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Biomedical subjects

B Dixon

Publications and source records attributed to B Dixon.

At least 127 records · Page 7Linked to original sources
PubMed1988

Malate dehydrogenase isozymes in flax genotroph leaves: differences in apparent molecular weight and charge between and within L and S.

Ferguson plots demonstrated that corresponding malate dehydrogenase (MDH) isozymes of Durrant's L and S flax genotrophs differ in apparent molecular weight (MW) and also in net negative charge. The MW differences explain heritable differences in electrophoretic relative mobility (Rm) between corresponding L and S isozymes. The MW for each MDH isozyme was higher for L than for S and resulted in a slower Rm for L. The net negative charge for each isozyme was higher for L than for S. MDH isozymes also differ in MW within L and S. MW was lower for isozymes in leaves from the bottom of the stem than in leaves from the top of the stem, particularly in L. Integration of information on the MDH isozyme system in the flax genotrophs and information on the peroxidase system suggests the possibility that common modifier loci may control Rm in both enzymes.

Isoenzymes↗
PubMed1987

Morphological changes caused by exposure of rabbit oesophageal mucosa to hydrochloric acid and sodium taurocholate.

The present authors have studied the light and electron microscopic changes in rabbit oesophageal mucosa which has been exposed to solutions of hydrochloric acid and sodium taurocholate (ST). In an in vivo model the oesophagus was perfused with saline, acid (0.1-40 mmol/l of H+) or taurocholate (0.1-1.0 mmol/l at pH 2.0 or 1.0 mmol/l at neutral pH). At the end of each perfusion experiment the oesophagus was removed and assessed by the naked eye, light and electron microscopy. Some desquamation of superficial stratum corneum cells occurred in all specimens perfused for 5 h. Injury was more evident to the stratum spinosum and basal cell layers. Damage was more severe in the bile salt plus acid perfused specimens, varying between margination of nuclear chromatin in the basal cells to complete necrosis and separation of the overlying layers. Taurocholate in neutral solution did not damage the oesophageal epithelium. Electron microscopy revealed that damage to cells in the basal layers and stratum granulosum occurred within 30 min of exposure to acidified taurocholate, this damage increasing with time. It is concluded that taurocholate is able to damage oesophageal mucosa, that the damage first occurs in the deeper layers of the oesophageal mucosa and that the damage may occur in the absence of gross or light microscopic changes in the mucosa.

Animals↗
PubMed1987

Radiation-resistant acquired immunity of vaccinated mice to Schistosoma mansoni.

Vaccination of mice with attenuated cercariae of Schistosoma mansoni induces specific acquired resistance to challenge infection. This resistance is immunologically-mediated, possibly via a delayed-type hypersensitivity. Studies of parasite migration have shown that the protective mechanism operates most effectively in the lungs of vaccinated mice. We have probed the mechanism by exposing mice to 500 rads of gamma radiation before challenge infection. Our results show that the effector mechanism operative against challenge larvae is resistant to radiation. In contrast, classical immune responses are markedly suppressed by the same treatment. While leukocyte populations in the blood fall dramatically after irradiation, numbers of cells recoverable by bronchoalveolar lavage are unaffected. We suggest that vaccination with attenuated cercariae establishes populations of sensitized cells in the lungs which trigger the mechanism of resistance when challenge schistosomula migrate through pulmonary capillary beds. Although the cells may be partially disabled by irradiation, they remain responsive to worm antigens and thereby capable of initiating the elimination mechanism. This hypothesis would explain the radiation resistance of vaccine-induced immunity to S. mansoni.

Animals↗
PubMed1987

Computed tomography in radiotherapy of prostatic carcinoma.

Hundred forty-four correlations are reported between radiological simulation and CT-scan in cases of prostate adenocarcinoma without metastases treated from 1980 to 1986 exclusively by transcutaneous radiotherapy using the box technique with 25 MV photons. Forty-eight percent of the cases were intracapsular forms. On the basis of correlation criteria defined, the prostatic boost volume was shifted in the sagittal plan in 18% of the cases. Suspect seminal vesicles were found in 60% of the cases. Our treatment plans were considered "correct" in 65% of the cases, "acceptable" in 26% of the cases and "unsatisfactory" in 29% of the cases. The corrections applied to the treatment plan do not vary according to grade but according to stage and concern mainly the posterior limit of the boost volume and to a lesser extent the superior and anterior limits. The boost volume should be determined specifically for each case. CT-scans thus seem indispensable in establishing treatment plans in prostate cancer.

Carcinoma↗
PubMed1986

Migration of the schistosomula of Schistosoma mansoni in mice vaccinated with radiation-attenuated cercariae, and normal mice: an attempt to identify the timing and site of parasite death.

The migration of the schistosomula of Schistosoma mansoni labelled with [75Se]methionine, has been followed from the skin to the hepatic portal system. Parasites were detected in all mouse tissues by compressed organ autoradiography. Two separate experiments were performed to track parasites in normal mice, and in mice previously vaccinated with irradiated cercariae. In normal mice, the profile of numbers of autoradiographic foci detected in the skin, lungs, systemic and splanchnic organs was described with time post-infection. The distribution of parasites to systemic organs, following exit from the lungs, paralleled the fractional distribution of cardiac output. Accumulation of schistosomula in the hepatic portal system was complete by day 21 post-infection. Only 2-3 passes of parasites around the vascular system would be required to produce the hepatic portal population. No significant decline in total foci was detected in the first 12 days post-infection. The majority of parasite elimination appeared to occur in the lungs as late as day 21, with lesser proportions in the systemic organs and skin infection site. The pattern of migration in vaccinated mice was similar to that in normal animals. One difference observed was the longer duration of stay in the skin; however, the majority of parasites eventually reached the lungs. The systemic phase of migration occurred on a reduced scale, as did accumulation of parasites in the hepatic portal system. The decline in total foci in vaccinated mice commenced approximately 7 days earlier than in normal mice and proceeded to a lower end-point. Again the majority of parasite elimination appeared to occur in the lungs with lesser proportions in the systemic organs and skin infection site. It is suggested that resistance to reinfection in vaccinated mice has two additive components which combine to retard the migration of schistosomula within the vasculature, preventing them from reaching the hepatic protal system.

Animals↗
PubMed1986

The lymphnodal clonogenicity and kinetics of metastatic cells disseminated by a transplanted rat carcinoma.

We report data on the transplantation of primary tumour cells and of lymph nodes containing metastatic cells disseminated by a mammary carcinoma (LMC1) implanted s.c. in the Johns' Strain Wistar rat. A new method is described for deriving the TD50 of metastatic cells and for comparing their lymphnodal clonogenicity in the transplanted and the original, i.e. 'primary' tumour host. The TD50 for transplanted primary LMC1 cells was approximately 12 (fiducial limits 8-20 cells), and the latency of the 8-10mm tumours formed (T8-10) after inocula of 10(2) to 10(5) cells decreased linearly with the logarithmic increase in the number of cells injected. From the T8-10 and tumour incidence data for transplanted inguinal, axillary and para-aortic nodes, the TD50 for metastatic cells was calculated to be 1120 cells (fiducial limits 790-1603 cells) indicating that the clonogenicity of naturally disseminated metastatic cells was about a 100 fold lower than that determined for transplanted primary tumour cells. The incidence and T8-10 data for axillary, inguinal and para-aortic lymph node metastases in primary-tumour-excised hosts suggests that, although metastatic cells may continue translymphnodal dissemination in situ, their TD50 is still consistent with that determined by node transplantation.

Animals↗
PubMed1985

Metastasis and the excision of irradiated LMCI tumours in the rat.

Lymph node metastases occurring within 150 days of local non-curative irradiation and excision of a transplantable mammary adenocarcinoma (LMCI) have been scored and their growth measured in isogeneic rats. Single doses (5-40 Gy) of 60Co gamma-rays were given to the primary at 8-10 mm diameter and these were excised either immediately or up to 30 days later. From the results it is concluded that approximately half of all rats have occult dissemination at the time of irradiation. Only these form metastases after the early excision of 10-40 Gy treated tumours but the number of positive sites per animal is significantly reduced. Delayed excision of the irradiated primary permits the further seeding of metastases and, with its regrowth, the incidence of positive rats and the mean number of metastases per animal is restored to that observed after control surgery. This process was dependent on the radiation-induced delay in growth of the primary tumour. However, all metastases, irrespective of site, radiation dose, and time of primary tumour excision showed a growth rate characteristic of the untreated LMCI tumour. No evidence was obtained for an enhancement in the dissemination of metastatic cells from the irradiated but regrowing primary tumour. However, an alteration in the pathways of lymphatic dissemination leading to an increased number of metastases seeding the mediastinum and abdominal lymph nodes may have occurred.

Adenocarcinoma↗
PubMed1983

The introduction of postpartum intrauterine devices in the People's Republic of China.

In China, which has a commitment to family planning and, in particular, to the one-child family, a postpartum IUD should be widely accepted and could have significant impact on the Chinese family planning program. This report presents the introduction of the Delta T and Delta Loop devices, with 200 immediate postpartum insertions. Fifty-two deliveries were by cesarean section. The 6-month expulsion rates were 13.3 and 17.2 for the Delta T and Delta Loop, respectively. There was one pregnancy reported. Analysis suggests that the two devices are suitable for use in the postpartum period for Chinese women.

Adult↗