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Biomedical subjects

D H Carr

Publications and source records attributed to D H Carr.

At least 55 records · Page 3Linked to original sources

Pneumocystis carinii pneumonia in renal transplant recipients--clinical and radiographic features, diagnosis and complications of treatment.

Six episodes of Pneumocystis carinii pneumonia in five renal transplant patients on low dose maintenance prednisolone are described. The infection was rare, occurring in 3 per cent of the recipients transplanted between 1978 and 1984. Diagnosis and treatment were not straightforward. Fever was the earliest evidence of illness, and in three episodes the chest radiograph was normal at presentation. At diagnosis, two to 16 days later, all had pulmonary infiltrates and severe hypoxia. Diagnosis was confirmed by cytological examination of bronchial lavage (two), transbronchial biopsy (one), open lung biopsy (one), and for two episodes clinically, from the rapid and complete resolution of fever, pulmonary infiltrates and hypoxia following a therapeutic trial of high dose cotrimoxazole. Pneumocystis antibody titres were low during the illness and in convalescence and did not contribute to diagnosis. Three patients had serological evidence of recent cytomegalovirus infection. All episodes responded to treatment with high dose cotrimoxazole. All the patients survived the illness but one died a year after recovery. The major complications of treatment were thrombocytopenia (three cases) and neutropenia (two cases) which did not respond to folinic acid.

Drug Combinations↗

Intravenous chelated gadolinium as a contrast agent in NMR imaging of cerebral tumours.

NMR imaging was performed on 12 patients with cerebral tumour before and after administration of intravenous gadolinium diethylene triamine penta-acetic acid (DTPA) (0.1 mmol/kg). Contrast enhancement was seen in all cases. Ring enhancement was most frequent (7 cases) but central, linear, patchy, and diffuse enhancement were also seen with both inversion-recovery and spin-echo sequences. The degree of enhancement was greater than that seen with X-ray computed tomography (CT) in 8 cases, equal to it in 3 cases, and less in 1 case. NMR distinguished between tumour and peritumoral oedema to the same extent as did CT. No side-effects were encountered and there was no significant change in urea, creatinine and electrolytes, liver function tests, blood coagulation, or urine testing after administration of gadolinium-DTPA. Gadolinium-DTPA is likely to be of considerable value in NMR imaging of the brain.

Adult↗

Computed tomography of sellar and parasellar lesions.

The findings in 50 patients examined by computed tomography (CT) of the pituitary fossa are described. The appearances in 43 were judged to be abnormal, four were normal and three were 'doubtful'. Abnormal features included deviation of the pituitary stalk (seven), localised increased enhancement after intravenous injection of contrast medium (18) and extrasellar extension of tumour (11). The CT scans enabled diagnoses of pituitary microadenoma, empty sella and combinations of the two to be made. Modern CT scanners (third or fourth generation) provide detailed information enabling the optimum assessment and treatment of sellar and parasellar lesions.

Adolescent↗

Visibility of the renal fascia at intravenous urography.

Contrary to the accepted understanding that visibility of the perirenal fascia at urography is a rare finding and when seen is usually associated with renal pathology, a recent report has suggested that it is a fairly common, normal finding. In a retrospective study, 261 unselected intravenous urograms performed over a 3-month period were analysed. The findings indicate a low incidence of perirenal fascia visualisation and, when present, an association with renal pathology.

Adult↗

Computed tomography in pre-operative assessment of bullous emphysema.

Nine patients with bullous emphysema for which surgery was being considered have been investigated with computed tomography (CT). In six out of nine patients (67%) CT showed more extensive disease or bilateral disease where only unilateral was suspected from postero-anterior and lateral chest radiographs. Only one patient proceeded to surgery and post-operative CT showed satisfactory re-expansion of the compressed lung. Surgery was abandoned in one patient as a result of the CT findings. Computed tomography is of value in patients with bullous emphysema in assessing the extent of disease and may assist the surgeon in operative planning.

Adult↗

Iron and gadolinium chelates as contrast agents in NMR imaging: preliminary studies.

Iron (Fe2+) and gadolinium (Gd3+) chelated to ethylenediaminetetraacetic acid and Gd3+ chelated to diethylenetriamine pentaacetic acid have been used as contrast agents in nuclear magnetic resonance imaging of the normal kidney and cerebral infarction in rabbits. All three agents produced observable changes with inversion-recovery images and marked changes in T1.

Animals↗

The fate of trophoblast retained within the oviduct in the mouse.

Pre-implantation blastocysts or trophoblast, obtained from ectoplacental cones, were transferred to the right oviducts of both pregnant and nonpregnant mice. Blastocysts which remained within the oviductal lumen did not show evidence of further differentiation into trophoblast although they readily implanted on various extratubal sites. Similarly, trophoblast from ectoplacental cones failed to show invasive properties when restricted to the lumen. In 3 cases where trophoblast giant cells were found within the tubal lumen, entry appeared to have been contingent on an existing breach in the epithelium. Invasive action on tubal epithelium by trophoblast was not seen.

Animals↗

Kinin activation as a predictive assay for adverse reactions to radiographic contrast medium.

The rate of conversion in vitro, of prekallikrein to kallikrein has been measured in 74 reactors to contrast medium and 70 controls. The conversion rate is significantly more rapid in reactors than controls. There was no difference in C1-esterase inhibitor and factor XII levels between reactors and controls. This retrospective investigation suggests that prekallikrein/kallikrein conversion rate may form the basis of a test for differentiating between reactors and non-reactors.

Adolescent↗

Contrast media reactions: experimental evidence against the allergy theory.

In order to clarify whether adverse reactions to radiographic contrast media may be allergic in nature, it is essential to show that contrast media can act as haptens and induce antibody formation in vivo. Experiments in Hooded Lister rats have been carried out using techniques specifically designed to produce favourable conditions for the production of antibodies. No evidence of any antibody formation was found in any of the experiments. These experiments suggest that radiographic contrast media in their native form do not act as haptens, contrary to previously published data, and it therefore seems unlikely that the majority of adverse reactions to radiographic contrast media are allergic in nature.

Animals↗

Gadolinium-DTPA as a contrast agent in MRI: initial clinical experience in 20 patients.

Magnetic resonance imaging (MRI) was performed in 20 patients before and after intravenous administration of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) in a dose of 0.1 mmol/kg. Twelve of the patients had clinical and histologic diagnoses of cerebral tumor, six had hepatic tumors, one had hepatic cysts, and one had transitional cell carcinoma of the bladder. Contrast enhancement was seen with all tumors, but not with the hepatic cysts. The degree of enhancement was greater than that seen with computed tomography (CT) in 13 cases, equal to it in six, and less in one. Contrast enhancement was detectable as long as 18 hr after injection of Gd-DTPA in one case of cerebral tumor. The margin between cerebral tumor and peritumoral edema could be delineated with contrast-enhanced MRI to the degree possible with contrast-enhanced CT. In the liver isointense enhancement was seen with saturation-recovery (SR), inversion-recovery (IR), and spin-echo (SE) sequences although not with all three sequences simultaneously. In general IR sequences were most sensitive for display of the contrast agent, but the enhancement often decreased the difference between abnormal and normal tissue. No short-term side effects were encountered and no significant change was seen in urea, creatinine, electrolytes, liver function tests, blood coagulation, or urine testing after injection of Gd-DTPA. Although much more work will be required to evaluate this contrast agent, these initial experiences are very promising.

Abdomen↗

The use of iron and gadolinium chelates as NMR contrast agents: animal and human studies.

Rapid development of paramagnetic NMR contrast agents has occurred over the past 3 years. Useful agents include chelates of iron and gadolinium. Gadolinium-DTPA was used safely in 23 human subjects with brain tumors, hepatic tumors and cysts, and a variety of abdominal and pelvic tumors. Various patterns of contrast-enhancement were noted. These agents can radically alter NMR image contrast. Optimum doses, pulse sequences and timing of imaging remain to be determined.

Abdominal Neoplasms↗

The regulation of parotid and submandibular salivary secretion in sheep.

During eating the parotid and submandibular salivary glands of sheep are stimulated via parasympathetic and sympathetic pathways. The response of the glands depends on the nature of the diet and the duration of a meal. In anaesthetized animals a continual activity in the parasympathetic nerve supply to the parotid gland reflects the excitatory effects of rumino-reticular (gastric) distension and contraction. This activity is reduced by high levels of rumino-reticular distension and increased osmolality of venous blood. It is argued that in conscious sheep these factors are important in determining the volume of saliva that is normally produced. Mechanoreceptors in the parotid glands of sheep are also a source of considerable afferent activity. Some of these receptors are active during naturally stimulated secretion and it is suggested they may also have a role in regulating salivary gland function.

Afferent Pathways↗

Manometric and electromyographic observations of the oesophagus of sheep in eructation, regurgitation and swallowing.

Manometric and electromyographic recordings during eructation, swallowing and the regurgitation of rumination in sheep revealed variable oesophageal activity during eructation in contrast to the uniform pattern of oesophageal activity in swallowing and regurgitation. In eructation the passive increase in pressure of about 7-15 mmHg--the filling phase--associated with entry of gas into the oesophagus was commonly (in 96.6% of thirty eructations) terminated by contractions in the caudal thoracic oesophagus (c.t.o.). Eructation contractions were present in 73.3% of thirty eructations in a site 130 mm cranial to the c.t.o. and in 36.6% of thirty eructations in a site 260 mm cranial to the c.t.o. These contractions moved cranially at about 420 mm.s-1. In contrast during regurgitation the contractions of the oesophagus which moved cranially at about the same rate (410 mm X s-1) were characteristically more intense (47-64 mmHg) than eructation contractions (10-36 mmHg). Also in contrast to those in eructation, regurgitation contractions were invariably of each site of the oesophagus from which recordings were made. Secondary contractions of the caudal cervical and thoracic oesophagus which sometimes followed eructation were interpreted as serving as clearing contractions returning residual gas in the oesophagus to the stomach. These swept over the oesophagus at about 200 mm X s-1 and occurred without associated swallows. The variability of reactions of the oesophagus in eructation and differences in reactions of its different regions are discussed as arising from different degrees of sensitivity to, and stimulation by, gaseous distension of the oesophagus and stomach.

Animals↗

Adult hemoglobins are synthesized in erythroid colonies in vitro derived from murine circulating hemopoietic progenitor cells during embryonic development.

Circulating peripheral blood cells and disaggregated yolk sac cells were obtained from normal mouse embryos as early as day 9 of gestation, prior to the formation of the fetal liver. These were cultured in vitro in plasma clots or methylcellulose, in the presence of either embryonic fluid or adult spleen cell-conditioned medium, with or without added erythropoietin. Large erythroid colonies were observed by the sixth day of culture. In all instances, these erythroid colonies synthesized adult hemoglobins. These results indicate that erythroid progenitor cells committed to adult hemoglobin synthesis are present in early embryonic circulation.

Animals↗

Parental origin of triploidy and D and G trisomy in spontaneous abortions.

A cytogenetic study of 15 triploid spontaneous abortuses, 12 trisomic abortuses, and their parents was carried out using the Q-banding technique. Polymorphic regions in abortus chromosomes were compared to corresponding regions of parental chromosomes to determine the origin of the extra chromosomes. Using marker chromosomes it was found that 7 triploids and only one trisomy were informative. Three triploids arose by failure to shed the second polar body during oogenesis. One triploid arose by dispermy. The other three triploids inherited an extra haploid set of chromosomes from the father, either by dispermy or by failure of the second meiotic division during spermatogenesis. The only informative trisomy, a trisomy 22, inherited the extra 22 from the mother. Chromosome polymorphisms are useful in determining the parental origin of extra chromosomes in certain cases.

Abortion, Spontaneous↗

Trophoblast growth in the lungs of mice.

Trophoblast giant cells grow from ectoplacental cones of 7 1/2 days' gestation that are implanted in the lung from the surface, intrabronchially, or via the circulation. When blastocysts of 3 1/2 days' gestation are implanted in lung, their behavior varies according to the route of implantation and the ages of the recipient mice. Blastocysts produced trophoblast giant cells when implanted in the bronchial tree. Trophoblast giant cells were not seen in adult lungs when blastocysts were introduced via the circulation. However, they were seen in 12-day-old mice injected in the same way 10 days previously. Something is apparently liberated from adult lung vessels which interacts with the blastocyst or zona pellucida and causes rapid degeneration of trophoblast. Experiments designed to extract this agent are in progress in the hope that the agent may be useful in the treatment of human trophoblastic disease.

Animals↗