modification of the cell cycle was observed and estimated immunohistologically. It was found that G1/G0 arrest induced by serum deprivation resulted in loss of the antigen in 24 h in all but a few (usually less than 10%) of cells. Return to normal medium and resumption of growth was accompanied by reappearance in 30 h. When entry into S-phase was prevented by desferrioxamine, reappearance of the antigen still occurred but only lasted for about 24 h. Inhibition of protein synthesis with cycloheximide also caused fading and eventual loss of immunostaining. In view of the ease with which this antigen becomes undetectable with cessation of protein synthesis and interruption of the cell cycle, we agree with those who advise caution in the use of Ki-67 to measure growth fraction in changeable cell populations such as tumours.

Blood↗
PubMed1991

Distribution and estimation of nucleolar organizer regions in various human lung tumours.

A quantitative study of nucleolar organizer regions in human lung carcinomas was carried out on routinely processed paraffin embedded tissue sections. We examined 104 lung carcinomas including 38 squamous cell carcinomas, 36 adenocarcinomas, 18 large cell anaplastic carcinomas, 6 small cell carcinomas and 6 carcinoids. No significant differences were found in mean number of NORs between squamous, adenocarcinoma and undifferentiated carcinomas including large cell and small cell carcinomas. Carcinoids had comparatively lower means except for one typical carcinoid. Considering the high incidence of overlap between ranges of NOR counts in these groups of tumours and in agreement with the only other study of lung tumours (which comprised only carcinoids and small cell carcinomas), we conclude that this technique cannot be reliably used to discriminate between various histologic types of lung cancers. However, long term follow up of these patients is needed to establish the value of the AgNOR technique for prognostic guidance.

Adenocarcinoma↗
PubMed1990

Growth fraction in lung tumours determined by Ki67 immunostaining and comparison with AgNOR scores.

Estimation of the growth fraction with the use of monoclonal antibody Ki67, which recognizes a nuclear antigen in proliferating cells, was compared with the nucleolar organizer region staining in 95 lung tumours. There was nuclear staining in most tumours; 12 tumours were negative. Cytoplasmic staining was observed in another seven tumours. The small cell carcinoma group had the highest mean Ki67 index (23.75); squamous carcinomas had a mean value of 15.71, adenocarcinomas 10.99, and large cell anaplastic 20.76. Carcinoids had few stained cells. Nucleolar organizer regions were demonstrated by the argyrophilic method (AgNOR). No correlation was found between Ki67 indices and AgNOR scores. Kinetic data obtained by the AgNOR technique were less discriminating in view of the overlap between scores of various groups including carcinoids. We conclude that use of the monoclonal antibody Ki67 is a more reliable method of assessing proliferative activity in lung tumours. This antibody may be effective in identifying slowly proliferating tumours which are less sensitive to chemotherapeutic agents.

Antibodies, Monoclonal↗
PubMed1990

Proportion of necrosis in transplanted murine adenocarcinomas and its relationship to tumor growth.

Percentage of necrosis has been measured in 30 murine adenocarcinoma transplants of known volume. It was found that changes in necrotic proportion during the growth of these particular tumors agree with the concept of a core of necrosis surrounded by a viable shell of constant thickness. This means that viable and necrotic fractions were proportional to the surface area of the tumor, which is consistent with the frequently observed superficial distribution of nutrient-supplying arteries. According to this model a plot of 1n tumor volume versus necrotic fraction is sigmoid and, if tumor growth is directly related to viable fraction, such a plot is not compatible with popular mathematical growth equations. However, the equation of von Bertalanffy gives a reasonable fit to the data here for total tumor growth, suggesting that growth too was proportional to surface area and in accord with a surface-related viable fraction and blood supply. An appropriate physiological explanation is given of necrosis development resulting from a superficial nutrient supply.

Adenocarcinoma↗
PubMed1989

Comparison of stains for image segmentation and measurement of nuclear parameters by computerised image analysis using IBAS 2000.

Nuclear measurements using image analysis largely depend upon the quality of the image presented for digitization. To investigate the effects of nuclear stains on image segmentation of nuclei, serial sections of kidney were stained by eleven different methods and presented to an IBAS 2000 interactive image analysis system (Kontron Bildanalyse) via a Zeiss IIIRS microscope at x 800 magnification and a Siemens K30 video camera. Digitised grey level images of each field were processed by an interactive technique and by an automatic segmentation procedure (thresholding). Nuclear areas were measured by each method and the results compared. We conclude that of the stains assessed the uncounterstained haematoxylins offer the best image segmentation for nuclear measurements. Thresholding techniques are suitable for performing measurements using these stains, particularly when additional interactive techniques are used to reject unwanted structures and to separate overlapping nuclei after segmentation. Comparable areas stained with five of the stains were studied to see if the staining techniques themselves affected nuclear area. Our results show that the use of different stains will substantially affect measurements of nuclear dimensions.

Cell Nucleus↗
PubMed1989

Problems of the third dimension.

The problems facing a pathologist or anatomist who wishes to embark on computer-assisted reconstruction of structures seen in serial light microscope sections are reviewed. They are illustrated by comparing a reconstruction of a bronchial gland made by cutting out polystyrene sheets with models generated by four computer-assisted systems, i.e. the IBAS 2000 system, the SSRCON (MRC) system, the AT-Videoplan system and the CHD (Cookson, Holman, Dykes) system. It is obvious that computer-assistance cannot solve the preparation problems of three-dimensional reconstruction (3DR) and that choosing a computer-assisted system is fraught with difficulties. It is recommended that intending purchasers of computer-assisted 3DR systems prepare material in advance to try out on the systems they are considering.

Bronchi↗
PubMed1989

Tissue distortion in three-dimensional reconstruction of wax or plastic embedded microscopic structures.

Three-dimensional reconstruction at the light microscopic level depends on obtaining reliable serial sections without "distortion" i.e., expansion and compression during section preparation. We have studied the extent of such distortion in serial sections from paraffin and resin embedded blocks of brain, kidney, liver and lung, using an IBAS 2000 Image Analyser. We found that, taking the uncut block as 100%, the section area, perimeter and minimum diameter varied by no more than 8%, except for the lung sections which varied up to 14%. There was no progressive compression due to knife bluntening. Resin sections also varied up to 8% (16% for lungs) but in addition creasing was a problem. We conclude that, provided the serial sectioning is carefully standardised for block shape and orientation, floating out temperature and time, serial paraffin sections are more suitable for three dimensional reconstruction than resin sections.

Acrylic Resins↗
PubMed1989

A method of image registration for three-dimensional reconstruction of microscopic structures using an IBAS 2000 image analysis system.

Registration of histological tissue sections is a longstanding problem in three-dimensional reconstruction. Our solution is to insert rigid straight narrow birefringent structures namely cactus spines as artificial registration points (ARPs) into the tissue block before embedding in wax or resin. The microscopic image of the tissue section with ARPs in situ is presented to an IBAS 2000 Image Analyser and digitised. Registration is performed in two stages using the ARP nearest to the area to be reconstructed as the principle reference point for alignment. The automatic stage is then used to align the structure under reconstruction. These reconstructions are more accurate than those produced without the use of ARPs.

Birefringence↗
PubMed1988

Conference previews.

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Abstracting and Indexing↗
PubMed1988

The morphology of ciliogenesis in the developing fetal human respiratory epithelium.

Segmental imaging studies of the respiratory epithelium from human embryos and fetuses of normal karyotype have demonstrated that ciliogenesis and ciliation of the respiratory epithelium starts at 7 weeks of gestation. Ciliated cell differentiation follows a pre-determined pattern of distribution. It starts exclusively in the upper segment of the membranous trachea and spreads distally. Ciliation of the carinal angle takes place at 8 weeks of gestation. Three patterns of basal body formation were identified. The various morphological features encountered are described and compared with those observed in cases of Immotile Cilia Syndrome and other pathological conditions. Ciliation of the respiratory epithelium in the cartilaginous trachea does not take place until after the 12th week of gestation. The morphological findings identified in our case material are in agreement with those observed in the developing respiratory epithelium of other higher mammals.

Bronchi↗